JPH03105236A - Apparatus for measuring water content of sheet-like object - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention... This article relates to a device for measuring moisture contained in sheet-like objects. BACKGROUND ART FIGS. 5 and 6 show a conventional example of a moisture meter for measuring the moisture content of a sheet-like object in a paper machine or the like.

In Fig. 5, 1 is a light emitting part, and 2 is a light receiving part, which are arranged opposite to each other with a paper 3, which is the object to be measured, sandwiched between them. In the light projection unit 1, the light from the light source 6 is converted into parallel light by the lens 7. Furthermore, after being made into an intermittent light by chopper wheel 8.
The paper 3 is irradiated through the irradiation window 4. The chopper wheel 8 includes a filter 9 that transmits 1.94 μm light (measurement light) that is absorbed by moisture, and a filter 10 that transmits 1.8 μm light (comparison light) that is not absorbed by moisture.
is provided, and irradiates the paper 3 with measurement light and comparison light alternately as it rotates. In the light receiving section 2, light that has passed through the paper 3 enters through the entrance window 5, is focused by the lens 11, and is focused on the light receiving element 12. This light receiving element detects the measurement light M and the comparison light R in time series. It is fed to the arithmetic unit 13 to calculate R/M and output it. In the conventional example shown in the sixth example, the light from the light source 6 is turned into a thousand lines by the lens 7 in the light projecting section 1, and the chopper wheel 8'
After making it an intermittent light, the paper 3 is irradiated through the irradiation window 4. This chopper wheel does not have a filter mounted on it like the conventional example shown in Figure 5. The wheel is used exclusively to remove the effects of stray light. The white light irradiated from the irradiation window 4 is multiple-reflected on the diffuse reflection surfaces 16 and 17 provided on the opposing surfaces of the light emitter 1 and the light receiver 2 while holding the paper 3 between them. The light enters the light receiving section 2 through the entrance window 5 provided at a position offset from the irradiation window 4. In the light receiving section 2. The incident light is split into two by the prism 18,
One side passes through a filter 9 that transmits the measurement light and a lens 11, and is guided to the light receiving element 12. The other light is guided to a light receiving element 12' through a filter 10 and a lens 11' that transmit the comparison light. Measurement light M detected by the light receiving element 12 and the light receiving element 12'
The comparison light R detected at is simultaneously given to the arithmetic unit l3,
R/M calculation is performed and output. Problems to be Solved by the Invention In the above-mentioned conventional device, the configuration shown in FIG.
On the one hand, it has the advantage of easy horizontal construction and low attenuation of the amount of light per unit, but because the object to be measured is a single sheet of paper, there is a problem that good sensitivity cannot be obtained if the thickness of this paper is thin. In the configuration shown in Figure 6, the optical axes of the light emitter and light receiver are placed several tens of millimeters apart, and the light reaches the light receiver while being transmitted and scattered through the paper by the scattering surface, resulting in a large amount of attenuation. There was a problem that the signal itself became smaller. moreover,
The problem was that it was not possible to measure the moisture content of multiple types of paper with one device. The present invention was made to solve the problems of the prior art described above, and by utilizing the property that light hitting paper propagates in the lateral direction, it can achieve a high S/N ratio and the water content of multiple types of paper. The purpose of the present invention is to provide a detection device that can measure .

Means for Solving the Problems> The configuration of the present invention for solving the above problems includes a light receiving element that receives light from a light projecting section via a sheet-like object. A moisture measuring device for a sheet-like object that measures the moisture content of the sheet-like object based on a signal from the light receiving element,
a first light guiding means that receives light from the light projecting section and emits it to the sheet-like object side; and n light guiding means having different diameters and arranged at a predetermined distance from an end side surface of the first light guiding means. The second light guiding means is arranged in an annular shape, and the light emitted from the first light guiding means receives the light propagated laterally in the sheet-like object, and the second light guiding means in the annular shape It is characterized in that the light received by each of the first means is horizontally formed so as to be incident on the light receiving element. Effect> Most of the light emitted from the first light guiding means and irradiating the paper passes through the paper, but also propagates in the lateral direction. The light propagating in the lateral direction has a long propagation optical path length in a material with a small basis weight such as thin paper, but the light quantity is small. On the other hand, in the case of a material with a large basis weight such as high-quality paper, the propagation optical path is short but the amount of light is large. If the light propagating in the lateral direction from the first light guiding means is received through the n second light guiding means arranged on a ring, the amount of light and the propagation distance of the propagating light can be detected simultaneously. It can be done. <Example> FIG. 2 is a sectional view of the main parts for explaining the principle of this invention. In the figure, reference numeral 20 denotes a first light guide means consisting of an optical fiber bundle, in which light from a light source (not shown) is guided in the direction of arrow A and exits from its end. Reference numeral 21 denotes a second light guiding means which is also shaped like an optical fiber bundle and is arranged at a constant distance from the four ends of the first light guiding means, and 3 faces the first and second light guiding means. This is a piece of paper arranged as follows.

In the above-mentioned case. The light emitted from the first light guiding means 20 illuminates the surface of the paper 3 placed opposite to each other. Most of the light passes through the paper, but some of it is transmitted laterally through the paper, being scattered by the paper's cellulose, as shown by the arrows B.
The light enters the second light guiding means 21 and is guided in the eight directions of the arrows, reaching a light receiving section (not shown). Note that the constant distance here differs depending on the relationship between the light exit port and the distance from the paper 3. The second light is directly reflected from the paper and is not involved in moisture detection.
The distance is such that it does not enter the light receiving part of the light guiding means 21,
The tip is configured to be movable in the two directions of the arrows.

Figure 3 shows the basis weight Log/
m' tissue paver. Regarding light propagating in the lateral direction using thin paper with a basis weight of 30 g/m2 and high-quality paper with a basis weight of 60 g/m'. The relationship between the detector output (R/M) and the moisture content 1 (g/m') was measured. According to the figure, R/M is smaller for paper with larger basis weight. It can be seen that the smaller the basis weight of the paper, the larger the value. This means that paper with a small basis weight has a long optical path propagating through the paper, so water absorption is large (high sensitivity), and conversely, paper with a large basis weight has a short optical path propagating through the paper, so water absorption is small. (low sensitivity). Figure 4 shows the configuration of Figure 2. Humidity is 30% and 70%
The tsubo, tlo, in which the water content in the paper is saturated in the atmosphere of
FIG. 2 is a diagram showing the relationship between relative light intensity and propagation distance when infrared light of 1.8 μm, which is not absorbed by water, is propagated using tissue webber of g/m2 and high-quality paper of 60 g/m' basis weight. . According to the diagram. It can be seen that when there are many water molecules, scattering occurs and the propagation distance becomes shorter. Furthermore, when compared at each humidity level, it can be seen that tissue paper with a small basis weight emits less light but has a long propagation distance, while high-quality paper with a large basis weight emits a large amount of light but has a short propagation distance.

The present invention was developed based on the above experimental results, and aims to realize a measuring device that detects the propagation distance as well as the intensity of the propagated light, and eliminates detection errors due to paper quality. An embodiment of the device of the present invention will be described below with reference to the drawings.
FIG. 1(a) shows the light projecting section shown in FIGS. 5 and 6. FIG. 3B is a block diagram showing the main parts of the present invention with the light receiving section omitted, and FIG. As shown in these figures, in this example, the first
A non-reflective resin 23a that absorbs infrared rays is formed with a predetermined thickness around the light guiding means, and the second light guiding means divided into n parts is formed in an annular shape. Note that here, the distance from the end of the first light guiding means to the center of the thickness of the second light guiding means on the outer periphery is defined as L, , L2 to LTL. In the above ellipse, the light irradiated onto the paper surface from the first four light means propagates within the paper and enters the second light guide means divided into n pieces, corresponding to each light guide means. The light is guided to a light-receiving element (not shown) provided in the figure. The signal from this light-receiving element becomes weaker as the distance is measured, but the finer the division of the second light guide means, the more accurate the distance measurement will be. The total light flea of R light and M light is detected by the signal from this light receiving element, and the R/M value is determined by a known method. As mentioned earlier, this value is smaller for paper with a larger basis weight, and larger for paper with a smaller basis weight. On the other hand, the propagation distance L obtained from the value of R light of each light receiving element is R/
Since the relationship between M value and basis weight is complementary, R/M is determined by taking propagation distance correction into consideration to avoid errors due to paper quality, and moisture content is measured. Note that the propagation distance can be determined by comparing the R light detection value with a threshold (detection limit). Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the first light guiding means receives light from the light projecting section and emits it to the sheet-like object side; n second light guide means having different diameters are arranged in an annular shape at a predetermined distance on the open end surface of the first light guide means, and the light emitted from the first light guide means is Since the structure is configured such that the light propagated in the transverse direction in the sheet-like object is received, and each of the annular second light guiding means makes the received light enter the light receiving element, the S/N is low.
The ratio can be increased, and papers with different basis weights can be measured with one detection device.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are configuration diagrams showing an embodiment of a sheet-like object characteristic measuring apparatus according to the present invention. Figure 2 is a sectional view of the main part to explain the principle of the present invention, Figure 3 is a diagram showing the relationship between the water content of paper and the detector output, and Figure 4 is a diagram showing the relationship between relative light intensity and propagation distance. The figures shown in FIG. 5 and FIG. 6 are diagrams showing conventional examples. 3... Sheet-shaped object paper), 20... First conductive material Figure/a) (b) Figure Z Figure 3 Figure 0 Contained water fleas (9/yn)

Claims (1)

[Claims] In the moisture measuring device for a sheet-like object, the device has a light-receiving element that receives light from a light projecting section through a sheet-like object, and measures the moisture content of the sheet-like object based on a signal from the light-receiving element. A first light guiding means that receives light from the light projecting section and emits it to the sheet-like object side; A second light guiding means is arranged in an annular shape, and receives light emitted from the first light guiding means and propagated laterally in the sheet-like object, and the second light guiding means in the annular shape 1. A moisture measuring device for a sheet-like object, characterized in that the light received by each of the means is configured to enter the light-receiving element.