GB190427921A - Certain Improvements in Pulley Blocks Hoists and the like. - Google Patents

Abstract

27,921. Holt, J., [trading as Holt & Willetts], Dec. 20. Pulley-blocks and lifting-tackle; hoists; brakes. -Self-sustaining mechanism for pulley-blocks, hoists, and the like, of thetype in which the lifting- chain works over a sprocket-wheel and is actuated by wheel-and-pinion lifting-gear to raise a load at either end of the chain, comprises a sleeve mounted on the operating-shaft and capable of combined longitudinal and partial rotary motion in either direction, thereby gripping one or other of two loosely-mounted ratchet-wheels, each engaging pawls for sustaining the load lifted in one direction. Fig. 1 shows the apparatus applied to a pulley-block actuated by a hand chain-wheel 2 mounted on a sleeve 4 of the shaft 1. This shaft has a flange 14 and carries a pinion 3, which is preferably formed solid with the shaft 2 and gears with the hoisting-wheel. The sleeve 4 has an internal screw thread 6 at one end, engaging a similar thread on the shaft 1, and also a pair of slots 18, 19 having the same inclination as the screw threads. A pin 17 engages the slots and connects the shaft 1 to the boss of a second sleeve 15 prevented from endways motion by bearings on the frame 12. When the hand-wheel 2 is operated, relative endways and rotary motion, limited by the pin 17, takes place between the sleeve 4 and shaft 1, and the flange 13 on the sleeve grips one or other of two ratchet-wheels 7, 8 which then sustain the load by engaging pawls 9, 10 on a shaft 11. Each ratchet-wheel sustains the load in one direction, and the load may be lowered by pulling the hand-chain in the direction required and obtaining slipping friction between the ratchet-wheels and the gripping-flanges. The mechanism may be used on pulley-blocks operated by turning a handle.