Fluid-pressure and analogous brake systems – Automatic – Supplementary control pipe
Reexamination Certificate
1999-02-01
2001-01-30
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Automatic
Supplementary control pipe
C303S086000, C303S081000, C303S008000
Reexamination Certificate
active
06179391
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention pertains to the art of brake systems for heavy vehicles, and more particularly to an air brake system that satisfies recent standards imposed with regard to emergency brake performance. It will be appreciated that as a result of the modifications taught by the present invention, the air brake systems can now meet new emergency stopping distance requirements with a failed rear axle service control line.
In presently available truck brake systems, depressing a foot pedal or treadle actuates a foot control valve to actuate air brakes associated with the wheels. Dual supply ports and dual delivery ports are provided with the foot control valve in order to achieve desired front and rear braking. In systems of this type, a relay valve is associated with the rear wheels. The relay valve includes a supply port that communicates with a source of compressed air and an exhaust port that communicates with ambient or atmosphere. A delivery port is in operative communication with the wheel brake actuators to effect desired braking. In addition, and in accordance with known systems, a service port of the service relay valve receives a control signal (e.g. pneumatic pressure) from the foot control valve. When the foot control valve is actuated by depressing the foot pedal, pressurized air is delivered to the service port. This, in turn, pressurizes a movable piston that actuates an inlet/exhaust valve in the relay valve to establish communication between the supply port and the delivery port to effect braking.
Recent revisions in the national standards require that a safe stopping distance be achieved with a failed rear axle service control line, i.e., if the service line from the foot control valve to the relay valve is insufficient, inoperative, etc. then the brake system still must satisfy the emergency stopping distance requirements.
It is also preferred that modifications to existing systems be minimized so that proven designs and components can be used.
Accordingly, a need exists for an effective, simple, and economical solution.
SUMMARY OF THE INVENTION
The present invention contemplates a new and improved relay valve in an air brake system for heavy vehicles that overcomes the above-referenced problems and others and addresses recently promulgated standards regarding emergency stopping distance requirements with a failed rear axle service control line.
According to the present invention, there is provided a relay valve that has a supply port, delivery port and exhaust port in selective communication with one another for effecting braking operation in response to air pressure from a service port. The relay valve, particularly the service port thereof, is modified to incorporate primary and secondary service control lines to accommodate a failed rear axle service control line requirement.
According to the invention, a secondary service line communicates with the foot control valve delivery port so that if pneumatic pressure from the primary service line is interrupted, pressure is still delivered to the service port and actuating piston of the relay valve.
According to another aspect of the invention, the primary and secondary service lines are in operative communication via a biased double check valve. Thus, if a pneumatic signal is present from the primary and secondary circuits, the primary line will control operation of the relay valve while the secondary line provides desired redundancy.
A principal advantage of the invention is the ability to meet the new emergency stopping distance requirements.
Yet another advantage of the invention resides in the simple modifications to the known system to achieve the desired benefits in an economical manner.
Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.
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Eberling Charles E.
Hendershot Gary R.
Kemer John J.
Marsh Andrew
Ross Richard T.
AllliedSignal Truck Brake Systems Company
Kramer Devon
Oberleitner Robert J.
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