Patent GB-570813-A (GB)
Title: Improvements in or relating to suspension devices for vehicles
IPC: F16F9/516
Filed: 1943-09-02
Abstract: 570,813. Vehicle suspension devices. RIBBESFORD CO., Ltd., and THORNHILL, P. W. Sept. 2, 1943, No. 14375. [Class 108 (iii)] A suspension device for a vehicle comprises a pair of relatively movable elements 10, 13, Fig. 1, adapted to be attached between the vehicle body and a vehicle wheel or similar parts, and defining a first variable volume space 17 containing gas under pressure, a second gas space 18 the volume of which changes simultaneously with, but oppositely to, the volume of the first space, a damping valve 30 adapted to connect the two spaces, and an auxiliary chamber having restricted communication with the first space 17 and bounded by a control piston which is acted on by gas within the auxiliary chamber and regulates the passage of gas through the damping valve during recoil movements of the elements. The device shown in Fig. 1 consists of a cylinder 10 closed at its upper end by a cap 11 integral with a securing lug 12 and fitted with an air inlet valve 29, and a plunger 13 having a piston head 19 slidable in the cylinder and a stem 14 slidable in a packing gland 15 at the lower end of the cylinder. The other securing lug 21 is formed with an axial spigot 22 fitting into the lower end of the stem 14 and held in position by a tension rod 23 which is threaded at its upper end 25 into an extension 24 of the piston head 19. A dirtexcluding, tubular, extensible boot 26 is secured at points 27, 28 respectively to the cylinder and plunger. Figs. 2, 3 show the positions taken by the damping valve 30 during shortening of the device and during the recoil extension stroke respectively. The damping valve comprises a hollow cylindrical piston valve 32 slidable in a bore 33 in the piston head and containing a constricted passage 35 in permanent communication with the space 17. The auxiliary chamber 37 is formed between the valve 32 and the lower end of the bore 33 and, when the device is stable, the pressure within the chamber is equal to that in the space 17. An annular groove 40 in the valve 32 is in permanent communication with radial passages 41 leading into a circumferential groove 42 formed in the piston head to accommodate a packing ring 20 which is movable axially in the groove and is constituted by an outer rubber &c. annulus 43 and an inner, outwardly-expanding metal ring 44. A clearance space around the periphery of the piston head allows flow of fluid from either of the spaces 17, 18 into the groove 42 or axial passages or grooves may be formed in the piston head for this purpose. In operation, when the vehicle is stationary or travelling on a smooth road, the load is supported by the fluid pressure in the space 17. On compression of the device, the increasing pressure in the space 17 presses down the piston valve 32 against the pressure in the auxiliary chamber 37 and simultaneously the packing ring 20 is forced into the position shown in Fig. 2. Fluid then flows freely from the space 17, through the clearance around the piston head 19 into the passages 41, the groove 40 and passages 31 to the space 18. On completion of the inward movement of the plunger 13, the pressure in the spaces 17, 18 is greater than normal and the piston valve 32 remains well depressed when the recoil stroke commences. Reverse flow of fluid from the space 18 is prevented by the ring 20 engaging the upper face of the groove 42. The outward recoil movement of the plunger 13 therefore takes place against considerable resistance due to compression of fluid in the space 18. Meanwhile, the pressure in the space 17 falls progressively and the valve 32 rises so that when the pressure becomes less than its normal value, the valve 32 has moved, e.g. to the position shown in Fig. 3. Fluid from the space 18 then flows through the passages 41 and groove 40 into the space 17. The valve 32 functions in a similar manner to control flow of fluid when the suspension device is lengthened owing, e.g. to the wheel dropping into a pothole. The device normally is charged with a substantial quantity of lubricating oil and the piston valve 32 is provided with a tube 36 to prevent the auxiliary chamber 37 from becoming completely filled with oil. Four other constructions of damping valve arrangements are shown in each of which the movable packing ring is dispensed with, fluid flowing through passages in the central portion of the piston head. In one construction, Fig. 4, annular washers 60, 61 functioning as non-return valves, control the flow through passages 58, 59 in a head member 51 secured on a control piston 48, frusto-conical surfaces 53, 54 on the head member being adapted to engage seatings 55, 56 on an enlargement 57 of the auxiliary chamber 37. In the second construction, the frusto-conical surfaces are formed on a spool-shaped control valve integral with the control piston and having an axial passage controlled by non-return ball valves pressed apart against their seatings by a common compression spring. In the third construction, the control piston operates a piston valve of substantially the same form as in Figs. 2, 3 but spring-separated non-return ball valves are fitted in the piston head. In the fourth construction, the piston valve is integral with the control piston and non-return valves constituted by spring-separated flat metal washers control flow of fluid through passages in the valve. The annular space surrounding the plunger need not constitute the second variable volume space. For example, the plunger may be double-ended with the two ends of different diameters and operating in corresponding cylinders to provide two variable volume spaces. Moreover, the double-acting damping valve may be disposed elsewhere than in the plunger and may be external to the telescopic members, being connected to the working spaces and/or the auxiliary chamber by pipes or passages. Specification 450,852 is referred to.