Patent Publication Number: US-11662029-B2

Title: Flow control valve

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application in a continuation of U.S. patent application Ser. No. 16/433,176, filed Jun. 6, 2019, entitled “Flow Control Valve”, which claims priority to U.S. Provisional Patent Application No. 62/681,834, filed Jun. 7, 2018, entitled “Flow Control Valve” and U.S. Provisional Patent Application No. 62/746,910, filed Oct. 17, 2018, also entitled “Flow Control Valve,” wherein each of the foregoing is incorporated by reference in its entirety herein. 
    
    
     FIELD 
     The present disclosure generally relates to valves and more particularly to flow control valves. 
     BACKGROUND 
     Flow control valves are used to control the flow of fluids, such as water. U.S. Patent Application Publication No. 2009/0289207 to Barreda et al. discloses a valve assembly that is adapted to be disposed within a water supply line. The valve assembly is structured to reduce or significantly eliminate the passage of air and water vapour through a water meter measuring the water supply line. The valve body includes a sealing structure which is biased under a predetermined force into sealing relation with an inlet of valve assembly. The predetermined force is sufficient to prevent displacement of the sealing structure out of the sealing relation with the inlet until the force from a desired water pressure is exerted thereon. As a result, any air or water vapour within the water supply line will be compressed to reduce the flow measured through the water meter, thereby preventing unnecessary charges being made to a metered facility. 
     U.S. Patent Application Publication No. 2014/0182717 to Edgeworth discloses a system and an associated valve assembly that are adapted to increase the efficiency of an upstream water meter. By way of the valve assembly, entrained gas bubbles can be removed from a water supply. This, in turn, increases the density of the water running through the water meter. This ensures that the water meter is not inaccurately including entrained air or water vapour as metered water. The result is more accurate water readings and reduced utility bills. 
     While the contributions of existing flow control valves are laudable, improvements are generally desired. It is therefore an object of the present disclosure to provide a new and useful flow control valve that can be used in a water supply line. 
     SUMMARY 
     It should be appreciated that this Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description of Embodiments. This Summary is not intended to be used to limit the scope of the claimed subject matter. 
     According to an aspect, there is provided a flow control valve comprising: a housing having an inlet, an outlet and a flow passage extending therebetween; a valve seat defined within the flow passage; a valve head positioned in the flow passage and movable between a closed position and an open position, wherein the valve head engages the valve seat in the closed position to seal the flow passage; a spring retained within the housing, the spring biasing the valve head to the closed position and configured to maintain the valve head in the closed position until a predetermined pressure is applied to the valve head from fluid at the inlet; and a guide assembly extending along at least a section of the flow passage, the guide assembly configured to engage the valve head to constrain radial movement of the valve head. 
     In some embodiments of the flow control valve, one or more of the following may be provided: the guide assembly is configured to constrain radial movement of the valve head when moving between the closed position and the open position; the guide assembly extends along the entire section of the flow passage; the guide assembly comprises at least one guide rail secured within the housing and positioned to engage the valve head; at least one void is formed in the valve head, the at least one void shaped to slidingly receive the at least one guide rail; and the at least one guide rail comprises a plurality of guide rails that are circumferentially positioned around the valve head. 
     In some embodiments of the flow control valve, one or more of the following may be provided: the flow control valve further comprises a shaft secured to the valve head and a support slidingly mounting the shaft within the housing; the support abuts an end of the spring to retain the spring within the housing; the support comprises a reversible bar secured to the housing and having a first face that is shaped to pre-compress the spring by a first amount and a second face that is shaped to pre-compress the spring by a second amount, the second amount being greater than the first amount; the predetermined pressure is approximately 45 psi when the spring is pre-compressed by the first amount and wherein the predetermined pressure is approximately 60 psi when the spring is pre-compressed by the second amount; the valve head comprises a removable wear cap that engages the valve seat when the valve head is in the closed position; the removable wear cap is formed of Teflon™; the valve seat is defined by a narrowed portion of the housing and the valve head is completely withdrawn from the narrowed portion when the valve head is in the open position; and the valve seat and the valve head define a seal plane and wherein the valve head comprises a flat face that does not extend upstream of the seal plane when in the closed positon and that is positioned downstream of the seal plane when in the open position. 
     According to another aspect, there is provided a flow control valve comprising: a housing having an inlet, an outlet and a flow passage extending therebetween, the housing defining a valve seat within the flow passage; a valve plug retained within the housing and movable between a closed position and an open position, the valve plug having a valve head for sealingly engaging the valve seat when the valve plug is in the closed position, to substantially prevent fluid flow through the flow passage, and further having a valve body extending downstream from the valve head and configured to slidingly engage an inner surface of the housing as the valve plug moves between the closed position and the open position, to constrain radial movement of the valve plug; and a spring retained within the housing, the spring biasing the valve plug towards the closed position and configured to maintain the valve plug in the closed position until a predetermined pressure is applied to the valve head from fluid at the inlet. 
     In some embodiments of the flow control valve, one or more of the following may be provided: the valve body comprises a plurality of fins that extend radially outward beyond an outer diameter of the valve head and are configured to slidingly engage the inner surface of the housing as the valve plug moves between the closed position and the open position, to constrain radial movement of the valve plug; the fins are arranged to constrain radial movement in a plurality of radial directions; the plural of radial directions includes a horizontal radial direction and a vertical radial direction; and the fins are arranged in one of a cross-shape and a Y-shape. 
     In some embodiments of the flow control valve, one or more of the following may be provided: the valve head has a flat upstream face that is configured to be completely retraced from the valve seat; the housing comprises a sleeve and an insert secured to the sleeve, and the sleeve defines the inner surface of the housing and the insert defines the valve seat; the sleeve has a hollow shape with an open upstream end and a partially closed downstream end, and the insert is secured at least partially within the upstream end of the sleeve; the partially closed downstream end includes at least one opening therethrough that defines the outlet of the housing; valve plug and the spring are retained within the sleeve and between the insert and the partially closed downstream end of the sleeve; and a downstream portion of the valve body in nested within the spring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described more fully with reference to the accompanying drawings, in which: 
         FIG.  1    is a schematic view of a water system; 
         FIG.  2    is a cross-sectional side view of a flow control valve, in a closed position; 
         FIG.  3    is a cross-sectional side view of the flow-control valve of  FIG.  2   , in an open position; 
         FIG.  4    is an axonometric cross-sectional view of the flow control valve of  FIG.  2   , viewed from a downstream end of the valve; 
         FIG.  5    is an axonometric cross-sectional view of the flow control valve of  FIG.  2   , viewed from an upstream end of the valve; 
         FIG.  6    is an exploded cross-sectional view of the flow control valve of  FIG.  2   ; 
         FIG.  7    is an exploded view of the flow control valve of  FIG.  2   , shown in transparency; 
         FIG.  8    is an exploded view of another embodiment of a flow control valve, shown with part of the housing in transparency; 
         FIG.  9    is a cross-sectional side view of another embodiment of a flow control valve, in a closed positon; 
         FIG.  10    is a downstream end view of the flow control valve of  FIG.  9   ; 
         FIG.  11    is an exploded view of the flow control valve of  FIG.  9   ; 
         FIG.  12    is a cross-sectional side view of a sleeve of a housing of the flow control valve of  FIG.  9   ; 
         FIG.  13    is a downstream end view of the sleeve of  FIG.  12   ; 
         FIG.  14    is a cross-sectional side view of an insert of the housing of the flow control valve of  FIG.  9   ; 
         FIG.  15    is a downstream end view of the insert of  FIG.  14   ; 
         FIGS.  16  and  17    are axonometric views of a bushing of the housing of the flow control valve of  FIG.  9   , viewing an upstream end and a downstream end of the bushing, respectively; and 
         FIGS.  18  and  19    are axonometric views of a valve plug of the flow control valve of  FIG.  9   , viewing an upstream end and a downstream end of the valve plug, respectively. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The foregoing summary, as well as the following detailed description of certain embodiments will be better understood when read in conjunction with the accompanying drawings. As will be appreciated, like reference characters are used to refer to like elements throughout the description and drawings. As used herein, an element or feature recited in the singular and preceded by the word “a” or “an” should be understood as not necessarily excluding a plural of the elements or features. Further, references to “one example” or “one embodiment” are not intended to be interpreted as excluding the existence of additional examples or embodiments that also incorporate the recited elements or features of that one example or one embodiment. Moreover, unless explicitly stated to the contrary, examples or embodiments “comprising,” “having” or “including” an element or feature or a plurality of elements or features having a particular property may further include additional elements or features not having that particular property. Also, it will be appreciated that the terms “comprises,” “has” and “includes” mean “including but not limited to” and the terms “comprising,” “having” and “including” have equivalent meanings. 
     As used herein, the term “and/or” can include any and all combinations of one or more of the associated listed elements or features. 
     It will be understood that when an element or feature is referred to as being “connected” another element or feature, that element or feature can be directly connected to the other element or feature or intervening elements may also be present. 
     It will be understood that spatially relative terms may be used herein for ease of describing the relationship of an element or feature to another element or feature as depicted in the figures. The spatially relative terms can however, encompass different orientations in use or operation in addition to the orientation depicted in the figures. 
     Reference herein to “example” means that one or more feature, structure, element, component, characteristic and/or operational step described in connection with the example is included in at least one embodiment and/or implementation of the subject matter according to the subject disclosure. Thus, the phrases “an example,” “another example,” and similar language throughout the subject disclosure may, but do not necessarily, refer to the same example. Further, the subject matter characterizing any one example may, but does not necessarily, include the subject matter characterizing any other example. 
     Reference herein to “configured” denotes an actual state of configuration that fundamentally ties the element or feature to the physical characteristics of the element or feature preceding the phrase “configured to.” 
     Unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to a “second” item does not require or preclude the existence of a lower-numbered item (e.g., a “first” item) and/or a higher-numbered item (e.g., a “third” item). 
     As used herein, the terms “approximately” and “about” represent an amount close to the stated amount that still performs the desired function or achieves the desired result. For example, the terms “approximately” and “about” may refer to an amount that is within engineering tolerances that would be readily appreciated by a person skilled in the art. 
       FIG.  1    shows a water system generally identified by reference character  10 . The system includes a water supply  12 , a distribution network  14 , a water meter  16 , a flow control valve  18  and a water consumer  20 . The water supply  12  can be, for example, a reservoir maintained by a utility or municipality. The reservoir may store a large volume of preferably potable water for distribution to one or more water consumers  20 . These various water consumers  20  may be, for example, dwellings such as houses or office buildings or other water outlets that are accessed by individuals such as water fountains. The various water consumers  20  may also be industrial facilities, for example, bottling plants or manufacturing facilities. The distribution network  14  can be, for example, a number of water supply lines and/or return lines that are interconnected to the water supply  12 . This distribution network  14  can interconnect the water consumers  20  to the water supply  12 , with the water consumers  20  being downstream of the water supply  12 . 
     The water meter  16  is interconnected and in line with the distribution network  14  upstream from an individual water consumer  20 . The water meter  16  may be of a conventional construction such as a positive displacement meter. Those of ordinary skill in the art will recognize other types of water meters that can be used in the water system  10 . The water meter  16  is typically maintained by the utility or municipality and is operable to measure the volume of water used by an individual water consumer  20  over a pre-determined period of time. As such, the water meter  16  is instrumental in determining the water bill for the water consumer  20 . However, water meters typically measure volume alone, regardless of whether that volume includes liquid water (“water”) or water with entrained water vapour and/or air (“water vapour”). Accordingly, measurements from water meters can be inaccurate and can overestimate the volume of water actually consumed. 
     Increasing the pressure in the water meter can help to compress any entrained water vapour and can help to reduce resultant inaccuracy and overestimation of water usage. Accordingly, the flow control valve  18  is positioned downstream of the water meter  16  and is intermediate the water meter  16  and the water consumer  20 . As will be described in greater detail below, the valve  18  includes a spring biased valve head that is triggered at a predetermined water pressure. Water is permitted to pass through the valve  18  and to the water consumer  20  only after a build-up of sufficient water pressure upstream of the valve  18  is achieved. This can have the effect of compressing entrained water vapour upstream of the valve  18 , which can increase the efficiency and accuracy of the water meter  16 . In some valves, such as the one described in U.S. Patent Application Publication No. 2014/0182717, the valve head may be connected to a shaft within the valve and may be free to move radially within the valve when not engaging the valve seat. This radial movement of the valve head can cause the shaft to bend and eventually break. Accordingly, savings realized at the water meter  16  may be offset by repair costs to the valve  18 . 
       FIGS.  2  to  7    show an embodiment of the flow control valve  18 . The valve  18  is configured to remain closed and substantially prevent fluid flow therethrough until a predetermined pressure is established upstream of the valve  18 . The valve  18  comprises a housing  22 , a valve seat  24 , a valve head  26 , a shaft  28 , a spring  30 , a guide assembly  32  and a support  34 . 
     The housing  22  is configured to support the various components of the valve  18  and to secure the valve  18  to adjacent elements in the system  10 , such as the water meter  16  or piping to the water consumer  20 . The housing  22  comprises an inlet  36  located at an upstream end of the valve  18 , an outlet  38  located at a downstream end of the valve  18  and flow passage  40  that extends within the housing  22  between the inlet  36  and the outlet  38 . The housing  22  includes a flange for connecting to the adjacent elements in the system  10 . Alternatively, the housing  22  may include other suitable means for connecting, such as a pair of flanges (as shown in  FIG.  8   ), threading or the like. The housing  22  comprises a plurality of interconnected pieces that are secured together by fasteners (as shown in at least  FIGS.  6  and  7   ) or, alternatively, may be secured by other known techniques such as welding, adhesives, etc. In yet other embodiments, the housing  22  can be integrally formed as a single piece. 
     The valve seat  24  has a complementary shape to the valve head  26  and is configured to form a seal with the valve head  26  when in a closed position (as shown in  FIG.  2   ). Specifically, when the valve head  26  is in firm contact with the valve seat  24 . The valve seat  24  is defined by a narrowed portion  42  of the housing  22 , within the flow passage  40 . The narrowed portion  42  of the housing  22  is integrally formed in the housing  22 . Alternatively, the narrowed portion  24  can be formed by an insert in the housing  22 . A seal plane  44  is defined by the valve seat  24  and the valve head  26  when in the closed position. As will be appreciated, fluid is substantially prevented from flowing past the seal plane  44  when the valve head  26  is in the closed position. Although the seal plane  44  is defined at the narrowest point in the valve seat  24  in the present embodiment (as shown in  FIGS.  2  and  3   ), the seal plane  44  may be defined elsewhere on the valve seat  24  in other embodiments. 
     The valve head  26  has a complementary shape to the valve seat  24  and is configured to form a seal with the valve seat  24 , when the valve head  26  is in the closed position. The valve head  26  is moveable between the closed position (shown in  FIG.  2   ) and an open position (shown in  FIG.  3   ), in a generally longitudinal direction of the valve  18 . As will be appreciated, in the closed position the valve head  26  substantially seals and prevents fluid from passing through the valve  18 . Whereas, in the open position, the valve head  26  allows fluid to pass through the valve  18 , via the flow passage  40 . Accordingly, the open position can be defined as any position where the valve head  26  does not seal the valve  18  and includes a fully open position, where the valve head  26  is spaced from the valve seat  24  by a maximum distance enabled by the valve  18 . To limit obstruction from the valve head  26  when in the open position, the valve head  26  may be completely withdrawn from the narrowed portion  42  of the housing  22  when in the open position. In some embodiments, as shown, the valve head  26  has a flat upstream face  46  that does not extend upstream of the seal plane  44  in the closed position and which is positioned downstream of the seal plane  44  in the open position. 
     The shaft  28  is configured to at least partially support and position the valve head  26  within the flow passage  40 . Accordingly, the shaft  28  is secured to a downstream face  48  of the valve head  26  and extends rearwardly therefrom, and the shaft  28  is slidingly mounted within the housing by support  34 . 
     The spring  30  is configured to bias the valve head  26  to the closed position and is further configured to maintain the valve head  26  in the closed position until a predetermined pressure is applied to the upstream face  46  of the valve head  26  from fluid at the inlet  36 . Accordingly, the spring  30  is secured within the housing  22 , and has one end abutting the downstream face  48  of the valve head  26  and an opposite end abutting the support  34 . In some embodiments, as shown, the spring  30  may be positioned surrounding the shaft  28 . When the predetermined pressure is applied to the valve head  26  from fluid at the inlet  36 , the force of the spring  30  is overcome and the valve head  26  will move out of the closed position and away from the valve seat  24 . This allows fluid to flow through the open valve  18 , via passage  40 . As will be appreciated, the predetermined pressure at which the valve  18  opens will be correlated to at least the strength of the spring  30  (i.e. the spring&#39;s stiffness constant), the amount the spring  30  is pre-compressed (i.e. the difference between the length of the spring  30  when relaxed and the length of the spring  30  when positioned between the support  34  and the valve head  26  in the closed position) and the projected areas of the upstream face  46  and the downstream face  48  of the valve head  26 . Accordingly, the predetermined pressure at which the valve  18  opens can be tuned based on the desired application of the valve  18 . Common values for the predetermined pressure include 45 psi and 60 psi, but other values may also be used. 
     The guide assembly  32  is configured to constrain radial movement of the valve head  26  (i.e. movement in a direction generally perpendicular to the longitudinal axis  50  of the valve  18 ), particularly when moving between the open position and the closed position. Accordingly, the guide assembly  32  comprises a pair of guide rails that extend along a section of the flow passage  40 . The guide rails  32  are secured within the housing  22  and extend along the entire section between the narrowed portion  42  and the support  34 . One end of each of the guide rails  32  is positively secured to the support  34  by fasteners or the like, and the opposite end of each of the guide rails  32  is pressed against the narrowed portion  42  of the housing  22 . The guide rails  32  are circumferentially positioned on opposite sides of the valve head  26  to engage the valve head  26  and constrain radial movement thereof. To further constrain radial movement, a pair of notches  54  are formed in the valve head  26  (as shown in  FIG.  7   ). Each of the notches  54  is shaped to slidingly receive a corresponding one of the guide rails  32  to increase engagement between the valve head  26  and the guide rails  32 . Accordingly, the notches  54  have complementary shapes to that of the guide rails  32  and are circumferentially spaced around the valve head  26  at positions corresponding to that of the guide rails  32 . For example, as shown in  FIG.  7   , each of the notches  54  has a semi-circular shape that corresponds to the circular cross-sectional shape of the guide rail  32  and is circumferentially positioned on opposite sides of the valve head  26 , similar to the guide rails  32 . However, other suitable shapes and positions will be apparent to those skilled in the art in view of the present description. 
     The support  34  is configured to slidingly mount the shaft  28  within the housing  22 . The support  34  is also configured to retain the spring  30  and the guide assembly  32  within the housing  22 . In some embodiments, the support  34  is secured to the housing  22  by fasteners. Alternatively, the support  34  may be integrally formed with the housing  22 . In the embodiment shown in  FIGS.  2  to  7   , the support  34  is secured to the housing  22  by fasteners and comprises a reversible bar. The reversible bar  34  has a first face  58  (shown in  FIG.  5   ) and an opposite second face  60  (shown in  FIG.  4   ). The first face  58  is shaped to pre-compress the spring  30  by a first amount and the second face  60  is shaped to pre-compress the spring  30  by a second amount that is different than the first amount. That is, the first face  58  is shaped to pre-compress the spring  30  to a first length when the support  34  is secured to the housing  22  and the spring  30  is positioned between the support  34  and the valve head  26  in the closed position, with the spring  30  abutting the first face  58 . While the second face  60  is shaped to pre-compress the spring  30  to a second length when the support  34  is secured to the housing  22  and the spring  30  is positioned between the support  34  and the valve head  26  in the closed position, with the spring  30  abutting the second face  60 . As shown in  FIGS.  2  to  7   , the first face  58  is flat and the second face  60  includes an extension  62 , which pre-compresses the spring  30  farther than the flat first face  58 . Accordingly, the second face  60  will pre-compress the spring  30  by a greater amount than the first face  58 . This configuration allows the pre-compression of the spring  30  to be easily changed by reversing the orientation of the reversible bar  34  and, since the predetermined pressure is correlated to the pre-compression of the spring, this configuration allows the predetermined pressure at which the valve  18  opens to be easily changed as well. In the embodiment shown, the predetermined pressure may be approximately 45 psi when the spring  30  is pre-compressed by the first amount, using the first face  58 , and may be approximately 60 psi when the spring  30  is pre-compressed by the second amount, using the second face  60  with extension  62 . Although, it will be appreciated that in other embodiments the support  34  may be shaped to pre-compress the spring  30  by other amounts to provide other predetermined pressures, depending on the desired application of the valve  18 . 
     When the valve  18  is in use, the spring  30  maintains the valve head  26  in the closed position until the predetermined pressure is applied to the upstream face  46  of the valve head  26  from fluid at the inlet  36 . As described above, increasing the pressure upstream of the valve  18  can help compress any entrained water vapour in the system  10  and can help reduce resultant inaccuracy and overestimation of water usage. Once the predetermined pressure upstream of the valve  18  is reached, the valve head  26  will move out of the closed position and away from the valve seat  24 , into the open position. Thus permitting water to flow through the valve  18 , via the flow passage  40 , to the water consumer  20 . 
     When the predetermined pressure is applied to the valve head  26  from fluid at the inlet  36  and the valve head  26  begins to move out of the closed position, the guide rails  32  engage the sides of the valve head  26  via the notches  54 . This engagement helps to constrain radial movement of the valve head  26  as it moves to the open position. Additionally, to constrain movement of the valve head  26  in radial directions that would not otherwise abut the guide rails  32 , the notches  54  slidingly receive the guide rails  32  and increase engagement between the valve head  26  and the guide rails  32 . Thus, the guide assembly  32  constrains radial movement of the valve head  26  when moving from the closed position to the open position and helps to reduce the likelihood that the shaft  28  will bend or break. 
       FIG.  8    shows another embodiment of a flow control valve generally identified by reference character  118 . As will be appreciated, the flow control valve  118  is similar to the flow control valve  18 , except the valve head  26  includes a removable wear cap  64  and a body  66 , and the housing  22  includes a pair of flanges for connecting to the adjacent elements in the system  10 . 
     The removable wear cap  64  is configured to form a seal with the valve seat  24 , when the valve head  26  is in the closed position. Accordingly, the wear cap  64  has a complementary shape to that of the valve seat  24 . As the flow control valve  118  is used over time, repeated sealing and unsealing of the wear cap  64  with the valve seat  24  can cause deterioration of the wear cap  64 . Accordingly, the wear cap  64  is configured to be replaceable. That is, the wear cap  64  is secured to the body  66  of the valve head  26  by fasteners or the like and can be removed and replaced with a new wear cap, as needed. Alternatively, the wear cap  64  can be secured to the body  66  by threading, adhesives or other suitable securing means. In the present embodiment, the wear cap  64  is formed of Teflon™. Although, in other embodiments, the wear cap  64  can be formed of plastic, metal or other suitable materials. As shown in the embodiment in  FIG.  8   , the notches  54  are formed in the wear cap  64  of the valve head  26 . Though, in alternative embodiments, it will be appreciated that the notches  54  can be formed in the body  66  of the valve head  26  and/or can be formed in both the body  66  and the wear cap  64 . 
     The body  66  of the valve head  26  is configured to support the wear cap  64 . Accordingly, the body  66  is secured to the wear cap  64 , as described above, and the shaft  28  extends from the body  66  to the support  34 . 
     Although the guide rails of the guide assembly  32  are shown and described as extending along the entire section of the flow passage  40  between the narrowed portion  42  of the housing  22  and the support  34 , it will be appreciated that in other embodiments the guide rails  32  may extend along only part of that section. Bending of the shaft  28  is generally correlated to the length the shaft  28  is extended from the support  34 , among other factors. Accordingly, in some embodiments it may only be necessary to constrain radial movement of the valve head  26  as the shaft  28  becomes increasingly extended from the support  34 , such as when the valve head  26  approaches the closed position. In such embodiments, the guide rails  32 , and hence the guide assembly  32 , may only constrain radial movement of the valve head  26  during a portion of the movement between the closed position and the open position. In some embodiments, that portion of the movement may be when the valve head  26  is adjacent the closed position. Thus, in some embodiments, the guide rails and/or the guide assembly  32  may extend along at least a part of a section of the flow passage  40 , such as along at least half of the section between the narrowed portion  42  and the support  34 . In some embodiments, the guide rails and/or the guide assembly  32  may extend along only the part of the section between the narrowed portion  42  and the support  34  that is adjacent the valve seat  24 . 
     Although the guide assembly  32  has been shown and described as comprising a pair of guide rails  32  and a pair of notches  54 , it will be appreciated that in other embodiments the guide assembly  32  may comprise three or more guide rails  32  that are circumferentially positioned around the valve head  26 . In some embodiments, such as embodiments with three or more guide rails  32 , the notches  54  may be omitted entirely. Similarly, although the valve head  26  has been shown and described as comprising a pair of notches  54 , it will be appreciated that in other embodiments the valve head  26  may comprise other types of voids, such as holes. In some embodiments, the valve head  26  may include a single void in the form of a hole through the valve head  26  and the guide assembly  32  may comprise a single guide rail  32  that passes through the hole to constrain radial movement of the valve head  26 . 
     Although the guide rails  32  have been shown and described as having circular cross-sectional shapes and the voids  54  have been shown and described as having corresponding semi-circular shapes, in other embodiments other suitable shapes will be appreciated. In some embodiments, the guide assembly  32  could comprise one or more guide rails  32  with T-shaped or I-shaped cross-sections that engage correspondingly shaped voids in the valve head to constrain radial movement thereof. In other embodiments, the guide rails  32  may be wedge shaped, with a wider face of the wedge shape being slidingly received within the void to constrain radial movement of the valve head  26 . A variety of suitable shapes for the guide rails  32  and the voids  54  will be apparent to those skilled in the art, in view of the present description. 
       FIGS.  9  to  19    show another embodiment of a flow control valve generally identified by reference character  220 . The valve  220  can be used in the system  10 , in a similar manner as the valve  18 . The valve  220  is configured to remain closed and substantially prevent fluid flow therethrough until a predetermined pressure is established upstream of the valve  220 . The valve  220  comprises a housing  222 , a valve plug  224  and a spring  226 . The valve plug  224  is secured within the housing  222  and is movable between a closed position (shown in  FIG.  9   ), wherein the valve plug  224  substantially prevents fluid flow through the valve  220 , and an open position, wherein the valve plug  224  permits fluid flow through the valve  220 . The spring  226  is secured within the housing  222  and biases the valve plug  224  towards the closed position. 
     The housing  222  is configured to movably retain the valve plug  224  and the spring  226  therein. The housing  222  is further configured to be secured to adjacent elements of the system  10 , such as the water meter  16  and the piping to the water consumer  20 . The housing  222  comprises a sleeve  228 , an insert  230  and a bushing  232 . The sleeve  228 , the insert  230  and the bushing  232  are interconnected by press-fits, threading, adhesives or the like to form the housing  222 . When assembled, the housing  222  defines an inlet  234  at an upstream end of the valve  220 , an outlet  236  at a downstream end of the valve  220  and a flow passage  238  through the valve  220  that extends from the inlet  234  to the outlet  236 . The housing  222  further defines a valve seat  240  within the flow passage  238  for sealingly engaging the valve plug  224 , when the valve plug  224  is in the closed positioned (as shown in  FIG.  9   ). To secure the housing  222  to the adjacent elements of the system  10 , the housing  222  includes an outwardly extending flange  242  that can be secured between the adjacent elements of the system  10 . For example, the flange  242  may be pinched between the water meter  16  and the piping to the water consumer  20 , such as between a downstream flange of the water meter  16  and an upstream flange of the piping to the consumer  20 . In other embodiments, the flange  242  may be omitted and the housing  222  may be secured to the adjacent elements of the system  10  by threading, a pair of opposite end flanges, or other suitable securing mechanisms as would be appreciated by a person skilled in the art. 
     The sleeve  228  is configured to retain the valve plug  224  and the spring  226 . The sleeve  228  has a hollow, generally cylindrical body  244  with an open upstream end  246  and a partially closed downstream end  248 . A flange  250  extends outwardly from the upstream end  246  and is securely positioned between the insert  230  and the bushing  232 , when the housing  222  is assembled. A plurality of openings  252  are formed in the downstream end  248  to permit fluid flow therethrough and define the outlet  236  of the housing  222 . The upstream end  246  is configured to securely receive the insert  230  by a press-fit, threading, adhesive or the like. The sleeve  228  is sized to slidably retain the valve plug  224  and the spring  226  within the body  224  and between the insert  230  and the partially closed downstream end  246 , when the insert  230  is secured in the sleeve  228 . When the housing  222  is assembled, the sleeve  228  defines a portion of the flow passage  238  downstream of the insert  230 . 
     The insert  230  is configured to secure the valve plug  224  and the spring  226  within the sleeve  228 . The insert  230  is further configured to form the valve seat  240 . The insert  230  has a generally ring-shaped body  254  with a through-passage  256  that is narrower than an outer diameter of the valve plug  224 . Accordingly, the valve plug  224  cannot pass through the through-passage  256 . The body  254  includes a tapered inner surface that defines the valve seat  240 . A flange  258  extends outwardly from the body  254  at an upstream end thereof and is securely positioned adjacent the flange  250  of the sleeve  228 , when the housing  222  is assembled. A downstream end of the insert  230  is sized to fit within the upstream end  246  of the sleeve  228  and is configured to be secured to the sleeve  228  by a press-fit, threading, an adhesive or the like. When the housing  222  is assembled, the insert  230  defines the inlet  234  of the housing  222 . The insert  230  further defines a portion of the flow passage  238  downstream of the inlet  236 . 
     The bushing  232  is configured to be secured to the adjacent elements of the system  10 . The bushing  232  is further configured to be secured to at least one of the sleeve  228  and the insert  230 , to secure the housing  222  to the adjacent elements of the system  10 . The bushing  232  has a generally ring-shaped body  260  that is sized to matingly receive the sleeve  228  therethrough and is configured to be secured to the sleeve  228  by a press-fit, threading, an adhesive or the like. The bushing  232  also includes the flange  242  of the housing  222 , which extends outwardly from the body  260  of the bushing  232  and is configured to be secured in the system  10 , as described above. The outer surface of the body  260  may include a plurality of ridges  262 . 
     The valve plug  224  is configured to substantially prevent fluid flow through the valve  220 , when the valve plug  224  is in the closed position (shown in  FIG.  9   ), and to permit fluid flow through the valve  220 , when the valve plug  224  is in the open position. The valve plug  224  is further configured to constrain radial movement of the valve plug  224  when moving between the closed position and the open position. The valve plug  224  comprises a valve head  264  and a valve body  266 . The valve head  264  is connected to the valve body  266  at an upstream end thereof. The valve head  264  has a complementary shape to the valve seat  240  and is configured to sealingly engage the valve seat  240  when the valve plug  224  is in the closed position, to substantially prevent fluid flow through the valve  220  and to seal the flow passage  238 . The valve head  264  has a flat upstream face  268  that can be completely retracted from the valve seat  240  when the valve plug  224  is in the open position, to limit obstruction of fluid flow through the valve  220 . The valve body  266  extends downstream from the valve head  264  and includes a plurality of outwardly extending fins  270 . The fins  270  extend radially beyond an outer diameter of the valve head  264  and are configured to slidingly engage an inner surface of the sleeve  228  as the valve plug  224  moves between the closed position and the open position, to constrain radial movement of the valve plug  224 . The fins  270  are arranged in a cross-shape to constrain radial movement in substantially all radial directions perpendicular to a longitudinal axis  274  of the valve  220  (such as movement in both a vertical radial direction and a horizontal radial direction). Although, in other embodiments, the fins  270  may be arranged in another suitable shape, such as a Y-shape. Each of the fins  270  includes a notch  272  at a downstream end thereof. The notches  272  are sized to receive the spring  226  and are configured to permit a downstream portion of the valve body  266  to be nested within the spring  226  (as shown in  FIG.  9   ). 
     The spring  226  is configured to bias the valve plug  224  to the closed position and is further configured to maintain the valve plug  224  in the closed position until a predetermined pressure is applied to the valve plug  224  from fluid at the inlet  234 . The spring  226  is positioned within the housing  222  and has one end abutting the valve plug  224  and an opposite end abutting the housing  222 . As will be appreciated, the predetermined pressure will be partially dependent on the force of the spring  226  biasing the valve plug  224  to the closed position. The force of the spring is correlated to at least the strength of the spring  226  (i.e. the spring&#39;s stiffness constant) and the amount the spring  226  is pre-compressed (i.e. the difference between the length of the spring  226  when relaxed and the length of the spring  226  when positioned between the valve plug  224  and the housing  222 , with the valve plug  224  in the closed position). Accordingly, the predetermined pressure can be tuned based on the desired application of the valve  220 . Common values for the predetermined pressure include 45 psi and 60 psi, but other values may also be used. 
     When the valve  220  is in use, the spring  226  maintains the valve plug  224  in the closed position until the predetermined pressure is applied to the valve plug  224  from fluid at the inlet  234 . When the predetermined pressure is applied the valve plug  224 , the force of the spring  226  will be overcome and the valve plug  224  will move out of the closed position and towards the open position. As the valve plug  224  moves out of the closed position, the valve head  264  will move away from the valve seat  240  and will no longer sealingly engage the valve seat  240 . This will allow fluid to flow through the valve  220 , via the flow passage  238 , from the inlet  234  to the outlet  236 . In this manner, the valve  220  can substantially prevent fluid flow through the valve  220  until the pressure upstream of the valve  220  is increased to the predetermined pressure and, thereafter, permit fluid flow through the valve  220 . As described above, increasing the pressure upstream of the flow control valve in a system  10  can compress entrained water vapour in the system  10  and may help reduce resultant inaccuracy and overestimation of water usage by the water meter  16  in the system  10 . 
     Moreover, as the valve plug  224  moves between the closed position and the open position, the fins  270  of the valve body  266  will slidingly engage the sleeve  228  of the housing  222  to constrain radial movement of the valve plug  224 . Constraining radial movement of the valve plug  224  may help to reduce wear and potential damage to the valve plug  224  caused by vibration of the plug  224  within the housing  222 . Additionally, constraining radial movement of the valve plug  224  as the valve plug moves from the open position to the closed position may help to align the valve head  264  with the valve seat  240  as the valve plug  224  moves to the closed position, which may help to ensure sealing engagement between the valve plug  224  and the valve seat  240 . 
     In an alternative embodiment, the fins  270  extend radially beyond the outer diameter of the valve head  264  and are configured to engage the inner surface of the sleeve  228  as the valve plug  224  moves between the closed position and the open position, to constrain radial movement of the valve plug  224 . Such a configuration may not constrain the radial movement of the valve plug  224  as much as the previously described embodiment, which slidably engages the inner surface of the sleeve  228 . However, the radial movement of the valve plug  224  may be sufficiently constrained, depending on the implementation. 
     Although embodiments have been described above and are shown in the accompanying drawings, it will be appreciated by those skilled in the art that variations and modifications may be made without departing from the scope defined by the appended claims, and the scope of the claims should be given the broadest interpretation consistent with the specification as a whole.