Patent Abstract:
A filter element for a pool or spa including a sintered plastic outer cylinder of a first diameter, a sintered plastic inner cylinder of a second diameter less than said first diameter; the inner cylinder being position coaxially with respect to the outer cylinder to define an annular interior chamber; and a selected granulated filter medium or combination of media residing in the annular interior chamber.

Full Description:
This application claims the Paris Convention priority of U.S. Provisional Application No. 61/242,749 entitled “Exchangeable Media Filter” filed Sep. 15, 2009, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The subject disclosure relates to pools and spas and more particularly to improved methods and apparatus for filtering contaminants from pools and spas. 
     2. Description of Related Art 
     Portable spas have become quite popular as a result of their ease of use and multiplicity of features such as varied jet and seating configurations. One area where the inventor has recognized that ease of use could be enhanced is the area of maintaining proper water chemistry and sanitation. 
     SUMMARY 
     The following is a summary description of illustrative embodiments of the invention. It is provided as a preface to assist those skilled in the art to more rapidly assimilate the detailed design discussion which ensues and is not intended in any way to limit the scope of the claims which are appended hereto in order to particularly point tout the invention. 
     In an illustrative embodiment, water chemistry and sanitation are improved by installing a novel filter element in a filter compartment of a portable spa or tub In one embodiment, the filter element comprises a sintered plastic outer cylinder of a first diameter and a sintered plastic inner cylinder of a second diameter less than the first diameter. The inner cylinder is positioned coaxially with respect to the outer cylinder to define an annular interior chamber. A selected granular filter medium or media may then be placed in the annular chamber to combat one or more particular contaminants in the spa water. 
     In an alternative embodiment, a donut shaped bag containing selected filter media is placed in the annular chamber. In such an embodiment, the inner cylinder may be a suitable plastic mesh material and the bag may be adapted to hook over the inner cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side sectional view of a portable spa; 
         FIG. 2  is a perspective view of an exchangeable media filter according to an illustrative embodiment; 
         FIG. 3  is a side sectional view of the filter of  FIG. 2  taken at  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a side sectional view of an alternate embodiment. 
         FIG. 5  is a side sectional view of an alternate embodiment; 
         FIG. 6  is a side sectional view of an embodiment employing a resin filled bag; 
         FIG. 7  is a perspective view illustrating a mesh structure forming an inner cylinder in one embodiment; 
         FIG. 8  is a top view of a resin filled bag with a top hook feature; 
         FIG. 9  is a side sectional view of the bag of  FIG. 8 ; and 
         FIG. 10  is a side sectional view of a media filter embodiment employing the bag of  FIGS. 8 and 9 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a first embodiment of a portable spa  11  containing an exchangeable media filter element  15 . The spa  11  includes a water circulation, purification and heating system, which includes a filter compartment or “filter bucket”  13 . In the system of  FIG. 1 , spa water  29  passes through a circulation pipe  16  to a circulation pump  19 . A “T” junction  21  may be provided to supply water to a water feature such as a waterfall. 
     The circulation pump  19  further pumps the spa water through a “no fault” heater  22 , with which are associated a regulating sensor  23  and a hi-limit sensor  25 . An ozone generator and associated injector or other water purification apparatus  27  is also positioned in the return flow path to the spa  11 , which may comprise an 8 to 10 foot contact chamber  29  and a spa inlet  31  where a circulation return jet is created. A secondary drain  33  may also be provided. An electronic control unit  17  controls the pump  19  and ozone generator  27 , as well as other accessories which may be provided as part of the spa  11 . In one embodiment, the filter bucket  13  may be a conventional filter bucket traditionally manufactured as part of the original spa equipment. 
     An exchangeable media filter  15  according to an illustrative embodiment is shown in  FIGS. 2 and 3 . The filter  15  includes inner and outer co-axially mounted annular filter cylinders  43 ,  44  with a top cap  50  and a bottom cap  52 . The cylinders  43 ,  44  are formed of sintered plastic, such as, for example, polypropylene or polyethylene. Other materials for the cylinders  43 ,  44  may include, for example, and without limitation, PTFE (poly tetrafluoroethylene), PVDF (poly vinylidene fluoride), EVA (ethyl vinyl acetate) Nylon, thermoplastic polyurethane. The top and bottom caps  50 ,  52  may be formed, for example, of plastisol, polyurethane, PVC, ABS, or Noryl, polypro, polyethylene, or chemically/thermally set plastic resin elastomer. 
     Presently preferred thicknesses W 1 , W 2  for each of the cylinders range from 1/16″ to ½″ with an exemplary thickness of ⅛″ for both W 1  and W 2 . Porosity of the cylinders may range from 25 to 150 microns, with 100 microns being a typical porosity. While the filter  15  is cylindrical, other geometrical shapes, such as square or star-shaped could be employed. Various heights and outer diameters may also be employed, including diameters of conventional filter elements such as, for example, 8 to 20 inches tall and 5 to 12 inches in outer diameter. 
     The respective filter elements  43 ,  44  define an annular hollow inner chamber  47 . The annular chamber  47  constitutes a space which is filled with a selected granulated or beaded medium or combination of granulated or beaded media. Such media may include, for example, and without limitation:
         Ion exchange resin   De-ionization resin   Zeolite   Activated carbon   Silver based media   Ceramic   Solid sanitizer (chlorine/bromine)       

     After filling the chamber  47 , the top cap  50  is fixed in place to close the unit. In operation, water flows radially from the outside larger diameter cylinder  43  to the inner cylinder  44 , at a flow rate of e.g. 1-10 gallons per minute, thus bringing the water in contact with the active media. An advantage of the illustrative embodiment is that cylinders containing different filter media can be added or exchanged after the spa has been filled with water in response to occurrence of a problem with a particular type of contaminant. 
     In use, when a spa is filled with water, there is an amount of contamination already in the water. Through usage, chemical addition, evaporation, and water addition; waste and other toxic elements can build up in the water. Traditionally, it is recommended to change the water when the total dissolved solids (TDS) exceed 1500 ppm, or based on a days of use measure; for example, according to the formula [(Spa size in gallons)/3] (times) (number of bathers per day)=the number of days before water change is needed. 
     A filter constructed according to the illustrative embodiments serves to extend the life of the water, reduce the number of water changes and save water by removing the accumulated TDS from the water. Such TDS include: toxic metals such as lead, iron, copper, manganese, minerals, calcium, magnesium, sodium, chloride, soaps, detergents, foaming agents, oils, suntan lotions, cyanuric acid, ammonia, pesticides, pharmaceuticals, organic acids, beer/wine, components of human sweat and waste, chlorinated by-products, humic acid, urine, body fluids, and tannins. 
     In an alternative embodiment, a screw-on cap is provided on a filter like that of  FIG. 1 , enabling a user to change the media. In such case, the filter is removed from the spa, the top is unscrewed, and the media is replaced. In some embodiments the media may be limited to consumer friendly media like carbon, resin beads, and zeolites. As illustrated in  FIG. 4 , such an embodiment may comprise two cylinders  143 ,  144  with a potted bottom cap  152 . A ring  155  with internal threads  157  is provided, which is seated and bonded to the top of the outer cylinder  143 . The top cap  150  has external threads  159 , which permits the top cap  150  to be screwed onto the top of the filter  140  until an internal sealing surface  161  on an inner ring  163  of the top cap  150  contacts and seals with the inner cylinder  144 . 
     In an alternative embodiment, a press-fit or friction fit, rather than screw-on, cap is provided on a filter like that of  FIG. 2 . As illustrated in  FIG. 5 , such an embodiment may comprise two cylinders  243 ,  244  with a potted bottom cap  252 . The top cap  250  has a grooved surface  259 , defining a groove  246 , which is dimensioned to press fittingly engage surface  243 . The internal sealing surface  261  on an inner ring  263  of the top cap  250  may also contact and press-fittingly seal with the inner cylinder  244 . 
       FIG. 6  illustrates an embodiment wherein the filter media  260  is contained within a donut-shaped or annular crossectioned bag  261  formed of a suitable water permeable, porous material. Such material may comprise, for example, polypropylene, polyester, cotton, rayon, polyethylene, nylon, PTFE (Teflon), ployacrylonitrile, or acrylic. In various embodiments, the fabric type may be woven, nonwoven, felt, or mesh of a thickeness of, for example, 0.01″-0.25″. Illustrative porosities range from 10 mirons to 500 microns. 
     In an embodiment such as  FIG. 6 , the inner cylinder  144  may comprise a plastic net/mesh material  263  as shown in  FIG. 7 , such as, for example, part No. 2370 as manufactured by Industrial Netting, Minneapolis, Minnesota. Additionally, in one embodiment, shown in  FIGS. 8 and 9 , the donut bag  261  may have a fabric flange, flap, or hook  267  formed as a part thereof or attached thereto for purposes of slipping over the top rim or edge of an inner filter core. Thereafter, a top cap can be installed to hold the bag  260  in place, as illustrated in  FIG. 10 . In one embodiment, an inner core or cylinder  244  of reduced height may be employed to accommodate the thickness of the fabric hook  267 . 
     Those skilled in the art will appreciate that various adaptations and modifications of the just described embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.

Technology Classification (CPC): 2