GB186191A - Improvements in lifting jacks - Google Patents

Abstract

186,191. Coryell, J. July 8, 1921. Screw-and-nut mechanism.-In screw jacks comprising two telescoping oppositely-threaded screws 18, 20, selectively operating mechanism is placed between the casing 10 and screw 18 and between the screws 18, 20 which can be set to cause the jack either to raise or lower continuously with successive reciprocations of the handle 28. Plates 40, 48 slidably but non-rotatably mounted on the screws 18, 20, respectively, are provided on their undersurface with two rings of oppositely-disposed ratchet teeth 42, 54 and 52, 76, respectively. The teeth 42, 52 are oppositely-disposed and can be engaged with teeth 32, 38 formed on the top of the casing 10 and on a collar 36 rigidly secured to the top of the screw 18. The teeth 54, 76 are also oppositely-disposed and can be engaged with teeth 58, 74 on ratchet rings 56, 72. Each ring has a series of cam slots similar to the slot 60, Fig. 7, in the ring 56 which is entered by pins 62 attached to the inside of the casing 64. Between the slots 60 are vertical slots 66 through which pass pins 68 fixed to the casing 10. The outer end of each pin 68 is within an horizontal slot 70 formed in the casing 64 and having locking notches at each end. When the casing 64 is rotated, one of the sets of teeth 54, 58; 42, 32 is engaged and the other disengaged. A similar casing 80 is provided for the actuation of the upper sets of ratchet teeth.