GB726979A - Improvements in or relating to apparatus for supervising slip in friction drives - Google Patents

Abstract

726,979. Belt conveyers. SIEMENSSCHUCKERTWERKE AKT.-GES. Feb. 11, 1953 [Feb. 11, 1952], No. 3870/53. Class 78 (1). [Also in Group XXXVII] Relates to means for switching off an electric motor in the event of excessive slipping by a motor-driven conveyer belt. In one embodiment, Fig. 1 (not shown), separate tachometer generators are respectively coupled directly with the motor and with a detector roller driven by the belt, and the electromotive forces generated thereby are arranged in opposition to one another. The difference voltage is applied to an electromotive counting mechanism which disconnects the drive after recording a predetermined number of slip revolutions. As shown, tachometer generators 1 and 2 are respectively coupled to the shaft of the driving motor and to a detector roller, and each generator supplies a capacitor 6, 7, through a resistor 4, 5, which provides a given time constant for the charging operation. Connected in parallel with each capacitor is a discharge resistor 8, 9, of high positive temperature coefficient, the winding of a relay 12 being connected between points 10, 11. If the electromotive force of the generator 2 falls, the voltage across the capacitor 7 decreases at a constant rate, and, when the potential difference between the points 10, 11 reaches a sufficient value, the relay 12 responds to disconnect the driving motor or effect other appropriate control action. In another arrangement, Fig. 3 (not shown), the speed-responsive generators are of the synchronous type having permanent magnet rotors, and each generator separately supplies a synchronous motor. Both motors are coupled to a common differential gear, the output shaft of which is connected to a counting and tripping mechanism for the main drive.