US1215662A - Hollow-cast ball. - Google Patents

Description

' G. R.'KITTLE.

HOLLOW CAST BALL.

APPLICATION mu) AUGJI, 191's.

1,215,662, Patented Feb. 13,1917.

TED STATES PAT i .FFTQE.

GILBERT n. KITTLE, or coLUMBUs, oiiro, nssrenon TO THE JEFFREY MANUEAm T BING coMrA vY, or COLUMBUS, orrIo,'A CORPORATION or 01110.

HOLLOW-CAST BALL.

Specification of Letters Patent.

Application filed August 17, 1915. Serial No. 45,936.

To all whom it may concern:

Be it known that I, GI BERT R. KITTLE, a citizen of the United States, residing at Columbus, in the county of Franklin and State of Ohio, have invented certain new and useful Improvements in Hollow-Cast Balls, of which the following is a specification, reference being had therein to the accompanying drawing.

The object of this invention is to provide an improved hollow cast metal ball, particularly a ball formed .of exceedingly hard metal and adapted for use as the pulverizing element in grinding mills.

As is well known, in mills of this class freely rolling metallic balls are used which are supported in such way that they can roll over the material that. is to be pulverized and continue so rolling until the material is brought to the degree of fineness that is desired. The continuous rolling and grinding action abrades the surfaces of the balls, and, unless they are exceedingly hard in theirgtexture, they rapidly wear, and unless they are uniform in their texture and in the character of the metal this wear brings them to a shape tending to the ellipsoidal, though of irregular conformation owing. to the lack of uniformity in the constitutionof structure of the metal. The halls hereto-fore made for this purpose are solid, the metal extending continuously.

across the center. And it is well known that if a casting of this character be solid throughout, internal strains are developed from the unevenness in shrinkage of the different parts of the mass, and these render the balls liable to fracture :and to theunevenness of wear above mentioned.

The interior or central part of the mass is of no avail in the work to which the ball is subjected, and therefore when the surface part becomes deformed, even to a small ex-.

tent, the entire article is useless for such work, and must be discarded or thrown away and replaced with another, although there remains from seventy-five to eightyfive per cent. of the original metal in each discarded ball. To obviate these difficulties and disadvantages it has been the practice heretofore, in some cases, to make the balls of steel forgings, with the expectation of having them sufficiently hard to decrease the rapidity of their wear and sufficiently uniform in texture to have them wear evenly. But there is so much expense incident to balls of such material that they are prohibited from general use. 7

The object of this invention is to provide, for grinding and similar purposes, a cast metal ball which shall have a perfectly smooth exterior spherical surface, which shall have its metal free from internal strains that result in the cooling of the solid casting, which can be made of exceedingly hard metal, and therefore will have a uniformity in texture and constitution through the parts which are subjected to wear, and which can be worn down to a point where the expense of waste is at a minimum.

These grinding balls are used, for ex ample, in large'numbers, in ore treating plants, in mining regions difficult of access, and where the item ofexpense in carrying articles is an important one. If the balls for the grinding mills at such places are rendered useless before a fourth of the metal has been made available for grinding, there has been large expense in transporting the other three-fourths, so large that the return of the balls for re-casting is prohibited.

Ithas not been practical to employ for this purpose hollow balls when made in any of the earlier ways known to me and followedin the. producing of hollow casting. In earlier work either there have been aper tures left in the casting formed by the supports for. the internal core, or these apertures have been filled by closures that were not homogeneous in respect to the-neighboring parts of the casting, or plugs that were liable to be dislodged.

My invention relates to the providing of a hollow cast ball having the characteristics above described and having the closures orplugs held against displacement either by mechanically locking them in place or by causing them to have a welding union with the neighboring metal, orboth.

Figure 1 shows in elevation a ball having my improvements;

Fig. 2 is a central section of the ball when completed; I

Fig; 3 shows one method that can be followed in welding the closure or plug in places.

It is not necessar to describe in detail the method followed by me in making balls having the features of structure which I have described. Suffice it to say that 1 form a mold with a spherical cavity, and,in conjunction with this, use a baked spherical core which is carried by a core extension or support which rests in a core print 111 the sand. If the ball is to be large and heavy, I provide two diametrically opposite supports or extensions which rest in suitable prints. Each core support or extension has, at its inner end, next to the spherical core, an inwardly narrowing conical part, and immediately outside of this a radial enlargement, preferably of the shape of a flattened sphere, and, outside of this, a cylindrical part. The inner tapering part of the extension is of less diameter than the outer cylindrical part, and the intermediate part is wider than both of them.

The core and its supporting extension are suitably positioned in the mold, in the usual manner, and then the molten metal for the ball is poured in in any well known i ffter the casting has cooled the core sand is removed by any suitable tools and is completely cleaned out by rumbling in a rattler, or similar mechanism.

At this time the ball consists of a main body part having an outer surface 1, which is completely spherical, except at the outer end of the aperture or apertures 2. The

aperture 2 is of the shape above set forthwhen describing the core extension which produces it. That is to say, it has an inner conical part 3, an outer cylindrical part 41, and an intermediate widened part 5.

The interior of the ball is hollow, having a chamber 6, and the thickness of the metal of the ball is reduced so that at any section through the center it is annular in shape extending from the inner surface at 7 to the outer surface at 1.

In cooling this metal contracts uniformly, the absence of metal at the center permitting the formation of a homogeneous texture at all places between the two surfaces 1 and 7.

The aperture is filled by a refractory plug 8 and a metal plug 9. The refractory plug is, here, a conical core which is pressed tightly into the conical part of the aperture near the inner surface 7. It may be outside of the surface of the sphere is re-' moved. This plug has the outer narrower part 11 and the inner expanded or ofl'set part 10 corresponding to the above specified sections of the aperture.

The core 8 prevents any molten metal from entering the interior chamber 6, and the laterally widened part 10 of the metal plug prevents the escape of the metal part 9, and locks in place the refractory part.

I desire to secure, however, a closer fit and a firmer union of the plug metal with the metal of the wall of the ball, and also to have the two masses of metal distributed as homogeneously as possible. I join the contacting surfaces by a species of welding action. ing external heat. after the plug 10, 11 is in place. But I prefer to produce this form of union at the time the molten metal is being introduced to form the plug. In Fig. 3 I have shown the devices by which this can be accomplished. 12 indicates a pouring gate the bottom of which is concave and fits the surface of the ball. It has a throat 13 which can register with the outer end of the aperture in the ball. let indicates a mass of sand which is arranged to form a dam above and around the gate and around the throat 13. G11 one side there is a spillway 15 to permit the flowing ofl of surplus metal. At 16 t iere is a weight to hold the gate and sand firmly in position. Molten metal is then poured into the cavity, as from a ladle 17. The pouring is not stopped as soon as a sufficient quantity of metal has entered the cavity to fill it. The flowing of the metal is allowed to continue for a period of time, and that which rises and overflows escapes by the spillway 15. This continued flowing of the metal soon heats highly the adjacent walls of the ball. And the heating is enhanced by y the shape of the walls of the aperture, particularly of the spherical or widened part at 5, as there is caused a whirling or vortex action of the hot fluid, so that it sweeps the walls of the passage and operates to rapidly raise the temperature.

The flow of the metal continues and the heating is kept up until all the metal. adjacent to the aperture has become so hot as to insure a welding or intimate union of the two bodies. When the plug or aperture-closing part has become cold it has not shrunk away from the metal of the ball, for that metal has also been highly heated, and follows the plug metal in cooling. And the tightening is further insured by having the mass of metal in the gateway at 13 sufficiently deep to supply enough metal and heat to prevent undue contraction.

After the plug or closure has been cooled the metal projecting beyond the outer surface is cut off and smoothed to spherical shape by emerv grinding or otherwise.

As above noted, if balls of large sizes are to be made, the interior spherical cores may require two or more supports or extensions. If two are used they are preferably arranged diametrically opposite to each other. TVhen filling and sealing up the apertures,

This can be accomplished by applythe first one is closed in the way above described; and then the ball is inverted, and the second is provided with a closure by repeating the steps described.

I am aware that it has been proposed to cast hollow cannon balls each having an aperture leading to the interior chamber and to close this with a plug and electrically weld the plug. But I have found that a ball constructed in the way I have'herein described is superior in several respects. In case the adjacent surfaces of the plug and the ball metal should not be effectively knit they are still mechanically and positively locked together and cannot be separated radially. Uniting them by prolonged pouring of the molten metal insures a firm union as all of the cavities and pores of the surfaces are filled and the two masses are brought to neighboring temperatures, so

that there is greater homogeneity attained when the mass has cooled.

I am also aware that it has been proposed to close the aperture of a hollow cast ball by casting into the aperture 21. bushing of softer metal, threading the bushing and introducing a threaded plug; and, again, that it has been proposed to secure a plug in such a ball by forming the plug with an inner grooved extension and introducing the latter into molten metal filling the cavity of the ball. It has also been proposed to provide a plug of malleable material and having a main chambered body part of cast metal and a plug part of cast metal similar to that of the body part, the plug part having an ofiset inner portion embedded in and interlocking with the metal of the body part, and an exterior surface forming part of the continuous exterior surface of the ball.

2. The herein described hollow metal ball having a main chambered body part of cast metal and a plug part of similar cast metal having an offset inner portion embedded in and interlocking with the metal of the body part and an exterior surface forming part of the continuous exterior surface of the ball, the metal of the plug and body parts being welded together to form a substantially unitary metallic body.

' 3. The herein described hollow cast metal ball having an open central chamber, and a unitary metallic plug embedded in the metal of the wall of the ball and having an outer narrower part and an inner wider part to prevent the narrower part from moving outward.

4. The herein described hollow cast metal ball having an open central chamber, and a unitary metallic plug embedded in the metal of the wall of the ball and formed with an outer narrower part and an inner wider part both having their surfaces secured by welding to the metal of the ball.

5. The herein described hollow cast metal ball having an open central chamber, a refractory plug in the metal of the wall adjacent the inner chamber, and a metal plug between the refractory plug and the surface of the ball adapted to lock the refractory plug in place and having the metal at its surface welded to the metal of the ball.

In testimony whereof I aflix my signature in presence of two witnesses.

GILBERT R. KITTLE.

IVitnesses: V

H. L. RAUscH, DUDLEY T. FISHER.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G.

Images