According to the United States Golf Association (U. S. G. A.) rules, a golf ball may not have a weight in excess of 1.620 ounces or a diameter smaller than 1.680 inches. The initial velocity of balls conforming to U. S. G. A. regulations may not exceed 250 feet per second with a maximum tolerance of 2%. Initial velocity is measured on a standard machine kept by the U. S. G. A. A projection on a wheel rotating at a defined speed hits the test ball, and the length of time it takes the ball to traverse a set distance after impact is measured. U. S. G. A. regulations also require that a ball not travel a distance greater than 280 yards when hit by the U. S. G. A. outdoor driving machine under specified conditions. In addition to this specification, there is a tolerance of plus 4% and a 2% tolerance for test error.

These specifications limit how far a struck golf ball will travel in several ways. Increasing the weight of a golf ball tends to increase the distance it will travel and lower the trajectory. A ball having greater momentum is better able to overcome drag. Reducing the diameter of the ball also has the effect of increasing the distance it will travel when hit. This is believed to occur primarily because a smaller ball has a smaller projected area and, thus, a lower drag when traveling through the air. Increasing initial velocity increases the distance the ball will travel.

Drag on a golf ball is also reduced by forming a plurality of dimples, often circular, in the outer surface of the ball. The dimples serve to reduce the pressure differential between the front and rear of the ball as it travels through the air.

BRIEF DESCRIPTION OF THE PRIOR ART Various dimple configurations have been provided in order to improve the aerodynamic properties of a golf ball as it travels through the air. In the Sullivan U. S. patent application Serial Number, there is disclosed a golf ball with contoured dimples, wherein a portion of a dimple is filled-in to provide a dimple of variable depth. In the Sullivan U. S. Patent application Serial Number , a golf ball having a plurality of dimples of different depth is disclosed.

Groups of similar dimples are arranged within a geometric pattern on the ball, with the groups having increasing or decreasing depth. Both of the Sullivan inventions are commonly owned with the present invention.

The present invention was developed in order to provide a further dimple configuration wherein the dimples have a non-symmetric profile in order to improve the aerodynamic properties of a golf ball.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the invention to provide a golf ball having a spherical surface which contains a plurality of dimples, each of the dimples having an outer edge at the intersection with the ball surface and a bottom surface defining a concavity. The bottom surface has a radius of curvature, and a portion of the bottom surface extends below the radius of curvature to define a non- symmetric depth profile.

According to another object of the invention, the outer edge of the dimples has a circular configuration and the portion of the dimple extending below the radius of curvature is contained within one half of the dimple.

According to a further object of the invention the dimples having a non- symmetric depth profile are arranged in a geometric pattern on the surface of the golf ball.

BRIEF DESCRIPTION OF THE FIGURES Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawing, in which: Fig. 1 is a top plan view of a circular dimple ; Fig. 2 is a sectional view of a conventional circular dimple showing its diameter and depth, Fig. 3 is a sectional view of a dimple having a non-symmetric depth according to a first embodiment of the invention; Fig. 4 is a sectional view of a dimple having a non-symmetric depth according to a second embodiment of the invention : Fig. 5 and 6 are plan views, respectively, of a spherical golf ball illustrating the manner of defining a geometric patter on the surface of the ball; and Fig. 7 is a plan view of a golf ball according to the invention including groups of dimples of non-symmetric depth arranged in a geometric pattern.

DETAILED DESCRIPTION In Figs. I and 2 are shown a circular dimple 2 which is formed in the spherical surface 4 of a golf ball 6. The dimple has an edge 8 defined where the dimple intersects with the surface of the ball. In the conventional dimple shown in Fig. 2, the bottom surface 10 of the dimple is a concavity having a radius of curvature R, a depth d defined as the maximum difference between the radius of the ball at the surface and the radius at the bottom of the dimple, and a diameter D measured across the dimple between where the edges thereof intersect the surface of the ball. The conventional dimple is symmetric throughout its bottom surface 10.

Turning now to Fig. 3, there is shown the profile of a non-symmetric depth dimple 102 according to a first embodiment of the invention. The bottom surface 110 of the dimple has a radius of curvature defining a concavity in the surface 104 of a golf ball 106. A portion 112 of the bottom surface extends below the radius of curvature (which is represented by the dashed lines extended along the arc of the surface 110) so that the depth profile of the dimple 102 is non-symmetric.

The edge 108 of the dimple 102 preferably has a circular configuration as shown in Fig. 1. However, other configurations may be provided including oval, elliptical, tapered, and the like. A line through the midpoint M in the bottom surface of the dimple divides the dimple into two halves. Preferably, the portion 112 below the radius of curvature is contained within in one half of the bottom surface of the dimple.

In Fig. 4 is shown an alternate dimple 202 having a non-symmetric depth profile. The radius of curvature is represented by the dashed line 210. A portion 212 of the bottom surface of the dimple extends below the radius of curvature. As

distinguished from the dimple of Fig. 3, a further portion 214 of the dimple bottom surface is contoured above the radius of curvature to"fill-in"a portion of the dimple and add to its non-symmetrical profile. As shown in Fig. 4, the contoured portion 214 is maintained below the surface 204 of the ball 206. If desired, the <BR> <BR> <BR> <BR> contoured portion 214 can surround the portion 12 although the contour around the perimeter of the portion 212 need not be symmetrical. Alternatively, the contoured portion can be restricted to one-half of the dimple as defined by the midpoint M. In the other half, beyond the portion 1 12. the bottom of the dimple can be along the radius of curvature.

Referring now to Figs. 5 and 6, the golf ball 306 according to the invention has a spherical configuration formed by injection molding in a cavity defined between two separable molding plates. Each plate has a hemispherical cavity, the cavities being adapted to mate when the plates are brought together. Thus, the golf ball has an equator E at the juncture of the molding plates which divides the ball into two identical hemispheres, each of which contains a pole P. Imaginary great circles are arranged on the surface of the ball and pass through the poles to divide the ball surface into a geometric pattern of equal sections or geometries. In Fig. 6, two circles 316, 318 are shown which divide each hemisphere into four equal triangles T. Other geometric patterns can be defined on the surface of the ball in accordance with the invention. For example, a third great circle through the poles would divide each hemisphere into six triangular geometries.

Each of the triangles T is filled with a plurality of non-overlapping dimples 302 as shown in Fig. 7. A pattern of dimples is arranged within the triangle T.

The dimples are all circular and may have the same diameter. Three groups X, Y, Z of dimples are shown in Fig. 7. The first group of dimples X for example may comprise symmetric dimples such as those shown in Fig. 2. The second group of

dimples Y may comprise non-symmetric dimples such as those shown in Fig. 3, and the third group of dimples Z may comprise non-symmetric dimples with contour portions such as those shown in Fig. 4. Any combination of the various types of dimples may be provided within the triangle in anv desired pattern.

The golf ball 306 incorporating the dimples having non-symmetric depth profiles has improved aerodynamic properties because of the manner in which air flows across the surface of the ball and within the dimples. The improved properties are increased length and less of a susceptibility to slice or draw.

While in accordance with the provisions of the patent statute, the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those of ordinary skill in the art that various changes and modifications may be made without deviating from the inventive concepts set forth above.