Wheatley v Drillsafe Ltd.

Wheatley v Drillsafe Ltd.[1]


Wheatley(W), the proprietor and licensee of a European patent relating to a threaded hole cutting device, appealed against a decision[2] holding that the patent was invalid on the ground of common general knowledge and accordingly should be revoked, and also that, in any event, there had been no infringement of the patent by Drillsafe (D) and others.


D maintained, inter alia, that its use of a semi-penetrating retractable probe within a cutting device in order to prevent the cutter from wandering did not infringe the patent on the ground that it was a permissible variant of the invention.

W contended that the judge had erred in his conclusion that the patent was invalid, and furthermore, he had failed to construe the words of the claim correctly and in accordance with the Protocol on Interpretation of the European Patent Convention 1973 Art.69 , as required under the Patents Act 1977 s.125(3).


  1. Whether the patent of W was invalid?
  2. Whether there was any infringement of W’s patent by D?


The appeal was allowed on the issue of invalidity of the patent. However, it was dismissed on the issue of infringement. It was observed that the judge had failed to adopt the correct approach when determining that the cutting tool was part of the common general knowledge. No distinction had been made between what was known and what formed part of the general knowledge. The judge in making his findings had erred by examining the question of inventive step from a position of hindsight. No evidence existed in support of his conclusion that a combined tap and cutter formed part of the general knowledge.

The three questions set out in Improver Corp v Remington Consumer Products Ltd.[3] were of assistance to the court in construing and reaching the appropriate purposive and contextual interpretation of a claim pursuant to s.125 of the 1977 Act and the Protocol on the Interpretation of the 1973 Convention.

In the instant case, a characteristic of the claim was that it related to the formation of a circular hole with a centre-less hole cutter. Reading the patent in its entirety, W had established that their rotary hole cutter worked without a central guiding or piloting device. Having regard to the questions set out in Improver[4], it was clear that the drilling method used by D did not infringe W’s patent, as a reader skilled in the art would have understood that the patentees intended there to be strict compliance with the primary meaning of their claim for a “centre-less” hole cutter.

The relevant paras which throw light on how the court went about interpreting the patent claim in this case have been reproduced below-

Para 20

“Strict literal interpretation using the drawings and specification gives to third parties the most certainty. That has always been seen as being unfair to inventors and of course is outlawed by the Protocol. However there must be a reasonable degree of certainty for third parties and therefore the language of the claim as interpreted in the light of the drawings and specification cannot be disregarded.”

Para 21:

“So far as the patentee is concerned it is important that the claim should be interpreted in accordance with his intention. A claim interpreted on the one hand too liberally can render the patent invalid and on the other too literally can allow third parties to avoid the monopoly.”

Para 22:

“The object of interpretation is to ascertain the intention of the author, in this case the patentee. This involves examining the words of the claim through the eyes of a person to whom the specification is directed, in the context of the specification as a whole. If the reader skilled in the art would have understood that the patentee intended that the claim should have a particular ambit, then to construe it as not confined to that ambit, by either strict or liberal construction, would be unfair to the patentee. It is the patentee that chooses the words and to widen the ambit contrary to his intention could invalidate the patent and to restrict the ambit could allow use of the invention without payment.”

[1] [2001] R.P.C. 7; Court of Appeal (Civil Division) 05 July 2000

[2] (1999) 22(5) I.P.D. 22044)

[3] [1990] F.S.R. 181

[4] Supra

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