The claim required the filament of tungsten used in the lamp to be ‘of large diameter’. The Court of Appeal had accepted that the word ‘large’ was ambiguous in that it did not enable the skilled person to decide when the claim was infringed.
Held: The view of the Court of Appeal was rejected. If the skilled person reading a patent claim would quickly realise that one method would work and another would fail, the specification is not insufficient because the claim is expressed in terms broad enough to include both methods. ‘It is easy, whenever language of generality and relativity applicable to size, measure, weight or the like have been employed, to put puzzles which might indicate that, at certain points, you are at that thin strip of mechanical territory in which, on the one side, there might be failure, and, on the other, success. But the reply to such criticism is that that is not how practical men work. They work to achieve success, and if, adopting the broad lines laid down in a specification, they do not find any real difficulty in achieving success, this may not conclude the matter, but it goes far to show that the vagueness of the specification has not mislead them – practical people who were not seeking for failure but for success – had not caused the invention to fail to reach their mind, but has, on the contrary, for all practical purposes, guided them, and that without difficulty, towards the success which prior to that no experiment nor invention had achieved. I think there is no rule, whether of benevolent or malevolent construction, which should apply to patent specifications. A specification must take its rank among all ordinary documents which are submitted to a reader for his guidance or instruction, and a reader ordinarily intelligent and versed in the subject-matter. Such a reader must be supposed to bring his stock of intelligence and knowledge to bear upon the document, not unduly to struggle with it, but anyhow to make the best of it; if, as the result, he understands what the invention is, can produce the object and achieve the manufacture by the help of the written and drawn page, then the subject-matter of the invention cannot fail on the head of vagueness.’ and ‘And as to the facts of the present case, there is no one, from beginning to end of it, who denies that the description in the Specification could be followed so as to produce the effect so much and so long desired. The one lamp-maker in the case is Mr. Swinburne, and he says, in effect, and says truly, that the invention produced a revolution, that as for working it out its explanation was plain and simple, and that, with the Specification in hand, the article embodying the invention could be made. I attach no weight to the suggestion in argument that you may extend your experiments of large and small in such a way as to come to a point at which the merit evaporates, because in all such cases, in which there is an ambit of the application of a principle, there must, or there may, come a point which is, as I have said, the outer edge of that ambit. The answer to which is, there is nothing intricate in the experiment: keep in view what you want to achieve, apply the principle reasonably and you will have success. But do not blame the patentees for vagueness if he accepts the common-sense rule that in applying an invention within its successful ambit it is expected that those operating the manufacture will be honestly looking, not to failure, but for success in the range in which the principle is applied.’
Judges:
Lord Shaw of Dunfermline
Citations:
(1922) 39 RPC 49
Jurisdiction:
England and Wales
Cited by:
Cited – Kirin-Amgen Inc and others v Hoechst Marion Roussel Limited and others etc HL 21-Oct-2004
The claims arose in connection with the validity and alleged infringement of a European Patent on erythropoietin (‘EPO’).
Held: ‘Construction is objective in the sense that it is concerned with what a reasonable person to whom the utterance . .
Lists of cited by and citing cases may be incomplete.
Intellectual Property
Updated: 06 May 2022; Ref: scu.218807