Mixer for mfr. of multi-reactant plastics esp. polyurethane - has relief pressure valve to minimise risk of contamination of recycled components

摘要

Device for mixing multi-component plastics, esp. polyurethane, has a mixing chamber with an inlet for each reactant and an outlet for the resulting mixt.; a control fitted inside the mixing chamber, which reciprocates from a position that clears the inlets as far as the outlet when it simultaneously closes the inlets towards the mixing chamber. Return grooves are provided at the control which connect the inlets, in synchronised fashion with their sepn. from the mixing chamber, to return pipelines that lead to the respective storage tanks for the reactants. In each return pipeline there are a pressure-meter and an adjustable throttle. In prior-art mixers, a switch-over of reactants from one return groove to another, may be caused by a pressure gradient arising between the return grooves. The device prevents generation of such a pressure gradient.