Games using tangible projectile – Golf – Ball
Reexamination Certificate
1999-06-15
2001-04-10
Arbes, Carl J. (Department: 3729)
Games using tangible projectile
Golf
Ball
C264S255000, C264S275000, C264S279000, C264S319000, C473S361000, C473S378000, C473S384000
Reexamination Certificate
active
06213897
ABSTRACT:
This invention relates to a method for preparing a golf ball comprising a core, an intermediate layer, and a cover, wherein the intermediate layer is provided in its outer surface with recesses and the cover penetrates into the recesses to form protrusions.
BACKGROUND OF THE INVENTION
A variety of studies and proposals have been made to find a good compromise between flight distance and “feel” of golf balls. For solid golf balls comprising a solid core and a cover, one common approach is to construct the core and the cover into multilayer structures for adjusting their hardness and dimensions (including diameter and gage).
For example, U.S. Pat No. 5,439,227 discloses a three-piece golf ball comprising a core, a cover inner layer and a cover outer layer, the cover outer layer being harder than the cover inner layer. U.S. Pat No. 5,490,674 discloses a three-piece golf ball comprising a solid core of inner and outer layers and a cover, the core inner layer being harder than the core outer layer.
While the respective layers of most golf balls define smooth spherical surfaces, the golf balls disclosed in U.S. Pat. Nos. 2,376,085 and 5,692,973 have a core which is provided with outwardly extending protrusions for preventing the core from being offset during injection molding of the cover therearound. The protrusions in these golf balls are substitutes for the support pins used during injection molding. These patents do not attempt to positively utilize the shape effect of support pin-substituting protrusions, but rather intend to avoid incorporation of a distinct material in the cover, by forming the protrusions from the same material as the cover.
Recently, JP-A 9-285565 proposes a two-piece solid golf ball in which the solid core and cover, or adjoining layers of a multilayer solid core or adjoining layers of a multilayer cover are provided with irregularities. When hit, the ball gives a different feel to the player, depending on the direction of external force applied to the ball. This golf ball is improved in feel, but insufficient in flight performance and durability. There is left a room for further improvement.
In the prior art, golf balls are often prepared by injection molding, typically by injection molding a cover around a core. One exemplary injection molding method is described with reference to
FIG. 7. A
mold
21
includes upper and lower sections
21
a
and
21
b
which are removably mated along a parting line P to define in the interior a spherical cavity
22
having a negative dimple pattern. A core
23
of a golf ball to be prepared is placed within the cavity
22
as an insert. The core
23
is supported in place by a plurality of support or knockout pins
24
(four pins in each of the upper and lower sections in the illustrated example). A cover stock or molding material
25
is injected into the cavity
22
. The support pins
24
are withdrawn from the cover stock
25
immediately before or simultaneously with the completion of injection of the cover stock. After cooling for solidification whereby the core
23
is enclosed within the cover having a multiplicity of dimples, the upper section
21
a
is opened and the support or knockout pins
24
are moved upward from the lower section
21
b
for separating the molded golf ball from the lower section
21
b
. Then, the molded golf ball is taken out of the mold. In
FIG. 7
, the mold is provided with gas venting holes
26
, in which stationary pins
27
are fixedly received to define gaps
28
therebetween. During molding operation, gases, typically air, are discharged from the cavity
22
to the exterior through the gaps
28
, and vent holes
26
.
Some consideration is needed when such an injection molding method is applied to a spherical core body in the form of a core enclosed within an intermediate layer having a multiplicity of recesses in its outer surface, more particularly when the spherical core body is supported at the center of the mold cavity by support pins and a cover stock is fed into the cavity. Usually, at least the distal ends of the support pins are carefully configured to minimize the formation of pin marks on the cover. The inventor found that it often occurs that some support pins
24
enter recesses
3
in the intermediate layer
2
around the core
1
while the remaining support pins
24
abut the intermediate layer
2
as shown in
FIGS. 5 and 6
. Then the spherical core body
4
consisting of the core
1
and the intermediate layer
2
is supported off the center of the mold cavity as best shown in FIG.
6
. As a result of off-centering of the spherical core body
4
, the molded golf ball becomes of poor quality.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel and improved method for preparing a golf ball comprising a core, an intermediate layer having a multiplicity of recesses, and a cover penetrating into the recesses to form protrusions, the method being capable of preparing golf balls with high precision while preventing any off-centering.
The invention provides a method for preparing a golf ball comprising a core of at least one layer, an intermediate layer enclosing the core, and a cover of at least one layer enclosing the intermediate layer, wherein the intermediate layer is provided in its outer surface with a multiplicity of recesses each defining an opening in the outer surface, and the cover penetrates into the recesses in the intermediate layer to form protrusions. The method involves the steps of providing a spherical core body having the core enclosed within the intermediate layer having the recesses; furnishing an injection mold defining a cover-forming cavity in the interior, in which a plurality of support pins are arranged for axial motion toward and away from the cavity and have distal ends with a greater diameter than the diameter of the recess openings; supporting the spherical core body at the center of the mold cavity by the support pins; injecting a cover stock into the mold cavity; and withdrawing the support pins from within the mold cavity immediately before the mold cavity is filled with the cover stock.
Since the distal ends of the support pins are formed to a greater diameter than the diameter of the recess openings in the intermediate layer, the support pins do not enter the recesses in the intermediate layer. This ensures that the spherical core body is always held at the center of the mold cavity, enabling high precision molding of golf balls having cores correctly centered.
REFERENCES:
patent: 2376085 (1945-05-01), Radford et al.
patent: 4267217 (1981-05-01), Brooker
patent: 4501715 (1985-02-01), Barfield
patent: 5112556 (1992-05-01), Miller
patent: 5122046 (1992-06-01), Lavallee
patent: 5201523 (1993-04-01), Miller
patent: 5225133 (1993-07-01), Ihara
patent: 5439227 (1995-08-01), Egashira et al.
patent: 5490674 (1996-02-01), Hamada et al.
patent: 5692973 (1997-12-01), Dalton
patent: 5759116 (1998-06-01), Kasasima
patent: 5820485 (1998-10-01), Hwang
patent: 5824258 (1998-10-01), Yamaguchi
patent: 5827548 (1998-10-01), Lavallee
patent: 5836834 (1998-11-01), Masutani et al.
patent: 5849237 (1998-12-01), Inoue
patent: 5874038 (1999-02-01), Kasashima
patent: 5882567 (1999-03-01), Cavallaro
patent: 9-285565 (1997-11-01), None
Arbes Carl J.
Bridgestone Sports Co. Ltd.
Kim Paul D.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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