Patent GB-517746-A (GB)
Title: Improvements in hydraulic shock absorbers
IPC: F16F9/22
Filed: 1938-08-11
Abstract: 517,746. Vibration-dampers. PRATT, J. H., MANLEY, G. E., and GIRLING, A. H. G. Aug. 11, 1938, No. 23684. [Class 108 (iii)] A hydraulic shock-absorber is characterized in that movement transmitted thereto causes a pumping action which delivers fluid into a chamber of variable capacity whereby the head of liquid produced is necessarily proportioned to the disturbing forces and offers a correspondingly proportioned resistance. When a lever 6, Fig. 1, is reciprocated pistons 8 pump liquid from a reservoir 9, 12 into a chamber 14 of variable capacity against a piston 15 and spring 16 so that the head of liquid in chamber 14 is proportioned to the disturbing forces applied to the lever 6. An orifice 15a in the piston 15 is of such a size that a slow movement of the lever 6 will not result in pumping more liquid than the orifice can pass at low pressure, but at a fast movement pressure rises until the delivered volume is just balanced by the leakage. In a modification, Figs. 2, 3, 4, a lever arm, not shown, operates a rotary shaft 17 in a casing 18. The shaft 17 operates cams 17b, Fig. 4, contacting extensions 20a of pistons 20 moving in axially arranged cylinders 21a, Fig. 3. Within each piston is a coil spring 22 abutting against a rubber disc 23 which serves as a valve. At the centre of a cylinder block 21 is a chamber 21b, Fig. 4, of variable capacity provided with a spring piston 24. The rubber disc 23 has cutaway portions 23a for each cylinder 21a and the marginal portions adjacent the cutaway portions lift on a suction stroke of the pistons 20 to place their respective cylinders 21a in communication with an annular channel 18f in a plate 18e. The disc 23 also has four recesses 23b, Fig. 3, located partially below its respective cylinder 21a and extending into an undercut in the periphery of a cup 23c, Fig. 4, fitting within the lower end of chamber 21b. The outer wall of cup 23c flexes on a delivery stroke of piston 20 from cylinder 21a to chamber 21b by way of recess 23b. The annular channel 18b communicates with the casing 18 by port 23d, Fig. 2, in the disc 23 and a port 21c in the block 21. A split shank of a screw 25 provides means for adjusting flow from delivery chamber 21b giving an orifice effect as in Fig. 1. The interior of the casing 18 constitutes liquid reservoir. Leakage is prevented by a sealing ring 18c. The cylinder block 21 has a port 21h for relief of excessive pressure. The centre portion of disc 23 rests on an annular disc 29 housed in a recess in the inner face of plate 18e, movement of shaft 17 oscillating pistons 20 in pairs and pumps liquid from reservoir into delivery chamber 21b to resist shock. Another modification, Fig. 5, deals with axle rise transmitted by a shaft 17. This shaft carries an arm 17b which reciprocates a double-ended piston. One of the ends 27a works in a cylinder 18g communicating with a chamber 18h by a passage 18k controlled by a one-way valve 28. The other end 27c of the piston has therein a spring piston 29. The space between the end of the piston 27c and the end of the piston 29 constitutes the delivery chamber which communicates by a valve-controlled passage 27d with the cylinder 18j within which the piston 27c reciprocates. Thus cylinder 18j communicates with passage 18k by a one-way valve 31. The piston 29 has an orifice 29a. Downward movement of axle pumps liquid from chamber 18g back to chamber 18h by port 27b, whereas upward movement forces liquid into delivery chamber against resistance of piston 29. In a further modification, not shown; several shock absorbers may be connected by pipe lines with a common delivery chamber and common reservoir with one or more return regulating valves. The setting of such valves or an over-riding valve may be adjusted by control means near driver.