| 摘要 |
PURPOSE:To prevent previously the stain and breakdown of a condensing lens by feeding a dry air to the torch and by preventing that the outside air comes into the torch in case of the working being suspended and assisting gas cut off. CONSTITUTION:In case of the working being suspended temporarily and so on, all of the driving of switching value are stopped and the feeding of assisting gas to a torch 4 is stopped. A dry air of low pressure is fed into the gas chamber 2b of the torch 4 with the switching valve having a throttle valve being driven by a driving circuit. Since this dry are is released slowly to the external part from the injection hole 5a of a nozzle 5, it is prevented that the metal vapor and steam caused in case of the working immediately before invade to the inner part of a housing 2 from the injection hole 5a. In this way no condensing lens is stained nor broken down by the outside air. |
