Abstract: The invention relates to a plant for the radiation hardening of a coating of a workpiece under protective or inert gas, with a hardening cabin or booth, on which is provided at least one irradiating device for irradiating the cabin or booth interior, and a conveyor for conveying the workpiece into the hardening cabin along a conveying path. In the vicinity of the hardening cabin and at the ceiling thereof is formed a collecting area where, compared with the surrounding atmosphere, lighter protective gas collects and that the conveying path of the workpiece passes through the collecting area located at the ceiling. The invention also relates to a method for the radiation hardening of a coating of a workpiece under protective gas.

Abstract: In a mixing head, a housing (1) has a bore (2) in which a control piston (7) can be moved to and fro. One portion of the bore constitutes the mixing chamber (4), which is bounded by the end face of the control piston and by a plurality of restrictors (9) and (10) which are arranged in a row one next to the other and/or one behind the other, and can be slid into the bore. The restrictors are preferably introduced into the bore (2) from diametrically opposite sides, forming a cascade-like structure. Inlet orifices (5) and (6) for each plastic component enter the mixing chamber. As it flows, the mixture of plastic components is divided, by the cascade-like structure, into a plurality of part-streams and thereby subjected to additional mixing, and passes, with sufficiently laminar flow, into a mold.

Abstract: The mixing head is provided with a flow restrictor 5 which can be driven into the mixing chamber 2 downstream of the inlet orifices 3, and whose front face (for 6) is matched to the contour of the mixing chamber to avoid leaving any space here which cannot be purged by the purging plunger. When the flow restrictor is pushed forward into its working or restricting position, it is simultaneously rotated, the extent of rotation being no more than 90.degree. by the time the restricting position has been reached. This makes it possible to drive the flow restrictor much further into the mixing chamber than when no rotation is effected. The tongues or projections 6 produced as a result of matching the front face to the contour of the mixing chamber only come into contact with the sections of the mixing chamber wall which are opposite the flow restrictor.

Abstract: A split mold for multi-component plastics, especially polyurethanes, with venting channels has heating devices in the zone of the said channels to prevent plastic from entering the channels and thus forming flash on the moldings.

Abstract: A mixing head for multicomponent plastics, especially polyurethane, in whose mixing chamber (2) a hollow piston (7) can be moved to and fro to control the component streams. The hollow piston contains an expulsion piston (8), which is movable independently of the hollow piston, and which can be passed through an outlet tube (3) which adjoins the outlet orifice (4). The end face (12) of the hollow piston forms, together with the mixing chamber wall (11) nearest the sprue, a shearing gap in which the components are mixed. As a result of the design and arrangement of the pistons (7) and (8), good mixing is achievable even under critical conditions, and the mixing chamber is also easily cleaned.

Abstract: A mixing apparatus for mixing components that interact chemically, preferably polyurethane-forming components, the apparatus including a control plunger disposed within a housing and movable along a mixing chamber between opposing inlet and return ports, the control plunger having along its wall surface return grooves for connecting the inlet ports to the return ports when the plunger is in a position blocking communication between the inlet ports and the mixing chamber wherein a wall surface portion of the control plunger which in the closing position of the plunger is disposed intermediate the return ports is provided with discrete recesses which mutually overlap in the direction of movement of the control plunger.