US 3504825 A
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April 1970 M. J. DIAMOND ETAL 3,504,825
PNEUMATIC CONTROL OF PRESSURE POURING LADLE Filed Aug. 15. 1966 COMPRESSED AIR SUPPLY rwL DIFFERENTIAL PRESSURE TRANSMITTER DWFERENTML PRESSURE TRANSMITTER VENT IN VEN'J'OR S ATTORNEY United States Patent 3,504,825 PNEUMATIC CONTROL OF PRESSURE POURING LADLE Milton J. Diamond, Saginaw, Mich., and Robert J. Kinsey, Danville, Ill., assignors to General Motors Corporation,
Detroit, Mich., a corporation of Delaware Filed Aug. 15, 1966, Ser. No. 572,259 Int. Cl. B22d 17/32; F27d 3/14 US. Cl. 22261 Claims ABSTRACT OF THE DISCLOSURE A pneumatic control circuit develops a pressure signal as a function of metal height in the pouring spout and controls the ladle air pressure to maintain constant metal height. A differential pressure sensor in the ladle air supply line controls a vent to relieve air pressure when metal is added to the ladle.
This invention relates to pneumatic control apparatus for pressure pouring ladles and articularly to pneumatic control systems for controlling the air pressure in a ladle.
Pneumatic ladles for pouring molten metal into foundry molds comprise an air-tight ladle having a pouring spout attached at the bottom of the main body of the ladle and having a receiving spout also attached at the bottom of the ladle, the open end of both spouts being near the top of the ladle. Air pressure is supplied to the top of a ladle by an air supply line and the air pressure acting on the surface of the molten metal within the ladle serves to force the metal out of the pouring spout. The rate at which the metal pours from the spout into the mold depends upon the height of the metal above the lip of the spout, which in turn depends upon the amount of air pressure within the ladle. For most pouring operations, it is important to maintain a constant pouring rate and hence a constant metal height in the spout because there is an optimum rate at which the metal should enter the mold and because the amount of metal delivered to each mold is often measured by the rate of flow and the duration of flow. When the metal within the ladle is nearly expended, it is desirable to pour in additional metal through the receiving spout without interrupting the normal pouring function of the ladle. However, if the additional metal rises within the ladle, the air entrapped therein tends to increase in pressure and control means must be provided to relieve the excess air without disturbing the critical pressure balance which controls the pouring rate.
Control systems for the control of ladle air pressure previously have been proposed, some of which are not sufliciently accurate and some of which are exceedingly complicated, thereby being expensive to install and expensive to maintain. Previous control systems have also failed to take into account the necessity of properly relieving excess air pressure from the ladle when additional metal is poured into the receiving spout.
It is an object of this invention therefore, to provide improved control means for a pneumatic ladle.
A further object of the invention is to provide improved and simplified pneumatic control means for a pneumatic ladle.
Another object is to provide a simple control for a pneumatic ladle which is capable of reliably maintaining a constant rate of flow from the pouring spout even while additional metal is being supplied to the ladle.
An additional object is to provide a control means for a pneumatic ladle which accommodates the excess pressure created when additional metal is supplied to the ladle.
The invention is carried out by providing means for detecting the metal height within the pouring spout, means for developing a signal which is a function of the metal height and means responsive to the signal for controlling the air pressure within the ladle to maintain a desired metal height.
The invention is further carried out by providing float means detecting the metal height within the pouring spout of a ladle, valve means controlled by the float for passing air through an orifice means at a rate which is a function of the metal height so that a pressure signal developed across the orifice means is proportional to the air flow rate, and means responsive to the pressure signal for adjusting a regulating valve in the air supply means to the ladle. In addition, the invention provides that the orifice means comprises a plurality of selectively utilized orifices, each corresponding to a different desired metal height.
In addition, the invention further provides a controllable vent means in the ladle supply line to relieve excess pressure from the ladle during refilling thereof.
The invention is further carried out by providing means in the air supply line to the ladle for relieving excess pressure from the ladle during refilling thereof including means for detecting the amount of excessive pressure in the ladle and for controlling the degree of venting which is required to maintain the desired metal height in the pouring spout. The above and other advantages will become more apparent from the following description taken in conjunction with the drawing which is a schematic diagram of a pneumatic control apparatus for a pneumatic ladle according to the invention.
Referring to the drawing, there is shown a pneumatic ladle 10 having a receiving spout 12 and a pouring spout 14. An upstanding lip or dam 15 is formed at the end of the pouring spout 14. A mold 16 is disposed adjacent the pouring spout 14 to receive the molten metal issued from the spout. As stated above, the rate at which the metal issues from the spout is dependent upon the height of the metal in the spout. An air line 18 is communicably connected to the top of the ladle. A pressure control system monitors the rate at which the air is supplied to or withdrawn from the ladle. A part of the pressure control system is a float 20 in the pouring spout arranged to detect the height of the metal in the spout by floating on the metal Within the spout, and the float is mechanically connected to an air regulating valve 22. A source 24 of compressed air having a pressure of p.s.i., for example, is connected to three pressure regulators 26, 28 and 30. The regulators feed air to a pressure control line 32, a pressure transmitter line 34 and an air supply line 36. Air floating through the air supply line 36 goes to a gauge 38, a diaphragm operated control valve 40, an orifice or restriction 42 and finally flows to the ladle via the air line 18. The control valve 40 is capable of supplying air to the ladle or venting air from the ladle depending on the valve posi tion. A vent valve 44 is connected to the air line 18 between the orifice 42 and the ladle 10, and is arranged to controllably vent air from the air line to the atmosphere. A pressure differential transmitter 46 is connected across the orifice 42 with the high pressure side of the transmitter connected at the side of the orifice closest to the ladle.
The differential pressure transmitter 46 has an output line connected to a diaphragm 48 which operates the vent valve 44. The transmitter 46 is a device well known in the art which serves to provide an amplified output pressure which is proportional to the input pressure differential. The ressure control line 32 extending from the pressure regulator 26 contains a gauge 50 and the air flow control valve 22 in series with an orifice means 52. The orifice means 52 comprises a pair of orifices or restrictions 54 and 56 in parallel having one side connected to the air line from the air flow valve 22, and other side being vented to atmosphere. One orifice 54 is used to control the high metal height in the pouring spout while the other orifice 56 of a smaller size controls the low metal height corresponding to a non-pouring condition. Each orifice has a valve 58 and 60 in series therewith for selectively admitting air to the orifices. The valve 58 and 60 are preferably solenoid controlled and are arranged so that one valve is normally opened while the other is normally closed. Other means of controlling the valves may be substituted, however. The orifices 54 and 56 are of different sizes so that for a given air fiow through the air flow valve 22, different pressure differentials will be created across the orifice means depending on which valve, 58 or 60, is open.
The pressure transmitter line 34 extends from the pressure regulator 28 to a gauge 62 and to a difierential pres sure transmitter 64. Input lines 66 of the differential pressure transmitter 64 extend to either side of the orifice means 52 so as to detect the pressure signal from the orifice means. The differential pressure transmitter 64 amplifies the pressure signal and supplies an output to the dia phragm 68 which operates valve 40 in the air supply line. Gauge 70 indicates the output pressure of the transmitter 64.
In operation, for the condition when the ladle is pouring molten metal into the mold 16, the position of the float 20 is determined by the height of the metal and the float in turn controls the position of the air fiow valve 22 in the pressure control line 32. The rate of air flow through the pressure control line and the orifice means 52 is therefore controlled by the position of the float operated air control valve. For the pouring condition, the valve 60 for the low height orifice 56 is closed and the valve 58 for the high height orifice 54 is open so that the pressure developed across the high height orifice 54 is proportional to the air flow therethrough. This pressure differential signal is supplied to the input 66 of the differential pressure transmitter 64. The latter device amplifies the pressure signal and the output thereof controls the diaphragm operated valve 40 in the air supply line so as to control the air flow therethrough in a manner to maintain the necessary ladle pressure to keep the metal height relatively constant. That is, when the metal height rises slightly from its desired level, the changing position of the fioat 20 causes the valve 22 to open further than its normal position to increase the air flow through the orifice 54. The resultant increase in pressure thereacross signals the transmitter 64 to increase the pressure on the diaphragm 86 which moves the valve 40 toward its closed position, thereby reducing the pressure to the ladle 10 and lowering the metal height in the pouring spout 14 to its normal level.
When it is desired to stop pouring from the ladle, the valves in the orifice means are returned to normal condition (valve 58 closed and valve 60 open) so that the air will pass through the small low height orifice 56 and the pressure developed thereacross will be greater than it was through the high height orifice. This. therefore increases the pressure signal which causes the diaphragm operated valve 40 to close, and if necessary, the valve 40 will be turned by the diaphragm to venting position to allow air to escape from the ladle until the metal height reaches the desired low level called for by the pressure signal, whereupon any variation thereafter in the metal height will be controlled by the system just described. The low level is preferably just below the top of the lip or dam 15 so that no pouring can occur at that level, yet a change to the high level for pouring can be rapidly accomplished with a minimum air pressure increase in the ladle.
When it is desired to replenish the molten metal in the ladle 10, new metal is poured into the receiving spout 12 causing the level of the metal within the ladle to rise, consequently causing the air within the ladle to become further compressed so that its pressure increases with the result that, in the absence of further control means, the metal height in the pouring spout would increase. The rising motion of the float, however, will cause the control system to turn the valve 40 to venting position so that the excess air within the ladle will be relieved by passing from the ladle through air line 18 and through the valve 40. It has been found, however, that this arrangement for relieving excess air pressure in the ladle is not adequate when additional metal is supplied to the ladle at a high rate. Accordingly, an equalizing system is provided to prevent a large increase in the ladle pressure. The air flowing from the ladle to the valve 40 passes through the orifice or restriction 42 and generates a pressure differen tial signal which is detected and amplified by the differential pressure transmitter 46. That device signals the diaphragm 48 to open the vent valve 44 in an amount proportional to the valve of the orifice pressure diiferential to thereby vent the excess air from the ladle at a rate which will maintain control of the metal height. It will then be possible to pour from the ladle in the normal controlled fashion even while new metal is being provided through the receiving spout.
It will be seen then that the system described herein provides a simple, accurate and improved pneumatic control system for a pneumatic ladle. The specific apparatus described above is the preferred embodiment of the invention and the scope of the invention is not intended to be limited thereto, but rather is limited only by the following claims.
1. Apparatus for controlling the height of metal in the pouring spout of a pneumatic pouring ladle comprising supply means for supplying air pressure to the ladle, pressure regulating means in the supply means, means for developing a signal responsive to metal height in the pouring spout, and means responsive to said signal for controlling the pressure regulating means according to said signal whereby the metal height is maintained at a desired value, wherein the means for developing a signal comprises orifice means, a compressed air supply connected to one side of the orifice means, the other side of the orifice means being vented to atmosphere, and means for controlling the said air supply to the orifice means in accordance with the height of the metal in the pouring spout whereby the pressure signal developed across the orifice means is a function of the metal height.
2. Apparatus as defined in claim 1 wherein the orifice means comprises a plurality of orifices of different sizes selectively connectable to the compressed air supply, whereby a plurality of desired metal heights may be selected.
3. Apparatus as defined in claim 1 wherein the means responsive to said signal for controlling the pressure regulating means according to said signal comprises a difierential pressure transmitter having its input connected to said signal and its output connected to the pressure regulating means.
4. Apparatus as defined in claim 3 wherein the means for controlling the said air supply to the orifice means in accordance with the height of the metal in the pouring spout comprises an air regulating valve between the compressed air supply and the orifice means and means for detecting the height of the metal and for controlling the air regulating valve.
5. Apparatus as defined in claim 4 wherein the means for detecting the height of the metal is a fioat in the pouring spout connected to the air regulating valve.
6. Apparatus for controlling the height of metal in the pouring spout of a pneumatic pouring ladle comprising supply means for supplying air pressure to the ladle, pressure regulating means in the supply means, means for developing a signal responsive to metal height in the pouring spout, and means responsive to said signal for controlling the pressure regulating means according to said signal whereby the metal height is maintained at a desired value, including vent means between the pressure regulating means and the ladle for controllably venting air from the ladle so that when metal is added to the ladle, air displaced thereby will be vented, and detecting means including a conduit connected to said supply means for directly sensing air pressure in the ladle in excess of that called for by the said signal, the detecting means controlling the vent means.
7. Apparatus as defined in claim 6 wherein the detecting means comprises an orifice in the supply means so that a pressure differential will occur across the orifice when air passes from the ladle to the supply means, and further comprises a differential pressure transmitter means connected across the orifice and controllably connected to the vent means for sensing the pressure differential and accordingly controlling the vent means.
8. In a system for controlling metal height in the pouring spout of a pressure ladle, air line means for supplying air pressure to the ladle and relieving pressure from the ladle, means for supplying a regulated air pressure to the air line, a vent means in the air line means for bleeding excess pressure from the ladle, and detecting means including conduit means connected to said air line means for directly sensing an excess of air pressure in the ladle over the regulated air pressure, the detecting means being connected to the vent means to eifect control thereof.
9. In a system for controlling metal height in the pouring spout of a pressure ladle, air line means for supplying air pressure to the ladle and relieving pressure from the ladle, a vent means in the air line means for bleeding excess pressure from the ladle, and detecting means for sensing excess pressure in the ladle, the detect- References Cited UNITED STATES PATENTS 716,321 12/1902 Webster 222397 X 1,714,296 5/1929 Carlson 222396 1,8 13,381 7/ 1931 Carrin gton 222397 X 2,816,334 12/1957 Edstrand 22264 X 3,229,337 l/ 1966 Holz et al 222399 X 3,286,311 11/1966 Rhoads 22261 3,347,427 10/ 1967 Willis 222399 3,058,180 10/1962 Port et al. 164-456 3,384,150 5/1968 Newsome 164155 ROBERT B. REEVES, Primary Examiner F. R. HANDREN, Assistant Examiner US. Cl. X.R.