Improver Corp v Remington Consumer Products Ltd.

Improver Corp v Remington Consumer Products Ltd.[1]


Plaintiff in this case were European patentees and inventor of a depilatory machine called “Epilady” which had a spring and, when rotated, plucked hairs from skin. Defendant produced a device called “Smooth and Silky” which plucked hairs using a rubber band. P alleged infringement. D denied infringement and alleged that the patent was invalid for obviousness and insufficency.


  1. Does the variant have a material effect on the way the invention works?
  2. Would it have been obvious to a man skilled in the art that the variant would work in the same way?


The action for infringement was dismissed. The Court applied Catnic Components v. Hill & Smith and observed that the language of the patent should be given a purposive construction and not necessarily a literal construction. It was observed that if the issue was whether a feature embodied in the alleged infringement which fell outside the primary, literal or a contextual meaning of a descriptive word or phrase in the claim (“a variant”) was nevertheless within its language as properly interpreted, the court should ask itself the following questions:

(i) Does the variant have a material effect upon the way the invention works? If yes, the variant is outside the claim. If no:—

(ii) Would this (i.e.: that the variant had no material effect) have been obvious at the date of publication of the patent to a reader skilled in the art? If no, the variant is outside the claim. If yes:—

(iii) Would the reader skilled in the art nevertheless have understood from the language of the claim that the patentee intended that strict compliance with the primary meaning was an essential requirement of the invention? If yes, the variant is outside the claim.

In this case, Lord Diplock’s three questions were to be answered “no”, “yes”, “yes” respectively. Accordingly the “Smooth and Silky” device was not held to be infringement the plaintiffs’ patent. The feature embodied in the Defendant’s product was a variant outside the scope of the Plaintiff’s patent and the inventive merits of the defendant’s product were proved by the market response.

As per Section 125(3) of the Patents Act 1977 and Article 69 of the European Patent Convention, the scope of the invention must be found in the language of the claims. Extrinsic material such as the description can be used to interpret those claims but cannot provide independent support for a cause of action which the language of the claim, literally or figuratively construed, simply cannot bear. On the other hand, the claims should not be interpreted literally but in a way which “combines a fair protection for the patentee with a reasonable degree of certainty for third parties.”

[1] [1990] F.S.R. 181; Chancery Division (Patents Court), 16 May 1989

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