Patent ID: 6983867
Filing Date: 2006-01-10
Classification: B05C,G01F

Abstract:
1. A material dispensing pump comprising: a feed screw including a cylindrical neck portion and a helical feed path defined between a major diameter and a minor diameter of the feed screw; the feed screw being driven in a first direction of rotation during a dispensing operation of material to be dispensed; a feed screw housing having a cavity, the feed screw extending through the cavity, the feed screw housing having an inlet port and an outlet port in communication with the cavity, the helical feed path being substantially sealed from ambient air between the inlet port and the outlet port by an O-ring positioned about the neck between the neck and the feed screw housing and a threaded spanner nut that applies pressure in a direction along a longitudinal axis of the feed screw that compresses the O-ring about the neck to substantially seal the helical path from ambient air; a pressure unit for applying positive pressure to cause material to be presented to the inlet port at a desired rate during a dispensing operation such that the material flows through the helical feed path toward the outlet port; and a material suspension unit for placing the material in the substantially sealed helical feed path in suspension by applying negative pressure to the material following the dispensing operation.