JPS6249Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a tape slack detection device for a video tape recorder or the like.

<Summary of the invention> The present invention is a tape slack detection device in which a photoelectric detection element for detecting light reflected from the tape is installed near a pinch roller. By inserting a switch that is turned on in conjunction with the loading operation, tape slack can be accurately detected without malfunctioning due to reflected light from the pinch roller.

<Prior Art> In general, a video tape recorder uses a slack detection device to detect whether or not the magnetic tape is normally wound onto a take-up reel without slack during recording and playback. In this type of detection device, a pair of photoelectric detection elements consisting of a light emitting diode and a phototransistor are installed near the pinch roller, and the photoelectric detection elements are constantly activated not only during recording and playback but also during fast forwarding, rewinding, stopping, etc. Tape slack was detected by detecting light reflected from the tape.

<Problems to be solved by the invention> However, there is a risk that the tape may become loose during recording and playback when the tape is loaded, and it is necessary to activate the photoelectric detection element during fast forwarding, rewinding, and stopping. Moreover, if the photoelectric detection element is always activated like this, depending on the mounting position and angle of the photoelectric detection element, fast forwarding,
There was a risk that the tape slack detection device would malfunction by detecting the reflected light from the pinch roller during rewinding, as if the tape were slack.

<Means for solving the problems> In order to solve the above-mentioned problems of the conventional tape slack detection device, the tape slack detection device of the present invention inserts a switch into the power supply path of the tape slack detection circuit, which is turned on in conjunction with the tape loading operation, so that the tape slack detection operation is performed almost simultaneously when the pinch roller presses against the capstan after loading is completed.

<Function> Therefore, during fast forwarding, rewinding, etc. when the tape is not loaded, the photoelectric detection element is in a non-operating state, so even if the pinch roller is close to the photoelectric detection element, the pinch roller is not activated as before. There is no risk of erroneous detection due to reflected light from the sensor.

<Example> The present invention will be described below according to an example shown in the drawings. FIG. 1 shows a circuit diagram of a tape slack detection circuit constituting the apparatus of the present invention. Here, 1 is a switch that is linked to the tape loading operation during recording or playback and is turned on for the first time when the loading operation is completed. +B is supplied. 2 is a photoelectric detection element consisting of an infrared light emitting diode D ₁ and a phototransistor P ₁ ; 3 is a resistor R ₃ and a capacitor C ₁
This is a filter that suppresses the voltage rise when the switch is turned on and prevents erroneous detection operations. Further, 4 is a Schmitt trigger circuit consisting of transistors Q ₁ and Q ₂ and resistors R ₅ , R ₆ , R ₇ and R ₈ . Furthermore, VR ₁ is a variable resistor for setting the detection level, and D ₂ is a Zener diode.

Only when the tape loading operation is completed during recording or playback at this point, the above switch 1 is turned on.
is turned on, and the tape slack detection circuit is supplied with DC power +
B is supplied, and tape slack detection operation is performed. That is, at this time, the light emitting diode D ₁ and the resistor R ₁
A current flows through the diode D1, and the diode _D1 emits infrared light. Note that the light emitting diode _D1 and the phototransistor _P1 constituting the photoelectric detection element 2 are attached to the mounting angle 7 near the capstan 5 and the pinch roller 6, as shown in FIGS. 2 and 3. The phototransistor _P1 is arranged so that the light emitted from the phototransistor _P1 is not directly received by the phototransistor P1.

Therefore, when the magnetic tape 8 is running normally without loosening, the phototransistor 2 does not receive any infrared light, so the internal impedance of the phototransistor 2 is extremely large and the Zener diode _D2 is cut off. It's just happening. Therefore, in this case, the Schmitt trigger circuit 4
Transistor Q ₁ is cut off, transistor
Q ₂ is turned on, and the collector potential of transistor Q ₂ is low and diode D ₃ remains cut off. That is, no tape slack is detected at this time.

However, if for some reason the tape 8 is not wound onto the take-up reel and becomes slack as shown by the dotted line in Figure 2, the light emitting diode
The infrared light emitted from _D1 is reflected by the tape 8, and the reflected light is received by the phototransistor _P1 . As a result, the internal impedance of the phototransistor _P1 becomes extremely small, thereby turning on the Zener diode _D2 and the transistor _Q1 , and turning the other transistor _Q2 into a cut-off state. As a result, the collector potential of the transistor _Q2 is increased, so that the diode _D3 is turned on, and the recording or reproducing operation is suddenly stopped, that is, the stop mode is entered. As a result, the pinch roller 6 separates from the capstan 5 and its rotation is stopped, so that the tape 8 does not loosen any further after that, and damage caused by tape entanglement is prevented.

When the tape loading operation is completed, the pinch roller 6 rotates together with the pinch roller lever 9 from the position shown by the dashed line in FIG. 2 and is pressed against the capstan 5. The tape slack detection operation is performed at approximately the same time as the tape slack detection operation, and the pinch roller 6 is
As shown by the solid line in FIG. 2, is pressed to the capstan 5 and is located away from the photoelectric detection element 2, so the light emitted from the light emitting diode _D1 is reflected by the pinch roller 6 and received by the phototransistor _P1 . There is no risk of that happening.

On the other hand, during operations such as fast forwarding and rewinding, the pinch roller 6 is moved away from the capstan 5 in conjunction with the unloading operation and rotated together with the pinch roller lever 9 to the position shown by the dashed line in FIG.
The pinch roller 6 is brought close to the photoelectric detection element 2, but in this case, the switch 1 is in the off state and the photoelectric detection element 2 is in the non-operating state. There is no risk of performing a detection operation.

<Effects of the invention> As described above, according to the tape slack detection device of the present invention, the power supply path of the tape slack detection circuit that detects tape slack using a photoelectric detection element is operated in conjunction with the tape loading operation. Because the switch is inserted, the tape slack detection operation is performed almost simultaneously when the pinch roller comes into contact with the capstan after tape loading is completed during recording or playback, and during other operations such as fast forwarding, rewinding, and stopping. This detection operation is not performed, and therefore there is no risk of malfunction due to reflected light from the pinch roller during this time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of a tape slack detection circuit used in the device of the present invention, FIG. 2 is a plan view of essential parts of one embodiment of the device of the present invention, and FIG. 3 is a front view of the same. 1...Switch, 2...Photoelectric detection element, 5...
Capstan, 6...pinch roller, 8...magnetic tape.

Claims (1)

[Scope of utility model registration request] In a tape slack detection circuit in which a photoelectric detection element consisting of a light emitter and a photoreceptor installed near the pinch roller detects tape slack by detecting reflected light from the tape, the tape is connected to the power supply path of the detection circuit. This tape slack detection device is characterized in that a switch that is turned on in conjunction with the loading operation is inserted so that the tape slack detection operation is performed almost simultaneously when the pinch roller is pressed against the capstan after loading is completed.