GB153988A - Improvements in high speed jack - Google Patents

Abstract

153,988. Percival, S., (Duff Manufacturing Co.). Aug. 29, 1919. Jacks.-Relates to a rapid-action screw-jack. The ram 30, Fig. 3, is slidably but non-rotatably mounted in the standard 3 and is formed with a shoulder which rests on a nut 40. A quick-threaded screw 20 engages the nut 40 and is supported by a broad end-thrust ball-bearing 21. The screw 20 is connected by gears 26, 49 to a vertical shaft 46 which is connected by bevel-gears to an horizontal shaft 52 turned through ratchet mechanism 53, 54, Fig. 2, by raising and depressing the handle 57. A ratchet-wheel 58 secured to the shaft 46 is engaged successively by a series of pawls 64 mounted in a member 60 free on the shaft which is formed with a worm-wheel 69 on its upper part. A worm 70 formed on a shaft 71 engages the worm-wheel and prevents the lowering of the ram when supporting a load unless the shaft 71 is turned by the handle 77. When the shaft is turned in the opposite direction, the ram is raised rapidly. When the jack is not loaded, the ram is lowered by coupling the member 60 and shaft 46 by a clutch collar 84 and then actuating the handle 77. The collar and member 60 are normally separated by a spring and are engaged by depressing the button 95. The jack is mounted on wheels 7 and can be wheeled about by disengaging the handle 57 from the ratchet mechanism and engaging it with sockets 102, 103, Fig. 1. Carrying- handles 105 are also provided. When the ram has been raised to the limit of safety, it is engaged by the nose of a dog 107 pivoted on the casing. Further movement of the ram breaks the connexion between the dog and the casing, and the fall of the dog warns the operator. The casing is closed so that the whole of the mechanism may work in a mass of grease.