Control arrangement for controlling a piston pump unit for liquid chromatography

• US 9,624,923 B2
• Filed: 06/14/2013
• Issued: 04/18/2017
• Est. Priority Date: 06/19/2012
• Status: Active Grant

• Current Assignee: Dionex Softron GmbH (Thermo Fisher Scientific Incorporated)
• Original Assignee: Dionex Softron GmbH (Thermo Fisher Scientific Incorporated)
• Inventors: Tuchan, Werner, Ruegenberg, Gervin, Schloderer, Richard
• Primary Examiner(s): FREAY, CHARLES GRANT
• Application Number:
  US13/917,963
• Publication Number:
  US 20130336803A1
• Time in Patent Office: 1,404 Days
• Field of Search: 417 2, 417 3, 417426, 417 442, 417 22
• CPC Class Codes: F04B 23/06 the pumps being all of reciprocating positive-displacement type
• CPC Class Codes: F04B 49/20 by changing the driving speed
• CPC Class Codes: F04B 49/22 by means of valves F04B49/03 takes precedence
• CPC Class Codes: G01N 2030/326 pumps
• CPC Class Codes: G01N 30/22 in high pressure liquid systems
• CPC Class Codes: G01N 30/32 of pressure or speed G01N30/36 takes precedence

Abstract

A control arrangement for controlling a piston pump unit for liquid chromatography, in particular high-performance liquid chromatography, is described. The piston pump unit has at least two piston-cylinder units which operate cyclically in a phase-offset manner and generate, at an outlet port, a predetermined flow of a liquid medium to be delivered. A system pressure is established at the outlet port, irrespective of an associated fluid load resistance. The control arrangement is configured to record the pressure in the cylinder volume of at least a first of the at least two piston-cylinder units. During a measurement phase of the compression phase of the first piston-cylinder unit or during a measurement phase of the decompression phase of the first piston-cylinder unit, the control arrangement stops the drive device for the first piston-cylinder unit for a predetermined time period and in the process records measurement data which characterize the time profile of the pressure.

Claims

1. A piston pump unit for liquid chromatography comprising:

(a) at least two piston-cylinder units configured to generate, at an outlet port, a predetermined flow of a liquid medium at a system pressure, in which each piston-cylinder unit has an independent drive device,

(b) a control device configured to

(i) control the independent drive devices for the at least two piston-cylinder units,

(ii) compress the liquid medium in a first cylinder of the at least two piston-cylinder units in a compression phase from a starting pressure to the system pressure,

(iii) decompress the first cylinder of the at least two piston-cylinder units in a decompression phase,

(iv) record pressure values as a function of time in a cylinder volume of at least a first of the at least two piston-cylinder units during a measurement phase,

(v) stop the independent drive device for the first piston-cylinder unit for a predetermined time period during the measurement phase, the measurement phase being either a measurement phase of the compression phase of the first piston-cylinder unit or a measurement phase of the decompression phase of the first piston-cylinder unit;

(vi) determine a correction dependence to correct a piston movement of at least one of the at least two piston-cylinder units during a compensation phase based on the recorded pressure values as a function of time, and

(vii) control the at least one of the at least two piston-cylinder units using the correction dependence during the compensation phase.

2. The piston pump unit of claim 1, in which the at least two piston-cylinder units are further configured to operate cyclically in a phase-offset manner.

3. The piston pump unit of claim 1. further comprising:

a pressure sensor configured to measure the pressure values in the cylinder volume of at least a first of the at least two piston-cylinder units.

4. The piston pump unit of claim 1, in which the correction dependence is further based on a compression coefficient, a pressure value and a time value when the compressing or decompressing of the first cylinder is stopped, and another time value at a start of the compensation phase.

5. The piston pump unit of claim 4, in which the compression coefficient is a ratio of a change in pressure values to an associated travel distance of a piston in the first cylinder of the at least two piston-cylinder units.

6. The piston pump unit of claim 5, in which the control device is further configured to

(vii) calculate the compression coefficient using a compression coefficient equation, the compression coefficient equation comprising:

Q_c=Δ

s/Δ

P,

where Q_c is the compression coefficient, and Δ

P is the change in the pressure values for the associated travel distance Δ

s of the piston in the first cylinder of the at least two piston-cylinder units.

7. The piston pump unit of claim 6, in which the control device is further configured to

(viii) calculate the correction dependence using a correction dependence equation for piston movement, the correction dependence equation for piston movement comprising:

8. The piston pump unit of claim 1, in which the control device is further configured to calculate parameters P_eDand τ

D of the correction dependence, where the measurement phase occurs during the decompression phase, using a pressure measurement equation and the recorded pressure values as a function of time, the pressure measurement equation comprising;

9. The piston pump unit of claim 8, in which the control device is further configured to

(viii) calculate the correction dependence using a correction dependence equation for piston movement, the correction dependence equation for piston movement comprising:

10. The piston pump unit of claim 7, in which the control device is further configured to calculate an effective time constant for the parameter τ

using an effective time constant equation, the effective time constant equation comprising;

11. A piston pump unit for liquid chromatography comprising:

(a) at least two piston-cylinder units configured to generate, at an outlet port, a predetermined flow of a liquid medium at a system pressure, in which each piston-cylinder unit has an independent drive device,

(b) a control device configured to

(i) control the independent drive devices for the at least two piston-cylinder units,

(ii) compress the liquid medium in a first cylinder of the at least two piston-cylinder units in a compression phase from a starting pressure to the system pressure,

(iii) decompress the first cylinder of the at least two piston-cylinder units in a decompression phase,

(iv) record piston positions or piston speeds as a function of time in a cylinder volume of at least a first of the at least two piston-cylinder units during a measurement phase,

(v) maintain a constant pressure in the cylinder volume of the first piston-cylinder unit for a predetermined time period during the measurement phase, the measurement phase being either a measurement phase of the compression phase of the first piston-cylinder unit or a measurement phase of the decompression phase of the first piston-cylinder unit;

(vi) determine a correction dependence to correct a piston movement of at least one of the at least two piston-cylinder units during a compensation phase based on the recorded piston positions or the recorded piston speeds as a function of time, and

(vii) control the at least one of the at least two piston-cylinder units using the correction dependence during the compensation phase.

12. The piston pump unit of claim 11, in which the control device is further configured to calculate parameters s_e and τ

of the correction dependence using a piston position equation and the recorded piston positions or the recorded piston speeds as a function of time, the piston position equation comprising;

13. The piston pump unit of claim 12, in which the control device is further configured to calculate an effective time constant for the parameter τ

using an effective time constant equation, the effective time constant equation comprising;

14. A method of pumping a liquid with a piston-pump unit for liquid chromatography, the method comprising:

decompressing a first cylinder of at least two piston-cylinder units during a decompression phase, in which a volume of the first cylinder increases;

compressing the liquid in the first cylinder of the at least two piston-cylinder units during a compression phase, in which a pressure of the liquid changes from a starting pressure to a system pressure;

measuring pressure values in the volume of the first cylinder as a function of time during a measurement phase of either the compression phase or the decompression phase;

during the measurement phase, stopping the compressing or the decompressing of the first cylinder for a predetermined time period;

after the compression phase, outputting the liquid at an outlet port at the system pressure during a delivery phase by decreasing the volume of the first cylinder; and

correcting a movement of a piston in the first cylinder of the at least two piston-cylinder units during a compensation phase of the delivery phase based on the measured pressure values.

15. The method of claim 14 further comprising:

determining a correction dependence to correct the movement of the piston in the first cylinder of the at least two piston-cylinder units, the correction dependence being based on a compression coefficient, a pressure and a time value when the compressing or decompressing of the first cylinder is stopped, and another time value at a start of the compensation phase.

16. The method of claim 15, in which the compression coefficient includes a ratio of a change in a pressure to an associated travel distance of the piston in the first cylinder of the at least two piston-cylinder units.

17. The method of claim 16, in which the compression coefficient is calculated using a compression coefficient equation, the compression coefficient equation comprising:

Q_c=Δ

s/Δ

P,

where Q_c is the compression coefficient, and Δ

P is the change in the pressure for the associated travel distance Δ

s of the piston in the first cylinder of the at least two piston-cylinder units.

18. The method of claim 17, in which the correction dependence is calculated using a correction dependence equation for piston movement, the correction dependence equation for piston movement comprising:

19. The method of claim 18, in which the compressing of the liquid in the first cylinder is stopped at the time t₃ for the predetermined time interval.

20. The method of claim 18 further comprising:

calculating the parameters P_e and τ

using the measured pressure values as a function of time and a method of least squares.

21. The method of claim 18 further comprising:

calculating an effective time constant for the parameter τ

using an effective time constant equation, the effective time constant equation comprising;

22. The method of claim 14, in which a control device controls the movement of the piston in the first cylinder of the at least two piston-cylinder units.

23. The method of claim 16 further comprising:

supplying the compression coefficient of the liquid to a control device, in which the control device controls the movement of the piston in the first cylinder of the at least two piston-cylinder units.

24. The method of claim 16 further comprising:

where the measurement phase occurs during the decompression phase, calculating parameters P_eD and τ

_D of the correction dependence using a pressure measurement equation and the measured pressure values as a function of time, the pressure measurement equation comprising;

25. The method of claim 24 further comprising:

calculating the correction dependence using a correction dependence equation for piston movement, the correction dependence equation for piston movement including;

26. The method of claim 25 further comprising:

calculating an effective time constant for the parameter τ

using an effective time constant equation, the effective time constant equation comprising;

27. A method of pumping a liquid with a piston-pump unit for liquid chromatography, the method comprising:

decompressing a first cylinder of at least two piston-cylinder units during a decompression phase, in which a volume of the first cylinder increases;

compressing the liquid in the first cylinder of the at least two piston-cylinder units during a compression phase, in which a pressure of the liquid changes from a starting pressure to a system pressure;

during a measurement phase of either the compression phase or the decompression phase, measuring piston positions or piston speeds in the first cylinder as a function of time;

during the measurement phase, stopping the compressing or the decompressing of the first cylinder, maintaining a constant pressure value in the volume of the first cylinder for a predetermined time period;

after the compression phase, outputting the liquid at an outlet port at the system pressure during a delivery phase by decreasing the volume of the first cylinder; and

correcting a movement of the piston in the first cylinder of the at least two piston-cylinder units during a compensation phase of the delivery phase based on the measured piston positions or piston speeds in the first cylinder as a function of time.

28. The method of claim 27 further comprising, calculating parameters s_e and τ

of the correction dependence using a piston position equation and the measured piston positions in the first cylinder as a function of time, the piston position equation comprising;

29. The method of claim 28 further comprising:

calculating an effective time constant for the parameter τ

using an effective time constant equation, the effective time constant equation comprising;