Patent GB-1250216-A (GB)
IPC: F16F9/50
Filed: 1968-11-28
Abstract: 1,250,216. Springs. T. TAKAGI. 28 Nov., 1968 [11 Dec., 1967; 10 Jan., 1968; 27 March, 1968], No. 56617/68. Heading F2S. A shock absorber, which develops a damping force during both the extension stroke and the compression stroke, comprises an outer shell 1, Fig. 1, a lower end 2 of which is attachable to a vehicle axle. A pressure tube 3 is mounted within the shell 1 and has a piston 4 therein. The latter has a piston-rod 5 with an end 6 attachable to a vehicle body, has a one-way valve 7, Fig. 2, on the upper surface thereof, the valve permitting working fluid to move upwardly, and has a primary valve 8 and a control valve 9 which allows working fluid to move downwardly. The primary valve 8 communicates with an upper chamber 11 via passages 10 in the piston 4, and the control valve 9 communicates with the chamber 11 via an axial passage 12 in the piston-rod 5 and radial passages 13 therein. The control valve 9 is opened and closed by means of a plunger-type switch valve 14 which has a valve-operating piston 15 in a cylinder 16, the piston being urged by a spring 17 so as to leave open the radial passages 13. The switch valve 14 has a throttling passage 18 which connects the upper chamber 11, through the passage 12 in the piston-rod 5, with a chamber beneath the piston 15. Working fluid can also be throttled by passing it through a discharge port 19 in the cylinder 16. The damping force characteristics of the control valve 9 are less than those of the primary valve 8 and the switch valve 14 keeps the valve 9 open when the shock-absorber is stationary, but closes the valve 9 when the shock-absorber is subjected to primary vibrations, these being the low frequency type which are above the springs of the vehicle. The switch valve 14 opens the control valve 9 when the shock absorber is subjected to secondary vibrations, these being the high frequency type which are below the springs of the vehicle. A dual action valve 20, Fig. 3, is provided at the lower end of the tube 3 and comprises a one-way valve 21 which permits lubricant to flow upwardly and a pressure control valve 22 which allows working fluid to flow downwardly. During a compression stroke the valve 22 develops a damping force as a greater length of the piston-rod 5 enters the tube 3, whereas, during an extension stroke, working fluid flows upwardly through the valve 21. Also during the extension stroke, the oneway valve 7 in the piston 4 is closed and pressure in the chamber 11 increases as the piston 4 moves upwardly. The valve 9 opens and develops a small damping force while the primary valve 8 remains closed. If a secondary vibration occurs, the throttle passage 18 prevents the piston 15 of the switch valve 14 from moving upwardly and the radial passages 13 remain open. When a primary vibration occurs, a larger quantity of fluid flows through the throttle passage 18 and into the chamber below the piston 15 of the switch valve 14, thus causing the latter to move upwardly to close the radial passages 13 and thus render the valve 9 ineffective. Under these conditions, the primary valve 8 opens during the extension stroke. In other embodiments the primary valve is a coil spring biased valve 8<SP>1</SP>, Fig. 4 (not shown), the primary valve is a dual disc valve 8<SP>11</SP>, Fig. 5 (not shown), a switch valve 14<SP>1</SP>, Fig. 6 (not shown), controls a valve 9 which is mounted in a piston 4 and which opens and closes radial passages 13<SP>1</SP>, and discharge 19<SP>1</SP> acts as a throttle to provide a time lag in the operation of the switch valve 14<SP>1</SP>, a primary valve 8<SP>111</SP> is mounted in the upper end of the tube 3, a valve 20<SP>1</SP> has only a suction valve 21<SP>1</SP>, and in the compression stroke the primary valve 8<SP>111</SP> develops a damping force as the pistonrod 5 moves downwardly in the cylinder 3, a valve 9, Figs. 8 and 9a (not shown), are closed by means of pusher members A or A<SP>1</SP>, the pusher members being moved upwardly and downwardly by floating cylinders 14<SP>11</SP>, a switch valve 14, Fig. 12 (not shown), and its piston 15 are not fixedly interconnected, and a switch spring 26, Fig. 14 (not shown), is provided to ensure that the members 14 and 15 move simultaneously.