Weber Electric Co. v. E. H. Freeman Electric Co.

Background

The dispute is between the owner of a 1903 patent for a simple lamp-socket locking design and a rival maker of lamp sockets. The patent describes a sheet-metal sleeve with slits and beveled projections that snap into matching recesses in a cap so the sleeve can be pushed in and locked, and later released by squeezing. The patent owner conceded validity of the claims at issue and limited the fight to the fourth claim, which describes this snap-locking construction. The rival's product uses riveted inward studs on the cap and bayonet slots in the sleeve that require first pushing the sleeve in and then rotating it so studs pass into transverse slots; a fourth stud snaps into a hole to complete the lock.

Reasoning

The Court asked whether the rival's socket falls within the fourth claim. It held that the patent, as amended during prosecution and read in light of later additions by the same inventor, was limited to a structure that locks by direct longitudinal push and snap action without any required rotation. The applicant had added words to distinguish earlier patents that used rotation, and later patents by the same inventor expressly provided antirotation features. Those facts show the inventor disclaimed any claim that required rotation, so the rival's rotary bayonet design does not infringe.

Real world impact

The ruling means the rival maker may keep selling its rotary bayonet socket. It confirms that inventors who narrow patent claims during approval cannot later read broader scope back into those claims, and it clarifies what kinds of socket designs remain outside the 1903 patent's reach.