Brake cylinder pressure maintenance valves for freight car brake equipment

1. A freight car brake system, comprising:

a brake pipe;

an auxiliary reservoir;

an emergency reservoir;

a brake cylinder; and

a brake control valve connected to the brake pipe, the auxiliary reservoir, the emergency reservoir, and the brake cylinder, the brake control valve comprising a valve for maintaining brake cylinder pressure, the valve comprising:

a first diaphragm defining a first side and a second side;

a second diaphragm defining a first side and a second side;

a first port for receiving pressure from one of the emergency reservoir or a control volume, the first port in fluid communication with the first side of the first diaphragm;

a second port for receiving pressure from the brake pipe, the second port in fluid communication with the second side of the first diaphragm;

a third port for receiving pressure from the brake cylinder, the third port in fluid communication with the second side of second diaphragm;

a piston coupled to the second diaphragm, the piston comprising a stem extending into the second side of the second diaphragm; and

a biasing element disposed in the first side defined by the second diaphragm, the biasing element configured to bias the piston towards the second side of the second diaphragm.

2. The system of claim 1 , further comprising a fourth port for receiving pressure from a quick service volume, the quick service volume charged by a brake pipe, the fourth port in fluid communication with the second side of the second diaphragm.

3. The system of claim 2 , further comprising:

a first check valve configured to close when the piston is moved to a first position towards the first side of the second diaphragm and open when the piston is moved to a second position towards the second side of the second diaphragm; and

a second check valve configured to close when the pressure from the quick service volume is below a predetermined pressure level.

4. The system of claim 3 , further comprising a passage defined in and extending through the stem of the piston, the passage comprising an inlet on the second side of the second diaphragm and an outlet on the first side of the second diaphragm, and wherein the inlet is closed when the first check valve is in contact with the stem and open when the first check valve is spaced from the stem.

5. The system of claim 4 , further comprising an exhaust port in fluid communication with the first side of the second diaphragm.

6. The system of claim 3 , further comprising a third check valve disposed between the third port and the second side of the second diaphragm, the third check valve configured to allow flow from the second side of the second diaphragm to the third port and prevent flow from the third port to the second side of the second diaphragm.

7. The system of claim 3 , wherein the first port receives pressure from the emergency reservoir.

8. The system of claim 3 , wherein the first port receives pressure from the control volume.

9. The system of claim 8 , further comprising:

a fifth port for receiving pressure from the emergency reservoir;

a sixth port for receiving pressure from the brake pipe;

an exhaust port;

a fourth check valve disposed between the first port and the fifth port, the fourth check valve configured to open when pressure from the first port is at a predetermined level greater than pressure from the fifth port, and wherein the first port and exhaust port are in fluid communication when the fourth check valve is open; and

a fifth check valve disposed between the first port and the sixth port, the fifth check valve configured to allow flow from the sixth port to the first port and prevent flow from the first port to the sixth port.

10. The system of claim 3 , wherein the biasing element is a first biasing element, and further comprising a second biasing element disposed between the first check valve and the second check valve, the second biasing element configured to bias the first check valve and second check valve towards closed positions.

11. The system of claim 1 , wherein the second side of the first diaphragm and the first side of the second diaphragm are partitioned from each other.

12. The system of claim 1 , wherein a surface area differential between the first diaphragm and the second diaphragm is from 1:1 to 4:1.

13. A freight car brake system, comprising:

a brake pipe;

an auxiliary reservoir;

an emergency reservoir;

a brake cylinder; and

a brake control valve connected to the brake pipe, the auxiliary reservoir, the emergency reservoir, and the brake cylinder, the brake control valve comprising a valve for maintaining brake cylinder pressure, the valve comprising:

a first diaphragm defining a first side and a second side;

a second diaphragm defining a first side and a second side;

a first port for receiving pressure from one of the emergency reservoir or a control volume, the first port in fluid communication with the first side of the first diaphragm;

a second port for receiving pressure from the brake pipe, the second port in fluid communication with the second side of the first diaphragm;

a third port for receiving pressure from the brake cylinder, the third port in fluid communication with the second side of the second diaphragm;

a first check valve movable between a closed position and an open position;

a second check valve movable between a closed position and an open position; and,

a biasing element disposed between the first check valve and the second check valve, the biasing element configured to bias the first check valve and second check valve towards closed positions.

14. The system of claim 13 , further comprising a fourth port for receiving pressure from a quick service volume, the quick service volume charged by a brake pipe, the fourth port in fluid communication with the second side of the second diaphragm.

15. The system of claim 13 , wherein the biasing element is a second biasing element, and further comprising:

a piston coupled to the second diaphragm, the piston comprising a stern extending into the second side of the second diaphragm; and

a first biasing element configured to bias the piston towards the second side of the second diaphragm,

wherein the first check valve is configured to close when the piston is moved to a first position towards the first side of the second diaphragm and open when the piston is moved to a second position towards the second side of the second diaphragm,

wherein the second check valve is configured to close when the pressure from the quick service volume is below a predetermined pressure level.

16. The system of claim 15 , further comprising a passage defined in and extending through the stem of the piston, the passage comprising an inlet on the second side of the second diaphragm and an outlet on the first side of the second diaphragm, and wherein the inlet is closed when the first check valve is in contact with the stem and open when the first check valve is spaced from the stem.

17. The system of claim 16 , further comprising an exhaust port in fluid communication with the first side of the second diaphragm.

18. The system of claim 15 , further comprising a third check valve disposed between the third port and the second side of the second diaphragm, the third check valve configured to allow flow from the second side of the second diaphragm to the third port and prevent flow from the third port to the second side of the second diaphragm.

19. The system of claim 15 , wherein the first port receives pressure from the emergency reservoir.

20. The system of claim 15 , wherein the first port receives pressure from the control volume.

21. The system of claim 20 , further comprising:

a fifth port for receiving pressure from the emergency reservoir;

a sixth port for receiving pressure from the brake pipe;

an exhaust port;

a fourth check valve disposed between the first port and the fifth port, the fourth check valve configured to open when pressure from the first port is at a predetermined level greater than pressure from the fifth port, and wherein the first port and exhaust port are in fluid communication when the fourth check valve is open; and

a fifth check valve disposed between the first port and the sixth port, the fifth check valve configured to allow flow from the sixth port to the first port and prevent flow from the first port to the sixth port.