JPH04275119A - Injection molding machine - Google Patents

Abstract

PURPOSE:To prevent a stringing phenomenon without generating pressure loss at the time of injection by providing a radiation fin to the tip part of a nozzle injecting a molten resin and further forming an air passage with the radiation fin, and flowing air to the radiation fin from an air blowoff nozzle to allow air to spread over the entire periphery of the nozzle. CONSTITUTION:A radiation fin 22 is attached to the tip part of a nozzle 20 and, further, this radiation fin 22 is formed from an annular plate material and a flange part 22a is formed to the entire inner peripheral part of the radiation fin and an air guide wall 22b is formed to the half of the outer peripheral part thereof to form an air passage 23. An air blowoff nozzle 24 is opened toward the inlet of the air passage 23. After a molten resin is injected in a cavity S from the nozzle 20, air is blown to the radiation fin 22 from the air blowoff nozzle 24 to control the temp. of the nozzle. By this constitution, a stringing phenomenon is prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine, and more particularly to an injection molding machine equipped with a stringing prevention means.

0002

[Prior Art] Generally, an injection molding machine injects melted resin in a heating cylinder from a nozzle into a cavity formed by a movable mold and a fixed mold, and after the resin in the cavity cools and solidifies. , open the mold and eject the molded product. During this one-sided opening, or when the nozzle is retracted prior to one-sided opening, the molten resin may be drawn out in the form of a thread between the sprue portion of the molded piece and the nozzle tip. This is a phenomenon called "string pulling."

When stringiness occurs, stringy resin adheres to the outer surface of the nozzle tip, and when the nozzle and the sprue bush of the mold are brought into close contact during resin injection, a gap is created there, causing resin leakage. This causes problems such as uneven injection amount and insufficient injection pressure. Furthermore, if the stringy resin adheres to the molded product, the product will be visually defective. In particular, the stringing phenomenon is a fatal flaw in unmanned operation of injection molding.

[0004] In order to prevent this stringing phenomenon, for example,
There is a so-called two-stage nozzle disclosed in Japanese Unexamined Patent Application Publication No. 131215/1983 filed by the present applicant. As shown in Fig. 4, the opening at the tip of the nozzle 1 is composed of a small diameter part 2 and a large diameter part 3, and although it is effective in preventing the stringing phenomenon, it is necessary to The diameter of the small diameter part had to be reduced significantly, and large pressure loss in this part during injection could not be avoided.

[0005] As a means of reducing this pressure loss and preventing the stringing phenomenon, it has been considered to lower the temperature of the tip of the nozzle without constricting it. This is to prevent the stringing phenomenon by blowing air from the air blowing nozzle 4 to the tip of the nozzle 5 to adjust the nozzle temperature as shown in FIG.

[0006]

However, in the above-mentioned means, since only the direction in which the air is blown from the nozzle is cooled, the effect of preventing stringing is low, and the temperature of the resin tends to vary, which impairs reliability.

An object of the present invention is to reduce the pressure loss at the nozzle during injection to effectively prevent the stringing phenomenon.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration. That is, in an injection molding machine that molds a molded product by injecting molten resin from a nozzle into a cavity formed by a fixed mold and a movable mold,
A radiation fin is attached to the circumference of the tip of the nozzle, an air blowing nozzle that opens facing the radiation fin is provided close to the tip of the nozzle, and the air is guided around the nozzle. The structure is characterized in that an air passage is formed in the radiation fin.

[0009]

[Operation] When molding a molded product by injecting molten resin from a nozzle into a cavity formed by a fixed mold and a movable mold, the molten resin is injected into the cavity formed by the fixed mold and the movable mold, toward the heat dissipation fin attached to the circumference of the tip of the nozzle. Air is blown from an air blowing nozzle installed close to the tip of the nozzle, and the air is flowed along the air passage to evenly distribute the air around the nozzle, thereby controlling the nozzle temperature without variation. do. This not only maintains an appropriate nozzle inner diameter size and reduces pressure loss in the nozzle, but also prevents stringiness.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, reference numeral 10 denotes an injection molding machine, which is roughly constructed as follows. That is, 11 is the flange 12
It is a mold clamping cylinder fixed on the machine base 13 via
A plurality of tie bars 14 are extended parallel to the longitudinal direction of the machine base 13 on the flange 12, and a fixed platen 1 is provided opposite the tip of the tie bars 14.
5 is attached on the machine base 13. Mold clamping cylinder 1
A movable platen 17 is fixed to the tip of a ram 16 inserted into the ram 1 and is movable along the tie bar 14. A fixed mold 18 is provided inside the fixed plate 15, and a movable mold 19 is similarly provided inside the movable plate 17. Further, a nozzle 20 configured as described later is provided on the outside of the fixed plate 15, and its tip passes through the opening of the fixed plate 15 and abuts on the outside of the fixed mold 18.

As is more clearly seen in FIGS. 2 and 3, a plurality of (four in this embodiment) heat radiation fins 22 are fitted and attached around the tip of the nozzle 20. The heat dissipation fin 22 is formed of an annular plate material, and has a flange portion 22a formed all around its inner circumference, and an arcuate air guide wall 22b extending approximately half the circumference of its outer circumference. They are formed in the same direction and at the same height. This heat radiation fin 2
2 are sequentially fitted into the tip of the nozzle 20 in the same direction,
The tip surfaces of the flange portion 22a and the air guide wall 22b are located on the vertical surface of the flange portion 20a on which the nozzle 20 is erected and the back surface of the adjacent radiation fin 22 (opposite to the surface on which the flange portion 22a and the air guide wall 22b are formed). side), and an arcuate sealed space, ie, an air passage 23, is formed in the lower half of the radiation fin 22. An air blowing nozzle 24 is opened and provided facing the entrance of the air passage 23, and the air blown into the air passage 23 from the air blowing nozzle 24 flows inside the air passage 23 along the air guide wall 22b.

Note that the radiation fins 22 in this embodiment use four integral annular plates, but the number of radiation fins is selected to obtain an appropriate cooling effect depending on the molded product, molding temperature, etc. Ru. It goes without saying that a single annular plate may be divided into two or four parts, or for example, four annular plates may be integrally molded. Furthermore, the plate material of the radiation fin may be formed into a half-ring shape.

The air blowing nozzle 24 is connected to an air source 28 via a solenoid valve 25, an air filter 26, and a stop valve 27, as shown in FIG. Next, the operation of this embodiment configured as described above will be explained.

The ram 16 of the mold clamping cylinder 11 is extended, the movable platen 17 fixed to the tip of the ram 16 moves along the tie bar 14, the movable mold 19 and the fixed mold 18 are clamped, and a predetermined mold is formed. A cavity S is formed. At the same time as this mold clamping, the nozzle 20 moves forward, and the tip of the nozzle 20 comes into close contact with the outside of the fixed mold 18. After the mold clamping pressure is increased, the molten resin is injected into the cavity S. After the injection ends, the electromagnetic valve 25 is opened for a certain period of time, for example, 3 to 5 seconds, before the nozzle starts retreating, and air is blown to the tip of the nozzle 20 where the radiation fins 22 are provided. The blown air flows from the entrance of the air passage 23 to the air passage 2 along the air guide wall 22b.
3 and turns around as shown by the arrow in FIG. In this way, nozzle temperature is controlled and stringing is prevented while maintaining appropriate nozzle inner diameter dimensions.

[0016]

Effects of the Invention As is clear from the above description, a radiation fin is attached to the tip of the nozzle, an air passage is formed in the radiation fin, and air is blown toward the radiation fin, so that the entire circumference of the nozzle is Since air is evenly distributed throughout the nozzle and the nozzle temperature is controlled without variation, pressure loss at the nozzle can be reduced and stringing phenomenon can be effectively prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the invention.

FIG. 2 is an enlarged sectional view of the main part of FIG. 1;

FIG. 3 is a sectional view taken along line AA in FIG. 2;

FIG. 4 is a sectional view showing a conventional nozzle.

FIG. 5 is a sectional view showing another conventional example.

[Explanation of symbols]

10 Injection molding machine 18 Fixed mold 19 Movable mold 20 Nozzle 22 Heat radiation fin 23 Air passage 24 Air blow nozzle

Claims (1)

[Claims] 1. In an injection molding machine that molds a molded product by injecting molten resin from a nozzle into a cavity formed by a fixed mold and a movable mold, a radiation fin is attached to the circumference of the tip of the nozzle. , an air blowing nozzle opened facing the heat dissipation fin is provided close to the tip of the nozzle, and an air passage for guiding air around the nozzle is further formed in the heat dissipation fin. injection molding machine.