Patent GB-667701-A (GB)
Title: Improvements in shock absorbers
IPC: F16F9/26
Filed: 1950-01-06
Abstract: 667,701. Hydraulic shock-absorbers. GRANET, C., and HELBIG, M. Jan. 6, 1950 [Jan. 22, 1949; Feb. 12, 1949], No. 438/50. Class 108(iii). A double acting piston shock absorber having a piston formed with symmetrical heads sliding in symmetrical end portions of a cylinder, is characterised in that, for drawing in liquid from a central reservoir to the ends of the cylinder, an intake valve is provided in each head while for the return of liquid from the ends of the cylinder to the reservoir, the body of the shock absorber comprises a common return duct opening into the reservoir and provided with a single spring loaded return valve, and channels branched on this duct, connecting the same to both ends of the cylinder and each provided with a check valve. In the arrangement according to Figs. 3 to 5, each head 9 of a double acting piston, which is slidable in a cylinder 1 of a shock absorber casing is formed at the end of a tube 8, the centre portion 10 of which is cut away for the reception of the forked end of a piston actuating member 47. The cylinder 1 communicates through an opening 3 with a liquid reservoir 4. A spring-loaded rubber intake valve 15 is sealed against the outer face of an annular partition 11 in each head 9 and a rubber washer 12 secured to the inner face of the partition carries a socket 13 which bears against the member 47. The spring for the valve 15 is loaded against a perforated washer 21 retained in a groove within the head 9. Both valves 15 are centred on a rod 16 which extends through the piston axially of the cylinder 1. Each end of the cylinder communicates with the reservoir 4 through a recess 24 and a channel 23 which is connected through a valved duct to a vertical chamber 34, Figs. 4 and 5. Each duct comprises a portion 25 housing an orificed metal ring 28, a portion 29 having a square block of rubber seated against the ring 28 by a spring 31 and a reduced portion 32 opening into the chamber 34. The chamber 34 houses a spring loaded non-return valve, Fig. 5, which opens towards a channel 38 communicating with the reservoir 4 and comprises a hollow shank-portion 42 having an orifice 44. Movement of the piston away from a central position towards one end of the cylinder during operation of the shock absorber forces liquid from that end into the reservoir 4 through the channel 23 the valved duct and the non-return valve in the chamber 34. Liquid flows from the reservoir into the other end of the cylinder through the relevant intake valve 15. The actuating member 47 is carried by a spindle 52 in bosses 53 and 54 in the casing and projects therefrom through a flexible flange 56 which is retained in a metal casing 57. In another arrangement, Fig. 7, the rod 16 is shorter than the length of the cylinder 1 and is freely mounted at the ends thereof to form small chambers 63, each of which communicates through a metered leakage port with a chamber 64 defined by the piston at that end of the cylinder. The rod is reduced in diameter at each end between the seating for the valve 15 and the outer end of the piston head and is also formed with tapered cut-outs 66 and 67. Each valved duct which communicates with the recess at one end of the cylinder and with a horizontally disposed chamber 69, comprises a valve 72 which is normally closed against a pin 71 of a screwed plug 70 by a spring 74. The chamber 69 communicates with the reservoir 4 through a non-return valve as above and a channel connecting a groove in the surface of the central part of the cylinder. Upon movement of the piston towards one end of the cylinder, build-up of pressure at that end thereof is prevented by leakage between the valve 15 and the reduced diameter portion 65 of rod 16 and no braking is produced until the piston approaches the end of its stroke, when the portion 65 is sealed by the valve 15. Upon return movement of the piston, the valve 15 may remain seated, liquid flowing from the reservoir to the end of the cylinder through the cut-out 67. Sudden re-opening of valve 15 when the piston regains its original position, is prevented by leakage of liquid through the cut-out 66. Liquid pressure at the other end of the cylinder builds up against spring 74 until the valve 15 at that end of the piston passes the reduced diameter portion 65 of the rod 16, and the pressure falls to zero. For a normal or balance position of the piston, as shown, the pressures in the chambers 63 are equal and the rod 16 assumes the central position shown. If the normal balance position of the piston is towards one end of the cylinder the braking pressure at the other end thereof during a return movement of the piston towards that end, persists longer than that occurring during a return movement of the piston towards the other end of the cylinder and the resulting unequal pressures in the chambers 63, positions the rod 16 symmetrically with the balance position of the piston.