GB731835A - Improvements in or relating to belt conveyors - Google Patents

Abstract

731,835. Differential switches. GENERAL ELECTRIC CO., Ltd., and MITCHELL, K. J. July 15, 1953 [July 21, 1952], No. 18398/52. Class 38 (5). [Also in Group XXX] In control apparatus for stopping the driving motor of a belt conveyer in the event of abnormal discrepancy between the speeds of the belt and driving drum (see Group XXX) a differential switch closes contacts in a control circuit when the speeds of two shafts 16, 13 driven respectively by the belt 12 and driving drum 11 differ by more than a predetermined amount. As shown, shafts 13 and 16 drive magnetic speedometer devices 18, 19 respectively which generate torques in the same direction on respective control members against the pressures of springs 20, the control member of device 18 consisting of a pair of arms 25, 26 carrying contacts 23, 24 while that of device 19 consists of a single arm 22 carrying a contact 21, which remains between contacts 23, 24 so long as the speeds of shafts 13, 16 remain equal. When a difference in speed occurs owing to slip of the belt on the driving drum, one of the control members is overtaken by the other so that contact 21 engages one of the contacts 23, 24 completing a circuit to stop the conveyer driving motor. The distance between the contacts 23, 24 determine the difference in speed of shafts 13, 16 necessary to operate the switch. In a modification (Fig. 2, not shown) the devices 18, 19 act in opposite directions on a common control member so that the control member moves only when a difference of speed of shafts 13, 16 occurs and will then engage one of a pair of fixed contacts spaced to suit the desired difference in speed to be permitted without operation of the switch.