A twin-cylinder impeller pump is disclosed. In the above pump, the twin-cylinder runner (3, 4) is provided with an elastic sealing means for removing any gap from the junction between the runner and the throat of a pump casing (10) with the runner being positioned at its upper or lower dead point. In a transmission gear mechanism of the above pump, the drive shaft does not directly engage with the driven shaft, but indirectly engages with the driven shaft through two idle gears (14, 17). In each of the idle gears (14, 17), both a circular concentric gear (14, 17) and an elliptical eccentric gear (15, 18) are commonly mounted to a shaft, thus forming a twin gear. The two elliptical eccentric gears (15, 18) engage with each other, while the two circular concentric gears (14, 17) engage with the drive and driven gears (13, 16) respectively, thus effectively reducing operational noises and vibrations during a pumping operation.
A pump which is easy to manufacture and which has a high efficiency and low vibration includes a pair of identical circular-shaped impellers which are respectively eccentrially and rotatably connected to respective parallel shafts so as to rotate oppositely to one another while keeping a constant spacing therebetween, a pair of identical cylindrical impeller chambers in which the impellers are respectively positioned such that the impellers circumferentially slide along an inner peripheral surface of the impeller chambers, one impeller acting to discharge fluid from the impeller chamber in which it rotates and the other acting to intake fluid into the impeller chamber in which it rotates, and a connecting plate that couples the impellers together and causes them to be spaced a constant distance apart.