State determination device of liquid pumping apparatus, and liquid pumping apparatus

A state determination device for a liquid pumping apparatus, comprising:

• a casing that forms a reservoir space for storing liquid flowed thereto;
• a feed valve that introduces working gas into the reservoir space;
• an exhaust valve that releases the working gas from the reservoir space;
• and
• a valve operating mechanism having a float arranged in the reservoir space, and performing a pumping stroke in which the liquid is pumped from the reservoir space under a pressure of the working gas by opening the feed valve and closing the exhaust valve when the float moves up to a predetermined high level, and an inflow stroke in which the liquid flows into the reservoir space and the working gas is released from the reservoir space by closing the feed valve and opening the exhaust valve when the float moves down to a predetermined low level, wherein
• the state determination device comprises:
• a pressure sensor that detects a pressure of the reservoir space;
• and
• a determination unit that determines whether the liquid pumping apparatus is in a first operating state of performing the pumping stroke or in a second operating state of performing the inflow stroke based on the pressure detected by the pressure sensor, and the determination unit determines that the liquid pumping apparatus is in the first operating state in which the pumping stroke is performed from when a predetermined amount of pressure rise is detected to when a predetermined amount of pressure drop is detected by the pressure sensor, and determines that the liquid pumping apparatus is in the second operating state in which the inflow stroke is performed from when a predetermined amount of pressure drop is detected to when a predetermined amount of pressure rise is detected by the pressure sensor.