×

Device for controlling a piston pump unit for liquid chromatography

  • US 10,801,479 B2
  • Filed: 07/02/2012
  • Issued: 10/13/2020
  • Est. Priority Date: 08/19/2011
  • Status: Active Grant
First Claim
Patent Images

1. A device for controlling a piston pump unit for liquid chromatography comprising:

  • (a) two phase-offset cyclically working piston-cylinder units that include two pistons, which produce a predefined flow of a liquid medium to be delivered at an outlet port, wherein a system pressure results at the outlet port, wherein, in a pre-compression phase of one cycle of at least one of the piston-cylinder units, an at least partially adiabatic compression of the medium from a starting pressure to the system pressure occurs, and wherein, in a following delivery phase of the one cycle, in which the flow is also determined by the piston-cylinder units, the medium, which is adiabatically heated during the pre-compression phase, is cooled during a transition phase of the delivery phase of the one cycle;

    (b) a pressure sensor located within at least one of the piston-cylinder units configured to detect the pressure of the medium in a cylinder volume of the at least one of the piston-cylinder units; and

    (c) a processor-controlled control unit, whichactivates a drive device for the two piston-cylinder units with respect to a speed, at which the two pistons of the piston-cylinder units are moved,detects a pressure of the medium in the cylinder volume of the at least one of the piston-cylinder units during the pre-compression phase of the one cycle in which a cooling of the adiabatically heated medium occurs,detects the pressure of the medium in the cylinder volume of the at least one of the piston-cylinder units during an initial phase of the pre-compression phase of the one cycle, in which substantially no heating of the medium by the adiabatic compression has yet occurred, and extrapolates a pressure profile as a function of a time or a position of the piston, and calculates a time t1 or a position of the piston xi, at which the extrapolated pressure profile, which represents an isothermal profile, reaches a value for the system pressure which would result in an idealized isothermal compression at an end of the pre-compression phase,ascertains a time t2 or a position xii of the piston at which the pre-compression phase is ended, andcontrols a piston speed of the two piston-cylinder units during the transition phase of the one cycle depending on at least one characteristic that includes a difference of the time t1 and the time t2 or a difference of the position xi and the position xii, such that variations of the system pressure as a result of the cooling of the adiabatically heated medium are at least partially compensated for.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×