GB2253818A

GB2253818A - Tyre belt making method and tyre

Info

Publication number: GB2253818A
Application number: GB9205802A
Authority: GB
Inventors: Yasushi Shinmura; Masayuki Sakamoto
Original assignee: Sumitomo Rubber Industries Ltd
Current assignee: Sumitomo Rubber Industries Ltd
Priority date: 1991-03-19
Filing date: 1992-03-17
Publication date: 1992-09-23
Anticipated expiration: 2012-03-17
Also published as: DE4208705C2; GB9205802D0; GB2253818B; JP3093812B2; JPH04290733A; DE4208705A1

Abstract

A method of making a belt for a radial tyre, comprises winding reinforcing elements 18 spirally around a cylindrical face 20 by advancing the reinforcing elements axially outwards from axially spaced starting points 18A to axially outward points, each on the cylindrical face 20, to form the axially spaced radially inner parts of band pieces 8. The reinforcing elements are left uncut at the axially outward points and a strip 12 of unwoven cord fabric is applied across the axially spaced radially inner parts and the strip around the cylinder to form a breaker ply, the strip 12 being wider than the width G2 between said starting points 18A but narrower than the width between the axially outward points. The reinforcing elements 18 are then wound from the respective axially outer points spirally around the outer surfaces of the breaker ply by advancing the reinforcing elements axially inwards from the axially outward points, to form the axially spaced radially outer parts of the band pieces. The winding operation may comprise winding a single cord or several cords in the form of a strip. The invention also includes the resultant tyre. <IMAGE>

Description

TYRE BELT MAKING METHOD AND TYRE 225331 C The present invention relates to

a method of making a c belt for use in a radial ply tyre to reinforce the tread portion thereof and a tyre incorporating said belt.

In general, a radial ply tyre is provided radially m outward of the carcass with a steel belt, the so called steel breaker, to reinforce the tread portion.

In particular, in radial ply tyres for high speed, to prevent lifting of the steel breaker by centrifugal force during high speed running, t C, an additional belt, the so called band, made of parallel cords laid at a substantially zero or small angle to the tyre circumferential direction is disposed radially outside the steel breaker.

For this band, a full width band extending across In the tyre equator is generally used. However, for lower tyre weight, better ride comfort and the like, an edge band consisting of a pair of axially spaced-apart narrow plies one disposed at each of the breaker edges, is often used.

Further, as shown in Fig. 9, in order to prevent separation of the edges of a breaker ply (B) from the surrounding rubber during running, especially high speed running, a folded ed.e band consistin.; ?D CY tn of a pair of axially spaced, folded pieces (C) has been proposed. Each folded piece (C) is, as shown in Fi8.10, made of a strip of unwoven cord fabric (D) in which organic fibre cords are arranged obliquely.

The strip (D) is first wound into an annular body (E) and the circumferential ends are overlap 1y, an overlap joint portion (F) jointed. According is formed.

Then, one edge (Ee) of the annular body (E) is folded axially inwards so as to form a radially outer part (C2) and a radially inner part (CI).

As a result, at the above-mentioned joint portion (F) the band becomes four-fold, and the thickness inevitably increases, which greatly effects tyre uniformity.

- 3 Further, the overlap joint (F) is liable to be broken by tension during very high speed running.

Furthermore, during the folding operation, the ZD diameter of the edge (Ee) is first increased and then decreased. Therefore, the cord spacings are 0 greatly disturbed, and an irregularity of the cord spacings results in the finished tyre, which deteriorates tyre uniformity, resistance to separation, high speed durability, and the like.

It is therefore an object of the present invention to provide a tread reinforcing belt, which comprises a breaker belt having a pair of axial ed,-I?es and a band belt composed of two pieces having a radially inner part and a radially outer part to wrap the breaker edge, which can solve the above-mentioned problems.

It is a more specific object of the present invention to provide a method of making the tyre tread reinforcing belt by which the above-mentioned problems are solved.

According to one aspect of the present invention, a method of making a belt for a radial tyre comprises a radial carcass and a belt disposed radially outside the carcass comprising a breaker ply of parallel cords having a pair of axially spaced apart edges and a band composed of a pair of axially spaced pieces each of which wraps an axial edge of the breaker for form a radially inner part and a radially outer part characterised in that the method comprises the steps of winding' reinforcing C, elements spirally around a cylindrical face by advancin-g7 the reinforcing elements axially outwards from axially spaced starting points to axially outward points, each on the cylindrical face, to form the axially spaced radially inner parts of the band pieces, maintaining said reinforcing elements uncut at said axially outward points, applying a strip of unwoven cord fabric across said axially spaced radially inner parts and winding said strip therearound, to form said breaker ply, such that the strip is wider than the width between said starting points and narrower than the width between said axially outward points, winding again the reinforcing elements from the respective radially - 5 outer parts spirally around the outer surfaces of said breaker ply by advancing the reinforcing elements axially inwards from said axially outward points, to form the axially spaced radially outer parts of the band pieces.

A single reinforcing cord or several reinforcing cords in the form of a strip may be wound.

Another aspect of the invention provides A radial tyre having a tread reinforcing belt comprising a breaker ply of cords having a pair of axially spaced apart edges and a band comprising a pair of D Z:1 spaced apart pieces each of which wraps an axial edge of the breaker to form a radially inner part and a radially outer part characterised in that the band piece comprises a winding of one or more reinforcing elements wound from axially spaced starting points to axially outward points and then spirally wound axially inwards so as to enclose the respective axial edge in a single winding.

C) The winding may comprise a single cord embedded in rubber or several cords for example fifteen or ten or less cords.

The breaker plies may be wrapped separately or together by the windinIgs at each edge.

Embodiments of the present invention will now be described in detail in conjunction with the attached drawin-gs, in which:

n Fi,-,?,.l is a cross sectional view of a radial tyre having a band made by a method according to the present invention; Fig.2 is an enlarged cross sectional view of zn ZD a band piece; Fi,-,Is.3(a)-(c) are schematic cross sectional views explaining, the method; Fig.4 is a perspective view of a reinforcing element comprising a plurality of band cords; Fig.5 is a perspective view of another reinforcing element comprising a single band cord; Fi,-,r,.6 is a schematic plan view of a strip of unwoven cord fabric; Figs.7(a)-(c) are schematic cross sectional views eNplaining another belt making method ID according to the present invention; Figg.8 is a schematic cross sectional vies.; of another example of the belt; and Fi,g?s.9-10 are a schematic cross sectional view and a perspective view explaining a method according to the prior art.

In Fig. 1, a radial tyre 1 comprises a tread 5, a pair of sidewalls 6, a pair of beads 9, a bead core 3 disposed in each bead 9, a toroidal carcass 2 extending between the beads 9, and a belt comprising a breaker belt 7 and a band belt 8.

The carcass 2 is composed of at least one ply of cords laid radially at an angle in the range from t3 C to 75 degrees with respect to the tyre equator turned tip around the bead cores 3 from the axially inside to the outside to be secured thereto.

In each bead 9, a bead apex 4 is disposed between the carcass main portion and each of the carcass turned up portions. The bead apex 4 is made of hard rubber strip which tapers radially outwards from the bead core 3.

- 8 The breaker belt 7 is disposed on the radial outside of the carcass 2, and comprises at least two plies of parallel cords 11 laid at an an-7le from 10 to 30 degrees with respect to the tyre equator.

In this example, the breaker belt 7 is composed of two crossed plies 7i and 7o having different widths, in which the radially inner ply 7i is wider than the radially outer ply 7o. However, the radially outer ply 7o may be wider than the radially inner ply 7i.

For the breaker cords 11, metallic or organic high L, C.

modulus cords, steel cords, aromatic polyamide fibre cords or the like are used.

The band belt 8 is composed of a pair of axially separated band pieces 8, one of which is disposed at each axial edge of the breaker 7.

Each band piece 8 wraps the breaker edge and has a =1 generally U-shaped cross sectional shape comprising a radially inner part 15 and a radially outer part 9 - s.1 and 2, the radially In this example shown in Fi,-, inner part 15 extends along the radially inner face of the inner breaker ply 7i and is in contact therewith. The radially outer part 16 extends along the radially outer face of the inner breaker ply 7i protruding from the edge of the outer breaker ply 7o, and then extends along the radially n outer face of the outer breaker ply 7o. The band piece 8 therefore, wraps the edges of both the breaker plies 7i and 7o.

Preferably, the folded-back edge 15a or axially outermost edge of the band piece 8 is extended axially outwards by 5 to 10 mm over the edge (ei) of the widest breaker ply 7i. In the extended part, idity no breaker ply exists. Therefore, the rig e, in the axial direction, of the belt as a chang whole at the edge regions is more gradual.

Each of the band pieces 8 is made of at least one organic fibre cord 17 wound spirally and continuously from the axially inner edge 15b of the 10 inner part 15 to the axially inner edge 16b of the outer part 16 through the axially outer edge 15a of the inner part 15 which is practically the same as the axially outer edge of the outer part 16. Therefore, the band piece 8 has no joint portion.

The windings of the cord(s) are laid substantially parallel to the tyre equator.

For the band cord 17, nylon 66, nylon 6, aromatic polyamide or the like can be used.

The axial distance G1 between the axially inner edge 16b of the radially outer part 16 of one of the band pieces 8 and that of the other band piece 8 is preferably in a range from 0.35 to 0.65 times the maximum breaker ply width WB which is the width of the widest ply in the breaker plies wrapped by the band pieces 8.

If the distance G1 exceeds 0.65 times WB, the tightening effect of the band pieces 8 to the breaker belt 7 is reduced and lifting of the breaker belt 7 can not be prevented. If the 11 - rigidity i S distance G1 is less than 0.35 times WB, the tread excessively increased which deteriorates the steering stability.

Further, in this example, the axial distance G2 between the axially inner edge 15b of the radially inner part 15 of one of the band pieces 8 and that of the other band piece 8 is smaller than the above-mentioned distance G1 and preferably in the range of 0.6 to 0.7 times the maximum breaker ply width WB.

Figs.3(a)-(c) show a method of making the abovementioned belt.

In Fig,.3(a), in order to form the radially inner part 15 of each of the band pieces 8, a reinforcing element 18 is wound around a cylindrical outer surface 20 of a shaping drum by rotating the drum in a predetermined direction and advancing the n point element 18 axially outwards from a, startin2D 18A.

The starting points 18A are spaced apart from each 12 - other by a distance equal to the abovementioned distance G2.

When the predetermined width has been wound, the reinforcing element 18 is not cut.

cord c The reinforcing element 18 may be composed of one r several parallel cords 17 embedded in rubber R. Fig.4 shows such a reinforcing element 18 composed of three parallel cords 17 embedded in rubber in the shape of a ribbon.

In the case where a multi-cord reinforcing element is used, the cord spacings or pitches P can be improved in accuracy, and further cord winding efficiency is improved.

As the inclination of the cord s.Qindin,,s is C5 increased by using a number of parallel cords, the number is preferably set to be not more than 15, and even more preferably not more than 10.

Fig.5 shows a reinforcing element 18 composed of a sin,gle cord 17 embedded in rubber R. The thickness 13 of the rubber coat is at about 0.1 or 0.2 mm.

The above-mentioned shaping drum can vary in the diameter of its cylindrical surface 20.

In Fig.3(b) showing the subsequent step of the belt making method, a strip 12 of unwoven cord fabric for the inner breaker ply 7i is applied between the radially inner parts 15 formed on the cylindrical surface 20 and wound onto the outer surfaces of the inner parts 15. Next, a second strip of unwoven cord fabric 12 to form the outer breaker ply 7o is wound over the inner breaker ply 7i.

The strips are arranged so that their cords cross each other, and the ends of each strip are bias cut and overlap jointed to form a bias joint. The strip for the innermost breaker ply 7i has a width such that its axial ed.es terminate axially inwards of the outer edges 15a of the radially inner parts 15.

Fig. 3 ( c) shows the next step of the belt making method, where in order to form the radially outer part 16 of each of the band pieces 8, the - 14 reinforcin- element 18 outer surfaces of the once again rotating the as for the inner part 15 and advancing the reinforcing element 18 axially inwards from the axially outermost edges 15a of the inner parts 15 until the windings have reached to a predetermined width.

is again wound around the breaker plies to and 7i by drum in the same direction Therefore, between the radially outer part 16 and the radially inner part 15, the spiral directions are reversed, and thus the cord inclinations are also reversed.

The cord tension during winding may be kept substantially constant across the entire width, but more preferably the tension is varied to increase gradually from the axially inside to the outside.

Figs.7(a)-8(c) show another belt and the method of making it.

In this example, the belt is composed of a breaker belt 7 composed of a radially inner ply 71i and a radially outer ply 7o and a band belt composed of a. pair of axially separated band pieces 8 which wrap only the outer breaker ply's edges, as shown in Fig.7(c).

tn The method comprises the steps of (1) winding a strip of unwoven cord fabric 12 around a cylindrical surface of the drum to form the inner breaker ply 7i as shown in Fig.7(a), ( 2) windingg reinforcing elements 18 around a cylindrical surface 20, which is the outer surface of the inner breaker ply 7i, as shown in Fig. 7(b), to form a pair of radially inner parts 15 of the band pieces 8 similarly to the former eHample, (3) applying a strip of unwoven cord fabric 12 around the outsides of the inner parts 15 and exposed central part of the inner breaker ply 7i to form the radially outer breaker ply 7o, and (4) winding the reinforcing elements 18, which es of the are continuous from the axially outer ed-g inner parts 15, around the outsides of the inner 16 parts 15 and radially outer breaker ply 7o, to form a pair of radially outer parts 16 of the band pieces 8.

Here, the axially outer edge of each of the inne parts 15 is substantially aligned with each of th axially outer edges of the inner breaker ply 7i, but generally positioned slightly axially inside thereof.

e During5' the winding operation of the reinforcing element 18 to make the radially inner part 15, th cord tension is gradually increased from th axially inside to the outside, so that the radiallinner part 15 can provide a tight hoop effect for the edge portions of the inner breaker ply 7i, and lifting of the inner breaker ply 7i can be effectively controlled.

e e For the radially inner part 15, the cord tension can be increased in the same way for the same reason, Fig.8 shows still another example belt, in which 17 the belt comprises two crossed plies 7i and 7o and two band belts each of which is composed of two axially spaced band pieces 8. Thus the two axial edges of the radially inner breaker ply 7i and the two axial edges of the radially outer breaker ply 7o are separately wrapped by four band pieces 8.

A detailed explanation of the method of making this Z:1 belt is omitted as it is easily seen from the foregoing examples, but roughly speaking it is made by repeating twice the steps (2) (3) and (4) of the second example.

As described above, the method according to the CI present invention provides a tyre tread reinforcing 1 belt, in which the band pieces have a jointless structure, and the edges of the breaker ply are respectively wrapped by the band pieces, whereby the radially outer parts of the band pieces provide an improved hoop effect in the edge regions of the breaker ply, and belt edge looseness is prevented. As a result tyre uniformity and tyre durability at hh speed are greatly improved.

i lg 1 - 18

Claims

A method of making a belt for a radial tyre, comprising a radial carcass (2) and a belt (7) disposed radially outside the carcass ( 2), comprising a breaker ply of parallel cords (11) having a pair of axially spaced apart edges and a band (8) composed of a pair of axially spaced pieces each of which wraps an axial edge of the breaker to form a radially inner part (15) and a radially outer part (16), characterised in that the method comprises the steps of winding reinforcing elements (18) spirally around a cylindrical face (20) by advancing,7 the reinforcing elements axially outwards from axially spaced starting points (18-A) to axically outward points, each on the cylindrical face (20), to form the axially spaced radially inner parts of the band pieces (8), maintain said reinforcing elements uncut at said D axially outward points, applying a strip ( 12) of unwoven cord fabric across said axially spaced radially inner parts and winding said strip C therearound, to form said breaker ply, such that the strip (12) is wider than the width (G2) between 19 - said starting points ( 18A) and narrower than the tD 1 width between said axially outward points, winding again the reinforcing elements (18) from the respective radially outer parts spirally around the outer surfaces of said breaker ply by advancing the reinforcing elements axially inwards from said axially outward points, to form the axially spaced radially outer parts of the band pieces.
2. A method accordine, to claim 1 characterised t:l in that a single cord is wound for each reinforcing element.
3. A method according to claim 1 characterised in that several parallel cords are wound in the form of a strip.
4. A radial tyre having a tread reinforcing belt 0 comprising a breaker ply (11) of cords having a pair of axially spaced apart edges and a band comprising a pair of spaced apart pieces each of which wraps an axial edge of the breaker to form a n radially inner part and a radially outer part characterised in that the band piece comprises a winding of one or more reinforcing elements wound from axially spaced starting points to axially outward points and then spirally wound axially - inwards so as to enclose the respective axial edge in a single winding.
A tyre according to claim 4 characterised in that the winding comprises a single cord embedded in rubber.
6. A tyre according to claim 4 characterised in that the winding comprises a strip of several cords embedded in rubber.
7. A tyre according to claim 6 characterised i that the winding comprises not more than 15 cords.
8. A tyre according to claim 6 characterised i that the winding, comprises not more than 10 cords.
9. A radial tyre according to any of claims 4 to 8 characterised by there being . two breaker plies each of which has its axial edges n wrapped by a winding of reinforcing elements.
10. A method of makin,:

g a belt for a radial tyre substantially as described herein.
11. A radial tyre having. a belt constructed and arran.ed substantially as described herein in tires 1 to 7 or 8 of the conjunction with Fil., attached dia&rammatic drawin-7s.

n