US2509079A

US2509079A - Casting metal

Info

Publication number: US2509079A
Application number: US679134A
Authority: US
Inventors: Trewin Charles Sydney; Robert A Gerhard
Original assignee: New Jersey Zinc Co
Current assignee: New Jersey Zinc Co
Priority date: 1946-06-25
Filing date: 1946-06-25
Publication date: 1950-05-23
Anticipated expiration: 1967-05-23
Also published as: ES176951A1; ES176952A1

Description

y 1950 c. s. .TREWIN ETAL 2,509,079

' CASTING METAL Filed June 25, 1946 T 11 Shee'tsSheet 1 INV TOR CH4 PL es .5 VON/5V FEW/IV R0 m r A. G's/7H4 an BY 7M, M, M vim ATTORNEY c. s. TREWIN EIAL 2,509,079

4 CASTING METAL May 23, 1950 Filed June 25, 1946 11 Sheets-Sheet 2 ATTORNEY M y 23, 50 c. s. TREWIN' ErAL 2,509,079

CASTING METAL Filed June 25, 1946 I 11 Sheets-She 3 9 l VENTOR C/MRLES SYDNEY REW/N R0351? T ABGYERHARD Z2-,M,MWW

ATTORNEY May 23, 1950 c. s TREWIN ETAL CASTING METAL 11 Sheets-Sheet 4 Filed June 25, 1946 W R Y ow 5 TE mm wm YH m w 3 STY 5MB m8 CASTING METAL l1 Shee ts-Sheet 5 C. S. TREWIN ETAL May 23, 1950 Filed June 25, 1946 INVEIIOR ,C/m mes SYDNEY REW/N Ross/ r A. GER/MRO Y ZM/ M, M WM ATTORNEY C. S. TREWIN EI'AL CASTING METAL May 23, 1950 ll Sheets-Sheet 6 Filed June 25, 1946 INVEI rQR CHARLES S n/var REW/N ROBER QA 6 FR HARD 72", M, W

ATTORNEY y 1950 c. s. TREWIN EI'AL 2,509,079

CASTING METAL Filed June 25, 1946 7 l1 Sheets-Sheet 8 2 44*, M, M Kim ATTORNEY 11 ShQtS-ShSBt 9 C. S. TREWIN El" AL CASTING METAL Roam r /1.GERHARO ATTORNEY m w u M O a a w mm H 8 m w a Q H m 9 m. 3 8 H A. A A v m f IIIJII lillllnllh m. 0/ W m U 1 v 2 n 6M 8 5 Lu 2 3 L u f n H a q! i n 8 E I m lllllll P Ill? :vl M N n .w n L n, a s m H w u m May 23, 1950 Filed June 25, 194e y 3,1950 c. s. TREWIN EI'ALI 2,509,079

CASTING METAL Filed June 25, 1946 11 SheetsSheet 1O INVE OR CM ass JrnNfv i li'Ewllw 8055s; A, Gnu/ma ATTORNEY y 1950 c. s. TREWIN ETAL 2,509,079

CASTING METAL Filed June 25, 1946 11 Sheets-Sheet 11 u I Q 2 g m V min N 5 Q INVENJZOR CHARLES S n/var HEW/N 8065/? hi. GEM/Ana M, m 0am ATTORNEY l Patented May 1950 CASTING METAL Charles Sydney Trewln, North Plalnlleld, N. J.,

and Robert A. Gerhard, Palmerton, Pa, as-

signors to The New Jersey Zinc Company, New York, N. Y., a corporation of New Jersey Application June 25, 1946, Serial No. 679,134

3 Claims. 1

This invention relates to the casting of metals such as zinc and, more particularly, to the casting of metals in forms of uniform size and substantially free of surface irregularities. The invention contemplates novel metal casting apparatus capable of producing such forms. Since the invention is particularly applicable to the casting of zinc, it ishereinafter described, for purposes of illustration, in connection with the casting of that metal.

,. The casting of molten zinc metal, particularly in the form of flat slabs in open molds, involves the observation of certain precautions which have confined such casting largely to manual methods. For example, flat slabs of zinc are commonly supplied to rolling mills wherein the slabs are rolled out into sheet form. Surface irregularities such as ripples or other protuberances interfere with the production of uniformly rolled sheets and are therefore undesirable in the cast slabs. Accordingly, an open slab mold filled with molten zinc metal must be kept quiescent to permit the exposed surface of the molten metal to freeze while unruflied. Furthermore, motion imparted to the molten metal in a mold, either by too, rapid pouring velocity or by irregular movement of the full mold, causes the molten metal to flow upwardly along the side walls of the mold where it freezes and forms a fringe of solidified metal. The fringes have sharp edges which make the slabs dan erous to handle and furthermore seriously interfere with proper stacking of the slabs in storage and transit. Fringes are a skimmage loss to consumers who remelt the slabs during subsequent fabrication.

In addition to the surface irregularities caused by motion of molten metal in the molds, large masses of skimmings are formed if the metal is poured from an appreciable height into the mold. These skimmings result from oxidation of the molten metal as it is poured and splashes in the mold, and they comprise a mass of solidified zinc m tal rendered porous and useless to a consumer by inclusion of a substantial amount of zinc oxide. In order to minimize the formation of skimmings during hand casting, the molten metal is first charged to a pouring ladle, skimmings are removed, and the ladle is tilted by hand to pour the metal into molds resting on a bench. It is difiicult to avoid irregular pouring rates and formation of kimmings during manual pouring. Although the skimmings can be substantially completely removed with a wooden paddle,

the procedure is hot and tedious for a workmanand the amount of skimmings represents a corresponding loss of castable metal.

Manual casting of zinc, particularly in the form of slabs, is an exacting procedure for the reasons pointed out hereinbefore. The requirement that the slabs be of uniform size, that is of uniform weight, makes it necesary to pour the metal at such a, level that it can be carefully watched. As a result, the workmen must continually bend over masses of hot metal. Under these difficult conditionsthe problem of pouring a slab of uniform thickness is aggravated. For example, commercial slab zinc about one inch thick, weighing nominally about 40 pounds per unit, frequently varies 5 pounds or more above or below the desired weight.

Considerable thought has been given to the possibility of pouring zinc forms, and particularly zinc slabs, by mechanical means which would at least be as effective as the hand casting method. It was realized that such mechanical casting equipment would have to pour a substan tially uniform amount of metal into each mold, that it would have to pour the metal in 811161]. manner as to avoid the formation of skimmings and fringes on the cast slab, and would have to handle the molds filled with molten metal suflic'iently smoothly to prevent the formation of fringes on the edges and ripples on the surface of the solidified forms. Proposals which have been made heretofore have not met the problem, and we are not aware of any metal casting machine proposed or constructed prior to the present invention which has fulfilled these requirements.

The metal casting machine of the invention produces castings such as slabs which are of substantially uniform size and substantially free of surface irregularities such as fringes, ripples and scum. For example, the machine is capable of producing cast slabs of zinc one and oneeighth inches thick and weighing forty-two pounds with an average weight variation within one-quarter of a pound and substantially free of fringes, ripples and the like. In terms of slab thickness, the machine is capable of continuously producing slabs of the aforementioned size which have an average variation in thickness from slab to slab within about M7 of an inch.

The casting machine of the invention comprises a mold carrier apable of moving each of a plurality of molds, such as open molds, serially and smoothly through a casting zone and a cooling zone, a pouring ladle, and pouring control means. The pouring control means is capable of controlling the pouring of molten metal from 3 the ladle into a mold in the casting zone so as to fill each mold to a predetermined level with substantially scum-free molten metal in such manner as to avoid substantially the formation of a fringe of solidified metal.

The mold carrier in one embodiment of the invention omprises a wheel mounted about a horizontal axis with the molds disposed adjacent the periphery of the wheel. The molds are advantageously mounted on shafts disposed adjacent the periphery of the wheel and substantially parallel to the axis of the wheel. Guide means are provided capable of maintaining the molds in a uniform position with respect to the horizontal as the wheel is rotated to move the molds through the casting and cooling zones. The molds are carried smoothly and without swaying or other irrelevant motion as they pass through the casting and cooling zones.

The pouring ladle is advantageously mounted for movement along a path substantially parallel to the movement of the molds through the casting zone. Means are provided for moving the pouring ladle reciprocally along this path in such manner as to follow the movement of each mold through the casting zone. The ladle is mounted adjacent the casting zone in such manner that molten metal is poured into each mold in the casting zone from a level only slightly above the top of the mold. These features permit relatively slow pouring of the molten metal into the molds so as to avoid the formation of skimmings and fringes on the solidified cast metal.

The pouring control means comprises tilting means associated with the pouring ladle and adapted to pour molten metal from the ladle into the mold and means for delivering molten metal from a body thereof to the pouring ladle in such manner as to maintain a substantially constant level of molten metal in the ladle. The delivery means, in a specific embodiment of the invention, comprises a dipping ladle mounted for rocking movement such as to transfer molten metal from a body thereof to the pouring ladle, rocking means operatively associated with the dipping ladle, and means independent of the rocking means capable of terminating the delivery of molten metal from the dipping ladle to the pour- I ing ladle. The pouring control means further comprises means responsive to the level of molten metal in the mold capable of terminating the pouring thereof from and the delivery thereof to the pouring ladle. The pouring control means makes possible the production of castings of uniform shape and size, and by controlling the level of molten metal in the pouring ladle contributes to the pouring of molten metal without the formation of skimmings and fringes on the solidified cast metal.

The foregoing and other novel features of the invention will be more fully understood from the following description taken in conjunction with the accompanying drawings, in which:

Fig. l is a side elevation in section of the casting apparatus of the invention;

. Fig. 2 is a plan view of the apparatus shown in Fig. 1;

Fig. 3 is an enlarged plan view of the casting wheel and pouring ladle assemblies;

Fig. 4 is a sectional rear elevation of the casting wheel taken along line 4-4 of Fig. 3 with the side of the casting wheel partially broken away and showing the upper horizontally disposed mold at the start ofits passage through the casting zone;

Fig. 5 is a sectional rearelevation of the casting wheel taken along line 55 in Fig. 3 with the side of the casting wheel partially broken away and showing the casting wheel rotated past its position shown in Fig. 4;

Fig. 6 is a sectional front elevation of the casting wheel taken along line 6-5 in Fig. 3 showing the wheel rotated still further than in Fig. 5 with the next successive mold in the casting position;

Fig. 7 is a sectional side elevation adjacent the front of the casing wheel taken along line l-I in Fig. 6;

Fig. 8 is a rear elevation of the pouring ladle assembly taken along line 8-8 in Fig. 3;

Fig. 9 is a side elevation of the pouring ladle assembly taken in the direction of the arrow 3 in Fig. 3;

Fig. 10 is an enlarged plan view of the dipping ladle assembly shown in Fig. 2;

Fig. 11 is a side elevation taken along line I ll I in Fig. 10;

Fig. 12 is a front elevation taken along line I2--I2 in Fig. 10;

Fig. 13 is a front elevation view of the dipping ladle rocking drive taken along line l3-l3 in Fig. 10;

Fig. 14 is a front elevation view of the capacitor plate assembly taken along line M-H in Fig. 9;

Fig. 15 is a plan view of a slab mold;

Fig. 16 is a sectional side view of another modification of mold structure and Fig. 17 is a schematic diagram of the hydraulic and electric circuits of the apparatus.

The casting apparatus of the invention comprises, as shown in Figs. 1 and 2, a vertically mounted casting wheel 20 carrying molds 2| which are maintained in a horizontal position. Molten metal such as zinc is poured into these molds from a pouring ladle 22. The level of molten zinc in the pouring ladle is maintained substantially constant by delivering metal to this ladle from a relatively large body of the metal maintained in the molten state in a suitable furnace. The furnace is advantageously divided into two communicating compartments by a bridge wall 23. Metal is kept molten in an oil-fired or otherwise heated compartment 24 of the furnace and a body of molten zinc free from unmelted metal is thus readily maintained at a substantially uniform level in the other compartment or forehearth 25. The delivery of molten metal from the forehearth to the pouring ladle is eflected in accordance with the invention by a dipping ladle 26 which intermittently dips into the body of metal and delivers it to the pouring ladle. The details of these and other novel features of the invention are shown in the remaining figures of the drawings.

The casting wheel is driven by a motor 21, preferably operating at relatively high speed, which is connected through a conventional variable speed belt drive 28 and a reduction gear assembly 30 to a heavy horizontal shaft 3| on which the casting wheel is mounted. The casting wheel is constructed of heavy steel plates forming two parallel disc-

like sides

32 and 33 mounted on the horizontal shaft. The shaft is advantageously supported in massive bearings 34. The high speed motor, the belt drive, precision gears in the reduction gear assembly, and the massive casting wheel and supporting bearings all contribute to imparting smooth continuous rotation to the casting wheel.

A plurality of shafts 35 (Figs. 4, 5 and 6) extend between the two sides of the casting wheel adjacent their peripheries. Each of these shafts carries a mold frame 36 keyed to the shaft and a mold 2| is mounted on each frame. 0n the end of each mold frame shaft extending exteriorly beyond one side of the casting wheelthere is mounted a mold guide bracket 31 which is also keyed to the shaft. Each bracket is provided with two

arms

38 and 40 having guide rollers 4| and 42, respectively, mounted at their extremities. The guide rollers are adapted to engage an appropriate guide track capable of maintaining each mold in a horizontal position as the casting wheel is rotated. Rotation of the casting wheel carries the molds serially and successively through what will be termed a casting zone, a cooling zone and a discharge zone.

The guide track is advantageously divided into four sections, as shown in Figs. 5 and 6. The

- first section 43 of the guide track serves to maintain the molds horizontal as they are moved from a position corresponding to the top of the wheel (in the casting zone) to a position corresponding to about the 4 oclock position in Figs. 4 and 5 (i. e., in the cooling zone). The roller 4| on the guide arm 38 engaging the inner surface of this track section 43 tends to fall away from the track as the mold is carried toward the bottom of the casting wheel and must therefore be transferred to the outside of a second main section 44 of the guide track. This transfer is effected by a third intermediate section 45 of the guide track the inner surface of which is engaged by the other guide roller 42 at the end of the other mold guide arm 40. The intermediate track section 45 supports the mold in the desired horizontal position until the first-mentioned guide roller 4| engages the outer surface of the second main track section 44. The second main track section supports the mold in the horizontal position as it is carried from the lower position of the casting wheel upwardly toward the 10 oclock position as viewed in Figs. 4 and 5.

As the mold guide'roller 4| reaches the end of the second main section of guide track, it is transferred to a channel-shaped movable guide track 46 (Figs. 4 nd 5) which is capable of tipping the mold upside down in order to discharge the solidified casting from the mold. The guide roller 4 I, if unrestrained at this point, would tend to pass freely from the end of the second main guide track section 44 into the movable g ide track in such manner as to allow the mold to tilt downwardly toward the interior of the casting wheel. In order to give the mold the opposite motion so as to discharge the casting outside of the wheel, another intermediate transfer section of guide track 41 is used to support the other guide roller 42 until the guide roller 4| is moved from the end of the second main track section 44 to a restraining stop or cam 46. This stop is so positioned as to restrain further upward movement of the guide roller 4| until the casting whe l carries the mold frame shaft 35 upwardly a sufficient distance to pull the guide wheel 4| in a trailing manner under the stop 48 and into the channel-shaped guide track 45. As a result of such restraint of the guide roller 4| as the mold frame shaft 34 is elevated by the casting wheel. the mold is tipped upwardly until it assumes a position as shown by the full-line position of the r old and guide roller in Fig. 5. The guide roller 4| will then be positioned in the channel-shaped guide track 46 which is operated to tip the mold further to an upside down position for discharge of the solidified casting.

As the mold guide roller 4| moves into the movable guide track 41, this portion of the track is rotated in a direction shown by the arrow in Fig.

5 to such an extent as to move the mold guide roller into the dotted position 4| shown in this figure. With the guide roller inthis position, the mold is. turned upside down (2111 so that the solidified cast metal may be discharged. The requisite rotation of the movable guide track is furnished by n intermittent gear 52 shown in Fig. 6. The intermittent gear is driven by the motor 21 and reduction gear assembly 3|! through another gear assembly 53 and drive shaft 54. It will be seen, accordingly, that the intermittent gear is driven by the same motor as the casting wheel itself.

The teeth of the intermittent gear (Fig. 6) engage the teeth of a spur gear 55 and intermittently impart one complete revolution to this spur gear. Rotation of the spur gear 55 moves a crank 56 through one complete revolution, and the motion of this crank 56 is transferred through a connectingarm 51 to a crank arm 58 operatively connected to a supporting shaft 59 which carries the movable guide track section 46. Rotation of the spur gear crank 56 thus pulls down the guide track crank arm 58 and returns it to its initial position so that only a minor portion of a complete revolution is imparted to the movable track section 46. In this manner, one complete revolution of the spur gear 55 rotates the movable guide track section 46 to the mold discharging position and returns the guide track to its initial position by the time the teeth on the intermittent gear have passed out of engagement with the spur gear. The mold guide roller 4| will have progressed by this time toward the end of the movable guide track section 46 as shown in Fig. 4, and continued rotation of the casting wheel carries the guide roller out of the movable track into engagement with the inner surface of the first main guidetrack section 43. It will be seen, therefore, that the casting wheel and the movable guide track are driven by the same power source so as to maintain the motion of each in perfect coordination.

The same power source is utilized to move the pouring ladle 22 along a path such as to follow each mold through the casting zone. The pouring ladle, as shown in Figs. 8 and 9, is of conventional shape and is provided with a lining 60 of suitable refractory material to prevent contamination of the molten zinc by the metal of the ladle and further to provide heat insulation for molten metal in the ladle. An underflow baflle I46 ,is positioned directly before the pouring lip to prevent skimmings formed in the ladle from being discharged into the mold. The ladle is advantageously provided with as wide a pouring lip 6| as possible consistent with the width of the mold. The pouring ladle is provided with trunnions 62 supported by an open bearing or yoke 63 carried by a supporting frame 64. The supporting frame is mounted on a carriage 65 capable of movement along a short section of track 66. The track is positioned parallel to the direction of r otion of the molds as they are moved through the casting zone adjacent the top sector of the casting wheel. The carriage is moved reciprocally along the track 66 by the movement of a rocker arm 61 one end 68 of which is connected to the carriage and the other end H! of which is conn cted to a crank mounted on the drive shaft 54. Inasmuch as the shaft 54 isdriven by the main driving motor 21,- a positive connection is established between the casting wheel and the pouring ladle carriage to insure correlated movement of both the ladle and the wheel. This correan... is such that the pouring nine :2 will :01-

low a mold 2| while zinc is being poured from the ladle into that mold and will return to its initial position for pouring molten metal into the next mold.

The pouring of metal from the ladle 22 into each mold is effected by a tilting mechanism, as shown in Figs. 8 and 9. This mechanism is capable of tilting the ladle from a non-pouring (upright) position to a pouring (tilted) position and back to the non-pouring position. The tilting mechanism is operated by a hydraulic plunger 12 supported on the carriage 95 adjacent one side of the pouring ladle. The plunger 12 is connected to one end of a lever arm 13 mounted on the end of a shaft 14 extending under the ladle. The shaft 14 is provided with a crank 15 directly below the ladle which engages a fork 19 depending from the bottom of the la'dle. The fork engagement with the tilting mechanism makes it possible to remove and replace the ladle simply by lifting it oif its yoke-shaped trunnion bearings 63 and by lowering another similar ladle in its place.

It will be noted that the tilting mechanism moves the pouring ladle from one to the other of two positions, namely, a non-pouring position and a pouring position. In its pouring position, the lip of the pouring ladle barely clears the upper edge of the end walls of the mold so that the molten metal is poured into the mold from the lowest possible height. The rate at which metal is poured from the ladle in its pouring position is controlled by maintaining a substantially constant level of molten metal in the ladle. This constant level is maintained in the specific embodiment of the invention by means of the dipping ladle 26.

The dipping ladle, as shown in Figs. 19, 11 and 12, comprises a metal supporting frame 11 provided at its sides with trunnions 18. The frame Tl carries a dipping vessel 89 formed of a. suitable refractory such as silicon carbide which is characterized by a heat conductivity approaching that of metals and which will not contaminate the molten zinc. The frame 11 is also provided with a pouring lip 81 lined with the same or similar refractory material 82. The dipping ladle is mounted over the body of molten metal in the forehearth 25 of the melting furnace, the ladle being so positioned that rocking movement imparted to the ladle will be capable of lifting molten metal from the forehearth and delivering it to the pouring ladle.

The trunnions 19 about which the dipping ladle is rocked are supported by one arm 83 of a bell crank 84. The bell crank 84 is operatively connected to a hydraulic plunger 95 which is capable of being operated in such manner as to raise or lower the dipping ladle trunnions. With the trunnions I8 raised to their upper position, the pouring lip 8| of the ladle is raised sufficiently high to prevent discharge of molten metal from the dipping ladle during any stage of the rocking movement of the ladle about its trun' nions. In the lowered position of the trunnions I8, delivery of molten metal from the dipping ladle to the pouring ladle is permitted when the large dipping end of the ladle (the dipping vessel 99) is raised by the rocking movement imparted to the ladle.

Rocking movement is imparted to the dipping ladle 26 by means of a. walking beam 89. One end of the walking beam is connected to the dipping end of the ladle and the other end of the beam is raised and lowered by suitable reciprocating mechanism. A counterweight 81 is carried by the latter end of the beam in order to counterbalance the weight of the dipping ladle. The reciprocating mechanism comprises a double crank assembly. One of these cranks 99 is mounted on a shaft 99 driven by the same drive shaft 54 which drives the intermittent gear mechanism and the pouring ladle carriage. The crank is provided with a channel guide 9|. A roller bearing 92 secured to the end of a second crank 93 of the double crank assembly is mounted in the channel guide 9! and is free to move along this guide. The second crank 93 is mounted on another shaft 94 offset from the supporting shaft 99 for the first-mentioned crank 88. Rotation of the drive shaft 54 is thus imparted to the sec-- ond crank 93 and the motion of this crank is imparted to the walking beam 89 by means of a connecting arm 95 extending from the bearing 92 at the end of the second crank to the end of the beam.

The double crank assembly is arranged as shown in the drawings to provide slow advance and quick return motion to the connecting arm 95 moving the walking beam. In this manner, the arm 95 is lowered rapidly to raise the dipping ladle rapidly almost to the pouring position, then slowly to provide a slow rise of the dipping ladle while pouring metal into the pouring ladle, and then the arm 95 is raised rapidly to provide rapid return of the dipping ladle to its dipping position. It will be apparent that other mechanism such as a cam may be used in lieu of the double crank, although the double crank is advantageous because of the relatively wide range of adjustment to which it is amenable. It will be seen that the clipping ladle is rocked by means of the same drive (the motor 27) which is used to rotate the casting wheel. Rocking of the dipping ladle may thus be synchronized with rotation of the casting wheel. This motion is preferably synchronized so as to deliver a single batch of moten metal from the forehearth to the pouring ladle for every charge poured into a mold. Accordingly, the walking beams is rocked as as to raise the dipping end 89 of the ladle once for each mold filled b the pouring ladle.

Initiation of the pouring of molten metal from the pouring ladle into the mold and for the delivery of molten metal from the forehearth to the pouring ladle is synchronized with the motion of the walking beam. This is accomplished with advantage by means of two cams 99 and 91 mounted on the shaft 94 carrying the second crank of the double-crank reciprocating mechanism. One of the cams 99 is arranged to operate a switch 98 which controls the hydraulic plunger 95 associated with the clipping ladle trunnions. The other cam 91 operates a second switch I99 which controls the hydraulic plunger 12 associated with the pouring ladle tilting mechanism. The dipping ladle cam 96 is so positioned as to lower the dipping ladle trunnions 18 to the pouring position before the dipping end 89 of this ladle is raised to the pouring level. The other cam 91 is so positioned as to tilt the pouring ladle 22 at substantially the same time that the dipping end 89 of the dipping ladle is raised sufiiciently high to deliver zinc to the pouring ladle. In this manner, molten metal is delivered from the dipping ladle to the pouring ladle substantially simultaneously with the casting of the metal from the pouring ladle into each mold. The delivery of molten metal from the dipping ladle during the noted. The level of molten metal rises in the mold until a predetermined critical electrical capacity is established between the molten metal and the capacitor plate IIlI. When this critical capacity is attained, the electronically controlled relay II3 operates to cause the two hydraulic plungers I2 and 85 simultaneously to return the pouring ladle to its non-pouring position and raise the dipping ladle trunnions to their nonpouring position. The dipping ladle continues to perform its rocking cycle and the cams 96 and 3'! on the walking beam crank shaft 94 continue to periodically operate their respective switches at and I to repeat the complete cycle of operations.

Each mold filled with molten zinc to the predetermined level passes beyond the casting zone and enters the cooling zone as it is carried around on the casting wheel. Cooling is effected advantageously by means of air jets II5 (Fig. 4) which direct streams of cooling air against the surface of the molten metal in the mold and against the mold itself. Additional air jets IIG may be used if desired to direct air against the filled molds as they continue through the cooling zone. The use of water sprays directed against the surface of the molten metal to effect cooling in the early stages of the cooling zone has been found to be undesirable because such sprays produce such rapid freezing of the metal that shrink age of the metal causes center cracks on the top of the cast form. Center cracks permit molten metal within the interior of the cast slab to bleed out of the cracks when the mold is turned upside down in the discharge zone.

It has been found desirable to accelerate the cooling at an intermediate point in the cooling zone by providing a circulating water bath in the bottom of a tank III enclosing the lower portion of the casting wheel. The water level II 8 is advantageously so maintained that each mold at the lowest point of its travel is partially immersed in the water. Such partial immersion effects a substantial amount of cooling and at the same time avoids an accumulation of water on top of the mold where it may be trapped so as to present an explosive hazard when molten metal is subsequently poured into the emptied mold. If desired, water sprays or fog may be I directed against the molds as they pass through the latter portion of the cooling zone.

Increased cooling of the metal in the mold may be obtained by the use of molds of the type shown in Fig. 16. These molds are provided with projections I20 depending from the bottom surface thereof. The projections increase the effective exterior surface of the mold and make possible more rapid cooling of the molten metal by imparting the cooling effect largely to the sides and bottom of the cast metal rather than to the exposed upper surface of the metal which develops center cracks if cooled too rapidly.

At the end of the cooling zone, the molds enter the discharge zone wherein the molds are turned over as previously described. Removal of the discharged casting is facilitated by means of a roller conveyor I2I. The roller conveyor is provided with compound motion furnished by two operating cranks I22 and I23 controlled by a single crank I24 mounted on the drive shaft 54 which controls the mold tipping mechanism, etc. The cranks are shown in detail in Fig. 8. Movement of the roller conveyor is so controlled by these cranks that the inner end of the conveyor is moved into the space between successive molds immediately below a mold being turned over by the tipping mechanism. The inner end of the conveyor is progressively raised b the cranks I22 and I23 so as to maintain clearance above the next successive mold being raised toward the tilting mechanism. Immediately afterthe casting is discharged from the overturned mold, the double crank action maintains the inner end of the conveyor in its elevated position and moves the entire conveyor out of the path of the next oncoming mold. The moving cycle of the conveyor is completed by lowering its inner end to the initial position preparatory to being introduced under the last-mentioned mold as it is turned over by the tipping mechanism.

Operation of the pouring control of the casting apparatus may-be more fully understood by reference to the schematic diagram shown in Fig. 17. At the start of the pouring cycle, the hydraulic plunger 85 of the dipp ng ladle is in the upper position so as to lower the clipping ladle trunnion to the pouring position. As the dipping end of the dipping ladle rises toward the dotted position shown in Fig. 11, molten metal is delivered from the dipping ladle to the pouring ladle. The pouring ladle cam 91 on the dipping ladle crank shaft is adjusted to close its electrical switch I00 at substantially this instant. The switch I00 operates a solenoid I25 on a fourway hydraulic valve I26 controlling the oil flow to the hydraulic plunger 12 of the pouring ladle tilting mechanism. Operation of the solenoid I25 causes the tilting mechanism to tilt the pouring ladle to its pouring position so that molten zinc will fiow into the mold in the casting zone. Operation of the hydraulic plunger also lowers the capacitor plate IIII into operating position on top of the mold 2 I. The dipping end of the dipping ladle continues to rise to the dot-dash position shown in Fig. 11 while the molten metal is being poured into the mold.

The metal level continues to rise in the mold until the electrical capacity between the molten metal and the capacitor plate IIlI' reaches a critical value. When this critical value is attained, the balance is upset in a normally balanced capacity bridge circuit I2I shown in Fig. 17. The bridge circuit is described andclaimed in the copending application of Robert A. Gerhard, Serial No. 695,067, filed September 5, 1946, now abandoned. This circuit includes the capacitor plate IIII in one side of the bridge and a variable condenser I28 in the other side of the bridge. This unbalanced condition causes current to flow through the primary I30 of a transformer cone nected into the bridge through its mid-tap connection. A corresponding voltage is induced in the secondary 'I3I of the transformer. This voltage is suilicient to operate the controlrelay H3.

The relay I I3 is connected to solenoids I32 and 4 I33 controlling the four-way hydraulic valves I25 and I34, respectively.- These valves control the oil supply to the hydraulic plungers I2 and 85, respectively. Thus, operation of the relay II3 operates the four-way valve I26 to supply oil to.

the hydraulic plunger I2 of the pouring ladle tilting mechanism in such manner as to return the ladle to its upright or non-pouring position. Operation of the relay II3 simultaneously operates the other four-way valve I34 to supply oil to the dipping ladle plunger in such manner as to raise the dipping ladle trunnions to the .nonpouring position. Operation of the relay II3 thus initiates termination of the flow of molten metal from the pouring ladle to the mold and pouring operation serves to maintain a substantially constant level in the pouring ladle while the metal is being poured from this ladle into a mold. As a result, the molten metal is poured into the mold under a substantially constant head and without an initial surge which is characteristic of pouring from a ladle initially containing a large excess (large head) of the metal.

with both the pouring ladle and dipping ladle in the pouring position, molten zinc is cast into the mold at a substantially uniform pouring rate until the metal in the mold reaches a predetermined level. The pouring is terminated by means of an electronic circuit responsive to variation in the electrical capacity between the surface of molten metal in the mold in a capacitor plate I! (Figs. 9 and 14). The capacitor plate, advantageously in the form of a disc having a diameter of at least a major portion of the width of the mold vinterior, depends from an insulator I02 mounted on a supporting frame I03. The supporting frame is carried at one end of a capacitor support comprising two pairs of parallel arms I04 and I05. The parallel arms are mounted adjacent their other end on shafts I05 and I0! mounted on a frame carried by the pouring ladle carriage 65. A crank arm I08 secured to the end of one of these shafts I01 which is keyed to one of the parallel arms I05 is connected through an adjustable linkage I I0 to the end of the ladle tilting lever 13 opposite that to which the hydraulic tilting plunger I2 is connected. Thus, movement of the hydraulic plunger I2 such as to tilt the pouring ladle into its pouring position raises the crank arm I08 in such manner. as to lower the capacitor plate IOI into operative position over the mold. The parallel arm support maintains the capacitor plate in a substantially horizontal position regardless of its vertical movement with respect to the mold.

' As the capacitor plate II is lowered toward the mold while the pouring ladle is being tilted to its pouring position, the operative position of the capacitor plate is determined by a pair of shoes III depending from the capacitor plate supporting frame I03. The shoes are spaced apart by the width of the mold and come to rest against adjustable screws H2 extending above the top of the mold. Two of these adjusting screws are mounted on the upper edge of one side of the mold and a single adjusting screw is mounted on the upper edge of the other side of the mold. The three adjusting screws II2 are capable of adjustment such as to maintain the shoes III in a position which insures accurate placement of the capacitor plate IOI at a predetermined height above the desired level of metal in. the mold. The individual shoes are of sufllcient width to permit relative motion between the shoes and the mold occasioned by the slight diilerence between the harmonic motion of the pouring ladle carriage along its track and the nearly linear motion of the mold through the casting zone. The capacitor plate support (the parallel arms I04 and I05) preferably extends out over that portion of the mold which is filled last by metal poured into the mold. Thus, in a divisional mold such as that shown in Fig. 15, where the molten metal is poured into one end compartment of the mold and overflows into the central compartment and finally into the other end compartment, the capacitor plate support is suspended over the last compartment to be filled so that the pouring will be With the pouring ladle tilted to its pouring position and with the capacitor plate MI in its operative position, the level of molten metal rises in the mold until the electrical capacity between the surface of the molten metal and the capacitor plate attains a critical value. At this point, an electrically operated relay I I3 mounted in a housing I (Fig. 2) supported adjacent the casting zone functions to reverse the motion of the hydraulic plunger I2 of the pouring ladletilting mechanism. Qperation of the plunger in this direction .retums the pouring ladle to its non-pouring position and simultaneously raises the capacitor plate supporting frame I03 into inoperative position above the mold. Operation of the relay I I3 simultaneously causes the hydraulic plunger 85 associated with the clipping ladle to be moved in the reverse direction so as to raise the trunnions 18 of the dipping ladle. The pouring lip ill of the clipping ladle is thus raised above its pouring position so as to terminate the delivery of metal from the dipping ladle to the pouring ladle.

It will be seen that operation of the relay H3, when the molten metal reaches a predetermined level in a mold, simultaneously initiates termination of flow of metal from the pouring ladle to the mold and from the clipping ladle to the pouring ladle. Although termination of pouring is initiated at both ladies simultaneously, the maintenance of a low head of metal in the pouring ladle may cause the pouring ladle to stop pouring before the delivery of metal from the dipping ladle is terminated. The small amount of excess metal delivered to the pouring ladle after pouring is terminated is discharged from the pouring ladle during the next pouring cycle for a short interval before metal starts to flow from the dipping ladle into the pouring ladle. Regardless of the slight out-of-phase pouring of molten metal from the two ladies, the amount of metal poured from each ladle is unaffected. Accordingly, a substantially uniform level of molten metal is maintained in the pouring ladle.

The operation of the casting machine is as follows. The main drive motor 21 runs continuously to rotate the casting wheel 20 and to drive the shaft 54 which operates (a) the mold tipping mechanism, (b) the pouring ladle carriage reciprocation and (c) the rocking mechanism of the dipping ladle. As an empty mold 2I near the top of, the casting wheel approaches the casting position, the pouring ladle is in its non-pouring position and the pouring ladle carriage is in its starting position about to follow the movement of this mold through the casting zone. At the same time, the trunnions 16 of the tilting ladle are lowered to the pouring position and. the walking beam 88 will have raised the dipping end of the dipping ladle almost to the point where molten zinc is delivered from the dipping ladle to the pouring ladle. The pouring ladle cam 91 mounted on the walking beam crank shaft 94 is timed to operate the pouring ladle plunger 12 immediately after the other elements are in the aforementioned position. Thus, the pouring ladle is tilted and casting is started as soon as the mold comes into alignment with the pouring ladle in the casting zone. The capacitor plate IIlI is simultaneously lowered by the plunger 12 into its operative position above the mold. The other cam 96 on the walking beam crank shaft 94 is timed to operate its switch 98 shortly before this point in the operating cycle so as to lower the dipping ladle trunnions I8 to the pouring position as previously from the dipping ladle to the pouring ladle. The walking beam continues its rocking cycle to lower the dipping end 80 of the clipping ladle into the body of molten metal in the forehearth. As this end of the clipping ladle is lowered, the dipping ladle cam 96 on the dipping ladle crank shaft 94 closes its electrical switch 98 to operate a solenoid I35 which causes the dipping ladle plunger 85 to lower the dipping ladle trunnions to the pouring position. Continued rotation of the dipping ladle crank shaft 94 repeats the cycle of tilting the pouring ladle to start pouring metal into the next succeeding mold passing through the casting zone.

The control circuit includes limit switches in automatic stopping circuits to safeguard the equipment in case of the failure of any-critical element of the machine. For example, an electrical switch I36 is operated by the pouring ladle tilting plunger I2 in such manner as to remain open when the plunger is in a position which returns the ladle to its upright or non-pouring position. If the electronic circuit or its relay or the hydraulic system for the ladle tilting mechanism should fail to return the pouring ladle to its non-pouring position, the switch I36 on the ladle tilting plunger will remain closed. This completes a circuit between the power line and a limit switch I31 at the end of the pouring ladle carriage travel. When the carriage reaches the end of its travel, its limit switch I3! is closed and completes the line circuit through a solenoid I38 which opens a control switch I40 for the main drive motor. When the drive motor 21 stops, the casting wheel and the walking beam stop so that no additional metal is delivered to the pouring ladle. The relatively low head of molten metal in the pouring ladle is consequently dissipated quickly without overflowing the mold in front of the ladle.

A similar automatic stopping circuit is provided for the dipping ladle trunnion plunger 85. If the dipping ladle hydraulic plunger fails to operate and fails to raise the dipping ladle trunnions to the non-pouring position, an electrical switch I4I associated with the plunger will remain in its closed position (while the plunger is in its position corresponding to the ladle pouring position). This completes a circuit paralleling the other automatic circuit and including the limit switch I 31 for the pouring ladle carriage.

When the carriage reaches the end of its travel.-

its limit switch I31 closes and completes the line circuit through the solenoid I38 which opens the control switch I40 to stop the drive motor.

When the casting machine is started without any reservoir of molten metal in the pouring ladle, no metal will be cast from the pouring ladle into the mold and there will be nothing to operate the electronic control circuit and its relay II3. Consequently, the automatic stopping circuits will stop the dipping ladle and casting wheel after the dipping ladle has made one complete rocking cycle. In order to continue operation of the dipping ladle, the control switch I4ll may be manually held in the closed position until enough molten metal has been delivered to the pouring ladle to be poured from the latter in its pouring position. The control switch is then released and will remain in the closed operating position during normal automatic operation of the machine.

The apparatus is provided with suitable adjusting features to make possible accurate control of the size and shape and surface uniformity of the cast forms. For example, in addition to the mold guide tracks which keep the molds horizontal without swaying or other irrelevant motion, the individual molds may be accurately aligned with respect to their supporting frames. Thus, as shown in Fig. 14. each mold issecured to its frame by bolts I42 extending upwardly through the frame into the bottom of the mold. Shims I43 may be inserted adjacent these bolts in order accurately to align the mold with the horizontal and to raise or lower each mold vertically with respect to the frame so as to insure the positioning of each mold directly below and close to the lip of the pouring The design of the casting wheel and its drive to avoid tremors which would produce ripples in the surface of the cast forms may be supplemented by providing the casting wheel shaft 38 with a brake I44, as shown in Fig. 2. The brake creates a constant drag on the shaft and dampens any tremor caused by lost motion in the driving gears. Other means than a friction brake may be used to dampen or eliminate backlash and similar tremor-producing factors. Smooth drive may also be obtained by a fluid drive or magnetic drive mechanism rather than a gear drive between the motor 21 and the casting wheel shaft 3i. Alternatively, the casting wheel shaft may be driven by a, small gear engaging a large diameter gear mounted. on the shaft. Such a gear arrangement minimizes the multiplication of lost motion or backlash effected by the use of a small drive gear mounted on the casting wheel shaft.

The amount of molten metal cast into the molds may be readily adjusted by altering the level of the capacitor plate IOI above the mold. This may be done by raising or lowering the capacitor supporting rods I41 (Fig. 14) which are adjustably mounted in the insulator I02, or by the adjusting screws I I2 on which the capacitor support shoes II I rest, or a combination of both ad justments. An additional fine adjustment may be made by the setting of the variable condenser I28 in the bridge circuit I21.

The amount of molten metal delivered to the pouring ladle by the dipping ladle may be controlled by adjusting the length of the connecting arm I45 between the plunger 85 and the bell crank 84 which carries the dipping ladle trunnions. The lower end of this connecting arm is threaded so that is may be screwed into or out of the end of the plunger 85. The amount of metal delivered may be so accurately adjusted that no perceptible change in level of molten metal in the pouring ladle can be observed from hour to hour. Thus, the pouring ladle comprises a reservoir of molten zinc of substantially constant level. The molten metal poured from this reservoir is replaced at it is discharged by the delivery of molten metal from the forehearth.

The metal level in the forehearth should be maintained substantially constant in order to insure a uniform rate of delivery of metal from the dipping ladle. This level may be maintained ciable variation in the molten metal level in the forehearth may be compensated by adjustment of the supporting position of the dipping ladle trunnions or by re-setting the miter gears 50 and wheel.

levelling ofthe molds in such manner as to elim- 15 ll in order to alter the phase of the dipping ladle rocking movement.

The flow velocity and the rate at which molten metal is poured from the pouring ladle to the molds and from the clipping ladle to the pouring ladle may also be further controlled by conven: tional hydraulic valve controls which vary the speed and motion of the hydraulic plungers. In this manner, initiation of pouring from either or both ladles may be started gently or rapidly, as desired, and termination or the pouring may be similarly controlled to give optimum results.

Other delivery means than a dipping ladle may be used to transfer molten metal from the forehearth to the pouring ladle, the principal requirement of such means being that it be capable of maintaining a substantially constant level of metal in the pouring ladle. For example, a siphon of suitable material such as silicon carhide, or the like, may be used to connect the forehearth to the pouring ladle. Metal will flow through the siphon from the forehearth to the ladle when the ladle is tilted into its pouring position because of the lowering of the metal level in the ladle with respect to the metal level in .the forehearth. The flow will stop when the pouring ladle is returned to its non-pouring positlon. The positioning of the baille I4'B near the lip of the pouring ladle prevents the discharge of any skimmings from the ladle to the molds regardless of the means for delivering .metal from the forehearth to the pouring ladle. Skimming formed on the surface of molten metal between the baffle H6 and the lip of the pouring ladle may be eliminated effectively by continuously delivering sal ammoniac to this surface of molten metal (as in the galvanizing art) or by providing a sulfur dioxide (S02) atmosphere in contact with this surface of the metal.

All elements of the apparatus cooperate toward achievement of a single endthe production of cast forms of substantially uniform shape and size and substantially free of surface irregularities.

. 16 rate of delivery may be adjusted as described to deliver metal at an established rate from a body of metal maintained at a substantially uniform level in the forehearth. The amount of metal delivered by the dipping ladle is controlled by coordination of movement of .the pouring and dipping ladies, their movement into pouring position being controlled ultimately by the main drive motor which operates the castingwheel and their movement to anon-pouring position being controlled by the electronically. controlled relay.

Operation of the relay at the desired level of molten metal in each mold, in-spite of surface irregularities caused by turbulent flow of metal as the mold is being filled, is insured by the averaging effect provided by the relatively large area of the capacitor plate with respect to the width of the mold.

We claim: I

1. Apparatus for casting molten metal into forms of uniform size and substantially free of surface irregularities comprising a frame, a casting wheel mounted on said frame for rotation about a horizontal axis, a plurality of molds disposed adiacent the periphery of the wheel, guide means capable of maintaining the molds in a uniform position with respect to the horizontal as the wheel is rotated and the molds are moved through a casting zone and a cooling zone, driving means for rotating the wheel at an uninterrupted uniform speed such that the molds are moved serially and smoothly through said casting and cooling zones, 9. pouring ladle mounted on said frame adapted to pour molten metal into each mold as the mold passes through the casting zone; said pouring ladle having its pouring lip positioned close to the top of the mold in the casting zone when the ladle is tilted to its pouring position, means for tilting the pouring ladle,- and pouring control means capable of initiating and terminating the pouring of molten metal from the ladle to the. mold, said pouring control Although the apparatus is particularly effective for casting flat slabs of metal in open molds, it may be used with advantage in casting other forms such as closed-mold slabs, billets, and the like. The massive casting wheel and its drive provide smooth rotation of the wheel and hence smooth movement of the molds carried by the The mold guide tracks insure uniform inate sway, jerking or other irrelevant movement of the molds carrying molten metal. The mold tipping device in the discharge zone efiects discharge of the solidified metal without disturbing the tranquility of molten metal in the other molds. The pouring ladle, in following each mold through the casting zone, permits pouring over a sumcient period of time to avoid an excessively high pouring rate. Incidentally, it is the pouring rate which determines the output capacity of the "apparatus; the diameter of the casting wheel and maintenance of a substantially uniform level of" molten metal in the pouring ladle. This uniform level is maintained by the dipping ladle whose means including (a) a capacitor plate of such size as to extend over a major portion of at least one horizontal dimension-of the mold, (b) spacing means for positioning the capacitor plate a fixed distance above the desired level to which the mold is to be filled, and (c) an electric control circuit responsive to the electrical capacity between said plate and the molten metal poured into the mold capable of operating the tilting means to terminate the pouring of metal into the mold when the mold is filled to said desired level. 2. Apparatus for casting molten metal into forms of uniform size and substantially free of 5 surface irregularities comprising a frame, a casting wheel mounted on said frame for rotation about a horizontal axis, a plurality of molds disposed adiacent the periphery of the wheel, guide means capable of maintaining the molds in a uniform position with respect to the horizontal as the wheel is rotated and the molds are moved through a casting zone and a cooling zone, driving means for rotating the wheel at an uninterrupted uniform speed such that the molds are moved serially and smoothly through said casting and cooling zones, a pouring ladle mounted on said frame adapted to pour molten metal into each mold as the mold passes through the casting: zone, said pouring ladle having its pouring lip positioned close to the top of the mold in the casting zone when the ladle is tilted to its pouring position-means for tilting the pouring ladle, means for delivering molten metal from a body thereof to the pouring ladle when the latter is tilted to its pouring position so as to maintain l7. a substantially constant, volume oi molten metal in the ladle whereby .the metal is poured into the mold from a substantially constant level, and pouring control means capable of initiating and terminating the pouring of molten metal from the ladle to the mold, said pouring control means including (a) a capacitor plate of such size as to extend over a major portion of at least one horizontal dimension of the mold,- (b) spacing means for positioning the capacitor plate a fixed distance above the desired level to which the mold is to be filled, and (c) .an electric control circuit responsive to the electrical capacity between said plate and the molten metal poured. into the mold capable of operating the tilting means to. terminate the pouring ofmetal into the mold when the mold isfllled to said desired level.

3. Apparatus for casting molten metal into forms of .uniform size and substantially free of surface irregularities comprising a frame, acasting wheel mounted on said frame 'for rotation about a horizontal axis. a plurality of molds dlsposed adjacent the periphery of the wheel, guide means capable of maintaining the'molds in a uniform position with respect to the horizontal as the wheel is rotated and the molds are moved through a, casting zone and a cooling zone, driving means for rotating the wheel at an uninterrupted uniform speed such that the molds are moved serially and smoothly through said casting andcooling zones, a pouring ladle mounted on said frame adapted to pour molten metal into each mold as the mold passes through the casting zone, said pouring ladle having its pouring lip positioned close to the top of the mold in the casting zone when the ladle is tilted to its pouring position, means for tilting the pouring ladle, means for delivering molten metal from a body thereof to the pouring ladle when the latter is tilted to its pouring position so as to maintain a substantially constant volume of molten metal in the ladle whereby the metal is poured into the mold from a substantially constant level, and

pouring means capable of so controlling the tilt 01' the pouring ladle as to deliver moltenv metal therefrom at low velocity to the mold'in the casting zone and to'tilt the ladle' to 'its nonpouring position when the molten metal in the mold has risen to a desired level, said pouring control means including (a) a capacitor plate of such size as to extend over a major portionof at least one horizontal dimensionof the mold, (b) spacing means for positioning the capacitor plate a fixed distance above the desired level to which the mold is to be filled, and (c) an electric control circuit responsive to the electrical'capacity between said plate and the molten metal poured into the mold capable of operating the tilting means to terminate the pouring of metal into the mold when the mold is filled to said desired level.

' ROBERT A. GERHARD.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 113,249 Broadmeadow Apr. 4, 1871 308,405 Durfee et a1 Nov. 25, 1884 623,053 Walker Apr. 11, 1899 729,755 Gates ..1 June 2, 1903 1,033,254 Lister July 23, 1912 1,336,768 Warren Apr. 13, 1920 1,367,059 Landon Feb. 1, 1921 1,792,545 McClure Feb. 17, 1931 1,809,623 Francis June 9, 1931 1,898,722 Ford Feb. 21, 1933 2,032,016 Hitner Feb. 25, 1936 2,064,734 Crawford Dec. 15, 1936 2,104,406 Sorensen Jan. 4, 1938 2,246,907 Webster June 24, 1941 2,290,083 Webster July 14, 1942 CHARLES SYDNEY TREWIN. I