Apparatus for volumetric metering of small quantity of powder from fluidized beds

A fluidized bed for dispensing powders, comprising:

• a) a housing defining an enclosure for containing particulate matter, said housing including at least one porous wall having a suitable porosity to allow flow of fluid through said porous wall while preventing most of the particulate matter contained within said housing from passing through said porous wall, a fluid injection means for injecting a fluid into said enclosure for fluidizing particulate matter contained within said housing for forming either a dilute phase only or a dilute phase and a dense phase of fluidized powder in said housing;
• and
• b) time controlled powder withdrawal means connected to said housing and in flow communication with said enclosure through an outlet passageway for withdrawing particulate matter from said housing for a preselected period of time.

A fluidized bed for dispensing powders including a housing defining an enclosure for containing particulate matter, said housing including a fluid injection means for injecting a fluid into said enclosure for fluidizing particulate matter contained within said housing for forming a dilute phase alone or a dilute phase and a dense phase of fluidized powder in said housing, and volumetric metering means connected to said housing and in flow communication with said enclosure through an outlet passageway for withdrawing pre-selected amounts of said particulate matter from said housing.