Precision flow control system

• US 7,927,477 B2
• Filed: 12/12/2008
• Issued: 04/19/2011
• Est. Priority Date: 06/13/2001
• Status: Expired due to Fees

• Current Assignee: AB Sciex LLC (Danaher Corporation)
• Original Assignee: AB Sciex LLC (Danaher Corporation)
• Inventors: Paul, Phillip H., Arnold, Don W., Rehm, Jason E.
• Primary Examiner(s): Phasge; Arun S
• Application Number:
  US12/334,375
• Publication Number:
  US 20090090174A1
• Time in Patent Office: 858 Days
• Field of Search: 204/600, 422/105, 422/110
• US Class Current: 204/600
• CPC Class Codes: B01D 61/56 Electro-osmotic dewatering
• CPC Class Codes: G01N 2030/285 electrically driven carrier
• CPC Class Codes: G01N 2030/324 speed, flow rate
• CPC Class Codes: G01N 2030/326 pumps
• CPC Class Codes: G01N 30/32 of pressure or speed G01N30/36 takes precedence
• CPC Class Codes: G01N 30/34 of fluid composition, e.g. gradient G01N30/36 takes precedence
• CPC Class Codes: G05D 11/132 by controlling the flow of the individual components G05D11/133 takes precedence
• CPC Class Codes: G05D 7/0694 by action on throttling means or flow sources of very small size, e.g. microfluidics microvalves F16K99/0001; microstructural devices per se B81B
• CPC Class Codes: Y10T 137/85978 With pump
• CPC Class Codes: Y10T 137/85986 Pumped fluid control
• CPC Class Codes: Y10T 137/86027 Electric

Abstract

A precision flow controller is capable of providing a flow rate less than 100 microliters/minute and varying the flow rate in a prescribed manner that is both predictable and reproducible where the accuracy and precision of the flowrate is less than 5% of the flow rate. A plurality of variable pressure fluid supplies pump fluid through a single outlet. Flowmeters measure the flow rates and a controller compares the flow rates to desired flowrates and, if necessary, adjusts the plurality of variable pressure fluid supplies so that the variable pressure fluid supplies pump fluid at the desired flow rate. The variable pressure fluid supplies can be pneumatically driven.

Claims

1. A low flow rate precision flow controller system comprising:

(a) a plurality of fluid supplies in fluid communication with a fluid outlet so that a plurality of fluids mix to yield mixed fluids before flowing through the outlet;

(b) a pressure source for each fluid, each pressure source applying pressure to the respective fluid;

(c) a flowmeter for each fluid, each fluid detecting the flow rate of the respective fluid; and

(d) a controller for each pressure source in communication with the respective flowmeter and the respective pressure source wherein the controller compares the respective measured flow rate to a respective desired flow rate and adjusts the respective pressure source so that the respective fluid flows at the respective desired flow rate, wherein the fluids flow out of the fluid outlet at a flow rate of less than approximately 100 microliters/minute.

2. The system of claim 1 wherein the desired flow rates are not the same for each fluid.

3. The system of claim 1 wherein the desired flow rates of the fluids vary as a function of time.

4. The system of claim 1 wherein the mixed fluids flow through the fluid outlet at a substantially constant flow rate.

5. The system of claim 1 further comprising a separation column in fluid communication with the fluid outlet.

6. The system of claim 5, further comprising a detector in fluid communication with an outlet end of the separation column.

7. The system of claim 1 wherein each flowmeter comprises:

(i) a metering capillary having a sufficiently long length and a sufficiently small inner diameter so that the pressure drop across the metering capillary is at least 5% of the input pressure to the metering capillary at the desired flow rate; and

(ii) a pressure sensor, for measuring the pressure drop across the metering capillary.

8. The system of claim 1 wherein each flowmeter comprises:

(i) a metering capillary having a sufficiently long length and a sufficiently small inner diameter so that the pressure drop across the metering capillary is at least 50 psi at the desired flow rate; and

(ii) a pressure sensor, for measuring the pressure across the metering capillary.

9. The system of claim 8 wherein the metering capillary has an inside diameter of less than 50 microns.

10. The system of claim 1 wherein at least one pressure source comprises an electrokinetic pump.

11. The system of claim 1 wherein at least one pressure source comprises an electrokinetic flow controller.

12. The system of claim 1 wherein at least one pressure source comprises a pneumatically activated pump.

13. The system of claim 1 wherein at least one pressure source comprises a mechanically activated pump.

14. The system of claim 1 wherein the system has a time response of less than one second so that when the measured flow rate does not substantially equal the desired flow rate, the measured flow rate will substantially equal the desired flow rate within one second.

15. The system of claim 1 wherein at least one pressure source comprises a dual piston pump.

16. A low flow rate precision flow controller system comprising:

(a) a plurality of fluid supplies in fluid communication with a fluid outlet so that a plurality of fluids mix before flowing through the outlet;

(b) a pressure source for each fluid applying pressure to the respective fluid;

(c) a flowmeter for each fluid for measuring the flow rate of the respective fluids;

wherein the flowmeter comprises;

(i) a metering capillary having a sufficiently long length and a sufficiently small inner diameter so that the pressure drop across the metering capillary is at least 5% of the input pressure to the metering capillary at the desired flow rate; and

(ii) a pressure sensor for measuring the pressure drop across the metering capillary; and

(d) a controller for each pressure source in communication with the respective flowmeter and the respective pressure source wherein the controller compares the respective measured flow rate to a respective desired flow rate and adjusts the respective pressure source so that the respective fluid flows at the respective desired flow rate, wherein the fluids flow out of the fluid outlet at a flow rate of less than approximately 100 microliters/minute.

17. The system of claim 16 wherein at least one pressure source comprises a dual piston pump.