JP3555529B2 - Rotary drum device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rotary drum device of a rotary magnetic recording / reproducing apparatus for recording / reproducing a signal helically on / from a magnetic tape with a magnetic head provided on a rotating drum.
[0002]
[Prior art]
In recent years, rotary drum devices have to record a large amount of information, such as high-bandwidth digital signals and high-definition television signals, on tapes housed in small cassettes at high density. It is getting thinner. Therefore, in a rotary drum device that records and reproduces a tape by helically winding a tape around a drum, the contact force between the head and the tape at the head entry side or the exit side corresponding to the end of the tape is significantly reduced, and the output of the recording / reproduction signal is reduced. The decline had occurred. Conventionally, as a means for solving this problem, there has been known a drum in which a concave portion is provided in a fixed drum in a tape entrance side and a tape exit side area.
[0003]
2. Description of the Related Art A conventional rotary drum device is disclosed in JP-A-8-306101.
[0004]
Hereinafter, a conventional rotary drum device will be described.
[0005]
FIGS. 10A and 10B are a plan view and a perspective view of the conventional rotary drum device. In the figure, a magnetic tape 1 is spirally wound around a tape running surface 9 of a fixed drum 3 having a spiral guide 2 and a rotating drum 4 and runs in the direction of arrow a. The rotary drum 4 rotating in the direction of arrow B incorporates magnetic heads 5 and 6 projecting from the rotary drum 4 by a predetermined amount, and records or reproduces signals on the magnetic tape 1. The guide posts 7 and 8 regulate the magnetic tape 1 to run stably along the guide 2 spirally provided on the outer periphery of the fixed drum 3. Further, on the head exit side of the fixed drum 3, a concave notch 10 is provided at the end of the tape running surface 9 on the side of the rotating drum 4, and this notch 10 is formed on the outer periphery of the tape running surface 9 as shown in FIG. There are edges 11 and 12 that are chamfered at the intersections with.
[0006]
The operation of the conventional rotary drum device configured as described above will be described below.
[0007]
First, when the rotating drum 4 is rotated in the direction of arrow B in the figure and the magnetic tape 1 is run in the direction of arrow A to supply recording signals to the magnetic heads 5 and 6 alternately, the magnetic tape 1 is inclined as shown in FIG. A recording signal track 13 is formed. Next, after the magnetic tape 1 is rewound, the magnetic tapes 5 and 6 reproduce the recorded signal tracks 13 by running under the same conditions as during recording. However, when the magnetic heads 5 and 6 perform recording and reproduction at the widthwise end of the magnetic tape 1, the spacing between the gap 14 (shown in FIG. 15) of the magnetic heads 5 and 6 and the magnetic tape 1 increases, and the recording and reproduction is performed. There is a problem that performance is deteriorated. This problem is remarkable when the concave notch 10 is not provided in the fixed drum 3.
[0008]
Hereinafter, a further description of this problem and the operation of the concave notch 10 as a solution will be described.
[0009]
The contact state between the magnetic heads 5 and 6 and the magnetic tape 1 near the center of the winding around the fixed drum 3 is such that the magnetic heads 5 and 6 come into contact with the front surfaces of the magnetic heads 5 and 6 in a well-balanced manner as shown by the two-dot chain line in FIG. Good contact. When this moves to the tape winding end (tape width direction end), the width direction pressure on the tape end side decreases, and the contact force on the upper side of the magnetic heads 5 and 6 relatively decreases sharply. When this state is confirmed on the tape winding-out side (upper end in the tape width direction), the state shown by the solid line in FIG. 16 is obtained. The spacing on the upper side of the gap area increases, and the performance for recording and reproduction deteriorates. As shown by the solid line in the waveform, the reproduction output on the head output side decreases. When a notch 10 is provided on the tape running surface 9 of the fixed drum 3 as shown in FIG. 11 to solve this problem, the magnetic tape 1 falls into the notch 10 as shown in FIG. The relative protrusion amount increases from H1 when there is no notch to H2. Therefore, the pressure of the magnetic tape 1 in contact with the magnetic head 5 relatively increases, and stable contact with little spacing can be secured over the entire gap region of the magnetic head 5 as shown in FIG. As shown by the two-dot chain line, a stable output can be obtained until the magnetic head 5 separates from the tape. Since this problem also occurs on the tape winding entry side (the lower end in the tape width direction), it is effective to provide the tape winding entry. However, in order to stabilize the tape running of the rotary drum device, it is general to make the magnetic tape tension on the guide side of the fixed drum relatively higher than on the opposite side. The side) is more problematic and more effective.
[0010]
Here, the reason why the core width is widened with respect to the gap region as shown in FIG. 15 is to secure a practical life with respect to head wear, for example, if the core width is close to the gap width. Although the spacing in the gap region is reduced, its life is shortened and is not practical.
[0011]
[Problems to be solved by the invention]
However, in the above-described conventional configuration, there is a problem in the edge processing of the notch 10, and the content will be specifically described below.
[0012]
The edges 11 and 12 of the notch 10 shown in FIG. 11 can be easily chamfered simultaneously with the machining of the notch 10. However, the edge 15 cannot be processed at the same time, and complicated post-processing is required in another step. Further, it is extremely difficult to chamfer a corner portion where the edge 15 intersects the edges 11 and 12, and further complicated post-processing is required. This is not a fundamental solution even if the edges 11 and 12 are inclined and the corners are made obtuse. Further, when the corner is formed in an R shape, extremely complicated processing is required together with the processing of the notch 10 itself. Furthermore, if the inclination of the edge 15 is configured to be parallel to the guide 2 that guides the magnetic tape 1, the edge processing for the magnetic tape 1 running in the normal mode matches the tape moving direction. Insufficient damage is reduced. However, when the tension of the magnetic tape 1 is strong, it is extremely dangerous. Further, when the tape is mounted on the guide posts 7 and 8 or when the tape is released, the tape often travels differently from the normal mode, and damage is easily caused. Further, the chamfering of the edges 11 and 12 and the processing of the notch 10 need to be performed before the processing of the tape running surface 9 in order to avoid generation of processing burrs on the tape running surface 9 side. Even if a proper R surface can be ensured, a sharp edge is generated in the subsequent processing of the tape running surface 9 including the guide 2, thereby causing tape damage. The shaving amount of the post-processing corresponds to the width of the guide 2, and when the magnetic tape 1 rises from the tape running surface 9, a sufficient amount that does not pass over the guide 2 is required. As described above, in order to achieve complete edge processing, complicated post-processing such as machining and buff grinding is required, and an increase in cost is inevitable.
[0013]
If the edge treatment is not performed, tape damage occurs, and magnetic powder and foreign matter accumulate in the notch 10 including the edge, causing dropout and head clogging.
Further, when the tape becomes thinner and the rigidity of the tape itself is reduced, the above-mentioned damage becomes more serious, and more precision is required for edge processing, which further increases the cost.
[0014]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. An inexpensive rotary drum device that forms a depression formed of an inclined surface where tape damage is unlikely to occur by simple machining and obtains a stable head output. Provision is the primary purpose.
[0015]
Furthermore, the present invention forms a depression formed of an inclined surface where tape damage is unlikely to occur by simple machining, suppresses tape vibration with an adjacent protrusion, and obtains a high-precision and stable head output with low noise. A second object is to provide an inexpensive rotary drum device that can be used.
[0016]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention is directed to a rotating drum side end of a tape running surface provided on a fixed drum is formed on an inclined surface which is inclined low toward the rotating drum, and the tape running surface and the inclined surface intersect with each other. In some cases, the entire length of the ridge is formed at an obtuse angle. This can reduce the intensive pressure that the ridge receives from the tape. Furthermore, the contact pressure between the head and the tape on the head exit side can be increased.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
(Embodiment 1)
FIG. 1 is a perspective view of a rotary drum device according to a first embodiment of the present invention. For example, a consumer digital VCR (SD specification) standard agreed by the HD Digital VCR Council, or a product developed based on the standard. A description will be given of a rotating drum device as an example.
[0023]
In FIG. 1, a magnetic tape 16 is wound around a fixed drum 18 having a spiral guide 17 and runs in the direction of arrow C. The rotary drum 19 that rotates in the direction of the arrow D incorporates a magnetic head 20 (two at 180 ° opposite positions) protruding from the rotary drum 19 by about 0.02 mm, and records signals on the magnetic tape 16. Or to play. In addition, on the head exit side of the fixed drum 18, a first recessed portion 22 (enlarged in FIG. 2), which is formed by a flat surface in a direction lowering toward the rotating drum 19, is provided at an end of the tape running surface 21 on the rotating drum 19 side. A projection 23 projecting from the tape running surface 21 by about 0.03 mm is provided behind the winding of the first depression 22. The projections 23 are provided in such a form that they are left uncut when the guide 17 and the tape running surface 21 are processed.
[0024]
The operation of the first embodiment of the present invention configured as described above will be described below.
[0025]
First, when the rotating drum 19 is rotated in the direction indicated by the arrow D in FIG. 1 and the magnetic tape 16 is moved in the direction indicated by the arrow C to supply a recording signal to the magnetic head 20, recording is performed on the magnetic tape 16 as in the conventional example shown in FIG. A signal track is formed. Next, after the magnetic tape 16 is rewound, the magnetic tape 20 is run under the same conditions as during recording, and the magnetic head 20 reproduces the recording signal track.
[0026]
Next, the operation when the magnetic head 20 scans the first depression 22 region will be described in detail. FIG. 3 is a cross-sectional view of a position where the magnetic head 20 passes through the first depression 22. The magnetic tape 16 runs down into the inclined first depression 22 as shown in FIG. At this time, the relative protrusion amount H3 from the drop position of the magnetic tape 16 to the tip of the magnetic head 20 becomes the protrusion amount of the first recessed portion 22, which is larger than the protrusion amount H4 when the first recessed portion 22 is not provided. Therefore, the pressure of the magnetic tape 16 contacting the magnetic head 20 is relatively increased, so that stable contact with little spacing can be secured over the entire gap region of the magnetic head 20 as shown in FIG. A stable output similar to the output waveform indicated by the two-dot chain line can be obtained.
[0027]
Next, tape damage due to contact between the depression 22 and the magnetic tape 16 will be described.
[0028]
As shown in FIG. 3, the magnetic tape 16 runs down into the recessed portion 22 due to the tape tension, and the ridge 25 shown in FIG. 2 contacts the magnetic tape 16 most strongly. It is necessary to configure a near obtuse angle. Here, the angle of the ridge 25 with the tape running surface 21 will be described with points A, B, and C. First, at points A and B, the angle θ shown in FIG. 5A is the ridge angle, and in this configuration, the drum diameter is set to 21.7 mm, and the amount of depression S from the tape running surface is set to about 0.1 mm. The ridge angle θ is about 172 degrees. The point C is the angle α shown in FIG. 5 (b). In this configuration, the surface shape angle δ of the tape running surface 21 and the inclination angle ε of the first depression 22 are substantially matched as shown in FIG. It is set to about 5 degrees (α = about 175 degrees). Therefore, the ridge 25 is formed at an obtuse angle of 172 degrees to 175 degrees over the entire area. Further, the processing procedure is such that the tape running surface 21 is processed after processing the depression 22 and the finishing is set to a small shaving amount of about 0.01 mm. This level is practically no problem since it does not occur at all on the 21 side. Even if a rotary drum provided with a recessed portion of this specification was prototyped and a tape of 0.006 mm thickness was repeatedly run over 1000 passes, tape damage, adhesion of magnetic powder falling to the recessed portion 22, increased dropout, and clogged head were not observed. It has been confirmed that it does not occur at all and there is no practical problem. The reason why the surface of the tape running surface 21 is made uneven is to prevent the tape from adhering in a humid environment or the like, and it has been confirmed by experiments that no tape damage occurs on this surface.
[0029]
The first depression 22 is formed of a flat surface. However, when it is desired to widen the range for improving the contact between the head and the tape, the cut of the flat surface must be deepened, and the ridge angle θ shown in FIG. And tape damage is likely to occur. At this time, if the depressed surface is formed by the curved surface 26 as shown in FIG. 6 and the ridge angle β intersecting with the tape running surface 21 is set equal to θ in FIG.
[0030]
Next, the protrusions 23 provided on the fixed drum 18 will be described. FIG. 4 is an enlarged plan view of the head exit side of the fixed drum 18, and the magnetic tape 16 having separated from the fixed drum 18 travels to the guide post 24. First, when there is no projection 23, when the magnetic head 20 projecting about 0.02 mm from the tape running surface 21 passes through the tape winding area, the magnetic tape 16 is lifted by the same amount, and the magnetic head 20 is rotated from the magnetic tape 16 in the rotation direction. Immediately after being separated, it returns to the position shown by the two-dot chain line in FIG. 4 at a stretch. After that, the vibration remains on the magnetic tape 16 and naturally attenuates and disappears. The tape longitudinal component of the tape vibration generated by this series of phenomena induces a time-axis error of the recording signal, and the component perpendicular to the tape longitudinal deteriorates the contact between the head and the tape and generates noise. The protrusion 23 solves this problem, and its operation will be described in detail below.
[0031]
The magnetic tape 16 at a position different from the protrusion 23 in the height direction is a path indicated by a two-dot chain line in FIG. 4, and the magnetic tape 16 at the position of the protrusion 23 is a path lifted by about 0.03 mm by the protrusion 23 as shown by a solid line. In this state, when the magnetic head 20, which is disposed slightly above the tape upper end than the protrusion 23, protrudes from the tape running surface 21 by about 0.02 mm, the magnetic tape 16 is raised by the amount of protrusion, and the magnetic head 20 However, since the protrusion 23 adjacent to the magnetic head 20 keeps the magnetic tape 16 raised by 0.03 mm at all times, the tape change amount after the magnetic tape 16 is separated from the magnetic head 20. And the change stabilizes in a short time. As a result, the tape vibration level can be reduced and the duration can be shortened, and the occurrence of a time axis error in the recording / reproducing signal, the deterioration of the contact between the head and the tape, and the generation of noise can be reduced. Further, in the embodiment of the present invention, the first depression 22 is arranged on the head exit side, but the same effect can be obtained by providing a similar depression on the head entrance side. However, in order to stabilize the tape running of the rotary drum device, it is general that the magnetic tape tension on the guide 17 side of the fixed drum 18 is relatively higher than the opposite side, and the head exit side where the tape tension is weaker. The problem is more pronounced on the (winding-out side) and the effect is greater. Therefore, it is practical to provide only the head outlet side.
[0032]
Further, in the present embodiment, both the first depressed portion 22 for securing a good head output and the projection 23 for suppressing the tape vibration are provided, but when the occurrence of the tape vibration is small, or the tape vibration itself is reduced. If there is no problem, only the first depression 22 may be used.
[0033]
As described above, in the present embodiment, the first recessed portion formed of a flat surface or a curved surface having a slope in a direction of decreasing toward the rotating drum is provided at the end of the tape running surface of the fixed drum 18 on the rotating drum 19 side. By forming the tape in the end area of the tape winding, the contact between the head and the tape in the end area of the tape winding where the contact between the head and the tape deteriorates can be increased, and a stable head output equivalent to that in the center part of the tape winding can be secured. it can. In addition, the ridge 25 where the tape running surface 21 intersects with the inclined surface of the first depression 22 is formed at an obtuse angle of 175 degrees or more over the entire length, so that the concentrated pressure exerted on the ridge 25 by the tape tension is significantly reduced. It can prevent tape damage, dropout and clogging with the simplest machining. Further, by providing the projections 23 on the tape winding end side of the first depressions 22, the vibration of the magnetic tape 16 can be suppressed, the time axis error of the recording / reproducing signal occurs, and the contact between the head and the tape occurs. Deterioration and noise can be reduced.
[0034]
However, there are the following problems.
[0035]
The contact between the magnetic head 20 and the magnetic tape 16 deteriorates toward the end of the tape, and it is preferable that the first recessed portion 22 is provided almost to the end where the tape is wound. However, since the protrusion 23 for suppressing the tape vibration is provided at the tape winding end portion, when both are too close, when the first depression 22 is processed as shown in FIG. And the tape vibration suppressing effect is reduced. In order to solve the problem, the first depression 22 must be wound and shifted inward, so that there is a problem that the contact improvement area is narrowed.
[0036]
Therefore, the second embodiment is configured so that the depression can be provided close to the projection.
[0037]
(Embodiment 2)
FIG. 8 is a perspective view of a rotary drum device according to Embodiment 2 of the present invention. In FIG. 8, a magnetic head 28 (one more at a 180 ° facing position) is attached to the rotating drum 27. Further, the tape running surface 29 is provided on the head exit side (winding-out side) with a first inclined surface 30 which is lower toward the rotary drum 27 and a second inclined surface 31 which is higher than the first inclined surface 30. A second depression 32 is provided. The first inclined surface 30 has the same size as the inclined plane (shown in FIG. 2) forming the first depression 22 described in the first embodiment. A projection 33 projecting from the tape running surface 29 by about 0.03 mm is provided behind the winding of the second depression 32. As in the first embodiment, the projections 33 are provided in such a form that they are left uncut when the tape running surface 29 is processed.
[0038]
The operation of the second embodiment of the present invention configured as described above will be described below.
[0039]
First, when the rotating drum 27 is rotated and the magnetic tape (not shown) is run, and a recording signal is supplied to the magnetic head 28, an inclined recording signal track is formed on the magnetic tape (not shown). Next, after the magnetic tape (not shown) has been rewound and run under the same conditions as during recording, the magnetic head 28 reproduces the recording signal track.
[0040]
Next, the operation when the magnetic head 28 scans the area of the second depression 32 will be described in detail. Since the first inclined surface 30 has the same dimensions as the inclined surface 22 shown in FIG. 3, the magnetic tape wound around the tape running surface 29 runs down on the inclined first inclined surface 30 as in FIG. The protrusion relationship between the magnetic tape and the magnetic head 28 at this time is the same as that in FIG. Therefore, the pressure of the magnetic tape in contact with the magnetic head 28 is relatively increased, and stable contact with little spacing can be ensured over the entire gap region of the magnetic head 28 as in FIG. A stable output similar to the output waveform indicated by the two-dot chain line of No. 13 can be obtained.
[0041]
Further, since the first inclined surface 30 has the same dimensions as the inclined surface 22 shown in FIG. 3, the angle of the ridge 34 where the second recessed portion 32 and the tape running surface 29 intersect is the same as in the first embodiment 172. Degrees to 1755 degrees, and tape damage due to contact with the magnetic tape does not occur. Therefore, there is no occurrence of the attachment of the magnetic powder falling off to the depressed portion, an increase in dropout, and clogging of the head. Although the second depression 32 is formed as a flat surface, it may be formed as a curved surface, as in the first embodiment, when it is desired to widen the range for improving the contact between the head and the tape.
[0042]
Next, the protrusion 33 will be described. As shown by a two-dot chain line in FIG. 3, the second inclined surface 31 is provided in a region where the magnetic tape does not contact when the magnetic head 28 passes, so that the effect of improving the contact between the magnetic head 28 and the magnetic tape is not hindered. It is provided in. In addition, by inclining the rotating drum 27 at a high angle, the amount of cutting of the upper end portion of the tape running surface during machining of the second depression 31 is reduced, and the tip region (the region E in FIG. 7) of the projection 33 is maximized. It is configured to remain. Thereby, a stable contact with little spacing can be secured to the entire end of the tape winding without impairing the vibration suppressing action of the magnetic tape, and a stable output similar to the output waveform shown by the two-dot chain line in FIG. 13 can be obtained. Can be.
[0043]
Further, in the present embodiment, the second inclined surface 31 is constituted by an inclined surface which tends to be higher toward the rotary drum 27, but the amount of inclination may be determined in relation to the tape vibration suppression amount. It may be a plane parallel to 29 or a plane with a gentle inclination in the same direction as the first inclined plane 30.
[0044]
Further, as shown in FIG. 9, the processing of the second recess 32 is performed by shaping the outer peripheral surface of the end mill into an angle equal to each inclined surface constituting the recess and setting a processing range to perform the processing. Inexpensive and highly accurate machining.
[0045]
Further, in the present embodiment, the second depression 32 is arranged on the head exit side, but the same effect can be obtained by providing the same depression on the head entrance side. However, in order to stabilize the tape running of the rotary drum device, it is general to make the magnetic tape tension on the guide side of the fixed drum relatively higher than on the opposite side, and the head exit side (winding) where the tape tension is weaker Outgoing side) is more problematic and more effective. Therefore, it is practical to provide only the head outlet side.
[0046]
As described above, in the present embodiment, the first inclined surface 30 formed of a flat surface or a curved surface having the inclination of the second depressed portion 32 decreasing toward the rotating drum, and the second inclined portion 32 being inclined higher toward the rotating drum 27. And the second inclined surface 31 can be brought close to the projection 33, and the output can be stabilized over a wide area where the head and the tape come into contact without impairing the vibration suppressing action of the magnetic tape. Can be obtained.
[0047]
【The invention's effect】
As described above, according to the present invention, the first depressed portion formed of a flat surface or a curved surface having a slope in a direction falling toward the rotating drum is provided at the end of the rotating drum side tape running surface of the fixed drum, With the configuration formed in the end region of the winding, it is possible to prevent tape damage, dropout, and clogging by extremely inexpensive processing, and to ensure a good head output up to the end of the winding of the tape.
[0048]
Further, according to the present invention, a protrusion protruding from the tape running surface is provided at the end of the tape running surface on the rotating drum side of the fixed drum near the tape winding end, and is lowered from the protrusion to the rotating drum side inside the tape winding. A first depressed surface formed of a flat surface or a curved surface having an inclination in a direction, and a tape or a tape that is formed continuously from the first depressed surface to the rotary drum side and has a gentler inclination than the first depressed surface. A second depression formed by a second depression formed of a flat surface or a second depression formed of a curved surface parallel to the running surface or inclined in a direction of increasing toward the rotating drum; Is provided in close proximity to the projection, so that a good head output can be secured at low cost even to the end of the tape winding, the vibration of the magnetic tape can be reliably suppressed, and the time axis error of the recording / reproducing signal can be reduced. Generation, and deterioration of the contact between the head and the tape, and further can reduce the generation of noise.
[Brief description of the drawings]
1 is a perspective view of a rotary drum device according to a first embodiment of the present invention; FIG. 2 is an enlarged perspective view of a first recessed portion of a rotary drum device according to a first embodiment of the present invention; FIG. 4 is an enlarged cross-sectional view of a first depressed portion of the rotary drum device according to Embodiment 1. FIG. 4 is an enlarged plan view showing a configuration of a projection 23 of the rotary drum device according to Embodiment 1 of the present invention. FIG. 6 is an enlarged plan view and an enlarged cross-sectional view showing a configuration of a ridge 25 of the rotary drum device according to the first embodiment. FIG. 6 is an enlarged plan view showing a ridge configuration according to an improved configuration of the rotary drum device according to the first embodiment of the present invention. FIG. 8 is an enlarged perspective view showing a problem of the rotary drum device according to the first embodiment of the present invention. FIG. 8 is a perspective view of the rotary drum device according to the second embodiment of the present invention. Of the second depression 32 of the rotary drum device according to FIG. 10 is a plan view and a perspective view showing a conventional rotary drum device. FIG. 11 is an enlarged perspective view showing a notch 10 of the conventional rotary drum device. FIG. FIG. 13 is an enlarged sectional view showing the state of the magnetic tape at the position of the notch 10. FIG. 13 is a head output waveform diagram of the conventional rotary drum device. FIG. 14 is a plan view showing the signal track recording state on the magnetic tape of the conventional rotary drum device. 15 is a plan view showing the front surface of the magnetic head 5 of the conventional rotary drum device. FIG. 16 is a plan view showing the state of the magnetic tape 1 in contact with the magnetic head 5 of the conventional rotary drum device. Enlarged sectional view showing the fine shape of the tape running surface of the rotary drum device according to the first embodiment.
16 Magnetic Tape 17 Guide 18 Fixed Drum 19 Rotary Drum 20 Magnetic Head 21 Tape Running Surface 22 First Depression 23 Projection

Claims (1)

A fixed drum for guiding the tape in a spiral,
A rotating drum having a head and rotating coaxially with the fixed drum,
Provided with a projection which projects from the tape running surface to the rotary drum side tape running surface ends of the fixed drum in the tape winding end near the head exit side, close to the inner winding tape to the projection, the direction to decrease the rotating drum side A first depressed surface formed of a flat surface or a curved surface having an inclination, and a tape that is formed continuously from the first depressed surface to the rotating drum side and has a gentler inclination than the first depressed surface, or the tape. running surfaces and parallel, or rotary drum apparatus and a second recessed surface that is a plane or a curved surface having a higher becomes the direction of inclination to the rotary drum side, characterized in that the formation of the formed Ru recess.

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