Abstract:
A resilient black flexible polymer mat is submerged on the bottom of a small pool or pond to promote the passive solar heating of the water. The upper surface is non-reflective, textured and provided with projecting elements to increase the surface area for enhancing the amount of solar radiation absorbed to heat the mat; the bottom surface has a plurality of spaced-apart projecting frictional supporting members to assist in retaining the mat in position on the bottom of the pool or pond; spaced-apart passages extending between the upper and bottom surfaces permit the movement of water.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a method and articles of manufacture for the passive solar heating of an outdoor pool or pond. 
       BACKGROUND OF THE INVENTION 
       [0002]    Large outdoor pools in temperate climates are generally provided with a heater to raise the water temperature to a comfortable level. With ever increasing energy costs, the residential pool owner may determine that the expenses associated with heating the pool mandate less use of the heater and therefore use of the pool will be curtailed or avoided by users. Smaller above ground pools and so-called kiddie pools are not equipped with heaters and users must rely upon the effect of the sun to heat the water. In most cases, the smaller pools can be erected or placed in a sunny portion of the yard to take advantage of the warming effect of the sun. 
         [0003]    Small pools for children are typically formed of molded plastic and filled with a garden hose for use. At the end of the day or other period of use, the water is discarded and the pool is set aside for subsequent use. Larger inflatable pools can range in size from three to eighteen feet in diameter. More permanent pools installed in a residential setting employ a flexible vinyl liner supported by an external frame and flexible wall panels from two to five feet in height. These larger installations typically can contain from two to four feet of water and may be from twelve to eighteen feet in diameter. They are also typically filled by the homeowner from a garden hose. Upon filling of the wading pool and/or the larger pools using domestic water, either from a well or a municipal water system, the water temperature will be well below that which feels comfortable to most bathers. 
         [0004]    Wading pools and other small pool installations are typically not equipped with water heaters or any other water circulation system. Cooler overnight temperatures can lower the water temperature in above ground pools, as does evaporative cooling. One solution that has been proposed are inflatable mats that are placed on the surface of a pool to be heated by the sun. In the evening and overnight when the ambient air temperature typically is lower, the pads provide an insulative effect to retain heat that has been absorbed from the sun during the day. Although a claim has been made that the inflatable floating article can provide benefits from solar radiation, any air between the upper and lower surfaces of the inflated mat would actually serve as an insulator. This feature is desirable and is the basis for retaining the heat in the body of water during the night used by this and other types of insulative pool covers. However, with the floating pads on the surface during the day, the pool cannot be used by bathers. 
         [0005]    The problem addressed by the present invention is how to economically increase the solar heating effect on the water in a wading pool or other relatively shallow above-ground pool installation, and how to do so without interfering with the use of the pool. 
       SUMMARY OF THE INVENTION 
       [0006]    The above problem is resolved and other advantages are provided by the method and articles of manufacture in accordance with the present invention that comprise flat, especially textured passive solar heating pads or disks that are placed on the bottom surface of the pool to enhance the absorption of the sun&#39;s rays and transfer that heat to the adjacent water. The sun&#39;s solar heating effect is amplified by the article of the present invention which comprises a black or other dark-colored flexible polymer mat, the polymer being chemical-resistant and having a specific gravity greater than one so that it will remain submerged on the bottom when placed in the pool. The mat has an upper and a bottom surface, the upper surface being non-reflective and including features to increase the absorption of the IR rays of the sun to raise the temperature of the mat above that of the surrounding water. The bottom surface is provided with a plurality of spaced-apart frictional members to assist in retaining the mat on the bottom of the pool or pond, and a plurality of spaced-apart openings or passages extending between the upper and bottom surfaces. 
         [0007]    Molded wading pools for children and larger above-ground installations are typically of a light or pastel color, or even white. These colors and surfaces are reflective of solar radiation and do little to raise the temperature of the water in the pool. By placing a plurality of black polymer mats having projecting surface elements on the bottom of the otherwise reflective wading pool or pool liner, much more of the sun&#39;s solar radiation is absorbed and this heat is transferred to the water by conduction and distributed by convection effects. 
         [0008]    The placement of a plurality of circular black rubber mats, each approximately 18 inches in diameter, has been shown to raise the water temperature in an inflatable backyard pool by a measurable amount. 
         [0009]    The mats are placed on the bottom of the pool where they absorb the radiant energy from the sun which is then transferred to the surrounding water. The use of a number of mats distributed on the bottom of the pool improves the efficiency and the increase in the temperature of the pool&#39;s water. 
         [0010]    The specific gravity of the pad is greater than 1 so that it will remain on the bottom of the pool and is sufficiently flexible so that it will generally assume the contour of the surface, which may include some irregularities in the case of a flexible pool liner that is placed on bare ground or a residential lawn. The interior surface of a kiddie pool may also be slightly contoured to provide decorative aesthetic effects. 
     
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
         [0011]    The invention will be described in further detail below and in conjunction with the attached drawings in which: 
           [0012]      FIG. 1  is a perspective diagrammatic view of one embodiment of a method of use of the article of the invention; 
           [0013]      FIG. 2  is an enlarged top perspective view of the articles shown in  FIG. 1 ; 
           [0014]      FIG. 3  is an enlarged perspective view of the bottom of the article of  FIG. 2 ; and 
           [0015]      FIG. 4  is a cross-sectional view of the article taken along line  4 - 4 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0016]    Referring to  FIG. 1 , an illustration of one embodiment of the method of using the passive solar heating mat of the invention, which is shown in a circular configuration, with three mats in position on the bottom of an inflated pool. It is to be understood that the mat can be of any convenient size and its shape can be curvilinear, i.e., round as in  FIG. 1 , rectilinear, or a combination of these shapes. The mat can also be configured in more fanciful shapes, i.e., of a fish, a sea horse, a boat, or another desired design. The surface can also be ornamented with other details, such as the logo or trademark of the manufacturer. 
         [0017]    The pads or mats are preferably black so as to maximize the absorption of the sun&#39;s rays and thereby raise their internal temperature, which in turn is transferred to the surrounding water, principally via conduction. Although the solar heating effect will be optimum for a black mat, other deep tone dark colors can also be used for aesthetic reasons, including enhanced customer appeal. 
         [0018]    As best shown in the enlarged view of  FIG. 2 , the upper surface ( 20 ) is provided with a plurality of features ( 22 ) that are raised above the planar upper surface ( 24 ) to thereby increase the surface area exposed to the sun&#39;s infra-red (IR) radiant energy which serves to heat the mat and raise its temperature. The raised features ( 22 ) project above the surface, are curvilinear and have a cross-section that is defined by a plane transecting a sphere at or above the diameter. The projections can also assume other geometric shapes such as rectangles, squares, diamonds and the like, that have a vertical or slightly angled peripheral surface to increase the overall surface area of the mat. In order to enhance the ornamental appearance, the surface projections ( 22 ) are spaced apart in a regular pattern and extend from proximate the periphery ( 12 ) of the mat across its entire surface. 
         [0019]    In order to enhance the absorption of radiant energy, the planar upper surface ( 24 ) is textured to provide an essentially non-reflective matte finish. Since the product is produced by molding, the planar surface can provided with a plurality of shallow parallel grooves, a cross-section formed by the intersection of parallel grooves at right angles, acute angles and any other combination that increases the surface area and, therefore, the surface for receiving radiant energy to raise the temperature of the mat. 
         [0020]    The mat ( 10 ) is also provided with a plurality of spaced-apart openings or passages ( 26 ) extending from the upper surface and through the bottom surface. These openings permit the escape of any air which may be trapped under the pad when it is placed on the bottom of the pool and to release any air bubbles that may be formed after the pad is placed in position, and provide passages for water and facilitate the specific placement of the mat on the bottom surface of pool or pond. 
         [0021]    The edge of the mat ( 10 ), whether it be round or of some other geometric shape or other configuration, is preferably provided with a peripheral rim ( 50 ) that is somewhat thicker than the adjacent portion of the mat between the planar surfaces. The rim serves the function of a reinforcement that reduces the likelihood that the mat might be torn or abraded along its edge during storage or in the event of misuse. This protective rim or edge member ( 50 ) can be from 20-30% thicker than the adjoining portion of the mat and extends inwardly from the periphery about ⅛ inch to 3/32 inch. 
         [0022]    Referring now to  FIG. 3 , the bottom surface ( 30 ) is provided with a plurality of projecting members ( 32 ) which serve the purpose of enhancing the frictional contact between the mat and the bottom of the pool, and also permit the passage of water under the mat to facilitate the transfer of heat via direct conduction with the bottom surface ( 30 ). As illustrated in  FIG. 3 , the projections ( 32 ) are in the form of a plurality of suction cups. The intermediate planar bottom surface ( 34 ) between the projecting members ( 32 ) is smooth and presents a reflective shiny surface to the viewer. This shiny surface serves to reduce algal growth and to facilitate cleaning and removal of any algae which does appear. 
         [0023]      FIG. 4  is a cross-section view of the mat showing the projections ( 22 ) from the upper surface ( 20 ) and the frictional projecting members ( 32 ) extending from the bottom surface ( 30 ). The rim member ( 50 ) is shown as projecting above the upper surface, but it can be extended as well. 
         [0024]    As noted above, the mat ( 10 ) is conveniently produced by injection molding of the hot polymer compound, followed by its partial cooling and removal from the mold to release any gases formed prior to packaging in preparation for shipping. The individual mats can also be die cut from a larger web or sheet of material. 
         [0025]    The polymeric material used in the production of the mat of the invention is selected to provide the properties of resilience for the comfort of pool users, a high tensile strength to provide resistance to abrasion and tearing, i.e., toughness, flexibility and the property that permits it to be folded upon itself to assume a compact form for packaging and storage and thereafter unfolded to assume a flattened configuration when positioned for use on the bottom of the pool. 
         [0026]    The polymer material is compounded with carbon black or other suitable dark-colored material which will provide a finished product that is black, or nearly so, and with a high enough specific gravity to assure that it will remain submerged on the bottom of the pool during play activities by children and others using the pool. Suitable polymeric compounds include rubber, silicone rubber, PVC and co-polymers of PVC. The polymer is preferably resistant to degradation by sunlight, and specifically ultra-violet (UV) radiation, and to pool sanitizing chemicals which may be present in the water. 
         [0027]    The invention has been described with reference to several preferred embodiments and it will be understood that other variations may be undertaken based on this description without departing from the scope of the invention which is to be determined by reference to the claims which follow.