Punch, and rotary compression molding machine using the same

A rotary compression molding machine comprising:

• a turret being rotatably mounted in a frame;
• dies each having a die bore mounted in the turret at a predetermined pitch;
• an upper punch and a lower punch vertically slidably held above and below each of the dies, the upper punch and the lower punch comprising a center punch and an outer punch surrounding the outer periphery of the center punch, both of which being slidable and capable of compressing operation;
• a plurality of molding material feeding and filling sections each configured to feed molding material into the die or a space defined above the lower center punch and surrounded by the lower outer punch;
• pre-compression means configured to press the upper center punch and the lower center punch for compression-molding the molding material fed and filled in the space defined above the lower center punch and surrounded by the lower outer punch;
• and main compression means configured to press the upper punch and the lower punch for compression-molding the whole molding including the molding material fed and filled by a last molding material feeding and filling section, wherein at least the upper punch has relative position restriction means for restricting a relative position of the center punch and the outer punch, the relative position restriction means being configured to restrict a first position in which the punch tip of the center punch is protruded from the punch tip of the outer punch and a second position in which the punch tip of the center punch is substantially coincident with the punch tip of the outer punch, and being configured to fail to restrict a third position in which the punch tip of the center punch is retracted in the punch tip of the outer punch,
• wherein the relative position restriction means comprises a first restricting component provided on the center punch and a second restricting component provided on the outer punch;
• both of the first restricting component and the second restricting component are shaped annular and comprise a projected-depressed portion having a projected portion and a depressed portion;
• the first restricting component and the second restricting component are positioned with their respective projected-depressed portions facing each other;
• at least one of the first restricting component and second restricting component is rotatable on a punch axis of the center punch;
• and as a result of its rotation, the projected portion of one of the restricting components and the depressed portion of the other restricting component are positioned to be allowed to come close to each other or the projected portions of both restricting components are positioned to be allowed to come into contact with each other.