Double vane pumps: Single-acting: the blade is embedded in the groove, and can slide freely, when generated by the rotation, blades flung under the centrifugal effect on the pump casing, the vane pump is a volumetric pump, and the two adjacent blade movement to closed volume with the pump housing and the rotor when the below minimum, maximum when the upper, when the clockwise rotation of the rotor, the experience of two adjacent blades from the lowermost to the uppermost of the process is the increase in the volume process, the oil absorption (from the fourth quadrant to the second quadrant); from the top to the bottom is a volume reduction process, so the oil pressure (from the second to the fourth quadrants). Dual role: when the motor driven rotor along the rotational blades under centrifugal force and the blades of the dual role of the pressure oil at the bottom extending outwardly, and its top is close to the inner surface of the stator. Four vanes in four concentric circular arcs on the composition of the working oil chamber of the four sealing with the outer surface of the rotor, the stator inner surface and two of the valve plate, respectively. These oil chamber from small to big or big to small changes with the rotation of the rotor, the sealing of the oil chamber through the valve plate of oil-absorbing window () or discharge of oil window (with the drain port connected to the suction port connected) oil inhalation or press out. Rotor per revolution process, each working oil chamber to complete two suction and pressure oil, so called double acting vane pump, due to the high and low pressure chamber mutual symmetry symmetrical axis force balance for unloading formula.