In a pump in which dual plunger is reciprocated with cams attached to the rotating shaft of a motor, the delivery pressure of liquid is measured during a certain period in each cycle of the pump. By setting the pressure during the certain period as a standard pressure value, the motor is controlled so...http://www.google.es/patents/US5664937?utm_source=gb-gplus-sharePatente US5664937 - Precisely flow-controlling pump
