Patent Application
20070247968
The present invention generally pertains to magnetic stir elements that are used for stirring of the contents of vessels in response to variations in the alignment of magnetic flux lines emanating from a source external to the vessels and is particularly directed to the configuration and composition of magnetic stir elements.
Prior art magnetic stir elements include magnetized magnetic material that is disposed to provide a magnetic flux axis that maintains alignment with the magnetic flux lines emanating from the external source to thereby cause the stir element to tumble, rock back and forth, or spin as the alignment of the externally emanated flux lines vary. One prior art magnetic stir element includes a disk of magnetized magnetic material configured for stirring the contents of a vessel and having oppositely polarized sides. Another prior art magnetic stir element includes an elongated component of magnetized magnetic material that is configured for stirring the contents of a vessel and has oppositely polarized ends.
In some prior art magnetic stir elements, the magnetic material is magnetized stainless steel. In other prior art magnetic stir elements, the magnetic material is a permanent magnet, which is preferred for enhancing the responsiveness of the magnetic stir elements to variations of magnetic flux lines emanating from a magnetic field source of limited magnetic field strength, especially when the stir elements are disposed for stirring the contents of large two-dimensional array of vessels.
The magnetic material of prior art magnetic stir elements is coated with or encased within a protective material that prevents the magnetic material from corroding and/or from leaching into and possibly reacting with the contents of the vessel that are being stirred. One protective material that is used in prior art magnetic stir elements for coating both stainless steel and permanent magnets is Parylene (Di-Para-Xylylene). However, Parylene is soft and can be worn away by extended use.
In some prior art magnetic stir elements, the magnetized magnetic material is encapsulated in a stirrer of nonmagnetic material that is configured for stirring the contents of a vessel by tumbling within the vessel. The magnetized magnetic material is disposed in the stirrer to provide a magnetic flux axis for the stirrer.
A preferred nonmagnetic material for the stirrers of prior art magnetic stir elements is PTFE (Polytetrafluoroethylene) plastic material. PTFE has the lowest coefficient of friction of any known solid material and is very non-reactive with other materials.
The present invention provides a magnetic stir element, comprising: a stirrer of nonmagnetic material that is configured for stirring the contents of a vessel, wherein the stirrer includes a pair of opposed cavities on opposite sides of the stirrer and a barrier that separates the opposed cavities; and magnetized magnetic material disposed in the pair of opposed cavities to provide a magnetic flux axis for the stirrer; wherein the magnetic material is so magnetized and disposed in the pair of separated opposed cavities that the magnetized magnetic material disposed in one of the pair of separated opposed cavities is magnetically attracted to the magnetized magnetic material disposed in the other of the pair of separated opposed cavities to thereby hold the magnetized magnetic material within the pair of separated opposed cavities. The barrier is sandwiched between the magnetized magnetic material that is disposed in the pair of separated opposed cavities and thereby provides a base upon which the magnetized magnetic material is held within the pair of separated opposed cavities.
The present invention also provides a process of manufacturing a magnetic stirrer, comprising the steps of:
(a) providing a stirrer of nonmagnetic material that is configured for stirring the contents of a vessel;
(b) providing a pair of opposed separated cavities within the stirrer on opposite sides of a barrier within the stirrer; and
(c) disposing magnetized magnetic material in the pair of opposed cavities to provide a magnetic flux axis for the stirrer,
wherein the magnetic material is so magnetized and disposed in the pair of separated opposed cavities that the magnetized magnetic material disposed in one of the pair of separated opposed cavities is magnetically attracted to the magnetized magnetic material disposed in the other of the pair of separated opposed cavities to thereby hold the magnetized magnetic material within the pair of separated opposed cavities.
The present invention readily facilitates the disposition of the permanent magnets in magnetic stir elements.
The present invention particularly facilitates the inclusion of NdFeB permanent magnets in magnetic stir elements that include a PTFE stirrer. NdFeB permanent magnets are preferred for enhancing the responsiveness of the magnetic stir elements because of the very high magnetic field strength of NdFeB permanent magnets. NdFeB has the highest magnetic energy of any material that is currently available for commercial applications. Heretofore, NdFeB permanent magnets have not been included in commercially manufactured magnetic stir elements that include PTFE stirrers because the step of encapsulating the permanent magnets in the prior art PTFE stirrers necessarily heated the PTFE to a temperature that is so high that when NdFeB permanent magnets are encapsulated in the PTFE plastic material the magnetic field strength of the NdFeB permanent magnets is severely diminished.
For other stirring applications in which the very high magnetic field strength provided by NdFeB permanent magnets is not required, alternative permanent magnets that do not include NdFeB are disposed in the pair of opposed cavities of the stirrer. Suitable alternative permanent magnet materials include SmCo, Alnico alloys and Ferrites.
The present invention also facilitates the manufacture of stirrers having different and unusual shapes rather inexpensively since the stirrers can be machined, punched or cut with dyes from sheets as opposed to being molded. Another advantage is that by using large “flat” shapes greater fluid movement is affected during stirring. Still another advantage is that the shape can be customized to specifically conform to the inside of a given vessel to thereby maximize stirring efficiency.
Additional features of the present invention are described with reference to the detailed description of the preferred embodiments.
Referring to
A barrier 16 is inserted into the tube 12 to separate the opposed cylindrical cavities 15. The barrier 16 is a disk that is slightly larger than the inside diameter of the tube 12 that may be either magnetic material or nonmagnetic material. In some embodiments, the barrier disk 16 is stainless steel.
The permanent magnets 14 are recessed within the pair of cylindrical cavities 15 at a level below the level of the respective surfaces 17 at the opposite ends of the tube 12 that adjoin the pair of cavities 15, to thereby prevent contact between the permanent magnets 14 and the vessel in which the magnetic stir element 10 is inserted for stirring the contents thereof.
In all of the embodiments described herein, the permanent magnets 14 are made of a permanent magnet material, such as NdFeB, SmCo, Alnico alloys and Ferrites. Preferably, the permanent magnet material is first shaped for disposition in the opposed cavities of the particular embodiment of the stirrer in which they are to be disposed before the permanent magnet material is magnetized to provide the permanent magnets.
In the embodiment shown in
The permanent magnet material cylinders are then coated with a protective material, such as Parylene. Two cylindrical permanent magnets 14, having a protective coating 18 are provided by magnetizing the pair of coated rods cylinders so that the opposite ends of the rods cylinders are of opposite magnetic polarity.
By recessing the coated permanent magnets 14 within the cavities 15, the protective-material-coating 18 is protected from being worn away by contact with the inside of a vessel in which the magnetic stir element 10 is inserted. This is particularly advantageous when the protective material is Parylene.
The coated permanent magnets 14 are disposed in the pair of opposed cavities 15 to provide a magnetic flux axis for the stirrer 12. The permanent magnets 14 are so magnetized and disposed in the pair of separated opposed cavities 15 that the permanent magnet 14 disposed in one of the pair of separated opposed cavities 15 is magnetically attracted to the permanent magnet 14 disposed in the other of the pair of separated opposed cavities 15 to thereby hold the permanent magnets 14 within the pair of separated opposed cavities. The barrier 16, which is slightly larger in diameter than the inside diameter of the tube 12, is sandwiched between the permanent magnets 14 that are disposed in the pair of separated opposed cavities 15 and thereby provides a base upon which the permanent magnets 14 are held within the pair of separated opposed cavities 15.
Referring to
The portion of the disk-shaped stirrer 22 between the opposed cavities 25 is a barrier 26 that separates the opposed cavities 25. The two disk-shaped permanent magnets 24 are recessed within the pair of cylindrical cavities 25 at a level below the level of the respective opposite broad surfaces 27 of the disk-shaped stirrer 22 that adjoin the pair of cavities 25, to thereby prevent contact between the permanent magnets 24 and the vessel in which the magnetic stir element 20 is inserted for stirring the contents thereof.
The disk-shaped permanent magnets 24 are so magnetized that the opposite broad surfaces thereof are of opposite magnetic polarity. The permanent magnets 24 are coated with a protective material 23, such as Parylene.
By recessing the coated permanent magnets 24 within the cavities 25, the protective-material-coating 23 is protected from being worn away by contact with the inside of a vessel in which the magnetic stir element 20 is inserted.
The coated permanent magnets 24 are disposed in the pair of opposed cavities 25 to provide a magnetic flux axis for the stirrer 22. The permanent magnets 24 are so magnetized and disposed in the pair of separated opposed cavities 25 that the permanent magnet 24 disposed in one of the pair of separated opposed cavities 25 is magnetically attracted to the permanent magnet 24 disposed in the other of the pair of separated opposed cavities 25 to thereby hold the permanent magnets 24 within the pair of separated opposed cavities 25. The barrier 26 that is sandwiched between the permanent magnets 24 provides a base upon which the permanent magnets 24 are held within the pair of separated opposed cavities 25.
Referring to
The portions of the elongated stirrer 32 between the respective pairs of opposed cavities 35, 36 are barriers 37, 38 that separate the respective opposed cavities 35, 36. Two disk-shaped permanent magnets 33 are recessed within one pair of opposed cylindrical cavities 35 at a level below the level of the respective opposite broad surfaces 39 of the elongated stirrer 32 that adjoin the pair of opposed cavities 35, and two disk-shaped permanent magnets 34 are recessed within the other pair of opposed cylindrical cavities 36 at a level below the level of the respective opposite broad surfaces 39 of the elongated stirrer 32 that adjoin the pair of opposed cavities 35, to thereby prevent contact between the permanent magnets 33, 34 and the vessel in which the magnetic stir element 30 is inserted for stirring the contents thereof.
The disk-shaped permanent magnets 33, 34 are so magnetized that the opposite broad surface thereof are of opposite magnetic polarity. The permanent magnets 33, 34 are coated with a protective material 31, such as Parylene.
By recessing the coated permanent magnets 33, 34 within the cavities 35, 36, the protective-material-coating 31 is protected from being worn away by contact with the inside of a vessel in which the magnetic stir element 30 is inserted.
The pair of coated permanent magnets 33 is disposed in the pair of opposed cavities 35 to provide a magnetic flux axis that is oppositely polarized from the magnetic flux axis provided by the pair of permanent magnets 34 that is disposed in the other pair of opposed cavities 36, to provide a magnetic flux axis for the stirrer 32.
The permanent magnets 33 are so magnetized and disposed in the pair of separated opposed cavities 35 that the permanent magnet 33 disposed in one of the pair of separated opposed cavities 35 is magnetically attracted to the permanent magnet 33 disposed in the other of the pair of separated opposed cavities 35 to thereby hold the permanent magnets 33 within the pair of separated opposed cavities 35. The barrier 37 that is sandwiched between the permanent magnets 33 provides a base upon which the permanent magnets 33 are held within the pair of separated opposed cavities 35.
The permanent magnets 34 are so magnetized and disposed in the pair of separated opposed cavities 36 that the permanent magnet 34 disposed in one of the pair of separated opposed cavities 36 is magnetically attracted to the permanent magnet 34 disposed in the other of the pair of separated opposed cavities 36 to thereby hold the permanent magnets 34 within the pair of separated opposed cavities 36. The barrier 38 that is sandwiched between the permanent magnets 34 provides a base upon which the permanent magnets 34 are held within the pair of separated opposed cavities 35.
Referring to
The stirrer 42 has a generally flat elongated configuration for stirring the contents of a vessel. In the embodiment shown in
In other embodiments the broad sides of an elongated stirrer having one pair of opposed cylindrical cavities proximate to only one end of the stirrer have a shape that is other than generally rectangular.
In other respects, the elongated magnetic stir element 40 is constructed in the same manner as the magnetic stir element 30 described above with reference to
Referring to
The stirrer 52 has a generally flat elongated configuration for stirring the contents of a vessel. One end 56 of the opposite broad sides of the elongated stirrer 52 has a generally rectangular shape with the corners being rounded and the other end 57 of the elongated stirrer 52 has a pair of blades 58 that extend generally parallel to the axis of elongation of the stirrer 52 and define an elongated space 59 between the blades 58 that permits a pipette or probe (not shown) to be inserted between the blades 58 to a relatively deep level within a vessel in comparison the level to which a pipette or probe may be inserted when using the elongated magnetic stir element 40 shown in
In other respects, the elongated magnetic stir element 50 shown in
Referring to
The stirrer 62 has a generally flat elongated configuration for stirring the contents of a vessel. One end 65 of the stirrer 62 has a generally convergent shape and the other end 66 of the elongated stirrer 62 has a pair of blades 67 that extend generally parallel to the axis of elongation of the stirrer 52 and define an elongated space 68 between the blades 67. The blades 67 terminate in ears 69 that extend generally outward from the blades 67 relative to the axis of elongation of the stirrer 62 to thereby prevent most of the magnetic stir element 60 from contacting the interior of the vessel.
The convergent shape of the one end 65 of the stirrer 62 enables the magnetic stir element 60 to reach a deeper level within a vessel having a convergent-shaped closed end than can be reached with a magnetic stir element which does not have a generally convergent shape at one end.
In other embodiments the broad sides of an elongated stirrer having one pair of opposed cylindrical cavities proximate to only one end of the stirrer have a shape that is other than generally rectangular.
In other respects, the elongated magnetic stir element 40 is constructed in the same manner as the magnetic stir element 30 described above with reference to
In still other embodiments (not shown) the various aspects of the different embodiments described herein are combined with one another to the extent that they are not incompatible with each other.
Examples of stirring systems in which magnetic stir elements are used are described in U.S. Pat. No. 6,176,609 and in U.S. patent application Ser. No. 11/166,831, the disclosures of which are incorporated herein by reference thereto.
Preferred embodiments of the magnetic stir elements are dimensioned for stirring the contents of vessels that are included within arrays of vessels, such as microplate wells.
The advantages specifically stated herein do not necessarily apply to every conceivable embodiment of the present invention. Further, such stated advantages of the present invention are only examples and should not be construed as the only advantages of the present invention.
While the above description contains many specificities, these should not be construed as being necessarily required for use of the present invention or as limitations on the scope of the present invention, but rather as examples of the embodiments described herein. Other variations are possible and the scope of the present invention should be determined not by the embodiments described herein but rather by the claims and their legal equivalents.
Regarding the method claims, except for those steps that can only occur in the sequence in which they are recited, and except for those steps for which the occurrence of a given sequence is specifically recited or must be inferred, the steps of the method claims do not have to occur in the sequence in which they are recited.
