Light-controlled safety switch for a punch press

Abstract

A light-controlled safety switch for an automated press includes an optical transmitter and receiver affixed to the press frame just above the press ram that redirects the light beam from vertical to horizontal. A light beam is directed downward from the transmitter to a 45-degree reflective surface on the ram. A cross-hole, perpendicular to the centerline of the ram, and a second 45-degree opposite-facing reflector opposite to the first reflective surface returns the light beam to the receiver. Thus, an optical path is achieved from the transmitter to the first reflector, through the ram, to the second reflector and then back up to the receiver. The opposing 45-degree reflectors are preferably provided by a 45-degree dished collar with a light-reflective interfacing surface fitted about the ram. The collar, and thus the reflective surfaces, stroke up and down with the movement of the ram, but maintains the optical path from the transmitter to the receiver because the send and receive light paths are parallel to the linear motion of the ram. A light-blocking shutter is connected to the top of a slidable punch holder assembly that breaks the horizontal light beam through the ram centerline whenever the punch contacts an object. Thus, the present optical system replaces the hard-wired punch contact safety switch of the prior art and its external wiring, thereby providing many advantages.