JPS63317995A - Tape cartridge and its prism forming method - Google Patents

Abstract

PURPOSE:To simplify the forming metallic die structure and the mirror surface processing of an incident side transmitting face by prolonging a part of a prism having the incident side transmitting face up to the inside of a detection hole and forming the incident transmission face and the outer face of the side wall so as to be nearly mated to each other. CONSTITUTION:A prism 9 is formed secondarily as soon as a window plate is formed to an upper case 1a. In this case, a slide core 22 for detection hole forming is retrogressed toward the S and its end face 22c is fixed so as to be mated with an outer face of the side wall 17. In retrogressing the slide core 22, a cavity forming a horizontal part 9a of the prism 9 is formed between the upper case 1a and the core block 23, a seal of a prism forming recessed part 28 is opened to attain the secondary forming. A transparent resin is filled in the cavity and recessed part 28 to form the prism 9 incorporated with the window plate is formed integrally with the upper case 1a. The incident side transmission face 11 of the horizontal part 9a of the prism 9 is formed into the mirror surface at the end face 22c of the slide core 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tape cartridge incorporating a prism for optically detecting tape ends, etc., and a method for molding the prism.

[Conventional technology]

Conventionally, tape cartridges incorporating this type of prism have been known, such as those shown in FIGS. 7 to 9 (for example, Japanese Patent Application Laid-open No. 71077/1983). There, a digital recording/playback type audio tape cartridge is shown, the main body case 1 of which is formed by abutting upper and lower plastic cases 1a and 1b and integrally connecting them with screws or the like. Hubs 4, 4 are rotatably arranged on the left and right sides inside the main body case 1, and a magnetic tape 5 is connected and wound around each hub 4, 4 via a translucent glue.

On the front side of the main body case 1, tape outlet ports 6, 6 are formed on the left and right sides, and a pocket 7 for tape loading is formed between the tape outlet ports 6, 6, and a pocket 7 is formed on the side closer to the pocket in each tape drawer 6. It has a tape guide member 8. The tape 5 is led out from one hub 4 through a tape outlet 6 at the front to a pocket 7 on the front of the case, passes through the other tape outlet 6, and is wound onto the other hub 4 located behind it.

Inside the main body case 1, a prism 9 for detecting tape ends is arranged at a rear position of each tape guide member 8, respectively.

This prism 9 is integrally molded with a transparent window plate 10 provided on the upper case 1a, and is formed in an L-shape as shown in FIG. It has a vertical part 9b bent downward at a right angle from the inner end in the left-right direction of the part 9a. The horizontal portion 9a has an outer end surface in the left and right direction formed as the incident-side transmission surface 11, a 45-degree slope on the inner end side as the first reflective surface 12, and a 45-degree slope on the inner end side of the vertical portion 9b as the first reflective surface 12. The two reflective surfaces 13 are formed with a vertical surface on the outer end side as the output side transmitting surface 14, respectively.

On the other hand, there are detection holes 18 in the left and right side walls 17, 17 of the main body case 1.
- The openings 19 are arranged above and below so as to face the entrance-side transmission surface 11 and the exit-side transmission surface 14, respectively. tape 5
passes between the exit-side transmission surface 14 and the detection hole 19 facing thereto. With the tape cartridge loaded in the recorder.

The detection holes 18 and 19 are positioned to correspond to the light emitting element 20 and light receiving element 21 on the recorder side.

When you load the tape cartridge into the recorder.

Light emitted from the light emitting element 20 enters the entrance-side transmission surface 11 of the prism 9 via the detection hole 18 . This incident light is the first
The direction of the light beam is changed by 90 degrees on the reflective surface 12 and the second reflective surface 13, and exits from the output-side transmission surface 14 parallel to the incident light beam, and further passes through the tape 5 and exits from the detection hole 19 to the outside of the case. The light reaches the light receiving element 21 of the recorder (Il+), and depending on the light intensity there, it is detected whether it is the magnetic tape 5 or the transparent leader tape connected to the end of the magnetic tape 5, and the start or end of the magnetic tape 5 is detected.

Such a prism 9 has a very small shape when viewed from the entire tape cartridge. Therefore.

Assembling the upper case 1a into a predetermined position is very troublesome.

Regarding this point, it has been proposed that the prism 9 is integrally molded into the upper case 1a, thereby simplifying the assembly and eliminating the trouble.

[Problem that the invention seeks to solve]

However, in the conventional prism 9, the incident-side transmitting surface 11 is spaced inward from the case-inward end surface of the detection hole 18 (the inner surface of the side wall 17). Therefore, the distance between the light source of the light emitting element 20 and the incident-side transmission surface 11 of the prism 9 is increased by the distance between the bones and the depth of the detection hole 18, and the light from one light emitting element 20 enters the detection hole 18 straight. In this case, there is no problem, but two light-emitting elements 20 and detection hole 18
If there is even a slight positional deviation between the two, the efficiency of light incident on the incident side transmission surface 11 (the ratio of the amount of light emitted from the light emitting element 20 to the amount of light incident on the incidence side transmission surface 11) will be reduced, resulting in the worst case. In this case, the amount of light emitted from the light emitting element 20 is
It was difficult to detect the sensor because it was blocked by the periphery of the sensor, or it was easy to cause a detection error.

An object of the present invention is to prevent a decrease in the efficiency of incidence on the incident side transmission surface of the prism in a tape cartridge in which a prism is integrally molded inside a three-body case.

The purpose is to prevent detection errors.

An object of the present invention is to make the incident-side transmission surface of a prism mirror-finished and to simplify the structure of its molding die.

[Means for solving problems]

The prism 9 of the present invention has a part 9 having a transmission surface 11 on the incident side.
A is extended into the detection hole 18 of the case side wall 17, and the incident side transmission surface 11 is formed substantially flush with the outer surface of the side wall 17.

In addition, when the prism 9 is integrally molded into the main body case 1, the method of the present invention uses a slide core 22 for molding the detection hole 18.
This is characterized in that the entrance-side transmission surface 11 of the prism 9 is shaped in this manner.

〔Effect of the invention〕

According to the prism of the present invention, the incident-side transmission surface 11 faces the outer end surface of the detection hole 18, that is, the outer surface of the case side wall 17 so as to be substantially flush with it.

The incident side transmission surface 11 can be placed as close to the light emitting element 20 as possible than in a conventional prism in which the incident side transmission surface 11 is located inside the main body case 1. Further, the amount of incident light is not blocked by the periphery of the detection hole 18 of the side wall 17. Therefore, the incidence of light on the incident-side transmission surface 11 is improved, and the reliability of detection accuracy is excellent.

Further, according to the prism forming method of the present invention.

The entrance-side transmission surface 11 of the prism 9 is formed using the slide core 22 that forms the detection hole 18.

This is advantageous in that it is possible to obtain a transparent surface 11 that is almost a mirror surface without irregularities, and the mold structure can be simplified.

〔Example〕

1 to 6 show embodiments of the invention.

Since the overall structure of the tape cartridge is basically the same as that of the conventional example described above, the same reference numerals are given and the explanation thereof will be omitted, and the explanation will focus on the points that are different from the conventional Priz J3 described above.

In FIG. 3, a transparent window plate 10 and a prism 9 are integrally molded on the upper case 1a using a core-back two-color molding method. It is integrally formed at the front end of 10a.

As shown in FIGS. 1 and 2, this prism 9 has a horizontal portion 9a connected to the front end of a connecting plate 10a, and a vertical portion 9b integrally formed at right angles to the horizontal portion 9a. The outer end surface of the vertical portion 9b is set as the incident-side transmission surface 11, the 45-degree inclined surface on the inner end side is set as the first reflective surface 12, and the 45-degree inclined surface on the inner end side of the vertical portion 9b is set as the second reflective surface 13, and the outer end surface is set as the second reflective surface 13. The vertical planes on the end sides are respectively set as the emission side transmission planes 14 . What should be noted here is that the horizontal portion 9a is extended into the detection hole 18 so that the incident side transmission surface 11 is substantially flush with the outer surface of the side wall 17 of the main body case 1. .

In this way, the light emitted from the light emitting element 20 on the recorder side directly enters the incident side transmission surface 11 facing the outer surface of the case side wall 17 and the road surface. The incident light passes through the first reflective surface 1
The direction of the light beam is changed by 90 degrees at each of the second and second reflecting surfaces 13, and exits from the transmitting surface 14 in parallel to the incident light beam, passes through the tape 5, exits from the detection hole 19 to the outside of the case, and enters the recorder side. The light reaches the light receiving element 21.

Next, a specific example of a prism molding method using a core-back two-color molding method will be described with reference to FIGS. 5 and 6.

As shown in FIG. 6fa), during the primary molding of the upper case 1a, a slide core 26 for molding the vertical portion of the prism 9.
Slide core 22 for forming detection holes. Core block 23.
A cavity 25 is formed with the lower die 24 and the upper case 1a having the side wall 17 and the detection holes 18 and 19 is formed by filling the cavity 25 with resin.

The slide core 22 for forming the detection hole has a protrusion 22a that forms the detection hole 19 of the case side wall 17, and a long protrusion 22b that forms the detection hole 18. As shown in FIG.
The central slide core 27 that intervenes in the middle is pushed forward in the direction of arrow F, and as shown in FIG.
By abutting against a part of the end surface 22C of the slide core 26, the resin is prevented from flowing into the prism molding recess 28 of the slide core 26.

Next, the prism 9 is secondarily formed on the upper case 1a at the same time as the window plate 10. At this time, as shown in Figure 6 (bl),
The slide core 22 for forming the detection hole is moved back in the direction of arrow S and stopped so that its end surface 22G is flush with the outer surface of the side wall 17.

By retreating the slide core 22, a cavity 29 for forming the horizontal portion 9a of the prism 9 is formed between the upper case 1a and the core block 23.
), the seals of the four prism molding parts 28 are opened, allowing secondary molding. By filling the cavity 29 and the recess 28 with transparent resin, the window plate 1
A prism 9 integral with the upper case 1a is molded integrally with the upper case 1a.

The incident-side transmission surface 11 of the horizontal portion 9a of the prism 9 is formed into a mirror surface by the end surface 22c of the slide core 22.

Note that when the mold is opened after secondary molding, the central slide core 27 in FIG. The undercasing to be molded comes off and can be ejected.

Fig. 10 f8), (b), and (C1 show the process order of the method of forming the prism 9 studied before completing the present invention. The horizontal part 9a of the prism 9 in this case is shown in Fig. 10. (As shown in C1, the incident side transmission surface 11 is shaped to be in contact with the inner surface of the case side wall 17.
As shown in FIG. 10(a), the entire end face 22C of the slide core 22 is brought into contact with the core block 23 during primary forming, and the core block 23 is retreated during secondary forming as shown in FIG. 10(b). Since the mold structure is adopted, the end face 22C of the slide core 22 that forms the incident side transmission surface 11 is easily scratched by rubbing against the core pro tack 23, which causes unevenness on the input side transmission surface 11. It was a disadvantage.

In this respect, according to the mold structure of the present invention described above.

Since the end surface 22c of the slide core 22 only needs to slightly abut against the slide core 26 having the concave portion 28, there is no problem of scratches on the end surface 22C, and the incident side transmission surface 1
1 could be formed into a mirror surface, which was advantageous.

[Brief explanation of drawings]

1 to 4 illustrate a tape cartridge according to the present invention. FIG. 1 is a sectional view taken along the line A-A in FIG. 3. FIG. 2 is a perspective view mainly showing the prism. FIG. 3 is a plan view showing the inner surface of the upper case. FIG. 4 is a sectional view taken along the line BB in FIG. 3. FIGS. 5 and 6 show the structure of a prism mold for carrying out the method of the present invention. Figure 5 is a plan view. Figure 6 (al and fbl are cross-sectional views taken along the line C-C in Figure 5;
1 indicates the secondary molding state. 7 through 9 show conventional tape cartridges. FIG. 7 is an external perspective view. FIG. 8 is an internal plan view of the upper case showing the assembled state. FIG. 9 is a sectional view taken along the line DD in FIG. 8. Figure 10+al・(b)・(C1 shows a comparative example. Figure 10(a) is a cross-sectional view of the prism in the primary molding state. Figure 10(g)) is the prism in the secondary molding state. A cross-sectional view. FIG. 10(C) is a sectional view mainly showing the prism after molding. 1... Main body case. 1a... Upper case. 1b...lower case. 4...Hub. 5...Tape. 9... Prism. 9a...Horizontal part of the prism. 9b... Vertical part of the prism. 10...Window board. 11...Incidence side transmission surface. 14... Output side transmission surface. 17... Side wall of the main case. 18...Detection hole. 19...Detection hole.

Claims (2)

[Claims] (1) A detection hole 18 is provided in the side wall 17 of the main body case 1, and a prism 9 is provided inside the main body case 1 to change the course of light entering from the detection hole 18 and output it to the outside of the case.
However, the part 9a having the incident side transmission surface 11 is connected to the detection hole 1.
A tape cartridge characterized in that the tape cartridge is formed so that the incident side transmission surface 11 and the outer surface of the side wall 17 are substantially flush with each other. (2) Main body case 1 having side wall 17 with detection hole 18
When integrally molding the prism 9 inside which changes the course of the light entering from the detection hole 18 and takes it out of the case,
A method for forming a prism for a tape cartridge, characterized in that the entrance-side transmission surface 11 of the prism 9 is formed by a slide core 22 forming the detection hole 18.