Mixing head for producing a preferably chemically reactive mixture of at least two plastics components

The mixing head comprises essentially a housing (1) with a central bore, a section of the bore being designed as a mixing chamber (2). Inlet openings (3) and (4) for the individual plastics components open out into the mixing chamber, in which a discharge piston (5) of uniform cross-section can be moved to and fro. Furthermore, the mixing chamber has an outlet opening (10) for the mixture of plastics components. The discharge piston is actuated by feeding a pressure medium to one or the other piston side of a working piston (19) which is firmly connected to the discharge piston. In order to improve the metering accuracy of the plastics components, there is incorporated into the pressure medium circuit of the working piston a disc piston (23) whose actuating face (23a) facing away from the working piston can be pressurised with a pressure medium until it reaches a shot stand-by position C of the discharge piston. In order to move the discharge piston into the mixing position B, the actuating face (23a) is relieved.