The 'Substantially' Seal: Infringement, Validity and Prior Use
Malaysian patent MY-123456 was granted on 15 January 2025, with a priority date of 10 June 2022. Claim 1 reads: 'A container closure comprising a cap and an elastomeric sealing ring consisting of silicone, wherein the ring has a Shore A hardness of 40-50 and a substantially uniform cross-section.' Your client owns the patent. A competitor sells a closure whose ring is made of thermoplastic elastomer (TPE), has a hardness of 45 Shore A, and varies in cross-section by 0.3 mm. The competitor made 500 prototypes in 2021 for leak testing, did not sell them, and launched sales in February 2025. The patent specification mentions silicone only and says the ring 'may be compression moulded'. The competitor's lawyer says: TPE is not silicone; 'consisting of' is closed; there is a prior-use right; and the 2021 tests were experimental. Your client wants to sue immediately and also asks whether it can amend the claim to cover TPE.
1. Analyse infringement by construing the claim, including 'consisting of', 'substantially uniform' and the TPE ring.
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The claim has a comprising preamble for the closure but a closed transitional phrase for the ring: consisting of silicone. Under Malaysian claim construction, the claims define the monopoly; the description and drawings are used to interpret them, but they cannot enlarge a closed list into an open one. Consisting of silicone means the ring is made of silicone, not silicone plus another material and not a different elastomer. A TPE ring is therefore outside the literal scope of claim 1. The specification mentions silicone only, so there is no basis to read TPE into the claim as an equivalent.
Substantially uniform cross-section is a relative term. The competitor's 0.3 mm variation may or may not be substantial, depending on the ring size and the function of the seal. If the claim is construed to require a uniform cross-section within normal manufacturing tolerances, 0.3 mm might still fall within the claim. But that does not matter if the material limitation is not met. Infringement requires all features of the claim. Because the TPE ring does not satisfy consisting of silicone, there is no literal infringement even if the cross-section is substantially uniform.
The client should not assume that a purposive construction will capture TPE. A court may consider the inventor's purpose, but it cannot ignore a clear closed limitation. The safer conclusion is that the competitor's TPE product is outside claim 1 on the current wording.
2. Assess the prior-use and experimental-use defences, and the effect of the February 2025 sales.
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The prior-use defence is directed to a person who, before the priority date, was doing acts in good faith in Malaysia which would otherwise infringe, and who continues those acts. The competitor made 500 prototypes in 2021, before the 10 June 2022 priority date. The critical question is whether prototype manufacture for leak testing is the kind of use that creates a prior-use right. Testing is usually not commercial exploitation. If the prototypes were secret, not sold and used only to evaluate the product, the competitor may struggle to show a good-faith use of the invention in the required sense. The defence also does not automatically cover a later commercial launch on a different scale; it is limited to the continuation of the earlier acts.
The experimental-use defence applies to acts done for experimental purposes relating to the subject matter of the invention. The 2021 leak tests may have been experimental, but that defence is not a licence to sell the product from February 2025. The 2025 sales are commercial acts. If the product fell within the claim, those sales would infringe. The experimental defence does not protect them.
On the facts, the stronger defence is non-infringement because the ring is TPE, not silicone. The prior-use and experimental arguments are secondary. If the competitor later changes to a silicone ring, the prior-use analysis becomes important, and the client should gather evidence of the competitor's 2021 activities. The February 2025 sales are after grant, so the patentee can claim damages or an account of profits for those sales only if infringement is established.
3. Advise on whether the patent can be amended to cover TPE, and identify the validity risks in doing so.
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An amendment after grant cannot broaden the claim or introduce new matter. Changing consisting of silicone to consisting of silicone or TPE would extend the scope of the monopoly and would not be allowable. Even changing it to elastomer would broaden the claim and would also lack support if the specification describes only silicone. The description says the ring may be compression moulded, but that does not disclose TPE as a material. The client therefore cannot amend the granted claim to capture the competitor's TPE product.
There are also validity risks in the existing claim. Substantially uniform cross-section is a relative term that could be attacked as unclear. If the specification does not define a tolerance or explain how uniformity is measured, the competitor may argue that the claim is invalid for lack of clarity. The closed consisting of silicone limitation is clear, but it also makes the claim narrow. If the patentee tries to argue that TPE is equivalent, that argument may undermine the clarity of the material limitation.
My advice is not to sue on the TPE product on the current claim. The client should consider a new application or a utility innovation for a TPE sealing ring if there is a novel and industrially applicable improvement, but the client must check whether the TPE product or the 2021 prototypes have already been disclosed. For the existing patent, the client should monitor for silicone-ring products and preserve evidence of the competitor's activities. If the client wants broader coverage in future, the specification must describe alternative materials and a measurable cross-section tolerance before filing.