US2743817A - Pneumatic separator - Google Patents

Description

May 1, 1956 M. N. MUSGRAVE ETAL 2,743,817

PNEUMATIC SEPARATOR 4 SheetsSheet 1 Filed July 9, 1951 INVENTORS MFR/PILL M NIL/569A V5 AXEL A W5TBERG V/PG/L 5. FAA/SHEE FAME? L. BLOMBERG' M awn B A rroeA/Ers PNEUMATIC SEPARATOR Filed July 9, 1951 4 Sheets-Sheet 2 2/ MERE/Ll. /v. MUSGPA v5 AXEL WESTBEEG wee/1.- B. FAA/6W5? ELMEE L. BAOMB'EG M y 1, 56 M. N. MUSGRAVE ETAL ,7 3, 17

PNEUMATIC SEPARATOR Filed July 9, 1951 4 Sheets-Sheet 3 B) I M y 1, 6 M. N. MUSGRAVE ETAL 2,743,817

PNEUMATIC SEPARATOR Filed July 9, 1951 4 Sheets-Sheet 4 INVENTORS. MERE/LL N. MUS'GAA VE AXEL L. WEjTEEEG V/EG/L B. FAA/5945B ELM e L. BZOMBEEG- BY W4,

United States Patent PNEUMATIC 'SEPARATOR Merrill N. Musgrave, Seattle,-Wasl1;, and Axel L. Westberg, Dundee, and VirgilzB; Eansher and Elmer L. Blomberg, .Newberg, Greg.-

Application July 9, 1951, Serial No. 235,806

4.Claims. (Cl. 2091-474) This invention concerns. thestratification by air flotationof, units jumbled heterogeneonsly in a mass, which units areof different density, or actual mass, leading to the segregation, ofthe units of one density or mass in one stratum,. andthose of difierent density or mass in another, and their ultimateseparation by what might be termed a skimming, operation.

The machine which istobe described, and the method, were ,first proposed as a solution to the problem of segregating w-hole nuts, such as filberts, from broken bits of shells andssimilar foreign matter, progressed from there to the segregationin additionof, the blanks, which are whole nuts that are classed-as culls. because they have voids in the kernels, or no, kernels at all, and has been found applicable to theseparating of lighter units of varionskinds from heavier unitsin the same mass. One example, wherein the units are all'appreciably lighter than the nuts first referred to, concerns the separation from wheat germ of particles of fi'our which tend to cling thereto,-,and"which ,cannot'besatisfactorily separated by the screening Process ,at the flourmills.

The invention 'will' be described primarily with reference to..the segregation. of :filberts from, broken bitsof shells, andjthe like, .or of sound, heavybodied filberts from. the lighter blanks, butibecauseit is applicable to so, many, andjisuch.varied,.,units,or particles, these will be referred 'toj hereinafter, generically, as units, regardless of'th'eir. particular. nature, size. or massllepresent. inventionincludes a generally horizontal, nonevibratory screen along which the units are passed, or ppn which they are spread out, ina blanket a number ofjunitsin depth, with the lighter andfh'eavier units heterogeneously mixed (together. S'olely by the application of, an air blast ,fr'ornbeneath, the screen in a particular mannerpandunder particular conditions,v the blanket of unitsissegregatedand stratified: This has been attempted heretofore, usually by means of rnech'anicalfvib'ration of the s,creen, such as We. do not employ, but bythe applijc'ati'on of the novel principles-of the present invention, to,.be explained'hereinafter in detail,,th'e desired end is now. capable of accomplishmentitozso complete a. degree, and .with, so small a margin .of'error, as to be in elfect .a completely new processsand machine.

The invention primarily" concerns; the segregation of units ona screen solely b'y' .means. .of a properly directed andcontrolled 'air blastf'r'orn below, as. has, just been stated, butmayadditionally include the imparting to the mass are directiQnalefiect, also by; a controlled air blast, causing,,th'e massv on the screen. to travelal'ong the screen in. a definite. directional. sense, continuously, during and following th'eir segregation. This directionalefiecnand the,,discovery' of "how' it may be achieved and controlled, althoughiitissecondary to the segregation by Stratification, and the resultant separation of the lighterunits from, the heavierones; yet is nevertheless-animportant additionalphase' of the present invention-:-

Qne'of the primaryobjects of the-present invention; in additidn'tm effecting th'e more" exact and complete ICC separation and segregation of the units as described above, is to lessen very materially the power requirements in effecting such separation and segregation by air flotation.

The principles of the invention will be explained more fully hereinafter. In the drawingthe invention is shown incorporated in a separator which in its form is somewhat difierent from a commercial separator, in that it is arranged alternatively for the segregation of nuts, or for the segregation of flour from wheat germ, whereas ordinarily one separator would be built and used for one particular purpose only, and features which would be employed in one usage would not be employed in the other usage, and vice versa. However, the provision of alternativelyusable means in one machine would be possible, and that is what has been illustrated.

Figure l is a general side elevation of such a machine, with parts broken away to show the interior construction.

Figure 2 is in part an end elevationand in part a transverse sectional view, the viewpoint being illustrated by the line 2-2 of Figure 1.

Figure 3 is an enlarged longitudinal sectional view vertically through the central part of the machine, in one possible form or arrangement, and Figure 4 is an enlarged, fragmentary, transverse sectional view of the same, both illustrating the machine operating on filberts, While Figure 5 is a View similar to Figure 4, but illustrating the machine operating on Wheat germ.

Figure 6 is a view similar to Figure 4, looking towards the suction nozzle, and with the machine arranged as it would normally be for handling nuts.

Figure 7 is a fragmentary isometric view with parts broken away to illustrate the relationship between a grid and a screen, according to the present invention, and Figure 8 is an enlarged sectional view of the grid and screen and of a blanket of nuts thereon during the emission of an air blast, illustrating the results thereof. Figure 9 is a view similar to Figure 8 showing the mechanism in operation for the segregation of flour from wheat germ.

Figure 10 is a diagrammatic cross section. through the screen and grid illustrating the result of their use in combination according to the present invention, and Figure 11 is a comparative view of the screen alone showing the theoretical explanation of what occurs when thescreen alone is used and the grid is omitted, as was prior pracrice.

The basis of this invention, insofar as concerns effective segregation with low power consumption, is the employment of a fixed, non-vibratory screen ll having a multiplicity of holes-10 through it,. and.the employment in conjunction with that screen of a grid generally designated by the numeral 2, whichconsists of a plurality of air-confining and controllingplates or bars 21, placed generally in parallelism one to another, and generally perpendicular to and contacting the under surface of the screen.

The sheet metal grid bars may be .wholly planar (see Figure 10), although those illustrated elsewhere are of a well'known commercial'type which, used alone, afford certain directional characteristics to air which passes through them. The directionalcharacteristics are afforde'd to the air by means of the inclinedupper edges at 22, and the similar directional elements. at 23. The directional characteristics of" thesev elements 22. and 23 can be combined with certain directionalcharacteristics of a particular screen which will be described' herein after, to produce a certain directional etfect on air which passes through the'grid, and'in turn upon the units above the grid, but it is desired to-emphasize that primarily Whatever-directional 'etle'ctdspresent, if-any, is that given the air by virtue-ofthenature'of a particular i in contact with, the upper edges of the grid bars 21.

, rounding the hole.

style of screen itself, as will be explained later in detail, and of the two the directional effect of the screen predominates. Morever, the directional effect is a secondary one, and the effective segregation with low power does not require that either the screen or the grid possess any directional characteristic.

The size and number of the holes in the screen are such that the screen will support virtually all the units in the heterogeneous mass which rests upon it, particularly as the smaller units are intermingled with the larger and heavier particles. In Figure the screen is shown with holes 10 which are of reasonably large size, yet small enough to support most, if not all, of the bits of broken shell or trash which would be found in the blanket of nuts, whereas in Figure 9, where the units include wheat germs, the holes 10 are somewhat smaller. It has been found that the size and, within reasonable limits, the number of holes per square inch in the screen, have not the major part in determining the amount of power required to blow through the screen, but rather that the amount of power is lessened by the collocation and cooperation of screen and grid properly related, one to another.

The screen rests directly upon, and its under side is No pains are taken to produce any particular registration, nor lack of registration, between the edges of the grid bars and the interstices between the holes of the screen. Generally speaking, however, it be assumed that the grid bars are disposed more or less in the interstices between rows of holes 10 in the screen, and hence by reference to Figure 10 it will be seen that the grid, when used, tends to straighten out the air flow, as indicated by the arrows at 46, so that it tends to be directed perpendicularly to the plane of the screen 1. Some of the air so directed impinges the under surface of the screen 1, and in the absence of the grid 21, that is, under the conditions prevailing in Figure 11, which represents prior practice, any of the air so impinging tends to become compressed as it spreads laterally. That impinging at one side of a hole 10 will tend to flow laterally past the margin of the hole, and toward that flowing from the opposite margin of the hole. The result is, as shown in Figure 11 at 49, there is a tendency to reduce the effective area of the holes 10, or virtually to close them, with a compressed layer of air, so that such air as is directed at the holes 10 hasdifiiculty forcing its way through, and when this difliculty is multiplied by the multiplicity of holes in the screen the result is there is required a large quantity of power to force the air through the simple screen. However, we have discovered that when the grid bars 21 are used, as in Figure 10, the power requirements are strikingly reduced. We do not attempt to explain the reason for this, although it can be reasoned that the air which strikes the under side of the screen may not spread far laterally until it encounters a grid bar 21, whereupon, as indicated at 48, it reverses its original sense and tends to create an eddy within a corner, and this in efiect builds up a nozzle of denser air, which does not so much reduce the area of the hole 10, as it concentrates and by Venturi effect increases the velocity of the air jet as it approaches and passes through the hole 10. The various individual eddies at 48, surrounding each hole, act the same as solid fillers or fillets sur- Whatever may be the correct theory, we know from observation that the use of grid bars in conjunction with the screen greatly reduces the power required to blow'air through the holes. The observe results, in a specific instance, are detailed hereinbelow. The effect may be increased by providing cross grid bars at intervals, and by maintaining the spacing of the grid bars to some degree in conformity with the spacing between rows of holes.

By reference now to Figure 8, it will be seen that the air blast, from whatever convenient source, seeks to pass upwardly through the holes 10 in the screen but is divided first, and confined and smoothed out as at 46, by the grid 2. The air in individual jets 47 corresponding to each hole ill, distributed over the entire area of the screen, lifts units which constitute a blanket laid upon the screen filberts as shown in Figure 8), spreads them out more or less uniformly over the entire area of the screen, and the blanket so constituted is of several units in depth, that is to say, of depth sufiicient that the jets will not :dily blow through, but each must impinge and lift sescral units before it works its way deviously to the top. Each unit at the bottom, acted on by the individual air blasts, is lifted, and in turn lifts the other units. They shift about; each unit impinges many other units. Apparently the heavier units are not lifted as high as the smaller and lighter units, nor to the top of .set, hence as all the units are kept in a state of g suspense by proper control of the force of the air blast, the lighter units quickly work to the top, and remain there, and the heavier units sink to the bottom of the blanket and remain there. Thus is stratification ac complished, and now the blanket may be skimmed by any of a number of processes, but preferably by the application of suction to the upper surface of the blanket. The suction so applied can be regulated to be of suflicient value to lift the top stratum of lighter units to whatever degree experience shows to be desirable, but of insuflicient value to lift the bottom stratum of heavier units. Thus there results a segregation between the lighter and the heavier units, and by proper regulation of the suction, not only may broken bits, shells, dust and trash be lifted from the blanket, but also the blanks. The suction effect may be concentrated at some one point and the blanket of nuts passed beneath that point, as in Figures 1 and 6, or as in Figure 5 the suction effect may be generalized throughout the space above the blanket, and the machine shown herein in most of the figures is capable of or may be arranged for operation in either such manner, depending upon the type of units with which it is employed.

The units may be advanced along the screen while they are in a state of dancing suspense; and this may be accomplished by mechanical means, although it has been discovered that by the use of a particular type of screen, with or without the use of directional elements in the grid, and indeed without employing any grid whatsoever, if power consumption be disregarded, the units in the blanket upon the screen may be caused to advance by the same air jets which cause them to be held in dancing suspense upon the screen, and without any increase in power consumption which can be attributed to the directional effect.

A screen which will produce a directional component is best illustrated in Figure 8, although the screen of Figure 9 has similar characteristics. It is intended to represent in these views a screen of sheet metal with holes 10 rollerpunched through the screen. Holes so formed have a slight burr at the underside of the screen, but as the roll with its protruding punches rolls over the screen, the burr is swaged off by the withdrawing punch, and the hole is somewhat rounded, at the receding edge, but is left unchanged at the opposite edge, at least at the underside of the screen; in other words, the burr remains there, as shown at 11. In similar fashion, and as a result of the withdrawal of the punch, the upper portion of the hole is rounded off as at 12 (see particularly Figure 8), and each hole is left with somewhat of an inclination, slight though it may be, but still definitely inclined in one direction. This inclination of the hole and the one-sided burr 11 cooperate to cause any air blast which passes through the holes, as indicated at 47, to be inclined slightly. This action is illustrated in Figures 8 and 9, and the individual air jets, thus inclined, not only raise and keep the units in dancing suspense in the manner already described, but also urge them slightly toward the left as viewed in Figures 8 and 9, as is indicated by the arrows The cumulative effectof this directionalcomponent is to advance the blanket of dancing unitscontinuouslyinthe direction-indicated by the arrow F.

It is to be emphasized-that this directional eifect of this particular type of screen occurs whether-or not the grid bars 21 be employed, and Whether or-not', ifemployed, they include the directional elements 22,f23,-or equivalent elements. Indeed, it has -been-found that ifthe'directional effect of the screen is reversed with relation-to the directional components of the grid, it is the screen which will control the sense of movement of the units dancing upon it, and notthe grid. The units will -advance in the sense controlled by the screen and opposite to'the'sense'which ordinarily would be given them by the grid.

Presumably because of the*nozzle-or--Venturi effect described above, or Whateverit'may be that is the direct result of the collocation and use in combination of the grid and the screen, the airblastrequiredto produce proper segregation of units in our device-requires only-a small fraction of the power which-would-berequired-if there were no grid but only the screen. Asan illustration, in one machine employing a screen only',(omitting any; grid) used for segregating filberts, having a-cap acity of sixtons per hour, there were employed fourblowers requiring two tenhorsepower motors, or atotal of twenty horsepower, to drive them, with additional power required for suction fans to remove the broken shells from'the, top, and yet the results; though good; still left somethirtcen percentyof broken shells, blanks, and 'trash' in the-mass, and-could not segregate blanks. With any less powerful air blast than could be produced by these fourblowers using, twenty horsepower, the segregation was not as perfect as has. been indicated, and with any greater airblast, not 0I1lYfdl (1;jthC power consumption increase disproportionately, but the air blast merely caused the mass of'nuts' and trash on the screen to boil, that is to say, the lighter units would rise to the top, but would be pushed or blown aside and displaced by heavier units, also blown to the top, the lighter units would sink again, and the mass would be in a constant state of boiling, with all units rising and sinking repeatedly, and the air jets tending to burst directly through the blanket of nuts. The lighter units would not stay on the top of the mass or blanket, and the heavier ones would not stay at the bottom. All light units which were submerged when concentrated suction was applied at the top of the blanket remained a part of the mass, and were not separated. The power consumption in this machine was not affected materially by altering the size of the individual holes in the screen or the number of holes per square inch in the screen.

When the grid of the present invention was applied to such a screen, in the same sort of machine and with the some sort of nuts, it was found that virtually one hundred percent complete separation was accomplished by the use of a two horsepower motor driving eight blower units, together with suitable suction fans, as before.

Details of the machine are largely unimportant, but will now be described in order that the invention may be fully understood. The screen 1 with the grid 2 immediately beneath it is disposed substantially horizontally. In a specific machine for segregating nuts the screen is ten feet long and one foot wide. These dimensions are given by way of illustration, rather than as restrictive. Air intaken at 41 into the blowers 4 of a battery of blowers driven by a motor 40, is delivered by riser ducts 44 past sets of turning vanes 45 into a plenum chamber 31 immediately beneath the grid. The quantity of air delivered is suitably controlled as, for example, by means of dampers 42 controlling the intakes 41 and mounted for adjustment upon a common shaft 43. The air rises from the chamber 31 through the grid and through the screen, with the results already described. Assuming that the screen is of a type to produce a directional effect, a heterogeneous mass of nuts delivered upon the screen by the chute 35 at one end travels toward the opposite end,

6. andth'ere, above the blanket, is disposed a suction nozzle' 51. The closeness of this suction nozzle-to thetop of the blanket, and therefore its effect upon the units inthe top stratum of the blanket, is-regulatable-by the means at 52, adjustable by the mechanism'suggested' at 53, or by equivalent mechanism. There, and by-theseor equivalent means, the already segregated upper stratum is-removed from the still-dancing unitsinthe blanket, and the heavier nutsare discharged at 36. Wh'enever-useof the suction nozzle at 51 is undesirable, it. can be closed off at56from the suction source.

In dealing with nuts, it is not at all important-that the blanket be enclosed. It is shown 'closedin-Figure 4; but ordinarily it would be left open asinFigure 6. When" dealing with units such as wheatgerm, from which flour is to be, segregated, or even'with nuts which contain muchdust or fine trash, it is preferred that the screen and the blanket of units thereon-be housedin; as indicated at 3 in Figures 4 and 5.' Likewise, with such light units as flour particles-'and'wheat germ, it is preferred to. omit the concentrated suction nozzle at 51, or to close it offfas by the damper at 56,- and to employ instead a generalized suction throughout the length of the enclosed tunnel 3,0 which confines the flour; Here suction nozzles 54 at the sides of and extending the length of thetunnel'are provided, and these may be omitted or closed off" by thedampers-SS- when a more concentrated suction, as at 51, is required. Suction is produced by a suction fan 5-- communicatingto the noz zle 51, or to the nozzles at 54, by the duct 50; Whereever there is likely to be dust in the air, such as would tend to clog the holes 10-, it-is preferred to take in'air to the .blowers at 4 through filters at 32 admitting to aplenum chamber 33v The use of filters'is almost always desirable.

It has been indicated that a mechanical conveyor may be employed, and may be desirable with some types of units, and a suggested form of mechanical conveyor is shown in Figures 3 and 4. As shown, it consists of a series of feed bars 6 suspended by hangers at at their ends, from a traveling chain 61, supported and driven by sprocket wheels 62. The feed bars 6, extending the width of the screen 1, and at whatever distance experience has shown to be desirable above the screen, sweep the dancing mass with them from the feed end toward the discharge end of the machine. The bars 6 and associated mechanism may return to the feed end through the chamber or tunnel 35.

Another optionally usable device shown in the drawing is the battery of infra-red sterilizing lamps illustrated at 7, within the roof of the casing 3. These may be mounted in a frame for adjustment upwardly or downwardly, as at 71, to vary their effect as required. They are particularly useful when dealing with wheat germ, but no particular need for them is apparent when dealing with nuts, and ordinarily they would be omitted; compare Figures 5 and 6.

The machine and the process work equally well on nuts of such diverse size, shape and unit mass as walnuts, pecans, Brazil nuts, filberts or almonds, yet the same air flotation process works admirably on such smaller and lighter units as wheat germ, with, of course, suitable choice of the fineness of the screens mesh.

We claim as our invention:

1. A classifier and separator for a heterogeneous mass of units of varying weights, comprising an elongated screen disposed fixedly in a generally horizontal plane, and extending from a feed end to a discharge end, having a multitude of perforations each formed with a burr outstanding on the screens under side, and each burr located at the side of its perforation nearer the screens discharge end, the size of the perforations being small enough to support the mass of material on the screen in the form of a blanket which is rather uniformly several units deep, means to supply the heterogeneous mass upon the screen at the feed end thereof, means to direct a continuous air blast upwardly through the screens perforations, as jets, with force sufficient to maintain the units in the mass dancing, and so to stratify them according 'to weight, and by the directional efiect of the bum on such air blast to advance the dancing mass towards the discharge end, and means adjacent the discharge end to segregate the different strata.

2. A classifier and separator as in claim 1, wherein the walls of the individual perforations are inclined upwardly and towards the screens discharge end, such inclination further directionally affecting the air blast to advance the dancing mass towards the discharge end.

3. A classifier and separator as in claim 1, including additionally an air-flow-directing grid of bars which are disposed in generally parallel upright planes oriented transversely of the length of the screen, said bars having their upper edges substantially in contact with the under surface of the screen, and directing the air blast upwardly through the screens perforations.

4. A classifier and separator for a heterogeneous mass of .units of varying weights, comprising an elongated screen sheetextending from a feed end to a discharge end, means including an air-flow-directing grid of bars which are disposed in generally parallel upright planes oriented transversely of the screen sheet and with their upper edges contacting the under side of the screen sheetjfor supporting the latter fixedly in a generally horizontal plane, said screen sheet having a multitude of perforations distributed over its area, each formed with a burr outstanding on the screen sheets lower surface, and each burr located at the side of its perforation which is nearer the screen sheets discharge end, the size of the perforations being small enough to support the mass of material on the screen in the form of a blanket which is rather uniformly several units deep, means to supply the heterogeneous mass upon the screen at the feed end thereof, means to direct a continuous air blast upwardly through the grid and the screens perforations, as jets, with force suflicient to maintain the units in the mass dancing, and so to stratify them according to weight, the burrs on the screens lower surface giving such jets a directional effect, to advance the dancing mass towards the discharge end, the grid bars, at least at their upper edges, being inclined to direct the air blast, as it enters the screens perforations, also towards the discharge end, and means adjacent the discharge end to segregate the different strata.

References Cited in the file of this patent UNITED STATES PATENTS 8,601 Wheeler Dec. 16, 1851 532,947 Closz Jan. 22, 1895 711,016 Stebbins Oct. 14, 1902 750,367 Jahraus Jan. 26, 1904 831,936 Crawford Sept. 25, 1906 1,515,965 Pardee Nov. 18, 1924 1,866,951 Soulary July 17, 1932 2,028,904 Haworth Ian. 28, 1936 2,161,500 Bird June 6, 1939 2,275,849 Fraser Mar. 10, 1942 2,404,414 Sutton July 23, 1946 2,574,493 McLean Nov. 13, 1951 FOREIGN PATENTS 104,258 Australia June 30, 1938 112,327 Sweden Nov. 7, 1944 574,549 Germany Mar. 23, 1933 634,431 Germany Aug. 6, 1936

Claims (1)

1. A CLASSIFIER AND SEPARATOR FOR A HETEROGENEOUS MASS OF UNITS OF VARYING WEIGHTS, COMPRISING AN ELONGATED SCREEN DISPOSED FIXEDLY IN A GENERALLY HORIZONTAL PLANE, AND EXTENDING FROM A FEED END TO A DISCHARGE END, HAVING A MULTITUDE OF PERFORATIONS EACH FORMED WITH A BURR OUTSTANDING ON THE SCREEN''S UNDER SIDE, AND EACH BURR LOCATED AT THE SIDE OF ITS PERFORATION NEARER THE SCREEN''S DISCHARGE END, THE SIZE OF THE PERFORATIONS BEING SMALL ENOUGH TO SUPPORT THE MASS OF MATERIAL ON THE SCREEN IN THE FORM OF A BLANKET WHICH IS RATHER UNIFORMLY SEVERAL UNITS DEEP, MEANS TO SUPPLY THE HETEROGENEOUS MASS UPON THE SCREEN AT THE FEED END THEREOF, MEANS TO DIRECT A CONTINUOUS AIR BLAST UPWARDLY THROUGH THE SCREEN''S PERFORATIONS, AS JETS, WITH FORCE SUFFICIENT TO MAINTAIN THE UNITS IN THE MASS DANCING, AND SO TO STRATIFY THEM ACCORDING TO WEIGHT, AND BY THE DIRECTIONAL EFFECT OF THE BURRS ON SUCH AIR BLAST TO ADVANCE THE DANCING MASS TOWARDS THE DISCHARGE END, AND MEANS ADJACENT THE DISCHARGE END TO SEGREGATE THE DIFFERENT STRATA.

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