US20100243788A1

US20100243788A1 - Web traveling position regulating method, web manufacturing method, web conveying device and web cutting device

Info

Publication number: US20100243788A1
Application number: US12/727,232
Authority: US
Inventors: Masatoshi Oku
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2009-03-24
Filing date: 2010-03-19
Publication date: 2010-09-30
Also published as: JP2010222100A; JP5388649B2

Abstract

The present invention provides a web traveling position regulating method, a web manufacturing method and a web conveying device that, without relying on a roller whose peripheral surface is crown-shaped, can carry out transverse direction position regulation of a web that travels, and provides a web cutting device to which the web conveying device is applied and that, by a simple structure, can carry out transverse direction position regulation of plural webs that travel.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 from Japanese Patent Application No. 2009-071563, filed Mar. 24, 2009, the disclosure of which is incorporated by reference herein.

BACKGROUND

1. Technical Field
The present invention relates a web traveling position regulating method, a web manufacturing method, a web conveying device and a web cutting device for a web that is a flexible elongated body such as, for example, a magnetic tape or the like.
2. Related Art
There is known a technique that uses a roller whose peripheral surface is crown-shaped in order to prevent lateral offset of a tape that is drawn-out from a tape supply source.
However, in a conventional technique such as that described above, in order to center the tape by the crown-shaped peripheral surface, the tape must be gripped at the peripheral surface of the roller. Thus, there are limitations on the applications of a conventional technique such as described above, and other methods and devices that regulate the transverse direction position of a web that travels are desired.

SUMMARY

The present invention provides a web traveling position regulating method, a web manufacturing method and a web conveying device that, without relying on a roller whose peripheral surface is crown-shaped, can carry out transverse direction position regulation of a web that travels, and provides a web cutting device to which the web conveying device is applied and that, by a simple structure, can carry out transverse direction position regulation of plural webs that travel.
A first aspect relating to the present invention is a web traveling position regulating method that includes training a web around a peripheral surface at a roller, which peripheral surface forms a concave shape at which an axial direction center has a smaller diameter than axial direction end portions, and causing the web to travel while sliding the web with respect to the roller, thereby regulating a traveling position in a transverse direction of the web.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present invention will be described in detail based on the following figures, wherein:

FIG. 1 is a side view showing the schematic overall structure of a centering roller that structures a magnetic tape manufacturing device relating to an exemplary embodiment of the present invention;

FIG. 2 is a side view schematically showing, in an enlarged manner, a portion of the centering roller that structures the magnetic tape manufacturing device relating to the exemplary embodiment of the present invention;

FIG. 3 is a side view schematically showing the schematic overall structure of the magnetic tape manufacturing device relating to the exemplary embodiment of the present invention;

FIG. 4 is a plan view schematically showing a slitter that structures the magnetic tape manufacturing device relating to the exemplary embodiment of the present invention;

FIG. 5 is a graph that shows, in comparison with comparative examples, results of centering by the centering roller that structures the magnetic tape manufacturing device relating to the exemplary embodiment of the present invention;

FIG. 6 is a side view schematically showing the schematic structure of a testing device for measuring the results of centering of FIG. 5;

FIG. 7A is a graph showing tension fluctuations of a magnetic tape in the magnetic tape manufacturing device relating to the exemplary embodiment of the present invention;

FIG. 7B is a graph showing tension fluctuations of a magnetic tape in a magnetic tape manufacturing device relating to a comparative example;

FIG. 8 is a drawing for explaining the effects of centering by the centering roller relating to the exemplary embodiment of the present invention, and is a graph showing the relationships between tension at a side before or at a side after the roller in a stationary state of the tape, and the roller peripheral speed;

FIG. 9 is a drawing for explaining the effects of centering by the centering roller relating to the exemplary embodiment of the present invention, and is a graph showing the relationship between a tape floating amount with respect to the roller in a stationary state of the tape, and the roller peripheral speed;

FIG. 10 is a drawing for explaining the effects of centering by the centering roller relating to the exemplary embodiment of the present invention, and is a graph showing the relationship between the standard deviation of relative displacement in the transverse direction of a tape with respect to the roller in a stationary state of the tape, and the roller peripheral speed; and

FIG. 11 is a schematic drawing of a testing device for obtaining the graphs of FIG. 8 through FIG. 10.

DETAILED DESCRIPTION

A magnetic tape manufacturing device 10, that serves as a web cutting device to which are applied a web traveling position regulating method, a web manufacturing method, a web conveying device and a web conveying device relating to an exemplary embodiment of the present invention, will be described on the basis of FIG. 1 through FIG. 7A and FIG. 7B. First, the schematic overall structure of the magnetic tape manufacturing device 10 will be described. Then, a centering roller 38, which is a main portion of the present invention, will be described in detail.
(Magnetic Tape Manufacturing Device)
A portion of the magnetic tape manufacturing device 10 is shown in a schematic side view in FIG. 3. As shown in FIG. 3, the magnetic tape manufacturing device 10 is a device that manufactures a high-density magnetic recording tape 11 (hereinafter simply called “magnetic tape 11”) that serves as a web for, for example, computer back-up. The magnetic tape manufacturing device 10 manufactures the plural narrow-width magnetic tapes 11 by cutting a magnetic tape original sheet 12, that has a wide width and serves as the web original sheet in the present invention, along the longitudinal direction.
Concretely, the magnetic tape original sheet 12 is formed in the shape of a strip having a wider width than that of the magnetic tape 11 that is the manufactured product. For example, the magnetic tape original sheet 12 is manufactured by forming a magnetic layer, that includes strong magnetic particulates, on a non-magnetic substrate by coating or vacuum deposition or the like, and carrying out orienting processing, drying processing, surface treatment, and the like on the magnetic layer. The magnetic tape original sheet 12 is wound in the form of a roll on a hub 14 that serves as a winding core, and forms a magnetic tape original sheet roll 16 that serves as a roll-shaped original sheet. The magnetic tape original sheet roll 16 is supported so as to rotate freely around the axis via the hub 14, and structures a draw-out section (also called unwinding section) 15. Due thereto, at the magnetic tape manufacturing device 10, continuous unwinding of the magnetic tape original sheet 12 from the magnetic tape original sheet roll 16 is possible.
The magnetic tape original sheet 12 is trained around a feed roller 18 that serves as a web traveling portion and is also a reference roller. By driving the feed roller 18, the magnetic tape original sheet 12 is continuously unwound and fed-out from the magnetic tape original sheet roll 16. A slitter 20, that serves as a cutting portion for cutting the magnetic tape original sheet 12 along the longitudinal direction at plural places thereof in the transverse direction, is disposed at the downstream side of the feed roller 18.
As shown in FIG. 4 as well, the slitter 20 has plural pairs of rotating upper blades 22 and rotating lower blades 24 that are paired upward and downward and that are parallel in the transverse direction of the magnetic tape original sheet 12. The respective rotating upper blades 22 are driven and rotated by a motor 26, and the respective rotating lower blades 24 are driven and rotated by a motor 28.
The magnetic tape original sheet 12, that is fed-in between the plural pairs of rotating upper blades 22 and rotating lower blades 24 that structure the slitter 20, is divided uniformly in the tape transverse direction such that the plural, narrow-width magnetic tapes 11 are formed. In the present exemplary embodiment, a width Wt (see FIG. 2) of the magnetic tape 11 is approximately 12.65 [mm].
Returning to FIG. 3, the magnetic tapes 11 after being cut by the slitter 20 are trained around path rollers 30, and thereafter, are taken-up onto take-up hubs 32 that rotate synchronously with the feed roller 18, such that so-called pancakes 24 are formed. A plurality of each of the path roller 30 and the take-up hub 32 (two of each in the present exemplary embodiment) are provided. The two path rollers 30 and the two take-up hubs 32 are disposed so as to be offset vertically with respect to one another in the transverse direction of the magnetic tape original sheet 12. The magnetic tapes 11 that are adjacent to one another in the tape transverse direction are offset from one another vertically, and are taken-up onto the take-up hubs 32. In other words, in the magnetic tape manufacturing device 10, downstream of the slitter 20, the traveling path of the magnetic tapes 11 branches off into an upper traveling path Wu and a lower traveling path W1.
Further, guide rollers 36, around which the magnetic tape original sheet 12 or the magnetic tapes 11 are trained, are appropriately disposed between the magnetic tape original sheet roll 16 and the feed roller 18, and between the feed roller 18 and the slitter 20, and between the slitter 20 and the upper and lower path rollers 30. The centering rollers 38 are respectively disposed between the guide rollers 36, that are furthest toward the path rollers 30 side, and the respective upper and lower path rollers 30. Due to each of the centering rollers 38 having a training surface 40 as will be described later, the centering rollers 38 carry out position regulation in the tape transverse direction of the magnetic tapes 11 that travel.
The magnetic tapes 11 that are wound onto the take-up hubs 32 are conveyed as the pancakes 34 to an unillustrated servo writing device. Servo signals are written to the magnetic tapes while the magnetic tapes 11 are unwound from the take-up hubs 32 in a servo process at the servo writing device. Thereafter, the magnetic tapes 11 are wound onto product reels.
(Structure of Centering Roller)
The centering roller 38, that serves as the roller in the present invention, is a roller for regulating the traveling position in the tape transverse direction of the magnetic tape 11. Due thereto, the centering roller 38 exhibits a function of centering the magnetic tape 11 in the tape transverse direction with respect to the corresponding take-up hub 32.
As shown in FIG. 1, the centering roller 38 has a roller portion 42, at which are formed the plural (40 in the present exemplary embodiment) training surfaces 40 around which are trained the magnetic tapes 11 that travel along the upper traveling path Wu or the lower traveling path W1, and a supporting shaft portion 44 provided at the axially central portion of the roller portion 42. In the present exemplary embodiment, the centering roller 38 is structured integrally (manufactured as a single product) such that the roller portion 42 (the respective training surfaces 40) rotates coaxially and integrally with the supporting shaft portion 44.
The respective training surfaces 40 of the centering roller 38, that structures the magnetic tape manufacturing device 10, are formed in concave shapes at which the respective central portions in the axial (tape width) direction thereof are recessed toward the rotational center side as compared with the both end portions. Accordingly, the centering roller 38 can be understood as being a so-called concave roller (a structure at which plural concave rollers are connected in the axial direction). In the present exemplary embodiment, viewed from a direction orthogonal to the axis of the centering roller 38, the respective training surfaces 40 form curves (circular arcs in the present exemplary embodiment) that do not have inflection points.
More specifically, as shown in FIG. 2, at each of the training surfaces 40, given that a radial difference between a minimum radius Rmin (≈40 mm) and a maximum radius Rmax is ΔR, then ΔR=0.2 mm. Further, a width Wr of each training surface 40 in the axial direction is approximately 25.3 mm that is twice the width Wt of the magnetic tape 11. As mentioned above, because each training surface 40 forms a circular arc when viewed from a direction orthogonal to the axis of the centering roller 38, it can be understood that a radius of curvature r of this circular arc is approximately 400 mm, from the above ΔR and width Wr.
Further, as shown in FIG. 2, when the magnetic tape 11 is trained around the training surface 40 such that the tape transverse direction center line is made to coincide, a radial difference ΔRr between the minimum radius Rmin and a trained maximum radius Rr in the trained range of that magnetic tape 11 is approximately 0.050 mm. In the present exemplary embodiment, the respective magnetic tapes 11 are trained over a range of approximately 90° on the corresponding training surfaces 40 at the centering roller 38 (see FIG. 3). Therefore, a trained peripheral length difference ΔLr between the tape transverse direction central portion and both end portions of the magnetic tape 11 is approximately 0.078 mm. Moreover, a peripheral length change rate ΔLrn, that is computed by dividing the peripheral length difference ΔLr by the width Wt of the magnetic tape 11 and non-dimensionalizing, is approximately 0.006. The relationship between the depth of each training surface 40 and the magnetic tape 11 is expressed (generalized) by this peripheral length change rate ΔLrn.
At each of the training surfaces 40, the indentations and protrusions are set to be extremely small, in order for slipping between the training surface 40 and the magnetic tape 11 traveling thereon to arise easily (in order for the coefficient of friction to be sufficiently small). Specifically, a surface roughness Ry of each of the training surfaces 40 is made to be less than or equal to 0.1 μm. In the present exemplary embodiment, the above surface roughness of the training surface 40 is set by coating diamond like carbon (hereinafter called “DLC”) on the surface of the roller portion 42. In the present exemplary embodiment, the surface roughness Ry of each of the training surfaces 40 is from 0.05 μm to 0.1 μm. Note that the surface roughness Ry of the magnetic tape 11 trained on the training surface 40 is made to be sufficiently smaller than 0.1 μm.
As shown in FIG. 1 and FIG. 3, the centering roller 38 structuring the magnetic tape manufacturing device 10 is driven and rotated around the axis of the supporting shaft portion 44 by a roller driving mechanism 46 serving as a roller driving means. The roller driving mechanism 46 is structured to include at least a variable speed motor.
In the magnetic tape manufacturing device 10, at the roller driving mechanism 46, the rotating speed of the motor is controlled by the controller 48 such that a peripheral speed Vr at (the portion of the minimum radius Rmin of) the training surface 40 is always greater than or equal to a predetermined speed Vs (200 m/min in the present exemplary embodiment). Specifically, at the roller driving mechanism 46, the rotating speed of the motor is controlled by the controller 48 such that, if a traveling speed Vt of the magnetic tape 11 that is made to travel due to rotation of the feed roller 18 is lower than the predetermined speed Vs (including cases in which the tape is stopped), the peripheral speed Vr is made to substantially coincide with the predetermined speed Vs, and, if the traveling speed Vt of the magnetic tape 11 is greater than or equal to the predetermined speed Vs, the peripheral speed Vr is made to substantially coincide with the traveling speed Vt of the magnetic tape 11. The predetermined speed Vs is set as a speed at which, even when the magnetic tape 11 is stopped, air is pulled-in between that magnetic tape 11 and the training surface 40 (hereinafter this air is called “accompanying air”), and that magnetic tape 11 and the training surface 40 do not contact at least at the transverse direction central portion (details will be described later). Note that the controller 48 obtains the traveling speed Vt from, for example, the rotating speed of the feed roller 18 that feeds the magnetic tape 11 without sliding.
Due to the above, in the magnetic tape manufacturing device 10, regardless of the traveling speed of the magnetic tape 11, the magnetic tape 11 travels while sliding substantially completely (in a non-contact state at least at the transverse direction central portion) with respect to the training surface 40 of the centering roller 38. Due thereto, the magnetic tape manufacturing device 10 is structured such that the position of the magnetic tape 11 is regulated (the magnetic tape 11 is centered) at the axial (tape transverse) direction central portion of the training surface 40. The mechanism of this centering will be described hereinafter together with the operation of the present exemplary embodiment.
Operation of the present exemplary embodiment will be described next.
In the magnetic tape manufacturing device 10 of the above-described structure, at the time of manufacturing the plural magnetic tapes 11 from the magnetic tape original sheet 12, the feed roller 18 is activated, and the magnetic tape original sheet 12, that is unwound from the magnetic tape original sheet roll 16 of the draw-out section 15, is led to the slitter 20. At the slitter 20, the magnetic tape original sheet 12 is divided uniformly in the transverse direction, such that the magnetic tapes 11 are formed. The traveling paths of the plural (80) magnetic tapes 11 are divided into the upper traveling path Wu and the lower traveling path W1 alternately in the tape transverse direction, and the magnetic tapes 11 pass along the guide rollers 36, the centering rollers 38, and the path rollers 30 that form the respective traveling paths, and are taken-up onto the take-up hubs 32. The plural pancakes 34 of the predetermined width Wt are thereby obtained from the wide-width magnetic tape original sheet 12.
At the time of manufacturing the magnetic tapes 11, the respective centering rollers 38 are driven and rotated by the respective roller driving mechanisms 46 such that, from before the start of traveling of the magnetic tapes 11 due to the feed roller 18, the peripheral speeds Vr coincide with the predetermined speed Vs. Due thereto, the accompanying air exists between the training surfaces 40 and the portions of the magnetic tapes 11 which portions are trained on the training surfaces 40, and, from immediately after the start of traveling, the magnetic tapes 11 travel while sliding (slipping) substantially completely (in a non-contact state at least at the transverse direction central portion) with respect to the training surfaces 40 on which the magnetic tapes 11 are trained. Further, if the traveling speed Vt of the magnetic tapes 11 is increased and becomes greater than or equal to the predetermined speed Vs, the respective centering rollers 38 are driven and rotated by the respective roller driving mechanisms 46 such that the peripheral speeds Vr coincide with traveling speed Vt of the magnetic tapes 11. For these reasons, accompanying air always exists between the magnetic tapes 11 and the training surfaces 40. Further, the surface roughnesses of the magnetic tapes 11 and the training surfaces 40 are made to be less than or equal to 0.1 μm. Therefore, the thickness of the accompanying air layer as compared with the indentations and protrusions of these surfaces is relatively large, and friction between the magnetic tapes 11 and the training surfaces 40 is reduced. The magnetic tapes 11 thereby travel while sliding substantially completely with respect to the training surfaces 40 as described above.
Due thereto, in the magnetic tape manufacturing device 10, the position of the magnetic tape 11 is regulated (the magnetic tape 11 is centered) at the axial direction center of the corresponding training surface 40, and meandering and swaying that accompany the traveling are suppressed. This point will be explained further on the basis of the experimental results that are shown in FIG. 5. The experimental results shown in FIG. 5 are results obtained by using a testing device 70 shown in FIG. 6. The testing device 70 is structured by a tape push-in portion 72 being provided at a position of a distance L2 (=450 mm) from the centering roller 38, between the guide roller 36, that is disposed apart by distance L1 (=750 mm) from the centering roller 38, and the centering roller 38 (or any of the modified example rollers or comparative example rollers that will be described later). The tape push-in portion 72 imparts forced displacement (pushes-in by a predetermined amount) in the tape transverse direction to the magnetic tape 11 that is traveling at that position. FIG. 5 shows the results of measurement of traveling position (offset amount in the tape transverse direction with respect to the tape transverse direction center) X1 of the magnetic tape 11 on the centering roller 38 (or any of the modified example rollers or comparative example rollers that will be described later), when forced displacement amount X0 in the transverse direction, that is applied to the magnetic tape 11 by the tape push-in portion 72, is imparted. Note that a first comparative example roller is a crown roller whose training surface is formed in a crown shape and that is generally used in centering applications. This is a structure in which, due to a groove, through which the accompanying air escapes, being formed in the training surface, the magnetic tape 11 is trained without sliding (the peripheral speed at the maximum diameter portion coincides with the traveling speed Vt of the magnetic tape 11). A second comparative example is a flat roller whose training surface is a cylindrical surface. Due to a groove, through which the accompanying air escapes, being formed in the training surface, the magnetic tape 11 is trained without sliding.
From FIG. 5, it can be understood that, with the second comparative example roller, when the forced displacement X0=10 mm is applied, the offset amount X1 is 5 mm, and the centering effect due to friction between the roller and the magnetic tape is hardly exhibited at all. Further, it can be understood that, in the first comparative example, when the forced displacement X0=10 mm is applied, the offset amount X1 is 0.5 mm, and when the forced displacement X0=20 mm is applied, the offset amount X1 is 2 mm, and a predetermined centering effect is obtained. On the other hand, in the present exemplary embodiment in which the magnetic tape 11 slides on the training surface 40 of the centering roller 38, when the forced displacement X0=10 mm is applied, the offset amount X1 is 0 mm, and when the forced displacement X0=20 mm is applied, the offset amount X1 is 1.5 mm, and it is confirmed that a centering effect is obtained when either of a small displacement or a large displacement is imparted. Further, it is confirmed that the centering roller 38 has a good centering function as compared with the crown roller relating to the first comparative example, when either of a small displacement or a large displacement is imparted.
Here, the mechanism of the centering operation by the centering roller 38 will be described further. It is known that the above-described crown roller exhibits a centering effect on the magnetic tape 11. This utilizes the property that, when the magnetic tape 11 is rotated integrally while gripping the surface of the crown roller by friction, the magnetic tape 11 attempts to approach the tape transverse direction central portion where the peripheral speed is the fastest. In contrast, it is assumed that, when the magnetic tape 11 slips at the training surface 40, the property that the magnetic tape 11 tends toward the portion where the peripheral speed is fast is not exhibited, and the magnetic tape 11 attempts to travel along the shortest path due to tension, and therefore, the position of the magnetic tape 11 is regulated at the tape transverse direction central portion that is the minimum diameter portion at the training surface 40.
Here, in the magnetic tape manufacturing device 10, because the magnetic tapes 11 slip at the respective training surfaces 40, differences in lengths of the magnetic tapes 11 that are conveyed in parallel are not problematic. For example, in a structure using crown rollers that the magnetic tapes 11 grip as described above, in order to absorb the difference in the lengths (traveling speeds Vt) of the plural magnetic tapes 11 that are parallel, the plural crown rollers are provided so as to rotate freely with respect to the supporting shaft portion 44 via bearings respectively. Namely, a complex structure in which the plural crown rollers, that are parallel in the axial direction, are provided via bearings so as to be able to rotate independently, is required.
In contrast, in the magnetic tape manufacturing device 10, as described above, the magnetic tapes 11 slip at the respective training surfaces 40. Therefore, the magnetic tapes 11 of different lengths can be made to travel (conveyed) at independent traveling speeds Vt, while the magnetic tape 11 centering function is exhibited by a simple structure in which the respective training surfaces 40 rotate integrally (in the present exemplary embodiment, the single product in which the roller portion 42 and the supporting shaft portion 44 are formed integrally).
Moreover, in the magnetic tape manufacturing device 10, the accuracy of the training surfaces 40 is high (the eccentric amounts are small) because bearings do not exist between the roller portion 42 and the supporting shaft portion 44. Therefore, in the magnetic tape manufacturing device 10, rotation deviation of the centering roller 38, and fluctuations in tension of the magnetic tapes 11 caused by such rotation deviation, are markedly suppressed as compared with the comparative example that uses that aforementioned bearings. Specifically, FIG. 7A illustrates measurement of the relationship (tension fluctuations) between tension and the longitudinal position of the magnetic tape 11 between the centering roller 38 and the path roller 30 at a tension fluctuation measuring section 50 shown in FIG. 3. It can be understood that the tension fluctuations are markedly suppressed as compared with the tension fluctuations of the comparative example that are shown in FIG. 7B. Note that the longitudinal position of the magnetic tape 11 can be read as time, if the traveling speed Vt is constant.
In this way, the magnetic tape manufacturing device 10 employs the simple structure of the magnetic tapes 11 slipping at the respective training surfaces 40. Therefore, the accuracy of the training surfaces 40 with respect to the rotational center is high, and a high deviation accuracy can be realized easily. Due thereto, in the magnetic tape manufacturing device 10, tension fluctuations of the magnetic tape 11, and adverse affects on tape quality due thereto, can be effectively suppressed.
Further, in the magnetic tape manufacturing device 10, if the traveling speed Vt of the magnetic tape 11 is lower than the predetermined speed Vs, the controller 48 drives and rotates the centering roller 38 so that the peripheral speed Vr of the training surface 40 is made to substantially coincide with the predetermined speed Vs. Therefore, from the start to the stoppage of operation of the magnetic tape manufacturing device 10, the state in which the magnetic tapes 11 is slid substantially completely with respect to the training surfaces 40 of the centering rollers 38 is substantially always maintained, and the centering function can be exhibited. This point will be described with reference to FIG. 8 through FIG. 11.
FIG. 8 through FIG. 10 illustrate results of testing by a testing device 80 shown in FIG. 11. The testing device 80 of FIG. 11 rotates the centering roller 38 in a stationary state of the magnetic tape 11, whose one end is fixed and whose intermediate portion is trained on the training surface 40 (ΔR=0.2 mm) of the centering roller 38 and to whose other end a predetermined tension T0 (≈0.98 N) is applied, and measures the tension of the magnetic tape 11 at the side before and at the side after the centering roller 38 by tension detectors 82, 84, and measures the floating amount of the magnetic tape 11 with respect to the training surface 40 by a floating amount detector (distance sensor) 86. Further, the testing device 80 measures a meandering amount of the magnetic tape 11 with respect to the training surface 40 by a meandering amount measuring device 88. FIG. 8 shows the relationship between the peripheral speed Vr of the training surface 40 and the tension of the magnetic tape 11 (a value that is non-dimensionalized by the aforementioned predetermined tension). FIG. 9 shows the relationship between the peripheral speed Vr of the training surface 40 and the floating amount of the magnetic tape 11 with respect to the training surface 40. FIG. 10 shows the relationship between the peripheral speed Vr of the training surface 40 and the standard deviation of the relative displacement in the tape transverse direction of the magnetic tape 11 with respect to the training surface 40 (the deviation with respect to an average meandering amount that is obtained by averaging the meandering amounts at respective peripheral speeds).
From FIG. 8, it can be understood that tension T1 at the side before the centering roller 38 decreases as the peripheral speed Vr increases, and, when the peripheral speed Vr is greater than or equal to 200 m/min (≈Vs), the difference between the tension T1 and tension T2 at the side after the centering roller 38 becomes substantially constant. Namely, it can be understood that, when the peripheral speed Vr is 200 m/min, the effects of the friction between the magnetic tape 11 and the training surface 40 (the dragging torque) on the tension T1 decrease, i.e., the magnetic tape 11 is substantially completely sliding with respect to the training surface 40. Note that the slight difference between the tensions T1, T2 is thought to be the effects of friction due to the magnetic tape 11 contacting the training surface 40 at the transverse direction end portions. Further, from FIG. 9, it can be understood that the floating amount of the magnetic tape 11 with respect to the training surface 40, i.e., the thickness of the accompanying air layer, increases as the peripheral speed Vr increases, and, in particular, when the peripheral speed Vr is greater than or equal to 200 m/min (≈Vs), the floating amount exceeds 10 μm. It is assumed that, in this state, the magnetic tape 11 slides completely (without contact) with respect to the training surface 40 at least at the transverse direction central portion. Further, it can be understood from FIG. 10 that, when the peripheral speed Vr is greater than or equal to 200 m/min (≈Vs), the meandering amount of the magnetic tape 11 with respect to the training surface 40 is kept small.
In this way, by setting, as the predetermined speed Vs, the peripheral speed Vr at which the tension T1 at the side before the centering roller 38 converges to a predetermined value (the peripheral speed Vr that does not cause effects on the dragging torque due to the training surface 40) as shown in FIG. 8, the magnetic tape 11 can be set in a state of being made to slide substantially completely with respect to the training surface 40 regardless of the traveling speed Vt of the magnetic tape 11 as described above, and, even during the time from the activation of the magnetic tape manufacturing device 10 until a steady operating state is reached, the function of centering the magnetic tapes 11 well can be exhibited. In other words, by obtaining data as in FIG. 8, the appropriate predetermined speed Vs can be set in accordance with the dimensions, shapes, surface roughnesses, materials, and the like of the training surfaces 40 and the magnetic tapes 11. Further, it can be understood that this is substantiated by the data of FIG. 9 and FIG. 10.
Note that the accompanying air, that is pulled-in between the magnetic tape 11 and the training surface 40, increases proportionally to the peripheral speed Vr of the training surface 40, and increases proportionally to the traveling speed Vt of the magnetic tape 11. Therefore, on the whole, the accompanying air increases proportionally to the sum of the peripheral speed Vr and the traveling speed Vt of the magnetic tape 11. Thus, after the traveling speed Vt of the magnetic tape 11 reaches a uniform speed (in the present exemplary embodiment, the aforementioned predetermined speed Vs), if the peripheral speed Vr is made to be the same as the traveling speed Vt of the magnetic tape 11, even if a speed difference is not set therebetween, sufficient accompanying air is pulled-in between the magnetic tape 11 and the training surface 40, and the magnetic tape 11 can be maintained in a state of being made to slide substantially completely (without contact) with respect to the training surface 40.
To summarize the above, in the position regulating method of the magnetic tape 11 that uses the centering roller 38, and in the magnetic tape manufacturing device 10 to which this method is applied, a good centering effect of the magnetic tape 11 can be obtained even as compared with a crown roller. Further, in the position regulating method of the magnetic tape 11 that uses the centering roller 38, and in a tape conveying device to which this method is applied, with a simple structure in which bearings are not provided respectively between the supporting shaft portion 44 and the respective training surfaces 40, the lengths of the respective magnetic tapes 11 can be absorbed, and the method and device can be applied appropriately to the magnetic tape manufacturing device 10 that causes the plural magnetic tapes 11 having different lengths to travel in parallel. Moreover, in the position regulating method of the magnetic tape 11 that uses the centering roller 38 and in a tape conveying device to which this method is applied and in the magnetic tape manufacturing device 10 to which these are applied, high accuracy is obtained easily and rotational deviation is effectively suppressed by making the centering roller 38 be a simple structure as described above.
Note that the above-described exemplary embodiment illustrates an example in which the radial difference ΔR, that corresponds to the depth (concave amount) of the training surface 40 that is a concave surface, is 0.2 mm. However, the present invention is not limited to the same. It is confirmed that, in respective structures (modified examples) in which at least ΔR is 0.2 mm, 0.5 mm, 1.0 mm, 2.0 mm, centering effects that are equivalent to or better than those of the above-described exemplary embodiment are obtained as shown in FIG. 5. The radius of curvature r, the radial difference ΔRr, the peripheral length difference ΔLr, and the peripheral length change rate ΔLrn of the arc of the training surface 40 in the respective modified examples are shown in Table 1.

TABLE 1

ΔR	r	ΔRr	ΔLr
[mm]	[mm]	[mm]	[mm]	ΔLrn

exemplary embodiment	0.2	400	0.050	0.078	0.006
first modified example	0.5	160	0.125	0.196	0.016
second modified example	1.0	81	0.247	0.388	0.031
third modified example	2.0	44	0.457	0.718	0.057

The centering effects in the respective modified examples are equivalent to or better than those of the above-described exemplary embodiment, as shown in FIG. 5. Accordingly, it is confirmed that the centering effect of the training surface 40 of the centering roller 38 in the present invention is obtained when the peripheral length difference ΔLr of the portion on which the magnetic tape 11 of the predetermined width Wt is trained is greater than or equal to 0.078 mm, and more generally, when the peripheral change rate ΔLrn in the tape transverse direction of the magnetic tape 11 is greater than or equal to 0.006. Note that it is confirmed that, if the radial difference ΔR, i.e., the peripheral length difference ΔLr, the peripheral length change rate ΔLrn, is great, it becomes easy for wrinkles to form in the magnetic tape 11 that travels. Even when ΔR is greater than or equal to 0.5 as shown in FIG. 5, differences do not arise in the centering effect (the centering effects of the first through third modified examples are equivalent). Taking these results into consideration, it is desirable that ΔR≦1.0. In other words, 0.2≦ΔR≦1.0 is desirable, and 0.2≦ΔR≦0.5 is even more desirable.
Further, the above exemplary embodiment describes an example in which the position regulating method of the magnetic tape 11 that uses the centering roller 38 and the tape conveying device to which this method is applied are applied to the magnetic tape manufacturing device 10. However, the present invention is not limited to the same, and can be applied to various types of web conveying devices. Accordingly, for example, the present invention may be applied to a take-up device that takes-up a single magnetic tape 11 onto a product reel such as a tape cassette or the like. Or, for example, the present invention may be applied to a conveying device of a web other than a magnetic tape.
The above exemplary embodiment describes an example in which control is effected such that, when the traveling speed Vt of the magnetic tape 11 is less than the predetermined speed Vs, the peripheral speed Vr coincides with the predetermined speed Vs, and, when the traveling speed Vt of the magnetic tape 11 is greater than or equal to the predetermined speed Vs, the peripheral speed Vr coincides with the traveling speed Vt of the magnetic tape 11. However, the present invention is not limited to the same. For example, when the present invention is applied to a device in which the traveling speed Vt of the magnetic tape 11 is always lower than the predetermined speed Vs, it suffices that the centering roller 38 be rotated at a uniform speed at which the peripheral speed Vr substantially coincides with the predetermined speed Vs.
Moreover, although the above exemplary embodiment describes an example in which the surface roughness Ry of the training surface 40 is less than or equal to 0.1 μm, the present invention is not limited to the same. For example, the peripheral speed Vr and the surface roughness Ry of the training surface 40 may be appropriately set in accordance with the web that travels. Further, the present invention is not limited to a structure in which the training surface 40 is smoothed (is made to be low friction) by DLC coating, and the training surface 40 can be smoothed by any of various types of surface treatments or mechanical workings.
As described above, in the above exemplary embodiment, the web is made to travel while sliding is caused between the web and the roller peripheral surface. Therefore, the web is led to the central portion in the axial direction of the roller (the transverse direction of the web), and its transverse direction position is regulated. The mechanism thereof is thought to be that the web, that is not guided by friction by sliding to a large-diameter portion at which the peripheral speed is great, is led by tension to the central portion in the axial direction of the roller that is the shortest path.
Accordingly, positional regulation in the transverse direction of a web that travels can be carried out without relying on a roller whose peripheral surface is crown-shaped.
By forcibly rotating the roller, the web that is traveling is stably slid with respect to the peripheral surface of the roller, and regulation of the transverse direction position of the web that travels can be carried out even better. Namely, at least when the traveling speed of the web is less than a predetermined speed, by making the roller peripheral speed be faster than the traveling speed of the web, the peripheral surface of the roller and the web can be slid reliably (stably as compared with cases in which the roller peripheral speed is slower than the web traveling speed and cases in which the roller peripheral speed is the same speed as the web traveling speed that is less than the predetermined speed). Therefore, regulation of the transverse direction position of the web that travels can be carried out even better. The control of the present web conveying device is effective particularly when the traveling speed of the web is low (including transient states such as during acceleration or the like). Note that the aforementioned predetermined speed can be set as the speed of (a vicinity of) the lower limit at which sliding arises between the web and the roller, even if the web traveling speed and the roller peripheral speed are the same.

Claims

1. A web traveling position regulating method comprising training a web around a peripheral surface at a roller, which peripheral surface forms a concave shape at which an axial direction center has a smaller diameter than axial direction end portions, and causing the web to travel while sliding the web with respect to the roller, thereby regulating a traveling position in a transverse direction of the web.

2. The web traveling position regulating method of claim 1, wherein the web is made to travel while being slid with respect to the roller, by driving and rotating the roller such that a peripheral speed of the peripheral surface of the roller is faster than a traveling speed of the web.

3. A web manufacturing method comprising:

training a web around a peripheral surface at a roller, which peripheral surface forms a concave shape at which an axial direction center has a smaller diameter than axial direction end portions,

causing the web to travel while sliding the web with respect to the roller, and regulating a traveling position in a transverse direction of the web; and

taking-up the regulated web coaxially.

4. The web manufacturing method of claim 3, further comprising:

drawing-out a web original sheet; and

dividing the web original sheet in the transverse direction and cutting the web original sheet into a plurality of webs.

5. The web manufacturing method of claim 3, wherein the web is made to travel while being slid with respect to the roller, by driving and rotating the roller such that a peripheral speed of the peripheral surface of the roller is faster than a traveling speed of the web.

6. A web conveying device comprising:

a web traveling section that causes a web to travel in a longitudinal direction;

a roller provided at a traveling path of the web by the web traveling section, and having a concave peripheral surface at which an axial direction center has a smaller diameter than axial direction end portions, the web being trained around the peripheral surface; and

roller driving means driving and rotating the roller at a speed at which sliding of the web with respect to the roller arises.

7. The web conveying device of claim 6, wherein the roller driving means is structured so as to drive and rotate the roller such that, at least when a traveling speed of the web is less than a predetermined speed, a peripheral speed of the peripheral surface of the roller is faster than the traveling speed of the web.

8. A web cutting device comprising:

a draw-out section for drawing-out a web original sheet;

a cutting section that divides the web original sheet in a transverse direction and cuts the web original sheet into a plurality of webs;

a take-up section for coaxially taking-up at least two or more webs among the webs that are formed by cutting at the cutting section; and

the web conveying device of claim 6 that is applied such that, due to the web traveling section, the web original sheet is drawn-out from the draw-out section and the webs are taken-up at the take-up section,

wherein the roller that structures the web conveying device is structured such that a plurality of the concave peripheral surfaces, at which the at least two or more webs that are to be taken-up at the take-up section are trained independently, are disposed in parallel in an axial direction.