Patent GB-606146-A (GB)
Title: Improved pneumatic springing and damping arrangement for vehicles
IPC: B60G17/027
Filed: 1945-11-27
Abstract: 606,146. Pneumatic springs; dashpots: WETTSTEIN, F. A. Nov. 27, 1945, No. 32040. Convention date, Nov. 30, 1944. [Classes 108 (ii) and 108 (iii)] A pneumatic vehicle suspension comprises a cylinder 72 having chambers 94, 96 defined by a differential piston 81, 86, a damping device for controlling the flow between the chambers 94, 96 and a pressure control device adapted to supply pressure air to the chamber 96 corresponding to the greater piston surface, on an increase in load, and release air from the other chamber 94 on a decrease in load so that mutual position of the cylinder 72 and piston 81, 86 is controlled with delay, and the average length thereof maintained constant. A metering rod 74 having tapering fluted portions 123 controls flow through a piston orifice 95, and on compression of the unit drives upwardly, a member 118 in conjunction with balls 122 and two conical rings 120, 121. The member 118 is connected by a compression spring (not shown) in a cylinder 116 with a forked member 117 which engages needle valves 111, 112 which respectively control the flow through passages 109, 110 leading to a compressed gas supply and to atmosphere. The cylinder 116 comprises a dashpot to delay by ten seconds the action of the valves 111, 112. The piston is divided by a tubular member 89 into outer and inner annular spaces 92, 91 which are in communication by spring-loaded non-return valves 105, 106 arranged in parallel and the space 92 is in communication with the annular cylinder space 94 by orifices 93 which may be progressively covered on inward movement by a gland skirt 76. The valves 105, 106 each have an associated ball valve 97, 98, each of which normally rests in an open position as shown, but is responsive to centrifugal force to close its respective port 104, 103. The ball valve housings are arranged to lie in a direction perpendicular to the longitudinal vehicle axis and are slightly inclined in opposite directions. The source of pressure to which the passage 109 is connected may be a cylinder of the vehicle engine connected via a non-return valve and a pressure cylinder containing a filter, cooling tubes and a float valve allowing escape of condensate. In operation, relative movement of the piston 86 and cylinder 72 is cushioned by gas in the spaces 91, 92, 94, 96 and damped by gas flow through the valves 105, 106, flow through the orifices 93, 95 only producing noticeable damping at the limits of the expansion and compression strokes respectively. Each unit is arranged on the vehicle so that the housing for the lower ball 97 has its lower end nearer the outside of the vehicle. In rounding, for example, a right-hand band centrifugal force maintains the ball 97 in an open position and throws the ball 98 on to its seat so that the hardness of the suspension on the left-hand side of the vehicle is increased for compressive movements, but is unaffected for expansion. Similarly, the hardness on the right side is increased for expansion, but remains normal for compression. If the vehicle load is increased, the length of the unit tends to shorten, thus causing the valve 111 to be opened to admit more gas to re-establish the original vehicle height. Similarly, on decreasing the vehicle load the valve 112 is opened to atmosphere. The valves 105, 106 are shaped to give a pressure drop proportional to the flow per unit time through the valve and the ball valve housings are arranged so that the balls when in the open position are not acted on by the gas flow. The ratio of the differential piston areas may be made such that the ratio of the dynamic to the static spring rates is more than 1.5 in respect of both sprung and unsprung masses.