Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605 (1950)
U.S. Supreme CourtGraver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605 (1950)
Graver Tank & Mfg. Co. v. Linde Air Products Co.
Argued March 30, 1950
Decided May 29, 1950
339 U.S. 605
1. This Court affirms the finding of the two courts below that, under the doctrine of equivalents, certain flux claims of Jones patent No. 2,043,960, for an electric welding process and for fluxes, or compositions, to be used therewith were infringed. Pp. 339 U. S. 606-612.
2. The essence of the doctrine of equivalents is that one may not practice a fraud on a patent. P. 339 U. S. 608.
3. The doctrine of equivalents is founded on the theory that, if two devices do the same work in substantially the same way and accomplish substantially the same result, they are the same, even though they differ in name, form or shape. Pp. 339 U. S. 608-609.
4. In determining equivalents, consideration must be given to the purpose for which an ingredient is used in a patent, the qualities it has when combined with other ingredients, the functions which it is intended to perform, and whether persons reasonably skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was. P. 339 U. S. 609.
5. A finding of equivalence is a determination of fact to be made by the trial court, and the trial court's decision should not be disturbed unless clearly erroneous. Pp. 339 U. S. 609-610.
6. On the record in this case, involving a claim of a combination of alkaline earth metal silicate and calcium fluoride, the trial court was justified in finding that the substitution in the accused composition of manganese silicate (which is not an alkaline earth metal
silicate) for magnesium silicate (which is an alkaline earth metal silicate), where the two compositions were substantially identical in operation and result, was so insubstantial, in view of the technology and the prior art, that the patent was infringed under the doctrine of equivalents. Pp. 339 U. S. 610-612.
The history of the case is summarized in the first paragraph of the opinion. On the aspect of the case involved in the rehearing, the prior decision of this Court is adhered to, p. 339 U. S. 612.