U.S. patent application number 14/959892 was filed with the patent office on 2016-06-02 for method for pumping fluid in a fluid separation device and related devices and systems.
The applicant listed for this patent is Aglient Technologies, Inc.. Invention is credited to Konstantin Shoykhet, Klaus Witt.
Application Number | 20160153439 14/959892 |
Document ID | / |
Family ID | 44243782 |
Filed Date | 2016-06-02 |
United States Patent
Application |
20160153439 |
Kind Code |
A1 |
Witt; Klaus ; et
al. |
June 2, 2016 |
METHOD FOR PUMPING FLUID IN A FLUID SEPARATION DEVICE AND RELATED
DEVICES AND SYSTEMS
Abstract
In a fluid separation device, fluid supplied to a fluid inlet
conduit at an inlet flow rate is split such that a first part of
the fluid flows into a first outlet conduit and into a pump at a
first flow rate, and a second part of the fluid flows from the
fluid inlet conduit into a second outlet conduit at a second flow
rate. The second flow rate is controlled by controlling the pump
such that, regardless of inlet pressure in the fluid inlet conduit,
the first part of the fluid is continuously conducted away from the
fluid inlet conduit at a defined value of the first flow rate. The
second flow rate is defined based on the defined value of the first
flow rate.
Inventors: |
Witt; Klaus; (Waldbronn,
DE) ; Shoykhet; Konstantin; (Waldbronn, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Aglient Technologies, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
44243782 |
Appl. No.: |
14/959892 |
Filed: |
December 4, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13441021 |
Apr 6, 2012 |
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14959892 |
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Current U.S.
Class: |
417/53 |
Current CPC
Class: |
Y10T 137/794 20150401;
F04B 13/00 20130101; G01N 30/7233 20130101; G01N 30/6095 20130101;
G01N 30/32 20130101; G01N 30/78 20130101; G01N 30/74 20130101; G01N
2030/324 20130101; F04B 39/0005 20130101; G01N 2030/326 20130101;
F04B 7/02 20130101; F04B 2205/09 20130101 |
International
Class: |
F04B 39/00 20060101
F04B039/00; F04B 7/02 20060101 F04B007/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 9, 2011 |
GB |
1107658.5 |
Claims
1. A method for pumping a fluid in a fluid separation device for
separating the fluid, the method comprising: supplying the fluid to
a fluid inlet conduit at an inlet flow rate; splitting the fluid
supplied to the fluid inlet conduit such that a first part of the
fluid flows from the fluid inlet conduit into a first outlet
conduit and into a pump inlet of a pump at a first flow rate, and a
second part of the fluid flows from the fluid inlet conduit into a
second outlet conduit at a second flow rate; and controlling the
second flow rate of the second part of the fluid, by controlling
the pump such that, regardless of a value of an inlet pressure in
the fluid inlet conduit, the first part of the fluid is
continuously conducted away from the fluid inlet conduit at a
defined value of the first flow rate, wherein the second flow rate
is defined based on the defined value of the first flow rate.
2. The method of claim 1, comprising at least one of: controlling
the pump such that the second flow rate is maintained at a constant
value, or according to a predefined profile, over a desired time
interval; controlling the pump such that the second flow rate is
maintained at a constant value, or according to a predefined
profile, over a desired time interval that is larger than one duty
cycle of the pump.
3. The method of claim 1, comprising at least one of: controlling
the pump such that the second flow rate is reduced relative to the
inlet flow rate by the defined value; controlling the pump such
that the second flow rate is in a range between 0.01 ml/min and 1
ml/min.
4. The method of claim 1, wherein supplying the fluid to the fluid
inlet conduit comprises outputting the fluid from a separation unit
configured for separating the fluid.
5. The method of claim 4, comprising detecting the separated fluid
in the first outlet conduit upstream of the pump inlet.
6. The method of claim 1, wherein controlling the pump comprises
adjusting the pump based on the inlet pressure to maintain the
first flow rate at the defined value.
7. The method of claim 1, wherein the pump comprises a first
chamber communicating with the pump inlet, a second chamber
communicating with the pump inlet, a first piston, and a second
piston, and controlling the pump comprises controlling
reciprocation of the first piston in the first chamber and
reciprocation of the second piston in the second chamber.
8. The method of claim 7, wherein controlling the pump comprises at
least one of: selectively connecting and disconnecting the first
chamber and the second chamber from the pump inlet; selectively
connecting and disconnecting the first chamber and the second
chamber from a pump outlet of the pump.
9. The method of claim 7, wherein controlling the pump comprises
switching a fluidic valve of the pump to perform at least one of:
selectively connecting and disconnecting the first chamber and the
second chamber from the pump inlet; selectively connecting and
disconnecting the first chamber and the second chamber from a pump
outlet of the pump.
10. The method of claim 7, wherein controlling the pump comprises
controlling the reciprocation of the first piston and the second
piston cooperatively to conduct the first part of the fluid away
from the fluid inlet when the first piston is moving rearwardly in
the first chamber and when the second piston is moving rearwardly
in the second chamber.
11. The method of claim 10, wherein controlling the pump comprises
controlling a fluidic valve switchable to selectively connect the
first chamber to the first inlet and selectively connect the second
chamber to the first inlet.
12. The method of claim 11, wherein controlling the pump comprises
controlling the fluidic valve to connect the first chamber to the
first inlet when the first piston reverses direction from moving
forwardly to moving rearwardly, and to connect the second chamber
to the first inlet when the second piston reverses direction from
moving forwardly to moving rearwardly.
13. The method of claim 10, wherein controlling the pump comprises
controlling the reciprocation of the first piston and the second
piston such that the first piston is disconnected from the fluid
inlet while the first piston is moving forwardly in the first
chamber, and the second piston is disconnected from the fluid inlet
while the second piston is moving forwardly in the second
chamber.
14. The method of claim 13, wherein controlling the pump comprises
controlling a fluidic valve switchable to selectively disconnect
the first chamber to from the first inlet and selectively
disconnect the second chamber from the first inlet.
15. The method of claim 14, wherein controlling the pump comprises
controlling the fluidic valve to disconnect the first chamber from
the first inlet when the first piston reverses direction from
moving rearwardly to moving forwardly, and to disconnect the second
chamber from the first inlet when the second piston reverses
direction from moving rearwardly to moving forwardly.
16. The method of claim 1, wherein the pump comprises a plurality
of pistons each being controllable for reciprocating forwardly and
rearwardly within a respective chamber to thereby conduct fluid
away from the fluid inlet with the definable flow rate (FT),
wherein the plurality of pistons are controlled so that: a sum of
displaced fluid volume per time by all presently rearwardly moving
pistons being in fluid communication with the fluid inlet, minus a
sum of displaced fluid volume per time by all presently forwardly
moving pistons being in fluid communication with the fluid inlet,
is constant over time.
17. The method of claim 1, comprising conducting the second part of
the fluid at the second flow rate toward a fluidic member
communicating with the second outlet conduit.
18. The method of claim 17, wherein the fluidic member has a
desired flow rate, and controlling the pump comprises controlling
the defined value of the first flow rate such that the second flow
rate equals the desired flow rate.
19. The method of claim 17, comprising at least one of: the fluidic
member comprises a mass spectroscopy device and the separation unit
comprises a chromatography device; the fluidic member is selected
from the group consisting of: a detector device; a device for
chemical, biological and/or pharmaceutical analysis; a capillary
electrophoresis device; a liquid chromatography device; an HPLC
device; a gas chromatography device; a gel electrophoresis device;
a mass spectroscopy device; a another pump; a sensor; and a
combination of two or more of the foregoing.
20. The method of claim 17, comprising operating the fluidic member
to analyze at least a portion of the second part of the fluid.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/441,021, filed Apr. 6, 2012, which claims priority from
UK Patent Application No. GB 1107658.5, filed May 9, 2011, which
are incorporated herein by reference in their entireties.
TECHNICAL FIELD
[0002] The present invention relates to a fluid pump, a flow
splitter, a sample separation device, and methods of handling
fluids.
BACKGROUND
[0003] US 2008/0022765 discloses a liquid chromatography device,
particularly a flow meter with a metering device for intaking and
metering an externally given volume of a fluid, and with a control
unit for controlling the fluid intake of the metering device for
determining a flow rate of the fluid.
[0004] In liquid chromatography, a fluidic sample and an eluent
(liquid mobile phase) may be pumped through conduits and a column
in which separation of sample components takes place. The column
may comprise a material which is capable of separating different
components of the fluidic analyte. Such a packing 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) by
conduits. The composition of the mobile phase can be adjusted by
composing the mobile phase from different fluidic components with
variable contributions. Under undesired circumstances, the flow and
sometimes also the composition of the delivered mobile phase may be
altered or disturbed, which may deteriorate proper operation of the
sample separation device.
[0005] In HPLC technology, a desired flow through a separation
column may be significantly larger than a desired flow through a
mass spectroscopy detector which is used for analyzing separated
components of the fluid. On the one hand, reducing the flow through
the separation column to meet the requirements of mass spectroscopy
may result in artifacts in the detection peaks such as peak
broadening. On the other hand, increasing the flow through the mass
spectroscopy device to meet the requirements of the separation
column is not easily possible as well. Thus, proper operation of a
fluid separation device may still be difficult particularly when a
mass spectroscopy device shall be implemented for analysis
purposes.
[0006] Therefore, there is a need to efficiently manage flow
streams for enabling improved performance of fluid separation.
SUMMARY
[0007] To address the foregoing problems, in whole or in part,
and/or other problems that may have been observed by persons
skilled in the art, the present disclosure provides methods,
processes, systems, apparatus, instruments, and/or devices, as
described by way of example in implementations set forth below.
[0008] According to an exemplary embodiment of the present
invention, a fluid pump for a fluid separation device for
separating a fluid is provided, wherein the fluid pump comprises a
fluid inlet being supplyable with fluid with an inlet pressure, and
a fluid conducting mechanism configured for conducting the fluid
supplied to the fluid inlet towards a connected fluidic path,
wherein the fluid conducting mechanism is controllable so that,
regardless of a value of the inlet pressure, the fluid is
continuously conducted away from the fluid inlet with a definable
(or defined) flow rate. It has to be understood that this can be
accomplished as an active pumping action, although in reverse
direction, in contrast to passive modes, which modulate the
restriction of a hydraulic path in order to control the rate of
flow.
[0009] According to another exemplary embodiment, a flow splitter
for a fluid separation device for separating a fluid is provided,
wherein the flow splitter comprises a fluid inlet conduit by which
fluid is supplyable, a first fluid outlet conduit and a second
fluid outlet conduit both being in fluid communication with the
fluid inlet conduit so that at least a part of fluid supplied by
the fluid inlet conduit is split between the first fluid outlet
conduit and the second fluid outlet conduit, wherein the flow
splitter is configured so that the portion of the fluid supplied
through the fluid inlet conduit is continuously conducted away from
the junction and thus from the first fluid outlet conduit with a
definable (or defined) flow rate. In other terms, a flow
subtraction unit can be provided.
[0010] According to still another exemplary embodiment, a fluid
separation device for separating a fluid is provided, wherein the
fluid separation device comprises a fluid drive, particularly a
pumping system, configured to drive the fluid through the fluid
separation device, a separation unit, particularly a
chromatographic column, configured for separating the fluid.
Additionally, a fluid pump having the above-mentioned features
and/or a flow splitter having the above-mentioned features may be
provided in the fluid separation device. The fluid pump and/or the
flow splitter may be arranged for example upstream of the
separation unit to operate the pump under its optimal conditions
while the separation unit is operated best at a smaller flow rate,
or downstream from the separation unit to operate a downstream
device, such as detection or post-separation treatment, which runs
best below the separation unit's best flow rate.
[0011] According to still another exemplary embodiment, a method of
pumping fluid in a fluid separation device for separating the fluid
is provided, wherein the method comprises supplying a fluid inlet
with the fluid with an inlet pressure, conducting the fluid
supplied to the fluid inlet by a fluid conducting mechanism towards
a connected fluidic path, and controlling the fluid conducting
mechanism so that, regardless of a value of the inlet pressure, the
fluid is continuously conducted away from the fluid inlet with a
defined flow rate.
[0012] According to still another exemplary embodiment, a method of
splitting a fluid flowing in a fluid separation device for
separating a fluid is provided, wherein the method comprises
supplying fluid to a fluid inlet conduit, splitting at least a part
of the fluid supplied by the fluid inlet conduit between a first
fluid outlet conduit and a second fluid outlet conduit both being
in fluid communication with the fluid inlet conduit, and
controlling the fluid flow so that the part of the fluid conducted
to the first fluid outlet conduit is continuously conducted away
from the fluid inlet conduit with a defined flow rate.
[0013] According to yet another exemplary embodiment, a method of
pumping fluid at a variable flow rate in a fluid separation device
for separating the fluid is provided, wherein the method comprises
supplying a fluid inlet with the fluid at an inlet pressure,
conducting the fluid supplied to the fluid inlet by a fluid
conducting mechanism towards a connected fluidic path, and
controlling the fluid conducting mechanism so that, regardless of a
value of the inlet pressure, the fluid is continuously conducted
away from the fluid inlet with an adequate flow rate to leave a
constant flow rate for a mass spectroscopy device independent of a
column flow rate.
[0014] According to yet another exemplary embodiment, a method for
pumping a fluid in a fluid separation device for separating the
fluid is provided, wherein the method comprises supplying the fluid
to a fluid inlet conduit at an inlet flow rate; splitting the fluid
supplied to the fluid inlet conduit such that a first part of the
fluid flows from the fluid inlet conduit into a first outlet
conduit and into a pump inlet of a pump at a first flow rate, and a
second part of the fluid flows from the fluid inlet conduit into a
second outlet conduit at a second flow rate; and controlling the
second flow rate of the second part of the fluid, by controlling
the pump such that, regardless of a value of an inlet pressure in
the fluid inlet conduit, the first part of the fluid is
continuously conducted away from the fluid inlet conduit at a
defined value of the first flow rate, wherein the second flow rate
is defined based on the defined value of the first flow rate.
[0015] In the context of this application, the term "inlet
pressure" may particularly denote an actual pressure value which
the fluid pump or the flow splitter is exposed to (or faces) at its
fluidic inlet. Hence, this inlet pressure is the starting point on
basis of which the fluid pump or the flow splitter adjusts its own
operation. Whatever the value of the inlet pressure is, the fluid
pump or the flow splitter will adjust its own operation (for
instance an internal piston motion and/or a switching state of a
fluidic valve) so that independently from this actual pressure
value, an appropriate fluid flow is set at the fluid inlet to be
intaken.
[0016] In the context of this application, the term "continuously
conducted away" may particularly denote that the fluid pump (or the
flow splitter) is operable so as to ensure that the flow through
the inlet of the fluid pump (or through the first fluid outlet
conduit) is controlled, for instance to be constant or to follow a
predefined profile over a certain time interval, without
uncontrollable sub intervals. For instance, the time interval over
which the flow through the inlet is uninterruptedly controllable
may be larger than one duty cycle, particularly larger than two
duty cycles, of the fluid pump. For instance, the time interval
over which the flow through the inlet is uninterruptedly
controllable may be particularly larger than at least twice or at
least three times of a time required by a reciprocating piston for
moving in a chamber of the fluid pump before changing its motion
direction. In contrast to conventional approaches, an exemplary
embodiment may allow an uninterrupted definition of the subtracted
flow without artifacts arising from an inversion of a motion
direction of a reciprocating piston at reversal points.
[0017] In the context of this application, the terms "definable"
and "defined" may particularly denote that it is possible to
indicate a target flow to be subtracted from a fluid inlet
interface of the fluid pump. The pump will then control its
internal operation so as to permanently attain the target flow
(which may be constant or time-dependent, depending on the
definition). In an embodiment, the target flow may be "defined" as
being an actually supplied flow (may be measured) minus a given
value. This way the flow at the said second outlet will be exactly
the given value, independent of the level of supplied flow.
[0018] In the context of this application, the term "flow rate" may
particularly denote a fluid volume (or a fluid mass, especially
when the fluid is exposed to substantial pressure levels at which
compressibility becomes noticeable) flowing per time through the
fluid inlet or through the first fluid outlet conduit.
[0019] In the context of this application, the term "flow splitter"
may particularly denote a fluidic member which is configured for
splitting or dividing an inlet flow from a fluid inlet conduit into
exactly two or more than two outlet flows. A flow splitter may
provide for a splitting of a source fluid flow into multiple target
flows, simply a bifurcation of the flow stream. Examples for a flow
splitter are a fluidic T-piece or a fluidic Y-piece (both having
one inlet conduit and two outlet conduits) or a fluidic X-piece
(having one inlet conduit and three outlet conduits, or having two
inlet conduits and two outlet conduits).
[0020] In the context of this application, the arrangement of a
first fluidic member "downstream" of a second fluidic member in a
fluidic path may particularly denote that, in a fluid flow
direction, the fluid passes firstly the second fluidic member and
subsequently the first fluidic member. Correspondingly, the
arrangement of a first fluidic member "upstream" of a second
fluidic member in a fluidic path may particularly denote that in a
fluid flow direction, the fluid passes firstly the first fluidic
member and later the second fluidic member.
[0021] According to an exemplary embodiment, a fluid pump is
provided which has the characteristic property that independently
of a present inlet pressure, the fluid pump ensures that, at its
fluid inlet, always a defined flow rate is subtracted or intaken.
In other words, a precisely definable negative flow to be conducted
away from the fluid inlet is the parameter which is controlled by
the fluid pump. Hence, it can be ensured that even in the case of
changes of the inlet pressure, the fluid conducting mechanism of
the fluid pump will either increase the power of sucking fluid in
its interior or will actively provide a counterforce if the inlet
pressure becomes so large that without such an active counterforce
the defined flow rate would be exceeded. Hence, the controlled
parameter is the flow rate intaken by the fluid pump.
[0022] Particularly, this principle or even such a fluid pump may
be advantageously implemented in a flow splitter to allow to
subtract a defined flow rate from an inlet flow so that one or more
other outlet fluid conduits will always carry a flow rate which is,
in comparison to the inlet flow, reduced by the subtracted flow
intaken by the fluid pump. Thus, an exceeding flow in the other
outlet conduit(s) may be prevented by the fluid pump. At the same
time, the other fluid outlet conduit(s) will not be influenced at
all by this defined flow reduction because the fluid pump is not
arranged in this or these other fluid outlet conduit(s) due to the
bifurcated structure of the flow splitter.
[0023] Such embodiments may be advantageously implemented in a
fluid separation device such as a HPLC because here it can be
desired that the fluid flowing through a separation column should
be significantly higher than a flow flowing towards a mass
spectroscopy device downstream of the column. By arranging the
separation column in the fluid inlet conduit, the fluid pump in the
first fluid outlet conduit and the mass spectroscopy device in the
second fluid outlet conduit, it can be controlled which fluid flow
is subtracted by the fluid pump and will therefore not be conducted
to the mass spectroscopy device. Consequently, the flow through the
separation column may be adjusted to be larger than the flow
through the mass spectroscopy device.
[0024] For example, flow rates as small as 0.5 ml/min or less can
be conducted towards the mass spectroscopy device, whereas the flow
rate at the separation column may for instance be 2 ml/min or more.
Depending on required conditions for a certain fluid separation
application, an active splitting which is to be performed by the
fluid pump may be fine-tuned.
[0025] The previously described advantageous effects of flow
reduction by a defined intake in a bifurcated fluidic path may be
achieved continuously, i.e. basically without interruptions.
Therefore, any discontinuity or unsteadiness of the fluid
characteristic which for instance may conventionally occur at
reversal points of reciprocating pistons of a fluid pump can be
prevented by a corresponding operation of the fluid pump according
to exemplary embodiments.
[0026] Next, further exemplary embodiments of the fluid pump will
be explained. However, these embodiments also apply to the flow
splitter, the fluid separation device, and the methods.
[0027] In an embodiment, the fluid pump comprises a control unit
configured for controlling the fluid conducting mechanism so that,
regardless of the value of the inlet pressure, the fluid is
continuously conducted away from the fluid inlet with the
definable, particularly with a constant, flow rate. Such a control
unit may be a central processing unit (CPU) or a microprocessor. It
may allow for a self-acting adjustment of the operation of the
fluid pump to meet the given target flow rate, for instance based
on sensor data, library data about solvent characteristics,
calibration data about technical characteristic of the fluid pump
or a user input.
[0028] In an embodiment, the fluid conducting mechanism is manually
controllable by a human user so that, regardless of a value of the
inlet pressure, the fluid is continuously conducted away from the
fluid inlet with the definable, particularly with a constant, flow
rate. In this embodiment, a user himself may control or define the
flow rate at the pump inlet which extends the possible applications
of the fluid pump to many technical fields.
[0029] In both embodiments, i.e. the adjustment by the control unit
or by the user, it is possible to support the controlling entity
with sensor measurements which may measure parameters such as
pressure, flow rate, temperature, etc. at one or various positions
of the fluidic system.
[0030] In an embodiment, the fluid conducting mechanism is
controllable so that, regardless of the value of the inlet
pressure, the fluid is continuously conducted away from the fluid
inlet with a constant flow rate. A constant flow rate, i.e. a
flowing fluid volume per time interval which does not change over
time, may be advantageous to achieve a constant separation
performance of a liquid chromatography apparatus.
[0031] In an embodiment, the fluid conducting mechanism is
controllable so that when the inlet pressure has a value which
would (in the absence of the controlling) result in a flow rate
exceeding the definable flow rate, the fluid conducting mechanism
applies a counterforce against the inlet pressure so as to adjust
the flow rate to the definable flow rate. Thus, the fluid pump may
actively fight against a force applied by the fluid. For instance,
a piston of the fluid pump may apply a certain pressure contrary to
a flowing direction of the fluid.
[0032] In an embodiment, the fluid conducting mechanism is
controllable so that when the inlet pressure has a value which
would (in the absence of the controlling) result in a flow rate
below the definable flow rate, the fluid conducting mechanism
enforces the inlet pressure by applying an additional sucking force
so as to adjust the flow rate to the definable flow rate. Hence,
under operation conditions being inverse to the previously
mentioned scenario, i.e. a quite small flow rate of the fluid, the
fluid pump may actively decrease the inlet pressure by applying a
corresponding enforcing or enhancing additional sucking force so
that the predefined fluid flow is intaken by the fluid pump.
[0033] In an embodiment, the fluid conducting mechanism comprises a
piston being controllable for reciprocating within a chamber so as
to conduct the fluid away from the fluid inlet with the definable
flow rate when moving rearwardly in the chamber during a part of a
duty cycle. In this context, the term "rearwardly" may particularly
denote a motion of the piston within the chamber which is parallel
to a motion direction of the streaming fluid. Therefore, when a
piston moves rearwardly, fluid is sucked in via the fluid inlet. In
contrast to this, a forwardly moving piston may move antiparallel
to the streaming fluid so that a coupling of such a forwardly
moving piston and the streaming would not result in fluid being
sucked in the fluid inlet. Therefore, a piston may be decoupled
from the fluid at the fluid inlet during the forward motion and may
be coupled to the fluid at the fluid inlet during the backward
motion. Since a piston in the chamber usually reciprocates, time
intervals of coupling and decoupling the piston with the fluidic
inlet may alternate. Particularly, a piston being coupled to the
fluid inlet close to a reversal point (i.e. an end position of the
piston in the chamber at which it changes from a rearward motion to
a forward motion, or vice versa) might cause artifacts in a flow
characteristic. Hence, it may also be possible to couple a piston
to the fluid inlet only when moving along a central part of the
chamber in the rearward direction, so that the piston may also be
fluidically decoupled from the fluid inlet when travelling in the
rearward direction but being sufficiently close to the end of the
chamber.
[0034] In an embodiment, the fluid conducting mechanism comprises a
further piston being controllable for reciprocating within a
further chamber so as to, in cooperation with the previously
mentioned piston, conduct the fluid away from the fluid inlet with
the definable flow rate when moving rearwardly in the further
chamber during a part of the duty cycle. According to such an
embodiment, at least two pistons are used which together can ensure
the continuous intake of a fluid with a definable flow rate. When
the two pistons are operated with a phase difference with regard to
their reciprocation, it can be ensured that there is always at
least one piston moving in a rearward direction so that a
continuous--particularly constant or at least definable (may be
ramping or according to a specific shape)--subtracted flow rate is
possible.
[0035] In an embodiment, any of the piston and the further piston
is controllable for moving forwardly within the respective chamber
during a part of the duty cycle so that, during moving forwardly, a
respective piston is fluidically disconnected from the fluid inlet.
Thus, it can be prevented that the subtracted fluid is reduced by a
forwardly moving piston. However, in case of three or more pistons,
it may also be possible to adjust (for instance reduce) a flow rate
by intentionally coupling also one or more presently forwardly
moving pistons to the fluid inlet.
[0036] In an embodiment, the fluid pump comprises a switchable
fluidic valve having fluidic interfaces in fluid communication with
the fluid inlet, with the fluidic path, with the chamber and with
the further chamber. In an embodiment, such a switchable valve may
be rotary valve. Such a rotary valve may be formed of two members
or components being rotatable relative to one another. By taking
this measure, it can be possible that fluid ports formed at certain
positions of one of the members of the fluidic valve can be
selectively brought in alignment or out of alignment with grooves
formed in the other one of the members of the fluidic valve.
Therefore, it is possible to properly define time intervals during
which a respective one of the chambers and pistons is coupled to
the fluid inlet and other time intervals where it is decoupled from
the fluid inlet. The switching logic of the rotary valve may be
configured so that at each time a defined target flow rate is
subtracted by the presently fluid coupled pistons from the fluid
inlet.
[0037] In an embodiment, the fluidic valve is switchable so as to
fluidically disconnect a respective piston from the fluid inlet
upon reversing its motion direction from a rearward motion to a
forward motion (or a predefined time interval or spatial section
before the reversing). According to this embodiment, the piston may
be decoupled from the fluid inlet at (or close to) the reversal
point of the reciprocating piston, i.e. at top or bottom dead
point, so as to prevent artifacts which may specifically occur at
such a reversal.
[0038] In an embodiment, the fluidic valve is switchable so as to
fluidically connect a respective piston to the fluid inlet upon
reversing its motion direction from a forward motion to a rearward
motion (or a predefined time interval or spatial section after the
reversing). Therefore, for instance a predefined delay time after
reversing the motion direction from forward to rearward motion, the
respective piston may be coupled to the fluid inlet so that it can
again contribute to the subtraction of the fluid flow over the
remaining part of the stroke width.
[0039] In an embodiment, the flow rate can be defined to be in a
range between about 0.001 ml/min and about 10 ml/min. This is a
proper range of flow rates for liquid chromatography applications.
However, other flow rates are possible, especially when the size of
pistons is altered (a smaller piston may correspond to a lower
flow, a larger piston may correspond to a higher flow.
[0040] In an embodiment, the fluid pump comprises a waste container
in fluid communication with the fluidic path. Such a waste
container may be a pressureless container at the end of a fluidic
conduit in which fluid (which is for instance no more needed) can
be accumulated.
[0041] In an embodiment, the fluid conducting mechanism comprises a
plurality of pistons (two, three, or more) each being controllable
individually for reciprocating forwardly and rearwardly within a
respective chamber to thereby conduct fluid away from the fluid
inlet with the definable flow rate. The plurality of pistons may be
controlled so that a difference between a sum of displaced fluid
volume per time by all presently rearwardly moving pistons (and
being presently in fluid communication with the fluid inlet, for
instance as a consequence of a present switching state of the
fluidic valve) and a sum of displaced fluid volume per time by all
presently forwardly moving pistons (and being presently in fluid
communication with the fluid inlet, for instance as a consequence
of a present switching state of the fluidic valve) is constant over
time. Thus, the integral forwardly displaced fluidic volume minus
the integral backwardly fluid volume can be adjusted to the
requirements. Other pistons being presently not in fluid
communication with the fluid inlet, for instance as a consequence
of a present switching state of the fluidic valve, do not
contribute to the adjustment of the actual flow rate.
[0042] Next, further exemplary embodiments of the flow splitter
will be explained. However, these embodiments also apply to the
fluid pump, the fluid separation device, and the methods.
[0043] In an embodiment, a fluid pump (for instance a fluid pump
having the above mentioned features) is arranged in the first fluid
outlet conduit. Thus, fluid at exactly the defined flow rate may be
sucked into the first fluid outlet conduit, so that the flow rate
from the fluid inlet conduit minus the flow rate in the first fluid
outlet conduit may be pumped into the second fluid outlet conduit.
Thus, by a manipulation of fluid flow in the first fluid outlet
conduit, a flow rate in the other second fluid outlet conduit may
be set without the need to arrange any control member in the second
fluid outlet conduit. Hence, the flow in the second fluid outlet
conduit is not disturbed by any control member in the second fluid
outlet conduit.
[0044] In an embodiment, the first fluid outlet conduit is
fluidically coupled to the fluid inlet of the fluid pump. Thus, the
fluid pump may selectively manipulate the flow condition in the
first fluid outlet conduit.
[0045] In an embodiment, the flow splitter is configured as a
fluidic T-piece or a fluidic Y-piece. Thus, the entire lines of the
"T" or "Y" may have an inner lumen, and the crossing point of the
lines may be fluidically coupled to one another.
[0046] In an embodiment, the flow splitter is configured so that
the part of the fluid conducted to the second fluid outlet conduit
is conducted away from the fluid inlet conduit with a flow rate in
a range between about 0.001 ml/min and about 1 ml/min. However,
other adjustable flow rates are possible, wherein the given range
is advantageous for liquid chromatography applications in which a
mass spectroscopy device with the need for small flow rates is
arranged in the second fluid outlet conduit.
[0047] Next, further exemplary embodiments of the fluid separation
device will be explained. However, these embodiments also apply to
the fluid pump, the flow splitter, and the methods.
[0048] In an embodiment, the fluid pump and/or the flow splitter
may be arranged downstream of the separation unit to operate a
downstream device, such as detection or post-separation treatment,
which runs best below the separation unit's best flow rate.
[0049] In an embodiment, the fluid pump and/or the flow splitter
may be arranged upstream of the separation unit to operate the pump
under its optimal conditions while the separation unit it operated
best at a smaller flow rate.
[0050] In an embodiment, the fluid separation device comprises an
electromagnetic radiation detector configured for detecting the
separated fluid (i.e. different fractions thereof) and being
arranged in the first fluid outlet conduit, i.e. in the same fluid
conduit as the fluid pump. Such an electromagnetic radiation
detector may be an ultraviolet detector having an ultraviolet
radiation source and a corresponding detector. Both these
components may be part of a flow cell. The separated fluid may be
conducted between source and detector so that the detector can
detect electromagnetic radiation after interaction with the fluid,
for instance measuring absorbance, fluorescence, etc. More
generally, the used detector may be based on an electromagnetic
radiation detection principle of any appropriate wavelength, i.e.
may detect electromagnetic radiation after interaction with the
fluid, particularly may detect secondary electromagnetic radiation
coming from the fluid in response to the irradiation of the fluid
with primary electromagnetic radiation.
[0051] In an embodiment, the electromagnetic radiation detector is
arranged upstream the fluid pump. Hence, the UV detector may be
arranged in the same fluidic path as the fluid pump. By arranging
it upstream of the fluid pump, the detection will not be negatively
influenced by any effects caused by the fluid pump and any
influence of the fluid pump on the fluid so as to obtain
reproducible data.
[0052] In an embodiment, the fluid separation device comprises a
mass spectroscopy device configured for analyzing the separated
fluid and being arranged in the second fluid outlet conduit. Such a
mass spectroscopy device can be arranged in the other fluid outlet
conduit so that its fluid flow (which is usually quite small) can
be defined by the fluid pump in the other parallel fluidic path.
Hence, this flow rate control architecture will not negatively
influence the operation of the mass spectroscopy device or the
sample conducted thereto.
[0053] In an embodiment, a flow rate of the fluid in the mass
spectroscopy device [[(80)]] is smaller than a flow rate of the
fluid in the separation unit. For instance, it is possible to
operate a separation column of a liquid chromatography device with
a flow in a range between 1 ml/min and 5 ml/min, a flow in an
outlet fluid conduit in which a mass spectroscopy device is
arranged in a range between 0.01 ml/min and 1 ml/min. It is also
possible to operate the fluid pump to subtract a flow rate (the
defined flow rate) in a range between 1 ml/min and 5 ml/min.
[0054] The separation unit may be filled with a separating
material. Such a 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 separating
material may be a liquid chromatography column filling material or
packing material comprising at least one of the group consisting of
polystyrene, zeolite, polyvinylalcohol, polytetrafluorethylene,
glass, polymeric powder, silicon dioxide, and silica gel, or any of
above with chemically modified (coated, capped etc) surface.
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.
[0055] At least a part of the separation unit may be filled with a
fluid separating material, wherein the fluid separating material
may comprise beads having a size in the range of essentially 0.1
.mu.m to essentially 50 .mu.m. Thus, these beads may be small
particles which may be filled inside the separation section of the
microfluidic device. The beads may have pores having a size in the
range of essentially 0.01 .mu.m to essentially 0.2 .mu.m. The
fluidic sample may be passed through the pores, wherein an
interaction may occur between the fluidic sample and the pores.
[0056] The fluid separation device may be configured for separating
components of the fluid. When a mobile phase including a fluidic
sample passes through the fluid separation device, for instance by
applying 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.
[0057] However, the fluid separation device may also be configured
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 band of
material may be selectively isolated as a purified sample.
[0058] The sample separation device may be configured to analyze at
least one physical, chemical and/or biological parameter of at
least one component of the mobile phase. The term "physical
parameter" may particularly denote a size or a temperature of the
fluid. The term "chemical parameter" may particularly denote a
concentration of a fraction of the analyte, an affinity parameter,
or the like. The term "biological parameter" may particularly
denote a concentration of a protein, a gene or the like in a
biochemical solution, a biological affinity of a component,
etc.
[0059] The fluid separation device may be implemented in different
technical environments, like a sensor device, a test device, a
device for chemical, biological and/or pharmaceutical analysis, a
capillary electrophoresis device, a capillary electrochromatography
device, a liquid chromatography device, a gas chromatography
device, an electronic measurement device, or a mass spectroscopy
device. Particularly, the fluidic device may be a High Performance
Liquid Chromatography device (HPLC) device by which different
fractions of an analyte may be separated, examined and/or
analyzed.
[0060] The separation unit may be a chromatographic column for
separating components of the fluidic sample. Therefore, exemplary
embodiments may be particularly implemented in the context of a
liquid chromatography apparatus.
[0061] The fluid separation device may be configured to conduct a
liquid mobile phase through the separation unit and optionally a
further separation unit. As an alternative to a liquid mobile
phase, a gaseous mobile phase or a mobile phase including solid
particles may be processed using the fluid separation device. Also
materials being mixtures of different phases (solid, liquid,
gaseous) may be processed using exemplary embodiments.
[0062] The fluid separation device may be configured to conduct the
fluid/mobile phase through the system with a high pressure,
particularly of at least 600 bar, more particularly of at least
1200 bar.
[0063] The fluid separation device may be configured as a
microfluidic device. The term "microfluidic device" may
particularly denote a fluidic device as described herein which
allows to convey fluid through microchannels having a dimension in
the order of magnitude of less than 500 .mu.m, particularly less
than 200 .mu.m, more particularly less than 100 .mu.m or less than
50 .mu.m or less. The fluid separation device may also be
configured as a nanofluidic device. The term "nanofluidic device"
may particularly denote a fluidic device as described herein which
allows to convey fluid through nanochannels having even smaller
dimensions than the microchannels.
[0064] Other devices, apparatus, systems, methods, features and
advantages of the invention will be or will become apparent to one
with skill in the art upon examination of the following figures and
detailed description. It is intended that all such additional
systems, methods, features and advantages be included within this
description, be within the scope of the invention, and be protected
by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] 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 accompanying
drawings. Features that are substantially or functionally equal or
similar will be referred to by the same reference signs.
[0066] FIG. 1 illustrates a liquid chromatography system according
to an exemplary embodiment.
[0067] FIG. 2 shows a more detailed view of a liquid chromatography
system allowing for a quantitative splitting of flow into multiple
streams.
[0068] FIG. 3 illustrates a flow splitter according to an exemplary
embodiment of the invention having a fluid pump according to an
exemplary embodiment of the invention.
[0069] FIG. 4 illustrates a fluid pump according to an exemplary
embodiment of the invention.
[0070] FIG. 5A illustrates an operation mode of the fluid pump of
FIG. 4, as described herein.
[0071] FIG. 5B illustrates another operation mode of the fluid pump
of FIG. 4, as described herein.
[0072] FIG. 5C illustrates another operation mode of the fluid pump
of FIG. 4, as described herein.
[0073] FIG. 5D illustrates another operation mode of the fluid pump
of FIG. 4, as described herein.
[0074] FIG. 5E illustrates another operation mode of the fluid pump
of FIG. 4, as described herein.
[0075] FIG. 5F illustrates another operation mode of the fluid pump
of FIG. 4, as described herein.
[0076] FIG. 6 illustrates a fluid pump according to another
exemplary embodiment of the invention.
[0077] FIG. 7 illustrates a fluid pump according to another
exemplary embodiment of the invention.
[0078] The illustrations in the drawings are schematic.
DETAILED DESCRIPTION
[0079] Before describing in detail the drawings, some more general
information with regard to exemplary embodiments of a flow
subtracting pump will be given. In an embodiment, a reverse
operation of a piston pump is used to control a split ratio.
[0080] In Liquid Chromatography (LC) systems there is often a
requirement to have both an ultraviolet (or visual light) signal,
and a mass spectroscopy signal captured at the same time. Modern
UHPLC-systems exhibit high peak capacity, while at the same time
they work with low sample amounts. Compromises are made in multiple
aspects to achieve utmost performance.
[0081] However, both mentioned detection types (electromagnetic
radiation-based, mass spectroscopy-based) are different with
respect to flow sensitivity and often require their own critical
operation set in order to deliver appropriate performance. While
UHPLC is run at higher flow rates, modern mass spectroscopy systems
find their optimum sensitivity in lower flow rates. For
semi-preparative work a user may like to collect fractions, which
is guided by the MS-signal. The above mentioned detectors may
couple downstream of the separation column via a T-piece, which
then allows parallel measurements.
[0082] According to an exemplary embodiment, the setup is like a
normal two-detectors-parallel approach. A fluid pump according to
an embodiment can be designed to basically deliver negative flow.
For proper performance the fluid pump may be coupled to the outlet
of the, for example, UV-detector, while the mass spectroscopy
device is on the other arm of the T. In order now to have good flow
rate on the mass spectroscopy arm while the liquid chromatography
flow rate it too high, the fluid pump will subtract a controlled
amount. Even in case the flow is non-constant the flow towards the
mass spectroscopy path can be kept at a constant level by
programming the flow subtraction. When recording the flow through
the fluid pump, even the UV-trace can give exact quantitative
information.
[0083] Referring now in greater detail to the drawings, FIG. 1
depicts a general schematic of a liquid separation system 10. A
fluid drive or pump 20 receives a mobile phase from a solvent
supply 25, typically via a degasser 27, which degases and thus
reduces the amount of dissolved gases in the mobile phase. The pump
20--as a mobile phase drive--drives the mobile phase through a
separating device 30 (such as a chromatographic column) comprising
a stationary phase. A sampling unit 40 can be provided between the
pump 20 and the separating device 30 in order to subject or add
(often referred to as sample introduction) a sample fluid into the
mobile phase. The stationary phase of the separating device 30 is
configured for separating compounds of the sample liquid. A
detector 50 is provided for detecting separated compounds of the
sample fluid. A fractionating unit 60 (or a waste) can be provided
for outputting separated compounds of sample fluid.
[0084] While the mobile phase can be comprised of one solvent only,
it may also be mixed from plural solvents. Such mixing might be a
low pressure mixing and provided upstream of the pump 20, so that
the pump 20 already receives and pumps the mixed solvents as the
mobile phase. Alternatively, the pump 20 might be comprised of
plural individual pumping units, with plural of the pumping units
each receiving and pumping a different solvent or mixture, so that
the mixing of the mobile phase (as received by the separating
device 30) occurs at high pressure and downstream of the pump 20
(or as part thereof). The composition (mixture) of the mobile phase
may be kept constant over time, the so called isocratic mode, or
varied over time, the so called gradient mode.
[0085] A data processing unit 70, which can be a conventional PC or
workstation, might be coupled (as indicated by the dotted arrows)
to one or more of the devices in the liquid separation system 10 in
order to receive information and/or control operation. For example,
the data processing unit 70 might control operation of the pump 20
(e.g. setting control parameters) and receive therefrom information
regarding the actual working conditions (such as output pressure,
flow rate, etc. at an outlet of the pump). The data processing unit
70 might also control operation of the solvent supply 25 (e.g.
setting the solvent/s or solvent mixture to be supplied) and/or the
degasser 27 (e.g. setting control parameters such as vacuum level)
and might receive therefrom information regarding the actual
working conditions (such as solvent composition supplied over time,
flow rate, vacuum level, etc.). The data processing unit 70 might
further control operation of the sampling unit 40 (e.g. controlling
sample injection or synchronizing sample injection with operating
conditions of the pump 20). The separating device 30 might also be
controlled by the data processing unit 70 (e.g. selecting a
specific flow path or column, setting operation temperature, etc.),
and send--in return--information (e.g. operating conditions) to the
data processing unit 70. Accordingly, the detector 50 might be
controlled by the data processing unit 70 (e.g. with respect to
spectral or wavelength settings, setting time constants, start/stop
data acquisition), and send information (e.g. about the detected
sample compounds) to the data processing unit 70. The data
processing unit 70 might also control operation of the
fractionating unit 60 (e.g. in conjunction with data received from
the detector 50) and provide data back.
[0086] As can be taken from FIG. 1, the control unit 70 also
controls a fluid pump 90. The fluid pump 90 is arranged downstream
of the separation column 30. The fluid pump 90 has a fluid inlet 92
being supplied with separated fluid at a certain inlet pressure
defined by the components upstream of a bifurcation point 85. An
internal fluid conduction mechanism 94 (described in more detail
referring to FIG. 4 and FIG. 5, for instance) of the fluid pump 90
is configured for conducting the fluid supplied to the fluid inlet
92 towards a connected fluidic path 96 (from where the fluid is
introduced into the fractioner 60 or a waste container) with a
defined flow rate of 2.5 ml/min. The fluid conducting mechanism 94
is configured so that, independently of a value of the inlet
pressure provided by the pump 20, the fluid is continuously intaken
in the fluid pump via the fluid inlet 92 with a definable flow
rate. The flow rate through the separation column 30 is 3 ml/min.
Therefore, by adjusting the flow rate through the fluid inlet 92 to
a value of 2.5 ml/min, it is possible to ensure that the flow rate
towards a fluidic path including a mass spectroscopy device 80 is,
in this shown embodiment, 0.5 ml/min. This is highly advantageous
because the relatively high flow rate through the separation column
30 allows for a high separation performance. On the other hand, the
small flow rate of 0.5 ml/min meets the specific requirements of
the mass spectroscopy device 80. Therefore, it is possible with the
fluid pump 90 (being located in a flow path which differs from the
flow path in which the separation column 30 and the mass
spectroscopy device 80 are arranged) to indirectly adjust a flow
rate value in the flow path including the mass spectroscopy device
80.
[0087] FIG. 2 shows another more detailed illustration of the
liquid chromatography device 10 of FIG. 1.
[0088] As can be taken from FIG. 2 it is possible to mix different
solvents, such as an aqueous solvent in a first vial 200 and an
organic solvent in a second vial 202 to constitute a mobile phase
to be pumped by pump 20. The two solvents in the vials 200, 202 may
be mixed after being conducted through individual pump drives 204
and 206 respectively, which form a dual pump drive as pump 20. At a
mixing T 208, the two solvents are mixed. An injection of a fluidic
sample to the mobile phase formed by the two solvents occurs at the
autosampler 40 (schematically shown in FIG. 2). A separation column
30 is located downstream the autosampler 40 and separates the
sample injected into the mobile phase. After separation in the
chromatography column 30, the fluid is split at bifurcation point
85 into a first path which connects to a mass spectroscopy
detection device 80 and into another parallel second path coupled
to an ultraviolet detector 50 for detecting the separated fractions
of the fluidic sample. A recording computer may be part of the
control unit 70.
[0089] An arrangement of the fluid pump 90 having fluid inlet 92
and internal fluid conducting mechanism 94 is provided downstream
of the ultraviolet detector 50 for defining a defined flow at the
fluid inlet 92. After having left the fluid pump 90, this part of
the fluid can be accumulated in waste container 60. As can be taken
from FIG. 2, the fluid pump 90 can be realized by two pistons
reciprocating within corresponding chambers in combination with a
certain fluidic switch. However, these components will be described
in more detail below referring to FIG. 4.
[0090] FIG. 3 shows a flow splitter 300 according to an exemplary
embodiment which can be implemented in the liquid chromatography
apparatus 10 shown in FIG. 1 or FIG. 2. However, other applications
are possible as well, because the flow splitter 300 is particularly
advantageous for all applications in which a certain fluidic member
350 requires a certain reduced flow rate. Such a fluidic member 350
can be a mass spectroscopy device, a separation column, a detector,
a pump, a sensor or any other fluidic component which requires or
desires that a certain flow rate, particularly a reduced flow rate,
flows through this fluidic member 350.
[0091] As can be taken from FIG. 3, the flow splitter 300 comprises
a fluid inlet conduit 306. Through this fluid inlet conduit 306 a
fluid (such as a gas or a liquid) is supplied. This fluid is
supplied with an inlet flow rate FI. The fluid flowing through the
fluid inlet conduit 306 is then divided or split at a splitting
position 360 into a first fluid outlet conduit 302 and a second
fluid outlet conduit 304. However, it is also possible to provide
more than two fluid outlet conduits 302, 304 among which the fluid
is split. The flow splitter 300 furthermore comprises a fluid pump
90 in the first fluid outlet conduit 302. A certain inlet pressure
pI is applied to a fluid inlet 92 of the fluid pump 90 by the
flowing fluid. The internal construction of the fluid pump 90 is
such that independently of the inlet fluid pI, a certain flow rate
FT is always subtracted or intaken at the fluid inlet 92.
Therefore, the flow rate of fluid flowing through the fluidic
member 350 is FI-FT. Hence, the fluid pump 90 reduces the flow rate
of fluid flowing through the fluidic member 350 as compared to the
inlet flow rate FI. By adjusting operation of the fluid pump 90, it
is possible to adjust the flow through the fluidic member 350.
[0092] FIG. 3 furthermore shows that the control unit 70 controls
operation of the pump 90, for instance for defining FT or for
coordinating the reciprocation of various pistons in an interior
thereof. Optionally, it is also possible that an input/output unit
370 is coupled to the control unit 70 so as to enable a user to
provide control instructions or can be supplied with output
information. Although not shown in FIG. 3, it is possible that one
or more sensors is or are arranged in the fluidic path, i.e. in one
or multiple of the conduits 306, 304, 302 or 96. After having left
a fluid outlet 98 of the fluid pump 94, the fluid may be conducted
into a waste container 308.
[0093] FIG. 4 shows a detailed view of the internal construction of
a fluid conducting mechanism 94 of the fluid pump 90 according to
an exemplary embodiment of the invention.
[0094] As can be shown in FIG. 4, the fluid conducting mechanism 94
comprises a first piston 400 which is controlled by control unit 70
for reciprocating within a first pump chamber 404 so as to conduct
the fluid away from fluid inlet 92 with a definable flow rate when
moving rearwardly in the first chamber 404 during a part of the
duty cycle of the first piston 400. FIG. 4, as indicated by an
arrow 420, shows the first piston 400 in an operation mode in which
it moves rearwardly. "Rearwardly" means that the fluid entering via
fluid inlet 92 and being conducted through a fluidic valve 408 is
flowing basically in parallel to the motion direction of the first
piston 400. In contrast to this, a forward operation of the first
piston 400 would mean that the piston motion is antiparallel to the
flow of the fluid which is indicated schematically by a further
arrow 422 (the position of the arrow 422 in FIG. 4 should of course
not be understood in a manner that medium flows into the piston
400).
[0095] Moreover, the fluid conducting mechanism 94 comprises a
second piston 402 which is controlled by the control unit 70 as
well for reciprocating within a separate second pump chamber 406.
Therefore, in cooperation with the first piston 400, the fluid is
conducted away continuously from the fluid inlet 92 with a
definable constant flow rate FT. However, in the shown embodiment,
the second piston 402 is presently not moving so that it presently
does not contribute to intaking a certain fluid flow from the fluid
inlet 92.
[0096] FIG. 4 furthermore schematically illustrates a switchable
fluidic valve 408 comprising two valve members which are sandwiched
perpendicular to the paper plane of FIG. 4. By rotation, the
fluidic valve 408 is switchable so as to fluidically disconnect a
respective piston 400, 402 from the fluid inlet 92 when this piston
400, 402 is moving forwardly or upon reversing its motion direction
from a rearward motion to a forward motion. A fluid intaking
performance of a corresponding piston 400 or 402 can only be
obtained when the piston 400, 402 moves rearwardly.
[0097] A presently enabled fluidic path can be defined by the
switching state of the fluidic valve 408 which can be changed by
rotating the two valve members relative to one another as indicated
schematically with a further arrow 424. One of the two members of
the fluidic valve 408 has multiple ports 410 (a total of 7 in this
case), whereas the other member of the fluidic valve 408 comprises
grooves 426 (two in this case). FIG. 4 shows the valve 408 in an
operation mode in which a fluidic path is enabled from the fluid
inlet 92 through the lower arcuate groove 426 towards two ports 410
coupled to the two fluidic chambers 404 and 406, respectively.
Furthermore, the fluid may be conducted past the rearwardly moving
piston 400 towards a respective connected intermediate conduit 432.
Correspondingly, an intermediate conduit 434 is provided for the
second chamber 406 as well. Depending on the switching state of the
fluidic valve 408 the intermediate conduits 432 or 434 may be
connected to a drain conduit 436 from where the corresponding fluid
may be conducted into waste container 308.
[0098] In order to obtain a continuous constant flow being
subtracted from the fluid inlet 92, the reciprocation of the
pistons 400, 402 may be coordinated by the control unit 70 as well
as a switching state of the fluidic valve 408. This is performed in
such a manner that the sum of the fluid flows subtracted by the
presently rearwardly reciprocating pistons 400, 402 (which may be
coupled to the fluid inlet 92) meets the desired defined flow rate
value FT. Upon moving forwardly, the respective piston 400, 402 may
be decoupled from the fluid inlet 92 because in this operation mode
the respective piston 400, 402 would not contribute positively to
the subtracting of fluid.
[0099] It is also possible that close to a reversal point 444 or
446 of the respective piston 400 or 402, artifacts or
discontinuities of the intaken flow rate FT may arise by the
respective pistons 400, 402 which could deteriorate the constant
continuous subtraction of the defined fluid flow. Therefore, it is
for instance possible that a certain piston 400 or 402 is only
connected to the fluid inlet 92 while its fluid displacing surface
450 is within a central reciprocating region 448, and
simultaneously providing that the respective other piston 400, 402
is moving rearwardly.
[0100] FIG. 5 again shows the system of FIG. 4 in a simplified
illustration, whereas it can be taken from FIG. 5 that there is a
constant continuous subtraction of the flow at the fluid inlet
92.
[0101] With regard to the embodiment of FIG. 5, the following
describes in more detail the operation of the system.
[0102] The fluid pump 90 is equipped with the rotary valve 408
which is designed so the fluid pump 90 can intake liquid from the
inlet line 92 into two piston pumps in parallel or in either one of
them, while the other one is connected to waste. This allows
continuous or seamless intake of fluid of a certain flow rate in
either one of the pistons 400, 402. The piston movement is
controlled by control unit 70 to provide a constant intake flow, so
it is matched to the flow rate of the liquid fed into the fluid
pump 90 via the inlet line 92. At any point in time the total
movement of the receiving pistons 400, 402 equals the volumetric
flow rate in the feeding line 92, providing a fast, direct and
absolute means for maintaining (and if desired determining)
volumetric flow.
[0103] Due to independent control of the two piston drives together
with the rotary valve 408 design, the fluid pump 90 is capable of
continuous pulsation-free fluid intake. This further improves the
operability under dynamic conditions and the precision of the
output data and flow rate control.
[0104] The fluid pump 90 may be operated in the following operation
modes, as shown in FIG. 5:
[0105] State IDLE (FIG. 5A): In idle state the rotary valve 408
position is such that the intake line 92 is connected directly to
the waste line 96 so the intake stays pressureless.
[0106] State INTAKE A (FIG. 5B): When operation is enabled, the
valve 408 is rotated to detach the intake line 92 from the waste
line 96 and connect it to both pistons 400, 402 simultaneously. The
left piston 400 is then slowly retracted to keep the intake flow
rate.
[0107] State INTAKE A END/B BEGIN (FIG. 5C): As the left piston 400
approaches its rearmost position, it is decelerated until it comes
to halt, while the right piston 402 is accelerated
synchronously.
[0108] State EJECT A/INTAKE B (FIG. 5D): The valve 408 is now
rotated to keep the right piston 402 connected to intake 92, while
the left piston 400 is detached from intake 92 and connected to the
waste line 96. The content of the left piston 400 is now ejected
into waste 96. When finished, the valve 408 is rotated back to its
previous position connecting both pistons 400, 402 to intake.
[0109] State INTAKE B END/A BEGIN (FIG. 5E): As the right piston
402 approaches its rearmost position, it is decelerated until it
comes to halt, while the left piston 400 is accelerated
synchronously.
[0110] State INTAKE A/EJECT B (FIG. 5F): The valve 408 is rotated
to keep the left piston 400 connected to intake 92, detach the
right piston 402 and connect it to waste 96. After ejecting the
right piston 402 into waste, the valve 408 is rotated to its
previous position connecting both pistons 400, 402 to intake.
[0111] The scheme of FIG. 5A to FIG. 5F shows that, in an active
state of the fluid pump 90, either one of the pistons 400, 402
sucks fluid from the inlet line 92 (first piston 400 in FIG. 5F,
second piston 402 in FIG. 5D) or both pistons 400, 402 suck fluid
from the inlet line 92 (FIG. 5C, FIG. 5E). The former scenario
applies when one of the pistons 400, 402 presently moves forwardly
and therefore is currently disconnected from the fluid inlet 92
(first piston 400 in FIG. 5D, second piston 402 in FIG. 5F), the
latter scenario applies when both pistons 400, 402 presently move
rearwardly. When one of the pistons 400, 402 presently moves
forwardly, its content is drained towards the drain line 96. So it
can be ensured that the fluid flow subtracted via fluid inlet 92 is
continuously and uninterruptedly the same (or more generally: is
continuously maintained at a desired value).
[0112] The fluid pump 90 may be equipped with high precision SSiC
pistons and ball screw drives, driven by brushless DC motors which
are field vector controlled by a 20 kHz control loop run on a
specific processor in a FPGA on a main board.
[0113] FIG. 6 illustrates a fluid pump 600 according to another
exemplary embodiment of the invention.
[0114] FIG. 6 comprises three pistons 400 in corresponding chambers
404 and also involves three different valves 602, 604, 606 each
being switchable independently under the control of the control
unit 70. In the respective drain lines 96, additional valves may be
provided (not shown) so as to allow to close the drain lines 96. In
the present operation mode shown in FIG. 6, valve 602 is open since
the corresponding piston 400 is moving rearwardly. The second valve
604 is presently switched from an on-state to an off-state because
the corresponding piston 400 is close to the reversal point, i.e.
the upper dead point. The third valve 606 is presently off since
the corresponding piston 400 moves forwardly.
[0115] FIG. 7 shows still another exemplary embodiment of a fluid
pump 700 in which two switchable valves 408 are switched by a
control unit 70, wherein each of the valves 408 operates two piston
chamber pairs 400, 404. Again, as in FIG. 6, in the respective
drain lines 96, additional valves may be provided (not shown) so as
to allow to close the drain lines 96.
[0116] It should be noted that the term "comprising" does not
exclude other elements or features and the term "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.
[0117] It will be understood that various aspects or details of the
invention may be changed without departing from the scope of the
invention. Furthermore, the foregoing description is for the
purpose of illustration only, and not for the purpose of
limitation--the invention being defined by the claims.
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