Note: Descriptions are shown in the official language in which they were submitted.
20~
RADIAL P~LY TIRE
The present invention relates to a radial tire
havin~ a carcass comprising several plies, reinforced by
substantially radially oriented parallel organic
filaments, yarns or cords, the plies being folded axially
around a pair of axially spaced bead cores. The tire
further comprises at least one belt ply disposed radially
outwardly of the carcass plies in a crown region of the
tire, the belt plies also being reinforced by organic
filaments, yarns or cordQ.
It is generally recognized in the tire art that
tires suitable for use on air-raft must be capable of
operating under conditions of very high speeds and large
loads as compared to tires used on automobiles, busses,
trucks or similar earthbound vehicles. It is understood,
however, that tires for such earthbound vehicles may
advantageously be made in accordance with the broad
aspects of the invention described herein. As used
herein and in the claims, a tire is "suitable for use on
an aircraft" if the tire is of a size and load range, or
ply rating, specified in either the YEAR~OOK OF THE TIRE
AND RIM ASSOCIATION, or the YEARBOO~ OF THE EUXOPEAN TYP~E
AND RIM TECHNICAL ORGANIZATION, for the year in which the
tire is manufactured, or in the current U.S.A. military
specification "MIL-T-5041".
It is an object of the present invention to provide
a radial pneumatic tire, having a low-weight carcass with
excellent dimensional stability.
It is a further object of the invention to create a
radial tire havin~ outstanding belt strength.
These objects are met by the invention as outlined
in the appended claims.
To acquaint persons skilled in the art with the
principles of the invention, certain presently preferred
embodiments illustrative of the best mode now
~032~2R
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contemplated for the practice of the invention are
described herein making reference to the attached
drawings forming a part of the specification and in which
drawings:
Fig. 1 is a cross-sectional ~iew of a tire according
to a first embodiment of the invention taken in a plane
that contains the axis of rotation of the tire;
Fig. 2 is a cross-sectional view of a tire according
to a second embodiment of the invention taken in a plane
that contains the axis of rotation of the tire; and
Fig. 3 is an enlarged fragmentary view of a belt of
a tire according to a further embodiment of the
invention.
With reference to Fig. 1, an aircraft tire 10 of
size 32 x 8.8 R 16 has a pair of substantially
inextensible annular bead cores 11, 12 which are axially
spaced apart with several carcass plies 13, 14, 1;
extending between the bead cores.
As used herein and in the claims, the terms "axial"
and "axially" refer to directions which are parallel to
the axis of rotation of a tire and the terms "radial" and
"radially" refer to directions that are radially toward
or away from to the axis of rotation of a tire. Each of
the carcass plies 13 to 15 comprises a plurality of
reinforcing elements oriented at 75 to 90, preferably
80 to 89~, wlth respect to an equatorial plane (EP) of
the tire. The "equatorial plane" of a tire is a plane
that is perpendicular to the axis of rotation of the tire
and passes through the center of the tire tread and an
"axial plane" is a plane that contains the axis of
rotation of the tire.
The carcass plies compri~e two turn-up carcass plies
13, 14 and one turn-down carcass ply 15. Each of the
turn-up carcass plies 13, 14 is folded axially a^.~
radially outwardly about each of the bead cores 11 a~.d
the turn-down carcass ply 15, is folded at le s.
partially radially and axially inwardly about each of ~e
2~3
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bead cores 11 and the turn-up carcass plies 13, 14. The
turn-down carcass ply 15 is folded around the bead cores
to such a degree that the respective edge of said turn-
down plies are located axially inwardly of the axial
midpoints 17 of the respective bead cores 11.
Tires have been manufactured in which the
reinforcing elements of the radially innermost turn-up
carcass plies 13 were oriented at 82 with respect to the
equatorial plane EP, the reinforcing elements of the
second turn-up carcass ply 14 were oriented at 85 with
respect to the equatorial plane EP, and the reinforcing
elements of the turn-down carcass ply 15 were oriented at
8~3 with respect to the equatorial plane EP. It is,
understood that in preferred embodiments of the invention
the orientation of the reinforcing elements in each
carcass ply, or pair of carcass plies, should be nearer
to 90 than the orientation of the reinforcing elements
of the radially next innermost ply, or pair of carcass
plies, and the included angles between the angles of
radially adjacent carcass plies should not be greater
than 10, and preferably not greater than 4. For
details about the best choice of ply angles, reference is
hereby made to commonly owned US patent No. 4,823,103.
lf the tire is of the tubeless variety, a
substantially air impervious layer (not represented) is
disposed radially inwardly of all of the carcass plies.
The reinforcing elements of all of the carcass plies
13 to 15 can be substantially the same and each comprises
a monofilament of 4,000 denier nylon. A monofilament is
by definition a cord consisting of one filament. The
monofilaments can either have a round section or can be
slightly flattened with a substantially oval section or
strongly flattened with rounded off edges. Such
flattened filaments for a given required strength offer
a gauge advantage and have a lower rivet area for a gl~en
fabric density than filaments with conventional circu'ar
cross-section. ~he fabric densities (expressed in E?',
_ 4 _ 2~
i. e. ends per inch) as well as the linear densities used
in the instant disclosure are those of reinforcing
elements in plies which have not yet been submitted to
any shaping. Pref¢rably, the nylon monofilaments should
have their greatest linear cross-sectional extent, i.e.
their width, two to five times the linear cross-sectional
extent perpendicular to said width, i.e. thelr thickness.
The monofilaments in each ply are preferably disposed
with a minimum density of 14 EPI, preferably of about 18
EPI, in order to yield the desired mechanical
characteristics of the tire carcass. Nylon monofilaments
have a tenacity of at least 7 cN/denier, a modulus of at
least 40 cN/denier, an elongation at break of at least 18
% and a shrinkage of at most 4 ~. Further details about
monofilaments can be found in co-pending application
serial No. 345,925 filed on May 1, 19~9.
A belt 20 is located outwardly of the carcass plies
13-1~ in a crown region of the tire 10. A ground
engaging tread portion 30 is disposed radially outwardly
of the belt structure 20, and a sidewall portion 26
extends radially inwardly from each axial edge of the
tread portion to a respective bead portion 28.
Each of the belt plies 21-23 comprises parallel high
twist aramid cords oriented at 10 to 40 with respect to
the equ~torial plane EP of the tire and has a fabrlc
density comprised between 10 and 35 EPI. As used herein,
"aramid" and "aromatic polyamide" are both understood to
mean a manufactured fiber in which the fiber forming
substance is generally recognized as a long chain
synthetic aromatic polyamide in which at least 85% of the
amide linkages are attached directly to the two aromatic
rings. Representative of an aramid or aromatic polyamide
is a poly (p-phenyleneterephtalamide). "High twis~"
aramid cords to be used in one embodiment of the
invention a~ reinforcing elements in a tread reinforclr.g
structure of a tire have a twist multiplier (TM) in r~.e
range of 7 to 9; the twist multiplier being defined ~s:
2C~3~
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TM-O . 0137xCTx~b
wherein CT is the number of turns per inch (2,54
cm) o~ ~ord length; and
CD is the sum of the deniers of the yarns
and/or subgroups of the yarns of the cord
before any twist is imparted to the yarns
or subgroup.
"Low twist" aramid cords to be used in another embodiment
of the invention as reinforcing ele~ents of the belt of
a tire, where strength is of lesser importance, have a
twist multiplier in the range of 4 to 7. It is believed
that belt plies reinforced with high twist aramid cords
lead to tires with an optimized carcass-belt
compatibility and a better durability whereas belt plies
reinforced with low twist aramid cords optimize the
1S landing capacity of aircraft tires. Details about hish
and low twist aramid cords can be found in commonly owned
US patent 4,832,102.
The belt 20 comprises one belt ply 21 folded around
two plie~ 22, 23. The folded ply is reinforced with high
twist 1,500/3 denier aramid, having a fabric density of
about 14 EPI and orming with the equatorial plane of the
tire an angle comprised between 18 and 26. The plies
22, 23 are also reinforced with 1,500/3 denier high twist
aramid cords, having a fabric density of about 18 EPI.
The angles formed by the reinforcement cords of the two
plies with the equatorial plane of the tire are opposed
and range between 12 and 24 and pre~erably between 16
and 20.
Between the ground engaging tread portion 30 and the
belt structure 20 is disposed at least one overlay ply 29
reinforced by 840/2 denier nylon cords. The nylon cords
ha~e a fabric density of about 22 EPI and are parallel to
each other in each ply. It is believed that overlay
plies only make a minor contribution to the propertles
and high-speed performance of the tire; their main
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function is to protect the belt 20 during retreading
operations, where they act as a visual warning layer when
the elastomeric material constituting the tire tread is
buffed away.
The disposition of reinforcing strips in the bead
portions of tires is believed to contribute to the
product performance, especially to its durability.
Furthermore, the reinforcing strips folded around the
bead cores compensate for the restriction of the ply ends
during the shaping of the tire. In the embodiment shown
on Fig. 1, one strip 41 reinforced by 840/2 denier nylon
cords has at least a portion interposed between the
radially innermost turn-up carcass ply 13 and the
neighboring turn-up carcass ply 14. It is preferred that
the reinforcing strip 41 extends in part around the
radially innermost side of the apex 43 and along the
radially outermost side of the apex 43 up into the
sidewall. The nylon cords of the reinforcing strip 41
should be disposed at angles of 30 to 60 with respect
to an axial plane intersecting the cord, preferably at
angles between 40 and 50. The apex 43 is made of
rubber having a Shore A hardness of 76 to 84.
~etween the radially outermost turn-down carcass ply
1; and the chafer 44, there are located two further
reinforcing plies 45, 46 known in the art as semi-
ch~pper. The semi-chippers are reinforced by nylon cords
h~ving ,an inclination between 20 and 70 and more
preferably between 40 and 509 with respect to an axial
plane passing through the cord. It is believed that the
reinforcing plies 45, 46 distribute the shear and
compression stresses due to the tire deflection. ~etween
the semi-chippers 45, 46, and the turn-down carcass ply
15 a rubber gum strip 47 having a Shore A hardness of
about 62 is located.
In Fig. 2 a tire 210 comprising carcass plies 213-
215 reinforced with nylon monofilaments having a linear
density of about 4,000 denier and a fabric density of
- 7 - ~ 4Z~
about 18 EPI is shown. The monofilaments of all the
plies have a strongly flattened section with rounded off
edges.
The belt 220, reinforced with low twist aramid
cords, comprises a helt ply 221 folded around two plies
222, 223. The folded ply is reinforced with 1,500/3
denier aramid, having ~ fabric density of about 16 EPI
and forming with the equatorial plane of the tire an
angle comprised between 18 and 26 and more preferably
between 20 and 24. The plies 222, 223 are reinforced
with aramid cords having a linear density of about
1,500/3 denier and a fabric density of about 16 EPI . The
angles formed by the reinforcement cords of the two plies
222, 223 with the equatorial plane of the tire are
opposed and have values ranging between 10 and 26 and
preferably between 16 and 20.
Between the ground engaging tread portion 230 and
the belt structure 220, one nylon reinforced overlay ply
229, protecting the belt 220 during retreading
operations, can be distinguished.
In the bead region of the tire two strips 241, 242,
reinforced by 840/2 denier nylon cords, are interposed
between the radially outermost turn-up carcass ply 214
and the apex 243. The reinforcing strips extend from the
bead cores 211 at least along the whole height of the
apex 243, up into the sidewall. The nylon cords of the
reinforcing strips 241, 242 are disposed at angles of 30
to 60 with respect to an axial plane intersecting the
cord, preferably at angles between 40 and 50.
Between the radially outermost turn-down carcass ply
215 and the chafer 244, there are located two semi-
chippers 245, 246. The semi-chippers are reinforced by
nylon cords having an inclination between 50 and 70
with respect to an axial plane intersecting the cord.
In Fig. 3 part of a tire section comprising t~o
turn-up carcass plies 313, 314, and two turn-down carcass
plies 315, 316, is represented. The carcass plies a-e
,,4
203~:~2~3
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reinSorced with nylon monofilaments having a linear
density of 840/2 denier and a fabric density of 24 EPI.
The monofilaments of all the plies have a strongly
flattened section with rounded off edges.
The belt 32Q is reinforced with high twist aramid
cords and comprises one belt ply 321 folded around three
plies 322-324. The folded ply is reinforced with 1,500/3
denier aramid, ha~ing a fabric density of about 14 EPI
and forming with the equatorial plane of the tire an
angle comprised between 18 and 26. The three plies
322-324 are reinforced with 1,500/3 denier aramid, having
a fabric density of about 16 EPI. The angles formed by
the reinforcement cords of the three plies with the
equatorial plane of the tire are opposed between
neighboring plies and range between 10 and 24. In a
preferred embodiment of the invention, the angles of the
plies have the following values: about -16 for the
radially innermost ply and about respectively ~18 and
-18 for the two radially outermost plies.
Between the ground engaging tread portion 330 and
the belt ~tructure 320 there is disposed one overlay ply
329 reinforced by nylon cords. As explained above, such
an overlay ply is particularly important in retreading
operations.
It is understood that the belt and carcass
structures illustrated in Fig. 1, 2 and 3 and described
herein, are merely examples used in preferred
embodiments. A tire designer may employ different
numbers of carcass plies, reinforced with nylon
monofilaments having different sections and different
linear and fabric densities, together with other
arrangements of unfolded or folded belt plies, reinfor_ed
with high twist or low twist aramid cords, in accordance
with the performance requirements of a particular t ~e
while still practicing the present invention.
