GB2033311A

GB2033311A - Improvements in or relating to pneumatic tires

Info

Publication number: GB2033311A
Application number: GB7927448A
Authority: GB
Original assignee: Pneumatiques Caoutchouc Manufacture et Plastiques Kleber Colombes SA
Current assignee: Pneumatiques Caoutchouc Manufacture et Plastiques Kleber Colombes SA
Priority date: 1978-08-11
Filing date: 1979-08-07
Publication date: 1980-05-21
Also published as: IT7968655A0; GB2033311B; LU81583A1; DE2932213A1; FR2432946B1; IT1119147B; FR2432946A1

Abstract

This invention relates to pneumatic tires for use in conjunction with wheel rims 10 having flanges 13 that are spaced apart transversely by a distance less than the width G of the tire, said tire being of the kind having a radial carcass 14 and a tread belt and comprising beads 17 spaced apart axially which each comprise a wire 19 around which the edges of the, carcass are folded over from the inside towards the outside. According to the invention the tire has a low profile in which the ratio between the height and the width does not exceed 0.8, said beads 17 include, situated axially outside the wires, interposed sections 23 whereof the thickness is such that said wires 19 are spaced apart from the flanges 13 of said rim 10 and mutually spaced apart, axial distance d being between 0.5 and 0.6 G, and the angle of inclination A of said carcass 14 in the low portion of the sides being smaller than 50 DEG . <IMAGE>

Description

SPECIFICATION Improvements in or relating to pneumatic tires The present invention relates to pneumatic tires for use in conjunction with wheel rims having flanges that are spaced apart transversely by a distance less than the width of the wire casing, said tires being of the kind having a radial casing and a tread belt and comprising heels or pads spaced apart transversely which each comprise a wire around which the edges of the casing are folded over from the inside towards the outside.

Hereinafter such tires will be referred to as "of the kind described".

It is known that the properties of a given tire are affected by the width of the rim on which this tire is installed. A wide rim having widely spaced flanges is advantageous regarding the lateral stability of the tire, but it reduces the radial flexibility of the tire because the low portions of the sides close to the rim are close to the vertical position. By contrast, a narrow rim having more closely set flanges accentuates the curvature of the sides and the slope of their low portion, which improves the radial flexibility but reduces the lateral stability. However, a very small number only of rims of different widths is available on the market for each tire size, so that the search for the optimum compromise between lateral stability and radial flexibility should apply substantially to the tire itself.But the design of the tire renders it mandatory nioreover to comply with a variety of structural arrangements, in particular in its heels or pads and low portions of the sides, to secure the durability required. If these conditions are not fulfilled, or if the tire is fitted on a rim differing too greatly in width frdm that for which the tire shaping mould has been set up, it is possible to incur premature failures, in particular in the heels or pads when the tire is exposed to substantial flexing actions.

It is an object of the invention to provide a novel pneumatic tire structure which, on the basis of available rims, offers greater opportunities to produce tires having great radial flexibility, satisfactory lateral stability and a satisfactory service life.

The invention relates quite specificaily to tires and wheels for high-speed vehicles, in which the tires are exposed to flexing actions under a load of substantial magnitude, and in particular to aircraft wheels.

In a pneumatic tire of the kind described, the invention consists in that the casing of the tire has a low profile in which the ratio between the height and the width does not exceed 0.8, the heels or pads include, situated axially outside the wires, interposed sections whereof the thickness is such that the wires are spaced apart from the flanges of the rim and mutually spaced apart by an axial distance smaller than the spacing of said flanges of said rim and comprised between 0.5 and 0.6 of the greatest tire width, and the angle of inclination of the casing in the low portion of the sides is smaller than 50 .

It is certainly known that rubber sections referred to as rim rubbers or chafer strips which are intended to isolate the pad wire against any direct contact with the rim flange may be arranged on the outer side of the tire heels or pads. Eor example, a structure of this kind is illustrated in the specification of United States Patent No.

4,019,551. Such rubber chafer strips are relatively thin however and do not substantially change the shape of the low portions of the tire sides nor the radial flexibility characteristics of the tire. A tire structure of the cross-ply casing type whereof the heels or pads each comprise at least three wires, the wire situated at the axially external side being inactive, that is to say unimpeded by any anchoring of the casing plies around the same, is described moreover in the specification of United States Patent No. 4,029,137. This structure increases the contact surface of the heels or pads (sometimes referred to also as shoulders) on the rim, and reduces the axial distance between the heels or pads.But, because of the fact that the tire specified in that specification is of the cross-ply casing and high-profile type, the incorporation of the inactive third wire in the heels or pads does not substantially modify the shape and radial flexibility of the low portion of the sides.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings showing certain embodiments thereof by way of example and in which: Figs 1 and 2 are eievational views in radial cross-section of two embodiments of tires fitted on their rim, and Fig. 3 is a view in cross-section illustrating a modified form of structure of the heel or pad of a tire.

In the embodiments illustrated, the wheel comprises a rim 10 on the one hand, and a pneumatic tire 11 on the other hand. The rim 10 comprises two assembled components with tapering seats 12 for the heels or pads of the tire, and flanges 13 raised radially in outward directions and acting as lateral supports for the heels or pads of the tire. The flanges 1 3 are axially spaced apart by a distance D smaller than the greatest width G of the tire casing and which, depending on rim type, is comprised between 0.6 and 0.8 G in practice.

The tire 11 is a tire of the radial low-profile type in which the ratio between the cross-sectional height H and the maximum width G does not exceed 0.8 and specifically is smaller than 0.8 and of the order of 0.6 to 0.7. This tire comprises a casing 14, a tread belt 15, a tread band1 6 which externally comprises the patterns appropriate for its use, heels or pads 1 7 and lateral strips 18 covering the sides of the casing. The casing 1 7 comprises one or a small number of superposed layers or "plies" of cord fabrics, without any weft or with a very iight weft, essentially consisting of parallel flexible strands embedded in a thin layer of rubber the number of these layers being a function of the size of the tire and of the strength to be obtained.The strands forming the casing are directed along radial or almost radial planes. The casing may be lined internally with an impermeable rubber layer or liner, in particular in the case of tubeless tires.

The belt 1 5 is formed, for example, by one or more pairs of superposed layers of cord fabric, the strands of each pair of layers of cord fabric, the strands of each pair of layers being positioned along directions subtending small and opposed angles with respect to the equatorial plane, for example of O to 20 . Use may be made of other belt structures amongst the many structures which have already been proposed.

Use may be made, for the belt as well as for the casing, of textile cord fabrics of any appropriate nature, of synthetic, inorganic or metal threads.

Figures 1 and 2 show the cross-sectional shape of the tires when fitted and inflated. The top of the tire is either wholly cylindrical (Fig. 1) or has a slight transverse curvature (Fig. 2). The rolling surface of the band 1 6 has a width L which either does not exceed or but slightly exceeds the width of the belt 1 5 and which is close to the spacing D of the flanges 13 of the rim.

Each heel or pad 17 comprises an inextensible wire 19 topped by a filling section 20 of hard rubber, the whole being at least partially sheathed by a wrapping or "flipper" 21 of biassed fabric of textile or metal cords. The edges of the casing 1 4 are laid around the assembly 19-20-21 from the inside to the outside and the extremity 22 of these edges laid against the outer edge of the wrapping 21 and/or of the section 20. This structure of the heels or pads 1 7 is conventional as a whole and the sections 20 have imparted to them an upwardly narrowing shape so that the heels or pads merge gradually into the thin portion of the sides of the tire casing.

The parts of the heels or pads as such 17, comprising the wires 19 and the folded over extremities 22 of the casing are kept spaced apart axially from the flanges 13 of the rim 10 by sections 23 of substantial thickness such that the axial distance d between the outer parts of the wires 1 9 is distinctly smaller than the spacing D of the flanges of the rim, this distance d being of the order of 0.5 to 0.6 G.

These interposed sections 23 extend radially outwards above the flanges 1 3 of the rim whilst thinning down gradually to merge into the curvature of the low portion of the tire sides.

With these interposed sections 23, the wires of the heels or pads are brought closer to each other axially, which in view of the low profile of the tire, has the result of accentuating the curvature of the low portion of the sides and of increasing the inclination of the portion of the casing 14 situated in the low part of the sides as compared to the shape it would assume in the absence of these sections. This inclination may be grasped by considering the tangent t to the casing 14 drawn from the geomatrical centre of the wires.The angle A of this tangent t with respect to the axis is smaller than 50 and is commonly comprised between 40 and SOC whereas it would otherwise be of the order of 60 . Consequently, the resuit for a particular tire structure is that the reinforced portions of the sides close to the rim are rendered more flexible in the radial direction since they operate under bending stress to an increased degree, which improves the radial flexibility of the tire as a whole. By contrast, the lateral stability is not impaired since the tire enjoys the benefit of a wide seat on its rim.It will also be observed that the part 23.1 of the interposed sections which extends beyond the flanges 1 3 of the rim form a flexible extension of these flanges playing an effective part in providing lateral stability without reducing the radial flexibility proportionately. This action may be controlled by adjusting the height and thickness of the projecting part 23.1 of the sections.

In this respect, Figure 2 shows an embodiment comprising sections 23 narrowing more extensively in upward direction so that the casing 14 is joined to the wires 19 in more tangential manner than in Figure 1.

The interposed sections 23 are preferably moulded in unit with the tire and are consequently integral with the heels or pads 1 7, in particular on the score of ease of production, assembly and sealing. They essentially consist of an incompressible pliable elastomer having a sufficiently high modulus of elasticity. The elastomer-based composition may be reinforced by means of appropriate pulverulent or fibrous reinforcing fillers, dispersed within the composition, the sections thus being substantially homogenous. The interposed sections 23 may also be reinforced by a comparatively incompressible annular core 24, such as a bundle of textile or metal cords (Fig. 3). In this last structure, the hard core 24 is advantageously arranged in close contact with the folded over edges 22 of the casing or with the wrapping 21 (if the latter is external to the casing), in such manner that these elements are gripped between the core 24 and the wire 1 9. This improves the strength of the gripping action and renders it possible to reduce the height of the folded over edges 22 and/or of the outer edges of the wrapping 21, in such manner as to position these lower in areas of lesser flexure. The durability and fatigue strength of the low portions of the sides are thus improved.

Claims

1. A pneumatic tire of the kind described, wherein the casing of the tire has a low profile in which the ratio between the height and the width does not exceed 0.8, the heels or pads include situated axially outside the wires, interposed sections whereof the thickness is such that the wires are spaced apart from the flanges of the rim and mutually spaced apart by an axial distance smaller than the spacing of the flanges of the rim and comprised between 0.5 and 0.6 of the greatest tire width, and the angle of inclination of the casing in the low portion of the sides is smaller than 50 .

2. A tire as claimed in claim 1, wherein the interposed sections of the heels or pads comprise a core, and the folded over edges of the casing are gripped between the core and the wire of the corresponding pad.

3. The combination of a tire as claimed in claim 1 or 2, assembled on a wheel rim having flanges spaced apart transversely by a distance less than the greatest width of the tire casing.

4. A pneumatic tire substantially as hereinbefore described with reference to Fig. 1 or Fig. 2 or Fig. 3 of the accompanying drawings.

5. The combination of a tire assembled on a wheel rim, substantially as hereinbefore described with reference to Fig. 1 or Fig. 2 or Fig. 3 of the accompanying drawings.