U.S. patent application number 11/622994 was filed with the patent office on 2007-05-24 for golf club head.
This patent application is currently assigned to Taylor Made Golf Company, Inc.. Invention is credited to David Anderson, Todd P. Beach, Benoit Vincent.
Application Number | 20070117652 11/622994 |
Document ID | / |
Family ID | 25233205 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070117652 |
Kind Code |
A1 |
Beach; Todd P. ; et
al. |
May 24, 2007 |
GOLF CLUB HEAD
Abstract
A club head for a golf club comprises a strike face and an outer
shell. The strike face and the outer shell define a head volume of
the club head. The club head has a first axis that extends
generally horizontally and parallel to the strike face, a first
moment of inertia about the first axis, a second axis that lies
generally vertically and perpendicular to the first axis, a second
moment of inertia about the second axis, and a center of gravity
lying below a horizontal centerline of the club head. The first
moment of inertia in units of kg-mm.sup.2 is greater than or equal
to approximately 77 plus 0.46 times the head volume in units of
cm.sup.3.
Inventors: |
Beach; Todd P.; (Carlsbad,
CA) ; Anderson; David; (Carlsbad, CA) ;
Vincent; Benoit; (Carlsbad, CA) |
Correspondence
Address: |
SHEPPARD, MULLIN, RICHTER & HAMPTON LLP
333 SOUTH HOPE STREET
48TH FLOOR
LOS ANGELES
CA
90071-1448
US
|
Assignee: |
Taylor Made Golf Company,
Inc.
5545 Fermi Court
Carlsbad
CA
92008
|
Family ID: |
25233205 |
Appl. No.: |
11/622994 |
Filed: |
January 12, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11214559 |
Aug 31, 2005 |
7198575 |
|
|
11622994 |
Jan 12, 2007 |
|
|
|
09821370 |
Mar 29, 2001 |
6991558 |
|
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11214559 |
Aug 31, 2005 |
|
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|
Current U.S.
Class: |
473/349 ;
473/313; 473/324; 473/335; 473/345 |
Current CPC
Class: |
A63B 60/00 20151001;
A63B 53/0408 20200801; A63B 53/0433 20200801; A63B 2053/0491
20130101; A63B 53/0416 20200801; A63B 53/0412 20200801; A63B
53/0466 20130101; A63B 53/04 20130101; A63B 60/02 20151001 |
Class at
Publication: |
473/349 ;
473/345; 473/324; 473/313; 473/335 |
International
Class: |
A63B 53/00 20060101
A63B053/00 |
Claims
1-29. (canceled)
30: A golf club head comprising: an outer shell; a strike plate
coupled to the outer shell, the strike plate having a strike face,
the outer shell and the strike face defining a club head volume
greater than 300 cm.sup.3; a heel/toe axis extending through a
center of gravity of the club head, generally parallel to the
strike face, and generally horizontal relative to a ground plane
when the club head is at an address position, wherein a rotational
moment of inertia about the heel/toe axis is related to the club
head volume by the equation I.sub.xx.gtoreq.0.46*HV+107, where
I.sub.xx is the rotational moment of inertia about the heel/toe
axis in units of kg-mm.sup.2 and HV is the club head volume in
units of cm.sup.3; and a vertical axis extending through the center
of gravity of the club head generally perpendicular to the heel/toe
axis, wherein a rotational moment of inertia about the vertical
axis is greater than or equal to 300 kg-mm.sup.2.
31: The golf club head of claim 30, further comprising a hosel axis
extending axially through the hosel, wherein a horizontal distance
measured between the center of gravity and the hosel axis is less
than 30 mm.
32: The golf club head of claim 31, wherein the club head has a
total mass within a range of about 180 grams to about 250
grams.
33: The golf club head of claim 32, wherein the center of gravity
is disposed below a horizontal centerline of the club head.
34: The golf club head of claim 32, wherein the center of gravity
is disposed at least 1 mm below the horizontal centerline.
35: The golf club head of claim 32, wherein the center of gravity
is disposed more than 2 mm below the horizontal centerline.
36: The golf club head of claim 31, wherein the club head has a
total mass within a range of about 180 grams to about 210
grams.
37: The golf club head of claim 36, wherein the center of gravity
is disposed below a horizontal centerline of the club head.
38: The golf club head of claim 36, wherein the center of gravity
is disposed at least 1 mm below the horizontal centerline.
39: The golf club head of claim 36, wherein the center of gravity
is disposed more than 2 mm below the horizontal centerline.
40: The golf club head of claim 30, further comprising a hosel axis
extending axially through the hosel, wherein a horizontal distance
measured between the center of gravity and the hosel axis is
between about 12 mm to about 25 mm.
41: The golf club head of claim 40, wherein the club head has a
total mass within a range of about 180 grams to about 250
grams.
42: The golf club head of claim 41, wherein the center of gravity
is disposed below a horizontal centerline of the club head.
43: The golf club head of claim 41, wherein the center of gravity
is disposed at least 1 mm below the horizontal centerline.
44: The golf club head of claim 41, wherein the center of gravity
is disposed more than 2 mm below the horizontal centerline.
45: The golf club head of claim 40, wherein the club head has a
total mass within a range of about 180 grams to about 210
grams.
46: The golf club head of claim 45, wherein the center of gravity
is disposed below a horizontal centerline of the club head.
47: The golf club head of claim 45, wherein the center of gravity
is disposed at least 1 mm below the horizontal centerline.
48: The golf club head of claim 45, wherein the center of gravity
is disposed more than 2 mm below the horizontal centerline.
49: The golf club head of claim 30, further comprising a hosel axis
extending axially through the hosel, wherein a horizontal distance
measured between the center of gravity and the hosel axis is
between about 16 mm to about 20 mm.
50: The golf club head of claim 49, wherein the club head has a
total mass within a range of about 180 grams to about 250
grams.
51: The golf club head of claim 50, wherein the center of gravity
is disposed below a horizontal centerline of the club head.
52: The golf club head of claim 50, wherein the center of gravity
is disposed at least 1 mm below the horizontal centerline.
53: The golf club head of claim 50, wherein the center of gravity
is disposed more than 2 mm below the horizontal centerline.
54: The golf club head of claim 49, wherein the club head has a
total mass within a range of about 180 grams to about 210
grams.
55: The golf club head of claim 54, wherein the center of gravity
is disposed below a horizontal centerline of the club head.
56: The golf club head of claim 54, wherein the center of gravity
is disposed at least 1 mm below the horizontal centerline.
57: The golf club head of claim 54, wherein the center of gravity
is disposed more than 2 mm below the horizontal centerline.
58: The golf club head of claim 30, further comprising a hosel axis
extending axially through the hosel, wherein a horizontal distance
measured between the center of gravity and the hosel axis is
between about 17 mm to about 18 mm.
59: The golf club head of claim 58, wherein the club head has a
total mass within a range of about 180 grams to about 250
grams.
60: The golf club head of claim 59, wherein the center of gravity
is disposed below a horizontal centerline of the club head.
61: The golf club head of claim 59, wherein the center of gravity
is disposed at least 1 mm below the horizontal centerline.
62: The golf club head of claim 59, wherein the center of gravity
is disposed more than 2 mm below the horizontal centerline.
63: The golf club head of claim 58, wherein the club head has a
total mass within a range of about 180 grams to about 210
grams.
64: The golf club head of claim 63, wherein the center of gravity
is disposed below a horizontal centerline of the club head.
65: The golf club head of claim 63, wherein the center of gravity
is disposed at least 1 mm below the horizontal centerline.
66: The golf club head of claim 63, wherein the center of gravity
is disposed more than 2 mm below the horizontal centerline.
67: A golf club head comprising: an outer shell; a strike plate
coupled to the outer shell, the strike plate having a strike face,
the outer shell and the strike face defining a club head volume
greater than 300 cm.sup.3; a plurality of weights attached to or
integrally formed with the outer shell, the plurality of weights
formed from a material having a density greater than that of the
materials used to form the outer shell and the strike plate,
wherein the plurality of weights comprise about 10 percent to about
40 percent of the total mass of the club head; a heel/toe axis
extending through a center of gravity of the club head, generally
parallel to the strike face, and generally horizontal relative to a
ground plane when the club head is at an address position, wherein
a rotational moment of inertia about the heel/toe axis is related
to the club head volume by the equation
I.sub.xx.gtoreq.0.46*HV+107, where I.sub.xx is the rotational
moment of inertia about the heel/toe axis in units of kg-mm.sup.2
and HV is the club head volume in units of cm.sup.3; and a vertical
axis extending through the center of gravity of the club head
generally perpendicular to the heel/toe axis, wherein a rotational
moment of inertia about the vertical axis is greater than or equal
to 300 kg-mm.sup.2; and a hosel axis extending axially through the
hosel, wherein a horizontal distance measured between the center of
gravity and the hosel axis is less than 30 mm; wherein the club
head has a total mass within a range of about 180 grams to about
250 grams.
68: The golf club head of claim 67, wherein: the outer shell is
comprised of a composite material; the center of gravity is
disposed below a horizontal centerline of the club head; and at
least one of the plurality of weights is disposed near a rear end
of the club head.
68. The golf club head of claim 68, wherein the center of gravity
is disposed at least 1 mm below the horizontal centerline of the
club head.
69: The golf club head of claim 69, wherein the center of gravity
is disposed more than 2 mm below the horizontal centerline of the
club head.
70: The golf club head of claim 68, wherein the horizontal distance
measured between the center of gravity and the hosel axis is
between about 12 mm to about 25 mm.
71: The golf club head of claim 71, wherein the horizontal distance
measured between the center of gravity and the hosel axis is
between about 16 mm to about 20 mm.
72: The golf club head of claim 68 wherein the plurality of weights
are disposed within corresponding recesses formed in the outer
shell.
73: The golf club head of claim 68, wherein the plurality of
weights are comprised of tungsten.
74: The golf club head of claim 68, wherein the plurality of
weights are disposed below a horizontal centerline of the club
head.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation of U.S. application Ser. No.
11/214,559, filed Aug. 31, 2005, which is a continuation of U.S.
application Ser. No. 09/821,370, filed Mar. 29, 2001, now U.S. Pat.
No. 6,991,558, which are herein incorporated by reference for all
purposes.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to golf clubs, and, in
particular, to a golf club head with a designated relationship
between the volume of the club head and the rotational inertia of
the club head about a particular axis.
[0004] 2. Description of the Related Art
[0005] A wood-type golf club typically includes a hollow shaft with
a golf club head attached to the lower end of the shaft. The club
head typically includes a load-bearing outer shell with an integral
or attached strike plate. The strike plate defines a front surface
or strike face adapted for striking a golf ball.
[0006] The mass of a club head is limited by various practical
considerations, such as the desire to keep the swing weight of the
golf club close to a conventional value. Accordingly, most club
heads have a mass between 180-250 grams. A certain portion of the
club head's mass is reserved for components that provide structural
support, such as the load bearing outer shell. The remaining mass,
which is referred to as performance mass, can be distributed within
the club head to optimize performance.
[0007] For some time, golf club manufacturers have searched for
ways to best distribute the performance mass so as to improve club
head performance. Recently, golf club manufacturers have attempted
to position most of the performance mass along the perimeter of the
club head so as to increase the rotational moment of inertia
("MOI") of the club head about the club head center of gravity
("CG"). In particular, many club heads include two or more weights
spaced along the heel/toe axis (i.e., an axis that extends through
the club head CG generally parallel to the strike face in a
generally horizontal direction relative to the ground when the club
head is at address position). Such perimeter weighting increases
the MOI of the club head about the vertical axis (i.e., an axis
that extends through the club head CG in a generally vertical
direction relative to the ground when the club head is at address
position). This tends to make the club head more resistant to
twisting during off-center hits. However, as will be explained
below, such perimeter weighting represents an inefficient use of
the performance mass.
[0008] An exception to the general trend of heel/toe weighting is
U.S. Pat. No. 5,176,383, which discloses a club head with a weight
positioned at the rear of a support. The support and the weight are
in-line with the center of percussion of the club head. This patent
claims that this arrangement concentrates the inertial energy of
the club head along the center of percussion, which, in turn,
maximizes the amount of energy that is imparted to the golf ball.
However, a golf club according to this patent disadvantageously has
a CG that is above the horizontal centerline of the golf club.
SUMMARY OF THE INVENTION
[0009] In one embodiment of the invention, a golf club head
comprises a strike face and an outer shell. The strike face and the
outer shell define a head volume of the club head. The club head
has a first axis that extends generally horizontally and parallel
to the strike face, a first moment of inertia about the first axis,
a second axis that lies generally vertically and perpendicular to
the first axis, a second moment of inertia about the second axis,
and a center of gravity lying below a horizontal centerline of the
club head. The first moment of inertia in units of kg-mm.sup.2 is
greater than or equal to approximately 77 plus 0.46 times the head
volume in units of cm.sup.3.
[0010] In another embodiment of the invention, the first moment of
inertia in units of kg-mm.sup.2 is greater than or equal to
approximately 107 plus 0.46 times the head volume in units of
cm.sup.3.
[0011] In another embodiment of the invention, the center of
gravity lies more than 1 mm below the horizontal centerline. In yet
another embodiment of the invention, the center of gravity lies
more than 2 mm below the horizontal centerline.
[0012] In another embodiment of the invention, the club head has a
mass of less than 250 grams. In yet another embodiment of the
invention, the club head has a mass of less than 230 grams. In yet
another embodiment of the invention, the club head has a mass of
less than 210 grams.
[0013] In another embodiment of the invention, the club head has a
volume greater than 300 cm.sup.3. In yet another embodiment of the
invention, the club head has a volume less than 200 cm.sup.3.
[0014] In another embodiment of the invention, the second moment of
inertia is greater than 250 kg-mm.sup.2. In yet another embodiment
of the invention, the second moment of inertia is greater than 300
kg-mm.sup.2.
[0015] In another embodiment of the invention, the club head
includes a plurality of weights.
[0016] For purposes of summarizing the invention and the advantages
achieved over the prior art, certain objects and advantages of the
invention have been described herein above. Of course, it is to be
understood that not necessarily all such objects or advantages may
be achieved in accordance with any particular embodiment of the
invention. Thus, for example, those skilled in the art will
recognize that the invention may be embodied or carried out in a
manner that achieves or optimizes one advantage or group of
advantages as taught herein without necessarily achieving other
objects or advantages as may be taught or suggested herein.
[0017] All of these embodiments are intended to be within the scope
of the invention herein disclosed. These and other embodiments of
the present invention will become readily apparent to those skilled
in the art from the following detailed description of the preferred
embodiments having reference to the attached figures, the invention
not being limited to any particular preferred embodiment(s)
disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] These and other features of the invention will now be
described with reference to the drawings of a preferred embodiment,
which are intended to illustrate and not to limit the invention,
and in which:
[0019] FIG. 1 is a front view of a golf club head centered about a
coordinate system;
[0020] FIG. 2 is a top plan view of a golf club striking a golf
ball;
[0021] FIG. 3 is a side view of a golf club striking a golf
ball;
[0022] FIG. 4 is another side view of a golf club illustrating the
location of the center of gravity;
[0023] FIG. 5 is a front perspective view of the golf club head
having certain features and advantages according to the present
invention;
[0024] FIG. 6 is a front view of the golf club head of FIG. 5;
[0025] FIG. 7 is a cross-sectional view of the golf club head of
FIG. 4;
[0026] FIG. 8 is a bottom perspective view of the golf club head of
FIG. 4;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] FIG. 1 is a perspective view of a club head 10 located about
a coordinate system 12. The coordinate system 12 is centered about
the center of gravity ("CG") of the club head. As is typical in the
art, the club head 10 comprises a strike plate 14, which defines a
front surface or strike face 16 for impacting a golf ball. A hosel
18 extends upwardly from the strike plate 14. The hosel 18 is used
to attach the club head 10 to a golf club shaft (not shown) as is
well known in the art. The club head 10 also includes a load
bearing outer shell 20 that is either integrally made with or
attached to the strike plate 14. A heel region 22 of the club head
10 is located close to the hosel 18 while the toe region 24 of the
club head is located opposite the heel region 22.
[0028] The coordinate system 12 comprises three axes: (i) a
vertical axis 26 that extends through the CG generally parallel to
the strike face 16 in a generally vertical direction relative to
the ground when the club head 10 is at address position, (ii) a
heel/toe axis 28 that extends through the CG generally parallel to
the strike face 16 and generally perpendicular to the vertical axis
26, and (iii) a front/back axis 30 that extends through the CG
generally perpendicular to the vertical axis 26 and the heel/toe
axis 28. Heel/toe axis 28 and front/back axis 30 both extend in a
generally horizontal direction relative to the ground when the club
head 10 is at address position.
[0029] The club head 10 has a rotational moment of inertia (i.e., a
resistance to twisting) about each of the three axes. Specifically,
the club head 10 has a moment of inertia ("Izz") about the vertical
axis 26, a moment of inertia ("Ixx") about the heel/toe axis 28,
and a moment of inertia ("Iyy") about the front/back axis 30. The
methods for determining these moments of inertia for any particular
club head are well known to those skilled in the art.
[0030] An aspect of Applicant's invention is the realization that
preferably most or more preferably all of the performance mass of
the club head 10 should be arranged so as to increase the moment of
inertia Ixx about the heel/toe axis 28 and the moment of inertia
Izz about the vertical axis 26. FIG. 2 is a top plan view of a golf
ball 32 hitting the strike face 16 of a club head 10. As is not
unusual in golf, the club head 10 is shown striking the golf ball
32 "off-center". In this case, the golfball 32 has hit the club
head 10 near the toe 24 of the club head (i.e., a "side off-center
hit"). The side off-center hit causes the club head 10 to twist
about the vertical axis 26 as shown by arrow 27A. This tends to
produce an inaccurate shot.
[0031] To mitigate the twisting about the vertical axis 26 during
such side off-center hits, golf club manufacturers have typically
sought to increase the golf club's moment of inertia Izz about the
vertical axis 26 by concentrating at least some of the performance
weight along the heel/toe axis 28. For example, heel/toe weights,
which are indicated by the reference number 25, can be added to the
club head 10 to increase the club head's moment of inertia Izz
about the vertical axis 26. This produces more accurate shots.
[0032] However, such heel/toe weights 25 do not necessarily improve
performance during all off-center hits. For example, FIG. 3 is a
side view of the club head 10 striking a golf ball 32. As with FIG.
2, the club head 10 has struck the golf ball 32 off-center.
However, in this case, the golf ball 32 has hit the club head 10
below the center of the club head (i.e., a "vertical off-center
hit"). This type of off-center hit causes the club head 10 to twist
about the heel/toe axis 28 as indicated by arrow 27B. However,
heel/toe weights 25 do not increase the club head's moment of
inertia Ixx about the heel/toe axis 28. Thus, they do not reduce
the tendency of the club head 10 to twist about the heel/toe axis
28. Accordingly, heel/toe weights 25 do not improve the golf club's
performance during vertical off-center hits. Heel/toe weights 25 do
increase the club head's moment of inertia Iyy about the front/back
axis 30. However, it has been determined that during off-center
hits the club head 10 tends not to rotate about this axis.
Accordingly, the moment of inertia Iyy about the front/back axis 30
is not as effective in improving club head performance.
[0033] In contrast, front/back weights 29, which are spaced
substantially about the front/back axis 30, increase the club
head's moment of inertia Ixx about the heel/toe axis 28. Thus,
front/back weights 29 improve the golf club's performance during
vertical off-center hits. Moreover, as shown in FIG. 2, such
front/back weights 29 also increase the club head's moment of
inertia Izz about the vertical axis 26. Therefore, front/back
weights 29 improve the club head's performance during side
off-center hits and vertical off-center hits.
[0034] Another aspect of the invention is the recognition that the
performance mass of the club head 10 should also be arranged such
that the club head has a low CG. More specifically, as shown in
FIG. 4, the CG of the club head 10 is preferably located below a
horizontal centerline 31 of the club head (i.e., the line 31 that
extends through the geometric center of the strike face 16 and
bisects a vertical line 33, which extends perpendicularly from the
ground 35 to the top of the strike face 16 when the club head 10 is
in the normal address position). Consequently, in some embodiments
the performance mass is concentrated below the physical center of
the club head. In contrast, most golf clubs have a CG above the
horizontal centerline 31.
[0035] The vertical distance between the CG and the horizontal
centerline 31 will be referred to as CGz. As mentioned above, a
club head 10 desirably has CG that lies below the horizontal
centerline 31, which extends through the geometric center of the
strike face 16. Preferably, the CG lies at least 1 millimeter below
the horizontal centerline 31 (i.e., CGz is at least 1 mm). More
preferably, CGz is at least 2 millimeters. It is difficult to
design wood-type clubs with a CG below the horizontal centerline
31. Accordingly, the front/back weights 29 of the club head 10
preferably are located entirely below the horizontal center line 31
of the club head. Moreover, moving the CG even a small distance
below the horizontal centerline 31 has a large effect on the golf
shot. For example, failure to get the golf ball air borne results
in drastically reduced shot distance. A low CG helps the golfer get
a golf ball air borne. Specifically, a lower CG increases the
launch angle of a golf shot because when the CG is below the point
of impact the strike face 16 rotates in such away that it increases
the loft of the golf club.
[0036] The club head 10 preferably should also be arranged such
that the CG is located not too far back from a shaft or hosel axis
37 of the club head (i.e., a line that extends axially through the
center of the shaft and the hosel). The horizontal distance
measured in a direction back from the strike face 16 between the CG
and the hosel axis 37 will be referred to as Delta 1. Preferably,
Delta 1 is in the range of 12-25 millimeters. More preferably,
Delta 1 is in the range of 16-20 millimeters. Most preferably,
Delta 1 is in the range of 17-18 millimeters. Delta 1 can be
manipulated by varying the mass in front of the CG (i.e., closer to
the face) with respect to the mass behind the CG. That is, by
increasing the mass behind the CG with respect to the mass in front
of the CG, Delta 1 can be increased. In a similar manner, by
increasing the mass in front of the CG with respect to the mass
behind the CG Delta 1 can be decreased. The above ranges for Delta
1 are preferred for several reasons. If Delta 1 is too far forward,
the trajectory of the golf ball tends to be too low and to the
right, especially in large club heads (e.g., club heads having a
head volume greater than 300 cm.sup.3). Conversely, if Delta 1 is
too far back the trajectory of the golf ball tends to be too high
and the golf ball tends to have too much spin.
[0037] With reference now to FIGS. 5-8 a preferred construction of
a golf club head 50 with certain features and advantages according
to the present invention will now be described. As shown in FIG. 5,
the club head 50 is comprised of a strike plate 58. The strike
plate 58 defines a front surface or strike face 60 for impacting a
golf ball. A hosel 62 extends upwardly from the strike plate 58.
The hosel 62 is configured to be coupled to a golf club shaft (not
shown) in a well known manner. The strike plate 58 and hosel 62 are
preferably made of a strong yet light weight metal, such as
titanium or a composite material. Of course, other suitable
materials can be used.
[0038] The club head 50 further comprises a load bearing outer
shell 64 that is preferably attached to the strike plate 58. As
with the strike plate 58, the outer shell is preferably made of a
strong yet light weight metal, such as, for example) titanium or a
composite material. Of course, other suitable materials can be
used. The outer shell 64 preferably defines an interior cavity 65
(see FIG. 7) within the club head 50. Together the strike plate 58
and the outer shell 64 define a head volume (i.e., "HV") of the
club head 50. The head volume HV represents the volume occupied by
the club head 50 and is traditionally measured in cm.sup.3. Head
volume is an important design parameter. Other things being equal,
it is easier to achieve a higher rotational moment of inertia about
the CG in a club head that defines a larger head volume as compared
to a club head that defines a smaller head volume. This is because
the performance weight can be distributed farther from the CG in a
club head with a large head volume. Conversely, other things being
equal, it is easier to achieve a lower CG in a club head with a
small head volume as compared to a club head with a large head
volume. Accordingly, a design compromise must be made between
desired inertial characteristics of the club head and the location
of the CG. Moreover, golfers generally do not like the look and
feel of unusually large or small club heads. Thus, the head volume
of the club head 50 preferably is between 200-450 cm.sup.3.
[0039] With reference to FIG. 6, the club head 50 includes a toe
region 66 and a heel region 68, as will be known to those of skill
in the art. The bottom of the club head 50 is delimited in part by
a sole 70 and the top of the club head is delimited by a crown 72.
The features of the club head 50 described up to this point can be
considered conventional.
[0040] Golfers prefer a driver type golf club to have a total mass
of less than 250 grams. Therefore, the club head 50 preferably has
a total mass of less than 250 grams. More preferably, the club head
50 has a total mass of less than 230 grams. Most preferably, the
club head 50 has a total mass of less than 210 grams. A lighter
club head 50 is preferred because it reduces the swing weight of
the golf club. However, a lighter club head 50 also has less
performance mass available to increase the rotational inertia of
the club head 50 about the club head CG. Thus, a design compromise
must be made between the total mass of the club head 50 and the
desired rotational inertia characteristics of the club head.
[0041] The structural members (i.e., the outer shell 64 and the
strike plate 58) comprise approximately 60%-90% of the total mass
of the club head 50. The remaining 40%-10% of the club head mass
constitutes the performance mass, which is preferably distributed
in weight plugs or weights 74 described below.
[0042] FIGS. 7 and 8 show cross-sectional side and bottom views,
respectively, of the club head 50. In the preferred embodiment, the
golf club head 50 includes two or more weights or plugs 74a, 74b
that are situated within corresponding recesses 76a, 76b formed in
the outer shell 64. In the illustrated embodiment, the weights 74a,
74b are removably coupled to the sole 70 of the club head 50 by
screws 78. However, it should be appreciated that the weights 74a,
74b can be coupled to the club head 50 by using an adhesive,
brazing, etc., or the weights may be integrally formed with the
sole 70. The weights 74a, 74b preferably are made of a material,
such as, for example, tungsten, that is denser than the material(s)
that form the outer shell 64 and the strike plate 58.
[0043] As best seen in FIG. 8, the weights 74a, 74b are preferably
located along a front/back axis 80 that extends generally
perpendicularly away from the strike face 60 of the club head 50.
More preferably, one of the weights 74a is located along the front
back axis 80 near the strike plate 58 and the other weight 74b is
also located along the front back axis 80 near a rear end 81 of the
club head 50.
[0044] In addition, as best seen in FIG. 7, both of the weights
74a, 74b are preferably located below the horizontal centerline 82
of the club head 50. This arrangement is preferred because it moves
the CG of the club head 50 to a position below the horizontal
centerline 82.
[0045] The club head 50 described above preferably has a moment of
inertia Ixx about the heel/toe axis 28 that is significantly
greater than conventional club heads (i.e., interior volumes
between 200-350 cm.sup.3 and a mass between 180-250 grams). As
mentioned above, the inertial properties of a club head are
dependent upon the head volume. Accordingly, the club head 50
preferably has a moment of inertia Ixx about the heel/toe axis 28
as set forth below in equation 1. Ixx.gtoreq.0.46*HV+77 (1) [0046]
where: HV is club head volume in units of cm.sup.3 [0047] Ixx is in
units of kg-mm.sup.2 More preferably, the club head 50 has a moment
of inertia Ixx about the heel/toe axis 28 as set forth below in
equation 2. Ixx.gtoreq.0.46*HV+107 (2) [0048] where: HV is club
head volume in units of cm.sup.3 [0049] Ixx is in units of
kg-mm.sup.2 The higher moments of inertia Ixx of equation 2 can be
achieved by reducing or holding constant the mass of the shell 64
and/or the strike plate 58 while increasing or holding constant the
mass of the weights 74a, 74b while also giving due consideration to
the structural integrity of the club head 50.
[0050] In addition, the CG of the club head 50 preferably lies
below the horizontal centerline 82 of the club head 50. More
preferably, the CG is more than 1 mm below the horizontal
centerline 82 of the club head 50. The lower CG can be achieved by
increasing the mass of the weights 74a, 74b while reducing or
holding constant the mass of the shell 64 and strike plate 58. The
CG can also be reduced by decreasing the thickness of the weights
74a, 74b and/or decreasing the density of the weights 74a, 74b.
[0051] Preferably, the club head 50 also has a moment of inertia
Izz about the vertical axis 26 that is at least 250 kg-mm.sup.2.
More preferably, the club head has a moment of inertia Izz about
the vertical axis 26 of at least 300 kg-mm.sup.2. As with the
moment of inertia Ixx about the heel/toe axis 28, the moment of
inertia Izz about the vertical axis 26 can be increased by reducing
or holding constant the mass of the shell 64 and/or the strike
plate 58 while increasing or holding constant the mass of the
weights 74 while also giving due consideration to the structural
integrity of the club head 50.
[0052] As mentioned above, the Delta 1 of the club head 50
preferably is less than 30 mm. Preferably, Delta 1 is in the range
of 12-25 mm. More preferably, Delta 1 is in the range of 16-20 mm.
Most preferably, Delta 1 is in the range of 17-18 mm.
[0053] The club head 50 described above has generally traditional
dimensions as a driver-type wood (i.e., the head volume is between
200 and 300 cm.sup.3). However, some golfers prefer a "large" club
head. That is, some golfers prefer a club head that defines an
interior volume greater than 300 cm.sup.3 and a mass between about
180-210 grams. If such a club head is desired, it can be
constructed as described above by enlarging the size of the strike
plate 58 and the outer shell 64.
[0054] As with the club head 50 described above, the club head
preferably has a moment of inertia Ixx about the heel/toe axis 28
as set forth above in equation 1. More preferably, the club head 50
has a moment of inertia Ixx about the heel/toe axis 28 as set forth
in equation 2. The CG of the club head 50 also preferably lies
below the horizontal centerline 82 of the club head. More
preferably, the CG is more than 1 mm below the horizontal
centerline 82 of the club head 50. Preferably, the club head 50
also has a moment of inertia Izz about the vertical axis 26 that is
at least 250 kg-mm.sup.2. More preferably, the club head has a
moment of inertia Izz about the vertical axis 26 of at least 300
kg-mm.sup.2. Preferably, Delta 1 is in the range of 12-25 mm. More
preferably, Delta 1 is in the range of 16-20 mm. Most preferably,
Delta 1 is in the range of 17-18 mm.
[0055] In a modified arrangement, the club head 50 may comprise a
smaller driver or a fairway wood club head. This smaller club head
defines a head volume of less than 200 cm.sup.3 and a mass between
about 200-250 grams. If such a club head 50 is desired, it also can
be constructed as described above by adjusting the shape and size
of the strike plate 58 and the outer shell 64. As with the club
bead 50 described above, a smaller driver or fairway wood type club
head preferably has a moment of inertia Ixx about the heel/toe axis
28 as set forth above in equation 1. More preferably, the club head
50 has a moment of inertia Ixx about the heel/toe axis 28 as set
forth in equation 2. The CG of the club head 50 also preferably
lies at least 1 mm below the horizontal centerline 82 of the club
head 50. More preferably, the CG is more than 2 mm below the
horizontal centerline 82 of the club head 50. Preferably, the club
head 50 also has a moment of inertia Izz about the vertical axis 26
that is at least 200 kg-mm.sup.2. More preferably, the club head 50
has a moment of inertia Izz about the vertical axis 26 of at least
250 kg-mm.sup.2. Delta 1 preferably is in the range of 12-25 mm.
More preferably, Delta 1 is in the range of 16-20 mm. Most
preferably, Delta 1 is in the range of 17-18 mm.
[0056] For purposes of describing the invention and the advantages
achieved over the prior art, certain objects and advantages of the
invention have been described above. Of course, it is to be
understood that not necessarily all such objects or advantages may
be achieved in accordance with any particular embodiment of the
invention. Thus, for example, those skilled in the art will
recognize that the invention may be embodied or carried out in a
manner that achieves or optimizes one advantage or group of
advantages as taught herein without necessarily achieving other
objects or advantages as may be taught or suggested herein.
[0057] Moreover, although this invention has been disclosed in the
context of certain preferred embodiments and examples, it will be
understood by those skilled in the art that the present invention
extends beyond the specifically disclosed embodiments to other
alternative embodiments and/or uses of the invention and obvious
modifications and equivalents thereof. In addition, while a number
of variations of the invention have been shown and described in
detail, other modifications, which are within the scope of this
invention, will be readily apparent to those of skill in the art
based upon this disclosure. It is also contemplated that various
combination or subcombinations of the specific features and aspects
of the embodiments may be made and still fall within the scope of
the invention. Accordingly, it should be understood that various
features and aspects of the disclosed embodiments can be combine
with or substituted for one another in order to form varying modes
of the disclosed invention. Thus, it is intended that the scope of
the present invention herein disclosed should not be limited by the
particular disclosed embodiments described above, but should be
determined only by a fair reading of the claims that follow.
* * * * *