Patent Application
20110300971
The present invention relates to a golf ball having a symbol.
Markings such as symbols, numerals, letters, and patterns are often applied on the surfaces of golf balls. Methods of applying such markings to the surface of a golf ball include methods of printing or transferring ink onto the surface of a golf ball and methods of engraving on the surface of the golf ball.
Because plural dimples are disposed at a high density on the surface of the golf ball, the former method has a problem of a tendency to yield poor printing. With the latter method, there is a problem of difficulty in engraving a marking such as a logo having a complex shape. Also, because the edges of the recessed parts are sharply pointed, there is the problem of an adverse affect on the aerodynamic characteristics of the golf ball.
U.S. Pat. No. 7,303,492 discloses a golf ball in which dimples are made into the shape of text letters or characters or other symbols. When a symbol is constituted by dimples, however, the symbol itself becomes very large, and in order to mark the surface of the golf ball with the desired symbol, there is the problem of an excessively large influence on the aerodynamic characteristics of the golf ball.
U.S. Pat. No. 7,273,426 and U.S. Pat. No. 7,618,332 disclose golf balls in which recesses having substantially uniform depth from the surface are formed in plural dimples and the land parts therebetween, wherein these recesses form patterns such as letters or graphic forms. The engraved marking to a depth that is substantially uniform can be formed simultaneously with the dimples when the cover layer of the golf ball is injection molded using a mold.
When the cover layer of a golf ball is molded, burrs often can occur at locations corresponding to the support pins and vent pins of the mold and to the seams. Because the presence of burrs greatly worsens the aerodynamic characteristics of the golf ball, it is necessary to remove them by grinding. When the golf ball is ground to remove burrs, there is the problem in that the depth of the engraved marking formed in the surface thereof is reduced, leading to the risk of destruction of the shape of the engraved marking.
Accordingly, an object of the present invention is to provide a golf ball, which is based on a technological concept completely different from conventional dimples and engraved markings representing symbols, thereby providing a golf ball with a novel appearance.
A golf ball according to the present invention includes a land part representing a symbol, and dimples defining the land part by outer edges thereof and disposed on a surface of the golf ball. The symbol may include a numeral, a letter, a picture, or a logo. The symbol may represent a company, a trademark, a person, or a mascot character. The golf ball according to the present invention may include at least two of the land parts representing symbols. The dimples defining the land part by outer edges thereof preferably include at least two non-circular dimples.
The dimples defining the land part by outer edges thereof may include a dimple having a wall surface having a linear shape extending substantially in a depth direction, the wall surface being adjacent to the land part representing the symbol. The dimples defining the land part may include a dimple having a flat bottom surface. Preferably, a pole point of the golf ball may be arranged at a position within the land part.
a) is a cross-sectional view showing an example of a dimple that defines a land part representing a symbol by its outer edge.
Embodiments of the present invention will be described below with reference to the drawings.
As shown in
In general, the land part 20 that is surrounded by a plurality of circular dimples has an irregular and meaningless shape. In this embodiment, however, as shown in
A non-circular dimple, as the term is used in this specification, refers to a dimple having an outer edge, which is a boundary line 13 between a land part and a dimple, and which is not circular. The non-circular dimple, for example, includes a dimple having a bent part in the boundary line 13, and a dimple having the boundary line 13 formed by a curved part and a linear part.
As shown in
In the case in which the wall surface 15 is provided, the part of the bottom surface 16 of the dimple from the position at which the dimple is deepest up until a part that is adjacent to the wall surface 15 may be made flat. Also, a smooth curve is maintained from the position at which the dimple is deepest up until the boundary line 13b with the usual land part 20. It will be naturally understood that, as shown in
The depth of the non-circular dimple 12 at the deepest position is preferably, for example, at least approximately 0.05 mm, and more preferably at least approximately 0.10 mm. Also, the upper limit of the depth of the non-circular dimple 12 is preferably approximately 0.45 mm and more preferably approximately 0.35 mm.
The size of the non-circular dimple 12, that is, the maximum distance between two points on the outer edge 13 of the non-circular dimple 12, is preferably at least approximately 0.5 mm, and more preferably at least approximately 1 mm. Also, the upper limit of the size of the non-circular dimple 12 is preferably approximately 8 mm, and more preferably approximately 7 mm.
Because if the spacing between the outer edges of a plurality of non-circular dimples is too long, the land part 20 will become partially widened and could influence the aerodynamic characteristics of the golf ball, the spacing is preferably no greater than approximately 2.0 mm, and more preferably no greater than approximately 1.8 mm. Also, the lower limit of the spacing between the non-circular dimples 12, although not particularly limited, is preferably approximately 0.05 mm, and more preferably approximately 0.1 mm.
Although
Preferably, the land part 22 representing a symbol may be arranged on the surface of the golf ball 1 such that a pole point 30 such as north or south pole of the golf ball falls within a region of the land part 22 representing a symbol, as shown in
Although
The total number of dimples, including non-circular dimples, formed on the surface of the golf ball, is preferably at least approximately 150, more preferably at least approximately 200, even more preferably at least 250, and still more preferably at least approximately 300. Also, the upper limit on the total number of dimples is preferably approximately 500, more preferably approximately 400, and even more preferably approximately 360.
The proportion of surface area occupied by the dimples, including non-circular dimples, is preferably at least approximately 70%, and more preferably at least approximately 80%. Also, although there is no particular restriction, from the standpoint of providing a land part 22 to represent a symbol, the upper limit of the proportion of the surface area occupied by the dimples is preferably approximately 90%.
Although
Although
For example, as shown in
Although
In the same manner as in the case of the usual circular dimples, the non-circular dimples that form land parts representing symbols by their outer edges can be formed in the process step of forming the cover layer of the golf ball. Specifically, the cover layer is formed by injection molding of the cover layer material into a die. The die for the cover layer (not shown) has a cavity wall surface for the purpose of forming the surface of the land part and concave parts protruding from the cavity wall surface for the purpose of forming dimples.
The die may be fabricated by using 3-dimensional CAD or CAM and by using a method in which an overall surface shape is directly and three-dimensionally formed in a reversing master die, or a method in which a cavity part of the die is directly and three-dimensionally machined.
Materials for the cover layer may be, but are not limited to, an ionomer resin, a polyurethane-based thermoplastic elastomer, or thermoplastic polyurethane. The golf ball may be of one-piece structure or of a multiple-piece structure having two or more pieces.
While a golf ball according to the present invention has been described in connection with preferred embodiments, it is not intended to limit the scope of the invention to the particular form set forth, and on the contrary, it is intended to cover such alternatives and modifications as may be included within the spirit and scope of the invention as defined by the appended claims.
