Golf ball mold

Details Golf ball mold Golf ball mold

1998-10-08

2001-01-02

Davis, Robert (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Distinct means to feed, support or manipulate preform stock...

Opposed registering coacting female molds

C264S279100, C425S120000, C425S573000

Utility Patent

active

06168407

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a golf ball mold adapted to mold a golf ball having dimples on the parting line to effectively avoid any abrasion of the dimples on the parting line when fins and burrs formed at or near the parting line are ground away. The present invention also relates to a golf ball prepared using the mold.
2. Related Art
As is well known in the art, golf balls are generally molded using a mold comprising a pair of mold sections. The mold sections are removably mated to define a spherical cavity by their concave surfaces which are provided with a plurality of dimple-forming projections. A parting line between the mold sections is located substantially at the equator of the cavity.
In the case of injection molding, about eight gates are equidistantly arranged along the parting line of the mold for injecting a cover stock (or resin material) into the cavity. On the ball molded by injecting the cover stock, those portions of the cover stock which have cured in the gates are left as fins projecting from the ball surface and additionally, fine burrs are formed at the parting line. In the case of heat compression molding, extra cover stock oozes out along the parting line to form an annular fin like Saturn's ring.
As a consequence, especially in the case of injection molding, the fins are previously cut to a predetermined length or height before grinding is effected along the parting line to abrade away the fins and burrs. The grinding operation is generally carried out using a grinding apparatus as shown in FIG.
7
. Referring to
FIG. 7
, a ball G having fins
16
(only two shown) at the horizontal parting line P is held between a support
22
and a holder
24
such that the ball G is rotatable about a vertical axis
26
passing the north and south poles of the ball. A grinding tool
15
is equipped with an abrasive bar
14
having at the tip a concave working face
14
a
shaped in conformity to the curved surface of the ball G. The grinding tool
15
is advanced toward the parting line position P of the ball rotating in a direction of arrow
28
and toward the center of the ball G until the face
14
a
comes in contact with the fins
16
. As shown in
FIG. 8
, there is a likelihood that the working face
14
a
of the abrasive bar
14
come in contact with the edge of a dimple
13
. If desired, a pair of grinding tools may be disposed on opposite sides of the ball though not shown.
In the prior art, due to the necessity for such grinding, golf balls are conventionally designed such that no dimples are arranged on the parting line, that is, an endless land strip is left along the parting line. The golf ball having an endless land strip (that is, a great circle across which no dimples lie) along the parting line, however, has the problem that its flight performance is inferior because the dimple arrangement lacks some uniformity owing to certain limits imposed on the dimple arrangement.
To overcome this problem, a variety of golf balls have been proposed in which dimples are also disposed on the parting line (coincident with the ball's equator). These golf balls which are generally known as seamless golf balls have a high degree of freedom of dimple arrangement, permitting dimples to be arranged on the ball surface uniformly and at a high population and thus providing superior flight performance.
The seamless golf balls, however, have the problem that when fins and burrs on the parting line are ground away, dimples nearby are also ground especially at the edge thereof (see FIG.
8
). As a result, these dimples become shallow, naturally contributing to disturbance against flight performance.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a golf ball mold adapted to mold a golf ball having dimples on the parting line so as to effectively avoid any abrasion of the dimples on the parting line when fins and burrs formed at or near the parting line are ground away at the end of molding. Another object of the present invention is to provide such a golf ball prepared using the mold.
The present invention is directed at a golf ball mold comprising a pair of mold sections which are removably mated to define a spherical cavity by their concave surfaces. The concave surfaces are provided with a plurality of dimple-forming projections. A parting line between the mold sections is located substantially at the equator of the cavity. According to the invention, at least one of the dimple-forming projections is located across the parting line, and a molding material injecting gate or a fin-forming pit is located near the at least one projection. Preferably, the gate or the pit is located across the parting line. Also preferably, a pair of gates or pits are spaced apart within 5 mm from the edge of the at least one projection located across the parting line such that the projection is interposed between the pair of gates or pits.
When a molding material is molded in the mold, there is obtained a golf ball having dimples disposed at the parting line and projecting fins or burrs located near the dimples. When the ball is ground by a grinding tool as shown in
FIG. 7
, the working face of the grinding tool comes in abutment against the projecting fins to be ground away. This effectively avoids the grinding tool from abutting against portions other than the projecting fins to abrade the dimples on the parting line, particularly at the edge thereof. The projecting fins and burrs are cleanly ground away without leaving residues. The dimples are prevented from being abraded and becoming shallow.
According to the invention, after a seamless golf ball having dimples on the parting line is molded, any abrasion of the dimples on the parting line can be effectively avoided during subsequent grinding operation. Then the ball can take full advantage of the dimple effect. In other words, the advantages of the seamless golf ball are maintained in that the ball has a high degree of freedom of dimple arrangement, permitting dimples to be arranged on the ball surface uniformly and at a high population and thus ensuring superior flight performance.


REFERENCES:
patent: 5407341 (1995-04-01), Endo et al.
patent: 5824258 (1998-10-01), Yamaguchi
patent: 5874038 (1999-02-01), Kasashima et al.
patent: 5-84329 (1993-04-01), None
patent: 7-178199 (1995-07-01), None

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