| 摘要 |
PURPOSE:To prevent dust from being floated when the gas is evacuated from a evacuated chamber and to eliminate the fluctuation of the pressure in the evacuated chamber by using the valve provided with the valve body controlling the evacuation quantity of the gas to be discharged and with the means controlling by itself the opening and closing of the valve body. CONSTITUTION:A valve body 2 controlling the evacuation quantity of the gas to be discharged, and a spring 3 controlling by itself the opening and closing of the valve body 2 are provided in the valve 12 used for evacuating the gas in the evacuated camber 10. Namely, when the evacuated chamber 10 is evacuated by a vacuum pump 11, a self-control is carried out by the relative relation between the pressure difference of the pressure of the evacuated chamber 10 to the pressure at a valve seat 1 in the side of vacuum pump and a compressing force of a spring 3 so that the continuous evacuation of the gas in the evacuated chamber 10 is carried out without abrupt fluctuations of pressure. As a result, the dust is prevented from floating up in the early period, the pressure in the evacuated chamber is speedily reduced in the middle period, and in the latter period the pressure in the chamber is slowly changed during evacuation. |
