Automatic vortex mixer

Abstract: A vortexing mixer drive has a rotatablee coupling rod where end face defines an offcenter countersink with a hose at the center of the countersink. The rod is axially displaced to engage a vessel's protuberant bolt on tip effect nutational movement.

Description: The present invention relates to an automatic apparatus for establishing a vortex in liquid materials contained in elongated compartments. It is known that creating a vortex in a compartment or in a reaction vessel is an effective means for mixing its contents. Common laboratory vortexers use a support cup or a resilient compartment receiving surface mounted eccentrically on a motor in order to translate the lower end of the compartment in a circular path or orbit at a high speed and thereby create an effective vortex in the fluid held by the compartment. Exemplary of this type of device are those disclosed in US-A-4 555 183 and US-A-3 850 580. These devices are manual in that an operator is required to hold the compartment or vessel in contact with the eccentrically movable means to create the vortex in the fluid disposed in the compartment or vessel. US-A-4 555 183 discloses the use of an eccentrically rotating cylinder having a cup to receive the lower portion of a laboratory test tube which is used as a reaction vessel in a V-shaped depression. The tube can only be removed or inserted into the cup by lifting or lowering the tube. Such vortex type device would be extremely advantageous in an automated chemical analysis instrument as it is not invasive and therefore avoids the concern of contamination associated with an improperly cleaned invasive mixing means. A device that incorporates this type of mixing into an automated testing apparatus is disclosed in an article by Wada et al. entitled "Automatic DNA Sequencer: Computer Program MIcro Chemical Manipulator for the Maxim-Gilbert Sequencing Method." Review of Scientific Instruments 54 (11). November 1983, pages 1569-1572. In the device disclosed in this article, a plurality of compartments or reaction vessels are held flexibly in a centrifuge rotor. A rotational vibrator is mounted on a vertically moving cylinder. When mixing is desired the compartment or reaction vessel is positioned in a mixing station directly above the rotational vibrator. The vertically moving cylinder is moved upwardly to contact the bottom of the compartment or reaction vessel with the rotary vibrating rubber portion of the rotational vibrator. The vibrating rubber portion is V-shaped in cross-section to engage a test tube having a V-shaped bottom. The eccentric drive for this rotational vibrator is mounted on a bearing and requires a rotation inhibitor coupling to be used. This type of device is not always satisfactory in that the drive mechanism is more complex than is needed and also the test tubes must be quite securely and yet flexibly mounted so as to permit their movement without slipping out of the drive mechanism. Vortex mixing is desirable in most automated chemical analyzers, as stated above, and can become necessary when solid supports such as glass beads or magnetic particles are used. Such particles often have a tendency to sink to the bottom of the compartment or reaction vessel. For example, in heterogeneous immunoassays, magnetic particles can be used as a basis for separation of the reagents from ligand-antibody bound particles. A particularly desirable particle for such use is the chromium dioxide particle which is disclosed in US-A-4,661,408. These particles have a tendency to settle at a rate which can result in non-uniform sample or reagent mixture. It is therefore desirable that the reagents and/or reaction mixtures be mixed regularly prior to reagent withdrawal. It is the object of the present invention to provide a relatively simple, inexpensive, yet effective automatic apparatus for establishing a vortex in liquid materials for use in an automatic chemical analyzer. This object is solved, according to the invention, with the features of claim 1. Preferably the countersink includes the axis of rotation and defines an acute angle with the face of the coupling. Also it is preferred that the bore have a peripheral edge lying at the center of the countersink. With this apparatus, the countersink, which is in the form of a crater-like depression in the face of the coupling, acts to guide the stem end of the compartment into a drive hole or bore formed in the end face of the coupling. The hole must be located so as to include the axis or center of the countersink such that when the coupling is translated to contact the stem end of the compartment, the rotating coupling engages the stem end. When the top portion of the compartment is flexibly mounted this nutational or orbital movement created at the bottom of the compartment creates a liquid vortex within the compartment to establish the desired mixing. According to the invention, each compartment is disposed on a transport means, which is, according to a particular embodiment of the invention, a reagent disc. The compartments are held at their upper portions by compartment carriers, which are, according to the particular embodiment of the invention, container strips disposed on the reagent disc. The invention may be more fully understood from the following detailed description thereof taken into connection with the accompanying drawings which form a part of this invention description and in which similar reference numbers refer to similar elements in all figures of the drawings in which: Figure 1 is a plan view of the processing chamber of a chemical analysis instrument using a chain transport for the reaction vessels and a reagent disc support for a container strip having a compartment with which the non-invasive vortex mixing drive of this invention may be used; Figure 2 is an isometric view of the container strip having multiple containers and a compartment that may be used with the vortex mixing drive of this invention; Figure 3 is a schematic view of a vortex coupling mechanism used with this invention; Figure 4 is a top view of the end face of the vortex coupling mechanism of Fig. 3 and; Figure 5 is a fragmentary side elevation view partly in cross-section, depicting the operation of the coupling vortex mechanism of Figs. 3 and 4. Chemical analyzer instrument in which the non-invasive mixing apparatus of this invention might be used is seen in Fig. 1. The analyzer, which may be conventional, includes a processing chamber 10 with a drive assembly 12 which is operable to translate individual reaction vessels 14 in a serial fashion to various processing stations 16 located within the processing chamber 10. The processing chamber 10 includes a reagent loading station 18, a sample dispensing station 22, a wash station 24, a mixing station 27, a measuring station 28, a reagent disc 30 for holding sample container strips 40, a sample carousel 32, and transfer arms 34 for transferring sample and reagents to the reaction vessels 14. The reagent disc 30 is adapted to hold a number of multi-comparted container strips 40. A preferred container strip 40 for this purpose is that described in the copending application entitled Vortexing liquid container. This container strip 40, as may be seen in Fig. 2, has a plurality of containers 38 and a compartment 50 arranged in a an end-to-end relationship to form a container strip 40. As is described in US-A-4,720,734 the container strip 40 may be fabricated in any convenient manner. In the embodiment shown, the container strip 40 includes a rigid peripheral band 36 formed of a suitable material such as an inert plastic. The band 36 is either joined to or formed integrally with each of the containers 38 such that in the preferred case the container strip 40 generally tapers in a substantially elongated wedge-like manner from a first edge to a second edge. This wedge-shaped plan profile for the container strip 40 facilitates the mounting of a plurality of such container strips 40 in a circumferentially adjacent, generally radially extending in relationship across the rotatable reagent disc 30 plate. It should be appreciated however that the individual containers 38 may take any predetermined configuration and may be used alone or arranged together in any convenient number and remain within the contemplation of this invention. Each of the container strips 40 includes either a single compartment 50 or a compartment 50 together with a plurality of containers 38 defined by generally opposed pairs of generally parallel and integrally formed sidewalls and endwalls and each of the compartment 50 and containers 38 is formed of a suitable inert plastic material. The upper surfaces of the sidewalls and the endwalls together with the upper surface of the band and the vicinity thereof define a substantially planar sealing surface 41 peripherally surrounding the open upper end of the containers 38. Each of the container 38 typically may be closed by a downwardly sloping inverted pyramidal floor. In the preferred embodiment, the sidewalls of each container 38 but not those of the vortex compartment are joined to the peripheral band 36. The band 36 extends slightly below the lower ends of the containers 38 and thus defines the support structure whereby the inner strip may be set on a suitable work face. The several containers 38 may be arranged in various configuration square, rectangle, etc. Each of the adjacent containers 38 are spaced from each other by a predetermined gap to enhance the thermal and vapor isolation of the containers 38. Preferably the container strip 40 is formed by injection molding and is formed of polypropylene. Alternatively polyethylene or other suitable materials of construction may be used, however polypropylene is preferred because of its ability to be flexed many times and not break. The compartment 50 is tubular and elongated and has a longitudinal axis. The compartment 50 also has a rim which defines a peripheral mounting surface similar to the peripheral mounting surfaces provided by the containers 38 and the band 36. The compartment 50 is connected to the band 36 only by an integral thin finger of plastic which forms a flexible hinge 46. The flexible hinge 46 is directed to a corner formed by the band 36 and the container adjacent the end container or compartment. The finger of plastic is located just below the rim such that it does not interfere with a vapor seal which is placed on top of the compartment 50 and the containers 38. The bottom of the compartment 50 is formed to have a downwardly extending protuberant tip portion 48 which is adapted to being engaged by an eccentric or orbiting type drive to create nutational movement of the bottom portion of the compartment 50 or urging the compartment 50 pivoting about the flexible hinge 46. The band forms a short skirt about the compartment 50 such that the compartment 50 is free for such nutational movement of its lower portion. While the containers 38 may be left open if desired, when reagents are stored therein it is best that a vapor barrier and rehealable lid be used to afford plural piercing by a probe for withdrawal of the reagents. For this reason, a suitable laminate may be heat sealed to the top rim of each of the compartment 50 and containers 38 in the container strip 40. This may be a three ply laminate covered by an elastomeric self-healing structure such as silicone rubber. The laminate is constructed with an outer layer of polyester film, a polyvinyldene chloride coating on the polyester film and an outer barrier sheet of polypropylene. This three ply sheet is slit immediately around the rim of the compartment 50 to facilitate the nutational movement of the bottom of the compartment 50. According to this invention, an automatically engageable nutator drive is provided for the compartment 50. This drive includes a coupling rod 52 which is rotated by a rotary translator 54, such as a stepping motor, operating through a drive coupling 56. The rotary translator 54 itself is mounted so as to be driven by a linear translator 58 operating through the linkage 60 to move the coupling rod 52 up to contact the protuberant tip portion 48. The end face 62 of the coupling rod 52 has an axis of rotation 64 and a countersink 66 formed therein. The center or axis 68 of the countersink 66 is further formed by a bore 70. The bore 70 must include the center 68 of the countersink 66. In like manner the countersink 66 must be off-axis but yet must include the axis 64 of the coupling rod 52. The angle that the countersink forms with the end face 62 must be an acute angle and preferably in the order of magnitude of 30°. Also preferably the peripheral edge of the bore 70 will lie right on the center 68 of the countersink. In its operation, as seen most clearly in Fig. 5, the compartment 50 which is part of the container strip 40 is mounted to the container strip 40 at its upper portion by the hinge 46. The coupling 52 is moved upwardly while rotating as depicted by the arrow 72 until the protuberant tip portion 48 is engaged by the countersink which directs the protuberant tip portion 48 into the bore 70. The utilization of the bore 70 provides a sure, firm contact on the protuberant tip portion 48 such that little upward pressure need be applied to the compartment 50 to effect the nutational rotation of the bottom of the compartment 50. The coupling device is thus an effective sure way of effecting the nutational movement. The coupling rod 52 may be constructed of any suitable material. Preferably a plastic material is used. Any of the suitable engineering plastics may be used; however, it is preferred that ABS plastic sold under the trade name cycolac X-17 be used.

Claims: An automatic apparatus for establishing a vortex in liquid materials contained in at least one elongated compartment (50), the compartment (50) having a longitudinal axis and being disposed on a transport means (30), the apparatus comprising: a plurality of compartment carriers (40) disposed on the transport means (30), each compartment carrier (40) being adapted to hold flexibly the upper portions of a compartment (50), the compartment (50) having a protuberant tip portion (48) at its bottom lying on the longitudinal axis, a rotatable coupling (52) having an axis of rotation (64), an end face (62) transverse to the axis of rotation (64), and located under a region in the path of movement of the compartment carrier (40), means for displacing the coupling (52) along the axis of rotation (64) to engage the protuberant tip portion (68) by the end face (62), the end face (62) of the coupling (52) defining a countersink (66) the center of which is off of the axis of rotation (64), the end face (62) of the coupling (52) also defining a bore (70) in the countersink (66) adapted to receive the protuberant tip portion (48), whereby when the coupling (52) is rotated and displaced to contact the protuberant tip portion (48), the protuberant tip portion (48) is translated radially along the end face (62) of the coupling (52) by the countersink (66) to be engaged by the bore (70) and orbited. The apparatus set forth in claim 1 wherein the countersink (66) includes the axis of rotation (64). The apparatus set forth in claim 1 or 2 wherein the countersink (66) defines an acute angle with the end face (62) of the coupling (52). The apparatus set forth in one of the claims 1-3 wherein the bore (70) has a peripheral edge lying at the center of the countersink (66).

Inventors: BENIN JOSHUA, DI MAIO WILLIAM G, MORIN CARL F, BENIN, JOSHUA, DI MAIO, WILLIAM G., MORIN, CARL F.
Applicants: DU PONT, E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1989
Main classification: B01F11
IPC codes: B01F11, G01N35