WO2010128445A1

WO2010128445A1 - Method for producing multilayer tablets with tablet cores, and rotary press for the same

Info

Publication number: WO2010128445A1
Application number: PCT/IB2010/051927
Authority: WO
Inventors: Frank BÖHM; Horst Müller; Jens Carstens
Original assignee: Ima Kilian Gmbh & Co. Kg
Priority date: 2009-05-08
Filing date: 2010-05-03
Publication date: 2010-11-11
Also published as: DE102009025779A1; DE102009025779B4

Abstract

The invention relates to a method for producing multilayer tablets with the use of tablet cores, so-called core tablets, on a rotary press, comprising the steps feeding of tablet cores 21, transfer of the tablet cores with a core-inserting device 20 to a die opening 9 in a die plate (2), finishing of a tablet and removal or discharge of the tablet from the rotary press. The invention further relates to a rotary press for producing core tablets of this type. In order to achieve a more reliable process control in the production of core tablets, according to the invention the position of the tablet core 21 in the die or die opening 9 is registered with an optical system 10 after the transfer station 25. Since, with the optical system 10, the position of each tablet core or the actual fill state of each die opening 9 is registered behind the transfer station 25 and, where necessary, is further processed with an image-analyzing device and/or with a processor, a positioning adjustment and a separating out of bad tablets can be automated.

Description

Title of Invention: METHOD FOR PRODUCING MULTILAYER TABLETS WITH TABLET CORES, AND ROTARY PRESS FOR

THE SAME

[1] The invention relates to a method for producing multilayer tablets with the use of tablet cores on a rotary press, comprising the steps feeding of tablet cores to a core- inserting device, transfer of the tablet cores with the core-inserting device to a die opening in a die plate of the rotary press, finishing of a tablet within the die opening with the pressing tools of the rotary press, and removal or discharge of the tablet from the rotary press. The invention further relates to a rotary press for producing multilayer tablets with the use of tablet cores, comprising a die plate having peripherally offset dies, comprising pressing tools for producing tablets within the dies, comprising a filling station for supplying material for at least one layer of the multilayer tablet, comprising a feed device for tablet cores, comprising a core-inserting device for transferring and positioning the tablet cores into the dies of the die plate at a transfer position, and comprising a run-off for the removal of the tablet from the rotary press.

[2] Rotary presses and rotary tablet presses are used, in particular, to produce tablets and pellets for the pharmaceutical industry, food industry and detergent industry and generally have a rotor which has guides for top and bottom punches and comprises a die plate having a multiplicity of dies or die bores, with which the pressing tools consisting of pressing punches interact. The rotor is driven by means of a suitable drive, in particular an electric motor, about a generally vertically upright, central rotation axis and the pressing punches are lowered and raised by means of guide ways. Assigned to the rotor is at least one filling device, which pours the powder, granulate or the like to be pressed into the bores of the dies. The pressing, for example of the powder material into tablets of approximately chosen form, which is primarily dependent on the geometry of the die opening and the punch surfaces of the pressing punches, is realized in at least one pressure station with upper and lower pressure roller, which pressure rollers press the associated pressing punches into the dies or die bores and compress between the punch surfaces of the bottom and top punch the material to be pressed. Behind the pressure station in the rotational direction is arranged an ejection station, in which tablets are fed, generally by means of a wiper, over the surface of the die plate to an outlet and are evacuated from the rotary press. The ejection station can contain in the outlet, for example, a diverter, in order to separate good tablets from bad tablets. A rotary press is usually accommodated in a housing, in order to prevent both process dust from forcing its way out and parts of the press from being contaminated by environmental influences. The output of a rotary press substantially depends on the number of dies and the rotation speed of the rotor, though special constructions are also known in which, during a 360° rotation of the rotor, two or three tablets are produced in the same die opening.

[3] Rotary presses can also be used to produce multilayer tablets, wherein either two or more powder materials are successively poured into the dies or die openings in a plurality of filling stations and/or a tablet core is inserted into a partially filled die opening before the appropriate die, where necessary after passing through a first pressure station and a further filling station, reaches the second and normally last pressure station, in which the tablet is finished. The invention relates to rotary presses of this type having an inserting device for tablet cores and, as supplement to the disclosure, reference is made to DE 10 2007 039 043 Al, in which a rotary press of this kind having a star distributor as an inserting device for tablet cores is shown and described.

[4] Particularly in the case of multilayer tablets with inserted tablet core, frequently also referred to as a core tablet, for the pharmaceutical industry the need exists to obtain as even a coating of the tablet core as possible with the material forming the at least one further layer. At the same time, it is necessary to ensure that each multilayer tablet contains a complete tablet core and that bad tablets are separated from good tablets and are separately discharged. The even coating is necessary, for example, in respect of pharmaceutical tablets or multiphase cleaning tablets in which, via the coating layer, an action time delay or action time duration of an active substance in the core tablet is intended to be influenced. In order to differentiate between a good tablet and a bad tablet in the continuous production process, the pressure signals from pressure sensors for measuring the pressing force are hitherto analyzed in order, on the basis of these pressure signals, to deduce the fill state of the dies. Insofar as the pressure signals are transmitted to a control terminal with processor, a discharge of bad tablets can also be controlled in dependence on the pressure signal. The pressure signal for the pressing force is, however, only an indirect parameter and, particularly in respect of fully coated core tablets for the pharmaceutical industry, the accuracy of this measuring and analysis method is inadequate.

[5] The object of the invention is to improve a method and a rotary press for the production of core tablets in such a way that a more reliable process control is achieved, which preferably also, where necessary, enables the discharge of bad tablets to be automated and/or the production method to be controlled.

[6] This object is achieved in a method according to the invention by virtue of the fact that, with an optical system, the position of the tablet core in the die or die opening is registered after the transfer step or core-depositing step. In particular, it is ad- vantageous if, with the optical system, the position of each tablet core in the die opening or the actual fill state of each die opening is registered behind the transfer station and the detection signal or image signal of the optical system is further processed with an image-analyzing device and/or with a processor. Due to the registering of the actual position, the state and the presence of the core in the die, i.e. of the actual fill state within the die opening after the transfer station, direct information concerning the tablet core is available, so that, in any event, all bad tablets of the kind which fail to meet previously defined quality criteria or requirements with regard to, for example, position, quality, completeness and position of the tablet core can be discharged.

[7] The rotation speed of the rotors of rotary presses for the production of core tablets is relatively high and can amount, in particular, to between about 20 rpm and 70 rpm. At the same time, the core-inserting device, particularly if containing a turntable having a plurality of core holders, has a necessary minimum diameter. In order to nevertheless obtain an optimal image signal with the optical system, it is particularly advantageous if the optical system is assigned to a position of a die opening of the die plate, which, in the rotational direction, lies offset by between one and five dies, preferably two or three dies, relative to the die opening positioned beneath the core-inserting device. The optical system can then be configured such that, in particular by positioning of a slanting mirror directly above this die opening, the fill state of the die opening is detected vertically from above. The mirror can be installed, particularly together with a camera, for example, in the optical system in a common optics or camera housing, and, where necessary, can be provided with a cooling air supply and/or lighting device, so as to able to be installed directly in the pressing chamber, i.e. in the housing of the rotary press, whilst at the same time being able to deliver image signals with sufficient contrast.

[8] The image- analyzing device is preferably designed such that, via a detection signal or via the image signal of the optical system, a differentiation is made between bad tablets and good tablets. The image- analyzing device can be provided with a processor and a visualization device, which are preferably separate and independent from a control terminal of the rotary press. The camera and a preferably digital image sensor of the optical system are preferably coupled to a machine control system in order to initiate with the machine control system a triggering signal if the camera is intended to register a single image of the fill state, the triggering signal serving to ensure that, at this triggering moment, a die opening is present within the range of the optical system. With the image- analyzing device, in turn, a control signal can be delivered to the machine control system to, where necessary, discharge a bad tablet, for example in the outlet by means of a diverter. [9] Further preferably, the production method can be provided with an automatic position correction for the core-inserting device, in that, from the detection signals or image signals for all tablets, or at least for all good tablets, a mean value for an average eccentricity of the tablet core within the die opening is formed, which is used as a control signal for controlling the core-inserting device. To this end, the core-inserting device can be provided with a servo or step motor, which enables a displacement of the core-inserting device, for example radially to the periphery of the rotor or of the die plate. The image signal of the optical system can hence be usable or be used as a control signal for a drive control system of the core-inserting device and also as a control signal for the machine control system for actuation of a discharging device for bad tablets. In order to achieve an automation of the correction of the set-down position of the tablet cores, the image signal can be further processed with a processor of the image- analyzing device or of the machine control system, in order to measure the real position coordinates of the tablet core on the basis of the image signal. For automated set-down correction, it is further advantageous if the core-inserting device has a turntable drivable with an electric motor and the die plate is driven with a separate electric motor, a phase displacement between these electric motors preferably being adjustable or being adjusted, preferably via the machine control system, in order to change the set-down position also in the rotational direction. Through an adjustment of the servo motor of the core-inserting device in the radial direction and through a phase displacement between the rotary drive for the die plate and the rotary drive for the turntable, the optimal set-down position can be automatically controlled in dependence on the detection signals of the optical system or in dependence on the determined position coordinates.

[10] In order to enable bad tablets to be separated out even in short time frames available for the image acquisition and analysis, it is particularly advantageous if the optical system receives from the machine control system a triggering signal, in dependence on which the optical system registers a single image as an image signal, whereupon the single image is compared with a desired image, preferably with an image-analyzing device, and, in the event of deviations from the desired image, a control signal for a discharging device, such as a diverter in the outlet, is generated. The entire signal processing for separating out the bad tablets can be realized by a pure image comparison in the image-analyzing device for the optical system and, in this respect, can be retrofitted also in existing tablet presses.

[11] The above object is achieved according to the invention in a rotary press by virtue of the fact that the rotary press has an optical system for registering the position of the tablet core in the die opening after the transfer station. In the rotary press also, the optical system is preferably assigned to a die opening or die position which in the ro- tational direction of the die plate lies offset by between one and five dies, preferably two or three dies, relative to the transfer station. Through use of the optical system and registration of the actual fill state of each die opening, with an analyzing and control device, which should at least be coupled to the machine control system, an analysis of detection signals or image signals of the optical system can be made in order to generate control signals for a drive control system for the core-inserting device and/or the controlling of an electric motor forming the rotary drive for the die plate or the rotor.

[12] For an optimal image signal, it is particularly advantageous if above a die, as far as possible in alignment with its die opening, a mirror is arranged peripherally offset relative to the transfer station. The mirror preferably has a mirror surface which stands obliquely to the surface of the die plate; the mirror surface preferably stands at an angle of 40° to 60°, in particular at an angle of about 45° obliquely to the surface. It is particularly advantageous if the mirror, together with the optical system, is disposed in a camera housing to allow the total unit to be installed within a housing of the rotary press, hence in the pressing chamber.

[13] Since, with the optical system, essentially only the actual fill state of the die opening is intended to be registered, for which, however, in dependence on the rotation speed and the number of dies, only a time span ranging from 20 ms to 100 ms is available, it is advantageous or sufficient if the optical system has an image sensor and/or preferably a lighting device. The lighting device can comprise one or more light sources, which, in particular, can consist of LED's such as, above all, high-power LED's. The image sensor preferably allows a digital registration and reprocessing of the detection or image signals, but can also operate on an analogue basis. The lighting device preferably has a plurality of light sources, which are arranged, for instance, annularly around the image sensor or a lens system (lens) assigned to the image sensor. A favourable illumination of the die opening can thereby be achieved in a space-saving manner, at the same time as the lighting device, because of the same beam paths as the image sensor, can also make use of the mirror. In the case of 2 high-power LED's, these can be arranged mutually offset by 180° around the lens. The light source can consist, in particular, of a high-power light-emitting diode (LED), which is preferably disposed in the housing of the optical system and generates via mirrors a diffuse light. Alternatively, the illumination can also be realized via light guides which are assigned to the light sources or LED's and the ends of which are positioned above the transfer station or peripherally offset relative to the transfer station above a die opening behind the transfer station in the rotational direction. The camera housing can further be provided with an air connection in order to utilize supplied air as cooling air for the light sources and/or for generating an air curtain in front of an optical window lying facing the die opening. The air curtain can serve to prevent dust from being deposited on the optical window. The air jet for the air curtain is preferably aligned roughly parallel to the surface of the die plate and substantially parallel to the optical window to prevent air turbulence or air jets directed into the die opening.

[14] In particular, it is advantageous if the core-inserting device has a turntable which can be rotary driven with an electric motor and has a servo drive that is preferably actuable in the radial direction of the die plate, a drive control system for the electric motor of the turntable and/or the servo drive being coupled by control engineering methods to the image- analyzing device of the optical system. Via the detection signals of the optical system and, for example, the analyzing device, an automatic adjustment can be made for the core-inserting device in order to increase the share of good tablets with optimally situated cores even without process interruption.

[15] Further advantages and embodiments of the invention are described below with reference to an illustrative embodiment, shown schematically in the drawing, of a rotary press according to the invention. In the drawing:

[16] Fig. 1 shows schematically, using a developed representation of the simultaneously occurring method steps, the structure and system parts of a rotary press according to the invention;

[17] Fig. 2 shows in schematic top view a rotary press according to the invention having the individual stations and having a core-inserting device with downstream optical system;

[18] Fig. 3 shows schematically, using a block diagram, the working method of the automation of the production method, using the image signals of the optical system;

[19] Fig. 4 shows schematically the structure of an optical system; and

[20] Fig. 5 shows schematic examples of the image signals detected with the optical system.

[21] Fig. 1 shows in developed representation, of a rotary press denoted in its entirety by reference symbol 1, a die plate 2, an upper punch guide ring 3 and a lower punch guide ring 4, in which the top punch 5 and bottom punch 6, as pressing tools of the rotary press 1, are moved up and down over an upper segmented cam track 7 and a segmented lower cam track 8, respectively, to form a core tablet between the punch surfaces of the pressing punches 5, 6. In the die plate 2, a number of dies 90 corresponding to the number of paired pressing punches 5, 6 are exchangeably installed, whereof the inner bore or opening respectively forms the die opening 9, in which die openings the core tablets are produced. By exchanging the dies 90 for dies having other die openings, it is possible to produce other tablets or pellets with other dimensions or shapes. With the rotary press 1 according to the invention, pellets for sintering processes or the like could also, of course, be produced, which are here referred to collectively as tablets.

[22] Figure 2 shows in schematic representation that the rotary press 1 is provided with an openable and closable housing 28 to encapsulate the pressing chamber 29 against the environment. The rotary press 1 has, in a manner which is known per se, a first filling station 40 for supplying a first pressing material for the core tablet, this material being generally fed in powder or granulate form, for example via a fill hopper (not shown) for maintenance of a continuous volume flow, to a schematically indicated first filling shoe 41, with which the material for the first layer or bottom layer of the core tablet is poured evenly into the die openings 9. In the region of the filling station 40, the upper pressing punches 5 are maximally raised over the associated segments of the cam track 7, as shown by Figure 1. Behind the first filling station 40 in the rotational direction R of the die plate 2 is generally arranged a metering device, in order to precisely meter the filling of the die opening 9. Behind the filling station 40 in the rotational direction, there follows a transfer station for tablet cores 60, denoted in its entirety by reference symbol 25, which has a core-inserting device 20 in the form, in particular, of a star distributor provided with a turntable 21, as described in DE 10 2007 039 043. With the core-inserting device 20, in the transfer station 25 the tablet cores 60 can respectively be placed individually into the previously preferably only partially filled die opening 9. The tablet cores 60 are led by a feeding device 24, for instance a conveyor belt or the like, to the turntable 21 and the feeding device 24 can have a separating device, such as a shaker conveyor or the like, in order to lead a continuous flow of tablet cores 60 to the core-inserting device 20. The turntable 21 is provided with an electric motor 22, indicated schematically in Figure 2, as a rotary drive. According to the process control and the configuration, in particular, of the lower guide cam 8, the respectively lower pressing punch 6 can be slightly lowered before the tablet core 60 is deposited with the core-inserting device 20 into the die opening 9. In the represented illustrative embodiment, the tablet core 21 rests on a non-compacted material layer 43 delivered in the first filling station 40 and is then subsequently pressed with pressure rollers 31, 32 of a first preliminary pressure station 30 into the material layer 43. To this end, the cam tracks 7, 8 bring together the punches 5, 6, so that both punches 5, 6 intrude into the die opening 9 and with the pressure rollers 31, 32 compress the layer 43 and the tablet core 60. After the first pressure station, an outlet 27 for sample tablets can be present, which outlet can also, however, be dispensed with.

[23] In the shown rotary press 1, the first pressure station 30 is followed by a second filling station 45 having a second filling shoe 46 and then a second pressure station 35 having pressure rollers 36, 37. In the shown illustrative embodiment, the finishing of the core tablet 66 is realized in this second or last pressure station 35 with the upper pressure roller 36 and the lower pressure roller 37, with which a pressing force is applied for compressing and pressing together the pressed blank with the second material layer fed in the second filling station into the die opening 9 in the die plate 2. The thus finished core tablet 66 is raised behind the second pressure station 35 by means of the bottom punch 6 and, where necessary, an ejector device 38 and is fed with a fixed wiper 71 from the top side 2' of the die plate 2 to an outlet 70. The outlet is provided with a controllable diverter 72 or the like, which can comprise, for instance, a compressed-air nozzle to direct bad tablets, i.e. tablets having a defective tablet core, into a separate outlet rail 73, whilst only core tablets 66 which form good tablets are evacuated via the standard outlet rail 74.

[24] An important aspect of the invention in respect of the rotary press 1 and the method which can be implemented therewith consists in the arrangement of an optical system, denoted in its entirety by reference symbol 10, behind the transfer station 25 with the core-inserting device 20, wherein, with the optical system 10, as is further explained, the presence, the quality and the position of the tablet core 60 in the die opening 9, hence the actual fill state of each die opening 9, is registered behind the transfer station 25 in the rotational direction. The optical system is disposed in a region in which the top punches 5 are raised by means of the upper cam track 7 and momentarily, i.e. when the associated die opening passes through the optical system, the production process has no effect on the tablet blank. In the schematically shown illustrative embodiment, the optical system 10 is assigned to that die opening 9 which in the rotational direction lies, offset by two dies 90, behind that die opening 9 into which a tablet core 60 is inserted by means of the core-inserting device 20. In the region of the optical system 10, the top punch 5 can remain fully raised insofar as the upper guide 7 still extends horizontally there, or else the downward motion of the top punches 5 towards the first pressure station 30 can already commence, insofar as the particular stroke height of the top punch 5 is still sufficient to place the optical system 10 between the top side of the die plate and the head of the top punch in such a way that the optical system 10, in an, as far as possible, vertical top view, can register an image of the die opening and, in this respect, also of the fill state of the die opening 9 with tablet core 60. The closer the optical system 10 is positioned to the transfer position 25, the more time is available for the signal analysis of the detection or image signals of the optical system 10, in order, in dependence on the analysis result, to actuate the diverter 72 of the discharging device 75 insofar as a bad tablet, i.e. a tablet without tablet core, with damaged tablet core or wrongly positioned tablet core has been detected via the signal of the optical system 10. Advantageously, the discharging device 75 or diverter 72 separates out only bad tablets, whilst good tablets 66 are evacuated via the run-off rail 74. Since the basic working method of corresponding discharging devices or diverters is known, no more detailed description is provided here. [25] The process control of the rotary press 1 is preferably entirely controlled via a machine control system 50 shown schematically in the block diagram according to Fig. 3. With the machine control system 50, an electric motor (not represented) as a drive motor for the rotor formed by the die plate 2 and the punch guides 3, 4 can be controlled, at the same time as the filling flow of material in the filling stations, and the pressing force at the pressure rollers 31, 32, 36, 37 (Fig. 1), can also be monitored via pressure sensors (not represented). To the machine control system 50 a generally separate control terminal 51 is assigned as a visualization and inputting unit for the machine control system 50, and at the control terminal all process parameters can be set and monitored by the staff. As represented in the block diagram, in the shown illustrative embodiment the optical system 10, the core-depositing device 20 and the discharging device 75 are also controlled with the machine control system 50. The machine control system 50 has a processor (also not represented), in addition to software routines for the analysis and control of the process stations. The machine control system 50 is coupled by signal engineering methods to an analysis and control unit (controller) 52, with which the image signals registered with the optical system 10 disposed in the pressing chamber 29, as indicated symbolically with the arrow 53, can here be analyzed at least to the point where the machine control system 50 receives a detection or valuation signal 55 signalling whether the tablet in question is good or bad. A display screen 52A can be assigned to the controller 52 to display the received individual images also to the staff. In order to register an optimal single image with the optical system 10, the machine control system 50, at a certain moment at which a die opening 9 with already inserted core 60 is located directly beneath the optical system 10, sends a triggering signal 56 to the controller 52, which, based on the receipt of this triggering signal 56, transmits a triggering signal 57 to the camera to register the actual fill state of this die opening 9 with a single image. With the controller 52, alternatively also with the machine control system 50, this single image can be analyzed as to whether the registered actual image tallies or not with a predefined desired image. The possible single images which can be registered with the optical system 10 are represented schematically in Fig. 5. In the upper row in Fig. 5, single images of this kind are represented, which show a core position of the tablet core 60 in a die opening 9 for a good tablet, whilst the lower row of Fig. 5 shows corresponding positions of the tablet core 60 in the die opening 9 for bad tablets. In dependence on the registered single image, the optical system 10 with the associated controller 52 can already deliver, on the basis of an image comparison, either a good signal G or a bad signal S as a control signal 55 to the machine control system 50 and, on the basis of this signal, preferably only when it is a bad signal S, the discharging device 75 is actuated via the discharge signal 58 at the moment when the appropriately finished core tablet passes through the diverter 72, (Fig. 2). The time delay up to the actuation of the discharging device 75 is dependent on the process parameters such as rotation speed, number of dies, plate diameter etc. A bad signal S is generated, for example, if, as represented with Sl in Fig. 4, the tablet core 60 lies too close to the rim of the die opening 9, if the tablet core 60 is incomplete, as represented in S2, if a tablet core is missing, as represented in S3, if a tablet core stands upright, as represented in S4, or some other deviation from an admissible desired image is registered and recognized. In the upper row of Fig. 5, on the other hand, image signals for good tablets are represented, an image signal corresponding to a desired image for an optimal core tablet being represented with Gl, whilst, in the case of the image signals G2, G3 and G4, the tablet core 60 respectively has a small positional deviation from the optimal desired image according to Gl. Where solely a discharge of bad tablets is desired, the detection signal of the optical system 10 could also be delivered by the controller 52 as a control signal directly to the discharging device 75, in order to cause the corresponding bad tablet to be discharged there at the right time. [26] In a particularly advantageous embodiment of a rotary press 1 according to the invention, it is additionally possible to automatically perform a positional correction of the tablet cores 60 within the die opening 9, reference again being made to Figs. 2 and 3 for further explanation. In Fig. 2, it is indicated schematically that the turntable 21 of the core-inserting device 20 is provided with a rotary drive such as, in particular, an electric motor 22, the rotation speed of which can be set via the machine control system 50. The core-inserting device 20 has a separate electric motor and is coupled non-mechanically to the die plate 2 in order that the rotation speed of the turntable 21 is independent of the rotation speed of the die plate 2. To the core-inserting device 20 there is also assigned a servo motor 26 (represented schematically), preferably a linear motor, with which the position of the turntable 21 can be displaced in the radial direction of the die plate 2, hence in the arrow direction x in Fig. 2. In service, the die plate 2 preferably rotates in the arrow direction R, hence anti-clockwise, and the turntable 21 is rotated by means of the separate motor 22 clockwise in such a way that, as near as possible at exactly the same moment, a die opening 9 and a core holder in the turntable lie one above the other in order to deposit a tablet core 60 as centrally as possible in the die opening 9. Via the fixed optical system 10, the result of the core set- down, hence the actual fill state of each die opening 9, is registered behind the transfer station by means of process engineering methods, and the controller 52, in the image analysis of the image signal 53, can additionally determine position coordinates x/y corresponding to the positional deviation of the tablet core in the radial and tangential direction in relation to the coordinate system x/y shown in Fig. 2, which position coordinates are relayed as position signals to the machine control system 50, as indicated with the arrow 59. The machine control system 50, in turn, can analyze the individual position signals 59 and can calculate from the mean values of the position signals, preferably only on the basis of all good signals G, control signals 59 A, 59B, in order to control the servo motor 26 in the event of a positional deviation relative to a centrally deposited tablet core in the x-direction and the drive motor 22 of the turntable in the event of a positional deviation in the y-direction. The coordinate deviations are hence used as control signals 59A, 59B for the core-inserting device 20 in order to optimize the set-down position of the tablet core 60 into the die opening 9 in the insert station 25. Since the electric motor 22 for the turntable 21 is decoupled from the drive motor of the rotor of the rotary press 1, the rotation speed of the turntable 21 can preferably be briefly changed by a phase displacement so as subsequently to restore a synchronism between the turntable 21 and the die plate 2. Via the phase displacement, only a brief retardation or acceleration of the turntable 21 is induced, until a tablet core 60 is deposited centrally in a die opening 9.

[27] Fig. 4 shows schematically, in heavily simplified representation, the structure and arrangement of an optical system 10 above a die opening 9 within the die plate 2. The punch head of the lower pressing punch 6 is already intruding from below into the die opening 9, and both a partial filling of the die opening 9 with the first layer 43 of the layer material and the depositing of the tablet core 60 is concluded. The optical system 10 comprises a camera housing 11, a camera 12 having an image sensor (also not represented), and a lens 14 (merely indicated), above and beneath which a light source 15, such as, for instance a high-power LED, is respectively disposed, said light sources being mutually offset by 180°. The camera housing 11 is provided and closed off on the end face, in the direction of view of the lens, with a mirror 17, the mirror surface 17' of which is aligned obliquely to the surface 2' of the die plate 2 and here runs obliquely at an angle of 45°. The optical system 10 is positioned such that the mirror 17, and a window 13 closed off with a transparent protective screen, are located directly above the die opening 9. Via the mirror surface 17', on the one hand the light beams of the light sources 15 are diverted to the die opening 9 in order to adequately light the die opening 9 from above, and, on the other hand, the image displaying there is directed to the lens 14. The power supply to the LED's 15 and to the camera 12, and also the whole of the signal transmission of the image signal and of the triggering signal, here takes place via cable, as indicated schematically with reference symbol 18. The camera housing 11 is further provided with air inlets for a cooling air supply and for an air supply for generation of an air curtain in front of the window 13, via an air inlet 19, the cooling air and/or, as represented, a separately supplied air current being blown out parallel to the window 13 and thus parallel to the surface 2' of the die plate 2 in order, by an air curtain, to prevent contaminations of the window 13 without the air jet being able to reach the layer material in the die opening or become turbulent. The image scanned with the camera 12 can also be transmitted via the cable 18, a separate signal cable or by radio.

[28] For the person skilled in the art, numerous modifications emerge from the preceding description which should fall within the range of protection of the appended claims. According to the configuration of the processor of the machine control system and of the controller for the camera, the scanned image signal can be optionally further processed and converted into control signals. The tablet core and the die opening can have basically any shape. The tablets in question can be core tablets with full coating, as shown, but also bull's eye tablets in which the tablet core, in the finished tablet, is exposed, since after the first pressure station no material for a second layer is loaded, as is commonly known per se for the production of different multilayer tablets with tablet cores, i.e. so-called core tablets. In principle, the core tablet could also be deposited first and then layer material applied on top. Even though allusion is made to tablets and tablet cores, the rotary press according to the invention can be used for all types of compacts with inserted core. The optical system can comprise all types of image sensors and lenses, particularly including a high-speed camera or the like, in particular cameras of the kind which can deliver a single image in dependence on a control signal. The core-inserting device can feed the tablet cores also linearly or vertically and/or can be provided with an actuator for the accelerated depositing of the tablet cores.

Claims

[Claim 1] 1. Method for producing multilayer tablets with the use of tablet cores on a rotary press, comprising the steps

- feeding of tablet cores to a core-inserting device (20),

- transfer of the tablet cores with the core-inserting device (20) to a die opening (9) in a die plate (2) of the rotary press,

- finishing of a tablet within the die opening (2) with the pressing tools (5, 6) of the rotary press, and

- removal of the tablet from the rotary press, characterized in that, with an optical system (10), the position of the tablet core (60) in the die opening (9) is registered after the transfer step.

[Claim 2] 2. Method according to Claim 1, characterized in that, with the optical system (10), the position of each tablet core in the die opening or the actual fill state of each die opening (9) is registered behind the transfer station (25), and the detection signal or image signal of the optical system is further processed with an image- analyzing device (52) and/or with a processor.

[Claim 3] 3. Method according to Claim 1 or 2, characterized in that the optical system is assigned to a die position of a die opening (9) of the die plate, which, in the rotational direction, lies offset by between one and five dies, preferably two or three dies, relative to the die opening positioned beneath the core-inserting device (20).

[Claim 4] 4. Method according to one of claim 1 to 3, characterized in that, via a detection signal (55) or via the image signal of the optical system, a differentiation is made between bad tablets and good tablets.

[Claim 5] 5. Method according to Claim 4, characterized in that, from the detection signals or image signals for all good tablets, a mean value for an average eccentricity of the tablet core within the die opening is formed, which is used as a control signal (59A, 59B) for controlling the core-inserting device (20).

[Claim 6] 6. Method according to one of claims 2 to 5, characterized in that the detection signal of the optical system is usable or is used as a control signal (59A, 59B) for the core-inserting device (20) and/or for a discharging device (75) for bad tablets.

[Claim 7] 7. Method according to one of claims 1 to 6, characterized in that the core-inserting device (20) has a turntable (21) drivable with an electric motor (22), and in that the die plate (2) is driven with a separate electric motor, a phase displacement between these electric motors being adjustable or being adjusted via a machine control system (50).

[Claim 8] 8. Method according to one of claims 1 to 7, characterized in that a machine control system (50) delivers a triggering signal (56) to the optical system (10), in dependence on which the optical system registers a single image as an image signal (53), whereupon the single image is preferably compared with a desired image in an analyzing device (52) of the optical system or in the machine control system (50) and, in the event of deviations from the desired image, a control signal (58) for a discharging device (75) is generated.

[Claim 9] 9. Rotary press for producing multilayer tablets with the use of tablet cores, comprising a die plate (2) having peripherally offset die openings (9), comprising pressing tools (5, 6) for producing tablets within the die openings (9), comprising at least one filling station (40) for supplying material for a layer of the multilayer tablet, comprising a feed device (24) for tablet cores, comprising a core-inserting device (20) for transferring and positioning the tablet cores into the die openings (9) of the die plate at a transfer station (25), and comprising a run-off (74) for the removal of the tablets from the rotary press, characterized by an optical system (10) for registering the position of the tablet core in the die opening (9) after the transfer station (25).

[Claim 10] 10. Rotary press according to Claim 9, characterized in that the optical system (10) is assigned to a die opening (9) or die position which, in the rotational direction (R) of the die plate (2), lies offset by between one and five dies, preferably two or three dies, relative to the transfer station (25).

[Claim 11] 11. Rotary press according to Claim 9 or 10, characterized by an analyzing and control device (52; 50) for analyzing detection signals or image signals (53) of the optical system (10) and for generating a control signal (59A, 59B) for the core-inserting device (20) and/or an electric motor as rotary drive for the die plate.

[Claim 12] 12. Rotary press according to one of claims 9 to 11, characterized in that, above a die (9), a mirror (17) is arranged peripherally offset relative to the transfer station (25), the mirror preferably being a constituent part of a camera housing (11) of the optical system.

[Claim 13] 13. Rotary press according to Claim 12, characterized in that the mirror (17) has a mirror surface (17') which stands obliquely to the surface (2') of the die plate, preferably at an angle of 40° to 60°, in particular at an angle of about 45° obliquely to the surface.

[Claim 14] 14. Rotary press according to one of claims 9 to 13, characterized in that the optical system has an image sensor and/or a lighting device (15), in particular an LED as light sources, preferably at least one high- power LED being disposed in the camera housing (11).

[Claim 15] 15. Rotary press according to Claim 14, characterized in that the lighting device has a plurality of light sources (15), in particular heavy duty LED's, The lighting device preferably has a plurality of light sources, which are preferably arranged annularly around the image sensor or a lens (14) assigned to the image sensor and/or generate via the mirror (17) a diffuse light.

[Claim 16] 16. Rotary press according to Claim 14 or 15, characterized in that the light source (15) consists of a high-power light-emitting diode (LED), which is preferably disposed in the housing (11) of the optical system.

[Claim 17] 17. Rotary press according to one of claims 13 to 16, characterized in that the optical system has a light guide which is assigned to the light sources and the end of which is positioned above the transfer station or peripherally offset relative to the transfer station above a die opening.

[Claim 18] 18. Rotary press according to one of claims 9 to 17, characterized in that a camera housing of the optical system is provided with an air connection for cooling air for the light sources, and/or with an air outlet (19) for generating an air curtain in front of an optical window (13) lying facing the die opening (9).

[Claim 19] 19. Rotary press according to one of claims 9 to 18, characterized in that the core-inserting device (20) has a turntable (21), which is rotary - drivable with an electric motor (22) and which has a servo drive (26) that is preferably actuable in the radial direction of the die plate (2), the machine control system (50) being coupled by control engineering methods to the electric motor of the turntable and/or the servo drive of the core-inserting device and being able generate control signals (59A, 59B) in dependence on the image signals (53) of the optical system.