JPH0780901A - Deaeration method and its device of injection molding machine - Google Patents

Abstract

PURPOSE:To enable deaeration at both an inexpensive initial and running costs and with easy maintenance by deaerating water and a volatile matter from a molten molding material within a cylinder barrel by imparting a forced gas flow into an air flow path possessing a large and small sectional parts in a combined state. CONSTITUTION:A main gas flow path 7 provided on a venturi mechanism 6 possesses a large sectional part 7a, a small sectional part 7b where the central part forms the minimum section and a large sectional part 7c in order from an upstream side. Accordingly, since a forced gas flow facing on a large sectional part 7c side on a downstream side from a large sectional part 7a side on an upstream side is imparted. a negative pressure part 0 is formed on the small sectional part 7b in accordance with a Bernoulli's theorem. Then since a compressor or an air feed device 9 having a fan is joined to one end of the main gas flow path 7 and the gas flow facing on the other end is imparted, an intermediate part of the cylinder barrel can be absorbed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a degassing method and apparatus for an injection molding machine.

[0002]

2. Description of the Related Art In a conventional vent type injection molding machine equipped with a deaerator, a molten molding material is deaerated in a measuring step. In an injection molding machine, if the screw in the cylinder barrel is driven to rotate by a hydraulic motor, the molten molding material supplied from the hopper is kneaded and melted, and is extruded by the thrust of the screw flight, and the screw head and nozzle are It gradually flows into the storage space between.

As the molten molding material is stored in the storage space, the reaction force of the conveying pressure acts rearward on the front end face of the screw and the screw flight, and the screw gradually retreats to store the storage space. The amount of the melt molding material is increased and a predetermined amount is measured. During the measurement process by such an injection molding machine, in the vent type injection molding machine equipped with the degassing device, it is possible to deaerate water and volatile components from the molten molding material in the molten state located in the middle part of the cylinder barrel. It is being appreciated. Degassing suppresses the generation of bubbles in the molded product, and pre-drying can be omitted for a melt-molded material (eg, nylon) having high water absorption.

Natural degassing methods and forced degassing methods are known as this type of degassing method. The natural degassing method is a method of degassing water and volatile components in the cylinder barrel under atmospheric pressure from a vent port that opens the inside of the cylinder barrel to the outside, resulting in poor degassing efficiency and melting with high water absorption. In molding material,
The volume of water and volatile components increases at the vent port, and the vent port is likely to be clogged, so that it can be applied only to a melt molding material having a low water absorption rate, and defects due to residual volatile components are likely to occur in a molded product.

On the other hand, the conventional forced degassing method is shown in FIG.
As shown in, a vacuum pump 52 is connected to the vent port 51 of the cylinder barrel 50 to forcibly deaerate water and volatile components from the molten molding material in the cylinder barrel 50.
Of course, the degassing method of sucking with the vacuum pump 52 is superior to the natural degassing method in degassing efficiency.
Volatile components, etc. accumulate in 2, so disassembly and cleaning are required, and the initial cost of installing the vacuum pump 52,
Both running costs increase. In addition, since the vacuum pump 52 discharges water and volatile components at a high concentration, the work environment may be deteriorated and a separate diluting device or recovery device may be required. 53 is a screw.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional technical problems.
In the degassing method of the injection molding machine, which is for degassing from the inside of the cylinder barrel 1 of the injection molding machine,
a, 17a and small cross-sections 7b, 17b in combination,
Main gas flow paths 7 and 17 that form a negative pressure portion O by giving a forced gas flow from one end side to the other end side by the air supply device 9, and one end opens to the negative pressure portion O, and the other. Sub-gas flow paths 8 and 18 having ends open to the cylinder barrel 1 are provided, and a forced gas flow is generated in the main gas flow paths 7 and 17 in accordance with the operation of the injection molding machine, so that the negative gas flow is generated in the cylinder barrel 1. A degassing method for an injection molding machine, which comprises depressurizing a molten molding material by generating pressure. The configuration of the invention of claim 2 is
A deaerator for an injection molding machine that deaerates from the inside of a cylinder barrel 1 of the injection molding machine. The deaerator has a large cross section 7a, 17a and a small cross section 7b, 17b in combination, and goes from one end to the other end. Main gas flow paths 7 and 17 that form a negative pressure portion O by applying a forced gas flow, an air supply device 9 that forcibly supplies air from one end side of the main gas flow paths 7 and 17, and one end of the main gas flow paths 7 and 17. Pressure part O
The degassing device of the injection molding machine is characterized in that the degassing device is provided with sub gas flow paths 8 and 18 that are open to the other end and open to the cylinder barrel 1 at the other end.

[0007]

[Function] Large cross section 7a, 17a and small cross section 7b, 17b
In the main gas flow paths 7 and 17 having a combination of
The negative pressure portion O is formed by applying the forced gas flow by Such a large cross section 7a, 17a and a small cross section 7a
As a combination with b and 17b, there is a venturi mechanism, a vacuum generating ejector, or the like. Since one end of the sub gas passages 8 and 18 is opened to the negative pressure portion O of the main gas passages 7 and 17, and the other end of the sub gas passages 8 and 18 is opened to the cylinder barrel 1, the negative pressure portion O is formed. The intermediate pressure of the cylinder barrel 1 communicating with O also becomes negative pressure.

Thus, the water and volatile components contained in the molten molding material in the cylinder barrel 1 are sent out from the main gas flow paths 7 and 17, and the molten molding material is deaerated. In this way, the water content and the volatile components contained in the molten molding material are diluted with the gas (usually air) sent from the main gas passages 7 and 17 by the air supply device 9, and the main gas passages 7 and 17 are then diluted. There is almost no need to attach a processing device separately because it flows out from the device. Thus, it is possible to prevent the problem that water and volatile components are mixed in the molded product and bubbles are generated in the molded product.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment in which the deaerator of an injection molding machine according to the present invention is applied to a vent type injection molding machine. First, the outline of the injection molding machine will be described with reference to FIG. In FIG. 1, reference numeral 1 indicates a cylinder barrel, and the cylinder barrel 1, specifically, the cylinder head 15
The nozzle 23 is connected to the tip of the. A screw 2 is rotatably inserted into the cylinder barrel 1, and the screw 2 is rotationally and longitudinally driven by a well-known screw drive mechanism 20 arranged at the rear end of the cylinder barrel 1. The injection unit including the cylinder barrel 1, the screw 2, the screw drive mechanism 20 and the like can be moved back and forth with respect to the die 21 by a moving cylinder device (not shown).

When the screw 2 is driven to rotate by the screw driving mechanism 20, the hopper 1 as a material supply unit is driven.
The molten molding material supplied from 9 is melted and kneaded by the screw 2 while being heated by the heater 14 attached to the cylinder barrel 1. Then, the screw 2 can be moved forward by the screw drive mechanism 20 and the melted molten molding material can be injected into the mold 21.

The screw 2 inserted in the cylinder barrel 1
Is the screw main body 2a forming the screw flight 2c.
And a screw head 2b. This screw body 2
A well-known backflow prevention device 22 is provided between a and the screw head 2b, and a storage space 4 for the molten molten molding material is formed between the screw head 2b and the nozzle 23. Then, the screw 2 is divided into a second metering zone A, a vent zone B, a first metering zone C and a supply zone D sequentially from the tip side, and the supply zone D
And the first metalling zone C forms the first stage E, and the vent zone B and the second metalling zone A form the second stage.
Forming stage F. The cylinder barrel 1, the screw 2, the screw drive mechanism 20 and the like are substantially the same as those of the conventional injection molding machine.

Then, the venturi mechanism 6 is provided so as to be connected to the vent zone B. The venturi mechanism 6 includes a main gas passage 7 and a sub gas passage 8 as shown in FIG.
The main gas flow path 7 has a large cross-section 7a, a small cross-section 7b whose central portion forms the smallest cross-section, and a large cross-section 7c sequentially from the upstream side, and the large cross-section 7a on the upstream side to the large cross-section on the downstream side. Cross section 7c
By applying the forced gas flow toward the side, the negative pressure portion O is formed in the small cross-section portion 7b according to Bernoulli's theorem.
The sub gas passage 8 has one end opening to the negative pressure portion O and the other end opening to an intermediate portion (vent zone B) of the cylinder barrel 1.
Then, an air supply device 9 having a compressor or a fan is connected to one end (the left end in the drawing) of the main gas flow path 7 and a forced gas flow toward the other end is given as shown by an arrow X. Thereby, the intermediate portion of the cylinder barrel 1 can be sucked.

Next, a degassing method using the above-mentioned vent type injection molding machine will be described. One cycle of the operation of such an injection molding machine is similar to each conventionally known process,
The mold closing process, the mold clamping process, the injection unit advancing process, the injection process, the measuring process, the injection unit retracting process, the mold opening process, the ejecting process, and the intermediate process are sequentially performed. Among them, the measuring process involving deaeration is performed as follows. First, if the screw 2 is rotated forward with the screw 2 set to the forward position,
The molten molding material supplied from the hopper 19 to the supply zone D is melted and kneaded by the kneading heat generated by the screw 2 and the heating by the heater 14, and the thrust is passed through the screw flight 2c to be melted in the first metering zone C. The molten molding material thus prepared is transferred from the first stage E to the second stage F.

In the second stage F, water / volatile components contained in the molten molding material are degassed in the vent zone B. That is, by supplying a forced gas flow to the main gas flow path 7 by the air supply device 9 as shown by the arrow X, the large cross section 7a
Gas is accelerated to the small cross section 7b, the pressure drops,
Since the small cross-section portion 7b has a negative pressure, the intermediate portion of the cylinder barrel 1 communicating with the small cross-section portion 7b through the auxiliary gas flow path 8 also has a negative pressure. In addition, the screw root diameter is usually formed to be shallow in the first metering zone C and deep in the vent zone B, and the feed amount of the molten molding material in the first stage E is in the second stage F. Since it is designed to be less than the above, the depressurized state of the vent zone B is satisfactorily obtained, and degassing of the molten molding material is promoted.

In this way, the middle portion of the cylinder barrel 1 is sucked, and the water content and volatile components contained in the molten molding material are forcibly sent out from the other end of the main gas flow path 7 and degassed. After that, the melt-molded material is in the second metering zone A.
Is melted and kneaded again, gradually accumulated in the storage space 4, and weighed. The metering process is completed by accumulating a predetermined amount of the molten molding material in the storage space 4. in this way,
Moisture and volatile components contained in the molten molding material are the main gas flow path 7
Gas (usually air) sent from the air supply device 9 from
Since it is diluted with and flows out from the large cross section 7c on the downstream side of the main gas flow path 7, there is almost no need to attach a processing device separately.

When a predetermined amount of the molten molding material is measured and stored in the storage space 4, the injection process is performed after the injection unit retracting process to the injection unit advancing process. In the injection step, the screw 2 is moved forward and the molten molten molding material in the storage space 4 is injected from the nozzle 23 into the mold 21 to obtain a molded product having a predetermined shape. At that time, the backflow prevention device 2
2 prevents backflow of the molten molding material. Thus, since the water and volatile components have been degassed from the molten molding material, it is possible to prevent the problem that these are mixed into the molded product and bubbles are generated in the molded product.

FIG. 3 shows a vacuum generating ejector having the same function as the venturi mechanism 6. That is, the vacuum generating ejector 16 includes a main gas passage 17 and a sub gas passage 18. The main gas passage 17 has a small cross section 17b.
And a large cross section 17a, and by applying a forced gas flow from the small cross section 17b side on the upstream side toward the large cross section 17a side on the downstream side, the small cross section 17b of the large cross section 17a A negative pressure portion O is formed near the boundary. The sub gas flow path 18 is
One end is opened to the negative pressure portion O, and the other end is opened to an intermediate portion (vent zone B) of the cylinder barrel 1. Then, the air feeding device 9 which is an air feeding device is connected to one end (the left end in the drawing) of the small cross-section 17b of the main gas flow path 17, and the forced gas flow toward the large cross-section 17a is indicated by the arrow X. By giving as shown, the intermediate portion of the cylinder barrel 1 can be sucked, so that the same operation as in the above embodiment can be obtained.

Further, in the above embodiment, the deaerator of the injection molding machine is applied to the vent type injection molding machine, and the auxiliary gas flow paths 8 and 18 are connected to the vent zone B of the vent type injection molding machine. It is also possible to connect the sub gas flow paths 8 and 18 to other zones of the injection molding machine to perform deaeration, and it is also possible to widely apply it as a vent device for other injection molding machines.

[0019]

As can be understood from the above description,
According to the degassing method and apparatus of the injection molding machine according to the present invention, water and volatile components are forcibly degassed from the molten molding material in the cylinder barrel, so that the degassing efficiency required for maintaining the quality of the molded product is improved. In addition to ensuring the air flow, a forced gas flow is provided by the air supply device, so that volatile matter etc. are not discharged to the outside and accumulated in the air supply device, maintenance is easy, and compared to installation of a vacuum pump. Both initial cost and running cost are low. In addition, since water and volatile components are diluted from the main gas flow path and discharged at a low concentration, it is difficult to deteriorate the working environment.

[Brief description of drawings]

FIG. 1 is a sectional view showing an injection molding machine according to one embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of the injection molding machine.

FIG. 3 is a sectional view showing a vacuum generating ejector.

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

[Explanation of symbols]

1: Cylinder barrel, 2: Screw, 2a: Screw body, 2b: Screw head, 2c: Screw flight,
4: Reservoir space, 6: Venturi mechanism, 7: Main gas flow path,
7a: large cross-section, 7b: small cross-section, 8: sub gas flow passage,
9: air supply device, 15: cylinder head, 16: ejector for vacuum generation, 17: main gas flow path, 17a: large cross section,
17b: small cross section, 18: auxiliary gas flow path, 19: hopper,
20: Screw drive mechanism, 21: Mold, 22: Backflow prevention device, 23: Nozzle, A: Second metering zone, B:
Vent zone, C: first metering zone, D: supply zone, E: first stage, F: second stage, O: negative pressure part.

Claims (2)

[Claims] 1. A degassing method for an injection molding machine, wherein deaeration is performed from the inside of a cylinder barrel (1) of the injection molding machine, wherein a large cross section (7a, 17a) and a small cross section (7b, 17b) are combined. A main gas flow path (7, 17) having a negative pressure portion (O) by providing a forced gas flow from one end side to the other end side by the air supply device (9), A sub gas flow path (8, 18) having an opening at the negative pressure portion (O) and the other end opening at the cylinder barrel (1) is provided, and the main gas flow path (7, 18) is provided in accordance with the operation of the injection molding machine. A degassing method for an injection molding machine, which comprises depressurizing the molten molding material by generating a forced gas flow in 17) to generate a negative pressure in the cylinder barrel (1). 2. A deaerator of an injection molding machine for deaerating from a cylinder barrel (1) of an injection molding machine, comprising a combination of a large cross section (7a, 17a) and a small cross section (7b, 17b). A main gas flow path (7, 17) having a negative pressure portion (O) by applying a forced gas flow from one end side to the other end side, and a main gas flow path (7, 17). An air feeding device (9) for forcedly feeding air from one end side, and one end of the negative pressure portion (O)
And a sub-gas flow path (8, 18) having the other end opening to the cylinder barrel (1).