GB2126502A - Tyre building fabric - Google Patents

Abstract

There is described a novel fabric for use in tyre building. The fabric is of open square construction and has a tackified finish to ease construction of tyre carcases. A method of making the fabric is described as well as a method of making a tyre using the fabric. A pneumatic tyre which is constructed using such fabric is also described. A preferred fabric has a warp set in the range 12 to 130 threads per decimeter and a weft set in the fabric of 15 to 70 threads per decimeter.

Description

SPECIFICATION Improved pneumatic tyres and fabrics for use in building same Background of the Invention This invention relates to pneumatic tyres and to fabrics for use in building pneumatic tyres.

At the present time most pneumatic tyres for passenger vehicles are of the radial ply type as described below and fall into three classes namely SR, HR and VR which are tested to operate at speeds up to 180, 210 and over 210 kilometres per hour, respectively. Radial ply type passenger tyres are in the main manufactured from a single or multiply carcase of substantially U-shaped section having metal beads at the inner perimeters of the walls. In such a radial ply tyre construction the carcase is formed from a rubberised woven fabric having relatively inextensible reinforcing cords running transversely, i.e. radially, from bead to bead. A carcase constructed in this manner requires to be supported in the area of the tread. Commonly this support is provided by two or more steel cord belt plies extending around the outer periphery of the carcase and across the width of the tread.

Such steel belt plies are relatively inextensible in the intended direction of rotation of the tyre and include steel belt cords disposed parallel to that direction or at a low angle thereto. The belt plies act to restrict the movement of the tread and give the tyre better road-holding properties.

In view of the severe speed tests mentioned above, technical dificulties have been encountered in incorporating steel belts into the tread area of the tyre. One of the difficulties lies in ensuring good adhesion between the steel and the rubber. When first introduced such steel belted tyres were susceptible to tread chunking at high speed due to temperature build-up causing the rubber to degrade to an extent which impaired the adhesion between the steel belt and the rubber tread. This breakdown was particularly prevalent at the edges of the steel belt where excessive temperature build-up takes place, leading to progressive adhesion failure and irregular and severe tread wear in the shoulder area of the tyre.

Two solutions to the aforementioned problem have been proposed. The first solution comprises forming a secondary carcase over the steel belt plies using one or two plies of calendered nylon tyre cord extending circumferentially around the tyre and across the surface of the steel belt and beyond the edges thereof. The tyre cord is disposed with its relatively inextensible warp running around the perimeter of the steel belt in the intended direction of rotation of the tyre. The addition of this tyre cord is commonly known as a "cap-ply", "overlay" or "nylon cording".

One example of this solution is disclosed in US Patent No. 4,284,117.

The second solution comprises utilising two or more steel belt plies in which the edge of each ply is folded upon itself.

Both of the aforementioned solutions are expensive in that they utilise relatively large amounts of either calendered nylon cord or steel cord and, in the second solution, tyre building problems can occur both in the folding of the steel belts and in the accurate positioning of each ply of the belt. Furthermore, both solutions inevitably result in a relatively heavy construction.

Summary Of The Invention An object of the present invention is to obviate or mitigate the aforementioned disadvantages by providing a pneumatic tyre and a fabric for use in tyre construction which provides improved stability, good mechanical and chemical adhesion, cost savings during tyre building and a fabric weight saving without adversely affecting the properties of the tyre in relation to ride-comfort, noise and rolling resistance.

According to the present invention there is provided a fabric for use in tyre building and comprising an open square construction having a tackified finish, a warp set in the range of 1 2 to 1 30 threads per decimetre and a weft set in the range of 1 5 to 70 threads per decimetre.

Preferably, the fabric is formed from yarns with counts in the range of 440 to 2500 decitex.

The warp and weft may be twisted, folded or texturised and may be rayon, nylon 6, nylon 66, polyester or aramid and the fabric may be formed by conventional or leno weaving or warp inlay and weft insertion knitting.

The tackified finish is preferably achieved by application of an aqueous blend of resin and rubber latices or, alternatively, tackifying may be achieved by application of a solvent solution of unvulcanised rubber compound.

The fabric may be applied as a cap-ply extending across the steel belt and over the edges thereof.

Alternatively, according to the present invention there is provided a method of constructing steel belted radial ply tyres and comprising applying strips of the fabric according to the invention over the edges of the steel belt as the carcase is being built.

Still further according to the present invention there is provided a pneumatic tyre constructed as aforesaid.

Description Of The Drawings An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cut-away section of part of a pneumatic radial ply tyre; Figure 2 is a cross-sectional view corresponding to Fig. 1; and Figure 3 is a view corresponding to Fig. 1 illustrating a modified embodiment.

Description Of The Embodiments Referring now to the drawings, a radial ply tyre indicated generally at 1, comprises a carcase 2 formed from one or more plies of tyre cord 3 terminating at the inner periphery of the tyre in metal beads 4. The tyre cord 3 is a rubberised woven fabric having its warps formed from relatively extensible reinforcing cords, indicated generally at 3a. In the radial ply tyre shown in Fig. 1 the carcase 2 is constructed so that the reinforcing cords are running substantially radially of the intended direction of rotation X of the tyre 1. Support is provided to the carcase 2 in the area of the tread 5 of the tyre by two or more woven steel cord belt plies 6.The belt plies 6 are formed with relatively inextensible steel cord reinforcing warps, indicated generally at 6A, which run in the intended direction of rotation X of the tyre or, more usually, at a slight angle thereto. The belt plies 6 extend across the width of the tread 5 of the tyre terminating in edges 6B in the shoulder portion 7 of the tyre i.e. the area where the tread 5 meets the side wall 8.

A shoulder cap ply 9 is provided which extends over the edge 6B of the belt plies 6.

The shoulder cap ply 9 comprises a fabric having an open square construction and a tackified finish so that during tyre building a strip approximately 5 centimeters wide can be readily applied across the edge 6B to adhere to the belt ply 6 and the tyre cord 3 of the carcase.

The shoulder cap ply fabric 9 may be manufactured by conventional weaving, leno weaving, or warp inlay and weft insertion knitting from untwisted, twisted, folded, or texturised rayon, nylon 6, nylon 66, polyester or aramid yarns having a yarn count between 440 and 2500 decitex. The warp may have a set in the range of 1 2 to 1 30 threads per decimeter and the weft a set in the range of 1 5 to 70 threads per decimeter. The weft should lie at right angles to the warp.

The fabric is slit into strips approximately 5 centimeters wide and has a tackified finish to facilitate adhesion during building. This tackified finish is achieved by coating the fabric with an aqueous blend of resin and rubber latices or, alternatively, with a solvent solution of an unvulcanised rubber compound.

In one specific example the shoulder cap fabric 9 is formed by plain leno weaving with a warp set of 48 threads per decimeter and a weft set of 22 threads per decimeter. The warp is a 1100 decitex polyester yarn with a twist of 100 t.p.m. and the weft is a 470 decitex textured nylon. The fabric is 0.79 mm. thick and has a weight of 90 gm/sqm.

In a modified embodiment the shoulder cap fabric 9 can extend across the entire width of the steel belt plies while still overlapping the edge portions 6B of the latter.

An alternative construction is shown in Fig.

3 for use in tyres designed for higher speeds i.e. HR and VR specification. In this construction a standard cap ply 10 is provided which extends across the width of and overlaps the edge 6b of the belt plies 6. On top of the full width cap ply 10, shoulder cap plies 9 are provided. These shoulder cap plies extend over the edges 6B of the belt plies 6 as well as over the edges of the full width cap ply 10.

In some constructions the layer of shoulder cap ply 9 is replaced by a second full width cap ply 1 0A formed from fabric according to the invention.

The use of the fabric as claimed in the invention reduces the likelihood of a breakdown of adhesion occurring in the shoulder area of the tyre due to the flexibility gradient provided by the square construction of the fabric.

Furthermore, the open square construction improves the mechanical adhesion properties and the tackified finish improves the chemical adhesive properties thereby providing a stable tyre construction.

The present invention also provides for cost savings in that it reduces the weight of fabric in the tyre and in particular reduces the requirement for calendered tyre cord. It faciiitates the tyre building operation by use of the tackified finish and it enables a reduction in the overall weight of the tyre while not adversely affecting its ride comfort, noise or rolling resistance.

The above described embodiments are given for the purpose of illustration only.

Improvements and modification may be made to those embodiments without departing from the scope of the invention.

Claims (21)

1. A fabric for use in tyre building and comprising an open square construction having a tackified finish, a warp set in the range of 1 2 to 1 30 threads per decimeter and a weft set in the range of 1 5 to 70 threads per decimeter.

2. A fabric as claimed in Claim 1, wherein the fabric is formed from yarns with counts in the range of 440 to 2500 decitex.

3. A fabric as claimed in either preceding claim, wherein the warp and weft are formed of material taken from the group consisting of rayon, nylon 6, nylon 66, polyester and aramid.

4. A fabric as claimed in any preceding claim, wherein the warp set is 48 threads per decimeter and the weft set is 22 threads per decimeter.

5. A fabric as claimed in any preceding claim, wherein the warp is polyester yarn having a count of 1100 dexitex and the weft is textured nylon having a count of 470 decitex.

6. A method of making a fabric for use in tyre building comprising forming an open square construction wherein the warp set is in the range of 1 2 to 1 30 threads per decimeter and a weft set in the range of 1 5 to 70 threads per decimeter, and wherein the fabric has a tackified finish.

7. A method as claimed in Claim 6, wherein the fabric is formed from yarns with counts in the range of 440 to 2500 decitex.

8. A method as claimed in either Claim 6 or Claim 7, wherein the tackified finish is provided by applying an aqueous blend of resin and rubber latices.

9. A method as claimed in any one of Claims 6 to 8, wherein the tackified finish is achieved by applying a solvent solution of unvulcanised rubber compound.

10. A method of constructing a steel belted tyre comprising forming a carcase of one or more plies of tyre cord, applying at least one belt ply which extends circumferentially of the tyre and providing a shoulder cap ply extending over the edges of the belt ply, the shoulder cap ply comprising a fabric having an open square construction and a tackified finish.

11. A method as claimed in Claim 10, wherein the fabric has a warp set in the range of

1 2 to 1 30 threads per decimeter and a weft set in the range of 1 5 to 70 threads per decimeter.

1 2. A method as claimed in either Claim 10 or Claim 11, wherein the fabric is formed from yarns with counts in the range of 440 to 2500 decitex.

13. A method as claimed in any one of Claims 10 to 12, wherein the tackified finish is achieved by application of an aqueous blend of resin and rubber latices.

14. A method as claimed in any one of Claims 10 to 12, wherein the tackified finish is achieved by application of a solvent solution of unvulcanised rubber compound.

1 5. A method as claimed in any one of Claims 10 to 14, wherein the shoulder cap ply extends across the entire width of the belt ply and overlaps both edge portions of the belt ply.

1 6. A pneumatic tyre comprising a carcase having at least one ply of tyre cord, at least one belt ply extending circumferentially of the tyre and shoulder cap plies extending over respective edges of the belt ply, the cap ply comprising a fabric having an open square construction and a tackified finish.

1 7. A tyre as claimed in Claim 16, wherein the fabric has a warp set in the range of 1 2 to 1 30 threads per decimeter and a weft set in the range of 1 5 to 70 threads per decimeter.

1 8. A tyre as claimed in either Claim 1 6 or Claim 17, wherein the fabric is formed from yarn with counts in the range from 440 to 2500 decitex.

1 9. A fabric for use in tyre building substantially as herein before described with reference to the accompanying drawings.

20. A method of making a fabric for use in tyre building substantially as hereinbefore described with reference to the accompanying drawings.

21. A pneumatic tyre substantially as hereinbefore described with reference to the accompanying drawings.