In light of fairly recent judicial decisions, UK-granted patents now offer greater protection under the newly adopted doctrine of equivalents; this rule broadens the scope of protection beyond the literal scope of a patent claim. The courts have now provided some useful questions to answer in cases like this.
The doctrine of equivalents was introduced in to UK patent law by the Supreme Court case pf Actavis v Eli Lilly  UKSC 48 – it allows a court to hold a party liable for patent infringement even though the infringing device or process does not fall within the literal scope of a patent claim, but nevertheless is equivalent to the claimed invention.
It has been applied in the following cases:
Excel-Eucan Limited v Source Vagabond Systems Limited  EWHC 3175
Excel developed an ammunition bag for holding linked rounds of ammunition, known as the ‘link-tail’, which is protected by a patent. The competitor developed its own bag known as the ‘2017 bag’, and sought a declaration of non-infringement of Excel’s patent.
Excel argued that despite the competitor’s ‘2017 bag’ not meeting the literal interpretation of the patent claim, it constituted an immaterial variation and was equivalent to the link-tail bag. The judge accepted this argument of immaterial variation and found there to be an infringement of Excel’s patent, despite the competitor’s bag not meeting the literal narrative of the claim. This decision confirms that courts in England and Wales may perceive patent holders’ arguments in a favourable light when deliberating the issues of equivalence by immaterial variants. This is clearly a positive outcome for the patent owner – a product without all of the features of their patent claim was still held to infringe.
Icescape Limited v Ice-World International Bv & Ors  EWCA Civ 2219
Icescape Limited and Ice-World International both operated mobile ice rinks and leased them out to third parties. Ice-World was the proprietor of a patent for a system that cooled the ice rinks. Icescape developed a system that also cooled mobile ice rinks. Ice-World claimed that Icescape infringed their patent.
Although the patent was found to be invalid and had to be revoked, Lord Kitchin provided guidance on the application of the doctrine of equivalents and remarked that to assess the scope of the claims for infringement, it is necessary to identify the ‘inventive core’ of the patent. Lord Kitchin highlighted three key questions which will help determine infringement:
- Does the variant achieve substantially the same result in substantially the same way as the invention?
- Would it be obvious to the person skilled in the art, reading the patent at the priority date, but knowing that the variant achieves substantially the same result as the invention, that it did so in substantially the same way as the invention?
- Would such a reader of the patent have concluded that the patentee nonetheless intended that strict compliance with the literal meaning of the relevant claim(s) of the patent was an essential requirement of the invention?
In order to show infringement, a patentee would have to establish that the answer to questions (a) and (b) was “yes” and that the answer to question (c) was “no”.
Icescape’s system had a parallel, rather than a series, connection between the manifolds which was said to possibly confer advantages but was judged to have nothing to do with the inventive core of the patent. The variant did not affect the inventive core, it would be obvious to the skilled person that Icescape’s system achieved substantially the same result as the invention and did so in substantially the same way. As the variants were outside the inventive core, these variants were not an essential requirement of the invention.
Despite Ice-World’s patent being revoked, there would have been infringement had it been valid.