GB635607A - Improvements in or relating to shock absorbers - Google Patents

Abstract

635,607. Hydraulic shock-absorbers. ELECTRO-HYDRAULICS, Ltd., and HOARE, R. G. Oct. 16, 1947, No. 27773. [Class 108 (iii)] In a shock-absorber of the type in which fluid is contained in a deformable chamber within the shock-absorber cylinder, the chamber being in communication with a second chamber through an orifice or orifices which may be valved, and in which the space in the second chamber is spring controlled in such a way that if the first chamber is deformed to force fluid through the orifices into the second chamber, the spring is strained and will, on the removal of the deforming force or part thereof, drive all or part of the fluid back into the first chamber, a third chamber is provided which is also spring controlled and is in ported communication with the second chamber, the arrangement being such that in the event of fluid pressure in the second chamber rising to a predetermined level, further damping is effected by communication between the second and third chambers. In the arrangement shown, a main cylinder is divided into first and second chambers by a fixed diaphragm 6 having a valved damping-orifice 7 and restrictor orifices 8a. A hollow piston-rod 9 slidable in the cylinder constitutes a third chamber and carries a hollow piston 12 to which is attached a hollow counter piston-rod 15 which is slidable through the diaphragm 6 and terminates in an annular type counter piston 16 in the second chamber. The hollow piston-rod 9 comprises spaces 3 and 3a which are formed by a floating piston 23 therein. The piston 16 is provided with one or more ports 17 which establish communication between spaces 2 and 2a formed by the piston in the second chamber. Ports 20 and 21, preferably having spring- loaded valves 20a and 21a in a secondary diaphragm 19 within the piston 12, allow communication between the spaces 2 and 3a. The cylinder including the space 3a is filled with oil to a predetermined level above the piston 16 and compressed air is admitted into spaces 2a and 3. Some oil may be admitted to space 3. In operation, compression of the shock-absorber is resisted initially by oil in the first chamber, due to the damping action of orifices 7, after which damping is reduced due to further compression of oil in space 2. Continued increase in oil pressure in space 2 opens valve 20a in the diaphragm 19 to force piston 23 against the air pressure in space 3. On extension of the shock-absorber oil is forced back to space 2 through valve 21a, by air pressure in space 3. Oil in the second and third chambers may be separated from the air therein by a floating piston or bellows device. The piston-rod 15 may be grooved at 18 over a portion of its length to provide additional communication between each side of the diaphragm 6 during movement of the piston-rod 15. In an alternative construction according to the Provisional Specification, the piston 23 may be attached to the piston-rod 15 so that the piston-rod 15, piston 23, piston 16 and the diaphragm 19 are floating.