Graver Tank v. Linde Air Products Co.
United States Supreme Court
339 U.S. 605 (1950)
Linde Air Products
Co. (Linde) (plaintiff) owned a patent for Unionmelt Grade 20, a flux
composition used in welding. Though the patent claimed alkaline earth metal
silicate and calcium fluoride as ingredients, Unionmelt actually contained
calcium and magnesium silicates. Linde sued Graver Tank & Manufacturing Co.
(Graver) (defendant), claiming Graver’s flux composition, Lincolnweld 660,
infringed the patent. Though the uses and welding quality produced by the
compositions were largely the same, Lincolnweld did not contain magnesium like
Unionmelt. Instead, Lincolnweld contained manganese, which is not an alkaline
earth metal. At trial, chemists skilled in the art testified that manganese and
magnesium act similarly in chemical reactions, and that, for purposes of the
patent, manganese could be considered an alkaline earth metal. Additionally,
evidence established that prior art taught the substitution of manganese
silicate in welding fluxes. Graver produced no evidence demonstrating that
Lincolnweld was discovered or developed based on independent research or
experimentation. The trial court concluded that Lincolnweld and Unionmelt were
substantially the same in use and quality of results, and that Lincolnweld was
equivalent to Unionmelt for purposes of metal welding. Thus, the trial court
held that the patent claims were infringed. On appeal before the United States Supreme
Court, the Court considered the applicability of the doctrine of equivalents to
the flux claims.
Rule of Law
Holding and Reasoning (Jackson, J.)
Dissent (Black, J.)
Dissent (Douglas, J.)
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