GB2139575A

GB2139575A - Radial pneumatic tyre belt cap ply

Info

Publication number: GB2139575A
Application number: GB08405868A
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: IT1173835B; GB2139575B; FR2542673A1; GB8405868D0; DE3308966C2; IT8420040A0; FR2542673B1; DE3308966A1; IT8421210V0

Abstract

The cap or cover ply (500) is a thermally contractile fabric made of light cord or single yarn e.g. polyamide or polyester having a total thickness of not more than dtex 1440 and in which the twist of the filaments is at least 350 turns per metre; preferably 350 to 550 turns/metre. The modulus for an extension of 4% lies in the range of 6-12 N. Belt bandages of such fabrics ensure only small tension during tyre finishing. <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.

In a motor vehicle pneumatic tyres bandaging of the belt of the tread reinforcement with an additional cover ply of textile fabric, the reinforcing elements of which shrink under the effect of heat and thus have a stabilising and protective function, is known. Cords or single yarns of polyamide or polyester are preferred for this application. The modulus of these reinforcing elements is relatively high so that high tensions are set up in the reinforcing elements as a result of heat and pressure inthe finishing of the tyre. As these tensions are not applied uniformly and cannot be maintained uniform over the tread or belt it is not unlikely that distortions, which must be avoided, will be produced in the tread.

It is an object of the invention to prevent undesirable stressing conditions in the belt as these affect the uniformity of the tyre, and the reinforcing elements in the cover ply must therefore be formed in such a way that such deformations are avoided when the cover ply is used.

In accordance with the present invention there is provided a motor vehicle pneumatic tyre comprising a radial ply carcase, a tread and a belt for reinforcing the tread comprising at least two crossing plies of steel fabric and at least one additional cover or cap ply of nonmetallic reinforcing elements which shrink under the effect of heat and which extend parallel to one another in the circumferential direction of the tyre, in which the cover or cap ply, which has substantially the same width as the tread or is divided into strips, surrounds the belt ply with at least one full turn and includes overlaps at the ends of the ply, in which the cover or cap ply consists of light cords or single yarns, the total filament thickness of which is not greater than 1440 dtex and the twist of the yarns is at least 350 turns per metre.

It is preferred that the modulus of the light cord or single yarn should lie within the low tension range, preferably between 6 and 1 2 N when the extension is 4%.

When a tyre is finished using pressure and heat, in particular in vulcanisation and prevulcanisation, there is a swelling of some 2-4%.

The necessary relaxation of the belt bandaged by the cover ply is of the same order of magnitude. In the case of bandaging fabric which has thermal contractile properties it is thus the modulus for a 4% extension in length which is of interest.

A relatively small tension per filament is achieved through the use of fabrics with the abovementioned overall density characteristics and a high twist in the filaments. The modulus of the reinforcing elements is consequently low. This ensures that the tension range over the width of the belt, athough it is not uniform, gives rise to no major tendency to distortion of the tread or belt region.

The small force which does not exceed 1 2 N for an extension of 4% results in a relatively small tensioning effect. This has no major disadvantageous effect on the belt so that the uniformity of the tyre is not adversely affected by the use of the cover ply with its advantages.

The present invention will be further illustrated by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a section through a tyre with a single turn of cover ply; Figure 2 shows a double cover ply; Figure 3 shows a layer of single cover strips; Figure 4 shows a double layer of cover strips.

A motor vehicle pneumatic tyre 100 consists essentially of a radial ply carcase 200, a tread 300 and a belt 400 for the tread. The covering layer of thermally contractile reinforcing elements is indicated by 500 in Fig. 1, 600 in Fig. 2, 700, as strips, in Fig. 3 and 800, again as Strips, in Fig. 4.

Preferrd fabrics in which the cord filaments have a twist of between 950 and 550 or more turns per metre are e.g. polyamide dtex 470/2, dtex 700/2 or polyester dtex 550/2.

Preferred fabrics, comprising single yarns with twists of 350 to 550 or more turns per metre, are e.g. polyamide dtex 700/1, dtex 940/1, dtex 1400/1 or polyester dtex 550/1, dtex 720/1, dtex 1100/1 or dtex 1440/1. These fabrics have not hitherto been used in the manufacture of tyres. The low modulus of the filaments nevertheless has its advantages as described and such filaments are advantageously used in cover ply fabrics.

1. A motor vehicle pneumatic tyre comprising a radial ply carcase, a tread and a belt for reinforcing the tread comprising at least two crossing plies of steel fabric and at least one additional cover or cap ply of non-metallic reinforcing elements which shrink under the effect of heat and which extend parallel to one another in the circumferential direction of the tyre, in which the cover or cap ply, which has substantially the same width as the tread or is divided into strips, surrounds the belt ply with at least one full turn and includes overlaps at the ends of the ply, in which the cover or cap ply consists of light cords or single yarns, the total filament thickness of which is not greater than 1440 dtex and the twist of the yarns is at least 350 turns per metre, 2. A motor vehicle pneumatic tyre as

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 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. In a motor vehicle pneumatic tyres bandaging of the belt of the tread reinforcement with an additional cover ply of textile fabric, the reinforcing elements of which shrink under the effect of heat and thus have a stabilising and protective function, is known. Cords or single yarns of polyamide or polyester are preferred for this application. The modulus of these reinforcing elements is relatively high so that high tensions are set up in the reinforcing elements as a result of heat and pressure inthe finishing of the tyre. As these tensions are not applied uniformly and cannot be maintained uniform over the tread or belt it is not unlikely that distortions, which must be avoided, will be produced in the tread. It is an object of the invention to prevent undesirable stressing conditions in the belt as these affect the uniformity of the tyre, and the reinforcing elements in the cover ply must therefore be formed in such a way that such deformations are avoided when the cover ply is used. In accordance with the present invention there is provided a motor vehicle pneumatic tyre comprising a radial ply carcase, a tread and a belt for reinforcing the tread comprising at least two crossing plies of steel fabric and at least one additional cover or cap ply of nonmetallic reinforcing elements which shrink under the effect of heat and which extend parallel to one another in the circumferential direction of the tyre, in which the cover or cap ply, which has substantially the same width as the tread or is divided into strips, surrounds the belt ply with at least one full turn and includes overlaps at the ends of the ply, in which the cover or cap ply consists of light cords or single yarns, the total filament thickness of which is not greater than 1440 dtex and the twist of the yarns is at least 350 turns per metre. It is preferred that the modulus of the light cord or single yarn should lie within the low tension range, preferably between 6 and 1 2 N when the extension is 4%. When a tyre is finished using pressure and heat, in particular in vulcanisation and prevulcanisation, there is a swelling of some 2-4%. The necessary relaxation of the belt bandaged by the cover ply is of the same order of magnitude. In the case of bandaging fabric which has thermal contractile properties it is thus the modulus for a 4% extension in length which is of interest. A relatively small tension per filament is achieved through the use of fabrics with the abovementioned overall density characteristics and a high twist in the filaments. The modulus of the reinforcing elements is consequently low. This ensures that the tension range over the width of the belt, athough it is not uniform, gives rise to no major tendency to distortion of the tread or belt region. The small force which does not exceed 1 2 N for an extension of 4% results in a relatively small tensioning effect. This has no major disadvantageous effect on the belt so that the uniformity of the tyre is not adversely affected by the use of the cover ply with its advantages. The present invention will be further illustrated by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a section through a tyre with a single turn of cover ply; Figure 2 shows a double cover ply; Figure 3 shows a layer of single cover strips; Figure 4 shows a double layer of cover strips. A motor vehicle pneumatic tyre 100 consists essentially of a radial ply carcase 200, a tread 300 and a belt 400 for the tread. The covering layer of thermally contractile reinforcing elements is indicated by 500 in Fig. 1, 600 in Fig. 2, 700, as strips, in Fig. 3 and 800, again as Strips, in Fig. 4. Preferrd fabrics in which the cord filaments have a twist of between 950 and 550 or more turns per metre are e.g. polyamide dtex 470/2, dtex 700/2 or polyester dtex 550/2. Preferred fabrics, comprising single yarns with twists of 350 to 550 or more turns per metre, are e.g. polyamide dtex 700/1, dtex 940/1, dtex 1400/1 or polyester dtex 550/1, dtex 720/1, dtex 1100/1 or dtex 1440/1. These fabrics have not hitherto been used in the manufacture of tyres. The low modulus of the filaments nevertheless has its advantages as described and such filaments are advantageously used in cover ply fabrics. CLAIMS

1. A motor vehicle pneumatic tyre comprising a radial ply carcase, a tread and a belt for reinforcing the tread comprising at least two crossing plies of steel fabric and at least one additional cover or cap ply of non-metallic reinforcing elements which shrink under the effect of heat and which extend parallel to one another in the circumferential direction of the tyre, in which the cover or cap ply, which has substantially the same width as the tread or is divided into strips, surrounds the belt ply with at least one full turn and includes overlaps at the ends of the ply, in which the cover or cap ply consists of light cords or single yarns, the total filament thickness of which is not greater than 1440 dtex and the twist of the yarns is at least 350 turns per metre,

2. A motor vehicle pneumatic tyre as claimed in claim 1, in which the twist of the yarns is 350 to 550 turns/metre.

3. A motor vehicle pneumatic tyre as claimed in claim 1, in which the modulus of the light cords or single yarns when extended by 4% lies in the range of 6 to 12 N.

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