US2212575A - Apparatus and method of treating bulk material - Google Patents

Description

m- 27, 1940 Y F. s. SMITH 2,212,575

APPARATUSND METHOD 0F TREATG BULK MATERIAL Filed nay 14, 195s zlsneets-shegt 1 ATTORN EY A118 27, '1940. F. s. sMrrH 2,212,575

APPARATUS AND METHOD OF TREATNG BULK MATERIAL FiledvMay 14, 1938 2 Sheets-Sheet 2 34 ATTORNEYS Patented Aug. 27, 1940 PATENT OFFICE APPARATUS AND METHOD OF TREATIN'G BULK MATERIAL Franklin S. Smith, New Haven, Conn. Application `May 14, 1938, Serial No. 208,029

26 Claims.

This invention relates to the treatment of'materials and more in particular to the art of and apparatus for the electrical treatment of ma.- terials for purposes such as the destruction of insect life, which term as herein used includes the egg, larva, pupa, and adult stages of insects.

Among the objects of this invention is the provision of practical apparatus of simple and durable construction and efficient and dependable action. Further objects are to provide apparatus of the above-nature for avoiding an explosive mixture of air and dust, for providing and regulating a desired electrical potential, for maintaining certain predetermined conditions within the zone where the material is treated, for removing ozone and the like from the finished product, and for the prevention of excessive heat at certain points. 4

Other points are to provide practical methods or arts for achieving the above aims which may be readily carried on and shall be characterized by certainty of the desired results. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly-consists in the features of construction, combinations of elements, arrangements of parts and in the several steps and relation and order of each of the same to one or more of the others, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

. In the drawings:

`Figure 1 is a view partly in elevation and partly broken away, .disclosing the general assembly-of the apparatus;

- Figure 2 is a plan View of the lower electrode; and

Figure 3 is an lenlarged sectional view of a portion of Figure 1 showing the details of construction of the parts associated with the treatment zone.

This application discloses mechanisms and processes of operation which are likewise disclosed in my co-pending application, Serial No. 150,522, led June 26, l193'?, entitled, Apparatus and method 'of treating bulk material. Certain details of construction disclosed herein may be more clearly understood by referring to that application,l the mechanisms and processes disclosed herein being in some respects improvements upon those disclosed in that application. f

Certain broad features of this invention contemplate the continuous treatment of Dmaterials by high-potential electrical discharges through a gaseous dielectric and the provision of a method and apparatus for carrying on this treatment With safety in a thoroughly eiicient and practical mannen An object of this invention is to provide for the treatment, in the above-men-A 5 tioned manner, of materials such as cereals, seeds, grains, corn, beans, etc.

This treatment is especially effective in completely destroying the insect life ofV all of the various insects of the type which infest products 10 of relatively small particle sizes, such as coarsely milled cereals, semolina, farina, grits, etc. However, in the treatment of products, it has been found that the desirable characteristics, such as viability of seeds, color, and baking properties of flour, etc., are unimpaired.

Treatment such as that contemplated in the present invention is particularly important in milling or similar operations where insect life is continually being introduced into the milling machinery by infested grain. Under vsuch circumstances, certain eggs an'd small larvae are not destroyed during the milling process, but often lodge within the equipment and form foci of infestation where they propagate and spread to the ilnished material. However, if the grain, or other material, entering the milling equipment is treated in accordance with the teachings of this invention, thisl insect life will be destroyed and infestation within the equipment will be substantially lessened if it is not completely eliminated.

In the present embodiment, means is provided to pass the grain or other material between two electrodes through an area which is termed the treatment zone. A relatively high-frequency,y high electrical potential is maintained across the electrodes with the result that when the material passes through the zone, an electrical discharge occurs between the electrodes. It has been found that this discharge seeks out and destroys insect life of the nature referred to above.

Very satisfactory results have beenv obtained with the use of a pair of annular, horizontally positioned, electrodes, the upperelectrode being stationary, and the lower electrode being rotatable. During operation, the grain or other material is passed upon the upper surface o1' the rotatable electrode near its center' and moves outwardly due to centrifugal force so .that it is thrown through the treatment zone.

The present embodiment differs from that of the above-mentioned co-pending application in the details of construction of the elements forming the treatment zone and the parts associated therewith, and in the process of treatment with- 55 in the zone. Among other diierences, the present treatment zone is somewhat the shape oi' the ner edge than at its periphery and is thus somewhat wedge-shaped in radial cross-section. Considering, however, the treatment zone as an extended opening with a cross-sectional area with a height equal to the thickness of the treatment zone and a Alength equal to its diameter, the

thickness of the zonedecreases from the inner edge to the periphery as the eiective length of the zone increases. Thus, as the material moves outwardly through the treatment zone and tends to spread fan-like radially, it moves between the converging upper and lower walls of the zone and is confined between restricted vertical limits. Under some conditions of usage this feature is important in obtaining eicient and dependable carries cover l.

sterilization, as will be more fully explained hereinafter.

Under certain conditions, dust accompanying or forming part of the material being treated, might be so distributed in the oxygen present vto form an explosivemixture. However, when desirable, an additional quantity of air, or other gaseous dielectric, such as carbon dioxide, is mixed with the material being treated immediately prior to its passage through the treatment zone; thus, the dust concentration is brought down below that necessary to form an explosive mixture.

When the material being treated is surrounded by air, the corona-like discharges produce ozone and certain oxides, such as oxides of nitrogen, all of which shall be referred to as "airionization products. By providing means for blowing air through the treatment zone with the grain and then providing means for removing air from the machine, the air-ionization products are effectively removed from the treatment zone, and the machine, and, at the same time,

heat produced incident to the treatment process is removed from the machine.

The general construction of the illustrative embodiment herein set forth is shown in Figure 1 where it will be seen that' the apparatus is mounted upon a frame of rectangular tubing which includes three pairs of vertical posts 4,

the tops oi' the posts of each pair being connect,

ed by a cross bar II. Mounted upon cross-bars II is the upper housing ring 6 of a casing supporting frame. The casing supporting frame provides mounting means for the entire casing and also includes four downwardly extending arcuate brace plates 203, supporting a lower housing ring 3, across which extend two horizontal rails 5. Attached to the under side of lower housing ring 3 is a funnel-like hopper l, which receives the treated grain and directsl it into an outlet conduit 2.

Mounted in a shoulder on the top 'inner edge of upper housing ring 6 isa cover rim 3, which The at top of cover 'I supports the electrode structures, the air blower means, the grain inlet means, and other elements, including the high voltage transformer, all in a manner that will fully appear below.

Brace plates 2M of the casing supporting frame are positioned as shown, there being one on each side of the apparatus (shown in section), and two in the back. These plates 2F13 divide the space between housing rings 3 and 6 into four arcuate openings through. which access may be had to the interior of the machine. One of these arcuate openings extends around the entire front of the machine.

Normally closing these arcuate openings and overlapping housing rings 3 and 6, is a band I0, which is tightened and, thus, held in position by clamping means (not shown), attached to flanges o'n its ends. The ends of band I0 are positioned along the side of one, of the brace plates 203 and in this mannerfa substantially sealed casing is formed of cover l; hopper I, and band Ill. ened and removed by slipping it down where it may be rested upon lugs 2li on posts Q.

Cover 'I is provided with three sealed doors (not shown), through which access may be had to the upper portion of the interior of the housing. It is also provided with windows (not shown), through which the corona-like dischargeand the operation of the machine within the housing may be observed.

Mounted on the top of casing cover 'I are two blowers, an air supply blower 48, and an air exhaust blower I8, both driven by a high-speed .motor I9 mounted therebetween. BlowersV I 8 and 68 and motor i9 are mounted'as a unit, one end being supported by an air supply conduit 68', and they other end being supported through an L. conduit Il by a casing head I2, which is centrally-positioned on casing cover 'I and is held in place by cap screws I3. Casing head I2 has integral therewith a downwardly extending hollow dead shaft I 4 upon which is mounted the When desirable, band I@ may be loosstator of an electrode motor 20, the rotor of which is within and carried by a motor casing 22 supported as later described. Extending downwardly from casing 22 is a neck 23, which supports the rotatable lower electrode 34 through a. releasable telescopic connection with a hub 25.

Casing head I2 (Figure 1) receives the grain cuit which is Vfrom hopper I, up through thel center of hub 25, through neck '23, through dead shaft I4, through passageways I5, annular manifold lIS, conduit l1, and blower I8 to a suitable exhaust conduit.

Also attached to casing cover 'I by cap screws I3 is a downwardly extending shell 38 which surrounds electrode motor 20 and casing 22, but.

is spaced throughout so as to form a grain passageway Mlbetween its inner surface and the outer surfaces of casing 22, neck 23, and hub 25.

Electrode 3d is depressed at its center to form a bowl-like portion 36 and shell 38 flares outwardly at its lower end and.cooperates with hub 25 in directing the grain outwardly through this bowl-like portion. The outer portion of electrode SIIk is provided with a. radially extending discharge surface which is substantially the shape wall of a truncated cone, and which forms the lower wall of the treatment zone. The grain thus passes from bowl 30 to the inner edge of the discharge surface and then moves outwardly and downwardly through the treatment zone and falls into hopper Directly above rotatable electrode 34 and spaced therefrom so as to form the upper wall of the treatment zone, is a dome 39 of vitreous dielectric material, such as lower power factor glass or quartz. Dome 39 is provided at its center with a circular opening through which shell 30 extends in definite spaced relationship. The dome is supported at its periphery by a retaining ring 308, which in turn is removably attached to upper housing ring 6 by a plurality of' pins 3|0, which have flattened heads 3II. Each pin 3l0 extends radially inwardly through a hole in housing ring 6 into a vertically elongated hole in retaining ring 303. The flattened head 3H of each pin fits in a suitably shaped recess in housing ring 6 and when band I0 (Figure 1), is properly positioned, 'it contacts these heads and holds pins 310 in place.

Glued to the periphery of dome 39, and covering the edge and the opposite sidesv adjacent thereto, is a strip of felt. This felt forms a cushioned seal between dome 39 and'retaining ring 308, and the dome is securely held in position without danger of injury thereto by vibration or mechanical stresses.

Under some conditions of usage it is desirable to concentrate and accurately control the discharges, and in the present embodiment these results are obtained by forming ridges upon the discharge surface of electrode 34. 'Ihese ridges arc shown in Figure 2 in the form of five nested Archimedes spirals, each of which extends arcuately substantially 360, and extends radially across the entire width of the treatment zone. To form these ridges,` grooves of the shape shown in Figure 3 are cut in electrode 34, and it is thus seen that the treatment zone is of minimum thickness along these ridges.

As shown best in Figure 3, directly above the discharge surface 31 and upon the upper surface of dome 39, is stationary electrode 42, which is of a few mils thickness. stationary electrode 42 is made by sand blasting an annular portion of the upper surface ol' over the lead while the lead vis still warm. Dome 39 is of uniform thickness and is spaced a predetermined distance from electrode 34. Stationary electrode 42 being in intimate contact with the upper surface of dome 39, is properly spaced from electrode 34, and is of suilicient conductivity and dimensions to function as an electrode, but is thin enough to permit the rapid trans- .er of heat from dome 39 to the surrounding air.

In operation, a relatively high potential is impressed between stationary electrode 42 and rotatable electrode 34; as the potential increases during a particular half cycle, the potential gradient within the zone rises and it is greatest along the spiral ridges, with the result that spiral zones of corona-like discharges occur along the ridges, the discharges stopping when the potention decreases during the latter part of the half cycle. During successive half cycles discharges occur, but as electrode 34 is rotating rapidly,

In this embodiment,

these discharges do not occur at the same place within the treatment zone. Thus, when there is a discharge,the heat produced at a particular point withinA the zone, and within the adjacent portion of dome 39, is dissipated before another discharge occurs at this point.

In considering this particular feature, it will be seen that a point upon a ridge (see Figure 2), such as that designated by the letter X will describe a circle, and that the discharges fromA this particular point will be distributed around this circle. The various factors, such as the rate of rotation of electrode 34, and the frequency of the high potential, are such that this distribution is uniform throughout the zone, and as a result each point along thesurface of dome 39 within the treatment zone isheated substantially the same `amount `as every other point; this avoids all danger of injury to the dielectric material due to uneven or 'excessive heating.

As indicated above, the thickness of the treatment zone is greater at the inner edge than at the periphery, and in this embodiment lthis dimension at A is 1.6 times the corresponding dimension at B. As the stream of the product moves through the treatment zone from the center of the electrode structure it tends to slide across the upper surface of the lower electrode, and accompanying it is a predetermined amount of excess air. During the movement toward B the product spreads out, and the amount of the product within a unit area of the zone at B is `Aless than the amount of the product within the same unit area at A. 'I'he potential necessary to cause a discharge at a particular point Within the zone depends upon the composite'dielectric constant of the product and the 'air at this point. Thus, when the treatment zone is of the same thickness at B as it is at A, with a smaller amount of the product at B, there is a larger amount of air at B, and the composite dielectric constant of this smaller amount of the product and this larger amount of airis 'different from the composite dielectric constant of the product and air at A. In the present embodiment, the thickness of the zone diminishes between A and B in such a manner as to maintain a ratio between the air andthe product to give a sufi'lciently uniform composite dielectric constant throughout the zone. Thus, as the potentialbetween the two electrode structures increases during a half cycle, discharges occur simultaneously throughout the zone.

At the same time, with this construction, the material and the air move through the zone at a uniform rate, so as to minimize the tendency for dust to separate from the product and collect upon the lower surface of dome 39. As a further aid in preventing the accumulation of dust within the treatment zone, wiper plugs are provided upon the rotatable electrode which move adjacent the surface of the dome. The details of construction of these wiper plugs are shown in lFigure 3, where a cylindrical plug 400 of dielecnular portion of the adjacent surface of dome 39. are shown mounted along a spiral line which Referring'to Figure 2, nineteen of these plugs extends from within the inner edge of the treat-l ment zone through` the treatment vzone and beyond the periphery thereof; adjacent wiper plugs 'are so positioned radially with respect to each other that the annular surfaces which they wipe overlap each other, with the 'result that the entire surface of the dome within and adjacent vthe treatment zone is maintained free of dust.

Referring to the left-hand side of Figure 3, and' the right-hand side of Figure 2, upon the downturned rim 32 of electrode 3G is adjustably mounte ed a bar wiper 406, which has a wiper portion G06 in definite spaced relationship with respect to the surface of dome 39 at the periphery of the treatment zone. Rim 32 is provided with a threaded recess 508, in which is mounted a stud dill, which is secured in place by a tapered key i'l (Figure 2). Stud lil is provided with a central enlarged portion M2 and is threaded at its right end to receive a sleeve nut Mii. Bar wiper Wl extends through a notch M6 in rim 32, and it is provided with an upwardly extending shank M8, which is rectangular in cross section and extends through a recess 11.120 in stud dit. A notched collar 522 is held in contact with shank H8 by nut Ml, and thus holds the shank against the left-hand side of recess 420 to rigidly position the wiper bar.

Referring to Figure 2, the wiper bar is illustratively positioned at an angle of 65 from the tangent of the electrode periphery. In the showing of Figure 2 the electrode rotates clockwise, and with the wiper plugsy 302 and the wiper bar tilt positioned as shown, dust which may tend to collect within the treatment zone is effectively moved through the zone and discharged with the product.

As shown in Figure 1, carried near the lower end of shell 38 is a triangular insulator 35 which is held in place by a plurality of cap screws d6. Extending through the corners of insulator 15 are three adjustable studs which cooperate to carry upon their lower ends an annular air manifold M having an air passageway 539 therethrough. Each stud is held in place by an adjusting acorn nut 30d which is locked by a set screw.

rIhe details of construction of manifold Mi are y best shown in Figure 3, there being an upper channel 3I2, a lower main channel 3M, and an inner lower channel 3l6. Channel 3M is provided with a plurality of interior postsi 3i3 and 3l5, and channel 3i2 is provided with cooperating yposts 3H. Channels 3I2 and 3l@ are held together by a plurality of screws 3H which are countersunk and extend through holes in posts 3H and are received in the threaded holes in pos-ts 3l3. The peripheries of channels 3I2 and 3i 4 are machined to inter-fit and form a substantial seal. Channel 3|2 is attached at its inner edge to inner lower member SIS by a plurality of screws 349. The adjacent edges of members Bld and 3|6 overlap to form an outwardly and downwardly extending slot or jet 2, which is annular, and which directs air outwar ly over the surface of stationary electrode 42.

Referring again to Figure l, attached to the upper side of channel member 3I2 is a manifold coupling 320 which is held in place by suitable screws and which receives air from air supply blower 48 and conduit 48 through a conduit fil of dielectric material.

Manifold lf3 is effectively insulated from the grounded frame of the machine by members i5 and di and at the same time vair is delivered through it to the upper surface of the upper `electrode d2. Manifoldfi isrounded at its in-1V ner and outer edges and extends beyond stationary electrode 32 so as to statically shield the stationary electrode edges. ifold Ml is at a high potential and the presence of the rounded edges or rims lessens flux con- During operation lmancentration and thus avoids the danger `of, sparking. I

In addition to its functions of distributing the air and shielding stationary electrode 42,`rnanifold M also provides the high potential electrical cona are in the position shown, coil' springs 5l are under tension, and an intimate contact is maintainedbetween the lower end'of earch contactor 54 and stationary electrode 42.

In Figure 1 the left-hand side zof motor 20 is cut away to show the details of construction. Rigidly mounted upon the upper end of dead shaft i@ and held in alignment by a stud 32d is upper frame 30; in a like manner, on the lower end of dead shaft it is lower frame 6l. These two frames are held in place by a spanner nut 65 which is locked in place on the lower end of dead shaft Iii by a set screw. Frames 60 and 6| provide a support for the electrode motor, casing 22, and the elements supported thereby. Casing 22 includes an upper casing cover l2, a center cylindrical portion 15, a lower casing cover 13, and neck 23. Casing covers 12 and 13 are held in place on the opposite ends of cylindrical portion 'l5 by a suitable number of cap screws 14.

Neck 23 is held in place on the lower end of casing cover 'i3 by a plurality of cap screws. The upper end of casing cover l2 is provided with a downwardly extending center flange 11 which extends into an annular recess in frame 6B, where it is supported by a ball bearing unit 18, mounted on this frame. In a like manner, lower casing cover 13 is provided with a flange 8l which extends downwardly into a recess and is supported by a ball bearing unit 82. 'I'he juncture of casing cover 72 and frame 60 is sealed by a dust seal of` leather' or other-suitable material, and the juncture of neck 23 and frame 6I is sealed with a similar dust seal.

Rigidly held in place upon upper frame 60 by clamping ring 62 and a suitable number of cap screws, is a stator core 69 which carries stator winding Se. Surrounding stator core 69 and rieidly clamped between casing covers 12 and 13, is rotor core 7l, which is provided with a suitable squirrel cage winding. In this embodiment, a three-phase motor has been used and it has been provided with 48 poles so as to obtain a relatively slow speed at 60 cycles. The conductors |02 from stator, winding 64 extend inwardly through a recess (not'shown) upwardly along dead shaft .trally positioned screw connection.v Thus, neck 75 like manner, hub 25 is provided with a spider 30 having a central collar |30, through which -ex tends a sleeve-like nut 29. The lower end of nut 29 is iianged, and is provided with radial slots so that it may be engaged by a wrench. Surrounding the upper end of nut 29 is a collar 3|, which acts as a stop to prevent the movement of nut 29 downwardly through collar |30. The lower end of neck 23 flares outwardly and is provided with arcuately extending tapered lugs 432, which extend into similarly shaped slots in hub 25.

To install rotatable electrode 34 in position, band 0 is loosened and rested upon lugs 2H on posts 4. The electrode, with its hub 25 and with nut 29 hanging in collar |30, is slid in from the side (the front or near side of Figure 1), on rails 5 until hub 25 is directly below neck 23, and nut 29 is directly below stud 21. Nut 29 is then raised until it engages stud 21 and is rotated while electrode 34 is manually held at its periphery so that it cannot rotate. As nut 29 rotates and progresses upwardly on` stud 21, the vanged portion of the nut engages the lower surface of collar |30 and lifts electrode 34.

During this engagement of nut 29 with stud 21, stud 21 may tend to rotate due to the fact that it is rotatably supported through spider 28l and neck 23 upon the rotatable motor casing 22. If such rotation occurs, lugs 432 on the lower end of neck 23 will engage and enter the slots in hub 25; at which time rotation'of stud 21 will stop because electrode 34 isA manually held from rotation. Continued rotation of nut 29 carries electrode 34 and hub 25 upwardly until the hub 25 securely engages the lower endof neck 23; nut 29 is then tightened and electrode 34 is securely supported so that it will be rotated by motor 20. Mounted in the bottom of hopper is a grating for the purpose of permittingthe grain to iiow from the hopper, and for preventing, nevertheless, the passage of foreign material, such as pieces of dome 39 if it should break. This grat-4 ingconsists of a series of posts 51 supporting superimposed louvers 58 through which the grain passes.v 'Ihese posts support a cap 59 which directs the grain through the louvers.

Extending between vertical posts 4 are two cross-frame members 220 which provide mounting means for a high frequency, low voltage alternator 55 at the right, and control apparatus 85 at the left. Control apparatus 85 includes a control switch 332 which operates switching means to control alternator 55 and the connection of its output, a control switch 334 which operates switching means to start and stop the electrode motor 20 and blower motor |9 which. are `connected in parallel, an alternator field control rheostat 336, and a wattmeter 338. Mounted on the top of casing cover 1 is`--a high frequency, high voltage auto-transformer 56, which receives the low Voltage, high frequency output of alternator 55, and raises the voltage so that a `high voltage, high frequency output is produced and this output is impressed across the electrodes.'

The three-phase motor circuit of alternator 55 is connected to the control apparatus 85 through conductors 352, and the alternator eld of alternator 55 is connected to its rheostat 336 by a pair of conductors 350. As indicated above, electrode motor 20 and blower motor |.9 operate in parallel and are connected to the switching means controlled by the control switch 334 through conductors 362. The current ycoil of wattmeter 338 is connected in conductor 92; one side of its potential coil is connected to conductor 92, and the other side is connected through a potential lead 354 to conductor 94. One side of the output of alternator 55 is connected directly by conductor 94 to the low side of the Winding of auto-transformer 56, and this conductor is connected directly at 88 to the grounded frame of the machine. The other side of the output voltage of alternator 55 is connected through switching means (not shown), and through conductor to conductor 92 and thence through low voltage insulator 342 to the tap 96 of the auto-transformer winding. The high side |00 of the auto-transformer is connected by a. conductor 344 through a high voltage insulator 346 to manlfold 44.

Rotatable electrode 34 is effectively grounded through its supporting means to the frame of the machine and thus, the high frequency, high voltage output of auto-transformer 56 is connected directly across the electrodes. This potential is of such a value that suitable discharges,

preferably of disruptive corona-like form, occurs in the treatment zone, which is between the lower surface of disc 39 and discharge surface 31 of the rotatable electrode 34. At the same time, the rounded edges of manifold 44 and the downwardly turned rim 32 at the periphery 0f rotatable electrode 34 effectively prevent undesirable concentration of ux which might result in sparking.

The switching mechanism controlled byswitch 334 is so arranged that alternator 55 cannot be started except when the circuit of blower motor I9 and electrode motor 20 is closed; likewise, alternator 55 will be stopped at any time that the blower and electrode motors are stopped.

During operation, the grain orother material moves down from grain supply pipe |42 through grain valve |43 Aand through passageways 4I. From passageways 4| it passes into passageway 40, where it contacts casing 22 and is given a swirling motion and is conveyed to the upper surface of the rotatable electrode 34. It then passes outwardly and slightly downwardly through the treatment zone to hopper from which it passes by ,an outlet conduit 2. During the movement of the grain through the treatment zone, it follows turbulent curvilinear paths, so that it is eiectively treatedand any insect life which is entrained with the'grain is sought out by the discharges and destroyed.

As indicated above, when dust accompanies or forms a part of the material being treated, it is desirable for the material to move through the zone without separating the dust from the material. With the present structure, it has been found that this object has been obtained, and the material moves through the zone in an even and uniform manner, and the excessive accumulation of dust ,upon the surface of dome 39 is surrounding area.

zone, and thus, as the grain passes through the treatment zone, it is accompanied by an additional quantity of air, which is sufcient to bring the dust concentration in the air below that necessary to form an explosive mixture. When air is present in the treatment zone, air-ionization products, including ozone, and certain oxides of nitrogen are formed and these are continually removed along with the heat incident to the process.

After leaving the treatment zone, the air moves into the lower part of the housing, and the dust settles from it; it is then withdrawn from the machine by exhaust blower i9, through the center of hub 25, neck 23, dead shaft it, passageways iii, manifold i6, and L vconduit il. Exhaust blower i8 delivers substantially more air than does air supply blower 56, with the result that a reduced pressure condition is maintained in the lower part of the housing and air is continually being drawn upwardly through grain outlet conduit 2. This air-washes the treated grain, and effectively removes any air-ionization products which might otherwise be trapped and carried downwardly with the grain.

This reduced pressure condition also tends to draw air into the housing through any leaks that might be present. rIfhus, the air-ionization products and dust accompanying or forming part of the material being treated do not escape to the In one embodiment, it was found that very satisfactory results could be obtained by delivering 200 cubic feet of air per minute from blower d8 and by exhausting 300 cubic feet of air per minute from blower it.

While the length of discharge gap, which is, in effect, the thickness of the treatment zone, varies with the materials being treated, the voltage, frequency, etc., it has been found that a gap of 1 9.; inch to inch at the inner edge of the zone, with dome 39 of inch thickness, and with a corresponding voltage which ranges from 20,000 volts to 30,000 volts, gives satisfactory results. The length of gap may be varied by changing the length df neck 23. In the present embodiment, the length of gap varies inthe radial direction; this variation is of value to maintain the cross-sectional area of the stream of the product and air constant. Thus, the lengthof gap varies radially through the zone inverse-ly as the diameter; the outside diameter of the zone is approximately 1.6 times the inside diameter and the length of gap at the inner edge of the zone is approximately 1.6 times the length of gap at l the outer edge. Y

A high frequency of 500 cycles per second has been used with excellent results, but lower and higher frequencies may be used. A frequency of 60 cycles has been found satisfactory except that the quantity of material being treated isY less; frequencies substantially higher than 500 cycles tend to result in higher dielectric losses and thus excessive heating of dome 39. I

When a material such as spring wheat is being treated, and with a now of 10 bushels per aaiasvc of the mechanical features of the above inven-y tion, and as the art herein described might be lvaried in various parts, all without departing from the 'scope of the invention, it is to be understood that all matter hereinabove set forth, or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense. l

I claim:

el. In apparatus of the class described, the combination of, a sheet of dielectric material, a rst electrode positioned upon one side of said sheet, a second electrode rotatably mounted upon the other side of said sheet and spaced therefrom to form a treatment zone therebetween, said treatment zone being substantially the shape of the outer enclosing annular surface of a truncated cone, and means to rotate said second electrode tomove the-product to be treated radially and downwardly through the treatment zone.

2. In apparatus of the class described, the combination of, a sheet of dielectric material, a first electrode positioned upon one side of `said sheet, a second electrode having a plurality of spirally extending ridges thereon rotatably mounted upon the other side of said sheet and spaced therefrom to form a treatment zone therebetween, said treatment zone being substantially the shape of the outer enclosing annular surface of a truncated cone, and means to rotate said second electrode to move the product to be treated radially and downwardly through the treatment zone.

3. In electrical apparatus in which a product is subjected to an electrical discharge,.the combination of, a pair of electrodes, a dielectric plate between said electrodes and spaced from one of said electrodes so as to form a treatment zone, said treatment zone being substantially the shape of the enclosing annular surface of a truncated cone, an air manifold having a jet adjacent one of said electrodes, and means to deliver air from saidmanifold through said jet into heat-conducting relationship with said dielectric plate and through said treatment zone.

4. In an electrical apparatus in which a product is moved onto a rotatable electrode and is moved along a surface of said electrode through a treatment zone, the combination of, a pair of electrodes, and a sheet of solid dielectric material positioned between said electrodes and forming an annular treatment zone between it and one of said electrodes, said one of said electrodes having an active discharge surface extending spirally along the lower surface of the treatment zone and being rotatable to move the product to be treated over said active discharge surface.

5. In electrical apparatus, the combination of, a member of dielectric material, a first electrode positioned upon one side of said member, and a second electrode upon the other side of said member and spaced therefrom, said second electrode having an active discharge surface which comprises an enclosing ridge construction formed by a plurality' of nested Archimedes spirals.-

. 6. In apparatus of the character described, an annular electrode comprising a plate the active surface of which is formed by an annular metallic ridge construction comprising a plurality of ridges, each of said ridges extending a substantial distance in a radial direction.

7. In apparatus of the class described, an ancombination of, a pair of wall constructions, one of said wall constructions comprising a sheet of dielectric material and the other of said wall constructions comprising the active discharge portion of an electrode, said wall constructions converging radially to define a treatment zone the thickness of which varies inversely as the radius.

9. In apparatus of the class described, the combination of, an electrode rotatably mounted and having an annular upper surface which forms the lower wall of a treatment zone, a sheet of dielectric material mounted above said electrode in spaced relationship thereto and forming the upper wall of said treatment zone, and means to move a product to be treated outwardly' through said treatment zone, said walls converging from the inner edge to the outer edge'of said treatment zone.

10. In electrical apparatus of the type wherein a material is sujected to discharges within a 'treatment zone, the combination of, a sheet of dielectric material, an electrode mounted in intimate `contact with one surface of said sheet, an air manifold having an elongated jet-construction impelling a sheet of air across said electrode, and an elongated contacter resiliently mounted on said manifold adjacent said electrode and forming an electrical connection therewith.

11. In apparatus of the class described, the combination of, a sheet of dielectric material, a

' first electrode positioned upon one side of said sheet, a second electrode rotatably mounted upon the other side of said sheet and spaced therefrom to form a treatment zone therebetween, wiper means of dielectric material mounted upon said second electrode and extending into operative relationship with respect to said sheet.

12. In apparatus of the class described, the combination of, a sheet of dielectric material, a first electrode positioned upon one side of said sheet, a second electrode rotatably mounted upon the other side of said sheet and spaced therefrom to form a treatment zone therebetween, a cylindrical plug of dielectric material mounted on said second electrode and extending into the treatment zone with one end wall positioned adjacen the surface of said sheet.

13. In apparatus of the 'class described, the

combination of, a sheet of dielectric materiaL'a first electrode positioned upon oneV siderof said sheet, a second electrode rotatably mounted upon the other side of said sheet and spaced therefrom to form a treatment zone therebetween, a plurality of wiper plugs mounted on said second electrode with their axes substantially at right angles to the adjacent surface of said sheet, said plugs being mounted along a spiral line extending through said treatment zone.

14. In apparatus of the class described, the combination of, a sheet of dielectric material, a first electrode positioned upon one side of said sheet, a second electroderotatably mounted upon the other side of said sheet and spaced therefrom to form a treatment zone therebetween, a wiper bar of dielectric material mounted on said second electrode and positioned adjacent the surface of said sheet at one edge of vsaid treatment zone.

15. In apparatus of the class described, the combination of, a sheet of dielectric material, a rst electrode positioned upon one side of said sheet, a second electrode rotatably mounted upon the other side of said sheet and spaced therefrom to form a treatment zone therebetween, a plurality of wiper members mounted on said second electrode along a curvilinear line extending through said treatment zone, and a wiper bar mounted on said second electrode with its outer end trailing with respect to the direction of rotation of said second electrode, said wiper barbeing positioned adjacent the 'periphery of said treatment zone.

16. In apparatus for treating bulk material within a treatment zone by subjecting it to the discharges resulting from impressing a high potential across a pair of electrodev structures, the combination of, a wiper bar of dielectric material having a shank rigid therewith, and means mounting said wiper bar to move along one wall of the treatment zone at the place where the treated product is discharged, said last-named means including a stud having an opening therethrough to receive said shank and a sleeve-'nut construction rotatably 'mounted on said stud torigidly clamp said shank in said opening.

17. In the art of treating bulk materials by passing them through an annular treatment zone wherein said materials are subjected to electrical discharges, the steps of, delivering the material to be treated at a substantially uniform rate to the center of the treatment zone, delivering a predetermined quantity of a gas to said center of said treatment zone, creating forces upon the material and upon the gas to cause both of them to move through the treatment zone together at a substantially uniform rate, and maintaining subforming an annular treatment zone with one of I said electrode structures; said one of said electrode structures having an annular surface adjacent the treatment zone whichr is generally the shape of the outer surface of a truncated cone, and which is terraced to form a plurality of ridges across which the material passes.

19. In apparatus for treating bulk materials Vin which the material is moved to the center of a substantially disc-like electrode structure and is caused to move by the rotation of the electrode structure outwardly through an annular treatment zone, a substantially disc-like electrode structure havingan annular active discharge surface, and a plurality of arcuately extending ridges extending along said active discharge surface to produce a terraced effect. l

20. In an electrical apparatus in which a material is moved onto a rotatable electrode and -isv moved along a surface of said electrode through a treatment zone, the combination of: a pair of electrode structures; a sheet of solid dielectric material positioned between said electrode structures and forming an annular treatment zone between it and one of said electrode structures, one of said electrode structures having an active discharge surface extending substantially spirally along one surface of the treatment zione; and means to cause relative movement between said sheet of dielectric material and said electrode structure having a spirally extending active discharge surface whereby the distribution of 4discharges within the treatment zone is accurately controlled.

21. In electrical treating apparatus, the combination of, anannular electrode comprising a thin metallic sheet, and air directing vmeans including a wall spaced from but extending along the surface of said electrode and a jet moving. air against one edge of said electrode and between Said electrode and said wall to the other edge of said electrode.

22. In electrical treating apparatus, the combination of, an annular metallic electrode, an annular wall construction spaced from said electrode and providing an annular passageway therebetween, and an annular jet adjacent one edge of said electrode and impinging a sheet of air into said passageway toward the other edge of said electrode; whereby a sheet of air moves across said annular electrode from one edge to the other.

23. In electrical treating apparatus, the combination of, a thin metallic electrode mounted upon one side of a dielectric plate, a rigid metallic member extending along said electrode, and a spring-pressed plunger mounted in said rigid metallic member and having a protruding end resiliently pressed against said electrode; wherebyan electrical connection is maintained between said rigid metallic member and said electrode.

amarre in spaced relationship thereto and forming the upper wall of said treatment zone,`said upper wall construction having means associated therewith constituting an upper electrode structure, said upper surface of said electrode and said wall construction converging radially to thereby limit said treatment zone so that the thickness of Said treatment zone varies inversely as the radius.

25. In an electrical apparatus in which a product is treated in a treatment zone by subjecting it to the discharges resulting from impressing a high potential across a pair of electrode structures, the combination of, a dome of dielectric material, a pair of annular electrode structures positioned upon opposite sides of said dome and having substantially coextensive discharge surfaces, one of said electrode structures being positioned substantially within said dome and having an outer surface spaced from the inner surface of said dome to thereby define an annular treatment Zone between said outer and inner surfaces.

26. In apparatus of the class described, the combination of, a pair of Wall constructions, one of said wall constructions comprising a dome of dielectric material, and the other of said wall constructions comprising the active discharge portion of an electrode, said constructions convergness of which-varies inversely as the radius.

FRANKLIN S. SMITH.

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