Equipment for analysing sound produced by particles

(54) NAME Equipment for the investigation of particles in loose materials (56) PUBLICATIONS Cited: - - - (57) SUMMARY:

The invention relates to an apparatus for particle analysis in which a sample with grains greater than 0.5 mm can be examined for the number, size distribution, shape and, to some extent, characteristics of these grains, by rotating a drum in which the sample is rotated and the sample is thereby exchangeable. grids / mesh are forced into the center axis of the cylinder so that each particle falls through the grate / mesh holes and then freely against the wall or bottom of the drum, thereby producing impact sound whose position; frequency and strength provide information on the number of particles and possible sorting in terms of size or elongation, the appearance of the grid / grid's equal / different size and uniform / different holes. Several different grids / grids can then be used for a particular material, and the results are compared. The sounds from the particles' fall to the drum are recorded by microphones and computer processed so that particle counting and other particle analysis can be done regarding grain size distribution, elongation or impact sound, which depends on the particle's sound velocity properties, and the sludge content.

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The numbers in brackets indicate international identification code, INID code. Letters in clamps indicate international document code.

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The invention relates to an equipment according to the preamble of claim 1.

Materials with different sized particles in the range of 0.1 mm to 5 cm can be examined by screening on cloths with different mesh sizes. After weighing the different fractions, the grain distribution can then be determined.

Thus, in the quality classification of natural gravel and rock crushing, such screening is a standardized method, with the designation SS 13 21 12. Similar methods are also used internationally.

In the analysis as above of e.g. a natural gravel material has several disadvantages in the present method. Testing can only take place in a laboratory environment, and the test must be dry. The screening is carried out with special machines such as noise and the handling generates dust. In case the sample was originally moist, it must be dried. From sampling to finished grain distribution analysis with a sieve curve, it can thus take a number of hours.

Since only dry samples can be analyzed, problems arise when the material contains such fine-grained components that they clump together during drying. The sample must then be screened, which is additional time and labor intensive, and dried, to be finally screened, weighed, etc.

In some cases, the control of an ongoing production is thus carried out with such a considerable delay that materials for SEK 10,000 can have been produced, before correction based on the test results can be made.

The technique of analyzing the sound of particles in a rotating drum is described, among other things. in U.S. Patent 4,024,768, patent application filed August 2, 1976, by the inventors MF Leach and GA Rubin. According to this technique, the internally smooth drum is inclined and the particles move primarily towards each other as the drum rotates. The resulting sound is recorded with a single microphone and then amplified and analyzed.

European patent EP 0 309 155 A2, with application registered on September 22, 1987, by the inventors RM Belchamber and MP Collins, describes the technique of analyzing the sound during ongoing painting from a mill, which is in the form of a rotating, internally smooth drum. The sound is then recorded and analyzed with computer technology.

The object of the invention is primarily to avoid completely the disadvantages of the standard method of grain size distribution analysis with another technical approach. Information on the size of a particular particle is transmitted to acoustic pulses suitable for data processing. In this way, the capacity of data technology for information processing can be utilized. This gives completely

509 447 new possibilities, especially in terms of speed of analysis, but further information can be obtained other than just the size of the particles. In addition, the accuracy as well as the safety of the analysis can be increased, and materials larger than 5 cm can be easily analyzed.

The invention may be tested with mobile equipment, e.g. at the production site, which further reduces the total waiting time for the analysis. Due to the design of the technique, all more fine-grained samples should be examined in water, which completely eliminates the problems of the standard method with moist samples that need to be dried, or muddy samples that need to be washed. The water can be added without hindrance with freezing point lowering means, so that analysis can be done outdoors even in cold weather. Rough samples can be analyzed optionally wet or dry.

A sample can be analyzed several times to achieve increased control, and several samples from a given material can be analyzed in rapid succession to increase the assay reliability. Large sized equipment can analyze very large samples; all result in higher analytical accuracy than with SS 13 21 12. One and the same sample can be analyzed with different designed grids / grids, thus obtaining increased information on the material's properties, e.g. medelelongation.

The grille / net can be formed with round or equally square stitches, or with elongated holes, or in the form of parallel rods which are different in length and thus give increased gap width further away from the wall of the drum.

The invention can measure the number, size and elongation of particles larger than 0.5 mm, and provide information on the sound velocity of particles larger than 10 mm, in a material. Survey can thus be carried out on e.g. soils, materials for road construction, materials for the manufacture of concrete, but also other materials in which any of the above particle properties may need to be investigated, such as grain and wood grain, or technical products such as lead shot.

Figure 1 shows the equipment. For a natural gravel material with, for example, particle size up to 20 mm, the cylindrical drum (1) can have the dimensions: length one meter and diameter 3 dm.

In several places, microphones (2) with wires (3,4) are attached to a chip or a small computer (5), which is attached to the drum. The drum is either open at the card ends or openable / closable through a door (6). Inside, a grille / net (7) sits out from the wall of the drum. The grid / grid may be proportionally short or so long that it adheres to the opposite wall. The grid / grid may have round, square or elongated holes. For analysis of the distribution of grain size, the grid / net has small holes near the bracket against the wall of the drum and larger holes further out from the bracket. There can be a series of different coarse grids for a particular measuring equipment, so that the grid / grid can be adapted to the material. The drum is suspended along the center shaft, with the possibility of turning it around, either manually or motor-driven. Along any portion, the drum may be provided with bumps internally. It is possible to construct the drum of sound-conducting material, which is divided by transverse layers of sound-insulating material, so that each individual sound impulse can be more easily identified.

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For coarse materials, the drum can be made large; there is no real limitation in this regard. Equipment on a much smaller scale than the standard case is also technically possible.

The sample is deposited in the drum and it is possibly filled with water and then sealed. For example examination of a soil type, the drum is first rotated a few turns for the sample to distribute, the fine material to be slurried in the water and lumps dissolved. Then, a few more turns are rotated during which the measurement takes place. As the drum is rotated, the sample will chase along the bottom until the grid receives. This lifts up the sample until it is lifted so high that it begins to filter down through the grid / net hole, first with fine-grained material, then gradually coarser. The defeat of e.g. A sand particle is thus characterized by its occurrence early, and close to the grid / grid, and also constitutes a slight sound impulse as opposed to a coarser particle. The particles can thus be calculated by counting the number of sound pulses, and in addition, the time state of the sound pulse in the sequence of sounds, as well as the amplitude and frequency of the sound pulse can be accurately recorded. Most microphones are mounted on the outside of the part of the drum where the inside is struck.

When the heaviest rock particles strike, sound is also obtained with microphones on the opposite side of the drum. These sounds are attenuated with an increasing sludge content in the water, so the water content of slurry of fine material can be estimated by comparing the sound following the metal drum with the sound passing through the sludge water.

By switching to different grids with different designs in terms of placement, size and shape of the holes, characteristic sequences of impact sounds are obtained for each material, e.g. that a material with high average elongation produces a different pattern of impact sound than a cubic, in case grids are used with elongated holes.

As the material rushes around on the bottom of the drum, characteristic sounds of each material type occur as the particles rub against each other, grab and release. The characteristic pattern of a particular material can be enhanced by unevenness on the inside of the drum.

Particles larger than 10 mm have impact sound for which analysis can be made of the sound velocity of the particle, which can provide information about the quality properties of the material.

Thus, the sequence of impact sounds, as well as the whole pattern of sounds obtained from a particular material, constitutes a very content-rich information suitable for computer processing.

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