Catalyst gas circuit for hardening sand moulds or cores - with accurate control of gas to avoid explosions or environmental pollution

摘要

This is an addn. to 2526875, which described the hardening of sand moulds or cores in mould- or core- boxes using a binder hardened by catalyst gas, a vacuum being used to draw the gas into the box, followed by fresh air, using a reservoir for circulation of the gas. After treating the sand with the gas, dry compressed air is fed through the sand and the mixt. of gas and air is fed through a freeze dryer before flowing to the reservoir or out to the free atmos. The amt. of catalyst gas is pref. is not >1 mol. % w.r.t. the mixt. of gas and air. The pref. appts. includes a compressed air supply fitted with control valves, and pipes and valves forming a circuit for the catalyst gas which includes the freeze dryer. Fluctuations in the amt. of gas in the gas/air mixt. are suppressed so there is no danger of forming an explosive mixt.