Patent GB-453898-A (GB)
Title: Improvements in or relating to ratchet mechanism
IPC: B66F5/02
Filed: 1935-03-26
Abstract: 453,898. Ratchet gearing. LAKE & ELLIOTT, Ltd., Albion Works, Braintree, and BESWICK, R. E., Batsmead, White Notley, Witham, both in Essex. March 26, 1935, No. 9398. [Class 80 (iii)] [See also Group XXX] A lifting-jack has a rack or ratchet wheel adapted to be engaged by a retaining pawl and an engaging pawl, the latter being mounted on an operating lever, the said pawls being formed or provided with cams or the like extending rearwardly from their pivots and adapted to co - operate with pressure means carried by the operating lever whereby the movement of the rack or ratchet wheel may be reversed. A U-shaped frame 4 provides a support for a fulcrum 3 of a lever 2 and for a spindle 5 of a ratchet wheel 1. The frame 4 comprises part of a base consisting of a pair of members 6 secured to the frame and carrying an axle for wheels 8. On this axle are mounted a pair of links 9 fulcrumed at 10 to a member 11 carrying a crutch member 12 and extended rearwardly and curved upwardly and connected at 13 to the ratchet wheel. Driving and retaining pawls 15, 18 are pivoted at 14, 17 respectively to the lever 2 and frame 4, the pawls being loaded either by gravity or by springs 16, 19. Both pawls are formed with cam tail-pieces 20, 21 adapted to be engaged by a pressure member 22 which may be actuated by an auxiliary handle 23 mounted on the main handle 24 of the lever 2. This pressure member consists of a plunger 25, Fig. 3, formed with a pressure pad 22 adapted to engage the pawl tails, and slidable in a bracket 26 on the lever 2. The plunger is engaged by a closed end 27 of a tubular member 28 containing a coiled spring 29 having an abutment at one end within the tube and at its other end against the end of a rod 30 slidably mounted in member 28 and connected with the handle 23. The tail pieces 20, 21 may be halved, or one may be forked to receive the other. The lever 2 is maintained in its normal position by a spring 31. To rotate the wheel 1 in the forward direction, e.g. to raise a load, the lever 2 is oscillated, the pawls being kept in engagement by their springs. To obtain reverse movement, or lowering of the load, the handle 23 is gripped to press pad 22 against the pawl tails. If the load on the crutch is small, both pawls are thrown out and the crutch falls to its lowest position. If, however, the jack is loaded, depression of the pad 22 releases pawl 15 only, and if lever 2 is depressed, this pawl passes over the tooth it would normally engage. Further depression of the lever causes pad 22 to engage tail 21 of pawl 18 which, being heavily loaded, resists being moved, and pad 22 is forced back against spring 29 leaving pawl 15 free to engage a tooth, Fig. 7. Still further depression of the lever causes pawl 15 to engage a tooth, and the load is taken by this pawl thereby freeing pawl 18 which flies out under the action of spring 29 and the load is then carried entirely by lever 2. By raising this lever, the load is lowered until pad 22 again contacts with the tail 20 of pawl 15. This, being now heavily loaded, resists the action of pad 22 and forces the latter against spring 29 leaving pawl 18 free to engage the ratchet wheel. Still further upward movement of the lever causes pawl 18 to engage the wheel and take over the load leaving pawl 25 free to fly out of engagement under the action of spring 29, Fig. 11. These actions are repeated until the load reaches the ground and at this moment both pawls are forced out of action by pad 22 and the jack assumes its initial or fully lowered position. The mechanism may be applied otherwise than to jacks ; the lever 2 may be moved in a horizontal plane ; the pawls may engage a rack and the wheel or rack may move against a spring load.