U.S. patent application number 12/410014 was filed with the patent office on 2009-11-12 for golf club head.
Invention is credited to Tomoya HIRANO.
Application Number | 20090280926 12/410014 |
Document ID | / |
Family ID | 41267323 |
Filed Date | 2009-11-12 |
United States Patent
Application |
20090280926 |
Kind Code |
A1 |
HIRANO; Tomoya |
November 12, 2009 |
GOLF CLUB HEAD
Abstract
A golf club head has a hollow structure comprising a face member
and a main member. The face member is made of a first titanium
alloy having a specific gravity G1 of less than 4.42. The main
member is made of a second titanium alloy having a specific gravity
G2 of less than 4.42, the first titanium alloy and second titanium
alloy have different compositions.
Inventors: |
HIRANO; Tomoya; (Kobe-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
41267323 |
Appl. No.: |
12/410014 |
Filed: |
March 24, 2009 |
Current U.S.
Class: |
473/342 ;
473/345; 473/349 |
Current CPC
Class: |
A63B 2209/00 20130101;
A63B 53/0416 20200801; A63B 53/0466 20130101; A63B 53/0458
20200801; A63B 53/0408 20200801; A63B 2053/0491 20130101; A63B
53/0437 20200801; A63B 60/02 20151001 |
Class at
Publication: |
473/342 ;
473/345; 473/349 |
International
Class: |
A63B 53/04 20060101
A63B053/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 12, 2008 |
JP |
2008-125011 |
Claims
1. A golf club head having a hollow structure comprising a face
member made of a first titanium alloy having a specific gravity G1
of less than 4.42, and a main member made of a second titanium
alloy having a specific gravity G2 of less than 4.42 and being
different in the composition from the first titanium alloy.
2. The golf club head according to claim 1, wherein the elastic
modulus E1 of the first titanium alloy is more than the elastic
modulus E2 of the second titanium alloy.
3. The golf club head according to claim 1, wherein the face member
is formed by forging or alternatively press molding, and the main
member is formed by casting.
4. The golf club head according to claim 1, wherein the specific
gravity of the first titanium alloy is less than 4.40, and the
specific gravity of the second titanium alloy is less than
4.40.
5. The golf club head according to claim 1, wherein the quotient
(E1/G1) of the elastic modulus E1 of the first titanium alloy
divided by the specific gravity G1 thereof is in a range of from
27.0 to 32.0, and the quotient (E2/G2) of the elastic modulus E2 of
the second titanium alloy divided by the specific gravity G2
thereof is not less than 23.0 and less than 27.0.
6. The golf club head according to claim 1, wherein the ratio
(G1/G2) of the specific gravity G1 of the first titanium alloy to
the specific gravity G2 of the second titanium alloy is in a range
of from 0.98 to 1.02.
7. The golf club head according to claim 1, wherein the elastic
modulus E1 of the first titanium alloy is not less than 110 GPa and
not more than 140 GPa.
8. The golf club head according to claim 1, wherein the elastic
modulus E2 of the second titanium alloy not less than 95 GPa and
not more than 120 GPa.
9. The golf club head according to claim 1, wherein the quotient
(E2/G2) of the elastic modulus E2 of the second titanium alloy
divided by the specific gravity G2 thereof is not less than 23.0
and not more than 27.5.
10. The golf club head according to claim 1, wherein the face
member comprises a face plate whose front surface defines the club
face, and a turnback extending backwards from the edge of the face
plate, and the weight W1 of the face member is not more than 75
grams and not less than 40 grams.
11. The golf club head according to claim 10, wherein the face
member comprises a face plate whose front surface defines the club
face, and a turnback extending backwards from the edge of the face
plate, the weight W1 of the face member is not more than 75 grams
and not less than 40 grams, and the weight W2 of the main member is
not less than 110 grams and not more than 155 grams.
12. The golf club head according to claim 1, which further includes
a separate weight member fixed to the main member and having a
weight W3 of not less than 3 grams and not more than 20 grams.
13. The golf club head according to claim 1, wherein the face
member is composed of a face plate whose front surface defines the
club face and not provided with a turnback, and the weight W1 of
the face member is in a range of from 35 to 60 grams.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a golf club head, more
particularly to a large-sized hollow head comprising a face member
and a main member made of different titanium alloys.
[0002] In recent years, based on the progress of manufacturing
technology, various golf club heads having very large volumes are
offered in the marketplace, such a large-sized golf club heads can
provide a larger sweet spot area and larger moment of inertia,
therefore, it has an advantage such that the directionality of the
hit balls are improved, in other words, even if ball hitting
positions are varied around the sweet spot, variations of the
initial directions of the balls become small.
[0003] The large-sized golf club heads however, have a problem with
the design freedom. In order to prevent the swing balance of a golf
club from deteriorating, the weight of the club head has to be
limited not to go beyond a certain value. Accordingly, the club
head has to be increased in the size within a weight limit. As a
result, a weight margin is decreased, which margin can be utilized
to deepen the center of gravity of the head, for example as the
weight of a separate weight member. The use of a magnesium alloy
having a smaller specific gravity might be conceived. But, it is
difficulty to obtain a sufficient durability because of the
relatively low strength of a magnesium alloy.
SUMMARY OF THE INVENTION
[0004] It is therefore, an object of the present invention to
provide a golf club head, in which a weight margin is increased to
increase the degree of design freedom, and the depth of the center
of gravity and moment of inertia of the head are improved.
[0005] According to the present invention, a golf club head has a
hollow structure comprising: a face member made of a first titanium
alloy having a specific gravity G1 of less than 4.42; and a main
member made of a second titanium alloy having a specific gravity G2
of less than 4.42 and being different in the composition from the
first titanium alloy.
EFFECTS OF THE INVENTION
[0006] According to the present invention, the different titanium
alloys are used in the face member and main member. Therefore, it
becomes possible to improve the characteristics of the face member
and main member by using alloys' compositions suitable for
obtaining the characteristics required for the respective members.
Both of the first titanium alloy and second titanium alloy have
specific gravities of less than 4.42. Therefore, it becomes
possible to reduce the weights of the face member and main member,
and thereby a large weight margin capable of utilizing for
adjusting the position of the center of gravity can be obtained.
Thus, the present invention can provide a golf club head in which
the design freedom of the weight distribution is high.
DEFINITIONS
[0007] In this specification, sizes, positions, directions and the
like relating to the club head refer to those under a standard
state of the club head unless otherwise noted.
[0008] Here, the standard state of the club head 1 is such that the
club head is set on a horizontal plane HP so that the center line
CL of the club shaft (not shown) is inclined at the lie angle while
keeping the club shaft center line CL on a vertical plane VP, and
the club face 2 forms its loft angle with respect to the horizontal
plane HP. Incidentally, in the case of the club head alone, the
center line of the shaft inserting hole 7a can be used instead of
the center line of the club shaft.
[0009] "Sweet spot SS" is the point of intersection between the
club face and a straight line N drawn normally to the club face 2
passing the center of gravity GH of the head.
[0010] "Front-back direction" is a direction parallel with the
straight line N projected on the horizontal plane HP.
[0011] "Toe-heel direction" is a direction parallel with the
horizontal plane HP and perpendicular to the front-back
direction.
[0012] "Leading edge Le" is a contact point between the club face 2
and a vertical plane parallel with the vertical plane VP.
[0013] "Depth LG of the center of gravity GH" is the horizontal
distance between the center of gravity GH and the leading edge
Le.
[0014] "Lateral moment of inertia" is the moment of inertia of the
head around a vertical axis passing through the center of gravity
GH.
[0015] "Vertical moment of inertia" is the moment of inertia of the
head around a horizontal axis passing through the center of gravity
GH in parallel to the toe-heel direction of the head.
[0016] "Elastic modulus": In this application, the elastic moduli
of the titanium alloys refer to the values determined as follows.
Firstly, the stress-strain curve of the alloy was obtained
according to JIS Z 2201 "Test pieces for tensile test for metallic
materials" and JIS Z 2241 "Method of tensile test for metallic
materials". Then, from the elastic deformation region of the curve,
the elastic modulus was determined. The speed of the crosshead of
the tensile tester was 1.0 mm/min.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of a wood-type golf club head
according to the present invention.
[0018] FIG. 2 is an exploded perspective view showing a two-piece
hollow structure for the wood-type golf club head.
[0019] FIG. 3 is an exploded perspective view showing another
example of the two-piece hollow structure for the wood-type golf
club head.
[0020] FIG. 4 is an exploded perspective view showing a tree-piece
hollow structure for the wood-type golf club head.
[0021] FIG. 5 is a cross sectional view of the wood-type golf club
head having the two-piece hollow structure shown in FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Embodiments of the present invention will now be described
in detail in conjunction with accompanying drawings.
[0023] In the drawings, golf club head 1 according to the present
invention is a hollow head for a wood-type golf club such as driver
(#1) or fairway wood.
[0024] As shown in FIG. 1, the head 1 comprises: a face portion 3
whose front face defines a club face 2 for striking a ball; a crown
portion 4 intersecting the club face 2 at the upper edge 2a
thereof; a sole portion 5 intersecting the club face 2 at the lower
edge 2b thereof; a side portion 6 between the crown portion 4 and
sole portion 5 which extends from a toe-side edge 2c to a heel-side
edge 2d of the club face 2 through the back face BF of the club
head; and a hosel portion 7 at the heel side end of the crown to be
attached to an end of a club shaft (not shown) inserted into the
shaft inserting hole 7a. Thus, the club head 1 is provided with a
hollow (i) and a shell structure with the thin wall. The hollow (i)
in this example is a closed void space, but it may be filled with a
foamed plastic, separating from the backside of the face 3.
[0025] In the case of a wood-type club head for a driver (#1), it
is preferable that the head volume is set in a range of not less
than 400 cc, more preferably not less than 425 cc, still more
preferably not less than 450 cc in order to increase the moment of
inertia of the club head 1 to thereby minimize the undesirable
rotational motion of the club head at the time of mishit and to
improve the directionality of the hit ball. If the volume of the
club head 1 is too large, on the other hand, since the club head
weight is increased, for example, the swing balance is liable to
deteriorate and the head speed decreases. Further, there is a
possibility that the wall thickness of the shell structure is
forced to decrease in order to control the weight of the head and
the durability is decreased. Therefore, the head volume is
preferably not more than 470 cc, more preferably not more than 460
cc.
[0026] As to the weight of the club head 1, in order to avoide
significant deterioration of the swing balance, the weight is
preferably set in a range of not less than 175 grams, more
preferably not less than 180 grams, still more preferably not less
than 185 grams, but not more than 210 grams, more preferably not
more than 205 grams.
Example Shown in FIG. 2
[0027] FIG. 2 shows a two-piece structure for the golf club head 1
comprising a face member 1A and a main member 1B.
[0028] In this embodiment, the main member 1B comprises the
above-mentioned crown portion 4, sole portion 5, side portion 6 and
hosel portion 7 which are integrally formed, and an opening o
closed by the face member is formed in the front thereof.
[0029] The face member 1A is not provided with the undermentioned
turnback 9 and is made up of a face plate 8 only. The face plate 8
or face member 1A has a shape similar but slightly smaller than the
shape of the club face 2 defined by the edge (2a-2e). The area of
the face plate is at least 60%, preferably at least 70%, more
preferably at least 80% of the area of the club face 2.
[0030] Preferably, the weight W1 of the face member 1A is set in a
range of from 35 to 60 grams. The weight W2 of the main member 1B
is preferably set in a range of from 120 to 165 grams.
Example Shown in FIG. 3
[0031] FIG. 3 shows another embodiment of present invention which
has another two-piece structure comprising a face member 1A and a
main member 1B.
[0032] In this embodiment, the face member 1A comprises a face
plate 8 whose front surface defines the club face 2, and a turnback
9 extending backwards from the edge of the face plate 8.
[0033] The face member 1A is formed by press molding, forging or
the like so as to include the face plate 8 and turnback 9
integrally. In other words, the face member 1A is not formed by
assembling two or more parts.
[0034] The face plate 8 forms a major part of the face portion 3
including the sweet spot. In this example, the entirety of the face
portion 3 is formed.
[0035] The turnback 9 is formed along at least part of the
peripheral edge (2a-2d) of the club face 2. In this example, the
turnback 9 is formed along almost entire length of the peripheral
edge (2a-2d), excepting a part corresponding to the hosel portion
7. Thus, the turnback 9 includes a crown-side turnback 9a forming a
front part of the crown portion 4, a sole-side turnback 9b forming
a front part of the sole portion 5, a toe-side turnback 9c forming
a front part of the side portion 5 on the toe-side, and a heel-side
turnback 9d forming a front part of the side portion 5 on the
heel-side.
[0036] The main member 1B accordingly comprises a major part 4a of
the crown portion 4, a major part 5a of the sole portion 5, a major
part 6a of the side portion 6 and the above-mentioned hosel portion
7 which are integrally formed, and in the front thereof, an opening
O closed by the face member is formed.
Example Shown in FIG. 4
[0037] FIG. 4 shows still another embodiment of the present
invention which has a three-piece structure comprising a face
member 1A, a main member 1B and a crown member 1C.
[0038] This three-piece structure is a modification of the
structure shown in FIG. 3, and this embodiment is the same as the
embodiment shown in FIG. 3 except that the main member 1B is
provided in the crown portion with a top opening O2, and the crown
member 1C closing the top opening is separately prepared.
Therefore, the main member 1B comprises an annular peripheral part
4a1 of the crown portion surrounding the top opening O2, and the
above-mentioned major part 5a of the sole portion 5, major part 6a
of the side portion 6 and hosel portion 7. As a result, between the
top opening O2 and the above-mentioned front opening O, a lateral
frame extending from the toe to heel is formed.
Materials
[0039] In the case of the two-piece structures, the face member 1A
is made of a first titanium alloy, and the main member 1B is made
of a second titanium alloy which is different in the composition
from the first titanium alloy.
[0040] In the case of the three-piece structures, the face member
1A, main member 1B and crown member 1C are made of a first, second
and third titanium alloys, respectively, which are different from
each other in the composition.
[0041] Preferably, the specific gravity G3 of the third titanium
alloy is set to be larger than the specific gravity G1 of the first
titanium alloy and the specific gravity G2 of the second titanium
alloy in order to deepen the center of gravity of the head.
[0042] In each case, the specific gravity G1 of the first titanium
alloy and the specific gravity G2 of the second titanium alloy are
set in a range of less than 4.42, preferably less than 4.40, more
preferably less than 4.39.
[0043] By using the titanium alloys having the specific gravities
G1 and G2 of which values are very small in comparison with
conventional values for the face member and main member, the weight
reduction of the large-sized golf club head becomes readily
possible. Accordingly, the club head 1 can produce a large weight
margin to move the center of gravity of the head to a desired
position, and the design freedom of the weight distribution is
increased.
[0044] If the specific gravities are increased over 4.42, it
becomes difficult to obtain a large weight margin while maintaining
the large head volume. The lower limit of the specific gravity is
conceptually not need to be defined, but, practically values more
than 4.30 are preferred.
[0045] It is possible that the specific gravity G1 is the same as
or different from the specific gravity G2.
[0046] Preferably, the ratio (G1/G2) is set in a range of from
about 0.98 to about 1.02.
[0047] In the case of a large-sized golf club head, generally,
there is a tendency that the spring-like effect becomes high and
not in compliance with the Rules of Golf. To increase the thickness
of the face portion is effectual for decreasing the spring-like
effect, but it lessens the design freedom of the weight
distribution since the club head weight is also increased.
Therefore, the first titanium alloy of the face member 1A is
increased in the elastic modulus more than the second titanium
alloy of the main member 1B. Thereby, the deflection of the face
portion at impact can be decreased so that the spring-like effect
becomes in compliance with the Rules of Golf without increasing the
thickness or weight of the face portion 3. Further, the use of such
high modulus first titanium alloy is also preferable in view of the
durability of the face portion 3. In this light, the ratio (E1/E2)
of the elastic modulus E1 of the first titanium alloy to the
elastic modulus E2 of the second titanium alloy is preferably not
less than 1.05, more preferably not less than 1.07, still more
preferably not less than 1.10. However, if the elastic modulus
ratio (E1/E2) is excessively increased, then the spring-like effect
is also decreased excessively or the durability of the main member
1B becomes insufficient. Further, there is a possibility that
stress concentrates on the boundary between the first titanium
alloy and second titanium alloy. Therefore, the elastic modulus
ratio (E1/E2) is preferably not more than 1.40, more preferably
less than 1.37, still more preferably less than 1.35.
[0048] More specifically, the elastic modulus E1 of the first
titanium alloy is preferably not less than 110 GPa, more preferably
not less than 115 GPa, still more preferably not less than 118 GPa,
but not more than 140 GPa, more preferably not more than 137 GPa,
still more preferably not more than 135 GPa.
[0049] If less than 110 GPa, the spring-like effect tends to
increase against the Rules of Golf. If more than 140 GPa, the
spring-like effect largely decreases and the carry distance is
accordingly decreased.
[0050] Further, in view of the durability of the club head,
preferably the elastic modulus E2 of the second titanium alloy of
the main member 1B is set to be not less than 95 GPa, more
preferably not less than 100 GPa, still more preferably not less
than 105 GPa. on the other hand, if the elastic modulus E2 is
excessively increased, the spring-like effect of the club head is
also decreased and the carry distance decreases. Therefore, the
elastic modulus E2 of the second titanium alloy is preferably not
more than 120 GPa, more preferably not more than 117 GPa, still
more preferably not more than 115 GPa.
[0051] The elastic modulus (E1/G1) of the first titanium alloy
divided by the specific gravity G1 (no unit) thereof, namely, the
ratio of the elastic modulus (E1) to the specific gravity G1 is
preferably not less than 27.0 GPa, more preferably not less than
27.5 GPa, still more preferably not less than 28.0 GPa, but not
more than 32.0 GPa, more preferably not more than 31.5 GPa, still
more preferably not more than 31.0 GPa.
[0052] If the ratio (E1/G1) is less than 27.0 GPa, it becomes
difficult to reduce the weight of the face member 1A while
maintaining the necessary strength. If more than 32.0 GPa, the
titanium alloy becomes embrittled, and the durability is
decreased.
[0053] For the similar reasons, the elastic modulus (E2/G2) of the
second titanium alloy divided by the specific gravity G2 (no unut)
thereof, namely, the ratio of the elastic modulus (E2) to the
specific gravity G2 is preferably not less than 23.0 GPa, more
preferably not less than 23.5 GPa, still more preferably not less
than 24.0 GPa, but preferably not more than 27.5 GPa, more
preferably not more than 27.0 GPa, still more preferably less than
27.0 GPa, most preferably not more than 26.5 GPa.
[0054] For the first titanium alloy and second titanium alloy
having relatively low specific gravities, preferably used are
[0055] Ti-8Al-1V-1Mo (specific gravity 4.37, elastic modulus 110
GPa), [0056] Ti-7Al-2V (specific gravity 4.35, elastic modulus 110
GPa), [0057] Ti-7.5Al-2V (specific gravity 4.35, elastic modulus
105 GPa), [0058] Ti-8Al-1V (specific gravity 4.34, elastic modulus
100 GPa), [0059] Ti-8Al-2V (specific gravity 4.35, elastic modulus
105 GPa), [0060] Ti-8Al-1V-1Mo-0.15C (specific gravity 4.37,
elastic modulus 118 GPa), [0061] Ti-5.5Al-1Fe (specific gravity
4.38, elastic modulus 125 GPa) and the like. Known as a titanium
alloy having a specific gravity of not less than 4.42 is
Ti-6Al-4V.
[0062] In the case of the face member 1A provided with the turnback
9 as shown in FIG. 3 and FIG. 4, in order to obtain a large weight
margin and to increase the depth of the center of gravity, the
weight W1 of the face member 1A is preferably decreased in a range
of not more than 75 grams, more preferably not more than 72 grams,
still more preferably not more than 70 grams, but not less than 40
grams, more preferably not less than 43 grams, still more
preferably not less than 45 grams to maintain the large club face
area.
[0063] In the case of the main member 1B used in combination with
the face member 1A with the turnback 9, the weight W2 thereof of is
preferably not less than 110 grams, more preferably not less than
115 grams, still more preferably not less than 120 grams to provide
durability necessary for the club head. But, the weight W2 is
preferably not more than 155 grams, more preferably less than 150
grams, still more preferably less than 145 grams to prevent the
swing balance from deteriorating and to obtain a large weight
margin.
[0064] The face member 1A and crown member 1C are formed by plastic
forming such as forging and press molding. The main member 1B is
integrally formed by casting such as lost-wax precision casting.
These members are welded each other.
Face Portion
[0065] In the above-mentioned embodiments show in FIG. 2, FIG. 3
and FIG. 4, in order to increase the durability and strength of the
face portion, the face portion 3 is locally increased in the
thickness. Thus, the face portion 3 comprises a central thick
region 3A and an annular thinner region 3B.
[0066] As best depicted in FIG. 5, the central thick region 3A has
a thickness t1 (in this example, largest in the club face). The
annular thinner region 3B surrounding the central thick region 3A
has a thickness t2 less than the thickness t1 (in this example,
smallest in the club face). The central thick region 3A has to
include the sweet spot SS.
[0067] Preferably, the thickness t1 of the central thick region 3A
is set in a range of not less than 2.90 mm, more preferably not
less than 2.95 mm, still more preferably not less than 3.00 mm, but
not more than 3.50 mm, more preferably not more than 3.40 mm, still
more preferably not more than 3.3 mm.
[0068] If the thickness t1 is less than 2.90 mm, there is a
possibility that the coefficient of restitution of the club head is
increased over the limit provided by the Rules of Golf. If more
than 3.50 mm, since the weight of the face portion 3 increases, it
becomes difficult to increase the depth of the center of
gravity.
[0069] In order to maintain the durability, the thickness t2 of the
annular thinner region 3B is set in a range of not less than 2.35
mm, preferably not less than 2.40 mm, more preferably not less than
2.50 mm, but not more than 2.70 mm, preferably not more than 2.60
mm in order to provide a desirable degree of the spring-like
effect.
[0070] In order to prevent a stress concentration on the boundary
between the central thick region 3A and annular thinner region 3B,
a transitional part 3C whose thickness continuously changes from t1
to t2 is formed along the boundary.
Thickness
[0071] The thickness t3 of the crown portion 4, crown major part 4a
and crown member 1C; the thickness t4 of the sole portion 5 and
sole major part 5a; the thickness t5 of the side portion 6 and side
major part 6a are preferably not less than 0.65 mm, more preferably
not less than 0.70 mm, but not more than 1.2 mm, more preferably
not more than 1.1 mm.
[0072] If less than 0.65 mm, it becomes difficult to provide
necessary durability. If more than 1.2 mm, the club head weight
increases, and the design freedom of the weight distribution is
liable to be restricted.
Turnback
[0073] The above-mentioned turnback 9 is preferably provided with a
length D (measurement in the front-back direction) of not more than
30 mm, more preferably not more than 28 mm, still more preferably
not more than 25 mm. If the length D is more than 30 mm, it becomes
difficult to form the face member 1A through plastic forming such
as forging and press molding, and the production efficiency
decreases. However, it is preferable that the length D of the
turnback 9 is not less than 7 mm, more preferably not less than 10
mm, still more preferably not less than 15 mm.
[0074] The face member 1A is welded to the main member 1B.
Therefore, by setting the length D more than 7 mm, a possible
adverse effect of the heat during welding on the face portion can
be minimized. Further, the stress at impact decreases and the
durability can be improved. Further, as shown in FIG. 5, even if a
large weld bead is formed, the rigidity of the face portion 4 is
not increased, and the additional weight increase occurs at the
back of the face portion which can facilitate increase in the depth
of the center of gravity of the head.
Separate Weight Member
[0075] The weight margin obtained as above can be utilized to
provide a separate weight member 20. In this case, the weight
member 20 can be fixed to the back part of the main member 1B in
the sole portion 5 and/or side portion 5 as shown in FIG. 5 by
utilizing an adhesive agent, screw cramp and the like. For the
weight member 20, preferably used is a metal material having a
large specific gravity which is more than the specific gravity G2
of the main member 1B, preferably not less than 8.0, more
preferably not less than 10.0. More specifically, copper alloy,
nickel alloy, brass, lead, stainless, tungsten, tungsten alloy and
the like can be used alone or in combination, usually, for the
practical reason, the specific gravity is set to be not more than
20.0, and the weight W3 of the weight member 20 is set to be not
less than 3 grams, preferably not less than 5 grams, more
preferably not less than 8 grams, but not more than 20 grams,
preferably less than 18 grams, more preferably less than 15
grams.
Comparison Tests
[0076] Wood-type golf club heads (volume 460 cc, lie 57.5 degrees,
loft 12.0 degrees) were made, changing the wall thickness of the
face member and main member and the weight and position of the
weight member (made of a tungsten alloy having a specific gravity
of 19.0), but not changing the total weight of the head inclusive
of the weight member as far as possible. And the depth of the
center of gravity and moment of inertia were measured. The
measurement values are shown in Table 1 together with the
specifications of the heads.
TABLE-US-00001 TABLE 1 Head Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ref. 1
Ref. 2 Ref. 3 Club head weight W (g) 195.2 196.3 195.5 194.5 195.2
195.6 195.6 194.5 Face member material TIX51AF TIX51AF TIX51AF
Ti--811--C TIX51AF Ti--6Al--4V TIX51AF Ti--6Al--4V manufacturing
process *1 HF PM HF HF HF PM HF PM weight W1 (g) 61.7 45.8 62.4
60.5 61.2 48.1 61.5 48.5 specific gravity G1 4.38 4.38 4.38 4.37
4.38 4.42 4.38 4.42 elastic modulus E1 (Gpa) 125 130 125 125 125
115 125 115 Main member material Ti-811 Ti--8Al--2V Ti--8Al--2V
Ti--811 Ti-811 Ti--6Al--4V Ti--6Al--4V Ti-811 manufacturing process
*1 CAS CAS CAS CAS CAS CAS CAS CAS weight W2 (g) 128.5 138.5 126.0
127.5 109.8 142.5 132.1 139.5 specific gravity G2 4.37 4.35 4.35
4.37 4.37 4.42 4.42 4.37 elastic modulus E2 (Gpa) 110 105 105 110
110 115 110 110 Crown member material -- -- -- -- Ti-15-3-3-3 -- --
-- specific gravity -- -- -- -- 4.76 -- -- -- manufacturing process
*1 -- -- -- -- PM -- -- -- weight -- -- -- -- 18.0 -- -- -- Weight
member weight W3 (g) 5.0 12.0 7.1 6.5 6.2 5.0 2.0 6.5 E1/E2 1.14
1.24 1.19 1.14 1.14 1.00 1.14 1.05 E1/G1 28.54 29.68 28.54 28.60
28.54 26.02 28.54 26.02 E2/G2 25.17 24.14 24.14 25.17 25.17 26.02
24.89 25.17 G1/G2 1.00 1.01 1.01 1.00 1.00 1.00 0.99 1.01 W3/W 0.03
0.06 0.04 0.03 0.03 0.03 0.01 0.03 Depth of center of 39.5 39.0
39.8 39.6 40.3 37.0 38.0 38.6 gravity (mm) Lateral moment of 4200
4165 4225 4260 4310 4055 4100 4130 inertia (g sq.cm) Vertical
moment of 2615 2590 2640 2625 2680 2510 2540 2565 inertia (g sq.cm)
*1 abbreviations are meant for the following manufacturing
processes. HF: hot forging PM: press molding CAS: casting
[0077] From the test results, it was confirmed that, according to
the present invention, the weight margine and degree of design
freedom can be increased, therefore, it is possible to increase the
depth of the center of gravity and moment of inertia.
* * * * *