Patent ID: 6877976
Filing Date: 2005-04-12
Classification: B29C

Abstract:
1. A molding apparatus having a die with a plastic flow passage which carries molten plastic from an extruder to a mold which is shaped to form ribbed pipe, said plastic flow passage having a first flow region parallel to, and a second flow region exiting through, an exterior surface of said die, said flow passage having inner and outer walls, said inner wall being located downstream of said outer wall in said second flow region of said plastic flow passage, each of said walls in said second flow region having a main wall part at an acute angle relative to, and a termination point at said exterior surface of said die, said inner wall in said second flow region further including a transition wall part between said termination point and said main wall part of said inner wall, said transition wall part being inclined relative to said exterior surface of said die and being sloped at an angle less than that of said main wall part of said inner wall; said second flow region gradually narrowing lengthwise thereof between the main wall parts and then widening between the transition wall parts of the inner and outer walls of the flow passage, said outer wall of said passage in said second flow region includes a minor wall part between the termination point and the main wall part of the outer wall, the transition wall part of the inner wall being flat axially of the die and having an axis which intersects with the minor wall part in the outer wall of the passage; to the minor wall part of the outer wall being inclined relative to the exterior surface of the die and being sloped at an angle greater than that of the main wall part of the outer wall.