Assembly for a Tire

Abstract

A non-pneumatic tire intended to be mounted on a rim and fitted to a lightweight vehicle, namely an assembly (A) for a tire, made up of a tire element (1) and of a clamping insert (9), and able to be wound onto a rim. To increase the load-bearing capability, the tire element (1) has two stiffening portions (6) at least partially not joined together, and each stiffening portion (6) extends in the open main interior cavity (5), from a transition zone between the bead (4) and the sidewall (3) as far as the vicinity of the middle of the crown (2), and delimits, with a portion of tire element (7) facing the stiffening portion (6), a closed secondary interior cavity (8). The clamping insert (9) may be a tape, with two transverse edges (91) inserted in the respective longitudinal grooves (41) of the two beads (4) of the tire element (1) so that to apply a clamping force to the two beads (4).

Claims

1. An assembly (A) for a tire, made up of a tire element and of a clamping insert, and able to be wound onto a rim to constitute a non-pneumatic tire for a lightweight vehicle: the tire element being a hollow tubular body having a longitudinal midline (L.sub.m) of length L and comprising at least one polymer material, the tire element comprising a crown, intended to come into contact with the ground, and connected by two sidewalls to two beads which are intended to collaborate with the rim, the assembly consisting of the crown, the two sidewalls and the two beads delimiting an open main interior cavity, each bead of the tire element comprising a longitudinal groove opening onto an interior face of a bead, facing the open main interior cavity, and extending along the entire length L of the longitudinal midline of the tire element, the clamping insert having a longitudinal length L1 at most equal to the length L of the longitudinal midline of the tire element, wherein the tire element comprises two stiffening portions at least partially not joined together, in that each stiffening portion extends in the open main interior cavity from each bead as far as the crown and delimits, with a portion of the tire element facing the said stiffening portion, a closed secondary interior cavity, and in that the clamping insert is a tape, comprising two transverse edges inserted in the respective longitudinal grooves of the two beads of the tire element so that the clamping insert is configured to apply a clamping force to the two beads, as the assembly (A) for a tire is wound onto the rim.

2. The assembly (A) for a tire according to claim 1, wherein the two stiffening portions of the tire element are symmetrical with respect to a longitudinal midplane (XZ), passing through the middle of the crown and containing the longitudinal midline (L.sub.m) of the tire element.

3. The assembly (A) for a tire according to claim 1, wherein each portion of the tire element facing a stiffening portion has, in any transverse plane (YZ) perpendicular to the longitudinal midline (L.sub.m) of the tire element, a transverse curvature C.sub.0, wherein each stiffening portion has, in any transverse plane (YZ), a transverse curvature C.sub.1 that has the opposite orientation to the transverse curvature C.sub.0 of the portion of the tire element facing the stiffening portion.

4. The assembly (A) for a tire according to claim 1, wherein the tire element is made of a single polymer material.

5. The assembly (A) for a tire according to claim 4, wherein the polymer material of which the tire element is made has a Shore hardness at least equal to 70.

6. The assembly (A) for a tire according to claim 5, wherein the polymer material of which the tire element is made is a thermoplastic elastomer material or a vulcanized thermoplastic material.

7. The assembly (A) for a tire according to claim 1, wherein the tire element has a curved longitudinal midline (L.sub.m) having a monotonic radius of curvature R.

8. The assembly (A) for a tire according to claim 7, wherein the clamping insert has, in any transverse plane, (YZ) a cross section that is curved, before the assembly (A) for a tire is wound onto the rim.

9. The assembly (A) for a tire according to claim 1, wherein the clamping insert is made of a polymer material, preferably a plastic material.

10. A method for mounting an assembly (A) for a tire, according to claim 1, on a rim, the assembly (A) for a tire being made up of a tire element, having a longitudinal midline (L.sub.m) of length L extending between two longitudinal end faces, and a clamping insert, having a longitudinal length L1, measured between two longitudinal ends, at most equal to the length L, the method comprising: a first step of circumferentially winding the assembly (A) for a tire onto the rim, a second step of setting the two beads of the tire element on the rim, by the collaboration between the clamping insert and the respective longitudinal grooves of the two beads, a third step of butting together the two longitudinal end faces of the tire element so as to constitute a non-pneumatic tire (P), the abutment zone constituting a circumferential through-discontinuity of the non-pneumatic tire (P).

11. The method for mounting an assembly (A) for a tire according to claim 10, comprising a fourth step of joining together the longitudinal ends of the clamping insert.

12. The method for mounting an assembly (A) for a tire according to claim 11, comprising a fifth step of locking the longitudinal ends of the clamping insert to the rim.

Description

[0047] The invention is illustrated in the figures referenced hereinbelow, which are not to scale and are described below:

[0048] FIG. 1A: Cross section through an assembly for a tire according to the invention.

[0049] FIG. 1B: Perspective view of an assembly for a tire according to the invention.

[0050] FIG. 1C: Side view of an assembly for a tire according to the invention.

[0051] FIG. 2: Cross section through a non-pneumatic tire which is obtained by winding an assembly for a tire according to the invention, in a compressed state.

[0052] FIG. 3A: Partial perspective view of a non-pneumatic tire in the process of being created, by winding an assembly for a tire according to the invention onto a rim.

[0053] FIG. 3B: Partial perspective view of a non-pneumatic tire obtained by winding an assembly for a tire according to the invention onto a rim.

[0054] FIG. 4: Longitudinal section, in a longitudinal midplane XZ, of a non-pneumatic tire obtained by winding an assembly for a tire according to the invention onto a rim.

[0055] FIG. 1A depicts a cross section, in a transverse plane YZ, of an assembly A for a tire according to the invention. The assembly A for a tire is made up of a tire element 1 and of a clamping insert 9. The tire element 1 is a hollow tubular body comprising at least one polymer material. It comprises a crown 2, intended to come into contact with the ground, and connected by two sidewalls 3 to two beads 4 which are intended to collaborate with a rim (not depicted). The assembly consisting of the crown 2, the two sidewalls 3 and the two beads 4 delimits an open main interior cavity 5. According to the invention, the tire element 1 comprises two stiffening portions 6 at least partially not joined together, and each stiffening portion 6 extends in the open main interior cavity 5 from each bead 4 as far as the crown 2 and delimits, with a portion of the tire element 7 facing the said stiffening portion 6, a closed secondary interior cavity 8. In the preferred embodiment depicted, the two stiffening portions 6 are symmetrical with respect to the longitudinal midplane XZ, passing through the middle of the crown 2 and containing the longitudinal midline L.sub.m (depicted in FIG. 1C) of the tire element 1. Furthermore, each stiffening portion 6 has, in the transverse plane YZ, a transverse curvature C.sub.1 that has the opposite orientation to that of the transverse curvature C.sub.0 of the portion of the tire element 7 facing the stiffening portion 6. Finally, each bead 4 comprises a longitudinal groove 41 opening onto an interior face 42 of a bead, facing the open main interior cavity 5, and extending along the entire length L of the longitudinal midline of the tire element 1. The clamping insert 9 is configured to apply a clamping force to the two beads 4 as the assembly A for a tire is wound onto the rim (not depicted). According to the invention, the clamping insert 9 is a tape, comprising two transverse edges 91 inserted in the respective longitudinal grooves 41 of the two beads 4 of the tire element 1 and has, in the transverse plane YZ, a curved cross section. FIG. 1B is a perspective view of an assembly for a tire according to the invention, the cross section of which is depicted in FIG. 1A. Finally, FIG. 1C is a side view of an assembly for a tire according to the invention, in the particular instance in which the tire element 1 has a curved longitudinal midline L.sub.m having a monotonic radius of curvature R.

[0056] FIG. 2 is a cross section, in a transverse plane YZ, of a non-pneumatic tire obtained by winding an assembly for a tire according to the invention, in a compressed state. FIG. 2 adds a rim 10 to the elements depicted in FIG. 1A. The clamping insert 9, in the case depicted, has the form of a tape with a cross section that is substantially rectilinear after the assembly A for a tire has been wound onto the rim 10, the said cross section being initially curved as depicted in FIG. 1A. The clamping insert 9 extends circumferentially, in the direction XX′, over the entire circumference of the non-pneumatic tire. As the non-pneumatic tire mounted on its rim 10 is compressed onto the ground, the stiffening portions 6 come into contact with one another and, by bearing against one another via their respective exterior faces, increase the stiffness of the non-pneumatic tire with respect to compression.

[0057] FIG. 3A is a partial perspective view of a non-pneumatic tire in the process of being created, by winding an assembly A for a tire according to the invention onto a rim 10. The tire element 1, cut to a length L substantially equal to the circumference of the rim 10 and provided with a clamping insert 9 in the form of a tape, is applied progressively to the rim 10, with the beads being fitted against the rim flanges. FIG. 3B is a partial perspective view of a non-pneumatic tire obtained by winding a tire element according to the invention onto a rim and depicts the final state of the mounting thus achieved.

[0058] Finally, FIG. 4 depicts a longitudinal section, in a longitudinal midplane X1Z1, of a non-pneumatic tire P obtained by winding an assembly for a tire according to the invention onto a rim 10. The tire element 1, comprising a crown 2 and beads 4, is mounted on the rim 10, it being clamped to the rim by a clamping insert 9. The longitudinal end faces 11 of the tire element 1 are butted together circumferentially in an abutment zone constituting a circumferential through-discontinuity 12 of the tire element 1. Furthermore, the longitudinal ends of the clamping insert 9, which are joined together, are secured to the rim 10 using locking means 13 that pass through a hole 14 in the rim, which hole is positioned circumferentially plumb with the circumferential through-discontinuity 12 of the non-pneumatic tire P.

[0059] The invention has been studied more particularly for the case of a non-pneumatic tire for a bicycle of size 37-622, according to the designation of the ETRTO standard.

[0060] Such a non-pneumatic bicycle tire has a section width, in the direction YY′, equal to 37 mm and a section height, in the direction ZZ′, equal to 39 mm. It is intended to be mounted on a rim having a diameter equal to 622 mm Each stiffening portion of the tire element has a thickness equal to 3 mm and a curvilinear length, comprised between its interface with the bead and its interface with the crown, equal to 22 mm. Furthermore, each stiffening portion of the tire element has an interface with the bead which is positioned, in the direction ZZ′, at a distance, from the end of the bead, equal to 3 mm, and has an interface with the crown which is positioned, in the direction YY′, at a distance, with respect to the longitudinal midplane XZ, equal to 2 mm. The polymer material of which the tire element is made is a vulcanized thermoplastic material having a Shore A hardness equal to 86, measured at 23° C., and a cure temperature of between 175° C. and 230° C. Finally, the tire element has a curved longitudinal midline having a monotonic radius of curvature R equal to approximately 300 mm.

[0061] In the example being studied, the clamping insert is a tape, comprising two edges inserted in the respective longitudinal grooves of the two beads of the tire element, and has a cross section that is curved, before the assembly for a tire is wound onto the rim. The curved cross section has a midline having a radius equal to 15 mm, and a curvilinear length equal to 18 mm before the assembly for a tire is wound onto the rim.

[0062] The inventors have demonstrated that the stiffening of the non-pneumatic tire leads to a significant reduction in the radial deformation of the crown, or deflection. The deflection changes from 15 mm, for a reference non-pneumatic tire without a stiffening portion, to a deflection of 5 mm for a non-pneumatic tire according to the invention, with two stiffening portions, which is to say that the deflection is reduced by a factor of 3, for the same applied load.