Abstract:
In accordance with the present invention, a pneumatic particle separator includes a base member formed with an elongated lumen. Also formed on the base member for fluid communication with the lumen are, in order, an air flow injection channel, the lumen, a diverter, and an n-number of type channels. Further, a particle injection channel is connected in fluid communication with the air flow injection channel. In this combination, when an air flow is established through the air flow injection channel and the lumen, particles are drawn by venturi action from the particle injection channel for single file transit through the lumen for analysis. A subsequent pneumatic diversion through the diverter then provides an exit for each particle from the base member through a preselected type channel for collection. The analysis performed in the lumen is used for an assay report.

Description:
FIELD OF THE INVENTION 
     The present invention pertains generally to geological assays, mineral processing, and particle analysis and sorting techniques. More particularly, the present invention pertains to field assay units that analyze samples containing powders or pre-crushed rock particles. The present invention is particularly, but not exclusively, useful as a field assay unit which pneumatically aligns all particles of the sample in single file during transport through the unit for an independent evaluation of each individual particle as to size and composition type. 
     BACKGROUND OF THE INVENTION 
     An assay involves the testing and examination of sample material to determine its composition and the quality of its ingredients. In the case of metals and ores it is sometimes necessary that the assay be done on site where the metal or the ore is located. In any event, the assay is preferably accomplished quickly, accurately and efficiently. 
     Heretofore, preparing an assay of an ore/mineral sample in real time has been quite labor intensive and has been limited by several operational considerations such as sampling and detection limitations. In general, it is first necessary to crush the ore/mineral into particles for bulk processing. Samples of the crushed material are then retrieved. Next, the samples are analyzed. As a practical matter, the specifics for a bulk analysis of samples are varied and can be quite different. For example, U.S. Pat. No. 8,151,632 for a “Method for defining element content and/or mineral content” discloses a mineral separation process in which a sample of crushed particles is bulk analyzed using a grain size analysis operation. 
     In the event, all ore/mineral assays have, as their primary objective, a determination of the mineral composition in the ore sample and its quality. The present invention, however, recognizes that a bulk analysis of ore/mineral samples for this purpose can be cumbersome, destructive and expensive. Further, the present invention recognizes that an analysis of an ore/mineral sample on a particle-by-particle basis provides for more precise measurements and more accurate results. 
     With the above in mind, it is an object of the present invention to provide a device and method for separating particles according to their composition, wherein each individual particle in a sample is individually evaluated and categorized, on a particle-by-particle basis, for an assay of the particles. Another object of the present invention is to provide a device and method for separating particles according to their composition, which pneumatically transports and separates the particles during processing. Yet another object of the present invention is to provide a device for separating particles according to their composition which is easy to manufacture, is simple to use and is comparatively cost effective. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a device for separating particles according to their composition (i.e. a particle separator) includes a base member which includes various embedded channels. Specifically, the channels are provided for moving particles through the base member. They include: an elongated central lumen, an air flow injection channel, a particle injection channel, a diverter, and a plurality of particle recovery channels. As envisioned for the present invention, the various channels are connected in fluid communication with each other so that pre-crushed particles can be pneumatically driven through the channels of the base member. Structurally, all of the channels have a characteristic dimension d L  that is less than two hundred fifty microns (d L &lt;250 μm). In the case of a circular cross-section, d L  is a diameter; and in the case of a rectangular shaped channel, d L  is a minimum distance between opposed sides. 
     For purposes of the present invention, the base member is a substantially flat, rectangular-shaped structure, and it is made of a transparent material, such as plastic, quartz, borosilicate or sapphire. The elongated lumen, noted above, is formed in the central portion of the base member and it has a first end and a second end. The air flow injection channel, also noted above, is formed in the base member to extend from the periphery of the base member for a connection in fluid communication with the first end of the lumen. Preferably, the air flow injection channel is coaxially oriented with the lumen and, importantly, the air flow channel is formed with a junction point. 
     Also formed into the base member is a particle injection channel which extends from the periphery of the base member for fluid communication with the junction point of the air flow injection channel. Additionally, a diverter is formed in the base member for fluid communication with the second end of the lumen. And further, an n-number of particle recovery channels are formed into the base member for respectively establishing fluid communication from the diverter to the periphery of the base member. 
     In an operation of the present invention, an air compressor is engaged with the air flow channel to create a flow of air through the air flow injection channel and into the central lumen. This air flow continues through the central lumen in the base member at an over-pressure p o  that is greater than ambient pressure (e.g. 15 psig). A consequence here is that the flow of air through the air flow injection channel is accelerated to establish a venturi pump at the junction point. 
     A burst generator for creating bursts of particles is connected in fluid communication with the particle injection channel. The particle injection channel also interconnects the burst generator with the junction point on the air flow injection channel. Consequently, bursts of particles are sequentially drawn from the burst generator and through the particle injection channel by the venturi pump at the junction point, for further pneumatic transit through the central lumen. Importantly, in this operation, particles from the particle injection channel are aligned for single file transit through the central lumen for subsequent analysis. To assist with this alignment, the particle injection channel can be formed with a microfluidic serpentine section. As envisioned for the present invention, each particle passing through the channels of the base member will have a unique diameter d p , where d p  is less than d L  (d p &lt;d L ). 
     Apart from the base member, the present invention includes an analyzer that is positioned with the base member for monitoring the central lumen of the base member. Its purpose is to determine a size, and a composition, for each particle as the particle transits through the central lumen. Structurally, the analyzer includes: a microcontroller, a camera, and a reflective spectrophotometer. 
     The camera of the analyzer is connected to the microcontroller for imaging each particle before it enters the lumen of the base member. Specifically, the image of the particle is used by the microcontroller to calculate a size for the particle, which is based on d p . The reflective spectrophotometer, which is also connected to the microcontroller, is used for identifying the composition of each particle. In more detail, the reflective spectrophotometer includes a broadband light source for producing a light beam that is directed along a first beam path toward the lumen in the base member. It also has a grating for receiving a return light beam which is caused by a reflection of the light beam from a particle in the lumen. In this instance, the return light beam is directed toward the grating along a second beam path to create a spectrum. A line image sensor is also provided for capturing the spectrum of the return light beam for use by the microcontroller in determining the composition of the particle. In this combination, the first beam path for the light beam is at an angle α relative to the second beam path of the return light beam, where α is less than 90°. Thus, in its operation, the microcontroller analyzes the size of each particle together with the composition type of the same particle. 
     After the particles have been analyzed by the microcontroller, a sorter is provided to pneumatically separate the particles according to their composition. In detail, the sorter includes an n-number of gate valves that are mounted on the base member. Further, each gate valve is connected in fluid communication with a respective particle recovery channel. Thus, each gate valve is interconnected in fluid communication with the diverter. 
     An n-number of collection bins are individually connected with a respective particle recovery channel for receiving all particles having a predetermined same composition. To do this, depending on the particle composition, the microcontroller simultaneously opens one gate valve and closes the remaining (n−1) gate valves. This action then selectively directs particles of the same composition toward the open gate valve and into its associated collection bin. An assay of the particles can then be made. 
     For another embodiment of the present invention, it is to be appreciated that a plurality of devices can be simultaneously employed in combination. The objective here for using a combined plurality of devices is, of course, to increase the system throughput. In particular, the present invention envisions that a large number of devices can be operationally integrated to process as much as one ton of material (i.e. particles) in an hour. 
     In another aspect of the present invention, it is to be appreciated that by using a device of the present invention, a relatively minute trace of a target mineral can be detected in a very large sample of material (particles). Importantly, the detection of such a small amount of the target material may well justify additional assays. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
         FIG. 1  is a schematic presentation of the operational components of a device for separating particles in accordance with the present invention; 
         FIG. 2  is a top plan view of the base member of the present invention showing various particle channels connected in fluid communication with each other; 
         FIG. 3  is a view of the venturi pump established for the present invention, as shown by the line  3 - 3  in  FIG. 2 ; 
         FIG. 4  is a view of the microfluidic serpentine established for the present invention, as shown by the line  4 - 4  in  FIG. 2 ; and 
         FIG. 5  is a schematic presentation of an operational configuration for components of the spectrophotometer of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A system for sorting particles and preparing an assay in accordance with the present invention is shown in  FIG. 1  and is generally designated  10 . As shown, the system  10  includes an injector unit  12 , an analyzer  14 , and a sorter  16 . For purposes of the present invention, these components cooperate to process and analyze an ore/mineral sample for the preparation of an assay report  18  on the sample. 
     Structurally, an essential component of the system  10  is its base member  20 . This base member  20  is preferably made of a transparent material, such as quartz, glass, borosilicate, sapphire or a clear plastic, and it is bounded by a periphery  22 . Importantly, various channels are embedded in the base member  20  to establish fluid communication paths through the base member  20 . 
     Referring to  FIG. 2 , it will be seen that the base member  20  is formed with an air flow injection channel  24  that extends from the periphery  22  to a venturi pump  26 . As shown, the venturi pump  26  is also formed in the base member  20 . Similar to the air flow injection channel  24 , a particle injection channel  28  also extends from the periphery  22  to the venturi pump  26 . An elongated central lumen  30  then extends from the venturi pump  26  to a diverter  32 . At the diverter  32 , the central lumen  30  divides into an n-number of particle recovery channels  34 , of which the recovery channels  34   a - e  are exemplary. As shown, the central lumen  30  is coaxially aligned with the air flow injection channel  24 , and the various particle recovery channels  34   a - e  extend from the diverter  32  to the periphery  22  of the base member  20 . A window  36  is formed into the base member  20  over the central lumen  30 . Functionally, the window  36  is an area of the base member  20  which has a diminished thickness to facilitate optical access to the central lumen  30 . 
     As envisioned for the present invention, the air flow injection channel  24 , the central lumen  30  and the recovery channels  34   a - e  will all have a characteristic dimension d L . In general, d L  will be less than around two hundred fifty microns (d L &lt;250 μm). On the other hand, the particle injection channel  28  has a characteristic dimension d Lp , where d Lp  will be less than about 150 microns (d Lp &lt;150 μm). Further, the cross-section of each channel  24 ,  28  and  34 , and central lumen  30 , may be either circular or rectangular. In the case of a circular cross-section, d L  will be the diameter of the channel. In the case of a rectangular cross-section, d L  will be a minimum distance between opposed sides of the channel. 
     Returning to  FIG. 1 , it will be seen that the system  10  includes a particle source  38 , such as a hopper, for feeding pre-crushed particles of a sample ore/mineral into the system  10 . As shown, the particle source  38  is connected to the burst generator  40  of the injector unit  12 . It will also be seen that the injector unit  12  of system  10  includes an air compressor  42 . For the system  10 , the burst generator  40  is connected to the particle injection channel  28  by a solenoid valve  44 , and the compressor  42  is connected to the air flow injection channel  24  by a solenoid valve  46 . Further, both  FIG. 1  and  FIG. 2  show that near the solenoid valve  44 , at the periphery  22  of the base member  20 , the particle injection channel  28  is formed with a microfluidic serpentine section  48 . 
     In detail, the venturi pump  26  is shown in  FIG. 3  to effectively draw particles  50  from the particle injection channel  28  into the central lumen  30  of the base member  20 . As is well known in the pertinent art, this pneumatic function is a result caused by pressure differentials in a fluid flow. Specifically, in the case of the present invention, the compressor  42  creates an over-pressure, p.sub.o, in the air flow injection channel  24  that causes accelerated air to flow from the air flow injection channel  24  into the central lumen  30 . As this air flow passes through the venturi pump  26 , its higher velocity relative to air in the particle injection channel  28  causes a relatively lower pressure in the air flow injection channel  24 . This pressure differential then draws particles  50  from the particle injection channel  28  into the venturi pump  26  for further transport through the central lumen  30 . As shown in  FIG. 3 , the particle injection channel  28  approaches the air flow injection channel  24  at an angle of approximately 45 degrees. The particle injection channel  28  is connected in fluid communication to the air flow injection channel  24  at the venturi pump  26  at an angle of approximately 20 degrees. 
     Still referring to  FIG. 3 , for a detailed consideration of the venturi pump  26 , it will be seen that various channels in the base member  20  have different characteristic dimensions. In particular,  FIG. 3  shows that the air flow injection channel  24 , and the central lumen  30 , both have a substantially same diameter, d L . On the other hand, the particle injection channel  28  and the venturi pump  26  at the juncture between the air flow injection channel  24  and the venturi pump  26  each have a diminished diameter d Lp . Specifically, d Lp  is approximately 150 μm and is less than d L  which is approximately 250 μm (d L &gt;d Lp ). The consequence here is that the velocity of air entering the venturi pump  26  from the air flow injection channel  24  is increased because d L &gt;d Lp . A further consequence of this is that the pressure differential in the venturi pump  26  is also increased because of the air velocity increase in the venturi pump  26 . 
     In the action described above for the venturi pump  26 , two factors are of particular importance. For one, the over-pressure p o  generated by the compressor  42  needs to be above the ambient pressure. For the other, each particle  50  needs to have an effective diameter, d p , which is less than the characteristic dimension d Lp  disclosed above for the particle injection channel  28  (d p &lt;d Lp ). This latter requirement can be satisfied by incorporating an appropriate mesh screen with the particle source  38  that will reject particles  50  which exceed the pre-determined d p . 
     In  FIG. 4  it is anticipated that as particles  50  enter the particle injection channel  28 , from the burst generator  40  (not shown in  FIG. 4 ) through the solenoid valve  44 , it may happen they will do so in clumps. To help in separating the particles  50  from each other, a microfluidic serpentine section  48  can be formed into the particle injection channel  28 . The intended consequence here is that the tortuous route which is created will cause collisions between the clumped particles  50  and walls of the microfluidic serpentine section  48 . These collisions can then assist in separating the particles  50  from each other. This separation is important. As intended for the present invention, and best appreciated with reference to  FIG. 3 , an important aspect of the present invention is that all of the particles  50  are aligned in single file as they pass through the central lumen  30 . As shown in  FIG. 4 , the microfluidic serpentine section  48  comprises multiple obtuse-angled bends in the particle injection channel  28  having a generally sinusoidal form and bumps on the segments between each bend of the particle injection channel  28 . 
     Returning to  FIG. 1  it will be seen that the analyzer  14  of the system  10  includes a microcontroller  52 . Further, a camera  54  and a spectrophotometer  56  are connected directly with the microcontroller  52 . Also, as shown in  FIG. 1 , the spectrophotometer  56  includes a light source  58 , a sensor  60  and a grating  62 . In their combined cooperation, the camera  54  and the spectrophotometer  56  are controlled by the microcontroller  52  to measure and analyze each individual particle  50  as it passes through the central lumen  30 . In detail, the camera  54  will take a picture of each particle  50  that is then used by the microcontroller  52  to determine a size for the particle  50 . Typically, this measurement of particle  50  will be accomplished before the particle  50  enters the central lumen  30 . Then, after its size is determined, the spectrophotometer  56  is activated to determine a composition of the particle  50 . 
       FIG. 5  shows the components of spectrophotometer  56  in a typical, operational configuration. As shown, it is to be appreciated that the particle  50  is transiting through the central lumen  30 . During this transit, the light source  58  directs a beam of light along the beam path  64 . Light that is reflected from the particle  50  will then return from the particle  50  along another beam path  66 . The angle α between beam path  64  and beam path  66  will preferably be an acute angle in the range between 45° and 60°. Positioned on the beam path  66  is the grating  62  which is used to spread light reflected from the particle  50  into a spectrum  68 . Then, using techniques well known in the pertinent art, the sensor  60  can analyze the spectrum  68  to determine the composition of the particle  50 . 
     In  FIG. 1 , along with the diverter  32  and the particle recovery channels  34   a - e , the sorter  16  is shown to include a plurality of solenoid valves  70   a - e  (only solenoids  70   a  and  70   e  are designated in  FIG. 1 ). Nevertheless, as shown, each solenoid valve  70   a - e  is connected between a respective particle recovery channel  34   a - e  and a collection bin  72   a - e . Further, for reasons set forth below, the solenoid valves  70   a - e  are each individually connected with the microcontroller  52  for their separate activation. For purposes of this disclosure, it is to be appreciated there can be an n-number of particle recovery channels  34  in the sorter  16 , with a corresponding n-number of solenoid valves  70  and collection bins  72 . The number  5  for “n” as used in this disclosure is merely exemplary. Moreover, it is to be appreciated that although the base member  20  may be formed with an n-number of particle recovery channels  34 , not all of the channels  34  need to be used for preparing the assay report  18 . 
     Prior to an operation of the system  10  of the present invention, a user/operator (not shown) will use a keyboard  74  for inputting desired operational parameters to the microcontroller  52 . For example, it may happen that the user/operator is interested in ascertaining the content of gold (Au) in a given sample of an ore/mineral. Further, consider the user/operator wants the gold particles  50  to be collected in collection bin  72   a , with all other particles  50  being sent to the collection bin  72   e . In this example, the fact that gold (Au) is to be investigated, the selection of collection bin  72   a  for this collection, the operation of burst generator  40 , and the over-pressure p o  that is selected for compressor  42 , are all typical inputs for microcontroller  52 . 
     In an operation of the system  10 , the compressor  42  is activated and the solenoid valve  46  is opened to admit compressed air at an over-pressure p o  into the air flow injection channel  24 . Burst generator  40  is also activated and the solenoid valve  44  is pulsed to allow predetermined bursts of pre-crushed particles  50  into the particle injection channel  28 . The particles  50  are then drawn into alignment by the venturi pump  26  for transit through the central lumen  30  in single file. During transit of the particles  50  through the central lumen  30  they are sized using images taken by the camera  54 , and their composition is determined by the spectrophotometer  56 . After passing through the central lumen  30 , each particle  50  is directed to a specific collection bin  72   a - e , according to its composition. In the example given here, gold particles  50  are pneumatically directed by the diverter  32  into the collection bin  72   a . Specifically, this pneumatic direction of gold particles  50  is accomplished by opening the solenoid valve  70   a , while closing all of the other solenoid valves  70 . On the other hand, the remaining particles  50  (i.e. non-gold) are pneumatically directed into the collection bin  72   e  by opening the solenoid valve  70   e  while the solenoid valves  70   a - d  are closed. It is envisioned for the present invention that the particles  50  may be native gold, native silver, acanthite, chalcopyrite, sphalerite, and rare earth minerals such as bastnasite, monazite and xenotime. As will be appreciated by the skilled artisan, this selective direction of particles  50  through the diverter  32  can be accomplished under computer-control, in accordance with input provided by the user/operator. 
     While the particular Universal Mineral Separator as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.