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: PNEUMATIC TIRE
2. Applicant(s)
NAME NATIONALITY ADDRESS
CEAT LIMITED Indian CEAT Ltd At: Get Muwala Po: Chandrapura Ta: Halol - 389 350 Dist: Panchmahal, Gujarat, 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.

TECHNICAL FIELD
[0001] The subject matter described herein, in general, relates to radial
tires, and in particular, relates to bead structure in the radial tires.
BACKGROUND
[0002] Radial tires are an essential requirement in passenger cars,
sports utility vehicles (SUVs), commercial vans, light trucks, trailers, commercial trucks, buses, etc., to meet modern transportation needs. Further, the radial tires are continuously being improvised for safe and efficient operation.
[0003] A radial tire is an assembly of numerous components such as
sidewalls, plies, bead, inner liner, belt system, treads, etc. The bead is made up of bands of high tensile-strength steel wires, which lie in a bead core of the radial tire and connects the radial tire to a wheel rim and hold the entire wheel together. The steel wires move perpendicular to the tread and radially from one bead core to another bead core. An area adjacent to the bead core is filled with rubber having a hardness different from that of the bead core. Furthermore, a reinforcing layer of the steel wires surrounds the plies for providing better strength to the bead core.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The detailed description is described with reference to the
accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.
[0005] Figure 1 is a prior art figure that illustrates a half cross-sectional
view of a conventional radial tire ranging from a sidewall portion to a bead portion and superimposed onto a wheel rim in a loaded condition;
[0006] Figure 2 shows a half cross-sectional view of a radial tire ranging
from a sidewall portion to a bead portion and superimposed onto the wheel

rim in an unloaded condition, in accordance with an implementation of the
present subject matter;
[0007] Figure 3 shows the half cross-sectional view of the radial tire
ranging from the sidewall portion to the bead portion and superimposed onto
the wheel rim in a loaded condition, in accordance with another
implementation of the present subject matter;
[0008] Figure 4 shows the half cross-sectional view of the radial tire
ranging from the sidewall portion to the bead portion and superimposed onto
the wheel rim in loaded condition, in accordance with another
implementation of the present subject matter; and
[0009] Figure 5 shows the half cross-sectional view of the radial tire
ranging from the sidewall portion to the bead portion and superimposed onto
the wheel rim in unloaded condition, in accordance with yet another
implementation of the present subject matter.
DETAILED DESCRIPTION
[0010] The present invention relates to maximizing the durability of a
bead portion of a radial tire (hereinafter referred to as tire), in accordance with the present subject matter.
[0011] Generally, a tire consists of a bead portion, wherein the bead
portion closely contacts with a bead seat of a wheel rim when the tire is mounted on the wheel rim of a vehicle and provides a tight air sealing effect. A carcass ply is wrapped over the bead portion of the tire such that, a space, approximately of a triangular cross-section, is created, on a radially inner side of a bead core. For the stability of the tire, this space is filled and preferably reinforced, by a "bead filler" component.
[0012] The bead portion is expected to be formed in such a manner that,
when the tire is mounted on the wheel rim, it enables the conformation of the tire in the shape of the wheel rim without displacing the bead core or significantly reducing the seating pressures at the tire to rim interface. The design of the bead portion also has a direct effect on the handling

performance of the vehicle. Also, a lateral movement(s) of the vehicle is directly influenced by the lateral stiffness of the tire. The tire's lateral stiffness is greatly influenced by the bead portion design. Bending elasticity of the lower bead portion of the tire with respect to the wheel rim is a major factor in the lateral stiffness of the tire. The radial stiffness of the tire also has a direct effect on the ride comfort of the vehicle.
[0013] As shown in prior art Figure 1, when a conventional tire 100
(radial) is mounted onto a wheel rim 102, generally three forces act on the tire 100 at the tire 100 and the wheel rim 102 interaction point, namely inflation force FI in a lateral direction that is exerted by inflation pressure created in a cavity of the tire 100 when the tire 100 is inflated; lateral loading force FL exerted in the lateral direction by weight of the vehicle when the tire 100 is mounted onto the wheel rim 102 and is fitted into the vehicle; and vertical loading force FV exerted in a vertical direction by the wheel rim 102 against a portion of the tire 100 contacting the wheel rim 102.
[0014] Generally, a profile of a bead portion 104 of the conventional tire
100 is such that, in a loaded condition, interference in a lateral direction is higher which in the presence of the vertical loading force FV gets worse, thereby leading to a rim digging phenomenon that may cause bead portion failure. For example, due to the rim digging, the bead portion 104 of the tire 100 may get torn away from the wheel rim 102 and slip from a flange 106 of the wheel rim 102.
[0015] Bead portion failure may cause loss of air pressure in the tire 100
as well as detachment of the tire 100 from the wheel rim 102. Bead failure may also cause loss of vehicle control and, possibly, an accident. Data suggests that users of the conventional tires face early bead portion failures at around merely 30% wear in overload conditions, thereby leading to lower tire life and higher cost of operation for the users of such tires.
[0016] Further, a non-uniform tire-rim interference along a ledge of the
wheel rim 102 may cause heat generation from the flange 106 of the wheel rim 102 when the tire 100 is in the loaded condition. This heat gets

transferred to abrasion gum strips (AGS) 108 that are generally provided as a layer of rubber in the tire 100 between carcass plies 110 and the wheel rim 102 for resistance against abrasion. Since the AGS 108 remains in direct contact with chafer turn-up 112, which is applied to the bead portion 104 for protection against the wheel rim chafing and other external damages, it creates higher shear stress between the AGS 108 and the chafer turn-up 112 due to acceleration and braking effect, thereby causing an early separation of the bead portion 104.
[0017] To this end, approaches for a tire to have bead portion with high
durability are discussed, which substantially prevent the damage to or separation of the bead portion, which are fatal flaws in the conventional radial tires for light-duty vehicles, such as light-duty trucks.
[0018] An implementation of the present subject matter describes a
radial pneumatic tire. The tire has a tread portion and a pair of sidewall portions provided on either side of the tread portion. Each of the pair of sidewall portions comprises a curved profile that is formed along an outer circumferential layer of the sidewall portion. The curved profile is such that it bulges in a lateral cross-sectional direction of the tire. Each of the pair of sidewall portions also includes a bead portion that is located at a distal end of the respective sidewall portion. The bead portion comprises a bead core and one or more carcass plies that are wounded outwardly around the bead core. These carcass plies extend toward the tread portion of the tire and together form a layer of turn-up portion that terminates at a turn-up end along the sidewall portion of the tire.
[0019] The bead portion further comprises a unique turn-up shield that
is located at a predefined distance relative to a base of the bead portion.
The turn-up shield covers the outermost layer of the turn-up portion.
[0020] Therefore, described herein, a tire consisting of a negative profile
in the sidewall region of the tire which, in the unloaded condition, provides higher interference between the tire and the wheel rim, however, in the loaded condition, nullifies the interference. Since there is no interference

between the tire and the wheel rim in the loaded condition, the tire takes the shape of the rim flange and hence the rim digging failure is avoided. Also, the unique turn-up shield profile delays the heat transfer between the AGS and the chafer turn-up. Implementation of the present subject matter thus eliminates the stresses and strains that are developed due to the shearing and straining at the turn-up portion in the bead portion and prolongs the life of the tire.
[0021] 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.
[0022] Figure 2 shows a half cross-sectional view of a radial tire 200
ranging from a sidewall portion 202 to a bead portion 204 and has the bead portion 204 superimposed onto a wheel rim 206 in an unloaded condition, in accordance with an implementation of the present subject matter. The bead portion 204 is located at a distal end of the sidewall portion 202 of the tire 200. The tire 200 also includes a tread portion (not illustrated) constituting a tread surface for contacting a ground surface to support a vehicle by transferring vehicular loads from the wheel rim 206 through the tire 200 to the ground surface.
[0023] The tire 200 further comprises a bead core 208 for use in light-
duty vehicles, as per implementation of the present subject matter. The bead core 208 may be composed of steel wires in varying numbers to form a loop in the bead portion 204 that seats against the wheel rim 206 and forms an anchor around one or more carcass plies 210. The carcass plies 210 are wounded to encapsulate the bead core 208 from an inner side to

an outer side forming the body of the tire 200. Also, the carcass plies 210 are wounded outwardly about the bead core 208 in such a manner that it extends toward the tread portion to form a layer of turn-up portion 216 that terminates at a turn-up end 218.
[0024] The sidewall portion 202 comprises a curved profile 212 that is
formed along an outer circumferential layer of the sidewall portion 202. The curved profile 212 bulges in a lateral cross-sectional direction of the tire 200. The curved profile 212 is provided in the tire 200 in such a way that in the unloaded condition it gives higher interference between the bead portion 204 of the tire 200 and flange 214 of the wheel rim 206. However, as shown in Figure 3, in a loaded condition, the bulged curved profile 212 adapts to the shape of the flange 214, thereby effectively nullifying the interference between the bead portion 204 of the tire 200 and the flange 214. Thus, the unique bulged or curved profile 212 enables the tire 200 to sit tightly onto the wheel rim 206, thereby reducing bead rotation or movements in the overload conditions. Accordingly, by implementing the present invention, the rim digging issue may be eliminated and thus the instances of the tire failure due to the rim digging may be minimized.
[0025] In an implementation of the present subject matter, the bead
portion 204 comprises a turn-up shield 220 that covers a chafer turn-up 222
forming the outermost layer of the turn-up portion 216. Thus, the present
invention maximizes the bead durability by protecting the chafer turn up 222
with an additional component, i.e., turn-up shield 220 against the pressure
exerted by the flange 214. Accordingly, this unique turn-up shield 220 near
the flange 214 area protects against the rim digging. Shear stress at chafer
turn-up 222 may lie in a range of -0.0053-0.0118 pascals, in an example.
[0026] Figure 4 illustrates the half cross-sectional view of the tire 200
ranging from the sidewall portion 202 to the bead portion 204 and superimposed onto the wheel rim 206 in a loaded condition, in accordance with an implementation of the present subject matter. As shown in Figure 4, the turn-up shield 220 is located at a predefined distance A relative to a

base 402 of the bead portion 204. A width C of the base 402 may lie in a range of 20-30 mm, for example. The turn-up shield 220 may be formed with a circular arc profile that bulges in the lateral cross-sectional direction of the tire 200. The circular arc profile of the turn-up shield 220 may have a height B in a range of 70-160% of the total width of the base 402, for example. With the use of the turn-up shield 220, direct contact between abrasion gum strips (AGS) 404 and the chafer turn-up 222 is avoided. Hence, the turn-up shield 220 helps minimize the shear stress at the chafer turn-up 222.
[0027] Further, the distance A of the turn-up shield 220 with respect to
the base 402 may lie in a range of 50-80% of the total width of the base 402.
[0028] Figure 5 illustrates the half cross-sectional view of the tire 200
ranging from the sidewall portion 202 to the bead portion 204 and superimposed onto the wheel rim 206 in an unloaded condition, in accordance with an implementation of the present subject matter. As shown in Figure 5, in the unloaded condition, there exists a higher tire-rim interference X between the flange 214 of the wheel rim 206 and the tire 200. This interference X however gets nullified when the tire 200 is in the loaded condition as shown in Figure 4.
[0029] In the conventional tires, the interference is very less which
causes additional pressure on the bead portion of the tire when the tire is inflated. Thus, the high interference X in the present invention allows the tire 200 additional space to adjust itself onto the wheel rim 206 without having to face the rim digging when in loaded condition. Also, since the tire 200 is able to fit properly onto the wheel rim 206, a tire-wheel rim movement will be restricted, which minizines the heat generation from the wheel rim 206 and the tire 200 friction.
[0030] Additionally, even if the tire-wheel rim movement occurs and, as
a result, the heat is generated, the turn-up shield 220 acts as a protection layer, thereby delaying the heat transfer between the AGS 404 and the chafer turn-up 222. This delay is basically promoted by the unique profile of

the turn-up shield 220 as shown in Figures 2-5. Further, the material of the turn-up shield maybe, but is not limited to, 100% natural rubber compound to reduce heat generation.
[0031] The interference X between the tire 200 and a wheel rim 206 onto
which the tire 200 may lie in a range of 2.5 to 4% of the total width of the base 402, for example. Further, the outer circumferential layer of the sidewall portion 202 may form an angle D of about 8-10 degrees outward from a line perpendicular to the base 402, for example. This deflection of the sidewall portion 202 enables the creation of the curved or bulged profile 212. The curved profile 212 bulges outside of the sidewall portion 202 thereby creating a space for the accommodation of the turn-up shield 220 in the tire 200, unlike the conventional tire where there is no or less space to accommodate turn-up shield 220. Also, due to the presence of the curved profile 212, the pressure exerted on the chafer turn-up 222 by the turn-up shield 220 in the loaded condition would be minimal.
[0032] In an example, the inventors of the present invention, through
simulation, have captured time-dependent changes in the fatigue crack growth rate law of the tire 200 discussed herein. It may also be coupled to a finite element solver to update stress and strain fields during the bead durability test. Table below shows simulated and actual tested life of the conventional and the tire 200:

Variant Simulated Life (in hours) Actual Tested Life (in hours)
Conventional Tire 57 60.5
Tire made as per the teachings of the present invention 76 72.0

[0033] It is to be understood that the shape of the tire 200 shown in the
figures of the present embodiment is in the shape of a bladder included in a
mold used for manufacturing the tire 200 and that the present shape of the
tire 100 is formed by unique bulged design of bladder of the mold.
[0034] The embodiments of this invention can be used in combination or
individually to form tires made by improved manufacturing processes and/or
with improved performance features. The combinations depend on the
intended use of the tire and include conventional as well as run-flat tire uses.
The overall design of the curved profile and the turn-up shield of the
invention disclosed herein results in a combination being an improved
process for making, namely but not exclusively, light-duty vehicle radial tires
having an improved bead portion durability, especially with a light-duty
vehicle designed tires and may also be used for other types of tires as well.
[0035] Although implementations for bead portion durability
improvement are described, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features are disclosed as implementations.

I/We Claim:
1. A tire (200) comprising:
a tread portion; and
a pair of sidewall portions (202) provided on either side of the tread portion, each of the pair of sidewall portions (202) comprising:
a curved profile (212) formed along an outer circumferential layer of the sidewall portion (202), wherein the curved profile (212) bulges in a lateral cross-sectional direction of the tire (200); and
a bead portion (204) located at a distal end of the sidewall portion (202), the bead portion (204) comprising: a bead core (208);
one or more carcass plies (210) wound outwardly about the bead core (208) and extends toward the tread portion to form a layer of turn-up portion (216) that terminates at a turn¬up end (218);
a turn-up shield (220) located at a predefined distance (A) relative to a base (402) of the bead portion (204), the turn¬up shield (220) is to cover outermost layer (222) of the turn¬up portion (216).
2. The tire (200) as claimed in claim 1, wherein a width (C) of the base (402) lies in a range of 20-30 mm.
3. The tire (200) as claimed in claim 1, wherein the turn-up shield (220) is formed with a circular arc profile that bulges in the lateral cross-sectional direction of the tire (200).
4. The tire as claimed in any claim 3, wherein a height (B) of the circular arc profile lies in a range of 70-160% of the width (C) of the base (402).

5. The tire (200) as claimed in any of claims 1-2, wherein the distance (A) of the turn-up shield (220) relative to the base (402) lies in a range of 50-80% of the width (C) of the base (402).
6. The tire (200) as claimed in any of claims 1-2, wherein interference (X) between the tire (200) and a wheel rim (206) onto which the tire (200) is to be mounted lies in a range of 2.5 to 4% of the width (C) of the base (402).
7. The tire (200) as claimed in claim 1, wherein shear stress at turn-up of the outermost layer (222) lies in a range of -0.0053-0.0118 pascals.
8. The tire (200) as claimed in claim 1, wherein the outer circumferential layer of the sidewall portion (202) forms an angle (D) of about 8-10 degrees outward from a line perpendicular to the base (402).
9. The tire (200) as claimed in claim 1, wherein the turn-up shield (220) is made up of a natural rubber compound.