Patent GB-663195-A (GB)
Title: Improvements in rubber compression springs
IPC: F16F3/087
Filed: 1948-12-09
Abstract: 663,195. Road-vehicle spring suspension ; springs. DUNLOP RUBBER CO., Ltd., and SEDDON R. M. Nov. 30, 1949 [Dec. 9, 1948]. No. 31935/48. Classes 108(ii) and 108(iii) In a compression spring comprising two relatively-moving members one of which comprises a rigid guiding member extending axially through a rubber cushioning element, the rubber element has an internal cross-sectional area in the unstressed condition, less than the exernal cross-sectional area of the guiding member. and greater than the area of the latter when the element is compressed under its maximum load. In the construction shown in Fig. 1 as applied to a motor cycle front fork, of the type described in Specification 660.135, inner and outer telescopic tubes 1. 2 are relatively slidable by virtue of bearing bushes 3, 4. The bottom end 7 of the fork (Fig. 1 is inverted) has provision for a wheel axle (not shown). An inner tube 17 is rigid with a plug 12, and is held, with a rubber seal ring 16 interposed, by a threaded closure cap 15 in the end of the tube 2. A guide rod 20 for a rubber cushioning element 21 is slidable within an annular member 18 rigid with the tube 17. The cushioning member is held on the rod 20 between an abutment 23 rigid with the lower end of the rod 20, and a metal spacing member 26 slidable on the rod 21. The member 26 is in engagement with an annular rubber sealing ring 29 seated on the member 18. A flat 22 formed on the rod 20, extends from the lower end of the rod to a point within the sealing ring 29. The upper end of the rod 20 is held by a nut 30, washer 32 and rubber sealing ring 31 within the tube 17. The abutment 23 and member 26 are flanged at 24. 27, 28 to prevent flowing of the rubber of the element 21 and ring 29. In operation, the tube 17 is charged with a light lubricating oil. On compression the element 21 is compressed between the abutment 23 and member 26 the upper end of the rod 20 passing further upwardly into the tube 17. The upper end of the flat 22 on the rod 20 thus passes into the tube 17 and oil is forced upwardly between the opposed surfaces of the rod and element 21. A rubber buffer 19 limits inward movement. On extension the ring 28 is engaged by a flanged member 10 rigid with the end of the tube 1 and the element 21 is again compressed between the abutment 23 and member 26. A rubber.buffer 25 cushions the return. The bushes 3, 4 may be of sintered metal with the space between them filled with oil, escape of which is prevented by a rubber sealing ring provided above the bush 4. In a modification, the rod 20 is replaced by a perforated tube. The uppermost perforation lies adjacent the bore of the sealing ring 28 in the normal position of the parts. The buffer 19 may be replaced by a rubber sleeve gripping the tube 17 and surrounded by a helical steel spring of less diameter than the bore of the tube 2. The spring is a tight fit on. but is axially longer than the sleeve. Under compression the spring becomes a sliding fit on the sleeve. The element 21 is formed in three sections cemented together at 21a and 21b. According to the Provisional Specification, the sections may be separated by flanged spacing members of a different metal from that of the tube 1. In the construction shown in Fig. 2 as applied to a motor vehicle suspension, a wheel (not shown) is carried by a link 49, each end of which (one end only shown) is pivoted to a bell crank 50, itself pivoted by a resilient sleeve-type bushing 51 to the chassis, and at 53 to a rod 39. A resilient element 42 is mounted on the rod 39 between washers 43, 44 and is held within an outer casing 35 rigid with the chassis. The washer 44 carries a resilient flange ring 47 and seats on a spacing member 45 in engagement with a lock nut 46 on the rod 39. The upper washer 43 engages a plug 34 secured by bolts 36 to the casing 35. The bell crank 50 is in the form of a split casing having an inspection cover through which a box spanner may be inserted to engage a hexagon head on the rod 39. By this means the rod 39 may be rotated to vary the setting of the nut 46. A rubber ring 38 co-operates with a stop 57 on the lever 50.