Variable valve for a rail vehicle braking system

Abstract

A variable valve is disclosed that proportionally adjusts the pressure supplied from a control valve to the brake cylinder of a rail vehicle according to the vehicle's loading status. The variable valve has an arm that extends in response to braking to contact the side frame of the rail vehicle, thereby detecting the vehicle's loading status. The arm applies a variable bias force to a proportional valve spool, which is movable to disconnect the pressure output of the control valve from the pressure inlet of the brake cylinder. Thus, for an unloaded rail vehicle, the proportional valve spool will disconnect the control valve from the brake cylinder at a lower pressure compared to a heavily loaded vehicle.

Description

Technical Field

[0001] This invention relates to a truck braking system, and more particularly, to a variable valve for adjusting the brake cylinder pressure according to the truck's loading status. Background Technology

[0002] Freight trains weigh significantly more when fully loaded than when empty, resulting in varying braking forces that can be applied under different operating conditions without damaging the wheels. Furthermore, applying the same braking force to all train wheels will lead to vastly different braking effects between fully loaded and empty cars, potentially making train dynamics unpredictable. Traditional solutions include using no-load / load valves that sense whether a vehicle is empty or loaded and adjust the braking force provided by the brake cylinders when unloaded. However, existing no-load / load valves cannot proportionally adjust the braking force across the full range of operating conditions a rail vehicle might face. Therefore, a valve is needed that can change the brake cylinder pressure in response to the rail vehicle's load status. Summary of the Invention

[0003] This invention relates to a variable valve capable of proportionally adjusting the pressure supplied from a control valve to the brake cylinder of a rail vehicle according to the vehicle's loading status. The variable valve has an arm that extends to contact the side frame of the rail vehicle during braking, thereby detecting the vehicle's loading status. The farther the arm extends to contact the side frame, the less loaded the rail vehicle. The arm provides a variable bias force acting on a proportional valve core, which is movable to disconnect the pressure output of the control valve from the pressure inlet of the brake cylinder. The magnitude of the force exerted by the arm against the movement of the proportional valve core depends on the arm's position. The farther the arm extends, the smaller the force applied to the proportional valve core. Therefore, for an empty rail vehicle, the proportional valve core will disconnect the connection between the control valve and the brake cylinder at a lower pressure compared to a heavily loaded vehicle. The variable valve includes a switching valve core that delays the actuation of the proportional valve core until a predetermined brake cylinder pressure threshold is reached; and an exhaust passage / exhaust valve core that can discharge the pressure acting on the proportional valve core when the control valve stops supplying pressure to the brake cylinder.

[0004] In another embodiment, the present invention relates to a method for regulating brake cylinder pressure supplied by a control valve to a brake cylinder of a rail vehicle. The method includes the steps of: connecting an inlet of a variable valve housing to a control valve and an outlet of the variable valve housing to a brake cylinder, wherein communication between the inlet and outlet is achieved via a proportional valve spool having a valve seat movable between an open position allowing communication between the inlet and outlet and a closed position blocking communication between the inlet and outlet. In response to the magnitude of the brake cylinder pressure received from the control valve at the inlet, an arm pivotally mounted on the housing moves from a retracted position to an extended position until it contacts the side frame of the rail vehicle. A movable valve spool disposed in a first chamber of the housing then moves in response to the movement of the arm, such that a spring disposed between the movable valve spool and the proportional valve spool provides a variable biasing force to the proportional valve spool according to the position of the arm, biasing the proportional valve spool to the open position. The method further includes the step of: pressurizing a second chamber receiving the head of the proportional valve spool until the valve seat moves to the closed position against the biasing force of the spring. Therefore, when the proportional valve is closed, the variable valve stops supplying brake cylinder pressure to the brake cylinder. Attached Figure Description

[0005] A more comprehensive understanding and appreciation of the invention will be achieved by reading the following detailed description in conjunction with the accompanying drawings, wherein:

[0006] Figure 1 This is a perspective view of the variable valve according to the present invention.

[0007] Figure 2 This is a schematic diagram of a rail vehicle braking system including a variable valve according to the present invention.

[0008] Figure 3 This is a side view of the variable valve according to the present invention.

[0009] Figure 4 This is a side view of the variable valve according to the present invention, showing different positions of the arm.

[0010] Figure 5 This is a longitudinal sectional view of the variable valve according to the present invention in the loaded position.

[0011] Figure 6 This is a partial cross-sectional view of the variable valve according to the present invention, showing the switching valve spool.

[0012] Figure 7 This is a partial cross-sectional view of the variable valve according to the present invention, showing the switching valve spool.

[0013] Figure 8 This is a longitudinal sectional view of the variable valve according to the present invention in the no-load position.

[0014] Figure 9This is a partial cross-sectional view of the variable valve according to the present invention, showing the exhaust valve.

[0015] Figure 10 This is a partial cross-sectional view of the variable valve according to the present invention, showing the exhaust valve and the proportional valve. Detailed Implementation

[0016] See the accompanying drawings, where the same reference numerals refer to the same parts throughout. Figure 1 A variable valve 10 for a rail vehicle (e.g., a freight car) is shown, which may be under different load conditions. The variable valve 10 includes a housing 12 mounted on the car body and an arm 14 pivotally mounted on the housing 12, movable between a retracted position and an extended position, in which the arm 14 contacts the side frame of the rail vehicle bogie. In response to pressure applied to the rail vehicle's brake cylinders by a control valve from the rail vehicle, the arm 14 pivots outward from the housing 12 to a fully extended position until it contacts the side frame of the bogie. Since the distance between the bogie and the side frame of the rail vehicle varies depending on the rail vehicle's load condition, the final position of the arm 14 when in contact with the bogie can detect the rail vehicle's load condition. The arm 14 may include an adjusting screw 16 on a threaded shaft 18 for adjusting the position of the variable valve 10 relative to the side frame when mounted on the rail vehicle.

[0017] like Figure 2 As shown, the variable valve 10 is positioned between the control valve CV and the brake cylinder BC of the rail vehicle. It is used to proportionally adjust the brake cylinder pressure actually supplied to the brake cylinder BC by the auxiliary air tank AR based on the load status of the rail vehicle detected by the arm 14. Therefore, the variable valve 10 can proportionally adjust the brake cylinder pressure actually supplied to the brake cylinder BC by the control valve CV according to the position of the arm 14.

[0018] See Figure 3 When the variable valve 10 does not receive pressure from the control valve CV, the arm 14 of the variable valve 10 retracts to the housing 12, and is in the unpressurized position. See also Figure 4 The pressurization of the variable valve 10 causes the arm 14 to pivot outward from the housing 12 until it contacts the side frame of the rail vehicle. If the rail vehicle is fully loaded, the contact point will occur earlier than that of a lightly loaded or completely unloaded rail vehicle. Figure 4 As further shown, arm 14 can be positioned at any location within distance D, which is the difference between the distance between the bogie and the side frame of a fully loaded rail vehicle and the distance between the bogie and the side frame of an unloaded rail vehicle.

[0019] See Figure 5The housing 12 includes an inlet 20 for connection to a brake cylinder pressure output 22 of a control valve CV and an outlet 24 for connection to a pressure inlet 26 of a brake cylinder BC. The housing 12 includes a piston 28 located within a chamber 30 and connected to a shaft 32 extending from the housing 12, which engages with an arm 14. The chamber 30 includes a diaphragm 34 connected to the piston 28 to provide a pressure side 36 and a non-pressure side 38. A passage 40 connects the inlet 20 to the pressure side of the diaphragm 34. Therefore, receiving pressure from the control valve CV through the inlet 20 causes the piston 28 to move within the chamber 30 and causes the shaft 32 to extend from the housing 12. As the pressure at the inlet 20 increases, the shaft 32 causes the arm 14 to extend further away from the housing 12 until the arm 14 contacts the side frame of the rail vehicle.

[0020] like Figure 5 As further shown, piston 28 is connected at pressure side 36 to a first end 48 of movable valve core 50, which extends longitudinally within housing 12 to a second end 52. The second end 52 of movable valve core 50 has a channel 54 that allows communication between inlet 20 and outlet 24 of housing 12. Movable valve core 50 is movable within housing 12 in response to movement of piston 28; therefore, in response to an increase in pressure at inlet 20, movable valve core 50 also moves longitudinally within housing 12 and stops when arm 14 contacts the side frame of the rail vehicle. Channel 54 extends through movable valve core 50 to ensure that communication remains between inlet 20 and outlet 24 when movable valve core 50 is in a first position corresponding to arm 14 contacting the loaded rail vehicle.

[0021] The housing 12 also includes a proportional valve spool 60 having a head 62 located within a pressure chamber 64 and a valve stem 66 extending longitudinally from the head 62 within the housing 12. The chamber 64 can be selectively connected to an internal or external volume. The valve stem 66 is interconnected with the movable valve spool 50 by a spring 68 having a predetermined spring force. The valve stem 66 of the proportional valve spool 60 also includes a valve seat 70 disposed adjacent to a ramp opening 72 connected to an outlet 24. The valve seat 70 may consist of a pair of spaced-apart flanges 74 and an O-ring 76 located therebetween. Thus, longitudinal movement of the proportional valve spool 60 within the housing 12 will selectively open or close the communication between the inlet 20 and the outlet 24, depending on whether the valve seat 70 is spaced apart from or in contact with the ramp opening 72. The proportional valve spool 60 has a stem 66 including a through-passage 80 and an opening 84 formed at the end of the stem 66. The through-passage 80 extends from a central portion of the proportional valve spool 60 near the outlet 24 to an internal cavity 82. The opening 84 at the end of the stem 66 includes a check valve 88 configured to allow only backflow of pressure from the outlet 24 to the inlet 20 within the cavity 82. Figure 5At the position shown, any pressure at inlet 20 can freely pass through housing 12 to brake cylinder BC, but due to the presence of check valve 88, the pressure will not pass through cavity 82.

[0022] like Figure 5 As further shown, the outlet 24 of the housing 12 is connected to a channel 90 that extends to an opening 92, which is positioned near a gap 94 formed around the intermediate section 96 of the movable valve spool 50. The intermediate section 96 of the movable valve spool 50 includes a pair of seals 98, such as O-rings 100 located between a pair of opposing flanges 102, to close the gap 94. Figure 6 As shown, gap 94 extends around the middle portion 96 of movable valve spool 50 to provide communication with channel 106, which extends through housing 12 to communicate with diverter valve spool 108. Therefore, longitudinal movement of movable valve spool 50 can selectively open or close the communication between outlet 24 and diverter valve spool 108. Diverter valve spool 108 includes a spring 110 that provides a predetermined force to keep diverter valve spool 108 biased against the pressure within channel 106, thereby preventing diverter valve spool 108 from moving until the pressure within channel 106 overcomes the predetermined force of spring 110. Once this occurs, diverter valve spool 108 will move longitudinally against the biasing force of spring 110, opening valve seat 112, thereby establishing communication between channel 106 and channel 124, as shown in Figure 7. Channel 124 extends to and communicates with pressure chamber 64 at head 62 of proportional valve 60. Therefore, when sufficient pressure to overcome spring 110 is formed, this pressure will be transmitted to head 62 of proportional valve 60. The switching valve spool 108 thus sets the pressure threshold at inlet 20 required to initiate proportional control of the variable valve 10. According to current American Railroad Association (AAR) rules and guidelines, 15 pounds per square inch (psi) is an acceptable threshold for initiating proportional control based on rail vehicle loading conditions, and therefore spring 110 can be configured accordingly.

[0023] See appendix Figure 8In response to the pressure at head 62, the proportional valve spool 60 moves longitudinally within housing 12 to close valve seat 70, thereby preventing the brake cylinder pressure at inlet 20 from further reaching outlet 24. The magnitude of the pressure at head 62 sufficient to close valve seat 70 depends in part on the position of moving valve spool 50, as the position of moving valve spool adjusts the magnitude of the biasing force applied by spring 68 to proportional valve spool 60. Furthermore, the pressure at inlet 20 also acts on end 86 with check valve 88. Therefore, the movement of proportional valve spool 60 in response to the pressure at head 62 depends on the pressure on end 86 and the biasing force applied by spring 68 at any given position on arm 14. Thus, the relative dimensions of head 62 and end 86, as well as the biasing force of spring 68, can be selected and configured to control how variable valve 10 proportionally regulates brake cylinder pressure at any position on arm 14. When arm 14 moves its entire distance D to the unloaded position, the force provided by spring 68 will be less than at any previous position, and therefore, the pressure on head 62 required to close valve seat 70 of proportional valve spool 60 will also be less. Therefore, compared to when arm 14 contacts the side frame of a heavily loaded rail vehicle, variable valve 10 interrupts the pressure flow from control valve CV to brake cylinder BC at a lower pressure value. Thus, at each arm position between loaded and unloaded states, the position of arm 14 effectively sets the maximum pressure value delivered by variable valve 10 to brake cylinder BC. It should be noted that the pressure level of arm 14 at any given position can be configured according to applicable rules. For example, when arm 14 contacts the side frame of a fully loaded rail vehicle, the proportional adjustment can be set to zero; while when arm 14 contacts the side frame of an unloaded rail vehicle, the maximum proportional adjustment can be set to a predetermined percentage of the typical brake cylinder pressure in full braking applications, such as fifty percent or sixty percent. The proportional adjustment occurring between fully loaded and unloaded states will vary between a minimum (or zero) proportional adjustment and a maximum proportional adjustment depending on the position of arm 14.

[0024] See Figure 9 The variable valve 10 also includes an exhaust valve spool 130 communicating with inlet 20 for releasing pressure on the proportional valve spool 60. The exhaust valve spool 130 is longitudinally movable within the housing 12 to selectively exhaust pressure into chamber 64, thereby releasing any pressure on the valve head 62 of the proportional valve spool 60. One end of the exhaust valve spool 130 responds to pressure at inlet 20, while the other end (e.g., Figure 10(As shown) is a passage 136 connected to a chamber 64 of the proportional valve spool 60. Longitudinal movement of the exhaust valve spool 130 will open communication between chamber 64 and exhaust port 138 to the atmosphere (EX). Therefore, a pressure drop at inlet 20 (e.g., when control valve CV has reduced the brake cylinder pressure output) will cause longitudinal movement of the exhaust valve spool and open communication between the head 62 of the proportional valve spool 60 and exhaust port 138. Exhausting through exhaust port 138 releases pressure in the head 62 of the proportional valve spool 60, allowing the proportional valve spool 60 to return to a depressurized position.

[0025] like Figure 8 As further shown, if the valve seat 70 of the proportional valve spool 60 remains closed, the pressure drop at inlet 20 will also allow pressure to flow back from outlet 24 to inlet 20 via check valve 88. Therefore, once the control valve CV stops supplying pressure to inlet 20, variable valve 10 will allow the brake cylinder pressure to be released through outlet 24, and also through exhaust valve spool 130 when the pressure at inlet 20 drops below the pressure within brake cylinder BC. The pressure drop at inlet 20 will also cause piston 28 to return to the depressurized position, thereby moving arm 14 back to its initial position, as... Figure 3 As shown.

[0026] Therefore, relative to the full pressure that control valve CV typically provides to brake cylinder BC, for unloaded rail vehicles, proportional valve spool 60 will close the connection between control valve CV and brake cylinder BC at a lower pressure than for heavily loaded rail vehicles, thereby limiting the brake cylinder pressure to a value equal to or lower than the standard brake cylinder pressure detected based on the rail vehicle's specific loading condition at arm 14 position. The release of braking pressure from control valve CV allows variable valve 10 to reset.

Claims

1. A variable valve for rail vehicles, comprising: A housing having an inlet for receiving pressure from a control valve of the rail vehicle and an outlet for supplying pressure to a brake cylinder of the rail vehicle; One arm, which is pivotally mounted to the housing, moves from a retracted position to an extended position in response to a predetermined pressure value received at the inlet of the housing; A movable valve core is located in the first chamber of the housing and connected to the arm at a first end, which moves within the first chamber of the housing in response to movement of the arm between the retracted position and the extended position; A proportional valve core includes a head, a valve stem, and a valve seat. The head is located in a second chamber of the housing connected to an outlet of the housing. The valve stem extends from the head into a first chamber. The valve seat moves in response to pressure in the second chamber from an open position that allows communication between the inlet and the outlet to a closed position that blocks communication between the inlet and the outlet. as well as A spring extends from the movable valve spool to the proportional valve spool and applies a biasing force to bias the proportional valve spool to the open position, wherein the magnitude of the force applied by the spring decreases according to the movement of the movable valve spool in response to the movement of the arm from the retracted position to the extended position.

2. The variable valve of claim 1 further includes a channel connecting the second chamber of the housing to the outlet of the housing.

3. The variable valve of claim 2 further includes a switching valve core disposed in the channel and biased to block communication between the outlet of the housing and the second chamber until the pressure at the outlet of the housing exceeds a predetermined value.

4. The variable valve according to claim 3, wherein, The channel extends to an opening leading to the first chamber, the opening being disposed adjacent to the middle portion of the movable valve core, the middle portion being connected to the outlet of the housing.

5. The variable valve according to claim 4, wherein, The middle portion of the movable valve core includes a pair of seals that selectively close or allow access to the opening based on the movement of the movable valve core within the first chamber, thereby selectively opening and closing the communication between the outlet of the housing and the switching valve core.

6. The variable valve according to claim 1 further includes an exhaust valve core connected between the second chamber of the housing and an exhaust port.

7. The variable valve according to claim 6, wherein, The exhaust valve core is capable of moving in response to any pressure drop at the inlet of the housing to connect the second chamber to the exhaust port.

8. The variable valve according to claim 1, wherein, The valve stem of the proportional valve core includes a channel that communicates with the inlet and outlet of the housing.

9. The variable valve according to claim 8, wherein, A one-way valve is provided in the channel, allowing pressure to flow only from the outlet of the housing to the inlet of the housing.

10. The variable valve according to claim 1, further comprising a diaphragm disposed in the first chamber.

11. The variable valve of claim 10, further comprising a channel connecting the inlet of the housing to a first side of the diaphragm.

12. The variable valve according to claim 11, wherein, The first end of the movable valve core is connected to the first side of the diaphragm.

13. The variable valve of claim 12 further includes a piston connected to a second side of the diaphragm.

14. The variable valve according to claim 13, wherein, The piston is connected to the arm and moves the arm according to the pressure exerted by the inlet on the first side of the diaphragm.

15. A method for regulating brake cylinder pressure supplied by a control valve to a rail vehicle brake cylinder, comprising the following steps: Connect the inlet of the variable valve housing to the control valve; The outlet of the housing of the variable valve is connected to the brake cylinder, wherein the inlet and the outlet are connected by a proportional valve core having a valve seat that is movable between an open position that allows communication between the inlet and the outlet and a closed position that blocks communication between the inlet and the outlet. In response to the magnitude of the brake cylinder pressure received from the control valve at the inlet, the arm pivotally mounted on the housing is moved from a retracted position to an extended position until it reaches a position where the arm contacts the side frame of the rail vehicle; In response to the movement of the arm, a movable valve core located within the first chamber of the housing moves, such that a spring extending between the movable valve core and the proportional valve core provides a variable biasing force to the proportional valve core according to the position of the arm, biasing the proportional valve core to the open position; and The second chamber housing the proportional valve core head is pressurized until the valve seat moves to the closed position against the biasing force of the spring, thereby stopping the variable valve from continuing to supply any brake cylinder pressure received from the control valve to the brake cylinder of the rail vehicle.

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