JPH09207180A - Screw preplasticating injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the plastication of a resin, to eliminate the nonuniformity of temperature, and to shorten a molding cycle by a method in which the plastication and measuring of the resin are carried out by the rotation and regression of a screw in a plastication apparatus, and the plasticated resin after measuring is sent into an injection apparatus through a thin resin passage by the advance of the screw. SOLUTION: An injection apparatus 1 in which a plunger 12 is set freely advanceably/retractably in an injection cylinder 10 and a plastication apparatus 2 in which a screw 22 is set freely rotatably and advanceably/retractably in a plastication cylinder 20 are made to communicate with each other by a thin resin passage 3 having a temperature conditioning means 32 on the periphery which is installed ranging from an inflow passage of a part corresponding to the plunger advance limit of the infection cylinder tip part to an outflow passage at the plastication cylinder tip. The measured resin in the cylinder tip part which is plasticated by the rotation of the screw can be packed from the resin passage 3 into the plunger front part of the injection cylinder 10 by controlling the advance velocity of the screw.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw pre-plastic type injection device used for injection molding of synthetic resin.

[0002]

2. Description of the Related Art In a general screw pre-plastic type injection device, a plasticizing cylinder having a screw inside is juxtaposed to an injection cylinder having a plunger inside, and the tip of the plasticizing cylinder and the tip of the injection cylinder are connected by a resin path. do it,
The resin is melted and kneaded (hereinafter referred to as plasticized) in a plasticizing cylinder, is filled and measured in the front part of the injection cylinder, and then is injected by advancing the plunger.

[0003]

In such a screw pre-plastic type injection device, since the resin that is rotated at a fixed position plasticizes the resin, an in-line screw type device that plasticizes with the screw that retreats while rotating is used. It is said that plasticization can be performed more uniformly than with an injection device, but this is not always the case, and depending on the screw design, material condition, characteristics, etc., plasticization tends to be non-uniform and It may even cause unevenness.

This temperature unevenness can be improved by making the resin passage communicating the injection cylinder and the plasticizing cylinder a small diameter resin passage provided with a heater on the outer periphery and forcibly flowing the resin passage. Although it is possible to improve the plasticized state uniformly during the flow process of the resin passage, the optimum rotation speed of the screw differs depending on the type of material resin and is determined by the material resin used.

Therefore, the speed of the plasticized resin delivered at the rotational speed determined by the material resin and passing through the resin path of small diameter is not always required from the viewpoint of further plasticization of the material resin and improvement of temperature unevenness. It cannot be said that the speed is optimum, and the state of the resin material used therefor cannot be controlled.

Further, since the speed of the plasticized resin passing through the small-diameter resin path is proportional to the rotation speed of the screw, increasing the rotation speed inevitably increases the passage speed, and for temperature stability. Even if it is desired to pass the screw slowly, the rotation speed of the screw becomes high if the rotation speed is large, and vice versa. Therefore, it is extremely difficult to realize the optimum condition by controlling the rotation speed.

Further, in the plasticization by the screw rotating at a fixed position, the plasticized resin is continuously discharged to the injection cylinder side, and the plunger is retracted by the discharging force to measure the resin. From the start of injection filling by forward movement to the holding pressure, the rotation of the screw is stopped and the plasticization is stopped. Therefore, there is a problem that it is difficult to shorten the molding cycle by making injection and plasticization parallel.

The present invention was conceived in order to solve the above-mentioned conventional problems, and its purpose is to plasticize the material resin and to control the plasticizing cylinder before the plasticizing cylinder by controlling the rotation speed of the screw in the plasticizing device. The primary measurement is performed inside the part, and the plasticizing resin is allowed to pass through the small-diameter resin passage at the optimum speed by controlling the screw forward speed, improving the plasticization of the material resin and solving temperature unevenness. Another object of the present invention is to provide a new pre-plastic injection device that can shorten the molding cycle.

[0009]

SUMMARY OF THE INVENTION According to the present invention according to the above object, an injection device in which a plunger is housed in an injection cylinder so as to move forward and backward, and a plasticizing device in which a screw is installed in a plasticizing cylinder so as to rotate and move forward and backward are injected. An inflow passage at a portion of the cylinder tip portion corresponding to the plunger forward end and a plastic passage of a thin tube having a temperature adjusting means on the outer periphery provided over the outflow passage of the plasticizing cylinder tip communicate with each other, and an opening / closing valve is provided in the resin passage, The metering resin in the tip portion of the cylinder that has been plasticized by the screw rotation can be filled in the plunger front portion of the injection cylinder from the resin passage by controlling the screw forward movement.

Further, according to the present invention, the speed of the plasticized resin passing through the small-diameter resin path can be arbitrarily changed by controlling the forward speed of the screw, and the screw is also preferably a screw groove having a constant depth. By adopting a screw with a L / D of 15 or less with a screw ratio of 1 or a compression ratio of 1,
It is also possible to suppress heat generation due to shearing force and frictional force during compression, and also to prevent discoloration of the resin due to overheating.

In the above construction, since the resin can be measured by rotating and retracting the plasticizing screw, the material resin can be plasticized and measured even during the injection filling by blocking the small-diameter resin passage, and the screw can be used. Since the measuring resin is forcibly pressed into the resin passage by the pressing force due to the forward movement of, the resin can be pressed into the injection cylinder and filled and measured in a short time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, 1 is an injection device, 2 is a plasticizing device, and this plasticizing device 2 has a tip 21 of a plasticizing cylinder 20 located rearward of a tip 11 of an injection cylinder 10, They are arranged side by side on the injection device 1. Further, the two devices are communicated with each other by a small-diameter resin path 3 obliquely provided over the tip portions 11 and 21.

The injection device 1 has a plunger 12 for injection.
And the injection cylinder 1 in which the nozzle member 13 is extended at the tip,
The piston 14 is connected to the rear end of
And a hydraulic cylinder 15 for injection connected to
A rotary on-off valve 16 is provided in the injection path of the nozzle member 13.

The injection cylinder 10 has an inflow passage of the resin passage 3 at an upper portion of the tip end 11 which is in contact with the plunger forward end, and the inflow passage is provided with a rotary opening / closing valve 17 having the same diameter as the resin passage 3. There is. Further, a resin drain hole 18 is provided in the wall portion behind the plunger stroke of the injection cylinder 10, and a band heater 19 is provided from the nozzle tip portion to the cylinder periphery after the resin drain hole 18 to extend the heater zone. It is set. As a result, the resin that has entered the periphery of the plunger is sent rearward each time the plunger 12 moves backward, and is discharged to the outside through the resin drain hole 18.

The plasticizing device 2 comprises a plasticizing cylinder 20.
A plasticizing screw 22 is rotatably and forwardly and backwardly provided inside the. The screw groove of this screw 22 has a constant depth, has no compression portion, and has an L / D of 1 with a compression ratio of 1.
5 or less, the rear end of which is a plasticizing cylinder 20
It is connected to a piston 25 of a hydraulic cylinder 24 provided on a rear holding member 23.

A hydraulic or electric motor 26 for screw rotation is attached to the rear end of the hydraulic cylinder 24. The rotary drive shaft 27 protruding from the motor 26 into the hydraulic cylinder and the piston 25 are connected to a spline or the like. With this, the screw 22 is movably fitted in the axial direction so that the screw 22 can be rotated via the piston 25.

A band heater 28 is attached to the outer periphery of the plasticizing cylinder 20, and a hopper 29 is attached to the supply hole at the rear end of the plasticizing cylinder 20 fitted with the holding member 23.

The thin resin passage 3 is made of a metal thin tube having an inner diameter of about 5 to 10 mm, and has a band heater 31 on the outer periphery.
Equipped with temperature control means such as. Further, the resin passage 3 is provided obliquely at an acute angle forward from the tip end portion 11 of the injection cylinder 10 and the tip end portion 21 of the plasticizing cylinder 20 at an inclination angle of 40 ° to 50 °.

The injection device 1 and the plasticizing device 2 are provided with a support base 30 provided on the hydraulic cylinder 15 of the injection device 1.
Then, the holding member 23 of the plasticizing device 2 is placed and fixed,
A base block 4 that is configured in a two-stage upper and lower screw pre-plastic injection device and is provided below the hydraulic cylinder 15.
Is mounted on the machine base 5 so as to be slidable in the front-rear direction and mounted on the machine base 5.

The forward / backward movement of the screw pre-plastic type injection device is performed by the hydraulic cylinder 7 and the piston 7a extending over the rear end of the base block 14 and the receiving member 51 protruding from the upper surface of the base plate 5, and the extension of the piston 7a. For each time, the injection device 1 and the plasticizing device 2 move forward together, and although the nozzle tip of the injection device 1 is not shown in the figure, the nozzle is touched on the sprue of the mold to perform the injection filling of the resin, and the backward movement. It is possible to perform material purging or equipment maintenance by moving away from the sprue or the like.

Next, the injection operation will be described. First, the resin passage 3 is closed by the opening / closing valve 17, and a predetermined back pressure is applied to the plunger 12 in the injection cylinder by the hydraulic cylinder 15.

After such preparation, while the screw 22 is rotated by the motor 26, the material resin of the pellets is fed into the plasticizing cylinder 20 from the hopper 29, and the material resin is transferred to the front portion of the cylinder by the screw groove having a constant depth. Will be transferred. During this transfer, the band heater 28 heats the cylinder side and the screw 22 rotates to generate a certain amount of shearing heat, and the melted and kneaded materials are sequentially fed under pressure. The screw 22 moves backward due to the resin pressure generated by the plasticization, but the plasticization is continued. As the screw 22 moves backward, the plasticized resin is sequentially accumulated in the cylinder at the front of the screw. This accumulated amount depends on the amount of retreat of the screw.

When the accumulated amount reaches a preset amount, the rotation of the screw 22 is stopped, the plasticization of the material resin is stopped, and the screw stops at the retracted position. As a result, a set amount of resin is primarily measured in the cylinder at the front of the screw. Almost at the same time as the stoppage, the opening / closing valve 17 is opened to allow the resin passage 3 to communicate with the injection cylinder side. Therefore, when the screw 22 is moved forward by the hydraulic cylinder 24, the measured plasticized resin is forcibly pushed into the small-diameter resin passage 3. The forward speed of the screw 22 can be arbitrarily changed by controlling the flow rate of the pressure oil supplied to the hydraulic cylinder 24.

On the injection cylinder side, only a predetermined back pressure is applied to the plunger 12, and there is nothing that prevents the resin from being pressed in. Therefore, the total amount of the plasticized resin that was primarily measured at the front of the screw 22 is It is passed through the resin passage 3 by the pressing force of the screw 22, and is filled in the front portion of the injection cylinder 10 while moving the plunger 12 backward. On this occasion,
In the resin path 3, the plasticized resin flows into the front part of the injection cylinder 10 while being further plasticized by the flow resistance while passing through the narrow tube and the heat from the outside.

The plasticized resin is again accumulated in the front portion of the injection cylinder 10 by the retreat of the plunger 12, and the injection amount is accurately measured. And the plunger 12
Is retracted to the set position, the opening / closing valve 17 is closed to close the resin passage 3, and the plunger 12 is closed on the injection device side.
The process is switched to the plasticizing resin injection process by the forward movement of. On the plasticizing device side, the screw 22 is rotated and the material resin is plasticized again.

When the plunger 12 is moved forward by the hydraulic cylinder 15 while the resin passage 3 is closed, the entire amount of the plasticized resin measured in the injection cylinder is injected and filled into the mold (not shown) from the tip of the nozzle. To be done. Even after this filling is completed, a predetermined pressure is applied to the plunger 12 by the hydraulic cylinder 15 to hold the resin. At the time when this holding pressure is completed, and in some cases, before the completion of the holding pressure, the opening / closing valve 16 is closed to shut off the injection passage, and the process shifts to cooling.

When the opening / closing valve 17 of the small-diameter resin passage 3 is opened after the injection passage is blocked, the injection device 1 is operated from the plasticizing device 2 side of the plasticized resin measured by the opening of the resin passage 3.
Filling on the side is possible. During this filling, screw 22
Since the rotation of the screw is already stopped, the filling can be performed by the forward movement of the screw 22 regardless of the screw rotation. Therefore, the process in which the plasticized resin passes through the resin path 3 having a small diameter can be arbitrarily controlled by controlling the forward speed of the screw, and as a result, the state of the plasticized resin can be further improved. Becomes

In the plasticizing device 2, the plasticizing work of the material resin is carried out in parallel with the injection filling work by the injection device 1. Therefore, immediately after the completion of the injection filling / holding pressure, the plasticizing work to the front part of the injection cylinder is performed. The measurement resin can be press-fitted and filled, and the resin previously measured on the plasticizing cylinder side can be re-measured on the injection cylinder side. Therefore, the measurement accuracy is improved and the cycle can be shortened by shortening the time.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of an embodiment of a screw pre-plastic injection device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection device 2 Plasticizing device 3 Small diameter resin path 10 Injection cylinder 12 Injection plunger 13 Nozzle member 15 Injection hydraulic cylinder 16 Injection path opening / closing valve 17 Resin path opening / closing valve 20 Plasticizing cylinder 22 Plasticizing Screw 24 Hydraulic cylinder for forward and backward movement of screw 26 Motor for rotating screw

[Procedure amendment]

[Submission date] August 29, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

SUMMARY OF THE INVENTION According to the present invention according to the above object, an injection device in which a plunger is housed in an injection cylinder so as to move forward and backward, and a plasticizing device in which a screw is housed in a plasticizing cylinder so as to rotate and move forward and backward are injected. The inflow passage of the portion of the cylinder tip end that corresponds to the plunger forward end and the outflow passage of the plasticizing cylinder tip communicate with each other by the resin passage of the thin tube having the temperature adjusting means on the outer circumference, and the inside of the cylinder tip end is plasticized by the screw rotation. The metering resin is configured so that it can be filled into the plunger front portion of the injection cylinder from the resin passage by controlling the screw forward movement.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

Further, according to the present invention, the speed of the plasticized resin passing through the small-diameter resin path can be arbitrarily changed by controlling the forward speed of the screw, and the screw is preferably a screw whose screw groove has a constant depth. , Or L / with a compression ratio of 1
By using a screw having D of 15 or less, heat generation due to shearing force and frictional force at the time of compression is suppressed, and discoloration of the resin due to overheating is also prevented.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

Furthermore, the present invention has an opening / closing valve in a small-diameter resin path that enables plasticizing and metering of the material resin by rotating and retracting the screw in parallel during the injection process, and metering by the forward movement of the screw. Together with the forced press-fitting of the resin into the resin passage, the press-fitting and filling and metering of the plasticized resin into the injection cylinder are completed in a short time.

Claims (4)

[Claims] 1. An injection device in which a plunger is installed in an injection cylinder so that the plunger can advance and retreat, and a plasticizing device in which a screw is installed in a plasticizing cylinder so that the screw can rotate and move forward and backward, flow into a part of the injection cylinder tip end portion that corresponds to the plunger advance limit. Of the cylinder tip, which is plasticized by the screw rotation, by communicating with a small diameter resin passage having a temperature control means on the outer circumference provided over the passage and the outflow passage at the tip of the plasticizing cylinder, and providing an opening / closing valve in the resin passage. A screw pre-plastic injection device, characterized in that a metering resin can be filled into the front part of the plunger of the injection cylinder from the resin passage by advancing the screw. 2. The screw pre-plastic injection according to claim 1, wherein the speed of the plasticized resin passing through the resin path having the small diameter is variable by controlling the forward speed of the screw. apparatus. 3. The screw pre-plastic injection device according to claim 1, wherein a screw groove of the screw is formed to have a constant depth. 4. The screw according to claim 1, wherein the screw has a compression ratio of 1 and an L / D of 15 or less.
Alternatively, the screw pre-plastic injection device described in 2.