Abstract:
A back seating service valve for air conditioning systems is provided wherein the valve includes an insert fitting having a valve seat. The insert fitting is attached to the valve body using a threaded connection that is then brazed to ensure that the insert fitting does not separate from the valve body during use.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 61/241,060, filed Sep. 10, 2009, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to valves which have a service port to enable evaluation of fluid in a fluid system and in particular to a valve utilizing a valve seat insert for back seat valves of the type typically used in residential air conditioning systems and commercial refrigeration systems. 
       BACKGROUND 
       [0003]    Back seating valves with service ports are known, and are used in a variety of applications, for example in refrigeration systems. The valve is located in a fluid system and includes first, second, and third fluid passages. The first and second passages comprise the inlet and outlet passage for the valve, while the third passage comprises a service port. A valve element can be moved between open, intermediate, and closed positions in the valve to i) allow fluid to pass from the inlet passage to the outlet passage in the valve substantially uninterrupted during normal system operation (open position); ii) open a flow path to the service port for evacuation, charging, reclaiming and pressure-tapping the system (intermediate position); or iii) completely close the flow path between the first and second passages during shipping and maintenance (closed position). The valve element is typically externally accessible to allow manual manipulation of the valve into the respective positions, although the valve could also be operated automatically using electromechanical devices (e.g., solenoids, etc.). 
         [0004]    Many of the commercially-available back seating valves include a valve seat insert fitting. The use of the valve seat insert fitting allows the valve element to be inserted into the valve and then captured within the valve when the valve seat insert is attached to the valve body, typically with a press fit and a brazing operation. 
         [0005]    The seat fitting provides a valve seat when the stem is fully extended. The seat fitting must stay attached to the main body of the valve while having a large compressive load applied to it by the stem to enable completion of a metal-to-metal seal. Using a press-brazed attachment may allow the seat fitting to be pressed off the valve body if the press or brazing processes are not fully in control. 
       SUMMARY 
       [0006]    At least one embodiment of the invention provides a fluid service valve comprising: a valve body having first, second and third fluid passages, the first and second fluid passages being fluidly interconnected; a seat insert fitting threadably attached to the main body and brazed to the valve body, the seat insert fitting including a valve seat; a valve element including a stem and a valve head, the stem being received within a central bore in the valve body and moveable to bring the valve head into and out of engagement with the valve seat of the seat insert fitting to close or open a flow path to the third fluid passage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Embodiments of this invention will now be described in further detail with reference to the accompanying drawings, in which: 
           [0008]      FIG. 1  is a cross-sectional view of an embodiment of the valve in accordance with the present invention; 
           [0009]      FIG. 2  is a side elevational view of the valve of  FIG. 1 ; 
           [0010]      FIG. 3  is a top view of the valve of  FIG. 1 ; and 
           [0011]      FIG. 4  is a detail view of the seat insert shown threaded-brazed to a valve in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to the drawings,  FIGS. 1-4 , a fluid service valve constructed according to the principles of the present invention is indicated generally at  10 . Valve  10  comprises a valve body  20  having a first fluid passage or inlet port  22  and a second fluid passage or outlet port  24 , and a third passage or service port  26 . The fluid passages or ports  22 ,  24 ,  26  open into a valve chamber  28  located centrally in the valve body  20  which fluidly interconnects the ports  22 ,  24 ,  26 . The valve body  20  includes an integral first or back valve seat  30  at one end of the valve chamber  28 . The inlet port  22  comprises an insert fitting  32  threadably attached to the valve body  20  and brazed to the valve body  20 . The insert fitting  32  comprises a second or front valve seat  34 . The threaded attachment of the insert fitting  32  will prevent the insert fitting  32  from coming off the valve body  20  on the occasion of a weak braze. 
         [0013]    First and second copper tubes  12 ,  14  are fixed (e.g., brazed, welded, etc.) to insert fitting  32  and second port  24 , respectively. First and second tubes  12 ,  14  can be fluidly connected in an appropriate manner (e.g., brazed or welded) within a fluid system, such as a refrigeration system, as should be appreciated by those of ordinary skill in the art. Typically, first tube  12  is an inlet tube directing fluid in the system to first port  22 , which is considered an inlet port; and second port  14  functions as an outlet port directing fluid to a second tube  14 , which is considered an outlet tube—but it should be appreciated that the valve  10  could be connected in a reverse manner, or the fluid system could operate in reverse, so that the terms “inlet” and “outlet” should be considered interchangeable. 
         [0014]    The valve  10  further comprises a valve element  40  including an elongated stem  42  and an integral, enlarged valve head  44 , the stem  42  having an externally threaded portion  50  being threadably received within a threaded through-bore  52  in the valve body  20  and including an end portion  48  projecting outwardly from an end of the valve body  20  and is externally accessible. The end portion  48  of the valve stem  42  is formed with an appropriate geometry (e.g., square or hex) to enable a tool (e.g., a wrench) to rotate the valve stem  42  within the valve body  20 . The valve head  44  has a circular configuration, and includes an annular tapered portion on its back (downstream) surface, which sealingly engages the back valve seat  36  when the valve element  40  is rotated in one direction into an open position. The valve head  44  also has an annular tapered portion on its front (upstream) surface, which sealingly engages the front valve seat  34  when the valve element  40  is rotated in an opposite direction into a closed position. The valve stem  42  and valve head  44  are preferably formed unitary with each other, although it is possible that they could be formed of separate pieces, and later secured together. In any case, the valve element  40  is preferably also formed of a material appropriate for the particular application, such as steel, although again, the valve stem could be formed of less-expensive and lighter weight material than steel, such as a plastic or elastomer. 
         [0015]    The valve  10  further comprises a valve plug  60  attached to the valve body  20  that provides a fluid-tight seal between the valve plug  60  and the valve body  20  and between the valve plug  60  and the stem  42  of the valve member  40 . An O-ring seal  62  carried by a channel in the valve plug  60  provides a fluid seal between valve plug  60  and valve stem  42  when the stem  42  is rotated. Another O-ring seal  64  provides a seal between the valve plug  60  and the valve body  20 . 
         [0016]    After assembly of the valve  10  and the connection of the valve  10  within a fluid system, the valve  10  can be used in open, closed or intermediate positions. The valve  10  is useful for normal system operation where the valve element  40  is secured into an open position where the valve head  44  is in sealing engagement with the back valve seat  30  and fluid can flow substantially uninterrupted (without significant pressure drop) from the inlet passage  22  to the outlet passage  24 . The valve element  40  can also be moved into a closed position, where the valve head  44  is in sealing engagement with the front valve seat  34 , to prevent fluid flow through the valve  10  during maintenance and shipping. The valve element  40  can still further be moved into an intermediate position, where the valve head  44  is spaced from both the front and back valve seats  30 ,  34 , such that a flow path is opened to the service passage  26 . The flow path can be used for evacuating, charging, reclaiming and pressure tapping the system.  10 . 
         [0017]    As indicated above, the valve stem  42  extends outwardly from the end of the valve body and can be rotated to screw the valve element into or out of the valve body  20 . When the valve element  40  is not being so rotated, a cup-shaped cap  70  can be attached to valve body  20  to protect the valve stem  42  and valve plug  60  from external elements. Likewise, service port  26  is protected by a cap  72 , when the service port  26  is not being used. 
         [0018]    It should be noted that first port  22  intersects one end of valve body  20 , and both second and third ports  24  and  26  intersect the body essentially perpendicular to the first port  22 , but this is merely for illustration purposes, and second and third ports  24  and  26  could intersect the valve body  20  at other than perpendicular angles. Valve body  20  is preferably formed of a light weight-metal (e.g., brass) using conventional techniques (e.g., molding, shaping, stamping). Finally, valve body  20  can include an integral flange or embossment as at  29  to enable the body to be secured at an appropriate location in the fluid system. 
         [0019]    Although the principles, embodiments and operation of the present invention have been described in detail herein, this is not to be construed as being limited to the particular illustrative forms disclosed. They will thus become apparent to those skilled in the art that various modifications of the embodiments herein can be made without departing from the spirit or scope of the invention.