US2752196A

US2752196A - Apparatus for atomizing metal

Info

Publication number: US2752196A
Application number: US354584A
Authority: US
Inventors: Douglas S Chisholm; Gordon F Hershey
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1953-05-12
Filing date: 1953-05-12
Publication date: 1956-06-26
Anticipated expiration: 1973-06-26

Description

June 26, 1956 s, cHlSHOLM ET AL 2,752,196

APPARATUS FOR ATOMIZING METAL.

Filed May 12, 1953 IN V EN TORS Doug /05 BY Gordon F. Hers/o eg APPARATUS FDR ATOIVHZING METAL Douglas S. Chisholm and Gordon F. Hershey, Midland,

Mich, assignors to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Application May 12, 1953, Serial No. 354,584

6 Claims. (Cl. 299-63) The invention relates to atomizing metal and particularly involves apparatus of the type in which the metal to be atomized is let fall in a molten stream upon a rapidly revolving disc, the disc flinging off the molten metal in fine globules which solidify as they cool in the ambient atmosphere.

An object of the invention is to provide a gas jet driven turbine having a stator and a rotor, the latter being directly coupled to the disc, the stator and rotor being arranged so that the disc is spun with the rotor at high speed on a gas cushion without resorting to liquid lubricated bearings for supporting the rotating parts. Another object is to provide an apparatus of the foregoing character in which the rotor and disc revolve together at high speed upon a gas cushion without perceptible wobble. With these and other objects, which will become apparent as the description of the invention proceeds, the invention involves certain novel features of construction, operation, and arrangement of parts an example of which is given in this specification and illustrated in the accompanying drawing wherein:

Fig. 1 is a side elevation largely in section showing a preferred form of the apparatus;

Fig. 2 is a plan view of the stator and appended piping partly fragmented;

Fig. 3 is a vertical section on the line 3-3 of Fig. 2;

Fig. 4 is a bottom view of the rotor.

In the several figures, like numerals parts.

Referring to the drawing in detail, numeral 1 designates the turbine which comprises a stator 2 and a rotor 3. The stator is formed preferably of a cylindrical block of metal with a recess 4 in the upper end, the surface of which conforms to the shape of a spherical segment. A cylindrical hole 5 having its axis coincident with that of the block is bored through the block.

Passageways 6 are drilled from the side of the stator into the recess at an upward inclination to form nozzles. The axis of each nozzle lies in a vertical plane which is parallel to and about midway between the vertical planes which are tangent to the walls of the hole 5 and the outside of the stator, respectively. The inner ends of the passageways terminate at the nozzle openings 7. The outer ends 3 of the pasageways are enlarged to receive one end of the pipes 9 which are connected to the ring pipe 1%, which encircles the stator, at points symmetrically disposed around itsinner periphery. The ring pipe is supplied with compressed gas at symmetrically disposed openings at opposite sides of the ring through

supply pipes

11 and 12 which are flexibly connected to a gas source, not shown, at suitable pressure. Exhaust passageways 13 are bored through the block providing openings 14 in the recess 4' somewhat above and between adjacent nozzle openings 7.

The stator 2 is supported by the cylindrical iron core 15 of an electromagnet, indicated generally by numeral 16, as by a shoulder 17. The upper end 18 of the core 7 designate like 2,752,196 Patented June 26, 1956 projects into the hole 5 and is spherically recessed, the recess having the same curvature as that of the stator recess 4 with which it forms a continuous surface. The lower end 19 of the core is secured to the bracket 20 of the flexible rubber or like mounting 21. A coil 22 of magnet wire encircles the core 15 below the shoulder 17 and is energized with direct current through leads 23. As shown, the upper end 18 of the core 15 is provided with a transverse slot 24 which divides the outermost portion of the upper end 18 into two

adpacent pole pieces

25 and 26. Fitted into the slot 24 is an oblong coil 27 of magnet wire leads 28 from which are connected to an A. C. frequency meter 29 calibrated in R. P. M.

Rotor 3 is formed of a solid block of steel, its shape being generally a segment of a sphere with a spherically shaped bottom 30 having a radius of curvature slightly less than that of the recess 4 of the stator so that the rotor can nest into the stator. Rotor 3 is provided with a slot 31 similar in size to the slot 24, diametrically across the bottom, the length and depth being more or less the same as that of slot 24.

The spherically shaped bottom of the rotor merges into the flange 32 at the periphery of the rotor which projects outwardly beyond the rim 33 of the recess of the stator, the lower side 34 of the flange becoming horizontal at its periphery. The central upper portion of the rotor block is bored out to form the cylindrical recess 35 which is internally threaded. Formed in the spherical portion of the rotor in a zone nearer to the bottom (apex of seg ment) than the top (base of segment) is a series of crescent shaped recesses 36 which serve as turbine buckets. They are uniformly spaced around the rotor, the number should equal or exceed two but is not sharply critical. On a rotor formed from a segment of a sphere having a radius of 1 /2 inches, exclusive of the aforementioned flange, 15 buckets suflice. These may be milled in the surface of the rotor using a round end milling tool. The length from tip-to-tip of the crescent may be inch with a maximum depth of A; inch, for example in the middle of the crescent. The lower ends of the recesses 36 lie in a horizontal plane 37 which cuts through the stator at a level close to the bottom side of the nozzle openings 7 when the rotor is in operating position. The upper ends of .the recesses 36 lie in a plane 38, parallel to plane 37, passing near the lower side of the passageways 13, which serve as exhaust ports, when the rotor is in operating position. The operating position of the rotor, as will be explained later, is a position in which the rotor is spaced from the stator a fraction of an inch by virtue of the impingement of gas from the nozzle openings 7 against the buckets 36, the gas lifting the rotor and maintaining it in suspension while spinning it, as on a cushion of gas.

Engaging the internal thread of the recess 35 is the thread of the externally threaded cylindrical boss 39 on the bottom of the atomizing disc 40 which is formed of a solid piece of metal, preferably tool steel. As shown, the atomizing disc 40 is symmetrical about the vertical axis and has a diameter somewhat less than that of the periphery of the flange 32. The face 41 of the disc is concave and is preferably shaped to conform to a segment of a sphere. Between the end 42 of the cylindrical boss 39 and the bottom 43 of the recess 35 may be placed a layer of thermal insulation 44 as a means to limit the cooling eflfect of the rotor upon the disc.

The device may be enclosed in a suitable vessel not shown as when it is desired to envelop the apparatus with an especial atmosphere and to catch the particles of atomized metal as it forms.

In operation, a suitable gas is compressed and delivered to the ring pipe 9 .through the symmetrically disposed

inlets

11 and 12 so as to force the gas through the nozzle openings 7 against the turbine buckets 36 of the rotor 3 at their lower ends. At the same time, the electromagnet 17 is energized so that a magnetic pull of the

pole pieces

25 and 26 is produced upon the rotor tending to hold the rotor from being blown away from the stator recess 4 more than a fraction of an inch (e. g. inch). The gas from the nozzle openings impinging against the rotor, lifts it off the stator recess slightly, and causes the rotor to spin at a high speed on a cushion of gas, the speed of rotation being determined by the velocity of the impinging gas, dimensions of the apparatus, and other factors. Rotational speeds great enough to cause the rotor to fly to pieces are easily attained. Exhaust gas in part escapes through the exhaust passageways 13 and in part from the space between the rim of the stator and the flange of the rotor, the underside 34 of the flange acting to direct this exhaust gas outwardly below the rim of the atomizing disc. This deflecting action prevents direct contact of the moving exhaust gas with the metal being flung off the disc. The turning of the rotor afiects the strength of the magnetic flux which passes between the

pole pieces

25 and 26 and the rotor. As a result of the rotation of the rotor, the intensity of the magnetic field traversing coil 27 rises and falls with each revolution of the rotor producing an alternating E. M. F., the frequency of which is registered by the frequency meter 29 as revolutions per minute.

Atomization of molten metal is effected as soon as the rotor attains a sufiicient speed, c. g. 20,000 R. P. M., as indicated by the meter 29, as by letting fall a stream of molten metal 45 from a spigot 46 arranged preferably a few inches above the center of the atomizing disc 40. On striking the atomizing disc 40, the molten metal rapidly moves toward the periphery of the disc from which it is flung off in fine spherical particles which cool and solidify in the ambient atmosphere as atomized metal.

Among the advantages of the invention are that the rotating elements, viz. rotor coupled with the atomizing disc, have no metal-to-metal bearing surfaces and all the difliculties attendant upon attempting to maintain metal bearings operating at high speed and elevated temperature are obviated; the rotating elements are symmetrical, easily constructed, and spin without undesirable wobbling. The rotational speed is readily and accurately ascertainable at all times. The rotating elements may be started and stopped at will without difficulty. The atomizing disc is easily replaced when worn and its temperature may be regulated simply by interposing a suitable amount of thermal insulation between the rotor and atomizing disc. In high speed operation, which requires relatively high gas pressure, the danger of blowing the rotor away from the stator is obviated by virtue of the exhaust ports relieving the gas pressure under the rotor combined with the magnetic pull of the electromagnet without resorting to hearing means.

We claim:

1. In an apparatus for atomizing a molten metal, the combination of a stator of generally upstanding cylindrical form and having a concave upper end, said stator having an axial opening from top to bottom and a plurality of gas inlet passageways, each passageway lying in a vertical plane and extending in an upward direction from the outer to the inner end and terminating in a nozzle opening at the said concave upper end, said stator having a plurality of exhaust passageways extending from the inside of the. said concave upper end to the outside of the stator, the bottom of the inner end of each exhaust passageway being above and between adjacent nozzle openings; an electromagnet comprising an energizing coil and an iron core, one end of said core extending into the said axial opening; a rotor comprising a solid piece of steel having the general form of a segment of a sphere the convex surface thereof being substantially parallel to the concave upper end of the stator and nesting therein, said rotor having a series of crescent shaped recesses formed in the convex surface in a zone parallel to the base and nearer to the apex than to the base of the segment and adapted to act as turbine buckets on receiving a jet of compressed gas from the nozzle openings, said rotor having a flange integral therewith extending outwardly from the upper edge, the outer margin of the flange on the underside being substantially horizontal; and an atomizing disc of steel secured to the upper side of the rotor, said disc having a concave upper surface.

2. In an apparatus for atomizing a molten metal, the combination of a stator of generally upstanding cylindrical form and having a concave upper end, said stator having an axial opening from top to bottom and a plurality of gas inlet passageways, each passageway lying in a vertical plane and extending in an upward direction from the outer to the inner end and terminating in a nozzle opening at the said concave upper end, said stator having a plurality of exhaust passageways extending from the inside of the said concave upper end to the outside of the stator, the bottom of the inner end of each exhaust passageway being above and between adjacent nozzle openings; an electromagnet comprising an energizing coil and an iron core, one end of said core having a reduced diameter forming a shoulder on which the stator rests, the reduced diameter end extending into the said axial opening and having a transverse slot dividing the end of the core into two pole pieces; a magnet coil in the slot; a rotor comprising a solid piece of steel having the general form of a segment of a sphere the convex surface thereof being substantially parallel to the concave upper end of the stator and nesting therein, said rotor having a series of crescent shaped recesses formed in the convex surface in a zone parallel to the base and nearer to the apex than to the base of the segment and adapted to act as turbine buckets on impinging a jet of compressed gas against them from the nozzle openings, said rotor having a flange integral therewith extending outwardly from the upper edge, the outer margin of the flange on the underside being substantially horizontal, said rotor having a slotlike recess in the apex of about the same length and width as the slot in the core; and an atomizing disc of steel secured to the upper side of the rotor, said disc having a concave upper surface.

3. In an apparatus for atomizing a molten metal, the combination of a stator of generally upstanding cylindrical form and having a concave upper end, said stator having an axial opening from top to bottom and a plurality of gas inlet passageways, each passageway lying in a vertical plane and extending in an upward direction from the outer to the inner end and terminating in a nozzle opening at the said concave upper end, said stator having a plurality of exhaust passageways extending from the inside of the said concave upper end to the outside of the stator, the bottom of the inner end of each exhaust passageway being above and between adjacent nozzle openings; an electromagnet comprising an energizing coil and an iron core, one end of said core having a reduced diameter forming a shoulder on which the stator rests, the reduced diameter end extending into the said axial opening and having a transverse slot dividing the end of the core into two pole pieces; a magnet coil in the slot; a rotor comprising a solid piece of steel having the general form of a segment of a sphere the convex surface thereof being substantially parallel to the concave upper end of the stator and nesting therein, said rotor having a series of crescent shaped recesses formed in the convex surface in a zone parallel to the base and nearer to theapex than to the base of the segment and adapted to act as turbine buckets on impinging a jet of compressed gas against them from the nozzle openings, said rotor having a flange integral therewith extending outwardly from the upper edge, the outer margin. of the flange on the underside being substantially horizontal, said rotor having a slot-like recess in the apex of about the same length and width as the slot in the core; an atomizing disc of steel secured to the upper side of the rotor, said disc having a concave upper surface; and alternating current frequency indicating means connected to said magnet coil to indicate the fre quency of the alternating E. M. F. generated when the rotor revolves while the electromagnet is energized.

4. In an apparatus for atomizing a molten metal, the combination of a stator of generally upstanding cylindrical form and having a concave upper end, said stator having an axial opening from top to bottom and a plurality of gas inlet passageways, each passageway lying in a vertical plane and extending in an upward direction from the outer to the inner end and terminating in a nozzle opening at the said concave upper end, said stator having a plurality of exhaust passageways extending from the inside of the said concave upper end to the outside of the stator, the bottom of the inner end of each exhaust passageway being above and between adjacent nozzle openings; an electromagnet comprising an energizing coil and an iron core, one end of said core having a reduced diameter forming a shoulder on which the stator rests, the reduced diameter end extending into the said axial opening and having a transverse slot dividing the end of the core into two pole pieces; a magnet coil in the slot; a rotor comprising a solid piece of steel having the general form of a segment of a sphere the convex surface thereof being substantially parallel to the concave upper end of the stator and nesting therein, said rotor having a series of crescent shaped recesses formed in the convex surface in a zone parallel to the base and nearer to the apex than to the base of the segment and adapted to act as turbine buckets on impinging a jet of compressed gas against them from the nozzle openings, said rotor having a flange integral therewith extending outwardly from the upper edge, the outer margin of the flange on the underside being substantially horizontal, said rotor having a slot-like recess in the apex of about the same length and width as the slot in the core; an atomizing disc of steel secured to the upper side of the rotor, said disc having a concave upper surface; alternating current frequency indicating means connected to said magnet coil to indicate the frequency of the alternating E. M. F. generated when the rotor revolves while the electromagnet is energized; and a layer of thermal insulation interposed between a portion of the stator and rotor.

5. In an apparatus for atomizing molten metal, the combination of a stator of generally upstanding cylindrical form and having a concave upper end, said stator having an axial opening from top to bottom and a plurality of gas inlet passageways each passageway lying in a vertical plane and sloping upwardly from the outer to the inner end, the inner end of each of the said passageways terminating in a nozzle opening at the said concave upper end of the stator; an electromagnet comprising an energizing coil and an iron core, the iron core being upstanding and having the upper end extending into the said axial opening, the said upper end having a transverse slot dividing the end of the core into two pole pieces; a magnet coil in the slot; a rotor comprising a solid piece of steel having generally the form of a segment of a sphere the convex surface thereof being substantially parallel to the concave upper end of the stator and nesting therein, said stator having a series of crescent shaped recesses formed in the convex surface in a zone parallel to the base and nearer to the apex than to the base and adapted to act as turbine buckets on impinging a jet of compressed gas against them from the nozzle openings; said rotor having a flange integral therewith extending outwardly from the upper edge, the outer margin of said flange on the underside being substantially horizontal, said rotor having a slot like recess in the apex of about the same length and width as the slot in the core; and alternating current frequency measuring means connected to the said magnet coil adapted to indicate the frequency of the alternating E. M. F. generated when the rotor revolves while the electromagnet is energized.

6. In an apparatus for atomizing a molten metal, the combination of a stator of generally upstanding cylindrical form and having a concave upper end, said stator having an axial opening from top to bottom and a plurality of gas inlet passageways, each passageway lying in a vertical plane and extending in an upward direction from the outer to the inner end and terminating in a nozzle opening at the said concave upper end; an electromagnet comprising an energizing coil and an iron core, one end of said core extending into the said axial opening; a rotor comprising a solid piece of steel having the general form of a segment of a sphere the convex sur face thereof being substantially parallel to the concave upper end of the stator and nesting therein, said rotor having a series of crescent shaped recesses formed in the convex surface in a zone parallel to the base and nearer to the apex than to the base of the segment and adapted to act as turbine buckets on receiving a jet of compressed gas from the nozzle openings, said rotor having a flange integral therewith extending outwardly from the upper edge, the outer margin of the flange on the underside being substantially horizontal; and an atomizing disc of steel secured to the upper side of the rotor, said disc having a concave upper surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,671,866 Linville et a1. May 29, 1928 1,853,682 Hechenbleukner Apr. 12, 1932 2,062,093 Kann Nov. 24, 1936 2,065,582 Heinze Dec. 29, 1936

Claims

6. IN AN APPARATUS FOR ATOMIZING A MOLTEN METAL, THE COMBINATION OF A STATOR OF GENERALLY UPSTANDING CYLINDRICAL FORM AND HAVING A CONCAVE UPPER END, SAID STATOR HAVING AN AXIAL OPENING FROM TOP TO BOTTOM AND A PLURALITY OF GAS INLET PASSAGEWAYS, EACH PASSAGEWAY LYING IN A VERTIVAL PLANE AND EXTENDING IN AN UPWARD DIRECTION FROM THE OUTER TO THE INNER END AND TERMINATING IN A NOZZLE OPENING AT THE SAID CONCAVE UPPER END; AN ELECTROMAGNET COMPRISING AN ENERGIZING COIL AND AN IRON CORE, ONE END OF SAID CORE EXTENDING INTO THE SAID AXIAL OPENING; A ROTOR COMPRISING A SOLID PIECE OF STEEL HAVING THE GENERAL FORM OF A SEGMENT OF A SPHERE THE CONVEX SURFACE THEREOF BEING SUBSTANTIALLY PARALLEL TO THE CONCAVE UPPER END OF THE STATOR AND NESTING THEREIN, SAID ROTOR HAVING A SERIES OF CRESCENT SHAPED RECESSES FORMED IN THE CONVEX SURFACE IN A ZONE PARALLEL TO THE BASE AND NEARER TO THE APEX THAN TO THE BASE OF THE SEGMENT AND ADAPTED TO ACT AS TURBINE BUCKETS ON RECEIVING A JET OF COMPRESSED GAS FROM THE NOZZLE OPENINGS, SAID ROTOR HAVING A FLANGE INTERGAL THEREWITH EXTENDING OUTWARDLY FROM THE UPPER EDGE, THE OUTER MARGIN OF THE FLANGE ON THE UNDERSIDE BEING SUBSTANTIALLY HORIZONTAL; AND AN ATOMIZING DISC OF STEEL SECURED TO THE UPPER SIDE OF THE ROTOR, SAID DISCHAVING A CONCAVE UPPER SURFACE.