Patent Publication Number: US-5427253-A

Title: Taconite pellet separator

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the separation of taconite pellets from a heterogeneous mixture of taconite pellets and other matter. Means of effecting such separation is dependent upon the different coefficients of friction and angles of rest, inherent in the various materials to be treated by the invention. 
     U.S. PATENT DOCUMENTS 
     4,624,370 Nov. 25, 1986 Danner 
     4,519,896 May 28, 1985 Vickery 
     3,749,240 Jul. 31, 1973 Spears 
     3,036,707 May 29, 1962 Walden 
     1,517,509 Dec. 2, 1924 Hokanson 
     SUMMARY OF THE INVENTION 
     Taconite pellets as manufactured in Minnesota are roughly spherical in shape and generally less than three-fourths of an inch in diameter. Although the pellets are about two-thirds iron, they are non-magnetic and electrically non-conductive. In Minnesota, the taconite pellets are generally transported by railcar from the manufacturing plants to shipping points on the shore of Lake Superior. As a normal consequence of shipping and handling, some pellets are spilled on the ground and railroad rights-of-way. Mechanized sweepers clean the ground and rights-of-way, as needed, yielding as much as several hundred tons of material per day, for a given sweeper. The swept material is a mixture of taconite pellets, track ballast, gravel, and other matter. The swept material must be discarded at a landfill, as it is unsuitable for roadbed, track ballast, or blast furnace feed. The invention is an economical means of separating and recovering taconite pellets from the sweepings mixture. The invention employs a vibratory conveyor which is slightly tilted along the primary axis of material flow across the conveyor. As the sweepings mixture is fed to the vibratory conveyor, materials on the surface of the conveyor travel in different trajectories according to the nature of the materials. Materials with a higher coefficient of friction travel faster on a vibratory conveyor than materials with a lower coefficient of friction. Materials with a lower angle of rest will roll, tumble, or slide downhill at a given angle more readily than other materials with a higher angle. One barrier on the surface of the conveyor guides the moving feed material to a &#34;free-roll&#34; zone on the conveyor surface. Another barrier on the surface of the conveyor divides the moving material into two distinct flow paths. One flow path is chiefly taconite pellets. The other flow path is chiefly non-taconite pellet material. The operator of the invention may control the frequency and amplitude of vibration, the slope of the conveyor surface, and the positions of the barriers, in order to achieve optimum separation of the materials being treated by the invention. The operator of the invention is at liberty to determine the best means of feeding the swept material to the conveyor and retrieving the materials after separation has been effected. 
     The invention does not rely upon density, particle size or fluidizing properties (Danner.) The invention does not effect separation on the basis of specific gravity (Vickery.) Separation is not effected by means of magnetism, high velocity air streams, or partial vacuum (Spears.) Neither weight nor hardness of the treated particles is material to the operation of the invention (Walden and Hokanson.) 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation of the current embodiment of the invention. 
     FIG. 2 is a top plan view of the current embodiment of the invention. 
     FIG. 3 is an end elevation of the current embodiment of the invention, showing the tilt of the conveyor, as seen from the feed-end. 
     FIG. 4 is a top plan view of the current embodiment of the invention, showing the feed mixture on the conveyor bed and the separation of the materials into two flow paths. 
    
    
     DETAILED DESCRIPTION 
     The embodiment of this invention is of a vibratory conveyor bed 2 coupled to a vibratory conveyor base 1 by means of suitable pivot links 6. A reciprocating action is imparted to the conveyor bed 2 by means of a suitable variable speed drive unit 3 which is made fast to the conveyor base 1. A suitable variable-throw crank 4 is appropriately secured to the output shaft of the drive unit 3. The variable-throw crank 4 is connected to the conveyor bed 2 by adjustable connecting rod 5 using suitable means. In the present embodiment of this invention, containment fences 7 and 8 are made fast to the lower and rear edges of the top surface of the conveyor bed 2. Fastened to the top of the conveyor bed 2 is a feed guide fence 9 which may be repositioned by the operator of this machine for optimum performance. Also fastened to the top of the conveyor bed 2 is a splitter guide fence 10 which may also be repositioned by the operator of this machine for optimum performance. Parts 1 through 10 inclusive, comprise part of the taconite separator, which is securely attached to a level foundation 11 of suitable mass and strength. It will be seen in FIG. 3 that the conveyor base 1 is raised on one edge by suitable support 12 in order to impart a slope to the conveyor bed 2 at right angles to the direction of material flow along the long axis of the taconite separator. The degree of slope may be adjusted by changing the height of the support 12 to afford the best performance of the taconite separator. 
     FIG. 4 shows a feed mixture of taconite pellets and track ballast on the conveyor bed 2. As the feed mixture travels away from the rear containment fence 8 the feed mixture also tends to travel downhill towards the lower containment fence 7. The taconite pellets travel more slowly longitudinally, and downhill more quickly, than the track ballast or other non-taconite material. Two different particle flow paths can be observed in the operation of this machine, and the splitter guide fence 10 is positioned in such a manner as to trap the non-taconite material, ensuring that it stays separated from the taconite pellets. Suitable means for collecting the two different materials is then provided at the discretion of the person or persons operating the taconite separator. 
     Since several suitable means are already in existence for feeding material to this taconite separator, none is shown in this embodiment of the taconite separator. 
     Since suitable means are already in existence for pre-screening the feed material to remove any particles which are substantially larger than the taconite pellets, none is shown in this embodiment of the taconite separator. 
     Since suitable means are already in existence for removing magnetic or electrically conductive materials from the feed material, none is shown in this embodiment of this taconite separator.