JPH02252513A - Low pressure degassing plasticizing apparatus - Google Patents

Abstract

PURPOSE:To discharge involved air without increasing back pressure by blocking a hopper and a heating cylinder from the atmosphere excepting the leading end of the heating cylinder in which a molten molding material is injected and providing an air vent hole connected to a vacuum source to the hopper or the communication passage of the hopper and the heating cylinder. CONSTITUTION:An air vent hole 5 is formed to a hopper base 4 and connected to a vacuum pump. A hopper 7 is separated into chambers 9, 10 by a central partition wall 8 and the molding materials received in the chambers 9, 10 are alternately supplied in a screw 2 by changing over a change-over valve 11. Valves 12, 13 are provided to the air vent hole 5 and air vent valves 15, 17 are provided to hopper lids 14, 15. When the molding material is supplied to the screw 32 from the chamber 9, the change-over valve 11 is changed over and the valve 12 is opened while the air vent valve 16 is closed. Air seals 18, 20 are arranged between the hopper 7 and the hopper lids 14, 15 and between the heating cylinder 1 and the screw 2 while the molding material in a molten state is present at the leading end of the screw 2 to seal the hopper and the heating cylinder from the outside and, therefore, the hopper and the screw grooves can be held to low pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a low-pressure degassing plasticizing device that prevents air from being entrained in the plasticizing process of an injection molding machine.

(Prior art) Conventionally, a molding material that has been heated and fluidized in a heating cylinder is injected into a mold under high pressure, cooled and solidified or hardened therein, and then the mold is opened to take out the molded product. In an injection molding machine, a screw for injecting a molding material into a mold uses a drive source such as a hydraulic motor or an electric motor.

FIG. 2 shows the conventional injection molding machine described above.

In the figure, 31 is a heating cylinder, and 32 is a screw supported within the heating cylinder 3I so as to be rotatable and movable forward and backward. Molding material 3 supplied from hopper 33
4 is guided by the groove 35 as the screw 32 rotates, moves forward through the supply section 36 and the compression section 37, and is stored in the storage space 38.

The screw 32 includes a drive spline shaft 39 and a transmission mechanism 4.
0 to the injection motor 41, and
A nut 43 is provided at the rear end of the drive spline shaft 39 to rotatably support the drive spline shaft 39 and engage with a ball screw 42 .

The ball screw 42 is connected to the injection motor 41 via a speed reduction mechanism 47.

Here, when the injection motor 41 is rotated, its rotation is appropriately decelerated by the operation of the deceleration mechanism 47 and transmitted to the ball screw 42 . The rotation causes the nut 43 to move, causing the screw 32 to move back and forth.

Further, a spline 44 is formed on the drive spline shaft 39, and is connected to a screw motor 46 via a gear 45.

Here, the screw motor 46 is driven to drive the screw 32.
Weighing can be done by rotating. That is, when the screw 32 rotates, the molding material 34 supplied from the hopper 33 is forced forward by the frictional supply force generated in the supply section 36, and is further compressed in the compression section 37 where the volume of the groove 35 is reduced. At the same time, it is heated by the heating cylinder 31, melted, and stored in the storage space 38.

When plasticizing is performed in an injection molding machine as described above, the molding material 34 is transferred to the front of the heating cylinder 31.
The screw 32 is designed to retreat due to the reaction force of
At that time, the molding material 3 pushed out in front of the screw 32
Air is drawn in along with 4.

The air is normally pushed back toward the hopper 33 by the pressure generated in the compression section 37 and is discharged.

However, when attempting to discharge air using the pressure generated in the compression section 37, the shape of the screw 32 becomes complicated, the pressure inside the heating cylinder 31 increases, and the driving force of the screw 32 also increases.

Therefore, a method has been proposed in which when the screw 32 is moved back due to the reaction force of the molding material 34, a back pressure that opposes the reaction force is applied by the rotation of the screw motor 46, and the air is discharged by the back pressure.

(Problem H to be solved by the invention) However, in the above conventional deaeration method that applies back pressure to the screw 32, a larger driving force is required than when forming the compression section 37, and the internal energy within the screw 32 is reduced accordingly. increases, and the temperature of the molding material rises.

Moreover, in the case of a molding material whose pressure does not increase even when back pressure is applied, plasticization becomes impossible or becomes unstable.

The purpose of the present invention is to solve the problems of the conventional deaeration method described above, and to achieve low-pressure deaeration plasticization that allows the trapped air to be discharged without increasing the back pressure applied during the plasticization process. The purpose is to provide equipment.

(Means for Solving the Problems) For this purpose, the present invention provides a heating cylinder, a screw supported in the heating cylinder so as to be able to move forward and backward, and a molding material being supplied between the heating cylinder and the screw. In a low-pressure degassing plasticizing device of an injection molding machine with a hopper,
The interior of the hopper and the heating cylinder are isolated from the atmosphere except for the tip of the heating cylinder through which the molten molding material is injected, and the tip of the heating cylinder is sealed by the molten molding material.

Then, an air vent hole connected to a vacuum source is provided in the hopper or in a passage connecting the hopper and the heating cylinder, so that the inside of the hopper and the inside of the heating cylinder are maintained at low pressure during the plasticizing process.

Further, the hopper is divided into a plurality of sections, and the sections and the inside of the heating cylinder are selectively connected via a switching valve.

(Function) According to the present invention, the inside of the hopper and the heating cylinder are isolated from the atmosphere except for the tip of the heating cylinder where the molten molding material is injected, and the tip of the heating cylinder is sealed by the molten molding material. .

Then, an air vent hole connected to a vacuum source is provided in the hopper or in a passage connecting the hopper and the heating cylinder, so that the inside of the hopper and the inside of the heating cylinder are maintained at low pressure during the plasticizing process.

The air trapped in the molding material during the plasticization process is
The air is discharged to the outside through the air vent hole, and the hopper is connected to a plurality of compartments, and the compartments and the inside of the heating cylinder are selectively connected via switching valves. Therefore, continuous operation under the above-mentioned low pressure is possible.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a molding material supply portion of the low-pressure degassing plasticizing device according to the present invention.

In the figure, reference numeral 1 denotes a heating cylinder, 2 & a screw supported within the heating cylinder 1 so as to be rotatable and movable forward and backward. Three cooling cylinders are disposed at the periphery of the material supply end of the heating cylinder IJ cylinder 1.

A hopper base 4 is disposed outside the cooling cylinder 3, and the hopper base 4 has a number of air vent holes 5 formed therein, and is connected to a vacuum pump (not shown). 6 is a screen disposed in the air vent hole 5.

The hopper 7 is disposed on the hopper base 4, and is internally divided into two chambers 9, 10 by a central partition wall 8. The molding material contained in the chambers 9 and 10 is
By switching the switching valve 11, it is alternately supplied into the screw 2.

The air vent holes 5 communicating with the chamber 9.10 are each provided with a valve 12.13, and the chamber 9.10 is provided with a valve 12.13.
The hopper lids 14 and 15 that cover the air vent valves 16 and
．． 17 are provided.

When supplying the molding material from the chamber 9 to the screw 32, the switching valve 11 is switched as shown, the valve 12 is opened,
Air bleed valve 16 is closed. At this time, the valve 13 is closed, the air bleed valve 17 is opened, and the pressure inside the chamber 10 becomes atmospheric pressure. In addition, when supplying from the chamber 0, the switching valve 11
is switched to a position opposite to that shown, valve 13 is opened, and air bleed valve 17 is closed. At this time, the valve 12 is closed, the air bleed valve 16 is opened, and the pressure inside the chamber 9 becomes atmospheric pressure.

With this configuration, when the molding material in one chamber runs out, the switching valve 11 is switched to the opposite position and the material is supplied from the other chamber, so the injection molding machine can be operated continuously without running out of molding material. can do.

Air seals 18 and 20 are provided between the hopper 7 and the hopper lid 14, 15, and between the heating cylinder 1 and the screw 2, while the tip of the screw 2 has a molten molding material, which prevents contact with the outside. Since the space is sealed, the inside of the hopper 7 and the inside of the screw groove can be kept at a low pressure. In addition, 2
1 is a frame, and 22 is an air seal holder that presses the air seal 20.

Therefore, since the molding material can be melted under low pressure, the amount of air present in the molding material after melting can be reduced in proportion to the pressure.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, the inside of the hopper and the heating cylinder are isolated from the atmosphere except for the tip of the heating cylinder where the molten molding material is injected, and the inside of the heating cylinder is isolated from the atmosphere. The tip is sealed with molten molding compound.

Then, an air vent hole connected to a vacuum source is provided in the hopper or in a passage connecting the hopper and the heating cylinder, so that the inside of the hopper and the inside of the heating cylinder are maintained at low pressure during the plasticizing process.

The air trapped in the molding material during the plasticization process is
The air is discharged to the outside through the air vent hole. The amount of air trapped between the pellets of molding material decreases in proportion to the air pressure within the heating cylinder. Therefore, the number of air bubbles mixed into the molded product is reduced, and it is possible to prevent the product from burning.

Furthermore, since the back pressure can be reduced during operation, the driving torque can be set low. Furthermore, since there is no need to increase the compression ratio for degassing, the compression ratio can be reduced compared to conventional degassing methods, reducing the amount of work required to melt the molding material. Therefore, in order to reduce the temperature of the molten resin, the hopper is divided into a plurality of sections, and the sections and the inside of the heating cylinder are selectively connected via a switching valve. Continuous operation under low pressure is possible.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a molding material supply section included in the low-pressure degassing plasticizing apparatus of the present invention, and FIG. 2 is a diagram showing a conventional injection molding machine. l, 31... Heating cylinder, 2.32... Screw, 4... Hopper base, 5... Air vent hole, 7.3
3...Hopper, 8...Partition wall, 9.10...Room,
11...Switching valve, 12°13...Valve, 14.15.
...Hopper lid, 16.17...Air bleed valve, 18,2
0... Air seal, 34... Molding material, 35...
Groove, 36... Supply section, 37... Compression section, 38...
Accumulation space, 39... Drive spline shaft, 40... Transmission mechanism, 41... Injection motor, 42... Ball screw, 43... Nut, 44... Spline, 45...
...Gear, 46...Screw motor.

Claims (2)

[Claims] (1) Low-pressure degassing plasticization of an injection molding machine that has a heating cylinder, a screw that is supported in the heating cylinder so as to be able to move forward and backward, and a hopper that supplies molding material between the heating cylinder and the screw. In the apparatus, (a) the inside of the hopper and the heating cylinder are isolated from the atmosphere except for the tip of the heating cylinder through which the molten molding material is injected; (b) the hopper or a passage connecting the hopper and the heating cylinder; A low-pressure degassing plasticizing device characterized by being provided with an air vent connected to a vacuum source. (2) The low-pressure degassing plasticizing apparatus according to claim 1, wherein the hopper is divided into a plurality of sections, and the sections and the inside of the heating cylinder are selectively connected via a switching valve.