The Vickers Vane Pump states that the single-acting vane pump consists of rotors, stators, blades, oil distribution plates and end caps. The inner surface of the stator is a cylindrical hole. There is an eccentricity between the rotor and the stator. The blade can flexibly slide in the groove of the rotor. Under the action of the centrifugal force of the rotor rotating and the pressure oil flowing into the blade root, the blade top is closely attached to the inner surface of the stator, so that two adjacent blades, the oil distribution plate, the stator and the rotor A sealed working chamber is formed between the two. When the rotor rotates in the counterclockwise direction, the blades on the right side of the figure protrude outward, and the volume of the sealed working chamber gradually increases to generate a vacuum, so that the oil is sucked through the suction port 6 and the window on the oil distribution plate 5. The blade is retracted inward, the volume of the sealed cavity is gradually reduced, and the oil in the sealed cavity is pressed out through the other window of the oil distribution plate and the pressure port 1 and outputted to the system. In the process of turning the rotor one turn, the pump sucks oil and pressure each time, so it is called single-acting pump. The rotor is subjected to radial hydraulic imbalance, so it is also called unbalanced pump, and its bearing load is large. By changing the amount of eccentricity between the stator and the rotor, the displacement of the pump can be changed, so the pumps are variable pumps.