Plastic and nonmetallic article shaping or treating: processes – With step of cleaning – polishing – or preconditioning...
Reexamination Certificate
2001-09-24
2004-01-13
Lechert, Jr., Stephen J. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With step of cleaning, polishing, or preconditioning...
C264S085000, C264S109000, C425S225000, C425S227000, C425S229000, C425S345000, C425S353000
Reexamination Certificate
active
06676863
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of priority from International Patent Application PCT/IB01/01631 filed on Sep. 5, 2001.
BACKGROUND OF THE INVENTION
The present invention relates to a rotary tablet press comprising a housing, a rotary die table detachably connected to a drive shaft arranged in the housing for rotation of the die table, a number of dies arranged circumferentially in the die table, each die being associated with at least a first punch having a first end receivable in the die through an opening of the die and arranged for compression of a powder or granular material in the die by reciprocation of the punch, and at least a cam for cooperation with a second end of the punches in order to effect axial displacement of the punches by rotation of the die table, whereby a compression unit detachably mounted in the housing comprises the die table with punches, a feeding device for the supply of material to be compressed into the dies, and a tablet dish charge device for removal of compressed material in the form of tablets.
EP 0288 798 describes a tablet press having a die table rotatable about a vertical axis, each die having associated top and bottom punches receivable therein and the punches being guided by top and bottom cams, respectively, whereby the cams are stationary relative to the press housing. In order to facilitate change-over as well as cleaning of components between batches, the die table with punches and cams is detachable as a unit from the press housing.
EP 1 050 399 describes a rotary tablet press of the same type, in which the exchange of components between batches has been further improved by the provision of a U-shaped rigid connection frame between the top and bottom cams. The connection frame is detachably connected with the press housing, whereby the unit comprising connection frame, die table, punches and cams may be removed in a single operation by disconnection of the connection frame from the housing and disengagement of the die table from its drive shaft, Further, it is possible to fit auxiliary equipment, such as powder feeder and tablet outlet, on the connection frame, so that these components may be removed together with the unit.
Although these prior art tablet presses make it possible to replace a unit comprising the die table and more or less other components with a corresponding unit which has been cleaned in the meantime, it is still necessary to manually clean the remaining part of the press housing which surrounds the die table during production. During these cleaning operations, the production stands still. Further, the contaminated die table with associated components must subsequently be transported to a cleaning site, manually disassembled, cleaned and eventually assembled. During all these operations, the environment is contaminated with the product and the operator is exposed to the product. In addition, the operations are very time-consuming and therefore costly.
Moreover, by change-over between batches of toxic products, it is necessary to employ a so-called isolator or glove box built around the tablet press in order to prevent any contamination of the surroundings by the product. In this case, cleaning is much more difficult due to the limited accessibility and manoeuvrability in the glove box or isolator.
EP 0 637 507 describes a rotary tablet press provided with equipment for so-called washing-in-place (WIP) in the form of spray nozzles for spraying of washing agent onto the die table and associated components as well as suction pipes for draining off the washing agent. In known tablet presses of this type, it is, however, a problem that the washing by means of spray nozzles is not efficient enough to achieve the required final cleanliness due to the fact that the washing agent cannot adequately enter the complex construction of the die table with punches, the powder feeder and tablet outlet etc. Consequently, a time-consuming final manual cleaning of the tablet press is still necessary. The preceding washing-in-place operations by means of the spray nozzles also take long time, for instance up to eight hours, mainly due to long drying and cooling cycles after the wash cycle. During these cycles, the tablet press is out of production. In addition, the equipment required for washing-in-place comprises several spray nozzles and suction pipes, etc., and consequently increases the price of the tablet press considerably.
U.S. Pat. No. 4,259,049 describes a rotary tablet press in which some of the negative effects of dust generation have been alleviated during production. The leading end portions of the punches are surrounded by cuffs, through which gas is blown towards the front ends of the punches to prevent deposition of dust on the punch surfaces. In order to prevent the dust blown away from the punches from deposition on other components in the press housing during operation, said cuffs are surrounded by suction chambers provided by stationary mounted shields. However, due to these shields, change-over as well as cleaning of the machine between batches are even more complicated and consequently time-consuming, as the shields have to be removed manually to access the dies and associated punches. As this tablet press does not provide for removal of the die table and punches as a unit, these components must subsequently be disassembled also manually and one by one, all operations which are very time-consuming and must be done during stand-still of the machine.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide a tablet press by which the time required for cleaning of the press between batches is reduced compared to prior art presses and by which the risk of contamination of the surrounding environment as well as exposure of the operator to the product may be reduced to a minimum.
In view of this object, the compression unit encloses each die opening and its corresponding first punch end in a chamber, the feeding device and the tablet discharge device are enclosed, the feeding device communicates with an inlet for detachable connection with an external supply channel, and the tablet discharge device communicates with an outlet.
By enclosing both the area around the die where the tablets are compressed and the feeding and discharge devices, it is possible to keep the product always confined in the detachable compression unit, and the external supply channel, and by furthermore providing a releasable connection between the feeding device and the external supply channel, the compression unit may between batches fast and easily in a single operation be exchanged for an already cleaned unit, without having to clean supplementary parts of the tablet press, other than the supply channel, and without the operator being exposed to the product. Whereas the supply channel may be readily cleaned by means of well known techniques, such as cleaning-in-place (CIP) by means of spray nozzles, the compression unit requires a much more thorough cleaning procedure.
According to the invention, because the used compression unit confines the product residues, the unit may be transported to a dedicated cleaning station without contamination of the environment. The cleaning of the unit may be carried out manually, possibly in an isolator, without delaying the production, as another already cleaned unit is mounted in the tablet press for the production, but the cleaning may advantageously be automated. In a dedicated automated cleaning station, it is possible to clean the compression unit much more thoroughly and also faster than it is possible in the known tablet presses provided with washing-in-place equipment, because the unit is separated from its surroundings in the press, so that the operation of the cleaning equipment is not restricted by the limited space in the press. Further, the function of the tablet press is not affected by the presence of the cleaning equipment. As a result, the unit may be manipulated much more extensively by dedicated equipment, for exam
Boeckx Jurgen
Christiaens Dirk
Van Zegbroeck Antonie
Vogeleer Jan
Courtoy NV
Lechert Jr. Stephen J.
Sughrue & Mion, PLLC
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