TYRE WITH IMPROVED BEAD REGION

Abstract: A tyre having a pair of axially spaced-apart bead regions each reinforced by an annular bead hoop around which one edge of a carcass reinforcing ply is wrapped and a filler strip positioned in the axially outer region of the bead which extends circumferentially around the bead, has one edge radially in­ wards of the bead hoop and one edge axially outwards of the bead hoop and comprises substantially weftless tyre cord fabric with the cords at an acute angle to the circumferential centreline of the bead hoop characterised in that the filler strips (6) in both beads have their cords (8) laid at an angle to the same specified direction circumferentially such that the cords (8) of one filler strip (6) are substantially parallel to the cords (8) of the other filler strip (6) and the tyre has an external direction marker (12) in the same circumferential direction to the speci­ fied direction so that in use the tyre may be fitted to a vehicle with the marker (12) in the opposite direction to the greatest torque force from the wheel. The filler strip may be cut edge tyre cord fabric or a single cord laid in a zig-zag to form the fabric.

Description: This invention relates to tyres with improved bead regions and in particular to heavy duty tyres such as are used for trucks and buses. Such tyres include in the bead region a filler or chafer strip laid around the outside of the bead over the carcass ply or plies and extending from beneath the bead hoop to a point radially outwards of the bead hoop. This chafer strip is usually made of cutedged weftless tyre cord fabric laid with the cords at an acute angle (bias angle) to the centreline of the bead hoop. In use of the vehicle cyclically varying tensile and compression forces are applied to the radially outer edge of the filler strip and tyre life can be reduced by failure in the edge region of the filler strip known as filler edge looseness. This failure is a a failure of the bond between the cords at their ends and the rubber compound of the tyre and can result in a complete tyre failure. It has been suggested in GB-A-2141676, which corresponds to the preamble of Claim 1, to use looped edge fabric to avoid the cut edges of the cords and reduce this problem by improving the resistance of the cord at the filler strip edges to filament separation. It is an object of the present invention to reduce the filler edge looseness problem by a different approach and to provide a construction which materially reduces the failure inducing forces in the filler strip. The present invention provides a tyre having a pair of axially spaced-apart bead regions each reinforced by an annular bead hoop around which one edge of a carcass reinforcing ply is wrapped and a filler strip positioned in the axially outer region of the bead which extends circumferentially around the bead, has one edge radially inwards of the bead hoop and one edge axially outwards of the bead hoop and comprises substantially weftless tyre cord fabric with the parallel cords at an acute angle to the circumferential centreline of the bead hoop wherein the filler strips in both beads have their cords laid at an acute angle to the same specified direction circumferentially such that the cords of one filler strip are substantially parallel to the cords of the other filler strip and the tyre has an external direction marker in the same circumferential direction to the specified direction so that in use the tyre may be fitted to a vehicle with the marker in the opposite direction to the greatest torque force from the wheel. In the case of a non-driven wheel the greatest torque force from the wheel is the torque from the brakes and in the case of a driven wheel the greatest torque force leading to tyre failure is that due to the drive torque , the braking force although sometimes the larger torque being of short duration. The filler strip may have its radially inner edge beneath the bead hoop or may be alongside it in the heel region of the tyre. The radially outer edge of the filler strip is preferably radially outwards of the edge of the carcass ply so that the filler strip overlies the said edge. The radially outer edge of the filler strip may be a folded edge with the filler strip folded back on itself. The filler strip may comprise cut edge tyre fabric or may comprise a narrow band formed by a single cord which extends back and forth across the band in a zig-zag formation to form a band substantially a single cord in thickness. The assembly is such that the range of stress applied to the filler strips at their radially outer edges are reduced because the predominant large torque forces what would otherwise lead to filler edge looseness are applied to the filler strip in predetermined directions so that the cords act in the most efficient manner. More than one filler strip may be used at each side of the tyre and any known filler strip material including steel cords may be utilised. Hitherto (See e.g. LU-A-68004) whilst cords have been placed in the same directions at both sides of the tyres it has been without the important tyre marker to provide correct usage and such matched directions have been purely to ease production problems such as rolling down of components during tyre assembly. The marker on the tyre may be on the sidewall or a directional tyre tread pattern. The invention will be apparent from the following description, by way of example only, of one embodiment in conjunction with the attached diagrammatic drawings in which:- Fig 1 is a scale view of a tyre on a non-driven wheel of a vehicle with the chafer strip fabric partially exposed. Fig 2 is a cross section of a single tyre bead with one type of filler strip construction. Fig 3 is a cross section of an alternative filler strip construction to Fig 2. Fig 4 is a plan of one filler strip fabric. Fig 5 is an alternative fabric to Fig 4. The tyre is shown in Fig 1 is a conventional radial carcass truck tyre having at each side of the tyre a tyre bead region for engagement with a wheel rim and through which is transmitted the drive and braking forces. The tyre bead is shown enlarged and in cross section in Fig 2 and comprises a steel wire reinforcement hoop 1 around which is wrapped a tyre carcass reinforcement ply 2. A hard rubber apex strip 4 projects radially outwards from the hoop 1 and provides an outer surface 5 to support the radially outer edge 3 of the carcass ply 2. A bead filler strip 6 is positioned axially outwards of the bead hoop 1 and extends as shown from adjacent the base of the hoop 1 to a point 7 beyond the carcass ply edge 3. The construction thus far is entirely conventional and the remainder of the tyre with a tread zone and tread reinforcing breaker is also conventional and not part of the present invention. The filler strip 6, as shown in Fig 4 comprises a weftless tyre cord fabric strip with the individual parallel cords 8 all at an acute angle A to a direction 9. The cords are cut at each edge 10 and 11 of the strip. The filler strip is assembled into the tyre beads taking care that for both beads of the tyre the direction 9 for the filler strip points in the same circumferential direction around the tyre. Thus the two filler strips, one at either side of the tyre, are arranged so that their cords are mutually parallel when viewed from one side of the tyre such as in Fig 1. The tyre assembly is then marked temporarily and when the tyre is cured in a mould the mould includes an arrow cavity which is positioned so as to form on the sidewall an arrow 12 pointing in the specified direction 9. (See Fig 1.) Thus the completed tyre has an outer marker 12 which is predetermined by the direction of the matched filler strips in both beads. The tyre may then be fitted to a vehicle such that the predominant torque force is in the same direction as the marker. The example of Fig 1 is for a non-driven wheel when the greatest torque force is the braking force B.F. In the case of a drive wheel the tyre is assembled so as to run the opposite way and thus in both cases the filler strip between is predetermined to give best filler edge durability. An alternative filler strip fabric construction is shown in Fig 5 where a single tyre cord is laid in a zig zag formation to form a non cut edge fabric. Once again the specified direction 9 is as shown. Fig 3 shows a bead construction where the radially outer edge 7 of the filler strip is formed by a fold in the strip and a short overlap region 10 leads to the cut ends of the cords. Other fabric constructions may be utilised as long as they are substantially weftless so that the cords may be laid in the preferred direction in all cases. Finally the tyre marker may of other forms including a directional tread pattern for example the 'V' formation pattern already proposed for use in wet conditions.

Claims: A tyre having a pair of axially spaced-apart bead regions each reinforced by an annular bead hoop (1) around which one edge (3) of a carcass reinforcing ply (2) is wrapped and a filler strip (6) positioned in the axially outer region of the bead which extends circumferentially around the bead, has one edge radially inwards of the bead hoop and one edge (7) axially outwards of the bead hoop (1) and comprises substantially weftless tyre cord fabric with the parallel cords at an acute angle to the circumferential centreline of the bead hoop characterised in that the filler strips (6) in both beads have their cords (8) laid at an angle (A) to the same specified direction (9) circumferentially such that the cords (8) of one filler strip (6) are substantially parallel to the cords (8) of the other filler strip (6) and the tyre has an external direction marker (12) in the same circumferential direction to the specified direction (9) so that in use the tyre may be fitted to a vehicle with the marker (12) in the opposite direction to the greatest torque force from the wheel. A tyre according to claim 1 characterised in that the filler strip (6) has its radially inner edge beneath the bead hoop. A tyre according to claim 1 characterised in that the filler strip (6) has its radially inner edge in the heel region of the tyre. A tyre according to claim 1, 2 or 3 characterised in that the radially outer edge (7) of the filler strip is radially outwards of the carcass ply edge (3) so that the filler strip (6) overlies said edge (3). A tyre according to anyone of claims 1 to 4 characterised in that the filler strip (6) comprises cut edge tyre fabric. A tyre according to anyone of claims 1 to 4 characterised in that the filler strip (6) comprises a narrow band formed by a single cord (8) which extends back and forth across the band in a zig-zag formation to form a band substantially one cord in thickness.

Inventors: WILLIAMS, ARTHUR ROGER
Applicants: SP TYRES UK LIMITED
Application year: 1986
Main classification: B60C15
IPC codes: B60C19, B60C15, B60C13, B60C5