GB2128695A - Disc Brakes - Google Patents

Abstract

A disc brake for a rail vehicle, in which disc segments are fastened to opposite sides of the web of a wheel. Each segment is secured to the wheel by a single fastening member 40 in a central position of the segment and additional fastening members 60-63 are provided in positions spaced from the central fastening member. The central fastening member does not permit relative movement between the segment and the wheel, whereas the additional fastening members permit some relative movement to take place. <IMAGE>

Description

SPECIFICATION Disc brakes The present invention relates to disc brakes, particularly, but not exclusively, for rail vehicles.

A disc brake for a rail vehicle may comprise a pair of friction pads arranged to be engageable with corresponding friction surfaces associated with a wheel of the rail vehicle. The friction pads may cover only a small portion ofthe friction surface (where the brake is ofthe "spot" type), butthefriction surface associated with each side ofthe wheel will normally be a complete annulus. The annularfriction surfaces may be provided as part of the wheel structure, integral with the web portion ofthe wheel, or may be provided by annular or segmental annular members fastened to the web ofthe wheel.

One problem in brakes ofthe above kind is that the heat generated in braking tends to cause distortion of the friction surfaces of the wheel, and the invention has the object of providing such friction surfaces in a manner so as to reduce the disadvantageous effects which result from such heat distortion.

According to the invention, a disc brake comprises a rotor member having attached thereto a plurality of disc segments arranged to provide an annularfriction surface thereon, each segment being secured to the rotor member by means of a single fastening member in a central position of the segment and a plurality of additional fastening members in positions spaced from the central fastening member, the arrangement being such that the central fastening member does not permit relative movement between the segment and the rotor member in its immediate vicinity whereas the additional fastening members provide clearances which enable some relative movement to take place between thesegmentand the rotor member.

In a preferred construction, as applied to a rail vehicle brake, the rotor member comprises the web of a wheel of the rail vehicle and annular friction surfaces are provided one on each side of the wheel by a series ofsegments secured to the opposite sides of the wheel. Conveniently, the fastening membersforthe segments on the two sides ofthe wheel are common, consisting of bolts passing through the segments and the web ofthewheel.

In a particular preferred example, the friction surfaces for the two sides of a rail vehicle wheel are each formed from four equal annular segments which togetherformafull annulusandarechamferedattheir ends, the segments being secured by means of four central bolts closely fitted in aligned holes in the segments and the web portion ofthe wheel and the segments being deeply recessed to enable the bolt heads on one side and associated nuts on the other side of the wheel to be well below the friction surfaces.

Whilst presenting a flat friction surface on each side ofthe wheel, the segments may be formed on their sides adjacent the web ofthe wheel with a finned configuration so as to provide radial channels for cooling air to pass between the web ofthe wheel and the friction surfaces.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial end view showing partofa friction surface and a part of an associated friction pad fora rail vehicle wheel brake; Figure 2 is a section on the line ll-ll of Figure 1, looking in the direction ofthe arrows; Figure 3 is a section on the line Ill-Ill of Figure 1; Figure 4 is a section on the line IV-IV of Figure 1; Figure 5 is an axial end view similarto Figure 1 showing a modified securing means, partly sectioned on the line V-V of Figure 6; and Figure 6 is a section on the line Vl-VI of Figure 5.

The friction surface 10, part ofwhich is shown in Figure 1, is provided byfoursegmentalfriction members, three ofwhich are indicated in Figure 1 by references 11, 12 and 13 respectively. The four segments are similarto one another, and are secured to the web portion 15 of a rail vehicle wheel 16 to provide a complete annularfriction surface, the ends 17,18, 19,20 ofthe segments being chamfered and lying closely adjacentthe ends of the neighbouring segment to provide a substantially unbroken friction surface.

The brake is of the spot type, part of an associated friction pad 25 being indicated in Figure 1. Forthe porposes of illustration only, a pair of friction pads 25, 26, are also shown in Figure 2, although their position as illustrated in Figure 1 would not normally be indicated on the section line ll-ll.

Figure 2 illustrates part of the hub 28 of the wheel and part ofthe rim 29 of the wheel, and shows the arrangement of friction members on each side of the wheel to provide friction surfaces 10 and 30 on opposite sides of the wheel. No mechanism for pressing friction pads 25, 26 againstfriction surfaces 10 and 30 is shown in the drawings: this mechanism is conventional in form, and may be ofthe pincertype operated by a conventional pneumatic system.

The means by which the friction segments are secured to the wheel 16 will now be described with reference to the segments 12 shown in Figure 1, the other three segments being similar, and the arrangement on the two sides of the disc also being similar.

Figure 2 iilustrates part of the segment 12 and partof the similar segment 31 on the opposite side ofthe wheel, and Figure 4 shows a part of the segment 12 from a different direction.

The circumferential load exerted during braking on the segment 12 is transmitted mainly by a fastening member in the form of a bolt 40 which passes through a hole41 inthesegment 12 and a hole42 in theweb 15, the bolt40 being a close fit in the holes 41 and 42so as to prevent any relative movement between the adjacent portion 43 ofthe segment 12 and the web 15.

The bolt 40 is secured in a recess 45 ofthe segment 12 by means of a nut 46 and washer 47 bearing on a shoulder 48 of the segment 12. On the other side ofthe web 15, the bolt 40 passes as a closefitthrough a corresponding hole in the associated segment 31 (not shown in Figure 3) and the head ofthe bolt40 is secured in a recess (also not shown) in the segment 31.

The rear surface ofthe segment 12 which engages the web 15 of the wheel is provided with fins 50 defining radial channels 51 for enabling cooling air to flowthrough the space between the segment 12 and the wheel web 15.

Four additional fastening members in the form of bolts 60,61,62,63 are provided to hold the segment 12 againsttheweb 15 whilstenabling minor relative movement between the adjacent portions ofthe segment 12 and the web 15to take place when the segment 12 expands underthe action of heat gener atedduring braking. Figure 4shows the arrangement ofthe bolt 62 which passes through a clearance hole 64 in the segment 12 and isa close fit in the web 15, a similar clearance hole being provided in the segment 31 on the opposite side ofthe wheel.

The bolt 62 (the arrangement ofthe bolts 60,61 and 63 being similar) is secured in position by a nut 65 and washer 66.

The portion 67 of the segment 12 adjacent to bolt 62 provides a shoulder 68 th rough which a clamping load is applied by the bolt 62 to hold the segment 12 against the web 15, butthis is insufficientto prevent move ment ofthe segment under thermal stress.

By the arrangement described above the segment 12 is firmly secured in its central region bythe bolt 40 but is enabled to expand and contract slightly in its peripheral regions by its relatively less rigid connection through the medium of the bolts 60-63. The distance between the central fastening member and the additional fastening members is such that the movement required at the peripheral regions is relatively small compared to any arrangement where a relativelytightfastening member is placed at one end of the segment and a fastening member with clearance is placed at the other end, and the construction according to the invention therefore combines a secure mounting forthe segment with a relatively small need for movement in its peripheral regions underthermal stress.

In the modification illustrated in Figures 5 and 6, in orderto provide means for positively resisting rotation ofthe segment 12 about the central bolt 40, one, 62 ofthe four bolts 61,62,63,64 atthe corners of the segments is located in a slot 70 formed in the segment in place of the hole 64. The slot 70 is aligned with the direction of a line X-X joining the corner bolt 62 and the central bolt 40, and is of such width as to provide a sliding fit to enable the segmentto move only in the direction ofthe line X-X. The clearances between the ends 71 and 72 ofthe slot and the boltwhenthis is disposed centrally in the slot as shown are approximately equal to the radial clearances around the bolts 60,61 and 63 in their respective holes 64, which are circular, similarto the holes 64 previously described.

The advantage ofthe modified arrangement of Figures Sand 6 is that it ensures that the segments 12, whilst free to distort slightly underthermal stress, are positively located and prevented from rotating about their central bolts 40. This avoids possible unbalance and noise in operation, and maintains a positive clearance around the otherthree corner bolts.

Claims (13)

1. Adisc brake comprising a rotor member having attached thereto a plurality of disc segments arranged to provide an annularfriction surface thereon, each segment being secured to the rotor member by means of a single fastening member in a central position of thesegmentand a plurality of additional fastening members in positions spaced from the central fastening member,the arrangement being such that the central fastening member does not permit relative movement between the segment and the rotor member in its immediate vicinity whereas the addi tional fastening members provide clearances which enable some relative movement to take place between the segment and the rotor member.

2. A disc brake according to claim 1 wherein the rotor member comprises the web of a wheel.

3. A disc brake according to claim 2 wherein a plurality of segments are secured to each ofthe opposite sides ofthe web ofthe wheel to provide annularfriction surfaces on opposite sides ofthe wheel.

4. A disc brake according to claim 3 wherein common fastening members are providedforthe segments on the two sides ofthe wheel.

5. A disc brake according to claim 4wherein the fastening members comprise bolts passing through the segments and the web of the wheel.

6. A disc brake according to any of claims 2-5 whereinthesegmentsareformed on their sides adjacent the web of the wheel with a finned configura tionto provide channelsforcooling airto pass between the web ofthe wheel and the friction surfaces.

7. A disc brake according to any of claims 2-6 wherein the ends ofthe segments are chamfered and lie closely adjacentthe ends of neighbouring segmentsto provide a substantially unbroken friction surface.

8. A disc brake according to any of claims 2-7 wherein the central fastening memberforeach segment comprises a bolt which is a close fit in aligned holes in thesegment and the wheel web.

9. A disc brake according to any of claims 2-8 wherein the additional fastening members comprise additional bolts positioned in the peripheral regions of the segment which are a close fit in thewheel web and pass through clearance holes in the associated segment, the additional bolts serving to apply a clamping load to hold the segments againstthe wheel web, said clamping load being insufficientto prevent movement ofthe segment underthermal stress.

10. A disc brake according to claim 1 wherein one ofthe additional fastening members for each segment is arranged to permit relative movement between the segment and the rotor member only in the direction between the said additional fastening member and the associated central fastening member.

11. A disc brake according to claim 1 wherein the said one ofthe additional fastening members comprises a boltwhich is a close fit in the wheel web and is aslidingfitin aslotformed inthesegment,saidslot being aligned with the direction between the said additional fastening member and the associated central fastening member.

12. A disc brake according to any of claims 1-11 wherein the rotormembercomprisesthewebofa wheel of a rail vehicle.

13. A disc brake constructed and arranged substantially as described herein and illustrated in the accompanying drawings.