PURPOSE: To obtain the reciprocating pump having a high discharging pressure, a large discharging quantity and a high quantitative accuracy by a method wherein a sealed chamber is formed by providing a bellows at the driving side of a shaft sealing part slidably contacted by a reciprocating shaft.
CONSTITUTION: When a plunger 25 is pushed to the side of a pump chamber 26, the bellows 33 is contracted into the axial direction thereof and the volume of the sealed chamber 36 is reduced while a gaseous body such as air or the like, which is the fluid in the sealed chamber 36, and a pump handling liquid 27 leaked from the shaft sealing part 28 are discharged to the suction side 41 of the pump from a passing port 37 through a returning pipeline 38. When the plunger 25 is retracted, the bellows 33 is extended into the axial direction thereof and the volume of the sealed chamber 36 is increased while the liquid which has been discharged to the suction side 41 of the pump is now sucked into the sealed chamber 36 from the returning pipeline 38 through the passing port 37. By repeating these operations, the pump handling liquid 27, leaked from the shaft sealing part 28 into the sealed chamber 36, is returned to the suction side 41 of the pump.
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