Opinion ID: 1568902
Heading Depth: 1
Heading Rank: 1

Heading: Operability

Text: On the question of operable invention, much evidence was introduced, and it was of a contradictory character. Tests had been made on behalf of both parties, and the results of those tests were introduced in evidence. The results appeared to be contradictory. Some of the seeming contradiction arises from the fact that in the defendants' tests, an amount of bentonite was used differing from the amount used in the plaintiff's tests. This diversity arose from a difference in construction of the patent by those directing the tests for defendants and those directing them for plaintiff. In the specifications of the patent is found this language: I use in concrete of normal composition, in addition to the usual materials, a small proportion of a dry mineral matter [bentonite].    (Italics ours.) Also in the specifications occurs this statement: Concrete made with 2 to 5 per cent. bentonite is capable of withstanding considerable hydrostatic heads of water. Higher proportions may be used. The exact amount, however, is not stated in the specifications. None of the claims specifies the amount except claims 7, 8, and 9. Claim 9 reads as follows: A waterproof Portland cement concrete of at least normal strength characterized by the admixture of approximately five per cent. of bentonite with the cement before it has set. The words approximately five per cent. of bentonite also occur in claims 7 and 8. Plaintiff contends that the language means that the amount of bentonite is to equal 5 per cent. of the amount of cement used. Defendants contend that the language means 5 per cent. of the whole concrete mix. We think the language in the three claims mentioned is ambiguous in reference to the amount of bentonite to be used. The trial court held that the percentage of bentonite was to be understood as calculated upon the amount of cement used and not on the amount of concrete. If this construction is adopted, the invention under the evidence is clearly operable. Furthermore, as we shall hereafter see, defendants have quite closely followed the process of plaintiff's reissue patent and have produced a correspondingly like product. An infringer is estopped from denying utility and operability. Dunkley Co. v. Cent. Calif. Canneries (C. C. A.) 7 F.(2d) 972, 976; Boyce v. Stewart-Warner Corp. (C. C. A.) 220 F. 118, 126. We think the view of the trial court as to the amount of bentonite to be used is correct; and we reach that conclusion the more readily because of the rule that where the language used in claims is ambiguous, that construction should be adopted which will render the patent valid rather than one which will render it invalid.