Bridgestone Sports Co., Ltd.

Bridgestone Corporation

Sports Co., Ltd.

Keisuke Ihara

Michio Inoue

Hirotaka Shimosaka

Atsuki Kasashima

Yutaka Masutani

Atuki Kasasima

Kazuto Maehara

Tamotu Kato

Yasuhide Alaki

Yasushi Ichikawa

Seisuke Tomita

Jumei Harada

Yoichi Omura

Jun Nomura

Masayuki Ohtake

Atuki Kasashima

June Nomura

A method of manufacturing a golf ball is disclosed. A cover is molded through use of either a thermoplastic resin having a group capable of reacting with an isocyanate group or a thermoplastic resin containing a compound having two or more groups capable of reacting with an isocyanate group. Subsequently, a polyisocyanate compound is caused to permeate into the surface layer of the cover to thereby cause the reaction between the polyisocyanate compound and the group(s) capable of reacting with the isocyanate group. As a result, a modified layer having excellent properties is formed at the surface of the cover formed from thermoplastic resin. In this case, a non-yellowing polyurethane resin is preferably used as the thermoplastic resin having a group capable of reacting with an isocyanate group, and 4,4-diphenylmethane diisocyanate (MDI) is preferably used as the polyisocyanate compound.

Golf ball

Disclosed is a golf ball including: a plurality of dimples arranged overall on the spherical surface of the golf ball by assuming the spherical surface of the golf ball as a spherical octahedron and using, as dimple arrangement units, eight spherical triangles constituting the spherical octahedron, on each of which a specific number of the dimples are arranged. In this golf ball, at least the four dimples are arranged on each of three sides of the spherical triangle; there is no great circle with which none of the dimples intersects; and the total number of the dimples is in a range of 380 to 450.

Using a mold having typically two split mold segments which are mated in a separable manner to define a spherical mold cavity therein, a golf ball having a multiplicity of dimples in its surface is molded by feeding a molding material into the mold cavity. The mold is split along a line off a horizontal great circle of the golf ball into two split mold segments having different areas of contact with the ball. The golf ball as molded is always caught and left in the larger mold segment and thus can be easily removed from the mold by a routine operation.

Golf ball with spaced parting line

A golf ball has a core and a cover and, the cover includes at least one thin spherical layer with a thickness of not more than 1.5 mm. The thin layer is molded by injecting an injection molding material at a selected fill speed which is correlated to the melt flow rate of the molding material. The invention facilitates the mass production of golf balls having thin spherical cover layers of uniform thickness which offer potential for further improvements in ball performance.

Golf ball and method of manufacture

Method of manufacturing a golf ball

In a dimpled golf ball, the parameters of dimples are optimized to improve the aerodynamic performance of the ball and thus increase its flight distance. The dimples have a planar shape which is circular, and are of at least three types of mutually differing diameter. At least one of the types of dimples has a cross-sectional shape differing from that of the other types. One of the dimple types may have a cross-sectional shape defined by the union of at least two concave portions of differing slope.

A golf ball includes a large number of two types pr more dimples different in diameter and/or depth, which are arranged on the surface of the golf ball; wherein an EAstdev value of the golf ball is in a range of 2 or less, the EAstdev value being expressed by the following equations:

Golf ball and method of evaluating golf ball

In a golf ball having a plurality of dimples ( ) formed in its surface, each dimple prior to paint coating consists of a major concave surface portion ( ) circumscribed by a peripheral convex surface portion ( ). The peripheral convex surface portion connects to the major concave surface portion at a point of inflection ( ) which is located at a distance of 10-50% of the dimple depth (d) from the edge ( ) of the peripheral convex surface portion.

Dimpled golf ball

When the spherical surface of a golf ball is divided into a plurality of substantially congruent spherical triangles, dimples are substantially equally distributed in the spherical triangles. The spherical triangles are minimum triangular units which are substantially congruent with each other. The dimples distributed in each minimum triangular unit include crossing dimples that each lie across a side of the minimum triangular unit. The total of the crossing lengths of the crossing dimples is 70-80% of the total side length of the minimum triangular unit. The golf ball is improved in the symmetry of elevation angle and carry, and has good aerodynamic performance and an increased total flight distance.

In a golf ball having on its surface a multiplicity of dimples, the dimples include a majority of large dimples with a diameter of 3.0 to 4.2 mm and account for at least 65% of the entire ball surface area. The large dimples have a depth of 0.1-0.35 mm, an edge angle of up to 30&deg;, and a radius of curvature at the edge of 1-50 mm. Not only excellent flight performance is achieved, but the ball can be smoothly released from a mold at the end of molding.

A spherical body having a core and a surface layer is manufactured by a method comprising a preforming step in which a pair of sheet blanks ( ) are formed into half-shells ( ) in a two-part mold ( ) having hemispherical concave mold halves by pressing each blank from one side while applying vacuum suction to the other side; a surface layer forming step in which the half-shells are loaded into another two-part mold ( ) having pattern-forming projections, the core ( ) is placed on one mold half, and the other mold half is joined thereto to close the mold, thereby pressing the core against the inner side of each half-shell, concurrent with which vacuum suction is applied to the outer side; and a molding step in which the surface layer is fused and solidified onto the core within the closed mold.

Spherical body and method of manufacture

In a golf ball having a plurality of dimples in its surface, the dimples as a whole are randomly distributed on at least a hemispherical surface. The golf ball has improved aerodynamic isotropy.

Dimpled golf ball and dimple distributing method

A golf ball has plural types of dimples on a spherical surface, which is assumed to be a regular icosahedron having twenty triangles. Apexes of five triangles join together at a vertex. Those dimples arranged in each triangle constitute an arrangement unit. A first dimple having a smallest diameter is located at the vertex, and second dimples having a greater diameter are equidistantly arranged around the first dimple. When a pentagon which circumscribes the second dimples is drawn, an average depth of those dimples located within the pentagon is up to 85% of the average depth of those dimples located in the remaining areas.

An injection mold for golf balls defines a spherical cavity therein and has a parting plane extending coplanar with the equator of the cavity. A plurality of molding material injecting gates are arranged in the mold body along or near the cavity equator, and a plurality of retractable core support pins are disposed in the mold at areas other than the cavity equator and poles so that the core support pins may be moved toward and away from the cavity center. A cover having a uniform gage and a smooth surface can be injection molded to produce a golf ball without radial misalignment of the core.

Golf ball injection molds

A golf ball is molded in a mold comprising a pair of removably joined mold sections. The golf ball has a plurality of dimples, the dimples being arranged in a polyhedral arrangement. The golf ball is free of a great circle which does not intersect with the dimples. The dimples (D,) lying across the parting line (P) between the mold sections, except for the dimples (D,) whose center lies on the parting line, are shifted upward or downward from the parting line or reduced in diameter so that these dimples are located outside the parting line (P). The dimple surface coverage is at least 71%. A golf ball having high symmetry and excellent flight performance can be prepared using a simple mold.

Growing community of inventors

Chichibu, Japan

Keisuke Ihara