Blow molding die

Abstract

A blow molding die includes a housing, and a mandrel with a core integrated therewith, combined to form a vertically extending annular melt passage communicating with a hole formed at its top portion for feeding a plasticized resin melt from an extruder, and terminating at die lips formed at its free bottom end. The mandrel has a pair or grooves symmetrical relative to its axis, formed at its peripheral surface so as to have hanger type profiles in its front developed view, and connecting to each other at lower ends thereof. The feed hole opens to the symmetrical hanger type grooves at top and central points thereof. Each groove has an arced surface and a cross-sectional area decreasing in a direction from the top and central point to the lower end. A single circumferential dam is formed at the peripheral mandrel surface below the grooves, and a pair of lower lands defined between the grooves and the dam are formed, while an upper land is formed above the grooves, so that the grooves are defined between the upper and lower lands and connect to the dam at the lower ends. The grooves, the lower lands and the dam have radial depths from a peripheral surface of the upper land, the lower land depth being smaller than the groove depth but larger than the dam depth over the entire periphery, while the upper land is sealingly fitted to an inner peripheral surface of the housing.