Electronically controlled magnetic stirrer

United States Patent

[11] 3,554,49'

<td> [72]</td><td> Inventor</td><td> Manfred Zipperer 141 Etzenbach, 7813 Grunern/Staufen, Germany</td>

<td> [21]</td><td> Appt. No.</td><td> 738,870</td>

<td> [22]</td><td> Filed</td><td> June 21,1968</td>

<td> [45]</td><td> Patented</td><td> Jan. 12,1971</td>

<td> [32]</td><td> Priority</td><td> June 22,1967</td>

<td> [33]</td><td></td><td> Germany</td>

<td> [31]</td><td></td><td> No. 1,638,968</td>

[54] ELECTRONICALLY CONTROLLED MAGNETIC STIRRER

Claims, 4 Drawing Figs.

[52] U.S.CL....................................................... 259/102,

259/72

[51] Int.CI......................................................... BO If 7/00

[50] Field of Search............................................ 269/107,

108, Magnetic Stirrer, 102,72, Vibrator Meeh;

259/106,102,111

[56] References Cited

UNITED STATES PATENTS 2,143,610 1/1939 Muller.......................... 259/1

3,138,370 6/1964 Anderson................. 259/IC

3,219,318 11/1965 Hershler....................... 259

3,279,765 10/1966 Sato............................. 259/IC

3,028,476 4/1962 Hug.............................. 259/108

FOREIGN PATENTS

531,130 10/1954 Belgium....................... 259/IC

1,383,201 11/1964 France......................... 259/10

Primary Examiner—Robert W. Jenkins

Attorney—Waters, Roditi, Schwartz &amp; Nissen

ABSTRACT: A magnetic stirrer for stirring low viscosit media comprises a plurality of stationary electromagnets ai ranged in a housing on which a receptacle containing th medium to be stirred can be mounted. The receptacle als contains one or more freely movable stirring arms controlle by the electromagnets which produce a rotary magnetic fie! by corresponding consecutive energization of the individuz electromagnets by means of an electronic control element.

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PATENTED JAN 121971

3,554,497

SHEET 1 OF 2

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PATENTED JAN 121971 . SHEET 2 OF 2

3,554,497

FIG. 3

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3,554,497

ELECTRONICALLY CONTROLLED MAGNETIC STIRRER

The invention relates to an electronically controlled magnetic stirrer for stirring media of low viscosity, wherein a rotating magnet which performs the stirring work is disposed in a housing, on which there is mounted a vessel container the medium to be stirred, there being freely movably disposed in the said vessel one or more stirring members which are driven by the rotating magnet and which stir the medium.

Since the stirring members in the vessel are driven by the rotating magnet lines of force pass through the vessel, the latter may consist of a material of any kind with the exception of a magnetic material. Such apparatus are employed primarily in chemical laboratories, so that the media to be stirred are primarily chemicals, and the stirring members are therefore preferably provided with an acid-resistant coating.

The object of the present invention is to provide a magnetic stirrer, wherein the field strength which acts on the stirring member and the speed of the later can be infinitely varied, and which has no mechanically or electrically moved parts and consequently requires no servicing and, in addition, has from the outset the properties of an explosion-proof apparatus.

Apparatus are already known in which a permanent magnet is rotated in some way within the housing during the operation. This permanent magnet transmits its rotational movement, by means of the magnetic field transmission, to a second permanent magnet situated in the stirring vessel, i.e. to the stirring member. In such cases, it is immaterial whether the permanent magnet in the housing of the stirrer is directly mounted on the shaft of the electric motor or is mounted on a shaft driven through a transmission system.

The disadvantage of such apparatus is that they are very costly by reason of the principle of their construction. From the physical viewpoint, they utilize two stators and two rotors.

The first stator and the rotor associated therewith form the driving motor, the second stator is the rotating permanent magnet, and the second rotor is the stirring member consisting of a permanent magnet and situated in the vessel.

In addition, stirring apparatus are known which employ an electric rotating-field generator within the housing. However, such apparatus operate only at a supply frequency of 50 c/s or 60 c/s and they therefore have no means for speed regulation.

The invention has for its object to provide an apparatus based upon a very simple principle and having no mechanically moving parts, which constitutes further development of the existing known apparatus, i.e. the apparatus is to operate silently, to be infinitely regulatable in speed and magnetic field strength, to have no wear and to be explosionproof.

In accordance with the invention, this object is achieved in an apparatus of the type mentioned at the beginning, by virtue of the fact that there are employed to drive the stirring member or members, instead of a rotating magnet, one or more fixed electromagnets disposed in the housing, which generate a rotating magnetic field, the speed of the magnetic field, by which the stirring frequency is determined, and the strength of the said field being infinitely variable within a wide range of limits by an electronic control element for feeding the electromagnets.

The electromagnets generate a rotating electromagnetic field, which in turn transmits this rotational movement to the stirring member situated in the stirring vessel and this initiates and maintains the stirring operation. In contradistinction to the known apparatus, the apparatus according to the invention requires only one stator and one rotor.

In consists of a fixedly mounted electromagnet within the housing constituting a stator and a soft-iron or permanent magnet, freely movable in the stirring vessel, constituting a rotor.

The intensity of the rotating magnetic field which is generated by the electromagnet makes it possible in accordance with the invention, to employ as stirring members in the vessel containing the medium to be stirred magnetizable soft-iron parts which are provided with blades or the like which promote the stirring action. In addition, it is possible accordance with the invention to provide the described a paratus with heating means and thus to supply heat to t medium during the stirring operation without magnetizatii of the permanent magnets being disadvantageously influenc by the heating as might happen in the stirring apparat hitherto operating with permanent magnets.

The advantages achieved by the invention consist mo especially in that, with low cost of construction, an apparat can be produced which employs no mechanically or elect cally movable parts and thus has an unlimited useful life, ai which operates silently and is explosionproof, since sparkir for example due to an electric motor, need not be given co cem. In addition, the speed of rotation of the magnetic fie and thus the speed and the magnetic field strength may regulated and thus adapted to the particular purpose of us Moreover, it is possible to make the overall height of the a paratus according to the invention substantially small· because no mechanical driving devices have to be accoi modated therein.

In a convenient further development of the invention, i stead of the vessel, there may be resiliently mounted upon t housing, in spaced relationship thereto, a soft-iron or pt manently magnetic plate, which is in turn intended to recei a vessel and which' performs a three-dimensional agitati movement with the vessel under the influence of the rotati magnetic field, whereby a further possibility of application the apparatus is afforded.

Also, by switching over, it is possible to alter the rotati magnetic field to an increasing and decreasing magnetic fie and thereby amplify the agitating effect. It is also possit within the scope of the invention to reverse the direction rotation of the magnetic field during the stirring operation reversing the polarity of the magnet. This is of particular a vantage whenever a stir spout is formed in the medium to stirred.

Embodiments of the invention are illustrated by way of e ample in the accompanying drawings and more fully describ in the following.

In the accompanying drawings:

FIG. 1 diagrammatically illustrates in section the constn tion of hitherto known magnetic stirrers,

FIG. 2 diagrammatically illustrates in section the princif of the invention,

FIG. 3 illustrates in section one embodiment of the invt tion, and

FIG. 4 illustrates in fragmentary form a stirring mechani: according to the invention with an attachment for vibrati the vessel.

In known stirrers, there is provided within a housing 6, diagrammatically illustrated in FIG. 1, an electric motor whi is schematically represented by the stator 1 and the rotor The said electric motor drives, for example through a belt p ley 7 and a V-belt 8, a belt pulley 10 mounted on a shaft which is in some way mounted in the housing 6. Secured that end of the shaft 9 which is further from the belt pulley is a permanent magnet 3 which rotates at a particular spe when the shaft 9 is rotated by the electric motor. The spe regulation of the motor and thus of the permanent magnet j effected through a potentiometer 5. Mounted on the up| side of the housing 6 is a vessel 11 which contains the medii 12 to be stirred. Situated on the base of the vessel 11 is a p manent magnet 4 which serves as a stirring member and whi is driven by the rotation of the permanent magnet 3 and si the medium 12.

In the construction of the stirrer according to the invent!· as diagrammatically illustrated in FIG. 2, there is disposed the housing 13 an electromagnet consisting of a core 14 an coil 15. The coil 15 receives current through the conduct 16,17 from an electronic control device 18 which generates the electromagnet a rotating magnetic field, the strength a speed of rotation of which are infinitely variable by the cont device 18. Mounted on the housing 13, as in known stirrers

3,554,497 stirring vessel 11 containing the medium 12 to be stirred, stirring member 19 consisting of a permanent magnet of a ft-iron member is situated on the base of the vessel 11. The id stirring member is driven by the rotating magnetic field of : electromagnet formed of the core 14 and the coil 15 and rs the medium 12.

In the embodiment of the invention as illustrated in section FIG. 3, the stirrer housing is denoted by 21, the coils of the ictromagnets installed therein by 22 and the cores of the ictromagnets by 23. The coils 22 of the electromagnets :eive current from the electronic control device 26, through pply conductors 24, 25 illustrated by way of example for the ;ht-hand coil in FIG. 3. The adjustment of the control device for regulating the strength of the magnetic field and its eed of rotation is effected through operating elements, of lich there is shown in FIG. 3, by way of example, a button . In the illustrated form of construction, the upper covering ill of the housing 21 is apertured for the passage of the cores of the electromagnets. A cover plate 28 consisting of a nontous metal for receiving the vessel 29 containing the medi130 rests on pillars 31 on the upper peripheral region of the using 21. Situated on the base of the vessel 29 is a stirring :mber 32 which, in the illustrated form of construction, is □vided with blades 33 to intensify the stirring movement, ovided within the cover plate 28 supporting the vessel 29 i heating bars 34 by means of which the medium 30 may be ated during the stirring.

In FIG. 4, the parts are denoted by the same reference nuirals as corresponding parts in FIG. 3. Instead of the heata; cover plate 28, there is here merely provided a simple ver plate 35. Instead of the vessel 29 of FIG. 3, there is here lunted on the cover plate 35 a ring 37 which encircles the id cover plate and is held in position by an indentation 36. A une 39 is resiliently suspended within the ring 37 by means springs 38 to receive a vessel 40, which may be secured to e frame 39 and secured against displacement, for example resilient bands 41. Situated on the lower side of the frame । is a soft-iron part or permanent magnet 42, which lies at a stance above the cover plate 35 and thus above the cores 23 the electromagnets. The soft-iron part or permanent magt 42, and thus the vessel 40, are given a three-dimensional ^rational movement by the rotating magnetic field.