| 摘要 |
A sprueless disc mold including: a gate insert; a hot plunger adapted to come into sliding contact with the gate insert and heated and held; drive means for moving the hot plunger to open/close the gate; and a cooling air passage. The hot plunger includes a shoulder portion formed at its leading end portion. The gate insert includes: a leading end face forming a portion of a cavity face together with the shoulder portion of the hot plunger; an annular recess for forming the disc into a shape having one face raised to the crest of a stack rib; and an inner circumference extending from the inner circumferential edge of the circumferential recess toward the gate. The hot plunger further includes at its leading end portion: an outer circumference forming the inner circumference near the gate and adapted to come into sliding contact with the inner circumference of the gate insert to close the gate; a chamfered portion formed on the corner, at which the outer circumference and the shoulder portion come into contact with each other, and having an inner slope leading from the crest of the stack rib to the face of the disc. At the protruded position of the hot plunger, the annular recess of the gate insert and the chamfered portion of the hot plunger are made to come into contact with each other to form a recess for forming the stack rib.
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