| United States Patent | 3,799,240 |
| Baumann , et al. | March 26, 1974 |
HORIZONTAL CENTRIFUGAL CASTING MACHINE
Abstract
A horizontal centrifugal casting machine capable of producing diversely dimensioned structures is characterized by a pair of motor driven rollers for rotating an axially open, wheeled mold seated thereon. Molten charge in a quantity corresponding to the size of the structure to be cast is deposited in a thermally insulated ladle situated at one end of the mold and a variable speed drive is utilized to transport the ladle into the mold interior at a rate determined by the quantity of molten charge within the ladle. The pour rate of molten charge from the ladle into the rotating mold also is regulated, e.g., by a piston driven rack communicating with a pinion secured to the ladle shaft, to permit diverse pour rates for casting structures of different dimensions. The casting machine also is provided with a hood which is moved axially into an overlying attitude relative to the mold to maintain the mold at an elevated temperature prior to casting and to protect against unseating of the mold from the rollers during casting.
| Inventors: | Baumann; Frederick W. (Scotia, NY), LaBahn; William C. (Scotia, NY), MacNary; Robert G. (Elnora, NY), Smith; William R. (Ballston Lake, NY) |
| Assignee: |
General Electric Company
(Schenectady,
NY)
|
| Appl. No.: | 05/220,285 |
| Filed: | January 24, 1972 |
| Current U.S. Class: | 164/298 |
| Current International Class: | B22D 13/00 (20060101); B22D 13/02 (20060101); B22d 013/04 () |
| Field of Search: | 164/98,298,299,300,301,292,295,175,176,84,114,118,286,289,294,297 266/31 |
| 3056179 | October 1962 | Lorang |
| 1309823 | July 1919 | Stokes |
| 1783094 | November 1930 | Moore |
| 2671260 | March 1954 | Jessen |
| 2857638 | October 1958 | Ribeiro |
| 2923227 | February 1960 | Hawley |
| 1656539 | January 1928 | Smith |
| 2597811 | May 1952 | Nolan |
| 2763041 | September 1956 | Doat |
| 2856655 | October 1958 | Abbott |
| 3648763 | March 1972 | Guenzi |
Assistant Examiner: Brown; John S.
Attorney, Agent or Firm:
What we claims as new and desire to secure by Letters Patent of the United States is:
1. A horizontal centrifugal casting machine comprising:
a. rotary drive means for applying rotational torque to a mold adapted to be driven by said drive means, said drive means including a pair of rollers spaced apart a fixed distance, said rollers being capable of sequentially accepting thereon different selected molds of diverse dimensions, that enable the respective molds to receive different size charges of molten material for producing structures of diverse size,
b. ladle means for receiving and storing a measured charge of molten material, said charge corresponding in size to the dimensions of the one of said molds, selected to cast a given structure, said ladle means being mounted for axial movement with respect to the axes of said rollers and being further mounted for tilting about one axis of said ladle means,
c. adjustable speed drive means operably coupled to said ladle means to axially transport said molten charge into said selected mold at a rate determined by the quantity of molten charge within said ladle means, and
d. variable speed pouring means operably connected to said ladle means to automatically tilt said ladle means to discharge said molten material into said mold at a given one of various pour rates determined by the dimension of the structure being cast in said selected mold, said pouring means being operable to tilt said ladle means in response to said molten charge being transported completely into said mold.
2. A horizontal centrifugal casting machine according to claim 1 further including hood means having a movably mounted hood, said hood being movable from a position adjacent one end of said rollers to an overlying attitude relative to said mold prior to pouring of said molten charge into said mold, said hood means being effective in said overlying attitude to substantially enclose said mold when the ladle means are positioned in the mold, thereby to thermally seal the mold from the ambient atmosphere outside of said hood means.
3. A horizontal centrifugal casting machine according to claim 2 wherein said hood is open at one end to permit said hood to be moved axially, with respect to axis of rotation of said mold, into an overlying attitude relative to said mold and further including plate means mounted adjacent the other end of said rollers and operable to cooperate with the movable hood to substantially close said hood means when said hood is moved into an overlying attitude relative to said mold and the ladle means are positioned within the mold.
4. A horizontal centrifugal casting machine according to claim 3 including a plate formed to mate with a ladle-receiving aperture in said plate means to seal said aperture responsive to movement of said ladle means into said mold, and further including means for passing air at a desired temperature through said hood to control the temperature of said mold.
5. A horizontal centrifugal casting machine according to claim 1 wherein said ladle means includes a discharge opening (124) having a substantially straight lip over which said molten material is poured, said lip being formed to extend at least 75% of the length of said selected mold measured along the axis of rotation thereof.
6. A horizontal centrifugal casting machine comprising:
a. rotary drive means including a pair of rollers capable of applying rotational torque to molds rotatably mounted on said rollers for producing cast structures of diverse dimensions, at least one of said rollers being motor driven and bearing against the outer periphery of said mold and further including an axially movable collar releasably mounted in fixed position on said roller near one end thereof for limiting the axial travel of said mold toward said one end;
b. hood means capable of being disposed in an overlying attitude relative to a mold being cast positioned on said rollers;
c. means for pouring molten metal into said mold at a selected one of a variety of different predetermined rates, determined by the size of said mold;
d. means for initiating said pouring and automatically maintaining said predetermined pouring rate, said means for initiating being operable after the hood means is disposed in said overlying attitude; and
e. means for retracting said hood from an overlying attitude relative to said mold subsequent to casting.
7. A horizontal centrifugal casting machine comprising:
a. rotary drive means including at least two elongated rollers upon which a mold is positioned and further including motor drive means connected to said elongated rollers for rotating said rollers at a speed suitable for casting, said drive means being capable of applying rotational torque to molds of diverse dimensions, and said rollers being tilted from a horizontal plane by an angle less than 3.degree. and further including at least one collar situated along said rollers for limiting axial movement of the mold upon said rollers;
b. ladle means movably mounted adjacent one end of said rotary drive means for storing a charge of molten material in sufficient quantity to cast a structure of given dimensions produced by a selected one of said molds mounted in driven relationship relative to said rotary drive means;
c. adjustable speed drive means for transporting said ladle axially with respect to the axis of rotation of said mold, toward said mold at a rate determined by the quantity of molten charge within said ladle;
d. hood means movably mounted adjacent the other end of said rotary drive means;
e. means for axially transporting said hood means relative to said mold to position said hood means in an overlying attitude relative to said mold; and
f. adjustable pouring means responsive to movement of said ladle within a mold for tilting said ladle at a controlled rate corresponding to the size of the mold being utilized for casting.
8. A horizontal centrifugal casting machine according to claim 7 including hold down means mounted in fixed relationship with respect to said drive means, and further including means fixedly secured to said hood means and operable to be positioned in locking relationship with said hold down means when said hood means is positioned over a mold, wherein vertical travel of said mold upon said rollers is restricted by the interaction of said hood means and the hold down means.
9. A horizontal centrifugal casting machine comprising:
a. rotary drive means capable of applying rotational torque to molds of diverse dimensions;
b. ladle means movably mounted adjacent one end of said rotary drive means for storing a charge of molten material in sufficient quantity to cast a structure of given dimensions produced by a selected one of said molds mounted in driven relationship relative to said rotary drive means;
c. adjustable speed drive means for transporting said ladle axially with respect to the axis of rotation of said mold, toward said mold at a rate determined by the quantity of molten charge within said ladle;
d. hood means movably mounted adjacent the other end of said rotary drive means;
e. means for axially transporting said hood means relative to said mold to position said hood means in an overlying attitude relative to said mold; and
f. adjustable pouring means responsive to movement of said ladle within a mold for tilting said ladle at a controlled rate corresponding to the size of the mold being utilized for casting, said adjustable pouring means including an air-liquid tandem cylinder (158) having a piston (156) reciprocally mounted therein, and selectively regulatable sources of pressurized air and liquid operatively connected to said cylinder, said piston being coupled to said ladle to tilt it in response to movement of said piston in a predetermined direction.
This invention relates to a centrifugal casting machine and in particular, to a horizontal centrifugal casting machine suitable for casting structures of diverse sizes with a minimum alteration of machine components.
Typically, machines employed for centrifugal casting heretofore have taken a variety of configurations dependent upon such factors as the geometric configurations of the structures to be cast and the amount of automation designed into the casting machine. For example, smooth surfaced cylinders heretofore have been centrifugally cast utilizing a cylindrical mold having a closed end fixedly secured in cantilever fashion to the rotary shaft of a horizontal centrifugal casting machine with the end of the mold remote from the machine being open to permit insertion therein of a carriage carried ladle for pouring molten charge into the rotating mold. In very early casting machines, the carriage was manually pushed to the mold and pouring of molten metal from the ladle generally was accomplished by hand, e.g., by turning a wheel secured to an end of the shaft carrying the ladle. While such early devices are suitable when operated by skilled manpower capable of pouring the charge from the ladle at a rate producing a high quality cast, demands for more economic operation and the dangers of operator injury from splashing metal have resulted in a gradual evolution of more automated centrifugal casting machines over the years. These automated centrifugal casting machines generally have been precisely designed for a mold of known dimension and a variety of automatic techniques have been employed to pour charge into the mold. For example, piston driven mechanical linkages have been utilized to rotate a ladle for pouring molten charge into a centrifugal mold at an approximately uniform rate. Other automated casting machines have utilized jaws to secure the mold in position during casting with compressed air being employed to hydraulically open the jaws for rapid removal of the mold. Still more automated centrifugal casting machine have employed an enlarged cylindrical housing to retain a plurality of compartments which are sequentially registered with various phases of the casting process, e.g., molten metal insertion apparatus, spray cooling heads, etc., as the housing is rotated. While the foregoing horizontal centrifugal casting machines generally are suitable for their designed purposes, there still remains need for a highly automated centrifugal casting machine to rapidly produce large diameter structures in a broad range of sizes.
It is therefore an object of this invention to provide an improved horizontal centrifugal casting machine capable of casting articles of diverse size.
It is also an object of this invention to provide a horizontal centrifugal casting machine wherein the rate of insertion of the ladle into the mold and the pour rate of molten charge from the ladle can be varied automatically dependent upon the size of the article being cast.
It is a further object of this invention to provide a horizontal centrifugal casting machine wherein the mold is not fixedly secured to the rotary drive source.
It is a still further object of this invention to provide a centrifugal casting machine wherein the mold is shielded by a retractable hood to retain heat within the mold prior to casting and to protect against spillage of metal from the mold during casting.
It is also an object of this invention to provide a horizontal centrifugal casting machine having protective means to inhibit disengagement of the mold from the rotary drive.
A still further object of this invention is to provide a centrifugal casting maching having means therein for controlling the flow of air through the mold during various stages of casting to regulate mold temperature.
These and other objects of this invention generally are achieved by a centrifugal casting machine having rotary drive means capable of applying torque to molds producing cast structures of diverse dimensions and ladle means for storing charges of molten material in quantities sufficient to cast structures of the dimensions produced by the molds. Adjustable speed drive means are provided in the machine for transporting the molten charge axially into the mold at a rate determined by the quantity of charge within the ladle and the ladle is tilted by variable speed pouring means to transfer the molten charge to the mold at a rate dependent upon the size of the structure being cast. Preferably, the rotary drive means of the casting machine are elongated motor driven rollers upon which wheels protruding from the mold are seated and the machine is provided with a hood positionable over the mold during casting to prevent disengagement of the mold from the rollers.
Although the invention is described with particularity in the appended claims, a more complete understanding of the invention may be obtained from the following detailed description of a specific embodiment of the centrifugal casting machine taken in conjunction with the appended drawings wherein:
FIG. 1 is a sectional view of a horizontal centrifugal casting machine in accordance with this invention,
FIG. 2 is a sectional view taken along lines 2--2 of FIG. 1 to illustrate the hood drive mechanism and mold containment structure of the machine,
FIG. 3 is a top view illustrating the hood and roller drive mechanisms in the casting machine of this invention,
FIG. 4 is an isometric view illustrating the dual braking mechanism employed for the mold of FIG. 1,
FIG. 5 is a sectional view taken along lines 5--5 of FIG. 1,
FIG. 6 is an isometric view of the ladle illustrating the shoulder screws employed to secure the ladle to the carriage, and
FIG. 7 is an end view taken along lines 7--7 of FIG. 1 to illustrate the pour rate control mechanism of the horizontal centrifugal casting machine.
A horizontal centrifugal casting machine 10 in accordance with this invention is illustrated in FIG. 1 and generally includes a centrally disposed roller section 12 for rotating wheeled mold 14, a hood assembly 16 having an open ended traversable hood 18 seated thereon and a ladle section 20 situated on the opposite side of the roller section to permit insertion of molten charge into the mold.
The primary component of hood assembly 16 is a substantially rectangular hood 18 having three sides 18a and a top section 18b of high pressure vessel plate welded together to form a mechanically secure structure. The hood is mounted on four wheels 24 rotatably secured to the hood through wheel housings 26 and plates 28 to permit longitudinal travel of the hood along angle iron rails 30. To impart longitudinal motion to the hood, the end of hood 18 remote from roller section 12 is fixedly secured to motor driven chain drives 32 by connecting plates 34 bonded between the hood and the underlying chain drives. When the hood is moved into an overlying position relative to mold 14, the hood mates with hood end plate 36 to substantially enclose the mold in conjunction with roller base assembly 38, i.e., except for central aperture 40 within end plate 36 to permit axial insertion of ladle 42 within mold 14. Because the mold is totally enclosed during casting, a 150 watt spotlight 43 and a television camera 45 desirably are mounted upon the hood side remote from the mold to permit external monitoring of the casting operation.
The operation of chain drives 32 for the hood is controlled by a hood drive gear motor 44 (of commercially available design) for rotating gear 46 about an axis perpendicular to the motor axis. As can be seen more clearly in FIGS. 2 and 3, rotation of gear 46 drives chain 48 meshed therewith to transmit the torque from the gear motor to shaft 50 rotatably supported within pillow block bearings 52 located at opposite ends of the shaft. Sprockets 54 are keyed to each end of the shaft adjacent the pillow block bearings to translate the rotational force on the shaft to chain drive 32 for longitudinally transporting the hood along rails 30 upon energization of gear motor 44. Desirably, sprockets 56 situated at the ends of the chain drives proximate roller section 12 are fastened to channel iron 58 of the hood base assembly by brackets 60 to permit individual adjustment of chain tension by longitudinal movement of sprockets 56. In conventional fashion, the maximum extent of hood travel is controlled by limit switches 62 situated at opposite ends of rails 30. Because hood drive gear motor 44 is disposed at a location remote from roller section 12 of the casting machine, potential damage to the motor resulting from spillage of molten metal during casting is minimized.
With hood 18 in an overlying attitude relative to mold 14, air flow through the mold is reduced and the loss of heat by convection is minimized. Moreover, any splashing of metal during casting or centrifugally thrown particles are contained by the overlying high pressure vessel plate hood. As can be seen from FIG. 2, hood 18 also is provided with L-shaped brackets 66 which become registered with and underlie hook shaped hold downs 68 on base assembly 38 when the hood overlies the mold to inhibit lifting of the hood from the base. Desirably, the span from top section 18b of the hood to the upper surface of rollers 72 is less than the diameter of wheel 74 on mold 14 to prevent the mold from riding up upon, and becoming disengaged from, the rollers during casting.
Roller section 12 includes a pair of horizontal rollers 72 spaced apart by a suitable distance, e.g., a mold wheel arc between 80.degree. and 100.degree., to securely seat wheels 74 of mold 14 thereon. The mold itself preferably is a sectionalized mold which is more fully described in co-pending U.S. patent application Ser. No. 220,286 and now U.S. Pat. No. 3,741,707, filed concurrently herewith. Opposite ends of rollers 72 are seated within bearings 76 fixedly secured to base assembly 38 to permit rotation of the rollers in a substantially horizontal plane while a pair of collars 78 are provided along each roller to axially contain the mold along the rollers during casting. Preferably, both collars are fixedly positioned along the rollers, e.g., by shrinking the collars thereon at an axial span slightly greater than the axial length of the longest mold to be utilized during casting, and rollers 72 are tilted slightly from a horizontal plane, i.e., at an angle less than 3.degree. and typically 0.degree. 10', to assure continuous bearing of the mold wheel against collars 78a adjacent ladle section 20. To inhibit marring of the wheel and/or collar by mutual contact during casting, grease normally is applied to the wheel/collar interface or a wheel 79' having an axis substantially perpendicular to the axis of mold 14 could be employed as a rotary bearing surface between the mold and hood end plate 36. When the molds employed for casting diverse size structures, for example, synchronous motor frames from 280 to 440 NEMA frame size, have end wheels of identical diameter, the molds can be interchanged upon the casting machine merely by substituting molds upon the rollers with the slight pitch of the rollers from a horizontal plane assuring the positioning of each mold against collar 78a regardless of mold length. Because mold 14 merely rests atop rollers 72 and is not otherwise fixedly secured to the machine, molds for different size motor frames can be inserted and removed rapidly from the casting machine.
Although both collars preferably are permanently secured in position along rollers 72, it will be readily apparent that collar 78 b remote from the ladle also could be made adjustable in position, i.e., by axially splitting the collar, to permit alteration in the axial span between collars dependent upon the length of the mold being employed for casting. In such event, the collar preferably would be secured in position by tightening bolts 80 extending across the split in the collar to provide a clamping force upon the rollers and by adjustment of set screw 81 extending radially through collars 78b to additionally secure the collars by the biting action of the set screw.
The rotary drive for rollers 72 is provided by a flexible timing belt 82 mounted on pulleys 84 (illustrated in FIG. 4) secured to the end of each roller with a baffle 86 serving to shroud the belt in conventional fashion to guard against operator injury and molten charge spillage. Belt 82 preferably is driven by an adjustable speed drive source, e.g., an adjustable speed drive motor 88, which permits the mold to be rotated at diverse speeds, i.e., from zero to approximately 460 RPMs over an infinite range, dependent upon such factors as the casting speed desired for a particular mold diameter and the configuration of the mold interior. As is customary, a belt tensioning screw 90 is provided in the platform upon which drive motor 88 is secured to permit removal and/or adjustment of the tension in flexible belt 82 driving rollers 72.
As can be seen more clearly in FIG. 4, drive motor 88 preferably is an AC adjustable speed drive motor which is energized by a 60 cycle AC source 92 through a cycloconverter 94 and normally open switch 96. Typically, drive motor 88 may be a motor such as is described in G.M. Rosenberry, Jr. U.S. Pat. No. 3,582,696 entitled "Dynamoelectric Machine With Solid Iron Rotor" (assigned to the assignee of the present invention) while cycloconverters suitable for adjustable speed drive of the motor are described in Brown et al. U.S. Pat. No. 3,582,737 entitled "Speed Control Of A Wye-Connected Induction Motor Utilizing Delta Connected Triggerable Biconductive Devices" (also assigned to the instant assignee). A portion of AC source 92 also is rectified within rectifier bank 98 and fed to the coils of drive motor 88 through normally closed switch 100 (mechanically interlocked with normally open switch 96) to dynamically brake the motor by the application of DC current to the motor windings when rotation of the mold is terminated by opening of switch 96. A centrifugal switch 101 also is provided in series with rectifier bank 98 to remove the D.C. current from the motor windings when rotation of drive motor 88 has ceased. To assure rapid braking of rollers 72 should AC source 92 be de-energized resulting in a loss of dynamic braking power for motor 88, a mechanical brake 102 also is provided at the end of one of rollers 72. Mechanical brakes for this purpose are commercially available and generally utilize energized electromagnetic coils (not illustrated) to magnetically restrain a rotationally stationary portion 102a of the brake from a brake surface fixedly secured to the rotating roller 102b. Should AC source 92 cease to supply power to adjustable speed drive motor 88, the electromagnetic coils maintaining the brake in a disengaged position are de-energized and the rotating surface of the brake bears against the stationary portion of the brake to mechanically stop rotation of the rollers. An emergency stop switch 104 also is provided in the mechanical brake circuit to permit simultaneous application of the electrical and mechanical braking forces to the rollers.
Returning again to FIG. 1, base assembly 38 of roller section 12 is fixedly secured in position by feet 108 secured to a platform 110 by bolts 112. Approximately at the center of the base assembly, substantially rectangular forced air apertures 114 are provided to admit hot air into the roller section from duct 115, illustrated more clearly in FIG. 5, prior to casting to maintain the mold at casting temperature and to permit cool air to flow into the roller section through duct 117 after casting to speed solidification of the cast. Although flow of forced air through the roller section generally is not needed for most applications, greater control of the quality of the cast and more rapid production rates often can be obtained by controlling the temperature of the air flowing through the roller section by the disposition of motor driven vane 119 within air ducts 115 and 117.
Ladle section 20 of the casting machine primarily includes a ladle 42 protruding outwardly from one end of a carriage 118 utilized to longitudinally transport the ladle into the mold. The ladle itself preferably has an outer metallic shell 120 and an inner insulating lining 122, e.g., a ceramic such as 99 percent pure silicon sand and binder, to conserve the heat of the molten metal, e.g., aluminum, poured into the ladle from material dispensing pump 121 through conduit 123. Typically, the insulating lining is at least three-fourths inch, and preferably 1 inch thick, to eliminate the need for auxiliary heating sources, such as Calrods, to maintain the molten metal at casting temperature. The upper portion of the ladle is opened, as identified by reference numeral 124, to permit acceptance of the molten metal charge into the ladle and discharge of the charge from the ladle into mold 14 upon rotation of the ladle. Ladle opening 124 should extend at least 75 percent of the length of the mold to assure good quality casts with ladle openings at least 85 percent - 90 percent of the mold length being preferred. Because it may be necessary to occasionally change ladles when the size of the frame being cast is substantially altered or when a ladle is not sufficiently large to contain the molten metal charge required for the cast, the ladles are provided with shoulder screws 123' (illustrated in FIG. 6) to slidably engage within slots (not shown) in ladle support 125. An aperture 127 also may be drilled and threaded into the ladle to additionally secure the ladle to the ladle support by means of a screw (not shown) passing through the ladle support into the ladle. At the end of carriage 118 proximate the mold, a plate 126 is provided to mate with aperture 40 within hood plate 36 to enclose the mold when the ladle is in position for casting.
Returning again to FIG. 1, carriage 118 is mounted on four wheels 128 which roll upon angle iron rails 130 when the carriage is driven by cable 132 bolted to the carriage underside by pins 153. The cable itself is wound about pulleys 134 having pulley housings 136 fixedly secured at opposite ends of carriage base assembly 138 and longitudinal motion is imparted to the cable by air pressure on piston 140 fixedly secured to the cable within piston cylinder 142. Orifices 144 are provided at opposite ends of the piston cylinder and air flow into the cylinder is controlled by forward and reverse dual acting valves 146 and 148, respectively, to produce the desired speed for the ladle. Preferably, the ladle is transported into the mold interior quickly after acceptance of the molten charge to conserve the thermal content of the charge. However, because the quantity of charge in the ladle is variable, e.g., a different quantity of charge is employed dependent upon the frame size being cast, the ladle should be driven at diverse speeds commensurate with the quantity of the metal within the ladle to prevent spillage. As was stated above, the desired speed regulation of ladle insertion can be achieved by controlled operation of valve 146 regulating the flow of air out of piston cylinder 142 to drive cable 132. Thus, for example, the speed of the ladle may vary from four to ten seconds for a four foot carriage transport dependent on whether 80 to 200 pounds of metal are contained within the ladle, i.e., whether a 280 or a 440 NEMA frame size is being cast. While a single speed could be utilized to insert the ladle within the mold, it will be appreciated that only variations in ladle speed maximize heat conservation while inhibiting spillage when the uncovered ladle contains large quantities of charge.
The rate of pouring molten charge from the ladle also is important to produce optimized casting quality. Control of the pour rate is accomplished in the casting machine of this invention by rotation of pinion 150 fixedly secured to ladle shaft 152 at a speed determined by the linear speed of rack 154 meshed therewith. As illustrated in FIG. 7, rack 154 is driven by a piston 156 within an air-oil tandem cylinder 158 permitting the linear speed of the rack (and the rotary speed of pinion 150) to be regulated by valve 160 controlling the flow of oil between chambers 161 and 162 of the air-oil tandem cylinder. A dual acting valve 167 controls the admission of pressurized air to air chamber 165 to apply a driving force to piston 156. Air-oil tandem drives of the foregoing type are available commercially and may be obtained from the Miller Fluid Power Division of the Flick Ready Corporation by ordering Model A50DJ61.
By adjusting valve 160, the pour rate from the ladle can be regulated, e.g., between two and fifteen seconds, dependent upon the frame size being cast (subsequent to the pressurization chamber 165 in the air-oil tandem cylinder by the admission of air through dual acting valve 167). If the pour rate is too slow, the resulting casting is not homogeneous and cold flow marks are produced in the casting surface. Similarly, if the pour rate is too rapid, molten charge may spill from the mold to contaminate adjacent equipment. In general, a charge of approximately 80 pounds should be poured into a finned motor frame mold rotating at approximately 400 revolutions per minute within four seconds while larger molds, e.g., those requiring approximately 200 pounds of molten charge, may require approximately six seconds to complete pouring. Thus, notwithstanding the fact that a uniform pour rate may be desirable for a single mold size, the pour rate optimumly is variable in the casting machine of this invention to permit different size molds to be utilized for casting. In general, commercially available air driven pistons (rather than air-liquid piston drive systems) were not found to provide sufficient control of the ladle pour rate to permit controlled pouring of molten metal charge for a plurality of frame sizes as can be accomplished by the casting machine of this invention.
Because ladle 42 is designed to accept different quantities of molten charge dependent upon the frame size to be cast, carriage 118 cannot be designed to counterbalance the diverse weights of the charge. To inhibit tipping of the carriage when large quantities of charge are required for casting, cam follower assembly 168 are provided beneath the rear wheels of the carriage to continuously apply a stabilizing force to the carriage. The cam followers basically include a roller 169 bearing against the underface of plate 170 upon which angle iron rails 130 are situated with the roller being pinned to a vertical plate 171 secured to the carriage housing to move the cam follower with the carriage. Limit switches 172 and 173 controlling the flow of air through valves 146 and 148, respectively, are provided at opposite ends of rails 130 to automatically vent sections of piston cylinder 142 through the double acting valves to limit the maximum span traversed by the carriage.
To operate horizontal centrifugal casting machine 10 in accordance with this invention, mold 14 is placed upon rollers 72 and hood 18 is moved longitudinally by gear motor 44 into an overlying position relative to the mold. A molten metal charge proportional to the size of the mold then is deposited in ladle 42, e.g., by any commercially available liquid metal pump capable of metered pumping, whereafter the ladle is moved rapidly into the mold by the admission of air into piston cylinder 142 at a rate designed to inhibit spillage of molten charge from the ladle, i.e., a rate inversely related to the elevation of charge within the ladle. After the ladle is inserted within the mold, valve 167 is opened to pressurize air-oil tandem cylinder 158 and valve 160 is adjusted by an amount to pour charge from the ladle at a rate dependent upon the size and interior surface of the mold utilized for casting. Tilting of carriage 118 containing the charge is inhibited by cam follower assembly 168 while unseating of the mold from rollers 72 during casting is prevented by the close proximity of hood 18 to the wheels of the underlying mold.
After casting is completed, the ladle is removed from the mold interior and the hood is rolled back to expose the mold. Because the mold is not fixedly secured to the rollers, the mold can be lifted from engagement upon the rollers and a different mold placed thereon to permit casting of a new frame. By the utilization of molds having wheels of constant size notwithstanding a difference in the frame size being cast by the molds, a change in frame size requires only an alteration in the quantity of charge to be deposited in the ladle (and occasionally a substitution of ladles). The quantity of charge in the ladle then determines the rate of insertion of the ladle within the mold while both the quantity of charge and the interior configuration of the mold determines the pour rate to be utilized for each size frame being cast. In general, both the rate of ladle insertion and the pour rate are initially determined empirically for each mold size to be cast. These empirically determined rates then are utilized for casting subsequent frames of identical size by noting the settings on valves 146 and 160 at the empirically determined optimum rates and adjusting the valves to these settings during casting of similar size frames.
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