GB2307889A

GB2307889A - Single axle suspension for rail vehicle allows steering effect - improving ride, and reducing noise emission and wheel flange wear

Info

Publication number: GB2307889A
Application number: GB9624756A
Authority: GB
Inventors: Michael Kibble; Brian Leslie Smith
Original assignee: POWELL DUFFRYN STANDARD Ltd
Current assignee: POWELL DUFFRYN STANDARD Ltd
Priority date: 1995-12-07
Filing date: 1996-11-28
Publication date: 1997-06-11
Also published as: GB9624756D0

Abstract

A suspension unit 11 for supporting an end of a rail vehicle wheelset (axle) comprises upper frame 12 mounted on the vehicle chassis, and lower frame 14 including bearing assembly 15 carrying an end of wheelset 10. Primary helical compression springs 20 are mounted between upper and lower frames fore and aft of the bearing. Oppositely inclined hydraulic dampers 24, which may be two-rate dampers, damp relative vertical and lateral movement between the two frames. A longitudinal track rod 27, which may have longitudinally flexible end connections 28 and 30, is connected between lower frame 14 and a fixed vehicle part 29 to restrain relative fore-and-aft movement. Secondary helical compression springs 23 are mounted on spring mounts 21, with flanges 22 bearing on the primary springs. These secondary springs are of lower rate, for a good ride in the unladen condition; but are bypassed by full compression in the laden condition.

Description

"A Suspension Unit for a Wheelset of a Rail Vehicle" The invention relates to suspension units for the wheelsets of a rail vehicle, and particularly for two axle rail wagons.

As is well known, each wheel set of such a wagon comprises an axle to the opposite ends of which are rigidly fixed the flanged wheels. Short journals project axially outwardly of the wheels and are rotatably received in bearing assemblies in respective suspension units at each side of the wagon.

One well known form of suspension unit comprises an upper frame mounted on the vehicle and a lower frame which carries the bearing assembly and is connected to the upper frame by vertical helical compression springs arranged fore and aft of the bearing assembly. The bearing assembly is mounted by means of comparatively stiff resilient pads within a saddle forming part of the lower frame, and the saddle is slidable up and down within a guideway which extends downwardly from the upper frame.

While such an arrangement allows the required relative up and down movement between the wheels and the wagon, it allows very little movement of the wheels laterally or longitudinally of the vehicle and also allows very little pivotal movement of the wheelset about a vertical axis relative to the vehicle. In practice the permitted relative movement in these modes may be of the order of only a millimetre or two. As a consequence of this the wheels cannot readily adapt to curvatures and deviations of the rails, with the result that there is little or no steering effect. Flange wear of the wheels can therefore be considerable. Also, the stiffness of the suspension units can cause heavy vibrations to be transmitted through the wheels and rails to the surrounding ground which may be unacceptable in some locations of railway lines.

The present invention sets out to provide an improved form of suspension unit for a two axle rail vehicle which may overcome the above-mentioned disadvantages.

In this specification "longitudinally" refers to the direction of travel of the rail vehicle along the rails, "laterally" refers to a horizontal direction transverse to the longitudinal direction, i.e. across the rails, and references to "fore" and "aft" are in respect of the longitudinal direction.

According to the invention there is provided a suspension unit for supporting an end of a wheelset of a rail vehicle, comprising an upper frame for mounting on the vehicle, a lower frame movable relative to the upper frame and including a bearing assembly in which the end of the wheelset is rotatably mounted, primary spring means located fore and aft of the bearing assembly and connecting the lower frame to the upper frame, damping means to damp relative vertical and lateral movement between the upper and lower frames, and a track rod connected between the lower frame and a fixed part of the vehicle to restrain relative fore-and-aft movement between the upper and lower frames.

Preferably said primary spring means comprise two helical compression springs connected substantially vertically between the lower frame and upper frame fore and aft of the bearing assembly.

Secondary spring means may be connected in series with each primary spring means, so that a maximum permitted deflection of the secondary spring means is caused by an initial pre-detennined vertical load, whereafter subsequent increase in the vertical load causes deflection ofthe primary spring means alone. Each secondary spring means may also comprise a helical compression spring coaxial with the primary helical compression spring.

In this case the secondary spring means will normally be of a lower rate than the primary spring means so as to provide comparatively soft vertical and lateral springing when the vehicle is unladen. When the vehicle is loaded, the deflection of the secondary spring means is taken up so that stiffer vertical and lateral springing, appropriate for the heavier load, is provided by the primary spring means alone.

The aforesaid damping means may comprise one or more hydraulic dampers.

Preferably the damping means comprise at least one hydraulic damper inclined in a direction having both a vertical component and a lateral component. There may be provided two hydraulic dampers connected between the upper and lower frames fore and aft of the bearing assembly. Preferably the hydraulic dampers are inclined in opposite directions with respect to a vertical plane passing through the upper and lower frames.

The or each hydraulic damper may be a two-rate damper providing an increased resistance to relative movement between the upper and lower frames after an initial predetermined relative movement. For certain purposes, however, it may be desirable to use a single-rate or variable-rate dumper.

In any of the above arrangements the aforesaid track rod preferably extends substantially longitudinally of the rail vehicle.

Preferably the track rod is connected to the lower frame and/or to the fixed part of the vehicle by a longitudinally flexible connection. For example, a body of resilient reflexible material, such as a suitable elastomer, may be connected between an end of the track rod and the lower frame and/or between an end of the track rod and said fixed part of the vehicle.

The following is a more detailed description of an embodiment of the invention, by way of example, reference being made to the accompanying drawings in which: Figure 1 is a diagrammatic side elevation of a suspension unit in accordance with the invention, and Figure 2 is a diagrammatic view of the unit looking longitudinally of the vehicle.

Referring to the drawings: a suspension unit 11 is provided at each end of each of the two wheelsets 10 on a two axial wagon. Each suspension unit comprises an upper cast metal frame 12 rigidly mounted on the vehicle underframe 13, and a cast metal lower frame 14.

The lower frame 14 is provided with a bearing assembly 15 in which is rotatable a journal 16 on the end of the wheelset 10, outboard of the flanged wheel 17.

An upstanding location member 18 extends upwardly from the bearing assembly 15 and extends loosely into a housing 19 at the centre of the upper frame 12.

Fore and aft of the bearing assembly 15, the upper and lower frames are connected by two vertical primary helical compression springs 20. A spring cup 21 is received within the upper end of each primary spring 20 and is formed with an outward peripheral flange 22 which bears on the upper end of the primary spring 20. A secondary helical compression spring 23 is received within the spring cup 21, and the upper end of each secondary spring 23 bears against the underside of the upper frame 12.

The provision of primary springs 20 and secondary springs 23 provides a tworate system. When the vehicle is unladen the secondary springs 23 are effectively in series with the primary springs 20, and since the secondary springs 23 are much less stiff than the primary springs, they provide comparatively soft vertical and lateral springing for the empty vehicle. As the vehicle is loaded the secondary springs 23 become compressed until the underside of the upper frame 12 bears downwardly on the flanges 22 on the upper ends of the spring cups 21, so that further loading of the vehicle is resisted solely by the stiffer primary springs 20.The stiffness of the springs 20 and 23 is tuned to provide a required two-rate resistance to lateral loads, as well as vertical loads, of a magnitude to permit a required degree of lateral and/or twisting movement of the wheelset relative to the vehicle body, to provide a steering action.

Adjacent each primary spring 20 the upper and lower frames are also connected by telescopic hydraulic dampers 24. Each damper 24 is pivotally connected between a bracket 25 on the upper frame 12 and a bracket 26 on the lower frame 14.

As best seen in Figure 2, each hydraulic damper 24 is inclined at 300 to the vertical, the two dampers being inclined in opposite directions with respect to a vertical plane extending longitudinally of the vehicle. Each damper 24 therefore provides both vertical and lateral damping between the lower frame 14 and upper frame 12 of the suspension unit.

Each hydraulic damper 24 is a two-rate damper, that is to say its stiffness increases beyond a predetermined load, so as to provide damping appropriate for both the unladen and laden vehicle.

A track rod 27 is provided on each suspension unit and extends longitudinally ofthe vehicle. One end ofthe track rod 27 is connected to the lower frame 14 adjacent the bearing assembly 15 by means of a flexible coupling 28, and the opposite end of the track rod is connected to a bracket 29 by means of a similar flexible coupling 30. The bracket 29 is rigidly connected to the underframe 13 of the vehicle.

Each of the flexible couplings 28, 30, comprises a cylindrical housing containing a sleeve of elastomer which closely encircles a vertical shaft on the part to which the end of the track rod is connected. The track rod 27 is inclined upwardly at a small angle as it extends from the coupling 28 to the coupling 30.

The track rods 27 at opposite ends of each wheelset each extend in a direction towards the other wheelset.

The suspension unit according to the invention allows greater, but controlled, movement of the wheelset in the lateral and longitudinal directions than is permitted by the prior art suspension units referred to previously, and thus allows adequate movement for the wheels to steer and follow deviations in the rails thus providing a smoother ride, with less ground transmitted vibration, and less flange wear. For example, the unit may permit movement of the wheelset of the order of 20mm, compared with the 1 or 2mm of the prior art arrangements.

Claims

1. A suspension unit for supporting an end of a wheelset of a rail vehicle, comprising an upper frame for mounting on the vehicle, a lower frame movable relative to the upper frame and including a bearing assembly in which the end of the wheelset is to be rotatably mounted, primary spring means located fore and aft of the bearing assembly and connecting the lower frame to the upper frame, damping means to damp relative vertical and lateral movement between the upper and lower frames, and a track rod for connection between the lower frame and a fixed part of the vehicle to restrain relative fore-and-aft movement between the upper and lower frames.

2. A suspension unit according to Claim 1, wherein said primary spring means comprise two helical compression springs connected substantially vertically between the lower frame and upper frame fore and aft of the bearing assembly.

3. A suspension unit according to Claim 1 or Claim 2, wherein secondary spring means are connected in series with each primary spring means, so that a maximum permitted deflection of the secondary spring means is caused by an initial pre-determined vertical load, whereafter subsequent increase in the vertical load causes deflection of the primary spring means alone.

4. A suspension unit according to Claim 2 and Claim 3, wherein each secondary spring means comprises a helical compression spring coaxial with the primary helical compression spring.

5. A suspension unit according to Claim 4, wherein the secondary spring means is of a lower rate than the primary spring means.

6. A suspension unit according to any of the preceding claims, wherein said damping means comprise one or more hydraulic dampers.

7. A suspension unit according to Claim 6, wherein said damping means comprise at least one hydraulic damper inclined in a direction having both a vertical component and a lateral component.

8. A suspension unit according to Claim 7, wherein there are provided two hydraulic dampers connected between the upper and lower frames fore and aft of the bearing assembly, and the hydraulic dampers are inclined in opposite directions with respect to a vertical plane passing through the upper and lower frames.

9. A suspension unit according to any of Claims 6 to 8, wherein the or each hydraulic damper is a two-rate damper providing an increased resistance to relative movement between the upper and lower frames after an initial predetermined relative movement.

10. A suspension unit according to any of the preceding claims, wherein said track rod extends substantially longitudinally of the rail vehicle.

11. A suspension unit according to any ofthe preceding claims, wherein said track rod is connected to the lower frame and/or to the fixed part of the vehicle by a longitudinally flexible connection.

12. A suspension unit according to Claim 11, wherein a body of resilient reflexible material is connected between an end of the track rod and the lower frame and/or between an end of the track rod and said fixed part of the vehicle.

13. A suspension unit for supporting an end of a wheelset of a rail vehicle, and substantially as hereinbefore described with reference to the accompanying drawings.