Method and apparatus for spray forming polyurethane skins with a hydraulic mixing head

摘要

An apparatus for spraying polyurethane to form a skin on a mold. Polyurethane forming constituents are provided from a plurality of separate supply sources to separate recirculating fluid circuits. A mix head receives polyurethane constituents from the fluid circuits and mixes them to form a polyurethane mixture. A hydraulically operated valve controls the flow of the polyurethane constituents. The valve has a first position in which the polyurethane components are permitted to flow into the chamber of the mix head. The polyurethane mixture is then dispensed through a spray nozzle assembly. When the valve is in a second position, the polyurethane constituents are recirculated through the fluid circuits. A liquid solvent may be injected into the mix head under pressure to purge the mixture from the mix head and spray nozzle assembly in the second position.