FIELD OF INVENTION

[0001] The present subject matter relates, in general, to manufacturing of vehicle tires and, particularly but not exclusively, to extruders used in the manufacturing of vehicle tires.

BACKGROUND

[0002] A tire has a tread portion and sidewalls on either side of the tread portion. In an example, the tread portion may comprise a center region and a shoulder region on each side of the center region connected to upper portions of the corresponding sidewall. The center region may be understood as an outer region of the tire formed along a complete circumference of the tire and spreads along width of the tire. Further, the center region contacts with surface during rotation. The tire also has beads connected to lower portions of the sidewalls. The beads may be understood as edges of the tire. The beads contact with wheel during the mounting of the tire on the wheel. To manufacture a tire, a rubber compound is extruded through an extruder to a die used to mould the tire in the required shape. [0003] However, different regions of the tire are generally manufactured using different rubber compounds having different properties to achieve the desired performance of the tire. To manufacture different regions of the tire as a single piece using different rubber compounds, a multiplex extruder is generally used. The multiplex extruder extrudes different or same rubber compounds at the same time through multiple flow channels. The number of rubber compounds that can be extruded depends on the flow channels provided in the multiplex extruder. For example, a triplex extruder has three flow channels to extrude three different or the same rubber compounds simultaneously. Depending on the layout of the tire and number of rubber compounds used to manufacture various regions of the tire, an extruder having an appropriate number of flow channels can be selected to manufacture the tire. 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 tire to be manufactured using an extruder, in accordance with an implementation of the present subject matter.

[0006] Figure 2A illustrates a back view and a front view, respectively, of a preformer for an extruder head of an extruder to extrude materials for tire manufacturing, in accordance with an implementation of the present subject matter. [0007] Figures 3A and 3B illustrate a back view and a front view, respectively, of a swivel box to insert the preformer therein and to be attached to the extruder head of the extruder, in accordance with an implementation of the present subject matter.

[0008] Figures 4A and 4B illustrate a back view and a front view, respectively, of the swivel box with the preformer inserted therein, in accordance with an implementation of the present subject matter.

[0009] Figure 5A illustrates a schematic of an attachment to be inserted into an outlet of a channel of the extruder, in accordance with an implementation of the present subject matter.

[0010] Figure 5B illustrates a schematic of the attachment inserted into the outlet of the channel of the extruder, in accordance with an implementation of the present subject matter.

[0011] Figure 6A illustrates a schematic of a restrictor plate to be affixed to the attachment inserted in the outlet of the flow channel of the extruder, in accordance with an implementation of the present subject matter.

[0012] Figure 6B, illustrates a schematic of the attachment having a restrictor plate affixed thereto and inserted in the outlet of the flow channel of the extruder, in accordance with an implementation of the present subject matter. DETAILED DESCRIPTION

[0013] As mentioned above, to manufacture different regions of a tire, different or same rubber compounds are used. For example, rubber compound used to manufacture a tread region of the tire may be different from the rubber compound used to manufacture a sidewall region of the tire or from the rubber compound used to manufacture cushioning inside the tire. The selection of an appropriate extruder for manufacturing the tire generally depends on the number of rubber compounds to be used to manufacture various regions of the tire and the layout of the tire. For instance, if the tread region and the sidewall region are to be manufactured using the same rubber compound and the cushioning inside the tire is to be manufactured, a duplex or triplex extruder having two or three flow channels respectively can be used to manufacture the tire. To manufacture a tire, wherein each of the tread region, the sidewall region, and the cushioning inside the tire is to be manufactured using different rubber compounds, a triplex or a quadruplex extruder having three or four flow channels, respectively may be used.

[0014] A triplex extruder has an extruder head providing outlets for three different flow channels arranged one on top of the other for extruding raw material, such as rubber compound for three different tire regions, such as the tread region, the sidewall region, and the cushioning inside the tire. The rubber compounds used to produce these different tire regions may be the same or different from each other. Further, flow channels in the triplex extruder also have different profiles, such as the screw-diameter or the size of the outlets of the flow channels used to extrude the compound may be different from each other. For example, size of the top, middle, and bottom flow channels may be 200 mm, 150 mm, and 90 mm respectively. Depending on the volume of the region of the tire to be created and the placement of the region in the layout of the tire, a flow channel having a suitable profile can be selected to extrude the compound for the respective region. To manufacture a semi-finished tire, a triplex extruder generally extrudes the compound for the tread region, which is the top-most region of the tire, from the top-most flow channel; compound for sidewall from middle or top flow channel; and compound for cushioning which is a base of the tire from bottom flow channel. However, in some cases, the positioning of an outlet of a flow channel in the extruder head having the profile suitable to extrude the rubber compound for the required volume of the region of the tire to be created may not be appropriate for the creation of the respective region. In such an event, rubber compound extruded from the bottom-most flow channel may need to flow to the top side of the tire. [0015] For instance, referring to Figure 1, a tire 100 to be manufactured using an extruder is illustrated. In an example, the tire 100 is to be manufactured using a triplex extruder. The layout of a sidewall region of the tire is such that along with a portion of the sidewall produced using carbon-based rubber compound of black color, a portion of the sidewall near a bead region of the tire needs to be made of a rubber compound of white color and based on zinc oxide. In such a case, three different tire regions 102, 104, 106 need to be created using three same or different rubber compounds.

[0016] A first carbon-based rubber compound is used to produce a first region 102, i.e., the tread region. A second carbon-based rubber compound is used to produce second region 104 comprising a first portion of the sidewall near the tread region and cushioning inside the tire. The cushioning inside the tire may be understood as various layers designed to provide a comfortable and smooth ride. The cushioning is located in innermost part of the tire, extending from one bead region to another bead region present on either side of the tread region. These layers absorb road imperfections and shocks while maintaining the tire's shape and structural integrity. The cushioning helps enhance traction, handling, and overall performance while ensuring a comfortable driving experience.

[0017] The first carbon-based rubber compound may be same or different from the second carbon-based rubber compound. A third zinc -based rubber compound is used to produce a third region 106. The third region 106 comprises a second portion of white sidewall adjacent to the first portion of the sidewall and near the bead region of the tire 100. During manufacturing of such tire 100, to produce the third region 106, i.e., the second portion of the sidewall, zinc -based rubber compound of white color needs to be extruded either from the top or middle flow channel due to the layout of the sidewall. Hence, white rubber compound needs to flow to the surface of the tire 100.

[0018] A triplex extruder, top or middle flow channel of which has a size substantially larger than needed to extrude the required volume of rubber compound for the second portion of the sidewall, i.e., white sidewall, is not suitable to manufacture such tire 100. The reason is that the extruder needs to be operated at a speed, less than the minimum prescribed operating speed of the triplex extruder, which is practically not feasible. Further, since all the flow channels need to be operated in synchronization with each other, operating the extruder at such speed disrupts the output of other flow channels.

[0019] For example, the triplex extruder with flow channels having the above- mentioned profile, wherein size of the outlets of the top, middle, and bottom flow channels are 200 mm, 150 mm, and 90 mm, respectively, is not suitable for the manufacturing of the above-described tire having three regions. In such a case, during the process of manufacturing, one of the top or the middle flow channels may be used to extrude the compound for the first region 102, i.e., the tread region, the other one may be used to extrude the rubber compound for the third region 106, i.e., the second portion of the sidewall and the bottom flow channel may be used to extrude the rubber compound for the second region 104. However, this is practically not feasible, since the second region 104 has highest volume amongst all the three regions of the tire 100 to be manufactured and the bottom flow channel having a size of 90 mm is not sufficient to extrude the required amount of compound even if operated at a maximum operating speed. Also, to extrude the required volume of compound for the third region 106 from the middle or top flow channel, the extruder needs to be operated at less than the minimum prescribed operating speed of the extruder due to the least volume requirement of the third region, which is also practically not feasible.

[0020] Depending on the volume of the third region 106 which has the least volume amongst all the three regions of the tire 100, the bottom flow channel having the outlet of smallest size from amongst the outlets of all of the three flow channels is most suitable to extrude the compound for producing the third region tire 100, the third region 106, i.e., the white sidewall region, lies in the upper part of the tire 100, which is adjacent to the bead region of the tire 100. Owing to this, the bottom flow channel cannot be used to extrude the compound for the third region 106.

[0021] An alternative approach to this is to install an additional flow channel with an outlet formed on top of the available outlets on the extruder head. The extruder head may be understood as a component of the extruder that is responsible for extruding the materials into specific regions of the tire by controlling the flow of the material through its outlets. However, this substantially increases the cost and time required for manufacturing the tire 100.

[0022] To this end, the present subject matter provides a preformer for an extruder head of an extruder to extrude materials for tire manufacturing. The preformer overcomes the above-described problems associated with the manufacturing of a tire having a portion of sidewall produced using white rubber compound through a triplex extruder. This is achieved by providing an elevated flow path for a material extruded from an outlet placed downward in an arrangement of the outlets formed at the extruder head such that the material may form top part of the tire.

[0023] In accordance with an embodiment of the present subject matter, the preformer comprises a first flow channel for extruding a first material to form a tread region of a tire. The preformer further includes a second flow channel for extruding a second material to form a first portion of a sidewall of the tire and a cushioning inside the tire. The preformer also comprises a third flow channel for extruding a third material to form a second portion of the sidewall of the tire. The second portion of the sidewall corresponds to the portion of the sidewall adjacent to a bead region of the tire and the first portion is adjacent to the second portion, and it is towards a shoulder region of the tire. In an example, the extruder head of the extruder comprises a first, a second, and a third outlet formed at the front side of the extruder head corresponding to the three flow channels of the extruder to extrude the first, the second, and the third materials, respectively, to a die that is used to mould the tire in the required shape.

[0024] In an example implementation, each of the first flow channels, the second flow channel, and the third flow channel of the preformer has an inlet and an outlet. Further, the inlet of each of the first, the second, and the third flow channels of the preformer are aligned with the first, the second, and the third outlet, respectively of a first, a second, and a third flow channel of the extruder formed at the extruder head of the extruder to allow the first, the second and the third material extruded from the respective outlets of the extruder to pass through the first, the second and the third flow channels of the preformer.

[0025] In an example, the outlets of the first and the third flow channels of preformer are horizontally aligned. Further, the third flow channel of the preformer creates an elevated flow path from an inlet of the third flow channel to an outlet of the third flow channel of the preformer to extrude the third material from the third outlet of the extruder to form the second portion of the sidewall.

[0026] According to the present subject matter, when the preformer is attached to the extruder head of the extruder, the outlets formed at the extruder heads are aligned with the inlets of the preformer. The third flow channel of the preformer provides an elevated flow path for the third material extruded from the outlet formed at the extruder head to flow upward. This allows the third material, e.g., a zinc -based white rubber compound to flow to the top side of the tire to form the second portion of the sidewall of the tire, even when the third material is extruded from the outlet placed downward in an arrangement of the outlets at the extruder head. Further, the first and the third outlet of the preformer are horizontally aligned to allow the second portion of the sidewall to be created adjacent to the first portion of sidewall which is to be formed adjacent to the tread region or shoulder region of the tire. Thus, the tire can be manufactured using the existing extruder without incorporating an additional flow channel which may incur a substantially high cost. [0027] 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.

[0028] Figures 2A and 2B illustrate a back view and a front view, respectively, of a preformer for an extruder head of an extruder to extrude materials for tire manufacturing, in accordance with an implementation of the present subject matter. Figures 3A and 3B illustrate a back view and a front view, respectively, of a swivel box to insert the preformer therein and to be attached to the extruder head of the extruder, in accordance with an implementation of the present subject matter. Figures 4A and 4B illustrate a back view and a front view, respectively, of the swivel box with the preformer inserted therein, in accordance with an implementation of the present subject matter. Figure 5A illustrates a schematic of an attachment to be inserted into an outlet of a flow channel of the extruder, in accordance with an implementation of the present subject matter. Figure 5B illustrates a schematic of the attachment inserted into the outlet of the flow channel of the extruder, in accordance with an implementation of the present subject matter. Figure 6A illustrates a schematic of a restrictor plate to be affixed to the attachment inserted in the outlet of the flow channel of the extruder, in accordance with an implementation of the present subject matter. Figure 6B, illustrates a schematic of the attachment having a restrictor plate affixed thereto and inserted in the outlet of the flow channel of the extruder, in accordance with an implementation of the present subject matter.

[0029] Referring to Figures 2 A and 2B, a preformer 200 for an extruder head of an extruder (not shown in Figures) to extrude materials for tire manufacturing is illustrated, in accordance with an implementation of the present subject matter. Figure 2A illustrates a back view of the preformer 200, while Figure 2B illustrates a front view of the preformer 200. As explained above, an extruder is used to extrude materials to a mould or die for manufacturing a semifinished tire. The extruder has multiple flow channels to extrude similar or different rubber compounds for manufacturing various regions of the tire as a single unit. In an example, a triplex extruder having three flow channels for extruding three same or different rubber compounds at the same time may be used to manufacture a tire having three different regions. Each of the flow channels of the extruder has an outlet formed on an extruder head of the extruder for extruding the material. A first, a second, and a third outlet of the three flow channels of the extruder may be arranged one below the other.

[0030] In an example, the tire to be manufactured is similar to a tire illustrated in Figure 1. The tire 100 comprises a tread region that corresponds to the first region 102 as illustrated in Figure 1. The tread region comprises a center tread region and a shoulder tread region on both sides of the center tread region. A sidewall region of the tire 100 extends from the shoulder tread region on both sides towards a bead region of the tire 100. The bead region may be understood as edges of the tire 100 that contact with wheel during mounting of the tire 100 on a wheel. In the example, embodiment illustrated in Figure 1, the sidewall region of the tire 100 comprises a first sidewall portion and a second sidewall portion corresponding to the portion of the sidewall adjacent to the bead region of the tire. The first portion is adjacent to the second portion and is towards the shoulder region of the tire. The first sidewall portion and a cushioning inside the tire together form the second region 104 of the tire as illustrated in Figure 1. Further, the second portion of the sidewall corresponds to the third region 106 of the tire 100 as illustrated in Figure 1.

[0031] In an example, the first outlet of the extruder extrudes a first material to produce the tread region, i.e., the first region 102, of the tire 100. The first material may be a carbon-based rubber compound such as natural rubber (NR), any synthetic rubber like styrene-butadiene rubber (SBR), butadiene rubber (BR), or combinations thereof, etc. In an example, the second outlet of the extruder extrudes a second material to produce the first portion of the sidewall and cushioning inside the tire, i.e., the second region 104, of the tire 100. The second material may be a carbon-based rubber compound such as natural rubber (NR), any synthetic rubber like styrene-butadiene rubber (SBR), butadiene rubber (BR), or combinations thereof, etc. The second material may be same or different from the first material. In an example, the third outlet of the extruder extrudes a third material to produce the second portion of the sidewall, i.e., the third region 106, of the tire 100. The third material may be a zinc-based rubber compound of white color such as Zinc Oxide. The extruder needs to be operated at a speed such that all the three flow channels can be operated in synchronization with each other to extrude the required volume of material as per the required profile of the tire 100, from the respective outlets.

[0032] The third material extruded from a third flow channel needs to flow to the top part of the tire 100 or over the second material since the third region is formed above the cushioning of the tire 100. To achieve such flow direction for the third material, the preformer 200 is attached to the extruder head of the extruder. [0033] The preformer 200 comprises a first flow channel, a second flow channel, and the third flow channel. Each of the first, the second, and the third flow channels comprises an inlet and an outlet. Figure 2A illustrates the back side of the preformer 200 with inlets 202; 204; 206-1, 206-2 of the first, the second, and the third flow channels of the preformer 200 formed thereon. When the preformer 200 is attached to the extruder head of the extruder, each of the inlets 202; 204; 206-1, 206-2 of the first, the second, and the third flow channels of the preformer 200 is aligned with the first, the second and the third outlet of the extruder, respectively formed at the extruder head of the extruder. Figure 2B illustrates a front side of the preformer 200 with outlets 208; 210; 212-1, 212-2 of the first, the second, and the third flow channels formed thereon.

[0034] In an example, the preformer 200 is made of a case hardening steel having low tensile strength. The case hardening steel has wear-resistant surfaces and high core toughness. Further, case-hardening steel has a relatively low carbon content. In an example, the case hardening steel is EN32 steel grade with hardening. [0035] In an example implementation of the present subject matter, the preformer 200 is inserted in a swivel box 300 as illustrated in Figures 3 A and 3B, and the swivel box 300 is attached to the extruder head via a hinge. Figures 3A and 3B illustrate the back view and the front view, respectively, of the swivel box 300. The back side of the swivel box 300 comprises opening for the inlets 202; 204; 206-1, 206-2 of the first, the second, and the third flow channels of the preformer 200 to allow the inlets 202; 204; 206-1, 206-2 to receive the first, the second and the third material. In an example, the openings at the back side of the swivel box 300 for the inlets 202; 204; 206-1, 206-2 of the first, the second, and the third flow channels of the preformer 200 correspond to a cavity defined within the swivel box 300 to receive the preformer 200. When the preformer 200 fits inside the cavity, the inlets 202; 204; 206-1, 206-2 of the first, the second, and the third flow channels of the preformer 200 are exposed at the back side of swivel box 300. Further, the front side of the swivel box 300 comprises opening 302 for the outlets 208; 210; 212-1, 212-2 of the first, the second, and the third flow channels of the preformer 200 to allow the first, the second and the third material to extrude therefrom. Figures 4A and 4B illustrate a back view and a front view, respectively, of the swivel box 300 with the preformer 200 inserted therein, in accordance with an implementation of the present subject matter.

[0036] In an example implementation, the inlet 202 of the first flow channel is arranged at top side of the preformer 200 and aligned with the first outlet formed at top of the extruder head. The inlet 202 of the first flow channel of the preformer 200 receives the first material extruded therefrom. The first material then flows through the first flow channel of the preformer 200 and is extruded from the outlet 208 of the first flow channel to a die or mould to form the tread region of the tire 100. The outlet 208 of the first flow channel is arranged at top side of the front side of the preformer 200. In an example, a length LI of the inlet 202 of the first flow channel of the preformer 200 is in a range of 500 mm-550 mm. In an example, a length L4 of the outlet 208 of the first flow channel of the preformer 200 is in a range of 150 mm- 180 mm. [0037] The inlet 204 of the second flow channel of the preformer 200 is arranged downward to the inlet 202 of the first flow channel and aligned with the second outlet formed at the extruder head. The inlet 204 of the second flow channel of the preformer 200 receives the second material extruded therefrom. This allows the second material to flow through the second flow channel of the preformer 200. The second material is extruded from the outlet 210 of the second flow channel to the die or mould to form the first portion of the sidewall and the cushioning inside the tire 100. In an example, a length L2 of the inlet 204 of the second flow channel of the preformer 200 is in a range of 250 mm-350 mm. In an example, a length L5 of the outlet 210 of the second flow channel of the preformer 200 is in a range of 220 mm-320 mm.

[0038] Further, the inlet 206-1, 206-2 of the third flow channel is arranged downward to the inlet 204 of the second flow channel and aligned with the third outlet formed at the extruder head to receive the third material extruded therefrom, thereby allowing the third material to flow through the third flow channel. In an example, the outlets 208; 212-1, 212-2 of the first and the third flow channels are horizontally aligned. As explained above, the inlet 206-1, 206-2 of the third flow channel is formed at a bottom end of the preformer 200 and the outlet 208 of the first flow channel is formed at top of the front side of the preformer 200. Thus, the third flow channel of the preformer 200 creates an elevated flow path from the inlet 206-1, 206-2 of the third flow channel to the outlet 212-1, 212-2 of the third flow channel of the preformer 200 to extrude the third material extruded from the third outlet of the extruder to form the second portion of the sidewall.

[0039] As would be understood, the second portion of the sidewall needs to be formed on both sides of the tread region, extending from the first portion of the sidewall towards the bead region of the tire 100. Thus, each of the inlets 206-1, 206-2 and the outlet 212-1, 212-2 of the third flow channel is divided into two parts separated by a first and a second predetermined distance, respectively to provide two different elevated flow paths for the third material. Since the sidewall region is created on both sides of the tread region of the tire 100, the outlet 208 of the first flow channel extruding the first material to form the tread region of the tire 100, is arranged between the two parts 212-1, 212-2 of the outlet of the third flow channel which extrudes the third material to form the second portion of the sidewall. Thus, the first and the second predetermined distances may be greater than a length of the outlet 208 of the first flow channel. In an example, a length L3 of each of the two parts 206-1, 206-2 of the inlet of the third flow channel of the preformer 200 is in a range of 50 mm-75 mm. In an example, a length L6 of each of the two parts 212-1, 212-2 of the outlet 212-1, 212-2 of the third flow channel of the preformer 200 is in a range of 40 mm-70 mm.

[0040] To align the inlet of the third flow channel of the preformer 200 with the third outlet formed at the extruder head of the extruder, the third outlet of the extruder needs to be divided into two parts separated by the first predetermined distance. For this purpose, an attachment 400 as illustrated in Figure 5A is inserted into the third outlet of the extruder. In an example, the attachment 400 is in a shape of a trapezium. In an example, holes 402 are provided on a surface of the attachment 400 and the attachment 400 is affixed inside the third outlet, i.e., inside the corresponding flow channel of the extruder via fastening the bolts through the holes. Figure 5B illustrates a schematic of the attachment 400 inserted into the third outlet 502 of corresponding flow channel 500 of the extruder, in accordance with an implementation of the present subject matter. Further, the attachment 400 provides a surface for a restrictor plate 600, as shown in Figure 6A, to be inserted in the middle to the third outlet 502 of the extruder for dividing the third outlet 502 into two parts 502-1, 502-2. In an example, the shape of the restrictor plate is triangular. In an example, holes 402 are also provided on the surface of the attachment 400 for affixing the restrictor plate 600 thereto through bolts.

[0041] Figure 6B, illustrates a schematic of the attachment 400 having restrictor plate 600 affixed thereto and inserted in the third outlet 502 of the corresponding flow channel 500 of the extruder, in accordance with an implementation of the present subject matter. In an example, a length of a base of the triangular shaped restrictor plate is equal to the first predetermined distance. The restrictor plate 600 divides the third outlet 502 of the extruder into two parts 502-1, 502-2 through its base 602. Thus, the two parts 502-1, 502-2 of the third outlet 502 of the extruder are aligned with the two parts 206-1, 206-2 of the inlet of the third flow channel of the preformer 200. The third material flowing through the corresponding flow channel of the extruder is extruded from the two parts 212- 1, 212-2 of the third outlet. Each of the two parts 206-1, 206-2 of the inlets of the third flow channel receives the third material from the corresponding part 502-1, 502-2 of the third outlet 502 of the extruder. The third material is then extruded from the two parts 212-1, 212-2 of the outlet of the third flow channel of the preformer 200 to form the second portion of the sidewall on both sides of the tread region, next to the first portion of the sidewall towards the bead region.

[0042] Thus, as a result of an example implementation of the preformer 200 disclosed in the present subject matter, a flow path is provided such that the material extruded from a bottommost outlet of a flow channel of the extruder can flow upward to form the top part of the tire, i.e., a portion of the sidewall region, adjacent the tread region of the tire, which is produced by the material extruded from the top most outlet of the flow channel of the extruder. This obviates a need to install another flow channel at the top of the extruder head to produce the portion of the sidewall of the tire, which may be produced using a material, e.g., a zinc- based rubber compound of white color, different than the material used to produce another portion of the sidewall of the tire.

[0043] Although implementations of a preformer 200 are described, it is to be understood that the present subject matter is not necessarily limited to the specific features of the systems described herein. Rather, the specific features are disclosed as implementations for the preformer 200.