LIGHT BARRIER FOR REOPENING ELEVATOR DOORS

An apparatus for detecting an object adjacent an elevator door includes a housing (47) mounted at an upper edge of a car door opening (38) and in whic h are mounted a plurality of short range detector pairs (50) and a plurality of lo ng range detector pairs (53). Each short range detector pair includes a transmitter (14,25,40) for generating a relatively short range infrared beam (18,27,42) toward a pa th of travel (16) of an elevator door (17) across the door opening and a short ran ge receiver (15,26,41) for detecting a reflection (31) of the beam from a facin g surface (17b) of the door and generating a short range beam detection signal. Each long range detector pair is positioned adjacent an associated one of the short range detector pairs and includes a transmitter (19,28,43) for generating a relatively long range infrared beam (21,30,45) across the path of travel and a receiver (20,29,44) for detecting a reflection (23) of the beam from an object (22) near the doo r opening and generating a long range beam detection signal. A control (11) is connect ed to each detector pair for turning on the transmitters and for reopening the closing door in response to the long range beam detection signal. The control responds to each short range detection signal during closing of the door to disable the associated long range transmitter and responds to termination of the short range detection signal during opening of the door to enable the associated long range transmitter t o prevent detection of the moving door by the long range receivers from reopening the door. 18