JP2525342Y2 - Vent-type injection molding machine for thermosetting resin - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vent-type injection molding machine used for molding a thermosetting resin.
The present invention relates to a thermosetting resin injection molding machine capable of performing injection molding by removing gas generated from a plasticized molding material at a screw tip.

[0002]

2. Description of the Related Art Thermosetting resins are conventionally formed by an injection molding machine equipped with a screw. An injection molding machine equipped with a screw for molding the thermosetting resin has a heating cylinder equipped with a temperature control device for heating and plasticizing a molding material, and a rotatable and reciprocating moving cylinder in the heating cylinder. A screw for feeding the inserted molding material forward, a molding material supply means for supplying the molding material into the heating cylinder, and an injection of the plasticized molding material in contact with the mold into the cavity. The heating cylinder is provided with a vent in order to release moisture, gas, etc. (hereinafter simply referred to as gas) contained in the resin when plasticizing the molding material. ing. The screw is divided into two stages, the first stage behind the injection direction,
The area ahead of this is classified as the second stage. In the conventional screw, both the first stage and the second stage have a feed zone in which the volume of the screw groove is constant and large, a compression zone in which the volume of the screw groove gradually decreases from the rear to the front, and a volume of the screw groove. A constant and small metering zone is sequentially formed from the rear to the front. In addition, since the thermosetting resin has a high viscosity at the time of plasticization, there is little backflow. Therefore, a backflow prevention device is not attached to a screw of an injection molding machine for molding the thermosetting resin.

[0003] The molding material is supplied into the heating cylinder by a supply means, and is sent to the tip of the heating cylinder while being kneaded along the screw groove by the rotational transfer action of the screw. In this process, the molding material is compressed due to the reduction in the volume of the screw groove, undergoes shearing action, generates frictional heat, plasticizes, and is maintained at a predetermined temperature by heating or cooling by the temperature control device of the heating cylinder. You. The thermosetting resin generates a gas when it is plasticized, and this gas is discharged from the vent. The plasticized molding material is stored at the tip of the screw, and is injected into the mold from the nozzle as the screw advances. After filling the molding material into the mold, temporarily release the mold clamping force of the mold,
Gas in the cavity is discharged from the mold separation surface.

[0004]

However, in the conventional vent-type injection molding machine, since the molding material is sent forward while being compressed and kneaded, the gas generated in the plasticized molding material in the first stage is vented. Although released to the outside of the heating cylinder, the gas generated in the molding material in the second stage is not released from the vent, and the gas is injected into the mold cavity while being mixed with the resin, and the mold clamping force is temporarily released. When it was discharged from the mold split surface. For this reason, it is difficult to obtain a molded product with no voids inside, dense and glossy on the surface, and with good dimensional accuracy. Also,
When the gas is discharged by temporarily releasing the mold clamping force, there is a problem that the resin enters the mold dividing surface together with the gas and burrs are generated.

Further, in the conventional vent-type injection molding machine, the volume of the screw groove in the compression zone is gradually reduced from the rear to the front in order to send the molding material forward while compressing and kneading the material. The volume of the groove of the feed zone was formed smaller than the volume of the groove of the feed zone, so when the molding material is precured by heating, to remove the solidified resin, remove the screw from the heating cylinder and clean Needed.

SUMMARY OF THE INVENTION The present invention provides a thermosetting resin which is capable of removing a gas of a molding material injected into a mold and easily removing precure generated in a heating cylinder in injection molding of a thermosetting resin. It is an object of the present invention to provide a vent-type injection molding machine for conductive resin.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a vent for a thermosetting resin having a screw rotatably and reciprocally inserted into a heating cylinder. In the injection molding machine, the screw groove of the second stage is made deeper than the screw groove of the first stage, and the compression ratio of the first stage and the second stage is 1: 1. is there. It is desirable to provide an aperture head at the tip of the screw.

[Action]

[0008] The molding material of the thermosetting resin is supplied into the heating cylinder by the supply means, and in the first stage, while being kneaded by the rotation of the screw, undergoes a shearing action to generate frictional heat to plasticize, thereby controlling the temperature. It is maintained at a predetermined temperature by the device and sent forward.

When the plasticized molding material is sent from the first stage to the second stage, the volume of the screw groove expands and expands to release gas mixed with the molding material. Gas is exhausted from the vent.

[0010] Since the amount of the molding material sent to the second stage is smaller than the volume of the screw groove of the second stage, the molding material is pressed between the wall surfaces of the screw groove and between the wall surface of the front screw groove. Sent with a gap,
The gas generated in the second stage is discharged from the vent through this gap.

The molding material from which the gas has been completely removed is stored at the tip of the heating cylinder, and the stored molding material is injected into the mold cavity by advancing the screw. Since a smear head having a predetermined interval between the screw and the inner wall of the cylinder head is provided at the tip of the screw, vent up due to resin backflow is prevented.

[0012] Even when the molding material is heated to a temperature higher than a predetermined temperature at which it plasticizes in the heating cylinder and hardened to generate precuring, the compression ratio of the screw is set to 1: 1. Sent forward of the screw without clogging. When removing the pre-cure, if the cylinder head is removed from the heating cylinder, the pre-cure is sent to the tip of the screw, so that it can be easily removed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a vent type injection molding machine for thermosetting resins according to the present invention will be described with reference to the drawings. In the vent-type injection molding machine for thermosetting resin according to the present invention, a screw 2 is inserted into a heating cylinder 1 and a cylinder head 3 is attached to the tip of the heating cylinder 1 as shown in FIG. ing.

A motor and a ram (not shown) are connected to the rear end of the screw 2 to drive the screw 2 rotatably and forward and backward. The heating cylinder 1
A hopper 5 is provided as a supply means for supplying a thermosetting resin molding material in the vicinity of the rear end (to the right in FIG. 1), and the cylinder head 3 is attached to the front end by bolts 7. 7, the cylinder head 3 can be detached from the heating cylinder 1. Further, the heating cylinder 1 is provided with a temperature adjusting means (not shown) capable of heating or cooling in order to maintain the molding material at a predetermined temperature. A screw portion 3a is formed in the cylinder head 3, and the nozzle 9 is screwed. The heating cylinder 1 according to the present invention
A description will be given of an example in which the hopper 7 is used to supply molding material to the inside. However, the invention is not limited thereto. For example, a feed screw may be provided as the molding material supply means.

As shown in FIG. 1, the screw 2 has spiral screw grooves 11 formed at a uniform pitch P over substantially the entire length. A step 15 is formed in the middle of the effective length in which the screw groove 11 is formed, and the screw 2 is ejected from the step 15 to the first stage 2A in the injection direction rearward (to the right in FIG. 1) and from the step 15. It is divided into two stages, that is, a second stage 2B in the front direction (left direction in FIG. 1). The depth H2 of the screw groove of the second stage 2B is formed to be greater than the depth H1 of the screw groove of the first stage 2A, and the volume per pitch is the first.
The second stage is larger than the stage.
At the tip of the screw 2, a drawing head (smear head) 13 having a predetermined distance from the inner wall of the cylinder head 3 is provided to prevent the molding material from flowing backward and venting up.

The depth H of the screw groove of the first stage 2A
1, the rear end H1a near the hopper and the stepped portion H1b near the hopper are formed to be the same as shown in FIG. 2, and the depth H2 of the screw groove of the second stage is set as shown in FIG. The portion vicinity H2a and the tip portion vicinity H2b are formed at the same depth, and the volume per pitch in the same stage has not changed. That is, the first stage 2A and the second stage 2B both have a compression ratio of 1 : 1 is set. In this embodiment, the ratio of the depth H1 of the screw groove 11 of the first stage 2A to the depth H2 of the screw groove 11 of the second stage 2B, that is, the volume per pitch between the first stage and the second stage. Is set to approximately 1: 2.

The heating cylinder 1 has a vent 17 opening upward.
Is provided to exhaust gas generated by plasticization of the molding material. The vent 17 is disposed at a position corresponding to the front of the step 15 provided on the screw 2.

The operation of the thermosetting resin injection molding machine configured as described above will be described. The molding material of the thermosetting resin is supplied from the hopper 5 into the heating cylinder 1. In the first stage 2A, the molding material receives heat due to the shearing action of the screw 2 and the friction caused by kneading when the screw 2 rotates, and is plasticized, as well as a heating cylinder used as necessary. While being kept at a predetermined temperature by the temperature control means.

The plasticized molding material is fed further forward by the screw 2, and the volume of the screw groove 11 is rapidly increased in the step portion 15, so that the gas expands and releases gas mixed in the molding material. . The gas released from the molding material is discharged from a vent 17 disposed forward of the step portion 15.

The pitch P of the screws 2 is evenly formed, and the depth H of the screw grooves 11 of the second stage 2B is increased.
2 is formed to be deeper than the depth H1 of the screw groove 11 of the first stage 2B, the volume per pitch of the second stage 2B is larger than the volume of the first stage 2A, and the screw 2 is moved to the first stage 2A. Since the two stages 2A and 2B are rotated at the same speed, the amount of molding material supplied to the first stage 2A is smaller than the volume of the screw groove 11 of the second stage 2B. Therefore, the molding material is sent in the second stage 2B while being pressed by the rear wall surface 11a of the screw groove 11 with a gap formed between the molding material and the front wall surface 11b of the screw groove 11. The gas generated in the second stage 2B is discharged from the vent 17 through this gap as shown by the arrow in FIG.

The molding material from which the gas has been discharged is weighed and accumulated in the second stage 2B, and the screw 2 is rotated in a state where the nozzle 9 provided on the cylinder head 3 is in contact with a mold spool (not shown). It advances and is injected into the mold cavity. A smear head 13 is provided at the tip of the screw 2, and the smear head 13 is
Since there is a predetermined distance between the inner wall and the inner wall, the resin does not flow backward and vent-up can be prevented.

When the molding material is heated to a temperature higher than a predetermined plasticizing temperature and precuring occurs, the compression ratio of the screw 2 according to the present invention is set to 1: 1. Since the pressure does not decrease, the precure is not clogged in the heating cylinder 1 and is sent to the tip of the screw 2. When removing the pre-cured, the bolt 7 is removed, the cylinder head 3 is removed from the heating cylinder 1, and the pre-cured sent to the tip of the screw 2 may be removed.

The vent-type injection molding machine according to the present invention can be applied to any thermosetting resin molded by this type of molding machine. For example, phenol resin, urea resin, melamine resin, epoxy resin And a thermosetting resin containing an unsaturated polyester resin and rubber.

[0024]

According to the present invention, the screw compression ratio of the vent-type injection molding machine for thermosetting resin is set to 1: 1 and the screw tip is provided with a smear head, thereby plasticizing the screw tip. The gas generated from the material inside is released to the back of the screw and injection molding can be performed while removing the gas, so the surface of the molded product can be a beautiful glossy surface without the influence of gas, and the molded product A dense product without voids can be obtained. In addition, even when pre-curing occurs in the plasticized resin, it is possible to easily remove the pre-cured resin by simply removing the cylinder head without removing the screw from the heating cylinder.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a thermosetting resin injection molding machine according to the present invention.

FIG. 2 is an enlarged sectional view showing a first stage of FIG.

FIG. 3 is an enlarged sectional view showing a second stage of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Screw 3 Cylinder head 5 Hopper 9 Nozzle 11 Screw groove 13 Smear head 15 Step 17 Vent P Pitch H Screw groove depth

Claims (2)

(57) [Scope of request for utility model registration] In a vented injection molding machine for a thermosetting resin provided with a screw rotatably and removably inserted into a heating cylinder, a screw groove of a second stage is shifted from a screw groove of a first stage. And a compression ratio of the first stage and the second stage is set to 1: 1 respectively. 2. The vent-type injection molding machine for thermosetting resins according to claim 1, wherein a drawing head is provided at the tip of the screw.