Graver Tank & Mfg. Co. v. Linde Air Products Co. (JWB)

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The Case

  • The Linde Air Products Company brought action for patent infringement against Graver Tank & Manufacturing Company
  • Judgment held that certain claims of Linde Air’s patent invalid and holding other claims valid and infringed (US District Court Northern Indiana)
  • Court of Appeals reversed ruling of invalid claims
  • Supreme Court reversed the Court of Appeals decision and reinstated District Court ruling of invalid claims
  • a rehearing was granted limited to the question of infringement of the four valid flux claims 18, 20, 22 and 23 in plaintiff's patent No. 2,043,960, relating to electric welding

Patent

  • An electric welding process and fluxes to be used therewith


Ruling

  • 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.
  • ‘if two devices do the same work in substantially the same way, and accomplish substantially the same result, they are the same, even though they differ in name, form or shape.’ (Union Paper-Bag Machine Co. v. Murphy)
  • equivalency must be determined against the context of the patent, the prior art, and the particular circumstances of the case
    • Equivalency is not a formula; it’s case by case
  • Unionmelt’s claims are a combination of alkaline earth metal silicate and calcium fluoride; Lincolnweld’s composition substitutes silicates of calcium and manganese for silicates of calcium and magnesium
  • Chemists testified that manganese and magnesium were similar in many of their reactions
  • the accused flux is the result of imitation rather than experimentation or invention

Dissenting Opinion

  • Court’s affirmance unquestioningly follows the findings of the trial court, this Court necessarily relies on what the specifications revealed. In so doing, it violates a direct mandate of Congress without even discussing that mandate.
  • What is not specifically claimed is dedicated to the public
    • Giving this patentee the benefit of a grant that it did not precisely claim is no less ‘unjust to the public’
  • Manganese was disclosed in the application and then excluded from the claims. It therefore became public property.


Class Notes

  • Doctrine of Equivalence: “if it performs substantially the same function in substantially the same way to obtain the same result” it is considered equivalent (infringing)
    • Without this doctrine, anyone can imitate your invention – patent system becomes nearly worthless
  • Question is whether substitution of manganese for magnesium is covered by doctrine of equivalence
  • Claim refers to ‘alkaline earth metals’, which magnesium is not and manganese is

Dissent

  • Alternative substance was mentioned in patent, but not in claims (prior art involved manganese?)
  • Allowing this patent to cover manganese gives a second patent for the same thing