Abstract:
A check valve is shaped and dimensioned to be installable inside a conventional pipe coupling, thereby reducing the amount of length required to install the check valve.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the filing benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/997,790 filed Oct. 5, 2007, which is herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention pertains generally to check valves used in plastic pipe installations, and more particularly to a thin check valve which may be fitted into a standard pipe coupling. 
     BACKGROUND OF THE INVENTION 
     A check valve is a mechanical device which allows fluid (liquid or gas) flow in only one direction. Such valves are used to prevent the back flow of the fluid in numerous applications, such as plastic swimming pool plumbing, fountains, water displays, and the like. A problem arises however in that a check valve assembly requires longitudinal distance along the pipe which is not available in some installations. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to a thin check valve which can be inserted into a pipe coupling (such as a conventional plastic pipe coupling) before the pipe is attached to the coupling, thereby eliminating the necessity of an expensive and extra part (i.e. a conventional check valve assembly). Unlike existing check valves which require considerable length when installed, the present invention requires much less length to perform the same function. The check valve is permanently installed in the pipe coupling prior to gluing the pipe in place. The present invention can also be installed in a universal quick disconnect pipe joint and can easily be replaced. Additionally, the check valve of the present invention may be easily installed without the use of hand tools. 
     In accordance with a preferred embodiment of the invention, a check valve for a pipe coupling includes a body and a valve plate which is rotatably connected to the body. A spring biases the valve plate to a closed position. The check valve is shaped and dimensioned to be installable inside the pipe coupling. 
     In accordance with an aspect of the invention, the pipe coupling has an inner ridge, and when the check valve is installed in the pipe coupling, the check valve abuts the inner ridge of the pipe coupling. 
     In accordance with another aspect of the invention, the check valve is installable in the pipe coupling without the use of hand tools. 
     In accordance with another aspect of the invention, when in the closed position, the check valve has a diameter and a thickness. The diameter is at least three times the thickness. 
     In accordance with another aspect of the invention, the thickness is about 0.5 inches. 
     In accordance with another aspect of the invention, the check valve has a first central axis, the valve plate has a second central axis, and the second central axis is off set from the first central axis. 
     In accordance with another aspect of the invention, the pipe coupling has an inner ridge and an inner surface, and the body has a circumference. A circular seal is disposed around the circumference, so that when the check valve is installed in the pipe coupling, the circular seal abuts both the inner ridge and the inner surface of the pipe coupling. 
     Other aspects of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of a check valve in accordance with the present invention with the check valve in the closed position; 
         FIG. 2  is a front elevation view of the check valve in the closed position; 
         FIG. 3  is a rear elevation view of the check valve in the closed position; 
         FIG. 4  is a side elevation view of the check in a partially open position; 
         FIG. 5  is a front elevation view of the check valve in the partially open position; 
         FIG. 6  is a rear elevation view of the check valve in the partially open position; 
         FIG. 7  is a cross sectional view of the check valve along the line  7 - 7  of  FIG. 3 ; 
         FIG. 8  is a reduced exploded side elevation view of the check valve being installed in a pipe coupling; 
         FIG. 9  is a cross sectional view of the check valve installed in the pipe coupling; 
         FIG. 10  is a cross sectional view of the check valve installed in a quick disconnect coupling; and, 
         FIG. 11  a reduced side elevation view of the check valve installed in a limited longitudinal distance. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to  FIGS. 1-3 , there are illustrated side elevation, front elevation, and rear elevation views respectively of a check valve for a pipe coupling in accordance with the present invention, generally designated as  20 . Check valve  20  includes a body  22 , and a valve plate  24 . Valve plate  24  is rotatably connected by pin  25  to body  22 , and is biased by spring  26  to a closed position as shown in  FIGS. 1-3 . In the shown embodiment, valve plate  24  includes a seal  28  made from rubber or a similar material which abuts body  22  when check valve  20  is in the closed position. Check valve  20  is shaped and dimensioned to be installable inside a pipe coupling  500  (refer to  FIGS. 8 and 9  and the associated discussions). When in the closed position, check valve  20  has a diameter D and a thickness T. In and embodiment of the invention, diameter D is at least three times thickness T, and diameter D can be as high as five times thickness T. As such, check valve  20  is much thinner than conventional check valve assemblies, and takes up little longitudinal distance along the pipe run (refer to  FIG. 11  and the associated discussion). In an embodiment of the invention, thickness T is about 0.5 inches. Body  22  has a circumference C, and a circular seal  30  (such as an O-ring) is disposed around circumference C. It is noted that check valve  20  comprises a completely separate unit which may be installed into a conventional pipe coupling (refer to  FIGS. 8 and 9  and the associated discussions). 
       FIGS. 4-6  are side elevation, front elevation, and rear elevation views respectively of check valve  20  in a partially open position. Fluid flow (indicated by arrow  32  in  FIG. 4 ) overcomes the bias of spring  26  and causes valve plate  24  to swing open as shown by arrow  34 . As the fluid velocity increases, valve plate  24  will open further. 
       FIG. 7  is a cross sectional view of check valve  20  along the line  7 - 7  of  FIG. 3 , showing body  22 , valve plate  24 , pin  25 , spring  26 , seal  28 , and circular seal  30 . Check valve  20  has a first central axis  33 , and valve plate  24  has a second central axis  35 . Second central axis  35  is off set from first central axis  33 . In other words, valve plate  24  is not centered in check valve  20 . 
       FIG. 8  is a reduced exploded side elevation view of check valve  20  being installed in a pipe coupling  500 . Pipe coupling  500  is a conventional circular coupling which has a circular inner ridge  502 . Check valve  20  is installed in pipe coupling  500  so that it is completely inside pipe coupling  500  and abuts inner ridge  502  (refer also to  FIG. 9 ). Pipe  504  is then installed in pipe coupling  500  in the conventional manner, so that it abuts check valve  20 , and is glued in place. It is noted that check valve  20  is installable in pipe coupling  500  without the use of hand tools such a wrenches or the like. As shown pipe coupling  500  is a straight coupling. However, it may be appreciated that other types of couplings such as 45° or 90° elbows could also be used. 
       FIG. 9  is a cross sectional view of check valve  20  installed in pipe coupling  500 , showing check valve  20  abutting the inner ridge  502  of pipe coupling  500 . Pipe coupling  500  has an inner surface  506 . When check valve  20  is installed in pipe coupling  500 , circular seal  30  abuts both inner ridge  502  and inner surface  506  thereby double sealing check valve  20  in place. It is noted that when installed, check valve  20  resides completely within pipe coupling  500 . It is also noted that when glued in place, check valve  20  is locked between inner ridge  502  and pipe  504 . 
       FIG. 10  is a cross sectional view of check valve  20  installed in a quick disconnect coupling  600 . Check valve  20  resides within quick disconnect coupling  600 , and is locked in place by the two coupling halves. 
       FIG. 11  a reduced side elevation view of check valve  20  installed in a limited longitudinal distance LD which is blocked on both ends by obstructions  800 . As such, a conventional check valve assembly  900  is too long to be installed. However, the available longitudinal distance LD is sufficient to accommodate a conventional pipe coupling  500  with check valve  20  installed, since check valve  20  does not contribute to the length of pipe coupling  500  nor the length of the pipe run. 
     In terms of use, a method for installing a check valve  20  in a pipe coupling  500  includes: (refer to  FIGS. 1-11 ) 
     (a) providing a pipe coupling  500  having an inner ridge  502 ; 
     (b) providing a pipe  504  which is shaped and dimensioned to be received by pipe coupling  500 ; 
     (c) providing a check valve  20  including;
         a body;  22     a valve plate  24  rotatably connected to body  22 ;   valve plate  24  biased to a closed position; and,   check valve  20  shaped and dimensioned to be installable inside pipe coupling  500 ;       

     (d) installing check valve  20  in pipe coupling  500  so that check valve  20  is completely inside pipe coupling  500  and check valve  20  abuts inner ridge  502  of pipe coupling  500 ; and, 
     (e) installing pipe  504  in pipe coupling  500  so that pipe  504  abuts check valve  20 . 
     The method further including: 
     performing step (d) without the use of hand tools. 
     The method further including: 
     in step (d), sliding check valve  20  into pipe coupling  500  until it abuts inner ridge  502  of pipe coupling  500 . 
     The method further including: 
     in step (a), pipe coupling  500  having an inner surface  506 ; 
     in step (c), body  22  having a circumference C; 
     in step (c), a circular seal  30  disposed around circumference C; and, 
     in step (d), circular seal  30  abutting both the inner ridge  502  and the inner surface  506 . 
     The method further including: 
     in step (c), when in the closed position, check valve  20  having a diameter D and a thickness T; and, 
     diameter D being at least three times thickness T. 
     The method further including: 
     thickness T being about 0.5 inches. 
     A method for installing a check valve  20  in a limited longitudinal distance, includes: 
     (a) providing a limited longitudinal distance LD which is too short to accommodate the installation of a conventional check valve assembly  900 ; 
     (b) providing a pipe coupling  500  having an inner ridge  502 ; 
     (c) providing a pipe  504  which is shaped and dimensioned to be received by pipe coupling  500 ; 
     (d) providing a check valve  20  including;
         a body  22 ;   a valve plate  24  rotatably connected to body  22 ;   valve plate  24  biased to a closed position; and,   check valve  20  shaped and dimensioned to be installable inside pipe coupling  500 ;       

     (e) installing check valve  20  in pipe coupling  500  so that check valve  20  is completely inside pipe coupling  500  and check valve  20  abuts inner ridge  502  of pipe coupling  500 ; and, 
     (f) installing pipe  504  in pipe coupling  500  so that pipe  504  abuts check valve  20 . 
     The preferred embodiments of the invention described herein are exemplary and numerous modifications, variations, and rearrangements can be readily envisioned to achieve an equivalent result, all of which are intended to be embraced within the scope of the appended claims.