Note: Descriptions are shown in the official language in which they were submitted.
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The present invention concerns tires. More
particularly, the invention concerns tires having a body
which is without reinforcement structure in its sidewalls
and in its crown. Such tires having an unreinforced
body have a part which is intended to reinforce the crown
and is arranged on the body. This part will be referred
to as acrown reinforcement in the following description
but it may also be called, for instance, ~<txead
reinforcement in the tire industry. These tires with an
unreinforced body have the advantage that they are simple
to manuracture, these tires being manufactured, for
instance, by producing the body by molding from one or
more polymers, for instance, by the molding of polyurethanes.
It is already known to produce tires having
the above-described unreinforced body in such a manner
that the sidewalls of said bodies have a concavity which
faces the outside of the tires.
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The sidewalls of these tires must be made of
substantial thickness in order to resist the compressive
force caused by the inflation pressure.
These tires have the drawback of being of high
weight and they are furthermore characterized in operation
by excessive resistance to rolling and excessive heating.
It is furthermore known to produce tires having
an unreinforced body in sucn a manner that the sidewalls
of said bodies have a concavity which faces the inside
of the tires. These tires have bodies with thinner side-
walls than the tires which were previously described.
Thus, their resistance to rolling and their heating can be
decreased, but these tires still require a s~lbstantial
amount of rubber and therefore are of high cost.
The object of the invention is to eliminate
these disadvantages.
Accordingly, the tire of the invention which
has a body and a crown reinforcement arranged on the
body, the body having two sidewalls and a crown, the
crown of the body being formed of three zones located
below the crown reinforcement, namely, two side zones
close to the edges of the crown reinforcement and a
central zone adjacent the side zones, the body being
without reinforcement structure in the sidewalls and
2S in the crown~ the concavity of the sidewalls facing
the inside of the tire, is characterized by the
following features:
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(a) the thic]cness eO of the body along the edges
of the crown reinforcement and the thickness el of the
body at any point in each of the side zones are related
- by the relationship: el > 0.6 e0;
(b) the width ~l of each side ~one and the width
L of the crown of the body are related by the relationship:
0.02 L < ~l < 0.30 L;
(c) the average thickness e2m of the body in
the central zone and the thickness e0 of the body along
the edges of the crown reinforcement are related by the
relationship: e 2m < 0-5 e0.
The invention will be easily understood from
the following e~amples and the igures referrin~ to the
examples. Of these figures, all of which are schematic:
- Fig. 1 shows a tire according to the invention,
seen in radial cross section;
- Fig. 2 shows in part, seen in top plan view,
the crown reinforcement of the tire shown in Fig. 1, the
tread being assumed removed;
- Fig. 3 shows the crown of the tire shown in
Fig. l, seen in radial cross section;
- Fig. 4 shows a portion of the crown shown
in Fig. 3, seen in radial cross section;
- Fig. 5 shows the crown of another tire according
to the invention, seen in radial cross section.
Fig. 1 shows a tire in accordance with the invention.
This tire 1 has a body 2 formed of two beads 3, two sidewalls
4 and a cro~n 5. Each of the beads 3 has a reinforcing
bead ring 6, these beads 3 making it possible to mount
the tire 1 on a rim 7. However, one can also contemplate
beads 3 without bead rings, as known per se. One can
even contemplate tires without a bead. The body 2 has
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no reinforcement structure in the sidewalls 4 or in the
crown 5, that is to say it is without reinfo.rcing wires
or cables at these places, but the body 2 may possibly
have short reinforcing fibers, for example metal fibers,
inorganic fibers, particularly glass fibers, organic fibers,
particularly cellulose fibers or fibers of synthetic polymers
such as, for example, aromatic or nonaromatic polyamide
fibers and polyester fibers. The body 2 has been prQdu~ed,
fo- example, by molding from one or more polymers in paste
or liquid form, for example, one or more polyurethanes,
these polymers containing, if desired, various additives
known per se, for example, the aforementioned short rein-
forcing fibers.
The concavity of the sidewalls ~ faces the inside
8 of the tire 1.
The tire 1 furthermore has a tread 9 and a crown
reinforcement 10 arranged on the body 2 namely on the
outside of said body. The c.rown reinforcement 10 may
~e either arranged directly on the body 2 or, for example,
wi~h the interposition of a connecting layer, in particular
a rubber which is in solid or liquid condition at the
time of its use. The tire 1 is produced, for example,
by arran~ing the crown reinforcement 10 on the molded
body 2 and then molding the tread 9 on the body 2 and
the crown reinforcement 10, this crown reinforcement 10
being thus arranged between the body 2 and the tread 9.
The molding of the tread 9 is effected with one or more
materials, particularly one or more polyurethanes. It
goes without saying that other methods of manufacture
are possible, for example, by applying a separately prepared
tread 9 of different rubbers, pa.rticularly natural rubber,
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onto the body 2 and the crown reinforcement lO. It goes
without saying, also, that one can possibly provide a
connecting layer between the tread 9, on the one hand,
and the body 2 and/or cxown reinforcement 10, on the other
hand, and that the crown reinforcement 10 can be applied
to the body 2 at the same time as the tread 9, these two
parts 9, 10 then forming, for example, a single part.
The assembly formed by the crown 5 of the body
2, the tread 3 and the crown reinforcement 10 constitutes
the crown lOQ of the tire l. The crown reinforcement
10 is formed, for example, of two pli.es 11, 12 referred
to as "crown plies" which are arranged one above the other~
the ply 11 ~eing the inner ply, that is to say the ply
closest to the body 2. The ply 11 has cables 110 which
are parallel to each other, each of these cables forming
an angle ~ with the equatorial plane of the tire 1, that
is to say the plane perpendicular to the axis of the tire
1 and passing through the middle of the crown 5. Likewise,
the ply 12 has cables 120 which are parallel to each other,
each of these cables formin~ an angle ~2 with the equatorial
plane of the tire 1. These angles ~l and ~2 have been
shown in Fig. 2, the equatorial plane being represented
by the line PP' and the axis of the tire 1 by th~ line
XX'. The angles ~1 and ~2 are each equal to at most 90
and will be described in greater detail below.
For the sake of the clarity of the drawing,
the outer ply 12 has been assumed in Fig. ~ to be partiall~
removed and in each of the plies 11, 12 the cables 110
and 120 have been shown further apart than they actually
are, the tread 9 being assumed removed.
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It goes without saying that instead of using
cables one could also possibly use unitary wires. The
cables 110, 120 are made, for e~ample, of metal, particularly
steel, possibly covered with a layer of a different metal
such as, for example, zinc or brass. In each ply 11,
12 the cables 110, 120 are, for example, covered with
rubber in known manner. It goes without saying that the
unitary wires or cables llO, 120 of the crown reinforcement
lO can be made of nonmetallic materials, fo.r example,
inorganic materials, and particularly glass, or organic
polymers, particularly synthetic polymers, such as, for
example, the aromatic or nonaromatic polyamides and the
polyesters.
Fig. 3 shows the crown lO0 of the tire l in
greater detail, Figs. l and 3 being radial cross sections,
that is to say sections taken along planes containing
the axis XX' of the tire 1. The inner ply 11 has been
shown wider than the outer ply 12 but it goes without
saying that the invention applies, for e~ample, to cases
in which the plies 11, 12 have the same width and to cases
in which the outer ply 12 is wider than the inner ply
ll. At the crown 5, the body 2 has two faces: an outer
face 13, arranged on the side of the reinforcement 10,
and an inner face 14 opposite the reinforcement 10.
The radial cross section of the crown 5 of the
body 2 is formed of three zones located below the crown
reinforcement lO, namely, two side zones Zl and a central
zone Z 2 which is adjacent to the side zones Z1. Each
side zone Zl is bounded on the one side by a straight
line Nl~ and on the other side by a strai~ht line Nl 6
the two straight lines Nl 6 being arranged between the
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two straigh~ lines Nls. The central zone Z 2 is bounded
by the two straight lines N 16 . Each of these straight
lines N1s, Nl 6 iS perpendicular to the outer face 13 of
~ the body 2 at the point where it passes through the outer
face 13. By definition, the straight lines Nls are such
that the entire crown reinforcement 10 is arranged between
these straight lines and limited by them, the points 15
of the crown reinforcement 10 which are located on these
straight lines being referred to as the "edges of the
crown reinforcement 10."
In the example shown in ~ig. 3, the edges 15
of the crown reinforcement 10 correspond to the edges
of the inner ply 11, the edges 12b of the outer ply 12
being closer to the equatorial plane than the edges 15,
the equatorial plane being schematically indicated by
the straight line EE'. If the edges 15 of the crown reinforce-
ment 10 were to correspond, for example, to a ply other
than the ply 11, the above definitions would apply with
respect to such other ply, the crown reinforcement 10
possibly also comprising a number of plies other than
two. The side zones Z1 are close to the edges 15 of the
crown reinforcement 10.
The width Q1 of each side zone Z1 corresponds
to the distance between the straight lines N1s, Nl6 which
define each side zone Zl. The width Q 2 of the central
zone Z 2 corresponds to the distance between the two straight
lines N1 6 which define the central æone Z 2 . The width
L of the crown 5 of the body 2 corresponds to the distance
between the two straight lines N15 ~ that is to say it
is equal to the sum of the two widths Ql and the width Q 2 -
All of these width measurements are made along the outer
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face 13 of the body 2 and in a radial plane which is,
for example, the plane of Fig. 3.
The thickness e0 of the body 2 along each edge
15 is measured by definition along the straight line Nls
passing through the edge 15. The thickness el of the
body 2 at any point in each side zone Zl and the thickness
e2 of the body 2 at any point in the central zone Z2
are measured along a straight line N perpendicular to
the outer face 13 of the body 2 and passing through said
point, these thickness measurements being made in a radial
plane which is, for example, the plane of Fig. 3.
The average thickness e2m of the body 2 in the
central zone Z 2 iS defined by the relationship:
e = S 2
S2 being the value of the surface (that is to say the
area) of the zone Z 2 measured in a radial plane which
is, for example, the plane of Fig. 3.
For purposes of simplification, the average
thickness e has not been shown in the drawing.
2m
In accordance with the invention, the thicknesses
e , el, eam and the widths Ql/ L satisfy the following
relationships:
el > 0.6 eO; 0.02 L < Ql ~ 0.30 L; e2m ~ 0~5 e0.
Preferably one applies at least one of the following
relationships:
0.6 eO ~ el < 1.2 eO; 0.05 L C Ql ~ 0.20 L; e2m ~ 0 3 e0;
and advantageously one has 0.6 e0 < el < e0. One can
even contemplate embodiments in which the central zone
Z 2 iS without any material, that is to say e 2 may be zero
or prac~ically zero over a part or all of the central
zone Z 2 -
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The crown reinforcement 10 is made in such a
manner that after inflation it can withstand the forces
transmitted by the sidewalls 4, despite the thinning of
the crown 5. As previously described, this crown rein-
forcement may, for example, comprise at least two plies,each ply having cables or unitary wires parallel to each
other, the angle of each ply being defined by the angle
which the cables or the wires of that ply form with the
equatorial plane. In this case, it is preferable for
the crown reinforcement 10 to be in accord with one of
the following two embodiments:
(1) the crown reinforcement 10 has two plles
and the angle of each ply is at least equal to the minimum
value ~m and at most equal to a maximum value ~M such
that
~ = 2
cos ~M = 0 9 cos ~0
the angle ~o being defined by the relationship:
2 R 2 ( 1 - ~ Rs 2 - Re 2
in which:
~ Ps represents the radius of curvature of the
ply in question, this radius beirlg determined in a radial
plane, at the intersection of that ply with the equatorial
plane or in the vicinity of that intersection; Fig. 3
represents in part the radius Ps relati~e to the ply 11;
- Rs represents the distance of the ply in question
from the axis XX' of the tire, this distance being determined
in the equatorial plane; Rs is represented in part in Fig.
3 in regard to the ply 11;
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- Re represents the distance from the axis XX'
of the tire of the points A, B where the body has the
greatest width in radial section, the curvature of the
body at these points being assumed uniform, that is to
say without protuberance or depression at these points;
the width of the body is determined along the straight
line A,B parallel to the axis XX'; the distance Re is
represented in part in Fig. 1.
The definitions given above for Ps, Rs~ Re
correspond to the tire 1 assumed not under load, mounted
on its rim 7 and inflated to its rated pressure with air
at ambient temperature (about 20C.).
In this case, the angles ~ 2 of the two plies
are crossed, that is to say the angles ~l and ~2 have
~opposite orientations with respect to the equatorial
plane p~', as shown in Fig. ~.
When the angle of each ply is less than the
minimum value ~m defined above, excessive axial flow of
the body takes place causing an increase of its width
in radial section. When the angle of each ply is greater
than the maximum value ~M~ there is an excessive increase
in the outside diameter of the tire at the time of travel.
These two defects then make the use of the tire uncertain.
(2) the crown reinforcement 10 has at least
three plies crossed in such a manner as to form a triangula-
tion, the angles of the three plies being different from
each other. In this case, the angles of these plies may
vary within wide limits.
The use of a crown reinforcement lO limited
to two plies, in accordance with the first embodiment
above, however, is preferredr because it makes it possible
to produce relatively light tires.
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The angle ~ is de~ined by each straight line
Nls and the inner face 14 of the body 2, this angle
being measured, in a r~dial plane, outside the body 2
- and in the direction towards the side zone Zl defined
by the straight line Nls (Fig. 4). This angle ~, called
the "inner connection angle" is preferably defined by
the relationship 70 < ~ < 130, so as to facilitate the
transmission of the forces between the sidewalls 4 and
the crown reinforcement lO. The angle ~ for this purpose
is advantageously defined by the relationship 90 < ~ < 110.
The thinning shown in Fig. 3 is practically
discontinuous, that is to say the thicknesses el, e~
are practically constant except in the vicinity of the
straight lines ~16 where these thicknesses suddenly vary.
However, one can contemplate cases in which the decrease
of the thickness of the body s~a~tincJ from
the straight lines N 15 is progressive in the direction
towards the equatorial plane EE' over at least a portion
of the crown 5, shown in ~ig. 5. This solution can have
the advantage of favoring the uniformity of the transfer
of the forces between the sidewalls 4 and the crown rein-
forcement 10.
The advantages of the invention are the followin~:
- the decrease in the thickness at the crown
results in a decrease in Ihe weight of material and thus
in a lower cost of manufacture, without diminishing the
performance of the tire;
- the thlnning at the crown makes it possible
to decrease the resistance to rolling of the tire.
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By way of example, two tires of size 135-13
were compared, each having an unreinforced body in the
sidewalls and at the crown, the body being made by the
molding of polyurethanes. Each of these tires furthermore
has a tread as well as a crown reinforcement arranged
on the body between the body and the tread, the rubber
used for the tread and the crown reinforcement being natural
rubber. The value Re is the same for both bodies, namely,
220 mm.
These two tires are identical except at the
crown where one has a body of constant thickness and the
other a thinned body in accordance with the invention.
I~he crown reinforcement of each tire is formed of two
plies of steel cables, the arrangement of which is similar
to that of the plies 11, 12 which have been described
above. The inner ply 11 has a width of 86 mm and the
outer ply 12 has a width of 78 mm, these widths being
measured in a radial plane along the ply in question.
The width L of the crown of the body is practically equal
to 86 mm. The characteristics Ps~ Rs are practically
the same for both plies, namely, Ps = 200 mm, Rs = 262 mm.
The plies are crossed, each of the angles ~ 2 being
between 18 and 29, for example, practically equal
to 23.
The crown of each body has the following
characteristics:
- for the tire of known type, the thickness
of the body is constant at the crown and equal to 5 mm;
- for the tire in accordance with the invention,
ec is equal to 5 mm, el varies from 5 mm to 3 m~ over
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a corresponding width Ql of 15 mm, el decreasing in the
direction towards the equatorial plane, e2m is equal to
1.5 mm over the central width Q2i Q2 = L - 2 Ql - 56 mm,
that is to say there is the relationships: 0.6 eO < el < eO;
Ql = 0.17 L; e2m = 0 3 eO-
The invention makes it possible in this embodiment to
effect a saving in weight of 25% with respect to the weight
of the body, namely, a saving in weight of about 12% with
respect to the -tota].weight of the tire, and a decrease
in the resistance to rolling of 5~.
Of course, the invention is not limited to the
embodiments which have been described above. Thus, for
example, the tire in accordance with the invention may
have parts known per se, which have not been described
above for purposes of simplification, which parts may,
in particular, be reinforcing or protective rubbers or
plies, and the crown reinforcement may comprlse at least
one folded ply.
