Patent ID: 6111374
Filing Date: 2000-08-29
Classification: E05F,E05Y,G05B,H02H

Abstract:
A movable barrier operator comprising:an electric motor;a transmission connected to the electric motor to be driven thereby and for connection to a movable barrier to be moved with respect to a barrier frame;means for detecting a quantitative indication of position of the movable barrier;means for comparing the quantitative indication of position of the movable barrier to a stored digital end of travel position and for providing a halt signal in response to the stored digital end of travel position having been exceeded;a controller for halting the electric motor in response to the halt signal;a barrier position signal generator for producing a barrier position signal indicative of the barrier moving past a location fixed with respect to the barrier frame, the barrier position signal generator comprising a beam emitter and a beam detector disposed to form a beam pathway and an opaque plate extending from the barrier and into the beam pathway when the barrier is at the fixed location, wherein the beam detector detects a break in the beam pathway from the opaque plate; andmeans for correcting the quantitative indication of position according to the barrier position signal.