Drying system with a low profile discharge check valve

Abstract: A low profile valve for discharging pressurized air to a system for utilizing such pressurized air. The valve includes a housing (24) for mounting in or to an associated structure (14), and has at least one opening (22) through which pressurized air is directed to and from the valve. A piston (20) is located in the housing for axial movement therein, and the piston has a face portion (18) containing a seal (34) for sealing the piston against a fixed surface (16) of the associated structure. In addition, a spring (26) can be located about the piston for biasing the piston in the direction of the fixed surface.

Description: CROSS-REFERENCE TO RELATED APPLICATION The invention disclosed in this application is related to the inventions taught in U.S. Patent 5.961.698, titled "Twin Tower Air Dryer", and U.S. Patent 5.901.464, titled "E-1 Twin Tower Air Dryer For An Air Compressor". FIELD OF INVENTION The present invention relates generally to check·valves having a low profile for compactness, and is particularly suitable for use in air dryers of the type disclosed in the above patents Twin drying towers are generally known in the art. BACKGROUND OF THE INVENTION All such dryers discharge dry pressurized air to systems utilizing such air, which systems often include main reservoirs that store the air for use by such systems. Dry air is discharged from the dryers through a check valve, and the valve remains closed when discharge air is not available to open the valve. The purpose of such a valve is to seal an air compressor and air dryer from the pressure contained within the main reservoir when the compressor is idle and to prevent any loss of main reservoir pressure (MRP) through the compressor. In the first of the U.S. patents cited above, it is an objective to make such an air dryer as compact as possible since ample space is not always available for containing dryers. Check valves have long been employed in a variety of fields. As it may aid the reader to understand the invention disclosed infra, the following reference is offered as background art EP-A-0298281 discloses a check valve 1 having a tubular housing 2, a piston 5 and a spring 6.The housing 2 defines no other parts besides an inlet 3 and an outlet 4 that are axially aligned. The housing 2 features an internal annular seat 7 against which the head of the piston 5 is biased by the spring 6. This seat 7, however, is part of the housing 2. As long as the pressure acting on the head of the piston 5 is kept below a threshold level, the inlet 3 remains closed off from the outlet 4. OBJECTS OF THE INVENTION Thus, an objective of the invention is to seal a compressor and air dryer from main reservoir pressure when the compressor is turned off, and not to allow the loss of main reservoir pressure through the compressor. This objective is obtained by use of a compact, low profile check valve that requires a minimum amount of space in the equipment and environment in which it is used. SUMMARY OF THE INVENTION A system using pressurized air and a check valve deployed in said system is defined in claim 1. The check valve of the present invention has a shallow housing containing a relatively shallow piston and a biasing spring. The face of the valve is provided with a seal, such as an O-ring, that seats and seals against a fixed surface of an associated structure to which the valve is attached or located within. When seated against this fixed surface, the piston closes off an inlet port. When pressure is introduced at the inlet port, however, the piston unseats and allows air to flow through the check valve from the inlet port to and out of flow openings defined in the housing. The check valve, in addition, can be provided with inner ports defined through an outer side wall of the housing to provide fluid communication with control components in the system within which the check valve is installed. When the check valve is opened the pressurized air also flows through these inner ports, and through radial ports defined in the structure, to the control components of the system or systems using such air. When no positive pressure is applied to the face of the piston, back pressure from the system using the air forces the piston against the fixed surface so that pressure does not leak from the system. A small spring located in the housing can assist in such sealing function. THE DRAWINGS The invention, along with its objectives and advantages, will be better understood from consideration of the following detailed description and the accompanying drawings in which: Figure 1 is a sectional view of the low profile valve of the invention, Figure 2 is an exploded view of the valve of Figure 1, and Figure 3 is a schematic view of the valve connected to two shuttle valves in a twin tower desiccant dryer system. PREFERRED EMBODIMENT OF THE INVENTION Referring now to the drawings, Figure 1 of which shows a shallow, low profile check valve 10 which, in Figure 1, is shown located in a shallow recess 12 of a structure 14. Structure 14 can, for example, be a manifold block of the type shown for a twin tower air dryer in U.S. Patent 5.961.698, though the invention is not limited thereto. Structure 14 provides a fixed surface 16 against which a face 18 of a piston 20 of valve 10 is shown seated thereagainst (Figure 1). An inlet port 22 is provided in structure 14 in fluid communication with the face of the piston and with the interior of valve 10 when the piston moves away from fixed surface 16. An outlet port provided in structure 14 is in communication with a reservoir 50. Valve 10 includes further a shallow housing 24 containing piston 20. A coil spring 26 is shown surrounding the piston and located between an enlarged section or flange 28 of the piston and the inner surface of lower wall portion 30 of the housing. The flange portion 28 of the piston provides a relatively broad face 18 having a dove tail groove 32 holding an O-ring 34 that protrudes from face 18. In addition, piston 20 has an integral extension or stem 36 that extends into an opening 38 provided in lower wall 30 for axial, sliding movement therein. The opening and extension are sized to provide a close fit yet allow easy sliding of the extension 36 in the opening 38 and in contact with the surface of the opening. Preferably, the piston and its extension are made of a non-metallic material, such as Nylon or Teflon, which are self-lubricating so that extension 36 and opening 38 do not require further lubrication. As seen in Figure 1, the distal end of extension 36 is located outside of valve housing 24 and beyond housing wall 30, and is provided with a ring 40, seated in the extension, that serves to retain the piston in the housing. In Figure 2, four inner ports 42 are shown provided in the outer side wall of shallow housing 24. They align and communicate with the radial ports 44 defined within structure 14. The inner ports 42 and radial ports 44 can communicate, for example, with the control valves disclosed in U.S. Patent 5.901.464 to affect the switching of twin drying towers. These control valves are shown schematically in Figure 3, and are labelled by numeral 47. A second O-ring 48 is provided for sealing valve housing 24 in and to structure 14. In Figure 1, the O-ring is shown seated in a peripheral groove 49 provided in the outside surface of the side wall of the housing. Valve 10 functions in the following manner. When pressurized air is received in inlet port 22 of structure 14, a force is created on face 18 of piston 20, which moves the face from surface 16 and translates the body of the piston to wall 30 of piston housing 24. Piston extension 36, of course, moves through opening 38 in wall 30, and spring 26 compresses between the piston body and wall 30 of housing 24. The pressure in inlet port 22 can be that pressure supplied by an air compressor supplying dry air to a reservoir 50 (Figure 3), the air having been dried by desiccant assemblies 52. In Figure 1, such air flows through flow openings 56 provided in housing wall 30 to the reservoir 50 via the outlet port defined in structure 14. When pressurized air is removed from the inlet port 22 in structure 14, such as when the air compressor is idle, pressure immediately builds up against the underside of flange 28. Previously built up in reservoir 50 while the check valve 10 was opened, this pressure now reaches the underside of piston 20 via the outlet port defined in structure 14 and the flow openings 56 defined in wall 30 of housing 24. Consequently, piston 20 moves upward causing the O-ring 34 on face 18 to effectively seal off inlet port 22. Spring 26 assists in closing the check valve 10. The check valve 10 is a simple structure, easily and inexpensively made, and is a compact, shallow structure, as discussed above, requiring a minimum amount of space. The check valve functions well in its assigned tasks, as described above. While a presently preferred embodiment for carrying out the instant invention has been set forth in detail, those persons skilled in the air valve art to which this invention pertains will recognize various alternative ways of practicing the invention without departing from the scope of the claims appended hereto.

Claims: In combination, a system of using pressurized air and a check valve deployed in said system, said system including twin drying towers (52) upstream of said check valve and a reservoir (50) downstream of said check valve, with a source of pressure for controlling operation of said check valve such that (i) air from said source dries by flowing alternatingly through each of said twin drying towers (52) causing air dried thereby to both open and flow through said check valve to said reservoir (50) and (ii) an absence of air flowing from said source causes said check valve to close, said system also having control valves (47) for switching said twin drying towers (52) alternatingly between an air drying function and a desiccant purging function; said combination characterized by : (a) said system having a structure (14) in which a shallow recess (12) is defined, said structure (14) also defining (i) an inlet port (22) for interconnection with said source of pressure, (ii) an outlet port for connection to said reservoir (50) and (iii) radial ports (44) for communicating with said control valves (47), with said shallow recess (12) being in communication with said inlet port (22), said outlet port and said radial ports (44); and (b) said check valve (10) having a shallow housing (24), a piston (20) and a spring (26); said shallow housing (24) disposed in said shallow recess (12); said shallow housing (24) having a lower wall (30) that defines flow openings (56) for communicating with said reservoir (50) via said outlet port of said structure (14); said shallow housing (24) also defining inner ports (42) in communication with said radial ports (44) of said structure (14); said piston (20) capable of being moved axially in said shallow housing (24) yet biased therein by said spring (26) so that a face (18) of said piston (20) seats against a fixed surface (16) of said structure (14) thus placing said check valve (10) in a closed position wherein communication between said inlet port (22) and said flow openings (56) is cut off; such that when air from said source is flowing through either of said twin drying towers (52) dried air flows into said inlet port (22) and acts against said face (18) causing said piston (20) to unseat thus forcing said check valve (10) to an open position wherein dried air continues flowing past said piston (20) through said flow openings (56) and said outlet port of said structure (14) to said reservoir (50) and through said inner and said radial ports (42, 44) to said control valves (47). The system and the check valve (10) of claim 1 further characterized by : (a) an annular groove (32) defined in said face (18) of said piston (20); and (b) an o-ring (34) secured in said annular groove (32) for sealing said face (18) against said fixed surface (16) of said structure (14) so that air is prevented from leaking from said reservoir (50) when said check valve (10) is in said closed position. The system and the check valve (10) of claim 1 further characterized by : (a) a peripheral groove (49) defined in an outer side wall of said shallow housing (24); and (b) an o-ring (48) secured in said peripheral groove (49) for sealing said shallow housing (24) in and to said structure (14). The system and the check valve (10) of claim 1 further characterized by : (a) said piston (20) having a stem (36); (b) said lower wall (30) of said shallow housing (24) defining a stem opening (38) through which said stem (36) extends; and (c) a retaining ring (40) secured around a distal end of said stem (36) that lies outside of said lower wall (30) for retaining said piston (20) in said shallow housing (24). The system and the check valve (10) of claim 1 wherein said spring (26) is compressively disposed about said piston (20) between an underside of a flange (28) of said piston (20) and a top of said lower wall (30). The system and the check valve (10) of claim 1 wherein said structure (14) of said system is a manifold block for said twin drying towers (52), said manifold block having said fixed surface (16) against which said face (18) of said piston (20) seals when said check valve (10) is closed.

Inventors: DOSSAJI MURTAZA R, JONES CHARLIE E, KAZAKIS MICHAEL V, DOSSAJI, MURTAZA R., JONES, CHARLIE E., KAZAKIS, MICHAEL V.
Applicants: WESTINGHOUSE AIR BRAKE CO, WESTINGHOUSE AIR BRAKE COMPANY
Application year: 1998
Main classification: F16K15
IPC codes: F16K15