JPH07290540A - Manufacture of plastic molded form - Google Patents

Abstract

PURPOSE:To provide an apparatus for manufacturing a plastic molded form without generating a weld line. CONSTITUTION:Molten resin is injected from resin injecting gates 2a, 2b provided at a resin passage 1 of molds. The resin flows in directions of 3a, 3b, and which are connected at a combining point d Temperature regulating inserts 5a, 5b, 5c having heating 4. cooling systems are installed in molds near the point 4, and so controlled that a temperature near the point 4 partly becomes about 60 deg.C. As a result, resin connecting parts are fusion-bonded to suppress generation of a weld line. When the fusion bonding of the resin is finished, cooling water is supplied to cooling circuits of the inserts 5a, 5b, 5c to be quickly cooled. Plastic molded form is taken out from molds. Thus, a manufacturing cycle of the form can be shortened to improve productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a plastic molded article, and more particularly to an apparatus for producing a plastic molded article capable of producing a plastic molded article having no weld line.

[0002]

2. Description of the Related Art Conventionally, various plastic molded products have been produced by injection molding. Cabinets, which are parts for attaching television cathode-ray tubes, have also been conventionally made by injection molding. This TV cabinet has a large opening for exposing the picture plane of the cathode ray tube, and the amount of plastic resin used is large, so a mold with multiple molten resin filling ports during injection molding. Are using.

When this mold is used, the resin injected from each molten resin filling port and circulating in the mold usually meets at an intermediate position between the filling ports, and a single weld line is generated at that position. .

This weld line also appears on the outer surface of the molded product, and is disliked in design parts such as television cabinets as a factor that deteriorates the quality. Therefore, conventionally, a large amount of high-temperature water or oil is caused to flow in the heating passage arranged in the mold so that the temperature of the molten resin does not fall below the fusion temperature so that the weld line does not occur. It is considered.

[0005]

However, in the above-mentioned prior art, there is a problem that the temperature of the entire die rises, the die sliding portion easily breaks, and the die accuracy decreases. . Further, after the injection of the molten resin, it is necessary to cool the mold for taking out the molded product, but this cooling requires a long time (for example, about 10 minutes), the molding cycle becomes long, and the productivity is lowered. There was a problem.

The object of the present invention is to eliminate the above-mentioned problems of the prior art, and to manufacture a molded product without a weld line without lowering the mold precision and lengthening the molding cycle. It is to provide an apparatus for manufacturing a plastic molded product.

[0007]

In order to achieve the above-mentioned object, the present invention is a device for manufacturing a plastic molded product having a mold having a plurality of resin injection gates, wherein a resin injected from the resin injection gate is used. The present invention is characterized in that it is provided with a temperature control insert provided with a heating / cooling system provided in the mold near the joint part of (1) and a controller for controlling the heating / cooling system of the temperature control insert.

[0008]

According to the present invention, by controlling the heating / cooling system of the temperature adjusting insert from the controller, the mold surface temperature in the vicinity of the joint portion at the time of molding can be partially adjusted. It will be possible. As a result, without lowering the mold accuracy or lengthening the molding cycle,
It becomes possible to manufacture a molded product without a weld line.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. 1 (a) and 1 (b) respectively show a schematic front view of a mold of one embodiment of the present invention and a right side view seen from the aa side.

In the figure, 1 is a resin passage (gap) formed by a mold of a television cabinet, for example.
2a, 2b are resin injection gates provided in the mold, 3
Reference numerals a and 3b respectively show a flow of the molten resin injected from the resin injection gates 2a and 2b, and 4 shows a confluence point of the molten resins. Further, 5a, 5b and 5c show temperature adjusting nests provided with a heating / cooling system provided at the confluence of the molten resins.

Next, regarding the structure of the temperature adjusting insert,
The details will be described. FIG. 2 is a plan view of the temperature adjusting insert 5a,
3 is a sectional view taken along the line bb of FIG. 2, and FIG. 4 is a sectional view taken along the line cc of FIG. Since the other temperature adjustment inserts 5b and 5c have the same configuration as the temperature adjustment insert 5a, the temperature adjustment insert 5a will be described as a representative of these and will be described in detail below.

As shown, the temperature control insert 5a
Is composed of three parts, a temperature adjusting piece 11, a heat insulating material 12, and an incorporated adjusting piece 13. Further, four heaters 14 are arranged in the temperature adjusting piece 11, as is apparent from FIG. A cooling circuit 15 is supplied with a cooling medium such as water through the cooling water valve 18 and the hose 20. 19 is the cooling circuit 15
And a connection plug for the hose 20. A temperature sensor 16 is built in the temperature adjusting piece 11, and the control device 17 controls the heater 14 and the heater 14 based on a detection signal from the temperature sensor 16 and a signal from a molding machine (not shown). A control signal for turning on and off the cooling water valve 18 is output. Reference numeral 21 is a mold temperature raising section.

FIG. 5 shows a sectional view of a part of the mold when the temperature adjusting insert 5a is attached to the mold 1a. Reference numerals 1a and 1b denote molds, and the molten resin flows from both directions of 3a and 3b and joins at a joining point 4. A temperature adjusting insert 5a is attached to the mold 1a so that the mold temperature raising portion 21 faces the junction point 4. Incidentally, reference numerals 11, 12, 13
Are the temperature adjusting piece, the heat insulating material, and the built-in adjusting piece, respectively.

Next, the operation of the control device 17 will be described with reference to the sequence diagram of FIG. First, when an extrusion plate return signal is input to the control device 17 from a molding machine (not shown), the control device 17 starts energizing the heater 14. The temperature of the mold temperature raising section 21 heated by the heater 14 is detected by the temperature sensor 16 and notified to the control device 17. Next, when the temperature detected by the temperature sensor 16 reaches a predetermined temperature (for example, 60 ° C. to 100 ° C.) after the mold clamping completion signal is received, the controller 17 completes the temperature rise and maintains this temperature. . At this time, the molten resin is injected from the resin injection gate by an injection device (not shown). When the injection completion signal reaches the control device 17, the control device 17 stops energizing the heater 14, opens the cooling water valve 18, and sends the cooling water to the cooling circuit 15. When it is determined by the detection signal from the temperature sensor 16 that the temperature has been cooled to a predetermined temperature, the cooling water valve 18 is closed, the supply of cooling water is stopped, and the mold is opened. Subsequently, the product is taken out. This completes the operation of one cycle.

FIG. 7 is a comparison of how weld lines are formed when injection molding is performed by the apparatus of the present invention and when injection molding is performed by a conventional apparatus. According to the apparatus of the present invention, it was confirmed that no weld line was generated in the product when the temperature of the mold temperature raising section 21 was set to 60 ° C to 100 ° C by the heater 14. On the other hand, in the conventional device, the temperature of the entire mold is 100
A weld line was generated even at ° C. Therefore, according to the present invention, at a much lower temperature than conventional devices,
Moreover, the local heating can suppress the generation of weld lines.

FIG. 8 is a view showing an example of a plastic molded product manufactured by the plastic molded product manufacturing method of the present invention. The figure shows a perspective view of the cabinet of the television receiver, 31 is an opening for exposing the image plane, 32 is
Indicates a cabinet. Since the cabinet 32 made according to the present invention does not have a weld line on its surface that deteriorates the quality of the design, in order to hide the weld line, the cabinet surface is painted or another sheet is used as in the conventional case. There is no need to attach them.

[0017]

According to the present invention, a part of the mold is heated and
Since the temperature adjusting insert having the cooling system is provided and the temperature of the joint portion of the molten resin can be set to the fusion temperature or higher, a molded product having no weld line can be manufactured. Further, since only a part of the mold is heated, the sliding part of the mold is not likely to be broken and the accuracy of the mold is not deteriorated. Further, the cooling of the mold after the injection of the molten resin can be performed in a short time (for example, about 1 minute), the molding cycle can be shortened, and the productivity can be improved.

[Brief description of drawings]

FIG. 1 shows a schematic front view and a right side view of a resin passage formed by a mold according to an embodiment of the present invention.

FIG. 2 is a plan view of a temperature adjusting insert used in the present invention.

FIG. 3 is a sectional view taken along line bb of FIG.

FIG. 4 is a sectional view taken along line cc of FIG.

FIG. 5 is a cross-sectional view of a part of a mold equipped with a temperature adjusting insert.

FIG. 6 is a sequence diagram showing a temperature control operation of the present invention.

FIG. 7 is a diagram for comparatively explaining the occurrence of weld lines in the present invention and a conventional device.

FIG. 8 is a perspective view showing an example of a plastic molded product molded according to the present invention.

[Explanation of symbols]

1 ... Mold resin passage 2a, 2b ... Resin injection gate, 3
a, 3b ... Flow of molten resin, 4 ... Confluence point of molten resin, 5
a, 5b, 5c ... Temperature adjusting insert, 11 ... Temperature adjusting piece, 1
2 ... Insulation material, 13 ... Built-in adjustment piece, 14 ... Heater, 15
... Cooling circuit, 16 ... Temperature sensor, 17 ... Control device, 18
… Cooling water valve, 19… Connection plug, 20… Hose, 2
1 ... Mold temperature raising section.

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technology display location B29C 45/78 7365-4F (72) Inventor Shu Furuta 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd. (72) Inventor Nobuo Fukuda 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside Hitachi Design Laboratory

Claims (2)

[Claims] 1. A manufacturing apparatus for a plastic molded product having a mold having a plurality of resin injection gates, wherein a heating / cooling system is provided in the mold near the joint of the resin injected from the resin injection gate. And a controller for controlling the heating / cooling system of the temperature adjusting insert, and the mold surface temperature in the vicinity of the joint during molding can be partially adjusted. An apparatus for manufacturing a plastic molded product, which is characterized in that 2. The apparatus for manufacturing a plastic molded product according to claim 1, wherein the temperature adjusting insert has a temperature adjusting piece, and the temperature adjusting piece has a heater, a cooling circuit and a temperature sensor built therein. Equipment for manufacturing plastic molded products.