I. T. S. Rubber Co. v. Essex Rubber Co.

Background

In this case a company that owns a reissued patent on resilient shoe heels sued a maker of rubber heels for infringement. The defendant admitted the patent was valid but said its heels did not infringe. Lower courts dismissed the suit for lack of infringement and found the defendant was not prevented from contesting infringement by earlier suits where a dealer defaulted and then settled with the defendant’s reimbursement. The Supreme Court granted review because different appellate courts disagreed about the patent’s scope.

Reasoning

The main question was whether the patent’s written record in the Patent Office (the file wrapper) narrowed the patent so much that the defendant’s heels fell outside it. The patent claims were amended during prosecution to require a concavo-convex heel whose upper surface touches the leather only at the rear edge and two front “breast” corners — a “three-point-contact” shape — and the drawings were altered to match. The Court held those amendments were a clear disclaimer that limited the claims to that precise form. Because the Essex heels have upper side edges lying in the same plane and lack the three-point vertical curve, they do not fall within the narrowed claims, even if they work similarly.

Real world impact

The decision means the patent owner cannot broaden its claim by arguing that different shapes are equivalent. Heel makers whose products lack the specific three-point-contact shape will not infringe these claims. The case underscores that changes made during patent prosecution can permanently narrow what a patent covers.