GB2123360A - Tyre bead reinforcements - Google Patents

Abstract

A tyre bead reinforcement comprises a circumferentially extending ring (1, 11) material, e.g. steel shaped in cross-section to define a pocket in which is located a circumferential winding (3, 12), e.g. of rubber-coated steel cord. The pocket may completely (Figure 1) or partly (Figure 9) enclose the winding. The ring may define a plurality of pockets each containing a respective winding. In cross-section, the outer profile of the ring may differ from the inner, winding contacting, profile. <IMAGE>

Description

SPECIFICATION Tubular articles This invention relates to tubular articles and in particular to tyre bead reinforcements.

Tyres are conventionally reinforced in each bead by a circumferentially extending hoop of high tensile steel wires in the form of a closely packed array.

Sometimes the wires are in the form of a cable in order to provide accurate positioning of each wire and thus good efficiency in using the strength of each wire but more usually in array comprises a number of turns one on top of another of a strip formed by three or more side-by-side steel wires.

The array is usually embedded in rubber and the wires may be plated prior to assembly to provide an effective bond to the rubber and form a sufficiently strong hoop.

In both the above constructions difficulties of forming a consistent cross-section and a continuous ring without a stiffened joint zone occur.

It is an object of the present invention to provide a bead reinforcement which effectively utilises the strength of the reinforcement material selected and which may be used in straightforward tyre building processes without the dangers of malformation of the structure of the reinforcement.

According to one aspect of the present invention a tyre bead reinforcement hoop comprises a circumferentially extending ring of material having a Ushaped cross-section pocket at least partially enclosing a circumferential winding of high tensile reinforcement material.

The U-shaped cross-section pocket may be closed so as to fully enclose the winding of high tensile material or may be open and enclose only a part of the cross-section of the winding of high tensile material. The ring of material may comprise a constant thickness sheet or be of varying thickness.

The cross-section of bead hoop may also include an encapsulating material such as for example rubber or resin to fill up the gaps or spaces between the reinforcement windings and the ring.

The cross-section of the ring may in some cases have a varying thickness so that the outer profile of the ring maybe different in shape to the inner profile.

The ring of material may be formed as a homogeneous continuous ring or as a ring having a joint for example a welded joint. The ring material is preferably metal such as steel and it may be zinc or brass plated to assist in bonding to the rubber of the tyre bead.

The winding is preferably tightly wound against the smallest diameter of the ring of material. A single wire may be wound around the ring or two or more wires may be wound either in separate parallel relationship or in the form of a strand or cord around the ring. The wire may be plated to assist bonding and/or may be coated with for example unvulcanised rubber resin. The reinforcement hoop may have various outer cross-sectional shapes but one preferred arrangement has a circular shape.

More than one winding may be arranged in two or more U-shaped pockets so as to provide a bead hoop of more complex form and having different hoop strengths in different portions of the bead hoop cross-section.

The U-shaped cross-section ring may also provide a location memberand/ora support for a bead apex component. The bead apex component may be precured and may be of any known type.

The U-shaped cross-section ring may be formed to have any required outer shape including a substantially flat tapered surface to match the required bead seat taper for the completed tyre bead e.g. 5" or 15" and thus the ring can be used to design into the bead construction control of bead/bead seat interference because the bead shape can be e fixed by the U- shaped ring cross-section chosen.

The U-shaped cross-section ring may have a constant material thickness or may vary in section; for example the outer profile of the ring may be a smooth curve and the inside profile may be rectangularto engage a square package of bead reinforcement wires.

Furthermore the walls of the U-shaped crosssection ring may be straight in the circumferential direction or they may be crimped so as to provide a channel of increased flexibility. Spaced apart crimps around the head hoop may be utilised or more closely spaced crimps so that the walls follow a sinusoidal wave in the circumferential direction are possible constructions of this type.

Another aspect of the present invention provides a method of manufacture for a tyre bead reinforcement hoop comprising forming a ring of material having a U-shaped cross-section pocket which is open and winding a high tensile reinforcement member into said U-shaped pocket.

The U-shaped pocket may be subsequently closed so that the winding is enclosed by the ring of material.

Further aspects of the present invention will be apparent from the following description, by way of example only, of some embodiments in conjunction with the attached diagrammatic drawings in which: Figure 1 is a cross-section of one tyre bead reinforcement according to the present invention having a fully closed U-shaped ring; Figures 2 and 3 are edge and side views of the U-shaped ring member for the bead reinforcement of Figure 1; Figure 4 shows in cross-section the bead reinforcement of Figure 1 partly completed; Figure 5 is a cross-section of an alternative fully enclosed bead reinforcement shown partly formed in Figure 6; Figure 7 shows yet another fully enclosed bead reinforcement again shown part formed in Figure 8; Figure 9 is a cross-section of a tyre bead having a part enclosing ring; Figure 10 is a cross-section of another tyre bead having a tapered base;; Figure 11 is a cross-section of an assembly including an apex strip; Figure 12 is a cross-section of yet another tyre bead having a varying thickness ring, and Figures 13 and 14 show embodiments in which the sidewall of the ring is formed to provide increased bead flexibility.

The bead reinforcement of the first example was made by forming from flat strip steel, which is brass plated, a continuous ring 1 (see Figures 1 and 2). The ring had a U-shaped or channel-like cross-section with the open centre portion 2 open to the radially outermost region of the ring.

An unvulcanised rubber coated high tensile steel cord 3 was wound around the ring so as to be tightly packed at the base of the U-channel there being 7 turns of wire cord. The arms of the U-channel were then closed tightly around the winding as shown in Figure 1 to form a bead hoop which on curing of the tyre including a winding 4 of steel cord and a thin walled steel tube 1 bonded together by the vulcanised rubber coating material.

The resultant bead hoop reinforcement hoop was of accurately held cross-section around the hoop.

A tyre made for the bead hoop included an accurate bead of high efficiency and with every wire correctly positioned.

The bead hoop shown in Figure 5 incorporates two windings 5 and 6 or wire which are within a pair of openings in a single ring 7. The windings are wrapped into the ring 7 as shown in Figure 6 following which operation the channels of the ring are closed. The resultant bead hoop again has accurately positioned wires which are kept in position throughout subsequent tyre manufacturing operations.

Another two core or two winding bead is shown in Figure 7 in which the two windings 8 and 9 are side-by-side. Once again a ring 10 is first shaped to provide two side-by-side U-shaped channels which are subsequently closed over the windings.

The bead reinforcement shown in Figure 9 uses a shallow U-shaped ring 11 to supportthe winding 12 of steel wire forming the main tensile reinforcement.

The ring 11 provides a smooth base for the winding 12 and in the use of a winding formed from three turns each of five wires this is particularly advantageous at the step on the radially inner surface where the winding begins. The gap adjacent to the step is filled by the rubber coating alternatively it may be filled by an added strip of rubber.

The bead reinforcement shown in Figure 10 comprises a deeper U-shaped channel or ring 13 which has its arms 14, 15 reaching to just above the radial height of the winding 16 but not fully enclosing the winding 16. Furthermore the bead core base is formed to lie at a constant angle to the axial direction. In car tyres the angle is usually Sand in truck tubeless tyres 15 although the special bead construction of the present invention allows the provision of any angle or in fact other shaped bead bases so that special requirements of bead fit on the wheel bead seat can be designed and thus the fit of the tyre bead can be better controlled.

Figure 11 has a ring 18 formed with a radially projecting limb 19 which locates a bead apex 20. The apex 20 is fitted after the reinforcement winding is wound into the ring 18 and the bead hoop assembly is then completed ready for building into a tyre. The apex 20 may be precured rubber or if required made of other materials such as plastics. Alternative shapes of limb 19 may be used and two limbs, one either side of the apex 20 can be provided to lock the assembly together.

The embodiment shown in Figure 12 uses a U-shaped ring 21 of non-constant thickness. The outer surface of the ring 21 is smoothly curved so that the tyre carcass ply or plies can be wrapped around the bead and the inner surface of the ring is generally rectangular so that the reinforcement winding is retained in a rectangular arrangement.

Finally Figures 13 and 14showtwo U-section rings which are in addition crimped at intervals. The arrangement of Figure 14 is a regular crimp so that the wall of the ring follows a sinusoidal path in the circumferential direction. These rings are subsequently filled by a winding as in the previous embodiments and may be left open or closed. The effect of the crimping is to provide a bead which is more flexible, which property can be advantageous to allow tyre fitting.

Claims (12)

1. Atyre bead reinforcement hoop comprising a circumferentially extending ring of material having a U-shaped cross-section pocket at least partially enclosing a circumferential winding of high tensile reinforcement material.

2. Atyre bead reinforcement hoop according to claim 1 wherein the U-shaped pocket is closed so as to enclose said winding of reinforcement material.

3. Atyre bead reinforcement hoop according to claim 1 or 2 wherein the ring of material comprises a constant thickness sheet.

4. Atyre bead reinforcement hoop according to claims 1 or 2 wherein the ring of material has a varying thickness.

5. Atyre bead reinforcement hoop according to any one of claims 1-4 wherein the cross-section of bead hoop includes an encapsulating material which fills the gaps or spaces between the reinforcement windings and the ring.

6. Atyre bead reinforcement hoop according to claim 5 wherein the encapsulating material is rubber.

7. Atyre bead reinforcement hoop according to any one of claims 1 to 6 wherein the hoop has a joint to form the continuous hoop.

8. Atyre bead reinforcement hoop according to any one of claims 1 to 7 wherein the ring of material comprises steel.

9. Atyre bead reinforcement hoop according to any one of claims 1 to 8 wherein two or more U-shaped pockets are provided each enclosing a winding or reinforcement material.

10. A method of manufacture for a tyre bead reinforcement hoop comprising forming a ring of material having a U-shaped cross-section pocket which is open and winding circumferentially a high tensile reinforcement member into said U-shaped pocket.

11. A method according to claim 10 wherein the U-shaped pocket is subsequently closed so as to enclose the ring of material.

12. Atyre incorporating a tyre bead reinforce ment in each bead hoop according to any one of claims 1 to 9.