Classifying – separating – and assorting solids – Magnetic – Paramagnetic
Reexamination Certificate
1998-10-08
2001-06-26
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Magnetic
Paramagnetic
C209S218000, C209S217000, C209S213000
Reexamination Certificate
active
06250474
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to metal separators. More specifically, but not by way of limitation, the invention is directed to an apparatus for separating nonferrous metal material from ferrous metals, rocks, glass, wood, rubber, dirt and other such debris by means of an eddy current.
DESCRIPTION
1. Background Art
In this present era of recycling and limited land-fill space, the necessity to reclaim reusable materials from debris and waste has become an utmost concern of our society. The reclamation of metal materials is additionally important due to the increasing scarcity of these natural resources and the cost-effectiveness of recycling versus mining and purification of metals. To recover metals from debris and waste, the recycling industry has developed numerous metal separating devices.
These separation devices include both magnetic separators and eddy current separators. Magnetic separators allow ferrous metal pieces to be easily removed by suitable magnets which sort the ferrous metals from the debris using attractive magnetic forces to pull the ferrous metals from the balance of the debris. Alternative methods are required in removing non-ferrous metals since they do not contain the magnetic properties of ferrous metals.
Magnetic separation typically works by attracting items to be separated from a group or mixture. Eddy current separators, on the other hand, repulsively act upon conductive materials or particles which are not magnetic in nature, such as aluminum, copper and brass. Eddy current separation functions by inducing or sweeping a high density, rapidly changing, magnetic flux through the mixture so that eddy currents are created in any appropriately conductive non-ferrous particles. The eddy current subjects these conductive particles to a resultant repulsive force away from the eddy current source. The magnitude of this repulsive force is defined by electrical resistivity, size and shape of the conductive particle, the strength of the magnetic flux field, and the frequency of pole changes in the magnetic flux field. If sufficiently strong, the repulsive force causes the non-ferrous particles to be thrust away from the magnetic flux field, thereby separating these particles from non-electrically conductive material in the mixture or debris. Thus, while similar structural elements may be employed in separators of both the magnetic and eddy current types, their modes of operation, the relative orientations of the structural elements, and the resulting effects caused by the two apparatus are substantially different.
A review of known patents discloses several inventions embodying this type of eddy current separation device. U.S. Pat. No. 5,080,234 to Benson utilizes a pair of cylinders, one positioned above the other, that are rotated synchronously in opposite directions from each other and are coordinated so that poles of opposite polarity face each other across an air gap. An eddy current is induced in electrically conductive particles as the particles are conveyed across the gap. The current repulses the particles thereby allowing their separate collection apart from the free-falling non-conductive material in the debris.
In another separating apparatus disclosed in U.S. Pat. No. 5,092,986 to Feistier et al., a rotating drum consisting of magnets is eccentrically placed adjacent to a belt drum. Debris is conveyed across the belt drum by means of a conveyor belt. The magnetic drum produces a magnetic flux field from which eddy currents are created in electrically conductive particles of the debris as the particles are conveyed along the belt over the belt drum. The conductive particles are projected further off of the belt than other material due to the repulsive magnetic force generated by the drum. In this manner, the electrically conductive particles are separated from the remaining debris. A scraper is employed to remove iron particles attracted to the magnets thereby aiding in preventing damage to the belt drum.
In today's recycling industry, predominately metal products such as automobiles, refrigerators, washing machines, etc., are shredded into small pieces. These small pieces are then run through trommel screens that sift out dirt, glass and other sufficiently fine particles from the shredded product. The larger pieces that remain within the drum of the trommel are collectively referred to as residue; a material that often includes dirt, rocks, glass, wood, rubber, and various metal s pieces such as aluminum, copper and brass.
The residue is classified and purchased on a relative percentage basis of metal to total material; for example, “30% residue” indicates that the combination is comprised of thirty percent metals, while the remaining matter is a mixture of non-metals that may include dirt, trash, rubber, and other matter. Typically, forty five thousand pound truckloads of residue are purchased at a time by a recycling or processing plant. In the instance of a thirty percent residue load, roughly thirty thousand and five hundred pounds of unusable material is shipped to the plant and must ultimately be discarded or otherwise processed. Obviously, the recycling plant desires the percentage of residue shipped to be as high as possible so that resources are not wasted on the transport of unusable material. In at least one past instance, residue was purified by water and/or heavy media plants which proved to be costly. Out of this dilemma the eddy current separating industry evolved.
Most present-day eddy current machines are typically comprised of a rotor within a nonmetallic drum pulley design. In some instances, the magnetic rotors have a rotational axis off the centerline of the drum pulley shaft for the conveyor belt and are referred to as eccentric designs. Others are concentrically oriented and the rotors rotate about a common axis with the pulleys about which the conveyor belts wrap. The inner rotor contains the magnet, or magnets and is enclosed within the larger, outer belt drum. The outer drum is typically comprised of a fiberglass or a ceramic coated material. Iron attracted to the magnets tends to accumulate on the outer drum. The presence of the iron creates resistance resulting in heat, thereby burning through the fiberglass belt drum and sometimes damaging or destroying the magnets, and possibly the rotor itself. This is due to the tight tolerances at which the two rotating components are run with respect to one another. To potentiate the combined performance of the two components, the inner magnetic rotor is run as closely as possible to the outer belt pulley drum so that the induced magnetic field is as close as possible to the material being separated.
In view of known complications associated with current separator designs, the magnetic separator of the present invention has been designed to provide a cost-effective means of overcoming damage to the magnetic rotor during the separation process of the fragmented material by eliminating required operation of the rotor within the belt pulley drum. The present invention provides a means whereby the magnetic rotor is separately included, as opposed to an eccentric or concentric arrangement of two rotating components. It also provides a means by which preventive maintenance, parts replacement and equipment repairs are greatly simplified due to the separator's design. These features also result in cost-savings and reduced downtime.
DISCLOSURE OF THE INVENTION
The present invention in its several disclosed embodiments alleviates the drawbacks described above with respect to the separation of non-ferrous metal material from ferrous metals, rocks, glass, wood, rubber, dirt and other such debris by means of any eddy current which incorporates several beneficial features. An eddy current separator apparatus is disclosed whereby electrically conductive metals are separated from other materials such as glass, rubber, wood, rocks and dirt in a novel and unique manner. The present invention separates non-ferrous metals from the debris by a shredding process through
Kilpatrick & Stockton LLP
Miller Jonathan R
Walsh Donald P.
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