Patent GB-1085301-A (GB)
Title: Hydropneumatic telescopic strut
IPC: B60G17/044
Filed: 1965-01-15
Abstract: 1,085,301. Hydropneumatic struts. STABILUS INDUSTRIEUND HANDELSGESELLSCHAFT m.b.H. Jan. 15, 1965 [Jan. 16, 1964; Nov. 21, 1964], No. 1952/65. Heading F2S. In a self-levelling hydropneumatic strut an upward stroke of a pump plunger 6, due to a spring 12, sucks liquid from an annular reservoir 27 through a valve 14 intc a pump cylinder 3 from which it is expelled, during a compression stroke of the plunger 6 as a damper piston 19 and rod 18 descends past the edges of a packing ring 11 and through pass ages 9, 7, 8 in the head of the plunger 6 and through a port 16 in the upper end of the cylinder 3 into a working cylinder 2. After the pressure in the work ing cylinder 2 has been increased to match the weight of the load the force of the plunger return spring 12 is not sufficient to raise the plunger 6. Removal of the load causes the piston rod 18 to be thrust out of the strut unti the damping piston 19 lifts an actuator 29 of a valve 31 so that excess pressure fluid is spilled into the reservoir. In a modification, Fig. 2 (not shown), the oil and gas of the pressure media are separated from one another by a movable piston (33) in the working cylinder (2). In both of the arrangements according to Figs. 1 and 2 pipes can be located in the base of the strut communicating respectively with the lower ends of the reservoir and the working cylinder for connection to corresponding chambers of a further strut. In a further modification, Fig. 5 (not shown), a plunger (6) fixed to the piston rod 18, pumps fluid into the working cylinder during the time that a larger diameter plunger portion sealingly traverses a guide (61) at the top of a pump cylinder fixed to the base of the strut. Extension of the unit is limited when the damper piston (19) trips a valve (44). An annular wall divides the space between the inner and outer cylinders. In another embodiment, Fig. 6 (not shown), a tubular differential plunger (6), fixed to the base of the strut and in communication with the reservoir, extends through a guide (52) in the damper piston (19), and into a hollow piston rod (18) which acts as a pump cylinder, a tubular valve (53), slidable within the plunger (6) and controlled by a tension spring (54), co-operating with the damper piston guide (52) to exhaust excess pressure fluid as the result of a reduced load. The strut includes an annular separating ring (64) the liquid and gas media being separated by a resilient tube (62). In another arrangement, Fig. 7 (not shown), a pump cylinder (69) with a suction valve (70) is enclosed by a further cylinder (67) leaving an annular space (68), a differential plunger (75), fixed to the piston rod (74), co-operating with two resilient guides (71), (72) at the upper ends of the cylinders (67), (69) and a passage (73) between these two guides leading from the inside of the inner cylinder (69) to the annular space (68). Pumping to the space (66) is by way of valves (70), (78) and passages (73), (76) pressure relief being obtained when the larger diameter portion of the plunger leaves the guide (71) the pumped pressure medium then flowing back to the supply chamber (93) through the passage (73) and the gap (68).