DE2105607A1 - Method and device for sorting materials - Google Patents

Description

description
to the patent application

de-r Establishment public dite: AGENCE NATIONALE DE VALORIZATION DE LA RECHERCHE (A ~ N V A R), Tour Aurore PARIS-DEFENSE COURBEVOIE (Hauts-de-Seine) and

Soci§te Anonyme dite: CIMENTS LAFARGE, 28 rue Emile Menier, Paris, France

concerning:
"Method and device for sorting materials"

The invention relates to a method for sorting certain proportions of composite or heterogeneous materials on the basis of their magnetic properties, for example of rock, minerals or the like. The invention made possible relates in particular to a method and devices which make it possible to separate out certain undesirable elements from a mixture, which are sometimes usable for themselves, or to enrich certain materials with others and / or to improve their final quality by simple and safe elimination of various impurities, especially with regard to the manufacture of cement.

It often happens that rocks, minerals or mining material from mines or open-cast mines are not homogeneous, but are more or less rich in usable components, and also have parts that are more or less poor, sometimes even completely sterile, so that they can be excreted or separated

109848/1136

have to be worked. The rock or the minerals can also be accompanied by impurities or by elements which are more or less undesirable because they unite the quality exerting a changing influence on the end product. Finally, there are other materials of whatever origin, for example industrial products or consumer goods that are any major Have parts that you want to keep, others that you want to eliminate.

The most varied of mechanical, physical, optical, electrical, radioactive, chemical, physicochemical and other methods have been proposed to solve the problem posed by the present invention deals. Some of the devices designated for this purpose, called magnetic separators, work with the direct effect of a magnetic field in order to avoid certain components, in particular magnetic, to be eliminated. Many of these well-known procedures haban the disadvantage that they require complicated procedures and devices, and consequently expensive investments require. Some of them have proven unsatisfactory or lack the desired sensitivity, depending on the problem at hand.

It is known that all substances have to a greater or lesser extent the property that they become magnets when they are exposed to a magnetic field. The magnetization thus required can be a temporary induced magnetization which is proportional to the field to which the body is exposed and which disappears at the same time as the field disappears. The induced magnetization comes from paramagnetism or diamagnetism. When exposed to a magnetic field, other substances retain a remanent Aa.g netization when the magnetic field in which they were magnetized has been switched off. These substances, which have become permanent magnates, are referred to as ferromagnets. The quasi-entirety of the gas stones or minerals,

10 9848/1136

~ ³ 21Q56Q7

even those commonly referred to as amagnetic exhibit some ferromagnetism because they almost always are interspersed with more or less large quantities of strongly ferromagnetic minerals - sometimes only with traces, such as of Magnetite. Since these rocks or minerals were in the earth's field before they were taken, and since they may have been during the geological development were exposed to natural earth fields that differ greatly in terms of direction or intensity they are actual permanent magnets to varying degrees. It has of course already been proposed to use these magnetic properties of the substances to make the materials or to sort minerals, either by measuring their magnetic susceptibility on samples in the laboratory or by removing the magnetic particles using permanent magnets or electromagnets.

The first method allows the determination of very small magnetizations, only allows a statistical control,

tffr
which is also slow and, moreover, completely unsuitable for the continuous sorting of successive batches of heterogeneous material, element by element.

The second method only allows the excretion of parcels of material, whose susceptibility is relatively strong, and appears to be far too coarse and accordingly useless in general Case in which the susceptibility of the materials is too weak to be affected by a magnetic field which is even very strong can be eliminated.

While working on finding a simple and safe solution for the task outlined above, one had the basic idea on which the invention is based, for this Purpose to take advantage of the changes in the magnetic field caused by certain constituents or proportions of materials in their vicinity

109848/1136

21056Q7

which are to be treated to be such a magnetic one Enable sorting. In other words, in order to achieve the desired sorting, one proceeds according to Invention so that the permanent magnetization of the materials or an induced magnetization is exploited, that the mass of materials to be sorted continuously presents two organs responsive to magnetic fields which are generally referred to here as detectors, and the sorting signals after certain processing, which are sent out by the organs, tr devices for the separation between the magnetized parts and the the least magnetized parts of the materials to be sorted, feeds. It goes without saying that these sorting signals can of course also be used to determine the proportions of the Indicate constituents that are present in the minerals or other materials.

It may sometimes be the case that the magnetization of the materials is too low for easy detection; about that In addition, the direction of magnetization of the individual fragments is irregular depending on how the materials were handled beforehand were subjected, for example during dismantling, and thus the shape of the signal from the sorting device is influenced. In addition, the fragments can have different field directions pass the detector at the same time, whereby the intensity of the sorting signal is reduced or even canceled will.

IM taking this into account can be carried out in accordance with a further training course According to the invention it can be provided that the materials are magnetized before they are presented to the detector by being exposed to an artificial magnetic field, which is much more intense than the earth's field, and through electromagnets with DC excitation or by strong permanent magnets will, or, preferably, by the materials

109848/1136

21Q56Q7

be demagnetized beforehand by exposing them to an alternating magnetic field, either immediately before they be magnetized again, or in a previous degaussing operation.

In the case of paramagnetic or diamagnetic materials where the magnetization is only induced and temporarily it is preferable to continuously present these materials in an intense magnetic field that is artificially created by means of Electromagnets or strong permanent magnets are generated; in this case the detector is directly connected to the electromagnet or permanent magnets, and placed as close as possible to the materials in their air gap. The ones from the materials magnetization assumed during its passage through the air gap acts on the detector both in the case of induced magnetization and in the case of remanence. This training, which is required for paramagnetic or diamagnetic materials is also useful for ferromagnetic ones Materials, whereby permanent magnets are preferably used rather than electromagnetic magnets; if namely the level of the excitation direct current is not kept very strictly constant for the electromagnets, there are changes in the magnetic field, the the detector or detectors are exposed, and these changes can be much larger than those actually detected should be. It goes without saying that the materials to be sorted can also be demagnetized in this case, before they enter the air gap of the electromagnet or the permanent magnets.

An apparatus for carrying out the method according to the invention essentially comprises according to a development of the Invention a support for the mass of material to be treated, at least one magnetic field detector close to this support for the generation of a sort signal in response to a magnetic signal from the immediately adjacent ground

109848/1136

proceeds, it also includes means for causing relative deflection of the mass and detector, as well Means for ejecting or separating the parts that have sent a magnetic signal according to the level of these proportions, which ejection devices are controlled by the sorting signal of the detector after a delay, which depends on the speed of the relative displacement is chosen between the mass and the detector. The sorting signal is preferably sent to the ejection devices via appropriate delay elements by means of an amplifier connected, and this connection is made at the exact moment in which the portion to be sorted begins to run past the detector, and the connection will be interrupted when that portion passes the detector has finished.

The device may have means for demagnetizing the mass, which mass, for example, crushes or can be pulverized, and the demagnetizing device can be arranged in front of the magnetizing device, which in turn is arranged in front of or at the level of the sorting detectors.

The support for the mass to be treated can be a conveyor belt, which is preferably on its surface with a certain number of parallel rows of recesses is provided, which are arranged at the same distance and in which there is always one element of the mass. The conveyor belt can

can also be smooth and the elemjiente of the earth preferably on it be arranged in parallel rows, but without being arranged equidistantly in each row. On one of these smooth surface can build up an even height of powdered material. In any case, the tape is by means of known devices to a fairly constant

109848/1136 _ _? _

Speed driven. Preferably at least the Support rollers and supporting members or rollers made of non-magnetic material, v / ie tetrachlorofluoroethylene, which is under various Trade names is available.

The magnetic field detector can be constructed from various devices which are suitable for a change in the Address the magnetic field and thus generate a sorting signal, which in turn is useful, an ejection or separation mechanism to control, for example, magnetometers with a moving magnet, induction-based devices, can be used Hall effect based, nuclear magnetic resonance based, optical pumping based or others. In practice you have to go for a normal Function under difficult operating conditions, such as those in mines and open-cast mines, preferably a robust detector chosen that is insensitive to strong temperature fluctuations, mechanical vibrations, electrical or magnetic interference fields, the origin of which can be a few meters away from the device, e.g. motors, Wagons, trucks, or piles of magnetic materials. The detector is also supposed to have a very high sensitivity only compared to magnetized materials, which in the next Close by so that its sorting effect is not noticeably reduced. A differential arrangement using induction processes makes a very useful detector under the conditions indicated above.

Such a detector can comprise at least one coil with or without a magnetically permeable core, which is located above the conveyor belt is arranged, and very close to the same, for example horizontally, with its larger dimension transverse to the Tape; this "lower" coil is advantageously combined

109848/1136

by a very solid connection with at least one "upper" coil, which is constructed identically and is located above the lower spool and the conveyor belt are at a certain distance from the latter. The top and bottom coils are connected in series so that the induction flux, which is of the Material placed on the belt between them emanates, has the same direction and is additively superimposed. At least a third coil is arranged in some form parallel to the other two and is securely connected to them, as well

h also connected in series with the other two coils such that the induction flux across the three coils is zero when the external field is uniform; this third coil is preferably arranged at some distance above or below the first two coils in such a way that the induction flux which penetrates the latter and emanates from the material on the conveyor belt is minimal in comparison with the flux which the first two coils interspersed. Under these circumstances, vibrations of the detector, which is formed from the three fixed coils, do not cause a parasitic signal. Likewise, displacement of an iron mass such as a wagon, truck, etc. that occurs at a distance from the detector which is great

^ is convenient compared to the overall dimensions of the detector no disturbance emerges, and the same applies to natural fluctuations in the earth's magnetic field, as well as to magnetic ones Storms.

Instead of using two identical or equiv ^ Lente detectors, which are mechanically firmly connected to one another, and are switched against one another in such a way that parasitic phenomena exert an overall effect of zero on the overall system in the environment, one can advantageously use a self-compensating effect Use a detector that is sensitive and has an increased separation effect; such a detector comprises according to the invention

109848/1136 - 9 -

21Q5607

a magnetic circuit made up of two parts or identical cores with two identical air gaps, two identical windings, which are connected in series and each sit on a part of the magnetic circuit, as well as to a differential amplifier are connected to bring the signal of the windings to a level and impedance that are usable.

The sorting signal picked up at the output of the detector can be further processed by means of known arrangements to ultimately control the ejection mechanism. It it is interesting to integrate the signal because the signal is proportional to the change in flux over time and therefore the integral becomes proportional to the flow itself. Depending on whether the entire induction flow integrated in this way has a certain exceeds predetermined level or not, there is an actuation of the ejection mechanism or not. The same The process starts again at the following mass fraction and so on.

Instead of "fixedly arranging the detector", it can also be arranged circumferentially and comprise a small coil which is arranged under the conveyor belt and revolves around a horizontal axis which runs transversely to the conveyor belt by means of a small motor with a high speed of a few tens of revolutions per second, for example, resulting in a small alternating current generator whose electromotive force is proportional to the induction flux emanating from the transported materials, it being understood that during the revolution the winding is alternately parallel and perpendicular to the plane of the conveyor belt above-mentioned embodiment with a fixed detector, one can also this detector to assign a second, identical detector, which is arranged above the conveyor belt and whose axis of rotation is firmly connected to the, so that the rotation is both exact synchronization of the first detector, and finally can be advantageous -

109848/1136

- Io -

It is advisable to provide a third detector, driven parallel to the other two by one of the two axes of rotation, so that parasitic disturbances are eliminated, since the induction flux which penetrates all three coils connected in series cancels one another. By means of brushes on collectors on the small alternating current generators, these are connected to the inputs of an amplifier, followed by a rectifier, which is preferably synchronized in order to obtain a direct voltage or rectified potential difference w that is proportional to the magnetic induction of the materials in walk past a given moment in the working area of the detector. If the materials are uniformly distributed in pits, the same case results as in the case of the fixed detector by integrating the DC potential difference.

The use of the rotating detector is special advantageous if the material is not arranged in evenly distributed depressions of the conveyor belt, as it is, for example This is the case with finely ground materials or powders, which appear as a uniform layer on the entire surface of the fc tape. It will be understood that in this case a fixed detector may be ineffective as it is more uniform Magnetization of the material does not change the magnetic flux at all results. In the case of the rotating detectors, on the other hand, the instantaneous intensity of the derived signal is already without every integration is suitable for activating the ejection mechanism after a certain threshold value has been exceeded.

In any case, the detectors must be constructed in such a way that a uniform magnetic field is constant or variable and none at all Signal results, and that the orbits of the detector in the earth's field under the influence of inevitable oscillations of the wind etc.

1Q9848 / 1136

if they cannot cause a parasitic signal. In addition, all measurements must be made in such a way that the The signal generated by the materials passing in the immediate vicinity of the detector is not disturbed as a result of the Magnetization of materials that have just passed under the detector that will pass in the next instant or moving away from or approaching it when the device has been made large enough to to treat several independent sorting channels simultaneously with several separate detectors, each of which has its own Detector and have their own ejection system.

The invention will be explained in more detail below with reference to the accompanying drawings.

Fig. 1 shows in semi-schematic perspective Representation of a system for carrying out the method according to the invention,

Fig. 2 is a perspective view of an additional magnetizing device,

Fig. 3 is a cross section through the device of Fig. 2,

Fig. 4 is a section along line IV-IV of Fig. 3,

Fig. 5 is a perspective view of an embodiment a fixed detector that is used for the Sorting of certain objects is designed with remanent magnetization,

Fig. 6 is a cross-section through the detector of Fig. 5,

Fig. 7 is a section along line VII-VII of Fig. 6;

8 is a block diagram of one embodiment

for a circuit which corresponds to the detector according to Fig.

is to be assigned,

109848/1136

- 12 -

Fig. 9 is a section through a circumferential

Detector specially designed for sorting finely divided or powdery Materials,

FIG. 10 shows the block diagram of an electronic circuit which can be assigned to the detector according to FIG is,

11 shows an example in perspective and schematically for an ejection mechanism,

Fig. 12 is a view of the mechanism of Fig. 11;

13 shows the basic diagram of another detector according to the invention,

Figs. 14, 15 and 16 illustrate the circulation of the magnetic flux

in the detector of Figl 13, depending on the direction of the field in which this is ordered,

17 is a section through a detector according to FIG

13 in a sorting device according to the invention,

Fig. 18 shows a section through a circumferential

Detector according to the invention offset bezeuch the materials to be treated.

One recognizes in Fig. 1 the perspective view of a system for performing the method according to the invention, which The system is intended for sorting crushed materials, such as stones, their dimensions, width, height, length in the order of magnitude of a few tens of centimeters.

- 13 -

109848/1136

The system includes a Iransportband 1, which by means of known and not shown means is driven for U-rotation around the cylinders 2 and 3; it gives the materials translational motion that is substantially uniform. To achieve high throughput, this is Tape sufficiently wide, for example on the order of Im, and the materials on it are in parallel rows arranged, for example ten rows, each about 10 cm wide, so that the best possible separation effect (sort stone around Stone) yields; this distribution in rows is ensured here by a gate arrangement 4 at the loading end of the conveyor belt.

The stones 5 accordingly present themselves one after the other in each row and pass one after the other Demagnetizer 6, a magnetizer 7, a detector 8 and a separating or ejecting device 9.

In the exemplary embodiment, the demagnetizing devices 6 and magnetizing devices 7 are only present once and assigned to all rows in such a way that a fairly uniform field extends over the entire width of the conveyor belt results. In contrast, the detectors 8 and the ejectors 9 each comprise a magnetic detector 10 and an ejector 11 per row.

As soon as a magnetic detector 10 detects a stone 5 that is to be discarded in the row that it queries it emits a signal that is deformed on the one hand and decelerated proportionally to the speed of the conveyor belt on the other 1 and the distance between the magnetic detector 10 and the ejector 11 to operate the latter.

- 14 10-9348 / 1 1 36

For this purpose, the detector 10 is connected to a switch box 12 which contains the organs and electronic circuits, which are designed for this purpose contains; as regards the necessary delay, it should be said that this means any delay line or by means of a memory, the duration of the delay being controlled on the speed of the conveyor belt via a link

The demagnetization device 6, which is not shown in detail, consists simply of coils which generate an alternating field, the maximum amplitude of which exceeds that of fields which the stones could previously have magnetized (generally the Erc / field). The amplitude of this field decreases _/ once the stones removed from the 6 ^ EntmagnetisierungseinriShtung and is negligible at the level of liagnetisiereinrichtung. 7

The magnetizing device, which is shown in FIGS. 2 to 4, comprises elongated 2-magnets 14 which are arranged vertically on both sides of the conveyor belt 1. The identical poles of these permanent magnets are connected to each other by legs 15 made of soft iron, which lie horizontally. Pole pieces 16 made of soft iron concentrate the field h in the air gap through which the materials 5 pass, v / obei the lower pole piece 16 is just below the conveyor belt 1 and the upper pole piece 16 ₂ about 10 to 15 cm above the conveyor belt 1 lies. The stones 5 are accordingly magnetized in the vertical direction, all in the same direction.

The detector group 8 comprises a magnetic detector 10 ₁

10 per row of stones 5 (see Figs. 5 to 7). Each detector 10 consists of a flat rectangular coil 17 from about 8 cm in length to, for example, 1 to 2 cm in width, which is arranged horizontally below the conveyor belt 1, wherein

109848/1136

- 15 -

the length extends across the conveyor belt. Another identical coil 18 is here advantageously exactly above the coil 17 arranged ten to fifteen centimeters above the conveyor belt. In each pair, coils 17 and 18 are fixed connected to one another in a structure 19 and connected in series with one another in such a way that the induction flux produced by the The stone located between them goes out, has the same direction and these rivers are additively superimposed. A third Coil 20 of any shape is parallel to the other two and firmly mechanically connected to them, also connected in series with those such that the induction flux across the three coils 17, 18 and 20 is zero when the external field is uniform is. This third coil 20 is arranged at a distance from the two first coils that the induction flux that passes through it and that emanates from the stone 5 on the conveyor belt is negligibly small in comparison with the flow which the two other coils 17 and 18 interspersed.

It can accordingly be seen that each row on the conveyor belt 1 is provided with a similar detector, and that the stability the entire detector assembly is secured in one block by the structure 19. You can optionally have a single Provide coil 20, which is assigned to each pair of coils 17 and 18 by appropriate decoupling.

Thanks to the stability of the assembly which is ensured in this way, vibrations of the coil assembly or displacements of iron masses such as wagons, trucks and the like occur at a distance from the detectors which is large in relation to the overall dimensions of the same, practically no interference; the same applies to fluctuations in the earth's natural magnetic field and to magnetic storms.

- 16 -

109848/1136

Under these conditions the passage gets a magnetized Stone 5 through the detector 10 of the corresponding row on the terminals of the assembly 17, 18, 20 of the coils, which form the detector, an electrical signal that can be processed in various ways in order to finally produce the To operate the ejector mechanism 11 of the corresponding row. The block diagram of Fig. 8 shows a circuit for this Processing with regard to the determination of certain objects. This circuit is in box 12 (Fig. 1). That Sorting signal from a detector 10 from the coils 17, 18 and arrives at the input of a preamplifier 21, after which it is integrated by means of an integrator 22, thus a potential difference is generated, which is proportional to the flux that passes through the detector 10 in question, since that in the the latter induced signal is proportional to the derivative of the induction flux with respect to time. If one assumes and this A prerequisite is preferably admissible, in order to really achieve an ideal sorting performance, that the stones 5 f are uniform are distributed on the conveyor belt 1 at equal intervals, for example by placing them in recesses of equal spacing, which are not shown are embedded, a gate 23 allows the integration to begin just at the moment in which a well, i.e. a stone, reaches the detector 10 and ends the integration as soon as this well reaches the detector leaves. The integrated signal is applied to a comparator 24. Depending on whether a reference level is specified and is fixedly selected by a circuit 25y is exceeded, the signal is passed on or blocked by comparator 24. When the signal is passed it is fed to a memory in delay line 26, which it restores after a delay during which the stone 5 that has been scanned is sent from the detector 10 to the Ejector 11 has been transported. This is accordingly controlled by the power amplifier 27.

109848/1136 - 17 -

The delay line 26 is formed here by means of a magnetic recording device with a self-contained one Magnetic tape or a magnetic tape loop. The delay required corresponds to the time required is that a point on the tape passes from the recording head 28 to the reproducing head 29, the distance between them measured in length of the band is adjustable. The transmission 13 (Fig. 1) forms a simple means of controlling the transport speed of the magnetic tape to make proportional to the speed of the conveyor belt 1 at any moment. The magnetic tape comprises at least as many lanes as there are rows on the conveyor belt. It can also have a permanent memory on an additional track for signals whose beginning and end represent the beginning and end of the passage through a recess on the detector assembly 8 over corresponds. These latter signals are read out by a further playback head 30 (which incidentally on the same block as heads 28 and 29); jV-e control the beginning and the end of the integration via the gate 23.

The advantage of this arrangement is that it is improved the signal ratio of the detector.

You can see that when the stones are lined up with one another follow the conveyor belt at different distances or even touch each other, it is no longer practical, the integration time to control the output signals. The comparator 24 accordingly receives a continuously variable signal which is different Has maxima and minima which follow one another when several magnetized stones follow one another. The reference level is set by the circuit 25 to an average level between maxima and minima. It will be easy to see that the level of these maxima and minima can change depending on the size and intensity of the magnetization of the trapped Stones and that some of them are not sorted out or in the

Opposite to be mistakenly sorted out; if a low ^y 109848/1136

- 18 -

Contamination is permissible without impairing the final quality of the products to be manufactured, taking into account the fact that it is generally the smallest stones that may escape sorting, this deficiency can advantageously be tolerated if it can simplify the system, not only in that the playback heads 30 can be saved as well as the gates 23 of FIG. 5, but also by the use of a conveyor belt which manages without special devices and which is able to deliver a higher throughput at a constant speed, which in addition also can be loaded relatively primitively, so that the profitability of the plant can be increased.

The rotating magnetic detector according to FIG. 9 comprises flat coils 2 ″ 31 which are arranged below the conveyor belt 1 are, one per row of "stones", as in the case of the coils 17 of FIG. 5; these coils 31 can about a horizontal axis 32 circulate, which liejt transversely to the conveyor belt and means a small motor 33 is driven at a relatively high speed on the order of several tens Revolutions per second. Each coil 31 forms a small alternating current generator whose electromotive force is proportional is the induction flux that emanates from the transported materials. Each coil 31 is, for example, a coil 34 and associated with a coil 35, which in turn are driven by an axis of rotation 36 and 37, which is rigidly connected to the axis 32 of the Coil 31 'is locked and accordingly in rigid synchronism with the latter revolves in such a way that the coils 31, 34 and 35 are parallel at every moment; The coils 34 and 35 play exactly the same role of superposition compared to the coil 31 or compensation \ tfie the coils 18 and 2O from Fig. compared to the coil 17. The coil 35 can here in the same way

- 19 109848/1136

be present only once and assigned to all pairs of coils 31, 34 by means of appropriate decoupling be. The synchronism of the three axes of rotation is ensured by gears 38 and 39. The structure 40 ensures the Stability of this assembly of detectors. Each coil is provided with a group of collectors on which, as with each Alternator, the induced electromotive forces are tapped by means of brushes.

One recognizes in FIG. 10 the block diagram of the electronic circuit which is to be assigned to the magnetic detector according to FIG is. The groups "" of revolving coils 31, 34 and 35 which form the detector 10 associated with each row provide a Signal which - as explained above - arrives at the input of a preamplifier 21 and then to a detector 41, preferably a synchronous detector such that a DC potential difference proportional to the induction of the materials is established which at that moment pass through the area of action of the detector. This potential difference is sent to the comparator 24 fed, where it is compared with a reference threshold, which in turn is determined by the circuit 25, exactly in described case of the fixed detector; the rest of the circuitry is the same as in the latter case. This encircling Detectors of Fig. 9 are sensitive to the induction flux itself which passes through them and not just to the derivative after the time. The arrangement of FIGS. 9 and 10 has a great advantage in the case where the materials are finely ground or are pulverized and present as a uniform layer on the entire surface of the conveyor belt; if in this If all of the material is magnetized uniformly, a fixed induction assembly 4 will not provide any change in the induction flux and would therefore be ineffective. A rotating detector, on the other hand, thanks to the fact that the signal obtained exceeds a has amplitude directly proportional to the flux without integration, a certain predetermined threshold and thus allows triggering of the ejection mechanism - goAO / iioe

- 20 -

It should be noted at this point that if a rotating detector for sorting certain separate Objects is used that rest in wells of the same distance, the system with the gate 23 for the signal - as above described - can still be used in the same manner as described above, for example for controlling the Duration of the detector 4l.

11 and 12 show a preferred ejection device for combination with a sorting system according to Fig. 1. In the example presented here, the sorting device is intended for sorting lime minerals, that have previously been crushed. It has been explained above that the stones 5 have a corresponding granulometry had been applied to a conveyor belt 1. They are shown in lines or rows in the longitudinal direction, below which the corresponding detectors 8 are arranged. Assuming a high selectivity of the detector 8 the interval between each stone is zero, i.e. that the stones practically touch each other. As soon as a to be sorted out Stone has been determined by one of the detectors 10, the emitted signal - as indicated above - is processed, then written into the memory on the magnetic tape by means of the recording head 28. The running speed of the magnetic tape is matched to that of the conveyor belt with the help of a torque converter and a corresponding multiplication. if the signal has been read by the playback head of the recording device (the position of this head is adjustable), a solenoid valve 42n of a ramp 42 is triggered, which is assigned to the detector 10, which the stone to be thrown has determined; this electrovalve 42n of known type releases a jet of compressed air 43. This jet of compressed air

- 21 -

109848/1136

directs the path of the stone 5 as it falls off the conveyor belt and the stone to be sorted out is thrown out of the normal path and thus eliminated. The ramp of solenoid valves 42 is fed by a compressed air source 44. Each valve is assigned to a track of the magnetic tape and accordingly one of the longitudinal rows on the conveyor belt, and thus also one of the detectors. A guide gate 45 is advantageous placed on the collecting tray of the products, with the stones to be thrown falling to the left, under the action of the compressed air jet 43.

Such an arrangement with compressed air has the advantage that it has very little inertia, and the stones Can sort out piece by piece.

You can of course use a different ejector, for example of the type that pushes it down transversely to the conveyor belt, but then a prior alignment of the stones in a single line is necessary, which of course the throughput of the entire system is greatly reduced.

The auto-compensated detector, as shown schematically in Fig. 13, is of the inductive type; it includes one Magnetic circuit 46 and two identical windings 47a and 47b. The magnetic circuit 46 comprises on the one hand two identical yokes 48a and 48b made of an alloy of high permeability and, on the other hand, two likewise identical air gaps 49a and 49b. A differential amplifier 50 serves to bring the signal of the windings to a level and an impedance of a usable size.

The windings 47a and 47b supply electromotive forces, each of which is proportional to the derivative of the magnetic induction flux with respect to time in the yokes 48a and 48b. the

109848/1136 " ²² "

Windings are connected in series so that their electromagnetic Superimpose forces additively as soon as a flux passes through the entire magnetic circuit in the same direction, while they superimpose subtractively when the two yokes 48a and 48b are traversed by rivers that are not in the same Senses circulate. This arrangement and the paired identity of the elements of the detector guarantee the compensation of the system for uniform ambient fields in the room in which the detector is located is housed.

Namely, when the detector is arranged with respect to a right-angled coordinate system (FIGS. 14, 15 and 16), detects one that a uniform field is variable. parallel to O-X obviously able to induce no electromotive forces in the coils 47a and 47b, since even under deformation by the magnetic circuit the field remains parallel to the plane of the turns of the windings.

A field which is variable parallel to OY is deformed by the permeable yokes (Fig. 14) in such a way that the turns of the windings 47a and 47b are indeed places of induction of electromotive forces, but due to the symmetry each winding supplies an electromotive force, whose resultant is zero because the fjiado. ABD and ACD present the same reluctance to the flux and enforce the same number of turns, and the same is of course true for the two windings connected in series.

From Fig. 15, it is understood that a field which is variable. parallel to O-Z, an identical one in each of windings 47a and 47b electromotive force is induced, but thanks to the series connection of the two coils in a corresponding sense there is also a result here Signal gives zero.

- 23 -

109848/1136

If the surrounding field has any direction with respect to the three axes mentioned above, it can always be decomposed corresponding to these three axes and consequently cannot generate a signal.

At this point it should be pointed out that the symmetry of the air gaps is essential for the correct functioning of the detector. This is because if the air gap 49b is much smaller than the air gap 49a, as shown in FIG In this case, the flux in the magnetic circuit is divided between the two paths ABD and ACQ in accordance with the ohm ¹ laws for such switching circuits, i.e. inversely proportional to the reluctance, as indicated in FIG Path ACD follows. In this case the electromotive forces at the terminals of the windings 47a and 47b are not only deviating from zero, but are also superimposed because the dominant flux also penetrates the windings in such a way that it "rotates" in the same sense.

Obviously, it is difficult to achieve perfect symmetry at the same time for the manufacture and assembly of the windings 47a and 47b of the yokes 48a and 48b and the air gaps 49a and 49b at the same time. For this reason, the amplifier 50 preferably provides an adjustment facility 51 for the differential properties of the detector, so that the relative gain of the input stages, which are respectively connected to the windings 47a and 47b, can be adjusted in such a way that any remaining signal is canceled which could result from a uniform variable field.

- 24 -

1QÖ84Ö / 1136

If the protection of the detector against ambient fields has been carried out in the manner indicated above, he is ready to detect the presence of all magnetic objects in in the immediate vicinity of its air gap. The fact that the magnetic circuit has only a small opening, gives the detector an increased separation sensitivity and its sensitivity decreases very quickly as a function of the Distance between the air gap and the objects to be scanned.

If minerals are to be sorted according to their magnetic properties by placing them continuously above the 13 can run past with the help of a conveyor belt, in this way one can very well find several successive stones, even if they are in contact with one another.

FIG. 17 shows a vertical section through an exemplary embodiment of a self-compensating detector according to FIG. 13 shown. In this embodiment, the windings are 47a and 47b arranged on lamellae made of mu-metal 48a and 48b, which serve as yokes and have a profile such that the Air gaps 49a and 49b result. A conveyor belt 1 is - as indicated above - driven and leaves the minerals 5 in the immediate Proximity of the air gap 49a, which detects there every trace of magnetization in the zones which the air gap are closest. The mechanical support of the detector is ensured by brackets and a housing 52, which at the same time can serve as an electrostatic shield.

A solder bar 53 is connected on the one hand to the winding connections of the windings 47a and 47b, and on the other hand to the connecting cable 54 for connection to the amplifier $ 50. The assembly is preferably embedded in a filling compound 55, which makes it insensitive to impacts and secures it firmly at the top .

109-8 48/1 136 - 25 -

The same detector (FIGS. 13 to 17) can be used for scanning solid objects. Its simple shift (or Pivoting in the manner of a pendulum) in the field to be examined can be sufficient to trigger a signal when it is at a magnetic object is passed.

FIG. 18 shows a preferred variant of the rotating detector according to FIG. 13, whereby the rotation can take place around one of the axes Ox, Oy or Oz, depending on the direction and the possible shape of the field to be detected. One recognizes in FIG. 18 the structure of such a revolving detector in the form of a probe for use on the site. The actual detector comprises coils 47a and 47b, as well as yokes 48a and 48b, and is located fairly close to the sensitive end 56 of the probe. In the example shown, the air gaps 49a and 49b are fairly large so as not to restrict the detectable zone of the detector too much, and the detector is rotated about the axis Oz defined above Bearing 58 and a socket bearing 59 is supported. The shaft is extended upwards, either directly or via a flexible shaft to a small motor, not shown here, arranged at the upper end of the probe. The mechanical strength of all these elements is ensured by a tube 60 with a round cross-section made of non-magnetic material. The connections of the windings are led through an insulating tube 61 and end at collector rings 62, where the signal is tapped by brushes 63 and is thus accessible at the terminals of the brush holder 64.

The signal passes from there to the input of an AC voltage amplifier, which is followed by a rectifier, which is preferably synchronized in a manner known per se and therefore not shown, so that the rectifier again

1 09848/1136

- 26 -

produces a signal proportional to that from the detector caught river. The detector according to FIG. 13 and in particular its embodiment according to FIG. 18 can also be used for sorting as well as for an initial examination of soils whose minerals are supposed to be degraded.

The dimensions and characteristics of the detectors shown here Possible can be a volume between a few cubic centimeters and a few cubic decimeters in the case of an arrangement for industrial sorting, the magnetizing device can even weigh a few tens of kilograms. In general, the proportions are between the components of the sorting devices those indicated in the figures, relative to the width of the conveyor belt, while the distance between the pole pieces must be greater than a few centimeters up to a maximum height, as required for the materials to be magnetized is.

In the foregoing description is one embodiment of the invention has been explained in which the material to be treated was moved relative to the sorting detector. It is obvious that the detector assembly is also movably arranged can be relative to materials that rest, for example, on solid floors, in recesses with folding door lock; In this case, the determination of an object to be eliminated triggers the opening of the corresponding FalC door without any delay, so that the object to be separated is transported to a lower position.

(Patent claims)

- 27 -

109848/1136

Claims (10)

Claims 1) Method of magnetically sorting materials, thereby characterized in that, using induced or remanent magnetization, the materials to be sorted are continuously * loaned to a device responsive to the magnetic field and that the signals derived from the device are fed to sorting devices after expedient ventilation for the separation of magnetized and minimally magnetized parts of the materials to be sorted. 2) Device for performing the method according to claim 1, characterized by a support for the materials to be treated, by at least one magnetic field detector arranged under the support for generating a sorting signal in response on the magnetic field of the immediately adjacent mass of material, by a drive device for a relative movement between mass and detector, and by an ejector or separating device for the mass components, which produce a magnetic signal have generated in the corresponding amount of these shares, which separating devices are controllable by a sorting signal with a Delay set as a function of the speed of the relative movement between mass and detector. 3) Device according to claim 2, characterized in that the detector can be connected via a delay circuit and amplification devices to the separating device at exactly the moment in which the materials to be sorted run past the detector, which connection can be interrupted after the materials have passed through. - 28 - 109848/1136 4) Device according to one of claims 2 and 3, characterized by a degaussing device for crushed or powdery materials, which is arranged in front of a magnetization device, the latter itself in front the detector or is arranged at the same level with this. 5) Device according to one of claims 2 to 4, characterized in that that the support is formed by a conveyor belt, which preferably has parallel rows of on its surface has spaced recesses for one element of the material mass each. 6) Device according to one of claims 2 to 4, characterized in that that the support is a smooth band on which the elements of the material mass in preferably parallel rows, but are distributed within the rows at an unregulated distance. 7) Device according to one of claims 2 to 6, characterized in that that the detector is designed to respond to changes in the magnetic field and has a magnetometer with a movable magnet Induction based, Kalle effect based, nuclear magnetic resonance based or includes based on optical excitation. 8) Device according to one of claims 2 to 7, characterized in that that the detector is designed to be self-aligning, with a two-part symmetrical magnetic core with identical yokes and with two windings connected in series one of the yokes connected to a differential amplifier are. 9) Device according to one of claims 2 to 8, characterized in that that the detector is fixed. - 29 - 109848/1 136 10) Device according to one of claims 1 to 8, characterized in that that the detector is arranged to rotate relative to the mass of material. 109848/1136 % 0 Blank page