US2456067A - Centrifugal casting machine - Google Patents

Description

Dec. 14, 1948. T. c. KUHLMAN 2,456,067

CENTRIFUGAL CASTING MACHINE Filed Aug. 23, 1943 2 Sheets-Sheet 1 Dec. 14, 1948. T. c. KUHLMAN 2,456,067

GENTRIFUGAL CASTING MACHINE Filed Aug. 23. 1943 2 Sheets-Sheet 2 INVENTORQ E .2. F W

HZ'Z'ORNE Y Patented Dec. 14. 19 48 UNITED STATES PATENT OFFICE CENTRIFUGAL CASTING MACHINE Theodore c. Kuhlman, Detroit, Mich.

Application August 23, 1943, Serial No. 499,619

' 2 Claims. (CI. 22-65) This invention relates to machines for centrlfugally casting metallic articles.

Dimculty has been experienced with centrifugal casting machines because of the necessity for maintaining the machine in balance. This difflculty has been especially pronounced in cases where the casting of relatively heavy parts was attempted. Although it is relatively easy to obtain balance in the machine when the molds are empty; as soon as the metal begins to flow, an unbalance is instantly set up. Because of this. centrifugal casting has been limited to the production of single pieces in-a mold arranged concentrically about the axis of rotation, and where two or more molds have been used they have been identical and symmetrically arranged about said axis. Castings weighing from 500 to 1,000 pounds have not been produced centrifugally because of these limitations.

The principal object of my invention is to provide a. machine for centrifugal casting which is free from the aforesaid difllculties and which is suitable for the production of heavy parts.

Another object is to provide a machine for making various castings at onetime without regard for symmetrical spacing or counterbalancing. I accomplish this by having a track arranged peripherally about the machine such that it bears the radial load. Further, the platform on which the molds are carried is divided into sections which are not necessarily connected to the center shaft.

Other objects and advantages of the invention will become apparent from the following description.

In the drawings,

Fig. 1 is a plan view of the casting machine.

Fig. 2 is a sectional view along the line 2-2 of Fig. i.

Fig. 2 is an enlarged detail section taken alongthe line 3-3 of Fig. 1.

Fig. 4 is a partial plan view of the Fig. 1 apparatuswith the spruering and molds in place.

Fig. 51s a section along the line 5-5 of Fig. 4.

Fig. 6 is a. plan view of a modified form of machine. parts being broken away to show sectional details thereof.

Fig. 7 is a partial elevation of the Fig. 6 structure.

Fig-8 is anenlarged detail of the latch mechanism as indicated by the arrows 8-8 in Fig. 7, and

Fig. 9 is a similar view as indicated by the arrows 8-9 in Fig. '7 and Fig. 10 is a section along line lO-lll of Fig. 7.

-Rei'erring now to Fig. 1 and its associated figures, it will be seen that my improved centritugal casting apparatus is mounted in a pit Ill, preferably of concrete. This pit is of circular shape and has a circular depressed portion ll at the center in which is disposed a crucible assembly l2.

The crucible assembly comprises a crucible I! which is rotatably mounted on a base It. The base it contains suitable driving means (not shown), such as an electric motor and gear box, for rotating the crucible about its central vertical axis at varying speeds. My copending application, Serial No. 493,495, filed July 5, 1943, now matured into Patent No. 2,450,832, dated 00- tober 5, 1948, shows in detail a crucible assembly which may be used with the apparatus being described if desired. v

Surrounding the crucible assembly is an annular rail l5 which is adapted to support a number (in this case four) of sector shaped cars l8. These cars l6 comprise the casting platform which carries the mold flasks and sprue ring.

Each of the cars is provided with a rotatable flanged wheel ll which bears on the rail l5. This wheel is mounted in a bracket l8 as illustrated. All ofthe wheels I! may be driven, but in most installations satisfactory performance is obtained by driving one wheel only and such an arrangement is simple and economical. In the illustrated embodiment of the invention, one

' of the wheels I! is directly connected to an electric motor l9 which is fastened to the corresponding car It by means of a bracket 20. The motor I9 is supplied with current through a pair of brushes 2i which engage slip ring contractors 22 mounted in the peripheral wall of the pit I0.

The cars l6 are further supported by an annular peripherally mounted rail 23 which also receives the horizontal thrust of the cars during rotation thereof. Double flanged wheels 24 (see Fig. 3) are carried by each of the cars, these wheels being mounted one at each side of the cars on axles 25. The axles are iournaled in brackets 26 as shown. It will be clear from the drawing that the wheels 24 in engagement with rail 23 together with the wheel H which rests on rail l5 provide a firm support for each of the cars. The latter are permitted individual movement during their travel about the central axis of the crucible, rubbing blocks 2l being provided to transmit driving thrust without transmitting twisting movement or vibration between cars.

Each of the cars it has a bottom floor ll of relatively heavy section and walls 2| of lighter section. The latter extend along the back of each car part way along each side as shown and are adapted to retain in place the mold of the part or parts to be cast. This mold may be of sand, plaster, or other suitable material. In Fig. 4 a sand mold III is shown in place on each of the cars. The mold has a pattern cavity 8| with runners 32 leading therefrom to a pouring mouth 83.

The molten metal is conducted from the crucible II to the pouring mouths II of the molds by means of a sprue ring 34. This ring consists of four segmental sections respectively carried by the four cars and is of suitable refractory material. Each section is formed with a cavity II which has a passage 38 connecting the cavity with the mouth 33 of the mold. The direction of rotation of the crucible and f the platform is clockwise as indicated by the arrow on Fig. 4 and each of the cavities 35 of the segmental section of the sprue ring is formed with a relatively high leading edge 31 and a relatively low trailing edge 38. This arrangement of edges is important in that it prevents the molten metal from flying out through the spaces between the sprue ring sections. The metal which hits the higher edge portions 38 will, because of its tangential velocity flow into the next lcavity at the lower edge portion thereof.

In operation the crucible I3 contains the metal to be cast. This metal may be melted in the crucible or it may be melted somewhere else and transferred to the crucible in molten state. When a cast is desired to be made, the molds and sprue ring are placed on the machine, the crucible is charged and the cars ii are started to revolve in clockwise direction. After the speed of the platform has reached a satisfactory value, the crucible is started and the speed of the crucible increased to cause the molten metal to be discharged therefrom. The speed of each is determined by the size and shape of the articles to be cast and by the characteristics of the alloy being cast. The speed of the crucible is usually higher than the speed of the platform (in revolutions per minute).

The speed at which the crucible will discharge is a critical one and depends on the shape of the crucible, the weight of metal, etc., but when this speed is reached the metal flows rapidly and smoothly over the lips of the crucible (which is raised above the platform floor as shown in Fig. 2) and into the cavities 35 thence through the passages 36 and 32 into the mold cavities.

If desired, the mold may be preheated before the cast is made.

Figs. 6 to 9 inc. illustrate a modification of my invention which differs from that Just described in several respects, chiefly in that the crucible itself revolves with the mold platform.

The apparatus of Figs. 6-9 may be mounted in a concrete pit if desired, but as illustrated a main central support 40 is provided and the horizontal thrust is taken by a circular rail 4| which is supported on uprights -42 suitably tied together by rods 43'.

The central support 40 mounts a vertical hollow shaft 42 in a thrust bearing 43. The shaft 42 is of heavy construction and carries gear teeth 44 which are in mesh with a pinion 45, the latter being mounted on the driving shaft of an electric motor 46.

Bolted at n to the top flange of the shaft i is a platform 48 on which the crucible assembly and mold flask assembly are adapted to slide by 7 means of the gibs '2, ll. At the outer end of the mold flask assembly, a wheel I. is Journaled for rotation about a vertical axis. This wheel engages the track rail ll and thus transmits the radial thrusttothe rail. 1

The crucible assembly II is mounted on the Platform 48 by means of the gibs l2, ll. The assembly has end walls ll, ll, between which is mounted a lining ll of refractory material or of graphite compound depending upon the character of the metal to be melted. The lining is surrounded by insulating material I! in which is embedded a water cooled induction coil It. The latter is electrically connected to a transformer by any suitable means such as wires II and contacts Oil, the latter being adapted to slide on the rings Ii which may be connected to the source by wires carried in the conduit 2. The latter is bearlnged at. 63 in a bracket 84 carried on the revolvable platform.

The crucible has a water cooled base ll which prevents overheating of the platform, the coil 58 being connected therewith as indicated at 19. Water connections 60 are centered in the shaft 42 and turn with the assembly, suitable water tight connections of any desired design beingprovidecl at the bottom of base ll.

The crucible has a charging spout I and a discharge mouth 81. The latter is closed when the apparatus is stationary by a rod I. The latter is preferably made of refractory material and has a conical end portion adapted to fit and close off the mouth 81. A spring 09 carried by the rod bears against a shoulder II and a lever II. The lever 1i (Figs. 8 and 9) is rigidly carried on a rod I2 journaled in the uprights", II, which are in turn carried by the platform.

On one end of the rod II a weight 14 is carried as shown in Fig. 8. The upright 13' has a lever I5 pivoted thereon. The lever 15 is adapted to be positioned so that it holds the weight 14 in such position that the spring 89 is compressed thereby causing the rod 88 to seat firmly in the crucible mouth. A trip arm II carried by the conduit '2 is disposed such that it will disengage the lever II from weight 14 during the last portion of the first revolution of the platform.

Disengagement of the lever I6 will permit the weight 14 to swing sharply outwardly under the combined influence of centrifugal force and spring 69. This will cause the bifurcated upper end portion of lever II to deal a hammer blow on the shoulder 'l'l of rod 00 thereby pulling the rod radially inward and opening the mouth of the crucible. 4

The means for disengaging the rod 88 from the crucible mouth by means of a hammer blow is an important feature of my invention. It frequently happens that accumulation of slag. metal, etc., at the mouth of the crucible will tend to cement the rod in place and a sharp blow is necessary to dislodge it. While the specific means described may be varied to suit different conditions,

some means for dealing the rod 8' a blow of conis suitably charged through the spout 86 and current is introduced into the soil 58 until the charge is molten..; A mold of the article to be cast is placed on the outer end of the platform 48 within the walls l8, l9 and rotation of the assembly is started by suitably controlling the motor 46.

With arrangement shown as the apparatus nears the end of the first revolution lever 15 will engage the trip lever 16 and weight 14 will be free to swing radially outwardly to thereby inflict a hammer blow on the shoulder 11 of rod 68. The outer end of the rod will thus be disengaged from thecrucible mouth 61 and the rod 68 will be moved radially inwardly by spring 69 to thereby permit the molten charge to be discharged through mouth 61 into the mold.

If desired, the crucible mouth 61 may be kept covered until the apparatus has gained speed through several revolutions in which case suitable means may be provided to deal the rod shoulder 1! aghammer blow and open the crucibleat any desired time. An electrical solenoid or other suitable control means may be provided for this purpose.

The apparatus just described is suitable for casting very heavy objects, particularly of alloys where the cast must be made at a critical temperature. It frequently happens that the temperature range at which the cast must be made is very narrow in order that the metal will not be scorched or burned, yet be fluid enough for casting. With the arrangement just described the crucible may be kept closed for any suitable period of time to prevent oxidation of the molten metal and then opened suddenly so that the cast may b made with extreme rapidity and with minimum exposure of the molten metal to the atmosphere before solidification thereof.

The rod '8 is preferably of ceramic material and the crucible lining I! may be of refractory material or of a graphite compound depending on the alloy to be cast as aforesaid.

If desired the shoulders l0, 11 on the rod 68 may be made adjustably by means of set screws or other retaining means so that the rod may be adjusted radially outwardly as the tip wears off.

Having thus described two preferred embodiments of my invention, I wish it to be clearly understood that this has been done for the purpose of illustrating the principles thereof and is not to be considered as limiting except as defined in the claims appended below.

I claim:

1. In a casting machine having a revolvable furnace, an outlet in said furnace for discharging molten metal in a mold by centrifugal pressure; a refractory rod for normally closing said outlet, means for retaining said rod in closing position, and means for moving said rod to opening position including means for inflicting a hammer blow on said rod to break it loose from said outlet, said last means being operable automatically in response to revolution of said furnace.

2. In a casting-machine, a revolvable furnace having an outlet for discharging molten metal by centrifugal pressure, a refractory rod having an end engaging said outlet for closing the same; latch means for yieldably holding said rod in closin-g position; a swingable lever disposed in operable relation with said rod; a weight on said lever, and means for suddenly releasing said lever when the machine is in operation such that the centrifugal force acting on said weight will cause said lever to inflict a hammer blow on said rod thereby to releas it from said outlet.

THEODORE C. KUHLMAN.

REFERENCES CITED The following references are of record in is file of this patent:

UNITED STATES PATENTS Number Name Date 768,309 Rivers Aug. 23, 1904 964,371 Bary July 12, 1910 1,949,021 Leuser Feb. 27, 1984 2,245,065 Berger June 10, 1941

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