JP2552862Y2 - Disc cartridge shutter - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shutter for a disk cartridge such as a magnetic disk, and more particularly to a shutter for a disk cartridge injection-molded from a synthetic resin.

[0002]

2. Description of the Related Art Generally, a disk-shaped recording medium such as a magnetic disk, an optical disk, and a magneto-optical disk is housed in a cartridge case 1 made of a synthetic resin having relatively high rigidity. A window for inserting a magnetic head or the like is opened when performing the above. A shutter is slidably mounted at the front of the cartridge case so that the window is opened only when necessary for dustproof purposes.

Conventionally, a shutter has been formed by punching a metal plate such as stainless steel and then bending it into a desired shape (a U-shaped cross section). The metal shutter since liable variations in quality, stainless even more than the sliding Kezukona is caused by the sliding with the synthetic resin cartridge
Since it is made of stainless steel, punching and bending processes are required, the number of processing steps is large, and the production cost is higher than other members. For these reasons, in recent years, shutters formed by injection molding of synthetic resin have been increasingly used. In order to obtain this shutter by injection molding, a POM (polyacetal) resin having low sliding resistance is considered to be optimal.

[0004]

However, when the shutter is made of a polyacetal resin, it is very difficult to print characters such as a maker name, a disc type, or a design on the resin. For example, after printing with a two-component curable ink (an ink that cures by blending two types of ink components), it is 10 to 20 at 120 ° C.
However, there is a problem that the shutter is deformed during the heat treatment, and no adhesion can be obtained with UV ink (a resin that is cured by irradiation of ultraviolet rays).

[0005] As another means, Japanese Patent Publication No. 4-22150 discloses a method by carving to represent a desired design. This involves uniformly mixing aromatic sulfonic acid capable of carving the polyacetal resin in the printing ink, printing this mixture on the surface of the polyacetal resin, and then heating it to design, etc. on this polyacetal resin surface. It is a method of chopping. Thus, this method must go through multiple steps,
Therefore, there is a problem that a long time is required for processing and productivity is low.

Although the shutter itself using the POM resin has advantages such as low cost and good productivity,
Since printing a design or the like requires a great deal of cost and labor, a method has been considered in which characters and designs are engraved in a molding die in advance, and these are transferred to a molded product and used as a substitute for printing. JP-A-61-105974, Jpn.
No. 67252).

However, Japanese Unexamined Utility Model Publication No. 4-67252 discloses a structure in which characters and symbols are formed on a glossy surface while the other portions are formed on a non-glossy surface. Such a configuration has a drawback that characters and symbols are poorly identified and are considerably inferior in design. In Japanese Utility Model Laid-Open Publication No. Sho 61-105974, letters and symbols having irregularities are simply integrally formed on the surface of a shutter.

[0008] However, the shutter to which the projection characters of the mold are transferred is originally thin, and as shown in FIG.
One of the members forming the mold is a thin plate member called a center core 5. As shown in FIG. 9, the deformation of the center core 5 easily occurs due to uneven local differences in the injection pressure. The unevenness of the injection pressure increases depending on the upper surface area and the depth occupied by the upper surface, and the thickness of the two flat plates is not uniform. Unless this problem is solved, the provision of uneven letters and symbols on the surface of the shatter results in lowering the formability and lowering the yield. This invention is, there is such has been made in view of the conventional problems, to be formed integrally with the character design of the mold at the mold, good molding without reducing the formability It is an object of the present invention to provide a shutter for a disk cartridge that can be used.

[0009]

The object of the present invention is to:
A U-shaped cross section including opposed front and rear flat plates for opening and closing a head insertion opening of a cartridge case for rotatably storing a disk, and end plates connecting one edge of each of the two flat plates. In the case of a synthetic resin disc cartridge shutter in which characters and designs are integrally displayed on the surface of a shutter, when a convex display body is engraved in advance on a molding die corresponding to the front side of the front surface plate and ejected. The height of the display body is h (μm), and the thickness of the flat plate is
t (μm), the plane area of the display body is S (mm ² ), the area of the display area of the display body is ws (mm ² ), and the molding reference value P represented by these conditions is represented by the following equation P = 3.5 × (h / t) × (S / WS), and the value of the molding reference value P is 0.01 to 0.125.
This is achieved by a disk cartridge shutter that is injection-molded in the range described above.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
1 to 6 show one embodiment of the present invention.
First, FIG. 4, FIG. 5, and FIG. 6 show a molded product according to the present embodiment, and illustrate a shutter of a 3.5-inch magnetic disk cartridge. 5 is a front view of the flat plate on the back side of the shutter 3, FIG. 6 is a front view of the flat plate on the front side of the shutter 3, and FIG. 4 is a side view as viewed from the right side in FIG.

4 to 6, opposed flat plates 4b (front side) and 4c (back side) are connected by an end face plate 4a. Usually, an engaging portion 17 of a spring (not shown) for sliding the shutter 3 in the cartridge case.
And small windows 15, 1 at the front end of the flat plate 4c to form sliding engagement portions 13, 14 with the cartridge case.
6 are provided. As described in the description of the prior art with reference to FIG. 9, since the engaging portion 17 and the sliding engaging portions 13 and 14 are formed by a mold, FIGS. 7 and 8 are sectional views thereof. Are present, and a cavity (injection space) B on the side where the protrusions are present (see FIG. 8)
In this case, since the molten resin injected from the gate 25 flows downward and increases the resin flow resistance, a large amount of the resin flows into the cavity A on the side having no protrusion, and the resin pressure in the cavity increases, and There is a pressure difference between them.
The opening area on the side A is 20% to 30% wider than the opening area on the side B.

However, in the present embodiment, as shown in FIG. 2, the projection 7 for the window and the display 6 are formed in a convex shape on the slide core 22 of the mold. Therefore, the character / design portion 30 is transferred to the flat plate 4b of the shutter 3 as shown in FIG. When the character / design part 30 is formed in a convex shape on the mold in this way, the resin flow resistance can be created as compared with the case where there is no character, depending on the area occupied by the character / design part 30 and the height of the character. it can.

Therefore, if the flow resistances of the two cavities B and A are balanced, the two flat plates 4b and 4 of the shutter are provided.
Although the thickness of c is uniform, as a practical matter,
The thickness of the center core 5 separating the two flat plates is 2.3 to
3.0 mm and the thickness of both flat plates after molding is 0.4
mm or less (300 μm to 380 μm), the injection pressure ranges from 1000 to 2000 kg / cm ² , while if the pressure between the two cavities differs by a few percent, the center core 5 is deformed by 50 μm and the thickness of the two flat plates 100μ difference
In this embodiment, a number of experiments were performed in an example before mass production, and the size of the character / design portion was strictly set based on the results.

Here, as a result of earnest research by the present inventors, the height h (μm) of the display body 6, the thickness t (μm) of the flat plate 4b,
The plane area S of the display body 6 (the area (mm ² ) of the upper end face of the display body in FIG. 3) and a rectangle surrounded by a, b, c, and d shown in FIG. Ws shape area
(mm ² ), in the shutter 3 molded under the above conditions by setting the value of P expressed by the following equation in a specific range, the thickness difference between the front and back flat plates 4a and 4b. Was kept in a good range, and a high-quality product could be obtained. P = 3.5 × (h / t) × (S / WS) In this specification, this P is referred to as a molding reference value. When the specific range of the molding reference value P expressed by the above equation is in the range of 0.01 to 0.125, a good molded product having a small difference in plate thickness between the two flat plates was obtained. Further, when the molding reference value P was in the range of 0.01 to 0.065, more preferable results were obtained.

According to the present invention, as described above, the surface of the center core of the mold is engraved on the slide core on the side receiving the injection pressure of the molten resin, so that the resistance of the resin flow is reduced by the cavities on both sides of the center core. At equilibrium. In other words, in the mold corresponding to one side of the flat plate of the shutter, the ratio of the upper surface area of the characters, designs, etc. in the flat plate of the shutter to the predetermined area of the flat plate properly maintains the balance of the resin flow appropriately. Molded. As a result, not only can the thickness of both flat plates of the shutter be made uniform, but also the degree of filling of the resin is uniform, and the cooling rate of the resin after injection is also uniform, so that the molding dimensions can be made accurate and the deformation can be achieved. It is possible to obtain a shutter integrally molded with characters and designs that are hardly seen.

Here, when the above formula is further explained, the ratio of the upper surface area of the character / design in the present invention is, as shown in FIG.
The extension line D and the intersection of edges 12b ₁ of the opening 12b b,
c and the opposite side (the left side in the figure) are square areas surrounded by corner portions a and d, and the numerator is the upper surface area of the character / design. This is because the center core corresponding to the area surrounded by abcd has no support at all, and corresponds to a portion which is easily deformed when a pressure difference is generated between the cavities forming the two flat plates. Within the range of the present invention, the difference between the thickness of the front and back plates of the shutter 3 became small. In this embodiment, various tests were performed using a POM resin having an MFR (flow index) of 27 to 75.

[0017]

[Effects of the Invention] As described above, according to the present invention,
Since the ratio of the upper surface area of the character / design in the flat plate of the shutter to the predetermined area of the flat plate and the molding reference value P expressed by the character / design and the like are formed in the specific range as described above, the shutter is formed. Not only can the thickness of both flat plates be uniform, but also the degree of resin filling is uniform, the resin cooling rate after injection is uniform, the molding dimensions can be accurate, and almost no deformation is seen. You can get a shutter.

Hereinafter, the effect of the present invention can be further clarified by the embodiment. (Example-1) As a molding die, a slide core 22 shown in FIG. 2 on which a display body 6 of characters and designs was formed was used, and a die having projections 5a and 5b as shown in FIG. 7 was used. A 3.5 inch MFD shutter 3 having the dimensions shown in FIG. 3 was formed. Conditions: As the molding resin, MFR (measured according to JIS K-721)
0) 27,45 POM resin were used.

As a difference in plate thickness, the plate thickness of a substantially central portion of the two flat plates 4b and 4c surrounded by the abcd and having no character was measured, and the side having no character was subtracted from the side where the character was formed. The value (flat plate 4b-flat plate 4c) was calculated. The dimensions of the shutter 3 are as follows: L ₁ = 47.5 mm, L _{2
= 3.6mm, L 3 = 31.9mm,} L 4 = 28mm, L 5 = 12.0mm, L 6 = 7.5
mm, L ₇ = 25.0mm, L ₈ = 5.0mm, L ₉ = 2.0mm, to = 0.46mm
The width of the projections (5a, 5b) in FIG.
2.8 mm. The plate thickness t was set to 300 μm to 380 μm. The height h of the character was changed in the range of 5 μm to 40 μm, and the ratio of the area of the character / design (the ratio to the area surrounded by the abcd) was 5% to 20%. Further, as the molding conditions, the temperature of the injection cylinder (almost the temperature of the injection resin) is 210 ° C. to 220 ° C., and the mold temperature is 80 ° C.
° to 85 ° C, injection time 0.1 seconds, dwell time 0.5 seconds,
Cooling time 4-6 seconds, total time for one injection is 10-12
A sample was made by injecting for a second. Table 1 shows the results.
Shown in

[0020]

[Table 1]

The thickness of the obtained molded product was measured at the center of the square abcd in FIG. 3 using both flat plates, and the difference in thickness was calculated. In the evaluation in the table, when the thickness difference is less than 50 μm, the mark is ○, when the difference exceeds 50 μm but is less than the practically usable range, the mark is Δ, and when there is a practical problem at 50 μ or more, the mark is X. did.

Example 2 As a molding die, a shutter 3 for a 3.5-inch MFD having dimensions as shown in FIG. 3 was molded using exactly the same mold as in the above-mentioned example. As the molding conditions, MFR is used as the molding resin (measurement is based on JIS K-7210).
Was used, and the other conditions were the same as in Example 1. Table 2 shows the results.

[0023]

[Table 2]

As shown in Tables 1 and 2 of the results, when the sheet thickness is between 300 and 380 μm, the molding reference value P is
In the range of 0.01 to 0.125, a good molded product having a small difference in thickness between the two flat plates was obtained. Further, when the molding reference value P was in the range of 0.01 to 0.065, more preferable results were obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a disk cartridge provided with a shutter according to the present invention.

FIG. 2 is a perspective view of a main part of a mold for molding a shutter according to the present invention.

FIG. 3 is a perspective view of the shutter according to the present invention;

FIG. 4 is a side view of the shutter according to the present invention.

FIG. 5 is a plan view of the back side of the shutter.

FIG. 6 is a plan view of the front side of the shutter.

FIG. 7 is a perspective view of a main part of a mold for molding the shutter of the present invention.

8 is a cross-sectional view of a main part taken along line XX in the shutter molding die of FIG. 7;

FIG. 9 is a sectional view of a main part of a shutter molding die in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc cartridge 2 Opening window of cartridge case 3 Shutter 4a End face plate 4b Flat plate of shutter 4c Flat plate of shutter 5 Center core 5a Projection 5b Projection 6 Display body 12b Opening window 12c Opening window 13 Cartridge engaging portion 14 Cartridge Engaging part 15 Small window 16 Small window 17 Spring engaging part 21 Slide core 22 Slide core 25 Gate 30 Character / design B Ejection space (cavity) A Ejection space (cavity) G Gate position

Claims (1)

(57) [Scope of request for utility model registration] 1. A front and rear flat plate for opening and closing a head insertion opening of a cartridge case for rotatably storing a disk, and an end plate connecting one edge of each of the two flat plates. In a synthetic resin disk cartridge shutter in which characters and designs are integrally displayed on the surface of a shutter having a U-shaped cross section, a convex display body is previously engraved on a molding die corresponding to the front side of the front surface plate. When injecting, the height of the display body is h (μm), the thickness of the flat plate is t (μm), the plane area of the display body is S (mm ² )
The area of the display area of the display body is defined as ws (mm ² ), and the molding reference value P represented by these conditions is represented by the following equation: P = 3.5 × (h / t) × (S / WS) The value of the molding reference value P is 0.01 to 0.125.
Injection molded disk cartridge shutters in the range.