04/19/23Allan Woodworth | UC Berkeley | Mechanical Engineering | IEOR 190G | Fall 2008 |

Linde Air Products Co. v. Graver Tank &

Manufacturing (1950)

Outline

04/19/23Allan Woodworth

Players

Welding

Claims of Infringement

Rulings and Appeals

Overall Impact

Players

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Linde Air Products Numerous products

such as the USA’s 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

Welding

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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.

Metal Arc Welding

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Flux

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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.

Patent

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

29 Claims

Dispute

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Linde sued Graver Co. and others for infringing the patent on their welding composition and process.

Graver Co. said we’re not infringing because our flux uses manganese instead of magnesium.

Magnesium

Manganese

Dispute Continued

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

District Court Ruling

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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…”

Appeals Court

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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.”

Doctrine of Equivalents

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It performs substantially the same function

in substantially the same way

to yield substantially the same result.

then it is EQUIVALENT

Questions?

04/19/23Allan Woodworth