Patent Application
20110300972
The present invention relates to a golf ball having an engraved marking.
Markings such as symbols, numerals, letters, and patterns are often applied to 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 the golf ball and methods of engraving on the surface of the golf ball.
Because plural dimples are disposed at high density on the surface of a golf ball, the former method has a problem of a tendency for produce 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 part 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 a 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 a golf ball in which recesses having substantially uniform depth from the surface are formed in plural dimples with land parts therebetween, in which 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 can often occur at locations corresponding to the support pins and vent pins of the mold and at the seams. Because the presence of such 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 a 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 with an engraved marking that has little influence on the aerodynamic characteristics of the golf ball, and that maintains its shape even after the surface of the golf ball is ground.
In order to achieve the above-noted object, a golf ball according to the present invention includes plural dimples provided on a surface of the golf ball; a first land part existing between the plural dimples and having as its surface a spherical surface of a sphere having the center of the golf ball as its center; a second land part having a boundary with the first land part or boundaries with the first land part and the plural dimples and having a surface having a smaller curvature than the spherical surface of the first land part; and an engraved marking disposed substantially on the second land part.
A part of the engraved marking may extend to the outside from the second land part. At least approximately 80% of the area of the engraved marking may be within the second land part. The surface of the second land part may be flat.
The changes in coefficient of drag CD and coefficient of lift CL between having and not having the engraved marking may be each within 0.005 at an initial ball velocity of 72 m/s and spin amount of 2800 rpm.
The engraved marking may include a symbol, word or a combination thereof related to golf or ball.
Embodiments of the present invention will be described below with reference to the drawings.
As shown in
In this embodiment, as shown in
A part of the engraved marking 18, as shown in
All of the dimples 12 formed on the surface of the golf ball may be the same size, or may be of two or more different sizes. It is preferable to dispose dimples of at least three different sizes, which enables uniform and tight coverage of the entire surface of the golf ball 10.
In the case of forming dimples 12 in this manner having two or more different sizes, it is preferable that the size of the second land part 16 be larger than the largest dimple. The area of the second land part 16 is preferably at least approximately 0.2 mm2 and more preferably at least approximately 0.8 mm2. Because if the area of the second land part 16 is too large, the influence on the aerodynamic characteristics of the golf ball becomes great, the area of the second lamp part 16 is preferable at most approximately 50.3 mm2 and more preferably at most approximately 38.9 mm2. The size of the second land part is preferably larger than the smallest dimple. The maximum length of the engraved marking 18 is preferably smaller than approximately 1.2 times the maximum length of the largest dimple. The maximum length of the engraved marking 18 is the maximum distance between two points on the contour line of the engraved marking 18. The maximum length of the dimple is the diameter thereof if the dimple is circular.
Only one engraved marking 18 or two or more engraved markings 18 may be formed on the overall surface of the golf ball 10. The number of dimples 12 surrounding the one or more engraved markings 18 is preferably at most approximately 30% of the total number of dimples formed on the surface of the golf ball. For example, in the case in which the total number of dimples is 272, it is preferable that the number of dimples surrounding the engraved marking be at most 82. Thus, for example, in the case in which the number of dimples surrounding one engraved marking is selected as four, it is possible to form from 6 to 20 engraved markings. In particular, the number of dimples 12 surrounding one or more engraved markings 18 is preferably at most approximately 10% of the total number of dimples. For example, in the case in which the total number of dimples is 272, it is preferable that the number of dimples surrounding the engraved markings be at most 27. Thus, for example, in the case in which the number of dimples surrounding one engraved marking is selected as five, it is possible to form from 1 to 5 engraved markings.
The total number of dimples formed on the golf ball surface is preferably at least approximately 150, more preferably at least approximately 200, yet more preferably at least approximately 250, and still more preferably at least approximately 300. Also, the total number of dimples is preferably at most than approximately 500, more preferably at most approximately 400, and still more preferably at most approximately 360.
As described above, because the engraved marking 18 is either substantially the same size as or smaller than a dimple and also has a shallow depth, the engraved marking 18 has little influence on the aerodynamic characteristics of the golf ball 10. It is preferably that, when the ball is struck with an initial ball velocity of 72 m/s and a spin amount of 2800 rpm, the differences between the coefficient of drag, CD0, and the coefficient of lift, CL0, for a ball without engraved markings and the coefficient of drag, CD1, and the coefficient of lift, CL1, for a ball with engraved markings be within 0.005.
In the process of manufacturing a golf ball, the second land part 16 and the engraved marking 18 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 mold. The cover layer mold has a cavity wall surface for the purpose of forming the surface of the first land part, concave parts protruding from the cavity wall surface for the purpose of forming dimples, and flat parts for the purpose of forming the second land part. A protrusion for forming the engraved marking is provided on the flat surface for forming the second land part. By using a mold such as this, it is possible to mold the golf ball having the engraved marking 18 on the flat surface of the second land part 16.
After the golf ball is molded using the mold, the entire surface of the golf ball is ground to remove the burrs that formed on the surface. A conventional grinding method can be used. Because the engraved markings 18 are formed in the second land parts 16 that are lower than the surface of the first land parts 14, it is possible to maintain the shape of the engraved marking 18 by preventing the grinding of the surface of the second land part 16, when the surface of the golf ball is ground.
The present invention is not limited to the above-noted embodiment, and may also include a golf ball 20 in another embodiment, which is shown in
Also, whereas in
Additionally, whereas in
A molding die for manufacturing a golf ball according to the present invention 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 molding die is directly and three-dimensionally machined. An ionomer resin, a polyurethane-based thermoplastic elastomer, and thermoplastic polyurethane can be used as materials for the cover layer. The golf ball may be of a 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.
