EP0775531B1 - Process and device for monitoring continuously the dispensing of fluid - Google Patents

Description

The invention relates to a method and an apparatus according to claim 1 and claim 3, in which liquid is sprayed onto solids via nozzles.

Such liquid additions take place, for example, in the pharmaceutical industry during the coating process. Especially during tablet coating. Usually, tablet cores are coated with a colorant-containing polymer film. On the one hand this is done to favorably influence the mechanical properties of the tablets, to achieve better swallowability of tablets and to mask unpleasant taste effects of active substances, and on the other hand to modify the release of active ingredients of tablets (for example enteric or retarding coatings). Especially with coatings that affect the effectiveness of a tablet, high demands are placed on the uniformity and homogeneity of the film coating.

A commonly used process today is the coating of tablet cores in rotating drums or boilers by spraying a lacquer suspension from suitable two-fluid nozzles. This process is also called "automated coating". In this process, the lacquer suspension is sprayed continuously over several hours on the tablet bed within the drum.

In all machines that operate on the principle described above, for example, the machine "Accela Cota" Manesty, "Glatt Coater" Glatt, "Driacoater" Driam, "Hi-Coater" Lödige and "Butterfly Coater "of the company Hüttlin, the uniformity of the spraying process must be constantly monitored by the staff. Irregularities of the coating process are often difficult for the monitoring personnel to perceive, since they take place inside the rotating drums. Frequently, the lack of uniformity of the spraying process is recognized only when faulty batches occur. Incorrect spraying will result in sticky tablets, loosened tablets, visual imperfections in the tablet surface, inhomogeneities or even poor drug release in the failed lots.

In EP-A-222258 (see the preamble of claim 3) describes a monitoring device for a spray apparatus which is used for fluid or semi-fluid products, such as abrasive pastes.

However, the problem presented here with reference to the example of tablet coating arises just as in the coating of foods in the food industry, for example coated chocolate or in the liquid addition of spray nozzles when granulating solids in the basic industries.

The object of the present invention is now to provide a method and a device for automatic continuous monitoring of the addition of liquid in a process in which a liquid is sprayed onto solids via nozzles.

This object is achieved by a method with the additional features of the characterizing part of claim 1. The object is also achieved by a device with the additional features of the characterizing part of claim 3.

According to the invention, in the coating process, which is used in particular for producing the surface of film tablets or dragees, the liquid addition is monitored continuously, during which a liquid is sprayed onto solids via nozzles. The emerging from the respective nozzle liquid spray cone is detected by means of an electro-optical monitoring unit and compared with a reference image, wherein the parts of the electro-optical monitoring unit, which are arranged in the vicinity of the monitored Flüssigkeitssprühkegels encapsulated and wherein within the enclosure for the encapsulated parts of the electro-optical monitoring unit, a gas pressure is generated, so that sets a laminar gas flow to the outside environment of the enclosure out. This can be automatically ensured by a spray pattern control that the liquid is sprayed uniformly in the desired distribution to the solid. Advantageously, each nozzle, which generates a corresponding spray cone of the liquid to be sprayed, is assigned a corresponding electro-optical monitoring unit. Alternatively, however, a corresponding movable electro-optical monitoring unit can be provided, which moves cyclically juxtaposed nozzles and checked in a predetermined time cycle.

By installing this electro-optical monitoring unit, the continuity of the matching process can be monitored and documented. If deviations occur, the production process can be interrupted so that the coating process or the granulation process becomes safer and reproducible. Due to the automatic monitoring, a later upgrade of different control levels is possible at any time. This way, a faulty nozzle can be switched off and a new nozzle can be switched on. The coater types mentioned above could be retrofitted with a device for carrying out the method according to the invention in a simple manner, so that here a subsequent Automation of the control process is possible.

According to a preferred embodiment of the invention, a warning signal or a signal for switching off the process can be issued if the electro-optical monitoring unit detects a deviation of the recorded image of the liquid spray cone, which is greater than a predetermined limit.

According to the invention, the object is achieved by a device for carrying out the aforementioned method, which has an electro-optical monitoring unit which is aligned such that it detects with its optical beam path emerging from the nozzle spray cone.

The electro-optical monitoring unit may consist of a device for emitting light and a receiving device for receiving the spray image information. In this case, the device for receiving the spray pattern can consist of a video camera. The current spray image information can be compared in a predetermined cycle, for example in a 5 second cycle with a stored image information, so as to detect any resulting deviations.

If the lighting conditions are sufficient, the device for receiving the spray pattern can also consist of a simple video camera.

Basically, the use of a video camera is not necessarily necessary. Rather, other photosensitive sensors can be used to detect a emitted from the device for emitting light beam path that absorb the intensity differences of the light with sufficient accuracy.

The individual optical components can be connected in a stationary manner to the liquid feed, in which the nozzles are integrated, via a corresponding holder.

The electro-optical monitoring unit may consist essentially of a video camera and an evaluation.

According to the invention, the above-described method or device can be used for a coating process, in particular for producing the surface of a film tablet or a dragee. In this case, the continuous monitoring can take place within a mixing drum of a drum coater.

Another use according to the invention of the previously described method or apparatus is the granulation of solids.

Fig. 1:

Einen schematisierten Schnitt eines Trommelcoaters, in welchem die Erfindung in einer Ausführungsform durchgeführt werden kann,

Fig. 2:

einen Schnitt entlang der Linie A-A gemäß Fig. 1.

Further details and advantages of the invention will be explained in more detail with reference to an embodiment shown in the drawing. Show it:

Fig. 1:

A schematic section of a Trommelcoaters in which the invention carried out in one embodiment can be,

Fig. 2:

a section along the line AA according to Fig. 1 ,

The in Fig. 1 only partially shown Trommelcoater 10 has a polygonal drum 12 which rotates in the direction of arrow a about its axis of symmetry. Into the interior of the drum coater projects a liquid feed line 14 in which spray nozzles 16 are integrated at uniform intervals. The spray nozzles are oriented so that the spray cone 18 produced by them sweep the fixed bed 20, which consists of tablet cores. The tablet cores are circulated by rotating the drum 12 in the direction of arrow a. The circulation process is supported by built-in mixing tools, not shown here, as they are well known in the art.

The liquid to be sprayed consists in the illustrated embodiment of a film former or paint, which is completed in a stirred tank, not shown here and is pumped via a metering pump, also not shown here in the liquid feed 14.

The not yet provided with the film tablet cores are filled in batch mode in the drum, so that the fixed bed 20 results, and after forming the desired film again emptied from the drum 12. Uneven film formation takes place when due to a clogging or malfunction of a nozzle 16 of the spray cone 18 collapses in itself and drips the applied liquid, for example in the form of drops 22 on the fixed bed. Here a number of tablet cores is not sprayed with the appropriate film former and other tablet cores on which the corresponding drops 22 impinge are coated unevenly, so that it fails to batches can come.

The spray pattern control according to the invention is now carried out by the in the sectional view according to Fig. 2 closer illustrated electro-optical monitoring unit 24, the in Fig. 1 is not shown in detail for reasons of simplification. Each nozzle 16 is associated with a corresponding electro-optical monitoring unit 24. The individual components of the electro-optical monitoring unit are connected to the liquid supply line 14 via a rigid linkage 26. In the embodiment shown here, the electro-optical monitoring unit 24 comprises a device for emitting light 28, which is aligned so that the beam path 30 intersects the spray cone, and as a receiving device, a video camera 32, which is arranged opposite to the device for emitting the light 28 like this in Fig. 2 is shown schematically. The recorded images are adjusted in predetermined time interval in the evaluation electronics not shown here with reference images. In the event of deviation of the compared images beyond a predetermined limit, a signal may be given to the controller of the drum coater to initiate the controlled departure of the coater.

Claims (9)

1. A coating method, in particular for the manufacture of the surface of film tablets or pills, having a continuous monitoring of the liquid dispensing during which a liquid is sprayed onto a solid via nozzles (16), wherein the liquid spray cone (18) discharged from the respective nozzle (16) is detected by means of an electro-optical monitoring unit and is compared with a reference image, wherein the parts of the electro-optical monitoring unit (28, 32) which are arranged in the proximity of the monitored liquid spray cone (18) are encapsulated and wherein an excess gas pressure is generated within the encapsulation for the encapsulated parts of the electro-optical monitoring unit (28, 32) such that a laminar gas flow toward the external surrounding of the encapsulation is adopted.
2. A method in accordance with claim 1, characterised in that a warning signal or a signal to shut down the process is emitted if the electro-optical monitoring unit (28, 32) determines a deviation of the taken image of the liquid spray cone (18) which is larger than a preset limit value.
3. An apparatus for the carrying out of the method in accordance with claim 1 or claim 2, which comprises a nozzle (16) via which a liquid is sprayed on in use, characterised in that it has an electro-optical monitoring unit (28, 32) which is aligned such that its optical ray path (30) detects the spray cone (18) discharged from the nozzle (16) in use and compares it with a reference image and which has means for the generation of a laminar gas flow, wherein the parts of the electro-optical monitoring unit (28, 32) which are arranged in the proximity of the monitored liquid spray cone (18) are encapsulated and wherein??? an excess gas pressure is generated within the encapsulation for the encapsulated parts of the electro-optical monitoring unit (28, 32) by the means for the generation of a laminar gas flow such that a laminar gas flow toward the external surrounding of the encapsulation is adopted in operation.
4. An apparatus in accordance with claim 3, characterised in that the electro-optical monitoring unit (28, 32) consists of an apparatus for the transmission of light (28) and of a receiver device for the reception of the spray image information (32).
5. An apparatus in accordance with claim 3 or claim 4, characterised in that the apparatus for the taking of the spray image (32) is a video camera.
6. An apparatus in accordance with any one of the claims 1-5, characterised in that the individual components are connected in a fixed position via a corresponding holder (26) to the liquid supply line (14) into which the nozzle (16) is integrated.
7. An apparatus in accordance with claim 3, characterized in that the electro-optical monitoring unit (28, 32) substantially consists of a video camera and an electronic evaluation system.
8. An apparatus in accordance with any one of the claims 1 -7, characterized in that the laminar gas flow can be generated inside the encapsulation of the electro-optical monitoring unit (28, 32) using sterile compressed air.
9. Use of a method in accordance with claim 1 or 2 or of an apparatus in accordance with any one of the claims 3-8, characterized in that the continuous monitoring takes place inside a mixing drum of a drum coater.

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