JP4085213B2 - Thickness measurement system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thickness measurement system, and more particularly, to a technique for measuring the thickness of a sheet-like material such as paper, pulp, or film while traveling using infrared rays.
[0002]
[Prior art]
One of the conditions for determining the quality of a sheet-like material (hereinafter abbreviated as a sheet) such as paper, pulp, film, etc. includes the thickness and the coating amount applied on the sheet. In particular, in the pre-stretching process of the sheet production line, the thickness management of the edge portion of the sheet is important. This is because if the thickness of the edge portion of the sheet is not uniform, there is a risk of loosening, cracking or cutting in the stretching process.
[0003]
Conventionally, there is a measurement technique as shown in FIG. 2 as a transmission type thickness measurement technique using an infrared absorption wavelength. In this measurement technique, infrared light emitted from the infrared light source 1 is transmitted through the optical filter 2 to select infrared light having a specific wavelength absorbed by the sheet to be measured from the infrared light. The light is condensed on the traveling sheet by being transmitted through the light projecting unit 4 including a lens or the like. Thickness conversion that converts the amount of light attenuated during transmission into thickness and outputs thickness data by projecting and transmitting infrared light of a specific wavelength focused and focused on the measurement spot toward the traveling sheet S This is a measurement technique in which the thickness is obtained using the vessel 7. In this measurement technique, it is common to replace the optical filter 2 capable of selecting a specific wavelength absorbed by the sheet S according to the type of the sheet S, and the thickness and thickness of the single thickness converter 7 are different. The thickness of the sheet can be measured.
[0004]
[Problems to be solved by the invention]
However, in the measurement method using the conventional transmission type measurement apparatus, the entire measurement apparatus requires a large space, for example, the infrared light source 1 and the light projecting / receiving units 4 and 5 are integrated. In other words, the light projecting side measuring device main body A composed of the infrared light source 1, the optical filter 2 and the light projecting unit 4 and the light receiving side measuring device main body C composed of the light receiving unit 5 and the thickness converter 7 are arranged in the measurement space B. It has been difficult to downsize the entire system by downsizing individual measuring devices. In the production process, when the place where the measuring device needs to be installed is very small, the size of the measuring device as a whole becomes an obstacle and cannot be easily installed. So far, it has been necessary to greatly modify the production line in order to secure a space in which the measuring device can be installed. In particular, the process before stretching is a complicated line of various devices, and the production process has already been completed. If you intend to install a thickness measurement device later, it will take a lot of labor and cost to modify the production line. Cost. For that reason, downsizing of the measuring device is an important issue, and there has been a strong demand for it.
[0005]
In addition, if the measuring device is installed in a place where it is difficult for people on the sheet production line to enter the production process, it is easy to replace the filter once installed just because the material of the sheet has changed. Not. In that case, the sheet to be measured is limited, or it is necessary to newly add a measuring device according to the sheet to be measured, and the installation cost (device purchase cost and facility construction cost) becomes large. For this reason, online thickness measurement in the pre-stretching process of a production line with many types of production sheets has been extremely difficult.
[0006]
Therefore, the object of the present invention is to eliminate the above-mentioned problems of the prior art, accurately measure the thickness of a wide variety of sheets, and substantially reduce the size of the apparatus related to the measurement, and change the material of the sheet to be measured. Another object of the present invention is to provide a thickness measurement system in which the filter can be easily replaced according to the conditions.
[0007]
[Means for Solving the Problems]
The above object can be achieved by the invention described in the claims. That is, the characteristic configuration of the thickness measurement system according to the present invention includes an infrared light source that emits infrared light,
An optical filter capable of selecting a specific wavelength to be measured sheet absorbs infrared emitting from the infrared light source,
A condensing lens that projects the infrared rays selected by the optical filter onto the sheet to be measured;
A first optical fiber for guiding infrared rays from the optical filter to the condenser lens;
A photodiode that receives light transmitted through the measurement sheet ;
A thickness data calculation means capable of calculating and outputting the thickness data of the measured sheet in response to a signal from the photodiode ;
A second optical fiber for guiding a signal from the photodiode to the thickness data calculation means,
The thickness data calculating means converts the amount of infrared light attenuated during transmission through the sheet to be measured into a thickness, and the condenser lens and the photodiode are disposed in proximity to the sheet to be measured. There is in being.
[0008]
When configured in this way, the light projecting unit and the light receiving unit are separated from the light projecting side measuring device main body and the light receiving side measuring device main body in which the light sources are housed, respectively. Such a device portion can be reduced in size. Therefore, when the installation location is small, it is possible to install only the light emitting / receiving unit on the production line and install the light emitting / receiving side measuring instrument body in another wide place away from the light emitting / receiving unit. Even when the type of sheet traveling inside changes, the filter can be easily replaced, and online thickness measurement of many types of sheets can be realized by using only one measuring instrument. In addition, since the signal propagation by the optical fiber has a small attenuation rate in the medium, the reliability of data is hardly affected even after a long propagation distance, and the measurement accuracy can be maintained high.
[0009]
It is preferable that the condensing lens and the photodiode are movable in the length direction or the width direction of the measurement target sheet. When configured in this way, thickness variations not only in the length direction but also in the width direction of the sheet to be measured can be accurately grasped, and it becomes easy to measure the thickness of the edge portion, which is a particularly important measurement location. convenient.
[0010]
The thickness data calculating means is a thickness converter, and it is preferable that a display unit for displaying the thickness data is connected to the thickness converter. Constituting in this way is convenient because the signal from the photodiode can be directly identified as thickness data, and various displays according to the purpose of use, such as graphing the thickness data as a display unit, can be realized. convenient.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an infrared transmission type thickness measuring system using an optical fiber which is a thickness measuring system of the present embodiment. This thickness measuring system includes a light source 1 for irradiating infrared light and a light-projecting side measuring device including an optical filter 2 as a wavelength selecting means for selecting only a specific wavelength absorbed by the sheet S from the infrared light. The main body A, a light projecting unit 4 composed of a condensing lens connected by the optical filter 2 and the optical fiber 3, and a photodiode disposed at a position facing the light projecting unit 4 across the traveling sheet S. The light receiving unit 5, the thickness converter 7 which is a thickness data calculating means connected to the light receiving unit 5 via the optical fiber 6, and the thickness data output from the thickness converter 7 are displayed as a graph or the like. The display unit 8 is configured to be provided. Thus, the thickness measuring system of this embodiment is composed of the light source 1 for infrared rays and the optical filter 2 on which the light projecting side measuring device main body A emits infrared light, and the light receiving side measuring device main body C is a thickness converter. 7, and only the light projecting unit 4 and the light receiving unit 5 are disposed in the measurement space B in close proximity to the traveling sheet. Therefore, the apparatus part substantially related to the measurement occupying the measurement space B can be greatly reduced compared to the case of the prior art, and only a small space is ensured even when newly installed in an existing production line. Therefore, it is not necessary to greatly modify the production line.
[0012]
Further, the optical filter 2 can be variously changed depending on the material of the traveling sheet S. In that case, select a filter that can select an infrared ray having a wavelength that maintains a linear relationship having a gradient as high as possible between the thickness of the sheet S and the light absorption amount, that is, the measurement sensitivity is high. Is preferred. In addition, since the optical filter 2 and the light projecting unit 4 are connected by the optical fiber 3, the attenuation rate of the light propagating through the medium is low even when the positions of both are considerably separated. There is no problem in measurement. As a result, the optical filter 2 can be replaced at a place where the replacement work is easy, away from the measurement space B. Therefore, even if the material of the sheet is changed as a production line, the filter replacement work can be performed without any problem. Can be carried out easily and quickly, and as a result, highly accurate thickness data can always be obtained.
[0013]
However, the thickness in the width direction of the sheet traveling on the sheet production line is not uniform, and depending on the product, the constituent components vary depending on the width direction or the length direction. There is a case. Even in such a case, it is necessary to keep the thickness of the sheet within the process control range in order to keep the sheet being produced within the product specification. In some cases, in the production process, it may be necessary to manage the process in a place where the measurement space is constrained by a place where a person cannot enter or an existing facility.
[0014]
In the thickness measurement system according to the present embodiment, only the light projecting / receiving units 4 and 5 are installed in the measurement space B, and the combination of the light projecting unit 4 and the light receiving unit 5 is moved along the width direction or length direction of the sheet S. By adopting a method that performs software processing while continuously changing the measurement position, it becomes possible to measure the thickness with high accuracy, and in some cases, the filter can be replaced to switch to the absorption wavelength corresponding to the measurement location, Accurate thickness measurement at an arbitrary position is possible. That is, by changing continuously or discontinuously across the width direction of the sheet S traveling between the light projecting and receiving parts 4 and 5, changes due to sheet thickness fluctuations (changes in absorption values are gentle and continuous). The thickness of the data that can be used to identify whether or not the material has changed (for example, the crystallization is progressing locally, or the change is due to segregation of components, and thus the change in absorption value is generally rapid). It is possible to store the data in the calculation means 7 and output the thickness data while determining which is the cause each time the measured value fluctuates. At this time, the absorption wavelength can be changed by exchanging the filter for a large change in the measured value. The movement of the light projecting / receiving units 4 and 5 is not shown, but the light projecting unit 4 and the light receiving unit 5 are synchronized with each other along the rail passed in the XY direction immediately above the traveling sheet. Then, it can be performed by driving so as to be movable.
[0015]
Furthermore, if the measured values obtained are continuously graphed and displayed, it is possible to immediately understand the thickness of the currently produced sheet, which is very useful as a means to enhance quality control. preferable. By moving the pair of light emitting and receiving parts in the length or width direction of the sheet and graphing the measurement results, the thickness variation or the cause of the variation can be immediately identified, and useful information for subsequent processing. Can contribute to improving the quality of the sheet. Of course, as the display means, not only a graph but also a simple digital display may be used, or a warning display may be issued for a measured value exceeding a predetermined range.
[0016]
[Another embodiment]
(1) The thickness data calculation means is not limited to the thickness converter, and the absorption value is output as a digital signal. When the signal exceeds the predetermined range, a warning display by sound or light or both is issued. Further, the seat may be configured to reduce the traveling speed of the seat or to stop traveling. In this case, the thickness data calculation means has a function of a display unit.
[0017]
(2) In the above-described embodiment, the pair of light projecting units and the light receiving unit are arranged in the measurement space. However, a plurality of combinations of the pair of light projecting / receiving units are arranged in the measurement space. It may be arranged. In particular, by separately arranging a combination of a pair of light projecting and receiving units that measure the edge portion exclusively, the thickness management of the edge portion can be strengthened, and a more convenient thickness measurement system can be configured.
[0018]
(3) A signal output from the thickness data calculation means is transmitted to the next process or the previous process, and the drawing force or the reduction force between the two rolls is automatically applied to the sheet that travels in accordance with the transmission data. You may utilize this invention so that it may be directly connected with the control system to act.
[0019]
【The invention's effect】
As described above, according to the present invention, the problems of the prior art are solved, the thickness of a wide variety of sheets can be accurately measured online, and the apparatus portion for measurement can be substantially downsized, and the sheet to be measured It was possible to provide a thickness measurement system in which the filter can be easily exchanged according to the material change. As a result, the breakage of the sheet during the manufacturing process was reduced, the yield was significantly improved, and the operability was improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a thickness measuring system according to the present invention. FIG. 2 is a schematic configuration diagram of a conventional thickness measuring system.
1 Infrared light source 2 Wavelength selection means (optical filter)
3, 6 Optical fiber 4 Projection unit 7 Thickness data calculation means (thickness converter)
8 Display S Sheet to be measured

Claims (3)

An infrared light source that emits infrared light;
An optical filter capable of selecting a specific wavelength to be measured sheet absorbs infrared emitting from the infrared light source,
A condensing lens that projects the infrared rays selected by the optical filter onto the sheet to be measured;
A first optical fiber for guiding infrared rays from the optical filter to the condenser lens;
A photodiode for receiving light transmitted through the measurement sheet ;
A thickness data calculation means capable of calculating and outputting the thickness data of the sheet to be measured in response to a signal from the photodiode ;
A second optical fiber for guiding the signal from the photodiode to the thickness data calculation means,
The thickness data calculating means converts the amount of infrared light attenuated during transmission through the sheet to be measured into a thickness, and the condenser lens and the photodiode are disposed in proximity to the sheet to be measured. A thickness measurement system characterized by that. The thickness measurement system according to claim 1, wherein the condenser lens and the photodiode are movable in a length direction or a width direction of the measurement target sheet. The thickness measurement system according to claim 1 or 2, wherein the thickness data calculation means is a thickness converter, and a display unit for displaying the thickness data is connected to the thickness converter.

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