US2591121A - Crossbelt magnetic separator - Google Patents

Description

April 1, 1952 K. A. BLIND 2,591,121

CROSSBELT MAGNETIC SEPARATOR Filed May 10, 1947 vi it ATToRm-ZVS removed magnetic particles.

Patented Apr. 1, 1952 CROSSBELT MAGNETIC SEPARATOR Karl A. Blind, Thiensville, Wis., assignor to Dings Magnetic Separator 00., Milwaukee, Wis., a corporation of Wisconsin Application May 10, 1947, Serial No. 747,229

2 Claims. 1 The present invention relates generally to im provements pertaining to the art of magnetic separatiop; and relates more specifically to improvements in the construction and operation of mapractice to utilize so-called cross-belt magnetic separators for the purpose of removing magnetic from non-magnetic particles contained in an advancing stream of dry granular mixture of the materials, by constantly passing a thin layer of the mixture through one or several successive zones of magnetic influence produced by complementary sets of magnetized poles, each set comprising one pole provided with a flat face exposed to the zone and spaced from a symmetrical wedge shaped face of the other pole of the set. In these separators, the thin layer of bulk mixture is transported through each zone of magnetic influence by a main lower conveyor belt coacting directly with the flat upper pole face and advancing transversely beneath the corresponding wedge edge, while the magnetic particles are lifted out of the loose mass of mixture by the V-shaped magnetic pole and are projected upwardly against an upper auxiliary belt advancing along and directly adjacent to the edge of the wedge shaped pole face.

This type of separator has been quite successfully and extensively employed for many years, especially in the mining industry for the removal of magnetic ore from granular masses of mixture, but I have discovered that the symmetrical wedge or V-shape of the lifting poles is relatively ineffective since the symmetrical formation and the ordinary utilization of a single wedge surface at each separating zone, produces excessive concentration of the highly intensified and most effective flux tubes along a single central strip of each cross-belt, and does not distribute these tubes throughout the maximum available area of the separating spaces. This concentration of the flux tubes in the previous separators, not only results in objectionable local or mass pick-up of magnetic particles along a comparatively narrow central path on the crossbelt of each zone, but also causes considerable non-magnetic material to be entrained with the I have found that the use of an asymmetrical apex or lifting face on the upper pole of each set, having a leading gradually inclined surface approaching the main conveyor in the direction of its advancement and also having a trailing face disposed perpendicular or more abruptly inclined relative to this conveyor, is far superior to the former symmetrical pole face; and that the provision of a succession of these asymmetrical lifting face formations distributed along each zone of magnetic influence, enhances the separating capacity and substantially reduces undesirable removal of gangue with the magnetic particles.

It is therefore a more specific object of the present invention to provide an improved crossbelt magnetic separator which more effectively removes the magnetic particles by eliminating the objectionable features of prior devices of this general type, above referred to.

Another specific object of the invention is to provide an improved pole face construction for the magnets of cross-belt separators or the like, which enables the flux tube to be most effectively utilized to extract the magnetic particles near the apex of the wedge face of each set of mag nets, without undesirable concentration of the removed particles. 1

A further specific object of this invention is to provide an improved magnet assemblage for cross-belt magnetic separators, wherein the capacity of the machine is materially enhanced by providing each separating zone with a number of similar successive lifting apices distributed uniformly throughout the zone.

Still another specific object of my invention is to provide an improved cross-belt separator wherein the belt for removing the magnetic particles is more uniformly loaded than was possible with the prior assemblages, and in which undesirable local or mass pick-up of the magnetic particles is avoided.

An additional specific object of my present invention is to provide an improved magnetic separator for effecting removal of magnetic particles from an advancing stream or layer of dry granular mixture in a most effective and automatic manner. 1

These and other specific object-sand advantages of the invention will be apparent from the following detailed description.

A clear conception of the features constituting my present improvement, and of the mode of constructing and of operatingseparators embodying the invention, may he had by referring to the drawing accompanying and forming a part of this specification and in .Which'like reference characters designate the same or similar parts in the various views. 1

Fig. l is a diagrammatic perspective view of a typical two zone cross-belt magnetic separator in which the invention has been incorporated;

Fig. 2 is a considerably enlarged fragmentary section through a set of complementary magnetic poles forming one of the separating zones, and

and against the cross-belt of each separating able thereby to cause its upper stretch 8 to travel in the direction of the arrow; a granular mat rial supply hopper 9 cooperating with a feed roller H] to spread a thin layer of the mixed dry magnetic and non-magnetic particles upon the feed end of the advancing conveyor stretch 8; upper and lower reversely disposed horseshoe magnets H, 12 respectively located one above the other on opposite sides of the main conveyor stretch the upper magnet I l having spaced poles iii each of which is provided with a series of serrations or similar asymmetrical lower wedges l located somewhat above and spanning the belt stretch 5, while the lower magnet 52 has similarly spaced poles l5 each of which is provided with a flat upper face ll 'coaoting directly with the underside of the moving stretch 8; an electric coil 58 for energizing each of the magnets ii, 32; and a pair of auxiliary or cross-belts l9 coasting with pulleys Eli and surrounding the upper poles oi the magnet i I, each of the belts i 9 having a lower pick-up stretch 2| spaced from the top surface of the conveyor stretch 8 and movable there-across in the direction of the arrows closely adjacent to the apices 22 of the corresponding pole wedges I 5.

The main conveyor stretch 8 and the auxiliary belt stretches 2! are adapted to be constantly advanced in the directions of the arrows applied thereto in Fig. l, by suitable power applied to the pulleys l, 26 respectively, and the magnets ll, l2 may be energized with the aid of the coils in a well known manner so as to produce a magnetic field or separating zone 24 between each complementary set of magnet poles Hi, 25. The constantly advancing upper stretch 8 of the conveyor 5 thus transports the granular mixture oil-magnetic and non-magnetic particles depos-- ited thereon in the form of a thin layer extending throughout its entire area by the hopper 6 and feed roller it, through a succession of the separating zones 24 beneath the crossebelt stretches 2|; and magnetic particles of the progressing stream of mixture are lifted out of the mass and are picked up by the transverse belt stretches 2| and are delivered laterally of the conveyor 6 in the form of constant streams 25, while the non-magnetic particles are carried away from the magnetic zones 24 and are ultimately discharged as a stream 26 over the end of the conveyor stretch 8, as illustrated in Fig. l. The main conveyor stretch 8 may be of any desired length and several successive pairs of magnets H, l2 may be applied to this stretch depending upon the characteristics of the material being treated, and the degree of separation desired,

and the general construction and mode of operation of this cross belt type of magnetic separator is well known to those skilled in the art.

It is also a well known fact that the gradients of the magnetic field at each separating zone 24, determines the intensity or force of the magnetic attraction acting upon the particles to be re-' moved from the mass res uing upon the belt stretch 3, and it is also recognized that flux tubes of short length and high intensity spanning the space between the magnet poles hi, it are most effective for magnetic separation purposes. It is a further fact that magnetic particles approaching the central planes or" the upper lifting poles in the direction of travel of the conveyor stretch 8, will be picked more readily than those travelling away from these central areas, and in case a magnetic particle is not removed while approaching a wedge edge 22 it will remain magnetized but willtnot be lifted and will merely pass through a non-magnetic portion of the separating zone on the trailing side of the edge From these known facts, it is desirable to utilize to the greatest possible extent, the lifting force available throughout the entire separating zone, and especially during the time that the particle is approaching the center of the magnetic field.

While the attractive force of a magnet is known to be proportional to the square of the induction so that term magnetic material subjected to the magnetic influence will move toward the magnet face while increasing the permeance of the magnetic path and thereby reducing the energy contained in the magnetic field, this theory may be somewhat modified as applied to practical cross-belt magnetic separation. For such purposes it may be considered that the intensity of the magnetic field or the magnetizing force in the magnetic zone or gap causes the magnetic particles to be attracted by a force Fr equal to Y dh where is is the susceptibility of the particle, and H and drc the strength and gradient of the part of the field occupied by the particle. In cross-belt separators, the lifting pole i i of each set is provided with a wedge or V -shaped face in order to provide a rapid increase in field density with a resultant increase in lifting power or force tending to elevate the magnetized magnetic particles from the main belt stretch 8 to the cross-belt stretch Referring more specifically to Figs. 2 and 3 of the drawing, the separating zone 24 formed between the magnet poles it, i6 is spanned vertically by a multiplicity of flux tubes 21 of which the shorter tubes have maximum intensity, and these tubes 27 may be crossed by equipotential lines 28 so as to subdivide the field into numerous approximate squares. The belts have been omitted from Fig. 2, but the direction of travel of the load carrying belt stretch 8 has been indicated by the arrows directed across the flat pole face H, and the upper pole id is provided with three parallel depending asymmetrical wedges l5, each having a leading surface or face 29 directed downwardly in the direction of travel of the belt stretch 8, and also having an approximately upright trailing surface or face 39-. The

resultant force Fr which attracts each particle toward the cross-belt stretch it, as the particle approaches one of the wedge edges is indicated in the diagram of Fig. 3, and the component Fe represents the force acting in the direction of travel of the main belt stretch. 8 while the noun ponent Fm likewise represents the force acting to lift the particle tangent to the flux tubes at the flat surface l'i. If the particle should fail to be removed prior to reaching a wedge edge 22 and passes beyond this edge, the horizontal com ponent Fl: will be reversed and the kinetic energy of the particle for lifting purposes will be lost since this reversal of the component is detrimental to the upward attraction.

Because of the fact that the trailing surface of each wedge I5 beyond the edge 22 is thus inactive and in fact has an effect detrimental to lifting of the magnetic particles, I provide an asymmetrical wedge on the upper pole; and in order to more effectively and uniformly distribute the lifting force throughout each separating zone 24, a series of these wedges [5 of similar formation is provided at the zone as. The widths of the effective pick-up localities resulting from this asymmetrical pole formation are represented in Fig. 2 by the distances a1, a2 and us, while the widths of the corresponding ineffective or dormant areas are represented by the distances b1, b2 and b3; and while the at distances gradually diminish as the b distances increase, the sum of the a values remains far greater than the sum of the 12 values. This fact indicates that the total pick-up area is considerably greater than the total detrimental area, and by providing a number of wedges I5 the pick-up area is distributed throughout the separating zone, and maximum pick-up or separating capacity results. The inclination of the leading wedge faces 2%] is approximately forty-five degrees while the trailing wedge faces 3!] are disposed approximately vertical to the corresponding lower pole faces IT, and while three wedges 15 have been utilized in the embodiment shown in order to uniformly distribute the pick-up areas throughout the separating zones 24, a single wedge it or more or less than the three wedges illustrated, may be advantageously utilized for the treatment of diverse materials.

From the foregoing detailed description it will be apparent that my present invention provides an improved cross-belt magnetic separator which besides being simple in construction, is also high ly efiicient in operation and provides for maximum capacity. The improved asymmetrical pole face enhances to a maximum the effective separating or lifting area and reduces to a minimum the ineffective area, and the enlarged effective area serves as an effective pre-magnetizer for the magnetic particles which are subsequently extracted from the mixture. If a magnetic particle is not in fact removed by the first wedge IE to which it is presented, it will probably be premagnetized to an extent sufficient to insure removal thereof by a subsequent wedge l5; and by providing a succession or plurality of these wedges I5 at each separating zone 2 most efficient pick-up of all magnetic particles regardless of their susceptibility, is assured. The capacity of the improved separating unit is thus materially increased over that of machines utilizing symmetrical \I-shaped pole faces, both because of the asymmetrical formation of the pole faces 29, and due to the use of several of these specially formed wedges at each separation zone 24; and the improved assembly enables attainment of this improved result without increasing the size of the magnet energizing coils It. The plural arrangement of the wedges l5 moreover uniformly distributes the load on the cross-belts l9 and eliminates objectionable mass pick-up of particles along a relatively narrow central area of these belts, and this feature is especially important when treating magnetic ores, as it avoids undue removal of gangue with the magnetic particles.

It should be understood that it is not desired to limit this invention to the exact details of construction or to the precise mode of use, herein shown and described, for various modifications within the scope of the appended claims may ocour to persons skilled in the art; and it is also contemplated that specific descriptive terms used herein be given the broadest interpretation consistent with the novelty of the invention.

11 claim:

1. In a cross-belt magnetic separator, a main conveyor deck constantly movable to transport mixed magnetic and non-magnetic particles in one direction along a definite path, a magnet pole having a flat face extending locally across said path beneath said deck, an auxiliary conveyor deck spaced from the top of said main deck and movable across said path above said fiat pole, and a complementary magnet pole above said auxiliary deck having a series of at least three parallel asymmetrical depending wedge projections ex tending across said path and cooperating through equal gaps with said fiat pole face to lift magnetic particles from said mixture onto the bottom of the auxiliary deck, one face of each wedge being perpendicular to said decks and the other being inclined downwardly in the direction of advancement of the main deck approximately forty-five degrees.

2. In a cross-belt magnetic separator, a main conveyor deck constantly movable to transport mixed magnetic and non-magnetic particles in one direction along a definite path, a magnet pole having a flat face extending locally across said path beneath said deck, an auxiliary conveyor deck spaced from the top of said main deck and movable across said path above said fiat pole, and a complementary magnet apole above said auxiliary deck having a series of at least three parallel asymmetrical depending wedge projections extending across said path and cooperating through equal gaps with said fiat pole face to lift magnetic particles from said mixture onto the bottom of the auxiliary deck, one face of each wedge being perpendicular to said decks and the other being inclined downwardly in the direction of advancement of the main deck approximately forty-five degrees while the apex of each wedge is bluntly rounded.

- KARL A. BLIND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Stearns June 13, 1950

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