Variable valve for rail car braking system

Abstract

NOT VISIBLE DUE TO STATUS OF PATENT

Description

TITLEVARIABLE VALVE FOR RAIL CAR BRAKING SYSTEMBACKGROUND1. FIELD

[0001] The present disclosure relates to freight car braking systems and, more specifically, to a variable valve for adjusting the brake cylinder pressure based on the loaded state of the freight car.2. DESCRIPTION OF THE RELATED ART

[0002] Freight rail cars weigh much more when fully loaded compared to when empty and how much braking force can be applied without damaging the wheels differs in each condition. In addition, if uniform braking force is applied to the wheels of all rail cars in a train, the braking effect will be much different on fully loaded and empty cars, which can lead to unpredictable train dynamics. Conventional approaches to this problem include empty / load valves that sense loaded or empty conditions and proportion the amount of braking power provided by the brake cylinders when the freight car is in the empty. Existing empty / load valves do not provide for proportioning of the braking force over the full spectrum of possible rail car conditions. Accordingly, there is a need in the art for a valve that can vary the brake cylinder pressure of a rail car in response to the loaded state of the rail car.BRIEF SUMMARY

[0003] The present invention is a variable valve that can proportion the amount of pressure provided by the control valve of a rail car to the brake cylinder of the rail car based on the loaded state of the rail car. The variable valve has an arm that extends to contact the side frame of a rail car in response to a brake application to detect the loaded state of the car. The farther the arm needs to extend to contact the side frame, the less loaded is the rail car. The arm provides a variable amount of biasing force against a proportional spool that is moveable to close communication between the pressure output from the control valve and the pressure inlet of the brake cylinder. The amount of force applied against the movement of the proportional spool by the arm depends on the position of the arm. The farther the arm extends, the less force is applied to the proportional spool. As a result, the proportional spool will close communication between the control valve and the brake cylinder at a lower pressure for an unloaded rail car than a more fully loaded car. The variable valve includes a change over spool that delays the actuation of the proportional spool until a certain thresholdlevel of brake cylinder pressure is reached, and a vent spool that can vent the pressure on the proportional spool when the control valve ceases providing pressure to the brake cylinder.

[0004] In another embodiment, the present invention is a method of adjusting the amount of brake cylinder pressure provided to a brake cylinder of a rail car by a control valve. The method includes the step of coupling an inlet of a housing of a variable valve to the control valve and coupling an outlet of the housing of the variable valve to the brake cylinder to the inlet of the housing via a proportional spool having a seat that can move between an open position permitting communication between the inlet and the outlet and a closed position preventing communication between the inlet and the outlet. An arm pivotally mounted to the housing is moved from a retracted position to an extended position until it contacts a side frame of the rail car in response to an amount of brake cylinder pressure received at the inlet from the control valve. A traveling spool positioned in a first chamber of the housing will then move response to movement of the arm so that a spring extending between the traveling spool and the proportional spool provides a variable amount of force biasing the proportional spool into the open position depending on the position of the arm. The method also includes the step of pressurizing a second chamber containing a head of the proportional spool until the seat moves into the closed position against the amount of force of the spring. The variable valve will thus stop providing brake cylinder pressure to the brake cylinder when the proportioning valve closes.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0005] The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which:

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

[0007] FIG. 2 is a schematic of a rail car braking system including a variable valve according to the present invention.

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

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

[0010] FIG. 5 is a longitudinal cross-section of a variable valve in the loaded position according to the present invention.

[0011] FIG. 6 is a partial cross-section of a variable valve according to the present invention showing the change over spool.

[0012] FIG. 7 is a partial cross-section of a variable valve according to the present invention showing the change over spool.

[0013] FIG. 8 is a longitudinal cross-section of a variable valve in the unloaded position according to the present invention.

[0014] FIG. 9 is a partial cross-section of a variable valve according to the present invention showing the vent valve.

[0015] FIG. 10 is a partial cross-section of a variable valve according to the present invention showing the vent valve and proportional valve.DETAILED DESCRIPTION

[0016] Referring to the figures, wherein like numerals refer to like parts throughout, there is seen in FIG. 1, a variable valve 10 for a rail car, such as a freight car, that is subject to different loaded states. Variable valve 10 has a housing 12 that is mounted to the body of the car and an arm 14 that is pivotally mounted to housing 12 for movement between a retracted position and an extended position where arm 14 can contact the side frame of the truck of the rail car. Arm 14 is responsive to the application of pressure from the control valve of a rail car to the brake cylinder of the rail car and will pivot away from housing 12 toward the fully extended position until contacting the side frame of the truck. As the distance between the truck and the side frame of the rail car varies according to the loaded state of the rail car, the final positioning of arm 14 when in contact with the truck detects the loaded state of the rail car. Arm 14 may include an adjusting screw 16 on a threaded shaft 18 for adjusting the positioning of variable valve 10 relative to the side frame when installed on a rail car.

[0017] Referring to FIG. 2, variable valve 10 is interposed between the control valve CV of the rail car and the brake cylinder BC to proportion the amount of brake cylinder pressure that is actually provided from the auxiliary reservoir AR to the brake cylinder BC based on the loaded state of the rail car as detected by arm 14. Variable valve 10 thus proportions the amount of brake cylinder pressure that is actually provided to the brake cylinder BC by the control valve CV in response to the position of arm 14.

[0018] Referring to FIG. 3, arm 14 of variable valve 10 is retracted against housing 12 in an unpressurized position when no pressure is received by variable valve 10 from control valve CV. Referring to FIG. 4, pressurization of variable valve 10 causes arm 14 to pivot away from housing 12 until it contacts the side frame of the rail car. If the rail car is fully loaded, the contact point will occur before the contact point of a less loaded or fully unloaded rail car. As further seen in FIG. 4, arm 14 can be positioned in any position throughdistance D, which is the change in distance between the truck and side frame of a loaded rail car and the distance between the truck and side frame of an unloaded rail car.

[0019] Referring to FIG. 5, housing 12 includes an inlet 20 for coupling to the brake cylinder pressure output 22 of control valve CV and an outlet 24 for coupling to the pressure inlet 26 of a brake cylinder BC. Housing 12 includes a piston 28 positioned in a chamber 30 within housing 12 and coupled to a shaft 32 that extends out of housing 12 to engage arm 14. Chamber 30 includes a diaphragm 34 coupled to piston 28 to provide a pressure side 36 and a non-pressure side 38. A passage 40 couples inlet 20 to the pressure side of diaphragm 34. As a result, the receipt of pressure from control valve CV via inlet 20 will cause piston 28 to move within chamber 30 and extend shaft 32 from housing 12. As pressure increases in inlet 20, shaft 32 will cause arm 14 to extend further away from housing 12 until arm 14 contacts the side frame of the rail car.

[0020] As further seen in FIG. 5, piston 28 is coupled on the pressure side 36 to a first end 48 of a traveling spool 50 that extends longitudinally within housing 12 to a second end 52. The second end 52 of traveling spool 50 has a passageway 54 that allows communication between inlet 20 of housing 12 and outlet 24 of housing 12. Traveling spool 50 is moveable within housing 12 in response to movement of piston 28, and thus will also move longitudinally within housing 12 in response to an increase of pressure at inlet 20 and stop when arm 14 contacts the side frame of the rail car. Passageway 54 extends through traveling spool 50 to ensure communication between inlet 20 and outlet 24 when traveling spool 50 is in a first position that corresponds to arm 14 contacting a loaded rail car.

[0021] Housing 12 further includes a proportional spool 60 having a head 62 positioned in a pressure chamber 64 and a stem 66 extending longitudinally from head 62 within housing 12. Chamber 64 may optionally be coupled to an internal or external volume. Stem 66 is interconnected to traveling spool 50 by a spring 68 having a predetermined spring force. Stem 66 of proportional spool 60 further includes a seat 70 positioned proximately to a ramped opening 72 that connects to outlet 24. Seat 70 may be formed by a pair of spaced apart flanges 74 and an O-ring 76 positioned therebetween. Movement of proportional spool 60 longitudinally within housing 12 will therefore selectively open or close communication between inlet 20 and outlet 24 depending on whether seat 70 is spaced apart from or is contact with ramped opening 72. Stem 66 of proportional spool 60 includes a passageway 80 formed therethrough that extends from an intermediate portion of proportional spool 60 that is proximate to outlet 24 to an interior cavity 82 and an opening 84 formed in the end of stem 66 of proportional spool 60. Opening 84 in the end of stem 66 includes a check valve 88configured to only allow back flow of pressure in cavity 82 from outlet 24 to inlet 20. In the position of FIG. 5, any pressure at inlet 20 is free to pass through housing 12 to brake cylinder BC, but not through cavity 82 because of check valve 88.

[0022] As further seen in FIG. 5, outlet 24 of housing 12 is coupled to a passageway 90 that extends to an opening 92 positioned proximately to a gap 94 formed around an intermediate section 96 of traveling spool 50. Intermediate section 96 of traveling spool 50 includes a pair of seals 98, such as O-rings 100 positioned between a pair of opposing flanges 102, to enclose gap 94. As seen in FIG. 6, gap 94 extends around intermediate section 96 of traveling spool 50 to provide communication with a passageway 106 that extends through housing 12 to communicate with a change over spool 108. As a result, longitudinal movement of traveling spool 50 can selectively open or close communication between outlet 24 and change over spool 108. Change over spool 108 includes a spring 110 that provides a predetermined force biasing change over spool 108 against pressure in passageway 106 to prevent movement of change over spool 108 until the predetermined force of the spring 110 is overcome by pressure in passageway 106. Once this occurs, change over spool 108 will move longitudinally against the bias of spring 110 to open a seat 112 and thus provide communication between passageway 106 and a passageway 124, as seen in FIG. 7.Passageway 124 extends to and is in communication with pressure chamber 64 at head 62 of proportional spool 60. As a result, when sufficient pressure to overcome spring 110 has developed, that pressure will be communicated to head 62 of proportional spool 60. Change over spool 108 thus sets a threshold amount of pressure at inlet 20 that is necessary to trigger proportioning by variable valve 10. Under current Association of American Railroads (AAR) rules and guidelines, 15 pounds per square inch (psi) is an acceptable threshold level to begin proportioning based on the loaded state of the rail car, so spring 110 can be configured accordingly.

[0023] Referring to FIG. 8, movement of proportional spool 60 longitudinally in housing 12 in response to pressure at head 62 will close seat 70, thereby preventing any further brake cylinder pressure at inlet 20 from reaching outlet 24. The amount of pressure at head 62 that is sufficient to result in closing of seat 70 is in part dependent on the positioning of traveling spool 50 because the position of traveling spool adjusts the amount of biasing force being applied by spring 68 to proportional spool 60. In addition, pressure at inlet 20 will also act upon end 86 having check valve 88. Thus, movement of proportional spool 60 is in response to the pressure on head 62 is dependent on the pressure on end 86 and the biasing force being applied by spring 68 at any given position of arm 14 The relative dimensions ofhead 62 and end 86, as well as the biasing force of spring 68 may therefore be selected and configured to control how variable valve 10 proportions the brake cylinder pressure at any position of arm 14. When arm 14 has moved the full distance D into the empty location, the force provided by spring 68 will be lower than in any prior position and thus less pressure on head 62 will be needed to close seat 70 of proportional spool 60. Variable valve 10 will therefore interrupt the flow of pressure from control valve CV to brake cylinder BC at a lower pressure amount than when arm 14 is in contact with the side frame of a more fully loaded rail car. As a result, the position of arm effectively sets the maximum amount of pressure that will be delivered by variable valve 10 to the brake cylinder BC at every arm position between loaded and unloaded states. It should be recognized that the pressure level at any given position of arm 14 may be configured to comply with applicable regulations. For example, the amount of proportioning when arm 14 is contact with the side frame of a fully loaded rail car may be set at zero and the maximum amount of proportioning available when arm 14 is in contact with the side frame of an empty rail car may be a predetermined percentage of the typical brake cylinder pressure in a full service brake application, such as fifty or sixty percent. The amount of proportioning that occurs between the fully loaded and the unloaded state will then vary between the minimum (or zero) proportioning and the maximum proportioning based on the position of arm 14.

[0024] Referring to FIG. 9, variable valve 10 additionally includes a vent spool 130 in communication with inlet 20 for releasing pressure on proportional spool 60. Vent spool 130 is moveable longitudinally in housing 12 to selectively vent chamber 64 and thus release any pressure on head 62 of proportional spool 60. One end of vent spool 130 is responsive to pressure at inlet 20 and the other end of vent spool 130, as seen in FIG. 10, is connected to passageway 136 in communication with chamber 64 of proportional spool 60. Movement of vent spool 130 longitudinally will result in open communication between chamber 64 and a vent 138 that is connected to atmosphere (EX). As a result, a drop in pressure at inlet 20 (such as when the control valve CV has reduced the brake cylinder pressure output) will cause vent spool to move longitudinally and open communication between head 62 of proportional spool 60 and vent 138. Venting through vent 138 releases pressure from head 62 of proportional spool 60 so that proportional spool 60 can return to the unpressurized position.

[0025] As further seen in FIG. 8, a drop in pressure at inlet 20 will also allow pressure to flow from outlet 24 through check valve 88 back to inlet 20 if seat 70 off proportional spool 60 remains closed. Thus, as soon as control valve CV has ceased providing pressure toinlet 20, variable valve 10 will allow brake cylinder pressure to be released via outlet 24 and then also by vent spool 130 when the pressure at inlet 20 drops below the pressure in brake cylinder BC. A drop in pressure at inlet 20 will also allow piston 28 to return to the unpressurized position, thereby moving arm 14 back to the original position, as seen in FIG.3.

[0026] As a result, proportional spool 60 will close communication between the control valve CV and the brake cylinder BC at a lower pressure for an unloaded rail car than a more fully loaded car relative to the full pressure normally provided by the control valve CV to the brake cylinder BC, thereby bottling the brake cylinder pressure at an amount that is equal or less than the standard brake cylinder pressure based on the particular loaded state of the rail car as detected by the position of arm 14. A release of brake pressure from the control valve CV allows variable valve 10 to reset.

Claims

CLAIMSWhat is claimed is:

1. A variable valve for a rail car, comprising: a housing having an inlet for receiving pressure from a control valve of the rail car and an outlet for providing pressure to a brake cylinder of the rail car; an arm pivotally mounted to the housing for movement from a retracted position to an extended position in response to a predetermined amount of pressure received at the inlet of the housing; a traveling spool positioned in a first chamber of the housing and coupled at a first end to the arm for movement within the first chamber of the housing in response to movement of the arm between the retracted position and the extended position; a proportional spool including a head positioned in a second chamber of the housing coupled to the outlet of the housing, a stem extending from the head into the first chamber, and a seat that will move from an open position allowing communication between the inlet and the outlet to a closed position preventing communication between the inlet and the outlet in response to an amount of pressure in the second chamber; and a spring extending from the traveling spool to the proportional spool and applying an amount of force biasing the proportional spool into an open position, wherein the amount of force applied by the spring will decrease according to movement of traveling spool in response to movement of the arm from the retracted position to the extended position.

2. The variable valve of claim 1, further comprising a passageway coupling the second chamber of the housing to the outlet of the housing.

3. The variable valve of claim 2, further comprising a change over spool positioned in the passageway and biased to prevent communication between the outlet of the housing and the second chamber until an amount of pressure in the outlet of the housing exceeds a predetermined amount.

4. The variable valve of claim 3, wherein the passageway extends to an opening into the first chamber that is positioned adjacently to an intermediate portion of the traveling spool that is in communication with the outlet of the housing.

5. The variable valve of claim 4, wherein the intermediate portion of the traveling spool includes a pair of seals that that block access to the opening and permit access to the opening to selectively open and close communication between the outlet of the housing and the change over spool based on the movement of the traveling spool within the first chamber.

6. The variable valve of claim 1 , further comprising a vent spool coupled between the second chamber of the housing and an exhaust.

7. The variable valve of claim 6, wherein the vent spool is moveable in response to any drop in pressure at the inlet of the housing to couple the second chamber to the exhaust.

8. The variable valve of claim 1, wherein the stem of the proportional spool includes a passageway in communication with the inlet of the housing and the outlet of the housing.

9. The variable valve of claim 8, wherein a check valve positioned in the passageway only permits a flow of pressure from the outlet of the housing to the inlet of the housing.

10. The variable valve of claim 1, further comprising a diaphragm positioned in the first chamber.

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

12. The variable valve of claim 11, wherein the first end of the traveling spool is coupled to the first side of the diaphragm.

13. The variable valve of claim 12, further comprising a piston coupled to a second side of the diaphragm.

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

15. A method of adjusting an amount of brake cylinder pressure provided to a brake cylinder of a rail car by a control valve, comprising the steps of: coupling an inlet of a housing of a variable valve to the control valve; coupling an outlet of the housing of the variable valve to the brake cylinder to the inlet of the housing via a proportional spool having a seat that can move between an open position permitting communication between the inlet and the outlet and a closed position preventing communication between the inlet and the outlet; moving an arm pivotally mounted to the housing from a retracted position to an extended position until it reaches a position where the arm contacts a side frame of the rail car in response to the amount of brake cylinder pressure received at the inlet from the control valve; moving a traveling spool positioned in a first chamber of the housing in response to movement of the arm so that a spring extending between the traveling spool and theproportional spool provides an amount of force biasing the proportional spool into the open position that is variable depending on the position of the arm; and pressurizing a second chamber containing a head of the proportional spool until the seat moves into the closed position against the amount of force of the spring to stop the variable valve from providing any more of the amount of brake cylinder pressure received from the control valve to the brake cylinder of a rail car.