GB2224794A

GB2224794A - Railway braking system

Info

Publication number: GB2224794A
Application number: GB8826587A
Authority: GB
Inventors: P H Powell; T A Radley
Original assignee: Westinghouse Brake and Signal Co Ltd; Westinghouse Brake and Signal Holdings Ltd
Current assignee: Siemens Mobility Ltd
Priority date: 1988-11-14
Filing date: 1988-11-14
Publication date: 1990-05-16
Anticipated expiration: 2008-11-14
Also published as: DE3937735A1; CA2002238A1; GB2224794B; GB8826587D0; FR2644419A1

Description

1 1 - 2224794 1 Railway Braking Systems This invention relates to railway

braking systems and, more particularly, to railway braking systems including a hand-brake system and a service brake system. The invention is applicable to such braking systems whether pneumatic, vacuum or electropneumatic.

With such braking systems it is feasible for a train of vehicles fitted with these braking systems to be driven off with the hand- brake system of one or more vehicles still applied. In this event, it is likely that "flatsn will be formed in the hand-braked wheels of the train. The formation of "flats" is a highly expensive fault to rectify and, further, can result in damage to the track.

Means to prevent movement of a train of which the hand-brake of at least one vehicle is still applied, would, therefore, be very desirable. This the present invention provides by ensuring that the service brakes of all the vehicles of the train are applied (and cannot be fully released) so long as the hand-brake system of any vehicle of the train remains applied.

Accordingly, the present invention provides a railway braking system including a hand-brake system and a service brake system, in which the hand-brake system is interlocked with the service brake system such that when the hand-brake system is applied the service brake system is rendered incapable of full brake release and is rendered incapable of being re-charged until the hand-brake system has been released.

The railway braking system may be a pneumatic system, a 2 vacuum system or an electro-pneumatic system.

The interlock may be effected by mechanical interlock of the hand-brake system with a fluid-control valve controlling capability of release and re-charge of the service brake system. The fluid-control valve may have two positions and three ports and the service brake system may then include an auxiliary reservoir, the first of the ports being connected to that auxiliary reservoirf the second of the ports being open to atmosphere and the third of the ports being connectable to one or other of the first and second ports in dependence upon whether the valve is in its first or its second positions. The connection of the auxiliary reservoir to the first port of the fluid control valve may include a choke. The fluid-control valve may constitute a first valve with the braking system then including a second control valve and a fluid-pressure brake cylinder, the second valve being operational between a first position in which the brake cylinder is connected to atmosphere and a second position in which it is disconnected from atmosphere. in this case. the second valve may include a fluid-pressure differential piston by which the second valve can be moved from its first to its second position and vice versa and one side of this piston may be connected via a port of the second valve to the third port of the first valve. The connection of the second valve to atmosphere may desirably be via a blow-down safety valve which retains a predetermined pressure in the brake cylinder which pressure is substantially below that to effect a full brake application but is also substantially above atmosphere - the predetermined pressure being, typically, 1.7 bar. The second valve, when provided, may have a port connected via a branch pipe connected 1 1 3 into the brake cylinder pipe by which pressure is transmitted to and from the brake cylinder and this branch pipe includes a cock by which the second valve can be isolated from the brake cylinder.

The braking system may be provided with a further fluid-control valve and include a brake pipe. the further fluid-control valve being operational between a first position in which the brake pipe is connected to atmosphere and a second position in which the brake pipe is disconnected from atmosphere. This further fluid-control valve may include a fluidpressure differential piston by which the further fluid-control valve can be moved from its first to its second position and vice versa. In this case, one side of the piston may be connected via a port of the further fluid-control valve to the third port of the first mentioned fluid-control valve. The further fluid-control valve may have a port connected to the brake pipe and this connection includes a cock by which the further fluidcontrol valve can be isolated from the brake pipe. This further fluidcontrol valve may have three ports of which one is the port connected to the brake pipe. the second port is the port connected to atmosphere and the third is connected to other braking system control devices. the further fluid-control valve being movable from its first position in which the said one of the ports is connected to said second port and its second position in which said one of the ports is connected to the third port. The connection of the port to the brake pipe may include an emergency application valve.

Embodiments of the present invention will now be described in greater detail, by way of example only, 4 with reference to the accompanying-drawings-of which:- Fig. 1 is a schematic drawing of one embodiment of the invention# Fig. 2 is a schematic drawing showing modifications of the embodiment of Fig. 1.

Fig. 3 is a schematic drawing showing an alternative embodiment.

Referring to Fig. 1, there is here shown a conventional pneumatic railway braking system to which the present invention has been applied.

The conventional part of the braking system includes a normally-charged brake pipe 1 reduction of pneumatic pressure in which controls operation of a distributor 2 to cause air pressure in an auxiliary reservoir 3 to be supplied to the brake cylinder 4 to apply the brakes (not shown). Conversely, re-establishment of the pneumatic pressure in the brake pipe 1 operates the distributor 2 to vent the brake cylinder 4 and release the brakes.

Tee'd off the connection between the auxiliary reservoir 3 and the distributor 2 is a branch pipe 10, this branch pipe incorporating a choke 11 which serves to protect the auxiliary reservoir from complete discharge should there be a rupture downstream of the choke 11. The pipe 10 leads to a three-ported two-positional port valve 12 which is mechanically interlocked with a hand-brake (not shown) via valve- operating gear 13. The pipe 10 is connected to the first port 14 of the three ports of the valve 12, 1 the second port 15 of the ports is open to atmosphere and third port 16 of the three ports is a common port connected, in one of the two positions of the valve 121 with the first port,_14and, in the second of the two positions of the valve 12, with the second port 15.

The common port 16 of the first valve 12 is connected over a branched pipe 17 to, by one branch, one side of a fluid-pressure differential piston 18 of a piston operated second valve 19 and, by the other branchf to one side of a fluid-pressure differential piston 20 of a piston-operated further valve 21. The valves 19 and 21 are also both three-ported two-positional valves.

Of the three ports of the valve 19, the first port 22 is closed, the second port 23 is open to atmosphere via pipe 25 and a blow-down safety valve 26 set to 1.7 bar and the third port 24 is a common port connected in one position of the valve 19 to the port 22 and in the other position of the valve 19 to the port 23. The common port 24 communicates with a branch pipe 27 tee'd off the brake cylinder connection between the distributor 2 and the brake cylinder 4 of the conventional part of the braking system. This branch pipe 27 incorporates a sealed cock 28 by which the valve 19 can be isolated if required.

Of the three ports of the valve 210 the first port 29 is closed, the second port3o is open to atmosphere and the third port 31 is a common port connected in one position of the valve 21 to the port 29 and in the other position of the valve 21 to the port 30. The common port 30 communicates with a branch pipe 32 tee'd off the brake pipe 1 of the conventional part of the braking system and incorporates a sealed cock 33 by 6 which the valve 21 can be isolated if required.

Operation When the hand-brake, (not shown) is operated to apply the brakes, through its mechanical interlock with the gear 13, the valve 12 will be operated to its position shown in full line on Fig. 1 in which the port 16 is connected to the port 14. Hence, the pneumatic pressure in the auxiliary reservoir 3 will be applied via the valve 12 to the branched pipe 17. The pressure thus generated in pipe 17 will therefore be applied to the pistons 18 and 20 of the valves 19 and 21 to move them (against suitable spring loading) to the one of the positions of these two valves in which the connections shown in full lines in Fig. 1 is effected i.e. in valve 19, port 24 is connected to port 23 and in valve 21, port 31 is connected to pot 30.

Considering, firstly, this operation of valve 21, the interconnection of its ports 31 and 30 will open the brake pipe 1 to atmosphere. This discharge will. firstly, generate considerable noise indicating that the hand-brake has been applied and, secondly, will cause the brakes of every other vehicle in any train of vehicles in which a vehicle having the present invention is incorporated and of which the hand-brake has been applied, to be operated to a "brakes fully-applied" condition. Howeverr on the vehicle on which the hand-brake has been appliedi the atove described operation of its valve 19 will have caused the connection between its distributor 2 and its brake cylinder 4 to be opened to atmosphere via the ports 24 and 23p the pipe 25 and the safety valve 26. Hence, on this vehicle only, the degree of pneumatic application 7 of its brakes (not shown) will be limited to the equivalency of the 1.7 bar setting of the safety valve 26. This limitation of the degree of pneumatic application of the brakes inhibits compounding of the hand- brake application and the pneumatic application.

It will be seen, therefore, that the application of the hand-brake on one of a train of vehicles effects pneumatic application of the brakes of every vehicle of the train. Movement of the vehicle with even a single hand brake applied will. therefore, be prevented.

Moreover, if the driver attempts to release the brakes by re-charging the brake pipe 1 not only will this be prevented by the brake-pipe 1 being open to atmosphere via the valve 21 on the vehicle the hand-brake of which is still applied, any such attempt will draw attention to that vehicle the hand-brake of which is still applied by virtue of the noise of the brake pipe air discharging to atmosphere through the valve 21 on that vehicle.

When the hand-brake is later released, the valve 12 will be operated to the other of its two positions in which other position the full-time connection of ports 14 and 16 will be severed and the dotted-line connection of ports 15 and 16 will be established. In this position of the interlock valve 12, the volumes above pistons 18 and 20 in the valves 19 and 21 respectively will be exhausted via port 15 in valve 12. Thus, valves 19 and 21 will be moved into the other of their positions by their respective spring loadings.

In this other position of valve 19 the connection of the brake cylinder 4 to atmosphere via the ports 24 and 8 23 of the valve 19 will be severed and the dotted-line connection of port 24 to the blanked-off port 19 established. Hence, the brake cylinder 4 can subsequently be pressurised from the auxiliary reservoir 3 for pneumatic operation of the brakes (not shown).

Similarly, the valve 21 will also take up its other position under the influence of its spring loading to disconnect port 31 from the port 30 thus severing the connection of the brake pipe 1 to atmosphere - and established the dotted-line connection of port 31 to the blanked-off port 29. Thus. the brake pipe 1 can now be charged to effect pneumatic release via the is respective distributors of the other vehicles of the train of the brakes of those vehicles.

All the brakes of the train now being released, the train can be moved.

Turning now to Fig. 2, the system here shown is identical to that of Fig. 1 save for two modifications which only. therefore, need here to be described.

The first modification is that the port 29 of the valve 21 is now not a simple closed port but is a port connected to other brake control equipment such as a conventional hot-box detection.

The second modification is that pipe 32 between the brake pipe 1 and the valve 21 also incorporates an emergency application valve 34 of which in its normal condition the brake pipe 1 is connected over the pipe 32 to the port 31 of the valve 21 but which can be 35 operated to connect the brake pipe 1 via the pipe 32 to r 9 atmosphere via exhaust port 35 of the valve 34.

In some railway braking systems, cut-off cocks are provided to allow isolation of the distributor 2 in the event of its developing a fault pending replacement of the faulty distributor. With the system shown in Figs.

1 and 21 the provision of such a cut-off cock in the event of its operation would render ineffective the systems therein shown for the cut-off cock would empty the auxiliary reservoir 3 and, therefore, prevent operation of the valve 21 to exhaust the brake pipe 1 to effect pneumatic operation of the brakes of the other vehicles of the train.

is To cope with systems having such cut-off cocks, the system shown in Fig. 3 was devised.

In this system the interlock valve 12 is still a two-position valve but now has five ports. In addition to the previously described three ports 14, 15 and 16 there are the two additional ports 41 and 42. of these two ports, port 41 is blanked-off and port 42 connects with a pipe 43 teeld into the pipe 32 downstream of the emergency application valve 34.

1 The valve 19 is retained but, it will be noted, the valve 21 has been omitted.

OPERATION The system of Fig. 3 operates as follows:

Assume, firstly. that the distributor 2 is operational and that its cut-off cock (not shown) has not been operated.

In this case, the auxiliary reservoir 3 will be charged.

If now the hand-brake is applied, the interlock valve 12 will be operated as before to the first of its positions to which the full-line connections are made. In this position of the valve 12 as in the Fig. 3 embodiment the brake pipe 1 will be discharged via branch pipe 32. cock 33, emergency application valve 34, pipe 43. and ports 42 and exhaust port 15 of the interlock valve 12.

Discharge of the brake pipe 1 will pneumatically apply the brakes of all of the vehicles of the train.

is However, again on the vehicle on which the hand-brake has been applied, auxiliary reservoir 3 pressure will be applied via ports 14 and 16 of the interlock valve 12 to the piston 18 of the valve 19. Again, as in Fig. 3, the brake cylinder 4 on the vehicle on which the hand-brake has been applied, will have its pressure held to the 1.7 bar by the blow-down safety valve 26.

If, however, the cut-off valve (not shown) has been operated to isolate the distributor 2 on that vehicle on which the hand-brake is applied. whilst the interlock valve 12 will (as before) be mechanically operated to connect brake pipe 1 to atmosphere thus effecting discharge of the brake pipe 1 to effect pneumatic application of the brakes on all the other vehicles of the train, the distributor 2 on the hand-braked vehicle will not be operated. However, by previous operation of that distributor's cutoff valve (not shown) the auxiliary reseroir 3 on the hand-braked vehicle will already have been vented by operation of the cut-off valve. Thus, the brakes (not shown) on t 1 11 that particular vehicle cannot be pneumatically operated but this will be of little consequence in the totality of the train for that vehicle's hand-brake has been operated and the brakes on every other vehicle pneumatically operated.

is When the hand-brake is eventually released the interlock valve 12 will be operated by its spring-loading to the other of its positions in which the connections in the valves 12 and 19 are those shown in dotted lines in Fig. 3. Such operation of the valve 12 will disconnect the brake pipe 1 from exhaust port 15 and, instead, connect pipe 17 via port 16 to the exhaust port 15. Such connection of the pipe 17 will exhaust the chamber above the piston 18 of valve 21 to allow it to be returned by its spring loading to its other position in which the connection of the brake cylinder 4 via pipe 27 and the blow-down safety valve 26 to atmosphere is severed and, instead. connected to the blanked-off port 22.

In all of the above described embodiments the conventional part of the braking system is a pneumatic braking system but it will be clear that the invention could equally well be applied to a vacuum braking systems or, indeed, to an elctro-pneumatic braking systems by using electrical circuits the equivalency of the pneumatic circuits above described.

12

Claims

Claims:-

A railway braking system including a hand-brake system and a service brake system. in which the hand-brake system is interlocked with the service brake system such that when the hand-brake system is applied the service brake system is rendered incapable of full brake release and is rendered incapable of being re-charged until the hand-brake system has been released.
A braking system as claimed in Claim 1. wherein the interlock is effected by mechanical interlock of the hand-brake system with a fluid-control valve controlling capability of release and re-charge of the service brake system.
3. A braking system as claimed in Claim 21 wherein the fluid-control valve has two positions and three parts and the service brake system includes an auxiliary reservoir, the first of the ports being connected to that auxiliary reservoir, the second of the ports being open to atmosphere and the third of the ports being connectable to one or other of the first and second ports in dependence upon whether the valve is in its first or its second positions.
4. A braking system as claimed in Claim 3, wherein the connection of the auxiliary reservoir to the first port of the fluid control valve includes a choke.
5. A braking system as claimed in either of Claim 3 and 4. wherein the fluid-cohtrol valve is a first valve and the braking system includes a second 13 fluid control valve and a fluidpressure brake cylinder, the second valve being operational between a first position in which the brake cylinder is connected to atmosphere and a second position inwhich it is disconnected from atmosphere.
6. A braking system as claimed in Claim 5, wherein the second valve includes a fluid-pressure differential piston by which the second valve can be moved from its first to its second position and vice versa.
7. A braking system as claimed in Claim 6. wherein one side of the piston is connected via a port of the second valve to the third port of the first valve.
8. A braking system as claimed in any one of Claims 5 to 7, wherein the connection of the second valve to atmosphere is via a blow-down safety valve which retains a predetermined pressure in the brake cylinder which pressure is substantially below that to effect a full brake application but is also substantially above atmosphere.
9. A braking system as claimed in Claim 8, wherein the predetermined pressure is 1.7 bar.
10. A braking system as claimed in any one of Claims 5 to 9. wherein the second valve has a port connected via a branch pipe connected into the brake cylinder pipe by which pressure is transmitted to and from the brake cylinder and this branch pipe includes a cock by which the second valve can be isolated from the brake cylinder.

1 14
11. A braking system as claimed in any one of Claims 2 to 10 wherein the braking system includes a further fluid-control valve and the braking system includes a brake pipe, the further fluid control valve being operational between a first position in which the brake pipe is connected to atmosphere and a second position in which the brake pipe is disconnected from atmosphere.
12. A braking system as claimed in Claim 11, wherein the further fluidcontrol valve includes a fluid-pressure differential piston by which the further fluid-control valve can be moved from its first to its second position and vice versa.
13. A braking system as claimed in Claim 12, wherein one side of the piston of the further fluid-control is connected via a port of the further fluid-control valve to the third port of the first mentioned fluid-control valve.
14. A braking system as claimed in any one of Claims 11 to 13l wherein the further fluid control valve has a port connected to the brake pipe and this connection includes a cock by which the further fluid-control valve can be isolated from the brake pipe.
15. A braking system as claimed in Claim 14 when dependent on Claim 13, wherein the further fluid control valve has three ports of which one is the port connected to the brake pipe. the second port is the port connected to atmosphere and the third is connected to other braking system control devices, the further fluid-control valve being i movable from its first position in which the said one of the ports is connected to said second port and its second position in which said one of the ports is connected to the third port.

is
16. A braking system as claimed in either of Claims 14 or 15. wherein the connection of the port to the brake pipe includes an emergency application valve.
17. A braking system substantially as herein described with reference to and as illustrated in any one of Figs. 11 2 and 3 of the accompanying drawings.

Pabhshed 1990 at The Patent Office, State House. 66 71 High Holborn. London WCIR4TP- Further copies maybe obtained from The Patent Office. Sales Branch. St Mary Cray. Orpington. Kent BR 3RD. Printed by Multiplex techniques ltd. St Mary Cray. Kent. Con. 187