Plasmaduese

DE 29919142 U UPAB: 20010724 NOVELTY - An insulating, tubular bush (26) is inserted into the nozzle tip at the outlet of the plasma channel (12). DETAILED DESCRIPTION - Preferred Features: The bush is ceramic, Near the outlet, the nozzle channel tapers conically. The upstream end of the bush is surrounded by a shoulder (24) of the casing, which serves as one electrode. Axial length of the plasma channel (12) from the electrode (18) tip to the upstream end of the bush, is at least twice the internal diameter of the bush. The axial length of the bush is at least twice its own internal diameter. USE - A plasma nozzle for treatment of plastics. An objective is e.g. plasma polymerization or plasma coating. ADVANTAGE - Though this nozzle is of compact design, it treats large surface areas. The nozzle bush alters the plasma jet, varying it from candle-flame geometry. Just inside the bush and beyond, the flame widens out, fan-like. The working gas is swirled ahead of the nozzle outlet, hence stabilizing rotary motion is maintained. The result is large-area, uniform plasma treatment of the workpiece surface. On the workpiece the plasma swirls outwardly, expanding radially. Centrally the vortex creates pressure reduction. The plasma is sucked down onto the surface, into intimate contact. This promotes very efficient treatment. Other effects at work include conventional gas acceleration stemming from intense heating and thermal expansion; also flow separation effects at the nozzle, which enhance jet spreading.