Method and apparatus for charging metal to a die cast

• US 5,388,633 A
• Filed: 04/15/1993
• Issued: 02/14/1995
• Est. Priority Date: 02/13/1992
• Status: Expired due to Fees

• Current Assignee: The Dow Chemical Company (Dow, Inc.)
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Baker, Carl F., King, Harvey L., Mercer, William E. II
• Primary Examiner(s): Bradley, P. Austin
• Assistant Examiner(s): PUKNYS, ERIK
• Application Number:
  US08/017,099
• Time in Patent Office: 670 Days
• Field of Search: 164/3, 164/4.1, 164/133, 164/136, 164/155, 164/312, 164/304, 164/305, 164/335, 164/337, 164/500, 164/250.1, 164/457, 164/155.5, 164/155.6, 164/155.7, 164/150.1 , 164/155.3, 266/230
• US Class Current: 164/457
• CPC Class Codes: B22D 17/30 Accessories for supplying molten metal, e.g. in rations supplying molten metal in ration in general B22D39/00
• CPC Class Codes: B22D 17/32 Controlling equipment

Abstract

An automatic ladling system is described for delivering a molten metal to the mold or die of a molding or casting machine. The ladling system comprises a programmable logic controller (PLC) for monitoring and controlling the sequential delivery of shots of a precise quantity of molten metal from a furnace or holding pot to a shot delivery apparatus of the casting machine. In the preferred system, the PLC also monitors and/or controls the temperature of the molten metal in the holding pot, the temperature of the molten metal in a metal transfer system, the operation of a pump for pumping molten metal from the holding pot to the shot delivery apparatus, the level of molten metal in the pot, and the operation of the casting machine.

Claims

1. A method for delivering molten metal from a source to a mold or die of a molding or casting machine, wherein the source of molten metal is a furnace or holding pot, or a combination thereof, comprising the steps of:

(a) transferring a predetermined volume of the molten metal from said holding pot to a shot delivery apparatus through a transfer means,

(b) allowing the molten metal to cool and solidify in the die following each charge,

(c) determining the volume of solidified metal charged into the die, and

(d) controlling the delivery of a subsequent volume of the molten metal from the holding pot to the shot delivery apparatus, in response to sequential detection of completion of a preceding charge of molten metal to the shot delivery apparatus, removal of a cast part from the die, and closure of the die; and

e) weighing the casting after removal of the casting from the die, and calculating the volume of the casting based on the density of the metal in the casting.

2. The method of claim 1, wherein said shot delivery apparatus comprises a shot sleeve having a chamber, an inlet for the molten metal in said sleeve, and a ram movable in the sleeve chamber for moving a charge of the molten metal from the sleeve into said mold or die, including the step of measuring the length of solidified metal extending into the shot sleeve, and calculating the volume of the casting including the length of solidified metal extending into the shot sleeve.

3. The method of claim 2, including the step of sensing the distance of travel of the ram with each charge of a quantity of the molten metal into the die to measure the length of solidified metal extending into the shot sleeve, determining the volume and weight of the casting, and then calculating the porosity of the casting.

4. The method of claim 1, wherein the holding pot is sealed to the atmosphere, and including the step of supplying a protective gas to the sealed pot to prevent oxidation of the molten metal in the pot.

5. The method of claim 1, wherein the transfer means comprises a conduit means, and including the step of heating the conduit means, sensing the temperature of the conduit means, and controlling the supply of energy to the conduit means for maintaining the temperature of the conduit means within a predetermined range.

6. The method of claim 5, including a removable hood at an end of the conduit means adjacent to the shot sleeve of the shot delivery apparatus, and including the step of supplying an inert gas to the hood to prevent oxidation of the molten metal when it is present in the conduit means and during the transfer of molten metal into the sleeve.

7. The method of claim 1, wherein the molten metal is transferred by a pump, including the step of controlling the level of energy and duration of operation of the pump to thereby control the delivery of a predetermined volume of the molten metal from the holding pot to the shot delivery apparatus.

8. The method of claim 7, wherein said pump is an electromagnetic pump which is substantially submerged in the molten metal, including the step of reversing the direction of flow of metal through the pump to return molten metal from the transfer means to the holding pot.

9. The method of claim 7, including the step of continuously operating the pump at a reduced operating power to maintain the transfer means filled with molten metal between charges of molten metal into the shot delivery apparatus.

10. The method of claim 7, including the step of sensing the temperature of the molten metal in the holding pot with a temperature controller, and adjusting the level of power to the pump in response to the detection of a change in temperature by the controller to change the output of the pump to compensate for changes in the viscosity of the molten metal in the pot.

11. The method of claim 7, including the step of sensing the temperature of the conduit means, and adjusting the level of power to the pump in response to the detection of a change in temperature by the controller to change the output of the pump to compensate for changes in the viscosity of the molten metal in the conduit means.

12. The method of claim 7, including the step of sensing the level of molten metal in the holding pot, providing an indication when the metal reaches a level above or below a predetermined level in the pot, and adjusting the level of power to the pump in response to the detection of a change in the level of molten metal in the holding pot.

13. The method of claim 1, including a source of energy for heating the metal in the holding pot, sensing the temperature of the molten metal in the pot, and a temperature controller for controlling the supply of energy to the pot in response to a detection of a change in the temperature of the molten metal.

14. The method of claim 1, wherein the molten metal is selected from the group consisting of magnesium, aluminum, and alloys of magnesium or aluminum.

15. A molten metal transfer system for delivering molten metal from a source of molten metal to a mold or die of a molding or casting machine, wherein said source of molten metal is a furnace or holding pot, or a combination thereof, comprising:

(a) means for transferring the molten metal from said holding pot to a shot delivery apparatus connected to the molding or casting machine, said means including a pump which is at least partially submerged in the molten metal, and a source of energy connected to the pump for transfer of the molten metal from the holding pot to the shot delivery apparatus,

(b) said shot delivery apparatus comprising a shot sleeve having a chamber, an inlet for the molten metal in said sleeve, and a ram movable in the sleeve chamber for moving molten metal from the sleeve into said die, and

(c) a controller operatively connected to a sensor for determining the volume of molten metal charged into the die, said controller including programming means for maintaining the volume of molten metal to be transferred from the holding pot into the die within a predetermined range, and said controller being responsive to a change in the volume, as sensed by the sensor, for controlling the delivery of an adjusted predetermined volume of molten metal to the die, and

(d) means for removing the solidified metal casting from the die, means for weighing the casting, and wherein said controller is adapted to determine the volume of the casting based on the weight and density of the metal in the casting.

16. The transfer system of claim 15, wherein the holding pot is sealed to the atmosphere, and means for supplying a protective gas to the sealed holding pot to prevent oxidation of the molten metal.

17. The transfer system of claim 15, wherein said sensor is adapted for sensing the distance of travel of the ram in the sleeve chamber between a retracted position and an extended or charging position following each charge of the molten metal into the die, and wherein said controller is adapted to determine the volume of metal transferred into the die following each charge, based on the biscuit length of solidified metal extending into the sleeve.

18. The transfer system of claim 15, including a temperature controller connected to a sensor and to the controller for sensing the temperature of the molten metal in the holding pot, said temperature controller being responsive to the controller for controlling the supply of power to the pump based on a change in temperature and viscosity of the molten metal.

19. The transfer system of claim 15, wherein said means for transferring the molten metal from said holding pot to the shot delivery apparatus comprises an outer conduit positioned concentrically with respect to an inner conduit for conveying the molten metal from the holding pot to the die, a thermal and electrical insulation positioned between the conduits, a connector between the inner and outer conduits at one end thereof for electrically connecting the conduits, an electrical power supply connected to the inner and outer conduits, respectively, at an opposite end thereof for conducting an electrical current through the conduits, and a temperature controller (TC-II) for adjusting the supply of current from the power supply to the conduits to control the temperature of the inner conduit.

20. The transfer system of claim 19, wherein said temperature controller is connected to a sensor and to said controller for sensing the temperature of the inner conduit, said controller controlling the level of power to the pump, based on a change in temperature and viscosity of the molten metal, for conveying a predetermined volume of molten metal from the holding pot to the die and for maintaining the inner conduit filled with molten metal.

21. The transfer system of claim 20, wherein said outer conduit comprises at least two conduit sections which are electrically separated from each other, each outer conduit section being electrically connected by a connector at one end thereof to the inner conduit, and said power supply being connected, respectively, to the opposite ends of the outer conduit sections.

22. The transfer system of claim 19, including a temperature controller (TC-I) connected to a sensor and to the controller for sensing the temperature of the molten metal in the holding pot, said temperature controller being responsive to the controller for controlling the supply of power to the pump and for maintaining the inner conduit filled with molten metal.

23. The transfer system of claim 21, wherein said power supply includes a transformer connected to the power supply and to the inner and outer conduits, respectively, for supplying a low voltage and high current to the conduits, said transformer being connected to a temperature controller for controlling the supply of power to the conduits in response to the temperature sensed by a sensor connected to the inner conduit.

24. The transfer system of claim 19, wherein said concentrically positioned conduits are inclined at an angle with respect to the horizontals a sensor for sensing the level of molten metal in the holding pot, said controller being operatively connected to the sensor for sensing the level of molten metal in the holding pot and for controlling the supply of energy to the pump to maintain the inner conduit filled with molten metal.

25. The transfer system of claim 15, including a sensor for sensing the level of molten metal in the holding pot, said controller being connected to the sensor for monitoring the level of molten metal in the pot and for providing an indication when the level of molten metal in the holding pot falls below a predetermined level and for controlling the supply of power to the pump.

26. The transfer system of claim 15, including a source of energy for supplying energy to the holding pot, a sensor connected to the holding pot for sensing the temperature of the molten metal in the holding pot, said sensor being connected to the controller for monitoring the temperature of the molten metal in the holding pot, and a temperature controller connected to the source of energy for controlling the supply of energy to the holding pot for maintaining the temperature of the molten metal within a predetermined range based on a programmed temperature range of the controller.

27. The transfer system of claim 15, including a hydraulic actuating mechanism connected by an actuating rod to the ram for moving the ram between said retracted and extended or charging positions for charging a quantity of molten metal from the sleeve into the die, said controller being operatively connected to the hydraulic actuating mechanism and to the molding or casting machine for controlling the operation of the mechanism.

28. The transfer system of claim 15, wherein the molten metal is selected from the group consisting of magnesium, aluminum, and an alloy of magnesium or aluminum.

29. The transfer system of claim 28, wherein the molten metal alloy comprises at least 50% Mg or Al.