BEAD REINFORCING STRUCTURE FOR HEAVY DUTY TIRE
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a bead reinforcing
structure for a heavy duty tire, such as a TBR tire, and
especially for a tire used under the conditions of high
pressure and heavy load. The present invention more
particularly relates to a bead reinforcing structure for a
heavy duty tire having a bead in which a carcass is turned up
to surround a bead core, the bead reinforcing structure having
a double reinforcing structure in which inside and outside
steel chafers having predetermined inclination angles are
disposed inside and outside the carcass to reinforce the
carcass from both the inside and outside of the carcass.
Description of the Related Art
Generally, it is necessary for a pneumatic tire used for a
heavy duty vehicle to have a bead reinforcing structure so that
the pneumatic tire can endure a heavy load. This is because a
pneumatic tire suffers from the strongest stress at an
interface portion thereof which is in contact with a wheel
joined with a rim and because the breaking down or detachment
of the bead is most likely to occur in this interface portion.

The structure of a typical bead includes a bead core which
is the inner part, a carcass which is turned up to surround the
bead core, and a chafer made of nylon or steel which covers and
reinforces the carcass.
Until recently, an effort to develop a technology for
improving durability of the bead has been made, and thus
dramatic technological advancements have been achieved. There
are two technological trends with respect to the bead. A first
one is a way of adjusting the shape of a carcass serving as a
backbone of a tire. Through this method, it is possible to
adjust magnitude and distribution of stress applied to the
carcass and to adjust deformation and/or stress of the carcass
attributable to movement of a tire while a vehicle is
traveling. A second one is a way of improving the physical
properties of a rubber adjacent to the carcass, resulting in
improvement in the performance of retaining physical properties
of the rubber under the same fatigue and temperature
conditions.
US Patent Application No. 1986-775004 (US Patent No.
4688616) assigned to Sumitomo Rubber Industries Ltd. discloses
a technology concerning the number and positions of reinforcing
structures for a bead, and Japanese Patent Application
Publication No. 1999-020423 filed by BRIDGESTONE CORP.
discloses a technology concerning an attachment position of a
steel chafer. Korean Patent Application Publication No. 2012-

0063901 discloses a technology in which a plate member is
provided in an inner side of a bead core in order to prevent
bead wires in the bead core from collapsing and prevent the
bead core from coming into contact with a carcass.
As disclosed in the conventional arts, there is a
technological trend toward slight reduction in accidents
associated with a bead, such as reduction in problems at a
turn-up edge and in breaking down of a carcass. However, a
fundamental solution to problems occurring in the bead is
needed. Especially in a market in which tires that can endure
over a 150% load and over 14 bars of tire pressure are
demanded, such as China where conventional beads having a well-
known structure cannot meet the demand. Accordingly, it is
necessary to develop a bead which is fundamentally improved in
structure.
The foregoing is intended merely to aid in the
understanding of the background of the present invention, and
is not intended to mean that the present invention falls
within the purview of the related art that is already known to
those skilled in the art.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping
in mind the above problems occurring in the related art, and

the present invention is intended to propose a bead reinforcing
structure for a heavy duty tire which can greatly alleviate
concentration of stress on the edge of a carcass, and
fundamentally prevent breaking down of the carcass attributable
to the edge of a bead core coming into contact with the
carcass.
According to one aspect of the present invention, there is
provided a bead reinforcing structure for a heavy duty tire
having a bead in which a carcass is turned up to surround a
bead core, the bead reinforcing structure being configured such
that inside and outside steel chafers having predetermined
inclination angles are disposed inside and outside the carcass,
respectively to reinforce the carcass from both the inside and
outside of the carcass.
The inside and outside steel chafers may intersect each
other, forming opposite angles in the range of 0° to 90°
therebetween.
The inside and outside steel chafers may have
corresponding angles in the same direction, and the
corresponding angles are in the range of 0° to 90°.
A height of an end of the inside steel chafer which is
near an end of the carcass may be higher or lower than that of
the end of the carcass and a height of an end of the outside
steel chafer which is near the end of the carcass may be higher
or lower than that of the end of the carcass.

The bead reinforcing structure for a heavy duty tire
according to the present invention reinforces a bead with use
of a double steel chafer structure. Accordingly, it is
possible to minimize deformation, like bending, of the bead
attributable to external force and tire pressure. Moreover, it
is possible to distribute stress by adopting a structure in
which the rigidity of the bead reinforcing structure gradually
decreases for every unit length from the bead core to a
sidewall. Furthermore, it is possible to minimize deformation
of the bead, such as decrease in thickness of the bead,
attributable to external force or heat.
Yet furthermore, since two steel chafers are arranged to
intersect each other to form opposite angles therebetween or to
extend in parallel with each other to form corresponding
angles, and the inside chafer and the outside chafer limit
movement of a carcass by encaging the carcass in therebetween,
it is possible to minimize stress applied to an end of the
carcass.
Yet furthermore, the structure having opposite angles
minimizes deformation of a tire in a widthwise direction even
under a heavy load, reducing stress applied to the end of
carcass. This leads to an extended lifespan of the bead. Yet
furthermore, since the steel chafers arranged to have opposite
angles therebetween restrain each other under driving or
braking torque during the traveling of a vehicle, the bead

reinforcing structure according to the present invention can
prolong the lifespan of the carcass.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and other advantages
of the present invention will be more clearly understood from
the following detailed description when taken in conjunction
with the accompanying drawings, in which:
FIG. 1 is an enlarged cross-sectional view illustrating a
bead reinforcing structure for a heavy duty tire according to
one embodiment of the present invention;
FIG. 2 is an enlarged side view illustrating the bead
reinforcing structure for a heavy duty tire according to the
embodiment of the present invention; and
FIG. 3 is an enlarged side view illustrating a bead
reinforcing structure for a heavy duty tire according to
another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Hereinbelow, preferred embodiments of the present
invention will be described in detail with reference to the
accompanying drawings. A description on the embodiments of the
present invention does not cover details of functions and

constructions which are well known in the art.
An embodiment of the present invention relates to a bead
reinforcing structure for a heavy duty tire having a bead in
which a carcass is turned up to surround a bead core. The bead
reinforcing structure has a double reinforcing structure which
reinforces a heavy duty tire from inside and outside the
carcass, using an inside steel chafer and an outside steel
chafer.
FIG. 1 is an enlarged cross-sectional view illustrating a
bead reinforcing structure for a heavy duty tire according to
one embodiment of the present invention, and FIG. 2 is an
enlarged side view illustrating the bead reinforcing structure
for a heavy duty tire according to the present embodiment of
the present invention. With reference to FIGS. 1 and 2, the
bead reinforcing structure for a heavy duty tire according to
the present embodiment includes an inside steel chafer 3 having
a predetermined inclination angle which is disposed inside a
carcass 1, and an outside steel chafer 2 having a predetermined
inclination angle which is disposed outside the carcass 1. The
two steel chafers 2 and 3 and the carcass 1 are superimposed on
one another while the carcass 1 is disposed between the steel
chafers 2 and 3. A laminate made up of the two steel chafers 2
and 3 and the carcass 1 is turned up in a position at which a
bead core 4 is located, forming a reinforcing structure.
With reference to FIG. 2, the inside steel chafer 3 and

the outside steel chafer 2 are arranged to incline with respect
to a vertical or horizontal direction but in opposite
inclination directions. That is, the inside steel chafer 3 and
the outside steel chafer 2 intersect each other, forming
opposite angles in the range of 0° to 90° therebetween. In
this structure, the carcass 1 is disposed between steel cords
arranged to have opposite angles therebetween.
In this condition, directions of force acting on the steel
cords are opposite so as to be offset, and thus the steel cords
with a zero angle confine the carcass 1 therebetween,
minimizing stress applied to an end 5 of the carcass 1. This
double steel chafer, including two . steel chafers 2 and 3,
restrain each other under load and thus minimizes deformation
of the carcass 1 in a width direction. This leads to a
decrease in displacement of the carcass 1. For this reason,
stress concentrating on the end 5 of the carcass 1 is
minimized.
Occasionally, the carcass breaks down, which means that
the carcass among the bead cores and the carcass in the bead
breaks down. In the bead reinforcing structure according to
the present embodiment, since the carcass 1 does not come into
direct contact with the bead cores 4, fatigue performance of
the carcass 1 increases and wear of the carcass 1 is prevented.
This fundamentally prevents breaking down of the carcass 1.
According to the present embodiment, a position of a

turned-up end of the inside steel chafer 3 may be higher or
lower than the end 5 of the carcass 1. In a tire according to
a related art, the carcass has only one end. Accordingly, most
failures of the bead are attributed to stress concentrating on
the end of the carcass. In the bead reinforcing structure
according to the present embodiment, the end of the inside
steel chafer 3 is higher or lower than the end 5 of the carcass
1 in a position located outside the bead. Accordingly, it is
possible to distribute the stress which is likely to
concentrate on the end 5 of the carcass 1 and thus to reduce
the stress at the inside steel chafer 3 which is unlikely to
receive strong shearing force and tensile force attributable to
tire pressure, resulting in reduction in the stress applied to
the end 5 of the carcass 1.
A turned-up end of the outside steel chafer 2 may be
higher or lower than the end 5 of the carcass 1. That is, it
does not matter if the turned-up end of the outside steel
chafer 2 is higher or lower than the end 5 of the carcass 1.
The structure in which the turned-up end of the outside steel
chafer 2 is higher than the end 5 of the carcass 1 can prevent
concentration of stress, and the structure in which the turned-
up end of the outside steel chafer 2 is lower than the end 5 of
the carcass 1 is advantageous in terms of reinforcement
complementation of the bead.. Both structures have their own
advantages, and any structure that is demanded under market

conditions may be adopted.
According to the present embodiment, it is preferable that
a step difference between a turned-up portion and a turned-down
portion of the inside steel chafer 3 and the outside steel
chafer 2 be at least 10 mm to alleviate concentration of the
stress. Here, the term "step difference" means a difference
between the heights of the ends of the outside steel chafer and
the carcass, and it is undesirable that both of the ends are
positioned with zero step difference. When both of the ends
are flush with each other, such a structure is likely to lead
to defective products in a manufacturing process and an
increase in radial and level force variations, which is
disadvantageous in terms of stress concentration.
FIG. 3 is an enlarged side view illustrating a bead
reinforcing structure for a heavy duty tire according to
another embodiment of the present invention.
In the present embodiment, two steel chafers 2 and 3
disposed outside and inside a carcass 1 incline at
corresponding angles, and restrain the carcass 1 interposed
therebetween. The outside steel chafer 2 and the inside steel
chafer 3 reduce stress applied to an end 5 of the carcass 5.
However, the other portions in the present embodiment are
similar to those in the embodiment illustrated in FIG. 2 and
exhibit the same advantageous effect as those in the embodiment
illustrated in FIG. 2.

The bead reinforcing structure according to the present
invention can be applied to both types of tires, i.e., tube-
type tires and tubeless-type tires. The bead reinforcing
structure according to the present invention is a structure
that can prevent carcass edge separation attributable to
excessive air pressure and overload and prevent the carcass
breaking down, and thus can be applied to tires.
In terms of the distribution of the rigidity of the bead,
the distribution of the rigidity of the bead reinforcing
structure is continuous from the bead core at which the
rigidity is highest to a side wall at which the rigidity is
lowest. The bead reinforcing structure according to the
present invention has a rigidity which gradually decreases for
every unit length from the bead core to the side wall. This
has the advantage of prolonging the lifespan of the bead.
The bead reinforcing structure according to the present
invention contributes to improvement in the safety margin of
the carcass of the bead.
Although a preferred embodiment of the present invention
has been described for illustrative purposes, those skilled in
the art will appreciate that various modifications, additions
and substitutions are possible, without departing from the
scope and spirit of the invention as disclosed in the
accompanying claims.

WHAT IS CLAIMED IS:
1. A bead reinforcing structure for a heavy duty tire
having a bead in which a carcass is turned up to surround a
bead core, the bead reinforcing structure comprising:
a carcass; and
an inside steel chafer having a predetermined inclination
angle and an outside steel chafer having a predetermined
inclination angle, the inside and outside steel chafers being
disposed inside and outside the carcass, respectively, thereby
reinforcing the bead from the inside and outside of the
carcass.
2. The bead reinforcing structure for a heavy duty tire
according to claim 1, wherein the inside steel chafer and the
outside steel chafer intersect each other, forming opposite
angles in a range of 0° to 90° therebetween.
3. The bead reinforcing structure for a heavy duty tire
according to claim 1, wherein the inside steel chafer and the
outside steel chafer have corresponding angles in the same
direction, and the corresponding angles are in a range of 0° to
90°.
4. The bead reinforcing structure for a heavy duty tire

according to any one of claims 1 to 3, wherein a height of an
end of the inside steel chafer which is near an end of the
carcass is higher or lower than that of the end of the carcass.
5. The bead reinforcing structure for a heavy duty tire
according to any one of claims 1 to 3, wherein a height of an
end of the outside steel chafer which is near the end of the
carcass is higher or lower than that of the end of the carcass.

ABSTRACT

Disclosed is a bead reinforcing structure for a heavy duty
tire having a bead in which a carcass is turned up to surround
a bead core. The bead reinforcing structure includes a
carcass, and an inside steel chafer having a first
predetermined inclination angle and an outside steel chafer
having a second predetermined inclination angle. The inside
and outside steel chafers are disposed inside and outside the
carcass, respectively, thereby reinforcing the bead from the
inside and outside of the carcass.