Minerals Separation North American Corp. v. Noranda Mines, Ltd.

Case Comment copyright 1997-2007 Donald M. Cameron





The Decision

At p. 111

"Two things must be described in the disclosures of a specification, one being the invention, and the other the operation or use of the invention as contemplated by the inventor, and with respect to each the description must be correct and full.  The purpose underlying this requirement is that when the period of the monopoly has expired the public will be able, having only the specification, to make the same successful use of the invention as the inventor could at the time of his application."

At p. 146:

"By his claims the inventor puts fences around the fields of his monopoly and warns the public against trespassing on his property. His fences must be clearly placed in order to give the necessary warning and he must not fence in any property that is not his own. The terms of a claim must be free from avoidable ambiguity or obscurity and must not be flexible; they must be clear and precise so that the public will be able to know not only where it must not trespass by where it may safely go. If a claim does not satisfy these requirements it cannot stand... The inventor may make his claims as narrow as he pleases within the limits of his invention but he must not make them too broad. He must not claim what he has not invented for thereby he would be fencing off property which does not belong to him. It follows that a claim must fail if, in addition to claiming what is new and useful, it also claims something that is old or something that is useless."

At p. 156

"These cases do not deny the principle that the specification is the dictionary by which the scope and effect of the terms in the claims is to be ascertained but merely indicate that it is not of general application and ought not to be applied in cases where a claim is expressed in simple and direct language or in wide or general terms whose meaning is plain and unequivocal."

At p. 156-157

"And in British Hartford-Fairmont Syndicate, Ltd. v. Jackson Bros. (Knottingley), Ltd. (1943), 49 R.P.C. 495 at 556 Romer L.J. said:

"But where the construction of a Claim when read by itself is plain, it is not in my opinion legitimate to diminish the ambit of the monopoly claimed merely because in the body of the Specification the Patentee has described his invention in more restricted terms than in the Claim itself."

In my opinion, this case is quite a different kind of case from those relied upon for the defendant. Xanthate is not a common word at all, nor is it a word whose meaning is so plain and unequivocal that it necessarily includes cellulose xanthate, for authority can be found in the dictionaries for two meanings of the word, the commonest one of which completely excludes cellulose xanthate and the other only possibly includes it...

At p. 158-159:

...Certainly, to borrow an expression from Duff C.J. in Western v. Baldwin (supra), at page 582, the word xanthate is not a term of art having "a generally understood signification in the art at the date of the patent". The term is a technical chemistry term, the meaning of which might not be known to the persons to whom the specification is addressed. Under the circumstances, it seems to me that it would be proper and reasonable for a reader unfamiliar with the term to look a the specifications to see whether the inventor has used it with a defined special meaning. If he did so he would find a definition of xanthates in paragraph 4 that is in accord with the common dictionary meaning but is more restricted by reason of the requirement of the second sentence in it. In my opinion, this case falls fairly within the proper application of the principle stated by Duff, C.J. in Western v. Baldwin (supra) that "the specification itself provides the dictionary by which the scope and effect of the terms in the claims is to ascertained". The word xanthate in claim 9 should, therefore, be read in the light of the inventor's definition in paragraph 4 of the kind of xanthate whose use in froth flotation be found useful. That is the only kind of xanthate he had in mind."

S.C.C. per Kellock J.

At p. 201:

"It is well settled that the specification is to be read as a whole and the claims, of course, are part of the specifications."

At p. 203:

"The claims then define and limit the ambit of the invention and may be read with the disclosure in the earlier part of the specification "in order to understand what the former says".


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