Abstract: A submerged pump used, for example, in a duplex treating tank for sewage includes a pump casing including an inlet portion, a pump chamber and a discharge portion, and a motor for driving and rotating an impeller provided in the pump chamber. The motor is integrally secured to the pump casing. The pump casing has at least two subcasings assembled together, at least one of the subcasings having a projection defining a narrowed passage portion. An obtusely oriented air vent hole is provided in the lower casing.

Abstract: A pump system comprising a pump having a centrifugal impeller driven by an electric motor, a pair of upper and lower float switches for detecting a high water level HWL and a low water level LWL, respectively, a controller for outputting a control signal on the basis of preset rotational speeds for low and high-speed operations and a preset rotational speed increment rate, together with output signals from the upper and lower float switches, and a frequency converter for varying the rotational speed of the electric motor on the basis of the control signal from the controller, the pump system is capable of exhibiting the required pumping performance and of controlling the flow rate and the pump head.

Abstract: A vortex pump is provided wherein an impeller is of an open type and plural blades are grouped into two or more groups, the axial width of each group of blades being different from the others so that the blades belonging to a certain group extend into a vortex chamber so as to directly drive the liquid in the vortex chamber while relatively large pieces of foreign matter are permitted to pass through the pump.