Abstract:
A gliding or flying hydrodynamic disc designed for recreational use upon and across a surface of water is provided. The disc is circular with a peripheral circular trough on the top surface to provide a grip for a user. The bottom of the disc contains a circular flat section to provide minimum drag and maximum hydrodynamic performance. The outer rim of the disc is rounded and extends above the planar surface of the disc to provide increased aerodynamics to keep the disc on the surface of the water and improve gliding duration.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of Provisional patent application Ser. No. 60/150,755, filed on Aug. 26, 1999, entitled Underwater Flying Disc, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to throwing discs for recreational use, and more specifically to a water-skimming disc for use in a swimming pool, lake or ocean. 
     2. Description of Related Art 
     There are many toys and recreational devices on the market for use in and around swimming pools and other bodies of water. Recreational throwing discs for skimming or skipping across bodies of water have been known for many years, much like skipping flat stones across water. A well-known toy or recreational device used out of water is the flying saucer device. Such devices are tossed from one user to another, exploiting their aerodynamic aspects to enable them to glide from the thrower to the catcher through the air. However, due to their emphasis on aerodynamic design, such flying saucer devices are not adapted towards skimming or skipping over bodies of water. In addition, most flying saucer devices are manufactured with rigid material that can injure people or damage property upon impact. 
     U.S. Pat. No. 5,836,840 to Bustamante (1998) discloses a hydroplaning disc designed to skip or skim over water; however, the design of this disc is complex and expensive to manufacture. 
     Several other types of water skimming or skipping devices have been proposed. Examples are U.S. Pat. No. 4,979,922 to Clark (1990), 4,463,954 to Panse, et al. (1984), 4,395,046 to Cosmopulos (1983), and 4,151,997 to Glovak (1979). However, none of these can easily skip off a body of water. U.S. Pat. No. 5,679,082 to Hincke (1997) is heavy and likely expensive to manufacture. 
     SUMMARY OF THE INVENTION 
     It is the general object of the present invention to provide a lightweight disc that is easily gripped and designed to safely and efficiently skim or skip upon and across the surface of a body of water, such as a pool or the ocean, from one user to another. The invention is a hydrodynamic disc that, in one embodiment, includes a central circular core of a solid construction with a predetermined diameter and height that tapers to an outer edge. The circular core includes a softer flexible material along the edge and radially inward a short distance along the top and bottom surfaces to provide a gripping surface and safety protection to disc users. 
     The bottom surface includes a center bulge that tapers to a thinner outer edge and has a flat circular bottom, giving the disc efficient hydrodynamic qualities that allow it to easily skip across a body of water. 
     The present invention provides for a multitude of gripping means at any point along its top surface. 
     The simple design of the present invention provides enhanced safety to a user, hydrodynamic efficiency, is lightweight and inexpensive to manufacture. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be better understood, and its numerous features and advantages made apparent to those skilled in the art, by referencing the accompanying drawings. For ease of understanding and simplicity, common numbering of elements within the illustrations is employed where the same element is in different drawings. 
     FIG. 1 is a top plan view of a water-skimming disc incorporating the principles of the invention; 
     FIG. 2 is a cross-sectional view in the direction of lines A—A through the water-skimming disc of FIG. 1; and 
     FIG. 3 is a bottom plan view of the water-skimming disc of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a top view of a water-skimming disc  100  that has an overall shape of a generally circular disc. Disc  100  includes at its center a circular core section  110  surrounded concentrically by an annular overlap section  120 , a cupped rim section  130 , and an outside lip section  140 . The overall diameter of disc  100  is preferably about 6½ inches, but could be in the range between 1½ inches and 12 inches to accommodate users of various ages and skills. 
     The circular core section  110  on the top of the water-skimming disc  100  is preferably about 4¼ inches in diameter and has an exposed flat surface except for about ¼-inch along the outer periphery of the circular core section, which is covered by the annular overlap section  120 . 
     The cupped rim  130  is a smoothly contoured trough with a textured surface that provides a grip to help a user to maintain adequate control when tossing the disc. 
     A raised surface of the outside lip section  140  further enhances the user&#39;s grip on the water-skimming disc  100 . Most flying saucer or flying disc toys have rounded edges that slope downward. The upward sloping rounded edge of the outside lip section  140  enables the disc  100  to skip off the surface of a body of water, rather than to dive through the surface and come to an abrupt halt as would most other flying saucer or disc toys. The shape of the outside lip section  140  not only allows the water-skimming disc  100  to glide on the surface of the water, but the aerodynamics of the outside lip section  140  create lift that keeps the disc on the water&#39;s surface, rather than flying up. 
     FIG. 2 is a cross sectional view showing the water-skimming disc  100  to be generally disc-shaped with a large width-to-height ratio. A top surface  210  shows the upper contours of the disc  100 , including the circular core section  110 , the annular overlap section  120 , the cupped rim section  130 , and the outside lip section  140 . FIG. 2 also shows the contoured radius of the cupped rim section  130  and the raised edge of the outside lip section  140 . The water-skimming disc  100  has a bottom surface  220  that is substantially elliptical or conical. In the center of the bottom surface  220  is a skimming plane  310 . The skimming plane  310  is preferably flat and circular, with a diameter of approximately one inch. Designing the bottom surface  220  with the substantially flat skimming plane  310  at its center gives the water-skimming disc  100  increased hydroplaning capabilities over that of purely elliptical or conical shaped discs. The disc  100  will therefore glide over the water surface faster and for longer distances. The entire bottom surface  220  is smooth to reduce friction. 
     FIG. 3 shows a bottom view of the water-skimming disc  100 . The skimming plane  310  is preferably about 1¼ inches in diameter. 
     Referring again to FIG. 2, the thickness between the top of the circular core section  110  and the bottom of the skimming plane  310  (see FIG. 3) is preferably about ¾ inch or 18 mm. The disc is preferably a monolithic structure, with the material comprising the annular overlap section  120 , the cupped rim section  130 , the outside lip section  140  and the bottom surface  220  being contiguous. Alternate embodiments may have a rigid core and flexible outer edge for improved performance. 
     While the preferred embodiment of the water-skipping disc  100  has a solid core of polyurethane foam with a density of 0.3 (relative to water), other embodiments could include other suitable materials with a density in the range from 0.1 to 2.0. The water-skimming disc  100  can be made either more or less dense than water, allowing a wide range of weights, skipping characteristics, speeds and distances. 
     The optimal weight for the water-skimming disc  100  is 3 ounces; however, other embodiments may weigh as little as two ounces and as much as 6 ounces. 
     The water-skimming disc  100  is launched by hand, and will operate properly only with the top surface  210  facing up. This orientation also allows the hydrodynamic design of the bottom surface  220  and the skimming plane  310  to interact with the surface of a body of water (for example, a pool, a lake or the ocean) upon which a user throws the water-skimming disc  100 . The shape of top surface  210  allows the user to grip the water-skimming disc  100  preferably by placing a thumb inside the cupped rim  130  and placing the outside lip  140  between the thumb and forefinger, with the other fingers supporting the bottom of the water-skimming disc. With the water-skimming disc  100  in a user&#39;s hand, the user would move his or her arm holding the water-skimming disc in a backhand motion across his/her body, away from the body, and nearly parallel to the surface of the body of water towards another user who is either in, or on the other side of, the body of water. As the user&#39;s hand passes in front of the user&#39;s body, the user releases his/her grip on the water-skimming disc and the weight of the disc and its forward motion causes the disc to glide towards the other user, skipping off the surface of the water one or more times like a flat rock. The hydrodynamic shape of the bottom surface  220  of disc  100  allows the disc to skip smoothly across the water to the other user, who can then catch the disc in his/her hand. The catcher can then launch the water-skimming disc  100  back to the thrower in the same manner. Users may find their own methods of launching the water-skimming disc  100  across water, resulting in any number of skips and in a variety of speeds and directions. 
     As preferred embodiments of the present invention are described above with reference to the aforementioned drawings, various modifications or adaptations of the methods and or specific stuctures described may become apparent to those skilled in the art. All such modifications, adaptations, or variations that rely upon the teachings of the present invention, and through which these teachings have advanced the art, are considered to be within the spirit and scope of the present invention. Hence, these descriptions and drawings are not be considered in a limiting sense as is understood that the present invention is in no way limited to the embodiments illustrated.