Respondent began the present litigation as three separate suits against the respective petitioners for infringement of the Nelson Patent No. 2,109,678 of March 1, 1938, for a 'contact switch for ball rolling games.' The defenses were non-invention in view of the prior art, anticipation by prior publication, use and sale, non-infringement and a file wrapper estoppel. The three suits were consolidated and tried together. Upon full consideration of the issues the District Court and the Circuit Court of Appeals for the Seventh Circuit held Claim 4 of the patent valid and infringed. 119 F.2d 349.
We granted certiorari, 314 U.S. 702, 62 S.Ct. 175, 86 L.Ed. -, on a petition which challenged only the decree of infringement below, on the ground that it enlarged the scope of the patent as defined by the claim, by resort to the doctrine of equivalents, and that Nelson, the patentee, by the amendment of his claims in the Patent Office, had surrendered Claim 4 so far as it would otherwise read upon the alleged infringing devices. Neither in their petition nor in their brief and argument in this Court have petitioners contended that the patent is invalid for want of invention. Although there is no conflict of decision, we were moved to grant the petition by the nature of the questions presented, together with a showing that the industry affected by the patent is located in the seventh circuit so that litigation in other circuits resulting in a conflict of decision would not be likely to occur.
The patent relates to the structure of a resilient switch or circuit closer, so disposed on the board of a game table as to serve as a target which, when struck by a freely rolling ball, will momentarily close an electrical circuit. Specifications and drawings disclose a target or switch comprising a conductor standard mounted in the table and carrying a coil spring having a leg pendantly disposed in a conductor ring located in the table and slightly offset from the standard. The standard and ring are wired in a circuit with a relay coil and a source of electrical energy. When a ball rolling on the table bumps the coil spring from any direction, the leg of the spring is deflected momentarily bringing it into contact with the ring, so as to close the circuit for operating the relay coil and any connected auxiliary game device. Any desired number of targets may be placed on the board in a suitably spaced relationship; in pin ball games a single ball may successively bump and close a number of the switch devices. In describing his invention the patentee declared it to be his intention 'to cover all changes and modifications of the example of the invention herein chosen for purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.'
The prior art as disclosed by the record shows no device in which the coil spring serves both as a target and a switch. The advantages of the device are said to be that the combination is peculiarly adapted to use in pin ball games; that the coil spring structure is so organized as to form both a switch for operating auxiliary recording or signalling devices and a target which is accessible from any direction.
Claim 4 claims as the elements of the invention the conductor standard anchored in the table, the coil spring surrounding the standard which carries the spring pendantly from its top, with the spring spaced from the standard to enable the spring to be resiliently flexed, 'and conductor means in said circuit and embedded in the table at a point spaced from the standard and engageable by a portion of the spring when it is flexed to close the aforementioned circuit.' The drawings of the patent show the 'conductor means' last mentioned in the form of a ring or ferrule set in the table with its axis at right angles to the table and with its flange projecting slightly above the surface of the table. The leg pending from the coil spring is so disposed at the center of the annular ferrule that a ball striking the spring in any direction will bring the pendant leg into contact with the ring so as to close the circuit.