U.S. patent application number 14/436371 was filed with the patent office on 2015-09-03 for golf club head.
This patent application is currently assigned to DUNLOP SPORTS CO. LTD.. The applicant listed for this patent is DUNLOP SPORTS CO. LTD.. Invention is credited to Hiroshi Abe, Tatsuhiko Kuwabara.
Application Number | 20150246268 14/436371 |
Document ID | / |
Family ID | 50488293 |
Filed Date | 2015-09-03 |
United States Patent
Application |
20150246268 |
Kind Code |
A1 |
Abe; Hiroshi ; et
al. |
September 3, 2015 |
GOLF CLUB HEAD
Abstract
[Object] It is an object of the present invention to provide a
golf club head being lightweight and having a high strength.
[Solving Means] A head 2 includes a face 4, a sole 8, and a crown
6. The face 4 includes a face surface fs and a face back surface
fr. A plurality of projections (A) are provided on the face back
surface fr. The projections (A) are point-like in a planar view. An
optional first direction and a second direction orthogonal to the
first direction are defined in the planar view. Preferably,
arrangement regularity of the projections (A) in the second
direction is higher than arrangement regularity of the projections
(A) in the first direction. Preferably, the first direction is a
longitudinal direction; and the second direction is a lateral
direction.
Inventors: |
Abe; Hiroshi; (Kobe-shi,
JP) ; Kuwabara; Tatsuhiko; (Tsubame-City,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DUNLOP SPORTS CO. LTD. |
Kobe-shi, Hyogo |
|
JP |
|
|
Assignee: |
DUNLOP SPORTS CO. LTD.
Kobe-shi, Hyogo
JP
|
Family ID: |
50488293 |
Appl. No.: |
14/436371 |
Filed: |
October 17, 2013 |
PCT Filed: |
October 17, 2013 |
PCT NO: |
PCT/JP2013/078169 |
371 Date: |
April 16, 2015 |
Current U.S.
Class: |
473/345 |
Current CPC
Class: |
A63B 53/0466 20130101;
A63B 53/0454 20200801; A63B 53/047 20130101; A63B 53/0416 20200801;
A63B 53/0458 20200801; A63B 53/0408 20200801; A63B 60/52
20151001 |
International
Class: |
A63B 53/04 20060101
A63B053/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2012 |
JP |
2012-229374 |
Claims
1. A golf club head comprising: a face; a sole; and a crown,
wherein the face includes a face surface and a face back surface; a
plurality of projections (A) are provided on the face back surface;
and the projections (A) are point-like in a planar view.
2. The golf club head according to claim 1, wherein if an optional
first direction and a second direction orthogonal to the first
direction are defined in the planar view, arrangement regularity of
the projections (A) in the second direction is higher than
arrangement regularity of the projections (A) in the first
direction.
3. The golf club head according to claim 2, wherein the first
direction is a longitudinal direction; and the second direction is
a lateral direction.
4. The golf club head according to claim 1, wherein if an area of
each of the projections (A) in the planar view is defined as Ma,
the two or more kinds of projections (A) have areas Ma
substantially different from each other.
5. The golf club head according to claim 1, wherein the projections
(A) include a projection (A1) of which the area Ma is an area Ma1,
a projection (A2) of which the area Ma is an area Ma2, and a
projection (A3) of which the area Ma is an area Ma3; the area Ma1
is greater than the area Ma2, and the area Ma2 is greater than the
area Ma3; the projection (A2) is disposed on a face peripheral side
with respect to the projection (A1) in the first direction; and the
projection (A3) is disposed on a face peripheral side with respect
to the projection (A2) in the first direction.
6. The golf club head according to claim 1, wherein the projections
(A) include a projection (A1) of which the area Ma is an area Ma1,
a projection (A2) of which the area Ma is an area Ma2, and a
projection (A3) of which the area Ma is an area Ma3; the area Ma1
is greater than the area Ma2, and the area Ma2 is greater than the
area Ma3; if a longitudinal distance between a periphery of the
face back surface and the projection (A1) is defined as a1; a
longitudinal distance between the periphery of the face back
surface and the projection (A2) is defined as a2; a longitudinal
distance between the periphery of the face back surface and the
projection (A3) is defined as a3; an average value of the distances
a1 is defined as Av1; an average value of the distances a2 is
defined as Av2; and an average value of the distances a3 is defined
as Av3, the average value Av1 is greater than the average value
Av2; and the average value Av2 is greater than the average value
Av3.
7. The golf club head according to claim 1, wherein an area Ma of
each of the projections (A) is 3 mm.sup.2 or greater and 40
mm.sup.2 or less in the planar view; and a height Ha of each of the
projections (A) is 0.03 mm or greater and 0.2 mm or less.
8. The golf club head according to claim 1, wherein a plurality of
projection arrangement regions are provided on the face back
surface; and arrangement regularity in the second direction is
higher than arrangement regularity in the first direction in at
least one of the projection arrangement regions.
9. The golf club head according to claim 1, wherein a plurality of
projection arrangement regions are provided on the face back
surface; a middle projection arrangement region including a face
back surface center is present as one of the projection arrangement
regions; and arrangement regularity in the second direction is
higher than arrangement regularity in the first direction in the
middle projection arrangement region.
10. The golf club head according to claim 1, wherein the golf club
head is manufactured by joining a face member and another member;
the face member is manufactured by forging; the forging includes a
preceding forging step and a subsequent forging step; projections
(B) higher than the projections (A) are formed on the face back
surface in the preceding forging step; and the projections (A) are
formed by crushing the projections (B) in the subsequent forging
step.
11. The golf club head according to claim 2, wherein if an area of
each of the projections (A) in the planar view is defined as Ma,
the two or more kinds of projections (A) have areas Ma
substantially different from each other.
12. The golf club head according to claim 3, wherein if an area of
each of the projections (A) in the planar view is defined as Ma,
the two or more kinds of projections (A) have areas Ma
substantially different from each other.
13. The golf club head according to claim 2, wherein the
projections (A) include a projection (A1) of which the area Ma is
an area Ma1, a projection (A2) of which the area Ma is an area Ma2,
and a projection (A3) of which the area Ma is an area Ma3; the area
Ma1 is greater than the area Ma2, and the area Ma2 is greater than
the area Ma3; the projection (A2) is disposed on a face peripheral
side with respect to the projection (A1) in the first direction;
and the projection (A3) is disposed on a face peripheral side with
respect to the projection (A2) in the first direction.
14. The golf club head according to claim 3, wherein the
projections (A) include a projection (A1) of which the area Ma is
an area Ma1, a projection (A2) of which the area Ma is an area Ma2,
and a projection (A3) of which the area Ma is an area Ma3; the area
Ma1 is greater than the area Ma2, and the area Ma2 is greater than
the area Ma3; the projection (A2) is disposed on a face peripheral
side with respect to the projection (A1) in the first direction;
and the projection (A3) is disposed on a face peripheral side with
respect to the projection (A2) in the first direction.
15. The golf club head according to claim 4, wherein the
projections (A) include a projection (A1) of which the area Ma is
an area Ma1, a projection (A2) of which the area Ma is an area Ma2,
and a projection (A3) of which the area Ma is an area Ma3; the area
Ma1 is greater than the area Ma2, and the area Ma2 is greater than
the area Ma3; the projection (A2) is disposed on a face peripheral
side with respect to the projection (A1) in the first direction;
and the projection (A3) is disposed on a face peripheral side with
respect to the projection (A2) in the first direction.
16. The golf club head according to claim 2, wherein the
projections (A) include a projection (A1) of which the area Ma is
an area Ma1, a projection (A2) of which the area Ma is an area Ma2,
and a projection (A3) of which the area Ma is an area Ma3; the area
Ma1 is greater than the area Ma2, and the area Ma2 is greater than
the area Ma3; if a longitudinal distance between a periphery of the
face back surface and the projection (A1) is defined as a1; a
longitudinal distance between the periphery of the face back
surface and the projection (A2) is defined as a2; a longitudinal
distance between the periphery of the face back surface and the
projection (A3) is defined as a3; an average value of the distances
a1 is defined as Av1; an average value of the distances a2 is
defined as Av2; and an average value of the distances a3 is defined
as Av3, the average value Av1 is greater than the average value
Av2; and the average value Av2 is greater than the average value
Av3.
17. The golf club head according to claim 3, wherein the
projections (A) include a projection (A1) of which the area Ma is
an area Ma1, a projection (A2) of which the area Ma is an area Ma2,
and a projection (A3) of which the area Ma is an area Ma3; the area
Ma1 is greater than the area Ma2, and the area Ma2 is greater than
the area Ma3; if a longitudinal distance between a periphery of the
face back surface and the projection (A1) is defined as a1; a
longitudinal distance between the periphery of the face back
surface and the projection (A2) is defined as a2; a longitudinal
distance between the periphery of the face back surface and the
projection (A3) is defined as a3; an average value of the distances
a1 is defined as Av1; an average value of the distances a2 is
defined as Av2; and an average value of the distances a3 is defined
as Av3, the average value Av1 is greater than the average value
Av2; and the average value Av2 is greater than the average value
Av3.
18. The golf club head according to claim 4, wherein the
projections (A) include a projection (A1) of which the area Ma is
an area Ma1, a projection (A2) of which the area Ma is an area Ma2,
and a projection (A3) of which the area Ma is an area Ma3; the area
Ma1 is greater than the area Ma2, and the area Ma2 is greater than
the area Ma3; if a longitudinal distance between a periphery of the
face back surface and the projection (A1) is defined as a1; a
longitudinal distance between the periphery of the face back
surface and the projection (A2) is defined as a2; a longitudinal
distance between the periphery of the face back surface and the
projection (A3) is defined as a3; an average value of the distances
a1 is defined as Av1; an average value of the distances a2 is
defined as Av2; and an average value of the distances a3 is defined
as Av3, the average value Av1 is greater than the average value
Av2; and the average value Av2 is greater than the average value
Av3.
19. The golf club head according to claim 5, wherein the
projections (A) include a projection (A1) of which the area Ma is
an area Ma1, a projection (A2) of which the area Ma is an area Ma2,
and a projection (A3) of which the area Ma is an area Ma3; the area
Ma1 is greater than the area Ma2, and the area Ma2 is greater than
the area Ma3; if a longitudinal distance between a periphery of the
face back surface and the projection (A1) is defined as a1; a
longitudinal distance between the periphery of the face back
surface and the projection (A2) is defined as a2; a longitudinal
distance between the periphery of the face back surface and the
projection (A3) is defined as a3; an average value of the distances
a1 is defined as Av1; an average value of the distances a2 is
defined as Av2; and an average value of the distances a3 is defined
as Av3, the average value Av1 is greater than the average value
Av2; and the average value Av2 is greater than the average value
Av3.
20. The golf club head according to claim 2, wherein an area Ma of
each of the projections (A) is 3 mm.sup.2 or greater and 40
mm.sup.2 or less in the planar view; and a height Ha of each of the
projections (A) is 0.03 mm or greater and 0.2 mm or less.
Description
TECHNICAL FIELD
[0001] The present invention relates to a golf club head.
BACKGROUND ART
[0002] In respect of an improvement in a degree of freedom of
design, a golf head being more lightweight and having a high
strength is required.
[0003] Japanese Patent Application Laid-Open No. 2012-95855
discloses a head having a face part with a thickness distribution.
The face part includes a middle thick part, a toe-crown side
thin-walled part provided on a crown side of the middle thick part
on a toe side of the middle thick part and having a small
thickness, and a heel-sole side thin-walled part provided on a sole
side of the middle thick part on a heel side of the middle thick
part and having a small thickness. In the head, rebound performance
in an off center shot is improved by providing the thin-walled part
on a peripheral part of a face.
CITATION LIST
Patent Literature
[0004] Patent Literature 1: JP-A-2012-95855
SUMMARY OF INVENTION
Technical Problem
[0005] It has been found that a structure different from the
structure of the conventional technique can provide a face being
lightweight and having a high strength.
[0006] It is an object of the present invention to provide a golf
club head being lightweight and having a high strength.
Solution to Problem
[0007] A golf club head of the present invention includes a face, a
sole, and a crown. The face includes a face surface and a face back
surface. A plurality of projections (A) are provided on the face
back surface. The projections (A) are point-like in a planar
view.
[0008] An optional first direction and a second direction
orthogonal to the first direction are defined in the planar view.
Preferably, arrangement regularity of the projections (A) in the
second direction is higher than arrangement regularity of the
projections (A) in the first direction.
[0009] Preferably, the first direction is a longitudinal direction;
and the second direction is a lateral direction.
[0010] An area of each of the projections (A) in the planar view is
defined as Ma. Preferably, the two or more kinds of projections (A)
have areas Ma substantially different from each other.
[0011] Preferably, the projections (A) include a projection (A1) of
which the area Ma is an area Ma1, a projection (A2) of which the
area Ma is an area Ma2, and a projection (A3) of which the area Ma
is an area Ma3. Preferably, the area Ma1 is greater than the area
Ma2. Preferably, the area Ma2 is greater than the area Ma3.
Preferably, the projection (A2) is disposed on a face peripheral
side with respect to the projection (A1) in the first direction.
Preferably, the projection (A3) is disposed on a face peripheral
side with respect to the projection (A2) in the first
direction.
[0012] A longitudinal distance between a periphery of the face back
surface and the projection (A1) is defined as a1. A longitudinal
distance between the periphery of the face back surface and the
projection (A2) is defined as a2. A longitudinal distance between
the periphery of the face back surface and the projection (A3) is
defined as a3. An average value of the distances a1 is defined as
Av1. An average value of the distances a2 is defined as Av2. An
average value of the distances a3 is defined as Av3. Preferably,
the average value Av1 is greater than the average value Av2.
Preferably, the average value Av2 is greater than the average value
Av3.
[0013] Preferably, an area Ma of each of the projections (A) is 3
mm.sup.2 or greater and 40 mm.sup.2 or less in the planar view.
Preferably, a height Ha of each of the projections (A) is 0.03 mm
or greater and 0.2 mm or less.
[0014] Preferably, a middle projection arrangement region including
a face back surface center is present as one of the projection
arrangement regions. Preferably, arrangement regularity in the
second direction is higher than arrangement regularity in the first
direction in the middle projection arrangement region.
[0015] Preferably, the head is manufactured by joining a face
member and another member. Preferably, the face member is
manufactured by forging. Preferably, the forging includes a
preceding forging step and a subsequent forging step. Preferably,
projections (B) higher than the projections (A) are formed on the
face back surface in the preceding forging step. Preferably, the
projections (A) are formed by crushing the projections (B) in the
subsequent forging step.
Advantageous Effects of Invention
[0016] A golf club head being lightweight and having a high
strength can be obtained.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a perspective view of a golf club head according
to a first embodiment of the present invention;
[0018] FIG. 2 is an exploded perspective view of the head of FIG.
1;
[0019] FIG. 3 is a plan view of a back surface of a face member,
and projections (A) are omitted in FIG. 3;
[0020] FIG. 4 is a cross-sectional view taken along line F4-F4 of
FIG. 3; FIG. 5 is a plan view of the back surface of the face
member;
[0021] FIGS. 6(a), 6 (b), and 6(c) are plan views showing the
shapes of the projections (A);
[0022] FIG. 7 is a plan view for describing arrangement
regularity;
[0023] FIG. 8 is a plan view of a face back surface according to a
second embodiment;
[0024] FIG. 9 is a plan view of a face back surface according to a
third embodiment;
[0025] FIG. 10 is a plan view of a face back surface according to a
fourth embodiment;
[0026] FIG. 11 is a plan view of a face back surface according to a
fifth embodiment; and
[0027] FIG. 12 is a plan view of a face back surface according to a
sixth embodiment.
DESCRIPTION OF EMBODIMENTS
[0028] The present invention will be described below in detail
based on preferred embodiments with appropriate reference to the
drawings.
[0029] FIG. 1 is a perspective view of a golf club head 2 according
to a first embodiment of the present invention.
[0030] The head 2 includes a face 4, a crown 6, a sole 8, and a
hosel 10. The face 4 includes a face surface fs. The face surface
fs is a hitting surface. The crown 6 extends toward the back of the
head from the upper edge of the face 4. The sole 8 extends toward
the back of the head from the lower edge of the face 4. The head 2
is hollow. The head 2 is a wood type golf club head.
[0031] FIG. 2 is an exploded perspective view of the head 2. The
head 2 has a four-piece structure. Members constituting the head 2
are a face member Fp1, a sole member Sp1, a crown member Cp1, and a
hosel member Hp1. The head 2 is manufactured by welding these
members.
[0032] FIG. 3 is a plan view showing a back surface fr of the face
member Fp1. FIG. 4 is a cross-sectional view taken along line F4-F4
of FIG. 3. As described later, a plurality of projections (A) are
formed on the back surface fr. However, these projections (A) are
omitted in FIGS. 3 and 4.
[0033] The face member Fp1 constitutes the whole face 4.
Furthermore, the face member Fp1 includes a backward extending part
Fp2 (see FIG. 4). The backward extending part Fp2 constitutes a
part of the crown 6. The backward extending part Fp2 constitutes a
part of the sole 8. The face member Fp1 including the backward
extending part Fp2 is also referred to as a cup face. A boundary k1
between the face member Fp1 and the other portion is shown by a
two-dot chain line in FIG. 1. The boundary k1 is not visually
recognized in the completed coated head 2.
[0034] The hosel 10 includes a shaft hole 12 to which a shaft is
attached. The shaft which is not shown is inserted into the shaft
hole 12. Although not shown in the figures, the shaft hole 12 has a
center axis line Z1. The center axis line Z1 coincides with a shaft
axis line of a golf club including the head 2.
[0035] In the present application, a base perpendicular plane, a
face-back direction, and a toe-heel direction are defined. A state
where the center axis line Z1 is included in a plane P1
perpendicular to a level surface H and the head 2 is placed at a
predetermined lie angle and real loft angle on the level surface H
is defined as a base state. The plane P1 is defined as a base
perpendicular plane. The predetermined lie angle and real loft
angle are described in, for example, a product catalog.
[0036] In the present application, the toe-heel direction is a
direction of an intersection line between the base perpendicular
plane and the level surface H.
[0037] In the present application, the face-back direction is a
direction perpendicular to the toe-heel direction and parallel to
the level surface H.
[0038] In the present application, a face center is defined. On the
face surface, a maximum width Wx in the toe-heel direction is
determined. Furthermore, a middle position Px of the maximum width
Wx in the toe-heel direction is determined. At the position Px, a
middle point Py of the face surface in an up-down direction is
determined. The point Py is defined as the face center.
[0039] In the present application, an up-down direction is defined.
The up-down direction is a direction perpendicular to the face-back
direction and perpendicular to the toe-heel direction.
[0040] In the present application, a longitudinal direction Dy is
defined (see FIG. 3). The longitudinal direction Dy is a direction
of a projection straight line obtained by projecting a straight
line drawn in the up-down direction onto a specific plane Ps (see
FIG. 4). The specific plane Ps is a plane perpendicular to a
straight line LN (described later).
[0041] In the present application, a lateral direction Dx is
defined (see FIG. 3). The lateral direction Dx is a direction on
the specific plane Ps, and perpendicular to the longitudinal
direction Dy. The lateral direction Dx is equal to the toe-heel
direction.
[0042] In the present application, a first direction D1 and a
second direction D2 are defined. The first direction D1 and the
second direction D2 are directions on the specific plane Ps. The
first direction D1 may be any direction. The second direction D2 is
orthogonal to the first direction D1. The longitudinal direction Dy
is an example of the first direction D1. The lateral direction Dx
is an example of the second direction D2.
[0043] In the present application, the disposition and areas of
projections on the face back surface fr are estimated in a planar
view. The planar view means a projection image Psi to the specific
plane Ps.
[0044] In the projection to the specific plane Ps, the projection
direction is a direction of a face normal line (described
later).
[0045] In the present application, a face back surface center CR is
defined. The straight line LN in FIG. 4 is a normal line of the
face surface fs passing through a face center CF. An intersection
point between the normal line LN and the face back surface fr is
the face back surface center.
[0046] In the present application, the direction of the straight
line LN is defined as the direction of the face normal line.
[0047] The face member Fp1 may be divided into a plurality of
regions based on a face thickness TF. As shown in FIG. 3, in the
face back surface fr, division lines are formed. These division
lines can be recognized visually as ridge lines. In a
cross-sectional view, the ridge line has a roundness. The whole
face back surface fr smoothly continues. As shown in FIG. 3, the
face back surface fr includes a region S, a region Bt, a region Bh,
a region Ct, a region Ch, a region Da, a region Db, a region Et,
and a region Eh. Regions other than these regions are transition
regions having the thickness TF gradually changed.
[0048] The height of each of the projections (A) is not included in
the face thickness TF.
[0049] In FIG. 3, hatching is applied to only the region S.
Hatching is omitted in the other regions.
[0050] The region S is located in a middle part of the face 4. The
region S includes a face center position. In other words, the
region S includes the face back surface center.
[0051] The region Bt is located below the region S. The region Bt
is located on a toe side with respect to the face center. The
region Bt is located below the face center.
[0052] The region Bh is located above the region S. The region Bh
is located on a heel side with respect to the face center. The
region Bh is located above the face center.
[0053] The region Ct is located on a toe side with respect to the
region S. The region Ct is located on a toe side with respect to
the face, center. The region Ct includes a face center up-down
position. The face center up-down position is a position of the
face center in the up-down direction.
[0054] The region Ch is located on a heel side with respect to the
region S. The region Ch is located on a heel side with respect to
the face center. The region Ch includes the face center up-down
position.
[0055] The region Da is located above the region S. The region Da
is located above the face center. The region Da includes a face
center right-left position. The face center right-left position is
a position of the face center in the toe-heel direction.
[0056] The region Db is located below the region S. The region Db
is located below the face center. The region Db includes the face
center right-left position.
[0057] The center of gravity of the region Et is located on a toe
side with respect to the region S. The region Et is located on a
toe side with respect to the face center. The region Et does not
include the face center up-down position. The region Et does not
include the face center right-left position. The center of gravity
of the region Et is located above the center of gravity of the
region Ct.
[0058] The center of gravity of the region Eh is located on a heel
side with respect to the region S. The region Eh is located on a
heel side with respect to the face center. The region Eh does not
include the face center up-down position. The region Eh does not
include the face center right-left position. The center of gravity
of the region Eh is located below the center of gravity of the
region Ch.
[0059] In the present embodiment, the thickness TF of each region
is as follows. [0060] region S: 3.3 mm or greater and 3.5 mm or
less [0061] region Bt: 2.5 mm or greater and 2.7 mm or less [0062]
region Bh: 2.5 mm or greater and 2.7 mm or less [0063] region Ct:
2.4 mm or greater and 2.6 mm or less [0064] region Ch: 2.4 mm or
greater and 2.6 mm or less [0065] region Da: 2.1 mm or greater and
2.3 mm or less [0066] region Db: 2.1 mm or greater and 2.3 mm or
less [0067] region Et: 2.0 mm or greater and 2.2 mm or less [0068]
region Eh: 2.0 mm or greater and 2.2 mm or less
[0069] These regions are common in all embodiments which will be
described later.
[0070] The difference between the maximum value and the minimum
value of the thickness TF in each region is preferably equal to or
less than 0.15 mm, and more preferably equal to or less than 0.1
mm.
[0071] The region S is a maximum thickness region Tm. If the
maximum value of the face thickness TF is defined as Tmax (mm), the
maximum thickness region Tm means a region in which the face
thickness TF is equal to or greater than [Tmax-0.2] mm. The face
thickness TF is a thickness in the direction of the face normal
line.
[0072] The face back surface fr has at least a projection
arrangement region. The projection arrangement region has two or
more projections (A). In the embodiment of FIG. 5, the projection
arrangement regions are the region S, the region Ct, the region Ch,
the region Et, and the region Eh.
[0073] As shown in FIG. 5, a plurality of projections (A) are
arranged on the face back surface fr. The plurality of projections
(A) are arranged in each of the longitudinal direction Dy and the
lateral direction Dx.
[0074] In the present application, an area of each of the
projections (A) in the planar view is defined as Ma. The two or
more kinds of projections (A) having the areas Ma substantially
different from each other are provided on the face back surface fr.
In the embodiment of FIG. 5, the three kinds of projections (A)
having the areas Ma substantially different from each other are
provided. The phrase "substantially different" means that the
difference between the areas Ma is equal to or greater than 5%.
[0075] In the embodiment of FIG. 5, the three kinds of projections
(A) include a projection (A1), a projection (A2), and a projection
(A3). The area Ma of the projection (A1) is Ma1. The area Ma of the
projection (A2) is Ma2. The area Ma of the projection (A3) is Ma3.
The area Ma1, the area Ma2, and the area Ma3 are substantially
different.
[0076] In the drawings of the present application, each of the
projections (A) is shown by reference character Ta. In the drawings
of the present application, the projection (A1) is shown by
reference character Ta1. In the drawings of the present
application, the projection (A2) is shown by reference character
Ta2. In the drawings of the present application, the projection
(A3) is shown by reference character Ta3.
[0077] Stress acting on the face is likely to be dispersed at
random by providing the two or more kinds of projections (A) having
the areas Ma substantially different from each other. The
dispersion of the stress can relieve stress concentration to
improve a face strength.
[0078] In the planar view, the projections (A) are point-like.
FIGS. 6(a), 6(b), and 6(c) show examples of point-like projections
Ta. FIG. 6(a) shows a circular projection Ta. In the embodiment of
FIG. 5, all the projections Ta are circular. FIG. 6(b) shows an
elliptical projection Ta. FIG. 6(c) shows an irregular projection
Ta.
[0079] As shown in FIG. 6(c), a longest transversal line CL1 in an
outline in the planar view is determined. Furthermore, a
transversal line CL2 which is the longest among transversal lines
perpendicular to the longest transversal line is determined. A
length of the transversal line CL1 is defined as N1, and a length
of the transversal line CL2 is defined as N2. In the case of the
ellipse as shown in FIG. 6(b), the transversal line CL1 is a long
axis, and the transversal line CL2 is a short axis. In the present
application, the case where N1/N2 is equal to or less than 8 is
defined to be point-like. In respect of improving the strength of
the face 4 while suppressing the mass of the projection Ta, N1/N2
is preferably equal to or less than 5, more preferably equal to or
less than 2, and still more preferably equal to or less than 1.5.
N1/N2 is equal to or greater than 1. In the case of the circle,
N1/N2 is 1.
[0080] Examples of the shape of the projection Ta in the planar
view include a regular polygon as well as the above-mentioned
circle and ellipse. Examples of the regular polygon include a
square, a regular pentagon, and a regular hexagon. In respect of
equally dispersing the stress acting on the face 4, the shape is
preferably the circle.
[0081] [Effects of Projections (A)]
[0082] The projections (A) are point-like, and thereby the strength
of the face can be improved without thickening the whole face. The
plurality of projections (A) are dispersively disposed, and thereby
the face strength can be improved in a wide range without
thickening the whole face. The point-like projections (A) can be
disposed at positions where an improvement in the strength is
required, and thereby the degree of freedom of design of the face
is improved. Therefore, a face 4 being lightweight and having a
high strength can be obtained. The point-like projections (A) are
suitable for obtaining a strength improvement effect (described
later) caused by forging.
[0083] In the present application, the arrangement regularity of
the projections (A) is defined. FIG. 7 is a view for describing the
arrangement regularity. Herein, the case where the first direction
D1 is the longitudinal direction Dy and the second direction D2 is
the lateral direction Dx is described. The arrangement regularity
is estimated in the planar view.
[0084] In order to determine the arrangement regularity, a lateral
direction line Lx and a longitudinal direction line Ly are
considered. The lateral direction line Lx is a straight line
extending in the lateral direction Dx. The longitudinal direction
line Ly is a straight line extending in the longitudinal direction
Dy. In FIG. 7, a lateral direction line Lx1, a lateral direction
line Lx2, and a lateral direction line Lx3 are determined as the
lateral direction line Lx. In FIG. 7, a longitudinal direction line
Ly1, a longitudinal direction line Ly2, and a longitudinal
direction line Ly3 are determined as the longitudinal direction
line Ly.
[0085] In the embodiment of FIG. 7, ten projections Ta are
disposed. That is, a projection 102, a projection 104, a projection
106, a projection 108, a projection 110, a projection 112, a
projection 114, a projection 116, a projection 118, and a
projection 120 are disposed.
[0086] The projection 102, the projection 104, and the projection
106 intersect with a first lateral direction line Lx1. The
projection 108, the projection 110, and the projection 112
intersect with a second lateral direction line Lx1. The projection
114, the projection 116, and the projection 118 intersect with a
third lateral direction line Lx1.
[0087] The projection 106, the projection 112, and the projection
118 intersect with a first longitudinal direction line Ly1. The
projection 104, the projection 110, and the projection 116
intersect with a first longitudinal direction line Ly2. The
projection 102, the projection 108, and the projection 114
intersect with a third longitudinal direction line Ly3.
[0088] A center of figure of the projection Ta is shown by
reference character gt in FIG. 7. A distance between the center of
figure gt of the projection Ta and the lateral direction line Lx is
shown by a double-headed arrow xd in FIG. 7. The lateral direction
line Lx intersects with the two or more projections Ta. The number
of the lateral direction line Lx which intersects with one
projection Ta is one. In the embodiment of FIG. 7, each of the
three lateral direction lines Lx intersects with the three
projections Ta.
[0089] The projection Ta intersecting with the lateral direction
line Lx is a measurement target for the distance xd. However, the
projection Ta which does not intersect with the lateral direction
line Lx may also be assumed. As shown in FIG. 7, the projection 120
which does not intersect with the lateral direction line Lx is also
a measurement target for the distance xd. The distance xd is
measured between the center of figure gt of the projection Ta and
the lateral direction line Lx closest to the center of figure
gt.
[0090] A distance between the center of figure gt of the projection
Ta and the longitudinal direction line Ly is shown by a
double-headed arrow yd in FIG. 7. The longitudinal direction line
Ly intersects with two or more projections Ta. The number of the
longitudinal direction line Ly which intersects with one projection
Ta is one. In the embodiment of FIG. 7, each of the three
longitudinal direction lines Ly intersects with three projections
Ta.
[0091] The projection Ta intersecting with the longitudinal
direction line Ly is a measurement target for the distance yd.
Furthermore, as shown in FIG. 7, the projection 120 which does not
intersect with the longitudinal direction line Ly is also a
measurement target for the distance yd. The distance yd is measured
between the center of figure gt of the projection Ta and the
longitudinal direction line Ly (Ly3) closest to the center of
figure gt.
[0092] As many lateral direction lines Lx and longitudinal
direction lines Ly satisfying the above-mentioned condition as
possible are determined. An average value Xv1 of the distances xd
and an average value Yv1 of the distances yd are calculated. If a
plurality of average values Xv1 can be calculated, the minimum
value of the average values Xv1 is employed. If a plurality of
average values Yv1 can be calculated, the minimum value of the
average values Yv1 is employed.
[0093] If Xv1 is smaller than Yv1, the difference of the following
arrangement regularity is realized.
[0094] [Difference of Arrangement Regularity]: The arrangement
regularity of the projections (A) in the lateral direction Dx is
higher than the arrangement regularity of the projections (A) in
the longitudinal direction Dy.
[0095] Also if at least one lateral direction line Lx is present,
and the longitudinal direction line Ly is not present, the
difference of the arrangement regularity is realized.
[0096] The difference of the arrangement regularity causes a
projection arrangement effect.
[0097] [Projection Arrangement Effect]
[0098] In order to describe the effect, a deformation in the
toe-heel direction and a deformation in the up-down direction are
defined. The deformation in the toe-heel direction in the present
application means a deformation in which the fold by the
deformation is generated in the up-down direction. Meanwhile, the
deformation in the up-down direction in the present application
means a deformation in which the fold by a deformation is generated
in the toe-heel direction.
[0099] The deformation in which the fold is generated in the
up-down direction is less likely to occur by decreasing the
arrangement regularity in the longitudinal direction Dy. That is,
the deformation in the toe-heel direction is less likely to occur
by decreasing the arrangement regularity in the longitudinal
direction Dy.
[0100] The length of the face in the toe-heel direction is greater
than the length of the face in the up-down direction. For this
reason, the deformation in the toe-heel direction is likely to be
greater than the deformation in the up-down direction. The
deformation in the toe-heel direction can be effectively suppressed
by decreasing the arrangement regularity in the longitudinal
direction Dy. The face strength can be improved by suppressing the
excessive deformation.
[0101] Meanwhile, the deformation in the up-down direction is not
excessively suppressed by increasing the arrangement regularity in
the lateral direction Dx. Therefore, the deterioration in rebound
performance can be suppressed. Balance between the deformation in
the toe-heel direction and the deformation in the up-down direction
is favorable, and thereby the face strength can be optimized.
[0102] Selective suppression of a deformation in a predetermined
direction may be desired due to variation in hitting points, and
design of a face thickness, or the like. In this case, the
direction in which the suppression of the deformation is desired
can be set to the second direction. The arrangement regularity of
the projections (A) in the second direction is set to be higher
than the arrangement regularity of the projections (A) in the first
direction. The deformation in the second direction can be
effectively suppressed by the arrangement.
[0103] In the embodiment of FIG. 5, the number of the projections
Ta (projections Ta1) intersecting with the first lateral direction
line Lx1 is X1. In the embodiment of FIG. 5, X1 is 10. In respect
of improving the projection arrangement effect, X1 is preferably
equal to or greater than 5, more preferably equal to or greater
than 6, and still more preferably equal to or greater than 7. In
respect of suppressing the weight of the face 4, X1 is preferably
equal to or less than 15, more preferably equal to or less than 14,
and still more preferably equal to or less than 13.
[0104] In the embodiment of FIG. 5, the number of the projections
Ta (projections Ta1) intersecting with the second lateral direction
line Lx2 is X2. In the embodiment of FIG. 5, X2 is 11. In respect
of improving the projection arrangement effect, X2 is preferably
equal to or greater than 5, more preferably equal to or greater
than 6, and still more preferably equal to or greater than 7. In
respect of suppressing the weight of the face 4, X2 is preferably
equal to or less than 15, more preferably equal to or less than 14,
and still more preferably equal to or less than 13.
[0105] In the embodiment of FIG. 5, the number of the projections
Ta (projections Ta1) intersecting with the third lateral direction
line Lx3 is X3. In the embodiment of FIG. 5, X3 is 9. In respect of
improving the projection arrangement effect, X3 is preferably equal
to or greater than 5, more preferably equal to or greater than 6,
and still more preferably equal to or greater than 7. In respect of
suppressing the weight of the face 4, X3 is preferably equal to or
less than 15, more preferably equal to or less than 14, and still
more preferably equal to or less than 13.
[0106] In the embodiment of FIG. 5, the arrangement regularity in
the lateral direction Dx is higher than the arrangement regularity
in the longitudinal direction Dy in the whole face back surface
fr.
[0107] In the embodiment of FIG. 5, the arrangement regularity in
the lateral direction Dx is higher than the arrangement regularity
in the longitudinal direction Dy in the projection arrangement
region S. The projection arrangement region S is a middle
projection arrangement region S including the face back surface
center CR. Large stress acts on the middle projection arrangement
region S when a ball is hit. A portion on which the large stress
acts can be selectively and effectively reinforced by applying the
projection arrangement effect to the region S.
[0108] In the embodiment of FIG. 5, the arrangement regularity in
the lateral direction Dx is higher than the arrangement regularity
in the longitudinal direction Dy in the projection arrangement
region Ct. The region Ct is a toe side projection arrangement
region located on a toe side with respect to the region S.
[0109] In the embodiment of FIG. 5, the arrangement regularity in
the lateral direction Dx is higher than the arrangement regularity
in the longitudinal direction Dy in the projection arrangement
region Ch. The region Ch is a heel side projection arrangement
region located on a heel side with respect to the region S.
[0110] In the embodiment of FIG. 5, the arrangement regularity in
the lateral direction Dx is higher than the arrangement regularity
in the longitudinal direction Dy in the projection arrangement
region Et.
[0111] In at least one projection arrangement region, the
difference of the arrangement regularity can be applied. The
projection arrangement effect can be applied to a desired
projection arrangement region according to the application.
Therefore, a region requiring a strength can be selectively
reinforced.
[0112] As shown in FIG. 5, in the longitudinal direction Dy (first
direction D1), the projection Ta2 is disposed on a face peripheral
side with respect to the projection Ta1. The projection Ta3 is
disposed on a face peripheral side with respect to the projection
Ta2. The position of the projection Ta is estimated based on the
center of figure gt. A longitudinal distance between the periphery
of the face back surface fr and the projection Ta1 is defined as
a1.
[0113] A longitudinal distance between the periphery of the face
back surface fr and the projection Ta2 is defined as a2. A
longitudinal distance between the periphery of the face back
surface fr and the projection Ta3 is defined as a3. The
longitudinal distance for each of the projections Ta is
measured.
[0114] The average value of the distances a1 is defined as Av1. The
average value of the distances a2 is defined as Av2. The average
value of the distances a3 is defined as Av3. The average value Av1
is greater than the average value Av2. The average value Av2 is
greater than the average value Av3.
[0115] The stress acting on the face 4 is comparatively large in
the middle part of the face 4. The stress acting on the face 4 is
comparatively small in the peripheral part of the face 4. In light
of this point, the projection Ta of which the area Ma is
comparatively small is disposed in the peripheral part of the face
4, and the projection Ta of which the area Ma is comparatively
large is disposed in the middle part of the face 4. For this
reason, the improvement in the face strength is achieved while the
total volume of the projections (A) is suppressed.
[0116] Preferably, the area Ma of the projection (A) (projection
Ta) is 3 mm.sup.2 or greater and 40 mm.sup.2 or less. In this
range, the strength of the face 4 can be effectively improved while
the increase in the mass of the face 4 is suppressed.
[0117] Preferably, the area Ma1 of the projection (A1) (projection
Ta1) is 12 mm.sup.2 or greater and 40 mm.sup.2 or less. In this
range, the strength of the face 4 can be effectively improved while
the increase in the mass of the face 4 is suppressed. The
projection (A) having the area Ma different from the area Ma1 can
be easily provided by limiting the area Ma1 to the range.
[0118] Preferably, the area Ma2 of the projection (A2) (projection
Ta2) is 6 mm.sup.2 or greater and 30 mm.sup.2 or less. In this
range, the strength of the face 4 can be effectively improved while
the increase in the mass of face 4 is suppressed. The projection
(A) having the area Ma different from the area Ma2 can be easily
provided by limiting the area Ma2 to the range.
[0119] Preferably, the area Ma3 of the projection (A3) (projection
Ta3) is 3 mm.sup.2 or greater and 20 mm.sup.2 or less. In this
range, the strength of the face 4 can be effectively improved while
the increase in the mass of face 4 is suppressed. The projection
(A) having the area Ma different from the area Ma3 can be easily
provided by limiting the area Ma3 to the range.
[0120] In respect of improving an effect caused by the presence of
the projection Ta, the height Ha of the projection (A) is
preferably equal to or greater than 0.03 mm, more preferably equal
to or greater than 0.05 mm, and still more preferably equal to or
greater than 0.07 mm. In respect of reducing the mass of the face
4, the height Ha is preferably equal to or less than 0.2 mm, more
preferably equal to or less than 0.17 mm, and still more preferably
equal to or less than 0.15 mm.
[0121] FIG. 8 is a plan view showing a face back surface fr of a
face member Fp20 according to a second embodiment. The plan view
shows the above-mentioned projection image Psi. Except for the
projections Ta, the face member Fp20 is the same as the face member
Fp1.
[0122] A projection occupation ratio Rs is considered in the face
member Fp20. The ratio Rs of the middle projection arrangement
region S is smaller than the ratio Rs of the other region. The
ratio Rs of the region S is smaller than the ratio Rs of the region
Et. The ratio Rs of the region S is smaller than the ratio Rs of
the region Ct. The ratio Rs of the region S is smaller than the
ratio Rs of the region Eh. The ratio Rs of the region S is smaller
than the ratio Rs of the region Ch. The ratio Rs is a ratio of the
total area of the projections (A) to the area of the entire region.
The ratio Rs is determined in the planar view.
[0123] In the face, the projection occupation ratio Rs of a face
middle part is decreased, and the projection occupation ratio Rs of
a face peripheral part is increased. Since the hardness of the
peripheral part is further improved, the thickness of the
peripheral part can be decreased. Therefore, the whole face 4 is
likely to bend, which can provide the enlargement of a sweet
area.
[0124] FIG. 9 is a plan view showing a face back surface fr of a
face member Fp30 according to a third embodiment. The plan view
shows the above-mentioned projection image Psi. Except for
projections Ta, the face member Fp30 is the same as the face member
Fp1.
[0125] In the face member Fp30, the projection occupation ratio Rs
of a middle projection arrangement region S is greater than the
ratios Rs of the other regions. The ratio Rs of the region S is
greater than the ratio Rs of the region Et. The ratio Rs of the
region S is greater than the ratio Rs of the region Ct. The ratio
Rs of the region S is greater than the ratio Rs of the region Eh.
The ratio Rs of the region S is greater than the ratio Rs of the
region Ch.
[0126] In the face, the projection occupation ratio Rs of a face
middle part is increased. Since the hardness of the middle part is
further improved, the thickness of the middle part can be
decreased. Therefore, the bending of the face 4 when a ball is hit
with the middle part is increased. For this reason, rebound
performance when the ball is hit with the face middle part is
improved, which can provide an increase in the maximum value of a
coefficient of restitution. A maximum flight distance can be
increased by the increase.
[0127] FIG. 10 is a plan view showing a face back surface fr of a
face member Fp40 according to a fourth embodiment. The plan view
shows the above-mentioned projection image Psi. Except for the
projections Ta, the face member Fp40 is the same as the face member
Fp1.
[0128] In the embodiment of FIG. 10, the arrangement regularity of
the projections (A) in a second direction D2 is higher than the
arrangement regularity of the projections (A) in a first direction
D1. The second direction D2 is inclined so as to be an upper side
toward a toe side. An angle between a lateral direction Dx and the
second direction D2 is shown by a double-headed arrow .theta.1 in
FIG. 10.
[0129] Usually, a golfer has variation in hitting points. The
golfer's hitting points tend to be distributed between the upper
side of a toe and the lower side of a heel. The arrangement of the
projections (A) is adapted for the distribution of the hitting
points by inclining the second direction D2 with respect to the
lateral direction Dx. For this reason, the projection arrangement
effect can be further improved. In light of the distribution of the
hitting points, the lower limit of the angle .theta.1 is preferably
equal to or greater than 10 degrees, and more preferably equal to
or greater than 15 degrees. The upper limit of the angle .theta.1
is preferably equal to or less than 50 degrees, and more preferably
equal to or less than 45 degrees.
[0130] FIG. 11 is a plan view showing a face back surface fr of a
face member Fp50 according to a fifth embodiment. The plan view
shows the above-mentioned projection image Psi. Except for the
projections Ta, the face member Fp50 is the same as the face member
Fp1.
[0131] In the embodiment of FIG. 11, a projection Ta2 is disposed
between projections Ta1. The area Ma2 of the projection Ta2 is
smaller than the area Ma1 of the projection Ta1. The projection
occupation ratio Rs is effectively improved by the disposition. In
respect of improving the projection occupation ratio Rs, Ma2/Ma1 is
preferably equal to or less than 0.3, and more preferably equal to
or less than 0.2. In respect of preventing Ma2 from being too
small, Ma2/Ma1 is preferably equal to or greater than 0.02, and
more preferably equal to or greater than 0.05.
[0132] FIG. 12 is a plan view showing a face back surface fr of a
face member Fp60 according to a sixth embodiment. The plan view
shows the above-mentioned projection image Psi. Except for the
projections Ta, the face member Fp60 is the same as the face member
Fp1.
[0133] In the embodiment of FIG. 12, the projection Ta has an
ellipse shape. The long axis of the ellipse is substantially
parallel to a lateral direction Dx. In other words, the absolute
value of an angle between the long axis of the ellipse and the
lateral direction Dx is equal to or less than 10 degrees. The
projection Ta may not have the ellipse shape, and may have a shape
shown in FIG. 6(c), for example. The absolute value of an angle
between the longest transversal line CL1 and the lateral direction
Dx is preferably equal to or less than 10 degrees. The projection
arrangement effect can be further improved by the constitution.
[0134] The volume of the head is not limited. The present invention
is effective when a face area is large. In this respect, the volume
of the head is preferably equal to or greater than 400 cc, more
preferably equal to or greater than 420 cc, and still more
preferably equal to or greater than 440 cc. In respect of observing
the rules for the golf club, the volume of the head is preferably
equal to or less than 470 cc, and more preferably equal to or less
than 460 cc.
[0135] The weight of the head is not limited. In respect of a swing
balance, the weight of the head is preferably equal to or greater
than 175 g, more preferably equal to or greater than 180 g, and
still more preferably equal to or greater than 185 g. In respect of
the swing balance, the weight of the head is preferably equal to or
less than 205 g, more preferably equal to or less than 200 g, and
still more preferably equal to or less than 195 g.
[0136] A method for manufacturing the head is not limited. Usually,
a hollow head is manufactured by joining two or more members. A
method for manufacturing the members constituting the head is not
limited. Examples of the method include casting, forging, and press
forming.
[0137] A method for manufacturing the face member Fp is not
limited. Examples of the method include casting, forging, and press
forming. However, the forging is preferable as described later. A
method for forming the projections (A) is not limited. The
projections (A) may be formed simultaneously with the formation of
the face member Fp, and process for forming the projections (A) may
be performed after the formation of the face member Fp. Examples of
the process include cutting by NC process, and chemical milling. As
described later, the projections (A) are preferably formed by
forging the face member Fp.
[0138] The structure of the head is not limited. Examples of the
structure of the head include a two-piece structure in which two
members each integrally formed are joined, a three-piece structure
in which three members each integrally formed are joined, and a
four-piece structure in which four members each integrally formed
are joined. The head 2 has the four-piece structure.
[0139] [Manufacture of Face Member Fp1]
[0140] Preferably, the face member Fp1 is manufactured by forging.
If the projection (B) is crushed to form the projection (A), the
forging number of the face member Fp1 is multiple. For example, the
forging number is 2 or greater and 4 or less. In respect of
productivity, the forging number is preferably 2 or 3, and more
preferably 2.
[0141] Generally, the first forging is also referred to as rough
forging. Generally, the last forging is also referred to as main
forging.
[0142] A plurality of forgings include a preceding forging step and
a subsequent forging step. The subsequent forging step is performed
after the preceding forging step. If the forging number is 2, the
first forging is the preceding forging step, and the second forging
is the subsequent forging step. If the forging number is equal to
or greater than 3, it is preferable that the last forging is the
subsequent forging step and the forging immediately prior to the
last forging is the preceding forging step.
[0143] The forging may be cold forging or hot forging. In respect
of the improvement in the strength caused by the densification of
the structure, the hot forging is preferable.
[0144] In the manufacture of the face member Fp1, in the preceding
forging step, the approximate shape of the face member Fp1 is
formed, and the projection (B) is formed. The projection (B) is
higher than the projection (A). The projection (B) is crushed in
the subsequent forging step. The crushed projection (B) constitutes
the projection (A).
[0145] The projection (B) is crushed to form the projection (A),
and thereby distortion is generated in metal crystal grains to
produce recrystallization. The metal structure is densified by the
recrystallization. The distortion can be generated by the crushing,
to cause work hardening. The projection (B) is crushed to form the
projection (A), and thereby the strength of the face member Fp1 can
be improved.
[0146] Although the projection (B) is crushed, the projection (B)
is not completely crushed, and the projection (A) remains.
Therefore, an effect caused by the crushing is obtained. At the
same time, the formation of the projection (A) is also
achieved.
[0147] The height of the projection (B) is defined as Hb. The
height of the projection (A) is defined as Ha. In respect of
increasing the deformation amount of the projection (B) to improve
the strength of the face member Fp1, Hb/Ha is preferably equal to
or greater than 1.5, more preferably equal to or greater than 2,
and still more preferably equal to or greater than 3. In respect of
suppressing excessive crushing deformation, Hb/Ha is preferably
equal to or less than 15, more preferably equal to or less than 12,
and still more preferably equal to or less than 10.
[0148] In respect of obtaining moderate crushing deformation, the
lower limit of the height Hb is preferably equal to or greater than
0.2 mm, and more preferably equal to or greater than 0.3 mm. The
upper limit of the height Hb is preferably equal to or less than
1.5 mm, and more preferably equal to or less than 1.2 mm.
[0149] The area of the projection (B) in the planar view is defined
as My. The area My is smaller than the area Ma. The area Ma of the
projection (A) is made to be greater than the area My by the
crushing. In respect of increasing the deformation amount of the
projection (B) to improve the strength of the face member Fp1,
Ma/My is preferably equal to or greater than 1.2, more preferably
equal to or greater than 1.5, and still more preferably equal to or
greater than 2. In respect of suppressing excessive crushing
deformation, Ma/My is preferably equal to or less than 20, more
preferably equal to or less than 15, and still more preferably
equal to or less than 12.
[0150] In respect of obtaining moderate crushing deformation, the
following items (a) and/or (b) are/is preferable:
[0151] (a) the area My of the projection (B) for forming the
projection (A) is greater as the area Ma of the projection (A) is
larger; and
[0152] (b) the height Hb of the projection (B) for forming the
projection (A) is greater as the area Ma of the projection (A) is
larger.
Example
[0153] Hereinafter, the effects of the present invention will be
clarified by Example. However, the present invention should not be
interpreted in a limited way based on the description of the
Example.
Example
[0154] A face member Fp1, a sole member Sp1, a crown member Cp1,
and a hosel member Hp1 as shown in FIG. 2 were obtained by forging.
A titanium alloy was used as a material for all the members. The
material of the face member Fp1 was "Super-TIX 51AF" (trade name)
manufactured by NIPPON STEEL & SUMITOMO METAL CORPORATION.
[0155] The forging number of the face member Fp1 was set to 2. The
face member Fp1 was manufactured by a preceding forging step and a
subsequent forging step. Both the preceding forging step and the
subsequent forging step were hot forging. A round bar as a material
was subjected to the preceding forging step in a state where the
round bar was set in a preceding forging mold. A preceding forged
molded body was obtained in the preceding forging step. The outer
shape of the preceding forged molded body was substantially the
same as the outer shape of the face member Fp1 as a last molded
body. The preceding forged molded body had projections (B). The
positions and number of the projections (B) were made the same as
the positions and number of the projections (A) shown in FIG.
5.
[0156] The projections (B) included a projection (B1) of which the
height Hb was Hb1, a projection (B2) of which the height Hb was
Hb2, and a projection (B3) of which the height Hb was Hb3. The
height Hb1 was greater than the height Hb2. The height Hb2 was
greater than the height Hb3. The height Hb1 was set to 1 mm. The
height Hb2 was set to 0.4 mm. The height Hb3 was set to 0.3 mm. The
preceding forged molded body was subjected to the subsequent
forging step in a state where the preceding forged molded body was
set in a subsequent forging mold. A subsequent forged molded body
(face member Fp1 shown in FIG. 5) was obtained in the subsequent
forging step. The subsequent forged molded body had a projection
(A1), a projection (A2), and a projection (A3).
[0157] The projection (B1) was crushed to form the projection (A1).
The projection (B2) was crushed to form the projection (A2). The
projection (B3) was crushed to form the projection (A3).
[0158] The area Ma1 of the projection (A1) was 15 mm.sup.2. The
height Ha1 of the projection (A1) was 0.1 mm. The area Ma2 of the
projection (A2) was 12 mm.sup.2. The height Ha2 of the projection
(A2) was 0.1 mm. The area Ma3 of the projection (A3) was 9
mm.sup.2. The height Ha3 of the projection (A3) was 0.1 mm.
[0159] The face member Fp1 and the other members were welded to
obtain a head of Example as shown in FIG. 1. A 46-inch golf club
was produced by using the head.
Comparative Example
[0160] A face member having no projection (A) was produced by
changing a forging mold. In the face member, a face thickness was
added as compared with Example. The face thickness was added to
each of regions shown in FIG. 3. The additional thickness was made
the same as the height of the projection (A) which was present in
each of the regions. A head and a golf club of Comparative Example
were obtained in the same manner as in Example except for the
constitution.
[0161] Although Comparative Example had no projection (A),
manufacturing conditions in Comparative Example were made the same
as manufacturing conditions in Example. Forging conditions such as
the forging number in Comparative Example were also made the same
as forging conditions in Example.
[0162] [Evaluation of Strength]
[0163] A swing robot was equipped with a golf club, and repeatedly
hit a commercially available two-piece ball at a head speed of 54
m/s. A hitting point was set to a face center. It was visually
confirmed whether cracks were generated on a face surface for every
100 hits.
[0164] In Example, the hitting number when the cracks were
confirmed was 10400. In Comparative Example, the hitting number
when the cracks were confirmed was 10500. Although the face of
Example was more lightweight than the face of Comparative Example,
the face strength of Example was equivalent to the face strength of
Comparative Example.
INDUSTRIAL APPLICABILITY
[0165] The present invention can be applied to all golf club heads
such as a wood type head, a utility type head, a hybrid type head,
and an iron type head.
REFERENCE SIGNS LIST
[0166] 2 Head [0167] 4 Face [0168] 6 Crown [0169] 8 Sole [0170] 10
Hosel [0171] 12 Shaft hole [0172] fs Face surface [0173] fr Face
back surface [0174] Fp1, Fp20, Fp30, Fp40, Fp50, Fp60 Face members
[0175] Cp1 Crown member [0176] Sp1 Sole member [0177] Hp1 Hosel
member [0178] Ta Projection (A) [0179] Ta1 Projection (A1) [0180]
Ta2 Projection (A2) [0181] Ta3 Projection (A3)
* * * * *