US3331429A - Pneumatic pressure casting apparatus - Google Patents

Description

July 18, 1967 HARRISON ETAL PNEUMATIC PRESSURE CASTING APPARATUS Filed June 8, 1965 haven-rams Games Hmmsow FEW wumrom United States Patent 3,331,429 PNEUMATIC PRESSURE CASTING APPARATUS George Harrison, Ber-Wyn, and Nelson K. Harrison, Riverside, Ill., assignors to Imperial-Eastman Corporation, Chicago, 111., a corporation of Illinois Filed June 8, 1965, Ser. No. 462,184 4 Claims. (Cl. 164-157) This invention relates to improvements in methods and apparatus for making metal castings.

It is an object of the present invention to provide a method and apparatus for casting metal by applying gas pressure to the surface of liquid metal to force the metal into a mold and in doing so controlling the application of the pressure so that the mold is filled without turbulence, thereby eliminating the formation of oxides in the casting. The method and apparatus are particularly suitable for the chill casting of brass.

It is a further object of the present invention to provide a method and apparatus of the type stated in which the pressure on the metal is regulated so as to increase progressively and be maintained at predetermined regulated pressures during the mold filling operation. In the preferred form of the invention a regulator valve is interposed in the gas pressure line that leads from a source of air or inert gas to a sealed box or chamber to which the surface of the metal is exposed. The pressure in the chamber tends to vary from the desired amounts at any given moment in the mold filling cycle due to imperfect sealing of the chamber and other factors diflicult to control. As a result, the flow of metal into the mold is sometimes erratic. However, the gas pressure regulator valve is responsive to decreases in pressure in the sealed chamber so that upon a drop in pressure therein below the regulated pressure, the valve will admit gas to the chamber to bring it up to the regulated pressure. Furthermore, the setting of the regulated pressure may be controlled automatically to increase progressively the desired regulated pressure during filling of the mold.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawing forming a part thereof.

FIG. 1 is a view partially in section and showing apparatus constructed in accordance with and embodying the present invention;

FIGS. 2 and 3 are fragmentary sectional views taken along lines 2-2 and 33 respectively of FIG. 1; and

FIG. 4 is a diagram showing the operation of certain control valves of the apparatus.

Referring now in more detail to the drawing, 1 designates a portion of the casting machine shown in FIG. 8 of our copending United States application Ser. No. 143,39l, filed Sept. 1, 1961, now Patent No. 3,228,073, and its corresponding French Patent No. 1,337,530. The entire disclosures of the aforesaid application and corresponding patent are by reference incorporated herein. Suflice to say that the aforesaid casting machine includes a cup 2 that supports an open top crucible 3 that is surrounded by heat insulation 4. Above the cup 2 is a platen 6 which supports a die or mold holder 7 into which a copper mold 8 having a mold cavity is threaded. The top of the mold cavity 10 may be closed off by a suitable member that includes a forging punch 11 and surrounding counterpunch 13. A passageway 14 surrounds the mold 8 through which cooling water may be circulated from inlet and outlet lines 16, 17. At its lower end the mold 8 has a mold-filling gate 18 which communicates with an inter nally tapered mold-filling tube 19 that projects downwardly from the mold holder 7 for immersion into the liquid metal 21 in the crucible 3.

An O-ring 22 forms a seal between the platen 6 and 3,331,429 Patented July 18, 1967 cup 2 to form a sealed chamber 24 so that gas may be supplied to the chamber 24 for applying pressure to the surface of the metal 1 to force it upwardly to the tube 19 and mold gate 18 to fill the mold cavity 10. Suitable mechanism of the type shown in the aforementioned co-pending application may be used to move the cup 2 together with the crucible 3 from the position shown in FIG. 1 herein to a downwardly retracted position in which the lower end of the mold-filling tube 19 is entirely outside of the liquid metal 21.

With the parts of the apparatus in the position shown in FIG. 1, gas from a compressed gas source may be supplied through a regulator valve assembly 26 and flexible air line 27 to apply air pressure to the top surface of the liquid metal 21. The assembly 26 has an inlet 29, an outlet 30, and a valve 31 which when seated closes oif communication to the outlet 30 and thus shuts off the supply of gas to the line 27. The valve 31 has a stem 32 which is attached to a diaphragm 33 that is peripherically clinched and sealed to cooperating parts of the housing 34 of the assembly 26. A port 35 provides communication with the adjacent side of the diaphragm 33 so that pressure in the line 27 and chamber 24 is applied to the exposed side of the diaphragm. Applying force to the other side of the diaphragm 33 is a coil spring 36. The force supplied by the spring 36 is controlled by a rod 37 that is axially slidable in a bushing 38 and projects outwardly of the assembly housing, terminating in a roller 39.

The regulated or controlled pressure of the valve 31 is determined by the force of the spring 36 against the diaphragm 33. When the force due to pressure on the side of the diaphragm 33 that is exposed to the port 35 (and hence to the pressure in the chamber 24) overcomes the force of the spring 36, the diaphragm will flex and pull the valve 31 closed. If the pressure in the chamber 24 drops below the regulated pressure, the spring 36 will flex the diaphragm 33, opening the valve 31 and thereby supply more gas to the chamber'24 to bring the pressure therein up to the regulated pressure.

The rod 37 may be moved progressively axially toward the diaphragm 33 to increase the pressure of the spring 36 on the diaphragm 33 and thereby progressively increase the regulated pressure on the surface of the metal 21 during filling of the mold cavity 10. The progressive increase of the gas pressure on the metal 21 is such as to raise the metal upwardly to fill the mold cavity 10 slowly and without turbulence. That pressure need be only that suflicient to overcome the weight of the liquid metal. During filling of the mold cavity, gas therein may be vented through one or more mold vents 41.

The movement of the rod 37 to increase the regulated gas pressure may be controlled in any suitable manner. In the form of the invention shown, the rod roller 39 engages the edge 42 of a cam 43 which is moved by a piston 44 and piston rod 45 from the full line positions shown in FIG. 1 to the dotted line position shown there in. The cam bar 43 is pivotally secured by a pin 47 that is mounted in a plate 48 having an elongated slot 49 which receives the cam bar 43. The angle of inclination of the cam edge 42 may be adjusted by pivoting the cam bar 43 upwardly and downwardly about the pivot pin 47 and securing the bar in position by a set screw 51 that threads into the end of the plate 48 and abuts the arcuate trailing end of the cam bar 43. The plate 48 has four rollers 52 which ride in elongated slots 53, 54 which are formed in supporting side members 56, 57. Four additional rollers 58 are mounted on the lower side of the plate 48 and roll along the inside surfaces of the side members 56, 57. These side members 56, 57 may be bolted or otherwise suitably secured together at the proper spaced apart distance. Forwardly of the pivot pin 47 an L-shaped arm 60 is welded or otherwise rigidly secured connected to the outwardly projected end of the piston rod 45, thereby forming a driving connection between the piston rod 45 and the plate 48. The cylinder 62 for the piston 44 may also be supported by the side members 56 or 57. Likewise the valve assembly 26 may be mounted on a cross piece 63 that extends between the upper edges of the side members 56, 57.

The piston 44 may be reciprocated by hydraulic fluid supplied through lines 66, 67 and valves V and V These valves are each of a conventional type that provide free flow in one direction and an adjustable flow control in the opposite direction. conventionally in these valves the adjustable flow control is a needle valve. The valves V V respectively have adjustable flow in the directions indicated by their adjacent arrows in FIG. 1 and free flow in the opposite directions. Since the controls of the valves V V may be adjusted to control the flow of hydraulic fluid therethrough, they may be used to regulate the speed I of movement of the piston 44. Preferably the adjustments of flow are such that the piston 44 has a return stroke (i.e. to the left, FIG. 1) that is faster than the forward stroke.

At the commencement of the mold filling operation, the gas pressure in the chamber 24 is at its lowest. The piston 44 moves the cam bar 43 to the right. The stroke of the piston 44 is accurately timed and the angle of inclination of the cam edge 42 is adjusted to fill the mold as rapidly as possible without turbulence of the liquid metal. Movement of the cam bar 43 to the right elevates the rod 37 so that progressively increasing force is applied to the spring 36 and thus progressively increasing regulated gas pressure is applied to the liquid metal 21. Any drop in gas pressure on the metal at any time during filling ofthe mold will result inmore gas being delivered to the chamber 24 to increase the pressure in the chamber 24 to the regulated pressure at that particular time of the mold filling cycle.

After the metal in the mold has solidified the cup 2 maybe retracted from the platen 6, and the casting may be forged by the punch 11 and the counterpunch 13 in a manner shown in our aforementioned copending application. Since the punching end of the punch' 11 is of a shape that is a counterpart of the mold gate 18 a slug of solid metal is punched out of the casting. The platen 6 may then be separated from the casting and the punches retracted to strip the casting therefrom.

Referring to FIG. 4, oil from a source of hydraulic pressure is supplied through line 71 and an electromagnetic valve V selectively to lines 66, 67. Line 72 is a return line to the oil source. The valve V is operated by coils 70, 73 to connect lines 71, 72 to lines 66, 67 respectively, or in a reverse relationship. When the coil 70 is energized, oil is supplied through lines 71 and 66 and oil is returned through lines 67 and 72 to move piston 44 in its forward stroke. When the coil 73 is energized, the valve V moves to the left and connects line 71 to line 67 and line 66 to line 72 to move the piston in its return stroke. The circuit for the coil 70 is from electric power line L through coil 70 to a switch contact 75. The circuit for the coil 73 is from the power line L, through coil 73 to a switch contact 76. A cam having sections 78, 79 engages selectively the switch contacts 75, 76 so that only one of the two coils 70, 73 is energized at any one time. The cam sections 78, 79 may be assumed to be connected to a power line L and the cam may be driven by an actuator, such as a timer motor, diagrammatically illustrated at 80. The circuit shown in FIG. 4 may form part of the automatic timer and control arrangement for the machine, as shown in FIGS. 13 and 14 of our aforesaid copending application. The cam sections are such that contact 75 is engaged by the cam section 78 to ini- A tiate the forward stroke of the piston 44 just after the cup 2 is sealed against the platen 6. The switch contact 7 76 is engaged by the cam section 79 to initiate the return stroke of the piston 44 just after the cup 2 is retracted from the platen.

When the invention has been shown and described in connection with the machine of our copending application, it will be apparent that the controlled mold filling is equally applicable to other types of permanent molds, to sand molds, and to other types of casting apparatus.

In compliance with the requirements of the patent statutes we have herein shown and described a preferred embodiment of the present invention. It should be understood, however, that the invention is not limited to the precise form shown and described, but same being merely illustrative of the principles of the invention. What is new and desired to be secured by Letters Patent is:

1. Casting apparatus comprising a mold, a liquid metal container, means forming a mold filling passageway extending from the mold and into liquid metal in the container, a source of gas pressure, and means for applying progressively increasing pressure from said source to the surface of the liquid metal sufficient to force the liquid through the passageway to fill the mold, said means including a valve through which gas from said source is discharged to said surface, said Valve having control means exposed to the discharge side of said valve through V a path bypassing the flow path of the gas from said discharge side to said surface for opening said valve responsive to decrease in gas pressure on the liquid and for.

closing said valve responsive to increase in pressure of the liquid.

2. Apparatus according to claim 1 in which the mold has a heat conductivity substantially that of copper, the apparatus further having means for chilling the mold.

3. Apparatus according to claim 2 in which a part of the mold cavity wall is a forging punch.

4. Casting apparatus comprising a mold, a liquid metal container below the mold, means forming a mold-filling passageway extending downwardly from the mold and into liquid metal in the container, a source of gas pressure, means forming a substantially sealed chamber to which the surface of the liquid is exposed, conduit means for delivering gas from said source to the chamber and thereby to the surface of the liquid to force the liquid upwardly through the passageway and into the mold, a

pressure regulator valve in the conduit means and having means against which gas pressure in the conduit means on the discharge side of said valve is applied for admitting gas from the gas pressure source to the surface of the liquid to increase the applied pressure on the liquid to a regulated pressure, said valve having control means operatively connected to the last-mentioned means whereby the regulated pressure may be varied, and means operatively connected to the control means and operable during predetermined intervalof time for progressively increasing the regulated pressure during said interval to set the regulated pressure at predetermined values at predetermined times during said interval; said means operatively connected to the control means including a movable member, means for driving said member, and means for adjusting the speed at which the member is driven to adjust the predetermined interval of time.

References Cited UNITED STATES PATENTS 1,981,381 11/1934 Wagner 2269 2,990,591 7/1961 Hursen 2279 XR 3,229,337 1/1966 Holz et al. 2279 WILLIAM J. STEPHENSON, Primary Examiner.

E. MAR, Assistant Examiner.

Claims (1)

1. CASTING APPARATUS COMPRISING A MOLD, A LIQUID METAL CONTAINER, MEANS FORMING A MOLD FILLING PASSAGEWAY EXTENDING FROM THE MOLD AND INTO LIQUID METAL IN THE CONTAINER, A SOURCE OF GAS PRESSURE, AND MEANS FOR APPLYING PROGRESSIVELY INCREASING PRESSURE FROM SAID SOURCE TO THE SURFACE OF THE LIQUID METAL SUFFICIENT TO FORCE THE LIQUID THROUGH THE PASSAGEWAY TO FILL THE MOLD, SAID MEANS INCLUDING A VALVE THROUGH WHICH GAS FROM SAID SOURCE IS DISCHARGED TO SAID SURFACE, SAID VALVE HAVING CONTROL MEANS EXPOSED TO THE DISCHARGE SIDE OF SAID VALVE THROUGH A PATH BYPASSING THE FLOW PATH OF THE GAS FROM SAID DISCHARGE SIDE TO SAID SURFACE FOR OPENING SAID VALVE RESPONSIVE TO DECREASE IN GAS PRESSURE ON THE LIQUID AND FOR CLOSING SAID VALVE RESPONSIVE TO INCREASE IN PRESSURE OF THE LIQUID.

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