Abstract:
A tablet tester has a screw-like vibratory conveyor and isolating unit, a positioning unit having a transport rake and an orientation unit between the two first-mentioned units, which in particular is in the form of a linear vibratory conveyor. A sensor arrangement triggers the transport rake and permits automatic ejection of tablet residues via a fragment trap.

Description:
This is a continuation of Internation Application PCT/EP97/06200 filed Nov. 7, 1997, of the same inventor, and claims benefit of Provisional application Ser. No. 029,889 filed Nov. 8, 1996. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This is a continuation of International Application PCT/EP97/06200 filed Nov. 7, 1997, of the same inventor. 
     The invention relates to a tablet tester. 
     Tablet testers are apparatuses which are used mainly in the pharmaceutical industry or in science and research. Since medicaments which are administered in tablet form must in some cases meet very precise quality and quantity requirements, parameters of the respective tablets which are determined at least on random samples are measured. 
     2. Discussion of Relevant Art 
     Apparatuses which accommodate a plurality of testing or measuring stations and in which tablets are transported from a storage container to the individual station are known for such measuring processes. An example of such an apparatus is the combination tablet tester “Multicheck” from ERWEKA, D-63150 Heusenstamm. It permits the automatic or computer-controlled measurement of weight, thickness, diameter and hardness of individual tablets, which have to be delivered in succession from a storage container. 
     However, it is precisely the individual delivery of tablets that is a problem in such apparatuses. Thus, the very company mentioned is attempting, by means of EP-B1-170670, to describe a particularly suitable transport means for tablets within such a combination tablet tester. The transport means is designed in such a way that a rake having V-shaped forks pushes the tablets over a guide track which has exactly dimensioned holes through which unsuitable tablets are intended to fall. This apparatus thus forms a sort of sieve, the size of the tablets and their (accidental) position relative to the forks determining whether they are transported further or fall through the holes. There remains therefore an uncertainty which may lead to delays in measurement or incorrect measurements. Apart from this, the solution offered by ERWEKA may be susceptible to faults in the region in which the tablets are fed to the rake or cannot always ensure that the tablets also reach the required position and enter the rake individually. For some of the individual measuring stations, it is in fact important whether the tablets are vertical or horizontal and whether they are delivered longitudinally or crosswise. If more than one tablet is present in a fork of the rake, these tablets cannot be measured or the result is a rejected measurement. 
     On the other hand, the rejection of tablet fragments before passage through the measuring stations is not ensured in the known apparatus, so that here too incorrect measurements can occur. 
     There is thus no satisfactory, universal technique in this context particularly for different tablet shapes. This leads to the necessity of conversions for different tablet shapes or to a loss of time during measurement. 
     In an attempt to improve the situation, Norbert Krämer of D-6100 Darmstadt has provided a relatively complicated isolating apparatus having baffles for tablets, which is described in DE-C2-3711827. His apparatus is intended to isolate tablets over particularly short distances. However, this description offers no solution for further transport to the individual measuring stations. Furthermore, the problem of positioning and of the rejection of tablet fragments is not solved by Krämer. 
     Another manufacturer, Elisabeth Hata, uses Krämer&#39;s isolating apparatus but without its baffles, which leads to adequate isolation in the case of relatively large tablets but to trouble-prone isolation in the case of smaller tablets. 
     SUMMARY OF THE INVENTION 
     It is therefore the object of the invention to provide a tablet tester which effects fault-free isolation, places the tablets in the correct position and as far as possible is universally applicable for a very wide range of tablet shapes. Incorrect measurements are to be avoided during operation, thus permitting in general faster measurement than in the past. 
     This object is achieved by the combination of individual apparatuses known per se in an inventive manner. Some of these apparatuses have furthermore been improved in an inventive manner compared with the known apparatuses. 
     The general structure consists, according to the invention, of an isolating unit, which is preferably in the form of a conventional “EMSE” vibratory screw conveyor having a chute, an orientation unit which is in the form of a linear vibratory conveyor converted according to the invention. A particular further development provides a tablet sensor having an inventive fragment trap and a special positioning rake above a transport surface, which transports the previously correctly positioned tablets, checked for waste, to measuring stations, as far as a residue trap. 
     This object is achieved according to the invention by a tablet tester comprising at least one measuring station and a conveyor that conveys and isolates tablets, having a downstream orientation unit and a positioning rake connected thereto above a transport surface that transports said tablets to said measuring station, wherein said orientation unit comprises a linear vibratory conveyor that has a structure L-shaped in cross-section and an inclination portion and a radius between two limbs of the L-shape, which conveyor has a horizontal conveying surface in a region where said conveyor enters said positioning rake. The specification describes inventive embodiments which can also be used independently and regardless of the main concept of the solution. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details, advantages and potential applications of these solutions are presented in the description of the Figures. 
     The information in this context in this patent application should be understood as being merely by way of example in that detailed solutions other than those described are also possible within the scope of the patent claims. 
     FIG. 1 shows a symbolic setup in plan view, 
     FIG. 2 shows a prototype setup in oblique view, 
     FIG. 3 shows the prototype setup in plan view without a cover, 
     FIG. 4 shows the transfer from a screw conveyor to a linear conveyor in the prototype setup, 
     FIG. 5 shows a rake in the prototype, 
     FIG. 6 shows the residue trap at the end of the rake and 
     FIG. 7 shows an exemplary detailed drawing of a tablet sensor in plan view, FIG. 7 a  showing the closed sensor and FIG. 7 b  showing the opened sensor with exposed fragment trap. 
     FIGS. 8 a - 8   f  show interchangeable support disks to support tablets of different shapes and sizes at a hardness measuring station. 
     FIG. 9 shows an adjustment arrangement for the radius of a linear vibratory conveyor. 
     FIG. 10 shows an adjustment arrangement for inclination of the linear vibratory conveyor. 
     FIGS. 11 and 12 show adjustable or pivotable prongs of a rake. 
     FIG. 13 shows brushes or felt strips on the underside of prongs of a rake. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The Figures are described in relation to one another, identical parts being denoted by the same reference symbols. 
     FIG. 1 shows a conventional vibratory screw conveyor  1  having a feed hopper  5  whose outlet ends in a chute  4 . The vibratory conveyor isolates tablets and transports them against the force of gravity into the chute  4 . Connected to this is a specially designed orientation unit  3  which could also be used independently in other comparable apparatuses. 
     The special feature of this unit which may also be used independently and which essentially consists of a linear vibratory conveyor is an inclination  12  which is shown in section and which results in the tablets—provided that they have an elongated structure—being oriented in the longitudinal direction parallel to the orientation unit  3 . Toward the end of the orientation unit  3 , the inclination  12  connects, according to the invention, with an approximately horizontal conveying surface  28 . At the lowest point of the orientation unit  3 , the latter is provided with a radius  13  which causes upright tablets to fall over so that they rest with their broad side on the inclination  12  and then on the conveying surface  28 . 
     As shown in FIG. 9, the angle a of the radius  13  is adjustable by a spring-based adjusting screw  40 . 
     FIG. 10 shows an arrangement  41  for adjustment of the inclination angle β of the orientation unit  3 . FIG. 10 also shows prongs  18  of the positioning rake  7  that are pivotable on the wall  43  of the rake  7  to receive tablets conveyed to the transport surface  24  by the orientation unit  3 . 
     For particularly difficult tablet shapes, it is also possible to arrange baffles  11  which can force a tablet  25  on the one hand to fall over but on the other hand also to adopt a certain longitudinal or crosswise orientation. According to the invention, these baffles  11  can easily be removed or replaced so that they can be changed if required, without having to interrupt operation for a long time. Owing to the carefully thought out shape of the orientation unit  3  with inclination  12  and radius  13 , however, the use of baffles  11  can be dispensed with for most tablet shapes. 
     The orientation unit  3  connects with a positioning unit  2 , at the beginning of which a fragment trap  9  is mounted and at the end of which a residue trap  10  is mounted. The positioning unit  2  holds measuring stations  8  and has a laterally displaceable positioning rake  7  with prongs  18  for laterally conveying tablets  25  to the individual measuring stations  8 , for example a weighing cell  8   a , a thickness measuring station  8   b  and a hardness measuring station  8   c.    
     As shown in FIGS. 11 and 12, according to the invention, some of the prongs  18  are inclined slightly more than 90° from the feed direction (cf. angle  30 ). This leads to an automatic displacement vector at the conveyed tablets  25  in the direction of the front support wall  31 , which is advantageous in that individual measuring stations  8  with their structures are also oriented relative to the support wall  31  and it is important that the tablets  25  arrive at these structures in the correct position. For the purposes of the invention, it is of course also possible to provide a different inclination of the prongs  18 , for example in the other direction, if the tablets  25  are also to be moved away from the support wall  31  during their further transport. This possibility also includes adjustable inclinations of the prongs  18  in order to be able to adapt them to changing circumstances. 
     According to a particular embodiment (FIG.  13 ), the prongs  18  have, on their lower side, brushes  34 , a felt strip or the like, which serve to free the guide track from dust (tablet dust). By moving the rake  7 , this is optimally effected simultaneously with the conveying of the tablets. The rake  7  executes a lateral displacement, is then raised and is moved back through the same lateral displacement distance and then lowered again, and the next lateral displacement can be carried out. 
     The last measuring station  8   c  has, as a special feature according to the invention, an elongated indentation  32  which permits final longitudinal positioning of elongated tablets before they are gripped by the clamping jaws  33   a, b.    
     According to a particular embodiment of the invention, clamping jaws  33  and the final prong  18  are designed in such a way that caked tablet residues on the jaws  33  and/or on the guide plane are eliminated. The results of the measurement are thus optimized. 
     According to the invention, the first fragment trap  9  is covered by a tablet sensor  6  which, on arrival of a tablet  25 , triggers the transport rake  7  and at the same time opens a gap of, for example, 3 mm (cf. FIG. 7 a ) in order simultaneously to allow tablet fragments also delivered to drop downward. 
     In the case of an impermissible double delivery, the sensor  6  according to the invention can also detect this and can open the fragment trap  9  in order to prevent further errors. 
     For the purposes of the invention, “sensor” also includes a straightforward, releasable “stop” for tablet residues or the like, provided that this is controlled as a function of the conveyed tablets or tablet residues. In particular, the sensor may also comprise a light barrier, optionally with an image-forming optical system. In one embodiment, however, the sensor is designed as a mobile slide provided with a piezoelectric switching surface. 
     In a particular variant of the sensor  6 , the latter has, for example, optical measuring sensors which are known per se, are not shown, detect the completeness of a tablet  25  and, in the negative case, open the gap to such an extent that even large fragments can fall downward through the fragment trap  9  (cf. FIG. 7 b ). 
     A possible sensor setting would be, for example, as follows: if a tablet having a diameter of 6 mm arrives, said sensor travels back briefly to the gap width of 2-3 mm and then forward again so that the tablet comes to rest 1-2 mm before the support surface of the support wall  31 . By widening the gap, any fragments fall away; by pushing back the tablet  25 , the latter is positioned for certain measuring stations. 
     Also within the scope of the invention are of course variants having a particular software control which makes it possible, for example, to transport excess tablets from a measuring series out of the vibratory screw conveyor  1  and the orientation unit  3  by virtue of the fact that, after a certain tablet quantity detected by the sensor and further conveyed by means of rake  7 , the fragment trap  9  is opened by the sensor. 
     The traps  9  and  10  each enter a box  15  at the front of the apparatus, so that these can be emptied in a user-friendly manner, which is also a particular advantage of this variant of the invention. 
     A transparent cover  14  protects the apparatus from dust and undesired access without obscuring the functions or the correct functional sequence. 
     An optionally coverable (FIG. 2) display  19  and an input unit  20  (FIG. 5) permit the control of the apparatus, unless it is in any case controlled by means of computer  17  (FIG.  2 ). 
     The drives and electrical controls of the apparatus are housed in the interior of a rack  16  which carries the parts described. 
     In a particular embodiment of the invention, all running surfaces or sliding surfaces with which the tablets  25  may come into contact are provided with a low-friction treatment, for example electrolytically polished, provided with high-gloss chromium plating or polished. 
     In a further embodiment of the invention, the weighing pan  26  of the weighing cell  8   a  is arranged in such a way that its axis transverse to the transport direction is identical to the transverse axis of a conveyed tablet, whereas the central axis of a tablet parallel to the support wall  31  does not necessarily correspond to the central axis of the weighing pan  26 . Preferably, the tablet is as close as possible to the support wall  31 , just so that its full circumference rests on the weighing pan  26 . This can also be achieved, inter alia, if the sensor  6  comes to rest with its stop edge about 1.5 mm before the support surface of the support wall  31 —and if necessary is moved forward. 
     Further information regarding the Figures is shown in the list of reference symbols. 
     The invention is not restricted by the embodiments stated so far. It covers a broader range: 
     For the purposes of the invention, “tablets” also mean “capsules” or the like. 
     “Baffles” also include “deflectors” and can, if required, also be formed by air nozzles or the like. 
     Air or vacuum nozzles can moreover be mounted in a plurality of locations, in a manner not described in detail, for example for the purpose of automatic cleaning, just as compressed air may also be provided for controlling the mechanical components. 
     In a further variant, the orientation unit  3  can also be provided with a diverter or a sensor ejector which, independently of the sensor  6 , can influence control of tablets. For example, isolation which is not yet satisfactory can thus be monitored and corrected. On the other hand, it would also be possible for a plurality of tablets to be present directly one behind the other in the orientation unit and to be further transported singly by opening such a diverter. As a rule, however, the tablets should be delivered singly. 
     As a further variant, it is possible to design the chute  4  to be rotatable, so that a further facility for emptying into a further container not shown is possible. However, owing to the sensor properties according to the invention, this will generally be superfluous. 
     In a further particular embodiment of the invention, the positioning or transport rake is provided with laterally adjustable or pivotable prongs  18  which are adjusted as a function of the width of tablets so that tablets whose longitudinal dimension is at right angles to the transport direction are moved in exactly this position. The prongs  18  of the transport rake thus rest laterally against tablets as soon as the latter are moved in the transport direction. After the movement of the tablets, the prongs open slightly, are then raised as in the variant described above and are moved back in order to grip the next tablets and to transport them. This prong movement is automatically controlled as a function of the tablet structure. This particular embodiment has the advantage that even tablets arriving in a slightly skew position can be correctly positioned and that moreover, with transport by means of the transport rake, the tablets cannot be accidentally swivelled out of their position. The opening of the prongs shortly before raising of the transport rake is advantageous according to the invention because it avoids the tablets being accidentally set on edge as a result of friction against the prong walls. 
     A further particular embodiment is provided in the region of the hardness measuring station  8   c.  Instead of the indentation  32  as shown in FIGS. 8 a - 8   f , it is also possible to provide there an interchangeable support disk which has a comparable indentation, the different support disks having different indentations. Tablets are in fact produced in different sizes, so that the function of the apparatus is improved if the indentation  32  is adapted to the tablet size. An indentation  32  which is too narrow would not produce a positioning effect since the excessively broad tablet would not sink into the indentation. A smaller tablet on the other hand could sink too deep in the indentation  32  so that the press jaws cannot engage the tablet optimally. 
     LIST OF REFERENCE SYMBOLS 
       1 . Isolating unit or vibratory screw conveyor 
       2 . Positioning unit 
       3 . Orientation unit with linear vibratory conveyor 
       4 . Chute 
       5 . Feed hopper 
       6 . Tablet sensor 
       7 . Positioning rake or transport rake 
       8 . Measuring stations 
       8   a . Weighing cell 
       8   b . Thickness measuring station 
       8   c . Hardness measuring station 
       9 . Fragment trap 
       10 . Residue trap 
       11 . Baffles 
       12 . Inclination; can if necessary also be adjustable 
       13 . Radius; can if necessary be adjustable or interchangeable 
       14 . Cover 
       15 . Box 
       16 . Rack 
       17 . Computer 
       18 . Prongs 
       19 . Coverable display 
       20 . Input field/input unit 
       21 . Chute cover 
       22 . Measuring slide 
       23 . Drive/brush 
       24 . Conveying track 
       25 . Tablet 
       26 . Weighing pan 
       27 . Positioning recess 
       28 . Approximately horizontal conveying surface 
       29 . Gap 
       30 . Angle 
       31 . Support wall 
       32 . Indentation, positioning recess 
       33 . Clamping jaws 
       34 . Brushes 
       35 . Conveying surface