Bellows pump apparatus

A bellows pump device that supplies pressurized air to one first air chamber of two first hermetic air chambers thereby to cause a first bellows to perform an expansion operation to suck a transport fluid, and supply pressurized air to the other first air chamber thereby to cause the first bellows to perform a contraction operation to discharge the transport fluid, the bellows pump device comprising:

• a first solenoid valve and a second solenoid valve, the first solenoid valve configured to switch between a supply of pressurized air to the one first air chamber and a supply of pressurized air to the other first air chamber;
• a control unit configured to control switching of the solenoid valves by transmitting a command signal to the solenoid valves;
• and
• a first electropneumatic regulator configured to adjust a first air pressure that is an air pressure of pressurized air supplied to the one first air chamber as switched by the first solenoid valve in response to the command signal, and a second air pressure that is an air pressure of pressurized air supplied to the other first air chamber as switched by the first solenoid valve in response to the command signal;
• wherein
• the control unit controls the first electropneumatic regulator such that, at least at a time point of end of expansion during the expansion operation of the first bellows, the first air pressure is lower than the second air pressure,
• the control unit controls the first electropneumatic regulator such that the first air pressure is higher during a first expansion period from a time point of start of expansion to a predetermined time point of the expansion operation than during a second expansion period from the predetermined time point to the time point of end of expansion, and
• the control unit controls the first electropneumatic regulator such that the first air pressure of the first expansion period is constant and the first air pressure of the second expansion period is constant.