US474860A - Island - Google Patents

Description

(N0 Model.)

R. A. ROBERTSON, Jr. APPARATUS POR CASTING CANNON.

Patented May E17, 1892.

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RICHARD A. ROBERTSON, JR., OF PROVIDENCE, RHODE ISLAND.

APPARATUS FOR CASTING CANNON..

SPECIFICATION forming part of Letters Patent No. 474,860, dated May 17, 1892. Application tiled January 14, 1891. Serial No. 377.774. (No model.)

To all whom t may concern:

Be it known that I, RICHARD A. ROBERTSON, Jr., a citizen of the United States, residing at Providence, in the county of Providence and .State of Rhode Island, have invented new and tion through the center of the molding-pit,

flask, mold, casting, and core. Fig. 2 is a vertical section through the same after the core has been withdrawn, showing a cooling-pipe inserted in the bore. Fig. 3 is a vertical section through the center of the mold, dmc., at the bottom thereof, showing a different cen tering device. Fig. 4 is a vertical section through the center of the mold, dac., at the top thereof after the core has been withdrawn, showing a dierent device for drawing the cooling-fluid from the bore.

Similar letters refer to similar parts.

The objects of my invention are to relieve the opposing initial stresses, to prevent opposing lines of crystallization, to furnish an accurate and easy method of centering the core, and to lessen the waste of metal and cost of casting.

To these ends my invention consists in the mechanism and combination of parts hereinafter described. o

An important part of my invention consists in the mechanism for the cooling of the casting uniformly at all times throughout its entire length from the bore outward, so that the lines of crystallization shall radiate from the bore normally to` its contour at every point throughout its entire length while the casting is solidifying, whereby the intensity of the initial stresses is uniform throughout the entire casting, and to the accomplishment of this result water or other cooling-fluid is forced first through a pipe inserted in a hol-` low core, which core extends entirely through the casting and also beyond the ends of the casting. Then said core, with its said pipe, is withdrawn as soon as the molten metal has set, and then said fluid is forced through another pipe inserted in thecavity of the casting obtained by withdrawing the core, which pipe preferably extends entirely through said cavity, hereinafter called the bore, the outlet of the pipe being preferably below the body of the casting. By the use of this apparatus the continuing `flow of the cooling-fluid in the core absorbs the heat from the interior of the casting to such a degree that the liquid mass solidiiies first nearest the core, and from thence outward, and when the casting is sufficiently solidified to be set the core, with its pipe, is withdrawn and the cooling-Huid then forced through said second pipe into the bore, as described, and flowing back to its `outlet touches the surface of the bore at every part thereof, thus cooling the casting more rapidly by direct contact therewith than if the core was retained and more effectively producing the desired conditions in the casting. The cooling being made uniform throughout the entire length of the casting in the manner shown, there is no opportunity for and consequently no intersection of different lines of crystallization, the intensity of the initial stresses is made uniform, and the formation of lines of weakness is prevented at any and all parts of the casting. While the casting is being cooled from the interior in the manner described, the radiation of heat from its eX- terior is retarded by fires kindled in the molding-pit for that purpose.

In describing my newly-invented mechanism I will first briefly sketch the old or Rod man apparatus and point out the particular defects in it which I claim to have remedied in my invention.

In the apparatus used for carrying out the old process of casting cannon, in which the system or method of cooling the casting from the interior was the basis, the core was suspended in the mold-cavityand a considerable distance left between its lower end and the bottom of the mold. This core was held bya frame called a spider,7 placed over-the top of the molding-pit. To center the core in the IOO mold-cavity, this spider was adj usted-. e., its position changed-by means of screws in the spiders legs. The core being necessarily of great length, and thus having considera-ble leverage, a slight change of its position at the top madea much greater variation at its lower end and rendered the centering of the corein relation to the mold-cavity a matter of great difficulty; also, its lower end being free or unsecured any irregularity in the How of the metal from the runners t t into t-he mold-cavity deflected the core from its position, and consequently when the core was withdrawn the bore of the casting would be eccentric and the value of the whole casting in its relation to cannon destroyed-a not infrequent occurrence. Again, the buoyancy of a core of great length when held in suspension in the mass of liquid 4metal created a powerful upward pressure, and to prevent the displacement of said core the spider and the adjusting-screws aforesaid had to be made enormously strong at a very considerable cost of time and money. In the cooling of cannon cast in this manner, the tendency of the lines of crystallization being to lie normal to the surfaces of thecrystallizing mass, those lines extending from the sides of the casting diverged from those at the bottom of the cast-` ing at almost, if not quite, right angles, the result being that lines of weakness and irregularinitial stresses were developed at the base of the casting. Again, the lines of crystallization from the bore near the escape-pipe, which was inserted at a right angle to the aXis of the core in one side of the sinking head, intersected the lines from said pipe with unequal intensity around the pipe, producing severe initial stresses and lines of weakness in that neighborhood, while the process of vcrystallization,being unequal below and above the water-level established by said pipe, also induced initial stresses of varying intensity. As a result, it was necessary to cut off a large part of the casting so weakened at its base, while the effect of the diiferent stresses near the escape-pipe was not only to crack the metal in the sinking head, but frequently sofarlongitudinally'as to ruin thewholegun. Myinventionovercomesthese defects in the following manner, viz: At the bottom of the usual mold A, I place a light metal pot or receiver K, filled with sand,and in this sand is preferably molded a print, so called, to exactly fit one end of the core B. This pot is held in place by sand thoroughly rammed around it, but so as to leave a rim or edge I'I of the pot projecting into the moldcavity. I prefer to'make this pot slightly larger than the core B, so that the projecting rim of the ptt will practically touch the outer surface of said core near its lower end, as shown in the drawings, Figs. l and 2. The

The core is lowered into the mold-cavity until its lower end rests in the print or indentation, itsupper end being steadied and centered byahght frame or spider C, through which' said core end is free to slide upward, but without any lateral change of position. Both ends of said core being thus secured from lateral movelnent by said spider and print, Fig. 1, 1t is self-evident that the core is accurately and easily centered with relation to the mold-cavity and that this central position cannot be changed during the process of casting.

While I prefer to use a print in the pot, as described, for greater accuracy in centering the core, still its use is not absolutely essential, and I do not limit myself to it as a centering device, since it is easy to place the pot itself so that its position will be concentric with the core and mold-cavity and have the projecting rim of the pot touching the outer edge of the core end, thus preventing its having any lateral movement. I may also omit the sand from the pot and substitute in the pot a cone-spindle Y or other suitable equivalent which will come in contact with and center said core, substantially as shown by Fig. 3. The core having been lowered into the pot and centered in the manner substantially as described, I then usually suspend a cylinder G from the spider in such a manner that it will inclose theupper end of and preferably be in contact, or nearly so, with said core, the lower end of the cylinder being depended into the mold-cavity a sufficient distance so that it will be submerged in the liquid metal when the mold is full, Fig. 1. In this cylinder I also prefer to place an escapepipe F, the position of said pipe being such as to leave a considerable distance between it and the surface of the sinking head S of the casting. The use of the escape-pipe is convenient, but not essential, as will be hereinafter shown.

My newly-invented apparatus, constituted substantially as described, is now ready to be used.

In the process of casting, the liquid metal is introduced into the mold-cavity,l as usual, through the gates or runners tt and in my apparatus attaches itself to or fuses itself with the projecting rim l-I of the pot K and also with the lower edge of the cylinder G, thus making them a part of the casting, Fig. 2. (Heretofore AI have used'the term body of the casting or casting proper with the object of distinguishing the bulk of the true casting from these false parts constituted by the union of the pot to the lower end and the cylinder with the upper end of said casting.) I prefer this method of connecting the cylinder with the casting; but it may be made a part of the casting or otherwise joined-c. g., the cylinder may be lowered into contact with the casting-and after a reasonable time the connection can be luted at the surface of the casting. The next step is to force the IOO IZO

cooling-fluid through the pipe R in the core B, which core was made hollow to carry'said pipe and as a return-conduit for said fluid, Fig. l. After said core has been withdrawn from the casting I next force the cooling-fluid into the bore of the casting itself through a pipe R in the manner already described hereinabove. (See Fig. 2.) I do not confine myself to having the inflow-pipes extending through the core and bore, since it is apparent that an outiow-pipe might be thus extended to the bottom of the casting, or a siphon, Fig. 4, or other means used for creating a current in the cooling-fluid throughout the entire length of the casting. The hollow formed by the print in the pot after the core is withdrawn (or the hollow pot itself, if no print is used) allows the water or other cooling-fluid to flow beyond the lower end of the body of the casting, and the cylinder at the top of the casting (also a part thereof, as shown) permits the fluid to risc above the sinking head S and casting proper to the escape-pipe F, Fig. 2, although this escape-pipe can be omitted and the fluid allowed to iiow over the top of the cylinder, to be thence carried oif in any suitable manner wit-hout its touching the exterior of the casting proper, the main object being to keep the level of the continuous flow of water or fluid above the top of the sinking head. Since the cylinder and pot were described as touching or nearly touching the outer surface of the core, it is evident that when they have been made a part of the casting, as shown, the cooling-fluid cannot touch any part of the casting proper except the bore, unless it be a very small part of the cxtreme outer ends of the casting at its top and bottom near the cylinder and receiver, as already explained, which part would be so small that the effect created would be inappreciable in its relation to initial stresses and may be neglected. Hence it follows, the fluid having been carried entirely through the bore of the casting and beyond the casting proper at both ends thereof, that the process of cooling will be uniform throughout the entire length of the casting from the exterior outward, that there is no opportunity for and hence no intersection of different lines of crystallization, that the intensity of the initial stresses is made uniform or regular throughout the casting, the formation of lines of weakness prevented, and consequently that there is no danger of losing a casting from 'these causes. Vhen a print is used in which the lower end of the core exactly fits, or when the projecting rim of the pot iits closely to the outer surface ot' the lower edge of the core,none of the liquid metal can get beneath the core and create any upward pressure thereon. A very slight spider, non-adjustable, can therefore be used. Also, the metalpot at the lower end of the casting, and which is lifted out with the casting, being light, is easily broken with a hammer, exposing the bore of the gun at once CAD at its breech, avoiding the necessity of cutting off any of the casting. The cost of casting cannon is thus greatly lessenedrby this saving of metal, time, and labor.

Having fully described my invention, what I claim, and desire to secure by Letters Patent, is-f 1. In an apparatus for casting cannon, the combination, with a mold, of a hollowr core eX- tending entirely through the mold-cavity, and a metal-receiver provided with a core-seat at the bottom ot the mold, the rim or edge of said receiver projecting upward into the moldcavity, ythe receiver and core being concentric with the moldcavity, substantially as described.

2. In an apparatus for casting cannon, the combination, with a mold, of a hollow core and a metal cylinder, the latter depending into the mold-cavity so that the lower end of the cylinder will come in contact with the surface of the casting or be submerged in the casting when the mold is full, the diameter of said cylinder where it touches the casting slightly exceeding that of the bore, and pipes or equivalent means for obtaining a continuous flow of cooling-Huid through the bore, all arranged substantially as described.

3. In an apparatus for casting cannon, the combination, with a mold, of a hollow core extending entirely through the mold-cavity, and a metal cylinder, the latter depending into the mold-cavity so that the lower end of the cylinder will come in Contact with the surface of the casting or be submerged in the casting when the mold is full, the diameter of said cylinder where it touches the casting slightly exceeding the bore of the casting, and pipes or equivalent means to secure a continuous flow of cooling-fluid through the bore, all arranged substantially as described.

et. In an apparatus for casting cannon, the combination,with a mold,of a hollow core extending entirely through the mold-cavity, a metal pot or receiver provided with a core-seat at the bottom of the mold and having a rim or edge projecting upwardinto the mold-cav ity, a metal cylinder whose diameter is slightly greater than that of the bore of the casting, said cylinder depending into the mold-cavity so that its lower end will be in contact with the surface of the casting orbe submerged in the liquid metal when the mold isA full, said core, receiver, and cylinder being concentric with the n1old-cavity, and pipes or equivalent means for obtaininga continuous flow of cooling-huid through the'core and after the core is withdrawn through the bore, all arranged substantially as described, and for the pur-l poses specified.

5. In an apparatusfor casting cannon, the combination,with a mold,of the hollow core B, having a pipe R inserted therein, said core extending entirely through the mold-cavity, a metal pot or receiver K, provided with a core-seat at the bottom of and having a pro- IOO IIO

jecting rim H extending upward into the moldczwity, a frame C at the top of the pit, a metal cylinder G, depending into lche mold-cavity from the frame C and having an escape-pipe inserted therein above the top of the moldingpit, and the pipe R preferablyof such a length as to extend entirely through the 1nold-cavity or bore of the casting after the Core is Withi drawn, all arranged substantially as set forth and described.

R. A. ROBERTSON, JR. Witnesses:

FREDERIC HAYES, J. W. BRIGHT.

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