PURPOSE: To improve the reliability by feeding low temperature pressurized gas onto the liquidized gas face in an enclosed adiabatic container immersed in liquidized gas then pressure feeding the liquidized gas through variation of volume.

CONSTITUTION: A pair of enclosed adiabatic containers 11, 11' are immersed in liquidized gas then suction pipes P1, P1' and pressure feed pipes P2, P2' associated with valves V1, V1', V2, V2' are coupled below said containers 11, 11' while adiabatic floats 12, 12' are floated on the liquidized gas face in said containers 11, 11' where the upper section is coupled through a heatexchanger 15 to a pressurized gas supply source 14 to pressure feed the liquidized gas through variation of gas volume. Consequently mechanical pressurization through a piston is not required thereby frictional problem caused through sliding between the piston and cylinder can be eliminated resulting in improvement of reliability.