U.S. patent application number 13/602917 was filed with the patent office on 2012-12-27 for mold for forming golf ball and golf ball manufactured using the same.
This patent application is currently assigned to BRIDGESTONE SPORTS CO., LTD.. Invention is credited to Takuma NAKAGAWA, Katsunori SATO.
Application Number | 20120329578 13/602917 |
Document ID | / |
Family ID | 43306664 |
Filed Date | 2012-12-27 |
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United States Patent
Application |
20120329578 |
Kind Code |
A1 |
NAKAGAWA; Takuma ; et
al. |
December 27, 2012 |
MOLD FOR FORMING GOLF BALL AND GOLF BALL MANUFACTURED USING THE
SAME
Abstract
There are provided a mold for forming a golf ball, which allows
a dimple formed near the equator of golf ball corresponding to the
partition surface of upper and lower molds to be formed so as to
have the same shape as that of a dimple formed in other regions,
and a golf ball manufactured using this mold. The mold for forming
a golf ball in accordance with the present invention includes at
least two body parts, a cavity is formed within the mold by the
joining of the at least two body parts, and in at least one of the
body parts, a groove for forming a projecting land part which is
ground after the formation of the golf ball is provided in a cavity
wall surface adjacent to the whole circumference of a parting line
formed by the joining.
Inventors: |
NAKAGAWA; Takuma;
(Chichibu-shi, JP) ; SATO; Katsunori;
(Chichibu-shi, JP) |
Assignee: |
BRIDGESTONE SPORTS CO.,
LTD.
Tokyo
JP
|
Family ID: |
43306664 |
Appl. No.: |
13/602917 |
Filed: |
September 4, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12483596 |
Jun 12, 2009 |
8282376 |
|
|
13602917 |
|
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Current U.S.
Class: |
473/378 ;
473/351 |
Current CPC
Class: |
B29C 45/0025 20130101;
B29C 2045/0034 20130101; B29C 45/372 20130101; B29L 2031/545
20130101; A63B 37/0003 20130101; A63B 45/00 20130101; A63B 37/0097
20130101 |
Class at
Publication: |
473/378 ;
473/351 |
International
Class: |
A63B 37/14 20060101
A63B037/14 |
Claims
1. A golf ball manufactured by the following process, the process
comprising: providing a mold, the mold comprising at least two body
parts, a cavity being formed within the mold by the joining of the
at least two body parts, wherein at least one of the body parts
comprise: a plurality of protrusions for forming a plurality of
dimples; a cavity wall surface for forming a land part of the golf
ball; and a groove for forming a projecting land part which is
ground after the formation of the golf ball, wherein the groove
extends along the whole circumference of a parting line formed by
the joining, except where the protrusion is arranged on the parting
line, and wherein the groove has a cliff portion projected from an
edge of the groove, the groove being adjacent to the dimple-forming
protrusion through the cliff portion which has a height to be
ground, forming a golf ball having the plurality of dimples and the
projecting land part by using the mold; and then grinding the
projected land part of the golf ball.
2. The golf ball according to claim 1, wherein the groove has a
depth of about 5 .mu.m to about 100 .mu.m from the imaginary
spherical surface of the cavity.
3. The golf ball according to claim 1, wherein the bottom surface
of the groove and the wall surface of the cavity are connected to
each other asymptotically.
4. The golf ball according to claim 1, wherein the width of the
groove is not more than about 10 mm.
5. The golf ball according to claim 1, wherein the bottom surface
of the groove includes a spherical surface part having the same
center as the center of the spherical surface shape of the wall
surface of the cavity.
6. The golf ball according to claim 1, wherein the groove extends
along continuously along both sides of the parting line.
7. The golf ball according to claim 1, wherein the groove is
adjacent to the protrusion that is arranged on the parting line.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. application Ser.
No. 12/483,596, filed Jun. 12, 2009, the entire contents of which
are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a mold for forming a golf
ball and to a golf ball manufactured using this mold.
BACKGROUND OF THE INVENTION
[0003] As is widely known, a golf ball may be formed by using a
forming mold that can be divided into two parts, the mold, having a
spherical cavity therein, is formed with a large number of
protrusions for forming dimples (dimple forming protrusions) on the
wall surface of the cavity, and has a parting line substantially at
the position of the equator of the cavity.
[0004] In the case in which the mold is of an injection molding
type, on the parting line thereof, forming material injection gates
for injecting a cover material (resin material) for a ball are
provided at equal intervals on the circumference. On a ball formed
by cover material injection, the cover material having hardened
within the gate remains in a projecting state, forming protrusions,
and in addition, fine burrs are also produced at the parting line
position of mold. The protrusions and burrs on the parting line are
removed by grinding after formation.
[0005] In recent years, there have been proposed various kinds of
seamless golf balls in which dimples are arranged even on the
parting line (usually, coinciding with the equator line of the
ball). These seamless golf balls have excellent flying performance
because the degree of freedom of dimple arrangement is high so that
dimples can be arranged evenly with high density on the surface of
the ball.
[0006] For the above-described seamless golf ball, unfortunately,
when the protrusions and burrs on the parting line are removed by
grinding, the dimple portions (especially, dimple edge portions)
are ground at the same time. As a result, the dimples are made
shallow, which is undesirable. Therefore, there arises a problem in
that the inherent ball performance is deteriorated and the
appearance is also marred.
[0007] Also, the deformation of dimples due to grinding is
sensitive to the degree of grinding, so that variations between
golf balls have occurred.
[0008] The specification of Japanese Unexamined Patent Application
Publication No. 11-114092 describes a method of forming protrusions
near the dimples on the equator to avoid abrasion of dimples due to
grinding.
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to provide a mold for
forming a golf ball, which allows a dimple formed adjacent to the
equator of golf ball corresponding to the partition surface of
upper and lower molds to be formed so as to have the same shape as
that of a dimple formed in other regions, and a golf ball formed
using this mold.
[0010] To achieve the above object, a mold for forming a golf ball
in accordance with the present invention comprises at least two
body parts, a cavity being formed within the mold by the joining of
the at least two body parts, in which at least one of the body
parts comprise a groove for forming a projecting land part which is
ground after the formation of the golf ball in a cavity wall
surface adjacent to the entire circumference of a parting line
formed by the joining.
[0011] In the mold for forming a golf ball in accordance with the
present invention, the groove preferably has a depth of about 0.005
mm to about 1 mm from the imaginary spherical surface of the
cavity.
[0012] Also, in the mold for forming a golf ball in accordance with
the present invention, the bottom surface of the groove and the
wall surface of the cavity are preferably connected to each other
asymptotically.
[0013] Also, in the mold for forming a golf ball in accordance with
the present invention, the width of the groove is preferably not
more than about 10 mm.
[0014] Also, in the mold for forming a golf ball in accordance with
the present invention, the bottom surface of the groove preferably
includes a spherical surface part having the same center as the
center of the spherical surface shape of the wall surface of the
cavity.
[0015] According to another aspect of the present invention, a golf
ball in accordance with the present invention is manufactured by
being formed using the above-described mold for forming a golf ball
and then by grinding the projected land part.
[0016] By making the land part on the parting line, which is
removed at the time of grinding after formation, high, the dimple
existing adjacent to the equator of the golf ball can be prevented
from being scraped by grinding and being deformed.
[0017] Also, thereby, the adjustment width of symmetry of dimples
arranged on the golf ball surface can be widened, and furthermore,
the appearance of the golf ball can be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a side sectional view showing one embodiment of a
mold for forming a golf ball in accordance with the present
invention;
[0019] FIG. 2 is a perspective view showing dimple forming
protrusions adjacent to the joint surface of a mold for forming a
golf ball in accordance with the present invention and a cavity
wall surface;
[0020] FIGS. 3A and 3B are side views of a golf ball manufactured
using a mold for forming a golf ball in accordance with the present
invention, FIG. 3A showing a state before grinding, and FIG. 3B
showing a state after grinding;
[0021] FIG. 4 is a perspective view showing the vicinity of the
equator of a golf ball injection molded using a mold for forming a
golf ball in accordance with the present invention;
[0022] FIGS. 5A and 5B are side views showing a part of the equator
surface of a golf ball manufactured using a mold for forming a golf
ball in accordance with the present invention, FIG. 5A showing a
state before grinding, and FIG. 5B showing a state after grinding;
and
[0023] FIGS. 6A and 6B are side views showing a part of the equator
surface of a golf ball manufactured using a conventional mold for
forming a golf ball, FIG. 6A showing a state before grinding, and
FIG. 6B showing a state after grinding.
DETAILED DESCRIPTION OF THE INVENTION
[0024] One embodiment of the present invention is described below
in detail with reference to the accompanying drawings.
[0025] In the case in which a golf ball is manufactured by an
injection molding process, an injection molding mold 1, for
example, shown in FIG. 1 is used. This injection molding mold 1
includes a body part 2 of a metallic upper mold and a body part 3
of a metallic lower mold. By separatably joining the body parts 2
and 3 of the upper and lower molds together, an internal cavity 4
is formed.
[0026] As shown in FIG. 1, the body parts 2 and 3 of the mold 1 in
accordance with the present invention each have a groove 6 in a
cavity wall surface 10 adjacently to a parting line 5 between the
body parts. This groove 6 is a groove for forming a projecting land
part for grinding that further projects from the land part of a
golf ball on the equator surface of a formed golf ball. The groove
6 is formed in both of the body parts 2 and 3 of the upper and
lower molds. In FIG. 1, protrusions for forming dimples are omitted
for ease of understanding. Also, a runner, gate, support pin, vent
pin, and the like arranged around the cavity are omitted. The kind,
number, and arrangement of these elements can be chosen in the same
way as the conventional mold.
[0027] The projecting land part for grinding formed on the equator
of an injection molded golf ball is designed so as to be higher
than the land part of the golf ball in regions other than the
region near the equator. Therefore, the groove 6 provided in the
body parts 2 and 3 of the mold 1 preferably has a depth .alpha.
from an imaginary spherical surface 7 of the internal cavity 4. The
depth .alpha. is preferably changed appropriately depending on the
grinding conditions. The upper limit of the depth .alpha. is
preferably about 100 .mu.m, further preferably about 80 .mu.m, and
still further preferably about 60 .mu.m. Also, the lower limit of
the depth .alpha. is preferably about 5 inn, and is more preferably
about 10 .mu.m. If the depth .alpha. is greater than the upper
limit, grinding work takes much time, and also a golf ball having a
low degree of sphericity may be formed. If the depth .alpha. is
less than the lower limit, the dimple shape may be
deteriorated.
[0028] Also, a connecting surface 9 between a groove bottom surface
8 and the cavity wall surface 10 of the body parts 2 and 3
preferably connects these two surfaces to each other
asymptotically. The phrase "connect asymptotically" means that
curves are connected smoothly to each other so as to approach the
asymptotic line gradually. That is to say, the groove bottom
surface 8 and the cavity wall surface 10 of the body parts 2 and 3
are connected to each other by the connecting surface 9 having a
smooth curve shape. As a result, the projecting land part for
grinding of an injection molded golf ball is connected smoothly to
the land part of the golf ball. Therefore, when grinding is
performed after injection molding, a change in grinding force can
be accommodated properly.
[0029] The groove bottom surface 8 preferably has a width .beta.
such that a preferred projecting land part for grinding is formed.
The width .beta. of the groove bottom surface 8 is preferably
changed appropriately depending on the grinding conditions. The
upper limit of the width .beta. is preferably about 10 mm, is more
preferably about 8 mm, and is still more preferably about 7 mm.
Also, the lower limit of the width .beta. is preferably about 0.2
mm, and is more preferably about 0.4 mm.
[0030] Also, the groove 6 preferably has a width .gamma. such that
a preferred projecting land part for grinding is formed. The width
.gamma. of the groove 6 is preferably changed appropriately
depending on the grinding conditions. The upper limit of the width
.gamma. is preferably about 10 mm, is more preferably about 8 mm,
and is still more preferably about 7 mm. Also, the lower limit of
the width .gamma. is preferably about 0.2 mm, and is more
preferably about 0.4 mm, and is still more preferably about 1 mm.
If the width .gamma. of the groove 6 exceeds 5 mm, the grinding
area becomes too large, so that the grinding process takes much
time, and also the symmetry of a golf ball may be marred. On the
other hand, if the width .gamma. of the groove 6 is narrower than
0.1 mm, deformation of dimple shape due to grinding cannot be
prevented.
[0031] The groove bottom surface 8 of the body parts 2 and 3 is
preferably of a shape having a spherical surface portion having the
same center as the center of the imaginary spherical surface 7.
Thereby, the projecting land part for grinding of an injection
molded golf ball is shaped so as to have a spherical surface
portion having the same center as the center of a spherical surface
consisting of the land part of golf ball, so that uniform grinding
can be performed.
[0032] FIG. 2 shows the parting line 5 and the cavity wall surface
10 in the body part 3 of the lower mold of the mold 1. FIG. 2 shows
protrusions 12 for forming noncircular dimples. However, needless
to say, the present invention can be applied to circular dimples.
Also, FIG. 2 shows a case in which the parting line is a zigzag
line. However, needless to say, the parting line can be made linear
or wavy. As shown in FIG. 2, a joint surface 11 and the groove
bottom surface 8 for forming the projecting land part for grinding
are continuous with each other. The groove bottom surface 8
continues to the projection 12 for forming the dimple or the
connecting surface 9.
[0033] In the case in which the dimples are arranged so as to
straddle the equator surface of golf ball, the protrusion 12 for
forming the dimple is continuous with the joint surface 11 directly
without the groove bottom surface 6 being interposed.
[0034] FIG. 3 shows a golf ball manufactured using a mold 1 for
forming a golf ball in accordance with the present invention. FIG.
3A is a side view of the golf ball before grinding which is formed
using a mold 1 for forming a golf ball in accordance with the
present invention. As shown in FIG. 3A, a golf ball 30A injection
molded using the mold 1 for forming a golf ball in accordance with
the present invention has a projecting land part 32 for grinding
around an equator 31 thereof. For ease of understanding, the
illustration of dimples is omitted. The projecting land part 32 for
grinding and a land part 34 of the golf ball are connected to each
other by a connecting land part 33. The connecting land part 33
preferably has a shape so as to be smoothly continuous with the
land part 34. The projecting land part 32 has a spherical surface
having the same center as the center of the spherical surface of
the golf ball land part 34. FIG. 3B is a side view showing the
state after grinding of the injection molded golf ball shown in
FIG. 3A. For the golf ball injection molded using the mold 1 for
forming a golf ball in accordance with the present invention, the
projecting land part 32 for grinding on the equator 31 is removed
by grinding work for removing burrs and the like. Thus, a spherical
golf ball 30B is manufactured.
[0035] FIG. 4 shows the relationship between the projecting land
part 32 for grinding and dimples 35. Many dimples 35 are formed in
the surface of golf ball. Around the equator 31 of the golf ball,
the projecting land part 32 for grinding is formed. Dimples 35a
adjacent to the equator 31 each have a predetermined depth from the
imaginary land part like other dimples 35. Therefore, at the edge
adjoining the projecting land part 32 for grinding of the dimple
35a, a cliff 36 corresponding to the height a of the projecting
land part 32 for grinding is formed. The projecting land part 32
for grinding is continuous with the land part 34 via the connecting
land part 33.
[0036] FIG. 5A is sectional views taken along the line A-A of FIG.
4. FIG. 5A is an equator surface side sectional view of the golf
ball before grinding, which is formed using the mold 1. As shown in
FIG. 5A, adjacent to the equator 31 of the formed golf ball, the
projecting land part 32 for grinding having a width in the
direction of upper and lower poles excluding the region of the
dimple 35a is formed. The projecting land part 32 for grinding is
continuous with the land part 34 via the connecting land part 33.
Also, the projecting land part 32 for grinding has the height of a
with respect to the land part 34. FIG. 5B shows a state after
grinding of the formed golf ball shown in FIG. 5A. As shown in FIG.
5B, the projecting land part 32 for grinding having been formed
adjacent to the equator 31 of golf ball is scraped by grinding.
However, grinding is not performed exceeding the height a of the
projecting land part 32 for grinding, so that the dimple 35a
existing adjacent to the equator 31 does not lose its shape.
[0037] Also, even if the scraped height somewhat varies depending
on the grinding force, the ball surface after grinding can maintain
the spherical shape because the connecting land part 33 connects
smoothly with the land part 34.
[0038] FIG. 6 is side sectional views of the equator surface of a
golf ball formed using a conventional mold for forming a golf ball.
FIG. 6A shows a golf ball after injection molding and before
grinding. As shown in FIG. 6A, near an equator 61 of a golf ball
having been injection molded using the conventional mold, a golf
ball land part 64 having a height almost the same as that of other
regions is formed. FIG. 6B shows a golf ball after grinding. As
shown in FIG. 6B, when the golf ball injection molded using the
conventional mold is ground, a portion near the equator 61 is
ground excessively as compared with other regions. Therefore, the
shape of the dimple existing adjacent to the equator 61 of golf
ball is changed from the desired shape.
[0039] Also, a golf ball can be formed using the mold 1 for forming
a golf ball in accordance with the present invention. In the
present invention, the core constituting the golf ball is not
subject to any special restriction, and various cores such as a
single-layer solid core, a solid core having a plurality of
vulcanized rubber layers, a solid core having a plurality of resin
layers, and a thread-wound core having a thread rubber layer can be
used. Also, a cover layer can be formed around the core by using
the mold in accordance with the present invention. As the material
of the cover layer, a publicly known thermoplastic resin or
thermoplastic elastomer, which uses ionomer resin or urethane resin
as a main ingredient, can be used suitably. The number of cover
layers is not limited to one, and the cover can be formed into a
multilayer structure having two or more layers. The thickness (per
one layer) of the cover layer can be chosen appropriately depending
on the core diameter and the number of cover layers, and is
preferably in the range of about 0.5 mm to about 3.0 mm.
[0040] The kinds and shapes of dimples formed in large numbers in
the surface of golf ball are not subject to any special
restriction. However, the dimples may be of a circular shape or
noncircular shape of the same kind or a different kind. Dimples
having a diameter of about 0.5 mm to about 6 mm and a depth of
about 0.05 mm to about 0.4 mm can be adopted appropriately. As the
arrangement mode of these dimples, various arrangement patterns
such as a regular dodecahedron, regular icosahedron, and regular
octahedron can be used.
[0041] In the above description, a specific embodiment of the mold
for forming a golf ball in accordance with the present invention
has been explained. However, the present invention is not limited
to this embodiment, and all changes and modifications that are
apparent to those skilled in the art are embraced in the technical
scope of the present invention.
DESCRIPTION OF SYMBOLS
[0042] 1 . . . mold for forming a golf ball [0043] 2 . . . upper
body part [0044] 3 . . . lower body part [0045] 4 . . . internal
cavity [0046] 5 . . . parting line [0047] 6 . . . groove [0048] 7 .
. . imaginary spherical surface [0049] 8 . . . groove bottom
surface [0050] 9 . . . connecting surface [0051] 10 . . . cavity
wall surface [0052] 11 . . . joint surface [0053] 12 . . .
protrusion for forming a dimple [0054] 30A . . . injection molded
golf ball [0055] 30B . . . ground golf ball [0056] 31, 61 . . .
equator [0057] 32 . . . projecting land part for grinding [0058] 33
. . . connecting land part [0059] 34, 64 . . . land part [0060] 35,
65 . . . dimple [0061] 36 . . . cliff
* * * * *