Flow rate feedback control chromatograph

Claim 2

IN CHROMATOGRAPH APPARATUS, A CHROMATOGRAPH COLUMN, A SOURCE OF LIQUID TO BE PASSED THROUGH SAID COLUMN, PUMP MEANS CONNECTED BETWEEN SAID SOURCE AND SAID COLUMN, FOR DELIVERING SAID LIQUID UNDER PRESSURE TO SAID COLUMN, DRIVE MEANS FOR DELIVERING MOTIVE POWER TO SAID PUMP MEANS, MEANS FOR DETECTING FLOW THROUGH SAID PUMP AND FOR DEVELOPING A FLOW FEEDBACK SIGNAL IN PROPORTION THERETO, CONTROL MEANS FOR VARYING THE OUTPUT OF SAID DRIVE MEANS, SAID CONTROL MEANS INCLUDING MEANS REPONSIVE TO SAID FLOW FEEDBACK SIGNAL, AND MEANS FOR COMPRISING SAID FLOW FEEDBACK SIGNAL WITH A SIGNAL REPRESENTING A PREDETERMINED DEMAND VALUE OF FLOW.

Claim 3

Apparatus as in claim 1 in which said drive means is an electric motor having a rotary shaft output and further including means for calibrating the flow rate during operation of the pump motor comprising means for sensing the position of the pump piston and for developing a signal when far enough through a stroke to pump up all the compliance of the system, means for developing a second signal when the pump motor drive velocity is in the highest portion of its range, means responsive to the occurence of both signals for varying the gain of said flow rate control means to a predetermined value calibrated on the known relationship between motor speed and flow rate during the interval when both said signals are present.

Claim 4

Apparatus as recited in claim 1 wherein said control means comprises a solvent programmer for providing a solvent programmer control signal indicative of a desired flow rate, and circuit means responsive to said solvent programmer control signal and said flow feedback signal for controlling said power means.

Claim 5

Apparatus as recited in claim 3 wherein said circuit means comprises a difference amplifier responsive to said solvent programmer control signal and said flow feedback signal for providing a flow correction error signal, amplifying means for receiving said flow correction error signal and said solvent programmer control signal for controlling said power means.

Claim 6

Apparatus as recited in claim 4 further comprising a calibration circuit connected for receiving said flow correction error signal from said difference amplifier, and for providing an output signal, a multiplier connected for receiving said solvent programmer control signal and for multiplying said solvent programmer control signal by the output signal of said calibration circuit for providing a multiplied solvent programmer control signal to said difference amplifier.

Claim 7

Apparatus as recited in claim 5 wherein said calibration circuit comprises an integrator connected for receiving said flow correction error signal for providing an integrated output signal to said multiplier.

Claim 8

Apparatus as recited in claim 6 wherein said calibration circuit further comprises means for connecting said integrated output signal to said multiplier in response to a preset timing signal.

Claim 9

Apparatus as recited in claim 6 wherein said calibration circuit further comprises means for connecting said integrated output signal to said multiplier in response to a preset solvent programmer control signal.

Claim 10

In a chromatograph, a chromatograph column, a source of liquid for delivery to said column, means for accurately metering said liquid, including a reciprocating dual-piston pump having at least two pistons driven out of phase with each other and provided with a combined output, a flow transducer connected to said output for providing electrical signal proportional to flow rate therefrom, a motor connected to said pump, means for controlling the speed of operation of said motor, said means having one input connected to the output of said flow traNsducer and being responsive thereto to vary the speed of said motor to cause the flow rate in said output to correspond to a preselected value.

Claim 11

In a chromatograph, a chromatograph column, a source of liquid for delivery to said column, means for accurately metering said liquid, including a reciprocating dual-piston pump having at least two pistons driven out of phase with each other and provided with a combined output, a flow transducer connected to said output for providing electrical signal proportional to flow rate therefrom, a motor connected to said pump, means for controlling the speed of operation of said motor, said means having one input connected to the output of said flow traNsducer and being responsive thereto to vary the speed of said motor to cause the flow rate in said output to correspond to a preselected value.

Claim 12

In a chromatograph apparatus, a chromatograph column, sources of liquid deliverable as plural streams to said column, means for combining said plural streams to produce a single stream including a plurality of pumps for respectively producing plural component streams, means for merging said plural streams into a single stream, power means for driving each of said pumps, flow measuring means in each of said streams for providing flow feedback signals, means for controlling each of said power means, said controlling means being responsible to said flow feedback signals for controlling said power means in accordance with a predetermined demand function for total flow rate of said single stream and realtive composition thereof from said component streams.

Claim 13

In a chromatograph apparatus, a chromatograph column, sources of liquid deliverable as plural streams to said column, means for combining said plural streams to produce a single stream including a plurality of pumps for respectively producing plural component streams, means for merging said plural streams into a single stream, power means for driving each of said pumps, flow measuring means in each of said streams for providing flow feedback signals, means for controlling each of said power means, said controlling means being responsible to said flow feedback signals for controlling said power means in accordance with a predetermined demand function for total flow rate of said single stream and realtive composition thereof from said component streams.

Claim 14

Apparatus as recited in claim 10 wherein said control means comprises a solvent programmer for providing a solvent programmer, control signal indicative of a desired flow rate, and circuit means responsive to said solvent programmer control signal and said flow feedback signal for controlling said power means.

Claim 15

Apparatus as recited in claim 11 wherein said circuit means comprises a difference amplifier responsive to said solvent programmer control signal and said flow feedback signal for providing a flow correction error signal, amplifying means for receiving said flow correction error signal and said solvent programmer control signal for controlling said power means.

Claim 16

Apparatus as recited in claim 12 further comprising a calibration circuit connected for receiving said flow correction error signal from said difference amplifier, and for providing an output signal, a multiplier connected for receiving said solvent programmer control signal and for multiplying said solvent programmer control signal by the output signal of said calibration circuit for providing a multiplied solvent programmer control signal to said difference amplifier.

Claim 17

Apparatus as recited in claim 13 wherein said calibration circuit comprises an integrator connected for receiving said flow correction error signal for providing an integrated output signal to said multiplier.

Claim 18

Apparatus as recited in claim 14 wherein said calibration circuit further comprises means for connecting said integrated output signal to said multiplier in response to a preset timing signal.

Claim 19

Apparatus as recited in claim 14 wherein said calibration circuit further comprises means for connecting said integrated output signal to said multiplier in response to a preset solvent programmer control signal.