JPH03203B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polymer kneading and granulating device used in the production of plastic pellets, etc., and more specifically, the amount of kneaded polymer supplied from a kneader (hereinafter referred to as a mixer) to a granulator, and the amount of kneaded polymer supplied to a granulator by a granulator. The present invention relates to a polymer kneading and granulating device in which the amount to be treated is always maintained in an equilibrium state. As is well known, plastic pellets and the like are manufactured by a polymer kneading and granulating apparatus consisting of a series of devices: feeder → mixer → granulator (consisting of an extruder, die, etc.). In this case, there is no problem if the amount supplied from the mixer to the extruder and the amount extruded from the extruder are balanced, but there may be slight differences in the throughput of these devices or for some reason. If this equilibrium is disrupted, the operation of the entire device will be seriously affected. For example, when the extruder capacity is relatively reduced,
The amount of kneaded polymer in the chute connecting the mixer and extruder gradually increases, causing blockage in the chute. In this case, the kneaded polymer discharged from the mixer is usually molten, but it has a high viscosity and is difficult to handle, and when it solidifies, it takes a lot of effort and time to remove it. Conversely, when the throughput of the extruder becomes relatively excessive, the level of kneaded polymer in the chute gradually decreases until the extruder runs dry. At this time, there is an inconvenience that metal contact between the screw of the extruder and the cylinder barrel occurs. In order to avoid these disadvantages, the following methods have been conventionally used. (1) A device is installed in the chute between the mixer and the extruder to detect the level (point) of the kneaded polymer, and an alarm is issued when the level deviates from a predetermined range. (2) A person constantly monitors and manually adjusts the level of the kneaded polymer in the chute. However, according to the first method, since the level of the kneaded polymer is detected at points, there is a drawback that the level cannot be detected properly. That is,
The kneaded polymer in the chute has various properties depending on the product brand, from molten to block-like. Non-molten polymer moves up and down as the screw of the extruder rotates. Since the amount decreases, it was not possible to capture the true amount simply by detecting the upper limit level. Also, for example,
When detecting the level with a phototube, stable measurement is difficult due to the influence of steam in the chute or dirt on the detection window. Furthermore, if it is desired to detect the level in a line rather than a point, a large number of phototubes must be used, which is impractical. On the other hand, in the second method, the operator determines the level by directly observing the state of the kneaded polymer in the chute or by watching the image displayed on a monitor TV by a TV camera, and then transfers the kneaded polymer from the feeder to the mixer. Adjust the amount of raw material supplied. This monitoring
Not only is the adjustment work itself complicated, but because the operator is often also responsible for operating other equipment, there are many cases where the adjustment operation is delayed and the operation has to be stopped, placing a great burden on the operator. It will always be forced. In view of the above circumstances, the present invention provides a polymer kneading and granulating device that can always maintain the amount of kneaded polymer in a chute at an appropriate value. ) to capture an image of the kneaded polymer in the chute, calculate the ratio of the pixels showing the kneaded polymer to the total number of pixels in the captured image, and then shoot the kneaded polymer from the feeder so that this ratio is kept within a predetermined range. It is characterized by automatically controlling the amount of raw materials supplied to the mixer. Embodiments of the present invention will be described below based on the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. In the figure, 1 is a raw material hopper, and the raw material hopper 1 is fed to a mixer 3 by a feeder 2.
The raw materials conveyed and supplied are kneaded in a mixer 3, turned into a kneaded polymer, temporarily retained in a chute 4, and sequentially extruded to the outside by an extruder 5.
Here, the kneaded polymer in the chute 4 is sent out while fluctuating up and down as the screw of the extruder 5 rotates. This scene is shown on the ITV installed diagonally above the outside of chute 4's observation window.
6, and the video signal Sa is sent to the central monitoring room 8.
The image sample unit 11 is supplied to a monitor 9 within the camera and an image sample unit 11 within a shoot level control device 10. In this way, the movement and level of the kneaded polymer are monitored by the monitor 9.
The image is displayed at all times, and is captured into the image sample unit 11 at regular intervals (for example, 0.5 to 1.0 seconds). That is, the image sample unit 11
In accordance with the command of the CPU 12, the video signal Sa for one screen consisting of 256 horizontal scanning lines is sampled, one screen is divided into 256 x 256 pixels, and each pixel is divided into two parts depending on the brightness of black and white. The pixel data is converted to a 16 (4 bit) image level and written into the RAM in the unit 11, forming pixel data of 256 x 256 x 4 bits for one screen. Next, the CPU 12 reads out one pixel every 13 pixels from the pixel data, and
20×20 pixel data Sb is written into the memory 14 via the data bus 13. In this way, one screen
The pixel data Sb is compressed to 20 x 20 x 4 bits, which allows for a significant reduction in processing time while maintaining sufficient accuracy. Also, CPU
12 detects the level La of the kneaded polymer in the chute 4 based on the pixel data Sb,
The rotation speed setting value Ns of the feeder 2 is calculated by comparing it with the level setting value Ls. Then, the rotation speed Na of the feeder 2 is subtracted from this rotation speed setting value Na to find the deviation, and depending on the positive/negative of the deviation, the speed increase command Ca/
A deceleration command Cb is supplied to the feeder drive device 17 via the I/O interface 15 and the sequence unit 16. Here, the sequence unit 16 controls the switching between automatic/manual operation, and during automatic operation, it uses the speed increase command Ca/deceleration command Cb, and when it uses manual operation, it uses push button switches 20a/20b, which will be described later. The feeder drive device 17 is controlled to increase or decrease the rotation speed of the feeder 2. Further, the feeder driving device 17 drives the feeder 2 by the output of the sequence unit 16.
At the same time, a signal corresponding to the rotation speed Na of the feeder 2 is supplied to the first input terminal of the indicator 18 and the I/O interface 15. The indicator 18 is installed in the central monitoring room 8 and displays the rotation speed Na of the feeder 2 and the level La of the kneaded polymer, and the signal corresponding to the level La is
The signal is supplied from the CPU 12 to the second input terminal of the indicator 18 via the I/O interface 15. Further, below the indicator 18, there is a push button switch 1 for switching the level control of the kneaded polymer between automatic and manual.
9 and push button switches 20a/20b for manually increasing/decreasing the rotational speed of the feeder 2, the outputs of which are supplied to the sequence unit 16. When manual operation is selected by operating the pushbutton switch 19, this is transmitted to the CPU 12 via the sequence unit 16, and automatic operation is stopped. Further, an alarm device 21 is provided near the indicator 18, and is configured to issue an alarm when the level La of the kneaded polymer deviates from a preset range. Next, FIG. 2 is a functional block diagram for explaining each operation of the CPU 12 mentioned above. As is clear from this figure, the CPU 12 first determines the rotation speed setting value of the feeder 2 based on the level La of the kneaded polymer.
Cascade control is performed in which the rotation speed of the feeder 2 is controlled by calculating Ns.
That is, the CPU 12 uses the level detection means 30 to determine the level of the kneaded polymer from the pixel data Sb.
After calculating La and subtracting it from the level setting value Ls to obtain a deviation, the level adjusting means 31 calculates the rotation speed setting value Ns of the feeder 2 from the deviation. Then, from the rotation speed setting value Ns, the rotation speed Na
The feeder rotation speed setting means 32 calculates an acceleration command Ca and a deceleration command Cb from the deviation, and supplies these to the feeder driving device 17 to control the rotation speed of the feeder 2. . In addition,
33 in FIG. 2 is a level process (device to be controlled) consisting of components 1 to 6. The operation of each block 30 to 32 will be explained in detail below. (1) Level detection means 30 First, the pixel level when the level La of the kneaded polymer is zero, that is, when the chute 4 is empty, is
Determine each pixel from the pixel data Sb and use Zij
(i, j=1, 2...20) is written into the memory 14. This means that even if shoot 4 is empty,
This is because there are variations in each pixel level due to dirt on the viewing window, etc., and by performing zero correction, it is possible to reliably determine the presence or absence of kneaded polymer. Next, when the kneaded polymer exists in the chute 4, depending on the pixel level of the pixel data Sb,
Calculate the level La of the kneaded polymer. in this case,
In the area occupied by the kneaded polymer, the spot illumination directed to the chute 4 is reflected by the surface of the kneaded polymer, so that the area appears whiter and the pixel level becomes higher.
Furthermore, areas without kneaded polymer appear dark and have low pixel levels. Therefore, each pixel level is defined as lij(i,
j = 1, 2...20), and if the zero level of each pixel is Zij, then compare the difference between the two, lij-Zij, with a predetermined threshold level a, and if liJ-Zij>a, it is determined that the kneaded polymer is present. When lij−Zij<a, it is determined that no kneaded polymer is present. By the way, the shape of the part (injection part) where the kneaded polymer falls from the mixer 3 to the chute 4 is as follows.
Depending on whether the kneaded polymer is molten or block,
This results in a molten column-shaped injection section 35 (FIG. 3) or a block-shaped injection section 36 (FIG. 4). Since these injection parts 35 and 36 do not fall within the level La of the kneaded polymer, they are masked and excluded from the level detection process. That is, in the case of the molten columnar shape shown in FIG. 3, the width of the injection part 35 is detected from the top pixel levels _l11 to _l120 , and masking is applied in the vertical direction using this width (shaded area in the figure), Find the percentage of pixels that project the kneaded polymer among all pixels excluding this part,
This is smoothed and the level of the kneaded polymer is La.
shall be. In addition, in the case of the block shape shown in Fig. 4, a search is performed vertically upward from each pixel level l ₂₀ j at the bottom, and all pixels after the pixel for which lij−Zij is smaller than the reference level a are determined to have no kneaded polymer. , Hereafter, the level La of the kneaded polymer is calculated by the same process as above. The level La obtained in this way is displayed on the indicator 18 via the I/O interface 15 (see Fig. 1), and the level setting value
It is subtracted from Ls, and the deviation value is supplied to the level adjustment means 31. Note that the masking process described above is not essential, and essentially, the level La can be determined by determining the ratio of pixels showing the kneaded polymer to all pixels. However, by masking processing, it is possible to obtain values close to the level obtained by visual inspection. (2) Level Adjustment Means 31 The control calculation of the level adjustment means 31 is a normal sample value PID control method having a dead zone and nonlinear gain characteristics. In other words, the level set value Ls is set every predetermined control calculation cycle.
Absolute value of the difference between and the level La of the kneaded polymer | Ls
When −La| is within the dead zone, the output of the level adjustment means 31, that is, the rotation speed set value Ns, does not increase or decrease, and when |Ls−La| deviates from the dead zone,
The amount of change ΔNs in the rotation speed setting value Ns is determined by the first derivative of the level La, the difference between the level setting value Ls and the level La, and the second derivative of the level La. In this way, the rotation speed setting value Ns that makes |Ls−La| zero is calculated and output. (3) Feeder rotation speed setting means 32 The rotation speed of the feeder 2 is set in the same period as in (2) above.
A speed increase command Ca and a deceleration command Cb consisting of a pulse train with a period of about 1 second and a duty ratio of 20% are output so that Na matches the rotation speed setting value Ns. In this case, when |Ns-Na| is within the dead zone, increase/decrease commands Ca and Cd are not issued. Also, if the rotation speed setting value Ns is changed significantly, it will cause level hunting, so the range of change, that is,
Upper and lower limits are set for the number of pulses for increase/decrease commands Ca and Cb. Next, the operation of this embodiment will be explained. First, adjust the level La of the kneaded polymer to 30% ± 5% by manual operation.
After setting the time within the range, push the pushbutton switch 19 (Fig. 1). As a result, the "autonomous operation" display lamp built into the switch 19 lights up.
It becomes automatic driving. When automatic operation is started, the CPU 12 refreshes the pixel data stored in the RAM in the image sample unit 11 at a predetermined period (0.5 to 1.0 seconds). Then, the CPU 12 extracts pixel data Sb consisting of 20×20 pixels from the RAM, detects the level La of the kneaded polymer in the chute 4 by the level detecting means 30, and then detects the command level La.
The level adjustment means 31 calculates the rotation speed setting value Ns based on the deviation from the rotation speed. Furthermore, the deviation between this rotational speed setting value Ns and the rotational speed Na of the feeder 2 is supplied to the feeder rotational speed setting means 32, and here, the speed increase command Ca of the feeder 2 is sent so that the level La is maintained at 30%. , calculates and outputs a deceleration command Cb.
In this way, the rotation speed Na of the feeder 2 is set to the level La
is constantly controlled to keep it at 30%. Then, the level La of the kneaded polymer and the rotation speed Na are displayed on the indicator 18. On the other hand, if the level deviation |Ls−La| deviates from 30%±20%, the CPU 12 drives the alarm device 21 to output an alarm to notify the operator, and also stops automatic operation and switches to manual operation. I do. This allows the operator to return the level of the kneaded polymer and the rotation speed of the feeder 2 to the predetermined range.
Perform manual operation. The above embodiment has been described in the case where the feeder 2 is of a continuous type, but if the feeder is of a batch type, as shown in FIG. The raw material supply command Cd (on/off signal) may be supplied to the feeder drive device 17. As explained above, the present invention images the kneaded polymer in a chute using an ITV, calculates the ratio of pixels showing the kneaded polymer to the total pixels in the captured image, and determines whether this ratio is within a predetermined range. The amount of raw material supplied from the feeder to the mixer is automatically controlled so that the amount of kneaded polymer in the chute can be maintained at an appropriate amount.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a functional block diagram for explaining each action of the CPU 12, and FIGS. 3 and 4 are diagrams for explaining the masking method. , FIG. 5 is a functional block diagram of a modification of the above embodiment. 2...Feeder, 3...Mixer, 4...Chute, 5
...Extruder, 6...ITV (industrial television camera), 1
1... Image sample unit, 12... CPU (control means), 14... Memory, Sa... Video signal (output of ITV), Sb... Pixel data.

Claims (1)

[Claims] 1. In a polymer kneading and granulation apparatus having a mixer for kneading polymer supplied from a feeder and a chute for guiding the kneaded polymer kneaded by the mixer to an extruder, an industrial television for imaging the kneaded polymer in the chute. a camera, an image sample unit that samples the output of the industrial television camera and outputs pixel data, a memory that stores the pixel data, and a zero level of each pixel data when the kneaded polymer is not in the chute. It is characterized by comprising a control means for storing the level in the memory, determining a proportion of pixels in which kneaded polymer is projected among the pixel data, and controlling the supply amount of the feeder based on this proportion. Polymer kneading and granulation equipment.