MXPA01007000A - Tyre with beads having improved structure - Google Patents

Abstract

The invention concerns a tyre (1) with a radial body ply reinforcement comprising, viewed in meridian cross-section, at least a first bead (12), whereof the seat (12B) is inclined outwards, the bead (12) heel being axially inside and being reinforced by at least a reinforcing element (14), whereas the bead toe is axially outside and comprises a profile (3)of rubber mix in the form of a wedge delimited by two sides (31, 32), said mix having a Shore A hardness higher than the Shore A hardness level(s) of the rubber mixtures (7) and (6) radially above. The invention is characterised in that the radial body ply reinforcement (13) is wound in the bead around the annular element (14) from inside outwards to form a ply turn-up (130), whereof the end is located axially outside a straight line P¿2 ?perpendicular to the axis of rotation and passing through the centre of gravity of the meridian cross-section of the element (14), and axially inside and radially outside the straight line P1 supporting the radially external side (31) of the profile (3).

Description

PNEUMATIC WITH HEELS OF IMPROVED STRUCTURE DESCRIPTION OF THE INVENTION The present invention relates to a tire intended to be mounted on a rim having at least one first frustoconical seat whose generatrix has an axially outer end closer to the axis of rotation than the axially inner end. A tire of this type is described in the application WO 94/13498 of the applicant. It comprises, at least, a first bead, intended to be mounted on said first rim seat inclined towards the outside, said first bead having axial width commonly and axially terminated externally at a bead point, a bead seat whose generatrix has its axially outer end closer to the axis of rotation than its axially inner end, said generatrix being extended axially to the outside by an external face delimiting the tip of the bead, said face with the axis of rotation forming an angle Y , radially and axially open to the outside, and below 90 °. The radial carcass reinforcement of said tire, anchored in each bead, at least to an inextensible annular reinforcing element, has a meridian profile, rtefr: 131220 when the tire is mounted on its service rim and inflated to its service pressure , with a sense of constant curvature at the sides and a heel terminated at the tip and which is such that, in said heel, the tangent at the point of tangency of said profile with the inextensible annular element of said heel forms with the axis of rotation an angle f open towards the outside of, at least, 70 °. The heel of a tire of this type and, more particularly, the structure of the anchor of the carcass reinforcement, can be variable. In the international application WO 95/23073, the radial carcass reinforcement is anchored to the inextensible element by winding around said element going from the heel to the tip of the bead, to form a fold extending in a profile of rubber mixture in the form wedge delimited by two sides emerging from a vertex A located below the section of the coated rod, forming the radially external side with a parallel to the axis of rotation passing through said vertex A, a sharp angle f, radial open and axially to the outside and comprised between 20 ° and 70 °, and forming the radially internal side, with said parallel, an acute cp2 angle, opened radially inwards and comprised between 0 ° and 30 °, and having the rubber mixture that forms the profile axially adjacent to the rod, a Shore A hardness, at least equal to 65, and greater than the Shore A hardness or hardness of the rubber mixtures axially and radially above the rod and the profile. The combination of the meridian profile of the carcass reinforcement, as it is described in said first international application, with a coupling structure such as that described in the aforementioned second international application, allows obtaining a very good compromise, between, for on the one hand, the properties of road behavior of the inflated tire at its recommended pressure and, on the other hand, the aforementioned properties when it is inflated at reduced or even zero pressure, keeping the heels of said tire perfectly in position during a taxi in degraded mode, thanks to its structure described above, structure that allows a modification (increase) of the tightening of the tip of the bead on the mounting rim as a function of the tension of the carcass reinforcement, which allows a small initial tightening on the rim, knowing that the aforementioned tightening will increase when the tire is inflated to its recommended pressure. The preferred solution described in WO 95/23073 is such that the fold of the carcass reinforcement has a length such that it is in contact with the total perimeter of the profile or wedge; shape, so, the two sides radially external and internal the rubber profile, as well as the side opposite the vertex or center of said profile, and its end is located axially beyond the point of intersection of the two external and internal sides. The part of the bend immediately adjacent to the part wound around the rod, can first form the radially outer side of the profile or wedge, then the side opposite the apex of said profile and, lastly, the radially inner side of the aforementioned profile, to finish beyond the point of union of the two external and internal sides. It can also form, firstly, the radially internal side of the profile or wedge, then the side opposite the vertex of said profile and, lastly, the radially external side of said profile, to end in the same manner as above. The two previous structures are complicated and difficult to implement industrially and, therefore, costly. On the other hand, under extremely severe conditions of loading, the pressure exerted by the tip of the bead on the projection axially to the outside of the rim and the elevated temperature that can reach said heel, are such that, at the end of the useful life, rubber cracks in the outer protective layer of the heel may occur, which propagate along the fold to reach the radially internal face of the anchor rod, with destruction of said heel. The object of the invention is to remedy the aforementioned disadvantages, while retaining the excellent properties against wedging or against de-tireing of the considered tire. The radial carcass reinforcement tire, according to the invention, comprises, seen in meridian section, at least one first bead, whose seat has a generatrix whose axially inner end is in a circle of diameter greater than the diameter of the circle in the that the axially outer end is located, the heel heel being axially inward and reinforced by at least one reinforcing, annular, inextensible element and coated with a rubber mixture, while the tip of the heel is axially to the outside and comprises a wedge-shaped rubber mixture profile delimited by two sides that exit from a vertex A located below the section of the annular element, forming the radially external side, with a parallel to the axis of rotation passing through said vertex A , an acute cpi angle, radially and axially open to the outside, and forming the radially internal side, with the said parallel, an angle f? sharp, open radially inwardly, the rubber mixture forming the profile axially adjacent to the annular element having a Shore A hardness greater than the hardness or Shore A hardness of the mixture or rubber mixtures radially above, respectively , of said annular element and of the axially adjacent profile. It is characterized in that the radial carcass reinforcement of said tire is wound, at least on the first bead, around said annular element going from the inside to the outside, to form a fold whose end is located, on the one hand, axially to the outside of a line P2 perpendicular to the axis of rotation and passing through the center of gravity of the meridian section of the annular element and, on the other hand, axially to the interior and radially to the outside of the line Pi supporting the radially external side of said profile axially adjacent to the cited annular element. The increased tightening of the bead tip on the mounting rim, depending on the tension of the carcass reinforcement, will be greater if the wedge-shaped rubber mix profile and delimited by the two sides leaving the vertex A is reinforced by, at least, the fold portion of the carcass reinforcement immediately adjacent to the part of the carcass reinforcement wound around the annular heel reinforcement element, whether said part is within the profile, as if it forms, at least, one of its sides. Advantageously, the radial carcass reinforcement of said tire is wound, at least on the first bead, around said annular element going from the inside to the outside, to form a fold extending along the radially inner side of the profile wedge-shaped, then along the side opposite the apex A to then axially and radially coat the outside, at least partially, the profile radially above the wedge-shaped profile. Preferably, the tire comprises a second bead whose seat has the same configuration as the seat of the first bead, that is to say, a seat whose generatrix has an axially inner end in a circle of diameter greater than the diameter of the circle in which it is located. the axially outer end, or seat called inclined towards the outside. Also, if the diameter of a seat inclined to the diameter of the circle in which the end of its generatrix farthest from the axis of rotation is located, the tire has, advantageously, two seats called inclined towards the outside and of different diameters. . The meridian profile of the carcass reinforcement, when the tire is mounted on its service rim and inflated to its operating pressure, has a constant curvature direction, at least on the first bead and on the side extending radially, and the tangent TT 'at the point of tangency T of said profile with the reinforcing annular element of said heel forms with the axis of rotation an angle f open towards the outside, at least, equal to 70 °. The invention will be better understood with the help of the drawing annexed to the description, which illustrates an example, not limiting, of the execution of a tire according to the invention, and which, associated with an adapted rim, forms a pneumatic-rim assembly. high performance. In the appended drawing, the single figure 1 schematically represents a tire bead according to the invention, mounted on the seat of its mounting rim. The rim (2), on which the tire (1) will be mounted, is formed, mainly, by two frustoconical seats whose generatrices form with the axis of rotation an angle ce ', open towards the interior of the tire, comprised between 4 ° and 30 ° and, in the example described, equal to 14 °, lower than the angle of the corresponding generatrices of the seats of the heels (12) of the tire. The said seats thus have axially outer ends in circles of smaller diameter than the circles in which the axially inner ends meet. The seat (23"), located, for example, on the outside of the vehicle, is extended axially to the outside by a projection or shoulder (25") whose inner face (250") forms with the axis of rotation an angle 7 >; ' , whose diameter DSE is less than the inner diameter DTE of the bead reinforcement rod (14) intended to be mounted on said seat, and whose height i, measured with respect to the axially outer end of the rim seat (23") is a height comparable to the height of the shoulders or projections used axially inside the usual and standardized touring rims.

On the exterior side of the vehicle, the rim seat (23") is joined to a cylindrical portion (21), on which will rest a tread support (4) .The diameter of the cylindrical portion ( 21) is the nominal diameter D of the rim (2).

The contour of the bead (12), mounted on the seat (23"), comprises, axially inside, a wall (12D) substantially perpendicular to the axis of rotation, wall that will rest laterally on the axially outer face of the support ring (12). 4) The said wall (12D) of the heel (12) is extended axially to the outside by a frustoconical generator (12C), which forms with an axis parallel to the axis of rotation an angle r »of 45 ° open axially inwards and radially The aforementioned generatrix (12C) is extended axially to the outside by a second frustoconical generatrix (12B) of bead seat which forms with the direction of the axis of rotation an angle equal to 15 °, open axially inwards and radially towards The exterior said generatrix (12B) is said to be inclined towards the outside, its axially outer end being in a circle of diameter smaller than the diameter of the circle in which its axially located end is located. nterior A truncated conical generatrix (12A), extending axially to the exterior of the generatrix (12B) and forming an angle with the direction of the axis of rotation. equal to 45 °, open axially and radially outwards, completes the outline of the base of the heel (12). The wall (12E), curved in the example described and generally oriented substantially perpendicular to the direction of the axis of rotation of the rim, completes the contour of the bead (12). While the generatrix (12B) will rest on the rim seat (23"), inclined to the outside, the generatrix (12A) will rest on the axially interior wall (250") of the projection (25") of the rim (2), inclined angle 3 * ', equal to the angle * -' of the generatrix (12A) .The portion of the heel, adjacent to the wall (12D) and the generatrix (12C), constitutes, seen in meridian section , the heel of the heel (12) The heel portion, adjacent to the generatrix (12B), to the generatrix (12A) and partially to the wall (12E), constitutes the tip of the heel (12). (12) is reinforced by the anchor rod (14) of the carcass reinforcement (13), rod coated with a high Shore A hard rubber mixture. The tip of the head (12) comprises a profile (3), arranged axially to the outside of the anchor rod (14) of the carcass reinforcement (13) .This profile (3) is presented in the form of a substantially circular sector with a vertex or ntro A located radially below the rod (14), two sides or spokes (31) and (32) starting from said vertex A, and a third side (30), opposite the vertex A. The radially outer side or radius ( 31) forms with an angle fi, open radially and axially outwardly, equal to 45 °, while the radially inner side (32) forms with the same parallel an angle f2, radially open inward and axially outward, equal to 15 °. This profile (3) is made of a rubber mixture having a Shore A hardness equal to 94 in the vulcanized state. The coated rod (14) has a profile (7) of rubber mixture of Shore hardness superimposed radially to the outside. In the same way as 37. Radially outside the profile (3) and axially to the outside of said profile (7) a third profile (6) of rubber mixture having a Shore A hardness equal to that of the profile (7) and , therefore, clearly lower than the hardness of the mixture of the profile (3), which allows, during an increase in tension of the carcass reinforcement, to facilitate the axial displacement of the braided rod (14) towards the outside of the bead ( 12) and, thus, create a compression of the profile (3) and a self-tightening of the tip of the bead (12) on the rim (2) of assembly, while, in the case described, the initial tightening of the bead (12) on the aforementioned rim is practically null, due to the almost equality between the angles and 'and to the almost equality between the larger diameters of the rim seats and the heels. The heel (12) is completed with the protector (5).

The carcass reinforcement (13) has a meridian profile, when the tire is mounted on its service tire and inflated to its service pressure, which has a constant curvature direction along its entire length, and is such that the tangents TT ' at the tangent points T of said profile with the coated rods (14) of the beads (12) form with the axis of rotation open angles f axially and radially outward and equal to 80 °. Said carcass reinforcement (13) is wound around the coated rod (14) going from the heel to the bead tip (12), or from the inside to the outside, to form a fold (130), substantially rectilinear and extending along the radially inner side (32) of the profile (3), then along the side (30) opposite the apex A, to then subsequently coat, at least partially, the axially and radially outer side of the profile (6) radially to the outside of the profile (3). The bend end (130) is located, on the one hand, axially to the interior and radially to the outside of a line Pi, said line Pi being the line that supports the side (31) of the profile (3) and, on the other hand, axially to the outside of a line P2, which is perpendicular to the axis of rotation and which passes through the center of gravity of the meridian section of the coated rod (14). The fold of the carcass reinforcement, thus structured, thus has a sufficient length to be able to present a good behavior against the unwinding of the carcass reinforcement, while allowing a lower speed of propagation of the cracks that arise in the layer outer (5) heel (12). It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Claims (7)

1. CLAIMS Having described the invention as above, the contents of the following claims are claimed as property: 1. Radial carcass pneumatic tire, characterized in that it comprises, seen in meridian section, at least one first bead, whose seat has a generatrix whose end is axially interior is in a circle of diameter greater than the diameter of the circle in which the axially outer end is located, the heel of the heel being axially to the interior and reinforced by at least one reinforcing element, annular, inextensible and coated with a mixture of rubber, while the tip of the heel is axially to the outside and comprises a profile of wedge-shaped rubber mixture delimited by two sides, which exit from a vertex A located below the section of the annular element, forming the radially outer side , with a parallel to the axis of rotation passing through said vertex A, a sharp angle, open radially and axially h to the outside, and forming the radially inner side with said parallel, an acute angle f2, open radially inwards, the rubber mixture forming the profile axially adjacent to the annular element, having a Shore A hardness greater than the hardness or the Shore A hardness of the mixture or of the rubber mixtures radially above, respectively, of said element and of the axially adjacent profile, characterized in that the radial carcass reinforcement of said pneumatic tire is wound, at least in the first bead, around the said annular element going from the inside to the outside, to form a fold whose end is located, on the one hand, axially outside a straight line P2 perpendicular to the axis of rotation and passing through the center of gravity of the meridian section of the element and, on the other hand, axially to the interior and radially to the outside of the line Pi that supports the radially external side of the profile.
2. 2. Tire according to claim 1, characterized in that the profile of rubber mixture, wedge-shaped and delimited by the two sides leaving the vertex A, is reinforced, at least, by the fold part of the carcass reinforcement. immediately adjacent to the part of the carcass reinforcement wound around the annular reinforcing element of the bead, whether said part is inside the profile, or if it forms at least one of its sides.
3. Tire according to claim 2, characterized in that the radial carcass reinforcement of said tire is wound, at least on the first bead, around said annular element going from the inside to the outside, to form a fold that extends along on the radially inner side of the wedge-shaped profile, then along the side opposite the apex A, to then axially and radially cover the outside, at least partially, the profile radially above the wedge-shaped profile.
4. 4. Tire according to claim 1, characterized in that it comprises a second bead whose seat has the same configuration as the seat of the first bead, that is to say, a seat whose generatrix has an axially inner end in a circle of diameter greater than the diameter of the circle in which is the axially outer end, or seat called inclined to the outside.
5. 5. Tire according to claim 1, characterized by two seats called inclined towards the outside and of different diameters.
6. Tire according to claim 4, characterized in that the generatrices of the heel seats are extended axially to the outside by frusto-conical generatrices, which form with the direction of the axis of rotation an angle v, open axially and radially outwards, equal to Four. Five.
7. 7. Tire according to claim 1, characterized in that 'the meridian profile of the carcass reinforcement, when the tire is mounted on its service rim and inflated to its service pressure, has a constant curvature direction at the sides and in the first bead and whose tangent T 'at the point of tangency T of said profile with the annular reinforcing element of said heel forms with the axis of rotation an angle f open towards the outside, at least, equal to 70 °.