Patent GB-786849-A (GB)
Title: Improved air suspension valve control mechanism
IPC: B60G17/04
Filed: 1956-06-29
Abstract: 786,849. Road-vehicle pneumatic spring- suspensions; dash - pots. GENERAL MOTORS CORPORATION. June 29, 1956 [July 1, 1955], No. 20131/56. Classes 108(2) and 108(3) Pneumatic suspension valve control mechanism comprises a first pivoted lever 40 (Figs. 2 and 4) adapted to be oscillated by relative movement of the sprung (11) and unsprung (20) parts of the suspension, a second lever 50 freely pivoted about the pivot of the lever 40 and resiliently connected thereto, the lever 50 being engaged with a valve means 65, 70, and a damper connected to the lever 50 to prevent synchronous movement of the levers 40, 50, on movement of the lever 40 at a rate greater than a predetermined rate. As shown, applied to a pneumatic road-vehicle suspension (Fig. 1) comprising pneumatic cushions 12, 13, supporting a chassis frame 11 on an axle 15, the lever 40 is connected by a 'spindle 33 and lever arm 35 to links 37, 36, connected to the axle 15. The cushions 12, 13, are in communication through openings 18 with a reservoir 17 formed by partition walls 16 in the frame 18 with a reservoir 17 formed by partition walls 16 in the frame member 11a of the chassis 11. The control mechanism comprises a housing 25 which is bolted to the wall of the reservoir 17. Aligned openings in the housing 25 and the wall of the reservoir 17 connect the latter with a chamber 26 formed within the housing 25. A tyre type valve 65 mounted in the housing 25 is connected to a pneumatic pressure supply pipe 24. An operating stem 64 of the valve 65 is in engagement with one limb 61 of a U-shaped plate 60 rigid with the lever 50. The other limb 62 of the plate 60 is in engagement with the operating stem of a valve 70, disposed between chamber 26 and atmosphere. The outer end of the lever 50 is rigid with a stem 96 of a dashpot piston 83 which is reciprocable within the bore of an annular land 82 formed on a member 80, each end of which is closed by a respective flexible diaphragm 86. The lever 50 is rotatably mounted on the spindle 33, and a torsion spring 55 is in operative connection between the levers 40 and 50. In operation, on an increasing static load of the vehicle, the lowering of the chassis frame 11 results in rotation of the lever arm 35. This causes lever 40 to act through spring 55 to rotate the lever 50 and so operate the valve 65 to admit air from the pipe 24 to the chamber 25 and thence to the reservoir 17 and cushions 12, 13. On reduction in the load, the valve 70 is similarly operated to release pressure air to atmosphere. On changes in dynamic load, the dashpot 80 prevents rapid movement of the lever 50, and the movements of the lever arm 35 are absorbed by the spring 55 without operation of the valves 65, 70. A predetermined amount of air is included with the liquid in the dashpot 80 so as to provide a degree of lost motion. This results in retarding the admission of air to, or exhaust of air from, the air springs 12 and 13, but allows immediate closure of the valves 65 or the valve 70 when the air pressure in the springs 12 and 13 is such as to return the frame 11 to its predetermined height above the axle. In a modified construction of dashpot (Fig. 7), a rotary spindle 182 is operated by the action of a toothed segment 151 rigid with the lever 50 and in mesh with a pinion 152 on the spindle 182. The end portion of the spindle 182 is formed with fiats 190 which engage with similarly shaped apertures in a series of plates 191 which are interleaved with plates 192 secured from rotation relative to the housing 181 of the dashpot by means of bolts 193. The housing is filled with a silicone liquid which offers sheer resistance to relative movement between the housing and the spindle 182. A peripheral series of circular apertures 196 is formed in the plates 191, 192, to allow the liquid to reach the working surfaces. Lost motion may be obtained in this dashpot by the omission of a tooth in the segment 151.