U.S. patent application number 11/726812 was filed with the patent office on 2007-07-26 for tire reinforced by hybrid cables.
Invention is credited to Pierre Chavaroche, Philippe Esnault, Pascal Fickinger, Jean-Marie Mus, Hubert Pacherie.
Application Number | 20070169867 11/726812 |
Document ID | / |
Family ID | 8871338 |
Filed Date | 2007-07-26 |
United States Patent
Application |
20070169867 |
Kind Code |
A1 |
Esnault; Philippe ; et
al. |
July 26, 2007 |
Tire reinforced by hybrid cables
Abstract
Presented is a tire that includes a crown, which is extended by
two sidewalls and two beads and which includes a carcass ply
anchored in the beads. The crown includes at least one reinforcing
crown ply that includes parallel cables, which are oriented
relative to the circumferential direction by an angle .alpha. of
between 10 and 45 degrees. The crown further includes at least one
hooping crown ply that includes cables oriented in the
circumferential direction, which are wound in a spiral. The hooping
crown ply is made of a composite fabric that includes a rubber
composition based on at least one diene elastomer which is
reinforced by hybrid cables that each have a ratio of final tensile
tangent modulus:initial tensile tangent modulus which is greater
than 10.
Inventors: |
Esnault; Philippe;
(Greenville, SC) ; Pacherie; Hubert;
(Clermont-Ferrand, FR) ; Chavaroche; Pierre;
(Clermont-Ferrand, FR) ; Fickinger; Pascal;
(Royat, FR) ; Mus; Jean-Marie; (Marsat,
FR) |
Correspondence
Address: |
COHEN, PONTANI, LIEBERMAN & PAVANE
551 FIFTH AVENUE
SUITE 1210
NEW YORK
NY
10176
US
|
Family ID: |
8871338 |
Appl. No.: |
11/726812 |
Filed: |
March 23, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10877364 |
Jun 25, 2004 |
7222481 |
|
|
11726812 |
Mar 23, 2007 |
|
|
|
PCT/EP03/00311 |
Jan 15, 2003 |
|
|
|
10877364 |
Jun 25, 2004 |
|
|
|
Current U.S.
Class: |
152/340.1 ;
152/527; 152/531 |
Current CPC
Class: |
D02G 3/22 20130101; Y10T
152/10594 20150115; D02G 3/48 20130101; Y10T 428/2913 20150115;
B60C 9/005 20130101 |
Class at
Publication: |
152/340.1 ;
152/531; 152/527 |
International
Class: |
B60C 9/00 20060101
B60C009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2002 |
FR |
FR 02/00571 |
Claims
1. A tire comprising: a crown which is extended by two sidewalls
and two beads and which comprises a carcass ply anchored in said
beads, said crown comprising: at least one reinforcing crown ply
comprising parallel cables which are oriented relative to the
circumferential direction by an angle .alpha. of between 10 and 45
degrees, and at least one hooping crown ply comprising cables
oriented in said circumferential direction which are wound in a
spiral, wherein said hooping crown ply is made of a composite
fabric comprising a rubber composition based on at least one diene
elastomer which is reinforced by hybrid cables that each have a
ratio of final tensile tangent modulus:initial tensile tangent
modulus which is greater than 10.
2. A tire according to claim 1, wherein said hooping crown ply is
arranged radially to the outside of every said reinforcing crown
ply.
3. A tire according to claim 1, wherein said hooping crown ply is
arranged radially to the inside of said carcass ply.
4. A tire according to claim 1, in which said crown comprises at
least two superposed reinforcing crown plies each comprising
parallel cables which are crossed from one ply to the other,
forming with said circumferential direction angles of between 10
and 45 degrees, wherein said hooping crown ply is arranged between
said reinforcing crown plies.
5. A tire according to claim 1, wherein said crown comprises at
least two superposed reinforcing crown plies each comprising
parallel cables which are crossed from one ply to the other,
forming with said circumferential direction angles of between 10
and 45 degrees, wherein said hooping crown ply is arranged between
said carcass reinforcement and the reinforcing crown ply located
radially furthest to the inside.
6. A tire according to claim 1, wherein, over its entire width, the
hybrid cables of said hooping crown ply have a high-temperature
contraction potential (CS), in the vulcanized, new state of said
tire, which is less than or equal to the high-temperature
contraction potential of these same cables which have been
adherised before their incorporation into said hooping crown
ply.
7. A mounted assembly usable for fitting on a heavy vehicle, said
mounted assembly comprising: a rim; a tire mounted on said rim; and
a support membrane which is mounted on said rim within said tire
and which is adapted to support said tire in the event of a drop in
the pressure within said tire, such that said mounted assembly
comprises in its inner space two mutually airtight cavities which
are separated from each other by said membrane, which is reinforced
in its crown by at least one reinforcing crown ply and by a hooping
crown ply, which comprises cables oriented in the circumferential
direction of said mounted assembly, wherein said hooping crown ply
is made of a composite fabric comprising a rubber composition based
on at least one diene elastomer which is reinforced by hybrid
cables that each have a ratio of final tensile tangent modulus:
initial tensile tangent modulus which is greater than 10.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of application Ser.
No. 10/877,364, filed Jun. 25, 2004, which is a continuation of
International Application No. PCT/EP 03/00311, filed Jan. 15, 2003,
published in French with an English Abstract on Jul. 24, 2003 under
PCT Article 21(2) as WO 03/060212, which claims priority to French
Patent Application No. 02/00571, filed Jan. 17, 2002.
FIELD OF THE INVENTION
[0002] The present invention relates to a tire reinforced by hybrid
cables and a mounted assembly which incorporates a composite
fabric.
BACKGROUND OF THE INVENTION
[0003] The development of tires intended to be fitted on passenger
vehicles of the type which travel at high speeds has given rise to
increasingly high-performance architectures being developed for
these tires.
[0004] One solution conventionally used for these "high-speed" tire
architectures consists of covering the working crown plies of these
tires, which comprise metallic or textile reinforcement elements,
with what is called a hooping crown ply, usually reinforced by
textile cables. This hooping crown ply, which is for example
arranged radially to the outside of the crown reinforcement of the
tire, is in particular characterized in that the cables which
reinforce it are arranged in a spiral at an angle of 0.degree. or
close to 0.degree. with the median circumferential plane of the
tire. It is also known to arrange relatively narrow strips or plies
at an angle of approximately 0.degree. instead of the
aforementioned cables, in order to fulfill a hooping function of
the crown reinforcement.
[0005] Hybrid cables of plied-yarn type, which are formed of two
threads based on materials of low and high initial moduli
respectively which are twisted together, in order to impart to the
cable thus obtained a tensile modulus which is reduced at low
deformation and on the contrary high at high deformation have in
the past been tested as textile cables for hooping crown plies.
This decoupling of the tensile moduli of the cable results in the
presence of a transition point on the force/elongation curve of
said cable, and it is for example obtained using a polyamide 6,6
for the material of low modulus and aramid for the material of high
initial modulus.
[0006] For the description of such hybrid cables, reference may be
made to US patent specification U.S. Pat. No. 3,977,172 and to the
proceedings of the conference Kautschuk+Gummi Kunststoffe, vol. 40,
No. 2, February 1987, pages 130-135, in Heidelberg (Germany), E. R.
Barron, entitled "Hybrid tire cords containing kevlar.RTM.
aramid".
[0007] One major drawback of these hybrid cables having a
plied-yarn structure is the excessive hooping tension of the ply
comprising these cables, including at reduced speeds typically less
than 120 km/h, (i.e., at relatively low deformations). This tension
or premature "stiffening" of the cables results in a running noise
due to the tire which is significant at these speeds, which
represents a significant source of discomfort for the occupants of
the vehicle.
SUMMARY OF THE INVENTION
[0008] One object of the present invention is to overcome this
drawback, and it is achieved in that the Applicants have recently
surprisingly obtained hybrid cables each having a ratio of final
tangent modulus:initial tangent modulus greater than 10, which
makes it possible for example to reinforce a hooping crown ply of a
tire such that:
[0009] at reduced deformations inherent at a speed of travel of
less than 100 or 120 km/h, the hooping crown ply produces reduced
running noise, and that
[0010] at high deformations inherent at a speed of travel typically
greater than 120 km/h, this crown ply performs its hooping function
satisfactorily.
[0011] It will be noted that the value of the ratio of final
tangent modulus:initial tangent modulus which characterizes the
hybrid cables according to the invention is greater than those of
the same ratios which characterize the hybrid cables obtained to
date, which are always less than 10.
[0012] Advantageously, this ratio is greater than 12 for the hybrid
cables according to the invention, and it is for example between 12
and 30.
[0013] It will be noted that the present invention is in no way
limited to use in a hooping crown ply of these hybrid cables, and
that it covers any use in tires which may be of passenger-vehicle
type or intended to bear heavy loads, for example heavy-vehicle
tires, or tires for agricultural or construction machinery.
[0014] It will also be noted that the hybrid cables according to
the invention make it possible to improve the endurance at high
speed (typically greater than 120 km/h) of the crown reinforcement
of tires the hooping crown ply of which is reinforced by these
cables.
[0015] "Hybrid cable" is understood in the present description to
mean a composite cable, i.e., one constituted of at least two
materials of different natures and/or properties.
[0016] Initial tangent modulus" of the hybrid cable according to
the invention is understood in the present description to mean the
slope of the tangent to the force/elongation curve of this cable
corresponding to a zero elongation. "Final tangent modulus" of this
hybrid cable is understood to mean the slope of the tangent to the
force/elongation curve of said cable for an elongation
corresponding to the breaking thereof.
[0017] It will be noted that the hybrid cables according to the
invention each have a force/elongation curve which is very close to
the trace of the aforementioned tangents to this curve
corresponding respectively to a zero elongation and to the breaking
of the cable, which results in decoupling of the tangent moduli of
said cable at low and high deformations (i.e., at travelling speeds
which are reduced and high respectively).
[0018] According to a preferred embodiment of the invention, said
hybrid cables are of the wrapped type, comprising a textile core of
an initial modulus of less than 900 cN/tex and a textile wrap of an
initial modulus greater than 1300 cN/tex which is wound on said
core.
[0019] "Initial modulus" of the core or the wrap is understood in
the present description to mean the tensile modulus at low
deformation of each of these constituents which has first been
extracted from the wrapped hybrid cable. This initial modulus is
defined as being the slope of the linear part of the
force/elongation curve of the core or of the wrap in the raw state,
measured just after a standard initial tension of 0.5 cN/tex.
[0020] Said initial moduli and said tangent moduli, as well as all
the mechanical properties in extension mentioned in the present
description (tenacity, elongation at break, in particular) are
measured in known manner by means of measurements of force
(daN)/elongation (%) type, carried out by means of an "INSTRON"
machine with "4D" grippers and using the following operating
parameters:
[0021] traction length: 400 mm,
[0022] traction rate: 200 mm/min,
[0023] standard initial tension: 0.5 cN/tex.
[0024] "Wrapped" cable is understood by definition in the present
description to mean a "straight" core on which a wrap is wound, for
example in a helix. Reference may for example be made to U.S. Pat.
No. 4,343,343 and U.S. Pat. No. 4,893,665 for the description of
wrapped cables which meet this definition.
[0025] The expression "straight core" (also conventionally
designated in English by the term "core" or "core yarn") is
understood to mean a single thread or several threads twisted
together on which is wound the wrap (also frequently designated in
English by the term "sheath" or "sheath yarn"), which is also
formed of a single thread or of several threads twisted together.
The assembly of the wrap on the core is therefore carried out
without a plying operation on these two constituents, unlike the
aforementioned cables of plied structure.
[0026] In the present description, the term "thread" designates
equally well a spun yarn based on a multitude of elementary
filaments of low diameter which are twisted together (for example a
spun yarn based on around one hundred elementary filaments each
having a diameter close to about ten microns), and a single
monofilament.
[0027] "Monofilament" is understood to mean a unit filament
(non-twisted by definition), the diameter or thickness D of which
(that is to say, the smallest transverse dimension of its
cross-section when this is not circular) is at least equal to 40
.mu.m (minimum linear density of 1.7 tex). This definition
therefore covers equally well monofilaments of essentially
cylindrical shape (i.e., with a circular section) and oblong
monofilaments, of flattened shape, or even strips or films of
thickness D.
[0028] According to one example of embodiment of said preferred
mode according to the invention, the wrapped hybrid cable is such
that said core is formed of a single spun yarn and that said wrap
is formed of one or more spun yarns twisted together, preferably
from two to four spun yarns twisted together. In this case, a twist
of the order of several tens or even several hundreds of
turns/meter was imposed on the spun yarn forming the core before
winding the wrap on said core.
[0029] According to another example of embodiment of said preferred
mode according to the invention, the wrapped hybrid cable is such
that said core is formed of several spun yarns twisted together and
that said wrap is formed of one or more spun yarns twisted
together.
[0030] According to another example of embodiment of said preferred
mode according to the invention, the wrapped hybrid cable is such
that said core is formed of a monofilament and that said wrap is
formed of a single spun yarn or of several spun yarns twisted
together.
[0031] According to another example of embodiment of said preferred
mode according to the invention, the wrapped hybrid cable is such
that said core is formed of a single spun yarn or of several spun
yarns twisted together and that said wrap is formed of a
monofilament.
[0032] According to another example of embodiment of said preferred
mode according to the invention, the wrapped hybrid cable is such
that said core and said wrap are each formed of a monofilament.
[0033] In the present description, the linear density of the spun
yarns was determined on at least three samples, each corresponding
to a length of 50 m, by weighing this length of spun yarn. The
linear density is given in tex (weight in grams of 1000 m of spun
yarn--reminder: 0.111 tex equals 1 denier).
[0034] The tenacity (breaking load divided by linear density) and
the various tensile moduli are indicated in cN/tex (1 cN/tex=011
g/den). The elongation at break is indicated in %.
[0035] In non-limiting manner, the core of the wrapped hybrid cable
of the invention may be formed:
[0036] of an aliphatic polyamide, such as a polyamide 6,6,
[0037] of an aliphatic polyester, such as polyethylene
terephthalate (PET), polyethylene naphthalate (PEN), or
[0038] of rayon.
[0039] The wrap of the wrapped hybrid cable according to the
invention may be for example formed: [0040] of an aromatic
polyamide, such as aramid, or
[0041] of an aromatic polyester, such as the polyester sold under
the name "VECTRA", or alternatively
[0042] of a cellulose or a cellulose derivative of liquid-crystal
origin of high initial modulus (in particular greater than 1500
cN/tex), such as described for example in patent specifications
WO-A-85/05115, WO-A-96/09356 and WO-A-97/06294.
[0043] According to one example of embodiment of said preferred
mode according to the invention, the wrapped hybrid cable comprises
a core of aliphatic polyamide, such as a polyamide 6,6, and a wrap
of aromatic polyamide, such as aramid, or of cellulose of high
modulus of liquid-crystal origin.
[0044] According to another characteristic of said preferred mode
according to the invention, the wrapped hybrid cable is such that
said core has an elongation at break greater than 10%.
[0045] According to another characteristic of said preferred mode
according to the invention, the wrapped hybrid cable has a force
(daN)/elongation (%) curve having a transition point, on this side
of which the tensile modulus of the cable is substantially equal to
that of the core and beyond which the tensile modulus of this cable
is substantially equal to that of the wrap, this transition point
corresponding to an elongation of between 1 and 7%, preferably of
between 2 and 4%.
[0046] In known manner, "transition point" (or point of change in
slope) refers to the point corresponding to the elongation for
which the two tangents at zero elongation and at break
intersect.
[0047] The wrapped hybrid cable in accordance with said preferred
mode of embodiment of the invention is obtained by a process
consisting essentially of:
[0048] obtaining separately a core and a wrap each formed of a
single thread or of a plurality of threads twisted together,
then
[0049] winding, for example in a helix, the wrap on the core, such
that the twisting pitch of the core in the wrapped cable is greater
than that of the wrap.
[0050] This assembly is effected for example by means of a
volumetric cabling device and a ring-type frame.
[0051] A composite fabric according to the invention comprises a
rubber composition based on at least one diene elastomer which is
reinforced by said hybrid cables according to the invention (i.e.,
each having a ratio of final tangent modulus: initial tangent
modulus greater than 10), and this composite fabric is usable
advantageously in a tire.
[0052] "Diene" elastomer is understood to mean, in known manner, an
elastomer resulting at least in part (i.e., a homopolymer or a
copolymer) from diene monomers, that is to say from monomers
bearing two double carbon-carbon bonds, whether conjugated or
not.
[0053] Preferably, this rubber composition is based on at least one
diene elastomer the molar ratio of units originating from
conjugated dienes of which is greater than 15% (such a diene
elastomer is commonly referred to as "essentially
unsaturated").
[0054] Thus, for example, diene elastomers such as butyl rubbers or
copolymers of dienes and of alpha-olefins of the EPDM type do not
fall within the preceding definition, and may be described as
"essentially saturated" diene elastomers (molar ratio of units
originating from dienes which is always less than 15%).
[0055] Even more preferably, this rubber composition is based on at
least one diene elastomer the molar ratio of units originating from
conjugated dienes of which is greater than 50% (such a diene
elastomer is commonly referred to as "highly unsaturated"). This
diene elastomer is then preferably selected from among the group
consisting of polybutadienes, natural rubber, synthetic
polyisoprenes, the various butadiene copolymers, the various
isoprene copolymers and mixtures of these elastomers.
[0056] Of the polybutadienes, in particular those having a content
of -1,2 units of between 4% and 80% or those having a content of
cis-1,4 greater than 80% are suitable.
[0057] Of the synthetic polyisoprenes, in particular
cis-1,4-polyisoprenes, preferably those having an amount of cis-1,4
bonds greater than 90%, are suitable.
[0058] Among the butadiene or isoprene copolymers, these are
understood to be in particular the copolymers obtained by
copolymerization of at least one of these two monomers with one or
more vinyl-aromatic compounds having from 8 to 20 carbon atoms.
Suitable vinyl-aromatic compounds are, for example, styrene,
ortho-, meta- and para-methylstyrene, the commercial mixture
"vinyltoluene", para-tert. butylstyrene, methoxystyrenes,
chlorostyrenes, vinylmesitylene, divinylbenzene and
vinyinaphthalene. The copolymers may contain between 99% and 20% by
weight of diene units and between 1% and 80% by weight of
vinyl-aromatic units.
[0059] Of the butadiene or isoprene copolymers above, mention will
preferably be made of butadiene/styrene copolymers,
isoprene/butadiene copolymers, isoprene/styrene copolymers or
isoprene/butadiene/styrene copolymers.
[0060] In summary, preferably a diene elastomer selected from the
group of "highly unsaturated" diene elastomers consisting of
polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes
(IR), butadiene/styrene copolymers (SBR), isopreneibutadiene
copolymers (BIR), isoprene/styrene copolymers (SIR),
butadiene/styrene/isoprene copolymers (SBIR) and mixtures of these
elastomers is suitable.
[0061] Advantageously, the rubber composition of the composite
fabric according to the invention comprises in a majority
proportion (i.e., in a mass fraction greater than 50%) or in its
entirety one or more "highly unsaturated" diene elastomers as
defined above, possibly in association with one or more
"essentially saturated" diene or non-diene elastomers used in a
minority proportion, and/or in association with polymers other than
elastomers (for example thermoplastic polymers) also used in a
minority proportion.
[0062] The rubber compositions of the composite fabrics according
to the invention also comprise all or some of the additives usually
used in the manufacture of tires, such as reinforcing fillers such
as carbon black or silica, anti-ageing agents, for example
antioxidants, extender oils, plasticizers or agents which
facilitate processing of the compositions in the uncured state, a
cross-linking system based on either sulfur, or on sulfur and/or
peroxide donors, accelerators, vulcanization activators or
retarders, methylene acceptors and donors, resins, known
adhesion-promoting systems of the type "RFS"
(resorcinol/formaldehyde/sil-ica) or metal salts, in particular
cobalt salts.
[0063] The composite fabric according to the invention may be
present in varied forms, for example in the form of a ply, a band,
strip or a block of rubber in which there is incorporated the
metallic reinforcing thread using different means known to the
person skilled in the art, such as for example molding, calendering
or extrusion means.
[0064] A tire according to a first embodiment of the present
invention comprises a crown which is extended by two sidewalls and
two beads and which comprises a carcass ply anchored in said beads,
said crown comprising:
[0065] at least one reinforcing crown ply comprising parallel
cables which are oriented relative to the circumferential direction
by an angle .alpha. of between 10 and 45 degrees, and
[0066] at least one hooping crown ply comprising cables oriented in
said circumferential direction which are wound in a spiral, and
this tire is such that said hooping crown ply is constituted of the
composite fabric according to the invention as defined
previously.
[0067] According to one example of embodiment of this first mode
according to the invention, this tire is such that said hooping
crown ply is arranged radially to the outside of said reinforcing
crown ply (plies).
[0068] According to another example of embodiment of this first
mode according to the invention, this tire is such that said
hooping crown ply is arranged radially to the inside of said
carcass ply.
[0069] According to another example of embodiment of this first
mode according to the invention, this tire is such that said crown
comprises at least two superposed reinforcing crown plies each
comprising parallel cables which are crossed from one ply to the
other, forming with said circumferential direction angles (.alpha.,
.beta.) of between 10 and 45 degrees, and that said hooping crown
ply is arranged between said reinforcing crown plies.
[0070] According to another example of embodiment of this first
mode according to the invention, this tire is such that said crown
comprises at least two superposed reinforcing crown plies each
comprising parallel cables which are crossed from one ply to the
other, forming with said circumferential direction angles (.alpha.,
.beta.) of between 10 and 45 degrees, and such that said hooping
crown ply is arranged between said carcass ply and the reinforcing
crown ply which is located radially farthest to the inside.
[0071] With reference to any one of these examples of embodiment of
said first mode according to the invention, said tire is
advantageously such that, over its entire width, the hybrid cables
of said hooping crown ply have a high-temperature contraction
potential (CS), in the vulcanized, new state of said tire, which is
less than or equal to the high-temperature contraction potential of
these same cables which have been adherised before their
incorporation into said hooping crown ply.
[0072] The Applicants have noted that this high-temperature
contraction potential characteristic of the hybrid cables of the
hooping crown ply makes it possible to reduce even more markedly
the running noise of the tire at reduced speed, while imparting
thereto a high level of resistance at high speed.
[0073] The hybrid cables laid circumferentially with laying
diameters which deviate, over the entire width of the crown, by
less than 0.5% from the final diameters of these cables in the tire
after vulcanization, do not undergo any significant shaping
operation during the building of the tire or its vulcanization.
Such significant shaping would involve, for example, during the
building or the vulcanization, a local extension of these cables
greater than 2 or 3%. This extension generally adversely affects
the properties of the cables thus deformed, in particular their
modulus, their contraction potential and their state of
tension.
[0074] As a result, the hybrid cables used, in the vulcanized tire
and over all of the ply, are in a state very close to that of the
adherised cables before they are placed in the tire.
[0075] "Adherised cables" is understood to mean cables which have
undergone an appropriate coating treatment, referred to as sizing
or adherising treatment, capable of making them adhere, after
suitable heat treatment, to the aforementioned rubber composition.
The cables are sized in a succession of steps by passing into glue
baths typical of the prior art, and heat-treated under a tension
making it possible to impart thereto the level of contraction
potential (CS) required.
[0076] "High-temperature contraction potential" (CS) is understood
to mean the relative variation in length of a textile reinforcing
thread positioned, under a prestress equal to the half-sum of the
linear densities of each of the elementary yarns, between the
shelves of an oven (TESTRITE.TM.-type) regulated at a constant
temperature of 185.+-.0.5.degree. C. This potential is expressed in
% by the following formula:
[0077] CS (%)=100.times.|L.sub.1-L.sub.0|/L.sub.0, where L.sub.0 is
the initial length of the adherised reinforcing thread, at ambient
temperature under a prestress equal to the half-sum of the linear
densities of each of the elementary yarns and L.sub.1 the length of
this same reinforcing thread at 185.degree. C. The length L.sub.1
is measured at the end of a reinforcing thread stabilisation time
at a temperature of 185.degree. C. equal to 120 s.+-.2%. The
standard deviation on the CS measurement is .+-.0.15%.
[0078] This potential is the direct consequence of the series of
operations which the reinforcing thread underwent on its
manufacture or on its use.
[0079] The high-temperature contraction potential of the hybrid
cables according to the invention before their incorporation in the
tire is preferably greater than 0.5% and, even more preferably,
greater than 1%.
[0080] After vulcanization of a tire according to the invention,
several sections of hybrid cables were extracted from the hooping
crown ply and their high-temperature contraction potential was
measured immediately (that is, the time interval separating
extraction of the cables from introduction of these same cables
into the TESTRITE.TM. oven is less than 60 seconds). These
measurements confirmed that the value of their CS is far less than
or equal to what they had before introduction into the tire,
whatever their axial position in the tire.
[0081] According to one embodiment according to the invention, the
tire according to the invention can advantageously be built on a
rigid core imposing the shape of its inner cavity, such as those
described in patent specifications EP-A-242 840 or EP-A-822 047.
There are applied to this core, in the order required by the final
architecture, all the constituents of the tire, which are arranged
directly in their final position, without undergoing shaping at any
moment of the building operation. The curing takes place on the
core, the latter only being removed after the vulcanization phase
has finished.
[0082] This method of manufacture has the advantage of greatly
reducing, or even eliminating, the pre-stresses imposed on the
cables, particularly the hybrid cables oriented at 0.degree.,
during the traditional shaping phases.
[0083] The non-pneumatic tire may also be partially cooled on the
core in order to keep the reinforcing threads in the state of
deformation imposed upon laying.
[0084] According to another embodiment of the invention, it is also
possible to manufacture the tire equivalently on a drum such as
described in patent specifications WO-A-97/47463 or EP-A-718 090,
on condition that the tire blank be shaped before laying the
circumferentially oriented hybrid cables.
[0085] According to another embodiment according to the invention,
the hybrid cables can also be laid on a form with geometry
identical to the form aimed at in the curing mould. The crown block
is then assembled with the complementary blank of the tire using
transfer techniques known to the person skilled in the art, then,
still using known principles, the tire is fitted and pressurized by
deploying a membrane inside the tire.
[0086] This embodiment also guarantees the absence of pre-stresses
due to the shaping in the vulcanization press.
[0087] All these embodiments make it possible to obtain
circumferentially oriented hybrid cables that are spiral-wound with
laying diameters diverging, over the whole width of the crown, by
less than 0.5% from the final diameters of these cables in the tire
after vulcanization.
[0088] A mounted assembly according to one example of embodiment of
the invention, usable for fitting on a heavy vehicle, comprises a
rim, a tire mounted on said rim and a support membrane which is
mounted on said rim within said tire and which is adapted to
support said tire in the event of a drop in the pressure within
said tire, such that said mounted assembly comprises in its inner
space two mutually airtight cavities which are separated from each
other by said membrane, which is reinforced in its crown by at
least one reinforcing crown ply and by a hooping crown ply, which
comprises cables oriented in the circumferential direction of said
mounted assembly.
[0089] This mounted assembly is such that said hooping crown ply is
constituted of the composite fabric according to the invention as
defined previously.
[0090] The cavity inside this membrane is intended to be inflated
to a pressure greater than that of the remaining cavity of the
tire. Under these conventional conditions of use, the membrane has
a rolling radius at the crown which is less than the loaded radius
of the tire used at its recommended pressure.
[0091] In the event of a puncture in the tire, as soon as the
pressure difference between the cavity inside the membrane and that
of the tire exceeds a given value, the hooping crown ply of the
membrane breaks, causing the membrane to be deployed beneath the
tire and thus enabling the mounted assembly to continue to travel
under acceptable conditions in degraded mode. Reference may be made
to patent specification WO-A-98/23457 for a description of the
general operation of this mounted assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0092] The aforementioned characteristics of the present invention,
as well as others, will be better understood on reading the
following description of several examples of embodiment of the
invention, which are given by way of illustration and not of
limitation, said description being made with reference to the
attached drawings, in which:
[0093] FIG. 1 is a graph illustrating the force/elongation
characteristic of a hooped hybrid cable according to the
invention,
[0094] FIG. 2 is a view in axial half-section of a tire comprising
a hooping crown ply arranged according to one embodiment of the
invention,
[0095] FIG. 3 is a view in axial half-section of a tire comprising
a hooping crown ply arranged according to another example of
embodiment of the invention,
[0096] FIG. 4 is a view in axial half-section of a tire comprising
a hooping crown ply arranged according to another example of
embodiment of the invention,
[0097] FIG. 5 is a view in axial half-section of a tire comprising
a hooping crown ply arranged according to another example of
embodiment of the invention,
[0098] FIGS. 6 and 7 represent respectively, diagrammatically,
diametrically opposed meridian sections through a mounted assembly
comprising a rim, a tire and a safety membrane, when the tire is
under load pressure and travelling under normal conditions,
[0099] FIGS. 8 and 9 represent respectively, diagrammatically
following the pattern of FIGS. 6 and 7, the meridian sections of
the same mounted assembly which is subjected to travel in degraded
mode, and
[0100] FIG. 10 shows a hybrid cable according to an embodiment of
the invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
Example of Embodiment of a Wrapped Hybrid Cable According to the
Invention
[0101] A wrapped hybrid cable according to the invention was
produced by producing separately, in the opposite direction and at
the same twisting pitch:
[0102] on one hand, a thread which is twisted on itself (commonly
referred to as "folded yarn" by the person skilled in the art)
based on a spun yarn of polyamide 6,6 of a linear density equal to
94 tex which is intended to constitute the core of the cable
and,
[0103] on the other hand, a thread based on two spun yarns plied
together (commonly referred to as "plied yarn" by the person
skilled in the art) made of Kevlar.RTM.(aramid), each having a
linear density equal to 167 tex, this thread being intended to
constitute the wrap of said cable.
[0104] More precisely, the core plied yarn is twisted in the S
direction at a pitch of 200 turns/meter (S200), and the wrap spun
yarns are twisted together in the Z direction at the same pitch
(Z200).
[0105] Then the wrap thread is wound in a helix on the core thread,
imparting an additional twist of 115 turns/meter, by means of a
volumetric cabling device and a ring-type frame, this additional
twist being effected in the twisting direction (S) of the core,
such that the twisting pitch of the core in the wrapped cable is
315 turns/meter in the S direction, and that that of the wrap in
said cable is 85 turns/meter in the Z direction.
[0106] The wrapped hybrid cable thus obtained is then sized, using
a treatment tension of 0.25 daN.
[0107] FIG. 1 shows the force/elongation curve obtained for this
sized wrapped hybrid cable according to the invention (reference 1
in this FIG. 1), in comparison:
[0108] with the curve 2 of a thread of plied-yarn type, which is
formed of two Kevlar.RTM. spun yarns twisted together (each having
a linear density of 167 tex and being twisted at a pitch of 315
turns/meter), and
[0109] with the curve 3 of a spun yarn of polyamide 6,6 (having a
linear density of 94 tex and being twisted on itself at a pitch of
300 turns/meter).
[0110] There are also shown in this FIG. 1 the tangents to the
curve 1 of the wrapped hybrid cable according to the invention, on
one hand, for a zero elongation (tangent T.sub.i) and, on the other
hand, for an elongation corresponding to the breaking of the cable
(tangent T.sub.R). These tangents intersect at a transition point
corresponding to an elongation of the cable of approximately
2.5%.
[0111] Calculating the slopes of these tangents T.sub.i and T.sub.R
gives the initial and final tangent moduli of the cable for a zero
elongation and an elongation at break, respectively. The ratio of
final tangent modulus:initial tangent modulus of said cable is
deduced therefrom.
[0112] There is obtained for the tangent T.sub.R a slope of
approximately 1.01 daN and, for the tangent T.sub.i, a slope of
approximately 0.078 daN, hence a value of 12.95 for the value of
the ratio of final tangent modulus:initial tangent modulus of the
wrapped hybrid cable according to the invention.
[0113] This very significant decoupling of the tangent moduli at
low and high deformations results in the fact that the
force/elongation curve of the wrapped hybrid cable according to the
invention is very close to the trace of the tangents T.sub.i and
T.sub.R.
[0114] It will be noted that at reduced deformations inherent at a
speed of travel of less than 120 km/h for example, the tensile
modulus of the wrapped hybrid cable corresponds substantially to
that of the core which it comprises (see the analogous slopes of
the characteristics 1 and 3 at low elongation in FIG. 1), which
results in reduced running noise, when this cable is used as
reinforcement element for a hooping crown ply of a tire.
[0115] It will also be noted that at high deformations inherent at
a speed of travel of greater than 120 km/h for example, the tensile
modulus of the wrapped hybrid cable corresponds substantially to
that of the wrap which it comprises (see the analogous slopes of
the characteristics 1 and 2 at high elongation in FIG. 1), which
results in a satisfactory hooping function of the crown ply
reinforced by these cables.
[0116] FIG. 10 shows such a hybrid cable 50 consisting of a
straight textile core 51 and single textile wrap 52 which is
helically wound around the core 51.
[0117] The two series of tests below illustrate the advantages
provided by the wrapped hybrid cables according to the invention in
tire hooping crown plies.
First Series of Running Tests on a Vehicle Fitted With
Passenger-Vehicle Tires the Crown of Which Comprises Two Crossed
Reinforcing Crown Plies and a Hooping Crown Ply.
[0118] These tests relate to tires A, B and C of dimensions
235/55-17 which are intended to be fitted on high-speed vehicles of
passenger-vehicle type. The crown block of each of these tires
comprises two crossed reinforcement plies each comprising
non-hooped metal 6.23 cables with a pitch of 1.5 mm, and also a
hooping crown ply comprising cables oriented in the circumferential
direction of the tire.
[0119] In the case of the tires A, the cables of this hooping crown
ply are made of polyamide 6,6 (conventional hooping solution for a
"high performance" tire). In order to obtain an acceptable speed
resistance, this ply is arranged in two superposed layers by a
technique of winding a band of cables coated in rubber in a spiral.
The density of these cables is 200 cables per dm.
[0120] In the case of the tires B, the cables of this hooping crown
ply are made of aramid. This ply is arranged in a single layer with
a cable density of 50 cables per dm.
[0121] In the case of the tires C, the cables of this hooping crown
ply are made of the wrapped hybrid cables according to the
invention manufactured in accordance with the above example of
embodiment (based on an aramid wrap wound in a helix on a polyamide
6,6 core). This ply is also arranged in a single layer with a cable
density of 50 cables per dm.
[0122] Four tests were carried out for each of these tires A, B and
C:
[0123] "body hum": this test is representative for a passenger of
the acoustic discomfort caused on passage of the vehicle at a
constant speed over a highway-type road of average grading. A
vehicle is run at a given speed over a standardized measurement
area, and microphones register the noise level in dB(A);
[0124] "coast by" noise: this test is representative for a nearby
resident of the acoustic discomfort produced on passage of the
vehicle at constant speed over a motorway-type road of intermediate
grading. The vehicle is made to pass at a given speed, transmission
in neutral and engine switched off, over a standardised measurement
area (standard ISO DIS 10 844), and microphones register the noise
levels in dB(A);
[0125] "contact": this test is representative for a passenger of
the vibration and acoustic discomfort caused on passage of the
vehicle at a constant speed over an obstacle of manhole-cover type.
The vehicle is made to pass over this cover at a given speed, and
the operator assesses the vibratory and acoustic level then
translates the gain (-) or the degeneration (+) on a scale from -2
to +2, the "control" tire (reference) being at 0;
[0126] speed resistance: at a given load and inflation pressure,
the speed of the tire is progressively increased until it is
destroyed, and the result of the test is given by the maximum speed
attained and by observation of the cause of destruction of the
tire.
[0127] Tables 1 and 2 below show the results obtained.
TABLE-US-00001 TABLE 1 Hooping Ply density.sup.0 Coast by Speed
Tires crown ply (cables/dm) Body hum noise Contact resistance A
Polyamide By-layer - 200 reference reference reference 100 6,6 C
wrapped Monolayer - 50 -0.4 dB(A) equal to -0.5 pts 110 hybrids
reference
[0128] This Table 1 shows that the wrapped hybrid cables used in
the hooping crown ply impart to the tires C according to the
invention, compared with the "control" tires A incorporating cables
of polyamide 6,6 in the hooping crown ply, an improvement in the
speed resistance and also a reduction in the "body hum" and
"contact" noise, despite the cable density which is lower than that
used in these "control" tires A.
[0129] It will be noted that these wrapped hybrid cables do not
adversely affect the "coast by " noise of the tires C according to
the invention, compared with that of the "control" tires A.
TABLE-US-00002 TABLE 2 Hooping Ply density.sup.0 Speed Tires crown
ply (cables/dm) Coast by noise resistance B aramid Monolayer 50
reference 100 C wrapped hybrids Monolayer - 50 -2 dB (A) 100
[0130] This table 2 shows that, considering the tire B as
"control", the wrapped hybrid cables impart to the tire C according
to the invention a great reduction in "coast by" noise, without the
speed resistance being adversely affected.
Second Series of Running Tests on a Vehicle Fitted With
Passenger-Vehicle Tires the Crown of Which Comprises Two Crossed
Reinforcing Crown Plies, Two Other Reinforcing Crown Plies and a
Hooping Crown Ply.
[0131] These tests also relate to tires D and E of dimensions
235/55-17 which are intended to be fitted on high-speed vehicles of
passenger-vehicle type. The crown block of each of these tires
comprises two crossed reinforcement plies each comprising
non-hooped 2.23 metal cables with a pitch of 0.7 mm, two other
reinforcing crown plies each comprising non-hooped 4.23 metal
cables with a pitch of 1.25 mm, and also a hooping crown ply
comprising cables oriented in the circumferential direction of the
tire.
[0132] In the case of the tires D, the cables of this hooping crown
ply are made of polyamide 6,6. This ply is arranged in two
superposed layers by a technique of winding a band of cables coated
in rubber in a spiral. The density of these cables is 200 cables
per dm.
[0133] In the case of the tires E, the cables of this hooping crown
ply are made of the wrapped hybrid cables according to the above
example of embodiment of the invention (based on an aramid wrap
wound in a helix on a polyamide 6,6 core). This ply is arranged in
a single layer with a cable density of 50 cables per dm.
[0134] An additional test was carried out for these tires D and
E:
[0135] determination of the drift rigidity: at given speed,
inflation pressure and load, a drift angle is set and the resultant
drift thrust is measured, the result being expressed by taking the
drift thrust:drift angle ratio. The measurement is conventionally
made between .+-.0.1 degree drift angle.
[0136] Table 3 hereafter shows the results obtained for the drift
rigidity, "body hum" (abbreviated to "BH" below) and "contact"
tests. TABLE-US-00003 TABLE 3 Ply density Drift Rigidity Hooping
(reinforcing at 0.5 Z at 0.5 Z at 0.5 Z Tires crown ply thread/dm)
(ETRTO) (ETRTO) (ETRTO) BH Contact D Polyamide Bi-layer - 200 100
100 100 reference reference 6,6 E Wrapped Monolayer - 50 110 115
120 -0.4 dB(A) +0.5 pts hybrid
[0137] This Table 3 shows that the wrapped hybrid cables used in
the hooping crown ply impart to the tires E according to the
invention a greatly improved drift rigidity and also reduced "body
hum" and "contact" noise, compared with the "control" tires D.
Examples of Arrangement in the Tire of Hooping Crown Plies
Comprising the Wrapped Hybrid Cables According to the Invention
[0138] FIG. 2 shows an axial half-section through a tire P
according to the invention, which comprises a crown 4 extended by
two sidewalls 5 and two beads (not shown).
[0139] The crown 4 comprises a carcass ply 6 anchored in known
manner in the two beads, two reinforcement plies 7 and 8 formed of
cables which are parallel within each ply and are crossed from one
ply to the next, forming with the circumferential direction angles
(.alpha., .beta.) of the order of 30 degrees, and a hooping crown
ply 9 comprising the wrapped hybrid cables according to the
invention.
[0140] These wrapped hybrid cables are wound in a spiral to ensure
good hooping of the crown 4, and they are oriented in the
circumferential direction of the tire P.
[0141] The carcass ply 6 is of radial type, being oriented
substantially at 90 degrees relative to this circumferential
direction.
[0142] FIG. 3 shows a partial axial half-section through a tire P'
comprising as previously a carcass ply 6, two crossed reinforcement
plies 7, 8 and a hooping crown ply 9 which is arranged radially
between the carcass ply 6 and the two crossed reinforcement plies 7
and 8. This arrangement has the advantage of protecting the hooping
crown ply 9 from possible damage due to perforation of the
tread.
[0143] FIG. 4 shows a partial axial half-section through a tire P''
comprising as previously a carcass ply 6, two crossed reinforcement
plies 7, 8 and a hooping crown ply 9 which is arranged between the
two crossed reinforcement plies 7 and 8.
[0144] FIG. 5 shows a partial axial half-section through a tire
P''' comprising as previously a carcass ply 6, two crossed
reinforcement plies 7, 8 and a hooping crown ply 9 which is
arranged radially within the carcass ply 6.
[0145] It will be noted that the wrapped hybrid cables according to
the invention impart to the tires P, P', P'' or P''' the hooping
crown ply 9 of which incorporates these cables the aforementioned
advantages of a reduction in running noise at reduced speed and of
satisfactory hooping at high speed.
Example of Embodiment of a Mounted Assembly According to the
Invention Intended to be Fitted on a Heavy Vehicle
[0146] FIGS. 6 and 7 show a mounted assembly E according to the
invention for heavy vehicle comprising a tire P, a mounting rim J
and a support membrane M.
[0147] The tire P conventionally comprises sidewalls 20 joined
radially to the outside to a tread 21, and extended radially to the
inside by two beads 22, each bead being reinforced by at least one
bead wire 23 around which is anchored a radial carcass
reinforcement 24 to form upturns 25. The carcass reinforcement 24
is radially surmounted in the crown by a crown reinforcement 26,
composed of at least two plies of metal wires or cables which are
parallel to each other within each ply and crossed from one ply to
the next, forming with the circumferential direction of the tire P
an angle which may be of between 5.degree. and 40.degree..
[0148] The tire P is said to be tubeless, and comprises an internal
layer formed of a rubber composition impermeable to the inflation
gases. The assembly of tire P and rim J defines a first airtight
inner cavity 27.
[0149] The pneumatic support membrane M defines within the first
cavity 27 a second airtight cavity 15. This membrane M is closed,
comprises sidewalls 11 and is reinforced in its crown by a crown
reinforcement 12. The latter, which is readily expansible, is
associated with a hooping reinforcement 13 composed for example of
a hooping crown ply 130 of circumferentially oriented cables.
[0150] According to the invention, these circumferential cables of
the hooping crown ply 130 are wrapped hybrid cables according to
the invention, for example made of an aramid wrap wound in a helix
on a polyamide 6,6 core.
[0151] These wrapped hybrid cables enable the ply 130 to provide a
satisfactory hooping function of the membrane M, on one hand,
against the forces due to the centrifugal force and, on the other
hand, against the forces due to the pressure differential
p.sub.0-p.sub.1, p.sub.0 being the inflation pressure in the cavity
15 of the support membrane M, equal for example to
9.5.times.10.sup.5 Pa, and p.sub.1 being the pressure in the cavity
27 of the tire P, equal for example to 9.0.times.10.sup.5 Pa. These
inflation values are the rated values in the cold state in the
example selected.
[0152] This hooping function enables the membrane M to maintain,
under normal conditions of travel of the mounted assembly E, that
is to say under the conditions of load, pressure and speed
recommended for the tire P in question, a radius R.sub.M which is
practically constant and less than the loaded radius R.sub.E of the
tire P (FIG. 7 representing the loaded part of the mounted assembly
E under normal conditions of travel).
[0153] The membrane M is completed by the covering of the hooping
reinforcement 13, by a layer of rubber 14 of low thickness.
[0154] This pressure loss (p.sub.1 decreases), the pressure
difference p.sub.0-p.sub.1 increases until it becomes such that the
cables of the ply 130 break and thus permit the expansion of the
support membrane M until it completely occupies the cavity 27 of
the tire P (see FIGS. 8 and 9).
[0155] As the increase in volume involves a reduction in the
initial internal pressure p.sub.0 of the membrane M, the mounted
assembly E operates at a lower pressure .sub.P2, resulting in a
loaded radius R'.sub.E during travel in degraded mode which is less
than the loaded radius R.sub.E during normal travel (see FIG. 9).
The radius R'.sub.E however permits travel at moderate speed
without major degradation of the tire P and without human
intervention until the next service area, at which service area it
is then possible to provide the additional pressure necessary in
order to obtain a radius very close to the radius R.sub.E and
permit travel under practically normal conditions.
* * * * *