VACUUM DEGASSING DEVICE

PURPOSE:To reliably prevent entrance of the open air into a pump by forming a valve in such a way that a valve seat positioned on the pump side is opened and closed by a valve body, in a device which brings a vacuum vessel into a vacuum state with the aid of a turbo-molecular pump connected to the vacuum vessel through the valve. CONSTITUTION:In a vacuum degassing device, the interior of a vacuum vessel is brought into a vacuum state with the aid of a turbo-molecular pump connected to the vessel through a piping. A valve 21 is located in the piping, and through running of a hydraulic rotary pump for roughing connected to the exhaust side of a turbo-molecular pump, the interior of the vacuum vessel is exhausted to the given degree of vacuum through opening operation of the valve 21 when the degree of vacuum of the piping is increased to a given value. In this case, the valve 21 is formed such that a valve body 14 thereof is forced into pressure contact with a valve seat 22, opened to the turbo-molecular pump side through a seal 15, through the force of a spring 17. This constitution forces the valve body 14 into pressure contact with the valve seat 22 when the vacuum vessel 12 side is brought into an atmospheric pressure state and prevents entrance of the open air to the pump.