Abstract:
A fluid regulating device includes a regulator valve, an actuator and a pilot regulator valve assembly. The pilot regulator valve assembly provides a pressure load to a surface of a diaphragm of the actuator in response to changes in downstream pressure being applied to the opposite surface of the diaphragm. An upper cavity of the pilot regulator valve assembly is in fluid communication with a control cavity of the actuator, allowing both the actuator diaphragm and the pilot regulator valve assembly diaphragm to simultaneously sense pressure variations within the cavities. As the downstream pressure varies, the diaphragms of both the actuator and the pilot regulator valve assembly displace to regulate the downstream pressure and the pilot regulator valve assembly maintains a load pressure. The regulator further includes a balanced regulator valve applying a balancing force to offset a force of upstream pressure on a balanced valve plug.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure relates to fluid control devices and, more particularly, to diaphragm-based fluid regulators. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    Pressure regulating valves are used in myriad industrial and residential applications for controlling the downstream pressure of a fluid. By controlling downstream pressure, pressure regulating valves compensate for variations in downstream demand. For example, as downstream demand increases, pressure regulating valves open to allow more fluid to flow through the pressure regulating valve, thus maintaining a relatively constant downstream pressure. On the other hand, as downstream demand decreases, pressure regulating valves close to reduce the amount of fluid flowing through the pressure regulating valve, again maintaining a relatively constant downstream pressure. 
         [0003]    Pressure regulating valves can be categorized as either balanced or unbalanced, and different valves are used in different global marketplaces due to variations in emission standards and methods of monitoring the amount of gas supplied. 
         [0004]    For example, a conventional balanced pressure regulator valve that is commonly used in Europe is illustrated in  FIG. 1 . The conventional gas regulator  10  comprises an actuator  12  and a balanced pressure regulator valve  14 . The regulator valve  14  defines an inlet  16 , an outlet  18 , and a valve port  22  disposed between the inlet  16  and the outlet  18 . Gas must pass through the valve port  22  to travel between the inlet  16  and the outlet  18  of the regulator valve  14 . The actuator  12  is coupled to the regulator valve  14  to ensure that the pressure at the outlet  18  of the regulator valve  14 , i.e., the outlet pressure, is in accordance with a desired outlet or control pressure. The actuator  12  includes a control assembly  22  for regulating the outlet pressure of the regulator valve  14  based on sensed outlet pressure. Specifically, the control assembly  22  includes a diaphragm  24 , a connecting post  32 , and a control arm  26  having a valve plug  28 . The diaphragm  24  divides a housing  23  of the actuator  12  into an atmospheric cavity  25  and a control pressure cavity  27 . The control pressure cavity  27  is in fluid communication with the outlet  18  of the regulator valve  14  such that a bottom side of the diaphragm  24  senses the outlet pressure and responds to move the valve plug  28  between open and closed positions. The control assembly  22  further includes a control spring  30  disposed in the atmospheric cavity  25  and in engagement with a top-side of the diaphragm  24  to offset the outlet pressure sensed by the diaphragm  24  in the control pressure cavity  27 . Accordingly, the desired outlet pressure, which may also be referred to as the control pressure, is set by the selection of the control spring  30 . 
         [0005]    One problem with the conventional regulator  10  having the outlet pressure controlled and set by the control spring  30 , however, is that as the valve plug  28  opens or moves away from the valve port  22  to open the valve  14 , the control spring  30  expands or elongates and loses force. As the force is reduced, outlet pressure decreases, resulting in a rated capacity reduction. In other words, the control spring  30  inherently generates less force as it expands towards an uncompressed length when displacing the control arm  26  to open the valve  14 . Additionally, as the control spring  30  expands, the diaphragm  24  deforms, increasing the area of the diaphragm  24 . The decreased force supplied by the control spring  30  and the increased area of the diaphragm  24  combine such that the force provided by the control spring  30  cannot adequately balance the force generated by the diaphragm  24 . As a result, the diaphragm  24  rises and the outlet control pressure falls below the desired control pressure. This phenomenon is known as “droop.” When “droop” occurs, the outlet pressure decreases below its set control pressure, and the amount of fluid transferred while maintaining the outlet pressure range, also known as the rated flow value, also decreases. 
         [0006]    In the United States, attempts to address the effects of “droop” include using a pilot regulator valve to control and adjust the delivery of loading pressure above the diaphragm. Such pilot regulators are typically limited to use with unbalanced regulator valves however, and in general, supply and control the amount of loading pressure applied to the actuator diaphragm during operation of the regulator. For example,  FIG. 2  depicts a conventional regulator  110  for the United States&#39; market having an unbalanced regulator valve  114 , an actuator  112  and a pilot regulator  160  operatively connected to both the regulator valve  114  and the actuator  112 . More specifically, the valve  112  defines an inlet  116 , an outlet  118 , and a valve port  122  disposed between the inlet  116  and the outlet  118 . Gas must pass through the valve port  122  to travel between the inlet  116  and the outlet  118  of the regulator valve  114 . The actuator  112  is coupled to the regulator valve  114  to ensure that the pressure at the outlet  118  of the regulator valve  114 , i.e., the outlet pressure, is in accordance with a desired outlet or control pressure. The actuator  112  includes a control assembly  122  having a diaphragm  124 , a connecting stem  132 , and a control arm  126  having a valve plug  128 . The diaphragm  124  senses the outlet pressure of the regulator valve  114  and provides a response to move the valve plug  128  to open and close the regulator valve  114 . The diaphragm  124  divides the actuator housing into a loading pressure cavity  125  and a control pressure cavity  127 . 
         [0007]    The regulator  110  in  FIG. 2  does not include a control spring in the loading cavity  125 , as the regulator  10  in  FIG. 1  does. Rather, the pilot regulator valve  160  is operatively connected to the actuator  112  to control and adjust the load or loading pressure delivered to the load pressure cavity  125 . Moreover, the pilot regulator valve assembly  160  does this in response to changes in pressure in the control pressure cavity  127  of the actuator  112 . More specifically, the pilot regulator valve assembly  160  includes a body  162  having an inlet  164 , an outlet  166 , and a valve port  168  disposed between the inlet  164  and the outlet  166 . The inlet  164  is in fluid communication with the inlet  116  of the unbalanced regulator valve  114  and the outlet  166  is in fluid communication with the control pressure cavity  125  of the actuator  112 . The pilot regulator valve assembly  160  further includes a bonnet  174  coupled to the body  162 , a valve plug  170  disposed within the body  162 , and a diaphragm  178  disposed within the bonnet  174 . The diaphragm  178  divides the bonnet  174  into a first cavity  179  and a second cavity  181 , wherein the second cavity  181  is operatively coupled to and in fluid communication with the control pressure cavity  127  of the actuator  112  and the first cavity  179  includes a pilot control spring  176 . So configured, the pressure in the control pressure cavity  127  of the actuator  112  is equal to the pressure in the second cavity  181  of the pilot regulator valve assembly  160 , while the pilot control spring  176  offsets or balances the position of the diaphragm  178 . Changes to the control pressure sensed by the diaphragm  178  cause the valve plug  170  to move between a closed position and an open position, for example. Such a configuration allows the pilot regulator valve  160  to control and adjust the loading pressure delivered to the loading pressure chamber  125  of the actuator  112  by responding to minor changes in the control or outlet pressure within the control pressure cavity  127  of the actuator  112 . 
         [0008]    While the effects of “droop” are reduced for the unbalanced regulator valve  114  by using the pilot valve, the unbalanced valve  114  has several drawbacks. For example, unbalanced valves have difficulty withstanding high inlet pressures, and high fluid pressure acting on valve ports  122  with large valve orifices can crush the valve port. As a result, unbalanced valves are not ideal for high pressure, large orifice applications. In addition, unbalanced valves suffer from an undesirable effect known as inlet pressure sensitivity. Inlet pressure sensitivity is a phenomenon in which an unbalanced valve experiences an unintended increase in control pressure as inlet pressure increases. 
         [0009]    In addition, different markets around the world have historically demanded different pressure regulating valves due to variations in emissions standards and methods of monitoring the amount of gas supplied to end users. For example, in the United States, meters typically only monitor the amount of pressure supplied, as such it is important to control the flow rate of pressure, and pilot-operated regulator valves are typically used to do the same. Not many balanced regulator valves, such as the valve depicted in  FIG. 1 , however, are used in the United States because balanced ports often clog the passageways through a throat in the valve, affecting and interfering with the operation of relief valves. Instead, unbalanced regulator valves, such as those operated by a pilot regulator valve and depicted in  FIG. 2 , are more commonly used in the United States. 
         [0010]    In Europe, emissions standards have historically been higher than in the U.S., such that relief valves are not acceptable. As such, balanced ports are typically used because there is not a concern with any clogging of passageways affecting the operation of any relief valves exhausting excess gas into the atmosphere. However, the conventional balanced regulator valves used in Europe, such as the balanced pressure regulator valve depicted in  FIG. 1 , suffer from the problems of “droop,” for example, as explained above. 
       SUMMARY 
       [0011]    One aspect of the present disclosure provides a fluid regulating device, comprising a valve having a first inlet, a first outlet, and a first valve port disposed between the first inlet and the first outlet. The device further includes an actuator coupled to the valve. The actuator has a housing coupled to the valve, and a first valve plug disposed within the valve and adapted for displacement between a closed position engaging the first valve port and an open position disposed away from the first valve port. Moreover the actuator has a balancing diaphragm operatively connected to the first valve plug and having a first side in fluid communication with an inlet pressure at the inlet of the valve, wherein the inlet pressure applies a first force to the first valve plug in the direction of the open position, and the inlet pressure acts on the balancing diaphragm to apply a second force to the first valve plug in a direction of the closed position, the magnitude of the first and second forces being approximately equal, a first diaphragm disposed within the housing and dividing the housing into a loading pressure cavity and a control pressure cavity, the first diaphragm being operatively coupled to the first valve plug and the control pressure cavity being in fluid communication with first outlet of the valve. The device further includes a pilot regulator valve assembly coupled to the actuator. The pilot regulator valve assembly can have a valve body with a second inlet, a second outlet and a second valve port disposed between the second inlet and the second outlet, wherein the second inlet is in fluid communication with the first inlet, and the second outlet is in fluid communication with the loading pressure cavity of actuator housing. Moreover, the pilot regulator valve assembly can include a bonnet coupled to the body, a second valve plug disposed within the body and adapted for displacement between a closed position engaging the second valve port and an open position disposed away from the second valve port, a second diaphragm disposed within the bonnet and dividing the bonnet into an first cavity and a second cavity, the second diaphragm being operatively coupled to the second valve plug, and the second cavity in fluid communication with the control pressure cavity of the actuator, such that a first surface of the first diaphragm of the actuator is in fluid communication with a first surface of the second diaphragm of the pilot regulator valve assembly, and a control spring disposed within the first cavity of the bonnet and engaging a second surface of the second diaphragm. So configured, the second diaphragm and the control spring are configured to cause the second valve plug to move toward the open position when pressure in the second cavity of the bonnet decreases and to cause the second valve plug to move toward the closed position when the pressure in the second cavity of the bonnet increases to maintain a pressure within the load pressure cavity of the actuator that is approximately equal to a predetermined load pressure. Moreover, the actuator is configured to cause the first valve plug to move toward the open position when pressure in the load pressure cavity increases and to cause the first valve plug to move toward its closed position when the pressure in the load pressure cavity decreases to maintain pressure at the first outlet approximately equal to a predetermined setpoint pressure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a side cross-sectional view of a conventional balanced port gas regulator; 
           [0013]      FIG. 2  is a side cross-sectional view of a conventional pilot-operated unbalanced port gas regulator; and 
           [0014]      FIG. 3  is side cross-sectional view of a pilot-operated balanced port gas regulator constructed in accordance with the teachings of the present disclosure. 
       
    
    
       [0015]    While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described in detail below. It should be understood, however, that there is no intention to limit the disclosure to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention. 
       DETAILED DESCRIPTION 
       [0016]    Although the following text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment of the invention since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention. 
         [0017]    Referring now to  FIG. 3 , a gas regulator is generally referred to by reference numeral  210 . The gas regulator  210  generally comprises an actuator  212  and a regulator valve  214 . The regulator valve  214  includes an inlet  216  for receiving gas from a gas distribution system, for example, and an outlet  218  for delivering gas to a facility having one or more appliances, for example. The actuator  212  is coupled to the regulator valve  214  and includes a control assembly  217  having a control element, such as a valve plug  228 . During a first or normal operational mode, the control assembly  217  senses the pressure at the outlet  218  of the regulator valve  214 , i.e., the outlet pressure, and controls a position of the valve plug  228  such that the outlet pressure approximately equals a predetermined setpoint or control pressure. 
         [0018]    The balanced pressure regulator valve  214  includes a body  219  having a passage  221  that fluidly connects the fluid inlet  216  with the fluid outlet  218 . The passage  221  includes a throat  224  in which a valve port  222  is disposed. Gas must travel through the valve port  222  to travel between the inlet  216  and the outlet  218  of the regulator valve  214 . The valve port  222  is removable from the regulator valve  214  such that it may be replaced with a different valve port  222  having a bore of a different diameter or configuration to tailor operational and flow characteristics of the regulator valve  214  to a specific application. 
         [0019]    A load spring  240  is connected to a valve stem  223  that is operatively attached to the balanced valve plug  228 . The plug  228  interacts with the valve port  222  to control fluid flow between the inlet  216  and the outlet  218 . More specifically, the valve plug  228  can include a circumferential recess into which a rubber disc  231  is disposed. The disc  231  of the valve plug  228  contacts the valve port  222  to achieve alignment and sealing engagement between the valve plug  228  and the valve port  222  for closing the valve  214 . 
         [0020]    The present version of the valve plug  228  further includes a balanced plug assembly  244  having a sleeve  246  and a retainer  248 . The sleeve  246  has a hollow bore that helps retain and guide the valve plug  228  as the valve plug  228  reciprocates within the valve body  219  to control fluid flow. The sleeve  246  may have an angled outer surface to enhance clearance within the valve body  219  and/or enhance assembly of the pressure regulator  214 . 
         [0021]    A diaphragm  250  is connected between the valve plug  228  and the sleeve  246 . In this embodiment, the sleeve  246  includes a first sleeve part  246   a  and a second sleeve part  246   b  between which an outer peripheral portion of the diaphragm  250  is sandwiched. 
         [0022]    The retainer  248  attaches the plug  228  to the stem  223 . The retainer  248  may include a fastener, such as a threaded bolt that is operatively attached to a portion of the valve stem  223 . One or more balancing passages or channels  254  are disposed in the plug  228  and fluidly connect passage  221  of the valve body  214  with a balancing chamber  256  defined between the second sleeve part  246   b  of the sleeve  246  and the diaphragm  250 . So configured, fluid forces acting on the valve plug  228  can be balanced by fluid moving through the balancing channels  254  and up to the chamber  256 . More specifically, fluid in the balancing chamber  256  applies a force on the balancing diaphragm  250  toward the valve port  222  to compensate for forces applied to the valve plug  228  away from the valve port  222  due to the upstream pressure at the inlet  216  of the valve  214 . The components of the balanced plug assembly  244  are therefore configured such that the force applied by the balancing diaphragm  250  is approximately opposite in direction and equal in magnitude to the force of the upstream pressure applied to the valve plug  228 . This effectively eliminates any influence of the upstream pressure on the operation of the balanced plug assembly  244 . As such, a more accurate control of the downstream pressure by the gas regulator  210  is achieved. 
         [0023]    As mentioned, the actuator  212  is operatively coupled to the balanced regulator valve  214  and includes a housing  220  having an upper housing component  220   a  and a lower housing component  220   b  secured together with a plurality of fasteners, for example. The lower housing component  220   b  defines a control cavity  227  and an actuator mouth  234 . The actuator mouth  234  is connected to a valve mouth  226  of the balanced regulator valve  214  to provide fluid communication between the actuator  212  and the balanced regulator valve  214 . The upper housing component  230   a  defines a pressure loading cavity  225  and also houses a portion of the control assembly  217 . 
         [0024]    The control assembly  217  includes a diaphragm  224 , a closing spring  230 , and a piston  232  that is operatively connected to both the diaphragm  224  and a control arm  226  having the valve plug  228  operatively attached thereto. The diaphragm  224  includes an opening through which the piston  232  is disposed, and may be constructed of a flexible, substantially air-tight, material. The diaphragm  224  periphery is sealingly secured between the upper and lower housing components  220   a ,  220   b  of the housing  220 . The control assembly  217  further includes an actuator stem  287  that is engaged by the control arm  226  to move the valve stem  223  and valve plug  228  between the open and closed positions as the diaphragm  224  flexes due to variations in the downstream pressure. 
         [0025]    Pressure supplied into the loading pressure cavity  225  acts against the pressure in the control cavity  227 . The pressure in the control cavity  227  is the same pressure at the outlet  218  of the balanced regulator valve  214 . Accordingly, the force or pressure supplied by the actuator  212  sets the outlet pressure to a desired setpoint or control pressure for the regulator  210 . 
         [0026]    To compensate for changes in the outlet pressure during operation, a pilot regulator valve assembly  260  is operatively connected to the actuator  212 . In this version, the body  262  of the pilot regulator valve assembly  260  is attached to the lower housing portion  220   b  of the body  220  of the actuator  212 , thereby forming an integral part of the fluid regulating device  210 . While the pilot regulator valve assembly  260  in this version is described as an integral part of the fluid regulating device  210 , the pilot regulator  260  could alternatively be an external component piped to the actuator  210  for achieving the same function described herein. 
         [0027]    The pilot regulator valve assembly  260  includes a pilot valve  261  and a pilot actuator  271  coupled thereto. The pilot valve  261  includes a body  262  having an inlet  264 , an outlet  266 , and a valve port  268  disposed between the inlet  264  and the outlet  266 . In this version, the inlet  264  is in fluid communication with the inlet  216  of the balanced regulator valve  214 , and the outlet  266  is in fluid communication with the control pressure cavity  225  of the actuator  212 . More specifically, an inlet pressure supply line  267  connects the inlet  264  to the inlet  216  of the balanced regulator valve  214 . In addition, a loading pressure supply line  269  connects the outlet  266  with the loading pressure cavity  225 . 
         [0028]    As further illustrated in  FIG. 3 , the pilot actuator  271  includes a control assembly  273  having a diaphragm  277 , a piston  278 , and a control arm  280  having a valve plug  270 . The pilot actuator  271  further includes a bonnet  274  that is coupled to the body  262  of the pilot valve  261 . The diaphragm  277  is disposed within the bonnet  274  and divides the bonnet  274  into a first or lower cavity  279  and a second or upper cavity  281 . The second or upper cavity  281  is operatively coupled to and in constant fluid communication with the control pressure cavity  227  of the actuator  212 , allowing control pressure to flow within the second or upper cavity  281  and be sensed by the diaphragm  277 . So configured, a bottom surface  224   b  of the diaphragm  224  of the actuator  212  is in fluid communication with a top surface  277   a  of the pilot actuator diaphragm  277 . Moreover, a top surface  224   a  of the diaphragm of the actuator  212  is in fluid communication with the outlet  266  of the pilot valve  261 . Changes to the control pressure sensed by the diaphragm  277  cause the valve plug  270  to move between a closed position and an open position. Such a configuration allows the pilot regulator valve assembly  260  to accurately and precisely control and adjust the loading pressure present in the loading pressure chamber  225  of the actuator  212 , and therefore also present on the top surface  224   a  of the actuator diaphragm  224 , by responding to minor changes in the control or outlet pressure sensed within the second cavity  281  of the pilot actuator bonnet  274 . 
         [0029]    The bonnet  274  further includes a control spring  276  that abuts and engages bottom surface  277   b  of the diaphragm  277 . An adjusting screw  283  is disposed within the bonnet  274  and engages a spring seat  285 . Configured in this way, the force generated by the control spring  276  is adjustable by turning the adjusting screw  283  to raise or lower the spring seat  285 . 
         [0030]      FIG. 3  depicts the regulator  210  of the present disclosure with the valve plug  228  in its closed or lock-up positions. So configured, gas does not flow through the valve port  222  of the regulator valve  214  or through the valve port  268  of the pilot valve  261 . More specifically, when demand is removed from the gas distribution system, e.g., such as when a user shuts off an appliance, pressure in the control cavity  227 , and, thus, the upper cavity  281  of the pilot actuator  271  in fluid communication with the control cavity  227 , increases. As a result, pressure in the second or upper cavity  281  of the pilot actuator  271  is greater than the force applied by the control spring  276  to the diaphragm  277 . Thus, the diaphragm  277  is pushed down, and the valve plug  270  is moved to the left relative to the orientation of  FIG. 3  to the closed position. 
         [0031]    When the pilot valve  261  is in the closed position, the loading pressure supplied by the pilot valve  261  is stopped, and a closed configuration is achieved within the regulator valve  214 . This occurs because the loading pressure, which corresponds to the pressure in the load pressure cavity  225  of the housing  220  and sensed by the diaphragm  224 , is less than the force applied by the pressure in the control cavity  227  of the actuator  212 . Accordingly, the diaphragm  224  and the piston  232  move up and the plug  228  moves to the right relative to the orientation of  FIG. 3  and into the closed position. 
         [0032]    When an operating demand is placed on the gas distribution system, e.g., a user begins operating an appliance such as a furnace, a stove, etc., the appliance draws gas from the outlet  218  and correspondingly the control cavity  227  of the actuator  212  and the upper cavity  281  of the pilot actuator  271 , reducing the pressure that is sensed by the diaphragm  277  of the pilot actuator  271 . This pressure reduction causes a force imbalance to occur between the control spring force and the pressure force on the diaphragm  277  of the pilot actuator  271 , such that the control spring  276  expands and displaces the diaphragm  277  upward relative to the body  262 . The displacement of the diaphragm  277  forces the control arm  280  to rotate counterclockwise, moving the valve stem  272  and valve plug  270  away from the valve port  268 . This open position allows fluid to flow through the valve port  268 , into the line  269  and into the load pressure cavity  225 . The fluid flowing into the load pressure cavity  225  increases the load pressure being applied to the diaphragm  224 . 
         [0033]    As the pressure in the loading pressure cavity  225  increases and the pressure sensed by the control cavity side of the diaphragm  224  decreases, a force imbalance occurs between a load pressure force into the loading pressure cavity  225  and an outlet pressure force on the diaphragm  224 . As a result, the diaphragm  224  moves downward relative to the housing  220 , causing the piston  232  to be displaced downward as well. This causes the control arm  226  to pivot in a counterclockwise direction, allowing the actuator stem  223  and the valve plug  228  to move away from the valve port  222 , and the regulator valve  214  to be opened 
         [0034]    When the downstream demand is removed from the gas distribution system, such as when the user shuts off the appliance, outlet pressure will increase and pressure in the control cavity  227  will increase. Because the control cavity  227  is in fluid communication with the upper cavity  281  of the pilot actuator  271 , the increased pressure sensed by the diaphragm  277  in the upper cavity  281  moves the diaphragm  277  and the piston  278  downward relative to the housing  262 , causing the control arm  280  to rotate. This drives the stem  272  and plug  270  toward the valve port  268  and reduces or ceases the flow in the pilot valve  261 . 
         [0035]    When the loading pressure supplied by the pilot valve  261  is reduced or ceased, the load pressure in the loading pressure cavity  225  decreases, and the spring  230  moves in an upward direction relative to the housing  220 . As a result, the diaphragm  224  and piston  232  are forced further upward relative to the housing  220 . The upward movement causes the control arm  226  to pivot in the clockwise direction, which in turn drives the actuator stem  223  and the valve plug  228  further toward the valve port  222  to reduce the fluid flow through the regulator valve  214 . Under normal operating conditions, the outlet pressure will drop to approximately the actuator setpoint pressure and remain there until the downstream demand changes in a manner that causes a response from by the actuator  212 . 
         [0036]    Several benefits may be derived from implementing pilot loading and balanced trim within a regulator as described above. For example, regulators in accordance with the present disclosure may be implemented in systems where higher inlet pressures are anticipated while maintaining a high level of control and accuracy over the resulting downstream pressures. At higher inlet pressures, the force applied to the valve plug  228  by the balancing diaphragm  250  increases to prevent influence on the control assembly  222  by the upstream pressures. The regulators may also be implemented where large upstream pressure variations are expected because the balanced plug substantially eliminates outlet pressure sensitivity to input pressure variations. Consequently, the balanced regulator valve  214  allows for higher rated capacities for the regulators and higher accuracy in the regulation of the downstream pressures by the regulator. Pressure loading via the pilot regulator valve assembly  260  also allows for a higher rated capacity for the regulator. The effects of “droop” on a regulator&#39;s ability to maintain the outlet control pressure at the desired setpoint pressure are reduced by the ability of the pilot regulator valve assembly  260  to maintain a more consistent load on the diaphragm of the regulator. Moreover, the load consistency results in an increase in the accuracy of the control provided by the regulator. 
         [0037]    While the preceding text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of a patent claiming priority hereto. The detailed description is to be construed as exemplary only and does not describe every possible embodiment of the invention since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims of the patent. For example, other fluid control devices including other regulators and control valves may also benefit from the structures and/or advantages of the present disclosure. More generally, although certain example apparatus and methods have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.