U.S. patent application number 11/216841 was filed with the patent office on 2007-03-01 for metal wood club.
Invention is credited to David A. Shear.
Application Number | 20070049416 11/216841 |
Document ID | / |
Family ID | 37805048 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070049416 |
Kind Code |
A1 |
Shear; David A. |
March 1, 2007 |
Metal wood club
Abstract
A golf club head is provided having a body and a face insert,
with a slot in a perimeter region of the body of the club head
adjacent the face insert. The slot increases the flex of the
hitting surface on impact with a golf ball, thereby increasing the
speed with which the ball rebounds off the hitting face and
increases the overall distance the ball is hit. The slot preferably
moves the sweet spot of the hitting face a distance X from the face
center of the hitting face. The slot may be filled with an
elastomeric material.
Inventors: |
Shear; David A.; (Carlsbad,
CA) |
Correspondence
Address: |
ACUSHNET COMPANY
333 BRIDGE STREET
P. O. BOX 965
FAIRHAVEN
MA
02719
US
|
Family ID: |
37805048 |
Appl. No.: |
11/216841 |
Filed: |
August 31, 2005 |
Current U.S.
Class: |
473/349 |
Current CPC
Class: |
A63B 53/0416 20200801;
A63B 53/0458 20200801; A63B 53/0433 20200801; A63B 53/0466
20130101; A63B 53/0408 20200801; A63B 53/047 20130101; A63B 60/52
20151001; A63B 53/0412 20200801; A63B 60/00 20151001 |
Class at
Publication: |
473/349 |
International
Class: |
A63B 53/00 20060101
A63B053/00 |
Claims
1. A golf club head, the club head comprising: a body having a
perimeter region defining an opening; a face insert disposed in the
opening, the face insert having a geometric face center and an area
of maximum coefficient of restitution; and at least one slot
disposed in the perimeter region of the body, wherein the speed at
which a golf ball rebounds from the face insert of the club head is
increased at least 0.5 mph as compared with a club head without a
slot.
2. The golf club head of claim 1, wherein the speed at which a golf
ball rebounds from the face insert of the club head is increased at
least 1 mph as compared with a club head without a slot.
3. The golf club head of claim 1, wherein the slot is an elongated
slot substantially parallel to a portion of an edge of the
body.
4. The golf club head of claim 1, wherein the slot has a width of
greater than 1 mm.
5. The golf club head of claim 1, wherein the slot has a length of
greater than 15 mm.
6. The golf club head of claim 1, wherein the slot comprises two
opposing ends, the ends having expanded slot portions.
7. The golf club head of claim 1, wherein the slot provides a space
in the body, such that the face insert flexes when the face insert
impacts a golf ball.
8. The golf club head of claim 1, wherein the face insert defines a
plane and the slot is disposed less than 30 mm from the face
plane.
9. The golf club head of claim 1, wherein the body is substantially
filled with at least one elastomeric material.
10. The golf club head of claim 1, wherein the area of maximum
resilience is disposed between the face center and the slot.
11. The golf club head of claim 1, wherein the area of maximum
coefficient of restitution is provided less than about 20 mm from
the geometric face center.
12. The golf club head of claim 11, wherein the area of maximum
coefficient of restitution is provided less than about 10 mm from
the geometric face center.
13. The golf club head of claim 1, wherein the area of maximum
coefficient of restitution is within 2 mm of the geometric face
center.
14. The golf club head of claim 1, wherein the face insert defines
a plane and at least one of the slots is disposed on a sole portion
of the perimeter region adjacent the face plane.
15. The golf club head of claim 1, wherein face insert defines a
plane and at least one of the slots is disposed on a crown portion
of the perimeter region adjacent the face plane.
16. The golf club head of claim 1, wherein the face insert defines
a plane and at least one of the slots is disposed on a heel portion
of the perimeter region adjacent the face plane.
17. The golf club head of claim 1, wherein the face insert defines
a plane and at least one of the slots is disposed on a toe portion
of the perimeter region adjacent the face plane.
18. The golf club head of claim 1, wherein the slot increases the
carry distance of a ball hit with the club head as compared with a
club head without a slot.
19. The golf club head of claim 1, wherein the slot increases the
launch angle of a golf ball leaving the face insert after impact
with the club head as compared with a club head without a slot.
20. The golf club head of claim 1, wherein the slot decreases the
back spin of a golf ball leaving the face insert after impact with
the club head as compared with a club head without a slot.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an improved golf club head.
More particularly, the present invention relates to a golf club
head having a through-slot provided in a perimeter region of a body
of the club head adjacent the face insert to improve the flex of
the face of the club head.
BACKGROUND
[0002] The complexities of golf club design are well known. The
specifications for each component of the club (i.e., the club head,
shaft, grip, and subcomponents thereof) directly impact the
performance of the club. Thus, by varying the design
specifications, a golf club can be tailored to have specific
performance characteristics.
[0003] The design of club heads has long been studied. Among the
more prominent considerations in club head design are loft, lie,
face angle, horizontal face bulge, vertical face roll, center of
gravity, inertia, material selection, and overall head weight.
While this basic set of criteria is generally the focus of golf
club engineering, several other design aspects must also be
addressed. The interior design of the club head may be tailored to
achieve particular characteristics, such as the inclusion of hosel
or shaft attachment means, perimeter weights on the club head, and
fillers within hollow club heads.
[0004] Golf club heads must also be strong to withstand the
repeated impacts that occur during collisions between the golf club
and the golf ball. The loading that occurs during this transient
event can create a peak force of over 2,000 lbs. Thus, a major
challenge is designing the club face and body to resist permanent
deformation or failure by material yield or fracture. Conventional
hollow metal wood drivers made from titanium typically have a
uniform face thickness exceeding 2.5 mm to ensure structural
integrity of the club head.
[0005] Players generally seek a metal wood driver and golf ball
combination that delivers maximum distance and landing accuracy.
The distance a ball travels after impact is dictated by the
magnitude and direction of the ball's translational velocity and
the ball's rotational velocity or spin. Environmental conditions,
including atmospheric pressure, humidity, temperature, and wind
speed, further influence the ball's flight. However, these
environmental effects are beyond the control of the golf equipment
manufacturer. Golf ball landing accuracy is driven by a number of
factors as well. Some of these factors are attributed to club head
design, such as center of gravity and club face flexibility.
[0006] The United States Golf Association (USGA), the governing
body for the rules of golf in the United States, has specifications
for the performance of golf balls. These performance specifications
dictate the size and weight of a conforming golf ball. One USGA
rule limits the golf ball's initial velocity after a prescribed
impact to 250 feet per second .+-.2% (or 255 feet per second
maximum initial velocity). To achieve greater golf ball travel
distance, ball velocity after impact and the coefficient of
restitution of the ball-club impact must be maximized while
remaining within this rule.
[0007] Generally, golf ball travel distance is a function of the
total kinetic energy imparted to the ball during impact with the
club head, neglecting environmental effects. During impact, kinetic
energy is transferred from the club and stored as elastic strain
energy in the club head and as viscoelastic strain energy in the
ball. After impact, the stored energy in the ball and in the club
is transformed back into kinetic energy in the form of
translational and rotational velocity of the ball, as well as the
club. Since the collision is not perfectly elastic, a portion of
energy is dissipated in club head vibration and in viscoelastic
relaxation of the ball. Viscoelastic relaxation is a material
property of the polymeric materials used in all manufactured golf
balls.
[0008] Viscoelastic relaxation of the ball is a parasitic energy
source, which is dependent upon the rate of deformation. To
minimize this effect, the rate of deformation must be reduced. This
may be accomplished by allowing more club face deformation during
impact. Since metallic deformation may be purely elastic, the
strain energy stored in the club face is returned to the ball after
impact thereby increasing the ball's outbound velocity after
impact.
[0009] A variety of techniques may be utilized to vary the
deformation of the club face, including uniform face thinning,
thinned faces with ribbed stiffeners and varying thickness, among
others. These designs should have sufficient structural integrity
to withstand repeated impacts without permanently deforming the
club face. In general, conventional club heads also exhibit wide
variations in initial ball speed after impact, depending on the
impact location on the face of the club. Hence, there remains a
need in the art for a club head that has a larger "sweet zone" or
zone of substantially uniform high initial ball speed.
[0010] Technological breakthroughs in recent years provide the
average golfer with more distance, such as making larger head clubs
while keeping the weight constant or even lighter, by casting
consistently thinner shell thickness and going to lighter materials
such as titanium. Also, the faces of clubs have been steadily
becoming extremely thin. The thinner face maximizes the coefficient
of restitution (COR). The more a face rebounds upon impact, the
more energy that may be imparted to the ball, thereby increasing
distance. In order to make the faces thinner, manufacturers have
moved to a forged or stamped metal face which are stronger than
cast faces. Common practice is to attach the forged or stamped
metal face by welding them to the body or sole. The thinner faces
are more vulnerable to failure. The present invention provides a
novel manner for providing the face of the club with the desired
flex and rebound at impact thereby maximizing COR.
SUMMARY OF THE INVENTION
[0011] The present invention relates to a golf club head adapted
for attachment to a shaft. An embodiment of the present invention
is a golf club head that includes a body having a perimeter region
defining an opening and a face insert disposed in the opening. The
face insert has a geometric face center and an area of maximum
coefficient of restitution. At least one slot is disposed in the
perimeter region of the body, wherein the area of maximum
coefficient of restitution is disposed between the geometric face
center and the slot. The club head may be for a fairway wood, a
driver or iron.
[0012] The slot may be an elongated slot substantially parallel to
a portion of an edge of the body. The slot may have a width of
greater than 1 mm and a length of greater than 15 mm. The slot may
comprise two opposing ends, the ends having expanded slot portions.
The slot may provide a space in the body, such that the face insert
flexes when the face insert impacts a golf ball. The slot may be
substantially filled with at least one elastomeric material.
[0013] The face insert defines a face plane and the slot may be
disposed less than 30 mm from the face plane. The area of maximum
coefficient of restitution may be provided less than 20 mm from the
geometric face center. In one embodiment, the coefficient of
restitution may be provided less than about 10 mm from the
geometric face center. In another embodiment, the area of maximum
coefficient of restitution is provided within 2 mm of the geometric
face center.
[0014] In one embodiment, the face insert defines a plane and at
least one of the slots is disposed on a sole portion of the
perimeter region adjacent the face plane. In another embodiment,
the face insert defines a plane and at least one of the slots is
disposed on a crown portion of the perimeter region adjacent the
face plane. In another embodiment, the face insert defines a plane
and at least one of the slots is disposed on a heel portion of the
perimeter region adjacent the face plane. In yet another
embodiment, the face insert defines a plane and at least one of the
slots is disposed on a toe portion of the perimeter region adjacent
the face plane.
[0015] The slot may increase the carry distance of a ball hit with
the club head as compared with a club head without a slot. The slot
may increase the speed at which a golf ball rebounds from the face
insert of the club head as compared with a club head without a
slot. In one embodiment, the speed at which a golf ball rebounds
from the face insert of the club head is increased at least 0.5 mph
as compared with a club head without a slot. The slot may increase
the launch angle of a golf ball leaving the face insert after
impact with the club head as compared with a club head without a
slot. In one embodiment, the launch angle of a golf ball leaving
the face insert is increased by at least 0.5 degrees as compared
with a club head without a slot. The slot may decrease the back
spin of a golf ball leaving the face insert after impact with the
club head as compared with a club head without a slot. In one
embodiment, the slot decreases back spin by at least 100 rpm as
compared with a club head without a slot.
[0016] In another embodiment, a golf club head is provided. The
club head includes a body having a perimeter region defining an
opening and a face insert disposed in the opening. The face insert
has a geometric face center and an area of maximum coefficient of
restitution. At least one slot disposed in the perimeter region of
the body, wherein the speed at which a golf ball rebounds from the
face insert of the club head is increased at least 0.5 mph as
compared with a club head without a slot. In one embodiment, the
speed at which a golf ball rebounds from the face is increased at
least 1 mph as compared with a conventional club head without a
slot.
[0017] In another embodiment, a golf club head is provided. The
club head includes a body having a perimeter region defining an
opening and a face insert disposed in the opening. The face insert
has a geometric face center and an area of maximum coefficient of
restitution. At least one slot is disposed on the perimeter region
of the body, wherein the area of maximum coefficient of restitution
is disposed within a zone on the face insert and the maximum
coefficient of restitution is closer to the geometric face center
as compared with a club without a slot. In one embodiment, the
coefficient of restitution over the entire face is a least 80% of
the maximum coefficient of restitution within the zone.
[0018] In another embodiment, a golf club head is provided. The
club head includes a body having a perimeter region defining an
opening and a face insert disposed in the opening. The face insert
has a geometric face center and an area of maximum coefficient of
restitution. At least one slot is disposed on the perimeter region
of the body, wherein a launch angle of a golf ball leaving the face
insert is increased by at least 0.5 degrees as compared with a club
head without a slot.
[0019] In another embodiment, a golf club head is provided. The
club head includes a body having a perimeter region defining an
opening and a face insert disposed in the opening. The face insert
has a geometric face center and an area of maximum coefficient of
restitution. At least one slot is disposed on the perimeter region
of the body, wherein back spin is decreased by at least 100 rpm as
compared with a club head without a slot.
[0020] In yet another embodiment, a golf club head is provided. The
club head includes a body having a crown forming the upper surface
of the body, a sole forming the lower surface of the body, a club
face disposed between the crown and sole, the club face having a
face center and an area of maximum resilience; and a transition
region adjacent the sole and club face. The transition region
defines a slot, wherein the area of maximum resilience is located a
distance X from the face center.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Preferred features of the present invention are disclosed in
the accompanying drawings, wherein similar reference characters
denote similar elements throughout the several views, and
wherein:
[0022] FIG. 1 is a perspective view of an embodiment of a club head
of the present invention;
[0023] FIG. 2 is bottom plan view of an embodiment of a club head
of FIG. 1;
[0024] FIG. 3 is a cross-sectional view of the club head of FIG. 2
taken along line 3-3 in FIG. 1;
[0025] FIGS. 4A-C are detailed cross-sectional views of other
embodiments of the club head of FIG. 2 taken along line 3-3 of FIG.
1;
[0026] FIG. 5 is a bottom perspective view of another alternative
embodiment of a club head of the present invention;
[0027] FIG. 6 is a bottom perspective view of another alternative
embodiment of a club head of the present invention;
[0028] FIG. 7 is a top perspective view of another alternative
embodiment of a club head of the present invention;
[0029] FIG. 8 is a front perspective view of another alternative
embodiment of a club head of the present invention;
[0030] FIG. 9 is a graph of estimated carry distance versus
vertical impact position for the inventive club and a conventional
club;
[0031] FIG. 10 is a graph of impact speed versus vertical impact
position and the club head construction for the inventive club and
a conventional club;
[0032] FIGS. 11-12 are graphs of launch angle versus vertical
impact position and the club head construction for the inventive
club and a conventional club;
[0033] FIGS. 13-14 are graphs of back spin versus vertical impact
position and the club head construction for the inventive club and
a conventional club; and
[0034] FIG. 15 is a graph of estimated carry distance versus
heel/tow impact position and club head construction for the
inventive club and a conventional club;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] COR or coefficient of restitution is a measure of collision
efficiency. COR is the ratio of the velocity of separation to the
velocity of approach. In this model, therefore, COR was determined
using the following formula:
(v.sub.club-post-v.sub.ball-post)/(v.sub.ball-pre-v.sub.club-pre)
where, v.sub.club-post represents the velocity of the club after
impact; [0036] v.sub.ball-post represents the velocity of the ball
after impact; [0037] v.sub.club-pre represents the velocity of the
club before impact (a value of zero for USGA COR conditions); and
[0038] v.sub.ball-pre represents the velocity of the ball before
impact.
[0039] COR, in general, depends on the shape and material
properties of the colliding bodies. A perfectly elastic impact has
a COR of one (1.0), indicating that no energy is lost, while a
perfectly inelastic or perfectly plastic impact has a COR of zero
(0.0), indicating that the colliding bodies did not separate after
impact resulting in a maximum loss of energy. Consequently, high
COR values are indicative of greater ball velocity and
distance.
[0040] Referring to FIG. 1, a first embodiment of a golf club head
10 of the present invention is shown. Club head 10 includes shell
12 with body 14 and a face insert 16. The body 14 includes a toe
portion 18, a heel portion 20, a sole portion 22, a hosel 24, a
crown portion 26 and a skirt portion 28. Optionally, the sole
portion 22 may include a plate (not shown) that fits in a recess
(not shown) in the bottom of the body 14. The body 14 also defines
a face perimeter or perimeter region 30 adjacent the face insert
16. The body 14 and face insert 16 create an inner cavity 32 (FIG.
3). The face insert 16 has an exterior surface 34 and an interior
surface 36 (FIG. 3). The exterior surface may have optional grooves
38.
[0041] A golf club shaft (not shown) is attached at hosel 24 and is
disposed along a shaft axis A-A. The hosel 24 may extend to the
bottom of the club head 10 and may terminate at a location between
the sole and crown portions 22 and 26 of the head 10, or the hosel
24 may terminate flush with the crown portion 26 and extend into
the cavity 32 in the head 10.
[0042] The inner cavity 32 of club head 10 may be empty, or
alternatively may be filled with foam or other low specific gravity
material. It is recommended that the inner cavity 32 have a volume
greater than 250 cubic centimeters, and more preferably greater
than 275 cubic centimeters. Preferably, the mass of the inventive
club head 10 is greater than 150 grams, but less than 220 grams;
although the club head may have any suitable weight. The body 14
may be formed of sheets welded together or cast, preferably from a
titanium alloy any other suitable material.
[0043] The perimeter region 30 defines an opening for receiving the
face insert 16. The face insert 16 is preferably connected to the
perimeter region 30 of the body 14 by welding. For example, a
plurality of chads (not shown) may be in alignment with an inner
surface of the body to provide a pocket for receiving the face
insert 16, which is therein integrally connected to the body 14 by
welding. The face insert 16 may be made by milling, casting,
forging or stamping and forming. The face insert 16 may be made of
any suitable material, including titanium, titanium alloy, carbon
steel, stainless steel, beryllium copper, and other metals or
composites.
[0044] Alternatively, the body 14 and face insert 16 may be cast
simultaneously forming a homogeneous shell and eliminating the need
to bond or otherwise permanently secure a separate face insert 16
to the body 14. Alternatively, the sole portion 22 or crown portion
26 may be formed separately and fitted to the remainder of the
shell as is known to those of skill in the art.
[0045] The thickness of the face insert 16 is preferably between
about 0.5 mm and about 3 mm, although the face insert 16 may have
any suitable thickness. The insert 16 may be of a uniform thickness
as shown in FIG. 3 or have a variable thickness. For example, the
face insert 16 may have a thicker center section and thinner outer
section. In another embodiment, the face insert 16 may have two or
more different thicknesses and the transition between thicknesses
may be radiused or stepped. Alternatively, the face insert 16 may
increase or decrease in thickness towards the toe, heel, sole or
crown portions 18, 20, 22 and 26 of the club head 10. It will be
appreciated that one or both of the exterior or interior surfaces
34 and 36 may have at least a portion that is curved, stepped or
flat to vary the thickness of the face insert 16. As will also be
appreciated, the face insert 16 may have any suitable
construction.
[0046] As shown in FIGS. 1-2, a slot 40 is formed in the perimeter
region 30. As illustrated, the slot 40 is elongated and is formed
in the sole portion 22 of the body 14 of the club head 10. The slot
40 provides a space or opening in the club head 10, such that the
face insert 16 flexes when the face insert 16 impacts a golf ball.
This slot 40 allows the face insert 16 to flex differently than
would otherwise be possible, and this flexure provides the benefit
of longer distance and reduction in error for miss-hit shots. The
slot 40 provides more forgiveness, such that a zone 42 for a sweet
spot on the face insert 16 is increased, resulting in the ball
being hit a consistent distance from a larger area on the face
insert 16.
[0047] The slot 40 may provide a localized benefit of longer
distance and reduction in error between the slot 40 and a geometric
face center GFC of the face insert 16. For example, by providing a
slot 40 in the perimeter region 30 adjacent the sole portion 22 of
the club head, a reduction in error for thin shots, shots hit low
on the club face, may be found. Thus, shots hit lower on the club
face of the inventive club head will go farther than when compared
with the same shot off a club face of a conventional club head.
Similar results may be found for a club head 10 with slots 40
provided on other portions of the perimeter region 30 and shots hit
away from the geometric face center GFC, between the face center
and the slot 40.
[0048] In a preferred embodiment, the slot 40 is provided such that
it is substantially parallel to a portion of an edge 44 of the body
14 and is provided within a certain distance D from a face plane 46
defined by the face insert 16. Preferably, the slot 40 is provided
a distance D within 30 mm of the face plane 46 of the face insert
16, more preferably within 20 mm of the face plane 46, and most
preferably within 10 mm of the face plane 46. The slot 40 has first
and second opposing ends 48 and 50. Preferably, the slot is
elongated. The slot 40 has a width W and a length L. Preferably,
the slot 40 has a width W greater than 1 mm and a length L of
greater than 15 mm. Although, it will be appreciated that the slot
may have any suitable width or length.
[0049] The 40 slot may be formed in the perimeter region 30 by any
suitable manner. Preferably, the slot is machined into the
perimeter region 30 of the body 14 of the club head 10.
Alternatively, the slot 40 may be cast, forged or stamped into the
perimeter region 30 of the body 14 while the club head 10 is being
formed.
[0050] The slot 40 may remain empty. However, as illustrated in
FIGS. 3-4C, in order to comply with the United States Golf
Association (USGA) rules, the slot 40 may be at least partially
filled with one or more nonstructural or cosmetic materials 52.
Preferably, the material is an elastomeric material, such as
silicone. As illustrated in FIG. 3, the slot 40 is simply an
opening in the body 14 of the club head 10. An elastomeric material
may be provided within the opening. The elastomeric material may be
held within the slot by an interference fit, adhesive, or any other
suitable means or combination thereof. The material may extend to
any desired degree into the cavity 32 of the club head 10. As will
be appreciated, if the cavity 32 of the club head is filled with a
foam or other low specific gravity material, this may also fill the
slot 40, such that it is not an exposed opening on the club head
10.
[0051] Referring now to FIGS. 4A-4C, the slot 40 may have numerous
different constructions other than being a simple opening in the
club head as shown in FIG. 3. Although, these embodiments
illustrate the slot 40 formed adjacent the sole, it will be
appreciated that slots of any of these constructions may be
provided at any location on the perimeter region 30. In one
embodiment, as illustrated in FIG. 4A, the slot 40 may be filled
with an elastomeric insert 54. In order to keep the elastomeric
insert 54 within the slot 40, the slot 40 may be provided with
grooves 56 in the edges of the slot 40 along at least a portion of
its length. The elastomeric insert 54 may have protrusions 58 that
fit within the grooves 56, such that the insert is kept within the
slot through normal use of the club head.
[0052] Alternatively, as shown in FIG. 4B, the slot 40 may be
formed in the perimeter region 30 by having a portion 60 of the
perimeter region 30 spaced from a portion 62 of the body 14 of the
club head 10. As illustrated, the portion 60 of the perimeter
region is bent into the cavity 32 of the club head 10 such that a
pathway 64 between the body 14 and the perimeter region 30 is
formed. The pathway 64 may be wholly or partially filled with one
or more elastomeric materials.
[0053] In another embodiment illustrated in FIG. 4C, the portion 62
of the body 14 of the club head 10 may instead be bent inward into
the cavity 32 of the club head forming a pathway 64 with the
portion 60 of the perimeter region 30 to make the slot 40. As
illustrated, the pathway 64 may be partially or wholly filled with
one or more elastomeric materials.
[0054] In another embodiment illustrated in FIG. 5, in order to
reduce stress on the slot 40, the opposing ends 48 and 50 of the
slot 40 may have expanded slot portions 66 and 68. The expanded
slot portions at the ends of the slot reduce stress on the slot
that may occur during normal play. This may reduce the chance of a
fracture occurring at one or both ends of the slot.
[0055] It will be appreciated that the slot may have different
shapes other than a simple straight slot, an elongated slot or a
slot with expanded slot portions. The slot may have a C-shape. For
example as illustrated in FIG. 6, the slot 40 may have the opposing
ends 48 and 50 angled from a center portion 70 of the slot 40. The
opposing ends 48 and 50 may be angled at any desired angle .theta.
relative to the center portion or have any desired curvature or
radius.
[0056] In an alternative embodiment illustrated in FIG. 7, the slot
40 may be provided in the perimeter region 30 on the crown portion
26 of the body 14 of the club head 10. Additionally, as illustrated
in FIG. 8, slots 40 may be provided in one or both of the toe or
heel portions 18, 20 of the body of the club head. By placing one
or more slots 40 in different areas of the perimeter region 30, the
flex of the face insert 16 may be modified compared with a
conventional club face. The change in flex may result in more
distance and greater accuracy for miss-hit shots. For example, by
providing the slot 40 in the perimeter region 30 adjacent the crown
portion 26 of the club head, a reduction in error for shots hit
high on the club face may be found. Thus, shots hit higher on the
club face of the inventive club will go farther than when compared
with the same shot off a club face with a conventional club head. A
slot provided adjacent the toe or heel portion 18, 20 will achieve
similar results for shots hit between the geometric face center GFC
and either the toe or heel.
[0057] It will be appreciated that one or more of the slots
illustrated in FIGS. 1-8 may be combined with one another. It will
be appreciated that providing slots in each of the toe, heel, sole
and crown portions 18, 20, 22 and 26 of the perimeter region 30 may
provide global improvement to the overall distance; however,
localized benefits between the geometric face center GFC and each
slot may be decreased. Additionally, it will be appreciated that
the slot 40 may not be a single slot, but may be comprised of
multiple openings (not shown) that form the slot 40.
[0058] As illustrated, the slot 40 is provided in a fairway wood;
however, it will be appreciated that the slot 40 may be provided in
a driver or iron. In particular, it may be beneficial to provide a
slot 40 on a driver in the crown portion and/or both the crown
portion and sole portion. For irons, a slot 40 in the sole portion
might provide the same benefits as for a fairway wood, increased
distance and forgiveness for thin shots. Preferably, an iron with a
slot according to the invention would have a thin face.
[0059] As will be appreciated, the face insert 16 has a geometric
face center GFC and an area of maximum coefficient of restitution
or maximum resilience. Preferably, the area of maximum resilience
is disposed between the geometric face center GFC and the slot 40.
In another embodiment, the area of maximum coefficient of
restitution is disposed within the zone 42 on the face insert 16
and the maximum coefficient of restitution is closer to the
geometric face center GFC as compared with a club head without a
slot. Preferably, the coefficient of restitution over the entire
face insert 16 is at least 70% and more preferably at least 80% of
the maximum coefficient of restitution within the zone 42.
[0060] In another embodiment, the area of maximum coefficient of
restitution MCR is provided a distance X from the geometric face
center GFC. Preferably, the distance X is less than about 20 mm,
more preferably less than about 10 mm. In another embodiment, the
maximum coefficient of restitution is within 2 mm of the geometric
face center GFC. It is expected that as the COR increases the ball
flight distance will increase and the maximum total distance will
increase. The COR of the area between the geometric face center GFC
and the slot 40 may be increased. For the inventive club head,
preferably the COR is greater than about 0.8, and more preferably
greater than 0.81. Preferably, the COR for the zone 42 is at least
about 0.81, and more preferably, at least about 0.82.
[0061] Now referring to FIG. 9, the graph plots carry distance
versus vertical impact position and head construction comparing a
conventional club with an inventive club having a slot 40 as
illustrated in FIG. 1. As illustrated, an impact at the geometric
face center GFC of the club face is 0 on the graph, with negative
numbers showing an impact toward the sole and positive numbers
showing an impact toward the crown. The inventive club may result
in an increase, for the average PGA Tour player, in his fairway
wood distance of 7 yards (245 yard to 252 yards) for a center shot,
and a 60% reduction in the error caused by a shot hit 1/8'' too low
on the face. Thus, the club with the slot 40 would hit a 1/8'' thin
shot 250.6 yards, versus 252.6 yards for a center shot for a
difference of 2 yards, while a conventional club would hit a 1/8''
thin shot 240.5 yards versus 245.3 yards for a center shot for a
difference of 4.8 yards. Thus, a club head according to the
invention as shown in FIG. 1 is more forgiving of shots hit low on
the club face.
[0062] FIG. 10 illustrates a graph showing ballspeed versus height
off the ground at impact for a conventional club without a slot, a
club according to the invention as shown in FIG. 5 with a slot 40
having expanded slot portions 66 and 68 in the perimeter region 30
of the sole portion 22, and a club according to the invention as
shown in FIG. 1 with an elongated slot in the perimeter region of
the sole portion 22. Generally, with shots hit lower on the club
face the slots 40 provide an increase in ballspeed. For example, at
about 12 mm from the ground the club with the slot having expanded
slot portions provides about an additional 1.5 mph of ballspeed
compared with a conventional club, while the club with the
elongated slot provides about an additional 4 mph of ball speed
compared to a conventional club. The higher off the ground the
impact, the less the increase in ballspeed when compared to a
conventional club. Preferably, the speed at which a golf ball
rebounds from the face insert of the inventive club head is
increased at least 0.5 mph as compared with a club head without a
slot. The speed at which a golf ball rebounds from the face insert
of the inventive club head may be increased by at least 0.3 mph,
preferably at least 0.5 mph and more preferably at least 1 mph as
compared with a conventional club.
[0063] Referring to FIGS. 11-12, graphs plotting launch angle
versus impact location for a fairway wood having a slot 40
according to the invention and for a conventional club without a
slot are illustrated. The conventional club is a Titleist 980F
Fairway wood with a 13.degree. loft, and the inventive club is the
same club having a slot 40 provided in the perimeter region 30 of
the sole portion 22 as illustrated in FIG. 1. A comparison of the
graphs illustrates that the club according to the invention has an
increase in launch angle for similar impact positions. Preferably,
the launch angle at which a golf ball leaves the face insert 16 of
the inventive club is increased by at least 0.5 degrees as compared
with a conventional club without a slot in the club head. The
launch angle at which a golf ball leaves the face insert 16 of the
inventive club may be increased by at least 0.3 degrees, preferably
at least 0.5 degrees and more preferably at least 1 degree as
compared with a conventional club.
[0064] FIGS. 13-14, illustrate graphs plotting back spin versus
impact location for a fairway wood having a slot 40 according to
the invention and for a conventional club without a slot. The
conventional club is a Titleist 980F Fairway wood with a 13.degree.
loft, and the club according to the invention is the same club
having a slot 40 provided in the perimeter region 30 of the sole
portion 22 as illustrated in FIG. 1. A comparison of the graphs
illustrates that the inventive club has a decrease in back spin for
similar impact locations. Preferably, the back spin of a golf ball
leaving the face insert 16 of the inventive club is decreased by at
least 100 rpm as compared with a conventional club without a slot
in the club head. Thus, a golf club according to the invention is
more forgiving of off-center hits than a conventional club without
a slot. The back spin of a golf ball leaving the face insert of the
inventive club may be decreased by at least 50 rpm, preferably 100
rpm, and more preferably 150 rpm as compared with a conventional
club.
[0065] As illustrated in FIG. 15, a graph of estimated carry
distance versus distance heelward of impact for a conventional club
having no slot and a club according to the invention having a slot
in the heel and toe as illustrated in FIG. 8 is shown. As
illustrated the farther from the geometric face center GFC of the
club face the ball is hit (the geometric face center GFC between
the heel and toe being 0 in the graph) the more distance a club
according to the invention provides. For example, at -16 mm from
geometric face center GFC the inventive club provides over an
additional yard of distance, while at +16 mm the inventive club
provides almost an additional yard. Thus, a club with a slot 40
according to the invention as illustrated in FIG. 8 is more
forgiving of hits not directly on the geometric face center GFC of
the club head 10 between the heel and toe than a conventional
club.
[0066] Tests results of the inventive and conventional golf clubs
illustrated in FIGS. 9-15 were performed using finite element
analysis (FEA) software, and these results were confirmed by robot
testing.
[0067] While various descriptions of the present invention are
described above, it should be understood that the various features
of each embodiment could be used alone or in any combination
thereof. Therefore, this invention is not to be limited to only the
specifically preferred embodiments depicted herein. Further, it
should be understood that variations and modifications within the
spirit and scope of the invention might occur to those skilled in
the art to which the invention pertains. For example, the face
insert may have thickness variations in a step-wise or continuous
fashion. In addition, the shapes and locations of the slots are not
limited to those disclosed herein. Accordingly, all expedient
modifications readily attainable by one versed in the art from the
disclosure set forth herein that are within the scope and spirit of
the present invention are to be included as further embodiments of
the present invention. The scope of the present invention is
accordingly defined as set forth in the appended claims.
* * * * *