JP2017159479A - Method for manufacturing cushion tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a bead core built-in cushion tire by which good productivity can be achieved.SOLUTION: A method for manufacturing a cushion tire 2 comprises a process in which a raw cover 30 is formed, and a process in which the raw cover 30 is vulcanized. The process for forming the raw cover 30 includes: (1) a step at which bead cores 8 are arranged in grooves 16 which are provided on an outer peripheral surface 15 of a drum D and extend in a circumferential direction; (2) a step at which an unvulcanized rubber layer is formed on the outer peripheral surface 15 of the drum D; (3) a step at which the bead core 8 and the rubber layer are removed from the drum D; and (4) a step at which the unvulcanized rubber layer is bonded to an inner face of the rubber layer removed from the drum D. Preferably, the process for forming the raw cover 30 further includes a step at which the bead core 8 and the unvulcanized rubber layer, which are combined with each other in the processes (1) to (4), are pre-heated.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for manufacturing a cushion tire. Specifically, the present invention relates to a method for manufacturing a cushion tire incorporating a bead core.

  The cushion tire is a solid tire having no air inside. As a cushion tire, a “pneumatic type” that can be used by being directly incorporated into a rim for a pneumatic tire is frequently used. Cushion tires are mainly used for industrial vehicles such as forklift trucks to which a large load is applied.

  When a vehicle loaded with a large load starts or stops, a large force is applied in the circumferential direction between the cushion tire and the rim. By repeatedly starting and stopping, the tire may slip relative to the rim. The sliding of the tire with respect to the rim is called rim slip. There is a need for a cushion tire in which rim slip is prevented.

  In order to prevent the rim slip of the cushion tire, a method of embedding a bead core in the base layer of the tire is used. A study on this method is reported in Japanese Patent Application Laid-Open No. 8-21661. The bead core described in this publication is composed of an outer bead core near the flange of the rim and an inner bead core positioned on the inner side in the axial direction. These bead cores extend in the circumferential direction of the tire. This bead core improves the force with which the tire tightens the rim. This tightening force prevents rim slip.

JP-A-8-21661

  Usually, in the manufacture of a cushion tire, a sheet of unvulcanized rubber is wound around a molding drum. A sheet of unvulcanized rubber is laminated to the molding drum. In a cushion tire in which a bead core is buried inside the tire, the bead core is disposed on the sheet while the rubber sheet is laminated on the drum. After placing the bead core, the unvulcanized rubber sheet is laminated again. As a result, the raw cover is formed. This raw cover is put into a mold. The raw cover is pressurized and heated by a mold. Thereby, the rubber composition of a raw cover raise | generates a crosslinking reaction. A cushion tire is obtained by this cross-linking reaction.

  In this method, a positioning device is used to determine where to place the bead core on the rubber sheet. This process takes time. Further, in order to bury the bead core in the rubber, the molding drum is expanded after the bead core is arranged. This process also takes time. In this cushion tire manufacturing method, productivity is reduced as compared with the case of manufacturing a cushion tire without a bead core.

  In order to facilitate positioning of the bead core, there is a method in which a recess is formed in advance on the sheet and the bead core is disposed in the recess. However, this method requires a step of forming a recess in the sheet. Also in this cushion tire manufacturing method, productivity is reduced as compared with the case of manufacturing a cushion tire without a bead core.

  The objective of this invention is providing the manufacturing method of the cushion tire by which the fall of productivity by containing a bead core was suppressed.

The present invention relates to a method of manufacturing a cushion tire including a bead core therein. This manufacturing method includes a step of forming a raw cover and a step of vulcanizing the raw cover. The step of molding the raw cover includes
(1) a step of arranging bead cores in a circumferentially extending groove provided on the outer peripheral surface of the drum;
(2) forming an unvulcanized rubber layer on the outer peripheral surface of the drum;
(3) A step of removing the bead core and the rubber layer from the drum, and (4) a step of attaching an unvulcanized rubber layer to the inner surface of the rubber layer removed from the drum.

  Preferably, the step of forming the raw cover further includes a step of preheating the bead core and the unvulcanized rubber layer combined in the steps (1) to (4).

  Preferably, the cushion tire includes a base including the bead core and a tread located on the radially outer side of the base. In the step (2), one of the unvulcanized rubber layers for the base is used. And the unvulcanized rubber layer for the tread are formed, and the remaining portion of the unvulcanized rubber layer for the base is formed in the step (4).

  The cushion tire includes a base including the bead core and a tread positioned radially outward of the base, and in the step (2), a part of the unvulcanized rubber layer for the base is formed. In the step (4), the remaining portion of the unvulcanized rubber layer for the base is formed, and the step of forming the raw cover is performed after the preheating step, after the preheating step. It may further include forming an unvulcanized rubber layer for the tread on the outside of the vulcanized rubber layer.

  Preferably, the preheating temperature is 50 ° C. or higher and 90 ° C. or lower.

  In the cushion tire manufacturing method according to the present invention, in the step of forming the raw cover, the bead core is disposed in a groove provided on the outer peripheral surface of the drum. A rubber layer is formed on the outer peripheral surface of the drum. The rubber layer is removed from the drum, and another rubber layer is attached to the inner surface. In this manufacturing method, the position of the bead core can be determined simply by disposing the bead core in the groove provided on the outer peripheral surface of the drum. There is no need to provide a bead core positioning step. There is no need to provide a step of expanding the molding drum after the bead core is disposed just to bury the bead core in the rubber. Further, there is no need to provide a step of creating a groove on the rubber sheet. In this manufacturing method, there is little decrease in productivity due to the incorporation of the bead core. This manufacturing method is excellent in productivity.

FIG. 1 is a cross-sectional view illustrating a part of a cushion tire manufactured by a manufacturing method according to an embodiment of the present invention. FIG. 2 is a schematic view showing a drum used in this manufacturing method. FIG. 3 is a cross-sectional view illustrating a process in which bead cores are arranged on the drum of FIG. FIG. 4 is a schematic view showing a state in which a sheet of unvulcanized rubber is wound around the outer peripheral surface of the drum of FIG. FIG. 5 is a cross-sectional view showing the middle of the process of forming an unvulcanized rubber layer on the outer peripheral surface of the drum of FIG. FIG. 6 is a cross-sectional view showing the middle of the process of forming an unvulcanized rubber layer on the outer peripheral surface of the drum of FIG. FIG. 7 is a cross-sectional view showing a raw cover of the cushion tire of FIG. FIG. 8 is a cross-sectional view illustrating a process in which the raw cover of the cushion tire of FIG. 1 is vulcanized.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a cross-sectional view of the cushion tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. What is indicated by the symbol R is a rim. This rim R is a regular rim. The regular rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In FIG. 1, the tire 2 is incorporated in a rim R. The cushion tire 2 is a pneumatic type.

  The tire 2 includes a tread 4, a base 6, a bead core 8, and a skin layer 10.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 12 that contacts the road surface. A groove 14 is carved in the tread surface 12. The groove 14 forms a tread pattern. The tread 4 is made of a crosslinked rubber having excellent wear resistance and grip properties. In the present embodiment, the tread 4 is formed from a single rubber. The tread 4 may be formed from two or more rubbers.

  The base 6 is located on the inner side in the radial direction of the tread 4. The base 6 is made of a crosslinked rubber. Although not shown, in the present embodiment, the base 6 includes short fibers. The short fiber is obtained by cutting a cord made of an organic fiber into a short piece. Examples of preferable organic fibers include polyester fibers, nylon fibers, polyethylene naphthalate fibers, and aramid fibers. A mixture of a plurality of types of short fibers may be used. The base 6 may not include short fibers. The base 6 may be formed of two or more rubbers.

  The bead core 8 is located inside the base 6. The bead core 8 is buried in the base 6. The bead core 8 extends in the circumferential direction. The bead core 8 has a ring shape. Although not shown, the bead core 8 includes a wound non-stretchable wire. A typical material for the wire is steel. The bead core 8 improves the force with which the tire 2 tightens the rim R. The bead core 8 contributes to prevention of rim slip. In the tire 2 of FIG. 1, three bead cores 8 are located in the base 6. The number of bead cores 8 is not limited to three. The number of bead cores 8 may be two or less. The number of bead cores 8 may be four or more.

  The skin layer 10 forms the side surface of the tire 2. The skin layer 10 is located on the outer side in the axial direction of the tread 4 and the base 6. The skin layer 10 protects the tread 4 and the base 6.

[First embodiment]
Below, one Embodiment of the manufacturing method of the cushion tire 2 which concerns on this invention is shown. The manufacturing method of the tire 2 includes a step of forming a raw cover and a step of vulcanizing the raw cover.

  In the step of forming the raw cover, a drum is used. FIG. 2 is a side view of the drum D. FIG. 3 shows a part of the cross section of the drum D. FIG. 4 shows the front of the drum D. The drum D is cylindrical. The outer diameter of the drum D can be expanded and contracted.

  As shown in the drawing, the outer peripheral surface 15 of the drum D is provided with a groove 16 extending in the circumferential direction. The number of grooves 16 is the same as the number of bead cores 8. In the tire 2 of this embodiment, since the number of bead cores 8 is 3, the number of grooves 16 is also 3. When manufacturing a tire having four bead cores 8, a drum having four grooves 16 is used. The interval between the grooves 16 is the same as the interval between the bead cores 8 in the base 6. The width of the groove 16 corresponds to the width of the bead core 8.

  Although not shown in this embodiment, sometimes a plurality of raw covers are molded in parallel. In this case, a plurality of low cover rubber layers are formed on one drum D. At this time, a plurality of sets of grooves are provided on the drum D, with the same number of grooves as the number of bead cores 8 as one set. For example, when two low covers for a tire shown in FIG. 1 are formed at a time, the three grooves shown in FIG. 2 are set as one set, and two sets of grooves are provided on the drum. That is, a total of six grooves are provided on the drum. In each set, the interval between the grooves 16 is the same as the interval between the bead cores 8. As will be described later, a layer of unvulcanized rubber is formed on this drum. This layer is then divided into two. In the following, for the sake of simplicity, a process of forming a raw cover in the case where one rubber cover layer is formed on the drum at a time will be described.

The process of molding the raw cover is as follows:
(1) a step of arranging the bead cores 8 in the grooves 16 provided on the outer peripheral surface 15 of the drum D;
(2) forming an unvulcanized rubber layer on the outer peripheral surface 15 of the drum D;
(3) Step of removing bead core 8 and rubber layer from drum D (4) Step of attaching another unvulcanized rubber layer to the inner surface of the rubber layer removed from drum D (5) Formed above It includes a step of attaching another unvulcanized rubber layer to the side surface of the rubber layer, and (6) a step of preheating the bead core 8 and the unvulcanized rubber layer combined in the above steps.

  In the step (1), the bead cores 8 are arranged in the grooves 16 on the outer peripheral surface 15 of the drum D. This is shown in FIG. In this figure, the vertical direction is the radial direction of the drum D, the horizontal direction is the axial direction of the drum D, and the direction perpendicular to the paper surface is the circumferential direction of the drum D. A bead is arranged in each groove 16. In the figure, the height of the bead core 8 is larger than the depth of the groove 16. A part of the bead core 8 protrudes from the groove 16. The height of the bead core 8 and the depth of the groove 16 may be the same.

  In FIG. 3, since one row cover is molded, the bead cores 8 are arranged in each of the three grooves. As described above, when a plurality of raw covers are formed at a time, the drum is provided with a plurality of sets of grooves. At this time, the bead cores 8 are arranged in all of these grooves. For example, when two raw covers are molded simultaneously, the drum is provided with six grooves. A bead core 8 is arranged in each of these six grooves.

  In the step (2), a first unvulcanized rubber sheet 18 for the base 6 is first prepared as shown in FIG. A sheet of first unvulcanized rubber 18 is wound on the drum D. The drum D is configured to rotate around a central axis indicated by a symbol O. The direction indicated by the arrow P is the rotation direction of the drum D. This rotational direction P corresponds to the circumferential direction of the tire 2.

  As shown in FIG. 4, the starting end of the sheet 18 is placed on the drum D. The drum D is rotated in the direction indicated by the arrow P. Thereby, the sheet | seat 18 is wound by the circumferential direction. Thereby, the layer 20 of the first unvulcanized rubber is provided on the outer peripheral surface 15 of the drum. The first unvulcanized rubber layer 20 is formed so as to cover all the grooves 16 in which the bead cores 8 are arranged. The width of the first unvulcanized rubber layer 20 corresponds to the width of one raw cover. FIG. 5 shows a state in which the layer 20 of the first unvulcanized rubber for the base 6 is formed on the drum D. As will be described later, an unvulcanized rubber layer for the base 6 is further formed inside the first unvulcanized rubber layer 20 in the following step (4). That is, in this step, a part of the unvulcanized rubber layer for the base 6 is formed.

  In the step (2), a second unvulcanized rubber sheet for the tread 4 is further prepared. A sheet of the second unvulcanized rubber is wound on the outer side in the radial direction of the layer 20 of the first unvulcanized rubber using the drum D. As shown in FIG. 6, a second unvulcanized rubber layer 22 for the tread 4 is formed on the radially outer side of the first unvulcanized rubber layer 20 for the base 6.

  When molding a plurality of raw covers at once, the first unvulcanized rubber layer 20 and the second unvulcanized rubber layer 22 are formed so as to cover all of the plurality of sets of grooves. For example, when two raw covers are formed at the same time, the first unvulcanized rubber layer 20 and the second unvulcanized rubber layer 22 are formed so as to cover all six grooves. At this time, the width of the first unvulcanized rubber layer 20 and the width of the second unvulcanized rubber layer 22 correspond to the width of two raw covers.

  In the step (3), the bead core 8, the first unvulcanized rubber layer 20, and the second unvulcanized rubber layer 22 are removed from the drum D. This is done by reducing the outer diameter of the drum D. At this time, the bead core 8 is fixed to the first unvulcanized rubber layer 20. The positional relationship between the bead core 8 and the first unvulcanized rubber layer 20 is maintained. In this embodiment, the bead core 8, the first unvulcanized rubber layer 20 and the second unvulcanized rubber layer 22 are referred to as an intermediate 24.

  When molding a plurality of raw covers at once, the bead core 8, the first unvulcanized rubber layer 20 and the second unvulcanized rubber layer 22 are arranged in a plane perpendicular to the axial direction before being removed from the drum D. Disconnected. These are divided into a plurality of parts. Each divided part includes a set of bead cores. For example, when two raw covers are molded simultaneously, the bead core 8, the first unvulcanized rubber layer 20 and the second unvulcanized rubber layer 22 are divided into two parts. Each part includes three bead cores. Each part has a width corresponding to one raw cover. After the division, these parts are removed from the drum D. In this case, each divided part is an intermediate 24. For each intermediate 24, the following steps (4)-(6) are performed.

  In the step (4), a third unvulcanized rubber sheet for the base 6 is further prepared. The composition of the third unvulcanized rubber is the same as that of the first unvulcanized rubber. The width of this sheet is the same as the width of the intermediate body 24. The length of this sheet is the same as the inner peripheral length of the intermediate body 24. This sheet is affixed to the inner surface of the first unvulcanized rubber layer 20 to which the bead core is fixed. That is, this sheet is affixed inside the intermediate body 24. The third unvulcanized rubber sheet is a single layer. As a result, a third unvulcanized rubber layer 26 is formed inside the intermediate body 24 as shown in FIG. As described above, in the step (2), a part of the unvulcanized rubber layer for the base 6 was formed. In this step, the remaining portion of the unvulcanized rubber layer for the base 6 is formed.

  When molding a plurality of raw covers at once, a third unvulcanized rubber sheet is attached to each of the plurality of intermediate bodies 24.

  In the step (5), a fourth unvulcanized rubber is prepared for the skin layer 10. This is laminated to the sides of the intermediate 24 and the third unvulcanized rubber layer 26. FIG. 7 shows the state after the fourth unvulcanized rubber layer 28 has been laminated. Thereby, the raw cover 30 is obtained. As described below, the raw cover 30 is preheated in the step (6). The raw cover 30 before preheating and the raw cover 30 after preheating are not exactly the same, but are referred to herein as the same raw cover.

  In the step (6), the raw cover 30 is placed in a heating tank. The raw cover 30 is heated in a heating tank. This heating is performed in order to discharge air remaining between the first unvulcanized rubber layer 20 and the third unvulcanized rubber layer 26 and the bead core 8 in a later vulcanization step. By this heating, the fluidity of each unvulcanized rubber is enhanced. The temperature in the heating tank at this time is lower than the temperature at which the first unvulcanized rubber, the second unvulcanized rubber, the third unvulcanized rubber, and the fourth unvulcanized rubber undergo a crosslinking reaction. At this time, the progress of the crosslinking reaction of the first unvulcanized rubber, the second unvulcanized rubber, the third unvulcanized rubber, and the fourth unvulcanized rubber is suppressed. By this heating, the process of forming the raw cover 30 is completed.

  Note that there is no need to preheat the raw cover 30. The raw cover 30 before preheating may be vulcanized as it is.

  In the process of vulcanizing the raw cover, a mold 32 is used. FIG. 8 is a cross-sectional view showing the mold 32. The left-right direction in FIG. 8 is the radial direction. This mold 32 is a two-piece mold. The mold 32 includes an upper mold 34 and a lower mold 36. FIG. 8 also shows the raw cover 30. In the view of the raw cover 30, the fourth unvulcanized rubber layer 28 is omitted.

  In this step, the mold 32 is first opened. That is, the upper mold 34 is separated from the lower mold 36. In this state, the raw cover 30 is set inside the lower mold 36. Thereafter, the mold 32 is closed. That is, the upper mold 34 is overlaid on the lower mold 36. At this time, air may remain between the mold 32 and the raw cover 30. In order to discharge air, the mold 32 is normally opened and closed repeatedly with the raw cover 30 set. This process is called bumping. As described above, in the raw cover 30, the fluidity of each unvulcanized rubber is enhanced by the above-described preheating. Therefore, the air remaining between the first unvulcanized rubber layer 20 and the third unvulcanized rubber layer 26 and the bead core 8 is also discharged by the bumping.

  The raw cover 30 set in the mold 32 is heated. This heating causes each unvulcanized rubber to undergo a crosslinking reaction. The base 6 is obtained from the first unvulcanized rubber layer 20 and the third unvulcanized rubber layer 26. The tread 4 is obtained from the second unvulcanized rubber layer 22. The skin layer 10 is obtained from the fourth unvulcanized rubber layer 28. By this crosslinking reaction, the cushion tire 2 is obtained.

  The effects of the present invention will be described below.

  Usually, in the manufacture of a cushion tire including a bead core, a positioning device is used when the bead core is disposed on a rubber sheet. This process takes time. Further, in order to bury the bead core in the rubber, the molding drum is expanded after the bead core is arranged. This process also takes time. In this cushion tire manufacturing method, productivity is reduced as compared with the case of manufacturing a cushion tire without a bead core. In order to facilitate positioning of the bead core, there is a method in which a recess is formed in advance on the sheet and the bead core is disposed in the recess. However, this method requires a step of forming a recess in the sheet. Also in this cushion tire manufacturing method, productivity is reduced as compared with the case of manufacturing a cushion tire without a bead core.

  In the method for manufacturing the cushion tire 2 according to the present invention, the bead core 8 is disposed in the groove 16 provided on the outer peripheral surface 15 of the drum in the step of forming the raw cover 30. A rubber layer is formed on the outer peripheral surface 15 of the drum. Another rubber layer is affixed to the inner surface of the formed rubber layer. In this manufacturing method, the position of the bead core 8 can be determined simply by placing the bead core 8 in the groove 16 provided on the outer peripheral surface 15 of the drum. There is no need to provide a process for positioning the bead core 8. There is no need to provide a step of expanding the molding drum after the bead core 8 is disposed just to bury the bead core 8 in the rubber. Further, there is no need to provide a step of forming the groove 16 on the rubber sheet 18. In this manufacturing method, the decrease in productivity due to the incorporation of the bead core 8 is small. This manufacturing method is excellent in productivity.

  In FIG. 7, the double arrow TG is the thickness of the first unvulcanized rubber layer to be attached in the step (4). A double arrow TB is the thickness of the bead core 8. The ratio of the thickness TG to the thickness TB (TG / TB) is preferably 1.2 or more. By setting the ratio (TG / TB) to 1.2 or more, the bead core 8 can be surely buried in the first vulcanized rubber. In this respect, the ratio (TG / TB) is more preferably equal to or greater than 1.3.

  In a tire incorporating a bead core, air tends to remain between the rubber and the bead core in the process of forming the raw cover. Also in this manufacturing method, air may remain in the step (4) of attaching the third unvulcanized rubber layer 26 to the inner surface of the intermediate body 24. Usually, when putting a raw cover into a mold, bumping is performed in order to discharge air remaining between the raw cover and the mold. Since the raw cover is put in the mold at room temperature, the fluidity of the rubber constituting the raw cover is low at this time. The air remaining between the rubber and the bead core is not sufficiently discharged even during bumping because the bead core and the rubber having low fluidity become an obstacle. The remaining air that is not discharged can cause a decrease in the adhesion between the rubber and the bead core. This can be a cause of separation between the rubber and the bead core.

  As described above, in this manufacturing method, the step of forming the raw cover 30 preferably includes the step (6). The fluidity of the unvulcanized rubber layer is increased by the preheating performed in the step (6). This rubber does not interfere with air discharge. Thereby, the air remaining between the bead core 8 and the rubber is discharged to the outside by bumping in the vulcanization process. The air remaining between the first unvulcanized rubber layer 20 and the third unvulcanized rubber layer 26 and the bead core 8 is easily discharged outside in the vulcanization process. In the method for manufacturing the tire 2, air is prevented from remaining between the rubber and the bead core 8. According to the present invention, a manufacturing method that is excellent in productivity and that prevents air from remaining is realized.

  The temperature in the heating tank during preheating is preferably 50 ° C. or higher. By setting the temperature in the heating tank to 50 ° C. or higher, the fluidity of the unvulcanized rubber is effectively enhanced. Thereby, the air remaining between the bead core 8 and the rubber can be effectively discharged. From this viewpoint, the temperature in the heating tank is more preferably 60 ° C. or higher, and further preferably 80 ° C. or higher.

  The temperature in the heating tank during preheating is preferably 90 ° C. or lower. By setting the temperature in the heating tank at the time of preheating to 90 ° C. or less, it is possible to prevent the unvulcanized rubber from causing a crosslinking reaction.

  The preheating time is preferably 3 hours or more. By setting the preheating time to 3 hours or more, the fluidity of the unvulcanized rubber is effectively enhanced. From this viewpoint, this time is more preferably 4 hours or more.

[Second Embodiment]
Below, other embodiment of the manufacturing method of the cushion tire 2 which concerns on this invention is shown. The manufacturing method of the tire 2 includes a step of forming a raw cover and a step of vulcanizing the raw cover.

  In the step of forming the raw cover, a drum is used. The drum is cylindrical. A groove extending in the circumferential direction is provided on the outer peripheral surface of the drum. The number of grooves is the same as the number of bead cores 8. In the tire 2 of this embodiment, since the number of bead cores 8 is 3, the number of grooves is also 3. When manufacturing a tire having four bead cores 8, a drum having four grooves is used. The interval between the grooves is the same as the interval between the bead cores 8 in the base 6. The width of the groove corresponds to the width of the bead core 8.

  Although not shown in this embodiment, a plurality of raw covers may be formed on the drum at once. At this time, a plurality of sets of grooves are provided on the drum with the same number of grooves as the number of bead cores 8 as one set. For example, when two low covers for tires of FIG. 1 are formed at a time, two sets of grooves are provided on the drum, with three grooves as one set. That is, a total of six grooves are provided on the drum. In each set, the groove spacing is the same as the bead core spacing.

The process of molding the raw cover is as follows:
(1) a step of arranging bead cores 8 in grooves provided on the outer peripheral surface of the drum;
(2) forming an unvulcanized rubber layer on the outer peripheral surface of the drum;
(3) Step of removing bead core 8 and rubber layer from the drum (4) Step of attaching another unvulcanized rubber layer to the inner surface of the rubber layer removed from the drum (5) Combined in the above steps A step of preheating the bead core and the unvulcanized rubber layer (6) a step of attaching another unvulcanized rubber layer to the outside of the preheated rubber layer; and (7) a step of forming the rubber layer formed above. It includes a step of attaching another unvulcanized rubber layer to the side surface.

  In the step (1), the bead cores 8 are arranged in the grooves on the outer peripheral surface of the drum. A bead is arranged in each groove. The height of the bead core 8 is larger than the depth of the groove. A part of the bead core 8 protrudes from the groove. The height of the bead core 8 and the depth of the groove may be the same.

  When molding a plurality of raw covers at once, the drum is provided with a plurality of sets of grooves. At this time, the bead cores 8 are arranged in all of these grooves. For example, when two low covers are molded simultaneously, the drum is provided with six grooves as described above. A bead core 8 is arranged in each of these six grooves.

  In the step (2), a first unvulcanized rubber sheet for the base 6 is prepared. A sheet of first unvulcanized rubber is wound on the drum. The leading edge of the sheet is placed on the drum. The drum is rotated. Thereby, the sheet is wound in the circumferential direction. Thereby, the layer of the first unvulcanized rubber is provided on the outer peripheral surface of the drum. The first unvulcanized rubber layer is formed so as to cover all the grooves in which the bead cores 8 are arranged. The width of the first unvulcanized rubber layer corresponds to the width of one raw cover. As will be described later, an unvulcanized rubber layer for the base 6 is further formed inside the first unvulcanized rubber layer in the following step (4). That is, in this step, a part of the unvulcanized rubber layer for the base 6 is formed.

  When molding a plurality of raw covers at once, the first unvulcanized rubber layer is formed so as to cover all of the plurality of sets of grooves. For example, when two raw covers are molded simultaneously, a first unvulcanized rubber layer is formed so as to cover all six grooves. At this time, the width of the first unvulcanized rubber layer corresponds to the width of two raw covers.

  In the step (3), the bead core 8 and the first unvulcanized rubber layer are removed from the drum. This is done by reducing the outer diameter of the drum. At this time, the bead core 8 is fixed to the first unvulcanized rubber layer. The positional relationship between the bead core 8 and the first unvulcanized rubber layer is maintained. In this embodiment, the bead core 8 and the first unvulcanized rubber layer are referred to as an intermediate.

  When molding a plurality of raw covers at once, the bead core 8 and the first unvulcanized rubber layer are cut in a plane perpendicular to the axial direction before being removed from the drum. These are divided into a plurality of parts. Each divided part includes a set of bead cores. For example, when molding two raw covers simultaneously, the bead core 8 and the first unvulcanized rubber layer are divided into two parts. Each part includes three bead cores. Each part has a width corresponding to one raw cover. After splitting, these parts are removed from the drum. In this case, each divided part is an intermediate. The following steps (4) to (7) are performed for each intermediate.

  In the step (4), a third unvulcanized rubber sheet for the base 6 is further prepared. The composition of the third unvulcanized rubber is the same as that of the first unvulcanized rubber. The width of this sheet is the same as the width of the intermediate. The length of this sheet is the same as the inner peripheral length of the intermediate body. This sheet is affixed to the inner surface of the first unvulcanized rubber layer to which the bead core is fixed. That is, this sheet is affixed inside the intermediate body. The third unvulcanized rubber sheet is a single layer. Thereby, the layer of the third unvulcanized rubber is formed inside the intermediate body. As described above, in the step (2), a part of the unvulcanized rubber layer for the base 6 was formed. In this step, the remaining portion of the unvulcanized rubber layer for the base 6 is formed.

  When molding a plurality of raw covers at once, a third unvulcanized rubber sheet is attached to each of the plurality of intermediate bodies.

  In the step (5), the intermediate body to which the third unvulcanized rubber sheet is attached is placed in a heating tank. These are heated in a heating tank. This heating is performed in order to discharge air remaining between the first unvulcanized rubber layer and the third unvulcanized rubber layer and the bead core in the subsequent vulcanization step. By this heating, the fluidity of each unvulcanized rubber is enhanced. The temperature in the heating tank at this time is lower than the temperature at which the crosslinking reaction of the first unvulcanized rubber and the third unvulcanized rubber occurs. At this time, the progress of the crosslinking reaction of the first unvulcanized rubber and the third unvulcanized rubber is suppressed.

  Note that there is no need to preheat the intermediate body to which the third unvulcanized rubber sheet is attached.

  In the step (6), a second unvulcanized rubber sheet for the tread 4 is prepared. A heated second unvulcanized rubber sheet is fed from an extruder or roll. This second unvulcanized sheet is wound on the radially outer side of the intermediate. A sheet of second unvulcanized rubber is wound on the radially outer side of the first unvulcanized rubber layer for the base 6. A layer of second unvulcanized rubber for the tread 4 is formed.

  In the step (7), a fourth unvulcanized rubber is prepared for the skin layer 10. This is laminated to the sides of the intermediate, the third unvulcanized rubber layer and the second unvulcanized rubber layer. As a result, the raw cover is formed. Thereby, the process of shape | molding a raw cover is complete | finished.

  In the process of vulcanizing the raw cover, a mold is used. This mold is a two-piece mold. This mold includes an upper mold and a lower mold.

  In this process, the mold is first opened. That is, the upper mold is separated from the lower mold. In this state, the raw cover is set inside the lower mold. The mold is then closed. That is, the upper mold is overlaid on the lower mold. At this time, air may remain between the mold and the raw cover. In order to discharge air, the mold is normally opened and closed repeatedly with the raw cover set. This process is called bumping. As described above, in the raw cover, the fluidity of each unvulcanized rubber is enhanced by the preheating described above. Therefore, the air remaining between the first unvulcanized rubber layer and the third unvulcanized rubber layer and the bead core 8 is also discharged by the bumping.

  The raw cover set in the mold is heated. This heating causes each unvulcanized rubber to undergo a crosslinking reaction. A base 6 is obtained from the first unvulcanized rubber layer and the third unvulcanized rubber layer. The tread 4 is obtained from the second unvulcanized rubber layer. The skin layer 10 is obtained from the fourth unvulcanized rubber layer. By this crosslinking reaction, the cushion tire 2 is obtained.

  The effects of the present invention will be described below.

  In the method of manufacturing the cushion tire 2 according to the present invention, the bead core 8 is disposed in a groove provided on the outer peripheral surface of the drum in the step of forming the raw cover. A rubber layer is formed on the outer peripheral surface of the drum. Another rubber layer is affixed to the inner surface of the formed rubber layer. In this manufacturing method, the position of the bead core 8 can be determined simply by disposing the bead core 8 in a groove provided on the outer peripheral surface of the drum. There is no need to provide a process for positioning the bead core 8. There is no need to provide a step of expanding the molding drum after the bead core 8 is disposed just to bury the bead core 8 in the rubber. Further, there is no need to provide a step of creating a groove on the rubber sheet. In this manufacturing method, the decrease in productivity due to the incorporation of the bead core 8 is small. This manufacturing method is excellent in productivity.

  As described above, in this manufacturing method, it is preferable that the step of forming the raw cover includes the step of preheating the intermediate body to which the third unvulcanized rubber sheet is attached. This preheating increases the fluidity of the unvulcanized rubber layer. This rubber does not interfere with air discharge. Thereby, the air remaining between the bead core 8 and the rubber is discharged to the outside by bumping in the vulcanization process. The air remaining between the first unvulcanized rubber layer and the third unvulcanized rubber layer and the bead core 8 is easily discharged outside in the vulcanization process. In the method for manufacturing the tire 2, air is prevented from remaining between the rubber and the bead core 8. According to the present invention, a manufacturing method that is excellent in productivity and that prevents air from remaining is realized.

[Evaluation results]
Actually, the manufacturing method of Embodiment 1 was applied to the manufacture of a cushion tire having the configuration shown in FIG. The tire sizes are “18 × 7-8 ES BE”, “600-9 ES BE”, and “21 × 8-9 ES BE”. In the manufacture of tires of size “18 × 7-8 ES BE” and “600-9 ES BE”, the low cover was preheated at 90 ° C. for 4 hours. In the manufacture of tires with a size of “21 × 8-9 ES BE”, the raw cover was preheated at 90 ° C. for 5 hours. 100 tires were each manufactured by this manufacturing method. As a result, the increase in the manufacturing time by including the bead core compared to the manufacturing time of the cushion tire not including the bead core is ¼ of the increase in the manufacturing time in the conventional manufacturing method. Furthermore, 10 tires were arbitrarily extracted from each size tire and disassembled. It was confirmed visually that air remained between the bead core and the rubber. As a result, no residual air was observed in any size tire.

  From the above results, according to the present invention, it is possible to obtain a cushion tire in which a decrease in productivity due to the incorporation of a bead core is suppressed and air remaining is suppressed. From this result, the superiority of the present invention is clear.

  The tire manufacturing method according to the present invention can be applied to tires for industrial vehicles.

2 ... Tire 4 ... Tread 6 ... Base 8 ... Bead core 10 ... Skin layer 12 ... Tread surface 14 ... Groove 15 ... Outer peripheral surface 16 ... Groove 18 ..Sheet 20 ... first unvulcanized rubber layer 22 ... second unvulcanized rubber layer 24 ... intermediate 26 ... third unvulcanized rubber layer 28 ... first Four unvulcanized rubber layers 30 ... Raw cover 32 ... Mold 34 ... Upper mold 36 ... Lower mold

Claims (5)

A method of manufacturing a cushion tire including a bead core therein,
Including a step of forming a raw cover and a step of vulcanizing the raw cover,
The step of forming the raw cover includes
(1) a step of arranging bead cores in a circumferentially extending groove provided on the outer peripheral surface of the drum;
(2) forming an unvulcanized rubber layer on the outer peripheral surface of the drum;
(3) a step of removing the bead core and the rubber layer from the drum; and (4) a step of attaching an unvulcanized rubber layer different from the rubber layer to the inner surface of the rubber layer removed from the drum. Cushion tire manufacturing method.   The method for manufacturing a cushion tire according to claim 1, wherein the step of forming the raw cover further includes a step of preheating the bead core and the unvulcanized rubber layer combined in the steps (1) to (4). The cushion tire includes a base including the bead core, and a tread located on the radially outer side of the base,
In the step (2), a part of the unvulcanized rubber layer for the base and the unvulcanized rubber layer for the tread are formed,
The method for manufacturing a cushion tire according to claim 2, wherein in the step (4), the remaining portion of the unvulcanized rubber layer for the base is formed. The cushion tire includes a base including the bead core, and a tread located on the radially outer side of the base,
In the step (2), a part of the base unvulcanized rubber layer is formed,
In the step (4), the remaining part of the unvulcanized rubber layer for the base is formed,
The step of forming the raw cover further includes a step of forming a layer of the unvulcanized rubber for the tread on the outside of the layer of the unvulcanized rubber for the base after the preheating after the step of preheating. The manufacturing method of the cushion tire as described in.   The method for manufacturing a cushion tire according to any one of claims 2 to 4, wherein the preheating temperature is 50 ° C or higher and 90 ° C or lower.

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