JP3017644U - Tape end detecting device in magnetic recording / reproducing apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] A tape end detection device for detecting a transparent leader tape provided at the end of a magnetic tape, and a reliable tape end detection operation that does not malfunction due to external light. The purpose is to get it done. A tape end detection device of a magnetic recording / reproducing apparatus, which detects when a transparent part of an end of a tape mounted on a magnetic recording / reproducing apparatus reaches a predetermined position, emits light for detecting the transparent part. Element 25 and light receiving elements 26a, 2
6b is provided, and the light receiving element 25 and the light emitting element 2 are provided.
6a and 26b are arranged on the same wiring board 23.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a tape end detecting device in a magnetic recording / reproducing device for detecting a transparent leader tape provided at an end of a magnetic tape.

[0002]

[Prior art]

 Conventionally, as a tape end detecting device in a magnetic recording and / or reproducing machine, a light emitting element and a light receiving element are provided at positions facing each other with a tape sandwiched between them, and a magnetic tape is provided at a detection position between these elements and intersecting with the tape. In some cases, when a transparent leader tape at the end arrives, the light from the light emitting element is transmitted through this leader tape and is received by the light receiving element, whereby the beginning or end of the tape is detected.

An example of such a tape end detecting device is shown in FIG. 5, for example. This tape end detecting device is provided with an optical switch including an LED 25 which is a light emitting element and a phototransistor 26 which is a light receiving element. In this optical switch, if the tape 45 located between the LED 25 and the phototransistor 26 is an opaque magnetic tape portion, the light 40 emitted from the LED 25 is blocked by this tape 45, so that the phototransistor 26 is It is kept off, and the output terminal 42 holds high level. On the other hand, in the optical switch, when the transparent leader tape portion connected to the end of the tape 45 arrives, the light 40 from the LED 25 is transmitted through this and enters the phototransistor 26 to be turned on. Therefore, the output terminal 42 becomes low level, and the tape end is detected there. In this type of tape end detecting device, the light emitted from the LED 25 is continuous light having a constant illuminance.

[0004]

[Problems to be solved by the device]

 However, in the above-mentioned conventional technique, since the light emitting element is continuously driven, in order to reliably detect the edge of the tape because the light emission illuminance is weak, a holder is erected on the wiring board, and the light emitting element is attached to the holder. Must be placed at approximately the same height as the wiring board, and when processing and assembling the wiring board, it is easy to damage the holder protruding from the board and wiring is required to connect the light receiving element provided on the deck chassis to the wiring board. There were structural and assembly problems.

[0005]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention provides a tape end detecting device for a magnetic recording / reproducing apparatus, which detects when a transparent portion of the end of a tape mounted on the magnetic recording / reproducing apparatus reaches a predetermined position. A light emitting element and a light receiving element for detecting the transparent portion are provided, and the light receiving element and the light emitting element are arranged on the same wiring board. Further, the wiring board is provided on the lower side of the chassis.

[0006]

[Action]

 The present invention is directed to a tape end detecting device of a magnetic recording / reproducing apparatus for detecting when a transparent part of an end of a tape mounted on a magnetic recording / reproducing apparatus reaches a predetermined position. Since the light emitting element and the light receiving element for detection are provided and the light receiving element and the light emitting element are disposed on the same wiring board, the wiring assembling work is easy and the production efficiency can be improved. . Further, since the wiring board is provided on the lower side of the chassis 2, the distance from the light emitting element to the light receiving element is shortened, so that malfunction can be further reduced.

[0007]

【Example】

 Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 shows a main part of a video deck 10 equipped with a tape end detecting device 11 of the present invention. The VCR 10 has a chassis 16 capable of receiving and storing the video cassette 15 guided by a guide (not shown), and a central prism 17 for guiding the pulsed light 13 is erected at the center of the bottom of the chassis 16 so as to stand up. Side prisms 18 and 19 are provided on the sides of the. Inside the video cassette 15, there is provided a cassette tape 21 wound around two reels (not shown) and moving between the two reels.

A wiring board 23, which forms a control circuit for controlling the operation of the video deck 10 and a motor control circuit, is attached to the lower side of the chassis 16. An LED 25, which is a light emitting element, is provided above the center of the wiring board 23. The pulsed light 13 from the LED 25 bends through the central prism 17 fixed to the chassis 16 and is emitted to the left and right in the direction of an angle of 7 degrees with respect to the reference line. The pulsed light 13 divided into right and left passes through the inspection holes 15a and 15b inside the video cassette 15, passes through the transparent leader tape portions 21a and 21b at both ends of the video tape 21, and is further outside the inspection holes. The light enters the left and right side prisms 18 and 19 through 15c and 15d, and is received by phototransistors 26a and 26b, which are light receiving elements mounted on the wiring board 23. The path of the pulsed light 13 is shown by a broken line in the figure. That is, the LED 25 and the phototransistors 26a and 26b are arranged so as to face each other across the traveling path of the video tape 21, and the central prism 17 passes through the inspection holes 15a to 15d and is set at an angle that maximizes the light receiving efficiency. .

A drive circuit 31 for driving the LED 25 is shown in FIG. In FIG. 1, the LED 25 is connected to the DC power supply Vcc on the anode side via resistors R1 and R2, and is connected to the collector of the transistor 32 on the cathode side. The base of the transistor 32 is connected to the output terminal of the pulse generation circuit 35. Therefore, the transistor 32 operates so as to light only when the output of the pulse generation circuit 35 is high level. The LED 25 corresponds to the LED 25 in the video deck 10 shown in FIG. 1. The pulsed light 13 output from the LED 25 passes through the central prism 17 and is split into two light beams at the upper end thereof. It is directed to phototransistors 26a and 26b (represented by 26 when represented) via rhythms 18 and 19. However, in the present invention, the light emitted from the LED 25 is the pulsed light 13 having a waveform as shown in FIG. 3, and the pulse drive uses the characteristic that a large amount of current can flow as compared with the DC drive to raise the light emission level. .

FIG. 4 shows a detection circuit 37 that outputs a predetermined detection signal when the pulsed light 13 having a predetermined frequency enters the phototransistor 26a. In FIG. 4, the collector of the phototransistor 26 is connected to the DC power supply Vcc, while the emitter is grounded via the load resistor RL and the non-inverting via the high pass filter composed of the capacitor C1 and the resistor R2. Connected to the positive (+) input of the type comparator 38. The minus (-) input of the comparator 38 is connected to the plus (+) input via the resistor R1, and is also connected to the reference voltage setting circuit composed of the capacitor C2 and the resistors R4 and R3. That is, the reference voltage at the point a is divided by the resistors R1 and R2 and is also applied to the point b, whereby the threshold level of the hysteresis value addition type is set. A similar detection circuit is also provided in the phototransistor 26b.

Next, the operation will be described. First, when the power of the VCR is turned on, a pulse signal is output from the pulse generation circuit 35 shown in FIG. 2, and the LED 25 is operated as shown in FIG. 3 by the action of the transistor 32 which receives this pulse signal and performs a switching operation. It outputs the pulsed light 13 having a different waveform. This pulsed light passes through the central prism 17 shown in FIG. 1, is split into two lights at its upper end and is directed to the two lateral prisms 18 and 19, but when the video tape 21 does not reach the end, Since the video tape 21 located at the position of the inspection hole 15a or 15b blocks this light, it does not reach the phototransistors 26a and 26b.

Next, when the tape reaches the end, the transparent lead tape portion connected to the end of the tape reaches the position of the inspection hole 15a or 15b, and the light from the central prism 17 passes through it through the side prism. 18 or 19 is reached through which either one of the phototransistors 26a or 26b operates. Here, since the light incident on the phototransistor 26a or 26b is the pulsed light as shown in FIG. 3, the phototransistor 26 also turns on and off in a pulsed manner, and is obtained by this on / off. The pulse signal is detected by the detection circuit 37 shown in FIG.

Now, assuming that pulsed light of a predetermined frequency is incident on the phototransistor 26, a pulse signal corresponding to this pulsed light appears at the emitter of the phototransistor 26. This pulse signal passes through a high pass filter that is set to pass a signal of that frequency, and is supplied to the + input of the comparator 38. When the level of this input signal is higher than the reference voltage at point b, the comparator 38 outputs an H level output signal to its output end, and this signal is used as a tape end detection signal to control the substrate 23. Sent to the circuit. Further, when light of a predetermined frequency or less enters the phototransistor 26, the output signal of the phototransistor 26 corresponding to this is removed by the high-pass filter, so that the output state of the comparator 38 does not change. In this way, the output signal can be made more accurate by making the tape end detection signal only when the pulsed light of a specific frequency is received.

By pulse-driving the LED 25, the light emission illuminance of the LED is increased in accordance with the duty ratio of the pulse, as compared with the case of direct-current driving with the same current value, and pulse driving is further performed as compared with direct current driving. Since the maximum allowable peak current increases, the current value can be set to a high value. Therefore, even if the distance between the LED 25 and the phototransistor 26 is increased by using the light guiding prism, the operation of the phototransistor can be performed more reliably. The advantage is obtained.

[0015]

The present invention has the following effects. The present invention is directed to a tape end detecting device of a magnetic recording / reproducing apparatus for detecting when a transparent part of an end of a tape mounted on a magnetic recording / reproducing apparatus reaches a predetermined position. Since the light emitting element and the light receiving element for detection are provided and the light receiving element and the light emitting element are disposed on the same wiring board, the wiring assembling work is easy and the production efficiency can be improved. . Further, since the wiring board is provided on the lower side of the chassis 2, the distance from the light emitting element to the light receiving element is shortened, so that malfunction can be further reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a main part of a video deck to which a tape end detecting device according to an embodiment of the present invention is applied.

FIG. 2 is a circuit diagram showing an LED drive circuit of the tape end detection device shown in FIG.

FIG. 3 is a waveform diagram of pulsed light output from the LED drive circuit shown in FIG.

4 is a circuit diagram showing a detection circuit of the tape end detection device shown in FIG.

FIG. 5 is a circuit diagram of a conventional tape end detecting device.

[Explanation of symbols]

 10 video deck (magnetic recording and / or reproducing device) 11 tape end detection device 13 pulsed light 15 video cassette 17 central prism 18, 19 side prism 21a lead tape portion 25 LED (light emitting element) 26a, 26b phototransistor (light receiving element) ) 35 pulse generation circuit 38 comparator

Claims (2)

[Scope of utility model registration request] 1. A tape end detecting device of a magnetic recording / reproducing apparatus for detecting when a transparent part of an end portion of a tape mounted on a magnetic recording / reproducing apparatus arrives at a predetermined position. And a light-receiving element, and the light-receiving element and the light-emitting element are arranged on the same wiring board. 2. The tape end detecting device in the magnetic recording / reproducing apparatus according to claim 1, wherein the wiring board is provided on a lower side of the chassis.