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: A MOULD FOR CURING A GREEN 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 present subject matter relates, in general, to vehicle tires and,
particularly but not exclusively, to a tire mould that may be used in the manufacturing of tires.
BACKGROUND
[0002] Tires are a crucial component of an automobile. In an automobile, a tire is
responsible for a plurality of functions. A tire is required to conform to a plurality of industry and safety standards, owing to which, the steps involved in any tyre manufacturing process are considered crucial. A plurality of different components are designed and attached together to form a preliminary uncured tyre, which is referred to as green tire. The processed green tire, once obtained, is then cured in a curing apparatus, as a final step for tire manufacturing process. During curing, the green tire is subjected to high pressure in a mould, and heat may be applied, which in turn enables the chemical reactions between the rubber and other materials of the tire, and the tire is imprinted with tread pattern.
[0003] The mould used to accommodate a green tire for curing is generally an
assembly of multiple portions, for example, tread ring, side plates and bead rings. These components may be assembled together in a container to form a toroidal cavity to accommodate a green tire for curing. During curing of the green tire in the assembled mould, excess material such as rubber used in manufacturing of tire may protrude out of inside of the mould through the joints of the components of assembled mould.
BRIEF DESCRIPTION OF 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 illustrates a segment of a mould comprising protruded pattern on
an inner surface of the segment, according to a conventional configuration.
[0006] Figure 2 illustrates a segment of a mould comprising protruded pattern on
an inner surface of the segment, in accordance with an implementation of the present
subject matter.
[0007] Figure 3 illustrates a front view of a tire cured inside the mould comprising
a plurality of segments, in accordance with an implementation of the present subject
matter.
[0008] The figures are not necessarily to scale, and the size of some parts may be
exaggerated to more clearly illustrate the example shown. Moreover, the drawings
provide examples and/or implementations consistent with the description; however,
the description is not limited to the examples and/or implementations provided in the
drawings.
DETAILED DESCRIPTION
[0009] Conventionally, rubber, along with other materials, is used as a raw
material for manufacturing the tires. A plurality of different components may be designed and assembled together, using a variety of techniques which involve both chemical and physical processes. For example, the raw materials may be processed into different components to form a toroidal shaped preliminary uncured tire, which is also referred to as a green tire.
[0010] Green tire, once obtained, is cured by subjecting it to a curing process in a
curing apparatus. As would be understood, curing may refer to a process of applying pressure and heat energy to the green tire in the curing apparatus. The curing apparatus comprises a mould having a toroidal shaped mould cavity to accommodate a green tire. As mentioned above, multiple portions may be assembled together in a toroidal shape to form a mould. These portions may include a tread ring, side plates and a bead

ring to define a tread region, a sidewall region and a bead region, respectively of the tire. The tread ring may also comprise multiple segments to be joined together in a circular shape. Each of the multiple segments comprises a protruded pattern on its inner surface. During curing, the protruded pattern gets imprinted on the tread region of the tire under the action of heat and pressure. Application of pressure and heat energy to the green tire accommodated in the mould in the curing apparatus enables chemical reactions between the rubber and other materials, to obtain the final shape of the tire.
[0011] Figure 1 illustrates a segment 100 of a tread ring of a mould comprising
protruded pattern on an inner surface of the segment 100, according to a conventional configuration. The protruded pattern 102 corresponds to the tread pattern of tire that comprise circumferential and lateral grooves on the surface of the tire that comes in contact with the road during movement of the tire on a road surface. Within the circumferential grooves of the tread pattern of the tire, protrusions are formed at some certain locations. The height of these protrusions within the circumferential grooves is generally less than the depth of the groove such that upper surface of protrusions is below the surface of the tire. With the passage of time, as the tire moves on the road surface, the surface of the tire wears down and surface of the tire coincides with the upper surface of the protrusions. Thus, the protrusions in the circumferential groove provide an indication of the amount of remaining tire life and are known as tread wear indicators.
[0012] To allow formation of the tread wear indicators on cured tires, the
protruded pattern on the segments of the tire ring comprises depressions 104 at locations corresponding to the locations of the tread wear indicator on the circumferential grooves of the tire. The locations of the tread wear indicators on the circumferential grooves of the tire and correspondingly the location of the depression 104 in the protruded pattern on the segments of the tread ring are randomly distributed in the circumference. There is no basis for selection of the location for tread wear

indicators and as mentioned earlier, the tread wear indicators are randomly located in the circumferential grooves.
[0013] Generally, a small gap exists between each portion of the mould and
between each segment of the tread ring to accommodate metal expansion upon heating. When heat and pressure is applied to the green tire accommodated in the mould, excess material such as rubber may protrude out from the gaps between the portions of the mould and the segments of the tread ring, e.g., from the adjoining edges of the tread ring, the side plates, the bead ring and the segments of the tread ring. Excess material that protrudes out of these joints forms small protuberances on the surface of the tire after curing. The excess material that protrudes out of the joints between the adjoining edges 106-1, 106-2 of the segments 100 of the tread ring of the mould also forms small protuberances inside the circumferential grooves of the tread pattern of the tire after curing. Protuberances inside the circumferential groove may also be created at the adjoining edges 106-1, 106-2 of the segments 100 of the tread ring because of the improper matching of the protruded pattern 102 formed on the inner surface of the adjacent segments of the tread ring.
[0014] As would be generally understood, during vehicle operation, a tire is the
only source of contact between the vehicle and the road, owing to which, a plurality
of dynamics of the vehicle operation may be controlled by the tire. The tires may be
responsible for guiding and maintaining the alignment and movement of a vehicle
while driving. In addition, the tires contribute to the safety of the vehicle while
carrying loads, and when the automobile is to be halted by application of brakes.
[0015] Owing to the complexity of roles performed by the tires in a vehicle, it may
be crucial for tire manufacturers to conform to quality parameters during any tire manufacturing process. However, the small protuberances on the surface of the tire caused by the excess material that bulge out from the joints of the multiple portions of the mould during curing may affect the aesthetic appearance of the tire that is also not admissible. Further, protuberances formed inside the circumferential grooves of the

tire may affect the air channeling through the grooves of the tire resulting in an unpleasant noise during the movement of the tire on a road surface. Thus, these protuberances on the surface of the tire and inside the grooves of the tread pattern of the tire caused by the excess material needs to be trimmed or removed after the process of curing. Protuberances on the surface of the tire can be easily removed using suitable machinery. However, protuberances created inside the circumferential grooves are not accessible for trimming.
[0016] To this end, the present subject matter provides a mould for curing a green
tire that overcomes the above-described problems associated with trimming of protuberances formed inside circumferential grooves of a tread pattern of the tire caused by flow of excess material out of joints between various portions of the mould during curing of the tire.
[0017] In accordance with an embodiment of the present subject matter, a mould
for curing a green tire is disclosed. The mould includes a plurality of segments to be adjoined to create a circular cavity to accommodate the green tire. The plurality of segments comprises at least a first segment and a second segment. Further, each of the plurality of segments comprises a first end and a second end, such that the second end of the first segment and the first end of the second segment coincide with each other when the plurality of segments are adjoined. A protruded pattern is formed on an inner surface of the plurality of segments for defining a tread region of a cured tire. The protruded pattern corresponds to a tread pattern that is to be imprinted in the tread region of the cured tire. The protruded pattern formed on each of the plurality of segments comprises at least one protrusion formed between the first end and the second end of the respective segment for defining at least one circumferential groove of the tread region of the cured tire. The at least one protrusion comprises a cavity portion formed at the first end and the second end of the respective segment. The cavity portion formed at the second end of the first segment and the cavity portion formed at

the first end of the second segment together define a tread wear indicator to be formed in the cured tire.
[0018] As described above, conventionally, tread wear indicators are formed in
circumferential grooves of the tire at random locations distributed circumferentially
and a mould used during the curing process to cure the tire comprises multiple
segments having a protruded pattern on the internal surface of each segment to create
a tread pattern in a tread region of the cured tire. To form the tread wear indicators,
protrusions 102 in the protruded pattern corresponding to circumferential grooves of
the tire comprises cavities at some random locations 104 as indicated in Figure 1.
However, in addition to these tread wear indicators, small protuberances are formed
in the circumferential grooves of the cured tire at a location where the two segments
of the mould are adjoined because of the flow of excess material therefrom under the
application of heat and pressure during curing process. Conventionally, number of
tread wear indicator provided in a circumferential groove of the tire does not match
with the number of segments used to form the mould, hence a cavity to form tread
wear indicator on the adjoining edges of segments is not feasible to design.
[0019] In contrast, according to the mould disclosed in the present subject matter,
protrusions in the protruded pattern of each of the plurality of segments of the mould corresponding to circumferential grooves of the tire to be cured comprises cavity portions at both the ends of respective segment, i.e., at the first end and the second end of the respective segment in order to define a tread wear indicator. The cavity portions formed at the adjoining end of the two segments, i.e., at the second end of the first segment and at the first end of the second segment together define a cavity in the protrusion corresponding to a circumferential groove of the tire to accommodate the material of the tire to form a tread wear indicator in the circumferential grooves of the cured tire at the adjoining ends of the at least two segments of the mould. Thus, no unwanted protuberance is formed inside the circumferential grooves of the cured tire.

This obviates the need of trimming of the excess material in the circumferential
grooves of the cured tire at the adjoining ends of the segments of the mould.
[0020] The above and other features, aspects, and advantages of the subject matter
will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components.
[0021] Figure 2 illustrates a segment 200 of a mould comprising protruded pattern
202 on an inner surface 204 of the segment 200, in accordance with an implementation of the present subject matter. While Figure 3 illustrates a front view of a tire 300 cured inside the mould comprising a plurality of segments, in accordance with an implementation of the present subject matter. For the sake of ease of explanation Figure 2 and Figure 3 are explained together.
[0022] In an implementation of the present subject matter, the mould for curing
the green tire is disclosed. Raw material comprising rubber and other materials is used for manufacturing a tire. Different components of a tire such as inner liner, sidewalls, body plies, beads, belt package are assembled together using different techniques on a drum in a tire building machine. The tire thus manufactured in an uncured state is called a green tire. The green tire is cured in a curing apparatus by applying heat and pressure. The curing apparatus comprises a mould to accommodate the green tire. In an example, the mould may be of toroidal shape. The green tire to be subjected to curing may be placed inside the mould. The curing apparatus also comprises a heating

mechanism thermally coupled to the mould to provide heat to the green tire placed
inside the mould. Generally, the curing apparatus includes a curing bladder placed
along the axis of the mould to interface with the internal surface of the green tire to be
cured in order to exert a pressure on the green tire during the process of curing.
[0023] As described earlier, the mould for curing the green tire comprises a
plurality of segments to be adjoined to create a circular cavity to accommodate the green tire. The circular cavity is generally a toroidal shaped cavity. The plurality of segments comprises at least a first segment 200 and a second segment 200. Generally, there are 8 or 10 segments that make up the circular cavity when joined together. As will be understood by one skilled in the art, the number of the segments depends on the size of the mould and the corresponding tire and is not to be construed as a limitation.
[0024] The segments are symmetrical in shape and size with each of the plurality
of segments having two ends, namely, a first end 206-1 and a second end 206-2, such that the second end 206-2 of the first segment 200 and the first end 206-1 of the second segment 200 coincide with each other when the plurality of segments are adjoined to create the circular cavity. In an example, the mould also comprises a pair of circular side plates. Each side plate in the pair of circular side plates may be arranged radially inward along each side of each of the plurality of segments 200 for defining the circular cavity to accommodate the green tire. The mould may also comprise a pair of bead ring. Each of the bead ring in the pair of bead ring is arranged in each of the side plate in the pair of side plates.
[0025] As would be understood, a cured tire generally has a tread region, a
sidewall region on either side of the tread region and a bead region connected to the sidewall region. The tread region of the tire comprises a tread pattern formed by plurality of circumferential tread rows separated by circumferential grooves. Circumferential grooves may be understood as grooves in solid tread region of the tire along circumference or length of the tire. The tread pattern includes at least one

circumferential groove along circumference or length of the tire. The tread pattern of the tire also includes lateral or transverse grooves. The lateral or transverse grooves may be understood as plurality of grooves in the solid tread region of the tire along tread width of the tire. A lateral groove may extend from a circumferential groove to another circumferential groove along a width of the tire.
[0026] The pair of circular side plates defines a sidewall region of the tire to be
cured and the pair of bead rings arranged inside the pair of circular side plates defines a bead region of the tire. A protruded pattern 202 is formed on an inner surface 204 of the plurality of segments 200 of the mould for defining a tread region of a cured tire. The protruded pattern 202 corresponds to a tread pattern of the tire to be cured. The protruded pattern 202 formed on each of the plurality of segments 200 comprises at least one protrusion 202-1 formed between the first end 206-1 and the second end 206-2 of the respective segment 200 for defining at least one circumferential groove of the tread region of the cured tire. The at least one protrusion 202-1 comprises a cavity portion 208 formed at the first end 206-1 and the second end 206-2 of the respective segment 200. That is, a cavity portion 208 is created in the at least one protrusion 202-1 of each the plurality of segments 200 at both the ends 206-1, 206-2 of the respective segment 200. When the plurality of segments 200 are adjoined together, the cavity portions 208 formed at the adjoining ends 206-1, 206-2 of the two adjacent segments 200 interfaces with each other. Further, the cavity portion 208 formed at the second end 206-2 of the first segment 200 and the cavity portion 208 formed at the first end 206-1 of the second segment 200 together define a tread wear indicator to be formed in the cured tire. The tread wear indicator may be understood as a protrusion of a predetermined length and a predetermined height created inside at least one circumferential groove of the tire.
[0027] In an example, a length of the cavity portion 208 is in the range of 8 to 10
mm. As would be understood, the width of the tread wear indicator is same as the width of the circumferential groove of the tire, however height of the cavity portion is

designed such as it forms a protrusion of the predetermined height in a range of 1.6 to 2.0 mm from a base of the circumferential groove. Thus, the height of the cavity portion is less than the depth of the circumferential groove. As the tire moves on a road surface, the tire gets wear down. Available depth of the circumferential groove above the upper surface of this protrusion, also known as tread wear indicator, indicates the remaining life of the tyre .
[0028] In an example embodiment of the present subject matter, the
circumferential groove of the tread region comprises upto five circumferential grooves and one or more tread wear indicators are defined in each of the circumferential grooves. The number of circumferential grooves in the tire to be cured is in a range of 1-5 and correspondingly, the number of protrusions 202-1 formed between the first end 206-1 and the second end 206-2 of each of the plurality of segments 200 of the mould for defining the circumferential grooves of the tread region of the cured tire is in the range of 1-5.
[0029] In an example, the tread wear indicator is to be formed in each of the
circumferential groove of the tire to be cured. Thus, in an exemplary embodiment of the present subject matter, each of the protrusion 202-1 between the first end 206-1 and the second end 206-2 of each of the plurality of segments 200 of the mould comprises a cavity portion 208. In an example, the cavity portion 208 formed at the first end 206-1 and the cavity portion 208 formed at the second end 206-2 of the respective segments 200 are symmetrical. However, the same is not necessary. In another example, the cavity portion 208 formed at the first end 206-1 and the cavity portion 208 formed at the second end 206-2 of the respective segments 200 may be asymmetrical. For instance, cavity portion 208 formed at a first end 206-1 of a segment 200 can differ in length compared to the other cavity portion 208 formed at the second end 206-2 of the respective segment 200 and cavity portions 208 formed at the ends 206-1, 206-2 of other segments 200. While the embodiment shown in Figure 2 shows all cavity portions 208 are symmetrical, other embodiments are possible.

[0030] Figure 3 illustrates a front view of a tire 300 cured inside the mould
comprising the plurality of segments 200. During the process of curing, a volume of curing media such as steam is circulated inside the curing bladder at an elevated temperature and pressure to increase the temperature of the bladder and transfer the heat to the green tire. As a result of circulation of curing media in the curing bladder, the curing bladder gets inflated, which further results in the inflated bladder exerting a substantial amount of radially outward physical pressure on the green tire, towards the internal walls of circular cavity of the mould. As a result of application of substantial amount of pressure on the green tire from the inflated curing bladder towards the internal walls of the toroidal mould cavity, the green tire gets pressed against the protruded pattern 202 of the inner surfaces 204 of each of the plurality of segments 200 of the mould, and thereby, gets imprinted with corresponding tread pattern. A cavity is formed in the at least one protrusion at a location corresponding to each pair of the adjoining ends 206-1, 206-2 of the two adjacent segments 200 by the cavity portions 208 formed at the adjoining ends 206-1, 206-2 of these segments 200 and material accommodated therein forms the tread wear indicator 304 in the circumferential grooves 302 as indicated in Figure 3. The heat energy provided by the curing media enables the chemical reactions between rubber and various other materials of the tire and the excess material protrudes out from the adjoining ends 206-1, 206-2 of the two adjacent segments 200. The excess material that protrudes out from the adjoining ends 206-1, 206-2 of the two adjacent segments 200 forms small protuberances at the respective locations at the surface of the cured green tire 300. The protuberances thus created on the surface of the tire may be easily trimmed off. However, no excess material is deposited inside the circumferential grooves 302 of the cured tire 300 that needs to be trimmed off.
[0031] Thus, in contrast to the conventional techniques for curing wherein no basis
for selection of the location for tread wear indicators 304 exists and the tread wear indicators 304 are randomly located along the circumferential grooves 302, in the

embodiments of the present invention, the location for the tread wear indicators 304 is such that a technical advance can be derived owing to the same. As explained, the location for the tread wear indicators 304 is such that the additional labor-intensive step of trimming of excess material deposited inside the circumferential grooves 302 of the cured tire 300 is eliminated from the tire manufacturing process. Thus, the mould for curing a green tire as claimed herein provides for an efficient the tire manufacturing process.
[0032] Although implementations of a mould for curing a green tire are described,
it is to be understood that the present subject matter is not necessarily limited to the specific features of the apparatus described herein. Rather, the specific features are disclosed as implementations of the mould for curing the green tire.

I/We Claim:
1. A mould for curing a green tire, the mould comprising:
a plurality of segments 200 to be adjoined to create a circular cavity to accommodate the green tire, the plurality of segments 200 comprising at least a first segment 200 and a second segment 200 with each of the plurality of segments 200 comprising a first end 206-1 and a second end 206-2, such that the second end 206-2 of the first segment 200 and the first end 206-1 of the second segment 200 coincide with each other when the plurality of segments 200 are adjoined;
a protruded pattern 202 formed on an inner surface 204 of the plurality of segments 200 for defining a tread region of a cured tire,
wherein the protruded pattern 202 formed on each of the plurality of segments 200 comprises at least one protrusion 202-1 formed between the first end 206-1 and the second end 206-2 of the respective segment 200 for defining at least one circumferential groove of the tread region of the cured tire, and
wherein the at least one protrusion 202-1 comprises a cavity portion 208 formed at the first end 206-1 and at the second end 206-2 of the respective segment 200,
wherein the cavity portion 208 formed at the second end 206-2 of the first segment 200 and the cavity portion 208 formed at the first end 206-1 of the second segment 200 together define a tread wear indicator to be formed in the cured tire.
2. The mould as claimed in claim 1, wherein the mould comprises:
a pair of circular side plates to be arranged radially inward along each side of each of the plurality of segments 200 for defining the circular cavity to accommodate the green tire.

3. The mould as claimed in claim 1, wherein the mould comprises a pair of bead rings arranged in the pair of side plates.
4. The mould as claimed in claim 1, wherein a length of the cavity portion 208 is in the range of 8 to 10 mm.
5. The mould as claimed in claim 1, wherein the at least one circumferential groove of the tread region comprises upto five circumferential grooves and wherein one or more tread wear indicators are defined in each of the circumferential grooves.
6. The mould as claimed in claim 1, wherein the plurality of segments 200 is symmetrical in shape and size.
7. The mould as claimed in claim 1, wherein the cavity portion 208 formed at the first end 206-1 and the cavity portion 208 formed at the second end 206-2 of the respective segments 200 are symmetrical.
8. A tire 300 cured inside the mould as claimed in any one of the claims 1-4, the tire 300 comprises at least one tread wear indicator 304 formed in the at least one circumferential groove 302 of the tread region of the tire 300, wherein the at least one tread wear indicator 304 is formed at a location where the cavity portion 208 formed at the second end 206-2 of the first segment 200 and the cavity portion 208 formed at the first end 206-1 of the second segment 200 are adjoined.