Belt

Abstract

To provide a belt having a static elimination effect while suppressing a misalignment with respect to a roll and suppressing reduction in gas permeability.SOLUTION: An endless-shaped belt 10 wound around a roll and driven by the rotation of the roll comprises: a belt-like fabric 12 with threads of a conductive material woven into it; and a projection part provided at a face located on the roll side of the fabric 12 and extending along the driving direction of the belt 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a belt attached to a roll and driven by the rotation of the roll. [Background technology]

[0002] Currently, various products using absorbent bodies as a part of them are being supplied. The absorbent body is a sanitary product that requires water absorption. Examples of such sanitary products that require water absorption include paper diapers, paper diapers for animals, training pads, sanitary napkins, sweat pads, incontinence pads, auxiliary sheets for bedding, and auxiliary sheets for nursing care. For example, in the process of manufacturing paper diapers using absorbent bodies, a back sheet unwound from a roll of raw material is conveyed onto a mesh belt, and short fibers that are the raw material of the absorbent body are placed on the back sheet. After this, tissues, gathers, and top sheets unwound from the roll of raw material are unwound on the nonwoven fabric as necessary, cut to the desired size with a side cutter and an end cutter, and passed through a folding device to produce the absorbent body, which is the final product. For example, Patent Document 1 discloses nonwoven articles such as diapers, training pants, tampons, surgical gowns, surgical masks, and feminine napkins. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-20157 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the belt is conveyed by the rotation of the roll, there is a risk of misalignment with the roll, which may cause the product to move on the belt, which may activate a sensor that detects defects in the product. Furthermore, when processing the product being conveyed by the belt, if the product moves on the belt, the processing accuracy may decrease and the product defect rate may increase. In addition, there is a risk of static electricity being generated due to friction between the belt and the roll.

[0005] An object of the present invention is to provide a belt which has a static elimination effect while suppressing slippage relative to a roll and reducing the decrease in breathability. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present invention is an endless belt that is wound around a roll and driven by the rotation of the roll, and includes a strip-shaped fabric having threads of conductive material woven into it, and a protrusion portion provided on the surface of the fabric facing the roll and extending along the driving direction of the belt. Effect of the Invention

[0007] According to the present invention, it is possible to provide a belt that has a static elimination effect while suppressing deviation from the roll and reducing the decrease in breathability. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a partial perspective view of the belt of the embodiment. [Diagram 2] FIG. 2(a) is a view showing the surface of the belt 10 of the embodiment located on the roll side, and FIG. 2(b) is a cross-sectional view of the belt as seen along the conveying direction. [Diagram 3] FIG. 2 shows an example belt mounted on a roll. [Figure 4] FIG. 11 is a partial perspective view of a belt according to a first modified example. [Diagram 5] FIG. 11 is a partial perspective view of a belt according to a second modified example. [Figure 6]FIG. 4 is a diagram illustrating the relationship between a first protrusion and a first recess of the roll. [Figure 7] FIG. 13 is a partial perspective view of a belt according to a third modified example. [Figure 8] FIG. 4 is a diagram illustrating the belt attached to a roll, illustrating the relationship between the second protrusions and the roll. [Figure 9] FIG. 13 is a partial perspective view of a belt according to a fourth modified example. [Figure 10] FIG. 13 is a partial perspective view of a belt according to a fifth modified example. [Figure 11] FIG. 11(a) is a diagram showing the surface of the belt of the sixth modified example located on the roll side, and FIG. 11(b) is a diagram showing the belt of the sixth modified example viewed along the conveying direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] FIG. 1 is a partial perspective view of a belt 10 of an embodiment. FIG. 2(a) is a view of the surface of the belt 10 of the embodiment located on the roll side, and FIG. 2(b) is a cross-sectional view of the belt 10 viewed along the conveying direction. The belt 10 shown in FIG. 1 shows a state in which a part of the belt 10 is cut away, but the belt 10 is actually formed in an endless shape by rotating. The belt 10 shown in FIG. 1 shows the surface side located on the roll side. The belt 10 is assembled in a device for manufacturing products such as nonwoven fabric, paper, diapers, and absorbent body manufacturing devices. The belt 10 is wound around a cylindrical roll provided in the manufacturing device and is driven by the rotation of the roll. Usually, a driving roll is present on the inside of the belt 10, and the conveyed object moves on the outside of the belt 10, but when the driving roll is on the surface side, a protrusion portion is present on the surface, and a conveying portion runs on the inside of the belt 10. The belt 10 conveys the material of the product. The roll may be a pulley having teeth on the outer circumferential surface.

[0010] The belt 10 includes a woven fabric 12, a first ridge 14, and a second ridge 16. The woven fabric 12 is formed in a belt shape with a constant width, and is formed by weaving warp and weft threads. The warp threads extend along the driving direction of the belt 10, and the weft threads extend along a direction perpendicular to the driving direction. The direction perpendicular to the driving direction is also called the width direction. The woven fabric 12 may be a multi-layered fabric including a first surface side fabric on which the material is placed and a second surface side fabric in contact with the roll. The mesh-like woven fabric 12 can form passages for water and air. The use of the woven fabric 12 can reduce the weight of the belt 10.

[0011] The fabric 12 is woven with conductive yarns (hereinafter, sometimes referred to as "conductive yarns"). The conductive yarns may be, for example, carbon fibers, metal fibers such as stainless steel fibers, copper, and amorphous alloys, conductive fibers in which synthetic fibers are coated with conductive polymers or copper sulfide, metal-dyed fibers, etc. That is, at least one of the warp yarns and the weft yarns includes conductive yarns. For example, both the warp yarns and the weft yarns may include conductive yarns. The conductive yarns are not included in all of the warp yarns and the weft yarns, but are included in some of the warp yarns and some of the weft yarns. The conductive yarns are, for example, conductive carbon yarns. By including the conductive yarns in the fabric 12, even if the material placed on the belt 10 or the belt 10 itself is charged with static electricity, the static electricity can be released to the roll side and eliminated.

[0012] There are two types of deviation of the belt 10 from the roll. The phenomenon in which the belt deviates in the axial direction of the roll is called meandering, and the phenomenon in which the belt rotation speed is slower than the roll rotation speed is called slipping. In a device that transports products on the belt 10, a plate is sometimes installed beside the belt 10 to prevent the belt 10 from meandering. If the belt 10 comes into contact with the plate for preventing meandering, the end of the belt 10 may be damaged. In addition, if the belt 10 slips, the surface of the belt 10 located on the roll side wears out, making the belt 10 more likely to be damaged, and the rotation speed of the belt 10 relative to the power input to the roll decreases, resulting in an increase in power costs. In addition, in both cases of meandering and slipping, the product may move on the belt, which may activate a sensor that detects product defects. Furthermore, if the device is equipped with a device that performs some kind of processing on the product at a certain position or interval, the movement of the product on the belt 10 may reduce the processing accuracy and increase the product defect rate. Therefore, the belt 10 of the embodiment includes the first protrusions 14 and the second protrusions 16 for suppressing the slippage relative to the roll.

[0013] The first ridge 14 and the second ridge 16 are provided on the surface of the fabric 12 that is located on the roll side. The material of the first ridge 14 and the second ridge 16 may be polyurethane, polyvinyl chloride, polyolefin, polyester, polyamide, natural rubber, synthetic rubber, or a substance obtained by modifying these materials, and may be a conductive material. The first ridge 14 and the second ridge 16 extend along the conveying direction C of the belt 10. This allows them to function as a guide when the fabric 12 moves in the conveying direction, and prevents the belt 10 from slipping relative to the roll. The first ridge 14 and the second ridge 16 are fixed to the fabric 12. The first ridge 14 and the second ridge 16 can improve the rigidity of the belt 10 and prevent the fabric 12 from stretching. This makes it possible to use a fabric 12 that is low in rigidity but has high breathability and large openings.

[0014] The first ridge portions 14 and the second ridge portions 16 are provided in parallel on both edge sides of the belt 10 in the width direction W. As a result, the central portion of the belt 10 is not blocked by the first ridge portions 14 and the second ridge portions 16, ensuring breathability and dewatering properties of the central portion.

[0015] The first protrusion 14 is a toothed belt having multiple teeth on its surface. The cross-sectional shape of the multiple teeth may be rectangular, semicircular, triangular, or the like. The multiple teeth mesh with teeth formed on the roll. The first protrusion 14 can prevent the belt 10 from shifting in the conveying direction relative to the roll. When the first protrusion 14 meshes with teeth in recesses formed on the roll, it can prevent shifting in both the conveying direction and the width direction.

[0016] The cross section of the second protrusion 16 along the direction perpendicular to the conveying direction C is formed into a substantially trapezoidal or substantially rectangular shape. The second protrusion 16 may engage with a recess formed in the roll. The second protrusion 16 can prevent the belt 10 from shifting in the width direction relative to the roll.

[0017] The woven fabric 12 is formed into an endless shape by joining the short sides of the rectangle, and then the first protrusion 14 and the second protrusion 16 are fixed to the surface side located on the roll side. When the woven fabric 12 is formed into an endless shape, a method of joining the short sides by weaving them together, a method of joining them by heat welding, etc. are used. The method of weaving the short sides can ensure breathability at the joints and increase strength. The joints are provided when the woven fabric 12 is formed into an endless shape. In addition, each of the first protrusion 14 and the second protrusion 16 is composed of one or more pieces, and can be formed with some parts spaced apart in the conveying direction. The parts where the first protrusion 14 and the second protrusion 16 are spaced apart in the conveying direction are provided so as not to overlap the joints of the woven fabric 12. In other words, the first protrusion 14 and the second protrusion 16 are fixed so as to cross the joints of the woven fabric 12. This allows the first protrusions 14 and the second protrusions 16 to reinforce the seams of the fabric 12.

[0018] The fabric 12 is formed by weaving warp yarns and weft yarns. The warp yarns and weft yarns may be a combination of PET yarns and conductive carbon yarns, a combination of polyamide yarns and conductive carbon yarns, or a combination of PET yarns, polyamide yarns and conductive carbon yarns woven together. The diameter of the warp yarns is set in the range of 0.1 to 0.7 mm. The diameter of the weft yarns is set in the range of 0.1 to 1.1 mm. This increases the rigidity of the belt 10.

[0019] The aperture number in the belt 10 is the number of holes penetrating the belt 10 from the upper surface to the lower surface, and in the case of the woven fabric, it is expressed as the product of the number of warp threads and the number of weft threads arranged per unit length. The aperture number of the woven fabric 12 is set to 300 to 5000 per square inch. The thickness of the woven fabric 12 is set in the range of 0.8 to 3.5 mm. The increased breathability makes it difficult for the product on the belt 10 to slip. By using the woven fabric 12 having such warp and weft thread diameters for the belt 10, the first protrusion 14 and the second protrusion 16 can be easily and firmly fixed to the woven fabric 12.

[0020] Furthermore, by ensuring a sufficient number of openings in the fabric 12, the anchor effect can be strengthened when welding the first ridges 14 and the second ridges 16, thereby enabling them to be firmly fixed. The anchor effect refers to the effect of the adhesive penetrating into holes and gaps in the objects to be adhered and hardening, thereby obtaining a strong adhesive force.

[0021] More preferably, the diameter of the warp yarns is set in the range of 0.2 to 0.6 mm, the diameter of the weft yarns is set in the range of 0.2 to 1.0 mm, and the aperture number of the fabric 12 is set in the range of 500 to 4000 per square inch. The thickness of the fabric 12 may be set in the range of 1.0 to 3.0 mm. More preferably, the diameter of the warp yarns is set in the range of 0.25 to 0.5 mm, the diameter of the weft yarns is set in the range of 0.25 to 0.9 mm, and the aperture number of the fabric 12 is set in the range of 800 to 3500 per square inch. The thickness of the fabric 12 may be set in the range of 1.1 to 2.5 mm.

[0022] When the first ridges 14 and the second ridges 16 are bonded to the fabric 12, the resin adhesive melts into the inner space of the fabric 12 located below the first ridges 14 and the second ridges 16. When the first ridges 14 and the second ridges 16 are welded to the fabric 12, the melted welded material of the first ridges 14 and the second ridges 16 melts into the inner space of the fabric 12. In this way, the adhesive or welded material that melts into the fabric 12 is called an invader that has invaded the inner space of the fabric 12. The filling rate of the invader in the fabric 12, that is, the thickness of the invader relative to the thickness of the fabric 12, is set to 20% or more. This ensures a sufficient fixing force between the fabric 12 and the first ridges 14 and the second ridges 16. More preferably, the filling rate of the invader in the fabric 12 may be set in the range of 50 to 100%. More preferably, the filling rate of the invading material in the woven fabric 12 may be set in the range of 85 to 100 percent. By configuring the woven fabric 12 in multiple layers, it becomes easier to fill it with adhesive or the like.

[0023] The proportion of conductive yarns contained in the warp and weft threads is as follows: At least two out of 96 continuously arranged warp and weft threads are conductive yarns. This allows the conductive yarns to be arranged at regular intervals in the conveying direction or width direction of the belt 10, ensuring the antistatic effect. More preferably, at least two out of 48 in at least one of the warp and weft threads may be conductive yarns. Even more preferably, at least two out of 16 in at least one of the warp and weft threads may be conductive yarns. The conductive yarns may be contained in a greater proportion in the weft threads than in the warp threads.

[0024] The total area covered by the first ridges 14 and the second ridges 16 on the roll side of the fabric 12 is 40% or less of the area of ​​the roll side of the fabric 12. As a result, 60% or more of the fabric 12 is not covered by the first ridges 14 and the second ridges 16, ensuring breathability and allowing the conductive yarn to be fully exposed to ensure static elimination performance. More preferably, the total area covered by the first ridges 14 and the second ridges 16 on the roll side of the fabric 12 may be 30% or less of the area of ​​the roll side of the fabric 12. Even more preferably, the total area covered by the first ridges 14 and the second ridges 16 on the roll side of the fabric 12 may be 20% or less of the area of ​​the roll side of the fabric 12.

[0025] 3 is a diagram showing the belt 10 attached to the roll 18. The roll 18 rotates around its axis by a driving source such as a motor. The roll 18 has a first recess 18a and a second recess 18b (when no distinction is made between them, they are referred to as "recesses"). The first recess 18a is formed on the outer peripheral surface of the roll 18, and forms a tooth portion in a recessed portion along the circumferential direction, which meshes with the first protrusion 14.

[0026] The second recesses 18b are formed on the outer peripheral surface of the roll 18 and are recessed in the circumferential direction to form grooves. The second recesses 18b engage with the second protrusions 16. In this manner, the protrusions engage with the recesses formed in the roll 18. This makes it possible to prevent the belt 10 from shifting relative to the roll 18 in the conveyance direction and width direction.

[0027] FIG. 4 is a partial perspective view of a belt 100 of a first modified example. The belt 100 of the first modified example differs from the belt 10 shown in FIG. 1 in that it does not have the second protrusion 16, and instead has two first protrusions 14. The belt 100 includes a woven fabric 12 and a pair of first protrusions 14 fixed to a surface of the woven fabric 12 located on the roll side. The pair of first protrusions 14 extend along the conveying direction on both edge sides of the woven fabric 12. When the roll 18 has the first recess 18a instead of the second recess 18b and has the first recess 18a on both edge sides, the pair of first protrusions 14 mesh with the teeth 19 of the pair of first recesses 18a formed on the roll 18. This makes it possible to prevent the belt 100 from shifting in the conveying direction relative to the roll 18. In addition, the side surface of the first protrusion 14 comes into contact with the side surface of the first recess 18a, thereby making it possible to prevent the belt 100 from shifting in the width direction.

[0028] FIG. 5 is a partial perspective view of a belt 200 of a second modified example. The belt 200 of the second modified example differs from the belt 100 shown in FIG. 4 in the arrangement and number of the first protrusions 14. The belt 200 includes a woven fabric 12 and a first protrusion 14 fixed to a surface of the woven fabric 12 located on the roll side. The first protrusion 14 extends in the conveying direction at the center of the woven fabric 12. Since there is only one first protrusion 14, the manufacturing cost can be reduced and the opening area of ​​the woven fabric 12 can be made large. In addition, since the first protrusion 14 is arranged in the center, the left and right balance is good, and the belt 200 is less likely to meander. The first protrusion 14 does not have to be arranged in the center. The outer peripheral surface of the roll 18 may be entirely composed of teeth.

[0029] FIG. 6 is a diagram for explaining the relationship between the first protrusion 14 and the first recess 18a of the roll 18. The difference (D-H1) between the protruding height D of the tooth 19 of the first recess 18a and the protruding height H1 of the tooth 14a of the first protrusion 14 is set to be −4.0% to +9.0% of the protruding height D of the tooth 19. This makes it difficult for the first protrusion 14 to come off the first recess 18a, and prevents the belt 10 from shifting in the conveying direction relative to the roll 18. Note that, since a stretchable material is usually selected for the first protrusion 14, even if the protruding height H1 of the tooth 14a is slightly larger than the protruding height D of the tooth 19, the tooth 14a will be crushed and the first protrusion 14 will engage with the roll 18. That is, the value of (D-H1) may be less than 0. More preferably, the difference (D-H1) between the protruding height D of the tooth portion 19 of the first recess 18a and the protruding height H1 of the tooth portion 14a of the first protrusion 14 may be set to be −3.5% to +8.5% of the protruding height D of the tooth portion 19. Even more preferably, the difference (D-H1) between the protruding height D of the tooth portion 19 of the first recess 18a and the protruding height H1 of the tooth portion 14a of the first protrusion 14 may be set to be −2.5% to +7.5% of the protruding height D of the tooth portion 19.

[0030] The total height H of the first protrusion 14 is the sum of the protruding height H1 of the tooth portion 14a and the height H2 of the base portion 14b. Here, the ratio R of the height H2 of the base portion 14b to the total height H is preferably set in the range of 10 to 60 percent. More preferably, the ratio R of the height H2 of the base portion 14b to the total height H may be set to 30 to 50 percent. R=H2 / H. The first protrusion 14 is composed of the tooth portion 14a and the base portion 14b, and the height of the base portion 14b is important so that the first protrusion 14 enters the first recess 18a of the roll 18 and suppresses the shift in the width direction. If the height of the base portion 14b is large, the contact area between the side surface of the base portion 14b and the inner surface of the first recess 18a becomes large, and the belt 10 can be easily configured to suppress the shift in the width direction. On the other hand, if the height H2 of the base portion 14b is too large, the first protrusion 14 becomes large, which increases the cost. Furthermore, the depth of the first recesses 18a becomes large relative to the roll diameter, and the strength of the roll decreases. The first recesses 18a of the roll 18 may be formed in accordance with the size of the first protrusions 14.

[0031] Fig. 7 is a partial perspective view of a third modified belt 300. The third modified belt 300 differs from the belt 10 shown in Fig. 1 in that it does not have the first protrusion 14 and is provided with two second protrusions 16 instead of the first protrusion 14.

[0032] The belt 300 includes a woven fabric 12 and a pair of second protrusions 16 fixed to a surface of the woven fabric 12 located on the roll side. The pair of second protrusions 16 extend on both edge sides of the woven fabric 12 in the conveyance direction.

[0033] FIG. 8 is a diagram illustrating the belt 300 attached to the roll 318, and is used to explain the relationship between the second protrusions 16 and the roll 318. As shown in FIG. 8(a) and FIG. 8(b), the pair of second protrusions 16 are disposed axially outward of both ends of the roll 318, and are provided so as to sandwich both ends of the roll 318. The pair of second protrusions 16 abut against or are close to both ends of the roll 318. This makes it possible to prevent the belt 300 from shifting in the width direction relative to the roll 318. In addition, it is not necessary to form recesses in the roll 318.

[0034] The protruding height H2 of the second protrusions 16 is set to 1 to 25 percent of the diameter φ of the roll 318. By ensuring the protruding height H2 of the second protrusions 16, the possibility of the second protrusions 16 riding on the outer circumferential surface of the roll 318 can be reduced. In addition, by reducing the protruding height H2 of the second protrusions 16, it is possible to prevent the second protrusions 16 from being easily damaged due to increased stress when the belt 300 is wound around the roll 318. More preferably, the protruding height H2 of the second protrusions 16 may be set to 2 to 20 percent of the diameter φ of the roll 318.

[0035] Fig. 9 is a partial perspective view of a belt 400 of a fourth modified example. The belt 400 of the fourth modified example differs from the belt 300 shown in Fig. 7 in the arrangement and number of the second protrusions 16. The belt 400 includes a woven fabric 12 and second protrusions 16 fixed to a surface of the woven fabric 12 located on the roll side. The second protrusions 16 extend in the conveying direction at the center of the woven fabric 12. The second protrusions 16 engage with second recesses 18b formed in the circumferential direction on the outer circumferential surface of the roll 18.

[0036] Fig. 10 is a partial perspective view of a belt 500 of a fifth modified example. The belt 500 of the fifth modified example has a different shape of a second protrusion 516 compared to the belt 300 shown in Fig. 7. The belt 500 includes a woven fabric 12 and a pair of second protrusions 516 fixed to a surface of the woven fabric 12 located on the roll side. The pair of second protrusions 516 extend along the conveyance direction on both edge sides of the woven fabric 12.

[0037] The second protrusion 516 has a plurality of grooves 20 formed on the lower end surface on the roll side. The belt 500 shown in FIG. 10 is viewed from below. The grooves 20 are formed at regular intervals in the conveying direction and extend in a direction perpendicular to the conveying direction. The grooves 20 are formed as linear cutouts on the lower end surface of the second protrusion 516. This makes the second protrusion 516 more likely to bend when wound around the roll 18, and less likely to be damaged. The depth of the grooves 20 may be in the range of 30% to 90% of the protruding height of the second protrusion 516, and more preferably in the range of 40% to 80%.

[0038] Fig. 11(a) is a view of the surface of the belt 600 of the sixth modified example located on the roll side, and Fig. 11(b) is a view of the belt 600 of the sixth modified example viewed along the conveying direction. The belt 600 of the sixth modified example has a different shape of the second protrusions 616 compared to the belt 300 shown in Fig. 7. The belt 600 includes a woven fabric 12 and a pair of second protrusions 616 fixed to the surface of the woven fabric 12 located on the roll side. The pair of second protrusions 616 extend along the conveying direction on both edge sides of the woven fabric 12.

[0039] The second protrusion 616 has a groove 22 formed on the lower end surface on the roll side. The grooves 22 extend in the conveyance direction and are formed in plurality. Note that, although there are two grooves 22 shown in Fig. 11(b) , this is not limiting, and there may be one or three grooves. [Explanation of symbols]

[0040] 10 belt, 12 fabric, 14 first ridge portion, 16 second ridge portion, 18 roll, 18a first recess, 18b second recess, 20, 22 groove.

Claims

1. An endless belt that is wound around a roll and driven by the rotation of the roll, A strip of fabric having conductive material threads woven into it; a protrusion provided on a surface of the fabric facing the roll and extending along a driving direction of the belt.

2. 2. The belt according to claim 1, wherein the protrusion is provided at a center in a width direction of the belt.

3. 2. The belt according to claim 1, wherein the protrusions are provided in pairs on both edge sides in the width direction of the belt.

4. The protrusion portion has a groove formed on a lower end surface on the roll side, 2. The belt of claim 1, wherein the grooves extend in the conveying direction.

5. The protrusion portion has a plurality of grooves formed on a lower end surface on the roll side, 2. The belt of claim 1, wherein the grooves extend in a direction perpendicular to the conveying direction.

6. 2. The belt according to claim 1, wherein the protrusions engage with recesses formed in the roll.

7. 2. The belt according to claim 1, wherein the protrusions are provided in pairs and are arranged along a side surface of the roll that does not have any recesses.

8. The woven fabric is formed by weaving warp yarns and weft yarns, The diameter of the warp yarn is set in the range of 0.1 to 0.7 mm, The diameter of the weft yarn is set in the range of 0.1 to 1.1 mm, 2. The belt of claim 1, wherein the fabric has an aperture count of 300 to 5000 apertures per square inch.

9. 2. The belt according to claim 1, wherein the area of ​​the surface of the fabric facing the roll that is covered by the protrusions is 40 percent or less of the area of ​​the surface of the fabric facing the roll.

10. 2. The belt according to claim 1, wherein the height at which the ridges protrude from the fabric is set within a range of 1 to 25 percent of the diameter of the roll.

11. 2. The belt according to claim 1, wherein the protrusions are toothed belts that mesh with the rolls having teeth.

12. 12. The belt according to claim 11, wherein a difference between a protruding height of the teeth of the protrusions and a protruding height of the teeth of the roll is set to be within a range of minus 4.0 percent to plus 9.0 percent of the protruding height of the teeth of the protrusions.

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