Powder compacting apparatus and method of forming helical gear wheel using said powder compacting apparatus

A powder compacting apparatus for forming an external helical gear wheel, comprising:

• a die having a helical gear contour formed on an inner circumferential portion thereof,
• an upper punch and a lower punch respectively having helical gear contours formed on outer circumferential portions thereof, the helical gears being meshable with the helical gear contour formed on the die;
• a core rod;
• and
• a guide mechanism with a fixed helical lead for guiding the die, said fixed helical lead being identical to a lead of the helical gear contour formed on the die,
• wherein the die, the upper punch, and the lower punch are rotatably supported;
• the guide mechanism with said fixed helical lead comprises a guide having a cam for filling and a cam for pressing and ejecting disposed opposite to the cam for filling and a cam follower slidably engaging with the guide;
• said cam for filling has a relief surface by which is formed a first axially extending spacing S.sub.1 and a second axially extending spacing S.sub.2 between said cam for filling and said cam for pressing and ejecting wherein said first axially extending spacing S.sub.1 is sufficient to accommodate the width of said cam follower and said second axially extending spacing S.sub.2 further comprises an axially extending space S such that S.sub.2 =S.sub.1 +S;
• the upper punch meshes with the die through the helical gear contours and is pushed into the die while rotating, so that a powder material within a cavity formed by the die, the upper punch, the lower punch, and the core rod is compressed;
• and a green compact formed after the powder material has been compressed is ejected out of the die in an axial direction of the die and the core rod relative to the upper punch and the lower punch;
• and
• during compression of the powder material, the amount of flexure of the lower punch during compressing is .delta. such that .delta..gtoreq.S and during restitutive expansion of said lower punch, the green compact is prevented from rotating.