Abstract:
The invention relates to a novel tire having beads of a specified structure. In particular, the tire, when viewed in meridian section, has a radial carcass reinforcement and a bead of specified structure. The bead features a reinforcement ring that is able to move axially. The tire also features structures that are responsive to axial movement of the reinforcement ring, which modify clamping of the bead on its rim causing the clamping to increase with increasing tension of the carcass reinforcement.

Description:
This is a division of Ser. No. 09/239,168, filed Jan. 28, 1999, (now U.S. Pat. No. 6,179,028) which was a continuation-in-part of Ser. No. 08/682,548, filed Jul. 25, 1996 (now U.S. Pat. No. 5,971,047), which was a national stage application of PCT/EP 95/00426 filed Feb. 7, 1995. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a tire intended to be mounted on a rim having at least a first frustoconical seat, the generatrix of which has an axially outer end closer to the axis of rotation than the axially inner end. 
     Such a tire is described in international application WO 94/13498. It comprises at least a first bead, intended to be mounted on a first seat inclined towards the outside, the said first bead, having a seat the generatrix of which has its axially outer end closer to the axis of rotation than its axially inner end, and the said generatrix being extended axially towards to the outside by an outer face delimiting the bead toe, the said face forming with the axis of rotation an angle γ, open radially and axially towards the outside and of less than 90°. The radial carcass reinforcement of the said tire, anchored in each bead to at least an inextensible annular bead ring, has a meridian profile, when the tire is mounted on its service rim and inflated to its service pressure, with a constant direction of curvature in the sidewall and bead terminated by the toe and which is such that, in said bead, the tangent to the point of tangency of said profile with the inextensible bead ring forms with the axis of rotation an angle ø open towards the outside of at least 70°. 
     The bead of such a tire and more particularly the structure of the anchoring of carcass reinforcement may be variable. In the application WO 95/23073, the radial carcass reinforcement is anchored to the inextensible bead wire by winding around the said wire passing from the heel to the toe of the bead to form an upturn extending in a rubber section, made of rubber mix in the form of a wedge defined by two sides coming from an apex A located beneath the meridian section of the coated bead wire, the radially outer side forming, with a line parallel to the axis of rotation passing through said apex A, an acute angle ø 1 , open radially towards the outside and between 20° and 70°, and the radially inner side forming with said parallel line an acute angle ø 2 , open radially towards the inside, the rubber mix forming the rubber section axially adjacent to the bead wire having a Shore A hardness greater than the Shore A hardness(es) of the rubber mixes located axially and radially above the wire and the rubber section. 
     The combination of the carcass reinforcement meridian profile such as described in the first cited application with a structure of hooking such as described in the second cited application makes possible to obtain a very good compromise between the handling properties of the tire inflated to its recommended pressure and the said properties when the tire is inflated to a reduced pressure or even zero. Whether the initial clamping on the rim be zero or of a given value, the axial displacement of the anchoring bead wire of the carcass reinforcement, which may result from the tension of said reinforcement, which tension is due, for instance, to the inflation pressure of the tire, makes possible, in combination with the axial disposition of the rubber section reinforced by the upturn, to obtain clamping of the toe of the bead on the rim seat. The value of this clamping increases as a function of the tension force to which the carcass reinforcement is subjected, and may become great in the case of high tension, for instance when one of the side walls of the tire is placed under great tension by a transverse force. 
     The preferential solution described in the application WO 95/23073 is such that the carcass reinforcement upturn has a length such that it is in contact with the total perimeter of the rubber section or wedge; it thus forms the two radially outer and inner sides of the rubber section and the side opposite the apex or center of said rubber section, and its end is located axially beyond the point of intersection of the two outer and inner sides. The part of the upturn immediately adjacent to the part of said upturn which is wound around the bead wire may, in the first instance, form the radially outer edge of the rubber section or wedge and then finally the radially inner side of said rubber section, ending beyond the junction point of the two outer and inner sides. It may also form firstly the radially inner side of the rubber section or wedge, then the side opposite the apex of said wedge, and then finally the radially outer side of said rubber section, ending in the same manner as previously described. 
     The above two structures are complicated and difficult to use industrially, and as a consequence, expensive. Furthermore, in severe conditions of load, the contact pressure exerted by the bead toe upon the axially outer hump of the rim and the great temperature that may be reached in the said bead are such that fissures of rubber may occur in the external protecting layer of the bead, fissures which are propagated along the upturn of the carcass reinforcement and reach the radially inner face of the anchoring bead wire with destruction of the bead. 
     The invention has for object to remedy these drawbacks while keeping the excellent properties of unseating of tire beads. 
     SUMMARY OF THE INVENTION 
     According to the invention, a tire with a radial carcass reinforcement, when viewed in meridian section, comprises at least a first bead, the seat of which has a generatrix the axially inner end of which is on a circle of a diameter greater than the diameter of a circle on which is the axially outer end, the heel of the bead being axially on the inside and being reinforced by at least a reinforcement ring, annular, inextensible and coated with a rubber mix, the toe of bead being axially on the outside and comprising a rubber section made of rubber mix in the form of a wedge delimited by two sides coming from an apex A located beneath the meridian section of the coated bead ring, the radially outer side forming, with a line parallel to the axis of rotation passing through said apex A, an acute angle ø 1 , open radially and axially towards the outside, and the radially inner side forming with said parallel line an acute angle ø 2 , open radially towards the inside, the rubber mix forming the rubber section axially adjacent to the bead ring, having a Shore A hardness greater than the Shore A hardness(es) of the rubber mixes located axially and radially above the bead ring and above the rubber section, is characterized in that the carcass reinforcement of the said tire is wound, at least in the first bead, around the bead ring passing from the inside to the outside to form an upturn extending along the radially inner side of the rubber section in form of a wedge, then along the side opposite the apex A, and then covers axially and radially on the outside, at least in part, the rubber section radially above the rubber section or wedge, the said upturn having an end located radially above the reinforcement annular ring of bead and axially between the straight line, extending the radially outer side of the wedge, and the straight line perpendicular to the axis of rotation and tangent at N to the said annular ring. 
     Preferably, the tire comprises a second bead, the seat of which has the same configuration as the seat of the first bead, i.e a seat the generatrix of which has an axially inner end on a circle of diameter greater than the diameter of the circle on which is the axially outer end or seat inclined towards the outside. 
     The invention also provides a tire which, when viewed in meridian section, has a radial carcass reinforcement and a bead of specified structure. The bead comprises a reinforcement ring that is able to move axially. The tire further comprises means in each bead permitting modification of clamping of the bead on a rim as a function of the tension of the carcass reinforcement. In one embodiment, the tire comprises, viewed in meridian section, a radial carcass reinforcement and a bead having a reinforcement ring, the reinforcement ring being able to be moved axially, and means responsive to the axial movement of the reinforcement ring for modifying clamping of the bead on its rim, so that the clamping is increased with increasing tension of the carcass reinforcement. 
     If the diameter of a seat is the diameter of the circle on which is the end of its generatrix farthest from the axis of rotation, the tire has preferably two seats inclined towards the outside and the two seats have unequal diameters. 
     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 direction of curvature, at least in the first bead and the sidewall which extends it, and the tangent TT′ to the point of tangency T of said profile with the reinforcement of the said bead forms with the axis of rotation an angle ø open towards the outside at least equal to 70°. 
    
    
     DESCRIPTION OF THE DRAWING 
     The invention will be better understood with reference to the drawing appended as FIG. 1 which illustrates a non-limiting example of an embodiment of a tire according to the invention, and which, when associated with a suitable rim, forms a high-performance tire-rim assembly. In this drawing, the figure shows a diagram of a tire bead according to the invention and mounted on the seat of its mounting rim. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The rim  2 , on which the tire  1  is mounted, is formed mainly by two frustoconical rim seats the generatrices of which form with the axis of rotation an angle α′, open towards the outside of the tire, of between 4° and 30°, and in the shown example equal to 14°, which is less than the angle of corresponding generatrices of the bead seats of the tire. The said seats have axially outer ends on circles, the diameters of which are smaller than the diameters of the circles on which the axially inner ends are located. The seat  23 ″, mounted for instance towards the outside of the vehicle, is axially extended on the outside by a projection or hump  25 ″, the inner face  250 ″ of which forms with the axis of rotation an angle γ′, the diameter D SE  of which is less than the inner diameter D TE  of the bead wire  14  reinforcing the bead intended to be mounted on the said seat, and the height h 1  of which, measured with respect to the axially outer of the rim seat  23 ″, is a height comparable with the height of humps or projections utilized axially on the inside of conventional rims for passenger cars. On the outside of the vehicle, the rim seat  23 ″ is connected to a cylindrical bearing surface  21  on which a bearing support will rest. The diameter of the cylindrical portion  21  is the nominal diameter of the rim. 
     The contour of the bead mounted on the seat  23 ″, comprises, axially on the inside a wall  12 D substantially perpendicular to the axis of rotation and bearing laterally on the axially outer face of the bearing support. The said wall  12 D is extended axially on the outside by a frustoconical generatrix  12 C forming with the axis of rotation an angle β of 45° which is open axially towards the inside and radially towards the outside. Said generatrix  12 C is itself extended axially on the outside by a second frustoconical generatrix  12 B of the bead seat, which forms with the direction of the axis of rotation an angle α′ of 15°, open axially towards the inside and radially towards the outside. Said generatrix is said to be inclined towards the outside, its axially outer end being on a circle of diameter less than the diameter of the circle on which its axially inner end is located. A frustoconical generatrix  12 A, extending the generatrix  12 B axially on the outside and forming an angle γ less than 90°, in the example equal to 45°, open axially and radially towards the outside, completes the contour of the base of the bead  12 . The wall  12 E, which is curved in the example described and is of substantially perpendicular general orientation to the direction of the axis of rotation of the rim, completes the contour of the bead. 
     Whereas the generatrix  12 B will bear on the rim seat  23 ″, inclined towards the outside, the generatrix  12 A will bear on the axially inner wall  250 ″ of the hump  25  of the rim  2 , inclined by the angle γ′ equal to the angle γ of the generatrix  12 A. The portion of bead adjacent the wall  12 D and to the generatrix  12 C forms, when viewed in meridian section, the heel of the bead. The portion of the bead adjacent the generatrix  12 B, the generatrix  12 A, and partially the wall  12 E forms the toe of the bead. The heel of bead is reinforced by the anchoring ring  14  of the carcass reinforcement  13 , the ring being coated with a rubber mix having a high Shore A hardness. The toe of the bead comprises a rubber section  3 , arranged axially on the outside of the anchoring bead ring  14 . This rubber section  3  is in the form of a substantially circular sector with an apex or center A located radially below the bead ring, with two sides or radii  31  and  32  starting from said apex, and a third side  30  opposite the apex A. The side or radius  31  radially on the outside forms an angle ø 1  of 45° with a line parallel to the axis of rotation and it is open radially and axially towards to the outside, whereas the radially inner side or radius  32  forms an angle ø 2  of 15° with the same parallel line and is open radially towards to the inside and axially towards the outside. This rubber section is made of a rubber mix having a Shore A hardness of  94  in the vulcanized state. 
     The coated bead ring  14  is surmounted radially on the outside by a rubber section  7  of rubber mix having a Shore A hardness of  37 . Radially on the outside of the rubber section  3  and axially on the outside of said rubber section  7 , there is located a third rubber section  6  made of rubber mix having a Shore A hardness equal to that of the rubber section  7  and therefor significantly less than the hardness of the mix of the rubber section  3 , which makes it possible, upon an increase of tension of the carcass reinforcement, to facilitate the axial displacement of the ring  14  towards the outside of the bead and thus create a compression of the rubber section  3  and a self-clamping of the toe of the bead on the mounting rim  2 , whereas, in the described example, the initial clamping of the bead on said rim is practically zero, owing to the quasi-equality between the angles of the rim and bead seats. 
     The carcass reinforcement  13  has a meridian profile, when the tire is mounted on its service rim  2  and inflated to its service pressure, which has a direction of curvature constant on its entire length, and is such that tangents TT′ to points of tangency T of said profile with the coated bead rings form with the axis of rotation angles ø open radially and axially towards the outside and equal to 80°. The said carcass reinforcement  13  is wound around the coated bead ring passing from the heel to the toe of the bead, or from the inside to the outside, to form an upturn  130  extending along the radially inner side  32  of the rubber section  3  in the form of a wedge, then along the side  30  opposite the apex A, and then covering axially and radially on the outside, at least in part, the rubber section  6  radially above the rubber section or wedge  3 . The end of the said upturn is located radially above the reinforcement annular ring  14  of the bead and axially between two straight lines, the line P 1  defining an extension of the radially outer side  31  of the wedge  3 , and the straight line P 2  perpendicular to the axis of rotation and tangent at the point N to the said annular ring  14 . The so structured carcass reinforcement upturn  130  has a sufficient length to have a good resistance to the unwinding of carcass reinforcement, while allowing a lesser propagation rate of fissures occurring in the external protecting layer  5  of bead, and to avoid the propagation towards the annular bead ring  14 .