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Publication numberUS3680843 A
Publication typeGrant
Publication dateAug 1, 1972
Filing dateJun 18, 1970
Priority dateJun 18, 1970
Publication numberUS 3680843 A, US 3680843A, US-A-3680843, US3680843 A, US3680843A
InventorsLu Maoyeh, Slooten Nico J Van
Original AssigneeBeckman Instruments Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Magnetic mixer for discrete sample systems
US 3680843 A
Abstract
There is disclosed a sample mixing system having a multiplicity of sample containers into which are inserted magnetic stirring rods. Each of a pair of pole pieces is connected to an alternating current electromagnet between which pole pieces the sample containers are positioned to intercept the alternating magnetic field generated by the electromagnet causing the magnetic stirring rods to move, thereby stirring the contents of the containers.
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Description  (OCR text may contain errors)

United States Patent Lu et al.

[is] 3,680,843 [451 Aug. 1,1972

[54] MAGNETIC MIXER FOR DISCRETE SAMPLE SYSTEMS [72] Inventors: Maoyeh Lu, Fullerton; Nico J. Van

Slooten, Chino, both of Calif.

[73] Assignee: Beckman Instruments, Inc. 221' Filed: June 18, 1970 [21] Appl. No.: 47,537

[52] US. Cl ..259/64, 259/DlG. 46 [51] Int. Cl. ..B0lf 13/08, BOlf 7/00 [58] Field of Search...259/DIG. 46, 61, 99, 102, 1 R, 259/64 [56] I References Cited UNITED STATES PATENTS 3,219,318 11/1965 Hershler "259/DIG. 46

3,220,802 11/1965 Hartley ..259/D1G. 46 3,356,346 12/1967 Landsberger ..259/71 Primary ExaminerWalter A. Sche'el Assistant Examiner-Alan I. Cantor At!0rneyPaul R. Harden and Robert J. Steinmeyer [5 7] ABSTRACT There is disclosed a sample mixing system having a multiplicity of sample containers into which are inserted magnetic stirring rods. Each of a pair of pole pieces is connected to an alternating current electromagnet between which pole pieces the sample containers are positioned to intercept the alternating magnetic field generated by the electromagnet causing the magnetic stirring rods to move, thereby stirring the contents of the containers.

1 Claim, 1 Drawing Figure VARIABLE FREQUENCY GENERATOR PATENTEU 1'97? 3.680.843

VARIABLE FREQUENCY GENERATOR INVENTORS NICO J. VAN SLOOTEN MA y MAGNETIC MIXER FOR DISCRETE SAMPLE SYSTEMS The present invention relates to liquid sample mixing systems and more particularly to discrete liquid sample mixers having magnetic stirring rods moved in response to an applied changing magnetic field.

In thefield of discrete sample analysis of liquids, it has been the general practice to employ permanent magnetic stirring bars or pellets having I a variety of shapes which are inserted into the liquid sample and rotated by the application of a rotating magnetic field produced by a motor driven permanent magnet to stir, mix or agitate the liquid sample. Although such devices have served the purpose, they have not proved entirely satisfactory under all conditions of service for the reason that considerable difficulty has been experienced in the failure and the wearing out of rotating parts, difficulties encountered in producing a magnetic field of sufficient strength and proper location and in finding sufficient space to locate the magnet and motor drive when used with analyzer apparatus.

The motor driven magnet has received wide acceptance due to its ability to operate over a wide range of speeds to accommodate a wide variety of liquid viscosities which may be encountered from sample to sample. Those concerned with' the development of discrete sample liquid analyzers have long recognized the need for mixing systems in'which there are a minimum of moving parts. The present invention fulfills this need for a variable speed mixer with a minimum of moving parts.

One of the most critical problems confronting designers of magnetically driven stirring bars or pellets has been to obtain a sufficient magnetic field in the vicinity of the stirring bar to obtain force of sufficient magnitude to move the stirring bar in the liquid sample. This problem is overcome by the present invention.

Afurther difficulty encountered in the development of magnetic stirrers has been the limit on the number of samples that can be mixed simultaneously by one rotating magnet and motor drive. The present invention overcomes this difficulty.

The general purpose of this invention is to provide a magnetic mixing system which embraces all the advantages of similarly employed motor driven magnetic mixers and possesses none of the aforedescribed disadvantages. To attain this, the present invention contemplates a unique arrangement using an alternating magnetic field rather than the prior art rotating magnetic field thereby avoiding motor driven moving parts. In addition, the present invention contemplates the use of magnetic field pole pieces to shape and direct the alternating magnetic field into a predetermined air gap through which the liquid sample cell containers are passed and in which containers the magnetic stirring rods are inserted to respond to the alternating magnetic field.

An object of the present invention is to provide a magnetic mixer in which a multiplicity of liquid sample containers can be mixed simultaneously.

Another object is the provision of an alternating magnetic field produced by a stationary electromagnet Still another object is to provide an alternating magpreferred embodiment of the present invention.

Referring now to the drawing, there are illustrated two sample cells 2 into which are inserted permanent magnet stirring rods or pellets 4. An electromagnet 6 formed by a multiplicity of turns of wire wound around a core of magnetic material generates a magnetic field in response to electrical excitation by variable frequency generator 7 attached to the coil. Pole pieces 8 are attached to each end of the electromagnet 6 to shape and direct the generated magnetic field. Each pole piece has fingers 10 formed thereon. When the pole pieces are mounted correctly at the ends of the electromagnet 6, the fingers 10 of one pole piece are located directly opposite the corresponding fingers of the other pole piece to form an air gap through which the alternating magnetic field is directed and in which the liquid sample cells 2 are placed. The pole piece fingers concentrate the magnetic field in the region of the sample cells containing the magnetic stirring bars.

In order to accommodate a wide variety of viscosities in the liquid samples, the frequency of variable frequency generator 7 can be changed, the frequency being set to a low value for high viscosity liquids and to a higher'value for low viscosity liquids.

The pole pieces 8can be shaped to accommodate simultaneously any number of liquid sample cell containers as may be desired for a given application. The sample cells may be placed on a stationary platform located between the pole pieces or a moving belt conveyor may be utilized to pass the sample cells between the pole pieces either manually or automatically in response to a predetermined program.

In operation, the alternating magnetic field impressed upon the magnetic stirring bar causes the bar to align its permanent magnetic field with the instantaneous direction of the applied alternating magnetic field. Therefore, as the alternating magnetic field changes direction, the magnetic stirring bar will change its position to align itself with the new direction of the alternating magnetic field. In the process of changing its position, the magnetic stirring bar moves through the liquid thereby agitating and stirring the contents within the sample cell in which it is located, the only moving part in the mixing system being the rotating mixing bar.

It now should be apparent that the present invention provides a magnetic mixer which may be employed with a multiplicity of liquid sample cells containing magnetic stirring bars to simultaneously stir the contents of the sample cells in response to the applied al.- ternating magnetic field.

Although particular components have been discussed in connection with a specific embodiment of a magnetic mixer constructed in accordance with the teachings of the present invention, others may be utilized. Furthermore, it will be understood that although an exemplary embodiment of the present invention has rality of uniformly spaced fingers, said pole pieces been disclosed and discussed, other applications and being oppositely disposed to form a corresponding arrangements are possible and that the embodiments plurality of air gaps between said fingers through disclosed may be subjected to various changes, modifiwhich air gaps said alternating magnetic field is cations and substitutions without necessarily departing 5 dlfected; from the invention. a multiplicity of sample cells into which the liquids to What is claimed is: be analyzed are placed, one of said cells being 1. In a discrete liquid sample analyzer of the type positiqned in each of the air p between Said wherein liquids to be analyzed must be thoroughly P P g d, a magnetic mixing system comprising: a plurality of magnetic stirring rods, one of said rods a two pole electromagnet having a multiplicity of bemg Placed wlthlll each of said sample cells, eifch turns of alternating current conducting wire for rod belflg rotated P to 531d altefnatmg generating an alternating magnetic fi ld; magnetic field to mix the contents of said mula pole piece fastened one to each pole of said electlpllclty of Sample Cellstromagnet, each of the pole pieces having a plu-

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3219318 *Aug 22, 1961Nov 23, 1965Hershler AbeFluid treating method and apparatus
US3220802 *Oct 5, 1960Nov 30, 1965Fisons Pest Control LtdSeparation of solutes by liquid-liquid extraction
US3356346 *Jan 3, 1966Dec 5, 1967Kurt LandsbergerTest tube stirring support
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3784170 *Jan 20, 1972Jan 8, 1974Beckman Instruments IncSample cell and stirrer therefor
US4040605 *Jul 14, 1976Aug 9, 1977Marvin Stanley TowsendMagnetic stirring apparatus
US4080663 *Mar 7, 1977Mar 21, 1978Wik GMagnetic stirrer
US4339241 *Oct 15, 1980Jul 13, 1982Stoecker Winfried AApparatus and method for simultaneously mixing specimens for performing microanalyses
US4568195 *May 9, 1983Feb 4, 1986Helmut HerzMagnet stirring apparatus
US4911556 *Mar 17, 1989Mar 27, 1990Lim Technology Laboratories, Inc.Turbulent stirring unit
US5676462 *Jan 15, 1997Oct 14, 1997Eastman Kodak CompanySuspended magnetic impeller/baffle apparatus for liquid
US6306658Dec 14, 1998Oct 23, 2001Symyx TechnologiesParallel reactor with internal sensing
US6455316Apr 13, 2000Sep 24, 2002Symyx Technologies, Inc.Parallel reactor with internal sensing and method of using same
US6489168Jan 29, 1999Dec 3, 2002Symyx Technologies, Inc.Analysis and control of parallel chemical reactions
US6528026Nov 19, 1998Mar 4, 2003Symyx Technologies, Inc.Multi-temperature modular reactor and method of using same
US6548026Oct 22, 1998Apr 15, 2003Symyx Technologies, Inc.Parallel reactor with internal sensing and method of using same
US6727096Nov 28, 2000Apr 27, 2004Symyx Technologies, Inc.Analysis and control of parallel chemical reactions
US6787112Nov 28, 2000Sep 7, 2004Symyx Technologies, Inc.Parallel reactor with internal sensing and method of using same
US6818183Apr 29, 2002Nov 16, 2004Symyx Technologies, Inc.Multi-temperature modular reactor and method of using same
US6864092Nov 28, 2000Mar 8, 2005Symyx Technologies, Inc.Parallel reactor with internal sensing and method of using same
US6890492Nov 28, 2000May 10, 2005Symyx Technologies, Inc.Parallel reactor with internal sensing and method of using same
US6924149Aug 28, 2002Aug 2, 2005Symyx Technologies, Inc.Parallel reactor with internal sensing and method of using same
US6988825 *Jul 2, 2003Jan 24, 2006Bio/Data CorporationMethod and apparatus for using vertical magnetic stirring to produce turbulent and chaotic mixing in various states, without compromising components
US6994827Jun 1, 2001Feb 7, 2006Symyx Technologies, Inc.Parallel semicontinuous or continuous reactors
US7288229May 8, 2001Oct 30, 2007Symyx Technologies, Inc.Parallel reactor with sensing of internal properties
US7364350 *Jan 24, 2006Apr 29, 2008Bio/Data CorporationMethod and apparatus for using vertical magnetic stirring to produce turbulent and chaotic mixing in various states, without compromising components
EP0052324A2 *Nov 9, 1981May 26, 1982Helmut Dipl.-Ing. HerzMagnetic mixer
Classifications
U.S. Classification366/273
International ClassificationB01F13/00, B01F13/08
Cooperative ClassificationB01F13/0818
European ClassificationB01F13/08C