Agitating – With test – signal – or indicator means
Reexamination Certificate
2003-01-08
2004-08-17
Soohoo, Tony G. (Department: 1723)
Agitating
With test, signal, or indicator means
C366S143000, C366S200000, C366S208000, C366S213000, C366S219000, C366S220000
Reexamination Certificate
active
06776517
ABSTRACT:
This invention relates to apparatus for and a method of mixing components, for example to effect blending of components to form a homogeneous mixture. The components will usually be in the form of powders but the invention is also applicable to the mixing of other fluent components such as liquids. Typically the components to be mixed comprise pharmaceutical actives and excipients prior to further processing thereof, e.g. tableting.
The production of homogeneous mixtures of actives and excipients is of particular importance in the pharmaceutical industry.
EP-A-0631810 discloses that in-line monitoring of the degree of homogeneity achieved in the course of blending components such as pharmaceutical actives and excipients is possible by detecting the spectroscopic characteristics of the mixture during the blending process. Where the blending process is carried out by means of a rotating mixing vessel, EP-A-0631810 teaches that the device for projecting radiation into and receiving reflected radiation from the mixture is associated with a shaft about which the vessel, specifically a V-blender, is rotated. This arrangement results in the device being located invasively with respect to the interior of the mixing vessel. The reflected radiation is conveyed to spectroscopic means located in the vicinity of the rotating mixing vessel for storage and analysis by the spectroscopic means or by a separate data acquisition and a control computer linked to the spectroscopic means.
The present invention seeks to provide improved in-line spectroscopic monitoring of mixing, especially but not exclusively blending, processes which may be non-invasive while affording greater freedom in terms of siting relative to the mixing zone.
According to one aspect of the present invention there is provided apparatus for mixing a number of components comprising a vessel for receiving the components, drive means for rotating or oscillating the vessel about an axis to effect mixing of the components within the vessel, and at least one spectroscopic monitoring means for repeatedly scanning the mixture to obtain data for use in monitoring changes in the spectroscopic profile of the mixture as mixing proceeds, the monitoring means being mounted off-axis relative to the axis about which the vessel is rotatable or oscillatable.
The monitoring means may be provided directly on-board the vessel or may instead be provided indirectly on-board the vessel as a result of being provided at least in part on a structure which rotates or oscillates with the vessel. In the former case for instance, the monitoring means may be mounted on a wall of the vessel while in the latter case the monitoring means may be carried at least in part by a frame which supports the vessel and through the agency of which the vessel is rotated or oscillated. References herein to the monitoring means being directly or indirectly on-board the vessel are to construed as referring the foregoing possibilities.
The profiles derived from scanning (hereinafter the “scanned profiles”) may be monitored for convergence towards a static condition. This may for example involve comparison with a predetermined target spectroscopic profile. In this context, it is to be understood that the initial spectra of the components before mixing will correspond generally to the spectrum of each of the components. As the mixing process proceeds, the spectra of the mixture will undergo change and begin to converge towards the spectra of the homogeneous mixture. Thus, the mixing process can be controlled with reference to the spectroscopic profile obtained by the monitoring means and, in particular, may be terminated when the scanned profiles meet a predetermined criterion, e.g. when the scanned profiles attain or converge towards a substantially static condition. This may for example be satisfied when the scanned profile substantially matches the target profile or when two or more scanned profiles (or parts thereof) of the mixture are substantially the same or differ from one another by no more than a predefined extent.
Where used, the target profile may be representative of a selected condition of the mixture; for instance, it may be representative of the homogeneous end-point for a mixture of the components undergoing blending or an intermediate state lying between the homogeneous end point and the unmixed state.
Often the components undergoing mixing will have different chemical compositions. However, the invention also encompasses the mixing of components having the same or substantially the same chemical composition. For example, the apparatus of the invention may be used for mixing components which have the same or substantially the same chemical composition but have differing physical characteristics, such as moisture content, particle distribution etc. Thus, one application of the invention lies in the combining of two fractions of the same material, one fraction comprising fines and the other comprising coarser particles, the mixing process being carried out to produce a mixture in which the fines are dispersed into the coarser particles, e.g. to secure a substantially uniform distribution of fines in the mixture.
Control means responsive to the monitoring means may be provided for controlling the mixing process.
Thus, the drive means may be controlled by the control means in dependence upon the result of the comparison so that the mixing process can be terminated when the profiles derived from scanning converge on or substantially match the predetermined profile or converge towards a static condition where the changes in scanned profiles (or parts thereof are no greater than a predefined extent.
The monitoring means may include or be associated with comparison means for comparing spectroscopic profiles corresponding to the scanning-derived data with the target profile or previously derived scanned profiles obtained during a given mixing cycle. Thus, the monitoring means may embody the comparison means so that the comparison of scanned profiles with target profile or previously derived scanned profiles is effected during rotation or oscillation of the monitoring means with the vessel.
When the scanned profiles have converged to a predetermined extent towards a static condition (e.g. when a desired level of matching between the scanned profile and a target profile is obtained), the monitoring means may be arranged to supply an output signal to signal utilising means for controlling the mixing process. For instance, the signal utilising means may be operable in response to receiving the output signal to terminate the mixing process by suitable control of the drive means, e.g. by disabling the drive means and terminating rotary or angular movement of the vessel.
In an alternative embodiment, the comparison means may be separate from the monitoring means and the vessel. In this case, data transferring means will be provided for transferring scanning-derived data from the monitoring means to the comparison means. The data transferring means may for example comprise a signal transmitter directly or indirectly on-board the vessel and a receiver associated with the comparison means whereby the data is transmitted radiatively from the monitoring means to the comparison means.
Matching of the newly derived scanned and target or previously obtained scanning profiles (at least to the desired extent) conveniently leads to automatic termination of the mixing process. However, we do not exclude the possibility that such matching, whether carried out directly or indirectly on-board the vessel or elsewhere, may instead give rise to an output signal, e.g. visual or audible, suitable for attracting an operator's attention to the fact that mixing to an acceptable level, e.g. an acceptable level of homogeneity, has been secured and that the mixing process can be terminated and the mixture transferred to a subsequent processing stage.
The monitoring means is preferably self-powered and to this end conveniently includes a power source which may be in the form of one or more batteri
Afnan Ali Mohammad
Chisholm Robert Symes
AstraZeneca UK Limited
Pillsbury & Winthrop LLP
Soohoo Tony G.
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