Abstract:
A rotary collider air mill apparatus that uses accelerated air moving at high velocities as the primary reduction medium is described. The apparatus produces turbulent air currents and shear waves within a polygonal housing whereby solid particles introduced into the housing repeatedly collide with each other and are fractured into smaller particles. An exemplary rotary collider air mill apparatus may include a polygonal housing having a front plate and a back plate and 5 or more side plates, a drive shaft passing through the central portion of the polygonal housing, a sprocket mounted on the drive shaft and having arms extending radially from a central hub, and 3 or more blade sections attached to the arms. The rotary collider air mill apparatus is scalable upward or downward in sizes ranging between 12 inches and 144 inches in diameter with the housing and internal mechanisms sized proportional to one another.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/965,078 entitled “Rotary Collider Air Mill” and filed on Jan. 22, 2014. The provisional application is hereby incorporated in its entirety by specific reference thereto. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a mill for crushing stone, minerals and other materials that may be fractured. More specifically, the present invention relates to a form of rotary mill which uses high speed air as a medium to cause various materials to be broken down into smaller pieces by repeatedly colliding into each other 
     BACKGROUND 
     There is a need for machinery suitable for crushing stone, minerals and other materials that may be fractured. There is also a need for a rotary mill that can fracture hard materials by colliding the input materials into each other repeatedly to break them into successively smaller and smaller pieces. Many rock crushing and breaking machines in use today rely upon the action of hardened steel to smash and pulverize rocks and minerals into smaller pieces. These machines can achieve a particle size reduction, but these machines are subject to a great deal of wear and tear in the course of normal operation. 
     Rock crushing machines are further limited in the size of particles that may be input and subsequently reduced to only a certain fraction of the previous particle size at the output. Using typical rock crushing machines, to reduce rock pieces of about 2 inches in diameter (about 500 mm) into a very fine powder having particles sizes which are less than 0.002 inches in diameter (about 0.5 mm), it would be necessary to process this material in a series of steps moving from one machine to another and requiring a considerable amount of processing time and additional handling. 
     Accordingly, there is a need for machinery for crushing or milling stone, minerals and other materials into very small particles or fine powders. It is further desired to produce a mill that can reduce input materials to approximately 1/1000 of the original size in just a single processing step. It would also be desired to create a mill that utilizes air circulating at high speed as a primary medium by which input material is crushed without causing undue wear and tear on the mill itself, thereby greatly reducing the frequency with which parts are replaced. There is also a desire to produce such a mill that is completely scaleable in size, both upward and downward, to better accommodate lager and smaller input materials by keeping the component parts of the mill sized proportionally to one another. 
     SUMMARY 
     The rotary collider air mill of the present invention is generally intended for application to rock, mineral or other materials that may be fractured by forcing the input materials to into a series of collisions. In short, the air mill of the present invention will create high velocity chaotic air currents within an enclosure that will force input materials to repeatedly collide with each other at very high speeds and cause the input materials to fracture into smaller and smaller pieces. In some embodiments the rotary collider air mill may be utilized in to produce cosmetic powders, food spices, building products, metallurgical products, plastic fillers and a number of other items. 
     In a number of exemplary embodiments of the present invention a rotary collider air mill comprising a polygonal housing having at least 5 sides, a sprocket having at least 3 blades attached thereto, a drive shaft for rotating the sprocket at high speeds, an input port and an output port is disclosed. In one embodiment of the present invention the apparatus of the present invention will be fully scalable upward or downward in volume by resizing the polygonal housing, the sprocket, and the blades proportionally to each other. By way of example only, the internal mechanisms of the sprocket and the attached arms may rotate through a space that has a diameter of 12, 18, 24, 48, 60, 96 or even 144 inches across by scaling the housing and internal mechanisms upward or downward proportionally to each other to preserve operational functionality. 
     In another embodiment of the present invention the rotary collider air mill will use high velocity chaotic air as a medium to repeatedly smash input materials into each other in a series of collisions to fracture the input materials into smaller and smaller pieces. In yet another embodiment of the present invention the apparatus will be capable of moving air at speeds in the transonic range of about 600 to 768 miles per hour (mph) and approaching the speed of sound. In a further embodiment of the present invention the rotary air collider mill will be able to reduce input materials to about 1/1000 of the original size in a single processing step. 
     By way of example only, the apparatus of the present invention may reduce input materials of about 1 to 2 inches in size to a fine powder of less than about 0.001 inches in size, a significant portion of which may be passed through a #200 mesh screen, particles having sizes of less than about 100 microns. The apparatus of the present invention represents a significant improvement and advance in technology over the existing ball mills, hammer mills, roller mills and jet mills now in use. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood in view of the detailed description in conjunction with the following figures and in which: 
         FIG. 1  is a front elevation view of the rotary air collider mill; 
         FIG. 2  is a left side cross sectional view of the rotary air collider mill; 
         FIG. 3  is a front elevation view of a regular octagonal housing for the rotary air collider mill; 
         FIG. 4  is a top view of a regular octagonal housing for the rotary air collider mill; 
         FIG. 5  is a left side detail view showing the assembled configuration of the drive shaft, sprocket and blades for the rotary air collider mill; 
         FIG. 6  is front detail view of a sprocket with three attached blades for the rotary air collider mill; 
         FIG. 7  is a front conceptual view of a sprocket having a central hub and three detachable arm and blade units; and 
         FIG. 8  is a detailed perspective view of a pin and retaining clip used to secure the detachable arm and blade units to the central hub. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment, the rotary air collider mill is an apparatus comprising a polygonal housing having at least 5 sides, a sprocket having at least 3 blades attached thereto, a drive shaft for rotating the sprocket at high speeds, an input port and an output port. These components should be precisely machined and sized proportionately to each other, but may be scaled up or down in size so long as the proportions of these components are preserved relative to one another. By way of example only, it will be possible to construct an apparatus in accordance with the present invention in which the sprocket and attached blades sweep through a diameter of about 12, 18, 24, 48, 60, 96 or 144 inches so long as the housing, sprocket, blades, drive shaft, input port and output port are all sized proportionately to each other. 
     One component of the rotary air collider mill is polygonal housing having at least 5 sides. The polygonal housing should be constructed of steel or similar materials that are particularly hard, durable and not brittle across a wide range of operating temperatures. The polygonal housing-should have a front plate, a back plate and at least 5 side panels. The front plate and the back plate should be placed vertically and positioned parallel to each other with the at least 5 side panels defining an enclosed volume between them. The at least 5 side panels may define a symmetrical or asymmetrical polygonal housing. By way of example only, it is possible to form useful housings for the present invention having 6, 8, 10, 12 or more side panels disposed between the front plate and the back plate. 
     In one embodiment of the present invention, it is possible to form a housing having 8 equally sized side plates to form a regular and symmetrical octagonal housing. This embodiment would have a cut away profile that resembles a typical “stop sign” shape that is familiar to all drivers as a traffic control device. Note that while the number of sides may vary the polygonal chamber should be oriented such that the bottom most portion is a flat side panel rather than a joint between two sides. This is intended to ensure that the rotating sprocket and attached blades will completely sweep the bottom of the apparatus when rotated and avoid an accumulation of rock or mineral debris at the bottom of the housing. The accumulation of rock or mineral debris within the housing would require cleaning and removal to prevent damage to the apparatus and could be rather time consuming. 
     By way of example only, a suitable housing for a rotary collider air mill with a 48 inch diameter and a regular octagonal chamber will now be described herein in some detail. Referring now to both  FIGS. 1 and 2 , the polygonal housing  100  should have a front plate  110  and a back plate  120  each formed of steel or similar materials. These plates should be not less than about ½ inch thick and preferably about 1 inch thick to ensure durability. Similarly, to form a regular octagonal model, the housing should have 8 equally sized side panels  131 - 138  about 1 inch thick also formed of steel or similar materials. 
     Still referring to both  FIGS. 1 and 2 , the front plate  110  and the back plate  120  should each measure about 60 inches high by about 55 inches wide by about 1 inch thick. The eight equally sized side plates  131 - 138  should be about 20 inches long by about 24.5 inches wide and about 1 inch thick. The front plate  110  and the back plate  120  should be positioned vertically and parallel to each other and spaced about 24.5 inches apart. The side plates  131 - 138  should be placed between and perpendicular to the front plate  110  and the back plate  120  and should form 45 degree angles to each other between adjacent side panels. The front plate  110 , back plate  120  and 8 side plates  131 - 138  should be securely attached to each other by various mechanical means, including mechanical fasteners, but most preferably by welding to permanently attach these pieces to each other. In one alternative embodiment, not shown, the front plate  110  and the back plate  120  may be slotted to allow tabs to be extended from the edges of the 8 side panels  131 - 138  and inserted into the small slotted openings in the front plate  110  and the back plate  120  to allow a sort of tongue and groove configuration for added strength and stability. 
     As shown in  FIG. 1 , the housing may be bisected near the midpoint into an upper half  105  and lower half  106 . By sectioning the housing  100  into an upper half  105  and a lower half  106 , it will be a relatively easily to open the housing  100  for servicing or cleaning. As shown in  FIG. 2 , the upper housing  105  and the lower housing  106  may have a number of flanges  108  attached to the exterior of the housing  100  and use a number of nut and bolt type fasteners to hold the upper housing  105  and the lower housing  106  securely in place during operation of the rotary air collider mill. 
     Still referring to  FIGS. 1 and 2 , the front plate  110  and the back plate  120  each have a number of openings or ports cut into them. The back plate has a centrally located opening  122  of about 4 inches in diameter to accommodate the drive shaft, not shown here. The front plate  110  has a centrally located opening  112  of about 4 inches in diameter to accommodate the drive shaft as well, but also features an input port  114  of about 8 inches in diameter to receive the input materials and guide them into the mill and an exhaust port  116  of about 10 inches in diameter to allow the processed rock or mineral powder to be removed from the mill. The sizing or location of the input port  114  and the exhaust port  116  may be changed somewhat depending on the size of the materials to be milled. As shown in  FIG. 1 , the front plate  110  may also have a cleaning or inspection port  118  of about 3 inches in diameter located near the bottom of the housing  100 . 
     It is critical that the input port  114  be located within the 24 inch radius defined by the rotation of the sprocket and attached blades, not shown here, minus the displacement of the blades themselves. In short, the input port  114  must be located between the outer radius of the drive shaft (about 2 inches from center) and the innermost radius defined by the moving blades (about 22 inches from center). As shown in  FIG. 1 , the input port  114  is located about 11 inches from the center of the front plate  110 . Similarly, it is critical that the exhaust port  116  be located outside the 24 inch radius defined by the sprocket and attached blades, not shown. In operation, the mill will tend to produce a negative air pressure or partial vacuum within the approximately 22 inch inner radius defined by the moving blades, and a positive air pressure outside the approximately 24 inch outer radius defined by the moving blades. The negative air pressure created near the input port  114  will be used to draw materials into or feed the mill, and the positive air pressure near the exhaust port  116  will be used to expel or push the processed powder out of the mill. Note that the difference between the outer radius and the inner radius defined by the moving blades will be referred to as the displacement of the blades. 
     Referring now to  FIG. 2 , in one embodiment of the rotary air collider mill, the exhaust port  116  may be located completely outside of housing  100  by incorporating an exhaust chamber  140  into the design. By creating an opening in the uppermost plate  131  of the housing  100  it is possible to vent the crushed rock powder, not shown, from the housing  100  into the exhaust chamber  140  and out through the exhaust port  116  in the front plate  110 . 
     Referring now to both  FIGS. 3 and 4 , a front elevation and a top view of a regular octagonal housing  100  formed of eight side plates  131 - 138  is shown. As best viewed in  FIG. 4 , the uppermost plate  131  is cut about 20 by 20 inches square to allow about a 4.5 inch wide opening to vent crushed rock powder upward into the exhaust chamber and out of the exhaust port, not shown. The other seven side plates  132 - 138  are cut about 20 inches long by about 24.5 inches wide. As best viewed in  FIG. 3 , the eight side plates are welded together at about 45 degree angles to form a regular octagonal housing  100 . 
     Referring now to  FIG. 5  and also referring back to  FIG. 2 , the next component of the rotary collider air mill is the drive shaft  200  which is a solid steel bar of about 3¾ inches in diameter to allow a clearance of about ⅛ inch completely around the drive shaft  200  as it passes through the front plate  110  and the back plate  120  of the mill. As shown here, the drive shaft  200  extends horizontally through and perpendicular to the front plate  110  and the back plate  120  of the mill. The drive shaft  200  may be mounted through the front plate  110  and the back plate  120  of the mill with bearing supports  210 ,  220  or bushings, not shown, to ensure that it is allowed to rotate freely while not impinging upon the plates  110 ,  120  and causing undue wear. 
     The drive shaft  200  is connected to a drive motor, not shown, which may be a gas, diesel or electric power source which is then connected to the drive shaft  200  by means of belts, gears or other transmissions to permit the drive shaft  200  to rotate at various speeds, as needed. The drive motor or power source is not specified with particularity here because it may take many different forms and may be rated at various levels of horsepower (hp) which need only to be sufficient to drive the apparatus at the desired number of revolutions per minute (rpm). By way of example only, a rotary collider air mill of 48 inches in diameter will typically operate at about 100 to about 5000 revolutions per minute. This type of operation would usually require a motor having a power rating of approximately 10 to 250 horsepower. By way of example only, a 125 horsepower motor turning at about 4800 rpm could produce blade speeds reaching about 660 miles per hour on a 48 inch diameter model. 
     Referring now to  FIG. 6  and referring back to  FIG. 5 , a sprocket  300  is welded or fixedly attached to the drive shaft  200 . The sprocket  300 , as shown here, features a 3 bladed design, but it is to be understood that the rotary collider air mill of the present invention may have more than 3 blades and that 5, 6, 8 or more blades in various embodiments that have also been contemplated. The 3 bladed design is shown in  FIG. 6  as it is known to be well balanced and to efficiently mill rocks and minerals. Designs featuring more blades will need to be balanced and calibrated accordingly before use. 
     Still referring to  FIGS. 5 and 6 , the sprocket is shown having 3 pairs of parallel arms  310 ,  320 ,  330 , each pair of arms supporting one of the 3 blades  315 ,  325 ,  335  that are each rotated through the air to create a very high speed chaotic airflow. This chaotic airflow, in turn, causes the input materials to be circulated about the interior of the polygonal housing  100  and to collide with each other. As shown in  FIG. 6 , the blades  315 ,  325 ,  335  are formed from three equal sections of steel pipe or tubing. For the 48 inch diameter model of the rotary collider air mill, a steel pipe having a nominal 6.75 inches exterior radius and a nominal 6.00 inches interior radius and a nominal wall thickness of about 0.75 inches. The pipe is to be cut into 3 equal 120 degree arcuate blade sections. The pipe, not shown, should have a length of about 24.0 inches. The resulting 120 degree arcuate blade sections  315 ,  325 ,  335  will be about 24.0 inches in width and will allow a clearance of about 0.25 inches on either side of the blades  315 ,  325 ,  335  from the front plate  110  and the back plate  120  of the mill. 
     As shown here, each arcuate blade section  315 ,  325 ,  335  is mounted on a pair of parallel arms  310 ,  320 ,  330  that extend radially outward from the hub  305  or central portion of the sprocket  300 . Although a pair of parallel arms are shown here, it is to be understood that each arcuate blade section  315 ,  325 ,  335  may be attached to the sprocket  300  by one arm, two arms, three arms or more. The arcuate blade section  315 ,  325 ,  335  may be mounted or welded to the pair of arms  310 ,  320 ,  330  at any angle ranging from about 0 to 60 degrees (half of 120 degrees) to alter or adjust the angle of attack with which the leading edge of the blade will meet the air inside the polygonal housing  100 . The angle at which the blade is mounted to the arms not only determines the angle of attack with the air within the housing but also helps to define the displacement of the blade. As noted earlier, the displacement of the blade is the difference between the outermost radius swept by the rotating blade and the innermost radius swept by the rotating blade. As shown in  FIG. 6 , the displacement of the blades is about 6 inches. 
     The displacement will be minimized when the blade is mounted at 0 degrees and will be maximized when the blade is mounted at 60 degrees. Accordingly, the more the blade is rotated to cup or catch the oncoming air, the greater the displacement of the blade. It is notable that the largest blade displacement is not always the most desirable configuration in when the air mill is in operation. In some cases, it may be desirable to reduce the displacement of the blades to increase the residence time of the input materials within the housing. Input materials which remain in the housing for longer periods of time will usually experience more collisions and produce smaller output particle sizes. 
     Referring now to  FIGS. 7 and 8 , in one alternative embodiment of the rotary collider air mill in accordance with the present invention, each pair of parallel arms  310 ,  320 ,  330  that are welded to and support the arcuate blade section  315 ,  325 ,  335  may be attached to the central hub  305  portion of the sprocket  300  by removable pins  311 . Each of the removable pins  311  is held in place by a thin metal retaining clip  312 . The retaining clip  312  is fitted into a groove located near the tapered end of the pin  311 . Alternatively, cotter pins (not shown) or some other retention means may also be used to hold the removable pins  311  in place and to keep the parallel arms  310 ,  320 ,  330  and attached blades  315 ,  325 ,  335  firmly attached to the hub  305  of the sprocket  300 . 
     The removable parallel arm and blade units would be particularly useful if one of the attached blade sections were to become severely damaged and in need of replacement. In this way, it would be possible to replace a just single blade section by removing two retaining pins rather than having to replace the entire sprocket and all of the attached blade sections at once. This alternative embodiment would also permit air mill operators to switch out the parallel arm and blade units to change the angle or the shape of the blades. Although the blade sections illustrated herein are three 120 degree arcuate portions that are formed from a single steel pipe, it is to be understood that the blade sections may have different thickness, radius of curvature or even be somewhat flattened out, if desired. 
     Another alternative embodiment of the present invention is contemplated by having a sprocket with welded or fixed arms and having removable blades attached to the arms by a number of small removable pins. In brief, rather than removing the entire arm and blade units as shown in  FIGS. 7 and 8 , it is possible to remove the blades only by attaching them to the arms with a number of small pins, not shown. By way of example only, the blades may have a C-shaped mount on the underside which fits over the outmost end of the arms. A number of small pins may be inserted through holes in the mount and pass in a perpendicular direction through the arm. It is believed that in some applications it may be desirable to replace the blade sections either due to wear or simply to change the angle at which the blade is mounted to the arms. It is further believed that it may be easier to access and replace the blades alone than the entire arm and blade units. 
     While a number of preferred embodiments of the invention have been shown and described herein, modifications may be made by one skilled in the art without departing from the spirit and the teachings of the invention. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations, combinations, and modifications of the invention disclosed herein are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow, that scope including all equivalents of the subject matter of the claims.