Graver Tank v. Linde Air Products Case Brief Summary | Law Case Explained

Graver Tank v. Linde Air Products Co. | 339 U.S. 605 (1950)

A welding flux is a substance used in welding to protect the weld from air, preventing oxidation. The alkaline earth metals are the chemical elements in the second column of the periodic table. They’re characterized by a full outer s-orbital, which gives them common chemical properties. Now that you know those two things, you’re ready to tackle the patent case Graver Tank versus Linde Air Products.

Linde Air Products owned a patent for a welding flux called Unionmelt Grade 20. Unionmelt’s patent described it as a combination of alkaline earth metal silicate and calcium fluoride. The actual product was made of silicates of calcium and magnesium, both alkaline earth metals.

Graver Tank made a competing product called Lincolnweld 660, which was identical to Unionmelt except that it contained silicates of manganese instead of magnesium. Manganese isn’t an alkaline earth metal. Lincolnweld and Unionmelt were made according to similar processes and used for the same applications.

Linde sued Graver for patent infringement. The trial judge spent three weeks hearing testimony from chemists and visiting laboratories to view welding demonstrations. The judge concluded that, for all practical purposes, manganese silicate could be used as a substitute for calcium and magnesium silicates, and that Lincolnweld was substantially identical to Unionmelt. The court held that Graver had infringed Linde’s patent. The court of appeals affirmed. The United States Supreme Court granted cert.

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