Patent Description:
The present invention relates to a <NUM>-dimensional (3D) kerf-forming blade for use in a tire vulcanization process, and more particularly, to a technique for minimizing the deformation of the shape of a kerf during tire vulcanization by improving the durability of the blade.

A pneumatic tire is composed of an inner liner, a body ply layered outside the inner liner, a belt layered outside the body ply, a tread layered outside the belt, and sidewalls that make up both sides of the tire, as well as a bead that joins with the wheel.

Additionally, the tread that comes into contact with the road is formed with specific patterns for grip, water drainage, braking power, and noise dispersal, and the shape of these patterns greatly affects wet grip, snow grip, and handling performance, making it a crucial factor in tire development. Kerf is a narrow, deeply-cut groove primarily in the tread blocks with a width of less than <NUM>, evenly distributing the contact surface and enhancing grip while providing a comfortable ride through damping action. Additionally, it also promotes drainage, which enhances driving power and braking power.

Recently, the trend in tire tread pattern design is to prioritize performance over simple design and appearance. To enhance tire performance, pattern performance technology is undergoing detailed subdivision and refined modifications.

Due to these changes, the thickness and shape of the kerf applied to tires has become diverse, leading to improved dry and wear performance. However, in order to achieve interlocking between blocks during tire operation, the thickness of the kerf must be reduced to improve the tire's dry performance, but it comes with a trade-off of reduced snow and ice performance as the thickness of the kerf becomes thinner. Additionally, as the thickness of the kerf becomes thinner, the possibility of the kerf being warped or broken during tire manufacturing may greatly increase.

<CIT> (Title of Invention: Kerf molding blade of tire vulcanization mold and vehicle tire and tire vulcanization apparatus using the same) discloses a curved molding blade in which a kerf-forming concave-convex portion <NUM> is formed on a blade frame <NUM>, a transverse protrusion <NUM> is formed at the lower portion of the kerf-forming concave-convex portion <NUM>, the transverse protrusion <NUM> includes a transverse concave portion <NUM> on the inside while the kerf-forming concavo-convex portion <NUM> and the transverse protrusion <NUM> are spaced apart from the lower end of the blade frame <NUM> by a predetermined distance such that the lowermost end of the transverse protrusion <NUM> is located at a point spaced apart from the lower end of the blade frame <NUM> by <NUM> to <NUM>% of the height L of the blade frame, the height L1 of the transverse protrusion <NUM> is formed at <NUM> to <NUM> % of the height L of the blade frame <NUM> to adjust the block rigidity to improve the grip required in driving on snow and ice roads, and The height L2 from one end of the transverse protrusion <NUM> to the upper end of the blade frame <NUM> is <NUM> to <NUM> % of the height L of the blade frame <NUM> to adjust the block stiffness so as to be used on dry roads, improving driving performance.

The present invention aims to solve the above problems by minimizing the deformation of the kerf's shape by enhancing the durability of the blade used in forming the kerf during tire vulcanization.

The technical objects of the present invention are not limited to the aforesaid, and other objects not described herein with be clearly understood by those skilled in the art from the descriptions below.

In order to achieve the above objects, a <NUM>-dimensional (3D) blade being installed in a tire vulcanization mold for forming a kerf according to the present invention includes a frame formed in a shape of a plate having a wave shape in a cross-section horizontal to a thickness direction and a support formed in a shape of a bar having one side connected to the frame and the other side connected to another frame, wherein the support prevents the frame from being deformed during a process of vulcanizing a tire.

According to an embodiment of the present invention, the support may include a main support body having a shape of a bar and a connecting member formed between the main support body and the frame to connect the main support body and the frame.

According to an embodiment of the present invention, the main support body may have a cross section in the shape of a circle or a polygon.

According to an embodiment of the present invention, the cross section of the main support body may be a circle having a radius of <NUM> to <NUM> millimeters (mm).

According to an embodiment of the present invention, the main support body and the connecting member may include a connecting portion having a curvature surface formed having a predetermined curvature radius.

According to an embodiment of the present invention, the curvature radius of the connecting portion of the main support body and the connecting member may range from <NUM> to <NUM> millimeters (mm).

According to an embodiment of the present invention, the main support body may be connected on the outside to an outer plane of the connecting member.

According to an embodiment of the present invention, the frame may include at least one amplitude portion formed by burying a part of one surface and protruding a part of the other surface correspondingly.

According to an embodiment of the present invention, the frame may further include a slope portion formed at a connecting portion between the amplitude portion and the support.

According to an embodiment of the present invention, the frame may further include a plate portion connected to an end of the amplitude portion and formed in a plate shape.

According to an embodiment of the present invention, the frame may have a thickness equal to or greater than <NUM>.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly describe the present invention, parts irrelevant to the description may be omitted in the drawings, and similar reference numerals may be used for similar components throughout the specification.

Throughout the specification, when a part is said to be "connected (coupled, contacted, or combined)" with another part, this is not only "directly connected", but also "indirectly connected" with another member in between. Also, when a part is said to "comprise" a certain component, this means that other components may be further included instead of excluding other components unless specifically stated otherwise.

As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" or "has," when used in this specification, specify the presence of a stated feature, number, step, operation, component, element, or a combination thereof, but they do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, elements, or combinations thereof.

<FIG> is a perspective view of a blade <NUM> according to an embodiment of the present invention, and <FIG> is a front view of a blade <NUM> according to an embodiment of the present invention. And <FIG> is a schematic diagram of a main support body <NUM> and a connecting member <NUM> according to an embodiment of the present invention.

As shown in <FIG>, the 3D kerf-forming blade <NUM> installed in a tire vulcanization mold for use in molding the kerf <NUM> according to the present invention includes a frame <NUM> having the shape of a plate with a wave-like cross-section in the horizontal direction relative to its thickness and a support <NUM> having the shape of a bar that is connected on one side to one frame <NUM> and on the other side to another frame <NUM>.

Here, during the vulcanization molding process for the tire, deformation of the frame <NUM> may be prevented by the support <NUM>. Here, the thickness of the frame <NUM> may be <NUM> or more. Since the frame <NUM> is formed with a thin thickness as described above, it is possible to form fine and various kerfs <NUM> on the tire. However, the thickness of the frame <NUM> is not limited to the above dimensions.

In the case where the frame <NUM> is formed with a fairly thin thickness as described above, the blade <NUM> is likely to have deformation or damage such as distortion, warping, or breakage due to such a thin thickness of the frame <NUM>, resulting in defects in the shape of the kerf <NUM> formed on the tire.

In order to prevent this phenomenon, the support <NUM> is disposed between two frames <NUM> to support each frame <NUM>, which improves the durability of the blade <NUM> of the present invention and prevents deformation of the frame <NUM> due to pressure and heat during tire vulcanization, making it possible for the kerf <NUM> to be formed in proper shape on the tire.

In detail, the blade <NUM> with only the frame <NUM> experiences bending at a force of <NUM>-<NUM> N when force is applied using a push-pull gauge, whereas the blade <NUM> of the present invention, which has the support <NUM>, may remain unbent even at forces exceeding <NUM> N.

The support <NUM> may include a main support body <NUM> formed in the shape of a bar and connecting members <NUM> formed between the main support body <NUM> and the frames <NUM> to connect the main support body <NUM> and the frames <NUM>. Here, the cross-section of the main support body <NUM> may be circular or polygonal. However, the shape of the cross-section of the main support body <NUM> is not limited to these shapes and other shapes such as elliptical may also be used.

The connecting member <NUM> may take the form of an extension from both sides of the main support body <NUM> towards the frames <NUM> in a plate shape. However, the shape of the connecting body <NUM> is not limited thereto, but may also be formed in other shapes.

The main support body <NUM> may have a circular cross-sectional shape, and in this case, the radius R1 of the cross-section of the main support body <NUM> may be <NUM> to <NUM>. In addition, as shown in <FIG>, the connecting part between the main support body <NUM> and the connecting member <NUM> may have a curved surface.

In detail, the connecting part of the main support body <NUM> and the connecting member <NUM> may undergo rounding treatment, with the thickness T of the connecting member <NUM> gradually increasing towards the main support body <NUM>, resulting in a predetermined radius of curvature R2 for the connecting part of the support <NUM> and the connecting member <NUM>.

By performing the curved surface treatment on the connection part between the main support body <NUM> and the connecting member <NUM> as described above, stress concentration at the connecting part may be avoided, which enhances the durability of the blade <NUM>.

Here, the radius of curvature R2 at the connecting part between the main support body <NUM> and the connecting member <NUM> may be <NUM> to <NUM>. When the radius of curvature R2 at the connecting part between the main support body <NUM> and the connecting member <NUM> is formed simultaneously along with the radius R1 of the cross section of the main support body <NUM> as described above, the horizontal strength at the connecting part is increased, resulting in enhancing the durability of the blade.

For the above configuration, it may be preferred for the radius of curvature R2 at the connecting part between the main support body <NUM> and the connecting member <NUM> to be formed as <NUM>, and for the radius of curvature R2 at the connecting part between the main support body <NUM> and the connecting member <NUM> to be formed as <NUM>. And the thickness T of the connecting member <NUM> may be <NUM> to <NUM>.

The connecting part between the main support body <NUM> and the connecting member <NUM> may have a curved surface as described in the embodiment, but the present invention is not limited thereto, and the outer surface of the main support body <NUM> and the outer plane of the connecting member <NUM> may be directly connected. This applies even when the cross-section of the main support body <NUM> is a circle or any other shape.

In this case, the connecting member <NUM> may be formed as a plate shape and extended from the outer surface of the main support body <NUM> to form a straight section directly in the direction of the extension of the connecting member <NUM> from the outer surface of the main support body <NUM>.

The formation of the connecting member <NUM> as described above enhances the coupling force between the main support body <NUM> and the frame <NUM>, and the connecting member <NUM>, being formed to support the main support body <NUM>, may increase the resistance of the main support body <NUM> to external forces.

The bar (or rod) shape of the main support body <NUM> and the wave shape of the frame <NUM> may increase the pulling force, or the force exerted when the blade <NUM> of the present invention is inserted into and withdrawn from a tire during the tire vulcanization. In addition, forming the cross-sectional shape of the amplitude portion <NUM>, which creates the wave shape as described, into a trapezoidal shape may further increase the pulling force.

As described above, forming the connecting members <NUM> on both sides of the main support body <NUM> facilitates the sliding of the blade <NUM> of the present invention on the tire when it is separated from the tire after the tire vulcanization, reducing the pulling force increased by the bar (or rod) shape of the main support body <NUM>, the wave shape of the frame <NUM>, and the trapezoidal shape of the amplitude portion <NUM>, thereby increasing the efficiency of pulling out the blade <NUM> from the tire after the tire vulcanization.

The frame <NUM> may have at least one amplitude portion <NUM> formed by burying a part of one surface and protruding a part of the other surface correspondingly. Furthermore, a slope portion <NUM> may be formed at the junction between the amplitude portion <NUM> and the support <NUM>. Here, the slope portion <NUM> may have at least one inclined surface.

As shown in <FIG>, a plurality of amplitude portions <NUM> forming a wave shape, i.e., a zigzag-shaped amplitude shape, are formed in the frame <NUM>, and each of the amplitude portions <NUM> may be connected to form the wave shape.

The cross-sectional shape of the amplitude portion <NUM> may be formed as a trapezoid as described above, but it is not limited to this shape and various shapes such as a semicircle may be used.

Since the frame <NUM> has a wave shape formed by the amplitude portions <NUM>, a gap may occur between the amplitude portions <NUM> and the support <NUM>. In detail, as one end of the amplitude portion <NUM>, which is attached to the connecting member <NUM>, is separated from the connecting member <NUM>, the slope portion <NUM> may be formed between the separated portion and the connecting member <NUM>.

Here, the slope portion <NUM> may be formed to extend from the amplitude portion <NUM> while being inclined toward the connecting member <NUM> and coupling the amplitude portion <NUM> and the connecting member <NUM> without separation between one end of the amplitude portion <NUM> and the connecting member <NUM>, which increases the coupling force between the amplitude portion <NUM> and the connecting member, leading to an increased shape retention force of the blade <NUM> of the present invention against external forces.

The frame <NUM> may further include a plate-shaped portion <NUM> coupled to the end of the amplitude portion <NUM> and formed in a plate shape. In detail, with reference to <FIG>, a plate-shaped portion <NUM> may be formed at the bottom of the blade <NUM> of this invention, specifically at the bottom of the frame <NUM>.

Such a plate-shaped portion <NUM> may be coupled to the tire vulcanization mold for vulcanizing the tire, thus the plane of the plate-shaped portion <NUM> and the tire vulcanization mold are coupled, enhancing the coupling strength of the blade <NUM> of the present invention to the tire vulcanization mold.

In addition, by extending the support <NUM> to form the plate-shaped portion <NUM>, the main support body <NUM> and the connecting body <NUM> also support the plate-shaped portion <NUM>, thereby increasing the coupling strength of the blade <NUM> of the present invention to the tire vulcanization mold and improving the durability of the plate-shaped portion <NUM>, leading to preventing deformation or damage of the blade <NUM> due to pressure during vulcanization.

The cross-sectional length, as the longest length between any one point of the edge and the other point of the edge in the cross-sectional shape of the main support body <NUM> (diameter if the cross-sectional shape of the main support body <NUM> is a circle) may vary from the top to the bottom of the main support body <NUM>.

In addition, the thickness of the frame <NUM> may vary from the top to the bottom of the frame <NUM>. In detail, as shown in <FIG>, the frame <NUM> may be divided into regions (L1, L2, and L3) at each part, and the thickness of the frame <NUM> may be different in each region.

Here, the boundaries for dividing each region may differ from the boundaries between the amplitude portions <NUM> to be described below. That is, the thickness of one amplitude portion <NUM> may also vary from the top to the bottom.

In a specific embodiment, the thickness of the frame <NUM> in the L1 region may be formed as <NUM> to <NUM>, the thickness of the frame <NUM> in the L2 region may be formed as <NUM>, and the thickness of the frame <NUM> in the L3 region may be formed as <NUM> to <NUM>.

In addition, the cross-sectional length of the main support body <NUM> may vary as described above, and especially when the main support body <NUM> is in the shape of a cylinder, a portion of the main support body <NUM> that supports the L2 region, which is formed with a relatively thin thickness, may have a diameter of <NUM> or more, while each part of the main support body <NUM> that supports the L1 and L3 regions, which are formed with a relatively thick thickness, may have a diameter of less than <NUM>.

By varying the cross-sectional length of the main support body <NUM> and the thickness of the frame <NUM> in this manner, the kerf <NUM> formed by the blade <NUM> of the present invention may have a three-dimensional design, leading to increase in the friction force and an improvement in various performance characteristics including interlocking performance.

<FIG> is a perspective view of a block <NUM> according to an embodiment of the present invention, <FIG> is a plan view of the block <NUM> according to an embodiment of the present invention, and <FIG> is a side view of the block <NUM> according to an embodiment of the present invention.

As shown in <FIG>, a tire may include a block <NUM> with a thread having a kerf <NUM> formed in a wave shape extending in the depth direction along with a kerf hole <NUM> formed extending in the depth direction by means of the blade <NUM> of the present invention as described above.

When using the blade <NUM> of the present invention as a part of the vulcanization mode in a vulcanization process of a tire, the kerf <NUM> may be formed on the block <NUM> (or rib) by the blade <NUM> of the present invention, and a kerf hole <NUM> of a hole shape may be formed by the main support body <NUM> in the kerf <NUM>.

In addition, the kerf <NUM> may have a convex portion extending from the wall forming the kerf <NUM> in the central direction and a corresponding concave portion according to the wave shape as described above, and the convex and concave portions come into contact during driving or braking of the tire to incur an interlocking, resulting in improved braking, rotation and friction performance of the tire.

<FIG> is a perspective view of the block <NUM> according to another embodiment of the present invention, and <FIG> is a side view of the block <NUM> according to another embodiment of the present invention. Here, the embodiment shown in <FIG> and <FIG> may be referred to as embodiment <NUM> of the present invention. The blade <NUM> used to form the kerf <NUM> in embodiment <NUM> can vary in thickness, with the thickness of the top region L1 being <NUM>, the thickness of the middle region L2 being <NUM>, and the thickness of the bottom region L3 being <NUM>.

<FIG> and <FIG> are perspective views of a block according to a comparative example of the present invention.

In detail, <FIG> depicts a block <NUM> of comparative example <NUM>, in which a kerf <NUM> extending from one side to the other in the block has a bend in its central portion and is uniform in width, compared to the block <NUM> of embodiment <NUM>. Here, the amplitude portion having the wave shape extending in the depth direction of the kerf <NUM> may have a trapezoid shape in the cross-sectional view.

That is, in order to form the kerf <NUM> in the block <NUM> of comparative example <NUM>, a blade with two bend parts and uniform thickness, in which the support <NUM> is removed from the blade <NUM> of the present invention, may be used. Here, the thickness of the blade used to form the kerf <NUM> in the block <NUM> of comparative example <NUM> may be uniform at <NUM>.

<FIG> illustrates the block <NUM> of comparative example <NUM>, in which the block <NUM> of comparative example <NUM> may have a shape excluding the kerf hole <NUM> from the block <NUM> of embodiment <NUM>, compared to the block <NUM> of embodiment <NUM>.

Thus, in order to form the kerf <NUM> in the block <NUM> of comparative example <NUM>, a blade without the support <NUM> from the blade <NUM> of the present invention may be used. Here, the thickness variation of the blade used to form the kerf <NUM> in the block <NUM> of comparative example <NUM> may be the same as the thickness variation of the blade <NUM> in embodiment <NUM>.

In addition, a block of comparative example <NUM> may be prepared, and the block of comparative example <NUM> may have a kerf formed as a planar shape without a wave shape extending in the depth direction of the kerf compared to the block <NUM> of comparative example <NUM>.

That is, a blade with a planar shape may be used to form the kerf of the block in comparative example <NUM>. Here, the thickness of the blade used to form the kerf in comparative example <NUM> may be fixed to <NUM>.

Each of the block shapes of embodiment <NUM> and comparative examples <NUM> to <NUM> as described above was created in a finite element analysis program, a load corresponding to the tire contact pressure was applied to each block, and each was moved in the forward and reverse directions.

<FIG> is a graph according to test result for each tire block. In detail, <FIG> is a graph depicting the relationship between sliding distance and friction force.

In <FIG>, graph A corresponds to the block in comparative example <NUM>, and graph B corresponds to the block <NUM> in embodiment <NUM>. It can be observed that the change in the degree of increase of the friction force during the convergence process varies depending on the shape of the kerf.

As shown in <FIG>, it can be observed that as the sliding distance increases, the block <NUM> of embodiment <NUM> using the blade <NUM> of the present invention shows superior maximum friction force compared to the block equipped with a kerf shape commonly used in tires as in comparative example <NUM>, indicating improved braking performance of a tire equipped with the block <NUM> incorporating the kerf <NUM> formed using the blade <NUM> of the present invention.

Each of the block shapes of embodiment <NUM> and comparative examples <NUM> and <NUM> as described above was created in a finite element analysis program, a load corresponding to the tire contact pressure was applied to each block, and each was moved in the forward and reverse directions.

<FIG> is a table summarizing data according to simulation test results for each tire block. In detail, <FIG> is a table summarizing the data obtained from [Simulation test <NUM>]. The table in <FIG> shows the coefficient of friction data derived when the braking force generated during tire braking is applied to each block and the coefficient of friction data derived when the traction force generated during tire driving is applied to each block.

In each table, the maximum frictional force ratio represents the percentage (%) of the maximum frictional force of comparative example <NUM> and each of the other comparative examples and embodiment <NUM>.

As seen in <FIG>, it can be observed that the coefficient of friction was improved by <NUM>% during braking for the block <NUM> incorporating the kerf <NUM> formed using the blade <NUM> of the present invention.

Also, as seen in <FIG>, it can be observed that the coefficient of friction was improved by <NUM>% during traction for the block <NUM> incorporating the kerf <NUM> formed using the blade <NUM> of the present invention.

Based on the evaluation of applying the blocks of comparative example <NUM> and embodiment <NUM> to actual tires, it can be observed that the block <NUM> of embodiment <NUM> showed a <NUM>% improvement in dry braking performance.

As described above, it can be observed that forming a kerf <NUM> in a block <NUM> using the blade <NUM> of the present invention as described above improves the interlocking performance of the kerf <NUM>, and simultaneously, the formation of a kerf <NUM> with a relatively thin thickness and minimized design errors in the convex and concave portions of the kerf <NUM> leads to an improvement in the friction performance of the tire.

<FIG> are images related to the stress concentration test on the blades according to each embodiment of the present invention.

In detail, <FIG> shows a simple connection blade without rounding treatment at the connection portion between the main support body <NUM> and the connecting member <NUM>, with the cross-sectional radius of the main support body <NUM> being <NUM> and the thickness of the frame <NUM> being <NUM>.

In addition, (a) in <FIG> is an image of the simple connection blade, (b) in <FIG> is an enlarged view of the connection portion between the main support body <NUM> and the connecting member <NUM> of the simple connection blade, and (c) in <FIG> is an image of the damage to the simple connection blade when a horizontal force of <NUM> N perpendicular to the surface of the connecting member <NUM> is applied to the center of the simple connection blade with both ends fixed. Here, the vertical force perpendicular to the horizontal force is measured to be <NUM> N.

<FIG> show a first curvature blade with a first curvature radius rounding treatment at the connection portion between the main support body <NUM> and the connecting member <NUM>, with the cross-sectional radius of the main body <NUM> being <NUM>, the thickness of the frame <NUM> being <NUM>, and the first curvature radius being <NUM>.

In addition, (a) in <FIG> is an image of the first curvature blade, (b) in <FIG> is an enlarged view of the connection portion between the main support body <NUM> and the connecting member <NUM> of the first curvature blade, and (c) in <FIG> is an image of the deformation of the first curvature blade when a horizontal force of <NUM> N perpendicular to the surface of the connecting member <NUM> is applied to the center of the first curvature blade with both ends fixed. Here, the vertical force perpendicular to the horizontal force is measured as <NUM> N.

<FIG> shows a second curvature blade with a second curvature radius rounding treatment at the connection portion between the main support body <NUM> and the connecting member <NUM>, with the cross-sectional radius of the main body <NUM> being <NUM>, the thickness of the frame <NUM> being <NUM>, and the first curvature radius being <NUM>.

In addition, (a) in <FIG> is an image of the second curvature blade, (b) in <FIG> is an enlarged view of the connection portion between the main support body <NUM> and the connecting member <NUM> of the second curvature blade, and (c) in <FIG> is an image of the deformation of the second curvature blade when a horizontal force of <NUM> N perpendicular to the surface of the connecting member <NUM> is applied to the center of the second curvature blade with both ends fixed. Here, the vertical force perpendicular to the horizontal force is measured varying between <NUM> to <NUM> N.

As seen in <FIG>, which illustrate a simple connection blade, a first curvature blade, and a second curvature blade, the rounding treatment of the connection portion between the main support body <NUM> and the connecting member <NUM> improves the durability of the blade <NUM> of the present invention.

In addition, as shown in the comparison between the first curvature blade and the second curvature blade, increasing the cross-sectional radius of the main support body <NUM> improves the durability of the blade <NUM> of the present invention.

The present invention according to the above configuration has the advantage of increasing the durability of a kerf-forming blade for shaping the kerf in a tire, by forming a supporting member between one frame and another to support each frame, thus preventing the deformation of the frames due to the pressure and heat generated during the tire vulcanization process.

The present invention has the advantage of improving the quality of the tire's kerf by minimizing deformation of the kerf after the tire vulcanization process through the improved durability of the kerf-forming blade, achieved by maintaining the shape of the kerf-forming blade during the tire vulcanization process as described above.

It should be understood that the advantages of the present invention are not limited to the aforesaid but include all advantages that can be inferred from the detailed description of the present invention or the configuration specified in the claims.

The above description of the present invention is for illustrative purposes only, and it will be understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the invention. Therefore, it should be understood that the embodiments described above are exemplary and not limited in all respects. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

Claim 1:
A <NUM>-dimensional (3D) blade being installed in a tire vulcanization mold for forming a kerf, the blade comprising:
a frame formed in a shape of a plate having a wave shape in a cross section horizontal to a thickness direction; and
a support formed in a shape of a bar having one side connected to the frame and the other side connected to another frame,
wherein the support prevents the frame from being deformed during a process of vulcanizing a tire.