JPS61170904A - Magnetic erasing device for magnetic tape - Google Patents

Abstract

PURPOSE:To improve the efficiency of magnetic erasure by using a high-frequency ringing oscillation means and an air core coil where a magnetic tape is arranged. CONSTITUTION:When the ringing oscillation means 156 is used as as driving current supply means for an erasing head 4, the erasing head 4 radiates and establishes a high-frequency alternating magnetic field which attenuates gradu ally with a sine-wave alternating current of high frequency whose envelopes attenuate gradually to form a high frequency attenuation waveform uniformly several times in one turn of the magnetic tape 3, thereby erasing magnetic records. Further, the alternating current of the frequency is generated, so reso nance is possible even if the inductance of an erasing coil 5 which forms a resonance circuit and theerasing head is composed of an air core type erasing coil 25 without any core. The magnetic field produced by the coil 25 is oriented for the magnetic erasure of the tape 3 in the center-axial direction, i.e. coinci dent with the lengthwise direction of the tape. Consequently, efficient magnetic erasure is performed.

Description

[Detailed Description of the Invention] Technical Field> The present invention relates to a magnetic erasing device for various magnetic tapes. It is something.

<Prior art> Generally, in order to erase magnetic records recorded on various magnetic tapes, a strong magnetic field is applied to the entire tape wound on a tape to erase the magnetic records in a relatively short time. The equipment is used frequently and becomes 0. FIG. 1 shows the erasing head section of such a magnetic erasing device.
It is rotatably supported by a rotating roller 2, and a magnetic tape 3 (wound on a reel) to be erased is placed on the rotating table 1. On the other hand, an erasing head 4 is disposed below the one-turn table 1, and the head 4 is made up of an erasing fill 5 and a core 6. The core 6
One leg 6a passes through the coil 5, and the leg 6a and the other leg 6
An air gap 7 for radiating a magnetic field is formed between the spacer and b.

Drive current supply means 1 for the erasing head 4
0, a drive circuit as shown in FIG. 2 was used. That is, commercial power supply 114 SOR switch 1
2 are connected in series, and a resonant capacitor 13 is connected here.
and an erasing coil 5 connected in parallel to this, and a resonance circuit is formed by the resonance capacitor 13 and the erasing coil 5. On the other hand, the 5CEL
A controller 14 is connected to the switch 12, which generates a trigger signal for driving the 8CR switch 12', controls the conduction angle of the SOR switch 120,
This adjusts the power supplied to the resonant circuit.

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

By the way, in the above device, the drive current supply means 10
Since the commercial power supply 11 is used as the power source for the
Hz or 60Hz, and the cycle of the alternating current is long, so there is a disadvantage that it takes a long time to obtain the desired number of alternating currents necessary for magnetic erasing the magnetic tape. During the long required time, heat is generated continuously at a high duty ratio, and the total amount of heat generated per unit time becomes quite large (as a result, the temperature of the device increases significantly and cannot withstand continuous use. There was a problem.

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

Purpose of the present invention In view of the problems such as the length of time required for erasing due to structural constraints in the magnetic erasing device for magnetic tape based on the above-mentioned prior art, it is an object of the present invention to eliminate high frequency ringing oscillation. It is an object of the present invention to provide an excellent magnetic erasing device in which the above-mentioned drawbacks and difficulties can be eliminated and the required processing time can be shortened by configuring the device to be used as a drive current supplying device.

In accordance with the above object, the present invention uses a high frequency ringing oscillation means as a driving current supply means for the erasing head to generate a ringing vibration and generate a high frequency sine wave whose envelope gradually attenuates. The gist of this technology is to intermittently and repeatedly output alternating current bursts and radiate and form a correspondingly high-frequency alternating magnetic field from an erasing head, thereby imparting a high-frequency attenuation waveform many times on the magnetic tape. In addition, by using the erasing coil in the erasing head as a hollow air-core coil and omitting the core, and arranging the magnetic tape within the air-core coil, the overall weight of the device is reduced, and the erasing coil Another key point is that the direction of the generated magnetic field is aligned with the orientation of the magnetic tape for magnetic erasing, so that efficient magnetic erasing can be performed.

<Example> Next, an example of the present invention will be described below with reference to FIG. 1 and the drawings from FIG. 3 onwards.

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 (approximately 600 V) DC power supply 16 is used as a power source.
is used, and the power supply 16 includes erase coils 5 and 8.
An eR switch 17 is connected in series, and a controller 18 that applies a trigger signal is connected to the switch 17. A resonant capacitor 19 is connected in parallel with the erasing coil 5 and the SCR switch 17, and a diode 20 for bypassing current of opposite polarity is connected to the 8
It is inserted in parallel with the CB switch 17.

Incidentally, the ringing oscillation means 15 is not limited to the above embodiment, but may be of the type shown in FIG. 4. t4ゎ9
,'fL @ E g 1a ;. 24. A1. mosquito
- A coil 5 and a resonance capacitor 19 are connected in parallel, a UTυ switch 21 is connected to this, and a controller 18 is connected to the switch 2.

The ringing oscillation means 15, as shown in FIG.
In response to the trigger signal shown in the figure, a high frequency sinusoidal alternating current burst 23 whose envelope gradually attenuates as shown in (B) is repeatedly output.

The ringing oscillation means 15 is used as a driving current supply means for the erasing head 4 shown in FIG. 1, and the erasing head 4 emits a high-frequency alternating magnetic field whose envelope is attenuated by a high-frequency sinusoidal alternating current whose envelope is attenuated. A high frequency attenuation waveform is uniformly applied many times during one rotation of the magnetic tape 3, and the magnetic recording is erased.

There is also an equation representing the frequency of the ringing vibration generated by the ringing oscillation means 15 (this is known, and in the above embodiment, it is selected to be about 500 Hz), and the damping alternating magnetic field due to the ringing vibration is reduced to 30 Hz.
By the way, the drive current supply means 10 in the prior art is applied to the magnetic tape by about a cycle.
As mentioned above, commercial power is used,
Since the commercial frequency is low, it is necessary to increase the inductance L of the erasing coil which is not used in the resonant circuit, so it is absolutely necessary to use a core from the viewpoint of increasing magnetic permeability. This has the disadvantage that the entire device becomes heavier and the cost increases accordingly.

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

As a result, as shown in FIG. 6, the core can be omitted and the erasing head can be configured with an 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 employing the erasing head 4 using such an air-core coil 25, the magnetic tape 3 is disposed within the hollow portion 26, and the magnetic tape 3 is supported by, for example, a rotating roller 27, and the coil 25 It is driven to rotate around a rotation axis perpendicular to the central axis of. In such an arrangement, the direction of the magnetic field formed by the air-core coil 4 is along the central axis direction, that is, the vertical direction in the figure, and the orientation for magnetic erasing of the magnetic tape 3, that is, Matches the length direction of the tape.

As described above, according to the present invention, the ringing oscillation means that has a high frequency and intermittently repeatedly outputs sinusoidal alternating current bursts whose envelopes gradually attenuate is used as the drive current supply means for the erase head. So,
It is possible to apply attenuation waveforms to the magnetic tape many times during one rotation, and since the cycle of the alternating current is short,
An excellent effect is achieved in that the time required to obtain the desired number of alternations required for magnetic erasing can be significantly shortened.

In addition, the erasing head generates heat intermittently at a low duty ratio for each burst, and the total amount of heat generated per unit time is significantly reduced, so the temperature rise of the device is not as great.
, can withstand continuous use, further improving work efficiency.

Furthermore, according to a second invention related to this invention, since the erasing coil in the erasing head is an air-core coil having a hollow portion and the core is omitted, it is possible to reduce the weight of the entire device and to save money in terms of cost. It also has the effect of bringing about change.

Then, by arranging a magnetic tape in the hollow part of the air-core coil so as to rotate around a rotation axis perpendicular to the central axis of the coil, the direction of the magnetic field formed by the air-core coil and the magnetic % f -i (DW1fA114 *
(D f: h (D t IJ x 7 + −y
Since it is possible to match the values of a' and a', extremely efficient magnetic erasing can be performed.

[Brief explanation of drawings]

Figure 1 shows the erasing head section of a magnetic erasing device.
The first device is a top view, Figure 1 (B) is a side view, Figure 1 (C
) is a cross-sectional view taken along the line X-X of FIG. 1, FIG. 2 is a conventional drive current supply means, and FIG. An example of the ringing oscillation means, FIG. 4 is another example of the same ringing oscillation means, and FIG. 5 is a diagram showing the relationship between the trigger pulse and the ringing vibration.
The fifth position shows a trigger pulse, FIG. 5(B) shows a ringing vibration, FIG. 6 shows another embodiment of the erasing coil, FIG. 6(A) is a perspective view, and FIG. 6+8 ) is a longitudinal section,
FIG. 6(C) is a side sectional view.

Claims (5)

[Claims] (1) It consists of an erasing head 4 that forms a magnetic field according to a drive current, and a drive current supply means 10 that supplies a sinusoidal alternating current whose envelope gradually attenuates to the erasing head 4 as a drive current. , a magnetic erasing device for a magnetic tape in which the magnetic tape is moved relative to the magnetic field formed by the erasing head 4, wherein the drive current supply means 10 generates a sine wave having a frequency considerably higher than the commercial frequency. 1. A magnetic erasing device for a magnetic tape, comprising a ringing oscillation means 15 that repeatedly outputs alternating current bursts intermittently. (2) The erasing head 4 includes an erasing coil 5 driven by a drive current, one leg of which passes through the coil, and a magnetically permeable body having an air gap between the leg and the other leg for radiating a magnetic field. A magnetic erasing device for a magnetic tape according to claim 1, comprising a core 6 of. (3) A magnetic tape according to claim 1, characterized in that the erasing head 4 is fixed and the magnetic tape is moved so as to pass through a magnetic field radiated from the erasing head. Magnetic eraser. (4) It consists of an erasing head 4 that forms a magnetic field according to a drive current, and a drive current supply means 10 that supplies a sinusoidal alternating current whose envelope gradually attenuates to the erasing head 4 as a drive current. , a magnetic erasing device for a magnetic tape in which the magnetic tape is moved relative to the magnetic field formed by the erasing head 4, wherein the drive current supply means 10 generates a sine wave having a frequency considerably higher than the commercial frequency. A ringing oscillation means 15 that repeatedly outputs alternating current bursts intermittently, and the erase head 4
is a magnetic eraser for a magnetic tape, which has a hollow part 26 inside which serves as a magnetic tape installation space, and is an air-core coil 25 that forms a magnetic field along the central axis of the hollow part. Device. (5) The air-core coil 25 is fixed, and the magnetic tape is rotated about a rotation axis perpendicular to the central axis of the coil in a magnetic field formed within the hollow portion 26 of the air-core coil. A magnetic erasing device for magnetic tape according to claim 4.