JPH07220325A - Detecting device for end of magnetic recording tape - Google Patents

Abstract

PURPOSE:To improve easiness of manufacturing by reducing the number of parts and unifying prisms belonging to each light receiving element and shapes of parts of holding parts of these parts. CONSTITUTION:Sensor holders 29, 30 (prism sensor holder) which holds light receiving sensors 27, 28 and fixes them at fixed positions on a chassis 23 are integrally formed with prisms 25, 26 using the same materials as the prisms 25, 26. Thereby, conventional fusing process for a prism is not required, and easiness of manufacturing is improved. Also, providing a holder of exclusive use for a prism is not required, and the number of parts can be reduced. Further, by providing integrally two prism parts which are optically independent each other in the prism sensor holders 29, 30 so that an angle 6 between each light receiving plane is made 180-alpha-beta, shapes of two prism sensor holders 29, 30 can be unified completely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording tape end detecting device used in a magnetic tape recording / reproducing device such as a video tape recorder.

[0002]

2. Description of the Related Art In a magnetic tape recording / reproducing apparatus such as a video tape recorder, the end of tape winding is detected by optically detecting transparent leader tapes provided at both ends of the magnetic recording tape.

FIG. 6 is a plan view showing a magnetic recording tape end detecting device using such an optical means, FIG. 7 is a side view thereof, and FIG. 8 is an exploded perspective view thereof.

In the figure, reference numeral 1 denotes a light emitting element such as an LED, which is constructed by providing light emitting portions in two opposite directions. Reference numerals 2 and 3 are prisms for refracting and reflecting the light of the light emitting element 1, and 4 and 5 are light receiving sensors for receiving the light refracted and reflected by the prisms 2, 3. Here, the light receiving sensor 4,
5 are fixed to predetermined positions on both ends of the chassis 6 by sensor holders 7 and 8, respectively. The prisms 2 and 3 are fixed on the chassis 6 by prism holders 9 and 10 independently of the light receiving sensors 4 and 5. Further, 11 is a holder for holding the light emitting element 1 and fixing it at a fixed position on the chassis 6.

In the tape end detecting mechanism having the above structure, the light of the light emitting element 1 is refracted and reflected by the prisms 2 and 3 as shown by the arrows in FIG.
Light on 5. When the tape is running, the tape T drawn from the reels 12 and 13 crosses the optical paths A1 and A2 between the light emitting element 1 and the prisms 2 and 3, and blocks the light paths. Then, when one of the leader tapes at the end of the tape appears, the light path on the corresponding side is unblocked, and the light from the light emitting element 1 passes through the prism (2 or 3) on one side and the light receiving sensor (4 or 5). The end of the tape is detected by receiving the light at, and the tape running is stopped.

By the way, in such a tape end detecting mechanism, due to various design restrictions, the light emitting element 1 and the light receiving sensors 4 and 5 have their optical paths A1 and A2 at the reference line X (reference on the chassis 6). Same angle (α =
It may not be possible to arrange so as to be β). in this case,
The prism holders 9 and 10 are required to have different prism mounting portions with different bending angles, that is, two prism holders 9 and 1 having different shapes.
0 must be manufactured separately.

Further, the prisms 2 and 3 need to be attached to the prism holders 9 and 10 by welding, which is difficult to manufacture.

Further, since the light receiving sensors 4 and 5 and the prisms 2 and 3 are individually held by dedicated holders 7, 89 and 10, there is a problem that the number of parts is increased.

[0009]

As described above, the conventional
In a magnetic recording tape end detection device using optical means, if the light emitting element and each light receiving element cannot be arranged so that both optical paths are at the same angle with respect to the reference line on the chassis, It is necessary to use different holders for the corresponding prisms,
There is a problem that the manufacturing cost is increased accordingly. Also,
Since the prism needs to be welded to the holder, it is inferior in manufacturability. Further, since the light receiving element and the prism are individually held by dedicated holders, there is a problem that the number of parts is increased.

The present invention is intended to solve such a problem, and improves the manufacturability by reducing the number of parts and making the shapes of the prisms associated with each light receiving element and the parts of these holding parts identical. It is an object of the present invention to provide a magnetic recording tape end detecting device that can be designed.

[0011]

In order to achieve the above-mentioned object, a magnetic recording tape end detecting device according to the present invention is configured so that light is emitted from a predetermined position on the surface of each magnetic recording tape pulled out from two tape rolls. When the light emitting means for irradiating the light and one of the light transmitting portions provided at both ends of the magnetic recording tape are pulled out from the one tape winding body, the light of the light emitting means transmitted through the light transmitting portion is received. A first light receiving element of
A second light receiving element for receiving the light of the light emitting means transmitted through the light transmitting portion when the other light transmitting portion provided at both ends of the magnetic recording tape is pulled out from the other tape winding body; , A first prism that refracts and reflects light that has passed through one of the light transmitting portions to enter the first light receiving element, and refracts and reflects light that has passed through the other light transmitting portion to the second light receiving element. A second prism that allows light to enter, a first holding unit that holds the first light receiving element and fixes the first light receiving element at a predetermined position, and is integrated with the same material as the first prism, and a second light receiving element. And a second holding portion which is made of the same material as the second prism and is integrated with the second prism for holding and fixing the same at a predetermined position.

The first prism and the second prism are formed by integrating two optically independent prism parts, and the angle formed by the light-receiving surfaces of the two prism parts is equal to the light emitting element. And a first straight line connecting the first light receiving element and a second straight line connecting the light emitting element and the second light receiving element are equal to each other.

[0013]

That is, in the present invention, the first holding portion and the second holding portion for holding the first and second light receiving elements and fixing them in place are made of the same material as the prism, respectively. Since it is molded integrally with the prism, the conventional prism welding process is unnecessary, and the manufacturability is improved. Further, it is not necessary to provide a holder dedicated to the prism, and the number of parts can be reduced.

Further, two optically independent prism parts are integrated to form a first prism and a second prism, and an angle formed by each light receiving surface of the two prism parts is the light emitting element and the first prism. The first straight line connecting the light receiving element and the second straight line connecting the light emitting element and the second light receiving element are equal to each other, so that the angle between the two prisms and the holding portion is The shapes can be made completely the same, and the productivity can be further improved.

[0015]

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

FIG. 1 is a plan view showing the structure of a magnetic recording tape end detecting device used in a magnetic tape recording / reproducing device such as a video tape recorder according to an embodiment of the present invention, and FIG. 2 is a side view thereof. 3 is an exploded perspective view thereof.

In the figure, reference numeral 21 denotes a light emitting element such as an LED, which is constructed by providing light emitting portions in two opposite directions. Reference numeral 22 is a holder for holding the light emitting element 21 and fixing it at a fixed position on the chassis 23. This holder 2
2 is fixed on the chassis 23 by screws 24. Reference numerals 25 and 26 are prisms for refracting and reflecting the light of the light emitting element 21, respectively. 27 and 28 are prisms 25,
It is a light receiving sensor that receives and detects the light refracted and reflected by 26. Further, reference numerals 29 and 30 denote sensor holders (prism / sensor holders) for holding the light receiving sensors 27, 28 and fixing them at fixed positions on the chassis 23. The sensor holders 29 and 30 are formed integrally with the prisms 25 and 26 by using the same material as the prisms 25 and 26, and are fixed in place on the chassis 23 by screws 31.

FIG. 4 is a view showing the details of the integrally formed prism / sensor holder. FIG. 4 (a) is a plan view of the prism / sensor holder as seen from above, and FIGS. 4 (b) and 4 (c) show (a) in two directions. It is the side view seen from the side surface.

In the figure, 41 is a base portion, 42 is a screw hole formed in the base portion 41, and 43 is a light receiving sensor 2.
It is a sensor holding hole portion that holds 7, 28. And 44
Is a prism part (25, 26). Prism part 44
As is clear from (a) and (b), is optically independent having a substantially V-shaped plane sectional shape, a trapezoidal longitudinal sectional shape, and a parallelogram lateral sectional shape. The two prism parts 44a and 44b are connected to each other so that each light receiving surface corresponding to the base of the trapezoid has a predetermined angle θ. The angle θ formed by each light receiving surface is set as follows.

In FIG. 1, the light path from the light emitting element 21 to one light receiving sensor 27 is A1, the light path from the light emitting element 21 to the other light receiving sensor 28 is A2, and the reference X coordinate axis on the chassis 23 is the reference line X. Assuming that the angle between the optical path A1 and the reference line X is α and the angle between the optical path B2 and the reference line X is β, the angle θ formed by each of the light receiving surfaces is set to 180-α-β.

As a result, the prism / sensor holder can be used as it is as a holder for holding both the left and right light receiving sensors 27, 28 as the left and right prisms 25, 26. That is, on each of the left and right sides, each prism component 4 shown in FIG.
Each of the light receiving surfaces 4a and 44b has a corresponding light path A.
1, the prism / sensor holder may be screwed onto the chassis 23 so as to be perpendicular to A1 and A2.

In the magnetic recording tape end detecting device having the above construction, the light from the light emitting element 21 is refracted and reflected by the prisms 25 and 26 as shown by arrows in FIG. Enter into. When the tape is running, the tape T drawn from each reel 51, 52 crosses the optical paths A1, A2 between the light emitting element 21 and the prisms 25, 26, and blocks the light paths. When one of the leader tapes at the end of the tape appears, the light path on the corresponding side is unblocked, and the light from the light emitting element 21 passes through the prism (25 or 26) on one side and the light receiving sensor (29 or 30) is detected. The end of the tape is detected by receiving the light at, and the tape running is stopped.

Thus, the magnetic recording tape end detecting device of this embodiment provides the following effects.

A sensor holder 2 for holding the light receiving sensors 27, 28 and fixing them in place on the chassis 23.
Since the prisms 9 and 30 are formed integrally with the prisms 25 and 26 by using the same material as the prisms 25 and 26, the conventional prism welding process is not required, and the productivity is improved. Further, it is not necessary to provide a holder dedicated to the prism, and the number of parts can be reduced.

Prism sensor holder 29, 30
And two optically independent prism parts 44a, 44
The angle θ between b and b is 180-α-
Since the prisms and sensor holders 29 and 30 are integrally formed so as to have β, the two prism / sensor holders 29 and 30 can have exactly the same shape, and the productivity can be further improved.

Next, another embodiment of the present invention will be described.

The prism sensor holder of the previous embodiment is constructed by integrating two optically independent prism parts together with the holder, but as shown in FIG. 5, a single prism is combined with the holder. It may be configured integrally. In this case, the prisms 64 and 65 of the prism / sensor holders 61 and 62 are arranged on the left and right sides, respectively.
Although it is necessary to manufacture two types of prism / sensor holders, the prism and sensor holders are integrated, the conventional prism welding becomes unnecessary, and at least the effect of reducing the number of parts can be obtained. ..

[0028]

As described above, according to the end detection device for a magnetic recording tape of the present invention, the first holding portion and the first holding portion for holding the first and second light receiving elements and fixing them in place. Since the two holding portions are formed integrally with the prism by using the same material as that of the prism, the conventional prism welding step is not required, and the productivity is improved. Further, it is not necessary to provide a holder dedicated to the prism, and the number of parts can be reduced.

Further, two optically independent prism parts are integrated to form a first prism and a second prism, and the angle formed by each light receiving surface of the two prism parts is the light emitting element and the first prism. The first straight line connecting the light receiving element and the second straight line connecting the light emitting element and the second light receiving element are equal to each other, so that the angle between the two prisms and the holding portion is The shapes can be made completely the same, and the productivity can be further improved.

[Brief description of drawings]

FIG. 1 is a plan view showing the configuration of a magnetic recording tape end detecting device used in a magnetic tape recording / reproducing device such as a video tape recorder according to an embodiment of the present invention.

FIG. 2 is a side view of an end detection device for the magnetic recording tape of FIG.

FIG. 3 is an exploded perspective view of an end detection device for the magnetic recording tape of FIG.

FIG. 4 is a diagram showing details of a prism sensor holder in the end detection device for the magnetic recording tape of FIG.

FIG. 5 is a diagram showing details of a prism sensor holder according to another embodiment of the present invention.

FIG. 6 is a plan view showing a conventional magnetic recording tape end detection device.

FIG. 7 is a side view of the end detection device for the magnetic recording tape of FIG.

FIG. 8 is an exploded perspective view of the end detection device for the magnetic recording tape of FIG.

[Explanation of symbols]

21 ... Light emitting element, 22 ... Holder, 25, 26 ... Prism, 27, 28 ... Light receiving sensor, 29, 30 ... Sensor holder (prism / sensor holder), 41 ... Base part
42 ... screw hole part, 43 ... sensor holding hole part, 44 ... prism part, 44a, 44b ... prism part.

Claims (2)

[Claims] 1. A light emitting means for irradiating light from a predetermined position onto the surface of each magnetic recording tape pulled out from two tape rolls, and one light transmitting portion provided at both ends of the magnetic recording tape. A first light receiving element for receiving the light of the light emitting means transmitted through the light transmitting part when the tape is pulled out from one of the tape winding bodies, and the other provided on both end portions of the magnetic recording tape. When the light transmitting portion of the other is pulled out from the other tape winding body, the second light receiving element for receiving the light of the light emitting means transmitted through the light transmitting portion and the one light transmitting portion are transmitted. A first prism that refracts and reflects light to enter the first light receiving element, and a second prism that refracts and reflects light that has passed through the other light transmitting portion to enter the second light receiving element. Holding a prism and the first light receiving element A first holding unit that is made of the same material as the first prism and is fixed to a fixed position, and a second holding unit that holds the second light receiving element and fixes the second light receiving element to a predetermined position. An end detection device for a magnetic recording tape, comprising: a prism and a second holding part which is made of the same material and is integrated. 2. The magnetic recording tape end detection device according to claim 1, wherein the first prism and the second prism are each formed by integrating two optically independent prism parts. The angle formed by each light receiving surface of the two prism components is a first straight line connecting the light emitting element and the first light receiving element and a first straight line connecting the light emitting element and the second light receiving element. An end detection device for a magnetic recording tape, which is equal to the angle formed by the straight line of 2.