Abstract:
An automatic shut-off valve for installation on a sing pool or spa main drain. The automatic shut-off valve has a soft gasket, ball, and ball spring between a grate and a housing. The grate is free to reciprocate up and down relative to the housing. Downward reciprocation of the grate urges the ball into sealable engagement with a valve seat in the housing. During operation, a swimmer covers sufficient grate apertures so that the grate is moved downwards as urged by the main drain suction, towards a swimming pool or spa main drain over which the automatic shut-off valve is mounted. The downward motion of the grate urges the ball into sealable engagement with a valve seat in the housing, where it is securely held by the main drain suction. In this fashion, the ball is entrapped instead of the swimmer, thus avoiding possible disembowelment and/or drowning on the part of the swimmer.

Description:
This application claims benefit and priority of provisional patent application Ser. No. 60/198,779 filed Apr. 21, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to valves, and in particular to an emergency shut-off valve for use in swimming pools, spas and hot tubs and the like, to help prevent main drain entrapment. 
     2. Background of the Invention 
     Most people are aware of the possibility of drowning associated with water activities. Fences are erected around swimming pools in residential back yards to prevent non-swimming children from wandering into the pool. A less well-known hazard connected with swimming pools and hot tubs is the horrifying possibility of becoming entrapped by the vacuum pulled by the pool or hot tub pump at the main drain. If an individual—typically a child between the ages of 2 and 16—were to sit an a main drain, completely blocking it, disembowelment could occur. Even if the child were to block the main drain with a different body part, thus avoiding disembowelment, entrapment could occur, holding the child underwater. If the pump is not stopped, interrupting the vacuum, the child could drown. 
     A typical swimming pool main drain circulation system is depicted in FIG.  1 . Pool  2  filled with water  4  comprises main drain  6  communicating with sump  9  covered by grate  8 . Pump  12  draws water through outflow pipe  10  (the main drain “line”) , and pumps it back into pool  2  through inflow pipe  14 . A pool filter (not shown) is typically installed on inflow pipe  14  between pump  12  and pool  2 . The pool circulation system is used to run pool water through the pool filter to clean water  4 , as well as to provide a mixing effect to homogeneously distribute pool water additives such as chlorine, algaecide, acidity/alkalinity pH equalizers, etc. 
     Between the years 1980 and 1996 fifteen incidents of disembowelment were reported to the U.S. Consumer Product Safety Commission. See  Guidelines for Entrapment Hazards: Making Pools and Spas Safer  pg. 2 (U.S. Government Printing Office 1998). The typical scenario involved children between the ages of 2 and 6 who sit on the uncovered drain of a public wading pool whose cover has been broken or is missing. Id. When the child&#39;s buttocks cover the drain, evisceration can occur through the ruptured septum extremely quickly, even where the change of pressure is small. Id. A 2.2 pound vacuum is considered the threshold for evisceration.  Pool and Spa News , pg. 22 (Apr. 23, 1997). The speed of the disembowelment in itself is frightening—the evidence indicates disembowelment injuries take place in a fraction of a second once the child sits on the drain.  Pool &amp; Spa News—Special Reports  Pg. 7 (1997). Although the disembowelment is not generally fatal, the loss is permanent and irreversible, and has a devastating effect on the victim&#39;s future health and happiness.  Guidelines for Entrapment Hazards: Making Pools and Spas Safer  pg. 2 (U.S. Government Printing Office 1998). 
     Nine cases of body entrapment, including seven which resulted in death, were reported between January 1990 and May 1996. Id. Six of the incidents occurred in spas, two in swimming pools, and one in a wading pool. In one case, a sixteen year old girl was trapped on a 12 in.×12 in. drain grate in a large public spa, and drowned. Id. These entrapment incidents involved primarily children between the ages of 8 and 16. 
     Still another entrapment scenario involves the victim&#39;s hair becoming entrapped in the main drain. At least 30 hair entrapment incidents were reported to the Consumer Product Safety Commission between 1990 and 1998, of which 10 were fatal. Id. at pg. 3. These incidents typically involved long, thin female head hair becoming entangled in the apertures and protrusions around main drain grates. The entrapment occurred because of entanglement, not strong suction forces. Id. 
     This main drain entrapment and disembowelment problem is viewed to be sufficiently serious to warrant legislative action: currently statutes exist in several states (including California and Ohio) requiring main drains safety features, and legislation is pending in several other states. 
     Existing Designs 
     A number of approaches have been taken towards preventing the disembowelment/entrapment problem. One approach has been to mandate at least two drains, so if one of them is obstructed, the other will operate to relieve excessive suction at the obstructed drain. Where only one drain has been installed in an existing pool or hot tub, this approach can be expensive, and may involve tearing up the existing concrete pool deck to install piping. In addition, independent valves for each resultant drain are typically provided. If one of the drain valves is closed, then the safety of the additional drain is defeated. Also, while two working drains may ameliorate the disembowelment problem and the suction entrapment problem, it does little to prevent the hair entrapment problem, which is not caused by suction. 
     Another approach has been to provide an indication and control system which senses a vacuum rise in the main drain line, and turns off the main drain pump, thus relieving the vacuum at the main drain after a certain time lapse. The presence of an indication and control system which includes a vacuum sensor attached to a switch, which then shuts down the main drain pump, which then after a period of time relieves the vacuum present at the main drain, necessarily involves a certain delay between the time the vacuum increases at the main drain and the time the vacuum is actually relieved at the main drain. If at any time during this inherent system delay the main drain vacuum exceeds the 2.2 pound threshold, permanent and irreversible damage has already been inflicted on the victim in the disembowelment scenario. 
     While the indication and control pump shut-off switch approach may help release individuals trapped by vacuum at the main drain before they drown, critics question whether these devices can prevent disembowelment, because disembowelment occurs so quickly, and it is difficult to determine exactly how much suction, and for what duration, the human body can tolerate vacuum without damage. See  The Great Entrapment Debate , Pool &amp; Spa News Pgs. 55, 56 (Aug. 18, 1999). 
     Although the currently available shut-off valves may prevent suction entrapments, they may be ineffectual in disembowelment accidents, because these occur in a fraction of a second. See  Pool &amp; Spa News—Special Reports  Pg. 7 (1997). 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an automatic shut-off valve which does not rely on an indication and control system, main drain pump shut-off, and subsequent release of vacuum at the main drain, along with the delay inherent in this scheme, to prevent dangerous vacuum build-up at the main drain. Design features allowing this object to be accomplished include an automatic shut-off valve installed at the main drain itself, which senses vacuum at the main drain itself, and which shuts off water flow at the main drain itself before vacuum at the main drain reaches dangerous levels. The automatic shut-off valve operates without having to shut off the main drain pump, and without having to wait until the main drain line vacuum dissipates, and thus provides main drain vacuum relief before main drain vacuum can reach dangerous levels. Advantages associated with the accomplishment of this object include prevention of disembowelment and suction-type entrapment incidents. 
     It is another object of the present invention to provide an automatic shut-off valve which provides a visual grate failure indication. Design features allowing this object to be accomplished include a ball having positive buoyancy which floats to the surface of the pool or hot tub if the grate becomes dislodged. A benefit associated with the accomplishment of this object is the provision of a warning to potential victims that the automatic shut-off valve requires servicing, before an accident can occur. 
     It is still another object of this invention to provide an automatic shut-off valve which incorporates a back-up function which blocks the main drain if the grate becomes dislodged and the positive buoyancy warning ball floats to the surface. Design features enabling the accomplishment of this object include a spring-loaded cap which automatically closes over the main drain in the event of grate failure and ball release. An advantage associated with the realization of this object is a back-up main drain shut-off function, and the associated increased reliability and safety advantages. 
     It is another object of the present invention to provide an automatic shut-off valve which is quickly and easily retrofittable to existing main drains. Design features allowing this object to be accomplished include a grate, soft gasket and housing which incorporate co-extensive bolt patterns sized to fit a standard main drain threaded bore pattern. Benefits associated with the accomplishment of this object include reduced time and cost of installation, and thus increased availability. 
     It is still another object of this invention to provide an automatic shut-off valve which provides protection against hair entrapment. Design features enabling the accomplishment of this object include a hair barrier installed over a grate. Advantages associated with the realization of this object include reduced chance of hair entrapment, and consequent reduced chance of associated entrapment injury. 
     It is still another object of this invention to provide an automatic shut-off valve which will not obstruct automatic pool cleaning equipment. Design features enabling the accomplishment of this object include a soft gasket ramp. Advantages associated with the realization of this object include uninterrupted pool cleaning, along with the attendant health advantages. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with the other objects, features, aspects and advantages thereof will be more clearly understood from the following in conjunction with the accompanying drawings. 
     Eight sheets of drawings are provided. Sheet one contains FIG.  1 . Sheet two contains FIG.  2 . Sheet three contains FIG.  3 . Sheet four contains FIG.  4 . Sheet five contains FIG.  5 . Sheet six contains FIG.  6 . Sheet seven contains FIG.  7 . Sheet eight contains FIGS. 8 and 9. 
     FIG. 1 is a side cross-sectional view of a typical pool water circulation system. 
     FIG. 2 is a side cross-sectional isometric view of an automatic shut-off valve in the open position. 
     FIG. 3 is a side cross-sectional isometric view of an automatic shut-off valve in the closed position. 
     FIG. 4 is a front cross-sectional isometric view of an automatic shut-off valve in the open position. 
     FIG. 5 is a side cross-sectional isometric view of an automatic shut-off valve missing its grate and soft gasket, whose cap has therefore closed automatically as a backup flow shut-off device. 
     FIG. 6 is a side cross-sectional isometric view of an automatic shutoff valve incorporating a hair barrier. 
     FIG. 7 is a side cross-sectional isometric view of a hair barrier installed in a main drain. 
     FIG. 8 is an exploded side cross-sectional isometric view of a hair barrier, grate and screws ready to be installed in a main drain. 
     FIG. 9 is a top isometric view of a section of mesh grate. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 2 and 3, we observe a side cross-sectional isometric view of automatic shut-off valve  20  in the open and closed positions, respectively. FIG. 4 is a front cross-sectional isometric view of automatic shut-off valve  20  in the open position. Automatic shut-off valve  20  comprises soft gasket  32  and ball  42  sandwiched between grate  22  and housing  36 . Ball  42  is fabricated of material with positive buoyancy, or air-filled, so as to float if it escapes from the instant automatic shut-off valve  20 . Thus, the buoyancy of ball  42  provides an important warning function: if ball  42  floats to the surface of a pool or spa into which automatic shut-off valve  20  has been installed, observers and swimmers will thereby receive notice that automatic shut-off valve  20  is in need of repair or maintenance. 
     Screws  28  fasten housing  36  to an existing sump lip  11 . The instant automatic shut-off valve  20  may be retrofitted to existing sumps  9  using existing threaded bores in sump lip  11 . Soft gasket  32  comprises soft gasket bore  34  and soft gasket ramp  35 . Soft gasket ramp  35  permits automatic pool cleaning apparatus to crawl over the instant automatic shut-off valve  20  without getting stuck. 
     As may be observed also in FIG. 8, screws  28  are stepped screws comprising a screw upper portion  29 , and a screw lower portion  31 . The diameter of screw upper portion  29  is greater than the diameter of screw lower portion  31 . Housing  36  comprises a plurality of housing screw bores  54  sized to slidably admit screw lower portion  31 , but not screw upper portion  29 . Screws  28  fasten housing  36  securely in place, sandwiched between screw upper portion  29  and sump lip  11 . 
     Grate  22  comprises a grate screw bore  26  corresponding to each housing screw bore  54 . Each grate screw bore  26  is sized to slidably admit a screw upper portion  29 , but not screw head  33 . Thus, grate  22  may slide up and down along screw upper portion  29 ; its end-of-travel upper stop is provided by screw head  33 , and its end-of-travel lower stop is provided by housing  36 . 
     Grate  22  also comprises grate apertures  23  which allow water to flow through grate  22 , and actuator finger  30 . One extreme of actuator finger  30  is rigidly attached to grate  22 ; an opposite extreme of actuator finger  30  is disposed in close proximity to ball  42 . As may be observed more clearly in FIG. 3, actuator finger  30  may be threadably attached to grate  22  by means of actuator finger male thread  16  threaded into mating grate threaded bore  18 . By means of this threaded connection, the precise length of actuator finger  30  may be easily set by simply rotating actuator finger  30  as indicated by arrow  17 . 
     Grate  22  further comprises grate foot  24  which rests on soft gasket  32 . Grate foot  24  is disposed around the perimeter of grate  22 . When automatic shut-off valve  20  is in the open position depicted in FIGS. 2 and 4, grate  22  slightly compresses soft gasket  32  in order to prevent any water flow between grate  22  and sump lip  11 : in order for the instant automatic shut-off valve  20  to function properly, all water flow must be through grate apertures  23  and housing  36 . 
     Soft gasket  32  is manufactured of resilient material which may be easily compressed. When a force holding soft gasket  32  compressed is removed, soft gasket  32  will tend to return to its original dimensions. Soft gasket  32  acts as a seal, to prevent water flow between grate  22  and sump lip  11 , and also acts to some extent like a spring, urging grate  22  upwards until stopped by screw heads  33 . 
     Housing  36  comprises housing ball chamber  38  communicating with housing spring chamber  40  through valve seat  56 . Housing spring chamber  40  communicates with sump  9  through at least one housing spring chamber aperture  41 . Housing spring chamber  40  contains ball spring  46 . When extended, ball spring  46  holds ball  42  out of valve seat  56 , permitting water to flow between ball  42  and valve seat  56 , and thence through housing spring chamber  40  and housing spring chamber apertures  41  into sump  9  and outflow pipe  10 . 
     Housing ball chamber  38  comprises vanes  44  which in concert with cap  48  act as guides to constrain the motion of ball  42  to reciprocation substantially along a line from actuator finger  30  through the center of ball spring  46 . Thus when automatic shut-off valve  20  is in the open position depicted in FIGS. 2 and 4, ball  42  is held out contact with valve seat  56  by ball spring  46 , constrained from floating upwards by actuator finger  30 , and held in place horizontally by vanes  44  and cap  48 . Conversely, when automatic shut-off valve  20  is in the closed position depicted in FIG. 3, ball  42  is held in intimate contact with valve seat  56  by the differential water pressure above and below ball  42  against the force of ball spring  46 , and held in place horizontally by valve seat  56 . 
     In the open position of automatic shut-off valve  20  depicted in FIG. 2, water being recirculated flows through grate apertures  23 , soft gasket bore  34 , housing ball chamber  38 , valve seat  56 , housing spring chamber  40  and housing spring chamber aperture(s)  41  into sump  9  and outflow pipe  10 , as indicated by arrows  51 . 
     Operation of Automatic Shut-off Valve  2   
     If grate  22  becomes partially or completely blocked (by a swimmer, for example), the water pressure differential between water above and below grate  22  pushes grate  22  downward as indicated by arrow  58  in FIG.  3 . In turn, actuator finger  30  rigidly attached to grate  22  pushes ball  42  downwards towards valve seat  56 , against the spring force of ball spring  46  and the resiliency of soft gasket  32 . 
     When ball  42  is sufficiently close to valve seat  56 , either actuator finger  30  or the water pressure differential between water above and below ball  42  (or both) pushes ball  42  into intimate contact with valve seat  56 , thereby stopping flow of water through automatic shut-off valve  20 . The water pressure differential between water above and below ball  42  then holds ball  42  securely in valve seat  56  until the recirculation pump is turned off. Thus in operation, ball  42  acts as a surrogate swimmer: ball  42  is entrapped by main drain vacuum instead of the swimmer! 
     It is important to note that the closing action of automatic shut-off valve  20  occurs directly at main drain  6 , within microseconds of any grate  22  blockage sufficiently great to create a risk of bodily injury. The virtually instantaneous action of the instant automatic shut-off valve  20  represents a significant injury protection advance over existing in-line vacuum sensing valves, which may not close until injury has already occurred. 
     Once the recirculation pump is turned off, and the partial vacuum within sump  9  is relieved, the spring force of ball spring  46 , the resiliency of soft gasket  32 , and the buoyancy of ball  42  push grate  22  back into the open position depicted in FIG.  2 . 
     Referring now to FIG. 5, an important back-up main drain shut-off function is provided by cap  48 . Cap  48  is sized to cover valve seat  56 . Cap  48  also comprises cap groove  49 , which is sized to admit the upper portion of ball spring  46 , so as to avoid interference between ball spring  46  and cap  48  when the latter is in the closed position. 
     Cap  48  is hingedly attached to housing ball chamber  38  by means of cap hinge  50 , and spring loaded into the closed position depicted in FIG. 5 by means of cap spring  52 . Thus, if grate  22  and ball  42  were to become dislodged, cap  42  would automatically close as urged by cap spring  52  and as indicated by arrow  60 , thereby covering valve seat  56 . When closed, cap  48  helps avoid the possibility that an individual could become trapped against main drain  6 , or that an individual&#39;s hair could become entangled, because water flow has been blocked by cap  48 . 
     In FIGS. 2-4 and  6 - 8  grate  22  is depicted comprising round grate apertures  23 . It is important to note, however, that the shape of grate apertures  23  may be any shape conducive to minimizing the restriction of water flow through grate apertures  23 , including square or rectangular grate apertures  23  commonly present in mesh type grates. A section of one such mesh grate  74  is depicted in FIG.  9 . Mesh grate  74  comprises criss-crossing strands  76  which define grate apertures  23 , which in this case are square. The small width of strands  76  contributes towards reducing resistance to water flow through mesh grate  74 . Strands  76  may be made of wire, plastic, nylon, other synthetic, or other appropriate material. 
     FIG. 5 is a side cross-sectional isometric view of automatic shut-off valve  20  missing its grate  22 , ball  42  and soft gasket  32 . As soon as ball  42  is no longer present to hold cap  48  open against the force of cap spring  52 , cap spring  52  urges cap  48  closed over valve seat  56  as indicated by arrow  60 . This closing of cap  48  interrupts any flow of water through automatic shut-off valve  20 , and the water pressure differential between water above and below cap  48 , and cap spring  52 , then hold cap  48  securely closed until the recirculation pump is turned off. In addition, as previously described, ball  42  is designed to float, so if it became dislodged, ball  42  would float to the surface of a pool or spa into which automatic shut-off valve  20  had been installed, thereby providing observers and swimmers notice that automatic shut-off valve  20  is in need of repair or maintenance. 
     FIG. 6 is a side cross-sectional isometric view of an alternate embodiment automatic shutoff valve  20  incorporating hair barrier  62 . Hair barrier  62  is a porous disc which permits water to pass, but which prevents hair from passing through. In fact, the passages through hair barrier  62  are so serpentine that a hair cannot penetrate sufficiently to even get stuck. Hair barrier  62  is installed on top of grate  22 , and snapped in place behind grate lip  64 . Grate screw bore  26  comprises lower grate screw bore  72  communicating with upper grate screw bore  70 . Lower grate screw bore  72  is sized to slidably admit screw upper portion  29 , but not screw head  33 ; upper grate screw bore  70  is sized to slidably admit screw head  33 . When the automatic shut-off valve  20  depicted in FIG. 6 is closing, grate  22  is free to move towards valve seat  56  without hair barrier  62  butting against screw heads  33 , by virtue of upper grate screw bores  70 . Grate  22  supports and provides strength and rigidity to hair barrier  62 . 
     When open, the automatic shut-off valve  20  depicted in FIG. 6 permits water to pass through hair barrier  62 , grate apertures  23 , soft gasket bore  34 , housing ball chamber  38 , valve seat  56 , housing spring chamber  40  and housing spring chamber aperture(s)  41  into sump  9  and outflow pipe  10 , as indicated by arrows  68 . The automatic shut-off valve  20  depicted in FIG. 6 closes automatically in the presence of blockage in the same manner as described previously. 
     Hair barrier  62  serves the dual functions of preventing hair entrapment, and acting as a filter to keep debris out of housing  36  which might interfere with the automatic closing function of automatic shut-off valve  20 . 
     FIG. 6 depicts an alternate embodiment of soft gasket ramp  35  embodiment: flexible skirt  66 . Flexible skirt  66  is shaped like a Belleville washer, and is attached at its inside diameter to soft gasket  32 . Flexible skirt  66  permits automatic pool cleaning apparatus to crawl over the instant automatic shut-off valve  20  without getting stuck. 
     FIG. 7 is a side cross-sectional isometric view of a hair barrier  62  installed in a main drain, without a housing  36  or ball  42  being installed. This figure is intended to illustrate an embodiment of the instant invention where a hair barrier  62  is installed without housing  36  or ball  42 . FIG. 8 is an exploded side cross-sectional isometric view of a hair barrier  62 , grate  22  and screws  28  ready to be installed in a main drain. 
     In the preferred embodiment, grate  22 , housing  36 , actuator finger  30 , cap  48  and screws  28  were manufactured of nylon, plastic, synthetic, metal, or other appropriate material. Soft gasket  32  was made of foam rubber, synthetic, or other appropriate material. Hair barrier  62  was made of porous plastic or other appropriate material. One such porous plastic material comprises interconnected pores ranging in size from 0.0008-0.01 inch, although larger pore sizes could also be used. The pores are interconnected along tortuous paths, thus preventing hair from penetrating hair barrier  62  sufficiently to become entwined. In addition, hair barrier  62  could be manufactured with an uneven top surface which would, by virtue of its unevenness, prevent total blockage by swimmers and thus avoid entrapment and/or disembowelment where the embodiment of the instant invention depicted in FIGS. 7 and 8 is used. Ball spring  46  and cap spring was manufactured of metal, synthetic, or other appropriate material. 
     While a preferred embodiment of the invention has been illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit of the appending claims. 
     DRAWING ITEM INDEX 
       2  pool 
       4  water 
       6  main drain 
       8  grate 
       9  sump 
       10  outflow pipe 
       11  sump lip 
       12  pump 
       14  inflow pipe 
       16  actuator finger male thread 
       17  arrow 
       18  grate threaded bore 
       20  automatic shut-off valve 
       22  grate 
       23  grate apertures 
       24  grate foot 
       26  grate screw bore 
       28  screw 
       29  screw upper portion 
       30  actuator finger 
       31  screw lower portion 
       32  soft gasket 
       33  screw head 
       34  soft gasket bore 
       35  soft gasket ramp 
       36  housing 
       38  housing ball chamber 
       40  housing spring chamber 
       41  housing spring chamber aperture 
       42  ball 
       44  vane 
       46  ball spring 
       48  cap 
       49  cap groove 
       50  cap hinge 
       51  arrow 
       52  cap spring 
       54  housing screw bore 
       56  valve seat 
       58  arrow 
       60  arrow 
       62  hair barrier 
       64  grate lip 
       66  flexible skirt 
       68  arrow 
       70  upper grate screw bore 
       72  lower grate screw bore 
       74  mesh grate 
       76  strand