Fluid-pressure and analogous brake systems – Multiple fluid-receiving devices – Multiple motors
Reexamination Certificate
2000-05-23
2001-11-06
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Multiple fluid-receiving devices
Multiple motors
C303S063000, C188S170000
Reexamination Certificate
active
06312060
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to fluid powered brake systems and, more particularly, to fluid powered brake systems used with automated people movers.
2. Background Art
An electrically powered automated people mover typically includes a propulsion system connected to a source of electrical power for propelling the people mover on running rails or along a predetermined path. Such people movers often include a fluid actuated brake system that is utilized to de-accelerate the people mover when it is moving and/or to maintain the people mover stationary during passenger loading and unloading. Because such people mover is automated, there is a need to provide braking in the event of a failure of the braking control system that controls the flow of fluid to a friction brake of the people mover.
It is, therefore, an object of the present invention to provide a brake system and a method of use thereof which provides a brake release mode, a service braking mode and a pressure emergency braking mode under normal, fluid braking operation and which provides a spring emergency braking mode in the event that one or more components of the brake system utilized for normal fluid braking operation fail. Still other objects of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.
SUMMARY OF THE INVENTION
Accordingly, we have invented a dual mode brake system for a vehicle. The dual mode brake system includes a first fluid actuated brake and a second spring actuated fluid released brake configured to spring actuate the first brake in the absence of receiving sufficient fluid pressure at the second brake. A first fluid control circuit controllably supplies fluid to the first brake from a source of pressurized fluid and a second fluid control circuit controllably supplies fluid to the second brake from the source of pressurized fluid. A third fluid control circuit controllably supplies fluid to the second brake from the first fluid control circuit or the second fluid control circuit as a function of a pressure of the fluid supplied to the third fluid control circuit from the first fluid control circuit and a pressure of the fluid supplied to the third fluid control circuit from the second fluid control circuit.
A controller controls the first fluid control circuit and the second fluid control circuit. The first fluid control circuit variably controls the pressure of the fluid supplied thereby as a function of a first signal from the controller. The second fluid control circuit on/off controls the fluid supplied thereby as a function of a second signal from the controller. The third fluid control circuit on/off controls the fluid supplied to the second brake from the first fluid control circuit or the second fluid control circuit.
The first fluid control circuit includes a flow control valve connected between the source of pressurized fluid and the first brake for variably controlling the pressure of the fluid supplied from the source of pressurized fluid to the first brake as a function of a pressure of the fluid supplied to a control input of the flow control valve. A proportional valve is connected between the source of pressurized fluid and the control input of the flow control valve for variably controlling the pressure of the fluid supplied to the control input of the flow control valve as a function of the first signal. A first two-way valve can be connected to the flow control valve, the proportional valve and the source of pressurized fluid. The first two-way valve has a first position where the control input of the flow control valve is in fluid communication with the proportional valve and a second position where the control input of the flow control valve is in fluid communication with the source of pressurized fluid. The first two-way valve has a control input connected to receive a third signal from the controller. The third signal selectively switches the first two-way valve between the first position and the second position. Preferably, the first signal is continuously variable and the second and third signals are binary.
The first fluid control circuit preferably includes a pressure regulator in fluid communication between the control input of the fluid control valve and the source of pressurized fluid when the first two-way valve is in the second position. The pressure regulator reduces the pressure of the fluid supplied to the control input of the fluid control valve when the first two-way valve is in the second position.
The second fluid control circuit includes a second two-way valve connected between the source of pressurized fluid and the third fluid control circuit. The second two-way valve has a first position where the source of pressurized fluid is in fluid communication with the third fluid control circuit and a second position where the third fluid control circuit is fluidly isolated from the source of pressurized fluid. The second two-way valve has a control input connected to receive the second signal from the controller. The second signal selectively switches the second two-way valve between the first position and the second position.
The third fluid control circuit preferably includes a double check valve having: (i) one input connected to the second fluid control circuit; (ii) another input connected to the first fluid control circuit and the first brake; and (iii) an output connected to the second brake. The double check valve fluidly connects the input thereof receiving the greatest fluid pressure to the output of the double check valve.
The dual mode brake system can be operated in a brake release mode, a service braking mode, a pressure braking mode and a spring emergency braking mode. In the brake release mode, the first fluid control circuit withholds fluid from the first brake, and the second brake receives fluid from the second fluid control circuit via the third fluid control circuit. In the service braking mode, the first brake receives from the first fluid control circuit fluid having a pressure corresponding to a desired braking effort of the first brake, and the second brake receives fluid from the second fluid control circuit via the third fluid control circuit. Preferably, the pressure of the fluid received by the first brake is less than the pressure of the fluid received by the second brake. In the pressure emergency braking mode, the first brake receives fluid from the first fluid control circuit, the second brake receives fluid from the first fluid control circuit via the third fluid control circuit and the second fluid control circuit fluidly isolates the third fluid control circuit from the source of pressurized fluid. In the spring emergency braking mode, the first fluid control circuit and the second fluid control circuit do not supply sufficient fluid to the second brake to compress a spring thereof whereby the spring actuates the second brake which provides a spring braking effort.
The dual mode brake system enters the spring emergency braking mode when the second fluid control circuit withholds fluid from the third fluid control circuit and the first two-way valve malfunctions whereby the flow control valve does not supply sufficient fluid to the second brake to maintain the spring thereof compressed. Under this circumstance, the spring actuates the second brake which provides the spring braking effort. The malfunction of the first two-way valve can include a blockage in the fluid path between the control input of the flow control valve and the source of pressurized fluid when the two-way valve is in the second position.
The dual mode brake system can also enter the spring emergency braking mode when the second fluid control circuit withholds fluid from the third fluid control circuit and the flow control valve malfunctions whereby the flow control valve does not supply sufficient fluid to the second brake to maintain the spring compressed. Under this circumstance, the spring actuates the secon
Lipscomb Jason
Zhou Joseph
Daimler-Chrysler AG
Schwartz Christopher P.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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