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Football with a modified surface conferring altered aerodynamic propertiesRelated Patent Categories: Games Using Tangible Projectile, Projectile, Per Se; Part Thereof Or Accessory Therefor, Having Fluid-retaining Bladder Removable From Within Enclosing Cover Or Casing (e.g., Football, Etc.)Football with a modified surface conferring altered aerodynamic properties description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060105866, Football with a modified surface conferring altered aerodynamic properties. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention relates to game balls having a generally prolate-spheroidal shape, particularly American-style footballs, and to altering the aerodynamic behavior of the balls by providing air-turbulence-generating depressions in the surface thereof. BACKGROUND OF THE INVENTION [0002] In sports involving throwing, hitting, kicking or otherwise impelling a game ball, the performance characteristics of the ball can greatly affect the play of the game. Properties of the ball such as the inflation pressure, rigidity, and surface characteristics all influence the speed with which the ball can be projected and the attributes of its flight. Although the size, shape and weight of a particular kind of ball are typically governed by the traditions and rules of the given game, it is possible to modify or improve the performance properties of a ball through altering its surface properties. For instance, tennis balls with differing surface properties of their felt coverings and different rigidities or inflation pressures are well known to be used under different circumstances. [0003] Golf balls, which are of solid construction having an enameled surface covering and a relatively dense resilient core formed of rubber or synthetic plastics, ordinarily are covered by dimples. In the history of development of the golf ball, the surface was originally smooth, but it was discovered from the experience of golfers that a dented ball whose surface had been more or less covered with minute depressions caused by impacts on the ball of hard objects flew further. Golf balls were then deliberately covered with dents or dimples, small depressions in the surface, substantially over their entire surface. This surface texturing provided such a distinct advantage that today all golf balls are covered with such dimpling. The depressions on a typical golf ball are about 1-3 mm in diameter and about 0.5-1.5 mm in depth, and are distributed over the surface uniformly. The physical basis underlying the improved flight characteristics of the dimpled golf ball has been explained as resulting from turbulent flow of the air around a dimpled ball which in turn causes less "flow separation" and a reduced aerodynamic resistance to the ball's travel. Lift may also be generated by a traveling golf ball which has been hit to impart a backspin. [0004] Few other examples of surface texturing designed to affect the aerodynamic performance, as opposed to the grip, of game balls appear to be known. Another solid and not inflatable ball, the baseball, has been modified by covering the surface with depressions of a size similar those found on golf balls. Thus, U.S. Pat. No. 4,256,304 discloses a baseball suitable for use in an automated pitching machine that is substantially covered with a multiplicity of cup-like or hemispherical depressions. This modification is disclosed to enable the ball to travel greater distances with enhanced accuracy. [0005] Depressions on an inflatable spherical game ball have also been disclosed in U.S. Pat. No. 5,518,234, although the depressions are much larger than those used on golf balls. The depressions are stated to be for the purpose of improving the player's grip on the ball. Each depression is of an approximate size to a fingertip to allow the player to grip a ball having a larger convex surface than is otherwise possible. No disclosure is provided regarding any alteration of aerodynamic properties of this ball. [0006] The type of ball used in the game of American-style football possesses an almost unique shape among the various types of game balls; perhaps only the ball used in the game of rugby resembles the elongate American-style football. The term "generally prolate-spheroidal shape" is used herein as a convenient characterization of a ball having, in essence, the shape of an American-style football, and not in the strict mathematical sense of an ellipse rotated about an axis. When the term "football" is used herein, it is understood to refer to an American-style football, rather than to the spherically shaped "football" or "soccer ball" that much of the world outside the United States usually understands the word to mean. [0007] The unusual shape of the American-style football produces some unique properties of flight when it is thrown, as rotation imparted to the ball such that it rotates about its longitudinal axis produces quite a different resulting flight than does rotation imparted to the ball about any other axis. The football being circular in transverse section but oval shape in longitudinal section, the first kind of rotation produces a "spiraling" flight in which the ball translates along a path defined by the longitudinal axis of the ball while spinning about that axis, whereas the second kind of rotation results in the ball tumbling end over end. In a spiraling flight, rotation or "spin" of the football about its longitudinal axis provides for lessened aerodynamic resistance to forward travel as the ball is gyroscopically stabilized to translate point first through the air, a configuration that is more streamlined than a tumbling flight produces. The rotation of the ball also provides for a more stable trajectory, similar to the stability of flight imparted to a bullet fired from a rifled barrel. Minor imperfections in the surface which would otherwise result in deviation from the planned flight path or unpredictability of position after the ball has traveled some distance, are averaged out by the spinning action, so the flight is more true. [0008] The surface of the football is typically smooth but may be slightly convexly textured to aid in gripping the ball. A common form of surface texturing to aid in gripping the ball on a football is a knobbly texture consisting of small bumps projecting outwardly from a base, covering the exterior of the ball. While regulation footballs also have a laced seam whereby an air bladder is placed inside the outer skin of the ball, which may also be gripped by the player and where the fingertips of someone endeavoring to throw the football are placed in common practice, many footballs such as those molded from plastic do not have a separate air bladder which must be inserted into the shell, but are inflated with a needle and thus do not have laces, or have only simulated laces. Otherwise, apart from the surface texturing, the football typically has a featureless surface. [0009] A number of examples of texturing of the surface of a football can be found. U.S. Pat. No. 2,866,644 discloses a football with a "non-slip" surface for improving the grip of the ball by the player. The surface is covered with ribbing whose main axis is at an angle of about 30 degrees to the longitudinal axis of the football. U.S. Pat. No. 4,772,020 discloses a football with helical groove that provides for improved handling. U.S. Pat. Nos. 5,851,161 and 5,984,812 disclose a gripable surface for throwable objects including footballs which comprise a mesh panel that fits over the surface of the ball. U.S. Pat. Nos. D488,524 and D491,240 show a football with pyramidal pebble texturing of the surface. However, these various texturing features address the handling of the football, rather than the aerodynamic properties of the football. SUMMARY OF THE INVENTION [0010] The present invention provides a generally prolate-spheroidal game ball with a plurality of air-turbulence-producing depressions distributed over a majority of the outer surface of the skin. The depressions are preferably circular in shape, with a breadth of less than about one-quarter inch and preferably having a breadth to depth ratio equaling about 2 to about 6, and a surface density of about 23 to about 27 depressions per square inch. The game ball of the present invention is preferably an American-style football, substantially covered by a regular array of the depressions. When the football translates through the air, particularly when the football is thrown in a spiral pass wherein it rotates only around its longitudinal axis while translating through the air, air turbulence induced by the depressions alters the aerodynamic properties of the football. The depressions reduce separation of the flow of air by the translating ball and thus reduce air resistance, resulting in a longer flight for a given initial impetus. The depressions also reduce air resistance to the spinning motion, thus allowing for a more prolonged spin and a decreased rate of loss of rotational velocity for a given initial rotational impetus, which results in improved, longer-lasting gyroscopic stabilization of the flight. DESCRIPTION OF THE DRAWINGS [0011] FIG. 1 shows side view of an inflatable, prolate-spheroidal game ball according to the present invention. [0012] FIG. 2 shows a cross-sectional view of a section of the skin of a game ball according to the present invention. [0013] FIG. 3 shows a detailed view of a preferred embodiment of the depressions in a game ball skin according to the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT [0014] Referring to FIG. 1, a preferred embodiment of a prolate-spheroidal game ball according to the present invention comprises an American-style football 10. As viewed from the side, the football is substantially oval-shaped, although the ends 12 are typically blunt rather than smoothly curving as in a perfect ellipse. However, the ends may be smoothly curving as in a rugby ball, rather than blunt, without departing from the principles of the present invention. Elsewhere the outer surface 14 of the football forms a smooth monotonic curve. In the preferred embodiment, the football has a length of about 111/2 inches, a diameter of about 61/2 inches, and a measurement from end to end over the surface of the football of about 131/2 inches. The football 10 is circular in any cross-section taken perpendicular to the longitudinal axis of the ball. The cross section taken along the mid-point line of FIG. 1 in the plane of longitudinal symmetry of the ball has the greatest diameter. [0015] Thus, a football according to the present invention has a generally prolate spheroidal shape, that is, the solid figure obtained by rotating an ellipse about its major axis. It may however deviate somewhat from the ideal form by not being prolate spheroidal in the strict mathematical sense, for instance not being truly elliptical in longitudinal cross-section, or as indicated above, in having the two blunt ends typical of the American-style football. [0016] The football 10, which is hollow and formed of an at least moderately flexible skin 16, sometimes enclosing an air bladder 18 as is shown in FIG. 2, preferably assumes substantially the dimensions stated upon inflation with air or another suitable gas. The skin is preferably formed of leather, rubber, plastic, or similar suitable material that is both at least moderately flexible and is resistant to tearing or puncturing. The preferred air bladder, which may be constructed of any suitable material, pressurizes the skin upon inflation. [0017] Alternatively, the skin of the football may be supported by a foam material in which the air pressure in the foam cells is introduced at the time of formation of the foam. In this alternative embodiment, the game ball is not hollow in the strict sense of the word, but is filled with an elastic foam which contains many minute individually hollow cells. Regardless, the skin 16 is preferably tough enough to withstand damaging abrasion during handling and play and to protect the air bladder, if any, from puncture and the resulting loss of air pressure. [0018] Typically, the football is inflated to a pressure within a range suitable to confer sufficient elasticity and rigidity to allow it to be firmly grasped, to maintain its shape when subject to acceleration upon being thrown or kicked, but also permitting elastic deformation allowing the football to bounce, or to be kicked substantial distances. Normally the football is filled with air via a port (not shown) in the skin and bladder that allows for insertion of a hollow needle attached to a source of compressed air, the port then closing to seal the air in the bladder when the needle is removed. Alternatively, the ball may be filled with an elastic foamed material, preferably a plastic, wherein the gas that induces the foaming in the resin used to form the foam is trapped within the cells of the foam, providing resiliency. When the term "inflated" or "inflatable" is used herein, it is defined as covering both means of providing internal air pressure to keep the ball elastic. [0019] If the skin is formed of leather, it typically comprises several segments of elongated shape that are stitched together at their edges and at the ends to form the covering. If the skin is formed of rubber or plastic, it may be molded into shape. During construction of the football, the air bladder is inserted into the interior prior to the final closing of the skin by stitches, adhesives or the like. Continue reading about Football with a modified surface conferring altered aerodynamic properties... 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