Law School Case Brief
Graver Tank & Mfg. Co. v. Linde Air Prods. Co. - 339 U.S. 605, 70 S. Ct. 854 (1950)
The doctrine of equivalents is that one may not practice a fraud on a patent. To temper unsparing logic and prevent an infringer from stealing the benefit of an invention, a patentee may invoke this doctrine to proceed against the producer of a device if it performs substantially the same function in substantially the same way to obtain the same result.
Linde Air Products Co. was the owner of the Jones patent for an electric welding process and for fluxes to be used therewith. The patented composition claimed essentially a combination of alkaline earth metal silicate (i.e., silicates of calcium and magnesium) and calcium fluoride. Linde thereafter brought an action for infringement against Lincoln, owner of Lincolnweld 660 – a flux whose composition was similar to the patented product of Linde, except that it substituted silicates of calcium and manganese (the latter not an alkaline earth metal) for silicates of calcium and magnesium. The trial court held four flux claims valid and infringed and certain other flux claims and all process claims invalid. The Court of Appeals affirmed findings of validity and infringement as to the four flux claims but reversed the trial court and held valid the process claims and the remaining contested flux claims.
Was the Jones patent infringed by Lincoln?
The Supreme Court held that that the doctrine of equivalents prevented Lincoln from stealing the benefit of Linde’s invention with a device that performed substantially the same function and in substantially the same way to obtain the same result. According to the Court, Lincoln’s flux was the result of imitation rather than experimentation or invention.
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