JPH08300417A - Injection molding die - Google Patents

Abstract

PURPOSE: To improve molding accuracy without generating a weld line in a relatively large-sized resin molded article. CONSTITUTION: A resin injection chamber 9 is installed in a die along a die joint on the periphery of a cavity 5, a slit-shaped opening 10 which communicates directly with the cavity 5 is formed in the resin injection chamber 9, and a runner 6 is provided which supplies a molding resin from the outside of the die to the chamber 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die used for producing a resin molding.

[0002]

2. Description of the Related Art Conventionally, a resin molded body such as an outer frame case of a television receiver has been produced by injection molding.
As a mold used for molding such a resin molded body, there is one shown in FIG. The mold 50 is configured by fitting an upper mold 52 to a lower mold 51 composed of a base mold 51a and a lower mold member 51b. A resin molding space is formed on a joint end surface between the lower mold 51 and the upper mold 52. The cavity 53 is formed. The cavity 53 is a molded body 1 as shown in FIG.
The lower mold member 51 is formed in a substantially cylindrical shape to fit the outer frame case of the television receiver, which is 00, and has no cavity 53.
A plurality of runners 54 are radially formed in the central portion of the joint end surface of b. On the other hand, at the center of the die-bonding end face of the upper die 52, the sprue 5 faces the base end of each runner 54.
5 are provided.

A tunnel gate 56, which communicates with the runner 54, is provided at the tip of each runner 54. The tunnel gate 56 is composed of a gate hole 56a that descends from the tip of the runner 54 to the inside of the lower mold member 51b, and a gate hole 56b that rises from the tip of the gate hole 56a to the cavity 53.

In this mold 50, the molding resin injected from the sprue 55 passes through each runner 54 to reach each tunnel gate 56, and the cavity 53 is filled from each tunnel gate 56 to form a cavity shape. The resin molded body 100 is manufactured.

Then, the resin molding 1 in the cavity 53
After 00 has cooled, the upper mold 52 is removed from the lower mold 51. As shown in FIG. 6, the sprue residue 101, the runner residue 102, and the gate residue 103 remain in the resin molded body 100 in this state. In addition, in FIG.
It is an imaginary view of a state in which the resin molded body 100 immediately after cooling is removed from the mold 50 without cutting as it is, and in reality, it is impossible to take out in such a state.

Then, as shown in FIGS. 7A and 7B, the resin molded body 100 and the lower mold member 51b are relatively moved in a direction in which they are separated from each other, whereby the resin molded body 100 is moved from the lower mold member 51b. And the gate hole 56
The gate remnant 103 is cut at the boundary between a and the gate hole 56b, whereby the resin molding 100 and each remnant 10 are cut.
1, 102, and 103 are separated.

The resin molded body 10 molded in this way
0 is completed after painting the surface exposed to the outside and adjusting the aesthetics.

The conventional injection molding die described above has the following disadvantages. That is, with the recent demand for lowering the manufacturing cost of the resin molded body, in the manufacture of the resin molded body 100, it is considered to omit the final coating step. However, the coating step could not be omitted in the resin molded body 100 produced using the conventional injection molding die 50. This is due to the following reasons.

The injected resin is injected into the cavity 53 from a plurality of tunnel gates 56 provided in the cavity 53, spreads in the cavity 53, and joins with each other at an intermediate position between adjacent tunnel gates 56. . However, the tip portion of the injected resin is cooled by the heat of the mold 50, and has a certain viscosity.

For this reason, the injected resins join together without sufficiently intersecting each other at the joining point, which causes a line-shaped mark on the surface of the resin molding 100 at the joining point.
That is, the weld line w is generated. Therefore, the coating cannot be omitted in order to conceal such a weld line w, and thus the coating process cannot be omitted.

On the other hand, conventionally, as an injection molding die capable of molding the resin molding 100 without causing a poor appearance such as a weld line w, as shown in FIG.
There is a mold 60 shown in (b). The mold 60 is characterized in that a film gate 62 is provided along one end of a peripheral edge of a cavity 61 inside the mold. Film gate 6
Reference numeral 2 is a thin gate hole having a length connecting the runner 63 and the cavity 61 and having a width across the entire width of one end of the cavity 61.

In this mold 60, since the resin can be easily injected and the weld line w is not formed, the normal 1
The resin molding is molded by injecting the molding resin supplied from the runner 63 to the film gate 62 into the cavity 61 over the entire width of the film gate 62, not at the point or other-point gate. Thus, the joining of the injected resin in the cavity 61 is eliminated as much as possible to prevent the weld line w from being generated.

[0013]

However, in the conventional mold 60 capable of preventing the weld line, a small resin molding can be molded without any problem, but a relatively large resin molding. There is a problem that it is difficult to mold the body.

The injected resin is a cavity 61 for a small resin molding 100, that is, a cavity 6 having a small capacity.
For 1, it is possible to reach the end of the cavity. However, the cavity 61 for the relatively large resin molded body 100, that is, the cavity 6 having a large capacity is used.
In No. 1, by the time it reached the end of the cavity 61, cooling further proceeded and the viscosity increased, so that it did not reach the end of the cavity 61.

Further, in order to increase the molding accuracy, it is necessary to apply a predetermined injection pressure to the resin injected into the cavity 61, but it is accurate with respect to the injected resin whose viscosity has been increased by cooling. The predetermined resin injection pressure could not be applied. For this reason, the conventional mold 6
With 0, the molding accuracy was not improved for the relatively large resin molded body 100, and molding was difficult.

Further, in the conventional molds 50 and 60, it is necessary to manually remove the unnecessary resin residue remaining on the resin molded body 100 after molding, which hinders the reduction of the manufacturing cost of the resin molded body. There was a problem of becoming.

That is, in the mold 60 having the film gate 62, the unnecessary resin residue remaining in the film gate 62 remains as a so-called burr even after the resin molding 100 is released from the mold 60. However, it was necessary to remove this burr in a later process.

In the mold 50 having the tunnel gate 56, the sprue residue 101 and the runner residue 102 are completely removed when the resin molding 100 is separated from the mold 50. However, the gate residue 103 is cut at the boundary between the gate hole 56a and the gate hole 56b, so that the resin residue in the gate hole 56b remains. Therefore, it is necessary to manually remove such unnecessary resin residue in a later step.

Usually, such unnecessary resin residue is often located on the inner surface of the resin molding 100 which cannot be seen from the outside. Therefore, the unnecessary resin residue should be left as it is without being removed. Has also been done.
However, for that purpose, it is necessary to position the unnecessary resin residue at a position where it does not interfere with the mounting of the structural parts mounted on the resin molded body 100 (such as a cathode ray tube when the resin molded body 100 is an outer frame case of the television receiver). However, this imposes restrictions on the mold design and makes the design troublesome.

Therefore, in the present invention, even a relatively large resin molding can be molded without causing a poor appearance of the resin molding such as a weld line, and unnecessary resin residues can be automatically removed. The purpose is to provide a mold for injection molding.

[0021]

In order to achieve such an object, the present invention has the following constitution.

That is, according to the first aspect, a resin injection chamber is provided in the mold along the mold bonding surface at the periphery of the cavity, and the resin injection chamber is provided with a slit-shaped opening that directly communicates with the cavity. On the other hand, a runner for supplying molding resin from outside the mold to the resin injection chamber was provided to form an injection molding mold.

A second aspect of the present invention is characterized in that, in the injection molding die of the first aspect, the resin injection chamber is formed over the entire circumference of the cavity.

According to a third aspect of the present invention, in the injection molding die according to the first aspect, the cutting is provided so as to be able to advance and retreat toward the slit-shaped opening in a direction that traverses the resin injection chamber and closes the slit-shaped opening when entering. It is characterized in that a block and an advancing / retreating mechanism for advancing / retreating the cutting block in the mold are provided.

A fourth aspect of the present invention is characterized in that, in the injection molding die according to the first or third aspect, a heating portion for heating the inside of the resin injection chamber is provided.

[0026]

In the first aspect, the molding resin supplied from the runner to the resin injection chamber first fills the resin injection chamber. Then, when the molding resin is further filled after the resin injection chamber is completely filled with the molding resin, the molding resin is uniformly injected from the slit-shaped openings at each position in the width direction of the slit-shaped openings. It will be injected into the cavity as it is. At this time, since the slit-shaped opening is directly opened to the cavity, when the molding resin is injected into the cavity from the slit-shaped opening, the molding resin is reheated by shearing heat generation, so that the molding resin can be prevented from being cooled.

In the second aspect, since the resin injection chamber is formed over the entire circumference of the cavity, the molding resin is injected from the entire circumference of the cavity into the cavity all at once. For this reason, the molding resin hardly merges in the cavity.

According to the third aspect of the present invention, at the time of releasing the mold, if the cutting block is advanced by the advancing / retreating mechanism to close the slit-shaped opening, the resin molding in the cavity and the unnecessary resin residue in the resin injection chamber are automatically separated. Will be done.

According to the fourth aspect, the molding resin injected into the resin injection chamber is heated by the heating section. Therefore, cooling of the molding resin injected into the cavity can be further prevented.

Further, since the unnecessary resin residue is cut by the cutting block in the heated state, the cutting becomes easy.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. 1 is a cross-sectional view of an injection molding die 1 used for molding a resin molded body 100 that is an outer frame case of a television receiver according to an embodiment of the present invention.
Is a plan view of the lower mold.

The injection molding die 1 is constructed by fitting an upper die 3 to a lower die 2 consisting of a base die 2a and a lower die member 2b. These upper mold 2 and lower mold 3 are placed on a base 4. A cavity 5, which is a resin molding space, is formed on the joint end surface between the lower mold 2 and the upper mold 3, and the cavity 5 is substantially cylindrical according to the resin molded body 100 (outer frame case of the television receiver). It is provided in. Lower mold member 2b
The cavity 5 does not exist in the central part of the joint end surface of the above, and a plurality of runners 6 that spread radially are formed here. On the other hand, a sprue 7 communicating with the base end of each runner 6 is formed at the center of the die joining end surface of the upper die 3. The sprue 7 serves as a resin passage that connects the heating cylinder 8 provided above the upper mold 3 and the runner 6.

A resin injection chamber 9 is provided between the cavity 5 and the runner 6, and the runner 6 communicates with the cavity 5 via the resin injection chamber 9. The resin injection chamber 9 is provided in a ring shape along the entire circumference of the inner peripheral edge of the cavity 5 provided in a substantially cylindrical shape. The cross-sectional shape of the resin injection chamber 9 has a large diameter at the inner end, that is, the runner-side end 9a, and an outer end, that is, the cavity-side end 9b.
Has a small diameter, and further, these end portions 9a and 9b are continuously connected to form a drop shape.

The tip of the runner 6 communicates with the runner side end 9a of the resin injection chamber 9. On the other hand, a slit-shaped opening 10 that opens to the cavity 5 is provided at the cavity-side end portion 9b of the resin injection chamber 9. Slit-shaped opening 10
Is formed over the entire circumference of the cavity-side end portion 9b and directly faces the cavity 5. The resin injection chamber 9 directly communicates with the cavity 5 through the slit-shaped opening 10.

A cutting block 11 is provided inside the lower mold member 2b.
Is stored. The cutting block 11 has an annular shape having substantially the same shape as the resin injection chamber 9, and is arranged so as to face the resin injection chamber 9. The cutting block 11 includes a thick base portion 11a and a thin cutting blade portion 11b provided on the upper end of the base portion 11a. The cutting block 11 thus configured is housed in the housing chamber 12 formed in the lower mold member 2b. The room depth of the storage chamber 12 is formed slightly deeper than the upper and lower dimensions of the cutting block base 11a in the figure. Therefore, the cutting block 11 is the storage chamber 1
2 is housed so as to be movable in the vertical direction in the figure, and the cutting blade portion 11b can be moved forward and backward in the direction crossing the resin injection chamber 9 toward the slit-shaped opening 10 (the vertical direction in the figure). Therefore, when the cutting blade portion 11b enters, the slit-shaped opening 10 is closed by the cutting blade portion 11b.

A moving shaft 13 is connected to the cutting block 11. The lower end of the moving shaft 13 penetrates the lower mold member 2b and the base mold 2a, and is connected to the movable plate 14 housed in the base 4. Lower surface 14 of movable plate 14
a is a sloping surface that spreads outward. On the other hand, hydraulic cylinders 15 and 15 are provided on both sides of the base 4. The rod 16 of the hydraulic cylinder 15 is inserted into the base 4, and the rod tip 16 a is buried under the movable plate 14. A taper portion 17 having a tapered shape is formed at the rod tip 16 a, and the taper portion 17 is engaged with the lower surface 14 a of the movable plate 14. Therefore,
When the rod 16 moves forward by driving the hydraulic cylinder 15, the movable plate 14 moves upward in the drawing due to the engagement between the tapered portion 17 and the lower surface 14a.

In the base 4, an elevating plate 18 is housed in addition to the movable plate 14. The elevating plate 18 is moved up and down by an elevating shaft 19 which penetrates the movable plate 14 and is inserted into the base 4.

On the other hand, the base mold 2a has a lifting block 20.
Is provided. The lifting block 20 includes a lower mold member 2b.
It is provided at a position facing the outer end of the cavity 5 along the peripheral edge of the. The elevating block 20 and the elevating plate 18 are connected by a connecting shaft 21 that penetrates the lower mold member 2b. Therefore, when the lift plate 18 is lifted by the lift shaft 19, the lift block 20 is also lifted.

Further, a heater 22 is embedded in the upper mold 3. The heater 22 is arranged in an annular shape so as to face the resin injection chamber 9, and is buried in a position slightly inside the upper mold 3 from the mold bonding surface of the upper mold 3.

Next, the molding process of the resin molded body 100 by the injection molding die 1 having the above-mentioned structure will be described.

First, the heated molding resin is supplied from the heating cylinder 8 to the sprue 7. The molding resin supplied to the sprue 7 passes through each runner 6 and is poured into the resin injection chamber 9. At this time, since the resin injection chamber 9 has a cross section and a drop shape, the poured molding resin first fills the runner side end portion 9a of the resin injection chamber 9 having the large diameter, and then the runner side end. After filling the portion 9a, the cavity side end portion 9b having a smaller diameter is gradually filled. At this time, the resin injection chamber 9 is heated by the heater 22, and the molding resin does not contact the inner wall of the resin injection chamber 9 to be cooled and its viscosity does not increase. Therefore, the molding resin is filled in the resin injection chamber 9 in a state where the temperature is sufficiently high and the viscosity is low.

It is conceivable that the molding resin poured from each runner 6 into the resin injection chamber 9 merges in the resin injection chamber 9 and a weld line w is generated at the junction. However, the resin in the resin injection chamber 9 only becomes the resin injection chamber residue 110 that does not become the resin molded body 100, and is separated from the resin molded body 100 after the molding is completed, as described later. ing. for that reason,
There is no problem even if the weld line w is formed to some extent here.

When the entire inside of the resin injection chamber 9 is filled with the molding resin, the injection tip side of the molding resin reaches the slit-shaped opening 10. Then, when the molding resin is further poured into the resin injection chamber 9, the injection tip side of the molding resin is poured into the cavity 5 from the slit resin opening 10 almost simultaneously and with substantially the same injection pressure. The molding resin poured into the cavity 5 is injected into the cavity 5 in the normal direction to the slit-shaped opening 10, that is, in a horizontal line from the entire circumference of the inner peripheral edge of the cavity 5. Go. Therefore, the molding resin does not merge in the cavity 5, and the weld line w does not occur in the cavity 5.

The molding resin injected into the cavity 5 is
Since it is poured directly into the cavity 5 from inside the resin injection chamber 9 through the slit-shaped opening 10, it is reheated by shearing heat generation between the resin injection chamber 9 and the cavity 5, so that cooling can be prevented. . Further, the molding resin is not cooled in the resin injection chamber 9 by the heating of the heater 22. For this reason, the resin heated by the heating cylinder 8 fills the inside of the cavity 5 at a sufficiently high temperature (low viscosity). Therefore, a relatively large resin molded body 1 such as an outer frame case of a television receiver
Even in the cavity 5 for forming 00, the molding resin does not completely reach the end portion of the cavity 5 to cause molding failure.

Further, as described above, since the molding resin fills the cavity 5 in a state where the temperature is sufficiently high (the viscosity is low), a molding pressure sufficient for the molding resin in the cavity 5 is externally applied. Can be applied. The molding pressure is an important factor for improving the molding accuracy, and since a sufficient molding pressure can be applied, even a relatively large resin molded body 100 can be molded accurately.

By the way, as shown in FIG. 4, the sprue residue 101, the runner residue 102, and the resin injection chamber residue 110 remain in the resin molded body 100 in this state. Note that FIG. 4 is an imaginary view of a state where the resin molded body 100 immediately after the cavity 5 is injected is removed from the mold 1 as it is, and normally, in this state, it is not taken out from the mold 1.

In this injection molding die 1, the sprue residue 101, the runner residue 102, and the resin injection chamber residue 110 are removed, and then the resin molded body 100 is taken out of the mold 1. That is, when the resin body 100 in the mold 1 is filled, first, the hydraulic cylinder 15 is driven to advance the rod 16. Then, the tapered portion 17 of the rod 16 slides on the lower surface 14 a of the movable plate 14 to lift the movable plate 14. Then, as shown in FIG.
As shown in (b), the moving shaft 13 rises to lift the cutting block 11, and the cutting block 11 moves the storage chamber 12 to the upper side in the drawing. As the cutting block 11 rises, the cutting blade portion 11b of the cutting block 11 rises to close the slit-shaped opening 10. As a result, the molding resin body 100 in the mold 1 is compressed and cut at the slit-shaped opening 10, and the resin molding body 1 in the cavity 5 is cut.
00 and the resin injection chamber residue 110 are separated. In addition,
In order to ensure the separation of the molded resin body 100 and the resin injection chamber residue 110, as shown in FIG.
1b is raised to a position where it is overlapped with the slit-shaped opening 11 by a dimension a. Resin molding 10
When 0 is the outer frame case of the television receiver, the overlap dimension a is appropriately about 0.2 mm.

At this time, the molding resin in the resin injection chamber 9 is heated by the heater 22 and is not sufficiently cooled and hardened. Therefore, the cutting by the cutting blade portion 11b can be surely and easily performed with a relatively small force.

After the resin molding 100 is separated from the resin injection chamber residue 110, the runner residue 102, and the sprue residue 101 in this manner, the upper mold 3 is moved to the lower mold 2.
Separate from. Then, the resin molded body 100 becomes the lower mold 2.
Will be attached to the. Therefore, this time, the elevating shaft 19 is raised. Then, the lifting plate 18 and the connecting shaft 21 are lifted to lift the lifting block 20. Lift block 20
When is lifted, the resin molded body 100B that is in contact with the elevating block 20 is pushed up by it and separated from the lower mold member 2b.

[0050]

According to the present invention, the following effects can be obtained.

Effect of Claim 1 The molding resin can be injected into the cavity all at once from the slit-shaped opening and with the injection pressure at each position in the width direction of the slit-shaped opening being uniform. Therefore, the resin injection can be performed uniformly, and the molding resin does not easily merge in the cavity, and molding defects such as weld lines due to the resin merging in the cavity hardly occur.
The appearance quality has improved accordingly.

Further, since the slit-shaped opening is provided so as to directly face the cavity, when the molding resin is injected from the slit-shaped opening into the cavity, it is reheated by shearing heat generation, so that the heating temperature condition suitable for injection is obtained. So it came to be injected into the cavity. Therefore, it is possible to accurately inject the resin into the relatively large cavity.

The effect of claim 2 The molding resin is injected all at once from the entire circumference of the cavity toward the inside of the cavity, and the molding resin almost never merges in the cavity. Therefore, molding defects such as weld lines due to resin merging in the cavity did not occur, and the appearance quality could be further improved. Therefore, it is not necessary to apply paint to hide the defective appearance, and the manufacturing process of the resin molded body can be reduced accordingly, leading to cost reduction.
If the heating portion is provided as in the fourth aspect, it is possible to further prevent the resin injected into the cavity from being cooled and further improve the appearance quality.

According to the effect of claim 3, at the time of mold release, if the cutting block is advanced by the advancing / retreating mechanism to close the slit-like opening, the resin molding in the cavity and the unnecessary resin residue in the resin injection chamber are automatically separated. Therefore, the step of removing the unnecessary resin residue later is not necessary, and the manufacturing step of the resin molded body can be reduced accordingly, resulting in cost reduction. If the heating unit is provided as in claim 4, the unnecessary resin residue is cut by the cutting block in a state where the heating block is not sufficiently cooled.
The effect of facilitating the cutting is obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an injection molding die according to an embodiment of the present invention.

FIG. 2 is a plan view of a lower mold member according to the embodiment.

FIG. 3 is an enlarged cross-sectional view of a main part of an embodiment showing states during operation.

FIG. 4 is a perspective view showing the shape of a resin molded body immediately after being molded using the injection molding die of the embodiment.

FIG. 5 is a cross-sectional view of a first conventional mold for injection molding.

FIG. 6 is a perspective view showing the shape of a resin molded body immediately after being molded using the injection molding die of the first conventional example.

FIG. 7 is a cross-sectional view showing a state when a resin molded body is taken out from an injection molding die of a first conventional example.

FIG. 8 is a partially cutaway plan view and a cross-sectional view showing the shape of a second conventional injection molding die.

[Explanation of symbols]

 5 cavity 6 runner 9 resin injection chamber 10 slit-shaped opening 11 cutting block 22 heater

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[Procedure amendment]

[Submission date] May 24, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5] ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 6, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

Claims (4)

[Claims] 1. A resin injection chamber is provided in a mold along a mold bonding surface at the periphery of a cavity, and a slit-shaped opening that directly communicates with the cavity is formed in the resin injection chamber. A mold for injection molding, comprising a runner for supplying a molding resin to the resin injection chamber. 2. The injection molding die according to claim 1, wherein the resin injection chamber is formed over the entire circumference of the cavity. 3. A cutting block, which is provided so as to be able to advance and retreat in a direction traversing the resin injection chamber toward the slit-shaped opening and closes the slit-shaped opening at the time of entry, and an advancing and retracting mechanism for advancing and retracting the cutting block in a mold. The mold for injection molding according to claim 1, further comprising: 4. A mold for injection molding according to claim 1, further comprising a heating part for heating the inside of the resin injection chamber.