The Perkin-elmer Corporation

Gianella, Edward P.

Spaulding, Mark F.

Garistina, Gregory

Gregory Garistina

Mark Frank Spaulding

Edward P Gianella

A powder feeding system includes closed loop regulation of powder feed rate. A feed gas is discharged under constant pressure into an enclosed hopper. A valve is disposed to constrict a carrier conduit conveying powder in a carrier gas. A load cell measures the rate at which powder is flowing from the hopper through an intake orifice into the carrier conduit, and filtered flow rate signal is produced. A first controller produces a reference signal representative of the difference between a set point signal and the flow rate signal. A differential signal is produced corresponding to the pressure difference between the hopper pressure and a carrier conduit pressure taken between the intake orifice and the valve. A second controller produces a control signal representative of the difference between the differential signal and the reference signal. The valve is responsive to the control signal to proportionately constrict the carrier gas stream such as to regulate the powder flow rate. Preferably the time constant of the second controller is faster than the time constant of the first controller.

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Bay Shore, NY, United States of America

Gregory Garistina