Schriber-Schroth Co. v. Cleveland Trust Co.

Background

A trust holding about eighty patents for automobile pistons sued in federal court to stop others from making pistons it said infringed five of those patents. Two patents at issue, by Gulick and Maynard, claimed a piston design that kept the piston cool and allowed a slitted skirt to yield under cylinder pressure. A trial master and the district court found the patents invalid; the Court of Appeals reversed as to the Gulick and Maynard patents, and the case reached the Supreme Court to decide whether a feature added or not described in the original filings could be treated as part of the patented combination.

Reasoning

The core question was whether the laterally flexible web element—used to let the slitted skirt contract and control thermal expansion—was properly part of the patents when Gulick’s original 1917 application described the webs as “extremely rigid” and did not disclose flexibility. The Court explained that the patent law requires the invention to be described clearly when filed so the public can know its limits. Because Gulick’s 1922 change introduced the flexible-web idea after other pistons were already in use, and because the drawings and original text did not show proportions that would imply flexibility, the Court found the amendment introduced new matter. Maynard likewise did not describe flexible webs in its specifications. The Court concluded the appeals court erred in treating the later-added flexible-web feature as part of the patents and reversed.

Real world impact

The decision narrows what the patent holder can enforce against makers of pistons and engine parts, limits the ability of patent owners to broaden claims by later additions, and sends the case back to lower courts to reconsider claims without the later-added feature. It affects manufacturers, designers, and patent owners involved in similar engine-part claims.