Optical safety shutoff for machine cover

摘要

An interlock system for a machine cover including an optical sensor providing a cover open signal, a housing secured to the cover and defining a hollow cavity communicating with the optical path with the cover closed, a reflector fixed to one end of the cavity to reflect light to the sensor with the cover closed, a wall forming part of the housing and disposed in an interference relationship with the optical path for blocking light with the cover open, the length of the optical path with the cover open being less than the length of the optical path with the cover closed, and circuitry to trigger the optical sensor to provide light pulses at a predetermined frequency.