Note: Descriptions are shown in the official language in which they were submitted.
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PIPETTING SYSTEM WITH IMPROVED CONTROL AND VOLUME ADJUSTMENT
DESCRIPTION
The present invention relates to the field of air displacement pipetting.
It more particularly relates to a device for controlling pipetting and
adjusting a volume to
be sampled.
The invention applies to the different types of sampling systems, that is
in particular the hand- or power-operated pipettes, as well as automatons.
Pipettes, also
referred to as sampling pipettes, laboratory pipettes or even liquid transfer
pipettes,
represent a privileged application. They are intended for removing and
dispensing liquid
into containers or the like.
Hand-operated pipettes are intended to be handheld by an operator
during the liquid sampling and dispensing operations, these operations being
performed
by moving a control knob by applying an axial pressure on the same knob. The
axial
pressure applied to the control knob is transmitted to a piston of the
pipette, which
undergoes an axial displacement and causes an air displacement leading to the
sampling
and dispensing operations. For power-operated pipettes, if the sampling stroke
and
dispensing stroke commands are also controlled by actuating a knob, the
displacement of
the piston is performed on the other hand due to an engine driven by an
electronic
device.
On the hand-operated pipettes, in order to be able to adapt the volume
quantity to pipette, means for adjusting this volume are generally provided.
By actuating
these means, the initial position of the piston is displaced, and the
pipetting stroke of the
piston is thus modified. Therefore, during the pipetting operations, the
displacement of
the control knob to be performed by the operator is flot the same when the
volume to be
sampled changes. Problems of pipetting comfort can result therefrom, in
particular for
the low strokes associated with the sampling of small liquid volumes.
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On the power-operated pipettes and automatons, variable amplitude
displacements of the control member, which depend on the volume to be sampled,
complicate the engines and their electronic control systems.
Therefore, whatever the type of air displacement pipetting system,
there is a need for optimizing its device for controlling pipetting and
adjusting the volume
to be sampled.
To do so, the object of the invention is a device for controlling pipetting
and adjusting a volume to be sampled, for an air displacement pipetting
system, said
device comprising:
- a translation displaceable pipetting control member;
- rotary actuating means coupled to the control member so that a
translation displacement thereof causes a rotation of the actuating means
about a first
rotation axis;
- a linking member slidably and movably mounted on the actuating
means, the linking member being intended to be connected to a piston of the
pipetting
system;
- means for adjusting the volume to be sampled;
- rotary means defining, for the linking member, a spiral-shaped guiding
path, said rotary means being coupled to said adjusting means so that the
actuation of
the latter causes a rotation of the rotary means about a second rotation axis
parallel to
the first axis and on which the spiral guiding path is centred, this rotation
simultaneously
leading to a relative displacement of the linking member along the spiral
guiding path,
and to a sliding of the linking member relative to said actuating means.
The invention is noteworthy in that it provides the implementation of a
spiral-shaped guiding path of the linking member, adapted to adjust the volume
to be
sampled while enabling a constant pipetting stroke to be maintained, whatever
the
sampled volume.
In the case of a hand-operated pipette, this improves the pipetting
comfort since the operator can repeat the same pipetting stroke for ail the
sampled
volumes. In the case of a power-operated pipette or an automaton, due to the
identical
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pipetting stroke for ail the volumes, the engines and their electronic control
systems
implemented for the displacement of the pipetting control member can be
simplified. A
gain regarding the cost of the pipetting system advantageously results
therefrom.
Finally, the spiral shape of the path guiding the linking member enables
the latter to draw a substantially circular movement which is particularly
reliable, and
hardly subject to errors and blocking risks. It also enables a great pipetting
accuracy to be
provided to the system.
Preferably, said actuating means comprise a toothed segment
cooperating with a rack made on the pipetting control member. Other coupling
means
can however be worth considering, such as friction means, without departing
from the
scope of the invention.
Preferably, said actuating means comprise a finger provided with a
groove in which the linking member is slidably mounted.
Preferably, the linking member is a pin.
Preferably, said first and second rotation axes are substantially merged.
Alternatively, they could be made parallel, at a distance from one another,
without
departing from the scope of the invention.
Preferably, said volume adjusting means are rotary.
Preferably, the adjusting means comprise a worm screw cooperating
with a helical toothing provided on the rotary means. These adjusting means
are distinct
from the control member, even if designed intertwining these two elements can
be
chosen, for example by arranging them coaxially one around the other.
Preferably, in a top position of the control member, the sliding axis of
the linking member is parallel to a translation axis of the control member. In
other words,
upon actuating the volume adjusting means, sliding the linking member relative
to said
actuating means is performed along an axis parallel to the translation axis of
the control
member, which is generally parallel to the sliding axis of the piston of the
pipetting
system.
Preferably, switching form the top position of the control member to its
low position causes a rotation of the actuating means at an angle
substantially equal to
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1800. A lower angle is of course worth considering, without departing from the
scope of
the invention.
Preferably, the guiding path has a number of turns equal to or greater
than two, and even more preferentially equal to or greater than four. However,
other
possibilities can be worth considering, such as a single turn, or even an
incomplete turn.
Preferably, the rotary means take the shape of a disk inside which the
spiral guiding path is made in a through way.
The object of the invention is also an air displacement pipetting system,
comprising a device for controlling pipetting and adjusting a volume to be
sampled such
as described above.
Preferably, the pipetting system includes a slidably mounted piston as
well as means for connecting the piston to said linking member. Preferably,
blade- or
elastic rod-type means are chosen, but any of other mean can be worth
considering,
enabling the spiral movement of the linking member moving in the spiral path
to be
transmitted, into a sliding movement of the piston during pipetting. It can be
for example
alternatively one or several hinged connecting rods.
Preferably, the system is a hand- or power-operated pipette, including a
handle forming top part fitted with the rod-shaped control member, at the end
of which a
control knob is provided.
Alternatively, the pipetting system is an automaton.
Further advantages and characteristics of the invention will appear upon
reading a non-limiting detailed description hereinbelow.
The description will be made with reference to the appended drawings
among which:
- Fig. 1 shows a perspective view of an air displacement sampling
pipette, according to a preferred embodiment of the present invention;
- Fig. 2 shows a schematic cross-section view of the pipette shown in
Fig. 1;
- Fig. 3 shows a perspective view of the device for controlling pipetting
and adjusting the volume to be sampled of the pipette shown on the previous
figures;
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- Fig. 4 shows an enlarged view of a part of the device of the previous
figure;
- Figs. 5a and 5b shown the pipette in different successive states during
a pipetting operation; and
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Figs. 6a and 6b are analogous views to those of Figs. 5a and 5b, with the
pipette adjusted to sample a different liquid volume.
With reference first to Fig. 1, a hand-operated air displacement
sampling pipette 1 is represented, according to a preferred embodiment of the
present
invention. Throughout the following description, the terms "top" and "low" are
to be
considered with the pipette held vertically, in a pipetting position or close
to this same
position.
ln Fig. 1, the pipette 1 is shown held by the hand 2 of an operator, who,
thanks to his/her thumb 4, actuates the pipette to produce the dispensing of a
liquid
which has been previously drawn.
More precisely, the pipette 1 comprises a handle 6 forming the upper
body of the pipette, handle from which a rod-shaped pipetting contrai member
10
emerges carrying at its top end, in a pipetting position, a contrai knob 12
the upper part
of which is intended to undergo the pressure of the operator's thumb. By way
of
indication, it is noted that a display screen (flot represented) can be
provided on the
handle 6. Also, as mentioned thereafter, means for adjusting the volume to be
sampled
can also be accessed by the operator on this handle 6.
Under the handle 6, the pipette 1 includes a removable low part 14,
which ends towards the bottom by a cone-holder cap 16 receiving a consumable
18, also
referred to as a sampling cane. ln a known manner, after pipetting, the cane
can be
mechanically ejected by an ejector 20 the actuating knob 22 of which is for
example
protruding on the top of the handle, close to the control knob 12.
ln Fig. 2, the pipette 1 is schematically shown, with its device 30 for
controlling pipetting and adjusting the volume to be sampled, integrated into
the handle
6. This device 30, specific to the present invention, will be described in a
more detailed
way thereafter. The piston 50 of the pipette is also shown, which enables the
air
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displacement necessary to the sampling operations to be generated. The piston
50 is
slidably movable along a vertical axis 26, in a suction chamber 52 defined
inside the low
part 14. The axis 26 corresponds to the longitudinal axis of the pipette, on
which a high
number of components, such as the cone 18 are centred.
With reference jointly to Figs. 2 to 4, the device 30 for controlling
pipetting and adjusting the volume to be sampled is shown. The device first
includes the
rod-shaped control member 10, translation displaceable relative to the handle
6, along a
translation axis 25 parallel to the axis 26. At its low end, the rod 10 has a
rack 10a.
The device 30 also includes rotary actuating means 32, rotatably
mounted relative to the handle 6 about a first rotation axis 34 preferably
orthogonal to
the axes 25, 26. The means 32 have a toothed segment 36 meshing the rack 10a,
as can
be seen especially in Fig. 3. Consequently, a translation of the rod 10 along
the axis 25
causes a rotation of the means 32 about the axis 24. Here, the segment 36
corresponds to
a disk segment of about 180'.
The means 32 also include a finger 38 rotatably engaged with the
segment 36, the finger being arranged in a plane orthogonal to the first
rotation axis 34
and extending along a direction cutting off this same axis 34. As can be seen
in Fig. 4, the
finger 38 is fitted with a straight groove 40 extending along the longitudinal
direction of
this finger. Within the groove 40, a pin-shaped linking member 42 is freely
slidably
mounted. The pin 42 is provided to be connected to the piston 50 in order to
apply
thereto the raising/lowing movements necessary to the pipetting operations. To
do so, an
elastic rod or blade 44 is provided, the top end of which is mounted on the
pin 42 and the
low end of which is mounted on the top end of the piston 50.
The device 30 also includes means for adjusting the volume to be
sampled. These are rotary means provided with a worm screw 54 extended by a
shaft 56
inside which an adjusting knob 58 distinct from the pipetting control knob 12
is located.
The adjusting knob 58 is controllable from the outside of the handle 6. These
adjusting
means are arranged along an axis 60 orthogonal to each of the axes 34, 26.
Finally, the device 30 comprises rotary means 62 having the overall
shape of a disk defining, for the linking member, a spiral-shaped guiding path
64. The
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path 64 then takes the shape of a through groove or throat, into which the pin
42 is
guided. In this respect, the diameter of the pin is substantially identical to
the width of
the groove/throat extending as a spiral, preferably as a spiral of Archimedes.
The number
of turns of the path 64 is for example between 2 and 6. This spiral is centred
on a second
rotation axis 66, which is preferably substantially merged with the first
abovementioned
rotation axis. This axis 66 corresponds to the one of the disk 62 which
therefore lies
within a plane parallel to the axes 25, 26.
The disk 62 has at its periphery 68 a helical toothing (flot shown)
meshing with the worm screw 54. For this reason, the disk is coupled to the
volume
adjusting means sa that actuating the latter into rotation causes a rotation
of the disk 62
about the second rotation axis 66.
In Figs. 5a and 5b, a part of the pipette 1 is shown in different states
during a lowering operation of the piston 50. This lowering operation is the
one
performed prior to sampling liquid, or corresponds to the liquid dispensing
operation
performed after sampling.
Ta fulfil such an operation, the operator actuates the control knob 12 to
cause the lowering of the rad 10. During this lowering, the meshing between
the rack 10a
and the toothed segment 36 leads to the rotation of the means 32 about the
axis 34.
During this rotation maintained by the lowering of the rad 10, a relative
displacement of
the pin 42 along the spiral guiding path 64 provided on the disk 62 remaining
fixed, as
well as a sliding of this pin in the groove 40 simultaneously take place. This
sliding is
necessary to cape with the graduai evolution of the diameter of the turn in
which the pin
42 is guided during the lowering operation.
During the lowering of the control rad 10, the pin 42 is displaced along
the path 64 starting from a top point relative to the pipette body, towards a
low point, by
following a spiral trajectory. For this reason, during the lowering, the pin
42 also deviates
from the axis 26 on which it was initially placed with the control rad at a
top position,
which leads the blade 44 to be elastically bending deformed. This blade then
drives the
sliding movement towards the bottom of the piston 50.
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In the represented embodiment, a complete lowering stroke of the
piston is achieved by a complete downwards stroke of the control rod 10,
leading to the
rotation of the toothed segment 36 at an angle of about 1800. Further, at the
end of the
lowering stroke, the pin 42, after deviating from the axis 26, returns to a
low position by
being again arranged on this same axis. During this stroke, the pin 42
therefore travels
along a half-turn of the spiral 64.
Raising the equipment is then made conventionally, by releasing the
control knob 12 and under the action of return springs (not shown). This
raising, made for
example for sampling liquid, is then following by a new downwards stroke for
dispensing
the sampled liquid.
In Figs. 6a and 6b, the pipette 1 is also shown respectively at the
beginning and the end of the piston lowering operation, but with a different
sampling
volume. To adapt the volume, the adjusting knob 58 is rotated, leading to a
rotation of
the disk 62 with the actuating means 32 remaining fixed. Here again, this
rotation
simultaneously leads to a relative displacement of the pin 42 along the spiral
guiding
path 64, and to a sliding of this pin in the groove 40. During this sliding,
the pin then tends
to be displaced upwards or downwards as a function of the direction of
rotation, driving
with itself the piston 50 the top position of which varies according to the
same amplitude.
In a top position of the control member 10 such as represented in Fig.
6a, the sliding axis 70 of the pin 42 is preferably provided to be
substantially merged with
the axis 26. This axis 70, corresponding to the longitudinal direction of the
groove 40, is
thus arranged so that actuating the adjusting knob 58 causes the pin 42 to be
displaced
along a vertical diameter of the spiral, while remaining on the axis 26. By
way of
indicating example, in Fig. 6a, the represented adjustment is achieved thanks
to two
complete revolutions of the disk 62 with respect to the position for sampling
a maximum
volume represented in Fig. 2.
Also, during a lowering operation performed from the adjustment of
Fig. 6a, a complete stroke of the control rod 10 leads the actuating means 32
to pivot on
about 180 , as in each of all the other positions for adjusting the volume to
be sampled.
The pin 42 is thus displaced along the path 64 starting from a top point
relative to the
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pipette body, towards a low point, by following a spiral trajectory which
deviates it from
the axis 26 before meeting it again at the low point, as shown in Fig. 6b.
In the example shown in Figs. 6a and 6b, the rotation of about 1800 of
the pin 42 being performed closer to the rotation axis 34 than in the
configuration shown
in Figs. 5a and 5b, the displacement of this pin 42 and of the piston 50 along
the axis 26 is
smaller. This thus makes it possible to sample a less significant liquid
volume.
The invention thus advantageously enables different liquid volumes to
be reliably and accurately sampled, while maintaining a substantially
identical pipetting
stroke.
lt is noted that the above-described device 30 can have a disengageable
aspect, enabling the implementation of a draining operation of the pipette
after
dispensing.
Of course, various modifications can be brought by those skilled in the
art to the invention which has been described, solely by means of non-limiting
examples.
In particular, the invention can be applied to a power-operated pipette or to
an
automaton for which the translation displacement of the control member is
performed
via an engine.
