GB2030085A - 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 are defined by grooves (14) having opposed side portions (16, 17) which extend in a generally radially outwards direction from the base (15) of the groove. Preferably each tyre bead (5) has a substantially inextensible bead core (6, 7) the diameter of which is less than the maximum diameter of the side portions (16, 17) of the associated groove (14) whereby the beads (5) are retained in the associated groove (14). Preferably the rim (2) comprises three similar elements (13), only one being shown, and sealing means between the abutting ends of the elements. After positioning the elements in the tyre, wheel disc 21 is applied and bolted to those elements. <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 is 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 sidewalls, a wheel rim constructed and arranged to define a pair of axially spaced grooves in each of which a respective one of a pair of axially spaced tyre beads is located and retained, each groove comprising a base portion and a pair of opposed side portions which extend in a direction generally radially outwards from the base portion.

Preferably the grooves are annular. Preferably the grooves are of arcuate cross-section.

Preferably the tyre beads have a bead core.

Preferably the bead core is of annular crosssection and is seated in the associated groove.

Preferably the core is substantially inextensible. The core may be of the steel cable type, other types of steel reinforcement or other substantially inextensible material.

In one preferred construction the axially outer side portion of each groove leads to an axially outwardly directed support ledge. Preferably each ledge is inclined radially outwards in the direction leading from the associated groove and the lower region of the adjacent tyre sidewall seats and is supported on the ledge when the tyre is inflated. Preferably the axially outer edge of each ledge is profiled to form a radius to reduce chafing of the adjacent tyre sidewall when the tyre is deflected.

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 axially outer side portions of the grooves. Preferably 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.

The wheel rim comprises a rim member profiled to define the grooves. The rim member is retained in position by the usual wheel disc.

The rim member may be formed by one or more components. Preferably the rim member is multi-component to facilitate assembly and in one preferred construction comprises three components.

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 diagrammatic drawing in which the single Figure is a crosssectional view of a pneumatic tyre and wheel rim assembly according to the present invention.

The pneumatic tyre and wheel rim assembly shown in the accompanying drawing 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 bead core having a steel wire cable 6 of annular cross-section and a triangular bead apex 7. The bead core is substantially inextensible and does not extend into the lower portion of the adjacent tyre sidewall 4 to any appreciable extent. 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 a rim member 10 having a cylindrical centre portion 11 and axially-spaced end portions defining bead seats 1 2. The rim member 10 is formed by three similar elements 1 3 (one only shown) which may be formed by rolling, casting or other suitable methods. Sealing means (not shown) is provided between the abutting ends of the elements 13.

Each bead seat 12 is similar and comprises an annular groove 14 having a base portion 15 and opposed side portions 16 and 17 respectively which extend radially outwards from the base portion 1 5. The side portion 16 leads to a radially inwardly directed extension 18 which leads to the centre portion 11. The side portion 1 7 leads to an axially outwardly directed support [edge 1 9 which is tapered radially outwards in a direction leading from the side portion 1 7 and terminates in a radius 20. The tread 3 is wider than the axial distance between the axially outer side portions of the grooves 14.A wheel disc 21 comprising a cylindrical element 22 fits within the centre portion 11 of the assembled outer rim member 10 and is secured to each ele ment 1 3 by bolts 23 which are rendered airtight by means of O-rings (not shown). Alternatively a tube may be fitted.

Assembly of the tyre and rim is as follows, the beads 5 are located in the associated portion of the bead seats of each element 13.

With all three elements 1 3 in position the wheel disc 21 is fitted and secured to the elements 13 by engaging the bolts 23 in threaded nuts 23bwelded to the elements 1 3. A valve (not shown) provided in the extension 18 of one of the elements 1 3 allows the tyre to be inflated.

As shown, the diameter of each bead cable 6 is less than the maximum diameter of the side portions 16, 1 7 of the associated groove 14. The bead cables 6 are substantially inextensible and consequently when the tyre is inflated the bead cables 6 and hence the beads 5 are retained in the associated groove 14.

When the tyre is deflected the lower portion of the tyre sidewalls 4 are supported by the associated axially outwardly directed ledge 1 9 so that chafing is substantially reduced or eliminated. It will be appreciated that the lower portion of the tyre sidewalls 4 are held in contact with the associated ledge 1 9 by the inflation pressure in the tyre so that when the tyre deflects the area of contact between the tyre sidewalls 4 and radii 20 remains substantially unchanged and movement is minimal.

Although the above-described wheel rim is a multi-component wheel rim it is possible to form the wheel rim of the invention as a single component, for example by casting. If the wheel rim is formed as a single component it is envisaged that the portions of each groove and the associated ledge may be formed to extend in an axially outwards direction to assist in location of the substantially inextensible reinforced beads and then pressed or crimped by a suitable tool to the appropriate shape.

Furthermore the wheel rim may have a well as in the above-described embodiment or the well may be omitted, it being understood that a well is not required for fitting the tyres according to the present invention.

Finally while it is preferred to have bead seats comprising grooves of arcuate crosssection and bead cores comprising cables of annular cross-section the bead cores may be of any type known to those skilled in the art while the grooves may be of any suitable cross-section.

Claims (18)

1. A pneumatic tyre and wheel rim assembly 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 of which a respective one of a pair of axially spaced tyre beads is located and retained, each groove comprising a base portion and a pair of opposed side portions which extend in a direction generally radially outwards from the base portion.

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

3. An assembly according to claim 2 wherein the bead reinforcement is substantially inextensible.

4. An assembly according to claim 2 or claim 3 wherein the diameter of the bead reinforcement is less than the maximum diameter of the associated groove side portions.

5. An assembly according to any one of claims 2, 3 or 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 groove is of arcuate cross-section.

7. An assembly according to any one of the preceding claims wherein the axially outer side portion of each groove leads to an axially outwardly directed support ledge.

8. An assembly according to claim 7 wherein each ledge is inclined radially outwards in the direction leading from the associated groove.

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

10. An assembly according to any one of the preceding claims wherein the tyre has an aspect ratio of 70% or less.

11. An assembly according to any one of the preceding claims wherein the width of the tyre tread exceeds the axial distance between the axially outer side portions of the grooves.

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

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

1 5. An assembly according to claim 14 in combination with claim 1 3 wherein the wheel disc has a cylindrical portion located within and secured to the rim components to retain the rim components in position.

16. A pneumatic tyre and wheel rim assembly substantially as hereinbefore described with reference to the accompanying drawing.

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

18. The wheel rim of the assembly according to any one of claims 1 to 1 6.