U.S. patent application number 15/562945 was filed with the patent office on 2018-04-26 for method for producing a reinforcement structure for a tire.
This patent application is currently assigned to COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN. The applicant listed for this patent is COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN. Invention is credited to Bertrand BOISDON, Thomas FABRE, Frederic PIALOT.
Application Number | 20180111419 15/562945 |
Document ID | / |
Family ID | 53274652 |
Filed Date | 2018-04-26 |
United States Patent
Application |
20180111419 |
Kind Code |
A1 |
FABRE; Thomas ; et
al. |
April 26, 2018 |
METHOD FOR PRODUCING A REINFORCEMENT STRUCTURE FOR A TIRE
Abstract
The reinforcing structure for a tire is in the form of a
stratified assembly formed of two layers of reinforcing strips of
completely connected cross section, and flattened in shape.
According to the method, the strips of each layer are laid side by
side in a main direction of laying. The strips of the first layer
are spaced apart by a distance that is less than the width of the
strips of the second layer and in such a way that the edges of the
strips of the first layer overlap the edges of the strips of the
second layer. The two layers of strips are separated by a layer of
uncoupling rubber.
Inventors: |
FABRE; Thomas; (Ladoux,
Clermont-Ferrand, Cedex 9, FR) ; PIALOT; Frederic;
(Ladoux, Clermont-Ferrand, Cedex 9, FR) ; BOISDON;
Bertrand; (Ladoux, Clermont-Ferrand, Cedex 9, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN |
Clermont-Ferrand |
|
FR |
|
|
Assignee: |
COMPAGNIE GENERALE DES
ETABLISSEMENTS MICHELIN
Clermont-Ferrand
FR
|
Family ID: |
53274652 |
Appl. No.: |
15/562945 |
Filed: |
March 30, 2016 |
PCT Filed: |
March 30, 2016 |
PCT NO: |
PCT/EP2016/056964 |
371 Date: |
September 29, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 43/28 20130101;
B60C 9/14 20130101; B60C 9/0057 20130101; B29D 30/38 20130101; B29D
2030/381 20130101; B29K 2105/0881 20130101; B29K 2667/003 20130101;
B29K 2105/20 20130101; B29D 30/3028 20130101; B29K 2995/0078
20130101; B29L 2030/00 20130101; B29C 43/24 20130101; B60C 9/023
20130101; B60C 9/2204 20130101; B29K 2021/003 20130101; B60C 9/0064
20130101; B60C 9/0042 20130101; B29K 2105/08 20130101; B60C
2009/2035 20130101; B60C 9/0028 20130101 |
International
Class: |
B60C 9/22 20060101
B60C009/22; B29D 30/30 20060101 B29D030/30; B29C 43/24 20060101
B29C043/24; B29C 43/28 20060101 B29C043/28; B60C 9/00 20060101
B60C009/00; B60C 9/02 20060101 B60C009/02; B60C 9/14 20060101
B60C009/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2015 |
FR |
1552667 |
Claims
1. A method of manufacturing a reinforcing structure for a tire in
the form of a stratified assembly formed of two layers of
reinforcing strips of completely connected cross section, and
flattened in shape, comprising the steps: laying the strips of each
layer side by side in a main direction of laying, spacing the
strips of the first layer apart by a distance that is less than the
width of the strips of the second layer and in such a way that the
edges of the strips of the first layer overlap the edges of the
strips of the second layer, and wherein the two layers of strips
are separated by a layer of uncoupling rubber.
2. The method of manufacturing a reinforcing structure according to
claim 1, wherein the strips of the first and the second layer have
the same width L and their edges overlap over at least 20% of the
width L.
3. The method according to claim 1, wherein the elastic modulus of
the strips is greater than 500 MPa.
4. The method according to claim 1, wherein the said stratified
assembly is arranged between and in contact with two layers of
rubber.
5. The method according to claim 1, wherein the said reinforcing
structure comprises, in this order: an external layer of elastomer
of a thickness comprised between 0.1 and 0.5 mm, a first layer of
reinforcing strips having a thickness comprised between 0.05 and
0.35 mm, a layer of uncoupling rubber of a thickness comprised
between 0.1 and 0.5 mm, a second layer of strips having a thickness
comprised between 0.05 and 0.35 mm, and an internal layer of
elastomer of a thickness comprised between 0.1 and 0.5 mm.
6. The method according to claim 1, wherein each strip has a width
L and the strips forming a layer are arranged with a pitch p of
less than 2L.
7. The method according to claim 6, wherein the amount of overlap
between the edges of the strips of the two layers of strips is
comprised between 0.2 and 0.5 times the pitch p.
8. The method according to claim 1, wherein the width L of the
strips is comprised between 1 and 12 mm, preferably between 3 and 7
mm.
9. The method according to claim 1, wherein the said strips are
made of a single material.
10. The method according to claim 9, wherein the said material is
selected from PET, PEN, aluminium, steel, or polyamides.
11. The method according to claim 1, wherein the reinforcing
structure is produced by calendering.
12. The method according to claim 1, wherein the reinforcing
structure is produced by winding successive layers onto a rotary
shell ring.
13. A tire reinforcing structure obtained using a method according
to claim 1.
14. A tire with no airtight inner liner, comprising a reinforcing
structure obtained using a method according to claim 1.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention falls within the field of tire
manufacturing and relates more particularly to the manufacture of
an improved carcass reinforcing ply structure for radial-carcass
tires, namely a reinforcement the reinforcers of which are
contained in radial planes containing the axis of rotation or form
small angles with these radial planes.
2. Related Art
[0002] As is generally known, the structure of a radial tire
comprises several zones each having a clearly defined role in the
operation of a tire. A tire thus comprises two bead regions
intended to collaborate with the seats of a mounting rim, these
beads comprising a reinforcing structure in the circumferential
direction, to which the carcass reinforcement is anchored. A crown
reinforcement is arranged radially on the outside of the carcass
reinforcement and hoops the latter when the tire is pressurized. A
tread is arranged radially on the outside of the crown
reinforcement and provides contact between the tire and the ground
during running. A tire sidewall extends between each bead and each
axial end of the crown and provides the mechanical connection
between the bead and the crown of the tire. Inside the tire,
between the two beads, there is a layer impervious to the inflating
gas and known by the name of "inner liner" because it covers the
entirety of the internal wall of the tire.
[0003] In order to create such a structure, a tire is generally
built by successively stacking several rubber plies on to a rotary
tire building drum, these rubber plies each having specific
properties, potentially being equipped with reinforcing elements,
some plies also being connected to bead wires around which the
beads are formed.
[0004] The first ply to be laid on the tire building drum is the
inner liner because it forms the internal wall of the tire that is
impervious to the inflating gas. Such an inner liner is described
in document WO 2008/145277 in the name of the Applicant Companies
and is formed from compounds based on butyl rubber which are known
for their airtightness properties or based on polystyrene and
polyisobutylene block copolymer thermoplastic elastomers. Although
these operate satisfactorily, the inflation pressure of a tire
equipped with such an airtight rubber must nevertheless be checked
regularly, because gas leaks may nevertheless occur over time.
[0005] With a view to enhancing the airtightness of the tire,
document EP 2205452 in the name of the Applicant Companies
describes a tire comprising an airtight rubber casing and a
reinforcing structure formed of fibres embedded in the rubber, the
reinforcing structure being formed of a carcass layer and a crown
layer and of means of connection between these layers. In this
document, the fibres used to create the reinforcing structure each
have a completely connected cross section, they are flattened in
shape and have mutually orthogonal dimensions of preestablished
dimensions and extend in a substantially radial direction on the
tire. The reinforcing structure described in this document allows
the airtightness of the tire to be enhanced and the mechanical
fatigue thereof to be reduced.
[0006] Also known, from document EP 1397262 is a tire comprising an
additional sidewall reinforcing reinforcement formed of strips of
rubber reinforced by cords that are inclined with respect to the
circumferential direction of the tire. The reinforcing rubber
strips are applied by winding and partially overlapping one strip
on another between the inner liner and the carcass ply when
building the green tire. The role of this additional reinforcement
is to give the sidewalls greater mechanical strength when the tire
is subjected to high stress loadings during running.
[0007] While it exhibits good performance in terms of longevity,
airtightness and strength, the tires described in these documents
have a structure that is complex and their methods of manufacture
involve numerous steps which prove tricky to perform and are
time-consuming.
[0008] Also known, from documents EP 2781369 et US 4011899 are
composite reinforcing structures produced on the basis of strips
embedded in an elastomeric material.
[0009] Such composite structures admittedly have better mechanical
strength, but the effect of this is to increase the weight of the
tire.
SUMMARY OF THE INVENTION AND ADVANTAGES
[0010] It is an object of the present disclosure to alleviate at
least one of the disadvantages of the documents described herein
and to propose a method of producing an improved reinforcing
structure that allows a significant reduction in the mass of the
tire without moreover reducing its performance.
[0011] To this end, the disclosure proposes a method of
manufacturing a reinforcing structure for a tire in the form of a
stratified assembly formed of two layers of reinforcing strips of
completely connected cross section, and flattened in shape,
wherein
[0012] the strips of each layer are laid side by side in a main
direction of laying, spacing the strips of the first layer apart by
a distance that is less than the width of the strips of the second
layer and in such a way that the edges of the strips of the first
layer overlap the edges of the strips of the second layer, and
wherein
[0013] the two layers of strips are separated by a layer of
uncoupling rubber.
[0014] According to an aspect of the disclosure, a stratified
reinforcing assembly is created using an advantageous method of
arranging the reinforcing strips in at least two layers separated
from one another by a layer of uncoupling rubber, the reinforcing
strips of the disclosure having both good mechanical properties and
good impermeability to the inflation gas. By virtue of this method,
a tire reinforcing structure is obtained that is arranged radially
furthest towards the inside of the tire because it is able to
remain airtight with respect to the inflation gas after the green
tire has been shaped, while at the same time providing the
mechanical strength of a carcass reinforcing ply of known type.
[0015] Such a reinforcing structure has the advantage of providing
airtightness with respect to the inflation gas that is at least
equivalent to the existing solutions while at the same time making
it possible to substantially reduce the thickness and weight of the
tire with respect to a conventional tire.
[0016] Indeed the reinforcing structure according to the disclosure
exhibits flattened monofilament strips, each impermeable to the
inflation gas, the various strips being arranged in a staggered
configuration when "out flat" or during the phase of building the
green tire on a building drum, and such that the edges thereof
continue to overlap during the shaping of the tire. According to
one important aspect of the disclosure, the layers of strips are
separated by a layer of uncoupling rubber to which the strips of
each layer adhere. The coefficient of elongation of the uncoupling
rubber is greater than that of the strips, which means that, when
the green tire is being shaped, the separation of the strips with
respect to one another is controlled by the elongation of the
uncoupling rubber that they follow. Thus, it has been found, during
laboratory testing, that, in the absence of a layer of uncoupling
rubber between the two layers of strips, during shaping, the strips
slide over one another, leading to a configuration in which there
are differences in pitch between the two layers of strips and,
therefore, a risk of a lack of airtightness in the structure
obtained. Now, tests performed with a layer of uncoupling rubber of
predetermined thickness have shown that the separation between the
strips remains constant because the strips follow the deformation
of the uncoupling rubber and move with it. What is more, laying the
strip on a layer of rubber makes manufacturing the reinforcing
structure easier.
[0017] Such a reinforcing structure exhibits good airtightness
properties and good mechanical strength and, as a result, on its
own can replace several plies involved in the construction of a
conventional tire. Thus, such a reinforcing structure replaces the
inner liner and the carcass ply, and even also the sidewall
reinforcing ply, when that is necessary.
[0018] For preference, the strips of the first and the second layer
have the same width L and their edges overlap over at least 20% of
the width L. This makes it possible to ensure good airtightness
after shaping, even in zones of the tire in which the shaping is
greatest, such as the shoulder zone.
[0019] Advantageously, the elastic modulus of the strips is greater
than 500 MPa. This allows the reinforcing structure to provide the
mechanical strength of the tire.
[0020] For preference, the said stratified assembly is arranged
between and in contact with two layers of rubber. This allows
better adhesion between the stratified assembly and the other
layers of rubber involved in the structure of a tire.
[0021] For preference, the said reinforcing structure comprises, in
this order: a layer of elastomer of a thickness comprised between
0.1 and 0.5 mm, a first layer of reinforcing strips having a
thickness comprised between 0.05 and 0.35 mm, a layer of uncoupling
rubber of a thickness comprised between 0.1 and 0.5 mm, a second
layer of strips having a thickness comprised between 0.05 and 0.35
mm, and a layer of elastomer of a thickness comprised between 0.1
and 0.5 mm.
[0022] Advantageously, each strip has a width L and the strips
forming a layer are arranged with a pitch p of less than 2L. The
strips are arranged side by side with a pitch p greater than the
width L of a strip but less than twice the width L of the
strip.
[0023] For preference, the amount of overlap between the edges of
the strips of the two layers is comprised between 0.2 and 0.5 times
the pitch p.
[0024] Advantageously, the width of the strips is comprised between
1 and 12 mm, preferably between 3 and 7 mm.
[0025] For preference, the said strips are made of a single
material.
[0026] For preference also, the said material is selected from PET,
PEN, aluminium, steel, or polyamides.
[0027] In a first embodiment of the disclosure, the said
reinforcing structure is produced by calendering.
[0028] In a second embodiment of the disclosure, the said
reinforcing structure is produced by winding successive layers onto
a rotary shell ring.
[0029] The object of the disclosure is also achieved with a tire
reinforcing structure obtained using the method of the
invention.
[0030] The object of the disclosure is also achieved with a tire
with no airtight inner liner, comprising a reinforcing structure
obtained using the method of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Further features and advantages of the disclosure will
become apparent from the following description. This description,
which is given by way of non-limiting example, refers to the
appended drawings, in which:
[0032] FIG. 1 is a view in radial section of a tire of known
type;
[0033] FIG. 2 is a schematic depiction in cross section of a
carcass reinforcement of known type;
[0034] FIG. 3 is a schematic depiction in perspective of a
reinforcing structure according to the disclosure;
[0035] FIG. 4 is a schematic depiction in cross section of a
reinforcing structure according to the disclosure prior to the
shaping of the green tire;
[0036] FIG. 5 is a schematic depiction in cross section of a
reinforcing structure according to the disclosure after the shaping
of the green tire;
[0037] FIG. 6 is a schematic depiction of a device for
manufacturing a reinforcing structure according to a first
embodiment of the disclosure; and
[0038] FIG. 7 is a schematic depiction of a device for
manufacturing a reinforcing structure according to a second
embodiment of the disclosure.
DETAILED DESCRIPTION OF THE ENABLING EMBODIMENT
[0039] In the various figures, identical or similar elements bear
the same references. Their description is therefore not
systematically repeated.
[0040] In FIG. 1, a diagrammatically depicted tire 1 comprises a
crown 2 comprising a tread 3, the radially outer part 3a of which
is intended to come into contact with the road, two inextensible
beads 4 in which a carcass reinforcement 6 is anchored. The crown
2, connected to the beads 4 by two sidewalls 5, is, in a way known
per se, reinforced by a crown reinforcement or "belt" 7 which is at
least partly metallic and which is radially outer with respect to
the carcass reinforcement 6. A tire belt is generally composed of
at least two superimposed belt plies, sometimes referred to as
"working" plies or "crossed" plies, the reinforcing elements or
"reinforcers" of which are positioned virtually parallel to one
another inside a ply, but crossed from one ply to the other, that
is to say inclined, symmetrically or asymmetrically, with respect
to the median circumferential plane, by an angle which is generally
between 10.degree. and 45.degree., according to the type of tire
under consideration. Each of these two crossed plies is composed of
a rubber matrix or "calendering rubber" which coats the
reinforcers. In the belt, the crossed plies can be supplemented by
various other auxiliary rubber plies or layers, with widths which
can vary as the case may be, comprising or not comprising
reinforcers; mention will be made, by way of example, of simple
rubber cushions, "protection" plies having the role of protecting
the remainder of the belt from external attacks or perforations, or
else "hooping" plies comprising reinforcers oriented substantially
along the circumferential direction ("zero-degree" plies), whether
radially outer or inner with respect to the crossed plies.
[0041] For the reinforcing of the above belts, in particular of
their crossed plies, protection plies or hooping plies, use is
generally made of reinforcers in the form of steel cords or textile
cords composed of thin threads assembled together by braiding or
twisting.
[0042] The carcass reinforcement 6 is here anchored in each bead 4
by winding around two bead wires 4a, 4b, the turn-up 6a, 6b of this
reinforcement 6 being, for example, positioned towards the
ouFcharacttside of the tire 1, which is here depicted mounted on
its rim 9. The carcass reinforcement 6 is made up of a ply
reinforced by radial textile cords, that is to say that these cords
are positioned practically parallel to one another and extend from
one bead to the other so as to form an angle of between 80.degree.
and 90.degree. with the median circumferential plane (plane
perpendicular to the axis of rotation of the tire which is located
mid-way between the two beads 4 and passes through the middle of
the crown reinforcement 7). Of course, this tire 1 additionally
comprises, in a known way, a layer 10 of inner rubber or elastomer
(commonly known as "inner liner") which defines the radially inner
face of the tire and which is intended to protect the carcass ply
from the diffusion of air originating from the space interior to
the tire.
[0043] The sidewalls 5 are sometimes reinforced with additional
reinforcing plies in order to react to high mechanical stress
loadings. These additional reinforcing plies generally comprise
reinforcing elements or "reinforcers" arranged parallel to one
another in a rubber matrix and arranged radially on the inside or
the outside with respect to the carcass reinforcement.
[0044] In a carcass reinforcement of known type, a reinforcer takes
the form of a thread of a cord comprising a collection of twisted
or braided threads. The thread or threads constituting the
reinforcer may be metallic, polymeric, natural or composite in
nature.
[0045] FIG. 2 illustrates the reinforcers 8 visible in a cross
section of the carcass reinforcement 6. The reinforcers 8 of a
carcass reinforcement 6 are spaced apart and are embedded in a
rubber matrix. X-X' indicates the path taken by the inflation gas
to pass through the carcass reinforcement 6.
[0046] As FIGS. 3 to 7 illustrate, the disclosure relates to the
manufacture of a reinforcing structure 20 which uses an
advantageous arrangement of strips 22 arranged in superposed layers
in order to form a stratified assembly. The strips 22 of the
disclosure have completely connected cross sections and are
flattened in shape. What is meant by a strip that is flattened in
shape is a narrow strip, the width of which is greater than the
height or thickness. It will be recalled that a completely
connected surface is a surface any two parts of which have to be
joined together.
[0047] What is meant by a stratified assembly is any product
comprising at least two layers of planar or non-planar shape, which
are in contact with one another, it being possible for these either
to be connected or not to be connected, in which "connected" is
understood to encompass any means of assembly, particularly
bonding.
[0048] What is meant by rubber or elastomer is preferably any type
of diene or non-diene elastomer, for example thermoplastic
elastomer, or a blend of elastomers: natural rubber and synthetic
rubber, reinforcing fillers: carbon black and silica, plasticizers:
oils, resins and other chemical elements such as sulfur for
example.
[0049] A layer means a strip having a thickness that is very small
relative to its other dimensions, for which the ratio of the
thickness to the largest of its other dimensions is less than 0.5,
preferably less than 0.1.
[0050] More particularly according to the disclosure, the
reinforcing structure is produced in the form of a stratified
assembly formed of two layers of strips spaced apart, overlapping
and comprising an uncoupling rubber arranged between and in contact
with two layers of strips.
[0051] These strips are made from a film stretched mono- or
multi-axially and having a tensile modulus E greater than 500 MPa.
This film is preferably made from a thermoplastic polymer which is
preferably a polyester, more preferably a PET (polyethylene
terephthalate) or a PEN (polyethylene naphthalate). The film may
also be made from a polyamide. The strips of the two layers may be
made from one and the same material or from different
materials.
[0052] For preference, a heat treatment is also applied to the
strip, so as to limit its thermal contraction as the temperature of
the whole rises. Such a heat treatment is, for example, an
annealing, a tempering or a combination of several of these
treatments.
[0053] In an alternative form, the film may be metallic, for
example made of aluminium or of steel.
[0054] In another alternative form, composite material comprising a
matrix of PET, PEN, PA or epoxy resin and reinforced with glass or
carbon fibres or synthetic fibres such as nylon, or aramid, etc.
fibres.
[0055] The material of the strip is chosen so that it exhibits good
impermeability to the inflation gas. By way of example, the strips
need to have a nitrogen permeability of between 0.001 and 10
cm.sup.3mm/m.sup.2/day/atm and preferably of between 0.1 et 1
cm.sup.3mm/m.sup.2/day/atm.
[0056] FIG. 3 illustrates, in a perspective view, a reinforcing
structure 20 according to the disclosure, which comprises: a first
layer 24 of strips 22 arranged side by side, spaced apart, a second
layer 26 of strips 22 arranged side by side, spaced apart and
parallel to the strips of the first layer and to the direction of
laying A. The strips of the first layer 24 are offset in relation
to the strips of the second layer in a direction perpendicular to
the direction of laying A. The two layers of strips are separated
by a layer of uncoupling rubber 30. The reinforcing structure is
supplemented by two layers of rubber, an external layer 32 and an
internal layer 34.
[0057] FIG. 4 illustrates, in a schematic view in section on a
plane transverse to the direction of laying A, a reinforcing
structure prior to the shaping of the green tire or during laying
while laid out flat, and FIG. 5 illustrates the same view taken
after the green tire has been shaped. It will be recalled that
shaping means an operation during which a green tire makes the
transition from a cylindrical overall shape to a toroidal overall
shape.
[0058] In the example illustrated in the figures, use is made of
identical strips having a width "L" and a thickness "e" and a first
layer 24 of strips is created by arranging several strips parallel
to one another, spaced apart by a distance "d" with a pitch "p".
The second layer 26 of strips is created in the same way, but
offsetting the strips 22 in such a way that their edges overlap
with the strips of the first layer 24 by an overlap distance "r".
It will be noted in FIG. 5 that the spacing between the strips
after shaping has become "d'", with d'>d , and the overlap
"r'"with r'<r.
[0059] After laboratory testing, it has been found that it is
advantageous to use strips 22 having a width L of between 1 and 12
mm and preferably of between 3 and 7 mm, and to lay them at a pitch
p less than twice the width L in order to create a first layer 24
of strips. The second layer 26 of strips is preferably created with
identical strips, laid at the same pitch but offsetting them by a
distance of between 0.2 and 0.5 of the value of the pitch p with
respect to the strips of the first layer 24. In this way, a
stratified assembly is obtained in which the edges of the strips of
the two layers overlap prior to shaping (FIG. 4). The value of the
overlap is chosen so that the strips of the two layers also overlap
after shaping, where FIG. 5 illustrates a cross section in the
shoulder region of the green tire. The reinforcing structure of the
bead zone is modified only a little during shaping and the offset
of the strips of the two layers is practically that of FIG. 4 even
after shaping. Y-Y' in FIGS. 4 and 5 indicates the path that the
inflation gas has to take in order to succeed in passing through
the reinforcing structure 20. It may thus be seen that the path
Y-Y' is longer than the path X-X' of FIG. 2 in which the inflation
gas passes through the carcass reinforcement in a direction
perpendicular thereto. In the reinforcing structure 20 of the
disclosure, the path of the gas is diverted by the strip 22 (the
direction of stretch of the strip is advantageously chosen to be
perpendicular to the movement of the inflation gas), forcing the
inflation gas to cover an additional length of path and making it
possible to reduce the losses of inflation gas via the reinforcing
structure 20.
[0060] One important parameter is also the thickness of the strips,
this thickness needs to be thin and well-controlled and is
comprised between 0.05 and 0.35 mm and preferably between 0.05 and
0.15 mm.
[0061] Another important parameter in the creation of the
stratified assembly of the disclosure is the thickness of the layer
of uncoupling rubber 30 and the adhesion thereof to the reinforcing
strips 22. Thus, the layer of uncoupling rubber needs to have a
well-controlled thickness so as to guarantee the uniformity of its
deformation across the entire surface of the stratified assembly.
The thickness of the layer of uncoupling rubber has a value
comprised between 0.1 and 0.5 mm with a tolerance of +/-5% of the
value of the thickness of this layer.
[0062] As far as the adhesion between the uncoupling rubber 30 and
the strips 22 is concerned, this needs to be perfect in order to be
able to ensure the controlled movement of the reinforcer during the
shaping of the green tire. There are a number of proposed solutions
for guaranteeing this adhesion. One of the solutions is to create
the stratified assembly in the hot state. Another solution for
causing the uncoupling rubber to adhere to the strip is to use a
suitable adhesive. For example, a textile adhesive of the "RFL"
(resorcinol-formaldehyde-latex) type is recommended for achieving
adhesion between a strip made of a thermoplastic polymer and the
layer of rubber. Any other suitable adhesive known for conferring
satisfactory adhesion between the rubber and the strips may thus be
used.
[0063] The strips of the stratified assembly are laid in a
direction of laying to each constitute a layer of strips, the two
layers extending in two parallel planes separated from one another
by a layer of uncoupling rubber. The direction of laying of the
strips is longitudinal or circumferential depending on the method
of manufacture of the stratified assembly, as will be explained
later on. When building the green tire, the stratified assembly is
laid on the drum in such a way that the main direction or direction
of laying of the strips is substantially axial (which means to say
parallel to the axis of symmetry of the green tire or to the axis
of rotation of the drum).
[0064] In order to implement the method, the disclosure proposes,
according to a first embodiment, a skimming device 50 as
illustrated in FIG. 6 and comprising two calendering rolls 52, 54,
the respective axes AA' and BB' of which are substantially parallel
to one another. The space between the two rolls defines a gap 53
through which there pass: the external layer 32 of rubber, the
first layer 24 of strips 22, the layer 30 of uncoupling rubber, the
second layer 26 of strips 22 and the internal layer 34 of rubber.
The layers of strips and the uncoupling rubber separating them are
sandwiched between the two layers of rubber and the pressure
applied by the rolls 52, 54 forces the rubber to penetrate the
spaces between the strips, making it possible to improve the
adhesion of the whole. The calendering device is supplied with
layers of rubber from rubber spools (not depicted), and the strips
are paid out from strip spools, the strips of each layer being
guided as they pass through a grooved roll with U-shaped grooves
situated upstream of the calendering rolls. Such strip-guiding
rolls (not depicted) are of the type known in the calendering of
reinforcing plies. Advantageously, the external layers 32 and
internal layers 34 may be supplied by two additional rolls with
axes parallel to those of the rolls 52, 54 which collaborate with
the latter so as to allow the external 32 and internal 34 layers to
be created simultaneously during manufacture in the gaps that they
form with the rolls 52, 54. This method thus allows hot calendering
of the assembly that forms the reinforcing structure in order to
achieve better adhesion of the various layers.
[0065] The stratified assembly thus obtained passes at high speed
in the direction of conveying C which is parallel to the main
direction of laying of the strips. In order to obtain a reinforcing
structure 20 used in the building of a green tire, a length of the
assembled ply derived from the calendering operation is cut to a
dimension approximately corresponding to the dimension of the
distance between bead wires of the green tire that is to be built.
The segment thus cut is then laid on a tire building drum and
constitutes the first layer of the assembly thus forming an
airtight carcass reinforcing structure.
[0066] FIG. 7 illustrates a device making it possible to implement
the method according to a second embodiment of the disclosure. This
device comprises a shell ring on which the various layers involved
in the composition of the reinforcing structure 20 are laid by
successive winding operations. FIG. 7 shows a shell ring 60 of
cylindrical shape with a circular cross section and longitudinal
axis CC'. The shell ring 60 comprises means of driving it in
rotation about its longitudinal axis CC'. A layer of rubber that
forms the external layer 32 has been laid on the shell ring on top
of which layer strips 22 of thickness e and pitch separation p have
been laid by helical winding, which strips are pressed down during
laying using a roller 62 so as to ensure adhesion between the strip
and the layer of rubber already laid. The main direction of laying
of the strips 22 in this case is the circumferential direction of
the shell ring 60.
[0067] Having completed the winding of the strips onto the shell
ring and having thus formed the first layer 24 of strips, this
layer is then covered with a layer 30 of uncoupling rubber. The
strips 20 are then applied to the layer of uncoupling rubber,
offsetting them by a distance d with respect to those of the first
layer 24 so as to obtain, again by helical winding, the second
layer 26 of strips. This second layer 26 is then covered with a
layer of rubber 34. This then yields a reinforcing structure in the
form of a stratified assembly that can be used in the building of a
tire. In order to be able to be used as a carcass reinforcing
structure for a radial tire, this wound stratified assembly needs
to be cut radially to a length corresponding approximately to the
distance between bead wires of the green tire that is to be built.
It is advantageously a shell ring 60 of large diameter that is
chosen, so as to obtain a stratified assembly of near-planar shape.
The segment thus cut is then laid on a rotary tire building drum
such that the direction of laying of the strips is substantially
parallel to the axis of rotation of the drum and constitutes the
first layer of the green tire thus forming an airtight carcass
reinforcing structure.
[0068] In an alternative form not illustrated in the figures, a
strip 22 of width is coated with rubber and laid on a tire building
drum. In order to do this, the dimensions (width and thickness) of
the coating of rubber around a strip 22 of width L and of thickness
e are calculated so as to obtain a reinforcing structure according
to the disclosure without laying an additional layer of rubber.
[0069] Other alternative forms and embodiments of the disclosure
may be envisaged without departing from the scope of these claims.
Thus, a structure having three or more layers of strips separated
from one another by an uncoupling rubber may also be envisaged.
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