Graver Tank & Manufacturing Co. V. Linde Air Products Co. - Result

Result

The Court, in an opinion written by Justice Robert Jackson, raised the doctrine of equivalents. It noted that if another party could use a process exactly the same as one that is patented, but escape infringement by making some obvious substitution of materials, it would deprive the patentee of the exclusive control meant to come with a patent. This would undermine the profitability of the patent, which would go against the policy of encouraging inventors to invent by giving the opportunity to profit from the labor of invention.

The Court also outlined how the doctrine should be used, noting that "what constitutes equivalency must be determined against the context of the patent, the prior art, and the particular circumstances of the case." The Court laid out two possible tests to determine equivalency. Under the first of these (which has since come to be known as the "triple identity" test), something is deemed equivalent if:

1. It performs substantially the same function
2. in substantially the same way
3. to yield substantially the same result.

Under the second test, something is deemed equivalent if there is only an "insubstantial change" between each of the features of the accused device or process and the patent claim.

In this case, the Court gave particular weight to the determination of "whether persons reasonably skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was." Finding that the substitution of magnesium for manganese was both obvious to anyone working in the field, and was an insubstantial change, the Court upheld the finding of patent infringement.