Convatec Ltd. & Ors v Smith & Nephew Healthcare Ltd & Ors

In these proceedings the claimants (“ConvaTec”) contend that the defendants have infringed various intellectual property rights held by ConvaTec relating to wound dressings. ConvaTec have a wound dressing product called Aquacel. It is based on a cellulose derivative, carboxymethyl cellulose (“CMC”). The nub of the complaint is that the first and second defendants (“Smith & Nephew”) wish to sell a wound dressing called Durafiber. Durafiber is made from a blend of cellulose fibres called Tencel and fibres made from cellulose ethyl sulfonate (“CES”). The CES fibres for Durafiber are made by the third defendant (“SFM”). The fourth defendant is an ex-employee of the claimants now working for the third defendant. ConvaTec contend that Durafiber infringes various of their rights.

As a whole the proceedings include or have included claims for infringement of three ConvaTec patents, a substantial claim for misuse of confidential information, a claim for trade mark infringement and a patent entitlement claim. The corporate defendants gave an undertaking in December 2010 not to sell Durafiber pending an expedited trial of the aspects of the proceedings which concern Durafiber itself. This is that expedited trial. There are other issues between the parties which remain live but which do not fall to be decided on this occasion because they do not concern rights relating to Durafiber itself. The other issues relate essentially to using silver with wound dressings.

Until two weeks ago this trial was to be concerned with three patents (EP (UK) 0 927 013, EP (UK) 1 085 912 and EP (UK) 0 616 650) and that part of the misuse of confidence claim which bore on Durafiber itself. Shortly before trial ConvaTec dropped this part of the breach of confidence claim as well as the claims in relation to EP (UK) 1 085 912 and EP (UK) 0 616 650. The breach of confidence claim which was not due to be heard at this trial (essentially about silverisation) remains as does the entitlement claim. In relation to EP (UK) 1 085 912 ConvaTec will submit to an order for revocation. In relation to EP (UK) 0 616 650 ConvaTec having dropped the infringement claim, the defendants have dropped their claim for revocation of that patent.

The only live issue for this trial therefore is the claim for infringement of EP (UK) 0 927 013 and the counterclaim for revocation on the ground of invalidity. The defendants rely on three items of prior art: PCT Application publication number WO 96/13282 (“Qin”), US patent 4,256,111 (“Lassen”) and PCT Application publication number WO 94/16746 (“Bahia”). They were all published before the priority date of the ‘013 patent. There was another item of prior art called Qin 2 but that was dropped at the start of the trial. There is also a plea of insufficiency.

The ‘013 patent is held by the second claimant and the first claimant is an exclusive licensee under the patent. ConvaTec alleges that Durafiber infringes claims 1, 3 and 9 and alleges that claims 1, 3 and 5 are independently valid. Thus the only issues I need to be concerned with are infringement and validity of claims 1 and 3 and validity (but not infringement) of claim 5. Claim 9 is not said to be valid independently of claims 1 and 3.

There is also a point on the liability of the second defendant even if (which the defendants deny) the patent is valid and infringed by the first and third defendants.

Mr Piers Acland QC leading Dr Brian Nicholson instructed by Latham & Watkins appeared for ConvaTec. Dr Justin Turner QC leading Mr Mark Chacksfield appeared for both SFM and Smith & Nephew. For this purpose counsel were instructed by Slaughter and May for SFM and by Bristows for Smith & Nephew. Given that the claim for misuse of confidential information insofar as it was to be addressed at this trial was no longer live, Dr Law did not appear and was not represented.

ConvaTec’s expert witness was Stephen Bishop. He has a BSc from Southampton University in Biochemistry and a Postgraduate Diploma in Industrial Pharmaceutical Sciences from the University of Brighton. He is a member of the British Association for Research Quality Assurance, a member of the Society of Biology, a Chartered Biologist and a member of the Institute of Materials Minerals and Mining (Packaging) Society. Mr Bishop has 26 years experience in the medical device industry. He started work in that area at Amersham International in their Cardiff Quality Control/Assurance Laboratories in 1984, moved to a division of Unilever in 1987 to work on the development of in vitro diagnostic products for monitoring pregnancy, fertility and the human endocrine system and moved to ConvaTec in 1990. He has worked at ConvaTec ever since and continues to do so. Since 1992 Mr Bishop has worked on the development of fibrous wound care products. In 1992-1996 he worked on Aquacel product development. He is one of the named inventors of the ‘013 patent in this case.

Mr Bishop has played a central role in this litigation from the outset and candidly accepted that he had been seeking to do the best for his employer in that regard. The defendants submitted that Mr Bishop was in an impossible position as an expert witness. They submitted that he was personally responsible for what they called the false allegations which had been at the heart of the confidential information claim namely that the way of making Aquacel was confidential. Mr Bishop oversaw ConvaTec’s experiments in this case and he accepted, candidly in my judgment, that if the experiments do not stand up then that will be a matter of personal embarrassment to him. He accepted he was under significant personal pressure.

As regards confidential information Mr Bishop explained that his factual evidence that the Aquacel process was confidential was given when he believed that state of affairs to be true. He had checked the position to his satisfaction. When the defendants showed that in fact the recipe had been published, it was to be found in patent specifications Mr Bishop had not checked because he did not think they were relevant. I accept his evidence on this issue. In my judgment this does not undermine Mr Bishop’s standing as a witness.

Nevertheless there is no doubt that Mr Bishop’s position as an expert witness in this litigation was not an easy one. He was only appointed to act as an expert relatively late on in the proceedings. Dr Turner asked him about his obligations as an expert. Mr Bishop was candid that until appointed as an expert he had been an advocate for ConvaTec but he said that after he was appointed, he accepted and understood his duties to the court. Mr Bishop was indeed in a difficult position but in my judgment when he was in the witness box he was doing his best to help the court. He gave fair answers to the questions asked and I have no reason at all to reject his evidence simply because of the position he was in save in one respect. The only aspect of his evidence which gave me any concern related to the experiments. The experiments in the Notice had been conducted well before Mr Bishop was an expert. At the time of the Notice he was simply an employee of ConvaTec doing his best for his employer. I have no doubt whatsoever about Mr Bishop’s integrity in giving his answers on this topic in cross-examination and trying his best to help the court but in my judgment his ability to be objective about what the experiments showed was compromised from the start. I cannot place much weight on Mr Bishop’s evidence about the experiments.

Mr Woodings is an experienced fibres scientist who specialises in cellulose chemistry. He is a consultant to the nonwoven and fibre industries and has over 50 years experience in the industry. Between 1982 and 1994 he worked in the Courtaulds Research Division and from 1994 and 1998 he was Market Development Director for Tencel Fibres Europe. He was commissioning editor and author of the book ‘Regenerated Cellulose Fibres’, and also contributed to Kirk Othmer’s Encyclopaedia of Chemical Technology and the Encyclopaedia of Polymer Science and Technology on the same topic. He was an excellent witness.

Dr Kettlewell is an R&D chemist with a PhD in polymer synthesis. He gave evidence about SFM’s manufacturing process. He was a good witness. There were aspects of SFM’s process that Dr Kettlewell was not fully familiar with (batch mixing) but in my judgment no criticism of him or the defendants can arise from that because the significance of these issues from the claimants’ point of view only emerged at trial.

This case is concerned with cellulose as used in gel forming wound dressing products. Cellulose comes from sources such as wood pulp and cotton. Chemically, cellulose is a polymer of glucose molecules forming a very long chain. Cellulose fibres consist of numerous polymer chains lying together. A cellulose fibre comprises a mixture of crystalline portions and amorphous portions. In a crystalline region the chains line up in an ordered structure, whereas when the chains are disordered, the region is amorphous. In nature the crystalline structure is called Cellulose I. The fibres in natural cellulose are capable of absorbing moisture, but not much, and only by penetration of the amorphous regions, not the crystalline regions. The water molecules cannot get into the crystalline regions.

Viscose rayon is a product based on cellulose which has been known for many years. It is made by starting with cellulose and converting the cellulose into a derivative called cellulose xanthate. The xanthate is then dissolved in sodium hydroxide and spun and extruded into sulphuric acid. Chemically the molecules lose the xanthate group and revert to being cellulose. Thus although the product is chemically changed during the process, at the end the product is cellulose.

Another relevant technique is solvent spinning. In solvent spinning there is no derivatization of the cellulose. The material is dissolved as cellulose and then spun. There is one particular commercial product in the evidence, called Tencel. This was a product launched by Courtaulds on an industrial scale in 1988. It is made by dissolving cellulose in an amine oxide and then spinning the material into water. Another solvent spinning process involves dissolving the cellulose into a mixture of ammonium and copper sulphate. It is called the cuprammonium process and was used to make a product called Super AB which is mentioned below.

The term “regenerated cellulose” is sometimes used as a reference to a viscose-type process and sometimes to describe both viscose and solvent spinning as an umbrella term. Regenerated cellulose is chemically identical to natural cellulose but the crystalline structure of the ordered regions are in a different form, known as Cellulose II. Cellulose II is the more thermodynamically stable form of crystal. Apparently the polymer chains lie parallel in Cellulose I and anti-parallel in Cellulose II.

Along the polymer chain of cellulose are many hydroxyl (OH) groups. One longstanding and accepted way of increasing the absorbency of cellulose is to modify it chemically by derivatizing some of the hydroxyls. That has the effect of disrupting the crystal structure. The hydrophilicity of the material can be changed by choice of appropriate derivatives. One class of derivatives is based on ether linkages. There are a variety of cellulose ethers. The most common is carboxymethylcellulose or CMC.

Cellulose ethers have been widely used in a variety of industries such as food production and pharmaceuticals. They have long been used as absorbents both in powder form and in the form of fibres. When using powdered cellulose ethers to absorb water, the idea is to render the cellulose water soluble by derivatisation and then crosslink the molecules. Thus when water is added the material forms a gel rather than dissolving completely. When using fibres the idea is either to partially derivatize or else to completely derivatize and then cross-link. Either way the end result is again a gel.

Cellulosic gel forming fibres, in particular ones made of CMC, were well established commercial products in the 1980s. There was one particular high profile application referred to in the evidence called Rely. Rely was a tampon launched by Proctor & Gamble which took approximately 45% of the US tampon market in 1980. It employed CMC fibres and was highly absorbent. It made headline news at least in part because it was associated with deaths from what was called toxic shock syndrome. Mr Woodings explained that this was not due to CMC as a material. In any case there is no doubt that the skilled team would have been very well aware of this at all material times.

The production of fluid (known simply as “exudate”) is a normal feature of wound healing. Exudate is composed of serum-like watery fluid together with other things such as cellular debris. Serum-like watery exudate is called “serous” exudate. Exudate can be bloody (called “sanguinous”) and it can be infected (called “purulent”). Purulent exudate is pussy in nature. It includes white blood cells (in particular neutrophils).

Over the course of the healing of a wound, the nature and amount of the exudate produced changes. Typically, wounds all produce copious amounts of serous watery exudate in the initial stages and as healing takes place, the level of exudate drops off. Serous exudate is a very complex mixture of electrolytes, glucose and other solutes. One of the properties of serous exudate which can change is the concentration of ions in the exudate.

Hippocrates observed that wounds heal better if kept moist with a poultice covered with “plenty of leaves” but this medical principle was lost in more recent times and it had been conventional wisdom that wounds should be allowed to dry out in order for them to heal. However following work done by Winter et al in the 1960s, it became clear that keeping wounds moist promoted healing. The basis on which the gel forming dressings in this case work is that they absorb exudate from the wound but at the same time maintain moisture levels within the wound. Although maintaining a moist wound is desirable, one does not want it to be too moist because if the wound becomes saturated with exudate that can lead to “maceration” of the surrounding skin. Maceration is a process of overhydration of the tissue. In addition exudate can contain proteolytic enzymes (enzymes which break down proteins) as well as other factors, all of which can cause inflammation. Thus although exudate is a necessary part of the healing process and provides a moist environment, is also has this negative side.

A number of gel forming commercial wound dressings were on the market at the priority date. In some cases the absorbent material was in the form of a hydrocolloid powder and in other cases gelling fibres. A number of the products were based on alginate. Alginate comes from seaweed. The principle on which alginate dressings work is by ion exchange. Two forms of alginate are relevant: calcium alginate and sodium alginate. Calcium alginate is insoluble while sodium alginate is soluble and forms a gel. So when a calcium alginate wound dressing is used in a wound, the sodium ions in the wound exudate can be exchanged with the calcium ions in the alginate. This allows the fibres to absorb water and form a gel. Another effect of this ion exchange is that calcium ions are released. These calcium ions can have a haemostatic effect – that is they prevent bleeding.

The gelling characteristics and the absorbent properties of the alginates can be modified by varying two characteristics: the ratio of calcium to sodium alginate and the ratios of two particular monosaccharide residues, known as M and G. Alginates with a high M ratio swell very rapidly; with high G they gel less well but have greater strength. Depending on the source of the alginate (e.g. from different species of seaweed), the materials can have different ratios of these two monosaccharides.

At the priority date there were a number of alginate fibre based dressings with different gelling properties and different absorbency properties. Two particular alginates are referred to in the evidence: Sorbsan and Kaltostat. Sorbsan is a straight calcium alginate while Kaltostat is a mixture of 80:20 calcium and sodium alginate. There were also alginate products in which the alginate fibre was mixed with other things. For example, Kaltocarb consisted of alginate fibres together with charcoal cloth and Sorbsan Plus was alginate fibres bonded to a viscose layer. Fibracol was a product consisting of alginate fibres together with collagen. There was also an alginate product called Carbonet but that was not a gelling product.

Another gel forming wound dressing at the relevant time was Granuflex. This was non-fibrous and consisted of a mixture of CMC, gelatin and pectin. The word “colloidal” is used sometimes to refer to this sort of non-fibrous gel forming dressings.

Also at the priority date were wound dressings based on CMC gelling fibre. The paradigm example of this was Aquacel itself. It had only been launched at the very start of 1996 (the priority date is 5^th September 1996) but it is common ground that the product was so successful and made such an impact that by September 1996 anyone relevant knew about it.

One of the differences between alginate fibres and CMC fibres is that they absorb water via different mechanisms. Alginates absorb as a result of the ion exchange mechanism discussed above whereas CMC fibres absorb water as a result of hydrogen bonding between water molecules and the polymer chain. In terms of behaviour, CMC fibres generally are more absorbent and absorb at a faster rate than alginates. On the other hand a high-salinity exudate will cause greater gelling and hence absorbency of alginates but a reduced absorbency for CMC.

The interaction between a wound dressing and the exudate is complex. For example all wound dressings preferentially absorb serous exudate but they struggle to absorb sanguinous or purulent exudate. Also the fact that the absorption process in alginates depends on ion exchange means that as the ion concentrations in wound exudate change over time, this can have an effect on absorption by alginates.

In conclusion as regards the technical background, it is common ground that at the priority date there were a variety of wound dressings which promoted the maintenance of a moist wound environment by gelling. These included dressings using alginates and dressings using CMC. There were also wound dressings consisting of alginate fibres plus something else and dressings which contain alginates but in colloidal form, rather than fibrous form.

There was no dispute that in this case the person skilled in the art would likely be a team. The team would consist of (i) a scientist with experience in developing wound dressings (such a person would typically have a science degree and may or may not have a PhD); (ii) a chemist with knowledge and experience of cellulose chemistry, experienced in developing cellulose fibres and fabrics, and additionally (iii) a clinician who could provide guidance on the required clinical properties of the products being considered. The clinician would only be consulted if necessary. Whether these three sets of skill and knowledge were to be found in a single individual or a group of two or three persons is irrelevant.

The common general knowledge was not in dispute. It included all the matters I have set out above by way of technical background and the following (taken from ConvaTec’s closing):

Production of gel-forming CMC fibres: was common general knowledge from as early as the 1970s.

The use of CMC gel-forming fibres in commercial products: for example, the Super AB wound dressing was common general knowledge in the mid 1980s.

How to make CMC gel-forming fibres: amongst other things by etherification was common general knowledge from the mid 1980s.

Variation of the gelling and absorbency properties of cellulose derivatives by varying the degrees of substitution and/or cross-linking: was common general knowledge from the mid 1980s.

The difference in crystal structure and thermodynamic stability between Cellulose I and Cellulose II fibres: was common general knowledge. In particular, it was well-known that Cellulose II has a modified crystal structure and is thermodynamically more stable than the naturally occurring cellulose, Cellulose I.

Alginate fibre wound dressings: had been on the market since the 1970s.

Different fibres can have different absorption capacities and rates of absorbency: for example, CMC is generally more absorbent and has a higher rate of absorption than alginates.

Another aspect of common general knowledge related to fibre processing to make webs for use in products like wound dressings. Techniques such as carding were very well known as was the making of non-woven felts e.g. by needle punching. Mixing or blending batches of fibre together was also common general knowledge.

The application for the ‘013 patent was filed on 5^th September 1997 claiming priority from a British application on 5^th September 1996. The patent was granted on 5^th March 2003. It is entitled “Wound Dressing”. The specification begins by explaining that the invention relates to a wound dressing and in particular to a non-adherent wound dressing comprising fibrous material.

A key paragraph in the document is Paragraph [0003] as follows:

Here the patentee is stating the problems the invention is setting out to address. Gel forming fibres are useful because they do not adhere to the wounds but a single kind of fibre behaves in its own particular way. It may preferentially absorb a particular kind of exudate and it will have its own rate of absorption. Thus, as was common general knowledge, cellulose based fibres have a high absorptive capacity initially but then tail off.

The specification acknowledges that a mixture of alginate and other water soluble materials has been proposed before (paragraph [0004]) albeit as a co-spun composite fibre and then states in paragraph [0005] that the disadvantages of the prior art (for which read the previous paragraphs [0003] and [0004]) can be mitigated by mixing different types of gelling fibres together. Such wound dressings provide good absorbency for a range of exudates and are relatively inexpensive. In addition a moist wound environment may be created which is beneficial to healing.

The specification explains that the gel forming fibres to be used are hygroscopic materials which become moist and slippery or gelatinous as they take up wound exudate. They can be of the type which retain their structural integrity on absorbtion of exudate or of the type which lose their fibrous form and become a structureless gel or solution on absorption of exudate.

The specification then lists the preferable kinds of fibres to be used. They include chemically modified cellulose fibres, particularly CMC fibres, as well as pectin fibres, alginate fibres, chitosan fibres, hyaluronic fibres and other polysaccharide fibres or fibres from gums.

In paragraph [0010] the patent states that the gel forming fibres are preferably mixed to give a dressing comprising fibres with different absorbencies and also different absorbency rates and profiles.

The dressing may contain other fibres as well and the preferred examples (paragraph [0011]) are textiles such as cellulosic fibres. Viscose rayon and regenerated cellulose are mentioned among others. In general these textile fibre are said to absorb water by capillary action and are not hygroscopic. They are not gel forming fibres.

The specification then explains (paragraph [0014]) how to make the wound dressing, by intimately mixing the gel forming fibres e.g. by carding, air-laying or needle punching the fibres together to form a web of mixed fibres. These techniques of carding, air-laying and needle punching of fibres to form a web were all part of the skilled person’s common general knowledge.

The patent contains two examples. In example 1 a wound dressing comprising the alginate fibres as used in the commercial dressing Kaltostat are mixed with the modified cellulose fibres used in the commercial dressing Aquacel (i.e. CMC). The ratio is 70% alginate fibres and 30% CMC fibres. The mixture was carded to form a web and then cross-lapped, needle punched and rolled up. The result was a homogeneous blend of fibres. In Example 2 this dressing (Dressing A) was tested for absorbency. Also tested was another mixed dressing (Dressing B) made in the same way but 60% alginate, 40% CMC. A control dressing of 100% CMC was also tested.

It is common ground that the table of results includes a mistake such that the figures for the absorbency of the dressings are labelled as “% difference” when they should be labelled “absorbency in g/g” or words to that effect.

In evidence Mr Bishop described a surprising experimental result he and his co-workers obtained when they were doing the work relating to the invention. He had expected the absorbency of the combination of CMC and alginate fibres to be lower than it turned out to be in practice, at least in some circumstances. However this point played no part in the trial and was not explored. ConvaTec did not suggest the point was relevant to any of the questions I have to decide.

The relevant claims are claims 1, 3, 5 and 9. They are as follows:

In Kirin Amgen Inc v Hoechst Marion Roussel [2004] UKHL 46, [2005] RPC 9 the House of Lords comprehensively reviewed the principles applicable to patent construction under the 1977 Act bearing in mind Article 69 of the European Patent Convention and the Protocol on the Interpretation of Article 69. Construction of a patent claim is purposive in nature and the question is always to work out what the person skilled in the art would have understood the patentee to be using the language of the claim to mean. Lord Hoffmann put it this way in paragraph 34:

A number of points emerge from this passage which are of particular relevance to these proceedings. First, the words of the claim are to be construed having regard to the patentee's purpose as set out in the rest of the specification. Second, the exercise is one of interpretation of the words of the claim. It follows that it is not permissible simply to ignore an integer of the claim; nor is it permissible to write a new integer into the claim.

In Virgin v Premium Aircraft[2009] EWCA Civ 1062, [2010] RPC 8 the Court of Appeal (Jacob and Patten LJJ and Kitchin J) considered the general approach to construction at paragraph 5 of the judgment of the court:

Finally I remind myself that it is always important to bear in mind that the skilled person reads the specification in light of the common general knowledge and appreciating that its purpose is to describe and demarcate an invention, that is to say a practical idea for a new product or process.

The issues of construction which arise in relation to claim 1 are:

Blend of discrete fibres - product by process claim

Type

Two questions arise, first whether the claim is a form of product-by-process claim and a second related question as to what the word “discrete” means. At the opening stage it appeared to me that ConvaTec were advancing a construction of claim 1 which made the claim a product by process claim. They contended that the reference to a “blend” of fibres referred to the need for a blending step taking two separate populations of fibres and mixing them together. “Discrete” was said to mean that the different fibres were separate prior to blending. I raised with Mr Acland whether that meant that his case was that claim 1 was a product by process claim. In other words although it appeared to be a claim to a product, a wound dressing, in fact properly construed it required certain particular process steps to be carried out in order to make the product. It would only cover a product made that way.

By closing Dr Turner was advancing the product by process construction of claim 1 and he submitted that Mr Acland had accepted in opening that the claim was indeed a product by process claim and that the matter was in effect closed. In my judgment (if it matters) Mr Acland did not close the matter off. Mr Acland’s reaction to my question was that he could see the construction he was advancing at that stage did appear to make claim 1 a product by process claim but he was going to think about it.

By the closing ConvaTec’s submission was that the claim did not have process features. “Blend” refers to the product being a blend, a mixture, howsoever made. “Discrete” refers to the fibres being discrete fibres, distinguishing them from the composite or “alloy” fibres referred to in paragraph [0004] of the patent. The defendants’ submission is that “discrete” refers to the fibres being separate before they are blended. They agree that the expression distinguishes the invention over known composite or “alloy” fibres, but does so because in these composite fibres the fibres are not separate before blending as the material is in solution. The defendant’s case is that “blend” must be the result of a prior mixing step.

I reject the idea that claim 1 would be understood by a skilled reader to refer back to the process by which the product was made. The claim is a claim to a thing – a wound dressing. The thing comprises a blend of (at least) two types of discrete fibres. In other words a mixture of discrete fibres.

The kind of mixture the patent is talking about is the kind described in paragraph [0014] of the specification. What is produced is a web of mixed fibres. The fibres there still keep their separate identities. The claims do not cover the case in which the two gel forming materials are put together into a single composite fibre, such as by using the co-spinning technique. Paragraph [0004] of the specification refers to an earlier patent application which discloses fibres which comprise alginate co-spun with some other material. These are described as fibres of a composite type, in clear contrast to the blend of discrete fibres of the invention, which are identifiable and separate fibres.

No doubt the reader would expect it to be likely that one would make such a wound dressing by mixing (blending) the two fibre populations but that processing is not what the claim is talking about. The claim is talking about a product. This interpretation of claim 1 fulfils the draftsman’s clear purpose of avoiding the composite fibres referred to in paragraph [0004]. The reader would understand that the invention is about using the mixture of fibres which gives beneficial properties as a wound dressing. It is not an invention focussed on manufacturing methods. How you choose to make the mixture is irrelevant.

Claim 1 refers to a blend of discrete modified cellulose gel forming fibres with “at least one other type” of discrete gel forming fibres. Thus the parties approached this case by advancing submissions about what a “type” was. There was also at one stage a submission that “type” was a term of art although whether it was maintained in the end I am not clear. In any event I reject the submission that “type” is a term of art.

In order to understand the rival submissions on construction it is necessary to understand their case on infringement as well since the two go hand in hand. The parties’ cases are as follows.

ConvaTec submitted that “type” referred to fibres with different absorbency properties. Mr Acland submitted that the thrust of the patent’s disclosure was concerned with mixing fibres having different absorbency properties, see in particular paragraph [0010]. The skilled reader would know as matter of common general knowledge that variation in the gelling and absorbency properties of cellulose derivatives can be achieved by varying the degree of substitution and/or cross linking of a cellulose derivative and thus the skilled reader would know that fibres with the same “chemistry” could be manufactured with quite different absorbency properties. (“Chemistry” in this sense refers to the defendants’ proposed construction – thus two lots of CMC fibres have the same “chemistry” even if they have different degrees of substitution because they are both carboxymethyl cellulose.) Thus, with an eye on the infringement case, ConvaTec submitted that the claim would cover a case in which an industrial manufacturer made fibres in a batch process and the operator made dressings by blending multiple batches. There would be infringement if (as here it is contended) the individual batches varied in their overall absorbency (g/g) property. The variation would have to be material rather than trivial or theoretical but on the evidence Mr Acland submitted that in this case SFM’s process did produce batch to batch variation which was “material”.

The defendants contended at trial that “type” refers to a particular polymer. So CMC was one type of polymer, and CES is another type of polymer. Another way of characterising the defendants’ submission was to say that “type” referred to chemistry of the fibre: CMC, CES, alginate and so on. They contended that this was consistent with the general teaching of the specification. They also contended, with an eye on the infringement case, that the claim was not concerned with batches or parts of batches of a given fibre type (e.g. CES) made in an industrial plant. Such material albeit made by the same chemical process might vary, either between batches or within a batch, in terms of crystallinity, degree of substitution and hydrophilicity. Those kinds of differences are not what the patent is concerned with, submit the defendants.

In my judgment both the claimants’ and the defendants’ submissions are wrong. I say that with some trepidation given that the parties’ submissions are the product of careful consideration and preparation of this case over many months. What in my judgment is the correct construction of claim 1 was something which occurred to me as a possibility in considering the parties’ written submissions between the oral evidence and the closing speeches and so, during the closing speeches I put it to the parties. It is a construction in the defendants’ favour. Dr Turner supported my proposed construction and maintained his submission as I have articulated it above as an alternative case. Mr Acland maintained his submission as to construction.

The flaw in each side’s submission is to approach the matter as one of construction of the word “type”. Type is a perfectly ordinary English word which ordinarily would not be expected to bear the kind of refined analysis each side have subjected it to. The key it seems to me is to appreciate that the correct question is to construe claim 1. Claims should, if they can, be construed as a whole.

The claim reads “a blend of discrete modified cellulose gel forming fibres with at least one other type of discrete gel forming fibres”. The claim is perfectly clear. One “type” of discrete gel forming fibre is “modified cellulose”. As well as fibres of that type, in order to be within the claim you must use fibres of at least one “other type”, in other words some discrete gel forming fibres which are not modified cellulose. Focussing on just the word “type” misses the way claim 1 is written.

In my judgment the meaning of claim 1 is actually rather simple. If all the gelling fibres in the wound dressing are modified cellulose then the claim is not satisfied. The claim requires a blend of (gel forming) modified cellulose fibres and some other type of fibres, that is to say some other fibres which are not modified cellulose. If I ask in a shop for a bowler hat and another type of hat, I do not expect to be given two bowler hats, differing only in their size or colour or whatever.

This is the reason the patent does not contain an elaborate definition of a “type” of gelling fibre. Asking, out of the context of claim 1, what a “type” is, is an example of meticulous over analysis of the words. Once you embark on asking the (wrong) question of what is a type, there is support in the specification for many different answers. In paragraph [0007] there is a reference to gel forming fibres which, when they absorb exudate, can be of the “type” which retain their structural integrity or of the “type” which lose their fibrous form and become a structureless gel. Each side’s approach, when applied to paragraph 7, would lead one to the view that type in claim 1 refers to this difference. It plainly does not.

Mr Acland’s submission takes the same approach but applies it to paragraph [0010] of the specification. Here the document states that the gel forming fibres are preferably mixed to give a dressing comprising fibres of different absorbencies and also different absorbency rates. So Mr Acland points to this paragraph in the patent and submits that it is telling the reader what different “types” are. They must have different absorbency properties. And since the skilled reader knows that as a matter of common general knowledge different absorbencies can arise from different degrees of substitution then the skilled reader would know that different batches of the same kind of fibre, which have different absorbencies, can be mixed together to produce a product within claim 1.

In my judgment both sides’ original arguments risk committing the fallacy warned against in Nobel v Anderson(1894) 11 RPC 519. A patent is to be construed as if the infringer had never been born. The claimants’ construction only arises at all because of the attempt to read this patent onto Durafiber. In my judgment the construction advanced by the claimants would not even occur to a skilled reader reading the document without knowledge of Durafiber and the argument in this case on infringement.

Paragraph [0010] of the patent includes the word “preferably” and in my judgment the skilled reader would understand that this is not an error. The gel forming fibres are preferably mixed to give a dressing comprising fibres of different absorbencies and also different absorbency rates and profiles, but not necessarily. It would be preferable but the fibres might not have different absorbencies and they might not have different absorbency rates and profiles. They will still be a mixture of different types of fibre even if those properties are the same. Why? Because there will be modified cellulose fibres present as well as another (different) type of fibre e.g. pectin, alginate or whatever. The fact that the skilled person knows in reading this document, as a matter of common general knowledge, that differences in absorbency can be due to different degrees of substitution in derivatised cellulose fibres is irrelevant.

ConvaTec’s construction necessarily imports a word of degree. The types must be “materially” different. How different is that? Mr Acland submitted that the evidence was that a difference of 2-3g/g absorbency would be regarded by the skilled person as a material difference. This arose from some passages in his cross-examination of Mr Woodings. In my judgment Mr Woodings’ evidence as a whole was not as helpful to ConvaTec’s construction as it was submitted to be. In my judgment he did not regard the point as clear cut. When Mr Woodings was first asked about it I took his view to be that fibres which differed by 2-3 g/g absorbency would be regarded as having different absorbency properties in a laboratory. Asked about it a second time Mr Woodings was shown an Aquacel monograph from 1998 which gave figures for absorbency of various dressings including a group of alginate dressings. The absorbencies of these alginate dressings did differ between themselves by about 2-3g/g according to a graph. Mr Woodings accepted the differences between these dressings were material differences but was in doubt about the significance of those differences. He was also concerned about testing methods. I took Mr Woodings’ evidence as a whole on this to be that as a technical matter a skilled person working in a laboratory would regard a difference of that magnitude as a difference which was a genuinely measurable or real difference. But whether it was a difference of any significance from a practical point of view, Mr Woodings did not know and if anything my impression was that he doubted it.

When the patent and in particular paragraph [0010] refers to “different absorbencies” it seems to me that the skilled reader would think the patentee was referring not just to differences which can be measured but to differences in the behaviour of two classes of fibre which are sufficiently great to make it worthwhile putting those classes of fibre together, from the point of view of the practical behaviour of a wound dressing. The brief cross-examination of Mr Woodings on this did not explore the issue in any depth. I doubt but do not have to decide whether the evidence is sufficient to make good a submission that a given difference in absorbency (in this case 2-3g/g) was different enough to be relevant from the point of view of wound dressing behaviour. If Mr Acland’s submission on construction is right then this analysis becomes vital. It is the key to ConvaTec’s infringement case. It seems to me that, as a matter of construction, these problems would be obvious to a skilled reader as a necessary facet of a construction which demanded two classes of fibre differing only in their relative absorbency properties and by some unspecified degree. Claims can be delimited by words of degree (see “large” in BTH v Corona(1922) 39 RPC 49) but the fact that ConvaTec’s construction introduces an issue of this kind into the construction of claim 1 is a point against it. The Protocol refers to reasonable certainty for third parties. In my judgment ConvaTec’s construction runs counter to that principle.

A further related problem of uncertainty for third parties, is knowing what the relevant characteristics are and how they are to be measured. There are different ways of testing absorbency. The skilled reader has no basis on which to say which test should be used.

The examples in the patent (which mix CMC and alginate fibres) do not decide the issue. They are plainly not meant to be limiting. They are consistent with all of the various constructions contended for but do not seem to me to distinguish between them.

Finally I remind myself that the exercise is one of purposive construction, looking at the claims in the context of the specification as a whole. What would the skilled reader think was the inventors’ purpose? In my judgment paragraph [0003] is revealing. This is an important part of the disclosure of the inventors’ purpose. When discussing the general problem they are setting out to solve, that gelling fibres used alone tend to preferentially absorb a particular type of exudate or at only one rate or rate pattern, the patent gives an example of the problem in the sentence at line 12: “For instance those fibres based on cellulose tend to show a high absorptive capacity for water ….”. The paragraph ends by stating “optimum treatment of a particular wound is not always achieved when such fibres are used alone”. So here the inventors are saying that optimum treatment is not achieved when gelling fibres based on cellulose are used alone. There is no distinction being drawn here between different sub-types of cellulose fibres (CMC, CES, different degrees of substitution or whatever). The purpose is to not use cellulose based fibres alone because using such fibres alone is the problem.

Then in paragraph [0004] there is a reference to a prior art proposal which involves combining alginate with at least one water soluble species “other than alginate”. This is not within the invention because it is co-spun and produces a composite fibre.

Then in paragraph [0005] the essence of the invention is set out – the disadvantages can be mitigated by mixing different types of gelling fibres together and, coming on to claim 1, there is then no surprise. The skilled reader can see that the claim requires mixing different types of fibre together. Fibres of modified cellulose must not be alone, there must be at least one other type of fibre. Something other than modified cellulose is needed in addition.

Claim 1 is a product claim. It requires the wound dressing to comprise a mixture of two classes of gel forming fibre. The mixture must be intimate but the fibres must retain their separate (discrete) nature. There must be modified cellulose gel forming fibres together with at least one other type of gel forming fibres, i.e. some gel forming fibres not made of modified cellulose.

It seems to me that this construction of claim 1 is in truth quite plainly what a skilled person would understand the language of claim 1 to mean, in its proper context, in the light of the specification as a whole and in the light of the common general knowledge. The two rival constructions of claim 1 advanced by the parties are not really interpretations of the words of the actual claims at all, they are both attempts to create new possible patent claims which could have been written in the light of the specification as a whole and which a skilled person might not have been surprised to see if they had read the specification first and then turned to the claims.

ConvaTec’s real point is that a claim in the form they contend for could be said to fit comfortably within the specification. ConvaTec’s argument on “construction” is really that claim 1 should be taken to be a claim to:

Equally the defendants’ “construction” is something like:

Both claims might be argued possibly to represent fair protection for the patentee as required by the Protocol, having regard to the nature of the disclosure but ignoring how the patentee has actually written claim 1. However to find that either represented the correct scope of protection in this case would not be an exercise in patent construction which I understand to be required by Kirin Amgen and Virgin v Premium Aircraft. It would be an exercise in going beyond the purposive and in context construction of the claims as they would be understood by a skilled person in the light of their common general knowledge. Moreover although I can see that the defendants’ construction might be said to give reasonable certainty for third parties (the other limb of the Protocol), in my judgment ConvaTec’s construction would not. ConvaTec’s construction would generate unreasonable uncertainty for third parties.

Two questions arise in relation to claim 3 but they are really facets of the same issue. One matter is the ambit of the term “modified cellulose” and the other matter is to understand the significance (or not) of the absence of the words “gel forming” as a qualification to “modified cellulose fibres”.

Before dealing with the points in issue, I should refer to the fact that claim 3 includes the terms “comprising” and “consisting of”. The parties were agreed (and I accept) that in claim 3 these terms are used in their familiar sense in patents. In patent drafting almost invariably “comprising” and “consisting of” are used in deliberately contrasting ways. “Comprising” is used to mean “includes but is not limited to” while by contrast “consisting of” means that the thing does not include anything else. Thus a wound dressing comprising a mixture of fibres type A and type B may have other things in it as well, other layers, other types of fibre and so on. Whereas a wound dressing consisting of fibres A and B means a wound dressing in which the only components are A and B.

Claim 3 would be understood by the skilled person in that fashion. The dressing “comprises” a wound contacting surface with certain properties because the dressing may also have other parts – perhaps a second layer above the wound contacting surface and so on. However the wound contacting surface is “a wound contacting surface consisting of a blend of discrete modified cellulose fibres with at least one other type of discrete gel forming fibres” (my emphasis). Thus the wound contacting surface is meant to be made up of the given blend and nothing more.

The parties did not agree about modified cellulose. Mr Acland submitted any modification would do, the term was not limited to chemical modifications. Dr Turner submitted the words meant cellulose which had been chemically modified. So the words include CMC but do not include a cellulose product like Tencel, which is made in a way which does not involve any chemical change to the cellulose molecules. This is an argument about infringement since Durafiber contains Tencel. Thus if Tencel is not modified cellulose, the combination of the words “consisting of” and “modified cellulose fibres with at least one other type of discrete gel forming fibres” exclude Durafiber from claim 3. Tencel, says the defendants is neither modified cellulose nor gel forming. The latter is common ground but not the former.

As used in the examples the term “modified cellulose” is clearly referring to CMC fibres, which of course consist of cellulose polymers which have been chemically modified or derivatised by the addition of carboxylmethyl groups.

The defendants contend that “modified cellulose” is a term of art and means chemically modified cellulose. The defendant’s case was supported by Mr Woodings. In his opinion the term is a term of art and bears the meaning above. He is of course a cellulose chemist. Mr Acland put to him the expression was not a term of art and challenged Mr Woodings to identify any documents (apart from the patent itself) in which the term was used as per Mr Woodings’ opinion. In cross-examination Mr Woodings could not identify any but in re-examination Dr Turner took Mr Woodings to two. One was the ‘912 patent of ConvaTec which did use the term to refer to chemically modified cellulose and the other was the expert’s report of Prof Heinze, filed by ConvaTec in this case as part of their case on breach of confidence. Prof Heinze had not been called now that the case was solely concerned with the ‘013 patent. Nonetheless the defendants pointed out that his report included an overview of the process of derivatizing cellulose which he described as “a process of derivatizing cellulose to make a modified cellulose fibre”.

Against that Mr Acland made the point that the expression “chemically modified cellulose” which appears from time to time (see e.g. paragraph [0008] of the patent itself) indicates that the term “modified” alone cannot mean that the modification must necessarily be chemical in nature – otherwise why add the word “chemically”.

Despite Mr Woodings’ opinion, it seems to me that “modified cellulose” is not a term of art. No technical dictionary was produced to bear out that definition. The only documents put to Mr Woodings in re-examination were a patent (filed later for what that may be worth) and an expert’s report which did not, it seems to me, attempt to address that issue at all. It is true that sometimes the expression is used to mean chemically modified cellulose but so what. Chemically modified cellulose is self evidently “modified” cellulose. The issue is whether any other kind of modification is excluded.

ConvaTec pointed to a passage in the defendants’ own opening skeleton (paragraph 82) which referred to Tencel as “a modified cellulose fibre”. Although in closing Dr Turner sought to explain this away, in my judgment it was not a mistake. The relevant paragraph in the defendants’ opening arises, I rather think, from the way in which Smith & Nephew themselves described Durafiber last year. I was shown a Durafiber leaflet which states that the product is composed of “a unique blend of specially modified cellulose fibres”. In my judgment this referred to the fact that Durafiber is made of a blend of derivatised cellulose fibres (CES fibres) and Tencel fibres. Thus Smith & Nephew were comfortable using the expression “modified cellulose” to refer to Tencel albeit Tencel itself is a regenerated cellulose material chemically in the form of cellulose. Indeed if “modified cellulose” does not include Tencel then that document would appear to be stating that Durafiber contains a blend of chemically modified (CES) cellulose fibres – which would run flatly contrary to the defendants’ case that all their CES fibres are one type of fibre. In truth, as the defendants’ opening skeleton put it “… Tencel is a modified cellulose fibre ...”. Dr Turner submitted that the leaflet was just an advertising document and therefore of little weight as evidence of the meaning of a technical term. I reject that. Leaflets of this kind describing medical products like Durafiber are not carelessly drafted. They are technical documents and are prepared with care and technical input.

I note that it is tolerably clear that the statement such as appears in the leaflet, that Durafiber is a blend of modified cellulose fibres, is what kicked off these proceedings in the first place. The first problem encountered by ConvaTec was when they discovered that the blend was of one gel forming fibre (CES) and a non-gel forming modified cellulose - Tencel. That led to the experiments on the CES fibres aimed at proving infringement which I will mention below.

As the expression is not a term of art, the issue is then to determine the meaning of the expression in the context of the ‘013 patent in the normal way.

In the examples “modified cellulose fibre” is referring to CMC fibre but clearly that does not mean it is limited to CMC. In my judgment “modified” is not a term which reader would think was meant to impose a tight limitation. The term is broad and is not intended to be limiting. I note that in claim 1 the composite expression is “discrete gel forming modified cellulose fibre”. There is no dispute that Tencel does not satisfy that definition because it is not gel forming, but in my judgment, taken in isolation the expression “modified cellulose” itself is not meant to impose a limitation to derivatized cellulose. However I say “in isolation” because as well as being in claim 1, the term comes up in claim 3 and claim 5. I will deal with the meaning of those claims below.

In claim 3 the expression “modified cellulose” has the same meaning as in claim 1. As an expression it is not limited to chemical modification.

By contrast with claim 1, claim 3 does not recite the words “gel forming” in the phrase “discrete modified cellulose fibres”. The absence appears to be deliberate but although I have not found this easy, it seems to me that the true construction of claim 3 is that the “discrete modified cellulose fibres” referred to are just the “discrete modified cellulose gel forming fibres” of claim 1. Claim 3 is of course dependent on claim 1. It is a form of synecdoche, using a partial description (discrete modified cellulose fibres) to refer to the whole (discrete modified cellulose gel forming fibres). The reasons for this as follows.

First, claim 3 is really about the wound contacting surface. That is the concept the claim is concerned with. A reader would see the claim as simply requiring that the blend referred to in claim 1 must be the wound contacting surface. The dressing can have other components elsewhere but wound contacting surface should consist of the new blend of gel forming fibres.

Second, although the change of wording in removing “gel forming” would strike the reader as deliberate, the consequences are odd. The patent contemplates non-gel forming modified cellulose fibres as a further component but this interpretation of claim 3 would be very odd way of bringing them in. Paragraph [0011] refers to such non gel forming cellulose but there is no suggestion they must be present at the wound contacting surface. Instead of a simple claim to the blend as the wound contacting surface, claim 3 would have this odd further aspect that non gel forming modified cellulose fibres could be employed as well but only on the wound contacting surface.

Third as a matter of language the reference at the end of the claim to “at least one other type of discrete gel forming fibres” makes little sense unless the thing referred back to is a type of gel forming fibres.

Fourth, claim 5 (dependent on the preceding claims including claim 1 and/or 3) also lacks the words “gel forming” either as a qualification for modified cellulose or alginate. Again I think this is a simple claim, intending to limit the gel forming fibre combination to modified cellulose and alginate. “Gel forming” is simply taken as read.

So overall I find that claim 3 simply requires that the wound contacting surface of the dressing consists of a mixture of gel forming modified cellulose fibres and at least one other type of gel forming fibre, i.e. something other than modified cellulose. All the fibres at the wound contacting surface of claim 3 must be gelling fibres.

In terms of the acts complained of, there is no question that the first defendant wishes to sell Durafiber dressings and therefore would infringe the patent if the product falls within the claims. There is also no dispute that SFM would also infringe, by supplying a means relating to an essential element under s60(2) of the 1977 Act, if Durafiber is within the claims.

There is a point taken by the defendants that there is no evidence of any act of infringement committed or threatened by the second defendant (Smith & Nephew Plc). I am told it is a holding company and does not trade in the UK. I did not have my attention drawn to any evidence or argument on behalf of ConvaTec that the second defendant had done any relevant act. Accordingly I find it has committed no relevant act (nor threatened to do so) and I will dismiss the action on this patent as against the second defendant on that basis.

Durafiber is a wound dressing product comprising a blend of Tencel fibres and fibres of CES. The fibres are discrete fibres. It is common ground that Tencel is not a gel forming fibre. Tencel is thus irrelevant.

The only gel forming fibres in Durafiber are made of CES, i.e. modified cellulose. In other words, as regards gel forming fibres, Durafiber uses modified cellulose alone and there is no other type of gel forming fibre present. Therefore on the true construction of the claims, Durafiber does not infringe claim 1.

Moreover since claim 3 is dependent on claim 1, Durafiber does not infringe that claim either, irrespective of the issues of construction of claim 3.

That is all that needs to be said as regards infringement.

However in deference to the time and effort spent on the issue, I will address the infringement case on ConvaTec’s construction of claim 1. They contended that the claim would have been satisfied by the presence of two “types” of gelling forming CES fibres differing in some non trivial way as to their absorbency properties.

It is common ground that the only gel forming fibres in Durafiber are made of CES. To prove its case on infringement, ConvaTec viewed the Durafiber product under a light microscope in hydrated and non-hydrated form. Their case is that two populations of gelling fibres were seen after hydration: thick and thin. The thick ones were labelled gelling type 1 and the thin ones gelling type 2. ConvaTec’s case was that this observation showed that there were two distinct and distinguishable populations of gelling fibre having different absorbency properties. A formal Notice of Experiments was given which included the photomicrographs relied on and repeats in the presence of the defendants’ team were organised. Although the images used in the Notice are bright and clear and do indeed, on the face of it, show a thick fibre and a thin fibre, the images generated by the repeats are much less clear. Nonetheless ConvaTec maintained that the presence of the thick and thin, distinct and distinguishable populations of gelling fibres could still be made out. Some time at trial was spent peering at green shadows and measuring lines with a ruler.

Dr Turner reminded me of the passage in the judgment of Kitchin J in Novartis v Johnson & Johnson[2009] EWHC 1671 (Pat) at paragraph 336 dealing with the reliance on the original notice of experiments rather than the repeats:

In my judgment it is not a principle of law that the results in a Notice can never be relied once the experiment has been repeated. However in the circumstances of this case I am in a similar position to the position Kitchin J describes in the passage I have quoted. The experiments in the Notice were carried out under Mr Bishop’s supervision but he did not conduct them.As I have said above, Mr Bishop’s position on the experiments was compromised. I have not heard from the person who performed the Notice experiments. Mr Woodings was able to witness the repeats and I consider it appropriate to focus on the results obtained there (since there is undoubtedly controversy about them).

Mr Woodings criticised the experiments severely and his criticisms were put to Mr Bishop by Dr Turner. Following that cross-examination Mr Acland did not press Mr Woodings in cross-examination and did not seek to defend the experiments to any great extent. The particular criticisms levelled at the experiments which seemed to me to be of real force were these:

the distinction between a so-called type 1 and a type 2 fibre was undefined and subjective. Fibres with different widths were classed together, but fibres of the same width were classified differently.

many of the photographs were almost entirely unintelligible. It was almost impossible to identify whether some visual features were even fibres or not; whether a feature was a single fibre or one or two overlaying each other (or in one case possibly 3 fibres); where the edges of a ‘fibre’ were; and whether or not any apparent differences between fibres were an artefact of focussing and set-up issues or real results.

there was not enough water present to fully hydrate the fibres. Only a tiny amount of water was added, and unhydrated material was visible on the slides. No experiments were done to titrate the effect of differing amounts of water. I am not satisfied that the amount of water a given fibre was exposed to was not a relevant uncontrolled variable in these experiments.

the experiments took no account of the possibility that fibres may have varied in thickness, either between fibres or along their length.

The point about the experiments put to Mr Woodings was on the basis that he was to assume that differences were observable. He then accepted that if the fibres were shown to have different gelling properties then one possible explanation is that the fibres have different degrees of substitution and hence different absorbency properties. However in my judgment the premise is flawed. I am not satisfied anything relevant is observable in these experiments. I accept Mr Woodings’ criticisms of them. I would add that the fact that the defendants were permitted by the claimants to choose where on the slide to point the microscope could never have remedied the flaws in the experiments.

The fact that different degrees of substitution and hence different absorbency properties is one possible explanation (even if an observable difference exists) does not begin to get an infringement case off the ground. The claimants sought to rely on Mr Woodings’ evidence that tests of the kind he thought ought to have been done were relatively simple, as a point on a shifting onus of proof but in my judgment the claimants’ experimental evidence did not come close to shifting the evidential onus onto the defendants on this issue.

Apart from the experiments, ConvaTec sought to rely on the SFM batch records and the evidence of Mr Kettlewell to prove their infringement case. This involved some evidence heard in private. I can deal with this part of the infringement case without (I believe) putting any of the defendants’ confidential information in the judgment. The claimants’ points were:

Individual batches of the defendants’ CES fibres vary in absorbency. The absorbency is one item of data measured by SFM’s operators on the plant. The difference in absorbency between the batch with the highest figure in g/g and the batch with the lowest was more than 2-3 g/g.

A difference of around 2-3g/g in absorbency is a material difference thus a larger variation is also a material difference.

The defendants blend 4 consecutive batches into a mix which they use to make individual Durafiber dressings. On occasions, individual Durafiber dressings are made by further combining a number of mixes.

Thus ConvaTec submits that Durafiber comprises a blend of different types of gel forming fibres because it is made from blends of batches. Each batch is a different type of gel forming fibre (or at least those batches for which the absorbency figure is different by more than 2-3 g/g are different) because the fibres in those batches have a materially different absorbency from the fibres in other batches.

I doubt 2-3 g/g was established to be a relevant (as opposed to measurable) difference. However the patentee’s argument suffers from a more fundamental flaw. The prior art ‘746 discloses at least making a wound dressing from fibres produced in a single batch. With an eye on this ConvaTec disputes the existence of evidence of differences in absorbency between samples from a single batch. The data ConvaTec relies on to establish infringement is the defendants’ absorbency data which on the face of it shows variation between batches of fibres. However the defendants point out that variation to a broadly similar degree can also be seen in the data taken for samples taken within a single batch. If there is such variation between samples from a single batch then using one batch of fibre to make a wound dressing as disclosed in ‘746 would, on ConvaTec’s construction of the claim, risk invalidity.

Mr Kettlewell’s evidence was that the batches were made in a kier (a vessel) into which a single length of cellulose tow was laid down. Once the reagents had been passed through the kier and the reaction complete, the tow was removed (it now being derivatized cellulose). In order to measure absorbency, four samples are taken from the tow. The four samples were made by first taking cuts from each end of the tow and then mixing the material from both ends together and taking out four samples from that mass. Mr Kettlewell explained that the reason samples were taken from each end was because the opposite ends of the two were the places where maximum variability would be seen. The bottom of the tow will be exposed to the most reactants and the top exposed to the least. These parts will have the extremes of absorbency.

The absorbency for each sample is measured. It is the variability which sometimes arises between these four pieces of data that the defendants point to in order to show that there is intra-batch variation in absorbency. The operators then take an average of the four numbers and this average is taken as the absorbency of a batch. It is the variability between the numbers representing different batches which ConvaTec point to in order to show that there is inter-batch variation in absorbency.

Thus one might think all this showed that there was indeed intra batch variation but in closing Mr Acland came up with an ingenious argument to show that this variation in intra batch values was due to variation in the test and did not reflect underlying variation in the material. He pointed to the fact that the samples from each end were mixed and then testing samples taken from the mix. So the variable intra-batch data must be due to variation in the testing because the samples tested were mixed. There was no evidence to support it and, if it mattered, I would have rejected the argument. A vital assumption before it even gets off the ground is that the mixing is so thorough that all the samples are homogenous. There is no evidence for that. If the point was to be run it could and should have been put to an expert. I also have a suspicion the argument is flawed for a more fundamental reason based on statistics – again not explored in the evidence. If the variability in the results is due to testing and the samples in fact have the same underlying absorbency, it is not clear to me where that leaves the assertion that differences in the values for batches compared to other batches (the values are just the means of four variable results) reflect a real difference between batches and not just the variability in the tests.

The reason none of these points were properly explored in evidence was that, as Dr Turner submitted, the claimants’ case on infringement was transformed during the trial. Mr Bishop’s expert’s reports were focussed on the experiments and so was the claimants’ opening skeleton. I do not say it was illegitimate for the claimants to raise the point but they must take the evidential basis for it that they find. In my judgment even if the claim was to be read in the way the claimants contend, infringement would not have been established. In summary all the evidence amounts to is that some variation in the absorbency data will exist. There will be some intra-batch variation and some inter-batch variation. I am not satisfied the magnitude of intra-batch variation is any more or less that the inter-batch variation. There is no basis to distinguish safely between variability in results due to variability in the test as opposed to variability in the underlying material. I am not satisfied the differences in the numbers represents actual differences in the properties of the materials. There is no basis to say whether any two given samples of material (intra batch or inter batch) have sufficiently different absorbency properties to satisfy the claimants’ claim construction.

Finally I should mention claim 3 on the same basis. Even if Durafiber fell within claim 1 as the claimants’ contend, on the basis that it comprises two types of gelling fibres, it would not infringe claim 3 because of the presence of Tencel. Although Tencel is modified cellulose, it is not a gel forming fibre. All the fibres at the wound contacting surface of claim 3 must be gelling fibres and that is not the case with Durafiber.

By the end of the trial, Mr Acland accepted (rightly in my judgment) that claim 1 was anticipated by Qin. It was also common ground that the insufficiency plea, which was conditional in nature depending on how ConvaTec put their case, did not arise because ConvaTec did not put their case in the relevant way.

Thus live issues on validity of claim 3 are obviousness over: -

Qin

Lassen

‘746

common general knowledge alone (CMC plus alginate)

The position of claim 5 is slightly involved. ConvaTec do not contend that claim 5 is independently valid if claim 1 is invalid over Qin. However claim 5 has a dependency from “any preceding claim” and its position as a dependent claim depends on the outcome as regards claim 3. That in turn may vary depending on the prior art and I will mention claim 5 separately for each item of prior art.

Section 3 of the 1977 Act provides that an invention shall be taken to involve an inventive step if it is not obvious to a person skilled in the art having regard to any matter which forms part of the state of the art by virtue of s2(2) of the 1977 Act. A structured approach to the assessment of obviousness was set out by the Court of Appeal in Windsurfing International Inc v Tabur Marine [1985] RPC 59 and was adjusted somewhat by Jacob LJ in Pozzoli v BDMO[2007] EWCA Civ 588, [2007] FSR 37. It is:

In Conor v Angiotech [2008] UKHL 49, [2008] RPC 28 the House of Lords considered the issue of obviousness. There Lord Hoffmann (with whom the others of their Lordships agreed) approved the following statement of Kitchin J made in Generics v Lundbeck[2007] RPC 32:

The person skilled in the art, and the common general knowledge, have been identified above. As far as inventive concept is concerned claims 3 and 5 speak for themselves.

Qin is entitled “Wound dressing”. It was published on 9^th May 1996. The abstract is a fair summary of its disclosure. The abstract states:

Thus Qin is based on the idea of a two layer dressing. The specification explains why on page 1 (taking page numbers from the document as published):

The idea is to have a generally relatively thin wound contacting layer (i) designed to provide positive action in assisting healing of the wound while layer (ii) has greater hydrophilicity than layer (i) so that exudate present in layer (i) may pass into layer (ii) so as to increase the time before layer (i) is saturated. So layer (i) might assist healing by providing clotting via agglutination of red blood cells or might debride the wound or deliver components to the wound like ions, drugs or antimicrobial agents. Examples of materials to be used in layer (i) are given. They include calcium alginate to provide calcium ions for haemostasis, chitosan for haemoglutination, pectin for stimulating autolysis and wound debridement. (Autolysis is a form of self destruction of cells.) Layer (i) may be provided as a woven, non-woven or knitted material or as a gel.

One example given for layer (i) is to use “pectin/carboxymethyl cellulose/alginate”. While this might sound like a blend similar to the claimed invention in the ‘013 patent it is in fact a reference to a co-spun material, as Mr Woodings accepted.

Layer (ii) is preferably a woven, non-woven or knitted fibrous material, e.g. a felt. The examples for what it may comprise include a sodium alginate/calcium alginate felt, a CMC felt and importantly “an alginate/CMC felt”. A particular example of a wound dressing taught by Qin is chitosan as layer (i) and an alginate or alginate/CMC felt as layer (ii) (page 4 line 8).

It is the disclosure of an alginate/CMC felt for layer (ii) which invalidates claim 1 of the ‘013 patent on any view. It is a blend of discrete modified cellulose gel forming fibres (CMC) with at least one other type of discrete gel forming fibres (alginate).

The defendants put their case in two ways as regards the difference between Qin 1 and claim 3. First by reference to the teaching in Qin 1 to use a co-spun pectin/CMC/alginate material as wound contacting layer (i), it would be obvious to make the same sort of mixture as a felt or in some other similar manner. That would satisfy the ‘013 patent as a blend of discrete fibres and hence claim 3 is invalid. The second approach is to start from the CMC/Alginate felt of layer (ii). That material would be obvious to use as the wound contacting layer (i) and would again fall within claim 3.

Although the defendants had served experts report from a wound care scientist Prof White, in the end the defendants did not call Prof White as a witness and his evidence was therefore withdrawn. ConvaTec contended that this meant that since Mr Woodings (the cellulose chemist) naturally enough accepted that before making a dressing from a blend of CMC and alginate he would always consult with the wound care scientist or clinician members of the team, and since Mr Bishop (the wound care scientist) did not accept the invention was obvious, the obviousness case against them could not succeed in the absence of Prof White. Since the reasons for an expert’s opinion are generally of the most significance rather than the simple fact that they have an opinion in one direction, it seems to me that I am not precluded from deciding this question in the defendants’ favour simply because they did not call witnesses to represent all the disciplines in the skilled team in this case. The matter will be considered on the evidence as a whole. Of course the expertise of Mr Bishop and that of Mr Woodings are relevant factors as are many others.

If one had two kinds of fibres with different properties and wanted to try to combine those properties, then an intimate mixing of those fibres such as a felt would be one obvious way of doing it from the point of view of a cellulose chemist. Felts could be made in various ways such as by needle felting. Making felts such as by needle punching was a matter of common general knowledge. However that does not decide the issue.

Equally it is obviously a point in the defendant’s favour that CMC and alginate were both used as wound contacting layers individually (and there were various sorts of mixed products too) and so one might think there would be few concerns about using a mixture of the two as a wound contacting layer.

It is important to appreciate that Qin is a two layer arrangement and that these two layers have distinct functions. The purpose of wound contacting layer (i) is to have a positive effect on healing, so for example the alginate would have that effect by promoting haemostasis. To employ a layer at the wound contacting surface which did not have a positive effect on healing would be to go flatly against Qin’s proposal and would not be an obvious way forward over Qin.

Qin does employ a material which includes (inter alia) a combination of CMC and alginate at layer (i) but it is a co-spun alloy fibre (pectin/CMC/alginate). Mr Bishop explained that alloys like this did not necessarily provide the benefit of both properties of alginate and pectin. One property may predominate depending on how it was made.

The contention that a felt was an obvious alternative to an alloy like the co-spun material was put to Mr Bishop. His evidence was that the skilled person would be concerned about knowing what the properties of the combined layer would be. Would the CMC predominate or the alginate? He was concerned that the CMC could disrupt the haemostatic potential of the alginate. So mixing CMC fibres with alginates at the wound contacting surface, when the mixture might interfere with the alginate’s function, could give you the worst of both worlds. This seems to me to provide prima facie evidence that it would not be obvious over Qin to employ such a felt as the layer (i) wound contacting surface. Moreover that applies whether one is looking at an alternative to the pectin/CMC/alginate co-spun layer (i) or to employing the CMC/alginate of layer (ii) as wound contacting layer (i).

Dr Turner submitted that Mr Bishop’s evidence in this respect was not really that mixing was not obvious, he was in effect accepting that a felt was one obvious way forward among a number of other obvious alternatives such as having the CMC on top of the alginate, which would be irrelevant in principle. If that is all that Mr Bishop’s evidence amounted to then I would accept it was irrelevant but it seems to me that Mr Bishop’s concern about interfering with alginate haemostasis means that he did not regard the alternatives as all equally obvious. His concern was about CMC at the wound contacting surface along with alginate and he made the point despite having the pectin/CMC/alginate alloy fibre (which can be said to include such a combination albeit in a different form) being put to him.

In another case such a point might have been debated between wound care experts but I have Mr Bishop alone. It seems to me that I do not have a basis to reject his concern as fanciful. These are the concerns of the wound care scientist and in my judgment it does not matter how obvious the material itself would be to a cellulose chemist. This invention is a wound dressing and the claim will only be obvious it if is obvious to the relevant team as a whole.

Thus claim 3 is not obvious over Qin.

A point which I did not regard as bearing much weight was a question Mr Acland posed: if it was obvious to use a CMC/alginate felt as layer (i) of Qin, why is it not disclosed in Qin? That does not seem to me to be a particularly useful question. It is rather like the anthropic principle in cosmology, which asks why the universe is habitable and answers that if it was not, we would not be here to ask the question. If Qin disclosed a CMC/alginate felt as layer (i), then claims 1, 3 and 5 of the patent would be anticipated and we would not be here considering obviousness.

Following the handing down of the judgment in its draft form (which barring typographical slips is the same as this version save for the existence of this paragraph), I was asked to address explicitly the question of the validity of claim 5 over Qin. Claim 5 is dependent on any preceding claim and claims 2 to 4 are similarly drafted. Thus claim 5 in fact encompasses within it a variety of sub-combinations. By my reckoning there are eight possible sub-combinations. Insofar as claim 5 is dependent on claim 1 alone, it is invalid. Insofar as it is dependent on claim 3, claim 5 is valid. The only valid sub-combinations will be the ones which include claim 3.

The question was whether Lassen rendered claim 1 or 3 obvious. ConvaTec accepts (in my judgment rightly) that if claim 1 is invalid over Lassen so too is claim 3. However the concession (above) that claim 1 is invalid relates to Qin 1 and not to Lassen. Thus I still need to decide whether claim 3 is obvious over Lassen. (There is a typographical slip in the defendants’ list of issues in referring to claim 5 in the context of Lassen. I understand paragraph 111 of the defendants’ Closing Skeleton to set out the correct position – that the defendants do not contend claim 5 is invalid over Lassen.)

The Lassen patent was published in 1981 entitled “Filaments of chemically modified cellulose fibers and webs and products formed therefrom”. It belongs to Kimberly-Clark Corporation of Neenah, Wisconsin, USA. The disclosure relates to chemically modified cellulose fibres and a method of extruding them into filaments. The filaments are then used to lay down a web which can be used to make disposable diapers and other such absorbent products.

The abstract summarises the disclosure as follows:

One particular filament disclosed by Lassen is a composite filament made from phosphorylated cellulose fibres and fibres of a product called Buckeye brand cross-linked CMC. The relevant examples are examples 3 (the composite filaments) and 4 (the web made of the composite filaments). There was a debate in the evidence as to whether these were gelling fibres or not but by the closing it was common ground that they are both gelling fibres.

One particular application mentioned in Lassen is “surgical sponges” (Col 1 line 19) and it is common ground that what are called “surgical sponges” in the USA are called “swabs” in the UK. The ‘013 patent specifically states that “the wound dressing of the present invention may be in the form of swabs …”. Thus by the closing speeches it was common ground that Lassen discloses products made using the filaments in question which are within the ambit of the term “wound dressing” in the claims of the ‘013 patent as it is used in that patent.

Although the point was put as a matter of obviousness, it is really a question of construction. In opening the question of obviousness was that ConvaTec denied that a surgical sponge was a wound dressing and denied that it was obvious to use Lassen’s material for the then said to be different purpose of making a wound dressing (ConvaTec Opening Skeleton paragraph 82). However in closing that point has fallen away.

Pulling this together, it is common ground that Lassen discloses (or at least renders obvious) a swab or surgical sponge made using the web of Example 4 which web will be the wound contacting surface. The web will be made from composite filaments made from phosphorylated cellulose fibres and fibres of Buckeye brand cross-linked CMC. These two fibres are both gel forming fibres.

Where does that leave claim 3? As I have construed claim 1 and claim 3, Lassen is irrelevant. Both fibres are modified cellulose fibres on any view and thus there is no other type of fibre in Lassen. Claim 3 is not invalid over Lassen.

However on ConvaTec’s construction of the claims, that distinction does not arise. There is no doubt that, on ConvaTec’s construction which I have rejected, the wound contacting surface of the Lassen swab would consist of two different classes of gelling fibres - phosphorylated cellulose fibres and Buckeye CMC fibres. The only issue on ConvaTec’s case is about the word “discrete”. All the other issues have fallen away. It is accepted that both phosphorylated cellulose and Buckeye CMC are gelling fibres and would retain that property after being made into filaments in Lassen. Mr Acland submits that the fibres in the composite filaments are fused together such that they are not discrete fibres as required by claim 1. In closing Dr Turner submits that “although the fibres in Lassen are contact bonded they remain ‘readily identified’ in the final product (Lassen Col 7 lines 47-49 and col 8 line 30-32)”. The fibres would be distinguishable and identifiable as separate types and are therefore within the meaning of claim 1 and claim 3.

The relevant part of Lassen’s process relates to how the filaments are made. Before being made into filaments the fibres are in a pulp and the individual fibres are in a “highly swollen gel like form” (col 5 line 19-21). The swollen material is extruded into filaments. The orifices through which the material is extruded are very small – figures of the order of 20 to 30 thousandths of an inch are mentioned. The filament is then subjected to solvent-drying e.g. using acetone. Lassen describes the state of the fibres before drying as follows: “The fibres are swollen and bonded within the filament by the cohesive nature of their gel like outer surfaces depending on the degree of refining.”

Lassen also refers to contact bonding and fused bonding. Contact bonding is a form of surface bonding while fused bonding involves a weld or merger between the materials.

Lassen states that the drying results in interfibre bonding and interstices between fibres within the dried filament (col 7 line 11-14). The defendants emphasised the existence of the interstices i.e. gaps, between the fibres and submitted that this meant that the fibres were still discrete fibres within the filament. They also submitted that the bonding between fibres was contact bonding.

However in cross-examination Mr Acland took Mr Woodings to the passage in Lassen which describes what the fibres and filaments are like after solvent drying. When the passage at col 7 line 11-14 mentioned above was put the exchange was as follows:

When Mr Acland took Mr Woodings to Example 4, which is one of the two relevant examples, he accepted that the fibres here would be likely to be fused together. That disposes of the defendants’ submission that the inter fibre bonds are just contact bonds.

In my judgment based on this evidence (which I accept) the material produced by Lassen cannot be fairly described as a blend of discrete, or identifiable and separate, fibres. The fibres might well be identifiable to an extent but they would not be separate. No doubt there are gaps or interstices present too to some extent but the fibres in the filaments are glued together into a mass. Accordingly Lassen would not render claim 3 invalid on ConvaTec’s construction of the claims.

‘746 is a PCT application published on 4^th August 1994. It is entitled “Wound dressings” and relates a wound dressing employing CMC fibres in the wound contacting surface. As published the applicant was Courtaulds Plc and I gather it is one of the applications which arose from the original Aquacel work.

The relevant example is example 1. This describes a solvent based process. A dried tow of solvent spun cellulose is put in a “reaction vessel”, typically a kier. The reaction performed and the result is a tow of CMC fibres. The CMC tow is cut and carded to form a web. These cutting and carding methods were typical at the priority date.

The point taken by the defendants is that if, contrary to their case, their CES fibres infringe the patent as a result of variability in the absorbency properties of their material, then the product of ‘746 would also fall within the claims and the claims must be invalid. It is a form of “Gillette” defence, picking up the famous dictum of Lord Moulton that:

On my construction of the patent the point does not arise but as before I will consider the case on ConvaTec’s construction of claims 1 and 3.

On ConvaTec’s case, the claims would not be vulnerable over ‘746 because, they submit, there is no evidence that working example 1 would involve producing a wound dressing which in fact did contain fibres with different classes of absorbency properties. Again the issue is not so much concerned with obviousness as with the underlying facts. It cannot be denied (and was not contended) that it required an inventive step to work Example 1 of ‘746 and make a wound dressing. The question is: what would the fibres be like in such a dressing?

Before going any further I should deal with the matter of blending batches. It seems to me that it was perfectly obvious to blend separate batches of product. Mr Woodings explained fibres from different bales of staple (which had been made from tow) are often blended. Although example 1 of ‘746 expressly involves making a web from a single batch produced in a kier, it seems to me to be fanciful to suggest that it would require an inventive step for a skilled person to take multiple batches of CMC fibres, each batch made as per example 1, and blend the fibres from different batches together before making the blended fibres into a web. This is nothing to do with whether the skilled person knew or cared whether the absorbency of the product of one batch varied as compared to another batch, so long as they were all within whatever specification the skilled person had set himself. It is just a manufacturing convenience. None of it involves any degree of invention.

When Example 1 was put to Mr Bishop he explained that he did not know whether the product of example 1 would fall within the claim because it would be totally dependent upon the variability of the characteristics of the fibres produced by the process. If it produced one distinct type of fibre then it would not fall within claim 1 in his view. He was not an expert on the process and could not comment on the variability in the degree of substitution in the fibres that would be produced. His conclusion was that he accepted there might be a slight variability but he could not comment on whether it would give two distinct fibre types.

Early in his cross-examination Mr Bishop had given related evidence concerning batches of Aquacel. The Aquacel production process has been optimised, in other words the plant operators have worked to achieve a degree of consistency in the operations. Mr Bishop accepted there would be some variation in the degree of substitution in a batch of Aquacel but he did not know whether he would be able to tell them apart by reference to their absorbency properties. I also took his evidence to accept that the degree of variation in an unoptimised process would be greater than that experienced in running an optimised process.

Dr Turner put to Mr Bishop a document which had derived from ConvaTec and showed absorbency measurements taken on batches of CMC which may be material used to make Aquacel. Mr Bishop was not familiar with the document. His oral evidence when the document was put to him does not assist the defendants. The document was not the subject of a Civil Evidence Act notice (nor was it exhibited by any witness) and therefore in my judgment does not stand as evidence in this case. While I sympathise to some extent with the defendants’ position since this issue really arose as a response to the shifting case on infringement, nevertheless it seems to me that I should not give the document itself any weight.

On the basis of my findings on the infringement side of the case, that ConvaTec has not established that the CES product of the defendants falls within the claim on their construction of it, plainly there is no basis for finding that the product of example 1 of 746 would fall within the claim. However I am far from convinced that a credible case has been made out that would save the claims from invalidity if in fact Durafiber did infringe. In other words I have grave doubts whether there is anything patentably distinct between ‘746 and the defendants’ actions which are alleged to infringe. My reasons are in summary:

When making derivatized cellulose in kiers (whether CMC or CES), variation in degree of substitution to some degree will always exist.

‘746 discloses a process of making a wound dressing using modified cellulose made from a mixture of fibres from a single kier and renders obvious a process of making a wound dressing using modified cellulose made from a mixture of fibres from different batches made in separate kier runs.

ConvaTec say that you infringe the claim if you have a mixture of fibres which have different absorbency figures, when the differences are more than trivial.

Considering ‘746, it is accepted that some variability in the CMC will exist, it is just that ConvaTec point out there is no evidence how big that variation is and therefore no evidence it passes some threshold between trivial and not-trivial.

However, the point that there is a lack of evidence showing that the variation which is accepted to exist in ‘746 is large enough to pass the threshold is really the same as the position as regards the defendants’ CES process.

As regards the defendants’ process, there is no evidence before me that the variation seen in the batch averages reflects variation in underlying qualities of CES product rather than variation in the test.

So in truth the position is the same as for ‘746. In both cases there is no doubt that some variation exists, but there is in fact no sufficient evidence on which to base a finding as to the magnitude of the actual variation in the underlying properties of the fibres. Accordingly there can be no evidence of the significance of any variation which does exist.

If this sort of evidential position is enough to say that the defendants’ modified cellulose product made from running a kier based process falls within the claim then the modified cellulose product made from running a kier based process based on what is obvious over 746 must also fall within the claim. That is a Gillette defence of the purest kind. In my judgment neither falls within the claims of the ‘013 patent but if one does so must the other.

In conclusion on ‘746, the claims are not invalid over this reference. However ConvaTec are on the horns of a dilemma. If the evidence did establish that the defendants’ product infringes the relevant claims (construed as per ConvaTec’s case) then that can only be on the basis that a mixture of fibres with some unspecified level of variation falls within the claim. On that basis the claims would be invalid as being obvious over ‘746.

The defendants also advanced an attack based on common general knowledge alone which was closely allied to the attack based on ‘746. I do not need to consider it separately.

None of this has anything to do with claim 5, which is limited to CMC and alginate combinations.

The defendants’ final attack on the validity of claim 3 was an approach based on common general knowledge alone on the basis simply that mixing CMC and alginate fibres to make a wound dressing (and to make the wound contacting surface thereof) was just an obvious thing to do in 1996.

This contention had not been pleaded out in detail. Mr Acland reminded me of the observations of Floyd J in Ratiopharm v Napp[2009] RPC 11 about such unpleaded points and also showed me other parts of Floyd J’s judgment on the issue as well as the judgment of Kitchin J in Abbott v Evysio [2008] EWHC 800 at para 180. The passage from Kitchin J is:

The passage from Floyd J is as follows:

I respectfully agree with both judges.

Although the obviousness argument is very similar to the one based on using the CMC/alginate in layer (ii) of Qin 1 as the wound contacting layer, it has the forensic advantage from the defendants’ point of view of side stepping the teaching in Qin 1 to have a material at the wound contacting surface with a positive effect on healing the wound. So it can be said that any worries that the skilled person might have about CMC interfering with the haemostatic properties of alginate cease to matter. The skilled person is just after absorbency and a moist wound environment, both materials deliver this, so why not put them together? This was supported by the evidence of Mr Woodings that once various gelling fibres became available it would be obvious to blend them for use in a wound contact layer in a wound dressing, albeit that (as usual) he would as a cellulose chemist wish to confer with the wound care scientist or clinician about the question of what material would be suitable to use.

In my judgment the combination was not obvious because this is a case in which the patentee can legitimately pose the question – if it was obvious why was it not done before? Wound dressings employing gel forming alginates had been well known on the market since the 1970s. Although as at the priority date of September 1996 the CMC fibre product Aquacel was a recent breakthrough, in fact gelling CMC fibres were well known since the 1970s and the use of gel forming CMC fibres in a wound dressing was common general knowledge to the skilled person since the mid 1980s. The particular product was Super AB.

When looking at a case based on nothing but the common general knowledge of the skilled person is it not only legitimate, it seems to me to be vital to look at what actually happened in the field. Although the person skilled in the art is a legal construct, he or she is not supposed to be so divorced from reality that one cannot consider such evidence when the question is one of this kind.

Thus if the combination had been obvious to a person skilled in the art in 1996, it would have been equally obvious for any time in the previous 10 years since Super AB became common general knowledge. And yet no such product emerged on the market. The fact that it did not seems to me to be sufficient in this case to dismiss the case based on obviousness over common general knowledge alone.

I reject the case based on common general knowledge alone that it was obvious to combine CMC and alginate fibres in a wound dressing.

The case pleaded by the defendants is as follows:

The objection is pleaded in a conditional form and only arises as an answer to a particular way in which ConvaTec might put its case on inventive step. The point is a challenge to an assertion (if made) about the capabilities of fibres with respect to different types of exudate, with watery serous exudate being one type, sanguinous exudate being another type and purulent exudate being a third type. However since it is common ground that ConvaTec have not made the relevant assertion, the point does not arise.

In summary:

Durafiber does not infringe.

Claim 1 is invalid over Qin.

Claim 3 is valid.

The patent is not invalid over Lassen or ‘746 (Bahia).

Even if the claimants’ construction of claim 1 was accepted infringement has not been established. Further, claim 3 would not be infringed in any event.

Even if the claimants’ construction of the claims was accepted, if the evidence before the court was sufficient to establish infringement, then claim 3 would be invalid over ‘746 Bahia.