GB2252943A

GB2252943A - Pneumatic tyre and wheel assembly.

Info

Publication number: GB2252943A
Application number: GB9203571A
Authority: GB
Inventors: Eric Holroyd; Colin Holroyd
Original assignee: Holroyd Associates Ltd
Current assignee: Holroyd Associates Ltd
Priority date: 1991-02-20
Filing date: 1992-02-20
Publication date: 1992-08-26
Also published as: GB9203571D0; WO1992014619A1; AU1206392A; GB9103567D0

Abstract

A pneumatic tyre and wheel assembly (10) particularly suitable for heavy duty use to replace a side-by-side pair of coaxial tyres comprises a flexible reinforced partition wall (17) which extends between the tyre tread region (15) and a third bead region (16) disposed between the bead regions (13) of the sidewalls (14). The third bead region (16) is dimensioned to seal against a wheel rim (11) such that the resulting tyre and wheel assembly (10) may comprise two independently pressurisable chambers (25, 26). Forces tending to deform the tyre either radially or transversely will place an upper part of the partition wall (17) in tension, tending to maintain the shape of the tyre. By this arrangement the need for heavy, stiff sidewalls (14) is avoided.

Description

"PNEUMATC TYRE AND WHEEL ASSEMBLY" This invention relates to a pneumatic tyre and wheel assembly and in particular, although not exclusively, to a heavy duty tyre such as may be used on a commercial vehicle or an aircraft.

Many heavy duty camrrercial vehicles and aircraft are provided with more than two tyre and wheel assemblies per axle, and commonly two such tyre and wheel assemblies are mounted axially and side by side but with a space between the tyres when in an unloaded condition so that when subject to load the tyres do not come into contact and abrade one another. The so called "twin-tyred back axle" is an example of this configuration.

The use of a pair of tyres arranged spaced but close together in a side by side configuration allows a large vehicle weight to be carried without the need to provide additional axles, but there are a number of disadvantages. For example, the total weight of the tyre and wheel assemblies as well as the overall space envelope is significant.

In an attempt to reduce the total weight of the tyre and wheel assemblies it has been proposed to replace a pair of tyres by a single tyre having a much wider, e.g. a double width, tread. A tyre of this type having a tread width and bead spacing substantially double that of a conventional tyre has often been known as a "Duplex" tyre. The wide construction achieves a saving of weight and also of space but there is a reduction in the margin of safety in the event of a puncture. Also the transverse stiffness of the tyre is often less than is preferred for many applications.

In known tyres, whether of the conventional or of the Duplex type, all lateral (i.e. transverse) and radial forces are resisted by the sidewalls and the deformability of the tyre is therefore wholly dependent on the structure of the sidewalls. A principal object of the present invention is to provide a tyre of improved strength and resistance to deformation without necessarily requiring that the sidewalls are of a relatively heavy and stiff construction and to permit the production of lighter yet stronger tyres, in which resistance to deformation is not limited by the present practical constraints on sidewall construction.

The present invention also seeks to provide an improved pneumatic tyre which facilitates or achieves a reduction in the weight and or overall space envelope of a conventional arrangement of a side-by-side pair of tyre and wheel assemblies without introducing a reduction in the margin of safety such as arises in use of the so-called Duplex tyre. The invention seeks to provide an improved tyre construction suitable for heavy duty applications and in which the safety limitation and low stiffness problem of a Duplex type tyre are mitigated or overcome as well as overccaning the problem of wrongly mixing tread structures when individual tyres are mounted on the same axle.

In accordance with the present invention there is provided a pneumatic tyre and wheel assembly, the tyre being of the kind constructed by applying to a former in sequence ply reinforcement and bead structures and then shaping to a toroidal configuration whereby a crown portion of the tyre engages an annular breaker-reinforced tread structure surrounding the former, wherein the tyre comprises axially spaced-apart reinforced bead formations seated on respective first and second bead seat regions of the wheel, ply-reinforced sidewalls of the tyre extending radially respectively fran the first and second bead seat regions, a crown portion of the tyre comprising two circumferentinlly extending but axially separate tread formations spanning the radially outer peripheries of the sidewalls, two breaker assemblies each associated with a respective one of the two tread formations, and a flexible, substantially inextensible membrane located between the sidewalls, the membrane being fixed at a radially outer periphery thereof to the crown portion between said tread formations and having at its radially inner periphery a reinforced bead formation seated on a third bead seat region of the wheel intermediate and spaced fran said first and second bead seat regions, the arrangement being such that deformation of the tyre when in use will place in tension an upper part of the membrane between the wheel and crown portion.

The membrane is preferably substantially air-impermeable.

The membrane preferably comprises tension resisting reinforcement, which may comprise flexible reinforced polymeric material.

The membrane may be of a construction substantially similar to that of one of said reinforced sidewall structures.

Preferably the membrane extends rectilinearly between the third bead region and the crown portion as considered in cross-section in a plane containing the rotational axis of the tyre.

The third bead region may have a diameter corresponding to that of at least one of the sidewall bead regions or it may have a diameter greater than the diameter ( s) of the sidewall bead regions.

The nembrane may have double the reinforcement of a sidewall structure.

Preferably said wheel provides a pair of axially spaced bead seat regions which cooperate with the tyre sidewall bead regions to locate the tyre on the wheel and form an air tight seal therebetween, and intermediate said bead seat regions a third, intermediate bead seat region to locate with the third bead region of the tyre and form an air-tight seal therewith.

The third bead region of the tyre is preferably restrained against axial movement relative to the wheel.

The wheel may comprise two rim portions and the third bead region may be located between said rim portions.

The third bead region may ccanprise a reinforcement such as the bead wire-type reinforcement conventionally incorporated in the sidewall bead regions of a tyre. Alternatively it may be devoid of any such reinforcement; it may for example be of a shape adapted to be secured to a wheel by clamping action between two parts of a split-type wheel.

The tyre may be constructed by applying liner material and one or more layers of reinforced polymeric material (so-called under-bead components) about a cylindrical former, applying three beads around said layers at axially spaced positions and then applying pressure to deform the reinforced polymeric material radially outwards between the beads as the beads move relatively axially towards one another. In contrast to the conventional manufacturing procedure, by virtue of the third bead this will result in the formation of two tread regions instead of just one such region.

During the aforedescribed inflation-procedure the reinforced polymeric material either side of the intermediate, third bead region may be arranged to come into contact and become united thereby to result in a membrane structure which has double the reinforcement and double the thickness of the sidewalls. Alternatively the reinforced polymeric material may be laid on the former such that axial end regions have a double layer of reinforcement, e.g. by folding back axial ends of the reinforcement. When this cylindrical structure is subject to inflation the resulting sidewalls and partition structure will have substantially identical amounts of reinforcement and thickness.

The shaping operation described in the preceding paragraph may then be followed by the conventional application of additional sidewall material.

The shaping operation may be Performed within a mould which contains a pair of pre-formed tread packages thereby to result in a tyre having two tread bands. Alternatively it may be performed in a mould having only a single tread package which in the assembled tyre will span the two crown regions; filler material may be provided as necessary between the two crown regions to ensure full width support for the single tread package.

The present invention further provides that the tyre may comprise in the crown portion two circumferentially extending axially spaced tread formations which are not identical. They may differ, for example, in type of breaker reinforcement, angle of lay of breaker reinforcement, tread pattern and orientation and material composition. The two tread regions may be spaced axially at a position axially aligned with the position at which the partition member interconnects with the tread region. The invention envisages that two breaker assemblies shall be provided and each associated with a respective one of the two tread formations.

The wheel may be a split wheel comprising two rim portions and the third bead region may be sandwiched between said bead regions.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: - Figure 1 is a transverse cross-section of a pneumatic tyre and wheel assembly of the present invention, in a plane containing the rotational axis of the tyre; Figure 2 is a sectional view in the plane of Figure 1 showing the tyre at an initial stage of construction; Figure 3 corresponds to Figure 2 but shows the tyre at a subsequent stage of construction; and Figure 4 shows another subsequent stage of construction.

A tyre and wheel assembly 10 (see Figure 1) comprises a split rim type wheel 11 and a triple beaded tyre 12. The tyre 12 comprises a pair of sidewall beads 13 and a pair of reinforced sidewalls 14 of a conventional construction and which extend radially outwardly towards a crown region 15 of the tyre.

The tyre 12 also comprises a third, intermediate bead 16 of a construction and size corresponding substantially to that of the sidewall beads with the exception that it is of a slightly smaller diameter for a reason that will be explained below. The bead 16 lies axially mid-way between the sidewall beads 13.

A mEmbrane or partition wall 17 of a flexible and reinforced construction corresponding substantially to that of the sidewalls 14 extends radially outwardly fran the third bead to an axially central zone 18 of the crown 15 of the tyre. The wall 17 extends in a rectilinear manner in a direction substantially perpendicular to the rotational axis of the tyre and thus is substantially of a flat disc-like form. The reinforcement of the membrane is of a tension resisting kind thereby to resist movement of the crown radially away from the associated third bead 16, and the reinforcement of the membrane is integral with reinforcement in the crown region 15.

The crown 15 comprises two axially spaced tread formations 19 and two breaker assenbifes 20, each breaker assembly being associated with a respective one of the tread formations. The two breaker assemblies lie axially to either side of the crown region central zone 18 to which the rrbrane extends and are substantially independent of one another whereby one breaker assembly and tread formation can deflect without a directly related significant deflection of the other breaker assembly and tread formation.

The split rim wheel 11 comprises two parts 21, 22 of substantially similar form, each having an annular shoulder formation 23 at its axial end which is bolted to the other wheel part. The formations 23 are shaped and dnmensioned such that when the two wheel parts are joined together their radially outer surfaces define a groove 24 in which the third bead 16 locates and is restrained thereby fran axial movement relative to the wheel.

In use of the aforedescribed tyre 12 on the wheel 11, the membrane 17, which is air-impermeable, results in the provision of two independently pressurisable air chambers 25, 26. It serves also to stabilise and control the tread region. It restrains movement of the central zone 18 of the crown radially outwards from the wheel and it increases the transverse stiffness of the tyre as compared with that of a tyre without the mambrane. It should here be noted that in the preferred embodiment illustrated the membrane 17 is substantially shorter, in the radial direction, than the sidewalls 14. It therefore has a relatively smaller arc A of possible deflection than that B of a sidewall 14, and this greatly enhances the lateral stability of the tyre in that transverse deflection forces will place the inextensible membrane 17 in tension, thus resisting forces tending to deform the tyre 12 laterally.

The aforedescribed tyre may be constructed on a cylindrical mandrel 30 (see Figure 2), with the liner and under-bead reinforcement layers 31 being formed on the mandrel, followed by formation of the bead assemblies (13, 16) which in this case number three. On top of the liner and under-bead reinforcement layers 31 an additional layer 50 of steel reinforced ply is laid so that it will be centrally below the centre bead 16. As shown in Figure 2 the mandrel comprises two collapsible, cylindrical halves 30A, 30B between which is located a collapsible, annular centre-bead support 35.

At opposite axial ends of the mandrel are the wheel rim halves 21, 22 and in the expanded condition of the mandrel parts 30A, 30B they are generally coextensive with the wheel rjin halves so as to present a substantially uninterrupted cylindrical surface about which the layers 31 of liner and ply can be wrapped. When subsequently the bead assemblies 13, 16 are applied over the layers 31, preferably by a winding technique known per se, they will lock the layers 31 into the bead seat grooves 36 of the rim halves and the bead seat groove 37 of the support 35. In a manner also known per se bead apex components 38 are applied over the bead reinforcements 13 and a somewhat similar but larger apex component 39 is applied over the centre bead reinforcement 16.All of the bead reinforcements 13 and 16 may be made in a manner known per se by winding wire. The apex components 38 and 39 may all be of rubber.

Following formation in this way of the so-called green cover the ply is turned up around each of the outer bead reinforcements 13 and associated apex assemblies 38 in a manner known per se and the green cover is expanded radially outwards as shown in Figure 3 to create two tread regions 33. To permit this expansion the collapsible mandrel parts 30A, 30B are collapsed and withdrawn and the two wheel parts 21, 22 are moved toward oneanother. In this way the additional reinforcement 50 is turned up (see Figure 3) on opposite sides of the apex 39 of the centre bead until it effectively encloses the body 39. The breaker assemblies 20 and associated tread packages 19 are located in respective mould top components 41 and 42 which also contain the additional steel ply reinforcement 51 extending between and terminating at the tread packages.The mould top components are located so that the tread regions 33 expand into contact with them and the additional ply 51 is applied to the green cover to extend fran one tread region 33 to the other. If desired a support 40 of a suitable wedge-shaped cross section may be interposed in the cleft of the green cover between the two breaker-and-tread-package assemblies and over the additional ply 51 to withstand subsequently applied pressure. Suitably the support 40 is of solid (cured) rubber.

The centre bead support 35 is now also collapsed and withdrawn and the wheel halves 21 and 22 moved fully into contact as shown in Figure 4, so that the centre bead 16 is now supported in the annular groove defined by the two shoulders 23 of the wheel halves. The mould is then completed by the addition of side components 43 and 44 and the tyre is subjected to curing heat and pressure.When subsequently the mould components 41-44 and the support 40 are removed the tyre 12 of Figure 1, already mounted on a wheel 21, 22, is complete, and it will be noted that in the completed tyre the membrane 17 comprises two ply layers 45 and 46 on opposite sides of the central reinforcement structure 16, 39, in contrast to the single ply layers of the sidewalls.

The two tyre tread formations 19 of the finished tyre are interconnected in the crown region of the tyre substantially only by the sidewall-type material of the membrane 17 in the central zone 18 and the additional ply 51. In consequence each tread formation is able to deflect at least an initial amount without associated deflection of the other tread formation.

The two tread formations may be of different types, and may be selected in cambinstion to provide desired properties such as of wet and dry road grip.

The triple beaded tyre of the invention achieves a weight and a space saving as compared with for example, a twin-tyred back axle configuration.

Two tread formations and breaker assemblies are supported by three rather than four wall members, and there is no need axially to space two tyres.

Furthermore, the resulting provision of two independently pressurisable air chasers provides an inherent safety feature and avoids the safety problem associated with the Duplex type tyre.

In the case of a triple beaded tyre having two tread formations of different types, there is the further advantage of use of two different tyres on a single axle in that there is no risk of an incorrect tread combination arising when a tyre is changed.

In use of the tyre of the present invention forces tending to deflect the tyre axially or to carpress it radially will be resisted by resulting tension of the membrane 17. Because of the provision of this membrane the sidewalls may be of a lighter, more deformable construction than hitherto in a tyre of given strength characteristics, permitting the overall weight of the tyre to be reduced.

In addition to achieving greater lateral stability even with more deformable sidewalls the tyre of the invention will have less tendency to burst under the impact forces generated e.g. when an aircraft lands.

Instead of being resisted solely by deformation of the sidewalls radial compressive forces will be translated into tension of the upper part of the membrane 17 tending to pull down the upper part of the crown and thereby maintain the integrity of the tyre structure.

Claims

CLAIMS:

1. A pneumatic tyre and wheel assembly, the tyre being of the kind constructed by applying to a former in sequence ply reinforcement and bead structures and then shaping to a toroidal configuration whereby a crown portion of the tyre engages an annular breaker-reinforced tread structure surrounding the former, wherein the tyre comprises axially spaced-apart reinforced bead formations seated on respective first and second bead seat regions of the wheel, ply-reinforced sidewalls of the tyre extending radially respectively fran the first and second bead seat regions, a crown portion of the tyre comprising two cirmirferentially extending but axially separate tread formations spanning the radially outer peripheries of the sidewalls, two breaker assemblies each associated with a respective one of the two tread formations, and a flexible, substantially inextensible membrane located between the sidewalls, the membrane being fixed at a radially outer periphery thereof to the crown portion between said tread formations and having at its radially inner periphery a reinforced bead formation seated on a third bead seat region of the wheel intermediate and spaced from said first and second bead seat regions, the arrangement being such that deformation of the tyre when in use will place in tension an upper part of the membrane between the wheel and crown portion.

2. An assembly according to claim 1 wherein the membrane is substantially air-impermeable.

3. An assembly according to clam 1 or claim 2 wherein said membrane comprises tension resisting reinforcement.

4. An assembly according to claim 3 wherein said membrane comprises flexible reinforced polymeric material.

5. An assembly according to any one of the preceding claims wherein the two tread formations differ from one another.

6. An assembly according to any one of the preceding claims wherein the membrane is of a construction substantially similar to that of one of said reinforced sidewall structures.

7. An assembly according to any one of the preceding claims wherein the roemrbrane extends rectilinearly between the third bead region and the crown portion as considered in cross-section in a plane containing the rotational axis of the tyre.

8. An assembly according to any one of the preceding claims wherein the third bead region has a diameter corresponding to that of at least one of the sidewall bead regions.

9. An assembly according to any one of claims 1-7 wherein the third bead region has a diameter greater than the diameter(s) of the sidewall bead regions.

10. An assembly according to any one of the preceding claims wherein the membrane has double the reinforcement of a sidewall structure.

11. An assembly as claimed in any one of the preceding claims, wherein said wheel provides a pair of axially spaced bead seat regions which cooperate with the tyre sidewall bead regions to locate the tyre on the wheel and form an air tight seal therebetween, and intermediate said bead seat regions a third, intermediate bead seat region to locate with the third bead region of the tyre and form an air-tight seal therewith.

12. A tyre and wheel assembly according to claim 11 wherein the third bead region of the tyre is restrained against axial movement relative to the wheel.

13. A tyre and wheel assembly according to claim 11 or claim 12 wherein the wheel comprises two rim portions and the third bead region is located between said rim portions.

14. A pneumatic tyre and wheel assembly substantially as hereinbefore described with reference to and as shown in Figures 1-3, 4 and 5 or Figure 6 of the accompanying drawings.

15. A pneumatic tyre for use in the assembly claimed in any preceding claim.