Pilot-type two-port vacuum valve

A pilot-type two-port vacuum valve comprising:

• a first port to be connected to a vacuum chamber and a second port to be connected to a vacuum pump;
• a main flow path for connecting said first port and said second port and having a large cross-sectional area and an auxiliary flow path having a smaller cross-sectional area than said main flow path;
• a main valve body for opening and closing said main flow path and an auxiliary valve body for opening and closing said auxiliary flow path;
• a first piston connected to said main valve body through a first shaft and a second piston connected to said auxiliary valve body through a second shaft;
• a main pressure operating chamber for causing fluid pressure in a valve opening direction to act on said first piston and an auxiliary pressure operating chamber for causing fluid pressure in a valve opening direction to act on said second piston;
• a connecting hole for connecting said main pressure operating chamber and said auxiliary pressure operating chamber to each other;
• one operating port for supplying pressure fluid to said main pressure operating chamber and said auxiliary pressure operating chamber;
• and
• first spring means having large repulsing force for repulsing said main valve body in a closing direction and second spring means having small repulsing force for repulsing said auxiliary valve body in a closing direction,
• wherein there are such relationships between piston diameters of said first piston and said second piston and repulsing forces of said first spring means and said second spring means that said second piston is actuated by lower fluid pressure than said first piston.