Patent GB-573275-A (GB)
Title: Improvements in or relating to telescopic suspension devices for vehicles
IPC: F16F9/49
Filed: 1943-09-02
Abstract: 573,275. Shock-absorbing suspensions. RIBBESFORD CO., Ltd., and THORNHILL, P. W. Sept. 2, 1943, No. 14378. [Class 108 (iii)] Relates to a telescopic suspension device for vehicles and the undercarriages of aircraft in which a plunger 14 having a piston-head 16 is slidable through packing 13 at the lower end of a cylinder 10, the diameter of the plunger being such that an annular working chamber 22 containing compressed gas is formed within the cylinder between the packing and the pistonhead, a damping valve 19 being interposed between the cylinder working space 20 and the chamber 22 and snubbing valve means being provided for isolating the chamber from the cylinder space 20 when the suspension device is extended beyond a predetermined length. According to the invention, the snubbing valve means closes independently of the damping valve 19 to seal the chamber 22 when the predetermined length of the device is exceeded. The pneumatic suspension device shown 'in Figs. 1, 2 has a damping valve 19 such as described in Specification 570,813 controlling flow of fluid between the cylinder space 20 and passages 21 leading into the annular chamber 22. The snubbing means which acts during recoil following an exceptionally strong shock, is provided in the chamber 22 and comprises a spring-supported triangular-section ring 26 of flexible material having an inwardly-facing frusto-conical surface 27 which is engaged by a similar surface 28 on the piston-head 16 when the device exceeds the predetermined length. On further extension of the device, owing to the resistance of the spring 29, the upper part of the ring 26 is caused by the surface 28 to stretch outwardly until it engages the cylinder 10 in a fluid-tight manner, thus sealing the chamber 22 so that the fluid therein is compressed with the spring during the latter part of the recoil stroke. In a modification, the ring 26 is replaced by a rigid ring slidable in a lower enlarged portion of the cylinder 10 and formed with a frusto-conical surface for engagement with the surface 28. In another construction, Fig. 4, a lip 37 is formed on the piston-head 16 below the passages 21 from the damping valve 19 and is adapted to engage in a fluid-tight manner with a flexible ring 38 supported by a spring 29 in the chamber 22. Downwardly-inclined resilient tongues or fingers 43 extend from a stamping 42 held in position on the piston-head so that when the ring 38 is engaged by the lip 37 on extension of the device, the tongues 43 are deflected upwardly and the chamber 22 is closed. During the succeeding compression stroke, as the spring 29 resumes its normal length, the tongues 43 lightly press the ring 38 away from the lip 37 enabling the piston-head to leave the ring 38 behind. In a modification, a resilient annular valve member secured to the plunger is adapted to engage in a fluid-tight manner with a spring- supported washer in the chamber 22. Fig. 6 shows another construction in which a spring- pressed sleeve 47 slidable on the plunger 14 is moved to close passages 21 leading from the chamber 22.when it engages a spring-supported washer 41 in the chamber. As lubricating liquid sometimes accumulates in the chamber 22, an auxiliary space may be provided in which gas is compressed when the snubbing device is operative. Thus, in Fig. 2, the piston head 16 is formed with a wide circumferential groove 51 producing an auxiliary space 52 which is in permanent communication with the chamber 22 through one or more holes 53 in the plunger 14. The invention may be applied to suspension devices employing liquid as the damping medium in which case the annular working space is placed in communication with the usual compressed gas chamber.