U.S. patent application number 10/208739 was filed with the patent office on 2003-02-13 for golf club head.
Invention is credited to Mori, Tomoaki, Nakahara, Norihiko, Nishizawa, Yoh.
Application Number | 20030032500 10/208739 |
Document ID | / |
Family ID | 19067645 |
Filed Date | 2003-02-13 |
United States Patent
Application |
20030032500 |
Kind Code |
A1 |
Nakahara, Norihiko ; et
al. |
February 13, 2003 |
Golf club head
Abstract
A golf club head is disclosed, which enables a low center of
gravity to be achieved without spoiling appearance of the head and
reducing strength thereof, and thus enables a carry to be
increased. This golf club head has a hollow structure, and includes
an opening in a crown portion and a plate member fixed to the
opening. The plate member is made of a material having a specific
strength of 294 N/mm.sup.2 or higher. For example, this head
includes a volume equal to or more than 350 cc, a center-of-gravity
retreating amount GR from a shaft axis equal to or more than 15 mm,
and a center-of-gravity position ratio GH/FH equal to or lower than
0.61. Here, the ratio GH/FH is calculated from a maximum height FH
of a face surface and a center-of-gravity height GH on the face
surface.
Inventors: |
Nakahara, Norihiko;
(Hiratsuka-shi, JP) ; Nishizawa, Yoh;
(Hiratsuka-shi, JP) ; Mori, Tomoaki;
(Hiratsuka-shi, JP) |
Correspondence
Address: |
Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Family ID: |
19067645 |
Appl. No.: |
10/208739 |
Filed: |
August 1, 2002 |
Current U.S.
Class: |
473/345 ;
473/346 |
Current CPC
Class: |
A63B 53/0466 20130101;
A63B 53/0412 20200801; A63B 2053/0491 20130101; A63B 53/0408
20200801; A63B 53/047 20130101; A63B 60/42 20151001; A63B 60/00
20151001; A63B 53/04 20130101 |
Class at
Publication: |
473/345 ;
473/346 |
International
Class: |
A63B 053/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2001 |
JP |
JP2001-236362 |
Claims
What is claimed is:
1. A golf club head having a hollow structure, comprising: a crown
portion; an opening in the crown portion; and a plate member fixed
to the opening, the plate member being made of a material having a
specific strength of 294 N/mm.sup.2 or higher.
2. A golf club head having a hollow structure, the head including:
a volume equal to or more than 350 cc; a center-of-gravity
retreating amount GR from a shaft axis equal to or more than 15 mm;
and a center-of-gravity position ratio GH/FH equal to or lower than
0.61, the ratio GH/FH being calculated from a maximum height FH of
a face surface and a center-of-gravity height GH on the face
surface.
3. A golf club head having a hollow structure, the head including:
a volume equal to or more than 300 cc but less than 350 cc; a
center-of-gravity retreating amount GR from a shaft axis equal to
or more than 18 mm; and a center-of-gravity position ratio GH/FH
equal to or lower than 0.55, the ratio GH/FH being calculated from
a maximum height FH of a face surface and a center-of-gravity
height GH on the face surface.
4. A golf club head having a hollow structure, the head including:
a volume equal to or more than 150 cc but less than 200 cc; a
center-of-gravity retreating amount GR from a shaft axis equal to
or more than 12 mm; and a center-of-gravity position ratio GH/FH
equal to or lower than 0.50, the ratio GH/FH being calculated from
a maximum height FH of a face surface and a center-of-gravity
height GH on the face surface.
5. A golf club head having a hollow structure, the head including:
a volume equal to or more than 100 cc but less than 150 cc; a
center-of-gravity retreating amount GR from a shaft axis equal to
or more than 8 mm; and a center-of-gravity position ratio GH/FH
equal to or lower than 0.50, the ratio GH/FH being calculated from
a maximum height FH of a face surface and a center-of-gravity
height GH on the face surface.
6. The golf club head according to any one of claims 2 to 5,
wherein an opening is provided in a crown portion, and a plate
member made of a material having a specific strength of 294
N/mm.sup.2 or higher is fixed to the opening.
7. The golf club head according to claim 1, wherein a surface area
ratio of the plate member to a portion above a position at half a
maximum height of the crown portion is set equal to or higher than
20%.
8. The golf club head according to claim 6, wherein a surface area
ratio of the plate member to a portion above a position at half a
maximum height of the crown portion is set equal to or higher than
20%.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a golf club head having a
hollow structure. More specifically, the invention relates to a
golf club head capable of increasing a carry by setting a low
center of gravity to reduce a spin of a ball and increase a launch
angle.
[0002] Conventionally, a metal golf club head having a hollow
structure has been used for a golf club such as a utility club, a
fairway wood and a #1 wood. In such a golf club head, because of
use of metallic materials not only for face and sole portions but
also for a crown portion, the center of gravity has been high.
Especially, in the case of using a titanium material for a
deep-face head of the #1 wood, the head having a volume of 300 to
400 cc, even if the head is designed based on a limit thickness to
secure minimum necessary strength, a limitation on maximum head
weight makes it difficult to adjust a position of a center of
gravity by deviation in a weight distribution. Thus, it has been
difficult to achieve a low center of gravity.
[0003] On the other hand, Japanese patent application Kokai
publication No. 5-317465 describes a golf club head having no
metallic materials disposed on the crown portion. However, this
golf club head has a hole bored on the crown portion, or only has a
plate of a lightweight resin or the like attached to the crown
portion. Consequently, an appearance of the head has been bad, and
strength thereof has been insufficient.
SUMMARY OF THE INVENTION
[0004] An object of the present invention is to provide a golf club
head capable of achieving a low center of gravity even in the case
of a so-called deep-face head without spoiling appearance of the
head and without reducing strength thereof, thereby reducing a spin
of a ball and increasing a launch angle to increase a carry.
[0005] In order to achieve the foregoing object, a golf club head
of the present invention includes an opening in a crown portion,
and a plate member fixed to the opening, the plate member being
made of a material having a specific strength of 294 N/mm.sup.2 or
higher.
[0006] Here, the specific strength is a result of dividing a
tensile strength (N/mm.sup.2) by a specific gravity, and it means
that as the specific strength is larger, the strength is higher
while weight is light. Accordingly, by replacing a metallic
material of the crown portion with the plate member, it is possible
to achieve a low center of gravity even in a so-called deep-face
golf club head without spoiling the appearance of the head and
without reducing the strength thereof. The achievement of the low
center of gravity enables the spin of a ball to be reduced, the
launch angle to be increased, and thus the carry to be increased to
a maximum.
[0007] In order to achieve a satisfactorily low center of gravity
of the golf club head, preferably, a surface area ratio of the
plate member to a portion above a position at half a maximum height
of the crown portion is set equal to or higher than 20%.
[0008] According to the present invention, it is possible to
provide a novel golf club head having a hollow structure, which is
provided with a weight distribution that has never existed in the
conventional art.
[0009] That is, the present invention provides a golf club head
having a hollow structure, which includes a volume equal to or more
than 350 cc, a center-of-gravity retreating amount GR from a shaft
axis equal to or more than 15 mm, and a center-of-gravity position
ratio GH/FH equal to or lower than 0.61, the ratio GH/FH being
calculated from a maximum height FH of a face surface and a
center-of-gravity height GH on the face surface.
[0010] The present invention provides a golf club head having a
hollow structure, which includes a volume equal to or more than 300
cc but less than 350 cc, a center-of-gravity retreating amount GR
from the shaft axis equal to or more than 18 mm, and a
center-of-gravity position ratio GH/FH equal to or lower than 0.55,
the ratio GH/FH being calculated from the maximum height FH of the
face surface and the center-of-gravity height GH on the face
surface.
[0011] The present invention further provides a golf club head
having a hollow structure, which includes a volume equal to or more
than 150 cc but less than 200 cc, a center-of-gravity retreating
amount GR from the shaft axis equal to or more than 12 mm, and a
center-of-gravity position ratio GH/FH equal to or lower than 0.50,
the ratio GH/FH being calculated from the maximum height FH of the
face surface and the center-of-gravity height GH on the face
surface.
[0012] The present invention still further provides a golf club
head having a hollow structure, which includes a volume equal to or
more than 100 cc but less than 150 cc, a center-of-gravity
retreating amount GR from the shaft axis equal to or more than 8
mm, and a center-of-gravity position ratio GH/FH equal to or lower
than 0.50, the ratio GH/FH being calculated from the maximum height
FH of the face surface and the center-of-gravity height GH on the
face surface.
[0013] Each of the above-described golf club heads can be achieved
by providing an opening in a crown portion, and fixing a plate
member made of a material having a specific strength of 294
N/mm.sup.2 or higher to the opening. However, it should be
understood that a golf club head having the above-described weight
distribution achieved by other means is also contained within the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a front view showing a golf club head according to
an embodiment of the present invention.
[0015] FIG. 2 is a side view showing the golf club head of the
embodiment of the invention.
[0016] FIG. 3 is a sectional view taken along a line X-X of FIG.
1.
[0017] FIG. 4 is a front view of a peripheral portion of the golf
club head for illustrating definition of a club length according to
the invention.
[0018] FIG. 5 is a front view of a peripheral portion of a golf
club grip for illustrating the definition of the club length of the
invention.
[0019] FIG. 6 is a side view showing an example of measuring device
of a center-of-gravity retreating amount.
[0020] FIG. 7 is a side view showing measurement of the
center-of-gravity retreating amount by the measuring device of FIG.
6.
[0021] FIG. 8 is a perspective view showing a measuring device of a
center of gravity of the head.
[0022] FIG. 9 is a side view showing a measuring method of the
center of gravity of the head in a state where the head is mounted
on the center-of-gravity measuring device.
[0023] FIGS. 10(a) and 10(b) show the measuring method of the
center of gravity of the head: FIG. 10(a) being a side view showing
a state where the head is mounted on a position balanced with
respect to the center-of-gravity measuring device; and FIG. 10(b)
being a side view showing a state where the head is mounted on a
position unbalanced with respect to the center-of-gravity measuring
device.
[0024] FIG. 11 is a side view showing a method of checking
levelness of a supporting portion of the center-of-gravity
measuring device in a state where a level is placed on the
center-of-gravity measuring device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Next, detailed description will be made for a constitution
of the present invention with reference to the accompanying
drawings.
[0026] Each of FIGS. 1 to 3 shows a golf club head according to an
embodiment of the present invention. As shown in FIGS. 1 and 2, the
golf club head of the embodiment has a hollow structure, in which a
crown portion 2 and a sole portion 3 are connected to a face
portion 1 to be continuous. This golf club head also includes a
hosel portion 4 provided on a heel side for fixing a shaft. As a
material constituting the golf club head, a metallic material such
as titanium, aluminum or stainless steel can be used.
[0027] In the golf club head, an opening 2a is provided in the
crown portion 2, and a plate member 5 is fixed to the opening 2a.
This plate member 5 is made of a material having a specific
strength of 294 N/mm.sup.2 or higher. The upper limit of the
specific strength is not especially limited in view of the
function, and the higher specific strength can be selected as long
as materials having the higher specific strength exist. As a
material constituting the plate member 5, a fiber reinforced
plastic is available, which is prepared by impregnating a
reinforced fiber such as a carbon fiber, a glass fiber and an
alamido fiber with a matrix resin such as an epoxy resin, an
unsaturated polyester resin and a vinylester resin. Especially, the
carbon fiber is preferred as a reinforced fiber. Preferably, a
material constituting the plate member 5 has a specific gravity of
0.5 to 2.0.
[0028] By replacing the metallic material of the crown portion 2
with the plate member 5 made of a material having such a high
specific strength, a weight distribution in an upper part of the
head is relatively reduced to lower a center of gravity G of the
golf club head. Moreover, since the plate member 5 is present on
the crown portion 2 to prevent exposure of the opening 2a, the
appearance of the head is not spoiled. Since the specific strength
of the plate member 5 is high, no reduction occurs in strength of
the head. Accordingly, a low center of gravity can be achieved even
in the case of the golf club head having a large volume and a deep
face (face having a vertical width of, e.g., 46 mm or more). The
lower center of gravity reduces a spin of a ball and increases a
launch angle, thereby enabling a carry to be increased to a
maximum.
[0029] In the foregoing golf club head, as shown in FIG. 2,
preferably, a surface area ratio of the plate member 5 to a portion
above a position at half a maximum height MH of the crown portion 2
is set equal to or higher than 20%. Accordingly, by setting the
surface area ratio of the plate member 5 equal to or higher than
20%, a satisfactorily low center of gravity can be achieved for the
golf club head. The upper limit of the surface area ratio is not
especially limited in view of the function. The upper limit,
however, is preferably set to 90% in consideration of the structure
of the golf club head.
[0030] The plate member 5 can be adhered to the opening 2a of the
crown portion 2. For example, as shown in FIG. 3, a step is formed
on a peripheral edge of the opening 2a of the crown portion 2. On
the other hand, a peripheral edge of the plate member 5 is
processed to match the step and adhered to the opening 2a. When
necessary, a plate member 6 made of a similar material to the plate
member 5 may be adhered to the plate member 5 from the inner side
of the head. Accordingly, the plate member 5 can be firmly fixed to
the crown portion 2. Needless to say, the method of fixing the
plate member 5 is not limited to the above, but other methods can
be used. The presence of the plate member 5 is apparent in the
drawing, but the appearance of the golf club head is not affected
at all if paint is applied.
[0031] According to the present invention, the following golf club
heads can be constructed.
[0032] As a first golf club head, a golf club head is provided,
which includes a volume equal to or more than 350 cc, a
center-of-gravity retreating amount GR from a shaft axis S equal to
or more than 15 mm, and a center-of-gravity position ratio GH/FH
equal to or lower than 0.61, more preferably equal to or lower than
0.55, the ratio GH/FH being calculated from a maximum height FH of
a face surface 1a and a center-of-gravity height GH on the face
surface 1a. In this case, the upper limit of the volume of the golf
club head is not especially limited in view of the function. The
upper limit, however, is preferably set to 600 cc, preferably 500
cc, more preferably 400 cc in order to obtain necessary strength to
the hit ball.
[0033] As a second golf club head, a golf club head is provided,
which includes a volume equal to or more than 300 cc but less than
350 cc, a center-of-gravity retreating amount GR from the shaft
axis S equal to or more than 18 mm, and a center-of-gravity
position ratio GH/FH equal to or lower than 0.55, more preferably
equal to or lower than 0.50, the ratio GH/FH being calculated from
the maximum height FH of the face surface 1a and the
center-of-gravity height GH on the face surface 1a.
[0034] As a third golf club head, a golf club head is provided,
which includes a volume equal to or more than 150 cc but less than
200 cc, a center-of-gravity retreating amount GR from the shaft
axis S equal to or more than 12 mm, and a center-of-gravity
position ratio GH/FH equal to or lower than 0.50, the ratio GH/FH
being calculated from the maximum height FH of the face surface 1a
and the center-of-gravity height GH on the face surface 1a.
[0035] As a fourth golf club head, a golf club head is provided,
which includes a volume equal to or more than 100 cc but less than
150 cc, a center-of-gravity retreating amount GR from the shaft
axis S equal to or more than 8 mm, and a center-of-gravity position
ratio GH/FH equal to or lower than 0.50, the ratio GH/FH being
calculated from the maximum height FH of the face surface 1a and
the center-of-gravity height GH on the face surface 1a.
[0036] Here, the center-of-gravity retreating amount GR means a
distance between a center of gravity G of the head and a plane
containing the shaft axis S and vertical to a reference surface B
in a state where the head is placed on the reference surface B
according to a lie angle, and the face surface 1a is directed to a
target line.
[0037] The placement according to the lie angle means that gaps
between a round of the sole surface of the head and a placement
surface made of a plane are roughly equal to each other at toe and
heel sides. If the round of the sole surface is unclear, the
placement of the head is made such that a score line and the
placement surface are parallel to each other. If the round of the
sole surface is unclear, and the placement surface and the score
line cannot be determined to be parallel to each other, for example
in the case where the score line is not linear, the head is placed
with the lie angle (degree) (=100-club length (inch)). For example,
if the club length is 44 inches, the lie angle is 56.degree.
(=100-44).
[0038] The club length is measured by a measuring method set up by
the Japan Golf Goods Association. As a measuring device, Club
Measure II by Kamoshita Seikojo Co., Ltd., or the like is
available. That is, as shown in FIGS. 4 and 5, when a heel end is
set as a base point P.sub.1, and a grip end is set as an end point
P.sub.2, then a distance C between the points P.sub.1 and P.sub.2
is set as the club length.
[0039] As shown in FIG. 6, the above-described center-of-gravity
retreating amount GR is measured by a seesaw balance 10 swingable
in an arrow direction U around a fulcrum 11. The balance 10
includes a shaft pin 12 to be fitted into the hosel hole of the
head without any gaps therebetween. The balance 10 is balanced in
such a way as to set an arm 13 horizontal while no heads or heavy
bodies are placed thereon. Here, as shown in FIG. 7, a head 31 of
mass W is fitted over the shaft pin 12 extended in a vertical
direction. The head 31 is then rotated and fixed so as to enable
the center-of-gravity retreating amount GR to be measured in an arm
longitudinal direction. In other words, the center-of-gravity
retreating amount GR coincides with a distance L between a plane P
passed through the fulcrum and set orthogonal to the arm
longitudinal direction and the center of gravity G of the head 31.
In the side view of the balance 10, the face surface 1a is somewhat
seen because of presence of a loft angle and the lie angle in the
head 31.
[0040] Then, by using a heavy body 14 of mass W', a length L' from
a center of gravity G' of the heavy body 14 to the fulcrum is
selected such that the arm 13 is horizontally balanced. As a
result, the center-of-gravity retreating amount GR can be
calculated by GR=L=(W'.times.L')/W based on an equation of
equilibrium W.times.L=W'.times.L'. The above description has been
made on the principle of measuring the center-of-gravity retreating
amount GR from the shaft axis. As a measuring device, a
center-of-gravity measuring device by Kamoshita Seikojo Co., Ltd.,
can be used.
[0041] On the other hand, as shown in FIG. 3, the maximum height FH
of the face surface is a height from the reference surface B to a
highest position of the face surface 1a while the head is placed on
the reference surface B according to the lie angle, and the face
surface 1a is directed to the target line. The center-of-gravity
height GH on the face surface is a height from the reference
surface B to a point g in a placement state of the head similar to
the above when a center of gravity position on the face surface 1a
is obtained, the center of gravity position being composed of the
point g at which a perpendicular from the center of gravity G to
the face surface 1a intersects the face surface 1a.
[0042] The point g on the face surface 1a of the head is obtained
by a center-of-gravity measuring device 41 similar to that shown in
FIG. 8. The center-of-gravity measuring device 41 includes a
supporting portion 42 for supporting an article to be measured for
a center of gravity thereon. This supporting portion 42 supports
the article to be measured in a balanced manner, and a position of
the article can be known. That is, when the center-of-gravity
position on the face surface 1a is obtained, as shown in FIG. 9,
the head 31 is mounted on the supporting portion 42, and an
equilibrium position, at which the head 31 does not fall off even
with hands off the head, is searched. In other words, as shown in
FIG. 10(a), if the point g is contained in a contact portion
between the face surface 1a and the supporting portion 42, the head
31 mounted on the supporting portion 42 will not fall off even with
hands off the head. However, as shown in FIG. 10(b), if the point g
is not contained in the contact portion between the face surface 1a
and the supporting portion 42, the head 31 mounted on the
supporting portion 42 will fall off with hands off the head. The
point g is obtained based on this.
[0043] Preferably, the supporting portion 42 supports the article
on a plane or at three points or more. Preferably, an area of the
supporting portion 42 is set equal to 15 mm.sup.2 or less. There is
no lower limit on the area as long as the head 31 can be supported.
The area of the supporting portion 42 is represented by an area of
a planar part in the case of the support on the plane, and by an
area of a figure connecting the respective points in the case of
the support at three points or more. By setting the area of the
supporting portion in the above range, the point g can be obtained
more accurately.
[0044] Preferably, the plane formed by the supporting portion 42
becomes horizontal or substantially horizontal. Here, the state of
being substantially horizontal means that an inclination with
respect to a horizontal plane is within 2.degree., preferably
within 1.degree.. The state of being either horizontal or
substantially horizontal can be checked by mounting and supporting
a plate 51 on the supporting portion 42, and placing a level 52 on
the plate 51. By setting the inclination of the plane of the
supporting portion 42 within the above range, the point g can be
obtained more accurately.
[0045] The foregoing center-of-gravity retreating amount GR is an
important factor for lofting a hit ball. The upper limit of the
center-of-gravity retreating amount GR is not especially limited in
view of the function. The upper limit, however, is preferably set
to, in consideration of arrangement of the hosel position and
weight distribution of the golf club head, 70 mm when the volume is
equal to or more than 350 cc, 70 mm when the volume is equal to or
more than 300 cc but less than 350 cc, 55 mm when the volume is
equal to or more than 150 cc but less than 200 cc, or 50 mm when
the volume is equal to or more than 100 cc but less than 150 cc. By
setting the center-of-gravity retreating amount GR in the above
range, a sufficient launch angle can be obtained.
[0046] The center-of-gravity position ratio GH/FH is an index for
setting a low center of gravity. The lower limit of the
center-of-gravity position ratio is not especially limited in view
of the function. The lower limit, however, is preferably set to, in
consideration of weight distribution of the golf club head, 0.35
when the volume is equal to or more than 350 cc, 0.33 when the
volume is equal to or more than 300 cc but less than 350 cc, 0.30
when the volume is equal to or more than 150 cc but less than 200
cc, 0.30 when the volume is equal to or more than 100 cc but less
than 150 cc. By setting the center-of-gravity position ratio in the
above range, a sufficient carry can be obtained.
[0047] Especially, if the volume of the head is set large as in the
cases of the first and second golf club heads, it is possible to
increase the center-of-gravity retreating amount GR as much as
possible, and reduce the center-of-gravity position ratio GH/FH as
much as possible without adding any heavy bodies.
[0048] On the other hand, if the volume of the head is set small as
in the cases of the third and fourth golf club heads, it is
possible to increase the center-of-gravity retreating amount GR as
much as possible, and reduce the center-of-gravity position ratio
GH/FH as much as possible without using any metals of high specific
gravity such as expensive tungsten as the heavy bodies.
EXAMPLES
[0049] With regard to a titanium alloy golf club head having a
hollow structure, golf club heads of examples 1 to 4 and
comparative examples 1 to 4 were respectively manufactured, in
which the volumes, the center-of-gravity retreating amounts GR and
the center-of-gravity position ratio GH/FH were varied as shown in
Table 1. In each of the golf club heads of the examples 1 to 4, an
opening was provided in the crown portion, and a plate member made
of carbon reinforced plastic having a specific strength of about
1415 N/mm.sup.2 was fixed to the opening. The surface area ratio of
the plate member to the portion above the position at half the
maximum height of the crown portion is as shown in Table 1.
[0050] Golf clubs having the forgoing golf club heads fixed were
respectively prepared. Test hitting was carried out by a swing
robot at a head speed of 40 m/s while a sweet spot of each golf
club head was set as a hitting position, and the spin, the launch
angle and the carry were evaluated. Results thereof are shown in
Table 1. The results of the evaluation are represented by indexes
using those of the comparative examples 1 to 4 corresponding to the
examples 1 to 4 set as 100. The spin is better as the index value
thereof is smaller, and the launch angle and the carry are better
as the index values thereof are larger.
1 TABLE 1 Surface area ratio of plate Volume GR member Launch (cc)
(mm) GH/FH (%) Spin angle Carry Comparative 396 14.2 0.62 -- 100
100 100 example 1 Example 1 400 16.2 0.51 30.8 94 106 112
Comparative 310 16.0 0.56 -- 100 100 100 example 2 Example 2 335
19.1 0.47 32.0 92 108 113 Comparative 170 13.0 0.53 -- 100 100 100
example 3 Example 3 151 15.0 0.48 27.5 96 105 109 Comparative 135
10.0 0.55 -- 100 100 100 example 4 Example 4 128 12.0 0.46 24.5 97
104 106
[0051] As understood from Table 1, compared with the corresponding
comparative examples 1 to 4, the examples 1 to 4 have less spins,
larger launch angles and longer carries.
[0052] According to the present invention, in the golf club head
having a hollow structure, by providing the opening in the crown
portion and fixing the plate member made of a material having a
specific strength of 294 N/mm.sup.2 or higher to the opening, a low
center of gravity can be achieved even in the case of the deep face
head without spoiling the appearance of the head and without
reducing the strength thereof. Thus, it is possible to reduce the
spin and increase the launch angle, thereby increasing the
carry.
[0053] Also, according to the present invention, by providing each
of following golf club heads (1) to (4), which is provided with a
weight distribution that has never existed in the conventional art,
a low center of gravity can be achieved. Thus, it is possible to
reduce the spin and increase the launch angle, thereby increasing
the carry.
[0054] (1) A golf club head having a hollow structure, which
includes a volume equal to or more than 350 cc, a center-of-gravity
retreating amount GR from a shaft axis equal to or more than 15 mm,
and a center-of-gravity position ratio GH/FH equal to or lower than
0.61, the ratio GH/FH being calculated from a maximum height FH of
a face surface and a center-of-gravity height GH on the face
surface.
[0055] (2) A golf club head having a hollow structure, which
includes a volume equal to or more than 300 cc but less than 350
cc, a center-of-gravity retreating amount GR from the shaft axis
equal to or more than 18 mm, and a center-of-gravity position ratio
GH/FH equal to or lower than 0.55, the ratio GH/FH being calculated
from the maximum height FH of the face surface and the
center-of-gravity height GH on the face surface.
[0056] (3) A golf club head having a hollow structure, which
includes a volume equal to or more than 150 cc but less than 200
cc, a center-of-gravity retreating amount GR from the shaft axis
equal to or more than 12 mm, and a center-of-gravity position ratio
GH/FH equal to or lower than 0.50, the ratio GH/FH being calculated
from the maximum height FH of the face surface and the
center-of-gravity height GH on the face surface.
[0057] (4) A golf club head having a hollow structure, which
includes a volume equal to or more than 100 cc but less than 150
cc, a center-of-gravity retreating amount GR from the shaft axis
equal to or more than 8 mm, and a center-of-gravity position ratio
GH/FH equal to or lower than 0.50, the ratio GH/FH being calculated
from the maximum height FH of the face surface and the
center-of-gravity height GH on the face surface.
[0058] The preferred embodiments of the present invention have been
described in detail. However, it should be understood that various
changes, modifications and substitutions can be made without
departing from the spirit and the scope of the invention as
specified in appended claims.
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