Abstract:
The present invention a material classifier includes a cyclone including a cyclone inlet, a cyclone outlet, a blower and a blower discharge; an air diffuser connected at a diffuser inlet to the cyclone outlet and at a diffuser outlet to an air lock such that the cyclone and air diffuser are in fluid communication; wherein the diffuser including a central cylindrical portion including an air inlet for admitting controlled amounts of diffuser air around substantially the entire cylinder outer periphery of the central cylindrical portion, wherein the material classifier separating fine particles from coarse particles and discharging the fine particles together with air out the blower discharge, and discharging the coarse particles through the air lock, such that increasing the amount of diffuser air increases the size of the fine particles being separated from the coarse particles. Preferably wherein the diffuser air is admitted into the cyclone in such a manner as to enhance and reinforce the formation of a strong interior vortex.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to material classification systems and in particular relates to material classifier using a cyclone.  
       BACKGROUND OF THE INVENTION  
       [0002]     In order to transport granular materials they are often entrained in air or some gas. By fluidizing granular material in air, one is capable of transporting the granular materials through pipes, long distances to desired locations. Once the material has reached its desired location, the material being transported must be separated from the air which is usually accomplished with a cyclone. Therefore in most material conveying systems using air fluidization or entraining granular particles within air, the final air material separation is often accomplished with a cyclone.  
         [0003]     Furthermore, there is often the requirement that the granular materials being transported, further needs to be classified into different sizes. The most fundamental classification that usually is required is separation of coarser material from finer material for subsequent operations. There are a number of existing devices which independently of the cyclone have the capability of classifying materials into different sizes. It would be desirable, however to use the cyclone in addition to its air separating ability to also be able to classify the materials into different sizes. This would eliminate an intermediate step and the equipment associated with classifying granular materials into various sizes.  
         [0004]     There have been attempts at accomplishing this within the cyclone, in for example prior art in International Application WO 03/033158 A1, titled Dust Separator, filed by Rapid Granulator AB on Oct. 19, 2001, wherein they describe a cyclone which is used for the separation of dust from granular material, using a separator chamber mounted on the lower side of a cyclone. Particles dropping out of the bottom of the cyclone pass into a separator chamber and impinge upon a deflector device, wherein via this impact any dust upon the particles settling out of the bottom of the cyclone is dislodged and carried upward through a “inner wall” of the cyclone. Further, the art teaches plates disposed within the inner walls, whose purpose is to prevent or reduce rotation of the flow which takes place with the major direction upwards within the “inner wall” of the cyclone. An air inlet is located below the separator chamber. A downwardly angled portion of the inlet conduit, introduces air and is controlled by a regulator valve. The art taught in this patent is directed towards removal of dust which is adhered to larger granular particles. The apparatus intends to dislodge the dust from the larger granular materials by impinging the larger granular materials upon the deflector devices within a separation chamber. This unit is limited to the collection and removal of extremely fine dust particles from granular materials.  
         [0005]     There is however, a need to be able to use a cyclone as a material classifier to be able to classify granular materials into coarse and fine in addition to having the capability of dust removal as indicated in the prior art PCT Application WO 03/033158 A1.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention a material classifier includes: 
        a) a cyclone including a cyclone inlet, a cyclone outlet, a blower and a blower discharge;     b) an air diffuser connected at a diffuser inlet to said cyclone outlet and at a diffuser outlet to an air lock such that said cyclone and air diffuser are in fluid communication;     c) wherein said diffuser including a central cylindrical portion including an air inlet means for admitting controlled amounts of diffuser air around substantially the entire cylinder outer periphery of said central cylindrical portion, wherein said material classifier separating fine particles from coarse particles and discharging said fine particles together with air out said blower discharge, and discharging said corse particles through said air lock, such that increasing the amount of diffuser air increases the size of the fine particles being separated from the coarse particles.        
 
         [0010]     Preferably wherein said diffuser air is admitted into said cyclone in such a manner as to enhance and reinforce the formation of a strong interior vortex.  
         [0011]     Preferably wherein said air inlet means including numerous air inlet apertures spaced around said cylinder outer periphery for admitting diffuser air  
         [0012]     Preferably wherein said air inlet means including numerous air slots spaced around said cylinder outer periphery for admitting diffuser air.  
         [0013]     Preferably wherein said air slots extending along a longitudinal axis, and said slots oriented at an angle theta measured between said longitudinal axis and vertical such that when diffuser air is admitted through said angled slots said air flow supporting development of an interior cyclone in said cyclone.  
         [0014]     Preferably wherein said angle theta between 10 and 80 degrees.  
         [0015]     Preferably wherein said slots are so oriented so as to enhance and reinforce a formation of a strong interior vortex.  
         [0016]     Preferably wherein said air inlet means further including a control means for adjustably controlling the amount of diffuser air being admitted through said air inlet means and into said air diffuser.  
         [0017]     Preferably wherein said control means including an annular adjustable band extending and clamping around the cylinder outer periphery for selectively covering off all or some of the slot area.  
         [0018]     Preferably wherein said control means including a barometric damper for adjusting the amount of diffuser air depending upon the material through put of the cyclone.  
         [0019]     Preferably wherein said central cylindrical portion being larger in diameter than a cyclone outlet diameter.  
         [0020]     Preferably wherein said central cylindrical portion having a diameter at least 1.2 times that of the cyclone outlet diameter.  
         [0021]     Preferably wherein said cyclone being a mid efficiency cyclone having a air inlet velocity of no more than 3000 feet per minute.  
         [0022]     Preferably wherein said cyclone dimensioned and adapted to promote formation of an exterior downwardly spiralling vortex and an up draft interior upwardly spiralling vortex.  
         [0023]     Preferably wherein said cyclone further including a stand pipe dimensioned to aid and enhance the development of a strong updraft interior vortex.  
         [0024]     Preferably wherein said air diffuser including an upper tapered portion for the transition between the diffuser inlet and the central cylindrical portion.  
         [0025]     Preferably wherein said central cylindrical portion being a hollow body and a vertical length greater than the diameter of the cyclone outlet.  
         [0026]     Preferably wherein the entrained particles being selected from the list including granulate, pellets, fibres, flakes, beans, plastic, metal, and paper. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]      FIG. 1  is an upright schematic perspective view of the present invention a material classifier.  
         [0028]      FIG. 2  is an upright schematic partial cut-away perspective view of the present invention a material classifier.  
         [0029]      FIG. 3  is a schematic perspective view of a regrind system including the present invention a material classifier.  
         [0030]      FIG. 4  is a schematic perspective partial cut away view of a regrind system showing the present invention the material classifier.  
         [0031]      FIG. 5  is an upright schematic perspective view of the air diffuser portion part of the material classifier.  
         [0032]      FIG. 6  is a side plan elevational view of an alternate embodiment of the body portion of a material classifier shown in  FIGS. 6, 8  and  9 .  
         [0033]      FIG. 7  is a upright schematic perspective view of an alternate embodiment of a material classifier showing various inlet heights.  
         [0034]      FIG. 8  is an upright schematic perspective view of the alternate embodiment of the material classifier shown in  FIG. 7 , showing by way of example two different inlet angles, alpha and two different bottom outlet diameters.  
         [0035]      FIG. 9  is an upright schematic transparent view of an alternate embodiment of the material classifier with a conical top showing the interior vortex and the exterior vortex. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0036]     The present invention a material classifier shown generally as  20  is shown in  FIG. 4  deployed together with other equipment making up a regrind system shown generally as  22 . Regrind system  22  takes plastic components and/or plastic parts or rejected plastic parts and feeds them through a grinder shown generally as  501  which produces granular material containing both coarser particles, finer particles and of coarse also some dust. All of this granular material is conveyed to material classifier  20 , wherein the coarse granular particles  106  are separated from the finer granular particles  107  as well as dust which may be entrained, such that coarse particles  106  are discharged from air lock housing  401  and finer granular materials as well as dust together with air is discharged from blower discharge  250  to bag house  502 .  
         [0037]     The present invention, material classifier shown generally as  20  as shown in  FIGS. 1 and 2  and includes the following major components namely cyclone  100 , blower  200 , air diffuser  300  and air lock  400 . Cyclone  100  includes cyclone housing  101 , tangential cyclone inlet  102 , cyclone outlet  103 , internal stand pipe  104  and blower air  105  shown generally as dark arrows. Note that blower air  105  shown as dark arrows will have entrained therein depending upon the location within the process, coarse particles  106 , fine particles  107 , diffuser air  304  as well as dust. Note that diffuser air flow is generally shown as light or white arrows  108  and diffuser air flow  108  will have entrained in it, depending upon the location within the device, fine particles  107  as well as dust. Cyclone  100  is the type known in the art and normally utilized for separating air from particles entrained or fluidized in the air.  
         [0038]     Blower  200  includes the following major components, blower housing  201  having mounted therein a fan  202  driven by a motor  203 , having a blower discharge  250 , wherein blower  200  draws in blower air  105  through cyclone inlet  102  and further through stand pipe  104  and out through blower discharge  250 .  
         [0039]     Air diffuser  300  includes a substantially hollow cylindrically shaped diffuser housing  301 , diffuser inlet  302 , diffuser outlet  303 , diffuser air  304 , shown generally as light or white arrows  108 . Diffuser air  108  is introduced into air diffuser  300  via air slots  305  which can be opened and closed with adjustable band  302  having an adjusting bolt  310 , such that adjustable band  306  can be moved along vertical direction  330 .  FIG. 5  shows adjustable band  306  in the fully opened position  320  in solid lines and the partially closed position  322  in dashed lines. Diffuser housing  301  includes an upper tapered portion  312 , a central cylindrical portion  314 , a lower tapered portion  314 , wherein diffuser inlet  302  has a inlet diameter  340  which is the same as the cyclone outlet diameter and wherein central cylindrical portion  314  has a cylindrical diameter  342 .  
         [0040]     Material classifier  20  further includes some type of air lock  400  shown in these diagrams buy way of example only as a rotary air lock  400 , including an air lock housing  401 , an air lock inlet  402 , a discharge  402  and a rotor  404 . Kindly note that air lock  400  can be any of the types known in the art, not necessarily a rotary air lock as depicted here as long as the air lock  400  is able to separate solid materials from air.  
         [0041]     The regrind system shown generally as  22  in  FIGS. 3 and 4 , includes a grinder  501  having a grinder housing  503 , and a raw material inlet  502  further including piping  511  for transportation of granular material to the material classifier  20 . Prior to the fluidized material entering cyclone  100 , it is preferably passed through an anti-static system  110 , wherein charged particles  172  enter into anti-static system  110  are neutralized such that uncharged coarse particles  106  leave anti-static system  110 . Anti-static system  110  will neutralize both coarse and fine particles as well as dust particles, even though this is not depicted in the drawings. Material classifier  20  separates coarse particles which exit through the bottom of discharge  403  of air lock  400 , wherein fine particles  107  exit at blower discharge  250  via piping  511  to a bag house  502  which includes a plenum  505 , air filters  506  and fine containers  507 .  
         [0042]     In Use  
         [0043]     Granular material is received into cyclone  100  through cyclone inlet  102  which is positioned in such a manner to set up cyclonic motion within cyclone housing  101  as depicted schematically with the dark black arrows which are denoted as blower air  105 . Blower  200  having fan  202  driven by fan motor  203 , creates a vacuum or suction on cyclone inlet end  102  and draws granular material in through cyclone inlet  102 . Granular material normally includes coarse particles  106 , fine particles  107 , and dust particles not shown as well as blower air  105  all mixed together at cyclone inlet  102 . Cyclone inlet  102  is normally positioned above a vertical stand pipe  104  centrally and coaxially mounted within cyclone housing  101 . This cyclone geometry well known in the art creates a circular flow around the exterior portion of cyclone housing  101  as depicted by the dark arrows of blower air  105  and the heavier coarse particles  106  through centrifugal force are swept to the exterior periphery of cyclone housing  101  and make their way downwardly in vertical direction  191  towards cyclone outlet  103 . Blower air  105  drawn into fan  202  of blower  200  enters stand pipe  104  and up and through fan  202  and out blower discharge  250 .  
         [0044]     It is believed that an up draft and or a counter rotating vortex is created vertically below stand pipe  104  which typically provides for the removal of blower air  105  through blower  200  and out through blower discharge  250 .  
         [0045]     Therefore there is an exterior spirally downwardly rotating vortex  701  with heavier coarser particles  106  entrained therein and moving vertically downwardly along vertical direction  191  and there is an interior updraft or spirally upwardly counter rotating vortex  702  developed proximate the central portion of cyclone housing  101  and in this manner blower air  105  is removed from cyclone housing  101  at times together with dust out of blower discharge  250 .  
         [0046]     Prior art International Application WO 03/033158 A1 adds an additional separator chamber  18  below cyclone  100  which has mounted therein a deflector device  19 , wherein coarser particles impinge upon the deflector device, such that additional dust is dislodged from coarser particles and by additionally allowing air to enter below a separator chamber, this dust is then carried out with the air discharge rather than through the air lock.  
         [0047]     In the present invention as coarse particles  106 , together with fine particles  107  as well as dust, makes its way downwardly in cyclone  100  towards cyclone outlet  103  and into air diffuser  300 , particles of all sizes meet with diffuser air  304  which is allowed to enter through air slots  305  which are defined around the entire cylinder outer periphery  350  of central cylindrical portion  314  of diffuser housing  301 .  
         [0048]     Diffuser air  304  entering through air slots  305  defined around the entire cylinder out periphery  350 , fluidizes or entrains, fine particles by supporting and enlarging the up draft interior vortex  702  and effectively strengthens the upward force of interior vortex  702  and diffuser air  304  rising upwardly into stand pipe  104  creates a strong upward draft such that by controlling the amount of diffuser air  304 , one controls the strength and velocity of air within interior vortex  702  and in this manner, one can control the size of particles which are fluidized by interior vortex  702  and which eventually make their way through blower  200  and out through blower discharge  250 .  
         [0049]     Experimentally, it has been found that it is important to support the existing up draft interior vortex  702  as well as the exterior vortex  701  through the design of the inlet of diffuser air  304  into cyclone  100 .  
         [0050]     Unlike the prior art as described in WO 03/033158 A1 which in fact indicates that they are using plates within a the stand pipe for the purpose of preventing or reducing rotation of flow which takes place with the major direction upwards inside the inner walls. The present invention utilizes the existing upwards flow within cyclone by controllably strengthening and enhancing the up draft flow within the interior vortex  702  in order to selectively fluidize particles of pre determined size.  
         [0051]     As a result, it has been found that by angling air slots  305  at an angle theta  344  measured between a longitudinal axis  345  and the vertical direction  191 , one is able to enhance and encourage the up draft interior vortex  702  by placing the air slots  305  around cylinder outer periphery  350  in an angled relationship having an angle theta  344  as shown in  FIG. 5 . Adjustable band  306  having an adjustment bolt  310  is strapped around central cylindrical portion  314  of air diffuser  300  and can be adjusted by loosening off bolt  310  to a fully opened position as shown in  320  in  FIG. 5  or a partially closed position  322  as shown as dashed lines in  FIG. 5  or in fact it can fully close off air slots  305  by placing adjustable band  306  entirely covering air slots  305 .  
         [0052]     Through trial and error and experimentation it has been found that it is important that central cylindrical portion  314  have a cylinder diameter  342  larger than inlet diameter  340  which is basically the same diameter as cyclone outlet  103 . It has been found that in order to enhance and aid the interior vortex  702  development, one needs to introduce diffuser air  304  at a cylinder diameter  342  which is larger than the cyclone outlet diameter  103 . In addition, it has been found very important that air be introduced around the entire periphery of cylinder outlet  350 , rather than at just a single point, once again in order to aid the development and strength of interior vortex  702  which is rotating counter clock wise and rising upwardly within cyclone housing  101 .  
         [0053]     In practice one has been able to control the classifier such that the material size exiting out of blower discharge  250  can be carefully controlled by allowing more or less diffuser air  304  through air slots  305  of air diffuser  300 . The heaviest particles will immediately tend to the outer diameter of cyclone housing  101  and will drop through air diffuser  300  undisturbed and into air lock  400 .  
         [0054]     However by introducing more diffuser air  304  through air slots  305 , the interior vortex  702  becomes stronger and more fully developed and will fluidize and carry upwardly larger and larger granules of particles up through stand pipe  104  and out through blower discharge  250 , such that one can select the size of particles into at least two distinct sizes, namely coarser particles  106  and fine particles  107 , in addition to dust removal.  
         [0055]     A person skilled in the art will note that cyclone  100  in any event removes dust particles not shown in the attached diagrams and the prior art in International Application WO 03/033158 A1 has indicated a method or a means of adding or enhancing dust removal through a conventional cyclone  100 .  
         [0056]     In addition to dust removal, material classifier  20  has the capability of selectively removing heavier particles and in fact can classify incoming particles into at least two classifications namely coarse particles  106  which are discharged from discharge  402  of air lock  400  and fine particles  107  which are discharged from blower discharge  250 . The fine particle size can be controllably selected by adjusting the amount of diffuser air  304 .  
         [0057]     Material classifier  20  appears to be most effective when using a mid-efficiency cyclone  100  rather than a high efficiency cyclone. A mid efficiency cyclone generally has an air velocity of less than 3000 feet/min. High efficiency cyclones tend to be smaller in diameter and longer in length and have a strong exterior vortex  701  and it is the inventors theory that the interior vortex  702  tends to be extremely weak and therefore it is difficult to support and/or enhance the interior vortex  702  development with the addition of diffuser air  304  through air slots  305 . In any event, through trial and error and experimentation, it has been found that a larger diameter cyclone  100  known in the industry as a mid efficiency cyclone, appears to develop a very strong interior vortex  702  which can be enhanced and utilized with the introduction of diffuser air  304  through air slots  305 .  
         [0058]     Material classifier  20  is shown in a typical installation of a regrind system  22  as depicted schematically in  FIGS. 3 and 4 .  
         [0059]     By way of example only and without limitation, a plastic regrind system takes existing plastic components or scrap from injection moulding machines or blow moulding machines and regrinds this plastic for later reuse. The plastic is introduced into grinder  501  through raw material inlet  502  and via piping  511  is conveyed in an air fluidized manner to material classifier  20 , wherein both coarse particles  106  and fine particles  107  enter material classifier  20  along with dust of coarse, and wherein through the cyclonic action of cyclone  100 , the larger particles fall quickly to the cyclone outlet  103  and out through air diffuser  300  and into air lock  400 , where they are dropped into material container  504 . Depending upon the amount of diffuser air  304  which one selects to enter through air slots  305 , the lighter, smaller granular particles as well as dust is carried upwardly with interior vortex  702 , up through blower  200  and out through blower discharge  250 . Therefore, larger particles of a certain size are discharged through air lock  400  and smaller particles of a certain size are discharged through blower discharge  250 .  
         [0060]     In order to separate blower air  105  from fine particles  107  and dust which also may be entrained, a bag house  502  is employed, wherein the air and particles discharged from blower discharge  250  pass through plenum  505  and drop down through air filters  506  wherein air is discharged and fine granular material is collected in fines containers  507 .  
         [0061]     In this manner a person skilled in the art will note that various granular materials can be classified using material classifier  20  including plastic materials, grains, sands, coffee, wood chips, rubber granular materials, fibre granular materials, plastics from metal, jute from wire, filaments and many other granular type materials too numerous to list here.  
         [0062]     Further it has been found that by using a barometric damper (not shown in the drawings) to control the amount of diffuser air  304  one can compensate for through put variations such as material surges or variations in material through put rates. The barometric damper would have an upstream sensor placed prior to cyclone inlet  102  which would adjust diffuser air  304  amounts according to material through put.  
       Description of Alternate Embodiment  
       [0063]     An alternate embodiment of the material classifier is shown in  FIGS. 6, 7 ,  8  and  9  and is shown generally as material classifier  700  which operates in an analogous fashion as material classifier  20  with the following modifications and improvements to the cyclone.  
         [0064]     Material classifier  700  includes a conical top  720  having a top diameter  712 , a cylindrical section  714  and a conical bottom section  710 . It further includes cyclone inlet  102  which can positioned at different inlet height  704  and/or different inlet angles alpha  706 . In addition, conical bottom  710  may have a differing bottom outlet diameter  708  as shown particularly in  FIG. 8  in dashed lines being the larger bottom outlet diameter  708  and the solid lines being the smaller bottom outlet diameter  708 .  
         [0065]     Referring now to  FIG. 9  which shows schematically the development of the interior vortex  702  which is rising upwardly and development of the exterior or vortex  701  which is moving downwardly. The modifications to material classifier  700  will now be explained in regard to optimizing the development and strength of interior vortex  702  which carries out fines through blower discharge  250 .  
         [0066]     It has been found by trial and error that in order to encourage development of the updraft in interior vortex  702  and more efficient separation of coarse particles  106  from fine particles  107 , a number of modifications to the cyclone have been shown to help develop a stronger interior vortex  702 . In particular the inlet height  704  shown in  FIG. 7  will aid in the development of interior vortex  702  as well as the inlet angle alpha  706  as shown in  FIG. 8  and  FIG. 6  and as well by adding a conical top section  720  on top of cylindrical section  714 , one also is able to enhance and aid the development of a strong interior vortex  702 .  
         [0067]     The inventor has also found that by having a smaller bottom outlet diameter  708  as shown in  FIG. 8 , one can also increase the updraft or the strength of interior vortex  702  within material classifier  700 .  
         [0068]     By optimizing inlet height  704 , inlet angle alpha  706 , bottom outlet diameter  708  as well as by the addition of a conical top section  720 , one can customize material classifier  700  to separate the coarse particles  106  from fine particles  107 .  
         [0069]     It should be apparent to persons skilled in the arts that various modifications and adaptation of this structure described above are possible without departure from the spirit of the invention the scope of which defined in the appended claim.