| 摘要 |
PROBLEM TO BE SOLVED: To operate a cryogenic pump at a suction head lower than zero by disposing a plurality of holes or passages and a supercharge valve, located at the inlet end part of an inside housing, just behind a piston so that they are not interfered with each other at the final end of a return stroke of the piston. SOLUTION: An inlet end part 14 of an inside housing 12 is provided with a plurality of holes or passages 58, connects liquefied gas from a pre-load chamber 60, located near the inlet end part 14, to a supercharging chamber 36. The passages 58 open directly to the supercharging chamber 36 on a surface perpendicular to a longitudinal axis x-x behind a movable piston 22. A flat supercharging valve 62 is movable in the direction of the longitudinal axis x-x, and can be moved from a closed position to an open position where the supercharging valve 62 is butted on a holding ring 64 fixed to an inside housing 12. The passages 58 and supercharging valve 62 are disposed just behind the piston 22, and the minimum volume of the supercharging chamber 36 is reduced because they are not interfered with each other at the final end of the return stroke of the piston 22. Then, the inside of the supercharging chamber 36 is maintained at a net positive suction head(NPSH) more than zero at the final end of the return stroke of the movable piston 22 to assure the inside of the pre-load chamber 60 at the NPSH lower than zero.
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