Abstract:
The present invention provides devices and methods for controlling the flow of fluids in very high pressure situations. The devices feature valve shafts having bearings and pins to hold stator surfaces and rotor surfaces in proper alignment.

Description:
RELATED APPLICATIONS 
   This application claims benefit of and is a continuation of International Application No. PCT/US2004/037640, filed Nov. 10, 2004 and designating the United States, which claims benefit of a priority to U.S. Provisional Application Ser. No. 60/523,165, filed Nov. 10, 2003. The contents of these applications are expressly incorporated herein by reference in its entirety. 

   FIELD OF THE INVENTION 
   The invention relates a to devices and methods for controlling the flow of fluid in a conduit. And, in particular, embodiments of the present invention relate to valves for high pressure applications such as ultra high pressure chromatography. 
   BACKGROUND OF THE INVENTION 
   High pressure valves have been used in analytical processes and chromatographic processes in particular. There has been interest in applying higher pressures to obtain faster separations and increase through put. However, at ultra high pressures valves and other components become less reliable. 
   As used herein, the term “chromatographic processes” refers to processes that separate one compound from another compound as a result of difference in the affinity of the compounds to a stationary phase as the compounds travel in or around such phase. 
   The term high pressure chromatography refers to chromatographic processes which use pressures up to and including four thousand pounds per square inch. Ultra high pressure chromatography refers to chromatography processes which use pressures of greater than four thousand pounds per square inch. 
   As pumps and detectors used in analytical processes are operated at higher pressures, components of such equipment exhibit higher rates of failure. The loads on seals, bearing elements, springs and motors is greater. The torque required to turn shafts and axles is greater. As loads increase, alignment and positioning of flow control and sealing features becomes more critical to valve performance and useful lifetime. 
   It is desirable to have valves that can operate precisely and reliably at very high pressure for chromatography. It is desirable to have a valve that can be serviced to replace parts and components which experience wear and deterioration and retain other elements which remain fully functional. 
   SUMMARY OF THE INVENTION 
   Embodiments of the present invention are directed to a device and methods for controlling the flow of fluid in a conduit and methods of making and servicing such a device. The device and methods have particular application in the field of chromatography. However, those skilled in the art of fluidics will recognize the wide application of the devices and methods of the present invention. 
   One embodiment of the present invention is directed to a device, such as a valve, for controlling the flow of fluid in a conduit. The device comprises a cartridge housing, a valve shaft, valve shaft bearings, a rotor, a stator and pressure means for pressing the rotor against the stator. 
   The cartridge housing has an interior wall, an exterior wall and an end wall. The interior wall defines a substantially cylindrical chamber. The chamber has a first end, a second end, a chamber axis and at least one diameter. The end wall is at one of the ends and has a bearing opening. 
   The valve shaft is within the chamber. The valve shaft is capable of rotation and has a valve shaft axis of rotation aligned with the chamber axis. The valve shaft bearings are held in the bearing opening and receive the valve shaft for rotation. 
   The rotor is coupled to the valve shaft for rotation, positioned at the end of the chamber opposite the end wall. The rotor has a rotor bearing surface having one or more fluid channels. 
   The stator has at least one stator exterior surface and at least one stator interior surface. The stator interior surface has a stator bearing surface for receiving the rotor bearing surface. The rotor bearing surface and the stator bearing surface cooperate to allow the rotor bearing surface to rotate in relation to the stator bearing surface. The stator is received and fixed about the end of the chamber opposite the end wall. The stator has at least two stator fluid openings. Each of the stator fluid openings extends from the stator exterior to the rotor bearing surface. In alignment with said one or more channels of the rotor, the opening define an open position upon the rotor assuming a first position. And, in alignment with a rotor bearing surface without one or more channels, upon the rotor assuming a second position, the opening have a closed position. Thus, the rotor and the stator have a first position, defining an open position, in which fluids are received in one of the stator fluid openings and flow through the channel and out a second stator fluid opening. And, the stator and the rotor have a closed position in which fluids are prevented from flowing from one stator fluid opening to the other stator fluid opening by means of the rotor bearing surface. 
   The device has pressure means for pressing said rotor bearing surface against said housing bearing surface such that rotation of the valve shaft and rotor allows fluid flow in one valve shaft position and does not allow fluid flow in a second valve shaft position. The pressure means engage said end wall and said valve shaft. Preferably, the pressure means comprises sealing and pressure springs. 
   Preferably, the device has stator retaining means securing said stator to the cartridge housing. And, preferably the stator retaining means releasably secures the stator to the cartridge housing to allow the rotor pressure means and shaft to be slidably received in the cartridge housing chamber, and the rotor stacked on the shaft. The stator retaining means preferable is selected from clamps screw fittings and the like. One preferred stator retaining means comprises one or more screws which cooperate with one or more screw openings in the stator and one or more threaded openings in cartridge housing. 
   Preferably, the device further comprising a rotor pin and wherein the rotor has a rotor pin opening, the stator has a stator pin opening and the shaft has a shaft pin opening. The rotor pin extends through the rotor opening and into the shaft pin opening and the stator pin opening to align the channels of the rotor with said stator fluid openings. 
   Preferably, the rotor and shaft are keyed. For example, the keying may comprise a shaft having an end hub and the end hub has means for keying the rotor such that said rotor rotates with said rotor shaft. The keying comprises at least one key opening having a position in at least one of the group selected from the rotor and the end hub. The key opening cooperates with and receives a key pin associated with the rotor and end hub that does not have the key opening or extends through key openings in the rotor and end hub. 
   Preferably, at least one of the group selected from said rotor and said shaft has stop means for preventing angular rotation of the rotor with respect to the housing. This provides means for placing the rotor at the first and/or second positions. One stop means comprises a stop element projecting from the cylindrical wall of the cartridge housing. At least one of the rotor and the shaft has stop abutment surfaces that abut against the stop element to prevent rotation. Preferably, The key pin has a stop abutment surface and the cartridge housing has a stop element projecting from the cylindrical wall. And, preferably, the abutment surface is an alignment pin extending through the cartridge housing into the chamber. 
   Preferably, at least one of the group selected from the rotor and shaft have position sensing means. The position sensing means produces a signal when the rotor is in the first position or second position. And, even more preferably, the position sensing means produces a first signal when the rotor is in the first position and a second signal when said rotor is in the second position. The position sensing means is for communication with control means. Individuals skilled in the art will recognize control means as computer processing units, CPUs, with appropriate memory and software. The control means receives the signal to determine the position of the rotor. 
   A preferred position sensing means comprises an optical sensor and light emitter associated with the housing and at least one of the group selected from the shaft and rotor. For example, the shaft and rotor have markings detectable by the optical sensor when illuminated by the light emitter in the nature of bar code readers. A preferred light emitter and optical sensor are affixed to the exterior of the cartridge housing and the cartridge housing has at least one window means in communication with the light emitter and optical sensor to allow light to enter and leave the chamber after illuminating the rotor or shaft. 
   Preferably, the pressure means comprises at least one spring and sealing means. Preferably, the spring is a floating spring substantially encircling the shaft. As used herein “floating” means that the spring is not secured to the shaft or housing and does not influence rotation. One preferred spring is a belleville assembly. A belleville assembly comprises stacked spring washers having a conical shape which exerts a inward and outward sealing force on the cylindrical wall and shaft when compressed. Preferably, the assembly comprises a thrust bearing allowing rotation without twisting the rotor from the stator. 
   Preferably, the shaft has a spring hub, for receiving the spring or belleville assembly. 
   Preferably, the pressure means is adjustable. One embodiment of the present invention features adjustment means comprising an adjustment load spider. The adjustment load spider has legs which cooperate with spider openings in the end wall of the housing. The legs and the openings have cooperating threads. Or, and the alternative the adjustment means comprises an adjustment load spider and the end wall of the housing has a load nut opening. The housing has means for receiving a load nut in communication with the spider to adjust the compression of the spring. For example, the housing has a load nut recess, and the load nut recess has threads for receiving said load nut. The load nut is tightened or loosened to adjust the compression of the springs held in the chamber via the spider&#39;s legs through spider openings in the end wall of the housing. The pressure means exerts a pressure on the rotor and stator to maintain a substantially closed system in pressure ranging from 4,000 psi and up. Pressures of up to 40,000 psi may be attained with some embodiments of the present device. 
   Preferably, the shaft has a toothed coupling for receiving cooperating toothed coupling on a power shaft. And, preferably the power shaft is associated with a transmission for receiving power from a motor. One embodiment of the present invention features a second housing having a first section and a second section. The first section holds the first housing. The second section comprises at least one interior wall, one exterior wall and one end wall. The interior wall defines a cylindrical chamber, and the end wall terminates the chamber. The end wall has an opening for receiving the power shaft. The chamber contains one or more gears constructed and arranged to transfer rotational force from a motor to the power shaft in the manner of a transmission. 
   Preferably, the device further comprises a motor coupled to the transmission to rotate the power shaft. 
   Preferably, the shaft sensing means comprises a encoder disk and an encoder. The encoder is affixed to the interior wall of the second housing and the encoder disk is received on the power shaft. The encoder disk has positioning indicia which correlate to the position of the power shaft. Preferably, the encoder disk has an indent which is sized to cooperate with the encoder chip, when such encoder chip is fitted to the interior wall, to allow such encoded disk to be placed in position axially. 
   Preferably, the device second housing contains power shaft sensing means. The power shaft sensing means producing one or more signals in response to the rotational position of the power shaft. 
   Preferably, the device has memory means recording the operation of the valve. The memory device is capable of communication with a computer to monitor the number of operations performed to give notice when routine maintenance would be in order. 
   A further embodiment of the present invention comprises a method of making a device for controlling the flow of fluids in a conduit. The method comprises the steps of providing a cartridge housing having an interior wall, an exterior wall and an end wall. The interior wall defines a substantially cylindrical chamber. The chamber has a first end, a second end, a chamber axis and at least one diameter. The end wall is at one of the ends and has a bearing opening. The method further comprises the step of fitting valve shaft bearings in the bearing opening. Next, pressure means is fitted about the valve shaft. And, the valve shaft placed for rotation within the chamber. The valve shaft is capable of rotation and has a valve shaft axis of rotation aligned with the chamber axis. The pressure means is for pressing a rotor bearing surface against a stator bearing surface such that rotation of the valve shaft and rotor allows fluid flow in one valve shaft position and does not allow fluid flow in a second valve shaft position. The pressure means engage said end wall and said valve shaft. Preferably, the pressure means comprises sealing and pressure springs. Next, the rotor is coupled to the valve shaft for rotation, positioned at the end of the chamber opposite the end wall. The rotor has a rotor bearing surface having one or more channels. A stator is fitted to the cartridge housing. The stator has at least one stator exterior surface and at least one stator interior surface. The stator interior surface has a stator bearing surface for receiving the rotor bearing surface. The rotor bearing surface and the stator bearing surface cooperate to allow the rotor bearing surface to rotate in relation to the stator bearing surface. The stator is received and fixed about the end of the chamber opposite the end wall. The stator has at least two stator fluid openings. Each of the stator fluid openings extends from the stator exterior to the rotor bearing surface. In alignment with said one or more channels of the rotor, the opening define an open position upon the rotor assuming a first position. And, in alignment with a rotor bearing surface without one or more channels, upon the rotor assuming a second position, the opening have a closed position. Thus, the rotor and the stator have a first position, defining an open position, in which fluids are received in one of the stator fluid openings and flow through the channel and out a second stator fluid opening. And, the stator and the rotor have a closed position in which fluids are prevented from flowing from one stator fluid opening to the other stator fluid opening by means of the rotor bearing surface. 
   Preferably, the method uses stator retaining means securing said stator to the cartridge housing. And, preferably the stator retaining means releasably secures the stator to the cartridge housing to allow the rotor pressure means and shaft to be slidably received in the cartridge housing chamber, and the rotor stacked on the shaft. Thus the device can be dismantled for servicing. 
   Preferably, the method further comprises fitting a rotor pin. In this embodiment the rotor has a rotor pin opening, the stator has a stator pin opening and the shaft has a shaft pin opening. The rotor pin extends through the rotor opening and into the shaft pin opening and the stator pin opening to align the channels of the rotor with said stator fluid openings. 
   Preferably, the method further comprises the step of affixing the rotor and valve shaft by fitting a key. For example, the keying may comprise a shaft having an end hub and the end hub has means for keying the rotor such that said rotor rotates with said rotor. Preferably, the keying comprises at least one key opening having a position in at least one of the group selected from the rotor and the end hub. The key opening cooperates with and receives a key pin associated with the rotor and end hub that does not have the key opening or extends through key openings in the rotor and end hub. 
   Preferably, the method comprises the step of fitting stop means. At least one of the group selected from said rotor and said shaft has stop means for preventing angular rotation of the rotor with respect to the housing. This provides means for placing the rotor at the first and/or second positions. One stop means comprises a stop element projecting from the cylindrical wall of the cartridge housing. At least one of the rotor and the shaft has stop abutment surfaces that abut against the stop element to prevent rotation. Preferably, The key pin has a stop abutment surface and the cartridge housing has a stop element projecting from the cylindrical wall. And, preferably, the abutment surface is an abutment pin extending through the cartridge housing into the chamber. 
   Preferably, the method further comprises one or more of the following fitting a position sensing means, control means, transmission means and motor means. 
   A further embodiment of the present invention is directed to a method of controlling the flow of fluid in a conduit. The method comprises the steps of providing in the conduit a device having a cartridge housing, a valve shaft, valve shaft bearings, a rotor, a stator and pressure means for pressing the stator against the rotor as described above. 
   These and other features and advantages of the present invention will be apparent to individuals skilled in the art upon studying the drawings and detailed description that follow. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  depicts in cutaway quarter section a device embodying features of the present invention; 
       FIG. 2  depicts a rotor embodying features of the present invention; 
       FIG. 3  depicts in cutaway quarter section a device embodying features of the present invention; 
       FIG. 4  depicts in cutaway quarter section a device embodying features of the present invention; 
       FIG. 5  depicts in partial cutaway quarter section a device embodying features of the present invention; and, 
       FIG. 6  depicts in cutaway a device embodying features of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Embodiments of the present invention will be described in detail as a device and methods for controlling the flow of fluid in a conduit and methods of making and servicing such a device. The device and methods have particular application in the field of chromatography. However, those skilled in the art of fluidics will recognize the wide application of the devices and methods of the present invention in areas other than chromatography and analytical processes. Indeed, embodiments of the present invention have application wherever valves are used. 
   Embodiment of the present invention, directed to a device, such as a valve, for controlling the flow of fluid in a conduit will be described in detail with respect to the Figures. Turning now to  FIG. 1 , a device  11 , embodying features of the present invention is depicted. The device  11  comprises a cartridge housing  13 , a valve shaft  15 , valve shaft bearings  17  A &amp; B, a rotor  19 , a stator  21  and pressure means  25  for pressing the rotor  19  against the stator  21 . 
   Cartridge housing  13  has an interior wall  27 , an exterior wall  29  and an end wall  31 . The interior wall  27  defines a substantially cylindrical chamber  33 . The chamber  33  has a first end  35 , a second end  37 , a chamber axis  41  and at least one diameter  43 . The end wall  31  is at one of the ends  37  and has a bearing opening  39 . 
   Valve shaft  15  is held within the chamber  33 . Valve shaft  15  is capable of rotation and has a valve shaft axis of rotation aligned with the chamber axis  41 . Valve shaft bearing  17 A is held in the bearing opening  39  and receives valve shaft  15  for rotation. Valve shaft bearing  7 B is held in end  35  of chamber  33  opposite the end wall  27 . 
   Valve shaft  15  is held in valves shaft bearing  17  A &amp; B. Rotor  19  is affixed to valve shaft  15 , proximal to stator  21 , for rotation, positioned at the end  35  of the chamber  33  opposite the end wall  27 . Turning briefly to  FIG. 2 , rotor  19  has a rotor bearing surface  45  having one or more channels  47  of which only one is depicted. 
   The stator  21  has at least one stator exterior surface  51  and at least one stator interior surface  53 . The stator interior surface  53  has a stator bearing surface  55  for receiving the rotor bearing surface  45 . The rotor bearing surface  45  and the stator bearing surface  55  cooperate to allow the rotor bearing surface  45  to rotate in relation to the stator bearing surface  55 . 
   Stator  21  is received and fixed about the end  35  of the chamber  33  opposite the end wall  31 . Stator  21  has at least two stator fluid openings  57  of which only one is shown in  FIG. 1 . Each of the stator fluid openings  57  extends from the stator exterior  51  to the rotor bearing surface  55 . In alignment with said one or more channels  47  of the rotor  19 , the openings  57  define an open position upon the rotor  19  assuming a first position. This first position is depicted in  FIG. 2  where circles  57   a  represent opening  57  at the end of channel  47 . 
   And, in alignment with a rotor bearing surface  45 , in which the opening  57  are not in communication with one or more channels, as depicted in  FIG. 2  by the circles  57   b , upon the rotor assuming a second position, the opening  57  have a closed position. Thus, rotor  19  and stator  21  have a first position, defining an open position, in which fluids are received in one of the stator fluid openings  57  and flow through channel  47  and out a second stator fluid opening  57 . And, stator  21  and the rotor  19  have a closed position in which fluids are prevented from flowing from one stator fluid opening  57  to the other stator fluid opening  57  by means of the rotor bearing surface  45 . 
   Device  11  has pressure means  25  for pressing said rotor bearing surface  45  against stator bearing surface  55  such that rotation of the valve shaft  15  and rotor  19  allows fluid flow in one valve shaft position and does not allow fluid flow in a second valve shaft position. The pressure means  25  engages the end wall  31  and valve shaft  15 . Preferably, pressure means  25  comprises bearings and springs. Preferably, the springs are floating, substantially encircling the shaft. As used herein “floating” means that the spring is not secured to the shaft or housing and does not influence rotation. One preferred spring and seal is a belleville assembly  61 . A belleville assembly  61  comprises stacked spring washers  63 . Each spring washer  63  has a conical shape which exerts a inward force on the valve shaft  15  and an outward sealing force on the loading nut  77  when compressed. The amount of compression that the belleville assembly can resist and reassert on the rotor  19  is controlled by the number and placement of the washers  63  in chamber  33 . Preferably, the belleville assembly  63  comprises a thrust bearing  65  allowing rotation of valve shaft  15  without undue friction. 
   Valve shaft  15  has a shoulder  71 , for receiving the spring washers  63  of belleville assembly  61 . 
   Preferably, the pressure means  21  is adjustable. One embodiment of the present invention features adjustment means  77  comprising an adjustment load nut  87  and load spider  79 . The adjustment load nut  87  has threads which cooperate with threads in cartridge housing  13 . The spider washer  79  has legs which co-operate with slots  81  in the end wall  31  of the cartridge housing  13 . In the alternative, as depicted, the adjustment means  77  comprises an adjustment load spider  79  and the end wall  31  of the housing  13  has a load nut opening  85 . The cartridge housing  13  has a threaded load nut recess  85  for receiving a load nut  87  in communication with the adjustment load spider  79  to adjust the compression of the belleville assembly  61 . The load nut  87  is tightened or loosened to adjust the compression of the springs  63  held in the chamber. The pressure means exerts a pressure on the rotor  19  and stator  21  to maintain a substantially closed system in pressure ranging from 4,000 psi and up. Pressures of up to 40,000 psi may be attained with some embodiments of the present device  11 . 
   Stator retaining means  95  releasably secures the stator  21  to the cartridge housing  13 . The stator retaining means  95  is selected from clamps [not shown], screw fittings and the like. As depicted stator retaining means  95  comprises one or more screws which cooperate with one or more screw openings  97  in stator  21  and one or more threaded openings  99  in cartridge housing  13 . Stator retaining means releasably secures the stator  21  to the cartridge housing  13  to allow pressure means  25  and valve shaft  15  to be slidably received in the cartridge housing chamber  33 , and the rotor  19  stacked on the valve shaft  15 . 
   A rotor pin  103  is received in stator pin opening  104 , rotor pin opening  105 , and shaft pin opening  109 . The rotor pin  103  extends from stator pin opening  104  through the rotor opening  105  and into the shaft pin opening  109  to align the channels  47  of the rotor  19  with said stator fluid openings  57 . 
   Rotor  19  and valve shaft  15  are keyed for unison rotation. As depicted in  FIG. 1 , valve shaft  15  has an integral end hub  111 . End hub  111  has at least one hub key opening  113  and rotor  19  has at least one rotor key opening  115 . The hub key opening  113  and rotor key opening cooperate and receives a key pin  117 . In the alternative, the rotor  19  and end hub  111  have other key means such as interfitting knobs and indents, or teeth. 
   As depicted in  FIG. 1 , rotor  19  and valve shaft  15  have stop means  129  for preventing angular rotation with respect to the cartridge housing  13 . Stop means  129  facilitates placing the rotor  19  at the first and/or second positions. Stop means  129  comprises a stop pin projecting from the cylindrical wall  33  of the cartridge housing  13 . Rotor  19  and the valve shaft  15  have stop abutment surfaces that abut against the stop pin  129  to prevent rotation. Key pin  117  has a stop abutment surface constructed and arranged to cooperate with stop pin  129 . Preferably, stop pin  129  extends through the cartridge housing  13  into the exterior to provide angular position of the cartridge assembly  11  in the housing. 
   Valve shaft  15  has a toothed coupling  177  for receiving cooperating toothed coupling  119  on a power shaft  121 , as best seen in  FIG. 3 . Power shaft  121  is associated with a transmission  123  for receiving power from a motor  170 . As depicted device  11  further comprises a second housing  131  having a first section  133  and a second section  135 . The first section  133  holds the cartridge housing  13 . The rotor  19  position is oriented in the housing  131 . The centering ring  139  provides center location of the cartridge assembly  11  in the second housing  131 , as best seen in  FIG. 3 . The second section  135  defines a cylindrical chamber  137  for containing one or more gears  123  constructed and arranged to transfer rotational force from a motor  171  to the power shaft  121  in the manner of a transmission. 
   Stop pin  129  cooperates with a centering groove  146  in the second housing  131  to facilitate the mounting of the cartridge housing  13  in the second housing  131 . A centering ring  139  and ring spring  139   a  centers and aligns the cartridge housing  13  in the second housing  131 . Centering ring  139  is affixed to second housing  131  by cooperating threads [not shown] or screws and threaded openings [not shown]. 
   The second housing contains power shaft, rotor or valve shaft sensing means.  FIG. 3  depicts power shaft sensing means  141  for producing one or more signals in response to the rotational position of the power shaft  121 . Power shaft sensing means  141  comprises an encoder disc  143  and an encoder chip  145 . Encoder chip  145  is mounted on an encoder chip support  147 . The power shaft sensing means  141  is shielded from the rest of the cartridge housing  13  by an encoder cover  142 . Turning now to  FIG. 6 , the encoder disc  143  has an indent  143   a  sized to allow axial insertion of the encoder disc  143  on the power shaft  121  and rotated into position under the encoder chip  145 . 
   Alternatively, the rotor  19  and valve shaft  15  have means for determining the position of the rotor  19 . Turning now to  FIG. 4 , device  11  is illustrated having an optical sensor and light emitter  151  associated with second housing  133 . Optical sensor and light emitter  151  cooperates with a fiber optic pair  153  extending through an opening in the cartridge housing  13  to illuminate and read marking [not shown] on the valve shaft  15 . Alternatively, the optical sensor and emitter  151  and fiber optic pair  153  cooperate with the markings [not shown] on rotor  19 . Markings, in the form of bar code type markings known in the art, are detectable by the optical sensor when illuminated by the light emitter. 
   The optical sensor and light emitter  151  produces a signal when the rotor  19  is in the first position and a second signal when the rotor is in the second position. The position sensing means  141  and optical sensor and light emitter  151  are in communication with control means [not shown]. Individuals skilled in the art will recognize control means as computer processing units, CPUs, with appropriate memory and software. The control means receives the signal to determine the position of the rotor. 
   Turning now to  FIG. 5 , the device  11  has memory disc  161  attached by means of a cable  163 . The memory disc  161  is capable of communication with a computer to update and monitor the number of operations performed to give notice when routine maintenance would be in order. Memory disc  161  is sold by several vendors such as Dallas Semi conductor. 
   A further embodiment of the present invention comprises a method of making a device  11  for controlling the flow of fluids in a conduit. The method comprises the steps of providing a cartridge housing  13  having an interior wall  27 , an exterior wall  29  and an end wall  31 . The interior wall  27  defines a substantially cylindrical chamber  33 . The chamber  33  has a first end  35 , a second end  37 , a chamber axis  41  and at least one diameter  43 . The end wall  29  is at one of the ends  37  and has a bearing opening  39 . The method further comprises the step of fitting valve shaft bearings  17  in the bearing opening  39 . Next, pressure means  25  is fitted about the valve shaft and the valve shaft  15  is placed within the chamber  33 . The valve shaft  15  is capable of rotation and has a valve shaft axis of rotation aligned with the chamber axis  41 . The pressure means  25  engages end wall  31 , load nut  87  and the valve shaft  15 . Next, the rotor  19  is coupled to the valve shaft  15  for rotation, positioned at the end  35  of the chamber  33  opposite the end wall  31 . The rotor  19  has a rotor bearing surface  45  having one or more channels  47 . A stator  21  is fitted to the cartridge housing  13 . The stator  21  has a stator bearing surface  55  for receiving the rotor bearing surface  45 . The rotor bearing surface  45  and the stator bearing surface  55  cooperate to allow the rotor bearing surface  45  to rotate in relation to the stator bearing surface  55 . The stator  21  is received and fixed about the end of the chamber  33  opposite the end wall  31 . The cartridge housing  13  is fitted to a second housing  133  and a motor  171 . 
   Preferably, the method uses stator retaining means  95  securing said stator  21  to the cartridge housing  13 . And, preferably the stator retaining means  95  releasably secures the stator  21  to the cartridge housing  13  to allow the pressure means  25  and valve shaft  15  to be slidably received and/or removed from chamber  33 . Thus the device can be dismantled for servicing. 
   Preferably, the method further comprises fitting a rotor pin  103  and abutment pin  115 . And, preferably, the spider  79  is adjusted to create an appropriate pressure in the pressure means  25 . And, finally, the second housing  133  having position sensing means, transmission gears  123  and motor  170  is secured to the cartridge housing  13 . 
   A further embodiment of the present invention is directed to a method of controlling the flow of fluid in a conduit. The method is described in relationship to the operation of the device  11 . The method comprises the steps of providing in the conduit a device  11  having a cartridge housing  13 , a valve shaft  15 , valve shaft bearings  17 , a rotor  19 , a stator  21  and pressure means  25  for pressing the stator against the rotor as described above. 
   The stator  21  has at least two stator fluid openings  57 . Each of the stator fluid openings  57  extends from the stator exterior  51  to the rotor bearing surface  45 . In alignment with said one or more channels  47  of the rotor  19 , the openings  57  define an open position upon the rotor  19  assuming a first position. And, in alignment with a rotor bearing surface  45  without one or more channels  47 , upon the rotor assuming a second position, the openings  57  have a closed position. Thus, the rotor  19  and the stator  21  have a first position, defining an open position, in which fluids are received in one of the stator fluid openings  57  and flow through the channel  47  and out a second stator fluid opening  57 . And, the stator  21  and the rotor  19  have a closed position in which fluids are prevented from flowing from one stator fluid opening  57  to the other stator fluid opening  57  by means of the rotor bearing surface  45 . 
   Thus, the present invention has been described with respect to a preferred embodiment with the understanding that the invention should not be limited to such description but should encompass the subject matter of the following claims.