Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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GAME BALL WITH A URETHANE GUM RUBBER SURFACE
Field of the Invention
The present invention relates generally to game balls and more
particularly is directed to game balls having a urethane gum rubber surface
which
provides for improved durability of the ball.
Background of the Invention
Traditionally, game balls are made with an outer cover of leather.
With a sport such as basketball, when played exclusively in a gymnasium on a
finished wooden floor, or football, which is played on a grass covered field,
the
durability of a leather covered game ball is not a critical factor. However,
when
these and other sports are played on a paved surface such as is present in
playgrounds, residential driveways, parking lots, or even in the street, the
leather
cover of the game ball wears excessively from contact with'the abrasive paved
playing surface.
The game ball industry has developed balls featuring covers formed
from molded materials such as rubber or polyvinyl chloride (PVC) to improve
ball
wear. In addition, synthetic leather covers have been developed which closely
simulate the appearance and feel of a natural leather cover, while providing
greater durability than could be provided by natural leather.
Game balls which have covers made of molded natural rubber or
PVC are often formed with a pebbled surface texture resembling a pebble-
grained
leather. When such balls are used on a paved playing surface the pebble
texture
tends to wear away leaving the surface of the ball smooth, slick and difficult
for
the player to handle. A small amount of dust on either the hands of the player
or on the surface of the worn ball may dramatically increase the slipperiness
of
the ball. Likewise, perspiration on the hands of the player or water on the
surface of the worn ball increase the slipperiness of the ball as well.
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Summary of the Invention
An object of the present invention is to provide a game ball with
improved wear resistance.
Another object of the present invention is to provide a game ball
with improved wear resistance and with play performance characteristics which
are similar to the play performance characteristics of a game ball with a
natural
rubber cover.
These and related objects are achieved by providing a game ball with
a cover formed of a urethane gum rubber composition. The urethane gum rubber
is a raw rubber, based on polyurethane, which is subjected to a cross-linking
process (vulcanization) during and after forming operations. The cured
urethane
rubber composition has a cross-linked structure similar to that of vulcanized
natural rubber, but exhibits abrasion resistance many times greater than
natural
rubber compounds. When used in the cover of a game ball the ball exhibits very
high durability with a high resistance to abrasion and wear as experienced in
normal use.
The cover of the ball is formed by molding the urethane gum rubber
in place over the substructure of the ball and subjecting the molded ball to
conditions to promote the cure and cross-linking of the urethane gum rubber.
The compositions of the cover optionally include other materials, such as
fillers,
coloring pigments or dyes, cross-linking promoters, processing aids, and cure
accelerators.
A urethane gum rubber cover may be applied to any game ball.
However, such a cover has particular utility when used in connection with
basketballs, footballs, softballs, baseballs, and generic play balls for use
on paved
surfaces. It is envisioned that other game balls may advantageously use the
urethane gum rubber compositions for their respective covers,
The invention accordingly comprises the several steps and the
relation of one or more of such steps with respect to the others and the
article
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possessing the features, properties, and relation of elements as exemplified
in the
following detail disclosure.
Description of the Drawings
Figure 1 is a sectional view of the cover of a game ball made
according to the invention.
Figure 2 is a sectional view of the cover of a game ball made
according to a second embodiment of the invention in which the cover has
multiple layers.
- Figure 3 is a view of a basketball, partially broken away and partially
in section, according to the second embodiment of the invention which features
a multiple layer covering.
Detailed Description of the Invention
For clarity of description and ease of understanding, the invention
will be described in connection with basketballs. It will be understood that
other
game balls including balls with various core structures which may include
solid
cores, hollow cores, wound cores, air-filled bladders and even air filled
balls
which have no bladder can advantageously employ the features of the present
invention. Furthermore, in the figures similar structures in the several
drawings
will be identified with the same numbers.
With reference to Figure 1, the basketball 10 includes a bladder 12
for holding air, a reinforcing layer of monofilament windings 14 which wrap
around the bladder 12 and help the ball maintain its shape, and a cover layer
16
of a urethane gum rubber which surrounds and encloses the winding wrapped
bladder. The bladder 12 is typically made of, for example, a butyl rubber
composition including halo-butyl rubber (chloro or bromo-butyl rubber), or
other
similar resilient, stretchable material for holding air. The bladder 12 has a
generally spherical shape and is equipped with a valve or other structure (not
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shown) for permitting air under pressure to be introduced to the interior of
the
bladder 12 for inflation and pressurization.
The wound reinforcing layer 14 is typically formed of monofilaments
of polyester and/or nylon and is wrapped around the bladder 12 in either a pre
y determined pattern or a random fashion to help the ball 10 retain spherical
shape
under typically inflation pressure and under the stresses of use. The windings
14
are coated with an adhesive which allows them to adhere to the bladder 12 and
also to each other to ease the winding process. The bladder 12 is ordinarily
fully
or partially pressurized to maintain a spherical shape while the wrappings are
applied. In addition, the bladder 12 may be cooled to stiffen and stabilize
the
material of the bladder to further ease winding of the reinforcing layer.
The cover 16 forms the exterior surface of the ball. The cover 16
in the present invention is formed of a urethane gum rubber composition which
is molded in place over the monofilament wrapped bladder and cured, preferably
in a spherical mold with the application of heat and pressure to promote the
cure
and cross-linking of the urethane cover material.
In Figure 2 a second embodiment of the invention is shown with the
ball 20 featuring a bladder 12 covered by a layer of windings 14 over which a
multiple layer cover 22 is formed. The multiple layer cover 22 features an
inner
or first layer 24 which surrounds and encloses the bladder 12 and wound layer
14, and an outer or second cover layer 26 which surrounds and encloses the
first
cover layer 24 and defines the ball exterior surface 18. The first cover layer
24
is formed of a natural rubber, while the outer cover layer 26 is formed of a
urethane gum rubber composition.
In Figure 3 a basketball with a multiple layer cover is shown partially
cut away. The ball 30 includes a bladder 12 covered with a layer of windings
14
which is enclosed by an inner cover layer 24 of a natural rubber composition,
the
whole being enclosed and enveloped within an outer cover layer 26 of urethane
gum rubber.
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The use of a multiple layer cover combining a layer of natural rubber
with a layer of urethane gum rubber in the cover reduces the total amount of
urethane gum rubber required in a ball of the present invention. At present
market prices, urethane gum rubber materials are quite expensive. Creating a
cover with a reduced amount of urethane gum rubber is of particular interest
in
controlling the cost of a game ball. By reducing the thickness of the urethane
gum rubber used in the cover of the ball and adding a layer of natural rubber,
the
desirable durability and long-wearing properties are retained while the total
expense of the materials from which the ball is made are reduced. The urethane
- 10 gum rubber used in the cover of the invention is a raw rubber material
based on
polyurethane which can be processed using conventional machinery intended for
processing natural rubber compounds. Like a natural rubber composition, the
urethane gum rubber is shaped and then subjected to a cross-linking process
(vulcanization) .
The cover of the ball of the present invention may be molded to
include a textured outer surface 18 for improving the grip and feel of the
ball.
It will be appreciated that the surface 1 S of a basketball can be molded with
a
surface texture simulating the pebbled texture of pebble-grained leather or
any
other texture as desired. Other surface detail including the manufacturer's
name,
trademarks, model numbers, inflation instructions, ball detailing such as
simulated
lacing or stitching, and graphics can also be molded into the surface of the
ball.
In terms of physical properties, once a urethane gum rubber is cross-
linked and cured it exhibits high tear resistance, high elongation at break,
high
rebound resilience, and depending on the composition, a Shore A hardness of
about 4.5 - 85. The cross-linked urethane gum rubber also has excellent
resistance to degradation from exposure to ultra-violet light, oxygen, and
ozone.
What is of greatest interest in the present invention is the high degree of
abrasion
resistance offered by the urethane gum rubber.
One particular urethane gum rubber highly suitable for use in this
invention is commercially available from Rhein Chemie Corporation, Trenton,
New
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Jersey, and is commercially available as UREPAN 50EL06G. This particular
urethane material is the poly-addition product made from diphenylmethane
diisocyanate and a C 4 polyether. According to the manufacturer, UREPAN
50EL06G may be processed using standard rubber industry processing
techniques and equipment without any restrictions. It will be appreciated by
the
practitioner of skill in the art that other UREPAN materials and similar
materials
available from other chemical manufacturers, may be selected according to
their
physical properties for the desired game ball application. The urethane gum
rubber of the present invention is mixed with other materials for processing
into
_ 10 a game ball cover. In general, these materials include vulcanizing agents
for
promoting the cross-linking of the urethane gum rubber and various other
components including fillers, coloring materials, and materials to improve
processing.
The vulcanizing agents act as cross-linking agents and as cure
accelerators. The use of sulfur plus mercapto accelerators has proven to be
favorable for use as vulcanizing agents in urethane gum rubber resin
compositions. Zinc stearate may be used as a coactivator. Therefore,
combinations of sulfur, mercaptobenzothiazole (MBT), dibenzothiazyl disulphide
(MBTS), complexes of zinc chloride and dibenzothiazyl disulphide (RHENOCURE
AUR available from Rhein Chemie Corp., Trenton, New Jersey) and mixtures
thereof may be used as cross-linking agents and cure accelerators in urethane
gum rubber resin compositions.
A general formula setting forth the amounts of. various components
and additives suitable for making a game ball cover is presented in Table 1
below.
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TABLE 1
URETHANE GUM RUBBER COMPOSITION
General Formula
Ingredient Parts by Weight
urethane 50 - 100
sulfur 1 - 4
- reinforcing filler 5 - 50
zinc stearate 0.25 - 2.0
curing agent 0.5 - 2.0
cure accelerators) 1.0 - 6.0
coloring pigments) 0 - 5
processing promoter 1.0 - 5.0
dispersing and tackifying 0.5 - 3.0
resin
The process of manufacturing a game ball of the present invention
is generally similar to that used in manufacturing a game ball having a
natural
rubber cover. In the case of a game ball having a cover 16 comprising a single
layer of urethane gum rubber, a bladder 12 of butyl rubber is manufactured by
conventional methods, such as by parison blow-molding or by blow-molding two
parallel sheets of uncured butyl rubber in a spherical mold. Typically, a
valve is
molded into the bladder 12 when the bladder is formed.
The bladder 12 is inflated to an appropriate pressure to stabilize its
spherical shape and monofilaments of polyester and/or nylon are then wrapped
around the bladder 12 to create the winding layer 14. To cause the windings to
adhere to the bladder and to each other, and thus simplify the winding
process,
the filaments are lightly coated with an adhesive (not shown) compatible with
the
materials of the bladder 12, the windings, and the cover 16. As the
monofilaments are wrapped in place around the bladder 12 the adhesive holds
them in place and prevents them from unraveling.
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A batch of urethane gum rubber is prepared having a general
composition as set forth in Table 1. The components of the composition are
mixed using standard rubber processing equipment, such as a Banbury mixer, to
thoroughly combine the ingredients. A pliable, moldable dough-like mass is
produced which can subsequently be molded and cured. For the cover of a ball,
such as a basketball, the dough-like mass of uncured urethane gum rubber is
formed into a sheet such as by passing it through the rollers of a calendaring
machine. The uncured sheet is cut to an appropriate size and shape for lining
the
interior surface of a hemispherical ball mold. For a basketball, the sheet can
be
cut into double-tapered panels or simple strips, for example, and laid in each
half
of the ball mold to completely cover the mold surface. A mold may feature a
vacuum system to hold the panels in place in the mold or, alternately, a light
adhesive may be used to hold the panels in place. Typically, the panels or
pieces
of uncured sheet of urethane gum rubber are overlapped at their edges to
ensure
the structural integrity of the molded cover. Alternatively, the urethane gum
rubber can be preformed into a hollow hemispherical shape ending at an equator
line. Two urethane hemispheres are then placed in opposition within the mold
with their equator lines facing.
The interior surface of the ball mold may be engraved or tooled to
impart a surface texture to the cover of the finished ball. Also, simulated
stitching, lacing, seams or panel lines may be added to the mold surface,
along
with manufacturers' names, model names and numbers, autographs of sport
figures and graphic designs, for molding into the ball cover.
A bladder 12 and winding layer 14 subunit is placed into the mold
lined with urethane cover material and the mold is closed around the subunit.
The bladder is inflated to force the subunit into full contact with the
urethane
material lining the interior of the mold cavity. Heat and pressure is applied
to the
mold to cause the raw urethane gum rubber to flow into and around the
monofilamenfis of the winding layer and to assume the shape and texture
imparted by the tooled mold inner surface. The heat and pressure also causes
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the urethane material to cross-link and cure, firmly bonding the cover and
subunit
into a unitary basketball and permanently creating the textured exterior
surface
of the ball. At the end of the time necessary to attain the desired level of
cross-
linking, the completed ball is removed from the mold and allowed to cool. Any
flash or mold marks left on the cover of the finished ball may be buffed out
or
otherwise removed. The ball may then be decorated through the application of
paint, decals, and other graphics or decorations.
The game ball 20 of the present invention which possesses a multi-
layer cover 22 may be made according to a process similar to that described
above. A layer of raw urethane gum rubber sheet is placed in contact with the
mold halves. A layer of raw natural rubber sheet is placed in contact with the
urethane gum rubber layer. The bladder and winding layer subunit is placed
within the mold, the mold is closed and the bladder inflated. Heat and
pressure
is applied and both the natural rubber and urethane gum rubber flow and are
cured within the mold. Naturally, one or both of the natural and urethane
rubber
layers could also be in the form of hollow hemispheres which are layered in
opposition within the mold.
The bail of the invention may also be manufactured using the
carcass and panel method as described in United States Patent No. 3,119,618.
This method is particularly suited for the manufacture of basketballs.
Following
this method a ball carcass which encapsulates the bladder and windings can be
molded from a natural rubber compound. The carcass is formed with protruding
channels which provide assistance in locating the cover panels in position on
the
ball. The cover panels are formed from a urethane gum rubber composition and
cured in a mold which provides cover panels of the exact size and shape need
to
fit between the channels of the carcass. The cured panels are glued in place
on
the carcass with an adhesive appropriate for the carcass and cover materials,
the
ball is given a final clean-up to remove manufacturing marks, and detail or
decoration are added, as needed.
When a multi-layered cover is to be made special care must be taken
in selecting and preparing the materials used in the cover and also special
care
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must be taken in the subsequent cross-linking process. It is well known that
natural rubber cross-links at a much faster rate than the urethane gum rubber.
For example, a typical natural gum rubber composition will typically vulcanize
within 5 minutes upon application of 150°C. In contrast, a urethane gum
rubber
as used in the present invention may take up to 15 minutes to achieve a
desired
level of cross-linking. (t is further known that exposing the natural rubber
to the
amount of heat necessary to achieve proper cross-linking for the urethane gum
rubber may damage the natural rubber. Conversely, exposing the urethane gum
- rubber to the amount of heat necessary to cause cross-linking of the natural
rubber will leave the urethane gum rubber under cured. To accommodate the
disparate cure rates of the natural rubber and the urethane gum rubber the
inventors have found that reduced amounts of accelerators in the natural
rubber
composition may be used.
It may be desirable for certain game ball applications to produce a
softer cover material. As the urethane gum rubber of the cover is typically
rather
hard, the inventors have found that foaming the natural rubber layer of the
multi
layered cover provides the finished ball with an appropriate level of cover
softness. In the case of a basketball cover, a foam rubber density in the
range
of 0.5 to 0.95 grams/ cubic centimeter (g/cm3) provides a ball with good feel
and
playability.
In a game ball with a single layer cover, the thickness of the
urethane gum rubber layer ranges from 0.3 to 3.5 mm, more preferably from 0.9
to 2.7 mm and optimally is about 1.9 mm. In a game ball with a multiple layer
cover, the thickness of the inner natural rubber layer ranges from 0.1 to 1.6
mm,
more preferably from 0.6 to 1.4 mm and is optimally about 1.1 mm. The outer
urethane gum rubber layer overlying the inner natural rubber layer ranges from
0.3 to 1.9 mm, more preferably from 0.5 to 1.4 mm and is optimally about 0.8
mm. Naturally, when a carcass with protruding channels is used, the thickness
of the inner natural rubber layer will be greater in the area of the channels.
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A batch ofi urethane gum rubber was prepared according to the
formulation found in Table 2 below. This composition is identifiied as STOCK
EXAMPLE 1 (Stock Ex.1).
TABLE 2
STOCK EXAMPLE 1 - URETHANE GUM RUBBER
COMPOSITION
Ingredient Parts by Weight
UREPAN 50EL06G' urethane rubber resin 100.00
sulfur 1.50
CABOSIL2 reinforcing filler 40.00
zinc stearate 0.50
RHENOCURE AUR3 curing agent 1.00
ALTAX (MBTS)4 cure accelerator 4.00
CAPTAX (MBT)5 cure accelerator 2.00
ORANGE MASTER BATCH6 coloring 3.50
Ti02 coloring pigment 2.00
AFLUX 12' processing promoter 1.00
RHENOSIN TM90$ processing promoter 4.00
TOTAL 159.5
' UREPAN 50EL06G is a urethane rubber resin commercially available from Rhein
Chemie Corp., Trenton,
New Jersey.
2 CABOSIL is a fumed silica reinforcing filler commercially available from
Cabot Corp., Atlanta, Georgia.
3 RHENOCURE AUR is a curing agent for sulphur cross-linkable polyurethane
rubbers and is
commercially available from Rhein Chemie Corp., Trenton, New Jersey.
4 ALTAX is an MBTS cure accelerator commercially available from R.T.
Vanderbilt, Norwalk,
Connecticut.
s CAPTAX is an MBT cure accelerator commercially available from R.T.
Vanderbilt, Norwalk,
Connecticut.
6 ORANGE MASTER BATCH is an orange colored pigment master batch commercially
available from
Disco Inc., Ringwood, New Jersey.
' AFLUX 12 is a processing promoter for synthetic rubber compounds and is
commercially available from
Rhein Chemie Corp.
a RNENOSIN TM90 is a processing promoter which improves the distribution of
fillers within the rubber
composition and is commercially available from Rhein Chemie Corp.
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The ingredients were mixed in a Banbury-type mixer to completely
mix the ingredients and obtain a batch of stock identified as Stock Example 1.
It will be appreciated that the urethane gum rubber of the invention may be
mixed
and processed using conventional rubber making equipment and techniques. The
uncured mixture was then passed through a calendaring machine or a 2 roll mill
to produce a sheet of uncured urethane gum rubber. The sheet was cut into
several pieces each sized to fit a plaque mold and the pieces were cured in an
electric press under various conditions which are outlined below. The samples
were tested to determine their physical properties.
Mock Ex. 1-A
A sample Stock Example 1 was placed in a mold preheated and
maintained at a temperature of 150°C. The material remained in the hot
mold
for 10 minutes under 7 tons of pressure to form a plaque and was removed while
hot. This plaque was tested and found to have a Shore A hardness of 77.
Stock Ex. 1-B
A plaque was prepared as in Example - 1 A above, with the
plaque remaining in the hot mold for 20 minutes. This plaque was tested and
found to have a Shore A hardness of 77.
Stock Ex. 1-C
A plaque was prepared as in Example 1-A above, with the plaque
remaining in the hot mold for 30 minutes. This plaque was tested and found to
have a Shore A hardness of 78.
COMPARATIVE EXAMPLE 1
A batch of natural rubber cover stock having a composition as set
forth in Table 3 below was also prepared. This composition is identified as
COMPARATIVE EXAMPLE 1 (Comp. Ex.1).
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TABLE 3
COMPARATIVE EXAMPLE 1 - NATURAL RU BBER COMPOSITION
Ingredient Parts by Weight
60 CV' Malaysian natural rubber resin59.00
ANDREZ 80002 high styrene resin 22.00
CARIFLEX BR-12203 polybutadiene 19.00
VERFLAKE (CaC03)4 filler 60.00
HISIL 2335 reinforcing filler 18.50
CIRCO6 light oil processing oil 5.00
Zn0 activator . 3.30
stearic acid activator 2.00
DEG diethylene glycol activator 1.00
CUMAR7 resin plasticizer 2.20
VANAX 1290$ antioxidant 2.20
ORANGE MASTER BATCH coloring pigment 3.50
sulfur 1.90
CAPTAX (MBT) cure accelerator .78
ALTAR (MBTS) cure accelerator .24
unads9 cure accelerator .50
m, tuads' vulcanization accelerator 1.00
Total 202.12
' SMR 60 CV is a natural butyl resin obtained from Malaysian rubber trees and
is commercially available
from Muehlstein, Leominster, Massachusetts.
z ANDREZ 8000 is a commercially available from high styrene/butadiene resin
commercially available from
Anderson Development, Adrian, Michigan.
3 CARIFLEX B2-1220 is a polybutadiene commercially available from Muehlstein,
Norwalk, Connecticut
4 VERFLAKE is a calcium carbonate filler commercially available from Hampden
Color & Chemical,
Springfield, Massachusetts.
5 HISIL 233 is a fumed silica reinforcing filler commercially available from
PPG Industries, Pittsburgh,
Pennsylvania
6 CIRCO light oil is a processing oil commercially available from Sun
Chemical, Cincinnati, Ohio.
' CUMAR is a plasticizer/softener commercially available from Neville
Chemical, Pittsburgh,
Pennsylvania.
a VANAX 1290 antioxidant commercially available from R.T. Vanderbilt.
9 unads is a tetramethyl thiuram monusulfide vulcanization accelerator
commercially available from R.T.
Vanderbilt, Norwalk, Connecticut.
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'° m. tuads is a methyl tetramethyl thiuram disulfide vulcanization
accelerator commercially available from
R.T. Vanderbilt, Norwalk, Connecticut.
The natural rubber composition was mixed in a Banbury mixer,
formed into a sheet on a 2 roll mill and pieces of the sheet were cut to fit a
plaque mold. The pieces were then cured in an electric press under various
conditions as outlined below. Tests were conducted to determine their physical
properties.
Comp. Ex. 1-A
A sample of the batch of stock identified as Comp. Ex. 1 was placed
in a mold preheated and maintained at a temperature of 140°C. The
material
remained in the hot mold for 10 minutes to form a plaque and them was removed
while hot. This plaque was tested and found to have a Shore A hardness of 70.
Coma. Ex. 1-B
A plaque was prepared as in Comp. Ex. 1-A above, with the plaque
remaining in the hot mold for 20 minutes. This plaque was tested and found to
have a Shore A hardness of 77.
Como. Ex. 1-C
A plaque was prepared as in Comp. Ex. 1-A above, with the plaque
remaining in the hot mold for 30 minutes. This plaque was tested and found to
have a Shore A hardness of 78.
Comparative testing was carried out on samples of the urethane gum
rubber and the natural rubber of the control stock using a Taber abrasion
testing
machine following the methods outlined in ASTM F 510-78. The results of the
Taber abrasion test are reported below in Table 4.
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TABLE 4
ABRASION TESTING (TABER)
Mass in grams
of amount
Material abraded after
1000 cycles
using
H-18 "GREY
WHEEL"
. 1 st RU N 2"d RU N
Comp. Ex. 1-A, natural rubber,0.84 1.03
10 min. cure time
Stock Ex. 1-A, urethane gum 0.11 0.12
rubber, 10 min. cure time
Comp. Ex. 1-B, natural rubber,1.08 1.04
20 min. cure time
Stock Ex. 1-B, urethane gum 0.11 0.10
rubber, 20 min. cure time
Comp. Ex. 1-C, natural rubber,1.11 1.08
30 min. cure time
Stock Ex. 1-C, urethane gum 0.11 0.10
rubber, 30 min, cure time
In each of the abrasion test runs it was found that the polyurethane
rubber provided substantially greater resistance to abrasion than did natural
rubber. It will be recalled that natural rubber cures more quickly than
urethane
rubber and consequently one might expect natural rubber to have greater
abrasion resistance than urethane rubber at the shorter cure times.
Surprisingly,
the urethane rubber exhibits higher abrasion resistance than natural rubber at
every cure time tested. It is also projected that the urethane rubber likewise
would perform superior to the natural rubber at every cross-link density. It
will
be appreciated that improved abrasion resistance translates directly into
longer
ball life and retention of molded surface texture.
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A ball made according to the present invention with a polyurethane
rubber cover was tested against several commercially available balls in a
bounce
test. The ball made according to the present invention was designated Example
2. In the bounce test each ball was propelled from a series of rotating wheels
(in
a manner similar to batting practice machines used to pitch baseballs) at an
angled barrier comprising a new, cross-hatched steel bounce plate. The ball
bounces off the angled barrier and is directed into a net where the energy of
the
rebounding ball is dissipated. A return ramp in the mechanism automatically
returns the ball to the wheels for repeated firing against the angled barrier.
The
firing is continued until the ball has been fired against the barrier 10,000
times;
each impact with the angled barrier being counted as a single bounce.
Prior to the testing each ball was measured to determine the initial
circumference (size) of the ball in inches, initial weight in grams, durometer
hardness (using a Type "O" gauge from Rex Gauge Company, 1250 Busch
Parkway, Buffalo Grove, Illinois), and out of round measurement or "0/R". Out
of round measurement is tested by placing a ball on a roller stand. A dial
indicator is placed against the ball outside surface and the gauge is set to
read
zero. The ball is rotated on the roller stand 360 degrees and the high and low
readings on the gauge are recorded. The ball is repositioned a total of three
times and the high and low measurements are averaged. The differences
between the high and low readings represent the out of round measurement.
After 10,000 bounces the size, weight, durometer hardness and O/R
measurements were taken again. In addition, the change in weight of each ball
was determined. The data accumulated is reported in Table 5, below.
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C
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-17-
CA 02396172 2002-07-04
WO 01/51132 PCT/USO1/00615
As shown in Table 5, the ball made according to the present
invention, Example 2, showed the lowest change in weight due to abrasion
incurred in the bounce test. The durometer hardness remained unchanged before
and after the test, a performance which was only equaled by the Nike "NSB
1000" ball. The Example 2 ball showed a slight increase in size (.18 inch) due
to the repeated impacts. This is well within acceptable limits and less than
the
Urax "ZR Cushion" and Urax "Kobe" balls.
As will be apparent to those skilled in the art, various modifications
and adaptations will become readily apparent without departure from the spirit
and scope of the invention.
-18-
