Patent GB-1158898-A (GB)
Title: Improvements in or relating to Gradually Adjustable Shock Absorbers
Inventor: BILSTEIN AUGUST
IPC: F16F9/46
Filed: 1966-10-31
Abstract: 1,158,898. Abjustable shock absorbers. AUGUST BILSTEIN. 31 Oct., 1966 [29 Oct., 1965], No. 48765/66. Heading F2S. A gradually adjustable hydraulic shockabsorber comprises a piston 1 which works in a liquid-filled cylinder and which is supported by a hollow piston-rod 2 having a longitudinal bore 28 therein in which a control rod 27 is disposed, the effective cross-section for passage through the bore being steplessly adjustable, a valve leaf spring 12, effective in both directions of flow of damping fluid and supported at its internal edge on the hollow piston-rod and at its external edge on a control piston 9 which is axially movable against a spring 20 acting on the working piston. The control pistons and the valve leaf spring co-operating to control fluid flow through ducts in the working piston and the control piston and the working piston defining an annular chamber 21 which is continuously in fluid connection, via throttle ports 22, 23 with the fluid flow ducts 15 and via the bore in the hollow piston rod with one or other of the working chambers 16 or 17 depending upon the direction of flow of the damping fluid. The piston 1 is clamped with a sleeve 3 between a nut 7 and centering, thrust, and spring washers 4, 5, 6, and the hollow piston-rod 2 receives the control rod 27 which is movable axially to adjust the position of an annular recess 26 in its outer face with respect to aligned ports 24, 25 respectively through the piston-rod 2 and the sleeve 3. The fixed piston 1 co-operates with the axially-slidable control piston 9 which is mounted on the sleeve 3 and has an outer flange 10 which slidably and sealingly engages a corresponding flange 8 on the piston 1 to form the variable volume static pressure chamber 21 which communicates with an upper chamber 16 in the main cylinder through the ports 22 in the spring washer 20, throttle ports 23 in the control piston 9, and ducts 15 in the fixed piston. The valve leaf spring washer 12 co-operates, at its inner periphery, with the centering washer 4 and at its outer periphery with the lower end of a skirt 11 on the adjustable piston 9 to form an annular chamber 13 which communicates with the upper chamber 16 through radial openings 14 and the ducts 15 and, with a lower chamber 17 in the main cylinder, through throttle ports 18 in the skirt 11. A bore 35 in the control rod 27 is always in communication with the chamber 17 through ports 36, an annular recess 29 in the rod 27, and a port 39 in the piston-rod 2. The bore 35 also communicates with the bore 28 of the piston-rod 2 through a duct 37 and a port 38 for the purpose of volume adjustment, its upper end leading to a bore 30a which slidingly receives a valve piston 30. The bore 30a leads, at its upper end, into a bore 34 in a locking screw 33. With the valve 30 in its upper or lower position, due respectively to an expansion or contraction stroke of the piston-rod 2, to close off either the bore 34 or the bore 35 the lower chamber 17 on the upper chamber 16 is placed in communication with static pressure chamber 21 to force the adjustable piston 9 downward and preload the valve spring washer 12 to a greater extent, so that the damping factor is increased. On expansion of the unit damping fluid passes from the chamber 17 to the chamber 16 past the inner surface of the spring washer 12 which lifts off the centering washer 4, through the opening 14 and into the ducts 15, contraction of the unit causing a reversal of fluid flow past the outer edge of the valve washer which lifts off the lower edge off the skirt 11. A bleed orifice 18 is provided in the skirt 11. The spring washer 20 urges the adjustable piston 11 downward toward a stop 40 and opposes the action of the valve washer 12. By varying the axial position of the control rod 27 the degree of coincidence between ports 31, 32 in the control rod and the ports 24, 25 is altered to adjust the static pressure in the chamber 21 which augments the force of the spring washer 20 and prestresses the valve washer 12 according to the degree of stiffness required. The ratio of damping reinforcement can be varied by providing one, or more, leakage grooves in the side of the valve piston 30.