Patent GB-993377-A (GB)
Title: Hydraulic suspension apparatus with damping device
IPC: F16F9/16
Filed: 1963-06-06
Abstract: 993,377. Hydro-pneumatic suspension devices. SFERMA SOC. FRANCAISE D'EUTRETIEN ET DE REPARATION DE MATERIEL AERONAUTIQUE. June 6, 1963 [June 12, 1962], No. 22579/63. Heading F2S. A hydro-pneumatic suspension device comprises a piston 1 in a cylinder 2 having a head 3 upon which is mounted a gas spring suspension unit 4, a reference pressure device 5 comprising another mass of gas imprisoned in a metal sphere 15, and an hydraulic device 6 for controlling the damping of the suspension. Ducts 17, 16 in the head 3, leading respectively from a chamber 7 above the piston 1 to the device 5 and from the latter to the damping device 6, are provided with constrictions 18, 19 which are preferably of regulatable cross-section to provide the desired time-constant characteristics. The body 20 of the damping device 6 is divided into three chambers 21, 22, 23 by two deformable diaphragms 25, 26 whose outer edges are fast with the body 1 and whose inner edges are secured to a cylindrical slide valve 27, the effective surface of the diaphragm 25 being greater than that of the diaphragm 26, and the three chambers 21, 22, 23 being subjected respectively to pressures P 1 , P 2 , P 3  of the chamber 7 and the devices 5, 4 through ducts 13, 14, 12 in the cylinder head 3. The slide valve assembly comprises a tubular part 41 on the ends of which are secured two diaphragm-clamping hub parts 42, 43 between which is interposed a tubular part 44. Slots 46, 47 formed in the ends of the two hubs 43, 42, which slide respectively in cylindrical bores 48, 49 in an end bearing-plate 36 and the body 20, constitute values for connecting the chambers 21, 23, respectively, with passages 63, 71 leading to a seatless valve device 58. Internal control elements of the slide valve 27 comprise an internal annular rib 51 on the tubular part 44 which co-operates with grooves 52 on a rod 53 fixed within the body 20 to regulate communication between the two end chambers 21, 23 through openings 55, 56 in the hubs 42, 43. The seatless valve 58 comprises two elastic diaphragms 61, 62 the diaphragm 61 controlling the passage of liquid from the chamber 21 through slots 46, the bore 48, the ducts 63, 64, annular space 65, holes 66, and past the diaphragm 61 to a duct 68 leading to the chamber 23. In a similar manner the diaphragm 62 controls the passage of liquid from the chamber 23 to the chamber 21. During moderate and relatively slow oscillatory movement of the suspended mass as the piston 1 is driven into the cylinder 2 the pressure P 1  in the cylinder chamber 7 rises relative to the reference pressure P 2  and the pressure P 3  in the suspension unit 4 so that the larger diaphragm 25 moves the slide valve 27 in the direction of the arrow f 1  to unmask the slots 46 and close the slots 47 liquid from the cylinder chamber 7 passing the diaphragm valve 61, into the chamber 23 and through the duct 12 into the suspension spring 4. The pressures P 1 , P 3  finally reach a common value which is greater than the reference pressure P 2 , the volume of. the intermediate chamber 22 being diminished When the piston 1 begins its return movement the pressure P 1  diminishes relative to P 3  whilst remaining greater than P 2 , the superior surface area of the diaphragm 25 over the diaphragm 26 reducing the restoring force of the suspension unit 4 in the direction f 1  to such a value that a slow flow of liquid through holes 56, 55 and the grooves 52 in the slide valve 27 takes place and the return movement to the position of rest is slowed down. Operation procedure past the diaphragm 62 and, in the reverse direction, through the slide valve 27 takes place when the piston 1 moves out of the cylinder 2. During rapid oscillations of the non-suspended mass the liquid passes from an end chamber 21 or 23 to the opposite chamber past a diaphragm valve 92, Fig. 4, which responds without inertia and is not sufficiently deformed by moderate forces to by-pass the inertia valve system 58. In a modification which operates in a generally similar manner, Fig. 5, not shown, the deformable diaphragms 25, 26 are replaced by coaxial, sliding pistons which are elastically pre-loaded by a helical spring, the communication duct between the intermediate chamber 22 and the reference pressure device including a calibrated restriction. Fig. 7 shows a device wherein a cylinder chamber 136 below a piston 133 is connected by a duct 147 to the chamber of a fourth piston added to the damping device of the kind described in respect of Fig. 5, not shown, a cylinder chamber 135 above the piston 133 communicating with the chamber 136 through slots 141 in a metering rod 138 and a port 142 in a hollow piston-rod 150 and also through a jet 140 in the piston 133. The chamber 136 communicates with an extra gas suspension unit 4a through a constriction 146. The suspension units 4, 4a operate in parallel when the piston 133 is displaced slowly within the cylinder 134, however when the piston moves rapidly the two suspension units act in opposition to provide a stiffening of the suspension.