Patent GB-1247179-A (GB)
Title: Pneumatic spring suspension unit containing a level control inside a cylinder casing
Inventor: STRAUFF GUNTER
IPC: B60G17/048
Filed: 1968-12-05
Abstract: 1,247,179. Springs. V. LANGEN, [trading as LANGEN & CO.]. 5 Dec., 1968, No. 57850/68. Addition to 1,241,807. Heading F2S. A suspension unit as described in the parent Specification wherein, in order to ensure that the piston chamber is rapidly closed when pressure is absent or insufficient, the pressure fluid entry contains a spring loaded check valve that opens in the downstream direction, the check valve is by-passed by a throttle, a branch pipe on the downstream side of the check valve leads to a two-way valve, and the bore 5 which contains the face of the control piston remote from the piston chamber is connected with the pressure fluid pipe at a location downstream of the check valve. The pressure fluid entry is connected to a main pressure pipe P and to pressure pipes P2, P3 and P4 by means of a pipe P1 as shown in Fig. 1 and the exit is connected to a main return pipe T and to exhaust pipes T2, T3 and T4 by means of an exhaust pipe T1. The pipe P contains a spring-loaded check valve 34 which opens when pressurized-fluid is supplied by a pump 33. The check valve 34 is by-passed by a throttle 35 and a branch pipe 36, located on the downstream side of the valve 34, connects to a two-way valve 37, the latter being movable, by the pressure differential generated across the throttle 35 between pipes 38, 39 against the resistance of a restoring spring 40, from an exhaust position a into a blocking position b. The bore 5 is connected to the pipe P by a pipe 41 containing a check valve 42. An overload valve 43 connects the pipe P to the exhaust pipe T, the latter leading to a reservoir and an accumulator 44 is connected to the pipe P. A number of individual features may be combined in one unit 45 as shown in Fig. 2 and which comprises a spring-loaded check valve, a throttle and a two-way valve. A plunger 48 is slidable in a bore 46 of a casing 47 and pressurized-fluid is applied to both sides thereof through pipe connections 49, 50 at the ends of the bore 46. The plunger 48 is urged by a restoring spring 51 which is supported by a ring 52 secured within the casing 47, has a downstream edge 53 which controls an exhaust port 54, and has a stepped axial bore 55 therein which contains a check valve 56 having a channel 59 therein and which opens to the downstream side against a spring 57, the latter being supported by a ring 58 mounted inside the plunger 48. The stroke of the latter is limited by a ring 60 supported by the casing 47. The pipe P is connected to the connections 49, 50, the former being in communication with the pump 33. The operative positions of the suspension unit shown in the Figures are when there is no pressure in the pipe P. When pressurized fluid is supplied by the pump 33 however, some of the fluid flows through the throttle 35 (or channel 59). The cross-section of the throttle 35 (or the channel 59) is designed to allow a build-up of static pressure head when the pump continues to deliver fluid. This pressure head moves the valve 37 against the spring 40 into blocking position a (or displaces the plunger 48 against the spring 51 until the exhaust port 54 is closed). The check valve 34 (or 56) remains closed and will not open until the static pressure head rises after the valve 37 (or the plunger 48) has been actuated. The fluid then flows through the pressure pipe P1 into the annular groove 20, through the bore 18 and the constriction 25, into the bore 5. The check valve 42 remains closed and, since the valve 43 in on the downstream side of the valve 34 (or 56), fluid flow will continue and the valve 37 will remain in the position a (or the plunger 48 will continue to cover the exhaust port 54). When the pump 33 is at rest, the absence of a pressure differential between the pipes 38 and 39 (or between the connections 49 and 50) allows the check valve 34 (or 56) to close. The spring 40 will return the valve 37 into the exhausting position b (or the spring 51 will move the plunger 48 to uncover the exhaust port 54). The downstream part of the pipe P, and hence the connections 20, 21, 18, 25, 5, 41 and 42, will be connected to the exhaust T.