ES292331A1 - Electric stress sensing devices for crushing machines - Google Patents

Abstract

A crusher, e.g. a gyratory, roller, hammer or jaw crusher, includes a stress-sensing electrical device comprising a low-voltage source 12 connected to the main shaft, which is insulated from the movable crushing members, and to the frame of the crusher, and a control member in the circuit to stop the crushing action and/or switch in an alarm when a conductive object is present in the system. As described, the gyratory shaft 1 of a gyratory crusher is insulated by a plastics foot ring 2, and a plastics cross-bar bearing 3 and attrition ring 4, or alternatively the suspension ring 5 may be made of insulating material. Low voltage D.C. or A.C. is applied to the shaft 1 via a flexible lead 6, and to the frame 7, to control the servo-system 13 which controls an alarm device and/or relay circuit-breaker 14 for the motor. Tramp metal causes contact between the shaft and the framework, via the mantle, to close the circuit and actuate a sound or luminous alarm. Operation of the circuit may be delayed by a timer combined with the servo-control device 13, to permit the passage of small size metallic pieces. Deformations in mechanical members of the crusher are detected and controlled, e.g. by an extensometric gauge 15, secured to the shaft 1 at a suitably selected point, or e.g. on the arms of the cross bar 8. In a modification the control device 13 controls the opening of a hydraulic circuit, and flow back to an oil tank feeding an hydraulic lifting-jack at the upper end of the shaft, so as to permit passage of the blocking material between the mantle and crushing ring, after which the jack returns the shaft to its normal position. If however the metallic material is too large to pass, the electric circuit remains closed long enough to operate the alarm and/or stop the crushing motor. The electrical connection to the frame may be combined with the extensometric gauge, or the latter may be separate.