Positive displacement gear pump

A positive displacement pump comprising:

• a casing having a central body and a pair of closing lids, said central body having a pair of communicating cylindrical chambers and a suction pipe and a discharge pipe;
• and
• a pair of rotors revolvingly mounted in said cylindrical chambers and supported by corresponding shafts revolvingly mounted in said pair of closing lids, said pair of rotors comprising:
• a male rotor having at least one protuberance and no cavities, said male rotor having a body with at least one seat, the protuberance being positioned in a sector having a base that is engaged in a seat of a body of said male rotor, said male rotor comprising a cylindrical body, said at least one protuberance protruding radially from said cylindrical body;
• and
• a female rotor having at least one cavity and without protuberances or teeth, said male rotor meshing with said female rotor, the protuberance of said male rotor being engaged in said at least one cavity of said female rotor without contact between said pair of rotors, said female rotor comprising a cylindrical body, said at least one cavity extending radially inside said cylindrical body of said second rotor, wherein the protuberance of said male rotor comprising a pair of flex-shaped sides converging into a rounded or flat head, said pair of flex-shaped sides being symmetrical with respect to a radial axis of symmetry passing through said rounded or flat head, said pair of flex-shaped sides having an outlet side and an inlet side, said at least one cavity of said female rotor comprises a pair of flex-shaped sides joined to a bottom surface, said bottom surface having a concave shape, said pair of flex-shaped sides of said female rotor having respective profiles that are not symmetrical with respect to a radial straight line passing through a bottom of said cavity, said pair of flex-shaped sides of said female rotor comprising an inlet side and an outlet side each having a flex-shaped profile, the flex-shaped profile of said inlet side having a greater curvature than a curvature of the flex-shaped profile of said outlet side, said female rotor and said male rotor being disposed in side-by-side relation, suction and delivery ducts being disposed on one side and on another side of said male and female rotors, said suction and delivery ducts having longitudinal axes that are orthogonal to each other.