Exhibit Supply Co. v. Ace Patents Corp.

Background

Three separate lawsuits by the patent owner (Nelson) against manufacturers accused of copying a "contact switch" used as a target on ball-rolling game tables were tried together. Lower courts held Claim 4 valid and infringed. The patent describes a vertical conductor standard carrying a coil spring that, when struck by a rolling ball, flexes and touches a conductor set in the table to close an electrical circuit. The accused devices used different ways of supporting the complementary conductor: some used a pin or nail driven into the table, others used plates or insulating sleeves resting on the surface.

Reasoning

The key question was whether the patentee, by amending the original claim language from "carried by the table" to "embedded in the table" during patent prosecution, gave up protection for conductors merely carried on the table. The Court held that the amendment was a clear disclaimer of the broader phrase and must be strictly construed. As a result, the patentee cannot use the doctrine of equivalents to recover what it surrendered in the Patent Office. The Court therefore found two accused devices that had a conductor embedded in the table infringed, but four others that had conductors merely supported on plates or sleeves did not.

Real world impact

The decision narrows the reach of this patent and limits enforcement against designs that change how the conductor is supported. Manufacturers who alter conductor supports to avoid an "embedded" arrangement may avoid infringement. The Court left open the larger questions about the full scope of the doctrine of equivalents and did not decide whether the patent lacked invention.

Dissents or concurrances

Justice Black, joined by Justice Douglas, dissented, arguing the device lacked patentable invention and the judgments should be reversed in full because no new element was shown.