GB2212122A

GB2212122A - Bead core assembly for pneumatic tyres

Info

Publication number: GB2212122A
Application number: GB8826443A
Authority: GB
Inventors: Norbert Zinnen
Original assignee: Uniroyal GmbH
Current assignee: Uniroyal GmbH
Priority date: 1987-11-12
Filing date: 1988-11-11
Publication date: 1989-07-19
Also published as: GB8826443D0; FR2623139B3; JPH01153309A; IT1229806B; IT8822580A0; FR2623139A1; DE3738446A1

Description

i BEAD CORE ASSEMBLY FOR PNEUMATIC TYRES r) 2 2 12 12 L The present

invention relates to a bead core assembly for pneumatic tyres which consists of wires looped in single or multiple layers having free wire ends at the beginning and end of the layers of loops which are arranged with respect to each other so as to have an overlap between the first and the last layers.

Bead core assemblies of this type are used for anchoring the carcase. For this purpose they are surrounded by the free ends of the carcase, the free ends of the carcase being wound round the bead core assembly. The bead core assembly is one of the most important components of a tyre, transferring the stress produced in the carcase by air pressure and the load to the wheel rim. In this the beads and in particular the bead core assemblies are subjected to high stresses and must be constructed to be sufficiently resistant to withstand such stresses without damage. For reasons of space and weight the dimensions of the bead core assembly are restricted.

In accordance with the method of manufacture, the bead core assembly is of a lapped construction for reasons of strength where the bead core assemblies are in layers this applies to the first and the last layers of wire. This overlapping of the wire layers, which represents a local region of stiffening, is highly at risk when peak stresses are applied. It represents a transition of differing cross-section and f orms both a region of material thickening and also, on account of the stiffness, an undesirable step at the point of transition from the free ends of the bead core assembly to the inner 1 i circumference. Maximum stressing occurs at this point. Under extreme load the bead core assembly as a rule fails at this point.

Known bead core assemblies are constructed in such a way that the free cut ends of the wire layers lie in a transverse plane, i.e. transverse to the direction of the circumference of.the bead wires.

In order to avoid the abovementioned failure of bead core assemblies it is proposed that in the context of a known bead core assembly the wire end or wire ends should be arranged with part of their cross-section alongside the loops in the bead wire assembly. Preferably the end of the wire in a layer of wire should be pressed between the wires of the neighbouring layer of wire.

The stiffness profile of such a bead core assembly is not substantially changed thereby. In that respect it is no more favourable then bead core assemblies having the normal blunt-ended overlap.

The object of the invention is to spread the stiffness profile of a bead core assembly at the points of overlap in such a way that the effect of the stresses on the layers or loops is more favourable as a result of a new arrangement of the wire ends, and stress effects are harmoniously distributed over the lengths of the loops.

According to the present invention there is provided a bead core arrangement for pneumatic tyres which consists of wires looped in single or multiple layers having free wire ends at the beginning and end of the 1 layers of loops which are arranged with respect to each other so as to have an overlap between the first and the last layers. in which the wire ends of the wires are in an offset arrangement with respect to each other in the direction of the circumference, wherein they have an overlap (u) and an overall overlap (1 = x.u) in which x represents the number of wires in each layer.

Also in accordance with the invention, there is provided a process for the manufacture of a bead core assembly consisting of individually looped wires, in which each wire drawn individually from a coil is looped into a single layer and cut off and in which the identical loops of wire are joined together axially to a bead, wherein the cut-off ends are offset with respect to each other in the direction of the circumference in accordance with the assembly referred to above.

The local stiffening at the points of overlap in the bead core assembly is achieved by a more favourably distributed arrangement of the existing wire ends per unit length. In accordance with further characteristics this may be achieved either by a stepped or obliquely cut arrangement of the wire ends. As a rule this depends on the method whereby the layers 9f wire are secured. As a result of the new arrangement of the wire ends the point of overlap is more flexible and furthermore permits less problematical mounting of the tyre since the point of local thickening is distributed over a greater unit length without adversely affecting its function as an overlapping point for strength. The region of high peak stresses is also distributed over a more favourable unit length. Depending upon the design of the bead core assembly in relation to the wire cross-section chosen, relatively short overlapping points can be formed in which the wire ends are either staggered or laid obliquely with respect to each other in the arrangement described above.

The arrangement of the wire ends may be distributed over the full extent of the bead core assembly. This can be arranged in such a way that for each individual wire either the individual wire ends are distributed inwards and outwards over the full extent of the bead or the wires are arranged in pairs, every second 9r every third etc., over the length of the circumference, the wire ends being taggered as already mentioned or arranged in some other arrangement with respect to each other.

This arrangement provides a more harmonious distribution of the points of overlap over the entire length of the bead. In accordance with a further characteristic, the individual wires may be looped with a sheet-like angle of height or inclination. These are then joined axially to the bead, with the free ends of each loop lying in the direction of the loop.

The present invention will be further illustrated, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 shows a bead core assembly having a rectangular cross-section in which the wire ends are displaced at the point of overlap; A 1 Figs. 2a, b, c, show details of the embodimen according to Fig. 1 in three views; Fig. 3 shows a bead core assembly in which the free wire ends are distributed over the circumference, Fig. 4 shows a bead core assembly having a rectangular cross-section in a displaced arrangement in which the offset wire ends lie in an inclined section.

Bead ring assembly 1 according to Fig. 1 Ppnsists of four layers of wires 2, 39 4 and 5, in which each layer of wire consists of five wires 6. The width of the bead core assembly is indicated by b and the height by h. Both the inner and the outer ends of this bead core assembly have wire ends 7 offset or staggered with respect to each other in the circumferential direction. The outer wires are indicated by V. The overlap of an individual wire in the first and last loops is indicated by means of U.

In comparison with a conventional bead core assembly with the wire ends cut smoothly transverse to the direction of the circumference, in which the overlapping lengths are for example 70 mm, the overlap position according to Fig. 1 is extended over a further distance in the case of the five wires in one layer of wire and lndicated by 1. In the case in question for example it amounts to 5 x 70 mm.

As may be seen from Figs. 2a, b and c, the individual wire ends are in a staggered arrangement with respect to each other. Fig. 2a shows a plan view of the bead core assembly according to Fig. 1 Fig. 2b shows a side view according to Fig. 2a and Fig. 2c shows an underneath view of the bead core assembly, that is a view of the wire ends 7 which are staggered with respect to each other at the inner circumference.

Rectangular bead core assemblies may consist of 3, 4 or more adjacent wires 6, which are looped over each other into 2, 3 or more looped layers. It is necessary that a certain overlap should be provided between the first and the last layer for reasons of strength. This 9verlap which represents a local stiffening in the bead core assembly is harmoniously distributed by the arrangement of wire ends offset with respect to each other. From the local point of view, the area of overlap is enlarged and the load due to the stresses applied to the carcase is thereby distributed more favourably over a larger length of the circumference. In addition to this, the local thickening produced by the offset wire ends is more flexible and permits pneumatic tyres to be mounted more satisfactorily in comparison with pneumatic tyres with known bead core assemblies which have their wire ends cut off in a transverse arrangement.

Fig. 3 shows a bead core assembly 11 in which the inner wire ends 17 and outer wire ends 17' of wire layers 12, 13 14 and 15 are distributed over the circumference. Through such an arrangement the points of overlap are deliberately distributed over the entire perimeter. The cross-section of the bead core assembly is therefore the same at all points around the circumference, with the exception of the wire ends, where undesirable local thickening is avoided.

i Fig. 4 shows a bead core or ring 21 in which the inner and outer wire ends are arranged with an oblique cut-off. The point off is indicated by 28. Depending on the size of the bead assembly an oblique cut with an apical angle o&- of 5 - 900 is proposed. A preferred angle isd-= 301. measured at the circumference.

In manufacture wire 6 or each layer of wires can be placed alongside each other without rubber or each layer of wires can be rubber coated together and then looped or each wire 6 can be rubber coated individually, laid alongside the others and then looped as a single layer of wires into a bead core assembly.

This depends on the desired form of the bead core assembly for particular selectable forms of pneumatic tyre construction.

Bead core assemblies may be constructed in such a way that either the overlying layers of wire are in a radial arrangement as in Fig. 1 and 2 or the layers of wire are looped radially and joined together axially into a loop as shown in the embodiment according to Fig. 4. The latter arrangement is of importance when the extended points of overlap should not result in massive local thickening at the point of overlap.

In addition to this the method of cutting is simplified.

In a bead core arrangement 21 according to Fig. 4 e.g. a single wire 26 is looped into a loop 30, in which the wire is looped radiallyg and then cut to length.

- 8 Af ter this another individual wire 27 is looped into a further loop 31 and cut to length. The two loops are joined axially with their wire ends in an offset arrangement.

The individual wires may be looped radially or obliquely, i.e. in a conical manner, and then joined together axially.

I

Claims

CLAIMS 1. A bead core arrangement for pneumatic tyres which consists of wires looped in single or multiple layers having free wire ends a-t the beginning and end of the layers of loops which are arranged with respect to each other so as to have an overlap between the first and the last layers in which the wire ends of the wires are in an offset arrangement with respect to each other in the direction of the circumference, wherein they have an overlap (u) and an overall overlap (1 = x.u) in which x represents the number of wires in each layer.

1

2.. A bead core arrangement as claimed in claim 1, in which the offset wire ends are stepped.

A bead core arrangement as claimed in claim 1, in which the offset wire ends have an oblique cut-off angle.

4. A bead core arrangement as claimed in claim 3, in which the offset wire ends have an acute cut-off angle.

5. A bead core arrangement as claimed in any preceding claim in which the -points of overlap of the offset wire ends are distributed around the circumference of the bead.

6. A bead core assembly as claimed in any preceding claim, in which the points of overlap (u) from one wire to another are arranged individually or in pairs.

7. - A bead core assembly, substantially as hereinbefore described with reference to the accompanying drawings.

a

8. A process for the manufacture of a bead core assembly consisting of-individually looped wires, in which each wire drawn individually from a coil is looped into a single layer and cut off and in which the identical loops of wire are joined together axially to a bead, wherein the cut-off ends are offset with respect to each other in the direction of the circumference in accordance with claim 1.

A process as claimed in claim 8, in which the individual wire ends ar-e looped radially or obliquely.

10. A process for the manufacture of a bead core assembly, as claimed in claim 8 or 9, substantially as hereinbefore described and illustrated.

Published 1989 at The Patent Office. 71H19Z Hotor-_LI_,'A2,!IVClR4TP F"Urth-crCODIESinky be cbLazziedfrom The Patent Office.

SEaes Brancl,,. St Mary Cray. Orpington, Ke.r" BR,5 3RD_ Printed bY MUltlPlex Lechniclues ltd. St Mary Cray, Ke=. Con. 1187