US2287029A - Method for making shot - Google Patents

Description

June 23, 1942. DOWDELL! 2,287,029

METHOD FOR MAKING SHOT v Filed Aug. '14, 1939 [QvEA/Toe I RALPH L. DOWDELL fa, M W wk ATToBNEY;

Patented June 23, 1942 Ralph L.

Dowdell, St. Paul, Minn., assignorto Regents of the University of Minnesota, Minneapolis, Minn., a corporation of Minnesota Application August 14, 1939, Serial No. 289,980

6- Claims. (or. 83-91) This invention relates to'a method and apparatus for the production of lead shot and more particularly to a process and apparatus'formaking disintegratable lead alloy shot of 'the type set' forth in Patent 2,167,328 issued August 1, 1939.

According to the usual methods of producing shot from lead or alloys of lead containing small percentages of arsenic and/or antimony, the

spherical shot is made bydropping the molten shot metal through perforations of small size.

The shot metal is permitted to fall through space for a distance suff cient to cool and solidify the same, and is finally collected in a bath of water or oil at the end of its fall.

When an alloy containing a small amount of magnesium is dropped in the ordinary fshot tower by usual procedures, the resultant shot is not of spherical configuration, but is of irregular configuration having small tails on the shot particles, which render the shot unsuitable for ballistic purposes.

According to the present invention, magnesiumlead alloy shot ofgood spherical configuration may be fabricated by a dropping procedure and it is therefore an objectof the invention to providea method of producing lead shot by dropping.

It is'more particularly an object of the invention to provide an apparatus for producing a. leadalloy shot of the type set forth .in Patent 2,167,828

y pin I d It is a further object of the'invention to provide a shot dropping method of fabricating spherical shot of good quality composed of lead and a small percentage of magnesium.

It is also an object of the invention to provide an apparatus for fabricating spherical lead shot of good quality by dropping and more particularly it is an object of the invention to provide an apparatus for producing shot composed of lead and a small percentage of magnesium.

Otherobiects of the invention are those inherent in the apparatus and methods herein illustrated, described and claimed.

The method and apparatus of the present inpartly in section of a modified form of the apparatus.

Throughout the drawing, like characters. are used to designate corresponding parts.

The apparatus for carrying out the method of dropping shot set forth in the present invention may consist generally of an alloying or shot metal melting arrangement represented in Figure 1 by the portion under the bracket A, in which the shot metal is melted or the lead alloy from which the shot is fabricated is prepared.

According to the preferred form of the invention, the melting furnace consists of a steel or cast iron kettle II), which is heated by any preferred means such as the electrical heating ele-' In the shot metal melting pot illusments H. trated, the heating element is placed in close content with the bottom of the kettle l0, and the entire kettle and heating. elements .are thoroughly insulated by a thick layer of insulating material l2 which may for example be asbestos or diatornaceous earth block.

The molten alloy within the kettle I0 is designated l5, and in its molten state is covered by a suitable molten flux l6, which inhibits oxidation of the shot metal. In order further to reduce the possibility of oxidation, the kettle is preferably provided with a cover I'I.

' Extending from the left of the kettle [0 as shown in Figure 1, there is a steel or iron tube 20,

' which may be insulated, having a regulating valve 2| therein. The tube 20 extends from the shot metal melting kettle III to the shot dropping apparatus, which in Figure 1 is the portion under vention are illustrated with reference to the drawing in which 7 Figure 1 illustrates a. schematic elevational View partly in section ofshot dropping apparatus for carrying out the method of the present invention, and V Figure 2 is a fragmentary. enlarged view partly in section of the shot dropping plate portion of the apparatus illustrated in Figure 1.

'rFigure 3 is a fragmentary, elevational view,

the bracket B. Preferably the tube 20 and the valve H are covered with a thick layer of insulation which extends from the insulated kettle ID to the insulated jacket of the shot dropping -apparatus. This tube may also be an iron pipe syphon elevating the molten lead alloy over the sidewall of thekettle and discharging it on the shot pan 30.

The-shot dropping apparatus, or shot tower consists of a shot dropping plate 30 having a plurality of apertures 3| therein. In Figure 2, which a fragmentary enlargement of the shot dropping plate portion of'Figure 1, the plate 30 is i1- lustrated as being provided with apertures 3! having ,a lower cylindrical bore portion 32 and an upper conical. portion 33. The diameter of plate 30 may be made anyfdimension desired I from a few inches to several feet in diameter de- .pending upon the shot dropping capacity dethe size of shot which it is desired to produce. As illustrated in Figures 1 and 2, the plate 30 is held between an upper tubular portion generally designated 40 and a lower tubular portion generally designated 60, which are joined together with the plate 30 between them by means of the screw connection 4|.

The plate 30 in its preferred formis nicely fltted to the tubular portion 40 at the point 42 so as to preclude flow of molten shot metal edgewise from the -plate. v

The tubular portion 40 extends upwardly from the plate 30 and is provided with an outside flange 43 which serves to support tube 40 and the attached lowertubular portion 80 from the frame and Jacket 89 of, the apparatus. The upper end of tube'4il is closed by means of a screw cap 45,

through which there extends tubes 48 and 41. The tube 48 is provided with a coupling v 48 by which it may be disconnected from the tube 48. It will be noted that the tube 46 in Figure 1 extends downwardly within the member 40 to within a.few inches of the shot dropping plate 30.-

Tube 41 on the other hand communicates with the upper portion 50 of the interior of tube 40 and has an outwardly extending branch 48 adjacent which there is a pilot light 5|. g The tubular portion 80 of the apparatus extends downwardly from the shot dropping plate 'for' a distance sufllciently great that the shot dropped through the plate is spherodized before it emerges from the lower end 6|. In practice. the dimension T of tube B is preferably made from to 30 feet depending upon the temperature at which the shot is dropped and other factors, and the height H through which the shot falls is preferably made from 50 to 150 feet.

The tubular portion 60 is provided with a pipe 62, which is coupled by means of a union 82 to the pipe 84. It will be noted that pipes 48 and 64 merge at-the junction 85 and are in communication with the pipe 66 which extends to a gas supply and purification apparatus, illustrated in Figure 1 under the'bracket C.

The shot plate zone and the adjacent portions of tubes 40 and 60 of the "shot tower" are preferably arranged to be heated so that the molten shot metal conducted'to the plate ill re mains in fluid condition on top of plate 30. In the preferred form of the apparatus, the heating is accomplished by means of an electrical heating coil which is fed by conductors ll from mains 12. It is preferable to provide a variable voltage regulator 13 so that the amount of heat emitted by coils 10 maybe regulated within close limits. The jacket 89 may be insulated as shown, or in some instances, it may be uninsulated. 1 i

The heating coil Ill may be used to warm the shot plate or pans at the outset of a run. Thereafterduring, the run the heatoutput of coil 10 is decreased or entirely interrupted. In some instances the coil Ill may be entirely eliminated where provision is made to heat the shot dropping plate (or pans 94 where they are used) externally of the tower-before the run is begun or where the shot metal is initially introduced at a suiliciently high temperature that it heats At the lower end of tube I, there is provided a pilot light 16, which serves to burn the gas supplied to the tube BI as hereinafter explained. At the bottom of the shot tower there is provided a sump 18 which is partially filled with a fluid such as carbon tetrachloride, oil or water. In the preferred form of the invention. the fluid II is carbontetrachloride although when special precautions are made, other fluids such aswater may be used.

The gas supply and purification apparatus illustrated under the bracket C of Figure l, preferably consists of a gas supply bottle 80 having a shut-off valve 8|, pressure gauge 02 and a pressure reduction device 43 bywhich the high from the last bubbling vessel 85, passes through pipe 86 to a drying tower II, which contains'a material for the absorption of any water or water vapor which may be present in the gas.- After passing through the drying material the gas emerges through pipe 88, which is provided with As explained above, the

a pressure gauge ll. pipe 48 communicates with pipes 4! and 44 at Junction BI. y

In the process of producing shot according to the present invention, the shot material such as theshot alloys of Patent 2,167,828 are reduced to a molten state in kettle II or the alloying may be accomplished'in thekettle Ill where the raw metallic materials are separately obtained. The alloying is preferably doneby' introducing the metallic constituents into the kettle ll under a molten flux consisting of drous, calcium chloride, magnesium chloride, barium chloride and calcium fluoride. Good results are obtained flux of the following compo-- when an anhydrous sition is used: v

I Per cent Calcium chloride Magnesium chloride '34 Barium chloride 9 Calcium fluoride 2 from the melting kettle i0 enters the shot dropping apparatus just above the plate 30 and the The alloy is melted-or made by the heat supplied through heating coil II or by P p r gas Y burners and after becoming'thoroughly fluid is conducted through pipe as to the shot. dropping plate 30 where 'it forms a thin film. The heat input to heating units H and 14 is adjusted so that the alloy is maintained at atemperature slightly above the temperature f solidification so that the molten shot metal accordingly drops through the holes ii and falls through the gas atmosphere within the tube 44.

Prior to the introductionof molten shot metal aboveplate 44, gas is introduced into the tubes 40 and 40 by means of the gas supply and purl: flcation apparatus C. For the gas supplied in the tubes 4| and 42, there is used a substantially water andoxygen free'gas which is inert to the metallic constituents of the molten shot alloy. Veryexcellent results hydrocarbon gases, more particularly the alkane gases such as .propane commercial" which is obtainable from the Mid-Continent oil flelds of Oklahoma and Texas. Thus "propane commercial, or what is known in the Northwest trade as Blaugas," gives excellent results without scrubbing oxygen and water vapor in II and I1. Suchfbottled propane" consists predominately are obtained when using of propane, about 95% to 99%, together with small percentages of other alkane gases such as methane, ethane, butane and the like. reducing gases inert to the molten shot metal may also be used. 1

When such bottled "propane, commercial gas is used,'it may be supplied in containers such as that illustrated 'at 89 in Figure 1 or it is also available in tank car lots. The commercial gas is relatively free of water vapor, the water having been frozen out in the manufacturing of the gas, and very little oxygen is normally present. However, it is preferable merely as a precaution to guard against any water and oxygen that may be' present by passing the gas through the bubbling towers 85 which contain an oxygen absorption material such as pyrogallic'acid, and hen through the drying tower 81 which prefer bly contains an anhydrdus strongly hygroscopic granular material such as calcium chloride.

Where the gas being used contains muchmoisture or oxygen, the purifying apparatus may be extended to cope with these unwanted constituents, the goal being to reduce the amount .of

oxygen, water vapor and the like unwanted constituents until spherical shot is obtained. The sufficiency of the purification procedure may easily be gauged by examining the shot produced, for when there is too much oxygen or water vapor slight tails will be formed on the spherical shot.

As the oxygen and water vapor is reduced, the tails disappear, and truly spherical shot is obtained. In some instances, propane, commercial gas is sufficiently free of oxygen to render the pyrogallic acid oxygen scrubbers '85 unnecessary, and these may accordingly be dispensed with when the oxygen content is low or where oxygen is absent.

The purified gas is introduced into pipe .66 at a few ounces pressure and, fills tubes 40 and 60. After the gas has been passed into the tubes 40 and 69 for a period sufficient to drive out oxygen and other gaseous constituents of the atmosphere, the gas is lighted at tube 48 by means of pilot and at the bottom of tube 69 by means of pilot light 16. Thereafter, throughout the dropping operation, gas is supplied to tube 40 above the shot dropping plate 39 by means of I nesium.

Other sult.

of an alloy of lead and ma the shot consists After the shot is removed from sump 18' and dried, it is graded by any of the usual procedures and then graphited, oiled or coated with grease or resinous material. -Any malformed or imperfect shot which is separated in the grading process may be returned along with fresh material to the shot metal melting kettle in where it again passes through the shot forming procedure In carrying out the invention care should be 4 taken to supply the molten shot metal to the plate 39 in a thin layer for if" the layer I5 of shot metal on the plate ness shot of'elliptical formation islikely to. re-

In the modification shown in Figure 3, tube 49 is provided with a door 99, hinged at 90 to tube 40. Access'to door 89 is made available by providing an opening 92 in the insulated or uninsulated jacket 69 of the shot tower. Door. 90 may be 9| if desired so as to enablethe' operator to judge'the procedure of dropping. (See Figure 1.) In this modification plate 39 is provided I with two or more holes 93 which are chamfered pans to produce to receive shot pans 94-94. The shot pans are, similar in shape to an ordinary frying pan and are of a size so that they can easily be removed through-door 89 for cleaning and for changing different sizes of shot. In this modification it is of course understood that each of the pans 94 has apertures in its lower surface which are preferably of the shape shown at 3| in'Figure 2. Only one pan is normally used at a time and the shot metal delivery tube 95 is thus made so that it can be moved from v the full line position 96 where it serves the pan 94 at the right of FigureB, to the position 91 at the left of Figure 3. Many obvious variations will be apparent to .those familiar with the art and may be made tubes 46 and to the tube below the shot dropping plate by means of tube 62 and the flow of gas is burned with a quiet flame at the end of tube 40 and at the bottom of tube 61.

With the gas thus supplied to tubes 40 and 60, the molten shot metal is introduced onto the shot dropping plate 39 by way of tube 29 as low that by the time the shot globules drop through quiet flame at the bottom of .tube 6|.

they have already assumed a spherical form'and I tube 69 and the temperature within this zone is sufficiently genand watervapor, and other gas purification 1 steps may be included for the removal ofconcooled sufilciently to resist deterioration while falling through the atmosphere ,to'sump l8.

Where the shot being dropped consists of ordinary lead or lead'arsenic and lead antimony alloys, the sump 18 may contain water, but where the shot is of a disintegratable lead. alloy such.

as that set forth in Patent 2,167,828 I prefer to use a light evaporatable fluid such as carbon tetrachloride. However, where provision is made forthe immediate removal and drying of a disintegratable alloy shot collects in sump 18','

water may be used as the fluid 19 even when constituents in the in the details of the apparatus and method herein described. Thus the exact proportions of the shot metal may be widely varied although the method is especially adapted for the production of good quality spherical shot of lead and a small percentage of magnesium,

and other disintegratable shot metals of the typev set forth in Patent 2,167,728. Likewise, the typeof. gas supplied above and below the shot dropping plate may be widely varied and may include normally gaseous alkanes derived from natural sources or manufacturing operations or normallyliquid hydrocarbons whichare converted to the gaseous phase at the temperatures used in the dropping procedure. Variations may be made in the gas purificatlonprocedure or may be omitted entirely where the source of gas supply is assuredly substantially free of oxy-' stituents of any selected gas which are not inert to the shot metal at the temperatures used in v procedure. Likewise the method of heating the shot metal melting shot and the method of'heating the shot tower apparatus may be varied to suit the conditions of any par' ticular installation and the dimensions of the the dropping 'shot' dropping plate, the size of the apertures 3|, tubes 40-40 and dimensions H and T may likewise be widely varied to meet the exigencies of any particular installation. Furthermore, in

some instances it'is desirable to incorporate the is increased in thickprovided with a glass sighting opening.

shot melting kettle with the shot tower" or to use other methods than that illustrated, for example a syphon, for conducting the molten shot metal from a melting kettle to the upper surface of the shot dropping plate. These and other variations may all be made without departing from the spirit of the invention herein illustrated, described and claimed as follows:

I claim:

1. A process of making spherical shot which comprises supplying a molten alloy of ,e to 1()% 8. A process of making spherical shot which comprises dropping an alloy of ii; to 10% magnesium and 99 to 90% lead through a perforated plate, said dropping being carried out in an atmosphere of propane which has been freed of oxygen and water vapor.

4. A process of fabricating spherical shot which comprises dropping an alloy comprising lead 99% to 90% and magnesium to 10% through an orifice and maintaining a gaseous atmosphere of an alkane hydrocarbon which has been freed of oxygen and water vapor around said molten metal until after it has dropped said orifice and partially solidified.

5. A process which comprises melting an alloy of 99% to 90% lead and A to 10% magnesium under an oxidation inhibiting flux comprising a chloride of an alkaiimetal, transferring said molten alloy out of contact with oxygen to a plate having perforations therein for dropping the alloy therethrough, and maintaining around said molten alloy an atmosphere of propane which is free of oxygen and water vapor around said alloy during the dropping thereof.

6. A process which comprises melting an alloy of 99 to 90% lead and to 10% magnesium under an oxidation inhibiting flux comprising a chloride of a metal selected from the group consisting of magnesium, sodium, potassium, barium and calcium, transferring said molten alloy out of contact with oxygen to a plate having perforations therein for dropping the alloy therethrough and maintaining an atmosphere of propane free of oxygen and water vapor around said alloy during dropping thereof.

RALPH L. DOWDELL.

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