GB719136A - Improvements in apparatus for automatically stopping a moving endless belt - Google Patents

Abstract

719,136. Belt gearing. COAL INDUSTRY (PATENTS), Ltd. April 15, 1952 [April 12, 1951], No. 8547/51. Class 80 (1) [Also in Group XXX] Apparatus for automatically stopping an endless belt whenever a rate of slip above a predetermined value is persisting between the belt and its driving drum or pulley comprises a differential gear drivably connected on one input side to an idler roller or the like rotating at a speed dependent upon the belt speed and on the other input side to the belt driving drum or pulley. The differential sum of the two input speeds derived from said gear being used to actuate a trip operative to cut off power supply to the motor driving the belt driving drum or pulley. The Figures show the application to a conveyer belt wherein the bevel wheels 3, 4 of the differential gearing are driven by chain wheels 1, 2 respectively, the chain wheel 1 being connected through a chain and gearing with an idler roller and the chain wheel 2 being connected by gearing to the belt driving drum. The chain wheels 1, 2 are so arranged that the bevel wheels 3. 4 rotate in opposite directions at the same speed when the belt is slipping at a pre-determined maximum allowable rate of slip. With no belt slip, the wheel 3 rotates at a higher speed than the wheel 4 and therefore through the pinions 5, 6, the cage 7 and bevel wheel 7A will be rotated and drive a pinion 8 secured to a spindle 18 whereby gear wheels 9, 10 of a gear pump are rotated in the direction indicated by the arrows A. The arrangement of the gear wheels is such that under these conditions no oil is delivered into the pressure chamber 11. If the belt slips an amount in excess of the maximum rate allowable, the gears 9, 10 are rotated in the opposite direction and oil is delivered by the pump from a sump 12 through an aperture 20 to the pressure chamber 11. Pressure is thereby built up on a spring-loaded plunger 13 forcing it to a position where an oil port (not shown) is opened and the oil then bypassed back to the sump 12. The movement of the plunger is used to operate a switch (not shown) to cut off the power supply to the driving motor and may also be used to give a warning such as to ring a bell or light a lamp. After the pump has operated, oil bleeds from the chamber 11 through an aperture 15 in the diaphragm 16 of the pump to allow the plunger 13 to return to its normal position for re-starting the motor. The aperture 15 may be provided with a needle valve or other variable area device.