Graver Tank & Mfg. Co. v. Linde Air Products Co. (901422128)

Read for 3/25/11

Reading Notes

• Decided by the USSC in 1950
• Linde sued Graver for infringement of a patent relating to electric welding
• Rulings
  • District court riled certain claims invalid and others valid and infringed
  • CAFC reversed the invalid claims
  • Supreme Court agreed with District Court and found four claims infringed by doctrine of equivalents
• Does the substitution of the manganese (not alkaline earth metal) for the magnesium constitute a substantial change as to make the doctrine inapplicable
• Two are equivalent for welding purposes
  • Identical in operation and result

Infringement

• First step is to resort to the first instance of the words of the claims
  • If accused matter is clearly withing the claim, it infringes
• Cannot limit infringement to exact duplications because that would not be fair the inventor because those who copy could make insignificant changes
  • Response to this was doctrine of equivalents
• Doctrine of equivalents
  • Purpose is that one may not practice fraud
  • "if it performs substantially the same function in substantially the same way to obtain the same result"
  • Applied to mechanical or chemical equivalents
  • Equivalence is not an absolute

Dissenting Judge

• Gracer's flux did not literally infringe the patent, as all agreed
  • What is not specifically claimed is dedicated to the public
• Congress created a statute which has been interpreted to allow inventors to expand their claims
• Inventor had even tested manganese and found the others more suitable
• Not a manufacturer cannot rely on the language of a patent claims
  • Business men should be free to utilize all knowledge not preempted by the precise language of a patent claims