JPS6231Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a metal foil detection circuit that detects a metal foil stuck to the surface of a recording magnetic tape.

The object of the present invention is to provide a metal foil detection circuit that can detect metal foil even if the detection time for the metal foil is short.

A conventional metal detection circuit was constructed as shown in FIG. In other words, the metal foil detection circuit 1 has a resistor 2
and a transistor 4 that is slightly biased to the conductive side by a bias circuit consisting of a diode 3.
A time constant circuit consisting of a transistor 5 whose emitter is commonly connected to the transistor 4, a transistor 6 which drives the relay A by the output of the transistor 5, a resistor 7 and a capacitor 8 is connected to the base of the transistor 4 through the contact a of the relay A. a grounded contact 10-2, and a holding circuit connected thereto;
The base of the transistor 5 is connected through a diode 9 to a contact 10-1 of a metal foil switch consisting of a contact 10-2 and a contact 10-1 which are bridged by the passage of a metal foil 10-3 pasted on a magnetic tape. ing.

The operation of the above circuit will now be explained using the case of rewinding a magnetic tape as an example. A negative pulse signal is applied to the input terminal IN as a magnetic tape rewind signal.

Application of this signal turns transistor 4 off, transistors 5 and 6 turn on, and relay A is energized. Relay contact a switches from the dotted line side to the solid line side, and when relay contact a is on the dotted line side, The capacitor 8 is charged through the resistor 7, and when the relay contact a is switched to the solid line side, the charge in the capacitor 8 maintains the off state of the transistor 4. The contact of relay A operates the magnetic tape rewind motor, and the magnetic tape is rewound. During this unwinding process, the metal foil 10
-3 bridges electrodes 10-1 and 10-2, metal switch 10 is activated, the base of transistor 5 becomes ground potential, transistors 5 and 6 are turned off, and relay A is switched again and becomes de-energized, and the magnetic The tape rewinding operation stops, and the magnetic tape is rewound to the position where the metal foil is attached and then stopped.

If the metal foil 10-3 deteriorates and the detection time becomes shorter or if it chattering, the position of the metal foil cannot be detected in the circuit described above. Furthermore, when a magnetic tape is sent in fast forward mode using a recorder, the detection time for the metal foil becomes shorter, making it impossible to detect the metal foil, resulting in the disadvantage that the length of the metal foil must be increased.

Therefore, in order to eliminate the above-mentioned drawbacks, this invention
As shown in FIG. 2, a latch circuit 11 is connected between the metal foil switch 10 and the metal foil detection circuit 1, and the reset circuit 1 receives the output of the metal foil switch 10.
2 For example, a delay timer is provided, and the reset circuit 12
The latch circuit 11 is reset by the output.

Therefore, the operation will be explained by taking as an example the case where the magnetic tape is rewound in the same manner as described above.

First, when a magnetic tape rewind signal (negative pulse signal) is input to the input terminal of metal foil detection circuit 1, relay A is energized as described above, and the magnetic tape rewind motor is activated to rewind the magnetic tape. It will be done.

This rewinding causes the metal foil switch 10 to operate at the metal foil attachment position. The output of the metal foil switch is latched by a latch circuit 11 and output to the metal foil detection circuit 1. Therefore, even if the metal foil switch is turned on for a short time or chatters, the first metal foil switch 10 remains on. Therefore, once the metal foil switch 10 is latched, it does not matter even if the metal foil switch 10 chattering or if its ON time is short, and the latch circuit 11 outputs the ground potential to the metal foil detection circuit 1. Then, the latch circuit 11 is reset by the output of the reset circuit 12. In this case, the reset timing is a predetermined time after the first activation of the metal foil switch 10, as described above, and during this period, the metal foil detection circuit 1 is supplied with the ground potential for a sufficient period of time, and the length of the metal foil and The position of the metal foil can be detected regardless of chattering. Furthermore, latch circuit 1
1 and the reset circuit 12 can be constituted by, for example, a monomultivibrator having a predetermined time constant.

As explained above, according to the present invention, since the metal foil is detected and latched, the end of the tape can be reliably detected without malfunctioning due to deterioration of the metal foil portion or catering of the metal foil switch. Since the reset signal is applied to the latch circuit after a certain period of time after the output from the foil switch is input, the reset of the latch circuit is less likely to cause deterioration of the metal foil than to reset the latch circuit using other metal foil detection signals or manually. This has the advantage that it does not require complicated operations and can be performed reliably.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional metal foil detection circuit. Second
The figure is a circuit diagram of a metal foil detection circuit according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Conventional metal foil detection circuit, 3... Diode, 4, 5 and 6... Transistor, A... Relay, a... Relay contact, 10... Metal foil switch, 10-1 and 10-2... ...Electrode, 10-3
...Metal foil, 11...Latch circuit, 12...Reset circuit.

Claims (1)

[Scope of utility model registration request] In a metal foil detection circuit that detects the output of a metal foil switch whose movable piece is a metal foil stuck to one side of a predetermined position of a magnetic tape and outputs it to another circuit, the output of the metal foil switch is latched. and a reset circuit that outputs a reset signal to the latch circuit after a certain period of time after the output from the metal foil switch is input. Foil detection circuit.