Patent ID: 7500650
Filing Date: 2009-03-10
Classification: B66B

Abstract:
1. A control circuit for a lift system having a lift cage movable in a lift shaft by a drive unit, a control for controlling the drive unit, a data bus connected with the control, shaft doors for closing the lift shaft, locking devices for locking the shaft doors at a shaft side and locking sensors for monitoring the setting of the locking devices, wherein the locking sensors are connected with the control by way of the data bus, the control circuit comprising means for repeatedly interrogating a locking sensor at short time intervals by way of the data bus whereby communications interruptions or transmission errors in data bus transmissions are detected, and for periodically testing the function of the locking sensors of all lift shaft doors by a) observing the signals locking sensors produce during opening/closing of the shaft doors in normal lift operation and b) automatically initiating a test travel of the lift cage to a story whose shaft door has not been operated within a defined period of time, opening and closing the shaft door, and observing the signals produced by the locking sensor associated with the shaft door.