The invention relates to a bead ring assembly for vehicle tyres of
a ring-like rubberised wire bundle of several wire layers arranged above one another
and a bead apex comprising an elastomeric material, arranged adjoining the wire
bundle and extending in the direction of the side wall of the tyre.
Bead ring assemblies of the kind are generally known. In such assemblies
the rings which are essentially non-extensible in the radial direction are so
wound that several wires which lie alongside one another, and which have been combined
by rubber material into a band-like strip, are wound into a ring with several
wire layers above one another. As a rule wires are used with a relatively small
diameter below lmm. Despite this small diameter of the wires the start and end
of the winding have an unfavourable effect with respect to the uniformity of the
tyre, even with corresponding mutual displacement of the beginning and end of the
Such bead rings are also known wound so that the ring surface defined
by the radially inwardly disposed wire layer extends slightly conically so that
an adaptation can be achieved to the shape of the associated surface of the rim
seat. In this way a uniform contact pressure is achieved when the tyre is installed
on a wheel rim. For bead ring arrangements formed in this way the danger exists
that faulty installation of the bead ring takes place during tyre manufacture
and that the angle of inclination of the radially inwardly disposed wire layer
does not extend in correspondence with the inclination of the associated surface
of the bead seat but rather opposite thereto. This faulty installation of the
bead ring is practically not recognisable in the finished tyre but can however
lead to the tyre provided with the faultily installed bead lifting in certain
driving situations from the surface of the rim seat. A sudden pressure loss in
the tyre can thereby occur causing critical driving situations.
The object of the invention is to design a bead ring arrangement
of the initially named kind in such a way that the effects resulting from the bead
ring layout on the tyre uniformity can be at least substantially reduced, in particular
with a simultaneous reduction of the manufacturing costs, and in such a way that
the danger of faulty installation of bead rings into the respective tyre is practically
precluded by the bead ring layout.
This object is satisfied in accordance with the invention essentially
in that the wire bundle is wound from a single wire; in that the number of wire
turns lying alongside one another is different in at least two of the wire layers
arranged on top of one another; in that the number of adjacent wire turns in the
wire layer adjacent the bead apex is less by one turn than the number in the wire
layer lying directly beneath it; and in that the bead apex contacts the wires
of both wire layers in form-matched manner.
More preferably the number of adjacent wires is two turns less than
the number in the wire layer lying directly below.
Through the winding of the wire bundle from a single wire, in particular
from a rubberised single wire, the points of abutment susceptible to breakage which
are present in customary bead rings, and which can have an unfavourable effect
on the tyre uniformity, are avoided. Moreover, a wire of larger diameter can be
used for the winding of the bead ring which leads to a notable reduction of cost
and also to a desirable reduction in weight.
It is of particular significance that the bead ring winding is executed
in such a way that the number of wire turns lying alongside one another in the
wire layer adjacent the bead apex is less by at least one turn and preferably
by two turns than the number of windings in the wire layer lying directly beneath
it, with the bead apex then simultaneously being so executed that it contacts
both the accessible layers essentially in a form-fitted manner. This leads to a
situation in which, during installation of the bead ring arrangement, not only
the layout of the wire layer at the bead apex side provides a criterion for the
correct installation of the bead ring in the tyre but rather the previously installed
unit of the bead ring and the bead apex which have been put together in the certain
manner can only be correctly built into the tyre as a result of the preforming
of the bead apex. In this way the initially indicated dangers of faulty installation
of a bead ring arrangement with a conically extending inner surface are removed.
Particularly advantageous embodiments of the invention are set forth
in the subordinate claims.
The invention will now be explained in more detail with reference
to exemplary embodiments and to the drawing; in the drawing there are shown:
- Fig.1. a schematic illustration of a bead ring region of a vehicle tyre with
a bead ring arrangement formed in accordance with the invention
- Fig. 2 an illustration correspondence essentially to Fig. 1 in a modified embodiment,
- Fig. 3 a schematic illustration of a bead region of a pneumatic vehicle tyre
with a further variant of a bead ring arrangement in accordance with the invention,
- Fig. 4 an illustration corresponding essentially to Fig.3 with a bead ring
arrangement modified in comparison thereto.
Fig.1 a bead region of a motor vehicle tyre comprises a bead ring
formed from a wire bundle 1 with an associated bead apex extending from the bead
ring in the direction of the sidewall 3.
The bead ring is wound from a single wire 4, in such a way that a
lower wire layer 5, a middle wire layer 6 and an upper or bead apex side wire layer
7 is obtained. The wire bundle 1 formed in this way is embedded in the customary
manner in rubber compound and forms an essentially non-extensible ring.
The lower wire layer 5 consists of four windings or turns lying alongside
one another, the middle wire layer 6 consists of five turns or windings lying
alongside one another, and the wire layer 7 at the bead apex side consists of two
turns or windings with the individual wire 4 being so wound that these two windings
are positioned nearer the inside of the tyre in the axial direction.
For the winding a single wire is used with a diameter of preferably
approximately 1.4 mm whereby it is possible to obtain, on the one hand, a saving
of cost and, on the other hand, a saving of weight of 20%. The use of an individual
wire of this wire thickness has no negative effects on the tyre uniformity since,
as a result of the winding being a single wire, no point of abutment arises which
extends over the full width of the bundle, as in customary wire bundles wound
from a strip of parallel wires embedded in rubber. Instead only two single wire
ends are present which can in turn be displaced relative to one another and are
preferably disposed diametrically opposite to one another.
As the layout of the wire layer 7 at the bead apex side is in the
form of only two windings a non-symmetrical assembly in cross-section results which
makes it possible to recognise at once during the installation of the bead ring
due to it being visible in the outer side of the bead ring. This is of substantial
importance in bead rings which are so wound to match the rim seat surface with
a conical ring surface 8. Such beads may have an inner surface which has for example
an inclination of 5°. A bead ring formed in this way must be so built into the
tyre that this inclination extends in the same direction as the bead toe inclination,
since only then is the required uniform contact pressure at the rim ensured. In
the event of a faulty installation of the bead ring, i.e. an installation with
the contrary inclination of the ring surface 8, extremely dangerous pairings of
tyres and rims can result so that it is of substantial importance to fundamentally
preclude such faulty installations.
When the wire bundle 1 wound in accordance with the invention is
combined with the bead apex 2 into a sub assembly the wire bundle pack 1 and the
bead apex 2 can only be combined or assembled in the correctly defined manner
because of the stepped layout of the wire layer at the bead apex side, since the
mutually oppositely disposed surface of the wire bundle 1 and the bead 2 are of
complementary shape. As a result of the deformation of the core apex one obtains
in this manner an overall unit which precludes any form of faulty installation.
Fig. 2 shows a modification with the winding being so executed that
the two windings of the layer 7 at the bead apex side are disposed at the axially
outer side of the tyre. Through the positioning of these windings at the bead
apex side, which leads to a lack of symmetry in the layout of the wire bundle 1,
the running behaviour of the tyre can be intentionally influenced. The illustration
of Fig. 2 furthermore makes it clear that the principle of the bead core layout
is realisable with a different number of turns per wire layer with the fundamental
hexagonal structure however being retained.
In the variant of Fig. 3 the winding is laid out in such a way that
two middle wire layers 6 are formed between the lower wire layer 5, i.e. the radially
inwardly disposed wire layer, and the layer 7 at the core apex side which consists
solely of one turn. The upper layer 7 consisting solely of a single turn is thereby
disposed at the inner side of the tyre and the core apex 2 is again corresponding
adapted shapewise and lies on the upper winding 7 and the layer 6 lying beneath
Fig. 4 shows a variant of the embodiment of Fig. 3 in which the upper
wire layer 7 consisting of a single winding or turn is disposed towards the outer
side of the tyre and is surrounded at both sides by the bead apex 2.
The advantages described above apply for all the illustrated variants.