DESCRIPTION

The present invention relates to an improved golf ball, In particular, the present invention relates to a ball suitable for use as a golf ball, but which may not necessarily be of regulation size or weight. The invention also relates to a method of manufacturing such a ball.

A conventional modern golf ball comprises a spherical core formed from a hard rubber, or like material, surrounded by a mantle or thick shell comprising a thin strip of elastomeric material repeatedly and evenly wrapped about the core and, an outer cover formed from a tough and cut resistant polymeric material. The elastomeric strip is held in tension as it is wound onto the core and the outer cover is normally formed with an even array of depressions in its outer surface. In a common alternative, the core

may comprise a bladder filled with a dense, substantially incompressible liquid.

Although the modern golf ball is much improved over its predecessors in terms of its durability, directability, stability in flight and the distance it will travel for a given impetus from a golf club, further improvements in these areas are always sought by competitive golfers.

It is an object of the present invention to provide a ball, suitable for use as a golf ball, which performs in a superior manner in at least one of the aforementioned aspects.

In accordance with a first aspect of the present invention there is provided a ball, suitable for use as a golf ball, having an array of depressions formed in its surface, characterised in that said depressions are arranged in a plurality of clusters of at least one form of depression, said clusters include north and south polar clusters both centred on a common axis extending through the centre of the ball, with the remaining clusters arranged such that the spacing

between the clusters in the equitorial region of the ball is greater than the spacing between the north and south polar clusters and the immediately adjacent clusters. Preferably, the remaining clusters are arranged with their centres lying along a plurality of pathways extending between the north and south polar clusters and, each pathway crosses a semicircular portion of a great circle extending between the north polar cluster and the south pol»ar cluster. A great circle is a circle of maximun diameter on the surface of a sphere.

In an embodiment, the clusters are formed from depressions of at least two and, preferably three different forms. At least one of said forms of depression may be substantially deeper than the remainder.

In a further embodiment, the circumferential spacing between the clusters is greatest at the equator of the ball, midway between the north and south polar clusters. Preferably the clusters are interspaced by additional, smaller depressions, the spacing between which is greatest in the equitorial region of the ball.

In a preferred embodiment, the clusters comprise at least one and preferably two regular pentangular arrays of like depressions surrounding a single central depresssion. The central depression may be pentagonal in plan and the depressions in one pentangular array may be different, preferably in depth, from those in the other pentangular array. It should be understood that all the members of the pentangular array lie along the sides or at the verticies of a regular pentagon.

Preferably, there are five pathways with the clusters arranged so that the cluster pattern has a C5 axis of symmetry in the north-south axis which joins the centres of the north and south polar clusters. Preferably the cluster pattern belongs to the C5v symmetry group. The preferred number of clusters is seventeen, equally distributed amongst the five pathways (3 clusters on each of the pathways plus the north and south polar clusters which lie on all of the pathways).

It is considered that a golf ball in accordance with this first aspect of the present invention will be caused to spin about its north-south axis when in

flight, by virtue of the interaction between air pockets trapped by the depressions and the air through which the ball is travelling. Thus the ball should travel in a true and straight line. It is thought that these interactions also will cause the ball to fly with its north-south axis substantially in line with its direction of travel.

In a second aspect, the present invention provides a golf ball having a mantle comprising a strip or the like of elastomeric material wrapped around a central core characterised in that, the strip or the like of elastomeric material forming the mantle extends through each of n equitorial locations, in such a way that each second equitorial location reached by the strip is spaced from an equitorial location diametrically opposite a first equitorial location from which the strip extends directly to the second equitorial location by an amount equal to - of the diameter of the ball, where n is an integer greater than 4. A golf ball in accordance with this aspect of the present invention is both very stable in flight and translates the energy provided by a golfer into ball velocity with great efficiency.

Preferably, the strip portions extend along the shortest routes between joined equitorial locations and n is greater than 8 and most preferably 16.

The elastomeric strip, preferably, extends five complete revolutions about the axis extending through the centre of the ball, normal to the plane including the equitorial locations.

In an embodiment, the elastomeric strip comprises three individual smaller strips, plaited together. Preferably the smaller strips are three millimetres in width and 0.9 millimetres in depth, before tensioning.

In an embodiment, a ball in accordance with the first aspect of the present invention is formed with a mantle in accordance with the second aspect of the present invention. Preferably, the axis joining the north and south polar clusters of depressions is substantially coincidental with the axis extending through the centre of the ball, normal to the plane including the equitorial locations. This embodiment provides a golf ball with enhanced directability and stability in flight, thought to be derived from a synergistic

combination of the effects of the first and second aspects of the invention.

In a further embodiment of the first aspect of the present invention, which embodiment may also be an embodiment of the second aspect of the invention, the outer cover carrying the depressions is formed from a „ polymer impregnated leather having cut resistant properties. The polymer may be a natural rubber or similar substance. The use of such an outer cover material gives the inventive ball superior 'feel' and allows the ball to grip the face of a golf club more firmly when being driven thereby.

In an embodiment of the second aspect of the present invention, which may also be an embodiment of the first aspect, the core of the ball is a void at least partially filled with a viscous liquid having a density similar to liquid rubber. Preferably, the void also contains air, or another gas, in addition to the liquid.

In a third aspect of the present invention, there is provided a method of manufacturing a golf ball, characterised by comprising, winding a mantle in accordance with the second aspect of this invention onto a substantially spherical former, removing said former from within the mantle to define a void, at least partially filling said void with a viscous liquid having a density similar to rubber and, covering the mantle with a suitable outer cover, preferably in accordance with the first aspect of the present invention. The spherical former can be formed from a low melting point material, such as a form of Babbitt's metal, which is removed by simply heating the completed mantle. Alternatively the former is eased out of the mantle after winding.

A specific embodiment of the present invention will now be described with reference to the following drawings:-

Figure 1 is a schematic view of a partially completed mantle for a golf ball in accordance with the second aspect of the present invention; Figure 2 is a view from above of a golf ball in accordance with the first aspect of the present

invention;

Figure 3 is a view from below of the lower hemisphere of the ball shown in figure 2; Figure 4 is a front view of the ball shown in figure 2; Figure 5 is a view of the rear hemisphere of the ball shown in figure 2;

Figure 6 is a detail of a cluster of depressions and Figure 7 is a section on A-A from figure 6.

The ball will be described using geographical terms conventionally employed to identify the locations of features on a globe, such as compass points etc., in order to clarify the orientation of its features. Thus, figure 1, showing the ball from above, shows the northern hemisphere of the mantle, with the north pole in the centre. Figure 2 is similar, in that it is a view of the northern hemisphere of the complete ball, with the north pole in the centre. Figure 3 shows the southern hemisphere, with the south pole in the centre. The relationship between figures 4 and 5 is similar in that figure 4 is a view of the western hemisphere of the ball, whereas figure 5 is a view of the eastern hemisphere of the ball.

Referring now to figure 1. This figure illustrates a partially completed mantle, in the process of being formed about a spherical steel ball 1. The mantle comprises an elongate strip of elastomeric material, schematically illustrated at 2. The thickness and structure of the strip 2 is not shown for clarity. The elastomeric strip 2 is wound about the former 1 under tension. A first end 3 of the elastomeric strip 2 is located at (a) on the equator of the steel ball 1. The strip 2 extends from (a), across the northern hemisphere of the steel ball 1 to location (b) and from location (b) , across the southern hemisphere of the steel ball 1 to location (c) and so on, through locations (d) to (p) and back to (a), in order to form one complete layer of mantle. In such a layer, the elastomeric strip 2 has been wound about the north south axis 4 of the steel ball 1 eight times. Although figure 1 only shows one layer of the mantle, four further layers are wound in the manner described above, giving a total of five layers in the completed mantle. The path followed by the strip is the shortest distance between the locations a - p joined thereby.

The elastomeric strip 2 comprises 3 smaller strips plaited together. Each of the smaller strips is 3 millimetres in width and 0.9 millimetres in depth, in its untensioned form.

After the mantle has been fully wound, the steel ball 1 is removed from within the finished mantle, by easing it between adjacent strands of the elastomeric strip 2. In an alternative embodiment, a ball 1 formed from a low melting point material such as

Babbit's metal is substituted for the steel ball. In this alternative, after the mantle is completed, it is heated until the low melting point ball melts to form a liquid which is allowed to pour out between temporarily parted adjacent strands of the strip 2. The resulting void in the centre of the mantle is then filled with a viscous liquid, such as a liquid rubber. Preferably, the void is not completely filled with the viscous liquid and an air gap is also left within the void.

The viscous liquid is chosen to be substantially freely flowing, not to include any globular matter and, so as not to solidify, or significantly evaporate at

temperatures normally encountered during a game of golf.

The filled mantle is then covered with a cover 10 (illustrated in figures 2-7 in its finished form) which is formed from leather impregnated with a polymeric material, such as a synthetic or natural rubber. The cover has a thickness of about 2.0 millimeters. Preferably, the leather component of the cover is thin and is both impregnated with the chosen polymer and sandwiched between layers of said polymer. The cover 10 is bonded into place on the mantle formed from the elastomeric strip 2.

Once the cover 10 has been installed upon the mantle, a pattern of pentagonal 11, large circular 12, oblong 13 and, small circular 14 depressions are then formed in the outer surface of the cover.

The pentagonal 11, large circular 12 and oblong 13 depressions are grouped together in clusters 15. A single cluster 15 is shown in figure 6. The small circular depressions 14 are distributed in between the clusters 15, in the manner shown in figures 2-5.

Clusters 16 and 17 respectively are located on each of the north and south poles of the ball and the remaining clusters 18 are centred along five pathways 16, illustrated by broken lines. In effect, the clusters 15 appear to spiral around the surface of the ball from the north pole to the south pole. The depressions 11, 12, 13 and 14 are distributed so that the outer surface of the ball has a C5 axis of rotational symmetry extending between the north and south poles, five σ-planes of symmetry which include the C5 axis and, has the symmetry properties of the C5v group.

The size of the depressions is set out in table 1 below and therein cross-sectional shape is shown in figure 7. Although the small circular depressions 14 are not shown in figure 7, their shape is similar to that of the large circular depressions 12.

TABLE I

Type of Dimensions Depression

Pentagon (11) 2.3 mm Across 0.35 mm Deep Large Circle (12 2.83 mm Diameter 0.35 mm Deep Oblong (13) 1.39 mm Length X 0.70 mm Wide x 0.71 mm Deep

Small Circle (14) 1.00 mm Diameter 0.35 mm Deep

The relative postion of all the depressions which is shown in figure 6, is of importance. The oblong depressions 13 tend to trap air pockets adjacent to the ball, whereas the large circular depressions 12 tend to release air away from the surface of the ball; thus minor air currents tend to move about adjacent to each cluster 15 and between individual clusters 15. These air currents are intended to interact with the

relatively still air, through which the ball is travelling and to cause it to spin about its north south axis.