GB1374587A - Hydropneumatic impact absorptive device - Google Patents

Abstract

1374587 Hydropneumatic shock-absorbers NISSAN MOTOR CO Ltd and ATSUGI MOTOR PARTS CO Ltd 23 Nov 1971 [26 Dec 1970] 54330/71 Heading F2S A shock absorber, e.g. for use with a fender 50 such as a motor vehicle bumper has a piston 36 slidable in a cylinder 16 (the "cylinders" herein need not be of circular section) with a one-way valve 42 in an end wall and a row of apertures 38 extending its whole length and immersed in liquid such as oil in the cylinder 16 and in an outer cylinder 10, there also being gas 26, such as nitrogen, under superatmospheric pressure, either in a compartment divided from the liquid compartment 24 by a movable partition such as a bellows, diaphragm or floating piston 30, or in intercommunicating upper portions of the cylinders 10 and 16, Fig. 2 (not shown), unseparated from the liquid which immerses the apertures 38 (which in such embodiment are in the lower portion of the inner cylinder wall). In these embodiments, the piston-rod 46 carries the fender 50 and the cylinder 10 is secured to a main structure such as a motor vehicle body. In a third embodiment, Fig. 3 (not shown), the outer cylinder (10) carries the fender and the piston-rod (46) is secured to a main structure together with a sleeve (54) in which the outer cylinder (10) telescopes so that the device is stiffened against bending. A resilient sleeve (56) covers some of the apertures (38) which are thus open only at high liquid pressure. The shock absorber may have a floating piston (30) as in Fig. 1, or the liquid and gas may be unseparated as in Fig. 2. In all the embodiments, impact on the fender 50 causes liquid to pass out of the inner cylinder chamber 22 to find its way back in behind the piston 36 through an aperture 38<SP>1</SP>. Build up of pressure in the compartment 24 acts, e.g. on the movable partition 30, to compress the gas 26 which thus causes the return of the piston 36 after the impact. When the pressure in the inner chamber 22 reaches a certain level, e.g. as a result of abnormal impact, the check valve 42 is opened to release liquid into the compartment 24. In Figs. 1 and 2, the valve 42 is a pliable plate. In Fig. 3, the valve (42<SP>1</SP>) is a plate loaded by Belleville washers.