Patent GB-890177-A (GB)
Title: Improvements in levelling systems for vehicles equipped with servo springs
IPC: B60G21/00
Filed: 1960-05-11
Abstract: 890,177. Levelling vehicle fluid suspensions. VOLVO A.B. May 11, 1960 [May 13, 1959], No. 16686/60. Class 108(2). A levelling system for fluid-spring suspensions comprises a valve 17 controlling the flow of a fluid to and from the springs which are situated between sprung and unsprung parts of a vehicle. The valve being actuated by two members, one a levelling device actuated according to the distance between the sprung and unsprung parts and the other a member actuated according to the ratio of loads on the springs on either side of the vehicle. Wheels or other unsprung parts are pivoted on arms 5 and 6 to the sprung frame 7. Differentially operating hollow pistons 8 slide in cylinders 9 pivoted to the frame 7 and force liquid into chambers 14 where a resilient diaphragm 15 separates the liquid from a gas 16 at high pressure. Simultaneously the liquid moves plungers 21 which bear against levers 22 separated by a spring 25. The levers 22 roll on curved surfaces 24 shaped to compensate for variation in load and bear with their other ends on springs 26 abutting on flanges at the ends of a push-bar 27 which in turn abuts on springs 28 which bear against one end of the valves 17. The other end of the valves abut on springs 29 compressed against cranked extensions on the arms 6. An equal increase in load on both wheels will bear equally on both the springs 29 which will open the valves 17 and admit extra fluid to the chambers 14 to restore the level of the frame 7. At the same time the plungers 21 will displace both of the levers 22 equally so that there will be no displacement of the push-bar 26. If, however, the vehicle rolls on turning a corner or stands on uneven ground, one spring 29 will be compressed and the other released and the levers 22 will pivot on the surfaces 24 in opposite senses causing the push-rod 27 to move towards the higher wheel and thereby acting against the displacement of the valves 17 caused by the springs 29. By a suitable choice of plunger size, lever length and spring rates it is possible to ensure balance of the valve displacement due to the spring 29 so that there is no correction for height under conditions of roll or on uneven standings. In an embodiment shown in Fig. 3 the compensating assembly is housed in a casing 34 on the sprung frame of the vehicle. The unsprung parts operate the valves 17 by way of torsio bars (Fig. 4, not shown), which do the work of the springs 29 of Fig. 1 and by way of levers 37 and pistons 38. The valve 17 connects with a high pressure source through conduit 39 with the chamber 14 (not shown in Fig. 3) through conduit 41 with the plunger 21 through conduit 42 and with the low pressure outlet through non-return restriction valves (Fig. 6, not shown) and a conduit 40. Conical springs 30 bear on thimbles on the ends of the plungers 21 and on the casing 34 to restrict, as the spring comes progessively coil to coil, transmission of movement from the plungers 21 through the springs 31 to a centrally pivoted lever 33 which bears on the inner side of the valves 17 through-springs 28.