Abstract: A flow meter with a metallic case and bearing plates but with a blocking rotor and displacement rotors that are polymeric. The rotors may be sized for a reduced clearance between the rotors and surfaces of the case, bearing plates and blocking rotor. Using closer clearances between the rotors and the case bearing plates reduces leakage and provides for a more accurate measurement of the fluid through the flow meter.

Abstract: A flow meter is disclosed with a hollow blocking rotor. The flow meter includes a housing that has a cavity with an inlet and an outlet. The flow meter also includes a pair of displacement rotors with a blocking rotor disposed between the displacement rotors. The blocking rotor includes a pair of convex walls and a pair of concave walls. The blocking rotor further includes a shaft coupled to the pair of concave walls. Each concave wall is disposed between and coupled to a pair of opposing convex walls. The concave walls provide clearance for rotation of the displacement rotors when the displacement rotors sweep along the concave walls. The hollow configuration of the blocking rotor reduces the impedance of the flow meter.

Abstract: A flow meter is disclosed with a hollow blocking rotor. The flow meter includes a housing that has a cavity with an inlet and an outlet. The flow meter also includes a pair of displacement rotors with a blocking rotor disposed between the displacement rotors. The blocking rotor includes a pair of convex walls and a pair of concave walls. The blocking rotor further includes a shaft coupled to the pair of concave walls. Each concave wall is disposed between and coupled to a pair of opposing convex walls. The concave walls provide clearance for rotation of the displacement rotors when the displacement rotors sweep along the concave walls. The hollow configuration of the blocking rotor reduces the impedance of the flow meter.