Site News  |   Monitor Keywords  |   Monitor Archive  |   Organizer  |   Account Info  |

High pressure pumping apparatus with coupled volumes in a pump working chamber

High pressure pumping apparatus with coupled volumes in a pump working chamber description/claims

The present invention relates to a pumping apparatus for delivering liquid at a high pressure at which compressibility of the liquid becomes noticeable.

In high performance liquid chromatography (HPLC), a liquid has to be provided usually at very controlled flow rates (e.g. in the range of microliters to milliliters per minute) and at high pressure (typically 200-1000 bar and beyond up to even 2000 bar) at which compressibility of the liquid becomes noticeable. A general introduction into HPLC can be found e.g. under http://hplc.chem.shu.edu/HPLC/index.html. Some basic principles of reciprocating single piston pumps used in HPLC are described e.g. in http://hplc.chem.shu.edu/HPLC/index.html.

GB 1522552 discloses a pumping system for HPLC having a flow inducer to provide a high pressure metering are liquid.

EP 0309596 A1 discloses an HPLC pump system providing stroke volume variation in order to reduce pulsations.

U.S. Pat. No. 6,712,587 B2 discloses a hydraulic amplifier pump for use in HPLC.

It is an object of the invention to provide an improved pumping apparatus for high pressure liquid delivery. The object is solved by the independent claim(s). Further embodiments are shown by the dependent claim(s).

Embodiments according to the present invention provide a pumping apparatus for delivering liquid at a high pressure at which compressibility of the liquid becomes noticeable. The pumping apparatus has a piston reciprocating in a pump working chamber having a first and a second volume. A movement of the piston into a first direction decreases the first volume and increases the second volume. Accordingly, a movement of the piston into a second direction opposite to the first direction increases the first volume and decreases the second volume. The first and second volumes are coupled to each other as long as a pressure in the first volume exceeds a pressure in the second volume. An outlet valve is provided for coupling the second volume with an outlet of the pumping apparatus as long as a pressure in the second volume exceeds a pressure at the outlet.

The coupling of the first and second volumes of the pump working chamber allows balancing forces onto the piston, so that a drive coupled to the piston for reciprocating the piston is exposed to lesser force requirements. This may allow using smaller drives which in turn may even provide an improved dynamic behavior and in general are usually less costly.

In one embodiment, the pumping apparatus has a given area proportion A between a first effective area of the piston facing the first volume and a second effective area of the piston facing the second volume. The first and second effective areas are opposing each other. With first effective area being greater than the second, a force required to move the piston is partly compensated, but still allowing to achieve a pressure increase in the second volume over the first volume. The force compensation becomes increased with the area proportion A getting closer to one, while greater area proportions A lead to less compensation and thus greater force requirements onto the drive of the piston. On the other hand, greater values of the area proportion A can lead to higher achievable pressure at the outlet of the pumping apparatus. Criteria for selecting the area proportion might be force requirements, dynamic, size, etc. of the piston drive. In some embodiments, area proportions (first effective area/second effective area) A of 2:1, 3:2, 4:3, etc. have been found useful for certain applications and balancing the contravening requirements of achievable outlet pressure and force requirements of the piston drive in certain applications.

In one embodiment, the first volume of the pump working chamber receives liquid at an inlet pressure, which can be ambient pressure or provided by an inlet pump. A control unit might be provided for controlling such inlet pressure to be in a given pressure proportion P to the pressure at the outlet of the pumping apparatus. The pressure proportion P (outlet pressure/inlet pressure) is preferably selected essentially in accordance with the area proportion A, to be A˜P. E. g. in case the pressure proportion is selected to be 2:1 (i.e. the first effective area is twice as large as the second effective area) the pumping apparatus can provide an outlet pressure of up to twice the inlet pressure. In case the pumping apparatus has to provide a certain outlet pressure (e.g. in order to drive a mobile phase through a stationary phase in a liquid chromatography application), the control unit might control the inlet pressure, whereas the outlet pressure then follows based on the given pressure proportion.

One or more pressure sensors for sensing values indicative of pressure might be provided at the inlet and/or outlet of the pumping apparatus, thus allowing to sense and control the pressures and/or the pressure proportion P.

The inlet pressure is preferably provided by an inlet pump coupled to at least one of the first and second volumes to provide liquid thereto at the inlet pressure. The inlet pump might be any kind of pump allowing to provide the liquid at the inlet pressure and might be embodied as a piston pump or a gear pump.

In one exemplary embodiment with A=P=2, the inlet pump is adapted to provide the liquid at 1/P (half in this example) of a required outlet pressure of the pumping apparatus, with the pumping apparatus providing a value of the area proportion A (2:1 in this example). If e.g. an outlet pressure of about 1200 bar is required with an inlet pump providing liquid to the inlet at about 600 bar, the pumping apparatus can thus deliver the liquid at the outlet at the about 1200 bar, but is only exerted to force requirements of 600 bar (i.e. the difference between the output and the input pressure: 1200 bar−600 bar=600 bar). In such embodiment, the inlet pump might be embodied mainly to provide the inlet pressure but with lesser accuracy requirements regarding liquid flow rate. The pumping apparatus, on the other hand, in this embodiment might be designed to provide flow rates at higher accuracy, so that in total a pump results allowing driving liquids with high flow rate accuracy and at high pressure.

In one embodiment, the piston is provided to have on one side the first effective area facing the first volume and on an opposing side the second effective area facing the second volume. The side of the piston facing the second volume is preferably coupled via a piston rod to a drive.

A return mechanism coupled to the piston and being adapted for counteracting against the movement of the piston might be provided to apply a force onto the piston in opposite direction as the drive, as well known in the art and disclosed e.g. in the aforementioned EP 0309596 A1, the teaching thereof shall be incorporated herein by reference.

Sealing might be provided for sealing the pump working chamber against the drive and/or to seal the first and second volumes against each other.

The drive might comprise at least one of a spindle drive mechanism, a linear motor, a stepper motor, a DC-Motor, a VR-Motor; a driving rod coupled to the piston.

The return mechanism might comprise at least one of a spring, a hydraulic cylinder, a drive mechanism, a deflection mechanism, a return rod coupled to the piston.

Valves applied might be one or more of a check valve, an active valve, a solenoid valve.

The inlet pressure might be in the range of 100 to 1000 bar, preferably between 300 and 700 bar, and more preferably about 600 bar. The achievable outlet pressure might be in the range of 500 to 2000 bar, preferably between 800 and 1500 bar, and more preferably about 1200 bar. A flow rate of the liquid at the outlet might be in the range of nanoliter per minute to milliliter per minute, and more preferably in the range of microliter per minute to milliliter per minute.

The coupling between the first and the second volumes can be provided by a conduit and preferably further comprises a coupling valve. In one embodiment, the first and second volumes are both coupled to the inlet pump, so that the coupling might also comprise the inlet pump.

• Provisional Patent
• Utility Patent

• What Is a Patent?
• What Is a Trademark or Servicemark?
• What Is a Copyright?
• Patent Laws