Patent ID: 8220669

Claim:
A material dispensing pump comprising: a feed mechanism including a cylindrical neck and a feed path; a closed-loop servo-motor having indexed rotational positions that drives the feed mechanism during a dispensing operation; a dispensing controller that generates control signals to control the servo-motor, wherein the servo-motor performs the dispensing operation in response to the control signals; a housing having a cavity, the feed mechanism extending through the cavity, the housing having an inlet port and an outlet port in communication with the cavity, the feed path being substantially sealed from ambient air between the inlet port and the outlet port by a seal positioned about the neck between the neck and the housing and a threaded spanner nut that applies pressure in a direction along a longitudinal axis of the neck and that retains the seal in position about the neck, wherein the seal substantially seals the feed 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 the dispensing operation such that the material flows through the feed path toward the outlet port; and a material suspension unit for placing the material in the substantially sealed feed path in suspension by applying negative pressure to the material following the dispensing operation.