Patent GB-509191-A (GB)
Title: Improvements in hydraulic shock absorbers
IPC: F16F9/348
Filed: 1938-07-08
Abstract: 509,191. Hydraulic shock-absorbers. GENERAL MOTORS CORPORATION. July 8, 1938, No. 20255. Convention date, July 29, 1937. [Class 108 (iii)] In a hydraulic shock-absorber of the direct-acting, piston-and-cylinder type having a fluid reservoir 52 connected to the cylinder 20 by a valve-controlled port 55, the valve comprises a flat resilient disc-member movable bodily and without flexing to permit a substantially unrestricted flow of fluid in one direction through the port and adapted to be flexed by fluid pressure to permit a restricted flow of fluid in the opposite direction. The shockabsorber shown comprises a piston 90 slidable in the inner of a pair of concentric relatively-fixed cylinders 20, 40, the annular space between which constitutes the fluid reservoir 52, flow of fluid from one side to the other of the piston and between the reservoir and cylinder 20, through the port 55 in a fixed member 50, being controlled by valve devices provided respectively on the piston and at the lower end of the cylinder 20. The lower valve device comprises a rigid backing- plate 120 having a number of radially-extending fingers 121, Fig. 13, and formed on the bottom with two coaxial grooves 123, 124 providing annular ridges 125, 126, the inner ridge being apertured for the fixed connection thereto of a stud 122. Normally, the ridges 125, 126 and surfaces 130 on the plate fingers 121 are engaged by a flat resilient disc-valve 131 having a central aperture 132 of greater diameter than that of the stud 122 and a notch communicating with the aperture and providing a constant fluid leak orifice. A second disc-valve 135 is arranged below the valve 131, the valves being pressed against the plate 120 by a heavy spring 137 bearing on an abutment 138 on the stud 122. The entire valve device normally is urged by a spring 140 upon the annular valve-seat 56 surrounding the port 55, so that the device may be lifted as a unit against the action of the spring 140, the lifting movement being limited by a spring clip 141 fitting into an inner groove in the member 50. The piston valve device comprises on top of the piston a backing-plate 72 fixed to the piston-rod 35 and containing a number of holes 76, resilient discs 77, 81 having radiallyextending fingers held in superposed relationship by a pin 82 on the plate 72, and a flexible disc-valve 85, Fig. 8, having two arcuate slots 87 adapted to be pressed by the discs 77, 81 against ridges 94, 95, 96 on the piston. On the underside of the piston ridges 102, 103 normally are engaged by a resilient disc-valve 106 which may have a peripheral, fluid-leak orifice and is engaged by a second disc 109 supported by a backing-plate 108, the discs and plate being clamped centrally on the piston-rod by a nut 110. The discs are also urged on the ridge 103, which forms a valve-seat, by a spring 112 acting between a pressure plate 113 and a flange on the nut 110. In operation, on downward movement of the piston 90, fluid in the chamber 70 passes substantially freely to the chamber 60 through piston passages 105, lifting the disc-valve 85. Owing to the entry of the piston-rod into the cylinder 20, some fluid is also forced between the radial fingers 121 of the backing-plate 120, through the orifice in the disc-valve 131, and openings in the end member 50 to the reservoir 52. If the orifice in the valve 131 cannot relieve the pressure, the discs 131, 135 are flexed about the valve-seat 56 away from the valve-seat 126, thus permitting an increased flow of fluid to the reservoir. On upward movement of the piston, the entire valve device at the lower end of the cylinder lifts bodily to permit unrestricted flow of fluid from the reservoir into the chamber 70. Simultaneously, fluid is forced from the chamber 60 to the chamber 70 through the arcuate slots 87 in the piston disc-valve 85 and inner piston passages 104, an initial flow being established through the orifice in the disc 106. If the pressure is excessive, the disc-valves 106, 109 are flexed away from the valve seat 103 permitting increased flow through the piston. The disc-valves are not initially flexed and therefore normally do not in themselves exert any appreciable pressure on the valve-seats. Instead of a plurality of disc valves, a single disc-valve may be used in each valve device. When applied to a vehicle, the shock-absorber is connected directly between the frame and axle in an inclined position and in order to indicate the exact position of a spring-pressed air-bleed valve 28 provided in the member 21 closing the upper ends of the cylinders 20, 40 an offset portion 41 of the cylinder 40 is adapted on assembling the shock-absorber to engage a notch 32 in the member 21. A dust-cover 48 is attached to a disc 36 secured to the piston-rod 35 and a perforated baffle-plate 58 prevents agitation and consequent emulsification of the fluid in the reservoir.