JP2001198778A - Polishing method for magnetic tape cutting blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and efficiently polish a cutting edge of an upper blade or a lower blade for cutting a magnetic tape original roll into a curved shape. SOLUTION: In a method for polishing a cutting edge of an upper blade or a lower blade of a magnetic tape cutting device for forming a magnetic tape by cutting a magnetic tape original roll by a plurality of circular upper blades axially mounted on an upper blade shaft and a plurality of circular lower blades axially mounted on a lower blade shaft, the cutting edge is polished by pressing a grinding wheel having the hardness not more than the hardness corresponding to 60 by an L scale of the Rockwell hardness against the outer peripheral surface of the upper blade or the lower blade while rotating the upper or lower blade. In a case where the lower blade 4 has a large diameter part 4f and a small diameter part 4g and a cutting edge 4a is formed on the outer peripheral end of the large diameter part, the outer peripheral surface 31a of the grinding wheel is pressed against the outer peripheral surface 4d of the lower blade while the lower blade 4 is rotated through the lower blade shaft 2 in a state where the lower blade 4 is mounted on the lower blade shaft 2, and the cutting edge 4a of the lower blade is polished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a magnetic tape cutting blade used for cutting a wide magnetic tape material to form an elongated magnetic tape.

[0002]

2. Description of the Related Art A magnetic tape for recording video information, audio information or other various information is usually provided with a base layer, a back layer provided on one surface of the base layer, and another surface of the base layer. The magnetic layer is run in the longitudinal direction of the magnetic tape while the magnetic layer of the magnetic tape is in contact with the head of the recording / reading apparatus, and information is recorded or read.

As shown in FIG. 1, which will be described later, a plurality of upper blades 3 and lower blades 4 are usually arranged in an axial direction on an upper blade shaft 1 and a lower blade shaft 2, respectively. An upper blade shaft 1 is mounted on the upper blade shaft 1 by using a cutting device in which the upper blades 3 and the lower blades 4 are mounted so that the blade edges are positioned at predetermined intervals, and the upper blades 3 and the lower blades 4 facing each other are arranged so that portions near the blade edges overlap in the radial direction.
1 while rotating the upper blade 3 and the lower blade 4 via the lower blade shaft 2 with the wide magnetic tape raw material 5 between the two blades 3 and 4 with the magnetic layer facing upward. The magnetic tape raw material 5 is transported in the direction and cut into a plurality of strips.

In a conventional cutting apparatus for forming such a magnetic tape, as shown in FIG. 14, both the upper blade 3 and the lower blade 4 generally have sharp edges 3a, 4a having a substantially right angle. It is formed in a square shape. The conventional magnetic tape cut by the upper blade 3 and the lower blade 4 both having a square edge is usually provided on both sides located at both ends in the width direction of the magnetic tape 6 as shown in FIG. Of the surfaces (cut surfaces cut by the upper and lower blades 3, 4) 7, 8, the side surface of the back layer 11 is more δ than the side surface of the base layer 10 on the side surface 8 on the upper blade side.
Although it is located in the width direction inside by u, the side surface of the back layer 11 is located outside by δd in the width direction on the side surface 7 on the lower blade side rather than the side surface of the base layer 10. 12 is a magnetic layer.

In FIG. 1, when the side surface 3b of the upper blade 3 facing the cutting edge 4a of the lower blade 4 is the antinode, and the other side surface 3c is the back, the side of the magnetic tape facing the antinode 3b is the lower blade side. The side surface of the magnetic tape facing the back surface 3c is referred to as an upper blade side surface. In FIG. 1, the left side surface of the magnetic tape 6 is the lower blade side surface, and the right side surface is the upper blade side surface.

By the way, as with other recording media,
In recent years, magnetic tapes are also required to have higher density recording and higher capacity, and as a result of various studies conducted by the present inventor to meet such demands, the side surface of the back layer 11 is higher than the side surface of the base layer 10 as described above. It has been found that the following inconveniences occur when the projections are located on the outside in the width direction and project.

That is, as high-density recording is required, the track density becomes higher. In order to accurately track the recording tracks, it is necessary to strengthen the regulation of the position of the magnetic tape in the width direction when the magnetic tape runs in a recording / reading apparatus. Therefore, the contact pressure between the side surface of the magnetic tape and the guide that regulates the position of the side surface is increased, and the side surface of the back layer that protrudes outward in the width direction is slid in contact with the guide and is shaved, and the shavings are dropped out. Found a problem that could cause

[0008] In the case of the magnetic layer as well, shavings may be generated if they protrude outward in the width direction from the base layer. However, since the position control in the width direction is performed particularly on the back layer side of the magnetic tape, the guide is mainly provided on the base layer. Sliding contact between the layer and the backing layer, and as a result, particularly the protrusion of the backing layer outward in the width direction significantly causes problems such as generation of the above-mentioned shavings and dropout due to the shavings.

Further, with the recent increase in capacity, it is required to reduce the thickness of the magnetic tape. Therefore, the base layer is made thinner and the strength of the base layer is reduced to avoid a corresponding decrease in strength. PEN, aramid, etc. have been used. However, if the material of the base layer becomes high in strength as described above, the back layer is likely to protrude outward in the width direction in the cutting by the upper blade and the lower blade, and the above disadvantages are caused. Has also been found to be more pronounced.

Therefore, as a result of various studies on a cutting method in which the side surface of the back layer does not protrude outward in the width direction from the side surface of the base layer, as described in detail later, at least one of the upper blade and the lower blade has: It has been found that by cutting using a curved blade instead of a sharp angular blade, the side surface of the back layer can be cut in the widthwise inner side of the side surface of the base layer.

[0011]

In the above-described cutting apparatus, if cutting is performed for a long period of time, the cutting edge wears and the cutting performance deteriorates. In this case, the cutting edge is polished to obtain an appropriate cutting edge shape. There is a need to.

When the edge is polished, the edge can be easily formed by simply grinding the outer peripheral surface of the edge by a predetermined amount. Must be applied along the curved shape,
There is a problem that polishing is troublesome, time and cost are high, and polishing efficiency is poor.

In addition, in the case of the above-described cutting device, particularly for the lower blade 4, extremely high precision is required for the axial distance between the blade edges 4a so that the width of the magnetic tape to be formed becomes uniform. If the lower blade 4 is removed from the lower blade shaft 2 and polished when the blade edge 4a is worn, the lower blade shaft 2
Since the positioning must be performed with high accuracy when assembling, there is a demand that after mounting on the lower blade shaft 2, polishing should be performed with the lower blade shaft 2 mounted as much as possible.

However, if it is attempted to grind it into a curved shape while being mounted on the lower blade shaft 2 as described above, when polishing with a normal grindstone, a blade receiving recess formed on the lower blade 3 as shown in FIG. The grinding wheel 23 is polished by applying a whetstone obliquely to the cutting edge 4a (in the direction of arrow A in FIG. 9 described below), but the cutting edge receiving recess 23 is very small.
It is difficult to grind with a grindstone there. As a result, it is very difficult as a practical problem to grind the cutting edge 4a into a curved shape while the lower blade 4 is mounted on the lower blade shaft 2.

In the case of the upper blade 3, as described later in detail, it is possible to remove the upper blade shaft 1 and perform polishing. However, in this case, it is difficult to grind one by one. There is a demand that a plurality of the blades 3 are mounted on a shaft and polished together while rotating them. However, also in this case, if the upper blade 3 is overlaid, only a small back slope corresponding recess 24 (see FIG. 11 described below) formed by the back slope 3 e is formed between the blades. It is also extremely difficult as a practical matter to polish a grindstone in the small recess 24 corresponding to the back slope.

Further, as will be described later, the preferable curved shape of the cutting edge is a curved shape width in the radial direction.
It is an extremely fine shape of about 3 μm. However, if the lower blade shaft 2 is rotated with the lower blade 4 attached to the lower blade shaft 2, the processing accuracy of the lower blade shaft 2 and the lower blade 4, the assembly accuracy of both, or the bending of the lower blade shaft 2 during rotation, etc. Even with a highly accurate device, the position of the cutting edge during rotation is about 3 μm in the radial direction,
In the axial direction, the vibration is about 1 μm.
In the method of polishing with a grindstone having a hardness generally used in the past, the degree of polishing differs at each position in the circumferential direction according to the run-out because the polishing is performed independently of the run-out of the cutting edge, as described above. It is difficult to uniformly polish and form a fine curved shape at each position in the circumferential direction. In addition, in the case of the upper blade 3 as well, a preferable curved shape of the blade edge is an extremely fine shape with a curved shape width in the radial direction of 0.3 to 3 μm as described later. Similarly, when it is attempted to grind while mounting and rotating, it is also difficult to uniformly grind and form a fine curved shape at each position in the circumferential direction due to runout of the cutting edge.

In view of the above circumstances, an object of the present invention is to provide a method for easily and efficiently polishing the cutting edge of an upper blade or a lower blade for cutting an original magnetic tape into a curved shape.

Another object of the present invention is to provide a method capable of easily and uniformly polishing a cutting edge into a curved shape while a lower blade is mounted on a shaft in view of the above circumstances.

Still another object of the present invention is to provide a method capable of easily and uniformly polishing the cutting edges into a curved shape in a state where the upper cutting edges are overlapped in view of the above circumstances.

[0020]

According to the present invention, there is provided a method for polishing a magnetic tape cutting blade according to the present invention, wherein a plurality of circular upper blades and a plurality of lower blade shafts mounted in an axial direction on an upper blade shaft are provided. A method of polishing a magnetic tape cutting blade for polishing a cutting edge of the upper blade or the lower blade of a magnetic tape cutting device for forming a magnetic tape by cutting a magnetic tape material with a plurality of circular lower blades mounted in different directions. Then, while rotating the upper blade or the lower blade, the outer peripheral surface has a hardness of L scale of Rockwell hardness.
It is characterized in that the edge of the upper blade or the lower blade is polished into a curved shape by pressing a grindstone having a hardness not higher than 60.

In the above polishing method, when the lower blade has a large-diameter portion and a small-diameter portion, and a cutting edge is formed at an outer peripheral end portion of the large-diameter portion, the lower blade is connected to the lower blade shaft. In a state in which the lower blade is mounted, the grindstone can be pressed against the outer periphery of the lower blade while rotating the lower blade via the lower blade shaft, and the cutting edge of the lower blade can be polished into a curved shape.

In the above-mentioned polishing method, when the upper blade has a cutting edge formed at one end of the outer periphery and a bevel at the other end, the upper blade is used as a polishing shaft. In a state in which the upper blade is mounted on the upper blade, the grindstone can be pressed against the outer periphery of the upper blade while rotating the upper blade via the polishing shaft, and the cutting edge of the upper blade can be polished into a curved shape.

The small-diameter portion of the lower blade and the bevel of the upper blade may have any shape as long as they form a concave portion from which a grindstone to be described later projects. The cutting edge of the lower blade may be formed at any one of the outer peripheral end of the large-diameter portion opposite to the small-diameter portion and the outer peripheral end of the small-diameter portion.

[0024]

According to the method for polishing a magnetic tape cutting blade according to the present invention, as described above, the upper surface or the lower blade is rotated while the outer peripheral surface thereof has an L scale hardness of Rockwell hardness.
A soft grindstone having a hardness equal to or less than 60 is pressed (a grindstone having such a hardness is referred to as an elastic grindstone in the present specification as described later) to grind the edge of the upper blade or the lower blade. By this, the grindstone portion hitting the outer peripheral surface of the blade is depressed, and the grindstone can be polished in a curved shape by contacting the blade edge in a mode in which the grindstone covers the blade edge. It is only necessary to press, and the blade edge can be very easily and efficiently polished into a curved shape.

In the case where the lower blade has a large-diameter portion and a small-diameter portion, and the cutting edge is formed at the outer peripheral end of the large-diameter portion, the lower blade is mounted on the lower blade shaft. In this state, if the elastic blade is pressed against the outer periphery of the lower blade and polished while rotating the lower blade through the lower blade shaft, a portion of the elastic stone that hits the outer peripheral surface of the lower blade is depressed and has a small diameter portion. The portion facing the concave portion formed by the protrusion protrudes, and the protruding portion contacts the cutting edge so as to cover the cutting edge, so that the cutting edge is polished into a curved shape, so that the cutting edge is polished into a curved shape even with the lower blade attached. In addition to the fact that the grinding wheel is soft even when the cutting edge swings in the radial or axial direction during rotation, the outer peripheral surface of the grinding stone follows the deflection of the cutting edge and is depressed. Polished uniformly at each position Rukoto can, because polished while still attached, there is no need to re-assemble the lower blade after polishing.

When the upper blade has a cutting edge formed at one end of the outer periphery and a bevel at the other end, the upper blade is mounted on the polishing shaft. In this state, if the grindstone is pressed against the outer periphery of the upper blade while rotating the upper blade through the polishing shaft and polished, the portion of the elastic grindstone that hits the outer peripheral surface of the upper blade is depressed,
The part facing the concave part formed by the bevel slope protrudes, and since this protruding part contacts the cutting edge so as to cover the cutting edge, the cutting edge is polished into a curved shape, so that even when the upper blade is overlapped, the cutting edge is formed into a curved shape. In addition to being able to polish, even if the cutting edge oscillates in the radial or axial direction during rotation, the whetstone is soft, so the outer peripheral surface of the whetstone follows the runout of the cutting edge, and therefore is depressed. Polishing can be performed uniformly at each position in the circumferential direction, and the polishing can be performed efficiently because the polishing is performed in an overlapping manner.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing a magnetic tape cutting device provided with one example of an upper blade and a lower blade for polishing according to the present invention. The cutting device shown in the figure, except for the cutting edge of the upper blade and lower blade,
It has the same configuration as a known magnetic tape cutting device.

The illustrated cutting apparatus includes an upper blade shaft 1 and a lower blade shaft 2 arranged in parallel with each other, and the upper blade shaft 1 has a circular outer periphery through a holder 20 having a circular outer periphery. A plurality of lower blades 4 having a circular outer circumference are directly mounted on the lower blade shaft 2. Each of the upper blades 3 is mounted so that their cutting edges 3a are arranged at regular intervals in the axial direction (the axial direction of the upper blade shaft 1 and the lower blade shaft 2), and the lower blade 4 also has its respective cutting edges 4a in the axial direction. The blades 3a of the upper blades are mounted so as to be arranged at regular intervals, and are adjacent to the blade edges 4a of the corresponding lower blades, and are paired with the upper blade 3 and the lower blade 4, respectively. As shown in FIG. 2 as viewed from the direction of arrow II in FIG. 1, the upper blade 3 and the lower blade 4 forming a pair have the upper blade 3a and the lower blade 4a in the vicinity of the upper blade 3a. And the lower blade 4 is disposed so as to overlap in the radial direction (radial direction centering on the upper blade shaft 1 and the lower blade shaft 2).

Each holder 20 has a blade mounting recess 21 formed by cutting out one outer peripheral corner (right side in the drawing) in the axial direction. The upper blade 3 is mounted in the blade mounting recess 21 and a spring 22 is provided. The spring 22 urges the upper blade 3 in one axial direction (to the right in the drawing). Further, each lower blade 4 cuts off the outer peripheral corner in the other axial direction (left side in the figure) to form a blade receiving recess 23, and receives the blade 3a of the upper blade corresponding to the blade receiving recess 23, As described above, since the upper blade 3 is urged in one axial direction (rightward in the drawing) by the spring 22, the blade edge 3a of the upper blade becomes the blade edge 4a of the lower blade.
And is positioned in contact with. Since the lower blade 4 is formed with the blade receiving recess 23 as described above, the lower blade 4 includes a large diameter portion 4f and a small diameter portion 4g. The large diameter portion 4f and the small diameter portion 4g may be integrated as shown in the figure, or may be separate.

FIG. 1 shows a part of the cutting apparatus.
Actually, both the upper blade 3 and the lower blade 4 are further mounted in the axial direction, and the width of the raw magnetic tape 5 is further extended in the axial direction.

FIG. 3 is an enlarged sectional view showing the cutting edge portions of the upper blade 3 and the lower blade 4. As shown in the drawing, the cutting edges 3a and 4a of the upper blade 3 and the lower blade 4 are formed in a curved shape, unlike the conventional sharp-edged cutting edges.

In this specification, "radial curved shape width" and "axial curved shape width" are used as indices indicating the degree of curvature. Here, the width of the curved shape in the radial direction is, as shown in FIGS. 4A and 4B, the upper blade 3 and the lower blade 4 as well.
In the case of the above, it also means the radial width W of the curved portions of the cutting edges 3a and 4a when viewed from the axial direction in a state where the cutting edges are mounted on the upper blade shaft 1 and the lower blade shaft 2, respectively. Further, the width of the curved shape in the axial direction is, as shown in FIGS. 4 (a) and 4 (b),
In the case of both the upper blade 3 and the lower blade 4, the curved portions of the blade edges 3a and 4a when viewed from the radial direction are mounted in the upper blade shaft 1 and the lower blade shaft 2, respectively. Width L
Means In addition, the curved shape means a smoothly curved shape such as an arc shape.

In the illustrated apparatus, the upper blade shaft 1 and the lower blade shaft 2 are each rotated by a drive source such as a motor (not shown) to rotate the upper blade 3 and the lower blade 4 as shown in FIG. Then, the wide magnetic tape raw material 5 is transferred between the upper blade 3 and the lower blade 4 in a direction perpendicular to the plane of the drawing, whereby the magnetic tape raw material 5 is paired with the upper blade 3 and the lower blade. 4 to form a plurality of elongated magnetic tapes 6 extending in a direction perpendicular to the plane of the drawing (the original magnetic tape portion located between the adjacent upper blades 3 is one magnetic tape 6 each). become).

FIG. 5 is a perspective view showing a magnetic tape 6 formed by cutting the magnetic tape raw material 5 by the above-described apparatus. As shown in the drawing, the magnetic tape 6 is provided on a base layer 10 and one surface side of the base layer 10. It has a back layer 11 provided and a magnetic layer 12 provided on the other surface side of the base layer 10. The base layer 10 is formed of, for example, PET, PEN or aramid, the back layer 11 is formed of, for example, carbon black, and the magnetic layer 12 is formed of a known magnetic material.

When the magnetic tape material 5 is cut by the cutting device, the cut surface becomes the side surfaces 7, 8 extending in the longitudinal direction of the magnetic tape 6, and the cutting edges 3a, 4 as described above.
By making a a curved shape, the side surface 8 on the upper blade side is located on the inner side in the width direction than the side surface of the base layer 10 by δu as in the case of cutting with a conventional square-shaped blade. At the same time, unlike the case of cutting with a conventional square-shaped cutting edge, the side surface 7 on the lower blade side also has a shape in which the side surface of the back layer 11 is positioned more inward in the width direction than the side surface of the base layer 10 by δd,
A magnetic tape 6 having a shape in which the back layer 11 is located on the inner side in the width direction of the base layer 10 on both side surfaces 7 and 8 can be obtained.

FIG. 6 shows the width W of the curved shape in the radial direction of the cutting edge 3a of the upper blade and the amount of protrusion of the back layer 11 on the side surface 7 on the lower blade side of the magnetic tape (the side of the back layer 11 is the side of the base layer 10). FIG. 7 shows the relationship between the width W of the lower blade 4a and the width W of the lower blade 4a.
FIG. 6 is a diagram showing the relationship between the height of the back layer 11 on the side surface 7 on the lower blade side of the magnetic tape, and in both figures, the other blade has a square shape with a right-angled cutting edge, and has a thickness of 7.5 μm. This shows data when a magnetic tape material is cut.

As can be seen from FIGS. 6 and 7, in either case of the upper blade 3 and the lower blade 4, the blade edge is formed in a square shape (the curved shape width W = 0 in the drawings corresponds to this).
When the shape is changed to a curved shape, the convex amount of the back layer 11 decreases.
Accordingly, by forming at least one of the upper blade 3 and the lower blade 4 into a curved shape, the amount of protrusion of the back layer 11 on the side surface 7 on the lower blade side can be reduced as compared with the conventional blade. Accordingly, generation of shavings of the back layer during running of the magnetic tape can be suppressed.

The convex amount of the back layer 11 does not necessarily have to be 0 or minus (the side surface of the back layer 11 is located on the inner side in the width direction than the side surface of the base layer 10). Even if the side surface of the layer 11 is located outside the side surface of the base layer 10 in the width direction), if the amount of shavings generated in the back layer does not cause a practical problem, there is no problem. As a result, it was recognized that the problem due to shavings hardly occurred when the protrusion amount of the back layer 11 was about 0.05 μm. Accordingly, the protrusion amount of the back layer 11 is preferably about 0.05 μm or less, and more preferably 0 μm or less from the viewpoint of suppressing generation of shavings to almost zero.

In order to reduce the convexity of the back layer 11 to such a value or less, in the case of the upper blade, the width W of the curved shape in the radial direction is 0.3 μm (in FIG. (Corresponding to about 0.05 μm) or more, and 0.5 μm (in FIG. 6, the convexity of the back layer is 0 μm
Is more preferable. Also,
In the case of the lower blade, the width W of the radially curved shape is 0.2 μm
(The convex amount of the back layer corresponds to about 0.05 μm in FIG. 7) or more, and more preferably 0.25 μm (the convex amount of the back layer corresponds to 0 μm in FIG. 6). .

On the other hand, the width W of the curved shape in the radial direction is preferably 3 μm or less, preferably 1 μm or less, in order to secure desired cutting performance, since cutting performance (sharpness) decreases as the width W increases. Is more preferable.

Therefore, from the viewpoint of both the convexity of the back layer and the cutting performance, in the case of the upper blade, the width W of the radially curved shape of the blade edge 3a is preferably 0.3 to 3 μm, and 0.5 to 3 μm.
More preferably, it is 1 μm. In the case of the lower blade, the width W of the radially curved shape of the blade edge 4a is 0.2 to 3
μm, more preferably 0.25 to 1 μm.

The data shown in FIGS. 6 and 7 are data obtained when an experiment was performed on a magnetic tape raw material having a thickness of 7.5 μm. Actually, the thickness of the magnetic tape raw material, the strength of the base layer, or the cutting conditions were used. Due to the difference of the back layer
The protrusion amount of 11 slightly fluctuates, but does not change so much, and in most cases, the range of the width W of the radially curved shape regardless of the thickness of the magnetic tape raw material, the strength of the base layer, or the cutting conditions. Within this range, the amount of protrusion of the back layer can be reduced to such an extent that practical problems due to shavings do not occur.

As described above, the amount of protrusion of the back layer varies depending on the width W of the radially curved shape of the cutting edge. At this time, the width L of the axially curved shape of the cutting edge is changed in the radial direction. If the width is smaller than the width W of the shape, it is expected that the effect of reducing the amount of protrusion of the back layer, particularly the effect of reducing the amount of protrusion, may not be obtained even if the blade edge is curved. Therefore, as the curved shape of the cutting edge, the width W of the curved shape in the radial direction is equal to or less than the width L of the curved shape in the axial direction (W ≦
L) is desirable. If W ≦ L, the above-described effect of reducing the convexity of the back layer can be expected in accordance with the width W of the curved shape in the radial direction. The data in FIGS. 6 and 7 are obtained using the upper blade and the lower blade having a curved cutting edge of L = 1.2 to 1.5 W.

Next, the upper blade 3 and the lower blade 4 serving as cutting blades
A method of polishing the cutting edge of the blade into a curved shape will be described.

FIG. 8 is a diagram showing an example of a procedure for polishing the lower blade edge 4a into a curved shape, FIG. 9 is a diagram showing an example of a method for polishing the lower blade edge 4a, and FIG. 10 is an upper blade edge 3a. FIG. 11 is a diagram showing an example of a procedure for polishing the surface, and FIG. 11 is a diagram showing an example of a method for polishing the cutting edge 3a of the upper blade. If the cutting is performed for a long time, the upper blade 3 and the lower blade 4 are worn and the cutting performance deteriorates. In this case, it is necessary to grind the cutting edge to obtain an appropriate curved shape.

First, the polishing of the cutting edge 4a of the lower blade will be described. In the case of the lower blade 4, as described above, if there is a variation in the interval between the cutting edges 4a, a variation occurs in the width of the formed magnetic tape. Since the lower blade 4 is detached from the lower blade shaft 2, it is difficult to reassemble the lower blade shaft 2. Therefore, once the lower blade 4 is attached to the lower blade shaft 2, polishing of the cutting edge is performed. It is desirable to do.

When the polishing is performed, as shown in FIG. 8, since the radially curved shape width W of the cutting edge 4a is increased due to wear, the outer peripheral surface 4d of the lower blade 4 is first positioned at a position indicated by a broken line C. Cylindrical grinding up to. This is, for example, by rotating the lower blade 4 with the lower blade shaft 2 mounted on the lower blade shaft 2 via the lower blade shaft 2 and rotating the outer peripheral surface of the mesh # 200 to # 1000 while rotating the cylindrical grindstone for rough finishing. By pressing against the outer peripheral surface 4d of the rotating lower blade, and moving the cylindrical grindstone for rough finishing in the axial direction of the lower blade shaft 2 in that state to rough finish grinding the outer peripheral surface 4d of all the lower blades. Grind to the dashed line C above or finer mesh # 150 after rough finish grinding
Using a cylindrical grinding wheel for finishing of 0 to # 8000, finish grinding is performed by the same method as in the above-mentioned rough finish grinding, and grinding is performed to a broken line C.

Next, the cutting edge 4a is polished to the position shown by the broken line D in FIG. 8 to form an initially proper curved cutting edge. This cutting edge polishing is performed by the method shown in FIG. In other words, with the lower blade 4 attached to the lower blade shaft 2, the lower blade shaft 2
The lower blade 4 is rotated through the shaft, and the grindstone shaft 30 is parallel to the lower blade shaft 2.
A cylindrical elastic grindstone (elastic grindstone in the present specification means a grindstone having a hardness equivalent to 60 on the L scale of Rockwell hardness or a hardness softer than the hardness) 31 is rotated while its outer periphery is rotated. While pressing the surface 31a against the outer peripheral surface 4d of the rotating lower blade with a predetermined pressing force, the elastic grindstone 31 is moved rightward in the axial direction (direction of arrow E) to perform polishing. When the elastic grindstone 31 is pressed in this way, as shown in FIG. 9, the portion of the outer peripheral surface 31a of the elastic grindstone that contacts the outer peripheral surface 4d of the lower blade is depressed in the radial direction, and the portion facing the edge receiving recess 23 projects in the radial direction. As a result, the protruding portion comes in contact with the blade edge 4a so as to cover the blade edge 4a, so that the blade edge 4a is polished into a curved shape.

When the lower blade 4 is mounted on the lower blade shaft 2 and is to be polished with a hard grindstone conventionally used, each of the blade edges 4a
Each time the grindstone is moved from the direction of arrow A in the blade receiving recess 23 to the blade 4a.
And it is very difficult to perform such polishing because the recess 23 is narrow.
There is a problem in that polishing is time consuming and costly because polishing is performed one by one every time.
If it is polished using, the lower blade 4 can be polished collectively with the lower blade 4 attached to the lower blade shaft 2.

Next, the polishing of the cutting edge 3a of the upper blade will be described. In the case of the upper blade 3, since the upper blade 3 is urged by the spring 22 and pressed against the blade edge 4a of the lower blade to be positioned, the positional accuracy of the upper blade 3 itself to the upper blade shaft 1 is particularly problematic. Therefore, in the case of the upper blade 3, the upper blade 3 is detached from the upper blade shaft 1 and mounted on a separately prepared polishing shaft 32 as shown in FIG.

In the case of polishing, as in the case of the lower blade 4, since the radially curved shape width W of the blade edge 3a is increased due to wear, as shown in FIG. The outer peripheral surface 3d is cylindrically ground to a position indicated by a broken line C.
In this cylindrical grinding, a plurality of upper blades 3 are mounted on the polishing shaft 32 as shown in FIG. 11, and then, as in the case of the lower blade, the upper blade 3 is rotated on its outer peripheral surface 3d while rotating. The cylindrical grindstone is moved in the axial direction of the upper blade shaft 1 while pressing the outer peripheral surface of the cylindrical grindstone for rough finishing of mesh # 200 to # 1000, and the outer peripheral surface 3d of all upper blades is rough-finished. In this manner, or after that, finish grinding is performed using a finishing cylindrical grindstone having meshes # 1500 to # 8000 in the same manner as rough finish grinding, thereby grinding to the broken line C.

Next, the cutting edge 3a is polished with an elastic grindstone to form an appropriately curved cutting edge. This cutting edge polishing is performed in the same manner as the lower blade 4. That is, as shown in FIG. 11, the upper blade 3 is rotated via the polishing shaft 32, and the outer peripheral surface 31a of the cylindrical elastic grindstone 31 attached to the grindstone shaft 30 parallel to the polishing shaft 32 is rotated. Is pressed against the outer peripheral surface 3d of the rotating upper blade with a predetermined pressing force, and the elastic grindstone 31 is moved leftward in the axial direction (the direction of arrow F) to perform polishing. When the elastic grindstone 31 is pressed in this manner, as shown in FIG. 11, the portion of the outer peripheral surface 31a of the elastic grindstone that contacts the outer peripheral surface 3d of the upper blade is depressed in the radial direction, and the back slope corresponding recess 24 formed by the back slope 3e. Is protruded in the radial direction, and as a result, the protruding portion covers the cutting edge 3a in such a manner that the protruding portion covers the cutting edge 3a.
The edge 3a is polished into a curved shape.

The upper blade 3 having the polished cutting edge 3a as described above
Is removed from the polishing shaft 32, and after the back slope 3e is ground to the broken line G in FIG. 10 to return to the original shape,
The upper blade shaft 1 is assembled in a state shown in FIG.

According to the above method, a plurality of upper blades 3 can be polished together in a state of being overlapped.

When the elastic grindstone 31 is pressed against the outer peripheral surface of the blade and polished as described above, the relationship between the width W of the curved shape in the radial direction and the width L of the curved shape in the axial direction is naturally W ≦
It becomes L. Also, when the elastic grindstone 31 is pressed and polished as described above, the elastic grindstone is soft even if the cutting edges of the upper blade and the lower blade swing in the radial and axial directions during rotation of the blade,
The outer peripheral surface 31a of the elastic grindstone is depressed following the run-out of the cutting edge, and therefore, regardless of the run-out of the cutting edge, the above-described 0.2 to 3 μm or
A fine curved shape of 0.3 to 3 μm can be uniformly polished in the circumferential direction.

In the above description, the polishing in the case where the cutting edge is worn to obtain an appropriate curved shape has been described. However, the polishing using the elastic whetstone can be applied to the case where the cutting edge is first formed.

FIGS. 12 and 13 show the relationship between the hardness of the grindstone and the width W of the curved shape in the radial direction when the cutting edge is polished as described above. FIG. 12 shows the Rockwell hardness. FIG. 13 is a diagram showing the relationship between the hardness on the L scale and the width W of the radially curved shape that can be polished by the hardness.
It is a figure which shows the relationship between the hardness on the D scale of Shore hardness, and the width W of the radially curved shape which can be grind | polished by this hardness. In addition, hardness 30 in Shore hardness D scale shown in FIG.
〜100 are softer than hardness 0 on the Rockwell hardness L scale shown in FIG. The Rockwell hardness L scale and Shore hardness D scale are described in detail in, for example, "Measurement Management Technology Soshou (7) Hardness Kentaro Yamamoto and Kozo Iizuka" edited by the Measurement Management Association published by Corona. Have been.

As shown in these figures, if the grindstone is hard (the hardness is large), even if the outer peripheral surface of the grindstone is pressed against the outer peripheral surfaces 3d, 4d of the upper blade and the lower blade, the lower blade is not affected. Blade receiving recess 23 in the case of あ る い は, or recess corresponding to the back slope in the case of the upper blade
The amount of protrusion of the outer peripheral surface of the grindstone into the 24 is small, so it is almost impossible to grind the cutting edge portion into a curved shape.However, when the cutting edge is soft, the protrusion amount to the concave portions 23 and 24 increases and covers the cutting edge portion. In this manner, the contact area is increased, and as a result, the cutting edge can be polished into a curved shape having a larger width W of the curved shape in the radial direction.

The relationship between the hardness of the grindstone and the width W of the curved shape in the radial direction at that time is as shown in FIGS.
As can be seen from these figures, a hardness equivalent to 60 on the L scale of Rockwell hardness or a hardness lower than the hardness (this range includes, of course, 30 to 100 on the D scale of Shore hardness described above). If so, the cutting edge can be polished into a curved shape. As described above, the desirable range of the width W of the curved shape in the radial direction is 0.3 to 3 μm for the upper blade and 0.2 for the lower blade.
In consideration of this point, the hardness corresponding to the width W of the radially curved shape W = 0.2 to 0.3 μm is about 45 on the L scale of Rockwell hardness. The hardness of the grindstone is more preferably a hardness corresponding to 45 on the L scale of Rockwell hardness or a hardness softer than the hardness.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the invention. Further, the cutting method and the cutting device described above,
The present invention can be applied not only to cutting of an original magnetic tape, but also to cutting of various other sheet-like materials, and particularly, it can be suitably used for cutting photographic photosensitive materials.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a magnetic tape cutting device provided with an example of an upper blade and a lower blade to be polished according to the present invention.

FIG. 2 is a view as seen from the direction of arrow II in FIG.

FIG. 3 is an enlarged sectional view showing the cutting edge portions of an upper blade and a lower blade shown in FIG. 1;

FIG. 4 is a diagram illustrating the width of a curved shape.

FIG. 5 is a perspective view showing a magnetic tape formed by cutting with the cutting device shown in FIG. 1;

FIG. 6 is a diagram showing the relationship between the width of the radially curved shape of the blade edge of the upper blade and the amount of protrusion of the back layer.

FIG. 7 is a diagram showing the relationship between the width of the curved shape in the radial direction of the cutting edge of the lower blade and the amount of protrusion of the back layer.

FIG. 8 is a diagram showing an example of a procedure for polishing the lower blade.

FIG. 9 is a diagram showing an example of a method of polishing the lower blade.

FIG. 10 is a diagram showing an example of a procedure for polishing the upper blade.

FIG. 11 is a diagram showing an example of a method of polishing the upper blade.

FIG. 12 is a diagram showing the relationship between the hardness of a grindstone and the width of a curved shape in a radial direction.

FIG. 13 is a diagram showing the relationship between the hardness of a grindstone and the width of a curved shape in a radial direction.

FIG. 14 is an enlarged cross-sectional view showing a cutting edge portion of a conventional upper blade and lower blade.

FIG. 15 is a perspective view showing a magnetic tape formed by cutting with a conventional upper blade and lower blade.

[Explanation of symbols]

 Reference Signs List 1 upper blade shaft 2 lower blade shaft 3 upper blade 3a upper blade edge 3e back slope 4 lower blade 4a lower blade edge 4f large diameter portion 4g small diameter portion 5 raw magnetic tape 6 magnetic tape 10 base layer 11 back layer 12 magnetism Layer 31 Grindstone W Width of cutting edge radius curved shape L Width of cutting edge axial curved shape

Claims (3)

[Claims] 1. A magnetic tape is formed by cutting an original magnetic tape with a circular upper blade axially mounted on an upper blade shaft and a circular lower blade axially mounted on a lower blade shaft. A method of polishing a magnetic tape cutting blade for polishing the cutting edge of the upper blade or the lower blade of the magnetic tape cutting device, wherein the hardness of the outer peripheral surface of the upper blade or the lower blade is Rockwell hardness L while rotating the upper blade or the lower blade. A method for polishing a magnetic tape cutting blade, comprising pressing a grindstone having a hardness equal to or less than 60 on a scale to grind the cutting edge of the upper blade or the lower blade into a curved shape. 2. When the lower blade has a large-diameter portion and a small-diameter portion, and a cutting edge is formed at an outer peripheral end of the large-diameter portion, the lower blade is mounted on the lower blade shaft. 2. The cutting edge of the lower blade is polished into a curved shape by pressing the grindstone against the outer periphery of the lower blade while rotating the lower blade through the lower blade shaft in a state as it is. Polishing method of magnetic tape cutting blade. 3. In a case where the upper blade has a cutting edge formed at one end of the outer periphery and a bevel at the other end, the upper blade is overlapped on a polishing shaft. 2. The method according to claim 1, wherein, in the mounted state, the grindstone is pressed against the outer periphery of the upper blade while rotating the upper blade through the polishing shaft, and the cutting edge of the upper blade is polished into a curved shape. Polishing method of magnetic tape cutting blade.