FORM 2
THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13) 1. Title of the invention: BEAD CONSTRUCTION IN RADIAL TIRES
2. Applicant(s)

NAME NATIONALITY ADDRESS
CEAT LIMITED Indian RPG HOUSE, 463, Dr. Annie Besant Road, Worli, Mumbai 400 007, Maharashtra, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

FIELD OF INVENTION
[0001] The subject matter described herein, in general, relates to pneumatic radial tires, and in particular relates to bead construction in pneumatic radial tires for heavy-duty vehicles.
BACKGROUND
[0002] Pneumatic radial tires are commonly used in heavy-duty vehicles, such as trucks or buses, to meet the modern-day transportation needs. The pneumatic radial tires have metal cords and are wear and puncture resistant. Further, the pneumatic radial tires are continuously improving for good, smooth roads with safe and efficient operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The following detailed description references the drawings, wherein:
[0004] FIG. 1 shows a cross sectional view of a bead portion of a pneumatic radial tire, as per an implementation of the present subject matter;
[0005] FIG. 2 shows a schematic view of the steel ply, the bead core, and the dislocation direction of the steel ply along the bead core;
[0006] FIG.3 shows a cross sectional view of the bead portion of the pneumatic radial tire highlighting a height of a tip of a chipper, as per an implementation of the present subject matter; and
[0007] FIG.4 shows a schematic view of a variation of the angle θ with respect to the height of the tip of the turn-up portion of the steel ply, as per an implementation of the present subject matter.
DETAILED DESCRIPTION
[0008] The present subject matter relates to bead construction in pneumatic radial tires for improving bead durability by optimizing a steel ply profile. The present subject matter describes limiting heights of a tip of

a turn-up portion and a tip of a chipper in a pneumatic radial tire to prevent separation of layers.
[0009] A pneumatic radial tire for a heavy-duty vehicle include a steel
ply that moves perpendicular to a tread of the tire and radially from one bead core to another bead core in the tire. An area adjacent to the bead core is filled with a rubber of different hardnesses. Further, a reinforcing layer of steel cords surrounds the steel ply for providing better strength to a bead area. However, stress concentrations developed at the ends of the reinforcing layers cause separation and rupture of the steel ply.
[0010] Conventionally, some improvement in reinforcing bead
sections of pneumatic radial tires may be provided with a carcass ply. The carcass ply may be made of steel cords. For example, US Patent US4688616 describes that by reinforcing an axially outer side and an inner side of a bead region of a pneumatic radial tire with same organic fibre cord reinforcing layer, the expansion of the steel ply at the stress concentration is effectively mitigated, thereby controlling of the crack failure or separation at the steel ply ends.
[0011] Generally, the bead construction of a pneumatic radial tire
includes a steel ply. The steel ply is turned up around a pair of bead cores from an inside portion to an outside portion with respect to an axial direction of the tire. Further, an additional layer of a steel cord, known as a chipper, is reinforced around the steel ply.
[0012] A pneumatic radial tire used in a heavy-duty vehicle, such as a
truck, is subjected to frequent acceleration and braking with heavy load tending the steel ply to remove or dislocate from the bead core due to repetitive stretching stresses and high stress concentration at the tip of the turn-up portion of the steel ply. Such a stress concentration causes separation and rupture of the steel ply. The optimization of the height of the tip of the turn up portion of the steel ply within a range from 40 mm to 50 mm from the centre of the bead core may prevent the steel ply pull-out-

structure failure in the bead area, but does not guarantee to solve the problem which might be fatal.
[0013] The present subject matter describes approaches for improved bead construction of pneumatic radial tires which substantially prevents peeling of a steel ply (carcass ply) at a turn-portion of the steel ply and peeling of a steel cord reinforcing layer.
[0014] The present subject matter describes pneumatic radial tires for heavy-duty vehicles, such as trucks. In accordance with the present subject matter, a pneumatic radial tire includes: a pair of bead cores; a steel ply at a core of the pneumatic radial tire, enveloping a bead core from one bead core to another bead core; a steel cord reinforcing layer (called a chipper) positioned adjacent to the steel ply; a tread portion; a bead base; and a pair sidewall. The steel ply has a turn-up portion enveloping a bead core. A tip of the turn-up portion is at a height T from a bead core centre in a range from 40 mm to 50 mm.
[0015] Further, a line joining the tip of the turn-up portion and a point of the steel ply at a bead core centre line subtends an angle d with respect to the bead core centre line in a range from 66º to 71º, such that T=
0.0039θ2-2.5611θ+201.96 and
D=0.0179θ2-2.860θ+115.99 .
Herein, D is a maximum disposition distance of the steel ply from the line joining the tip of the turn-up portion and the point of the steel ply at the bead core centre line. In an example, D is a maximum disposition distance of the steel ply from a point on the line joining the tip of the turn-up portion and the point of the steel ply at the bead core centre line, where the point on the line is at a height H from the bead core centre line, such that H/T = 0.5.
[0016] In an example implementation of the present subject matter, the chipper has a tip at a height C from the bead core centre line, such that 0.7 ≤ C/T ≤ 0.8. Further, the pneumatic radial tire is made of rubber with different Shore A hardnesses in different portions. In an example, the

rubber provided at a region adjacent to the bead core is hard and has a Shore A hardness in a range from 75- 85. In an example, the rubber provided at a region, adjacent to the hard rubber, between the tip of the turn-up portion and the steel ply is soft and has a Shore A hardness within the range from 55 to 65.
[0017] With the above disclosed implementations of the present
subject matter, the turn-up portion of the steel ply from the bead core centre to the tip of the turn-up portion follows a particular pattern defined by the curve and constraints, as described above. This efficiently eliminates the slippage of the steel ply from the bead core and also eliminates the stresses and strains that are developed due to the shearing and straining at the turn-up portion of the steel ply in the bead area.
[0018] The above-mentioned implementations are further described
herein with reference to the accompanying figures. It should be noted that the description and figures relate to exemplary implementations and should not be construed as a limitation to the present subject matter. It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and embodiments of the present subject matter, as well as specific examples, are intended to encompass equivalents thereof.
[0019] FIG. 1 shows a cross sectional view of a bead portion of a
pneumatic radial tire 100, as per an implementation of the present subject matter. The pneumatic radial tire 100, hereinafter referred to as the tire 100, includes two bead cores and a steel ply at a core of the tire 100, wherein the steel ply at each of its ends has a turn-up portion enveloping one of the bead cores. Although the tire 100 includes two bead cores, FIG.1 shows one of the bead cores and the steel ply at the core of the tire.
[0020] As shown in FIG. 1, the tire 100 has an inner side wall 1 and
an outer side wall 1’. The tire 100 includes a bead core 3 composed of

steel wires in varying numbers. The bead core 3 forms a loop in a bead area of the tire 100 that seals against a rim and forms an anchor on which a body ply of the tire 100 is wound. The steel ply 2, at the core of the tire 100, includes a turn-up portion enveloping the bead core 3 from an inner side to an outer side. The steel ply 2 is made of steel cords that gives sufficient strength to hold air pressure and also providing impact resistance to the outer side wall 1’ of the tire 100. The outer side wall 1’ protects the steel ply 2 from flex fatigue and abrasion.
[0021] Further, the tire 100 includes a steel cord reinforcing layer 4.
The steel cord reinforcing layer 4 is also referred as a chipper 4. The chipper 4 is positioned adjacent to the steel ply 2. The chipper 4 is provided to prevent slipping of the steel ply 2 in the tire 100.
[0022] The turn-up portion of the steel ply 2 has a tip 2’ at a height T
from a bead core centre 7 (or from a bead core centre line (Line 1)) in a range from 40 mm to 50 mm. When the height T of the tip 2’ is less than 40 mm from the bead core centre line (Line 1), the bead core area is less rigid and less wear resistant. When the height T of the tip 2’ is less than 40 mm from the bead core centre line (Line 1), the bonding of the steel ply 2 with the other components in the tire 100 reduces, thereby causing the slippage of the steel ply 2 from the bead core 3. FIG. 2 shows a schematic view of the steel ply 2 and the bead core 3 and the dislocation direction of the steel ply 2 along the bead core 3. Fig. 2 illustrates the height T of the tip 2’ of the turn-up portion of the steel ply 2 is less than 40 mm from the bead core centre line (Line 1). With this, when the tire is loaded, the steel ply 2 tends to move upward along a direction indicated by arrow 6 and the turn-up portion of the steel ply tends to move downward along a direction indicated by arrow 5 causing slippage of the steel ply 2 from the bead core 3. This causes straining in the bead core area and due to the slippage shearing takes place around the bead core 3 as the bead core 3 tends to rotate clockwise. Further, when the height T of the tip 2’ is greater than 50

mm from the bead core centre line (Line 1), the flexure becomes more severe causing the generation of crack at that point, and rigidity of the tire 100 becomes different.
[0023] Further, a line (Line 2) joining the tip 2’ of the turn-up portion
and a point O of the steel ply 2 at the bead core centre line (Line 1) subtends an angle θ with respect to the bead core centre line (Line 1) in a range from 66º to 71º, such that:
, and ,
wherein D is a maximum disposition distance of the steel ply 2 from the line (Line 2) joining the tip 2’ of the turn-up portion and the point O of the steel ply 2 at the bead core centre line (Line 1). The point O is at an outer side of the steel ply 2 at the bead core centre line (Line 1). D is the maximum disposition distance of the steel ply 2 from a point on the line (Line 2) joining the tip 2’ of the turn-up portion and the point O of the steel ply 2 at the bead core centre line (Line 1), where the point on the line (Line 2) is at a height H from the bead core centre line (Line 1), such that H/T = 0.5.
[0024] The abovementioned equations are obtained from graphs
plotted for T and D, respectively, with respect to angle θ, where angle θ varies from 66º to 71º. These equations give the profile of the turn-up portion of the steel ply 2 (body ply line) from the bead core centre 7. At a particular angle θ, the equations give the height T of the tip 2’ from Line 1 and the disposition distance D of the turn-up portion from Line 2.
[0025] FIG.3 shows a cross sectional view of the bead portion of the
tire 100 highlighting a height of a tip of the chipper 4, as per an implementation of the present subject matter. The chipper 4 has a tip 4’ interfacing the turn-up portion. Another tip 4’’ of the chipper 4 interfaces the steel ply 2 from the other end. The tip 4’ is at a height C from the bead

core centre line (Line 1), such that 0.7 ≤ C/T ≤ 0.8. Thus, the height C of the tip 4’ is less than the height T of the tip 2’.
[0026] When C/T is less than 0.7, the resistance to wear is lowered due to the decrease in rigidity of the bead section. When C/T is higher than 0.8, separation of the steel ply and the surrounding rubber occurs early. When C/T is greater than 0.8 or equal to 1, then the overlapping of the steel ply and the chipper causes stress concentration, thereby inducing early bead failure.
[0027] FIG.4 shows a schematic view of a variation of the angle θ with respect to the height T of the tip 2’ of the turn-up portion of the steel ply 2, as per an implementation of the present subject matter. The angle θ varies between θmax and θmin. θmax is 71º and θmin is 66º. As the angle θ decreases, the height T increases.
[0028] For confirmation of the effect of the present subject matter, the durability of the tire 100 has been tested with more than 15 embodiments of 10.00R20 radial tires with θ variation from 66° to 71°. While examining the durability, the time for any damage in the bead area occurs is measured under drum test condition of 3000 kg load on tire, running speed of 80km/h and internal pressure of 80 psi. The endurance test results for various experiments at random angles within the range 66° to 71 ° showed consistent results for 58 hrs to 65 hrs of the running of the tire 100.
[0029] The apex area between the steel ply 2 and the turn-up portion of the steel ply 2 is composed of hard and soft apex of rubber having different hardnesses, in order to enhance the bead durability. It may be noted that the tire 100 is made of rubber. The tire 100 at a region (hard apex) adjacent to the bead core 3 is made of a first rubber having Shore A hardness within a range from 75 to 85. The flexibility of the tire 100 is gradually decreased preventing premature failure in the bead area. Also, the tire 100 at a region (soft apex) adjacent to the first rubber and between

the tip 2’ of the turn-up portion and the steel ply 2 is made of a second rubber having Shore A hardness within a range from 55 to 65. The region made of the second rubber gives a damper effect thus increasing the durability of the bead area of the tire 100.
[0030] Although implementations of pneumatic radial tires for
improvement of bead durability are described, it is to be understood that the present subject matter is not necessarily limited to the specific features described. The specific features of pneumatic radial tires are disclosed as example implementations.

I/We Claim:
1. A pneumatic radial tire comprising:
a bead core (3); and
, and ,
a steel ply (2) at a core of the pneumatic radial tire, the steel ply (2) including a turn-up portion enveloping the bead core (3), wherein the turn-up portion has a tip (2’) at a height (T) from a bead core centre (7) in a range from 40 mm to 50 mm, and wherein a line (Line 2) joining the tip (2’) of the turn-up portion and a point (O) of the steel ply (2) at a bead core centre line (Line 1) subtends an angle (θ) with respect to the bead core centre line (Line 1) in a range from 66º to 71º, such that:
T=0.0039θ2-2.5611θ+201.96, and
D=0.0179θ2-2.860θ+115.99, ,
wherein D is a maximum disposition distance of the steel ply (2) from the line (Line 2) joining the tip (2’) of the turn-up portion and the point (O) of the steel ply (2) at the bead core centre line (Line 1).
2. The pneumatic radial tire as claimed in claim 1, wherein the pneumatic
radial tire comprises a steel cord reinforcing layer (4) positioned adjacent
to the steel ply (2), wherein the steel cord reinforcing layer (4) has a tip
(4’), interfacing the turn-up portion, at a height (C) from the bead core
centre line (Line 1), such that 0.7 ≤ C/T ≤ 0.8.
3. The pneumatic radial tire as claimed in claim 1, wherein D is the
maximum disposition distance of the steel ply (2) from a point on the line
(Line 2) joining the tip (2’) of the turn-up portion and the point (O) of the
steel ply (2) at the bead core centre line (Line 1), the point on the line
(Line 2) being at a height (H) from the bead core centre line (Line 1), such
that H/T = 0.5.
4. The pneumatic radial tire as claimed in claim 1, wherein the pneumatic
radial tire at a region adjacent to the bead core (3) is made of a first rubber
having a Shore A hardness in a range from 75 to 85.

5. The pneumatic radial tire as claimed in claim 4, wherein the pneumatic radial tire at a region adjacent to the first rubber and between the tip (2’) of the turn-up portion and the steel ply (2) is made of a second rubber having a Shore A hardness in a range from 55 to 65.