EP0439983A2 - Magnetic separator for non-ferrous metal particles or pieces - Google Patents

Abstract

A magnetic separator (1) for non-ferrous metal particles or pieces (3) comprises a conveyor belt (2) onto which the said particles (3) are unloaded, this conveyor belt (2) being wound, partially, around an active cylindrical casing (5) having a horizontal axis of rotation (8) and inside which is mounted, coaxially, a magnetic system (6). This magnetic separator is characterised in that it comprises means (17, 18) for limiting the partial winding of the conveyor belt (2) about the active cylindrical casing (5) to a zone (20) which is located in the two upper quadrants (20a, 20b) of the periphery of the latter. <IMAGE>

Description

The invention relates to a magnetic separator of particles and pieces of non-ferrous metal comprising a conveyor belt on which said particles are poured, this conveyor belt being wound, partially, around an active cylindrical envelope with horizontal axis of rotation designed in a non-conductive material and inside which is mounted, coaxially, a magnetic system subjected to a speed of rotation greater than that of said active cylindrical envelope.

The present invention will find its application in the field of industrial recycling of waste composed, mainly, of non-ferrous metal products.

FOUCAULT current separation, based on the principle that conductive materials undergo, through an alternating magnetic field, a different influence according to their conductivity coefficient, is well known. However, its industrial application poses a certain number of problems due, in particular, to the low separation yields which it provides.

Thus, more particularly, from document US-A-3,448,857, a magnetic separator for industrial application operating according to the above principle is known. This magnetic separator consists of a strip fed with non-ferrous particles and pieces, this strip partially winding around an active cylindrical envelope and made of a non-conductive material. In fact, inside this envelope is arranged, coaxially, a magnetic system, also called, polar wheel.

More specifically, this magnetic system consists of a succession of permanent magnets or electromagnets arranged radially with respect to an axis of rotation corresponding to the axis of rotation of the cylindrical envelope. In fact, the latter is driven by a speed of rotation substantially slower than that of the polar wheel so that the non-ferrous particles and pieces are effectively subjected to an alternating magnetic field.

Ultimately, the combination of the speed of movement of the conveyor belt and the influence of the pole wheel has the consequence of subjecting these non-ferrous particles and pieces to a speed whose value of the horizontal component differs according to their conductivity, this resulting in a distinct fall trajectory and, ultimately, their reception in different containers.

The drawback associated with such a magnetic separator is that the zone of influence of the non-ferrous particles and pieces is too large, the conveyor belt winding over the entire front half of the cylindrical envelope with dimensions adjusted to the polar wheel. In fact, this has the effect of subjecting said non-ferrous particles and pieces not only to an acceleration with horizontal components, but, moreover, to a vertical acceleration when leaving the conveyor belt. This results, of course, in a restriction of the desired primary effects, therefore of an inconsistent distinction in the trajectories of the particles and pieces, leading to a significant reduction in the efficiency of the separation.

In order to remedy the aforementioned problems and limit the influence of the polar wheel on the non-ferrous particles at a determined location in the cylindrical envelope, a magnetic separator has been designed, the polar wheel of which is offset at the interior of this cylindrical envelope, its diameter being reduced by half compared to the latter. Such a magnetic separator is described in particular in document EP-A-0.339.195. In this prior document, reference is also made to means making it possible to tilt the pole wheel relative to the axis of rotation of the cylindrical envelope in order to adjust, at the level of the latter the zone of influence of the particles to be separated.

Although such an arrangement makes it possible to make negligible the vertical accelerations undergone by the ferrous particles and pieces under the influence of the polar wheel, they are accompanied, moreover, by a reduction in general of this influence.

Indeed, in this regard, it should be noted that the alternating magnetic field, produced by the rotating polar wheel, tends to decrease quickly when you move away from it. Also, it is advisable to respect, between this polar wheel and the cylindrical envelope, an air gap which is reduced as much as possible. However, having to do with an eccentric polar wheel inside the cylindrical envelope, the minimum air gap is located along a generator of the latter, this air gap coming to increase on either side of this generator leading to less influence of non-ferrous particles and pieces. In short, the latter are no longer subjected to a magnetic field exerting its influence on what can be determined as an area of the active cylindrical envelope but, more precisely, to a very localized magnetic field at the level of the latter. Here again, the results obtained by means of such magnetic separators are unsatisfactory, the efficiency of the separation being poor.

The present invention aims to remedy all of the aforementioned drawbacks by proposing a magnetic separator which is capable of subjecting the non-ferrous particles and pieces to a sufficient influence of an alternating magnetic field while avoiding giving them, by through this influence, accelerations with vertical components so that the path taken is sufficiently distinctive as a function of their conductivity allowing, ultimately, a separation with high efficiency.

The invention as characterized in the claims, solves the problem and consists of a magnetic separator of particles and pieces of non-ferrous metals, comprising a conveyor belt onto which are poured said particles and pieces of non-ferrous metals, this conveyor belt partially winding around an active cylindrical envelope with horizontal axis of rotation made of a non-conductive material and inside which is mounted, coaxially, a magnetic system subjected to a speed of rotation greater than that of said envelope active cylindrical, this magnetic separator also comprising means for limiting the partial winding of the conveyor belt around the active cylindrical envelope over an area situated in the upper two quarters of the periphery of the latter.

In fact, the aim sought by the present invention is that the zone of maximum influence of the particles on the conveyor belt is not limited to the level of a generator of the latter but that, for all that, it does not result therefrom not an acceleration with vertical components of the particles and non-ferrous pieces to be separated.

The obvious advantage obtained by means of this invention consists in an amplification of the phenomenon of separation, resulting in a very clear distinction of the paths taken by the particles according to their conductivity which allows, ultimately, to obtain yields particularly high separation rates.

Other objects and advantages of the present invention will appear during the description which follows and whose understanding will be facilitated by referring to the attached drawing:
- Figure 1 is a schematic representation of the magnetic separator, object of the present invention.

The invention relates to a magnetic separator 1 allowing the recovery of waste consisting mainly of non-ferrous metal particles and pieces, and this, by ensuring their sorting according to their conductivity.

More specifically, this magnetic separator 1, as shown in FIG. 1 comprises a conveyor belt 2 on which the particles and pieces 3 to be sorted are poured. This conveyor belt 2 comes to wind, partially and substantially at its downstream end 4, around a cylindrical envelope 5, with horizontal axis of rotation 8, integrating a magnetic system 6 capable of subjecting said particles and pieces 3 to an alternating magnetic field.

In fact, the interaction of this alternating magnetic field and of the eddy currents thus induced results in the creation of forces acting differently on the particles and pieces according to their conductivity, force coming to influence the fall trajectory of these particles and pieces when they come out of the conveyor belt 2.

More precisely, this magnetic system 6 is similar to a polar wheel arranged coaxially inside said cylindrical envelope 5 and consists of a plurality of permanent magnets or electromagnets 7 arranged radially with respect to the axis of rotation 8.

In order to subject the particles and pieces 3 to an alternating magnetic field, this magnetic system 6 is subjected to a rotation whose speed is substantially greater than that of the cylindrical envelope 5 which is dependent on the running speed of the conveyor belt 2.

Note, moreover, that the latter evolves in a closed circuit and, therefore, comes to wind, partially, around a deflection roller 9 disposed in the upstream part 10, this conveyor belt 2 thus defining , an upper strand 11 on which the particles 3 are arranged and a lower strand 12 ensuring the looping of the circuit.

In view of the above description, it is understood that during the operation of the magnetic separator 1, the particles and pieces, deposited, initially on the upper strand 11 of the conveyor belt 2, come to move in the direction of the cylindrical envelope 5 containing the magnetic system 6. Then, under the effect of the speed of advance of the conveyor belt 2 and the influence produced by this magnetic system 6, these particles and pieces 3 follow a fall path 13, 14 which differs according to their coefficient of conductivity. These particles 3 are thus sorted and recovered in separate containers 15, 16.

In fact and according to a characteristic of the present invention, this magnetic separator 1 comprises means 17, 18 for limiting the partial winding of the conveyor belt 2 around the active cylindrical envelope 5 over an area 20 located, according to a reference fixed (X, Y) 23, in the upper two quarters 20a, 20b of the periphery of the latter.

In fact, the objective aimed by such means 17, 18 is that it is possible to subject the particles and pieces 3 to an alternating magnetic field of maximum intensity so as to obtain a maximum yield of the effect produced. resulting in trajectories well distinct drop depending on their conductivity. Also, it should be avoided, by means of these means 17, 18 that this prolonged influence undergone by the particles 3 via the magnetic system 6 leads to accelerations with vertical components of said particles and pieces 3 which would have as a consequence of lessening the desired effects.

According to a preferred embodiment of the present invention, these means 17, 18, consist, on the one hand, of a deflection roller 9 whose position, relative to the active cylindrical envelope 5, is determined so that the location 22, where the conveyor belt 2 enters into contact with said active cylindrical casing 5, is located precisely, in the upper two quarters 20a, 20b of the latter.

On the other hand, these means are supplemented by a second roller 21 disposed below the cylindrical casing 5 and around which the conveyor belt 2 is partially wound. In fact, this second deflection roller 21 is capable of intervening on the coordinates, with respect to this fixed mark 23, of the point 24 where this conveyor belt 2 again comes to leave the cylindrical casing 5 and to ensure that this point 24 is preferably located in the two upper quarters 20a , 20b of said active cylindrical envelope 5.

In addition and according to a preferred embodiment of the invention, the deflection roller 9, arranged in the upstream part 10 of the circuit of the conveyor belt 2, may be associated with means allowing its height adjustment.

Thus, the lower the deflection roller 9 is lowered by means of the height adjustment means so as to give the upper strand 11 of the conveyor belt 2, an inclination 25 relative to the horizontal tending to impart to the particles and pieces. 3 an upward movement in the direction of the cylindrical casing 5, the earlier the contact takes place between the latter and said conveyor belt 2, contributing to an increase in the area 20.

Note, moreover, that such an inclination 25 of the conveyor belt 2 makes it possible to increase the distance 26 traveled by the particles and pieces 3 during their fall which makes it possible to increase the differences observed between two particles and pieces of different conductivity, at the level, precisely, of their point of fall. This facilitates, of course, their recovery in separate containers.

Furthermore and in accordance with the invention, the roller 21 can also be equipped with height adjustment means and in a horizontal direction.

As a result, the area 20 of influence of the magnetic system 6 on the particles and pieces 3 can be further increased or, on the contrary, decreased when the deflection roller 21 is pivoted counterclockwise, respectively, in the clockwise around the cylindrical envelope 5. More precisely, it suffices to modify the angle 21a, formed by the strand 21b described by the conveyor belt 2 between this deflection roller 21 and the cylindrical envelope 5 and, this, with respect to the vertical.

It is thus possible to limit this zone of influence 20 in the upper part of the cylindrical envelope 5 and thereby avoid subjecting the particles and pieces 3 to vertical acceleration under the impulse of the rotating magnetic field. .

Note, moreover, that due to its arrangement, the deflection roller 21 may also include a magnetic system with permanent or electromagnetic magnet allowing the treatment of the more or less ferromagnetic particles and pieces which are residual. In this case, the latter are collected in an additional container 50.

According to a preferred embodiment, the deflection roller 9, disposed in the upstream part 10, is mounted on an axis 27 the ends of which are capable of sliding in slots of oblong shape 28 arranged at the level of vertical supports 29 made integral with the machine chassis (not shown).

Furthermore, as regards the deflection roller 21, this can be mounted on an axis 30, the ends of which can also slide in oblong slots 31 arranged vertically and formed in supports 32 which can be moved horizontally on the chassis to which they are attached. Note, however, that a reverse arrangement can be adopted consisting of making the supports 32 movable in the vertical direction while allowing a certain mobility of the axis 30 of the deflection roller 21 in oblong slots 33 machined in the horizontal direction at level of said supports 32. FIG. 1 represents the two possible embodiments.

This same FIG. 1 illustrates, moreover and in broken lines, a third embodiment of the means allowing the pivoting of the deflection roller 21 around the cylindrical envelope 5. More precisely, within the framework of this embodiment, the axis 30, on which the deflection roller 21 is mounted, is capable of moving, at its ends, in oblong slots 34 made, this time in the end 35 of the support arms 36 pivotally mounted around the axis of rotation 8 corresponding to the axis of rotation of the cylindrical casing 5.

In all cases, it will be understood that in the various embodiments set out above, it is possible to modify the arrangement of the deflection roller 21 both in a horizontal and a vertical direction. This characteristic also makes it possible for this deflection roller 21 to tension the conveyor belt 2.

It is likely that, having determined the length 19 of the zone of influence 20 for maximum efficiency, this length 19 is to be kept for the sorting of a whole range of non-ferrous metal particles and pieces with different conductivity coefficients and that only the angle of inclination 25 of the upper strand 11 corresponding to the conveyor belt 2 is to be modified. In this case, it is recommended to make the axes 27 and 30 integral, corresponding, respectively, to the deflection roller 9 and to the deflection roller 21, by means of link arms 37 (illustrated in broken lines in the drawing) thus a given movement of said deflection roller 9 corresponds to a displacement of identical amplitude of the deflection roller 21. The length 19 of the zone of influence 20 is, therefore, maintained. In addition, this arrangement avoids taking up the tension of the conveyor belt 2 during the various adjustments.

In this regard, it will be recalled that the various means for adjusting the deflection roller 9, located upstream 10, and the roller 21, are not essential from the moment when the optimum parameters for the operation of the magnetic separator are known depending on the data relating to the products which should be separated later. Thus and by way of example, when it is known, as a function of these usage data, the inclination 25 which should be given to the upper strand 11 of the conveyor belt 2, the deflection roller 9 can be positioned definitively in the frame of the magnetic separator 1 during the design of the latter and this, so as to obtain this inclination 25. The same applies to the roller 21.

The present invention also proposes to avoid any possible deterioration of the cylindrical envelope 5 in the event of insertion of a ferromagnetic particle or piece found by chance in the non-ferrous particles and pieces between this cylindrical envelope and the conveyor belt 2. More particularly, in the event of punctual wear of the latter, not justifying, however, its replacement, it is likely that certain ferromagnetic particles or pieces are found by chance in the non-ferrous particles and pieces come to s '' inlay in the conveyor belt 2 at this wear and, finally, are inserted between the conveyor belt 2 and the cylindrical casing 5. However, if this ferromagnetic particle or piece is found by chance in the particles and pieces not ferrous is maintained for a prolonged period under the influence of the alternating magnetic field, it is brought to heat strongly tending destroying the cylindrical envelope 5 made of a non-conductive material. Also, it is strongly advised to remove, as quickly as possible, this ferromagnetic particle or piece found by chance in the non-ferrous particles and pieces of the external surface of this cylindrical envelope 5.

For this purpose, use is made of a scraper 38 of semi-cylindrical shape with a radius greater than the radius of the cylindrical casing 5 and disposed between the upper strand 11 and the lower strand 12 of the conveyor belt 2. This scraper 38 is mounted pivoting about a horizontal axis 39 situated substantially downstream from its vertical median plane so as to create an imbalance tending to maintain applying one of the ends 41 of this scraper 38 against the cylindrical casing 5. This end 41 of the scraper 38 acting tangentially is preferably of tapered shape which contributes to its effectiveness.

In the case of the use of a roller 21 provided with a magnetic system with permanent magnet or electromagnetic, this roller 21 is also provided with a scraper 38.

Thus, in the event of introduction between the cylindrical envelope 5 and the conveyor belt 2 of a ferromagnetic particle found by chance in the non-ferrous particles or pieces, this is immediately removed from the periphery of this cylindrical envelope 5 under the action of the scraper 38. It is then moved away from the magnetic system 6 by progressing along the lower surface 42 of said scraper 38. This ferromagnetic particle being found by chance in the non-ferrous particles or pieces then comes to fall on the strand lower 12 of the conveyor belt 2. A second scraper 43 ensures, finally, the ejection at the side parts.

In view of the above, it is understood that the magnetic separator, object of the present invention, has the advantage of an optimized operation leading to high separation rates. Also, such magnetic separators, in accordance with the invention, provide a solution to the problem posed, until now, by the industrial application of separators by FOUCAULT current.

Claims (13)

Magnetic separator (1) of particles and pieces of metal (3) made of non-ferrous metal comprising a conveyor belt (2) on which said particles (3) are poured, this conveyor belt (2) being partially wound around '' an active cylindrical envelope (5) with horizontal axis of rotation (8) made of a non-conductive material and inside which is mounted, coaxially, a magnetic system (6) subjected to a speed of rotation greater than that of the active cylindrical envelope (5), magnetic separator (1), characterized in that it comprises means (17, 18) for limiting the partial winding of the conveyor belt (2) around the active cylindrical envelope (5) on an area (20) located in the upper two quarters (20a, 20b) of the periphery of the latter. Magnetic separator according to claim 1, characterized in that the means (17, 18) consist of: - on the one hand, by a deflection roller (9), disposed upstream (10) of the circuit of the conveyor belt (2) and around which the latter is partially wound, the position of this deflection roller ( 9) being determined such that the location (22), where the conveyor belt (2) comes into contact with said active cylindrical envelope (5), is located in the upper two quarters of the latter; - And on the other hand, by a second roller (21) disposed below the active cylindrical envelope (5) and around which is partially wound said conveyor belt 2, this second roller (21) being arranged in such a way so that the point (24), where this conveyor belt (2) comes, again, to leave said active cylindrical envelope (5) is located in the upper two quarters (20a, 20b) of the latter. Magnetic separator according to claim 2, characterized in that the deflection roller (9) is associated with means allowing its height adjustment, these means being constituted by vertical supports (29) in which oblong lights are formed (28 ) capable of receiving the ends of an axis (27) supporting said deflection roller (9). Magnetic separator according to claim 2, characterized in that the idler roller (21) is associated with means for adjusting the height and in a horizontal direction making it possible to modify the angle (21a) described by the strand (22b) formed by the conveyor belt (2) between this second roller (21) and the cylindrical envelope (5) and, this, relative to the vertical. Magnetic separator according to claim 2, characterized in that the roller (21) is a non-magnetic deflection roller. Magnetic separator according to claim 2, characterized in that the roller (21) comprises a magnetic system with permanent or electromagnetic magnet to treat the particles and the more or less ferromagnetic pieces remaining. Magnetic separator according to claim 4, characterized in that the deflection roller (21) is mounted on an axis (30) the ends of which are capable of moving in vertical oblong slots (31) machined in supports (32) able to move in a horizontal direction. Magnetic separator according to claim 4, characterized in that the deflection roller (21) is mounted on an axis (30) the ends of which are capable of moving in horizontal oblong openings (33) formed in supports (32) movable in the vertical direction. Magnetic separator according to claim 4, characterized in that the deflection roller (21) is mounted on an axis (30) whose ends are capable of moving in oblong slots (34) formed in the end (35) support arms (36) pivotally mounted about an axis of rotation (8) corresponding to the axis of rotation of the cylindrical casing (5). Magnetic separator according to claims 4 and 7 to 9 characterized in that the deflection roller (9) is associated with the deflection roller (21) by means of link arms (37) cooperating with their axes (27, 30 ) respective. Magnetic separator according to claim 1, characterized by the fact that it comprises a semi-cylindrical scraper (38) mounted pivoting about a horizontal axis (39) and lying between the upper strand (11) and the lower strand (12 ) described by the conveyor belt (2), one of the ends (41) of this scraper (38) coming to cooperate tangentially with the cylindrical casing (5). Magnetic separator according to claims 1 and 11, characterized in that it comprises a second scraper (43) cooperating with the lower strand (12) of the conveyor belt (2) to remove the particles (3) and ensure its ejection at the side parts. Magnetic separator according to claims 1 and 6 characterized in that the roller (21) provided with the magnetic system (6) with permanent or electromagnetic magnet comprises a scraper (38).

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