JPS5954061A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To detect the end of a tape with extremely high accuracy without giving any processing to the tape, by comparing the pulses generated within a prescribed time by pulse generators corresponding to the number of revolutions of plural reels, respectively. CONSTITUTION:If a tape is set in a rewind mode, for example, a comparator 11 compares the number of pulses of a counter 6 which are delivered to specific pulse number of a counter 5 with the number of pulses stored in a storage circuit 9. When the coincidence is obtained between both pulse numbers or the pulse number of the counter 6 is larger than the pulse number of the circuit 9, the signal is sent to a tape end detecting circuit 12. Then the circuit 12 delivers a tape end detecting signal. Receiving this signal, a reel driving circuit 13 decelerates or stops the revolutions of reels 3 and 4. The circuit 9 is reset when a tape 20 is completely taken up. In such a way, the end of a tape can be detected with extremely high accuracy without giving any processing to the tape.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording/reproducing apparatus (hereinafter referred to as a VTR) that is capable of extremely accurately detecting the end of a tape without performing any processing on the tape.

On a VTR, when rewinding the tape or fast forwarding the tape,
It is necessary to know the tape edge. This is because when the tape is run at high speed, if the end of the tape passes through the tape running system while still at high speed, it will give a strong impact not only to the tape end but also to the tape running system.

To prevent this from happening as it will damage them.

Decrease the tape running speed near the tape edge.

This is because it needs to be stopped. In particular, in a helical type VTFR in which the tape is wound around the head drum by 180° or nearly 360°, it is essential to slow down or stop the tape running speed at the tape end.

Conventional methods for detecting tape ends include using tape with markers etc. on the tape end, or connecting transparent tape and detecting it electro-optically, but these methods require special tape to be prepared. This is invariably time consuming and cumbersome.

The purpose of the present invention is to avoid applying any processing to the tape.

It is an object of the present invention to provide a detection means for detecting a tape end extremely accurately.

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

\ The figure shows an embodiment according to the present invention. 1.2 is a conventionally known pulse generator that obtains frequency signals corresponding to the number of rotations of the supply reel 39 and the take-up reel 40, respectively.

5.6 are counters that count the pulses generated by the pulse generators 1 and 2 via the switches S, S2, respectively. The counter 5 sends a signal to the counter 6 every time the pulse generator 1 counts a certain number of pulses also generated.
as a reset signal. The counter 6 counts or detects the number of pulses until it receives this signal, that is, the number of pulses generated by the pulse generator 2 within the same time period in which the pulse generator 1 also generates a specific number of pulses, and stores this in the memory circuit 9. ．． The configuration is such that the signal is output to the comparator 11 and the counter 6 is reset. Here, the number of pulses of the counter 6 stored in the memory circuit 9 indicates the tape end.

Therefore, in order to detect a point an arbitrary length before the final end of the tape, an offset circuit 14 is provided.
is turned off, and the counters 5 and 6 are configured not to operate. As a result, one take-up reel 4 has 20 tapes.
It is possible to detect the point where the curve has turned around 20 times. That is, by appropriately selecting the offset time, any position from the final end of the tape can be detected.

Now, when the tape 20 is loaded, the photosensor 21 provided in the tape running system detects the tape and turns off, and this signal is sent to the control circuit 7.

Next, when the standby mode is entered, the signal from the mode detector 8 is sent to the control circuit 7, and in response to these two signals, the control circuit 7 sends a control signal to the offset circuit 14. The signal is sent to switch S3. In the offset circuit 14, if the pulse signal sent to the pulse generator 2 becomes too low, for example, corresponding to the first 20 revolutions of the take-up reel, the switch 8 is activated.
Turn on +182.

The signals from the pulse generators 1.2 are respectively input to the counters 5.
6.

The control circuit 7 also switches the switch S3 by the sent signal.
is ON, the number of pulses of the counter 6 is stored in the memory circuit 9 after the off-cent time has elapsed. The memory circuit 9 is configured so that once the information is stored, it will not be reset until the tape is rewound and the photosensor is turned on.

Next, the tape end detection operation will be explained. Put the tape in rewind mode. The comparator 11 compares the number of pulses output from the counter 6 with respect to the specific number of pulses from the counter 5 and the number of pulses stored in the storage circuit 9. And these: When the two pulse numbers match or the pulse number of the counter 6 exceeds the stored pulse number, this signal is sent to the tape end detection circuit 12, and a tape end detection signal is sent from the circuit. Reel drive circuit 13 receives this signal and operates to slow down or stop the rotation of reel 3.4.

When the tape 20 is completely wound onto the supply reel 3,
When the photosensor 21 is turned ON, the memory circuit 9 is turned on.

Detection of the end of the tape in the tape fast forward mode can be considered in the same way as in the tape rewind mode. In other words, in Figure 2, from counter 6 to comparator 1
The connection to counter 1 may be changed to the connection from counter 5 to the comparator.

Note that the memory circuit 9 includes a drive circuit 15 driven by a battery.
is connected, and if the entire device is powered off, it is configured to automatically operate and continue to hold the memory contents of the memory circuit 9.

As explained above, according to the present invention, the tape end can be detected extremely accurately without any processing on the tape.

Therefore, it can be constructed to prevent damage to the tape or head at the end of the tape, which is very effective when applied to a VTR.

[Brief explanation of the drawing]

The figure is a block diagram of an embodiment according to the present invention. 1.2: Pulse generator, 3: Supply reel, 4: Take-up reel, 5.6: Counter, 9: Memory circuit. 11: Comparator, 2o: Tape.

Claims (3)

[Claims] (1) A first pulse generator that generates a number of pulses corresponding to the number of rotations of the supply reel (or one-turn reel) and a number of pulses corresponding to the number of rotations of the two-turn reel (or supply reel) a second pulse generator that generates a specific number of pulses, and a second pulse generator that generates a specific number of pulses from the first pulse generator within the same time after a tape is loaded and activated and an arbitrary time elapses. means for detecting the number of pulses generated; means for storing the number of pulses; and when unwinding the tape, the output of the first pulse generator generates a specific number of pulses within the same time period. A magnetic recording/reproducing device characterized in that it is configured to detect an edge. (2) A first pulse generator that generates a number of pulses corresponding to the number of rotations of the supply reel (or take-up reel) and a first pulse generator that generates a number of pulses corresponding to the number of rotations of the first take-up reel (or supply reel). a second pulse generator that generates a specific number of pulses in the first pulse generator after an arbitrary period of time has elapsed after loading the tape and starting the tape; means for detecting the number of pulses; means for storing the number of pulses; and pulses generated by the first pulse generator within the same time period during which the second pulse generator generates a specific number of pulses during tape fast forwarding. 1. A magnetic recording and reproducing apparatus, comprising means for comparing the number of pulses with the stored number of pulses, and the end of the tape is detected based on the output of the means. (3) The magnetic recording/reproducing apparatus according to claim 1 or 2, wherein the means for storing the number of pulses includes a battery drive circuit.