JPH03207068A - Magnetic tape cassette half and forming device for the same - Google Patents

Abstract

PURPOSE:To improve sealing capability between an inner layer and a fixed metal mold at the time of secondary formation by providing first and second projecting parts on a primary forming metal mold and providing a seal part, which is equipped with a seal surface and an abutting surface, on a secondary forming metal mold. CONSTITUTION:On a fixed metal mold 26 to form an inner layer 19, a first projecting part 28 is formed to form a first recessed part at prescribed depth so that molten resin for outer layer formation can be injected, and a second projecting part 30 is formed to form a second recessed part shallower than the first recessed part. Further, a third projecting part 31 is formed at the first projecting part 28. On the fixed metal mold 27 to form an outer layer, a seal part 34 is provided with the seal surface, which is adhered to the second recessed part formed on the inner layer 19, and the butting surface for changing the flow of the resin and the seal part 34 is formed on a separate object which can be freely slid to the other part of the fixed metal mold 27. Thus, at the time of secondary formation, the sealing capability between the inner layer 19 and the fixed metal mold 27 can be improved and burrs can be prevented from being generated near the outer layer edge part of a half case equipped with double layer structure.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to upper and lower half cases in a magnetic tape cassette and a molding device therefor, and more specifically, to a molding device for the upper and lower half cases in a magnetic tape cassette.
Related to improving sealing performance in layer molding.

[Prior Art] It has been known to manufacture a magnetic tape cassette having at least a portion of a two-layer structure by sequentially injection molding two resin materials of different materials or colors. For example, in Utility Model Application No. 29214 of 1983, upper and lower half cases are integrally formed by injection molding with an inner layer made of hard resin and an outer layer made of elastomer bonded to its outer surface, which provides impact resistance and vibration damping. We offer high quality magnetic tape cassettes. In general, the resin materials for the inner and outer layers may be different or the same for the inner and outer layers, and by using different colorants, lubricants, fillers, etc., the inner and outer layers have different physical properties or coloring. It can be layered.

[Problems with the prior art] A half case with a two-layer structure is manufactured by first injection molding the inner layer, and then injection molding the outer layer on the outer surface of the inner layer, but the inner layer must not be covered with resin during injection molding of the outer layer. The surface must be completely sealed by the mold. However, conventional methods do not provide a perfect seal and leave a crust of outer layer material along the edges of the outer layer. The main reason for this is that when molding the outer layer after molding the inner layer, the pressure of the outer layer molding resin is high, which lifts the secondary mold and causes slight deformation, which causes the seal between the secondary mold and the inner layer. This is due to the fact that gaps tend to form between the inner and outer layers, and the molding pressure is applied directly to the sealing part.Other causes include the temperature of the primary mold for molding the inner layer and the temperature of the primary mold for molding the outer layer when the inner and outer layer materials are different. This is because the temperatures of the secondary molding molds used for this purpose are different, and the pitch accuracy tends to be distorted due to the difference in the linear expansion of the molds. For this reason, the outer layer resin is likely to leak into this gap, and the outer layer resin material is, for example, an elastomer such as polyurethane.
The use of other highly fluid resins further exacerbates this problem.

As an example, a conventional two-layer molding method using rotational molding will be described with reference to FIGS. 1 to 3. In the two-layer molding method using rotational molding, a lower mold is used as a movable mold, a fixed mold for primary molding and a fixed mold for secondary molding are respectively fixed as upper molds in two places, and the movable mold is first used for primary molding. Primary molding is performed by aligning the molds with a fixed mold, then the movable mold is rotated while holding the primary molding, and the mold is clamped into a fixed mold for secondary molding, and then secondary molding is performed. Figure 1 shows the magnetic tape cassette to be molded, and Figure 2 is a sectional view taken along line A-A in the same figure, showing the upper half case (the lower half case is omitted as it is the same), and shows the inner layer L and its outer surface. It consists of an outer layer 2 that is integrated into a shape that fills a recess of a predetermined depth. Outer edge of outer layer 2 and inner layer 1
It abuts the peripheral wall of the recess. Conventionally, in the vicinity of this abutting portion (divided surface) 3, burrs were likely to occur on the outer surface side of the inner layer. The reason for this is thought to be as follows.

FIG. 3 shows the structure of a secondary molding die in a conventional injection molding process. The mold consists of a movable mold 4 and a fixed mold 5, and the movable mold 4 is a primary molding mold for the inner layer. This mold is used as it is for secondary molding while holding the molded inner layer. In the primary molding, instead of the fixed mold 5 for secondary molding, a movable mold 4 is clamped against a fixed mold for primary molding (not shown) to form a primary molding space therebetween, and this state First, the resin for the inner layer is injected and the inner layer 1 is primarily formed. When the hardening of the inner layer 1 is almost completed by cooling, the fixed mold for primary molding is opened, rotated, and clamped to the fixed mold 5 for secondary molding shown in the figure to form a secondary molding space. . Next, when the resin for outer calendar 2 is introduced, the resin flows as shown by the arrow and fills the secondary molding space. However, the resin for the outer layer flows in the direction of the arrow, hits the dividing surface 3 of the inner layer and is deflected upwards, applying resin pressure to the fixed mold, which lifts and deforms the fixed mold, causing the outer surface of the inner layer and the metal A minute gap is created between it and the sealing surface 7 of the mold. Since the sealing surface of the mold is in the same plane as the molding surface of the outer layer so that the surface of the outer layer is flush with the surface of the inner layer, resin pressure is applied directly to the gap, thereby promoting resin leakage. Furthermore, this problem is further exacerbated by precision deviations due to thermal distortion of the mold. When the outer surface of the inner layer is patterned with fine irregularities (graining), the sealing performance of the seal part is further reduced. In this way, cracks are generated in the vicinity of the abutting portion 3 of the molded product, reducing the commercial value or producing defective products. Furthermore, in order to improve the vibration damping properties of the tape cassette, it is necessary to It is better to form an elastomer outer cover on the part, but since this inclined part is a compound inclined surface as shown in the figure (the term "compound inclined" is used here, the direction of the dividing plane is X, and the main part of the cassette half is When the direction parallel to the surface and perpendicular to ), it is extremely difficult to manufacture the part of the fixed mold 5 for secondary molding corresponding to the composite sloped surface with the same angle and same dimensional accuracy as the composite sloped surface in the sloped part of the inner layer. It was extremely difficult to ensure sealing performance. Therefore, in the past, this part had to be avoided and two-layer molding was performed, resulting in poor design flexibility.

It is conceivable to ensure the sealing performance of the secondary mold by increasing the pressure on the inner layer of the mold, but this cannot be adopted because the dimensions of the secondary molding space will vary. In particular, if the exposed surface of the inner layer is textured (fine uneven pattern), the sealing performance will further deteriorate.

[Object of the Invention] The object of the present invention is to form a cassette half by two-layer molding, particularly in the molding of a head house, and to form the outer layer on the outer surface of the inner layer during secondary molding, between the inner layer and the fixed mold. To provide a molding device with improved sealing performance,
Another object of the present invention is to provide an excellent cassette half in which no flashing occurs near the edge of the outer layer.

[Summary of structure and operation and effect of the invention] The present invention has a pair of hubs around which a magnetic tape is wound, which are housed between upper and lower half case members, and a guide roller and a tape guide for guiding the magnetic tape are provided on the front side. Provided are an upper half case and/or a lower half case in a tape cassette having a tape cassette, and a molding device therefor. That is, in the molding apparatus of the present invention, a space for shaping the inner layer of the half case is formed using a primary mold, a resin for forming the inner layer is introduced into the space to form the inner layer, and the inner layer formed in this way is A method for manufacturing a half case for a magnetic tape cassette, in which a secondary molding mold is positioned on the outer surface side of the magnetic tape cassette to form a space for forming the outer layer, and a resin for forming the outer layer is introduced into this space to form the outer layer. This is a mold used for. The molding apparatus of the present invention is characterized in that the primary molding mold is composed of a movable mold and a fixed mold, and the fixed mold is used at a predetermined position for injecting a highly fluid resin for forming the outer layer onto the outer surface of the inner layer. depth first
a first convex portion forming a recess; and a second convex portion shallower than the first convex portion forming a second recess shallower than the first recess in at least a portion of the outer surface of the inner layer in contact with the first recess. The secondary molding mold has a sealing portion having a convex portion, and a sealing surface that closely contacts the second recess of the inner layer and an abutting surface that is located on the molding space side and turns the resin. do.

According to this feature of the present invention, during secondary molding, the flow of the resin for the outer layer hits the abutment surface of the seal portion of the secondary mold and is diverted toward the inner layer. Therefore, the flow of resin toward the seal portion is relaxed, and leakage of resin is prevented.

Preferably, the abutment surface of the seal portion is an inclined surface, and more preferably, the inclined surface is processed with minute irregularities, so that good mold release properties can be obtained. Preferably, the abutting surface is located closer to the molding space than the second recess, so that the diverted resin does not go toward the sealing surface but toward the inner layer, creating a low pressure on the sealing surface side and preventing resin leakage.

Furthermore, by configuring the sealing part of the secondary mold as a separate body that can slide freely relative to other parts, the sealing pressure can be adjusted without affecting the thickness accuracy of the outer layer, improving sealing performance and improving molding performance. It can prevent the occurrence of cracks on the product.

Further, according to the present invention, sealing can be ensured regardless of the texture (fine uneven pattern) on the outer surface of the inner layer.

More preferably, during primary molding, the first recess of the inner layer forms a third recess extending along the second recess in a portion adjacent to or in contact with the second recess, and during secondary molding, the first recess of the inner layer forms a third recess extending along the second recess. When the outer layer type resin turned from the abutting surface is allowed to flow into the third recess, the pressure of the resin against the seal portion pressed against the inner layer is further relieved, and leakage of the resin can be further prevented. Further, according to this aspect, since the third recess is filled with the resin for the outer layer, the bonding force of the outer layer to the inner layer is increased due to the wedge effect.
Peeling of the outer layer can be prevented.

In particular, it has already been mentioned that it is difficult to ensure good sealing performance on the compound slope of the slope of the head house portion of the half case, but if the slope of the second recess in this slope is made monoslant, (Here, the term "single slope" is defined as the normal line of the slope having substantially no y component according to the expression used when defining the complex slope). Since it can be manufactured with precision, the sealing performance of the inclined portion is perfect during secondary molding.

[Specific Description of the Invention] The present invention will be specifically described below with reference to Examples. The present invention provides an upper half case and/or a lower tape cassette in which a pair of hubs around which a magnetic tape is wound are housed between upper and lower half case members, and has a guide roller and a tape guide for guiding the magnetic tape on the front side. Concerning improvements to the half case. In the following explanation, it will simply be referred to as a half case. Although the following description does not refer to the materials of the inner layer and outer layer, it is assumed that two types of conventionally known resin materials are used.
Even if the same resin has different colors, it is defined as different materials. However, the advantages of the present invention are obtained when a highly fluid material is used as the outer layer. Preferred combinations are described in the patent applications cited above. For example, the inner layer is a hard resin and the outer layer is an elastomer.

A first embodiment of the present invention will be described in detail with reference to FIGS. 4 to 10. In this example, the outer layer was formed particularly in the head house portion, but the principles of the present invention can also be applied to other portions of the half case. However, when applied to the head house part, the advantages and benefits of the present invention can be fully utilized.

FIG. 4 shows a magnetic tape cassette using the half case of the present invention. In the figure, a pair of movable hubs 11 and 12 on which magnetic tape is wound are housed in a space formed between the housing portions 17 of upper and lower half cases 13 and 14 (lower half case 714 is not shown), and are placed on the front side. is provided with a head house 15 having guide rollers and tape guides (not shown) for guiding the magnetic tape. The head house has an inclined part 16 which merges into a planar receiving part 17 of the half case. FIGS. 5 and 6 are sectional views taken along line A-A through only the upper half case of FIG. 4, and clearly represent the features of the present invention. The details will be revealed below. The half case molding apparatus and molding method according to this embodiment and the structure of the half case of the present invention manufactured thereby are described in 9th to 1st.
1. Explanation with reference to Figure 1.
I will clarify.

First, as shown in FIG. 9, primary molding is performed to form the inner layer 19. The primary molding die for molding the inner layer consists of a movable mold 25 and a fixed mold 26, and when they are closed and clamped together, a primary molding space for the inner layer is formed. The fixed mold 26 has a height t1 measured from the finished surface 29 of the molded product in order to form a first recess 22 of a predetermined depth into which the fluid resin for forming the outer layer is to be injected onto the inner layer. A second protrusion 30 having a first protrusion 28 and a planar top surface having a height t2 lower than the height of the first protrusion 28 is further formed around the first protrusion 28. . This second convex portion extends to a position corresponding to the flat portion and the inclined portion 16 of the head house 15. Here, the second recess 23 formed in the inner layer has a single slope in the slope part 16 of the head house, unlike its compound slope (the normal thereof has an X*y+Z direction component as defined above). (its normal has substantially only x and z direction components). Furthermore, a third protrusion 31 is formed on the first protrusion 28 and is adjacent to the second protrusion 3o and extends along the second protrusion. When the resin for the inner layer is introduced into the primary molding space, the inner layer 19 having the first recess 22, second recess 23, and third recess 24 described above is formed. Also, the slope l of the head house l6
The surface 6 is a compound slope as shown in FIGS. 7 and 8, but the slope 32 of the second recess 23 is a single slope.

Next, the secondary molding process for forming the outer layer will be explained with reference to FIGS. 10 and 11. The movable mold 25 is rotated from the fixed mold for primary molding to the fixed mold 27 for secondary molding for forming the outer layer 2o, and is clamped. As a result, an outer layer molding space is formed on the almost hardened inner layer 19.

The seal portion 34 of the fixed mold 27 is formed as a separate member so as to be slidable with respect to other parts of the fixed mold, and
6 makes it possible to independently control the sealing pressure. The sealing portion 34 includes a sealing surface 33 that presses against the surface of the second recess 23, including the sloped surface 32 of the inner layer, for sealing.
has. Since the sloped surface 32 of the inner layer is a single slope, it is easy to manufacture the seal portion 34 having a sealing surface that precisely matches the sloped surface 32 of the inner layer.

Furthermore, the molding space side of the seal portion 34 has an inclined abutment surface 35.
Equipped with: The main function of this abutment surface 35 is to block the flow of resin and divert it downward so that the pressure of the resin does not act on the sealing surface. Therefore, the abutment surface 3
5 needs to protrude into the molding space, unlike conventional fixed molds for secondary molding, and therefore the inner layer 19 is removed during primary molding.
Therefore, it is necessary to form the second recess 23 on the outer surface side. Incidentally, when the abutment surface is inclined, the turning action of the resin increases, and at the same time, mold release properties are imparted to the solidified resin. More preferably, this inclined surface is textured to further improve mold releasability.

As shown in FIG. 11, another important point is that the abutment surface 35 is offset from the peripheral wall of the first recess of the inner layer 19 by a small distance d toward the molding space. This further prevents resin leakage since the molding pressure of the resin is reduced when it is applied between the sealing surface and the inner layer.

In secondary molding, a fluid resin for the outer layer 20 is introduced into the space. The introduction point is set at the outer layer gate 36 shown in FIG. 4 (not shown in FIGS. 10 and 11), and the resin flows in the direction of the arrow to fill the resin to the edge of the space. The resin abuts the seal portion 34 at the edge as shown in FIG. 11, changes direction, and flows into the third recess 24.

Furthermore, since the resin is diverted to the third recess 24, the resin pressure applied to the sealing surface between the inner layer and the seal portion is relieved, and leakage of the resin can be further prevented.

In the half case manufactured in this manner, a second recess 23 shallower than the first recess 22 is formed on the outer surface of the inner layer 19 adjacent to the first recess 22 formed in the head house 15. . As shown in FIGS. 4 to 8, this second recess extends linearly on the flat surface of the head house 15 and extends to the inclined portions 16 on both sides. The slope 32 of the second recess 23 in the slope l6 is independent of the slope of the slope 16 forming a composite slope. That is, as shown in FIGS. 7 and 8, the surface of the second recess 23 is parallel to the plane part, and the inclined part 16 has a single inclined surface 32. For this reason, this second recess 23
As described below, it can be tightly adhered to the sealing surface of the sealing part of the mold during secondary molding, completely preventing resin leakage and preventing the occurrence of paris even if the outer layer resin has high fluidity. do.

Also, the depth of this groove may be small, 0.03 to 0.5 mm.
The purpose can be achieved to a certain extent.

The first recess 22 of the inner layer 29 further has a third recess 24 extending along the second recess 23 in a portion adjacent to or in contact with the second recess 23, and the outer layer 20 has a third recess 24 extending along the second recess 23. 24 is filled. As a result, even if a highly fluid secondary molding resin for the outer layer such as an elastomer is used in the secondary molding for molding the outer layer 20, most of the resin is diverted toward the third recess 24. By easing the cutting pressure applied to the portion of the secondary mold that acts as a seal, leakage of the resin is further reduced, and the occurrence of paris is further suppressed. Moreover, because the resin of the outer layer 20 fills the third recess 24 with this construction, the bonding force between the inner layer 19 and the outer layer 20 is increased due to the wedge effect, and the problem of peeling can be prevented. Tradoro △'' Figure 12 shows another embodiment. The only difference between this example and Example 1 is that the primary mold for forming the inner layer does not form the third recess 24 that was formed in Example 1. Therefore, although the sealing performance is slightly inferior, other points are the same as in Example 1. During secondary molding, the fluid resin for the outer layer is injected in the direction of the arrow, but the pressure of the resin is diverted by the abutment surface of the seal, so the pressure applied to the seal is relaxed. As described in connection with Embodiment 1, since the contact surface between the second recess 23 and the sealing part can be precisely formed, sufficient sealing performance can be ensured in this part.Furthermore, since an independent sealing part is used, there is no substantial difference in the accuracy of the outer layer. It is possible to ensure sufficient sealing performance without affecting the performance.

[Brief explanation of drawings]

Fig. 1 is a front view showing the structure of a conventional magnetic tape cassette, Fig. 2 is a sectional view taken along line A-A through the upper half case of the same figure;
FIG. 3 is a sectional view showing a molding process using a conventional molding die. FIG. 4 is a front view of the magnetic tape cassette of the present invention, FIG. 5 is a sectional view taken along line A-A through the half case of the same figure, and FIG. 6 is a partially enlarged view of FIG. 5. Figure 7 shows part C of the cassette in Figure 4.
, FIG. 8 is a sectional view taken along the line DD in FIG. 7, FIG. 9 is a sectional view showing the primary forming process of the half case according to the first embodiment of the present invention, and FIG. 10 is the secondary forming process. A sectional view showing,
FIG. 11 is an enlarged sectional view of the same, and FIG. 12 is a second embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a secondary forming process according to an example. Hiroshi Kazama and 1 Figure 1 Figure 2 Figure 3 Figure 7 5 Murasaki 1 Figure 6 Figure 7 Figure 9 Figure 12 Figure O Figure 11

Claims (1)

[Claims] 1) A space for forming the inner layer of the half case is formed using a primary molding die, an inner layer forming resin is introduced into the space to form the inner layer, and the outer surface side of the inner layer thus formed. In a half case molding apparatus for a magnetic tape cassette, the secondary molding mold is positioned to form a space for forming the outer layer, and a resin for forming the outer layer is introduced into this space to form the outer layer. The mold includes a first convex portion for forming a first recess 22 of a predetermined depth into which the outer layer forming resin is to be injected into the outer surface of the inner layer, and at least one portion of the outer surface of the inner layer in contact with the first recess. a second convex portion lower in height than the first convex portion for forming a second concave portion 23 shallower than the first concave portion in the secondary molding die; A half-case molding device characterized in that a seal portion 34 is provided having a sealing surface 33 that comes into close contact with the second recess 23 formed in the second recess 23 and an abutment surface 35 for diverting the flow of resin. 2) The half-case molding device according to item 1, wherein the seal portion 34 is formed as a separate body that is slidable with respect to other parts of the secondary mold. 3) The second convex portion extends from the planar outer surface of the front head house of the half case to the compound sloped portion around it to form a second recess 23, and corresponds to the sloped portion 16. 3. The half-case molding device according to claim 1 or 2, wherein the second convex portion has a single slope at a portion where the second convex portion is tilted. 4) The molding device according to item 1 or 2 above, wherein the abutment surface 35 of the seal portion 34 of the secondary mold mold slightly protrudes toward the molding space beyond the second recess 23 of the inner layer. 5) The half-case molding device according to item 1 or 2 above, wherein the abutment surface 35 is an inclined surface. 6) The half case forming apparatus according to item 5 above, wherein the inclined surface is subjected to fine unevenness processing. 7) The first convex part of the secondary molding mold has a third convex part higher than the first convex part along the second convex part in a part close to or in contact with the second convex part. 7. The half-case molding device according to any one of items 6 to 6. 8) A half case comprising a magnetic tape accommodating portion having a planar outer surface and a front head house having a planar outer surface connected to the accommodating portion via a composite inclined portion, the half case including an inner layer; In the half case, the head house includes a first recess 22 having a predetermined depth formed from the outer surface of the accommodating part to a part of the outer surface of the head house, and an outer layer covering the first recess. A second recess 23 having a constant depth shallower than the first recess is formed on the outer surface of the inner layer adjacent to an edge of the first recess extending on the outer surface and the composite slope, and furthermore, this second recess 1. A half case for a magnetic tape cassette, characterized in that the compound slope portion has a single slope. 9) The bottom of the first recess 22 has a third recess 24 proximate or in contact with the second recess 23 that extends at least partially along the first recess 23, and the outer layer 9. The half case according to item 8, wherein the recess is filled.