Abstract:
A backflow prevention device includes a main body holding a removable cartridge. The removable cartridge houses two independently acting check valves and, optionally, a relief valve. A first portion of the cartridge may be retracted into a second portion of the cartridge, thereby reducing the overall length of the cartridge and facilitating the removal of the cartridge from the main body without the need to remove the backflow prevention device from a water supply system. The relief valve is contained in a removable cartridge. Each check valve may have a self cleaning plunger bore comprising at least one spiral groove.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation-in-part of co-pending U.S. application Ser. No. 11/365,413, filed Mar. 1, 2006. This application hereby incorporates by reference the foregoing related application. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention generally relates to a backflow prevention device and, in particular, to a removable cartridge housing check valves, a relief valve cartridge, and/or a self cleaning check valve for a backflow prevention device.  
       BACKGROUND OF THE INVENTION  
       [0003]     Backflow prevention devices are used to protect potable water supplies from contamination. Backflow prevention devices are typically installed in pipelines between a main water supply and service lines that feed users such as industrial or commercial sites or residences. Many localities legally mandate their use.  
         [0004]     Backflow is caused by abnormalities in the water distribution system such as backpressure or backsiphonage. Backpressure occurs when the water pressure is higher in the downstream system than in the water supply. Backsiphonage can occur when the water supply pressure drops, such as when a water main breaks or severe demands are placed on the water supply. Either condition could lead to backflow, the flow of water from the downstream system back into the water supply. Backflow is undesirable because it may cause contamination of the potable water supply.  
         [0005]     Two common types of assemblies are the double check (DC) and the reduced pressure (RP) backflow prevention devices. The double check devices, commonly used with non-health hazards, have two check valves between two shut-off valves. The reduced pressure devices, commonly used to prevent health hazard, have two check valves, with a relief valve located between them, and two shut-off valves.  
         [0006]     Backflow prevention devices commonly include two independently acting check valves, internally loaded to a closed position. Each check valve permits water flow in only a single direction, from the main water supply toward the service line. If the pressure drop across a check valve falls below a predetermined threshold, typically about 1 psi, the loading of the check valve should cause it to close, thereby preventing the flow of water backwards through the device. The first check valve (in the direction of flow) provides redundancy in case of failure of the second check valve.  
         [0007]     Some backflow prevention devices further include a hydraulically operated relief valve to vent the zone between the two check valves to atmosphere. The relief valve is configured so that if the pressure in the zone between the two check valves gets within a predetermined threshold of the supply pressure, typically about 2 psi, the relief valve will open and dump water from the zone. The relief valve is usually installed over a drain or plumbed to a drain with an appropriate air gap.  
         [0008]     Ball valves are provided upstream and downstream of backflow prevention devices, allowing isolation of the device. Test cocks provide the ability to measure pressure at various points in the backflow prevention device and to supply water at desired pressures for purposes of testing the functionality of the check valves to insure proper operation of the device without removing the device from the water line. Test cocks are typically located at four sites: on the upstream side of the inlet ball valve; between the inlet ball valve and the first check valve; between the two check valves; and between the second check valve and the outlet ball valve.  
         [0009]     It is desirable to access the check valves or the relief valve (when present) from time to time for purposes of inspection, maintenance, repair, or replacement. With current backflow prevention devices, this generally requires either removing the device from the water line or accessing the valves through ports provided on the device.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is an cutaway side view of a preferred embodiment of a backflow prevention device embodying features of the present invention;  
         [0011]      FIG. 2  is a perspective view of the backflow prevention device of  FIG. 1 ;  
         [0012]      FIG. 3  is cutaway view of a slider receiver of the backflow prevention device of  FIG. 1 ;  
         [0013]      FIG. 4  is a cutaway view of a slider of the backflow prevention device of  FIG. 1 ;  
         [0014]      FIG. 5  is an exploded view of a check valve assembly of the backflow prevention device of  FIG. 1 ;  
         [0015]      FIG. 6  is a cutaway side view of an alternative embodiment of a backflow prevention device embodying features of the present invention;  
         [0016]      FIG. 7  is a perspective view of a slider receiver of the backflow prevention device of  FIG. 6 ; and  
         [0017]      FIG. 8  is a cutaway perspective view of a relief valve of the backflow prevention device of  FIG. 6 ;  
         [0018]      FIG. 9  is a cutaway side view of an alternative embodiment of a backflow prevention device embodying features of the present invention;  
         [0019]      FIG. 10  is a perspective view of a main body of the backflow prevention device of  FIG. 9 ;  
         [0020]      FIG. 11  is a perspective view of a main body and check valve cartridge of the backflow prevention device of  FIG. 9  having the check valve cartridge in an extended position;  
         [0021]      FIG. 12  is a perspective view of a main body and check valve cartridge of the backflow prevention device of  FIG. 9  having the check valve cartridge in a retracted position;  
         [0022]      FIG. 13  is an exploded view of a check valve cartridge of the backflow prevention device of  FIG. 9 ; and  
         [0023]      FIG. 14  is an exploded view of an alternative embodiment of a check valve cartridge of the backflow prevention device of  FIG. 9 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]     In  FIG. 1 , there is illustrated a backflow prevention device  2 . A main body  4  provides structural support for the other components and defines fluid flow passages  6 ,  8  at each end of the main body  4 . Test ports  10 ,  12  are each in fluid communication with one of the fluid flow passages  6 ,  8  via a test port channel  18 ,  20 . The test ports  10 ,  12  allow for evaluation of the function of the backflow prevention device  2  in a manner described below. A test port valve  22 ,  24  is attached to each test port  10 ,  12 .  
         [0025]     An inlet ball valve  26  and an outlet ball valve  28  make it possible to isolate the backflow prevention device  2  from the water system to which it is connected. The inlet ball valve  26  is mounted in a ball valve housing  30  which is mounted to the main body  4 , preferably by means of a threaded engagement. The ball valve housing  30  may comprise a mounting portion  36  and a valve containment portion  38 , each defining a fluid flow passage  40 ,  42  respectively. A test port  14  is in fluid communication with the fluid flow passage  40  of the valve containment portion  38  via a test port channel  44 . A test port valve  46  is attached to the test port  14 . The upstream end  48  of the ball valve housing  30  is configured for connection to a source of water, preferably via internal threads  50 .  
         [0026]     The outlet ball valve  28  is mounted in a second ball valve housing  52  which is mounted to the main body  4 , preferably by means of a threaded engagement. The second ball valve housing  52  may comprise a mounting portion  58  and a valve containment portion  60 , each defining a fluid flow passage  62 ,  64 . The downstream end  56  of the second ball valve housing  52  is configured for connection to a downstream system, preferably via internal threads  66 .  
         [0027]     Referring now to  FIG. 2 , the main body  4  comprises an upstream portion  112  and a downstream portion  114 , each having a fluid flow path  6 ,  8  ( FIG. 1 ) respectively, therethrough. Generally flat, parallel bridging portions  120 ,  122  join the upstream portion  112  and downstream portion  114  of the main body  4 . The upstream portion  112 , the downstream portion  114  and the two bridging members  120 ,  122  define a generally rectangular access passage  124  through the main body  4 . The access passage facilitates the installation, removal, and manipulation of a removable cartridge, denoted generally by the reference numeral  68 .  
         [0028]     Referring again to  FIG. 1 , the removable cartridge  68  is mounted in the main body  4 . The removable cartridge  68  comprises a slider receiver  70  and a slider  72 . The slider receiver  70 , best seen in  FIG. 3 , defines a fluid flow passage  74 . A test port  16  is in fluid communication with the fluid flow passage  74  of the slider receiver  70  via a test port channel  76 . A test port valve  78  is attached to the test port  16 . In the preferred embodiment, the upstream end  80  of the slider receiver  70  is configured to fit with the main body  4 . An o-ring  82  ( FIG. 1 ), held in place by a groove  83  in the outer surface of the slider receiver  70 , provides for a water tight seal between the slider receiver  70  and the main body  4 . The downstream portion  84  of the slider receiver  70  is configured to receive the upstream portion  86  of the slider  72 , best seen in  FIG. 4 . The downstream portion  84  of the slider receiver  70  contains female threads  90  configured for engagement with male threads  92  on the upstream portion  86  of the slider  72 .  
         [0029]     A first check valve  94  ( FIG. 1 ) is located in the slider receiver  70 . A ridge  96  on the inside surface of the slider receiver  70  helps to fix the check valve  94  in position against the main body  4  when the removable cartridge  68  is mounted in the main body  4 . The check valve  94  is of a standard type well known in the industry and is biased to a normally closed position. The check valve allows flow through the valve in only one direction, downstream.  
         [0030]     Referring now to  FIG. 5 , the check valve  94  comprises a valve seat  150  and a valve cage  152 . A valve seal  154  is fixed to a plunger  158  using a seal retainer  156 . The plunger  158  fits into a central bore  160  in the valve cage  152  and is free to move in a reciprocating fashion within the central bore  160  of the valve cage  152 . A spring  162  provides force to bias the check valve  94  toward a closed position.  
         [0031]     It is desirable that the plunger  158  not stick within the central bore  160  lest the check valve  94  jam in an open position. Under reverse flow conditions, contaminated water will flow into the valve cage  152  from the normally downstream direction. Spiral grooves  164  are provided in the central bore  160  in order to assist the plunger  158  in flushing any particulate matter that might have flowed into the central bore and reducing the chance of the particulate matter wedging between the plunger  158  and the central bore  160  and causing the check valve  94  to stick.  
         [0032]     The downstream end of the slider  72 , best seen in  FIG. 1 , is configured to fit with the main body  4 . An o-ring  98 , held in place by a groove  99  ( FIG. 4 ) in the outer surface of the slider  72 , provides for a water tight seal between the slider  72  and the slider receiver  70  downstream of the threads  90 . A second check valve  100  is located in the slider  72 . A ridge  102  on the inside surface of the slider  72  helps to fix the position of the check valve  100  against the main body  4  when the removable cartridge  68  is mounted in the main body  4 . An o-ring  104 , held in place by a groove  105  in the outer surface of the slider  72 , provides for a water tight seal between the slider and the main body  4 .  
         [0033]     Under normal operating conditions, if the water flow through the backflow prevention device  2  reduces to the point that the pressure drop across the second check valve  100  is less than 1.0 psi, the second check valve  100  would close, preventing flow in the reverse direction. If the second check valve  100  fails, the first check valve  94  would close, providing backup protection.  
         [0034]     A geared or knurled exterior surface  106  allows for manual rotation of the slider  72  relative to the slider receiver  70  and the main body  4 . Rotating the slider  72  in one direction causes the slider  72  to telescopically screw into the slider receiver  70 , thereby reducing the overall length of the removable cartridge  68  and facilitating the removal of the cartridge  68  from the main body  4 .  
         [0035]     Removing the cartridge  68  makes it possible to inspect, maintain, repair, or replace the check valves  94   100 . After inspecting or servicing the check valves  94 ,  100  the cartridge  68  can be replaced by inserting either end of the cartridge  68  into the main body  4  and then unscrewing the slider  72  from the slider receiver  70  until the two ends of the cartridge  68  seat against the main body  4 .  
         [0036]     Many localities and several industry organizations mandate the location of the four test ports  10 ,  12 ,  14 ,  16  as described herein. The test ports  10 ,  12 ,  14 ,  16  allow testing of the functionality of the backflow prevention device  2  without removing the device  2  from the water supply system. For example, pressure sensors can be attached to the test ports  10 ,  12 ,  14 ,  16  and the various pressure readings compared. Under normal operating conditions, the pressure should drop as we move from each test port to the next downstream and the static pressure drop across each check valve  94 ,  100  should be at least 1.0 psi. If the pressure downstream of a check valve  94 ,  100  is greater than the pressure upstream of the check valve  94 ,  100 , or if the downstream pressure is within 1.0 psi of the upstream pressure, the check valve  94 ,  100  should close and prevent flow back through the check valve  94 ,  100 .  
         [0037]     Alternatively, the backflow prevention device  2  can be isolated from the water supply system by closing both of the ball valves  26 ,  28  by rotating the ball valve handles  108 ,  110  ( FIG. 2 ). Water can then be supplied to the individual test ports  10 ,  12 ,  14 ,  16  at various pressures in order to exercise and test the individual check valves  94 ,  100 . When water is supplied to a test port immediately downstream of a check valve at a pressure greater than the water upstream of the check valve, the check valve should close and no water should flow through the valve. Conversely, when the water pressure upstream of the check valve is sufficiently higher than the water pressure downstream of the check valve, the valve should open and water should flow through the check valve.  
         [0038]      FIG. 6  depicts an alternative embodiment of a backflow prevention device  200  with a removable cartridge  202 . The removable cartridge  202  comprises a slider receiver  204  and a slider  206 . The slider receiver  204  is configured as described above, but with the addition of a relief valve docking station  208 . A relief valve  210  is mounted in a relief valve cap  220  which is attached to the docking station  208 , preferably by means of a threaded engagement. The relief valve cap  220  has an exit port  222 . A relief channel  214  in the slider receiver  204  provides fluid communication between the fluid flow path  212  in the zone between the two check valves  216 ,  218  and the relief valve  210 .  
         [0039]      FIG. 7  shows a perspective view of the slider receiver  204  and relief valve docking station  208 . Two supply pressure channels  224 ,  226  provide fluid communication between the flow path  212  ( FIG. 6 ) on the upstream side of the first check valve  216  and the relief valve  210 .  
         [0040]     As best seen in  FIG. 8 , relief valve  210  ( FIG. 6 ) comprises a valve seat  228  and a valve seal  230 . A flexible diaphragm  232  divides the valve into a supply pressure chamber  234  and a control pressure chamber  236 . Water is supplied to the supply pressure chamber  234  via the supply pressure channels  224 ,  226  ( FIG. 7 ). Water is supplied to the control pressure chamber  236  via the relief channel  214 . Water from the relief channel  214  flows through a channel  238  in a relief valve spacer  240 , around the diaphragm  232  via gaps between the spacer  240  and the relief valve cap  220  ( FIG. 6 ), and into the control pressure chamber  236  beneath the diaphragm  232 . A spring  242  provides a force biasing the relief valve  210  toward an open position.  
         [0041]     When the supply water pressure is greater than the pressure in the zone between the two check valves  216 ,  218 , by more than a predetermined threshold, typically about 2 psi, the pressure in the supply pressure chamber  234  is sufficient to overcome the force of the water in the control pressure chamber  236  and the biasing force of the spring  242 . If the pressure in the zone between the two check valves  94 ,  100  should approach within 2 psi of the supply pressure, the relief valve  210  opens and water from the zone is vented to atmosphere.  
         [0042]     Under normal operating conditions, if water flow through the backflow prevention device  200  reduces to the point that the pressure drop across the second check valve  218  is less than 1.0 psi, the second check valve  218  should close, preventing flow in the reverse direction. If the second check valve  218  fails, the first check valve  216  should close, providing backup protection. If the second check valve fails  218 , or if it does not seal tightly, leakage back through the valve  218  will cause the pressure in the zone between the two check valves  216 ,  218  to increase. If the pressure in the zone between the two check valves  216 ,  218  gets within a predetermined threshold of the supply pressure, typically about 2 psig, the relief valve  210  will open, dumping water from the zone between the two check valves  216 ,  218  out to atmosphere through the exit port  222 , thereby reducing the possibility of contaminated water flowing back through the device  200  to the water supply system. Ordinarily, the relief valve  210  should be installed over a drain or plumbed to a drain with an appropriate air gap.  
         [0043]     A second alternative embodiment of a backflow prevention device  302  is depicted in  FIGS. 9-14 . A main body  304  provides structural support for the other components. The main body  304  comprises an upstream portion  412  and a downstream portion  414 , each having a fluid flow path  306 ,  308 , respectively, therethrough at opposite ends of the main body  304 . The test ports  310 ,  312  are in fluid communication with the fluid flow passages  306 ,  308  via test port channels  318 ,  320 , respectively. The test ports  310 ,  312  allow for evaluation of the function of the backflow prevention device  302  in the manner described above with respect to the first described embodiment. A test port valve  322 ,  324  is attached to each test port  310 ,  312 , respectively.  
         [0044]     An inlet ball valve  326  and an outlet ball valve  328  make it possible to isolate the backflow prevention device  302  from the water system to which it is connected. The inlet ball valve  326  is mounted in a ball valve housing  330  which is mounted to the main body  304 , preferably by means of a threaded engagement. A test port  314  is provided on the ball valve housing  330  and defines a fluid flow passage  315  that is in fluid communication with a fluid flow passage  340  of the ball valve housing  330 . A test port valve  346  is attached to the test port  314 . The upstream end  348  of the ball valve housing  330  is configured for connection to a source of water, preferably using a threaded connection via internal threading  350 .  
         [0045]     The outlet ball valve  328  is mounted in a second ball valve housing  352  which is mounted to the main body  304 , preferably by means of a threaded engagement. The downstream end  356  of the second ball valve housing  352  is configured for connection to a downstream system, preferably using a threaded connection via internal threading  366 .  
         [0046]     Referring now to  FIG. 10 , bridging portions  420 ,  422  join the upstream portion  412  and the downstream portion  414  of the main body  304  and have tabs or shoulders  424 ,  426 , respectively, projecting from their inner faces. The upstream portion  412 , the downstream portion  414 , and the two bridging portions  420 ,  422  define an access passage  428  through the main body  304 . The access passage  428  facilitates the installation, removal, and manipulation of a removable cartridge  368  ( FIG. 9 ). Annular projections  430 ,  432  extend into the access passage  428  from the upstream portion  412  and downstream portion  414 , respectively, of the main body  304 . Each annular projection defines an outward facing annular groove  434 ,  436 , respectively.  
         [0047]     As illustrated in  FIGS. 11-12 , the removable cartridge  368  is designed to be easily mounted in the main body  304 . The removable cartridge  368  comprises a central cartridge body  370  and a collar  372 . The collar can be rotated from an extended position ( FIG. 11 ) for securing the cartridge  368  in the main body  304  to a retracted position ( FIG. 12 ) to release the cartridge  368  from the main body  304  for removal or installation.  
         [0048]     Referring now to  FIGS. 9 and 13 , the central cartridge body  370  defines a fluid flow passage  374 . A test port  316  is in fluid communication with the fluid flow passage  374  of the central cartridge body  370  via a test port channel  376 . A test port valve  378  is attached to the test port  316 . The upstream end  380  of the central cartridge body  370  is configured to fit over the annular projection  430  ( FIG. 10 ) at the upstream portion  412  of the main body  304 . An o-ring  438 , held in place by the annular groove  434  in the outer surface of the annular projection  430 , provides for a watertight seal between the central cartridge body  370  and the main body  304 .  
         [0049]     Two check valves  382 ,  384  are disposed in series inside the central cartridge body  370 . O-rings  386 ,  388 , held in place by annular grooves  387 ,  389 , respectively, provide essentially watertight seals between the check valves  382 ,  384 , respectively, and the central cartridge body  370 . An annular groove  390  near the downstream end of the central cartridge body  370  holds an o-ring  392 . External threading  394  on the central cartridge body  370  upstream of the annular groove  390  is configured to mate with internal threading  396  of the inside of the collar  372 . The o-ring  392  provides an essentially watertight seal between the central cartridge body  370  and the collar  372  downstream of the threading  394 . The downstream end  398  of the collar  372  is configured to fit over the annular projection  432  ( FIG. 10 ) on the downstream portion of the main body  304 , as illustrated in  FIG. 11 . An o-ring  440  ( FIG. 9 ), held in place by an annular groove  436  ( FIG. 10 ) defined by the outer surface of the annular projection  432 , provides for a watertight seal between the collar  372  and the main body  304  when the collar  372  is in the extended position ( FIG. 11 ).  
         [0050]     When the removable cartridge  368  is mounted in the main body  304 , with reference to  FIGS. 11 and 12 , the upstream end  380  of the central cartridge body  370  slides snugly on to the annular projection  430  of the upstream portion  412  of the main body  304 , and the downstream end  398  of the collar  372  slides snugly on to the annular projection  432  of the downstream portion  414  of the main body  304 , effectively holding the removable cartridge  368  in place.  
         [0051]     The outer surface of the collar  372  includes a plurality of equally spaced, longitudinally extending ribs  373  to aid in the rotation of the collar  372 , either manually or with a tool. When the collar is rotated in one direction, the threading  394 ,  396  ( FIG. 13 ) causes the collar  372  to retract onto the central cartridge body  370  as depicted in  FIG. 12 , thereby reducing the effective overall length of the removable cartridge  368  and facilitating its removal from the main body  304 .  
         [0052]      FIG. 14  depicts an alternative configuration of a removable cartridge  500 . A central cartridge body  502  defines a fluid flow passage  504 . A test port  506  is in fluid communication with the fluid flow passage  504  via a test port channel  508 . The upstream end  510  of the central cartridge body  502  is configured to fit over the annular projection  430  ( FIG. 10 ) on the upstream portion  412  of the main body  304 .  
         [0053]     Two check valves  512 ,  514 , an o-ring  516 , and a collar  518  are configured as described above for the second alternative embodiment of the removable cartridge  368 . The central cartridge body  502  further includes a relief valve docking station  520 . A relief channel  522  in the central cartridge body  502  provides fluid communication between the fluid flow path  504  through the central cartridge body  502  in the region between the two check valves  512 ,  514  and the relief valve docking station  520 . One or more supply pressure channels  532  provide water at supply pressure from fluid flow path  504  upstream of the first check valve  512  to the relief valve docking station  520 .  
         [0054]     The relief valve docking station  520  mates with a relief valve  210  ( FIG. 6 ) mounted in a relief valve cap  220  ( FIG. 6 ) as described above in relation to the first alternative embodiment of the backflow prevention device. The relief valve components are as described above and depicted in  FIG. 8 .  
         [0055]     The foregoing relates to preferred exemplary embodiments of the invention. It is understood that other embodiments and variants are possible which lie within the spirit and scope of the invention as set forth in the following claims.