| 摘要 |
<p>Casting moulds (book moulds) comprising a shallow tray with an annular seal on a hinged lid are fitted with a pair of non-return valves, one of which allows enclosed air etc. to vent from the mould during heating, and one which allows air to enter the mould during cooling, to facilitate subsequent opening. Used esp. for moulding castings to be cured by high frequency induction (HF) heating, e.g. for making artificial leather work, shoes, etc. from PVC based plastisols in a series of portable moulds passing through an HF oven and then cooled under pressure. The seals and vents inhibit moisture condensn. within the cavity, which could otherwise provoke local spark discharging and scorching of the mouldings.</p> |
