JP2503655Y2 - Tape cassette tape position detection mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a tape position detection mechanism of a tape cassette, and more particularly, to prevent erroneous detection of the tape position.

[Outline of the Invention] In the present invention, a prism is fixed in a tape cassette, and when a drive is mounted, the light of a light emitting portion under the cassette is reflected in the prism and emitted from an emission surface to an optical path to a light receiving portion on the front surface of the cassette. In the tape position detection mechanism configured to detect the tape position depending on whether or not the light of the light emitting section passes through the tape that crosses the optical path, the light of the light emitting section is reflected in a path different from the optical path, and a gap between the tape and the case is formed. By providing a cut surface for preventing the tape from passing through and penetrating into the light receiving portion below the exit surface facing the tape, erroneous detection of the tape position is prevented.

[Prior Art] Among tape cassettes, one having a high track density as an external recording device of a computer is known (US Pat. No. 3861619).

As shown in FIG. 3, the tape cassette 1 has a case 2 in which a pair of (supply / winding) reels 5 and 6 are rotatably provided. A tape running path 7 is formed between the pair of reels 5 and 6 so that the tape 8 wound around the reels 5 and 6 runs on the front surface side 1a of the cassette.
A drive belt is pressed against the outermost periphery of the tape 8 wound around the pair of reels 5 and 6, and the tape 8 is run by the movement of the drive belt 18 to which the driving force of the drive device 19 is transmitted.

The case 2 includes a plastic upper case portion 3a,
The base plate 4 is made of aluminum alloy. The base plate 4 supports the pair of reels 5 and 6. A mirror 21 as a tape position detecting mechanism is fixed to the base boot 4.

As shown in FIG. 4 as a mirror 21 of the tape position detecting mechanism, a light-transmitting window 4a is provided on the base plate 4, and an upright prism (a right-angled isosceles triangular prism shape) is provided so as to close the through-hole window 4a. It is considered that the one that adheres) is fixed. An entrance surface 22a forming an isosceles side of the prism 22 faces the translucent window 4a, and an exit surface 22b faces the running tape 8. The entrance surface 22a and the exit surface 22b intersect at a right angle, and the reflecting surface 22c is inclined at 45 °.

Then, when the drive is mounted, the light of the light emitting portion 24 arranged below the tape cassette 1 passes through the light transmitting window 4a, enters from the incident surface 22a, and is totally reflected by the reflecting surface 22c, and then the emitting surface.
An optical path 26 indicated by a chain line extending from 22b to the light receiving section 25
Is composed.

When such reflection of the prism 22 is used, there is no problem because a material having a high refractive index such as glass is likely to be totally reflected, but in a material having a low refractive index such as an acrylic resin, light is reflected on the reflecting surface. There is a problem that a sufficient amount of light is not received by the light receiving unit 25 because it does not undergo total reflection due to leakage from 22c to the outside.

Therefore, as shown in FIG. 5, it is conceivable to form a metal coating 23 such as a hot stamp on the reflecting surface 22c of the prism 22 made of acrylic resin or the like to increase the reflectance.

[Problems to be Solved by the Invention] The light emitted from the light emitting portion 24 is obliquely incident from the incident surface 22a due to an attachment error of the light emitting portion 24 to the drive device 19, an attachment error of the cassette tape 1 to the drive device 19, and the like. May be incident on.

In the case of the prism 22 made of a material having a low refractive index such as acrylic resin, most of the light thus obliquely incident on the incident surface 22a does not undergo total reflection as shown by the chain double-dashed line in FIG. Emits light to the outside from the reflecting surface and reflects a slight amount of light, but since the amount of light is very small, no problem occurs.

However, as shown in FIG. 5, in the prism 22 or the like in which the metal coating 23 is formed on the reflecting surface 22c, obliquely incident light indicated by a two-dot chain line is totally reflected by the metal coating 23, After traveling along a path 27 different from the optical path indicated by the one-dot chain line and reflecting again on the incident surface, it may be refracted at the lower part of the exit surface 22b, pass through the gap s between the tape 8 and the base plate 4, and be received by the light receiving section 25. Occur. In this way
Since the path 27 of the light received by 25 does not cross the tape 8, there is a problem that the tape position is erroneously detected.

The present invention has been devised to solve the above problems, and an object thereof is to prevent erroneous detection of a tape position.

[Means for Solving the Problems] The present invention provides a drive device having a light emitting portion on a lower surface of a cassette mounting portion and a light receiving portion on a front surface thereof, and a lower portion in a case of a tape cassette mounted on the cassette mounting portion. The prism is fixed, the light of the light emitting portion is incident from the incident surface of the prism and is reflected by the reflecting surface thereof, and then an optical path that exits from the exit surface and reaches the light receiving portion is configured, and a tape that crosses the optical path is formed. In a tape position detection mechanism that detects the tape position by whether or not the light of the light emitting portion is transmitted, the light emitted from the light emitting body is reflected in a path different from the optical path in the prism, and a gap between the tape and the case is generated. The configuration is such that a cut surface that prevents the light from passing through and entering the light receiving portion is provided at an end portion on the gap side of the emission surface facing the tape.

[Operation] The light emitted from the light emitting unit and obliquely incident on the incident surface is reflected by the reflecting surface, is reflected again by the incident surface, and travels below the exit surface. And is reflected again and travels in a direction different from the gap between the tape and the cassette.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

As shown in FIG. 1, the tape cassette 1 has a rectangular case 2. The case 2 includes a box-shaped upper case portion 3 made of transparent plastic and a base plate 4 made of metal. The sidewalls 3a provided on the peripheral edge of the upper case portion 3 are screwed together while the lower surface of the side wall portion 3a is butted against the peripheral edge of the base plate 4.

A supply reel 5 and a take-up reel 6 are rotatably provided in the case 2. A tape running path 7 passing through the front side of the case 2 is formed between the supply reel 5 and the take-up reel 6. The supply reel 5 and the take-up reel 6
The tape 8 wound around the tape runs on the tape running path 7 by the tape running transmission mechanism 9.

A pair of large-diameter flanged guides 10 and 11 are provided at both ends of the tape running path 7 on the front side 1a of the cassette, and a straight guide pin 12 is provided between the pair of flanged guides 10 and 11. The two flanged guides 10 and 11 and the straight guide pin 12 are arranged linearly and are erected on the base plate 4. A head arrangement section L is formed between the flanged guide 10 and the straight guide pin 12 at the one end.

When the drive is mounted, a head (not shown) is pressed against the tape 8 running in the head arrangement section L. A pair of flanged guides 10 and 11 arranged at both ends of the cassette front side 1a are provided upright on the base plate 4.
The tape 8 is wound around the pair of flanged guides 10 and 11, and the traveling direction thereof is changed.

The head placement section L is composed of a tape exposing portion 14 where the tape 8 is exposed by cutting a part of the case 1. The exposed tape portion 14 is opened and closed by a cover 15. The cover 15 has a shape that covers the notched portion of the case 1, one end of which is rotatably supported by the base plate 4, and is biased to the closed position by the spring force of a coil spring (not shown). There is.

On the other hand, the tape traveling transmission mechanism 9 is provided with a corner roller 16 at the rear left and right corners inside the case 1 and a drive roller 17 at the cassette front side 1a. The drive roller 17 and the corner roller 16 are the base plate 4
It is rotatably supported by. The upper portion of the drive roller 17 has a large diameter portion 17a. A part of the large-diameter portion 17a projects from the opening 3b of the upper case portion 3, and when the tape cassette 1 is mounted on a drive device (not shown), the rotational force is transmitted by the drive roller of the drive device.

An endless drive belt 18 is hung between the corner roller 16 and the drive roller 17. The portion of the drive belt 18 located between the drive roller 17 and the respective corner rollers 16 is pressed against the outermost periphery of the tape 8 wound around the supply reel 5 and the take-up reel 6, and the rotational force of the drive roller 17 is increased. The frictional force between the drive belt 18 and the tape 8 is transmitted to the tape 8, and the tape 8 travels along the tape running path 7.

A tape position detecting mechanism 21 for detecting the tape position is provided in the tape cassette 1. The tape position detecting mechanism 21 includes a prism 22 inside the case 2. The prism 22 is fixed to the upper surface of the transparent window 4a formed on the base plate 4 and closes the transparent window 4a. On the drive device side where the tape cassette 1 is mounted, a light emitting section 24 is provided below the cassette mounting section,
A light receiving unit 25 is provided on the front side.

The transparent window 4a is formed in a rectangular shape, and a pair of locking grooves 4b is formed on both sides of the transparent window 4a.

The prism 22 is an upright prism of isosceles right triangular prism shape made of acrylic resin. The entrance surface 22a and the exit surface 22b of the prism 22 intersect at a right angle, and the reflection surface
The 22c has an inclination angle of 45 °. A metal coating 23 is formed on the surface of the reflecting surface 22c.

As shown in FIG. 2, stoppers 22f that come into contact with the base plate 4 are formed on both sides of the prism 22. The lower surface of this stopper 22f has a locking protrusion 22g.
Are formed. Then, the incident surface 22 of the prism 22
The a is arranged in parallel with the upper surface of the base plate 4 while its periphery is in contact with the upper surface of the translucent window 4a and closes it. The locking projection 22g is fitted in the locking groove 4a, and the stopper 22f is in contact with the base plate 4 at the stopper 22f.

In FIGS. 1 and 2, the incident surface 22a faces the translucent window 4a, and the reflecting surface 22b faces the tape 8. The light emitted from the light emitting unit 24 passes through the light transmitting window 4a, enters from the incident surface 22a of the prism 22, is reflected at a right angle by the reflecting surface 22c, and exits from the emitting surface 22b, as indicated by a dashed line. Side wall 3a on the front side of the upper case 3 which emits light
An optical path 26 that passes through the optical path and reaches the light receiving section 25 is configured. The tape 8 runs so as to cross the optical path 26.

Predetermined holes or transparent portions are formed in the tape 8 at the tape end or its intermediate position, respectively.
The position of the tape is detected by whether or not the light crossing the light is received by the light receiving unit 25.

A cut surface 22d is formed at the end of the exit surface 22b of the prism 22 facing the tape 8 on the side of the gap s between the tape 8 and the case 2, that is, at the corner between the exit surface 22b and the entrance surface 22a. Has been done. The cut surface 22d is formed at about 45 to 60 degrees. As indicated by the chain double-dashed line, the light is emitted from the light-emitting portion 24 into the incident surface 22a obliquely and enters a path 27 different from the optical path 26.
Then, after being reflected by the reflecting surface 22c and then again by the incident surface 22a, the light receiving portion is received from the gap s between the tape 8 and the base plate 4.
The cut surface 22d is formed at an angle and a position at which all the light that travels to 25 is reflected.

Similar cut surfaces 22e are formed on both side surfaces of the reflecting surface 22c of the prism 22.

Next, the operation of the above embodiment will be described with reference to FIGS. 1 and 2.

When the tape cassette 1 shown in FIG. 1 is mounted in the cassette mounting portion of a drive device (not shown), as shown in FIG.
The light obliquely incident on 22a is totally reflected by the reflecting surface 22c, and then is reflected again by the incident surface 22c, and the optical path from the gap s between the tape 8 and the base plate 4 to the light receiving portion 25.
The light indicated by the alternate long and two short dashes line that travels on a path 27 different from 26 is reflected by the cut surface 22d and blocked.

Then, of the light emitted from the light emitting section 24, only the light that travels in the regular optical path 26 indicated by the alternate long and short dash line that is incident on the incident surface 22a at a substantially right angle and is reflected by the reflective surface 22c at a substantially right angle is the reflective surface 22b. Since it is possible to emit light from the tape 8 and travel across the tape 8 to the light receiving section 25, the light receiving section 25 does not cross the tape 8.
The light is prevented from being received by 25, and erroneous detection of the tape position such as the tape end and the intermediate position of the tape is prevented.

[Effects of the Invention] As is apparent from the above description, according to the present invention, the prism is fixed in the tape cassette, and when the drive is mounted, the light of the light emitting portion below the cassette is reflected in the prism and emitted from the exit surface. In the tape position detection mechanism that forms an optical path to the light receiving section on the front surface of the cassette and detects the tape position depending on whether the light from the light emitting section passes through the tape that crosses the optical path, the tape is located below the ejection surface facing the tape. Since the cut surface is provided, it is prevented that the light of the light emitting portion is reflected on a path different from the optical path, passes through the gap between the tape and the case, and enters the light receiving portion, thereby preventing erroneous detection of the tape position. effective.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is an explanatory view of the operation of a tape position detecting mechanism, FIG. 2 is an exploded perspective view of a tape cassette, and FIG. 3 is a conventional example. FIG. 4 is a partially cutaway plan view when the tape cassette is mounted on a drive, FIG. 4 is an explanatory view of the action of a prism, and FIG. 5 is an explanatory view of the action of another prism. 1 ... tape cassette, 2 ... case, 4 ... base plate, 8 ... tape, 22 ... prism, 22a ... reflective surface, 22b ... emission surface, 22c ... reflective surface, 22d ... cut surface, 24 …… Light emitting part, 25 …… Light receiving part, 26 …… Optical path.

Claims (1)

(57) [Scope of utility model registration request] 1. A light emitting section provided on a lower surface of a cassette mounting section and a light receiving section on a front surface of a drive device, wherein a prism is fixed to a lower surface in a case of a tape cassette mounted on the cassette mounting section. Light from the incident surface of the prism is reflected by the reflecting surface of the prism, then exits from the exit surface to form an optical path to the light receiving section, and whether the light of the light emitting section passes through a tape that crosses this optical path. In a tape position detection mechanism that detects the tape position depending on whether or not the light emitted from the light emitting unit is reflected in a path different from the optical path in the prism, passes through a gap between the tape and the case, and enters the light receiving unit. A tape position detecting mechanism for a tape cassette, characterized in that a cut surface for preventing this is provided at an end portion on the gap side of an ejection surface facing the tape.