Abstract:
A number of improved excess flow valves are disclosed wherein pressure drop is optimized through the device to maximize efficiency while minimizing shut-off flow rates. Flow restrictions are minimized throughout the valve structure and maximized across a valve closure plate, eliminating flow restriction variations caused by orientation of the valve components. A magnet having radially opposing poles optimizes the magnet&#39;s attractive force relationship with the valve plate.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to excess flow valves for controlling flow through a conduit and more particularly to an excess flow valve that minimizes pressure drops within the valve through a simplified valve construction.  
           [0002]    Excess flow valves are utilized to limit the amount of fluid flow through a conduit. Generally, some way of holding the valve in a generally open position maintains the valve in an open position, allowing flow through the conduit if the flow rate through the conduit is below a predetermined limit. If the flow rate increases causing the pressure drop across the valve to exceed a certain value, then the valve is moved to a closed position restricting flow through the conduit.  
           [0003]    One type of excess flow valve uses a magnet to hold the valve at a generally open position. The typical prior art magnetic excess flow valve has been incorporated into a capsule, wherein the entire structure for providing a valve seat, a valve guide, and a magnet holder are all incorporated as a single capsule item. Ideally, any pressure drops across the valve will help close the valve. Prior art valve structures are inefficient, however, because the structures often interfere with fluid flow through the valve, causing excessive pressure drops that do not aid in closing the valve. Further, even though magnets should have sufficient force to re-open a closed valve, current magnet structures may not always have force characteristics that also allow the attractive force to be minimized in the open position to improve the sensitivity of the valve plate for valve closing.  
           [0004]    In addition, prior art valves have had non-symmetric structures, making valve operation dependent on the orientation between valve components. This causes the pressure drop required to close the valve to be, undesirably, a function of both the valve&#39;s component orientation and the flow rate rather than a function of the flow rate alone. When fluid pressure drops are a function of the orientation of components within the valve as well as fluid flow, the valve operation becomes unpredictable.  
           [0005]    There is a desire for an excess flow valve structure that does not interfere with fluid flow and responds accurately and consistently to fluid pressure drops in a conduit.  
           [0006]    There is also a desire for an excess flow valve structure that optimizes pressure drops to maximum valve efficiency while still maintaining a desired valve closure flow rate.  
         SUMMARY OF THE INVENTION  
         [0007]    Accordingly, one embodiment of the invention is directed to a simplified excess flow valve structure that improves the efficiency of valve operation by ensuring that any pressure drops across the valve aid closing of the valve. This is achieved by reducing the number of valve parts, minimizing flow restrictions through the conduit due to the valve assembly to the extent possible when the valve is open. In one embodiment, a valve body portion incorporating a valve guide and a magnet holder is separate from the valve seat. In some embodiments the valve seat may be provided by a separate valve seat component, and in other embodiments the valve seat is integrated into a conduit structure.  
           [0008]    In another embodiment, the valve is mounted at an interface between two conduit portions. In this embodiment, there is less structure at the outer periphery of the valve to disrupt or otherwise restrict fluid flow. The excess flow valve allows fluid to flow around the outer periphery of the valve plate when the valve plate in the valve is in its open position. The inventive structure therefore avoids fluid flow obstacles that cause unnecessary pressure drops in the valve. In a further embodiment, the valve has a disk-shaped magnet rather than a cylindrical magnet, improving the force characteristics of the magnet and minimizing the attractive force in the open position to improve the sensitivity of the valve plate for valve closing.  
           [0009]    By minimizing undesirable flow restrictions in the valve, the inventive structure improves valve efficiency, allowing a minimal valve size for a desired flow rate. The inventive structure also eliminates orientation-specific flow restrictions, ensuring that fluid pressure drops through the valve are caused only by the flow rate and not component orientation, thereby providing consistent efficiency and valve closure flow rates. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a section view taken along line  1 - 1 ′ of one embodiment of the inventive valve as shown in FIG. 4.  
         [0011]    [0011]FIG. 2 is a compound section view taken along line  2 - 2 ′ in FIG. 4.  
         [0012]    [0012]FIG. 3 is a perspective view of the valve shown in FIG. 1.  
         [0013]    [0013]FIG. 4 is plan view of the valve shown in FIGS. 1 and 2.  
         [0014]    [0014]FIG. 5 illustrates another embodiment of the invention having a valve seating structure integrated into a conduit.  
         [0015]    [0015]FIG. 6 is a sectional view of the invention shown in FIG. 5.  
         [0016]    [0016]FIG. 7 is a sectional view of yet another embodiment of the present invention.  
         [0017]    [0017]FIG. 8 is a representative diagram of a magnet according to one embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0018]    Referring to FIGS. 1 through 4, an excess flow valve  20  is positioned within a conduit  22 . In this embodiment, a valve seat component  26  is provided as a separate element from a valve body  27  in the excess flow valve  20 . The valve seat  26  may be made of a resilient material to create a fluid-tight seal. An outer surface  28  of the valve seat  26  engages the inner surface of the conduit  22 . An outer peripheral portion  30  of the valve body  27  is ring-shaped and also engages the inner surface of the conduit  22 . The valve body  27  in this embodiment also includes an inner hub  32  supported by a first set of arms  33  extending between the outer peripheral portion  30  and the inner hub  32 . In one embodiment, the arms have a axial portion  33   a  and a radial portion  33   b.  Guide protrusions  35  on the arms  33  form a magnet retention structure to hold a magnet  34 , preferably a disk-shaped magnet. Note that the inner hub  32  is an optional structure; if the inner hub  32  is eliminated, the arms  33  may intersect somewhere inside the boundaries of the outer peripheral portion  30  at a central point. Alternatively, the arms  33  may be linked to each other in some other fashion. The arms  33  may also not contact each other at all and be attached only to the outer peripheral portion  30 . The arms  33  may also be configured so that they cannot open out in a radial direction, ensuring that the magnet  34  is retained firmly in the valve  20 .  
         [0019]    A disk-shaped valve plate  40  is movable between an open position, where the valve plate  40  moves toward the magnet  34 , and a closed position, where the valve plate moves toward the valve seat  26  to close the conduit  22 . FIGS. 1 through 3 show the valve plate  40  in an open position. The circumferential edge of the valve plate  40  and the inside surface of the conduit  30  form a fluid path (shown in FIG. 1 by arrow A) that is unobstructed by any portion of the valve body  27  when the valve plate  40  is in the open position. As shown in the Figures, the plate  40  sits slightly upstream of the outer peripheral portion  30  while still being guided by the axial portion  33   a  of the arms  33  when in the open position, leaving a gap  41  through which fluid can flow easily between the plate  40  and the conduit  22 . Although the arms  33  do act as a minor obstacle in the fluid path, the effect of the arms  33  on fluid flow is minimal because the circumference of the valve plate  40  is otherwise free, without any portion of the valve body  27  surrounding the plate  40  when the plate  40  is in the open position.  
         [0020]    The disk-shaped valve plate  40  is preferably symmetrical so that the valve plate&#39;s  40  orientation with respect to the hub  32  and arms  33  does not affect the fluid flow through the conduit  22 . In one embodiment, the arms  33  act as a guide for the valve plate  40  as well as a magnet holder, eliminating the need for separate guiding structures on the valve plate  40  itself.  
         [0021]    As noted above, the first set of arms  33  connect the outer peripheral portion  30  of the valve  20  with the inner hub  32 . One embodiment of the inventive valve structure  20  may also include an optional second set of arms  42  that extend outwardly and radially from the inner hub  32  and end between the inner hub  32  and the outer peripheral portion  30 . The additional arms  42  distribute additional contact points to guide the valve plate  40  while still minimizing the total contact surface between the plate  40  and the arms  33 ,  42 , preventing the plate  40  from being stuck in a tilted position (e.g., with one portion of the plate  40  lying farther upstream than other portions of the plate  40 ) within the valve body  27 . In one embodiment, the first and second arms  33 ,  42  alternate around the inner hub  32  to distribute the contact points evenly on the plate  40 . Further, because the arms  33 ,  42  are arranged to minimize the area of the plate  40  contacting the arms  33 ,  42 , the inventive structure maximizes the area of the plate  40  facing the upstream side of the conduit  22 .  
         [0022]    To minimize the contact between the valve plate  40  and the arms  33 ,  42 , contact pads  43  may be formed in either or both sets of arms  33 ,  42 . The pads  43  extend slightly from the arms  33 ,  42  and act as point contacts on the plate  40  surface. Alternatively, the arms  33  themselves may extend upstream and emanate inwardly from the outer peripheral portion  30  of the valve body  27  to form contact pads  43  at the point where the outer peripheral portion  30  and the arms  33  join. Regardless of the pad  43  structure, the pads  43  minimize contact between the plate  40  and the arms  33 ,  42  or any other portion of the valve body  27 . In one embodiment, the pads  43  contact less than 10%, and preferably around 2%, of the plate  40  surface.  
         [0023]    To hold the magnet  34  more securely, the valve body  27  may include a magnet retention structure that positions the magnet  34  upstream of the valve plate  40 . In one embodiment, one or more of the arms  33 ,  42  may include a clip portion  44  to form the magnet retention structure. The magnet  34  may then be engaged with the clip portions  44  during valve assembly. The thin profile of the disk-shaped magnet  34  allows it to be held firmly in the valve  20  without requiring bulky attachment structures that would interfere with fluid flow. In the illustrated embodiments, the clip portions  44  are placed on the second set of arms  42 , but they may also be formed on first set of arms  33  instead of or in addition to the guide protrusions  35 .  
         [0024]    Shaping the magnet  34  into a disk rather than a cylinder further reduces the amount of space that the valve  20  occupies in the conduit  22 . The clip portions  44  create a positive engagement between the arms  33 ,  42  and the magnet  34 , ensuring that the magnet  34  will not be partially inserted or jarred out of position during shipping.  
         [0025]    The magnet  34  is preferably magnetized across a face surface  46  of the magnet  34  (i.e., wherein the poles lie radially opposite each other), as shown in FIG. 8, rather than magnetized parallel to the fluid flow because the thin profile of the magnet  34  makes magnetizing in the axial direction impractical. In other words, the north and south poles of the magnet  34  would each be on the outer perimeter of the face surface  46  across from each other. In one embodiment, the center of the face surface  46  is left unmagnetized, acting as a transition zone between the north and south poles of the magnet  34 . A disk-shaped magnet has a more desirable force characteristic than a cylindrical magnet due to the disk-shaped magnet&#39;s greater diameter-to-thickness ratio. This improved force characteristic provides a more constant magnet force attracting the valve plate  40  as it travels between the open and closed positions. To control the overall magnet strength after selecting the optimal magnet shape, inert material may be added into the magnet  34 .  
         [0026]    Note that the magnet  34  does not necessarily have to be disk-shaped; any magnet  34  having radially opposed poles will have characteristics that are advantageous in the inventive structure. For example, the magnet  34  may be shaped as a cylinder, but magnetized with radially opposed poles. The magnet  34  may also be formed in an annular shape, with a hole in the center of the magnet  34  that can provide an additional fluid flow path through the middle of the valve  20 . Regardless of the actual magnet shape, the radially opposed poles provide improved force characteristics over magnets that are magnetized parallel to fluid flow.  
         [0027]    [0027]FIG. 5 is an exploded view illustrating one embodiment of the excess flow valve  20  incorporated into a two-piece conduit, while FIG. 6 is a section view taken along line  6 - 6 ′ of FIG. 5. First and second conduit portions  50 ,  52  are coupled together via a threaded connection  60  and a valve seat  64  is formed as an integral part of the conduit  22  rather than a separate component. An opposed end surface  66  of the second conduit portion  52  captures the valve body  27 . While the valve  20  is shown axially captured in the figure, the outer periphery of the valve body  27  could also be formed to be an interference fit within the conduit  22 .  
         [0028]    The valve body  27  holds the magnet  34  adjacent the valve plate  40 . As shown in FIG. 6, the valve body  27  does not have material disposed around its entire circumference to hold the magnet  34  and guide the valve plate  40 . Instead, as noted above, the first and second sets of arms  33 ,  42  are circumferentially spaced to reduce resistance to fluid flow past the valve  20 .  
         [0029]    [0029]FIG. 7 illustrates another embodiment of the present invention. In this embodiment, the excess flow valve  20  is designed to fit inside a conduit  70  having a threaded area  72  at the end of the conduit  70  such that the valve seat  26  terminates at or near the end of the threaded area  72 .  
         [0030]    Although the valve structure focuses on guiding the valve plate  40  and supporting the magnet  34  with arms, other valve plate guide and/or support structures may be incorporated into the valve body  27  without departing from the scope of the invention.  
         [0031]    As a result, the inventive structure improves valve operation by incorporating a disk-shaped magnet in the valve and a disk-shaped valve plate that is guided by the valve body instead of protrusions on the valve plate itself. Further, the outer peripheral portion is formed on the valve body so that the circumference of the valve plate is not enclosed by the outer peripheral portion when the valve plate is in the open position, leaving the valve plate edge exposed to form a fluid path defined by the valve plate and the inside surface of the fluid conduit instead of the valve plate and the valve body. By minimizing fluid path obstructions, minimizing contact between the valve plate and the valve body, and taking advantage of the force characteristics of the disk-shaped magnet, the inventive excess flow valve offers improved valve efficiency.  
         [0032]    It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby.