Load proportional brake cylinder pressure limiting system

• US 6,217,130 B1
• Filed: 01/26/2000
• Issued: 04/17/2001
• Est. Priority Date: 06/08/1998
• Status: Expired due to Fees

• Current Assignee: Westinghouse Air Brake Technologies Corporation
• Original Assignee: Westinghouse Air Brake Technologies Corporation
• Inventors: Engle, Thomas
• Primary Examiner(s): Butler, Douglas C.
• Application Number:
  US09/491,847
• Time in Patent Office: 447 Days
• Field of Search: 303/22.6, 303/22.7, 303/22.8, 303/22.1, 303/22.2, 303/22.3, 303/22.4, 303/22.5, 303/20, 303/198, 303/199, 303/9.69, 188/195, 188/349, 701/70
• US Class Current: 303/22.2
• CPC Class Codes: B60T 8/1831 pressure reducing or limiting valves
• CPC Class Codes: B60T 8/1893 especially adapted for railway vehicles

Abstract

A continuously variable load responsive brake pressure control valve controls the amount of brake pipe pressure for a railway vehicle. The system also includes an isolator therefor for isolating the load sensor therefor from transient inputs caused by normal vehicle motion. A spring loaded isolator coupled with a matched hydraulic cylinder isolate wheel truck deflections with respect to the car body, preventing erroneous inputs to the load sensor of the variable load braking system so as to provide more accurate brake cylinder pressure according to vehicle load weight. The variable load limiting valve is continuously operable between an empty vehicle condition and a fully loaded vehicle condition and assures a minimum braking pressure, while also helping prevent sticking of the brakes.

Claims

1. A system for adjusting vehicle brake cylinder pressure according to the vehicle load condition comprising:

a limiting valve having means for continuously varying the pressure of fluid supplied to a fluid operable braking apparatus on a vehicle in accordance with the load carried by said vehicle, said limiting valve having means for sensing a load bearing on a vehicle wheel assembly; and

means for isolating said load force sensing means from transient deflections of the vehicle not cause by vehicle load, whereby erroneous inputs to said load sensing means caused by such transient deflections are prevented.

2. The vehicle brake cylinder pressure system as recited in claim 1, wherein said isolating means comprising:

an upper bracket secured to a vehicle body;

a lower bracket secured to the vehicle wheel assembly;

a damper having a first section secured to the upper bracket and a second section movably mounted to the first section;

an isolator having a first portion secured to the lower bracket and a second portion slidably mounted to the first portion; and

an input lever having a first end rotatably mounted to the second portion of the isolator and a second end rotatably mounted to the second section of the damper, said input lever being pivotally mounted at an intermediate section between said first and second end to the upper bracket, said input lever being operatively associated said load force sensing means of the limiting valve.

3. The vehicle brake cylinder pressure system as recited in claim 2, wherein said limiting valve means comprises:

a valve body having an inlet port connected to the control valve device and an outlet port connected to the brake cylinder device;

a sensing piston slidably disposed within the valve body and defining a pressure chamber between the sensing piston and the valve body adjacent the outlet port and providing a fluid communication path between the inlet port and the outlet port, said load sensing means being slidably connected to said sensing piston for providing an indication according to the vehicle load, said load sensing means operable between an empty position and a fully loaded position;

a limiting check valve in contact with one end of said load sensing means and generally movable therewith; and

a valve seat operatively connected to said sensing piston and movable therewith, the valve seat movable between an open position wherein a first chamber is provided between the valve seat and the limiting check valve and a closed position wherein the valve seat contacts the limiting check valve to close the fluid communication path under pressure to the brake cylinder device.

4. The vehicle brake cylinder pressure system as recited in claim 3, wherein the first portion of the isolator is slidably mounted to the second portion by a spring.

5. The vehicle brake cylinder pressure system as recited in claim 4, wherein the spring has a limiting force substantially equivalent to the damper rate such that the input lever does not provide an input to the variable load limiting valve upon deflection of the wheel assembly with respect to the vehicle body.

6. The vehicle brake cylinder pressure system as recited in claim 2, wherein the first portion of the isolator is slidably mounted to the second portion by a spring having a limiting force substantially equivalent to the damper rate such that the input lever does not provide an input to the variable load limiting valve upon deflection of the wheel assembly with respect to the vehicle body.

7. The vehicle brake cylinder pressure system as recited in claim 1, wherein said limiting valve means comprises:

a valve body having an inlet port connected to the control valve device and an outlet port connected to the brake cylinder device;

a sensing piston slidably disposed within the valve body and defining a pressure chamber between the sensing piston and the valve body adjacent the outlet port and providing a fluid communication path between the inlet port and the outlet port, said load sensing means being slidably connected to said sensing piston for providing an indication according to the vehicle load, said load sensing means operable between an empty position and a fully loaded position;

a limiting check valve in contact with one end of said load sensing means and generally movable therewith; and

a valve seat operatively connected to said sensing piston and movable therewith, the valve seat movable between an open position wherein a first chamber is provided between the valve seat and the limiting check valve and a closed position wherein the valve seat contacts the limiting check valve to close the fluid communication path under pressure to the brake cylinder device.

8. The vehicle brake cylinder pressure system as recited in claim 7, said load sensing means comprising an input stem slidably connected with the valve body, and the sensing piston further comprises a lower portion and a top portion defining the first chamber therebetween, the limiting check valve being resiliently connected to the lower portion, the first chamber being in fluid communication with the inlet port.

9. The vehicle brake cylinder pressure system as recited in claim 8, further comprising a limiting check valve seat connected to the top portion of the sensing piston and including an annular passage between said load sensing means and the limiting check valve seat, the first chamber being in fluid communication with the pressure chamber via the annular passage.

10. The vehicle brake cylinder pressure system as recited in claim 9, further comprising a cutoff spring connected between the lower portion of the sensing piston and the valve body.

11. The vehicle brake cylinder pressure system as recited in claim 9, wherein the limiting check valve is connected to the lower portion of the sensing piston by a spring urging the limiting check valve against said load sensing means whereby the sensing piston is movable with respect to the limiting check valve such that the limiting check valve seat can contact the limiting check valve to close the fluid communication path.