Note: Descriptions are shown in the official language in which they were submitted.
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PIPETTE FOR SAMPLING AN EXTENDED RANGE OF VOLUMES OF LIQUID
DESCRIPTION
TECHNICAL FIELD
The invention relates to the field of sampling pipettes, also called
laboratory pipettes or even liquid transfer pipettes, for sampling and
dispensing liquid in
containers or the like.
The pipettes concerned by the present invention are manual pipettes
and motor pipettes. These pipettes are intended to be held in the hand by an
operator,
during liquid sampling and dispensing operations. For manual pipettes, these
operations
are made by moving a pipetting control knob, obtained by applying an actuation
pressure
on the same knob which is mechanically transferred to a control rod. On motor
pipettes,
the pressure of the operator onto the control knob generates a signal which is
transmitted to the control unit of the pipette, such that the same triggers
the movement
of the control rod through an appropriate motor embedded in the pipette.
It is noted that the manual pipettes concerned by the present invention
can have an electronic counter and/or display, the pipette thereby having a
"hybrid"
nature because it combines both a mechanical aspect and an electronic aspect.
STATE OF PRIOR ART
Since many years, designing sampling pipettes has undergone many
improvements, essentially aiming at simplifying the pipettes designing, or
even enhancing
their ergonomies.
Usually, to benefit from an acceptable precision, the volume range that
can be sampled by a pipette is between about 10% of the nominal volume, and
100% of
this nominal volume corresponding to the maximum volume that the pipette can
sample.
Consequently, when an operator has to pipette different samples
extending on a wide range, these operations require the use of several
pipettes. By way
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of example, when a series of operations require pipetting volumes falling
within a range
from 3 to 1,250111, it can be required to have the following three pipettes:
- a first pipette with a nominal volume of 30 1, that can be used on a
volume range from 3 to 30 I;
- a second pipette with a nominal volume of 3000, that can be used on
a volume range from 30 to 300111; and
- a third pipette with a nominal volume of 1,250111, that can be used on a
volume range from 300 to 1,250111.
Under this situation, the plurality of pipettes ensures precision and
accuracy performance, but it results in taking too much room on the lab bench.
DISCLOSURE OF THE INVENTION
One purpose of the present invention is thus to overcome at least
partially the drawback identified above.
For this, the object of the invention is a sampling pipette comprising:
- a pipette body;
- a control rod translationally movable relative to the pipette body,
along a longitudinal axis of the pipette; and
- a suction chamber.
According to the invention, the pipette also includes:
- a set of N concentric pistons, N corresponding to an integer higher
than or equal to two, each of the pistons participating in delimiting said
suction chamber;
and
- a module for coupling the control rod with the set of N concentric
pistons, said module being configured sa as to be capable of being brought
into N distinct
configurations in which it provides coupling of the control rod with 1, 2,
..., N pistons
respectively.
The invention is thus remarkable in that it enables the volume range
that can be sampled to be extended, by implanting several pistons within the
pipette as
well as a module for coupling the control rod with each of these pistons.
Consequently,
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during a pipetting operation, the number of operating pistons is a function of
the volume
to be sampled.
This solution has the advantage of reducing the required number of
pipettes when the pipetting operations require to sample various volumes,
without
altering the accuracy and precision performance of the pipette. As a result,
there is
advantageously a room gain on the lab bench. In addition, by replacing several
pipettes
by a single pipette, this offers a traceability possibility of a protocol by
recording all the
pipetting operations made with this same pipette.
Further, the pipette according to the invention has a reduced bulk, by
virtue of a concentric arrangement of its pistons.
On the other hand, the present invention has at least any of the
following optional characteristics, taken alone or in combination.
It is provided:
that the coupling module comprises at least one piston attachment
finger radially extending relative to the longitudinal axis of the pipette,
that at least N-1 pistons each have an attachment slot circumferentially
oriented and open, the slots having different circumferentially lengths for
each of said at
least N-1 pistons,
and that said pipette is configured such that the attachment finger is
capable of being circumferentially moved in and out of the slots radially
facing each
other.
In other words, coupling/uncoupling each piston with the control rod is
made by a bayonet type connection, with the finger making up the lug of this
connection.
By virtue of the inventive design which has been developed, the number of
pistons
coupled to the control rod simply depends on the relative angular position
between the
finger and the slots radially facing each other. This angular relative
position can be
manually obtained by the operator using an appropriate control member
positioned on
the pipette, or more preferentially, in an automatic way by virtue of motor
means
controlled by a control unit of the pipette.
e
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However, the coupling module can take any other form supposed to be
appropriate, without departing from the scope of the invention. By way of
example, this
module can be based on a mechanical, magnetic gripping, etc.
The coupling module comprises a coupling rotary member provided at
its bottom end with said finger, and rotatably mounted at its top end to the
control rod,
along the longitudinal axis of the pipette.
The coupling rotary member is preferably made using two parts slidably
mounted with respect to each other, along the longitudinal axis of the
pipette, an
expansion spring being arranged between both these parts so as fo generate a
strain
tending to move them away from one another.
The coupling module includes a control rod extension translationally
integral with the control rod, and said two parts of the coupling rotary
member are
respectively formed by a top part and a bottom part, the latter being
translationally
movably mounted along the longitudinal axis, relative to the control rod
extension.
The coupling module further comprises a motion transforming body
cooperating with the coupling rotary member such that a relative translation
movement
between them along the longitudinal axis simultaneously results in a relative
rotation
with respect to each other, also along the longitudinal axis. In other words,
the
cooperation between the motion transforming body and the coupling rotary
member
causes a helical motion of the latter.
Preferably, the motion transforming body includes at least one first
helical ramp as well as at least one second helical ramp, and the coupling
rotary member
is provided with a follower roller which, when it cooperates with the first
ramp enables
the rotation of the coupling rotary member to be caused along a first
direction of rotation
and which, when it cooperates with the second ramp enables the rotation of the
coupling
rotary member to be caused along a second direction of rotation. This design
enables
coupling and uncoupling of the pistons to be achieved in a simple and reliable
manner.
The sampling pipette is preferentially designed such that the rotation of
the coupling rotary member along the first direction of rotation is achieved
by a first
overstroke downwards of the control rod from a purge stroke end position
thereof, and
i
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the rotation of the coupling rotary member along the second direction of
rotation is
achieved by a second overstroke upwards of the control rod from a top
pipetting position
of this control rod. Thus, the pipette is designed to achieve coupling and
uncoupling of
the pistons by simple translations of the control rod, in overstrokes going
respectively
5 beyond
the purge stroke and retracted from the top pipetting position. One of the
advantages relative to this specificity resides in the pipette design
simplicity, given that it
is the same control rod, in a motion along a same translation degree of
freedom, which
makes it possible to perform alternately pipetting operations and piston
coupling and
uncoupling operations.
Preferably, the first overstroke is made acting against a strain generated
by a first centring spring tending to repel the coupling rotary member
upwardly relative
to the motion transforming body, and the second overstroke is made acting
against a
strain generated by a second centring spring tending to repel the coupling
rotary member
downwardly relative to the motion transforming body.
Preferably, the pipette is configured such that the movement of the
control rod is made manually or in a motorised manner, as previously
indicated. In this
regard, it is noted that hybrid pipettes are also within the scope of
protection of the
invention.
Preferably, the number N of pistons is higher than or equal to three, but
a solution with two concentric pistons is also possible, without departing
from the scope
of the invention.
The sampling is preferentially designed so as to be able to sample a
volume range from 0.5 to 1,250111, or designed so as to be able to sample a
volume range
from 500 to 10,000111.
The inner most piston is permanently integral with the coupling module.
Alternatively, it could also be coupled and uncoupled to the control rod, via
the coupling
module. According to another alternative, it is the outermost piston which
could be
permanently integral with the coupling module.
The pipette comprises a control member for adjusting the volume to be
sampled, of the knob, button-type or any other conventional form.
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Finally, it is noted that the sampling pipette can be a single-channel or
multi-channel pipette.
Further advantages and characteristics of the invention will appear in
the non-limiting detailed description below.
BRIEF DESCRIPTION OF THE DRAWINGS
This description will be made with regard to the appending drawings in
which:
- Fig. 1 represents a front view of a motor sampling pipette according to
a preferred embodiment of the present invention;
- Fig. 2 is an axial cross-section view of a bottom part of the pipette
shown in the previous figure;
- Fig. 3 is a perspective view of a piston coupling module implemented in
the pipette shown in the previous figures;
- Fig. 4 is an axial cross-section view of the previous figure;
- Fig. 5 is cross-section view taken along line V-V of the previous figure;
- Fig. 6 is a perspective view of a bottom part of the coupling module
shown in Figs. 3 and 4, cooperating with the pistons of the pipette;
- Figs. 7a to 7c depict pipetting operations with the coupling module in a
first configuration;
- Figs. 8a to 8c depict pipetting operations with the coupling module in a
second configuration;
- Figs. 9a to 9c depict pipetting operations with the coupling module in a
third configuration;
- Figs. 10a to 11b depict the coupling module switching from the first to
the second configuration;
- Figs. 12 to 13b depict the coupling module switching from the second
to the third configuration;
- Figs. 14a to 15b depict the coupling module switching from the third to
the second configuration; and
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- Figs. 16a to 17b depict the coupling module switching from the second
to the first configuration.
DETAILED DISCLOSURE OF PREFERRED EMBODIMENTS
In reference to Figs. 1 to 5 first, a motor sampling pipette 1 is
represented according to a preferred embodiment of the invention.
Conventionally, this motor pipette 1 is intended to be held by an
operator's hand who, using his/her thumb, is capable of actuating a control
knob of the
pipette to generate dispensing a liquid which has been sucked beforehand.
More precisely, the single-channel pipette 1 comprises a handle 6
forming the upper body of the pipette, and above which the pipetting control
button 3 is
located, the upper part of which is intended to undergo the operator's thumb
pressure.
By way of indicating purposes, it is noted that an electronic display screen 4
is provided
on the handle 6, as well as control members 8 such as knobs or buttons, and in
particular
a control member for adjusting the volume to be sampled.
The top part of the pipette is also provided with an electronic control
unit 10 and a motor 11, the latter being preferentially a direct current motor
controlled
by the unit 10.
The output shaft 13 of the motor 11 is mechanically coupled to a
device 15 for translating a control rod 12 of the pipette, along a
longitudinal axis 9 of the
pipette also corresponding to the longitudinal direction of the same. It is
noted that most
of the elements making up the pipette are of revolutionary shapes, and centred
on this
axis 9.
Under the handle 6, the pipette 1 includes a removable bottom part 14,
which downwardly terminates with a cone-carrying tip 16 accommodating a
consumable 18, also called a sampling cone.
A cone ejector 20 opens downwardly of the handle 6. Conventionally,
the ejector 20 can be moved relative to the handle 6 and the bottom part 14,
both
forming a fixed body 22 of the pipette.
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One of the features of the invention lies in the fact that the pipette is
equipped with several concentric pistons, here three pistons referenced 24a,
24b, 24c.
The number N of pistons could however be higher or lower than 3, without
departing
from the scope of the invention.
The three pistons are housed in the bottom part 14, and centred on the
longitudinal axis 9. The first piston 24a, located inside, has a circular
shaped cylindrical
cross-section. The second piston 24b has an annular transverse cross-section,
surrounding
the first piston 24. The top end 24b' of the second piston 24b defines an
upwardly open
axial housing 26, and the bottom of which is equipped with an 0-ring 28
through which
the first piston 24a passes. However, usually for the second piston 24b, a
small radial
clearance is provided between both pistons 24a, 24b, such that air can
penetrate
therethrough. It is indicated that throughout the description, the terms "top"
and
"bottom" are to be considered with respect to the pipette maintained in the
operator's
hand, with an orientation such as that assumed during pipetting operations,
that is with
the control knob 3 upwardly oriented.
Analogously to that set out above, the top end 24c' of the third
piston 24c defines an upwardly open axial housing 30, and the bottom of which
is
equipped with an 0-ring 32 through which the second piston 24b passes.
However,
usually for the third piston 24c, a small radial clearance is provided between
both
pistons 24b, 24c, such that air can penetrate therethrough.
The third piston 24c has a bottom end equipped with a lip seal 40
snuggly fitting the internai surface of the fixed body 22.
Each of the second and third pistons 24b, 24c has lugs 34 outwardly
radially extending and slidably mounted in vertical internai grooves 36 of the
fixed
body 22, as is visible in Fig. 4. This enables the rotation of the pistons to
be blocked
relative to the fixed body 22 of the pipette.
The pistons participate with their lower ends in delimiting a single
suction chamber 42, the bottom part of which communicates with a channel 44
passing
through the cone-carrier 16.
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By way of indicating example, the pipette is intended ta enable liquid ta
be sampled in a volume range from 0.5 ta 1,250111, or in a volume range from
500 ta
10,000 I. In the first case for example, a first piston 24a is provided, the
intrinsic sampling
capacity of which is in the order of 50111, and a second piston 24b is
provided which, when
associated with the first piston 24a, has together an intrinsic sampling
capacity in the
order of 350p.1, and finally a third piston 24c is provided which, when
associated with the
first and second pistons 24a, 24b, has an intrinsic sampling capacity in the
order of
1,2500.
Depending on the desired volume, adjusted by the operator via the
dedicated control member on the pipette, the control unit 10 is capable of
commanding
switching ON either:
- the first piston 24a only;
- the first and second pistons 24a, 24b;
- the first, second and third pistons 24a-24c.
For this, the pipette 1 is equipped with a coupling module 50 specific ta
the invention, enabling each of the pistons ta be coupled and uncoupled with
the control
rad 12. More precisely, the module 50 is configured sa as ta be able ta be
brought into
three distinct configurations in which it provides coupling of the control rad
12 with the
first piston 24a only, the first and second pistons 24a, 24b, and finally the
first, second
and third pistons 24a, 24c respectively.
More specifically in reference ta Figs. 3 and 4, the coupling module 50
will now be described in more details.
First, the module 50 includes a control rad extension 52 translationally
integral with the control rad 12, and downwarclly extending from the same rad.
Preferably, the extension 52 is mounted screwed at its top end ta the bottom
end of the
control rad 12.
The bottom end of the extension 52, centred on the axis 9, fixedly and
permanently carnes the first piston 24a, a screwed, glued connection or else,
being for
example provided between their respective ends.
,
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Further, the module 50 includes a coupling rotary member 56, arranged
about the control rod extension 52. Preferably, this member 56 is made using
two parts
slidably mounted with respect ta one another, along the axis 9. There is first
a top
part 56a translationally fixed with respect ta the rad 12 and its extension
52, but
5 rotatably movable relative ta the same, along the axis 9. There is then a
bottom part 56b
rotatably coupled ta the top part 56a, for example through a key 60.
An expansion spring 62 is arranged between bath parts 56a, 56b, sa as
ta generate a strain tending ta move them away from one another. This
expansion
spring 62 presses against an internai pressing surface of the bottom part 56b,
and a ring
10 for coupling the upper ends of the top part 56a and the extension 52.
The bottom part 56b is thus translationally movably mounted along the
axis 9, relative ta the extension 52 and ta the control rad 12. It is
additionally equipped,
at its bottom end, with at least one piston attachment finger 64, preferably
two
diametrically opposite fingers as is shown in Fig. 3.
Each attachment finger 64 radially outwardly extends from the bottom
part 56b. As will be described hereinafter, the angular position of these
fingers 64
conditions the num ber of pistons coupled ta the module 50.
Ta vary the angular position of the fingers 64, the coupling module 50
further includes a motion transforming body 66, for transforming a
translational motion
into a rotational motion along the same axis 9. Indeed, this body 66
cooperates with the
top part 56a of the coupling rotary member 56 such that a relative translation
movement
between bath of them along the axis 9 simultaneously results in a relative
rotation
between them along the same axis. The aim is therefore ta obtain a helical
motion of the
coupling rotary member 56, which is made possible thanks ta ramps provided on
the
body 66 as well as follower rollers carried by the rotary member 56.
More precisely, the member 56 is equipped with two follower rollers 68
arranged in a diametrically opposite way, and rotatably mounted along a same
transverse
axis 76 orthogonal ta the axis 9. A first helical ramp 70a located inside the
body 66, as
well as a second helical ramp 70b also located inside the body 66, facing the
first ramp,
are associated with each follower rouer 68. The design is such that when each
follower
,
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rouer 68 cooperates with its associated first ramp 70a, it enables the
rotation of the
rotary member 56 to be caused along the first direction of rotation 72a about
the axis 9.
Reversely, when it cooperates with its associated second ramp 70b, it enables
the
rotation of the rotary member 56 to be caused along a second direction or
rotation 72b
opposite to the first direction.
ut is additionally noted that each follower rouer 68 is carried by a
rotational support pin 74 centred on the axis 76, this pin opening into a
radial opening 76
of the motion transforming body 66.
The axial positioning of the coupling rotary member 56 with respect to
the body 66 is ensured by two compression springs, that is a first centring
spring 80a
tending to repel upwardly the member 56 relative to the body 66, and a second
centring
spring 80b tending to repel downwardly the coupling rotary member relative to
the
motion transforming body 66.
For this, the first spring 80a is housed inside the body 66 between a
bottom end thereof and a shoulder 82 located at the top end of the rotary
member 66,
whereas the second spring 80b is housed inside the body 66 between a top end
of the
same and the same shoulder 82. It is additionally noted that it is on this
shoulder that the
follower rollers 68 are preferentially mounted, via the pins 74.
In reference now to Fig. 6, in combination with Figs. 3 and 4, the
cooperation between the coupling module 50 and the first and second pistons
24b, 24c
will now be described, given that the first piston 24a remains permanently
integral with
this coupling module 50.
At its top end 24b', the second piston 24b has two diametrically
opposite attachment slots 84b (a single one being visible in Fig. 6). Each
slot 84b is
circumferentially oriented, open in the same direction at one of its ends, and
has a slot
bottom at the opposite end. These slots 84b, for cooperating with the fingers
64 as lugs,
are thus defined by notches 86b that would be considered as those of a bayonet
connection.
Analogously, at its top end 24c', the third piston 24c has two
diametrically opposite attachment slots 84c (a single one being visible in
Fig. 6). Each
,
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slot 84c is also circumferentially oriented, open in the same direction at one
of its ends,
and has a slot bottom at the opposite end. These slots 84c, also for
cooperating with the
fingers 64 as lugs, are defined by notches 86c that could also be considered
as those of a
bayonet connection.
The slots 84b, 84c are gathered by pairs. For a same pair of slots 84b,
84c as that visible in Fig. 6, these are radially facing each other. In other
words, they are
considered as superimposed along the radial direction, by only partially
covering each
other along the circumferential direction. lndeed, both slots 84b, 84c of a
same pair have
different circumferential lengths, while having their slot bottoms aligned
along the radial
direction. Consequently, in the preferred embodiment which is described and
represented in the figures, this implies that each notch 86b provided on the
second piston
24b and delimiting the slot 84b, is longer than the notch 86c provided on the
third
piston 24c and delimiting the slot 84c.
The width of the slots 84b, 84c is preferentially identical, and provided
such that the attachment fingers 64 can be circumferentially moved in and out
these
slots. Preferably, the slot width is slightly higher than the diameter of the
fingers.
With this configuration, the number of pistons coupled to the bottom
part 56b of the module 50 thus depends on the relative angular position
between each
finger 64 and its associated pair of slots 84b, 84c. Fig. 6 does depict this
principle, since in
a first configuration of the module 50 which is represented with the finger 64
in solid line,
the same finger 64 assumes an angular position such that it is located outside
the two
slots 84b, 84c. In this first configuration, both pistons 24b, 24c are not
coupled to each
other, only the first piston remaining integral with the module 50. This first
configuration
is for example assumed by the control unit for pipetting volumes being in a
range from
0.5 to 300.
In a second configuration of the module 50, represented with the
finger 64 in dotted line in the middle of Fig. 6, each finger 64 assumes an
angular position
such that it is located in the slot 84b, but outside the slot 84c. The
cooperation between
the finger 64 and the notch 86b is related to a bayonet connection. For
example, an
angular offset of 20 to 25 is provided between the position of the finger 64
of the first
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configuration, and that of the second configuration. In the same, both pistons
24a, 24b
are therefore coupled to the module 50, but not the third piston 24c. This
second
configuration is for example assumed by the control unit for pipetting volumes
being in a
range from 30 to 300111.
In a third configuration of the module 50, represented with the finger 64
in dotted line in Fig. 6, the finger 64 assumes an angular position such that
it is located in
the slots 84b, 84c, close to or in contact with the slot bottoms. The
cooperation between
the finger 64 and the notches 86b, 86c is related to bayonet connections. For
example, an
angular offset of 20 to 25 is provided between the position of the finger 64
of the second
configuration, and that of the third configuration. In the same, the three
pistons 24a-24c
are therefore coupled to the module 50. This second configuration is for
example
assumed by the control unit for pipetting volumes being in a range from 300 to
1,2501.1I.
In reference now to Figs. 7a to 7c, the operation of the pipette 1 will
now be described when its coupling module 50 is in the first configuration,
that is with
only its first internai piston 24a coupled to this module.
Fig. 7a shows the pipette 1 with its control rod in the top pipetting
position, for example in a suction stroke end. The piston 24a coupled to the
module 50 is
thus in its topmost position relative to the fixed body 22 of the pipette. As
regards the
other two pistons 24b, 24c, they are in an inactive position abutting down
against the
fixed body 22. At this stage, the follower rollers 68 are substantially
centred with respect
to the motion transforming body 66, also in a top position.
Dispensing the sucked liquid is then controlled by the control knob,
which causes actuation of the motor resulting in the control rod 12 to be
downwardly
moved. During this dispensing stroke, the downward motion of the rod 12 drives
the
module 50 which therefore also slides along the fixed body 22. As regards the
pistons
24b, 24c, they remain stationary, unlike the first piston 24a which moves
down. The state
of the pipette at the dispensing stroke end is represented in Fig. 7b, whereas
the
continuing moving down of the rod 12 results in performing a purge stroke, the
final state
of which is represented in Fig. 7c.
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In reference now to Figs. 8a to 8c, the operation of the pipette 1 will be
described when its coupling module 50 is in the second configuration, that is
with only its
first and second pistons 24a, 24b coupled to this module.
Fig. 8 shows the pipette 1 with its control rod in the top pipetting
position, for example at the suction stroke end. The pistons 24a, 24b coupled
to the
module 50 are in their topmost position relative to the fixed body 22 of the
pipette.
During pipetting, the relative axial position of both these pistons remains
unchanged. As
regards the third piston 24c, it remains in an inactive position abutting down
against the
fixed body 22. At this stage, the follower rollers 68 are substantially
centred with respect
to the motion transforming body 66, also in a top position.
Dispensing the sucked liquid is then controlled by the control knob,
which causes actuation of the motor resulting in the control rod 12 being
downwardly
moved. During this dispensing stroke, the downwarcl motion of the rod 12
drives the
module 50 which therefore also slides along the fixed body 22. The pistons 24c
remains
stationary, unlike the pistons 24a, 24b which simultaneously move down. The
state of the
pipette at the dispensing stroke end is represented in Fig. 8b, whereas the
continuing
moving down of the rod 12 results in performing a purge stroke, the final
state of which is
represented in Fig. 8c.
In reference now to Figs. 9a to 9c, the operation of the pipette 1 will be
described when its coupling module 50 is in the third configuration, that is
with all its
pistons 24a-24c, coupled to this module.
Fig. 9a shows the pipette 1 with its control rod in the top pipetting
position, for example at the suction stroke end. The pistons 24a-24c coupled
to the
module 50 are in their topmost position relative to the fixed body 22 of the
pipette.
During pipetting, the relative axial position of these three pistons remains
unchanged. At
this stage, the follower rollers 68 are substantially centred with respect to
the motion
transforming body 66, also in a top position. As in the other two
configurations, the
position of the rollers 68 within the module is flot caused to change during
pipetting.
Dispensing the sucked liquid is then controlled by the control knob,
which causes actuation of the motor resulting in the control rod 12 to be
downwardly
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moved. During this dispensing stroke, the downward motion of the rod 12 drives
the
module 50 which therefore also slides along the fixed body 22. The three
pistons 24a-24c
then simultaneously move down, pushed by the rod 12 and the module 50. The
state of
the pipette at the dispensing stroke end is represented in Fig. 9b, whereas
the continuing
5 moving down of the rod 12 results in performing a purge stroke, the final
state of which is
represented in Fig. 9c.
Figs 10a to 10c and Figs. 11a and 11b depict an operation aiming at
switching from the first configuration to the second configuration of the
module 50. For
this, a first overstroke is commanded by the control unit, downward from the
purge
10 stroke end position as shown in Fig. 7c.
The body 66 first abuts down against the fixed body 22. As the first
overstroke continues, the top part 56a of the rotary member 56 is rotated
because of the
follower rollers 68 pressing against their ramps 70a. This helical motion is
transmitted to
the bottom part 56b, as well as to its attachment fingers 64. It is made
against the return
15 strain generated by the first centring spring 80a, by compressing the
same. During this
motion, the fingers 64 of the bottom part 56b also axially abut down against
the top ends
24b', 24c' of the pistons 24b, 24c, this state corresponding to that
represented in Figs.
10a and 11a. Then, the first overstroke is continued and the top part 56a
continues to be
helically driven, whereas the bottom part 56b only undergoes a rotation along
the axis 9
in the first direction 72a, since it is translationally blocked. The relative
translational
motion between both parts 56a, 56b is made against the return strain generated
by the
expansion spring 62, by compressing the same.
During this rotation the angular extent of which is perfectly controlled
because it directly depends on the extent of the axial overstroke of the
control rod 12,
the attachment fingers 64 penetrate the slots 84b. However, this angular
movement of
the fingers 64, for example in the order of 22.5', is not sufficient for thenn
to penetrate
the slot 84c. The insertion of the fingers 64 into the slots 84b causes the
second piston
24b to be coupled with the module 50. This mechanical coupling state is
represented in
Figs. 10b and 11b.
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Once the coupling is made, the control unit of the pipette commands
the rod 12 to be lifted back to the purge end position, which results in
simultaneously
lifting back the first and second pistons 24a, 24b, as is shown in Fig. 10c.
As regards the
third piston 24c, it remains in a fixed position.
Then, pipetting operations can be commanded conventionally, for
volumes corresponding to the range associated with all of the two pistons 24a,
24b.
Figs. 12 to 12c and Figs. 13a and 13b depict an operation aiming at
switching from the second configuration to the third configuration of the
module 50. For
this, another first overstroke with a larger amplitude than the previous one
in
commanded by the control unit, downwardly from the purge stroke end position
as
shown in Fig. 12.
The body 66 first abuts down against the fixed body 22. As the first
overstroke is continued, the top part 56a of the rotary member 56 is rotated
because the
follower rollers 68 press against their ramps 70a. This helical motion is
transmitted to the
bottom part 56b, as well as to its attachment fingers 64. During this motion,
the fingers
64 of the bottom part 56b then axially abut down against the top end 24c' of
the piston
24c, this state corresponding to that represented in Figs. 12a and 13a.
Then, the first overstroke is continued and the top part 56a continues to
be helically driven downwardly, whereas the bottom part 56b only undergoes a
rotation
along the axis 9 in the first direction 72a, since it is translationally
blocked. During this
rotation the angular extent of which is perfectly controlled because it
directly depends on
the extent of the axial overstroke of the control rod 12, the attachment
fingers 64
penetrate the slots 84c. This angular movement of the fingers 64 is for
example in the
order of 22.5 , and sufficient to come against or in the proximity of the
bottom of the
slots 84b, 84c. The insertion of the fingers 64 into the slots 84c causes the
third piston
24b to be coupled with the module 50. This mechanical coupling state is
represented in
Figs. 12b and 13b.
Once the coupling is made, the control unit of the pipette commands
the rod 12 to be lifted back to the purge end position, which results in
simultaneously
lifting back the three pistons 24a-24c, as is shown in Fig. 12c. Then,
pipetting operations
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can be commanded conventionally, for volumes corresponding to the range
associated
with ail of the three pistons 24a-24c.
Of course, it is noted that directly switching from the first to the third
configuration can be commanded by the control unit of the pipette, by adapting
the
amplitude of the first downward stroke accordingly.
Figs. 14a to 14d and Figs. 15a and 158 depict an operation aiming at
switching from the third configuration to the second configuration of the
module 50. For
this, a second overstroke is commanded by the control unit, upwardly from the
top
pipetting position as shown in Fig. 14a.
In this state of sampling the nominal volume associated with the third
configuration, the body 66 is abutting up against the fixed body 22. As the
second
overstroke is continued upwardly, the top part 56a of the rotary member 56 is
rotated
because the follower rollers 68 press on their ramps 70b, as is depicted in
Fig. 15a. This
helical motion is transmitted to the bottom part 56b, as well as to its
attachment
fingers 64. It is made against the return strain generated by the second
centring
spring 80b, by compressing the latter. During this motion during which both
pistons 24b,
24c slide while remaining rotatably fixed, the fingers 64 in helical motion
progressively
leave the slot 84c. At the end of the second overstroke, the fingers 64 are
completely
outside the slot 84c, such that the third piston 24c is uncoupled from the
module 50. This
state is shown in Figs. 14b and 15b.
Then, the control unit of the pipette commands a downward movement
of the control rod 12, such that the fingers 64 repel the third piston 24c in
its bottom
position, abutting against the fixed body 22. This phase is represented in
Fig. 14c. It
precedes the final lifting back phase of the module 50 and of both pistons
24a, 24b, by
virtue of an upward axial movement of the control rod 12 as depicted in Fig.
14d.
Then, pipetting operations can be commanded conventionally, for
volumes corresponding to the range associated with ail of the two pistons 24a,
24b.
Figs. 16a and 16b as well as Figs. 17a and 17b depict an operation
aiming at switching from the second configuration to the first configuration
of the
module 50. For this, another second overstroke with a larger amplitude than
the previous
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one is commanded by the control unit, upwardly from the top pipetting position
as shown
in Fig. 16a.
In this state of sampling the nominal volume associated with the second
configuration, the body 66 is abutting up against the fixed body 22. As the
second
overstroke is continued upwardly, the top part 56a of the rotary member 56 is
rotated
because the follower rollers 68 press on theirs ramps 70b, as is depicted in
Fig. 16a. This
helical motion is transmitted to the bottom part 56b, as well as to its
attachment
fingers 64. During this motion during which the piston 24b slides while
remaining
rotatably fixed, the fingers 64 in helical motion progressively leave the
slots 84b. At the
end of the second overstroke, the fingers 64 are completely outside the slots
84b, such
that the second piston 24b is uncoupled from the module 50. This state is
shown in Figs.
16b and 17b.
Then, the control unit of the pipette commands the downward
movement of the control rod 12, such that the fingers 64 repel the second
piston 24b in
its bottom position, abutting against the fixed body 22 or against the third
piston 24c
already in a down abutting position. This phase, similar to that represented
in Fig. 14c,
precedes the final lifting back phase of the module 50 and of the single
piston 24a, by
virtue of an upward axial movement of the control rod 12.
Then, pipetting operations can be commanded conventionally, for
volumes corresponding to the range associated with the single first piston
24a.
Once again, it is noted that directly switching from the third to the first
configuration can be commanded by the control unit of the pipette, by adapting
the
amplitude of the second upward stroke accordingly.
Of course, various modifications can be provided by those skilled in the
art to the invention just described, only by way of non-limiting examples.
