EP3216524B1 - Pipette with a plurality of pistons independently driven by an electric motor - Google Patents

Description

The present invention relates to a pipetting device with a piston-cylinder system comprising a cylinder extending along a cylinder axis, a piston and a working space bounded by the cylinder and the piston and filled with a working fluid for changing a pressure of the working fluid at one of Coupling a Pipettierspitze formed coupling point, which is pressure-transmitting connected to the working space, by relative movement of the piston relative to the cylinder along a relative movement path, wherein the piston linear motor to the relative movement relative to the cylinder is driven and this has at least one piston magnet arrangement, and further on the cylinder at least one cylinder magnet arrangement is provided, wherein at least one magnet arrangement comprising a piston magnet arrangement and a cylinder magnet arrangement comprises a series of electromagnets which are generated by means of a control device of the pipetting apparatus for generating a nes along the relative movement path migratory magnetic field can be energized, thereby providing the necessary for effecting the relative movement magnetic driving force.

Such a pipetting device is known in the prior art from the published patent application DE 10 2010 000 690 A1 known.

The WO2011 / 083125A1 is also part of the state of the art. Taking advantage of the basically known operative relationship between two magnet arrangements in linear motor drives, the pipetting piston can be driven linearly relative to the cylinder for relative movement.

This generally very advantageous drive method, which, for example, by appropriate wiring of the series of electromagnets such that their magnetic field travels along the relative movement path and the magnetically coupled other magnet arrangement "entrains" is reached, allows an immediate Movement drive of the piston relative to the cylinder without the need for linkage or gear would be necessary. In the prior art, as well as in the present invention, the piston magnet assembly is for this purpose designed and provided for common movement with the piston. Likewise, the cylinder magnet assembly is designed and provided for common movement with the cylinder, wherein with respect to a device frame of the pipetting the cylinder is usually mounted fixed to the frame, so that the cylinder magnet assembly is usually fixed to the frame.

Modern pipetting devices are commonly used in laboratories, in particular medical laboratories, where the magnetic field emanating from the linear motor drive of the piston can cause disturbances of other nearby sensitive laboratory equipment. At the very least, the fear of such an effect may cause pipetting devices with linear motor relative movement driven pistons to lack the attention due to the technical advantages they offer.

In addition, modern pipetting devices are often multichannel pipetting devices in which a plurality of pipetting channels are arranged in parallel and in a matrix, ie in rows and columns. Again, there may be the fear that pipetting channels, the closer they are arranged in a Mehrkanalpipettiervorrichtung together, the more unwanted magnetic influence on each other.

The object of the present invention is therefore to further develop the generic pipetting device known from the prior art in such a way that the magnetic field influence emanating from a pipetting channel is reduced to the environment outside the pipetting channel or even completely eliminated.

This object is achieved by a pipetting device of the type mentioned above, which has a magnetic shield radially outside of the piston magnet assembly and the cylinder magnet assembly, which is the radially outside of the location of the shield existing magnetic field of at least one magnet arrangement consisting of piston magnet arrangement and cylinder magnet arrangement, weakens compared to a state without shielding.

By arranging a magnetic shield radially outwardly of the two magnet assemblies of piston and cylinder magnet assembly, the magnetic field emanating from both magnet assemblies can be shielded by a common shield. The reference state for judging whether a component is an effective magnetic shield is the state of the same device without the component concerned.

Effective magnetic shielding can be achieved by having the shield comprise a shielding member with a ferromagnetic material. Of course, in addition to the ferromagnetic material, the shielding component may also comprise other material. To achieve the advantageous shielding effect is only sufficient that it has ferromagnetic material, since this has a lower magnetic resistance than other materials, including the ambient air, so that magnetic flux preferably takes place through the ferromagnetic material.

In order to reduce the magnetic field emanating from a magnetic arrangement of piston and cylinder magnet arrangement, the shielding component can surround a device frame-fixed magnet arrangement of piston and cylinder magnet arrangement at least along an axial section thereof. However, the greater the common axial region over which the device frame-fixed magnet arrangement and the shielding component extend, the higher the shielding effect. Preferably, the shielding member surrounds the device frame fixed magnet assembly along its entire axial extent.

In this case, the above orientation on the device frame fixed magnet arrangement is chosen because in this the attachment location and its extension length is established. The relative to a device frame movable magnet assembly, in the So usually the piston magnet assembly moves in operation relative to the device frame, so that it occupies different positions at different times and is located at different locations. Particularly preferably, the complete shielding of the magnetic field which originates from the magnet arrangement that is movable relative to the device frame can be thought of, in that the shielding component surrounds the entire relative movement path of the two magnet arrangements, so that particularly preferably each magnet arrangement is located in the axial extension region of the shielding component at all times ,

In principle, it is advantageous for the most uniform possible shielding in the circumferential direction around a pipetting channel or around at least one magnet arrangement belonging to it, if the shielding component surrounds the device frame-fixed magnet arrangement in the circumferential direction as far as possible. However, it has already proved to be sufficiently advantageous if the shielding member surrounds the device frame fixed magnet assembly at least half its circumference. This considerably facilitates the mounting of the shielding component, since it can simply be plugged with its opening side onto a pipetting channel and its magnet arrangements orthogonal to the cylinder axis. However, for the reasons mentioned above, the shielding component surrounding the device frame-fixed magnet arrangement by three-quarters of its circumference is even better in its shielding effect. Therefore, the shielding component particularly preferably surrounds the device frame-fixed magnet arrangement around its complete circumference. Then, the assembly can be carried out by sliding the Abschirmbauteils on the pipetting along its cylinder axis.

An easy-to-manufacture shape of the Abschirmbauteils represents a U-profile, which can be achieved by bending a sheet around an axis in a simple and cost-effective manner. In order to achieve a shielding effect which is as uniform as possible in the circumferential direction, it is advantageous if the shielding component has a symmetrical construction with respect to its direction of longitudinal extension, that is to say generally along the cylinder axis. This can be realized, for example, by shielding components which, when viewed in cross-section, are orthogonal to the cylinder axis Cutting plane have a polygonal and / or a part-circular or / and a circular contour.

Since the shielding component also surrounds the electromagnetic magnet arrangement for the above-mentioned reasons, in order to avoid an undesirably high heating of the electromagnetic magnet arrangement, it may be provided that the shielding component has at least one opening passing radially through it, such as a hole or slot, in particular one along the cylinder axis extending slot, has. Warm air can thus escape from the volume surrounded by the shielding component through such openings and can flow in cool air, whether by natural convection or by forced convection by means of a fan or the like. Then, when the hole or slit extends along the cylinder axis, cooling can be achieved over the largest possible axial area of the pipetting device, since as a rule magnet arrangements also run along the cylinder axis.

Furthermore, it can basically be thought of to carry out the shielding component in several parts and to assemble the individual parts to form a shielding component. However, a greater component stability with at the same time as possible closed, montagespaltfreier shielding is preferably achieved in that the cylinder axis associated shielding member is integrally formed.

In particular, the one-piece design, but apart from the basic shape of the Abschirmbauteils, can be facilitated by the fact that the Abschirmbauteil comprises a composite material with a matrix material and ferromagnetic filler.

The filler material may be spherical or / and fibrous and may be held in place by the matrix material. As a matrix material, a castable plastic or generally a pourable material can be used, so that the composite material introduced in the pourable state of the matrix material with filler material mixed therein in a mold and thus in the desired Shape can be brought. In this case, the use of injection molding processes for producing the shielding component is particularly preferred, so that the matrix material may be a preferably thermoplastic.

The shielding component may have other materials in addition to the composite material, but is preferably formed entirely from such a composite material due to the preferred injection molding process.

In order to prevent or suppress the formation of eddy currents in the shielding component, it can be provided that the spherical or / and fibrous or / and otherworm-shaped particles of the ferromagnetic filler material are provided with an electrically insulating coating. Such a coating may, for example, be a correspondingly electrically insulating lacquer which surrounds the individual particles of the ferromagnetic filling material. Insulating wraps of silica filler particles have proven particularly advantageous.

The use of a composite material of matrix material and ferromagnetic filler material for the production of the shielding component allows a mechanically stable, high-strength component, which can be brought into any desired shape by injection molding and, if necessary, can be mechanically machined after removal from the injection mold. As a result, the mechanically often critical attachment of a coupling formation to the, preferably detachable, coupling of pipette tips thereto on the cylinders, which are often made of glass, can be omitted. Instead, the coupling formation can be provided directly on the shielding component. Particularly preferred is the at least partially integral formation of coupling formation and Abschirmbauteil, for example by injection molding and, but not necessarily, with mechanical finishing. If the coupling formation requires moving parts, they can be mounted on a coupling forming portion formed integrally with the shielding member.

Another technical advantage of using castable composite materials of matrix material and filling material is that at least one further component can be cast directly into the shielding component. This may for example be a sensor, for example a temperature sensor for monitoring the temperature of one or more components of the pipetting device, in particular the pipetting channel, and / or it may be a proximity sensor which can detect the presence or absence of the piston at a predetermined position. Likewise, one or more signal and / or energy transmission lines can be cast into the shielding component, for example for supplying electrical energy to the electromagnets of the at least one electromagnetic magnet arrangement. Even the electromagnets can be cast into the shielding component.

Preferably, the proportion of filling material in the matrix material is dimensioned such that under the predetermined intended use of magnets in the magnet assemblies, the shielding member is at least partially magnetically in saturation.

In order to realize the shielding component with a ferromagnetic material component, it may be provided that the shielding component comprises steel and / or cobalt and / or nickel or is formed from steel and / or cobalt and / or nickel.

Although, in principle, the shielding component may be movable with the piston, such a device of a movable shielding component requires considerable manufacturing and assembly costs. Therefore, it is preferable that the shielding member is fixed to the apparatus rack, as stated above in connection with the linear overlap of the shielding member with the apparatus frame fixed magnet assembly.

So that the piston in the cylinder can perform a relative movement relative to the cylinder without interference, it can be provided that the cylinder magnet arrangement, relative to the cylinder axis passing through the cylinder, radially outside the cylinder is arranged. Here, it has proved to be advantageous to produce the piston at least in sections from graphite-containing material, in particular from graphite itself, so that the graphite-containing portions of the piston can be in sliding engagement directly on an inner surface of the cylinder. Thereby, a self-lubricating property of graphite can be utilized to facilitate the relative movement of the piston relative to the cylinder. Magnets of the piston magnet arrangement can be provided in the piston. Preferably, these are permanent magnets to get along without power supply to the usually movable relative to the device frame and enclosed by the cylinder piston magnet arrangement. So then the cylinder magnet assembly is preferably the electromagnetic magnet assembly. Thus, it can be provided structurally that the cylinder magnet arrangement has a plurality of conductor coils following one another along the cylinder axis and / or that the piston magnet arrangement has a plurality of permanent magnets which follow one another along the cylinder axis.

With the present invention, it is possible in a particularly simple manner to design the pipetting device such that it has a plurality of pipetting channels which can be operated separately from one another. This greatly facilitates the performance of different metering tasks in a metered liquid receiving, metering liquid transporting and metering liquid dispensing operation. Thus, different amounts of a dosing liquid can be aspirated and / or dispensed from different pipetting channels of one and the same pipetting device.

The present invention therefore also encompasses the idea of providing a plurality of piston-cylinder systems, each having a cylinder axis, to a generic pipetting device or to a pipetting device of the present invention, wherein the control device is designed to provide the magnet arrangements comprising at least one electromagnet of at least two piston-cylinder systems, preferably powered by all piston-cylinder systems simultaneously different to cause in at least two, preferably in all piston-cylinder systems simultaneously different relative movements of the piston and cylinder of each system.

Hereinafter, we will illustrate the present invention with reference to the accompanying figure. It shows:
Fig. 1 a rough schematic cross-sectional view of an embodiment of a pipetting device according to the invention with example two pipetting channels in longitudinal section.

In Fig. 1 is an embodiment of a pipetting device according to the invention only roughly in schematic longitudinal section generally designated 10.

The pipetting device may comprise a plurality of pipetting channels, in the example illustrated, for example, the pipetting channels 12 and 14.

Since the pipetting channels 12 and 14 are configured substantially identically, only the pipetting channel 12 will be described below as representative of both pipetting channels. If the pipetting channels 12 and 14 differ in relevant features, will be discussed separately below.

The pipetting channel 12 extends along a Pipettierkanalachse P, which preferably extends preferably rectilinear. The pipetting channel 12 comprises a piston-cylinder system 16, with a cylinder 18, in which a piston 20, preferably at least partially made of graphite or graphite-containing material, relative to the cylinder 18 along the Pipettierkanalachse P is slidably received. The Pipettierkanalachse P coincides in the present example with the cylinder axis Z of the cylinder 18 together.

In the piston 20, a number of permanent magnets 22 may be provided, which form a piston magnet assembly. The magnets 22 are preferably arranged in succession in the direction of the pipetting channel axis P, which is preferably also a piston longitudinal axis K, around a piston 20 of small diameter to get to the Pipettierkanalachse P. The entirety of the permanent magnets 22 of a piston 20 thus forms a piston magnet arrangement 24.

The magnets 22 of the piston magnet assembly 24 may be separated from each other by spacers 25.

The cylinder 18 is preferably surrounded radially in relation to the Pipettierkanalachse P outside by a series of magnets 26, which are preferably also along the Pipettierkanalachse P successively, particularly preferably equidistant from each other, are arranged. Preferably, the magnets 26 are electromagnets, so that they can be energized by a control device 28. The control device 28 may be designed to energize the electromagnets 26, which form a cylinder magnet arrangement 30, such that their magnetic field travels along the pipetting channel axis, so that the magnetizing field of the electromagnets 26 is the magnetic field of the magnets 22, preferably designed as permanent magnets Piston magnet assembly 24 and with these the piston 20 are driven relative to the cylinder 18 for relative movement.

The electromagnets 26 are preferably arranged identically and equidistant from each other along the pipetting channel axis P.

Radially outside the cylinder 18 and the cylinder magnet assembly 30 is a, preferably injection molded, Abschirmbauteil 32 is provided which surrounds the magnets 22 and 26 of the two magnet assemblies 24 and 30 radially outward, and which also radially into the axial spaces between two immediately axially adjacent magnets 26th the cylinder magnet assembly 30 protrudes.

The shielding component 32 can be formed from a composite material comprising a pourable, in particular injection-moldable matrix material into which ferromagnetic particles, which can have a spherical shape and / or a fiber shape, can be incorporated.

To prevent the propagation of eddy currents, the particles of ferromagnetic filler are preferably surrounded by an electrically insulating coating, for example of silica.

Usually, the filling degree of the composite material for the shielding member 32 is so high that filling material bridges are formed, so that sufficient electrical insulation by the matrix material is not necessarily ensured. However, the electrical insulation can be ensured by said coating.

By the Abschirmbauteil 32, which is preferably integrally formed so that the magnets 26 can be poured with their signal and / or energy transmission lines in the manufacture of Abschirmbauteils 32 in this can not only be achieved that radially outward of the two magnet assemblies 24 and 30, a significantly reduced magnetic field is measurable compared to the state of the same pipetting apparatus without the shielding member 32. Moreover, the magnetic flux return achieved with the shielding member 32 can increase the efficiency of the linear motor driving means formed by the magnet assemblies 24 and 30. Thus, with the shielding component 32 effecting a magnetic return, a higher driving force acting on the piston 20 can be exerted on the magnets 26 with the same amount of power fed into the magnets than if the shielding component 32 were not present.

At the pipettierseitigen longitudinal end 12a of the pipetting channel 12, a coupling device 34 may be provided, which carries a coupling formation 36 for coupling a pipetting tip 38 thereto. The coupling formation 36 can be configured in a manner known per se.

The original shaping of the shielding component 32 and its arrangement radially on the outside of the cylinder 18 advantageously enable the attachment of the coupling component 34 to the shielding component 32. For this purpose, an attachment component 40 can be interposed be, which connects the coupling member 34 with the Abschirmbauteil 32.

Alternatively or additionally, the coupling component 34 may be formed at least partially in one piece with the shielding component 32.

The cylinder 18 and the piston 20 define a work space 42 filled with working fluid, usually air or another gas, which fluidly communicates via a connection channel 44 in the coupling component 34 with a metering chamber 46 of a pipetting tip 38, which can preferably be detachably coupled to the coupling component 34 can stand.

By relative movement of the piston 20 relative to the cylinder 18 along the Pipettierkanalachse P, which may also constitute a relative movement path B of the piston 20 relative to the cylinder 18, the pressure of the working fluid in the working space 44 can be changed relative to the environment, which is due to the channel 44 also on the pressure of the working fluid in the metering chamber 46 of the pipette tip 38 effects. Through such deliberately induced pressure differences between the pressure of the working fluid in the working space 42 and the ambient pressure 38 in a known manner through a metering 48 at the coupling remote longitudinal end of the pipette tip 38 dosing into the dosing chamber 46 sucked (aspirated) and output from this (dispensed) ,

The control device 28, which can preferably control the electromagnets 26 of all pipetting channels 12 and 14 of one and the same pipetting device 10, is advantageously designed to supply the cylinder magnet arrangement 30 of the pipetting channel 12 and the cylinder magnet arrangement of the pipetting channel 14 separately from one another in order to be identical in the pipetting channels Time to cause different piston relative movements. This preferably continues with the increase in the number of pipetting channels of the pipetting device 10. More preferably, each cylinder magnet assembly 30 of a pipetting channel of Pipetting device 10 are operated separately from any other cylinder magnet assembly.

However, it is also possible to combine the pipetting channels of a pipetting device 10 into blocks of common, coinciding relative movement, for example in rows and / or columns, provided the known and advantageous matrix arrangement of pipetting channels in rows and columns.

Such a separate control of pipetting channels for effecting an individual relative movement of the piston and cylinder is advantageous not only in linear motor driven pipetting channels, as they are in FIG. 1 but can also be in conventional mechanically, for example by electric motor and transmission, driven piston of a multi-channel pipetting advantageous.

Claims (15)

1. Pipetting device (10) with a piston-cylinder-arrangement (16), comprising a cylinder (18) extending along a cylinder axis (Z), a piston (20) and a working chamber (42) confined by the cylinder (18) and the piston (20) and filled with a working fluid, for changing a pressure of the working fluid at a coupling site (at 34) adapted for coupling a pipetting tip (38), which coupling site is connected to the working chamber (42) transferring pressure (at 44), by a relative movement of the piston (20) in relation to the cylinder (18) along a relative movement path (B), wherein the piston (20) can be driven in the manner of a linear motor for a relative movement in relation to the cylinder (18) and for this purpose comprises at least one piston magnet arrangement (24), and wherein furthermore at least one cylinder magnet arrangement (30) is provided at the cylinder (18), wherein at least one magnet arrangement (24, 30) out of piston magnet arrangement (24) and cylinder magnet arrangement (30) comprises a series of electromagnets (26), which can be supplied with current by means of a control device (28) of the pipetting device (10) for creating a magnetic field moving along the relative movement path (B), for providing the drive force required for effecting the relative movement, wherein it comprises a plurality of piston-cylinder systems (16) with one cylinder axis (Z) each,
   characterized in that the control device (28) is adapted for simultaneously supplying different amounts of current to the magnet arrangements (30) comprising the at least one electromagnet (26), in order to simultaneously effect in at least two piston-cylinder-systems (16), preferably in all piston-cylinder systems (16), different relative movements of piston (20) and cylinder (18) of the respective system (16), in order to aspirate and/or to dispense different amounts of a dosing liquid at different pipetting channels (12, 14) of the pipetting device (10).
2. Pipetting device according to claim 1,
   characterized in that the pipetting device (10) comprises a magnetic shielding (32) radially outside the piston magnet arrangement (24) and the cylinder magnet arrangement (30) which weakens the magnetic field radially outside the site of shielding (32) originating from at least one magnet arrangement (24, 30) out of piston magnet arrangement (24) and cylinder magnet arrangement (30), compared to a condition without shielding.
3. Pipetting device according to claim 2,
   characterized in that wherein the shielding (32) has a shielding component (32) comprising a ferromagnetic material and surrounding a magnet arrangement (30), which is fixed with respect to a device frame, out of piston magnet arrangement (24) and cylinder magnet arrangement (30) at least along an axial section of the latter, preferably along its entire axial extension.
4. Pipetting device according to claim 3,
   characterized in that the shielding component (32) surrounds the magnet arrangement (30) fixed with respect to the frame at least around half of its circumference, preferably around three quarters of its circumference, particularly preferred around the entire circumference.
5. Pipetting device according to claim 3 or 4,
   characterized in that the shielding component (32) comprises at least one radially penetrating opening, such as for example a hole or a slot, in particular a slot extending along the cylinder axis (Z).
6. Pipetting device according to one of claims 3 to 5,
   characterized in that the shielding component (32) associated to a cylinder axis (Z) is formed in one single piece.
7. Pipetting device according to one of claims 3 to 6,
   characterized in that the shielding component (32) comprises a composite material, comprising a matrix material and a ferromagnetic filling material, in particular a filling material with globular or/and fibrous particles or is formed by such a composite material, wherein the composite material is preferably moldable, in particular injection-moldable.
8. Pipetting device according to claim 7,
   characterized in that the particles of the ferromagnetic filling material are provided with an electrically insulating coating.
9. Pipetting device according to claim 7 to 8,
   characterized in that a coupling structure (34) is directly connected to the shielding component (32) for a preferably releasable coupling of pipetting tips (38), in particular at least partially connected in one single piece.
10. Pipetting device according to one of claims 7 to 9,
    characterized in that the composite material is moldable and in that at least one further component, such as for example a sensor, in particular a temperature sensor, proximity sensor or/and energy or/and signal transport lines, is molded into the shielding component (32).
11. Pipetting device according to one of claims 3 to 10,
    characterized in that the shielding component (32) comprises steel or/and cobalt or/and nickel or is formed from steel or/and cobalt or/and nickel.
12. Pipetting device according to claims 3 to 11,
    characterized in that the shielding component (32) is fixed with respect to the device frame.
13. Pipetting device according to one of the preceding claims,
    characterized in that the cylinder magnet arrangement (30) is arranged radially outside the cylinder (18) in relation to the cylinder axis (Z) passing through the cylinder (18).
14. Pipetting device according to one of the preceding claims,
    characterized in that the cylinder magnet arrangement (30) comprises a plurality of conductive coils succeeding each other along the cylinder axis (Z) or/and in that the piston magnet arrangement (24) comprises a plurality of permanent magnets (22) succeeding each other along the cylinder axis (Z).
15. Pipetting device according to one of the preceding claims,
    characterized in that the cylinder magnet arrangement (30) is fixed with respect to a device frame and in that the piston magnet arrangement (24) is movable in relation to the device frame.

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