| 摘要 |
Installation and means for the selective application of dyes to moulding masses based on plastics materials. In order to avoid colour contamination in moulded parts obtained after an operation using a particular dyestuff, valve sealing means 12 are provided at the intersection of the outlets of the dyestuff tanks 4 and the main conduit 2 so that the moulded mass expands in such a way as to prevent the existence of a residual quantity of dyestuff 11 previously used, which is incorporated in the moulded mass by a venturi effect. In a preferred embodiment each valve unit comprises a valve 15 with a double action piston 16, the piston 17 of which coaxially supports a sealing needle 18 guided by a bush 20. The invention has application in installations or machines for the moulding of shoe soles coloured using expanded polyurethane. <IMAGE>
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