GB2030086A - Improvements in or relating to a pneumatic tyre and wheel rim assembly - Google Patents

Abstract

A pneumatic tyre (1) and wheel rim (2) assembly is disclosed in which the rim bead seats comprise grooves (18) having mouth portions (22) of reduced cross-section relative to the tyre beads (5) whereby the tyre beads (5) are retained in the grooves (18). The rim (2) is preferably multi-component comprising an inner and three or more outer rim members (10, 11) with the grooves (18) being defined by the adjacent axially outer edges of the rim members (10, 11) to facilitate location of the tyre beads (5) during assembly. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a pneumatic tyre and wheel rim assembly This invention concerns improvements in or relating to a pneumatic tyre and wheel rim assembly.

Pneumatic tyres are retained on their wheel rims by the engagement of beads, one at the radially inward edge of each sidewall, on bead seats. The bead seats are tapered so that inflation pressure forces the bead onto the taper to effect the engagement. The bead regions of tyres are accordingly designed to provide for the taper engagement as well as anchorage of the carcass reinforcement. This requires a comparatively rigid zone in the tyre bead which extends into the lower sidewall and in heavy duty tyres such as are used for trucks this rigid zone may extend for up to 20% of the section height of the tyre. Flexing of the sidewall is therefore transmitted to a rigid bead zone which is stiff and inefficient in absorbing deflection. As a result premature failure of the tyre is often caused by failure of the bead.In addition the provision of a relatively large bead zone reduces the length of the sidewall and consequently the sidewall is not able to be very efficient in absorbing deflection. Furthermore the complexities of providing the necessary bead zone stiffness incurs cost.

One object of the present invention is to provide an improved means of retaining a tyre on a wheel rim which obviates some of the above problems.

According to the present invention we provide a pneumatic tyre and wheel rim assembly comprising a tyre having a pair of side walls, a wheel rim constructed and arranged to define a pair axially spaced grooves in each of which a respective one of a pair axially spaced tyre beads is located and retained, each groove having a pair of opposed side portions which are relatively convergent to define a mouth portion of reduced cross-section relative to the associated bead whereby the beads are retained in the associated groove.

Preferably the grooves are annular. Preferably the side portions of each groove extend generally in an axially outwards direction relative to the tyre and wheel rim assembly and the lower portion of the tyre sidewalls curve axially inwardly to meet the associated bead at a relatively small angle, preferably 40 or less, with respect to a line parallel to the rotational axis of the tyre. More preferably the lower portion of the tyre sidewalls curve axially inwardly at 30 or less with respect to said line.

Preferably the beads have a bead core.

Preferably the bead core is of annular crosssection. Preferably the bead core is substantially inextensible. The bead core may be of the steel cable type.

Preferably the tyre is a low aspect tyre having an aspect ratio of 70% or less, preferably 60% or less and is preferably a radial tyre. Preferably the tyre tread is wider than the axial distance between the mouth portions of the grooves.

The wheel rim is a multi-component wheel rim to facilitate assembly and comprises an outer rim member and an inner rim member which is secured to the outer rim member to retain the components in position. Conveniently each groove is defined by the adjacent axially outer edges of the rim members. Preferably the axially outer edge regions of each groove are profiled to form radii to avoid chafing of the tyre sidewalls The outer and inner rim members may each be formed by one or more components. In one preferred construction the outer rim member is formed by three components and the inner rim member is formed by one component. The inner rim member may be separate from the wheel disc or may be formed integrally with the wheel disc.

According to a further aspect of the present invention we provide a pneumatic tyre for the assembly according to the present invention.

According to yet a further aspect of the present invention we provide a wheel rim for the assembly according to the present invention.

The invention will now be described in more detail by way of example only, with reference to the accompanying drawings wherein: Figure 1 is a cross-sectional view of a pneumatic tyre and wheel rim assembly according to the present invention, and Figure 2 shows a modification to the assembly shown in Fig. 1.

The pneumatic tyre wheel rim assembly shown in Fig. 1 comprises a steel ply radial tyre 1 having an aspect ratio of 50% and a multi-component wheel rim 2.

The radial tyre 1 has a tread 3, a pair of sidewalls 4 and a pair of annular axially spaced beads 5. Each bead 5 comprises a core having a steel wire cable 6 of generally annular cross-section and a triangular shaped bead apex 7. A single steel cord ply 8 extends circumferentially around the tyre from one bead to the other bead. The ends of the ply 8 are wrapped around the associated bead core.

Tread reinforcements indicated generally by the reference numeral 9 are provided radially outwards of the ply 8 and reinforce the crown of the tyre.

The wheel rim 2 comprises outer and inner rim members 10 and 11 respectively. The outer rim member 10 comprises a cylindrical centre portion 1 2 and axially spaced end portions 1 3 having the shape shown. The outer rim member 10 comprises three similar elements 14 (one only shown) which may be produced by rolling or casting or other suitable methods. The inner rim member 11 comprises a cylindrical element 1 5 which fits within the centre portion of the assembled outer rim member 10 and is secured to each element 1 4 by bolts 1 6 which are rendered air tight by means of O-rings (not shown).The end portions 1 3 of the outer rim member 10 and the adjacent end portions 1 7 of the inner rim member 11 define axially spaced annular grooves 1 8 in which the beads 5 are located.

Each groove 1 8 is similar and comprises a base portion 1 9 and opposed side portions 20, 21 which extend axially outwards from the base portion 19. The side portions 20, 21 are relatively convergent to define a mouth portion 22 of reduced cross-section relative to the associated bead 5. The outer edge region of the side portion 20 is curved radially outwards and the outer edge region of the side portion 21 is curved radially inwards to form radii 23, 24 respectively. Each bead base is formed with a slight taper so that the beads 5 are an interference fit in the associated groove 18 when the rim members are assembled.

The tyre tread 3 is wider than the axial distance between the mouth portions of the grooves 18.

Assembly of the tyre and rim is as follows, each element 14 of the outer rim member is inserted in the tyre and the beads 5 are located in the associated end portions 1 3 of each element. With all three elements in position the inner rim member 11 is fitted and secured to the elements 14 by engaging the bolts 1 6 in threaded nuts 1 6 b welded to the elements 14 thus clamping the beads 5 in the associated groove 1 8. A valve (not shown) in the wheel rim allows the tyre to be inflated.

When the tyre is inflated, tension in the steel ply 8 pulls the beads 5 tighter into seaiing engagement with the converging side portions 20, 21 of the associated groove 1 8 which clamp the beads 5 in position thereby preventing the beads being pulled out of the groove through the mouth portion 22.

In use the tyre sidewalls may contact the radii 23, 24 of the side portions 20, 21. It will be appreciated that the radii 23, 24 are shaped so as to avoid chafing in the bead/ lower tyre sidewall regions and additional bead reinforcements which usually extend into and thereby stiffen the lower tyre sidewall regions are unnecessary. As a result the flexi bility of the sidewalls of the tyre of the assembly according to the invention is not reduced by bead reinforcements extending into the sidewalls and the dynamic perfor mance characteristics of the assembly are thereby improved.

Fig. 2 illustrates a modification to the assembly shown in Fig. 1 and like reference numerals are used to indicate similar parts.

The end portions 1 7 of the inner rim mem ber 11 are shaped to form a radially outwardly extending flange 30 which is engaged by the heel 31 of the associated tyre bead and the edge of the flange 30 is profiled to form a radius 32.

The end portions 1 7 of the inner rim member 11 and the adjacent end portions 1 3 of the outer rim member 10 again define annular grooves 1 8 having mouth portions 22 of reduced cross-section relative to the associated bead 5 so that the beads 5 are retained in the grooves.

It will be appreciated that the above-described beads 5 are incompressible so that the beads 5 cannot be forced out of the associated groove 1 8 either mechanically or by the inflation pressure.

In each of the above-described embodiments the mouth portion of each groove is axially outwardly directed so that the lower portion of the tyre sidewalls curve axially inwardly to meet the associated bead at a relatively small angle with respect to a line parallel to the rotational axis of the tyre.

Although the above-described wheel rim is a multi-component wheel rim it is possible to form the wheel rim as a single component, for example by casting. If the wheel rim is formed as a single component it is envisaged that the side portions of each groove will be formed so as to allow the associated bead to be inserted through the mouth portion of the groove and then one or both of the side portions would be pressed or crimped by a suitable tool to form the appropriate groove shape.

Furthermore while it is preferred to have inextensible bead cores comprising cables 6 of annular cross-section the bead cores may be of any type known to those skilled in the art. Alternatively the beads may comprise regions of rubber, preferably hard rubber, which is sufficiently incompressible to prevent the beads being forced out of the associated groove either mechanically or by the inflation pressure.

In each of the above-described embodiments the wheel rim 2 is separate from the conventional wheel disc (not shown) which is secured to the inner rim member by any suitable means. However the inner rim member may be formed integrally with the wheel disc, for example by extending one of the radii 24 of the inner rim member.

Finally while the above described assemblies are tubeless it will be appreciated that an inner tube may be provided.

Claims (24)

1. A pneumatic tyre and wheel rim assem bly comprising a tyre having a tread and a pair of sidewalls, a wheel rim constructed and arranged to define a pair of axially spaced grooves in each if which a respective one of a pair of axially spaced tyre beads is located and retained, each groove having a pair of opposed side portions which are relatively convergent to define a mouth portion of reduced cross-section relative to the associated bead whereby the beads are retained in the associated groove.

2. An assembly according to claim 1 wherein the side portions of each groove extend generally in an axially outwards direction relative to the assembly.

3. An assembly according to claim 1 or claim 2 wherein each tyre bead has a bead reinforcement.

4. An assembly according to claim 3 wherein the bead reinforcement comprises a substantially inextensible bead core.

5. An assembly according to claim 3 or claim 4 wherein the bead reinforcement does not extend into the lower portion of the adjacent tyre sidewall to any appreciable extent.

6. An assembly according to any one of the preceding claims wherein each tyre bead is substantially incompressible.

7. An assembly according to any one of the preceding claims wherein each tyre bead is an interference fit in the associated groove.

8. An assembly according to any one of the preceding claims wherein the axial width of the tyre tread exceeds the axial distance between the mouth portions of the grooves.

9. An assembly according to any one of the preceding claims wherein the tyre is a radial tyre.

10. An assembly according to claim 11 wherein the tyre has an aspect ratio of 70% or less.

11. An assembly according to any one of the preceding claims wherein the lower portion of the tyre sidewalls curve axially inwardly to meet the associated bead at a relatively small angle with respect to a line parallel to the rotational axis of the tyre.

1 2. An assembly according to claim 11 wherein the lower portion of the tyre sidewalls curve axially inwards to meet the associated bead at an angle of 40 or less with respect to a line parallel to the rotational axis of the tyre.

1 3. An assembly according to any one of the preceding claims wherein the wheel rim is multi-component.

14. An assembly according to claim 1 3 wherein the rim comprises an outer rim member and inner rim member which is secured to the outer rim member to retain the components in position.

1 5. An assembly according to claim 14 wherein each tyre bead is located and retained between adjacent axially outer edges of the inner and outer rim members which define said grooves.

16. An assembly according to claim 14 or claim 1 5 wherein the outer rim member comprises three or more components.

1 7. An assembly according to any one of claims 14, 15 or 1 6 wherein the inner rim member comprises a single component.

1 8. An assembly according to any one of the preceding claims further comprising a wheel disc for mounting the assembly on a vehicle.

1 9. An assembly according to claim 1 8 wherein the wheel disc is integral with the rim.

20. An assembly according to claim 1 8 wherein the wheel disc is detachable from the rim.

21. A pneumatic tyre and wheel rim assembly substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

22. A pneumatic tyre and wheel rim assembly substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings as modified by Fig. 2 of the accompanying drawings.

23. The pneumatic tyre of the assembly according to any one of the preceding claims.

24. The wheel rim of the assembly according to any one of claims 1 to 22.