Note: Descriptions are shown in the official language in which they were submitted.
9Q~Z
~ACXGROUND OF THE INVENTION
Field of the Invention
This invention relates to a puncture sealing
tire having ribbon wire belt plies and a tacky puncture
sealant positioned between the air chamber and the belt
plies.
DESCRIPTION OF THE PRIOR ART
A great deal of e~ort, in the paæt, has gone
into attempts to make automobile tires more reliable.
Reliability has improved to the point where automobile
manufacturers are considering eliminating the spare tire
to save space. Unfortunately, the reliability of tires
still leaves much to be desired.
The use of ribbon wire in tires to solve various
problems has been disclosed in U.S. Patent 4,011,899
Chamberlaln (1977), U.S. Patent 3,667,529 Mirtaln (1972),
and Vaniels B.K. "Steel Ribbon Belt Reinforcement Mech-
- anics" Tire Science and Technology, TSTCA, Vol~ 59 No. 1,
Feb. 1977.
Prior art patents which disclose the use of
puncture sealant compositions in tires include U.S.
Patent 3,903,947 Emerson (1975) and U.S. Patent
3,935~893 Stang, et al (1976). The Emerson patent utilizes
a partially cured ethylene propylene non-con~ugated diene
rubber in combination with other ingredients as a sealant.
The Daniels reference discloses that ribbon
wire tires pro~ably will hold nails mor`e firmly, thus, ~ ~
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allow them to run longer without deflation.
The Stang, et al patent utilizes a mixture of high
molecular weight curable isobutylene, isoprene, low molecular
weight curable isobutylene, isoprene, liquid butylene as a tack-
ifier partially hydrogenated styrene isoprene carbon black cross-
link and initiator. While these puncture sealants were effective
to a degree in rigid thick-walled four-ply bias tires, they were
not so effective in the flexible two-ply radial tires.
By four-ply and two-ply is meant body plies. The
prior art, in attempting to solve the air loss due to puncture
: problems, has not suggested the functional relationship which can
exist between ribbon wire and puncture sealant in solving the
problem of air loss due to puncture and the removal of the punc-
turing object.
The present invention provides a pneumatic tire hav-
ing an air chamber, beads, a carcass reinforced with one or more
carcass plies, a tread surrounding the crown region of the car-
cass and one or more tread reinforcing belt plies disposed circum-
ferentially about the crown region of the carcass between the
carcass and the tread, wherein the improvement comprises the com-
bination of at least one reinforcing ply oE the belt comprising
flat steel wires, the wires being twice as wide as they are thick,
with the wide faces of the wires being perpendicular to tha rad-
ius of the tire in combination with a puncture sealant positioned
between the air chamber and the one or more belt reinforcing
plies.
Evidence obtained indicates that a functionalrelation-
ship exists between the ribbon wire plies in the belt and the
puncture sealant which greatly reduces leaks due to nail punctures
in the tire. The ribbon wire preferably has a thickness of 0.1
to 0.5 mm preferably 0.2 to 0.4 and a width of 0.2 to 6.0 mm,
preferably 0.5 to 2.0 mm.
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Th~ rlbbon wire can be made by either ro]ling
a steel wire to a flat conflguration or by cuttlng a
steel sheet to ~orm ribbon. ~he ribbon wire is pre-
ferably brass plated. The ribbon wire in the tire is
positioned in the belts so that it is perpendicular to
the radius of the tlre. Pre~erably the rib~on wire plies
of the tire are at an angle of from 15 to 30 to the
circumferential centerline of the tire and at an angle
of from 30 to 60 with respect to each other. In other
words, they are laid at a bias angle similar to the
steel cords in conventional tires. Also, preferably the
steel ribbon wire covers from 50 to 98%, preferably 80 to
90% of the entire tread area, assuming that the tread area
has no depth. The tire preferably is a one or two ply
radial tlre having curved sidewalls and a thlck, rigid
tread with a broad groove width.
A typlcal recipe for a preferred sealing com-
position of this invention comprises 100 parts by weight
of an EPDM rubber, lO0 to 180 parts, preferably 120 to
140 parts by weight per lO0 partæ of rubber of a paraf-
finlc oil, lO to 50, preferably 15 to 30 parts by weight
per lO0 parts rubber of a coarse partlcle size carbon
black, 2 to 8, preferably about 5 parts by weight per
100 parts rubber of a heat stabilizer such as zlnc oxide
and l to 3, preferably about 2 parts by weight per lO0
parts rubber of an antioxidant such as the commercial
high temperature condensation product of acetone and di-
phenylamine.
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The separating and covering layers or squeegee
sheets serve two ma~or ~unctions. The first iB mechanical
ln that they prevent the uncured or sllghtly cured
sealant from sticking to the curing bladder used ln vul-
canizing the green tire. The second functlon is to pre-
vent migration of plasticizer oils out of the sealant
layer. It is preferred in this invention to utilize
nitrile rubbers having medium to high acrylonitrile
contents of at least 20 weight percent, more preferably
at least 30 weight percent acrylonitrile, in the ~queegee
sheets. Typlcal suitable nitrile rubbers generally
contaln about 30 to 35 weight percent acrylonitrile unlts
and range in Mooney viscosity ~MLl+4 at 212F) from
about 30 to about 60. Nitrile rubbers are widely known
as extremely resistant to parafflnic oll. Therefore,
the use of nitrile rubber in the separatlng and covering
~heets ef~ectlvely prevents the paraffinic oil employed
ln the synthetic rubber sealing composition from mi-
grating therefrom. It is preferred that the nitrlle
rubber comprlse at least about one-half of the total
rubber content of the separating and coverlng sheets.
ln place of part or all of the nltrile rubber there can
be used a rubbery vulcanizable copolymer of propylene
oxide and allyl glycidyl ether containlng from about
5 to 10% by weight of copolymerlzed allyl glycidyl
ether or slmllar propylene oxlde rubber.
Since the separating and covering sheet compo-
sitions are vulcanized, they must necessarily contaln
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ingredients ~or effectlng vulcanization along wlth a
number of other addltives to get the desired properties.
The total amount of these materials may range from 50
to 150 parts by weight per 100 parts by weight of total
rubber in the composition. Examples of these ingredlents
and other additives include carbon black, zinc oxide,
stearic acid, accelerators, antloxldank~, fillers and
the like. A typical squeegee sheet formulation of this
invention comprises 70 to lO0 parts by weight of a
medium to hlgh nltrile hydrocarbon rubber, 0 to 30
parts by weight o~ natural rubber, 20 to 100, preferably
50 to 70, phr o~ carbon black and other ~lller, O to
20 phr of tackifier, 0.8 to 1.6 phr of sulfur and l to
10 phr of stabillzers, accelerators, antioxidants and
other additives. The rubbers and other ingredients are
combined using conventional rubber mixing and blending
practlces. A~ter the laminate is formed, the covering
layers are vulcanized during the cure cycle of the tire.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross section of a tire having
ribbon wire belt plies and a puncture sealant l encap-
sulated between the air chamber and the belt plies.
FIG. 2 is a view of a partially cross section
through the tread of the tire showlng the bias configur-
ation of the ribbon wire plies in the belk.
FIG. 3 is a cross sectional view of a ribbon
wire ply showlng ribbon wire embedded in rub~er stock
(calendered wire).
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 shows a radial tire having curved
flexible sidewalls 17 and a tread 13. The tread 13
preferably is a relatively sti~f compound which re$ists
flexing having broad grooves 2. The sidewalls 17 are
curved and flexible so that the tlre will run smooth.
The stiff tread 13, the broad grooves 2 and heavy tread
ribs 21, it is contemplated~ will prevent movement of a
nail after it has penetrated the tire and, thus, reduce
the amount o~ enlargement of the hole. The sidewalls
contain two plles 19 and 20 which extend radially ~rom
bead 15 to bead 15 of the tlre and overlap beads 15.
Posltioned under the tread 13 are two belt plles 9 and
11. The belt plies are made of ribbon wire strand~ 23
as shown in FIG. 2. The ribbon wire was obtained from
Baekert, a maJor wire supplier located in Belgium.
The number for the wire is V4554 ribbon wire. The wire is
brass plated, has a thickness of .25~m and a wldth o~
1.Omm. The wire has a break strength of 556 Newtons and
it is used at an end count per inch of 15. To produce
the belt ply, the rubber wire is calendered with rubber
to a thlckness o~ about 1.39mm.
The angle of the rlbbon wire cords to the cir-
cumferential centerline o~ the tire after cure is about
22. Posltioned under the ribbon wire and the kwo cord
ply is the puncture sealant 1. The puncture sealant
contains:
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60 parts of Nordel 1070~ ethylene propylene non-con~ugated
diene rubber avallable from duPont; 40 parts of ethylene
propylene ethylidine norbornene. This materlal is avail-
able as Epsyn 70 from Copolymer Rubber and Chemicals Co.,
Baton Rouge, La. It is a zinc oxide-phenolic resin curable
gumj 120 parts of a high viscoslty paraffinlc oil avall-
able as Sunpar 20-80 from the Sun Oil Company, 15 parts of
Austin Black. Austln Black is bituminous coal ~ines
available from the Slab Fork Coal Co., and/or Columbia
Carbon; 2 parts BLE-25 amine antioxidan~, a diphenyl
amine-acetone reaction product available from Uniroyal
Chemlcalg Naugatuck, Conn, 12 parts of SP1055 brominated
phenolic, a bromomethyl alkyl phenyl formaldehyde resin
available from Schenectady Chemicals.
To partially cure the puncture sealant, the tire
containing the sealant is sub~ected to the cure procedure
set ~orth below. The combination o~ the zinc oxide and
the brominated phenolic causes cross linking of the Epsyn
70A EPDM only. For further details as to the maklng and
encapsulation of the puncture sealant, see U.S. Patent
3,903,947 o~ Emerson (1975).
The puncture sealant composition is encapsu-
lated in a nitrile rubber envelope 3, 5. The nltrile
rubber envelope is incompatlble wlth the punctùre sealant
compositlon an~ does not bond to lt during curlng. The
nltrile envelope 3, 5 contains 100 parts by weight of a
nltrile hydrocarbon rubber, 35 parts of a HAF, high abraslon
furnace black, 20 parts of Austin Black, 2 parts of
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n-cyclohexyl-2-benzothiazole-sulrenamide and 1.2 parts of
sulfur. The rubber and other ingredient~ are combined
uslng conventional rubber mixing and blendlng practices.
The covering layers are cured and the puncture sealant is
partially cured during vulcanizing of the tire. The
tire ls cured for 20 minutes using 1379 kilopascals (kPa)
at a steam temperature of 196~ followed by 9-1/2 minutes
o~ hot water at 1724 kPa at 166C followed by eight minutes
of clrculatlng water at 38C at 1724 kPa input. Care
should be taken not to lose pressure inside the tire
between the curing steps. For further details concerning
the nitrile rubber envelope, see U.S. Patent 3,903,947 of
Emerson (1975).
The puncture sealant is extruded onto one sheet
O~ uncured nitrile rubber after which a second sheet of
nltrile rubber is placed over the sealant as a cover.
To prevent flow, the cover can be sectioned into a mul
tiplicity of compartments. The tires are made in a
¢onventional manner using somewhat longer cure cycles. If
a conventional spray type sealant is used, the tire is
cured ln a normal manner. In making the tire~ first the
inner llner 7 i8 placed on the building drum then the
sealant package 1, 3, 5 is centered on the building drum
and a sheet of fiber filled squeegee 24,ply beads and
other conventional components are added to the tire in the
conventional manner. The ~iber filled squeegee 24 prevents
cords from pulling through the sealant package. The
sealant packages used in making the tires of the present
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invention were quike old and the age, plus other ~actors,
influenced the flow properties of the sealant.
The sealant, after the tires were cured~ was
somewhat more flowable than expected. To compare the
present invention with khe prior art, a number of tires
were built using the combination of the ribbon wire in
the belt plies and the sealant package between the inner
liner and the body plies. The tire size was GR78-15.
The body plies were two radial ply polyester. The tires
had a normal in~lation pressure. Nails were driven lnto
the tires and then removed from the tires to determine
whether or not a leak would occur. Half of the nails
used were six penny nails and half of the nails used
were sixteen penny nails. In 96% of the cases, no air
loss occurred after removal of the nails. The same test
had been run earlier using tires made from the same en-
capsulated sealant and ha~ing cable wlre ln the belt plies.
Only 39% of the tlres retained their air pressure on
removal of the nails. Inspection of the nails removed
~rom the ribbon wire belt tires shows that not only was
sealant scraped from the surface of the nails, but also
that metal was scraped from the surface.
It is contemplated that a sealant such as the
commercially available Rocket Research sealant will be
comparable or even better than the sealant used above.
It is contemplated that the nitrile rubber cover of the
sealant package used above tended to wipe off from the
~ealant be~ore the nail entered the opening in the tread.
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In this applicatlon, all parts and percentages
are by welght unless otherwise specified.
Body plies may also be made using rlbbon wire.
The present invention is not based upon the
concept of making a tire or belt plies uslng ribbon
wire or the sealant composi~ion~ These are old and
well known in the art and, there~ore, will not be de-
scrlbed in detall in thls appllcation. It is believed
that any type of tire reinforcing ribbon wire and any
type of tire puncture sealant will work in the present
invention. The present invention is based upon khe
synergistic combination o~ ribbon wire and puncture
sealant.
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