JPS645369B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape stop device suitable for use in magnetic recording and reproducing devices, particularly VTRs (video tape recorders).

Generally speaking, when a magnetic head in a VTR (video tape recorder) or the like uses a tape more often, the magnetic material on the tape surface adheres to the tape contact surface of the head and becomes dirty, resulting in a decrease in head output and an increase in SN.
Phenomena such as deterioration of the ratio occur. The above-mentioned phenomenon is particularly noticeable when metal tapes, which have been put into practical use in recent years, are used.

In order to remove dirt from the magnetic head, a method has been proposed in which a cleaning tape is placed at the end of the magnetic tape and the tape is cleaned uniformly every time the rewound tape starts running. However, since the amount of dirt on the magnetic head varies depending on the number of times the tape is used, it is desirable to change the amount of cleaning depending on the state of dirt on the magnetic head.

The present invention has been made in view of the above points, and when a cassette tape having a cleaning tape and a plurality of sensing tapes at the end of the magnetic tape is used, the amount of cleaning of the tape is changed depending on the degree of dirt on the magnetic head. The present invention provides a tape stop device that can change the winding stop position of the tape.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a cassette tape, in which 1 is a supply reel, 2 is a take-up reel, and 3 is a cleaning tape connected between one end of a magnetic tape 4 and one end of a leader tape 5. It is. Sensing tapes 6a, 6b, and 6c are made of aluminum foil, and are arranged at three locations at the middle and both ends of the cleaning tape 3. The sensing tape is detected as a non-magnetic portion by a sensing coil, which will be described later, and allows the tape winding stop position to be changed in three stages.

Next, a case will be described in which, using the above-mentioned cassette tape, the tape winding stop position is automatically changed to three levels depending on the dirt on the magnetic head, and the amount of cleaning is varied. FIG. 2 shows a block diagram of the tape stop device, in which 7 is a sensing coil for detecting the passage of a sensing tape section;
9 is an oscillation circuit that oscillates when the magnetic tape portion passes over the sensing coil 7 and stops oscillating when the sensing tape portion passes, and 9 is an amplifier that amplifies the output of the oscillation circuit. 10 is a low pass filter, 1
1 is a detection circuit that detects the filter output and outputs a pulse every time the sensing tape passes, and 12 is a 2-bit BCD that counts the pulses of the detection circuit output.
This is a pulse counter circuit that outputs an output. On the other hand, 13 is an input terminal to which a head output that changes depending on the degree of dirt on the magnetic head is input; 14 is an envelope detection circuit that performs envelope detection of the input and outputs a DC level; 15a, 15b, 15c
16 is an encoder that converts the output of the comparison circuit into a 2-bit BCD code according to the degree of dirt on the head; 17 is a latch circuit that holds the encoder output for a certain period of time. It is. Numeral 18 is a digital comparison circuit which compares the output of the latch circuit with the output of the pulse counter circuit 12 and outputs the result.The stop solenoid 19 is controlled by the circuit output.

Next, the operation of the circuit having such a configuration will be explained.

This circuit automatically adjusts 3 times depending on the dirt on the magnetic head.
It operates to vary the amount of cleaning in stages, i.e. if the magnetic head is very dirty,
When the third sensing tape 6a passes over the sensing coil 7 during tape winding, the stop solenoid 19 is operated to stop the tape from running, and the amount of contact between the head and the cleaning tape 3 is adjusted when the tape starts running. If the head is slightly dirty, the tape is stopped when the second sensing tape 6b passes and the amount of cleaning is halved, and if the head is not dirty at all, the amount of cleaning is halved when the sensing tape 6c passes. It operates so that the tape is stopped and cleaning is not performed.

To explain the operation during this time in more detail, first,
When the magnetic tape 4 passes over the sensing coil 7, the Q value of the sensing coil 7 becomes large and the oscillation circuit 8
An oscillation output of several 100 KHz is obtained as the output, and after this output is amplified, it is detected by the detection circuit 11 and outputs a DC high level.

Next, when the sensing tapes 6a, 6b, and 6c pass over the sensing coil 7, the Q value becomes small, oscillation stops, and a DC low level is output to the detection circuit 11. That is, pulses are sequentially output to the detection circuit 11 each time the sensing tape passes. The output of this detection circuit 11 is counted by a pulse counter circuit 12 and converted to 2 bits.
Output as BCD output and digital comparison circuit 18
This is one of the inputs.

On the other hand, the head output input from the input terminal 13 is envelope-detected in the envelope detection circuit 14, and the output terminal is given a DC level according to the level of dirt on the head, that is, a high level when the head is not very dirty, and a low level when there is a lot of dirt. is output. This output is provided by the comparator circuits 15a, 15b,
15c, each comparison circuit is compared with a different reference voltage, and one of the comparison circuits becomes high, and the encoder 16
is input. The encoder 16 converts the output of the comparison circuit into a binary code and outputs it as a 2-bit BCD code. This output becomes the other input of the digital comparison circuit 18 and is compared with the output of the pulse counter circuit 12, and when the two are equal, the output becomes high. This high output activates the stop solenoid, which stops tape rewinding.

Therefore, the tape winding stop position changes depending on the dirt on the magnetic head, and the amount of contact between the magnetic head and the cleaning tape 3 changes accordingly when the tape starts running at the normal speed.

In this embodiment, the case has been explained in which the sensing tape is placed at three locations and the tape stop position changes in three stages. It goes without saying that the stop positions may be subdivided by providing four or more locations. Further, in this embodiment, a sensing tape made of aluminum foil is used to detect the stop position as a change in magnetic resistance, but the sensing tape may be a transparent tape and optical detection may be performed. Furthermore, in this embodiment, dirt on the magnetic head is detected and the tape stop position is automatically selected. In FIG. 2, a multiplexer is connected in series between the encoder 16 and the latch circuit 17, Connect a selection circuit with a selection switch to or
Alternatively, the pulse counter circuit may be replaced with a normal n-ary counter by an n-ary Johnson counter, a selection switch may be connected to the output terminal of the counter, and the stop solenoid 19 may be disconnected from the digital comparison circuit 18 and connected to the selection switch. Alternatively, the selection switch may be manually selected depending on how dirty the magnetic head is.

As described above, according to the present invention, the amount of cleaning of the magnetic head can be varied in a plurality of stages depending on the dirt on the magnetic head, and appropriate cleaning can be performed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a cassette tape used in the present invention, and FIG. 2 is a block diagram of a tape stop device in one embodiment of the present invention. Explanation of main figure numbers 3...Cleaning tape, 4
...Magnetic tape, 5...Leader tape, 6a, 6
b, 6c... Sensing tape, 7... Sensing coil, 8... Oscillation circuit, 9... Amplifying circuit, 10... Low pass filter, 11... Detection circuit, 12... Pulse counter circuit, 14... Envelope detection circuit, 15
a, 15b, 15c...Comparison circuit, 16...Encoder, 17...Latch circuit, 18...Digital comparison circuit, 19...Stop solenoid.

Claims (1)

[Claims] 1. A cassette tape comprising a cleaning tape disposed at least at one end of a magnetic tape and a plurality of sensing tapes disposed on or near the cleaning tape, and a detection means for detecting passage of the sensing tape; The magnetic tape apparatus comprises a comparison means for comparing the output of the detection means and a head output which changes depending on the degree of contamination of the magnetic head, and a tape stop means for stopping the tape running based on the output of the comparison means. A tape stop device configured to change a tape running stop position into a plurality of stages depending on the dirt on the magnetic head.