Abstract:
A poppet-style check valve for allowing uni-directional flow in a fluid conducting system. The check valve comprises a valve body, and a poppet mounted therein for reciprocal axial movement between a first position in which the poppet is pressed against a valve seat restricting flow through the check valve, and a second position in which the poppet is spaced from the valve seat permitting flow through the check valve. An inner bore of the valve body is expanded in the area of the poppet to maximize flow through the check valve, and the external dimensions of the check valve are minimized by eliminating a conventional liner between the poppet and the valve body. Additionally, the elements of the valve mechanism are designed such that they lock in place within the valve body during assembly.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to check valves, and in particular to valves used to prevent backflow through a fluid-conducting passage.  
       BACKGROUND OF THE INVENTION  
       [0002]     Particularly in the plumbing and waterworks industries, situations frequently arise where it is important to ensure that a fluid flows through a conduit in only one direction. Such a result is often achieved by introducing a check valve into the conduit. Check valves utilize any of a variety of valve mechanisms, including balls, flaps, swing doors, and poppets to allow fluids to flow in one direction, but not the other.  
         [0003]     One exemplary situation in which uni-directional flow is desirable is in residential water supply applications. In such applications, it is preferable to allow water to flow only from the water main into the residence, and not vice versa. This is because should water flow from the residence to the water main (which can occur when there is a pressure drop in the water main caused by, for example, a broken water main or burst fire hydrant), the municipal water supply can be contaminated. Traditionally, residential water supply applications have not included check valves. However, in view of increasing concerns about the safety of municipal water supplies, a demand has arisen among municipalities to retrofit existing residential water supply plumbing to install check valves therein.  
         [0004]     Many existing check valves however have been found to be unsuitable for use in such retrofits for various reasons. For example, many existing check valves are simply too long or are otherwise too large to fit in the available space. Others utilize valve mechanisms which do not allow for sufficient flow rates thereby unacceptably reducing residential water pressure. Other valves have too many moving parts or parts which can fall out of the valves during handling, resulting in difficulties during installation. Finally, many check valves are simply not suitable for situations where neither of the connections between which the valve is to be mounted, is rotatable, as may be the case when inserting a check valve between a water meter and a supply line in a retrofitting application.  
         [0005]     Poppet-style valves are particularly advantageous for such applications because they tend to be simple, durable, reliable and compact. Typically, poppet-style valves consist of one or more sealed valve units contained within a sleeve. Such valve units have a first and a second end and include a poppet, a disk having a guidepost extending perpendicularly from its center, reciprocally slidable axially within the valve unit. The poppet has a sealing surface which can seat against an annular surface at the first end of the valve unit. The poppet is biased towards the first end such that its sealing surface seats against the annular surface when no flow exists through the valve unit. When the fluid pressure at the second end of the valve unit is greater than that at the first end, this pressure differential tends to hold the poppet tightly against the annular surface thereby increasing the sealing force. When the fluid pressure at the first end exceeds the fluid pressure at the second end by an amount sufficient to overcome the biasing of the poppet towards the annular surface, the poppet moves away from the annular surface allowing for fluid flow through the valve unit from the first end to the second end. The sleeve has connections at either end to allow the valve to be mounted in-line in a conduit.  
         [0006]     Despite its advantages, poppet-style valves have only seen limited use in residential water supply retrofit applications. This is because conventional designs result in valves having limited flow rates, valves which are often too large for retrofitting applications, and valves which are difficult to service in the field.  
       SUMMARY OF THE INVENTION  
       [0007]     In a broad aspect, the present invention provides a poppet-style check valve comprising: a valve body having a bore therethrough and having an upstream inlet end, a downstream outlet end, an interior surface, and an exterior surface; inlet connection means for connecting said inlet end of said valve body to a fluid supply; outlet connection means for connecting said outlet end of said valve body to a fluid outlet; a valve seat located within said valve body, said valve seat having a valve seat surface defining a bore therethrough; a poppet having a face parallel to the valve seat surface, and a stem substantially perpendicular to said face, said poppet face being sized and shaped to be capable of covering the bore defined by the valve seat surface; a poppet support for receiving said stem of said poppet for reciprocal movement therein between a first position in which the face of the poppet is held against the valve seat surface and a second position in which the poppet face is spaced from the valve seat surface; sealing means for preventing flow through the check valve when the poppet is in its first position; flow means for permitting flow through the check valve when the poppet is in its second position; poppet control means for moving the poppet between its first position and its second position in response to changes in a differential between fluid pressure at the inlet end and fluid pressure at the outlet end of the valve body; wherein said flow means for permitting flow through the check valve when the poppet is in its second position comprises at least one flow passage through each of the valve seat, the valve seat surface, and the poppet support, at least one flow passage around the poppet face, and an expansion of the valve body bore around the poppet face; wherein the flow passage around the poppet face when the poppet is in its second position, is defined by a periphery of the poppet face and the valve body.  
         [0008]     Other aspects of the invention include the above check valve wherein:  
         [0009]     the poppet support locks into place within the valve body once it is inserted into the valve body during assembly of the check valve;  
         [0010]     the poppet support is inserted through the inlet end of the valve body during assembly of the check valve, and locks into place within the valve body by means of upstream facing teeth along a periphery of the poppet support engaging an annular poppet support locking recess on the interior surface of the valve body;  
         [0011]     the poppet support is further locked into place within the valve body by means of a downstream-facing surface of the poppet support abutting an upstream-facing poppet support shoulder on the interior surface of the valve body;  
         [0012]     the valve seat locks into place within the valve body once it is inserted into the valve body during assembly of the check valve;  
         [0013]     the valve seat is inserted through the inlet end of the valve body during assembly of the check valve, and locks into place within the valve body by means of upstream facing teeth along a periphery of the valve seat engaging an annular valve seat locking recess on the interior surface of the valve body;  
         [0014]     the valve seat is further locked into place within the valve body by means of a downstream-facing surface of the valve seat abutting an upstream-facing valve seat shoulder on the interior surface of the valve body;  
         [0015]     the valve seat is an annular sleeve, the at least one flow passage through the valve seat is a bore defined by the annular sleeve, and the valve seat surface is a downstream end of the annular sleeve;  
         [0016]     the valve seat is located within the valve body upstream of the expansion of the valve body bore;  
         [0017]     the poppet support has a poppet guide sleeve for receiving the poppet stem, an annular support rim for connecting the poppet support to the interior surface of the valve body, and connecting means for connecting the poppet guide sleeve to the support rim;  
         [0018]     the connecting means is a plurality of spokes extending from the poppet guide sleeve to the support rim, spaces between the spokes comprising the at least one flow passage through the poppet support;  
         [0019]     exactly three spokes extend from the poppet guide sleeve to the support rim;  
         [0020]     the support rim is located within the valve body downstream of the expansion of the valve body bore, and the poppet guide extends upstream from a plane defined by the support rim;  
         [0021]     the poppet is located intermediate the valve seat and the poppet support within the valve body, and the poppet stem extends downstream from the poppet face;  
         [0022]     the poppet includes an annular poppet seal associated with the poppet face, and the sealing means for preventing flow through the check valve when the poppet is in its first position includes a seal created between the poppet seal and the valve seat surface when the poppet is in its first position;  
         [0023]     the poppet seal is held within an annular poppet seal recess on the periphery of the poppet face, said poppet seal recess being defined by an upstream portion of the poppet face, a poppet sleeve extending downstream from the upstream portion of the poppet face, and an annular seal-retention flange extending radially outwardly from the poppet sleeve;  
         [0024]     both the poppet seal and the seal-retention flange extend radially outwardly beyond a periphery of the upstream portion of the poppet face such that when the poppet is in its first position, the upstream portion of the poppet face fits within the valve seat surface, the poppet seal contacts the valve seat surface, and the seal-retention flange supports the poppet seal against the valve seat surface;  
         [0025]     an upstream surface of the poppet face has a central protrusion to direct fluid flowing downstream through the check valve toward the periphery of the poppet face;  
         [0026]     biasing means are provided for biasing the poppet towards its first position;  
         [0027]     the poppet control means for moving the poppet between its first position and its second position in response to changes in a differential between fluid pressure at the inlet end and fluid pressure at the outlet end of the valve body comprises the biasing means, as well as upstream and downstream surfaces of the poppet face being substantially perpendicular to a direction of flow through the check valve which causes a force to be exerted on the poppet when a pressure differential exists between the inlet and outlet ends of the valve body, said poppet moving from its first position to its second position when the force exerted on the upstream surface of the poppet face by a higher fluid pressure at the inlet end of the valve body is sufficient to overcome a force exerted by the biasing means, and the poppet moving from its second position to its first position otherwise;  
         [0028]     said biasing means is a spring located between the poppet and the poppet support;  
         [0029]     the valve seat has an annular valve seat seal mounted within an annular seal recess on a periphery of the valve seat, said sealing means for preventing flow through the check valve when the poppet is in its first position including a fluid seal created by the valve seat seal between the valve seat and the valve body;  
         [0030]     the inlet connection means comprises a threaded female connector sealably and rotatably mounted on the inlet end of the valve body; and/or  
         [0031]     the outlet connection means comprises external threading on the outlet end of the valve body.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]     Preferred embodiments of the invention will now be described with reference to the attached drawings in which:  
         [0033]      FIG. 1  is a perspective view of the check valve in accordance with a preferred embodiment of the present invention;  
         [0034]      FIG. 2  is a perspective exploded view of the check valve;  
         [0035]      FIG. 3  is a perspective view of a valve cartridge of the check valve;  
         [0036]      FIG. 4  is a cross-sectional side view of the check valve in a closed position;  
         [0037]      FIG. 5  is a cross-sectional side view of the check valve in an open position;  
         [0038]      FIG. 6  is a cross-sectional side view of a valve body of the check valve;  
         [0039]      FIG. 7  is a cross-sectional side view of an inlet connection nut of the check valve;  
         [0040]      FIG. 8  is an end view of a valve seat of the check valve;  
         [0041]      FIG. 9  is a cross-sectional side view of the valve seat;  
         [0042]      FIG. 10  is a cross-sectional side view of a poppet of the check valve;  
         [0043]      FIG. 11  is an end view of a poppet support of the check valve;  
         [0044]      FIG. 12  is a side view of the poppet support; and  
         [0045]      FIG. 13  is a cross-sectional side view of a further embodiment of the present invention without the inlet connection nut. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0046]     A preferred embodiment of the check valve of the present invention will now be described in the context of an exemplary application of retrofitting a residential water supply system to inhibit backflow from a residence to a water main.  
         [0047]     In a typical residential water supply system, water from a municipal water main is conveyed to an interior wall of the residence through an underground pipe. A water meter which tracks water use by the residence for billing purposes is mounted to this pipe at the residential end. A supply pipe then conveys the water from the water meter to the various outlets within the residence.  
         [0048]     When retrofitting such a residential water supply system to install a check valve, the valve is normally installed between the water meter and the supply pipe. Most typically, the female threaded connector of the supply pipe is disengaged from the male threaded connector of the water meter, the check valve is placed between the two, and the water meter and supply pipe are each connected to each end of the check valve. The check valve is oriented such that it permits flow from the water meter to the supply pipe, but not from the supply pipe to the water meter.  
         [0049]     The preferred embodiment check valve  10  is illustrated in  FIGS. 1 through 12 .  FIGS. 1, 4  and  5  show the check valve  10  in its assembled state while  FIG. 2  is an exploded view of the check valve  10 , showing its constituent parts. Broadly, the check valve  10  consists of a valve body  12 , a valve cartridge  14  (as shown in its assembled form in  FIG. 3 ) located within the valve body  12 , and an inlet connection nut  16  attached to an inlet end of the valve body  12 . Each of these broad elements will now be discussed in turn.  
         [0050]     In this description and in the claims, the terms “axial” and “axially” are used to describe a direction parallel to a centerline of the check valve  10 , while “radial” and “radially” are used to describe a direction perpendicular to and extending from the centerline of the check valve  10 . Further, “downstream” is used to describe features which are located nearer an outlet end  13  of the check valve  10 , while “upstream” is used to describe features which are located nearer an inlet end  11  of the check valve  10 .  
         [0051]     The valve body  12 , shown in detail in  FIG. 6 , has an inner bore  17  therethrough, and consists of an upstream inlet section  18 , a downstream outlet section  20 , and an expanded section  22  intermediate the inlet and outlet sections  18 ,  20 .  
         [0052]     An exterior surface of the inlet section  18  is provided with an annular retaining ring recess  24  to accommodate a retaining ring  26 , as discussed further below. An interior surface of the inlet section  18  is provided with an annular valve seat locking recess  28  near an upstream end of the valve body  12 , and an annular valve seat shoulder  32  near an interface between the inlet section  18  and the expanded section  22 . The valve seat locking recess  28  and the valve seat shoulder  32  cooperate to lock a valve seat  34  into its proper position within the valve body  12 , as discussed further below.  
         [0053]     The inner bore  17  of the expanded section  22  of the valve body  12  has a diameter greater than that for either the inlet section  18  or the outlet section  20 . This greater diameter accommodates the flow of fluid through the expanded section  22  around a poppet  36  of the valve cartridge  14  as discussed further below. An exterior surface of the expanded section  22  is provided with two faceted annular protrusions  38  facilitating engagement of the valve body  12  by a tool such as a wrench when threadedly connecting the check valve  10  with the supply pipe. An interior surface of an interface between the expanded section  22  and the outlet section  20  is provided with an annular poppet support locking recess  40  and an annular poppet support shoulder  42  which cooperate to lock a poppet support  44  into its proper position within the valve body  12 , as discussed further below.  
         [0054]     The outlet section  20  of the valve body  12  is provided on its exterior surface with exterior threading  46  to accommodate connection with the female threaded connector of the supply pipe (not shown).  
         [0055]     The valve cartridge  14 , shown in  FIG. 3 , consists of the poppet  36 , a poppet seal  47 , the poppet support  44 , a spring  48  interposed between the poppet  36  and the poppet support  44 , and the valve seat  34 .  
         [0056]     The poppet  36 , as shown in detail in  FIG. 10  has a disc-shaped poppet face  50 , with a poppet stem  52  extending downstream from the center thereof. The poppet face  50  has an upstream-facing central protrusion  54  to direct downstream-flowing fluid towards the periphery of the poppet face  50  when the check valve  10  is in its open position. Extending downstream from an upstream portion of the poppet face  50 , coaxial with, and surrounding a portion of the poppet stem  52 , is an annular spring-retention sleeve  56 . The spring-retention sleeve  56  is spaced from the poppet stem  52  so as to accommodate both the poppet support  44  and the spring  48 . Extending radially outwardly from the spring-retention sleeve  56  is an annular seal-retention flange  58 . The seal-retention flange  58  is spaced downstream from the upstream portion of the poppet face  50  so as to accommodate the annular poppet seal  47  therebetween. The diameter of the upstream portion of the poppet face  50  is less than the diameter of the seal-retention flange  58  so as to allow the poppet seal  47  to be slipped over the upstream portion of the poppet face  50  and into the space between the upstream portion of the poppet face  50  and the seal-retention flange  58  during assembly of the check valve  10 . Additionally, this differential in the outer diameters of the upstream portion of the poppet face  50  and the seal-retention flange  58  allows the poppet seal  47  to contact the valve seat  34 , and also allows the seal-retention flange  58  to support the poppet seal  47  against the valve seat  34 .  
         [0057]     The poppet support  44 , as seen in detail in  FIGS. 11 and 12 , includes a poppet guide  60 , a sleeve whose purpose is to guide reciprocal axial movement of the poppet  36 . The inner diameter of the poppet guide  60  is slightly larger than an outer diameter of the poppet stem  52  such that there exists a close fit between the two parts when the poppet stem  52  is inserted into the poppet guide  60 . The outer diameter of the poppet guide  60  is sized so as to be spaced radially inwardly from the annular spring-retention sleeve  56  when the check valve  10  is in its open position, so as to accommodate the spring  48  therebetween. A downstream portion of the poppet guide  60  has support spokes  62  extending radially outwardly therefrom, said spokes connecting the poppet guide  60  with a support rim  64 . The support spokes  62  are fin-like, having a narrow profile when viewed from a downstream end. Further, the number of support spokes  62  is kept low. Preferably, only three support spokes  62  are provided. The narrow profile of the support spokes  62  as well as the low number of support spokes  62  maximizes the cross-sectional flow area of the poppet support  44 . The support rim  64  is annular and is adapted to be locked in position on an interior surface of the valve body  12  at the interface between the expanded section  22  and the outlet section  20 . In particular, a downstream portion of the support rim  64  is adapted to abut against the poppet support shoulder  42  of the valve body  12  while a plurality of poppet support locking protrusions or teeth  66  are adapted to be secured within the poppet support locking recess  40  of the valve body  12 . The poppet support locking protrusions  66  are spaced circumferentially around an outer surface of the support rim  64  and have a steep upstream face  68  and a sloped downstream face  70  such that the poppet support  44  can be slid into the valve body from its upstream end, and locked into place. The combination of the support rim  64  and the support spokes  62  serves to maintain the poppet guide  60  positioned centrally within the valve body  12 , and co-axial therewith.  
         [0058]     The valve seat  34 , as shown in detail in  FIGS. 8 and 9 , is an annular sleeve adapted to be locked into place within the inlet section  18  of the valve body  12 . Near its upstream end, an outer surface of the valve seat  34  is provided with a plurality of valve seat locking protrusions or teeth  72  adapted to be secured within the valve seat locking recess  28  of the valve body  12 . The valve seat locking protrusions  72  are spaced circumferentially around the outer surface of the valve seat  34  and have a steep upstream face  74  and a sloped downstream face  76  such that the valve seat  34  can be slid into the valve body  12  from its upstream end, and locked into place. The outer surface of the valve seat  34  is also provided with an annular shoulder  78  adapted to abut against the valve seat shoulder  32  of the valve body  12  when the valve seat  34  is locked into place within the valve body  12 . Still on the outer surface of the valve seat  34 , an annular O-ring recess  80  is provided upstream of the shoulder  78 . The O-ring recess is adapted to support and retain a valve seat O-ring  82 . A downstream end of the valve seat  34  provides an annular valve seat surface  84  against which the poppet seal  47  is pressed when the check valve  10  is in its closed position. The valve seat surface  84  has an inner diameter greater than the outer diameter of the upstream portion of the poppet face  50 .  
         [0059]     By eliminating a conventional lining wall (not shown) within the valve body  12  in the region surrounding the poppet  36 , the flow area around the poppet  36  can be maximized, while the external diameter of the check valve  10  can be minimized.  
         [0060]     The inlet connection nut  16  has a downstream section  86  and an upstream section  88 . An inner surface of the downstream section  86  is sized to fit closely over the outer surface of the inlet portion  18  of the valve body  12 , and is provided with an annular retaining ring recess  90  adapted to receive the retaining ring  26 . An outer surface of the downstream section  86  is provided with facetted tool-engaging surfaces  92  to allow the inlet connection nut  16  to be engaged by a tool for turning purposes. The upstream section  88  is provided with internal threading  94  to accommodate a threaded connection with the male threaded connector of the water meter (not shown). A gasket  96  is provided within the inlet connection nut  16  near an interface between the downstream section  86  and the upstream section  88 . The internal threading  94  and the gasket  96  serve to provide a sealed connection between the check valve  10  and the water meter.  
         [0061]     An exemplary manner in which the preferred embodiment check valve  10  may be assembled will now be described.  
         [0062]     First, the poppet seal  47  is pushed over the upstream portion of the poppet face  50  and into the annular space between the upstream portion of the poppet face  50  and the seal-retention flange  58 . Similarly, the valve seat O-ring  82  is placed into the O-ring recess of the valve seat  34 .  
         [0063]     Second, the poppet support  44  is slid in through the upstream end of the valve body  12  with its poppet guide  60  facing upstream, until the downstream surface of the support rim  64  abuts against the poppet support shoulder  42  of the valve body  12 , and the poppet support locking protrusions  66  engage the poppet support locking recess  40 . The resilient flexibility of the support rim  64  and the sloped downstream face  70  of the poppet support locking protrusions  66  cooperate to allow the poppet support locking protrusions  66  to be pushed radially inwardly while the poppet support  44  is being pushed into its locked position, while the steep upstream face  68  of the poppet support locking protrusions  66  serve to lock the poppet support  44  in place within the valve body  12 .  
         [0064]     Next, the spring  48  is placed over the poppet guide  60  and the poppet  36  is inserted into the valve body  12  with the poppet stem  52  sliding into the poppet guide  60  and the spring-retention sleeve  56  sliding over the spring  48 .  
         [0065]     The valve seat  34  is then pushed into the valve body  12  with its valve seat surface  84  facing downstream, until the valve seat  34  locks into place with its shoulder  78  abutting the valve seat shoulder  32  of the valve body  12 , and the valve seat locking protrusions  72  engaging the valve seat locking recess  28 . The resilient flexibility of the valve seat  34  and the sloped downstream face  76  of the valve seat locking protrusions  72  cooperate to allow the valve seat locking protrusions  72  to be pushed radially inwardly while the valve seat  34  is being pushed into its locked position, while the steep upstream face  74  of the valve seat locking protrusions  72  serve to lock the valve seat  34  in place within the valve body  12 .  
         [0066]     Finally, the retaining ring  26  is placed into the retaining ring recess  24  of the valve body  12 , the inlet connection nut  16  is pushed onto the upstream end of the valve body  12  until the retaining ring  26  engages the retaining ring recess  90  of the inlet connection nut  16 , and the gasket  96  is inserted into the inlet connection nut  16  until it abuts the upstream end of the valve body  12 . The split-ring structure of the retaining ring  26  allows it to be expanded radially to fit over the upstream end of the valve body  12  while fitting the retaining ring  26  into the retaining ring recess  24  of the valve body  12 , and to also be compressed radially to allow the downstream end of the inlet connection nut  16  to be slid thereover. Once the retaining ring  26  is engaged within the retaining ring recesses  24 ,  90  of both the valve body  12  and the inlet connection nut  16 , it resists axial movement of the inlet connection nut  16  away from the valve body  12  while allowing the inlet connection nut  16  to rotate relative to the valve body  12  to facilitate connection of the check valve  10  to the water meter.  
         [0067]     Although an exemplary manner of assembling the check valve  10  has been described, it is to be understood that the check valve  10  may be assembled using other methods and in other sequences, as will be understood by those skilled in the art.  
         [0068]     In use, the supply pipe of the residential water supply system is first disconnected from the water meter. The downstream end of the check valve  10  is then connected to the supply pipe by engaging the external threading  46  of the valve body  12  with internal threading of the female supply pipe connector. To facilitate tightening of the connection, a torquing tool such as a wrench may be used to engage the annular protrusions  38  of the valve body  12 .  
         [0069]     Next, the inlet connection nut  16  is connected to the water meter by engaging the internal threading  94  of the inlet connection nut  16  with external threading of the male water supply connector. The retainer ring  26  connection between the inlet connection nut  16  and the valve body  12  allows the inlet connection nut  16  to be turned relatively to the valve body  12  to facilitate the threaded connection between the inlet connection nut  16  and the water meter. Again, to facilitate tightening of the connection, a torquing tool may be used to engage the faceted tool-engaging surfaces  92  of the inlet connection nut  16 . The gasket  96  ensures a sealed connection between the valve body  12  and the water meter.  
         [0070]     When the pressure at the downstream and upstream ends of the check valve  10  are equalized, or when the pressure differential is small, the spring  48  pushes the poppet  36  upstream such that the poppet seal  47  is pressed against the valve seat surface  84  of the valve seat  34 , as shown in  FIG. 4 . In this state, the check valve is closed, and flow through the check valve is restricted.  
         [0071]     If the water pressure at the downstream end of the check valve  10  exceeds the pressure at the upstream end, this pressure differential tends to increase the force with which the poppet  36  is pressed against the valve seat  34 , thereby improving the seal between the poppet seal  47  and the valve seat surface  84 .  
         [0072]     If the water pressure at the upstream end of the check valve  10  exceeds the pressure at the downstream end by a degree sufficient to overcome the spring force exerted by the spring  48 , then the increased pressure of the water against the poppet face  50  moves the poppet  36  downstream away from the valve seat  34  allowing water to flow from the upstream end of the check valve  10  to the downstream end, as shown in  FIG. 5 . In this open state, the large central bore of the valve body  12 , valve seat  34 , the large cross-section openings of the poppet support  44  and the expanded internal diameter of the expanded section  22  of the valve body  12  all serve to maximize the rate at which water can flow through the check valve  10  and to thereby minimize the water pressure drop through the check valve.  
         [0073]     In applications where the prevention of backflow through the valve is particularly important, redundant valve systems are frequently used.  FIG. 13  illustrates a second embodiment  100  of the present invention (without the inlet connection nut  16 ) in which the valve cartridge contains two valve seat  34 /poppet  36 /poppet support  44  combinations. In this figure, like elements are identified using the same reference numbers as used in describing the first embodiment, and the two instances of each element are differentiated using the suffixes “a” and “b”.  
         [0074]     As is apparent from  FIG. 13 , the second embodiment check valve  100  is substantially the same as the first embodiment check valve  10 , with a duplication of some features and the merging of other features. There are now two expanded sections  22   a ,  22   b  of the valve body  12  to accommodate the two valve systems. The first expanded section  22   a  houses the first valve seat  34   a , the first poppet  36   a  and the first poppet support  44   a , while the second expanded section  22   b  houses the second valve seat  34   b , second poppet  36   b  and the second poppet support  44   b . The second valve seat  34   b  is combined with the first poppet support  44   a  into a single element. Thus, the support rim  64   b  of the first poppet support  44   a  is merged into the features of the second valve seat  34   b.    
         [0075]     The second embodiment check valve  100  therefore provides redundant protection, such that if one of the valve systems fails, the second will function to prevent backflow through the check valve  100 .  
         [0076]     In both the preferred and second embodiment check valves  10 ,  100 , the valve body  12  and inlet connection nut  16  are made of either brass or bronze, the valve seat  34 , poppet  36  and poppet support  44  of the valve cartridge  14  are made of plastic, and the seals and gaskets  47 ,  82 ,  96  are made of rubber. However, it is to be understood that other suitable materials may be used as will be appreciated by persons skilled in the art.  
         [0077]     In the exemplary application described, the check valve is installed between a water meter and a residential supply pipe to prevent backflow of water from a residence to a water main. However, it is to be understood that the check valve of the present invention may be used in various other applications. For example, the check valve can be used in many plumbing or waterworks application to ensure uni-directional flow through a conduit. It can also be used to ensure uni-directional flow of other fluids, sewage or gasses for example.  
         [0078]     Very specific geometries of the various elements have also been provided. However, it is to be understood that other suitable geometries may be used by persons skilled in the art without necessarily departing from the scope of the invention.  
         [0079]     Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practised otherwise than as specifically described herein.