GB805121A - Improvements relating to apparatus for controlling the drive of a conveyor belt or other driven belt - Google Patents

Abstract

805,121. Endless belt conveyers. NILOS G.m.b.H., FORDERBAND - AUSRUSTUNG. Feb. 10, 1955 [Feb. 10, 1954; July 30, 1954], No. 4070/55. Class 78 (1). The drive to a conveyer belt is cut off if its speed falls below a predetermined level owing to slip between the belt and its drive by apparatus, including a speed-responsive roller driven by the belt which operates hydraulic means to supply fluid in accordance with the speed of the roller to a ram cylinder at least partly accommodated in the roller, the fluid acting on a spring-loaded piston within the cylinder which acts on means for cutting off the drive when the speed of the roller drops below a predetermined level. As shown, the speed-responsive roller 1 is one of the outer rollers of a set of troughing rollers 1, 33, 34 supported in a carrier frame 32 which is constructed such that these rollers lie higher than those of adjacent sets of troughing rollers to ensure continuous engagement of roller 1 with the belt. A cam 2 secured to the inside of the roller operates a pump 3 having inlet and outlet valves 4, 5 and supplying fluid from the interior of the roller to a ram cylinder 6 connected externally with the frame 32 and a control box 22. Piston 7 has a bore through it whose exit is adjusted in size by a needle valve 10 threaded in the piston rod allowing some of the fluid to return under the pressure of a spring 8 acting on the piston. Normally the spring is compressed until another bore 9 in the cylinder wall is uncovered, allowing the fluid to escape also through this bore. At this position a switch 13, linked by a push-rod 12 and bell-crank 11 to the piston-rod, is in the ON position. When the belt slows owing to slip between it and its driving drum, the bore 9 is first covered and then the piston slides inwardly, a pointer 15 on rod 12 indicating the rate of slip on a scale 16 while a rack 19 connected by lever 17 to rod 12 actuates a counter 20 whereby successive slippages are counted. When the belt speed falls to a value determined by valve 10, switch 13 is switched off, de-energizing the conveyer driving motor. The motor is restarted through a relay 14 which is adapted to maintain its contacts closed until the normal time for the conveyer belt to run up to speed, whereupon in the absence of further slip the contacts 13 will have re-closed.