Title of Invention

A TYRE

Abstract

The invention concerns a tyre, for heavy loads and having tyre beads (B) designed to be mounted on flat rim seats or with an inclination of 5°, comprising at least one radial body ply formed with inextensible reinforcing elements and anchored in each tyre bead (B) to a bead core (2) to form a ply turn-up (10) whereof the end is located at a radial distance H¿RNC? from the tyre bead base. Each tyre bead (B) is reinforced by at least two additional reinforcing armouring, at least one first armouring formed by at least one ply (8) of radial textile reinforcing elements, located axially outside a second armouring (6) formed by at least a ply (6) of inextensible elements forming with the circumferential direction an angle $g(a) such that 0° $m(F) $g(a) $m(F) 45°.

Full Text

FORM 2 THE PATENTS ACT, 1970 [39 OF 1970] COMPLETE SPECIFICATION [See Section 10] "A TYRE" COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN-MICHELIN 8B CIE, a French company, of 12, Cours Sablon, F-63040 ClermontFerrand, Cedex 09, France, The present invention relates to a tyre with radial body reinforcement, and more particularly to a "heavy-vehicle" tyre, intended to be fitted on vehicles such as lorries, road tractors buses, trailers and others, and in which a novel reinforcement structure for the tyre beads is adapted to improve the life of said beads. Generally, a tyre of the type in question comprises a body reinforcement formed of at least one ply of metal cables, which is anchored in each tyre bead to at least one bead core, forming a turn-up. The body reinforcement is radially surmounted by a crown reinforcement, composed of at least two plies of metal cables, crossed from one ply to the next and forming angles of between 10° and 45° with the circumferential direction. The body reinforcement turn-ups are generally reinforced by at least one ply of metal cables oriented at a small angle relative to the circumferential direction. In the case of the presence of a single tyre bead reinforcement ply, the latter may be located along the reinforcement turn-up with a radially upper and located above or below the radially upper end of the reinforcement upturn. As for the radially lower end of such a ply, it is generally located either on a straight line parallel to the axis of rotation and passing approximately through the centre of gravity of the meridian section of the anchoring tyre bead core of the body reinforcement, in the case of a tyre having tyre beads intended to be mounted on rim seats inclined at 15°+ 2°, or on a straight line parallel to the axis of rotation and passing through a point located between the centre of gravity of the meridian section of the anchoring tyre bead core and the point of maximum axial width of the body reinforcement, in the case of a tyre having tyre beads intended to be mounted on rim seats inclined at 0° or at 5° + 1°. In this second case, the bead reinforcement ply is then wound around the tyre bead core, so as to have an axially outer strand and an axially inner strand, the radially upper end of the axially inner strand -2- being generally located beneath the radially upper end of the axially outer strand. Furthermore, the life of "heavy-vehicle" tyres, owing to the progress achieved, and to the fact that certain types of travel are made less of a handicap as far as wear of the tread is concerned, has become such that it is also necessary to improve the life of the beads, and more particularly of tyres subject to prolonged travel, this travel frequently inducing a high temperature of the beads owing to the temperatures reached by the mounting rims. Numerous solutions have been described for improving the life of the beads of tyres, whether they are intended to be mounted on 15°-seat rims or flat rims or 5°-seat rims: for example, it has been proposed to replace the metallic reinforcement ply by a plurality of plies of reinforcement elements, textile ones, for example, crossed from one ply to the next and said plies being located axially either on the same side of the upturn or on either side of said turn-up, or alternatively partly along the turn-up and partly along the body reinforcement. The life of the tyre beads can also be improved by arranging two reinforcement plies along the body reinforcement, whereas the turn-up of said reinforcement is not reinforced. From reading French application FR 2 730 190, said improvement can be obtained by the presence in the beads of at least one reinforcement ply formed of circumferential metallic elements, which ply is wound around the bead wire, on the outside of the wound part of the carcass reinforcement, such that the radially upper ends respectively of the axially outer strand and of the axially inner strand are radially located above a straight line parallel to the axis of rotation and passing through the point of the bead wire which is farthest from said axis of rotation. The carcass -3- reinforcement, formed of radial cords or cables, is thus formed, at the level of its contact surface with the bead wire, as is known, of substantially circumferential elements which are generally metallic in the form of wound cords, cables, bands or strips, inserted between said elements with substantially circumferential orientation and the additional ply of metallic elements, which are also circumferential. This structure thus makes it possible to take up the tensile stresses to which the carcass reinforcement is subjected, and thus minimizes all the deformations at the ends of the carcass reinforcement upturn, whatever the traveling conditions. The solution of a bead reinforcement ply with circumferential reinforcement elements does not appear to be the technically and industrially optimal solution for tyres having beads intended to be mounted on so-called flat rims or rims having seats inclined at 5°, since the important factor does not seem to be the presence of circumferential elements. Furthermore, and with the aim of lightening tyres for heavy vehicles which are mounted on rims having seats inclined at 0° or 5°+ 1°, numerous attempts have been made to dispense with the axially inner strand of the reinforcement ply of the bead, and to have substantially the same architecture of carcass reinforcement and reinforcement ply for the two types of rims used. Although said known solutions, the object of which is to avoid deradialisation of the cables of the upturn of the carcass reinforcement and to minimize the radial and circumferential deformations to which the end of said upturn and the radilly upper end of the reinforcement ply are subjected respectively, have improved the life of the bead reinforcements, the performance of the tyres mounted on rims having 0° seats or 5°+ 1° seats is on the other hand reduced by the appearance and propagation of -4- breaks in the outer layer of rubber covering the bead and providing the connection to the rim. The invention proposes to overcome the above disadvantages. In order to improve the life of a tyre required to bear heavy loads and having beads intended to be mounted on flat rim seats or rim seats which are inclined at 5°, said tyre according to the invention, comprising at least one radial body reinforcement, formed of at least one ply of inextensible reinforcement elements and anchored in each tyre bead B to a tyre bead core to form turn-up, the end of which is located at a radial distance HRNC from the base of the tyre bead, each tyre bead B being reinforced by at least two additional reinforcement armourings, at least one first armouring formed of at least one ply of radial reinforcement elements and at least one second armouring formed of at least one ply of inextensible elements forming an angle a with the circumferential direction such that 0° -5- Reinforcement elements will be considered to be radial if the angle which they form with the circumferential direction of the tyre lies within a range of 80° -100°. Likewise, in the spirit of the invention, "radially upper end" of a tyre bead reinforcement armouring which may be formed of one or more plies is to be understood to mean the end of the reinforcement ply which is farthest from the axis of rotation, the reinforcement plies possibly having upper ends included in a range of radial distance of at most 20 mm. Likewise, the radially lower end of a bead reinforcement armouring will be the lower end of the ply least far from the axis of rotation. The first armouring of radial reinforcement elements is advantageously formed of a single ply of aliphatic polyamide textile cables composed of two plied cords, at least 250/250 twists per meter. It is preferably separated from the second armouring by a profiled element of rubber mix of a thickness of at least 2 mm. The second additional tyre bead reinforcement arnouring may be formed of at least one ply of circumferential metallic reinforcement elements; in this case, it is advantageous, in order to facilitate manufacture and to reduce the cost thereof, to select as reinforcement elements for said ply lengths or assemblies of lengths of metal cables, of a circumferential length less than the circumferential length of the centre axis of the bead wire. It may also be formed, as known per se, of a single ply of metal cables parallel to each other in the ply and forming a small angle of between 5° and 30° with the circumferential direction. In all cases, it is preferably separated from the body reinforcement turn-up by a second profiled element of rubber mix of a thickness of at most 3 mm. The characteristics of the invention will be better understood with reference to the following description, which refers to the accompanying -6- drawing, which illustrate examples of embodiment in non-limiting manner, and in which the single Figure 1 is a diagram of a bead variant according to the invention. The tyre bead B shown in Figure 1 is that of a 10. 00. R.20 X tyre, intended to be mounted on a rim comprising rim seats inclined at 5°. Said bead is reinforced by a bead core (2). Around said bead core (2) there is anchored a body reinforcement (1) composed of a single ply of metal cables. The anchoring is effected by turn-up (10) around the layer (20) of rubber mix which covers the bead core (2), the radial distance HRNC between the radially upper end of said turn-up (10) and the base of the tyre bead, said bead being represented by convention by the straight line D parallel to the axis of rotation passing through the point of the bead core (2) closest to said axis of rotation, being equal, in the example in question of the tyre of dimension 10. 00. R.20, to 0.25 times the height H of the tyre on its rim, the latter being the radial distance between the point of the tyre which is radially farthest from the axis of rotation from the straight line for measuring the nominal diameter of the mounting rim, and equal to 270mm. Between the body reinforcement (1) and its turn-up (10), radially above the bead core (2), there is arranged a first bead filler (3) of rubber mix of a generally high shore A hardness, said first filler (3) being extended radially by a second filler (4) of rubber mix of a lower Shore A hardness than the previous one and the radially upper end of said filler (4) being substantially located at the level of the maximum axial width of the tyre. Axially to the outside of the turn-up (10) of the ply (1) there is arranged a second bead reinforcement armouring composed, in the example described, of a single ply (6), not turned up about the bead core (2). The radially upper end of said ply (6) is located relative to the base of the tyre bead at a height HR equal to 50mm, the distance HR being equal to 66% of the distance HRNC, the radially inner end being located practically on the -7- straight line parallel to the axis of rotation defining the base of the bead. The ply (6) of said second armouring is formed of metal cables oriented at 22° to the circumferential direction. The radially upper half of the ply (6) is axially separated from the upturn (10) of the body reinforcement (1) by a profiled element (5) of rubber mix having a Shore A hardness substantially equal to the hardness of the same name of the mixture constituting the filler (4), and the thickness eo of which, measured perpendicular to the turn-up (10) and at the level of the radially upper end of the ply (6), is equal to 3 m. The two radially outer ends respectively of the turn-up (10) of the body reinforcement (1) and of the reinforcement ply (6) of the tyre bead are covered axially to the outside by a fourth profiled element or filler (7), referred to as an "infill filler" and bearing on the second bead filler (4), on the profiled element (5) and on part of turn-up (10), and the thickness ei of which, measured at the level of the radially outer end of the second bead reinforcement armouring, is equal to 2 mm. Axially to the outside of the infill filler (7) and along said filler there is arranged the first bead reinforcement armouring composed of a single ply (8) of 94/2 (tex) aliphatic polyamide cables twisted at 485/485 twists per metre. In known manner, such a formulation indicates that each plied thread or cable is formed of two strands (multifilament fibres), each having a linear density of 94 tex before twisting, which are first of all twisted individually at 485 twists per metre in a given direction, then secondly twisted together at 485 twists per metre in the opposite direction. Said cables of the ply (8) are radial, and precisely in the example described form an angle equal on average to 89°. The radially outer end of the ply (8) is located at a radial distance HLE from the base of the tyre bead of 80 mm, or 106% of the distance HRNC between the end of the turn-up of the body ply (a) and said base. As for the radially inner end of said ply (8), it is practically located on the straight line parallel to the axis of rotation to the tyre which passes through the centre of gravity of the cross- section of the anchoring bead core (2), and between the straight line D previously -8- defined and the straight line D", parallel to the axis of rotation and passing through the tip of the bead core (2) farthest from said axis. The first reinforcement ply (8) isolates from the rest of the axially outer tyre bead the protective rubber mix (9), which, as is known per se, surrounds the major part of the tyre bead, said mix (9) being axially to the inside extended radially to the outside by the conventional layers of inner rubber reinforcements (12), whilst axially to the outside it is extended radially to the outside by the sidewall layer (11). The combined presence, axially to the outside of the turn-up (10) of the body reinforcement, of a first reinforcement armouring (8) of radial textile elements which is not wound around the anchoring bead core (2) of the radial body reinforcement (1) and of a second reinforcement armouring (6) which minimizes the deradialisation of radial cables of the body reinforcement makes it possible not only to reduce substantially the stresses on the rubber mixes forming the tyre bead, more particularly at the ends of plies, but also substantially to delay the appearance of breaks in the protective layer (9), since the tyres thus described have covered, in tyre endurance travel on tyre, a mileage of 85, 000 km (average of two results), whereas all the tyres without a ply of radial textile cables only covered an average of 32, 500 km (average of about ten tyres) under the same traveling conditions. -9- WE CLAIM: 1. A tyre required to bear heavy loads and having beads (B) intended to be mounted on flat rim seats or rim seats which are inclined at 5°, comprising at least one radial carcass reinforcement (1), formed of at least one ply of inextensible reinforcement elements and anchored in each bead (B) to a bead wire (2) to form an upturn (10), the end of which is located at a radial distance HRNC from the base of the bead, each bead (B) being reinforced by at least two additional reinforcement armatures, at least one first armature not wound around the anchoring bead wire (2) of the carcass reinforcement, formed of at least one ply (8) of radial textile reinforcement elements and located axially to the outside of a second armature, and formed of at least one ply (6) of inextensible elements forming an angle a with the circumferential direction such that 0° ≤ a ≤ 45°, the radially inner end of said first armature being located between two straight lines D and D" parallel to the axis of rotation and passing respectively through those points of the anchoring bead wire (2) which are respectively farthest and least far from the axis of rotation, characterized in that, viewed in meridian section, the radially outer end of the first armature is located at a distance HLE from the base of the bead D of between 80% and 120% of the distance HRNC, whereas, the second armature (6), which is not wound around said anchoring bead wire (2), has a radially inner end located between the straight line parallel to the axis of rotation passing through the centre of gravity of the cross-section of the bead wire (2) and the base D of the bead and a radially outer end at a distance HR from said base of between 60% and 75% of HRNC -10- 2. A tyre as claimed in claim 1, wherein the first armouring of radial reinforcing elements is advantageously formed of a single ply (8) of aliphatic polyamide textile cables, composed of two plied cords, at at least 250/250 twists per metre. 3. A tyre as claimed in any one of claims 1 or 2, the first reinforcing armouring (8) is axially separated from said second armouring (6) by a fourth profiled element (7) of rubber mix of a thickness ei of at least 2 mm 4. A tyre as claimed in any one of claim 1 to 3, wherein the second additionally tyre bead reinforcement armouring is formed of a single ply (6) of metal cables parallel to each other in the ply and forming a small angle of between 5° and 30° with the circumferential direction. 5. A tyre as claimed in any one of claims 1 to 3, wherein the second armouring is axially separated from the turn-up (10) of the body reinforcement (1) by a second profiled element (5) of rubber mix of a thickness eo of at most 3 mm. Dated this 28th day of November, 2000. -11-

Documents:

abstract1.jpg

in-pct-2000-00673-mum-absract(10-60-2006).doc

in-pct-2000-00673-mum-abstract(10-06-2004).pdf

in-pct-2000-00673-mum-cancelled pages(10-06-2004).pdf

in-pct-2000-00673-mum-claims(granted)-(10-06-2004).pdf

in-pct-2000-00673-mum-claims(granted)-(10-6-2006).doc

in-pct-2000-00673-mum-correspondence(14-06-2004).pdf

in-pct-2000-00673-mum-correspondence(ipo)-(25-08-2004).pdf

in-pct-2000-00673-mum-form 1(10-06-2004).pdf

in-pct-2000-00673-mum-form 1(18-02-2004).pdf

in-pct-2000-00673-mum-form 1(28-11-2000).pdf

in-pct-2000-00673-mum-form 2(granted)-(10-06-2004).pdf

in-pct-2000-00673-mum-form 3(28-11-2000).pdf

in-pct-2000-00673-mum-form 4(20-02-2004).pdf

in-pct-2000-00673-mum-form 5(28-11-2000).pdf

in-pct-2000-00673-mum-form-pct-ipea-409(28-11-2000).pdf

in-pct-2000-00673-mum-form-pct-isa-210(28-11-2000).pdf

in-pct-2000-00673-mum-form2(granted)-(10-6-2006).doc

in-pct-2000-00673-mum-petition under rule 137(10-06-2004).pdf

in-pct-2000-00673-mum-petition under rule 138(10-06-2004).pdf

in-pct-2000-00673-mum-power of authority(10-06-2004).pdf

in-pct-2000-00673-mum-power of authority(28-11-2000).pdf