Pump equipment with plural rotary pumps and method for assembling same

A pump equipment comprising:

• a drive shaft;
• plural rotary pumps to be driven by the drive shaft;
• an intake port provided in each of the plural rotary pumps for sucking fluid;
• and
• a discharge port provided in each of the plural rotary pumps for discharging the fluid in high pressure;
• wherein the respective discharge ports are located at the places where the respective reaction forces against the drive shaft to be produced by the high pressure fluid are cancelled out and counterbalance each other,
• wherein the plural rotary pumps are a first rotary pump and a second rotary pump that are arranged in series along the drive shaft,
• wherein the respective discharge ports of the first and second rotary pumps are located at the points opposite each other with respect to the center axis of the drive shaft,
• wherein the first rotary pump is comprised of first rotors to be rotated by the drive shaft, a first cylindrical center plate, first and second cylinders and a first pump room constructed by putting the first cylindrical center plate between the first and second cylinders for containing the first rotors therein;
• wherein the second rotary pump is comprised of second rotors to be rotated by the drive shaft, a second cylindrical center plate, the second cylinder, a third cylinder and a second pump room constructed by putting the second cylindrical center plate between the second and third cylinders for containing the second rotors therein;
• wherein a first intake conduit communicating to the intake port for the first rotary pump and a first discharge conduit communicating to the discharge port for the first rotary pump are respectively provided in the first cylinder;
• wherein a second intake conduit communicating to the intake port for the second rotary pump and a second discharge conduit communicating to the discharge port for the second rotary pump are respectively provided in the third cylinder;
• wherein the first cylinder, the first cylindrical center plate, the second cylinder, the second cylindrical center plate and the third cylinder are piled up and integrated;
• and
• wherein the first cylinder, the first cylindrical center plate and the second cylinder are fixed by a screw and all around the peripheral borders of the first cylinder, the first cylindrical center plate and the second cylinder are welded;
• and the second cylindrical center plate and the third cylinder are fixed by a screw and all around the peripheral border of the second cylindrical center plate and the third cylinder is welded.