JP2818980B2 - Injection molding machine - Google Patents

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 provided with stringing prevention means.

[0002]

2. Description of the Related Art In general, an injection molding machine injects a resin melted in a heating cylinder from a nozzle into a cavity formed by a movable mold and a fixed mold, and cools and solidifies the resin in the cavity. The mold is opened, and the molded product is ejected and ejected. When the nozzle is retracted prior to the one-sided opening or the one-sided opening, the molten resin may be drawn out in a thread form between the sprue portion of the molded piece and the tip of the nozzle. This is a so-called "stringing" phenomenon.

When stringing occurs, thread-like 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 with each other during resin injection, a gap is formed in the sprue bush, causing resin leakage. For this reason, troubles such as uneven injection amount and insufficient injection pressure occur. Further, if the stringing resin adheres to the molded product, it becomes a defective product in appearance. In particular, the stringing phenomenon is a fatal defect in unmanned operation of injection molding.

In order to prevent this stringing phenomenon, for example,
There is a so-called two-stage nozzle according to Japanese Patent Application Laid-Open No. 60-131215 of the present applicant. As shown in FIG. 4, the opening at the tip of the nozzle 1 is composed of a small-diameter portion 2 and a large-diameter portion 3, which is effective in preventing the stringing phenomenon. The diameter of the small diameter portion had to be reduced very much, and a large pressure loss at this portion during injection could not be avoided.

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

[0006]

However, in the above-mentioned means, since the cooling is performed only in the direction in which the air is blown out from the nozzle, the effect of preventing stringing is low, and the temperature of the resin tends to fluctuate.

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

[0008]

Means for Solving the Problems To achieve the above object, the constitution of the present invention is as follows. That is, in an injection molding machine for molding a molded product by injecting a molten resin from a nozzle into a cavity formed by a fixed mold and a movable mold,
A radiation fin is attached to a peripheral portion of the tip of the nozzle, and an air blowing nozzle opened to face the radiation fin is provided near the tip of the nozzle, and further, air is guided around the nozzle. An air passage is formed in the radiating fin.

[0009]

When a molten resin is injected from a nozzle into a cavity formed by a fixed mold and a movable mold to form a molded product, the molded product is directed toward a radiating fin attached to a peripheral portion of a tip portion of the nozzle. Air is blown from an air blowing nozzle provided in the vicinity of the tip of the nozzle, the air flows along the air passage, and the air is evenly distributed around the entire nozzle to control the nozzle temperature without variation. I do. Thereby, an appropriate nozzle inner diameter is maintained, pressure loss at the nozzle is reduced, and a stringing phenomenon is prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral 10 denotes an injection molding machine, which is constructed as follows. That is, reference numeral 11 denotes a mold clamping cylinder fixed on the machine base 13 via the flange portion 12, and a plurality of tie bars 14 are extended on the flange portion 12 in the longitudinal direction of the machine base 13 and in parallel with the front end thereof. A fixed platen 15 is mounted on the machine base 13 so as to face the unit. Ram 16 inserted into mold cylinder 11
A movable plate 17 is fixed to the tip of the, and is configured to be movable along the tie bar 14. A fixed mold 18 is provided inside the fixed board 15, and a movable mold 19 is similarly provided inside the movable board 17. Further, a nozzle 20 configured as described later is provided outside the fixed platen 15, and the tip end of the nozzle 20 penetrates the opening of the fixed platen 15 and contacts the outside of the fixed mold 18.

As is clear from FIGS. 2 and 3, a plurality (four in the present embodiment) of radiation fins 22 are fitted and attached around the periphery of the tip of the nozzle 20. The radiating fin 22 is formed of an annular plate material, a flange portion 22a is formed over the entire circumference of an inner peripheral portion thereof, and an arc-shaped air guide wall 22b is formed substantially the same as the flange portion 22a over substantially a half circumference of an outer peripheral portion thereof. It is formed in the same direction and at the same height. The heat dissipating fins 22 are sequentially fitted in the same direction to the tip of the nozzle 20, and the respective end surfaces of the flange 22 a and the air guide wall 22 b are perpendicular to the flange 20 a erected on the nozzle 20 and the adjacent heat dissipating fins 22. Back (opposite the surface on which the flange portion 22a and the air guide wall 22b are formed)
, A closed space on an arc, that is, an air passage 23 is formed in the lower half of the radiation fin 22. An air blowing nozzle 24 is provided facing the inlet of the air passage 23 so as to open, and the air blown into the air passage 23 from the air blowing nozzle 24 flows through the air passage 23 along the air guide wall 22b.

The radiation fins 22 in this embodiment are
Although four integral annular plates are used, the number of radiating fins is selected so as to obtain a proper cooling effect from the molded product, molding temperature, and the like. Also, the integral annular plate is divided into two parts.
It may be divided into a plurality of parts such as four parts.
It goes without saying that the annular plate members may be integrally formed. Further, the plate material of the radiation fins may be formed in 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 apparent from FIG. Next, the operation of the present embodiment configured as described above will be described.

The ram 16 of the mold clamping cylinder 11 is extended,
The movable platen 17 fixed to the end of the movable die 17 moves along the tie bar 14, the movable die 19 and the fixed die 18 are clamped, and a predetermined cavity S is formed. Simultaneously with this mold clamping, the nozzle 20 advances, 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 is completed, a certain time before the nozzle retreat starts,
For example, open the solenoid valve 25 for 3-5 seconds to release air
It sprays on the tip of the nozzle 20 provided with 22. The blown air flows from the inlet of the air passage 23 to the air guide wall 22b.
Along the air passage 23 and wraps around as shown by the arrow in FIG. 3 to take heat from the entire circumference of the nozzle 20 and radiate heat from the surface of the radiating fin 22. In this way, the nozzle temperature is controlled while maintaining an appropriate nozzle inner diameter, and stringing is prevented.

[0016]

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 the air is evenly distributed to the nozzles and the nozzle temperature is controlled without variation, the pressure loss at the nozzles can be reduced and the stringing phenomenon can be effectively prevented.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a sectional view taken along line AA of 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 Radiation fin 23 Air passage 24 Air blow nozzle

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 45/20-45/24 B29C 45/46-45/84

Claims (1)

(57) [Claims] 1. An injection molding machine for molding a molded product by injecting a molten resin from a nozzle into a cavity formed by a fixed mold and a movable mold, and attaching a radiation fin to a peripheral portion of a tip portion of the nozzle. An air blowing nozzle opened to face the radiation fin, provided near the tip of the nozzle, and an air passage for guiding air around the nozzle is formed in the radiation fin. Injection molding machine.