LU82968A1 - TIRES WITH SIDEWALLS COMPRESSED - Google Patents

Abstract

A tire 10 capable of operation inflated and deflated comprises shoulder portions 14 extending axially outward and radially inward from the tread portion to terminate in junction portions 22 from which sidewalls 16 extend axially and radially inward to rim-seating portions 18. The sidewalls 16 are shaped as shown such that inflation pressure causes them to be in compression between the rim 20 and junction portions 22, the tire having a reinforcement 30 extending from one portion 22 to the other. The shoulder portions 14 are reinforced on one or, as shown, both surfaces by a plurality of circumferentially spaced ribs 49 disposed in radial planes or at up to 10 DEG thereto, and one or more circumferentially annular ribs 53 may also be positioned on the exterior surface of each junction portion 22 to further reinforce the tire. The reinforcement 30 comprises a ply 32 which has cords disposed at 35-55 DEG to the circumferential and is folded around annular members 35 of elastomer or fibrous material, cross-laid plies 45, 46 being superposed on the ply 32. <IMAGE>

Description

3.12.1979 Ε, ϋ, Α, Nö 099.693

Said company: THE GOODYEAR TIRE & RUBBER COMPANY.

. "

774 / GR

Tire with sidewalls subject to compression. 1 '

SUMMARY OF THE TECHNICAL CONTENT OF THE INVENTION

This tire is reinforced so that it can roll. without damage to the deflated state. It comprises a tread 12 joined to shoulders 14 which are joined to the sides 16 by junction zones 22. The sides are inclined axially and radially inward between 22 and the rim 20 and the shoulders are inclined. radially inwards and axially outwards from the tread 12 to the junction zones 22. A carcass extends in the junction zones, the shoulders and the tread, and the shoulders are reinforced by circumferentially spaced ribs 49 which resist the flattening of the shoulders on the ground when the tire is rolling in the deflated state and under normal load.

F ± g13 φ

The present invention relates to tires the sidewalls of which are subjected to compression and more particularly to tires suitable for working in the deflated state. - ·· 5 Conventional tires have a reinforcing structure composed of one or more plies, which extends around the carcass, from one bead to the other. In the absence of such a structure, the tires would tend to "grow", that is to say to expand outward when * - T.

10 puts their internal cavity under pressure, without resistance * opposing this deformation. In recent years, a sidewall tire under compression has been developed which has eliminated the need for reinforcing cords in the sidewall and bead regions.

Since these regions are devoid of such cords, the manufacture of this type of tire is particularly well suited for the application of methods such as molding, casting or injection molding.

In a tire with sidewalls subjected to compression, each sidewall is constructed so that its section, taken in a radial plane, comprises a concave external surface and a convex internal surface. The term “radial plane” is understood here to mean a plane which contains the axis of rotation of the tire. For the operation of a tire with sidewalls subjected to compression, ‘25 it is necessary that the sidewalls are retained between the rim at one end and a restraint means such as a tread belt at the other end. When the interior cavity of the tire is inflated to normal inflation pressure, the internal forces due to the air pressure exerted against the sidewalls tend to compress the elastomeric material of the sidewalls. If the elastomeric material is compressed beyond a certain point, the internal forces compel the sides to expand axially outwards. The flanks must therefore have sufficient characteristics of flexural rigidity of curvature and thickness of 1/2 thickness, in accordance with the rules of the art, to resist this resulting force so that the flanks can be retained .

The main problem which has to be solved in the case of tires with sidewalls subjected to compression as well as in the case of conventional tires during rolling in the deflated state, resides in the destructive heating which results from the friction between the internal surfaces of the tire during the displacement which each part of the matt tire undergoes, passing through the imprint of the tire. f

Another problem which one has to solve in the case of the tire with sidewalls subjected to compression which rolls in the deflated state consists in the friction of the region of the shoulders and the sidewalls on the ground. This friction occurs because the portions of the shoulders and flanks located radially inward relative to the tread have a circumference smaller than that of the tread. All parts of the tire must rotate at the same angular speed and, therefore, the linear speed of the sidewalls and shoulders which are in contact with the ground when the tire is deflated, must be greater than the speed linear tread. There is therefore produced in these conditions · a friction * of the sides and shoulders on the ground.

.25 With the construction according to the invention, the tire is reinforced in a way which reduces to a minimum the abrasion and friction undergone by the deflated tires. The shoulders of the tire also extend outside so that the sidewalls bend in an orderly fashion during the rolling in the deflated state and are axially outside the rest surfaces of the rim. . The term "axially" is used in the present specification as well as in the claims to designate a direction parallel to the axis of rotation of the tire. The term "radially" 35 designates a direction perpendicular to the axis of rotation of the tire.

• If there is an internal contact between various parts of the tire during rolling in the deflated state, the tire is produced in such a way that this contact 5 occurs practically between the sidewalls and the shoulders.

The shoulders have a configuration such that they are killed radially inwards relative to the tread, so that the resulting abrasion which occurs between the internal surfaces is reduced. provided with ribs with a rigidity function which serve to keep them out of contact with the ground while the tire is rolling in the deflated state. This helps to eliminate friction while causing minimal weight gain. These ribs give the tire a 15; characteristic of hooping in the regions where the flanks and the shoulders meet (joining parts) to maintain the high shape of the shoulders. The term "hooping characteristic" means the resistance which results from the application of a bandage or a hoop around an object. This hooping also contributes to maintaining the flanks.

Briefly, one aspect of the invention relates to a tire capable of rolling in the inflated and deflated state, which comprises an annular body of elastomeric material, a circumferential tread, intended to come into contact with the tire. ground, which extends to the periphery of the body, two shoulders which are joined to the tread and which extend axially outward and radially inward from the tread. with two junction zones, two sidewalls extending radially and axially inwards from the junction zones to two spaced-apart mounting zones provided for mounting the tire on a rim, a reinforcement structure with ply, continuous in the circumferential direction which extends between the two junction zones, several reinforcing ribs 35 circumferentially spaced on at least one face of each of the shoulders, these ribs extending from the junction zones up to 'at the tread.

According to another aspect, the invention relates to a tire capable of rolling in the inflated state and in the de-inflated state which comprises an annular body of elastomeric material, a circumferential tread intended for. come into contact with the ground, which extends at the outer periphery of the body, two shoulders which are joined to this tread and extend axially towards the outside and radially towards the inside at from the tread to two junction zones, two sidewalls which extend radially and axially inwards from the junction zones to two spaced mounting zones provided for mounting the tire " on a rim, a continuous ply reinforcement structure in the circumferential direction, which extends between the junction zones, and at least one continuous reinforcement rib in the circumferential direction, provided on the external surface of each of the zones junction, this rib entirely surrounding the tire.

According to another aspect, the subject of the invention is a tire capable of rolling in the inflated and deflated state, which comprises an annular body of elastomeric material, a circumferential tread, intended to come into contact with the ground, formed at the periphery of this body, two shoulders joined to the tread, which extend axially outward and radially inward from the tread to two junction zones , two sidewalls which extend radially and axially inwardly, from the junction zones up to two spaced-apart mounting areas provided for mounting on a rim, a continuous reinforcement structure ply in the direction circumferential, which extends between the junction zones, this nap-35 reinforcing structure comprising at least two superposed layers of reinforcing cords which extend from the tread to the junction areas, the cables of one of the superimposed layers being inclined in the opposite direction of the cables of the other of the superimposed layers, and the cables of the 5 superimposed layers being inclined at an angle of 35 to 55 ° relative to the median circumferential plane tire.

According to another aspect, the invention relates to a tire with sidewalls subjected to compression capable of rolling in the deflated state. - ·; »T.

ÎO According to another aspect, the invention relates to a 'pneumatic r which can be easily manufactured by methods such as molding, casting or injection molding.

According to yet another aspect of the invention, the object of the invention is a reinforced tire structure intended to support the shoulders and the sidewalls during rolling in the inflated state and in the deflated state.

Other characteristics and advantages of the invention will emerge during the description which follows. In the 20 accompanying drawings, given solely by way of example, - FIG. 1 is a partial sectional view along a radial plane of a tire according to the invention, this view showing the tire in the unloaded and inflated state, mounted on a rim j * 25 - FIG. 2 is a section on a larger scale of a part of the tire, along the line II-II of FIG. 1; - Fig. 3 is a partial sectional view similar to that of FIG. 1, which shows the tire under normal load in the deflated state; 30 - FIG. 4 is a partial view of the tread, along the line IV-IV of FIG. 1, with partial cutaway, to show the relative angular arrangement of the cables of the protector and the reinforcement plies.

As indicated in FIG. 1, the invention relates to a tire 10 of the pneumatic type which comprises a / - 6 tread 12 arranged circumferentially, intended to come into contact with the ground, two shoulders 14 joined to the tread and two sides 16 which end in two mounting zones 18 intended to cooperate with a rim 20. Two junction zones 22 connect the shoulders 14 to the sidewalls 16. Each of these parts of the tire 10 is preferably made of an elastomeric material such as rubber or urethane. The tire 10 is symmetrical with respect to the median circumferential plane MP of the tire. This median circumferential plane MP is a plane perpendicular to the axis of rotation of the tire and located midway between the two axially outer ends of the tire.

The width of the tread is defined by 15. the axially outer ends of a tire which is pressed against the ground in the imprint region of the tire when the tire is inflated to its normal inflation pressure and works under its normal load. The imprint of a tire relates to the traces left by a tire in contact with the ground when it is mounted in a normal manner on a vehicle under its normal load and when it is inflated to its normal inflation pressure. . The normal load and the normal inflation pressure are the load and the pressure at which a tire is intended to work. 25 work in normal conditions.

Each of the shoulders 14 is oriented axially outward and radially inward from the tread 12. Each of the flanks 16 extends axially outward and radially outward from the corresponding mounting area 18, so that the tire size SD of the tire 10 is located at the junction areas 22. The size of the tire tire is the maximum distance in a section by a radial plane of the tire between the axially extreme surfaces 35 of the tire, excluding the inscriptions or signs, measured on a line parallel to the axis of rotation of the tire. The junction zones 22 therefore constitute the axially extreme parts of the tire 10 when this tire is in its normal inflation pressure and load conditions.

As can be seen in Figs. 1 and 3, the length of the shoulders 14 is approximately equal to that of the flanks 16, although the lengths of the shoulders and flanks may vary depending on certain considerations relating to the configuration. Furthermore, the section height (sh) of each sidewall 16 is preferably less than half the section height SH of the tire ÎO. In the present specification, including in the claims, the section height SH of the tire 15 is understood to mean the distance measured along a line perpendicular to the axis of rotation between the radially extreme internal bearing surfaces of the mounting zones. and the radially extreme external point of the external surface of the tread 12 when the tire is under its normal inflation pressure and is not under load. The radially extreme external point of a sidewall is defined by the radially extreme internal point Y of the cords of the tire reinforcement plies. The section height (sh) of each sidewall is the distance measured along a line perpendicular to the axis of rotation in a radial plane of the tire between the radially extreme internal bearing surface of the mounting zones and the radially extreme external point of the flank.

The sidewalls 16 are preferably made of a high-modulus elas-30 material and, as shown in FIGS. 1 and 3, they have a concave outer surface 27 and a convex inner surface 29. A tire 10 having this type of sidewall configuration is well known in the art and can be referred to as "sidewall tire subjected to compression". The sidewalls 16 have a significantly thicker wall 8 than those usually found in conventional tires. The shoulders 14 have a relatively thin wall and the wall thickness of the shoulders is less than that of the sides 16.

5. The tire 10 also includes a ply reinforcing structure 30 which extends between the junction zones 22. This structure 30 comprises a layer or ply 32 of reinforcing cords. The ply 32 preferably extends between the junction zones 22 and it is folded 10 in each junction zone around a rigidity means *? # if or heel 35 so as to be superimposed on itself to form a radially inner layer 32a and a radially outer layer 32b. In this embodiment, the ta-Ion 35 has a modulus of elasticity of at least 100 kg / cm at 10% 15. of elongation, its mechanical strength being greater than that of the surrounding elastomeric material. The bead 35 extends circumferentially over the entire tire • 10 and is preferably made of an elastomeric or rubbery material, without its nature being limited to these materials.

For example, heel 35 could be made of a fibrous material. The folded portion of the radially inner ply 32 which surrounds the bead 35 extends in a closed loop along the circumference of the tire 10 to form a practically rigid hoop 36 which serves to transmit the forces> 25 from the structure of the ply reinforcement 30 and retain the sidewalls 16 between the rim 20 and the junction zones 22. The hoop 36 is preferably curved and has a concave internal surface 41 and a convex external surface 43, as shown in FIG. 1.

As can be seen in Figs. 1 and 3, an inextensible annular protector for reinforcing the tread 44 is located radially inside the tread 12. As shown in FIG. 4, this protector 44 comprises two layers 45 and 46 made up of parallel cables 35 oriented in forming acute angles with the circular plane.

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. 9 median MP conference of tire 10, 1 * angle of a layer being in the opposite direction to the angle of the other layer. The protector 44 extends circumferentially over the entire tire 10 to reinforce the tread 12 and S can be of any construction and be made of any desired material compatible with the rules of the art. The axial width of the radially outer layer 45 of the protector is preferably approximately equal to the axial width of the tread 12 and greater than the width '. . Axial of the radially inner layer 46 of this protector, so that the radially outer layer covers the radially inner layer of the protector.

The radially outer layer or ply 32 extends from the freight te 36, in the thickness of the shoulder 15 14 and preferably up to a point located radially inside the tread 12, in the region adjacent to the axially outer edge of the radially in- layer. 46 of the protector, and axially inside the axially outer edge of the radially outer layer 20 45 of the protector. In the case where the ply 32 extends axially over the entire width at the top 47 of the tire 10, radially inside the tread 12, as in the present embodiment, the protector 44 can be omitted. If a protector 44 is provided, the ply 32 25 may extend axially inward from each shoulder 14 only up to a point which covers a corresponding edge 48 of the annular protector. In this case, each shoulder region of the tire 10 is reinforced by separate layers of reinforcing cords.

In the preferred embodiment of the invention, the angle (a) of inclination of the cables of the ply 32 relative to the median circumferential plane MP of the tire 10 is 45 ° but this angle can be between 35 and 55 °. The angle (a) of the cords of the radially inner layer 32a 35 of the ply 32 is the opposite of the angle (b) of the cords of the 4 • 10 radially outer layer 32b of the ply 32. These cords of the ply 32 mainly serve to reinforce the tire 10 with respect to shear stresses.

Reinforcement means such as ribs 49 5 provided on the shoulders 14 support these shoulders so as to keep them out of contact with the ground when the tire 10 is deflated and it is under normal load. The ribs 49 may comprise massive pieces * of rigid rubber, or equivalent elements, but they preferably include a series of ribs, as shown in Fig. 2, which are located in circumferentially spaced positions. on the tire 10, both on the external surfaces 40 and on the external surfaces 51 of the shoulders 14. The ribs 49 of the inland surface 50 preferably extend from the junction zone 22, along from the internal surface of the tire 10, to positions, indicated by the letter X in FIG. 1, which are at least axially inside the axially external edges E of the tread 12. Each of the 20 positions X is preferably located in such a way that the distance D separating the position.X from the median circumferential plane MP is not less than the distance T comprised between the positions X and the axially outer edges E of the tread 12 The p X positions are preferably killed so that the distance D is approximately equal to the distance X. If the position X is placed closer to the median circumferential plane MP, the increase in length of the ribs 49 would cause an increase weight without appreciable additional advantage.

The ribs 49 formed on the external surface 51 of the shoulders 14 are placed at points circumferentially spaced on the tire 10 and extend from the junction zones 22 to the outer edges E of the tread.

The ribs 49 may be made of an elastic material such as rubber which has suitable properties for reinforcing the shoulders 14, as has been described herein. An example of a suitable material that may be mentioned is a rubber-based elastomer mixture having a shore A hardness of between 70 and 85, 2 a static elastic modulus greater than 45 kg / cra, a low hysteresis value and a low value of permanent compression deformation of the order of 10% when it undergoes compression of 25% in a 24-hour test.

The ribs 49 are preferably molded onto the corresponding surfaces of the tire 10 during hardening or vulcanization, but they can optionally be formed, in accordance with good engineering practice, by any process and bonded to the corresponding surfaces. dantes of the tire in any suitable manner, either before or after the vulcanization of the tire 10,

As seen in Fig. 2, the ribs 49 are spaced such that a series of grooves 52 alternate with the ribs 49 so as to give a general on-dulê appearance to the surfaces of the tire. Each of the ribs 49 is preferably situated in a radial plane of the tire 10 but the angle that each rib forms with the radial plane passing through this rib can vary by a value which can reach 10 ° in each direction.

. As shown in Fig. 2, the preferred profile shape for the ribs 49 is sinusoidal, but other profiles such as a triangular or square tooth profile can be used.

A function of the ribs 49 is to strengthen or stiffen the shoulders 14 by strengthening the tire 10 in the regions of the shoulders in the radial direction, that is to say in a direction roughly perpendicular to the road surface. on which the tire 10 circulates, in order to prevent the shoulders 14 from being in contact with the ground while the deflated tire travels through its imprint zone. Each of the ribs 49 is arranged so as to provide this reinforcement in the most efficient way with the minimum quantity of material. In this way, thanks to the geometric arrangement of the ribs 49, the optimum resistance is obtained with the minimum increase in weight.

To further improve the quality of reinforcement of the ribs 49 in the radial direction, the ribs and grooves 52 are equally spaced inside and outside of the shoulders 14 so that each rib 10 or groove located on the one of the two surfaces is in coincidence with that located on the other surface. This spacing mode also avoids the undulation of the cords of the reinforcement structure 30 which otherwise would normally tend to occur during the vulcanization operation.

The expression "space the same way" is understood to mean an arrangement in which the ribs 49 and the grooves 52 provided on the surfaces 50 and 51 of the shoulders 14 are each placed opposite to each other. This gives alternately in the tire 10, in line with the shoulder 14, 20 a minimum thickness (e) as shown in FIG. 2, which is equal to the thickness of the shoulder without any rib formed on the latter, and a maximum thickness (t) which is equal to the thickness of the shoulder plus the maximum thickness of the rib 49 situated on the internal surface 50 and more the maximum thickness of a rib 49 situated on the external surface 51.

The range of values for the maximum thickness (t) on the shoulder 14 depends on the load and the dimensions of the tire. The ratio of the minimum thickness to the maximum thickness (e / t) is preferably between 0.3 and 0.7.

In the present specification, the term "thickness" denotes a measurement taken in a radial plane along a line perpendicular to the structure to be measured.

The width (w) of one of the ribs 49 is the distance between this point of a groove 52 and the corresponding point of the adjacent groove. The total width of a number N of ribs 49 arranged side by side is equal to the product wN. The 2w / t-e ratio is preferably between 0.5 and 5.

5 As can be seen by referring again to * Figs. 1 and 3, in the preferred embodiment of the invention, three continuous reinforcing elements in the circumferential direction, for example circumferential ribs 53 are formed on the inner surface of each of the joining zones 22 to reinforce these last. Each of the ribs 53 extends continuously, in the circumferential direction, on the tire 10, to create a hooping in this tire. The ribs 53 are spaced apart to form a corrugated surface and are made of an elastomeric material having sufficient mechanical strength to limit lateral swelling in a direction oriented axially outward from the tire 10 during rolling of the tire to the deflated state.

The ribs 53 also help to contain the side walls 16 between the junction zones 22 and the rim 20 when the tire 10 is deflated. The circumferential ribs 53 can be molded on the surface of the tire 10 during vulcanization. However, they can also be formed by any method and bonded to the surface of the junction zones 22 in any way compatible with the rules of the art, either before or after the vulcanization of the tire 10.

During the operation of the tire 10 in the deflated state, the sidewalls 16 flex so that the cross-sectional shape of the tire takes almost the appearance shown in FIG. 3. The sidewalls 16 can be made of an elastomeric mixture having a modulus of elasticity not less than 50 kg / cm, measured at 10% elongation. The sidewalls 16 also have a combination of flexural stiffness, curvature and thickness characteristics, which is determined in accordance with proper engineering work, so as to retain the sidewalls between the rim 20 and the junction parts 22 in all the running conditions of the tire 10.

5 Cut filaments, or equivalent elements, may be provided in the radial ribs 49 and the circumferential ribs 53. Bars disposed circumferentially (not shown) may also be provided between the ribs 49 to establish trans-ÎO connections sideways improving mechanical resistance. A suitable lubricant 54 can be introduced into the tire cavity to reduce abrasion between the internal surfaces of the tire 10 and to cool the tire during operation in the deflated state.

Since the mounting areas 18 need not have bead beads like those used in conventional tires, the rim 20 on which the tire 10 is mounted is constructed so as to wrap around almost fully the 20 mounting areas, as shown in the drawings, and at. . constitute means capable of retaining the areas of my floor on the rim during the use of the tire in the deflated state.

As shown in Fig. 1, the rim 20, 25 comprises a central ring 56 and two outer rings 58 and 60. The central ring 56 and one of the outer rings 58 or 60, roughly envelop totally the corresponding mounting area 18, on the radially inner, axially inner and axially outer surfaces of this area. Mounting surfaces 62 and 64 are provided on the central ring 56 to apply the mounting areas 18; with a tight seal against the rim 20 so as to seal the tire cavity in a leaktight manner.

At least three retaining locks 66 self-locking, 35 /

T

- v 15 4 on the circumference of the Rim 20, maintain the assembled rim and retain the outer rings 58 "and 60 against the lateral forces, ie against the forces which act on these rings in the axial direction. A screw 5 safety (not shown) or another similar fastening element can be added to ensure the locking of the rim.

: t - ·

Claims (12)

16 1. A tire capable of rolling in the inflated state and in the deflated state, characterized in that it comprises. An annular body of elastomeric material, a tread (12) 5 intended to come into contact with the ground, extending circumferentially and located at the outer periphery of the body, two shoulders (14) which are joined to the tread and extend axially outward and radially inward from the strip rolling it. 10 (12) up to two junction zones (22), two flanks (16) which extend radially and axially inwards from the junction 2ones (22) up to two spaced apart mounting 2ones (18 ) provided for mounting the tire on a rim (20), a reinforcement structure (30) composed of one or more plies, continuous in the circumferential direction, which extends between the junction 2ones (22 ); a series of circumferentially spaced reinforcing ribs (49) provided on at least one surface (50 or 51) of each of the shoulders (14), these ribs (49) extending from the junction 2ones (22) to the tread (12). '' 2. A tire according to claim 1, characterized in that each of the sidewalls (16) has a curved shape to resist external expansion. * 25 3 - A tire according to one of claims 1 and 2, characterized in that ribs (49) extend along the external surface (51) of each of the shoulders (14) between the junction zone (22 ) corresponding and the tread (12) and in that the. ribs (49) also extend along the internal surface (50) of each of the shoulders (14) between the junction zone (22) and the tread (12), the width (w) of the ribs (49) provided on J The internal surface (50) of the shoulder (14) being roughly equal to the width (w) of the ribs (49) pre-dj * <=> / 17 views of the outer surface (51) of this shoulder, the ribs (49) being spaced from one another on the opposite surfaces (50, 51) of the shoulder (14) so that the thickness (t) of the tire in 1 * shoulder (14) 5 is approximately equal to the thickness of 1 * shoulder (14) plus the maximum thickness of a rib (49) provided on the external surface (51) of the shoulder (14) and plus the maximum thickness of a rib (49) provided on the internal surface (50) of this shoulder, while the minimum thickness (e) of the tire in the region of the shoulder is approximately equal to the thickness of the shoulder devoid of rib (49). 4. Tire according to one of claims 1 to 3, characterized in that it further comprises at least one reinforcing rib (53), continuous in the circumferential direction, provided on the external surface of each of the zones junction (22), this reinforcing rib (53) extending over the entire tire. 5. Tire according to one of claims 1 to 4, characterized in that each of the ribs (49) is arranged practically in a radial plane of the tire. 6. A tire capable of operating in the inflated and deflated state, characterized in that it comprises an annular body of elastomeric material, a tread (12) intended to come into contact with the ground, s' extending * circumferentially and situated at the periphery of the body, two shoulders (14) which are joined to the rolling strip (12) and extend axially outwards and radially inwards from the tread (12) to two junction zones (22), two sidewalls (16) 30 which extend radially and axially inwards from the junction zones (22) to two spaced-apart mounting zones (18) provided for mounting the tire on a rim (20), a reinforcement structure (30), continuous in the circumferential direction, composed of one or more plies, which extends between the joining zones (22), and at least one reinforcing rib (53), continues in the circumferential direction 1c, provided on the external surface (51) of each of the junction zones (22), this rib (53) extending over the entire tire. 7. A tire according to claim 6, character-ized in that each of the sidewalls (16) has an in-curved shape to resist expansion to the outside. 8. A tire capable of working in the inflated state ÎO and in the deflated state, characterized in that it comprises an annular body of elastomeric material, a tread (12) intended to come into contact with the ground s' extending circumferentially and situated at the periphery of this body, two shoulders (14) which are joined to the roll strip-15. ment (12) and extend axially outwardly and radially inwardly, from the tread (12) to two joining zones (22), two sides (16) which s '' extend radially and axially inwards, from the junction zones (22) up to two spaced mounting regions (18) provided for mounting the tire on a rim (20), a reinforcement structure (30 ), continuous in the circumferential direction, formed of one or - of several plies, and which extends between the junction zones (22), this reinforcement structure (30) comprising at least 25 superimposed layers (32a , 32b) of reinforcing cords which extend from the tread (12) up to the junction zones (22), the cords of one of the superimposed layers being inclined in the opposite direction to that of the cords on the other of the superimposed layers, the 30 cables of these superimposed layers (32a, 32b) being inclined at an angle of 35 to 55 ° relative to t at the median circumferential plane (MP) of the tire. 9. A tire according to claim 8, characterized in that the superimposed layers (32a, 32b) of the structure 4> 19 4, reinforcing structure (30) are folded back to form a hoop having a radially inner surface (41) of concave shape and a radially outer surface (43) of convex shape, the tire further comprising in each of the junction zones (22) a bead (35) around which the superimposed layers (32a, 32b) are folded to form the hoop (36) and the heel (35) having a modulus of elasticity of at least 100 kg / cm ^ at 10% elongation. 10. A tire according to one of claims r 10. and p, characterized in that each of the sidewalls (16) has a curved profile to resist the external radial expansion. 11. Tire according to one of claims 8 to 10, characterized in that it further comprises at least one reinforcing rib (53), continuous in the circumferential direction, on the external surface of each of the junction zones ( 22), this reinforcing rib (53) extending over the entire tire. 12. A tire according to one of claims 20 8 to 11, characterized in that it further comprises a series .. of reinforcing ribs (49) circumferentially spaced on at least one surface (50 or 51) of each shoulders (14), these ribs extending from the corresponding junction zone (22) up to the tread * 25 (12), each of the ribs (49) being arranged so as to form a angle from 0 to 10 ° with a radial plane which passes through the rib, and. in that the circumferentially spaced ribs (49) extend as well along the internal surface (50) as on the external surface (51) of each of the e-shoulders (14), between the junction zone (22) corresponding and the tread (12), the width (w) of the ribs (49) provided on the internal surface (50) of this shoulder-leraent (14) being approximately equal to the width (w) ribs (49) provided on the outer surface (51) of this shoulder - / 20 ment, the ribs (49) being spaced from each other on the opposite surfaces (50, 51) of each shoulder (14) in such a way that the maximum thickness (t) of the tire in the shoulder (14) is approximately equal to the thickness 5 (e) of this shoulder plus the maximum thickness of the rib (49) provided on the external surface ( 51) of the shoulder and 'plus the maximum thickness of the rib (49) provided on the internal surface (50) of this shoulder and in that the minimum thickness of the tire, in the shoulder is about 10 equal to the thickness (e) of this ribbed shoulder. £ Λ