U.S. patent application number 10/981628 was filed with the patent office on 2005-07-21 for golf club head.
This patent application is currently assigned to BRIDGESTONE SPORTS CO., LTD.. Invention is credited to Ezaki, Hiroshi, Hiruta, Masaomi, Imamoto, Yasunori.
Application Number | 20050159239 10/981628 |
Document ID | / |
Family ID | 34687092 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050159239 |
Kind Code |
A1 |
Imamoto, Yasunori ; et
al. |
July 21, 2005 |
Golf club head
Abstract
A golf club head includes a front body formed of a metal
material, an FRP body, a metallic sole plate, and a weight member.
The front body has a face portion, a metal sole portion, a metal
side portion (toe), a metal crown portion, a metal side portion
(heel), and a hosel portion. A slight gap in a range of 4 mm to 12
mm is formed between a front side of the sole plate and the metal
sole portion. This part is formed of the FRP body. Preferably, the
weight of the front body is in a range of 20% to 70% of the weight
of the golf club head.
Inventors: |
Imamoto, Yasunori; (Tokyo,
JP) ; Ezaki, Hiroshi; (Tokyo, JP) ; Hiruta,
Masaomi; (Tokyo, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
BRIDGESTONE SPORTS CO.,
LTD.
|
Family ID: |
34687092 |
Appl. No.: |
10/981628 |
Filed: |
November 5, 2004 |
Current U.S.
Class: |
473/338 ;
473/345; 473/349 |
Current CPC
Class: |
A63B 53/0466 20130101;
A63B 53/0416 20200801; A63B 53/0408 20200801; A63B 53/0433
20200801; A63B 53/0437 20200801; A63B 2209/02 20130101 |
Class at
Publication: |
473/338 ;
473/345; 473/349 |
International
Class: |
A63B 053/04; A63B
053/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2003 |
JP |
P2003-375836 |
Claims
What is claimed is:
1. A golf club head of a hollow shell structure, comprising: a
first member that includes an amorphous metal material and includes
a hosel portion, a face portion and an edge portion continuous with
the face portion; a metal plate that is different member from the
first member, extends in a direction, which is different from a
toe-heel direction of the golf club head, and includes at least a
part of sole portion; and a second member formed of a fiber
reinforced plastic, wherein weight of the first member is in a
range of 20% to 70% of weight of the golf club head.
2. A golf club head of a hollow shell structure, comprising: a
first member that includes an amorphous metal material and includes
a face portion and an edge portion continuous with the face
portion; a metal plate that is different member from the first
member, extends in a direction, which is different from a toe-heel
direction of the golf club head, and includes at least a part of
sole portion; and a second member formed of a fiber reinforced
plastic, wherein the first member and the metal plate are apart
from each other, and the second member joints the first member with
the metal plate.
3. The golf club head according to claim 1, wherein the amorphous
metal material is a zirconium alloy.
4. The golf club head according to claim 1, wherein the
non-crystallinity of the amorphous metal material is in a range of
75% to 100% in the face portion.
5. The golf club head according to claim 1, wherein a portion of
the second member between the first member and the metal plate
recesses from the metal plate and a bottom surface of the first
member.
6. The golf club head according to claim 1, wherein the metal plate
is made of a metal material, which is larger in specific gravity
than the amorphous metal material.
7. The golf club head according to claim 2, wherein the amorphous
metal material is a zirconium alloy.
8. The golf club head according to claim 2, wherein the
non-crystallinity of the amorphous metal material is in a range of
75% to 100% in the face portion.
9. The golf club head according to claim 2, wherein a portion of
the second member between the first member and the metal plate
recesses from the metal plate and a bottom surface of the first
member.
10. The golf club head according to claim 2, wherein the metal
plate is made of a metal material, which is larger in specific
gravity than the amorphous metal material.
11. The golf club head according to claim 10, wherein the metal
material of the metal plate includes stainless steel.
12. The golf club head according to claim 1, further comprising: a
weight member that is fixed to the metal plate and is larger in
specific gravity than the metal plate.
13. The golf club head according to claim 2, further comprising: a
weight member that is fixed to the metal plate and is larger in
specific gravity than the metal plate.
14. The golf club head according to claim 12, wherein the metal
plate defines a cylindrical portion to which the weight member is
fixed.
15. The golf club head according to claim 13, wherein the metal
plate defines a cylindrical portion to which the weight member is
fixed.
16. The golf club head according to claim 1, wherein the second
member is fixed on the edge portion in a superposed state.
17. The golf club head according to claim 2, wherein the second
member is fixed on the edge portion in a superposed state.
18. The golf club head according to claim 1, wherein a back face of
the first member is lined with the fiber reinforced plastic.
19. The golf club head according to claim 2, wherein a back face of
the face portion is lined with the fiber reinforced plastic.
20. The golf club head according to claim 1, wherein the first
member includes a crown portion and a sole portion, and widths of
the crown portion and the sole portion of the first member on a
heel side and a toe side are larger than that in a center portion
thereof.
21. The golf club head according to claim 2, wherein the first
member includes a crown portion and a sole portion; and widths of
the crown portion and the sole portion of the first member on a
heel side and a toe side are larger than that in a center portion
thereof.
22. The golf club head according to claim 1, wherein volume of the
golf club head is in a range of 300 cc to 500 cc; and the weight of
the golf club head is in a range of 180 g to 210 g.
23. The golf club head according to claim 2, wherein volume of the
golf club head is in a range of 300 cc to 500 cc; and weight of the
golf club head is in a range of 180 g to 210 g.
24. The golf club head according to claim 1, wherein the fiber
reinforced plastic includes a carbon fiber reinforced plastic.
25. The golf club head according to claim 2, wherein the fiber
reinforced plastic includes a carbon fiber reinforced plastic.
26. The golf club head according to claim 18, wherein the fiber
reinforced plastic includes a carbon fiber reinforced plastic.
27. The golf club head according to claim 19, wherein the fiber
reinforced plastic includes a carbon fiber reinforced plastic.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a hollow golf club head,
and particularly to a golf club head being of a wood type or
similar type thereto.
[0003] 2. Description of the Related Art
[0004] As wood-type golf club heads such as drivers and fairway
woods, metallic heads of a hollow shell structure are widely in
use. Generally, the hollow wood-type golf club head has a face
portion for hitting a ball, a crown portion constituting an upper
surface portion of the golf club head, a sole portion constituting
a bottom surface portion of the golf club head, a side portion
constituting side surface portions on the tow side, the rear side,
and the heel side of the golf club head, and a hosel portion. A
shaft is inserted into the hosel portion, and is fixed by an
adhesive agent or the like. It should be noted that golf clubs
called utility clubs are also commercially available on the market
in large numbers, and various golf clubs having a head similar to
the aforementioned wood-type golf club head (i.e., having the face
portion, the sole portion, the side portion, the crown portion, and
the hosel portion) are also commercially available on the
market.
[0005] As metals for forming this hollow golf club head, an
aluminum alloy, stainless steel, and a titanium alloy are used. The
titanium alloy, in particular, has come to be used widely in recent
years.
[0006] In JP-A-2002-11122 and JP-A-2002-224249, the hollow golf
club head in which the face portion is made of an amorphous alloy
such as zirconium group, and the other portions are metallic was
described. In these patents, it was described that the face portion
made of an amorphous alloy is useful to increase the carry.
[0007] Generally, it becomes possible to enlarge the sweet spot by
increasing the volume of the hollow golf club head. If the volume
is increased, the weight of the golf club head tens to increase
correspondingly. Accordingly, to prevent an increase in the weight,
it has been conceived to adopt a fiber reinforced plastic whose
specific gravity is smaller than those metals.
[0008] JP-A-2001-340499 discloses a golf club head in which a face
portion and a sole portion are made of a metal, and the other
portions including a crown portion and side portions on the tow
side and the heel side are formed of a carbon-fiber reinforced
thermosetting plastic (CFRP). If the crown portion is made of CFRP,
the flexure of the crown portion becomes large during ball hitting,
so that it is possible to make the launch angle large, and increase
a coefficient of restitution. With this golf club head, however,
the seam between a peripheral edge of the face portion, on the one
hand, and the crown portion and the side portion formed of CFRP, on
the other hand, is in an abutted state. During ball hitting an
extremely large stress occurs in this seam between the peripheral
edge of the face portion and the crown portion and the side
portion. If the golf club head is used repeatedly, this joint
portion is likely to peel off.
[0009] In the U.S. Pat. No. 6,471,604, a golf club head is
described in which the crown front edge portion, the sole front
edge portion, and both the side front edge portions are made to be
a return portion made of an amorphous alloy, the face plane is a
face plate made of an amorphous alloy, a latter half body (aft
body) made of resin material is connected to lead to the return
portion, and an aluminum plate is disposed on the sole portion.
SUMMARY OF THE INVENTION
[0010] A first object of the invention is to provide a golf club
head that is easily designed in terms of a position of a center of
gravity.
[0011] The golf club head as disclosed in U.S. Pat. No. 6,471,604
has a small flexure on the sole side when hitting the ball, because
the aluminum plate on the sole portion leads directly to the bottom
of the return portion. A second object of the invention is to
provide a golf club head having a large flexure on the sole side
when hitting the ball, and a large restitution coefficient.
[0012] To achieve the above objects, according to one aspect of the
invention, there is provided a golf club head of a hollow shell
structure, including: a first member that includes an amorphous
metal material and includes a hosel portion, a face portion and an
edge portion continuous with the face portion; a metal plate that
is different member from the first member, extends in a direction,
which is different from a toe-heel direction of the golf club head,
and includes at least a part of sole portion; and a second member
formed of a fiber reinforced 20% to 70% of weight of the golf club
head.
[0013] According to another aspect of the invention, there is
provided a golf club head of a hollow shell structure, including: a
first member that includes an amorphous metal material and includes
a face portion and an edge portion continuous with the face
portion; a metal plate that is different member from the first
member, extends in a direction, which is different from a toe-heel
direction of the golf club head, and includes at least a part of
sole portion; and a second member formed of a fiber reinforced
plastic, wherein the first member and the metal plate are apart
from each other, and the second member joints the first member with
the metal plate.
[0014] In the golf club head of the invention, the weight of the
first member is in a range of 20% to 70% of the weight of the golf
club head. Since the second member is made of the fiber reinforced
plastic, which has the significantly smaller specific gravity than
that of metal, a weight other than the first member can be
allocated to the metal plate and a weight member disposed on the
metal plate. Thereby, the golf club head can be easily designed to
have a center of gravity at lower position or on a rear side, and
so on as desired.
[0015] In the golf club head of the invention, a portion between
the first member made of amorphous metal and the metal plate is
flexed when hitting a ball, whereby the coefficient of restitution
is great and a carry of the ball is increased.
[0016] Preferably, the portion of the second member between the
first member and the metal plate recesses from the metal plate and
a bottom surface of the first member. By virtue of this
arrangement, even if a sole surface of the golf club head strongly
strikes the ground, the portion is difficult to become damaged.
[0017] Since the second member is fixed on the edge portion in a
superposed state, the first member and the second member can be
firmly fixed together.
[0018] Since a back face of the first member is lined with the
fiber reinforced plastic, the first member can be reinforced or
made less flexible.
[0019] Preferably, widths of a crown portion and a sole portion of
the first body are larger on a toe side and a heel side than those
of a central portion between these portions. By virtue of this
arrangement, the moment of inertia of the golf club hear can be
made large.
[0020] The invention is suitable for application to a large-size
driver head whose weight needs to be suppressed to 180 g -210 g or
thereabouts, although its volume is large in a range of 300 cc-500
cc.
BRIEF DESCRIPTION OF THE DRAWING
[0021] FIG. 1 is a perspective view of a golf club head in
accordance with the embodiment;
[0022] FIG. 2 is a perspective view, as taken from the front side,
of a front body and a sole plate of this golf club head;
[0023] FIG. 3 is a perspective view, as taken from the rear side,
or the front body;
[0024] FIG. 4A is a plan view of this golf club head;
[0025] FIG. 4B is a bottom view of this golf club head;
[0026] FIG. 5A is a section view taken along line V-V in FIG.
4A;
[0027] FIGS. 5B and 5C are enlarged views of a portion B and a
portion C in FIG. 5A;
[0028] FIG. 6 is a section view illustrating a method of
manufacturing this golf club head;
[0029] FIG. 7A to 7E are explanatory diagrams of prepreg sheets
used in the manufacture of an FRP body of this golf club head;
and
[0030] FIG. 8 is a section view of a golf club head according to
another embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Hereafter, a description will be given on an embodiment of
the invention with reference to the drawings. FIG. 1 is a
perspective view of a golf club head in accordance with the
embodiment. FIG. 2 is a perspective view of a front body and a sole
plate of this golf club head as viewed from a front side. FIG. 3 is
a perspective view of the front body as viewed from a rear side.
FIG. 4A is a plan view of this golf club head. FIG. 4B is a bottom
view of this golf club head. FIG. 5A is a section view taken along
line V-V in FIG. 4A. FIGS. 5B and 5C are enlarged view of a portion
B and a portion C in FIG. 5A. FIG. 6 is a section view illustrating
a method of manufacturing this golf club head. FIGS. 7A to 7E are
explanatory diagrams of prepreg sheets used in the manufacture of
an FRP body of this golf club head.
[0032] This golf club head 1 is a wood-type golf club head of a
hollow shell structure including a face portion 2, a sole portion
3, a side portion 4, a crown portion 5, and a hosel portion 6.
[0033] The face portion 2 is a surface for hitting a ball, and is
provided with grooves (scoring lines), which are not shown. The
sole portion 3 constitutes a bottom portion of the golf club head.
The side portion 4 constitutes side surface portions on the toe
side, the heel side, and the rear surface side. The crown portion 5
constitutes an upper surface portion of the golf club head. A shaft
is inserted into the hosel portion 6, and is secured by means of an
adhesive agent.
[0034] This golf club head 1 includes a front body 10 formed of an
amorphous metal material, a fiber reinforced plastic body
(hereinafter referred to as the FRP body) 20, a metallic sole plate
30, and a weight member 40. The weight of this front body 10 is
preferably in a range of 20% to 70%, especially 30% to 60% of the
total weight of the golf club head.
[0035] As shown in FIGS. 2 and 3, the front body 10 includes the
face portion 2, a metal sole portion 13, a metal side portion (toe)
14, a metal crown portion 15, a metal side portion (heel) 16, and a
hosel portion 6.
[0036] The metal sole portion 13 constitutes a front edge portion
of the sole portion 3. The metal side portions 14 and 16 constitute
front edge portions of the side portion 4. The metal crown portion
15 constitutes a front edge portion of the crown portion 5. The
metal crown portion 15 is continuous with the metal side portion
(toe) 14 and the metal side portion (heel) 16. The metal side
portion (toe) 14 and the metal side portion (heel) 16 are
respectively continuous with the metal sole portion 13. The metal
side portions 14 and 16 and the metal sole portion 13 are
continuous with the face portion 2.
[0037] As for the metal sole portion 13 and the metal crown portion
15, widths in the forward and rearward direction (widths in a
direction perpendicular to the face portion 2) are large on the tow
side and the heel side, and their widths in the forward and
rearward direction in the remaining central portions 13a and 15a
are small. As a result, the moment of inertia of the golf club head
can be made large. It should be noted that these widths in the
forward and rearward direction are made gradually smaller from the
toe side and the heel side toward the central portions 13a and
15a.
[0038] The length in the toe-heel direction of the center portions
13a and 15a having small widths in the forward and rearward
direction is preferably 50%-85% of the maximum width of the front
body 10 in the crown portion, and is preferably 55%-80% of the
maximum width of the front body 10 in the sole portion.
[0039] The width of the central portion 15a of the metal crown
portion 15 in the forward and rearward direction is preferably
50%-95%, particularly 55%-70% of the maximum width of the front
body 10 in the forward and rearward direction, while the width of
the central portion 13a of the metal sole portion 13 in the forward
and rearward direction is preferably 50%-95%, particularly 55%-65%
of the maximum width of the front body 10 in the forward and
rearward direction.
[0040] A gap of 4 mm-12 mm, particularly 7 mm-9 mm is formed on an
average between a front side 31 of the sole plate 30 and the metal
sole portion 13, as clearly shown in FIGS. 5A and 5C. The FRP body
20 is interposed between these two members. The FRP body 20 between
the metal sole portion 13 and the front side 31 of the sole plate
30 is upwardly recessed from the bottom surfaces of the metal sole
portion 13 and the sole plate 30. The average depth of this recess
is preferably 0.7 mm-1.5 mm. Since the FRP body 20 is thus
recessed, the FRP body 20 is prevented from becoming damaged by
strongly striking the ground during a duff shot. The bottom of the
FRP body 20 at this recessed portion is curved in an arch shape in
the forward and rearward direction of the golf club head, as shown
in FIG. 5C.
[0041] A rear side 34 of the sole plate 30 is located in proximity
to a rearmost portion of the golf club head 1, but is located
slightly forwardly of the rearmost end of the golf club head 1.
[0042] The sole plate 30 is disposed in a whole area in the
vicinity of the central portion, in the toe-heel direction, of the
metal sole portion 13. As shown in FIG. 2, this sole plate 30 has a
substantially quadrangular shape having the front side 31 facing
the metal sole portion 13, sides 32 and 33 extending in the
rearward direction from both ends of the front side 31, and the
rear side 34. The front side 31 is longer than the rear side 34,
and the sides 32 and 33 approach each other toward their rear
sides. Accordingly, the sole plate 30 is substantially trapezoidal
in a plan view shape. The sole plate 30 is curved in conformity
with the sole surface of the golf club head 1.
[0043] The length of the front side 31 of the sole plate 30 is
preferably 50%-75%, particularly 60%-75% of the length in the
toe-heel direction of the central portion 13a of the metal sole
portion 13. The length of the rear side 34 is preferably 50%-80%,
particularly 55%-75% of the length of that front side 31.
[0044] The length of the sole plate 30 in the forward and rearward
direction is preferably 65%-90%, particularly 75%-85% of the
maximum length of the golf club head 1 in the forward and rearward
direction.
[0045] This sole plate 30 is formed of a metal material such as
stainless steel, aluminum, a copper alloy, a titanium alloy, or the
like.
[0046] A cylindrical portion 35 protrudes in a rear portion of this
sole plate 30 toward the interior of the golf club head 1. The
weight member 40 is secured in an inner hole of the cylindrical
portion 35 by screwing-in.
[0047] The weight member 40 is formed with a flange portion 41 on a
lower end thereof. The cylindrical portion 35 is formed with a
stepped portion 35a for receiving the flange portion 41 at a lower
edge thereof.
[0048] The sole plate 30 is slightly depressed around the periphery
of the cylindrical portion 35.
[0049] The weight member 40 is formed of a metal whose specific
gravity is greater than that of the sole plate 30, such as tungsten
or a tungsten alloy. The specific gravity of the weight member 40
is preferably 10 or more, particularly in a range of 10 to 13. The
central position of the weight member 40 is located on a rear
portion side of a center of the golf club head 1 in the forward and
rearward direction.
[0050] Next, a description will be given on a method for
manufacturing the golf club head according to the embodiment of the
invention.
[0051] To manufacture this golf club head 1, the metallic front
body 10, the sole plate 30, and a plurality of prepreg sheets are
used. A connecting face between the front body 10 and the FRP body
20 is desirably treated by blasting or spray coating to enhance the
connectivity.
[0052] FIGS. 7A to 7E are plan view illustrating the prepreg sheets
adopted in this embodiment. A prepreg sheet 51 shown in FIG. 7A is
one in which a carbon fiber cloth is impregnated with a
thermosetting synthetic resin. Prepreg sheets 52, 53, 54 and 60
shown in FIGS. 7B, 7C, 7D and 7E are those in which carbon fibers
are oriented in one direction and are impregnated with the
thermosetting synthetic resin. The prepreg sheets 51 to 54
constitute the lower half side of the FRP body 20, and are
respectively provided with circular openings 50 for allowing the
cylindrical portion 35 of the sole plate 30 to pass
therethrough.
[0053] The prepreg sheet 51 is directly superposed on the sole
plate 30, and has a substantially trapezoidal shape, which is
slightly larger than the sole plate 30.
[0054] The prepreg sheets 52, 53 and 54 are directly superposed on
the prepreg sheet 51 in that order. In order to constitute the
lower half of the FRP body 20, each of these prepreg sheets 52 to
54 has such a size that the lower half of the FRP body 20 is
developed. A plurality of slits 55 are cut in both sides and rear
edges of these prepreg sheets 52 to 54 at predetermined intervals,
so that the sides and the rear edges of the prepreg sheets 52 to 54
are easily curved along the inner surface of a molding die.
[0055] In the case of the prepreg sheet 52, the carbon fibers are
oriented in the toe-heel direction. In the case of the prepreg
sheet 53, the carbon fibers are oriented obliquely to the toe-heel
direction 60.degree. clockwise. In the case of the prepreg sheet
54, the carbon fibers are oriented obliquely to the toe-heel
direction 60.degree. counterclockwise.
[0056] The prepreg sheet 60 is used for constituting the upper
surface side of the FRP body 20 and is formed with a substantially
semicircular notched portion 61, with which the hosel portion 6
engages.
[0057] In manufacturing of the golf club head 1, the sole plate 30
is first fitted in the die having a cavity surface conforming to
the sole and sides. The prepreg sheets 51 to 54 are superposed in
that order. Then, these prepreg sheets 51 to 54 are semihardened on
heating for a short time, so as to be formed into the shape of a
sole portion 22 of the FRP body 20 and to be integrated with the
sole plate 30, as shown in FIG. 6.
[0058] The prepreg sheet 60 is also fitted in the die having a
cavity surface conforming to the crown portion, and is semihardened
on heating for a short time, so as to be formed into the shape of a
crown portion 21 of the FRP body 20, as shown in FIG. 6.
[0059] Subsequently, the prepreg sheet 60, the prepreg sheets 51 to
54 with the sole plate and the metallic front body 10 are 1.
[0060] At this time, the front edge of the crown portion 21 formed
of the prepreg sheet 60 is superposed on the lower surface of the
metal crown portion 15 (inner side surface of the head). In
addition, the front edge of the sole portion 22 formed of the
prepreg sheets 51 to 54 is superposed on the upper surface of the
metal sole portion 13 (inner side surface of the head). It should
be noted that the front edge of the sole portion 22 projects
forwardly of the front side 31 of the sole plate 30, and the rear
edge of the sole portion 22 projects rearwardly of the rear side 34
of the sole plate 30, as shown in FIG. 6. The rear edge of the
crown portion 21 is superposed on the outer surface of the rear
edge of this sole portion 22.
[0061] Next, the molding die is heated, and gas pressure of air or
the like is introduced into the molding die through the cylindrical
portion 35. This causes the crown portion 21 and the sole portion
22 formed of the semihardened prepreg sheets to be pressed against
the inner surface of the molding die, the prepreg sheets to become
fully hardened, the crown portion 21 and the sole portion 22 to be
secured to the front body 10, and the crown portion 21 and the sole
portion 22 to be joined together.
[0062] During this molding, part of the synthetic resin in the
prepreg sheets enters the gap between the metal sole portion 13 and
the sole plate 30, and the recessed portion in which the FRP body
20 is curved in the arch shape is formed, as shown in FIG. 5C.
[0063] Subsequently, the molded piece is released, the weight
member 40 is threadedly secured to the cylindrical portion 35, and
finishing such as deburring and coating is performed to form the
product golf club head.
[0064] With the golf club head thus constructed, since all the
portions continuous with the front body 10, including the portion
between the front body 10 and the sole plate 30, are formed of FRP,
the head can be easily flexed and have high repulsion during ball
hitting. At the same time, the center of gravity can be made deep.
In particular, in this embodiment, since the crown portion of the
FRP body 20 is easily flexed, the launch angle can be made large,
and the flight distance can be increased.
[0065] Since the FRP body 20 is superposed and fixed on the inner
face of the metal sole portion 13, the metal crown portion 15 and
the metal side portion 14 of the front body 10, the connection
strength between the front body 10 and the FRP body 20 is high. The
foremost edge of the FRP body 20 is preferable to contact with the
face portion 2.
[0066] In this invention, the amorphous metal material is not
specifically limited in its composition, as long as it has a
supercooling liquid zone, and can form an amorphous phase. Hence,
various amorphous metal materials can be employed, but preferably
have the composition represented by the general formula of MaXb (a
and b are atom %, 65.ltoreq.a.ltoreq.100,
0.ltoreq.b.ltoreq.35).
[0067] Herein, M is al least one selected from the group consisting
of Zr, V, Cr, Mn, Fe, Co, Ni, Cu, Ti, Mo, W, Ca, Li, Mg, Si, Al,
Pd, and Be, and X is at least one selected from the group
consisting of Y, La, Ce, Sm, Md, Hf, Nb, TaAg, Pt, Au, and Pd.
Particularly, a Zr-based amorphous alloy (having the greatest atom
% of Zr) is desirable. With the Zr-based amorphous alloy, the
amorphous structure is relatively easily produced, even if the
cooling speed is reduced. The amorphous alloy is not necessarily
composed of a single phase of a pure amorphous alloy, but may
contain from several vol % to several tens vol % of
micro-crystalline or quasi-crystalline phase that can be produced
under the manufacturing conditions or heat treatment for an
amorphous alloy.
[0068] The amorphous alloy is more prone to crack beyond an elastic
limit, as the non-crystallinity is higher. Thus, to suppress the
flexure at the time of batting the ball, it is preferable to
dispose the fiber reinforced plastic layer on the back face of the
face portion 2 as well, as shown in FIG. 8. Carbon fiber, and
organic fibers such as glass fiber and aramid fiber are usable.
[0069] The other constitution of FIG. 8 is the same as that of FIG.
5A. The same reference numerals are used to designate the same
parts.
[0070] The non-crystallinity of an amorphous alloy is from
75%-100%, or preferably from 80%-98%, at least on the face portion.
If the crystallinity is lower than 75%, there is a fear that the
strength of the face portion may be insufficient. If the
crystalline phase exists in a part of amorphous metal, the plastic
deformation is allowed, whereby the amorphous metal is superior in
terms of the workability and strength.
PRACTICAL EXAMPLE
[0071] In a golf club having the golf club head of the embodiment
that is manufactured by way of trial using a zirconia-based
amorphous alloy, a center of a face was batted at a ball speed of
40 m/s, 500 shots, using two piece of golf ball, whereby strength
evaluation was conducted.
[0072] Thickness of face was 3 mm. Also, workability evaluation for
the amorphous metal was conducted based on whether the polishing is
easy or not.
[0073] As a result, it was found that if the non-crystallinity is
75% or more, especially 80%, strength of the amorphous metal in the
head is sufficiently high. Also, it was found that the workability
is sufficiently excellent if the non-crystallinity is 60% or more,
and remarkably excellent if it is 98% or less.
COMPARATIVE EXAMPLE
[0074] It is preferred that an amorphous alloy making a face
portion in the embodiment has lower Young's modulus than that of a
titanium alloy, and has a breakdown characteristic equal to or
stronger than that of the titanium alloy.
[0075] By making a face portion A with the amorphous alloy having
the breakdown characteristic equal to or stronger than that of the
titanium alloy, it is possible to configure a thickness of the face
portion A in a range of 2.3 mm to 2.9 mm. Moreover, by making the
face portion A with the amorphous alloy having Young's modulus in a
range of 7000 kgf/mm.sup.2 to 9000 kgf/mm.sup.2, preferably 7200
kgf/mm.sup.2 to 8500 kgf/mm.sup.2, the face portion A becomes
flexible when hitting a ball, and make an initial velocity of the
ball faster even the thickness of the face portion A is equal to
that of a face portion B made of titanium alloy.
[0076] However, when the thickness of the face portion A is
configured to be 2.6 mm and Young's modulus thereof is 5000
kgf/mm.sup.2, it is too flexible that the initial velocity of the
ball becomes slower than that when hitting the ball with the face
portion B made of the titanium alloy.
[0077] The breakdown characteristic of the amorphous alloy is
preferably equal to or stronger than that of a common titanium
alloy (Ti-6Al-4V). If the breakdown characteristic of the amorphous
alloy is lower than that of the common titanium alloy, the
thickness of the face portion A needs to be thicker so that a
flexure of the face portion A can not be fully used when hitting
the ball even Young's modulus of the amorphous alloy is set lower
than that of the common titanium alloy. Correspondingly, the
initial velocity of the ball cannot be faster. Therefore, the equal
to or more than 80 kgf/mm.sup.2, especially in a range of 100
kgf/mm.sup.2 to 160 kgf/mm.sup.2.
[0078] A thickness of a central portion of the face portion A is
configured to be in a range of 2.3 mm to 2.9 mm, a thickness of a
peripheral portion of the face portion A connecting to a crown
portion and the sole portion is configured to be in a range of 1.3
mm to 1.6 mm so as to be the thinnest portion in the face portion
A. By this configuration, strength of a hitting portion becomes
stronger and a repulsive force becomes larger. The peripheral
portion of the face portion A is preferably in a range of 0.5 mm to
5 mm.
[0079] Herein, comparative experiments are conducted with three
materials. Material I is employed in the embodiment. Material II
and III are comparative examples.
[0080] The result of a comparison, a carry of a ball is longest
when the ball was hit by a golf club head having a face portion
made of Material I. And a carry of the ball is shortest when the
ball was hit by a golf club head having a face portion made of
Material II.
1 Young's Breakdown modulus Characteristic Thickness Material
(kgf/mm.sup.2) (kgf/mm.sup.2) (mm) I Zirconium-based 7200 to 8000
130 to 150 2.6 amorphous alloy 11000 112 2.6 II Titanium alloy
(Ti-6Al-4V) III Zirconium-based 5000 to 6000 130 to 150 2.6
amorphous alloy
[0081] The foregoing description of preferred embodiments of the
invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed, and modifications and
variations are possible in light of the above teachings or may be
acquired from practice of the invention. The embodiments were
chosen and described in order to explain the principles of the
invention and its practical application to enable one skilled in
the art to utilize the invention in various embodiments and with
various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the claims appended hereto, and their equivalents.
* * * * *