Patents - DLP Ltd v Coram UK Holding Ltd.

Douglas, Isle of Man

Author: Zairon; Licence: CC BY 4.0; Source: Wikimedia Commons

 

Jane Lambert

Intellectual Property Enterprise Court DLP Limited v Coram UK Holding Limited. [2026] EWHC 2448 (IPEC)

This was an action for the infringement of UK patent GB2446666, a counterclaim for its revocation on the grounds of anticipation and obviousness and an application for its amendment.  The action and counterclaim came before Mr David Stone, sitting as a judge of the High Court on 21 and 22 July 2026.  He delivered judgment in DLP Limited v Coram UK Holding Limited [2026] EWHC 2448 on 25 Sept 2026.  By para [90] of that judgment, Mr Stone found the patent to be valid but not infringed.  He therefore dismissed both the claim and counterclaim.

The Parties
The claimant was DLP Limited ("DLP"), a Manx company specialising in the design, development and manufacture of products for the assisted living sector, particularly focusing on bathrooms and kitchens.  The defendant, Coram UK Holding Limited ("Coram"), manufactured wetrooms, shower enclosures, bath screens and accessories.

The Invention
The patent in suit was for a Shower waste pump and control unit.   The abstract described the patented invention by reference to fig 5 of the drawings:

"An electric shower-waste pump and control unit 110 for pumping run-off shower water from a waste outlet to a drain, the unit 110 comprising a housing 112 having a first chamber 114 and a separate second chamber 116 which is water-tightly sealable, a removable housing cover 118 for closing the housing 112, an electric pump 122 provided in the first chamber 114, electronic control circuitry 124 provided in the second chamber 116, and a removable second chamber cover 120 for water-tightly sealing the second chamber 116 against ingress of water leakage from the pump 122."

Mr Stone explained at para [19] that the invention addressed the need to protect the electrical elements of shower waste pumps from water.  An early solution was the "pump in a box", an all-in-one unit in which the pump and other components were sealed against potential sources of water ingress. That, however, did not deal with the situation where the pump itself leaked. The invention provided an improvement over the prior art by making a simple arrangement of components.

The Claims

S.125 (1) of the Patents Act 1977 provides that an invention for which a patent has been granted shall be taken to be that specified in a claim of the specification.   Claims 1, 2, 4, 5 and 7 are broken down into integers, in paras [23] and [25] of the judgment.  Mr Stone construed claim 1 between paras [34] and [37].

The Dispute

Coram's products included a "Premium Pump" and a "Bluetooth Pump".  Para [16] of Mr Stone's judgment describes those items in detail.  DLP alleged that those products infringed claims 1 and 7 of its patent.  Coram argued that the patent was invalid in light of the following prior art:

"i) Grumbach, a German patent application DE3516656 A1 published on 13 November 1986 and titled "Pumpenaggregat für Badewannen und dergl" translated as "Pump unit for bathtubs and the like" (novelty and obviousness);
ii) Gontar, a UK patent application titled "apparatus for draining a shower tray" published on 27 August 1997 (obviousness); and
iii) Quantum, a commercialised product which was agreed to be part of the Common General Knowledge (CGK) at the Priority Date (obviousness)."

DLP proposed the amendments to claim 1 which appear in para [24],  Coram resisted the proposal on the grounds of added matter.

The Issues

At a case management conference held on 24 Nov 2025, His Honour Judge Hacon ordered the following issues to be tried:

"Infringement
1. Does the Premium Pump satisfy the requirements of the Selected Claims?
2. If and insofar as it is maintained to be materially different from the Premium Pump, does the Bluetooth Pump satisfy the requirements of the Selected Claims?

Validity
3. In relation to each of the Prior Art Citations:
...
(b) are the Selected Claims (or any of them) obvious in light of the Prior Art Citations?

Amendment
4. If and insofar as they are opposed, are the proposed amendments to the Patent allowable?"

Applicable Law

Mr Stone referred to para [5] of Lord Justice Jacob's judgment in Virgin Atlantic Airways Ltd v Premium Aircraft Interiors UK Ltd. (2010) 33(1) IPD 33001, [2009] EWCA Civ 1062, [2010] RPC 8:

"One might have thought there was nothing more to say on this topic after Kirin-Amgen v Hoechst Marion Roussel  [2005] RPC 9, [2005] 1 All ER 667, [2004] UKHL 46, (2005) 28(7) IPD 28049, [2005] RPC 169. The judge accurately set out the position, save that he used the old language of Art 69 EPC rather than that of the EPC 2000, a Convention now in force. The new language omits the terms of from Art. 69. No one suggested the amendment changes the meaning. We set out what the judge said, but using the language of the EPC 2000:

'[182] The task for the court is to determine what the person skilled in the art would have understood the patentee to have been using the language of the claim to mean. The principles were summarised by Jacob LJ in Mayne Pharma v Pharmacia Italia [2005] EWCA Civ 137 and refined by Pumfrey J in Halliburton v Smith International [2005] EWHC 1623 (Pat) following their general approval by the House of Lords in Kirin-Amgen v Hoechst Marion Roussel [2005] RPC 9. An abbreviated version of them is as follows:
(i) The first overarching principle is that contained in Article 69 of the European Patent Convention;
(ii) Article 69 says that the extent of protection is determined by the claims. It goes on to say that the description and drawings shall be used to interpret the claims. In short the claims are to be construed in context.
(iii) It follows that the claims are to be construed purposively—the inventor's purpose being ascertained from the description and drawings.
(iv) It further follows that the claims must not be construed as if they stood alone—the drawings and description only being used to resolve any ambiguity. Purpose is vital to the construction of claims.
(v) When ascertaining the inventor's purpose, it must be remembered that he may have several purposes depending on the level of generality of his invention. Typically, for instance, an inventor may have one, generally more than one, specific embodiment as well as a generalised concept. But there is no presumption that the patentee necessarily intended the widest possible meaning consistent with his purpose be given to the words that he used: purpose and meaning are different.
(vi) Thus purpose is not the be-all and end-all. One is still at the end of the day concerned with the meaning of the language used. Hence the other extreme of the Protocol—a mere guideline—is also ruled out by Article 69 itself. It is the terms of the claims which delineate the patentee's territory.
(vii) It follows that if the patentee has included what is obviously a deliberate limitation in his claims, it must have a meaning. One cannot disregard obviously intentional elements.
(vii) It also follows that where a patentee has used a word or phrase which, acontextually, might have a particular meaning (narrow or wide) it does not necessarily have that meaning in context.
(vii) It further follows that there is no general "doctrine of equivalents."
(viii) On the other hand purposive construction can lead to the conclusion that a technically trivial or minor difference between an element of a claim and the corresponding element of the alleged infringement nonetheless falls within the meaning of the element when read purposively. This is not because there is a doctrine of equivalents: it is because that is the fair way to read the claim in context.
(ix) Finally purposive construction leads one to eschew the kind of meticulous verbal analysis which lawyers are too often tempted by their training to indulge.'"

Citing para [60] of Lord Kitchin's judgment in Icescape Limited v Ice-World International BV and Others [2018] EWCA Civ 2219, Mr Stone observed that the exercise is a purposive one.   He added that the patent must be construed in context, and as a whole so as to give a sensible consistent meaning to every part of it. The specification and the claim are part of the same document and should be construed as such as in Brugger v Medic-Aid [1996] RPC 635 at 642.

Infringement

At para [43] Mr Stone considered whether Coram's Premium Pump and Bluetooth Pump fell within claim 1:

"i) The skilled addressee taking into account purposive construction would not, in my judgment, describe the flat backplate as "a removable non-watertight housing cover for closing the housing". The parties were agreed that the purpose of the removable housing cover in the Patent was to provide access to the components within the unit. This is also set out in the first and second embodiments of the Patent. The backplate does not do that. It is not "removable" in the sense that, in context, the skilled addressee would understand that word, because it is affixed to the wall. The housing can be removed from the wall allowing access to the internal components of the unit, but that is not what the Patent says. Coram's counsel also noted that, if the Premium Cover is removed, the pump and the electronics are still connected to the backplate (said to be the "housing cover" - so it cannot be said that removal of the housing cover is to provide access to the workings of the unit). Rather, what is said to be the housing cover remains attached to the second watertight chamber which houses the electrics. In my judgment, DLP's proposed construction is an unnatural reading of the Patent, and I reject it.
ii) Further, as set out in the PPD, the backplate of the Premium Pump is not attached to the Premium Cover - rather, the Premium Cover attaches to the same wall to which the backplate attaches. The two do not touch and there are large gaps (as seen in Figure 31). It therefore cannot be said to "close" the "housing". Some of the "closing" is done by the wall to which the unit is attached, and the wall is not part of the unit. DLP's counsel submitted that that does not matter - the Patent does not say that the housing cover must "close entirely" the housing. Indeed, he submitted that the requirement that the closure not be watertight supported his position. I agree to an extent - entire closing is not required. But closing is. The Patent, as I have found, requires a unit. It should be self-contained, as DLP averred. If part of the closing of the chamber is effected by the wall to which both the backplate and the Premium Cover are attached, then that does not, in my judgment, fall within the integer providing that the cover closes the housing.
iii) The position with respect to the Bluetooth Pump is similar. My finding in relation to the Premium Pump's backplate not touching the Premium Cover is an additional reason why the Premium Pump does not fall within the claims of the Patent, but the Bluetooth Pump's connection at that point is insufficient to bring it within the scope of the Patent: the backplate on the Bluetooth Pump is also not a "housing cover" within the terms of the Patent."

The infringement claim therefore failed.

Validity

As I noted above, Coram had counterclaimed for the revocation of the patent on grounds of anticipation and obviousness.  It abandoned its lack of novelty challenge in its counsel's closing argument.

Obviousness

Mr Stone directed himself as follows at para [49]:

"Essentially, the question for the Court is whether it would require an inventive step to bridge the gap between what is disclosed to the skilled addressee by the prior art document in question (read in isolation from any other prior art citation, without any preconceived notions as to what it will contain or whether it will be useful, and with the background CGK as it would have been known to them at the priority date) and the relevant claim in the patent. That analysis is fact dependent. As Kitchin J (as he then was) said in Generics (UK) Limited v H Lundbeck [2007] EWHC 1040 (Pat) at [74]:

'The question of obviousness must be considered on the facts of each case. The court must consider the weight to be attached to any particular factor in the light of all the relevant circumstances. These may include such matters as the motive to find a solution to the problem the patent addresses, the number and extent of the possible avenues of research, the effort involved in pursuing them and the expectation of success.'"

The deputy judge continued in the next paragraph that the longstanding approach of the English courts has been to follow the structured approach set out in Pozzoli SPA v BDMO SA [2007] EWCA Civ 588 at [23]:

"(1)  (a)    Identify the notional 'person skilled in the art';

        (b)    Identify the relevant common general knowledge of that person;
(2) Identify the inventive concept of the claim in question or if that cannot readily be done, construe it;
(3) Identify what, if any, differences exist between the matter cited as forming part of the 'state of the art' and the inventive concept of the claim or the claim as construed;
(4) Viewed without any knowledge of the alleged invention as claimed, do those differences constitute steps which would have been obvious to the person skilled in the art or do they require any degree of invention?"

Mr Stone noted that Coram had submitted that a sensible way to proceed where there was no inventive concept would be to construe the relevant claims and compare them to the disclosures of the prior art as he had previously done in Clearswift Limited v Glasswall (IP) Limited [2018] EWHC 2442 (Pat) at [92].  Next, Mr Stone referred to Lord Justice Jacob's remarks in Technip France SA's Patent [2004] EWCA Civ 381 at [122]:

"The question 'why was it not done before' is always a powerful consideration when considering obviousness, particularly when all the components of a combination have been long and widely known."

He cautioned himself at para [53] that it does not follow that just because something was not done it must not have been obvious to do it.   He added that there may have been other reasons as to why it was not done.  He was reminded of the dangers of hindsight by Lord Justice Oliver's words in Windsurfing International Inc v Tabur Marine (Great Britain) Ltd [1985] RPC 59 at 71:

"[The question of obviousness] is one which has to be answered, not by looking with the benefit of hindsight at what is known now and what was known at the priority date and asking whether the former flows naturally and obviously from the latter, but by hypothesising what would have been obvious at the priority date to a person skilled in the art to which the patent in suit relates, who is assumed to have access to what was known of the art in the United Kingdom immediately before the priority date."

Mr Stone reminded himself that Mr Justice Meade had said in para [157] of his judgment in Fisher & Paykel Healthcare Limited v Flexicare Medical Limited and another [2020] EWHC 3282 (Pat) that avoiding hindsight is a particularly acute concern in the case of relatively simple inventions.  He 

was also reminded that a skilled addressee is not bound to embark on any particular, or indeed any course of action, simply because he or she has read a prior art document. He referred to para [41] of Judge Birss's judgment in Vernacare Limited v Environmental Pulp Products Limited [2012] EWPCC 41:

"... As a matter of principle, the skilled person reads any given piece of prior art with interest. However, as a matter of principle again, once they have done so, there is nothing to say as a matter of law that the skilled person is not entitled to say having read it with interest, 'I have read it with interest, but I am not interested.' The context is vital. ..."

Finally, the deputy judge noted that obviousness is a question of technical obviousness.  Recalling Lord Justice Slade's judgment in Hallen Company v Brabantia (UK) Limited [1991] RPC 195 at 213, he added at para [57]: "it does not matter whether or not it would have appeared commercially worthwhile to exploit the thing that is technically obvious."

Identify the Notional "Person skilled in the Art"

Mr Stone identified "a designer of shower-waste pump systems" as the skilled addressee in para [26] of his judgment.

Identify the Relevant Common General Knowledge of that Person

The learned deputy judge noted in the next paragraph that it was common ground that the skilled addressee would know about various existing shower-waste pump systems.   The parties submitted a joint statement of common general knowledge after trial which Mr Stone accepted with definitional amendments. The few differences that remained were addressed between paras [28] and [31].

Third and Fourth Steps of the Windsurfing/Pozzoli Test

Mr Stone seems to have taken the third and fourth steps together.    He considered Grumbach between [60] and [69], Gontar between [70] and Quantum between [79] and [85].   In the case of Quantum, however, he applied the full test at [84].  Although Coram had already dropped its want of novelty attack at trial, the deputy judge said at [65] that he would not have found the patent to be anticipated over Grumbach. He also held that the invention was not obvious over any of the items of prior art.

Amendments

The proposed amendments to claim 1 of the patent are shown in para [24].  As the patent was valid, Mr Stone did not have to consider them.   The Comptroller-General of Patents, Designs and Trade Marks did not object to the amendments, and Mr Stone would have allowed them for the same reason.

Comment

Although there appears to have been no dispute between the parties on the law, Mr Stone discussed the applicable principles on claim construction and obviousness in great detail.  For that reason, this judgment is likely to be referred to in the future.  Anyone wishing to discuss this article may call me during UK office hours on +44 (0)20 7404 5252 or send me a message through my contact form at any time.