Patent ID: 7337920
Filing Date: 2008-03-04
Classification: B67D,F04B,G01F

Abstract:
1. A displacement pump for dispensing a predetermined volume of fluid comprising: a cylindrical chamber coupled to a fluid dispensing outlet having a first one-way check valve, the cylindrical chamber defining an internal volume for storing at least the predetermined volume of fluid; a fluid inlet coupled to the cylindrical chamber, the fluid inlet including a second one-way check valve; a piston slidable in the cylindrical chamber towards the fluid dispensing outlet; a threaded drive rod connected to the piston; a stepper motor in threaded engagement with the threaded drive rod, the stepper motor rotatable by a number of steps to slide the piston towards the fluid dispensing outlet by a distance corresponding to the predetermined volume; a guide tube having one end coupled to the cylindrical chamber and another end coupled to the steeper motor, the guide tube housing a portion of the threaded drive rod for shielding the portion of the threaded drive rod from contaminants, and a rod guide fixed to the threaded drive rod and slidable within the guide tube, the rod guide matingly engaging an inner surface of the guide tube to inhibit rotation of the threaded drive rod.