EP0154112A2 - Magnetic stirring device - Google Patents

Abstract

1. Magnetic stirring apparatus with a base containing a magnetic winding system, in which pole cores (2) are arranged at the crossings of raster lines running essentially in the same direction, onto which vessels (15) of non-magnetic material, each containing a magnetic stirring rod (16) and liquid to be stirred, can be placed in the region of a plurality of stirring stations (R), characterized in that the magnetic winding system is constituted by elongated conductor members (3 to 14) running parallel to the raster lines in the gaps between the pole cores (2) and crossing each other, in which a current can be produced in such a way that the direction of current in adjacent gaps between poles, running lengthwise in the same direction, is different in each case, and the direction of current can be reversed at regular intervals or cyclically, first in the one group of parallel conductor members (3 to 8) and then in the other group of conductor members (9 to 14) running transversely to them.

Description

The invention relates to a magnetic stirring device with a base containing a magnetic winding system, on each of which a magnetic stirring rod and the vessels to be stirred, made of non-magnetic material, can be placed in the region of a plurality of stirring points. Magnetic stirring devices of this type are known for example from German Offenlegungsschrift 31 35 961.

The magnetic winding system of the known magnetic stirring devices of the type just mentioned contains a large number of magnetic coils surrounding each pole core, which are wired in such a way and can be supplied with current that magnetic rotating fields are generated in the area of the stirring points above the surface of the base, which are generated with the stirring rod interact and set the stir bar in rotation.

In the manufacture of the known magnetic stirring devices, it is difficult to avoid wiring errors due to the plurality of stirring points and the resulting large number of magnetic coils, which is why the manufacture of the base of these devices is comparatively complex and expensive. In addition, it is due to the construction of the known magnetic stirring devices at the manufacturer development of the magnetic winding system necessary. to provide the individual pole cores with the magnetic coils, which, if a large number of very small stirring points are to be formed, have very small dimensions, which further complicates the manufacture and makes them more expensive.

The object of the invention is to achieve a magnetic stirring device of the type briefly described at the beginning. that the magnetic winding system can be manufactured quickly and cheaply and is also suitable for miniaturization.

Starting from a magnetic stirring device with a base containing a magnetic winding system, in which pole cores are arranged at the crossover points of groups in approximately the same direction, and on each of which contains a magnetic stirring rod and vessels to be stirred made of non-magnetic material in the area of a According to the invention, the above-mentioned object is achieved in that a plurality of stirring points are achieved in that the magnetic winding system is formed by elongated conductor tracks that intersect and intersect in the spaces between the pole cores and intersect with one another. in which a current flow can be generated in such a way that the current direction in neighboring pole gaps running longitudinally in the same direction is different and intermittently or periodically the current direction once in one group of conductor tracks lying in the same direction and then in the other group running transversely in the same direction of mutually lying conductor tracks is reversible.

It turns out that with such a configuration of the magnetic stirring device, the magnetic winding system does not have to be formed from individual magnetic coils wrapping around the pole cores, but rather by inserting elongated conductors lanes can be produced that only need to be wired or connected outside the arrangement of the pole cores. In the case of a magnetic stirring device of the type proposed here, a complete current-carrying turn around a pole core is composed of four conductor sections which run past this pole core on the four sides of a pole core, which projects from a base plate forming the magnetic yoke. ,

Advantageous refinements and developments are the subject of the attached claims which are subordinate to claim 1, the content of which is hereby expressly made part of the description without repeating the wording at this point.

• Fig. l eine schematische perspektivische Abbildung eines Ausschnittes der Basis einer Magnet-Rühreinrichtung, wobei mit den Polkernen verbundene Polschuhe sowie ein den magnetischen Rührstab und die zu rührende Flüssigkeit enthaltendes Gefäß nur im Bereich einer einzigen Rührstelle angedeutet sind, um die Darstellung zu vereinfachen und zu verdeutlichen,
• Fig. 2 eine schematische Aufsicht auf eine Anordnung von Polkernen mit jeweils Polkernreihen umschlingenden langgestreckten Spulen, welche jeweils aus einer einzigen Spule großen Durchmessers gebildet sind,
• Fig. 3 eine schematische Aufsicht auf eine Polkernanordnung mit einer Anordnung langgestreckter Spulen, welche jeweils eine Polkernreihe umschlingen und welche jeweils einzeln zur Verwirklichung eines bestimmten Wicklungssinnes verdrahtet sind,
• _Fig. 4 eine schematische perspektivische Ansicht eines einzigen, im Querschnitt quadratischen Polkernes mit an diesem vorbei verlaufenden Leiterbahnen in Gestalt hochkant stehender Leiterbänder,
• Fig. 5 eine schematische perspektivische Ansicht eines einzigen Polkerns mit resultierendem quadratischem Querschnitt, wobei dieser Polkern aus vier im Eckenbereich aufragenden Polkernelementen gebildet ist und
• Fig. 6 eine schematische perspektivische Explosionsdarstellung der Basis einer Magnet-Rühreinrichtung, bei der die Leiterbahnen auf Substratplatten nach Art gedruckter Schaltungen gebildet sind.

Exemplary embodiments are described below with reference to the drawing. They represent:

• Fig. L is a schematic perspective illustration of a section of the base of a magnetic stirring device, wherein pole shoes connected to the pole cores and a vessel containing the magnetic stirring rod and the liquid to be stirred are only indicated in the area of a single stirring point in order to simplify and illustrate the illustration clarify
• 2 shows a schematic plan view of an arrangement of pole cores with elongate coils wrapping around each pole core row, which are each formed from a single coil of large diameter,
• Fig. 3 is a schematic plan view of a pole core arrangement with an arrangement of elongated coils, which each loop around a pole core row and which are each individually for Ver a certain sense of winding are wired,
• _F ig. 4 shows a schematic perspective view of a single pole core with a square cross section with conductor tracks running past it in the form of upright conductor strips,
• 5 shows a schematic perspective view of a single pole core with a resulting square cross section, this pole core being formed from four pole core elements which protrude in the corner region and
• Fig. 6 is a schematic exploded perspective view of the base of a magnetic stirring device, in which the conductor tracks are formed on substrate plates in the manner of printed circuits.

Figure 1 shows a part of the base of the magnetic stirring device forming base plate 1 made of ferromagnetic material, from which a plurality of pole cores 2 protrudes, which are shown in the illustration of Figure 1 with a cylindrical shape to improve the clarity of the illustration. In practice, however, pole cores are used which have a prismatic shape, as is shown, for example, in FIGS. 4 to 6.

The pole cores 2 are located at the crossover points of a square grid of groups of grid lines parallel to one another that cross over one another. However, it should be expressly pointed out that the design principles given here can also be applied to pole core arrangements in which the pole cores protrude at the crossover points of rectangular grids or parallelogram grids or trapezoid grids.

In the longitudinal spaces between the rows of pole cores bind elongated conductor tracks 3 to 8 and 9 to 14 inserted in such a way that the conductor tracks 3 to 8 form a group of mutually parallel conductors in the unidirectional pole core spaces, while the conductors 9 to 14 a group of mutually parallel conductor tracks crossing the former-mentioned conductors in the transverse pole core spaces. The conductor tracks 3 to 14 are now wired and can be supplied with current such that, as indicated by arrows in FIG. 1, the current direction in the conductors within a pole core gap is opposite to the current direction in the conductors of the adjacent, parallel pole core gap, which is both applies to the longitudinal conductor tracks of one group as well as to the transverse conductor tracks of the other conductor group. Furthermore, the current direction is alternately reversible in one conductor group and then in the other conductor group. This can be done intermittently by loading both conductor groups with rectangular wave-shaped supply voltages with a corresponding phase shift, or continuously by applying two phase waves to the two groups of conductor tracks with sine-wave-shaped supply voltages.

If one considers a state of the current flow through the conductor tracks corresponding to the arrows drawn in FIG. 1; len, it can be seen that in the area of the stirring point R indicated in the drawing at the top left, the pole core 2 drawn at the top left and the bottom right are flowed around by the currents in the conductor tracks running past the relevant pole cores in such a way that a constant sense of direction around the _P. olkern is realized around, so that the pole core 2 drawn in the top left-hand corner is surrounded by the conductor currents in the relevant adjacent conductor track sections in a clockwise direction, while the pole core 2 shown in the bottom right corner is surrounded by the conductor currents in the respective adjacent conductor track sections in a counterclockwise direction.

A south pole or a north pole thus forms at the upper ends of the pole cores mentioned, as shown in FIG. 1.

Because of the changing current direction in the conductor track sections next to those pole cores that belong to the other pair of poles, which are diametrically opposed with respect to the stirring point center, these pole cores experience no excitation in the operating state shown. Only when, for example, the current direction in conductor group 3 to 8 is reversed; while the current direction in the conductor group 9 to 14 is maintained, the situation is reversed and magnetic poles are formed on those pole cores which were not previously excited, namely in the operating state shown in FIG. 1, while the magnetic poles on the previously excited pole cores disappear.

If a vessel 15 made of non-magnetic material with a liquid to be stirred therein and a magnetic stirring rod 16 in the vessel is placed on the stirring point R, the magnetic field above the pole cores 2, which progressively progresses in the direction of rotation, causes the stirring rod 16 to be within the position stirring liquid in the vessel 15 is rotated. An improvement in the field distribution above the pole cores 2 is achieved by attaching pole shoes 17, indicated by dash-dotted lines in FIG. 1, which extend from the upper ends of the pole cores 2 to the center of the stirring points R. After, apart from the pole cores at the corners; Each pole core belongs to several stirring points, the pole shoes 17 are generally multi-armed, so that the pole core 2 shown in the center of the illustration in FIG. 1 bears a star-shaped pole shoe 17 which has its arms towards the four neighboring stirring point centers While a pole shoe arrangement is shown in the illustration of FIG. 1, which is located substantially in the plane of the upper ends of the pole cores 2, the pole shoes 17 are practically preferably bent upwards from their fastening points at the upper ends of the pole cores 2 and then bent into a horizontal plane which is essentially in the plane of the base top side is located on which the vessels 15 are placed. In this way, not only is an improved field concentration in the area of the stirring points R achieved, but there is also an enlargement of the space for inserting the conductor tracks into the interstices of the pole cores.

A stabilization of the circulation of the stirring rod 16 even at slow stirring speeds is achieved by auxiliary pole cores 18 which protrude from the base plate 1 in the spaces between the pole cores 2. Four such auxiliary pole cores are arranged around a stirring point center, each of which is located essentially in the middle of the pole core spaces and, in the direction of the longitudinal extension of the pole core spaces, has a cross-sectional dimension which is essentially the same as the corresponding dimensions of the pole cores. In this way it is achieved that the conductor tracks can be guided past the auxiliary pole cores 18 without undergoing a bend, as is readily apparent from the illustration in FIG. It should be noted that, for reasons of greater clarity, only auxiliary pole cores are shown in FIG. 1 only grouped around two stirring points.

The person skilled in the art recognizes that in practical embodiments of the magnetic stirring device proposed here to generate sufficient excitation in the pole cores 2, not only individual conductor tracks are inserted into the interpole spaces, as is shown in the schematic illustration in FIG. 1. Rather, in practical embodiments, there are each in the spaces between pole cores 2, for example square in cross section Conductor bundles covering the pole core spaces. essentially complete completely. These bundles of conductors can be produced relatively quickly and easily, which will now be discussed in greater detail in connection with FIGS. 2 and 3.

To manufacture the magnetic winding system of the arrangement shown in FIG. 2 in supervision, two coils of large circumference consisting of a number of turns are first produced, one of which is used to form a group of conductors running in parallel, while the other coil is used to form the conductor tracks running transversely thereto. In FIG. 2, one coil is designated by 19 and is indicated schematically in a solid line, while the other coil is designated by 20 and is symbolized by a broken line. After the large-scale coils have been produced, individual coil loops 19a, 19b and 19c are first braided around the rows of pole cores from one of these coils, so that the individual coil loops each wrap around a row of pole cores and an arrangement is obtained in which one coil side of the coil largely runs through the parallel pole core spaces in a continuous wavy line and the other side of the coil runs through the pole core spaces in a mirror-image continuous wavy line.

The coil 20 is then moved in a corresponding manner with the formation of coil loops 20a, 20b and 20c, which loop around the pole core rows which run perpendicular to the former pole core rows. It should be noted that in order to fill the available winding space in the spaces between the rows of pole cores, the manufacturing process explained with reference to FIG. 2 can be repeated several times, so that several groups of coil loops are stacked on top of one another in the manner of the coil loops 19a to 19c and 20a to 20c will.

In certain cases, it may be expedient to choose the long dimension of the coil loops in the manner shown in FIGS. 2 and 3 to be larger than the longitudinal dimension of the wrapped pole core row in question, since then the edge pole cores with respect to the excitation by the currents in each case Conductor sections running past the pole cores result in the same conditions as for the pole cores in the interior of the arrangement.

Another possibility of producing the magnetic winding system Another possibility of producing the magnetic winding system provides, according to FIG. 3, that individual elongated coils are wound, which are then pushed in groups which cross one another over the rows of pole cores and are wired in such a way that elongated ones run parallel to one another Coils results in a changing direction of winding. Also, in the magnetic winding system according to Figure 3, the arrangement is such that the individual elongated coils protrude at the ends over the respective looped olkernreihe _P, as indicated in Figure 3 at 21 and 22nd The influence of this design feature has been discussed above.

FIG. 4 shows a perspective view of a section of the base of a magnetic stirring device in the region of a pole core 2, which here has a square cross section and in turn protrudes from a ferromagnetic base plate 1. In the entire arrangement, a corresponding plurality of pole cores 2 are provided, which protrude from the crossover points of a square grid, the gaps between the pole cores 2 having dimensions which are comparable to those of the pole core cross section. In the embodiment according to FIG. 4, the conductor tracks have the shape of thin conductor strips standing upright in the interstices between the pole cores, which, for example, consist of copper or aluminum, in the latter case a very high-quality thin insulation an oxide layer can be applied to the conductor strips.

At the crossover points of the conductor tapes of the intersecting conductor groups, the conductor tapes are provided with transverse incisions reaching to the middle, with care being taken, of course, by appropriate insulation that no short circuits occur in the region of the crossovers of the conductor tapes. In this way, a base with a low overall height and an optimal use of the space between the pole cores 2 for accommodating the winding is obtained.

1

Pole shoe plates 23 are attached to the upper ends of the pole cores 2, which are approximately square in shape when viewed from above and carry pole shoe extensions 24 at the corners, which are initially bent upwards from the pole shoe plate 23 and then bent horizontally. The pole shoe lugs 24 extend with their outer ends close to the stirring point centers.

While in the embodiment according to FIG. 4 the individual pole cores 2 are solid, in certain cases it may be expedient to improve and equalize the rotating field above the surface of the base of the magnetic stirrer, an accumulation of ferromagnetic material in the area of the upper ends of the pole cores 2 to avoid. For this purpose, according to an embodiment not shown in the drawing, the upper ends of the pole cores 2 are provided with a conical countersink, so that in the case of a square cross section of the pole cores 2, pole core elements which run diagonally upward in the corner region remain, which form the magnetic field lines Lead diagonally upwards from the lower area of the pole core to the pole shoe arms, which then direct the field lines towards the stirring point centers. According to a modification of this design idea shown in FIG. 5 The individual pole cores 2 consist of four pin-like pole core elements 2a, 2b, 2c and 2d which protrude at the corners of a square corresponding to the pole core cross section and are each fastened to the base plate 1. At the upper ends of the pole core elements 2a to 2d, pole shoe plates can each be fastened in the manner of the pole shoe plate 23 according to FIG. 4. Around the individual pole cores, the conductor tracks are inserted in a number of intersecting layers, the pole core spaces.

Finally, FIG. 6 shows an embodiment of the base of the magnetic stirring device of the construction specified here, in which a multiplicity of prismatic pole cores 2 with a square cross section protrude from a base plate 1 made of ferromagnetic material and serving as a magnetic yoke the crossing points of a regular grid in the above-mentioned manner. In the embodiment shown here, the magnetic winding system is formed by a number of stacked, insulated circuit carrier plates 25, 26, 27 and 28, which are provided with bridges 29, which are aligned with one another in the different circuit carrier plates and serve to receive the pole cores 2. Conductor tracks are produced on the individual circuit carrier boards in the manner of printed circuits, whereby according to an embodiment not shown in FIG. 6, the circuit carrier boards can each be provided with conductor tracks on both sides, such that complete elongated coils, each wrapping around the rows of pole cores, form on a circuit carrier board, as is the case with Arrangement according to Figures 2 and 3 corresponds. In these cases, intermediate insulation layers are to be provided between the individual circuit carrier plates, which are indicated schematically in FIG. 6 at 30 and with which it is prevented that conductor tracks on the mutually facing sides of the circuit carrier plates form a short circuit. In the case of Fi Construction shown in FIG. 6, however, the circuit carrier plates 25 to 28 are each provided on one side with conductor tracks which run in a wavy line between the rows of openings 29. If it is a square arrangement of pole cores 2 on a square grid, one and the same components can be used to form the circuit carrier plates 25 to 28, which are stacked on the pole cores 2 rotated relative to each other. as can be seen easily from FIG. 6.

While the exemplary embodiments shown in the drawing only provide a small number of stirring points, for example four such stirring points, the construction described here enables a significantly larger number of stirring points to be implemented, so that practical magnetic stirring devices can be implemented with comparatively little effort allow twenty stirring points, thirty stirring points and more, which can have extremely small dimensions and can also be used in connection with small test tubes.

Claims (14)

1. Magnetic stirring device with a base containing a magnetic winding system, in which pole cores (2) are provided in the raster lines running essentially in the same direction and on each of which a magnetic stirring rod (16) and the vessels (15 ) made of non-magnetic material in the area of a plurality of stirring points (R). characterized in that the magnetic winding system is formed by intersecting elongated conductor tracks (3 to 14) which run parallel to the grid lines in the spaces between the pole cores (2) and in which a current flow can be generated in such a way that the current direction in adjacent ones , in the same direction longitudinal pole spaces are different and the current direction is reversible intermittently or periodically once in one group of parallel conductor tracks (3 to 8) and then in the other group of conductor tracks (9 to 14) running transversely thereto. 2. Device according to claim 1, characterized in that the grid lines form a rectangular grid, in particular a square grid, or a parallelogram grid or a trapezoid grid. 3. Device according to claim 1 or 2, characterized in that both groups of parallel conductor tracks are each formed by means of a coil (19, 20) of large circumference, from each of which a series of pole cores wrapping, elongated coils (19a to 19c; 20a to 20c) in are formed in such a way that one coil side of the coil of large circumference traverses the parallel pole core spaces in a continuous wavy line and the other coil side the Interstices between the pole cores in a continuous wavy line that is mirror-inverted (Fig. 2). 4. Device according to claim 1 or 2, characterized in that the two groups of parallel conductor tracks (3 to 8 and 9 to 14) are each formed from individual elongated coils, each of which wraps around a pole core row, elongated coils parallel to one another with an alternating winding sense are connected in series (Fig. 3). 5. Device according to claim l'or 2, characterized in that the mutually parallel conductor tracks on insulating with openings (29) for receiving the pole cores (2) provided substrate plates (25 or 28) on the type of printed circuits provided on one or both sides are and that a plurality of substrate plates with a crossing course of the conductor tracks thereon are stacked on top of one another (FIG. 6). 6. Device according to claim 1 or 2, characterized in that the conductor tracks are formed by upright in the pole core spaces between conductor strips (Fig. 4). 7. Device according to claim 6, characterized in that the conductor strips at the crossover points of the conductor tracks of one and the other group of parallel conductor tracks have cross-cuts reaching to the middle thereof for receiving the correspondingly incised, transverse conductor strips. 8. Device according to one of claims 1 to 7, characterized. that the pole cores have recesses in the center. 9. Device according to claim 8, characterized in that the pole cores are provided in the center with in particular conical countersinks. 10. The device according to claim 8, characterized in that the pole cores (2) are each formed from four upstanding at the corners of a square, pin-like pole core elements (2a to 2c) (Fig. 5). 11. Device according to one of claims 1 to 10, characterized in that; that pole shoes (17 or 23) are attached to the pole cores (2) and extend to the respectively adjacent stirring point centers, which are located at the point of intersection of the diagonals of the quadrilaterals, at the corner points of which the pole cores (2) are located; 12. The device according to claim 11, characterized in that on a pole core (2) attached, square pole shoe plate (23) from the corners in particular upward and then horizontally bent pole shoe extensions (24) extend in the direction of the stirring point centers . 13. Device according to one of claims 1 to 12, characterized in that the pole cores (2) protrude from a base plate (1) forming the magnetic yoke of the base. 14. Device according to claim 13, characterized in that from the base plate (1) four auxiliary pole cores (18) arranged around each stirring point center, which are located in the pole core spaces essentially in the middle thereof and in the direction of the longitudinal extension of the pole core spaces one corresponding Dimensions of the pole cores (2) have essentially the same cross-sectional dimension.

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