US1924976A - Centrifugal casting machine - Google Patents

Description

g. 29, 1933. H BROWN 1,924,976

CENTRIFUGAL CASTING MACHINE Filed June '7, 1929 3 Sheets-Sheet l M gw-mv, INVENTOR,

, WE Z3: l ATroRNEYs,

Aug. 29, 1933. L, H. BROWN CENTRIFUGAL CASTING MACHINE Filed June 7, 1929 s sheets-smetV 2 Tl'ORNEYS 6am, INVENTOR/ ug. 29, 1933. L, H, BROWN l 1,924,976

CENTRIFUGAL CASTING MACHINE Filed June 7. 1929 5 Sheets-Sheet 3 1 NVENTQR l BY Y M, ATroRNEYs.

Patented Aug. 29, -1933 PATENT OFFICE oEN'rarrUGAL CASTING MACHINE Lucian H. Brown, Kokomo, Ind., assignor to Haynes Stellite Company, a corporation o! Indiana Application June 7, 1929.- Serial No. 369,208.` 9 Claims. '(Cl. 22-65) This invention pertains to centrifugal casting machines and more specifically to such a machine especially adapted for casting alloys that melt at a temperature of upwards of about 1700 C. A

v Alloys that melt at extremely 'high temperatures tend to freeze so quickly when the source of heat is removed that it is impossible to handle them in ladles like low melting alloys, or even to pour them directly from the crucible in which they are melted into stationary molds and secure good castings. Therefore, in order to produce good castings from such an alloy it must be transferred from the crucble to the mold instantly and in addition pressure must be applied to force l5 it into the mold.

Such pressure may be most readily produced in the form of centrifugal force and applied in the manner practiced in the art of' centrifugal casting, but centrifugal casting as applied to met- .20 als having a low melting point is impractical when applied to metals having a' high melting point because too much time is spent in getting the metal from the furnace into the mold. This is especially true when casting alloys high in tungsten such as those having a composition of:

., Percent W 70.0 t0 95.0 C .5 to 6.0 Other metals 0.0 to 25.0

Therefore, one object of this invention is to provide a centrifugal casting machine adapted for fusing a high melting alloy and then casting it instantly in a rotating mold. Another object isto provide such a machine with facilities for positioning the rotating mold in the furnace close to the crucble at the time of casting. Another object is to provide such a machine with facilities for tilting the entire machine as a unit to perform the casting operation. Another object is to provide such a machine with facilities for keeping the mold cool while the alloy is being fused and for introducing the comparatively cool mold into the furnace at the time of casting. These and other aims, objects, and novel features will be apparent from the following description taken with the accompanying drawings, in which:

- Fig. 1 is a side elevation of one embodiment of my'improved casting machine with portions thereof cut away to show'the interior construction of the furnace and the position of the crucble and mold therein at the time of casting;

Fig. 2 is a front elevation of the improved casting machine of Fig. 1;

- Fig. 3 is a plan view of the same with the mold and its supporting and rotating mechanism swung to one side in the position it occupies while the alloy is being fused;

Fig. 4 is a front elevation of the mold and mold holder of Fig. 1; i

Fig. 5 is a horizontal section of the mold and mold holder of Fig. 4;

Fig. 6 is an elevation of the front portion of the mold taken along the parting line;

Fig. 7 is a transverse section of the front por- 65 tion of the moldshown in Fig. 6;

Fig. 8 is an elevation of the back portion of the mold taken along the parting line, and;

Fig. 9 is a transverse section of the back portion of the mold shown in Fig. 8.

My improved centrifugal casting machine may comprise a furnace A having a crucble Cthat is adapted for holding the ingredients of an alloy while'they are being fused by an electric arc from an electrode 27, and a. rotatable mold M into which the molten alloy may be cast instantly by tilting the entire 'machine as a unit on its supporting trunnions Q.

The furnace A may be cylindrical in form and have an outer wall 10 and bottom l1 of a metal 80 such as steel or iron. Attached to opposite sides of the furnace A by suitable means such as fusion welding are trunnions Q that are carried by stationary supports 12 and 13 of suitable material such as cast iron. In one side of the furnace wall 10 there is 'a lateral opening 14 for the purpose of admitting a mold M that will be described later. In the bottom of the furnace A is a quantity of electroconductive material 15 such as a mixture of crushed coke and tar covered by a layer of graphite dust that fills the furnace to approximately the bottom of the opening 14. Resting on the graphite dust 15 is an open topped electroconductive crucble C of a material such as Acheson graphite or its equivalent having a lateral aperture 16 in one side thereof located substantially opposite the center of the opening 14 in the furnace wall 10. Filling the space between the crucble C and the outer wall 10 of the furnace A is a refractory 17 of any suitable material such as magnesite brick or crushed magnesite.

Attached to one side of the outer wall 10 of the furnace A by means of bolts 18 is a plate 19 having outwardly extending brackets 20 and 21 re- ,spectively carrying two intermeshed miter gears 22 and 23. Threaded in gear 22 is a verticalelectrode support 24 having an electrode holder 25 at the upper end thereof but insulated therefrom by insulating washers 26. The electrode holder 25 may be cooled by circulating water therethrough in a manner well known in the art but not shown. `The electrode holder 25 supports an electrode 27 so the lower end thereof projects into the open top of the crucible C. Secured to the gear 23 is a manually operable crank 28 by which the gears 22 and 23 may be rotated to raise and lower the electrode support 24, electrode holder 25, and electrode 27, with relation to the crucible C. Electric current may be conducted to the electrode 27 by a conductor 29 attached to the electrode holder 25 by a bolt 30, and to the crucible C by a conductor 31 attached tothe furnace A by a bolt 32. While this means for controlling the electrode gives good results it may, however, be controlled by other types of manual or automatic mechanisms.

Secured to the outside of the furnace A by means of rivets 33 is a bracket 34 that carries a table 35 by means of a vertical pivot 36 that is substantially parallel to the axis of the furnace A. Secured tothe table 35 by any suitable means such as bolts are two supports 37 and 38 provided with bearings in which a shaft 39 is carried in such a manner that it is free to rotate. One end of the shaft 39 projects into the opening 14 in thefurnace A (when the table is in the Vproper position) and is provided with a threaded portion upon which the mold M may be screwed to attach it to the shaft. The shaft 38 is also provided with a pulley 40, by which it may be driven through a belt 41 from a pulley 42 that is carried by an electromotor 43 secured to the table 35. The shaft 39 is also provided with a manually operable brake 44 by which it may be quickly stopped for a purpose that will .be explained presently. Operating current may be conducted to the motor 43 by a pair of conductors 45 such as lamp cord. A handle 46 fitting in a transverse aperture in one of the trunnions Q may be manually manipulated to tilt the entire furnace as a unit to perform the casting operation. A stop 47 attached to the bottom of the furnaceAstrikes against the support 13 and holds the furnace in an upright position when it is not manually tilted. The table 35 may be held stationary with respect to the furnace A during the casting operation by a latch 59 secured to the outer wall of the furnace so that it hooks into a notch 60 in the side of the table 35 away from the pivot 36. Other manually releasable holding means may be employed to secure the table besides that shown.

The mold M may comprise a front portion 48 and a back portion 49 held in a recess 50 in a metal mold holder 51 that is of circular outline and provided with a rearwardly extending boss 52 having a threaded recess therein adapted to receive the threaded end of the shaft 39. Other means may be employed for coupling the mold M to the shaft 39 but the one described has partcular advantages that will be explained in connection with the operation of the casting machine. The front and back portions 48 and 49 of the mold M may be of any suitable material but in practice superior results have been secured with a mold machined from a block of artificial graphite such as Acheson graphite o r its equiv#- alent. The assembled mold has an axial sprue 53 leading into a gate 54 from which a plurality of semi-cylindrical matrices 55 radiate. It is understood, of course, that the size and shape of the mold may Vary to accommodate matrices of various sizes and shapes which may also vary in number from that shown.

In order to prevent the centrifugal force of the molten metal from bursting the mold M during casting, it is fitted tightly in the mold holder 5l so the periphery of the mold is supported by the wall of the mold holder. This tight fit between the mold holder and the mold is secured by makinglthe outer diameter of the mold M slightly larger than the inner diameter of the cavity 50 in the mold holder 51, and the mold is assembled in the mold holder by first heating the mold holder 51 until it has expanded slightly and then the mold M is gently pressed into the cavity 50 where it is securely held when the mold holder has cooled and contracted upon it. In order to prevent the force of the molten metal from bursting the mold laterally during casting, a metal plate 56 is placed at the end of the cavity 50 over the mold M where it is securely held by a plurality of bolts 57 that pass through the rim of the mold holder 51 just outside of the cavity 50 so one edge of each bolt head presses against the outer edge of the plate 56 when the nuts 58 are screwed on the threaded ends of the bolts protruding from the rear of the mold holder. Thus the plate 56 reenforces the front ofthe mold M and at the same time holds it securely in the cavity 50 of the mold holder 5l. While the particular form of mold and mold holder just described has many advantages, other forms may be used and the tight t between the mold and mold holder may be secured in other ways such as-by pressing a tapered mold into a mold cavity having a similar taper.

As this casting achine is capable of being operated at a very high rate of speed a quantity of supplies should be kept on hand to avoid operating delays, and an adequate supply of molds assembled in mold holders should be provided. For the mold shown in the illustration about a pound of alloy is required for each cast so, to facilitate operation, it has been found convenient to provide a quantity of paper bags with suflicient ingredients in each to make a pound of alloy.

The operating cycle of the casting machine shown herein may be completed in less than one minute and the sequence of operations may be substantially as follows: The ingredients in one of the paper bags are emptied in the crucible C;

electric current is connected to the electrode 27 and to the furnace A. As the crucible C is already hot an arc is formed immediately. About 35 seconds are required to completely fuse the ingredients in the crucible. During this time a mold M is screwed on the threaded end of shaft 39 and then, when the alloy is ready to cast the table 35 is swung on its supporting pivot 36 and locked in casting position so the cold mold M is close to the crucible C with its sprue opposite the lateral A Current is then H aperture 16 as shown in Fig. 1. connected to the electromotor 43 which rotates the mold M at a high rate of speed. This rotating speed may vary according to the size and shape of the matrices and the viscosity of the molten alloy but satisfactory results have been attained by rotating the mold at a speed of 1725 revolutions per minute. The casting operation is performed by an operator who grasps the handle 24 and tilts the entire casting machine on its trunnions Q so the molten alloy in the crucible C is poured out through the aperture 16 into the rotating mold M through the sprue 53. When the crucible C reaches a horizontal position the elec- It is-understood, of course, that the alloy may be poured over the top edge of the crucible into the mold, but better results have been secured by pouring through the aperture in the side of the crucible. As the mold is comparatively cold the alloy hardens instantly; therefore the crucible C is not left in tilted position but is moved right back to vertical position. As soon as the crucible C is back in an upright position the table 35 is swung on its pivot so the mold M is brought out of the opening 14 in the furnace. The electric current is then disconnected from the electromotor 43 and the brake 44 is quickly applied. This stops the shaft 39 quickly but the momentum of the rotating mold M keeps it spinning and unscrews it from the shaft 39 from which it drops into a receptacle such as a box placed underneath the casting machine for the purpose. r1`he operator then moves the handle 28 and lowers the electrode 27 a distance equal to the amount burned off during the fusing operation. This completes one cycle of operation and in practice another cycle is started immediately.

During the period in which the alloy is being fused the path of the electric current through the casting machine is from the conductor 29, to the electrode holder 25, electrode 27, either the ingredients for forming the alloy or the alloy in the crucible C, the crucible C, the electroconductive material 15 in the bottom of the furnace A, and the furnace A to the conductor 31.

When the casting machine is started after having cooled to room temperature it is understood that the electrode 27 must be lowered into contact with the crucible C or the ingredients there,-

in and then raised to draw an arc between thev electrode and the ingredients in a manner well known to persons familiar with the operation of electric arc furnaces.

Means other than that shown may be employed to support and rotate the mold M. For instance, the mold may be attached directly to the end of the motor shaft instead of to a separate shaft driven by the motor and the motor may be mounted on a bar fixed radially to the furnace, along which it may be moved to introduce the mold into the furnace instead of using a swinging table.

The castings produced by this improved casting machine are well formed and free from holes or other defects. Drawing dies, tool tips, etc., may be cast Very closely to size, thus materially reducing the labor required to finish them.

While this improved casting machine has been described in connection with a high melting a1- loy of a particular composition, superior results may be secured when it is used to cast other alloys melting at different degrees of temperature.l

Various alterations and substitutions may be made in the construction and arrangement of the centrifugal casting machine Without departing from the spirit of the invention or sacrificing any of the rights thereunder.

I claim:

1. The combination in a centrifugal casting machine of a furnace; a crucible in said furnace adapted for holding the ingredients of an alloy and provided with a lateral aperture therein above said ingredients; heating means carried by said furnace for fusing said ingredients to form an alloy; a rotatable mold carried by said furnace outside thereof but movable into said furnace opposite said aperture at the time of casting; and means for tilting said furnace, crucible, heating means and rotating mold, as a unit to cast said alloy.

2. The combination of a centrifugal casting machine and an electric arc furnace for melting a charge; said furnace having a discharge opening therein; said casting machine comprising a rotatable mold carried by said furnace; means for.l moving said mold away from and toward said vvopening for discharging the furnace melt; means for securing said mold adjacent to said opening to receive the furnace melt; means for rotating said mold; and means for tilting said furnace to pour the melt into said mold While said mold is rotating.

3. The combination in a centrifugal casting machine of an electric arc furnace having trunnions thereon; supports for said trunnions; a crucible within said furnace; an electrode holder carried by said furnace but electrically insulated therefrom; an electrode in said holder with one end thereof projecting into said crucible; means for conducting electric current to said electrode and to said crucible; an electromotor carried by said furnace; a mold carried by said furnace and adapted for being rotated by said electromotor; said mold being movable relative to said furnace so it may be positioned away from said crucible where it remains comparatively cool while the ingredients of said crucible are being fused, and so it may be positioned close to said crucible for casting; and means for tilting saidmachine as a unit to perform the casting operation.

4. A centrifugal casting machine comprising a furnace having trunnions `thereon and a lateral opening therein; supports for said trunnions; an electroconductive material in the bottom of said furnace; an open topped electroconductive crucible resting on said electroconductive material and having a lateral aperture therein opposite said opening; a refractory between said crucible and the wall of said furnace; an electrode carried by said furnace so one end thereof projects into the open top of said crucible; a rotatable mold carried by said furnace so its sprue is opposite said aperture; and means for tilting said machine as a unit to perform the casting operation.

5. A centrifugal casting machine comprising a furnace; an open topped crucible in said furnace; an electrode support carried by said furnace; an electrode holder carried by said electrode support but insulated therefrom; an electrode carried by said electrode holder so one end thereof projects into the open top of said crucible; means for moving said electrode with relation to said crucible; a mold carried by said furnace and adapted for being rotated during casting; and means for tilting said machine as a unit from vertical to horizontal position to perform the casting operation.

6. A centrifugal casting machine comprising a furnace; an open topped crucible in said furnace; a gear carried by said furnace; an electrode support threaded in said gear; an electrode holder carried by said electrode support but insulated therefrom; an electrode carried by said electrode holder so onev end thereof projects into the open top of said crucible; means for rotating said gear to move said electrode with relation to said crucible; means for conducting electric current to said electrode and to said crucible; a mold carried by said furnace and adapted for being rotated; and means for tilting said machine to perform the casting operation.

'7. yA casting machine comprising a furnace; a

furnace; means for rotating said shaft; a mold threaded to said shaft; means for casting said alloy in said rotating mold; and means for stopping said shaft suddenly so the momentum of said mold unscrews it from said shaft.

9. In a centrifugal casting machine; a furnace having a crucible therein adapted for holding the ingredients of an alloy; means for fusing said ingredients to form an alloy; a table carried by said furnace but movable with relation thereto; a shaft carried by said table and adapted for being rotated; an electromotor carried by said table and adapted for rotating said shaft; a mold threaded to said shaft; means for casting said alloy in said mold while it is being rotated; and a manually operable brake carried by said table and adapted for stopping the rotation of said shaft.

LUCIAN H. BROWN.

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