Method and apparatus for manufacturing metallic parts by injection molding from the semi-solid state

Abstract

An injection molding system includes a feeder in which a metal is melted and a first chamber into which a desired amount of melted metal is introduced. A piston in a second chamber first retracts to create suction, assisting in drawing in the melted metal into the second chamber from the first chamber and evacuating gas. A ram then pushes some melted metal remaining in the first chamber into the second chamber, forcing out gas present in the second chamber. The piston then injects the melted metal out of the second chamber into a mold. The melted metal is maintained in a semi-solid state prior to injection into the mold.

What is claimed is:  
     
         1 . A method of injecting melted material into a mold, comprising: 
 introducing the melted material into a first chamber;    allowing at least a portion of the melted material to pass through said first chamber into a second chamber;    maintaining the first chamber and the second chamber at a temperature between liquidus and solidus temperatures of the melted material to maintain the melted material in a semi-solid state in at least the second chamber;    pushing at least a portion of the melted material remaining in the first chamber into said second chamber; and    injecting the melted material from the second chamber into the mold.    
     
     
         2 . The method as claimed in  claim 1 , comprising creating a suction in the second chamber to draw the melted-material from the first chamber into the second chamber.  
     
     
         3 . The method as claimed in  claim 2 , wherein the suction in the second chamber is created before the pushing of the melted material portion from the first chamber into the second chamber.  
     
     
         4 . The method as claimed in  claim 2 , wherein a piston in the second chamber retracts to create suction that draws the melted material into the second chamber.  
     
     
         5 . The method as claimed in  claim 1 , wherein a ram in the first chamber advances to push the melted material portion from the first chamber into the second chamber.  
     
     
         6 . The method of  claim 5 , wherein the first chamber includes a valve that permits melted material to pass only in a direction toward the second chamber.  
     
     
         7 . The method of  claim 6 , wherein the ram is advanced so that an end of the ram seals off an outlet port of the first chamber during injection to prevent melted metal from passing between the first and the second chambers.  
     
     
         8 . The method as claimed in  claim 5 , comprising rotating the ram to enhance the uniform temperature distribution of the melted material in the first chamber, and wherein the ram contains supporting fins.  
     
     
         9 . The method of  claim 1 , wherein the melted material is a metal.  
     
     
         10 . The method as claimed in  claim 9 , wherein the melted material is a melted magnesium alloy.  
     
     
         11 . The method as claimed in  claim 9 , wherein the injected metal solidifies into a metal part in the mold.  
     
     
         12 . The method as claimed in  claim 1 , wherein the first chamber is located above the second chamber to allow gravity to assist passage of the melted material from the first chamber into the second.  
     
     
         13 . The method as claimed in  claim 12 , wherein the melted material passing into the second chamber forces out at least a portion of at least one gas present in the second chamber out of the second chamber.  
     
     
         14 . The method as claimed in  claim 1 , wherein at least a portion of at least one gas present in the second chamber escapes the second chamber through a second material which resists passage of the melted material.  
     
     
         15 . The method as claimed in  claim 1 , comprising 
 introducing solid material into a feeder;    melting the material in the feeder; and    introducing the material into the first chamber from the feeder.    
     
     
         16 . The method as claimed in  claim 15 , wherein the solid material is at least one metal ingot.  
     
     
         17 . The method as claimed in  claim 16 , comprising 
 introducing the at least one metal ingot into a third chamber; and transferring the at least one metal ingot from the third chamber into the feeder.    
     
     
         18 . The method as claimed in  claim 17 , wherein at least one of the third chamber and the feeder contain an inert gas ambient.  
     
     
         19 . The method as claimed in  claim 18 , wherein the inert gas comprises a at least one of argon, nitrogen, SF 6  and CO 2 .  
     
     
         20 . The method as claimed in  claim 18 , comprising maintaining the inert gas ambient by at least one of 
 a) at least one door;    b) a vacuum pump;    c) at least one inert gas screen.    
     
     
         21 . The method as claimed in  claim 17 , comprising 
 opening a first door to the third chamber;    advancing at least one metal ingot into the third chamber;    closing the first door;    opening a second door; and    advancing the at least one metal ingot from the third chamber into the feeder.    
     
     
         22 . The method as claimed in  claim 17 , comprising 
 introducing the metal ingots into the third chamber; and passing the metal ingots down a sloping surface into the feeder.    
     
     
         23 . The method as claimed in  claim 17 , comprising controlling access to the feeder from the third chamber by movable cover plate.  
     
     
         24 . The method as claimed in  claim 23 , wherein the movable cover plate contains an access aperture.  
     
     
         25 . The method as claimed in  claim 15 , comprising controlling access to the feeder by movable transfer chamber.  
     
     
         26 . The method as claimed in  claim 25 , wherein the movable transfer chamber comprises a cylinder containing an access aperture.  
     
     
         27 . The method as claimed in  claim 1 , comprising 
 uncovering an injection nozzle in the second chamber;    injecting the melted material into the mold through the injection nozzle by advancing a piston; and    covering the injection nozzle.    
     
     
         28 . The method as claimed in  claim 27 , wherein the injection nozzle is covered by a nozzle shut-off plate.  
     
     
         29 . The method as claimed in  claim 27 , comprising 
 partially advancing the piston, which is surrounded by a seal, to squeeze at least a portion of at least one gas present in the second chamber out of the second chamber through at least one of a material which resists passage of melted material prior to injecting the melted material into the mold.    
     
     
         30 . The method as claimed in claim S, comprising 
 advancing the ram in the first chamber so that the ram seals off an outlet port of the first chamber during injection to prevent melted metal from passing between the first and the second chambers;    uncovering an injection nozzle in the second chamber;    injecting the melted material into the mold through the injection nozzle by advancing a piston;    retracting the ram; and    retracting an outer portion of the piston to create a suction in the second chamber to draw the melted material from the first chamber into the second chamber, while leaving an inner portion of the piston fully advanced to cover the injection nozzle.    
     
     
         31 . A molded metal part produced by the method of  claim 1 , having at least one structure with a thickness less than or equal to 1 mm that measures approximately 21.0 cm by 29.7 cm.  
     
     
         32 . An apparatus for injecting melted material into a mold, comprising 
 a first chamber which holds melted material,    a ram that moves through said first chamber to force at least a portion of the melted material from the first chamber through an outlet port leading into a second chamber,    at least one heating element adjacent the second chamber to maintain the melted material in a semi-solid state in at least the second chamber;    and a piston in the second chamber that 
 (a) retracts to create suction that assists in drawing into the second chamber at least a portion of the melted material through the outlet port from the first chamber; and that  
 (b) advances to inject the melted material into a mold.  
   
     
     
         33 . The apparatus as claimed in  claim 32 , wherein the first chamber includes a valve at one end that permits melted material to pass only in a direction toward the outlet port.  
     
     
         34 . The apparatus as claimed in  claim 32 , wherein the ram contains supporting fins.  
     
     
         35 . The apparatus as claimed in  claim 32 , further comprising heating elements adjacent the first chambers to regulate temperatures therein.  
     
     
         36 . The apparatus as claimed in  claim 32 , further comprising an open nozzle at one end of the second chamber through which the melted metal is injected into a mold.  
     
     
         37 . The apparatus as claimed in  claim 36 , further comprising a nozzle shut-off plate which covers the nozzle and moves longitudinally to permit the nozzle to engage a mold during injection.  
     
     
         38 . The apparatus as claimed in  claim 37 , further comprising a heating element in contact with the nozzle shut-off plate.  
     
     
         39 . The apparatus as claimed in  claim 32 , wherein the first chamber is positioned above the second chamber.  
     
     
         40 . The apparatus as claimed in  claim 32 , wherein the first chamber is inclined at an angle between 30 and 60 degrees with respect to the second chamber.  
     
     
         41 . The apparatus as claimed in  claim 32 , wherein the second chamber comprises at least one gas outlet port.  
     
     
         42 . The apparatus as claimed in  claim 41 , wherein the gas outlet port comprises at least one of 
 a) a void between the piston and the walls of the second chamber;    b) a seal surrounding the piston; and    c) an opening in the wall of the second chamber connected to a gas permeable but liquid resistant material.    
     
     
         43 . The apparatus as claimed in  claim 32 , comprising 
 a feeder connected to the first chamber by a feeder port;    and at least one heating element for the feeder.    
     
     
         44 . The apparatus as claimed in  claim 43 , comprising a third chamber in communication with the feeder.  
     
     
         45 . The apparatus as claimed in  claim 44 , wherein the third chamber comprises 
 a push arm to push metal ingots into the third chamber; and    a sloping surface to assist passage of the metal ingots into the feeder.    
     
     
         46 . The apparatus as claimed in  claim 44 , comprising an inert gas introduction nozzle in at least one of the feeder and the third chamber.  
     
     
         47 . The apparatus as claimed in  claim 44 , wherein the third chamber comprises at least one of 
 a) at least one door;    b) a vacuum pump connected to the third chamber;    c) a conveyor belt;    d) at least one heating element; and    e) at least one inert gas screen.    
     
     
         48 . The apparatus as claimed in  claim 44 , wherein the third chamber comprises a movable cover plate.  
     
     
         49 . The apparatus as claimed in  claim 48 , wherein the movable cover plate comprises an access aperture.  
     
     
         50 . The apparatus as claimed in  claim 43 , comprising a movable transfer chamber containing an access aperture.  
     
     
         51 . The apparatus as claimed in  claim 44 , comprising an elevator for delivering metal ingots; and a conveyor for transferring the metal ingots from the elevator to the third chamber.  
     
     
         52 . The apparatus as claimed in  claim 51 , wherein the elevator comprises 
 at least one rotatable platform;    at least one connector about which the platform rotates; and    a lifting member which lifts up the platform causing it to rotate about the connector.    
     
     
         53 . The apparatus as claimed in  claim 43 , wherein the feeder contains a filter to prevent solid material from entering the first chamber.  
     
     
         54 . The apparatus as claimed in  claim 53 , wherein the filter comprises a grate or at least one vertical rod.  
     
     
         55 . The apparatus as claimed in  claim 32 , wherein the piston comprises an outer portion and an inner portion and wherein the inner portion is moved independently of the outer portion to prevent material flow through an injection nozzle into the mold.  
     
     
         56 . The apparatus as claimed in  claim 32 , wherein the ram comprises an outer portion and an inner portion and wherein the inner portion is moved independently of the outer portion.  
     
     
         57 . An apparatus for injecting melted material into a mold, comprising 
 a passing means for passing the melted material;    forcing means for forcing at least a portion of the melted material from the passing means into an accumulation means for accumulating melted material;    suction means for creating a suction in the accumulating means to draw at least a portion of the melted material into the accumulating means;    heating means for maintaining the melted material in a semi-solid state in at least the second chamber;    injection means for injecting the melted material from the accumulation means into the mold.    
     
     
         58 . The apparatus as claimed in  claim 57 , comprising means which permit passage of the melted material only in a direction toward the accumulation means.  
     
     
         59 . The apparatus as claimed in  claim 57 , comprising heating means for heating said accumulation means.  
     
     
         60 . The apparatus as claimed in  claim 57  comprising means to cover an injection nozzle in the accumulating means.  
     
     
         61 . The apparatus as claimed in  claim 57  comprising egress means for removing at least one gas from the accumulation means.  
     
     
         62 . The apparatus as claimed in  claim 57 , comprising melting means for melting a solid material to form the melted material.  
     
     
         63 . The apparatus as claimed in  claim 62 , comprising filtering means for preventing entry of the solid material into the passing means.  
     
     
         64 . The apparatus as claimed in  claim 62 , comprising holding means for holding the solid material prior to its introduction into the melting means so as to maintain an inert gas ambient in the melting means.  
     
     
         65 . The apparatus as claimed in  claim 64 , comprising transfer means for transferring solid material into the holding means.  
     
     
         66 . The apparatus as claimed in  claim 65 , wherein said transfer means is synchronized with a door to the holding means to transfer the solid material into the holding means when the door is opened.