Abstract:
A method and apparatus for magnetically separating magnetizable particles from a mixture of magnetizable and nonmagnetizable particles of similar size and density by passing the particles through a magnetic field generated by a cylindrical coil around the outside of the column of the separator, and enhanced by a ferrous metal mass or ring within the column located generally centrally of the coil.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     REFERENCE TO A MICROFICHE APPENDIX 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the art of separation of one type of material from a mixture of two or more types of materials; and more specifically, it relates to the separation of such types as they pass through a magnetic field. 
     2. Description of Related Art 
     Russian Patent No. 1338-894-A discloses an electromagnet with ferromagnetic material inside the separator chamber. U.S. Pat. Nos. 4,828,711 and 4,902,428 to Cohen disclose magnets disposed within the flow path of the materials being separated. U.S. Pat. No. 4,306,970 to Tanaka discloses a separation device employing a solenoid using amorphous metal elements. This art teaches how to trap metals rather than how to separate one type from another. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention relates to an apparatus for magnetically separating magnetizable particles from a mixture of particles, some of which are magnetizable while others are less magnetizable or nonmagnetizable. The mixture of particles to be separated are dropped vertically down a pathway generally perpendicular to a horizontally positioned steel rod that is in the middle of a magnetic field surrounding the pathway and the rod. The pathway is fashioned to circumvent the rod through 180 degrees and resume its downward direction below the rod. A splitter is positioned below the rod to separate magnetizable particles from nonmagnetizable particles. In another embodiment of the invention a mixture of particles is fed into a pathway to form a thin curtain of mixed magnetizable and nonmagnetizable particles passing through a magnetic field generated by an outer circumferential coil and enhanced by an inner circumferential core; the curtain of particles dropping between the coil and the core. A circumferential splitter is positioned immediately following the coil directing the magnetizable particles into an axially central conduit and the nonmagnetizable particles to an outer doughnut-shaped space around the central conduit. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The novel features believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a vertical cross-section of a magnetic separator employing a single horizontal core rod and a vertical passageway curling partially around the core to lead the particles through the magnetic field for separation; 
     FIG. 2 is a vertical cross-section of a second embodiment of a magnetic separator employing a toroidal magnetic field generated by a cylindrical coil around the outside of the separator and enhanced by a cylindrical core inside the separator with a thin passageway for particles to fall between the core and the coil and be separated at a cylindrical splitter immediately below the magnetic force region at the tip of the core; and 
     FIG. 3 is an enlarged portion of the cross-section of FIG. 2 at the outlet of the particle passageway and the inlet to the splitter without the ferrous mass ring. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention relates to a device and a process for using the device to separate one type of particle from another. Generally, the particles are all of about the same size and density such that a mixture of the particles will not stratify to any significant extent. The separation is based on the fact that a ferromagnetic component (a pole piece) within a homogeneous magnetic field will enhance the magnetic field locally. The background field, created here by a solenoid coil, will increase when approaching the ferromagnetic component. It will reach its maximum in the center of this component and will fall again outside the component to the background field level. In the region where the field rises or falls a field gradient is created. This gradient, combined with the underlying magnetic field, creates a force that acts on a magnetizable particle. When a magnetizable particle passes through this region of field and field gradient, it will be attracted towards the ferromagnetic component. 
     Magnetizable particles will move across the flow of the mixture of particles to get closer to the pole piece. If the flow of particles is long enough and the time is long enough the magnetizable particles will move to the edge of the pathway closest to the pole piece while the other type of particle will either be less attracted or not attracted at all, and will follow its natural trajectory. In any event, the effect is to separate the magnetizable particles from the remaining particles. The remaining process is to permanently separate the magnetizable particles from the remainder. The usual way to accomplish this is to employ a knife blade or splitter to divert the desired particles from the remainder of the mass being subjected to the separation process. The entire separation process may be accomplished in stages or the quality of the separation may be improved by subjecting the original mass to the same procedure a plurality of times or by subjecting the first cut to a second or third purification step. In the former procedure the first throughput will produce MAG (particles diverted to the magnetized side of the splitter) and NONMAG (particles non diverted to the magnetized side of the splitter). NONMAG is then sent through the same process a second time and any particles diverted to the magnetized side of the splitter are added to MAG. This may be repeated as many times as desired to retrieve all of the magnetized particles from the treated mass. In contrast to this procedure of repeatedly treating the NONMAG cut one may treat MAG to a second and third treatment in the same magnetic separation so as to purify the original MAG to contain only magnetized particles and to return to NONMAG any nonmagnetizable particles that may have been inadvertently carried along to the splitter and recovered along with the magnetized particles. Either of these two procedures may be applied to purify or enlarge the original cut from this process. 
     In accordance with the teachings of this invention the process may be carried out in an apparatus as shown in FIG. 1 of the attached drawings. A mixture of particles  12  of about the same size, comprising some magnetizable particles and some nonmagnetizable particles, is fed into the top of a chute  11  leading downwardly into a magnetic field of the separation machine of this invention. The direction of particle flow of the mass  12  is shown by arrow  22 . A horizontally positioned steel bar  13  is situated in the center of a nonmagnetic housing  16  surrounded by a coil of magnet wire  17 . Housing  16  may have any convenient shape, e.g., cylindrical, prismatic, or other convenient shapes. When the coil is activated a magnetic field is generated in the direction of arrow  15 . This field rises near the top of rod  13 , reaches its peak in the center of rod  13 , and decays at the bottom of rod  13 . It is in these regions of changing fields where an attractive magnetic force towards rod  13  occurs. The path for the particles to follow is curvaceous as seen at  14  as it bends circumferentially around rod  13  maintaining a space from the surface of rod  13  which is most effective in magnetizing whichever particles in the field. Magnetizable particles are shown in FIG. 1 by the letter “x”; and nonmagnetizable particles are identified by the letter “o”. It may be seen that as the particles move farther and farther around rod  13  the magnetizable particles move closer and closer to the inside surface of path  12  which is closer and closer to the magnetism source, rod  13 . The cross-sectional shape of rod  13  is not critical and may be round as shown in FIG. 1 or any other smoothly curved shape that is aerodynamically quiescent, e.g., oval, tear-drop or the like. At the end  21  of the path  12  the particles fall against the leading edge of splitter  20  which divides the magnetized particles “x” from the nonmagnetized particles “o”, so as to collect each type separately. The splitter is shown with two parts,  19  and  20 , the latter being hinged to the former so as to provide adjustability to produce a better division between magnetized particles and nonmagnetized particles. 
     A second specie of the apparatus of this invention is shown in FIGS. 2 and 3, where the enhanced magnetic field is in the form of a ring and the particles to be treated are in the form of a cylindrical curtain falling vertically through the magnetizing ring. The magnetized particles are eventually separated from the nonmagnetized particles. A mixture of particles  24  to be separated in this process is fed into the apparatus over a distribution cone  25  and thence into a feed funnel  23  which distributes the particles exit through the lower end of channel  28  and are guided by wall  30  to fall against splitter  43  to divide magnetized particles  40  from nonmagnetized particles  39 . A closed tubular channel  41  guides the magnetized particles downward to an exit at  50 . Annular enclosure  48  guides nonmagnetized particles to an exit at  51 . A short magnet coil  42  surrounds the apparatus adjacent to the lower section of channel  28  working in conjunction with mild separation of magnetizable particles from nonmagnetizable particles before the particle mass reaches splitter  43 . Magnetized particles migrate toward the center of the apparatus while nonmagnetizable particles remain in the center of the channel or migrate toward the outside of the channel as they approach splitter  43 . 
     There is a structure around the vertical axis of the apparatus which is employed to adjust the size of the opening of the outlet  29 , at the exit of channel  28 . Spindle tube  27  telescopes vertically inside tubular guide  47 . Tube support  34  is connected to cross brace  33  and spaced upwardly therefrom by connector  35 . Support  34  provides a housing for a set screw at  37  to form a firm attachment to spindle tube  27 . Positioned downwardly from the outer extremity of cross brace  33  is skirt  38  which forms the inside surface of channel  28  guiding particles to exit  29  immediately before the particles meet splitter  43 . Tip  29  is adjustable vertically by moving support arm  46  (which in turn supports ring  44 ) up and down tube  47  and tightening it in place with nut  45 . Steel ring  44  can be removed from the separation zone for cleaning. 
     In general the parts of the apparatus of this invention are made of brass, plastic or other nonmagnetizable material. Of course, this does not apply to ring  44 , which serves as a pole to the magnetic field produced by coil  42 . This invention is admirably suited to a stage-wise operation of purification by allowing the magnetized product from outlet  50  to be a feed to a second apparatus similar to that of FIG. 1 so as to produce a product of relatively pure magnetizable particles. The apparatus of this application also lends itself well to a continuous operation as well as to a batch operation. 
     While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.