JP2000155047A - Liquid level detecting mechanism for fine grain- containing liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a float lift type liquid level detecting mechanism with a low-cost structure and having the extremely high reliability of liquid level control by the detection of the highest liquid level and the presence or absence of a liquid. SOLUTION: This liquid level detecting mechanism for a fine grain-containing liquid 2 in a liquid storage tank 3 is provided with a float floating in the fine grain-containing liquid 2 slidably along a vertical guide 32 arranged on the outside of the liquid storage tank 3. A position detecting means A detecting the vertical position of the float 28 due to liquid level changes is arranged on the outside of the liquid storage tank 3. The position detecting means A is composed of a control sensor S1 of the highest liquid level where the supply of the fine grain-containing liquid 2 is stopped based on the detection of the upper limit liquid level of the stored liquid 2 and a control sensor S2 of the lowest liquid level where the supply of the fine grain-containing liquid 2 is resumed based on the detection of the lower limit liquid level of the stored liquid 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting mechanism for a liquid containing fine particles, which is provided in an apparatus for measuring the particle size distribution of fine particles contained in the liquid.

[0002]

2. Description of the Related Art Fine particle measurement technology is indispensable for determining and evaluating the performance of powdery substances in a wide range of fields such as medicines, foods, ceramics, cosmetics, paints, and pigments. The importance of the measurement of fine particles, such as the measurement of fine particles contained in, is increasing day by day.

One method of measuring the distribution of such fine particles is a laser diffraction type particle size distribution measuring device. This particle size distribution measuring apparatus disperses a powder sample (or slurry) in a liquid called a dispersion medium (for example, pure water or alcohol) to form a suspension, or disperses fine particles such as milk. The liquid containing the solution is introduced into a flow cell, irradiated with laser light, and the diffraction / scattered light at that time is detected by a detector, and the intensity distribution of the obtained diffraction / scattered light is obtained. Based on this, the particle size distribution of the sample is determined.

In general, the flow cell is connected to a liquid circulation line provided with a storage tank for the liquid containing fine particles and a liquid feed pump.
For example, a liquid supply line provided with an electromagnetic on-off valve, and a liquid level detection mechanism for ON / OFF-controlling the on-off valve based on detection of the upper and lower liquid levels of the stored liquid in the tank are provided. By keeping the surface within a predetermined range, the overflow of the liquid containing fine particles and the abnormal shortage of the liquid are prevented.

FIG. 6 schematically shows a conventional liquid level detecting mechanism 41. The liquid level detecting mechanism 41 is configured as follows. That is, the guide column 43 is erected inside the liquid storage tank 42 and the fine particle-containing liquid 4
4 is provided so as to be slidable along the guide column 43, and a magnetic body 46 is built in the float 45, while the guide column 43 is provided on the basis of detection of the magnetic body 46. A position detecting means (for example, a proximity switch) 47 for detecting an ascending / descending position of the float 45 due to the liquid level fluctuation is provided.

The position detecting means 41 detects a change in the liquid level of the liquid stored in the tank 42 with a certain width based on the detection and non-detection of the magnetic substance 46. The open / close valve 49 of the liquid supply line 48 is controlled to be OFF based on the detection of the upper limit of the stored liquid to prevent overflow, and based on the detection of the lower limit of the stored liquid to prevent an abnormal shortage of the liquid. The on-off valve 49 of the liquid supply line 48 is controlled to be ON so that the contained liquid level falls within a predetermined range.

In the drawing, reference numeral 50 denotes a liquid circulation line extending from the storage tank 42 to the flow cell 51.
Further, a liquid discharge line 54 provided with, for example, an electromagnetic on-off valve 53 is connected.

[0008]

According to the liquid level detecting mechanism 41 having the above-described structure, a simple movement of the float 45 can control the stored liquid within the upper and lower limits at low cost. However, the target of liquid level control is the fine particle-containing liquid 44, and the float 45 slides in this liquid, so that the fine particles in the liquid enter the slide portion of the float 45, and the slide of the float 45 is moved. In some cases, the liquid level control became impossible, which caused an overflow of the fine particle-containing liquid 44 or an abnormal liquid shortage.

[0009] The abnormal shortage of the fine particle-containing liquid 44 has a problem in that the ultrasonic vibrator of the dispersing means 55 provided to prevent aggregation of the fine particles in the liquid is damaged.

That is, the liquid storage tank 42 is generally provided with a dispersing means 55 provided with an ultrasonic vibrator in order to disperse the fine particles in the fine particle-containing liquid 44 to prevent aggregation of the fine particles. However, when the liquid storage tank 42 is emptied due to an abnormal shortage of liquid, the ultrasonic vibrator is damaged.

As another configuration of the liquid level detection mechanism 41, there is a configuration using a prism 57 as shown in FIG. The liquid level detection mechanism 41 arranges the prism 57 so as to be immersed in the liquid 44 containing fine particles.
A light source 58 for irradiating light toward the prism surface S and a photodetector 59 for catching light reflected on the prism surface S are arranged. When the prism 57 is immersed in the fine particle-containing liquid 44, Is transmitted through the prism surface S, and when the fine particle-containing liquid is reduced below the prism surface S, the light reflected by the prism surface S is detected by the photodetector 59, and the fine particle-containing liquid is detected. The liquid level is detected.

The liquid level detection mechanism 41 having such a configuration also controls the opening / closing valve 49 to be OFF based on the detection of the liquid level at the upper limit of the stored liquid, and to turn the opening / closing valve 49 ON based on the detection of the liquid level at the lower limit of the stored liquid.
It is described that the liquid level can be kept within a predetermined range.

However, in the liquid level detecting mechanism 41 having such a structure, not only is the prism 57 expensive and costly, but also when the prism surface S becomes dirty, the fine particle-containing liquid is applied to the dirty prism surface S. Even if the liquid containing fine particles decreases below the prism surface S, the photodetector 59 detects the remaining liquid containing fine particles, so that the fine particle-containing liquid 44 exists in the tank. There was a problem of malfunction.

The present invention has been made in view of such circumstances, and is directed to a float-type liquid level detecting mechanism having a low cost in structure as described above. The purpose is to increase the character.

[0015]

In order to achieve the above object, according to the first aspect of the present invention, a float floating in the fine particle-containing liquid is used as a liquid level detecting mechanism for the fine particle-containing liquid in the liquid storage tank. It is characterized in that it is provided slidably along a lifting guide arranged outside the liquid storage tank, and that a position detecting means for detecting the elevation position of the float due to the liquid level fluctuation is arranged outside the liquid storage tank.

According to the second aspect of the present invention, as a liquid level detecting mechanism for the fine particle-containing liquid in the liquid storage tank, a float floating in the fine particle-containing liquid is rotatable around a horizontal axis disposed outside the liquid storage tank. It is characterized in that the position detecting means for detecting the rotational position of the float due to the liquid level fluctuation is arranged outside the liquid storage tank.

That is, according to the first aspect of the present invention, the float is slidably provided along the elevating guide outside the tank, and in the second aspect of the present invention, the float is provided around the horizontal axis outside the tank. By arranging the float position detecting means outside the liquid storage tank after being rotatably provided, any inconvenience caused by the slide portion or the rotary portion of the float being immersed in the liquid containing fine particles is eliminated.

The position detecting means includes, for example, a maximum liquid level control sensor for stopping supply of the fine particle-containing liquid based on the detection of the upper limit of the contained liquid, and a fine particle-containing control sensor based on the detection of the lower limit of the contained liquid. A liquid level control sensor for resuming the supply of liquid (claim 3), or a supply liquid for stopping and restarting the supply of the particulate-containing liquid based on detection of the upper and lower liquid levels of the stored liquid. It is constituted by a lower limit liquid level control sensor (claim 4).

It is particularly preferable that the position detecting means is configured to detect the occurrence of an abnormal situation based on the detection of the liquid level outside the upper and lower limits of the contained liquid (claim 5). According to the configuration, when the liquid level control of the upper and lower limits of the contained liquid becomes impossible due to some trouble, for example, the driving of the dispersion unit is stopped or the occurrence of the abnormal situation is notified based on the detection of the occurrence of the abnormal situation. For example, the liquid level control becomes extremely reliable.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the configuration of a laser diffraction type particle size distribution measuring apparatus. In this figure, reference numeral 1 denotes a liquid in which fine particles to be measured are dispersed in a medium (hereinafter referred to as fine particle-containing liquid). 2 is a flow cell composed of a transparent container for accommodating the fine particle-containing liquid 2 as shown in FIG.
Liquid circulation line 5 provided with a liquid storage tank 3 and a pump 4
Is connected to the liquid circulating line 5 and, for example, an electromagnetic on-off valve 6 for discharging the fine particle-containing liquid 2 from the liquid circulating line 5 when the fine particle-containing liquid 2 to be measured is replaced. The provided discharge line 7 is connected.

Reference numeral 8 denotes a replenishment line for the fine particle-containing liquid 2 to the liquid storage tank 3, which is provided with, for example, an electromagnetic on-off valve 9, and controls the on-off operation of the on-off valve 9. 3 is provided with a liquid level detection mechanism 10.

Returning to FIG. 1, reference numeral 11 denotes a laser light source that emits a laser beam to the fine particle-containing liquid 2 in the flow cell via a reflection mirror 12, and 13 denotes a laser light source between the laser light source 11 and the flow cell 1. With the provided condenser lens, the laser light emitted from the laser light source 11 is appropriately converged light (hereinafter, referred to as “light”).
The particle-containing liquid 2 is irradiated as a focused laser beam.

Reference numeral 14 denotes a photodetector (ring detector).
It is arranged at a position where the condensed laser light passing through the flow cell 1 is focused. The photodetector 14 includes the condenser lens 1
A plurality of photosensors having ring-shaped or semi-ring shaped light-receiving surfaces having different radii from each other about the optical axis 3 are arranged concentrically. Of these, light scattered / diffracted at a relatively small angle is received at each scattering angle, and the light intensity is measured. Reference numeral 15 denotes a preamplifier for amplifying the output of the photo sensor constituting the photodetector 14.

In the vicinity of the flow cell 1, a wide-angle scattering device for individually detecting, at each scattering angle, light scattered / diffracted at a relatively large angle among the condensed laser light diffracted or scattered by the fine particles in the flow cell 1. An optical light detection group 16 is provided.

The wide-angle scattered light detection group 16 includes a plurality of photosensors 1 provided at different angles from the photodetector 14.
7 to 22, and detects scattered light exceeding a predetermined angle due to the fine particles in the flow cell 1 according to the respective arrangement angles.

That is, the photo sensors 17 to 20 detect forward scattered light, the photo sensor 21 detects side scattered light, and the photo sensor 22 detects back scattered light. Reference numeral 23 denotes an electric circuit board that holds the photo sensors 17 to 22 at a predetermined angle, and includes a preamplifier.

Reference numeral 24 denotes a multiplexer for sequentially taking in the outputs from the preamplifier 15 and the electric circuit board 23 and sequentially sending them to the AD converter 25. Reference numeral 26 denotes a computer as an arithmetic processing unit to which the output of the AD converter 25 is inputted. The computer 26 processes the outputs (digital data relating to the light intensity) of the photodetector 14 and the photosensors 17 to 22 converted into digital signals based on the Fraunhofer diffraction theory or the Mie scattering theory, A program for obtaining the distribution is stored. Reference numeral 27 denotes a color display for displaying calculation results and the like.

In the particle size distribution measuring apparatus configured as described above, the condensed laser light applied to the fine particle-containing liquid 2 in the flow cell 1 is diffracted or scattered by the fine particles in the flow cell 1, and the scattering angles are compared. The smaller one is the photodetector 14
Imaged on top.

At this time, in the photodetector 14, the photosensor on the outer peripheral side receives light with a large scattering angle, and the photosensor on the inner peripheral side receives light with a small scattering angle. Therefore,
The light intensity detected by the photosensor on the outer peripheral side reflects the amount of fine particles having a smaller particle diameter, and the light intensity detected by the photosensor on the inner peripheral side reflects the amount of sample particles having a larger particle diameter. Will be. The light intensity detected by each of these photo sensors is converted into an analog electric signal,
Further, the signal is input to the multiplexer 24 via the preamplifier 15.

On the other hand, among the condensed laser beams diffracted or scattered by the fine particles, those having a relatively large scattering angle are detected by the wide-angle scattered light photodetection group 16 and the light intensity distribution is measured. At this time, scattered light from fine particles having a small particle size is detected in the order of the forward scattered light photosensors 17 to 20, the side scattered light photosensor 21, and the back scattered light photosensor 22. Each of these photo sensors 1
The light intensities detected by 7 to 22 are converted into analog electric signals, and further input to a multiplexer 24 via a preamplifier provided on an electric circuit board 23.

In the multiplexer 24, measurement data from the photodetector 14 and the photosensors 17 to 22, that is, analog electric signals, are sequentially taken in a predetermined order and are converted into serial signals. The digital signal is sequentially converted into a digital signal, further input to the computer 26, and the light intensity data for each scattering angle obtained by the photodetector 14 and the photosensors 17 to 22 are obtained based on the Fraunhofer diffraction theory and the Mie scattering theory. It is processed.

As described above, in the above particle size distribution measuring apparatus, the light intensity distribution of the scattered light in the particle size range where the particle diameter is large is measured by the photodetector 14, and the light intensity distribution in the particle size range where the particle diameter is small is measured. The light intensity distribution of the wide-angle scattered light is measured by the photosensors 17 to 22, and the photodetector 14 and the photosensors 17 to
Since the output of 22 is processed by the computer 26, the particle size distribution in the group of fine particles can be determined all at once in a wide range from a relatively large particle size to a fine particle size.

Next, the liquid level detecting mechanism 10 for the fine particle-containing liquid 2
Will be described in detail with reference to FIGS. This liquid level detection mechanism 10 forms a float 28 that floats in the fine particle-containing liquid 2 stored in the liquid storage tank 3 from a cylindrical and lightweight shaft 29 and a hollow floating body 30. The pipette with its barrel portion cut off is used as a hollow floating body 30, and a cylindrical metal shaft 29 is joined to this hollow floating body 30 so as to close the opening formed by cutting off the barrel portion, thereby forming a float 28. On the other hand, a bracket 31 is arranged outside the liquid storage tank 3.

A linear guide type elevating guide 32 having a ball bearing a therein is mounted on the bracket 31 to the outside of the tank with its guide axis oriented in the vertical direction. The float 28 is configured to slide up and down as the level of the particulate-containing liquid 2 in the liquid storage tank 3 fluctuates by inserting and holding the shaft body 29 of the liquid storage tank 3.

Further, a light-shielding plate 33 is provided on the shaft 29 of the float 28, and two sets of photodetectors 35 and 36 each including a light projector b and a light receiver c are provided on a receiving member 34 connected to the bracket 31. , The light emitting and receiving devices b,
The light path from the light projector b to the light receiver c is shielded by the light shielding plate 33 as the float 28 is moved up and down. .

That is, the liquid 2 containing fine particles in the liquid storage tank 3
The position detecting means A of the float 28 is configured so that two sets of the photodetectors 35 and 36 detect the two rising and falling positions of the float 28 due to the fluctuation of the liquid level based on the above-mentioned light path shading. .

More specifically, the upper photodetector 35 is disposed at a position where it detects that the fine particle-containing liquid 2 has been supplied to the specified maximum liquid level, and is housed by the light shielding plate 33. The control sensor S1 of the highest liquid level for detecting the liquid level at the upper limit of the liquid is formed.

On the other hand, the upper photodetector 36 is located at a position for detecting a liquid level lower than the above-specified maximum liquid level and higher than an abnormally insufficient liquid level accompanied by inconvenience. It is arranged and constitutes the control sensor S2 of the minimum liquid level which detects the liquid level of the lower limit of the contained liquid by the light shielding plate 33.

Then, the highest liquid level control sensor S1 detects the liquid level from the light emitter b by the light shielding plate 33 and detects the liquid level in the tank 3 reaching the specified maximum liquid level ( The liquid replenishment line 8 is configured to stop the replenishment of the fine particle-containing liquid 2 based on the liquid level detection information on the upper limit of the contained liquid.
Control valve S of the lowest liquid level
2 indicates that the fine particle-containing liquid 2 in the tank 3 is reduced,
Is blocked by the light shielding plate 33, and the liquid containing fine particles is detected based on the liquid level detection information that the liquid level in the tank 3 has reached the specified minimum liquid level (liquid level detection information on the lower limit of the contained liquid). The on / off valve 9 of the liquid supply line 8 is controlled to be ON so that the supply of the liquid 2 is restarted.

Further, the position detecting means A having the above-mentioned sensors S1 and S2 detects the occurrence of an abnormal situation based on the detection of the liquid level outside the upper and lower limits of the stored liquid. It stops the driving of the dispersing means 37 (see FIG. 2) by the sonic transducer, stops the driving of the particle size distribution measuring device itself, or notifies the occurrence of the above abnormal situation. Control means 38 are linked.

That is, when the sensor S2 detects the lowest liquid level, the on-off valve 9 is turned on to supply the fine particle-containing liquid 2 to the tank 3, and the float 28 rises with this liquid supply. Normally, the sensor S2 does not immediately detect the lowest liquid level. Then, when a predetermined time has elapsed and the sensor S1 detects the maximum liquid level, the on-off valve 9 is turned off, and the sensor S1 normally detects the maximum liquid level.

Here, if the supply of the fine particle-containing liquid 2 from the liquid supply line 8 is continued due to some trouble, despite the fact that the sensor S1 detects the liquid level at the upper limit of the contained liquid, the float 28 and hence the light shielding plate 33 rises (the phantom line X in FIG. 3).
Indicated by ), The sensor S1 is immediately
No. 3 is no longer detected, and based on this, the liquid level exceeding the upper limit of the contained liquid is detected. If the liquid level continues to drop, float 2
8 and the light-shielding plate 33 descends (indicated by the imaginary line Y in FIG. 3), and the sensor S2 does not detect the light-shielding plate 33 even after the predetermined time has elapsed. The liquid level detection is performed below the lower limit of the stored liquid, and the occurrence of an abnormal situation is detected by the control means 38 based on the detection of the liquid level falling outside the upper and lower limits of the stored liquid.

According to the liquid level detecting mechanism 10 having the above structure, the lifting guide 32 of the float 28 is disposed outside the tank.
By preventing the slide part of the float 28 from being immersed in the liquid 2 containing fine particles, the trouble caused by the fine particles in the liquid entering the slide part of the float 28 can be solved. In addition to the liquid level control based on the detection, the control of the overflow of the fine particle-containing liquid 2 and the prevention of the abnormal shortage of the liquid are properly performed in a highly reliable state.

In the above-described embodiment, the float 28 is provided so as to be slidable in the vertical direction so as to detect the maximum liquid level and the presence or absence of the liquid. However, as shown in FIG. A bracket 31 is arranged outside the tank 3, and a float 28 floating in the fine particle-containing liquid 2 is rotatably provided around a horizontal axis 39 provided on the bracket 31, and a light shielding plate 33 is provided on the float 28. On the other hand, the highest liquid level detection sensor S1
Sets of photodetectors 3 constituting the liquid presence / absence detection sensor S2
The liquid level detecting mechanism 10 may be configured by disposing the brackets 5 and 36 on the bracket 31.

In FIG. 5, when the float 28 is drooping under its own weight, an abnormal liquid shortage level detection is performed. Liquid level detection, and in the state where the float 28 is further raised, the fine particle-containing liquid 2
Is caused to perform liquid level detection of overflow.

In this embodiment, the liquid storage tank 3 is installed obliquely in order to perform the liquid level detection in a state where the amount of the stored liquid is small, but this is not an essential requirement. Needless to say.

In each of the above embodiments, the light shielding plate 3
3 and the photodetectors 35 and 36, two sets of sensors S1,
The configuration of the sensors S1 and S2 can be variously modified, for example, by replacing the light shielding plate 33 with a magnetic material and replacing the photodetectors 35 and 36 with proximity switches.

Further, when controlling the liquid level of the upper and lower limits of the stored liquid, a sensor of a type for detecting the fluctuation of the liquid level of the stored liquid in the liquid storage tank with a certain width is used as a sensor of the position detecting means used therefor, It is possible to use one liquid level control sensor that stops and restarts the replenishment of the liquid containing fine particles based on the detection of the upper and lower liquid levels of the stored liquid.

[0049]

As described above, according to the present invention, the float is provided so as to be slidable or rotatable outside the tank so that the slide portion or the rotatable portion of the float is not immersed in the liquid containing fine particles. As a result, the trouble caused by the intrusion of fine particles in the liquid can be reliably eliminated, and as a float type liquid level detecting mechanism with a low cost structure, not only the liquid level control of the upper and lower limits of the contained liquid, but also the fine particles It is provided that the control of the overflow of the contained liquid and the prevention of the abnormal liquid shortage are appropriately performed in a highly reliable state.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a laser diffraction type particle size distribution measuring device.

FIG. 2 is a supply system diagram of a liquid containing fine particles.

FIG. 3 is a configuration diagram showing a float elevating type liquid level detecting mechanism.

FIG. 4 is an explanatory diagram of a sensor configuration example.

FIG. 5 is a configuration diagram illustrating a float rotation type liquid level detection mechanism according to another embodiment.

FIG. 6 is a configuration diagram showing a conventional float elevating type liquid level detecting mechanism.

FIG. 7 is a configuration diagram showing a conventional prism type liquid level detection mechanism.

[Explanation of symbols]

2 ... Particle-containing liquid, 3 ... Liquid storage tank, 28 ... Float, 32 ... Elevation guide, 39 ... Horizontal axis, S1 ... Control sensor for maximum liquid level, S2 ... Control sensor for minimum liquid level.

Claims (5)

[Claims] 1. A liquid level detection mechanism for a liquid containing fine particles in a liquid storage tank, comprising:
Fine particles characterized by being provided so as to be slidable along an elevating guide disposed outside the liquid storage tank and having a position detecting means for detecting a rising / lowering position of the float caused by fluctuations in the liquid level outside the liquid storage tank. Liquid level detection mechanism for contained liquid. 2. A mechanism for detecting the level of a liquid containing fine particles in a liquid storage tank, wherein the float floating on the liquid containing fine particles is
The liquid storage tank is provided so as to be rotatable around a horizontal axis, and a position detecting means for detecting a rotation position of the float due to a liquid level fluctuation is arranged outside the liquid storage tank. Level detection mechanism for the liquid containing fine particles. 3. The control device according to claim 1, wherein said position detecting means stops the replenishment of the liquid containing fine particles based on the liquid level detection of the upper limit of the contained liquid, and a liquid sensor containing fine particles containing liquid based on the detection of the liquid level of the contained liquid lower limit. 3. The liquid level detecting mechanism for fine particle-containing liquid according to claim 1, further comprising a control sensor for controlling a minimum liquid level for resuming the supply of the fine particles. 4. A liquid level control sensor according to claim 1, wherein said position detecting means comprises a maximum and minimum liquid level control sensor for stopping and restarting the supply of the fine particle-containing liquid based on the detection of the upper and lower liquid levels of the contained liquid. The described liquid level detection mechanism of the fine particle-containing liquid. 5. The liquid level detection of a fine particle-containing liquid according to claim 3, wherein the position detection means detects occurrence of an abnormal situation based on detection of a liquid level outside the upper and lower limits of the contained liquid. mechanism.