JP2787656B2 - Method and apparatus for analyzing particle size within fine-grain range - Google Patents

Abstract

In order to provide a method for grain-size analysis in the fine and very fine range by means of a gas-jet screen, the screening material being delivered onto the screen fabric, a gas jet being blown through the screen fabric and the screening material by means of a slit nozzle (2) rotating underneath the screen fabric, fine fractions being entrained by the gas stream and being transported by the latter in the opposite direction through the screen fabric to a discharge orifice located underneath the screen fabric, the said method allowing exact and accurately reproducible measured values, it is proposed that the gas stream be recorded quantitatively and be kept constant over the course of the screening operation. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for analyzing particle size within a range of fine particles and fine particles by using a gas flow type sieve. The gas stream is blown through the sieve cloth and the sieve by means of a channel nozzle rotating downwards, the fine-grained components are entrained by the gas stream and conversely by the gas stream through the sieve cloth. It relates to a device adapted to be conveyed to a lower outlet and to a device for carrying out the method.

[0002]

2. Description of the Related Art So-called laboratory air-jet sieves having a strainer held in an instrument casing are known in the prior art. An air supply port is pouring below the strainer. The groove-shaped nozzle connected to the air supply port is rotatably supported in a sieve casing and is electrically driven. This channel-shaped nozzle rotates at a fixed rotation speed below the sieve cloth of the strainer, and the sieving loaded in the sieve cloth swirls and rises. The supplied air is discharged through a discharge fitting tube, and the fine-grained component is discharged through the discharge fitting tube. The fine-grained component is entrained by an air stream and conveyed through a sieve cloth. The strainer is closed with a lid. In addition, the device is equipped with a mechanical timer. The sieving time can be adjusted via this. Furthermore, indirect air volume adjustment is performed by an outside air restrictor provided in the blower connection port or by a rotational speed setting device separately provided in the negative pressure generating assembly, and the assembly is fitted with an air discharge fitting of the device. Connected to the tube.

Conventional devices of this kind for laboratory applications are relatively inaccurate, on the one hand, resulting in inaccuracies in that mechanical timers have a slight adjustment and repeatability, and, on the other hand, indirectly. Only an airflow measurement is taken,
As a measure for adjusting the air amount, the negative pressure at a limited location in the exhaust passage is used. However, this negative pressure is dependent on the geometry and does not accurately infer the process-critical parameters. As a result, the measurements are only approximately comparable on the same instrument, and inferring the product load is only poorly possible from experience.

[0004]

Given this prior art, the object of the present invention is to provide a method and a device for implementing this method that enable exact and accurately reproducible measurements. .

[0005]

The solution according to the method of the present invention is specified in claims 1 to 8. The solution according to the device for this problem is specified in claims 9 to 16.

According to the invention, the disadvantages of regulation accuracy are eliminated by precisely detecting the charge air volume or by controlling the volume flow of the air charge. The gas supply amount can be detected by a bench lily nozzle and a differential pressure measuring device provided in the nozzle. However, other types of flow measurement can also be used, for example flow measurement with a Prandtl tube, a hot wire or a measuring turbine. To ensure measurement accuracy, the humidity and temperature of the supply gas are also detected (gas, in this case, in particular, also air).

The feed rate is continuously adjusted to the target value by changing the fan speed, depending on the measured and corrected volume flow.

A blower can be used in an intake operation or a compression operation. In the intake operation, the blower is mounted on an exhaust port, and in the compression operation, the blower is mounted on an air supply port. Rigorous and reproducible measurement of the amount of gas flowing through a channel nozzle, besides the general requirements for the best analytical quality, is of utmost importance in allowing the sieving results of different instruments to be comparable. Otherwise, particularly in the case of products which are sensitive to attrition and which can be ground, serious errors in the results can occur.

The stepless change in the number of rotations of the nozzle and the change in the shape and size and the rotation direction of the nozzle aim at the same direction.
The number of rotations of the nozzle is an important criterion for the load time and load frequency of the sieved product. The nozzle can be replaced with a nozzle with a different groove geometry or a multi-arm nozzle for product adaptation.

[0010] While it is conventionally known to seal the strainer purely within the instrument to the instrument casing, pure static sealing often results in leaks, and therefore, incorrect air supply,
This also distorts the measurement results.

The compressed air-loaded annular tube provided according to the invention eliminates this disadvantage and allows a reliable sealing of the strainer, and thus the sieving chamber, to the instrument casing, even in the case of large strainer tolerances. This is an essential prerequisite for a rigorous analysis. In one embodiment of the invention, a diaphragm compressor for generating pressure can be used, the compressor being switched such that upon shutoff of the compressor, the annular tube is switched to pressureless by a valve. Can be. In this case, the strainer can be easily removed and reinserted without expending large forces.

Changing the height and shape of the sieving chamber by changing the sieving chamber cover (lid) also helps to change the product load.

The lid to be inserted is preferably flat. However, the lid can also be concave or convex and / or be provided with a structured surface in order to properly regulate and control the flow. The sieving chamber is sealed with an inflated rubber cord or flat gasket.

In order to achieve comparability of the measurement and analysis results, it must be ensured that the humidity and temperature of the media causing the sieving are also detected and controlled. The control can be performed by a heating element, a dryer or an air humidifier provided in the preceding stage. These components are included together in the calculation of the air volume by means of temperature and humidity measurements and the displayed values are corrected. Furthermore, they
It is integrated into the process control system for proper conditioning of the sieve. In the case of a hygroscopic product, the air can be preheated to reduce the relative air humidity, thus providing sieving. In the case of electrostatic charging, the charging of the sifted material can be reduced by increasing the air humidity. The measurement time is pre-adjusted and strictly adhered to in seconds. This is particularly important for products that are sensitive to dispersion and must not be exposed, for example, to high mechanical loads. In this case, some products only withstand a sieving time of one minute, so incorrect timing control significantly impairs the sieving result.

In order to keep the sieving time as short as possible, the exhaust stream is monitored optically and the particle stream is measured. If a specific debris criterion is met, for example the 0.1% per minute criterion specified in DIN, the measurement is terminated after an adjustable wake time. In this case, it is particularly advantageous to perform the measurement without a set time, and thus to automate the measurement sequence.

In order to process large amounts of information and to be able to perform various functions reproducibly, all control of the apparatus is performed by an electronic single-chip computer control system. This control system includes necessary hardware and software. The display of adjustment values and measured values is done digitally and can be read on an illuminated liquid crystal display. Moreover, the single-chip computer realizes the RS-232 interface, through which print output of records and input / output of a PC are possible. Due to these interfaces and the above-mentioned technical arrangement of the laboratory sieving machine, this system still has to automate the strainer exchange and weighing only. Element.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS The schematic embodiment shown in the drawings is described in more detail below.

The analytical sieving machine comprises a sieving machine casing 1 in which a channel-shaped nozzle 2 is held rotatably and can be driven via a drive motor 5. A strainer 3 removably provided above the channel nozzle 2 is closed by a sieving chamber lid 4. A bench lily nozzle 6 is connected to the air inlet pipe 7, from which air is supplied to the channel nozzle 2. Reference numeral 8 denotes an intake pipe through which supply air is sucked. Numeral 9 is an annular tube gasket which can be inflated by a compressor for sealing purposes and evacuated for replacement of the strainer 3. In the inlet pipe 7, as shown in FIG. 2, the humidity sensor 10 and the temperature sensor 1
1 and the signal detection board 12 are integrated. When operating the analytical sieving device, the lid 4 is first removed, the sieved material is poured into the strainer and the lid is tightly closed again. Subsequently, compressed air is supplied through the inlet fitting tube 7 or suction air is sucked into the apparatus through a suction member connected to the suction fitting tube 8. The amount of air flowing in at the point 7 is detected in the area of the bench lily nozzle 6 by measuring the differential pressure at this nozzle. Further, the relative air humidity and the supply air temperature are measured by the humidity sensor 10 and the temperature sensor 11. As long as these measurements do not match the target values (set), the flow rate of the supply air is reduced or increased until the target values are reached, the air humidity is increased or decreased, and the temperature is also increased or decreased. Can be

The supplied air then passes through a channel-shaped nozzle 2, by means of which the air passes through the sieve cloth of a strainer 3 from below. In this case, the sieving material placed on the sieve cloth is also passed through, the fine-grained components are entrained by the air flow, are sucked downward through the sieve cloth in the opposite direction and are discharged from the suction fitting tube 8.

FIG. 4 shows the logical combination of the input value, the measured value, and the control value by the single-chip computer.
The differential pressure, the temperature, the relative humidity, and the number of rotations of the nozzle are detected as measured values. The sieving time, the volume flow rate, the air temperature, the nozzle rotation speed, and the nozzle rotation direction are input as input values. Aspirator rotation speed, nozzle motor (nozzle drive motor) voltage, heating voltage of heating device, compensator voltage for inflating the annular tube gasket, and operation time are output as control values by a single chip computer. .

Thus, an accurate and repeatable sieving analysis can be performed. Moreover, as a result of the arrangement according to the invention, the device can be used as a component in an air-jet automatic sieve analyzer, the analysis process being controlled via a computer, with a slight change of the strainer and a proper metering. Only have to automate.

The present invention is not limited to this embodiment, but can be variously modified within the scope of the disclosure.

All novel and combined features disclosed in the specification and / or drawings are considered essential to the present invention.

[Brief description of the drawings]

FIG. 1 is a central sectional view of an analytical sieving apparatus.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is another partially enlarged view.

FIG. 4 is a principle diagram of control of a single chip computer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 3 Strainer 4 Lid 5 Electric motor 6 Supply gas detection device 7 Gas inlet 9 Annular tube gasket 10, Sensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 15/02 B07B 11/04 B07B 4/08

Claims (17)

(57) [Claims] 1. A method for analyzing particle size in a fine-grained / fine-grained range by means of a gas-flow sieve, wherein a sieve is fed onto a sieve cloth and is rotated below the sieve cloth. By means of a nozzle, a gas stream is blown through the sieve cloth and the sieving material, fines components are entrained by the gas stream and conversely through the sieve cloth by the gas stream, at the outlet below the sieve cloth. in those and summer as conveyed towards, wherein the gas flow is detected the amount is kept constant during the course of the screening process. 2. The temperature and / or humidity of a supplied gas stream is detected and controlled to a target value.
The method of claim 1. 3. The supplied gas is cleaned by a filtration device.
Characterized in that it is in the method according to claim 1 or 2. 4. The method according to claim 1, wherein the sieving time is set and maintained in seconds.
A method according to one of the preceding claims. 5. The method as claimed in claim 1, wherein the amount of particles in the exhaust gas stream is determined and a debris criterion for analysis is derived therefrom. 6. The method according to claim 1, wherein the data acquisition and the target value control are performed digitally by a single-chip computer control system. 7. The method according to claim 1, wherein the measurement results are recorded by a standard data interface and a printer or other storage device. 8. The method according to claim 1, wherein the control of the machine and the recording of the data are performed by a computer via the same interface. 9. A sieving machine comprising a strainer , a groove-shaped nozzle driven and rotated by an electric motor , a gas supply device, and a gas outlet, according to claim 1. In the apparatus for performing the method, the gas inlet (7) is provided with a supply gas amount detection device (6) , and the control device is connected to a device for generating the supply gas flow and keeping the gas amount constant. An apparatus characterized in that: 10. A supply gas amount detecting device (6) comprising:
Lily nozzle and differential pressure measurement provided on the bench lily nozzle
Measuring device, or Prandtl tube, or hot wire flow meter, or measurement
10. The method according to claim 9, wherein the turbine comprises a turbine.
The described device . 11. A sensor (10, 11) for detecting humidity and temperature, and a heating device and a humidifying device for a supply gas connected thereto are provided in a supply gas flow. An apparatus according to claim 9 or claim 10 . 12., characterized in that the preliminary filter is mounted in the feed gas stream, according to claim 9 or 10 or 11
An apparatus according to claim 1. 13. analytical measurement time device is in the form of a single multichip-computer control system, and / or, characterized in that provided in the form of a timer with seconds indicator, according to one of claims 9 to 12 Equipment. Characterized in that 14. A device is a component of a gas flow type automatic sieve analyzer, the preceding claims 9 13
An apparatus according to one of the preceding claims. 15. The grooved nozzle (2) is held exchangeably and can be driven by an electric motor (5) whose rotation speed and direction can be changed. br /> system of any one of 14. 16. The strainer (3) is constructed so as to be replaceable and can be sealed to the device casing (1) by means of an annular tube gasket (9) connected to a ventilation generator. , Claims 9 to 15
An apparatus according to any one of the preceding claims. 17. A lid (4) for closing a strainer (3).
Device according to one of the claims 9 to 16 , characterized in that is configured flat, concave or convex.