Golf ball

#1. Field of the Invention

#The present invention relates to a golf ball and, more particularly, to an improvement of the aerodynamic characteristics of the outer surface of a golf ball having a plurality of dimples formed in the outer surface of the ball.

#2. Disclosure of Related Art

#FIG. 1 is a front view of a golf ball illustrating a preferred embodiment of the present invention;

#FIG. 2 is a schematical enlarged view of a part A of the surface of the ball shown in FIG. 1;

#FIG. 3 is an enlarged cross-sectional view of a part of the ball shown in FIG. 1;

#FIGS. 1 to 3 show a preferred embodiment of the present invention. Referring to these Figures, a golf ball has a spherical body 10 having a spherical outer surface 10a and a plurality of first circular dimples 11 arranged substantially uniformly in the outer surface 10a. The first dimples 11 have the same or similar shapes as those of conventional balls having dimples. Each of the first dimples 11 may have a form of double dimples, as known in conventional golf balls. According to the present invention, a plurality of second fine dimples (or indentations) 12, which are smaller than the first dimples 11, are arranged in the outer surface 10a and the inside surface of the first dimples 11 of the body 10, as apparent from FIGS. 2 and 3. Preferably, the second fine dimples (or indentations) 12 are formed by grit blasting with particles of sand or glass. The second fine dimples (or indentations) 12 may be formed together with the first dimples 11 by a mold.

#In the golf ball according to the present invention, a turbulent air flow boundary layer can be easily produced on the outer surface of the ball during flight due to the existence of the second fine dimples (or indentations) 12 in the spherical outer surface 10a and the inside surface of the first dimples 11. Therefore, the critical speed of the golf ball according to the present invention can be reduced to less than that of a conventional golf ball having dimples, due to earlier projection of the turbulent air flow boundary layer, and after the ball speed exceeds the critical speed, the magnitude of the pressure drag imposed on the golf ball according to the present invention can be reduced to less than that of the conventional golf ball having dimples, due to broader projection of the turbulent air flow boundary layer on the outer surface of the ball.

#FIG. 4 schematically shows a state of air streams produced around the above-mentioned ball according to the present invention during flight at a certain speed higher than a critical speed, and FIG. 5 schematically shows a state of air streams produced around a conventional golf ball 1 having dimples (not shown) during the flight at the same speed as that of the ball shown in FIG. 4. The ball shown in FIG. 4 is different from the conventional ball shown in FIG. 5 only in the point that the second fine dimples are formed in the spherical outer surface and the inside surface of the first dimples. In both cases shown in FIGS. 4 and 5, a laminar air flow boundary layer is produced on the outer surface of the ball within a first region of from a point A to a point B, and a turbulent air flow boundary layer is produced on the outer surface of the ball within a second region of from the point B to a point C, and at the point C, the air stream is exfoliated from the outer surface of the ball. However, in the case of the ball according to the present invention, the turbulent air flow boundary layer is extended toward the front and back of the ball, and thus the exfoliating point C of the air stream is shifted toward the back of the ball, as apparent from the comparison of the states of air streams shown in FIGS. 4 and 5. Therefore, in the case of the ball according to the present invention, a subatmospheric pressure produced in a region behind the ball due to the exfoliation of the air stream is reduced, and thus an air pressure difference produced in front of and behind the ball is reduced. Accordingly, a pressure drag imposed on the ball is particularly reduced when the ball speed is higher than the critical speed.