GB1345725A - Control system for a balancing hoist - Google Patents

Abstract

1345725 Hoists GARDNER-DENVER CO 27 May 1971 [18 Nov 1970] 17536/71 Heading B8B [Also in Division F2] A control system for a fluid operated balancing hoist 10 having a pressure fluid operated motor including an expansible chamber 36 drivably connected to a load rope drum 26, comprises a pressure regulator 84 between the fluid supply source and the chamber 36 and including means 85, 160 for sensing the pressure in the chamber and adjusting the regulator 84 to maintain a pressure value, and locking means 90, 172 operable to lock the sensing means at a predetermined pressure setting corresponding to a balanced condition of the load connected to the hoist. To raise a load 32, lever 120 on a depending controller 76 is depressed to operate valves causing air to be supplied to the chamber 36 to wind up the rope 28, an adjustable pressure sensing valve in this supply line restricting the fluid flow to the chamber if a low pressure (hence low or no load on the hoist) exists, or unrestricting the flow if a load is sensed. If the load is to be balanced, the lever 120 is further depressed to operate valves causing the locking means 90, 172 to be fluid pressure released against spring bias so that the sensing means 160, 85 may be displaceable by pressure from the chamber 36 acting on the end face 166 of the sensing means. This displacement is opposed by springs 86 and 150 supporting therebetween a valve spool 136. When the hoisting distance is reached, the lever 120 is released whereupon the sensor 160, 85 is locked by the means 90, 172 in a position corresponding to the prevailing pressure in the chamber 36. The chamber pressure is now communicated to the end 148 of the valve spool 136, this line being vented during the balancing and the spool 136 is moved into its balance position shown, where the port 130 leading to the chamber 36 is isolated from both ports 128, 132 which may be coupled to pressure and exhaust respectively. Thereafter, any manual raising or lowering of the load changes the pressure in the hoist chamber 36 whereupon the spool 136 moves to appropriately connect the port 130 to air supply or exhaust ports 128, 132 to again balance the load in its new position. Further valves are provided on the controller 76 for a restricted venting of the chamber 36 to permit gravitational lowering of the load and for an unrestricted venting for rapid pay out of slack cable from the hoist.