Kohler Mira Ltd v Norcros Group (Holdings) Ltd

Factual and Procedural Background

This is an appeal by the Defendant, Company B, against an order of Judge Clarke (Intellectual Property Enterprise Court) dated 9 January 2025 granting relief to the Claimant, Company A, for infringement of United Kingdom Patent No. 2466504 entitled "Ablutionary installation". The patent was filed on 24 December 2008. The first-instance judgment of Judge Clarke dated 16 December 2024 (reported as [2024] EWHC 3247 (IPEC)) found infringement by Company B's DuElec range of electric (instantaneous) showers and rejected challenges to validity on the grounds of insufficiency, excessive breadth and lack of novelty/obviousness over an item of prior art referred to as Deeley. Company B obtained permission to appeal on six grounds; Company A resisted and advanced a respondent's notice relying on the doctrine of equivalents if necessary.

Legal Issues Presented

1. How should integer [d] of claim 1 be construed, specifically the meaning of "the diverter valve is configured so that"?
2. What is the meaning of "[the flow rate is] substantially unchanged" in integer [d] of claim 1?
3. On the correct interpretation of claim 1, do Company B's DuElec showers infringe claims 1 and 4 (and therefore claim 4 if claim 1 is infringed)?
4. Are the claims invalid for uncertainty/insufficiency under section 72(1)(c) of the Patents Act 1977 because "substantially unchanged" lacks a discernible boundary?
5. Are the claims invalid for excessive claim breadth?
6. Are the claims obvious over the common general knowledge?

Arguments of the Parties

Appellant's Arguments (Company B)

• The judge misconstrued claim 1 (Grounds 1 and 2): the phrase "the diverter valve is configured so that" requires that the diverter valve itself (by its configuration) achieves the specified result.
• "Substantially unchanged" is uncertain because the specification gives no criterion for what change in flow falls within the claim.
• On the correct construction, Company B's products do not infringe claim 1 because any maintenance of temperature during changeover is due to other components (flow stabilisation valve and thermal cutoff), not the configuration of the diverter valve.
• All claims are invalid for uncertainty (insufficiency) and, alternatively, for excessive breadth; claims are also obvious over common general knowledge (other grounds).

Respondent's Arguments (Company A)

• Claims should be purposively construed; the skilled reader would read "substantially unchanged" against the specification and understand the applicable criterion to be avoidance of a risk of scalding ("risk of scalding criterion").
• If normal construction did not capture infringement, Company A advanced a respondent's notice alleging infringement under the doctrine of equivalents (but only if the Court accepted Company B's construction of the diverter-valve phrase and rejected Company A's view of "substantially unchanged").

Table of Precedents Cited

Court's Reasoning and Analysis

The court proceeded from the established purposive approach to claim construction and the factual findings at trial (skilled person an engineer; expert evidence preferring Expert Witness Mills over Expert Witness Murray; detailed findings as to common general knowledge for mixer and electric showers). The court made the following legal analysis:

• Nature of claim 1: the claim is to an instantaneous water heater; it must be possible to determine whether a particular instantaneous water heater falls within claim 1 without reference to any larger apparatus in which it may be incorporated.
• Meaning of "the diverter valve is configured so that": read in context, the language requires that the diverter valve (as part of the instantaneous water heater) must be configured to achieve the specified result. The configuration may include the diverter valve together with other components of the instantaneous water heater, but not components of a larger assembly in which the heater might be incorporated.
• Meaning of "substantially unchanged": the specification does not provide an explicit criterion. Company A's proposed "risk of scalding" criterion was rejected for three reasons set out by the court: (i) it would improperly limit general claim language to a preferred embodiment; (ii) claim 1 is not limited to showers (and scalding may be irrelevant or desirable in other applications of an instantaneous heater); and (iii) the specification's language shows the purpose is broader than avoiding scalding (aiming to avoid "any sudden unexpected change in temperature").
• Infringement on normal interpretation: because the DuElec showers' avoidance of scalding during changeover was attributable to other components (flow stabilisation valve and thermal cutoff) rather than to the configuration of the diverter valve itself, and because Company A did not advance an alternative criterion for "substantially unchanged", the court concluded that Company B's DuElec range did not infringe claim 1 on its normal construction.
• Equivalents: Company A's respondent's notice relying on the doctrine of equivalents was not decided because the court's primary construction disposed of infringement; the respondent's notice was only advanced in a narrow hypothetical which did not arise for decision.
• Insufficiency: applying the Anan Kasei principle, the court concluded that, absent any criterion for "substantially unchanged" other than the rejected risk-of-scalding approach, the boundary of claim 1 is impossible to determine (e.g. no indication whether 1%, 5%, 25% change falls within the claim). Claim 1 is therefore insufficient under section 72(1)(c). Dependent claims said to be independently valid derived from claim 1 were also invalid on this ground.
• Excessive breadth and obviousness: the court held these grounds did not require separate determination once insufficiency and non-infringement were established.

Holding and Implications

DISPOSITION: The appeal is allowed.

Consequences:

• The Patent (United Kingdom Patent No. 2466504) is revoked for insufficiency (section 72(1)(c) Patents Act 1977) because the term "substantially unchanged" lacks a discernible boundary in the specification.
• Company B (the Appellant) has not infringed the Patent on its normal construction; the DuElec range was found not to infringe for the reasons given above.
• No broader precedent was asserted to be created by this decision in the opinion; the effect described is the direct effect on the parties (revocation of the Patent and declaration of non-infringement).