You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
   The present invention relates to pool drains, and, in particular, to main and skimmer drains for swimming, wading, and circulating pools incorporating safety devices for preventing inadvertent blockage by pool users. 
   BACKGROUND OF THE INVENTION 
   Swimming and wading pools, as well as certain spas, are equipped with powerful water circulation filtration systems. Such pools use one or more drains in the pump return line that generate high flow, high suction conditions at their inlets. It is now recognized that such drain conditions can pose considerable risks to pool users, particularly children. The drain conditions can entrap swimmers, resulting in numerous reported annual drownings as a result of an inability to break free of the extreme suction condition. Hair and apparel may also be entangled in the drain, resulting in traumatic and physically dangerous situations. Disembowelments have also been reported. 
   As a result of these repetitive accidents, many jurisdictions have enacted regulations to obviate the prime causal factors. To limit suction conditions in the event of blockage, plural drains have been proposed. To limit local suction conditions at a particular drain, anti-vortex covers and grated openings have been required. Maximum pump suction conditions have also been specified. During use, however, the covers and openings may become dislodged and the protective features are lost. Accordingly, even the currently proposed circulation conditions do not entirely overcome acute suction conditions at the drain inlet. 
   Most of such regulatory approaches have focused on new installations, or conditioned approval of alterations to the installations on retrofitting the drainage system for compliance. The economics of retrofit have limited the use of these approaches in existing pool installations where the governmental control is not applicable. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides a safety inlet assembly that may be readily and inexpensively incorporated into existing suction drains for pools, spas and other water circulation facilities and limits suction conditions. The safety inlet assembly is adapted for use with existing main and skimmer drain designs, requiring only conventional couplings. The inlet assembly comprises a domed perforated tube having a lower mounting collar that attached with the coupling to the drain inlets. The drain cover is attached to the tube. Should the cover become dislodged, the tube provides a three dimensional hole array that eliminate high suction conditions even if the hole pattern is partially obstructed. The inlet assembly in one embodiment utilizes telescoping tubes providing protective redundancy in the event a tube and associated cover are dislodged. 
   Accordingly, it is an object of the present invention to provide a flow control device for swimming pool suction drains that may be inexpensively and readily installed into existing pools. 
   Another object is to provide a suction inlet drain with an auxiliary device that limits drain suction conditions if the drain cover is dislodged. 
   A further object of the invention is to provide a drain safety device that can be adapted to existing pool installations using easy to obtain components. 

   
     DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages of the present invention will become apparent upon reading the following detailed description, taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a top view of a swimming pool incorporating safety inlet drain assemblies in accordance with the invention; 
       FIG. 2  is a side cross sectional view of a swimming pool main drain having a safety inlet assembly according an embodiment of the invention; 
       FIG. 3  is an exploded perspective view of the safety inlet of  FIG. 2 ; 
       FIG. 4  is a side cross sectional view of the safety inlet of  FIG. 3 ; 
       FIG. 5  is a side cross sectional view of a swimming pool main drain having a safety inlet assembly according to another embodiment of the invention; and 
       FIG. 6  is a side cross sectional view of a swimming pool skimmer drain having a safety inlet assembly in accordance with a further embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to the drawings for the purpose of illustrating a preferred embodiment of the invention and not for limiting same,  FIG. 1  shows a swimming pool  10  having a plurality of water supply outlets  12  around the base  14  for circulating water to the pool, and a main drain  16  and a skimmer drain  18  for returning water from the pool  10 . 
   The outlets  12  are serially connected by an outlet conduit  20  in a supply line from a pump  22  and a filter  24 . The main drain  16  is connected by main conduit  26  in a return line to the pump  22 . The skimmer drain  18  is connected with the main drain  16  by branch conduit  28 . Conventionally the main drain  16  is located at the deepest portion of the pool and centrally thereof. The skimmer drain  18  may be deployed in varying modes. The skimmer drain may be integrated into the sidewalls of the pool for straining upper level debris. The skimmer drain may also be employed as a floating device and coupled to the branch conduit by a flexible hose. In the latter case, the skimmer drain may be used during normal pool usage. Additionally, the skimmer drain may be used in conjunction with a pool cover for removing accumulated water and debris during off-season periods. 
   As illustrated in the preferred embodiment, the skimmer drain  18  is connected in series with the main drain  16  to provide a secondary inlet to the pump in the event the main drain  16  is obstructed, both as a personnel and a mechanical safety measure. Moreover, particularly in older installations, the skimmer drain may be connected in parallel with the main drain  16 . The present invention is compatible with all of the foregoing variants. 
   Referring to  FIG. 2 , a main drain  16  includes a drain body  30  having an upwardly opening cavity  32  covered by an apertured cover plate  34  or other grillwork provided with flow passages. The body  30  includes a peripheral sidewall  36  having a threaded apertured boss  38  that is coupled to the threaded end  40  of the branch conduit  28  leading to the skimmer drain  18 . The body  30  includes a base  42  having a central apertured boss  44  that receives the threaded terminal end  46  of the main drain conduit  26 . The foregoing is exemplary of many main drain designs, however, differing configurations are compatible with the invention. Further, the location and terminal ends of the conduits may vary from design to design, however, the coupling with the safety inlet assembly described below uses well-known commercially available components. 
   A safety inlet assembly  50  is mounted in the cavity  32  and includes a perforated sleeve assembly  52  having a coupling member  54  for attachment to the terminal end  46  of the main drain conduit  26 . The drain cover plate  34  is attached to the upper end of the sleeve assembly  52  by fastener assembly  56  comprising a stainless self tapping screw and washer. 
   Referring to  FIGS. 3 and 4 , the sleeve assembly  52  comprises an outer sleeve  60  and an inner sleeve  62 . The outer sleeve  60  includes a cylindrical body  64  having a plurality of axially and circumferentially spaced openings  65 . A cylindrical collar  66  is attached to the lower end of the body  64 . The inner sleeve  62  includes a cylindrical body  68  having a plurality of axially and circumferentially spaced openings  69 , a cover cap  70  and a cylindrical collar  72  attached at the lower end thereof. The cover cap  70  has a hemispherical upper portion  74  and a lower circumferential skirt  76 . The upper portion  74  of the cap  70  includes a plurality of openings  78 . The sleeve bodies  64 ,  68 , cap  70  and collars  66 ,  72  are preferably formed of non-corrosive materials such as plastic. Suitable flow openings in the range of ⅛ to ¼ inch are preferred. 
   The inner sleeve  62  is telescopically received within the outer sleeve  60 . The collar  72  is sized to provide a sliding compressive fit with the inner surface of the outer sleeve  62  thereby providing for assembly with or without the cover plate  34  attached thereto ( FIG. 2 ) while resisting inadvertent disassembly in use. 
   For use in a main drain of the type described above, a suitable coupling  54  includes a threaded base  80  for assembly with the threaded terminal  46  of the conduit  26 , and an upper cylindrical rim  82  providing a socket for receiving the collar  66  of the outer sleeve  60 . The collar  66  may be mechanically or adhesively mounted at the rim socket. For alternative non-threaded terminations of the conduit  26 , other widely available coupling components may be employed for assembling the safety sleeve to the main conduit. Moreover, male or female connected for external or internal coupling at the collar  66  may be utilized. 
   The sleeve assembly  52  may be incorporated on existing drains by removing the existing cover plate or grill, threading the coupling  54  onto the treaded end  46 , mounting the cover plate  34  over the cavity  32 , and attaching the cover plate  34  to the inner sleeve  62  with fastener assembly  56 . Alternatively, as described above the inner sleeve  62  may be assembled to the cover plate  34  and the unit telescopically assembled. 
   The openings in the sleeve assembly provide an entrance area to the main conduit substantially greater than the flow area of the main conduit  26  thereby providing an unimpeded flow rate to the pump in the event of partial obstruction. If for any reason, the cover plate  34  detaches, the safety inlet provides a three dimensional inlet that maintains full flow rates and reduces the chances that pool users and/or apparel could be dangerously sucked into the conduit  26 . 
   Another embodiment is shown in  FIG. 5  wherein the safety inlet assembly  90  comprises a single sleeve assembly  92  having a cap  94  attached to the cover plate  34  by fastener assembly  95 , and a lower cylindrical collar  96  mounted on the coupling  54  as described above. 
   The inlet assembly  30  may also be incorporated into the skimmer drain  18  as shown in  FIG. 6 . Therein, the skimmer drain  18  includes a skimmer body having a circular base  100  centrally carrying a curved pre-drain pipe  102  having a socket sleeve  104  for receiving the collar  66  of the outer sleeve  60 . The pipe  102  is attached as appropriate for the skimming application to the branch conduit  28 . A cylindrical meshed screen  104  is carried by the base  100  defining a center cavity housing the inlet assembly  50 . The top of the screen  104  is covered by a circular lid  106 . The lid  106  is attached to the cap  70  of the inner sleeve  62  by fastener assembly  108 . 
   It will be appreciated that the safety inlet assembly may be provided as desireable safety equipment for new pool installations or provided as an aftermarket kit for the replacement market. In both applications, the safety inlet assembly may be readily integrated with conventional designs using widely available coupling components. 
   Having thus described a presently preferred embodiment of the present invention, it will now be appreciated that the objects of the invention have been fully achieved, and it will be understood by those skilled in the art that many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the sprit and scope of the present invention. The disclosures and description herein are intended to be illustrative and are not in any sense limiting of the invention, which is defined solely in accordance with the following claims.

Summary:
A safety inlet drain assembly for main and skimmer drains of a swimming pool includes a perforated cylinder in the drain cavity mounted at a lower end on the drain return line and having a domed cap on the upper end to which the drain gate cover is attached by fasteners. The safety drain assembly is configured for precluding complete blockage by pool users in the event of displacement of the cover plate thereby preventing excessive suction conditions otherwise posing physical danger to the users.