US2990592A - Automatic pressure pouring control mechanism - Google Patents

Description

July 4, 1961 H. H. HuRsEN AUTOMATIC PRESSURE POURING coNTRoL MECHANISM Filed May' 15, 1959 f H//l /1 1/ /1 /f I l/ INVENTOR. M gareel?, @mum-42,.

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United States Patent Wheel Company, Chicago, Ill., a corporation of Y Delaware Filed May 13, 1959, Ser. No. 812,937 Claims. (Cl. 22-69) This invention relates to a method and an apparatus for producing castings, and particularly castings of ferrous metal such as steel Wheels, and is a continuation-impart of my application Serial No 641,362, tiled February 20, 1957.

The invention is concerned with a novel method of accurately and automatically controlling the rate at which molten metal is introduced into a mold during a pressure casting operation.

The basic idea of pressure casting is to force molten metal, against the force of gravity, from a container through a pouring tube and mold gate into a casting cavity of a mold by the application of pneumatic pressure fluid, such as compressed air or other gas, against the metal in the container.

Because the rate of flow of the metal, against the force of gravity, from the container or tank to the mold is dependent upon the application of superatmospheric fluid pressure upon the metal in the tank, accurate control of the applied pressure is highly essential to a successful pressure casting operation.

For example, it is well known that if molten metal is introduced into a permanent mold too slowly, the metal tends to freeze or harden, thus preventing proper filling of all portions of the mold and causing incomplete or defective castings. `On the other hand, too rapid an introduction of metal into the mold causes defective castings because of splashing of the molten steel and, further, results in erosion or other damage to the mold surfaces which either `renders the mold unfit for the particular casting or which necessitates the repair of the mold before it can be re-used. This defeats one of the advantages of pressure casting, namely, greater speed of production over conventional casting methods.

As stated above, the ilow of molten metal from the container to the mold is effected by an increase of pressure in the container which forces the metal to iiow against the force of gravity. 'Ihe flow rate of the molten steel is directly proportional to .the rate of fluid pressure increase. For example, it can be said generally that an increase in air pressure of one pound per square inch will cause the level of molten steel to rise approximately 31/2 inches in a tube. However, because the heat in the container expands lthe pneumatic pressure iluid and tends to build up the pressure, it is extremely difficult to maintain a constant pressure increase in the container. Because of this condition, the rate of the flow of metal is often uneven or erratic 'and this is undesirable from the standpoint of proper casting practice for the reasons stated above. It is well known to those familiar with the art of metal founding that the particular rate of llow of metal into a mold cavity which will result in the best casting is determined by such variable factors as the size of the piece to be cast, the composition of both the metal to be cast and the mold itself, and the temperature at which the metal is poured into the mold. Although the particular pouring rate varies with different casting operations, the optimum condition is, of course, one wherein the particular rate is a constant `and uniform rate of ow. No appreciable deviation from the predetermined rate is desirable.

Although some early patents suggest the basic concept of pressure casting, none of these patents actually teach a method of, or apparatus for, pressure casting that has Patented July 4, 1961 proven successful from the standpoint of commercial production of steel castings in permanent molds.

An important reason why these early patents have not resulted in the commercial production of steel castings by a counter-gravity pressure casting method is that they were not primarily concerned with the casting of steel, as distinguished from other metals. Another reason is that the patentees did not recognize or attempt to solve many of the problems peculiar to the art of pressure casting steel, particularly the problem of providing a constant and uniform rate of flow of metal into the mold.

I have discovered that a pressure forced flow of metal at a substantially even or uniform flow rate can only be achieved by the application against the metal of pressure which is progressively increasing in terms of pounds per square inch per second (or seconds per pounds per square inch) at a constant and uniform rate. Such a rate cannot be attained by prior art devices. For example, attempts have been made, with only moderate success, to achieve such a constant progressive rate increase by means of cam actuated devices. However, such devices not only require a separate, accurately formed, cam for each rate pattern, but, furthermore, cannot compensate for back-pressure buildup, leaks, tempera-ture variables and the like.

Accordingly, it is a primary object of my invention to provide a means of accurately controlling the ow rate of metal into a mold in a pressure casting operation.

Another object of my invention is to provide a method of accurately controlling the pressure applied to molten metal in a pressure casting operation to insure a constant and uniform rate of flow of the metal int-o the mold.

A further object of my invention is to provide an apparatus adapted to automatically provide a predetermined const-ant rate of increase in the pressure of the pneumatic fluid applied to the molten metal to force it into the mold, whereby a constant uniform iiow rate for the metal can be achieved.

A more specific object of the invention is the provision of an electrically operated automatically controlled valve Asystem adapted to provide a constant rate of pressure increase in a pressure casting operation.

Another specific object of the invention is to provide an electrically operated control mechanism which automatically controls the valve system regulating the flow of pressure iluid in a pressure casting arrangement.

These and other objects of my invention will be apparent from an examination of the following description and drawings, wherein:

FIGURE l is a schematic diagram of a pneumatic pressure fluid system including a pneumatic controller device, adapted to control the Supply of fluid to a pressure casting apparatus shown in fragmentary vertical section; and

FIGURE 2 is a diagram of an electrical control circuit adapted to control the controller device of FIGURE 1.

Describing the invention in detail and referring to the drawings, it is seen that a substantially fluid-tight pressure tank or container, designated generally at 10, is connected to a pneumatic pressure fluid line, designated generally at 12, adapted to deliver pneumatic pressure iluid such as compressed air to the tank. The tank is adapted to house a ladle 14 containing molten metal 16, such as steel, to be used in a casting operation.

The container or tank 10 is preferably closed by a removable cover 18 seated on an annular resilient seal 22 and secured -to the container by releasable clamps 24 to afford a substantially air-tight seal between a chamber 26 of the container and the cover 18. The cover 18 is provided with an aperture 28 adapted to receive a pouring tube 32 which is disposed to extend through the cover and into the container to afford a means of transferring the molten metal from the ladle 14 to a mold, indicated generally at 34, which is mounted on the upper extremity of the tube above the cover of the container.

The mold 34 preferably comprises cope and drag sections 36 and 38, respectively, which define therebetween a casting cavity 40. The cope section also presents a riser opening 42 open to the atmosphere and communieating with casting cavity 40.

The drag section is seated on the upper surface of a ange -46 formed on the upper end of pouring tube 32. The drag section also includes la gate 44 extending downwardly from the casting cavity 40 and substantially aligned to communicate with a bore 50 of tube 32 to afford a passageway for metal between the ladle and the mold cavity.

A tapered ring A48 having a central aperture 49 may be provided between the upper surface of cover 18 and the lower surface of tube flange 46 to permit adjustment of the angle of the tube relative to the vertical.

The cope section 36 is provided with a nonconductive sleeve 52 having an opening 53 adapted to receive therethrough a plunger '4. The lower end of plunger 54 extends into casting cavity 40 and is provided with a downwardly facing preferably conical seat S6 adapted for engagement with a complementary upwardly facing seat 58 presented by the upper end of gate 44 to close the latter as hereinafter described. The plunger 54 is formed of `electrically conductive material so that it may act as an electrode, as hereinafter described in conjunction with the operational description of the system.

Pneumatic pressure fluid, such as compressed air is delivered to the line 12 from a main pressure uid intake line 62. The supply of pressure uid from the intake line 62 to the container line 12 is controlled by an intake valve 64 and a control valve 66, and exhaust of pressure fluid from container line 12 is controlled by an exhaust valve 68. All three valves are preferably pneumatically operated diaphragm type valves. Intake and control valves 64 and 66 are located in the intake line 62 adjacent its connection to container line 12, while exhaust valve 68 is located in an exhaust air line 70 adjacent the connection of line 70 to line 12.

yControl of intake valve 64 and exhaust valve 68 is achieved by means of a pneumatcally operated 4-way diaphragm valve 72 connected to the respective valves by control air lines 74 and 76, respectively.

Valve 72 is arranged to communicate with control lines 74 and 76 as well as with a pilot line 86 and a line 88 which in turn communicates with a 3-way solenoid valve 90 which serves to pneumatically operate valve 72. Pressure fluid for valve 90 is supplied from pilot line 86 by a yline 96. Pilot line `86 may also be provided with Ia conventional gate valve 98 preferably located between line 96 and valve 72. Actuation of solenoid valve 90 is achieved by relays in an electrical circuit which is hereinafter described.

Valve 66 is regulated automatically by a pneumatic valve control mechanism, indicated generally at 100, which is driven by a motor and clutch arrangement, indicated generally at 101. The arrangement 101 is electrically operated by the novel control circuit shown in FIGURE 2.

The control mechanism 100 is a conventional unit such as sold yby the Brown Instrument Company, Philadelphia, Pennsylvania, a division of the Minneapolis- Honeywell Company and illustrated and described in detail in their catalogue No. 8950 and bulletin No. B112. The mechanism is of the type wherein the desired pneumatic pressure is set or called for by means of a normally manually operated gear 122 indicated diagrammatically in FIGURE l. For example, for each incremental setting of gear 122, a predetermined pressure is obtainable in the controlled unit which, in the present instance, is chamber 26.

The -mechanism 100 is connected to valve 66 by an air line 102 and by a branch line 104. The line 104 is connected to a main supply source (not shown) of pressure fluid and is provided with a restriction 108 through which pressure fluid passes to the control valve 66 and also the mechanism 100. It will be apparent to those familiar With this art that the mechanism described thus far will regulate the valve 66 to furnish an amount of pneumatic pressure fluid to the chamber 26 so that the pressure called for by the setting of gear 122 will be obtained in the chamber. However, as pointed out earlier, there are certain unpredictable variables such as back-pressure buildup in the chamber 26, leaks in the tank or in the associated piping and temperature changes which cause a pressure in the tank different from the pressure called for by the particular setting in gear 122. To this end `a conventional pressure sensing device 118, of the type illustrated in the above-mentioned catalogue No. 8950, is also provided yand is connected by a line to the chamber 26 of pressure tank 10 and is also connected by a line 119 to the mechanism 100.

The sensing device, in a conventional manner well known to those familiar with pneumatic devices is responsive to the actual pressure in the chamber 26 and controls the mechanism 100 to compensate for any deviation in the preselected pressure value in chamber 26 by varying the ow of fluid through line 102 to the valve 66. The valve 66, responsive to the ow variation in line 102, varies the ow of pressure fluid through line 62, line 12 and into chamber 26, whereby the desired pressure condition, as called for by the pre-positioning of gear 122, is maintained in chamber 26 within very close limits.

As mentioned earlier it is necessary, in order to force the metal into the mold at a controlled uniform ow rate, to have a variable pressure which is increasing at a constant rate. It is desirable also that a plurality of rates of pressure increase be provided in order to accommodate, for example, different rates of ow and various shapes and sizes of the mold cavity. To accomplish these functions, a motor and clutch arrangement, indicated generally at 101, is provided. The arrangement i101, which will be described in greater detail hereinafter, is arranged to drive the gear i122 at a predetermined constant rate thereby increasing at a constant rate the pressure condition called for by the gear. The flow of fluid through the valve 66 is thereupon regulated and controlled to provide a constantly increasing pressure in chamber 26 and as a result a constant rate of flow of molten metal from the ladle 14 into the cavity r40 of mold 34. The conventional pressure sensing device `118 which is responsive to the pressure in the chamber 26, controls the mechanism 100 to compensate for any deviations from the incremental constant pressure increase as called for in the mechanism 100 by the predetermined constant rotational speed of the gear 122.

The motor and clutch arrangement 101 comprises a variable speed direct current motor 126 having a shaft which carries a drive gear 127. The gear y127 meshes with an input gear 128, which is keyed or otherwise secured to an external shaft 129 of a single end electromagnetic clutch unit 130. The clutch unit 1=30 is preferably a conventional unit such as Model T-50l2 manu- `factured by the Sterling Precision Instrument Company. The clutch unit 130 also comprises an output shaft 131 which is received internally of the shaft 1129 and which carries at the Outer end thereof an output gear 132 which meshes with the gear 122 in the control mechanism y100.

Power is supplied to the motor 126 by means of a conventional direct current power source, indicated generally a-t 134 in FIGURE 2, and comprising a rectifier and transformer of the kind normally used to convert alternating current to direct current. Output of the D.C. source is selectively directed by means of a multiposition switch, indicated generally at 136, through one of a plurality of resistances, indicated in IFIGURE 2 as R, AR, BR, CR, DR, ER, and FR. The dial of switch 136, which has a plurality of contacts, each ofwhich is connected to an associated resistance, may be calibrated into the circuit and marked in terms of pressure rate increase for the convenience of the operator. The calibration, =for example, may Abe in seconds per pound of pressure increase.

The remaining elements of the electrical control circuit are ybest described in conjunction with a description of a typical cyc/le of operation of the arrangement. The various electrical elements, when described hereinafter, will be designated :by a numeral in parentheses. These numerals correspond to and represent the numerals at the extreme left of the electrical diagram of FIGURE 2.

In order for the device to be operated, a switch -138 is manually closed, whereupon the red indicater light 133 (l) and the green indicator light 135 (13) are energized. The red indicator light remains lit as long as the system is in operation, whereas the green indicator light is lit only during the rst portion of an operating cycle.

The operator then momentarily depresses a start button 140 (2) which completes a circuit to energize the coil of `a relay CRI (2). Energizing relay CRI (2) closes normally open contacts ORI (3) and CRI (11.). Closing contact CRI (3) completes a holding circuit for relay CRI (2) and also completes a circuit to energize the coil of relay CR2 3). Depressing the start lbutton also completes a circuit through the 110 volt coil of a step-down transformer 144. Closing contact CRI (Il) completes the circuit to energize the coil of relay CRA (11). Energization of CRA (ll) closes' contact CRA (12) to energize the coil of solenoid operated valve 90 (12), whereby lthis valve pneumatically actuates control valve 72 (FIG- URE 1) to open the main intake valve 614 and close the main exhaust valve 68.

Depressing the start button 1140 (2) also completes a circuit through the D C. power source 134 ('10) which is arranged to provide both a 6 vol-t and a 24 volt source of direct current. Energization of source y134 (l0) completes a 24 volt circuit through the coil of electromagnetic clutch 130 (12), whereby the clutch is engaged so that any motion transmitted to the input shaft 129 thereof is imparted to the output shaft 131. Simultaneously a 6 volt D.C. circuit is completed through normally closed contact CR3 (14), contacts CR2 (14), a Resistance R 14), and the coil of motor 126 (14). Driving the motor 126 (14) through a predetermined Resistance R rotates the gear 122 (FIGURE l) of control mechanism i100 at a predetermined constant rate of speed which provides the desired initial -rate of pressure increase through the control of valve 66, as described heretofore, until the metal 16 rises in tube 32 and contacts electrode 54 in the mold gate 44. This initial rate is preferably fast to shorten the time of the operational cycle as much as possible.

When the metal contacts electrode 54, a 24 volt circuit is completed from line 2 through the 24 volt coil of transformer 144 (4), relay CR4 (6), electrode 54 (6), the the metal 16 and the tank 10 back to tine 2. Energizing relay CR4 (6) closes normally open contact CR4 (8) to complete a circuit through the coil of relay CR3 (8), whereby contacts CR3 (9') and CR3 (22) are closed and normally closed contacts CR3 13) and CR3 (14) are opened. Closing contacts `CR3 (9) completes a holding circuit through the coil of relay CR3 8) and also completes a circuit to light the white indicator light 137 (9). Opening contact CR3 (13) simultaneously extinguishes the green indicator light 135 (13 Opening contact CR3 (14) breaks the circuit through resistance R to the coil of motor 126. However, the simultaneous closing of contact CR3 (22) completes a ci-rcuit through thelatter contacts, through a preselected contact, for example C, of switch 136, and thence through the preselected resistance, in this instance CR, which corresponds to the desired flow rate, and thence through the coil of motor 126. The speed of motor 126, because of the change in resistance, is reduced and drives the gear i122 through the clutch unit 130 at a ditferent lower rate of speed, and the control '6i mechanism 100 regulates valve 66 to provide a pressure rate increase in chamber 26 which is necessary to lill the mold cavity at the desired uniform rate.

This ow rate continues until the operator sees the molten metal rise in the riser 42, at which time he presses the stop button `142 (3) and also depresses the electrode plunger 54 6) to shut olf the flow of metal into the mold cavity. `Depressingthe stop button 142 (3) breaks the circuits through relays CRI (2) and CR2 (3), de-energizes'the 110 volt circuit of transformer 144, and also de-energizes the D C. power source 134. The motor 126 (14) and clutch -unit 130 (13) are thereby de-energized and, simultaneously, a circuit is completed through the green lightc135 (13), while the circuit is broken through the white indicator light 137 (9). De-energizing the coil of relay'CRI (2) 'also opens contact CRI (1l) to deenergize the coil of relay CRA (11). This relay provides a time delay on de-energization in order to ensure that the'stopper is completely seated before the air supply is shut olf. De-energizing relay CRA (V11) opens contact CRA (12) to de-energize the coil of solenoid operated valve (l2), whereby valve 72 (FIGURE 1) is shifted to close intake valve 64 and to open exhaust valve 68. De-energizing the clutch 130 disengages the connection between gears 128 and 132 whereupon the gear 122 and associated mechanism inthe control are returned to the starting position preferably by means of suitable spring means, not shown. At this time the system is ready for the next pouring cycle.

Thus it is apparent that I have provided a method and apparatus to accurately automatically control the pouring rate of molten metal in a pressure casting operation that are entirely new and novel to the foundry art.

I claim:

1. A pressure casting arrangement including a pressure tank containing molten metal, a mold, means interconnecting the metal in the tank and the mold, a source of pneumatic pressure fluid, means to deliver the uid to the tank to create a superatmospheric pressure in the tank and thereby force the metal against the force of gravity from the tank to the mold, valve means connecting the source to the tank to control the pressure in the tank, said second mentioned means including pneumatic control means operatively connected to the valve means, a

variable speed electric motor, means operatively connecting the motor to the control means for adjusting the latter, and a plurality of selectable resistances associated with said motor whereby the rate of speed of the motor can be regulated to etiect the continuous adjustment of the control means at a predetermined constant rate of change to effect the increase of prsure in the tank at a constant rate, said control means including means responsive to the pressure in the tank to regulate the control means to compensate for any deviation in the rate of pressure increase in the tank from said predetermined rate.

2. A casting arrangement comprising a pressure tank containing molten metal, a mold located without the tank, supply line means to deliver pneumatic pressure uid to the tank, said supply line means including valve means to control the supply of liuid admitted to the tank to regulate the pressure in the tank, automatic control means connected to said valve means to regulate flow of said fluid through said valve means, and motor means connected to the control means to continuously adjust the control means to cause the valve means to provide a pressure increase in the tank at a predetermined constant rate, said control means including means responsive to the pressure in the tank to regulate the control means to compensate for any deviation in the rate of pressure increase in the tank from said predetermined rate.

3. A pressure casting arrangement comprising a pressure tank containing molten metal, a mold, means interconnecting the metal in the tank and the mold, a source of pneumatic pressure timid, pige line ineens t9 deliver said fluid from said source to said tank, valve means in said pipe line means to regulate the pressure build-up in the tank, automatic control means in said pipe line means connected to said valve means to pneumatically regulate said valve means to effect a change of pressure in the tank, and means to automatically eect the continuous adjustment of the control means at a constant rate to provide through the valve means a predetermined constant rate of pressure increase in the tank, said control means including means responsive to the pressure in the tank to regulate the control means to compensate for any deviation in the rate of pressure increase in the tank from said predetermined rate.

4. An arrangement according to claim 3, wherein the means to continuously adjust the control means comprises an electrical circuit including a variable speed electric motor operatively connected to the control means, a plurality of resistances wired in parallel, and readily adjustable means to selectably connect certain of the resistances in series with the motor and thereby operate the motor at a predetermined constant speed to effect the desired adjustment in the control means.

5. A pressure casting arrangement comprising a pressure tank containing material to be cast, a mold, means to transfer the material from the tank to the mold, means to deliver pneumatic pressure Huid to the tank, said delivery means including pneumatically operated valve means to regulate the pressure in the tank by controlling the amount of fluid supplied to the tank, pneumatic control means to pneumatically regulate the valve means to control the supply of liuid supplied to the tank, and means to continuously adjust the control means to provide a constant rate of pressure increase in the tank, said control means including means responsive to the pressure in the tank to regulate the control means to compensate for any deviation in the rate of pressure increase in the tank from said predetermined rate.

6. A pressure casting apparatus comprising a pressure tank, a mold, means affording communication for molten metal between the tank and mold, means to supply pneumatic pressure fiuid to the tank to force the metal from the tank to the mold, said supply means including valve means to control the rate at which said iiuid is supplied to the tank, control means to pneumatically regulate said valve means to provide a predetermined constant rate of pressure increase in the tank, and means to continuously adjust the pneumatic control means at a constant rate, said last mentioned means comprising an electric circuit including a variable speed electric motor operatively connected to said control means, a plurality of resistances, and readily adjustable means to selectably interconnect certain of said resistances with said motor to provide a predetermined speed for the motor, said control means including means responsive to pressure in the tank to regulate the control means to compensate for any deviation in the rate of pressure increase in the tank from said predetermined rate.

7. A device for the pressure casting of molten metals comprising a substantially fluid-tight container adapted to hold molten metal, a mold disposed without said container, means affording communication between said container and a casting cavity presented by said mold, means to supply pneumatic pressure liuid to the container, means to automatically control the supply of said pressure liuid to said container so that the pres- ,ply of said pressure fluid to said container so that the pressure in the container is increased at a constant rate to `force the metal from the container to the mold cavity at a'uniform rate of flow, said automatic control means comprising an electrical circuit and including a pneumatic controller device, a variable speed electric motor operatively connected to said device, and a plurality of resistances wired in parallel wi-th each other and adapted to be selectively connected in series with said motor, said control means also including means responsive to the pressure in the tank to regulate the control means to compensate for any deviation in the rate of pressure increase in the tank from said predetermined rate.

8. A pressure casting arrangement comprising a substantially fluid-tight container for holding molten metal, a mold located above said container, means interconnecting the mold and the molten metal in the container, means to deliver superatmospheric pneumatic pressure liuid at a constantly increasing rate to said container to force the metal against the weight of gravity from the container to the mold at a predetermined constant rate, said last mentioned means including valve means to control the supply of pressure fiuid to the chamber, and control means responsive to the pressure in the container to automatically regulate the valve means to compensate for any deviation from said constant rate.

9. A pressure casting system comprising a container containing molten metal, a mold having a mold cavity connected to the molten metal in the container, a source of pneumatic pressure fluid, valve means connecting the source to the container, control means for regulating said valve means, an electric motor having an operative connection to said control means to cause pressure in the tank to rise at a predetermined constant rate governed by the speed of the motor, and means responsive to pressure in the container for actuating the control means to compensate for variations of pressure in the tank tending to create deviations from said rate.

y l0. A pressure casting arrangement for forcing molten metal, at a predetermined uniform rate, from a pressure tank into a mold having a cavity connecting with the tank comprising: a source of pneumatic pressure fluid; a supply line to deliver uid to the tank to create a superatmospheric pressure therein; valve means for controlling the rate at which fiuid is admitted through said line to said tank; means for automatically electing continuous adjustment of said valve means to provide a predetermined constant rate of pressure increase in the tank and a uniform rate of flow of metal into the cavity; means responsive to pressure in the tank for actuating said adjusting means to compensate for deviation from said predetermined rate; said adjustment means including a pneumatic control device responsive to movement of a movable member, a variable speed electric motor operatively connected to said movable member for driving the latter at a predetermined constant speed, an electric circuit having a first resistance wired in series with the motor to provide a first rate of speed for said movable member and a consequent frst ow rate of metal from said tank to said cavity, a plurality of resistances wired in parallel with said first resistance and with each other, means for disconnecting said first resistance from the circuit and for selectively connecting one of said plurality of resistances in series with the motor to provide a second rate of speed for said movable member and a consequent second flow rate of metal -from said tank into the cavity to till the latter.

References Cited in the tile of this patent UNITED STATES PATENTS 2,847,739 Sylvester Aug. 19, 1958 FOREIGN PATENTS 718,744 Great Britain July l2, 1951 UNITED STATES PATENT OFFICE CERTIFICATE 0F-CORRECTION Patent No., 299o592 July 4@ 1961 Horace Hursen i It is hereby Certified that error appears in the above numbered patent requiring correction and 'that the said Iietters Patent. should read. as

corrected below g Column 7z linev 66 strike out "ply of said pressure fluid to said container so that the pres==" Signed and sealed this 14th day of November 1961.

(SEAL)4 Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer l Commissioner of Patents USCOMM-DC-

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