| 摘要 |
PROBLEM TO BE SOLVED: To prevent a vent-up and a closure of a vent hole even by adhering a low viscosity molten material to the hole by connecting the hole on the way of a cylinder to a negative pressure sucking means, and providing a valve member for advancing the means into the hole to close it and retracting the means to open the hole. SOLUTION: A valve member 8 for advancing into and retracting from a vent hole 4 to close and open the hole 4 is arranged in a negative pressure chamber 5. The member 8 is driven to be advanced and retracted by a dual acting cylinder 9 provided on the chamber 5 to negative-pressure suck a gas in a cylinder 3. A clearance between the member 8 advanced into the hole 4 and an inner periphery of the hole 4 is set to a predetermined range to prevent introduction of a molten material between the member 8 and the hole 4. Then, an end face of the member 8 advanced into the hole 4 is formed in a shape aligned with an inner periphery of the cylinder 3. Thus, a vent-up can be prevented, and a fear of a closure of the hole due to an adhesion or a deposition of the molten material can be removed.
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