GB739133A - Improvements in and relating to hydraulic shock-absorbers - Google Patents

Abstract

739,133. Hydraulic shock-absorbers. BENARD, L. Oct. 6, 1953 [Oct. 13, 1952; Sept. 15, 1953], No. 27444/53. Class 108 (3). The invention relates to hydraulic shock - absorbers of the type comprising a piston 44 sliding in a cylinder 1, and having an annular flow-restriction passage 52, formed between a portion of the piston, and a member 53 slidably mounted between two opposing springs 58, 59. According to the invention, the annular passage 52 is formed by an internal flange 48 on the body of the piston 44, and a flange 51 on the member 53, washers 55, 56 being disposed between the flanges 48, 51, and the springs 58, 59, and having apertures 57 in front of the passage 52. The piston comprises an annular member 44 held between members 41 and 42 which are secured rigidly to the piston-rod 8. The flange 51 is normally aligned with the flange 48 by the action of the washers 55, 56 and springs 58 and 59. The passage 52 normally provides damping, but on excessive load, one or other spring is deflected, and the flange 51 moves axially to increase the passage area. The spring 59 is stronger than the spring 58. The flange 51 may be of nylon, or of a material known by the Registered Trade Mark " Zamac." The piston member 44 is of a material having a lower coefficient of expansion such as sintered iron. This is to avoid a reduction in damping due to temperature change. Both of the peripheral edges of the flange 48 are chamfered, but only the upper edge of the flange 51 is chamfered. Damping is also provided by a 1 mm. clearance between the piston and the wall of the cylinder 1. An annular recess 64 in the piston is to prevent emulsification of the working liquid. The apertures 57 in the washers 55, 56 may also contribute to the damping. Flow into a reserve space 20 is controlled by a piston valve 34. Flow back into the cylinder from the space 20 occurs through a valve 28, and emulsification is prevented by baffles 23, 29.