Patent GB-966985-A (GB)
Title: Improvements in or relating to tandem axle suspension units
Inventor: CHAMBERS HARRY DONALD
IPC: B60G11/28
Filed: 1961-03-27
Abstract: 966,985. Tandem axle suspensions; mounting bodies on, and springs for, rail vehicles. EATON AXLES Ltd. March 27, 1961, No. 11193/61. Addition to 857,554. Headings B7D and B7L. [Also in Division F2] A road or rail vehicle tandem axle suspension system comprises at each side of the vehicle a member 1 secured to the vehicle frame or body, axles 3, 4 connected by leading and trailing links 7, 8, to member 1, a hydropneumatic spring unit rigidly secured in relation to member 1 comprising a hollow enclosed body 15 with a space 40 containing a mass of gas, the remainder of the space containing hydraulic fluid and a pair of hydraulic rams 12 directed inwardly and upwardly in said body and acting on links 7, 8. In Fig. 1, the axles 3, 4 are mounted on members 5, 6, the upper ends of which are connected by links 9, 10 to the frame 2. In the construction shown in Fig. 2, the left-hand ram 18 is guided by a hollow cylindrical extension 28 sliding in the body of the spring unit and 12 connected to link 7 by a connecting rod is pivoted to the link and having a cup-shaped upper end 19 sliding between spherical surfaces 20, 21 of the ram. The chamber 14<SP>1</SP> above the ram communicates through ram extension 28, passage 14 and damper valve 17 with chamber 15, the whole system containing hydraulic fluid except for the mass of air in chamber 15 which is preferably separated from the fluid by a flexible bladder 40 (Fig. 3) or a piston (see Fig. 5, not shown). The hydraulic system, Fig. 6, comprises an engine driven pump 90 supplying the spring unit 11 through a non- return valve 93, the fluid being released by levelling valve 70 to return through a shut-off valve 95 which is held open against spring pressure by pressure hydraulic fluid in line 96 when the pump is operating, to a reservoir 91. The levelling valve in Fig. 2 takes the form of a spool valve 70, the end 72 of spool 71 bearing on a cam face 73 on ram extension 28 to control the vehicle height by cutting off the flow of fluid from the spring unit into the valve through port 78 when the height falls, the fluid normally flowing from the valve through output port 79 back to the reservoir. The damping valve 17 comprises a spider 53 round which the fluid can pass, a valve seat 54<SP>1</SP>, and a poppet valve member 55 loaded by tension spring 57. The annular gap between seating 54<SP>1</SP> and valve member 55 and hence the damping can be varied with the load by admitting hydraulic fluid at the springing gas pressure through lead 62, the pressure on the upper face of piston portion 60 of valve member 55 being relieved by connecting space 59 to the reservoir. Alternatively, by using a driver controlled twoway valve the lead 62 may be connected to the pump output to give maximum damping. In the alternative ram construction shown in the right-hand side of Fig. 2 the connecting rod has a spherical end 33 and the ram is guided by portions sliding in both cylinders 36 and 29, vehicle height being controlled by the edge of the ram cutting off the port 99 in cylinder 36 leading to the reservoir. In further alternatives, Fig. 4, the rams are connected rigidly to the links 7, 8, a flexible diaphragm between each ram and the spring unit body retaining the hydraulic fluid. Levelling is provided in the right-hand construction by edge 124<SP>1</SP> of hollow piston member 126 cutting off port 123 which communicates with the reservoir through annular chamber 121 and tube 122. Movement of the ram is communicated to piston member 126 by attached roller 127. In the left-hand construction alternative ports 123<SP>1</SP>, 123<SP>11</SP> provide for two alternative vehicle heights. When the greater vehicle height is required hydraulic fluid from the pump is admitted through port 130 into groove 131 forcing annular member 132 down to mask port 123<SP>1</SP>.