Abstract:
A service valve for a refrigerant system comprising a valve body and a system port. The valve body has at least one fluid passage integrated therein including a longitudinal bore. An orifice is located at one end of the bore. An annular protrusion axially extends from the valve body and is symmetrical about the orifice. A valve seat generally surrounds the orifice. The system port includes a valve stem having a first end, a second end, and a bore integrated within. The stem is axially movable within the annular protrusion between at least a first position in which the orifice is closed when the valve stem first end sealingly abuts the valve seat and a second position in which the orifice is open when the valve stem first end is offset from the valve seat. The valve stem is restricted from moving further away from the valve body by the annular protrusion.

Description:
CROSS-REFERENCE TO RELATED CASES 
   The present application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/482,342; filed Jun. 25, 2003, the disclosure of which is expressly incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to valve system ports, and particularly to those ports used in refrigeration systems for charging and evacuating the refrigerant system with refrigerant. 
   BACKGROUND OF THE INVENTION 
   Service valves are used in refrigerant systems to conveniently, add and remove refrigerant. Referring to  FIG. 13 , a common type of service valve is the front-seat valve  730 . An example of such a valve is shown in U.S. Pat. No. 4,644,973 to Itoh et al. Front seat valve  730  contains a charge port  735  through which the installation/service technician can gage the system pressure, evacuate the system, or add refrigerant charge to the system. Front seat valve  730  has a front seat  744  that seals against a mating portion of valve body  732 . Charge port  735  is equipped with a valve core  737 , which prevents refrigerant from escaping charge port  735  until a stem  738  of valve core  737  is depressed by the service hose connection. Valve core  737  is sealed with elastomeric seals which can lose their sealing characteristics over time. When connected to a service hose, a flow path through charge port  735  is opened and the system can be accessed. The volumetric flow rate of gas, into or out of the system, is restricted by this generally small flow path. Therefore, the time required to service the system is negatively increased due to the size. 
   Another well-known charge port configuration is found on the more costly and bulky back-seat service valve  780 , shown in  FIG. 14 . The back-seat valve has both a front seat  794  and a back seat  791  which seal against sealing surfaces of valve body  783 . Front seat  794  works the same way as front-seat valve  730 . Back-seat valve  780  offers an isolated charge port without employing a valve core, therefore it must be capped (not shown). A valve stem  787  in this design is back-seated (at  791 ) during normal operation. Back seat  791  is typically a metal-to-metal seal and offers greater leak prevention than that of front seat valve  730 . In the back-seated position, a charge port  785  is sealed off, or isolated, from the system. Thus, the charge port cap can be removed while valve  780  is back-seated without any concern of refrigerant escaping the system. Once the service hose is attached to charge port  785 , valve&#39;s stem  787  is mid-seated so that charge port  785  is in communication with the system. Servicing the system (evacuation and charging of refrigerant) can be executed with a higher volumetric flow rate due to the lack of restriction in the flow path (no valve core). This larger flow path results in a shorter service time. However back-seat valve  780  is bulky and expensive to manufacture. Plus valve stem  787  has to be manipulated in order to access charge port  785 , which is inconvenient for the end user. 
   Other prior art service valves utilize valve stems that have a component which must be rotated in order to add or remove refrigerant. For example, in many designs the valve stem is threadedly connected to the charging hose assembly in order to add refrigerant. The valve stem is also threadedly connected to the service valve body. Since the valve stem has to be rotated in order to open the service port, the stem may undesirably rotate relative to the service hose. This can be problematic since the sealed threaded connection between the valve stem and charging hose assembly may come unsealed. It is helpful to provide a valve stem that doesn&#39;t rotate when it is being opened and closed. 
   Other prior art service valves have valve stems that can be completely removed from the service valve. If this happens, then a complete loss of refrigerant from the system will occur. This, of course, is quite undesirable not only from an end user vantage point, but also from an environmentally friendly one. For example, the component, which typically is the valve stem, needs to be unseated from the valve body in order to add and remove refrigerant from the system. Prior art designs do not prevent the complete removal of this component and a complete loss of system refrigerant will occur when this happens. 
   SUMMARY OF THE INVENTION 
   The present invention provides a service valve for a refrigerant system having a valve body with at least one fluid passage integrated therein including a longitudinal bore. An orifice is located at one end of the bore and an annular protrusion extends axially from the valve body and is symmetrical about the orifice. A valve seat generally surrounds the orifice. The service valve also includes a valve stem having a first end, a second end and a bore integrated within the service valve. The stem is movable within the annular protrusion between at least a first position and a second position. In the first position, the orifice is closed when the valve stem first end sealingly abuts the valve seat. In the second position, the orifice is open, the valve stem first end is offset from the valve seat and the valve stem is restricted from moving away from the valve body by the annular protrusion. 
   A further feature of the noted service valve is that the movement of the valve stem is in the axial direction. Another feature of the noted service valve is that annular protrusion is an annular collar having a first end affixed to the valve body and a second end having an internal groove with a base portion, a front wall and a rear wall. A further feature has the valve stem having a radially extending flange located between its first and second ends, an annular notch located between the first end and the flange for housing a stem retaining ring, and an annular valley located between the flange and the second end for housing a nut retaining ring. The stem retaining ring contacts the groove rear wall when the valve stem is in the second position. Still another feature has the annular collar second end having a series of external threads on its outer surface for threaded engagement with a series of internal threads of a nut. The nut has a first end with the internal threads and a second end with an inwardly directed shoulder. The shoulder has a front end abutting the stem flange and a rear end abutting the nut retaining ring. Wherein when the nut is rotated in a first direction, the nut shoulder forcedly contacts the stem flange, urging the stem axially towards the valve body, and when the nut is rotated in the opposite direction, the nut shoulder forcedly contacts the nut retaining ring, urging the stem axially away from the valve body. Still yet another feature has the stem retaining ring having a greater resistance to stress than the nut retaining ring. 
   Another attribute of the noted service valve includes having the valve stem with an outwardly projecting annular portion between the stem first and second ends having a surface shaped for mating with a torque tool. The stem also has an annular notch located between the stem first end and the outwardly projecting annular portion for housing a stem retaining ring, and a series of external threads on its outer surface located axially between the annular notch and the first end. The annular protrusion has a first end, a second end having an internal groove with a base portion, a front wall and a rear wall, and a series of internal threads located between the internal groove and the first end for mating engagement with the series of external threads of the valve stem. 
   Yet another attribute of the noted service valve includes the annular protrusion having a distal end with an internal groove having a base portion, a front wall and a rear wall. The valve stem further has an annular flange located between the first and second ends, an annular notch located between the first end and the annular flange, and an annular valley located between the annular flange and the second end. The annular notch houses a stem retaining ring. The annular valley houses a nut retaining ring. The stem retaining ring contacts the groove rear wall when the valve stem is in the second position. Further the valve can include a nut having a first end with a series of internal threads for threaded engagement with a series of external threads of the annular protrusion distal end. The nut has a second end with an inwardly directed shoulder having a front end abutting the stem annular flange and a rear end abutting the nut retaining ring. 
   Still yet another feature of the noted service valve includes the annular protrusion having a series of internal threads located at its distal end. The valve stem further has an annular flange located between the first and second ends, a series of external threads located between the first end and the annular flange, and an annular valley located between the annular flange and the second end for housing a nut retaining ring. The stem external threads abut the annular protrusion internal threads when the valve stem is in the second position. Further, the stem external threads and the annular protrusion internal threads are not engaged in the first and second positions. Yet further, the annular protrusion can have a series of external threads on the outer surface of its distal end for threaded engagement with a series of internal threads of a nut. The nut has a first end having the internal threads and a second end having an inwardly directed shoulder. The shoulder has a front end abutting the stem annular flange and a rear end abutting the nut retaining ring. Still yet, the stem external threads and the annular protrusion internal threads can be of the left-handed variety, whereas the nut internal threads and the annular protrusion external threads can be of the right-handed variety. 
   Yet another feature of the noted service valve has the annular protrusion with a proximal end, a distal end, an outwardly directed radial extension located between the proximal and distal ends, a flat outer surface located between the proximal end and the radial extension, and a series of external threads located between the radial extension and the distal end. The valve stem has an outwardly directed radially extending flange located between the first and second ends, and an outwardly directed radial extension located between the flange and the second end. The service valve also has a nut with a first end, a second end and a series of internal threads located between the first and second ends. The first end has an inwardly directed front shoulder. The second end has an inwardly directed rear shoulder with a front end abutting the stem radially extending flange and a rear end abutting the stem radial extension. The internal threads matingly engage with the annular protrusion external threads. The inner surface of the front shoulder abuts the annular protrusion flat outer surface and the front shoulder contacts the annular protrusion radial extension when the valve stem is in the second position. When the nut is rotated in a first direction, the nut shoulder front end contacts the stem radially extending flange and urges the stem axially towards the valve body. When the nut is rotated in the direction opposite the first direction, the nut shoulder rear end forcedly contacts the stem radial extension and urges the stem axially away from the valve body. 
   Still another feature of the present invention provides a service valve for a refrigerant system comprising a valve body, an annular protrusion extending from the valve body and a valve stem. The valve body has at least one fluid passage integrated therein including a bore and an orifice located at one end of the bore. The annular protrusion is symmetrical about the orifice and has a proximal end affixed to the valve body with an inwardly directed extension which provides a sealing edge. The extension has an inner diameter less than the inner diameter of the remainder of the annular protrusion. The annular protrusion further has a distal end with an internal groove with a base portion, a front wall and a rear wall. The valve stem has a first end, a second end and a bore integrated within. The stem is movable within the annular protrusion between at least a first position in which the orifice is closed when the valve stem first end sealingly abuts the protrusion extension sealing edge and a second position in which the orifice is open, the valve stem first end is offset from the protrusion extension and the valve stem is restricted from moving away from the valve body by the groove rear wall. Yet another feature of this noted service valve has the valve stem including an annular flange, an annular notch, and an annular valley. The flange is located between the first and second ends. The notch is located between the first end and the annular flange and houses a stem retaining ring. The valley is located between the annular flange and the second end and houses a nut retaining ring. The stem retaining ring contacts the groove rear wall when the valve stem is in the second position. Further, the annular protrusion second end can have a series of external threads on its outer surface for threaded engagement with a series of internal threads of a nut. The nut has a first end with the internal threads and a second end with an inwardly directed shoulder. The shoulder has a front end abutting the stem annular flange and a rear end abutting the nut retaining ring. When the nut is rotated in a first direction, the nut shoulder contacts the stem annular flange, urging the stem axially towards the valve body. When the nut is rotated in the direction opposite the first direction, the nut shoulder contacts the nut retaining ring and urges the stem axially away from the valve body. 
   Still a further attribute of the present invention includes having a charge port, in fluid communication with at least one internal passage inside a valve body, with an annular collar, a valve stem, and a nut. The annular collar extends from the valve body and has a proximal end affixed to the valve body with an inwardly directed extension defining a valve seat. The collar further has an external surface with a series of threads located on a portion thereof, and an internal notch for housing a stem retaining ring. The valve stem has a first end, a second end, a bore integrated within, an outwardly directed annular flange located between the first and second ends, a first outwardly directed shoulder located between the annular flange and the first end, and a second outwardly directed nut retaining shoulder located between the annular flange and the second end. The valve stem is moveable within the annular collar between at least a first position in which the stem first end abuts the valve seat and a second position in which the stem first shoulder abuts the stem retaining ring. The nut has a series of internal threads for engagement with the collar series of threads, an inwardly directed shoulder axially affixed to the valve stem between the stem annular flange and the stem nut retaining shoulder. When the nut is rotated in a first direction, the nut shoulder moves the stem axially towards the valve body, and when the nut is rotated in the direction opposite the first direction, the nut shoulder moves the stem axially away from the valve body. 
   Further features and advantages of the present invention will become apparent to those skilled in the art upon review of the following specification in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of a first embodiment for a charge valve according to the present invention. 
       FIG. 2  is a partial sectional view of the valve body bore for receiving the isolated port shown in  FIG. 1 . 
       FIG. 3  is a longitudinal, cross-sectional view of the braze body shown in  FIG. 1 . 
       FIG. 4  is a side, elevational view of the valve stem shown in  FIG. 1 . 
       FIG. 4   a  is a longitudinal, cross-sectional view of the valve stem shown in  FIG. 4 . 
       FIG. 5  is a longitudinal, cross-sectional view of a second embodiment braze body component. 
       FIG. 6  is a side, elevational view of a valve stem according to the second embodiment of the present invention. 
       FIG. 7  is a longitudinal, cross-sectional view of a fourth embodiment braze body component according to the present invention. 
       FIG. 8  is a side, elevational view of a valve stem according to the fifth embodiment of the present invention. 
       FIG. 8   a  is a longitudinal, cross-sectional view of the valve stem shown in  FIG. 8 . 
       FIG. 9  is a longitudinal, cross-sectional view of a braze body component according to the fifth embodiment of the present invention. 
       FIG. 10  is a longitudinal, cross-sectional view of a nut having a crimped end for attachment with a braze body component according to the sixth embodiment of the present invention. 
       FIG. 11  is a side, elevational view of the braze body component according to the sixth embodiment. 
       FIG. 11   a  is a longitudinal, cross-sectional view of the braze body component shown in  FIG. 11 . 
       FIG. 12  is a cross-sectional view of third embodiment of a charge valve according to the present invention. 
       FIG. 13  is a cross-sectional view of a prior art front-seat valve. 
       FIG. 14  is a cross-sectional view of a prior art back seat valve. 
       FIG. 15  is a cross-sectional view of a seventh embodiment for a charge valve according to the present invention. 
       FIG. 16  is a side, elevational view of the braze body component shown in  FIG. 15 . 
       FIG. 16   a  is a longitudinal, cross-sectional view of the braze body component shown in  FIG. 16 . 
       FIG. 17  is a side, elevational view of the nut component shown in  FIG. 15 . 
       FIG. 17   a  is a longitudinal, cross-sectional view of the nut component shown in  FIG. 17 . 
       FIG. 18  is a side, elevational view of the valve stem component shown in  FIG. 15 . 
       FIG. 18   a  is a longitudinal, cross-sectional view of the valve stem component shown in  FIG. 18 . 
       FIG. 19  is a side, elevational view of the isolated port shown in  FIG. 15 , removed from the valve body and without the end cap. 
       FIG. 19   a  is a longitudinal, cross-sectional view of the isolated port shown in  FIG. 19 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings and in particular to  FIGS. 1 through 4   a , one embodiment of a refrigerant service valve  10 , according to the present invention, is shown. Service valve  10  has a unique self-contained isolated port  12  comprised of a valve body  15 , an annular braze body  17 , a valve stem  19 , a nut  23 , and a cap  29 . Isolated port  12  is used for conveniently charging and evacuation of a refrigerant system. Valve body  15  has a plurality of passages  31  integrated within for fluidly communicating and controlling refrigerant. Although the following passages are detailed for sake of description, it should be noted that service valve  10  could have differing passages without limiting the scope of the invention. Passages  31  include a first passage  32  that receives a front seat valve stem  95  which, as is well known in the art and discussed above, seals against valve body  15  in order to control the flow of refrigerant. A second passage  33  and a third passage  34  are also integrated within valve body  15  and receive tubing which leads to componentry, e.g. the evaporator, compressor and condensing unit, of the refrigerant system. Third passage  34  is shown connected with a tube  97  that would lead to such a component. While isolated port  12  will be described in the context of a refrigerant system, it is to be understood that this description is not intended to be limiting. 
   Valve stem  19  has a nose  42  at its front end which sealingly contacts valve body  15  and a rear portion  55  which sealingly fits within the charging conduit. In between, valve stem  19  has an annular groove  44 , an annular notch  46  and an annular valley  48 . Between notch  46  and valley  48  is an outwardly extending annular flange  50 . Adjacent rear portion  55  are external threads  52  which mate with internal threads of cap  29 . Valve stem  19  has an internal longitudinal bore  53  fluidly connected with an internal radial bore  54 . It should be noted that valve stem  19  does not have a valve core  737  as is shown in prior art  FIG. 13 . As discussed above, the elimination of valve core  737  not only expedites the charging and evacuation of refrigerant, but also eliminates a leak path. Valve core  737  has elastomeric seals around its peripheral surface which can leak. 
   Valve body  15  has a first orifice  84  which leads into a braze counter bore  85  to accept a front end  57  of braze body  17 , and a second orifice  88  which lead into a bore  87  having a sealing shoulder  89  onto which the nose  42  of valve stem  19  abuts in order to seal the charge port. Braze body  17  is permanently affixed, e.g. by brazing, to valve body  15  and symmetrically surrounds orifice  88 . Braze body  17  further has a rear end  59  with external threads  61  and an inner annular groove  63 . Annular groove is defined by a front annular wall  64  and a rear annular wall  65 , both having an inner diameter smaller than that of groove  63 . When fully assembled, annular groove  63  forms a cavity  72  with the outer surface of stem  19 , and particularly stem annular notch  46 . Cavity  72  houses a stem retaining ring  67 . Nut  23  has an inwardly directed shoulder  25  having an inner surface that abuts stem annular flange  50  when nut  23  is assembled onto valve stem  19  and internal threads  26  which mate with braze body external threads  61 . When fully assembled, shoulder  25  has an outer surface that contacts a nut retaining ring  75  which rests within stem annular valley  48 . 
   When it is not necessary to charge or evacuate the system, valve stem  19  is in the position shown in  FIG. 1 . By applying torque to nut  23 , valve stem  19  is forced to seal against valve body  15 . Specifically, when nut  23  is threaded (onto braze body  17 ) towards body  15 , nut shoulder  25  pushes valve stem annular flange  50  also towards body  15 . Valve stem nose  42  sealingly abuts valve body shoulder  89  and cap  29  is threaded onto stem external threads  52  so that isolated port  12  is sealed, preventing the escape of refrigerant. 
   In order to charge (or evacuate) the refrigerant system, valve stem nose  42  must be moved away from valve body  15 , and in particular sealing shoulder  89 . When unthreading nut  23  (away from valve body  15 ), shoulder  25  contacts retaining ring  75  and axially moves valve stem  19  away from valve body  15 . Stem  19  is restricted from fully separating from braze body  17  by stem retaining ring  67  located within cavity  72 . As nut  23  is unthreaded, shoulder can push valve stem  19  away from valve body  15  until ring  67  contacts rear wall  65  stopping stem  19  from moving further. When stem  19  is moved away from valve body  15 , an O-ring  77  seals the leak path between stem  19  and braze body  17 . O-ring  77  is located in valve stem annular groove  44 . 
   Refrigerant can be supplied by a conduit, more specifically a hose assembly, having an attached fitting (not shown). When cap  29  is unthreaded and removed from valve stem  19 , the hose assembly fitting is threaded onto valve stem external threads  52 . The fitting seals against the mating surface of valve stem rear portion  55  in order to prevent refrigerant from leaking at this connection. Refrigerant from the hose assembly enters the system through valve stem longitudinal bore  53  and passes through valve stem radial bore  54  before entering valve body  15  through bore  87 . 
   It should be noted that when nut  23  is rotated during its threading towards valve body  15 , in order to seal valve stem  19  against valve body  15 , or rotated during its unthreading, in order to move valve stem  19  away from valve body, valve stem  19  moves axially without rotation. This is important in order to retain the seal between valve stem  19  and the charging conduit assembly. If valve stem  19  were allowed to rotate (with nut  23 ) relative to charging hose assembly, it would begin to unthread from the charging assembly fitting and allow refrigerant to leak. Specifically, when nut  23  rotates during the threading, shoulder  25  pushes valve stem annular flange  50  without causing same to rotate. Annular flange  50 , and the entire stem  19 , moves in the longitudinal direction without any rotation. Further, when nut  23  rotates during the unthreading, shoulder  25  pushes nut retaining ring  75 , and valve stem  19 , away from valve body  15  without rotating valve stem  19 . 
   Another important feature of the present invention is the restriction of valve stem  19  from being completely removed from braze body  17 . It is imperative to prevent the removal of valve stem  19  so that refrigerant does not freely escape from the system. The torque used to remove valve stem  19  from braze body  17  is transmitted from nut  23  to nut retaining ring  75 . Retaining ring  75  is housed within and moves stem  19 . Since stem  19  is axially moving, then so does stem retaining ring  67 . Stem retaining ring  67 , which is housed within cavity  72 , comes in contact with rear wall  65  of braze body inner annular groove  63 , but can not move braze body  17  which is affixed to valve body  15 . In the event of excessive torque to nut  23 , nut retaining ring  75  will fail before stem retaining ring  67  fails. This is due to the fact that, by design, stem retaining ring  67  has a greater resistance to stress than nut retaining ring  75 . When this happens, nut  23  can continue to rotate but the input torque will no longer be transferred to stem  19 . Consequently, valve stem  19  cannot be removed from braze body  15  through over torque (and its resultant movement) of nut  23 . 
   A second embodiment of the present invention is shown in  FIGS. 5 and 6 . Components and features of this embodiment that are identical to that explained above with service valve  10  will retain the same element numbers as above but will not again be discussed for sake of brevity. This embodiment is similar to service valve  10  except that nut  23  and valve stem  19  have been combined into a one-piece valve stem  119 . Valve stem  119  has a hex  123  which replaces the function of nut  23 . Valve stem  119  has external threads  145  which mate with female threads  169  of braze body  117 . By torquing hex  123 , valve stem  119  rotates within braze body  117  and moves towards valve body  15  until stem nose  142  sealingly abuts valve body sealing shoulder  89 . 
   Similar to service valve  10  discussed above, valve stem  119  can not be completely removed from braze body  117 . In order to fluidly communicate stem radial bore  154  with the passages within valve body  15  (during the charging and evacuation steps), stem  119  is rotated away from body  15  by torquing hex  123 . Similar to the above embodiment, braze body  117  has an inner annular groove  163  that forms cavity  72  with stem annular notch  146 . Stem annular notch  146  receives stem retaining ring  67 . When stem  119  is unthreaded from braze body  117 , it moves away from valve body  15 . Stem  119  can no longer move outward when stem retaining ring  67  contacts shoulder  179  of groove  163 . This prevents the unwanted removal of stem  119 . 
   This embodiment provides a lower cost design with fewer components than the embodiment discussed above, but it does not provide the ability of stem  119  to be unthreaded from braze body  117  without the rotation of stem  119  relative to the charging hose assembly. When stem  119  is torqued (e.g. by a wrench) in order to rotate same within braze body  117 , it rotates relative to the charging hose assembly attached at its rear portion  155 . 
   Referring to  FIG. 12 , a third embodiment according to the present invention is shown. Again, components and features of this embodiment that are identical to that explained with service valve  10  will retain the same element numbers as above but will not again be discussed for sake of brevity. This embodiment illustrates a valve body  215  with an annular protrusion  217  integrated in one piece. Annular protrusion  217  is formed by directly machining the braze body features (shown in the previous embodiments) into valve body  215 . This eliminates any joint needed to connect separate components if the braze body and valve body were not of the same piece. This embodiment has the same additional attributes and functionalities as that described above. 
   Referring to  FIGS. 1 ,  2  and  7 , a fourth embodiment according to the present invention is shown. Once again, since changes have been made to few components, and not the entire service valve, components and features of this embodiment that are identical to that explained with service valve  10  will retain the same element numbers as above but will not again be discussed for brevity sake. As discussed above, when valve stem  19  is moved towards valve body  15  so that its stem nose  42  abuts sealing shoulder  89 , valve stem bores, or passages,  53  and  54  are fluidly disconnected from those within valve body  15 . This embodiment has located a sealing diameter within a radially directed extension  387  of braze body  317 . On an edge of extension  387  is a sealing shoulder  389 . Therefore when valve stem  19  is moved completely inwards, stem nose  42  does not abut sealing shoulder  89  (as shown in  FIG. 1 ), but rather abuts braze body sealing shoulder  389 . This eliminates the possibility of the sealing diameter  87  on valve body  15  from becoming misaligned with the braze body during assembly of the braze body within valve body  15 . 
   Referring to FIGS.  1  and  8 - 9 , a fifth embodiment of the present invention is shown. Again, components and features of this embodiment that are identical to that explained with service valve  10  will retain the same element numbers as above but will not be discussed. This embodiment provides a valve stem  419 , having a series of male threads  436 , originally engage with braze body female threads  443  until all male threads  436  have passed female threads  443  so that there is no thread engagement there between during its use. During its operation all stem male threads  436  will be positioned longitudinally between valve body  15  and female threads  443 . When it is necessary to seal valve stem  419  against valve body  15 , nut  23  is torqued, as discussed above, and nut shoulder  25  abuts stem annular flange  450  and axially moves stem  419  so that stem nose  442  sealingly contacts body sealing shoulder  89 . This discontinues any fluid connection between stem bore  454  and passages within valve body  15 . 
   When it is desired to fluidly connect stem bore  454  with the passages within valve body  15 , nut  23  is rotated and unthreaded away from valve body  15 . Nut shoulder  25  contacts nut retaining ring  75 , housed within valve stem annular valley  448 , and axially moves stem  419  away from valve body  15 . It is important to note that valve stem  419  can not be completely removed from braze body  417  on account of threads  436  and  443 . Specifically, stem  419  is moving axially but not rotating so stem male threads  436  do not engage with braze body female threads  443 . Once stem external threads  436  abut with braze body female threads  443 , stem  419  no longer moves axially, since stem external threads  436  have not engaged with braze body female threads  443 . This provides a safety feature in that valve stem  419  is not inadvertently removed from braze body  417  during the rotation of nut  23 . To further provide a safe-guard, threads  436  and  443  can be of the left-handed variety if nut internal threads  26  and braze body external threads  61  are of the right-handed variety. Similarly, threads  436  and  443  can be of the right-handed variety if nut internal threads  26  and braze body external threads  61  are of the left-handed variety. This ensures that when nut  23  is rotated in a first direction (in mating contact with braze body external threads  61 ), valve stem threads  436  can not mate with braze body internal threads  61 . Valve stem  419  would have to be rotated in the opposite direction in order to engage with braze body internal threads  443 . Also, valve stem male threads  436  and braze body female threads  443  can have different thread pitches when compared to the threads on nut  23 . 
   Referring to  FIGS. 1 ,  2 ,  4  and  10 - 11   a , a sixth embodiment according to the present invention is shown. Again, components and features of this embodiment that are identical to that explained with service valve  10  will retain the same element numbers as above but will not be discussed. This embodiment permanently affixes a nut  523  to a braze body  517  by crimping a front shoulder  534  of nut  523  over a shoulder  541  of braze body  517 . Nut  523  is free to swivel on braze body  517 , but is restricted in its axial movement. Similar to the embodiment shown in  FIG. 1 , braze body front end  557  is permanently affixed to valve body  15  within counter bore  85 . When it is desired to bring valve stem  19  into abutment with valve body  15 , nut  523  is rotated, or torqued, towards valve body  15  so that a series of internal threads  526  of nut  523  engage with a series of external threads  561  of braze body  517 . While nut  523  moves towards valve body  15 , the inside surface of nut front shoulder  534  travels on a flat outer surface  581  of braze body  517  away from braze body shoulder  541  and towards braze body front end  557 . Meanwhile nut rear shoulder  525  contacts valve stem annular flange  50  thus causing valve stem  19  to axially move towards valve body  15  until stem nose  42  contacts sealing shoulder  89 . 
   In order to remove stem  19  from valve body  15  (and fluidly connect passages within stem  19  and body  15 ), nut  523  is torqued in the opposite direction and moves away from valve body  15 . In doing so, nut rear shoulder  525  contacts nut retaining ring  75  and axially moves stem  19  away from valve body  15 . When nut  523  moves away from valve body  15 , the inside surface of nut front shoulder  534  travels on braze body flat outer surface  581  towards braze body shoulder  541 . Nut  523  is restricted in its movement away from valve body  15  when nut front shoulder  534  contacts braze body shoulder  541 . Since nut  523  is restricted in its axial movement at this point, so is the travel of stem  19 . Therefore the removal of stem  19  is prevented. It should be noted that the stem retaining ring  67 , shown in  FIG. 1 , is not needed in this embodiment since nut front shoulder  534  provides the same feature. The elimination of stem retaining ring  67  provides for an easier assembly of the components. 
   Referring to  FIGS. 15-19   a , a seventh embodiment of the present invention is shown. Again, components and features of this embodiment that are identical to that explained with service valve  10  will not be discussed in detail. A service valve  610  is shown that retains the main components and features of service valve  10  but has several minor components that have been altered. Again, service valve  610  has an isolated port  612  that is comprised of an annular braze body  617 , a valve stem  619 , a nut  623 , and a cap  629 . Also again, valve stem  619  is axially moved towards and away from a valve body  615  and can not be completely removed from isolated port  612 . Further, isolated port  612  does not contain a valve core as is present with prior art designs. 
   Valve body  615  has a plurality of passages  631  integrated within for fluidly communicating and controlling refrigerant. Although the following passages are detailed for sake of description, it should be noted that service valve  610  of the present invention could have differing passages without limiting the scope of the invention. Passages  631  include a first passage  632  that receives a front seat valve stem  695  which, as is well known in the art and discussed above, seals against valve body  615  in order to control the flow of refrigerant. A second passage  633  and a third passage  634  are also integrated within valve body  615  and receive tubing which leads to componentry, e.g. the evaporator, compressor and condensing unit, of the refrigerant system. Third passage  634  is shown connected with a tube  697  that would lead to such a component. Also included within passages  631  is a first orifice  684  that leads into a braze counter bore  685  and a second orifice  688  that lead into longitudinal bore  686 . Braze body  617  has a proximal end  657  that is permanently affixed, e.g. by brazing, to valve body  615  and symmetrically surrounds both orifice  684  and  688 . 
   Braze body proximal end  657  has a radially inwardly directed extension  687  that defines a sealing shoulder  689 . Braze body  617  has a distal end  659  with external threads  661 . On the inside surface of braze body  617  is an annular groove  644  for housing an O-ring  677  located between proximal end  657  and distal end  659 . Also located on the inside surface of braze body  617  is an annular notch  646  for housing a stem retaining ring  667  located between annular groove  644  and distal end  658 . It should be noted that both groove  644  and notch  646  are now located on braze body  617  which differs from their location within the stem as in the prior embodiments. 
   Nut  623  has a first end  624  and a second end  627 . Nut second end has an inwardly directed shoulder  625  with an inner surface that abuts the outer surface of valve stem  619  when nut  23  is assembled onto valve stem  619 . It should be noted that in  FIG. 17   a  nut shoulder  625  is shown radially offset. During assembly of service valve  610 , nut  623  is slipped over valve stem  619  and nut second end  627  is inwardly moved, or crimped, into permanent position. Shoulder  625  is free to swivel on the outer surface of valve stem  619 , but it is generally locked into place. Nut first end  624  has a series of internal threads  626  which mate with braze body external threads  661 . Nut first end  624  has an outer surface  628 , for example a hexagonal surface, which is engagable with a torque tool in order to rotate nut  623 . 
   Valve stem  619  has a nose  642  at its front end which sealingly contacts sealing shoulder  689  on a radially inwardly directed extension  687  of braze body  617 . As discussed above, since sealing shoulder  689  is located on braze body  617 , the possibility of the sealing interface from becoming misaligned is minimized. Valve stem  619  has a rear portion  655  which sealingly fits within the charging conduit (not shown). Between nose  642  and rear portion  655  is an outwardly extending annular flange  650 . Located between nose  642  and flange  650  is an outwardly extending shoulder  665 . Located between flange  650  and rear portion  655  are external threads  652  which mate with the internal threads of seal cap  629 . When seal cap  629  is removed, threads  652  will mate with the charging hose assembly fitting internal threads. Between threads  652  and flange  650  is a nut retaining shoulder  675 . A valley  648  is located between flange  650  and nut retaining shoulder  675 . When nut  623  is assembled onto stem  619 , nut shoulder  625  is received within valley  648 . As mentioned above, nut  623  is free to rotate about stem  619  but is axially restricted by flange  650  and shoulder  675 . Valve stem  619  has an internal longitudinal bore  653  fluidly connected with an internal radial bore  654 . It should be noted that valve stem  619  does not have a valve core  737  as is shown in prior art  FIG. 13 . As discussed above, the elimination of valve core  737  not only expedites the charging and evacuation of refrigerant, but also eliminates a leak path. Valve core  737  has elastomeric seals around its peripheral surface which can leak. 
   When it is not necessary to charge or evacuate the system, valve stem  619  is in the position shown in  FIG. 15 . By applying torque to nut  623 , valve stem  619  is forced to seal against braze body sealing shoulder  689 . Specifically, when nut  623  is threaded (onto braze body  617 ) towards body  615 , nut shoulder  625  contacts valve stem annular flange  650  and pushes valve stem  619  towards body  15 . When valve stem nose  642  sealingly abuts braze body sealing shoulder  689 , valve stem  619  can no longer move. Cap  629  is then threaded onto stem external threads  652  so that isolated port  612  is sealed, preventing the escape of refrigerant. 
   In order to charge (or evacuate) the refrigerant system, valve stem nose  642  must be moved away from valve body  615 , and in particular sealing shoulder  689 . When unthreading nut  623  (away from valve body  615 ), shoulder  625  contacts nut retaining shoulder  675  and axially moves valve stem  619  away from valve body  615 . Stem  619  is restricted from fully separating from braze body  617  by stem retaining ring  667  located within annular notch  646 . As nut  623  is unthreaded, shoulder  625  can push valve stem  619  away from valve body  615  until stem outwardly extending shoulder  665  contacts stem retaining ring  667  stopping stem  619  from moving further. When stem  619  is moved away from valve body  615 , an O-ring  77  seals the leak path between stem  619  and braze body  617 . O-ring  677  is located in braze body annular groove  644 . 
   Again, it should be noted that when nut  623  is rotated during its threading towards valve body  615 , in order to seal valve stem  619  against braze body sealing shoulder  689 , or rotated in the opposite direction, in order to move valve stem  619  away from valve body  615 , valve stem  619  moves axially without rotation. This is important in order to retain the seal between valve stem threads  652  and the charging assembly fitting (not shown). When it is desired to charge or evacuate the system, the charging assembly fitting is attached to valve stem threads  652 . Then nut  623  is rotated in order to axially move valve stem  619  away from sealing shoulder  689 , thus fluidly connecting passages  653 ,  654  to valve body bore  686 . If valve stem  619  were allowed to rotate (with nut  623 ) relative to charging hose assembly, it would begin to unthread from the charging assembly fitting and allow refrigerant to leak at this connection. To prevent this leakage, when nut  623  rotates in order to seal off isolated port  612 , shoulder  625  pushes valve stem annular flange  650  without causing same to rotate. Annular flange  650 , and the entire stem  619 , moves in the longitudinal direction without any rotation. Further, when nut  623  rotates during the opening of isolated port  612  to bore  686 , shoulder  625  pushes nut retaining  675 , and valve stem  619 , away from valve body  615  without rotating valve stem  615 . It should be noted nut retaining shoulder  675  has replaced the nut retaining ring  75  shown in the prior embodiments. 
   Another important feature of the present invention is the restriction of valve stem  619  from being completely removed from braze body  617 . It is imperative to prevent the removal of valve stem  619  so that refrigerant does not freely escape from the system. The torque used to remove valve stem  619  from braze body  617  is transmitted from nut  623  to nut retaining shoulder  675  thus moving stem  619  and its outwardly extending shoulder  665 . Stem shoulder  665  will contact stem retaining ring  667 , which is housed within fixed brazed body annular notch  646 , and will stop since it can not move braze body  617  which is affixed to valve body  615 . This is the greatest extent of axial movement of valve stem  619  away from valve body  615 . In the event of excessive torque to nut  623 , nut retaining shoulder  675  will fail before stem retaining ring  667  fails. By design, stem retaining ring  667  has a greater resistance to the stress forces than does nut retaining shoulder  675 . When this happens, nut  623  can continue to rotate but the input torque will no longer be transferred to stem  619 . Consequently, valve stem  619  cannot be removed from braze body  615  through over torque (and its resultant movement) of nut  623 . 
   It should be noted that the present invention is not limited to the specified preferred embodiments and principles. Those skilled in the art to which this invention pertains may formulate modifications and alterations to the present invention. These changes, which rely upon the teachings by which this disclosure has advanced, are properly considered within the scope of this invention as defined by the appended claims.