Abstract:
An integrated fluid valve assembly comprising a valve having a flexible head, a stem, and at least one leg. In at least one embodiment of the present invention, a fluid valve assembly comprises a retainer and a valve. The valve may be made of a single integrated part that interacts with the retainer to control fluid flow through a fluid system, such as to maintain fluid flow through an automotive oil filter when the filter itself becomes clogged. The valve automatically permits fluid flow through an aperture when the fluid pressure rises to a predetermined set point. In another embodiment of the present invention, a cartridge fluid filter comprises a center tube, a filter media, and a valve that reversibly closes a bypass aperture. In another embodiment of the present invention, a fluid filter includes a center tube, a filter media, a valve that reversibly closes a bypass aperture, and a canister enclosing the center tube, filter media, and valve.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    There is known a wide variety of valves used to control fluid flow. Such valves may have a number of uses, including to provide a pressure relief when fluid pressure increases above a certain point or to prevent fluid backflow. Although such valves can be used in various applications, they are commonly used in, for example, oil filters for automobile engines or other internal combustion engines. Many fluid filters include some type of relief valve to help regulate fluid pressure. A relief valve, which can also be known as a bypass valve, allows fluid to flow through the filter assembly to its destination despite a blockage in the filter itself. For example, many automotive oil filters include relief valves that permit oil flow to the engine even when the oil filter media becomes clogged with particulate impurities. Such relief valves protect the engine from damage due to inadequate lubrication by enabling the oil to bypass the clogged filter media and reach the engine, albeit in an unfiltered state. Similarly, an anti-backflow valve, or anti-siphon valve, in an automotive oil filter protects the engine from inadequate lubrication by preventing oil in the engine from flowing backwards out of the engine into the filter. 
         [0002]    Many types of fluid valves, including fluid filter relief valves, are often made from several components, which must be carefully formed and assembled during production. Valves made from fewer components are easier and less expensive to make than those made from a greater number of components. For example, many current filter assemblies use a relief valve made from at least three separate parts, including a steel retainer, a plastic valve, and a steel spring. In most of these assemblies, the plastic valve and steel spring must be made so that they connect during production. Such a connection not only increases the complexity and cost of making one or both of the parts, but it also increases the complexity and cost of assembling the filter. 
         [0003]    It is therefore desired to provide an integrated fluid valve assembly that uses fewer parts, is easier to make, and costs less, but that nevertheless provides proper fluid control based on fluid pressure. 
       SUMMARY 
       [0004]    Certain embodiments of the present invention comprise fluid valve assemblies. Other embodiments of the present invention comprise fluid filters containing valve assemblies. Filters and valves made in accordance with various aspects of the present invention have fewer parts, are easier to manufacture, and are less expensive to produce than many other filters and valves, particularly those traditional filters and valves having a steel retainer, plastic valve, and steel spring. In addition, the parts used to make various filters and valves of the present invention are less costly to handle and store, reducing inventory-related costs. 
         [0005]    In at least one embodiment of the present invention, a fluid valve assembly comprises a retainer and a valve. The retainer may be of a substantially planar or substantially conical shape, with a first surface and an opposing second surface, and includes an outside edge framing its circumference and an inside annular edge framing an aperture in the retainer. Disposed circumferentially adjacent to the inside annular edge on the first surface of the retainer is an annular ledge. 
         [0006]    The valve fits within the aperture of the retainer and comprises a flexible valve head, a valve stem, and at least one leg. One end of the valve stem is axially connected to the valve head, while the other end is connected to the at least one leg. The valve may be made of a single integrated part. 
         [0007]    The valve head is generally shaped like a disc and is configured so that it can contact the annular ledge of the retainer, covering the entirety of the aperture. When the valve head and the annular ledge are engaged, such as, for example, during the normal operation of a fluid filter, the valve head engages the annular ledge of the retainer to form a seal so that a substantial amount of fluid cannot leak through the aperture in the retainer. However, when the valve head and the annular ledge are not engaged, fluid can flow through the aperture in the retainer. 
         [0008]    The valve disengages from the retainer, thereby opening the retainer aperture, when the fluid pressure rises to a predetermined set point, causing the valve head to raise and forcing the leg or legs to flex outwardly, thereby causing the valve head to disengage from the annular ledge. Once the seal between the valve head and the annular ledge is broken, fluid begins to flow through the aperture. For example, when the valve assembly is installed in a fluid filter as a relief valve, the aperture provides a route for fluid to bypass the filter media in the fluid filter and flow out of the fluid filter. 
         [0009]    In another embodiment of the present invention, a cartridge fluid filter is capable of insertion into a receptacle for fluid filtration. One embodiment of a cartridge fluid filter of the present invention comprises a top end cap, a filter media, a bottom end cap, a center tube, a retainer, and a relief valve. The center tube is hollow and may contain multiple holes through which fluid can flow. Formed around the outside of the center tube is the filter media. The top end cap is attached to one end of the filter media, while the bottom end cap is attached to the other end of the filter media. The relief valve comprises a flexible valve head, a stem, and at least one leg. The valve is configured to regulate fluid flow into or out of the center tube by opening and closing a bypass aperture formed in the retainer. 
         [0010]    In another embodiment of the present invention, a fluid filter comprises a center tube, a filter media, and a relief valve assembly enclosed in a canister. The filter media surrounds the center tube, and the relief valve reversibly closes a bypass aperture to regulate fluid flow through the fluid filter. Between the filter media and the canister is an outer circumferential space that serves as a fluid passageway for delivering fluid to or from the filter media. In a bypass situation, the relief valve opens, permitting fluid to flow through the bypass aperture, bypass the filter media, and flow out of the canister to its destination. The fluid filter thereby delivers substantially uninterrupted fluid flow even when the filter media becomes clogged. In some embodiments of the fluid filter of the present invention, the fluid filter further comprises a second valve assembly that acts as an anti-siphon valve. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a perspective view of an embodiment of a valve assembly according to the present invention, wherein the valve is in the closed position; 
           [0012]      FIG. 2  shows a top perspective view of an embodiment of a retainer according to the present invention; 
           [0013]      FIG. 3  shows a bottom perspective view of the retainer of  FIG. 2 ; 
           [0014]      FIG. 4  shows a side view of an embodiment of a valve according to the present invention; 
           [0015]      FIG. 5  shows a bottom perspective view of the valve of  FIG. 4 ; 
           [0016]      FIG. 6  shows a sectional view of an embodiment of a valve assembly according to the present invention, wherein the valve is in the closed position; 
           [0017]      FIG. 7  shows a sectional view of the valve assembly of  FIG. 6 , wherein the valve is in an open position; 
           [0018]      FIG. 8  shows a sectional view of an embodiment of a valve assembly according to the present invention, wherein the valve is in the closed position; 
           [0019]      FIG. 9  shows a sectional view of an embodiment of a fluid filter according to the present invention; 
           [0020]      FIG. 10  shows a sectional view of an embodiment of a cartridge fluid filter according to the present invention; and 
           [0021]      FIG. 11  shows a sectional view of another embodiment of a cartridge fluid filter according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    It will be appreciated by those of skill in the art that the following detailed description of the preferred embodiments is exemplary in nature and is not intended to limit the scope of the appended claims. 
         [0023]    Referring now to  FIG. 1 , there is shown one embodiment of a fluid valve assembly of the present invention. In this embodiment, valve assembly  10  comprises retainer  20  and valve  100 . Retainer  20  may be substantially planar or substantially conical. The embodiment of retainer  20  shown in  FIGS. 2 and 3  is substantially conical, such that first surface  22  of retainer  20  is substantially convex and second surface  24  of retainer  20  is substantially concave. Retainer  20  may be made of any suitable material with sufficient strength, such as steel or plastic. 
         [0024]    As shown in  FIGS. 2 and 3 , retainer  20  includes outside circumferential edge  30  and inside annular edge  40 . Outside circumferential edge  30  is substantially rectangular, as shown in  FIGS. 1-3 , but may instead be of any shape, such as substantially circular, depending on the specific application in which the valve assembly is to be used. 
         [0025]    Inside annular edge  40  defines aperture  50 , as shown in  FIG. 2 . Inside annular edge  40  may be of any configuration such that aperture  50  is of any shape, but a substantially circular shape is preferred for many applications. Annular ledge  60  is that portion of first surface  22  of retainer  20  that circumferentially surrounds inside annular edge  40 . In the embodiment shown in  FIG. 2 , annular ledge  60  is a flat, horizontal portion of first surface  22 . However, annular ledge  60  may be of any size and shape, and may be configured on either first surface  22  or second surface  24  of retainer  20 , so long as annular ledge  60  is capable of engagement with valve  100  to form a seal through which a substantial amount of fluid cannot pass. 
         [0026]    Referring now to  FIGS. 4 and 5 , valve  100  fits within aperture  50  and consists of flexible valve head  110 , valve stem  120 , and legs  130 ,  140 . Flexible valve head  110  has first surface  112 , which is generally convex-shaped, and second surface  114 , which is generally concave-shaped. Flexible valve head  110  is formed in the same general circumferential shape as aperture  50 , so that flexible valve head  110  can cover aperture  50 , as shown in  FIGS. 1 and 6 , when retainer  20  and valve  100  are fully engaged. Further, flexible valve head  110  is shaped such that second surface  114  of flexible valve head  110  can engage annular ledge  60  to seal aperture  50  so that only minimal fluid can flow through aperture  50 . While it is preferable for most applications that flexible valve head  10  completely cover aperture  50  so that no fluid can flow through aperture  50  when retainer  20  and valve  100  are fully engaged, embodiments of the present invention also include valve assemblies that do not completely block fluid flow through aperture  50 . Flexible valve head  110  is made from a relatively flexible material, which may include plastic, rubber, flexible metal, carbon fiber, silicon, or any other flexible material having sufficient stiffness to maintain suitable engagement between retainer  20  and valve  100 . 
         [0027]    Referring again to  FIGS. 4 and 5 , one end of valve stem  120  is attached to second surface  114  of flexible valve head  110 . Valve stem  120  is preferably attached near the center of second surface  114 , as shown, but may be attached anywhere on second surface  114  so long as the positioning of valve stem  120  does not obstruct engagement of second surface  114  with annular ledge  60  to form a seal. Similarly, valve stem  120  is shown extending axially from flexible valve head  110 , but valve stem  120  may extend from flexible valve head  110  at almost any angle, so long as the positioning of valve stem  120  does not obstruct engagement of second surface  114  with annular ledge  60  to form a seal. Although one valve stem is preferred, multiple valve stems may be used. 
         [0028]    Attached to the opposite end of valve stem  120  are legs  130 ,  140 . Although two legs is preferred, as shown in  FIGS. 4 and 5 , a valve may have only one leg or more than two legs. Legs  130 ,  140  are preferably made from the same material as valve stem  120  and flexible valve head  110 , but may be made of a different material, so long as legs  130 ,  140  are capable of sufficient flexion. As shown in  FIG. 6 , each of legs  130 ,  140  should be of sufficient length to contact second surface  24  of retainer  20  when flexible valve head  110  and annular ledge  60  are fully engaged to form a seal. Legs  130 ,  140  should be made so that they flex outwardly from valve stem  120  when the fluid pressure against second surface  114  of flexible valve head  110  raises to a predetermined set point. 
         [0029]    During production of valve assembly  10 , flexible valve head  110  is compressed at first surface  112  while inserted into aperture  50  of retainer  20 . When flexible valve head  110  is compressed, legs  130 ,  140  are drawn toward valve stem  120 . When flexible valve head  110  is released, legs  130 ,  140  move away from valve stem  120  and engage second surface  24  of retainer  20 , which creates constant pressure between annular ledge  60  of retainer  20  and second surface  114  of flexible valve head  110 , creating a seal. 
         [0030]      FIG. 6  shows valve assembly  10  in the closed position. In this position, second surface  114  of flexible valve head  110  engages annular ledge  60  to form a seal so that a significant amount of fluid cannot escape through aperture  50 . Second surface  114  and annular ledge  60  are held in contact by legs  130 ,  140  pressing against second surface  24  of retainer  20 , creating constant pressure between flexible valve head  110 , retainer  20 , and legs  130 ,  140 . The valve assembly exists in the closed position when fluid pressure against second surface  114  of flexible valve head  110  is below a predetermined set point. 
         [0031]      FIG. 7  shows valve assembly  10  in an open position. In this position, second surface  114  of flexible valve head  110  and annular ledge  60  are spaced apart such that fluid can flow through aperture  50 . Valve assembly  10  opens when fluid pressure against second surface  114  of flexible valve head  110  reaches a predetermined set point. At that point, the fluid presses against second surface  114  with sufficient force to raise flexible valve head  110  and cause legs  130 ,  140  to flex outwardly from valve stem  120 . This disengages second surface  114  of flexible valve head  110  from annular ledge  60  of retainer  20 , opening aperture  50 . Fluid then flows through aperture  50 . When the fluid pressure against second surface  114  of flexible valve head  110  drops below the predetermined set point, legs  130 ,  140  return to their original position, thereby returning valve assembly  10  to the closed position. 
         [0032]    Those of skill in the art will understand that valve  100  can be made of plastic using several known techniques, including injection molding. Because injection molding is typically a repeatable process, valve  100  can be made so that legs  130 ,  140 , as well as the connections between legs  130 ,  140  and valve stem  120 , will flex to allow the seal between flexible valve head  110  and annular ledge  60  to release when the fluid pressure reaches a predetermined set point. Methods of creating the injection-molded pieces are well known to those of skill in the art. 
         [0033]    The fluid pressure required to disengage valve  100  from retainer  20 , i.e., the predetermined set point, will vary depending on the circumstances. The specific application in which valve  100  is used will dictate the predetermined set point. Those of ordinary skill in the art will readily understand that the predetermined set point is calibrated for each valve embodiment by changing one or more of at least three primary factors: (1) the size of aperture  50  of retainer  20 ; (2) the geometry of legs  130 ,  140 , valve stem  120 , and flexible valve head  110 ; and (3) the material used to make valve  100 . For example, a larger aperture  50  will enable valve  100  and retainer  20  to disengage at a lower fluid pressure than when aperture  50  is smaller. Similarly, when valve  100  is made from a relatively stiffer material, the pressure at which valve  100  and retainer  20  will disengage is higher than when valve  100  is made from a more flexible material. By varying one or more of these primary factors, a person of ordinary skill in the art can develop a suitable predetermined set point for using one or more embodiments of the present invention in a variety of applications. Persons of ordinary skill in the art will recognize that such calibration may be aided by using commercially-available finite element analysis software packages. 
         [0034]    Although it is preferable for legs  130 ,  140  to attach to valve stem  120  at the farthest point from flexible valve head  110 , as shown in  FIGS. 4 and 5 , attachment may be at any point on valve stem  120  so long as legs  130 ,  140  are sized to exert the proper amount of constant pressure against second surface  24  of retainer  20  when valve assembly  10  is in the closed position. 
         [0035]      FIG. 8  shows another embodiment of a fluid valve assembly of the present invention. In this embodiment, valve assembly  10 ′ comprises retainer  20 ′ and valve  100 ′. First surface  22 ′ of retainer  20 ′ is substantially convex and second surface  24 ′ of retainer  20 ′ is substantially concave. Retainer  20 ′ includes inside annular edge  40 ′, which defines aperture  50 ′. Along inside annular edge  40 ′ is lip  42 ′. Annular ledge  60 ′ is that portion of first surface  22 ′ of retainer  20 ′ that circumferentially surrounds inside annular edge  40 ′ and lip  42 ′. Ridge  26 ′ circumferentially surrounds annular ledge  60 ′. 
         [0036]    Valve  100 ′ fits within aperture  50 ′ and includes flexible valve head  110 ′, valve stem  120 ′, and legs  130 ′,  140 ′. Flexible valve head  110 ′ has first surface  112 ′ and second surface  114 ′. In the embodiment shown in  FIG. 8 , flexible valve head  110 ′ has a circular circumferential shape and fits against the depressed portion of first surface  22 ′ of retainer  20 ′ between ridge  26 ′ and lip  42 ′. Second surface  114 ′ of flexible valve head  110 ′ engages annular ledge  60 ′ when valve  100 ′ and retainer  20 ′ are fully engaged. Ridge  26 ′ is sufficiently pronounced to serve as a guide to align flexible valve head  110 ′ in the proper position against annular ledge  60 ′ when flexible valve head  110 ′ is brought into contact with annular ledge  60 ′ during closing of valve assembly  10 ′. Similarly, lip  42 ′ is sufficiently extended to help align legs  130 ′,  140 ′ during opening and closing of valve assembly  10 ′. 
         [0037]    Referring now to  FIG. 9 , there is shown one embodiment of a fluid filter of the present invention. In this embodiment, fluid filter  200  comprises center tube  210 , which is cylindrical and generally hollow, defining middle cavity  212 . Center tube  210  contains multiple holes through which fluid can flow transversely into middle cavity  212 , and center tube  210  is substantially open at both ends so that fluid may flow longitudinally through center tube  210 . Center tube  210  may be made from any suitable material, such as steel or plastic. 
         [0038]    Formed circumferentially around the outside of center tube  210  is filter media  220 , which is cylindrically shaped and is approximately the same length as center tube  210 . Filter media  220  is preferably made of pleated paper, but those of skill in the art will recognize that filter media  220  may be made of any suitable material capable of filtering fluid. Many such suitable filtering materials are well known. 
         [0039]    Fluid filter  200  further comprises top end cap  230  and bottom end cap  240 . As shown in  FIG. 9 , top end cap  230  is relatively thin and substantially disc-shaped. Top end cap  230  is attached to one end of center tube  210  and filter media  220 . Top end cap  230  preferably has approximately the same circumference as the outside surface of filter media  220 , as shown in  FIG. 9 , but may be larger in circumference. Formed generally in the center of top end cap  230  is top opening  232 , which has approximately the same diameter as center tube  210  such that the open end of center tube  210  generally corresponds to top opening  232  of top end cap  230 . Top opening  232  may be larger or smaller in diameter than the open end of center tube  210 , so long as top end cap  230  does not prevent fluid access through the open end of center tube  210  to middle cavity  212 . Top end cap  230  may be made from almost any material with sufficient strength, for example, steel, cardboard, or plastic. 
         [0040]    Bottom end cap  240 , which is relatively thin and substantially disc-shaped as shown in  FIG. 9 , is attached to the opposite end of center tube  210  and filter media  220  from the end to which top end cap  230  is attached. Bottom end cap  240  preferably has approximately the same circumference as the outside surface of filter media  220 , as shown in  FIG. 9 , but may be larger in circumference. Formed generally in the center of bottom end cap  240  is bottom opening  242 , which has approximately the same diameter as center tube  210  such that the open end of center tube  210  generally corresponds to bottom opening  242  of bottom end cap  240 . Bottom opening  242  may be larger or smaller in diameter than the open end of center tube  210 , so long as bottom end cap  240  does not prevent fluid access through the open end of center tube  210  to middle cavity  212 . 
         [0041]    Fluid filter  200  further comprises retainer  250  and valve  260 . Retainer  250  is substantially conical and includes substantially cylindrical portion  252  that houses valve  260 , as shown in  FIG. 9 . Valve  260  fits substantially within bypass aperture  254  formed in the apex of substantially cylindrical portion  252 . Bypass aperture  254  is preferably substantially circular, but may be of any suitable shape. Valve  260  includes flexible valve head  262 , valve stem  264 , and legs  266 ,  268 . Flexible valve head  262  is formed in the same general circumferential shape as bypass aperture  254  so that flexible valve head  262  can cover bypass aperture  254 , as shown in  FIG. 9 , when valve  260  and retainer  250  are fully engaged. When valve  260  and retainer  250  are fully engaged, flexible valve head  262  and retainer  250  form a seal through which substantial fluid cannot pass, and therefore substantial fluid is prevented from flowing through bypass aperture  254 . However, when valve  260  and retainer  250  are not fully engaged, substantial fluid can pass through bypass aperture  254  into middle cavity  212 . 
         [0042]    Substantially cylindrical portion  252  of retainer  250  is configured in size and shape to be inserted through top opening  232  of top end cap  230  and into the end of center tube  210 , as shown in  FIG. 9 . Insertion of substantially cylindrical portion  252  of retainer  250  into center tube  210  closes top opening  232  of top end cap  230  so that little or no fluid can pass through top opening  232 , except through bypass aperture  254  of retainer  250  when valve  260  and retainer  250  are not fully engaged. 
         [0043]    Fluid filter  200  further comprises anti-drain back gasket  270 , which includes raised lip  272  and outer flange  274 . Raised lip  272  forms substantially circular opening  273  and is configured in size and shape to fit within bottom opening  242  of bottom end cap  240  and the corresponding open end of center tube  210 , such that fluid in middle cavity  212  can exit middle cavity  212  through substantially circular opening  273  of anti-drain back gasket  270 . Outer flange  274  extends radially from the bottom of raised lip  272  such that substantial fluid cannot escape from middle cavity  212  through bottom opening  242  of bottom end cap  240  except through substantially circular opening  273  of anti-drain back gasket  270 . 
         [0044]    Held against the underside of outer flange  274  of anti-drain back gasket  270  is tapping plate  280 . Tapping plate  280  includes center opening  282 , the inner wall of which is threaded to removably engage a threaded fluid receptacle (not shown), such as on an automotive engine. Tapping plate  280  further includes raised ridge  284 , which is configured to surround center opening  282  and engage the underside of anti-drain back gasket  270  to form a seal through which substantial fluid cannot pass. Tapping plate  280  also includes outer openings  286  located radially from raised ridge  284 . 
         [0045]    Canister  290  is generally cylindrical with closed end  292  and open end  294  and is configured to enclose filter media  220 , retainer  250 , and tapping plate  280 . The outside edge of retainer  250  is configured to fit within canister  290  and to hold filter media  220  stable within canister  290 . Canister  290  surrounds filter media  220 , but between the inside surface of canister  290  and the outside surface of filter media  220  is outer circumferential space  300 . 
         [0046]    Outer flange  274  of anti-drain back gasket  270  covers outer openings  286  and is configured so that fluid can flow through outer openings  286  and into outer circumferential space  300 , but cannot flow from outer circumferential space  300  through outer openings  286 . In this way, anti-drain back gasket  270  prevents fluid from draining back out of canister  290 , except through substantially circular opening  273  of anti-drain back gasket  270 . Anti-drain back gasket  270  may be made of rubber or any suitable material with sufficient flexibility to permit proper fluid flow through outer openings  286 . 
         [0047]    Bottom plate  310  is configured to attach to open end  294  of canister  290  so that a significant amount of fluid cannot leak through the connection. Bottom plate  310  includes a center opening through which substantial fluid can flow and, on its outer surface, a circumferential groove that holds o-ring  320  or any other structure suitable for sealing (e.g., a gasket). O-ring  320  is configured to form a fluid-tight seal between fluid filter  200  and its fluid source (not shown) when filter  200  is attached to the fluid source. 
         [0048]    Bottom plate  310  and canister  290  may be made of steel, plastic, or any other suitable material. O-ring  320  is preferably made of rubber or any material suitable for creating a seal. 
         [0049]    As assembled, fluid filter  200  accepts a flow of fluid, filters the fluid through filter media  220 , and then returns the fluid in a substantially filtered state. When fluid filter  200  is operating in a normal state, fluid enters fluid filter  200  through the opening in bottom plate  310 , then flows through outer openings  286  in tapping plate  280 , into outer circumferential space  300  between canister  290  and filter media  220 , and transversely through filter media  220  and center tube  210  to middle cavity  212 . Then, the fluid returns to its source in a substantially filtered state by exiting middle cavity  212  through opening  273  in anti-drain back gasket  270  and center opening  282  of tapping plate  280 . 
         [0050]    However, fluid filter  200  permits the continuous flow of fluid to its destination even when filter media  220  is clogged. When fluid cannot pass through filter media  220  because of a clog, fluid pressure builds in outer circumferential space  300  and in the space between retainer  250  and canister  290 . When the fluid pressure rises to a predetermined bypass set point, valve  260  is pushed away from retainer  250 , disengaging flexible valve head  262  from retainer  250  so that fluid flows through bypass aperture  254  and therefore enters middle cavity  212 . The unfiltered fluid exits middle cavity  212  to its source in the same way that the filtered fluid exits, through opening  273  in anti-drain back gasket  270  and center opening  282  of tapping plate  280 . When the filter is in a bypass situation, the fluid returns to its source without filtering, but this is more desirable than allowing the fluid flow to stop because the filter media is clogged. 
         [0051]    Referring again to  FIG. 9 , there is shown an optional means to prevent fluid backflow into fluid filter  200 , namely anti-siphon housing  400  and anti-siphon valve  410 . Anti-siphon housing  400  includes orifice  402  and circumferential flange  404 . Anti-siphon housing  410  is substantially located within middle cavity  212  of center tube  210  and encloses opening  273  of anti-drain back gasket  270  such that substantial fluid cannot flow through opening  273  of anti-drain back gasket  270  into middle cavity  212  unless it flows through orifice  402  of anti-siphon housing  400 . Circumferential flange  404  of anti-siphon housing  400  fits between bottom end cap  240  and anti-drain back gasket  270 . 
         [0052]    Anti-siphon valve  410 , which consists of anti-siphon flexible valve head  412 , anti-siphon valve stem  414 , and anti-siphon valve legs  416 ,  418 , fits substantially within orifice  402  of anti-siphon housing  400 . Anti-siphon flexible valve head  412  is configured to substantially close orifice  402  to fluid flow when anti-siphon valve  410  and anti-siphon housing  400  are fully engaged. 
         [0053]    Like valve  260 , anti-siphon valve  410  operates according to fluid pressure. Anti-siphon valve  410  is open to permit substantial fluid flow through orifice  402  when fluid pressure within middle cavity  212  is above a predetermined set point. However, when the fluid pressure in middle cavity  212  drops below the predetermined set point, anti-siphon flexible valve head  412  engages anti-siphon housing  400  to close orifice  402  so that a substantial amount of fluid cannot flow through orifice  402 . This prevents fluid from the fluid source (not shown) from flowing backwards through center opening  282  of tapping plate  480  and into middle cavity  212  of fluid filter  200 . 
         [0054]    Referring now to  FIG. 10 , there is shown one embodiment of a cartridge fluid filter of the present invention. In this embodiment, cartridge fluid filter  500  comprises top end cap  510 , filter media  520 , bottom end cap  530 , center tube  540 , relief valve  550 , and retainer  560 . Center tube  540  is cylindrical, is generally hollow, and defines middle cavity  542 . Center tube  540  contains multiple holes  544  through which fluid can flow into middle cavity  542 . In addition, center tube  540  has first end  546  and second end  548  and is substantially open at both ends  546 ,  548  so that fluid may flow longitudinally through center tube  540 . Center tube  540  may be made of any suitable material, such as steel or plastic. 
         [0055]    Formed circumferentially around the outside of center tube  540  is filter media  520 , which is cylindrically shaped. 
         [0056]    Top end cap  510  may be substantially disc-shaped and defines top opening  512 . Top end cap  510  may have approximately the same circumference as the outside surface of filter media  520 , but may be larger in circumference than the outside surface of filter media  520 . Circumferentially disposed around the outside of top end cap  510  is top lip  514 , which extends axially toward bottom end cap  530  and attaches to filter media  520 , as shown in  FIG. 10 . Top opening  512  is generally no larger in diameter than center tube  540 . Top opening  512  may have a smaller diameter than that of center tube  540 , so long as it is large enough to accommodate relief valve  550  and retainer  560 . 
         [0057]    Bottom end cap  530  may be substantially disc-shaped and defines bottom opening  532 . Bottom end cap  530  may have approximately the same circumference as the outside surface of filter media  520 , but may be larger in circumference than the outside surface of filter media  520 . Circumferentially disposed around the outside of bottom end cap  530  is bottom lip  534 , which extends axially toward top end cap  510  and attaches to filter media  520 , as shown in  FIG. 10 . Bottom opening  532  is generally no larger in diameter than center tube  540 . Bottom opening  532  may have a smaller diameter than that of center tube  540 , so long as substantial fluid may pass through bottom opening  532 . 
         [0058]    Retainer  560  of cartridge fluid filter  500  fits within top opening  512  of top end cap  510  and first end  546  of center tube  540 , as shown in  FIG. 10 . Retainer  560  comprises bypass aperture  562  and is configured to close first end  546  of center tube  540  so that substantial fluid cannot flow through first end  546  of center tube  540  unless it flows through bypass aperture  562  of retainer  560 . Bypass aperture  562  is preferably substantially circular, but may be of any shape. 
         [0059]    In some embodiments of a cartridge fluid filter made according to various aspects of the present invention, retainer  560  is integral with top end cap  510 . 
         [0060]    Relief valve  550  of cartridge fluid filter  500  includes flexible valve head  552 , valve stem  554 , and legs  556 ,  558 . In the embodiment shown in  FIG. 10 , relief valve  550  fits substantially within bypass aperture  562  of retainer  560 . Flexible valve head  552  is formed in the same general circumferential shape as bypass aperture  562 , so that flexible valve head  552  can cover bypass aperture  562 , as shown in  FIG. 10 , when relief valve  550  and retainer  560  are fully engaged. When relief valve  550  and retainer  560  are fully engaged, flexible valve head  552  engages the inner surface of retainer  560  to form a seal through which substantial fluid cannot pass, and substantial fluid is prevented from flowing through bypass aperture  562  and therefore top opening  512 . However, when relief valve  550  and retainer  560  are not fully engaged, flexible valve head  552  and retainer  560  do not form a seal, and substantial fluid can pass through bypass aperture  562  and top opening  512 . 
         [0061]    Referring again to  FIG. 10 , cartridge fluid filter  500  is configured for standard fluid flow inside a fluid filter assembly (not shown) such that fluid flows laterally from outside cartridge  500  through filter media  520 , through multiple holes  544  of center tube  540  and out bottom opening  532  of bottom end cap  530 . During normal operation of cartridge  500 , relief valve  550  and retainer  560  are fully engaged so that substantial fluid is prevented from passing through bypass aperture  562  and top opening  512 . However, when filter media  520  becomes sufficiently clogged that fluid cannot pass into cartridge fluid filter  500 , fluid pressure in the filter assembly (not shown) and around cartridge fluid filter  500  rises. When the fluid pressure reaches a predetermined bypass set point, relief valve  550  disengages from retainer  560 , permitting substantial fluid flow through bypass aperture  562  into middle cavity  542  and out bottom opening  532  of bottom end cap  530 . In this way, cartridge fluid filter  500  prevents substantial loss of fluid flow when filter media  520  becomes clogged, thereby preventing damage. 
         [0062]    The embodiment of a fluid filter cartridge of the present invention shown in  FIG. 11  is similar to cartridge fluid filter  500  shown in  FIG. 10 , except that cartridge fluid filter  600  of  FIG. 11  is configured for reverse fluid flow. In cartridge fluid filter  600 , relief valve  610  is configured such that flexible valve head  612  engages retainer  620  and thereby closes bypass aperture  622 . As such, valve stem  614  and legs  616 ,  618  extend into middle cavity  632  of center tube  630 . 
         [0063]    When cartridge fluid filter  600  is operating normally in a fluid filter assembly (not shown), fluid enters bottom opening  642  of bottom end cap  640  into middle cavity  632 . The fluid then flows through multiple holes  634  of center tube  630  into and through filter media  650 , exiting cartridge fluid filter  600  to the fluid filter assembly (not shown) so that the filtered fluid can continue to its destination. However, when filter media  650  is clogged such that fluid does not pass through filter media  650  and out of cartridge fluid filter  600 , fluid pressure builds in middle cavity  632  of center tube  630 . When the pressure in middle cavity  632  reaches a predetermined bypass set point, flexible valve head  612  disengages from retainer  620  so that fluid escapes through bypass aperture  622 , thereby exiting cartridge fluid filter  600  and continuing to its destination in an unfiltered state. 
         [0064]    As will be understood by those of skill in the art, fluid valve assemblies and fluid filters made according to various aspects of the present invention have fewer parts, are easier to manufacture, and are less expensive to produce than many other valves and filters, particularly those traditional valves and filters having a steel retainer, plastic valve, and steel spring. In addition, the parts used to make valves and filters of various embodiments of the present invention cost less to handle and store than parts for more complex valves and filters. 
         [0065]    The present invention can be further modified within the scope and spirit of this disclosure. It will be understood by those of skill in the art that the preferred embodiments disclosed herein describe the present invention in detail, but do not limit or restrict the scope of the invention. The disclosure is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this disclosure is intended to cover such departures from the disclosed embodiments as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.