GB554947A - Improvements in or relating to liquid damped telescopic shock absorbing struts - Google Patents

Abstract

554,947. Shock absorbers. AUTOMOTIVE PRODUCTS CO., Ltd., and FOSTER, S. Feb. 18, 1942, No. 2193. [Class 108 (iii)] A fluid-damped teles. copic shock-absorbing strut is of the kind comprising a cylinder 10 in which slides a tubular plunger 14 having at its inner end an annular pis. ton 18, a stem 20 carried by the cylinder 10 and extending axially through the piston 18 into the interior of the plunger 14, a recoildamping piston 28 on the free end of the stem 20 and forming a slidable partition dividing the plunger space into a recoil chamber 31 and a plunger chamber 32, damping liquid which fills the cylinder 10 the recoil chamber 31, and part of the plunger chamber 32, and resilient means for bearing the axial load on the shock absorber by urging the plunger in a direction out of the cylinder, the recoildamping piston 28 being arranged to trap liquid between it and the piston 18 during lengthening of the device so as to retard the recoil movement. The resilient axial load-bearing means consists of air in the space 33 between a piston 30 slidable in the plunger 14 and having its upper surface in contact with the liquid in the upper part of the chamber 32. The stem 20 may be furnished with a rib or ribs 21 which prevent it from rotating relatively to the piston 18 through which it can slide to an extent determined by a head 24 on a spigot 23 depending from the cover 11 of the cylinder 10. A spring 26 within the stem 20 bears against the head 24 and against a flange 27 near the lower end to tend to keep the piston 28 down, and a valve 42 slidable in the bottom end of the stem 20 has a head 46 which can close a coned orifice 47 in the piston 28. The plunger 14 carries at its lower end forks 17 between which are journalled a ground wheel, and this is allowed a castoring action by the rotatory mounting of the plunger 14 in the piston 10, this being biased, however, by wave-form contacting surfaces between the head 24 and the cover 22 of the stem 20. Turning of the ground wheel causes, through the ribs 21, a corresponding movement of the stem 20, with rise thereof and compression of the spring 26. Openings at 50 and 51 permit charging with liquid and compressed air respectively. A ring valve 37 can close ducts 38 in the piston 18, but bleed valves 39 give constant connection therethrough. Sudden upward pressure on the plunger 14 is taken up first by the air in chamber 33, and transmitted through the piston 30 to the liquid in chamber 32. The orifice 47 is opened by reason of the larger diameter of the piston head 45 of the valve 42. The liquid then passes through the valve 42 by way of a restricted passage 44, by way of the stem 20 and the spigot 23 from the cylinder chamber 34, and it is transferred to the plunger chamber 31 by way of the ducts 38, 39. Passages 49 connect the chambers 31, 32. The rebound due to the increased air pressure is, however, damped by the reversely flowing liquid causing the ring 37 to close the ducts 38 and permit of slow flow only, by way of the ducts 39. Three modified forms of the valve 42 and its co-acting adjacent parts are described, and in all forms a non-castoring wheel may be fitted.