1. Field of the Invention
This invention relates to an air dryer system for use in a compressed air system. More particularly, the invention relates to a trailer air dryer system having a purge arrangement that is responsive to actuation of a parking brake.
2. Discussion of the Art
The assignee of the present application commonly owns related U.S. Application, Ser. No. 09/399,285, Filed Sep. 17, 1999, directed to a trailer air dryer. The trailer air dryer protects air operated devices associated with a trailer (for example, an air braking system, an air suspension system, or still other systems that use compressed air associated with the trailer) by removing moisture and contaminants from the air before it reaches these devices.
A preferred trailer air dryer is shown and described in that application, the details of which are incorporated herein by reference, although not deemed necessary to a full and complete understanding of the present invention. The trailer air dryer employs a desiccant material or drying agent through which the air passes to remove entrained moisture and thereby limit problems associated therewith. The moisture is adsorbed by the desiccant and removed from the compressed air before it is communicated to the air tank or storage reservoir. In addition, foreign particles and contamination are also removed by the trailer air dryer so that a filtered, relatively dry air is sent to the air tank.
In the device shown and described in the commonly owned pending application, moisture is adsorbed during wet air consumption and previously captured moisture is periodically released in a non-cyclic fashion when the incoming air is dry. Thus, the trailer air dryer system relies on ambient dry air to regenerate the desiccant in a non-cyclic fashion. Without a cyclic purging, the dryer acts as a buffer holding water vapor when the trailer is receiving wet air and periodically passing along some of the entrained moisture when the trailer is receiving dry air. Ultimately, the water vapor trapped during wet operation is passed through the air brake system during dry operation. If the trailer air dryer is completely saturated, it will unfortunately pass wet air as if there were no air dryer in the system.
Accordingly, a need exists to periodically purge the trailer air dryer in an effort to decrease the prospects for moist air being conveyed to the braking system.
The present invention solves the noted problems and others and provides a purge system for a trailer air dryer that reduces or eliminates the disadvantages of the existing trailer air dryer.
According to the invention, an air dryer system includes a valve in operative communication with a supply end of a trailer air dryer. An air reservoir is in communication with a delivery end of the trailer air dryer. When the valve communicates with atmosphere or ambient in response to a park brake application, a purge flow from the air reservoir and through the trailer air dryer to the valve is established.
According to another aspect of the invention, a restricting orifice limits the purge flow through the trailer air dryer to extend the purge time and maximize removal of moisture from the trailer air dryer.
According to another aspect of the invention, the air reservoir is separate from an air tank associated with the trailer.
According to yet another aspect of the invention, a check valve is associated with the restricting orifice and precludes air flow into the air reservoir and permits purge flow from the reservoir to a preselected pressure level.
Still another aspect of the invention relates to a method of purging a trailer air dryer by opening a valve port to atmosphere in response to a park brake application and directing a purge flow from the air source through the trailer air dryer.
A primary benefit of the present invention is the ability to eliminate or reduce disadvantages associated with moisture in the existing trailer air dryer design.
Still another benefit resides in the ability to maintain all of the performance advantages of the existing trailer air dryer.
Yet another benefit of the invention is associated with the ease in which the existing trailer air dryer can be modified to incorporate the purge system.
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.