Abstract:
An inlet/exhaust valve having a cylindrical portion with a cavity therethrough for use in a pneumatic control valve is disclosed. The inlet/exhaust valve has at least two seats, one of which is on an inner diameter of the cylindrical portion and the other of which is on an outer diameter of the cylindrical portion. Both seats are rounded for self-aligning seating with corresponding seating surfaces.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to pneumatic flow control valves, and, more particularly, to inlet/exhaust valves used to assist in directing the pneumatic fluid.  
           [0002]    Inlet/exhaust valves are conventionally used as poppet valves in pneumatic control valves to direct the pneumatic fluid. Conventional inlet/exhaust valves have rubber or bonded rubber face seal designs, which use a rubber seat to contact seating surface and provide an appropriate seal. These designs generally use an expensive bonding process to attach the rubber seat to the inlet/exhaust valve. Bonding processes can be unreliable and can only be checked for bond quality by destructive analysis.  
           [0003]    Leakage and performance variations due to changes in temperature, contamination, and/or degradation of the rubber seat, are typical of these face seal designs for the inlet/exhaust valves. Moreover, the flow characteristics of these designs are generally turbulent, due to, among other things, flat seats and sharp turns in the airflow. This turbulence slows down the airflow through the valve.  
           [0004]    The conventional designs usually require close guiding to ensure that the mating parts seat squarely in order to minimize leakage. The rubber seat designs also have an inherent hysteresis due to the compression of the rubber seat and the necessity for it to decompress prior to completely unseating.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention discloses a valve for use in an pneumatic brake system, including a housing having at least a supply port, a control port, a delivery port, and a exhaust port for flow of the pneumatic fluid therethrough. A piston in the housing responds to pressure from a control pneumatic fluid exerted via the control port to communicate with the inlet/exhaust poppet valve to selectively open and close the supply port, the delivery port, and exhaust port. The inlet/exhaust valve has a cylindrical portion with a cavity extending therethrough providing an inner diameter and an outer diameter. A first valve seat is formed on the outer diameter at a first end of the cylindrical portion and has a rounded seating surface, preferably spherical, and, most preferably, a convex surface. The inlet/exhaust valve has a second valve seat with a rounded seating surface, preferably spherical, and most preferably a concave surface, on the inner diameter of the cylindrical portion. The inlet/exhaust valve seats are rounded for self-alignment with corresponding seating surfaces with which they engage. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a cross-sectional representation of a conventional pneumatic control valve having an inlet/exhaust valve;  
         [0007]    [0007]FIG. 2 is a cross-sectional view of an inlet/exhaust valve in accordance with the present invention;  
         [0008]    [0008]FIG. 3 is an enlarged and separate view of the inlet/exhaust valve of FIG. 2; and  
         [0009]    [0009]FIG. 4 is an enlarged detail view of the inlet/exhaust valve of FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]    The present invention is described in relation to an air brake system such as used for heavy vehicles. While the invention has applications for this use, the invention is not limited to the specific embodiments herein described and the details of the preferred embodiments may be modified as warranted by other applications without departing from the spirit or scope of the invention. For example, while a preferred embodiment relating to pneumatic air brakes is detailed, the present invention may be used in any system for direction of a fluid through different flow paths. Use of the term “or” herein is the inclusive, and not the exclusive, use. See BRYAN A. GARNER, A DICTIONARY OF MODERN LEGAL USAGE 624 (2d Ed. 1995). The term “pneumatic fluid” as used herein means of or relating to use of a gas or liquid. The preferred pneumatic fluid is air.  
         [0011]    A conventional pneumatic control valve  10  of the type that is used in an air brake system for heavy vehicles is shown in FIG. 1. The pneumatic control valve  10  has a housing  12  that includes a supply port  14 , an exhaust port  16 , a delivery port  18 , and a control port  20 . A control signal is transmitted through the control port  20  and acts upon a piston  30  to move downwardly (as illustrated in FIG. 1—the actual direction will depend on the specific valve configuration selected by the user) against the force exerted by the pneumatic fluid in the delivery port  18 . A differential spring  32  may be installed if, for example, there is a desire for additional differential pressure between the pressure of the fluid of the control port  20  and the pressure of the fluid of the delivery port  18 . If there is no differential spring  18 , then the force balance around piston  30  relative to the pressures exerted through the control port  20  and the delivery port  18  determine the movement and position of the piston  30 . For this discussion, it will be presumed that the differential spring  32  is present, and the scope and spirit of the invention are not changed by the presence or absence of the differential spring  32 .  
         [0012]    The control signal may be actuated by depression of a brake pedal (not shown) and is generally transmitted via a control pneumatic fluid that may or may not be the same fluid as the pneumatic fluid for which the pneumatic control valve is designed to provide control. This urges an exhaust seat  34  into engagement with an inlet/exhaust valve  40 .  
         [0013]    The inlet/exhaust valve  40  includes a radial shoulder  42  on which is bonded a rubber seat  44 . The engagement between the exhaust seat  34  and the rubber seat  44  precludes communication between the delivery port  18  and the exhaust port  16 . Continued downward movement of the piston  30  moves the rubber seat  44  of the inlet/exhaust valve  40  from an associated seat  46  on the housing  12  and establishes communication between the supply port  14  and the delivery port  18 . With this flow path open, pneumatic fluid is provided to the brake actuator or other pneumatic load through delivery port  18 . Upon release of the control signal via control port  20 , the return spring  32  (and the pneumatic fluid in the delivery port  18 ) exerts force upon the piston  30 , moving it in an upward direction and allowing rubber seat  44  to again contact the associated seat  46  interrupting the flow path of pneumatic fluid from supply port  14  to delivery port  18 . Further movement of the piston  30  in an upward direction in response to the change in force balance with the reduction in control pressure disengages exhaust seat  34  from rubber seat  44  and opens a flow path between delivery port  18  and exhaust port  16  such that pneumatic fluid is exhausted through exhaust port  16 .  
         [0014]    [0014]FIG. 2 illustrates an inlet/exhaust valve  50  in accordance with the present invention, which is generally cylindrical having a central passage  52  therethrough. A radially extending shoulder  54  is provided at one end with a face  56  that is engaged by a biasing spring  58  to urge the inlet/exhaust valve  50 , and particularly a first or inlet seat  60 , toward a first seating surface  61  on valve housing  64 .  
         [0015]    The first or inlet seat  60  of the inlet/exhaust valve  50  is rounded, preferably generally spheroidal, and, most preferably, is a convex surface. The first seating surface  61  is typically rounded, and the rounded first or inlet seat  60  sealingly seats against the rounded first seating surface  61 .  
         [0016]    As control pneumatic pressure is applied to the piston  80  via the control port  90 , the piston  80  moves and engages the inlet/exhaust valve  50  at an exhaust seat  62  provided on the inner diameter of the inlet/exhaust valve  50  at second seating surface  72 . The second seating surface  72  that engages the exhaust seat  62  is typically rounded, and preferably spherical, and the rounded second seating surface  72  sealingly engages the rounded exhaust seat  62  to interrupt the flow path of pneumatic fluid between the delivery port  88  and the exhaust port  86 .  
         [0017]    Upon further application of control pneumatic pressure on the surface of the piston  80 , the piston  80  moves the inlet/exhaust valve  50  in an upward direction against the biasing force of biasing spring  58  the pneumatic fluid force acting on the inlet/exhaust valve  50  (upward as illustrated in FIG. 2—the actual direction will depend on the specific valve configuration selected by the user). This provides a flow path between the supply port  84  and the delivery port  88  such that pneumatic fluid may flow therethough.  
         [0018]    Upon release of the control pressure signal from the control port  90  upon the piston  80 , the biasing spring  58  exerts force against the face  56  and the delivery pressure acting on the opposite side of piston  80  move the inlet/exhaust valve  50  and the piston  80  in a downward direction such that inlet seat  60  again engages first seating surface  61 , thus interrupting the flow path between supply port  84  and delivery port  88 . The pressure from the delivery port  88  (and a differential spring, if present) further exerts a downward force on the piston  80  such that the second seating surface  72  disengages from the exhaust seat  62 , providing a flow path between the delivery port  88  and exhaust port  86 .  
         [0019]    As shown in a preferred embodiment illustrated in FIGS. 2, 3, and  4 , the first or inlet seat  60  and the second or exhaust seat  62  are provided at the same end of the inlet/exhaust valve  50 . In other configurations, one of the inlet seat  60  and exhaust seat  62  may be provided at the opposite end of the inlet/exhaust valve  50 , depending upon the configuration of the seating surfaces with which the seats shall engage, and depending upon the configuration of the remainder of the pneumatic control valve assembly. In other configurations, the seats  60 ,  62  may be located at any location along the cylinder, depending on the preference of the user and the circumstances of the specific application, including the specific configurations of the pneumatic control valve assembly. As shown on FIG. 3, preferably the first or inlet seat  60  is rounded, generally spherical, and of a convex shape. The second or exhaust seat  62  is preferably rounded, generally spherical, with a concave shape.  
         [0020]    [0020]FIG. 4 illustrates the engagement between rounded inlet seat  60  and rounded first seating surface  61 , as well as the engagement between rounded exhaust seat  62  and rounded second seating surface  72  of the piston  80 . As illustrated in FIG. 4, when the piston  80  continues in a downward direction, the sealing seating between inlet seat  60  and first seating surface  61  will be interrupted, providing a flow path therethrough. As piston  80  travels in an upward direction in FIG. 4, then the sealing seating between rounded exhaust seat  62  and rounded second seating surface  72  will be interrupted providing a flow path therethrough.  
         [0021]    The rounded configurations of inlet seat  60  and exhaust seat  62  allow for self-alignment of these seats with their respective seating surfaces  61 ,  72 . No additional guide is necessary to ensure that the seats  60 ,  62  sealingly engage the seating surfaces  61 ,  72 , because the rounded portion of the seats  60 ,  62  allow for self-aligning engagement of the rounded seating surfaces  61 ,  72  without the need for additional guides. These rounded configurations ensure seat sealing with a line contact seal when the parts are not perfectly aligned, which may result in a more uniform unit load.  
         [0022]    The inlet/exhaust valve  50  is preferably a single piece, and most preferably, manufactured from plastic, but other configurations are contemplated, depending on the circumstances for each particular valve arrangement. A preferred method of making the inlet/exhaust valve  50  is by molding, such as injection molding of the plastic piece. The inlet/exhaust valve  50  may also be made from other materials, whether metallic or non-metallic, and may also be made such that the seating surfaces or the shoulder  54  are made from a different material as is the body of the inlet/exhaust valve  50 . Elimination of the rubber seat  44  from the conventional inlet/exhaust valve, as shown in FIG. 1, reduces hysteresis due to compression of the rubber seat  44  and improves cold temperature performance over the conventional flat rubber seated valves. Moreover, use of a single-piece plastic inlet/exhaust valve enables a user to select a plastic to provide improved chemical resistance over the use of a rubber seat  44 , thus extending the life of the part for those applications requiring improved chemical resistance.  
         [0023]    While the present invention has been illustrated by the above description of embodiments, and while the embodiments have been described in some detail, it is not the intention of the applicants to restrict or in any way limit the scope of the invention to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown or described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicants&#39; general or inventive concept.