| 摘要 |
In the vacuum moulding process for production of casting moulds from binder-free moulding sand, the mould box filled with moulding sand must be coupled to, or uncoupled from, the vacuum mains of the moulding plant. The mould box, uncoupled after the casting process, must be ventilated. To perform this process, a valve has, between the two pipe unions for the vacuum connection or the mould box, a ball which can be actuated from the outside, the spring-loaded ball closing the annular gap between a diaphragm and the handle for the ball when in the position coupled to the vacuum mains, and in the other position freeing the annular gap for ventilation of the mould box. <IMAGE>
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