GB2151730A

GB2151730A - Calliper brake mechanism

Info

Publication number: GB2151730A
Application number: GB08431039A
Authority: GB
Inventors: Arthur Brewster
Original assignee: Underground Mining Machinery Ltd
Current assignee: Underground Mining Machinery Ltd
Priority date: 1983-12-07
Filing date: 1984-12-07
Publication date: 1985-07-24
Also published as: GB8431039D0; GB8332689D0

Abstract

A calliper brake mechanism (B) is arranged to engage a rail (R) having a vertical web (23) supporting an enlarged head portion (21). The brake mechanism (B) comprises a pair of calliper arms (6 and 7), each of which carries brake pads (12, 13) at one end thereof. Means (5) are provided for biassing the calliper arms (6, 7) in such a manner that, in use, the brake pads (12, 13) grip lateral edge portions of a rail to effect braking action. The brake pads (12, 13) are shaped and positioned to engage, at least partly, underneath the head portion of the rail. Rails are joined together and to a base 24 by members 25 held by bolts 26 between the base and the rail web 23. Additional braking may be provided (Figure 5, not shown) by lowering the rail vehicle bogie such that pads (48) contact the upper surface of the rail. <IMAGE>

Description

SPECIFICATION Calliper brake mechanism This invention relates to a calliper brake mechanism, to a railway vehicle incorporating a calliper brake mechanism, and to a railway system constituted by such a railway vehicle and a rail track. The invention is particularly concerned with a mine rail vehicle having an improved calliper brake mechanism.

It is known to provide mine rail vehicles with calliper brake mechanisms. Usually, the bogies of such vehicles have respective calliper brake mechanisms at each side thereof. Each calliper brake mechanism has a hydraulic piston-and-cylinder unit, each of the components of which is connected to a respective brake pad. Each mechanism is mounted on the frame of the bogie, and heavy duty springs are provided for biassing the two brake pads towards one another. In normal running conditions, the two brake pads are held apart (on opposite side of a rail) by hydraulic pressure in the piston-and-cylinder unit. When the vehicle is to be braked, the hydraulic pressure is released, and the springs force the brake pads towards one another to grip the rail with a calliper action.

When mechanisms of this type are provided on mine rail vehicles having flanged wheels which run on standard bull head rails, the callipers are arranged to have a horizontal gripping action, so that the brake pads grip the sides of the heads of the rails. A major disadvantage of calliper brake mechanims of this type is that their brake pads tend to ride up the sides of the rails, thereby reducing (or completely removing) the braking force. In extreme cases, this could even lead to vehicle derailment.

The aim of the invention is to provide a calliper brake mechanism which does not suffer from this disadvantage.

The present invention provides a calliper brake mechanism for engagement with a rail having a vertical web supporting an enlarged head portion, the brake mechanism comprising a pair of calliper arms, each of which carries a brake pad at one end thereof, and means for biassing the calliper arms in such a manner that, in use, the brake pads grip lateral edge portions of a rail to effect braking action, wherein the brake mechanism is shaped and positioned to engage, at least partly, underneath the head portion of the rail.

Because the brake mechanism engages underneath the rail head portion, it constitutes brake pad lift-off prevention means.

Advantageously, the brake pads are shaped and positioned to engage, at least partly, underneath the head portion of the rail.

In a preferred embodiment, spring means constitute the means for biassing the calliper arms.

Preferably, means are provided for holding the brake pads out of engagement with the rail until the braking mechanism is actuated. Advantageously, a hydraulic piston-and-cylinder device constitutes said holding means. In this case, a set of heavy-duty disc springs provided within the hydraulic piston-and-cylinder device may constitute the spring means.

Conveniently, one of the calliper arms is fixed to the cylinder of the hydraulic piston-and-cylinder device, and the other calliper arm is fixed to the piston rod of said device. Preferably, the piston rod of the hydraulic piston-and-cylinder device is fixed to said other arm at a point spaced from its brake pad, and said other arm is pivotally connected to said one arm at a position between the brake pad carried by that arm and the fixing point of the piston rod. Alternatively, the calliper arms may be pivotally mounted to a support member substantially at their mid-points, and the hydraulic pistonand-cylinder device acts between the upper ends of the calliper arms, the lower ends of the calliper arms carrying the brake pads.

The invention also provides a bogie for a mine rail vehicle, the bogie having a pair of side members, a bridge joining the side members, a pair of wheels supported by each of the side members, and a respective calliper brake mechanism supported by each of the side members, wherein each of the calliper brake mechanisms is as defined above.

In a preferred embodiment, the cylinder of each hydraulic piston-and-cylinder device is attached to transverse slideways associated with its respective side member, so that each of the cylinders can move transversely with respect to the longitudinal axis of the bogie, whereby the brake pad associated with each said one calliper arm can move into contact with the adjacent lateral edge of the rail.

In another preferred embodiment, each of the wheels is pivotally supported on its side member by means of an arm pivotally connected to that side member, and wherein the arms associated with each of the side members are interconnected by a hydraulic ram, the piston rod of each ram being pivotally connected to one of the associated arms, and the cylinder of that ram being pivotally connected to the other associated arm. The hydraulic rams interconnecting the wheel support arms are normally retracted to maintain the side members (and hence the brake mechanisms) in a raised position, in which the brake pads are above the rails heads. When these rams are vented, the side members collapse (under the forces of gravity and of internal springs within the rams), so that the brake mechanisms are aligned with the rail heads.The brake mechanisms can then be actuated, preferably by a sensor which detects when said hydraulic rams are fully vented. Advantageously, each of the side members is provided with at least one additional brake pad, the additional brake pads engaging the tops of the rail heads when said hydraulic rams a,e vented.

The invention also provides a mine rail car having a chassis, two pairs of wheels supported at the sides of the chassis, and a respective brake device positioned each side of the chassis in general alignment with the wheels at that side, wherein each of the brake devices includes a brake mechanism as defined above.

Advantageously, each brake device is pivotally mounted on the chassis for pivotal movement between a first, raised position and a second, lowered position, each of the brake mechanisms being operable, when in said second position, so as to bring its brake pads into engagement with the head of a rail along which the associated wheels are travelling. Preferably, each brake device is spring biassed towards its second position, and is biassed towards its first position by a hydraulic ram.

In a preferred embodiment, each brake device includes two calliper brake mechanisms. Conveniently, each calliper brake mechanism comprises a pair of calliper arms which are pivotally mounted, substantially at their mid points, on a support member, the lower ends of the arms carrying the brake pads, and the upper ends of the arms being interconnected by a hydraulic ram. Preferably, each of said hydraulic rams is provided with internal springs.

The invention further provides a railway system comprising a mine rail vehicle and a rail track, the rail track having a pair of parallel rails, each of which is constituted by a plurality of rail sections, each pair of rail sections being connected together by respective joining means, each of the rail sections having a head joined to a base plate by a web, the web and the base plate of each rail section defining a T-shaped configuration, each joining means being constituted by a pair of wedges which can be driven into gaps between the webs of the rail sections and abutment members provided on a support member, thereby clamping the adjacent ends of the base plates between the wedges and the support member, and each calliper brake mechanism comprises a pair of calliper arms, each of which carries a brake pad at one end thereof, and means for biasing the calliper arms in such a manner that, in use, the brake pads grip lateral edge portions of a rail section to effect braking action, wherein each brake mechanism is shaped and positioned to engage, at least partly, underneath the head portion of that rail section.

The invention will be now described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a first form of bogie incorporating brake mechanisms constructed in accordance with the invention; Figure 2 is a schematic end elevation of part of the first form of bogie; Figure 3 is an enlarged, schematic end elevation of part of Fig. 2, and shows a rail joint; Figure 4 is a plan view of the rail joint of Fig. 3; Figure 5 is a side elevation of the second form of bogie incorporating brake mechanisms constructed in accordance with the invention, this figure showing one of the brake mechanisms schematically; Figure 6 is a part-sectional end elevation of the second form of bogie; Figure 7 is a side elevation of a rail car incorporating brake mechanisms constructed in accordance with the invention; and Figure 8 is a schematic end elevation of part of the car and brake mechanisms of Fig. 7.

Referring to the drawings, Figs. 1 and 2 show a bogie for a mine rail vehicle (not shown). The mine rail vehicle has a load platform supported, at each end, by a bogie of the type shown in Figs. 1 and 2.

The bogie runs on a track constituted by a pair of standard bull head rails, only one of which (rail R) is shown.

The bogie has a frame constituted by a pair of side members 1 (only one of which is shown), and a bridge 2 joining the side members. Each side member 1 supports a pair of aligned, load-bearing, flanged wheels 3. The bridge 2 is pivotally supported by the side members 1 via bridge support shafts 4 provided at the ends of the bridge. Alternatively, the bridge 2 could be pivotally supported by complementary arcuate bearing sections provided on the bridge and the side members 1. Each side member 1 is provided with a calliper brake mechanism (only one of which is shown). The brake mechanism shown is indicated generally by the reference B. The other brake mechanism is identical to the mechanism B, so only the mechanism B will be described. The brake mechanism B has a pair of laterally-spaced, hydraulic piston-andcylinder units 5, and a pair of calliper arms 6 and 7.The cylinders 5a of the units 5 are mounted in slideways 8 fixed to the associated side member 1.

The slideways 8 extend transversely with respect to the rail R, so that the units 5 can slide transversely relative to the bogie.

The calliper arm 6 is fixed to the cylinders 5a by a pair of pins 9. The calliper arm 7 is pivotally attached to the piston rods (not shown) of the units 5 by pivot joints 10. The arm 7 is pivotally attached to the arm 6 by a pivot joint 11 positioned about halfway along the arm 7. The arm 6 carries a pair of brake pads 12 at its lower end, and the arm 7 carries a pair of brake pads 13 at its lower end. The brake pads 12 and 13 are aligned with one another, and are positioned on opposite sides of the lateral edges of the head H of the rail R. As shown in Fig.

2, each of the brake pads 12 and 13 has a J-shaped configuration. Each of the cylinders 5a contains a set of heavy-duty disc springs (not shown) which bias the piston rods of the units 5 outwardly. Light springs (not shown) are also provided for biassing the units 5 away from the rail R (that is to say to the left as seen in Fig. 2).

When the mine rail vehicle is travelling along the track, the brake mechanism B is in the "brakes off" position. In this position, the piston-and-cylinder units 5 are pressurised in the direction of retraction, so that the biassing force of the heavy-duty springs is overcome, and the brake pads 12 and 13 each form a small clearance with the rail R (see Fig. 2). When the vehicle is to be braked, the piston-and-cylinder units 5 are vented, so that the heavy-duty springs force the piston rods out. This causes the arm 7 to pivot about the pivot joint 11, thereby forcing the brake pads 13 into engagement with the adjacent lateral edge of the head H of the rail R. The rail head H then acts as an abutment for the heavy-duty springs, which then force the cylinders 5a of the units 5 to slide in the slideways 8 towards the rail head.This forces the brake pads 12 into engagement with the other lateral edge of the rail head H. Thus, the brake mechanism B exerts a clamping or calliper action on the rail R. In order to release the brake mechanism B, its pistonand-cylinder units 5 are retracted. This pivots the arm 7 about the pivot joint 11, thereby moving the brake pads 13 away from the rail head H. The light springs 15 are then effective to slide the units 5 back to their original positions, in which the brake pads 12 are spaced from the rail head H. The brake mechanism associated with the other side member acts in the same way, so that effective braking of the bogie is ensured.

Because the brake pads 12 and 13 are J-shaped, they engage underneath the rail head H, thereby preventing the brake pads riding up the lateral edges of the rail head during braking. The brake pads 12 and 13 thus constitute brake lift-off prevention means, so that the braking force is not reduced by the riding up of the brake pads.

It should be noted that the brake mechanisms described above will work satisfactorily only when the rails of the track are joined together by means which do not occupy the upper parts of the rail webs. This means that fishplates, which are usually used to join rails, cannot be used. This is because the brake pads would hit the fishplates during braking, and this would damage the brake pads, reduce braking, and reduce vehicle stability. One satisfactory way of joining rails is to clamp the base plates of each pair of adjoining rails to a chair by means of wedges. The wedges are driven into gaps formed between the webs of the rails and upstanding lateral edge portions of the chairs, thereby clamping the rail base plates against the chairs. The wedges are held in place by bolts.The wedges extend only about halfway up the rail webs, so that the upper portions of the webs remain unobstructed, and so that the brake pads of the calliper brake mechanisms are not interfered with.

A rail joint of this type is shown in greater detail in Figs. 3 and 4. Fig. 4 shows the adjacent end portions of the rail R and an adjacent rail R'. As shown in Fig. 3, the rail R is a bull head rail having a head 21 joined to a base plate 22 by a vertical web 23.

The base plate 22 of the rail R defines with the vertical web 23 a generally T-shaped formation, the base plate defining outwardly-extending base flanges 22a. The other rail R is of identical construction. The heads 21 of the rails R and R' are shown in dashed lines in Fig. 4.

The adjacent end portions of the rails R and R' are supported by a chair 24, the base plates 22 of the rails fitting in a complementary groove 24a formed in the chair. The rail end portions are joined together by means of a pair of clamping members 25 and a plurality of bolts 26. The rail joint is effected by clamping the base flanges 22a of the rail end portions between the clamping members 25 and the chair 22. In order to effect the joint, the clamping members 25 are positioned in the gaps between the webs 23 and upstanding lateral edge portions 24b of the chair 24. The bolts 26 are then positioned in respective apertures 25a in the clamping members 25, the apertures 25a being aligned with U-shaped cut-outs 22b (shown in dash-dot lines in Fig. 4) in the rail base flanges 2, and threaded apertures 24c in the chair 24.The bolts 26 are then tightened, to force the clamping members 25 into the gaps between the rail webs 23 and the lateral upstanding 15 portions 24b of the chair 24. This results in the clamping members 25 clamping the base plates 22 of the adjacent rail end portions against the chair 24. The clamping members 25 also exert clamping forces against the rail webs 23, in order to stabilise the rail heads 21, particularly against lateral and twisting forces resulting from passage of vehicles across the rail joints. As the bolts 26 pass through the U-shaped cut-outs 22b in the rail base flanges 22a, the rails R and R' are retained against axial loading. This provides positive retention in addition to the frictional grip which results from the wedging action referred to above. The heads of the bolts 26 are received within recesses 25a formed in the upper surfaces of the clamping members 25.

The arrangement described above provides excellent rail retention against tension, bending and torsion forces. Moreover, because the clamping members 25 grip the webs of the rails R and R' over only about the lower half of their height, the upper portions of the webs 23 remain unobstructed, so as not to interfere with the action of the calliper brake mechanisms B of rail vehicles overhead. Furthermore, rails joints of this type can be used to replace the fishplates of an already-laid rail track.

In a modified joint arrangement, only one clamping member 25 is required This clamping member clamps one of the flanges 22a of each of the rail end portions, the chair 24 being modified to retain the other base flanges 22a of the rail end portions For example, the associated upstanding lateral edge portion 24b of the chair 24 could be provided with inturned portions which engage over these base flanges 22a. In order to complete the joint, in this modified arrangement, a key would be positioned in complementary aligned recesses formed in the adjacent end portions of the heads 21 of the rails R and R'.

It will be apparent that the brake mechanism described above could be modified in a number of ways. For example, the calliper arms could be modified so that the brake pads act entirely on the web of the rail (or on the web of the rail and the underneath edges of the rail head). In either of these cases, the brake pads would be shaped to complement the shape of the rail surfaces engaged thereby. It would also be possible to modify the brake mechanism to work on ATC rails.

Figs. 5 and 6 show a second form of bogie for a mine rail vehicle (not shown). Here again, the mine rail vehicle has a load platfrom supported, at each end, by a bogie of the type shown in Figs. 5 and 6; and the bogies run on a pair of standard bull heads rails R" (see Fig. 6).

The bogie has a frame constituted by a pair of side members 41, and a bridge 42 joining the side members. Each side member 41 supports a pair of flanged wheels 43, each wheel being pivotally mounted to its side member by a respective arm 44. The arms 44 are pivoted to their side members 41 about horizontal pivot axes 45. The arms 44 of each side member 41 are pivotally connected, about pivot axes 46, to a common hydraulic ram 47. Operation of the rams 47 is effective to displace the arms 44 about the axes 45, and hence displace the bogie relative to the wheels 43. The side members 41 are each provided with a pair of "drop down" brake pads 48, which are engageable with the heads of the rails R", upon exhaustion of hydraulic fluid from the rams 47.

Each side member 41 is also provided with a calliper brake mechanism B'. Each brake mechanism B' has a hydraulic piston-and-cylinder unit 49, and a pair of calliper arms 50 and 51. The arms 50 and 51 carry shaped brake pads 52 and 53 respectively at their lower ends. The arm 50 of each brake mechanism B' is fixed to the cylinder 49a of the associated piston-and-cylinder unit 49, and the corresponding arm 51 is attached to the piston rod 49b of that unit. As shown in Fig. 6, each of the units 49 contains a set of heavy-duty disc springs 54, which bias the arms 50 and 51 towards one another.

When the mine rail vehicle is travelling along the track, the rams 47 are pressurised so that the side members 41 of the bogies are in the raised position, with the brake pads 48 spaced from the heads of the rails R". The piston-and-cylinder units 49 are also pressurised, so that the brake pads 52 and 53 of each brake mechanism B' are spaced wide apart. When the vehicle is to be braked, the rams 47 are exhausted. This causes the side members 41 to drop under the combined forces of gravity and of springs 47a provided within the rams. The brake pads 48 are, therefore, forced down on to the tops of the heads of the rails R" to provide a primary braking action.Upon receiving a signal from a sensor (not shown) that the rams 47 are fully exhausted, the piston-and-cylinder units 49 are exhausted, so that the springs 54 close the calliper arms 50 and 51 of the brake mechanisms B', thereby providing a secondary braking action. As with the embodiment of Figs. 1 and 2, the shaped pads 52 and 53 engage underneath the heads of the rails R", thereby preventing the brake pads 52 and 53 riding up the sides of the rail heads. Not only does this prevent a reduction of the braking force of the pads 52 and 53, but it also prevents a reduction in the braking force of the pads 48.

Figs. 7 and 8 show a mine rail car 60 which runs on standard bull head rails (not shown). The car 60 has a respective calliper brake mechanism B" associated with each side thereof. Each mechanism B" is pivotally mounted on the car 60 for pivotal movement about an axis 61. Each mechanism is biassed downwardly (that is to say towards the associated rail head) by a leaf spring 62. During normal running, the mechanisms B" are held up by hydraulic rams 63 (only one of which is shown see Fig. 7). Each brake mechanism B" includes two pairs of scissor-action calliper arms 64, 65. Each of the arms 64, 65 is pivotally mounted to the body of the associated mechanism B" at its mid point. The upper ends of each pair of arms 64, 6are interconnected by a hydraulic piston-and-cylinder unit 66.

The units 66 contain heavy-duty springs (not shown) which tend to bias the upper ends of the arms 64, 65 apart. During normal running, the units 66 are pressurised to hold the upper ends of the arms 64, 65 in the illustrated positions. The lower ends of the arms 64, 65 carry shaped brake pads 67.

When the car 60 is travelling along the track, the rams 63 are pressurised so that the brake mechanisms B" are held above the rail heads. The pistonand-cylinder units 66 are also pressurised, so that the brake pads 67 are forced apart. When the car 60 is to be braked, the 25 rams 63 are exhausted, so that the brake mechanisms B" pivot down, under the forces of gravity and the leaf springs 62, until the pads 67 are aligned with the rail heads (this position being shown in Fig. 7). The pistonand-cylinder units 66 are then exhausted, to allow the internal springs to close the calliper arms 64, 65, and force the brake pads 67 against the sides of the rail heads. As with the embodiment of Figs.

1 and 2 and the embodiment of Figs. 5 and 6, the shaped pads 67 engage underneath the rail heads, thereby constituting brake lift-off prevention means.

As mentioned above with reference to Figs. 1 and 2, the calliper brake mechanism B' and B" will work satisfactorily only when the rails of the track are joined together by means (such as those described with reference to Figs. 3 and 4) which do not occupy the upper parts of the rail webs.

Claims

1. A calliper brake mechanism for engagement with a rail having a vertical web supporting an enlarged head portion, the brake mechanism comprising a pair of calliper arms, each of which carries a brake pad at one end thereof, and means for biassing the calliper arms in such a manner that, in use, the brake pads grip lateral edge portions of a rail to effect braking action, wherein the brake mechanism is shaped and positioned to engage, at least partly, underneath the head portion of the rail.

2. A brake mechanism as claimed in claim 1, wherein the brake pads are shaped and positioned to engage, at least partly, underneath the head portion of the rail.

3. A brake mechanism as claimed in claim 1 or claim 2, wherein springs means constitute the means for biassing the calliper arms.

4. A brake mechanism as claimed in any one of claims 1 to 3, wherein means are provided for holding the brake pads out of engagement with the rail until the braking mechanism is actuated.

5. A brake mechanism as claimed in claim 4, wherein a hydraulic piston-and-cylinder device constitutes said holding means.

6. A brake mechanism as claimed in claim 5 when appendant to claim 3, wherein a set of heavy-duty springs provided within the hydraulic piston-and-cylinder device constitutes the spring means.

7. A brake mechanism as claimed in claim 5 or claim 6, wherein one of the calliper arms is fixed to the cylinder of the hydraulic piston-and-cylinder device, and the other calliper arm is fixed to the piston rod of said device.

8. A brake mechanism as claimed in claim 7, wherein the piston rod of the hydraulic piston-andcylinder device is fixed to said other arm at a point spaced from its brake pad, and said other arm is pivotally connected to said one arm at a position between the brake pad carried by that arm and the fixing point of the piston rod.

9. A brake mechanism as claimed in claim 5 or claim 6, wherein the calliper arms are pivotally mounted to a support member substantially at their mid-points, and the hydraulic piston-and-cylinder device acts between the upper ends of the calliper arms, the lower ends of the calliper arms carrying the brake pads.

10. A calliper brake mechanism substantially as hereinbefore described with reference to, and as il- lustraed by, Figs. 1 and 2, Figs. 5 and 6 or Figs. 7 and 8 of the accompanying drawings.

11. A bogie for a mine rail vehicle, the bogie having a pair of side members, a bridge joining the side members, a pair of wheels supported by each of the side members, and a respective calliper brake mechanism supported by each of the side members, wherein each of the calliper brake mechanisms is as claimed in any one of claims 1 to 10.

12. A bogie as claimed in claim 11 when appendant to claim 7, wherein the cylinder of each hydraulic piston and-cylinder device is attached to transverse slideways associated with its respective side member, so that each of the cylinders can move transversely with respect to the longitudinal axis of the bogie, whereby the brake pad associated with each said one calliper arm can move into contact with the adjacent lateral edge of the rail.

13. A bogie as claimed in claim 11, wherein each of the wheels is pivotally supported on its side member by means of an arm pivotally connected to that side member, and wherein the arms associated with each of the side members are interconnected by a hydraulic ram, the piston rod of each ram being pivotally connected to one of the associated arms, and the cylinder of that ram being pivotally connected to the other associated arm.

14. A bogie as claimed in claim 13, wherein the brake mechanisms are actuated by a sensor which detects when said hydraulic rams are fully vented.

15. A bogie as claimed in claim 13 or claim 14, wherein each of the side members is provided with at least one additional brake pad, the additional brake pads engaging the tops of the rail heads when said hydraulic rams are vented.

16. A mine rail car bogie substantially as hereinbefore described with reference to, and as illustrated by, Figs. 1 and 2 or Figs. 5 and 6 of the accompanying drawings.

17. A mine rail car having a chassis, two pairs of wheels supported at the sides of the chassis, and a respective brake device positioned each side of the chassis in general alignment with the wheels at that side, wherein each of the brake devices includes a brake mechanism as claimed in any one of the claims 1 to 10.

18. A mine rail car as claimed in claim 17, wherein each brake device is pivotally mounted on the chassis for pivotal movement between a first, raised position and a second, lowered position, each of the brake mechanisms being operable, when in said second position, so as to bring its brake pads into engagement with the head of a rail along which the associated wheels are travelling.

19. A mine rail car as claimed in claim 18, wherein each brake device is spring biassed towards its second position, and is biassed towards its first position by a hydraulic ram.

20. A mine rail car as claimed in any one of claims 17 to 19, wherein each brake device includes two calliper brake mechanisms.

21. A mine rail car as claimed in claim 20, wherein each calliper brake mechanism comprises a pair of calliper arms which are pivotally mounted, substantailly at their midpoints, on a support member, the lower ends of the arms carrying the brake pads, and the upper ends of the arms being interconnected by a hydraulic ram.

22. A mine rail car as claimed in claim 21, wherein each of said hydraulic rams is provided with internal springs.

23. A mine rail car substantially as hereinbefore described with reference to, and as illustrated by, Figs. 7 and 8 of the accompanying drawings.

24. A railway system comprising a mine rail vehicle and a rail track, the rail track having a pair of parallel rails, each of which is constituted by a plurality of rail sections, each pair of rail sections being connected together by respective joining means, each of the rail sections having a head joined to a base plate by a web, the web and the base plate of each rail section defining a T-shaped configuration, each joining means being constituted by a pair of wedges which can be driven into gaps between the webs of the rail sections and abutment members provided on a support member, thereby clamping the adjacent ends of the base plates between the wedges and the support member, and each calliper brake mechanism, comprises a pair of calliper arms, each of which carries a brake pad at one end thereof, and means for biasing the calliper arms in such a manner that, in use, the brake pads grip lateral edge portions of a rail section to effect braking action, wherein each brake mechanism is shaped and positioned to engage, at least partly, underneath the head portion of that rail section.

25. A railway system substantially as hereinbefore described with reference to, and as illustrated by Figs. 1 to 4, Figs. 3 to 6, or Figs 3, 4, 7 and 8 of the accompanying drawings.