JPH04286617A - Apparatus and method for continuous plasticizing type injection molding - Google Patents

Abstract

PURPOSE:To operate completely continuously a plasticizing unit consisting of a plasticizing device, an injection device and an accumulator device interposed between the two devices. CONSTITUTION:An outflow path 19 of a continuous plasticizing unit 10 is opened to an accumulator chamber 23 even when a plunger 22 of an accumulator device 20 is on the extrusion limit position. Plasticized resin from the outflow path 19 can be made to flow into either the accumulator chamber 23 or a metering chamber 33 of an injection device 30 by controlling the extrusion force applied to the plunger 22 or a plunger 32 to the values with which the plungers 22 and 32 are movable backward regardless of the position of the plunger 22. The continuous operation of a continuous plasticizing unit 10 can be carried out by the arrangement, and molding of high quality and high efficiency can be achieved.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an injection molding device for synthetic resin materials and an injection molding method using the device, and more particularly to a continuous plasticizing injection molding device in which a plasticizing device and an injection device are connected via an accumulator. and an injection molding method.

0002

[Prior Art] In order to improve the efficiency of injection molding,
By separating the plasticizing device and the injection device, for example, by rotating the screw of the plasticizing device in a cylinder and retracting it, plasticized resin is accumulated on the tip side of the screw, and the accumulated plasticized resin is transferred to the injection device by moving the screw forward. There was a continuous plasticization type injection molding device in which injection molding was performed using an injection device, and during this injection molding, the screw of the plasticization device was rotated and retreated again to perform plasticization continuously. In addition, instead of accumulating plasticized resin on the tip side of the screw by retracting the screw as described above, there was also a device in which an accumulator consisting of another cylinder and a plunger was interposed.

0003

[Problems to be Solved by the Invention] Plasticizing devices that move a screw forward and backward within a cylinder have a complicated screw driving device, and especially when a two-axis screw is used, the driving device for rotation is complicated. And because it is large,
Adding a drive device for advancing and retracting to this has the disadvantage that the device becomes increasingly complex and bulky. Furthermore, since the screw position changes with respect to the cylinder, the plasticizing conditions change, making stable plasticizing difficult.

[0004] In addition, an accumulator consisting of a separate cylinder and a plunger is interposed between the plasticizing device and the injection device. The plasticizing resin could not be allowed to flow in, and therefore the plasticizing device could not be operated completely continuously, resulting in the disadvantage that stable plasticization could not be performed.

The present invention solves the above-mentioned drawbacks and
It is an object of the present invention to provide a continuous plasticization type injection molding device and an injection molding method that can perform complete continuous plasticization and perform stable plasticization without changing the operating conditions of the plasticization device.

[0006]

[Means for Solving the Problems] A continuous plasticizing injection molding device according to the present invention for achieving the above object includes a continuous plasticizing device for synthetic resin material, and a continuous plasticizing device connected to an outflow path of the continuous plasticizing device. It is equipped with an accumulator device including a cylinder and a plunger, and an injection device including an injection cylinder and an injection plunger connected to an outflow path of the accumulator device via an on-off valve, and the outflow path of the continuous plasticizing device is connected to the accumulator device. Even when the plunger is at the extrusion limit position, the plasticized resin is connected to the accumulator device at a position where it can flow in, and at least one of the plunger of the accumulator device and the injection plunger is continuously plasticized when the opening/closing valve is in the open state. The inflow of plasticized resin from the device applies a retractable pressing force, the plunger of the accumulator device receives the retractable pressing force at least when the opening/closing valve is closed, and the injection plunger receives the retractable pressing force at least when the opening/closing valve is closed. It is configured so that it can be ejected when it is in the state.

[0007] The continuous plasticizing device is preferably equipped with a twin screw, and when the plunger of the accumulator device is at the extrusion limit position, the plunger and cylinder connect the outflow path of the continuous plasticizing device and the accumulator. It is preferable to form a flow path with a constant or smoothly changing cross-sectional area between the flow path and the outflow path of the device.

Further, the continuous plasticization injection molding method according to the present invention for achieving the above object includes the above-described continuous plasticization injection molding apparatus according to the present invention, in which the plunger of the accumulator device is pushed out to the extrusion limit position. After the plasticized resin accumulated in the device is transferred to the injection cylinder, the plasticized resin from the continuous plasticization device is flowed into the injection cylinder via the accumulator device while the plunger is stopped at the extrusion limit position, and the injection plunger is Once the meter has retreated to a predetermined position and metering has been completed, the injection operation begins.

[0009]

[Operation] The continuous plasticizing device operates completely continuously, and the plasticized resin is first accumulated in the accumulator device by retracting the plunger of the accumulator device under a retractable pressing force. When the amount of plasticized resin smaller than the amount of resin required for one injection is accumulated, the plunger of the accumulator device is pushed out to transfer the plasticized resin accumulated in the accumulator device into the injection cylinder. At this time, the on-off valve is opened and the injection plunger is given a retractable pressing force, so that the plasticized resin from the accumulator device is accumulated in front of the injection plunger.

The accumulator device connects the continuous plasticizing device and the injection cylinder even when the plunger reaches the extrusion limit position, and the plasticized resin from the continuous plasticizing device is transferred into the injection cylinder through the accumulator device. supply Once the amount of plasticized resin required for one injection has been measured into the injection cylinder, the opening/closing valve is closed and at the same time the plunger pressure of the accumulator device is switched to a pressure force that allows retraction, and the continuous plasticization device is removed. The plasticized resin is again accumulated in the accumulator device, and during this accumulation operation, the injection plunger is advanced to perform injection and pressure holding steps to complete one molding cycle.

[0011]

Embodiments An embodiment of the present invention will be described below with reference to FIG. Reference numeral 10 denotes a continuous plasticizing device, which includes a plasticizing cylinder 11 having a heating and cooling device (not shown) and a plasticizing screw 12 engaged with the plasticizing cylinder 11. The plasticizing screw 12 is a twin screw that rotates in the same direction or in different directions.
Only rotation is provided by the drive device 13. A first supply port 14 is opened near the base end of the plasticizing cylinder 11, and a synthetic resin material is supplied by a first feeder 15. A second supply port 16 is opened at approximately the center position in FIG. 1 of the plasticizing cylinder 11, and a second feeder 1
7 allows for the provision of reinforcing or filling materials such as glass fibers, carbon fibers and mica. A vent port 18 is opened from the left side of the plasticizing cylinder 11 in FIG.

A plasticizing resin outflow path 19 opened at the tip of the plasticizing cylinder 11 is connected to an accumulator device 20 . The accumulator device 20 consists of a cylinder 21 and a plunger 22, and an accumulator chamber 23 is provided on the tip side (lower end side in FIG. 1) of the plunger 22.
is formed. The area around the accumulator chamber 23 is heated by a heater (not shown). A piston 26 of a drive cylinder 25 is connected to the upper end of the plunger 22 via a rod 24.

When the plunger 22 is at the extrusion limit position shown in FIG.
It is designed to form a Further, the stepped portion 22b formed at the base of the small diameter protruding portion 22a of the plunger 22 is formed obliquely so that the side facing the flow path 19 of the continuous plasticizing device 10 is higher and the opposite side is lower. is at the extrusion limit position, the outflow path 19 is at the step portion 22b.
It is arranged so as to open below the highest position of the annular flow path 23a, that is, at the upper end of the annular flow path 23a.

The annular flow path 23a is formed so that the cross-sectional area of the flow path changes as smoothly as possible from the outflow path 19 to the outflow path 27 of the accumulator device 20 opened at the lower end of the cylinder 21. Note that the annular flow path 23a is
By appropriately forming the tip shape of the plunger 22, the outflow passages 19 and 27 are formed as close to a straight line as possible.
In addition, it may be a non-annular flow path with a constant cross-sectional area.

The outflow path 27 of the accumulator device 20 is connected to the injection device 30 via a first on-off valve 28 . The injection device 30 consists of an injection cylinder 31 heated by a heater (not shown) and an injection plunger 32 engaged with the injection cylinder 31. It is designed to accumulate in the measuring chamber 33 on the left end side). A piston 36 of an injection drive cylinder 35 is connected to the rear end of the injection plunger 32 via a rod 34. The metering chamber 33 is connected to a nozzle 38 via a second on-off valve 37.

The upper chamber 25a of the drive cylinder 25 of the accumulator device 20 is connected to a tank 43 via a first relief valve 41 and a first switching valve 42, and the pressure in the upper chamber 25a is the set pressure of the first relief valve 41. When P1 is exceeded, the pressure oil in the upper chamber 25a is released to the tank 43, and by switching the first switching valve 42, the pressure oil controlled to a predetermined pressure and flow rate is transferred from the first hydraulic source 44 to the first switching valve. 42, and is supplied via a check valve 45.

The rear chamber 35a of the injection drive cylinder 35 is connected to a tank 53 via a second relief valve 51 and a second switching valve 52.
When the pressure in the rear chamber 35a exceeds the set pressure P2 of the second relief valve 51, the pressure oil in the rear chamber 35a is released to the tank 53, and the second hydraulic pressure source is switched on by switching the second switching valve 52. 54 to the second switching valve 52, check valve 5
Pressure oil is supplied through 5. The pressure and supply flow rate of the second hydraulic power source 54 are controlled in accordance with the injection and pressure holding processes, but since this is the same as a known one, a detailed explanation will be omitted.

The set pressures P1 and P2 of the first and second relief valves 41 and 51 are the pressure of the plasticized resin extruded from the outflow path 19 of the plasticizing device 10, that is, the back pressure of the continuous plasticizing device 10. is set to maintain an appropriate value suitable for
While maintaining the back pressure at a desired value, the accumulator chamber 23,
As the plasticized resin flows into the measuring chamber 33, the plunger 2
2. The injection plungers 32 are moved backward.

Next, the operation of this device will be explained. A first feeder 15 feeds a synthetic resin material such as polypropylene in a fixed amount from the first supply port 14 of a twin-screw continuous plasticizing device 10 that preferably rotates in the same direction. Plasticize and knead. From the second supply port 16, a reinforcing or filling material such as glass fiber is supplied by a second feeder 17 at a total weight ratio of about 10 to 60%, and mixed with the plasticized synthetic resin material, Degassing at vent port 18 (vacuum suction)
Then, it is extruded from the outflow path 19. At this time, since the biaxial plasticizing screw 12 is rotating at a fixed position, the above-mentioned plasticizing is performed under fixed conditions.

Now, assuming that the process is to accumulate the plasticized resin extruded from the outflow path 19 in the accumulator device 20, the first on-off valve 28 is closed and the first switching valve 42 is placed in the state shown. ing. Therefore, the outflow path 19
The plasticized resin extruded from the upper chamber 25a pushes up the plunger 22, releases the pressure oil in the upper chamber 25a to the tank 43 via the first relief valve 41 and the first switching valve 42, raises the plunger 22, and releases the pressure oil from the upper chamber 25a to the tank 43. 23 is enlarged and accumulated therein.

During the above accumulation process, the injection plunger 32 is performing the previous injection and pressure holding process one cycle. When this pressure holding step is completed, the second on-off valve 37 is closed, the second switching valve 52 is returned to the illustrated neutral position, and the first on-off valve 28 is opened. At this time, the accumulator device 2
The plunger 22 of No. 0 is raised by a predetermined amount, and an amount of plasticized resin less than the amount of one injection is accumulated in the accumulator chamber 23.

After opening the first opening/closing valve 28, the first switching valve 42 is moved to the left from the illustrated position and switched to the right switching position, and the pressure of a predetermined pressure and a predetermined flow rate is supplied from the first hydraulic source 44. Oil is supplied to the upper chamber 25a via the check valve 45. This causes the plunger 22 to descend at a predetermined speed. At this time, the rear chamber 35a of the injection drive cylinder 35 is connected to the tank 53 via the second relief valve 51 and the second switching valve 52, and the second relief valve 51 is similar to the first relief valve 41 as described above. Since the set pressure P2 is set so as to maintain the back pressure of the outflow path 19 at a predetermined value, the plasticized resin in the accumulator chamber 23 flows downward without blocking the supply of plasticized resin from the outflow path 19. The liquid flows from the outflow path 27 through the first opening/closing valve 28 into the metering chamber 33, causing the injection plunger 32 to retreat.

Plunger 2 of accumulator device 20
2 is lowered to the illustrated extrusion limit position and held at this position. At this time, the amount of plasticized resin that is combined from the accumulator chamber 23 and the continuous plasticizing device 10 and sent to the metering chamber 33 is set to be equal to or smaller than the amount required for one injection.

Plunger 2 placed at the illustrated extrusion limit position
2 is formed with an annular flow path 23a as described above, and the plasticized resin continuously extruded from the outflow path 19 is smoothly sent to the measuring chamber 33 through the annular flow path 23a, that is, without stagnation. It will be done. When a predetermined amount of plasticized resin necessary for one injection is measured into the measuring chamber 33 in this way, it is detected from the position of the injection plunger 32 by a detection device (not shown), and the first opening/closing valve 28 is closed and the first opening/closing valve 28 is closed. 2
The on-off valve 38 is opened, the second switching valve 52 is moved to the left in FIG. , the injection plunger 32 is advanced, and the plasticized resin in the metering chamber 33 is injected from the nozzle 38 into a mold (not shown) to perform molding.

At the same time as closing the first opening/closing valve 28, the first switching valve 42 is switched to the neutral position shown, and the outflow path 19
The plasticized resin continuously sent out from the accumulator chamber 23 is accumulated again in the accumulator chamber 23. This state continues until the post-injection pressure holding process is completed, and the same operation is repeated thereafter.

In the above-mentioned embodiment, a twin-screw type extruder rotating in the same or different directions was used as the continuous plasticizing device 10, but other plasticizing devices such as a single-screw type can also be used. good. Furthermore, in the above embodiment, the timing of transferring the plasticized resin from the accumulator chamber 23 to the metering chamber 33 was controlled by the completion of the pressure holding process, but the accumulation amount in the accumulator chamber 23 is detected, and the It may also be controlled by a signal. Furthermore, although the above-described embodiment shows an example in which the pressing force and movement of the plunger 22 and the injection plunger 32 are controlled by hydraulic pressure, various modifications are possible, such as control by an electric servo.

[0027]

[Effects of the Invention] As described above, according to the present invention, plasticization can be performed completely continuously, and there is no need to move the plasticizing screw, etc., so it is extremely stable under predetermined conditions. This allows high-quality molded products to be produced with high efficiency.

[Brief explanation of the drawing]

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

[Explanation of symbols]

10 Continuous plasticizing device 11 Plasticizing cylinder 12 Plasticizing screw 13 Drive device 14 First supply port 15 First feeder 16 Second supply port 17 Second feeder 18 Vent port 19 Outflow path 20 Accumulator device 21 Cylinder 22 Plunger 23 Accumulator room 23a Annular flow path 25 Drive cylinder 27 Outflow channel 28 First opening/closing valve 30 Injection device 31 Injection cylinder 32 Injection plunger 33 Measurement room 35 Injection drive cylinder 37 Second opening/closing valve 38 Nozzle 41 First relief valve 51 Second relief valve

Claims (4)

[Claims] Claim 1: A continuous plasticizing device for synthetic resin material; an accumulator device comprising a cylinder and a plunger connected to an outflow path of the continuous plasticizing device; and an accumulator device connected to the outflow path of the accumulator device via an on-off valve. an injection device comprising an injection cylinder and an injection plunger, the outflow path of the continuous plasticizing device allows plasticized resin to flow into the accumulator device even when the plunger of the accumulator device is at the extrusion limit position. and at least one of the plunger and the injection plunger of the accumulator device is given a retractable pressing force by the inflow of plasticized resin from the continuous plasticization device when the opening/closing valve is in the open state. , the plunger of the accumulator device is provided with the pressing force that allows it to retreat at least when the on-off valve is in the closed state, and the injection plunger is configured to be able to inject when the on-off valve is in the closed state. Continuous plasticization injection molding equipment. 2. The continuous plasticizing injection molding apparatus according to claim 1, wherein the continuous plasticizing apparatus is equipped with a twin screw. 3. The accumulator device is such that when the plunger is at the extrusion limit position, the plunger and the cylinder provide a constant or smooth cross-sectional area between the outflow path of the continuous plasticizing device and the outflow path of the accumulator device. 3. The continuous plasticizing injection molding apparatus according to claim 1, wherein the continuous plasticizing injection molding apparatus is configured to form a flow path that changes in temperature. 4. The continuous plasticizing injection molding apparatus according to claim 1, 2 or 3, wherein the plunger of the accumulator device is pushed out to the extrusion limit position to transfer the plasticized resin accumulated in the accumulator device to the injection cylinder. After the transfer, the plasticized resin from the continuous plasticizing device is allowed to flow into the injection cylinder via the accumulator device while the plunger is kept at the extrusion limit position, and the injection plunger is retreated to a predetermined position. A continuous plasticization injection molding method characterized in that the injection operation begins after measurement is completed.