Linde Air Products Co. v. Graver Tank

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Linde Air Products Co. v. Graver Tank
Manufacturing (1950)
Doctrine of Equivalents
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Outline

• Players
• Welding
• Claims of Infringement
• Rulings and Appeals
• Overall Impact

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Players

• Linde Air Products
• Numerous products such as the USAs first oxygen
  liquidation plant and hydrostatic forklift.
• Grover Tank Co.
• Makes tanks (the kind that hold things such as
  air or oil)
• Lincoln Electric Co.
• Makes flux

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Welding

• What is welding?
• A process that joins materials (usually metals)
  through coalescence.
• Generally done by melting the workpieces and
  adding a filler material that cools to become a
  strong joint.

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Metal Arc Welding
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Flux

• Flux protects the weld from oxygen and other
  gases.
• As the electrode melts the flux disintegrates
  giving off protective vapors and creating a
  protective molten slag.

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Patent

• Linde owned a patent for an electronic welding
  process (2034960)
• 29 Claims

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Dispute

• Linde sued Graver Co. and others for infringing
  the patent on their welding composition and
  process.
• Graver Co. said were not infringing because our
  flux uses manganese instead of magnesium.

Magnesium
Manganese
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Dispute Continued

• The patent claims the use of an alkaline earth
  metal silicate which includes Magnesium Silicate
  but not Magnesium silicate.

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District Court Ruling

• District Court found that the Lincoln Electric
  Co. made, and the other petitioners used and
  sold, a flux substantially identical with that
  set forth in the valid composition claims of the
  patent in suit, and which could be made by a
  person skilled in the art merely by following its
  teachings. The petitioners introduced no evidence
  to show that their accused flux was derived
  either from the prior art, by independent
  experiment, or from any source other than the
  teachings of the patent in suit. The court found
  infringement of each of the four claims, and
  concluded that the respondent was entitled to a
  permanent injunction against future infringement
  and to an accounting for profits and damages

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Appeals Court

• The case was sent to an appeals court which
  agreed with the decision made by the district
  court.
• The case was then sent to the 7th district court
  which actually strengthened the infringement case
  claiming even more of the claims were infringed
  than originally ruled by the court.
• Finally, the case was sent to the Supreme Court
  and upheld claiming that though the infringement
  was not literal there was still infringement
  based on the Doctrine of Equivalents.

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Doctrine of Equivalents

• It performs substantially the same function
• in substantially the same way
• to yield substantially the same result.
• then it is EQUIVALENT

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Questions?