U.S. patent application number 12/746923 was filed with the patent office on 2010-10-14 for valve based or viscosity based control of a fluid pump.
This patent application is currently assigned to AGILENT TECHNOLOGIES, INC.. Invention is credited to Hans-Georg Haertl.
Application Number | 20100260617 12/746923 |
Document ID | / |
Family ID | 39711865 |
Filed Date | 2010-10-14 |
United States Patent
Application |
20100260617 |
Kind Code |
A1 |
Haertl; Hans-Georg |
October 14, 2010 |
VALVE BASED OR VISCOSITY BASED CONTROL OF A FLUID PUMP
Abstract
A pump control for controlling a fluid pump for pumping a fluid,
the pump control comprising a pump oil path comprising an oil pump
and at least one valve, the oil pump being adapted for pumping pump
oil to the fluid pump, the at least one valve being arranged
downstream of the oil pump, and a control unit adapted for
controlling a pump oil pressure in the fluid pump by switching the
at least one valve so that the fluid can be pumped in response to
the pump oil pressure.
Inventors: |
Haertl; Hans-Georg;
(Karlsruhe, DE) |
Correspondence
Address: |
Agilent Technologies, Inc. in care of:;CPA Global
P. O. Box 52050
Minneapolis
MN
55402
US
|
Assignee: |
AGILENT TECHNOLOGIES, INC.
Loveland
CO
|
Family ID: |
39711865 |
Appl. No.: |
12/746923 |
Filed: |
December 13, 2007 |
PCT Filed: |
December 13, 2007 |
PCT NO: |
PCT/EP2007/063872 |
371 Date: |
June 9, 2010 |
Current U.S.
Class: |
417/53 ; 417/228;
417/300 |
Current CPC
Class: |
G01N 2030/326 20130101;
F04B 43/073 20130101; F04B 49/06 20130101 |
Class at
Publication: |
417/53 ; 417/228;
417/300 |
International
Class: |
F04B 49/06 20060101
F04B049/06; F04B 39/06 20060101 F04B039/06; F04B 49/00 20060101
F04B049/00 |
Claims
1. A pump control (100) for controlling a fluid pump (102) for
pumping a fluid, the pump control (100) comprising a pump oil path
comprising an oil pump (104) and at least one valve (106, 108), the
oil pump (104) being adapted for pumping pump oil to the fluid pump
(102), the at least one valve (106, 108) being arranged downstream
of the oil pump (104); and a control unit (110) adapted for
controlling a pump oil pressure in the fluid pump (102) by
switching the at least one valve (106, 108) so that the fluid can
be pumped in response to the pump oil pressure.
2. The pump control (100) according to claim 1, comprising at least
one of the following features: the oil pump (104) is a
high-pressure pump; the oil pump (104) is adapted for generating a
pressure of at least 500 bar, particularly of at least 800 bar,
more particularly of at least 1000 bar; the at least one valve
(106, 108) comprises an electric field generator unit (300) adapted
for generating an electric field for adjusting a viscosity of the
pump oil comprising an electrorheological fluid; the at least one
valve (106) comprises a cylinder capacitor (302, 304) through which
the pump oil is guidable via a lumen (306) formed between two
cylindrical electrodes of the cylinder capacitor (304, 306); the
pump control (100) comprises a pump oil reservoir (112)
accommodating an electrorheological fluid; the pump control (100)
comprises at least one further valve (502) arranged downstream of
the oil pump (104); the pump control (100) is adapted as a
piston-free pump control.
3. The pump control (100) according to claim 1 or any one of the
preceding claims, comprising a pump oil reservoir (112) for
accommodating pump oil.
4. The pump control (100) according to claim 3, comprising at least
one of the following features: the at least one valve comprises an
inlet valve (106) arranged, in a pumping direction of the oil pump
(104), downstream of the pump oil reservoir (112) and upstream of
the fluid pump (102); the at least one valve comprises an outlet
valve (108) arranged, in a pumping direction of the oil pump (104),
downstream of the fluid pump (102) and upstream of the pump oil
reservoir (112).
5. The pump control (100) according to claim 1 or any one of the
preceding claims, wherein the control unit (110) is adapted for
controlling pump oil pressure in the fluid pump (102) by switching
the at least one valve (106, 108) based on an electric control
signal (114).
6. The pump control (100) according to claim 5, wherein the
electric control signal (114) has a frequency of at least 1 Hz,
particularly of at least 5 Hz, more particularly of at least 10
Hz.
7. A pump system (150), the pump system (150) comprising a fluid
pump (102) for pumping a fluid; a pump control (100) according to
claim 1 or any one of the preceding claims for controlling the
fluid pump (102) for pumping a fluid.
8. The pump system (150) according to claim 7, wherein the fluid
pump (102) comprises a housing (130) and a flexible membrane (132)
dividing an interior of the housing (130) into a pump oil
department (134) and into a fluid department (136); wherein the
control unit (110) is adapted for controlling the pump oil pressure
in the pump oil department (134) thereby exerting a pumping force
on fluid in the fluid department (136) via the flexible membrane
(132).
9. The pump system (150) according to claim 8, wherein the fluid
department (136) comprises an inlet (138) coupled to a fluid
reservoir (140) and comprises an outlet (142).
10. The pump system (150) according to claim 9, comprising a fluid
pre-pump (144) arranged between the fluid reservoir (140) and the
inlet (138).
11. The pump system (150) according to claim 10, wherein the fluid
pre-pump (140) is a low-pressure pump.
12. The pump system (150) according to claim 8 or any one of the
preceding claims, wherein the fluid department (136) comprises an
outlet (142) coupled to a fluid separation unit (146).
13. The pump system (150) according to claim 12, wherein the fluid
separation unit (146) comprises a chromatographic column.
14. The pump system (400) according to claim 7 or any one of the
preceding claims, comprising at least one further fluid pump (102);
wherein the pump control (100) is adapted for controlling pumping
of the fluid by the fluid pump (102) and by the at least one
further fluid pump (102).
15. The pump system (100) according to claim 8 or any one of the
preceding claims, wherein the fluid department (136) comprises an
outlet (142) coupled to a fluidic device (146).
16. The pump system (100) according to claim 15, comprising at
least one of the following features: the fluidic device (146) is
adapted to analyze at least one physical, chemical and/or
biological parameter of at least one compound of a fluidic sample;
the fluidic device comprises at least one of the group consisting
of a sensor device, a test device for testing a device under test
or a substance, a device for chemical, biological and/or
pharmaceutical analysis, an electrophoresis device, a capillary
electrophoresis device, a liquid chromatography device (146), a gas
chromatography device, a gel electrophoresis device, an electronic
measurement device, and a mass spectroscopy device.
17. The pump system (100) according to claim 7 or any one of the
preceding claims, comprising a separation unit (146), particularly
a chromatographic column, adapted for separating different
components of the fluid and being in fluid communication with the
fluid pump (102).
18. A method of controlling a fluid pump (102) for pumping a fluid,
the method comprising providing a pump oil path comprising an oil
pump (104) and at least one valve (106, 108) arranged downstream of
the oil pump (104); pumping pump oil by the oil pump (104) to the
fluid pump (102); controlling a pump oil pressure in the fluid pump
(102) by switching the at least one valve (106, 108) so that the
fluid can be pumped in response to the pump oil pressure.
19. A pump control (100) for controlling a fluid pump (102) for
pumping a fluid, the pump control (100) comprising an adjustment
unit (106, 108, 110) adapted for adjusting a viscosity of pump oil
to thereby adjust a pumping characteristic of the fluid pump
(102).
20. The pump control (100) according to claim 19, comprising at
least one of the following features: the adjustment unit (106, 108,
110) is adapted for adjusting a viscosity of pump oil comprising an
electrorheological fluid by applying an electric field to the pump
oil in at least a portion of a pumping path; the adjustment unit
(106, 108, 110) is adapted for adjusting a viscosity of pump oil
comprising a magnetorheological fluid by applying a magnetic field
to the pump oil in at least a portion of a pumping path; the
adjustment unit (106, 108, 110) is adapted for adjusting a
viscosity of pump oil by adjusting a temperature of the pump oil in
at least a portion of a pumping path; the pump control (100) is
adapted for controlling a microfluidic fluid pump (102); the pump
control (100) is adapted for controlling a fluid pump coupled with
a fluid separation unit (146), particularly with a chromatographic
column.
21. A method of pumping a fluid by a fluid pump (102), the method
comprising adjusting a viscosity of pump oil to thereby adjust a
pumping characteristic of the fluid pump (102).
Description
BACKGROUND ART
[0001] The present invention relates to a pump control.
[0002] In liquid chromatography, a fluidic analyte may be pumped
through a column comprising a material which is capable of
separating different components of the fluidic analyte. Such a
material, so-called beads which may comprise silica gel, may be
filled into a column tube which may be connected to other elements
(like a control unit, containers including sample and/or buffers)
using fitting elements. In liquid chromatography, the mobile phase
containing the dissolved analyte may be moved through a stationary
phase which is capable of separating different components of the
analyte. A liquid chromatography setup may then be connected to
other elements like sampling unit, detection unit, sample and
solvent pump oil reservoirs and control unit. The movement of the
liquid may be enforced through pressure.
[0003] U.S. Pat. No. 4,599,049 discloses a high pressure meter pump
system with improved accuracy provided by subdividing a large meter
pump capacity into metered subvolume charges which are
incrementally delivered to a high pressure slave pump. This enables
the pump system to achieve improved accuracy independent of flow
rate and therefore increasing the range of flow rates available
with acceptable accuracy. Additionally, the pump system self-primes
independently of flow rate and therefore does not require degassing
of the solvent being pumped.
[0004] EP 0,115,672 discloses a mechanism for pulsation damping in
a reciprocating diaphragm pump system which is especially suitable
for solvent delivery in modern high pressure liquid chromatography
requiring a wide range of solvent flow rates and pressures. The
disclosed damper has good overall performance over the full range
of liquid chromatographic conditions, a dead volume independent of
solvent pressure, and largely eliminates the necessity for
continuously pumping the working oil of the diaphragm pump to a
maximum operating pressure.
[0005] EP 0,309,596 discloses a pumping apparatus for delivering
liquid at a high pressure, in particular for use in liquid
chromatography, and comprises two pistons which reciprocate in pump
chambers, respectively. The output of the first pump chamber is
connected via a valve to the input of the second pump chamber. The
pistons are driven by linear drives, e.g., ball-screw spindles. The
stroke volume displaced by the piston is freely adjustable by
corresponding control of the angle by which the shaft of the drive
motor is rotated during a stroke cycle. The control circuitry is
operative to reduce the stroke volume when the flow rate which can
be selected by user at the user interface is reduced, thus leading
to reduced pulsations in the outflow of the pumping apparatus. The
pumping apparatus can also be used for generating solvent gradients
when a mixing valve connected to different solvent containers is
coupled to the input of the pumping apparatus.
[0006] Particularly for modern HPLC (high performance liquid
chromatography) requirements, fluids of small volumes have to be
pumped with high pressure through the fluidic apparatus. With
further decreasing volumes and further increasing pressures, this
task may become difficult for conventional pumping systems.
DISCLOSURE
[0007] It is an object of the invention to provide an efficient
pumping system. The object is solved by the independent claims.
Further embodiments are shown by the dependent claims.
[0008] According to an exemplary embodiment of the present
invention, a pump control for controlling a fluid pump (for
instance a main pump for pumping a liquid and/or gaseous substance)
for pumping a fluid is provided, the pump control comprising a pump
oil path (for instance a conduit system having one or more flow
controlling components) comprising an oil pump (for instance an
auxiliary pump for pumping a pump oil for indirectly effecting the
pumping characteristic of the fluid) and at least one valve (which
may be any component switched in a flow path of the pump oil and
selectively controlling whether or not or to which extent the pump
oil is guidable through the pump oil path), the oil pump being
adapted for pumping pump oil to the fluid pump, the at least one
valve being arranged downstream (in a pump oil flow direction) of
the oil pump, and a control unit (for instance a processor) adapted
for controlling a pump oil pressure in the fluid pump (for instance
exclusively) by switching the at least one valve so that the fluid
can be pumped in response to the pump oil pressure (for instance as
a consequence of a functional coupling between the pump oil path
and a fluid path, for instance mediated through an impermeable
membrane separating the pump oil from the fluid).
[0009] According to another exemplary embodiment, a pump system is
provided, the pump system comprising a fluid pump for pumping a
fluid, and a pump control having the above mentioned features for
controlling the fluid pump for pumping a fluid.
[0010] According to still another exemplary embodiment, a method of
controlling a fluid pump for pumping a fluid is provided, the
method comprising providing a pump oil path comprising an oil pump
and at least one valve arranged downstream of the oil pump, pumping
pump oil by the oil pump to the fluid pump, and controlling a pump
oil pressure in the fluid pump by switching the at least one valve
so that the fluid can be pumped in response to the pump oil
pressure.
[0011] According to still another exemplary embodiment of the
present invention, a pump control for controlling a fluid pump for
pumping a fluid is provided, the pump control comprising an
adjustment unit (for instance a processor) adapted for adjusting
(for instance increasing or decreasing) a viscosity (which may be
denoted as a material's resistance to flow) of pump oil to thereby
adjust a pumping characteristic of the fluid pump.
[0012] According to yet another exemplary embodiment, a method of
controlling a fluid pump for pumping a fluid is provided, the
method comprising adjusting a viscosity of pump oil to thereby
adjust a pumping characteristic of the fluid pump.
[0013] According to a first exemplary aspect, a pump control is
provided having an oil pump in functional interaction with a fluid
pump to be controlled. The pump oil system and the fluid system are
hydraulically coupled so that the control of a pump oil pressure
within the pump oil path has an impact on the fluid pressure of the
fluid pump and is controlled by switching one or more valves.
Therefore, (for instance electronic) valve control signals may
allow to control the fluid pressure in a defined manner, thereby
allowing to control the fluid pump with improved precision and time
resolution. Such a configuration may allow to combine the high
pressure capability of a high-pressure oil pump with the low fluid
volume requirements of a fluid pump such as a microfluidic
pump.
[0014] According to a second exemplary aspect, a viscosity of pump
oil in a pumping system is controlled or modulated to thereby
adjust or set a desired pumping characteristic, for instance to set
a flow or an effective pumping pressure. Such a pump oil viscosity
can be controlled by the variation of electric fields, of magnetic
fields, of temperature or of any other physical parameter having an
impact on the viscosity of the material of the pump oil. For
example, the viscosity of an electrorheological fluid used as a
pump oil may be controlled over a very broad range and with a very
fast time resolution by applying and releasing electric fields.
[0015] In the following, further exemplary embodiments of the pump
control according to the first exemplary aspect will be explained.
However, these embodiments also apply to the pump system according
to the first exemplary aspect, to the method of controlling a fluid
pump according to the first exemplary aspect, and to the pump
control and the method of pumping a fluid by a fluid pump according
to the second exemplary aspect.
[0016] The oil pump may be a high-pressure pump. For example, this
high pressure pump may be realized as a commercially available
hydraulic oil pump in order to bring oil to a high pressure, for
instance of hundreds to thousands bar.
[0017] The oil pump may be adapted for generating a pressure of at
least about 500 bar, particularly of at least about 800 bar, more
particularly of at least about 1000 bar. These pump oil pressures
may be appropriate to bring a fluid to be conducted via the coupled
fluid pump to a sufficiently high pressure, particularly so that it
can be used with modern chromatographic systems such as HPLC
systems (high performance liquid chromatography).
[0018] The pump control may comprise a pump oil reservoir for
accommodating pump oil. Such a pump oil reservoir may be a
container in which pump oil is accommodated. For pump oil, silicone
oil or any mineral or vegetable oil may be used. It may be
particularly advantageous to use an electrorheological fluid as
pump oil. Electrorheological fluids (ERFs) may be denoted as
suspensions of extremely fine non-conducting particles (for
instance up to 50 .mu.m diameter) in an electrically insulating
fluid. The viscosity of such fluids may change reversibly over an
extremely broad range (for instance by an order of 10 or even
100.000) in response to an electric field. For example, a typical
ERF can be converted from the consistency of a liquid to that of a
gel or even a solid, and back, with fast response times for
instance in the order of milliseconds. Examples of the ERFs are
crude oil, silicone oil, vegetable oil such as olive oil or
sunflower oil, mixed with corresponding particles such as natural
polymers, polymeric salts, etc. By using an ERF as pump oil, the
application of electric fields in capacitor-like valves may be used
to control the viscosity and therefore the pressure conditions in
the system.
[0019] As an alternative to an architecture in which a pump oil
reservoir is used having a dedicated storage volume for oil and an
inlet and an outlet, it is also possible to provide the pump
control system as a closed loop without a dedicated oil reservoir,
so that the pump oil may then be accommodated in closed loop lines
or conduits.
[0020] The at least one valve may comprise an inlet valve arranged,
in a pumping direction, downstream of the pump oil reservoir and
upstream of the fluid pump. In other words, the pump oil may then
be conducted from the pump oil reservoir to the oil pump, from
there to the inlet valve and subsequently to the fluid pump. Thus,
by controlling whether the inlet valve is open or closed, and to
which extent the inlet valve is open, it is possible to control a
pressure of pump oil to be supplied from the pump oil reservoir to
the fluid pump, so that an impact of the pump oil system to the
fluid system is adjustable.
[0021] The at least one valve may comprise an outlet valve
arranged, in a pumping direction, downstream of the fluid pump and
upstream of the pump oil reservoir. In other words, the pump oil
may then be conducted from the fluid pump, from there to the outlet
valve and subsequently to the pump oil reservoir. Such an outlet
valve may bridge an impact region of the pump oil on the fluid pump
and a backflow into the fluid container. Also by controlling the
outlet valve to be closed, opened, or opened to a certain extent,
it is possible to precisely influence the pressure conditions
within the fluidic system.
[0022] The at least one valve may comprise an electric field
generator unit adapted for generating an electric field for
adjusting a viscosity of the pump oil comprising an
electrorheological fluid (ERF). By implementing an electric field
generator such as capacitor plates, particularly a cylinder
capacitor, it is possible to locally manipulate the viscosity of
the pump oil within the electric field generator unit with high
precision so that a high oil throughput can be achieved by
switching off the electric field and a slow pump oil flow can be
achieved by applying an electric field, wherein the fast response
time of electrorheological fluids which may be in the order of
magnitude of milliseconds can be beneficially used.
[0023] The at least one valve may comprise a cylinder capacitor
through which the pump oil is guidable via a lumen (such as a
hollow cylindrical conduit) formed between two cylindrical
electrodes of the cylinder capacitor. The cylinder capacitor may be
formed by an inner cylinder and an outer hollow cylinder being
arranged concentrically to one another and delimiting a lumen in
between. By applying an electric voltage between the two
cylindrical electrodes to generate an electric field, an
electrorheological fluid flowing through the lumen can be
controlled over a very wide range regarding fluid viscosity,
thereby effectively controlling the pressure in the system.
[0024] The control unit may be adapted for controlling a pump oil
pressure in the fluid pump by switching the at least one valve
based on an electric control signal (for instance a current or a
voltage signal, which may be pulsed). Since an electric control
signal such as a pulse may be used as a switching signal, a fast
switching and controlling of the pressure may be achieved, for
instance with a frequency of at least about 1 Hz, particularly of
at least about 5 Hz, more particularly of about at least 10 Hz.
Therefore, a very fast switching may be enabled which cannot be
obtained easily with mechanical valves. As an alternative to an
electric switching signal, it is possible to use an electromagnetic
radiation switching signal which may be a light pulse (which, for
instance, can be converted into an electric signal using
optoelectronic converters).
[0025] At least one further valve may be provided in addition to
the inlet valve and/or the outlet valve and may be arranged
downstream of the oil pump. In such a configuration, a single pump
control may be used in combination with a plurality of fluid pumps,
wherein individual valves may be arranged between the pump control
and the individual ones of the fluid pumps.
[0026] The pump control, more precisely a membrane-based interface
between the pump oil path and the fluid path may be free of a
piston. In other words, it may be dispensable to provide a piston
acting on pumping oil in a housing having a membrane dividing the
housing into a pump oil compartment and a fluid compartment.
Therefore, by omitting a mechanically reciprocating piston, the
number of movable parts can be reduced and the system can be kept
simple and small. The pump control can then be achieved by simply
controlling viscosity of the fluid passing electrically controlled
valves.
[0027] In the following, further exemplary embodiments of the pump
system according to the first exemplary aspect will be explained.
However, these embodiments also apply to the pump control according
to the first exemplary aspect and to the method of controlling a
fluid pump for pumping a fluid according to the first exemplary
aspect. These embodiments also apply to the pump control and to the
method of pumping a fluid by a fluid pump according to the second
exemplary aspect.
[0028] The fluid pump may comprise a housing and a mechanically
flexible (particularly impermeable) membrane dividing an interior
of the housing into a pump oil department (in fluid communication
with the pump oil) and into a fluid department (in fluid
communication with the fluid). The control unit may be adapted for
controlling pump oil pressure in the pump oil department thereby
exerting a pumping force on fluid in the fluid department via the
resulting motion of the flexible membrane. In other words, the
valves may define the pump oil pressure characteristics in the pump
oil department. Via the flexible membrane, the corresponding forces
are transferred or translated to the fluid which is controlled
accordingly.
[0029] The fluid department may comprise an inlet coupled to a
fluid reservoir (such as one or more solvent containers) and may
comprise an outlet via which the pressurized fluid may be supplied
to a unit to further process the pressurized fluid. A fluid path
may be directed from the fluid reservoir, through the inlet,
through the fluid department, and through the outlet.
[0030] The inlet may be coupled to a fluid reservoir (for instance
storing solvents or a sample, for instance a biological sample),
and the outlet may be connected to a fluid separation system such
as a chromatographic column. Therefore, a fluid separation may be
performed with a high pressure which may be particularly
advantageously for modern HPLC arrangements.
[0031] The pump system may further comprise a fluid pre-pump
arranged between the fluid reservoir and the inlet. The fluid
pre-pump may be a low pressure pump for precisely adjusting a
desired fluid flow and may be a precise piston pump or plunger pump
(for instance operating at a pressure of about 5 bar). This low
pressure fluid pre-pump in combination with the valve controlled
high pressure pump and the pump oil path may define both an
accurate and a high pressure system which allows to process even
very small fluid volumes.
[0032] The fluid department may comprise an outlet coupled to a
fluid separation unit, particularly a chromatographic column. In
liquid chromatography, a fluidic analyte (brought to a high
pressure by the pump system) may be pumped through a column
comprising a material which is capable of separating different
components of the fluidic analyte. Such a material, so-called
beads, may be filled into a column tube which may be connected to
other elements (like a processor, containers including sample
and/or buffers) using fitting elements. Before analysis on a
column, the fluidic analyte is loaded into the liquid
chromatography apparatus. A steering unit controls an amount of
fluidic sample to be loaded on the liquid chromatography
apparatus.
[0033] In addition to the above described fluid pump, the pump
system may comprise at least one further fluid pump. The pump
control may be adapted for controlling pumping of the fluid by the
fluid pump and by the at least one further fluid pump. For example,
in such an embodiment, it is possible that one pump control is used
to simultaneously control multiple fluid pumps, thereby allowing
the implementation of very complex systems with a simple
construction.
[0034] The fluid department of the oil-fluid interface housing may
comprise an outlet coupled to a fluidic device. Thus, a fluidic
device may be supplied with a liquid, fluid or sample under a
desired pressure condition, for instance under high pressure.
[0035] The fluidic device may be adapted to analyze at least one
physical, chemical and/or biological parameter of at least one
compound of a fluidic sample. Examples for physical parameters are
temperature, pressure, volume or the like. Examples for chemical
parameters are concentration of a component, a pH value of a
liquid, or the like. Examples for biological parameters are the
presence or absence or concentration of proteins or genes in a
solution, the biological activity of a sample, or the like.
[0036] The fluidic device may comprise at least one of a sensor
device, a device for chemical, biological and/or pharmaceutical
analysis, a capillary electrophoresis device, a liquid
chromatography device, a gas chromatography device, an electronic
measurement device, and a mass spectroscopy device. Exemplary
application fields are gas chromatography, mass spectroscopy, UV
spectroscopy, optical spectroscopy, IR spectroscopy, liquid
chromatography, and capillary electrophoresis (bio-) analysis. The
fluidic device may be integrated in an analysis device for
chemical, biological and/or pharmaceutical analysis. When the
fluidic device is a device for chemical, biological and/or
pharmaceutical analysis, functions like (protein) purification,
electrophoresis investigation of solutions, fluid separation, or
chromatography investigations may be performed with such an
analysis device. Particularly, the fluidic device may be a high
performance liquid chromatography device (HPLC) by which different
fractions of an analyte may be separated, examined and
analyzed.
[0037] In the following, further exemplary embodiments of the pump
control according to the second exemplary aspect will be explained.
However, these embodiments also apply to the method of pumping a
fluid by a fluid pump according to the second exemplary aspect, the
pump control according to the first exemplary aspect, the pump
system according to the first exemplary aspect and the method of
controlling a fluid pump for pumping a fluid according to the first
exemplary aspect.
[0038] The adjustment unit may be adapted for adjusting a viscosity
of pump oil comprising an electrorheological fluid (ERF) by
applying an electric field to the pump oil in at least a portion of
a pumping path. Selectively modulating the viscosity of an ERF by
the pump control may allow to adjust the viscosity of the pump oil,
thereby effecting an indirect but well-defined, accurate and
reliable impact on the fluid to be pumped.
[0039] Additionally or alternatively, the adjustment unit may be
adapted for adjusting a viscosity of pump oil comprising a
magnetorheological fluid (MRF) by applying a magnetic field to the
pump oil in at least a portion of a pumping path. A
magnetorheological fluid may be a suspension of micrometer sized
magnetic particles in a carrier fluid, for instance a type of oil.
When subjected to a magnetic field (which may be generated for
instance by a coil having an opening through which the
magnetorheological fluid flows), the fluid greatly increases its
viscosity to the point of becoming a viscoelastic solid. The
viscosity can be controlled precisely by varying the magnetic field
intensity.
[0040] Further additionally or alternatively, the adjustment unit
may be adapted for adjusting a viscosity of pump oil by
manipulating a temperature of the pump oil (for instance by
selectively cooling or heating the pump oil) in at least a portion
of the pumping path. For instance, the fluid can be pumped through
a chamber having a controllable temperature where it may be brought
in contact with a thermoelectric heating/cooling element which can
control the temperature of the fluid efficiently, thereby having an
impact on the viscosity. Thus, also the temperature dependence of
the viscosity of pump oil may be used for pump control
purposes.
[0041] The pump control may be adapted for controlling a
microfluidic fluid pump. The term "microfluidic" may particularly
denote that a volume of the fluids pumped through the system may be
in the order of magnitude of microlitres or hundreds of
microlitres. Furthermore, the dimensions of channels of the fluid
pump may be in the order of magnitude of micrometres to
millimetres.
[0042] The pump control may be adapted for controlling a fluid pump
coupled with a fluid separation unit, particularly with a
chromatographic column. Such a chromatographic column may be filled
with beads and may allow for a separation of a mobile phase based
on a characteristic interaction with a stationary phase.
[0043] Exemplary embodiments may overcome the conventional
shortcoming that the dynamic switch stroke of valves may be too
small. Typically, it may be 20:1. In contrast to this, exemplary
embodiments may operate with a significantly larger switch stroke
(i.e. ratio of pressure drop in an open state/pressure drop in a
closed state or flow in an open state/flow in a closed state).
According to an exemplary embodiment, since significantly more pump
oil under pressure is available than required, it is possible to
pump back a part thereof without use. When switching two ERF valves
in series and switching a non-linear dissipation resistance in
between, it is possible that always a part of the pressure oil
flows away without being used, but when the two ERF valves are
closed, this portion is significantly larger than in an opened
state. By taking this measure, the switch stroke of the arrangement
may be significantly increased. Even under undesired circumstances
where such a measure may be not sufficient, it is possible to add
one or more further stages in a serial configuration.
[0044] According to an exemplary embodiment, a common rail booster
pump may be provided. Such a booster pump may be a further
development of a pump implemented in a 1090 liquid chromatography
system of Agilent Technologies. Conventional pistons in a control
section may be substituted by a valve controlled high pressure pump
with an inlet valve and an outlet valve which may be switched in a
controlled manner, so that at each time, the pulses may control
opening of one of the valves and closing of another one. By taking
this measure, high frequencies of up to 20 Hz or more may be
obtained.
[0045] Such valves may be ERF valves. In an embodiment, at least
three of these ERF valves may be provided. This may allow to
increase the dynamical range, particularly the ratio between a
maximum pressure and a minimum pressure which, for instance may be
1200 bar/3 bar=400. Exemplary embodiments may allow for a common
rail construction with a plurality of booster arrangements
connected in parallel to one another.
[0046] Exemplary embodiments may particularly be appropriate for
small flow volumes and high pressure values. In such an operation
mode, the incompressibility of liquids does no longer apply
strictly. For a precise pump flow it may be therefore necessary to
know the fluid properties. For solving such problems by exemplary
embodiments, the viscosity of pump oil may be adjusted in order to
control a fluid pump. By controlling the time dependence of the
pumping scheme by means of electrical signals in contrast to a
mechanical control, high pumping frequencies of 10 Hz and more are
achievable, and a user-defined adjustment of the pump frequency is
possible. The stress acting on the pump may be reduced since a load
only has to be applied when this is necessary.
[0047] ERFs may be particularly advantageous for a use in a pump,
since these materials may have non-abrasive properties (i.e. they
do not destroy or deteriorate the pump). Furthermore, ERFs do not
have a strong tendency to sediment, may be long-lasting and
applicable even under harsh conditions. Furthermore, ERFs are
appropriate since they have a fast frequency response. For
instance, silicone oil with small particles may be used as ERFs.
Since ERFs may be cheap, they are appropriate as pump oil which may
be required to be replaced from time to time.
[0048] It is possible to provide a plurality of ERF valves (some of
them may have a high resistance, other ones may have a low
resistance, so as to allow for different pressure drops). These
effects are enhanceable, and the pressure of the oil booster may be
varied over a wide range. Simultaneously, the low pressure pump may
be prevented from damage. A non-linear flow resistor may be
switched into the pump oil path, which can also be realized as an
ERF valve. Such an element may ensure that the resistance does not
increase in a non-linear manner with the flow. In this context,
non-linear turbulence effects may be considered.
[0049] Due to the electronic control, a high degree of freedom
regarding the adjustability can be achieved. Particularly, a pump
control with a high pressure pump may be provided controlling the
oil pressure in a booster pump, wherein at least one valve is
switched in a piston-free manner to realize such a control
performance. This may allow for a fast switch by using
electronically adjustable valves. The pump may be controlled by
modification of the viscosity of the pump oil. With such a
configuration, high switching frequencies of 20 Hz and more may be
obtained and it is no longer necessary to know the fluid
characteristics (such as a temperature-pressure dependency or
behaviour and fluid compressibility). A high pressure pump
implementable in the pump oil path can be a commercially available
hydraulic pump (for instance a vane-type pump or a piston
pump).
[0050] A fluid processing element, such as a chromatographic
column, may be provided downstream of the housing in which the
membrane is mounted and may be filled with a fluid separating
material. Such a fluid separating material which may also be
denoted as a stationary phase may be any material which allows an
adjustable degree of interaction with a sample so as to be capable
of separating different components of such a sample. The fluid
separating material may be a liquid chromatography column filling
material or packing material comprising at least one of the group
consisting of polystyrene, cellulite, polyvinylalcohol,
polytetrafluoroethylene, glass, polymeric powder, silicon dioxide
and other suitable metal oxides. However, any packing material can
be used which has material properties allowing an analyte passing
through this material to be separated into different components,
for instance due to different kinds of interactions or affinities
between the packing material and fractions of the analyte.
[0051] The processing element may be filled with a fluid separating
material, wherein the fluid separating material may comprise beads
having a size in the range of essentially 1 .mu.m to essentially 50
.mu.m. Thus, these beads may be small particles which may be filled
inside the separation columns. The beads may have pores having a
size in the range of essentially 0.02 .mu.m to essentially 0.03
.mu.m. The fluidic sample may be passed through the pores, wherein
an interaction may occur between the fluidic sample and the pores.
By such effects, separation of the fluid may occur.
[0052] Optionally, the described fluid processing element may be
followed by a further processing element and may have a size which
differs from a size of the further processing element.
Particularly, the processing element (enrichment-column) may be
significantly smaller than the further processing element (main
column). This different size may result in a different volume
capability and in different fluid separation probabilities of the
two processing elements, which may be adjusted or adapted to one
another.
[0053] The fluidic system may be adapted as a fluid separation
system for separating components of the mobile phase. When a mobile
phase including a fluidic sample is pumped through the fluidic
system, for instance with a high pressure, the interaction between
a filling of the column and the fluidic sample may allow for
separating different components of the sample, as performed in a
liquid chromatography device or in a gel electrophoresis
device.
[0054] However, the fluidic device may also be adapted as a fluid
purification system for purifying the fluidic sample. By spatially
separating different fractions of the fluidic sample, a
multi-component sample may be purified, for instance a protein
solution. When a protein solution has been prepared in a
biochemical lab, it may still comprise a plurality of components.
If, for instance, only a single protein of this multi-component
liquid is of interest, the sample may be forced to pass the
columns. Due to the different interaction of the different protein
fractions with the filling of the column (for instance using a gel
electrophoresis device or a liquid chromatography device), the
different samples may be distinguished, and one sample or a band of
material may be selectively isolated as a purified sample.
BRIEF DESCRIPTION OF DRAWINGS
[0055] Other objects and many of the attendant advantages of
embodiments of the present invention will be readily appreciated
and become better understood by reference to the following more
detailed description of embodiments in connection with the
accompanied drawings. Features that are substantially or
functionally equal or similar will be referred to by the same
reference signs.
[0056] FIG. 1 and FIG. 2 show pump systems according to exemplary
embodiments.
[0057] FIG. 3 shows an ERF valve realized by a cylinder capacitor
according to an exemplary embodiment.
[0058] FIG. 4 and FIG. 5 illustrate pump systems according to
exemplary embodiments.
[0059] FIG. 6 illustrates a high performance liquid chromatography
apparatus according to an exemplary embodiment.
[0060] The illustration in the drawing is schematically.
[0061] In the following, referring to FIG. 1, a pump system 150
according to an exemplary embodiment will be explained.
[0062] The pump system 150 comprises a fluid pump 102 for pumping a
fluid such as a solvent for a biochemical separation procedure.
Furthermore, a pump control 100 is provided for controlling the
fluid pump 102 for pumping the fluid.
[0063] The pump control 100 is adapted for controlling the fluid
pump 102 for pumping the fluid and comprises a closed pump oil path
comprising a pump oil container 112, an oil pump 104 and two valves
106, 108. The oil pump 104 is adapted for pumping pump oil from the
pump oil container 112 to the fluid pump 102 (in a direction as
indicated by arrows in FIG. 1) and back into the pump oil container
112. The valves 106, 108 are arranged downstream of the oil pump
104, in the pumping direction. A control unit 110 such as an
electronic control box is provided for controlling a pump oil
pressure in the fluid pump 102 by selectively switching the valves
106, 108 using electric switch signals 114 so that the fluid in the
fluid pump 102 (which is hydraulically coupled to the pressurized
pump oil via a flexible impermeable membrane 132) can be pumped in
response to the pump oil pressure.
[0064] The oil pump 104 is a high pressure pump for generating a
pressure of, for instance, 800 bar. The pump oil reservoir 112 is
provided for accommodating a pump oil which is a mixture of a
silicone oil and small particles selected so that the pump oil is
an electrorheological fluid (ERF).
[0065] The inlet ERF valve 106 is provided and arranged, in a
pumping direction, downstream of the pump oil reservoir 112 and
upstream of the fluid pump 102. The outlet ERF valve 108 is
provided in a pumping direction downstream of the fluid pump 102
and upstream of the pump oil reservoir 112. The valves 106, 108 are
controlled by the control unit 110. For that purpose, the pulsed
electronic control signals 114 are supplied from the control unit
110 to the valves 106, 108. Since these control signals 114 are
electronic control signals, the control can be performed with a
high time precision of, for instance, a frequency of 10 Hz. The
control signals 114 may be provided individually for each valve
106, 108, or may be provided in common for multiple valves 106,
108. The control signals 114 for the valves 106, 108 may be
identical or may differ, for instance may have a phase shift of
90.degree. or 180.degree. with respect to one another.
[0066] No piston is required in a housing 130 in which the pump oil
effects the fluid, as will be explained in the following in more
detail. The fluid pump 102 namely comprises the housing 130 and a
movable displaceable flexible impermeable membrane 132 dividing an
interior volume of the housing 130 into a pump oil department 134
for accommodating the pump oil and into a fluid department 136 for
accommodating the fluid. The control unit 110 is adapted for
directly controlling the pump oil pressure in the pump oil
department 134 thereby exerting a pumping force also on the fluid
in the fluid department 136 via the flexible membrane 132 so that
the control unit 110 indirectly controls the fluid pressure in the
fluid department 136.
[0067] The fluid department 136 comprises an inlet 138 coupled to a
fluid reservoir 140 (in which a solvent or a sample may be
provided) and comprises an outlet 142. A fluid pre-pump 144 is
arranged between the fluid reservoir 140 and in the inlet 138. The
fluid pre-pump 140 is a low pressure pump having a maximum pressure
of, for instance, 5 bar. The outlet 142 is coupled to a
chromatographic column 146.
[0068] Since the container 112 comprises an electrorheological
fluid which is pumped by the high pressure pump 104 through the
pump control 100, the valves 106, 108 may control the pumping
characteristics by applying electric field on the basis of the
control signals 114 thereby effecting the viscosity of the pump oil
in a time dependent manner to thereby open, close or partially open
the valves 106 and/or 108. In addition to the already described
components, a high pressure damping unit 152 is provided between
the high pressure pump 104 and the inlet valve 106. The high
pressure damper 152 may serve as a damping element to keep the
pressure constant. The control unit 110 may be an electronic
control box, and may be realized by a central processing unit (CPU)
or a microprocessor. The fluid pre-pump 144 may be a low pressure
solvent pump. FIG. 1 illustrates a booster with ERF valves 106,
108.
[0069] In the following, referring to FIG. 2, a pump system 250
according to another exemplary embodiment will be explained.
[0070] The pump system 250 is formed by a pump control 200 and a
fluid pump 102 of the type as explained above. The pump system 250
may allow for a dynamic range extension of the inlet valve
configuration.
[0071] In addition to the components shown in FIG. 1, the
embodiment of FIG. 2 further comprises a non-linear flow resistor
202 which may be realized as an ERF valve. An additional ERF valve
204 is provided downstream of the inlet valve 106 and upstream of
the fluid pump 102. In FIG. 2, the nonlinear restrictor 202 is
adapted for restricting the oil flow from between the two valves
106, 204 upstream of the chamber 130.
[0072] FIG. 3 shows an exemplary construction of the ERF valve 106,
wherein the ERF valves 108, 204 may be constructed in a similar or
identical manner.
[0073] The ERF valve 106 comprises an electric field generator unit
300, namely a current or voltage source for generating an electric
field by applying a corresponding voltage between an inner
cylindrical metallic member 302 and an outer cylindrical metallic
member 304 of the cylinder capacitor structure 106. For applying
and non-applying the electric field in a selective manner, a switch
308 (such as a transistor switch) may be selectively closed or
opened. A fluid flowing through a lumen 306 between the inner full
cylinder 302 and the outer hollow cylinder or tube 304 may then be
controlled regarding viscosity, in dependence of the presently
applied electric field value.
[0074] In other words, the valve 106 comprises a cylinder capacitor
formed by the cylindrical elements 302, 304 delimiting the lumen
306 through which the pump oil is guidable. Other designs are also
possible.
[0075] FIG. 4 shows a pump system 400 according to another
exemplary embodiment having a pump control 100 as shown in FIG. 1.
Additionally, a plurality of fluid pumps 102 are connected in
parallel to the pump control 100 which controls the plurality of
fluid pumps 102 simultaneously. Outlets 142 of the fluid pumps 102
are connected so as to perform a mixing between different fluids at
a mixing point 402. Alternatively, it is possible to further
process some or all of the fluids at the fluid outlets 142 of the
fluid pumps 102 individually, instead of mixing them.
[0076] FIG. 5 illustrates a pump system 510 according to another
exemplary embodiment having a modified pump control 500 which is
based on the pump control 100 but comprises additional ERF valves
502 assigned to each individual one of the several fluid pumps 102.
As indicated by reference numeral 100', the pump control 100 of
FIG. 1 may be modified for the configuration of FIG. 5 in a manner
that the valves 106, 108 of FIG. 1 may be dispensable in view of
the provision of separate ERF valves 502 assigned to each of the
fluid pumps 102. Thus, the pump control 100 may or may not comprise
the ERF valves 106, 108, since their function can be supplemented
or substituted by the individual valves 502. Outlets 142 of the
fluid pumps 102 are connected so as to perform a mixing between
different fluids at a mixing point 402. Alternatively, it is
possible to further process some or all of the fluids at the fluid
outlets 142 of the fluid pumps 102 individually, instead of mixing
them.
[0077] FIG. 6 shows a HPLC system 610 implementing a pump system
620 according to an exemplary embodiment. Such a pump system 620
may be configured for instance similar to the pump systems 150, 250
shown in FIG. 1 or FIG. 2.
[0078] The HPLC system 610 may be used in the context of liquid
chromatography. The pump 620 pumps a mobile phase towards a
separation device 630 (for instance a chromatographic column),
which includes a stationary phase. A sample supply unit 640 is
arranged between the pump 620 and the separation device 630 in
order to insert a sample into the mobile phase, if desired. The
stationary phase of the separation device 630 is provided to
separate components of the sample. A detector 650 detects separate
components of the sample, and a fractioning device 660 can be
provided to output separate components of the sample fluid, for
instance into a waste container or sample containers provided for
that purpose.
[0079] In a simple embodiment, the pump oil of a mechanical
reciprocating oil pump (similar to the 1090 Booster pump) can be
replaced by an ER-Fluid and the override valve is then supplemented
or replaced with an ERF-Valve.
[0080] It should be noted that the term "comprising" does not
exclude other elements or features and the "a" or "an" does not
exclude a plurality. Also elements described in association with
different embodiments may be combined. It should also be noted that
reference signs in the claims shall not be construed as limiting
the scope of the claims.
* * * * *