US3256985A - Slotted cylindrical electrode electrostatic separator - Google Patents

Description

June 21, 1966 J. H. CARPENTER 3,256,985

SLOTTED CYLINDRIGAL ELECTRODE ELECTROSTATIC SEPARATOR Filed Deo. 4, 1961 5 Sheets-Sheet l my@ J.

ATTORNEYS June 2l, 1966 J. H. CARPENTER SLOTTED CYLINDRICAL ELECTRODE ELECTROSTATIC SEPARATOR 3 Sheets-Sheet 2 Filed Dec. 4, 1961 INVENTOR SLOTTED CYLINDRICAL ELECTRODE ELECTROSTA'I'IC SEPARA'I'OR Filed Dec. 4, 1961 3 Sheets-Sheet 5 INVENTOR BwmMw/w ATTORNEYS United States Patent O 3,256,985 SLOTTED CYLINDRICAL ELECTRODE ELECTROSTATIC SEPRATOR James Hall Carpenter, 4120 Haines St., Jacksonville, Fla.

Filed Dec. 4, 1961, Ser. N0. 157,321 8 Claims. V(Cl. 209-129) This invention relates to the separation of particles and more particularly to the separation of fibers or other elongated particles from substantially non-elongated particles.

Separation of minerals and other materials has been accomplished by various vtechniques in accordance with certain characteristics of the materials being separated such as electrical conductivity, magnetic attraction, size and the like. It is frequently desirable to separate minerals and other materials in accordance with the shape of the particles but there has been a lack of a commercially successful apparatus for effectively accomplishing such separation.

It is a primary object of this invention to provide an improved separator which effectively removes libers or other elongated particles from substantially non-elongated particles. f

Another object of this invention is to provide an improved high tension apparatus for separating dipolar particles from substantially equipolar particles..

Another object of the invention is to provide an irnproved high tension separator wherein the separated particles are efeiently and easily collected.

Still another object of the invention is to provide an improved high tension separator apparatus which is substantially free of moving parts and is economical to construct and maintain. v

Generally and in accordance -with one aspect of the invention there is provided an apparatus for separating elongated particles from substantially non-elongated par ticles comprising an upright at electrode, an upright generally cylindrical hollow electrode spaced from said flat electrode to permit an unseparat-ed mixture of elongated and substantially non-elongated .particles to fall freely by lgravity in the space therebetween, said hollow electrode having a longitudinal slot extending through its side Wall narrower than and facing said flat electrode, and means to electrically charge said electrodes with opposite polarity to create an electrostatic field therebetweento cause the elongated particles to move toward said slot away from the non-elongated particles. The bottom of the slotted electrode is preferably inclined away from the flat Wall of the opposing electrode. The conguration of the electrodes is such as to provide converging lines of electrostatic force extending between them so that the elongated particles which become dipolar move horizontally in the direction of convergence and the substantially nonelongated particles which are substantially equipolar drop vertically downwardly. p

Although the invention is useful in separating many different types of elongated or dipolar particles from substantially non-elongated or equipolar particles, it is particularly advantageous in the separation of elongated asbestos fibers from substantially non-elongated particles or lumps of asbestos rock or foreign materials. Thus, the invention will be described primarily with reference to the separation of asbestos.

The invention having been generally described, a preferred specific embodiment will now be set forth in detail with reference to the accompanying drawings in which.:

FIGURE 1 is a front elevation partially broken away of a separating apparatus according to the invention;

FIGURE 2 is a side elevation partially broken away of such apparatus;

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FIGURE 3 is a fragmentary vertical section taken along the line 3-3 of FIGURE 2; and

FIGURE 4 is a horizontal section taken along the line 4 4 of FIGURE 3.

Depicted in the drawing is a three stage apparatus according to the invention which apparatus includes a housing 11 constructed in three sections 12, 13 and 14 which are stacked upon each other in vertical alignment. Each of the housing sections includes front and rear walls and a pair of channel-shaped side covers 15, 16. The housing sections 12, 13 and 14 enclose separating assemblies 17, 18 and 19,- respectively. Since such assemblies are identical to each other only one of them will hereinafter be described in detail.

Each of the separating assemblies receives in turn an unseparated mixture of asbestos particles including thin elongated fibers 21 and substantially non-elongated lumps 22. As will be described in more detail hereinafter, the unseparatedr mixture of particles is fed first through a hopper 23 to the separating assembly 17 where elongated fibers 21 are removed from the mixture and deposited on one side of a splitter plate 24 where they slide down an inclined bottom wall 25 which begins in the housing section 12 and extends into the top of housing section 13 into the interior of the channel-shaped housing cover 15. Since all of the channels 15 of the three sections are in communication with each other, the particles drop straight downwardly to the bottom of the housing 11 where they are collected by any suitable means. The portion of the mixture containing the lumps or non-elongated particles falls to the other side of the splitter plate 24 `and slides down the inclined bottom wall 26 into the hopper 23 of the separator assembly 18. The separating process is then repeated and additional elongated 'fibers 21 are removed from such mixture and deposited into the channel 15. The remaining portion of the mixture is ypassed downwardly into the hopper 23 of the separator assembly 19 where a final separation is effected. It will be understood that only one separator vassembly or as many such assemblies Ias desired may be employed. Moreover, the elongated fibers 21 which are separated in any particular separating assembly may be subjected to further separation in another such assembly to remove Iany substantially non-elongated particles which may still remain among g the fibers.

With particular reference to the separator assembly 18, one of such assemblies will now be described in detail. The unseparated mixture of yasbestos particles is deposited from the hopper 23 of the separator assembly 18 onto'a feeder 20 which may be any suitable device for moving the particles to the desired location before permitting them to drop downwardly by gravity. The ow of the particles from the hopper 23 into the trough 25 may be controlled by an `adjustable ap 31 at the hopper throat. The'specic feeder shown in the drawing comprises a commercially available vibratory feeder which includes a vibrating trough 25 and a motor 26 which reciprocates the trough in the conventional manner to propel the particles longitudinally therealong. The motor 26 is attached to a bracket 27 which in turn is mounted on a table 28 which is welded or otherwiseaixed to the housing section 13. It will be understood than an endless belt or other type of conveyor may be employed instead of the vibratoryv feeder.

The unseparated mixture of particles falls from the end of the vibratory trough y25 between 'a pair of spaced upright electrode assemblies 32 and 33. The electrode assembly 32 comprises a wide iiiat plate 34 having rounded 0 top and bottom edges 35 and 36. The plate 34 is stif- Y 42 of the `table 28. Suitable nuts 43 are provided to adjust the position of each rod 41 thereby moving the bottom of the plate 34 horizontally toward or away from the electrode 33. The electrode plate 34 is connected to ground .by the wire 44.

The electrode assembly l33 includes a plurality of electrode components 45 each of which is substantially in the form of a hollow cylinder. Each cylindrical electrode 45 is open ended and provided `with a longitudinal slot 46 extending through the cylinder wall facing the plate electrode 32. The slot 46 is narrower than the plate 34 and preferably extends the entire length of the cylindrical electrode 45. The slot 46 is delined by the enlarged and rounded edges 47 and 48 running longitudinally of the laxis of each cylindrical electrode 45. .Such rounded edges 47 and 4S and the rounded edges 35 and 36 of the plate 34 prevent or minimize undesirable corona discharge which would Itend to occur from any sharp edges on Ithe electrodes. The electrode components 45 are welded or otherwise attached to a pair of generally horizontal supporting bars 5l which are mounted at vertically spaced positions at the rear of such electrodes. Each of the bars 51 is attached -to a channel-shaped bracket 52 which in turn is supported by the lower end of one of the insulator assemblies 53 and 54. The insulator assemblies 53 and 54 are connected at their upper ends to brackets 5S and 156, respectively. The lower end of the electrode assembly 33 is inclined rearwardly away from the electrode 32 for a purpose to tbe explained hereinafter. The electrode assembly l33 is connected to a source of high voltage electricity by the wire v57.

In addition to or instead of the rearward inclination, the cylindrical electrode components may if desired be slightly inclined laterally with respect to -a vertical plane passing between the spaced electrodes.

The plate electrode 32 and the cylindrical electrode 33 are electrically connected to a high voltage power supply to permit such electrodes to be charged with opposite polarity to create an electrostatic `field between the electrodes. The electrostatic ield between the oppositely charged electrodes has lines of force which converge from the `fiat plate electrode 32 toward each of the longitudinal slots 46 in the cylindrical electrode 33. Charging of the electrodes may be accomplished, for example, by connecting the electrode 33 to a high voltage power source to receive a negative charge while the elec-trode 32 is grounded to receive a positive charge. Although the polarity may be reversed, `best results are usually obtained with `the cylindrical electrode negative and the plate electrode positive. It is believed that a higher degree of undesirable corona discharge occurs when the plate electrode is negatively charged.

When the asbestos bers 21 and lumps 22 are dropped from the vilbratory feeder trough 25 substantially all of such particles initially fall freely out of contact with either electrode. When the particles are subjected to the converging electrostatic lines of force between the electrodes, the elongated iibers pass through ythe slots 46 into the interior of the cylindrical electrode components 45. It is -believed that the electrostatic field causes the elongated particles to `become dipoles which align themselves 4in the direction of the lines of force. Such dipoles then tend to move in the direction of convergence of the lines of force. High speed motion pictures reveal that the acceleration of the particles in the direction of the convergence of the lines of force increases with the ratio between the length of the particles to their thickness. The substantially non-elongated lumps or chunks remain sub- 1, stantially equipolar and thus do not tend to move along the lines of force.

The spaced electrodes 32 and 33 may be characterized by any specific configuration which provides converging lines of force between Ithe electrodes when they are charged by a high volt-age source. Thus, any dipolar particles will tend to be separated from any substantially equipolar particles. Moreover, in view of the circumstance that the acceleration of the particles in the direction of the convergence of the lines of force increases with the length of the particles to their thickness, the apparatus of the invention may be employed to separate particles having a greater ratio of length to thickness from particles having a lesser ratio of length kto thickness. The term substantially non-elongated as employed herein denotes particles of such a lesser degree of elongation as to `be essentially unaffected by `the electrodes of the apparatus described and thus fall substantially vertically.

The most desirable horizontal spacing between the electrodes 32 and 33 depends upon several -factors including the character of the particles being separated, the voltage applied and the like. Where the lsp-acing is too close, the fibers tend to link together in chains extending from the edges of the slots 46 to the plate 34. Where the spacing is too great, good separation is not achieved. The determination of the optimum spacing for any set of circumstances is within the skill of the art.

As best shown in FIGURE 3, the lower portion of the electrode 33 is preferably inclined rearwardly away from the electrode 32. Such inclining of the electrode 33 has a decided advantage. With such arrangement, the upper ends of the electrodes 32 and 33 may be relatively close together to afford maximum separating effect without inducing chaining of the fibers across the gap between the electrodes. lf the bottom of electrode 33 is that close to the electrode 32, however, there is a relatively small space in which to divide the elongated iibers from the nonelongated chunks. It has been found that the bottom of the electrode 33 may be inclined rearwardly away from the electrode 32 without materially deltracting from the etectiveness of the separation. The fibers at the top of the separating zone are accelerated in the direction of the electrode 33 and are also accelerated downwardly by gravity and lthus they move in a trajectory. The electrode 33 may be inclined generally to correspond to such trajectory and thereby afford maximum separating effect at the top and provide a relatively wide space for division of the particles at the bottom.

Moreover, the rearward inclining of the lower portion of the electrode 33 decreases the possibility of actual contact between the fibers 21 with the surface of the electrode 33. Such contact is undesirable because it imparts a negative charge to the particles and tends to move them back toward the positively charged plate electrode. The electrostatic lines of force within each component of the cylindrical electrode 33 converge to the cylinder axis and thus the iibers `tend to remain at such axis. The momentum of the particles entering the cylinder, however, tends to cause them to move toward the .rear of the cylinder. The effects of such momentum are minimized by inclining the bottom of the cylindrical electrode away from the separating zone. It has `been found that a tilt of about 15 from the vertical is highly satisfactory in most installations.

At the bottom of the separating zone between the electrodes, the elongated fibers 2l fall to one side of the splitter plate 24 and the non-elongated chunks or rocks fall to the opposite side of such splitter plate. The position of the upper end of the plate 24 preferably may be adjusted to Various positions across the separating zone. Such adjustment may be achieved by mounting the splitter plate 24 on a pivot 58. After passing the splitter plate the elongated fibers slide downwardly along the inclined floor 25 and move through an opening 59 in the housing wall into the interior of the channel cover 15. The rocks Vparts are in the vibratory feeder.

or chunks move downwardly along the inclined floor 26 into the hopper 23 of the next lower separator assembly. The apparatus of the invention is simple in construction and embodies few moving parts. Indeed, the only moving The components for achieving the actual separation of the particles involve no moving parts. Further, the gravity feed system eliminates the necessity for conveyors for moving the particles through'the apparatus. Accordingly, the device is very economical to construct, operate and maintain.

'There has been illustrated and described what is considered to be a preferred embodiment of the invention. It will be lunderstood, however, that various modifications will occur to persons skilled in the art without departing from the scope of the invention which is defined solely' by the appended claims.

I claim:

1. An apparatus for separating elongated particles from substantially non-elongated particles comprising an upright flat electrode, an upright generally cylindrical hollow electrode spaced from said flat electrode to permit an unseparated mixture of elongated and substantially non-elongated particles to fall freely by gravity in the space therebetween, said hollow electrode having a longitudinal slot extending through its side wall narrower than and facing said flat electrode, and means to electrically charge said electrodes with opposite polarity to create an electrostatic field therebetween to cause the elongated particles to move toward said slot away from the non-elongated particles.

2. The apparatus as recited in claim 1 wherein said charging means imparts a negative charge to said cylindrical electrode.

3. The apparatus as recited in claim 1 wherein the lower end of said cylindrical electrode is rearwardly inclined with respect to said flat electrode.

4. The apparatus as recited in claim 1 wherein said slot Vand said at wall are characterized by rounded edges.

5.- The apparatus as recited in claim 1 wherein said slot extends the entire length of said cylindrical electrode.

6. The apparatus as recited in claim 5 wherein said cylindrical electrode is open at both ends.

7. An apparatus for separating elongated particles from substantially non-elongated particles comprising an vupright plate electrode, an upright generally cylindrical hollow electrode spacedfrom said plate electrode and having a longitudinal slot extending through itsside wall narrower than and lfacing said plate electrode, means to deposit an unseparated mixture of elongated and substantially non-elongated particles into the -upper portion of the space between said electrodes to permit said particles to drop freely downwardly by gravity in said space, means to electrically charge said electrodes with opposite polarity to causethe elongated particles to move toward said slot away from the non-elongated particles, and means for collecting the elongated particles separately from the non-elongated particles.

8. The apparatus as recited in claim 7 wherein said charging means imparts a negative charge to said cylindrical electrode.

References Cited by the Examiner UNITED STATES PATENTS 1,995,790 3/1935 Anderson 55-154 X 2,706,044 4/ 1955 Cook 209-127 2,782,923 2/ 1957 Cook 209-127 v2,803,344- 8/ 1957 Morrison 209-127 2,839,189 6/ 1958 Johnson 209-127 FOREIGN PATENTS 644,638 5 1937 Germany.

FRANK W. LUTTER, Primary Examiner.

HARRY B. THORNTON, ROBERT A. OLEARY,

Examiners.

Claims (1)

1. AN APPARATUS FOR SEPARATING ELONGATED PARTICLES FROM SUBSTANTIALLY NON-ELONGATED PARTICLES COMPRISING AN UPRIGHT FLAT ELECTRODE, AN UPRIGHT GENERALLY CYLINDRICAL HOLLOW ELECTRODE SPACED FROM SAID FLAT ELECTRODE TO PERMIT AN UNSEPARATED MIXTURE OF ELONGATED AND SUBSTANTIALLY NON-ELONGATED PARTICLES TO FALL FREELY BY GRAVITY IN THE SPACE THEREBETWEEN, SAID HOLLOW ELECTRODE HAVING A LONGITUDINAL SLOT EXTENDING THROUGH ITS SIDE WALL NARROWER THAN AND FACING FLAT ELECTRODE, AND MEANS TO ELECTRI-

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