GB1597657A

GB1597657A - Pneumatic tyre having a tubular bead reinforcement

Info

Publication number: GB1597657A
Application number: GB17511/78A
Authority: GB
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 1977-05-09
Filing date: 1978-05-03
Publication date: 1981-09-09
Also published as: NL173149B; BE866468A; IT7868046A0; NL7804633A; LU79620A1; IT1107139B; OA05959A; CA1072870A; JPS6158322B2; BR7802908A; FR2390299B1; ZA782630B; NL173149C; AU3588578A; AU515545B2; JPS53138110A; DE2820182C2; FR2390299A1; ES469549A1; MX145692A

Description

(54) PNEUMATIC TYRE HAVING A TUBULAR BEAD REINFORCEMENT (71) We, MICHELIN & CIE (Compagnie Generale des Establissements Michelin a French Body Corporate, of 63 Clermont-Ferrand, France, do hereby declare that the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to improvements in pneumatic tyres and more particularly to tyres of very large size which are intended to be fitted on heavy load-carrying vehicles such as those used in civil engineering.

At the present time, such tyres are usually fitted without an inner tube on rims having frustoconical bead seats. Thus the bead has to carry out two main tasks, to ensure sealing-tightness between the tyre and the rim, and to make the tyre integral with the rim whatever the amount of the tangential driving force which is to be transmitted.

The beadwires or bead reinforcement for the beads make the main contribution to carrying out these two functions, but at the cost of quantity of material, e.g. steel strip or wire, and this becomes expensive.

Furthermore, the fatigue strength of the components forming the bead seems to be related to the value of the cross-section chosen for the bead reinforcement.

Furthermore, the cross-sectional shape of the beadwires formed of steel strips or wires brings about on the rim a distribution of bead pressures which is disadvantageous because there are zones of local pressures which are. too high and zones of local pressures which are too low. Consequently, the beads become worn and/or slide in a circumferential direction relatively to the nm.

The beadwires or other bead reinforcement used, therefore, have an exaggerated cross-section relatively to that required for example for reasons of static strength.

To lighten the bead reinforcement, it has already been proposed to use an annular member, of for example metal, having in radial section a cavity which is filled with plastic material, or a hollow annular member made of extruded plastics material.

However, such bead reinforcements are not suitable for large tyres particularly because of their inadequate resistance to fracture and crushing.

The invention has, therefore, been made with these points in mind and it is an object of the invention to provide a bead reinforcement which can withstand these large crushing forces but which is not too heavy and which gives a reasonably uniform distribution of the pressures of the bead on the nm.

According to the invention there is provided a pneumatic tyre having a carcass anchored in each bead to at least one bead reinforcement, the bead reinforcement being constituted by an annular metal member having cross-section as seen in radial section which is hollow and which has a strengthening element extending across the hollow region, the bead reinforcement being arranged in the tyre bead in such a manner that, when the tyre is mounted and inflated on its designed wheel rim which has a seat which the tyre bead engages and a flange against which the side of the bead bears, the strengthening element forms an angle of less than 60 with the bisector of the angle formed between the seat of the bead on the wheel rim and a tangent to the flange of the wheel rim adjacent to this seat where the side of the bead bears against that flange, the bisector being directed towards the interior of the tyre.

By the term "strengthening element" we mean not only a strengthening element itself or its axis of symmetry in the case of a straight strengthening element or a strengthening element with a straight axis of symmetry, but also the chord joining the two ends of the strengthening element in cases where the strengthening element is curved.

Thus, in a tyre according to the present invention, the bead reinforcement has a hollow cross-section to promote the lightness but is made to resist deformation by a triangulated structure, particularly against forces between the rim and the structural reinforcement which tend to crush the bead reinforcement.

Preferably, the radial cross-section of a bead reinforcement in a tyre according to the invention is formed by two sides of slight or zero curvature facing the rim, and by two other curved sides. However, that crosssection may be either circular or elliptical with the minor axis of the elipse substantially parallel to or coincident with the strengthening element. That cross-section could also be in the form of a square or parallelogram with rounded corners, the smaller diagonal of the parallelogram being substantially parallel to or coincident with the strengthening element.

It is advantageous to arrange the strengthening element along the bisector of the angle formed by the convergent sides facing the rim or by the chords subtending those sides, or so that the strengthening element uses this bisector as an axis of symmetry.

The sides of the cross-section of the bead reinforcement facing towards the rim, or the chords subtending these sides may form an angle near to that formed by the bead seat on the rim and the tangent to the rim flange.

In the bead, it is also possible to arrange the bead reinforcement in such a manner that the internal strengthening element or its axis of symmetry is parallel to the bisector of the angle formed by the seat of the bead on the rim and the tangent to the rim flange, or that this strengthening element contains the bisector or uses it as an axis of symmetry.

Such bead reinforcements are very well suited to pneumatic tyres whose carcass is essentially formed of radial metal cords, and which are intended for load-carrying vehicles and vehicles carrying very heavy loads.

In a tyre according to the invention the pressure on the rim of the portion of the bead in which the bead reinforcement is situated is made more uniform than before.

Furthermore, it is possible to give the section of the bead reinforcement a shape and an area suitable for giving the components of the bead a satisfactory strength and giving the bead reinforcement itself a suitable resistance to forces which would tend to deform it.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows the bead of a radial tyre according to the invention; and Figures 2 to 8 show other sections of bead reinforcement to be used in tyres according to the invention.

In Figure 1, a bead 1 of a tyre with a radial carcass 2 is shown. The carcass 2, preferably of metal cords, extends about the metal bead reinforcement 3 and its turned-over portion 21 extends upwards again beyond the bead reinforcement 3. The bead 1 is arranged on a rim on which there is shown only the portion forming a seat 4 and a flange 5 intended to come into contact with the bead 1. This seat 4 is, in the case of the example selected, inclined relatively to the axis of rotation of the rim Y-Y. The seat 4 and the tangent t1 to the flange 5 form an angle cr.,ead reinforcement 3 a.

The bead reinforcement 3 has a radial cross-section formed essentially by two convergent sides 31 and 32 forming with one another an angle nearly equal to the angle a, and with an arc of a circle 33 connecting the non-common ends of the sides 31 and 32. Internally, the bead reinforcement 3 has a strengthening element which is symmetrical relatively to the bisector S of the angle formed by the two convergent sides 31 and 32. This reinforcement is formed by an integral rib 34 projecting from the region surrounding the point where the two sides 31 and 32 meet, and another integral rib 35 wider than the rib 34 projecting from the arc 33 and provided at its free end with a groove 36. The free end of the rib 34 bears in the groove 36 of the rib 35. The strengthening element opposes deformation, more particularly due to crushing forces, of the bead reinforcement dividing the section of the bead reinforcement into two triangles (shown in broken lines) of which the strengthening element forms a common side.

The axis of symmetry S and consequently the strengthening element itself form an angle ss of about 20 relatively to the bisector C of the angle formed by the bead seat 4 on the rim and the tangent tl to the rim flange 5.

The two sides 31 and 32 are substantially straight, and therefore have substantially zero curvature and face the seat 4 and flange 5 of the rim. The angle formed by these two sides 31 and 32 is near to the angle a formed by the bead seat 4 and the tangent t1 to the flange 5.

The embodiment of Figure 2 shows a bead reinforcement 40 whose cross-section is externally circular. An internal diametral strengthening element in two portions 41 and 42 divides this section into two triangles (shown in broken lines), this strengthening element constituting a side common to these two triangles.

The embodiment of Figure 3 shows a bead reinforcement 50 whose cross-section has an approximately oval or elliptical configuration. The strengthening element is made in two parts 51 and 52 and divides this configuration into two triangles (shown in broken lines), the strengthening element constituting a common side to these two triangles. The overall outside dimension A of the section of the bead reinforcement measured perpendicular to the strengthening element is, as in the case of Figures 1, 5, 7 and 8 also, larger than its outside dimension B measured parallel to the strengthening element. In this case, the side which is common to the two triangles is coincident with the minor axis of the elliptical section of the bead reinforcement.

A further embodiment is illustrated in Figure 4 having bead reinforcement 60 of a square shape with rounded corners. A strengthening element made in two parts 61 and 62 forms one of the diagonals of the square. This diagonal is identical with the common side of the two triangles (in broken line) into which the outline of this reinforcement element may be subdivided.

Another embodiment is illustrated in Figure 5 having a bead reinforcement 70 the external section of which is in the form of a parallelogram with rounded corners. An internal strengthening element made in two parts 71 and 72 and contains the smaller diagonal of the parallelogram. This diagonal is identical with the side common to the two triangles (in broken lines) into which the outline of this bead reinforcement may be subdivided.

The strengthening element 81 of the bead reinforcement element of square section shown in Figure 6 is distinguished from the strengthening elements described hereinbefore by the fact that it is made in one single portion, the root 82 of which is situated in the region where the two sides 83 and 84 meet, whilst the opposite end 87 is situated in the region where the two opposite convergent sides 85 and 86 meet one another.

The bead reinforcement element 90 illustrated in Figure 7 differs from all the foregoing elements in that two of its convergent sides, namely the sides 92 and 92' are contiguous and do not integrally join one another. Likewise its strengthening element is composed of two contiguous lengths 91 and 91' which are prolongations of the sides 92 and 92' respectively.

Furthermore, the bead reinforcement element 100 according to Figure 8 has a strengthening element composed of two portions 101 and 101' connected to one another at their common apex 102. Its two sides 103 and 104 have a zero curvature, the opposite sides 105 and 106 being curved.

It will be apparent that the underlying idea of the invention may be extended to hollow bead reinforcement elements comprising a plurality of cavities of triangular cross-section which are juxtaposed and have a single side in common from one cavity to the next.

WHAT WE CLAIM IS: 1. A pneumatic tyre having a carcass anchored in each bead to the bead reinforcement, the bead reinforcement being constituted by an annular metal member having a cross-section as seen in radial section which is hollow and which has a strengthening element extending across the hollow region, the bead reinforcement being arranged in the tyre bead in such a manner that, when the tyre is mounted and inflated on its designed wheel rim which has a seat which the tyre bead engages and a flange against which the side of the bead bears, the strengthening element forms an angle of less than 60 with the bisector of the angle formed between the seat of the bead on the wheel rim and a tangent to the flange of the wheel rim adjacent to this seat where the side of the bead bears against that flange, the bisector being directed towards the interior of the tyre.

2. A pneumatic tyre as claimed in Claim 1 in which the radial cross-section, the bead reinforcement is formed by two sides having small or zero curvatures which face towards the wheel rim, and two other curved sides.

3. A pneumatic tyre as claimed in Claim 1 in which the outside radial cross-section of the bead reinforcement is in the shape of a circle of a square with rounded corners.

4. A pneumatic tyre as claimed in Claim 1 in which the outside radial cross-section of the bead reinforcement is approximately in the shape of an ellipse whose minor axis is substantially parallel to or coincident with the strengthening element.

5. A pneumatic tyre as claimed in Claim 1 in which the outside radial cross-section of the bead reinforcement is the shape of a parallelogram with rounded corners whose smaller diagonal is substantially parallel to or coincident with the strengthening element.

6. A pneumatic tyre as claimed in any preceding claim in which the strengthening element is arranged along the bisector of the angle formed by the convergent sides or by the chords subtending these sides, or is arranged such that it uses this bisector as an axis of symmetry.

7. A pneumatic tyre as claimed in any preceding claim in which the bead reinforcement has sides or the chords subtending these sides which face the rim and form an angle substantially equal to the angle formed by the bead seat on the wheel rim and the tangent to the wheel rim flange.

8. A pneumatic tyre as claimed in any

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The embodiment of Figure 3 shows a bead reinforcement 50 whose cross-section has an approximately oval or elliptical configuration. The strengthening element is made in two parts 51 and 52 and divides this configuration into two triangles (shown in broken lines), the strengthening element constituting a common side to these two triangles. The overall outside dimension A of the section of the bead reinforcement measured perpendicular to the strengthening element is, as in the case of Figures 1, 5, 7 and 8 also, larger than its outside dimension B measured parallel to the strengthening element. In this case, the side which is common to the two triangles is coincident with the minor axis of the elliptical section of the bead reinforcement. A further embodiment is illustrated in Figure 4 having bead reinforcement 60 of a square shape with rounded corners. A strengthening element made in two parts 61 and 62 forms one of the diagonals of the square. This diagonal is identical with the common side of the two triangles (in broken line) into which the outline of this reinforcement element may be subdivided. Another embodiment is illustrated in Figure 5 having a bead reinforcement 70 the external section of which is in the form of a parallelogram with rounded corners. An internal strengthening element made in two parts 71 and 72 and contains the smaller diagonal of the parallelogram. This diagonal is identical with the side common to the two triangles (in broken lines) into which the outline of this bead reinforcement may be subdivided. The strengthening element 81 of the bead reinforcement element of square section shown in Figure 6 is distinguished from the strengthening elements described hereinbefore by the fact that it is made in one single portion, the root 82 of which is situated in the region where the two sides 83 and 84 meet, whilst the opposite end 87 is situated in the region where the two opposite convergent sides 85 and 86 meet one another. The bead reinforcement element 90 illustrated in Figure 7 differs from all the foregoing elements in that two of its convergent sides, namely the sides 92 and 92' are contiguous and do not integrally join one another. Likewise its strengthening element is composed of two contiguous lengths 91 and 91' which are prolongations of the sides 92 and 92' respectively. Furthermore, the bead reinforcement element 100 according to Figure 8 has a strengthening element composed of two portions 101 and 101' connected to one another at their common apex 102. Its two sides 103 and 104 have a zero curvature, the opposite sides 105 and 106 being curved. It will be apparent that the underlying idea of the invention may be extended to hollow bead reinforcement elements comprising a plurality of cavities of triangular cross-section which are juxtaposed and have a single side in common from one cavity to the next. WHAT WE CLAIM IS:

1. A pneumatic tyre having a carcass anchored in each bead to the bead reinforcement, the bead reinforcement being constituted by an annular metal member having a cross-section as seen in radial section which is hollow and which has a strengthening element extending across the hollow region, the bead reinforcement being arranged in the tyre bead in such a manner that, when the tyre is mounted and inflated on its designed wheel rim which has a seat which the tyre bead engages and a flange against which the side of the bead bears, the strengthening element forms an angle of less than 60 with the bisector of the angle formed between the seat of the bead on the wheel rim and a tangent to the flange of the wheel rim adjacent to this seat where the side of the bead bears against that flange, the bisector being directed towards the interior of the tyre.

8. A pneumatic tyre as claimed in any

preceding claim in which the bead reinforcement is arranged in the tyre bead such that the strengthening element or its axis of symmetry is parallel to the bisector of the angle formed by the bead seat on the wheel rim and the tangent to the wheel rim flange.

9. A pneumatic tyre according to any of claims 1 to 7 in which the bead reinforcement is arranged in the tyre bead such that the strengthening element contains the bisector or uses as its axis of symmetry the bisector of the angle formed by the bead seat on the wheel rim and the tangent to the wheel rim flange.

10. A pneumatic tyre as claimed in any preceding claim which has a radial carcass.

11. A pneumatic tyre as claimed in Claim 10 in which the cords of the radial carcass are of metal.

12. A pneumatic tyre substantially as herein described with reference to Figure 1 or that Figure as modified by any of Figures 2 to 8, of the accompanying drawings.