Patent ID: 7905142

Claim:
A servo type volumetric flowmeter employing a pump unit system, comprising a pump unit formed by providing inside a pump portion casing a pump portion having a first rotor and a second rotor having rotation shafts and a measuring chamber formed so as to surround the first rotor and the second rotor, wherein the pump unit has a fluid inflow port communicating with the measuring chamber, a fluid outflow port, and a pressure guide port formed in the pump portion casing, with one of the rotor shafts extending to an exterior of the pump portion casing as a drive shaft, wherein the servo type volumetric flowmeter with the pump unit further includes a main body casing, a unit accommodating recess formed in the main body casing and detachably accommodating the pump unit, a cover member covering the unit accommodating recess and fixed to the main body casing, an inflow path formed in the main body casing and guiding a fluid to be measured toward the pump unit, the inflow path being continuous with the fluid inflow port, an outflow path formed in the main body casing and guiding the fluid to be measured to an exterior of the main body casing from the pump unit in the recess of the unit accommodating recess, the outflow path being continuous with the fluid outflow port, a shaft driving unit mounted to the main body casing and driving one of the rotor shafts extending from the pump portion casing, a differential pressure detector for detecting a differential pressure between front and rear sides of the first rotor and the second rotor, and a controller for controlling the shaft driving unit based on the differential pressure, and wherein, due to a presence of the pressure guide port, both inner and outer surfaces of the pump unit, which is accommodated in the unit accommodating recess and covered with the cover member, are kept wet, with the fluid pressures applied to inner and outer sides of the pump unit being equalized.