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 several key 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. 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 in the 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 chemical reactions between the rubber and other materials of the tire, and the tire is imprinted with tread pattern and sidewall deign in the predefined profile shape.
[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 from 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 cross sectional view of a conventional mould for
curing a green tire, according to a conventional configuration.

[0006] Figure 2a illustrates an expanded view of a section of the mould
illustrating an adjoining edge of a side plate of the mould and a segment of tread
ring of the mould, according to a conventional configuration.
[0007] Figure 2b illustrates a vent provided in the side plate of the mould,
according to a conventional configuration.
[0008] Figure 3a illustrates a vent assembly to be installed in the vent provided
in the mould, according to a conventional configuration.
[0009] Figure 3b and Figure 3c illustrate the vent assembly in an open position
and in a closed position, respectively, according to a conventional configuration.
[0010] Figures 4a-4d illustrate various states of the vent during the curing
process, according to a conventional configuration.
[0011] Figure 5 illustrates an expanded view of a section of a mould for curing
a green tire, in accordance with an implementation of the present subject matter.
[0012] 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
[0013] Conventionally, rubber, along with other materials, is used as a raw
material for manufacturing 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 manufacturing the tires. 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.
[0014] Green tire 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. Figure 1 illustrates a cross sectional view of a conventional mould of a tire. As illustrated in Figure 1, the mould 100 comprises

multiple portions assembled together in a toroidal shape to form the mould 100.
These portions may include a tread ring 102, a pair of side plates 104 and a pair of
bead ring 106 to define a tread region, a sidewall region and a bead region,
respectively of the tire. The tread ring 102 may also comprise multiple segments
to be joined together in a circular shape. The pair of side plates 104 may include
top and bottom side plates. The top and bottom side plates may be arranged radially
inward along either side of the multiple segments of the tread ring 102 adjoined in
a circular shape such that multiple segments of the tread ring 102 are placed
between the top and bottom side plates to form a toroidal shaped cavity to
accommodate green tire therein. The pair of bead rings may be installed on a
surface of each of the top and bottom side plates facing inside the cavity. Tread
ring 102 may comprise 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.
[0015] Generally, a small gap exists between each portion of the mould 100
and between each segment of the tread ring 102, to accommodate metal expansion
upon heating. Plurality of vents may be provided at regular intervals in various
portions of the mould 100, i.e., plurality of segments of the tread ring 102, top and
bottom side plates 104 and bead rings 106. The plurality of vents extends from an
inner surface 108 of the mould 100 either to an outer surface 110 of the mould 100
or up to a point on periphery of the respective portion of the mould 100. More
specifically, a first end of each of the plurality of vents is provided at the inner
surface 108 of the mould 100 and a second end of each of the vents is provided
either at the outer surface 110 of the mould 100 or at the adjoining edges 112 of
respective portions of the mould 100 and the segments of the tread ring 102.
[0016] Figure 2a illustrates an expended view of a section 100-A of the mould
illustrating an adjoining edge 112 of a side plate 104 of the mould 100 and a segment of tread ring 102 of the mould 100, while Figure 2b illustrates a vent 114 provided in the side plate 104 of the mould 100, according to a conventional

configuration. Generally, vents 114 provided in the top and bottom side plates 104 of the mould 100 extend from the inner surface 108 of the respective side plate 104 to the edge 112 of the side plate 104 that coincide with the plurality of segments of the tread ring. For instance, a first end 116-1 of the vent 114 is provided at the inner surface 108 of the respective side plate 104 and a second end 116-2 of the vent 114 may be provided at the adjoining edge 112 of the respective side plate 104 and the corresponding segment of the tread ring 102. Each of the plurality of vents 114 comprises a first section 114-1 and a second section 114-2 as illustrated in Figure 2b. The first section 114-1 of each of the plurality of vents 114 encloses the first end 116-1 of the respective vent 114 and the second section 114-2 encloses the second end 116-2 of the respective vent 114.
[0017] Figure 3a illustrates a vent assembly 118 to be installed in a vent 114
provided in the mould 100, according to a conventional configuration. The vent assembly 118 may be installed in the first section 114-1 of each of the plurality of vents 114 to release the air entrapped between the tire and the mould 100. The vent assembly 118 may comprise a housing 118-1 and a vent cap 118-2 to be installed in the housing 118-1. The housing 118-1 may be affixed to the first section 114-1 of the respective vent 114 formed in the corresponding portion of the mould 100 as illustrated in Figure 2 and the vent cap 118-2 is installed in the housing 118-1. The housing 118-1 may be cylindrical in shape and may comprise a slot along its length to receive the vent cap 118-2 therein as illustrated in Figure 3a. Figure 3b illustrates vent assembly 118 in an open position and Figure 3c illustrates vent assembly 118-2 in a closed position, according to a conventional configuration. The vent cap 118-2 may comprise a spring mounted thereon to allow the vent cap 118-2 to move from the open position to the closed position. At the start of the curing process, the vent cap 118-2 may be installed in the open position in the housing 118-1 to allow the air entrapped between the tire and the mould 100 to pass outside through the respective vent 114. However, as the curing process progresses, with the application of heat and pressure, the green tire presses the vent cap 118-2 to move to a closed position.

[0018] During the curing process, 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 102, e.g., from the adjoining edges of the tread ring 102, the side
plates 104, the bead rings 106 and the segments of the tread ring 102.
[0019] Figures 4a-4d illustrates various states of the vent 114 formed in various
portions of the mould during the curing process, according to a conventional configuration. In case of the vent 114 formed in a top or bottom side plate 104, where the second end of the vent 114 is provided at the adjoining edge 112 of the respective side plate 104 and the segments of the tread ring 102, the material that protrude out from the adjoining edge 112, starts flowing inside the vent 114 through the second end 116-2 of the vent 114 as illustrated in Figure 4a. After crossing the second section 114-2 of the vent 114, when the material reaches the first section 114-1 of the vent 114 as shown in Figure 4b, the material starts forcing the vent cap 118-2 installed in the housing 118-1 placed in the first section 114-1 to move towards the outer surface of the green tire as shown in Figure 4c and 4d and the vent cap gets entrapped in the surface of the finished tire after the curing process. Generally, the vent assembly installed in the mould has an actuation of the spring which leads the vent cap to have both open and close condition during its functioning. The vent cap is free to move to and fro within the housing as explained with reference to Figure 3b and 3c and is kept assembled in the housing until there is a push through the material entered in vent from back side of vent cap which causes the vent cap to get disassembled from the housing and get stuck in the outer surface of cured tire. This condition is considered as a major defect in tire and is termed as vent open scenario or foreign material in tire. The tire produced with vent cap stuck therein is not repairable by trimming or any other operation and is directly considered as scrap.
[0020] To this end, the present subject matter provides a mould for curing a
green tire that overcomes the above-described problems associated with overflowing of excess material out of joints between a segment of a tread ring of the mould and a side plate of the mould during curing of the tire.

[0021] 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 tread segments to be adjoined together in a circular shape. The mould also comprises a pair of side plates to be arranged radially inward along either side of each of the plurality of tread segments arranged in a circular shape to define a toroidal cavity to accommodate the green tire. The pair of side plates may comprise top and bottom side plates. A step is defined at a predetermined distance from a surface of the cavity along a side of each of the side plates in the pair of side plates that coincide with the plurality of tread segments. The predetermined distance is such that a vent to eject air for curing of the green tire is provided on the side of a side plate beyond the predetermined distance. In an example, the vent to eject the air during the curing process extends from the surface of the cavity to the side of the side plate that coincide with the plurality of tread segments.
[0022] As described above, conventionally, during the curing process, when
heat and pressure is applied to the green tire accommodated in the mould, excess material such as rubber protrudes out from the adjoining edge of the plurality of segments of the tread ring and the side plate start flowing inside the vent provided in the side plate to eject the air during curing, blocks the vent and pushes a vent cap installed in the vent towards an outer surface of the green tire as indicated in Figure 4a-4d. However, according to the mould disclosed in the present subject matter, the excess material protruding out from the side of the side plate that coincide with the plurality of tread segments is pressed for the predetermined distance between the side of the side plate and the respective tread segment. When the squeezed material reaches the step defined at the predetermined distance, the excess material is cut and eliminated through the step and can be discharged through the gap formed by the step. Since, the vent is provided after defining the step at the predetermined distance, the excess material does not flow inside the vent.
[0023] 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.
[0024] In an implementation of the present subject matter, the mould for curing
the green tire is disclosed. The mould is similar to the mould 100 as described
above in reference with Figure 1 but for the new aspect subsequently elaborated.
Figure 5 illustrates an expanded view of a section of a mould 200 for curing a green
tire, in accordance with an implementation of the present subject matter.
[0025] 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. As explained previously, the curing apparatus comprises a mould 200 to accommodate the green tire. In an example, the mould 200 may be of toroidal shape. The green tire to be subjected to curing may be placed inside the mould 200. 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.
[0026] As described earlier, the mould 200 for curing the green tire comprises
a plurality of tread segments 202 to be adjoined in a circular shape. Generally, there are 8 or 10 segments that are joined together in circular shape. As will be understood by one skilled in the art, the number of the segments depends on the

size of the mould 200 and the corresponding tire to be cured and is not to be construed as a limitation.
[0027] The tread segments 202 are symmetrical in shape and size. In an
example, the mould 200 also comprises a pair of side plates. The pair of side plate 204 may include top and bottom side plates. Each side plate 204 in the pair of side plates may be arranged radially inward along either side of each of the plurality of tread segments 202 adjoined together in the circular shape for defining a toroidal cavity to accommodate the green tire. The mould 200 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 204 in the pair of side plates.
[0028] 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 plurality of tread segments plates 202 adjoined in the circular shape define the tread region of the tire to be cured. 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. A protruded pattern is generally formed on an inner surface of the plurality of segments of the mould 200 for defining the tread region of a cured tire. The protruded pattern corresponds to a tread pattern of the tire to be cured.
[0029] The pair of side plates 204 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. Each of the side plate 204 in the pair of side plates may be circular in shape.

[0030] As described above, to release the air entrapped between the tire and
the mould 200 during the curing process in order to prevent the entrapment of air in the cured tire, plurality of vents (not shown in Figure 5) are provided in various portions of the mould 200 at regular intervals. The configuration of each of the plurality of vents is similar to the vent 114 as illustrated in Figure 2b. A vent (not shown in Figure 5) extends from a surface of the cavity or an inner surface 206 of the mould 200 to an outer surface 208 of the mould 200 or upto a point on periphery of the respective portion of the mould 200. That is, a first end of the vent may be provided on the surface of the cavity 206 defined by mould 200 or the inner surface of the mould 200 and a second end of the vent may be provided on the outer surface 208 of the mould 200 or at the adjoining edges of the corresponding portions of the mould 200. A vent formed in a side plate 204 of the mould 200 may extend from the surface of the cavity 206 or the inner surface of the respective side plate 204 upto a point on a side or edge 210 or periphery of the respective side plate 204 that coincide with the plurality of tread segments 202. As would be understood, the first end of the vent may be provided on the inner surface of the side plate 206 and the second end of the vent may be provided on the side of the respective side plate that coincide with the corresponding segment of the tread ring plate. Similar to the vent 114, each of the plurality of vents may comprise a first section enclosing the first end of the vent and a second section enclosing the second end of the vent. A vent assembly similar to the conventional vent assembly 118 as described above in reference to Figure 3a, 3b and 3c, may be installed in the first section of each of the plurality of vents to release the air entrapped between the tire to be cured and the mould 200. The vent assembly comprises a housing and a vent cap to be installed in the housing. The housing may be affixed to the first section of the vent, the vent being the hole provided in the mould. The vent cap may be installed in the housing in an open position as illustrated in Figure 3b.
[0031] While green tire is placed in mould, the mould is in open condition, i.e.,
the tread segments are radially away from the side plates. Before curing starts, the mould gets closed through the radial movement of tread segments towards side plate. The mould is, generally, fitted inside a container during curing. The container

is such designed for having the radial movement of the tread segments in open and close condition. The radial closing of tread segments happens after the green tire is placed in mould and hence this process can also result in entrapment of material in between the tread segments and the side plates. 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 200. As a joint result of radial closing of tread segments and 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 inner surface of mould 200. The tire starts pressing the vent cap to move to a closed position as illustrated in Figure 3c.
[0032] In an example embodiment, a step is defined at a predetermined
distance Y from a surface 206 of the cavity defined by the various portions of the
mould 200, along a side 210 of each of the side plates 204 in the pair of side plates
that coincide with the plurality of tread segments 202. The predetermined distance
Y is such that the vent to eject air for curing of the green tire is provided on the
side 210 of the side plate 204 beyond the predetermined distance Y. That is, the
second end of the vent is provided at the side 210 of the side plate 204 that coincide
with the plurality of tread segments 202 beyond the step defined therein. In an
example, the predetermined distance Y is in the range of 5 mm to 30 mm.
[0033] 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 edges of the various portions of the mould 200. Excess material that protrudes out from the adjoining edge or side 210 of the side plate 204 and the plurality of tread segments 202 is pressed between the side 210 of the respective side plate and the tread segment 202 in the area defined by predetermined distance Y. The pressed or squeezed material when reaches the

step, the squeezed material is removed therefrom and discharged through the gap defined by the step between the side 210 of the side plate 204 and the corresponding tread segment 202.
[0034] In an example implementation, the step comprises a first portion 212
perpendicular to a portion 214 of the side 210 of the side plate 204 that corresponds to the predetermined distance Y from the surface 206 of the cavity. In an example, the length X of the first portion is in the range of 3 mm to 10 mm. In an example, the first portion 212 has a curved profile at its one end which coincide with the portion 214 of the side 210 of the side plate 204 that corresponds to the predetermined distance Y. That is, the first portion 212 of the step defined at the predetermined distance Y starts with a curved profile. In an example, a curvature R of the curved profile is in a range of 0.10 mm to 5.00 mm. In an example, the step also comprises a second portion 216 defined at an angle A greater than 90 degree with the first portion 212. In an example, the range of the angle A is in the range of 91 degree to 95 degree. The second portion 216 extends upto an outer surface 208 of the side plate 204.
[0035] The curvature R of the curved profile of the first portion 212 is defined
in such a way that the portion 214 of the side 210 of the side plate 204 defined upto the predetermined distance Y gets ended with a smooth curved surface, having curvature R, of the first portion 212 of the step. The curved profile with curvature R helps the protruded excess material that has been squeezed between the adjoining edges of the side plate 204 and the corresponding tread segment 202 to roll out after the predetermined distance Y and to enter into the free space created by the first portion 212 and the second portion 216 of the step. The angle A is designed to capture the rubber, if any, that may have flown through the first portion 212 of the step. The gap formed by the step having the second portion 216 with tilted face due to angle A, does not allow any rubber material to remain in the region defined between the side 210 of the side plate 204 and the tread segment 202. Since the excess material is removed through the step and does not get stuck in the region defined between the side 210 of the side plate 204 and the tread segment 202, the material does not enter into the vent which has an opening, i.e., the second end of

the vent defined at the side 210 of the side plate 204 after the step. This prevents
the entrapment of vent cap in the surface of the cured tire because of the pressure
exerted by the excess material entering into the corresponding vent as happened in
case of conventional flat profile of the side 112 of the side plate 104 that coincide
with the tread segment 102. Since, vent cap does not get entrapped in the surface
of the cured tire, no foreign material in the surface of the tire is observed in the
cured tire that may otherwise happen as a result of removal of the vent cap from
the housing fixed in mould. Thus, quality of the finished tire does not get affected.
[0036] Although implementations of a mould 200 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 200 for curing the green tire.

I/We Claim:
1. A mould 200 for curing a green tire, the mould comprising:
a plurality of tread segments 202 to be adjoined together in a circular shape and a pair of side plates 204 to be arranged radially inward along either side of each of the plurality of tread segments 202 to define a toroidal cavity to accommodate the green tire,
wherein a step is defined at a predetermined distance Y from a surface 206 of the cavity along a side 210 of each of the side plates 204 in the pair of side plates 204 that coincide with the plurality of tread segments 202, the predetermined distance Y being such that a vent 114 to eject air for curing of the green tire is provided on the side 210 of a side plate 204 beyond the predetermined distance Y.
2. The mould 200 as claimed in claim 1, wherein the mould 200 comprises a pair of bead rings arranged in the pair of side plates.
3. The mould 200 as claimed in claim 1, wherein the predetermined distance Y is in the range of 5 mm to 30 mm.
4. The mould 200 as claimed in any one of the previous claims, wherein the step comprises a first portion 212 perpendicular to a portion 214 of the side 210 of the side plate 204, the portion 214 corresponding to the predetermined distance Y from the surface 206 of the cavity.
5. The mould 200 as claimed in claim 4, wherein the length of the first portion 212 is in the range of 3 mm to 10 mm.

6. The mould 200 as claimed in claim any one of the preceding claims,
wherein the step comprises a second portion 216 defined at an angle A greater than
90 degree with the first portion 212.
7. The mould 200 as claimed in claim 6, wherein the angle A is in the range of 1 degree to 5 degree.
8. The mould 200 as claimed in claim 6, wherein the second portion 216 extends upto an outer surface 208 of the side plate 204.
9. The mould 200 as claimed in any one of the preceding claims, wherein the first portion 212 has a curved profile at one end which coincide with the portion 214 of the side 210 of the side plate 204 that corresponds to the predetermined distance Y.
10. The mould 200 as claimed in any one of the preceding claims, wherein a curvature R of the curved profile is in a range of 0.10 mm to 5.00 mm.