Powder molding apparatus and compact manufacturing method

Abstract

Provided is a powder molding apparatus including: a die; an upper punch and a lower punch; a middle platen attached to the upper punch; an upper platen mounted on a press machine and the upper platen being attached to a push rod; a link mechanism connecting the upper platen and the middle platen; a first actuator that fixes the link mechanism and cancels a fixation of the link mechanism; a bolster attached to the lower punch, and a lower platen attached to the die, in which descending of the upper platen and the push rod causes the lower platen and the die to be pushed downward by the push rod, and along with a downward movement of the die, the lower punch makes a upward movement inside the hollow with respect to the die.

What is claimed is: 
     
         1 . A powder molding apparatus comprising:
 a die having a hollow;   an upper punch and a lower punch that slide inside the hollow of the die and form a cavity jointly with an inner wall of the hollow;   a middle platen attached to the upper punch;   an upper platen attached to a push rod;   a press machine that pushes down the upper platen;   a link mechanism that connects the upper platen and the middle platen;   a first actuator that fixes the link mechanism and cancels a fixation of the link mechanism;   a bolster attached to the lower punch; and   a lower platen attached to the die, the lower platen being biased upward from the bolster via a spring, wherein   descending of the upper platen and the push rod causes the lower platen and the die to be pushed downward by the push rod, and along with a downward movement of the die, the lower punch makes a upward movement inside the hollow with respect to the die.   
     
     
         2 . The powder molding apparatus according to  claim 1 , wherein
 the link mechanism includes two links and three joints, the three joints connecting the links, the upper platen and the middle platen, respectively, and connecting the two links.   
     
     
         3 . The powder molding apparatus according to  claim 2 , wherein
 the first actuator includes an air cylinder and a piston, and a distal end of the piston is attached to the joint that is a middle joint among the three joints.   
     
     
         4 . The powder molding apparatus according to  claim 1 , further comprising a second actuator between the upper platen and the middle platen. 
     
     
         5 . The powder molding apparatus according to  claim 4 , wherein
 a relief valve is provided in the second actuator.   
     
     
         6 . A compact manufacturing method using the powder molding apparatus according to  claim 1 , the method comprising:
 charging powder into the cavity;   manufacturing a compact by fixing the link mechanism via the first actuator, and pushing down the upper platen, the middle platen and the upper punch via the press machine to mold the powder in the cavity;   cancelling the fixation of the link mechanism via the first actuator, pushing down the upper platen via the press machine, and pushing down the lower platen and the die via the push rod to expose the compact from the cavity.   
     
     
         7 . The compact manufacturing method according to  claim 6 , wherein
 the powder molding apparatus according to  claim 4  is used,   during exposure of the compact from the cavity, a first pressing force is applied from the second actuator to the upper punch to expose the compact from the cavity while the compact being pressed by the first pressing force, the first pressing force being lower than a second pressing force applied to push down the upper platen, the middle platen and the upper punch via the press machine to mold the powder in the cavity.