US20100144506A1

US20100144506A1 - Guide roller and fiber bundle arranging device

Info

Publication number: US20100144506A1
Application number: US12/595,485
Authority: US
Inventors: Genki Yoshikawa; Junji Takeuchi; Yoshiharu Yasui
Original assignee: Toyota Industries Corp
Current assignee: Toyota Industries Corp
Priority date: 2007-04-11
Filing date: 2008-04-10
Publication date: 2010-06-10
Also published as: JP4697174B2; EP2154095A4; JP2008260609A; CN101674994B; CN101674994A; WO2008126885A1; EP2154095A1

Abstract

A guide roller 34 includes a cylindrical portion 44 fixed to a support shaft 341, flanges 45, 46 provided at he axial ends of the cylindrical portion 44, a plurality of columnar contact bars 47 extending between the flanges 45, 46. The contact bars 47 are annularly arranged about a rotational axis 340 of the guide roller 34. A fiber bundle F is wrapped around the guide roller 34 so as to contact some of the contact bars 47. The contact bars 47 form a circumferential guide surface S, which contacts the fiber bundle F, about the rotational axis 340. A plurality of through holes 451, 461 are formed in the flanges 45, 46.

Description

TECHNICAL FIELD

The present invention relates to a guide roller having a circumferential guide surface that contacts and guides an untwisted fiber bundle, and to a fiber bundle arranging device having the guide roller.

BACKGROUND ART

Conventionally, composites that use three-dimensional fabric (three-dimensional fiber structure) as reinforcing material have been proposed as fiber-reinforced composites, which are widely used as light structural material. Fiber-reinforced composites have extremely high strength, and are used as part of structural material of, for example, aircraft. As a method for producing the three-dimensional fiber structure for use in reinforcing material for such fiber-reinforced composites, a method has been proposed in which a group of laminated fiber bundles is formed by laminating fiber bundle layers, each of which is formed by folding back a fiber bundle, to be at least biaxially oriented, and the group of laminated fiber bundles is connected by a thickness direction thread arranged perpendicular to the fiber bundle layers. Patent Document 1 discloses a fiber bundle arranging device that forms fiber bundle layers by feeding a fiber bundle from a guide pipe, which moves along an arranging surface, and arranging the fiber bundle to be folded back and forth between pins arranged at a predetermined pitch in a state where the fiber bundle is flat and the flat surface of the fiber bundle is arranged along the arranging surface.
A fiber bundles sent out from a supply source contacts circumferential guide surfaces of guide rollers, so as to be guided to a guide pipe. Some of the guide rollers are driven by a motor. The motor driven guide rollers are rotated such that the circumferential velocity of the circumferential guide surfaces is greater than the movement speed of a fiber bundle (that is, the movement speed of the guide pipe). This allows the fiber bundle to be moved smoothly.
However, when the circumferential velocity of the motor driven guide rollers is great, an accompanying air flow is generated around the circumferential guide surface of each guide roller, and such an accompanying air flow can cause monofilaments of the fiber bundle to be twined about the circumferential guide surfaces. If even a single monofilament is cut and twined about a guide roller, other monofilaments are drawn to and twined about the guide roller. Consequently, the entire fiber bundle is twined about the guide roller. It is then no longer possible to feed the fiber bundle to the guide pipe.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-16347

DISCLOSURE OF THE INVENTION

Accordingly, it is an objective of the present invention to prevent untwisted fiber bundles from being twined about a guide roller.
To achieve the foregoing objective and in accordance with one aspect of the present invention, a rotatable guide roller for guiding an untwisted fiber bundle is provided. The guide roller includes a circumferential guide surface, side surfaces, and an air passage. The circumferential guide surface contacts the fiber bundle so as to guide the fiber bundle. The side surfaces are provided on both sides of the circumferential guide surface in an axial direction. Through rotation of the guide roller, the air passage draws air from at least one of the side surfaces and blows the air radially outward relative to the circumferential guide surface.
The present invention also provides a fiber bundle arranging device that arranges a fiber bundle fed out from a bobbin in a flat state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a side view illustrating a fiber bundle arranging device according to a first embodiment of the present invention;

FIG. 1( b) is a partially enlarged cross-sectional view of FIG. 1( a);

FIG. 1( c) is a cross-sectional view taken along line 1 c-1 c of FIG. 1( b);

FIG. 2( a) is a partially omitted cross-sectional plan view illustrating the fiber bundle arranging device of FIG. 1( a);

FIG. 2( b) is an enlarged partial plan view illustrating the fiber bundle arranging device of FIG. 1( a);

FIG. 3( a) is a perspective view illustrating an arrangement of the fiber bundle;

FIG. 3( b) is an enlarged partial perspective view illustrating a guide pipe;

FIG. 4 is an enlarged partial cross-sectional view illustrating a guide roller according to a second embodiment of the present invention;

FIG. 5( a) is an enlarged partial cross-sectional view illustrating a guide roller according to a third embodiment of the present invention;

FIG. 5( b) is a cross-sectional view taken along line 5 b-5 b of FIG. 5( a);

FIG. 6( a) is an enlarged partial cross-sectional view illustrating a guide roller according to a fourth embodiment of the present invention;

FIG. 6( b) is a cross-sectional view taken along line 6 b-6 b of FIG. 6( a);

FIG. 7( a) is an enlarged partial cross-sectional view illustrating a guide roller according to a fifth embodiment of the present invention; and

FIG. 7( b) is a cross-sectional view taken along line 7 b-7 b of FIG. 7( a).

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the present invention will now be described with reference to FIGS. 1 to 3. FIG. 1( a) shows an overall view of a fiber bundle arranging device 10 according to the present embodiment.
As shown in FIG. 2( a), a pair of linear sliders 12, 13 are provided on a rectangular base 11 to extend in a longitudinal direction of the base 11 (hereinafter, referred to as an X-axis direction). The linear slider 12 includes a ball screw mechanism (not shown) and a movable body 121, which is moved in the X-axis direction by the ball screw mechanism. The linear slider 13 includes a ball screw mechanism (not shown) and a movable body 131, which is moved in the X-axis direction by the ball screw mechanism. In the linear sliders 12, 13, the ball screw mechanisms are operated in synchronization with each other, and the movable bodies 121, 131 are moved in the X-axis direction in synchronization with each other.
A linear slider 14 is provided on the movable bodies 121, 131 to extend in a direction perpendicular to the X-axis direction (hereinafter, referred to as a Y-axis direction). When the linear sliders 12, 13 are operated, the linear slider 14 is translated in the X-axis direction. The linear slider 14 includes a ball screw mechanism (not shown) and a movable body 141, which is moved in the Y-axis direction by the ball screw mechanism.
As shown in FIG. 1( a), the moving body 141 includes a support frame 15. A motor 16, which rotates both in forward and reverse directions, is secured to the side of the support frame 15. A threaded shaft 161, which is the output shaft of the motor 16 extends in the vertical direction (hereinafter, referred to as a Z-axis direction). A nut 18 is threaded to the threaded shaft 161, and a support plate 17 is secured to the nut 18. When the threaded shaft 161 rotates, the support plate 17 is moved in the Z-axis direction together with the nut 18.
A bracket 19 is fixed to an upper part of the support frame 15. The bracket 19 supports a support shaft 20, such that the support shaft 20 extends in the Z-axis direction and is rotatable. A support plate 21 is secured to the support shaft 20. The support plate 21 supports a motor 22 and a bobbin holder 23. A bobbin 24 formed by a fiber bundle F is mounted on the bobbin holder 23, and the bobbin 24 is rotated by the operation of the motor 22 in a direction to feed the fiber bundle F (the direction shown by arrow R in FIG. 1( a)). The fiber bundle F is formed by bundling monofilaments in a flat state without twisting them.
A support column 33 is vertically arranged on the support plate 21, and a pair of guide rollers 34, 35 and a motor 36 are mounted on the upper part of the support column 33. The guide rollers 34, 35 are actively rotated by the operation of the motor 36. A tension roller 37 is arranged below the guide rollers 34, 35 to be movable in the vertical direction. Also, a guide roller 38 is attached to the lower part of the support column 33 to be freely rotatable. The fiber bundle F fed from the bobbin 24 is guided to a space below the support plate 21 by the guide rollers 34, 35, the tension roller 37, and the guide roller 38. The fiber bundle F is placed under proper tension by a tension applying mechanism including the tension roller 37.
A motor 25 is fixed to the support plate 17. An output shaft 251 of the motor 25 extends in the Z-axis direction, and a support bracket 26 is secured to the output shaft 251. When the motor 16 is operated, the motor 25 and the support bracket 26 are moved in the Z-axis direction. The support bracket 26 is caused to rotate about the output shaft 251 by the operation of the motor 25. The support bracket 26 has a coupler bar 27, which is upright and extends in the Z-axis direction. The coupler bar 27 is passed through a hole formed in the support plate 21 and is engaged with the support plate 21. When the support bracket 26 moves in the Z-axis direction, the coupler bar 27 is moved in the Z-axis direction. When the motor 25 is operated, the support bracket 26, the coupler bar 27, and the support plate 21 are rotated integrally about the output shaft 251.
An arrangement head 28 is attached to a lower part of the support bracket 26 directly below the output shaft 251. The arrangement head 28 includes a guide pipe 29, which feeds the fiber bundle F. As shown in FIG. 3( b), a guide hole 291 in the guide pipe 29 is flat, and the guide pipe 29 feeds the fiber bundle F from the guide hole 291 in a flat form.
As shown in FIG. 1( a), guide rollers 30, 31 and a motor 32 are mounted on the support bracket 26. The guide roller 30 is actively driven by the motor 32 so as to be rotated in the direction of arrow Q, while the guide roller 31 is allowed to rotate freely. The fiber bundle F guided via the guide roller 38 is introduced into the guide pipe 29 via the guide rollers 31, 30.
As shown in FIG. 2( a), a frame 39 is placed on the base 11. The frame 39 is formed into a rectangular shape, and pins 40 are arranged on the upper surface of the frame 39 along the frame 39 at a predetermined pitch (for example, a pitch of a few millimeters). The guide pipe 29 shown in FIG. 1( a) is arranged at an appropriate height by the operation of the motor 16, and is moved in the X-axis direction, Y-axis direction, or bias direction (diagonal direction) by the combination of the operation of the linear sliders 12, 13 and the operation of the linear slider 14. When the guide pipe 29 is moved in the X-axis direction, the Y-axis direction, or the bias direction, the fiber bundle F extending through the guide pipe 29 is fed out from the guide pipe 29 while being engaged with the pins 40. FIG. 3( a) shows an example of arranging the fiber bundle F while the fiber bundle F is engaged with the pins 40.
The orientation of the guide pipe 29 is adjusted by the operation of the motor 25 such that the flat surface of the fiber bundle F fed out from the guide pipe 29 faces in the movement direction of the guide pipe 29 except when the fiber bundle F is engaged with the pins 40 by moving the guide pipe 29 to invert around the pins 40. The arrangement state of the support plate 21 shown by the solid line in FIG. 2( a) is a state where the flat surface of the guide pipe 29 fed out from the guide pipe 29 faces in the X-axis direction, and the arrangement state of the support plate 21 shown by the chain line in FIG. 2( a) is a state where the flat surface of the fiber bundle F fed out from the guide pipe 29 faces in the Y-axis direction.
As shown in FIG. 2( b), support shafts 341, 351 of the guide rollers 34, 35 are rotatably supported by the support column 33 with bearings 41, 42. Driven gears 342, 352 are secured to the support shafts 341, 351. The driven gear 342 is meshed with a drive gear 361 of the motor 36. Also, the driven gears 342, 352 are meshed with a transmission gear 43. When the drive gear 361 of the motor 36 is rotated, the guide rollers 34, 35 are rotated in the same direction (the direction indicated by arrow P in FIG. 1( a)).
Since the guide rollers 34, 35 and the guide rollers 30 have the same structure, the structure of the guide roller 34 will hereafter be described.
As shown in FIG. 1( b), the guide roller 34 includes a cylindrical portion 44 fitted and fixed to the support shaft 341, flanges 45, 46 integrally formed with the cylindrical portion 44 at the axial ends, a plurality of contact bars 47 extending between the flanges 45, 46. As shown in FIG. 1( c), through holes (inlets) 451, 461 are formed in the flanges 45, 46. The contact bars 47 are annularly arranged about the rotational axis 340 of the guide roller 34 to extend parallel with the rotational axis 340 and to be at an equal distance from the rotational axis 340. The distance between adjacent contact bars 47 is constant. The fiber bundle F is wrapped around the guide roller 34 so as to contact some of the contact bars 47. The contact bars 47 form a circumferential guide surface S, which contacts the fiber bundle F, about the rotational axis 340.
Although, only an operation achieved by rotation of the guide roller 34 will hereafter be described, operations achieved by rotation of the guide rollers 35, 30 are the same as the case of the guide roller 34.
As the fiber bundle arranging device 10 starts operating, the guide roller 34 is rotated in the direction of arrow P in FIG. 1( a). The circumferential velocity of the contact bars 47, which form the circumferential guide surface S, is set to be greater than the movement speed of the guide pipe 29, that is, the movement speed of fiber bundle F. The circumferential velocity of the contact bars 47 is, for example, 1.5 times the movement speed of the fiber bundle F. The fiber bundle F, which is wrapped around the guide roller 34 so as to contact the contact bars 47, is moved to draw out the fiber bundle F wound about the bobbin 24 as the guide roller 34 rotates. As the contact bars 47 revolve, air in the clearance K between each adjacent pair of the contact bars 47 (see FIG. 1( c)) is moved (discharged) toward the outside in the radial direction from the rotational axis 340 by the effect of centrifugal force and a blowing effect from the contact bars 47. The blowing effect of the contact bars 47, that is, radial outward movement of air, is surmised to be brought about when a circumferential region E (shown in FIG. 1( c)) that is on the leading side in the movement direction of the contact bar 47 and outside in the radial direction from the rotational axis 340 as a center is moved as the guide roller 34 rotates. The circumferential surface region E is a descending slope (descending surface) that approaches the rotational axis 340 toward the leading end in the rotational direction (direction shown by arrow P) of the guide roller 34.
As air in the clearance between each adjacent pair of the contact bars 47 is moved radially outward from the circumferential guide surface S, air is drawn in to an inner space N (see FIG. 1( c)) formed by the flanges 45, 46 and the circumferential guide surface S through the through holes 451, 461 from side surfaces 343, 344 (see FIG. 1( b)) of the guide roller 34. That is, as the guide roller 34 rotates, the air in the inner space N radially inside of the circumferential guide surface S is discharged to the outside of the circumferential guide surface S.
As the guide roller 34 rotates, an accompanying air flow is generated about the circumferential guide surface S, and this accompanying air flow acts on monofilaments of the fiber bundle F, which are moving away from the contact bars 47, so as to cause the monofilaments to be twined about the guide rollers 34. The air flow from the inner space N of the circumferential guide surface S to the outside of the surface S prevents such twining.
The through holes 451, 461 and the inner space N of the circumferential guide surface S form air flow passages that, through rotation of the guide roller 34, draw air from the side surfaces 343, 344 of the guide roller 34 and blow the air to the outside of the circumferential guide surface S. The clearance K between each adjacent pair of the contact bars 47 functions as an outlet that moves air from the inner space N of the circumferential guide surface S to the outside of the surface S.
The first embodiment has the following advantages.
(1) The air flow that blows from the inner space N of the circumferential guide surface S to the outside of the circumferential guide surface S prevents monofilaments from being twined about the guide roller 34. As a result, the fiber bundle F is prevented from being twined about the guide roller 34, so that the fiber bundle F is stably fed to the guide roller 34.
(2) Since each clearance K extends from one flange 45 to the other flange 46, the entire width of the fiber bundle F wrapped around the circumferential guide surface S is exposed to the air flow blown out from the inner space N of the circumferential guide surface S to the outside of the circumferential guide surface S. This reliably prevents the fiber bundle F from being twined about the guide roller 34.
(3) The structure in which the contact bars 47 are arranged annularly simplifies the formation of the clearances K which are outlets for moving air in the inner space of the circumferential guide surface S to the outside of the surface S. The smaller the clearances K, the greater the air movement effect becomes as brought about the centrifugal force.
(4) The circumferential velocity of the circumferential guide surface S of the guide roller 34 is set to be greater than the movement speed of the fiber bundle F. If the movement speed of the fiber bundle F contacting and guided by the circumferential guide surface S is less than the circumferential velocity of the circumferential guide surface S, monofilaments acting to separate from the circumferential guide surface S are likely to be twined about the guide roller 34 by accompanying air flow generated about the circumferential guide surface S, which rotates at a circumferential velocity greater than the movement speed of the fiber bundle F. The guide roller 34 of the present embodiment, in which the circumferential velocity of the circumferential guide surface S is greater than the movement speed of the fiber bundle F, is particularly suitable as an application of the present invention.
A second embodiment of the present invention will now be described with reference to FIG. 4. The same reference numerals are given to those components that are the same as the corresponding components of the first embodiment.
In the second embodiment, flat plate-like contact bars 47A form a circumferential guide surface S. Each contact bar 47A has a flat surface on its leading side in the movement direction (the direction of arrow P). The flat surface forms a descending surface (descending slope) 471, which approaches the rotational axis 340 toward the leading end in the rotational direction (the direction shown by arrow P) of the guide roller 34A. The descending surface 471 is inclined relative to the radial direction of the guide roller 34A, and the radially inner end is located on the leading side in the rotational direction of the guide roller 34A compared to the radially outer end. As the guide roller 34A rotates, the descending surface 471 discharges air in the inner space N of the circumferential guide surface S to the outside of the surface S.
The second embodiment has the same advantages as the advantages (1) to (4) of the first embodiment.
A third embodiment of the present invention will now be described with reference to FIGS. 5( a) and 5(b). The same reference numerals are given to those components that are the same as the corresponding components of the first embodiment.
As shown in FIG. 5( b), a guide roller 34B includes a cylindrical portion 48 that encompasses the rotational axis 340, and an inner space 481 of the cylindrical portion 48 opens at the side surface 343 of the guide roller 34B. As shown in FIG. 5( a), the outer circumferential surface of the cylindrical portion 48 forms a circumferential guide surface Sb, and a plurality of passages 49 extend in radial directions of the guide roller 34B from the circumferential guide surface Sb and through the cylindrical portion 48 and reach an inner space 481. As the guide roller 34B rotates, air in the passages 49 is discharged to the outside of the circumferential guide surface Sb by centrifugal force. Accordingly, air flows into the inner space 481 through the opening (inlet) in the side surface 343 of the guide roller 34B. The inner space 481 and the passages 49 form air flow passages that, through rotation of the guide roller 34B, draw air from the side surface 343 of the guide roller 34B and blow the air to the outside of the circumferential guide surface Sb.
The third embodiment has the same advantages as the advantages (1) and (4) of the first embodiment.
A fourth embodiment of the present invention will now be described with reference to FIGS. 6( a) and 6(b). The same reference numerals are given to those components that are the same as the corresponding components of the third embodiment.
As shown in FIG. 6( a), a plurality of slits 50 are formed in the outer circumferential surface of the guide roller 34C between flanges 45, 46. The slits 50 extend parallel with the rotational axis 340. The slits 50 are arranged along the circumferential direction of the guide roller 34C at regular intervals. As shown in FIG. 6( b), a plurality of introduction passages 51 are formed in the guide roller 34C to extend from one side surface 343 to the other side surface 344. Each introduction passage 51 communicates with the bottom of one of the slits 50 through at least one passage 52 (two in FIG. 6( b)) extending in the radial direction of the guide roller 34C. As the guide roller 34C rotates, air in the slits 50 and the passages 52 is discharged to the outside of the circumferential guide surface Sc by centrifugal force. Accordingly, air flows into the introduction passages 51 through the side surfaces 343, 344 of the guide roller 34C. The introduction passages 51, the passages 52, and the slits 50 form air flow passages that, through rotation of the guide roller 34C, draw air from the side surfaces 343, 344 of the guide roller 34C and blow the air to the outside of the circumferential guide surface Sc. The passages 52 and the slits 50 form outlets that uses the centrifugal force of rotation of the guide roller 34C to move air to the outside of the circumferential guide surface Sc. Both ends of each introduction passage 51 function as air inlets.
Air that has flowed out to the slits 50 from the passages 52 blows out to the outside of the circumferential surface Sc while spreading to some extent in the longitudinal direction of the slits 50, thereby exposing the entire width of the fiber bundle F wrapped around the circumferential guide surface S to air flow blowing to the outside of the circumferential guide surface S.
The fourth embodiment has the same advantages as the advantages (1), (2), and (4) of the first embodiment.
A fifth embodiment of the present invention will now be described with reference to FIGS. 7( a) and 7(b). The same reference numerals are given to those components that are the same as the corresponding components of the first embodiment.
A guide roller 34D includes a pair of flanges 45D, 46D, a plurality of contact bars 47 extending between the flanges 45D and 46D, and a fan 53, which is fitted and fixed to one flange 45D and to the support shaft 341. That is, the fan 53 is provided at the inlet of air. As the guide roller 34D rotates, the fan 53 actively sends air into an inner space N of the circumferential guide surface S from the side surface 343 of the flange 45D. Accordingly, air in the inner space N of the circumferential guide surface S blows out through the clearance K between each adjacent pair of the contact bars 47 to the outside of the circumferential guide surface S through the clearance K.
The fifth embodiment has the same advantages as the advantages (1) to (4) of the first embodiment.
The present invention may be modified as follows.
A guide roller may have an air tube that extends from a side surface of the guide roller to the circumferential guide surface, thereby forming an air passage. In this case, one opening (inlet) of the air tube that opens at the side surfaces of a guide roller is located closer to the rotational axis of the guide roller than the other opening (outlet) of the air tube that opens in the circumferential guide surface.
In this construction, air in the guide tube is discharged to the outside of the circumferential surface by the centrifugal force generated by rotation of the guide roller.
In the second embodiment, the contact bars 47A may be arranged radially along the radial direction of the guide roller 34A, or so as not to be inclined relative to the radial direction. In this case, air between each adjacent contact bars 47 is discharged to the outside of the circumferential guide surface S by centrifugal force as the guide roller 34A rotates.
Guide rollers that are not rotated by a motor (drive source), that is, guide rollers that are not actively driven (the guide rollers 31, 38 in the illustrated example) may be used in the present invention.

Claims

1. A rotatable guide roller for guiding an untwisted fiber bundle, the rotatable guide roller comprising:

a circumferential guide surface that contacts the fiber bundle so as to guide the fiber bundle, the circumferential guide surface having a pair of sides;

side surfaces provided on both sides of the circumferential guide surface in an axial direction; and

an air passage that, through rotation of the guide roller, draws air from at least one of the side surfaces and blows the air radially outward relative to the circumferential guide surface.

2. The guide roller according to claim 1, further comprising an outlet that uses centrifugal force generated when the guide roller rotates, to move air in the air passage radially outward relative to the circumferential guide surface.

3. The guide roller according to claim 2, wherein the circumferential guide surface is formed by annularly arranging a plurality of contact bars about a rotational axis of the guide roller, and wherein the outlet is a clearance between each adjacent pair of the contact bars.

4. The guide roller according to claim 2, further comprising a cylindrical portion encompassing a rotational axis of the guide roller, wherein the cylindrical portion has an inner space and an outer circumferential surface, the inner space having an opening at least at one of the side surfaces of the guide roller, and the outer circumferential surface forming the circumferential guide surface, and wherein the outlet is a passage that extends from the circumferential guide surface through the cylindrical portion to reach the inner space.

5. The guide roller according to claim 2, wherein the outlet comprises a plurality of slits that are formed in the outer circumferential surface of the guide roller to extend parallel with the rotational axis.

6. The guide roller according to claim 1, wherein the circumferential guide surface is formed by annularly arranging a plurality of contact bars about a rotational axis of the guide roller, and wherein each contact bar has a descending surface that approaches the rotational axis toward the leading end in the rotational direction of the guide roller.

7. The guide roller according to claim 1, further comprising a fan that, through rotation of the guide roller, actively draws air from at least one of the side surfaces into the air passage.

8. The guide roller according to claim 1, further comprising an inlet that opens at least at one of the side surfaces and an outlet that opens in the circumferential guide surface, wherein the inlet is located inside of the outlet with respect to the radial direction of the guide roller, and the air passage extends from the inlet to the outlet.

9. The guide roller according to claim 1, wherein the guide roller is capable of being driven to rotate by a drive source.

10. The guide roller according to claim 9, wherein the guide roller is capable of being driven such that the circumferential velocity of the circumferential guide surface is greater than the movement speed of the fiber bundle.

11. A fiber bundle arranging device having the guide roller according to claim 1, wherein the device arranges a fiber bundle fed out from a bobbin in a flat state.