Abstract:
An improved conveyor belt for use in a magnetic waste separator characterized by the provision of protective cleats mounted transverse the conveyor belt. The cleats are strategically positioned to protect the belt from abrasion caused by the sharp-edged metal fragments being processed. Further, the particular configuration and spacing of the cleats enhances tumbling or bouncing of the separated metal fragments which serves to reduce the amount of entrained nonmagnetic materials, thereby increasing separator efficiency.

Description:
SUMMARY OF THE INVENTION 
     The present invention relates to conveyor systems and more particularly, to conveyor belts for use in magnetic waste separators. 
     Magnetic waste separators, of the type having a continuous belt moving past a magnetic assembly which generates a magnetic field through which the belt moves, are well known, as, for example, Barrett et al 3,809,239. In these separators, magnetic material is attracted to the belt by the magnetic assembly and drawn along by the belt to a collection area whereat further separating or processing may be performed. Prior to separation, the waste is shredded to insure that particle size does not exceed managable levels. Unfortunately, this process produces sharp or razor-edged metal particles which puncture or gouge the belt when attracted thereto. Further, the tendency of the attracted particles to remain in a fixed position relative to the magnetic assembly results in a sliding contact between the particles and the moving belt which causes cutting, scoring and abrading of the belt. Finally, a certain amount of relatively light non-magnetic waste, such as rags and paper, tangled with, or draped over the magnetic particles, is carried along therewith, thus rendering the separation process incomplete. Attempts to solve this problem of entrained non-magnetic materials by agitating the attracted magnetic particles with alternating magnetic polarities have proved only partly successful. 
     It is therefore a primary object of the present invention to provide an improved conveyor belt, for use in a magnetic waste separator, which provides increased wear resistance and extended belt life. 
     This is accomplished by providing a plurality of protective, non-magnetic, cleats on the belt strategically positioned shielding the same from the impacts of the attracted magnetic materials and limiting the sliding contact therebetween and effecting erratic bouncing of the aggregate. 
     It is a further object to reduce the amount of non-magnetic material carried along with the magnetic materials by the bouncing action produced, thereby increasing the efficiency of the magnetic separation process. 
     This is accomplished by arranging and designing the cleats or slats to promote tumbling of the attracted magnetic particles whereby the entrained non-magnetic materials are freed and enabled to drop away from the conveyor belt. 
     With the above and other objects in view that will hereinafter appear, the nature of the invention will be more readily understood by reference to the following description, the appended claims and the several views illustrated in the accompanying drawings. 
    
    
     IN THE DRAWINGS 
     FIG. 1 is a side perspective view of a magnetic separator system having the conveyor belt of the present invention associated therewith. 
     FIG. 2 is a side elevational view of a portion of the conveyor belt. 
     FIG. 3 is a top elevational view of the portion of conveyor belt of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the drawing there is illustrated a preferred mode of the invention comprising a magnetic waste separation system including a supply conveyor 1 and a magnetic materials collection chute 2, with a non-magnetic materials collection area 3 therebetween. A magnetic assembly 4 comprising one or more permanent or electro-magnets is located above the collection area 3, and a separator conveyor 5, including sidewalls 5a, rollers 5b and belt 6, is positioned in association therewith, such that the belt 6 is interposed between the magnetic assembly 4 and the supply conveyor 1 and passes over the non-magnetic materials collection area 3 and the magnetic materials collection chute 2. 
     In operation, the supply conveyor 1 carries shredded waste material 7, composed of magnetic and non-magnetic materials 7a and 7b respectively, toward the magnetic assembly 4. As the waste 7 approaches the end 1a of the supply conveyor 1, the magnetic materials 7a are drawn toward the assembly 4 by the magnetic field generated thereby and are thus held against the belt 6. 
     The conveyor belt 6 comprises a flat conveying member 6a composed of a suitable flexible material, preferably an elastomer such as fiber impregnated rubber, and has a plurality of regularly spaced, substantially rigid sweep bars 6b mounted transversely thereon. The belt 6 moves in a direction urging the magnetic material 7a being held thereagainst toward the collection chute 2. Upon reaching the end 4a of the magnetic assembly 4, the magnetic materials 7a leave the magnetic field and drop onto the collection chute 2. The non-magnetic materials 7b, upon reaching the end 1a of the supply conveyor 1, discharge into the non-magnetic materials collection area 3. 
     The natural laws governing magnetic attraction are such that the magnetic materials 7a are drawn to the center of the magnetic field and resist movement therefrom. As a result, the materials 7a, which have sharp, jagged edges produced during the shredding process, tend to concentrate along the centerline of the conveyor belt 6 where they are held in sliding contact therewith. Although the amount of slippage between the materials 7a and the moving belt 6 is limited by the sweep bars 6b, there is considerable scoring and abrading of the conveying member 6a in the areas between the sweep bars 6b, with the wear being most severe along the belt centerline. Further wear results from the &#34;punching effect&#34; as the material 7a strikes the member 6a after being drawn from the supply conveyor 1, thereby producing punctures and gouges. The net result of both of these effects is to severely limit the useful life of the belt 6. In practice belt life averaged 6 weeks. 
     It has been discovered that by disposing protective cleats 6c on the conveying member 6a in a manner and arrangement hereinafter described, belt life was increased to 6 months. The cleats 6c are disposed transverse to the belt 6 and are regularly spaced between the sweep bars 6b. There are cleats 6c flanking each sweep bar 6b and positioned in abuting relation, but not connected thereto. 
     Experiments indicate that the optimum dimensions of the cleats 6c, the spacing therebetween, and the height of the sweep bars 6b are related to the mode of the diametric dimensions of the magnetic materials 7a being separated. Preferably, cleat width is substantially equal to the space between two consecutive cleats 6c, where at least one of which cleats 6c does not abut a sweep bar 6b. This dimension is preferably between one-fourth and one-half of the modal diameter, with one-third the modal diameter being optimum. Likewise, it was found that the preferred height of the cleats 6c is substantially one-half their width and that the minimum height for the sweep bars 6b to prevent material from &#34;climbing over&#34; is three-fourths the modal diameter. 
     Thus, when separating waste wherein the magnetic materials 7a have a modal diameter of three inches, the belt 6 would preferably have cleats 6c one inch wide and one-half inch high, spaced one inch apart. The sweep bars 6b should be a minimum of 21/4 inches high. Both the cleats 6c and the sweep bars 6b should end at least one inch inwardly of the lateral edges 6f, 6f of the conveying member 6a. 
     Problems caused by materials jamming between the sidewalls 5a and the ends of the sweep bars 6b and cleats 6c are eliminated by having the ends 6d, 6d of the cleats 6c and ends 6e, 6e of the sweep bars 6b terminate inwardly of the lateral edges 6f, 6f of the conveying member 6a, leaving unobstructed borders on the member 6a of at least one-third of the modal diameter. 
     The cleats 6c are preferably formed of elastomeric material and are of rectangular cross-section to provide flexible edges which are deflectable by the material accelerating toward the belt 6. This feature, together with the mechanical raking of the edge 6j through the material 7a maximizes the tumbling or rolling of the attracted magnetic materials 7a as the moving belt 6 drags on the resisting materials 7a. This tumbling causes entrained non-magnetic material 7b to be released or shaken free whereupon it falls into the non-magnetic materials collection area 3. It will be noted that both the sweep bars 6b and the cleats 6c are formed as single linear sections to accommodate passage of the belt 6 over the rollers 5b. Preferably the top side 6g of each cleat 6c is flat and the leading and trailing sides 6h and 6i are normal to the belt base web 6g.