JPH06293021A - Deaerating method of powder molding machine and vent device for molding powder - Google Patents

Abstract

PURPOSE:To suck moisture and a volatile matter from a resin forcibly and prevent suction to the outside of a powder resin under an unmelted state fowarded to a vent by reducing the suction force of a vacuum pump when the torque value of a screw reaches a specified value or less when moisture, the volatile matter, etc., produced from the resin in a vent section are sucked and exhausted by the vacuum pump. CONSTITUTION:When an initial stage passes and a resin is supplied at every fixed quantity, the torque value of a screw 10 rises because specified shearing force, frictional force, etc., work, and the on signal of a vacuum pump 4 is output when the torque value is larger than a set value. A space not filled with the resin can be formed during the flight of a vent section 13, and the specific degree of vacuum works. Consequently, moisture, a volatile matter, etc., produced from the resin are sucked and exhausted by the pump 4. Driving torque is made smaller than the set value though the supply of the resin is stopped, the quantity of the resin fed to a supply section is decreased, melting is delayed and the resin under an unmelted state reaches the vent section 13, the pump 4 is turned off, then preventing suction to the pump 4 of the resin under the unmelted state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a cylinder and a screw provided in the cylinder. When the screw is driven, the resin is melted and kneaded in the process of being forwardly fed along the groove of the screw. The present invention relates to a deaeration method of a powder molding machine for sucking and exhausting water, volatile matter, and the like generated from a resin in a vent portion, and a vent apparatus for powder molding used for carrying out the method.

[0002]

2. Description of the Related Art As is well known, an injection device of an injection molding machine is generally composed of a cylinder and a screw driven in the cylinder. A vent type injection device capable of releasing moisture, volatile matter and the like generated from the resin to the outside in the process of melting and kneading the resin also includes a cylinder and a screw driven in the cylinder. The cylinder or screw includes a supply unit to which the powder material is supplied from the hopper, a first metal ring unit located on the downstream side of the supply unit, a vent unit on the downstream side of the first metal ring unit, and a second metal ring on the downstream side. A screw head is provided at the tip of the second metering portion. The groove of the screw located at the vent is deep. Alternatively, the shaft diameter of the screw in the vent portion is smaller. Further, the resin feed amount in the first stage including the supply unit and the first metalling unit is configured to be smaller than the resin feed amount in the second stage including the vent unit and the second metalling unit. A vent hole is provided in the cylinder located at the vent portion, and a vacuum pump is connected to the vent hole.

Therefore, when the resin is supplied from the hopper to the supply portion and the screw is driven to rotate, the resin is plasticized and kneaded by the heat applied from the outside and the exothermic action due to shearing, friction, etc. due to the rotation of the screw to cause the screw to rotate. Sent to the tip. At this time, the feed amount of the resin in the second stage is larger than the feed amount in the first stage, so that a space not filled with the molten resin is formed in the flight at the vent portion. Since a space is created in this way, moisture, volatile matter, etc. generated from the resin can be prevented without leaking the molten resin to the outside.
A vacuum pump can be used to forcibly suck and exhaust air from the vent hole.

[0004]

As described above, even with the conventional vent type cylinder, it is possible to suck and exhaust only water, volatile matter and the like generated from the resin. However, since the conventional vacuum pump is adapted to be activated in association with the melting / kneading operation, there is a drawback in some cases that the powdered resin is sucked from the vent hole into the piping system, the vacuum pump or the like. More specifically, when a sufficient amount of powder resin is supplied from the hopper, the powder resin is melted by heat obtained by heat generating action such as shearing force and frictional force due to rotation of the screw and heat applied from the outside. Although it is sent to the vent part, if the supply amount is reduced, sufficient shearing force, frictional force, etc. cannot be obtained, so that melting may be delayed and powder may be sent to the vent part as it is. Then, since the powdery resin is light, it is sucked by the vacuum pump. Once sucked, powdery resin adheres to the vacuum pump including the piping system, which requires troublesome cleaning. Therefore, according to the present invention, moisture, volatile matter, etc. generated from the resin can be forcibly sucked to the outside, and even if the powdered resin is sent to the vent portion in the unmelted state, the unmelted resin remains outside. It is an object of the present invention to provide a deaeration method for a powder molding machine, which is not sucked into the air, and a powder molding vent apparatus used for carrying out the method.

[0005]

In order to achieve the above-mentioned object, the present invention is to drive a screw to melt and knead the resin while sending the resin forward along the groove of the screw, and to perform resin melting at the vent portion. When sucking and exhausting water, volatile matter, and the like generated from the vacuum pump with a vacuum pump and the torque value of the screw is a predetermined value or less, the suction force of the vacuum pump is reduced. The invention according to claim 2 comprises a cylinder and a screw provided in the cylinder, wherein the resin is melted and kneaded in the process of being forwardly fed along the groove of the screw, and the resin is melted and kneaded by a vent device. A vent device for an injection molding machine, wherein generated water, volatile matter, and the like are sucked and exhausted, wherein the vent device is connected to the vent hole provided in the cylinder and the vent hole. A vacuum pump for forcibly sucking water, volatile matter, etc. generated from the resin, a control means for controlling the suction force of the vacuum pump, and a torque detection means for detecting the torque of the screw. When the torque value detected by the torque detection means is lower than a predetermined value, the vacuum degree of the vacuum pump is controlled to be small.

[0006]

The invention according to claim 2 operates as follows.
That is, the resin is supplied and the screw is driven. Then, the resin is melted and kneaded in the process of being sent forward along the groove of the screw. At this time, the torque value of the screw is input to the control device from the torque detection means. Then, when the input torque value has reached the predetermined value, the control device keeps the vacuum pump, for example, in the ON state. Therefore, water, volatile matter and the like generated from the resin in the process of melting and kneading are forcibly sucked and exhausted by the vacuum pump. On the other hand, when the input torque value is smaller than the predetermined value due to a decrease in the resin supply amount, the control device controls so that the vacuum degree of the vacuum pump becomes smaller, for example, the vacuum pump is turned off. As a result, even if the unmelted resin reaches the vent portion, it is not sucked by the vacuum pump.

[0007]

EXAMPLES Examples of the present invention will be described below. Figure 1
It is sectional drawing which shows 1 Example of this invention. As shown in the figure, the injection machine according to the present embodiment also includes a cylindrical cylinder 1 and a screw 10 provided inside the cylinder 1 so as to be rotatable in the rotational direction and the axial direction. . The screw 10 corresponds to the supply unit 1 from the right to the left in the figure.
1, the first metering part 12, the vent part 13, and the second metering part 14 are structurally divided, and a screw head 15 is provided in the front part of the second metering part 14. Further, the supply unit 11 and the first metering unit 12 are connected to the first stage S
The vent portion 13 and the second metering portion 14 are divided into the second stage ST2 at T1. Also in this embodiment, the resin feed amount in the first stage ST1 is
It is smaller than the feed amount of stage ST2. In addition, the vent portion 13
The groove of the screw 10 is deeper than the other portions.

In the cylinder 1 corresponding to the vent portion 13,
A vent pipe 2 is provided, and a suction pipe 3 is connected to the vent pipe 2. A vacuum pump 4 is installed in the suction pipe 3. The vacuum pump 4 is driven by an electric motor in this embodiment, and the electric motor is controlled by the control device 5. To drive the screw 10 to rotate, an electric motor 7 is provided on the right side of the drawing. The electric motor 7 is a screw 1 via a reduction mechanism.
Although 0 is rotationally driven, the torque of the screw 10 is measured by the current value of the electric motor 7 and input to the control device 5 via the line 8. The control device 5 controls the components necessary for injection molding, and can preset the torque value of the screw 10, and compares the set torque value with the torque value measured by the electric current value of the electric motor 7. When the measured torque value is smaller than the set torque value, the line 6 also has a function of outputting a signal for turning off the motor of the vacuum pump 4.

Next, the operation of the above embodiment will be described.
The torque value of the screw 10 when the resin is melted and sent to the vent portion 13 is preset in the control device 5.
The powdery resin is supplied from the hopper 16 to the supply unit 11, and the screw 10 is rotationally driven by the electric motor 7. Then, as is well known, the resin is the first stage S
In the process of being transferred from T1 to the second stage ST2, heating by the heaters 17, 17, ... Provided on the outer peripheral portion of the cylinder 1 and shearing force by rotational driving of the screw 10,
It is melted and kneaded by the heat generated by frictional force, etc., and accumulated in the front. When a predetermined amount is accumulated, the screw 10 is driven to inject from the nozzle into the mold 19. After cooling and solidification, the mold is opened and the molded product is taken out. The mold is clamped, and the same operation is repeated thereafter to obtain a molded product.

When the molded product is obtained as described above, for example, at the initial stage when the molding machine is started, the resin is not filled between the flights of the screw 10, so that large shearing force, frictional force, etc. do not act. Therefore, screw 1
The rotational drive torque of 0 is also small. Therefore, the electric motor 7
The torque value of the screw 10 measured by the current value is smaller than the preset value set in the control device 5, and the control device 5 outputs a signal for turning off the electric motor of the vacuum pump 4 through the line 6. Then, since the vacuum pump 4 does not start, even if the unmelted powdered resin is sent to the vent portion 13, the powdered resin flows from the vent pipe 2 to the suction pipe 3,
It is not sucked by the vacuum pump 4 or the like.

When the initial amount is passed and a predetermined amount is supplied, a shearing force, a frictional force, etc. having a predetermined magnitude come to act, so that the torque value of the screw 10 increases. Since the torque value is input to the control device 5 through the line 8, when it becomes larger than the set value, a signal for turning on the electric motor of the vacuum pump 4 is output. First stage ST
The feed amount of the resin in 1 is smaller than the feed amount of the second stage ST2, and the groove of the screw 10 of the vent portion 13 is deeper than the other portions, so that between the flights of the vent portion 13, There is a space not filled with resin,
A predetermined degree of vacuum acts on this space through the vent pipe 2 and the suction pipe 3. Therefore, water, volatile matter and the like generated from the resin in the process of melting and kneading are sucked and exhausted by the vacuum pump 4. If the supply of the resin to the hopper 16 is interrupted for some reason and the amount of the resin supplied to the supply unit 11 is reduced, that is, if the resin is not filled during the flight of the screw 10, the shearing force, the frictional force, etc. are sufficient. Since such a heat-generating effect cannot be obtained, melting is delayed, and unmelted resin reaches the vent portion 13. At this time, since the rotational driving torque of the screw 10 becomes smaller than the set value as described above, the control device 5 outputs a signal to turn off the electric motor of the vacuum pump 4. Therefore, even if the unmelted resin reaches the vent portion 13, it is not sucked by the vacuum pump 4 or the like.

In the above embodiment, the electric motor of the vacuum pump 4 is turned on according to the rotational driving torque value of the screw 10.
Although turned off, the vacuum degree of the vacuum pump 4 can be controlled to such an extent that the unmelted resin is not sucked by the vacuum pump 4 or the like. For example, the rotation driving torque of the screw 10 is compared with a set value, and the vacuum pump 4 is operated according to the difference.
The number of rotations of the electric motor can also be phase-controlled. Further, as shown in the figure, a branch pipe 3'is provided on the suction pipe 3 on the upstream side of the vacuum pump 4, a flow control valve or an on-off valve 9 is provided on the branch pipe 3 ', and the on-off valve is provided. 9 can also be controlled by the control device 5. For example, as described above, the screw 1 measured by the current value of the electric motor 7
The torque value of 0 is compared with a preset value set in the control device 5, and the control device 5 causes the open / close valve 9 to operate according to the difference.
It is also possible to carry out so as to open and close or to adjust the opening degree. When the on-off valve 9 is opened or the opening is increased, the vacuum pump 4 sucks the outside air, so that a large negative pressure does not act on the vent portion 13. Therefore, even if the unmelted resin is sent, it is not sucked by the vacuum pump 4 or the like. Further, the suction pipe 3 is provided with an opening / closing valve 9 ', and when the torque value of the screw 10 is equal to or less than the set value, the suction pipe 3 is shut off by the opening / closing valve 9', and the suction force of the vacuum pump 4 is applied to the vent portion 13. You can choose not to exceed it. By carrying out in this way, compared with the case where the electric motor of the vacuum pump 4 is turned on / off, the effect of extending the life of the electric motor can be obtained.

[0013]

As described above, according to the present invention, since the vent device is provided with the vacuum pump, the screw is driven to melt and knead the resin while feeding the resin forward along the groove of the screw. At this time, water, volatile matter, etc. generated from the resin can be forcibly sucked and exhausted by a vacuum pump.
Moreover, when the torque value of the screw is less than or equal to the predetermined value,
That is, when powdery resin may be sent, the controller reduces the suction force of the vacuum pump, so even if unmelted resin is sent, it is not sucked by the vacuum pump. The effect peculiar to the present invention can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention with a partial cross section.

[Explanation of symbols]

1 cylinder 2 vent pipe (vent hole) 4 vacuum pump 5 controller 10 screw 13 vent part

Claims (2)

[Claims] 1. A screw 10 is driven to melt and knead resin while feeding the resin forward along a groove of the screw, and water generated from the resin in the vent portion 13
When the volatile matter and the like are sucked and exhausted by the vacuum pump 4, and when the torque value of the screw 10 is less than or equal to a predetermined value,
A deaeration method for a powder molding machine, comprising reducing the suction force of the vacuum pump 4. 2. A cylinder 1 and a screw 10 provided in the cylinder, wherein the resin is melted and kneaded in the process of being forwardly fed along the groove of the screw 10, and is vented from the resin by a vent device. A vent device for an injection molding machine, wherein generated water, volatile matter, and the like are sucked and exhausted, and the vent device includes a vent hole 2 provided in the cylinder 1 and a vent hole. A vacuum pump 4 which is connected and forcibly sucks water, volatile matter, etc. generated from the resin, control means 5 for controlling the suction force of the vacuum pump, and torque detection means for detecting the torque value of the screw 10. When the torque value detected by the torque detection means is lower than a predetermined value, the control means 5 reduces the degree of vacuum acting on the vent portion 13 of the vacuum pump 4. Control Powder molding vent apparatus, characterized by.