Braking system for a light rail vehicle

• US 3,924,902 A
• Filed: 06/17/1974
• Issued: 12/09/1975
• Est. Priority Date: 08/31/1973
• Status: Expired due to Term

• Current Assignee: Knorr Brake Holding Corporation (Knorr-Bremse GmbH)
• Original Assignee: Thomas Engle
• Inventors: Engle, Thomas
• Primary Examiner(s): Reger, Duane A.
• Application Number:
  US05/480,441
• Time in Patent Office: 540 Days
• Field of Search: 188/170,181A 303/6C,3,13,15,21A,22R,22A,21P
• US Class Current: 303/132
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 3/108 whilst braking, i.e. ABS
• CPC Class Codes: B60L 7/24 with additional mechanical or electromagnetic braking
• CPC Class Codes: B60T 13/44 with two-chamber booster units
• CPC Class Codes: B60T 13/586 the retarders being of the electric type
• CPC Class Codes: B60T 13/74 with electrical assistance or drive
• CPC Class Codes: B60T 8/1893 especially adapted for railway vehicles
• CPC Class Codes: B60T 8/3235 Systems specially adapted for rail vehicles
• CPC Class Codes: B61H 5/00 Applications or arrangements of brakes with substantially radial braking surfaces pressed together in axial direction, e.g. disc brakes self-applying brakes B61H11/02; combinations of different types of brakes B61H11/14; discs adapted for mounting on the wheel of a railway vehicle F16D65/124
• CPC Class Codes: F16D 2125/026 Pressure-to-pressure converters, e.g. hydropneumatic
• CPC Class Codes: F16D 55/2245 in which the common actuating member acts on two levers carrying the braking members, e.g. tong-type brakes similar brakes for rail vehicles B61H5/00

Abstract

A brake system for a light rail vehicle having both dynamic and friction braking systems is disclosed. Further, this light rail vehicle has both motored and nonmotored axles. The system has several individual and redundant systems which may act independently on each truck. The system uses a dynamic brake means which converts the propulsion motors to brake motors as the prime braking means for the motored axles. The system includes a fluid operated friction brake system with a proportional control means to supplement the dynamic braking with proportional friction braking as needed to achieve the total braking force required. The system includes an air spring and variable load means for each truck to regulate the maximum amount of fluid pressure available for the friction brake means to prevent over application of the friction brakes and skidding of the wheels. The system further includes parking brake and emergency brake means with independent actuators to effect actuation of the friction brakes.

Claims

1. A brake system for vehicles having at least one axle with friction and dynamic brakes and at least one axle with only friction brakes, said system comprising:

fluid operated friction brake means for said vehicle, said friction brake means including means responsive to variations in fluid pressure to actuate said friction brake means, said brake means having;

first and second pressure-responsive fluid motors, said first fluid motor being responsive to positive fluid pressure variations to actuate said brake means;

spring motor means responsive to reductions in fluid pressures applied to said second fluid motor to actuate said brake means;

a first fluid pressure control means for providing variations in the fluid pressure applied to the first pressure-responsive fluid motors of said axle having friction and dynamic brakes, said first control means responding to a supplied signal which is inversely proportional to the amount of dynamic braking effort applied to said axle;

a second fluid pressure control means for providing fluid pressure to the first pressure-responsive fluid motors of said axle having friction brakes, said second control means responding to a supplied signal which is independent of the amount of braking effort applied to said axle with friction and dynamic brakes; and

a third fluid pressure control means for providing reductions in fluid pressure to said second fluid motors, said third pressure control means being responsive to both emergency braking control signals and parking brake control signals.

2. A brake system for vehicles as claimed in claim 1 wherein:

a. said first and second pressure-responsive fluid motors are hydraulic motors, and b. said first and second fluid pressure control means include a pneumatic to hydraulic convertor for each pressure control means.

3. A brake system for vehicles as claimed in claim 2 wherein said first and second control means comprises electro-pneumatic transducers for translating an electrical control signal to a pneumatic control pressure.

4. A brake system as claimed in claim 1 wherein said first fluid control means includes:

a. an electropneumatic transducer which responds to electrical variations and control signals supplied by a controller for said dynamic brakes, said transducer including a first and second torque motors, said first torque motor responding to variations in said electrical control signal and said second torque motor responding inversely to variations in the pneumatic output of said fluid control means, the combined output of said torque motors producing variable plot pressures, b. proportioning valve means for regulating the fluid pressure applied by said transducer, said proportioning valve being responsive to variations in said pilot pressures.

5. A brake system as claimed in claim 2 wherein said pneumatic to hydraulic convertor comprises a hydraulic motor means between said fluid pressure control means and said pressure-responsive hydraulic motors.

6. A brake system for vehicles as claimed in claim 1 wherein:

a. said first and second pressure-responsive fluid motors are hydraulic motors, and b. manifold means for directing fluid under pressure to said first and second fluid motors, said means including a first supply line for said first fluid motor and a second supply line for said second fluid motor, c. first valve means actuated by said third control means arranged between and normally blocking communication between said first and second supply lines, d. pressure-responsive valve means arranged between and establishing one-way communication between said first and second supply lines, said valve means permitting a transfer of fluid under pressure from said first supply line to said second supply line when the former exceeds the latter.

7. An emergency and handbrake control system as claimed in claim 6 wherein each of said motors defines a pressure-responsive working area, and the pressure-responsive working area for said second fluid motor is larger than the pressure-responsive working area for said first fluid motor.

8. An emergency and handbrake control system as claimed in claim 6 wherein said first valve means comprises an electro-magnetic valve which established hydraulic communication between said first and second supply lines in response to an elelctrical control signal from said third control means.

9. A brake system for vehicles as claimed in claim 6, wherein said pressure-responsive valve means comprises a spring loaded ball check valve.

10. A brake system for vehicles as claimed in claim 1 wherein said friction brake means further includes a threaded retraction means for compressing said spring motor means.

11. A brake system for vehicles as claimed in claim 10 wherein said threaded retraction means further includes:

a. means for manually rotating said threaded retraction means, b. resilient means for rotating said threaded retraction means after said spring motor has been retracted, c. means for resisting the rotation of said threaded retraction means after said spring motor has been retracted, said means providing for the release and rotation of said threaded retraction means when said second pressure-responsive fluid motor is actuated.

12. A brake system according to claim 2, wherein said pneumatic to hydraulic convertor comprises:

third pressure-responsive motor means comprising a housing defining a variable volume chamber having a moveable wall, said third motor means being responsive to admission of pneumatic pressure to drive said moveable wall;

said housing also defining a fixed volume dump chamber adjacent said variable volume chamber for receiving a predetermined portion of the admitted fluid pressure;

dump valve means responsive to an input control signal to open communication between said variable volume chamber and said dump chamber; and

hydraulic cylinder and piston means operatively connected to said moveable wall for delivering hydraulic fluid under pressure to said first and second pressure-responsive fluid motors in response to movement of said moveable wall.

13. A brake system according to claim 12, wherein said dump valve includes mEans for simultaneously stopping admission of pneumatic pressure to said variable volume chamber while opening communication between said variable volume chamber and dump chamber.

14. A brake system according to claim 13, wherein said dump chamber includes an orifice connecting it to atmosphere.

15. A brake system according to claim 5, further comprising a hydraulic slack adjuster operatively connected to said convertor, including a reciprocating reaction element with first and second working chambers on either side thereof, said first working chamber communicating with said convertor, said second working chamber communicating with said first and second pressure-responsive fluid motors;

and transfer valve means for permitting the transfer of hydraulic fluid from said first working space to said second working space when the volume in said second working space is at its minimum.

16. A brake system according to claim 1, wherein said first and second pressure-responsive fluid motors comprise first and second pistons, respectively, further comprising:

two cooperating members connecting said first and second pistons, the first of said members being permitted substantial rotary movement and limited axial movement, and the second of said members being permitted axial but not rotary movement;

resilient means yieldably permitting greater axial movement of said first member when said brake are applied by said spring motor than when said brakes are applied by said first fluid pressure-responsive motor; and

retraction means for retracting said handbrake piston, said retraction means including a threaded retraction screw rotatably, slidably mounted in said housing and threadably engaged for axial movement with said second piston during parking brake application, said retraction screw comprising abutting means for limiting axial movement of said screw during retraction, whereby positive retraction of said second piston is provided when said screw is rotated in a first direction, said retraction means further comprising resilient drive means for rotating said screw in the opposite direction when said second pressure-responsive fluid motor is pressurized.