Patent ID: 6020703
Filing Date: 2000-02-01
Classification: E05F,E05Y,G05B,G07C

Abstract:
In a door operator of the type comprising a power actuator for opening and closing a door, a control circuit for controlling energization and deenergization of the power actuator, a beam break system having a beam transmitter including a beam emitter for transmitting a pulsed beam of radiant energy across the doorway of said door and a beam receiver including a beam detector for receiving said pulsed beam, said control circuit including a pulse detector circuit for controlling energization of said power actuator in response to an obstruction of said beam or misalignment of said transmitter and receiver, the improvement wherein said control circuit comprises:an emitter drive circuit for generating emitter drive pulses and having an output coupled with said beam emitter for energizing said emitter to emit said pulsed beam as a train of transmitter pulses,said pulse detector circuit having an input coupled with said beam detector,a synchronizing coupling between said emitter drive circuit and the pulse detector circuit and means in said pulse detector circuit for producing a normal control signal when a transmitter pulse is received by said beam detector in synchronism with an emitter drive pulse and for producing a fault control signal in the absence of receipt of a transmitter pulse by said beam detector in synchronism with an emitter drive pulse,and means responsive to said normal output signal for enabling energization of said power actuator for closing said door,and an annunciator circuit coupled with said pulse detector circuit and responsive to said fault output signal for producing a perceptible warning signal.