Abstract: The differential velocity vane pump is a new type of positive pump. It’s composed of eccentric circular—noncircular gear driving system, hull and two coaxial impeller fixed inside the hull. It forms compartments of varying volume by following the movement of closing and opening between the two neighboring vanes which are driven by two pairs of eccentric circular—noncircular gears to allow liquid in and out. The eccentricity e and relative center distance d have been obtained in the condi-tion of that centrode of noncircular gear is closed and by the relationship between rotated angles of the eccentric circular gear and noncircular gear at the time when the neighboring vanes are closing. Furthermore, the centrode is designed. The theoretic maximal opening angle q max, theoretic vane angle g and theoretic stretching angle b of the pumping holes are determined by analyzing transmission of eccentric circular—noncircular gears. The practical vane angle g0 and practical stretching angle b0 are determined on conditions that the neighboring pumping holes can not be connected to each other.

Key words: Differential velocity vane pump, Eccentric circular gear, Noncircular gear, Positive pump