GB2182108A

GB2182108A - Railway wheels with braking surfaces

Info

Publication number: GB2182108A
Application number: GB08625520A
Authority: GB
Inventors: Joseph Latham
Original assignee: Marmon Holdings UK Ltd
Current assignee: Marmon Holdings UK Ltd
Priority date: 1985-10-24
Filing date: 1986-10-24
Publication date: 1987-05-07
Also published as: GB2182108B; GB8526225D0; GB8625520D0

Abstract

Railway wheels and brake assemblies therefor are described, and each wheel comprises an inner hub 2, an outertread 4 having a flange 4a at one side thereof, and a web 5 between the tread and the hub. In one wheel, the face of the web 5 against which a braking pad 6 will act is bounded by inner and outer circumferential edges 11 and 12 each of which is bounded by a respective clearance, and the axial thickness of the webs 5 is at least 1 DIVIDED 2, and preferably equal to or greater than, that of the tread. A further wheel has a diameter less than 550mm with a web having an axial thickness of at least a half that of the tread. The web of this latter wheel has a radial centre plane which is off-set from that of the tread and also from the plane containing the running centre line of the wheel. A still further wheel has brake discs or the like secured to opposite faces of the web. In this wheel, the web has an axial thickness of at least a third that of the tread and the total axial thickness of the web and the brake discs is at least half that of the tread. All wheels may be used with in-board bearings. <IMAGE>

Description

SPECIFICATION Railway wheels The present invention relates to railway vehicle wheels and the braking thereof.

The invention relates more particularly to railway vehicle wheels which are particularly adapted to be braked buy a braking surface (e.g. a brake pad) which is moveable into and out of contaactwith a face of the wheel (or brake component secured thereto) to effect braking thereof. One example of such a braking arrangement is that known as a disc-brake in which a brake pad is applied to a brake ring or disc secured to the web ofthe wheel. In a further ex ample,the brake pad maybeapplieddirectlytothe web ofthe wheel to effect braking thereof.

In accordance with a first aspect ofthe present invention we provide a railway wheel comprising an inner hub, an outer tread having a flange atone side thereof, and a web between the tread and the hub wherein the portion of the face of the web against which a braking surface will act is bounded by respective inner and outer clearances.

The wheel ofthe first aspect of the invention is particularly suited for use with a brake arrangement in which a braking surface (e.g. a brake pad) is moveable towards and away from the web portion to which it is applied directly during braking. Generally, of course, such axially moveable braking surfaces will be provided at both sides of the web portion in which case each face oftheweb is bounded by inner and outerannularedges each bounded by respective clearances.

The clearances around the or each face of the web may be provided, for example, by annular grooves.

Alternatively, at least one ofthe clearances (usually the outer clearance) on the face ofthe web may be provided by a recess.

The provision ofthe inner and outer clearances on theface oftheweb against which the braking surface is applied has the advantage that any wear of the web caused by repeated brake application does not result in formation of a groove in the web against the walls of which the brake pad may catch during suspension travel of the wheel.

More particularly, in the wheel ofthe first aspect of the invention, anywearcaused by the braking surface merely causes the depth of the clearance to be reduced thereby avoiding the formation of a wear groove in the web. Thus suspension travel ofthe wheel merely causes the braking surface to project overthe innerorouterclearance as the case maybe.

For preferance the web ofthe wheel has an axial thickness (i.e. at viewed in a cross-sectional plane containing the rotational axis ofthe wheel) of at least halfthat of the tread. Most preferably the axial thick ness of the web is not substantially less than that of the tread and may in fact be equal to orgreaterthan this thickness.

The provision of a web of such substantial thickness has the advantage that it acts as a substantial heat sink for absorbing heat generated as a result of application ofthe braking surface to the web. A further advantage is in relation to cracks may which form in the surface oftheweb (e.g. as a resultofthe web being heated during heavy braking duties and then rapidly quenched - as may occur in wet weather). The propagation rate of these cracks slows down with increasing depth away from the surface of the web in which the crack was generated so that beyond a certain distance from the web face there may be no substantial propagation of the crack.

Clearly, if both sides of the web are being braked then its thickness should be such that there is no chance of the cracks generated on both sides ofthe web approaching so closely as to failure ofthe wheel.

Preferably also, the web ofthe hub has an axial thickness greater than that of the tread to ensure maintenance of the interference between the hub and axle when the wheel is mounted thereon.

The wheel ofthe first aspect ofthe invention is particularly suitable for 'small-wheel' bogies or railway vehicles such as that described in WO 86/02609 and to this end may have a diameter of 550mm (e.g. 400- 550mm) or less. As used herein the wheel diameter is measured across the running centre line ofthewheel i.e. the line defining the mid-point of the contact of the wheel tread on a railway track as it travels along a straight section thereof. Such a wheel is particularly suited for use in conjunction with bearings mounted inboard of the wheel as shown in WO 86/02609.

According to second aspect ofthe invention there is provided a railway wheel having a diameter less than 550mm (e.g. 400-550mm) and comprising an inner hub, an outertread having a flange at one side thereof and a web between the tread and the hub wherein the web has an axial thickness of at least 1/2 that ofthetread, and the web has a radial centre plane which is off-set from that of the tread and also from the plane containing the running centre line of the wheel.

The running centre is generally about 70mm from theinnersideofthewheelflange. Generally,fora wheel in accordance with the second aspect ofthe invention the axial thickness ofthe tread will be 127 to 135mm so that radial centre plane ofthe tread is 63.5 - 67.5mm from the inner side of the wheel flange.

The advantage of using an off-set web as defined for the second aspect of the invention is that greater space for accomodating movement of the braking surfaces may be obtained at one side or the other of the wheel.

In accordance with a third aspect of the invention there is provided a railway wheel having a diameter less than 550mm (e.g. 400-550mm) and comprising inner hub, an outer tread having a flange at one side thereof, a web between the hub and the tread, and respective brake discs or the like secured to opposite faces ofthe web wherein the web has an axial thickness a least 1/3 that ofthe tread and the total axial thickness ofthe web and the brake discs is at least 1/2 that of the tread.

The provision of a web with an axial thickness of at least 1/3 that ofthe tread ensures that the web acts as a substantial heat sink (for absorbing heat generated during braking) for the comparatively small diameter wheels.

Moreover, the overall thickness of the brake discs and the web (i.e. at least 1/2 that ofthe tread) ensures that access can be gained to facilitate changing of brake pads.

The axial thickness of the hub of wheel of the third aspect of the invention is preferably greaterthan that of the tread for maintenance ofthe interferencefit between the hub and the axle on which it will be mounted.

The wheel of the third aspect of the invention is particularly suitable for use in conjunction with bearings mounted inboard ofthewheel.

In accordance with the fourth aspectofthe invention there is provided a railway wheel assembly comprising a railway wheel associated with a brake arrangementthereforwherein the wheel has a dia meterlessthan550mm (e.g.400-550mm),the bearings forthewheel are mounted thereof, and the brake arrangement incorporates a braking surface which is applied to during braking to a face of said wheel or a brake disc orthe like secured thereto.

The railway wheel used inthefourth aspectofthe invention may, for example, be of the construction described above in relation to the first, second and third aspectofthe invention.

The invention will now be described by way of example onlywith reference to the accompanying drawings which illustrate various wheel configurations and the braking thereof.

Figures 1 to 3 show embodiments of wheel in ac cordancewith the first aspect of the invention.

Figures 4to 5show embodiments of wheel in accordance with the second aspect of the invention, Figures 6and 7so illustrate the third aspect ofthe invention.

Figure 8illustrates a wheel with inboard bearings, in accordance with the fourth aspect ofthe invention.

All wheels 1 shown in the drawings comprise a hub 2 (mounted as an interference fit on an axle 3), a wheel tread 4with a flange 4a and a thickness t1 (see Figure 4), and an annularweb 5with athicknesstz.

Additionally for all illustrated wheels the radial centre plane of the web 5 is coincident with a radial plane of the axle 3.

Each ofthe wheels is associated with a brake arrangement (eg a caliper-brake arrangement) which is not shown in detail buy which incorporates brake pads 6 which are arcuate as viewed in a direction parallel to the rotational axis of the wheel . These pads 6 are moveable by the brake arrangementtowards and way from the web 5 of the wheel (as indicated bythe solid double headed arrows) to apply and release the brakes. Additionally, certain of the wheeels incorporate annular brake discs 7 secured to web 5.

In the wheel shown in Figure 1 the web 5 has an axial thickness equal to that ofthe tread which in turn is less than that of the hub 2.

Each face 10 oftheweb 5 is bounded by inner and outer annular grooves which provide clearances around the faces 10, 11 and 12 respectively. The depth of these grooves (as measured from the face 10) is depicted as a in the drawings. The value of a is greaterthan thewear allowance oftheweb.

Brake pads 6 act (during braking) directly against the faces 10 of web thus saving space as compared to the case where brake discs are provided on the webs. Such space saving may be of particular importance in the case where space on the railway vehicle for accomodating and operating the brakes is at a premium, e.g. on a vehicle with wheels of small diameter (less than 550mm).

Any wear of the web5 during braking, results in a decrease in the valve of a rather than the formation of a wear groove in the web face. Consequently, during suspension travel, (as indicated by the chain-dot arrows) the brake pads are able to project over grooves 11 or 12 (as the case may be) such as illustrated in the chain-dot position of a pad 6.

After a certain length of service, the faces l0ofthe web may require surface treatment (e.g. machining) to remove cracks and/or other defects. Although such treatment must not reduce the depth ofthe grooves around the face of the web to an unacceptably low value.

The wheel shown in Figure 2 is similar two that of Figure 1 save that the web 5 is of lesser axial thickness than the tread 4 (but more than half the value thereof). The use of such a web provides extra space for the movement of the pads during braking.

For the wheel shown in Figure 3, the web 5 is of an axial thickness greater than that of the tread 4. The inner edge oftheweb 5 is bounded by a groove 11 (as for Figures 1 and 2) butthe clearance around the outer edge of web 5 is provided by a recess 13, as illustrated. The use of a web with a thickness greater than that of the tread has the advantage that reads access is provided to facilitate changing of brake pads. In a modification ofthewheel shown in Figure 3, and annular groove (similarto groove 11) may be provided in the face of the wheel in the base of clearance 13.

Figures 4 and 5 illustrate wheels with a diameter of lessthan 550mm in accordance with the second aspect of the invention. All of these wheels have web portions 5 with a radial centre plane P2 axially offset from both the radial centre plane P1 of tread 4 and the radial plane P3 drawn through the running centre line of the wheel which lies at a distance t3 (usually 70mm) from the inner side of flange 4a.

The wheels shown in Figures 4 and 5 each have webs 5 whereof the thickness t2 is greater than half the axial thickness ofthetread.Thesewheelsare both braked by the direct application of the brake pads 6 to the web 5.

In the wheel of Figure 4the outer face of web 5 is 'flush' with the outer edge of tread 4therebyproducing a recess on the inner side ofthe wheel. Conversely, in the wheel of Figure 5, a similar recess is provided on the outer side ofthe wheel. These recesses as produced by the off-set webs are particularly advantageous since the space available at oneorotherside of the wheel for brake movement may be restricted, e.g. as may be the case in small wheeled railwayvehicles or railway vehicle bogies.

The wheels shown in Figures 4 and 5 may of course be modified such that the webS is positioned to give recess at both sides of the wheel. Alternatively the web may, at one or both sides of the wheel, stand proud ofthetread orfiange.

The wheels of Figures 6 and 7 are each in accord ance with the third aspect of the invention. Each has a web portion 4 with a thickness t2 which is at least 1/3 that ofthe tread. Additionally, each face of web 5 has secured thereto brake rings (or discs) 7 such that the total overall thickness of web Sand the two discs 7 is at least 1/2 that of the tread. The discs 7 each have an innerface of lessee radial width than the outer face. This ensures that, at leastforthe recess in which the disc is incorporated, there is a greater sur- face onto which the pad may brake then would be the case if it braked directly onto the wheel.

Figure 8 illustrates the fourth aspect ofthe invention in which a wheel 1 with a diameter less than 550mm and associated with inboard bearings 8 (e.g.

as shown in WO 86/02609 is braked by means of pads 6 acting against discs 7. Alternatively, pads 6may act directly against wb 5 provided that it is of sufficient axial thickness. This latter embodiment may be used, for example, with 'solid' wheels (i.e. t1 = t2).

Additionally, it will of course be appreciated that all the wheels of Figures 1 to 7 and associated brake arrangements may be used in conjunction with inboard bearings in accordance with the fourth aspect ofthe invention.

Claims

1. Arailwaywheel comprising an inner hub, an outertread having a flange at one side thereof, and a web between the tread and the hub wherein the portion oftheface oftheweb againstwhich a braking surfacewill act is bounded byinnerand outercircumferential edges and each of said edges are bounded buy a respective clearance.

2. Awheel as claimed in claim 1 wherein face of the web is bounded by inner and outercircumferential edges each ofwhich are bounded by respective clearance.

3. Awheel as claimed in ciaim 1 or2whereinthe or each face of the web portion is bounded by annular grooves which define said clearances.

4. Awheel as claimed in any one of claims 1 to 3 wherein the web has an axial thickness of at least half that of the tread.

5. Awheel as claimed in claim 4 wherein the web has an axial thickness less than that ofthetread.

6. Awheel as claimed in claim 1 or2 wherein the web has an axial thickness greaterthan that of the tread.

7. A wheel as claimed in claim 6 wherein the clearance bounding the or each inner edge is provided by a respective groove and the or each clearance bounding each outer edge is a recess.

8. Awheel as claimed in any one of claims 1 to 7 wherein the axial thickness of the hub is greaterthan that of the tread.

9. Awheel as claimed in any one of claims 1 to 8 having a diameter less than 550mm.

10. A railway wheel assembly comprising a wheel as claimed in any one of claims 1 to 9 associated with a brake arrangement therefor incorporating a braking surface which is moveable into an out of contact with the face ofthe web or a brake component secured thereto to effect braking ofthe wheel.

11. An assembly as claimed in claim 10when dir- ectly indirectly dependantfrom claim 2 wherein two braking surfaces are provided each being moveable towards and away from an associated face of the web.

12. An assembly as claimed in claim 10 to 11 wherein the each braking surface acts directly against the face or each face of the web.

13. An assemblyas claimed in anyone of claims 1 to 12 having bearings located inboard of the wheel.

14. A railway wheel assembly substantially as hereinbefore described with reference to any one of Figures 1 to 3 ofthe accompanying drawings.

15. Asecond railway wheel having a diameter less than 550mm and comprising an inner hub, an outer tread having a flange at one side thereof and a web between the tread and the hub wherein the web has an axial thickness of at least 1/2 that of the tread, and the web has a radial centre plane which is off-set from that ofthe tread and also from the plane containing the running centre line ofthewheel.

16. Awheelasclaimed inclaim 15whereinthe web has an axial thickness less than that of the tread.

17. A railway wheel assembly comprising a wheel as claimed in claim 15 or 16 associated with a brake arrangementtherefor incorporating a braking surface which is moveable into and outofcontact with the web or a brake component secured thereto to effect braking ofthewheel.

18. An assembly claimed in claim 17 wherein two braking surfaces are provided each being moveabletowards and away from an associated face of the web.

19. An assembly as claimed in claim 17 or 18 wherein the or each braking surface acts directly against the or each face of the web.

20. An assembly as claimed in any one of claims 16to 19 having bearings located inboard ofthe wheel.

21. A railway wheel assembly substantially as hereinbefore described with reference to Figures 4 or 5 ofthe accompanying drawings.

22. A railway wheel having a diameter less than 550mm and comprising an inner hub, an outertread having a flange at one side thereof, and a web between the hub and the tread, and respective brake discs or the like secured to opposite faces of the web, wherein the web has an axial thickness at least 1/3 that of the tread and the total axial thickness of the web and the brake discs is at least 1/2 that ofthe tread.

23. Awheel as claimed in claim 22 wherein the axial thickness ofthe hub is greaterthan that ofthe tread.

24. A railway wheel assembly comprising a wheel as claimed in claim 22 or 23 associated with a brake arrangementtherefor incorporating two braking surfaces which are moveable into and out of contact with respective ones of said brake discs so asto effect braking of the wheel.

25. A railway wheel assembly substantially as hereinbefore described with reference to Figures 6 or 7 of the accompanying drawings.

26. A railway wheel assembly comprising a railway wheel associated with a brake arrangement therefor wherein the wheel has a diameter less than 550mm, the bearings for the wheel are mounted inboard thereof, and the brake arrangement incorporates a braking surface which is applied during braking to efface the said wheel or a brake compo nent secured thereto.

27. A railway wheel assembly substantially as hereinbefore described with reference to Figure 8 of the accompanying drawings.

28. Railway vehicles having wheels orwheel assemblies as claimed in any one of claims 1 to 27.

29. Railway vehicle bogies having wheels or wheel assemblies as claimed in any one of claims 1 to 27.