Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-06-30
2001-05-29
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C188S352000, C137S627500
Reexamination Certificate
active
06238013
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a relay valve for a pneumatic brake system and, in particular, to a brake relay valve having the ability to periodically purge liquid and other contaminants from the pneumatic system.
BACKGROUND OF THE INVENTION
Pneumatic brake systems which use pressurized air to operate the service brakes and possibly also to release the parking or safety brakes are known in the art. Pneumatic systems are particularly desirable for tractor trailer combinations which are frequently connected/disconnected from one another. The pressurized air (so-called “supply pressure”) is stored in a reservoir which is charged by a compressor through a series of check valves and/or including a pressure protection valve. In these pneumatic brake systems, the driver's brake pedal or other controls directs the flow of so-called “control air.” The brake pedal, when applied, opens the reservoir air supply and sends control air, which generates control air pressure, to a relay valve. The relay valve, in response to the control air pressure, connects the reservoir air supply to the brake actuators, which applies mechanical force to the brakes.
In these truck systems, the pressure generated by the driver's foot on the pedal is not applied directly to the brakes; rather, it is used only to control the relay valve which in turn delivers air pressure from the reservoir to the brake actuators, applying mechanical force to the brakes. While the truck is in use, the supply air pressure remains at a high level. It may fluctuate somewhat, but it generally remains above 90 psig (pounds per square inch, gauge). When the mechanical parking brakes of the truck are needed and the pneumatic brakes are no longer needed, the brake system is normally de-pressurized and the trailer supply line air pressure drops to zero psig (or atmospheric pressure), thus applying the trailer parking brakes.
In general, pressurized air is an effective means to control the brakes; however, contaminants introduced either intentionally or accidentally can have detrimental effects on the system. For example, in cold weather, users often inject alcohol and other de-icing compounds into the air brake system to keep the brake components from freezing. Alcohol is detrimental to the valves because it removes necessary lubricants from them and may also degrade seals and hoses. Alcohol which builds up in the brake system may create a hydraulic-type system (which is a slower pressure transmitter than a dry pneumatic system) and/or vary the operating characteristics of the system due to the relative incompressibility of the liquid. Moreover, the alcohol or other contaminants build up at the relay valve because it is the last device in the control air system; this build-up hampers brake control.
Air dryers are commonly used in pneumatic brake systems to remove condensates and other contaminates prior to delivery of air to storage reservoirs and the like. But contaminates can be introduced down stream from the air dryer, thus they remain in the trailer brake system.
U.S. Pat. No. 5,154,204 to Hatzikazakis discloses a drain valve for removing moisture from these air dryers. The drain valve includes a spring which normally biases a ball against a seat thereby closing the valve. Periodically, pneumatic pressure is applied to a piston which unseats the ball and opens the valve, allowing any moisture accumulated in the air dryer to drain by the force of gravity. The '204 patent does not disclose pressurized ejection of moisture and other contaminants and the device taught is not generally usable to remove moisture which accumulates downstream in the braking system, e.g., in the relay valve.
U.S. Pat. No. 3,967,706 to King discloses a brake actuator housing having a passage through which pressurized air may pass to purge contaminants which may enter the housing due to the environment in which the brake is used. The device taught by King provides for purging contaminants from the supply side of the system; however, it does not provide for purging contaminants from within the control side of the system and thus is not effective in avoiding the above-mentioned problems.
What is desired therefore is a device which periodically purges contaminants, such as alcohol, from a pneumatic brake system and specifically from the control side of the system and/or from a relay valve in order to maintain optimal response and control of the pneumatically-controlled brake system. A device which provides for the pressurized ejection of contaminants is also desired.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a valve, for use with a pneumatic brake system, which is capable of ejecting contaminants, such as alcohol, which have been injected or have accumulated therein.
It is another object of the present invention to provide a valve, for use with a pneumatic brake system, which is capable of purging contaminants from a control side of the pneumatic system.
It is still another object of the present invention to provide a valve of the above character having an exhaust passage which is periodically opened to vent contaminants from the valve.
It is still a further object of the invention to provide a valve of the above character having a movable exhaust piston, housed within a stem of the main piston, to open and close the exhaust passage.
It is yet another object of the invention to provide a valve of the above character wherein the exhaust piston is actuated by control air pressure to open the exhaust passage.
These and other objects are achieved by a contaminant-ejecting valve comprising: a housing enclosing a main chamber; a main piston movable between first and second positions; a control port in the housing in fluid communication with the main chamber for moving the main piston from the first to the second position; an exhaust port; an exhaust passage through the main piston connecting the main chamber and the exhaust port in fluid communication; and a blocking member which opens the exhaust passage under control pressure. When the exhaust passage is open, contaminants, such as alcohol, may be expelled from the chamber through the exhaust passage and to the exhaust port.
The valve also includes a supply port and a delivery port, the delivery port being in fluid communication with the supply port when the main piston is in the second position and blocked from the supply port when the main piston is in the first position. Preferably, a spring biases the main piston to the first position.
Preferably, the valve is a relay valve in a pneumatic brake system. Preferably, the blocking member is an exhaust piston mounted in a hollow stem of the main piston and the exhaust passage extends from the main chamber to the hollow stem and from there to the exhaust port.
In pneumatic embodiment of
FIGS. 1-6
, the blocking member is responsive to pilot air pressure provided from a pilot port in the valve to close the exhaust passage. In this embodiment, the blocking member is slidably mounted within the hollow stem to move between an exhaust passage open position and an exhaust passage closed position. It should be understood that pilot air could be either supply air or control air, as described in more detail herein.
During normal operation, i.e., when the vehicle is being driven, pressurized pilot air acts on an end of the exhaust piston and forces it to block the exhaust passageway. Pressurized control air exerts a substantially opposite (i.e., upwardly) force on the exhaust piston which is insufficient to overcome the force exerted by the pilot air pressure when the vehicle is being driven.
When the pilot air pressure is released (e.g., when the parking brake is applied), the pressurized control air acting on the exhaust piston overcomes the force of the released pilot air and moves the exhaust piston to open the exhaust passage and allow escape of control air to the exhaust port. The escaping control air expels any moisture or other contaminants that may have accumulated on the main piston, i
Haldex Brake Corporation
Oberleitner Robert J.
Siconolfi Robert A.
St. Onge Steward Johnston & Reens LLC
LandOfFree
Solenoid-activated contaminant ejecting relay valve does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solenoid-activated contaminant ejecting relay valve, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solenoid-activated contaminant ejecting relay valve will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2443410