| 摘要 |
PURPOSE:To start surely and easily a plasma torch equipped with a cathode mantle, by exhausting a starting stream through a port other than the 2nd nozzle in the 2nd annular passage before shifting the arc in the torch. CONSTITUTION:When a plasma torch equipped with a cathode mantle 4 is started, a starting air current 8 is made to flow through the 1st annular passage 2 and the 2nd annular passage 5 is exhausted of air. A power source 12 is actuated and an arc 15 is generated between a cathode bar 1 and the cathode mantle 4 by means of a high-frequency oscillator. When a switch 14 is closed and another switch 13 is opened, the arc 15 moves to the space between the cathode bar 1 and a plasma mantle 7 and becomes an arc 16, and thus, the plasma torch is started. Then, a plasma stream 9 is made to flow and, at the same time or thereafter, the starting stream 8 is stopped and a plasma jet 24 is discharged upon a work 23 from the 2nd nozzle 6. When this method is applied, the starting operation is surely performed, because the pressure inside the torch is lowered before shifting the arc. |
