| 摘要 |
PURPOSE:To eliminate the effect due to fluctuation of suction pressure by controlling the open degree based on the pressure difference of each pressure converted by a first and a second orifices. CONSTITUTION:Laser beam L of a laser oscillator 1 is radiated to a chip paper moving at a constant speed to open continuous holes. The paper passes on a ventilation degree detecting part 5 and sucked by suction pressure of a suction part 7 through a detection window 5a while the refuse of the paper at the time of making the holes is collected 4. Due to the difference of ventilation degree of the ventilation holes of the paper passing the window 5a, the flow rate of the sucked air changes and an orifice 6 converts the flow rate of the air into pressure and the result is sent to a differential pressure type pressure converter 8. Meanwhile, a needle valve 9 is simultaneously sucked with the detecting part 5 by the suction pressure and the flow rate of the air passing the needle valve 9 is converted into pressure by an orifice 10 and the result is sent to the converter 8. The converter 8 converts the pressure difference of the results from two directions into an electric signal and the result is sent back to an oscillator 1 as a feedback through an integration circuit 12 and the system is so controlled as to make the pressure difference be zero. Consequently, fluctuation of ventilation degree due to the fluctuation of the suction pressure is eliminated. |
