GB1023177A - Improvements relating to apparatus for positioning heavy loads - Google Patents

Abstract

1,023,177. Hydraulic jacks. M. L. AVIATION CO. Ltd. May 4, 1964 [Feb. 7, 1963], No. 729/63. Headings B8H and B8J. A self-contained hydraulic hoist for positioning heavy loads comprises an inner cylinder 1 with a closed lower end to which a load hook 16, Fig. 4 (not shown), is attached and an open upper end with a flange 4 slidingly sealed to an outer cylinder 2. The outer cylinder 2 is closed at the top by a block 13 carrying an eye 14 for a crane hook (not shown) and is sealed to the inner cylinder 1 by a sealing ring 3 through which the inner cylinder 1 slides. The space within the outer cylinder 2 is thus divided into two: a part 6 above and within the inner cylinder 1 and an annular part 7 between the two cylinders 1, 2. The inner cylinder 1 has a separating cylinder 8 sliding within it and sealed by seals 10, 11. Practically constant pressure is maintained on hydraulic fluid in the space 6 by a device comprising springs 43, 44 and a tube 46. To raise a load a lever 23, Fig. 2 (not shown) is used to actuate a double-action pump with a cylinder 18 and a piston 17 to force fluid from the space 6 to the annular space 7. Fine control is achieved by a single-acting smaller pump actuated by a lever 28 operating on a piston 26 sliding in a cylinder 27 formed by a hole in one end of the cylinder 18. A release valve 32, Fig. 1 (not shown) operated by a handle 31 is spring- loaded into a closed position and may be opened by a cam 34 to allow fluid to flow from the annular space 7 to the space 6. A safety valve 42 allows recirculation of fluid to the space 6 under overload conditions. A gauge 49 measures the fluid pressure in the annular space 7 and is calibrated to read directly the load on the hook 16.