Breathing apparatus of a mold

摘要

On mating surfaces of a pair of mold members are formed a breathing groove communicating with a cavity, a detection chamber for detecting a melt pressure at an end of the breathing groove, a detour groove diverging from the detection chamber and a valve chamber communicating with a vent passage at an end of the detour groove. A valve element of a shut-off valve member is positioned in the valve chamber and retracts to a valve closing position when the shut-off valve member moves in a direction perpendicular to and separating from the mating surface. A detection pin having an end fronting toward the detection chamber and a operation pin having an end fronting toward the valve chamber and abutting against the valve element are connected through a reverse mechanism so that the pins move in opposite directions to each other. When the detection pin detects a predetermined melt pressure in the detection chamber and retracts, the operation pin is projected into the valve chamber through the reverse mechanism and pushes the shut-off valve member to bring the valve element into the valve closing position.