JPH0743807B2 - Magnetic erasing device for magnetic tape - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic erasing device for various magnetic tapes, and more particularly to a magnetic erasing device in which the time required for magnetic erasing is significantly shortened. Is.

<Prior Art> Generally, in order to erase the magnetic recording recorded on various magnetic tapes, there is an apparatus that erases the magnetic recording in a relatively short time by applying a strong magnetic field to the entire tape wound on a reel. It is used a lot. FIG. 1 shows an erasing head portion of such a magnetic erasing device. In the figure, reference numeral 1 is a rotary table, which is rotatably supported by an appropriate driving means, in the illustrated example, a rotary roller 2. The magnetic tape 3 (wound on a reel) to be erased is placed on the rotary table 1. On the other hand, an erasing head 4 is arranged below the turntable 1, and the head 4 is composed of an erasing coil 5 and a core 6. One leg 6a of the core 6 penetrates the coil 5, and a gap 7 for radiating a magnetic field is formed between the leg 6a and the other leg 6b.

The drive current supply means 10 for the erase head 4 is provided.
As such, a drive circuit as shown in FIG. 2 was used. That is, an SCR switch 12 is connected in series to a commercial power source 11, and a resonance capacitor 13 and an erasing coil 5 connected in parallel with the SCR switch 12 are connected to the commercial power supply 11. The resonance capacitor 13 and the erasing coil 5 are connected to each other. A resonance circuit is formed by. On the other hand, a controller 14 is connected to the SCR switch 12, generates a trigger signal for driving the SCR switch 12, controls the conduction angle of the SCR switch 12, and supplies power to the resonance circuit. To adjust.

The drive current supply means 10 supplies the erasing coil 5 of the erasing head 4 with a sinusoidal alternating current of a commercial frequency whose envelope is gradually attenuated. Alternating magnetic field is formed, and this magnetic field is uniformly applied to the magnetic tape 3 on the rotary table 1 to erase the magnetic recording.

By the way, in the above apparatus, since the commercial power supply 11 is used as the power supply of the drive current supply means 10, it goes without saying that the frequency is 50 Hz or 60 Hz as the commercial frequency.
Since the cycle of the alternating current is long, the disadvantage is that the time required to obtain the desired number of alternating magnetic erases of the magnetic tape is long. Further, for this reason, heat generation in the erasing head section is continuously performed at a high duty ratio during the long required time, and the total heat generation amount per unit time becomes considerably large, so that the temperature rise of the apparatus is remarkable. However, there was a drawback that it could not withstand continuous use.

In addition, there was a drawback that it was necessary to have two models for 50Hz and 60Hz.

<Objective> An object of the present invention is to provide a high-frequency ringing oscillation in view of the problems such as the length of time required for erasing due to structural restrictions in the magnetic erasing device for a magnetic tape based on the above-mentioned prior art. It is an object of the present invention to provide an excellent magnetic erasing device which can eliminate the above-mentioned drawbacks, solve the problems, and shorten the required processing time by using the means as the drive current supplying means.

<Structure> According to the structure of the present invention in accordance with the above object, a ringing oscillation means of high frequency is used as a drive current supply means for the erasing head to generate ringing oscillation, and a large number of high frequencies in which the envelope is gradually attenuated. The sine wave alternating current burst of is repeatedly output intermittently during one relative rotation of the magnetic tape, and an alternating magnetic field having a high frequency corresponding to this is radiated from the erasing head to form 1 The gist of the present invention is to apply an alternating magnetic field having a high-frequency attenuation waveform many times during the rotation period. Further, the erasing coil in the erasing head is a hollow air-core coil, and the core is omitted. By arranging the magnetic tape in the air-core coil, the weight of the entire device is reduced and the direction of the magnetic field formed by the erasing coil is changed to Aligned with orientation for removed by by the fact that to perform efficient magnetic erasure it is an gist.

<Embodiment> Next, the embodiment of the present invention will be described below with reference to FIG. 1 and the drawings starting from FIG.

In FIG. 3, the drive current supply means 10 is configured as a ringing oscillation means 15, and in the means 15, a high voltage (about 600 V) DC power supply 16 is used as a power supply, and the power supply 16 is The erase coil 5 and the SCR switch 17 are connected in series, and the switch 17 is connected to a controller 18 for applying a trigger signal. A resonance capacitor 19 is connected in parallel with the erasing coil 5 and the SCR switch 17, and a bypass diode 20 having a reverse polarity current is inserted in parallel with the SCR switch 17.

The ringing oscillating means 15 is not limited to the one described above, but may be one as shown in FIG. That is, the erasing coil 5 and the resonance capacitor 19 are connected in parallel to the DC power supply 16, the GTO switch 21 is connected to this, and the controller 18 is connected to the switch 21.

As shown in FIG. 5, the ringing oscillating means 15 has a high frequency sinusoidal alternating current burst 23 of which the envelope is gradually attenuated as shown in (B) in response to the trigger signal shown in (A). Is repeatedly output.

When the ringing oscillation means 15 is used as a drive current supply means for the erasing head 4 shown in FIG. 1, the erasing head 4 radiates a high frequency alternating magnetic field which is gradually attenuated by a high frequency sinusoidal alternating current whose envelope is attenuated. The magnetic recording is erased by forming an alternating magnetic field having a high-frequency attenuation waveform many times during one rotation of the magnetic tape 3.

And, the expression expressing the frequency of the ringing vibration generated by the ringing oscillation means 15 is also well known,
In the above embodiment, about 500 Hz is selected,
The damping alternating magnetic field due to the ringing vibration is applied to the magnetic tape for about 30 cycles.

By the way, in the drive current supply means 10 in the prior art, as described above, the commercial power source is used, and the commercial frequency thereof is low. Therefore, the inductance L of the erasing coil in the resonance circuit must be increased. Therefore, it was necessary to use the core from the viewpoint of increasing the magnetic permeability. Therefore, there is a drawback that the entire apparatus becomes heavy and the cost becomes correspondingly high.

However, according to the present invention, since an alternating current having a high frequency is generated, resonance can be sufficiently performed even if the inductance L of the erasing coil 5 forming the resonance circuit is small, and the core can be omitted. became.

As a result, as shown in FIG. 6, the erasing head can be constructed by omitting the core and using the air-core erasing coil.

In the figure, the erasing head 4 is composed of an air-core coil 25, and a hollow portion 26 is formed in the air-core coil 25.

When the erasing head 4 with such an air-core coil 25 is adopted, the magnetic tape 3 is arranged in the hollow portion 26, and the magnetic tape 3 is supported by, for example, a rotating roller 27 to form a coil. It is driven to rotate about a rotation axis orthogonal to the central axis of 25. In such an arrangement, the direction of the magnetic field formed by the air-core coil 25 is along the central axis direction, that is, the vertical direction of the drawing, and the orientation for magnetic erasing of the magnetic tape 3, that is, Match the length direction of the tape.

As described above, according to the present invention, as the drive current supplying means for the erasing head, a large number of sinusoidal alternating current bursts having a high frequency and whose envelope is gradually attenuated are used for one relative rotation of the magnetic tape. By employing the linking oscillating means for intermittently repeating the output during the period, it is possible to give the magnetic tape a burst of an alternating magnetic field having an attenuation waveform many times during one rotation. The rotation speed of the magnetic tape at that time is not strictly limited by the repetition frequency of the burst of the alternating magnetic field and the alternating frequency in the burst, and as a result, even if the magnetic tape is not rotated at a high speed, As a result, the excellent effect that the magnetic erasing process can be uniformly applied is exhibited. And, in this case, the frequency of the alternating current forming each burst of the alternating magnetic field is sufficiently high,
In other words, since the cycle is sufficiently short, the time required to secure the desired number of alternating currents required for sufficient magnetic erasing processing at a predetermined location on the magnetic tape is short, and as a result, There is also an excellent effect that the magnetic erasing processing time can be significantly shortened.

In addition, heat is generated in the erase head section at an intermittently low duty ratio for each burst of the alternating magnetic field, and the total amount of heat generated per unit time is significantly reduced. Withstands continuous use and improves work efficiency.

Further, according to the second invention linked to this invention, the erasing coil in the erasing head is an air-core coil having a hollow portion, and the core is omitted. Therefore, the weight of the entire apparatus can be reduced and the cost can be reduced. The effect of being able to bring about is also exhibited.

In this case, the rotation speed of the magnetic tape during the magnetic erasing process is
Since there is no strict restriction from the repetition frequency of the alternating magnetic field burst or the alternating frequency in the burst, it is possible to select a high frequency that is suitable from the viewpoint of the inductance of the erasing coil with respect to the alternating frequency in the burst. As a result, even if the erasing coil is an air-core coil, the power supply device does not increase in size because a large current does not pass through the low-inductance air-core coil, and the air-core coil is large in size to secure high inductance. There is also an excellent effect that it does not change.

Then, by arranging the magnetic tape in the hollow portion of the air-core coil so as to rotate about the rotation axis orthogonal to the central axis of the coil, the direction of the magnetic field formed by the air-core coil and the magnetic tape Since the orientation for magnetic erasing can be matched, extremely efficient magnetic erasing can be performed.

[Brief description of drawings]

FIG. 1 shows an erasing head portion of a magnetic erasing device.
1 (A) is a top view, FIG. 1 (B) is a side view, FIG. 1 (C) is a sectional view taken along line XX of FIG. 1 (A), and FIG. 2 is a conventional drive current supply means. FIG. 3 and the following figures show an embodiment of the present invention. FIG. 3 shows an example of ringing oscillation means as drive current supply means, FIG. 4 shows another example of the ringing oscillation means, and FIG. 5 shows a trigger. FIG. 5 (A) shows a trigger pulse, FIG. 5 (B) shows ringing vibration, and FIG. 6 shows another embodiment of the erasing coil. 6A is a perspective view, FIG. 6B is a vertical sectional view, and FIG. 6C is a side sectional view. 3 ... Magnetic tape, 4 ... Erase head 5 ... Erase coil, 6 ... Core 10 ... Drive current supply means 15 ... Ringing oscillation means 23 ... Sine wave alternating current burst 25 ... Air core coil, 26 ... Hollow part

Claims (5)

[Claims] 1. An erase head 4 for forming a magnetic field according to a drive current, and a drive current supply means 10 for supplying to the erase head 4 a sinusoidal alternating current whose envelope is gradually attenuated as a drive current. In the magnetic erasing device for a magnetic tape, which is configured to rotate the magnetic tape relative to the magnetic field formed by the erasing head 4, the drive current supply means 10 operates at a frequency considerably higher than the commercial frequency. A magnetic erasing device for a magnetic tape, which comprises linking oscillating means 15 for intermittently repeatedly outputting a large number of sinusoidal alternating current bursts during one relative rotation of the magnetic tape. 2. The erasing head 4 includes an erasing coil 5 driven by a drive current, and one leg of the erasing coil 5 penetrates the coil.
The magnetic erasing device for a magnetic tape according to claim 1, comprising a magnetically permeable core 6 having a gap for radiating a magnetic field between the leg and the other leg. 3. The magnetic tape according to claim 1, wherein the erasing head 4 is fixed and the magnetic tape is rotated so as to pass through a magnetic field radiated from the erasing head. Magnetic eraser. 4. An erasing head 4 for forming a magnetic field according to a driving current, and a driving current supplying means 10 for supplying to the erasing head 4 a sinusoidal alternating current whose envelope is gradually attenuated as a driving current. In the magnetic erasing device for a magnetic tape, which is configured to rotate the magnetic tape relative to the magnetic field formed by the erasing head 4, the drive current supply means 10 operates at a frequency considerably higher than the commercial frequency. The erasing head 4 is a linking oscillating means 15 for intermittently and repeatedly outputting a large number of alternating sine wave alternating current bursts during one relative rotation of the magnetic tape.
Is a coreless coil 25 that has a hollow portion 26 inside which is a space for disposing a magnetic tape, and forms a magnetic field along the central axis of the hollow portion. Magnetic erase for magnetic tape apparatus. 5. The magnetic tape is rotated about a rotation axis orthogonal to the central axis of the coil in the magnetic field formed in the hollow portion 26 of the air-core coil with the air core coil 25 fixed. A magnetic erasing device for a magnetic tape according to claim 4.