Patent Publication Number: US-6216367-B1

Title: Classifying and air-stratifying gold separator with inclined sequential chute cone array and size-classifying screen

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to gold concentrators, including dredgers and high-bankers used in placer mining, and more particularly to a staged sluice for increment size classification and ore extraction. 
     2. Prior Art 
     The prior art in placer mining techniques discloses a large number of various devices sometimes termed collectors, separators, or extractors but all directed to extracting small amounts of gold from large volumes of mineral matter. It is known that the majority of gold in placer deposits is fine and very fine grain ore, the larger part of which is typically uncaptured in prior extraction techniques. Though all of the techniques seek to exploit the high specific gravity of gold, the difficulty of removing ore from the matrix in which it is found rests in overcoming detrimental effects of physical forces acting on such fine particles, such as suspension action in a slurry of the matrix in water and surface tension. These effects are exacerbated when fine ore competes with action of larger mineral aggregates, and separation and settling of ore due to its higher specific gravity is defeated. Therefore, the preliminary task before separation by specific gravity is first classification of the matrix and ore by size until ore and gangue can compete in terms of relative specific gravity with minimal effects, or at least non-dominating effects of other physical forces. 
     SUMMARY OF THE INVENTION 
     Ore with much higher density tends to settle out of suspension if allowed to compete with particles of similar size. Therefore, the present invention overcomes these difficulties in placer mining of very fine, or flour, gold generally by repeatedly classifying the gangue and ore mix by size until even the small minerals compete equally in size, thus allowing fine gold to settle out of suspension by its specific gravity higher than surrounding gangue into a scheme of traps that hold the ore for later removal. Repeated processing of the mix further classifies by size at an decreasingly smaller scale. Within each stage, ore and gangue in suspension are stratified by size within suspension with larger particles flowing above smaller particles. The larger particles are flushed away and out of the dredger with water flow while fine ore remains in suspension in lower stratification levels. The stratification is destroyed between stages along the dredger and restratified to enable separation and settling of ever finer ore with comparatively larger gangue being carried away in faster flowing upper levels of stratification, thus further concentrating the ore out of the gangue at each stage. 
     The primary object of the invention is therefore to provide a device to classify mineral matter by size preliminary to extracting fine gold ore from a slurry. 
     Another object is to provide incremental classifying in the device, at each incremental stage separating larger mineral matter from smaller mineral matter while allowing smaller matter to stratify and settle to collecting traps. 
     Another object is to provide a device that inverts stratified mineral matter between stages thereby destroying previously stratified matter, which matter has been previously classified by size in each stage, so that stratification of remaining mineral matter not settled out of suspension during a previous stage begins anew at each stage. 
     Another object is to provide a matrix of ore-capturing cones into which heavy mineral matter settles as lighter matter is carried away. 
     Another object is to provide a means to lift settled matter back into a less turbulent suspension in a second water flow below the cone matrix to further concentrate the ore and allow lighter matter to be carried away in suspension. 
     The approach to extract previously lost fine gold is to treat all size and weight material by incrementing. Optimum separation of smaller and heavier material in general has been compromised in approaches previous to the present concentrator by larger gangue that opposes selective settling by specific gravity and tends to keep fine material in suspension. It is imperative therefore in successfully capturing even fine grain ore to separate materials by size to allow similar size materials to be classified by weight. Thus, a series of size classification stages is employed within each stage, while weight classification is effected. 
     These objects are achieved in a sluice comprising a series of sequential, interconnected chutes. Between chutes is an inverter which inverts a stratified slurry such that an upper stratified slurry layer and lower stratified slurry layer in a given chute generally reverse position as the slurry is directed into a following chute, the slurry also reversing direction between the sections from downhill in the feed chute to uphill as it exits the inverter into the receiving chute entry end. In doing so, materials classified somewhat by size but still carried in the water, being stratified by size but not settled out of suspension, are inverted in the inverter, material of larger size being predominantly discharged first to a subsequent chute over a mesh screen and eventually out of the sluice faster than smaller material. Consequently, lighter materials carried characteristically lower in the slurry are turbulently deposited later and over larger materials with the larger materials carried away from off the screen, destroying the stratification of the remaining smaller mineral matter. Thus, each stage reclassify by size starting with remaining smaller mineral matter while larger materials move more quickly and out of the concentrator sluice. 
     With each incremental stage designed to treat smaller matter, the mesh of each chute screen is smaller than meshes of preceding chutes. Thus, each stage treats a material of smaller size defined by the screen mesh size eliminating size competition that tends to carry smaller heavier material in suspension with larger materials. 
     An array of cones is disposed on each chute bottom over which the slurry passes, adapted such that heavy matter settling from the mineral matrix is drawn into a cone of the array where it is trapped. Each cone in the array has an opening oriented downwater and includes a ridge over-hanging its opening also oriented downwater. As the slurry flows rapidly over the ridges, a low pressure region develops below in the cone cavity. The majority of the water flows over the ridges from one cone to a successive cone carrying light and large material from chute to chute through and out of the dredger. A small portion of the water flowing close to the ridges is drawn into the respective low-pressure cavities. In doing so, small, heavy material—“fines”—falling under gravity out of the slurry mainstream are biased by the small portion of water into a low pressure cone cavity. 
     Below the cone array is a perforated mat, commonly known as miner&#39;s moss. Because heavy gold ore tends to fall immediately when the mineral matrix is deposited on the mesh screen, it is generally sufficient to locate the miner&#39;s moss at least on the chute upper portion under the mesh screen. Also below the array, beginning at the minor&#39;s moss mat and extending downwater, is a textured mat, typically with upstanding ribs transverse to the chute water flow that also tends to capture settling material. 
     Because ore and unwanted material inevitably settles in the perforated mat, or miner&#39;s moss, the material needs to be lifted from the moss to reenter the classification process. If left on the minor&#39;s moss, the settled material quickly covers or clogs it, leaving it ineffective, and the concentration process at that phase is defeated. Therefore, below the miner&#39;s moss is provided a plurality of fluid nozzles, typically air holes in a network of tubes connected to an outside air compressor. With air jetted from the holes upward into the minor&#39;s moss, settled mineral matter is lifted upward with ore of high specific gravity falling back and past the air nozzles and with lighter gangue once again returned to suspension in the slurry. 
     With such a classification system of sequential chutes and ore-trapping cone arrays, the chutes can be steeply inclined, even at 45 degrees or more. The steep incline not only quickly removes large gangue from the classification process allowing increased throughput of a mineral matrix, the more rapid-moving slurry inherent in a steeper incline actually enhances classification at the cone array as the flow over the cones further reduces pressure in the cone, better drawing heavy ore within. 
     The described ore concentrator can be employed as a high-banker or as a dredger. As a high-banker, a preliminary screen is typically placed inclined over a mixer box to reject grossly large matter deposited onto it before the mixer box feeds the first chute. Water is separately introduced into the mixer box usually by a pump drawing water from a nearby water body, such as a river. 
     As a dredger, the concentrator may be mounted on a river bank or floated on a river. Water and a mineral mix is pumped into a dredger hose and deposited into a mixer box. To assist the size classification process in the present invention, air is introduced into the dredger hose to assist in lifting the matrix and to begin size classification. That is, gangue pumped into the hose is eventually discharged into the concentrator, but within the hose the material is partially separated by size and stratified. Thus, when the material is discharged into the separator, competition between sizes is already somewhat reduced and the classification process in the separator is enhanced, requiring fewer classification stages. 
     If the chutes become tilted, either on the float or on a bank, settling material quickly concentrates in low areas, quickly covering and clogging collecting mats. It is therefore necessary to maintain the separator level so the full mat is employed and settling material is dispersed over a larger area. This is effected by hanging the separator by an adjustable-length chain. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a separator stage of the present invention. 
     FIG. 2 is a perspective of view of several connected separator stages. 
     FIG. 3 is a chute of a stage with inverters shown at each end. 
     FIG. 4 is a perspective of a portion of the separator cone matrix. 
     FIG. 5 is a pictorial view of a floating dredger comprising hanging separators. 
     FIG. 6 is a dredger hose comprising a classifying air nozzle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, the separator  1  of the present invention includes a sequential series of ore-separating chutes  10  within which ore is separated from gangue, each chute classifying ore and gangue by size at a finer scale than a preceding chute, generally known as incremental classification. Thus, the separator comprises at least two inclined chutes  10  and a curvilinear inverter  11  between each pair of chutes  10  directing a slurry of ore and gangue from a discharge end  12  of one chute  10   a  into the entry end  13  of a following chute  10   b , inverting the slurry stratified in the size-classification action of the discharging chute. A size-classifying mesh screen  14  is located at the chute entry end  13  onto which the slurry is deposited, the screen of each subsequent chute having a finer mesh than preceding screens to further classify by size. 
     Below each mesh screen  14  is a cone array  15  comprising a plurality of cones  16  with an opening  17  to a cavity  26  directed downwater. Each cone  16  includes an overhanging ridge  18  over which the slurry rapidly passes for developing a low-pressure region in the cavity  26  below the ridge  18  and within the cone  16 . Typically, the cone array  15  comprises a plurality of connected transverse ribs  20  in an approximately sinusoidal weave with inner and outer edges  21  and  22 , the ribs  20  leaning downwater and staggered such that lows  23  of preceding rib outer edges  22  attach to highs  24  of successive rib inner edges  21 . A rise  25  on the high  24  of each rib  20  extends each high  24  downwater therein forming the ridge  18 , with the ridge  18  of preceding ribs  21  bridging the lows  23  and meeting the highs  24  of successive ribs  20 , resulting in a repetitive pattern of cones with ridges  18  over formed cavities  26  thereunder. 
     A collecting mat  27  with a textured collecting surface  28  is positioned below the screen  14  and cone matrix  15  for collecting material passing through the screen  14  and settling out of the slurry into the cone matrix  15 . The mat  27  typically is perforated, or equivalently comprises “miner&#39;s moss,” at least under the mesh screen  14 . 
     To lift gangue settled into the perforated mat  27  back into suspension, a plurality of nozzle holes  29  is provided in a nozzle  30  connected to a fluid source (not shown) under the perforated mat  27  for jetting fluid into the mat  27 , adjusted with valve  31  such that heavy material falls immediately to the mat  27  while lighter gangue is lifted into suspension in a water slurry between the mat  27  and the cone matrix  15 . Although the fluid may be pressurized water, typically compressed air is employed. 
     The nozzle  30  typically comprises a network of tubes  34  with several holes  29  connected to an air compressor  35 . On the chute bottom  36 , below the tubes  34  in the preferred embodiment, is a plurality of traps in a mat  37  under the perforated collecting mat  27  for capturing heavy ore. The trap mat  37  generally includes one or more strips  38  transverse in the chute  10  disposed to retain fine ore as slurry flows over the strips  38 . 
     In combination with a dredger  39 , a dredging hose  40  with an entry end  41  and a discharge end  42  is employed with its discharge end  42  disposed to discharge water into a separator mixer box  43  (or first chute). A water pump  44  is connected to the dredging hose  40  for pumping water into the entry end  41  and through the dredging hose  40  defining a hose water flow. A dredger hose nozzle  45  is connected to the dredger hose  40 , and an air compressor  35  in fluid communication with the hose nozzle  45  feeds compressed air to the nozzle  45  for introducing compressed air into the hose water flow. The compressed air in the dredger hose  40  commences stratifying and classifying of gangue within the hose  40  before discharging it into the mixer box  43 . 
     When the dredger  39  is floated, a vertical support frame  46  is provided which includes a frame support bar  48  supported by legs  49  on each end  50 . The separator  1  is adjustably supported vertically on the support frame  46  to maintain the concentrator chutes  10  transversely level such that the slurry runs over the chutes  10  without preference from side-to-side on the transversely-level inclined chutes  10 . Typically, the separator  1  is hung from the support bar  48  by a plurality of chains  51  adjusted in length to establish and maintain the chutes level. The support frame  46  is mounted on a float assembly  52 , generally comprising one or more interlinked floats  53 . Tracks  54  may be provided on the floats  53  aft to bow and port to starboard on which the support frame  46  may be secured to right the float level by appropriately positioning the separator  1 .