GB2306924A - Tyre tread - Google Patents

Abstract

The tread comprises continuous chevrons 6 that incorporate leading edges 10 and trailing edges 11. This enables water and air to be directed into grooves 12 and to the outer edges of the tyre, to be discharged, enabling the tyre tread to give maximum contact with the road surface in either wet or dry conditions, thus increasing safety and economy. The leading edges 10 are sharper than the trailing edges 11 and gutters 18 are formed below the leading edges to improve the collection of water displaced by the leading edges.

Description

VEHICLE TYRES This invention relates to vehicle tyres.

Motor vehicle tyres have a long history and are nowadays available in a very wide variety of shapes and sizes.

Characteristic of most tyres is a relief surface designed to enhance grip between the tyre and the surface on which the vehicle equipped with the tyre is resting or travelling. Such a relieved surface is called a "tread".

For ease of expression, it is convenient to define certain terms used in this specification in connection with such tyre treads. Looked at geometrically, the surface of a tyre tread, when the tyre is inflated (whether tubeless or tubed), consists of a plurality of spaced discrete first areas all lying in a notional surface of slightly bulged cylindrical shape, a plurality of second areas all lying in a notional surface of a concentric similar slightly bulged cylindrical shape, but where the cylinder is of slightly smaller radius, and a plurality of walls connecting the edges of each of the first areas with edges of each of the second areas. These walls are denoted herein "flanks". The second areas may be spaced from one another or may constitute a network, and are called "grooves" herein, while the first areas are called "lands".

It can be seen without difficulty that the outer running surface of a standard motor car tyre is made up of a pattern of lands, each with flanks, the flanks merging at their edges away from the lands with the grooves.

Much effort has been directed over the decades into the development of tread structures and tread patterns which enhance grip on the one hand while incurring as few adverse effects as possible on the other. Among the adverse effects are reduced fuel economy for the vehicle concerned, given otherwise identical running conditions, as between some tread patterns and others. Another adverse effect is the variation in behaviour under different conditions of running. In particular, it is desirable that the behaviour does not vary too much as between running in dry conditions and running in the wet.

Much attention has been given to the design of tread patterns which are believed to perform better in wet conditions by reducing the amount of water between the part of the tyre contacting the road or other surface, i.e. the lands, and the surface itself, thus reducing the risk that a film of water can build up between the tyre and the surface leading to markedly reduced grip and the potential phenomenon of "aquaplaning" with its attendant dangers.

The tread on a tyre is conventionally formed by moulding.

Tyre components such as steel or textile wires or cords and fabrics are assembled into position in a mould into which a rubber or rubbery material is introduced under heat and pressure, with the exterior tread-forming surface of the mould being appropriately configured with a reverse of the tread pattern desired. In order to facilitate stripping of the completed tyre from the mould following the introduction of the rubber or rubbery material and its setting or vulcanising, each of the lands is customarily surrounded by flanks which slope slightly outwardly from each of the edges of the lands, or, in some cases, which lie in planes essentially perpendicular to the lands.Of course, looked at overall, the lands are not flat, but rather slightly curved, but the relationship between the lands and the flanks is essentially as just described particularly in order to enable the mould to be easily removed from the formed tyre.

I have now found that tyres with improved performance may be made if the flanks of each land are not all perpendicular to the plane of that land or sloping slightly outwards therefrom, but are in part undercut, thus producing areas of the tyre tread where one edge at least of some or all of the lands have an included angle, in a plane perpendicular to the line of the edge, of less than 900.

When tyres in accordance with my invention are used, the undercut edge or edges of the individual lands are arranged to be leading rather than trailing as the tyre is rotated. The undercut leading edge acts to pass through any water on the surface over which the tyre is rolling more efficiently than a square cut or obtuse angled edge would do, and the corresponding channel including an acute angle between flank and groove acts as a gutter for the collection of water. The gutter should preferably run at an angle relative to the direction of rotation of the tyre across the surface on which it rolls and accordingly act to divert water to both sides of the tyre.

Most preferably (and most efficiently), the tread pattern is one where the lands consist of a series of chevrons with their points in a circle around the tyre periphery midway between its sides and pointing in the direction of rotation of the tyre. The angle between the two bars of each chevron may vary, an included angle between 500 and 600 being preferred for everyday road use, but by sharpening the angle of the chevrons the tyre would be ideally suited to high performance cars and racing cars.

The basic construction of the tyre may vary widely, but will normally consist of basic structural and reinforcing components overlaid by a rubber, rubber compound or rubbery polymer. The method of manufacture of the tyre may follow the conventional approach with such modifications as are needed to facilitate stripping the moulded tyre from the mould.

A generally preferred tyre tread of a tyre manufactured in accordance with the present invention is illustrated by way of example in the accompanying drawings in which: Figure 1 shows diagrammatically a section of a tyre tread of a tyre according to my invention viewed as though the tread had been laid out flat; Figure 2 is a diagrammatic section through the tyre tread along the lines A-A shown in Figure 1; and Figure 3 is a diagrammatic section along the lines B-B shown in Figure 1.

Referring to the drawings, the tyre consists basically of a pair of side walls 1, 2 joined by a cylindrical tread portion 3. The radially inner edges of the tyre walls 1, 2 are formed into a thickened bead at 4 which fits against, e.g. a metal wheel.

The tread consists of a series of chevron formations 6, each of which constitutes a land and has its apex midway between the side walls 1, 2 and which, when the tyre is on a vehicle, is directed in the direction of rotation shown by arrow 8. Thus, each chevron has a leading edge 10 and a trailing edge 11. Between the trailing edge of one land and the leading edge of the next is a groove 12 connected to the land via leading and trailing flanks 15 and 16 respectively.

As can most clearly be seen in Figure 2, the leading edge 10 of each chevron is sharper than the trailing edge 11, i.e. the included angle in a plane perpendicular to the edge is less than 900. Where the leading flank 15 of each chevron merges into the groove 12, a gutter 18 is formed below each leading edge which acts to collect water displaced by the leading edge and channel it outwardly towards the intersection of the tread 3 with the tyre wall 1 or 2.

Using this type of tread configuration, tyres may be produced which give good grip, satisfactory handling and enhanced fuel economy on the vehicles on which they are used.

Claims (3)

1. The continuous chevron design transfers air and water away from the centre of the tyre, to the outer edges in the shortest time.

2. The design ofthe leading edge, collects and clears, water and air away from the surface ofthe continuous chevron design tyre tread.

3. The trailing edge transfers and directs the water and air into the gutters to be removed as in Claim 1 and 2.