U.S. patent application number 09/985138 was filed with the patent office on 2002-06-27 for golf ball.
Invention is credited to Sajima, Takahiro, Yoshida, Kazunari.
Application Number | 20020082121 09/985138 |
Document ID | / |
Family ID | 18813868 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020082121 |
Kind Code |
A1 |
Yoshida, Kazunari ; et
al. |
June 27, 2002 |
Golf ball
Abstract
A golf ball has three kinds of dimples A to C on a surface. The
A, B and C dimples are circular and have different diameters from
each other. In each of the A, B and C dimples, a ratio of the
number of dimples to the total number of dimples is 5% or more. The
C dimple has a minimum diameter. Moreover, the C dimple also has a
maximum depth. In the C dimple, a value of K calculated by the
following equation (I) is 0.03 or more: K=de-Di.times.0.04 (I)
(wherein Di represents a diameter of the specific circular dimple
kind and de represents a mean depth of the specific circular dimple
kind).
Inventors: |
Yoshida, Kazunari;
(Kobe-shi, JP) ; Sajima, Takahiro; (Kobe-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
18813868 |
Appl. No.: |
09/985138 |
Filed: |
November 1, 2001 |
Current U.S.
Class: |
473/378 |
Current CPC
Class: |
A63B 37/0087 20130101;
A63B 37/0012 20130101; A63B 37/0004 20130101; A63B 37/008 20130101;
A63B 37/0019 20130101; A63B 37/002 20130101; A63B 37/0083 20130101;
A63B 37/0018 20130101; A63B 37/0006 20130101; A63B 37/0021
20130101; A63B 37/0017 20130101 |
Class at
Publication: |
473/378 |
International
Class: |
A63B 037/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2000 |
JP |
2000-338694 |
Claims
What is claimed is:
1. A golf ball comprising, on a surface thereof, a large number of
dimples including plural kinds of circular dimples having different
diameters from each other, wherein when kinds of circular dimples
having a ratio of 5% or more to the total number of dimples is set
to be specific circular dimple kinds, there are two or more
specific circular dimple kinds, and when a kind having a minimum
diameter in the specific circular dimple kinds is set to be a
minimum circular dimple kind, a specific circular dimple kind
having a maximum mean depth in all the specific circular dimple
kinds is set to be a minimum circular dimple kind.
2. The golf ball according to claim 1, wherein a ratio of the
number of dimples of the minimum circular dimple kind to the total
number of dimples is 10% or more.
3. The golf ball according to claim 1, wherein a value of K
calculated by an equation (I) in the minimum circular dimple kind
is 0.03 or more: K=de-Di.times.0.04 (I) (wherein Di represents a
diameter of the specific circular dimple kind and de represents a
mean depth of the specific circular dimple kind).
4. The golf ball according to claim 3, wherein the value of K
calculated by the equation (I) in the specific circular dimple
kinds excluding the minimum circular dimple kind is -0.02 to
0.02.
5. The golf ball according to claim 1, wherein there are three or
more specific circular dimple kinds.
6. The golf ball according to claim 1, wherein a ratio of a total
dimple area to a surface area of a virtual sphere of the ball is
70% to 90% and a total dimple volume is 250 mm.sup.3 to 350
mm.sup.3.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a golf ball and more
particularly to an improvement in dimples of the golf ball.
[0003] 2. Description of the Related Art
[0004] A golf ball has approximately 300 to 550 dimples on a
surface thereof. The role of the dimples resides in one aspect that
such dimples disturb an air stream around the golf ball during the
flight of the golf ball to accelerate the transition of a turbulent
flow at a boundary layer, thereby causing a turbulent flow
separation. The acceleration of the transition of the turbulent
flow causes a separating point of air from the golf ball to be
shifted backwards so that a pressure resistance is reduced,
resulting in an increase in a flight distance of the golf ball.
Moreover, the acceleration of the transition of the turbulent flow
increases a distance between upper and lower separating points of
the golf ball which is caused by a back spin. Consequently, a lift
acting on the golf ball is increased.
[0005] A general dimple has a circular shape (a circular plane
shape). Examples of an element to greatly influence a flight
performance in the circular dimple include a diameter and a depth.
In order to enhance an aerodynamic characteristic, various
proposals have been made for the diameter and depth of the circular
dimple. For example, Japanese Laid-Open Patent Publication No. Sho
62-79072 (1987/79072) has disclosed a golf ball in which two kinds
of dimples having different diameters from each other are formed
and the ratio of the diameters of both kinds is set to be within a
predetermined range. Moreover, Japanese Laid-Open Patent
Publication No. Hei 7-155402 (1995/155402) has disclosed a golf
ball in which the depths of two kinds of dimples having the same
diameter are different from each other.
[0006] In the golf ball, a flight symmetry is one of important
evaluation items. In order to realize an excellent flight symmetry,
dimples should be evenly present on the surface of the golf ball.
For this reason, usually, plural kinds of circular dimples are
provided in combination. While the diameter and depth of the
circular dimple have been variously improved as described above,
the relation of the diameter between dimple types and the relation
of the depth between dimple types has rarely been investigated for
a conventional golf ball. Usually, a dimple kind having a great
diameter has a great depth or the depth is equal for each type. The
present inventor has examined that a value of (de-Di.times.0.04) is
-0.02 to 0.02, wherein a diameter is represented by Di and a depth
is represented by de in the general circular dimple.
[0007] Although the main role of the dimple has an enhancement in
the lift of the golf ball as described above, a golf ball having an
excessively great lift provides an insufficient flight distance by
the head wind. Moreover, while the flight distance of a golf ball
having a comparatively great lift is great in a driver shot, a
trajectory tends to be too high in an iron shot so that the flight
distance is reduced. To the contrary, in case of a golf ball having
a great flight distance in the iron shot, a lift becomes
insufficient in the driver shot so that a flight duration becomes
insufficient and a flight distance is reduced (so-called drop).
Moreover, in case of a golf player having a low head speed, a golf
ball having a great lift tends to provide a great flight distance.
When such a golf ball is hit by a golf player having a high head
speed, a trajectory tends to be excessively high so that the flight
distance is reduced. To the contrary, in case of a golf player
having a high head speed, a golf ball having a small lift tends to
provide a great flight distance. When such a golf ball is hit by a
golf player having a low head speed, the flight duration becomes
insufficient so that the flight distance is reduced. A golf player
is very interested in making a good score and causing the golf ball
to fly to a distance. A large number of golf players have desired a
golf ball capable of providing a flight distance under any
circumstance.
[0008] In consideration of the circumstances, it is an object of
the present invention to provide a golf ball having an excellent
flight performance.
SUMMARY OF THE INVENTION
[0009] In order to achieve the object, the present invention
provides a golf ball comprising, on a surface thereof, a large
number of dimples including plural kinds of circular dimples having
different diameters from each other,
[0010] wherein when kinds of circular dimples having a ratio of 5%
or more to the total number of dimples is set to be specific
circular dimple kinds, there are two or more specific circular
dimple kinds, and
[0011] when a kind having a minimum diameter in the specific
circular dimple kinds is set to be a minimum circular dimple kind,
a specific circular dimple kind having a maximum mean depth in all
the specific circular dimple kinds is set to be a minimum circular
dimple kind.
[0012] In the golf ball, it is possible to obtain a trajectory
having a comparatively small height and a sufficient flight
duration by the presence of the minimum circular dimple kind in the
specific circular dimple kinds which has a maximum mean depth and a
minimum diameter. Accordingly, a great flight distance can be
obtained irrespective of a wind direction, a used club and a head
speed. The reason why such an advantage can be obtained is not
clear. However, it can be supposed that a contribution ratio to an
enhancement in the lift of the minimum circular dimple kind is low
in the first half of a trajectory having a high flight speed (up to
the highest point) and a contribution ratio to the enhancement in
the lift of the minimum circular dimple kind is high in the second
half of a trajectory having a low flight speed.
[0013] It is preferable that a ratio of the number of dimples of
the minimum circular dimple kind to the total number of dimples is
10% or more. Consequently, the effect of enhancing a flight
distance can be produced remarkably.
[0014] It is preferable that a value of K calculated by an equation
(I) in the minimum circular dimple kind is 0.03 or more:
K=de-Di.times.0.04 (I)
[0015] (wherein Di represents a diameter of the specific circular
dimple kind and de represents a mean depth of the specific circular
dimple kind).
[0016] Consequently, the effect of enhancing a flight distance can
be produced more remarkably.
[0017] It is preferable that the value of K calculated by the
equation (I) in the specific circular dimple kinds excluding the
minimum circular dimple kind is -0.02 to 0.02. Consequently, a
difference between the minimum circular dimple kind and other
specific circular dimple kinds becomes clear so that the effect of
enhancing a flight distance can be increased by the minimum
circular dimple kind.
[0018] It is preferable that the golf ball should have three or
more specific circular dimple kinds. Consequently, the dimple
effects of enhancing a lift and reducing a drag can be produced
still more.
[0019] It is preferable that a ratio of a total dimple area to a
surface area of a virtual sphere of the ball is 70% to 90% and a
total dimple volume is 250 mm.sup.3 to 350 mm.sup.3. Consequently,
it is possible to obtain a golf ball having a great flight
distance.
[0020] The present invention will be described below in detail
based on a preferred embodiment with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a plan view showing a golf ball according to an
embodiment of the invention,
[0022] FIG. 2 is a front view showing the golf ball in FIG. 1,
and
[0023] FIG. 3 is an enlarged sectional view showing a part of the
golf ball in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] A golf ball shown in FIGS. 1 and 2 usually has a diameter of
approximately 42.67 mm to 43.00 mm. The golf ball has three kinds
of dimples A to C on a surface thereof. FIG. 2 shows the dimple
kinds (that is, A, B and C) in one compartment obtained by dividing
a hemisphere into ten portions. A dimple pattern identical to or
symmetrical with a dimple pattern in the compartment is developed
over the whole sphere so that a whole dimple pattern can be
obtained.
[0025] All of the A, B and C dimples are circular. The number of
the A dimples is 70, the number of the B dimples is 210 and the
number of the C dimples is 130. Accordingly, the total number of
the dimples of the golf ball is 410. The ratio of the number of the
A dimples to the total number of the dimples is 17%, the ratio of
the number of the B dimples to the total number of the dimples is
51%, and the ratio of the number of the C dimples to the total
number of the dimples is 32%. In the present invention, the kind of
the circular dimple having a ratio of 5% or more to the total
number of the dimples is a specific circular dimple kind. All of
the A dimples, the B dimples and the C dimples are the specific
circular dimple kinds. The golf ball has three specific circular
dimple kinds.
[0026] FIG. 3 is an enlarged sectional view showing a part of the
golf ball in FIG. 1. In FIG. 3, the vicinity of the circular dimple
is shown. In FIG. 3, points X and Y are boundaries of a virtual
spherical surface Sb and a dimple surface Sd in the golf ball. A
segment Di connects the points X and Y and is a diameter of a
circular dimple. Moreover, a space between the segment Di and the
deepest portion of the dimple surface Sd has a depth of de.
Moreover, the volume of a region surrounded by a horizontal plane
including the segment Di and the dimple surface Sd indicates a
dimple volume and the sum of the volumes of all the dimples
indicates a total dimple volume. Furthermore, the area of a circle
having the diameter Di indicates a dimple area and the sum of
dimple areas of all the dimples indicates a total dimple area.
[0027] In the present invention, the specific circular dimple kind
having a minimum diameter will be hereinafter referred to as a
minimum circular dimple kind. In the golf ball shown in FIGS. 1 and
2, the A dimple has a diameter of 4.1 mm, the B dimple has a
diameter of 3.8 mm and the C dimple has a diameter of 3.35 mm. In
the golf ball, accordingly, the C dimple has the minimum circular
dimple kind. For example, also in the case in which the A dimple is
formed in a process for manufacturing a golf ball, the diameter of
the dimple has a deviation from 4.1 mm due to a manufacturing error
in some cases. In the present invention, the dimple making such a
manufacturing error is also set to be the A dimple. Usually, an
error may be made within a range of .+-.0.1 mm with respect to a
design value. The depth of each of the A dimples may also make a
manufacturing error in some cases. Furthermore, a deep A dimple and
a shallow A dimple are arranged in the design stage in some cases.
A mean value of the depths of all the A dimples is set to be a mean
depth of the A dimple, and so are other specific circular dimple
kinds.
[0028] In the golf ball, the mean depth of the C dimple is greater
than that of each of the A dimple and the B dimple. Accordingly, a
specific circular dimple kind having a maximum mean depth is the
minimum circular dimple kind (that is, the C dimple).
[0029] In the golf ball, a trajectory is comparatively low by the
presence of the C dimple and can be thereby prevented from being
excessively high. In addition, the flight duration is not extremely
short. Accordingly, the golf ball can also be prevented from being
dropped. In the golf ball, therefore, a flight distance can be
prevented from being extremely reduced by the head wind. Moreover,
even if the golf ball is hit with any of a wood club such as a
driver, a long iron, a middle iron and a short iron, a flight
distance can be obtained to some extent. In addition, the golf ball
can provide a flight distance to some extent irrespective of the
head speed of a golf player.
[0030] In some cases, the mold of the golf ball is provided with a
hold pin in order to hold a core and easily carry out releasing. In
some cases, moreover, a vent pin is provided for ventilation from a
cavity. The tips of the pins are convex in respect of a dimple
pattern design, and the mold is constituted such that a dimple can
also be formed by the tip of the pin in some cases (the dimple will
be hereinafter referred to as a "pin tip dimple"). The pin tip
dimple has a specific shape or a very small size in some cases. The
number of the pin tip dimples is usually very small, that is,
approximately 6 to 14. In some cases, moreover, the small number of
minimum dimples are provided in order to reduce a land portion (a
portion on the surface of the golf ball other than the dimples) or
the small number of maximum dimples are provided in respect of the
dimple pattern design in some cases. The kind of the small number
of dimples provided on the surface of the golf ball less influence
the flight performance of the golf ball. In the present invention,
"the ratio of the number of dimples to the total number of dimples
is 5% or more" is a requirement for the specific circular dimple
kind based on the effect that the number of substantially minimum
dimple kinds is defined excluding the small number of dimple
kinds.
[0031] The ratio of the number of the dimples of the minimum
circular dimple kinds (the C dimple in this example) to the total
number of the dimples is preferably 10% or more, and more
preferably 15% or more. Consequently, it is possible to further
produce the advantage of the minimum circular dimple kind that a
trajectory can be reduced and a drop can be suppressed.
[0032] It is preferable that a value of K in the minimum circular
dimple kind which is calculated by the equation (I) should be 0.03
or more. A circular dimple having a value of K of 0.03 or more is
small and deep. By providing such a minimum circular dimple kind,
it is possible to further produce the advantage of the minimum
circular dimple kind that the trajectory can be lowered and the
drop can be suppressed. If the value of K is too great, the golf
ball is formed with difficulty and the dimple is easily clogged
with dust. Therefore, the value of K is preferably 0.10 or less,
more preferably 0.08 or less, and most preferably 0.05 or less. In
order to obtain a golf ball having an excellent flight performance,
it is necessary to achieve a proper total dimple volume and a
proper surface area occupation ratio as will be described below in
detail. In this respect, it is preferable that the values of K in
specific circular dimple kinds other than the minimum circular
dimple kind should be -0.02 to 0.02.
[0033] It is preferable that the surface area occupation ratio (the
ratio of the total area of the dimples to the surface area of the
virtual sphere of a ball) should be 70% to 90%. If the surface area
occupation ratio is less than 70%, the trajectory becomes too high
in a second half. In this respect, it is particularly preferable
that the surface area occupation ratio should be 75% or more. It is
hard to attain a dimple pattern having a surface area occupation
ratio which is more than 90%. In this respect, it is particularly
preferable that the surface area occupation ratio should be 85% or
less.
[0034] It is preferable that the total dimple volume should be 250
mm.sup.3 to 350 mm.sup.3. In some cases in which the total dimple
volume is less than 250 mm.sup.3, the trajectory becomes too high.
In this respect, it is particularly preferable that the total
dimple volume is 290 mm.sup.3 or more. To the contrary, if the
total dimple volume is more than 350 mm.sup.3, the trajectory might
be dropped. In this respect, it is particularly preferable that the
total dimple volume should be 330 mm.sup.3 or less.
[0035] The diameter of the specific circular dimple kind is usually
2.0 mm to 5.0 mm, preferably 2.2 mm to 4.8 mm, and more preferably
2.4 mm to 4.6 mm. Moreover, the diameter of the minimum circular
dimple kind is usually 2.0 mm to 4.0 mm, preferably 2.2 mm to 3.8
mm, and more preferably 2.4 mm to 3.6 mm.
[0036] The mean depth of the specific circular dimple kind is
usually 0.05 mm to 0.28 mm, preferably 0.06 mm to 0.26 mm, and more
preferably 0.07 mm to 0.24 mm. Moreover, the mean depth of the
minimum circular dimple kind is usually 0.10 mm to 0.30 mm,
preferably 0.13 mm to 0.28 mm, and more preferably 0.15 mm to 0.25
mm.
[0037] In the present invention, there are two or more specific
circular dimple kinds. Since plural kinds of specific circular
dimple kinds are present together, an air flow is more disturbed
when the golf ball flies. Consequently, it is possible to
sufficiently produce dimple effects that a lift can be enhanced and
a drag can be reduced. By using plural kinds of specific circular
dimple kinds, moreover, the degree of freedom for the design of a
dimple pattern can be enhanced. As a result, it is possible to
obtain a golf ball which has an excellent even aerodynamic
characteristic (a difference in the aerodynamic characteristic is
small even if the golf ball is rotated in any direction). In this
respect, it is preferable that three or more specific circular
dimple kinds should be provided. If the number of the specific
circular dimple kinds is too large, the number of the dimples for
each specific circular dimple kind is decreased, and furthermore,
it is hard to manufacture a mold. From this viewpoint, it is
preferable that the number of the specific circular dimple kinds is
20 or less, preferably 10 or less, and more preferably 8 or
less.
[0038] While all the dimples formed in the golf ball shown in FIGS.
1 and 2 are circular, the circular dimple and a non-circular dimple
may be present together.
[0039] The structure of the golf ball according to the present
invention is not particularly restricted. By forming the
above-mentioned dimple pattern, it is possible to obtain the effect
of enhancing a flight performance in a wound golf ball having a
wound core and a solid golf ball (a one-piece golf ball, a
two-pieces golf ball and a multi-piece golf ball).
EXAMPLES
EXAMPLE 1
[0040] A core formed of a solid rubber was put in a mold and an
ionomer resin composition was subjected to injection molding to
form a cover around the core. The surface of the cover was coated
so that a golf ball according to an example 1 which has a dimple
pattern shown in a plan view of FIG. 1 and a front view of FIG. 2
was obtained. An A dimple had a mean depth of 0.1541 mm, a B dimple
had a mean depth of 0.1421 mm, and a C dimple had a mean depth of
0.1668 mm. Moreover, a total dimple volume was 300 mm.sup.3 and a
surface area occupation ratio was 77.7%. Moreover, the golf ball
had an outside diameter of approximately 42.70 mm, a weight of
approximately 45.4 g and a compression of approximately 90 (by an
ATTI compression tester produced by Atti Engineering Co.,
Ltd.).
EXAMPLE 2 AND COMPARATIVE EXAMPLES 1 AND 2
[0041] Golf balls according to an example 2 and comparative
examples 1 and 2 were obtained in the same manner as in the example
1 except that a mold was changed. The dimple patterns of the golf
balls are the same as the dimple pattern of the golf ball according
to the example 1 and have dimple depths different from the dimple
depth according to the example 1. Moreover, a value of K and a
total dimple volume are also different from those in the example 1
with a variation in the dimple depth. The dimple depth, the value
of K and the total dimple volume are shown in the following Table
1.
Flight Distance Test
[0042] A golf ball according to each of the examples and the
comparative examples was launched by the "ULTRA BALL LAUNCHER"
produced by Wilson Co., Ltd. and a trajectory, a carry (a distance
from a hitting point to a dropping point) and a total flight
distance (a distance from the hitting point to a stationary point)
were measured. A mean value of results of measurement for 20 golf
balls is shown in the following Table 1. The flight distance test
was carried out for each of the golf balls on the following three
conditions.
1 Condition 1 (target values) A launch speed of a golf ball 73 m/s
A launch angle of a golf ball 12 degrees An initial back spin speed
2800 rpm
[0043] The condition 1 is almost equal to the condition on which a
golf player having a high head speed hits the golf ball with a
driver.
2 Condition 2 (target values) A launch speed of a golf ball 58 m/s
A launch angle of a golf ball 12 degrees An initial back spin speed
2800 rpm
[0044] The condition 2 is almost equal to the condition on which a
golf player having a low head speed hits the golf ball with a
driver.
3 Condition 3 (target values) A launch speed of a golf ball 49 m/s
A launch angle of a golf ball 15 degrees An initial back spin speed
4500 rpm
[0045] The condition 3 is almost equal to the condition on which a
golf player hits the golf ball with a No. 5 iron.
4TABLE 1 Result of Flight Distance Test Ex. 1 Ex. 2 Com. Ex. 1 Com.
Ex. 2 A dimple Number 70 70 70 70 Diameter (mm) 4.1 4.1 4.1 4.1
Depth (mm) 0.1541 0.1638 0.1651 0.1748 K value -0.01 0.00 0.00 0.01
B dimple Number 210 210 210 210 Diameter (mm) 3.8 3.8 3.8 3.8 Depth
(mm) 0.1421 0.1518 0.1531 0.1628 K value -0.01 0.00 0.00 0.01 C
dimple Number 130 130 130 130 Diameter (mm) 3.35 3.35 3.35 3.35
Depth (mm) 0.1668 0.1766 0.1351 0.1448 K value 0.03 0.04 0.00 0.01
Total dimple volume (mm.sup.3) 300 320 300 320 Surface area
occupation 77.7 77.7 77.7 77.7 ratio (%) Condi- Trajectory
elevation 14.0 13.8 14.2 13.9 tion 1 angle (deg) Carry (m) 245.6
244.5 242.6 243.6 Total (m) 250.8 249.9 247.3 248.5 Condi-
Trajectory elevation 11.9 11.8 12.0 11.8 tion 2 angle (deg) Carry
(m) 185.4 184.1 184.4 181.1 Total (m) 207.5 202.7 202.5 199.1
Condi- Trajectory elevation 14.5 14.4 14.8 14.6 tion 3 angle (deg)
Carry (m) 150.1 149.0 146.1 149.2 Total (m) 155.2 154.3 151.2
153.8
[0046] In the Table 1, the golf balls according to the examples 1
and 2 have great flight distances on any condition. The golf ball
according to the present invention has an excellent flight
performance irrespective of a wind direction, a golf player and a
used/club. The advantages of the present invention are apparent
from the results of evaluation.
[0047] The above description is only illustrative and can be
variously changed without departing from the scope of the present
invention.
* * * * *