Abstract: A motor/pump unit for pumping vapor in response to a flow of liquid, and particularly useful in systems for dispensing fuel to a vehicle wherein vapor given off by the fuel is to be returned from the filling port of the vehicle back to the fuel dispensing apparatus to avoid atmospheric contamination. One inventive embodiment, with available conventional fuel dispenser pressure and flow rate, allows abnormally small motor and pump chambers and motor/pump rotor assembly size and abnormally high rotor assembly rotation rate and abnormally quick rotor assembly acceleration to operating speed with sufficient vapor pumping capability. The resulting abnormally small motor/pump enables same to be easily adapted to a variety of existing dispensing pump and hose configurations. Under another embodiment, structure is provided for maximizing fuel flow rate and minimizing pressure drop across the motor/pump unit while providing adequate vapor pumping rate.

Abstract: A motor/pump unit for pumping vapor in response to a flow of liquid, and particularly useful in systems for dispensing fuel to a vehicle wherein vapor given off by the fuel is to be returned from the filling port of the vehicle back to the fuel dispensing apparatus to avoid atmospheric contamination. One inventive embodiment, with available conventional fuel dispenser pressure and flow rate, allows abnormally small motor and pump chambers and motor/pump rotor assembly size and abnormally high rotor assembly rotation rate and abnormally quick rotor assembly acceleration to operating speed with sufficient vapor pumping capability. The resulting abnormally small motor/pump enables same to be easily adapted to a variety of existing dispensing pump and hose configurations. Under another embodiment, structure is provided for maximizing fuel flow rate and minimizing pressure drop across the motor/pump unit while providing adequate vapor pumping rate.