JPH05253992A - Core pin for mold - Google Patents

Abstract

PURPOSE:To provide a core pin for a mold which can cool a boss part in a short time, prevent a sink and reduce a cycle time in injection molding. CONSTITUTION:A pin main body 15 of a core pin 14 forming a core by inserting the tip part 16 within a cavity 4 into which heat-meltable resin is filled by being formed into a mold main body 1 is constituted of the tip part 16 inserted into the cavity 4 and a base end part 17 over an outer circumference of which an ejector cylinder 12 is fitted movably freely in an axial direction. Then an air passage 20 communicating with a compressed air supply source 22 is provided on the base end part 17 of the pin main body 15, the tip part 16 of the pin main body 15 is cooled by air circulating through the air passage 20 and the tip part 16 of the pin main body 15 is cooled by the air even if the tip part 16 is heated directly by molten resin through which heat of a boss 7a is taken away from the boss 7a and the core pin 14 can be cooled efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core pin for a molding die used when molding a molded product having a hollow boss in a part of the molded product.

[0002]

2. Description of the Related Art For example, a cabinet made of synthetic resin for electric equipment such as a television and an electric vacuum cleaner is integrally molded by an injection molding die.
A large number of bosses are provided on the inner surface of the cabinet. These bosses are used as a mount for mounting a printed circuit board and electric parts.

Therefore, usually, at the same time when the cabinet is molded, a mounting hole is formed in the boss and a hollow boss is molded. Then, after molding, a female screw is engraved in this mounting hole to fix the printed circuit board and electric parts with the mounting screw.

In the molding die for injection-molding the cabinet having the boss in this way, a cavity for forming the main body of a molded product is provided between the fixed die and the movable die, and the cavity is formed in the movable die. A cavity for a boss that communicates is provided. Further, the movable mold is provided with a core pin having a tip portion inserted into the boss cavity, and a sleeve is fitted to the outside of the core pin.

Therefore, the main part of the cabinet as a molded product is thin, but the boss part is thick, and the boss part solidifies more slowly than the main part of the cabinet. Therefore, in order to concentrate and cool the boss portion, a cooling medium passage such as cooling water is provided around the boss cavity so that the time for the resin in the boss portion to solidify is close to the time for the resin in the main cabinet portion to solidify. I have to.

However, the boss is close to the inner peripheral surface of the cabinet, and in the structure having a plurality of ribs for reinforcing the outer circumference of the boss, the cooling medium passages are not provided close to each other. Can not. Therefore, the molding cycle time is actually long in a molded product having a thick portion such as a boss.

Further, in the past, in order to solve the above-mentioned problems, Japanese Utility Model Laid-Open No. 63-6154, Japanese Patent Laid-Open No. 63-194920, Japanese Utility Model Publication No. 1-85014 and Japanese Utility Model Publication No. As disclosed in Japanese Patent No. 85015,
A structure has been proposed in which a thick portion such as a boss is concentrated and cooled.

That is, Japanese Utility Model Laid-Open No. 63-6154 discloses a core pin provided with a cooling hole and a cooling pipe communicating with the cooling hole for circulating a cooling medium.

In Japanese Patent Laid-Open No. 63-194920, a fixed pin and a movable pin which can be connected with abutting portions sandwiched therebetween are provided in a cavity of a molding die, and compressed air is applied to the axis of the fixed pin and the movable pin. The fixed pin and the movable pin are cooled by the compressed air by providing the small holes for circulation.

In Japanese Utility Model Laid-Open No. 1-85014, a cooling pin for forcibly cooling the thick portion of a molded product is provided, the mold is first cooled, and then the mold is opened. Cooling air is blown onto the thick portion from the tip.

Further, Japanese Utility Model Laid-Open No. 1-85015 discloses that
A sleeve is fitted on the outside of a core pin inserted into a tubular portion such as a boss, and a cooling air circulation hole communicating with a cooling air passage is provided in the middle of the sleeve to forcibly cool the core pin. Is.

[0012]

However, in the cooling structure for the core pins of Japanese Utility Model Laid-Open No. 63-6154, the cooling water or the cooling air is provided by providing a cooling pipe communicating with the cooling holes of the core pins. It is a structure that circulates, and the seal structure of the connection part becomes complicated.

Japanese Unexamined Patent Publication No. 63-194920 has a structure in which a fixed pin and a movable pin are provided with a small hole through which compressed air flows, and there is a limit to the diameter reduction of the pin and the length of the pin. If the length is too long, it will be difficult to manufacture, and it will increase the cost.

Further, Japanese Utility Model Laid-Open No. 1-85014 discloses a structure in which cooling air is blown from the outer periphery to a thick portion such as a boss, so that the cooling efficiency is poor, and if the distance of the cooling air to the nozzle becomes long, cooling will be performed. The temperature of the air rises and it cannot be cooled sufficiently.

Further, Japanese Utility Model Laid-Open No. 1-85015 has a structure in which the middle portion of the core pin is cooled and the boss is cooled by heat conduction of the core pin. Cooling efficiency is poor unless the vicinity of the tip of the core pin is cooled. In many cases, it is difficult to design an air passage for use near the tip of the core pin.

The present invention has been made in view of the above circumstances, and an object thereof is to efficiently insert the tip end portion of a core pin which is inserted into a cavity filled with a hot melt resin and forms a core. It is an object of the present invention to provide a core pin for a molding die, which can be cooled and solidified by cooling even a thick portion such as a boss in a short time, and the cooling passage of the molding die can be simplified.

[0017]

In order to achieve the above-mentioned object, the present invention is a molding for forming a core by inserting a tip into a cavity formed in a mold and filled with a hot-melt resin. In the die core pin, the pin body is composed of a tip end portion inserted into the cavity and a base end portion around which an ejector cylinder is axially movably fitted, and the pin body is attached to the base end portion of the pin body. An air passage communicating with the compressed air supply source is provided, and the tip portion of the pin body is cooled by the air flowing through the air passage.

[0018]

The air supplied from the compressed air supply source is guided to the tip portion of the pin body through the air passage of the pin body, and the tip portion is cooled by this air. Can be cooled.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show a first embodiment, and FIG. 1 is an overall view of an injection molding die. Reference numeral 1 denotes a mold body, which is composed of a fixed mold 2, a movable mold 3, and a cavity 4 which is formed between the molds 2 and 3 and forms a main body 4a of a molded product. A spool bush 6 having a resin injection port 5 communicating with the cavity 4 is provided in the center of the fixed mold 2.

A boss cavity 7 for forming a boss 7a on a part of the molded product is provided in a part of the movable mold 3 so as to communicate with the cavity 4. The movable mold 3
A movable-side template 9 is provided in the interior of the ejector plate 1 through a frame body 8, and the ejector plate 1 is provided in a space portion 10 surrounded by the frame body 8.
1 is provided.

The ejector plate 11 is fixed to the base end of an ejector cylinder 12 made of a cylindrical pipe, and projects in the direction of the movable mold 3. That is, the movable mold 3 is provided with a through hole 13 coaxially formed with the boss cavity 7. The ejector cylinder 12 is inserted into the through hole 13 so as to be movable back and forth in the axial direction, and its tip end surface is in contact with the tip end surface of the boss 7a.

Further, a core pin 14 is inserted inside the ejector cylinder 12. As shown in FIG. 2, in the core pin 14, a tip portion 16 of a pin body 15 formed by a small-diameter shaft has a small diameter. The base end portion 17 of the pin body 15 which remains the tip end portion 16 is formed to have a diameter slightly smaller than the inner diameter of the ejector cylinder 12, and a gap g is formed between the two so as to allow air to flow therethrough.

A flange portion 18 is provided at the end of the base end portion 17 of the pin body 15. Further, an air passage 20 formed of a fine hole is bored in the axial center portion of the pin body 15. The air passage 20 is formed by the base end portion 17 of the pin body 15.
To the vicinity of the tip portion 16, and the hole end portion 2
The nozzle 21 is formed of a plurality of (four in this embodiment) fine holes penetrating the outer periphery of the pin body 15 obliquely upward from 0a. Therefore, the air passage 2
0 communicates with the gap g through the nozzle 21.

The core pin 14 constructed as described above is inserted into the ejector cylinder 12, and the base end side of the core pin 14 penetrates the ejector plate 11 and the movable side mold plate 9 to form the base end portion 17. The flange portion 18 is the movable side mold plate 9
It is fixed to. Then, the tip portion 16 of the core pin 14
Is extended to the inside of the boss cavity 7 and is inserted into the central portion thereof to form a mounting hole 7b in the boss 7a.

Further, the air passage 20 opening to the base end portion 17 of the core pin 14 is a compressed air supply source provided outside the mold body 1 via an air circulation port 19 formed in the movable side mold plate 9. It communicates with 22.

Next, the operation of the molding die core pin configured as described above will be described. When the heated molten resin is injected from the resin injection port 5 by the injection molding machine, as shown in FIG.
As shown in (a), the molten resin is filled in the cavity 4 and the boss cavity 7. On the other hand, when compressed compressed air is supplied from the compressed air supply source 22, the air flows through the air passage 20 of the pin body 15, is guided to the tip portion 16 and is ejected from the nozzle 21.

The air ejected from the nozzle 21 is guided below the ejector cylinder 12 through the gap g between the ejector cylinder 12 and the pin body 15, and leaks to the outside from the joint between the ejector cylinder 12 and the ejector plate 11. .. Therefore, the tip 16 of the pin body 15 is constantly blown with new cooling air, and the tip 16 of the pin body 15 is directly cooled by the cooling air.

That is, since the tip portion 16 of the pin body 15 is inserted into the boss cavity 7, it is directly heated by the molten resin.
Since 6 is cooled by the air, the heat of the boss 7a can be removed to efficiently cool the boss.

After the main body 4a and the boss 7a of the molded product 4 are cooled and the resin is solidified, as shown in FIG. 2B, when the movable mold 3 is released from the fixed mold 2 in a direction away from the fixed mold 2,
The main body 4a of the molded product is released from the fixed mold 2,
As shown in FIG. 2C, the boss 7 a is the ejector cylinder 12
Is ejected at the tip end surface of the mold and is released from the movable mold 3.

At this time, the ejector cylinder 12 and the core pin 1
4, the tip portion 16 of the pin main body 15 is housed in the ejector cylinder 12 and a wide gap is formed between the two pipes, so that the air introduced into the gap g is ejected from the ejector cylinder 12 Is jetted toward the boss 7a on the tip side through the inside of the.

In this way, the boss 7a is cooled from the inside by the tip portion 16 of the pin body 15, and the ejector cylinder 12 is
Since it is cooled by air even when it is projected at the tip end surface of the molded article, it can be cooled in a short time, and it is possible to prevent a sink mark caused by a delay in cooling the boss 7a from the main body 4a portion of the molded product, as in the conventional case. Further, there is an effect that the cycle time of injection molding can be shortened.

Although the core pin 14 in the first embodiment is formed with the air passage 20 by drilling from the base end side of the pin body 15 composed of a small diameter shaft, it may be formed hollow by a pipe. Good.

FIG. 3 shows a second embodiment, in which a part of the core pin is constructed by a heat pipe.
That is, 23 is a core pin, and the tip end portion of the pin body 24 is formed by the heat pipe 25 and the base end portion is formed by the shaft portion 26.

The end side of the heat pipe 25 is formed to have a small diameter so that it can be inserted into the boss cavity 7. An air passage 27 is formed in the shaft portion 26. The air passage 27 penetrates to the vicinity of the upper end portion of the shaft portion 26, and the pin main body 2 extends obliquely upward from the hole end portion 27a.
4 penetrating the outer periphery of 4 (in this embodiment, 4
The nozzle 28 formed of a fine hole is provided. Therefore, the air passage 27 communicates with the gap g via the nozzle 28.

Inside the heat pipe 25, a wick having a capillary action and a working fluid are enclosed from the base end side, and the base end opening is sealed by a blind plate 25a. Then, the end portion of the heat pipe 25 has the heat absorbing portion 2
The base end portion is formed on the heat radiating portion 25c at 5b.

Therefore, when the cooling air is circulated in the air passage 27, the air circulates in the air passage 27 of the pin body 24, is guided to the tip side, and is ejected from the nozzle 28. Therefore, the heat dissipation portion 25c of the heat pipe 25 is directly cooled by the cooling air.

Since the tip of the heat pipe 25 of the pin body 24 is inserted into the boss cavity 7, it is directly heated by the molten resin, but the tip is a heat absorbing section.
Since the base end portion is formed in the heat radiating portion, when the heat absorbing portion is heated, the working liquid contained in the wick robs the latent heat of vaporization and is vaporized, so that the pressure of the heat absorbing portion becomes higher than that of the heat radiating portion.

Due to this pressure difference, the vapor moves to the heat radiating portion at a high speed, and the vapor is cooled and condensed in the heat radiating portion, and the same amount of latent heat of condensation as at the time of vaporization is released. The working fluid condensed in the heat radiating section is returned to the heat absorbing section by the capillary action of the wick. In this way, heat is transported by the cycle of evaporation → movement of vapor → condensation → reflux, and the radiating portion is forcibly cooled by the cooling air, so that the boss 7a can be rapidly cooled.

As described above, since the boss 7a can be cooled from the inside by the tip portion of the heat pipe 25 of the core pin 24, the boss 7a can be cooled in a short time and the cycle time of injection molding can be shortened.

[0041]

As described above, according to the present invention, the pin main body is composed of the tip end portion inserted into the cavity and the base end portion around which the ejector cylinder is axially movably fitted. Since the air passage communicating with the compressed air supply source is provided at the base end portion of the pin body, and the tip portion of the pin body is cooled by the air flowing through the air passage,
It can cool thick parts such as bosses in a short time.

Therefore, it is possible to cool in a short time, it is possible to prevent a sink mark caused by delaying the cooling of the boss from the main body of the molded product as in the conventional case, and it is possible to shorten the cycle time of injection molding, thereby improving productivity. There is an effect that it can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of a molding die showing a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional front view for explaining the action of the core pin of the embodiment.

FIG. 3 is a vertical sectional front view of a core pin showing a second embodiment of the present invention.

[Explanation of symbols]

4 ... Cavity, 12 ... Ejector cylinder, 14 ... Core pin, 15 ... Pin body, 16 ... Tip part, 17 ... Base end part, 2
0 ... Air passage, 22 ... Compressed air supply source.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area // B29L 31:34 4F

Claims (1)

[Claims] 1. A core pin for a molding die, wherein a tip is inserted into a cavity formed in a die and filled with a heat-melting resin to form a core. A pin body is inserted into the cavity. It is composed of a tip and a base end on the outer circumference of which an ejector cylinder is fitted so as to be movable in the axial direction. An air passage communicating with a compressed air supply source is provided at the base end of the pin body. A core pin for a molding die, characterized in that the tip end of the pin body is cooled by the air.