GB294774A - Improvements in or relating to lifting jacks - Google Patents

Abstract

294,774. Powell, A. D., and Bradbury &. Sons, Ltd., J. Aug. 4, 1927. Jacks. - A lever jack operated by ratchet and screw-and-nut mechanism has the screw adapted to permit the crutch to be rapidly adjusted to the load. The frame A has side plates B, to which the lifting lever D is pivoted, the crutch E being mounted at one end of the lever D and a parallel motion link D<1>. An extension D<2> of the lever has at its end a trunnion F, Fig. 3. A vertical screw G passes freely through the trunnion F and through a second trunnion H mounted in the frame and is anchored to the trunnion H by collars I, the lower collar having a friction disc J. A handle O can be inserted in a pivoted socket N and rocked so as to rotate by means of a pawl P a ratchet wheel P<1> formed on a bevel wheel M engaging with a nut L on the screw. In operation, the handle O is inserted in a socket W on the base and the jack positioned under the load. The crutch is then rapidly adjusted to the load by rotating the handle Q on the screw G, the nut L being held against rotation by friction pads S, Fig. 5, held by clamps R so that the trunnion end of the lever is depressed and the crutch raised into contact with the load. Further rotation of the handle Q causes the friction disc J to be pressed against the lower trunnion, so preventing further rotation of the screw. The handle O is now engaged in the socket N and rocked to rotate the nut L which traverses the screw and raises the load.