Abstract:
Apparatus providing samples for evaluating the sensitivity of bulk particulate solids to segregation when permeated by a gas. A plurality of stacked discs are rotatably mounted on a vertical shaft. 
     Each disc has a bore, the bores being alignable to form a columnar sample chamber. A gas is introduced under pressure at the bottom of the chamber to fluidize the solids, inducing segregation. Apertures in the discs are adapted to support sample jars. The discs are independently and sequentially rotatable to cause the portion of the segregated sample within each bore to be separately deposited in a sample jar.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to methods and apparatus for evaluating the tendency of sample bulk particulate solids to segregate by fluidization or exposure to permeation by gases. More particularly, it relates to apparatus for controlled fluidization of a vertical column of the solids by a gas such as air and subsequent collection of samples from separate segments of the column. The samples are suitable for conventional evaluation and comparison by screening, assays or other measurements to quantify the potential segregation by fluidization effects or gas entrainment. 
     Bulk solids generally comprise particles of different sizes. It is commonly desirable to maintain a uniform concentration of each size throughout the body during industrial processing, storage and packaging. However, segregation of the particles by size frequently occurs during processing steps such as the filling or discharge of a bin, tumble blending, pneumatic conveying and other gas assisted bulk solid handling processes. As a result of segregation by fluidization, different regions within a body of the solids comprise different proportions of fine and coarse particles and uniformity of the mixture is lost. 
     Vertical segregation frequently occurs, resulting in horizontal layers comprising differing proportions of fine and coarse particles. Fine particles generally have a lower permeability for gas than coarse particles and therefore tend to retain the gas longer. Thus for example, on filling a hopper the coarse particles tend to become more concentrated in the lower layers while the fine particles become more fluidized and tend to become concentrated in the upper layers. Similar effects occur after tumble blending if the solids are susceptible to fluidization. These effects are particularly noticeable in materials that contain a significant concentration of particles below 100 microns in size. Fluidization segregation is also likely to occur when fine materials are pneumatically conveyed, filled or discharged at high rates, or if gas counterflow is employed. 
     A principal object of this invention is to provide a test method and apparatus for precisely controlled fluidization of a sample body of particulate solids, followed by the separate retrieval of portions of the sample from different vertical levels of the fluidized body. 
     A second object is to provide apparatus that facilitates the retrieval of the segregated samples without disturbing the state of the samples. 
     A third object is to provide test apparatus adapted for improved containment of the sample solids during the test procedure. This is particularly desirable for the testing of very fine powders. 
     A further object is to provide apparatus adapted for accurately repeatable fluidization of successive samples, permitting greater reliability and accuracy in comparing the results of repeated test procedures on samples from the same body of bulk solid or from differing bodies of solids. 
     BRIEF SUMMARY OF THE INVENTION 
     With the above and other objects hereinafter appearing in view, this invention provides apparatus for obtaining samples of bulk particulate solids from a columnar sample chamber containing fluidized particulate solids, for evaluating their sensitivity to segregation by fluidization. The apparatus includes a plurality of stacked discs rotatably mounted on a vertical shaft. The discs are provided with bores that are alignable to form a columnar sample chamber comprised of segments each to be separately collected. The discs are also provided with apertures for supporting sample jars, and the discs are independently and sequentially rotatable to cause the segment of the segregated sample solids within the bore of each disc to be separately deposited in a sample jar. 
     Means are provided to compress the discs during fluidization, thus minimizing leakage. When the discs are being rotated the compression force is reduced. 
     Other features, as hereinafter described, are employed to provide a compact apparatus in which the fluidization is precisely controlled for uniformity in repeated tests, thus increasing the reliability of evaluation procedures for comparing the results of separate samplings of the same or different solids. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevation in section through the sample chamber of the presently preferred embodiment of the invention. 
     FIG. 2 is a front elevation of the apparatus on a reduced scale. 
     FIG. 3 is a fragmentary plan view in section corresponding to FIG.  2 . 
     FIG. 4 is an elevation showing a sample jar and its adapter. 
     FIG. 5 is a plan view of the base of the apparatus. 
     FIG. 6 is an elevation of the subassembly of the base and shaft of the apparatus. 
     FIG. 7 is an elevation similar to FIG. 6 at right angles thereto. 
     FIG. 8 is a plan view of the bottom disc. 
     FIG. 9 is an elevation partly in section corresponding to FIG.  8 . 
     FIG. 10 is a bottom view of the bottom disc. 
     FIG. 11 is a side elevation corresponding to FIG.  8 . 
     FIG. 12 is a plan view of an intermediate disc. 
     FIG. 13 is an elevation partly in section corresponding to FIG.  12 . 
     FIG. 14 is a bottom view of an intermediate disc. 
     FIG. 15 is a side elevation corresponding to FIG.  12 . 
     FIG. 16 is a plan view of the top disc. 
     FIG. 17 is an elevation partly in section corresponding to FIG.  16 . 
     FIG. 18 is a bottom view of the top disc. 
     FIG. 19 is a side elevation partly in section corresponding to FIG.  16 . 
    
    
     DETAILED DESCRIPTION 
     The preferred embodiment of the invention, shown generally at  10  in FIGS. 1 and 2, comprises a base  12  preferably constructed of metal, a bottom disc  14  shown in detail in FIGS. 8,  9 ,  10  and  11 , intermediate discs  16  and  18  which are of similar construction as shown in detail for the disc  16  in FIGS. 12,  13 ,  14  and  15 , and a top disc  20  shown in detail in FIGS. 16,  17 ,  18  and  19 . 
     The tester  10  also includes a detachable funnel  22  insertable in a counterbored recess within a thru bore  24  in the disc  20 . The sloping wall of the funnel is sufficiently steep to satisfy the conditions for recovery (flow) of any of the particulate solids to be tested by the apparatus. 
     The base  12  supports a vertical shaft  26  on a fixed axis  28 , and means are provided within the base for adjustable axial movement of the shaft. Details of the shaft support are shown in FIGS. 1,  5  and  7 . The shaft  26  is slidably supported vertically and rotatably within a flanged sleeve  30  fixed to a cover plate  32  on the base. A dust cap  34 , press fit on the shaft within a central recess in the disc  14 , fits slidably over the sleeve  30 . A flanged adjusting wheel hub  36  bears upwardly on the sleeve  30  and downwardly on the bottom of the base  12 . The hub  36  is threaded on the shaft  26  and is secured by screws  38  to a thumb wheel  40 . Thus rotation of the wheel  40  produces axial movement of the shaft  26 . 
     The discs  14 ,  16 ,  18  and  20  are preferably formed of an acrylic plastic material, of cylindrical shape, bored axially and received over the shaft  26  in stacked formation. The intermediate discs  16  and  18  and the top disc  20  are rotatable on the shaft. The bottom disc  14  is prevented from rotation by a pin  42  screwed onto the cover plate  32  of the base and extending into a bore in the disc  14 . Since the disc  14  is fixed in position relative to the base  12  in use, it may be made integral with the base if desired. 
     The discs  14 ,  16  and  18  are provided with bores  44 ,  46  and  48 , respectively. Each of the discs  16 ,  18  and  20  is rotatable on the shaft to a position in which all of the bores  44 ,  46 ,  48  and  24  are axially aligned with the hopper  22 , forming a columnar sample chamber designated generally at  50  and comprised of segments  50   a ,  50   b  and  50   c.    
     The discs  14 ,  16 ,  18  and  20  are each formed with an arcuate shaped aperture. 
     The apertures of the discs  14 ,  16  and  20  are respectively identified as  52 ,  54  and  58 . 
     The apertures of the discs  14 ,  16  and  18  have flanges for receiving and supporting sample jars  60 . Adapters  62  (FIG. 4) are threaded on the jars  60  and rest on these flanges flush with the top surfaces of the discs as shown for the discs  14  and  16  in FIG. 2 (the uppermost jar in this figure being shown out of position for purposes of illustration). The jars of all discs are vertically aligned when the segments  50   a ,  50   b  and  50   c  are also aligned as shown in FIG.  1 . 
     The bottom disc  14  and the intermediate discs  16  and  18  are each provided with a pin  64  that projects upwardly into an arcuate peripheral groove  66  in the adjacent disc. The cooperation of these pins and grooves facilitates the sequential collection of samples as hereinafter described. 
     The shaft  26  has a section  26   a  of reduced cross section as shown in FIG.  1 . The disc  20  has a horizontal thru bore into which a pin  68  is inserted in position to bear slidably on the section  26 ( a ). By rotation of the thumb wheel  40  the shaft may be caused to bear downwardly on the pin and on the stack of discs, causing them to be compressed against the cover plate  32  of the base. The compressive force may be released or varied according to the requirements of the test procedure. 
     A laterally extending threaded bore  70  in the disc  14  communicates with the bore  44 , and the latter also receives an assembly comprising a porous membrane  72 , a membrane retaining ring  74  and a compression spring  76  formed of a wave spring  76 . The bore  70  is adapted for connection to an external source of air or other gas under pressure (not shown). The membrane  72  acts as a diffuser providing a uniform stream of the gas into the test chamber  48 . 
     In use, the test apparatus  10  is initially placed in the position shown in FIGS. 1 and 2 with three empty sample jars  60  in place in the apertures  52 ,  54  and  56  of the discs. A measured quantity of sample solids with uniform particle size distribution is poured into the funnel  22  and fills the sample chamber  50 . 
     Air or other gas under pressure is then admitted through the bore  70  and through the membrane  72  into the test chamber. The pressure of the gas and the duration of flow is precisely controlled, causing fluidization of the material. The fluidized material expands upwardly because of the presence of gas therein and rises into the hopper  22 . 
     After the gas flow is terminated material in the sample chamber  50  is allowed to remain at rest and deaerate. Then, the discs  20 ,  18  and  16  are sequentially rotated to deposit the material in the segments  50   a ,  50   b  and  50   c  of the column  50  respectively into the sample jars  60 . First, the disc  20  is rotated 90° between the limits of the arcuate groove  66  therein by engagement with the pin  64  projecting from the disc  18 , filling the sample jar located in the latter disc. Continued rotation in the same direction through another 90° causes rotation of both of the discs  18  and  20 , resulting in the deposit of the material in the segment  50   b  in the sample jar located in the disc  16 , between the limits defined by the groove  66  in the disc  18 . Further rotation through another 90° causes all of the discs  16 ,  18  and  20  to rotate together, resulting in the deposit of the material in the segment  50   c  in the sample jar located in the disc  14 . 
     The samples in the three jars  60  are then measured or tested by any known assay method, screening method or other test procedure to evaluate the differences in the particle size or chemical concentrations of the material in the respective samples.