US 3749369 A
A combination weighing and mixing device adapted for use as the mixing element of a magnetic stirring apparatus including a container and magnetic drive means for rotating the mixing element in the container, said device comprising a generally ellipsoidally-shaped housing, a magnetic element encapsulated in said housing and at least one cavity formed in said housing defining a measuring chamber for additives to be mixed with a liquid in the container.
Claims available in
Description (OCR text may contain errors)
United States Patent Landsberger July 31, 1973 1 1 MAGNETIC STIRRING ELEMENT 2,951,689 9/1960 Asp et al 259/DIG. 46
 Inventor: Kurt Landsberger, c/o Bel-Art Products, Pequannock, NJ. 07440 Prlmary Examiner-Wuhan Pnce Assistant ExaminerAlan l. Cantor Filedi J y 1971 Att0mey-Howson and Howson  Appl. No.: 161,009
[5 7] ABSTRACT 52 us. Cl. 259/1 R, 23/252 R, 259/50, A combination Weighing and mixing device adapted for 259/102, 5 46 use as the mixing element of a magnetic stirring appara- 51 1111. c1 B011 13/08 including a container and magnetic drive means for  Field of Search 259/DIG. 46, 5, 21, rotating the mixing element in the container, Said 59 4 50 23/252 R vice comprising a generally ellipsoidally-shaped housing, a magnetic element encapsulated in said housing 5 References Cited and at least one cavity formed in said housing defining UNITED STATES PATENTS a measuring chamber for additives to be mixed with a liquid in the container. 2,518,758 8/1950 Cook 259/DlG. 46 2,699,378 1/1955 Koelle 259/D1G. 46 4 Claims, 5 Drawing Figures MAGNETIC STIRRING ELEMENT The present invention relates broadly to mixing apparatus, and more specifically to a combination mixing and measuring device for use in magnetic stirring apparatus.
The present invention is especially adapted for use in laboratory procedures where magnetic stirring apparatus are used for mixing or blending various components of a composition. These apparatus generally include a support structure for a mixing container or the like and a magnetic bar suitably mounted for rotation adjacent the base of the container to produce a magnetic field operable to effect actuation of a magnetic elementin the container, usually in the form ofastirring or mixing bar. v}
Typically in the use of these magnetic stirring apparatus, a predetermined quantity of at least one of the constituents is weighed or measured in a separate implement such as a weighing dish, scoop or container and then emptied into the mixing container. This system has certain disadvantages and drawbacks which the present inventionis designed to resolve. For example, it has been found that these conventional procedures are not totally satisfactory in mixing liquid constituents of a composition where the precise quantities of the constituents must be measured. For example, addition of a predetermined small accurate volume is difficult since the liquid normally adheres to the utensil in which it is measured, necessitating washing the utensil with a suitable'liquid' and adding the washings to the mixing container in order to transfer all of the liquid ingredient -to be added; This is disadvantageous, of course, when the.added volume of the wash liquid would be undesirable. In addition, such adhesion of additives to measuring or transfer implement can be costly where the additives are precious materials and can not be completely emptied into the mixing container. Further, the presently known system presents the risk of introducing foreign substances, in the wash liquid, for example, which in some instances may contaminate the final composition.
The present invention provides a new and useful combination measuring and stirring device, particularly adapted for use in magnetic mixing apparatus ofthe type discussed above. The device of the present invention consists of a magnetic element housed in a generally ellipsoidally-shaped housing preferably made of a low-friction, inert material. The housing is provided with at least one'cavity defining a measuring chamber of predetermined volumetric capacity and a flat seat diametrically opposed to the cavity so that the device may be supported on a flat surface for filling the measuring chamber with a desired amount of additive. The device is constructed so that it rotates on its side with the cavity disposed transversely to the axis of rotation. In this manner, with the normal spinning attitude of the device on its side, the cavity is open to the stirring action of the fluid in the mixing container.
The mixing and measuring device of the present invention is designed for use in the following manner. The user places the tared device on a flat surface of a scale and fills the cavity with the precise measured quantity of an additive to be mixed. The device is deposited into the mixing container and then placed on a magnetic mixing apparatus. The field created by the mixer magnet effects rotation of the device on its side,
thereby positioning the cavity in the best position to be exposed to the mixing action of the fluid in the container. Thus, the device of the present invention eliminates the problems of inaccuracy due to adhesion of additives to transfer equipment of addition of wash liquid and also eliminates the problem of waste which is important, particularly where the additives are precious materials.
These and other objects of the present invention and the various details of the operation and the construction thereof are hereinafter more fully set forth with reference to the accompanying drawings, wherein:
FIG. 1 is a side view partly in section of a magnetic mixing apparatus with a measuring and mixing device of the present invention in an operative position;
FIG. 2 is a side view of the measuring and mixing device of the present invention with parts broken away to show the construction more clearly;
FIG. 3 is a plan view of the device; and
FIGS. 4 and 5 are sectional views taken on lines 4-4 and 5-5 of pages 1 and 2 respectively.
Referring now to the drawings and particularly to FIG. 1 thereof, there is illustrated a conventional magnetic stirring apparatus 10 for which the mixing and measuring device 12 of the present invention is adapted for use. The magnetic stirring apparatus 10 includes a support structure 14 including a flat base on which a container 16 for the liquids to be mixed is supported. The apparatus includes a rotatably mounted magnetic bar 18 actuatable by a motor 20 to produce a magnet field to effect rotation of the mixing and measuring device 12 of the present invention in the container 16.
The mixing and measuring device 12 of the present invention comprises an elongatedbar magnet 20 encapsulated in a generally ellipsoidally-shaped housing 22 preferably made of a low-friction, inert material such as a tetrafluoroethylene polymer. The housing is formed with a flat base as at 26 and at least one measuring chamber or cavity diametrically opposed to the base 26. In the present instance, there is one measuring chamber 27 defined by a cavity30 in the housing terminating in an upwardly projecting oval-shaped peripheral lip 32. The bottom wall 33 of the chamber is flat, parallel to the base 26 and merges with they lip 32 in a radiused side wall 35. The plane of the upper edge of the lipis also parallel to the base 26. I
In the present instance, the device is constructed in such a manner that its normal spinning attitude in the mixing container is on its side, that is about an axis A, normal to the axis A through the center of the measuring chamber 27. In the present instance, this is accomplished by offsetting the center of gravity C of the device from the center C of a truly ellipsoidal shape of the device. In other words, the cylindrical bar magnet 20 is disposed in the housing so that it is symmetrical with respect to a longitudinal plane PP through the center C dividing the device into upper and lower sections 12a and 12b respectively. The bar magnet 20 is also symmetrical relative to planes P,P and P P through the center C transverse to the plane PP. As illustrated, the major and minor axes of the generally ovalshaped measuring chamber 27 and base 26 are aligned with the axes of the section through the center of the device defined by the plane PP. By this arrangement the device is truly symmetrical relative to planes P,-P, and P -P and that except for the measuring chamber and flat base, would be symmetrical about the plane P-P. Accordingly, since the volume of measuring chamber cavity 30 is greater than the volume enclosed between the arcuate trace of the lower section 12b of the housing and the flat base 26, there is a greater concentration of mass in the lower section 12b and the cen ter of gravity C is therefore located in the lower section 12b on the axis A to one side of the longitudinal plane P-P. Note that the planes PP, P,P, and P l are taken through the device at points of greatest cross section; that is, the elliptical sections defined by the planes P-P and P,--l=' have the greatest major and minor axes and the trace of the circular section defined by plane P -l has the greatest diameter.
Accordingly, when the device is placed in the liquid in the mixing container 16, it will assume a spinning attitude about the axis A, when a magnetic field is created on rotation of the magnet 18 of the magnetic stirring apparatus. This spin attitude is effected by means of the interaction of centrifugal force with the constrained movement of the magnet 18 in the rotating magnetic field. In this position as noted previously, the measuring chamber 27 faces sideways to the central axis of the container and the additive therein is subjected to the stirring action of the liquid, thus insuring complete mixing of the additive into the larger volume of liquid.
Thus, in using the device of the present invention, the tared device 12 is placed on a scale and then the desired measured quantity of additive is deposited into the mixing chamber 27. Thereafter, the device 12 is placed into the container 16 with the larger volume of liquid to be mixed with the additive, and the magnetic stirring apparatus is actuated. Then as noted above, the device is rotated on the axis A, whereby thorough mixing of the additive with the larger volume of liquid in the container is effected. Accordingly, by the present invention, accurately measured amounts of additives can be added to a larger volume of liquid without incurring any loss in the transfer or introducing any foreign inert materials into the mixture and thorough mixing results.
I claim: g
l. A combination weighing and mixing device adapted for use as the mixing element of a magnetic stirring apparatus including a container and magnetic drive means for rotating the mixing element in the container, said device comprising a generally ellipsoidallyshaped housing, at least one cavity formed in said-housing defining a measuring chamber for additives to be mixed with a liquid in the container, said housing including a flat base section formed in the housing diametrically opposed to the measuring chamber and parallel to the plane through the upper edge of the measuring chamber, and a magnetic element encapsulated in said housing.
2. The device as claimed in claim 1 wherein said housing is made of a low friction inert material.
3. The device as claimed in claim 1 wherein the cen-' ter of gravity is non-coincident with the geometric center so that the device spins about an axis parallel to said plane through the upper edge of the measuring chamber when subjected to a magnetic field in the container, due to the action of centrifugal force upon rotation.
4. The device as claimed in claim 1 wherein the magnetic element is symmetrical about the'center of a truly ellipsoidally-shaped housing and wherein the volume of the measuring chamber cavity is greater than the volume enclosed between an arcuate trace of the housing adjacent the base and the base so that the center of gravity is displaced from a true geometric center whereby the spinning attitude is about an axis parallel to the said plane through the upper edge of the measuring chamber, due to the action of the centrifugal force upon rotation.
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