U.S. patent application number 13/022467 was filed with the patent office on 2011-06-02 for golf ball with very low compression and high cor.
This patent application is currently assigned to CALLAWAY GOLF COMPANY. Invention is credited to DAVID M. BARTELS, STEVEN S. OGG.
Application Number | 20110130217 13/022467 |
Document ID | / |
Family ID | 42076223 |
Filed Date | 2011-06-02 |
United States Patent
Application |
20110130217 |
Kind Code |
A1 |
OGG; STEVEN S. ; et
al. |
June 2, 2011 |
GOLF BALL WITH VERY LOW COMPRESSION AND HIGH COR
Abstract
A golf ball having a very low compression and a high COR is
disclosed herein. The core preferably comprises a single
neodymium-catalyzed polybutadiene, and has a diameter ranging from
1.575 inch to 1.62 inch with a PGA compression ranging from 20 to
45. The cover preferably has a thickness ranging from 0.038 inch to
0.045 inch, and a Shore D hardness ranging from 50 to 58. The golf
ball preferably has a coefficient of restitution of at least 0.780,
and a PGA compression ranging from 35 to 50.
Inventors: |
OGG; STEVEN S.; (CARLSBAD,
CA) ; BARTELS; DAVID M.; (CARLSBAD, CA) |
Assignee: |
CALLAWAY GOLF COMPANY
CARLSBAD
CA
|
Family ID: |
42076223 |
Appl. No.: |
13/022467 |
Filed: |
February 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12469470 |
May 20, 2009 |
7918748 |
|
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13022467 |
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61102918 |
Oct 6, 2008 |
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Current U.S.
Class: |
473/372 ;
473/377 |
Current CPC
Class: |
A63B 37/0067 20130101;
C08K 5/098 20130101; A63B 37/0078 20130101; A63B 37/0083 20130101;
A63B 37/0033 20130101; A63B 37/0065 20130101; C08K 5/375 20130101;
A63B 37/005 20130101; C08K 5/375 20130101; A63B 37/0087 20130101;
A63B 37/0031 20130101; C08K 5/098 20130101; A63B 37/0064 20130101;
C08L 9/00 20130101; C08L 9/00 20130101 |
Class at
Publication: |
473/372 ;
473/377 |
International
Class: |
A63B 37/04 20060101
A63B037/04; A63B 37/12 20060101 A63B037/12 |
Claims
1. A two-piece golf ball comprising: a core comprising a single
neodymium-catalyzed polybutadiene, zinc diacrylate ranging from 10
to 20 weight percent of the core, zinc oxide ranging from 10 to 17
weight percent of the core, zinc stearate in an amount of 3 to 8
weight percent of the core and zinc pentachlorophenyl in an amount
of 0.25 to 1.0 weight percent of the core, wherein the core has a
mass ranging from 38 grams to 42 grams, a diameter ranging from
1.575 inch to 1.62 inch, and a PGA compression ranging from 20 to
45; a cover disposed on the core, the cover composed of a material
comprising a very-low modulus ionomer in an amount of 5 to 20
weight percent of the cover material, a first high acid ionomer in
an amount of 20 to 30 weight percent of the cover material, a
second high acid ionomer in an amount of 30 to 50 weight percent of
the cover material, and an additional ionomer in an amount of 5 to
15 weight percent of the cover material, the cover having a
thickness ranging from 0.038 inch to 0.045 inch, the cover material
having a Shore D hardness ranging from 50 to 58; wherein the golf
ball has a diameter of at least 1.68 inches, a mass of at least 45
grams, a coefficient of restitution of at least 0.780, and a PGA
compression ranging from 35 to 50.
2. The two-piece golf ball according to claim 1 wherein the core
has a diameter of 1.59 inches.
3. The two-piece golf ball according to claim 1 wherein the core
has a PGA compression ranging from 20 to 30.
4. The two-piece golf ball according to claim 1 wherein the cover
material has a Shore D hardness of 56.
5. A two-piece golf ball comprising: a solid core comprising a
single neodymium-catalyzed polybutadiene, wherein the core has a
mass ranging from 38 grams to 42 grams, a diameter ranging from
1.575 inch to 1.62 inch, and a PGA compression ranging from 20 to
45; a cover disposed on the core, the cover composed of a material
comprising at least four different ionomers, the cover having a
thickness ranging from 0.038 inch to 0.045 inch, the cover material
having a Shore D hardness ranging from 50 to 58; wherein the golf
ball has a diameter of at least 1.68 inches, a mass of at least 45
grams, a coefficient of restitution of at least 0.780, and a PGA
compression ranging from 35 to 50.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The Present Application is a continuation application of
U.S. patent application Ser. No. 12/469470, filed on May 20, 2009,
which claims priority to U.S. Provisional Patent Application No.
61/102918, filed on Oct. 6, 2008, now abandoned.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to a golf ball. More
specifically, the present invention relates to a golf ball with a
low PGA compression and a high coefficient of restitution.
[0005] 2. Description of the Related Art
[0006] The prior art discloses various two-piece golf balls.
[0007] Sullivan et al., U.S. Pat. No. 4,911,451, for a Golf Ball
Cover Of Neutralized Poly(ethylene-acrylic acid) Copolymer,
discloses in Table One a golf ball having a compression of below 50
and a cover composed of ionomers having various Shore D hardness
values ranging from 50 to 61.
[0008] Sullivan, U.S. Pat. No. 4,986,545, for a Golf Ball discloses
a golf ball having a Rhiele compression below 50 and a cover having
Shore C values as low as 82.
[0009] Egashira et al., U.S. Pat. No. 5,252,652, for a Solid Golf
Ball, discloses the use of a zinc pentachlorothiophenol in a core
of a golf ball.
[0010] Pasqua, U.S. Pat. No. 5,721,304, for a Golf Ball
Composition, discloses a golf ball with a core having a low
compression and the core comprising calcium oxide.
[0011] Sullivan, et al., U.S. Pat. No. 5,588,924, for a Golf Ball
discloses a golf ball having a PGA compression below 70 and a COR
ranging from 0.780 to 0.825.
[0012] Sullivan et al., U.S. Pat. No. 6,142,886, for a Golf Ball
And Method Of Manufacture discloses a golf ball having a PGA
compression below 70, a cover Shore D hardness of 57, and a COR as
high as 0.794.
[0013] Tzivanis et al., U.S. Pat. No. 652,870, for a Golf Ball,
discloses a golf ball having a core compression less than 50, a
cover Shore D hardness of 55 or less, and a COR greater than
0.80.
[0014] The prior art fails to disclose a golf ball with a very low
PGA compression and a high coefficient of restitution.
BRIEF SUMMARY OF THE INVENTION
[0015] The present invention provides a golf ball with a very low
PGA compression and a high coefficient of restitution. The present
invention is able to achieve these results by providing a core with
a PGA compression less than 45, a cover with a Shore D hardness
less than 60 and a thickness ranging from 0.035 to 0.050 inch, and
a ball coefficient of restitution greater than 0.780.
[0016] One aspect of the present invention is a golf ball including
a core and a cover. The core includes a single neodymium-catalyzed
polybutadiene, zinc diacrylate ranging from 10 to 20 weight percent
of the core, zinc oxide ranging from 10 to 17 weight percent of the
core, zinc stearate in an amount of 3 to 8 weight percent of the
core and zinc pentachlorothiophenol in an amount of 0.25 to 1.0
weight percent of the core. The core has a mass ranging from 38
grams to 42 grams, a diameter ranging from 1.575 inch to 1.62 inch,
and a PGA compression ranging from 20 to 45. The cover is disposed
on the core and is composed of a material comprising a blend of
ionomers. The cover has a thickness ranging from 0.038 inch to
0.045 inch. The cover material has a Shore D hardness ranging from
50 to 58. The golf ball has a diameter of at least 1.68 inches, a
mass of at least 45 grams, a coefficient of restitution of at least
0.780, and a PGA compression ranging from 35 to 50.
[0017] Another aspect of the present invention is a golf ball
having a solid core comprising a single neodymium-catalyzed
polybutadiene. The core has a mass ranging from 38 grams to 42
grams, a diameter ranging from 1.575 inch to 1.62 inch, and a PGA
compression ranging from 20 to 45. The golf ball also has a cover
disposed on the core. The cover is composed of a material
comprising a blend of ionomers. The cover has a thickness ranging
from 0.038 inch to 0.045 inch. The cover material has a Shore D
hardness ranging from 50 to 58. The golf ball has a diameter of at
least 1.68 inches, a mass of at least 45 grams, a coefficient of
restitution of at least 0.780, and a PGA compression ranging from
35 to 50.
[0018] Yet another aspect of the present invention is a golf ball a
having a diameter of at least 1.68 inches, a mass of at least 45
grams, a coefficient of restitution of at least 0.780, and a PGA
compression ranging from 35 to 50. The golf ball has a solid core
having a mass ranging from 38 grams to 42 grams, a diameter ranging
from 1.575 inch to 1.62 inch, and a PGA compression ranging from 20
to 35. The golf ball also has a cover disposed on the core. The
cover is composed of a material comprising a blend of ionomers. The
cover has a thickness ranging from 0.035 inch to 0.050 inch. The
cover material has a Shore D hardness ranging from 50 to 58.
[0019] Yet another aspect of the present invention is a golf ball
having a cover composed of a material comprising a blend of
ionomers and having a Shore D hardness ranging from 50 to 58. The
cover is disposed on a solid core having a mass ranging from 38
grams to 42 grams and a PGA compression ranging from 20 to 30. The
golf ball has a diameter of at least 1.68 inches, a mass of at
least 45 grams, a coefficient of restitution of at least 0.790, and
a PGA compression ranging from 35 to 50.
[0020] Having briefly described the present invention, the above
and further objects, features and advantages thereof will be
recognized by those skilled in the pertinent art from the following
detailed description of the invention when taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0021] FIG. 1 is a cross-sectional view of a golf ball.
[0022] FIG. 2 is a graph of golf ball compression (utilizing an
INSTRON machine at a 200 pound load) vs. Coefficient of Restitution
at 125 feet per second.
DETAILED DESCRIPTION OF THE INVENTION
[0023] As shown in FIG. 1, a golf ball 20 includes a core 25 and a
cover 30. The core 25 is a solid core and cover 30 is disposed on
the core 25. Preferably, the core 25 is compression molded into a
spherical shape and the cover 30 is injection molded over the core
25.
[0024] The golf ball 20 preferably has a diameter of at least 1.68
inches and a mass of approximately 45 grams. The golf ball 20
preferably has a coefficient of restitution ("COR") of at least
0.780, more preferably at least 0.790, and most preferably at least
0.8. The golf ball 20 preferably has an aerodynamic surface pattern
such as disclosed in U.S. patent number, which is hereby
incorporated by reference.
[0025] The core 25 is preferably composed of a polybutadiene-based
mixture generally comprising a single neodymium-catalyzed
polybutadiene, zinc oxide, zinc stearate, peroxide and zinc
pentachlorothiophenol. The polybutadiene is preferably present in
an amount ranging from 55 to 75 weight percent of the core, more
preferably from 60 to 70 weight percent of the core, and most
preferably approximately 65 weight percent of the core. The zinc
oxide is preferably present in an amount ranging from 5 to 20
weight percent of the core, more preferably ranging from 10 to 17
weight percent of the core, and most preferably 14 weight percent
of the core. The zinc stearate is preferably present in an amount
ranging from 1 to 15 weight percent of the core, more preferably
from 3 to 8 weight percent of the core and most preferably 5 weight
percent of the core. The zinc pentachlorothiophenol is preferably
present in an amount ranging from 0.25 to 1.0 weight percent of the
core, more preferably from 0.5 to 0.75, and most preferably 0.68
weight percent of the core.
[0026] The core 25 preferably has a diameter ranging from 1.575 to
1.62 inches, more preferably ranging from 1.58 to 1.60 inches, and
mot preferably 1.595 inches. The core 25 preferably has a PGA
compression below 50, more preferably below 45, and most preferably
ranging from 20 to 35. The core 25 preferably has a mass ranging
from 38 grams to 42 grams, most preferably approximately 40
grams.
[0027] The cover 30 is preferably composed of a material that has a
Shore D hardness ranging from 50 to 58 and a thickness ranging from
0.035 to 0.050 inch. Cover Shore D hardness and thickness are the
two primary contributions from the cover 30 in providing a golf
ball 20 that can achieve a very low compression (softness) and a
high COR.
[0028] The cover 30 is preferably composed of a blend of ionomers.
One preferred embodiment comprises a SURLYN 8320, a SURLYN 8945, a
SURLYN 9945, a SURLYN 8940 and a masterbatch. The SURLYN 8320 is
preferably present in an amount ranging from 5 to 20 weight percent
of the cover, more preferably 10 to 15 weight percent, and most
preferably 13 weight percent. The SURLYN 8945 is preferably present
in an amount ranging from 15 to 35 weight percent of the cover,
more preferably 20 to 30 weight percent, and most preferably 26
weight percent. The SURLYN 9945 is preferably present in an amount
ranging from 30 to 50 weight percent of the cover, more preferably
35 to 45 weight percent, and most preferably 41 weight percent. The
SURLYN 8940 is preferably present in an amount ranging from 5 to 15
weight percent of the cover, more preferably 7 to 12 weight
percent, and most preferably 10 weight percent.
[0029] SURLYN 8320, from DuPont, is a very-low modulus
ethylene/methacrylic acid copolymer with partial neutralization of
the acid groups with sodium ions. SURLYN 8945, also from DuPont, is
a high acid ethylene/methacrylic acid copolymer with partial
neutralization of the acid groups with sodium ions. SURLYN 9945,
also from DuPont, is a high acid ethylene/methacrylic acid
copolymer with partial neutralization of the acid groups with zinc
ions. SURLYN 8940, also from DuPont, is an ethylene/methacrylic
acid copolymer with partial neutralization of the acid groups with
sodium ions.
[0030] The compositions of the cover 30 may include other ionomers
from DuPont (E. I. DuPont de Nemours & Company), sold under the
SURLYN brand, and ionomers sold by Exxon Corporation under the
ESCOR or IOTEK brands, or blends thereof. Examples of other
compositions which may be used as the material of the cover 30 are
set forth in detail in U.S. Pat. No. 5,688,869, which is
incorporated herein by reference.
[0031] The high acid ionomers which may be suitable for use in
formulating the cover material compositions are ionic copolymers
which are the metal (such as sodium, zinc, magnesium, etc.) salts
of the reaction product of an olefin having from about 2 to 8
carbon atoms and an unsaturated monocarboxylic acid having from
about 3 to 8 carbon atoms. Preferably, the ionomeric resins are
copolymers of ethylene and either acrylic or methacrylic acid. In
some circumstances, an additional comonomer such as an acrylate
ester (for example, iso- or n-butylacrylate, etc.) can also be
included to produce a softer terpolymer. The carboxylic acid groups
of the copolymer are partially neutralized (for example,
approximately 10-100%, preferably 30-70%) by the metal ions. Each
of the high acid ionomer resins which may be included in the inner
layer cover compositions of the invention contains greater than 16%
by weight of a carboxylic acid, preferably from about 17% to about
25% by weight of a carboxylic acid, more preferably from about
18.5% to about 21.5% by weight of a carboxylic acid. Examples of
the high acid methacrylic acid based ionomers found suitable for
use in accordance with this invention include, but are not limited
to, SURLYN 8220 and 8240 (both formerly known as forms of SURLYN
AD-8422), SURLYN 9220 (zinc cation), SURLYN SEP-503-1 (zinc
cation), and SURLYN SEP-503-2 (magnesium cation). According to
DuPont, all of these ionomers contain from about 18.5 to about
21.5% by weight methacrylic acid. Examples of the high acid acrylic
acid based ionomers suitable for use in the present invention also
include, but are not limited to, the high acid ethylene acrylic
acid ionomers produced by Exxon such as Ex 1001, 1002, 959, 960,
989, 990, 1003, 1004, 993, and 994. In this regard, ESCOR or IOTEK
959 is a sodium ion neutralized ethylene-acrylic neutralized
ethylene-acrylic acid copolymer. According to Exxon, IOTEKS 959 and
960 contain from about 19.0 to about 21.0% by weight acrylic acid
with approximately 30 to about 70 percent of the acid groups
neutralized with sodium and zinc ions, respectively.
[0032] The base copolymer is made up of greater than 16% by weight
of an alpha, beta-unsaturated carboxylic acid and an alpha-olefin.
Optionally, a softening comonomer can be included in the copolymer.
Generally, the alpha-olefin has from 2 to 10 carbon atoms and is
preferably ethylene, and the unsaturated carboxylic acid is a
carboxylic acid having from about 3 to 8 carbons. Examples of such
acids include acrylic acid, methacrylic acid, ethacrylic acid,
chloroacrylic acid, crotonic acid, maleic acid, fumaric acid, and
itaconic acid, with acrylic acid being preferred.
[0033] The softening comonomer that can be optionally included in
the cover 30 of the golf ball 20 may be selected from the group
consisting of vinyl esters of aliphatic carboxylic acids wherein
the acids have 2 to 10 carbon atoms, vinyl ethers wherein the alkyl
groups contain 1 to 10 carbon atoms, and alkyl acrylates or
methacrylates wherein the alkyl group contains 1 to 10 carbon
atoms. Suitable softening comonomers include vinyl acetate, methyl
acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate,
butyl acrylate, butyl methacrylate, or the like.
[0034] Consequently, examples of a number of copolymers suitable
for use to produce the high acid ionomers included in the present
invention include, but are not limited to, high acid embodiments of
an ethylene/acrylic acid copolymer, an ethylene/methacrylic acid
copolymer, an ethylene/itaconic acid copolymer, an ethylene/maleic
acid copolymer, an ethylene/methacrylic acid/vinyl acetate
copolymer, an ethylene/acrylic acid/vinyl alcohol copolymer, etc.
The base copolymer broadly contains greater than 16% by weight
unsaturated carboxylic acid, from about 39 to about 83% by weight
ethylene and from 0 to about 40% by weight of a softening
comonomer. Preferably, the copolymer contains about 20% by weight
unsaturated carboxylic acid and about 80% by weight ethylene. Most
preferably, the copolymer contains about 20% acrylic acid with the
remainder being ethylene.
[0035] The cover material compositions may include the low acid
ionomers such as those developed and sold by E. I. DuPont de
Nemours & Company under the SURLYN and by Exxon Corporation
under the brands ESCOR and IOTEK, ionomers made in-situ, or blends
thereof.
[0036] In determining PGA compression using the 0 to 200 scale, a
standard force is applied to the external surface of the ball. A
ball that exhibits no deflection (0.0 inches of deflection) is
rated 200 and a ball that deflects 0.2 inches is rated 0. Every
change of 0.001 inch in deflection represents a 1 point drop in
compression value. Consequently, a ball that deflects 0.1 inches
(100.times.0.001 inches) has a PGA compression value of 100 and a
ball that deflects 0.110 inches (110.times.0.001 inches) has a PGA
compression value of 90.
[0037] In order to assist in the determination of PGA compression,
several devices have been employed in the art. For example, PGA
compression is determined by a golf ball compression tester
fashioned in the form of a press with an upper and lower anvil. The
upper anvil is at rest against a 200 pound (lbs) die spring, and
the lower anvil is movable through 0.300 inches by means of a crank
mechanism. In the open position, the gap between the anvils is
1.780 inches, allowing a clearance of 0.200 inches for insertion of
the ball. As the lower anvil is raised by the crank mechanism, it
compresses the ball against the upper anvil, with such compression
occurring during the last 0.200 inches of lower anvil stroke. The
golf ball then loads the upper anvil, which in turn loads the die
spring. The equilibrium point of the upper anvil is measured by a
dial micrometer. When the upper anvil is deflected by the golf ball
more than 0.100 in (a lesser extent of deflection is simply
regarded as zero compression), the reading on the micrometer dial
is referred to as the compression of the ball. In practice,
tournament quality golf balls have PGA compression ratings around
80 to 100, which means that the upper anvil was deflected a total
of 0.120 to 0.100 inches. When golf ball components (i.e., centers,
cores, mantled core, etc.) with diameters smaller than 1.680 inches
are utilized, metallic shims are included such that the combined
diameter of the shims and the component is 1.680 inches.
[0038] Determining golf ball compression can also be carried out
via a compression tester sold by OK Automation, formerly, Atti
Engineering Corporation. This golf ball compression tester is
calibrated against a calibration spring provided by OK Automation.
The compression value obtained by such a tester (referred to as
Atti compression) relates to an arbitrary value expressed by a
number that may range from 0 to 100 (a value of 200 can also be
measured by two revolutions of a dial indicator, which is described
below). Atti compression values that are obtained define the
deflection that a golf ball undergoes when subjected to compressive
loading. The golf ball compression tester consists of a lower
movable platform and an upper movable spring-loaded anvil. A dial
indicator of the compression tester is mounted such that it
measures the upward movement of the spring-loaded anvil. A golf
ball to be tested is placed in the lower platform, which is then
raised a fixed distance. The upper portion of the golf ball comes
in contact with and exerts a pressure on the spring-loaded anvil,
forcing the anvil upward against a spring.
[0039] Alternative devices, apparatuses or testers have also been
employed to determine golf ball compression. For example, a
modified Riehle compression device (Riehle Bros. Testing Machine
Company) can be used to evaluate the compression of various golf
ball components (i.e., cores, mantle cover balls, finished balls,
etc.). The modified Riehle compression device determines golf ball
deformation in thousandths of an inch via a load designed to
emulate the 200 lbs spring constant of other golf ball compression
testers such as those described above. With a modified Riehle
compression device, a Riehle compression value of 61 corresponds to
a load deflection of 0.061 in. Furthermore, additional golf ball
compression devices, apparatuses or testers may also be utilized to
monitor and evaluate ball compression. Such devices, apparatuses or
testers include a Whitney tester and Instron.TM. device, which can
correlate or correspond to, for example, PGA or Atti compression
values.
[0040] Additionally, an approximate relationship between Riehle
compression and PGA compression exists for balls of the same size.
It has been determined by Applicant that Riehle compression
corresponds to PGA compression by the general formula. PGA
compression=160--Riehle compression. Consequently, 80 Riehle
compression corresponds to 80 PGA compression, 70 Riehle
compression corresponds to 90 PGA compression, and 60 Riehle
compression corresponds to 100 PGA compression. For reporting
purposes, Applicant's compression values are usually measured as
Riehle compression and converted to PGA compression.
[0041] Compression was measured using an Instron.TM. device,
namely, model 5544. Compression of golf ball components were
measured based on the deflection (in inches) caused by a 200 lbs
load applied during a load control mode with a rate of 15
kilopounds per second (kips s.sup.-1), an approach speed of 20 in
per minute and a preload of 0.2 pound-force (lbf) (in addition to
device system compliance).
[0042] The resilience or coefficient of restitution (COR) of a golf
ball is the constant "e," which is the ratio of the relative
velocity of an elastic sphere after direct impact to that before
impact. As a result, the COR ("e") can vary from 0 to 1, with 1
being equivalent to a perfectly or completely elastic collision and
0 being equivalent to a perfectly or completely inelastic
collision.
[0043] COR, along with additional factors such as club head speed,
club head mass, ball weight, ball size and density, spin rate,
angle of trajectory and surface configuration (i.e., dimple pattern
and area of dimple coverage) as well as environmental conditions
(e.g. temperature, moisture, atmospheric pressure, wind, etc.)
generally determine the distance a ball will travel when hit. Along
this line, the distance a golf ball will travel under controlled
environmental conditions is a function of the speed and mass of the
club and size, density and resilience (COR) of the ball and other
factors. The initial velocity of the club, the mass of the club and
the angle of the ball's departure are essentially provided by the
golfer upon striking. Since club head, club head mass, the angle of
trajectory and environmental conditions are not determinants
controllable by golf ball producers and the ball size and weight
are set by the U.S.G.A., these are not factors of concern among
golf ball manufacturers. The factors or determinants of interest
with respect to improved distance are generally the coefficient of
restitution (COR) and the surface configuration (aerodynamic
surface pattern, land area, etc.) of the ball.
[0044] The coefficient of restitution is the ratio of the outgoing
velocity to the incoming velocity. In the examples of this
application, the coefficient of restitution of a golf ball was
measured by propelling a ball horizontally at a speed of 125.+-.15
feet per second (fps) and corrected to 125 fps against a generally
vertical, hard, flat steel plate and measuring the ball's incoming
and outgoing velocity electronically. Speeds were measured with a
pair of Oehler Mark 55 ballistic screens available from Oehler
Research, Inc., P.O. Box 9135, Austin, Tex. 78766, which provide a
timing pulse when an object passes through them. The screens were
separated by 36'' and are located 25.25'' and 61.25'' from the
rebound wall. The ball speed was measured by timing the pulses from
screen 1 to screen 2 on the way into the rebound wall (as the
average speed of the ball over 36''), and then the exit speed was
timed from screen 2 to screen 1 over the same distance. The rebound
wall was tilted 2.degree. from a vertical plane to allow the ball
to rebound slightly downward in order to miss the edge of the
cannon that fired it. The rebound wall is solid steel 2.0 inches
thick.
[0045] As indicated above, the incoming speed should be 125.+-.5
fps but corrected to 125 fps. The correlation between COR and
forward or incoming speed has been studied and a correction has
been made over the .+-.5 fps range so that the COR is reported as
if the ball had an incoming speed of exactly 125.0 fps.
[0046] The coefficient of restitution must be carefully controlled
in all commercial golf balls if the ball is to be within the
specifications regulated by the United States Golf Association
(U.S.G.A.). As mentioned to some degree above, the U.S.G.A.
standards indicate that a "regulation" ball cannot have an initial
velocity exceeding 255 feet per second in an atmosphere of
75.degree. F. when tested on a U.S.G.A. machine. Since the
coefficient of restitution of a ball is related to the ball's
initial velocity, it is highly desirable to produce a ball having
sufficiently high coefficient of restitution to closely approach
the U.S.G.A. limit on initial velocity, while having an ample
degree of softness (i.e., hardness) to produce enhanced playability
(i.e., spin, etc.).
[0047] As used herein, "Shore D hardness" of a cover 30 is measured
generally in accordance with ASTM D-2240, except the measurements
are made on the curved surface of a molded cover 30, rather than on
a plaque. Furthermore, the Shore D hardness of the cover 30 is
measured while the cover 30 remains over the core 25.
[0048] As shown in FIG. 2, and in Table One below, the golf ball of
the present invention has a much lower compression (utilizing an
INSTRON machine with a 200 pound load) and a much higher COR than
commercially available golf balls.
TABLE-US-00001 TABLE ONE Ball Compression COR (125 ft/sec) Example
1 53 0.80 NIKE Precision Power Distance Soft 73 0.78 WILSON STAFF
50 62 0.76 PINNACLE RIBBON 84 0.78 BIRDGESTONE TREO SOFT 78 0.78
SRIXON soft feel 78 0.78 PRECEPT XP3 79 0.78 TOP-FLITE D2 DISTANCE
73 0.79
[0049] From the foregoing it is believed that those skilled in the
pertinent art will recognize the meritorious advancement of this
invention and will readily understand that while the present
invention has been described in association with a preferred
embodiment thereof, and other embodiments illustrated in the
accompanying drawings, numerous changes, modifications and
substitutions of equivalents may be made therein without departing
from the spirit and scope of this invention which is intended to be
unlimited by the foregoing except as may appear in the following
appended claims. Therefore, the embodiments of the invention in
which an exclusive property or privilege is claimed are defined in
the following appended claims.
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