Dual plunger gooseneck for magnesium die casting

Abstract

A mechanical apparatus and method for the casting of metal components is disclosed. The apparatus includes a gooseneck having dual plungers for drawing molten metal from a crucible of hot metal and for forcing the drawn molten metal through the system, a hot runner assembly having a thermal valve developed in time and positioned adjacent the mold cavity, and a machine nozzle positioned between the gooseneck and the hot runner assembly. The dual plunger is fitted with a shot plunger and a shutoff plunger which work in conjunction to allow for molten metal to be drawn into the gooseneck but to stop its passage into the gooseneck when the metal is forced through the system into the die. Both temperature and flow rate are carefully monitored and controlled. Two embodiments of the gooseneck are provided in which the positions of the shot plunger and the shutoff plunger are altered and in which the molten metal is drawn into the gooseneck at different locations.

1 . A dual plunger gooseneck for use in metal casting, the gooseneck comprising:
 a plunger body;   a shot plunger cylinder formed in said plunger body;   a shot plunger reciprocatingly fitted in said shot plunger cylinder, said shot plunger being movable between a molten metal drawing position and a molten metal injecting position;   a shutoff plunger cylinder formed in said plunger body; and   a shutoff plunger reciprocatingly fitted in said shutoff plunger cylinder, said shutoff plunger being movable between a molten metal flow blocking position and a molten metal flow passing position.   
   
   
       2 . The dual plunger gooseneck of  claim 1  wherein said shot plunger cylinder has a long axis and said shutoff plunger cylinder has a long axis, said axes being parallel. 
   
   
       3 . The dual plunger gooseneck of  claim 1  wherein said shot plunger includes a sacrificial ring. 
   
   
       4 . The dual plunger gooseneck of  claim 1  wherein said shutoff plunger includes a sacrificial ring. 
   
   
       5 . The dual plunger gooseneck of  claim 1  wherein said shot cylinder is lined with a ceramic liner. 
   
   
       6 . The dual plunger gooseneck of  claim 1  wherein said shutoff cylinder is lined with a ceramic liner. 
   
   
       7 . The dual plunger gooseneck of  claim 1  wherein said shutoff cylinder includes a molten metal passageway. 
   
   
       8 . The dual plunger gooseneck of  claim 1  further including a molten metal outlet passageway. 
   
   
       9 . The dual plunger gooseneck of  claim 8  wherein said molten metal outlet passageway is in fluid communication with said shutoff plunger cylinder. 
   
   
       10 . An apparatus for the casting of metal in a mold cavity defined between a cover die and an ejector die, the apparatus comprising:
 a crucible containing a liquid metal;   a dual plunger gooseneck including a shot plunger cylinder, a shot plunger, said shot plunger being reciprocatingly fitted within said shot plunger cylinder, a shutoff plunger cylinder, and a shutoff plunger, said shutoff plunger being reciprocatingly fitted within said shutoff plunger cylinder, said dual plunger gooseneck including a molten metal inlet and a molten metal outlet, said molten metal inlet being in fluid communication with said crucible;   a hot runner being at least partially recessed within the cover die half, said hot runner having a molten metal passageway formed therethrough, said molten metal passageway of said hot runner having an inlet and an outlet, said inlet of said molten metal passageway being in fluid communication with said outlet of said shot plunger; and   a hot runner tip operatively associated with said outlet of said hot runner.   
   
   
       11 . The dual plunger gooseneck of  claim 10  wherein said shot plunger cylinder has a long axis and said shutoff plunger cylinder has a long axis, said axes being parallel. 
   
   
       12 . The apparatus of  claim 10 , further including a machine nozzle having a molten metal passageway formed therethrough, said molten metal passageway of said machine nozzle having an inlet and an outlet, said inlet of said machine nozzle being in fluid communication with said outlet of said plunger. 
   
   
       13 . The apparatus of  claim 10  wherein said shot plunger is fitted with at least two spaced apart sacrificial rings. 
   
   
       14 . The apparatus of  claim 10  wherein said shutoff plunger is fitted with at least two spaced apart sacrificial rings. 
   
   
       15 . The apparatus of  claim 10  further including a shot plunger cylinder liner. 
   
   
       16 . The apparatus of  claim 15  wherein said liner is formed from a ceramic material. 
   
   
       17 . The apparatus of  claim 10  further including a shutoff plunger cylinder liner. 
   
   
       18 . The apparatus of  claim 17  wherein said liner is formed from a ceramic material. 
   
   
       19 . The apparatus of  claim 10  further including a heating element fitted to said machine nozzle. 
   
   
       20 . The apparatus of  claim 19  wherein said heating element is selected from the group consisting of a band heater, a tube heater, and a tubular heater. 
   
   
       21 . The apparatus of  claim 10  further including a heating element fitted to said hot runner. 
   
   
       22 . The apparatus of  claim 21  wherein said heating element is selected from the group consisting of a band heater, a tube heater, and a tubular heater. 
   
   
       23 . The apparatus of  claim 10  further including a heating element fitted to said hot runner tip. 
   
   
       24 . The apparatus of  claim 23  wherein said heating element is selected from the group consisting of a band heater, a tube heater, and a tubular heater. 
   
   
       25 . A method for casting a metal part in a die cavity defined between a lower die and an upper die, the method comprising the steps of:
 forming a metal part casting apparatus comprising a crucible containing a liquid metal, a dual plunger gooseneck, said dual plunger gooseneck having a shot plunger and a shutoff plunger, a hot runner, and a hot runner tip having a heating element and a tip opening adjacent the die cavity, said shot plunger being movable between a liquid metal drawing position and a liquid metal injecting position, said shutoff plunger being movable between a liquid metal flow blocking position and a liquid metal flow passing position;   applying energy to said heating elements to effect heating of said hot runner tip to a pre-selected temperature;   moving said shutoff plunger to said liquid metal flow passing position and moving said shot plunger to said liquid metal drawing position whereby liquid metal is drawn from said crucible into said dual plunger gooseneck;   moving said shutoff plunger to said liquid metal flow blocking position and moving said shot plunger to said liquid metal injecting position to force said liquid metal through said hot runner and said thermal valve and into the mold cavity; and   regulating the temperature of said hot runner tip to form a substantially solid blockage within said hot runner tip after said step of forcing said liquid metal through said hot runner and said hot runner tip.