Method for molding rubber member

Abstract

To provide a method for molding a rubber member capable of reducing overlapping of rubber strips.SOLUTION: In a method of attaching a leading part 3a of a long rubber member 3 to a drum 15 and winding the long rubber member 3 onto the drum 15 by rotating the drum 15 while feeding the long rubber member 3, by making the leading part 3a tapered and moving the drum 15 in its axial direction when attaching the leading part 3a, a tip 3b of the leading part 3a is brought outside of a center position of the long rubber member 3 in a width direction of the drum, and when wrapping the long rubber member 3 to a position overlapping the leading part 3a in the drum axial direction, by moving the drum 15 in the axial direction, a portion of the long rubber member 3 overlapping the leading part 3a in the drum axial direction becomes an inclined part 3c in a drum circumferential direction, and the portion of the long rubber member 3 other than the inclined part 3c is wound parallel to the drum circumferential direction.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to a method for molding a rubber member. [Background technology]

[0002] Cylindrical rubber components for tires (e.g., treads, sidewalls, inner liners, squeegees, etc.) are formed by spirally winding a rubber strip, which is a long rubber component extruded from an extruder, around a forming drum. In detail, the first and last turns of the rubber strip are formed by winding the rubber strip in the circumferential direction of the drum. Also, the second turn from the first to the second to last turns of the winding are formed by winding the rubber strip in a spiral shape.

[0003] Here, the leading portion of the rubber strip is formed by cutting the rubber strip in a direction perpendicular to its longitudinal direction. The leading portion of the rubber strip thus formed overlaps with the spirally wound portion of the rubber strip, as shown in FIG. 5 of Patent Document 1, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-116040 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional method, the leading edge of the rubber strip largely overlaps with the adjacent portion in the axial direction of the drum (the portion where the rubber strip is spirally wound). As a result, the overlapping portion with the leading edge of the rubber strip becomes heavy, which adversely affects the uniformity of the completed tire.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a method for molding a rubber member that can reduce uneven overlapping of rubber strips. [Means for solving the problem]

[0007] The present invention includes the embodiments set forth below.

[0008] [1] A rubber member molding method in which a leading portion of a long rubber member is attached to a molding drum, and the molding drum is rotated while the long rubber member is supplied from a supply section of the long rubber member, thereby winding the long rubber member around the molding drum to form a cylindrical rubber member for a tire, characterized in that the leading portion is tapered to have a tip, and when the leading portion is attached, at least one of the supply section and the molding drum is moved in the drum axial direction, so that the tip of the leading portion is moved outward in the drum axial direction from the center position of the width direction of the long rubber member, and when the long rubber member is wound around a position where it overlaps with the leading portion in the drum axial direction, at least one of the supply section and the molding drum is moved in the drum axial direction, so that the portion of the long rubber member that overlaps with the leading portion in the drum axial direction is made an inclined portion inclined with respect to the drum circumferential direction, and the portion of the long rubber member other than the inclined portion is wound parallel to the drum circumferential direction.

[0009] [2] The rubber member molding method described in [1], in which upper and lower molding rollers which form a gap as the supply section are disposed between an extruder which extrudes rubber and the molding drum, and the long rubber member extruded from the extruder is passed through the gap formed between the upper and lower molding rollers, thereby making the leading portion have a tapered shape.

[0010] [3] The rubber member molding method described in [1] or [2], wherein the leading portion is an isosceles triangle with its tip at the widthwise center position, and when attaching the leading portion to the molding drum, at least one of the supply section and the molding drum is moved in the drum axial direction, and the tip of the leading portion is moved outward in the drum axial direction from the widthwise center position of the elongated rubber member, thereby deforming the leading portion into a right-angled triangle. Effect of the Invention

[0011] According to the above method, the overlap of the rubber strips can be reduced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 4 is a left-right view of the rubber member molding device. [Diagram 2] Rear view of the upper and lower forming rollers. [Diagram 3] Top view of the area from the gear pump to the molding drum. [Figure 4] FIG. 13 is a left-right view of the area from the gear pump to the forming drum when the forming roller is in the attachment position. [Diagram 5] 1 is a left-right view of the portion from the gear pump to the building drum when the pressure roller is in the pressing position. FIG. [Figure 6] FIG. [Figure 7] FIG. 4 is a plan view of the leading portion of the rubber strip after passing through the forming rollers and before it is attached to the forming drum. [Figure 8] FIG. 2 is a plan view of the leading portion of the rubber strip in a state where the leading portion of the rubber strip is attached to the building drum. [Figure 9] A view of the building drum from the radial outside, just after the leading edge of the rubber strip has been attached to the building drum. [Figure 10] A view of the building drum from the radial outside, with the rubber strip attached for at least one revolution. [Figure 11]View of the building drum from the radial outside, when most of the rubber strips have been attached. [Figure 12] A view of the building drum from the radial outside, showing the end of the rubber strip after attachment. [Figure 13] FIG. 11 is a plan view of the leading portion of a modified rubber strip. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As shown in Figure 1, the rubber member molding apparatus 10 of this embodiment includes an extruder 11 that extrudes extruded rubber 2, a let-off device 12 that is on the way to supplying raw rubber sheet 1, which is the raw material of the extruded rubber 2, to the extruder 11, upper and lower molding rollers 13 and 14 that sandwich the extruded rubber 2 extruded from the extruder 11 from above and below to form a rubber strip 3, a molding drum 15 to which the rubber strip 3 that has passed through the molding rollers 13 and 14 is attached, a pressing roller 16 that presses the rubber strip 3 attached to the molding drum 15, and a control unit (not shown) that controls the rubber member molding apparatus 10.

[0014] The raw rubber sheet 1, the extruded rubber 2, and the rubber strip 3 are all unvulcanized long rubber members. In the following description, the cross section of the long rubber member refers to a cross section perpendicular to the extension direction of the long rubber member.

[0015] In the following description, the side where the molding drum 15 is located is referred to as the front, and the side where the let-off device 12 is located is referred to as the rear. The raw rubber sheet 1, extruded rubber 2, and rubber strip 3 move forward in the rubber member molding apparatus 10. Furthermore, the left-right direction is expressed when the rubber member molding apparatus 10 is viewed from the front. The left-right direction coincides with the axial direction of the molding drum 15 and molding rollers 13, 14.

[0016] The let-off device 12 is of a known structure and has a function of adjusting the tension applied to the raw rubber sheet 1 and a function of detecting when the raw rubber sheet 1 breaks. A bobbin 17 around which the raw rubber sheet 1 is wound is disposed behind the let-off device 12. The raw rubber sheet 1 unwound from the bobbin 17 is sent to the extruder 11 via the let-off device 12.

[0017] The extruder 11 is a supply device that supplies the extruded rubber 2 toward the molding drum 15, and has a general structure as a rubber extruder. The extruder 11 has a cylindrical hollow barrel 20, a rotating screw 21 provided inside the barrel 20, and an input port 25 for inputting the raw rubber sheet 1 into the barrel 20.

[0018] The extruder 11 also includes a gear pump 22 and a nozzle 23 as a part of the extruder 11, located forward of the screw 21. The gear pump 22 is attached to the front end of the barrel 20. The gear pump 22 includes two meshed gears, which rotate to cause the rubber to flow forward. The nozzle 23 is provided at the front end of the gear pump 22. The nozzle 23 has an open end 24 (see Figs. 2 and 6) which is the front end of the rubber flow path in the nozzle 23 and also serves as the rubber extrusion port. This open end 24 is the front end of the entire extruder 11. The amount of rubber extruded from the open end 24 is determined by the rotation speed of the gears of the gear pump 22. Here, the extrusion amount refers to the volume of rubber extruded from the open end 24 per unit time.

[0019] As the screw 21 rotates and the gear pump 22 is driven, the raw rubber sheet 1 fed from the feed port 25 becomes the extruded rubber 2 and is extruded horizontally from the open end 24 of the die 23. As shown in Fig. 2, the open end 24 of the die 23 is circular when viewed from the front-to-back direction. Here, a circle is not only meant to mean a perfect circle, but also to include shapes that can be approximated as a circle, such as an ellipse whose major axis length is 110% or less of the minor axis length, and a regular polygon with 12 or more sides.

[0020] In addition, the opening end 24 of the die 23 is disposed forward of the rear end of at least one of the upper and lower forming rollers 13, 14, and in this embodiment, is disposed between the upper and lower forming rollers 13, 14. In detail, as shown in Fig. 6, the opening end 24 of the die 23 is located forward of the rear end of the upper forming roller 13 by a distance L2, and is located forward of the rear end of the lower forming roller 14 by a distance L3.

[0021] The upper and lower forming rollers 13, 14 are each a substantially cylindrical roller. The upper and lower forming rollers 13, 14 have the same radius. The rotation axes 13a, 14a (see Figs. 2 to 4) of the upper and lower forming rollers 13, 14 are parallel to the rotation axis 15a (see Figs. 3 and 4) of the forming drum 15. It is preferable that the rotation center of the rotation axis 13a of the upper forming roller 13 is at the same height as the rotation center of the rotation axis 15a of the forming drum 15.

[0022] 4 to 6, the upper forming roller 13 is disposed forward of the lower forming roller 14. The distance L1 (see FIG. 6) in the front-rear direction between the rotation shaft 13a of the upper forming roller 13 and the rotation shaft 14a of the lower forming roller 14 is, for example, equal to or less than half the radius of the forming rollers 13, 14. Here, the distance between the rotation shafts means, strictly speaking, the distance between the rotation centers of the rotation shafts.

[0023] As shown in FIG. 2, the upper and lower forming rollers 13 and 14 are in contact (line contact) on both the left and right sides. Meanwhile, in the center in the left and right direction, a gap 18 is formed between the upper and lower forming rollers 13 and 14. The gap 18 is formed between a recess 13b formed around the entire circumference of the outer circumferential surface of the upper forming roller 13 and the outer circumferential surface of the cylindrical lower forming roller 14. This gap 18 is a place where the extruded rubber 2 enters and is crushed from above and below to be formed into the rubber strip 3. Therefore, the shape of the gap 18 is the target cross-sectional shape of the rubber strip 3. The gap 18 is also a supply section that faces the outer circumferential surface of the forming drum 15 and supplies the rubber strip 3 to the forming drum 15.

[0024] The upper forming roller 13 has a constant radius on both the left and right sides of the gap 18. The lower forming roller 14 has an outer circumferential surface that is a single curved surface, and the radius is constant from one side to the other in the left-right direction.

[0025] When viewed from the front-rear direction, the shape of gap 18 is wide in the vertical direction at the left-right center and narrow in the vertical direction on both left-right sides, with the left-right length being longer than the up-down height, specifically a low trapezoid. It is preferable that the left-right length of gap 18 (the length of the longer base side 18a) is 20 to 40 times the up-down height.

[0026] When viewed from the front-to-rear direction, the area of ​​the opening end 24 of the die 23 is at least two times and at most five times the area of ​​the gap 18. The area of ​​the gap 18 refers to the area of ​​the gap 18 on the plane connecting the rotation shafts 13a, 14a of the upper and lower forming rollers 13, 14. The plane connecting the rotation shafts 13a, 14a of the upper and lower forming rollers 13, 14 is a plane that passes through the position where the upper and lower forming rollers 13, 14 make line contact. As shown in FIG. 2, the center (center of the circle) of the opening end 24 of the die 23 is located at a higher position than the base 18a of the gap 18.

[0027] The outer circumferential surfaces of the upper and lower forming rollers 13, 14 are made of metal. A temperature adjustment device (not shown) is provided to adjust the temperature so that the outer circumferential surface of the lower forming roller 14 is hotter than the outer circumferential surface of the upper forming roller 13. The temperature adjustment device includes a heating element provided inside at least the lower forming roller 14 of the upper and lower forming rollers 13, 14, or a heating element disposed closer to the lower forming roller 14 than the upper forming roller 13. The temperature adjustment device also includes a device for controlling heat generation by the heating element.

[0028] The temperature control device makes the outer peripheral surface of the lower forming roller 14 hotter than the outer peripheral surface of the upper forming roller 13. This temperature relationship makes the outer peripheral surface of the upper forming roller 13 more adhesive to the long rubber material than the outer peripheral surface of the lower forming roller 14. Furthermore, since the outer peripheral surface of the upper forming roller 13 becomes colder than the outer peripheral surface of the lower forming roller 14, the upper side of the long rubber material becomes colder than the lower side, causing it to shrink and warp upward. Due to these two factors, the rubber strip 3 that passes through the gap 18 between the upper and lower forming rollers 13, 14 sticks to the outer peripheral surface of the upper forming roller 13.

[0029] Two motors (not shown) are arranged near the upper and lower forming rollers 13, 14, and the upper and lower forming rollers 13, 14 are each connected to one motor. The upper and lower forming rollers 13, 14 can be rotated by driving each motor. The rotation speeds of the upper and lower forming rollers 13, 14 can be adjusted independently. The upper forming roller 13 and the lower forming roller 14 rotate in opposite directions, and are in the direction of forward movement of the long rubber member sandwiched therebetween.

[0030] The extruder 11 and the forming rollers 13, 14 can move together in the front-rear direction by operating a moving device (not shown). Even if the extruder 11 and the forming rollers 13, 14 move together in the front-rear direction, the positional relationship between the extruder 11 and the forming rollers 13, 14 does not change. When the extruder 11 and the forming rollers 13, 14 are at the attachment position at the frontmost part of their movement range as shown in FIG. 4, the upper forming roller 13 can sandwich the rubber strip 3 between itself and the forming drum 15. When the extruder 11 and the forming rollers 13, 14 are at the rear part of their movement range, a space is formed between the forming rollers 13, 14 and the forming drum 15 as shown in FIG. 5.

[0031] The outer peripheral surface of the molding drum 15 is cylindrical. The rubber strip 3 is spirally wound around the outer peripheral surface of the molding drum 15 to mold a cylindrical rubber member for a tire. Examples of cylindrical rubber members include an inner liner and a squeegee. The rotation axis 15a of the molding drum 15 is perpendicular to the front-rear direction and extends horizontally. The molding drum 15 rotates in an upward direction at a location opposite the molding rollers 13 and 14. The molding drum 15 rotates at a constant speed.

[0032] The outer peripheral surface of the molding drum 15 is formed by arranging a plurality of metal segments that are long in the axial direction of the molding drum 15 (hereinafter, "drum axial direction") in the drum circumferential direction. At least a predetermined portion of the outer peripheral surface of the molding drum 15 is more likely to have the rubber strip 3 attached thereto than the outer peripheral surface of the upper molding roller 13. This predetermined portion is a portion to which the leading portion 3a (see Figs. 7 and 9) of the rubber strip 3 that has reached the molding drum 15 is attached. The length of this predetermined portion in the drum axial direction is equal to or greater than the width of the rubber strip 3, and the length of this predetermined portion in the drum circumferential direction is equal to or greater than the length of the leading portion 3a. In order to make it easier for the rubber strip 3 to attach to this predetermined portion, for example, the surface roughness (e.g., arithmetic mean roughness Ra or maximum height roughness Rz) of this predetermined portion is smaller than that of the outer peripheral surface of the upper molding roller 13, thereby increasing the adhesiveness of the rubber. This predetermined portion can be said to be the attachment start portion of the rubber strip 3.

[0033] In addition, on the building drum 15, a wider area including a specified portion may be a portion to which the rubber strip 3 is likely to stick, or the entire outer circumferential surface may be a portion to which the rubber strip 3 is likely to stick.

[0034] The pressing roller 16 is a pressing device for pressing the rubber strip 3 on the forming drum 15. The pressing roller 16 can move forward and backward with respect to the forming drum 15. As shown in FIG. 4, when the forming rollers 13, 14 are in the pasting position, the pressing roller 16 is away from the forming drum 15. Also, as shown in FIG. 5, when the forming rollers 13, 14 move backward and the gap between the forming rollers 13, 14 and the forming drum 15 becomes wider, the pressing roller 16 advances between the forming rollers 13, 14 and the forming drum 15 and reaches a pressing position close to the forming drum 15. When in the pressing position, the pressing roller 16 can press the rubber strip 3 on the forming drum 15.

[0035] In the rubber member molding apparatus 10 having the above-mentioned configuration, a rubber member molding method, which will be described next, is carried out based on the control by the control unit.

[0036] In the method of molding a member using the rubber member molding apparatus 10, a raw rubber sheet 1 drawn off from a bobbin 17 is fed into an inlet 25 of an extruder 11 via a let-off device 12. The raw rubber sheet 1 passed through the inlet 25 and fed into the inside of a barrel 20 is kneaded by a rotating screw 21. The kneaded rubber reaches an open end 24 of a die 23. Before the extruder 11 starts to extrude the extruded rubber 2, the extruder 11 is in a standby state with the rubber filled up to the open end 24 of the die 23.

[0037] When extrusion of the extruded rubber 2 from the extruder 11 begins, the rubber inside the barrel 20 becomes the extruded rubber 2, which is a long rubber member, and is extruded forward from the open end 24 of the nozzle 23. The amount of extrusion is adjusted by the gear pump 22. The cross-sectional shape of the extruded extruded rubber 2 is circular.

[0038] The forming rollers 13, 14 each start rotating at a uniform speed before the leading edge of the extrusion rubber 2 reaches the gap 18 between the upper and lower forming rollers 13, 14. In this embodiment, the upper and lower forming rollers 13, 14 rotate at the same speed in opposite directions.

[0039] The extruded rubber 2 extruded from the open end 24 of the die 23 enters the gap 18 between the upper and lower forming rollers 13, 14. By passing through the gap 18 between the upper and lower forming rollers 13, 14, the extruded rubber 2 changes its shape into a rubber strip 3 having the same cross-sectional shape as the gap 18 between the upper and lower forming rollers 13, 14.

[0040] The leading portion 3a of the rubber strip 3 is pressed by the upper and lower forming rollers 13, 14 while passing through the gap 18 between the upper and lower forming rollers 13, 14, and becomes tapered as shown in Fig. 7. In the following explanation, this tapered portion (the portion that is gradually narrower than other portions) will be referred to as the "leading portion 3a" as a whole. The leading portion 3a of the rubber strip 3 is an isosceles triangle with the center of the rubber strip 3 in the width direction protruding in the extrusion direction. The apex of this protrusion in the extrusion direction is the tip 3b of the leading portion 3a of the rubber strip 3.

[0041] The rubber strip 3 that has passed through the gap 18 adheres to the upper forming roller 13 and rises as the upper forming roller 13 rotates.

[0042] When the upper forming roller 13 rotates 90° after the leading portion 3a of the rubber strip 3 passes through the gap 18, the tip 3b of the leading portion 3a of the rubber strip 3 reaches the front end of the upper forming roller 13. Prior to this, the extruder 11 and the forming rollers 13, 14 have started to move forward together, and the forming rollers 13, 14 reach the attachment position at the same time as or just before or after the leading portion 3b of the rubber strip 3 reaches the front end of the forming roller 13. When the upper forming roller 13 reaches the attachment position, the leading portion 3a of the rubber strip 3 is sandwiched between the upper forming roller 13 and the attachment start portion of the forming drum 15, as shown in FIG.

[0043] As described above, the rubber strip 3 is more likely to stick to the attachment start portion of the forming drum 15 than to the forming roller 13. Therefore, after the leading end portion 3a of the rubber strip 3 is sandwiched between the forming roller 13 and the attachment start portion of the forming drum 15, it leaves the forming roller 13 and sticks to the forming drum 15.

[0044] Here, while the leading end 3a of the rubber strip 3 is being attached to the molding drum 15, the molding drum 15 moves at a constant speed in the drum axial direction. The direction of movement is the direction indicated by the arrow in Fig. 9, which is the opposite direction to the winding direction of the rubber strip 3. Due to this movement, as shown in Figs. 8 and 9, the leading end 3b (the apex of an isosceles triangle) of the rubber strip 3 is closer to the outside in the drum axial direction than the center position in the left-right direction of the rubber strip 3, and the leading end 3a of the rubber strip 3 is attached to the molding drum 15 in a deformed shape of a right-angled triangle with the side in the spiral progression direction as the hypotenuse. It should be noted that the left-right direction coincides with the width direction of the rubber strip 3.

[0045] After the leading end 3b of the rubber strip 3 has been attached to the molding drum 15, while the succeeding portion (leading portion 3a, etc.) of the leading end 3b is being attached, the extruder 11 and the forming rollers 13, 14 move backward together, and the upper and lower forming rollers 13, 14 move away from the molding drum 15. At the same time that the extruder 11 and the forming rollers 13, 14 start to move backward, or before or after that, the pressing roller 16 starts to advance toward the molding drum 15. Then, when the pressing roller 16 reaches the pressing position, it presses the rubber strip 3 attached to the molding drum 15, as shown in FIG. 5.

[0046] Thereafter, the rubber strip 3 is wound around the molding drum 15 as the molding drum 15 rotates. During the winding, the pressure roller 16 continues to press the rubber strip 3 attached to the molding drum 15.

[0047] 10 and 11, when the rubber strip 3 is wound around the position overlapping with the leading end 3a of the rubber strip 3 in the drum axial direction, the molding drum 15 moves in the drum axial direction, so that the rubber strip 3 is wound spirally around the molding drum 15. Here, the direction of movement of the molding drum 15 is the direction shown by the arrow in Figs. 10 and 11, which is the opposite direction to the proceeding direction of the winding of the rubber strip 3. At the position where the molding drum 15 has moved in the drum axial direction, the rubber strip 3 forms an inclined portion 3c that is attached at an angle with respect to the drum circumferential direction.

[0048] When winding the rubber strip 3 in the region other than the position overlapping the leading portion 3a of the rubber strip 3 in the drum axial direction, the building drum 15 does not move in the drum axial direction. Therefore, in that region, the rubber strip 3 is wound in the drum circumferential direction. As a result, the portion of the rubber strip 3 other than the inclined portion 3c is wound parallel to the drum circumferential direction.

[0049] When the winding of the rubber strip 3 around the molding drum 15 is nearing completion, the screw 21 of the extruder 11, the gear pump 22, and the molding rollers 13 and 14 are stopped in this order. The gear pump 22 rotates in the reverse direction for a short period of time after the screw 21 has stopped, and then stops.

[0050] Even after the screw 21 and gear pump 22 have stopped and extrusion of the extruded rubber 2 from the open end 24 of the die 23 has stopped, the forming rollers 13, 14 continue to rotate and pull the extruded rubber 2 forward, causing the extruded rubber 2 to be torn off and cut at the open end 24 of the die 23. The cut portion passes through the gap 18 between the forming rollers 13, 14 to become the rear portion 3d of the rubber strip 3 (see FIG. 12), and then the forming rollers 13, 14 stop. This cuts out the rubber strip 3 to the length to be wound around the forming drum 15.

[0051] The rear portion 3d of the rubber strip 3 is cut by being torn off at the open end 24 of the mouthpiece 23 and is crushed by the forming rollers 13, 14, so that it has a tapered shape similar to the leading portion 3a. This entire tapered portion (the portion that is gradually narrower in width than the other portions) is referred to as the "rear portion 3d." The rear portion 3d of the rubber strip 3 is an isosceles triangle with the center of the rubber strip 3 in the width direction protruding, similar to the leading portion 3a in Fig. 7.

[0052] While the rear portion 3d of the rubber strip 3 is being attached to the molding drum 15, the molding drum 15 moves at a constant speed in the drum axial direction as shown by the arrow in Fig. 12. The direction of movement is opposite to the winding direction of the rubber strip 3. Due to this movement, the rear portion 3d of the rubber strip 3 is attached to the molding drum 15 in a shape that is deformed into a right-angled triangle with the side in the opposite direction to the spiral progression as the hypotenuse, as shown in Fig. 12. At this time, the hypotenuse of the rear portion 3d of the rubber strip 3 matches the shape of the inclined portion 3c of the rubber strip 3 from one revolution before.

[0053] When the attachment of the rear portion 3d of the rubber strip 3 is completed, a cylindrical rubber member for a tire is completed. From the leading portion 3a to the trailing portion 3d of the rubber strip 3, the overlap width between adjacent portions in the drum axial direction is almost constant. The leading portion 3a and the trailing portion 3d of the rubber strip 3 also overlap with the inclined portion 3c of the adjacent rubber strip 3 by a nearly constant width. Therefore, the thickness of the cylindrical rubber member is almost constant, including the portion where the leading portion 3a and the trailing portion 3d of the rubber strip 3 are attached.

[0054] As described above, the extruded rubber 2 is cut at the opening end 24 of the die 23. Therefore, after one extruded rubber 2 has been extruded, the extruder 11 waits in a state where the rubber is filled up to the opening end 24 of the die 23 until the extrusion of the next extruded rubber 2 is started.

[0055] By repeating the above operations, a plurality of cylindrical rubber members are molded.

[0056] As described above, the rubber member molding method of this embodiment is a method in which the leading portion 3a of the rubber strip 3 is attached to the molding drum 15, and the molding drum 15 is rotated while the rubber strip 3 is being supplied, thereby winding the rubber strip 3 around the molding drum 15. In this method, the leading portion 3a of the rubber strip 3 is tapered to have a leading end 3b. Then, as the molding drum 15 moves in the drum axial direction when the leading portion 3a is attached to the molding drum 15, the leading end 3b of the leading portion 3a moves outward in the drum axial direction from the center position of the rubber strip 3 in the width direction.

[0057] Furthermore, when the rubber strip 3 is wound around the position where it overlaps with the leading portion 3a in the drum axial direction, the building drum 15 moves in the drum axial direction. As a result, the portion of the rubber strip 3 that overlaps with the leading portion 3a in the drum axial direction becomes an inclined portion 3c that is inclined with respect to the drum circumferential direction. The portion of the rubber strip 3 other than the inclined portion 3c is wound parallel to the drum circumferential direction.

[0058] This method makes it possible to make the overlap between adjacent portions of the rubber strip 3 in the drum axial direction constant at all locations. Also, the amount of overlap between the leading portion 3a of the rubber strip 3 and the portion adjacent to it in the drum axial direction can be made equal to the amount of overlap in other portions. Therefore, it is possible to reduce unevenness in the overlap of the rubber strip 3 in the entire completed cylindrical rubber member.

[0059] In this embodiment, the extruded rubber 2 extruded from the extruder 11 passes through the gap 18 between the upper and lower forming rollers 13 and 14 to become the rubber strip 3. This allows the leading portion 3a of the rubber strip 3 to have a more tapered shape.

[0060] In this embodiment, the extruded rubber 2 is cut by stopping the extrusion of the extruder 11. Therefore, the leading portion 3a of the rubber strip 3 formed from the extruded rubber 2 can be made to have a more tapered shape.

[0061] In this embodiment, the leading portion 3a of the rubber strip 3 is an isosceles triangle as described above, and the leading portion 3a is deformed into a right triangle as described above by moving the molding drum 15 in the drum axial direction when the leading portion 3a is attached to the molding drum 15. This causes the leading portion 3a on the molding drum 15 to become a right triangle, making it easier to wind the rubber strip 3 for the second turn and thereafter.

[0062] In this embodiment, the rear portion 3d of the rubber strip 3 also has a tapered shape, and like the leading portion 3a, the rear portion 3d is also attached to the molding drum 15 while the molding drum 15 is moving in the drum axial direction. Therefore, the amount of overlap between the rear portion 3d of the rubber strip 3 and the portion adjacent to it in the drum axial direction can be reduced.

[0063] Various modifications can be made to the above embodiment. Any one of the modifications described below may be applied to the above embodiment, or any two or more of them may be combined and applied to the above embodiment. Combinations can be freely made.

[0064] <Change Example 1> The shapes of the leading and trailing parts of the rubber strip are not limited to triangular as long as they are tapered. For example, they may have a rounded tapered shape like the leading part 103a of the rubber strip 103 shown in Fig. 13. When the extruded rubber 2 passes through the gap 18 between the forming rollers 13 and 14 to form the rubber strip 3, the tapered shape of the rubber strip 3 and the length of the tapered part can be adjusted by adjusting the rotation speed of the forming rollers 13 and 14.

[0065] Regardless of the tapered shape of the leading and trailing portions of the rubber strip, while the leading and trailing portions are attached to the molding drum 15, the molding drum 15 moves in the opposite direction to the winding direction of the rubber strip, thereby making it possible to move the leading end of the rubber strip outward in the drum axial direction from the left-right center position of the rubber strip.

[0066] <Change Example 2> While the leading and trailing portions of the rubber strip 3 are being attached to the molding drum 15 or while the rubber strip 3 is being wound around the molding drum 15, instead of the molding drum 15 moving in its axial direction, a supply section of the rubber strip 3 to the molding drum 15 may move in the drum axial direction. In addition to the molding drum 15 moving in its axial direction, the supply section of the rubber strip 3 to the molding drum 15 may also move in the drum axial direction. It is sufficient that the supply section and the molding drum 15 move relatively in the drum axial direction.

[0067] In the above embodiment, the supply portion of the rubber strip 3 to the molding drum 15 is the gap 18 between the upper and lower molding rollers 13, 14. In order for the gap 18 to move in the drum axial direction, the extruder 11 and the molding rollers 13, 14 must move together in the drum axial direction.

[0068] <Change Example 3> In the above embodiment, the rubber strip 3 is directly attached to the outer circumferential surface of the building drum 15, but it is also possible that some kind of cylindrical rubber member is first attached to the outer circumferential surface of the building drum 15, and the rubber strip 3 is attached on top of that cylindrical rubber member by the method of the above embodiment. For example, an inner liner may first be attached to the outer circumferential surface of the building drum 15, and the rubber strip 3 may be attached on top of that inner liner by the method of the above embodiment to mold the squeegee.

[0069] <Change Example 4> Even if there are no forming rollers 13, 14 between the extruder 11 and the molding drum 15 in the above embodiment, the leading and trailing portions of the rubber strip can be tapered. For example, when the rubber strip is cut simply by stopping the extrusion of rubber from the extruder 11, the trailing portion of the rubber strip becomes tapered. When the extrusion of rubber from the extruder 11 is then resumed, the leading portion of the rubber strip that first comes out of the extruder 11 becomes tapered.

[0070] When there are no forming rollers 13, 14 between the extruder 11 and the forming drum 15, the open end 24 of the die 23 of the extruder 11 faces the outer circumferential surface of the forming drum 15 and serves as a supply section for supplying the rubber strip 3 to the forming drum 15. [Explanation of symbols]

[0071] Reference Signs List 1...raw rubber sheet, 2...extruded rubber, 3...rubber strip, 3a...head portion, 3b...tip, 3c...inclined portion, 3d...rear portion, 10...rubber member molding device, 11...extruder, 12...let-off device, 13...molding roller, 13a...rotating shaft, 13b...dent, 14...molding roller, 14a...rotating shaft, 15...molding drum, 15a...rotating shaft, 16...pressure roller, 17...bobbin, 18...gap, 18a...bottom, 20...barrel, 21...screw, 22...gear pump, 23...mouthpiece, 24...opening end, 25...feeding port, 103...rubber strip, 103a...head portion

Claims

1. A rubber member molding method comprising: attaching a leading end of a long rubber member to a molding drum; supplying the long rubber member from a supply unit for the long rubber member while rotating the molding drum; and winding the long rubber member around the molding drum to form a cylindrical rubber member for a tire, comprising: The leading portion is tapered to have a tip; When attaching the leading portion, at least one of the supply unit and the building drum is moved in a drum axial direction, so that the leading end of the leading portion is moved outward in the drum axial direction from the center position in the width direction of the elongated rubber member, A rubber member molding method characterized in that, when winding the long rubber member around a position where it overlaps with the leading portion in the drum axial direction, at least one of the supply section and the molding drum is moved in the drum axial direction, so that the portion of the long rubber member that overlaps with the leading portion in the drum axial direction becomes an inclined portion inclined with respect to the drum circumferential direction, and the portion of the long rubber member other than the inclined portion is wound parallel to the drum circumferential direction.

2. Upper and lower forming rollers are disposed between an extruder for extruding rubber and the forming drum to form a gap as the supply unit; 2. The rubber member molding method according to claim 1, wherein the leading end portion of the elongated rubber member extruded from the extruder is tapered by passing the elongated rubber member through the gap formed between the upper and lower molding rollers.

3. the leading portion is an isosceles triangle whose tip is located at the center position in the width direction, 3. The rubber member molding method according to claim 1, wherein when attaching the leading portion to the molding drum, at least one of the supply section and the molding drum is moved in the drum axial direction, and the tip of the leading portion is moved outward in the drum axial direction from the widthwise center position of the elongated rubber member, thereby deforming the leading portion into a right-angled triangle.

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