Abstract:
A back pressure valve, comprises: a first housing including a first chamber formed therein having an inlet and an outlet for a first fluid; a second housing including a second chamber formed; a flexible diaphragm having an outer peripheral edge portion abutting the second housing; and closing off the second chamber; a back pressure member moveably disposed in the first chamber of the first housing, wherein the first chamber is defined by the first housing and the back pressure member; wherein the flexible diaphragm is fixed onto and moveable together with the back pressure member, whereby pressure in the second chamber determines fluid pressure required to maintain the back pressure member in a steady position.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a back pressure valve. More particularly, the present invention relates to a combination of a back pressure valve and a pressure controlling device. 
   BACKGROUND OF THE INVENTION 
   Back pressure valves are well known in the art and are generally employed in fluid exhaust lines. A back pressure valve is designed to maintain a given pressure drop across it as a fluid flows past it. Various designs of back pressure valves are available, including a valve that comprises a flexible diaphragm resiliently urged against a valve seat. 
   The basic principle of diaphragm-based back pressure valves is to provide an outlet member with an end or sealing face. A flexible diaphragm is mounted spaced slightly from the sealing face surrounding the outlet member. An adjustable spring is provided for adjusting a load on the diaphragm, pressing the diaphragm against the sealing face. An inlet chamber is usually annular and surrounds the outlet member. Thus, for fluid to flow from the inlet chamber to the outlet member, the fluid pressure must be high enough to displace the diaphragm away from the sealing face, and then fluid flows from the annular inlet chamber across the sealing face to an outlet chamber. If the fluid pressure is too low, then the load or pressure set by the spring maintains the diaphragm pressed against the sealing face. 
   There are a number of problems associated with conventional back pressure valves. Firstly, conventional back pressure valves tend to be large and cumbersome. Secondly, conventional back pressure valves only serve to relieve pressure, and thus do not accurately sense or control the pressure. Accordingly, separate measuring and controlling devices must be provided to work in conjunction with the back pressure valve to maintain a stable pressure. This necessitates additional lines and/or hoses, thus increasing the size and complexity of the system. Additionally, since conventional systems have two separate devices for the relief and control of fluid pressures, the systems tend to be slow acting, and possess inadequate dynamic controllability. In conventional back pressure valves, the area of the diaphragm subject to fluid pressure is larger in the open state than in the closed state, as in the closed state only an outlet annular area is subject to fluid pressure. This again affects the performance of the valve. 
   There remains a need for a back pressure valve with a pressure controlling device that can offer rapid dynamic fluid pressure control, as well as precise and accurate control of fluid pressures in a line. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, there is provided a back pressure valve, comprising: 
   (a) a first housing including a first chamber formed therein having an inlet and an outlet for a first fluid; 
   (b) a second housing including a second chamber formed therein; 
   (c) a flexible diaphragm having an outer peripheral edge portion abutting the second housing; and closing off the second chamber; 
   (d) a back pressure member moveably disposed in the first chamber of the first housing, wherein the first chamber is defined by the first housing and the back pressure member; 
   wherein the flexible diaphragm is fixed onto and moveable together with the back pressure member, whereby pressure in the second chamber determines fluid pressure required to maintain the back pressure member in a steady position. 
   The back pressure member preferably is moveable to a closed position wherein the back pressure member seals off the passage between the fluid inlet from the fluid outlet. 
   The second housing can include at least one port for supply of a second fluid to the second chamber to set the pressure in the second chamber and thereby determine said preset pressure required to maintain the back pressure member in the steady position. 
   In one embodiment, the first housing defines a bore, wherein the fluid inlet and the fluid outlet open into the bore, and wherein the back pressure member is slidably mounted in the bore for movement within the bore. 
   Preferably, the back pressure valve further comprises a sleeve member disposed within the first housing and providing said bore for the back pressure member, the sleeve member being fixed onto the first housing and having an opening that is closed by the back pressure member in the closed position and that permits the fluid to flow from the fluid inlet to the fluid outlet when the back pressure member is in the open position. 
   Preferably, the back pressure valve further comprising a holding means attached to the flexible diaphragm and holding the back pressure member to the diaphragm, whereby the back pressure member and the diaphragm are moveable together. 
   Preferably, the second housing accommodates pressure controlling devices therein. More preferably, the second housing is provided with pressure adjusting mechanism to adjust the pressure in the second chamber. 
   The present invention has many advantages over the prior art. The valve is very compact and thus can be used in applications where size restrictions apply. The valve is more responsive and can dynamically controls the pressure of the fluid, thus allowing rapid changes and providing precise and accurate fluid pressures. This removes the need for additional lines and/or hoses, thus simplifying the overall system and making it more energy efficient and cost effective. 

   
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, which show a preferred embodiment of the present invention and in which: 
       FIG. 1  shows a sectional view of a conventional back pressure valve; 
       FIG. 2   a  shows a longitudinal sectional view of a back pressure valve in accordance with the present invention; 
       FIG. 2   b  shows a perspective sectional view of a back pressure valve in accordance with the present invention; 
       FIG. 3   a  shows a longitudinal sectional view of a back pressure regulator body in accordance with the present invention; 
       FIG. 3   b  shows a perspective view of a back pressure regulator body in accordance with the present invention; 
       FIG. 3   c  shows a perspective sectional view of a back pressure regulator body in accordance with the present invention; 
       FIG. 4   a  shows a longitudinal sectional view of an inner trim assembly in accordance with the present invention; 
       FIG. 4   b  shows a perspective sectional view of an inner trim assembly in accordance with the present invention; 
       FIG. 5   a  shows a longitudinal sectional view of a pressure controller body in accordance with the present invention; and 
       FIG. 5   b  shows a perspective sectional view of a pressure controller body in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a conventional back pressure valve as disclosed in U.S. Pat. No. 5,944,050, with a flexible diaphragm. This conventional back pressure valve has a valve body  10  with a tubular outlet member  30  having an outlet  36  surrounded by an end face  32 , and an annular inlet chamber  28  surrounding the outlet member  30 . The annular inlet chamber  28  has an outer periphery defined by a wall member  26 . The wall member  26  has an end face  54  in a plane spaced away from a plane defined by the end face  34  of the outlet member  30 . 
   A flexible diaphragm  80  has an outer peripheral edge portion clamped between the end face  54  of the wall member  26  and a clamping member  14 . The central portion of the flexible diaphragm  80  is spaced from the end surface of the outlet member  30  when the diaphragm is in an undeflected position. A resilient force applying device, usually a spring  90 , is operable to apply a predetermined force to the diaphragm  80  to cause the diaphragm to be deflected into engagement with the end face  34  of the outlet member  30 . A release device, for example a handle  76 , is operable to remove the force from the diaphragm to permit the diaphragm  80  to move away from the end face  34  of the outlet member  30  and otherwise to regulate or to adjust the force applied by the spring  90 . An aperture  44  is provided in the annular inlet chamber  28 . 
   In operation, the diaphragm  80  is deflected by the spring  90  against the end face  34  of the outlet member  30 , such that the outlet  36  and hence the valve are closed. When the fluid pressure, supplied through an inlet  48 , exceeds a pre-set or reference pressure, the diaphragm  80  is pushed away from the end face  34  against the resilient force of the spring  90 , thus opening the valve. Once the valve is open, fluid flows from the inlet  48  and through the aperture  44  into the inlet chamber  28 . Then, the fluid continues to flow through the outlet  36 , and ultimately exits the valve through the outlet  40 . 
   Referring first to  FIGS. 2   a  and  2   b , different views of a back pressure valve  100  according to the present invention are shown. By way of simplicity, the preferred embodiment will refer to the control and regulation of a gas. However, it is understood that the back pressure valve might be used to control and regulate any fluid, including various gases liquids, vapors or mixtures thereof. 
   Still referring to  FIGS. 2   a  and  2   b , the back pressure valve  100  generally comprises a pressure controller body  200 , a pressure regulator body  330 , and a flexible diaphragm  180  disposed between the controller body  200  and the pressure regulator body  330 . During operation, the valve  100  may be in a substantially vertical position, with the pressure controller body  200  on top of the pressure regulator body  330 . Alternatively, the valve may also be placed in any non-vertical positions, including horizontal position. However, for simplicity in description, the valve will be described in a vertical position, and terms such as “vertical”, “horizontal”, “upper”, “lower”, etc., should be construed accordingly. 
   As shown in  FIGS. 2   a  and  2   b , the pressure regulator body  330  has a regulator inlet  310  and a regulator outlet  320  that are preferably in the form of two connector members that are separate from and attached to the pressure regulator body  330 . Now referring to  FIGS. 3   a - 3   c , different views of the pressure regulator body  330  are shown. Preferably, the pressure regulator body  330  is generally cylindrical, and has a tubular inner space  305  for accommodating an inner trim assembly  150  (not shown in FIG.  3 ). At the upper end of the pressure regulator body  330 , a flange  340  is provided. A plurality of holes  341  are provided around the flange  340  to enable the pressure regulator body  330  to be affixed to the pressure controller body  200 . An annular recess  350  is provided in the central portion of the flange  340 , and is defined by a wall member  351  and a bottom face  352 . The annular recess  350  is axial with the tubular inner space  305 . The central portion of the bottom face  352  is in fluid communication with the tubular inner space  305  of the pressure regulator body  330  while not in operation. Thus, the tubular inner space  305  has a smaller diameter than the annular recess  350 . 
   Still referring to  FIGS. 3   a - 3   c , the tubular inner space  305  has a section at the bottom with a reduced diameter, thereby defining a first shoulder  353 . Optionally, the tubular inner space  305  may have a second shoulder  355  to accommodate the regulator inlet connector  310 . The pressure regular body  330  has a port  360  provided on the side wall thereof. The port  360  is in fluid communication with the tubular inner space  305 , and is adapted to connect to the regulator outlet connector  320 . More particularly, an annular collection channel  306  is provided in the tubular space  305 , for reasons detailed below. On the bottom face  352  of the annular recess  350 , a plurality of holes  354  are provided for affixing the inner trim assembly  150  (not shown) onto the pressure regulator body  330 . Additionally, as shown in  FIGS. 2   a ,  2   b  and  3   a , a tapered bore  362  is provided on the bottom face  352  to accommodate a connector  364  (shown in  FIGS. 2   a, b ). A connector  368  is in fluid communication with the regulator inlet  310 . In operation, the connectors  364  and  368  are in fluid communication with each other, and hence the fluid in the recess  350  and the fluid in the main stream are communicated with each other and possess the same pressure. It is to be understood that the wall of the cylindrical pressure regulator body  330  can be provided with an internal bore to provide communication between diaphragm the recess  350  and the inlet  310 . For simplicity, it is not shown herein. 
   Now referring to  FIGS. 4   a  and  4   b , different views of the inner trim assembly  150  are shown. The inner trim assembly  150  generally comprises a flexible diaphragm  180 , and a valve plug  110 . The diaphragm  180  is clamped between an upper holding plate  181  and a lower holding plate  182 . The diaphragm  180  is preferably circular in shape, and has a plurality of holes  183  provided on the periphery thereof. The plurality of holes  183  are positioned to correspond with the plurality of holes  341  on the flange  340  of the pressure regulator body  330 . Here, the diaphragm  180  has the same diameter as that of the flange  340 . The upper and lower holding plates  181 ,  182  are also circular in shape, and have diameters that are less than the inner diameter of the recess  350  of the pressure regulator body  330 . The valve plug  110  is also cylindrical in shape, and is positioned below the lower holding plate  182 . The upper and lower holding plates  181 ,  182 , the diaphragm  180  and the top end of the valve plug  110  each have a hole in the center thereof, to accommodate a fixing means, such as a screw or the like. In known manner, O rings can be provided between the holding plates  181 , 182  and the valve plug  110 . 
   Still referring to  FIGS. 4   a  and  4   b , as the valve plug  110  extends downwardly in the axial direction, it has a reduced diameter portion  185 . The reduced diameter portion  185  has a retention portion  186  extending radially from the lower end thereof. A first annular, flow channel  187  is defined by the reduced diameter portion  185  and the retention portion  186 . The central portion of the reduced diameter portion  185  continues to extend downwardly, thereby forming an annular recess together with the retention portion  186 . An annular seat disc  190  is disposed in the annular recess and abuts against the end face thereof. The central portion of the reduced diameter portion  185  is provided with a threaded base, on its axis. A fixing means, such as a screw, is inserted into this threaded base, fixing the seat disc  190  and the valve plug  110  together. The lower end of the seat disc  190  has an annular beveled sealing surface  191 . 
   Still referring to  FIGS. 4   a  and  4   b , a sleeve  192  encloses the valve plug  110  and the seat disc  190 . The sleeve  192  has a plurality of lugs  193  and holes  194 , which are positioned to correspond with the plurality of holes  354  on the bottom end face  352  of the recess  350  of the pressure regulator body  330 . Thus, screws or other fixing means are used to affix the sleeve  192  onto the pressure regulator body  330 . A plurality of openings  195  are provided in the side wall of the sleeve  192 , which are positioned to correspond to the first annular channel  187  of the valve plug  110 . A circular shoulder  196  that extends radially inwardly from the inner wall of the sleeve  192  is provided below the openings  195 . The circular shoulder  196  preferably has a beveled or conical sealing surface, for the beveled sealing surface  191  of the seat disc  190 . As such, the seat disc  190  abuts against the circular shoulder  196 , thereby isolating a second flow channel  188  defined by the seat disc  190  and the sleeve  192 , from the first annular flow channel  187 . The lower end of the sleeve  192  has a reduced diameter portion so that a sealing means, such as a gasket  197  or the like, may be disposed around it. The sealing means  197  has substantially the same diameter as that of the sleeve  192 , and is adapted to abut against the first shoulder  353  of the pressure regulator body  330 . The valve plug  110  is slidably fitted into the sleeve  192 . As can be seen in  FIGS. 2 and 4 , an O-ring seal is provided between the valve plug  110  and the sleeve  192  above the openings  195 . 
   Referring now to  FIGS. 5   a  and  5   b , different views of the pressure controller body  200  are shown. The pressure controller body  200  is preferably cylindrical in shape, and has a flange  240  on one end thereof. A plurality of blind holes are provided on the flange  240  (not shown). The plurality of holes are positioned to correspond with the plurality of holes  341  on the flange  340  of the pressure regulator body  330 . Accordingly, fixing means, such as screws or the like, may be used to attach the pressure controller body  200 , the diaphragm  180 , and the pressure regulator body  330  together there. The screws pass through plain holes  341  and engage threaded holes in the flange  240 . 
   Still referring to  FIGS. 5   a  and  5   b , the pressure controller body  200  has a cylindrical chamber  210  formed therein for accommodating pressure sensing and controlling devices  280  (shown in  FIG. 2   a  and  2   b ). Preferably, a reduced diameter portion  211  is formed in the chamber  210 , thereby defining an annular shoulder  212 . A plurality of mounting holes  213  may are provided on the shoulder  212  or radially inner extensions thereof, for mounting pressure controlling devices. The chamber  210  extends downwardly towards the flange  240 . An end wall  214  having a certain thickness is provided at a position adjacent to and spaced from the flange  240 . A recess  260  is thus formed in the central portion of the flange  240 . The recess  260  has a limited depth and shares the end wall  214  with the chamber  210 . A through hole  215  is provided in the center of the end wall  214  fluidly connecting the recess  260  with the chamber  210 . A reference gas inlet  270  is provided around the side wall of the pressure controller body  200  at axial positions corresponding to that of the end wall  214 . The gas inlet  270  extends radially inwardly within the end wall  214  to a certain depth. A plurality of through holes  216  are provided in the end wall  214 . The through holes  216  are in fluid communication with the gas inlet  270 . 
   As can be best seen in  FIG. 2   a , a gas dome  450  is mounted inside the chamber  210  on the end wall  214 , closing the through hole  215  on one side. The gas dome has a generally cylindrical portion and a flange portion  451  on the lower end of the cylindrical portion. A gas inlet valve  440  and a gas outlet valve  460  are mounted on the flange portion  451 . A plurality of holes (not shown) are provided on the flange portion  451 . Some of the holes fluidly communicate between through holes  216  and the inlet (not shown) of the gas inlet valve  440 , while the others fluidly communicate between the outlet (not shown) of the gas inlet valve  440  and the gas dome  450 . Therefore, reference gas enters the pressure controller body  200  through the gas inlet  270  and flow along through holes  216 , through holes on the flange  451 . From here, the gas flows through the gas inlet valve  440  into the gas dome  450  which in turn communicates with the recess  260  via the through hole  215 . Therefore, the gas flows to the recess  260  and applies reference pressure on one side of the diaphragm  180 . 
   A reference gas outlet is also provided on the side wall of the pressure controller body. Particularly, since in this embodiment, the outlet is not in the same cross section as the inlet  270 , it is not shown in  FIG. 2   a . However, it is to be understood that similar arrangement of flow path is provided between the gas dome  450  and the gas outlet. Pressure controlling devices  280  are disposed above the gas dome and control the gas inlet valve  440  and gas outlet valve  460  to adjust the reference gas pressure supplied to the gas dome  450 . In addition, at least one port (not shown) for wires of the pressure controlling devices is provided on the side wall of the pressure control body  200 . The pressure controlling devices  280  are in electronic communication with a processor, such as a computer  400  to transfer signals to and receive commands from the computer  400 . 
   Referring now to  FIGS. 2   a  and  2   b , the open end of the chamber  210  of the pressure controller body  200  is closed by a cap  201 . In operation, the pressure controller body  200  is mounted on top of the pressure regulator body  330  with the flexible diaphragm  180  being clamped between the flange  240  of the pressure controller body  200  and the flange  340  of the pressure regulator body  330 . The gas inlet  270  is then in fluid communication with an external reference gas source (not shown) with a known reference pressure, and the interior of the gas dome  450  and the recess  260  form a second chamber, whose internal reference gas pressure is applied to the diaphragm  180 . Therefore, the diaphragm  180  is subjected to a controlled pressure on the pressure controller side. 
   As shown in  FIG. 2   a , during operation, the incoming fluid enters the back pressure valve  100  through the inlet connector  310  of the pressure regulator body  330 . Under steady conditions, that is, when the valve plug  110  is stationary at a certain position with respect to the sleeve  192 , the forces applied on the valve plug  110  by the incoming fluid pressure and the reference pressure of the gas in the gas dome  450  satisfy a certain condition under which the system reaches equilibrium. The incoming fluid flows through the second flow channel  188 , around the end of the valve plug  110  and into the first, annular flow channel  187 . From the flow channel  187 , the fluid flows through port  360  via openings  195  in the sleeve  192  and through the annular collection channel  306  and the port  360  the outlet connector  320 , and ultimately exits the valve through the outlet connector  320 . 
   By adjusting the set points in the computer  400 , the computer will instruct the controlling devices  280  to actuate the gas inlet and outlet valves  440 ,  460  and hence adjust the reference pressure applied on the diaphragm  180  by the gas in the gas dome  450 . As the reference pressure changes, the valve plug  110  may correspondingly move upward or downward since the diaphragm  180  is flexible, thereby adjusting the incoming fluid pressure by changing the flow path between the first flow channel  187  and the opening  195 . When the valve plug  110  reaches a new equilibrium at a new position with respect to the sleeve  192 , the incoming fluid pressure will be adjusted to a desired value. While the valve  100  is in the closed position, the bevel sealing surface  191  of the seat disc  190  presses against the bevel plane of the shoulder  196  of the sleeve  192 . The valve plug  110  may reach equilibrium at any position with respect to the sleeve  192  and therefore, the incoming fluid pressure can be adjusted by changing the pressure of the reference gas. A pressure transducer  420  may be provided downstream of the pressure regulator to provide feedback signal to the pressure controlling device in the pressure controller body  200 . 
   The present invention has many advantages over the prior art. The valve is very compact and thus can be used in applications where size restrictions apply. The valve is more responsive and can dynamically controls the pressure of the fluid, thus allowing rapid changes and providing precise and accurate fluid pressures. This removes the need for additional lines and/or hoses, thus simplifying the overall system and making it more energy efficient and cost effective. 
   While the above description constitutes the preferred embodiments, it will be appreciated that the present invention is susceptible to modification and change without departing from the fair meaning of the proper scope of the accompanying claims. For example, the shape of the present invention may be modified without affecting the operability of the device. The reference fluid may be any liquid instead of gas. It should be appreciated that the pressure sensing and controlling devices do not form part of the present invention. 
   It will be understood that the pressure regulator body  330  provides a first housing for the fluid whose flow is to be regulated, i.e. a first fluid. Correspondingly, the pressure controller body  200  provides a second housing, the recess  260  of which at least partially defines the second chamber. The upper part of the pressure controller body  200  forms another chamber.