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Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605, 70 S.Ct. 854, 94 L.Ed. 1097, 85 U.S.P.Q. 328

Facts

The Linde Air Products Company initiated a patent infringement lawsuit against Graver Tank & Manufacturing Company regarding certain claims of its patent related to electric welding. The District Court found some claims valid and infringed while others were deemed invalid. The Court of Appeals reversed the invalidity ruling, but the Supreme Court ultimately reinstated the District Court's judgment, affirming the infringement of four specific flux claims under the doctrine of equivalents.

Linde Air Products Co., owner of the Jones patent for an electric welding process and for fluxes to be used therewith, brought an action for infringement against Lincoln and the two Graver companies. The trial court held four flux claims valid and infringed and certain other flux claims and all process claims invalid.

Issue

Whether the trial court's holding that the four flux claims have been infringed will be sustained.

Whether the trial court's holding that the four flux claims have been infringed will be sustained.

Rule

The doctrine of equivalents allows a patentee to claim infringement if an accused device performs substantially the same function in substantially the same way to achieve the same result as the patented invention. This doctrine is applicable even if the accused device does not literally fall within the patent claims, provided that the differences are insubstantial and do not alter the fundamental nature of the invention.

The essence of the doctrine of 'equivalents' is that one may not practice a fraud on a patent. A patentee may invoke doctrine of 'equivalents' to proceed against producer of a device if it performs substantially the same function in substantially the same way to obtain same result as patentee's device.

Analysis

In applying the doctrine of equivalents, the court examined whether the accused device, Lincolnweld 660, was substantially identical in operation and result to the patented composition, Unionmelt Grade 20. The trial court found that the substitution of manganese for magnesium did not constitute a significant change, as both elements served similar functions in the welding process. The evidence presented, including expert testimony and prior art, supported the conclusion that the two compositions were equivalent for practical purposes.

In determining whether an accused device or composition infringes a valid patent, resort must be had in the first instance to the words of the claim. If accused matter falls clearly within the claim, infringement is made out and that is the end of it. But courts have also recognized that to permit imitation of a patented invention which does not copy every literal detail would be to convert the protection of the patent grant into a hollow and useless thing.

Conclusion

The Supreme Court affirmed the trial court's judgment, concluding that the finding of infringement regarding the four flux claims was not clearly erroneous.

Finding that composition claims 18, 20, 22 and 23 of patent No. 2,043,960, relating to electric welding, were infringed by defendants' device under doctrine of equivalents was not clearly erroneous.

Who won?

The Linde Air Products Company prevailed in this case as the Supreme Court upheld the trial court's finding of infringement on the four flux claims of its patent. The court emphasized the importance of the doctrine of equivalents in preventing infringement through minor alterations that do not change the fundamental nature of the invention. The ruling reinforced the protection afforded to patent holders against unscrupulous imitation.

The trial judge found on the evidence before him that the Lincolnweld flux and the composition of the patent in suit are substantially identical in operation and in result. He found also that Lincolnweld is in all respects equivalent to Unionmelt for welding purposes.

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