GB1030717A - Improvements in or relating to two-stage fluid pressure operated piston and cylinderassemblies - Google Patents

Abstract

1,030,717. Hydraulic jacks. DECCA Ltd. Aug. 26, 1964 [Sept. 17, 1963], No. 36583/63. Heading B8J. [Also in Division F1] In a two-stage double-acting telescopic piston and cylinder assembly wherein an inner piston 15 is slidable in a movable cylinder 14 having an outer piston 13 slidable in a fixed outer cylinder 12, the outer piston 13 is provided with a spring-loaded valve 23 opened by a plunger 32 when the cylinder 14 is in its fully extended position to allow fluid trapped in the inner cylinder 14 to be exhausted, whereby the inner piston 15 can thereafter move to its extended position. To extend the assembly pressure fluid is supplied to a port 30 whereby the pistons 13, 15 move together to a position in which the valve 23 is opened by an abutment 34 whereafter the inner piston 15 moves to its extended position, the fluid in the cylinder 14 exhausting through a port 19 in the cylinder 14, an annular chamber 20, the valve 23, a port 25 in the outer cylinder 12, and an annular passage 26 connected to a port 28. To contract the assembly fluid is supplied to the port 28 and exhausted from the port 30, the valve 23 being opened by the pressure of the fluid entering the outer cylinder 12 to retract the inner piston 15 followed by the outer piston 13 which is initially prevented from moving by catches 36 engaging an annular recess 37 in a member 21 secured to the piston 13.