Apparatus and method for controlling molten metal pouring from a holding vessel

Abstract

A molten metal holding and pouring apparatus ( 10 ) including a holding vessel ( 12 ) with a sealable chamber ( 22 ) and a pour spout ( 26 ) extending from the chamber ( 22 ), a gas supply assembly ( 40, 42, 44 ) formed and coupled to pressurize the chamber ( 22 ), and a control assembly controlling the pressure-induced outflow of molten metal ( 14 ) from the chamber ( 22 ) through the pour spout ( 26 ). The control assembly includes a pressure sensor ( 54 ) coupled to sense chamber pressure, a distance sensor ( 50 ) formed and positioned to directly sense the level of molten metal ( 14 ) in the chamber ( 22 ) without contacting the molten metal and a controller ( 80 ) responsive to the sensors ( 50, 54 ) to control operation of the gas supply assembly. Additionally, a pour spout level sensor ( 46 ) senses the level of the metal ( 14 ) in the pour spout ( 26 ) and signals a pour timer ( 76 ) or integration module ( 77 ) when each pour begins. The apparatus also includes a low flow rate capacity inlet valve ( 45 ) and pressure booster assembly ( 90, 96 ). A method of pouring molten metal ( 14 ) from the apparatus ( 10 ) is also disclosed.

1 . A molten metal holding and pouring apparatus comprising: 
 a holding vessel having a sealable molten metal containing chamber with a pour passageway extending from the chamber to a pour spout outlet;    a gas supply assembly formed and coupled to pressurize the chamber in order to control the level of molten metal in the pour passageway; and    a control assembly including a pressure sensor formed and positioned to sense the pressure in the chamber above the molten metal, a chamber distance sensor formed to sense the distance to the top of the molten metal in the chamber, and a controller coupled to the pressure sensor and the chamber distance sensor to receive sensor signals therefrom and coupled to the gas supply assembly, and the controller being responsive to signals received from the sensors to cause the gas supply assembly to pressurize the chamber to control the level of molten metal in the pour passageway and to control the outflow of molten metal from the vessel.    
   
   
       2 . The apparatus as defined in  claim 1  wherein, 
 the control assembly further includes a pour spout level sensor formed and positioned to sense the level of molten metal in the pour passageway.    
   
   
       3 . The apparatus as defined in  claim 2  wherein, 
 the pour spout level sensor is a distance sensor formed and positioned to sense the distance to the top surface of the molten metal in the pour passageway.    
   
   
       4 . The apparatus as defined in  claim 2  wherein, 
 the pour spout level sensor is a contact and withdraw level sensor.    
   
   
       5 . The apparatus as defined in  claim 1  wherein, 
 the gas supply assembly includes a relatively low flow rate capacity inlet valve fluid coupled to control of the flow of pressurized gas to the chamber, and    the gas supply assembly includes a gas supply booster device formed to boost the pressure of the gas at the inlet valve to effect an increase in the flow rate of gas through the inlet valve as the sensed level of molten metal in the chamber diminishes.    
   
   
       6 . The apparatus as defined in  claim 5  wherein, 
 the booster device increases the flow rate of gas through the inlet valve continuously and in an increasing manner as the level of molten metal in the chamber lowers.    
   
   
       7 . The apparatus as defined in  claim 1  wherein, 
 the chamber distance sensor is provided by a wave-operated distance sensing device.    
   
   
       8 . The apparatus as defined in  claim 7  wherein, 
 the wave-operated distance sensing device employs radar frequency waves to sense distance.    
   
   
       9 . The apparatus as defined in  claim 3  wherein, 
 the chamber distance sensor and the pour spout distance sensor are both wave-operated distance sensing devices.    
   
   
       10 . The apparatus as defined in  claim 1  wherein, 
 the gas supply assembly includes a source of pressurized gas, a conduit array coupling the source of compressed gas to the chamber, a valve assembly mounted in the conduit array and formed to control the gas pressure supplied to the chamber, and wherein the pressure sensor is positioned to sense gas pressure in at least one of the conduit array and the chamber.    
   
   
       11 . The apparatus as defined in  claim 8  wherein, 
 the pressure sensor is mounted in the conduit array.    
   
   
       12 . The apparatus as defined in  claim 11 , and 
 a booster device mounted in the conduit array in advance of the inlet valve and formed to increase the pressure at the inlet valve to increase the flow rate of gas to the chamber for any given inlet valve opening.    
   
   
       13 . The apparatus as defined in  claim 12  wherein, 
 the booster device includes a computation module receiving control signals from the chamber distance sensor representing the level of molten metal in the chamber, the computation module generating an output signal which is inverse to the control signal received from the distance sensor, and the booster device being responsive to the inverse output signal from the computational module to gradually increase the flow of pressurized gas from the source of compressed gas to the chamber as the level of molten metal in the chamber lowers.    
   
   
       14 . The apparatus as defined in  claim 13  wherein, 
 the computation module output signal comprises an electrical signal, and a converter coupled to receive the electrical signal and responsive thereto to generate an analogous pneumatic computation module signal, the pneumatic computation module signal being fluid coupled to and operating the booster device.    
   
   
       15 . The apparatus as defined in  claim 10  wherein, 
 the gas supply assembly further includes:    a. a summing junction formed to receive signals from the pressure sensor and the chamber distance sensor and formed to add the values of the signals received to produce a process variable signal representative of the level of molten metal in the pour passageway;    b. a set point module formed to and generating a set point signal representative of a desired level of molten metal in the pour passageway;    c. a controller receiving the process variable signal from the summing junction and the set point signal from the set point module, and responsive thereto to generate a controller signal as an output; and    d. wherein the inlet valve is responsive to the controller signal to control the flow rate of gas to the chamber.    
   
   
       16 . The apparatus as defined in  claim 15 , and 
 a timer coupled to maintain the set point signal for a predetermined duration of time.    
   
   
       17 . The apparatus as defined in  claim 15 , and 
 an integration module coupled to maintain the set point signal until a predetermined amount of molten metal has been poured from the vessel.    
   
   
       18 . The apparatus as defined in  claim 15 , and 
 a device formed and coupled to varying the value of the set point signal during the passing of molten metal through the pour passageway.    
   
   
       19 . The apparatus as defined in  claim 15  wherein, the controller signal comprises an electrical signal, and wherein the inlet valve assembly further includes a converter for receiving the electrical signal from the controller and converting the electrical signal into a pneumatic output signal.  
   
   
       20 . The apparatus as defined in  claim 15  wherein, 
 the inlet valve is located in the conduit array entering the vessel for controlling the flow of pressurized gas into the chamber, and an exhaust valve in the conduit array for exhausting pressurized gas from the conduit array.    
   
   
       21 . The apparatus as defined in  claim 20  wherein, 
 the inlet valve and exhaust valve operate as a split range pneumatic control device responsive to the pneumatic output signal.    
   
   
       22 . The apparatus as defined in  claim 21  wherein, 
 the split range control device is formed to open the exhaust valve and close the inlet valve in the absence of a control signal.    
   
   
       23 . The apparatus as defined in  claim 22  wherein, 
 the split range control device closes the exhaust valve as the output signal increases from a low value to a mid-range value and opens the input valve as the output signal increases from the mid-range value to a maximum value.    
   
   
       24 . The apparatus as defined in  claim 1  wherein, 
 the vessel includes a fill passageway communicating with the chamber, the fill passageway including a receiving inlet positioned at an elevation higher than the pour spout outlet of the pour passageway, such that the fill passageway facilitates the refilling of the chamber with molten metal while the chamber contains pressurized gas.    
   
   
       25 . A molten metal holding and pouring apparatus comprising: 
 a holding vessel having a sealable molten metal containing chamber with a pour passageway extending from the chamber to a pour outlet;    a gas supply assembly formed and coupled to pressurize the chamber in order to control the level of molten metal in the pour passageway; and    a control assembly including a pressure sensor formed and positioned to sense the pressure in the chamber above the molten metal, a chamber level sensor formed and positioned to sense the level of molten metal in the chamber, a pour spout distance level sensor formed to sense the level of molten metal in the pour passageway, and a controller coupled to the sensors to receive signals therefrom and coupled to send control signals to the gas supply assembly, and the controller being responsive to the sensor signals to send control signals to the gas supply assembly pressurizing the chamber to control the level of molten metal in the pour passageway and to control the outflow of molten metal from the vessel.    
   
   
       26 . The apparatus as defined in  claim 25  wherein, 
 the pour spout distance level sensor is a wave-operated distance sensing device.    
   
   
       27 . The apparatus as defined in  claim 26  wherein, 
 the wave-operated distance sensing device utilizes radar frequency waves.    
   
   
       28 . The apparatus as defined in  claim 25  wherein, 
 the chamber level sensor is a distance level sensor.    
   
   
       29 . The apparatus as defined in  claim 28  wherein, 
 the chamber level sensor is a wave-operated distance sensing device.    
   
   
       30 . The apparatus as defined in  claim 29  wherein, 
 the wave-operated distance sensing device utilizes radar frequency waves.    
   
   
       31 . The apparatus as defined in  claim 25  wherein, 
 the gas supply assembly includes a computation module receiving a signal from the chamber level sensor representing the level of molten metal in the chamber, the computation module generating an output signal which is inverse to the signal from the chamber level sensor, and a pneumatic booster coupled to receive the computation module output signal, the pneumatic booster producing an increased flow of pressurized gas to the chamber as the level of metal in the chamber diminishes.    
   
   
       32 . The apparatus as defined in  claim 31  wherein, the computation module output signal is an electrical signal, and a converter coupled to receive the electrical signal and formed for transforming the electrical signal into a pneumatic signal, the pneumatic signal being fluid-coupled to operate the pneumatic booster.  
   
   
       33 . The apparatus as defined in  claim 31  wherein, 
 the chamber level sensor is a weight sensing device.    
   
   
       34 . The apparatus as defined in  claim 25  wherein, 
 the control assembly further includes:    a. a summing junction coupled and formed to add the values of an input signal from the pressure sensor and an input signal from the chamber level sensor, the summing junction being responsive to the input signals to output a process variable signal representative of the level of molten metal in the pour passageway;    b. a set point module generating a signal representative of a desired level of molten metal in the pour passageway;    c. a controller receiving the process variable signal from the summing junction, and receiving the set point signal from the set point module, and generating a control signal as an output; and    d. a valve assembly being responsive to the control output signal from said controller to control the pressurization of the chamber.    
   
   
       35 . The apparatus as defined in  claim 34 , and 
 a timer coupled to maintain the set point module signal for a predetermined duration of time.    
   
   
       36 . The apparatus as defined in  claim 34 , and 
 an integration module coupled to maintain the set point module signal until a predetermined amount of molten metal has been poured from the chamber.    
   
   
       37 . The apparatus as defined in  claim 34  wherein, 
 the set point module is formed for variation of the set point module signal during the outflow of molten metal through the pour passageway.    
   
   
       38 . The apparatus as defined in  claim 34  wherein, the controller output signal is an electrical signal, and wherein the valve assembly further includes a converter for receiving the electrical signal from the controller and converting the electrical signal into a pneumatic signal.  
   
   
       39 . The apparatus as defined in  claim 34  wherein, 
 the valve assembly includes an inlet valve located in the conduit array for controlling the flow of pressurized gas into the chamber and an exhaust valve located in the conduit array for exhausting pressurized gas from the conduit array.    
   
   
       40 . The apparatus as defined in  claim 39  wherein, 
 the inlet valve and the exhaust valve are fluid coupled in a split range control configuration acting oppositely with respect to one another in response to the pneumatic signal.    
   
   
       41 . The apparatus as defined in  claim 25  wherein, 
 the pour spout distance level sensor is an electrical contact and withdraw level sensor.    
   
   
       42 . The apparatus as defined in  claim 25  wherein, 
 the chamber level sensor is a load cell mounted to sense the weight of the vessel and charge.    
   
   
       43 . A molten metal holding and pouring apparatus comprising: 
 a holding vessel having a sealable molten metal containing chamber with a pour passageway extending from the chamber to a pour spout outlet;    a gas supply assembly formed and coupled to pressurize the chamber with a gas in order to control the outflow of molten through the pour passageway; and    a gas supply booster device fluid coupled to the gas supply assembly and formed to boost the pressure of the gas delivered to the chamber as the volume of molten metal in the chamber decreases.    
   
   
       44 . The apparatus as defined in  claim 43  wherein, 
 the gas supply assembly includes an inlet valve having a relatively low flow rate capacity, mounted between the booster device and the chamber.    
   
   
       45 . The apparatus as defined in  claim 44 , and 
 a chamber level sensor mounted to sense the level of molten metal in the chamber and formed to produce a chamber level sensor signal, the gas supply booster device being coupled to receive the chamber level sensor signal and being responsive thereto to boost the flow rate of pressurized gas delivered through the inlet valve to the chamber.    
   
   
       46 . The apparatus as defined in  claim 45  wherein, 
 the chamber level sensor is formed to sense the distance from the level sensor to the top surface of the molten metal.    
   
   
       47 . The apparatus as defined in  claim 45  wherein, 
 the chamber level sensor is provided by a weight sensing assembly.    
   
   
       48 . The apparatus as defined in  claim 45  wherein, 
 the booster device includes a computation module receiving the chamber level sensor signal representing the level of molten metal in the chamber, the computation module generating an output signal which is inverse to the chamber level sensor signal, and the booster device receiving the computation module output signal and being responsive thereto to increase the flow of pressurized gas to the chamber as the level of metal in the chamber diminishes.    
   
   
       49 . The apparatus as defined in  claim 48  wherein, 
 the computational module output signal is an electrical signal, and a converter for transforming the electrical computation module output signal into a pneumatic computation module signal for operation of the booster device.    
   
   
       50 . A molten metal holding and pouring apparatus comprising: 
 a holding vessel having a sealable molten metal containing chamber with a pour passageway extending from the chamber to a pour spout outlet;    a gas supply assembly formed and coupled to pressurize the chamber with a gas in order to control the outflow of molten through the pour passageway; and    a pour spout distance level sensor formed and positioned to sense the level of the top surface of molten metal in the pour passageway and coupled to the gas supply assembly.    
   
   
       51 . The apparatus as defined in  claim 50  wherein, 
 the pour spout distance level sensor is a wave-operated distance sensing device.    
   
   
       52 . The apparatus as defined in  claim 41  wherein, 
 the wave-operated distance sensing device utilizes radar frequency waves.    
   
   
       53 . A pressure-based method of pouring molten metal from a metal holding vessel comprising the steps of: 
 sensing the distance from a sensor to the top of a charge of molten metal in a sealed chamber of a molten metal holding vessel;    sensing the pressure of a gas in the chamber over the molten metal; and    pressurizing the chamber over the molten metal in response to a combination of the sensed distance and the sensed pressure to produce a controlled outflow of molten metal from the chamber through a pour passageway.    
   
   
       54 . The method as defined in  claim 53  wherein, 
 the step of sensing the distance is accomplished by employing a wave-operated distance sensor.    
   
   
       55 . The method as defined in  claim 53  wherein, 
 the step of sensing the distance is accomplished by employing a radar distance sensor.    
   
   
       56 . The method as defined in  claim 53 , and the steps of: 
 sensing the level of molten metal in the pour passageway; and    employing the sensed level of molten metal in the pour passageway to control the duration of outflow of molten metal through the pour passageway.    
   
   
       57 . The method as defined in  claim 56  wherein, 
 the step of sensing the level of molten metal in the pour passageway is accomplished using a distance measuring sensor that does not contact the molten metal.    
   
   
       58 . The method as defined in  claim 57  wherein, 
 the step of sensing the level of molten metal in the pour passageway is accomplished using a radar-based distance sensor.    
   
   
       59 . The method as defined in  claim 56  wherein, 
 the step of sensing the level of molten metal in the pour passageway is accomplished using a contact and withdraw level sensor assembly.    
   
   
       60 . The method as defined in  claim 53  wherein, 
 the sensing steps and the pressurizing step provide a self-correcting closed loop control process.    
   
   
       61 . The method as defined in  claim 53 , and the step of: 
 repeating the pressurizing step to produce a plurality of successive controlled outflows of molten metal.    
   
   
       62 . The method as defined in  claim 61 , and the step of: 
 between each outflow of molten metal, maintaining a partial pressure over the metal in the chamber.    
   
   
       63 . The method as defined in  claim 53 , and the step of: 
 boosting the flow of compressed gas to the chamber as the level of molten metal in the chamber decreases.    
   
   
       64 . The method as defined in  claim 53  wherein, 
 the pressurizing step is accomplished by controlling the flow of gas from a source of compressed gas to the chamber with a self-correcting, closed loop control circuit.    
   
   
       65 . The method as defined in  claim 63  wherein, 
 the pressurizing step is accomplished by controlling the flow rate of gas into the chamber using an inlet valve having a relatively low flow rate capacity.    
   
   
       66 . A method of pouring molten metal from a containment vessel having a sealable chamber and a fluid connected pour passageway extending from the chamber comprising the steps of: 
 pressurizing the chamber with a gas in response to a combination of a level of molten metal sensed in the chamber and the pressure sensed in the chamber to control outflow of molten metal from the chamber through the pour passageway; and    sensing the level of molten metal in the pour passageway to control the length of time of the pour.    
   
   
       67 . The method as defined in  claim 66  wherein, 
 the step of sensing the level of metal in the pour passageway is accomplished by employing a distance sensor without contacting the molten metal.    
   
   
       68 . The method as defined in  claim 67  wherein, 
 the step of sensing the level of metal in the pour passageway is accomplished by employing a wave-operated distance sensor.    
   
   
       69 . The method as defined in  claim 68  wherein, 
 the step of sensing the level of metal in the pour passageway is accomplished using a radar sensor.    
   
   
       70 . The method as defined in  claim 66  wherein, 
 the pressurizing step is accomplished in response to a level of molten metal sensed directly using a distance sensor sensing the level from a position out of contact with the molten metal.    
   
   
       71 . The method as defined in  claim 70 , and the step of: 
 mounting a relatively low flow rate capacity inlet valve to control gas flow into the chamber, and    boosting the rate of gas flow through the inlet valve to the chamber in response to a sensed diminished level of molten metal in the chamber.    
   
   
       72 . A pressure-based method of pouring molten metal from a sealed chamber of a holding vessel comprising the steps of: 
 pressurizing the chamber to produce an outflow of molten metal from the chamber through a pour passageway;    sensing the level of molten metal in the chamber; and    boosting the rate of pressurization of the chamber during the pressurizing step as the level of molten metals in the chamber diminishes.    
   
   
       73 . A method of pouring molten metal from a sealed containment chamber of a vessel through a pour passageway comprising the steps of: 
 a. pressurizing the chamber to effect the steps of 
 1) first bring the level of molten metal in the passageway up to a ready-to-pour level closely proximate and below an outlet of the passageway;  
 2) thereafter raise the level of molten metal from the ready-to-pour level through the threshold of pouring level to a pour level above the outlet for the outflow of molten metal from the outlet; and  
 3) thereafter lower the level of molten metal in the passageway to below the outlet level; and  
   b. during the pressurizing step, timing the interval from the moment the threshold of pouring level is reached to the start of the lowering step to enable an accurate determination of the quantity of molten metal outflowed from the passageway outlet.    
   
   
       74 . A method of pouring molten metal from a containment vessel comprising the steps of: 
 pressurizing a sealed chamber in the vessel containing a molten metal charge to urge molten metal out of the chamber and up a pour passageway to a ready-to-pour level in the passageway closely proximate an outlet of the passageway;    increasing the pressure in the chamber to urge the level of molten metal up to a known pour level above the outlet of the passageway outlet; and    continuing to increase the pressure in the chamber to maintain the level of molten metal at the pour level for a period of time producing an outflow of a desired quantity of molten metal from the outlet; and    reducing the pressure in the chamber to allow the molten metal in the passageway to fall below the outlet level.