Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Reexamination Certificate
2001-03-02
2004-01-06
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
C422S091000, C422S105000, C422S063000, C220S640000, C220S655000
Reexamination Certificate
active
06673319
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to the preparation or testing of sample substances contained in vessels in which stirring devices or other instruments operate. More particularly, the present invention relates to the centering and alignment of such vessels with respect to the stirring device.
BACKGROUND ART
In the pharmaceutical industry, the stirring or agitation of sample drugs or other substances in vessels is an important step in sample preparation procedures. Examples of such procedures include those performed for the purpose of testing and analyzing the rate at which doses release from pharmaceutical products, such as tablets or capsules, under controlled conditions. The procedural steps, test duration, dissolution medium, and apparatus employed in dissolution tests typically must comply with established, well-recognized guidelines, such as those promulgated by United States Pharmacopeia (USP), in order for the test to be accepted as valid for the specific substance tested.
The apparatus utilized for carrying out dissolution testing typically includes a vessel plate having an array of apertures into which test vessels are mounted. When the procedure calls for heating the media contained in the vessels, a water bath is often provided underneath the vessel plate such that each vessel is at least partially immersed in the water bath to enable heat transfer from the heated bath to the vessel media. In one exemplary type of test configuration (e.g., USP-NF Apparatus 1), a cylindrical basket is attached to a metallic drive shaft and a pharmaceutical sample is loaded into the basket. One shaft and basket combination is manually or automatically lowered into each test vessel mounted on the vessel plate, and the shaft and basket are caused to rotate. In another type of test configuration (e.g., USP-NF Apparatus 2), a blade-type paddle is attached to each shaft, and the pharmaceutical sample is dropped into each vessel such that it falls to the bottom of the vessel. When proceeding in accordance with the general requirements of Section <711> (Dissolution) of USP24-NF19, each shaft must be positioned in its respective vessel so that its axis is not more than 2 mm at any point from the vertical axis of the vessel.
It is therefore an important criterion in certain uses of vessels in which shafts operate that the vessel, and especially its inner surfaces, be aligned concentrically with respect to the shaft, and various approaches have heretofore been taken to assist in meeting this criterion.
One approach is disclosed in U.S. Pat. No. 5,403,090 to Hofer et al., in which at least two embodiments of a vessel aligning structure are provided to lock a standard USP dissolution test vessel into a stable, centered position in a vessel plate relative to a stirring shaft. The vessel is extended through one of the apertures of the vessel plate such that the flanged section of the vessel rests on the top of the vessel plate.
In one embodiment disclosed in U.S. Pat. No. 5,403,090, the vessel aligning structure includes an annular ring having a tapered cylindrical section depending downwardly against the inner surface of the vessel, and an annular gasket surrounding the annular ring. When the vessel aligning structure is pressed onto the vessel, the annular gasket is compressed between the vessel aligning structure and the flanged section of the vessel. A mounting receptacle is secured to the vessel plate adjacent to each aperture of the vessel plate. The vessel aligning structure further includes a horizontal bracket arm which slides into the mounting receptacle and is secured by a wing nut and associated threaded stud. The bracket arm also supports the mounting assembly for the motor and stirring shaft associated with that particular vessel location of the vessel plate.
In another embodiment disclosed in U.S. Pat. No. 5,403,090, the vessel aligning structure includes a plurality of mounting blocks secured to the vessel plate. One mounting block is positioned over each aperture of the vessel plate. Each mounting block includes a tapered cylindrical section depending downwardly against the inner surface of the vessel. The mounting block has two alignment bores which fit onto corresponding alignment pegs protruding upwardly from the vessel plate.
Another approach to vessel alignment is disclosed in U.S. Pat. No. 5,589,649 to Brinker et al, in which each aperture of a vessel plate is provided with three alignment fixtures circumferentially spaced in 120 degree intervals around the aperture. Each alignment fixture includes two semi-rigid alignment arms or prongs extending into the area above the aperture. The flanged section of the vessel rests on top of the alignment arms, such that each pair of alignment arms contact the outer surface of the vessel and the vessel is thereby supported by the alignment fixtures. The alignment arms are described as exerting compressive or “symmetrical spring” forces that tend to center the vessel within the aperture of the vessel plate in which the vessel is installed in order to align the vessel with respect to a stirring element.
Many current vessel centering systems require an unacceptably large footprint around the vessels of a dissolution testing apparatus. As acknowledged by those skilled in the art, a vessel centering system that takes up less area would permit the design of a smaller overall apparatus. The use of a smaller apparatus would be highly desirable in view of the costs associated with building and maintaining pharmaceutical laboratory space.
In addition, current vessel centering systems require the manipulation of two or more components to account for the often poor and/or inconsistent manufacturing tolerances observed in the wall thickness of the extruded glass tubing from which vessels are formed and in the vessel manufacturing process itself. As noted in the publication “Dissolution Discussion Group®,” Vol. 1, Section 29.2 (VanKel Technology Group, 1999), glass vessels can be made by hand from large-bore glass tubing. The glass tubing is placed in a rotating device similar to a lathe, heat is applied, and the tubing is separated and sealed to form a hemispheric or other shaped bottom section. Heat is continually applied while the vessel is blown into the desired shape. This labor-intensive process can result in dimensional irregularities in the finished glass product. While plastic vessels are manufactured with better tolerances since they are fashioned from molds, plastic vessels are generally less desirable in many applications due to drug affinity with the surface and slower heat-up rate. Accordingly, there presently exists a need for developing a vessel centering system that adequately addresses the poor tolerance issue.
It is believed that a continuing need exists for practical and effective solutions to providing a vessel centering system. The present invention is provided to address these and other problems associated with the centering and alignment of vessels.
DISCLOSURE OF THE INVENTION
The present invention generally provides a vessel centering or alignment system which establishes and maintains a high degree of concentricity between the inner surfaces of a vessel and its associated shaft. The invention finds advantageous utility in any application in which concentricity is desired as between a vessel and a shaft or other elongate instrument extended into and operating within the vessel. The invention is particularly useful in connection with a sample handling or dissolution apparatus in which one or more vessels are to be installed onto or into some type of a vessel plate or rack. The invention is broadly characterized as providing a vessel which has a structurally distinct, locking flanged section.
According to one embodiment of the present invention, a vessel is adapted for improved centering with respect to a spindle when such vessel is installed in a vessel plate. The vessel comprises a vessel wall, an annular, spacer member, and a fastening or locking element. The vessel wall includes an outer surface
Dean Stephen D.
Fernando C. J. Anthony
Swon James E.
Gloekler David
Gordon B. R.
Varian Inc.
Warden Jill
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