US2269528A

US2269528A - Method of manufacturing metal spheres

Info

Publication number: US2269528A
Application number: US326847A
Authority: US
Inventors: John L Gallup
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1940-03-30
Filing date: 1940-03-30
Publication date: 1942-01-13
Anticipated expiration: 1959-01-13

Description

Jan. 13, 1942. 'J. GALLUP 7 2,269,528

METHOD OF MANUFACTURING METAL SPHERES Filed March 30, 1946 NO/V OX/D/Z/NG ATMOSPHERE INVEN TOR. JUHN L. GALLUP A TTORNE I".

- those obtained by sintering metal powers.

Patented Jan. 13, 1942 v UNITED STATES PATENVTP OFFICE.

Mrrrnon or'mmumcruamc METAL srneaas John L. Gallup, Newark, N. 1., assigncr to Radio Corporation of America, a corporation of Delaware ' My invention relates to a method of manufacturing small metal spheres and particularly to a method of making metal spheres of uniform size and shape.

In my U. S. Patent No. 2,175,689 I have disclosed an electrode of the mosaic type suitable for use in television transmitting tubes. The electrode of the type described includes sintered metal particles or plugs mutually separated and insulated from a conducting foundation by an intermediate insulator. I have found that it is desirable to provide denser metal plugs than It is desirable that these metal plugs be uniform in size and shape but various methods of manufac-' turing such small particles, which usually range in size from .01" to .005", have been found unsatisfactory. Small metal spheres are particu larly suited to this use, but attempts to make small metal spheres by spraying the metal from a spray gun of the Schoop type or passing molten metal through a fine mesh screen as in the shottower process do not meet with success. In the first method the particles produced are of nonuniform shape and size so that less than. 4% of the product is usable. In the latter process the molten metal will not pass through a fine refractory in character. feed the wire 2 into the melting region or flame with gas and air, although oxygen-and hydrogen may be used when melting certain metals highly The rollers 3 preferably being such that the wire is melted at the rate wire mesh screen but rather collects in large drops on the under side of the screen, the drops bearing no apparent relationship to the size of the openings in the screen.

It is an object of my invention to provide a method of manufacturing small metal particles or spheres of uniform size and shape. It is a further object of my invention to provide equipmerit for and a method of manufacturing metal spheres in which the percentage yield of the desired size range is increased. In accordance with my invention, I melt a metal which it is desired to make into small particles, allow the molten metal to fall a considerable distance through space and interrupt the fall on an inclined plane of resilient material to break the melted metal into small metal particles which are solidified and cooled. These and other ob-.

. interruption, the smaller the particle size.

burner 5. The burner 5 is preferably supplied 55 at which it is fed. After the wire is melted in the flame 4 the molten metal is allowed to fall through space for a distance determined by the size of the metal particles desired, as will be referred tolater. If the metal is of such a material as to be readily oxidized, the path of the falling molten metal may be surrounded by a tube 6 containing a non-oxidizing atmosphere which may enter the tube 5 such as through the inlet 1,. although I have found this to be unnecessary when making metal particles of such metals as silver, copper, zinc, nickel or nickel chrome alloys.

' plane of the platform may be varied. The platform 8 supports a sheet 9 of resilient material 'such as at its four corners so that the molten metal, when interrupted in its fall, will bounce from the resilient sheet 9, whereupon it may be collected and cooled such as by a water bath I0.

I have found the size of the particles made of any given metal to be dependent upon a number of variables. Thus I have found that the hotter the melting region, such as the flame 1, the smaller will be the particles size. Likewise I have found that the greater the distance that the molten metal is allowed to fall before This distance may vary from 6 inches to 8 feet when making silver particles, the only requirement being that the metal should be molten at the time it is interrupted by the resilient sheet 9. The particle size may be further controlled by varying the angle of incidence between the path of the falling metal and the plane of the resilient sheet 9. Thus for grazing incidence I have found the particles to be considerably larger than for angles nearer the perpendicular, although I have obtained the best results, both with respect to the uniformity of particle size and the maximum yield of spherical particles, when this angle of incidence is approximately 45. I have tried a number of materials for the purpose of interrupting the fall of the molten metal and have shown in the drawing.

The resultant product made in accordance with my invention are particles of metal which are substantially spherical, the size of the parti-.

cles being quite uniform. In addition, my equipment and method are particularly suited for making metal particles of other metals than silver, such as copper, zinc, nickel and nickel chrome alloys. For metals which ha e a tendency to oxidize while being melted, I prefer to use a reducing type flame to prevent the formation of oxide, but for metals such as zinc I have found that the use of an oxidizing flame is advantageous.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or theiise indicated, but that many variations may be made in the particlular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

I claim:

1. Apparatus for manufacturing small metal particles comprising a source of metal to be melted, means to melt the metal into relatively large particles, said means being elevated so that upon melting the particles of metal immediately drop through space, means to intercept the particles which drop through space while the particles are still in a molten state, said means comprising an inclined base of heat insulating nonmetallic resilient material of sufllcient thinness as to be flexible under the impinging particles causing the particles to rebound and subdivide into smaller particles.

2. Apparatus for manufacturing small metal particles comprising means to melt a quantity of metal, said means being elevated so that the metal falls through space immediately upon becoming molten, a thin base of resilient material of suflicient thinness as to be flexible under impact of said molten metal and positioned to intercept the falling molten metal and cause the metal to be subdivided into small particles, the base being supported from its sides so that the impinged area of the base is free to flex under the impact of said particles.

3. Apparatus for manufacturing small metal particles comprising a resilient non-metallic base capable of deformation by small molten particles impinging thereon, said base being inclined at an angle to the vertical and" supported from the edges thereof, means directly above an unsupported area of said base to melt a quantity of metal which when molten falls on the said area of said base and'means to collect and cool said metal following the impingement of said metal on said base causing a flexure thereof.

JOHN L. GALLUP.