US2214508A - Mold for centrifugal casting - Google Patents

Description

Sept.' 1o, 1940. E. A, NELSNA f .2,214,5o-v

MOLD FOR CENTRIFUQAL CASTING I i Filed ,octl 13, 195e l Patented Sept. 10, 1940 Vm1111510 STAT Es APAfrlslijr oFF-ICE vMOL) FOR CENTBIFUGAL CASTIN Emil A. Nelson, st.- Clair shores, Mich. Application October 13, 1939, Serial No'. 299,349

United States for improvements in Centrifugal casting method, filed November 13, 1937 and serially numbered 174,296.

' Objects of the invention include the provision of a mold for centrifugally casting hollow articles so constructed and arranged that when the mold is positioned with its axis vertical and'is charged with metal it-will automatically predetermine its own charge; the provision of a centrifugal casting moldso constructed and arranged as to predetermine its own charge of metal when charged with molten metal while in a stationary position; the provision of a centrifugal casting mold having a cylindrical'interior surface and an end wall provided with an inwardly axially extending hollow projection serving as an overflow pipe when the mold is charged with its axis in vertical position and the mold is not, rotating; the provision of a centrifugal casting mold comprising a bucket.

shaped member of refractory characteristics having a standpipe positioned centrally of its bottom whereby to predetermine the liquid contents of the mold when the mold is charged while stationary and with its axis in a vertical position; and

the provision of a mold for a centrifugal casting operation of such character as to' permit it to be, charged with molten metal independently of the centrifugalcasting machine and thereafter inserted with its charge of molten metal into` the machine, the mold being so constructed and arranged as to predetermine the charge of metal receivable thereby prior to its application to a cntrifugal casting machine.-

'I'he above being among' the objects of the pres- 40 entinvention, the same consists in certain novel features of construction and combinations of parts to be hereinafter `described with reference to the accompanying drawing, and then claimed,

having the above and other objects in view.

In"the accompanying drawing which illustrates a suitable embodiment of the present invention and in which like numerals refer to like parts throughout the several different views,

' Fig. 1 is a partially broken, partially sectioned side elevational view of a centrifugal casting machine in which a mold constructed in accordance with the present invention is illustrated as being oyperatively positioned and shown in vertical section; y Fig. 2 is a more or less diagrammatic view i1- lustrating the mold shown in Fig. 1 in side elevation land separate from. the centrifugal casting machine, supported by a conveyor in a position to receive a charge of molten metal from a furnace, oo cupola, or the like;

, Fig. 3 is a vertical sectional view taken centrally through my improved mold and illustrating the same'with its charge of metal after it has been subjected to a centrifugal casting operation and before the finished cast article has been removed therefrom;

Fig. 4v is a slightly enlarged partially broken, partially sectioned side elevational view of the article which is cast by the mold shown in the 4preceding views.

As vis generally understood in the art it is customary practice in connection with the centrifugal casting of metals and particularly where the article to be cast has a material' axial dimension as compared to its diameter, to position the mold with its axis in horizontal position and to provide a machine to support and to rotate the mold while in such position. Particularly where such machines are `used in quantity production, in order to conserve metal and to limit the amount of machining required to bring the article to finished condition aftercasting, it is necessary to carefully predetermine the charge of metal which is to be placed in the mold and to be distributed Y around the inner walls thereof by centrifugaly g5 force during. the actuall casting operation. In accordance with conventional practices molten metal in a cupola or furnace is tapped into a relatively large ladle, an estimated desired quantity 'of the metal is then poured into a' smaller or pouring ladle, the smaller ladle and its contents are hurriedly weighed and metal is either added or discharged from the pouring ladle until approximately the required amount remains therein, the pouring ladle is then transported 35 to the centrifugal casting machine, and the molten metal is then poured from the pouring .ladle through a pouring spout and .into the interior of the mold which has previously been set in rotation. Thus in conventional practice the metal has an opportunity to cool while it is in the large ladle, also when it is in the small pouring ladle; and also when it passes Athrough the pouring spout into the mold. Considerable time elapses in conventional practice between the timeA the xnetal is actually discharged from the cupola or furnace before it enters the mold and, accordingly, loses a considerable amountA of its heat before it isiinally in the position to be acted upon by centrifugal force inthe mold proper. Particularly the small or pouring ladle and the spout leading to the mold proper are relatively cold and contact with-these 4is responsible for a considerable loss of heat in the molten metal.A When the molten metal strikes these cold surfaces, and this is particularly true in case of the pouring spouts, the metal spatters andsmall globules thereof become chilled and are often carried into the final product in such form. It will be"realizedthat the maintenance to the proper heatof the molten n metal is important in centrifugal casting operations if a final product of a desired high quality and texture of material is to be obtained and, accordingly, any loss of heat because of the above mentioned reasons is a material disadvantage.

In lling the pouring ladles and attempting to weight them to obtain an accurate amount of metal therein, the need for speed in getting the molten metalinto the mold is so great that the actual error in the final charge in the mold is often considerable, with the result that an undesirable variation in the thickness of the nal product is common and results in a disadvantage in the subsequent machining operation which the article cast must usually undergo. Attempts at more accurately weighing the molten metal to be furnace although they may be charged directly4 from a relatively large ladle. In carrying out this feature of the present invention it will be realizedthat `it eliminates at least the heat loss occurring in conventional practices in the pourl ing ladle and in the pouring, spout, the bulk of any heat lostby the molten metal being transferred directly to the mold whichI is a necessary loss in any case'and this, accordingly, aids in conserving the heat -in the metal between the time it is actually poured and the time at whic it is subjected to centrifugal'force.

In accordance with the present invention in order to accurately predetermine the charge of metal in the, mold ina quick and accurate manner, the mold is so constructedz and arranged as to predetermine the amount of metal which may be charged into it. This is accomplished by soconstructing and arranging the mold as to provide it with an overflow means which becomes `effective when a predetermined amount of metal has been introduced into the mold. By this means the mold is charged with molten metal' until the molten metal begins to be discharged from the overflow at which time the charging' is discontinued with the assurance that the. amount of metal remaining in the mold accurately coincides with the mass desired therein; In carrying out the last mentioned step it will usually be found desirable to fill the mold when the mold is positioned with its axis in a vertical position and the overow means in such case.

will usually take the form of a standpipe positioned axially of the mold with the corresponding end of the mold closed except for the opening through the standpipe.

Where the mold is so constructed and yarrangedas to be charged-when its axis is in a vertical position., due to the 'fact that it is desirable to effect or at least complete the spinning operation o f they mold when the axis of the mold is in a horizontal or approximately horizontal position,

it will be. found necessary to insertthe charged mold in the machine and commence spinning of the same while the axis of the mold 'is in vertical or approximately vertical position and after the mold has reached a suiiicient rate of speed to insure throwing of the molten metal to the radial wallsthereof to move the mold so as to bring its axis into the desired position for completion of Y the casting operation. While this may obviously be accomplished in a number of different ways, one structure is illustrated in the drawing which may be satisfactorily employed and includes a rotatable spindle for supporting and rotating the mold and a support for rotatably supporting the spindle, the support and spindle together with the mold carried thereby being capable of being moved as a unit from a position in which the mold is positioned with its axis vertical to a position in which the mold is positioned with i-ts axis at a material angle to the vertical, or even to a horizontal position where such is desired. It will be appreciated that positioning of the mold with its axis in a horizon-tal position makes it easier to remove the mold ,and the article cast therein from the machine-after the material from which the article is made has solidified.

Referring now to Fig. 1, the centrifugal casting machine itself is indicated as being provided with a base l which is provided with a pair of spaced apart upstanding arms I2 between the upper ends of which extends a horizontal shaft vI4 supported thereby. A hollow generally cylindrical housing member I6 positioned with its axis'in offset relation with respect to theraxis of the shaft I4 is exteriorly provided with a laterally offset boss portion I8 which embraces the shaft I4 between the arms I2 thereby to provide a. pivotal support for the housing I6 upon the shaft I4'. When the machine is in loading position the axis of the housing I6 extends vertically but as will be apparent its axis may be positioned horizontally or at any other angle to the vertical, as indicated by dotted lines in Fig. 1, by causing the housing I6 to swing about the shaft I4. As a matter of convenience only, in the followingdescription it will be assumed, unless otherwise speciiled, in describing the construction of the machine, that reference to direction is intended to mean when the machine is positioned as indicated in full lines in Fig. 1, namely with the axis of the housing I6 vertical. l

Rotatably mounted within the-housing I6 is a hollow spindle positioned with. its axis coincident with the axis of the housing I6 and projecting both above and below the housing I6, its upper end being outwardly flanged as at 20 to forma supporting surface and the lower end thereof having fixed thereto a dual pulley 22. The pulley 22 is connected by a.l pair of belts 24 with adual pulley 26 secured to the shaft 28 of an electric motor 30 suitably mounted in fixed relation with respect to the housing I6 and movable bodily therewith about the axis of the shaft I4. Seated upon. the upper marginal face of the flange 20 are a plurality of spacer blocks 32 arranged in equally angularly spaced relation around the circumference of the flange 20 and these spacerblocks 32 receive upon them a disclike member 34 which in turn receives and supports the flanged end of the rigid mold support lil 36. Bolts 38 extend through the flange of the A mold support 36, the disc 34, spacers 32 and flange 20 of the spindle and secure all of these parts rigidly together in assembled relation.

conventional piston (not shown) having a connecting rod 44 projecting upwardly through the upper end thereof and pivotally connected as at 46 to the upper portion of the housing I6 eccentrically to the axis of the shaft I4.A Suitable connections 48 adjacent the upper and lower ends of the cylinder 4U are provided for the admission and exhaust of iuid under pressure to control the position of the piston in the cylinder 40 and consequently the rotatable position of the housing I6 about the axis of the shaft |4. An air hose- 50 is connected by means of a conduit 52 and slip connection .54 with a tube 56 positioned centrally of the housing and the spindle rotatable therein for feeding the air to a mold ej ecting device 58 positioned centrally of the disc 34. For a fuller description of the centrifugal casting' machine per se and a more detailed description of the manner of operation, reference may be had to the parent application above identified of which the present application is-a con inuation in part. v Referring now to the mold proper which forms the subject-matter of the present invention and which is shown in Figs. 1, 2 and 3, it will be understood that the actual construction of the mold, that is whether it is made up of an assembly of a plurality of separately formed parts or is made up as an integral structure is of no moment as far as the present invention is concerned. In most cases it will be made 'up as av-baked sand product although in some cases it may be desirable to form it 'of metallic sections provided with a suitable lining of heat insulating material such as is commonly employed in connection with socalled permanent molds. It will alsobe appreciated that the interior conguration of the mold will vary in accordance with the article to be formed. As a matter of illustration only in the present instance it is assumed that the mold is intended'to form cylinder liners for internal combustion or other engines and which liners take the form of a hollow cylinder having a radially outwardly projecting ange at one end only' thereof-and as specically illustrated at 60 in Fig. 4. For the purpose of forming a cylinder liner 60 it is assumed for the purpose of illustration here that the mold which is indicated generally at 62 isiormed in two parts from baked sand, namely an upper part 64 and a lower part 66, the upper part being approximately cylindrical and being provided with the usual flange 68 at its open end for predetermining the length in this direction of the article being cast. The lower portion 66 comprises. a disc-like portion sealed to the corresponding axial face of .the portion 64 and centrally provided with an upwardly projecting boss-like portion` or projection 10 provided with a central opening 12 therethrough and which opening is on the axis of the mold. A metal disc or plate 14 underlies the lower face of the portion 66 and is provided with a central aperture aligned with the opening 12. A metallic ring or annular plate 16 overlies the upper face of the portion 64 and threaded rods 18 extend through the mold and cooperate between the plates 14 and 16 to maintain the two portions 64 and 66 in properly assembled relationship. Eyes on the upper ends of the rods 18 provide means by which the mold 62 and its charge of molten metal, here indicated at 82, may be easily transported.v It may also be noted at this point that the interior walls of the mold support 36 are slightly tapered and the outer walls of the mold 62 are tapered in a complementary manner so as to insure a proper t between these parts under all circumstances when assembled together. As will be noted from an inspection of Fig. 1, when the mold 62 is properly assembled in the mold support 36, the disc 14 overlying the lower end of the mold 62 is preferably positioned a slight distance above the upper face oi the disc 34 and member 58.

It is possible to employ a mold of the type shown and described and to insert it in the support 36 while the apparatus is positioned as indicated in full lines in Fig. 1, charging the mold while in such position, and then after initiationof the-spinning operation, swing the housing I6 with the mold 62 downwardly to either of the two positions indicated in dotted lines for completion of the spinning operation. In such case advantage may be taken of the particular characteristics of the mold |52 shown except that in such case provisions must be made for eliminating any overflow of the molten metal charge which may pass down the opening 12 from the machine and which provisions are not necessary when vthe preferred method of employment is used. f

In the preferred method of employing the mold shown and described, particularly when used in connection with a centrifugal casting machine of the general characteristic shown and described, is chargedwith molten metal before it is placed in the mold'support 36. Because of this it will be realized that the mold 62 must be self-sustaining under a charge of molten metal therein when stationary and it will be readily recognized that the construction of the mold 62 .as-previously described in detail is such as to effect this result: Accordingly, in accordance with the preferred method of procedure, a mold 62 is suspended through suitableI engagement with the eyes 80 and the rod 18 from a suitable traveling-lifting device |20 suspended for movement from a monorail track |22 as illustrated in Fig. 2. The lifting device |20 may be of any suitable type, either actuated by fluid pressure, electricity, or manually, and is shown by way of illustration only as a chain fall. The mono-rail track |22 is preferably extended past the spout |24 of a suitable cupola or furnace such as |26 so that the mold 62 while supported from the mono-rail track. |22, and preferably after it has been initially heated by a torch or the like to reduce the heat losses from the metal to it, may be moved below the spout |24 so as to receive a charge of metal therefrom. As previously mentioned, instead of receiving a charge directly from the cupola or furnace, molten metal from such cupola or furnace may be drawn off into a relatively large ladle and the mold 62 charged Idirectly from the ladle with substantially the same results as here outlined except that in such event a greater heat loss will occur in the metal than where it is charged directly from the cupola or furnace. The height of the boss 10 in each mold 62 will, of course, be so constructed and arranged that when a charge of molten `metal is introduced into the mold 62 and its level reaches the height of the top of the projection or boss 10, exactly the required amount of metal for the desired finished article will have been introduced into the mold. Accordingly, in charging the mold 62 as illustrated in Fig. 2, a slight excess of metal is introduced into the mold 62, such excess overowing the top of the 'boss or projection 16 and 'being discharged from the mold through the opening 12 therein, thus vinsu'ring in every case thai-I exactly the required amount of molten metal remains in the mold 62 and withnsl tice. It will be appreciated that this feature materially shortens the pouring operation as compared to conventional practice.

The mold 62 and its molten contents are then' moved along themono-rail track |22 which extends over the top of one or more machines such as illustrated in Fig. 1, and when over the top of such machine the chain fall |20 is operated to lower the mold 62 and its liquid contents into a mold support 36, it being understood, of course, that during this operation the housing I6 is so positioned relative to the axis of the shaft I4 as to bring the axis of the mold 36 into a vertical position. Because of the tapered exterior surface of the mold 62 and the complementary taperedinterior surface of the mold support 36, when the mold 62 is lowered into the mold support 36 it will iinally come to rest therein in snug engagement with the inner walls thereof. 'I'he mold support 36 thus provides a reinforcement for the walls of the mold 62 against the pressure of the molten metal exerted thereagainst during the subsequent centrifugal spinning action.

It will be appreciated from the above description and in following out the preferred procedure of operation, not only does it insure an extremely accurately charged amount of molten metal in each mold, but because of the fact that the metal is charged directly into the mold from the furnace or at least from a relatively large ladle, the

heat losses occurring in accordance with conven f tionalpractices through charging into a small ladle carrying an individual. charge and in passing through a charging spout is entirely eliminated, and, accordingly, that any loss of heat from a charge is to the mold itself which in any event must eventually absorb the heat from the molten metal.

Furthermore, because of the fact that the time element consumed between the time the metal is poured from the furnace to the time the mold is inserted in a machine in running posirtion is substantially less than that required in following out conventional practice, the molten metal at the time it is subjected to centrifugal action in the machine is at a relatively higher temperature, consequently more fluid, vand results in sounder castings free of such defects as occur in conventionalpractices from chilled metal.

As soon as the charge in mold 62 as above described is inserted in the mold. support 36 and the chain fall |20 released from it, the motor 30 is energized so as to immediately set the mold support 36 and the mold 62 therein in rotation. As soon asthe speed of rotation has increased to such an extent as to insure maintaining of the molten charge of metal in the mold 62 in contact with the outer walls. thereof, suitable.

tation as viewed in Fig. 1. Preferably suicient air is admitted into' the cylinders 40 to bring the mold support 36 and the mold 62 carried thereby Y to the position indicated in dotted lines in Fig. 1

and labeled spin position, short of a true horizontal position. The mold support 36 may, of course, be moved to a wholly horizontal position if desired but it has been found of advantage toV As soon as the molten metal has solidied additional air may be introduced into the cylinders 40 to move the mold part 36 to a wholly horii zontal position as indicated in dotted lines in Fig.

1 and labeled unload position, and as soon as the apparatus has reached this position the mold and the cast article therein may be withdrawn from the mold support 36. l As soon as the mold 62 has been removed from the mold support 36, air may be admitted to the lower ends of the cylinders 40 whereby to cause the apparatus to resume the vertical position indicated in full lines in Fig. 1 and in which position it is again ready to receive another mold 62 and its charge of molten metal for a repetition of the above described operation.

From the above description it will be appreciated 'that the mold provided in accordance with the present invention provides a means by which the excessive heat losses-occurring in conventional centrifugal casting operations and the occurrence of chilled particles of metal therein is largely eliminated, it provides a means whereby the molds of centrifugal molding machines may be quickly and accurately charged with a desired amount of metal for a casting operation, it provides a means whereby the time element occurring between the time the metal is drawn off from the furnace or cupola to the time it is placed in a centrifugal casting machine and operation of the machine begun is materially shortened, further aiding in avoiding heat losses and retaining the desired fluidity of the molten metal, and is of material importance in eliminating the relatively high proportion of scrap now occurring in centrifugal casting operations and particularly where the article .being cast is of a relatively thin wall section.

Formal changes may be made in the specific embodiment of the invention described without departing from the spirit or substance of the br'oad invention, the Scope of which is commensurate with the appended claims.

What is claimed is:

A unitary mold of 'refractory material including an open and a closed end and provided with internal forming walls complementary in part in size, shape and contour to that desired in the finished cast product and adapted to receive and retain a mass of molten metal introduced thereinto and distributed over and maintained-in contact with the interiorforming walls thereof by -a centrifugal force until solidified, a radially in- -wardly directed annular flange at the open end of said mold for preventing escape ofmolten metal from said. open end when rotating, a stand pipe carried by said closed end and projecting axially into said' mold therefrom and serving to limit the volume of 'molten metal in said mold when stationary, and said niold being so constructed and .arranged as to be capable per se of holding a suflicient mass of molten metal for a desired casting operation while stationary, said mold being constructed of'a non-metallic heat insulating refractory material sufficiently selfsustaining to hold said charge of metal when unsupported but requiring radial support against bursting during a centrifugal casting operation.

EMIL A. NELSON.

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