JP2002264193A - Mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably mold a molded product of high precision at a low cost even if the molded product has a thick wall or a non-uniform wall thickness shape. SOLUTION: When a molten resin injected in the cavity 7 formed by cavity pieces 2-4 to fill the cavity is cooled to the softening temperature of the resin, a gap is formed to the surface other than the transfer surface of the resin in the cavity to be cooled and the cooling speed of the gap 16 is made equal to that of other cavity surface to prevent the deformation of the molded product caused by the temperature distribution difference generated in the molded product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die for a plastic molded product applied to, for example, a digital copying machine or laser printer of a laser system, an optical scanning system of a facsimile machine, an optical device such as a video camera, an optical disk, and the like. In particular, the present invention relates to molding of a thick-walled or uneven-walled plastic lens or plastic mirror having a highly accurate mirror surface.

[0002]

2. Description of the Related Art Plastic lenses, plastic mirrors and the like used in digital copying machines of the laser system are manufactured by injection molding. In the injection molding method, usually, the molten resin whose mold temperature is lower than the softening temperature of the molding resin is injected and filled into a cavity of a fixed volume, cooled while controlling the holding pressure, and then the mold is opened to form a molded product. It is a method of taking out. In this method, when the molten resin is cooled and solidified, the resin pressure and the resin temperature in the mold can be made uniform,
This is desirable to ensure desired shape accuracy.
However, when the molded product has an uneven thickness, the resin temperature becomes uneven between the thick portion and the thin portion during cooling, and residual pressure is generated in the thin portion, or an incomplete transfer surface, so-called sink mark, is formed in the thick portion. There was a problem that occurs. Also, in the case of a thick-walled shape, shrinkage is likely to occur due to a large volume shrinkage during the cooling process of the resin. There was a disadvantage that a molded product could not be obtained.

In order to solve such a drawback, for example, an injection mold disclosed in Japanese Patent Application Laid-Open No. Hei 6-304973 is provided with a vent on a surface other than the transfer surface (mirror surface) so as to allow the transfer surface to communicate with the ventilation surface. A pressure difference is generated between the transfer surface and the surface other than the transfer surface where the opening is formed, causing sinks on the surface other than the transfer surface where the vents are provided. Is prevented from occurring. In addition, in the injection mold described in Japanese Patent Application Laid-Open No. H11-28745, a cavity piece forming a surface other than the transfer surface is slid so as to be separated from the resin, thereby forcing the resin between the resin and the cavity piece. A void is formed in the resin portion, and a sink is generated in a resin portion facing the void to prevent sink of the transfer surface and to obtain a molded product having small internal distortion.

[0004]

However, in any of the above-mentioned injection molds, the cooling rate of the forcibly generated void portion is lower than that of the other cavity surfaces, so that the temperature inside the molded product is low. There is a disadvantage that a difference occurs and the molded product is deformed. In addition, there is a disadvantage in that the cooling time (molding cycle) is prolonged due to the accumulation of heat in the voids, and the productivity is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and is capable of forming a high-precision molded product stably at low cost even in a thick-walled or uneven-walled molded product. The purpose is to provide.

[0006]

SUMMARY OF THE INVENTION A molding die according to the present invention has a plurality of cavity pieces that define a cavity having a predetermined volume and a transfer piece having at least one transfer surface. When the molten resin injected and filled into the cavity is cooled to the softening temperature in one of the cavity pieces in the molding die that transfers the transfer surface to the resin by the pressure of the resin, a gap is formed in the cavity other than the resin transfer surface. And means for cooling is provided.

Means for forming a gap on a surface other than the transfer surface of the resin in the cavity and cooling the nest is provided slidably in one of the cavity pieces, and is provided with a movable nest pressed in the cavity direction by a pressure control device. Having a ventilation port and an exhaust port provided through the movable nest, when the molten resin injected and filled in the cavity is cooled to a softening temperature, the movable nest is retracted by a pressure control device, and the resin in the cavity is retreated. It is preferable to form a gap on a surface other than the transfer surface of the above, and supply cooling gas from the vent to the formed gap and discharge the gas from the exhaust port to cool the gap. Further, it is desirable to control the flow rate and temperature of the cooling gas supplied from the vent.

As means for cooling by forming an air gap on a surface other than the resin transfer surface in the cavity, a movable insert slidably provided in one of the cavity pieces and pressed in the cavity direction by a pressure control device. And a cooling medium circulation line provided in the movable nest, and when the molten resin injected and filled in the cavity is cooled to a softening temperature, the movable nest is retracted by the pressure control device to remove the resin in the cavity. A gap may be formed on a surface other than the transfer surface, and the cooling medium may be circulated through the cooling medium circulation pipe to cool the movable nest to cool the gap.

Further, as means for cooling by forming a gap on a surface other than the transfer surface of the resin in the cavity, a movable nest slidably provided in one of the cavity pieces and pressed in the direction of the cavity by a pressure control device. And a heat pipe having one end provided in the movable nest and the other end provided in the outside air, and when the molten resin injected and filled in the cavity is cooled to a softening temperature, the movable nest is provided. May be retracted by a pressure control device to form a gap on a surface other than the resin transfer surface in the cavity, and the movable nest may be cooled by a heat pipe to cool the gap.

As means for cooling by forming a gap on a surface other than the transfer surface of the resin in the cavity, a vent hole and an exhaust port provided through one of the cavity pieces are provided. When the injection-filled molten resin is cooled to the softening temperature, a pressurized gas is supplied from a vent to form a void on a surface other than the resin transfer surface in the cavity, and the formed void is supplied from the vent and exhausted. Cooling may be performed with pressurized gas discharged from the mouth.

Another molding die according to the present invention has a plurality of cavity pieces for defining a cavity having a predetermined volume and a transfer piece having at least one transfer surface, and is provided with a resin pressure generated in the cavity. In a molding die for transferring a transfer surface to a resin, a movable insert slidably provided in one of the cavity pieces and pressed in the cavity direction by a pressure control device, and a cavity piece opposed to the movable insert with the cavity interposed therebetween. When the molten resin injected and filled in the cavity is cooled to the softening temperature, the movable nest is retracted by the pressure control device to form a gap on a surface other than the resin transfer surface in the cavity, and the heating unit is provided. To heat the cavity piece facing the gap.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A molding die according to the present invention has a plurality of cavity pieces, a mirror piece and a movable insert, and a plurality of cavity pieces, a mirror piece and a movable insert form a cavity having a predetermined volume. The cavity surface forming the cavity of the mirror piece has at least one or more transfer surfaces. The movable nest is provided movably through one of the cavity pieces, and a pressure control device is connected to a surface opposite to the surface forming the cavity. The movable nest has a ventilation port for communicating the inside of the cavity with the outside, and an exhaust port for communicating the inside of the cavity with the outside when the movable nest is retracted. The vent is connected to a gas supply source such as a compressor via a flow control valve and a temperature control device.

When a plastic molded article is molded with this molding die, a molten resin is injected and filled into the cavity through a gate, and the transfer surface is transferred to the molded article by the resin pressure generated in the cavity, and cooled and solidified. The molded product is later taken out. In this injection molding step, the resin injected and filled into the cavity is cooled and solidified, and when the resin pressure reaches a predetermined pressure, the movable nest is retracted by the pressure control device and moved in a direction away from the molding surface, and the movable nest is moved. Voids are formed between the molded products. When the movable nest 6 moves, the compressed gas flows into the gap from the ventilation port and is discharged from the exhaust port to cool the gap, and the gap becomes a heat insulating layer, so that heat is trapped during molding and the temperature of the molded article rises. In addition, it is possible to prevent the cooling rate of the gap from becoming slower than that of the other cavity surfaces, and to prevent a temperature distribution difference inside the molded product from deforming the molded product, thereby forming a molded product with less distortion.

[0014]

Embodiment 1 FIG. 1 is a sectional view showing the structure of an embodiment of the present invention. As shown in the figure, a molding die 1 for molding a plastic molded product such as a plastic lens or a plastic mirror has cavity pieces 2, 3, and 4, a mirror piece 5, and a movable insert 6, and the cavity pieces 2 to 4 and a mirror face. The piece 5 and the movable nest 6 form a cavity 7 having a predetermined volume. The cavity surface forming the cavity 7 of the mirror piece 5 has at least one transfer surface 8. The movable nest 6 is provided movably through one of the cavity pieces 2, and a pressure control device 9 is connected to a surface opposite to a surface on which the cavity 7 is formed. Further, the movable nest 6 has a vent 10 communicating the inside of the cavity 7 with the outside, and an exhaust port 11 communicating the inside of the cavity 7 with the outside when the movable nest 6 is retracted. Vent 10 is a flow control valve 12
And a gas supply source 14 such as a compressor via a temperature controller 13.

When a plastic molded product is molded by the molding die 1, a molten resin of either a crystalline resin or an amorphous resin is injected and filled into the cavity 7 through a gate (not shown). The transfer surface 8 is transferred to the molded product by the generated resin pressure, and after being cooled and solidified, the molded product is taken out. When molding a molded product in this way, when the molten resin is injected and filled into the cavity 7, a pressing force higher than the maximum resin pressure generated in the cavity 7 is applied, and the movable nest 6 does not move due to the injection pressure. As shown in FIG.
As shown in the figure, the movable nest 6 is fixed by a pressure control device 9. When the resin injected and filled into the cavity 7 is cooled and solidified, and the resin pressure reaches a predetermined pressure,
As shown in FIG.
Is retracted and moved in a direction away from the molding surface to form a gap 16 between the movable nest 6 and the molded product 15. When the movable nest 6 moves as described above, compressed gas flows into the gap 16 through the vent 10 and is discharged from the exhaust port 11 to remove the compressed gas.
Cool 6 The resin in the portion of the molded article 15 facing the gap 16 becomes easier to move than other portions, and becomes a convex shape or a concave shape 17 while absorbing the stress generated by cooling.

As described above, since the compressed gas flows into the gap 16 formed by the movement of the movable nest 6 through the ventilation port 10 and is cooled, the gap 16 becomes a heat insulating layer and heat is trapped during molding. Rise, and the cooling rate of the cavity 16 can be prevented from becoming slower than that of the other cavity surfaces. This prevents a temperature distribution from occurring inside the molded product 15 and prevents the molded product 15 from being deformed. And the cooling time (molding cycle) is prevented from being lengthened.

If the cooling rate is too high when cooling the gap 16, the temperature of the part facing the gap 16 inside the molded article 15 becomes too low, and the opposite temperature distribution difference occurs inside the molded article 15. Resulting in. Therefore, the flow rate of the compressed gas to be supplied from the gas supply source 14 is adjusted by the flow rate control valve 12 to change the flow rate of the compressed gas for cooling, and the temperature of the compressed gas is adjusted to an appropriate temperature by the temperature control device 13 to thereby form the molded product 15. Cooling rate can be properly controlled. Thus, the void 1
When the ventilation port 10 or the exhaust port 11 for cooling 6 is provided at a position in contact with the resin, the opening width is 0.005 to 0.05 m.
m is desirable. By limiting the opening width of the ventilation port 10 or the exhaust port 11 as described above, it is possible to prevent the resin from entering during injection filling and generating burrs.

[Embodiment 2] In the above embodiment, the movable nest 6 is used.
The case where the compressed gas flows into the gap 16 created by the movement of the air through the ventilation port 10 and is discharged from the exhaust port 11 to cool the inside of the gap 16 has been described. However, as shown in FIG. A passage 18 may be provided, and a cooling medium such as water or oil may be circulated through the cooling pipe passage 18 from the refrigerant temperature controller 19. The cooling medium may be appropriately selected depending on the operating temperature. That is, the operating temperature range of the cooling medium is, for example, 10
It can be applied to a wide temperature range by using water if it is 0 ° C or less and using oil if it is 100 ° C or more. In this way, the cooling medium is provided in the movable nest 6 and the cooling medium is circulated to cool the movable nest 6 itself and cool the inside of the gap 16, so that the compressed gas flows directly into the gap 16 in a mold configuration. Even when this is not possible, the inside of the gap 16 can be cooled.

Third Embodiment As shown in FIG. 4, a heat pipe 20 is embedded in a movable
By performing air cooling on portions other than the portion embedded in the movable nest 6 of 0, the movable nest 6 itself can be cooled and the inside of the gap 16 can be cooled. In this case, by providing the cooling fins 21 in the portion of the heat pipe 20 embedded in the movable nest 6, the cooling effect can be further enhanced. By embedding the heat pipe 20 in the movable nest 6 and cooling the movable nest 6 itself to cool the inside of the gap 16, the mold structure can be simplified, and a supply device for compressed air, a cooling medium, and the like can be provided. Equipment can be eliminated.

[Embodiment 4] In each of the above embodiments, the compressed gas flows into the gap 16 formed by the movement of the movable nest 6 through the vent 10 and is discharged from the exhaust port 11, or the movable nest 6 is cooled by itself. Although the case where the inside of the gap 16 is cooled has been described, as shown in FIG. 5, a planar heating element 22 and a temperature sensor 23 are provided at the center of the cavity pieces 3 and 4 facing the movable insert 6 with the cavity 7 interposed therebetween. Cavity piece 2
When the movable nest 6 is moved to form the gap 16, the gap 16 becomes a heat insulating layer. When the temperature rises during molding and the temperature of the molded product 15 increases, the gap 16 is detected by the temperature sensor 23. The cavity piece 24 may be heated by the sheet heating element 22 while measuring the temperature of the opposed cavity piece 24 so that a difference in temperature distribution of the molded product 15 in the cavity 7 does not occur.

As shown in FIG. 6, the compressed gas flows into the gap 16 formed by the movement of the movable nest 6 through the ventilation port 10 and is discharged from the exhaust port 11 to cool the gap 16 without cooling the temperature sensor. The cavity piece 24 may be heated by the sheet heating element 22 while measuring the temperature of the cavity piece 24 facing the gap 16 at 23 so that a difference in the temperature distribution of the molded product 15 in the cavity 7 does not occur.

Further, a circulation path of a rod-shaped heater or a heating medium is provided in the cavity piece 24, or a sheet heating element 22, a rod-shaped heater or a circulation path of the heating medium is provided in the cavity pieces 3 and 4 without providing the cavity piece 24. May be provided.

[Embodiment 5] In each of the embodiments described above, the case where the movable nest 6 is provided is described. However, as shown in FIG. When the molten resin injected into the cavity is cooled and solidified and the resin pressure reaches a predetermined pressure, a compressed gas is sent from the vent 10 into the cavity 7 to form a gap 25 between the cavity piece 2 and the resin. Alternatively, the formed void 25 may be cooled by a compressed gas supplied from the ventilation port 10 and discharged from the exhaust port 11.

[0024]

As described above, according to the present invention, when the molten resin injected and filled in the cavity is cooled to the softening temperature in any of the cavity pieces, voids are formed on surfaces other than the transfer surface of the resin in the cavity. Since the cooling means is provided, the cooling rate of the gap can be made equal to that of the other cavity surface, a temperature distribution difference occurs inside the molded product, and the molded product is prevented from being deformed, and the distortion is reduced. A molded article can be formed stably.

A movable insert slidably provided in one of the cavity pieces and pressed in the cavity direction by a pressure control device, and a vent and an exhaust opening provided through the movable insert are provided. When the molten resin injected and filled in the cavity is cooled to the softening temperature, the movable nest is retracted by the pressure control device to form a gap on the surface other than the resin transfer surface in the cavity, and the formed gap is cooled by the cooling gas from the vent. Is supplied and exhausted from the exhaust port to cool the gap, whereby a gap having a predetermined volume can be formed in the resin in the cavity, and the formed gap can be surely cooled.

By controlling the flow rate and temperature of the cooling gas supplied from the vent, the temperature of the air gap can be controlled with high precision, and a molded product with little distortion can be formed stably.

Also, a movable nest slidably provided in one of the cavity pieces and pressed in the direction of the cavity by the pressure control device, and a cooling medium circulation pipe provided in the movable nest are provided. When cooling the injection-filled molten resin to the softening temperature, the movable insert is retracted by the pressure control device to form a gap on a surface other than the resin transfer surface in the cavity, and the cooling medium is circulated through the cooling medium circulation pipe. By cooling the movable nest to cool the gap, the temperature of the gap can be controlled with high accuracy with a simple configuration.

Further, a movable insert slidably provided in one of the cavity pieces and pressed in the cavity direction by the pressure control device, one end is provided in the movable insert, and the other end is provided in the open air. When the molten resin injected and filled in the cavity is cooled to the softening temperature, the movable nest is retracted by the pressure control device to form a gap on the surface other than the resin transfer surface in the cavity. By cooling the movable nest by the heat pipe to cool the gap, the structure of the molding die can be simplified.

A vent and an exhaust are provided through one of the cavity pieces to supply a pressurized gas from the vent when cooling the molten resin injected and filled into the cavity to a softening temperature. By forming a gap on the surface other than the transfer surface of the resin in the cavity, and cooling the formed gap with pressurized gas supplied from the vent and discharged from the exhaust port, forming a gap with a simple configuration It can be cooled, and the structure of the molding die can be further simplified.

Further, a movable insert slidably provided in one of the cavity pieces and pressed in the direction of the cavity by the pressure control device, and a heating section provided on the cavity piece opposed to the movable insert with the cavity interposed therebetween, are provided. When the molten resin injected into the cavity is cooled to the softening temperature, the movable insert is retracted by the pressure control device to form a gap on the surface other than the resin transfer surface in the cavity, and the heating unit is heated to face the gap. By heating the cavity piece to be formed, the temperature of the molded article in the cavity can be made uniform, and a molded article with less distortion can be formed stably.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a molding die according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the operation of the embodiment.

FIG. 3 is a cross-sectional view illustrating a configuration of a molding die according to a second embodiment.

FIG. 4 is a sectional view showing a configuration of a molding die according to a third embodiment.

FIG. 5 is a sectional view showing a configuration of a molding die according to a fourth embodiment.

FIG. 6 is a sectional view showing the configuration of another molding die according to the fourth embodiment.

FIG. 7 is a sectional view showing a configuration of a molding die according to a fifth embodiment.

[Explanation of symbols]

1; Mold, 2-4; Cavity piece, 5; Mirror piece,
6; movable nest, 7; cavity, 8; transfer surface, 9; pressure control device, 10; ventilation port, 11; exhaust port, 12; flow control valve, 13; temperature control device, 14;

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Kiyotaka Sawada 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 4F202 AK02 AR06 AR14 CA11 CB01 CK18 CK43 CK52 CN01 CN05 CN21 CP01 CP04 4F206 AK02 AR067 AR14 JA03 JA07 JL02 JM05 JN25 JN43 JP17 JQ81

Claims (7)

[Claims] A molding die having a plurality of cavity pieces defining a cavity having a predetermined volume and a transfer piece having at least one transfer surface, and transferring the transfer surface to a resin by a resin pressure generated in the cavity. In the mold, one of the cavity pieces is provided with a means for forming a gap on a surface other than the transfer surface of the resin in the cavity to cool the molten resin injected and filled into the cavity to a softening temperature, and cooling the resin. Mold. 2. A means for forming a gap on a surface other than the transfer surface of the resin in the cavity and cooling it is slidably provided in one of the cavity pieces, and is movable in a direction of the cavity by a pressure control device. A nest, having a ventilation port and an exhaust port provided through the movable nest, when the molten resin injected and filled in the cavity is cooled to a softening temperature, the movable nest is retracted by a pressure control device, and The molding die according to claim 1, wherein a void is formed on a surface other than the resin transfer surface, and a cooling gas is supplied to the formed void from a vent and discharged from an exhaust outlet to cool the void. 3. The molding die according to claim 2, wherein the flow rate and the temperature of the cooling gas supplied from the vent are controlled. 4. A means for forming a gap on a surface other than the transfer surface of the resin in the cavity and cooling it is provided slidably in one of the cavity pieces, and is movable in a direction of the cavity by a pressure control device. A nest, and a cooling medium circulation pipe provided in the movable nest. When the molten resin injected and filled in the cavity is cooled to a softening temperature, the movable nest is retracted by a pressure control device to reduce the resin in the cavity. The molding die according to claim 1, wherein a gap is formed on a surface other than the transfer surface of the mold, and a cooling medium is circulated through a cooling medium circulation pipe to cool the movable nest to cool the gap. 5. A means for forming a gap on a surface other than the transfer surface of the resin in the cavity and cooling it, the means being slidably provided in any of the cavity pieces, and being movable in the direction of the cavity by a pressure control device. A nest, one end of which is provided in the movable nest, and the other end of which has a heat pipe provided in the outside air, and is movable when the molten resin injected and filled in the cavity is cooled to a softening temperature. The molding die according to claim 1, wherein the nest is retracted by a pressure control device to form a gap on a surface other than the resin transfer surface in the cavity, and the movable nest is cooled by a heat pipe to cool the gap. 6. The means for forming a gap on a surface other than the transfer surface of the resin in the cavity and cooling it has a vent and an exhaust provided through one of the cavity pieces.
When the molten resin injected and filled in the cavity is cooled to the softening temperature, a pressurized gas is supplied from the vent to form a void on the surface other than the resin transfer surface in the cavity, and the formed void is supplied from the vent. A molding die cooled by pressurized gas discharged from an exhaust port. 7. A molding die having a plurality of cavity pieces defining a cavity having a predetermined volume and a transfer piece having at least one transfer surface, and transferring the transfer surface to the resin by a resin pressure generated in the cavity. The mold has a movable insert slidably provided in one of the cavity pieces and pressed in the direction of the cavity by the pressure control device, and a heating section in the cavity piece opposed to the movable insert with the cavity interposed therebetween. When the injection-filled molten resin is cooled to the softening temperature, the movable nest is retracted by the pressure control device to form a void on a surface other than the resin transfer surface in the cavity, and the heating unit is heated to face the cavity. A molding die characterized by heating a piece.