The Perkin-elmer Corporation

Gianella, Edward P.

Spaulding, Mark F.

Garistina, Gregory

Edward P Gianella

Bernard Roy Katz

Mark Frank Spaulding

Stephen A Bauman

Gregory Garistina

Bernard R Katz

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.

Closed loop powder flow regulator

In a system and a method for measuring the rate at which powdered material flows from a container wherein a first analog signal representing the weight of the container is produced, the analog signal is differentiated to obtain a second signal corresponding to the flow rate and the second signal is passed through an adaptive filter. The adaptive filter includes a first low pass filter having a first time constant for producing a third signal and a second low-pass filter to produce a fourth signal. The time constant of the second filter is varied between a minimum equal to the time constant of the first filter and a maximum equal to a preselected multiple of the time constant of the first filter by comparing the absolute value of the difference between the third and fourth signals to a preselected deadband and effecting the maximum time constant when the absolute value of the difference is less than the deadband and the minimum time constant when the absolute value of the difference is greater than the deadband. A combination signal is provided from the fourth signal during the time when the absolute value of the difference is less than the deadband and the third signal during the time when the absolute value of the difference is greater than the deadband. The combination signal is scaled to indicate the powdered material flow rate.

Measurement of flow rate of powder from a hopper

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Teaneck, NJ, United States of America

Edward P Gianella