JPH1097745A - End detector of magnetic tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an end detector of a magnetic tape which is easily built into the main substrate of a video cassette recorder and is capable of preventing the scattering of the rays emitted from a light emitting element. SOLUTION: This end detector has the light emitting element 61 which emits rays, a prism 65 which divides the rays emitted from this light emitting element 61, a pair of prisms 31 which again reflect the rays reflected from this prism 65, a pair of light receiving elements 35 which receive the rays from these prisms 31 and a cylindrical holder 70 which receives the prism 65 through a pair of projecting parts 66 formed on the outer peripheral surface of the prism 65.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video cassette recorder (VCR), and more particularly, to a magnetic tape end detecting device for detecting a start end and / or an end of a magnetic tape.

[0002]

2. Description of the Related Art In a magnetic recording / reproducing apparatus such as a video cassette recorder, a magnetic tape is completely wound on a take-up reel or a supply reel in order to prevent the tape from being damaged due to a sudden stop when the tape running mechanism is operated. Previously, a device was needed to detect both ends (ie, start or end) of the magnetic tape.

For this reason, a magnetic tape used for a video cassette has transparent portions at a start end and an end end, and a VCR detects the start end and the end end on the magnetic tape. Device is provided.
Such an edge detection device stops the running operation of the tape by the microcomputer when detecting the transparent portions on both ends of the magnetic tape.

FIG. 1 is a schematic sectional view of a conventional magnetic tape end detecting device 10. As shown in FIG.

[0005] As shown in FIG.
Comprises a light-emitting sensor 20 and a light-receiving sensor 30.

The light emission sensor 20 has a light emitting element 21 for emitting a light beam and a prism 25 for separating the light beam emitted from the light emitting element 21. The light emitting element 21 is mounted on a printed circuit board (PCB),
Is provided to face the light emitting element 21 by being inserted into the opening 2 on the main substrate 1 and fastened to the main substrate 1. Further, the prism 25 with respect to the main substrate 1
In order to improve the fastening force, the prism 25 is provided with an aperture pad 26 extending outward from the outer peripheral surface thereof so as to be perpendicular to the central axis in the longitudinal direction. The pad portion 26 is attached to the main substrate 1 by being tightened by a set screw 3 through an opening (not shown) and a screw hole 4 formed in the main substrate 1.

The light receiving sensor 30 includes a pair of L-shaped prisms 31 for reflecting the light reflected from the prism 25 again, and a pair of light receiving elements 35 for receiving the light from the L-shaped prism 31. Each of the L-shaped prisms 31 is appropriately positioned on a main chassis (not shown) of the video cassette recorder to receive the light reflected from each prism 25 and to reflect the light to the light receiving element 35. . Each of the light receiving elements 35 is provided on the PCB and serves to receive the light beam reflected from the corresponding L-shaped prism 31.

With the above-described configuration, the magnetic tape end detecting device 10 includes the prism 25 and the pair of L-shaped prisms 3.
1 by detecting the difference in the amount of light passing through the running magnetic tape and outputting a start signal or an end signal to a microcomputer (not shown), thereby causing the tape to start or end. Is determined.

However, in such a conventional device, the prism may be damaged when the prism is fastened to the main substrate, and may be further damaged by dust existing in the surrounding air or on the surface of the light emitting element. Due to the attachment of such a foreign substance, there is an inconvenience that light emitted from the light emitting element is scattered.

[0010]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a magnetic tape end detecting device which can be easily incorporated into a main board of a video cassette recorder.

It is another object of the present invention to provide an apparatus for detecting the end of a magnetic tape that can prevent scattering of a light beam emitted from a light emitting element.

[0012]

According to a preferred embodiment of the present invention, a video cassette recorder includes a pair of first prisms and a pair of light receiving elements. A magnetic tape end detecting device for detecting an end of a magnetic tape running on a main substrate, wherein the light emitting element for emitting a light beam and the light beam emitted from the light emitting element are divided and corresponded. A second prism that reflects to each of the light receiving elements via the first prism, and fastening means for fastening the second prism to the main substrate;
The fastening means includes a pair of protrusions provided on an outer peripheral surface of the second prism, and a holder for receiving the second prism by inserting the protrusions therein. An apparatus for detecting an end of a magnetic tape is provided.

According to another preferred embodiment of the present invention, the end portion of the magnetic tape running on the main board, which has a pair of first prisms and a pair of light receiving elements, is incorporated in a video cassette recorder. An end detecting device for detecting a magnetic tape, wherein the light emitting device emits a light beam, and the light beam emitted from the light emitting device is split and reflected to each of the light receiving devices via the corresponding first prism. A second prism, and a fastening unit for fastening the second prism to the main substrate, wherein the fastening unit includes a pair of projections provided on an outer peripheral surface of the second prism; A holder for receiving the second prism by being inserted thereinto, preventing unnecessary external light from being incident on the second prism;
An apparatus for detecting the end of a magnetic tape, further comprising a light shielding means for preventing scattering of a light beam incident on the prism.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic tape end detecting device according to a preferred embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 2 is a schematic sectional view of a magnetic tape end detecting device 50 according to the present invention. Here, it should be noted that the same portions are denoted by the same reference numerals in the respective drawings for description.

The end detecting device 50 of the magnetic tape according to the present invention comprises a light emitting sensor 60, a substantially cylindrical holder 70 for stably fixing the light emitting sensor 60, and the light receiving sensor 30.

The light-emitting sensor 60 has a light-emitting element 61 for emitting a light beam and a prism 65 for separating the light beam emitted from the light-emitting element 61. The light emitting element 61 is appropriately provided on a printed circuit board (PCB), and the prism 65 is fixed to the main substrate 1 using a holder 70 as described later, and is provided to face the light emitting element 61. Further, the prism 65
A pair of protrusions 66 tapered along the central axis in the longitudinal direction of the prism 65 is provided on the outer peripheral surface of the prism 65. In this case, each projection 66 is at a predetermined angle (for example, 180 °).
Facing.

The cylindrical holder 70 made of an elastic material has a hook portion 71 for engaging with the light splitting prism 65 and a C-chamfering main body portion 73 for fitting to the main substrate 1. As shown in FIG. 4, when the projection 66 of the prism 65 is inserted into the holder 70, the hook 71 is elastically deformed by the elasticity of the holder 70, thereby receiving the prism 65. Holder 70
Is, for example, an outsert molding method (outsert m
The main substrate 1 is formed by an old method. Further, the holder 70 may be made of another member. In this case, the holder 70 is attached to the main board 1 by inserting its lower end into the opening 2 of the main board 1.

As shown in FIG. 3, an annular guide surface 72 is formed at, for example, an introduction portion of the prism 65 (that is, an upper end portion of the holder 70) so that the prism 65 can be easily inserted into the holder 70. ing. More specifically, the diameter of the guide surface 72 is gradually reduced so that the lower end of the prism 65 can be smoothly inserted into the holder 70 without damaging the prism 65.

The inner diameter of the C-chamfer main body 73 is
The prism 6 is firmly fitted to the holder 70.
It is almost the same as the diameter of 5.

Incidentally, as shown in FIG.
Has a convex surface 67 for converging light rays emitted from the light emitting element 61, and the holder 70 shields unnecessary external light incident on the prism 65, and
It is preferable to further include a light shielding portion 74 for preventing scattering of a light beam incident on the prism 65 from 1. Here, the light shielding portion 74 extends downward from the lower end of the holder 70.

Referring again to FIG.
Are a pair of L-shaped prisms 31 for reflecting light rays reflected from the prism 65 again, and the L-shaped prisms 3
It has a pair of light receiving elements 35 for receiving the light beam reflected from 1. Each of the L-shaped prisms 31 receives a light beam reflected from each prism 65 and appropriately reflects the light beam toward each light receiving element 35 on a main chassis (not shown) of the video cassette recorder. Is located. Each of the light receiving elements 35 is mounted on the PCB so as to receive the light reflected from the corresponding L-shaped prism 31.

Thus, the magnetic tape end detecting device 50 of the present invention detects the difference in the amount of light transmitted through the running magnetic tape between the prism 65 and the pair of L-shaped prisms 31 and starts the operation. By outputting a signal or an end signal to a microcomputer (not shown), it is possible to determine whether the tape is at the beginning or end.

[0024]

Therefore, according to the present invention, the holder facilitates the mounting of the prism on the main substrate, reduces the possibility of damage to the prism, and blocks unnecessary external light incident on the light splitting prism. The end of the tape can be easily detected by preventing scattering of the light beam incident from the light emitting element.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a conventional magnetic tape end detecting device.

FIG. 2 is a schematic sectional view of a magnetic tape end detecting device according to the present invention.

FIG. 3 is a perspective view of a holder of the magnetic tape end detecting device according to the present invention.

FIG. 4 is a schematic cross-sectional view for explaining a process of assembling a prism incorporated in the apparatus of the present invention into a holder.

FIG. 5 is a sectional view of a magnetic tape end detecting device according to another preferred embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main board 2 Opening 3 Set screw 4 Screw hole 10 Conventional magnetic tape end detection device 20 Light emitting sensor 21 Light emitting element 25 Prism 26 Opening pad part 30 Light receiving sensor 31 L-shaped prism 35 Light receiving element 50 Magnetic tape of the present invention End detecting device 60 light emitting sensor 61 light emitting element 65 prism 66 tapered protrusion 67 convex 70 cylindrical holder 71 hook 72 guide surface 73 C chamfering body 74 light shielding

Claims (7)

[Claims] An apparatus for detecting an end of a magnetic tape which is incorporated in a video cassette recorder, has a pair of first prisms and a pair of light receiving elements, and detects an end of a magnetic tape running on a main substrate. A light emitting element that emits a light beam; a second prism that splits the light beam emitted from the light emitting element and reflects the light through the corresponding first prism to each of the light receiving elements; A fastening means for fastening to the main substrate, wherein the fastening means comprises: a pair of protrusions provided on an outer peripheral surface of the second prism; and An apparatus for detecting an end of a magnetic tape, comprising: a holder for receiving a prism. 2. The magnetic tape end detecting device according to claim 1, wherein the holder is formed in a substantially cylindrical shape. 3. The end of the magnetic tape according to claim 2, wherein a guide surface for facilitating insertion of the second prism into the holder is formed at an upper end of the holder. Part detection device. 4. Each of the projections is tapered along a central axis in a longitudinal direction of the second prism, and the holder is made of an elastic material so as to be elastically deformed when receiving the projection. 2. The magnetic tape end detecting device according to claim 1, further comprising a hook portion. 5. The end detection of a magnetic tape according to claim 1, wherein the second prism has a convex surface facing the light emitting element for converging a light beam emitted from the light emitting element. apparatus. 6. Preventing unnecessary external light from being incident on the second prism, and preventing the second light from the light emitting element.
2. The magnetic tape end detecting device according to claim 1, further comprising light shielding means for preventing scattering of a light beam incident on the prism. 7. The magnetic tape end detecting device according to claim 6, wherein the light shielding means is formed of a member extending downward from a lower end of the holder so as to surround the light emitting element. apparatus.