A high pressure mixing head for continuously producing polymeric foam comprises a body including a mixing chamber and injectors for injecting two polymeric liquids. The mixing head also includes a delivery duct which is disposed transversely to the mixing chamber, wherein a rod is slidably received in an internal passageway of the delivery duct. An alternate delivery duct is also included. The delivery duct and the alternate delivery duct are in flow communication with the mixing chamber via a switchable flow connection, and a control unit is configured to control the switchable flow connection and the positions of the rods in the delivery duct and the alternate delivery duct such that flow from the output opening of the mixing chamber can be selectively directed either to the delivery duct or to the alternate delivery duct.

A mixing and extrusion machine (10) for the manufacture of rubber mixtures has a mixer with a converging conical twin screw (12) with a fixed frame (14) that supports sleeves (16). Two screws (18), being mounted at an angle, are mounted in the mixer (12) so as to move in translational movement between an opening (22) arranged upstream and an outlet (25) arranged downstream of the sleeves, so that the thread tips of each screw contact tangentially the surfaces of the opposite screw so that the screws remain substantially in contact with each other when the screws rotate at an angle and at a center distance that facilitates self-cleaning. The screw threads maintain tangential contact with the inner surfaces of the sleeves, thus preventing the retention of mixing material on these surfaces.

The invention relates to a supply apparatus (100) for supplying at least one molding device (500) with a polymerizable mixture, comprising: a tank (110) where is stored the polymerizable mixture, a line (120) for supplying the at least one molding device with said polymerizable mixture, the line being connected to an outlet of the tank for receiving the polymerizable mixture and to an inlet of said at least one molding device, and means for making the polymerizable mixture circulate in said line. According to the invention, the line includes remove means (190) for removing the gas from said polymerizable mixture and for evacuating said gas out of said supply apparatus.