JPH1024484A - Method and device for measuring size of bank in extrusion of thermoplastic resin sheet, method and device for controlling film thickness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure thickness of a bank formed in the just upper flow of a roll in the case of extrusion of a thermoplastic resin sheet. SOLUTION: In the device for measuring the size of a bank provided in the production device of a thermoplastic resin sheet, the bank 21 is photographed by a CCD camera 32 equipped with an endoscope 31. Lightness value of the picture element in the image of the photographed bank 21 is continuously measured in the longitudinal direction in a prescribed position in the axial direction of a roll. A function for the position in the longitudinal direction of the lightness value, namely, a lightness function is calculated and two positions in the longitudinal direction, in which the lightness value becomes minimum value in the lightness function, are calculated and thereafter distance between both positions is calculated. Thickness of the bank is calculated according to the distance. Even when lighting of the bank 21 is not uniform, thickness of the bank is accurately measured by this measuring method for the thickness of the bank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a bank size at the time of extrusion molding of a thermoplastic resin sheet, and a method for measuring the thickness of a thermoplastic resin sheet using the measuring method or the measuring apparatus. A method and apparatus for control.

[0002]

2. Description of the Related Art Generally, in an apparatus for manufacturing a thermoplastic resin sheet, after the thermoplastic resin heated and melted by an extruder is extruded from a die (for example, a T-die), the axes are parallel to each other. Through a gap (roll gap) between a pair of (two) rolls (cooling rolls) arranged in close proximity to each other, whereby the thermoplastic resin is formed into a sheet shape and a thermoplastic resin sheet (hereinafter, referred to as This is simply referred to as “resin sheet”). The thermoplastic resin in the present specification includes not only general resins such as plastics such as polyethylene and rubber but also photosensitive resins used for flexographic printing plates and the like. Here, the thermoplastic resin has appropriate plasticity when extruded from the die, but is cooled and solidified by a roll when passing through a roll gap. In such a resin sheet, the film thickness is required to be as uniform as possible. However, the film thickness depends on the operating condition or operating condition of the die, for example, the die lip opening or the die choke bar insertion length. And the like, or by preferably adjusting the operating condition or operating condition of the roll, such as the roll rotation speed or the roll gap length.

When manufacturing such a resin sheet, a thermoplastic resin swells in the thickness direction of the resin sheet immediately upstream of the roll to form a bank. The size of the bank, for example, the length of the bank in the sheet thickness direction (hereinafter referred to as “bank thickness” for convenience) correlates with the thickness of the resin sheet (product). That is, as viewed in the roll axis direction, the greater the bank thickness at a certain position, the greater the thickness of the resin sheet at that position, while the smaller the bank thickness, the smaller the thickness of the resin sheet.
Therefore, the operating condition or operating condition of the die or roll (eg, die lip opening, choke bar insertion length, roll rotation speed, roll gap length, etc.) so that the bank thickness is constant at all positions in the roll axis direction. By adjusting the thickness, the thickness of the resin sheet can be made uniform. Thus, in recent years, a resin sheet manufacturing technique that controls the thickness of the resin sheet based on the bank size has been proposed (for example,
See JP-A-1-160631).

When the thickness of the resin sheet is controlled based on the bank size as described above, the bank size must be accurately measured. In recent years, a method of measuring the bank size using an image processing technique has been used. Proposals have been made (for example, Japanese Patent Application Laid-Open No. 60-217120,
-186708). In the conventional method of measuring the bank size using the image processing technique, the bank size is usually measured in the following procedure.

That is, first, a bank is photographed using a camera such as a CCD camera. Then, a binarization process is performed on the photographed image to make a portion corresponding to the bank in the image stand out. Specifically, a portion in the image where the brightness exceeds a predetermined threshold is white, and a portion below the threshold is black. In this case, since the brightness of the portion corresponding to the bank in the image is different from that of the other portions, the difference in brightness causes the portion corresponding to the bank and the other portions to have colors (white or black) opposite to each other. Become. For example, if the part corresponding to the bank is brighter than the other parts, the part corresponding to the bank will be white and the other parts will be black. If the part corresponding to the bank is darker than the other parts, the black and white are reversed. Then, the bank size is calculated by calculating the area of the color (white or black) portion corresponding to the bank in the binarized image or the length of the portion in a predetermined direction.

[0006]

When the bank size is measured by the binarization process as described above, it is necessary to equalize the illumination of the bank, and the brightness of the portion corresponding to the bank and the brightness of the other portion are required. It is necessary to illuminate so that the difference is clear. That is, since the portion corresponding to the bank and the other portion are distinguished by a single threshold value, if the brightness difference between the two is small and the illumination of the bank is non-uniform, both of them can be accurately determined. This is because they cannot be distinguished. For this reason, in the conventional method of measuring the bank size using the image processing technique, the structure of an illumination device (light source) for illuminating the bank becomes complicated or large.
In addition, a special screen needs to be provided to make the illumination more uniform.

However, in a thermoplastic resin sheet manufacturing apparatus using a T-die, a bank is usually formed immediately upstream of a roll, while a die is arranged at a position relatively close to the upstream of the roll. . On the upstream side of the roll, the resin sheet material exists over substantially the entire length in the axial direction. Further, it is necessary to move a roll or a die when cleaning the manufacturing apparatus. Therefore, it is difficult to arrange an illuminating device or a screen at an appropriate position near the bank so that the illumination of the bank is equalized. For this reason, the bank is uniformly arranged while clarifying the difference in brightness between the bank and other parts. There is a problem that it is difficult to illuminate the light.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. In extrusion molding of a thermoplastic resin sheet, the size of a bank formed immediately upstream of a roll can be accurately and easily adjusted. An object to be solved is to obtain a means capable of measuring, and further, a means capable of making the thickness of a thermoplastic resin sheet uniform.

[0009]

According to a first aspect of the present invention, which has been made to solve the above-mentioned problems, a thermoplastic resin extruded from a die is arranged close to each other such that respective axes are parallel to each other. The sheet is formed into a sheet by passing through a gap between a pair of rolls.
This is simply a method of measuring the size of a bank of thermoplastic resin formed immediately upstream of a roll when manufacturing a "resin sheet". The brightness value of the pixel of the image of the bank is continuously measured at a predetermined position in the roll axis direction in a vertical direction that is a direction perpendicular to the roll axis direction, and the brightness value is measured with respect to the vertical position. A functional relationship (hereinafter referred to as a “brightness function”) is calculated, and two positions in the vertical direction where the brightness value takes a minimum value (two brightness values are the smallest) in the brightness function are calculated. Calculate the distance between positions, and based on this distance, the bank size (bank thickness)
Is calculated.

According to this method of measuring the bank size, the bank thickness is measured at an arbitrary position in the roll axis direction based on the interval between two vertical positions where the brightness is minimized in the brightness function. Here, the minimum point in the brightness function is not affected by the lighting state of the bank. That is, in the brightness function, two minimum value points can be detected regardless of the illumination state, and the vertical position corresponding to the two minimum points is not affected by the illumination state. Therefore, the bank thickness can be accurately obtained at any position as viewed in the roll axis direction. Thus, by performing such a measurement at a plurality of different positions in the roll axis direction, the bank thickness at each position is accurately measured. Here, even if the illumination condition is different at each of the plurality of positions, the bank thickness at each position is accurately measured. Therefore, even if the illumination of the bank is not uniform, the bank thickness at an arbitrary position is determined. It can be measured accurately.

In a second aspect of the present invention, a thermoplastic resin extruded from a die is passed through a gap between a pair of rolls arranged close to each other so that each axis is parallel to each other. A method for controlling the thickness of a resin sheet when the resin sheet is manufactured by forming the resin sheet into a sheet shape, and is formed immediately upstream of a roll by using the measuring method according to the first aspect. The thickness of the resin sheet is controlled by measuring the size of the bank of the thermoplastic resin and adjusting the operation state of the die and / or the roll based on the measured value of the bank size. Is what you do.

According to this film thickness control method, the first aspect of the present invention
The operating state or operating condition of the die and / or the roll is adjusted based on the bank thickness accurately measured using the measuring method according to the aspect, and the film thickness of the resin sheet is controlled. The thickness of the sheet is made uniform, and the quality of the resin sheet is improved.

[0013] In the film thickness control method according to the second aspect, the film thickness of the resin sheet is measured by a film thickness measuring device, and based on the measured value of the bank size and the measured value of the film thickness measuring device. It is preferable to control the thickness of the resin sheet by adjusting the operating state or operating conditions of the die and / or the roll. By doing so, the accuracy of controlling the thickness of the resin sheet is improved, and the quality of the resin sheet is further improved.

Here, as the film thickness measuring device, it is preferable to use a non-contact type which measures without contacting the resin sheet. Examples of such a non-contact type include a type using air, a type using IR, and a type using β-ray, and a type using air is preferable. A film thickness measuring device using such air is provided with, for example, an air jet nozzle that can be freely displaced with respect to the resin sheet, and jets air from the nozzle toward the resin sheet, and the back of the nozzle. The distance between the nozzle and the resin sheet is kept constant based on the pressure, and the thickness of the resin sheet is measured from the amount of change in the position of the nozzle.

In each of the above-described film thickness control methods, it is preferable that the operating state or operating condition of the die is adjusted by changing the lip opening of the die or the insertion length of the choke bar of the die. Further, it is preferable that the operating state or operating condition of the roll is adjusted by changing the rotation speed of the roll or the gap between the two rolls.

In a third aspect of the present invention, a thermoplastic resin extruded from a die is passed through a gap between a pair of rolls arranged close to each other so that each axis is parallel to each other. This is a device for measuring the size of a bank of thermoplastic resin that is formed immediately upstream of a roll when manufacturing a resin sheet by molding into a resin sheet, and photographing the bank optically connected to an endoscope. A brightness function calculating means for calculating a brightness function by continuously measuring brightness values of pixels of an image of a bank taken by the camera at a predetermined position in the roll axis direction and calculating a brightness function; In the lightness function calculated by the function calculating means, two positions in the vertical direction where the lightness value takes a minimum value (two lightest lightness values) are calculated, and then a distance between the positions is calculated. Calculator When, is characterized in that the bank size calculating means for calculating the size of the bank based on the distance calculated by the position distance calculating means.

According to this bank size measuring device, the bank thickness is measured at an arbitrary position in the roll axis direction based on the interval between two vertical positions where the lightness is minimized in the lightness function. Here, the minimum point in the brightness function is not affected by the lighting state of the bank. That is, in the brightness function, two minimum value points can be detected regardless of the illumination state, and the vertical position corresponding to the two minimum points is not affected by the illumination state. Therefore, the bank thickness can be accurately obtained at any position as viewed in the roll axis direction. Thus, by performing such a measurement at a plurality of different positions in the roll axis direction, the bank thickness at each position is accurately measured. Here, even if the illumination condition is different at each of the plurality of positions, the bank thickness at each position is accurately measured. Therefore, even if the illumination of the bank is not uniform, the bank thickness at an arbitrary position is determined. It can be measured accurately.

In a fourth aspect of the present invention, a thermoplastic resin extruded from a die is passed through a gap between a pair of rolls arranged close to each other so that each axis is parallel to each other. An apparatus for controlling the thickness of the resin sheet when manufacturing the resin sheet by molding into,
A die and / or a roll based on the bank size measuring device according to the third aspect, and a measured value of the size of the bank of the thermoplastic resin formed immediately upstream of the roll measured by the bank size measuring device. And a film thickness control means for controlling the film thickness of the resin sheet by adjusting the operation state of the resin sheet.

According to this film thickness control device, the third aspect of the present invention
The operating state or operating conditions of the die and / or the roll are adjusted based on the bank thickness accurately measured using the bank size measuring device according to the aspect, and the thickness of the resin sheet is controlled. The thickness of the resin sheet is made uniform, and the quality of the resin sheet is improved.

In the film thickness control device according to the fourth aspect, a film thickness measuring device for measuring the film thickness of the resin sheet is provided, and a measured value of the bank size and a measured value of the film thickness measuring device are provided. It is preferable that the thickness of the resin sheet is controlled by adjusting the operating state of the die and / or the roll based on the above. By doing so, the accuracy of controlling the thickness of the resin sheet is improved, and the quality of the resin sheet is further improved.

Here, as the film thickness measuring device, it is preferable to use a non-contact type which measures without contacting the resin sheet. Examples of such a non-contact type include a type using air, a type using IR, and a type using β-ray, and a type using air is preferable. A film thickness measuring device using such air is provided with, for example, an air jet nozzle that can be freely displaced with respect to the resin sheet, and jets air from the nozzle toward the resin sheet, and the back of the nozzle. The distance between the nozzle and the resin sheet is kept constant based on the pressure, and the thickness of the resin sheet is measured from the amount of change in the position of the nozzle.

In each of the above film thickness control devices, the operating state or operating condition of the die is preferably adjusted by changing the lip opening of the die or the insertion length of the choke bar of the die. Further, it is preferable that the operating state or operating condition of the roll is adjusted by changing the rotation speed of the roll or the gap between the two rolls.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. FIG. 1 is a schematic diagram of a thermoplastic resin sheet manufacturing apparatus showing one embodiment of the present invention. First,
The overall structure or function of this thermoplastic resin sheet manufacturing apparatus will be described. As shown in FIG. 1, in a thermoplastic resin sheet manufacturing apparatus M, various materials (hereinafter, referred to as “resin sheet material”) such as thermoplastic resin selected according to a resin sheet to be manufactured are prepared. Is done.

The resin sheet material is heated and melted (softened) in an extruder 5 (see FIG. 2), and then sent to a die 9 (T die) by a gear pump 8. Part), while maintaining appropriate plasticity, X
Extruded in _one direction. Resin sheet material extruded from the die 9 in the X ₁ direction, passes through a pair of rolls 6a of each axis is arranged close to be parallel to each other, the roll gap of the cooling roll 6 consisting 6b in the direction X ₁ It is cooled, solidified, formed into a sheet, and
It becomes 0. Note that reference numeral 21 denotes a bank. The film thickness of the resin sheet 20 is measured by the film thickness measuring device 12. Here, the upper roll 6a rotates in the R ₁ direction, the lower side of the roll 6b is rotated in the R ₂ direction.

The thermoplastic resin sheet manufacturing apparatus M
In the resin sheet 20 is basically is transferred to X ₁ direction, for convenience in the following, the X ₁ direction is referred to as "downstream", "upstream (the direction opposite to the X ₁ direction) X ₂ direction "

Next, the specific structure and function of the die 9 for extruding the resin sheet material will be described. 1 and 3
As shown in FIG. 2, the die 9 is provided with a number of choke bolts 28 for adjusting the flow rate of the resin sheet material flowing in a resin passage (not shown) provided therein. Further, the die 9 is provided with a large number of lip adjustment bolts 22 for adjusting the lip opening, that is, for adjusting the film thickness of the resin sheet 20.

Thus, by changing the insertion length of any of the multiple choke bolts 28 into the resin passage,
The flow rate of the resin sheet material in the portion corresponding to the choke bolt 28 (and thus the thickness of the resin sheet) can be adjusted. Also, by changing the degree of tightening of any of the many lip adjustment bolts 22, the lip opening at the portion corresponding to the lip adjustment bolts 22, that is, the film thickness of the resin sheet 20 can be adjusted.

By the way, as described in the “Prior Art” section, the size of the bank 21, for example, the bank thickness (the length of the bank 21 in the thickness direction of the resin sheet, that is, the length in the vertical direction) of the resin sheet 20 is Since it is correlated with the film thickness, the choke bar insertion length (flow rate of the resin sheet material) and the degree of tightening of the lip adjustment bolt (die) are set so that the bank thickness is constant at all positions in the roll axis direction (resin sheet width direction). Lip opening), the rotation speed of the cooling roll 6, the length of the roll gap, etc., are adjusted.
Can be made uniform. Therefore, the thermoplastic resin sheet manufacturing apparatus M is provided with a bank size measuring device for measuring the bank thickness of the bank 21.
Hereinafter, this bank size measuring device will be described.

That is, as shown in FIGS. 2 to 4, this bank size measuring apparatus is substantially an industrial endoscope 3.
1, a CCD camera 32 optically connected to the endoscope 31, and an electric signal corresponding to an image captured by the CCD camera 32 is received via a cable 33, and a predetermined image An image processing device 34 for performing processing,
A monitor 35 for displaying the processing results and the like in the image processing device 34, a light source device 36 for generating light suitable for illuminating the bank 21, and guiding the light emitted from the light source device 36 to the endoscope 31. An optical fiber 37 is provided.
This endoscope 31 is used when there is no space for installing a camera between the die and the roll.

As shown in FIG. 5 and FIG.
Is substantially above the resin sheet material.
A housing 41 (stainless steel tube) formed in a slender cylindrical shape so that it can be inserted into a narrow gap between the light source device 36 and the optical fiber 37.
A light guide 42 for guiding the light guided to the endoscope 31 through the light guide to its light emitting portion (objective portion) to illuminate the subject 47, an objective lens 44 for receiving light from the subject 47, and a relay lens 45 (combination of lenses) and a series of lens groups including an eyepiece 46. In FIG. 5, θ indicates a viewing angle, and D indicates a portion that can be inserted into a gap or the like.

Here, the light guide 42 is provided in accordance with a direction in which light is to be emitted or a direction in which the subject 47 is to be viewed.
Various specifications are used. For example, when looking forward, the one shown in FIG. 7A is used, when looking sideways, one shown in FIG. 7B is used, and when looking diagonally forward, 7C is used as shown in FIG. 7C, and FIG.
The one having the specifications shown in FIG.

Specifically, in the bank size measuring apparatus according to this embodiment, the housing 41 of the endoscope 31 has an outer diameter of 8 mmφ, and the housing 41 is arranged such that its axis is horizontal. Have been. The light guide 42 of the horizontal endoscope 31 is of a side view type as shown in FIG. 7B. The endoscope 31 may use an optical fiber. Further, a polarizing lens may be inserted between the endoscope 31 and the CCD camera 32.

In this bank size measuring apparatus, the light source device 36 is a 150 W halogen lamp, and the light emitted from the halogen lamp is adjusted in its light amount, and the light of the optical fiber 37 and the endoscope 31 is adjusted. Guide 4
2 to the bank 21. The wavelength of the illumination light may be set to a specific wavelength using a band pass filter. Further, the illumination device may be different from the endoscope 31 (not the accessory of the endoscope).

Further, as described above, the thermoplastic resin sheet manufacturing apparatus M is provided with the film thickness measuring device 12 (a non-contact air type thickness gauge manufactured by Yamabun Co., Ltd.). 8 are used. That is, as shown in FIG.
Is a nozzle 51 (for example, having an outer diameter of 10 mmφ) that can move freely in the vertical direction, and a cylinder portion 52 (for example, having an outer diameter of 7 mm) having an appropriate size.
0 mmφ), a displacement meter 53 for detecting the amount of displacement of the nozzle 51, and first to third air passages 54 to 56. The nozzle 51 is supplied with pressurized air (for example, dry air of ² kg / cm ² or less) at a predetermined pressure P ₁ (nozzle air pressure P ₁ ) through the first air passage 54. The back pressure P _{2 of the} nozzle 51 is introduced into the lower chamber of the cylinder part 52 through the first air passage 55, and the predetermined pressure P ₃ (the lowering control) is passed through the third air passage 56 to the upper chamber of the cylinder part 52. Pressurized air for controlling the air pressure P ₃ ) is introduced.

Thus, in the film thickness measuring device 12, the air supplied to the nozzle 51 through the first air passage 54 is blown out from the lower part of the nozzle toward the surface of the resin sheet 20. The back pressure of the nozzle 51 changes in correlation with (corresponding to) the gap C between the sheet 20 and the sheet 20. That is, the smaller the gap C is, the higher the back pressure of the nozzle 51 is. Here, as the thickness of the resin sheet 20 increases, the gap C becomes equal to the set value (for example, 0.1 m).
m), the back pressure of the nozzle 51 increases.
As a result, P ₃ > P _2. Accordingly, the nozzle 51 rises, and the nozzle 51 balances and stops at the position where P ₃ = P ₂ , that is, the position where the gap C matches the set value. On the other hand, when the thickness of the resin sheet 20 becomes smaller and the gap C becomes larger than the set value, the back pressure of the nozzle 51 becomes lower. As a result, P
₃ <P _2, and the nozzle 51 is lowered along with this, P ₃
= P ₂ , that is, at a position where the gap C matches the set value, and stops.

Thus, in the film thickness measuring device 12, the nozzle 51 is displaced up and down according to the change in the film thickness of the resin sheet 20, and the gap C between the lower end of the nozzle 51 and the surface of the resin sheet 20 is increased. While being kept at the set value (constant value), the displacement amount of the nozzle 51 is detected by the displacement meter 53, and the thickness of the resin sheet 20 is accurately calculated (for example, within 1% error) from the nozzle displacement amount. You.

Hereinafter, a method for measuring the bank size in the thermoplastic resin sheet manufacturing apparatus M will be described. In the image processing device 34 of the bank size measuring device, the measurement of the bank thickness (bank size) is performed by the following method.
That is, first, the endoscope 31 is moved in the width direction of the resin sheet (the direction of the roll axis), and its objective portion (the portion that emits illumination light or receives light from the bank 21) is the portion of the bank 21 to be photographed. Are arranged at positions corresponding to the sheet width direction.

Next, the bank 21 (a part in the sheet width direction) is photographed by the CCD camera 32 through the endoscope 31, and an electric signal corresponding to this image is transmitted to the image processing device 34 via the cable 33. Send. Then, the image processing device 34, based on the received electric signal,
After the image is reproduced, the image is subjected to noise removal processing such as smoothing processing.

Then, the brightness value (average brightness) of the pixels of the image is continuously measured in a direction perpendicular to the resin sheet width direction (roll axis direction), that is, in a vertical direction at a predetermined position in the resin sheet width direction (roll axis direction). , The functional relationship of the lightness value with respect to the vertical position, that is, the lightness function is calculated. If such a brightness function is displayed in a two-dimensional coordinate system, for example, FIG. 9 or FIG.
A graph (curve) as shown in FIG. Here, the brightness function (brightness curve) in FIG. 9 is obtained by processing an image as shown in FIG. 11, for example. The graphs G _{1 to} G ₃ are created based on data collected under different lighting conditions. The brightness function in FIG. 10 is, for example, as shown in FIG.
This is obtained by processing an image that has been subjected to shading processing in addition to smoothing processing.

As can be seen from FIG. 9 or FIG.
In this lightness function (lightness curve), there are a plurality of points (minimum points) that take a minimum value. Then, if the two minimum points having the smallest lightness value are selected, one of them corresponds to the upper end of the bank 21 and the other corresponds to the lower end of the bank 21. Therefore, the distance between the vertical position corresponding to one of the minimum points and the vertical position corresponding to the other minimum point accurately corresponds to the bank thickness. Thus, the bank thickness can be accurately calculated from the distance. The measurement of the bank thickness by such image processing is performed at a plurality of positions separated by a predetermined distance in the roll axis direction (for example, a position where the image is divided into five equal parts), and the bank thickness at these roll axis direction positions is determined. Is obtained. Therefore, if the interval is preferably set, the bank size (bank thickness) of the entire photographed portion of the bank 21 can be accurately grasped. In addition, the endoscope 31 is moved (or scanned) in the width direction of the resin sheet.
By doing so, the measurement of the bank thickness can be performed over the entire width of the resin sheet 20. In the case where the endoscope 31 has a structure that cannot be moved in the sheet width direction, a plurality of endoscopes 31 may be arranged so as to be shifted in the resin sheet width direction.

According to this method for measuring the bank size, the minimum point in the brightness function is not affected by the illumination state of the bank. That is, in this lightness function, the minimum two minimum points can be detected regardless of the illumination state, and the vertical position corresponding to the two minimum points is not affected by the illumination state. That is, FIG. 9 shows graphs G _{1 to} G ₃ of three types of measurement results having different illumination states, and the vertical positions corresponding to the two minimum points of these graphs are substantially equal. ing. Therefore, regardless of the lighting condition of the bank 21 or the lighting conditions, the bank thickness can be accurately obtained at a desired position in the roll axis direction.

The method of controlling the thickness of the resin sheet 20 in the thermoplastic resin sheet manufacturing apparatus M will be described below. this,
The film thickness is controlled by the following method. That is, first, the bank thickness is measured over the entire width of the resin sheet 20 by the bank size measuring device. Then, based on the measured bank thickness, the choke bar insertion length (of the resin sheet material) is set so that the bank thickness becomes a value corresponding to the set value of the thickness of the resin sheet 20 at all positions in the resin sheet width direction. The flow rate), the degree of tightening of the lip adjusting bolt (lip opening degree of the die), the rotation speed of the cooling roll 6, a part or all of the roll gap length, and the like are preferably adjusted. Thereby, the film thickness of the resin sheet 20 is made uniform, and the quality of the resin sheet 20 is improved. Note that the adjustment of the choke bar insertion length, the die lip opening, the roll rotation speed, the roll gap, and the like may be performed manually or automatically.

In this film thickness control, a choke bar insertion length, a die lip opening degree, and a roll thickness are determined based on the thickness of the resin sheet 20 measured by the film thickness measuring device 12 in addition to the bank thickness described above. It is preferable to adjust a part or all of the rotation speed, the roll gap, and the like to make the thickness of the resin sheet 20 uniform. In this way, the accuracy of controlling the thickness of the resin sheet 20 is improved, and the quality of the resin sheet 20 is further improved.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a thermoplastic resin sheet manufacturing apparatus according to the present invention.

FIG. 2 is a side view schematically showing the extruder.

FIG. 3 is an enlarged side view showing a part near a die of the extruder shown in FIG. 2;

FIG. 4 is an elevational view of the extruder shown in FIG.

FIG. 5 is a side sectional view of the endoscope.

FIG. 6 is a diagram showing an arrangement of lenses of the endoscope.

FIGS. 7A to 7D are diagrams showing radiation characteristics of light from a light guide of an endoscope.

FIG. 8 is an elevation view of a film thickness measuring device.

FIG. 9 is a graph showing a change characteristic of a grayscale value (brightness value) of an image with respect to a coordinate position in a vertical direction.

FIG. 10 is a graph showing a change characteristic of a grayscale value (brightness value) of an image subjected to shading correction in addition to a smoothing process with respect to a coordinate position in a vertical direction.

FIG. 11 is a photograph instead of a drawing, showing a halftone image of a bank displayed on a display.

FIG. 12 is a photograph instead of a drawing, showing a halftone image of a bank after smoothing processing, which is displayed on a display.

[Explanation of symbols]

M thermoplastic resin sheet manufacturing equipment, 5 extruder, 6
Cooling roll, 6a upper roll, 6b lower roll, 9 dies, 12 film thickness measuring machine, 20 resin sheet,
21 banks, 22 lip adjustment bolts, 28 choke bolts, 31 endoscope, 32 CCD camera, 34 image processing device, 36 light source device, 51 nozzles.

Claims (13)

[Claims] 1. A thermoplastic resin extruded from a die,
1 arranged close so that each axis is parallel to each other
This is a method for measuring the size of a bank of thermoplastic resin formed immediately upstream of the rolls when a thermoplastic resin sheet is manufactured by forming the same into a sheet by passing through a gap between a pair of rolls. The bank is photographed by a camera, and the brightness value of the pixel of the image of the bank photographed by the camera is calculated at a predetermined position in the roll axis direction in a vertical direction which is a direction perpendicular to the roll axis direction. Continuous measurement is performed to calculate the functional relationship of the lightness value with respect to the vertical position. In the functional relationship, the vertical position of the two minimum points where the lightness value takes a minimum value is determined, and then the position between the two positions is determined. And calculating the size of the bank based on the distance. 3. A method for measuring the size of a bank in extrusion molding of a thermoplastic resin sheet. 2. A thermoplastic resin extruded from a die,
1 arranged close so that each axis is parallel to each other
A method for controlling the film thickness of the thermoplastic resin sheet when the thermoplastic resin sheet is manufactured by forming the sheet into a sheet by passing through a gap between a pair of rolls. Using the measurement method, the size of the thermoplastic resin bank formed immediately upstream of the roll is measured, and based on the measured value of the bank size, the operating state of the die and the operating state of the roll Wherein the thickness of the thermoplastic resin sheet is controlled by adjusting at least one of the above methods. 3. A thermoplastic resin extruded from a die,
1 arranged close so that each axis is parallel to each other
A method for controlling the film thickness of the thermoplastic resin sheet when the thermoplastic resin sheet is manufactured by forming the sheet into a sheet by passing through a gap between a pair of rolls. While measuring the size of the thermoplastic resin bank formed immediately upstream of the roll using the measurement method, the thickness of the thermoplastic resin sheet is measured by a film thickness measuring machine, the bank size of the above By adjusting at least one of the operation state of the die and the operation state of the roll, based on the measurement value and the measurement value of the film thickness measurement device,
A film thickness control method in extrusion molding of a thermoplastic resin sheet, wherein the film thickness of the thermoplastic resin sheet is controlled. 4. The method according to claim 3, wherein the thickness measuring device is a non-contact type. 5. The apparatus according to claim 1, wherein the film thickness measuring device includes an air injection nozzle which can be freely displaced with respect to the thermoplastic resin sheet, and injects air from the nozzle toward the thermoplastic resin sheet. The distance between the nozzle and the thermoplastic resin sheet is kept constant based on the back pressure of the nozzle, and the thickness of the thermoplastic resin sheet is measured from the amount of change in the position of the nozzle. 4. The method for controlling a film thickness in extrusion molding of a thermoplastic resin sheet according to claim 3, wherein: 6. The operating state of the die is adjusted by changing at least one of the lip opening of the die and the insertion length of the choke bar of the die. A method for controlling the film thickness in extrusion molding of the thermoplastic resin sheet according to any one of claims 1 to 5. 7. An operation state of the roll is adjusted by changing at least one of a rotation speed of the roll and a gap between the two rolls. 5. The method for controlling a film thickness in extrusion molding of a thermoplastic resin sheet according to any one of 5. 8. A thermoplastic resin extruded from a die,
1 arranged close so that each axis is parallel to each other
An apparatus for measuring the size of a bank of a thermoplastic resin formed immediately upstream of the rolls when a thermoplastic resin sheet is manufactured by forming a sheet by passing through a gap between a pair of rolls. A camera for photographing the bank, and a brightness value of a pixel of an image of the bank photographed by the camera at a predetermined position in the roll axis direction in a vertical direction that is a direction perpendicular to the roll axis direction. Brightness function calculating means for continuously measuring and calculating a functional relationship of the brightness value with respect to the vertical position; and two vertical axes in which the brightness value takes a minimum value in the functional relationship calculated by the brightness function calculating means. An inter-position distance calculating means for calculating a distance between the two positions after obtaining a direction position; and a size of the bank based on the distance calculated by the inter-position distance calculating means. And a bank size calculating means for calculating the bank size of the thermoplastic resin sheet. 9. A thermoplastic resin extruded from a die,
1 arranged close so that each axis is parallel to each other
An apparatus for controlling the film thickness of the thermoplastic resin sheet when producing a thermoplastic resin sheet by forming the sheet into a sheet by passing through a gap between a pair of rolls, wherein the apparatus is described in claim 8. The operation state of the die and the operation of the roll based on a measured value of the size of the bank of the thermoplastic resin formed immediately upstream of the roll measured by the bank size measurement device. A film thickness controller for controlling the film thickness of the thermoplastic resin sheet by adjusting at least one of the states. 10. A thermoplastic resin extruded from a die is formed into a sheet by passing through a gap between a pair of rolls arranged close to each other so that each axis is parallel to each other. An apparatus for controlling the film thickness of the thermoplastic resin sheet when manufacturing the sheet, comprising: the bank size measuring device according to claim 8; and a film thickness for measuring the film thickness of the thermoplastic resin sheet. Measuring device, measured by the bank size measuring device, based on the measured value of the size of the thermoplastic resin bank formed immediately upstream of the roll, based on the measured value of the film thickness measuring device,
By adjusting at least one of the operating state of the die and the operating state of the roll, a film thickness control means for controlling the film thickness of the thermoplastic resin sheet is provided, A film thickness control device for thermoplastic resin sheets. 11. The film thickness measuring device includes an air injection nozzle that can be freely displaced with respect to the thermoplastic resin sheet, and injects air from the nozzle toward the thermoplastic resin sheet. The distance between the nozzle and the thermoplastic resin sheet is kept constant based on the back pressure of the nozzle, and the thickness of the thermoplastic resin sheet is measured from the amount of change in the position of the nozzle. The film thickness control device for a thermoplastic resin sheet according to claim 10, wherein: 12. The operating state of the die is adjusted by changing at least one of a lip opening of the die and an insertion length of a choke bar of the die. 10. The method of claim 9, wherein
An apparatus for controlling the thickness of a thermoplastic resin sheet according to claim 1. 13. The roll state is adjusted by changing at least one of a rotation speed of the roll and a gap between the two rolls. The film thickness control apparatus for a thermoplastic resin sheet according to any one of claims 9 to 11, wherein: