ES317977A1 - Safety lock for use in connection with hoisting appliances - Google Patents

Abstract

A safety lock for preventing the unintentional lowering of a load on a driven cable drum shaft 5 comprises a freewheel arrangement 1, 13, 3 which blocks in the lowering direction, the movable part 3 of which is connectible through an automatically operated friction clutch 14, 16 to a reversible drive motor shaft 8 when the load tends to either rotate the shaft 5 in the lowering direction or to rotate the shaft more rapidly than corresponds to the lowering rotational speed of the shaft 8. The clutch comprises friction discs 14, 16 secured to the movable part 3 of the freewheel and the driven shaft 5 respectively, the discs being pressed into engagement with each other by a sleeve 6 threaded on end 4 of the shaft 5 for axial movement therealong upon relative rotation between shaft 5 and the sleeve 6. The latter has its axial movement limited by a stop ring 7 and a thrust plate 18 adjacent the friction discs, and is coupled to the drive shaft 8 through axially yieldable buffers 21. The outer race 1 of the spring pawl and ratchet-type freewheel 1, 13, 3 is keyed to a stationary easing 10. In operation, when a load tends to rotate shaft 5 in the lowering direction, the section 4 is screwed into the sleeve 6 until the latter compresses the friction discs, whereupon shaft 5 becomes coupled to the freewheel part 3 which is blocked in the lowering direction. The same sequence occurs when a load being lowered by drive shaft 8 rotating in the lowering direction, tends to rotate the shaft 5 faster than that of the shaft 8.