GB1151295A - Sheave and Drive Assembly - Google Patents

Abstract

1,151,295. Fluid pressure apparatus acting through cables. JERED INDUSTRIES Inc. 19 Sept., 1967, No. 42537/67. Heading B8B. [Also in Division F2] An arrangement for raising and lowering an elevator platform 446 comprises two sets of sheaves 52, 84 and 338, 390 movable relatively to each other by an hydraulic piston and cylinder arrangement 16, such that cables extending from a framework anchorage 202, 436 and passing around both sets of sheaves and further guide sheaves to opposite ends of the platform, move the latter at twice the velocity of the piston. The sheave 52 which rotates about a fixed axis, comprises a drum, mounted adjacent each axial end thereof on a roller bearing engaging the external periphery of the drum and cable grooves are provided in the drum adjacent each bearing. The sheave 84 comprises a grooved ring which is roller mounted on the exterior of the sheave 52 intermediate its axial ends. The interior of the sheave drum 52 houses an epicyclic gear unit comprising a sun gear driven at constant speed by an hydrostatic motor, an annular gear rigid with the drum 52 and a planet gear carrier mechanically coupled through a rack- and-pinion and linkage to a control valve for a pressurized fluid supply to the piston and cylinder arrangement 16. Any deviation from a pre-determined velocity of the sheave 52, at which the planet carrier remains stationary, causes the carrier to rotate and therefore adjust the fluid supply to the cylinder 16. Torque limit slip clutches are provided at the input and output of the epicyclic unit. The set of sheaves 338, 390 is arranged in similar fashion to the set 52, 84, the external roller bearings on the sheave drum 338 being received in a frame which is connected to the piston-rod of the cylinder arrangement 16, for movement therewith. Movement of the axis of the sheave set 338, 390 is facilitated by wheels mounted at the ends of the drum 338 for engagement with tracks. Cams on the frame associated with the sheaves 338, 390 engage levers as either end of the piston stroke is approached, which levers move the fluid supply valve into a neutral position whereby the piston in cylinder 16 comes to a halt. A safety limit switch is provided at each end of the piston stroke, which switches cause stoppage of the motor driving the epicyclic gear unit whereby the fluid supply valve is held in a fixed position. The movable sheave assembly is stabilized by track-engaging wheels on the frame.