Abstract:
A check valve in which a stop pin assembly is situated so as to prevent the movement of a flapper beyond a predetermined position. In a preferred embodiment the check valve has two flappers with the stop pin assembly situated therebetween to prevent either one of them from pivoting beyond an essentially vertical position. The stop pin assembly is configured such that it can be inserted and locked in place when the check valve is inserted within a valve body that contains the check valve. The stop pin assembly can comprise three elements including a central portion and first and second end portions, although the stop pin assembly could instead comprise a single element. The stop pin assembly is inserted between two holders and in a preferred embodiment is rotatable to a locking position where it is affixed in place by fasteners.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on, and claims priority to, U.S. Provisional Application No. 61/509,814, filed Jul. 20, 2011, the entire contents of which are fully incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to field of check valves and, more particularly, to a dual plate check valve incorporating a stop pin assembly, with the stop pin assembly preventing valve flappers from pivoting beyond a predetermined position. 
     2. Description of the Related Art 
     Check valves are one-way valves that permit a fluid to flow in one direction but not in the other direction. They come in a variety of sizes, shapes, and types and are usually self-controlling, meaning that the flow of the fluid itself will typically control the opening and closing of the check valve. They are often used in systems that utilize pumps to pump the fluid through piping or other similar vessels; a heart valve (natural or man-made) is one example of a check valve. 
     A certain type of check valve, sometimes referred to as a swing check valve or tilting disc check valve, utilizes one or more movable discs, sometimes referred to as “flappers”, to block the reverse flow of fluids. In a typical arrangement, the flapper is hinged on an axis of some kind, such as a hinge pin. In a two-flapper (dual-plate) arrangement, the hinge pin is centrally located with each flapper pivoting on the hinge pin towards each other like the wings of a butterfly. 
     SUMMARY OF THE INVENTION 
     The claimed invention provides a novel structure for a check valve in which a stop pin is situated between two flappers to prevent either one of them from pivoting beyond an essentially vertical position, as described and shown in more detail in connection with the drawings provided herewith. In a preferred embodiment, the stop pin is configured such that it can be inserted and locked in place when the check valve is inserted within a valve body that contains the check valve. In a more preferred embodiment the stop pin comprises three elements comprising a central portion and first and second end portions, although it is contemplated that the stop pin could instead comprise a single element in which the first and second end portions are integrated with the central portion. The stop pin is inserted between two holders and in a preferred embodiment is rotatable to a locking position where it is affixed in place by fasteners. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a check valve in accordance with the claimed invention comprising a valve body and a disc (flapper) assembly; 
         FIGS. 2-5  show a check valve according to the claimed invention and components thereof in varying degrees of detail. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 to 5  illustrate a preferred embodiment of the claimed invention.  FIG. 1  is an exploded view of a check valve comprising a valve body  1  and a disc (flapper) assembly  2 . The stop pin assembly of the claimed invention is not shown in  FIG. 1  for sake of simplicity, but is described in detail below. The valve body  1  has a valve body bore  12  in which is positioned a seat  13 . The seat  13  provides a base against which disc assembly  2  is placed when inserted within valve body bore  12  during use. A web  14  extends diametrically across the valve body bore  12  and divides the seat  13  into two halves, each half comprising a flow opening  14 A corresponding to each of the flappers  4 , discussed below. Gasket surfaces  15  and  16  respectively are at each end of the valve body and provide mounting surfaces for gaskets in a known manner. When the check valve of  FIG. 1  is inserted in a pipe, fluid flow would normally be in the upward direction relative to  FIG. 1 , as indicated by arrow A. 
     The disc assembly  2  is shown in more detail in  FIGS. 2 and 3 . In this embodiment the assembly comprises two substantially semi-circular flappers  4  (first and second flappers), two holders  5  (first and second holders), and a hinge pin  7  (axle pin). In each holder  5  is an elongated (essentially oval-shaped) bore  17 , with a longitudinal axis  11  of elongated bore  17  being substantially parallel to a longitudinal axis of the valve body  1  corresponding to the direction of travel of fluid flowing within the check valve. Each end of the hinge pin  7  is mounted in one of the elongated slots and the flappers  4  are mounted on the hinge pin  7 . In this configuration, the flappers  4  can pivot on hinge pin  7 , for example, from shown in  FIG. 2  to the position shown in  FIG. 3 . 
     In this embodiment the flappers  4  are mounted on the hinge pin  7  using bosses  18 , as can be best seen in  FIG. 3 . An outer surface  19  of each of the holders  5  is of the same profile as that of the inner surface of the valve body bore  12 , so that they will fit snugly against the inner surface. In this preferred embodiment the valve body bore  12  is essentially circular in shape and the outer surface  19  of the holders  5  are curved so as to correspond to the essentially circular shape of the valve body bore  12 . 
     The disc assembly  2  is positioned in the bore  12  by holding the disc assembly  2  with the flappers  4  urged towards the open position, as shown in  FIG. 1 , and inserting the disc assembly  2  into the valve body bore  12 , until it is stopped by seat  13 . 
     By design, the dual plate configuration shown in  FIGS. 1-5  contemplates that each flapper  4  is essentially responsible for blocking or allowing flow through one half of the valve body bore diameter, i.e., each disc is associated with one half of the valve body bore  12  and with one of the flow openings  14 A. As shown in  FIG. 1 , each of the flappers  4  could theoretically be urged far enough towards the open position such that one of them could move past the vertical position, i.e., one of the flappers  4  could be moved into a position whereby it impinges on the half of the valve body bore diameter associated with the other flapper  4 . To ensure that the flappers  4  do not move such that one of the flappers  4  moves past the vertical position, a stop pin assembly  6  is provided. As seen in  FIGS. 2-5 , the stop pin assembly  6  is mounted in bores  21  in the holder  5 . 
       FIG. 4  shows details of a preferred embodiment of a sub-assembly comprising the hinge pin  7 , stop pin assembly  6 , and holders  5  of the claimed invention, with the flappers  4  and associated elements (bosses  18 , spring  8 ) removed for sake of simple explanation. As noted above, in each holder  5  is an elongated bore  17 . The elongated bores  17  permit upward and downward movement of the hinge pin  7  within the elongated bore  17 , along the axis of the check valve, to permit the back edges or “heels” of the flappers  4  to clear the seat  13  as they rotate to the open position and also back to the closed position. 
     The stop pin assembly  6  is designed so that it can be inserted into the holders  5 , and locked into place, while the disc assembly is sitting inside the valve body  1 . In a preferred embodiment illustrated in  FIG. 4 , the stop pin assembly  6  comprises a three-piece assembly comprising stop pin  6 A (center element or central pin portion) and two retainer pins  9  (first and second end elements). A retainer pin bore  21  is formed through the outer surface of each holder  5  as shown. The inside diameter of retainer pin bore  21  is sized so that that a shaft portion of retainer pins  9  can slide snugly therethrough. In the inner surface of each holder  5 , a slot  22  is formed, having a flat-sided top portion  22 A and a generally circular bottom portion  23  as shown. In this embodiment, the diameter of the circular bottom portion  23  is slightly larger than the diameter of retainer pin bore  21 , so that a head portion of retainer pins  9  will prevent the retainer pins  9  from sliding through the retainer pin bore  21  when the shaft portion of a retainer pin  9  is inserted through a retainer pin bore  21  in the holder as shown in the drawing figures. The stop pin  6 A can have first and second ends with the first retainer pin being positionable adjacent to said first end and said second retainer pin being positionable adjacent to said second end. 
     To enable the locking of the stop pin assembly  6  in place in the holders  5 , each end of stop pin  6  has flat sides formed as shown, corresponding to the flat sided top portion  22 A of retainer pins  9 . In this configuration, when oriented properly, the stop pin  6  can slide through the flat sided top portion  22 A and into the circular bottom portion  23 . Through each flat side of stop pin  6  is formed a hole or other means cooperating with a fastener  10  to enable the rotational movement of the stop pin  6  around its longitudinal axis to be prevented/inhibited. In the preferred embodiment shown in the figures, the hole in each flat side of stop pin  6  is a threaded hole that has threading matching threading on fastener  10 , which enables a fastener  10  to be threaded into each hole. A head portion of fastener  10  should be sized such that it fits within the flat-sided top portion  22 A as shown, thereby securing the stop pin assembly in place and preventing it from moving rotationally about its longitudinal axis. In a preferred embodiment, fastener  10  comprises an allen screw, i.e., a screw having a hexagonal hole in its head for use with a hex or alien wrench. However, it is understood that numerous other fastening means may be utilized to enable the fixing of the stop pin assembly  6  in place as shown and described, and such alternative fastening means are within the scope of the claimed invention. 
     To assemble the full disc assembly  2  into the valve body, the hinge pin  7 , with the flappers  4  and spring  8  situated thereon, is inserted into the elongated bores  17  of holders  5 , and then as a group are inserted into the bore to rest on the seat. The retainer pins  9  are then inserted into bores  20  of the valve body (only one is visible in the drawing but in a preferred embodiment there is a second one situated 180° from the one shown, to accommodate the second retainer pin  9 ) through the bores  21  of the holders  5  until flushed into it. Then, as described below, the stop pin  6 A is fastened in to complete the disc assembly  2 . 
     A step by step procedure of locking the stop pin  6 A into the holders  5  is illustrated in  FIG. 5 . Stop pin  6 A is inserted through the slots  22  of the holders  5  in a way that its flat ends slide through the slots  22  and come to rest in circular bottom portion  23  of holders  5 . Next, stop pin  6 A is rotated 90° to allow the fasteners  10  to be screwed into holes  24  through the slots  22 , locking the stop pin  6 A in position. Although not required, a portion of the stop pin  6 A away from its ends can be formed with flat sides (see center of stop pin  6 A in the drawing figures) so that a wrench or other device can be secured thereon and torqued to rotate the stop pin  6 A as described). 
     As noted above, the elongate bores  17  permit movement of the stop pin  6 A, along the axis of the valve, to permit the back edges or “heels” of the flappers  4  to clear the seat as they rotate to the open position and also back to the closed position. In the event that these bores become worn to an extent that replacement is necessary only the holders  5  need be replaced, rather than the entire valve. 
     In general, dual plate check values are made in various grades of ferrous (such as various grades of Carbon and Stainless Steels) and non-ferrous metals, copper alloys, nickel alloys and other such metals depending on the metal compatible/suitable for the various materials (flow media) which flows within the dual plate check valves. Thus, the preferred material to be used depends on compatibility of the flow media. In a preferred embodiment, the internal parts are made of various grades of stainless steels. 
     Further, non-metals, such as polymers and such advanced engineered and engineering plastics, and ceramics can also be used. 
     Although the present invention has been described with respect to a specific preferred embodiment thereof, various changes and modifications may be suggested to one skilled in the art and it is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims. For example, although the stop pin assembly is described and shown as a three piece element, it is contemplated that it could also comprise a single element with the stop pin  6 A and the two retainer pins  9  being formed integrally such that they are a single piece. Further, although the valve body bore in which the disc assembly  2  is inserted is shown as being essentially circular (pipe-shaped) in shape, it is understood that the valve body bore could be essentially any shape, in which case the components of the disc assembly  2  would merely need to be modified in shape to correspond to the shape of the valve body bore. In addition, although the preferred embodiment described herein uses two bores  20  corresponding to two retainer pins  9 , it is understood that the device could instead be designed with a single bore  20  and a single corresponding retainer pin  9  and still provide the benefits and functionality described herein.