US2428224A

US2428224A - Wiper for rotary electrodes

Info

Publication number: US2428224A
Application number: US491347A
Authority: US
Inventors: Herbert B Johnson; Ralph H Johnson
Original assignee: RITTER PRODUCTS CORP
Current assignee: RITTER PRODUCTS Corp
Priority date: 1943-06-18
Filing date: 1943-06-18
Publication date: 1947-09-30
Anticipated expiration: 1964-09-30

Description

Se t, 30 51947.

WIPER FOR ROTARY ELECTRODES Filed June 18, 1943 56 000000 00000 00 00000 00000000000000 000 0000 00000000000 y 00000000000000000 0000 00000 000000000000 30 OOOOOOOOOOOOOOO 000000000000 0000000000 00039 o ooooqoooo mm. make; 6 000 0000000000 00000000 7 0000000000 0 0000000000 0000 0000000000 oooqoooooo 00600 000000006 000000000 ogoooo o/ INVENTORS c/imonl H. B. JOHNSON ET AL 2,428,224

Patented Sept. 30, 1947 WIPER FOR ROTARY ELECTRODES Herbert B. Johnson and Ralph H. Johnson, Rochester, N. Y., assignors to Ritter Products Corporation, New York Rochester, N. Y., a corporation of Application June 18, 1943, Serial No. 491,347

8 Claims. -(ci. 15-2565) This invention relates to wipers for cleaning rotary electrodes such as employed in electrostatic separation apparatus and, more particularly, to improvements in the construction and composition of such wipers for increasing the operating efliciency and durability of the wipers, and thereby promoting the operating efficiency of the electrodes as well. One object of the invention is to provide an improved and more efficient wiper of the above character for continuously cleaning and polishing an electrode, to keep its surface smooth and free from projecting particles, or other surface portions tending to form spray discharge or sparking points such as would reduce its operating efiiciency.

Another object is the provision of such a wiper capable of effectively preventing the collection on the electrode of contaminating films or coatings tending to insulate the electrode from electrical contact with the materials to be separated and thereby reduce or destroy their operating efficiency.

Another object is to afford a wiper capable of operating with a minimum of frictional drag on the electrode, and thereby avoiding breakage of its porcelain insulating mountings, as well as excessive consumption of power for rotating it.

Another object is to supply a type vor wiper adapted to prevent the formation on the electrode of films or coatings capable of retaining particles of material so as to form sandpaper surfaces such as tend to rapidly destroy wipers as hereto fore constructed.

A further object is to provide a more durable wiper oi the character indicated and reduce the expense of frequent replacements.

To these and other ends the invention resides in certain improvements and combinations of parts, all as will be hereinafter more fully described, the novel features being pointed out in the claims at the end of the specification.

In the drawings:

Fig. 1 is an elevation, partly diagrammatic in character, illustrating the action of a pair of separating electrodes of an electrostatic separation apparatus and the application to such electrodes of wipers embodying the present invention;

Fig. 2 is an enlarged, perspective view of the main body portion of one of said wipers;

Fig. 3 is an enlarged, sectional view tially on the line 3a-3a in Fig. 2;

Fig. 4 is a similar, sectional view, but showing additional supporting means for the wiper, and

substan- Fig. 5 is a sectional elevation of a molding apparatus for forming said wipers.

United States patents, Nos. 2,135,716, granted Nov. 8, 1938, and 2,258,767, granted October 14, 1941, to Herbert B. Johnson, describe improvements in electrostatic separation methods and apparatus, comprising the important use of wipers for continuously maintaining clean, smooth and polished surfaces on the separating electrodes. Such apparatus, as illustrated in Fig. 1 of the present drawings, commonly includes one or more pairs of spaced, cylindrical, metal electrodes l0 and Il, each rotatably mounted at its ends on suitable bearings comprising insulating porcelain parts. These electrodes are connected across a suitable source of high voltage current so as to give th'em high potential charges ofoppo site polarity, as indicated by the plus and minus signs, and to create an electrostatic field in the air gap between them.

The material l2 to be separated, in finely divided form, is supplied from any suitable hopper l3, so as to be fed in a thin layer to the top of electrode 1,0 which rotates in the direction -indicated by the arrows, so as to convey the material through the'electrostatic field in the gap between the electrodes. At 14 is a partition 0r divider extending below and longitudinally of the electrode and including suitable containing means on either side, as l5, for separately collecting or otherwise disposing of the separated materials. As well understood in the art, materials of different kinds are differently responsive to the influence of the electrostatic field. Thus, particles of some materials which are less responsive tend to drop vertically by gravity, as at It, and fall on one side of divider M, while particles of other kinds take up a modified charge of such a character that they are repelled from the negatively ch'arged conveyor electrode 80, toward the positively charged electrode I I, and are separated and fall on the other side of divider M, as at Ill.

It is important in the operation of such apparatus that the electrode surfaces be kept clean, smooth and polished to prevent the adherence thereto of particles of material or the development of other uneven or rough surface conditions tending to form sparking or spray discharging projections acting to adversely affect the charges intended to be induced in the materials to be separated and the proper operation of the electrodes. The maintenance of clean electrode surfaces is important also for the purpose of maintaining good electrical contact between the materials and the electrode surfaces, as, for example.

grounded electrode, as indicated at i8, and the' trode II, as indicated at ticles tend to form spray i9. Such adhering pardischarge and sparking .Yproje'ctions which seriously impair the operating efllciency of the. apparatus.

Such separating methods, furthermore, are frequently carried out under conditions in which the electrodes tend to acquire contaminating films or coatings, asmore particularly described hereafter, in which the adhering particles of material become imbedded and tenaciously retained.

Thus, many electrostatic separation processes are encountered, such, for example, as disclosed in United States patent No. 2,197,865, to Herbert B. Johnson, involving the treatment of flotation concentrates comprising particles of materials having their surfaces coated with various reagents used in the flotation process. Other processses involve the pretreatment and conditioning of the materials to be, separated with suit-v able reagents for affecting their response to the action of an electrostatic field. In separating materials carrying such reagents, especially while they are cooling and separating after being heated and dried, fumes and vapors from such reagents frequently cause, a coating to be deposited on the charged electrode and also in some cases on the material conveying electrode. This coating is usually of gummy, sticky nature, and may build up in time to a thickness of s to of an inch, thereby completely covering and' insulating the electrode SllLl'fB-OG.

The finer particles of the materials which tend to collect on the electrodes are frequently hard minerals such as quartz. and if such films or coatings are allowed to cover the electrodesurof material become imbedded and retained, so that the electrode surface takes on the character, more or less, of a"sandpaper surface which rapidly abrades and destroys the wipers. This excessive wear on the wipers is at times accelerated by the action of the same vapors or fumes which form the coatings referred to, since these fumes tend, at their temperature range of between 100 and 600 F., .to penetrate fibers or fabrics of ordinary wipers and disintegrate. The electrode, surfaces may become so rough as to produce a strong, frictional resistance in contact with the wipers sufficient at times to break the porcelain elements by which the electrode bearings are insulated, so that the 06 development of such conditions involves excessive replacement of parts and attendant expense.

We have found that these dimculties may be successfully overcome and a much more efficient wiper provided by constructing the wiper body of a special composition comprising a compact, felted mass of fine metallic fibers coated with a binder which is adapted to be cured, solidified and hardened to unit the more conductive particles to the charged elecasbestos or the like, or

rigid body capable of being molded or machined to desired size and shape. The mass of metal fibers forming the main constituent of this composition is preferably a metallic wool such, for example, as the known steel wool of commerce, except that we preferably employ the commercially available long-fiber steel wool, the fibers of which are graded as coarse, medium or fine, as conditions may indicate, and having a length up to twenty feet. While steel wool is preferred for most installations, we may employ fibers of copper or other metal best adapted to supply a definite polarity-charge through frictional contact with the particles to be separated, or in conjunction with the particular metal of the electrode surface, as we find that there is a definite relationship between the behavior of the particles to be separated and the metal of the electrode surface, as well as the kind of metal of which the wiper fibers are made, involving the advantages of both natural contact potentials and also special superimposed charges which may be selectively applied.

The felted mass of metal fibers or metal wool, preferably in the form of a strip of the approximate length of the wiper, is saturated with a suitable plastic bonding material, such as shellac, gums, Bakelite, sodium silicate or other resins and molding compounds derived from phenol, cresol, or xylenol and formaldehyde, phenolicmixtures thereof which are adapted, on curing. to solidify and unite the metal fibers together in a substantially rigid body, capable of being molded or machine out to definite cross-sectional shape. Such binders, it will be noted, are generally resistant to acids.

After first saturating the metal wool strip, which is to form a wiper, we prefer to press out excess binder by passing the strip between rollers until the retained binder forms, say, seven to ten per cent by weight of the composition. After such pressure, the strip is molded to shape and cured under pressure in a suitable mold. Such a mold may comprise, for example, a metallic tube portion 2 i Fig. 5, having approximately the same outer diameter as the electrode with which the wiper is to be used. To the opposite sides of the tube ii are secured walls 22, of wood or other suitable material, to provide, with the tube 2|,

fees. h y f r a ma i i which t pa ti s so mold cavities 2: corresponding to the desired cross-sectional shape of the wiper body, the surfaces of the tube forming the bottoms of the cavities being perforated, as shown at 24, for supplying the heated air, or other curing medium,

to the material in the mold.

cause them to o are U -shaped clamps Each mold cavity, after insertion of the wiper composition, is closed by a somewhat convex metal plate 25, which is formed with closely arranged perforations 26, as shown. The plates 25 preferably pressed into the mold cavities, to compress the wiper composition, as by means of any suitable clamps (not shown) ,after which rigid, 21 are fitted over the plates 25, as shown, to hold them and the wiper body under suitable compression. Such compression preferably causes some of the binder to exude into, or through the openings 26 of plate 25, to more securely bond the plate to the wiper body. Air or other gas is then supplied by any convenient means to the interior of tube 2 I, at any suitable fibers in asubstantially so to cure, solidify and harden the binder. When ported by angular metal straps 33 trode surface is maintained free the binder is cured, the mold is opened and the wiper body with its reinforcing backing plate 25 is removed in permanently set, cross-sectional shape with one surface 28 shaped or curved to conform to the surface of the electrode with which the wiper is to be formed as a compact felted mass of metal fibers and binder united in a substantially rigid body with one face shaped for.close wiping contact with the rotary electrode surface.

The means for supporting the wiper in place preferably comprises a plurality of threaded posts 29 fixed to the backing plate 25, to which is preferably fitted a heavier and rigid supporting bar 30 of substantially the same shape as the plate 25 so as to lie closely against the same. Posts 29 project through openings in the bar 30 and are secured therein by nuts 3! and washers 32. The supporting bar 30 is provided at its ends with suitable terminal brackets (not shown) of porcelain, metal or the like, as desired, or it may be sup- (Fig. 1), secured thereto by the nuts ill and supported at their opposite ends, as by attachment to the hopper l3, as shown.

The multiplicity of metal fibers projecting at the contact surface offer sharp, cutting edges in substantially point contact with the electrode surface, progressively changing with thewear of the wiper surface .and operating to effectively scrape, clean, smooth and polish the electrode surface, without grooving the same, although, if desired, the wiper may be given an oscillating endwise movement to equalize its wear, as described in the above patent No. 2,258,767.

The rigid wiper body maintains its predetermined shape and close contact with the electrode surface and removes all of the fine particles of material collected on the electrodes, as indicated in Fig. 1. The point contacts of the metal fibers serve to intensively scrub and clean the electrode surface, so as to prevent the building up thereon of any film or coating. The wiper composition is not subject to chemical attack by fumes or vapors emanating from the materials to be separated, and is sufiiciently tough and resistant in character to avoid any appreciable wear by the particles adhering to the electrode,

6 used. The body 2.0 is thus appreciable wear and with a. reduction in the power consumed in driving the electrodes of approximately 80%. proved cleaning and polishing of the electrodes has been found to increase their separating efliciency by from 10% to 12%.

While we have described our invention herein in connection with the. details of a preferred embodiment, it is to be understood-that such description is intended to be merely illustrative, rather than limiting, as it is contemplated that various modifications. in composition and construction of the wiper will readily occur to those skilled in so that. such wipers have been found to be highly durable and economical in use. Since the elecof any film or coating, the braking action, or frictional resistance, of the wiper remains low, as well as the horse power required for driving the electrode, and no undue strain is applied to the mountings of either the electrode or the wiper itself.

Depending upon the nature of the reagents or other materials used for coating the particles of material to be separated, or other special conditions, we prefer, in some cases, to use a binder for the metal wool containing suitable percent ages of abrasive material, natural or artificial, such as powdered carborundum or silicon carbide, or garnet emery, or the like. On the other hand, we prefer in some cases to combine with the binder of the wiper body a lubricating material such as graphite, mica, vermiculite, soapstone, and the like, in relative proportions, depending upon the conditions of particular applications. Thus, we have found that one half pound of powdered or flaked graphite to three gallons of shellac provides a successful binder for many uses.

For the purpose of increasing the point contacts of the wiper fibers with the electrode sur- 7 the art within the spirit of the invention and the scope of the appended claims.

We claim:

1. A wiper for a rotary, cylindrical electrode of an electrostatic separation apparatus, said wiper having a body comprising as its main constituent by weight a compact felted mass of fine, metallic fibers, together with a binder of a material which is substantially unaffected by temperatures up to 250 F. and is relatively inert to chemical attack, said binder coating and uniting said fibers to form a substantially rigid body of predetermined shape and low frictional resistance, and means for supporting said body for wiping contact with said rotary electrode.

2. A wiper for a, rotary, cylindrical electrode of an electrostatic separation apparatus. said wiper having a body comprising as its main con stituent by weight a compact mass of metal wool. together with a binder of material other than rubber and which is relatively inert to chemical attack, said binder coating the fibers of said wool and uniting said fibers in a substantially rigid sistance, said body cylindrical electrode of an electrostatic separation apparatus, said wiper having a body comprising as its main constituent by weight a compact felted mass of fine metal fibers, together with a binder other than rubber coating said fibers and containing a finely divided abrasive material, said binder being solidified to unite said fibers and material and provide a substantially rigid body of elongated shape having a face thereof shaped to conform to a portion 'of the circumference of said electrode, and means for supporting said body with said face in longitudinally extending, wiping contact with said electrode.

4. A wiper for a rotary, cylindrical electrode of an electrostatic separation apparatus, said stituent by weight a compact mass of metal wool, together with a binder coating the fibers of said wool and containing a finely divided, lubricating material, said binder being substantially unafiected by temperatures up'to 600 F. and being At the same time, the imsolidified to unite said ilbers and material and iorm a substantially rigid body oi elongated shape having a lace thereof shaped to conform to a portion oi the circumference of said electrode extending longitudinally thereof, and means for supporting said body with said race in longitudinally extending, wiping contact with said electrode.

5. A wiper for a rotary, cylindrical electrode of an electrostatic separation apparatus, said wiper having a body comprising as its main constituent by weight a compact mass of steel wool, together with a binder of material which is substantially unaffected by relatively high temperatures or by chemical attack, said binder coating the fibers of said wool and being solidified to unite the same in a substantially rigid body of elongated shape, said body having a face thereof curved to conform to, a portion of the circumference of said electrode, a backing member attached to an opposite face of said body for reinioreing and holding the same, and means on said member for attaching the same to a support.

6. A wiper for a rotary, cylindrical electrode of an electrostatic separation apparatus, said wiper having a body comprising as itsmain constituent by weight a quantity of fine metallic fibers matted together in a compact felted mass together with a binder of a, material which is substantially resistant to high temperatures and to chemical attack, said binder coating and uniting said fibers in a substantially rigid, elongated body of uniform cross-sectional shape and having a, surface shaped to conform to a portion of the circumference of said electrode, a backing member attached to said body for reinforcing and holding the same, and means on said member for connecting the same with a support.

'l. A wiper for a, rotary, cylindrical electrode of an electrostatic separation apparatus, said wiper having a body comprising as it's main constituent by weight a quantity of fine metal fibers closely matted together in a compact, dense mass together with a binder of a material other than rubber and which is substantially resistant to high temperatures and to chemical attack, said binder coating said fibers and solidified to unite the same in a substantially rigid, elongated body of uniiorm cross-sectional shape and having a face thereof shaped to conform to a portion of the circumference of said electrode, a ioraminous, metallic backing member having openings therein penetrated by said binder to secure said member to said body, and means on said backing member for connection with a support.

8. A wiper for a, rotary, cylindrical electrode of an electrostatic separation apparatus, said wiper having a body comprising as its main constituent by weight a compactly matted, dense shellac binder coating the fibers of said wool and uniting the same in a substantially rigid, elongated body, said body having a face shaped to engage a portion of the circumference of said electrode, a foramlnous, metal backing member having openings therein penetrated by said binder to secure said member to said body, and means on said member for detachably connecting the same with a support.

HERBERT B. JOHNSON. RALPH H. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS