JPH0647779A - Injection nozzle for molding liquid silicone rubber - Google Patents

Abstract

PURPOSE:To prevent a phenomenon such as trailing when a liquid silicone rubber is injection-molded from occurring by designing an injection nozzle so that a temperature boundary generates in a nozzle tip and a sprue is cut near the temperature boundary. CONSTITUTION:The subject nozzle is composed of a main nozzle system 13 equipped with a cooling means around an outer periphery, and a nozzle tip 18 with a screw attached to the tip. The nozzle orifice 19 at the extreme end of the nozzle tip 18 is formed slightly smaller than the opening of a sprue. A passage 17 between the nozzle orifice 19 and a flow path 15 in the main nozzle system is formed smaller in diameter than the nozzle orifice 19 and a stepped part 20 is formed in the nozzle orifice 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection nozzle used when a liquid silicone rubber is injected and filled in a mold to form a predetermined molded product.

[0002]

2. Description of the Related Art Injection molding of silicone rubber (hereinafter referred to as molding material) is carried out by injection-filling a liquid molding material into a mold whose temperature is controlled to a vulcanization temperature, and vulcanizing the molding material at the mold temperature for molding. It is described as an item. Further, as the injection nozzle, one having the same specifications as the injection nozzle in the case of injection molding a thermoplastic resin has been used. Therefore, there are problems as shown in FIG.

[0003]

As shown in FIG. 2, in the injection filling of a liquid molding material, the nozzle portion 4 at the tip of the nozzle body 3 is brought into contact with the opening of the sprue 2 of the mold 1 (nozzle touch). Although not shown in the figure, the molding material in the injection cylinder at the rear of the nozzle body is pressurized by the plunger and injected from the flow path 5 to the mold side through the nozzle port 6 after the above.

If the nozzle is still touching after injection and filling, the mold sprue 2 will be released when the molded product (not shown) is released.
The unvulcanized molding material in the flow path 5 connected to the sprue 7 in the inside causes string pulling, and a part 7a thereof is cut off and pulled into the mold sprue while attached to the sprue 7, May remain attached to the.

Further, when the nozzle touch time is long, the temperature of the nozzle portion 4 rises due to heat conduction from the mold side, and as shown in FIG. 3, even the molding material in the flow path 5 is vulcanized. After the molded product is released from the mold, it remains as a vulcanized material in the injection nozzle. These residual materials, including those in the mold sprue, impede the flow of the molding material during injection filling and also cause the deterioration of the quality of the molded product when filled in the mold together with the molding material.

Therefore, as a means for solving the above problem, the tip of the injection nozzle is separated by retreating after injection filling.
However, since the sprue 7 is in the process of vulcanization immediately after the injection filling is completed and the molding material in the nozzle mouth is liquid, as shown in FIG. It is easy, and a part thereof adheres to the tip surface of the injection nozzle 4, and further adheres around the sprue opening when the nozzle is touched.

When the nozzle touch is performed again in such a state, the nozzle touch comes to be performed under the interposition of the adhering substance, and the adhering substance is vulcanized by the heating from the mold side to open the sprue. The close contact between the nozzle and the tip surface of the nozzle is impaired, and a gap is created, which easily causes material leakage. Further, if molding is repeated while leaving the adhered substance as it is, the adhered substance is caught in the molding material at the time of injection filling and filled in the mold together, which causes deterioration of the quality of the molded product.

The present invention has been conceived in order to solve the problems involved in the injection and filling of the above-mentioned liquid molding material into a mold, and its purpose is to create a temperature boundary inside and Another object of the present invention is to provide a new injection nozzle that enables cutting of sprue near the boundary, thereby making it difficult for stringing and deposits to occur even if nozzle touch is continued.

[0009]

The feature of the present invention according to the above object is that it comprises a nozzle body having a cooling means on the outer periphery and a nozzle tip screwed to the tip portion of the nozzle body. The opening is formed to have a diameter slightly smaller than the sprue opening of the mold, and the passage between the nozzle opening and the flow path in the nozzle body is made smaller in diameter than the nozzle opening to form a step in the nozzle opening. .

[0010]

[Operation] In the above configuration, since there is a step in the nozzle opening due to the difference in diameter with the passage, when a tensile force acts on the sprue when the molded product is released, the molding material in the nozzle opening is vulcanized at that step. The part is separated from the unvulcanized part. At this time, even if the unvulcanized portion causes stringing, it is extremely small and does not affect the subsequent molding.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the embodiment shown in FIG. In the figure, 11 is a mold and 12 is a mold sprue having an opening peripheral surface formed into a concave spherical surface. A nozzle body 13 is provided with a cooling jacket 14 around the nozzle body.

Although not shown in the drawing, the nozzle main body 13 is mounted on the tip of an injection cylinder in which an injection plunger is installed so as to move forward and backward, and has a flow passage 15 at the center of the inside. Further, a core 16 having a thread on the outer peripheral side is provided in a protruding manner at the center of the tip of the nozzle body 13, and the end of the flow path 15 is located inside the core 16 and the tip from the end. A small-diameter passage 17 is provided through the surface.

Reference numeral 18 denotes a cap nut-shaped nozzle tip having a convex spherical end surface, which is screwed to the core 16 by a screw provided on the inner peripheral side. The nozzle opening 19 at the tip of the nozzle tip 18 is formed with a diameter slightly smaller than the opening of the mold sprue 12, and a through hole serving as an extension of the passage 17 is formed at the center of the nozzle opening 19. I am doing it.

The diameter of the passage 17 between the nozzle opening 19 and the flow path 15 is smaller than that of the nozzle opening 19 (1;
(Ratio of 2 to 0.5), thereby forming the step portion 20 in the nozzle opening.

Liquid molding material (2000 pos.
The mold 11 used in the injection molding of 00 pos.
The temperature is adjusted to a temperature of ℃ to 180 ℃. In addition, the nozzle body 1
3 is cooled to a temperature of 5 ° C. to 20 ° C. by the cooling jacket 14. Even if the rear end surface of the nozzle tip 18 is separated from the front end surface of the nozzle body 13, the core 16 is cooled.
Since it reaches the nozzle tip 18 through the above, the nozzle tip 18 is also maintained at a low temperature in a state of being separated from the mold 11.

The injection molding of the liquid molding material into the mold 11 is always performed with the nozzle being touched. Therefore, the nozzle tip 18 is heated by heat conduction from the mold 11. However, due to the cooling from the core 16, it is difficult for the heating to reach the deep portion of the nozzle tip where the passage 17 is present, and the surroundings of the nozzle opening are maintained at a low temperature. For this reason, the periphery of the nozzle port is located in the vulcanization temperature region, and the periphery of the passage is located in the non-vulcanization temperature region, so that the vulcanization of the molding material after injection filling occurs even in the nozzle port.

Since the molding material in the passage is unvulcanized and has the step portion 20 at the boundary with the nozzle opening 19 due to the difference in diameter, the sprue 21 integrated with the molding product (not shown) is formed. When a tensile force acts at the time of release, the vulcanized portion is separated from the unvulcanized portion at the step portion 20. Even if the unvulcanized portion causes stringing at this time, since the diameter of the passage 17 is small, the amount thereof is extremely small and does not affect the subsequent molding.

[0018]

As described above, according to the present invention, the passage 17 between the nozzle opening 19 of the nozzle tip 18 and the flow passage 15 in the nozzle body 13 is made smaller in diameter than the nozzle opening 19 and the step portion 20 is formed in the nozzle opening. Since the temperature around the nozzle mouth is maintained at the vulcanization temperature and the temperature around the passage is maintained at the unvulcanized temperature, the injection molding of the liquid silicone rubber can be performed while the nozzle is touching. Since the vulcanization reaches the molding material in the nozzle mouth and does not extend to the molding material in the passage at the nozzle tip deep portion, the molding material does not remain in the passage after vulcanization.

Further, since there is a step at the boundary between the vulcanized molding material in the nozzle mouth and the molding material in the unvulcanized passage, the sprue from the nozzle mouth can be easily pulled by the pulling force at the time of mold release. Since it is separated and the passage has a small diameter, it is difficult for stringing to occur.

Since the weight reduction of the molding material which is different for each molding is eliminated by the stringing, the injection filling amount for each molding is stable,
In addition, since the inconvenience in molding due to the stringing residue is prevented, the molding loss is extremely small, the quality of the molded product is improved, and the molding can be performed with the nozzle touching, so the efficiency is further improved than before. And so on.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a liquid silicone rubber molding injection nozzle according to the present invention.

FIG. 2 is a cross-sectional view showing thread drawing in a mold sprue in a conventional liquid silicone rubber molding injection nozzle.

FIG. 3 is a sectional view showing in-nozzle vulcanization in a conventional injection nozzle for molding liquid silicone rubber.

FIG. 4 is a cross-sectional view showing stringing in a conventional liquid silicone rubber molding injection nozzle.

[Explanation of symbols]

 11 Mold 12 Mold Sprue 13 Nozzle Main Body 14 Cooling Jacket 15 Flow Path 16 Core 17 Path 18 Nozzle Tip 19 Nozzle Port 20 Step 21 Sprue

Claims (1)

[Claims] 1. A nozzle main body having a cooling means on the outer periphery thereof, and a nozzle tip screwed to the tip of the nozzle main body,
The nozzle opening at the tip of the nozzle tip is formed slightly smaller than the sprue opening of the mold, and the passage between the nozzle opening and the flow passage in the nozzle body is made smaller than the nozzle opening to form a step in the nozzle opening. An injection nozzle for molding liquid silicone rubber, characterized by being formed.