US3369717A - Sharp cut-off in pressure pour apparatus - Google Patents

Description

Feb. 20, 1968 J. s. CAMPBELL SHARP CUT-OFF IN PRESSURE POUR APPARATUS 2 Sheets-Sheet 1 Filed May 3, 1966 IN VE/v TOR JA MES s. CAMPBELL y v WARREN, BROSLER,

CYPHER 8 ANGL/M ATTORNEYS Feb. 20, 1968 J. s. CAMPBELL. 3,369,717

SHARP CUTOFF IN PRESSURE POUR APPARATUS Filed May 5, 1966 2 Sheets-Sheet 2 i 7/ 69 I a! START STOP 97 POUR 85 POUR 7 95 4Q m E f 5'9 23 93 TE j 75 l/Vl/EA/TOH JAMES s. CAMPBELL WA RREMBROSLER, CYPHE'R 8 AiNGL/M 4 T TOR/VEYS United States Patent 3,369,717 SHARP CUT-OFF IN PRESSURE POUR APPARATUS James S. Campbell, Orinda, Calif., assignor to Quality Casting Systems, a limited partnership Filed May 3, 1966, Ser. No. 547,285 7 Claims. (Cl. 222399) My invention relates to pressure pour apparatus for pouring of liquid, through application of gas under pressure thereto, and more particularly to means for effecting a sharp cutoif of discharge from a pouring tube or the like, at the desired termination of a pour cycle.

Pressure pouring is realized by the application of gas under pressure to the surface of liquid in a confining receptacle or vessel. Where accuracy of pour is a factor, a sharp cut-off of discharge flow can become an important factor toward realizing this.

One thing which complicates the realization of a sharp cutoff in pressure pour apparatus, is the fact that the gas, being under pressure in a confining vessel, it constitutes a resilient gas cushion, and even though one might suddenly drop the pressure of the infiowing gas from thatvalue required for pouring, to that value which will establish a non-pour condition, the gas cushion pressure will not drop as suddenly, but will gradually decay to the lower value and at a rate depending on the nature of the load.

- Thus a sharp cut-off under these conditions is impossible.

A previous approach toward solving this problem involved the sudden bleeding off of some of the gas from the gas cushion, simultaneously with the sudden dropping of the pressure of incoming gas, and immediately directing such released gas against the end of the discharge or pouring tube through which the liquid was being discharged.

This provided two beneficial etI'ects toward realizing a sharp cut-off. Not only did the sudden withdrawal of this gas from the gas cushion, serve to suddenly lower the pressure in such cushion, but such released gas, being under pressure, created a resulting blast against the discharge end of the pouring tube to sever the flow. Thus the two effects cooperated to produce a sharp cut-off.

This solution to the problem, however, posed its own problem, for following such sharp cut-off, a slight after discharge would occasionally follow.

As a possible explanation of this, it is believed that the application of the blast of gas to the end of the pouring tube served to partially drive the column of liquid back into the interior of the receptacle, which in turn, developed a surge to momentarily increase gas pressure in the cushion in spite of the withdrawal of gas from such cushion. In seeking a quick equilibrium from the surge, the resulting expansion of the gas cushion conceivably drove the liquid back up into the pouring tube, and it is believed that the momentum imparted thereto might, on occasion, be sufiicient to produce the slight after effect before equilibrium could be established.

Thus, such apparatus would necessarily, have to be critically designed to minimize such surges, under the conditions under which the apparatus was to function.

Among the objects of my invention are:

(1) To provide novel and improved pressure pour apparatus;

(2) To provide novel and improved pressure pour apparatus having means for assuring sharp cut-off of discharge flow at the desired end of the pour cycle;

(3) To provide novel and improved pressure pour apparatus in which cut-off of discharge flow at the discharge end of a pour cycle can be adjusted, to the characteristics of such apparatus to assure a clean cut-off of flow;

(4) To provide novel and improved pressure pour apparatus in which a sharp clean cut-off of discharge flow at the desired end of a pour cycle may be conveniently obtainable.

Additional objects of my invention will be brought out in the following description of a preferred form of the same, taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a view depicting the apparatus of the present invention in schematic form; and

FIGURE 2 is a circuit diagram applicable to the apparatus of FIGURE 1.

Referring to the drawings for details of my invention in its preferred form, the same, for illustrative purposes, has been shown as embodied in apparatus for the discharging of molten metal from a receptacle which may be a furnace or crucible.

Such apparatus has been fully and completely illustrated and described in the application of Wilfred Ernest Willis for Pressure Pour Apparatus, Serial No. 524,955, filed November 30, 196-5. Briefly, such apparatus entails a receptacle 1 which may be a furnace or crucible for holding metal 3 in molten condition, the receptacle being sealed during operation and having a discharge or pouring tube 5 extending therefrom, to the end of which is afilxed a nozzle assembly 7.

Gas is supplied to the receptacle at either of two pressures, one pressure being a ready-to-pour pressure capable of sustaining a column of the molten metal in the pouring tube to a level 9 just short of pouring, while the other pressure, termed the pour pressure, is sufficient to raise the column of molten metal to the level 11 for pouring, at full capacity of the pouring tube.

Such selective pressures are accomplished, using a tank 13 of gas under pressure, which is selectively coupled through either of a pair of parallel lines 15, 17 to a gas inlet tube 18 entering the receptacle. In one of the branch lines 15 is a pressure regulator 19 adjusted to the pour pressure, while in the other line 17, is a pressure regulator 21 adjusted to the ready-to-pour pressure, the pour pressure line including a shut-off valve 23 which may be of the solenoid operated type with solenoid winding 25, enabling it to be automatically controlled.

Where the metal to be handled is of the non-ferrous type, such as aluminum, magnesium, or the alloys of either, the gas employed should prefer-ably be of the inert type, such as dry nitrogen, argon or the like, which will serve to protect the molten metal from the adverse effects of exposure to gases to be found in the atmosphere.

While for the purpose of the present invention, the gas may enter the furnace above the level of the molten metal therein, in the specific embodiment of the invention illustrated, the gas is conducted into the furnace through the gas inlet tube 18 which terminates at a level substantially below the maximum contemplated level of molten metal in the furnace, but preferably above the lower end of the pouring tube. This relationship, as fully described in the above referred to Willis application, not only makes it impossible to lower the liquid level to the point of exposing the pouring tube to the gas within the receptacle and cause a blowing out of metal in the tube and loss of gas cushion, but what is of just as much, if not greater importance, it permits of the two fixed pressures in controlling the discharge of liquid from the receptacle. This enables one to readily maintain a fixed pouring rate, which is of considerable importance where repeat pouring of quantities of metal of uniform weight is to be realized, such as would be the case in die casting.

Inherent in the operation of this system is the fact that both the pressure and volume of the gas cushion will increase as the liquid level drops toward the lower end 0 the gas inlet tube 18. I

During quiescent conditions, the pour regulator branch line is normally blocked by the valve 23, while the gas, at the lower pressure, which should be just sufficient to maintain a column of liquid in the pouring tube at the ready to pour level 9 just below the lip 35 at the end of the pouring tube, flows through the ready to pour pressure branch line 17. A pouring cycle is then initiated by opening the valve 23, which immediately jumps the pressure of the gas flowing into the furnace, to the pour value which is suflicient to raise the liquid in the pouring tube to the pour level 11 above the lip.

A flow line 39 from the upper end of the receptacle or furnace to a point above the lip, at the junction of the discharge line and nozzle, permits of a flow of gas from the gas cushion to the region at the end of the discharge tube, to blanket the molten metal flowing at this point and thus offer the same protection thereto as the gas in the furnace does for the molten metal therein. A needle valve 41 in this flow line may be adjusted to control the flow therein, which flow at best, will be more in the nature of a leak.

With such flow line installed, elevation of the column of molten metal from the ready to pour level 9 to the pour level 11 will build up pressure in the region adjacent the end of the pouring tube, and such pressure, if permitted free increase, might conceivably interfere with the ability of the column to reach the desired pour level.

Accordingly, there is coupled into this flow line 39, at a point adjacent the discharge end of the pouring tube, a pressure switch 43 which is adjusted to sense and respond to a rise in pressure at this point, to a value deemed insufficient to adversely afiect the ability of the column of molten metal to reach the pour level, and this pressure switch in responding to such pressure build up, brings about a partial venting of the gas flowing from the gas cushion to this region.

Specifically, this may be accomplished by providing a vent line 45 from the leak flow line 39, and installing in this vent line, a normally closed solenoid valve 47, having a solenoid winding 49 to be controlled through the pressure switch.

Inasmuch as this solenoid valve 47 will open during pouring, the inert gas escaping through the vent line might, to great advantage, be directed around the nozzle assembly, so as to blanket with the inert gas, any mold 51 being poured, so as to extend the protection of the inert gas to the molten metal as it flows into such mold.

During a pour cycle, it will be appreciated that the pressure of the gas cushion will exceed that necessary to support a column of molten metal at its ready to pour level in the pouring tube, and consequently, at the termination of the pour cycle, when the pressure of the inflowing gas is dropped to the ready to pour value, there will be a tendency for pouring to continue fllntll the gas cushion pressure decays to a value which will permit the level in the pouring tube to drop to the ready to pour level. This of course, cannot be tolerated under conditions where accuracy of pour is a requirement. A rapid cut-off of the discharge at the termination of a pour cycle is accordingly highly desired, and in fact becomes essential, as when die casting.

This has been accomplished in the aforementioned Willis application, by installing a gas flow line 55 in shunt with or around the needle valve 41 located in the leak flow line 39, and in this shunt flow line is included a normally closed solenoid valve 59 controlled by a solenoid winding 61. At a desired termination of a pour" cycle, this solenoid valve is energized to its open condition, to bring about a blast of gas from the gas cushion, to impact the flowing metal at the end of the pouring tube and effect a severance of the flow at the lip 35. The degree of impact is controllable in the Willis system by a pressure regulator acting as a relief valve, though, I accomplish such adjustment by the installation of a valve 57 in this shunt line.

In view of the variation in pressure and volume of the gas cushion with changing liquid level in the furnace, one could not with this shunt circuit, as such, always be assured of the absence of any reaction following a shgirp cut-off of flow at the discharge end of the pouring tu e.

T o remedy this situation, I provide a reservoir 65 having a flow connection 67 leading thereto, from the upper end of the furnace, to flow couple the gas cushion to the reservoir, and in this flow connection, I install a normally open solenoid actauted valve 69 having a solenoid winding 71, which valve is energized during a pour cycle to hold it closed, and which is de-energized at the termination of a pour cycle to place the reservoir in flow communication with the gas cushion chamber.

From the reservoir, leads a low line 73 which ties in with the vent line 45, and in this flow line is a normally closed solenoid actuated valve 75 having a Winding 77, this valve being energized to its open condition during a pouring cycle, to permit the reservoir to discharge accumulated gas during pouring, to mix with that in the vent flow line for use in protecting the molten metal as it flows into a mold. Control of the flow of gas at the mold is made possible by a manually adjustable valve 79 in the line.

With the reservoir thus connected into the system, it will, upon opening of the valve in the flow connection from. the gas cushion chamber, enable full flow discharge of gas from the gas cushion to the reservoir, which will greatly exceed that previously permissible by the combined slow leak flow line 39 and the shunt line 55, whereby any tendency which might otherwise exist for the gas cushion to compress and expand in response to the cut-off blast at the discharge end of the pouring tube, is avoided.

For most efiicient operation, the size of the reservoir should he correlated to the worst condition apt to prevail in the furnace, which would occur when the liquid level therein drops to its lowermost permissible level, namely around the lower end 'of the gas inlet tube 18, for as previously noted, both the gas cushion pressure and gas cushion volume increases with a lowering of the level in the furnace.

The discharge line 73 from the reservoir performs two quite important functions in the system. In the first place, in discharging the gas which had previously accumulated in the reservoir, and directing it to a mold being poured, it puts such gas to useful service, and thus, the gas is not wasted. In the second place, in so discharging the gas from the reservoir, it conditions the reservoir for the next cut-olf operation.

To assure proper functioning of the system, the various solenoid actuated valves and pressure switch may be connected into a suitable electrical circuit, an illustrative example of which is depicted in FIGURE 2 of the drawings, to which reference will now be made.

Across the lines 79, 81 of a power source 83, is a series arrangement of a spring biased start switch 85 and a spring biased stop switch 87, and the holding coil 89 of a relay 91 having a pair of normally open contacts 93 connected in shunt across the start switch. Upon pressing the start switch, the relay will become energized and close its contacts around the start switch to effect a holding circuit.

In parallel with the relay coil 89 are the solenoid winding 25 of the normally closed solenoid valve 23 located in the branch line of the pour regulator 19, and the winding 77 of the solenoid actuated valve 75 in the discharge line 73 from; the reservoir 65.

Also in parallel with the relay coil 89, and solenoid windings 25 and 77, is the Winding 95 of a relay 97 having a pair of normally open contacts 99. These contacts are in circuit across the lines with the winding 71 of the normally open solenoid actuated valve 69. When the relay 97 becomes energized, the valve 69 closes the flow line to the reservoir 65.

The solenoid winding 61 of the valve 59 is connected across the line 7981 in circuit with normally open contacts 100 associated with the spring biased stop switch 87 and will be energized upon depressing the stop switch.

The pressure switch 43 is one having a pair 'of normally open contacts 103. This switch is connected from one side of the stop switch through the winding 105 of a relay 107 having normally open contacts 109 shunting the pressure switch, whereby upon energization of this relay, its contacts will close to establish a holding circuit.

In parallel with this relay winding 105 is the solenoid winding 49 of the normally closed solenoid valve 47 located in the vent line, and accordingly this solenoid valve unbloc-ks such line when the solenoid winding of this valve is energized.

Thus all conditions will have been established for initiating a pour cycle, the duration of which may be controlled manually by merely depressing the stop switch when desired, which in turn de-energizes (1) the holding relay winding 89, (2) the winding 25 of the solenoid valve associated with the pour regulator, (3) the winding 77 of the solenoid valve in the reservoir discharge line, and (4) the relay winding 95 of the relay which controls the solenoid actuated valve in the line to the reservoir 65. Depressing 'of the stop switch, will, in addition, automatically connect the winding 61 of valve 59 in circuit to open this valve and release a blast of gas against the end of the pouring tube 5. The duration of such blast may be controlled by the operator, for upon release of the stop switch, it will restore itself to its previously prevailing condition, with the winding 61 in open circuit.

The presence of the reservoir 65 in the system, with its associated solenoid valve controls, makes it possible to adjust the gas flow in the shunt circuit to a flow rate which will be just sufficient to accomplish its purpose, the reservoir assuring the minimizing of any disturbances which might be caused by such discharge of gas against the flowing metal at the end of the pouring tube, and such adjustments may be carried out by means of the manually adjustable valve in the line.

In fact, with a reservoir of adequate capacity, the shunt circuit may be dispensed with, for the reservoir, under the circumstances, can drop the gas cushion pressure sufiiciently fast to effect a sharp cut-01f by itself, and without the after effects occasionally experienced with the system of the aforementioned pending application.

While the invention has been disclosed in a system adapted for the dispensing of molten metal from a crucible or furnace, the system may also be employed in the dispensing of liquids in general, and such sharp cut-off feature would be quite desirable in filling successive containers or receptacles with like quantities of liquid. Where the liquid to be dispensed is'one which should be protected from exposure to the atmosphere, inert gas may be employed in the manner described above. Where the liquid is not of such nature, air under pressure may be employed in lieu of an inert gas.

From the foregoing description of my invention in its preferred form, it will be apparent that the same is subject to alteration and modification Without departing from the underlying principles involved, and I, accordingly, do not desire to be limited in my protection to the specific details illustrated and described, except as may be necessitated by the appended claims.

I claim:

1. Pressure pour apparatus for dispensing of liquid comprising a sealable receptacle for holding liquid to be dispensed and providing a gas cushion chamber above such liquid,

a discharge passageway extending from said receptacle from a point substantially below the maximum anticipated liquid level therein to a discharge point at a level above said maximum liquid level,

means for supplying gas under pressure to said chamber to build up a gas cushion against liquid in said receptacle, to a value of pressure sufiicient to cause discharge of liquid through said discharge passageway and initiate a pour cycle,

a reservoir adapted to contain gas at a lower value of pressure,

a flow line from said gas cushion chamber to said reservoir,

means for blocking said flow line during a pour cycle,

and means for unblocking said flow line upon shutting otf of the supply of gas at pour pressure to said receptacle to effect a completion of a pour cycle.

2. Pressure pour apparatus in accordance with claim 1 characterized by a flow line from said gas cushion chamber and terminating adjacent the upper end of said discharge passageway, means for blocking this latter flow line during a pour cycle, and means for unblocking said latter flow line substantially simultaneously with the unblocking of the flow line to said reservoir.

3. Pressure pour apparatus in accordance with claim 1, characterized by said flow line blocking means as including a solenoid actuated valve in said flow line.

4. Pressure pour apparatus in accordance with claim 3, characterized by said solenoid actuate-d valve as being of the normally open type.

5. Pressure pour apparatus in accordance with claim 1, characterized by a leak fiow line from said gas cushion chamber and terminating adjacent the upper end of said discharge passageway.

6. Pressure pour apparatus in accordance with claim 1, characterized by a flow line from said gas cushion chamber and terminating adjacent the end of said discharge passageway, means for blocking said flow line during a pour cycle, means for unblocking said flow line substantially simultaneously with the opening of the flow line to said reservoir, and a continuous leak flow line from said gas cushion chamber and terminating adjacent the end of said discharge passageway.

7. Pressure pour apparatus in accordance with claim 1, characterized by said discharge passageway starting at its lower end in proximity to the bottom of said receptacle, and said means for supply gas to said receptacle as including a gas inlet tube terminating substantially below maximum contemplated liquid level in said receptacle but above the lower end of said discharge passageway, and said reservoir as being of suflicient capacity to substantially instantaneously reduce gas-cushion pressure to 'a value insufficient to sustain discharge of liquid, when the liquid level in said receptacle is in the neighborhood of the lower end of said gas inlet tube.

References Cited UNITED STATES PATENTS 2,520,175 8/1950 Socke 22261 3,208,637 9/1965 Heick 222373 X M. HENSON WOOD, IR., Primary Examiner. HADD S. LANE, Examiner.

Claims (1)

1. PRESSURE POUR APPARATUS FOR DISPENSING OF LIQUID COMPRISING A SEALABLE RECEPTACLE FOR HOLDING LIQUID TO BE DISPENSED AND PROVIDING A GAS CUSHION CHAMBER ABOVE SUCH LIQUID, A DISCHARGE PASSAGWAY EXTENDING FROM SAID RECEPTACLE FROM A POINT SUBSTANTIALLY BELOW THE MAXIMUM ANTICIPATED LIQUID LEVEL THEREIN TO A DISCHARGE POINT AT A LEVEL ABOVE SAID MAXIMUM LIQUID LEVEL, MEANS FOR SUPPLYING GAS UNDER PRESSURE TO SAID CHAMBER TO BUILD UP A GAS CUSHION AGAINST LIQUID IN SAID RECEPTACLE, TO A VALUE OF PRESSURE SUFFICIENT TO CAUSE DISCHARGE OF LIQUID THROUGH SAID DISCHARGE PASSANGEWAY AND INITIATE A "POUR" CYCLE, A RESERVOIR ADAPTED TO CONTAIN GAS AT A LOWER VALUE OF PRESSURE, A FLOW LINE FROM SAID GAS CUSHION CHAMBER TO SAID RESERVOIR, MEANS FOR BLOCKING SAID FLOW LINE DURING A "POUR" CYCLE, AND MEANS FOR UNBLOCKING SAID FLOW LINE UPON SHUTTING OFF OF THE SUPPLY OF GAS AT "POUR" PRESSURE TO SAID RECEPTACLE TO EFFECT A COMPLETION OF A "POUR" CYCLE.

Images