An object of the present invention is to provide a golf ball having an improved aesthetic appearance and enhanced flying performance. The present invention provides a golf ball on which a plurality of dimples are arranged on the spherical surface thereof, wherein each of the dimples has at least two contour main parts and contour connecting parts, and the at least two contour main parts are connected to each other by the contour connecting parts, and the contour connecting parts are formed so as to be curved toward the inside of the contour main parts from the outermost points.

The present invention relates to a golf ball having a spherical surface. More particularly, it relates to a golf ball provided with dimples of a characteristic shape on the spherical surface and having excellent flying performance.

For the conventional golf ball, the design freedom for dimples is degraded by the restriction on the fabricating technique such as the structure of a die used for manufacturing the golf ball and the restriction on the performance such as the enhancement of flying performance of golf ball. Therefore, it is difficult to enhance the flying performance of golf ball while dimples having a characteristic shape such as to improve the aesthetic appearance of golf ball are adopted.

In recent years, the performance of golf gear such as a golf ball and a golf club has been enhanced. Therefore, the golf ball is often flied by being hit under a low spin condition, and a low spin condition of about 2000 rpm is not rare. When the golf ball is flied under such a low spin condition, in the region of ball trajectory from hitting to the highest terminal point, a drag, which is an air resistance against the flying golf ball, is small, so that the carry of golf ball increases. However, in a low-speed region after the highest terminal point of ball trajectory, a lift for floating the golf ball cannot be obtained sufficiently, so that the carry of golf ball decreases. Therefore, it has been demanded that the flying performance of golf ball be enhanced by devising the shape of dimples considering the balance between the drag and lift under such a low spin condition.

Next, the relationship between dimples and flying performance is explained. The flying performance can be enhanced by regulating the volume percentage of dimples (total volume of dimples/volume of an imaginary spherical body (imaginary spherical body: a golf ball assumed to have no dimples)), the area percentage of dimples (total area of dimples/surface area of an imaginary spherical surface (imaginary spherical surface: the spherical surface of a golf ball assumed to have no dimples)), or the like for golf balls having various structure. The flying performance can be enhanced by devising the cross-sectional shape of dimples (ratio of depth to diameter of dimple, smoothness, etc.). Further, in the case where a plurality of dimples are arranged on the whole spherical surface of golf ball so as to be symmetrical, high aerodynamic characteristics can be obtained, and therefore the flying performance can be enhanced.

Golf balls having variously shaped dimples are present. The literature relating to such golf balls is cited below. Japanese Unexamined Patent Application Publication No. 2002-534237 discloses a golf ball provided with dimples having a sickle-shaped contour. Japanese Unexamined Patent Application Publication Nos. 8-276035 and 10-108921 disclose a golf ball provided with connecting grooves having a straight line shaped contour, which are arranged so as to connect a plurality of dimples to each other and formed into a concave shape having a depth shallower than the depth of dimple.

However, for the golf ball described in Japanese Unexamined Patent Application Publication No. 2002-534237, the dimples are formed so that the contour of dimple is greatly curved into a sickle shape. In the case where such dimples are arranged at a plurality of locations on the spherical surface of the golf ball, sufficient flying performance is possibly not provided.

For the golf ball described in Japanese Unexamined Patent Application Publication Nos. 8-276035 and 10-108921, the contour of the connecting groove connecting the dimples to each other is of a straight line shape, and not of a streamline and smooth shape. Due to such connecting grooves, the drag at the time when the golf ball is flied may increase, and therefore sufficient flying performance is possibly not provided. The depth of the connecting groove is shallower than the depth of the dimple, and the depths of the dimple and the connecting groove are uneven. Therefore, it is intricate to regulate the volume of dimples by adjusting the dimensions of dimples, so that a golf ball having enhanced flying performance is difficult to manufacture.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a golf ball having an improved aesthetic appearance and enhanced flying performance.

To achieve the above object, the present invention provides golf balls as described below. (1) A golf ball on which a plurality of dimples are arranged on the spherical surface thereof, wherein each of the dimples has at least two contour main parts and contour connecting parts; and the at least two contour main parts are connected to each other by the contour connecting parts, and the contour connecting parts are formed so as to be curved toward the inside of the contour main parts from the outermost points. (2) The golf ball described in the item (1), wherein all of the at least two contour main parts each are formed into a circular shape. (3) The golf ball described in the item (1), wherein the at least two contour main parts are formed by combination of a circular shape and a noncircular shape. (4) The golf ball described in the item (1), wherein all of the at least two contour main parts each are formed into a noncircular shape. (5) The golf ball described in the item (1), wherein the number of the dimples is about 150 to 500. (6) The golf ball described in the item (1), wherein the bottom part of the dimple is formed into a flat shape. (7) The golf ball described in the item (1), wherein the bottom part of the dimple is formed into a spherical surface shape. (8) A golf ball on which a plurality of dimples are arranged on the spherical surface thereof, wherein each of the dimples has at least two contour main parts and contour connecting parts; the at least two contour main parts are connected to each other by the contour connecting parts, and the contour connecting parts are formed so as to be curved toward the inside of the contour main parts from the outermost points; and a curved part is provided which is formed so as to be curved toward the center direction of the spherical surface between the contour main parts and contour connecting parts and the bottom part of the dimple. (9) The golf ball described in the item (8), wherein all of the at least two contour main parts each are formed into a circular shape. (10) The golf ball described in the item (8), wherein the at least two contour main parts are formed by combination of a circular shape and a noncircular shape. (11) The golf ball described in the item (8), wherein all of the at least two contour main parts each are formed into a noncircular shape. (12) The golf ball described in the item (8), wherein the number of the dimples is about 150 to 500. (13) The golf ball described in the item (8), wherein the bottom part is formed into a flat shape. (14) The golf ball described in the item (8), wherein the bottom part is formed into a spherical surface shape.

According to the golf ball described in the item (1), the area percentage and volume percentage of the dimples can be changed by the portion surrounded by the contour main parts and the contour connecting parts, so that the lift and the drag can be balanced. Since the contour connecting part has a curved streamline shape, the flow of air can be made smooth between the contour main parts. By changing such a curved shape, the drag etc. can be restrained. Therefore, the lift and the drag acting on the golf ball when the golf ball is flied can be balanced easily. The flying performance of golf ball can be enhanced. The curved contour connecting part has a characteristic shape. By the dimples having the contour connecting parts, the appearance of golf ball can be made characteristic.

According to the golf ball described in the item (2), excellent aerodynamic characteristics are provided, so that the flying performance of golf ball can be enhanced. The dimple has streamline beauty emphasized by the contour main parts formed into a circular shape only and the curved contour connecting parts. By the dimples having such characteristics, the aesthetic appearance of golf ball can be improved further.

According to the golf ball described in the item (3), excellent aerodynamic characteristics are provided, so that the flying performance of golf ball can be enhanced. The dimple has both of a characteristic shape emphasized by the noncircular contour main parts and streamline beauty emphasized by the circular contour main parts and the curved contour connecting parts. By the dimples having such characteristics, the aesthetic appearance of golf ball can be improved further.

According to the golf ball described in the item (4), excellent aerodynamic characteristics are provided, so that the flying performance of golf ball can be enhanced. The dimple has both of a characteristic shape emphasized by the contour main parts formed into a noncircular shape only and streamline beauty emphasized by the curved contour connecting parts. By the dimples having such characteristics, the aesthetic appearance of golf ball can be improved further.

According to the golf ball described in the item (5), the area percentage of the dimples is secured sufficiently, so that the flying performance of golf ball can be enhanced further.

According to the golf ball described in the item (6), the dimple has a characteristic shape due to the flat shaped bottom part. By the dimples having such characteristics, the aesthetic appearance of golf ball can be improved further.

According to the golf ball described in the item (7), further excellent aerodynamic characteristics are provided, so that the flying performance of golf ball can be enhanced. Especially in the case where the bottom part of the dimple is formed into a spherical surface shape of a spherical body having the center at a position approximately equal to the center of the spherical surface, in designing, the volume of the dimple can be changed by adjusting the radius of the spherical surface shape of the bottom part. By adjusting the radius of the spherical surface shape, even if the dimple has an intricate shape as in the present invention, the volume can be adjusted effectively for the golf balls having various structure. Thereby, the lift and the drag acting on the golf ball when the golf ball is flied can be balanced easily, so that the flying performance of the golf ball 1 can be enhanced further.

According to the golf ball described in the item (8), the same effects as those of the golf ball described in the item (1) can be achieved. Further by the curved part curved toward the center direction of the spherical surface between the contour main parts and contour connecting parts and the bottom part, the flow of air on the spherical surface from the dimples is made smooth, so that the drag can be restrained. Therefore, the flying performance of golf ball can be enhanced further.