GB2355442A - Spring assembly for a rail vehicle primary suspension - Google Patents

Abstract

The spring assembly is of at least two-rate form, comprising a helical compression spring 26 connected in series with an elastomeric spring 27. The spring 27 is annular, with an outer bonded support 33, for mounting on a vehicle body 32 e.g. wagon under frame, and an inner bonded support 34, together with an adaptor plate 35 locating the upper end of the spring 26. The spring 27 provides soft suspension for tare conditions, the spring 27, optionally with a further parallel helper spring to provide a three-rate assembly, provides stiffer suspension for loaded conditions.

Description

2355442 "Pdm= Suspension for a Rail Vehicle" The invention relates to

primary suspensions for rail vehicles of the kind in which wheel and axle sets extend transversely beneath the vehicle body, opposite ends of the axle of each set being rotatable in respective bearing assemblies, each of which is 5 connected to the vehicle body by a primary suspension.

In a rail vehicle of this kind the primary suspension allows each wheel and axle set to perform limited vertical movement relative to the side frames and also to be twisted relative to the side frames, in a yaw sense, and to be able to translate laterally. Commonly the primary suspension may comprise pairs of vertical helical compression springs which are connected between each bearing assembly and the vehicle body, on either side of the bearing. Usually the spring assemblies are two-rate assemblies so as to provide different vertical stiffnesses for the laden and tare (unladen) conditions of the vehicle.

Various designs of two-rate spring assemblies are known and are commonly used on rail vehicles. The present invention provides a novel form of two-rate spring assembly for such use which can allow the provision of spring characteristics which are particularly advantageous.

According to the invention there is provided a primary suspension for a rail vehicle of the kind first referred to, wherein the primary suspension includes at least one spring assembly of at least two-rate form comprising a helical compression spring connected in series with an elastomeric spring.

Preferably the stiffiess of the elastomeric spring is significantly less than the 2 stifffiess of the helical compression spring.

Thus, in the tare condition the primary suspension is provided mainly by the elastomeric springs and is hence comparatively soft. As the rail vehicle is loaded and the vertical loading on the spring assemblies increases, a point is reached where the elastomeric spring bottoms out and the primary suspension is provided solely by the helical compression springs, so that the stifffiess of the suspension is substantially increased.

The elastomeric spring may be connected between two relatively movable support members. For example, the elastomeric spring may be bonded to each of the 10 support members.

Preferably means are provided to limit the deformation of the elastorneric spring under increasing load. For example, abutments means may be provided to limit the relative movement of the support members towards one another.

One of the support members may be connected to the helical compression spring, 15 the other support member being connected to a part of the vehicle body.

The elastorneric spring may comprise a body of elastomer so connected between said support members as to be deformed in shear when under load. For example, the body of elastomer may be generally annular in configuration, having an inner periphery connected to an inner support member and an outer periphery connected to an outer 20 support member.

In this case, the inner support member may comprise a cylindrical part, to the outer surface of which the inner periphery of the body of elastomer is connected, and an 3 end part providing an annular flange projecting outwardly from one end of the cylindrical part.

The outer support member may be generally cup-shaped, comprising an end part and a peripheral wall extending from the end part, the inner surface of the peripheral wall 5 being connected to the outer peripheral surface of the body of elastomer.

In this arrangement the aforesaid means to limit the defon-nation of the elastomeric spring may comprise engagement between the outwardly projecting flange on the inner support member with the peripheral wall on the outer support member, and/or engagement between the cylindrical part of the inner support member and the end part of the outer support member.

One end of the helical compression spring may be connected to the end part of one of the support members, preferably the inner support member. Said end part may be formed with a central projection which projects into the interior of the end of the helical compression spring to locate the end part with respect to the spring.

In any of the arrangements according to the invention, the helical compression spring is preferably generally vertically orientated. In this case the elastorneric spring is preferably located above the helical compression spring.

An additional helical compression spring is conveniently located in parallel with the first mentioned helical compression spring. The additional helical compression spring, referred to hereafter as the helper spring, may be arranged to be operative over the full operating range of the first mentioned helical compression spring. Alternatively, it may be arranged to become active only when the first mentioned helical compression 4 spring has been compressed beyond a predetermined amount.

Such an arrangement is advantageous in that the suspension can be used in a wide range of applications using a standard size helical compression spring and elastomeric spring, the helper spring being chosen depending upon the application.

Where the helper spring becomes active only after displacement of the first mentioned helical compression spring beyond a predetermined distance, then- it will be appreciated that the spring assembly is of three-rate form.

In a preferred embodiment of the invention each primary suspension means comprises a pair of spring assemblies disposed fore and aft respectively of the associated bearing assembly.

The invention includes within its scope a spring assembly of at least tworate form, for use in a rail vehicle of the kind first referred to, and comprising a helical compression spring connected in series with an elastomeric spring according to any of the arrangements referred to above.

The following is a more detailed description of a preferred embodiment of the invention, by way of example, reference being made to the accompanying drawings in which:

Figure 1 is a plan view of a prior art form of primary suspension which may be used on a rail vehicle, Figure 2 is a side elevation of the primary suspension shown in Figure 1, Figure 3 is a diagrammatic section through part of a two-rate spring assembly according to the present invention for use in the primary suspension of a rail vehicle, Figure 4 is a typical load/deflection curve for one form of two-rate spring according to the present invention, Figure 5 is a diagrammatic section through part of another spring assembly in accordance with the invention, and Figures 6 and 7 are graphs similar to Figure 4 for two finther spring assemblies.

Referring to Figure 1, there is shown in chain fines a wheelset 10 extending transversely beneath the body of a rail vehicle. The wheelset 10 comprises an axle I I on opposite ends of which are rigidly mounted flanged wheels 12. Outboard of each wheel 12 the wheel set comprises a journal which is rotatable in a bearing assembly 16 (see Figure 2).

As best seen in Figure 2, each bearing assembly 16 comprises an axle box 17, containing the bearing, the axle box including support arms 18. In this prior art arrangement, a vertical helical compression spring assembly 19 is disposed on each side of the axle box 17 with its lower end engaging in a recess in one of the support arms 18 and its upper end received in a bracket 20 connected to the underside of the vehicle body 13. The helical compression spring assemblies 19 constitute the primary suspension of the vehicle and also provide the lateral stiffness for the vehicle. A vertical hydraulic damper 21 is disposed outboard of the axle box 17 and is pivotally connected between brackets 22, 23 on the axle box 17 and the vehicle body 13 respectively. A fore-and-aft extending track rod 24 is pivotally connected between each bearing assembly 16 and a mounting 25 on the vehicle body 13.

In the prior arrangement shown in Figures I and 2, each spring assembly of the 6 primary suspension is a single helical compression spring. However, as previously mentioned, it is desirable that each spring assembly is a two- rate assembly, the vertical stifffiess of which increases between the tare and laden conditions of the vehicle.

Figure 3 illustrates diagrammatically a two-rate spring assembly according to the present invention which may be used in the arrangement of Figure 2 and in other similar types of primary suspension systems for rail vehicles.

Referring to Figure 3, the two-rate spring assembly comprises a conventional helical compression spring 26 connected in series with an elastomeric spring 27. The right-hand section of Figure 3 shows the spring assembly in the tare or unladen condition whereas the left half of the drawing shows the assembly in the laden condition.

Referring to the right-hand half of Figure 3, the elastomeric spring comprises an annular body of elastomer 28, for example of rubber or synthetic rubber, mounted between an inner support member 29 and an outer support member 30. The outer support member 30, which is, in use, mounted on the underside of the vehicle body, comprises an upper end wall 31 from which extends downwardly an outer peripheral wall 32. The outer peripheral surface of the elastomer 28 is bonded to a metal sleeve 33 which is in turn connected, for example by bonding or by mechanical connection, to the wall 32. The end wall 31 and outer wall 32 may be part of the wagon underframe.

The inner periphery of the body of elastomer 28 is bonded to the outer surface of ahollowcyfindrical sleeve 34 which is mounted on a lower circular adaptor plate 35, the plate having a central upward projection 36 which fits within the lower end of the sleeve 34. The adaptor plate 35 also has a downwardly projecting central portion 37 7 which fits within the upper end of the helical compression spring. The lower end of the compression spring is received in a lower support on the axle box, in similar fashion to the way in which the lower ends of the springs 19 are located in recesses in the support arms 18 in Figure 2.

When the vehicle is unladen, as represented by the right-hand half of Figure 3, the upper end of the inner sleeve 34 is spaced below the top wall 31 of the fixed upper support member 30. In this condition, since the stiffiess of the elastorneric spring 27 is considerably less than the stiffness of the helical compression spring 26, the primary suspension is comparatively soft, the soft suspension being mainly provided by deflection of the elastorneric spring 27.

As the vehicle is loaded, the annular body of elastomer 28 is deformed downwardly in shear until, at a vertical load of about 18.2 kN, the lower end of the peripheral wall 32 engages the outer edge of the adaptor plate 35, as shown at the left band side of Figure 3. At the same time as the peripheral wall 32 engages the adaptor plate 35, the upper end of the cylindrical sleeve 34 engages the buffering lower face of the top end part 31 of the cup-shaped support member 30. At this point no further deformation of the elastomer spring is possible and fimher vertical load is restrained by the helical compression spring 26 alone which is significantly stiffer in the vertical sense than the elastorner so that consequently the overall vertical stiffness of the two-rate spring assembly is increased.

Figure 4 shows diagrammatically the vertical deflection of the two-rate spring plotted against the vertical load. It will be seen that, while the elastomeric spring is 8 effective the vertical deflection of the spring increases linearly with vertical load but at the point indicated at 38 where the elastomer spring reaches its maximum deformity, the stiffness of the spring assembly substantially increases so that increasing vertical load is accompanied by smaller increments of vertical deflection.

Figure 5 illustrates a spring assembly similar to that illustrated in Figure 3, and like reference numerals will be used to denote parts similar to or performing substantially the same function as the parts of the arrangement of Figure 3. The main distinction between the arrangement of Figure 5 and that of Figure 3 is that in the arrangement of Figure 5 an additional helical compression spring referred to hereafter as the helper spring 39 is provided. The helper spring 39 is arranged in parallel with the helical compression spring 26 to assist the helical compression spring 26 in urging the inner support member 29 away from the lower support. The helper spring 39 may be arranged to engage both the inner support member 29 and the lower support at all times, assisting the helical compression spring 26 at all times. In such an arrangement, the spring assembly will be of two rate form. Figure 6 illustrates the relationship between the load and the deflection of the spring assembly for such an arrangement. In Figure 6, the point at which the elastomeric spring becomes inactive is denoted by reference numeral 40.

Rather than being active throughout the range of movement of the inner support, the helper spring 39 may be packed in such a manner as to ensure that, for the first part of the movement of the inner support member 29 after the elastomeric spring 27 has been compressed to its inactive condition, movement of the inner support member 29 takes place against the action of the helical compression spring 26 alone, the helper 9 spring 39 becoming active in assisting the helical compression spring 26 only after the inner support member 29 has moved beyond a predetermined position. It will be appreciated that such a spring assembly is of three rate form, and Figure 7 illustrates the relationship between the load and deflection of such a spring assembly. In Figure 7, numeral 40 denotes the point at which the elastomeric. spring becomes inactive, and numeral 41 denotes the point at which the helper spring 39 becomes active.

The arrangements including the helper spring 39 are advantageous in that the spring assembly can be used in a wide range of applications with just the helper spring 39 being selected specifically for that application, standard values or rates of spring being used for the helical compression spring 26 and the elastomeric. spring 27. By way of example, the same elastomeric spring and helical compression spring can be used for applications of all axle loads between 20 tome and 25.5 tonne, only the helper spring 39 being chosen specifically for the application. Where the helper spring 39 is packed to cause the spring assembly to be of three-rate form, then it will be appreciated that the suspension is suitable for use in applications having a relatively high tare weight.

It will be appreciated that the spring assemblies shown in Figures 3 and 5 are just examples of primary suspension spring assemblies according to the present invention and other arrangements are possible where an elastomeric spring is effectively connected in series with a conventional helical compression spring. Similar effects can be achieved with the elastomeric spring and helical spring(s) in different relative dispositions and orientations other than the arrangements shown in Figures 3 and 5. Also, the particular overall arrangement of the primary suspension system shown in Figure 2 is merely by a way of example, and the two-rate spring assembly according to the present invention may also be used in other layouts of primary suspension systems for rail vehicles.

Claims (19)

1. A primary suspension for a rail vehicle, the primary suspension including at least one spring assembly of at least two-rate form comprising a helical compression spring 5 connected in series with an elastorneric spring.

2. A suspension as claimed in Claim 1, wherein the stiffness of the elastomeric spring is significantly less than the stiffness of the helical compression spring.

3. A suspension as claim in Claim I or Claim 2, wherein the elastomeric spring is connected between two relatively movable support members.

4. A suspension as claimed in Claim 3, wherein the elastorneric spring is bonded to each of the support members.

5. A suspension as claimed in Claim 3 or Claim 4, wherein one of the support members is connected to the helical compression spring, the other support member being connected to a part of the vehicle body.

6. A suspension as claimed in any one of Claims 3 to 5, wherein the elastomeric spring comprises a body of elastorner so connected between said support members as to be deformed in shear when under load.

7. A suspension as claimed in Claim 6, wherein the body of elastorner is generally annular in configuration, having an inner periphery connected to an inner support member and an outer periphery connected to an outer support member.

8. A suspension as claimed in Claim 7, wherein the inner support member comprises a cylindrical part, to the outer surface of which the inner periphery of the body of 12 elastomer is connected, and an end part providing an annular flange projecting outwardly from one end of the cylindrical part.

9. A suspension as claimed in Claim 7 or Claim 8, wherein the outer support member is generally cup-shaped, comprising an end part and a peripheral wall extending 5 from the end part, the inner surface of the peripheral wall being connected to the outer peripheral surface of the body of elastorner.

10. A suspension as claimed in any one of Claims 3 to 9, wherein abutments means are provided to limit the relative movement of the support members towards one another.

11. A suspension as claimed in any one of the preceding claims, wherein means are provided to limit the deformation of the elastomeric spring under increasing load.

12. A suspension as claimed in -any one of the preceding claims, further comprising a helper spring located in parallel with the helical compression spring.

13. A suspension as claimed in Claim 12, wherein the helper spring is operative over the full operating range of the helical compression spring.

14. A suspension as claimed in Claim 12, wherein the helper spring is arranged to become active only when the helical compression spring has been compressed beyond a predetermined amount.

15. A suspension as claimed in any one of the preceding claims, wherein the helical compression spring is generally vertically orientated.

16. A suspension as claimed in Claim IS, wherein the elastomeric spring is located above the helical compression spring.

13

17. A suspension as claimed in any one of the preceding claims, further comprising an additional spring assembly, the spring assemblies being disposed fore and aft respectively of an associated bearing assembly.

18. A spring assembly of at least two-rate form, for use in a rail vehicle, and 5 comprising a helical compression spring connected in series with an elastomeric spring according to any one of the preceding claims.

19. A primary suspension for a rail vehicle substantially as hereinbefore described with reference to any one of Figures 3 to 7.