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BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a drain cover assembly interlock having a releasable plug for obstructing a discharge port upon removal of a drain cover.  
           [0003]    2. Description of Related Art  
           [0004]    Properly designed pool and spa drain covers provide several safety functions; namely, they prevent or mitigate evisceration, hair entanglement, finger and toe entrapment and body suction entrapment. If the drain cover is missing from the drain, body entrapment and evisceration are prevalent hazards which are particularly devastating to children. These hazards arise because of the drain suction from the now exposed discharge port positioned behind the drain cover.  
           [0005]    The suction associated with evisceration and body and limb entrapment may be eliminated by “interlocking” the drain cover, i.e., when the covers are removed all flow and suction are interrupted.  
         SUMMARY OF THE INVENTION  
         [0006]    Accordingly, it is one object of this invention to provide a drain cover assembly that interrupts suction from the discharge port upon removal of the drain cover.  
           [0007]    It is another object of this invention to provide a drain cover assembly that discharges a plug into the discharge port upon removal of the drain cover.  
           [0008]    It is another object of this invention to provide a drain cover assembly that retains a plug, such as a ball, within a retainer that responsively releases the ball into the path of the discharge port upon removal of the drain cover.  
           [0009]    It is another object of this invention to provide an interlocked drain cover assembly that includes components that will not entangle a bather&#39;s or swimmer&#39;s hair.  
           [0010]    These and other objects of this invention are addressed by a drain cover that responsively releases a suitably-sized plug, such as an elastomeric ball preferably having a diameter somewhat larger than the drain discharge port, into the vicinity of the drain when the drain cover is removed. This ball becomes entrained in the discharge flow and, because of its size, lodges itself in the entrance to the drain discharge port which is somewhat smaller in diameter than the ball. This “check valve” action isolates a swimmer from the suction proclivities of the drainage pump.  
           [0011]    Several devices are described for securing the ball when the drain cover is in situ; such devices release the ball when the cover is removed. The freely movable nature of the unrestrained ball is a unique attribute of the present invention. The unrestrained ball will be urged into contact with the discharge outlet by water flow, gravity and/or other means. To function efficiently, two additional properties should be realized: hair entanglement with the interlock mechanism should be minimized or eliminated; and the flow rate should not be compromised significantly. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    These and other objects and features of this invention will be better understood from the following descriptions taken in conjunction with the drawings wherein:  
         [0013]    [0013]FIG. 1 is a side cross-sectional view of a drain cover assembly in situ, according to one preferred embodiment of this invention;  
         [0014]    [0014]FIG. 2 is a side cross-sectional view of the drain cover assembly shown in FIG. 1, in a ball plug deployed position;  
         [0015]    [0015]FIG. 3 is a side cross-sectional view of a drain cover assembly in situ, according to one preferred embodiment of this invention;  
         [0016]    [0016]FIG. 4 is a side cross-sectional view of the drain cover assembly shown in FIG. 3, in a ball plug deployed position;  
         [0017]    [0017]FIG. 5 is a side cross-sectional view of a drain cover assembly in situ, according to one preferred embodiment of this invention;  
         [0018]    [0018]FIG. 6 is a side cross-sectional view of the drain cover assembly shown in FIG. 5, in a ball plug deployed position;  
         [0019]    [0019]FIG. 7 is a side cross-sectional view of a drain cover assembly in situ, according to one preferred embodiment of this invention;  
         [0020]    [0020]FIG. 8 is a perspective view of a ball plug retainer according to one preferred embodiment of this invention;  
         [0021]    [0021]FIG. 9 is a side cross-sectional view of the drain cover assembly shown in FIG. 7, in a ball plug deployed position;  
         [0022]    [0022]FIG. 10 is a side cross-sectional view of a drain cover assembly in situ, according to one preferred embodiment of this invention;  
         [0023]    [0023]FIG. 11 is a perspective view of a ball plug retainer according to one preferred embodiment of this invention;  
         [0024]    [0024]FIG. 12 is a side cross-sectional view of the drain cover assembly shown in FIG. 10, in a ball plug deployed position;  
         [0025]    [0025]FIG. 13 is a side cross-sectional view of a drain cover assembly in situ, according to one preferred embodiment of this invention;  
         [0026]    [0026]FIG. 14 is a perspective view of a ball plug retainer according to one preferred embodiment of this invention; and  
         [0027]    [0027]FIG. 15 is a side cross-sectional view of the drain cover assembly shown in FIG. 13, in a ball plug deployed position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]    FIGS.  1 - 15  show various embodiments of drain cover assembly  10 . Drain cover assembly  10  according to this invention is preferably used in connection with swimming pools, spas, whirlpool baths and other vessels that require drains drawing water, particularly where bathers and/or swimmers may come into contact with such drains. Applicant has used the term “pool” surface to describe the surface or surfaces adjacent drain cover assembly  10 , however such term is intended to also describe whirlpools, bathtubs, spas and any other similar surface having a recessed discharge drain  15  with a discharge port  20  out of a drain cavity  25 .  
         [0029]    According to a preferred embodiment of this invention, drain cover assembly  10  includes drain cover  30  configured for attachment with respect to discharge drain  15  and plug  50  retained by at least a portion of drain cover  30 , such as retainer  70 . Plug  50  is responsively discharged from drain cover  30  upon removal of drain cover  30  from discharge drain  15 . Plug  50  is then responsively positioned, by flow of the water, over discharge port  20  thereby blocking fluid flow into discharge port  20 . Various specific embodiments of this invention are described in more detail below.  
         [0030]    According to a preferred embodiment of this invention, and as shown in the drawings, plug  50  comprises a ball, more specifically an elastomeric ball preferably having a diameter larger than a diameter of discharge port  20 . Plug  50  or ball  50  may be elastomeric, polymeric or any other structure, preferably having flexible, deformable and/or conforming characteristics. However, additional shapes, configurations and materials are contemplated for use as plug  50  including polyhedrons, discs, cones and any other suitable shape having suitable properties to block fluid flow into discharge port  20 . However, the term “ball” will be used throughout the remaining specification for the purposes of consistency.  
         [0031]    In addition, ball  50  preferably has a specific gravity greater than unity so that the ball does not float and is thereby, when released, more easily urged into contact with the discharge port  20 . Ball  50  may comprise a material having a lower specific gravity however a tether or other device may be necessary to maintain ball  50  within close proximity to discharge port  20 .  
         [0032]    The following headings and related descriptions describe various preferred embodiments of the present invention. Other variations are contemplated that accomplish the same purpose of releasing a plug into the vicinity of a discharge port upon removal of a drain cover.  
         [0033]    FIGS.  1 - 15  show that discharge drains  15  may be configured with two discharge ports  20  and  20 ′. Usually one discharge port is open, shown as element  20 , and one is plugged, shown as element  20 ′. The preferred embodiments of this invention work equally well when discharge port  20  is plugged and discharge port  20 ′ is open. Further, the preferred embodiments of this invention work equally well when both discharge port  20  and discharge port  20 ′ are open; but then require that drain cover assembly  10  include two cup and ball assemblies.  
       External Ball Retention  
       [0034]    [0034]FIGS. 1 and 2 show one preferred embodiment of this invention wherein retainer  70  of drain cover assembly  10  includes a generally spherical segment, such as cup  75  for restraining ball  50 . As shown in FIG. 1, cup  75  is positioned outside of drain cover  30  relative to drain cavity  25  and restrains ball  50  against the surface of the pool floor. By positioning cup  75  outside of drain cavity  25 , the flow rate of the drain system is not reduced by retainer  70 . In addition, hair entrapment or entanglement is eliminated or minimized by positioning cup  75  flush with the bottom surface of the pool.  
         [0035]    Cup  75  preferably protects the ball from UV radiation, particularly an elastomeric ball. Cup  75  may include one or more holes  77  to permit viewable confirmation of the presence of ball  50  in retainer  70 . Conventional wisdom in the aquatics industry suggests that small holes will not entangle hair. Cup  75  may be constructed of stainless steel or other material that will not degrade in the pool environment.  
         [0036]    According to this embodiment of the invention, and as shown from FIG. 1 to FIG. 2, removal of drain cover  30  releases ball  50  which will quickly be entrained into the water discharge flow pattern. This will bring ball  50  up against the discharge port  20  in drain  15  as shown in FIG. 2. Because the ball diameter is preferably larger than the inside diameter of discharge port  20 , ball  50  will remain fixed to discharge port  20  thereby stopping all fluid flow therethrough. As a result, when drain cover  30  is removed from the drain, either intentionally or accidently, ball  50  will obstruct discharge port  20  thereby maintaining a safe condition in the vicinity of the drain.  
         [0037]    The safe flow rate established for drain cover  30  using the protocol in ASME/ANSI A112.19.8M-1987 is unaffected by the interlock drain cover assembly  10  described herein and shown in FIGS. 1 and 2. Two cup and ball interlocks may be used if two discharge ports  20 ,  20 ′ are active in drain cavity of the main drain.  
         [0038]    According to a preferred embodiment of this invention, ball  50  should have a specific gravity greater than unity. This prevents flotation of ball  50  and thus ensures that ball  50  is urged into drain cavity  25  by gravity and water flow and remains in the vicinity of discharge port  20 .  
       Internal Ball Retention  
       [0039]    According to a preferred embodiment of this invention shown in FIGS. 3 and 4, retainer  70  includes tube  80  associated with or integrated with drain cover  30 . Tube  80  preferably extends downwardly into drain cavity  25  bound by drain cover  30 . Ball  50  is preferably positioned within tube  80  which surrounds and/or encloses ball  50  until drain cover  30  is removed or disassociated from the vicinity of discharge port  20 .  
         [0040]    As shown in FIG. 3, tube  80  preferably extends from drain cover  30  downwardly until flush with a bottom surface of drain cavity  25  against which ball  50  is retained. Tube  80  is preferably tightly fitted against the side wall within drain cavity  25 , in part to minimize flow rate disruptions through discharge port  20 .  
         [0041]    As described above, ball  50  is preferably elastomeric and is captured within tube  50 . The diameter of ball  50  is preferably somewhat larger than the diameter of discharge port  20 . Ball  50  preferably has a specific gravity greater than unity if it is solid. In general, ball  50 , solid or not, should sink in water, in part, to maintain a close proximity to discharge port  20  in the event that drain cover  30  is removed. Two balls  50  may be used in tube  80  when two discharge ports  20 ,  20 ′ are active. If tube  80  is closed at the top, ball  50  will be protected from UV attack.  
         [0042]    As shown in FIG. 4, when drain cover  30  is removed, ball  50  is released into the discharge flow. Ball  50  will be pulled against discharge port  20  by the water flow through discharge port  20  and will accordingly block all fluid flow into and through discharge port  20  by the vacuum generated therein.  
         [0043]    Human hair cannot be entangled around tube  80  because tube  80  preferably remains flush against the side and bottom of drain cover  30  during normal operation with drain cover  30  in situ.  
       Internal Ball Retention—Tube on Discharge Port  
       [0044]    According to a preferred embodiment of this invention shown in FIGS. 5 and 6, drain cover assembly  10  includes retainer  70  having tube  80  associated with or integrated with drain cover  30  and extending downwardly into drain cavity  25  bound by drain cover  30 . Like the embodiment described for FIGS. 3 and 4, tube  80  preferably surrounds ball  50  until drain cover  30  is removed from discharge port  20 . However, according to this preferred embodiment and as best shown in FIG. 5, tube  80  extends from drain cover  30  into proximity with and above discharge port  20  instead of flush with a lower surface of drain cavity  25 .  
         [0045]    In addition, a lower edge of tube  80  includes an angled edge to prevent hair entanglement. The bottom end of tube  80  is preferably cut on an angle to prevent hair from hanging up or becoming entangled on the bottom end of tube  80 . The bottom plane of tube  80  should include an angle α with the horizontal plane such that α≧tan −1 μ, where μ is the friction coefficient between the tube material and human hair. α is preferably less than 45° to retain ball  50  in tube  80  when drain cover  30  is in situ.  
         [0046]    As described above, ball  50  is preferably elastomeric and is captured within tube  80  while resting on the protrusion of port  20  as shown in FIG. 5. The diameter of ball  50  is preferably somewhat larger than the inside diameter of discharge port  20 . Ball  50  preferably has a specific gravity greater than unity if it is solid. In general, ball  50  should sink in water, in part, to maintain a close proximity to discharge port  20  in the event that drain cover  30  is removed. Two balls  50  may be used in tube  80  when two discharge ports are active, specifically in deep main drains where there may be enough tube  80  height to capture two elastomeric balls. A cap at the top end of tube  80  may be used to protect ball  50  from UV attack.  
         [0047]    As shown in FIG. 6, when drain cover  30  is removed, ball  50  is released into the flow pattern of fluid through drain cavity  25  and into drain port  20 . Ball  50  will quickly seal itself against discharge port  20  when its diameter is somewhat larger than that of drain port  20  in drain cavity  25 . Fluid flow is thereby terminated and no suction-related hazards are present at drain cavity  25 .  
       Internal Ball Retention—Stem and Hoop  
       [0048]    FIGS.  7 - 15  show drain cover assembly  10  wherein retainer  70  includes stem  90  extending downwardly from drain cover  30  and hoop  95  (FIGS.  7 - 9 ); capped tube  100  (FIGS.  10 - 12 ); or cup  105  (FIGS.  13 - 15 ) positioned at a distal end of stem  90 .  
         [0049]    FIGS.  7 - 9  show a preferred embodiment of this invention having hoop  95  attached to a distal end of stem  90 . Hoop  95  preferably includes an open lower edge generally flush with a bottom surface of drain cavity  25  formed behind drain cover  30 .  
         [0050]    Stem  90  and hoop  95 , such as shown in FIG. 8, are preferably corrosion-resistant metal, or other suitable material, and are preferably fastened to drain cover  30  so that stem  90  hugs the side wall of drain cavity  25 . Stem  90  is preferably of a sufficient length and shape to position hoop  95  against the bottom of drain cavity  25 . Hair cannot become entangled with retainer  70  of this embodiment because both stem  90  and hoop  95  preferably remain flush against the drain structure  15  defining drain cavity  25 .  
         [0051]    Ball  50 , preferably elastomeric and somewhat heavier than water so it sinks, is retained in hoop  95  while drain cover  30  remains in situ. When drain cover  30  is removed, the previously captured ball  50  is released into the discharge flow of the drain cavity  25  and is brought against the mouth of discharge port  20  by the water flow through discharge port  20 . Because ball  50  has a larger diameter than that of discharge port  20 , ball  50  will seal discharge port  20  against further discharge flow. All suction hazards are thereby removed by this action at drain cavity  25 .  
         [0052]    FIGS.  10 - 12  show drain cover assembly  10  having retainer  70  that includes stem  90  extending downwardly from drain cover  30  and a tube  100  capped on top but open at the bottom attached to a distal end of stem  90 . The open bottom end of tube  100  is in generally flush contact with the bottom surface of drain cavity  25 .  
         [0053]    Ball  50 , preferably elastomeric and somewhat heavier than water so that it sinks, is retained in capped tube  100  while drain cover  30  remains in situ, such as shown in FIG. 10. When drain cover  30  is removed, the previously captured ball  50  is released into the discharge flow of drain cavity  25  and is brought against the mouth of discharge port  20  by the water flow through discharge port  20 , such as shown in FIG. 12. Because ball  50  has a larger diameter than that of discharge port  20 , bail  50  will seal discharge port  20  against further discharge flow. All suction hazards are thereby removed at drain cavity  25  by this action.  
         [0054]    FIGS.  13 - 15  show drain cover assembly  10  having retainer  70  that includes stem  90  extending downwardly from drain cover  30  and cup  105  attached to a distal end of stem  90 . The open bottom end of cup  105  is in generally flush contact with the bottom surface of drain cavity  25 .  
         [0055]    Ball  50 , preferably elastomeric and somewhat heavier than water so it sinks, is retained in cup  105  while drain cover  30  remains in situ, as shown in FIG. 13. When drain cover  30  is removed, the previously captured ball  50  is released into the discharge flow of drain cavity  25  and is brought against the mouth of discharge port  20  by the water flow through discharge port  20 , as shown in FIG. 15. Because ball  50  has a larger diameter than that of discharge port  20 , ball  50  will seal discharge port  20  against further discharge flow. All suction hazards are thereby removed at drain cavity  25  by this action.  
         [0056]    The embodiments of this invention as described and shown in FIGS.  7 - 15 , should include ball  50  that is heavier than water so it should sink. If solid, ball  50  should have a specific gravity greater than unity. A UV resistant ball  50  is desired to survive the pool environment.  
         [0057]    The bottom area of drain cavity  25  should be large enough to accommodate the preceding embodiments without compromising the flow rate of the discharge system.  
         [0058]    While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

Summary:
Missing drain covers used in connection with swimming pools, spas and/or other applications expose humans and animals to discharge ports in the drains that can develop near vacuums which eviscerate, entrap the body and entangle hair. A drain cover is disclosed that releases an elastomeric plug in the neighborhood of the drain upon removal of the drain cover. The plug becomes entrained in the discharge flow and eventually plugs up the smaller diameter discharge port eliminating vacuum hazards by checking all discharge flow and pressure.