Imperial Oil v.
Lubrizol

It is important to set out the numerical parameters exactly, rather than paraphrase even to the limited extent the trial judge did: 

        (a) a Mn value of 1300 to about 5000;

If, as said in Beecham, it is unnecessary to have recourse to the disclosure to construe a claim where its words are plain and unambiguous, it is likewise unnecessary to have recourse to parol evidence, however expert. It follows, for example, that, while recourse to the disclosure and experts is necessary to understand what a succination ratio is and how it is tot be calculated, there can be no question that the claims in issue do not assert a monopoly over compositions having a succination ratio of 1.25%; the plain and unambiguous meaning of "at least 1.3" cannot include 1.25. It is likewise as to the lower limit of the first parameter, where the Mn value of 1300 is unqualified.

What may still be asked, however, is whether a composition with a succination ratio of 1.25 infringes because that is but a minor or immaterial variant of the invention, or to put it another way, because the "pith and marrow" of the invention has been taken. As was said in Lightning Fastener Co., Ltd. v. Colonial Fastener Co. Ltd., [1932] Ex. C.R. 89 at p.98; reversed [1933] 3 D.L.R. 791, [1933] S.C.R. 363; reversed [1934] 3 D.L.R. 737, 51 R.P.C. 349 (P.C.):

That the principle remains alive and well and applicable in the present circumstances was confirmed by the House of Lords in Beecham Group v. Bristol Laboratories, [1978] R.P.C. 153 at p. 200, per Lord Diplock, a pharmaceutical case.

At one point in this judgment the trial judge said (at p.44):

At an earlier point, had said (at p. 33):

Imperial argues that the first is a finding that a succination ratio of at least 1.3 is of the very pith and marrow, while the second dismisses it as not essential.

Imperial also suggested that the references to "defendant", i.e. Imperial, in the first must have been a slip and that it should have said "plaintiff", i.e., Lubrizol. Imperial is mistaken in this. The trial judge was clearly dealing with its argument that, a succination ratio of at least 1.3 being an essential element, "it is not colourable evasion to go outside an essential element (transcript, vol. XXVII, p.p. 71-2).

To find conflict between the two statements requires that each be taken out of its context. As tot he first, his appreciation of "minor variant" and "pith and marrow" is much to be preferred to that urged on him by Imperial which, in my view, was an inversion of the law. However strictly one construes a claim, the pith and marrow doctrine precludes its colourable evasion. In the second, the choice of words may have been less than precise but the trial judge was simply saying that the exclusions of unreacted PIB from the calculation of the succination ratio was not precluded by strict adherence to "at least 1.3".

This was the only attack on the finding of infringement as it is related to the products in Columns A, B and C of the schedule as well as those in Columns D, E and F. It is without merit.