GB570609A - Improvements in or relating to hydraulic jacks particularly applicable to vehicle-body tipping mechanism - Google Patents

Abstract

570,609. Hydraulic apparatus. HOULDSWORTH, R. Dec. 1, 1943, No. 20082. [Class 69 (ii)] [Also in Group XXX] A telescopic hydraulic jack for road vehicle tipping gear or operating aircraft undercarriages &c., operates a pressure-relief valve automatically by a supplementary movement at the end of its stroke, whereby excess pressure fluid is returned to the reservoir. Pressure fluid supplied by a pump from a reservoir 5 through passages 7b, 4c moves the rams 2, 1 in succession, until, near the limit of extension, a partial sleeve 16, normally spring pressed against the end of ram 1, engages a stop 18. Continued actuation of the pump moves the ram 1 against the action of spring 28 until ports 1a therein communicate with the ports in the sleeve 16 and place the pressure chamber into communication with the interior of the ram, and thence, through a pipe 27 and passages 20c, 3a, with the reservoir 5. A non- return valve may be provided in the pressure supply ; and a hand-operated release valve 11 controls a connection between the suction and pressure conduits. Trunnions 8 are provided for mounting on the vehicle. In an alternative form, the pressure-relief valve 37 is mounted at the lower end of a ram 36 working in a fixed cylinder 35 and having a head 39 forming a guide and stop for a second ram 40 surrounding the cylinder 35. Pressure is supplied to the ram 40 through pipes 54, and the interior of ram 36 is connected to the reservoir 43 through a pipe 53. Trunnions 34 and a spherical member 42 on the ram 40 provide connections for the vehicle chassis and body respectively.