Claims:We Claim:

1. A brake control unit for controlling a pressure of air inside a brake pipe for controlling an operation of a braking of a rail vehicle having a main reservoir for storing a pressurized air and configured to provide the pressurized air to the brake pipe, the brake control unit comprising:
a transmission valve configured for controlling a flow of air from the main reservoir to the brake pipe and from the brake pipe to an ambient;
a control reservoir in fluid communication with a control chamber of the transmission valve, wherein a pressure of air inside the control reservoir is adjusted to control a pressure of the control chamber to control a flow of air between the main reservoir and the brake pipe and the brake pipe and the ambient;
a release electropneumatic valve to control a pressure of air to the control reservoir from the main reservoir;
a backup brake valve to control a flow of air to the control reservoir from the main reservoir; and
a three-way valve to adapted to move to a first position and a second position, wherein
in the first position, the three-way valve allows a flow of air received from the release electropneumatic valve to the control reservoir and prevents a flow of air from the backup brake valve to the control reservoir, and
in the second position, the three-way valve allows a flow of air received from the backup brake valve to the control reservoir and prevents a flow of air from the release electropneumatic valve to the control reservoir,
wherein the there-way valve is moved to the second position when an electric or electronic failure of the brake control unit is detected.

2. The brake control unit as claimed in claim 1, wherein the there-way valve is a manually operated valve.

3. The brake control unit as claimed in claim 1 further including
an isolation valve for controlling flow of air between the transmission valve and the brake pipe, and
a running electropneumatic valve to control a flow of air form the main reservoir to the isolation valve to facilitate a partial opening of the isolation valve to allow a flow air between the transmission valve and the brake pipe.

4. The brake control unit as claimed in claim 1, wherein
the three-way valve is disposed in the first position during a normal mode, and
the three-way valve is moved to the second position during a failure mode, the failure mode corresponds to the electrical or an electronic failure of the brake control unit.

5. The brake control unit as claimed in claim 4, wherein the backup brake valve is configured to reduce a pressure of air provided to the control chamber to apply the brakes during the failure mode and to increase the pressure of air provide to the control chamber to release the brakes during the failure of the brake control unit..

6. The brake control unit as claimed in claim 5, wherein, in response to the reduction in pressure in the control chamber, the transmission valve allows a release of air from the brake pipe to reduce an air pressure inside the brake pipe to facilitate an application of the brake to the rail vehicle.

7. The brake control unit as claimed in claim 1, wherein the three-way valve includes a mechanical lock to prevent a movement of the three-way valve from the first position to the second position, wherein the three-way valve moves from the first position to the second position upon a removal of the mechanical lock.

8. A method for controlling a pressure in a brake pipe of a rail vehicle, the method comprising:
detecting a failure mode of a brake control unit configured to control an air pressure inside a brake pipe, wherein the failure mode corresponds to an electrical or electronic failure of the brake control unit;
moving, upon detection of the failure mode, a three-way valve of the brake control unit to a second position to allow a flow of air from a backup brake valve to a control chamber of a transmission valve of the brake control unit; and
controlling the backup brake valve to modulate an air pressure of the air provided to the control chamber to control the pressure inside the brake pipe to control a braking of the rail vehicle.

9. The method as claimed in claim 8 including operating the three-way in a first position during a normal mode of the brake control unit, wherein, an application electropneumatic valve and/or a release electropneumatic valve is controlled to control an air pressure inside the control chamber during the normal mode of the brake control unit.

10. A method for retrofitting a pre-exiting brake control unit for a rail vehicle to form a brake control unit, the method comprising:
removing one or more valves from a control body of the pre-existing brake control unit;
attaching an intermediate plate to the control body;
coupling the one or more valves to the intermediate plate; and
mounting a three-way valve to the intermediate plate, wherein the three-way is adapted to move to a first position and a second position, wherein the three-way valve is adapted to move to the second position upon detection of a failure mode of the brake control unit to facilitate a braking of the rail vehicle.

Dated this the 23th day of December, 2019
[VIVEK SINGH- IN/PA 2786]
OF SAGACIOUS RESEARCH
AGENT FOR THE APPLICANT
To
The Controller of Patents
The Patent Office
Chennai
, Description:BRAKE CONTROL UNIT FOR A RAIL VEHICLE AND A METHOD FOR CONTROLLING A BRAKE FUNCTION
Technical Field
The present disclosure generally relates to a brake control unit for a rail vehicle. More specifically, the disclosure relates to a brake control unit and a method for controlling a braking a rail vehicle when an electric or electronic control failure occurs.

Background
For over the last century, trains have employed pneumatic braking systems to control the movement of railcars and locomotives. Railcar brake application or release is typically configured to respond to changes in brake pipe pressure, the brake pipe being a long continuous pipe that runs from the lead locomotive to the last railcar. When the brakes of the train are to be applied, pneumatic control valves reduce the brake pipe pressure, and the individual brakes at each railcar are applied in response. When the brakes of the train are to be released, pneumatic control valves modulate brake pipe pressure, and the individual brakes at each railcar are released in response. The pneumatic control valves for controlling the pressure of the brake pipe may be housed in a control unit in the locomotive, which may receive electronic control input from a locomotive driver Brake Controller.

If the electronic controls operating the pneumatic valves fail, brake pipe pressure will not be in a position to be reduced or modulated. However, the train may still be brought to a stop through emergency brake application. Typically, emergency brake valves are used to rapidly reduce air pressure in the brake pipe to trigger application of the train's brakes. However, failure of the electronic controls prevents normal operation of the train and may prevent the train from effectively continuing the journey until it can be serviced and repaired. Furthermore, current systems may not allow a train operator to continue operating the locomotive under the default brake application and release functions. There is a need in the art for a system that allows a train to operate with the default brake functionality, even after failure of one or more primary electronic control systems.

Summary
According to an aspect of the disclosure, a brake control unit is disclosed. The brake control unit controls a pressure of air inside a brake pipe for controlling an operation of a braking of a rail vehicle. The rail vehicle has a main reservoir for storing a pressurized air and is configured to provide the pressurized air to the brake pipe. The brake control unit includes a transmission valve, a control reservoir, a release electropneumatic valve, a backup brake valve, and a three-way valve. The transmission valve is configured to control a flow of air from the main reservoir to the brake pipe and from the brake pipe to an ambient. The control reservoir is in fluid communication with a control chamber of the transmission valve. A pressure of air inside the control reservoir is adjusted to control a pressure of the control chamber of transmission valve to control a flow of air between the main reservoir and brake pipe and the brake pipe and the ambient. Further, the release electropneumatic valve controls a pressure of air to the control reservoir from the main reservoir. Further, the backup brake valve controls a flow of air to the control reservoir from the main reservoir. Furthermore, the three-way valve is adapted to move to a first position and a second position. The three-way valve, in the first position, allows a flow of air received from the release electropneumatic valve to the control reservoir and prevents a flow of air from the backup brake valve to the control reservoir. In the second position, the three-way valve allows a flow of air received from the backup brake valve to the control reservoir and prevents a flow of air from the release electropneumatic valve to the control reservoir. The there-way valve is moved to the second position when an electric or electronic failure of the brake control unit is detected.

In one embodiment, the there-way valve of the brake control unit is a manually operated valve.

In another embodiment, the brake control unit further includes an isolation valve and a running electropneumatic valve. The isolation valve controls the flow of air between the transmission valve and the brake pipe. The running electropneumatic valve controls a flow of air from the main reservoir to the isolation valve to facilitate a partial opening of the isolation valve to allow a flow air between the transmission valve and the brake pipe.

In yet another embodiment, the three-way valve is disposed in the first position during a normal mode. Further, the three-way valve is moved to the second position during a failure mode. The failure mode corresponds to an electric or an electronic failure of the brake control unit.

In one embodiment, the backup brake valve is configured to reduce a pressure of air provided to the control chamber to apply the brakes and to increase the pressure of air provided to the control chamber to release the brakes during the failure of the brake control unit.

In one embodiment, in response to the reduction in pressure in the control chamber, the transmission valve allows a release of air from the brake pipe to reduce an air pressure inside the brake pipe to facilitate an application of the brake to the rail vehicle.

In one embodiment, the three-way valve includes a mechanical lock to prevent a movement of the three-way valve from the first position to the second position. The three-way valve moves from the first position to the second position upon a removal of the mechanical lock.

In another aspect, a method for controlling a pressure in a brake pipe of a rail vehicle is disclosed. The method includes detecting a failure mode of a brake control unit configured to control an air pressure inside a brake pipe. The failure mode corresponds to an electrical or electronic failure of the brake control unit. The method further includes moving, upon detection the failure mode, a three-way valve of the brake control unit moves to a second position to allow a flow of air from a backup brake valve to a control chamber of a transmission valve of the brake control unit. Moreover, the method includes controlling the backup brake valve to modulate an air pressure of the air provided to the control chamber to control the pressure inside the brake pipe to control a braking of the rail vehicle.

In one embodiment, the method includes operating the three-way valve in a first position during a normal mode of the brake control unit. During the normal mode of the brake control unit, a release electropneumatic valve and/or an application electropneumatic valve is controlled to control an air pressure inside the control chamber.

In yet another aspect, a method for retrofitting a pre-exiting brake control unit for a rail vehicle to form a brake control unit is disclosed. The method includes removing one or more valves from a control body of the pre-existing brake control unit and attaching an intermediate plate to the control body. The method further includes coupling the one or more valves to the intermediate plate and mounting a three-way valve to the intermediate plate. The three-way is adapted to move to a first position and a second position. Also, the three-way valve is adapted to move to the second position upon detection of a failure mode of the brake control unit to facilitate a braking of the rail vehicle.

Brief Description of the Drawings
In the following, the invention will be described in greater detail with reference to embodiments shown by the enclosed figures. It should be emphasized that the embodiments shown are used for example purposes only and should not be used to limit the scope of the invention.

FIG. 1 illustrates a brake control unit having a three-way valve disposed in a first position, in accordance with an embodiment of the disclosure;

FIG. 2 illustrates the brake control unit having the three-way valve disposed in a second position, in accordance with an embodiment of the disclosure;

FIG. 3 illustrates a brake control unit formed by retrofitting a pre-existing brake control unit by using an intermediate plate and depicting the three-way valve disposed in the first position, in accordance with an embodiment of the disclosure;

FIG. 4 illustrates the brake control unit of FIG. 3 depicting the three-way valve disposed in the second position, in accordance with an embodiment of the disclosure;

FIG. 5 illustrates a top view of the pre-existing brake control unit, in accordance with an embodiment of the disclosure;

FIG. 6 illustrates a top view of the intermediate plate with the three-way valve mounted on the intermediate plate, in accordance with an embodiment of the disclosure; and

FIG. 7 illustrates a sectional view of the intermediate plate and the three-way valve depicting a first channel, a second channel, and a third channel, in accordance with an embodiment of the disclosure.

Detailed Description

Referring to FIG. 1 and FIG. 2, a schematic view of a brake control unit 100 for controlling pressure in a brake pipe 200 of an electronic brake system 300 is shown. The brake control unit 100 is adapted for controlling a flow of pressurized air from a main reservoir 400 to the brake pipe 200 and controlling air pressure in the brake pipe 200 for controlling an application and/or release of the brakes (not shown) of a rail vehicle having a locomotive and/or one or more passenger or freight stock. Further, the brake control unit 100 includes a backup brake valve 104 for providing and controlling flow of air from the main reservoir 400 to the brake pipe 200 during a failure mode of the brake control unit 100.

The brake control unit 100 includes a running electropneumatic (EP) valve 110, a release EP valve 112, an application EP valve 114, a full-bore EP valve 116, an isolation valve 118, a control reservoir 120, a transmission valve 122, and a three-way valve 124. The running EP valve 110 is adapted to control a flow of air from the main reservoir 400 to brake pipe 200 by controlling a flow of air from the main reservoir 400 to the isolation valve 118. In an embodiment, the running EP valve 110 is configured to be actuated between a first position and a second position. In the first position, the running EP valve 110 allows a flow of air from the main reservoir 400 to the isolation valve 118, while in the second position the running EP valve 110 prevents a flow of air from the main reservoir 400 to the isolation valve 118. As shown, the running EP valve 110 is in fluid communication with the main reservoir 400 via a first fluid conduit 130, and is in fluid communication with the isolation valve 118 via a second fluid conduit 132. The air received by the isolation valve 118 via the second fluid conduit 132 facilitates a partial opening of the isolation valve 118.

The isolation valve 118 is adapted to control a flow of air between the transmission valve 122 and the brake pipe 200 to control a pressure of air in the brake pipe 200. The isolation valve 118 is fluidly connected to the transmission valve 122 through a first fluid passage 134, and is fluidly connected to the brake pipe 200 via a second fluid passage 136. Further, the isolation valve 118 includes a first chamber 140 (also referred to as a bottom chamber 140) fluidly connected to the running EP valve 110 via the second fluid conduit 132 and is configured to receive pressurized air from the main reservoir 400 when the running EP valve 110 is at the first position. In response to an entry of the pressurized air into the bottom chamber 140, the isolation valve 118 provides a restricted/partial opening to allow a passage of air between the transmission valve 122 and the brake pipe 200.

Further, the isolation valve 118 also includes a second chamber 142 fluidly connected to the full-bore EP valve 116 via a passage 144. The full-bore EP valve 116 is adapted to control a flow of air from the main reservoir 400 to the second chamber 142. The full-bore EP valve 116 is adapted to be actuated to a first position in which the full-bore valve 116 allows a flow of air from the main reservoir 400 to the second chamber 142 via the passage 144 and a second position in which the full-bore valve 116 prevents a flow of air from the main reservoir 400 to the second chamber 142 via the passage 144. In response to an entry of the pressurized air into the first chamber 140 and the second chamber 142, the isolation valve 118 is fully opened, thereby allowing a full flow of air from the transmission valve 122 to the brake pipe 200 via the first fluid passage 134, the isolation valve 118, and the second fluid passage 136.

The transmission valve 122 is configured to control a flow air from the main reservoir 400 to the brake pipe 200 and from the brake pipe 200 to an ambient, thereby controlling an application or release of the brake. The transmission valve 122 is fluidly connected to the control reservoir 120 and configured to maintain, increase, or reduce air pressure in the brake pipe 200 in response to a pressure of the air inside the control reservoir 120. The control reservoir 120 is fluidly connected to a control chamber 150 of the transmission valve 122 via a fluid line 152 and is configured to provide pressurized air to the control chamber 150 to control an application or release of the brakes. Further, the transmission valve 122 is fluidly connected to the main reservoir 400 via a first conduit 154 for receiving the air from the main reservoir 400, and is fluidly connected to the isolation valve 118 via the first fluid passage 134. The transmission valve 122 is adapted to provide air to the brake pipe 200 to maintain the air pressure inside the brake pipe 200 when the air pressure in the control chamber 150 (i.e. the control reservoir 120) is equal to or above a predefined pressure value. Further, the transmission valve 122 is adapted to exhaust the air from the brake pipe 200 to an ambient via an exhaust conduit 156, and thereby reduces the pressure in the brake pipe 200 in response to a reduction in the pressure in the control chamber 150 (i.e. the control reservoir 120). The pressure of air inside the control reservoir 120 is maintained equal to or above the predefined threshold value to prevent an application of the brakes and thus maintain the rail vehicle in a running condition, while the pressure of air inside the control reservoir 120 is reduced below the predefined threshold value to apply brakes.

The control chamber 150 is configured to receive the air from the main reservoir 400, and is fluidly connected to the three-way valve 124 via a first channel 160. The three-way valve is fluidly connected to the release EP valve 112 and the application EP Valve 114 via a second channel 162, and is fluidly connected to the backup brake valve 104 via a third channel 164. A pressure inside the control reservoir 120 is controlled by opening and closing the application EP valve 114 and the release EP valve 112 when the brake control unit 100 is functioning properly. In an optional embodiment, the brake control unit 100 may include a low pressure over charge valve 119 to fill the brake pipe 200 to a higher pressure by the over charging the control reservoir 120. Further, the brake control unit 100 may include a pressure regulating valve 166 to control a pressure of air being supplied to the control reservoir 120 via the release valve EP 112. As shown, the three-way valve 124 is disposed downstream of the release EP valve 112 the application EP valve 114 and the low pressure overcharge EP Valve 119 and upstream of the control reservoir 120 to control a flow of the air to the control reservoir 120. In an embodiment, the three-way valve 124 is a manually operated valve and is adapted to fluidly connect the main reservoir 400 to the control chamber 150 (i.e. the control reservoir 120) via the release EP valve 112 in a first position. In a second position, the three-way valve 124 fluidly connects the backup brake valve 104 to the control reservoir 120. Therefore, in the first position (shown in FIG. 1), the three-way valve 124 allows pressurized air to flow from the main reservoir 400 to the control reservoir 120 through the pressure regulating valve 166 and the release EP valve 112, while preventing a flow of the pressurized air to the control reservoir 120 from the main reservoir 400 via the backup brake valve 104. Further, in the second position, the three-way valve 124 allows pressurized air to flow from the main reservoir 400 to the control reservoir 120, and hence the control chamber 150, through the backup brake valve 104, while prevents a flow of the pressurized air to the control reservoir 120, and hence the control chamber 150, from the main reservoir 400 via the pressure regulating valve 166 and the release EP valve 112. The three-way valve 124 is moved to the second position when an electronic failure of the brake control unit 100 or loss of electrical power supply to the brake system 300 is detected. In an embodiment, the three-way valve 124 is manually moved to the second position by the operator of the rail vehicle to enable a proper functioning of the brakes even after the electric or electronic failure of the brake control unit 100. The backup brake valve 104 is a manually operated valve and is adapted to control a flow of pressurized air from the main reservoir 400 to the three-way valve 124 via the backup brake valve 104 in response to an operation of a backup brake lever 170 by an operator of the rail vehicle.

An operation of the brake control unit 100 is now explained when the brake control unit 100 is functioning normally (i.e. in a normal mode). At first, an operation of the brake control unit 100 is explained during a normal running condition of the rail vehicle. To enable the normal running condition of the rail vehicle, the operator may position a handle of a driver brake controller in a running position. Upon detecting the handle in the running position, the brake controller may control the release EP valve 112 and the application EP valve 114 in a close loop manner to maintain/charge/discharge the control reservoir 120 at the predefined pressure value. Further, the brake controller may move the running EP valve 110 to the first position to allow the flow of air from the main reservoir 400 to the bottom chamber 140 of the isolation valve 118. In response to the entry of the pressurized air inside the bottom chamber 140, the isolation valve 118 is partially opened to provide a restricted opening for the flow of air between the transmission valve 122 and the brake pipe 200.

In addition, as the three-way valve 124 is disposed in the first position during normal operation of the brake control unit 100, the pressurized air flows from the main reservoir 400 to the pressure regulating valve 166 which supplies air at a reduced pressure to the control chamber 150, and hence the control reservoir 120, via the release EP valve 112, the application EP valve 114, the second channel 162 and the first channel 160. The pressure of air inside the control chamber 150 of the transmission valve 122 causes a diaphragm assembly 172 to move in a first direction (i.e. upwards), resulting into a lifting of an inlet valve 174 off its seat, thereby allowing the pressurized air received from the main reservoir 400 via the first conduit 154 to the isolation valve 118 via the first fluid passage 134, and subsequently to the brake pipe 200 though the second fluid passage 136. In this manner, the pressure in the brake pipe 200 is increased.

Moreover, a proportion of the air from the main reservoir 400 received by the transmission valve 122 via the first conduit 154 flows to an equalizing chamber 176 of the transmission valve 122. As shown, the equalizing chamber 176 is separated from the control chamber 150 by the diaphragm assembly 172, hence the air present in the equalizing chamber 176 pushes the diaphragm assembly 172 in a second direction (i.e. downwardly), while the air present in the control chamber 150 pushes the diaphragm assembly 172 upwards. In this manner, when the air in the brake pipe 200 reaches a predetermined pressure, the force exerted downwardly, by the air, on the diaphragm assembly 172 equals the upward force exerted on the diaphragm assembly 172 by the air present in the control chamber 150. In so doing, the inlet valve 174 is closed, thereby preventing a flow of air from the main reservoir 400 to the brake pipe 200 via the isolation valve 118, thereby preventing any further increase in brake pipe pressure. In this manner, by keeping the pressure in the brake pipe 200 at the predetermined pressure, the brakes are not applied, resulting into a normal running of the rail vehicle.

When the handle of the brake controller is placed in a braking position, the running EP valve 110 remains in the first position, while the brake controller controls the release EP valve 112 and the application EP valve 114 to reduce the pressure inside the control reservoir 120, and hence the control chamber 150 to a second threshold value. The second threshold value may correspond to a level of braking required on the rail vehicle.

Since the running EP valve 110 remains in the first position, the isolation valve 118 remains partially opened as the bottom chamber 140 is maintained at the main reservoir pressure, thereby fluidly connecting the brake pipe 200 to the transmission valve 122 and hence the equalizing chamber 176. In this manner, the pressure inside the equalizing chamber 176 of the transmission valve 122 is equal to the pressure inside the brake pipe 200, while there is a drop in the pressure in the control chamber 150. As a result, a net downward force acts on the diaphragm assembly 172, causing a downward movement of the diaphragm assembly 172. In so doing, a fluid communication between the brake pipe 200 and the exhaust conduit 156 is established, causing pressurized air to flow from the brake pipe 200 to the ambient. In this manner, the pressure in the brake pipe 200 reduces, resulting into application of the brakes.

Further, a fall in the pressure inside the brake pipe 200 is communicated to the equalizing chamber 176 and when the pressure in the equalizing chamber 176 and the control chamber 150 become equal, the inlet valve 174 is again closed, this preventing any further loss of air from the brake pipe 200 to the ambient via the exhaust conduit 156. The pressure inside the brake pipe 200 is then held constant at a reduced level, which corresponds to the particular braking requirement.

To release the application of the brakes, the operator may move the the handle of the brake to a release position. In this position, the brake controller energizes the full-bore EP valve 116 and the running EP valve 110. In this condition, the brake control unit 100 operates as described for the running condition, except that the full-bore EP valve 116 is also energised. The actuation of the full-bore valve 116 to the first position allows air to flow from the main reservoir 400 to the second chamber 142 of the f isolation valve 118. In this manner, the isolation valve 118 is fully opened due to pressure air acting in the first chamber 140 and the second chamber 142, and thus permitting an unrestricted flow of air from the main reservoir 400 to the brake pipe 200 via the transmission valve 122 and the isolation valve 118. This action reduces the time taken to recharge the brake pipe 200 to its normal pressure i.e. the predefined threshold value. When the handle is released from the release position, the handle may automatically move to the running position.

An operation of the brake control unit 100 in a failure mode of the brake control unit 100 is now explained. Upon detecting the electric or electronic failure of the brake control unit 100, the operator may operate the three-way valve 124, and switch the three-way valve 124 to the second position (as shown in FIG. 2). In the second position, a flow of pressurized air to the control reservoir 120, and hence the control chamber 150, from the main reservoir 400 via the backup brake valve 104 is enabled, while the flow of air from the main reservoir 400 to the control reservoir 120 via the release EP valve 112 and the application EP valve 114 is blocked/disabled. Therefore, in the failure mode, the brake release and application are initiated and achieved by the operator of the rail vehicle by moving the backup brake valve 104 in a release zone and in an application zone.

In the failure mode, the running EP valve 110 remains in the first position, thereby allowing a flow of air from the main reservoir 400 to the bottom chamber 140 via the first fluid conduit 130 and the second fluid conduit 132. In this manner, the isolation valve 118 remains partially opened to facilitate a flow of air between the brake pipe 200 and the transmission valve 122 via the first fluid passage 134 and the second fluid passage 136. For facilitating the normal running condition of the rail vehicle or releasing the brake, the air from the backup brake valve 104 enters the control chamber 150 of the transmission valve 122 via the first channel 160, the third channel 164, and fluid line 152 through the three-way valve 124. As the pressure in the control chamber 150 received from the backup brake valve 104 is equal to or above the predefined pressure value, the inlet valve 174 is opened allowing a flow of air from the main reservoir 400 received via the first conduit 154 to the isolation valve 118 via the first fluid passage 134. Subsequently, as the isolation valve 118 is partially open, the air from the first fluid passage 134 flows to the brake pipe 200 via the second fluid passage 136, and charges the brake pipe to the predefined pressure value required to prevent the brake from being applied. Also, a portion of the air flowing from the main reservoir 400 to brake pipe 200 via the transmission valve 122 may enter the equalizing chamber 176 and may close the inlet valve 174 once the desire pressure in the brake pipe 200 is achieved. In this manner, the transmission valve 200 is closed to prevent any air flow from the main reservoir 400 to the brake pipe 200.

In order to apply brakes to slow down or stop the rail vehicle, the operator may move the backup brake valve 104 in a brake application zone. In response to the movement of the backup brake valve 104 in the brake application zone, the backup brake valve 104 may modulate and reduce the pressure of air provided to the control chamber 150 from the main reservoir 400 via the first channel 160 and the third channel 164. In an embodiment, the backup brake valve 104 reduces the pressure of air supplied to the control chamber 150 in proportion to a displacement of the backup brake lever 170. As the pressure of air inside the control chamber 150 reduces to level below the air pressure in the equalizing chamber 176, the diaphragm assembly 172 moves downward allowing a fluid communication between the exhaust conduit 156 and the brake pipe 200 through the isolation valve 118, the first fluid passage 134 and the second fluid passage 136. In this manner, a portion of the air inside the brake pipe 200 is exhausted, resulting into a reduction of air pressure inside the brake pipe 200. Further as the brake pipe 200 is in fluid communication with the equalizing chamber 176, a reduction in the air pressure inside the brake pipe 200 also results into a reduction of air pressure inside the equalizing chamber 176. In this manner, the fluid communication between the exhaust conduit 156 and the brake pipe 200 is cut-off when the pressure in the equalizing chamber 176 is equal to pressure in the control chamber 150, hence the control reservoir 120. Further, in response to a decrease in the air pressure in the brake pipe 200, the brake is applied on the rail vehicle. In an embodiment, the amount of brake applied on the rail vehicle is proportional to the amount of pressure reduction inside the brake pipe 200. In this manner, the brake control unit 100 facilitates and maintains proper functioning of the brakes of the rail vehicle in the event of the electrical or an electronic failure of the brake control unit 100.

In an embodiment, to enable a retrofitting of the three-way valve 124 into a pre-existing brake control unit of the rail vehicle, an intermediate plate is assembled to the pre-existing brake control unit manifold. The pre-exiting brake control unit includes all the valves of the brake control unit 100 except the three- way valve 124. Therefore, to convert the pre-existing brake control unit into the brake control unit 100 of the disclosure, all the valves including the three-way valve 124 is mounted on an intermediate plate and the arrangement is mounted on the pre-existing brake Control Unit. In an embodiment, the three-way valve 124 also includes a micro switch to generate signal corresponding to health status signal indicating a normal working of the rail vehicle.

Referring to FIGS. 3 and 4 a brake control unit 100’ assembled by retrofitting a pre-existing brake control unit 500 (shown in FIG. 5) is shown. The brake control unit 100’ is similar in function to the brake control unit 100. The brake control unit 100’ is formed by retrofitting a pre-exiting brake control unit 500 with the three-way valve 124 by using an intermediate plate 600. As shown, brake control unit 100’ includes a control body 502 of the pre-existing brake control unit 500, the intermediate plate 600 assembled on a surface of the control body 502, and the valves 112, 114, 119, 110, 116, attached to the intermediate plate 600. The intermediate plate 600 includes various ports 504, 506, 508, 510, 512 (shown in FIG. 6) that aligns with the corresponding ports of the control body 502. Further, the intermediate plate 600 includes at least some portions of the channels 160, 162, 164 to facilitates a fluid connection of the release EP valve 112, the application EP valve 114, and low pressure overcharge valve 119 to the control chamber 150, and a fluid connection of the backup brake valve 104 to the control chamber 150 through the three-way valve 124. As shown, the three-way valve 124 is mounted on the intermediate plate 600 and may be moved from the first position to the second position by operating a handle 520 of the three-way valve 124 from a first position (shown in FIG. 3) to a second position (shown in FIG. 4) respectively. In an embodiment, to move the handle 520 from the first position to the second position, the operator or driver need to break and remove a mechanical lock, such as a seal wire 522 (shown in FIG. 3), form the handle 520. Therefore, the seal wire 522 prevents any inadvertent movement of the handle from the first position to the second position, and hence movement/actuation of the three-way valve 124 to the second position.

A method of retrofitting the pre-existing brake control unit 500 is now discussed. The pre-existing brake control unit 500 includes the control body 502 and the running EP valve 110, the release EP valve 112, the full- bore EP valve 116, the application EP valve 114, the low pressure over-charge valve 119, the transmission valve 122, the isolation valve 118, and the pressure regulating valve 166 and various other components mounted to the control body 502. To retrofit the pre-existing brake control unit 500, at first, various valves, such as, the release EP valve 112, the running EP valve 110, the application EP valve 114, the full-bore EP valve 116, and the low pressure overcharge valve 119 is removed from the control body 502. Further, a transducer may be removed from the control body 502. Thereafter, the intermediate plate 600 is attached with surface of the control body 502 such that ports 504, 506, 508, 510, 512 for each valve 110, 112, 114, 116, 119 in the intermediate plate 600 aligns with the ports of the respective valves 110, 112, 114, 116, 119 formed into the control body 502. Thereafter, the running EP valve 110, the release EP valve 112, the application EP valve 114, the full-bore EP valve 116, and the low pressure overcharge valve 119 is mounted on the intermediate plate 600. Also, the three-way valve 124 is mounted on the intermediate plate 600 in the first position, thereby fluidly connecting the first channel 160 to the second channel 162 and fluidly disengaging the third channel 164 from the first channel 160. In this manner, the pre-existing brake control unit 500 is retrofitted and converted into the brake control unit 100’.

it is to be noted that the figures and the above description have shown the example embodiments in a simple and schematic manner. Many of the specific mechanical details have not been shown since the person skilled in the art should be familiar with these details and they would just unnecessarily complicate this description.