U.S. patent application number 13/230306 was filed with the patent office on 2012-03-15 for golf club head.
This patent application is currently assigned to BRIDGESTONE SPORTS CO., LTD.. Invention is credited to Hideo MATSUNAGA, Kozue WADA.
Application Number | 20120064994 13/230306 |
Document ID | / |
Family ID | 45807254 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120064994 |
Kind Code |
A1 |
WADA; Kozue ; et
al. |
March 15, 2012 |
GOLF CLUB HEAD
Abstract
A face member of a golf club head includes first and second main
ribs disposed inside thereof. The first main rib is extended from a
crown side to a sole side and the second main rib is extended from
a hosel side to a toe side of the sole. The first and the second
main ribs intersect with each other at an intersection portion.
Additionally, a first groove is provided from the intersection
portion of the rib toward the sole side, and a second groove is
provided from the intersection portion of the rib toward the toe
side.
Inventors: |
WADA; Kozue; (Chichibu-shi,
JP) ; MATSUNAGA; Hideo; (Chichibu-shi, JP) |
Assignee: |
BRIDGESTONE SPORTS CO.,
LTD.
Tokyo
JP
|
Family ID: |
45807254 |
Appl. No.: |
13/230306 |
Filed: |
September 12, 2011 |
Current U.S.
Class: |
473/346 |
Current CPC
Class: |
A63B 53/0408 20200801;
A63B 53/0458 20200801; A63B 60/00 20151001; A63B 53/0454 20200801;
A63B 53/0466 20130101; A63B 53/0412 20200801 |
Class at
Publication: |
473/346 |
International
Class: |
A63B 53/04 20060101
A63B053/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 2010 |
JP |
2010-205523 |
Claims
1. A golf club head having a hollow internal structure, the golf
club head comprising: a face portion having a hitting surface; and
first and second main ribs disposed inside the face portion,
wherein the first main rib is extended from a crown side to a sole
side and the second main rib is extended from a hosel side to a toe
side of the sole, and the first and second main ribs intersect with
each other at an intersection portion, and the first and the second
main ribs are so constructed that stiffness of the sole side is
lower than that of the crown side.
2. The golf club head according to claim 1, wherein a first groove
is provided from the intersection portion of the first main rib up
to the sole side, and the depth of the first groove is not more
than about 3/4 of the maximum height of the first main rib, and a
second groove is provided from the intersection portion of the
second main rib up to the toe side, and the depth of the second
groove is not more than about 3/4 of the maximum height of the
second main rib.
3. The golf club head according to claim 1, wherein the height of
the first and second main rib is about 0.5 mm to about 1.5 mm.
4. The golf club head according to claim 1, wherein the height of
the first and second main ribs is smaller on the sole side than on
the crown side.
5. The golf club head according to claim 1, wherein the width of
the first and second main ribs is about 8 mm to about 14 mm.
6. The golf club head according to claim 1, further comprising: a
reinforcement rib which is disposed inside the face portion and
extends from the intersection portion toward an end of the face
portion, wherein the height of the reinforcement rib is decreased
gradually from the intersection portion toward the end, and the
reinforcement portion is formed part of the way to the end of the
face portion.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority on Japanese Patent
Application No. 2010-205523 filed on Sep. 14, 2010, which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a golf club head, and more
particularly relates to a golf club head in which improvement is
made by providing a back side of its face portion with thick
portions.
[0004] 2. Description of Related Art
[0005] In most of the recently marketed wood club heads, at least a
face portion thereof is formed of metallic material. The face
portion must be so thick so as to maintain strength capable of
withstanding an impact with a ball. Although the size of the head
has been currently tending to increase, large heads of 460
cm.sup.3, which is an upper official limit according to a golf
rule, take up most of the driver head share because the driver
heads must be formed in a smaller volume than 460 cm.sup.3+an
allowance of 10 cm.sup.3.
[0006] If the head size is expanded, the weight of the face portion
is increased. Thus, generally, while reduction of weight of the
face portion has been attempted, the thickness of a face portion
has been decreased in order to maintain the strength of the face
portion and a measure of providing a back side of the face portion
with ribs has been adopted. For example, Japanese Unexamined Patent
Application Publication No. 2006-141806 has described provision of
six ribs extending from a central portion of the face toward a
periphery of the face.
[0007] If a rib is provided in the shape of the letter X on the
central portion of a back surface of the face portion, restitutive
performance of the face portion drops drastically when a ball is
hit on a sole side or a crown side off a face center, as compared
to a case in which a ball is hit on the face center. To solve this
problem, Japanese Unexamined Patent Application Publication No.
2008-36050 has described that the thickness of four division faces
on the back side of the face, which are defined by dividing with
the ribs is so determined that those on the sole side and the crown
side are smaller than those on the toe side and the heel side.
[0008] Conventionally, a number of highly restitutive heads whose
coefficient of restitution was increased considerably were
invented. However, it has been officially decided that highly
restitutive heads whose coefficient of restitution is 0.830 or more
cannot be used in games from 2008 on. Accordingly, there have been
currently developed golf clubs whose coefficient of restitution at
a center of its face portion is suppressed. However, it has been
made evident that if the coefficient of restitution at the center
of the face portion is suppressed, the restitutive performance of a
face surface other than the center is lower on the sole side than
on the crown side.
SUMMARY OF THE INVENTION
[0009] In view of the above-described problem, accordingly, an
object of the present invention is to provide a golf club head in
which with the weight of its face portion is reduced and the
strength of its face portion is maintained, the restitutive
property of its face center is held within a range complying with
golf rules, and even if a ball is hit off the face center,
substantially the same restitutive performance as when the ball is
hit at the face center can be exerted.
[0010] To achieve the above-described object, according to the
present invention, there is provided a golf club head having a
hollow internal structure, the golf club head including: a face
portion having a hitting surface; and first and second main ribs
disposed inside the face portion. The first main rib is extended
from a crown side to a sole side and the second main rib is
extended from a hosel side to a toe side of the sole, and the first
and second main ribs intersect with each other at an intersection
portion. Additionally, the first and the second main ribs are so
constructed that stiffness of the sole side is lower than that of
the crown side.
[0011] According to another embodiment of the golf club head, a
first groove is provided from the intersection portion of the first
main rib up to the sole side, and the depth of the first groove is
3/4 or less the maximum height of the first main rib. Furthermore,
a second groove is provided from the intersection portion of the
second main rib up to the toe side, and the depth of the second
groove is 3/4 or less the maximum height of the second main
rib.
[0012] According to another embodiment of the present invention,
the height of the first and second main rib is 0.5 mm to 1.5
mm.
[0013] According to another embodiment of the golf club head, the
height of the first and second main ribs is less on the sole side
than on the crown side.
[0014] According to another embodiment of the present invention,
the width of the first and second main ribs is 8 mm to 14 mm.
[0015] According to another embodiment of the present invention,
the golf club head further includes a reinforcement rib which is
disposed inside the face portion and extended from the intersection
portion toward an end of the face portion. The height of the
reinforcement rib decreases gradually from the intersection portion
toward the end, and the same reinforcement portion is formed part
of the way to the end of the face portion.
[0016] The golf club head of the present invention has a hollow
internal structure and includes a face portion having a hitting
surface and first and second main ribs disposed inside the face
portion. Then, the first main rib is extended from a crown side to
a sole side and the second main rib is extended from a hosel side
to a toe side of the sole. The first and second main ribs intersect
with each other at an intersection portion. The first and the
second main ribs are so constructed that stiffness of the sole side
is lower than that of the crown side. According to the structure of
such a golf club head, a light weight face portion can be formed
and a sufficient strength of the face portion can be maintained,
while restitutive property of the face center can be kept within a
rule complying range. Additionally, restitutive performance when a
ball is hit off a face center is brought close to the same
restitutive performance as when the ball is hit at the face
center.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In the accompanying drawings:
[0018] FIG. 1(A) is a front view showing an embodiment of a golf
club head according to the present invention;
[0019] FIG. 1(B) is a front view showing another embodiment of the
golf club head according to the present invention;
[0020] FIG. 2 is a sectional view of the golf club head taken along
the line II-II in FIG. 1(A);
[0021] FIG. 3 is a back side view showing a face member
constituting the golf club head shown in FIG. 1(A);
[0022] FIG. 4 is a schematic sectional view of the face member
taken along the line IV-IV in FIG. 3;
[0023] FIG. 5 is a schematic sectional view of the face member
taken along the line V-V in FIG. 3;
[0024] FIG. 6 is a front view showing angles of ribs on the face
member in FIG. 1(A);
[0025] FIG. 7 is a sectional view showing another embodiment of a
groove provided in the rib;
[0026] FIG. 8 is a sectional view showing still another embodiment
of the groove provided in the rib;
[0027] FIG. 9 is a sectional view showing another embodiment of the
groove in the rib;
[0028] FIG. 10 is a sectional view showing another embodiment of
the groove provided in the rib;
[0029] FIG. 11 is a front view showing another embodiment of the
golf club head according to the present invention;
[0030] FIG. 12 is a schematic sectional view of a rib according to
a comparative example;
[0031] FIG. 13 is a front view showing hitting points in
simulations of examples;
[0032] FIG. 14 is a distribution diagram of CT values of an example
1-1;
[0033] FIG. 15 is a distribution diagram of the CT values of an
example 1-2; and
[0034] FIG. 16 is a distribution diagram of the CT value according
to a comparative example 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] Hereinafter, an embodiment of a golf club head according to
the present invention will be described in detail with reference to
the accompanying drawings.
[0036] As shown in FIG. 1(A) and FIG. 2, a golf club head 1 is
constituted mainly of a face member 11a which is part of a face
portion 10 and a main body member 20. The main body member 20
includes part of the face portion 10, a sole portion 21, a crown
portion 22, a side portion extending from a toe 23 to a heel 24 via
a back face (not shown) and a hosel portion 25, which are formed
integrally. The face member 11a and the main body portion 20 are
joined together by welding, so that a hollow structure is formed
inside the head.
[0037] Preferably, the face member 11a contains at least a sweet
spot in the face portion 10. Preferably, the width of the face
member 11a is about 55% or more the width of the face portion 10,
more preferably about 60% or more. Furthermore, the width of the
face member 11a is preferably about 90% or less the width of the
face portion 10 and more preferably to be about 85% or less. The
height of the face member 11a is preferably about 50% or more the
height of the face portion 10 and more preferably to be about 55%
or more. Furthermore, the height of the face member 11a is
preferably about 90% or less the height of the face portion 10 and
more preferably about 85% or less. Preferably, outer edges on the
toe side and the heel side of the face member 11a are substantially
parallel to a central axis 31 of a first main rib 12, which will be
described later. Preferably, the main body member 20 has a toe side
portion 26 of the face portion and a heel side portion 27
thereof.
[0038] FIG. 1(A) indicates a structure of a face on the hollow
structure side of the face member 11a, namely, a back side face by
the broken line. Ribs are formed on the back side face of the face
member 11a by intensifying the thickness of the face member 11a
partially.
[0039] In the meantime, the face member of this embodiment is not
limited to the face member 11a which is to be fit to a U-shaped
opening portion made in part of the face portion 10, but the entire
area of the face portion 10 may be used as the face member 11b as
shown in FIG. 1(B). Then, main ribs 12, 13 may be provided on the
entire face portion 10. In this case, the main rib 12 is extended
up to the vicinity of an outer periphery on the sole side of the
face portion 10. The main rib 13 is extended from the vicinity of
the outer periphery on the hosel side of the face portion 10 up to
the vicinity of the outer periphery on the toe side. Because the
main ribs 12, 13 are not extended up to ends of the outer periphery
of the face portion, the face member may be fit easily to a crown
front end portion and a sole front end portion where the opening
portion of the face portion is made. Next, the back side face of
the face member 11a shown in FIG. 1(A) will be described.
[0040] As shown in FIG. 3, the first main rib 12 extending from the
sole side to the crown side and the second main rib 13 extending
from the hosel side to the toe side of the sole are formed on a
substantially flat back side face of the face member 11a. The first
and second main ribs 12, 13 intersect with each other at a flat
circular intersection portion 15 disposed on a sweet spot of the
face portion 10. Intersection of the first and second main ribs 12,
13 at the central portion of the face portion 10 suppresses
restitutive performance at the central portion of the face portion
10.
[0041] A first groove 50 is provided in a sole side portion of the
first main rib 12 as viewed from the intersection portion 15 along
the longitudinal direction of the same rib 12. Furthermore, a
second groove 51 is provided in the sole side portion of the second
main rib 13 as viewed from the intersection portion 15 along the
longitudinal direction of the same rib 13. Provision of the first
groove 50 and the second groove 51 can reduce stiffness of the sole
side portion of the ribs 12, 13 thereby increasing restitutive
performance on the sole side of the face portion up to a
substantially equivalent level to the restitutive performance on
the crown side.
[0042] The back side face of the face member 11a is divided into
four sections, toe-crown section 16, toe-sole section 17,
heel-crown section 18 and heel-sole section 19 by the first main
rib 12 and the second main rib 13. The thickness of the face member
11a is defined to differ across the first main rib 12. That is, the
thickness of the toe-crown section 16 and the toe-sole section 17
is defined to be smaller than the thickness of the heel-crown
section 18 and the heel-sole section 19. Defining the thickness of
the face member 11a such that the thickness on the toe side is
smaller than that on the heel side intensifies the restitutive
performance on the toe side, so that the restitutive performance on
the toe side comes close to the restitutive performance on the heel
side.
[0043] Additionally, a reinforcement rib 14 extending from the
toe-crown section 16 to the heel-sole section 19 is formed on the
back side face of the face member 11a. The reinforcement rib 14
intersects with the first and second main ribs 12, 13 at the
intersection portion 15. In the meantime, the reinforcement rib 14
is formed only part of the way to an end of the face portion. By
forming the reinforcement rib 14 in case in which the restitutive
performances of the toe-crown section 16 and the heel-sole section
19 exceed a golf rule complying range, the same reinforcement rib
14 can suppress the restitutive performance of these sections.
[0044] The reinforcement rib 14 may contain a third groove 52 on
its sole side with respect to the intersection portion 15, along
the longitudinal direction of the same rib 14. Provision of the
groove 52 in the reinforcement rib 14 may adjust the restitutive
performance of the face portion by reducing stiffness of the
reinforcement rib 14. Respective parts on the back side face of the
face member 11a will be described in more detail.
[0045] As shown in FIG. 4, the first main rib 12 is so constructed
that the first groove 50 is provided near the center of a top side
of its substantially trapezoidal formation. The section of the
first groove 50 is rectangular. The height of the first main rib 12
may be defined to be decreased gradually toward the flat toe-sole
section 17 and heel-sole section 19. As shown in FIG. 4, the
thickness of the toe-sole section 17 is defined to be smaller than
the thickness of the heel-sole section 19. As a result, on the sole
side of the face portion, the coefficient of restitution can be
intensified on the toe side as compared to the heel side. This
sectional view is intended to make the structure of the present
invention understood easily, but it is not drawn to scale. The
first main rib 12 is formed in an equal height from the
intersection portion 15 toward an outer edge of the face member
11a. The height of the second main rib 13 is defined in the same
manner as the first main rib 12.
[0046] The height of the first main rib 12 refers to a largest
difference T.sub.R in thickness between the top of the rib and the
surface of a section 19 which is thicker than a neighboring
section. The T.sub.R is preferably about 0.5 mm or more and more
preferably about 0.7 mm or more. Furthermore, the T.sub.R is
preferably about 1.5 mm or less and more preferably about 1.2 mm or
less. Then, a depth T.sub.G of the first groove 50 is preferably
smaller than T.sub.R and T.sub.G is more preferably 3/4 or less
T.sub.R. The height of the second main rib 13 is equal to that of
the first main rib 12 and the depth of the second groove 51 is
equal to that of the first groove 50. The first and second main
ribs 12, 13 are preferably formed up to an end of the face member
11a or the vicinity thereof. The first and second main ribs 12, 13
are formed each in a substantially equal width. The width of the
first and second main ribs 12, 13 is preferably about 8 mm or more
at their portions in contact with the back side face of the face
portion and more preferably about 9 mm or more. The width of the
first and second main ribs 12, 13 is preferably about 14 mm or less
and more preferably about 13 mm or less.
[0047] The configuration of the first groove 50 has been already
described above. The configurations of the second groove 51 and the
third groove 52 are similar to that of the first groove 50.
[0048] The reinforcement rib 14 is so constructed that like the
main ribs, the height of its central portion is the greatest and
the height thereof decreases gradually from the central portion
toward the flat toe-crown section 16 and heel-sole section 19. On
the other hand, as shown in FIG. 5, the height of the reinforcement
rib 14 is defined so as to decrease gradually from the intersection
portion 15 toward the outer edge of the face member 11a. In the
meantime, this sectional view is not drawn to the scale.
Additionally, the width of the reinforcement rib 14 is defined so
as to decrease gradually from the intersection portion 15 toward
the outer edge of the face member 11a. Forming the reinforcement
rib 14 to be gradually thinner and narrower from the center thereof
toward the outer edge can suppress a quick change in stiffness.
[0049] A length of the reinforcement rib 14 from the intersection
portion 15 is preferably about 45% or more and more preferably
about 50% or more a length from the intersection portion 15 up to
the outer edge of the face member 11a. Furthermore, it is
preferably about 90% or less and more preferably about 85% or less.
The length on the toe side and the length on the heel side may be
equal to or different from each other. Although the height of the
highest portion of the reinforcement rib 14 is preferably equal to
the height of the highest portion of the first and second main ribs
12, 13, it may be lower than the first and second main ribs 12, 13.
In case in which it is lower, the difference is preferably about
0.1 mm or more and about 0.5 mm or less. The width of the
reinforcement rib 14 is preferably about 2 mm or more at its
greatest portion and more preferably about 3 mm or more.
Furthermore, the width of the reinforcement 14 is preferably about
12 mm or less and more preferably about 10 mm or less.
[0050] On the crown side, the first main rib 12 is preferably
inclined toward the toe side, and on the sole side, toward the heel
side. Inclination of the first main rib 12 in this way can extract
restitutive performance along a direction from the toe upper side
to the heel lower side, where hitting points by amateur golfers
concentrate, to a maximum extent. More specifically, an angle
.theta.a of a center line 31 of the first main rib 12 with respect
to a ground line (G.L) 30 when the golf club head 1 is placed on an
ordinary address position as shown in FIG. 6 is preferred be about
90.degree. or less and more preferably about 85.degree. or less.
Furthermore, the inclination .theta.a of the rib is preferably
about 25.degree. or more and more preferably about 30.degree. or
more.
[0051] On the toe side, the second main rib 13 is preferably
inclined toward the sole side and on the heel side, toward the
crown side, that is, toward the hosel side. Inclination of the
second main rib 13 in this way can extract restitutive performance
in an upward direction at the toe to a maximum extent. More
specifically, an inclination .theta.b of a center line 32 of the
second main rib 13 with respect to the ground line 30 is preferably
about 5.degree. or more and more preferably about 10.degree. or
more. Furthermore, the inclination .theta.b of the rib is
preferably about 80.degree. or less and more preferably about
70.degree. or less. Preferably, a center line 33 of the
reinforcement rib 14 divides an angle formed by both the center
lines 31, 32 of the first and second main ribs 12, 13 respectively
into two equal parts.
[0052] By curving the first main rib 12 smoothly into an S-shape or
Z-shape instead of the straight line along the center line 31 and
by curving the second main rib 13 smoothly into an S-shape or
Z-shape instead of the straight line along the center line 32,
areas of both the toe-crown section 16 and the heel-sole area 19
can be increased. The reinforcement rib 14 is preferably of a
straight line along the center line 33.
[0053] The toe-crown section 16, the toe-sole section 17, the
heel-crown section 18 and the heel-sole section 19 each have a
substantially uniform thickness. To equalize the coefficient of
restitution of the toe side with that of the heel side, the
thickness of the toe-crown section 16 can be made less than the
thickness of the heel-sole section 19. Furthermore, the thickness
of the toe-sole section 17 can be made less than the thickness of
the heel-crown section 18. Preferably, a difference of these
thicknesses is at least about 0.05 mm or more, more preferably
about 0.1 mm or more. On the other hand, no uniform restitutive
performance can be obtained if the difference of these thicknesses
is excessive. Thus, it is preferably about 0.5 mm or less, and more
preferably about 0.4 mm or less.
[0054] Although the thickness of the toe-crown section 16 may be
equal to or different from the thickness of the toe-sole section
17, preferably, the thickness of the toe-sole section 17 is made
less than the thickness of the toe-crown section 16 in order to
equalize the coefficient of restitution of the crown side with that
of the sole side as much as possible. A difference of these
thicknesses is preferably about 0.05 mm or more, and more
preferably about 0.1 mm or more. On the other hand, no uniform
restitutive performance can be obtained if the difference of these
thicknesses is excessive. Thus, it is preferably about 0.5 mm or
less and more preferably about 0.4 mm or less.
[0055] The thickness of the heel-crown section 18 and the thickness
of the heel-sole section 19 may be equal to or different from each
other. When defining the thickness of the heel-crown section 18 to
be different from the thickness of the heel-sole section 19, the
difference of the thickness is preferably about 0.05 mm or more and
about 0.5 mm or less.
[0056] The intersection portion 15 contains the sweet spot of the
face portion 10, that is, a center of gravity of a golf club head
projected to the face plane. The intersection portion 15 contains
an intersection point of the center lines of the first and second
main ribs 12, 13. The intersection point of the main ribs and the
sweet spot may be equal to or different from each other. The
intersection point of the main ribs 12, 13 is disposed so as not to
be on a score line formed on the surface of the face portion 10 or
so as not to be on an extension line of the score line 28 formed
partially on the toe side and the heel side, as shown in FIG.
1.
[0057] Although the height of the intersection portion 15 is
preferably the same as that of the highest portion of the first and
second main ribs, it may be greater. In a case in which the height
of the intersection portion 15 is set to be greater than that of
the main ribs, a difference of those heights is preferably about
0.1 mm or more and about 0.5 mm or less. The surface of the
intersection portion 15 is preferred to have a circular section,
and as shown in FIG. 5, the section of the intersection portion 15
has a substantially semicircular or substantially semielliptical
shape. The radius of the flat, circular intersection portion 15 is
preferably about 5 mm or more and about 12 mm or less at its widest
portion. In addition, the intersection portion 15 is not limited to
the circular shape, and it may be elliptical, square, such as
rectangular and diamond shaped, or polygonal such as pentagonal and
hexagonal.
[0058] Although the toe-crown section 16, the toe-sole section 17,
the heel-crown section 18 and the heel-sole section 19 have the
above-mentioned difference with respect to the thicknesses of other
sections, each thickness is preferably about 1.0 mm or more and
more preferably about 1.5 mm or more. The thickness of each section
is preferably about 3.0 mm or less and more preferably about 2.5 mm
or less.
[0059] The face member 11a can be formed either by forging or
casting. As material of the face member 11, titanium, titanium
alloy or stainless steel may be used. Preferably, the volume of the
golf club head 1 is about 100 cc or more, more preferably about 150
cc or more. On the other hand, the volume of the golf club head 1
is preferably about 500 cc or less and more preferably about 460 cc
or less. Furthermore, the weight of the golf club head 1 is
preferably about 170 g or more and more preferably about 175 g or
more. On the other hand, the weight of the golf club head 1 is
preferably about 250 g or less and more preferably about 245 g or
less.
[0060] FIGS. 7-10 show sectional views of other examples of the
first groove 50. In FIG. 7, the section of the first groove 50 is
of an inverted trapezoid in which its upper base is longer than its
lower base. Referring to FIG. 8, the section of the first groove 50
is U-shaped. In FIG. 9, the section of the first groove 50 is of an
inverted triangle. In FIG. 10, the section of the first groove 50
is substantially semicircular. Although in FIGS. 4, 7, and 8, the
top face of each rib having the maximum height T.sub.R has a
specific area, the top face area of the ribs having the maximum
height T.sub.R shown in FIGS. 9 and 10 is substantially zero.
[0061] As shown in FIGS. 8 and 10, the height of the rib decreases
gradually as it goes from the top face of the rib 12 toward the
heel-sole section 19 and the toe-sole section 17. Portions of the
rib 12 which come into contact with the sections 19 and 17 are
formed into a curved shape so that the same rib 12 maintains smooth
contact with the sections 19 and 17.
[0062] Although in the above-described embodiments, the
reinforcement rib 14 is provided as shown in FIGS. 1 to 6, the
present invention may contain no reinforcement rib as shown in FIG.
11. In a case in which no reinforcement rib is provided,
preferably, joined portions of the adjacent first and second main
ribs 12, 13 are formed into a smooth curved shape.
[0063] According to another embodiment, the height of the rib may
be changed depending on its position instead of providing the rib
with a groove. That is, in regard to the heights of the first and
second main ribs 12, 13, the height on the sole side is set smaller
than the height on the crown side. In the main ribs 12, 13,
preferably, with respect to the intersection portion 15, the
maximum height on the sole side is about 30-80% of the maximum
height on the crown side. Furthermore, the height of the
reinforcement rib 14 may be defined so that the height on the sole
side is smaller than that on the crown side. In the reinforcement
rib 14, preferably, with respect to the intersection portion 15,
the maximum height on the sole side is about 30-80% of the maximum
height on the crown side.
EXAMPLES
Examples 1-1, 1-2 and Comparative Example 1
[0064] The face member of the present invention was produced and
its coefficient of restitution (COR) was evaluated. In this
example, a characteristic time (CT) was measured instead of
actually measuring the COR value. The CT value is a quantitative
value capable of measuring a spring effect of the face simply and
at a high precision, which has been adopted by the US golf
association (USGA) and Royal and Ancient Golf Club of St. Andrews
(R&A) and can be measured with a portable pendulum machine
approved by R&A Rules Limited. Because generally, the more the
face is deflected, the smaller the energy loss is, so that the
initial velocity of a ball is higher, the CT value expresses the
deflection with a contact time of the ball and the face. Currently,
its maximum limit is determined to be 257 (239 officially
stipulated+allowance of 18) .mu.ec according to the rule.
[0065] The Example 1-1 presents a structure shown in FIG. 3, in
which the rib height T.sub.R of the rib was 0.8 mm and the depth of
the grooves 50 to 52 was 0.6 mm. According to the Example 1-2, the
depth of the grooves 50 to 52 was set to 0.4 mm. On the other hand,
for comparison, the Comparative Example 1 without any groove in the
rib was produced. FIG. 12 shows a sectional view of the first main
rib 12 according to the Comparative Example 1. The second main rib
13 and the reinforcement rib 14 were also provided with the same
sectional shape as in FIG. 12. In the Examples 1-1 and 1-2 and the
Comparative Example 1, the height of the first main rib 12 and the
second main rib 13 was set to 0.8 mm and the height of the
intersection portion was set to 1.2 mm. The reinforcement rib 14 as
shown in FIG. 5 was provided. Furthermore, the thickness of the
four sections, toe-crown section 16, toe-sole section 17,
heel-crown section 18 and heel-sole section 19 was set to 2.4
mm.
[0066] As a common condition of the face member, the width and the
height of the face member were set to 75 mm and 43 mm respectively,
and the first and second main ribs were tilted in the same way as
FIG. 1. The length of the reinforcement rib was set to 27 mm on the
toe side, and 25 mm on the heel side. The width of the first and
second main ribs was set to 9.5 mm and the width of the
reinforcement rib was set to 7.1 mm. As a common condition of the
golf club head, a titanium alloy (Ti-6Al-4V) was employed for
material of the face member, the head volume was set to 460 cc and
the head weight was set to 190 g. Then, the thickness of the crown
portion was set to 0.7 mm and the thickness of the sole portion and
the side portion was set to 0.9 mm.
[0067] For the Examples 1-1, 1-2 and the Comparative Example 1, the
CT value at a hitting point of the ball was measured. With regard
to the hitting points of the ball, 15 hitting points, which are
different in the vertical direction and the horizontal direction,
were investigated as shown in FIG. 13. A hitting point 40c in the
center assumes hitting the ball at the sweet spot and was supposed
to be within the intersection portion of the face member. The other
fourteen hitting points assume hitting the ball off the sweet spot.
Positions 10 mm away from the central hitting point 40c toward the
toe side and the heel side are assumed to be hitting points 40b,
40d, respectively, and positions 10 mm further away toward the toe
side and the heel side are assumed to be hitting points 40a, 40e,
respectively. Positions 10 mm away from these five hitting points
40a to 40e toward the crown side and the sole side are assumed to
be 40aH to 40eH and 40aL to 40eL respectively.
[0068] Of the above-described 15 hitting points, hitting points
40bH and 40dL are located on the first main rib 12 and hitting
points 40dH and 40bL are located on the second main rib 13.
[0069] Under the above-described condition, the CT values of
respective hitting points of the Examples 1-1, 1-2 and the
Comparative Example 1 were measured. Tables 1 to 3 show the
results. Tables 1 to 3 show a percentage of the CT values of other
hitting points with respect to the CT values of the central hitting
point 40c regarding the Examples 1-1, 1-2 and the Comparative
Example 1. FIGS. 14 to 16 show distribution maps of the CT values
on the face member obtained by computer simulation based on these
results. With the position of the central hitting point 40c assumed
to be 0 mm, in Tables 1 to 6 and FIGS. 14 to 16, a distance toward
the heel side and the crown side is expressed as positive and a
distance toward the toe side and the sole side is expressed as
negative.
TABLE-US-00001 TABLE 1 Percentage of CT value in Example 1-1 20 mm
10 mm Horizontal 10 mm 20 mm to toe to toe center to heel to heel
-20 -10 0 10 20 10 mm up 10 97% 99% 96% 99% 91% Vertical 0 101%
105% 100% 103% 97% center 10 mm down -10 88% 97% 100% 91% 75%
TABLE-US-00002 TABLE 2 Percentage of CT value in Example 1-2 20 mm
10 mm Horizontal 10 mm 20 mm to toe to toe center to heel to heel
-20 -10 0 10 20 10 mm up 10 96% 99% 97% 99% 92% Vertical 0 100%
104% 100% 102% 97% center 10 mm down -10 85% 95% 98% 89% 75%
TABLE-US-00003 TABLE 3 Percentage of CT value in Comparative
Example 1 20 mm 10 mm Horizontal 10 mm 20 mm to toe to toe center
to heel to heel -20 -10 0 10 20 10 mm up 10 98% 101% 98% 100% 93%
Vertical 0 101% 105% 100% 102% 98% center 10 mm down -10 84% 91%
94% 88% 75%
[0070] In regard to the CT value of the face member (Example 1-1)
provided with a rib having a groove 0.6 mm deep as shown in FIG.
14, the CT value on the sole side is higher than a face member
(Comparative Example 1) provided with a rib having no groove as
shown in FIG. 16, so that a face portion area having a CT value
similar to that of the hitting point 40c is greater. Furthermore,
the CT value of a face member (Example 1-2) provided with a rib
having a groove 0.4 mm deep as shown in FIG. 15 is higher than the
Example 1-1, so that a distribution of the CT values is
uniform.
Examples 2-1, 2-2, 2-3 and Comparative Example 2
[0071] In the Example 2-1, the height of the intersection portion
15 was set to 1.2 mm and the maximum height on the crown side of
the first main rib 12 and the second main rib 13 was set to 1.0 mm.
On the other hand, the maximum height on the sole side of the first
main rib 12 and the second main rib 13 was set to 0.7 mm. In regard
to the reinforcement rib 14, the maximum height on the crown side
was set to 1.1 mm and the maximum height on the sole side was set
to 1.0 mm. The thickness of the four sections 16 to 19 was set to
2.4 mm.
[0072] In the Example 2-2, the thickness of the toe-crown section
16 was set to 2.4 mm and the thickness of the toe-sole section 17
was set to 1.9 mm. Then, the thickness of the heel-crown section 18
was set to 2.3 mm and the thickness of the heel-sole section 19 was
set to 2.4 mm. Other conditions were set to the same as the Example
2-1.
[0073] In the Example 2-3, no reinforcement rib 14 is provided and
the first main rib 12, the second main rib 13, the first groove 50
and the second groove 51 were set to the same as the Example 2-1.
The thickness of the four sections 16 to 19 were set to the same as
the Example 2-2.
[0074] In the Comparative Example 2, the maximum heights of the
first main rib 12, the second main rib 13 and the reinforcement rib
14 were set to 1.2 mm. The thickness of the four sections 16 to 19
was set to 2.4 mm. All ribs had no groove.
[0075] For the Examples 2-1 to 2-3 and the Comparative Example 2,
the CT values of respective hitting points in FIG. 12 were measured
under the above-described conditions. Tables 4 to 7 show the
results. Tables 4 to 7 show a percentage of the CT values of other
hitting points when the CT value of the central hitting point 40c
is assumed to be 100% in the Examples 2-1 to 2-3 and the
Comparative Example 2. With the position of the central hitting
point 40c assumed to be 0 mm, in Tables 4 to 7, a distance toward
the heel side and the crown side is expressed as positive and a
distance toward the toe side and the sole side is expressed as
negative.
TABLE-US-00004 TABLE 4 Percentage of CT value in Example 2-1 20 mm
10 mm Horizontal 10 mm 20 mm to toe to toe center to heel to heel
-20 -10 0 10 20 10 mm up 10 95% 98% 95% 97% 97% Vertical 0 99% 100%
100% 105% 96% center 10 mm down -10 83% 94% 94% 94% 82%
TABLE-US-00005 TABLE 5 Percentage of CT value in Example 2-2 20 mm
10 mm Horizontal 10 mm 20 mm to toe to toe center to heel to heel
-20 -10 0 10 20 10 mm up 10 96% 100% 98% 99% 99% Vertical 0 99%
103% 100% 101% 99% center 10 mm down -10 88% 96% 97% 98% 83%
TABLE-US-00006 TABLE 6 Percentage of CT value in Example 2-3 20 mm
10 mm Horizontal 10 mm 20 mm to toe to toe center to heel to heel
-20 -10 0 10 20 10 mm up 10 105% 100% 98% 99% 97% Vertical 0 102%
103% 100% 103% 103% center 10 mm down -10 88% 96% 98% 98% 92%
TABLE-US-00007 TABLE 7 Percentage of CT value in Comparative
Example 2 20 mm 10 mm Horizontal 10 mm 20 mm to toe to toe center
to heel to heel -20 -10 0 10 20 10 mm up 10 94% 95% 94% 96% 96%
Vertical 0 94% 99% 100% 99% 94% center 10 mm down -10 83% 91% 92%
89% 76%
[0076] As is evident from Tables 4 to 7, the CT values of the
Examples 2-1 to 2-3 are higher than the CT values of the
Comparative Example 2, so that the distribution thereof is more
uniform. In particular, the CT values of the four hitting points
40bH, 40dH, 40bL, 40dL on the ribs in the Examples 2-1 to 2-3 are
higher than the CT values of the Comparative Example 2.
* * * * *