Patent GB-943646-A (GB)
Title: Improvements in or relating to lever-type hydraulic shock absorbers
Inventor: DICKINSON RONALD SIDNEY
IPC: F16F9/28
Filed: 1960-12-22
Abstract: 943,646. Shock-absorbers. ARMSTRONG PATENTS CO. Ltd. Dec. 14, 1961 [Dec. 22, 1960], No. 44178/60. Heading F2S. A double-acting lever type hydraulic shockabsorber for road vehicles comprises a housing 10 having a pair of hydraulic cylinders 14 communicating at their upper ends with a reservoir space 12, a piston 16 in each cylinder each piston having a valved passage 62 which allows flow of hydraulic fluid from the reservoir to the respective lower cylinder chamber, a lever arm, not shown, for displacing, through a crank-plate 20 and connecting rods 22, the pistons 16 and passage means 26, 24 including fluid flow restricting means 38, 44 connecting the lower ends of the cylinders, a leak passage 58, 50 of variable cross-section being arranged in the housing between the reservoir 12 and the passage means 38, 44. Bores 26; which connect the cylinders 14 with the valve passage 24, register with a peripheral groove 30 in an axially-bored plug 28 which is screwed within the valve passage 24, the groove 30 communicating through oblique passages 48 with a plug counterbore 34 around which is formed a valve seat 36. A hollow valve 38, which is urged by a spring 40 against the seat 36, is also formed with a valve seat 42 for a second valve 44 loaded by a spring 46. The groove 30 also communicates with the passage 58 which leads to radial passages 60 in an adjustable needle valve 56 which is accommodated in the lower end of the vertical passage 50 which leads into the reservoir 12. If desired, the needle valve 56 can be remotely controlled by the use of a cable or a solenoid. In operation a downward stroke of the pump piston forces liquid through the corresponding bore 26, the groove 30, the passages 48, and past the valve 38 and into the valve chamber 24 from which it flows through the other bore 26 and into the rebound cylinder within which the piston is moving upward. A parallel flow path for the hydraulic fluid to the reservoir 12 is provided through the passages 58, 50 and the needle valve 56 which can be set to provide the required softness to the suspension. The parallel path 58, 50 also provides an escape passage for excess hydraulic fluid due, e.g., to volume expansion. In both the bump and rebound strokes cavitation is avoided by the operation of the recuperation valves 62 in the pistons 16, the rebound stroke of the righthand piston, Fig. 1, being stiffer due to the more restrictive valve 44. In a modification, Figs. 4, 5, an alternative flow path is formed below the cylinders 14, through an auxiliary valve chamber 70, the inner end of which leads to a passage 72 which opens into the reservoir 12. A screw-plug 74, which with the chamber 70 defines an annular space 76 has an annular groove 78 which, through a filter 80, communicates with a port 82 which extends from the lower end of the right-hand cylinder 14, an oblique bore 84 leading from the groove 78 to the annular space 76. The plug 74 holds a metering washer 86, grooved at 90, against a shoulder 88 between the chamber 70 and the passage 72. Adjustment is effected by replacing the washer 86 with one having metering grooves of a different size.