Rotary vane pump with plural outlet ports and relationship for cam surface radii

Claim 1

A rotary pump comprising: a housing having a circumferentially extending cam surface on the inner surface thereof; a rotor in said housing and provided with radial slots; piston means in each of said slots and movable radially in the slots and engaging said circumferentially extending cam surface; said housing further having an inlet port and at least two outlet ports circumferentially spaced from each other and from said inlet port, whereby rotation of the rotor causes fluid from the inlet port to be delivered to said outlet ports, the profiles of the two portions of said cam surface extending circumferentially on opposite sides of at least one of the outlet ports along which two piston means move respectively for jointly carrying out the instantaneous delivery through said one outlet port, having radii relative to the axis of rotation of said rotor which decrease progressively in the direction of rotation of said rotor, and the difference between the squares of the radii of said two portions relative to the axis of rotation of the rotor at the instantaneous points of contact of said two piston means with the two portions respectively is a constant.