U.S. patent application number 11/072670 was filed with the patent office on 2006-09-07 for low-weight two piece golf balls.
Invention is credited to Douglas E. Jones.
Application Number | 20060199667 11/072670 |
Document ID | / |
Family ID | 36944791 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060199667 |
Kind Code |
A1 |
Jones; Douglas E. |
September 7, 2006 |
Low-weight two piece golf balls
Abstract
The present invention is directed to a golf ball with a core and
a cover layer surrounding the core. The golf ball preferably has a
weight between about 44.5 grams and about 45 grams, a diameter of
at least about 1.68 inches, and a deflection of about 3.0 mm to
about 4.0 mm at 100 kg. Additionally, the golf ball preferably has
a coefficient of restitution of at least about 0.82 at a club head
speed of 100 ft/sec. The golf ball includes aerodynamics to provide
an optimal trajectory and overall distance for the low weight ball.
Thus, a low weight golf ball is provided delivering improved
distance with superior feel. This golf ball is specifically
designed to optimize its play characteristics for low swing speed
players.
Inventors: |
Jones; Douglas E.;
(Dartmouth, MA) |
Correspondence
Address: |
ACUSHNET COMPANY
333 BRIDGE STREET
P. O. BOX 965
FAIRHAVEN
MA
02719
US
|
Family ID: |
36944791 |
Appl. No.: |
11/072670 |
Filed: |
March 4, 2005 |
Current U.S.
Class: |
473/371 |
Current CPC
Class: |
A63B 37/0083 20130101;
A63B 37/0024 20130101; A63B 37/0012 20130101; A63B 37/008 20130101;
A63B 37/0004 20130101; A63B 37/0018 20130101; A63B 37/0078
20130101; A63B 37/0062 20130101; A63B 37/0096 20130101; A63B
37/0033 20130101; A63B 37/0021 20130101; A63B 37/009 20130101; A63B
37/0087 20130101; A63B 37/0006 20130101; A63B 37/0031 20130101;
A63B 37/0074 20130101; A63B 37/0081 20130101; A63B 37/0089
20130101; A63B 37/0027 20130101; A63B 37/002 20130101 |
Class at
Publication: |
473/371 |
International
Class: |
A63B 37/04 20060101
A63B037/04 |
Claims
1. A golf ball comprising: a core; a cover layer surrounding the
core, the cover layer having an exterior surface; and a dimple
pattern on the exterior surface having a plurality of dimples
providing optimal trajectory and overall distance for the golf
ball, wherein the golf ball has a weight between about 44.5 grams
and about 45 grams, a diameter of at least 1.68 inches and a
coefficient of restitution of about at least 0.82 at a club head
speed of about 100 ft/sec.
2. The golf ball of claim 1, wherein the dimple pattern includes
dimples having at least three different diameters.
3. The golf ball of claim 1, wherein the dimples cover at least 80%
of the exterior surface.
4. The golf ball of claim 1, wherein the dimples have an edge angle
greater than 14 degrees to a phantom sphere concentric with and
having a same diameter as the exterior surface of the cover.
5. The golf ball of claim 1, wherein the exterior surface defines
between about 200 and about 600 dimples.
6. The golf ball of claim 1, wherein the plurality of dimples
comprise an aerodynamic coefficient magnitude defined by C.sub.mag=
(C.sub.L.sup.2+C.sub.D.sup.2) and an aerodynamic force angle
defined by Angle=tan.sup.-1(C.sub.L/C.sub.D), wherein C.sub.L is a
lift coefficient and C.sub.D is a drag coefficient, wherein the
golf ball comprises: an outer land surface, wherein the outer land
surface comprises, at least one first substantially constant width
and at least one second substantially constant width, wherein said
first and second widths separate the dimples; a first aerodynamic
coefficient magnitude from about 0.24 to about 0.27 and a first
aerodynamic force angle of about 31 degrees to about 35 degrees at
a Reynolds Number of about 230000 and a spin ratio of about 0.085;
and a second aerodynamic coefficient magnitude from about 0.25 to
about 0.28 and a second aerodynamic force angle of about 34 degrees
to about 38 degrees at a Reynolds Number of about 207000 and a spin
ratio of about 0.095.
7. The golf ball of claim 6, further comprising: a third
aerodynamic coefficient magnitude from about 0.26 to about 0.29 and
a third aerodynamic force angle of about 35 degrees to about 39
degrees at a Reynolds Number of about 184000 and a spin ratio of
about 0.106; and a fourth aerodynamic coefficient magnitude from
about 0.27 to about 0.30 and a fourth aerodynamic force angle of
about 37 degrees to about 42 degrees at a Reynolds Number of about
161000 and a spin ratio of about 0.122.
8. The golf ball of claim 7, further comprising: a fifth
aerodynamic coefficient magnitude from about 0.29 to about 0.32 and
a fifth aerodynamic force angle of about 39 degrees to about 43
degrees at a Reynolds Number of about 138000 and a spin ratio of
about 0.142; and a sixth aerodynamic coefficient magnitude from
about 0.32 to about 0.35 and a sixth aerodynamic force angle of
about 40 degrees to about 44 degrees at a Reynolds Number of about
115000 and a spin ratio of about 0.170.
9. The golf ball of claim 8, further comprising: a seventh
aerodynamic coefficient magnitude from about 0.36 to about 0.40 and
a seventh aerodynamic force angle of about 41 degrees to about 45
degrees at a Reynolds Number of about 92000 and a spin ratio of
about 0.213; and an eighth aerodynamic coefficient magnitude from
about 0.40 to about 0.45 and an eighth aerodynamic force angle of
about 40 degrees to about 44 degrees at a Reynolds Number of about
69000 and a spin ratio of about 0.284.
10. The golf ball of claim 1, wherein at a 100 kg load the golf
ball has a deflection of about 3.0 mm to about 4.0 mm.
11. The golf ball of claim 1, wherein the golf ball has a
coefficient of restitution of about 0.83 to about 0.87 at a club
speed of about 100 ft/sec.
12. The golf ball of claim 11, wherein the golf ball has a
coefficient of restitution of about 0.83 to about 0.85 at a club
speed of about 100 ft/sec.
13. The golf ball of claim 1, wherein the golf ball has a
coefficient of restitution of about at least 0.82 at a club head
speed of about 125 ft/sec.
14. The golf ball of claim 1, wherein the surface of the core has a
Shore C material hardness of between about 50 and about 80.
15. The golf ball of claim 1, wherein the cover layer has a
thickness less than or equal to about 0.08 inch.
16. The golf ball of claim 1, wherein the cover layer is formed of
a thermoplastic material.
17. The golf ball of claim 16, wherein said thermoplastic material
is selected from the group including: partially or fully
neutralized ionomers, thermoplastic polyurethane, metallocene,
thermoplastic urethane, fusabond, or other single site catalyzed
polymer, or blends thereof.
18. The golf ball of claim 1, wherein the cover layer is formed of
a thermoset material.
19. The golf ball of claim 18, wherein said thermoset material is
selected from the group including: aromatic urethane, light stable
urethane, light stable polyurea, polyurethane-ionomer or blends
thereof.
20. The golf ball of claim 1, wherein the cover layer has a Shore D
material hardness of between about 30 and about 75.
21. The golf ball of claim 1, wherein the cover layer has a Shore D
material hardness of less than about 60.
22. A golf ball comprising: a core; a cover layer surrounding the
core, the cover layer having an exterior surface; and a plurality
of dimples on the exterior surface of the cover layer to provide an
optimal trajectory and overall distance for the golf ball, wherein
the golf ball has a weight between about 44.5 grams and about 45
grams; a deflection at 100 kg of about 3.0 mm to about 4.0 mm; a
diameter of a least 1.68 inches; and a coefficient of restitution
of about 0.82 to about 0.87 at a club head speed of 100 ft/sec.
23. The golf ball of claim 22, further comprising dimples having at
least three different diameters.
24. The golf ball of claim 22, wherein the dimples cover at least
80% of the exterior surface.
25. The golf ball of claim 22, wherein the dimples have an edge
angle greater than 14 degrees to a phantom sphere concentric with
and having a same diameter as the exterior surface of the
cover.
26. The golf ball of claim 22, wherein the exterior surface defines
between about 200 and about 600 dimples.
27. The golf ball of claim 22, wherein the plurality of dimples
comprise an aerodynamic coefficient magnitude defined by C.sub.mag=
(C.sub.L.sup.2+C.sub.D.sup.2) and an aerodynamic force angle
defined by Angle=tan.sup.-1(C.sub.L/C.sub.D), wherein C.sub.L is a
lift coefficient and C.sub.D is a drag coefficient, wherein the
golf ball comprises: an outer land surface, wherein the outer land
surface comprises, at least one first substantially constant width
and at least one second substantially constant width, wherein said
first and second widths separate the dimples; a first aerodynamic
coefficient magnitude from about 0.24 to about 0.27 and a first
aerodynamic force angle of about 31 degrees to about 35 degrees at
a Reynolds Number of about 230000 and a spin ratio of about 0.085;
and a second aerodynamic coefficient magnitude from about 0.25 to
about 0.28 and a second aerodynamic force angle of about 34 degrees
to about 38 degrees at a Reynolds Number of about 207000 and a spin
ratio of about 0.095.
28. The golf ball of claim 27, further comprising: a third
aerodynamic coefficient magnitude from about 0.26 to about 0.29 and
a third aerodynamic force angle of about 35 degrees to about 39
degrees at a Reynolds Number of about 184000 and a spin ratio of
about 0.106; and a fourth aerodynamic coefficient magnitude from
about 0.27 to about 0.30 and a fourth aerodynamic force angle of
about 37 degrees to about 42 degrees at a Reynolds Number of about
161000 and a spin ratio of about 0.122.
29. The golf ball of claim 28, further comprising: a fifth
aerodynamic coefficient magnitude from about 0.29 to about 0.32 and
a fifth aerodynamic force angle of about 39 degrees to about 43
degrees at a Reynolds Number of about 138000 and a spin ratio of
about 0.142; and a sixth aerodynamic coefficient magnitude from
about 0.32 to about 0.35 and a sixth aerodynamic force angle of
about 40 degrees to about 44 degrees at a Reynolds Number of about
115000 and a spin ratio of about 0.170.
30. The golf ball of claim 29, further comprising: a seventh
aerodynamic coefficient magnitude from about 0.36 to about 0.40 and
a seventh aerodynamic force angle of about 41 degrees to about 45
degrees at a Reynolds Number of about 92000 and a spin ratio of
about 0.213; and an eighth aerodynamic coefficient magnitude from
about 0.40 to about 0.45 and an eighth aerodynamic force angle of
about 40 degrees to about 44 degrees at a Reynolds Number of about
69000 and a spin ratio of about 0.284.
31. The golf ball of claim 22, wherein the golf ball has a
coefficient of restitution of about 0.83 to about 0.85 at a club
speed of about 100 ft/sec.
32. The golf ball of claim 22, wherein the golf ball has a
coefficient of restitution of about at least 0.82 at a club head
speed of about 125 ft/sec.
33. The golf ball of claim 22, wherein the cover layer has a Shore
D material hardness of less than about 60.
Description
TECHNICAL FIELD OF INVENTION
[0001] The present invention generally relates to golf balls, and
more particularly to a low weight two piece golf ball for golfers
with a low club head speed.
BACKGROUND OF THE INVENTION
[0002] The flight of a golf ball is determined by many factors, but
only three factors are typically controlled by the golfer. By
impacting the ball with a golf club, the golfer controls the speed,
the launch angle and the spin rate of the golf ball. The launch
angle sets the initial trajectory of the golf ball's flight. The
speed and spin of the ball give the ball lift which will define the
ball's overall flight path along with the weight and drag of the
golf ball. Where the ball stops after being struck by a golf club
also depends greatly on the weather and the landing surface the
ball contacts.
[0003] Many golfers have what is termed a "low swing speed." This
means that the club head speed at impact is relatively slow when
compared to a professional golfer's. Typically, when driving a golf
ball the average professional golf ball speed is approximately 234
ft/s (160 mph). A person having a low swing speed typically drives
the ball at a speed less than 220 ft/s (150 mph). A person with a
low swing speed has a low ball speed. Consequently, his or her ball
does not fly very far because of the lack of speed and lift. A
significant percentage of all golfers today use such low swing
speeds and consequently produce drives of less than 210 yards.
[0004] Standard balls are optimized for distance at swing speeds
generally greater than 90 mph. Standard balls weigh more than 45
grams, while lightweight balls generally weigh less than 44 grams.
Typically, lightweight golf balls are designed for low swing speed
golfers. These lightweight golf balls usually are two-piece solid
balls made with a single-solid core, encased by a hard cover
material. The resiliency of the core can be increased so that the
compression is high, which in addition to making the balls stiffer,
increases the initial velocity and decreases the ball's spin rate.
This maximizes the distance achieved by low swing speed players.
However, these balls tend to have a hard feel and are difficult to
control around the greens. Additionally, these golf balls can have
insufficient mass to provide good distance at the target
audience.
[0005] Golf balls generally include a spherical outer surface with
a plurality of dimples formed thereon. Conventional dimples are
circular depressions that reduce drag and increase lift.
Lightweight golf balls typically have a dimple package tuned for a
standard weight golf ball, which results in a ball that flies too
high and short.
[0006] A need exists for a high performance golf ball designed for
low swing speed players, particularly those with a club head speed
of less than 90 mph that offers improved distance with superior
feel.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a golf ball comprising
a core and a cover layer surrounding the core. In addition, the
golf ball has a weight between about 44.5 grams and 45 grams, a
diameter of at least 1.68 inches and a coefficient of restitution
of about at least 0.82 at a club head speed of about 100 ft/sec.
The golf ball has a dimple pattern to provide optimal trajectory
and overall distance.
[0008] In one preferred embodiment, the dimple pattern includes
dimples having at least three different diameters. The dimples
preferably cover at least 80% of the exterior surface. The dimples
also preferably have an edge angle greater than 14 degrees to a
phantom sphere concentric with and having a same diameter as the
exterior surface of the cover.
[0009] According to one aspect of the invention, the exterior
surface defines between about 200 and about 600 dimples.
[0010] According to another aspect of the invention, the plurality
of dimples may comprise an aerodynamic coefficient magnitude
defined by C.sub.mag= (C.sub.L.sup.2+C.sub.D.sup.2) and an
aerodynamic force angle defined by
Angle=tan.sup.-1(C.sub.L/C.sub.D), where C.sub.L is a lift
coefficient and C.sub.D is a drag coefficient. Additionally, the
golf ball may include an outer land surface, wherein the outer land
surface comprises at least one first substantially constant width
and at least one second substantially constant width, wherein said
first and second widths separate the dimples. Additionally, the
golf ball may have a first aerodynamic coefficient magnitude from
about 0.24 to about 0.27 and a first aerodynamic force angle of
about 31 degrees to about 35 degrees at a Reynolds Number of about
230000 and a spin ratio of about 0.085 and a second aerodynamic
coefficient magnitude from about 0.25 to about 0.28 and a second
aerodynamic force angle of about 34 degrees to about 38 degrees at
a Reynolds Number of about 207000 and a spin ratio of about
0.095.
[0011] According to another aspect of the invention, the golf ball
may have a third aerodynamic coefficient magnitude from about 0.26
to about 0.29 and a third aerodynamic force angle of about 35
degrees to about 39 degrees at a Reynolds Number of about 184000
and a spin ratio of about 0.106. Also, the golf ball may have a
fourth aerodynamic coefficient magnitude from about 0.27 to about
0.30 and a fourth aerodynamic force angle of about 37 degrees to
about 42 degrees at a Reynolds Number of about 161000 and a spin
ratio of about 0.122.
[0012] According to yet another aspect of the invention, the golf
ball may have a fifth aerodynamic coefficient magnitude from about
0.29 to about 0.32 and a fifth aerodynamic force angle of about 39
degrees to about 43 degrees at a Reynolds Number of about 138000
and a spin ratio of about 0.142 and a sixth aerodynamic coefficient
magnitude from about 0.32 to about 0.35 and a sixth aerodynamic
force angle of about 40 degrees to about 44 degrees at a Reynolds
Number of about 115000 and a spin ratio of about 0.170.
[0013] According to yet another aspect of the invention, the golf
ball may have a seventh aerodynamic coefficient magnitude from
about 0.36 to about 0.40 and a seventh aerodynamic force angle of
about 41 degrees to about 45 degrees at a Reynolds Number of about
92000 and a spin ratio of about 0.213 and an eighth aerodynamic
coefficient magnitude from about 0.40 to about 0.45 and an eighth
aerodynamic force angle of about 40 degrees to about 44 degrees at
a Reynolds Number of about 69000 and a spin ratio of about
0.284.
[0014] According to another aspect of the invention, a 100 kg load
on the golf ball has a deflection of about 3.0 mm to about 4.0
mm.
[0015] According to another aspect of the invention, the golf ball
preferably has a coefficient of restitution of about 0.83 to about
0.87 at a club speed of about 100 ft/sec, and more preferably a
coefficient of restitution of about 0.83 to about 0.85 at a club
speed of about 100 ft/sec. According to another aspect of the
invention, the golf ball has a coefficient of restitution of about
at least 0.82 at a club head speed of about 125 ft/sec.
[0016] Preferably, the surface of the core has a Shore C material
hardness of between about 50 and about 80.
[0017] The cover layer preferably has a thickness less than or
equal to about 0.08 inch.
[0018] In one embodiment, the cover layer may be formed of a
thermoplastic material, and the thermoplastic material may be
selected from the group including: partially or fully neutralized
ionomers, thermoplastic polyurethane, metallocene, thermoplastic
urethane, fusabond, or other single site catalyzed polymer, or
blends thereof.
[0019] In yet another embodiment, the cover layer is formed of a
thermoset material, and the thermoset material may be selected from
the group including: aromatic urethane, light stable urethane,
light stable polyurea, polyurethane-ionomer or blends thereof.
[0020] The cover layer may have a Shore D material hardness of
between about 30 and about 75. In another embodiment, the cover
layer may have a Shore D material hardness of less than about
60.
[0021] The present invention is also directed to a golf ball
comprising a core, a cover layer surrounding the core. In addition,
the golf ball has a weight between about 44.5 grams and about 45
grams, a deflection at 100 kg of about 3.0 mm to about 4.0 mm, a
diameter of at least 1.68 inches, and a coefficient of restitution
of about 0.82 to about 0.87 at a club head speed of 100 ft/sec. The
golf ball has a plurality of dimples provided on an exterior
surface of the cover layer to provide an optimal trajectory and
overall distance for the golf ball.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The advantages and features of this invention will be more
clearly appreciated from the following detailed description, when
taken in conjunction with the accompanying drawings, wherein like
numbers are used for like features, in which:
[0023] FIG. 1 is a perspective view of a first embodiment of a golf
ball of the present invention;
[0024] FIG. 2 is a cross-sectional view of the golf ball of FIG. 1;
and
[0025] FIG. 3 is an illustration of the forces acting on a golf
ball.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] The distance that a golf ball would travel upon impact is a
function of the coefficient of restitution (CoR) and the
aerodynamic characteristics of the ball. The CoR is defined as the
ratio of the relative velocity of two colliding objects after the
collision to the relative velocity of the two colliding objects
prior to the collision. The CoR varies from 0 to 1.0. A CoR value
of 1.0 is equivalent to a perfectly elastic collision, and a CoR
value of 0.0 is equivalent to a perfectly inelastic collision. For
golf balls, CoR has been approximated as a ratio of the velocity of
the golf ball after impact to the velocity of the golf ball prior
to impact.
[0027] CoR is an important measurement of the collision between the
ball and a large mass. One conventional technique for measuring CoR
uses a golf ball or golf ball subassembly, air cannon, and a
stationary vertical steel plate. The steel plate provides an impact
surface weighing about 100 pounds or about 45 kilograms. A pair of
ballistic light screens, which measure ball velocity, are spaced
apart and located between the air cannon and the steel plate. The
ball is fired from the air cannon toward the steel plate over a
range of test velocities from 50 ft/sec to 180 ft/sec. Unless noted
otherwise, all CoR data presented in this application are measured
using a speed of 100 ft/sec. As the ball travels toward the steel
plate, it activates each light screen so that the time at each
light screen is measured. This provides an incoming time period
proportional to the ball's incoming velocity. The ball impacts the
steel plate and rebounds though the light screens, which again
measure the time period required to transit between the light
screens. This provides an outgoing transit time period proportional
to the ball's outgoing velocity. The CoR can be calculated by the
ratio of the outgoing transit time period to the incoming transit
time period.
[0028] Another CoR measuring method uses a titanium disk. This
method is described in U.S. Pat. No. 6,688,991, and is assigned to
the same assignee as the present invention.
[0029] The CoR of the golf ball is affected by a number of factors
including the composition the core and the composition of the
cover. The core may be single layer core or multi-layer core. It
may also be solid or fluid filled. It may also be wound or foamed,
or it may contain fillers. The cover may also be single layer cover
or multi-layer cover. The cover may be thin or thick. The cover may
have a high hardness or low hardness to control the spin and feel
of the ball. Any of the above factors can contribute to the CoR of
the ball.
[0030] Hardness is preferably measured pursuant to ASTM D-2240 in
either button or slab form on the Shore D scale. More specifically,
Shore D scale measures the indentation hardness of a polymer. The
higher Shore D value indicates higher hardness of the polymer. The
Shore D material hardness is measured on the ball according to ASTM
D-2240 in either button or slab form.
[0031] Specific gravity as used in this application is defined in
terms of test ASTM D-297.
[0032] The flexural modulus is preferably measured according to
ASTM D6272-02. These tests may be carried out using a 0.5 in/min
crosshead speed and a 2 inch span length in the four point bending
mode. Test samples may be conditioned at 23.degree. C., 50% RH for
2 weeks and then the tests performed.
[0033] Deflection is measured by applying loads of 10 kg, 100 kg
and 130 kg to either the core or golf ball. Typically tests measure
the deflection under a 100 kg load, or the deflection at 130 kg
minus the deflection at 10 kg (the 130-10 kg test). Different
apparatus may be used, such as a compression/tensile tester
manufactured by Stable Micro Systems in Surrey, UK, Model MT-LQ. A
cross-head speed of 2.5 cm/min is preferably used.
[0034] Compression is measured by applying a spring-loaded force to
the golf ball center, golf ball core or the golf ball to be
examined, with a manual instrument (an "Atti gauge") manufactured
by the Atti Engineering Company of Union City, N.J. This machine,
equipped with a Federal Dial Gauge, Model D81-C, employs a
calibrated spring under a known load. The sphere to be tested is
forced a distance of 0.2 inch (5 mm) against this spring. If the
spring, in turn, compresses 0.2 inch, the compression is rated at
100; if the spring compresses 0.1 inch, the compression value is
rated as 0. Thus more compressible, softer materials will have
lower Atti gauge values than harder, less compressible materials.
Compression measured with this instrument is also referred to as
PGA compression. The approximate relationship that exists between
Atti or PGA compression and Riehle compression can be expressed as:
(Atti or PGA compression)=(160-Riehle Compression).
[0035] In accordance with one aspect of the present invention, when
golf balls with larger diameter cores and a thin ionomeric cover
layer are made with less weight, i.e., less than 45.93 grams and
preferably between about 44.5 grams and about 45 grams, the balls
fly longer when struck with lower swing speed clubs. The clubs can
launch the balls on to higher flight trajectories and therefore
longer distance. A dimple pattern specifically tuned for a low
weight ball may be provided. The specifically tuned dimple pattern
assists in providing a higher flight trajectory and longer distance
for the ball.
[0036] Additionally, with lower overall ball deflection in the
range of 3.0 mm to 4.0 mm, the ball spin rate is sufficiently high
to improve greenside play.
[0037] Hence, a high performance ball, i.e., long distance with
good greenside play, for low swing speed players is achieved, as
described below.
[0038] Referring to FIGS. 1 and 2, a golf ball 10 comprises a core
12 and at least one cover layer 14 surrounding the core. Cover
layer 14 preferably includes a plurality of dimples 16.
[0039] Preferably, core 12 has an outer diameter greater than 1.50
inches and the ball 10 has a weight of between about 44.5 grams and
about 45 grams, thereby forming a low weight golf ball with a large
core.
[0040] In addition, golf ball 10 preferably has a deflection of
between about 3.0 mm to 4.0 mm at 100 kg, a coefficient of
restitution (CoR) at 100 ft/s of greater than 0.820, and a ball
diameter of at least 1.68 inches. More preferably, the ball has a
CoR at 100 ft/sec between about 0.83 and about 0.87, and still more
preferably between about 0.83 and about 0.84. In another
embodiment, the ball has a CoR at 125 ft/sec of at least 0.82.
Preferably, the ball has a diameter between about 1.68 inches and
1.685 inches and the cover has a thickness of about 0.08 inches or
less.
[0041] According to one aspect of the present invention the golf
ball core is formulated so that the golf ball core has a
compression of between about 30 and about 90 or a deflection of
about 3.0 to about 5.0 at 100 kg. A representative base composition
for forming golf ball core 12 comprises polybutadiene rubber (PBD)
that has a mid to high Mooney viscosity. Preferably, the core has a
Mooney viscosity greater than about 35, more preferably greater
than about 40, even more preferably greater than about 45, and most
preferably in the range from about 50 to about 52 Mooney. PBD with
higher Mooney viscosity may also be used, so long as the viscosity
of the PBD does not reach a level where the high viscosity PBD
clogs or otherwise adversely interferes with the manufacturing
machinery. It is contemplated that PBD with viscosity less than 65
Mooney can be used with the present invention. A "Mooney" unit is a
unit used to measure the plasticity of raw or unvulcanized rubber.
The plasticity in a "Mooney" unit is equal to the torque, measured
on an arbitrary scale, on a disk in a vessel that contains rubber
at a temperature of 100.degree. C. and rotates at two revolutions
per minute. The measurement of Mooney viscosity is defined
according to ASTM D-1646.
[0042] Golf ball cores made with mid to high Mooney viscosity PBD
material exhibit increased resiliency, hence distance, without
increasing the hardness of the ball. Commercial sources of suitable
mid to high Mooney PBD include Bayer AG. "CB 23", which has a
Mooney viscosity of about 51 and is a highly linear polybutadiene,
is a preferred PBD. If desired, the polybutadiene can also be mixed
with other elastomers known in the art, such as natural rubber,
styrene butadiene, and/or isoprene in order to further modify the
properties of the core. When a mixture of elastomers is used, the
amounts of other constituents in the core composition are typically
based on 100 parts by weight of the total elastomer mixture.
[0043] Preferably, the core has a surface hardness of between about
40 JIS C and about 100 JIS C. More preferably, the core has a
surface hardness of between about 45 JIS C and about 90 JIS C. Most
preferably, the core has a surface hardness of between about 50 JIS
C and about 80 JIS C. The surface is at least 5 Shore C harder than
the center of the core (as measured on the core).
[0044] In accordance with another aspect of the invention, the
addition of sulfur compound to the core further increases the
resiliency and the CoR of the ball. Preferred sulfur compounds
include, but are not limited to, pentachlorothiophenol (PCTP) and a
salt of PCTP. A preferred salt of PCTP is ZnPCTP. The utilization
of PCTP and ZnPCTP in golf ball cores to produce soft and fast
cores is disclosed in U.S. Pat. No. 6,635,716, which is
incorporated by reference herein, in its entirety. A suitable PCTP
is sold by the Structol Company under the tradename A95. ZnPCTP is
commercially available from EchinaChem.
[0045] Metal salt diacrylates, dimethacrylates, and
monomethacrylates suitable for use in this invention include those
wherein the metal is magnesium, calcium, zinc, aluminum, sodium,
lithium or nickel. Zinc diacrylate (ZDA) is preferred, but the
present invention is not limited thereto. ZDA provides golf balls
with a high initial velocity. The ZDA can be of various grades of
purity. For the purposes of this invention, lower quantity of zinc
stearate in the ZDA indicates higher ZDA purity. ZDA containing
less than about 10% zinc stearate is preferable. More preferable is
ZDA containing about 4-8% zinc stearate. Suitable, commercially
available zinc diacrylates include those from Sartomer Co. The
preferred concentrations of ZDA that can be used are about 15 pph
to about 40 pph based upon 100 pph of polybutadiene or alternately,
polybutadiene with a mixture of other elastomers that equal 100
pph. Advantageously, the PCTP organic sulfur reacts with the ZDA
used in the core to further increase the initial velocity of golf
balls.
[0046] Free radical initiators are used to promote cross-linking of
the metal salt diacrylate, dimethacrylate, or monomethacrylate and
the polybutadiene. Suitable free radical initiators for use in the
invention include, but are not limited to peroxide compounds, such
as dicumyl peroxide, 1,1 -di(t-butylperoxy) 3,3,5-trimethyl
cyclohexane, a-a bis(t-butylperoxy) diisopropylbenzene,
2,5-dimethyl-2,5di(t-butylperoxy) hexane, or di-t-butyl peroxide,
and mixtures thereof. Other useful initiators would be readily
apparent to one of ordinary skill in the art without any need for
experimentation. The initiator(s) at about 70% to about 100%
activity are preferably added in an amount ranging between about
0.05 pph and about 2.5 pph based upon 100 parts of butadiene, or
butadiene mixed with one or more other elastomers. More preferably,
the amount of initiator added ranges between about 0.15 pph and
about 2 pph and most preferably between about 0.25 pph and about
1.5 pph. Suitable commercially available dicumyl peroxides include
Perkadox BC, which is >90% active dicumyl peroxide, and DCP 70,
which is >70% active dicumyl peroxide.
[0047] As discussed above, when ZDA or another metal salt of
diacrylates, dimethacrylates, and monomethacrylates are used in the
core, about 1 pph to about 20 pph of zinc oxide (or a smaller
amount of calcium oxide and higher amount of peroxide) is
preferably added to the core composition to react and neutralize
any acrylic acid that may be present. More preferably, about 1.5
pph to about 12 pph of zinc oxide is added and most preferably
about 2 pph to about 8 pph of zinc oxide is added.
[0048] Antioxidants may also be included. Antioxidants are
compounds, which prevent the breakdown of the elastomer.
Antioxidants useful in the present invention include, but are not
limited to, quinoline type antioxidants, amine type antioxidants,
and phenolic type antioxidants.
[0049] Other ingredients such as accelerators, e.g., tetra
methylthiuram, processing aids, processing oils, dyes and pigments,
as well as other additives well known to the skilled artisan may
also be used in the present invention in amounts sufficient to
achieve the purpose for which they are typically used.
[0050] Preferably about 1 pph to about 25 pph of regrind may be
used. Most preferably, about 5 pph to about 20 pph of regrind may
be used.
[0051] Low density fillers can also be added to the core
formulation. Preferably about 1 pph to about 15 pph of low density
fillers may be used. Most preferably, about 5 pph to about 10 pph
of low density fillers may be used. Low density fillers can be used
to reduce the weight of the ball. Suitable low density fillers may
include hollow spheres or microspheres that can be incorporated
into the core material including, for example polybutadiene.
[0052] High density fillers can also be added to the core
formulation. Preferably about 0 pph to about 15 pph of high density
fillers may be used. More preferably, about 3 pph to about 12 pph
of high density fillers may be used. Most preferably, about 5 pph
to about 10 pph of high density fillers may be used. Depending on
the weight of the core, high density fillers can be added to the
cover to improve the moment of inertia of the ball. High density
fillers can be used, so long as the ball has the preferred weight,
discussed above. High moment of inertia balls are fully discussed
in U.S. Pat. No. 6,494,795, which is incorporated by reference
herein, in its entirety.
[0053] Suitable high density fillers may have specific gravity in
the range from about 2 to about 19, and include, for example, metal
(or metal alloy) powder, metal oxide, metal searates, particulates,
carbonaceous materials, and the like or blends thereof. Examples of
useful metal (or metal alloy) powders include, but are not limited
to, bismuth powder, boron powder, brass powder, bronze powder,
cobalt powder, copper powder, inconel metal powder, iron metal
powder, molybdenum powder, nickel powder, stainless steel powder,
titanium metal powder, zirconium oxide powder, aluminum flakes,
tungsten metal powder, beryllium metal powder, zinc metal powder,
or tin metal powder. Examples of metal oxides include but are not
limited to zinc oxide, iron oxide, aluminum oxide, titanium
dioxide, magnesium oxide, zirconium oxide, and tungsten trioxide.
Examples of particulate carbonaceous materials include but are not
limited to graphite and carbon black. A more preferred high density
filler is tungsten, tungsten oxide or tungsten metal powder due to
its particularly high specific gravity of about 19.
[0054] Examples of other useful fillers include but are not limited
to graphite fibers, precipitated hydrated silica, clay, talc, glass
fibers, aramid fibers, mica, calcium metasilicate, barium sulfate,
zinc sulfide, silicates, diatomaceous earth, calcium carbonate,
magnesium carbonate, regrind (which is recycled uncured center
material mixed and ground to 30 mesh particle size), manganese
powder, and magnesium powder.
[0055] In accordance to another aspect of the present invention,
the cover layer 14 thickness is minimized. To that end, the
thickness of cover layer 14 (as shown in FIG. 2) is equal to or
less than about 0.08 inches. Most preferably, the thickness of the
cover layer is equal to or less than 0.07 inches. Preferably, the
cover layer 14 is made of one layer, although it will be
appreciated that multiple layers may form the cover layer 14. The
thinness of the cover layer provides more volume for the core 12,
and thereby more resilient polymeric core materials can be included
in the core layer. Preferred compositions and properties of the
cover layer in accordance to the present invention are described
below.
[0056] Preferably, the cover layer is formed as a single layer of a
thermoplastic material. In another embodiment, the cover layer is
formed as a single layer of thermoset material.
[0057] Thermoplastic materials include for example, partially or
fully neutralized ionomers, thermoplastic polyurethane,
metallocene, thermoplastic urethane, fusabond or other single site
catalyzed polymer, or blends thereof. Thermoset materials include
polyurethane, polyurea, aromatic material, aliphatic material, or
blends thereof. Exemplary preferable forms of such materials
include aromatic urethane, light stable urethane,
polyurethane-ionomer, and light stable polyurea. The cover layer
can be cast or reaction-injection molded as known by those of
ordinary skill in the art. If a urethane or urea cover layer is
used, the ball preferably has a moisture barrier between core 12
and cover layer 14. The use of moisture barriers is described in
U.S. Pat. No. 6,632,147, which is incorporated by reference herein
in its entirety. As discussed above, an ionomer such as Surlyn can
be included between core 12 and a urethane urea cover 14 to be the
moisture barrier layer.
[0058] If the cover layer is formed of thermoplastic material, the
cover layer preferably has a flexural modulus of between about 500
psi and about 80,000 psi. More preferably, the flexural modulus is
between about 20,000 psi and about 80,000 psi and most preferably,
the flexural modulus is between about 25,000 psi and about 70,000
psi.
[0059] If the cover layer is formed of thermoset material, the
cover layer preferably has a flexural modulus of between about 500
psi and about 80,000 psi. More preferably, the flexural modulus is
between about 500 psi and about 45,000 psi and most preferably, the
flexural modulus is between about 1000 psi and about 40,000
psi.
[0060] If the cover layer is formed of thermoplastic material, the
cover layer preferably has a Shore D hardness of between about 30
and about 75. More preferably, the Shore D hardness is between
about 40 and about 70, and most preferably, the Shore D hardness is
between about 45 and about 68.
[0061] If the cover layer is formed of thermoset material, the
cover layer preferably has a Shore D material hardness of between
about 30 and about 75. More preferably, the Shore D material
hardness is between about 35 and about 65, and most preferably, the
Shore D material hardness is between about 40 and about 65.
[0062] In another embodiment, the cover layer has a Shore D
material hardness of less than about 60, and preferably less than
about 55.
[0063] The core 12 and cover layer 14, as described above, are
formed according to methods well known by those of ordinary skill
in the art.
[0064] With respect to FIGS. 1 and 2, the cover layer 14 preferably
has between about 200 and about 600 dimples 16. More preferably,
the cover layer 14 has between 300 and 450 dimples 16. Preferably,
the dimples are spherical or circular. Any suitable dimple pattern
may be used on the golf ball 10.
[0065] In accordance with one aspect of the present invention, a
modified dimple pattern is provided to adjust incrementally the
distance that the ball would travel without affecting the other
qualities of the ball. This modified dimples pattern is discussed
below and is disclosed in more detail in co-pending U.S.
application Ser. No. 10/980,203 filed on Nov. 11, 2004, and is
assigned to the same assignee as the present invention. This
co-pending application is incorporated by reference herein in its
entirety.
[0066] As shown generally in FIG. 1, the golf ball 10 has a
spherical surface. The spherical surface is defined by points lying
on at least a 1.68 inch diameter of golf ball 10 for USGA
regulation golf balls. For non-regulation golf balls, the spherical
surface may instead be considered an inner-sphere which is covered
by an outer surface, such as is described in the U.S. Pat. No.
6,290,615 patent ('615 patent), incorporated herein by reference in
its entirety. In the '615 patent, the spherical surface is covered
by a raised tubular lattice. Either concept for the spherical
surface applies to the present invention.
[0067] The plurality of dimples 16 separated by outer un-dimpled or
land surfaces, designated generally as 18, is provided on an outer
surface of golf ball 10. As shown, dimples 16 are circular.
Suitable dimples for use with this invention include dimples of any
shape, including triangular, square, rectangular, pentagon,
hexagon, heptagon, octagon, any other polygons, circular,
hemispherical, elliptical, spherical or any other shape.
[0068] Preferably, dimples 16 are depressions extending into the
cover of golf ball 10. Alternatively, dimples 16 may be raised
projections extending beyond the spherical surface of golf ball 10.
In one preferred embodiment, the golf ball 10 has dimples with at
least three different diameters, more preferably five different
diameters. The dimples preferably cover at least 80% of the surface
of the golf ball and have an overall edge angle of greater than 14
degrees.
[0069] The dimple pattern is preferably arranged into identifiable
sections or regions that form an overall pattern on the surface of
golf ball 10. Preferably, dimples 16 are generally arranged in an
icosahedron pattern, i.e., comprising twenty (20) identifiable
triangular sections. Other suitable patterns include tetrahedron,
octahedron, hexahedron and dodecahedron, among other polyhedrons,
or any other discernable grouping of dimples.
[0070] As used herein, "inter-dimple spacing" is the width of land
area 18 between any two adjacent dimples 16, as shown in FIG. 1. An
inter-dimple spacing may have a circular or other non-polygonal
configuration, such as spacing 20. Preferably, the inter-dimple
spacings between any two adjacent polygonal dimples are
substantially constant. In other words, the sides of adjacent
polygonal dimples are substantially parallel to each other forming
constant spacing between them. The aggregate of all inter-dimple
spacings forms land area 18. Preferably, the surface area of land
area 18 is not more than about 40% of the total surface area of the
spherical surface of golf ball 10. More preferably, less than about
30% of the total surface area of golf ball 10 is land area. Even
more preferably, less than about 20% of the total surface area of
golf ball 10 is land area.
[0071] The present invention is further described herein in terms
of aerodynamic criteria that are defined by the magnitude and
direction of the aerodynamic forces, for the range of Spin Ratios
and Reynolds Numbers that encompass the flight regime for typical
golf ball trajectories. These aerodynamic criteria and forces are
described below.
[0072] The forces acting on a golf ball in flight are enumerated in
Equation 1 and illustrated in FIG. 3: F=F.sub.L+F.sub.D+F.sub.G
(Eq. 1) Where F=total force vector acting on the ball
[0073] F.sub.L=lift force vector
[0074] F.sub.D=drag force vector
[0075] F.sub.G=gravity force vector
[0076] The lift force vector (F.sub.L) acts in a direction dictated
by the cross product of the spin vector and the velocity vector.
The drag force vector (F.sub.D) acts in a direction that is
directly opposite the velocity vector. The magnitudes of the lift
and drag forces of Equation 1 are calculated in Equations 2 and 3,
respectively: F.sub.L=0.5C.sub.L.rho.AV.sup.2 (Eq. 2)
F.sub.D=0.5C.sub.D.rho.AV.sup.2 (Eq. 3) where .rho.=density of air
(slugs/ft.sup.3)
[0077] A=projected area of the ball (ft.sup.2)
((.pi./4)D.sup.2)
[0078] D=ball diameter (ft)
[0079] V=ball speed (ft/s)
[0080] C.sub.L=dimensionless lift coefficient
[0081] C.sub.D=dimensionless drag coefficient
[0082] Lift and drag coefficients are typically used to quantify
the force imparted to a ball in flight and are dependent on air
density, air viscosity, ball speed, and spin rate. The influence of
all these parameters may be captured by two dimensionless
parameters: Spin Ratio (SR) and Reynolds Number (N.sub.Re). Spin
Ratio is the rotational surface speed of the ball divided by ball
speed. Reynolds Number quantifies the ratio of inertial to viscous
forces acting on the golf ball moving through air. SR and N.sub.Re
are calculated in Equations 4 and 5 below: SR=.omega.(D/2)/V (Eq.
4) N.sub.Re=DV.rho./.mu. (Eq. 5) where .omega.=ball rotation rate
(radians/s) (2.pi.(RPS))
[0083] RPS=ball rotation rate (revolution/s)
[0084] V=ball speed (ft/s)
[0085] D=ball diameter (ft)
[0086] .rho.=air density (slugs/ft.sup.3)
[0087] .mu.=absolute viscosity of air (lb/ft-s)
[0088] There are a number of suitable methods for determining the
lift and drag coefficients for a given range of SR and N.sub.Re,
which include the use of indoor test ranges with ballistic screen
technology. U.S. Pat. No. 5,682,230, the entire disclosure of which
is incorporated by reference herein in its entirety, teaches the
use of a series of ballistic screens to acquire lift and drag
coefficients. U.S. Pat. Nos. 6,186,002 and 6,285,445, also
incorporated by reference herein in their entirety, disclose
methods for determining lift and drag coefficients for a given
range of velocities and spin rates using an indoor test range,
wherein the values for C.sub.L and C.sub.D are related to SR and
N.sub.Re for each shot. One skilled in the art of golf ball
aerodynamics testing could readily determine the lift and drag
coefficients through the use of an indoor test range, or
alternatively in a wind tunnel.
[0089] The aerodynamic property of a golf ball can be quantified by
two parameters that account for both lift and drag simultaneously:
(1) the magnitude of aerodynamic force (C.sub.mag), and (2) the
direction of the aerodynamic force (Angle). It has now been
discovered that flight performance improvements are attained when
the dimple pattern and dimple profiles are selected to satisfy
preferred magnitude and direction criteria. The magnitude and angle
of the aerodynamic force are related to the lift and drag
coefficients and, therefore, the magnitude and angle of the
aerodynamic coefficients are used to establish the preferred
criteria. The magnitude and the angle of the aerodynamic
coefficients are defined in Equations 6 and 7 below: C.sub.mag=
(C.sub.L.sup.2+C.sub.D.sup.2) (Eq. 6)
Angle=tan.sup.-1(C.sub.L/C.sub.D) (Eq. 7)
[0090] To ensure consistent flight performance regardless of ball
orientation, the percent deviation of C.sub.mag for each SR and
N.sub.Re plays an important role. The percent deviation of
C.sub.mag may be calculated in accordance with Equation 8, wherein
the ratio of the absolute value of the difference between the
C.sub.mag for any two orientations to the average of the C.sub.mag
for these two orientations is multiplied by 100. Percent deviation
C.sub.mag=|(C.sub.mag1-C.sub.mag2)|/((C.sub.mag1+C.sub.mag2)/2)*100
(Eq. 8) where C.sub.mag1=C.sub.mag for orientation 1, and
[0091] C.sub.mag2=C.sub.mag for orientation 2.
To achieve the consistent flight performance, the percent deviation
is preferably about 6 percent or less. More preferably, the
deviation of C.sub.mag is about 3 percent or less.
[0092] Aerodynamic asymmetry typically arises from parting lines
inherent in the dimple arrangement or from parting lines associated
with the manufacturing process. The percent C.sub.mag deviation is
preferably obtained using C.sub.mag values measured with the axis
of rotation normal to the parting line plane, commonly referred to
as a poles horizontal, "PH" orientation and C.sub.mag values
measured in an orientation orthogonal to PH, commonly referred to
as a pole over pole, "PP" orientation. The maximum aerodynamic
asymmetry is generally measured between the PP and PH
orientation.
[0093] The percent deviation of C.sub.mag as outlined above applies
to the orientations, PH and PP, as well as any other two
orientations. For example, if a particular dimple pattern is used
having a great circle of shallow dimples, different orientations
should be measured. The axis of rotation to be used for measurement
of symmetry in the above example scenario would be normal to the
plane described by the great circle and coincident to the plane of
the great circle.
[0094] It has also been discovered that the C.sub.mag and Angle
criteria for golf balls with a nominal diameter of 1.68 and a
nominal weight of 1.62 ounces may be advantageously scaled to
obtain the similar optimized criteria for golf balls of any size
and weight. Any preferred aerodynamic criteria may be adjusted to
obtain the C.sub.mag and angle for golf balls of any size and
weight in accordance with Equations 9 and 10.
C.sub.mag(ball)=C.sub.mag(nominal)
(sin(Angle.sub.(nominal))*(W.sub.ball/1.62)*(1.68/D.sub.ball).sup.2).sup.-
2+(cos(Angle.sub.(nominal)).sup.2) (Eq. 9)
Angle.sub.(ball)=tan.sup.-1(tan(Angle.sub.(nominal))*(W.sub.ball/1.62)*(1-
.68/D.sub.ball).sup.2) (Eq. 10)
[0095] It is believed that a golf ball made in accordance with the
present invention will share similar characteristics with the golf
balls discussed in U.S. Pat. No. 6,729,976 ('976 patent), the
disclosure of which is incorporated herein in its entirety. Table 1
illustrates the anticipated aerodynamic criteria for a golf ball of
the present invention that results in increased flight distances.
The criteria are specified as low, median, and high C.sub.mag and
Angle for eight specific combinations of SR and N.sub.Re. Golf
balls with C.sub.mag and Angle values between the low and the high
number are preferred. More preferably, the golf balls of the
invention have C.sub.mag and Angle values between the low and the
median numbers delineated in Table 1. The C.sub.mag values
delineated in Table 1 are intended for golf balls that conform to
USGA size and weight regulations. The size and weight of the golf
balls used with the aerodynamic criteria of Table 1 are 1.68 inches
and 44.8 grams, respectively. TABLE-US-00001 TABLE 1 Aerodynamic
Characteristics For Ball Diameter = 1.68'', Ball Weight = 44.8
grams Magnitude Angle N.sub.Re SR Low Median High Low Median High
230000 0.085 0.24 0.26 0.27 30 32 34 207000 0.095 0.25 0.27 0.28 33
35 37 184000 0.106 0.26 0.28 0.29 34 37 38 161000 0.122 0.27 0.29
0.30 36 39 41 138000 0.142 0.29 0.31 0.32 37 40 42 115000 0.170
0.32 0.34 0.35 39 41 43 92000 0.213 0.36 0.39 0.40 40 42 44 69000
0.284 0.40 0.43 0.44 39 41 43
[0096] Other anticipated aerodynamic characteristics of the golf
ball are described and discussed in greater detail in the '976
patent.
[0097] While the above invention has been described with reference
to certain preferred embodiments, it should be kept in mind that
the scope of the present invention is not limited to these
embodiments. One skilled in the art may find variations of these
preferred embodiments which, nevertheless, fall within the spirit
of the present invention, whose scope is defined by the claims set
forth below.
* * * * *