FIELD OF THE INVENTION

The present invention relates broadly to an electronically controlled pneumatic (ECP) brake system for a rail carriage or wagon. The invention relates particularly, though not exclusively, to an ECP brake system that is retrofitted to or a modification of an existing pneumatic brake installation. The ECP brake system is suitable for both relayed and non- relayed brake setups.

BACKGROUND OF THE INVENTION

Australia is leading a world-wide trend with, bigger, longer and faster trains. It is thought that by 2020 train load will double and five (5) km length and longer trains will become a common sight in Australia, However, much of the Australian rail infrastructure and its rolling stock have been inherited from a 19 ^th century legacy, The upcoming changes will create difficult problems for traditional braking systems that may require introduction of more modem systems. It is thought that ECP brakes or systems providing similar advantages are probably going to be pushed onto the rail industry by market forces at some stage in the not too distant future.

Present day pneumatic brake suffers from several problems. The most important of all is its slow response time in brake application and release. Although the AAR (Association of American Railway) standard sets a pneumatic transmission speed of 250 m/s in the brake pipe, in reality a delay of up to 180 seconds for a 2-3 km long train in the application or release of brakes between the lead locomotive and Jast wagon is common. Hence, during braking, wagons at the back bunch forward and during brake release, wagons in the front pull on wagons at the back. In situations where a service application is quickly followed by service release, wagons in the front can be moving forward while the wagons at the back are still braking. These actions often cause large stresses at the couplings and warrant frequent servicing that adds to the cost of maintenance, but more importantly, the slack actions can lead to breakaway or derailment

Conventional pneumatic brakes also lack gradual release and suffer from poor handling. In an over braked train, train operators are unable to partially release the brakes without first performing a full service release followed by a service reapplication to achieve the

correct braking pressure. Over braking often caiises wheel skid which can result in flattened wheels. Flattened wheels can generate unwanted vibrations that lead to possible derailment, hence, this adds to maintenance cost and downtime. Furthermore, without partial brake release, train handling suffers when operating on terrain with variable gradients, In a situation where a train is moving downhill from a steeper to a flatter gradient, the train operator has to release the brakes fully and rely on the dynamic brake to provide retardation force downhill. They must then wait for the reservoir to charge up before reapplying the pneumatic brakes to supplement the dynamic brake if needed. Lastly, trains equipped with conventional pneumatic brakes running a single pipe (brake pipe only) system, lack the ability to continuously recharge the reservoirs. After service release, full brake reapplication will not be possible before the reservoirs are fully recharged. On a long train, this recharge can take up to 10 minutes or more. This is important in safety critical situations such as travelling downhill where the train has to rely on dynamic brakes while the reservoir is being charged.

ECP brakes were first developed by TSM (Technical Service & Marketing) in the early

1990s. They were soon followed by WABTEC (Westinghouse Air Brake Technologies), New York Air Brakes (a subsidiary of Knorr-Bremse), Zeftron Inc. in mid 1990s with emulation system and GE Harris in late 1990s with radio controlled ECP system. Although ECF brakes have been available in the market for over 10 years, they have not been widely accepted by the railway industry. Several factors are believed to have contributed to this slow take-up of ECP brakes. Firstly, ECP brakes have yet to prove their reliability and there are doubts on the reliability and robustness of the electronics to withstand the harsh operating conditions and environments experienced on wagons. Secondly, the costs associated with refurbishing existing wagons require significant capital investment with small returns for wagon owners. Although present day ECP brakes offer significant benefits to railway operators with improved performance, reduced trip times, increased productivity and moderate fuel savings, wagon owners only enjoy small savings in reduced maintenance cost. This is sufficient enough to deter wagon owners from adopting ECP brakes. Lastly, trains equipped with stand alone ECP brakes are unable to operate with wagons equipped with conventional pneumatic brakes. This creates logistical problems that lead to significant amount of downtime as railway operators are unable to mix and match different wagons. This means that whole trains need to be sidelined to be fitted with ECP brakes.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an electronically controlled pneumatic (ECP) brake system for a rail carriage or wagon, said system comprising: a brake application relay control valve being electronically controlled and adap ted to connect to a pneumatic relay control line located between a pressurised reservoir and a relay valve of the wagon, the pressurised reservoir also being connected to the relay valve via a pressurised line; a brake cylinder connected to the relay valve via a brake actuation line; a brake release relay control valve of a normally open configuration being electronically controlled for closure and coupled to the relay control line; and a relay control pressure sensor operatively coupled to the brake actuation line or the relay control line and being in electronic communication with the brake application and/or the brake release relay control valves whereby braking is effected by opening the brake application relay control valve and closing the brake release relay control valve to provide control air to the relay valve via the relay control line for actuation of the relay valve to provide pressurised air to the brake cylinder via the pressurised line and the brake actuation line whereas on brake release the brake release relay control valve is normally opened and the brake application relay control valve closed to allow venting of control air from the relay control line and brake cylinder pressure from the brake actuation line via the relay valve while closure of the brake application relay control valve isolates the control line from the pressurised reservoir.

In one embodiment of this aspect of the ECP brake system there is a pneumatic control valve or triple valve connected to a brake pipe and one or more pressurised reservoirs of the wagon.

In this embodiment the pneumatic control valve or triple valve is connected to the relay valve via a brake relay control line which includes a double check valve also being connected to the pneumatic relay control line of the ECP system. Ih one position the double check valve isolates the pneumatic control valve or triple valve from the relay valve for relayed ECP braking, whereas in another position the check valve isolates the relay valve from the pressurised reservoir and provides pneumatic only braking.

According to a second aspect of the invention there is provided an ECP brake system for a wagon, said system comprising: a brake application relay control valve being electronically controlled and adapted to connect to a pneumatic relay control line located between one or more pressurised reservoirs and a relay valve of the wagon, at least one of the pressurised reservoirs also being connected to the relay valve via a pressurised line; a brake cylinder connected to the relay valve via a brake actuation line; a two-way valve assembly connected to the relay valve and being operable in two (2) positions for electronically controlled pneumatic (ECP) and air only braking, respectively a pneumatic control valve or triple valve connected to at least one of the pressurised reservoirs, said control valve also being connected to the two-way valve assembly which: (i) in one position isolates the control valve or triple valve from the relay valve wherein ECP braking is effected by opening the brake application relay control valve to provide control air to the relay valve via the relay control line for actuation of the relay valve to provide pressurised air to the brake cylinder via the pressurised line and the brake actuation line, and

(ii) in another position isolates the relay valve from the brake application relay control valve wherein air only braking is effected by deploying the control valve or triple valve to provide control air to the relay valve for its actuation to provide pressurised air to the brake cylinder via the pressurised line and the brake actuation line.

Preferably the two-way valve assembly is a double check valve being automatically actuated by differential pressure across the valve. The double check valve may be in the form of a shuttle valve.

Alternatively the two-way valve assembly includes either:

(i) A relatively large solenoid actuated valve; or (ii) A relatively small solenoid actuated valve connected to the pressurised reservoir and a pneumatic pilot valve connected to and actuated by the solenoid valve.

Preferably the triple valve is connected to a brake pipe and auxiliary reservoir of the wagon.

Preferably the ECP brake system of the second aspect also comprises a brake release relay control valve of a normally open configuration being electronically controlled for closure and adapted to connect to a vent line connected to the relay control line.

In one form of the invention, the ECP brake system is a relayed brake system including the relay valve and the pressurised line wherein the brake application and brake release relay control valves and associated line together with the relay control pressure sensor are modifications or retrofits to the existing relayed brake system.

Preferably the ECP system also comprises an isolation system including an isolation valve connected to the ECP system between the brake pipe and the pneumatic control valve or triple valve. More preferably the isolation valve is actuated manually into either of its closed or open positions.

Alternatively the isolation, valve is pilot operated and operatively coupled to an isolation solenoid valve connected to the pneumatic relay control line.

Preferably the ECP system further comprises a low brake pipe pressure valve which is pilot operated via a connection to the brake pipe, said valve being located in parallel with the isolation valve wherein at low brake pipe pressures it resets to open wherein the pneumatic control valve or triple valve is exposed to brake pipe air.

Preferably the ECP system also comprises an emergency brake valve being electronically controlled and coupled to the brake pipe whereby on emergency braking the emergency brake valve is opened to release pressure from and the brake pipe for deployment of the pneumatic control valve or triple valve. More preferably the emergency brake valve is connected to a vent line which is connected to a vent valve.

Preferably the ECP system further comprises an emergency cut-in valve which is pilot operated via a connection to the brake pipe, said cut-in valve being connected to an auxiliary of the pressurised reservoirs upstream of the pneumatic control valve or triple valve and also being connected to an emergency, reservoir of said pressurised reservoirs.

In another aspect of the invention the ECP system is a modification of an existing: non- relayed brake system wherein the relay valve and the brake application and brake release relay control valves and associated line, together with the relay control pressure sensor convert the non-relayed system to a relayed system.

Preferably the double check valve isolates the pneumatic control valve from the relay valve for ECP braking, whereas in another position the double check valve isolates the relay valve from the brake application relay control valve and provides pneumatic only braking.

Preferably the emergency brake valve is a solenoid actuated valve which is configured normally dosed and when energised it opens.

Preferably the brake application and brake release relay control valves are solenoid actuated valves.

Preferably the brake application relay control valve is configured normally closed and when energised it opens whereas the brake release relay control valve is normally open and when energised it closes. More preferably these solenoid actuated control valves are biased in a de-energised condition using a spring.

Preferably the relay control pressure sensor is one of a plurality of sensors mounted to the pneumatic relay control line or the brake actuation line. More preferably the relay control pressure sensor is one of a plurality of sensors designed for diagnostic purposes only or configured to provide feedback ECP brake control for safety critical braking

Preferably the ECP brake system also comprises a microprocessor dedicated to each of the wagons and being in electronic communication with the pressure sensor(s) together with the brake application and/or tfie brake release relay control valves whereby feedback pressure is provided by each of said sensors to the microprocessor which accordingly and electronically controls actuation of the corresponding valve for that wagon. More preferably there is a control modulo electronically coupled to each of the microprocessor mounted remote from one of a plurality of the wagons which are together but independently controlled by the control module. Even more preferably the control module is a single control module mounted on-board a lead locomotive associated with the wagons.

BRIEF DESCRIPTION OF THE FIGURES

In order to achieve a better understanding of the nature of the present invention several preferred embodiments of an electronically controlled pneumatic (ECP) brake system for

a wagon will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic diagram of a traditional pneumatic relayed brake system;

Figure 2 is a schematic diagram of a relay valve from the traditional arrangement of Figure 1;

Figure 3 is a flow diagram of an Australian ECP brake system according to one aspect of the present invention;

Figure 4 is a flow diagram of a variant of the Australian ECP brake system of figure 3;

Figure 5 is a flow diagram of an AAR ECP brake system according to another aspect of the invention;

Figure 6 is a flow diagram of a variant of the AAR ECP system of Figure 5;

Figure 7 is a flow diagram of a UIC ECP brake system according to a further aspect of the invention; and

Figure 8 is a flow diagram of a variant of the UIC ECP brake system of figure 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one form the ECP brake system of the invention is designed to be retrofitted to an existing relayed pneumatic brake installation such as that illustrated in Figure 1. In order to obtain a better understanding of this retrofit ECP brake system it is necessary to understand the arrangement and operation of a traditional pneumatic only brake system. Figure 1 illustrates a typical relayed brake system designated generally as 1, The brake system 1 includes a pneumatic control valve (PCV) or triple valve 2, reservoirs (dummy 3, auxiliary 4 and supplementary 5), relay valve (E/L) 6, VTA changeover valve 7 and brake cylinders 8. Typically, each of the wagons of a train includes one of these traditional pneumatic brake systems which are actuated by pressurised air transmitted from a lead locomotive via a brake pipe which extends along the train.

In steady state (brake release), the brake pipe and the auxiliary reservoir 4 are charged at full pressure of 450 kPa to 650 kPa. During service application, the brake pipe pressure is

vented through the lead locomotive and the pressure drop is propagated along the brake pipe through the length of the train. When the pressure drop reaches the pneumatic control valve or triple valve 2., pressure differential between the auxiliary reservoir 4 and the brake pipe deploys the triple valve 2 into an applied position and allows auxiliary reservoir air to flow into a control volume (chamber B) of the relay valve 6 (for relayed brake) or the brake cylinder (non-relayed brake). The amount of auxiliary reservoir air fed into the relay valve 6 or the brake cylinder 8 is proportional to the drop in brake pipe pressure. That is, if the brake pipe pressure drops from 500 kPa to 450 kPa, the auxiliary reservoir 4 will exhaust air into the relay valve 6 or the brake cylinder 8 until the reservoir 4 reaches 450 kPa.

As also shown in Figure 2 and in a relayed brake, charging of the control volume (chamber B) of the relay valve 6 pushes its diaphragm and spindle upward, thus allowing supplementary reservoir air to fill the brake cylinder 8. A portion of pressurised air from the supplementary reservoir 5 Is also fed into chamber C through a choke. Once the pressure in chamber B and chamber C equalises, the spindle is forced downwards and closes the supply valve. Any leakage in the brake cylinder will be detected by the pressure difference between chamber B and chamber C. This will force the spindle upwards opening the supply valve and allow supplementary air to compensate for leakage. When a wagon is loaded, the changeover valve 7 will redirect a portion of pressurised air feeding into the brake cylinder 8 back into chamber A of the relay valve 6. In effect, it increases the upward force (the sum of chamber B and chamber A) exerted on the spindle. This keeps the supply valve open for a longer period of time for increased braking until the pressure in chamber C can overcome the combine pressure of chamber A and chamber B.

During service release, compressed air is fed into the brake pipe to increase its pressure to normal operating pressure. Pressure differential between the auxiliary reservoir 4 and the brake pipe actuates the triple valve 2 into a release position and refills the auxiliary reservoir 4. With the triple valve 2 in the release position, the control volume (chamber B) air on the relay valve 6 (relayed brake) or the brake cylinder (non-relayed brake) air is exhausted through a vent port on the triple valve 2. In a relayed brake, venting the control volume (chamber B) air decreases the upward pressure exerted by chamber A and chamber B, thus pushing the spindle downward. The brake cylinder 8 is then allowed to vent through the exhaust port on the relay valve 6.

For the purpose of this specification the term wagon is to be understood as including freight cars.

Figures 3 and 4 are flow diagrams of alternate embodiments of an ECP brake system which in this form is retrofitted to or a modification of an existing Australian relayed brake setup. In these embodiments the relayed ECP brake system include four (4) main components, a brake control module 11, a brake pipe isolation module 13, an emergency module 15 and a pressure sensor module 17. For ease of reference and to avoid repetition, like components of the alternate embodiments have been, designated with the same reference numeral.

The brake control module 11 includes a pair of solenoid valves for brake release 12 and brake application 14, a shuttle valve 18, and a choke 19 and a dummy volume 21 installed on a pneumatic relay control line 16 between the application valve 14 and the shuttle valve 18, For a non-relayed brake system such as that illustrated in figures 5 and 6, this module will also include a relay valve and another dummy volume to be installed on the brake relay control line between the triple valve and the shuttle valve. The solenoid application valve 14 is normally closed while the solenoid release valve 12 is normally open. Alternatively and as shown in figure 4, the shuttle valve 18 can.be replaced by a solenoid valve or a solenoid valve 23 and a pilot actuated valve 25. In either a relayed or a non-relayed brake system the additional dummy volumes 21 and choke 19 are optional. The dummy volume 21 on the pneumatic relay control line 16 is to smooth out any hysteresis and reduce the sensitivity of the system to small leakage while the dummy volume 3 on a brake relay control line 24 is to provide pressure equalisation.

The brake pipe isolation module 13 includes an isolation valve 27, a low brake pipe pressure cut-in valve 29 and a non-return valve 31. The preferred isolation valve 27 of figure 3 is a manually operated valve such as a ball valve. Alternatively and as shown in figure 4, the isolation valve 27 can be replaced by a solenoid valve or a solenoid 23 and a pilot actuated valve 33. The low brake pipe pressure cut-in valve 29 is a pDot actuated valve. It is held closed by pilot pressure from the brake pipe 9 and reset to open when the brake pipe 9 drops below a predetermined pressure threshold. The purpose of the isolation module 13 is to isolate the triple valve 2 from brake pipe 9 pressure fluctuation

(which occurs during ECP brake application), that can deploy the triple valve 2 unnecessarily. The non-return valve 31 allows the brake pipe 9 to charge the reservoirs,

such as the auxiliary reservoir 4, connected to the triple valve 2 while the triple valve 2 is isolated from the brake pipe 9. The low brake pipe pressure cut-in valve 29 is to provide a safety critical function that allows the triple valve 2 to re-establish communication with the brake pipe 9 and allows deployment of conventional air brake 1 when the brake pipe 9 pressure drops below a critical level.

The emergency module 15 includes a vent valve 35 and solenoid valve 37 for emergency application. A pilot actuated valve 39, a non-return valve 41 and an emergency reservoir . 43 are optional and are used to provide extra braking during emergency brake application. On an AAR brake system or brake system that already has a vent valve such as those illustrated in figures 5 and 6, the emergency module 15 will only include a solenoid valve 37 for emergency application. The emergency application solenoid valve 37 is normally closed. The pilot actuated valve 39 is normally open and held closed by pilot pressure from the brake pipe 9.

The pressure sensor module 17 includes four pressure transducers. Pressure sensors T1 (26), T2 (28), T3 (45) and T4 (47) provide pressure reading for the pneumatic relay control line 16, the brake cylinder S, the brake pipe 9 and fhe supply or supplementary reservoir 5, respectively. Pressure sensor T1 (26) is always used as feedback for ECP brake control. Pressure sensors T2 (28), T3 (45) and T4 (47) are normally used for diagnostic purpose bur can also be used to provide feedback control especially on safety critical situation to deploy the brake.

Operation of the Australian ECP brake system of figures 3 and 4 will now be explained in some detail. With the brake pipe 9 fully charged, the pilot valves 29 and 39 are held closed by the brake pipe 9 pressure. The auxiliary reservoir 4 and the emergency reservoir 43 are charged by the brake pipe 9 through the triple valve 2. The supplementary reservoir 5 is charged by the brake pipe 9 through a non-return valve 40 and a choke 51. When operating in ECP mode, the isolation valve 27 or 33 is manually or electronically /pneumatically switched to closed, isolating the triple valve 2 from the brake pipe 9.

During brake application, the solenoid release valve 12 is energised to closed while the solenoid application valve 14 is energised to open to supply pilot air from the supplementary reservoir 5 into the relay valve 6 through me shuttle valve 18. This actuates the relay valve 6 to provide pressurised air from the supplementary reservoir 5 to

the brake cylinder 8 to apply the brake. When the desired braking pressure is reached, the solenoid application valve 14 is de-energised into the dosed position. Pressure feedback control is provided by the pressure transducer T1 (26).

During gradual brake release, the solenoid release valve 12 is de-energised into the opened position to vent pilot pressure from the relay valve 6 through the double check valve or shutter valve 18. When the desired pressure is reached, the solenoid release valve

12 is re-energised into the closed position. Similarly, pressure feedback control is provided by the pressure transducer T1 (26). A reduction in the relay pilot pressure allows the brake cylinder 8 air to partially vent to atmosphere through the relay valve 6, thus partially releasing the brake. In full release, all the solenoid valves 12, 14 and 37 are de-energised. Pilot pressure from the relay valve 6 is vented into atmosphere through the solenoid release valve 12.

During a pneumatic emergency braking procedure, the solenoid emergency valve 37 is energised into the open position to vent brake pipe 9 air. A rapid drop of local brake pipe 9 pressure will actuate the vent valve 35 to dump brake pipe 9 air thus accelerating emergency braking. If the brake pipe 9 pressure drops below a predetermined threshold (e.g. BP of less than or equal to 300kPa), the pilot valves 29 and 39 are reset to the open position. This allows the triple valve 2 to Te-establish communication with the brake pipe 9 and deploys the brake. The emergency reservoir 43 is also in communication with the triple valve 2 to supply extra pilot pressure to the relay valve 6 to provide extra braking pressure in the brake cylinder 8. After a pneumatic emergency braking procedure, the brakes are released by de-energising solenoid emergency valve 37 and charging the brake pipe 9 up to full pressure. The pilot valves 29 and 39 actuate to the closed position when the brake pipe 9 pressure is above me predetermined pressure threshold (e.g. BP greater than 300kPa).

Table 1 below shows operation of the ECP valves for Australian relayed brake systems in their various operational stages.

Table 1: Operational state of various valves during full release, service application, holding/lap, graduated release, and pneumatic emergency application.

When the control and solenoid valves are all de-energised and the isolation valve is switched to open position, the system can operate as a conventional pneumatic brake. In essence this is a dual mode system and able to operate in a mixed train without the need, to sideline a whole train for refurbishment. The double check valve or shuttle valve 18 is added and acts as a switch between electronic mode and conventional pneumatic only braking mode. When operating in electronic mode, the double check valve 18 isolates the triple valve 2 from the relay valve 6, but allows the relay valve 6 to communicate with the supplementary reservoir 5 through the solenoid application valve 14 or vent to atmosphere through the solenoid release valve 12. In conventional pneumatic mode, the double check valve 18 allows the triple valve 2 to communicate with the relay valve 6, but isolates the relay valve 6 from communicating with the solenoid valves 12 and 14.

Practically all wagons in North America and slightly under half of the wagons in Australia are not equipped with brake systems including a relay valve. As shown in figures 5 and 6, the conventional and known AAR brake system includes two parts, an emergency portion 53 and a service portion 55. The service portion 55 operates in the same manner as the Australian triple valve 2 while the emergency portion 53 is a backup unit providing additional braking during emergency. The emergency portion 53 also incorporates a vent valve 57 to speed up emergency brake application by exhausting local brake pipe air. There are also two reservoirs, an emergency reservoir 59 and an auxiliary reservoir 61 and both are charged by the brake pipe 9 through the service portion 55. During normal braking, the auxiliary reservoir 61 air is used to provide braking energy to the brake cylinder 8. When an emergency brake application is demanded, emergency reservoir 59 air is supplied to the brake cylinder 8 to supplement the auxiliary reservoir 61 air giving 120% braking pressure.

Figures 5 and 6 are flow diagrams of the alternate AAR ECP brake systems according: to this other aspect of the invention where in this case it is a retrofit or modification of an existing non-relay pneumatic brake system. For ease of reference and to avoid repetition, like components of the alternate embodiments have been designated with the same reference numeral. The non-relay pneumatic system generally includes the auxiliary reservoir 61, the emergency reservoir 59, the emergency portion 53 and the service portion 55, but does not include the supplementary reservoir 5 of the previous aspect of the invention. Retrofitting to the AAR brake system involves converting the AAR brake system from non-relayed to a relayed brake system. The retrofit will in essence include an ECP unit, such as the Australian ECP brake system of figures 3 or 4, installed between the service portion 55 and a pipe bracket 63 together with a relay valve 65 and a supply or supplementary reservoir 67. The ECP unit includes a brake control module 69, an isolation module 71, an emergency module 75, a pressure sensor module 73 and 3 non- return charging valve 79.

The brake control module 69, the isolation module 71 and the pressure sensor module 75 are essentially the same as the corresponding unit for the Australian relayed brake system. However, since the emergency module 75 already has the vent valve 57, the emergency module 75 includes a solenoid emergency valve 37 only. The non-return charging valve 79 is added to the corresponding Australian unit for the AAR brake system to allow the brake pipe 9 to charge the reservoirs 59 and 61 while the service

portion 55 is being isolated from the brake pipe 9. The relay valve 65 is installed downstream, of the pipe bracket 63 between the pipe bracket 63 and the brake cylinder 8. The supply or supplementary reservoir 67 is installed externally and is charged by the brake pipe 9 through a non- return valve 79 and a choke 81 to provide braking energy to the brake cylinder S through the relay valve 65,

In ECP operation, with the brake released and Che brake pipe 9 fully charged, the pilot valve 29 is held closed by the brake pipe 9 pressure. The auxiliary reservoir 61 and emergency reservoir 59 are charged by the brake pipe 9 through the Service portion 55. The supplementary reservoir 67 is charged by the brake pipe 9 through the non-return valve 79 and a choke 81. When operating in ECP mode, the isolation valve 27 is in figure 5 manually switched to dosed isolating the service portion 55 from the brake pipe 9.

During brake application, the solenoid release valve 12 is energised to closed while solenoid, application valve 14 is energised to supply pilot air from the supplementary reservoir 67 into the relay valve 65 through the shuttle valve 18. This actuates the relay valve 65 to provide pressurised air from the supplementary reservoir 67 to the brake cylinder 8 to apply the brake. When the desired braking pressure is reached, the solenoid application valve 14 is de-energised into the closed position. Pressure feedback control is provided by the pressure transducer T1 (26).

During gradual brake release the solenoid release valve 12 is de-energised jnto the opened position to vent pilot pressure from the relay valve 65 through the double check valve 18. When the desired pressure is reached, the solenoid release valve 12 is re- energised into the closed position. Similarly, pressure feedback control is provided by the pressure transducer T1 (26). A reduction in the relay pilot pressure allows the brake cylinder 8 air to partially vent to atmosphere through the relay valve 65, thus partially releasing the brake. In full release, all the solenoid valves 12, 14 and 37 are de-energised- Pilot pressure from the relay valve 65 is vented into atmosphere through the solenoid release valve 12.

During a pneumatic emergency braking procedure, the solenoid emergency valve 37 is energised into the open position to vent brake pipe air. A rapid drop of local brake pipe pressure will actuate the vent valve 57 to dump brake pipe air thus accelerating emergency braking procedure. When the brake pipe drops below a predetermined pressure threshold (e.g. BP of less than or equal to 300kPa), the pilot valve 29 is reset to

the open position. This allows the service portion 55 to re-establish communication with the brake pipe 9 and deploys the brake. Sensing an emergency rate brake pipe reduction, the emergency portion 53 will also deploy and supply emergency reservoir air to the relay valve 65 thus providing extra braking pressure in the brake cylinder 8. After a pneumatic emergency braking procedure, the brakes are released by de-energising the solenoid emergency valve 37 and charging the brake pipe 9 up to full pressure. The pilot valve 29 will actuate to the dosed position when the brake pipe 9 pressure is above the predetermined pressure threshold (e.g. BP greater than 300KPa).

Table 2 below shows operation of the ECP valves for AAR non-relayed brake systems in their various operational stages.

Table 2: Operational state of valves during full release, service application, holding/lap, graduated release and pneumatic emergency application.

When the control and solenoid valves are all de-energised and the isolation valve switched to the open position, the system can operate as a conventional pneumatic non- relayed brake. This enables the train to operate in a mixed train without the need to sideline a whole train for refurbishment. The double check valve or shuttle valve 18 enables the train to switch between electronic braking mode and conventional pneumatic only braking mode. When operating in electronic mode, the double check valve 18 isolates the service portion 55 from the relay valve 65, but allows (he relay valve 65 to communicate with the supplementary reservoir 67 through the solenoid application valve

14 or vent to atmosphere through the solenoid release valve 12. In conventional pneumatic mode, the double check valve 18 allows the service portion 55 to communicate with the relay valve 65, but isolates the relay valve 65 from communicating with the solenoid valves 12 and 14,

Figures 7 and 8 are flow diagrams of embodiments of European or UlC ECP brake systems. For ease of reference and to avoid repetition, like components of the alternate embodiments have been designated with the same reference numeral. In these examples the European (UIC) relayed brake system operates in a similar manner to the Australian relayed brake system but with some minor differences. The UIC relayed brake system has a control reservoir 4 and an auxiliary reservoir 5. Both reservoirs 4 and 5 are charged by the brake pipe 9 through the triple valve or distributor 2, while in the Australian relayed brake system only the auxiliary reservoir 4 is charged through the distributor 2. The control reservoir 4 fulfils a similar function as the auxiliary reservoir 4 in the Australian relayed brake system. The brake is deployed when there is a pressure differential between

the brake pipe 9 and control reservoir 4. However, the control reservoir 4 does not supply a pilot pressure to the relay valve 6 to apply the brake unlike the auxiliary reservoir 4 in the Australian relayed brake system. When the distributor 2 is deployed the auxiliary reservoir 4 in the UlC relayed brake system supplies the pilot pressure to the relay valve and braking pressure to the brake cylinder 8 through the relay valve 6 to apply the brakes.

The UIC brake system (relayed and non-relayed) has the ability to gradually release the brake.

In ECP mode, the brake system operates exactly the same on the UlC relayed brake system as the Australian relayed brake system. When the brake is released and the brake pipe 9 is fully charged, the pilot valve 29 is held closed by the brake pipe 9 pressure. The auxiliary reservoir 5 and the control reservoir 4 are charged by the brake pipe 9 through the distributor 2. When operating in ECP mode, the isolation valve 27 is manually switched to closed, isolating the distributor 2 from the brake pipe 9.

During brake application, the solenoid release valve 12 is energised to closed while the solenoid application valve 14 is energised to supply pilot air from the auxiliary reservoir 5 into the relay valve 6 through the shuttle valve 18, This actuates the relay valve 8 to provide pressurised air from the auxiliary reservoir for braking to the brake cylinder 8. When the desired braking pressure is reached, the solenoid application valve 14 is de- energised into the closed position. Pressure feedback control is provided by the pressure transducer T1 (26).

During gradual brake release, the solenoid release valve 12 is de-energised into the opened position to vent pilot pressure from the relay valve 6 through the double check valve 18, When the desired pressure is reached, solenoid release valve 12 is re-energised into the closed position. Similarly, pressure feedback control is provided by the pressure transducers T1 (26). A reduction in the relay pilot pressure allows the brake cylinder 8 auto partially vent to atmosphere through the relay valve 6, thus partially releasing the brake. In full release, all the solenoid valves 12, 14 and 37 are de-energised- Pilot pressure from the relay valve 6 is vented into atmosphere through solenoid release valve 12.

During a pneumatic emergency braking procedure, the solenoid emergency valve 37 is energised into the open position to vent brake pipe 9 air. A rapid drop of local brake pipe pressure will actuate the vent valve 35 to dump brake pipe 9 air thus accelerating emergency braking procedure. When the brake pipe 9 drops below a predetermined

pressure threshold (e.g. BP less titan or equal to 300kPa), pilot valve 29 is reset to the open position. This allows the distributor 2 to re-establish communication with the brake pipe 9 and deploys the brake. After a pneumatic emergency braking procedure, the brakes are released by de-energising the solenoid emergency valve 37 and charging the brake pipe 9 up to full pressure. The pilot valve 29 will actuate to the closed position when the brake pipe 9 pressure is above the predetermined pressure threshold (e.g. BP greater than 300kPa).

Table 3 below shows operation of the valves of these UIC relayed ECP brake systems in their various operational stages.

Table 3: Operational state of valves during full release, service application, høiding/lap, graduated release and pneumatic emergency application.

For the purpose of this specification the terms triple valve, control valve and distributor are to be understood as covering the same general brake valve component. The ECP unit of the various aspects of the invention are designed to retrofit onto wagons with WF Type Triple Valve (the Australian brake system), SW Type Distributor (for European or UIC brake system) and ABD, ABDW and ABDX Type Control Valve (for North American or AAR brake system).

Now that several preferred embodiments of the various aspects of the ECP brake system have been described in some detail it will be apparent to those skilled in the art that the ECP brake system has at least the following advantages over the admitted prior art:

1. the design of the ECP brake system lends itself to upgrading or retrofitting existing wagons equipped with conventional pneumatic brakes;

2. the ECP brake system retains the functions of existing pneumatic brakes;

3. the ECP brake system provides a relatively inexpensive alternative to current ECP brakes and effectively fills the gap between stand alone ECP brakes and conventional pneumatic brakes;

4. the ECP brake system provides an entry level system which assists the rail industry in transition to full electronic braking;

5. the ECP brake system is suitable for use with both relayed brakes and non-relay brakes equipped wagons;

6. the ECP brake system is a dual mode system and as such can operate mixed train without the need to sideline a whole train for refurbishment;

7- the relayed ECP brake system allows for the addition of a double check valve to switch between electronic braking mode and conventional pneumatic braking mode and thus provides a modular setup;

8. the pneumatic control valve or triple valve in at least one aspect is no longer used during electronic braking where pilot pressure is vented from the relay valve directly to atmosphere through a brake release relay control valve;

9. according to at least one embodiment an isolation valve is installed between the brake pipe and pneumatic control valve to isolate the pneumatic control valve from pressure fluctuation in the brake pipe during brake application and this prevents the pneumatic control valve or triple valve from being inadvertently triggered by pressure fluctuations in the brake pipe during electronic braking;

10. according to at least one embodiment emergency control valve and vent valve are added to provide emergency braking by dumping local braise pipe air to speed up emergency brake application;

11. the ECP system in one embodiment allows for brake release without electrical power;

12. the ECP system can include an isolation system which prevents the triple valve from deploying unnecessary and thus reduces wear and tear on the triple valve; and

13. the control valves used in at least one aspect of the present design are small flow capacity valves and are used to supply small amounts of pilot pressure to actuate braking thereby reducing power consumption;

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. For example, although the service, release and relay control valves described are solenoid actuated and spring biased, they need not be of this construction. The ECP brake system need not be a retrofit but in fact may be manufactured as an "integral" component in an ECP brake system. All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description.

It is to be understood that any acknowledgement of prior art in this specification is not to be taken as an admission that this prior art forms part of the common general knowledge in Australia or elsewhere.