Press forming device

A press forming device for forming a plurality of inwardly directed projections on a circumferential wall of a tubular article to be formed, the press forming device comprising:

• a lower die holder adapted to be mounted on a lower base of a press machine;
• a die fixed on said lower die holder, said die having a plurality of inside forming parts on a circumferential surface of said die, each for forming one of said projections, respectively;
• a plurality of punches mounted on said lower die holder around an outer circumference of said die, each of said punches being arranged to be capable of being moved towards or away from said die, and each of said punches having an outside forming part in a position facing one of said inside forming parts for forming one of said projections, respectively;
• an upper die holder adapted to be mounted on an upper raising and lowering base of said press machine;
• and
• a plurality of pressing members of wedge shape mounted on said upper die holder, each of said pressing members being mounted at a position above one of said punches for moving one of said punches in a direction towards said die with lowering said raising and lowering base, to thereby press said tubular article between one of said inside forming parts of said die and one of said outside forming parts of said punches, respectively;
• whereby said plurality of said projections are formed on said circumferential wall of said tubular article to be formed;
• the press forming device further comprising:
• a plurality of inserts arranged in the circumference of said die, each of said inserts being movable in a radial direction of said die and being arranged in a position between adjacent two of said inside forming parts of said die, respectively, wherein a radial movement of said inserts facilitate an extraction of said tubular article from said die.