Apparatus for applying mold wash

Nov. 7, 1950

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T. K. GRAHAM

APPARATUS FOR APPLYING MOLD WASH

Filed Dec. 17, 1948

2,529,291

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FIG. 2

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FIG. 3

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INVENTOR

77?077?as

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Patented Nov. 7, 1950

2,529,291

UNITED STATES PATENT OFFICE

2,529,291

APPARATUS FOR APPLYING MOLD WASH

Thomas K. Graham, Great Falls, Mont., assignor to Anaconda Copper Mining Company, New York, N. Y., a corporation of Montana

Application December 17,1948, Serial No. 65,763

Claims.

This invention relates to apparatus for applying mold wash to molds, and for like purposes. In the casting of molten metal in metallic molds it is customary to coat the mold with an aqueous suspension of finely divided bone ash, finely divided alumina, or other refractory material. Such a suspension is called “mold wash.” It serves to improve the quality of the casting, especially its surface, and to prevent sticking of the casting to the mold. Heretofore it has usually been applied by swabbing or painting it on the mold surface shortly before casting the molten metal.

The apparatus of the invention is effective for applying mold wash to molds automatically. It is designed to insure-even and complete coating of the mold; It is especially adapted to apply mold wash automatically-to permanent metallic molds mounted at intervals about the periphery of a casting wheel-such-as is used in casting copper anodes, wirebars, etc. When used in connection with such molds-it reduces to a minimum the manual-labor incident to applying tlie? mold wash,- and thereby its use leads to important operating economies;

The new apparatus comprises a pivotally mounted pneumatic spray nozzle to which is connected a source of mold wash. A spring is arranged for urging the nozzle to one limit of its pivotal mounting, in which position it is normally held; and a pneumatic cylinder having a piston connected to the nozzle is provided for moving the nozzle on its pivotal mounting through an arc against the force of the spring to direct it from one end to the other of the mold. A source of compressed air is connected through a normally closed, electrically opened control valve (e. g. a solenoid valve) both to the air cylinder and to the nozzle. An electrical relay connected to the valve opening means and to a power source serves when energized to effect opening of the control valve. Thereby compressed air is admitted to the nozzle for spraying mold wash therefrom, and simultaneously compressed air is admitted to the pneumatic cylinder for moving the nozzle through its limited path of travel to direct the mold wash over the length of the mold. An adjustable needle valve is best provided in the pipe through which compressed air enters the pneumatic cylinder so that the rate at which the nozzle is moved through its arcuate path may be adjusted in relation to the pressure of the compressed air. A timer is connected to the relay for de-energizing it, and through it for de-energizing the valve opening means, upon (Cl. 22—88) &lt;

elapse of a predetermined time interval following initial energization of the relay. Thereby, alt the end of such time: interval, the control valve is closed, the flow of mold wash from the nozzle ⁵ is discontinued, and ·the nozzle is returned by the spring to its original position. . .

A presently preferred embodiment of the invention, incorporating the foregoing and other features, is shown in the accompanying drawings, 10 in which

Fig. 1 is a plan of the new apparatus positioned at the periphery of' an anode casting wheel;

Fig. 2 is an elevation of the apparatus shown ¹⁵ in Fig: 1; and . .

Fig. 3-is a diagram of one'form of electrical control circuit for automatic operation, of the apparatus. ^; 7

The new apparatus 10 for applying mold wash ²⁰ is shown in Figs; 1 and 2 positioned near the periphery of a casting wheel f l carrying a series of anode (or other) molds 12, 13, etc., at spaced angular intervals. At various stations around the periphery of the casting wheel a coating of ²⁵ mold wash is applied to an empty mold 12, molten copper is. cast into a previously coated mold, hot cast anodes in. molds are cooled with water sprays, and soiidifled'anOdes are removed from the molds. . Periodically,. as these operations are completed 3₀ at each station, the casting wheel is . rotated through the-angular distance between molds to bring a new mold to each station and the operations are repeated. This conventional operation of the casting wheel is not itself a part of 35 the invention, but the operation of the apparatiis 10 for applying the-mold wash, which does constitute the- subject matter of the invention, is correlated with operation of the casting wheel so as to apply a coating-of rhold wash to each mold as it? comes - into the position occupied by the mold 12 in Fig.,1.

The· apparatus- IB comprises a tank (4 supported'on legs and kept filled to a constant level with- a supply of mold wash delivered from a reservoir or mixing tank through a pipe 15 and a float-controlled valve 16. A light framework' 17 advantageously made of pipes and pipe fittings extends upwardly from the tank 14 and supports a series of pneumatic nozzles 18 by which mold wash is sprayed into the cavity of the anode mold 12 in position for. receiving mold wash.: The nozzles are mounted in a row on a supporting bar 19 which is free to turn on its axis through at least a small arc. A lever 26 is also secured, to this support bar for rotating it and the nozzles

2,629,291 mounted on it through the arc of travel, so that a stream of mold wash 21 being discharged from the nozzle may be directed from one end to the other of the mold, thereby to coat the entire mold cavity.

A pneumatic cylinder 22 mounted for tilting movement on a pivot support 23 carried by the framework contains a piston 24. A connecting rod 25 connects the piston with the lever 20 by which the nozzle support bar is turned. A compression spring 26 bearing against the end of the cylinder 22 and against the lever 20 urges the support bar into the position shown in Fig. 2 for directing the spray of mold wash into the end of the mold cavity that is nearest the spray apparatus. When, however, compressed air is admitted to the cylinder, the piston is forced to the rear of the cylinder and pulls the lever 20 back against the pressure of the spring 26, thereby tilting the nozzles in a clockwise direction (as viewed in Fig. 2) to direct the stream of mold wash along the length of the mold to the end of the. cavity that is remote from the spray apparatus.

Compressed air is supplied to the cylinder 22 for the above purpose from a header pipe 27 through a flexible branch hose 28 and an adjustable needle valve 28. The needle valve permits adjustment of the rate at which the piston 24 is forced to the rear of the cylinder 22 in relation to the pressure of compressed air in the header 27, and thereby permits control of the time of travel of the mold wash spray from one end to the other of the mold cavity.

The position at which the connecting rod 25 is pivotally fastened to the lever 20 is made adjustable so that the magnitude of the arc. through which the nozzles are tilted by the pneumatic cylinder may be adjusted to conform with the length of the mold. The mounting of the cylinder 22 on the pivot support 23 permits this adjustment to be made, and permits back and forth movement of the piston 24, even though the connecting rod be rigidly connected to the piston.

' A series of flexible branch hoses 30 are provided to connect each nozzle i 8 with the compressed air header pipe 27. Each nozzle is also connected to the constant level tank by a flexible hose 3 1 through which mold wash is delivered to the nozzles. The hoses 31 are provided at their lower ends with ball weights 32 for keeping them immersed in the mold wash in the tank 14; and to avoid supporting the ball weights from the spray nozzles, a plate 33 supports the ball weights just below the liquid level.

Compressed air is admitted to the header pipe 27 through a main supply pipe 34 from a compressor 35. A pressure gauge 36 and a pressure regulator 37 are connected in series to the supply Pipe 34. Also connected in series with this pipe is a solenoid-operated main control valve 38 for turning on and off the supply of air to the header pipe 27 during normal operation of the apparatus. The solenoid valve is normally closed, and normally there is no discharge of mold wash from the nozzles and the nozzle support bar is tilted by the spring to the limit of its travel shown in Fig. 2. When the solenoid valve 38' is opened, however, and compressed air is thereby admitted to the header pipe, some of the air flows to the nozzles 18 and causes the spray of mold wash to be discharged therefrom, and some of the air flows into the pneumatic cylinder and causes the nozzles to be tilted in the manner described above. When the solenoid valve is again closed, the flow of compressed air through the pneumatic nozzles 18 is cut off and the spray of mold wash stops. Thereupon the cylinder 22 is vented to the atmosphere through the header pipe and the nozzles, permitting the spring to return the piston and the nozzle support bar to their original positions.

To facilitate venting the air cylinder 22, and also to permit finer adjustment to be made by the needle valve 29 in the rate of travel of the piston 24 to the rear of the cylinder when compressed air is admitted to the header pipe, a very small hole 39 is drilled in the cylinder wall near the needle valve. The hole is made small enough so that the flow of compressed air into the cylinder through the needle valve when the control valve 38 is opened is faster than its escape from the cylinder to the atmosphere through this hole.

In order to provide for automatic operation of the apparatus, the solenoid 40 which when energized opens the main control valve 38 is connected in circuit with a relay 41, a timer 42, a normally opened switch 43, and a power line 44. The arrangement is such that when the switch 43 is closed momentarily, the relay 41 closes, thereby energizing the solenoid and opening the valve 38. At the same time the timer 42 is set in operation, and after a predetermined time interval, it effects reopening of the relay 41, thus deenergizing the solenoid and causing the valve 38 to close again. The time interval provided by the timer 42 for keeping the valve 38 open is made just sufficient for spraying the interior of the mold cavity uniformly from one end to the other with a coat of mold wash.

The switch 43, which is of the type that is normally held open by a spring, is mounted near the periphery of the casting wheel 11. It is provided with a lever 45 by which it may be momentarily closed, and this lever is located so as to be engaged by any of a series of switch-tripper lugs 46 mounted about the periphery of the wheel. These, switch-tripper lugs are spaced apart by angular intervals equal to the spacing of the molds. The position of the switch and of the lugs 46 on the casting wheel is such that the switch 43 is momentarily closed each time a mold 12 comes into position to receive a coat of mold wash, and upon such closure of the switch 43, the mold wash applying apparatus 10 is set into operation in the manner described.

An advantageous electrical control circuit including the relay 41, the timer 42, and the switch 43 is shown diagrammatically in Fig, 3, The relay 41 includes a solenoid 47. which operates two normally opened contacts 48 and 49 and a normally closed contact 50. The valve solenoid winding 51 is connected to the. power, line 44 through one of the normally opened contacts 49. One terminal of the relay solenoid 47 is connected to one side of the power line 44 through- a parallel circuit one leg of which includes the switch 43 and the other leg of which includes the other normally opened relay .contact 48. The other terminal of the relay solenoid is connected to the other side of the power supply line through a timer relay contact 52 which is held closed so long as a timer solenoid 53 is energized. This timer solenoid is supplied with direct current from a rectifier 54 through the normally closed contact 50 of the relay. The rectifier is energized from the power line 44 through a transformer 55.

Operation of the control circuit is as follows:

The circuit is shown in Fig. 3 in the position in

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Which the solenoid coil 51 is de-energized-and in which therefore the valve 38. is closed. When the casting wheel 11 rotates enough to bring a new mold into position to receive a coat of mold wash, the switch 43 is momentarily closed by one of the switch-tripper lugs 48. Thereby a circuit connecting the relay solenoid 47 to the power supply line 44 is completed through the switch 43 and through the timer contact 52. In consequence the normally opened relay contacts 48 and 49 are closed, and the normally closed relay contact 50 is opened. This at once completes a circuit from the power line through the relay contact 49 and valve solenoid winding 5 ί and causes the valve 38 to open. - At the same time the circuit through the relay, solenoid. 47 is- closed through the relay contact 4'8; so^: that; if flow the switch 43 is reopened, the relay solenoid is not on that account de-energized. The circuit through the timer solenoid 53 is broken as a result of opening the normally closed² relay contact 50, but^: the timer relay contact 52 does not open- at once because when the magnetic field in the timer solenoid 53 begins to decay, a^: current tending to oppose such decay-is generated in- a copper ring 58 surrounding the solenoid. The effect· of this ring is to delay the decay of the magnetic field in the timer solenoid for an appreciable-period of time. After a lapse of some time interval, however, it does decay to the point at which the timer contact 52 opens, and when this occurs, the relay 47 is at once de-energized. Thereupon the circuit through the valve solenoid winding 5i is broken and the valve closes. Simultaneously the circuit through the timer solenoid is closed again through the normally closed relay contact 50, once, again causing the timer contact 52. to close; but now the relay solenoid 47 remains de-energized because both the switch 43 and the normally opened relay holding contact 48 are both open. Thus the circuit is once more in the position to go through the same cycle of operations.

It is evident that the length of time for which the valve 38 is held open is 'determined by the time required for decay of the magnetic field in the timer solenoid 53. This may be controlled by increasing or decreasing the number or size of the copper rings 56. In lieu of the copper rings, the timer solenoid may include a separate timer winding in which the current opposing decay of the magnetic field is induced. The rate at which this current is allowed to dissipate, and hence the timing cycle of the timer, may be controlled by short-circuiting such timer winding through an adjustable high resistance potentiometer or rehostat.

The particular construction of the timer and relay is not a part of the present invention. A suitable form of timer and relay has been described solely for the purpose of providing a full disclosure of a complete operative apparatus. There are many different types of relays and many different types of timers, including mechanical timers and electronic timers in addition to electromagnetic timers such as that described above, available on the market and any of them may be adapted for use in the apparatus of the invention.