Court Opinion

ID: 9420490
Source: CourtListenerOpinion
Date Created: 2023-08-02 22:54:46.761367+00
Date Added: 2024-06-11T17:22:25.281113
License: Public Domain

Mr. Justice Douglas,
dissenting.
The Court applies the doctrine of equivalents in a way which subverts the constitutional and statutory scheme for the grant and use of patents.
The claims of the patent are limited to a flux “containing a major proportion of alkaline earth metal silicate.” Manganese silicate, the flux which is held to infringe, is not an alkaline earth metal silicate. It was disclosed in the application and then excluded from the claims. It therefore became public property. See Mahn v. Harwood, 112 U. S. 354, 361. It was, to be sure, mentioned in the specifications. But the measure of the grant is to be found in the claims, not in the specifications. Milcor Steel Co. v. Fuller Co., 316 U. S. 143, 145, 146. The specifications can be used to limit but never to expand the claim. See McClain v. Ortmayer, 141 U. S. 419, 424.
The Court now allows the doctrine of equivalents to erase those time-honored rules. Moreover, a doctrine which is said to protect against practicing “a fraud on a patent” is used to extend a patent to a composition which could not be patented. For manganese silicate had been covered by prior patents, now expired. Thus we end with a strange anomaly: a monopoly is obtained on an unpatented and unpatentable article.