GB2139574A

GB2139574A - Radial pneumatic tyre belt cap ply

Info

Publication number: GB2139574A
Application number: GB08405867A
Authority: GB
Inventors: Dionysius Joseph Poque
Original assignee: Uniroyal GmbH
Current assignee: Uniroyal GmbH
Priority date: 1983-03-14
Filing date: 1984-03-06
Publication date: 1984-11-14
Also published as: IT1173834B; IT8420039A0; FR2542672B1; GB2139574B; JPS601005A; FR2542672A1; DE3308965C2; IT8421209V0; GB8405867D0; DE3308965A1

Abstract

The belt comprises plies (5) of textile, glass or steel fabric and is provided with an additional cover or cap ply (6) of circumferentially extending parallel, single thermally contractile filaments e.g. of polyamide or polyester. The filaments have a small twist of 40 to 100 turns per metre. The packing density of these single filaments preferably amounts to 20 to 70% in the fabric layer. This can be applied either as a full ply or separated into strips. This construction improves the rolling resistance and control of site increase with speed in high speed car tyres. <IMAGE>

Description

SPECIFICATION Motor vehicle pneumatic tyre The present invention relates to a motor vehicle pneumatic tyre; more particularly to a motor vehicle pneumatic tyre having a cover or cap ply for the tyre belt.

A motor vehicle pneumatic tyre having a belt with an additional cover or can ply in which the reinforcing elements thereof consists of a single yarn of a contractable material is- known. This cover of cap ply surrounds the belt ply with at least one full turn and thus fulfils a bandaging function which is advantageous to the motor vehicle pneumatic tyre as a whole. Resistance to parting of the plies, particularly at the edges of the belts, is improved. Protection is ensured against the in gress of moisture into the belt plies and the effects of corrosion on steel fabric plies is thus avoided. The cover or cap ply is relatively light in weight and inexpensive.

It is also known that motor vehicle pneumatic tyres deform, the diameter ofthe motor vehicle pneumatic tyre increasing, with increasing speed of rotation as a result of the centrifugal forces applied, particularly in the region of the tread and the belt. These effects are largely taken account of in construction and in the selection of materials.

With reference to high speed tyres for private motor vehicles, for which stricter construction, finishing, testing and approval requirements apply, the safety bandage takes the form of a cover or cap ply of filamentary elements which contract through the effect of heat, the modulus of elasticity of these elements being further improved when they are extended by some 4%.

It is an object of the invention to improve the rolling resistance of high speed tyres in order to save on energy costs and improve the cover or cap ply with reference to the tension force of the rubberised filamentary reinforcing elements for reliable control of the increase in size of the tyre at high speeds using a cover or cap ply as an aid to ensuring safety.

In accordance with the present invention there is provided a motor vehicle pneumatic tyre comprising a radial ply carcase, a thread and a belt for reinforcing the tread, the belt being formed of at least two plies of cords, the belt cords in each ply extending obliquely to the circumferential direction of the tyre at a sharp angle and being in crossing relation with respect to the cord of the next adjacent belt ply, at least one ply of cords being provided over a width corresponding approximately to the width of the tread, and at least one additional cover or cap ply interposed between the radially outward most one of said belt plies and said tread, said cover or cap ply comprising rubberised non-metallic reinforcing elements which extend substantially parallel to one another in the circumferential direction of the tyre and which shrink under the effect of heat, and said cover or cap ply surrounding the belt ply in at least one full turn with overlapping ends and having a width equal to at least that of the widest belt ply, in which the reinforcing elements of the additional cover or cap ply consist of single yarns only having a small twist of from 40 to 100 turns per metre.

Single yarns with such a low twist have a high load capacity per filament of 1 5 N and more when extended by 4%. The diameter of the filament is small. The fabric is light and is particularly suitable for the safety cover ply of high speed tyres.

The modulus of elasticity of the filaments when extended by 4% is an important parameter for the tension of the filament, which should be high, but nevertheless a light fabric is essential. The largest increase in the diameter of the tyre of some 4% is reliably taken up by the fabric of single filaments having a small twist without damage to the belt or the running surface.

The high stresses in the dynamic increase in size of the tyre are safely taken up by the carcase and suitable belt reinforcement. They are advantageously supported by a cover or cap ply of single filaments having a small twist per metre. The rolling resistance is also improved in this way. The cover ply with high loading reinforcing elements ensures satisfactory and simple stabilisation of the belt, this function being ensured in the range of high tyre speeds.

Suitable single yarns may be manufactured from polyamides or polyesters.

Examples are e.g. nylon dtex 700/1, 1440/1, or 1880/1; polyester dtex 720/1 or 1100/1,1440/1 or 2200/1.

The packing density of these single filaments generally lies in the range of from 20 to 70%, 40 to 50% being preferred.

The cover ply can be used in one full turn or two full turns. In some situations it is desirable to divide it into axial strips. Preferred examples of embodiments of the cover ply are illustrated in the accompanying drawings in which: Figure 1 illustrates a single cover ply in a section of the tyre; Figure 2 illustrates a double cover layer; Figures 3 and 4 illustrate a combined cover ply of one portion of full breadth and one portion of covering strip; Figure 5 illustrates a cover ply formed of strips.

A motor vehicle pneumatic tyre 1 is comprised essentially of the radial ply carcase 2, the tread strip 3 and the side walls 4.

The tread strip is reinforced with a belt 5 of plies of textile, glass or steel fabric. This is surrounded by a cover ply 6 extending in the circumferential direction of the tyre.

The reinforcing element 7 of this cover ply 6 comprises a single yarn with a small twist of the filaments per metre. The twist lies in the range of from 40 to 100 turns per metre. As a result of this structure of the single yarn the tensional force when extended by 4% is, in the case of polyamide or polyester, 15 to 22 N and more.

The single yarn of the abovementioned filamentary structure has a small diameter and is suitable for the construction of a thin and light fabric, the lie of the filaments largely amounting to 0g. The single yarn with 40 to 100 turns per metre achieves a high 4% modulus. This high loading capacity of the individual filaments is particularly suitable for use of the fabric as an additional protection for the belt strip of high speed tyres.

The speed range of passenger motor vehicle tyres is up to 190 km/h for the mark TR, up to 210 km/h for the mark HR and over 210 km/h for the mark VR.

Cover plies of single yarns, as illustrated in Figs. 1-5, may be used for these motor vehicle pneumatic tyres.

Cover ply 6 has a full turn and an overlap of some 1 5 mm at the ends. Its width covers the belt edges 5a, 5b.

Cover ply 16 has a double turn with a slightly larger overlap (Fig. 2).

The packing density in % is equivalent to: filament diameter multiplied by the number of filaments per unit length. It amounts to 20 to 70%.

Cover ply 17 is formed of a complete portion 19 of full width and length over one turn and a portion consisting of strips 18.

These may lie radially inside or outside (see Figs. 3 and 4).

Cover strips 20 are an example of the arrangement at the edges of the belt and centrally in the centre of the belt strip (Fig. 5).

All the embodiments can be used in combination.

Claims

1. A motor vehicle pneumatic tyre comprising a radial ply carcase, a tread and a belt for reinforcing the tread, the belt being formed of at least two plies of cords, the belt cords in each ply extending obliquely to the circumferential direction of the tyre at a sharp angle and being in crossing relation with respect to the cord of the next adjacent belt ply, at least one ply of cords being provided over a width corresponding approximately to the width of the tread, and at least one additional cover or cap ply interposed between the radially outward most one of said belt plies and said tread, said cover or cap ply comprising rubberised non-metallic reinforcing elements which extend substantially parallet to one another in the circumferential direction of the tyre and which shrink under the effect of heat, and said cover or cap ply surrounding the belt ply in at least one full turn with overlapping ends and having a width equal to at least that of the widest belt ply, in which the reinforcing elements of the additional cover or cap ply consist of single yarns only having a small twist of from 40 to 100 turns per metre.

2. A motor vehicle pneumatic tyre as claimed in claim 1, in which the packing density of the reinforcing elements amounts to 20 to 70% per dm.

3. A motor vehicle pneumatic tyre as claimed in claim 2, in which the packing density amounts to 40 to 50% per dm.

4. A motor vehicle pneumatic tyre as claimed in claim 1, 2 or 3, in which the cover ply has an axial width which covers the edges of the belt plies and in which this cover ply extends in the circumferential direction of the tyre with a full turn and an overlap at the ends of the ply of from 15 to 50 mm.

5. A motor vehicle tyre as claimed in any one of claims 1 to 4, in which the cover ply is present in two full turns.

6. A motor vehicle pneumatic tyre as claimed in any one of claims 1 to 5, in which at least part of the encircling length of the cover plies is divided into axial strips.

7. A motor vehicle pneumatic tyre as claimed in any one of claims 1 to 6, in which the cover ply consists of axially divided strips which are arranged with spaces between their edges.

8. A motor vehicle pneumatic tyre, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.