Gas injection device

A gas injection device, which is used to pass a gas into a liquid device containing a liquid, comprising:

• a chamber having an upper part and a lower part;
• a gas inlet conduit, connecting to the upper part of the chamber for passing a gas into the chamber;
• a gas outlet conduit, connecting to the upper part of the chamber for passing the gas out of the chamber;
• the gas outlet conduit containing a first check valve which is vertically operable;
• and
• a liquid discharging conduit, connecting to the lower part of the chamber and extending into the chamber, with an end of the liquid discharging conduit inside the chamber bending downward and containing a second check valve which is vertically operable;
• wherein,
• the first check valve has a blocker, the weight of which facilitating it to close the first check valve is selected to be smaller than the upward force imposed by the gas on the blocker in the chamber;
• the second check valve has a blocker, the weight of which facilitating it to close the second check valve is selected to be smaller than the upward force imposed by the gas on the blocker in the chamber, but is greater than the upward force imposed on the blocker by the liquid which flows back through the gas outlet conduit from the liquid device and is accumulated at the bottom of the chamber.