U.S. patent application number 17/656371 was filed with the patent office on 2022-07-07 for golf club heads with internal undercuts.
The applicant listed for this patent is KARSTEN MANUFACTURING CORPORATION. Invention is credited to Suraj Megharaja, Eric J. Morales, Alex G. Woodward.
Application Number | 20220212070 17/656371 |
Document ID | / |
Family ID | |
Filed Date | 2022-07-07 |
United States Patent
Application |
20220212070 |
Kind Code |
A1 |
Woodward; Alex G. ; et
al. |
July 7, 2022 |
GOLF CLUB HEADS WITH INTERNAL UNDERCUTS
Abstract
Described herein is a hollow body iron-type golf club head
having a sole and ballast configured to relieve stress within a
forward portion of the sole. In a first configuration, the golf
club head comprises a ballast undercut for relieving stress. In
other configurations, the ballast undercut is combined with
additional stress relief features, such as a cascading sole near
the face sole juncture, for further reductions to face
thickness.
Inventors: |
Woodward; Alex G.; (Phoenix,
AZ) ; Morales; Eric J.; (Laveen, AZ) ;
Megharaja; Suraj; (Phoenix, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KARSTEN MANUFACTURING CORPORATION |
Phoenix |
AZ |
US |
|
|
Appl. No.: |
17/656371 |
Filed: |
March 24, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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17237010 |
Apr 21, 2021 |
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17656371 |
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63013341 |
Apr 21, 2020 |
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63200726 |
Mar 24, 2021 |
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International
Class: |
A63B 53/04 20060101
A63B053/04 |
Claims
1. A golf club head comprising: a hollow body defining an enclosed
internal cavity, the hollow body comprising: a strikeface; a heel
portion; a toe portion opposite the heel portion; a sole; a top
rail; a rear portion extending between the top rail and the sole,
and separated from the strikeface by the internal cavity; a solid
ballast within the internal cavity extending substantially between
the heel portion and the toe portion; wherein the solid ballast
extends upward from the sole and forward from the rear portion;
wherein the solid ballast comprises a ballast top surface, a
ballast forward surface, and a ballast juncture between the ballast
top surface and the ballast forward surface; a ballast forward
plane tangent to the ballast juncture and parallel to the
strikeface; wherein a ballast angle is defined between the ballast
forward surface and an interior surface of the sole; wherein the
ballast angle is between 30 and 80 degrees; an undercut formed
between the ballast forward surface and the interior surface of the
sole; wherein the undercut comprises: an undercut bottom edge
formed by the interior surface of the sole; an undercut top edge
formed by the ballast forward surface; an undercut juncture located
at a transition between the interior surface of the sole and the
ballast forward surface; an undercut height measured as a vertical
distance between the undercut bottom edge and the undercut top
edge; and wherein the undercut height measured at the ballast
forward plane is greater than 0.250 inch.
2. The golf club head of claim 1, further comprising: a cascading
region defining an internal transition region from the strikeface
to the sole, the cascading region comprising; a first tier
comprising a first thickness; a second tier comprising a second
thickness different than the first thickness; and a tier transition
region between the first tier and the second tier.
3. The golf club head of claim 2, further comprising a cascading
region perimeter defining a boundary between the cascading region
and the sole; and wherein the cascading region perimeter comprises
a cascade front edge proximate a leading edge of the strikeface and
a cascade rear edge spaced rearwardly from the strikeface.
4. The golf club head of claim 3, wherein the cascade rear edge is
arcuate and bows rearward relative to the cascade front edge;
wherein the cascading region comprises a depth measured as a
front-to-rear distance between the cascade front edge and the
cascade rear edge; and wherein the depth of the cascading region is
greater proximate a center of the club head than the depth of the
cascading region near the toe portion and the heel portion.
5. The golf club head of claim 3, wherein a width of the cascading
region is greater proximate the cascade front edge than near the
cascade rear edge.
6. The golf club head of claim 1, further comprising an undercut
depth measured as a perpendicular distance between the ballast
forward plane and the undercut juncture; wherein the undercut depth
is greater than 0.100 inch.
7. The golf club head of claim 1, wherein the ballast angle is
between 60 degrees and 80 degrees.
8. The golf club head of claim 1, wherein the ballast forward
surface comprises a concave curvature relative to the
strikeface.
9. The golf club head of claim 1, further comprising a top
rail-to-sole moment of inertia ranging from 95 gin.sup.2 to 130
gin.sup.2 and a heel-to-toe moment of inertia ranging from 350
gin.sup.2 to 420 gin.sup.2.
10. A golf club head comprising: a hollow body defining an enclosed
internal cavity, the hollow body comprising: a strikeface; a heel
portion; a toe portion opposite the heel portion; a sole; a top
rail; a rear portion extending between the top rail and the sole,
and separated from the strikeface by the internal cavity; a solid
ballast within the internal cavity extending substantially between
the heel portion and the toe portion; wherein the solid ballast
extends upward from the sole and forward from the rear portion;
wherein the solid ballast comprises a ballast top surface, a
ballast forward surface, and a ballast juncture between the ballast
top surface and the ballast forward surface; a ballast forward
plane tangent to the ballast juncture and parallel to the
strikeface; wherein a ballast angle is defined between the ballast
forward surface and an interior surface of the sole; wherein the
ballast angle is between 30 and 80 degrees; an undercut formed
between the ballast forward surface and the interior surface of the
sole; wherein the undercut comprises: an undercut bottom edge
formed by the interior surface of the sole; an undercut top edge
formed by the ballast forward surface; an undercut juncture located
at a transition between the interior surface of the sole and the
ballast forward surface; a cascading region defining an internal
transition region from the strikeface to the sole, the cascading
region comprising; a first tier comprising a first thickness; a
second tier comprising a second thickness different than the first
thickness; a tier transition region between the first tier and the
second tier; wherein the cascading region comprises a perimeter
boundary comprising a cascade front edge proximate a leading edge
of the strikeface, a cascade rear edge spaced rearwardly from the
strikeface, a cascade heel edge extending between the cascade front
edge and the cascade rear edge proximate the heel portion, and a
cascade toe edge extending between the cascade front edge and the
cascade rear edge proximate the heel portion; wherein the cascading
region comprises a depth measured as a front-to-rear distance
between the cascade front edge and the cascade rear edge; wherein
the depth of the cascading region is greater proximate a center of
the club head than the depth of the cascading region near the toe
portion and the heel portion; and wherein the depth of the
cascading region at the cascade heel edge is between 50% and 90% of
the depth of the cascading region at the center of the club
head.
11. The golf club head of claim 10, wherein the cascading region
further comprises a cascading region depth measured between the
cascade heel edge and the cascade toe edge in a heel to toe
direction; wherein the cascading region depth is greater near the
cascade front edge than near the cascade rear edge.
12. The golf club head of claim 10, wherein the cascade rear edge
is arcuate and bows rearward relative to the cascade front
edge.
13. The golf club head of claim 10, wherein the cascading region
further comprises a third tier.
14. The golf club head of claim 10, wherein the tier transition
region linearly declines at an angle less than 45 degrees.
15. The golf club head of claim 10, wherein the ballast forward
surface comprises a concave curvature relative to the
strikeface.
16. The golf club head of claim 10, wherein the ballast angle is
between 60 degrees and 80 degrees.
Description
RELATED APPLICATIONS
[0001] This is a continuation in part of U.S. patent application
Ser. No. 17/237,010, filed on Apr. 21, 2021, which claims the
benefit to U.S. Provisional Patent Application No. 63/013,341,
filed on Apr. 21, 2020. This also claims the benefit to U.S.
Provisional Patent Application No. 63/200,726 all of which are
incorporated herein by reference.
FIELD
[0002] The present disclosure relates generally to golf equipment,
and more particularly, to flexure structures for improved
performance characteristics of hollow body irons and methods to
manufacture hollow body irons with flexure structures.
BACKGROUND
[0003] Hollow body irons, ideally, operate as a diving board,
flexing rearward during impact. In club design, the degree to which
a hollow body iron behaves as a diving board, or spring is
constrained by peak stress values. To ensure that traditional golf
clubs do not exceed maximum stress limits, the face and sole are
thickened such that the club is made more rigid. The rigidity of
the traditional golf clubs results in a degradation to the diving
board, or spring behavior of the club head. Therefore, there is a
need in the art to produce a golf club head having a construction
which expands the limit of modifications to the face to improve
energy transfer from the club to the ball at impact.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 depicts a toe end perspective view of a hollow body
club head according to one embodiment.
[0005] FIG. 2A depicts a toe side cross-sectional view of the
hollow body club head of FIG. 1.
[0006] FIG. 2B depicts a view of a portion of the hollow body club
head of FIG. 2A.
[0007] FIG. 3 depicts a front view of an internal cavity of FIG.
1.
[0008] FIG. 4A depicts a cross-sectional view of a hollow body
club, similar to the hollow body club of FIG. 1, according to
another embodiment comprising a ballast with an angled forward
surface.
[0009] FIG. 4B depicts a close-up view of the ballast and undercut
of the hollow body club of FIG. 4A.
[0010] FIG. 5 depicts a toe end perspective view of the hollow body
club of FIG. 4A with the strikeface removed, showing the internal
cavity.
[0011] FIG. 6A depicts a cross-sectional view of a hollow body
club, similar to the hollow body club of FIG. 1, according to
another embodiment.
[0012] FIG. 6B depicts a view of a portion of the hollow body club
of FIG. 6A.
[0013] FIG. 7 depicts a top cross-sectional view of the hollow body
club of FIG. 6A, highlighting the cascading region within the
internal cavity.
[0014] FIG. 8 depicts a cross-sectional view of a prior art hollow
body club, according to another embodiment.
[0015] FIG. 9 depicts comparative a graph of ball velocity of a 7
iron measured in mph for various undercut embodiments described in
this disclosure.
[0016] FIG. 10 depicts a comparative graph of vertical launch angle
of the 7 iron of FIG. 9 in degrees for various undercut embodiments
described in this disclosure.
[0017] FIG. 11 depicts a comparative graph of spin rate of the 7
iron of FIG. 9 in rpm for various undercut embodiments described in
this disclosure.
[0018] FIG. 12 depicts a comparative graph of vertical launch angle
of a pitching wedge in degrees for various undercut embodiments
described in this disclosure.
[0019] FIG. 13 depicts a comparative graph of spin rate of the
pitching wedge of FIG. 12 for various undercut embodiments
described in this disclosure.
[0020] FIG. 14 depicts comparative a graph of ball speed of the
pitching wedge of FIG. 12, measured in mph, for various undercut
embodiments described in this disclosure.
[0021] For simplicity and clarity of illustration, the drawing
figures illustrate the general manner of construction, and
descriptions and details of well-known features and techniques may
be omitted to avoid unnecessarily obscuring the invention.
Additionally, elements in the drawing figures are not necessarily
drawn to scale. For example, the dimensions of some of the elements
in the figures may be exaggerated relative to other elements to
help improve understanding of embodiments of the present invention.
The same reference numerals in different figures denote the same
elements.
[0022] The terms "first," "second," "third," "fourth," and the like
in the description and in the claims, if any, are used for
distinguishing between similar elements and not necessarily for
describing a particular sequential or chronological order. It is to
be understood that the terms so used are interchangeable under
appropriate circumstances such that the embodiments described
herein are, for example, capable of operation in sequences other
than those illustrated or otherwise described herein. Furthermore,
the terms "include," and "have," and any variations thereof, are
intended to cover a non-exclusive inclusion, such that a process,
method, system, article, device, or apparatus that comprises a list
of elements is not necessarily limited to those elements, but may
include other elements not expressly listed or inherent to such
process, method, system, article, device, or apparatus.
[0023] The terms "left," "right," "front," "back," "top," "bottom,"
"over," "under," and the like in the description and in the claims,
if any, are used for descriptive purposes and not necessarily for
describing permanent relative positions. It is to be understood
that the terms so used are interchangeable under appropriate
circumstances such that the embodiments of the invention described
herein are, for example, capable of operation in other orientations
than those illustrated or otherwise described herein.
[0024] The terms "couple," "coupled," "couples," "coupling," and
the like should be broadly understood and refer to connecting two
or more elements or signals, electrically, mechanically and/or
otherwise.
[0025] The term "ground plane," as used herein, can refer to a
reference plane associated with the surface on which a golf ball is
placed. The ground plane can be a horizontal plane tangent to the
sole at an address position.
[0026] The terms "loft" or "loft angle" of a hollow body golf club
(hererafter "hollow body" or "hollow body iron" or "iron-type golf
club head" or "golf club head"), as described herein, refers to the
angle formed between the club face and the shaft, as measured by
any suitable loft and lie machine. A loft plane lies tangent to the
strikeface at the geometric center. A loft angle is measured
between the ground plane and the loft plane. In many embodiments,
the loft angle of the club head is less than approximately 50
degrees, less than approximately 49 degrees, less than
approximately 48 degrees, less than approximately 47 degrees, less
than approximately 46 degrees, less than approximately 45 degrees,
less than approximately 44 degrees, less than approximately 43
degrees, less than approximately 42 degrees, less than
approximately 41 degrees, less than approximately 40 degrees, less
than approximately 39 degrees, less than approximately 38 degrees,
less than approximately 37 degrees, less than approximately 36
degrees, less than approximately 35 degrees, less than
approximately 34 degrees, less than approximately 33 degrees, less
than approximately 32 degrees, less than approximately 31 degrees,
less than approximately 30 degrees, less than approximately 29
degrees, less than approximately 28 degrees, less than
approximately 27 degrees, less than approximately 26 degrees, less
than approximately 25 degrees, less than approximately 24 degrees,
less than approximately 23 degrees, less than approximately 22
degrees, less than approximately 21 degrees, less than
approximately 20 degrees, less than approximately 19 degrees, less
than approximately 18 degrees, 17, or less than approximately 16
degrees. Further, in many embodiments, the loft angle of the club
head is greater than approximately 16 degrees, greater than
approximately 17 degrees, greater than approximately 18 degrees,
greater than approximately 19 degrees, greater than approximately
20 degrees, greater than approximately 21 degrees, greater than
approximately 22 degrees, greater than approximately 23 degrees,
greater than approximately 24 degrees, greater than approximately
25 degrees, greater than approximately 26 degrees greater than
approximately 27 degrees, greater than approximately 28 degrees,
greater than approximately 29 degrees, greater than approximately
30 degrees, greater than approximately 31 degrees, greater than
approximately 32 degrees, greater than approximately 33 degrees,
greater than approximately 34 degrees, greater than approximately
35 degrees, greater than approximately 36 degrees, greater than
approximately 37 degrees, or greater than approximately 38
degrees.
DESCRIPTION
[0027] The present disclosure describes technologies for an
improved hollow body iron-type golf club head (hererafter "hollow
body" or "hollow body iron" or "iron-type golf club head" or "golf
club head") having a sole and ballast configured to relieve stress
within a forward portion of the sole. In a first configuration, the
golf club head comprises a ballast undercut for relieving stress.
In other configurations, the ballast undercut is combined with
additional stress relief features, such as a cascading sole near
the face sole juncture, for further reductions to face
thickness.
[0028] The hollow body can comprise a strikeface, a rear portion,
opposite the strikeface, a heel portion, a toe portion, opposite
the heel, a sole, and a top rail to define an interior cavity. The
rear portion can further include a ballast extending forward from
the rear portion and into the interior cavity. In many embodiments,
the ballast is an internal component such that it is not visible
from the exterior of the golf club. The ballast can further
comprise a geometry configured to increase the interior surface
area of the sole. For example, in some embodiments, the ballast can
comprise a top surface, a forward surface, and a bottom surface
defined as an undercut region. In such embodiments, when viewed
from a toe side cross section, an undercut is formed by the bottom
surface's concave geometry relative to the face. In other
embodiments, a forward surface of the ballast may be angled towards
the face such that the forward surface overhangs a portion of the
sole. In such embodiments, an undercut is formed between the
ballast forward surface and the interior surface of the sole. The
undercut allows the thinner, forward portion of the sole to extend
beneath the ballast. A ballast comprising a bottom undercut surface
and/or an angled forward surface, as opposed to a forward surface
that meets the interior surface of the sole at a right angle, (1)
prevents stress from concentrating along the sole between the face
and the ballast and (2) increases the portion of the sole capable
of storing strain energy. Hollow body irons comprising an undercut,
therefore, comprise sole and face geometries with greater range of
thinning, as compared to hollow irons without an undercut.
[0029] The sole of the hollow body iron can be divided into two
regions, the forward portion and the rear portion. The forward
portion defines the thin region of the sole adjacent the
strikeface, which can store strain energy. The rear portion of the
sole describes the region of the sole adjacent to the to the rear
portion of the of the body, which does not store strain energy. In
other words, the forward portion of the sole 132 is the portion of
the sole 110 that behaves as a spring. Hollow body irons having a
thinner face and extended forward sole portion, as a result of the
ballast undercut, store more strain energy (i.e., potential energy)
than the face and forward sole portion of a club without an
undercut. Consequently, the undercut improves the spring-like
energy transfer between the club body and the golf ball (as
compared to a golf club without an undercut). This energy transfer
can be further improved in hollow body irons when the forward sole
portion also comprises a cascade, in addition to the undercut. The
cascading sole improves the flow of stress within the forward
portion of the sole near the face sole juncture, while the undercut
improves the flow of stress near the ballast. Accordingly, the
application of the undercut and/or the combined application of the
undercut and cascading sole can result in a golf club head, which
can tolerate a 3-8% thinner face. Thus, the thinner face, which had
been previously unattainable, results in an improved flight
trajectory and distance.
[0030] I. Undercut
[0031] a. Undercut formed by Bottom Surface of Ballast
[0032] FIG. 1 of the drawings depicts a perspective view of an
iron-type golf club head 100 exterior having an internal stress
relieving sole 110 and ballast 114 having an undercut 102, shown in
FIG. 2A. The golf club head 100 comprises a hollow body structure
with an internal cavity 104. The hollow body structure of golf club
head 100 is further defined by a strikeface 106, a rear portion 108
opposite the strikeface 106, a heel portion 103, a toe portion 105
opposite the heel portion 103, a sole 110, and a top rail 112
opposite the sole 110.
[0033] FIG. 2A illustrates a heel cut away view of the FIG. 1 golf
club head 100. FIG. 2A shows the internal cavity 104 and stress
relieving features of golf club head 100. The rear portion 108
further comprises a ballast 114 located within the internal cavity
104. As shown in FIG. 2A, the ballast 114 is an integral weighting
element necessary for optimal CG (center of gravity) positioning in
golf club head 100. The ballast 114 is a solid structure protruding
vertically from the sole 110, forward from the rear portion 108,
and extending along the sole 110 in a heel to toe direction. A
forward portion 132 of the sole 110 is defined between the
strikeface 106 and the ballast 114.
[0034] Continuing to refer to FIG. 2B, the ballast 114 comprises a
top surface 116, a forward surface 118, and a bottom surface 120.
As illustrated, the bottom surface 120 is contoured to create a
relief defining an undercut region 128 with undercut 102. The
undercut region 128 of the ballast 114 can be studied as an
undercut region 128 of material that has been removed from the
ballast 114 adjacent an interior surface 122 of the sole 110. The
undercut region 128 comprises undercut 102 and an undercut
transition 141. The undercut region 128 extends laterally in a heel
to toe direction over a heel to toe length 124 of the ballast 114.
In the illustrated embodiment, the undercut 102 is generally
centered within the golf club head 100 between the heel portion 103
and toe portion of the golf club head 100. As shown in FIG. 2B, the
undercut 102 extends beneath the ballast 114, such that forward
portion 132 of the sole 110 is bounded between the face and the
undercut 102/bottom surface 120 of the ballast 114. The forward
portion 132 of the sole 110 is effectively lengthened, as compared
to golf club head without an undercut (i.e., a forward portion
defined between the strikeface and the forward surface of the
ballast). Therefore, the undercut 102 not only reduces stress in
the forward portion 132 of the sole, but creates a larger spring
(i.e., the forward portion of the sole) for transferring energy
back to the ball at impact.
[0035] FIG. 2B depicts a zoomed-in view of the ballast 114 and
undercut 102 shown in the FIG. 2A cross section. As shown in FIG.
2B, the ballast 114 comprises top surface 116, forward surface 118,
and bottom surface 120. The ballast 114 protrudes vertically from
an interior surface of the sole 110 along an interior surface of
the rear portion 108. The bottom surface 120 comprises a contoured
geometry that extends inward, from the forward surface 118 toward
the rear portion 108 to define the undercut 102, which extends in a
heel to toe direction. Continuing to refer to the FIG. 2B cross
section, the ballast bottom surface 120 further comprises an
undercut juncture 130 defined as the juncture between the ballast
bottom surface 120 and the interior surface 122 of the sole 110.
The undercut juncture 130 is a rearmost point of the ballast bottom
surface 120 that defines the undercut 102. As shown, the forward
portion 132 of the sole is defined between the strikeface 106 and
the undercut juncture 130, rather than the strikeface 106 and the
forward surface 118 in a hollow body iron without undercut 102.
[0036] Referring to FIG. 2B, the undercut 102 is defined by four
parameters: undercut depth 134, undercut height 136, undercut
length 138, an undercut sole thickness 123. Further, the ballast
bottom surface 120 can be curved such that the undercut 102 is
defined between an undercut bottom edge 139 and an undercut top
edge 137. The undercut depth is measured as a perpendicular
distance between a ballast forward plane 20 and the undercut
juncture 130 (i.e., the rear most point of the undercut). The
undercut height 136 is defined as the vertical distance between an
undercut top edge 137 and an undercut bottom edge 139. The undercut
length is measured parallel to a ground plane between the undercut
toe end 133 and the undercut heel end 135. Finally, the undercut
sole thickness 123 is measured as the perpendicular distance from
the exterior surface of the sole 121 and an interior surface of the
sole 121. In a first embodiment, the undercut 102 has a depth 134
of 0.065 inch, a height 136 of 0.083 inch, a length of 1.16
inches.
[0037] The undercut depth 134, between the ballast forward plane 20
and the undercut juncture 130, has a range of 0.010 inch to 0.100
inch. For example, the undercut depth 134 can be 0.010 inch, 0.015
inch, 0.020 inch, 0.025 inch, 0.030 inch, 0.035 inch, 0.040 inch,
0.045 inch, 0.050 inch, 0.055 inch, 0.060 inch, 0.065 inch, 0.070
inch, 0.075 inch, 0.080 inch, 0.085 inch, 0.090 inch, 0.095 inch,
or 0.100 inch. Alternatively, an undercut face depth 131 can be
measured as the perpendicular distance between an interior surface
of the strikeface 106 and the undercut juncture 130. In some
embodiments, the undercut depth from the face ranges from 0.200
inch to 0.500 inch. For example, the undercut depth from the face
can be 0.200 inch, 0.220 inch, 0.240 inch, 0.260 inch, 0.280 inch,
0.300 inch, 0.320 inch, 0.340 inch, 0.360 inch, 0.380 inch, 0.400
inch, 0.420 inch, 0.440 inch, 0.460 inch, 0.480 inch, or 0.500
inch.
[0038] The undercut height 136, measured between the undercut
bottom edge 139 and undercut top edge 137, can range from 0.030
inch to 0.200 inch. For example, the undercut height 136 range from
0.030 inch to 0.040 inch, 0.040 inch to 0.050 inch, 0.050 inch to
0.060 inch, 0.060 inch to 0.070 inch, 0.070 inch to 0.080 inch,
0.080 inch to 0.090 inch, 0.090 inch to 0.100 inch, 0.100 inch to
0.110 inch, 0.110 to 0.120 inch, 0.120 inch to 0.130 inch, 0.130
inch to 0.140 inch, 0.140 inch to 0.150 inch, 0.150 inch to 0.160
inch, 0.160 inch to 0.170 inch, 0.170 inch to 0.180 inch, 0.180
inch to 0.190 inch, or 0.190 inch to 0.200 inch.
[0039] FIG. 3 depicts a front view of golf club head 100 wherein
the strikeface 106 is removed to expose the undercut length 138
extending from the undercut heel end 135 to the undercut toe end
132. In some embodiments, the undercut length 138 ranges from 0.5
inch to 3.0 inches. In other embodiments, the undercut length
ranges from 0.50 inch to 0.75 inch, 0.75 inch to 1.00 inch, 1.00
inch to 1.25 inches, 1.25 inches to 1.50 inches, 1.50 inches to
1.75 inches, 1.75 inches to 2.00 inches, 2.00 inches to 2.25
inches, 2.25 inches to 2.50 inches, 2.50 inches to 2.75 inches, or
2.75 inches to 3.00 inches. FIG. 3 further shows the ballast length
124, which can be measured from a ballast heel end 125 to a ballast
toe end 127. In some embodiments the ballast length 124 ranges from
1.0 inch to 3.0 inches. In other embodiments the ballast length 124
is 1.2 inches, 1.4 inches, 1.6 inches, 1.8 inches, 2.0 inches, 2.2
inches, 2.4 inches, 2.6 inches, 2.8 inches, or 3.0 inches.
[0040] The undercut length 138, measured as the distance between
the undercut heel and toe ends, may further define a percent of the
ballast length 124, to describe the portion of the ballast 114
comprising the undercut 102. In embodiments of iron type golf club
heads comprising an undercut 102, the undercut 102 can increase the
surface area experiencing impact loading. The percent ballast
length can be calculated as the undercut length 138 divided by the
ballast length 124. In some embodiments, the undercut percent
ballast length ranges from 20% to 100%. The length of the undercut
can range from 10% the length of the ballast length up to the same
length as the ballast length (i.e., 100%). For example, the percent
ballast length is 20%, 25%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%,
75%, 80%, 85%, 90%, or 95%.
[0041] In addition, an undercut transition height 142, as shown in
FIG. 2B, is defined as the perpendicular distance between an
interior surface 122 of the sole 110 and forward surface lower edge
140. In some embodiments, the transition height 142 can range from
0.150 inch to 0.300 inch. The transition height can range from
0.150 inch to 0.160 inch, 0.160 inch to 0.170 inch, 0.170 inch to
0.180 inch, 0.180 inch to 0.190 inch, or 0.190 inch to 0.200 inch,
0.200 inch to 0.210 inch, 0.210 to 0.220 inch, 0.220 inch to 0.230
inch, 0.230 inch to 0.240 inch, 0.240 inch to 0.250 inch, 0.250
inch to 0.260 inch, 0.260 inch to 0.270 inch, 0.270 inch to 0.280
inch, 0.280 inch to 0.290 inch, or 0.290 inch to 0.300 inch In the
first embodiment discussed above, the transition height is 0.185
inch. The undercut transition 141 having transition height 142 and
a contoured profile allows the undercut 102 to smoothly transition
to the ballast forward surface 118. This smooth transition promotes
an even flow of stress through the undercut 102 and the ballast
114.
[0042] As discussed above, the undercut 102 and undercut region 128
can be considered as a region of ballast material that has been
removed, when compared to iron-type golf club heads lacking an
undercut. An undercut volume is defined by a surface 146 of the
undercut region 128 and the ballast forward plane 20. For example,
in one embodiment, the surface 146 of the undercut region and the
ballast forward plane 20 define an undercut volume of 0.018 cubic
inches. In other embodiments, the undercut volume ranges from 0.018
cubic inches to 0.050 cubic inches. For example, the undercut
volume can be 0.018 cubic inches, 0.020 cubic inches, 0.022 cubic
inches, 0.024 cubic inches, 0.026 cubic inches, 0.028 cubic inches,
0.030 cubic inches, 0.032 cubic inches, 0.034 cubic inches, 0.036
cubic inches, 0.038 cubic inches, 0.040 cubic inches, 0.042 cubic
inches, 0.044 cubic inches, 0.046 cubic inches, 0.048 cubic inches,
or 0.050 cubic inches. The undercut volume can be used to calculate
mass removed from the ballast 114 by the undercut region 128. Mass
is calculated by multiplying the undercut volume by the material
density of the ballast 114. For example, an undercut volume ranging
from 0.018 cubic inches to 0.030 cubic inches. The undercut volume
can be 0.018 cubic inches, 0.020 cubic inches, 0.022 cubic inches,
0.024 cubic inches, 0.026 cubic inches, 0.028 cubic inches, or
0.030 cubic inches. The amount of material removed from the ballast
to form the undercut with a material density ranging from 6.0
g/cm.sup.3 to 7.75 g/cm.sup.3 or a range of mass from 1.75 grams to
2.40 grams. The amount of material removed from the ballast to form
the undercut with a material density of 6.0 g/cm.sup.3, 6.5
g/cm.sup.3, 7.0 g/cm.sup.3, or 7.75 g/cm.sup.3 or a mass of 1.75
grams, 2.0 grams, 2.20 grams, 2.32 grams or 2.40 grams from the
ballast 114.
[0043] The forward portion 132 of the sole 110 extending from the
strikeface 106 to the ballast 114 affects the impact response of
golf club head 100 with a golf ball. As shown in FIG. 2B, the
undercut juncture 130 is spaced further rearward from the
strikeface 106 than the ballast forward surface 118. The undercut
juncture's additional distance from the strikeface 106, means that
the thinner, forward portion 132 of the sole 110 has been
effectively lengthened (relative to an overall front-to-rear sole
width) such that part of the forward sole portion extends beneath
the ballast 114 (as compared to traditional golf club heads, which
lack the undercut 102). A forward sole length can be measured as
the perpendicular distance between the undercut juncture 130 and
the strikeface 106. In some embodiments, the effective increase in
length ranges from 6% to 12%. For example, the undercut 102 can
increase length of the forward sole portion 132 by 6% to 7%, 7% to
8%, 8% to 9%, 9% to 10%, and 11% to 12%. Increasing the length of
the thinned out forward portion 132 of the sole 110 reduces peak
stress values in golf club head 100. Rather than behaving as a
rigid connection, the undercut 102 generates stress relief at the
face-sole transition by allowing the forward portion 132 of the
sole 110, between the strikeface 106 and the ballast 114, to
deflect to a greater extent under impact loads. The undercut's
effective increase in forward sole 132 length increases the total
surface area over which impact load is distributed for a stress
reduction of 1000 psi to 2000 psi within the forward portion 132 of
the sole. Undercut 102 dually reduces stress concentrations within
forward sole portion 132 and increases the bending/spring effect of
the forward sole portion 132. Additionally, undercut 102 reduces
peak stress values within the strikeface 106 by 2000 psi to 3500
psi. For example, the undercut can reduce peak stress values in the
strikeface between 2000 psi to 2100 psi, 2100 psi to 2200 psi, 2200
psi to 2300 psi, 2300 psi to 2400 psi, 2400 psi to 2500 psi, 2500
psi to 2600 psi, 2600 psi to 2700 psi, 2700 psi to 2800 psi, 2800
psi to 2900 psi, 2900 psi to 3000 psi, 3100 psi to 3200 psi, 3200
psi to 3300 psi, 3300 psi to 3400 psi, or 3400 psi to 3500 psi.
[0044] Alone, the above decrease in stress, within the sole 110 and
strikeface 106, can translate to an improved wear life of golf club
head 100. In other words, golf club head 100 comprising ballast 114
with undercut 102 can be hit more times and played longer than a
traditional golf club head without an undercut. For example, a
hollow body golf club comprising an undercut 102 can have a failure
count increase of 50 hits, 100 hits, 150 hits, 200 hits, 250 hits,
or 300 hits. Fatigue failure in a cyclically loaded golf club
occurs over time in locations of peak stress where small cracks
form in the material. Cracks, in turn, amplify stress. Therefore,
golf club head 100, with reduced peak stresses, experiences the
crack growth and eventual fatigue failure at a slower rate.
[0045] Alternatively, the stress reduction achieved by the above
ballast 114 and undercut 102 can be leveraged to improve club
performance and ball speed. In some embodiments, the ballast 114
with undercut 102 can be provided in conjunction with a thinned
strikeface 106. The extent to which the strikeface of a golf club
head without the undercut 102 has been constrained by peak stress
levels at the face-to-sole transition. Said another way, it is not
possible to improve the performance of traditional golf clubs with
a thinner face because the added stress from the thinner face
results in peak stresses that exceed the critical K value. Golf
club head 100, as discussed above, comprises ballast 114 with
undercut 102 for stress reduction. Therefore, in some embodiments,
strikeface 106 can be thinned without raising peak stress values
beyond the critical K value at the sole-to-face transition.
[0046] The thinness reductions can be applied throughout the face.
For example, in the geometric center of the face of the undercut
club, the thickness at this region of the face can range between
0.080 to 0.150 inches. The thickness of the face at the geometric
center of said face can be 0.150 inches, 0.140 inches, 0.130
inches, 0.120 inches, 0.110 inches, 0.100 inches, 0.090 inches, or
0.080 inches. In the perimeter toe region of the face of the
undercut iron club, the thickness of the face can range from 0.050
to 0.090 inches. The thickness of the face at the perimeter toe
region can be 0.050 inches, 0.060 inches, 0.065 inches, 0.070
inches, 0.071 inches, 0.074 inches, 0.076 inches, 0.077 inches,
0.079 inches, 0.080 inches, 0.082 inches, 0.084 inches, 0.086
inches, 0,088 inches, or 0.090 inches. The thickness of the face at
the heel perimeter end of the undercut iron club can range from
0.045 inches to 0.090 inches. The thickness of the face at the heel
perimeter end can be 0.045 inches, 0.050 inches, 0.055 inches,
0.060 inches, 0.065 inches, 0.070 inches, 0.075 inches, 0.080
inches, 0.085 inches, or 0.090 inches.
[0047] In some examples, the ballast 114 with undercut 102 reduces
face thickness by 0.003 inches. In other examples the undercut 102
can allow the strikeface 106 to be thinned by 0.004 inches, 0.005
inches, 0.006 inches, 0.007 inches, 0.007 inches, 0.008 inches,
0.009 inches, or 0.010 inches. In an already thin strikeface 106,
this reduction equates to a thinning of roughly 6%, or an increase
in ball speed of 0.5 mph to 0.7 mph. In some examples, the undercut
102 allows the strikeface to be 3 to 8% thinner than the strikeface
of a golf club head without an undercut. For example, the
strikeface 106 can be 3% thinner, 4% thinner, 5% thinner, 6%
thinner, 7% thinner, or 8% thinner.
[0048] As discussed above, the undercut region 128 has a volume
representative of mass removed from ballast 114. Ballast 114
functions as a mass pad for controlling the center of gravity (CG)
for golf club head 100, such that the undercut 102 can alter club
head CG. The CG can be defined relative to a geometric center 126
of the strikeface 106. The geometric center 126 of the strikeface
106 can be determined in accordance with Section 6.1 of the USGA's
Procedure for Measuring the Flexibility of a Golf Clubhead
(USGA-TPX3004, Rev. 1.0.0, May 1, 2008) (available at
http://www.usga.org/equipment/testing/protocol
s/Procedure-For-Measuring-The-Flexibility-Of-A-Golf-Club-Head/)
(the "Flexibility Procedure"). A CG height can be defined as a
vertical distance between the CG and the ground plane. A front-rear
CG depth 144 can be defined as a horizontal distance between the
geometric center 126 the CG. For example, the front-rear CG depth
144 can range from 0.080 to 0.110 inches. The front-rear CG depth
can be 0.080 inches, 0.082 inches, 0.084 inches, 0.086 inches,
0.088 inches, 0.090 inches, 0.092 inches, 0.094 inches, 0.096
inches, 0.098 inches, 0.100 inches, 0.105 inches, or 0.110
inches.
[0049] A ratio of undercut face depth 131 to the front-rear CG
position is constrained between 3.0 and 5.5. For example, the face
depth ratio 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0,
4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0. In this range,
the undercut 102 improves peak stress within the forward sole
portion 132 without removing material from the ballast to the
extent that CG position is compromised.
[0050] Furthermore, because of the CG position, the undercut does
not affect the overall MOI of the club. For the purpose of
determining club head moments of inertia, a coordinate system may
be defined at the CG via mutually orthogonal axes (i.e., an x-axis,
a y-axis, and a z-axis) (Figure not shown). The y-axis extends
through the head CG from the top rail 112 to the sole 110,
perpendicular to a ground plane when the golf club head 100 is at
an address position. The x-axis extends through the head CG from
the heel portion 103 to the toe portion 105 and perpendicular to
the y-axis. The z-axis extends through the head CG from the
strikeface 106 to the rear portion 108, and perpendicular to the
x-axis and the y-axis.
[0051] Moments of inertia then exist about the x-axis Ixx (i e top
rail-to-sole moment of inertia), about the y-axis Iyy (i.e.
heel-to-toe moment of inertia) and about the z-axis (i.e.
strikeface to rear). In many embodiments, the golf club head with
undercut comprises a top rail-to-sole moment of inertia, Ixx, from
95 gin.sup.2 to 130 gin.sup.2. In many embodiments, the golf club
head with undercut comprises a top rail-to-sole moment of inertia
Ixx greater than approximately 95 gin.sup.2, greater than
approximately 98 gin.sup.2, greater than approximately 100 gin,
greater than approximately 102 gin.sup.2, greater than
approximately 103 gin.sup.2, greater than approximately 104
gin.sup.2, greater than approximately 105 gin.sup.2, greater than
approximately 106 gin.sup.2, greater than approximately 110
gin.sup.2, greater than approximately 115 gin.sup.2, greater than
approximately 120 gin.sup.2, greater than approximately 125
gin.sup.2, greater than approximately 130 gin.sup.2, greater than
approximately 135 gin.sup.2, greater than approximately 140
gin.sup.2, greater than approximately 6750 gin.sup.2, or greater
than approximately 145 gin.sup.2. Further, in many embodiments, the
golf club head with undercut comprises a heel-to-toe moment of
inertia Iyy, which may be greater than approximately 350 gin.sup.2,
greater than approximately 360 gin.sup.2, greater than
approximately 370 gin.sup.2, greater than approximately 380
gin.sup.2, greater than approximately 390 gin.sup.2, greater than
approximately 400 gin.sup.2, greater than approximately 410
gin.sup.2, greater than approximately 420 gin.sup.2, or greater
than approximately 430 gin.sup.2. In many embodiments, the golf
club head with undercut comprises a heel-to-toe moment of inertia
Iyy from 350 gin.sup.2 to 420 gin.sup.2. Further, the golf club
head with undercut comprises a strikeface to rear moment of inertia
Izz, which may be greater than approximately 400 gin.sup.2, greater
than approximately 4100 gin.sup.2, greater than approximately 420
gin.sup.2, greater than approximately 430 gin.sup.2, greater than
approximately 440 gin.sup.2, greater than approximately 450
gin.sup.2, greater than approximately 460 gin.sup.2, greater than
approximately 470 gin.sup.2, or greater than approximately 480
gin.sup.2. In many embodiments, the golf club head with undercut
comprises a strikeface to rear moment of inertia Izz from 400
gin.sup.2 to 450 gin.sup.2. The undercut of the golf club head does
not significantly alter the moment of inertia of the Ixx, Iyy, and
Izz axes over a golf club head without the undercut.
[0052] b. Undercut formed by Angled Forward Surface of Ballast
[0053] FIG. 4A illustrates a heel cut away view of an iron-type
golf club head 300 comprising an alternative ballast 314 design
forming an undercut 302. The golf club head 300 is substantially
similar to golf club head 100, but for the difference in the
geometry of the ballast 314 and the undercut 302. The ballast 314
is a solid structure located within the internal cavity 304
protruding vertically from the sole 310, forward from the rear
portion 308, and extending along the sole 310 in a heel to toe
direction. A forward portion 332 of the sole 310 is defined between
the strikeface 306 and the ballast 314. The ballast 314 extends
forward from the rear portion 308 towards the strikeface 306 and
positions mass low and forward in the internal cavity 304.
[0054] As illustrated in FIG. 4A, the ballast 314 comprises a top
surface 316, a forward surface 318, and a ballast juncture 317
forming a transition between the top surface 316 and the forward
surface 318. The ballast 314 does not form a bottom surface. The
ballast forward surface 318 transitions directly into the sole 310.
As illustrated in FIG. 4B, an undercut juncture 330 is formed at
the transition between the forward surface 318 and the sole
310.
[0055] Referring to FIGS. 4A and 4B, the ballast forward surface
318 is angled with respect to the forward portion 332 of the sole
310. The ballast 314 forms an acute angle 399 between the ballast
forward surface 318 and the interior surface 322 of the sole 310.
The ballast angle 399 creates a configuration in which the ballast
juncture 317 is located forward of the undercut juncture 330 and at
least a portion of the ballast 314 extends forward relative to the
undercut juncture 330 to overhang the forward sole portion 332.
Specifically, the ballast forward surface 318 overhangs at least a
portion of the forward sole portion 332. The angled configuration
of the ballast 314 distributes mass low in the golf club head 300
without compromising the length of the forward sole portion 332. In
this way, the club head CG height can be lowered without a
reduction in spring energy stored within the forward sole portion
332.
[0056] In many embodiments, the ballast angle 399 between the
ballast forward surface 318 and interior surface 322 of the sole
310 can be between approximately 30 degrees and approximately 80
degrees. In some embodiments, the ballast angle 399 can be between
30 and 50 degrees, 35 and 55 degrees, 40 and 60 degrees, 45 and 65
degrees, 50 and 70 degrees, 55 and 75 degrees, or 60 and 80
degrees. In some embodiments, the ballast angle 399 can be less
than 80 degrees, less than 75 degrees, less than 70 degrees, less
than 65 degrees, less than 60 degrees, less than 55 degrees, less
than 50 degrees, less than 45 degrees, less than 40 degrees, less
than 35 degrees, or less than 30 degrees.
[0057] The ballast angle 399 can be selected to allow ballast 314
to project substantially forward toward the strikeface 306. The
smaller the ballast angle 314, the greater the ability of the
ballast 314 to position mass low and forward, which provides a more
desirable CG location.
[0058] Referring to FIG. 4B, the angled ballast 314 defines an
undercut 302 extending beneath the ballast 314. The undercut 302 is
formed between the ballast forward surface 318 and the interior
surface 322 of the sole 310. The undercut 302 can be defined as the
volume of the internal cavity 304 that is both beneath the ballast
forward surface 318 and above the forward portion 332 of the sole
310. In the illustrated embodiment, the ballast forward surface 318
forms a top edge 337 of the undercut 302, and the sole interior
surface 322 forms a bottom edge 339 of the undercut 302. The
undercut 302 can further be defined as the volume bounded between
the undercut top edge 337 and the undercut bottom edge 339 over a
heel to toe length 324 of the ballast 314. In the illustrated
embodiment, referring to FIG. 4B, an opening between the undercut
302 and the remainder of the internal cavity 304 is formed along a
ballast forward plane 350, wherein the ballast forward plane 350 is
tangent to the ballast juncture 317 and extends parallel to the
strikeface 306. The ballast forward plane 350 defines a forwardmost
boundary of the undercut 302, and the undercut juncture 330 forms a
rearmost point of the undercut 302.
[0059] Similar to undercut 102, the undercut 302 formed by the
angled ballast 314 effectively lengthens the forward portion 332 of
the sole 310. The undercut 302 not only reduces stress in the
forward sole portion 332, but also creates a larger spring by
lengthening the amount of thin sole 310 material that is configured
to flex. This larger spring increases the amount of energy
transferred back to the ball at impact.
[0060] Referring to FIG. 4B, the undercut 302 comprises an undercut
depth 334, an undercut height 336, and an undercut length (not
shown). The undercut depth is measured as a perpendicular distance
between a ballast forward plane 350 and the undercut juncture 330
(i.e., the rear most point of the undercut). The undercut height
336 is defined as the vertical distance between an undercut top
edge 337 and an undercut bottom edge 339. The undercut length (not
shown) is measured parallel to a ground plane between the undercut
toe end 133 and the undercut heel end 135. Finally, the undercut
sole thickness is measured as the perpendicular distance from the
exterior surface of the sole 321 and the sole interior surface
332.
[0061] In many embodiments, the undercut depth 334 between the
ballast forward plane 350 and the undercut juncture 330, can range
between 0.010 inch and 0.300 inch. In some embodiments, the
undercut depth 134 can range from 0.010 inch to 0.030 inch, 0.030
inch to 0.050 inch, 0.050 inch to 0.070 inch, 0.070 inch to 0.090
inch, 0.090 inch to 0.110 inch, 0.110 inch to 0.130 inch, 0.130
inch to 0.150 inch, 0.150 inch to 0.170 inch, 0.170 inch to 0.190
inch, 0.190 inch to 0.210 inch, 0.210 inch to 0.230 inch, 0.230
inch to 0.250 inch, 0.250 inch to 0.270 inch, 0.270 inch to 0.290
inch, or 0.290 inch to 0.300 inch. In some embodiments, the
undercut depth 134 can be greater than approximately 0.010 inch,
greater than approximately 0.015 inch, greater than approximately
0.020 inch, greater than approximately 0.025 inch greater than
approximately 0.05 inch, greater than approximately 0.075 inch,
greater than approximately 0.100 inch, greater than approximately
0.125 inch, greater than approximately 0.150 inch, greater than
approximately 0.175 inch, greater than approximately 0.200 inch,
greater than approximately 0.225 inch, greater than approximately
0.250 inch, greater than approximately 0.275 inch, or greater than
approximately 0.300 inch.
[0062] In many embodiments, the undercut height 336, measured
between the undercut bottom edge 339 and undercut top edge 337, can
range from approximately 0.030 inch to approximately 0.500 inch. In
some embodiments, the undercut height 336 can range from 0.030 inch
to 0.050 inch, 0.050 inch to 0.070 inch, 0.070 inch to 0.090 inch,
0.090 inch to 0.110 inch, 0.110 to 0.130 inch, 0.130 inch to 0.150
inch, 0.150 inch to 0.170 inch, 0.170 inch to 0.190 inch, 0.190
inch to 0.210 inch, 0.210 to 0.230 inch, 0.230 inch to 0.250 inch,
0.250 inch to 0.270 inch, 0.270 inch to 0.290 inch, 0.290 inch to
0.310 inch, 0.310 to 0.330 inch, 0.330 inch to 0.350 inch, 0.350
inch to 0.370 inch, 0.370 inch to 0.390 inch, 0.390 inch to 0.410
inch, 0.410 inch to 0.430 inch, 0.430 inch to 0.450 inch, 0.450
inch to 0.470 inch, or between 0.470 inch and 0.500 inch. In some
embodiments, the undercut height 336 can be greater than
approximately 0.010 inch, greater than approximately 0.015 inch,
greater than approximately 0.020 inch, greater than approximately
0.025 inch, greater than approximately 0.05 inch, greater than
approximately 0.075 inch, greater than approximately 0.100 inch,
greater than approximately 0.125 inch, greater than approximately
0.150 inch, greater than approximately 0.175 inch, greater than
approximately 0.200 inch, greater than approximately 0.225 inch,
greater than approximately 0.250 inch, greater than approximately
0.275 inch, greater than approximately 0.300 inch, greater than
approximately 0.325 inch, greater than approximately 0.350 inch,
greater than approximately 0.375 inch, greater than approximately
0.400 inch, greater than approximately 0.425 inch, greater than
approximately 0.450 inch, greater than approximately 0.475 inch, or
greater than approximately 0.500 inch.
[0063] Due to the angled nature of the ballast 314, the undercut
height 336 can vary in a front to rear direction. The ballast
juncture 317, which forms the forwardmost extent of the undercut
top edge 337, is also the highest point of the undercut top edge
337. Accordingly, in many embodiments, the undercut height 336
decreases in a front to rear direction, with the undercut height
336 being greatest at the ballast forward plane 350 and smallest at
the undercut juncture 330.
[0064] In many embodiments, the undercut 302 comprises an undercut
length (not shown) similar to the length 138 of undercut 102. The
undercut length is measured between the undercut heel end 335 and
the undercut toe end 337. In many embodiments, the length of
undercut 302 can range from 0.5 inch to 3.0 inches. In some
embodiments, the length of undercut 302 can range from 0.50 inch to
0.75 inch, 0.75 inch to 1.00 inch, 1.00 inch to 1.25 inches, 1.25
inches to 1.50 inches, 1.50 inches to 1.75 inches, 1.75 inches to
2.00 inches, 2.00 inches to 2.25 inches, 2.25 inches to 2.50
inches, 2.50 inches to 2.75 inches, or 2.75 inches to 3.00 inches.
In some embodiments, the length of undercut 302 can be greater than
0.5 inch, greater than 0.75 inch, greater than 1.0 inch, greater
than 1.25 inches, greater than 1.50 inches, greater than 1.75
inches, greater than 2.0 inches, greater than 2.25 inches, greater
than 2.50 inches, greater than 2.75 inches, or greater than 3.0
inches.
[0065] In some embodiments, referring to FIG. 5, the ballast
forward surface 318 can define a curvature in a heel to toe
direction. In many embodiments, such as the embodiment illustrated
in FIG. 5, the ballast forward surface 318 comprises a concave
curvature relative to the strikeface 306. In such embodiments, the
ballast forward surface 318 is closer to the strikeface 306 near
the heel portion 303 and the toe portion 305 than near the center
of the golf club head 300. The concave configuration of the ballast
forward surface 318 effectively lengthens the forward sole portion
332 near the center of the golf club head in comparison to forward
sole portion 332 near the heel portion 303 and the toe portion 305.
Because iron-type golf club heads typically experience peak
stresses in the center of the club head and lower stresses near the
heel and toe, the forward sole portion 332 can be shortened near
the heel portion 303 and the toe portion 305 without sacrificing
durability.
[0066] The concave configuration of the ballast forward surface 318
allows portions of the ballast 314 near the heel portion 303 and
the toe portion 305 to extend further towards the strikeface 306.
This configuration allows the overall mass of the ballast 314 to be
placed lower and further forward in the internal cavity 304.
Providing the ballast forward surface 318 with a concave curvature
in a heel to toe direction allows the CG of the golf club head 300
to be controlled without sacrificing the durability of the forward
sole portion 332. In many embodiments, the curvature of the ballast
forward surface 318 can be configured to complement the geometry of
a cascading sole region (discussed in further detail below) or any
other stress relieving feature included in the forward sole portion
332.
[0067] II. Undercut and Cascading Sole
[0068] FIG. 6A illustrates another embodiment of a golf club head
200 comprising a ballast 214, undercut 202, and a cascading forward
portion 232 of the sole 210. FIG. 6A depicts a cross-sectional view
of golf club head 200. Golf club head 200 is substantially similar
to golf club head 100 and comprises a thin forward portion 232 of
sole 210 that has been effectively lengthened via the undercut 202.
Golf club head 200 is further defined by a strikeface 206, a rear
portion 208 opposite the strikeface 206, a heel portion 203, a toe
portion 205 opposite the heel portion 203, a sole 210, and a top
rail 212 opposite the sole 210. Together, these components define a
hollow body club with an interior cavity 204. The rear portion 208
further comprises a ballast 214 located within the internal cavity
204. As shown in FIG. 6A, the ballast 214 comprises the top surface
216, the forward surface 218, and the bottom surface 220. Ballast
bottom surface 220 is similar to ballast bottom surface 120. The
contoured bottom surface 220 is indented toward the rear portion
208 to create undercut 202.
[0069] FIG. 6B provides a zoomed in view of the ballast 214 and
sole 210 illustrated in FIG. 6A. As shown, the forward portion 232
of the sole 210 extends from the undercut 202 in ballast 214 to the
strikeface 206. The forward portion 232 of the sole further
comprises an inner region 260 and a cascading region 262. The
cascading region 262 can comprise an internal radius transition 264
between an internal surface of the strikeface 206 and an internal
surface of the sole 210. The cascading region 262 can comprise at
least two thickness tiers, or levels. The tiered structure creates
successive thinning of the forward sole portion 132. In some
embodiments, the cascading region 262 can comprise an internal
radius transition 264 having 2, 3, 4, 5, 6, or 7 tiers.
[0070] Continuing to refer to FIG. 6B, the cascading region 262
comprises a first tier 266, second tier 268, and a tier transition
270 between the first tier 266 and second tier 268. The cascading
region 262 of the forward sole portion 232 can have a thickness
measured as the perpendicular distance between the exterior surface
221 of the sole and interior surface 222 of the sole. This
thickness can decrease in a front to rear direction over the
cascading region 262. The first tier 266 can have a first thickness
272 defined as the perpendicular distance between the exterior
surface 221 and interior surface 222 of the sole within the first
tier 266. The second tier 268 can have a second thickness 274
defined within the second tier 268 as the perpendicular distance
between the exterior surface 221 and interior surface 222 of the
sole. In some embodiments, the first thickness 272 is greater than
the second thickness 274, such that the overall thickness of the
cascading region 262 decreases in the front to rear direction. The
first thickness 272 and/or the second thickness 274 can have a
constant thickness over a tier length in the front to rear
direction. In other embodiments, the first thickness 272 and/or the
second thickness 274 can be sloped to decrease in thickness over
the tier length in the front to rear direction.
[0071] The cascading region can comprise a first tier 266, second
tier 268, a third tier (not shown), and a first tier transition 270
between the first tier 266 and second tier 268, and a second tier
transition between the second tier and the third tier. As described
above, the cascading region of the forward sole region with three
tiers can have a thickness measured as the perpendicular distance
between the exterior surface of the sole and interior surface of
the sole. Again, the thickness decreases in a front to rear
direction over the cascading region. As described above, the first
tier can have a first thickness. The second tier can have a second
thickness. The third tier can have a third thickness, wherein the
third tier thickness (like the first and second tier thicknesses)
is measured as the perpendicular distance between the exterior
surface and interior surface of the sole. In some embodiments, the
first thickness is greater than the second thickness, and in turn,
the second thickness is greater than the third thickness, such that
the overall thickness of the cascading region 262 decreases in the
front to rear direction. The first thickness and/or the second
thickness and/or third thickness can have a constant thickness over
a tier length in the front to rear direction. In other embodiments,
the first thickness and/or the second thickness and/or third
thickness can be sloped to decrease in thickness over the tier
length in the front to rear direction.
[0072] The tier transition 270, between a rear edge of the first
tier and a forward edge of the second tier, can be declined in a
front to rear direction to steadily decrease the cascading region
thickness between the first thickness 272 and second thickness 274.
Alternatively, in a cascading region with two tier transitions
(i.e., a first transition between the first tier and second tier,
and a second transition between the second tier and third tier),
the transitions can be declined in a front to rear direct to
steadily decrease the cascading region thickness between the first
thickness, second thickness and third thickness (or first tier,
second tier and third tier). In some embodiments, such as FIG. 6B,
the tier transition 270 is linearly declined at an angle less than
45 degrees between adjacent first 266 and second tiers 268. In some
embodiments, the tier transition 270 is linearly declined at an
angle ranging between 10 degrees and less than 45 degrees. The
linear decline can be gradual between 5 degrees and 10 degrees, 10
degrees and 15 degrees, 15 degrees and 20 degrees, 20 degrees and
25 degrees, 25 degrees and 30 degrees, 30 degrees and 40 degrees,
or 40 degrees and 45 degrees. In other embodiments, not shown, the
tier transition 270 can be a steeper, and more like a step. For
example, tier transition 270 can be between 45 and 50 degrees, 50
degrees and 55 degrees, 55 degrees and 60 degrees, 60 degrees and
65 degrees, or 65 degrees and 70 degrees.
[0073] As mentioned above, the forward sole portion 232 further
comprises inner region 260 between the cascading region 262 and
ballast undercut 202. The uniform inner region 260 also comprises
an inner thickness 276 defined as the perpendicular distance
between the exterior surface 221 of the sole 210 and the inner
surface 222 of the sole 210. The inner thickness 276 is less than
the thickness of an adjacent tier, or final tier within the
cascading region 262. As shown in FIG. 6B, the inner thickness 276
is less than the second thickness 274.
[0074] In many embodiments, the cascading region 262 comprising at
least a first tier 266 and second tier 268, and alternatively a
third tier (not numbered) can comprise a specific profile
configured to efficiently relieve stress within the forward sole
portion 232. FIG. 7 illustrates one embodiment of a profile of the
cascading region 262. The cascading region 262 can comprise a
perimeter separating the cascading region 262 from the inner region
260 (which forms the remainder of the forward sole region 232).
[0075] In the illustrated embodiment of FIG. 7, the perimeter of
the cascading region 262 comprises a cascade front edge 279, a
cascade rear edge 281, a cascade toe edge 280, and a cascade heel
edge 282. The cascade front edge 279 extends in a heel to toe
direction and is located proximate a leading edge 215 of the
strikeface 206. The cascade rear edge 281 extends in a heel to toe
direction and is spaced rearwardly from the cascade front edge 279.
The cascade toe edge 280 extends between the cascade front edge 279
and the cascade rear edge 281 near the toe portion 205. The cascade
heel edge 282 extends between the cascade front edge 279 and the
cascade rear edge 281 near the heel portion 203.
[0076] In many embodiments, as illustrated in FIG. 7, the cascade
rear edge 281 can be arcuate, such that the cascade rear edge 281
comprises a curvature as it extends in the heel to toe direction.
In the illustrated embodiment of FIG. 7, the cascade rear edge 281
bows rearward relative to the strikeface 206. As such, the cascade
rear edge 281 is spaced further from the strikeface 206 near the
center of the golf club head 200 than near the heel portion 203 and
the toe portion 205. In many embodiments, the cascade front edge
279 is generally parallel to the strikeface 206. In such
embodiments, the arcuate cascade rear edge 281 is therefore also
bowed rearward relative to the cascade front edge 279.
[0077] In some embodiments, as illustrated in FIG. 7, one or more
of the plurality of tiers 266, 268, 269 can substantially match the
curvature of the arcuate rear edge 281. One or more of the
plurality of tiers can be bowed rearward relative to the cascade
front edge 279 and/or the strikeface 206. In some embodiments
wherein the ballast forward surface 218 comprises a curvature in a
heel to toe direction, the curvature of the arcuate cascade rear
edge 281 may substantially match the curvature of the ballast
forward surface 218. The cascading region 262 can comprise a
cascading region depth 290 and a cascading region width 292.
Referring to FIG. 7, the cascading region depth 290 is the distance
between the cascade front edge 279 and the cascade rear edge 281,
measured perpendicular to the strikeface 206. In many embodiments,
the cascading region depth 290 can range between 0.050 inch and
0.250 inch. In some embodiments, the cascading region depth 290 can
be between 0.050 inch and 0.075 inch, between 0.075 inch and 0.100
inch, between 0.100 inch and 0.125 inch, between 0.125 inch and
0.150 inch, between 0.150 inch and 0.175 inch, between 0.200 inch
and 0.225 inch, or between 0.225 inch and 0.250 inch. In some
embodiments, the cascading region depth 290 can be greater than
0.050 inch, greater than 0.075 inch, greater than 0.100 inch,
greater than 0.125 inch, greater than 0.150 inch, greater than
0.175 inch, greater than 0.200 inch, greater than 0.225 inch, or
greater than 0.250 inch. In some embodiments, the cascading region
depth can be approximately 0.125 inch, 0.130 inch, 0.135 inch,
0.140 inch, 0.145 inch, 0.150 inch, 0.155 inch, 0.160 inch, 0.165
inch, 0.170 inch, or 0.175 inch. In some embodiments, the cascading
region depth 290 can be substantially constant in a heel to toe
direction. In many other embodiments, such as described below, the
cascading region depth 290 can vary in a heel to toe direction.
[0078] In the illustrated embodiment of FIG. 7, wherein the
cascading region 262 comprises a rearward bowing cascade rear edge
281, the cascading region depth 290 is greatest proximate the
center of the forward sole portion 232 and lesser near the cascade
heel edge 282 and cascade toe edge 280. In many embodiments,
cascading region depth 290 at the cascade heel edge 282 and/or the
toe edge 280 can be between 50% and 95% than the maximum cascading
region depth 290. In some embodiments, the cascading region depth
290 at the cascade heel edge 282 and/or the cascade toe edge 280
can be between 50% and 60%, between 60% and 70%, between 70% and
80%, between 80% and 90%, or between 90% and 95% the maximum
cascading region depth 290. In some embodiments, the cascading
region depth 290 can be less than 95%, less than 90%, less than
85%, less than 80%, less than 75%, less than 70%, less than 65%,
less than 60%, less than 55%, or less than 50% of the maximum
cascading region depth 290. In many embodiments, such as the
illustrated embodiment of FIG. 7, the maximum cascading region
depth 290 is located at or near the center of the forward sole
portion 232.
[0079] The increased cascading region depth 290 near the center of
the forward sole portion 232 allows the cascading region 262 to
relieve peak stresses that commonly occur near the center of golf
club head 200. Similarly, in embodiments with arcuate tiers (such
as the illustrated embodiment of FIG. 7), each tier bows rearward
near the center of the golf club head 200, contributing to the
relief of peak stresses occurring near center. Because the stress
experienced in the forward sole portion 232 is not as severe near
the heel portion 203 and the toe portion 205, the cascading region
262 can comprise a lesser depth 290 near the cascade heel edge 282
and the cascade toe edge 280 and still be able to relieve such
stresses. Shortening the cascading region depth 290 near the
cascade heel edge 282 and the cascade toe edge 280 allows the
uniform inner region 260 to be effectively lengthened near the heel
portion 203 and the toe portion 205. Effectively lengthening the
uniform inner region 260, which has a lesser thickness than any
tier within the cascading region 262, increases the bending/spring
effect of the forward sole portion 232.
[0080] Referring to FIG. 7, the cascading region width 292 is the
distance between the cascade heel edge 282 and the cascade toe edge
280, measured in a heel to toe direction (i.e. parallel to the
strikeface 206). In many embodiments, the cascading region width
292 can range between 0.50 inch and 2.5 inches. In some
embodiments, the cascading region width 292 can be between 0.50
inch and 0.75 inch, between 0.75 inch and 1.00 inch, between 1.00
inch and 1.25 inch, between 1.25 inch and 1.50 inch, between 1.50
inch and 1.75 inch, between 2.00 inch and 2.25 inch, or between
2.25 inch and 2.50 inch. In some embodiments, the cascading region
width 292 can be greater than 0.50 inch, greater than 0.75 inch,
greater than 1.00 inch, greater than 1.25 inch, greater than 1.50
inch, greater than 1.75 inch, greater than 2.00 inch, greater than
2.25 inch, or greater than 2.50 inch. In some embodiments, the
cascading region width 292 can be less than 2.50 inches, less than
2.25 inches, less than 2.00 inches, less than 1.75 inches, less
than 1.50 inches, less than 1.25 inches, or less than 1.00 inches.
In some embodiments, the cascading region width 292 can be
approximately 1.25 inches, 1.30 inches, 1.35 inches, 1.40 inches,
1.45 inches, 1.50 inches, 1.55 inches, 1.60 inches, 1.65 inches,
1.70 inches, or 1.75 inches. In some embodiments, the cascading
region width 292 can be substantially constant in a front to rear
direction. In many other embodiments, such as described below, the
cascading region width 292 can vary in a front to rear
direction.
[0081] In some embodiments, the cascade heel edge 282 and the
cascade toe edge 280 can extend substantially perpendicular to the
strikeface 206, such that the cascading region width 292 is
constant. In many embodiments, such as the embodiment illustrated
in FIG. 7, cascade heel edge 282 and the cascade toe edge 280 are
shaped to converge inwards such that the width 292 of the cascading
region 262 is tapered in a front to rear direction. In such
embodiments, the cascading region width 292 is greatest proximate
the cascade front edge 279 and lesser near the cascade rear edge
291.
[0082] Similar to the variable cascading region depth 290, the
tapering of the cascading region width 292 allows the uniform inner
region 260 to be effectively lengthened near the heel portion 203
and the toe portion 205. The increased cascading region width 292
near the cascade front edge 279 allows the cascading region 262 to
relieve peak stresses that commonly occur at the forwardmost
portions of the forward sole portion 232. Because the stress
experienced in the forward sole portion 232 is not as severe
rearward of the strikeface 206, the cascading region 262 can
comprise a lesser width 292 near the cascade rear edge 281 without
sacrificing durability. The tapering of the cascading region width
292 in a front to rear direction effectively lengthens the uniform
inner region 260 and increases the bending/spring effect of the
forward sole portion 232.
[0083] Continuing to refer to FIG. 6B, the inner region 260 of
forward sole portion 232 can be effectively lengthened by ballast
214 comprising undercut 202. Ballast 214 is substantially similar
to the geometry of ballast 114. Ballast bottom surface defines an
undercut region 228 comprising the undercut 202, undercut
transition 241, and undercut juncture 230. As shown in FIG. 6B, the
inner region 260 is positioned adjacent undercut 202. The undercut
region 228 functions in a substantially similar manner as undercut
202 and undercut region 228. Specifically, undercut region 228 also
reduces stress concentrations within forward sole portion 232 and
increases the bending/spring effect of the forward sole portion
232. The cascading region 262 can be combined with any undercut or
ballast geometry described above, including an undercut 102 formed
by the bottom surface 120 of a ballast 114 or an undercut 302
formed by an angled forward surface 318 of a ballast 314.
[0084] In many embodiments, performance improvements from the
cascading region 262 and the undercut 202 are compounding. In other
words, golf club heads having both a cascading region and undercut
202, such as hollow body club head 200, have a greater reduction in
peak stress than golf club heads comprising one of a cascading
region or an undercut. Reduction of peak stress within forward sole
portion 232 increases the region's tolerance to modifications for
improving ball speeds. Specifically, hollow body club 200
comprising forward sole region 232, which is defined by undercut
202 and comprising cascading region, can comprise a thinner face
(as compared to a hollow body club lacking either or both of the
undercut and cascading sole). This results in better ball speeds
and flight distance. In some embodiments, the undercut 202 and
cascading sole 242 allow the forward portion of the sole 232 to be
made more reactive. Rather than remaining rigid, the forward
portion 232 can be thinned, such that the forward portion 232
behaves as a spring under impact loads. This means that the golf
club head 200 is more efficient at transferring swing energy to the
golf ball. The ultimate increase in ball speed via reduction in
average thickness of the forward portion 232 of the sole is the
result of stress reduction at the face-to-sole transition 226. The
undercut and the cascading sole work together to improve the flow
of stress within the forward portion 232, thereby reducing stress
concentration levels at impact.
EXAMPLES
Example 1: Study of Undercut in Hollow Body Iron
[0085] As described in detail above, the ballast and undercut can
be applied to a golf club head alone and in conjunction with other
features, such as a cascading sole, to improve club performance. In
the example below, performance improvements generated by the
undercut 102 were studied by comparing a golf club head without an
undercut (golf club A, hereafter "Club A"), a golf club head with
an undercut (golf club B, hereafter "Club B"), a golf club head
without an undercut and with a cascading sole (golf club C,
hereafter "Club C"), and a golf club head with an undercut and with
a cascading sole (golf club D, hereafter "Club D"). Performance
improvements were measured and analyzed using finite element
analysis (FEA). Specifically, FEA was used to measure peak stress
values within the forward portion. Average peak stress, along with
a measured surface area experiencing peak stress, were used to
determine the potential for each club to efficiently transfer
impact energy back to the ball. Reductions in average peak stress
serve as an indicator for improved durability and potential
performance enhancement via face thinning and sole thinning.
[0086] Each of the example Clubs A, B, C, and D were substantially
similar having the same overall mass, material construction, and
loft angle. Impact loading in each club was simulated at 105 mph.
The example clubs each comprise unique internal cavity
configurations, described above. Average peak stress between the
strikeface and ballast, within the forward portion of the sole, was
calculated for each example. Likewise, an area of average peak
stress was calculated for each example. Finally, average peak
stress within the strikeface was calculated for each example. Table
1 below, shows the peak face stress, peak stress of the forward
sole portion, and the peak stress area within the forward portion
of the sole, for each of the example clubs discussed below. Stress
values were used to determine the undercut's effect on club
performance through face and sole thinning. Example Club A was
compared to Club B. Example Club C was compared to Club D. The
control club head was similar to the example club heads, but devoid
of any stress relieving features.
TABLE-US-00001 TABLE 1 Peak Face Stress Peak Forward Sole Stress
Club A 218469 psi 158169 psi Example 1 217117 psi 156858 psi
Example 2 213311 psi 155419 psi Example 3 209851 psi 154689 psi
Club A
[0087] Club A was representative of a prior art golf club head
lacking all stress relieving features and was similar to FIG. 8. As
the representative of a traditional hollow body golf club head,
Club A comprised a ballast without an undercut and without a
cascading sole. Without an undercut, the forward portion of the
sole and the ballast met at a substantially right angle. Likewise,
without the cascading sole, the strikeface transitioned smoothly to
the forward portion of the sole.
[0088] As shown in Table 1, FEA analysis was used to calculate a
value for peak stress within the strikeface of the Club A. Under a
105 mph impact load, the peak stress of the strikeface was 218469
psi. Under the same impact load, the forward portion of the
strikeface had a peak stress of 157440 psi.
Club B
[0089] Club B was representative of a hollow body golf club head
with an undercut stress relieving feature. Hollow body Club B was
similar to Club A, but Club B included an undercut as stress
relieving feature. Rather than meeting at a right angle, the
undercut allowed the forward portion of the sole to extend beneath
the ballast. The undercut of Example 1 comprised a depth of 0.065
inch, a height of 0.083 inch, an undercut transition height of
0.185 inches, and 1.16 inches.
[0090] The values for peak face stress, peak forward sole stress,
and peak stress area were determined with FEA analysis and
simulated impact with a golf ball at 105 mph. The peak face stress
was 217117 psi and the peak forward sole stress 156257 psi. When
compared to the Club A, the undercut reduced peak stress within the
strikeface by 1352 psi and reduced peak stress within the forward
portion of the sole by 1183 psi. This club showed that the ballast
and undercut allow the both the strikeface and forward portion of
the sole to store more strain energy. This means that Club B showed
improved durability and improved spring response to impact
loading.
[0091] Club C
[0092] The hollow body Club C was representative of a club head
comprising a forward portion of the sole with a cascade, only. Club
C was similar to Club A and B, but comprised a cascading sole as a
singular form of stress relief. The transition from face to sole
comprised first tier, a second tier and a tier transition between
the first tier and the second tier. The first tier had a first tier
thickness and second tier thickness, less than the first tier
thickness. The tier transition was sloped to gradually transition
the first tier thickness to the second tier thickness. The example
did not comprise an undercut and the forward portion of the sole
and ballast met at a substantially right angle.
[0093] Referring again to Table 1, the Example 2 hollow body golf
club head had a peak face stress of 213311 psi, or a 5158 psi
reduction of peak stress within the strikeface. The Example 2 club
had a peak forward sole stress of 154742 psi (pounds per square
inch), or a reduction in peak forward sole stress of 2698 psi This
example showed that cascading sole reduced stress through increased
storage of strain energy for improved durability and spring
response under impact loading.
Club D
[0094] Club D was representative of a club head comprising an
undercut and a cascading sole as two forms of stress relief for the
strikeface and forward sole portion. The ballast comprised an
undercut, which effectively lengthened the forward sole portion
beneath the ballast. The cascading sole comprised a first tier, a
second tier, and a tier transition between the first and second
tiers. The first tier comprised a first tier thickness and the
second tier comprised a second tier thickness, less than the first
tier thickness. The tier transition was sloped to gradually
transition the first tier thickness to the second tier
thickness.
[0095] Club D was also subjected to FEA analysis under simulated
ball impact at 105 mph. The peak face stress was 209851 psi, for a
reduction of peak stress in the strikeface of 8618 psi. In other
words, the Club D had a 4% reduction in peak stress within the
strikeface. The peak stress of the forward sole portion was 154689
psi. The forward sole portion had a peak stress reduction of 3480
psi, or a 2.2% reduction from the Club A. This example showed that
the undercut and cascading sole worked together to reduce peak
stresses. Further, this example indicated that the forward portion
of the sole could tolerate additional loading without reaching
fatigue failure. The example showed that ball speed could be
improved by thinning the face and sole to match the loading
capacity of the forward sole portion.
[0096] The peak stresses of the forward sole portion in each of the
club heads, specifically, indicated the potential for adjusting
sole and face thickness and the resulting changes to ball speed.
The peak stress of the forward sole portion was compared to the
critical K yield stress value of the forward sole portion. Stresses
that indicated that the strikeface and sole must be thickened,
signaled that the internal cavity configuration would have reduced
ball speed. Stresses that indicated that the strikeface and sole
could be thinned, signaled that the internal cavity configuration
would have increased ball speed.
[0097] Club A and Club B were compared to each other relative to a
critical K value of 156 ksi. The peak stress of Club A, without an
undercut, was 158169 psi. This peak stress value suggested that the
sole and face would have needed to be thickened by roughly 2.5% in
order to achieve stress values that did not exceed 156 ksi. The
thickened face and sole indicated that the internal cavity
configuration that would degrade ball speed. Club B, which
comprised an undercut, improved peak stress within the forward sole
portion. Club B had a peak stress of 156868 psi. The lower peak
stress of Club B indicated Club B required the sole and face to be
thickened less than the sole and face of Club A. These results
showed that, after modifications, Club B and the undercut indicated
better ball speed over Club A, without an undercut.
[0098] Similarly, Club C and Club D were compared to each other
relative to the same critical K value of 156 ksi. The peak stress
of Club C, with a cascading sole and without an undercut, was
155416 psi. Club C, with peak stress slightly less than the
critical K stress, indicated that no modifications for improving or
degrading ball speed would have been necessary. The slightly lower
peak stress did indicate that the cascading sole in Club C would
have increased durability. Club D comprised an undercut in addition
to the cascading sole and had a peak stress of 154689 psi. Club D
showed that the undercut provided further reduction to peak stress.
This reduction in stress indicated that Club D had a face and sole
that could tolerate thinning in order to improve ball speed.
[0099] The comparison of Club A and Club B and the comparison of
Club C and Club D showed that the undercut reduced peak stress
within the forward portion of the sole. These results further
showed that the undercut could be applied to hollow body golf club
heads to improve ball speed by leveraging stress reduction to thin
the face and sole.
Example 2: Club Performance with Undercut
[0100] In a second example, player testing of physical clubs was
used to study the performance benefits of the undercut. In this
example, a 7 iron comprising an undercut was compared to a
structurally similar 7 iron, which lacked an undercut. The sole and
face of the 7 iron having the undercut were optimized and reduced
in thickness. Over 700 shots were taken on each golf club to
analyze ball speed, launch angle, and spin rate.
[0101] FIG. 9 compared the average ball speed of the 7 iron having
an undercut and the 7 iron without an undercut. The average ball
speed of the iron with the undercut was 119.7 mph. The average ball
speed of the iron without the undercut was 118.7 mph. FIG. 10
compared the average vertical launch angle of the 7 iron with an
undercut and the 7 iron without the undercut. The data showed that
the 7 iron with the undercut and the 7 iron without the undercut
had substantially similar launch angles. FIG. 11 compared the
average spin rate of the same 7 iron with an undercut and 7 iron
without an undercut. The 7 iron without an undercut had an average
spin rate of 6079.9 rpm. The 7 iron without an undercut had a
reduction in average spin with 5990.6 rpm.
[0102] Finally, the stat area (data not shown) of the 7 iron with
the undercut was compared to the 7 iron without the undercut. The
stat area data was used to determine the consistency of each of the
golf club heads by plotting shot distance according to the
left-right deviation from a straight shot. The 7 iron without the
undercut had a distance deviation of 20 m, while the 7 iron with
the undercut had a distance deviation of 14 m. The data showed that
the undercut 7 iron produced shots that with more consistent
distance.
[0103] The player results of Example 2 highlighted the performance
benefits of the undercut. Specifically, the data showed that the
undercut reduced spin on low lofted golf club heads, such as a 7
iron, and improved ball speed for improved distance. Reduced spin
on low lofted golf clubs was preferred due to the distance
requirements and expectations of longer, low lofted golf clubs. The
Example also highlighted a tighter stat area for irons with an
undercut and showed that the undercut irons performed more
consistently for distance.
Example 3: Club Performance with Undercut and Cascading Sole
Region
[0104] In a third example, automated testing of physical clubs
using a golf swing apparatus was used to study the increased
performance of an exemplary club head comprising an undercut in
conjunction with a cascading region within the forward sole
portion. The ball speed the exemplary club head was compared to the
ball speed of a structurally similar control club head, which
lacked an undercut. The exemplary club head was similar to club
head 300 described above and comprised an undercut formed by the
angled forward surface of a ballast. The exemplary club head
further comprised a cascading region with a profile similar to
cascading region 262, wherein the cascading region depth was
greater near the center of the club head than near the heel and
toe. The control club head was devoid of an undercut and comprised
a ballast that met the sole at a substantially right angle. The
control club head further comprised a cascading region with a
rectangular profile, wherein the cascading region depth was
constant in a heel to toe direction.
[0105] The inclusion of the angled ballast in the exemplary club
head led to a reduction in CG height (measured vertically from the
ground plane). The exemplary club head comprised a CG height of
0.580 inch and the control club head comprised a CG height of 0.654
inch. The control club head exhibited a reduction in CG height of
0.074 inch.
[0106] Table 2 below compares the average ball speed of exemplary
club head in comparison to the average ball speed of the control
club head. The ball speed of each club was measured both on center
hits and low-center hits (i.e. strikes occurring 0.25 inches below
center).
TABLE-US-00002 TABLE 2 Ball Speed (mph) Club Head Control Exemplary
Increase Center Hit 139.1 140.1 1.0 Low Center 134.3 137.8 3.5
[0107] Referring to Table 2, the exemplary club head exhibited
significant ball speed gains over the control club head for both
center hits and low-center hits. In particular, the exemplary club
head exhibited a 1.0 mph increase over the control club head on
center hits and a 3.5 mph increase over the control club head on
low-center hits. The angled ballast, undercut, and variable depth
cascading region resulted in significant improvements in ball
speed, particularly on low-center shots, which is a common mis-hit
for an iron-type club head.
[0108] In general, lowering the CG in an iron-type club head
results in an increase in ball speed. The lowering of the CG height
in the exemplary club head achieved by the inclusion of the angled
ballast provided a significant contribution to the increase in ball
speed of the exemplary club over the control club.
[0109] The variable depth cascading region of the exemplary club
head further contributed to the increase in ball speed over the
control club head comprising a rectangular cascading region. The
variable depth cascading region effectively lengthened the uniform
inner region of the exemplary forward sole portion near the heel
and toe. Therefore, the proportion of the forward sole portion made
up by the uniform inner region was greater in the exemplary club
head, and the proportion of the forward sole portion made up by the
cascading region was greater in the control club. Because the
uniform inner region comprises a lesser thickness than the
cascading region, the forward sole portion of the exemplary club
head was able to store more spring energy. The increase in spring
energy of the exemplary forward sole portion is especially
significant in the drastic increase in ball speed measured on
low-center hits.
[0110] The undercut of the exemplary club head allows for a further
potential increase in ball speed by effectively lengthening the
forward sole portion. Effectively lengthening the forward sole
portion reduces peak stress within the forward sole portion.
Although the sole and strikeface thicknesses of the exemplary club
head and the control club head were the same, the extra stress
relief achieved by effectively lengthening the forward sole portion
would allow for the sole and/or strikeface to be thinned without
sacrificing the durability of the forward sole portion. Such
thinning would allow the exemplary club head to store more spring
energy and achieve even greater ball speeds.
Example 4: Wet and Dry Conditions Performance with Undercut
[0111] In a fourth example, player testing of physical clubs was
used to study the performance benefits of the undercut in varying
turf conditions. In this example, a pitching wedge comprising an
undercut was compared to a structurally similar pitching wedge,
which lacked an undercut. Each golf club was hit in wet conditions
and dry conditions and values for average launch angle, spin rate,
and ball speed were measured.
[0112] FIG. 12 compared the launch angle of a wedge with an
undercut and a wedge without an undercut in both wet conditions and
dry conditions. The wedge with an undercut had an average launch
angle of 24.0 degrees in dry conditions and an average launch angle
of 24.5 degrees in wet conditions. The wedge without an undercut
had an average launch angle of 23.6 degrees in dry conditions and
an average launch angle of 25.1 degrees in wet conditions.
Therefore, launch angle in wedges with an undercut and without an
undercut was comparable under wet conditions.
[0113] FIG. 13 compared the spin rate of the same wedge with an
undercut and wedge without an undercut in both wet and dry
conditions. The wedge with an undercut had an average spin rate of
8617 rpm (revolutions per minute) in dry conditions and an average
spin rate of 8031 rpm in wet conditions. The wedge without an
undercut had an average spin rate of 8310 rpm and a spin rate of
7144 rpm in wet conditions. Therefore, the wedge with the undercut
had increased spin rates to indicate better turf interaction in
both wet and dry conditions for the undercut wedge.
[0114] FIG. 14 compared the ball speed of the wedge with the
undercut and the wedge without the undercut. The wedge with the
undercut had an average ball speed of 97.3 mph (mile per hour) in
dry conditions and an average ball speed of 96.9 mph in wet
conditions. The wedge without the undercut had an average ball
speed of 97.4 mph in dry conditions and an average ball speed of
96.9 mph in wet conditions. The ball speed for the wedge with the
undercut and wedge without the undercut were comparable in both wet
and dry conditions.
[0115] The data above showed that the pitching wedge with the
undercut performed more consistently in variable turf conditions
than the wedge without an undercut. The launch angle of the wedge
with the undercut varied by 0.5 degrees between wet and dry
conditions, while the wedge without the undercut had a launch angle
that 1.5 degrees. The data showed that the launch angle of the
wedge without the undercut varied three times as much as the wedge
with the undercut. Similarly, the spin rate of the ball coming off
the wedge with the undercut was more consistent than the spin rate
of the wedge without the undercut. The spin rate varied by just 586
rpm between dry and wet conditions for the wedge with the undercut,
while the spin rate varied by 1166 rpm between dry and wet
conditions for the wedge without the undercut. Consistent spin
rates for wet and dry conditions of the undercut wedge were
preferred, as the purpose of wedge-type golf clubs is consistent
ball delivery on the green regardless of weather conditions. The
ball speed of the wedge with and without the undercut were
substantially similar.
[0116] Clause 1: A golf club head comprising: a hollow body
defining an enclosed internal cavity, the hollow body comprising: a
strikeface; a heel portion; a toe portion opposite the heel
portion; a sole; a top rail; a rear portion extending between the
top rail and the sole, and separated from the strikeface by the
internal cavity; a solid ballast within the internal cavity
extending substantially between the heel portion and the toe
portion; wherein the solid ballast extends upward from the sole and
forward from the rear portion; wherein the solid ballast comprises
a ballast top surface, a ballast forward surface, and a ballast
juncture between the ballast top surface and the ballast forward
surface; a ballast forward plane tangent to the ballast juncture
and parallel to the strikeface; wherein a ballast angle is defined
between the ballast forward surface and an interior surface of the
sole; wherein the ballast angle is between 30 and 80 degrees; an
undercut formed between the ballast forward surface and the
interior surface of the sole; wherein the undercut comprises: an
undercut bottom edge formed by the interior surface of the sole; an
undercut top edge formed by the ballast forward surface; an
undercut juncture located at a transition between the interior
surface of the sole and the ballast forward surface; an undercut
height measured as a vertical distance between the undercut bottom
edge and the undercut top edge; and wherein the undercut height
measured at the ballast forward plane is greater than 0.250
inch.
[0117] Clause 2: The golf club head of clause 1, further
comprising: a cascading region defining an internal transition
region from the strikeface to the sole, the cascading region
comprising; a first tier comprising a first thickness; a second
tier comprising a second thickness different than the first
thickness; and a tier transition region between the first tier and
the second tier.
[0118] Clause 3: The golf club head of clause 2, further comprising
a cascading region perimeter defining a boundary between the
cascading region and the sole; and wherein the cascading region
perimeter comprises a cascade front edge proximate a leading edge
of the strikeface and a cascade rear edge spaced rearwardly from
the strikeface.
[0119] Clause 4: The golf club head of clause 3, wherein the
cascade rear edge is arcuate and bows rearward relative to the
cascade front edge; wherein the cascading region comprises a depth
measured as a front-to-rear distance between the cascade front edge
and the cascade rear edge; and wherein the depth of the cascading
region is greater proximate a center of the club head than the
depth of the cascading region near the toe portion and the heel
portion.
[0120] Clause 5: The golf club head of clause 3, wherein a width of
the cascading region is greater proximate the cascade front edge
than near the cascade rear edge.
[0121] Clause 6: The golf club head of clause 1, further comprising
an undercut depth measured as a perpendicular distance between the
ballast forward plane and the undercut juncture; wherein the
undercut depth is greater than 0.100 inch.
[0122] Clause 7: The golf club head of clause 1, wherein the
ballast angle is between 60 degrees and 80 degrees.
[0123] Clause 8: The golf club head of clause 1, wherein the
ballast forward surface comprises a concave curvature relative to
the strikeface.
[0124] Clause 9: The golf club head of clause 1, further comprising
a top rail-to-sole moment of inertia ranging from 95 gin.sup.2 to
130 gin.sup.2 and a heel-to-toe moment of inertia ranging from 350
gin.sup.2 to 420 gin.sup.2.
[0125] Clause 10: A golf club head comprising: a hollow body
defining an enclosed internal cavity, the hollow body comprising: a
strikeface; a heel portion; a toe portion opposite the heel
portion; a sole; a top rail; a rear portion extending between the
top rail and the sole, and separated from the strikeface by the
internal cavity; a solid ballast within the internal cavity
extending substantially between the heel portion and the toe
portion; wherein the solid ballast extends upward from the sole and
forward from the rear portion; wherein the solid ballast comprises
a ballast top surface, a ballast forward surface, and a ballast
juncture between the ballast top surface and the ballast forward
surface; a ballast forward plane tangent to the ballast juncture
and parallel to the strikeface; wherein a ballast angle is defined
between the ballast forward surface and an interior surface of the
sole; wherein the ballast angle is between 30 and 80 degrees; an
undercut formed between the ballast forward surface and the
interior surface of the sole; wherein the undercut comprises: an
undercut bottom edge formed by the interior surface of the sole; an
undercut top edge formed by the ballast forward surface; an
undercut juncture located at a transition between the interior
surface of the sole and the ballast forward surface; a cascading
region defining an internal transition region from the strikeface
to the sole, the cascading region comprising; a first tier
comprising a first thickness; a second tier comprising a second
thickness different than the first thickness; a tier transition
region between the first tier and the second tier; wherein the
cascading region comprises a perimeter boundary comprising a
cascade front edge proximate a leading edge of the strikeface, a
cascade rear edge spaced rearwardly from the strikeface, a cascade
heel edge extending between the cascade front edge and the cascade
rear edge proximate the heel portion, and a cascade toe edge
extending between the cascade front edge and the cascade rear edge
proximate the heel portion; wherein the cascading region comprises
a depth measured as a front-to-rear distance between the cascade
front edge and the cascade rear edge; wherein the depth of the
cascading region is greater proximate a center of the club head
than the depth of the cascading region near the toe portion and the
heel portion; and wherein the depth of the cascading region at the
cascade heel edge is between 50% and 90% of the depth of the
cascading region at the center of the club head.
[0126] Clause 11: The golf club head of clause 10, wherein the
cascading region further comprises a cascading region depth
measured between the cascade heel edge and the cascade toe edge in
a heel to toe direction; wherein the cascading region depth is
greater near the cascade front edge than near the cascade rear
edge.
[0127] Clause 12: The golf club head of clause 10, wherein the
cascade rear edge is arcuate and bows rearward relative to the
cascade front edge.
[0128] Clause 13: The golf club head of clause 10, wherein the
cascading region further comprises a third tier.
[0129] Clause 14: The golf club head of clause 10, wherein the tier
transition region linearly declines at an angle less than 45
degrees.
[0130] Clause 15: The golf club head of clause 10, wherein the
ballast forward surface comprises a concave curvature relative to
the strikeface.
[0131] Clause 16: The golf club head of clause 10, wherein the
ballast angle is between 60 degrees and 80 degrees.
[0132] As the rules to golf may change from time to time (e.g., new
regulations may be adopted or old rules may be eliminated or
modified by golf standard organizations and/or governing bodies),
golf equipment related to the methods, apparatus, and/or articles
of manufacture described herein may be conforming or non-conforming
to the rules of golf at any particular time. Accordingly, golf
equipment related to the methods, apparatus, and/or articles of
manufacture described herein may be advertised, offered for sale,
and/or sold as conforming or non-conforming golf equipment. The
methods, apparatus, and/or articles of manufacture described herein
are not limited in this regard.
[0133] Although a particular order of actions is described above,
these actions may be performed in other temporal sequences. For
example, two or more actions described above may be performed
sequentially, concurrently, or simultaneously. Alternatively, two
or more actions may be performed in reversed order. Further, one or
more actions described above may not be performed at all. The
apparatus, methods, and articles of manufacture described herein
are not limited in this regard.
[0134] While the invention has been described in connection with
various aspects, it will be understood that the invention is
capable of further modifications. This application is intended to
cover any variations, uses or adaptation of the invention
following, in general, the principles of the invention, and
including such departures from the present disclosure as come
within the known and customary practice within the art to which the
invention pertains.
* * * * *
References