Elevator excess speed detector with multiple light barrier

摘要

An apparatus for detecting excess speed of an elevator car travelling in an elevator shaft includes a vertically extending measuring strip is mounted at one side of the shaft and a multichannel forked light barrier assembly mounted on the car with a pair of legs extending on opposite sides of the strip. The measuring strip has a vertically extending markings track in the form of flags side-by-side with a check track, each of which is scanned by a separate light barrier transmitting a light beam between the legs of the forked light barrier assembly. At the position of each flag there is formed a window in the check track. The speed of the elevator car is measured by detecting the time required to pass each flag and the elevator car is stopped in the case of excess speed. By reason of the arrangement of the flag track and the check track, possible faults can be detected since one light barrier must always be interrupted by reason the flags and the windows.