Agitating – Stirrer within stationary mixing chamber – Magnetic stirrer
Patent
1989-11-03
1991-08-20
Jenkins, Robert W.
Agitating
Stirrer within stationary mixing chamber
Magnetic stirrer
366127, 366178, B01F 1308
Patent
active
050408984
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the mixing of two or more fluids especially for purposes related to chemical analysis.
BACKGROUND ART
Several magnetic mixing devices for fluid streams have been described. U.S. Pat. Nos. 3,219,318 to Herschler, 3,680,843 to Lu et al, 3,689,033 to Holmstrom et al, 3,907,258 to Spaziani, and 4,054,270 to Gugger et al disclose the location of permanent magnets in a fluid stream within a conduit for agitation by an external magnetic field which reverses in polarity. This magnetic field is typically provided by a single electromagnet having its poles to opposite sides of the condut. Another device, described in U.S. Pat. No. 3,763,873 to Saunders, uses a magnetically susceptible tubular reed which also serves as an inlet tube and is therefore fixed at one end. The free end is agitated and indeed vibrated by a spinning permanent magnet. Other prior magnetic mixing configurations are disclosed in U.S. Pat. Nos. 2,999,673 to Kessler, 3,784,170 to Peterson et al, 3,793,886 to Rosenwald and 3,995,835 to Cichy et al.
Many flow based methods for chemical analysis, for example high pressure liquid chromatography and discontinuous flow analysis (described in the present applicant's international patent application No. PCT/AU86/00323), require two or more fluid streams to be mixed uniformly transverse to the direction of flow but so that any time variation in the ratio of comonents of the streams is maintained without appreciable broadening in the direction of the flow. In this respect, the arrangements of the prior art are severely limited, particularly where small bore tubing, for example less than 1 mm internal diameter, is involved. Minature magnets suitable for insertion in such tubing are not commonly available and must be matched in size to the external magnetic field to provide effective coupling. Further, the turbulence arising from the Y and T fluid junctions of the aforementioned U.S. Pat. Nos. 3,689,033 and 3,907,258 respectively will cause disruption of the ratio of components prior to mixing. The violent agitation at the point of confluence in U.S. Pat. No. 3,763,873 will cause considerable broadening, as will the movement of the "plurality of permanent magnets" of U.S. Pat. No. 3,219,318. U.S Pat. No. 3,763,873 does not use a permanent magnet for agitation, but the mixing action is restricted to a very small part of the flow line in the vicinity of the end of the tubular reed and is not considered effective for high flow rates.
SUMMARY OF THE INVENTION
A principal object of the present invention is therefore to provide for simple effective mixing of two or more fluids with minimal longitudinal broadening of the components. The process is preferably operable at high or low flow rates and at any pressure, and the apparatus is desirably constructed from commonly available material.
The present invention entails the realization that substantial benefits in line with these objects can be achieved by utilising a novel magnetic mixing arrangement in which a rod of magnetically susceptible material for example a ferro-magnetic material and preferably a common arculable material such as iron wire, is vibrated by two magnetic fields which are switched alternately, thus relaxing the matching size conditions of permanent-magnet vibrating elements and providing maximum magnetic attractive force with maximum efficiency. This arrangement, inter alia, allows extension of the agitating rod beyond the vicinity of the magnets to incorporate debubbling and scouring of the sensing zone of a conduit.
According to one aspect of the present invention there is therefore provided fluid mixing apparatus comprising: said conduit, which rod is substantially not permanently magnetized; each may, when activated, individually cause movement of said rod across the conduit; and induce an effective vibratory mixing motion of said rod within the conduit.
According to another aspect of the invention, there is provided a method of mixing two or more fluids, comprising: susceptible rod wh
REFERENCES:
patent: 2212288 (1940-08-01), Decker
patent: 3268212 (1966-08-01), Ziselberger
patent: 3433465 (1969-03-01), Szpur
patent: 3689033 (1972-09-01), Holmstrom
patent: 3763873 (1973-10-01), Saunders
patent: 3995835 (1976-12-01), Cichy
patent: 4526046 (1985-07-01), Oberli
Peachey Russell M.
Petty John D.
Sweatman Denis R.
Ionode Pty. Ltd.
Jenkins Robert W.
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