JP2000280239A - Vent-up preventing device of plastic molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vent-up preventing device making it possible to always monitor the interior of a vent part to prevent the clogging of the vent part and performing vent cleaning work without stopping operation. SOLUTION: In the vent-up preventing device of a plastic molding machine wherein a monitor camera 1 having an object lens 5 for observing the state of plastic 13 in a vent portion 17 is provided to the vent portion 17 and the object lens 5 is housed in a protective pipe 7 and a heating jacket 9 being a heating means for heating the protective pipe 7 is provided, the inner space part 6 of the protective pipe 7 is pref. purged by inert gas such as nitrogen gas or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vent-up preventing device for a plastic molding machine.

[0002]

2. Description of the Related Art A vented molding machine is used for granulating plastics and for producing molded articles such as plastic sheets. The vented molding machine includes a raw material feeder for supplying a plastic raw material into a heating cylinder of the molding machine, a screw for extruding the plastic supplied from the feeder forward and plasticizing the plastic, and a molding machine. And a vent portion provided at a part of the heating cylinder for removing volatile components in the plastic by decompression. When molding plastic using a vented molding machine, components such as air, moisture, and residual monomers are removed from the plastic under reduced pressure at the vent, so high-quality pellets and molded products with a small amount of residual bubbles and the like can be obtained. can get.

When plastics are granulated by using a molding machine with a vent, for example, an extruder with a vent, the level of the plastic in the vent changes and sometimes rises (vents up), and the plastic is exhausted from the vent. There is a problem of clogging the tube. In order to prevent this, a method of periodically inspecting the vent and visually inspecting the vent, a method of detecting the temperature of the vent to prevent venting, and a method of detecting the level of plastic in the vent are performed. Have been done. However, in the case of these methods, the detection is delayed because additives such as a lubricant and an antioxidant added to the plastic evaporate at the vent portion, and the evaporated components such as the additive solidify at the vent portion. As a result, the operation of the extruder had to be stopped and the vent part had to be cleaned.

[0004]

If the occurrence of vent-up can be always directly observed in the monitoring room of the extruder, the operation of the molding machine can be performed by performing treatment in the pattern immediately before the occurrence or in such a condition that it can be recovered. Stopping cleaning of the vent can be avoided. For this reason, it is effective to install a camera at the vent, but conventionally, the vapor of the additive solidifies at the vent, causing the lens to be fogged by a normal CD camera and obstructing the visual field. It could not be used because the inside of the vent could not be observed immediately.

[0005] The present invention provides a plastic which can prevent the vent from being clogged by observing the inside of the vent at all times, eliminates the vent cleaning work when the operation is stopped, and obtains a high quality molded product. An object of the present invention is to provide a vent-up prevention device for a molding machine.

[0006]

SUMMARY OF THE INVENTION A vent-up prevention device of a plastic molding machine according to the present invention (hereinafter referred to as a "vent-up prevention device") is a device for venting a monitoring camera having an objective lens for observing the state of plastic in a vent portion. A vent-up prevention device provided in a portion, wherein the objective lens is housed in a protection tube, and a heating means for heating the protection tube is provided. In the vent-up prevention device, it is preferable that control means is provided for changing the plastic extrusion amount before the plastic closes the vent portion based on a signal from the monitoring camera. In addition, the vent-up prevention device of the present invention has a surveillance camera having an objective lens for observing the state of plastic in a vent portion of a plastic molding machine, and corresponds to the level of plastic in the vent portion from an electric signal from the surveillance camera. This is a vent-up prevention device having means for obtaining the number of pixels to be processed and means for converting the number of pixels into a plastic level. In the vent-up prevention device, based on the converted plastic level, it is preferable to provide a control means for changing the amount of plastic extruded before the plastic closes the vent portion,
It is preferable that the objective lens be accommodated in the protective tube and provided with heating means for heating the protective tube. In the vent-up prevention device, it is preferable that the inside of the protection tube is purged with an inert gas.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram for explaining an example of a vent-up prevention device, and is a diagram showing a cross section of a vent portion. The case where the molding machine shown in FIG. 1 is an extruder will be described below as an example. The vent-up prevention device shown in FIG. 1 is an objective lens 5 for observing the state of the plastic 13 in the vent 17 of the plastic molding machine.
The objective camera 5 is located in the vent 17, and the objective 5 is housed at a predetermined distance in the protective tube 7. A heating jacket 9 serving as a heating means for heating the tube 7 is provided outside the protective tube 7 to prevent evaporation components in the plastic 13 from being deposited on the surface of the objective lens 5 and the surface of the protective tube 7. This is a vent-up prevention device in which the internal space 6 of the protection tube 7 is purged by an inert gas.

The vent-up prevention device shown in FIG. 1 displays an image obtained by the surveillance camera 1 as an image, takes in the image of the image receiver 21, processes the image, and outputs a signal. An image processor 31 and a control means (drive controller 35) for taking in a signal output by the image processor 31 and controlling the rotation speed of the drive motor 16 to change the extrusion amount of the plastic 13. The drive controller 35 is capable of controlling the number of rotations of the drive motor 16 by outputting a signal with a digital signal output from the image processor 31 and is, for example, a distributed control system (DCS). Control.

Further, the vent-up prevention device shown in FIG. 1 issues an alarm based on an analog signal output by the image processor 31 before the plastic 13 closes the vent portion 17. In the example shown in FIG. 1, the surveillance camera 1 is attached to a removable vent cover 18.

According to the vent-up prevention device, the inside of the vent 17 can be constantly monitored by the monitoring camera 1 and the clear image obtained by the objective lens 5 is processed so that the plastic 13 It is possible to prevent the vent portion 17 from being blocked by issuing an alarm before the vent portion 17 is blocked and changing the throughput of the extruder itself.

The surveillance camera 1 includes an objective lens 5 for forming an image for observing the level of the plastic 13 in the vent portion 17, a camera body 3 for converting an image obtained by the objective lens 5 into an electric signal. It has. Objective lens 5
Is mounted in the distal end of a lens barrel 5 a forming the distal end of the monitoring camera 1, and a part thereof is exposed in the space 6. The camera lens 5 is located inside the heating cylinder 11 of the extruder. The monitoring camera 1 includes a TV camera. The camera body 3 is located above the vent cover 18 in order to protect it from the heat from the heating cylinder 11.

As shown in FIG. 1, the objective lens 5 is accommodated in a protective tube 7 at a predetermined interval (preferably, approximately 2 to 10 mm). An opening 8 is provided in the lower part of the protection tube 7.
The inside of the vent 17 is monitored through the opening 8. The protection tube 7 is forcibly heated by a heating jacket 9 located outside the protection tube 7. Here, forcibly heating means that the protection tube 7 is heated by supplying heat from the outside of the heating tube 11 instead of the heat due to the heat transfer from the heating tube 11 or the like. Steam or a heat medium is used to heat the protection tube 7. As the heating jacket 9, as shown in FIG. 2, a coil-shaped heating jacket 9 in which steam or the like passes through the inside and is wound on the protective tube 7 is preferable.
The steam that has passed through the heating jacket 9 may flow out of the heating cylinder 11 and be recycled. The forcible heating of the protection tube 7 is for securing a visual field of the objective lens 5 by preventing volatile components such as additives from depositing inside and outside the objective lens 5 and the protection tube 7. The heating temperature of the protection tube 7 is, for example, about 12
0-250 ° C.

An inert gas (preferably, nitrogen) is introduced into the inside of the protective tube 7 from the end thereof, and the space 6 between the objective lens 5 and the protective tube 7 is purged with the inert gas to remove the objective gas. High temperature deterioration of the lens 5 is prevented. The inert gas (inert gas) prevents the temperature of the objective lens 5 from rising too high, thereby preventing the objective lens 5 from deteriorating at high temperatures. The inert gas introduced into the space 6 in the protection tube 7 flows out into the vent 17 through the opening 8 formed at the tip of the protection tube 7 while purging the space 6 and is exhausted together with the volatile components. The gas is exhausted from the pipe 19. When the inert gas is passed from the inside of the protection tube 7 to the inside of the vent portion 17 as described above, the evaporated components such as additives are unlikely to enter the inside of the objective lens 5 and the inside of the protection tube 7. Evaporation components are prevented from being deposited inside the objective lens 5 and the protection tube 7. As a result, the objective lens 5
, A clear image is obtained, and as a result, a clear image is obtained on the image receiver 21. The diameter of the opening 8 at the distal end of the protective tube 7 is preferably about 5 to 20 mm. The flow rate of an inert gas such as nitrogen gas is, for example, about 0.5 to ⁵ Nm ³ /
hr.

The electric signal obtained by the surveillance camera 1 is imaged by the image receiver 21. Of the images monitored by the image receiver 21 (for example, a TV image receiver), a portion related to vent-up may be trimmed, converted into an electric signal by a TV camera, and then subjected to image processing to obtain quantitative data. FIG. 3 shows an example of a method for obtaining quantitative data from an image of the image receiver 21. An image processor 31 takes a picture on the image receiver 21 and converts it into an electric signal.
The pixel based on the electric signal obtained by the camera 32 is set to 2 according to the level of the plastic 13 in the vent 17.
This is an example comprising a TV image processing unit 33 for performing a binarization process and an arithmetic unit (hereinafter, referred to as a PLC) 34 for converting the level of the plastic 13 based on the binarized pixels.

FIGS. 4 and 5 are diagrams for explaining an example of the image processing method. In an example of the image processing method, an electric signal obtained by the TV camera 32 is digitized using the CV image processing device 33, binarized, and integrated as shown in FIGS. 4B and 4C. This is a method to obtain the area. For example, FIG.
As shown in (a), a scale 33 indicated by a white ellipse
a is caused by the vent-up phenomenon and scale 3
The area of 3a is set to increase as the level of the plastic 13 in the vent 17 increases (that is, when the amount of resin in the vent 17 increases). The hatched portions (actually black) shown in FIG. 4A represent other than the resin (for example, the metal of the screw 14). And FIG.
Pixels on the scale 33a shown in (a) are subjected to binarization processing to obtain white areas as shown in FIGS. 4B and 4C at predetermined intervals. Therefore, FIG.
4B shows a state in which the level of the plastic 13 in the vent portion 17 is high (that is, a state close to vent up), and FIG. 4C shows a state in which the level is low (that is, the risk of vent up). State without). And FIG.
4B, the number of pixels in the white portion shown in FIG. 4C (the number of pixels corresponds to the level of the plastic 13 in the vent 17) is obtained.

The pixels binarized and displayed by the CV image processing device 33 are converted into the level of the plastic 13 by the PLC 34 and subjected to an averaging process. For this,
Using the PLC 34, as shown in FIG. 5A, a calibration curve indicating the relationship between the number of pixels and the level is obtained in advance. Then, based on this calibration curve, the number of pixels in the white portion as shown in FIGS. 4B and 4C is converted into the level of the plastic 13 in the vent 17 and this is displayed over time. A graph as shown in FIG. 5B is obtained. The graph shown in FIG. 5B is inconvenient due to pulsation.
Therefore, the levels shown in FIG.
It is displayed as shown in (c). Note that the level of the plastic 13 in the vent 17 changes periodically with the rotation of the screw 14.

According to such an image processing method, the level of the plastic 13 is extracted as an analog signal. On a surface of a CRT or the like of an image display (not shown), FIG.
By displaying a graph as shown in FIG.
You can know the status of the plastic 13 inside. still,
In FIG. 5, the horizontal axis indicates the extrusion time, and the vertical axis indicates the level of the plastic 13 in the vent portion 17. From the graph shown in FIG.
Level progress can be grasped. Then, based on this level, an alarm (ANN) is issued, and the extrusion amount can be reduced.

As shown in FIGS. 1 and 3, an alarm can be issued by the analog signal to prevent vent-up and the like. In addition, it is also possible to obtain the maximum throughput without venting by maintaining the signal from the analog at an optimum value, determining the upper limit of the level (height) of the plastic 13 in the vent part 17, and controlling the throughput. it can.

In the example shown in FIG. 1, the monitoring camera 1 obtains a vent-up prevention device that changes the amount of plastic 13 to be pushed out before the plastic 13 closes the vent portion 17 based on a signal from the monitoring camera 1. A signal is input to the image receiver 21, and the drive controller 3 is input via the image processor 31.
5 is input. However, the image receiver 21 and the image processor 3
Signal from the surveillance camera 1 without passing through the drive controller 3
5 is directly input to the drive motor 1 by the drive controller 35.
The extrusion amount of the plastic 13 may be changed by controlling the number of rotations of 6.

Next, an example of manufacturing an extruded product using the vent-up device of the present invention will be described with reference to FIG. A mixture of a plastic raw material and an additive (for example, a lubricant or an antioxidant) is supplied to a heating cylinder 11 by a raw material feeder (not shown).
The plastic 13 supplied from the feeder is melted by a screw 14 rotating in the heating cylinder 11, extruded forward and reaches a vent 17. Then, the molten plastic 13 that has passed through the vent portion 17 is extruded from the die to the outside of the extruder, and is thereafter formed into granules or sheets. During this extrusion, the inside of the vent 17 is evacuated by a vacuum pump through an exhaust pipe 19. Due to this reduced pressure, the volatile components in the plastic 13 reaching the vent 17 are exhausted to the outside of the extruder through the exhaust pipe 19.

Further, nitrogen gas is caused to flow into the space 6 in the protective tube 7 of the surveillance camera 1, the nitrogen gas having passed through the space 6 is allowed to flow out of the opening 8 into the vent 17, and
At the same time, the exhaust gas is exhausted from the heater 9 and the steam is passed through the heating jacket 9 to heat the objective lens 5 and the protective tube 7 to a predetermined temperature.

In the above extrusion molding, the situation of the plastic 13 in the vent portion 17 is converted into a signal by the monitoring camera 1, a signal from the monitoring camera 1 is converted into an image by the image receiving device 21, and the image is processed by the image processor 31. Then, the state of the plastic 13 in the vent portion 17 is monitored by displaying a graph as shown in FIG. 5C on the image display.

As described above, the vent 17 is constantly monitored by the monitoring camera 1, and an image processing is performed to give an alarm before the plastic 13 accumulates in the vent 17 and closes. The blockage of the vent 17 can be prevented by changing the extrusion amount, the amount of the additive, and the like. When a vent-up phenomenon in the vent section 17 is detected based on the alarm, the processing amount of the plastic 13 is reduced by a predetermined amount, for example, about 2 to 20% as an emergency measure, so that the vent-up phenomenon can be prevented from becoming severe. Then, when the condition of the vent is stabilized, the processing amount is gradually returned to the original.

[0024]

As described above, the main effects of the vent-up prevention device of the present invention are as follows. (1) Visual judgment can be made with a clear TV image, and abnormality of the molding machine can be detected. By confirming the data and the situation of the image analysis, the advance situation of the vent-up can be grasped by a pattern, and the vent-up can be prevented by taking measures such as reducing the processing amount. In the actual example, venting up about five times a month was eliminated, and vent cleaning work was stopped twice a month after the operation of the extruder was stopped, leading to an improvement in the operation rate and a reduction in repair costs. (2) Use of the vent-up prevention device of the present invention prevents a situation in which the vent portion is blocked with resin and gas cannot be released. Therefore, it is possible to efficiently and stably produce a molded article having no air bubbles and having no odor component.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of a vent-up prevention device of the present invention.

FIG. 2 is a perspective view showing an example of a heating means for heating a protective tube used in the vent-up prevention device of the present invention.

FIG. 3 is a system diagram showing an example of an image processor used in the vent-up prevention device of the present invention.

4 (a) is a diagram showing an example of a method of indicating a level of a plastic in the vent-up prevention device of the present invention, and FIGS. 4 (b) and 4 (c) are diagrams of FIG. 4 (a). FIG. 6 is a diagram showing an example in which pixels in a level display portion shown in FIG. 4 are binarized and the level of plastic in a vent portion is displayed as an area.

FIG. 5 is a diagram showing an example of displaying the level of plastic in a vent portion in a graph, and FIG. 5 (a) shows a calibration curve showing the relationship between the number of pixels and the level; 5
(C) is an example of a graph in which the number of pixels is converted into the level of plastic in the vent, and the converted level is displayed together with the extrusion time.

[Explanation of symbols]

1. surveillance camera, 3. camera body, 5. objective lens, 5a lens barrel, 6. space part, 7. protection tube,
8. Opening, 9 Heating jacket, 11 Heating cylinder,
13 ・ ・ Plastic 、 14 ・ ・ Screw 、 16 ・ ・
Drive motor, 17 vent section, 18 vent cover, 19 exhaust pipe, 21 image receiver, 31 image processor, 32 TV camera, 33 TV image processing device, 33a · Scale, 34 ··· Arithmetic unit (PL
C), 35 .. Drive controller (DCS)

Claims (6)

[Claims] 1. A monitoring camera having an objective lens for observing a state of plastic in a vent portion is provided in a vent portion, the objective lens is housed in a protective tube, and heating means for heating the protective tube is provided. Vent-up prevention device for plastic molding machines. 2. The vent-up prevention device for a plastic molding machine according to claim 1, further comprising control means for changing the amount of plastic extruded before the plastic closes the vent portion based on a signal from the monitoring camera. 3. A surveillance camera having an objective lens for observing the state of plastic in a vent of a plastic molding machine, and means for obtaining the number of pixels corresponding to the level of plastic in the vent from an electric signal from the surveillance camera. And a means for converting the number of pixels into a plastic level. 4. A vent-up preventing device for a plastic molding machine according to claim 3, further comprising control means for changing the amount of the plastic extruded before the plastic closes the vent portion based on the converted plastic level. . 5. The vent-up preventing device for a plastic molding machine according to claim 3, wherein the objective lens is housed in a protective tube, and heating means for heating the protective tube is provided. 6. The vent-up preventing device for a plastic molding machine according to claim 1, wherein the inside of the protective tube is purged with an inert gas.