Patent GB-671925-A (GB)
Title: Improvements in or relating to shock absorbers
IPC: F16F5/00
Filed: 1948-07-23
Abstract: 671,925. Hydro-pneumatic shock-absorbers. ELECTRO-HYDRAULICS, Ltd.; and NEILSON, C. B. V. Aug. 12, 1949 [July 23, 1948; Dec. 16, 1948], Nos. 19771/48 and 32615/48. Class 108(iii) In a shock absorber in which energy is absorbed by the passage of liquid between two deformable chambers via ports, at least one of which is valved, energy being stored by means of a separate spring which may be a fluid, the valve port is governed by spring means biassing the valve into its closed position, the valve being opened when the pressure in one of the chambers exceeds a predetermined amount, the operation of the valve being independent of pressure difference between the two chambers. In the construction shown in Fig. 1, a hollow plunger 8 carries a piston 5 slidable within a cylinder 1. A counter piston 7 is carried by a hollow rod 6 which is rigid with the piston 5 and passes through a fixed diaphragm 2. The latter defines deformable liquid chambers A, B. A piston 9 in the plunger 8 carries a valve 10 which seats on the piston 5 to control flow from the chamber A via piston ducts 14 to the chamber B via the hollow rod 6 and a port 15. The piston 9 is acted on by air at a predetermined pressure charged into the plunger 8 through an opening 12. A space C in the cylinder 1 contains compressed air which acts on the counter piston 7. Ports 3 in the diaphragm 2 are controlled by a valve 4. In operation, on compression the valve 4 is maintained closed and flow between chambers A and B occurs by lifting of the valve 9 against the constant pressure in the chamber 11. On rebound, liquid pressure in chamber B acting on the smaller area of the valve 9, is unable to lift the latter and return flow takes place through the ports 3. The space C may include a floating piston, bellows, or similar device, the counter piston being valved for liquid flow therethrough. The arrangement may be modified so that flow occurs through the ports 3 on compression as well as rebound. In a modification Fig. 2, (not shown), the counter piston rod is rigid with the cylinder and carries a counter piston slidable within the hollow rod of the main piston. The latter fulfils the function of the diaphragm 2 of Fig. 1. In the construction shown in Fig. 3, a floating piston 46 is acted on by compressed air C and is slidable within the hollow rod 43ofa main piston 41. A cylinder 42 is divided by the piston 41 into working chambers B, B<SP>1</SP>, (freely connected by a port 61), and A. The chambers A, B are connected by damping passages 47, 48, flow through the latter being controlled by a valve 49. The piston 41 is slidable over a plunger 51, rigid with the cylinder 42. A piston 55 slidable within the plunger 51, is connected by a spindle 56 with a sleeve valve 58. A spring 60 urges the sleeve valve 58 into the position shown in which it covers an aperture 53 in the wall of the plunger 51. On compression, fluid passes from the chamber A with damping action through the passage 47 and valve 49, to the chambers B, B<SP>1</SP>. Fluid from chamber A passing through a port 52 in the plunger 51, acts on the piston 55 and at a pre-determined pressure displaces the valve 58 to permit flow to the chambers B, B<SP>1</SP> through the port 53. Air in the chamber C may be replaced bv a plurality of springs and the piston 46 by a bellows device.