Abstract: A high pressure mixing head is disclosed for combining a plurality of reactive fluid polymeric components to form a mixture thereof for molding purposes. The mixing head incorporates an expulsion plunger operating in a mixing chamber into which the several components are admitted through individual inlet openings which are covered and uncovered by reciprocation of the plunger. The mixing head further incorporates inlet valves and valve chambers located respectively upstream of the several inlet openings and so arranged that the inlet valves prevent admission of the individual components into the mixing chamber, irrespective of the plunger position, unless a predetermined pressure of the respective components is attained. Each valve chamber is connected to component feed and return lines forming part of the respective component circulating systems so that component flow at relatively low pressure takes place at all times between mixing/molding periods of operation.

Abstract: The invention relates to a frothing method for mixing a liquid propellant having a low boiling point with further components for the production of foamed material, more particularly polyurethane. The invention also relates to an apparatus for carrying out the method with a mixing head for high pressure mixing of the main components in a mixing chamber. The foam production is carried out in two stages involving a first chamber for receiving and premixing reactive polymeric components, and a second chamber intersected by the first into which the mix components are advanced while the frothing propellant is injected at the intersection. The frothed reactive polymeric mix is then discharged from the second chamber into a suitable mold for forming the finished polymerized product.

Abstract: A high pressure mixing head is disclosed for combining a plurality of reactive fluid polymeric components to form a mixture thereof for molding purposes. The mixing head incorporates an expulsion piston operating in a mixing chamber into which the several components are individually admitted through separate inlet openings which are covered and uncovered by reciprocation of the expulsion piston. This piston is actuated by connection to a power piston operating in a power cylinder, and means such as a limit switch assembly is mounted on the power cylinder to detect the position of the power piston and hence the expulsion piston in the mixing chamber. This switch is used to control the "shot time" of the mixing head cycle of operation; that is, the time during which the inlet ports to the mixing chamber remain uncovered by the expulsion plunger to allow the components to enter the mixing chamber through the respective inlet ports.