Abstract: A rotary fluid pump has a rotor with a sinusoidal, undulating, vane projecting radially from a hub portion rotatable in a pump chamber having a suction chamber, discharge chamber and a transport zone extending circumferentially from the suction chamber to the discharge chamber. The transport zone has a cylindrical inner periphery which is slidably engaged by the periphery of the rotor vane and opposite planar end walls slidably engaged by crests of the undulating vane. Between the suction chamber and the discharge chamber there is a gate assembly with two sliders engaging opposite sides of the vane respectively and interconnected by a bow spring so that they move together. The gate assembly, rotor and casing parts forming the pump chamber are all contained in a cylindrical outer housing, from which they are easily removed for cleaning, inspection and replacement.