Patent GB-1043273-A (GB)
Title: Hydraulic elevator control system
IPC: B66F3/42
Filed: 1963-06-04
Abstract: 1,043,273. Hydraulic lifts. BATOR A.G. June 4, 1963 [June 6, 1962], No. 22113/63. Heading B8L. [Also in Division F1] A control system for an hydraulic lift in which a car-moving ram 3 is fed from a pump 27 through a main control valve 7, 8 has a differential by-pass valve comprising a piston 22 movable in a cylinder 23, 24 which is connected at its upper end through a three-way solenoid valve 40 to a conduit 4 leading to the ram cylinder 3 or to a return conduit 26, and at its lower end to a pressure chamber 29 and is provided with an opening 25 leading to the return conduit 26. The relationship between the effective areas of piston 22 is such that the piston is raised from the position shown when the pump pressure exceeds, in a fixed ratio, the pressure in the cylinder 24. The main control valve comprises a piston 8 which is slidable in a conical bore 7 and which is secured to a piston 11 in a cylinder 10. In operation, initially the valve 7, 8 is retained in the closed position by pressure in the cylinder 10, which communicates through a regulating valve 31 and a three-way solenoid valve 32 with the cylinder 3. On starting the pump, with the valve 40 in the position shown, the piston 22 of the differential valve rises and allows free circulation through the opening 25 to the return conduit 26. Automatic change-over of the pump motor from start circuit to lift circuit causes the valve 40 to be reversed to connect cylinder 24 with the cylinder 3, thereby causing the piston 22 to drop. Valve 32 and a valve 36, connecting the bottom of cylinder 10 with the cylinder 3 or return conduit 26, are then reversed, thereby connecting the bottom of the cylinder 10 to the cylinder 3 and causing the pistons 11, 8 to rise at a rate determined by the regulating valve 31. As the piston 8 rises, pressure fluid passes from the chamber 29 into the bore 7 at an accelerating rate and through an opening 5 into the conduit 4 leading to the cylinder 3, thereby causing the lift to accelerate progressively. As the lift approaches its required level, the valves 32, 36 are returned to the positions shown, thereby causing the pistons 8, 11 to be lowered, so that the lift decelerates, until a lug 14 secured to a piston-rod 12 on the piston 11 actuates a micro-switch 16, thereby closing a valve 43 which stops the descent of pistons 8, 11 and allows the lift to continue to rise at a slower rate. When the lift reaches required level, the valve 43 is opened to allow the piston 8 to drop to its closed position to half the lift. If an excess pressure develops in the chamber- 29, a valve 17 opens against the action of a spring 18 and allows the fluid to pass to a return conduit 21. If the lift settles because of leakage so that it is not supported by the ram piston, although the differential valve will be fully open, the pressure fluid from the pump impinges directly on the lower face of the piston 8 and opens the valve sufficiently to allow the pressure to build up gradually to close the differential valve. The piston 22 of the differential valve may be replaced by a membrane controlling a suitable valve in dependence upon the pressure difference between the pressure chamber 29 and the ram cylinder 3.