Patent Publication Number: US-2020278290-A1

Title: Tablet measuring apparatus and tablet measuring method

Description:
TECHNICAL FIELD 
     The present invention relates to a tablet measurement technique for measuring physical properties of tablets, including the film thickness, contents of active ingredients and the like and, more particularly, to a tablet measuring apparatus and a tablet measuring method for measuring physical properties of tablets using an optical sensor. 
     BACKGROUND ART 
     In the manufacture of pharmaceutical products, in recent years, process analytical technology (PAT) is becoming increasingly important in view of the manufacture of tablets of stable physical properties. While, for example, various functions such as masking and enteric properties are imparted with a tablet by coating a film on its surface, film thickness control of a coated film may be needed as one of the steps in the process analysis. As a solution to the need, heretofore, there has been known a technique of controlling the coating thicknesses of tablets, including the step of sampling a fixed number of tablets during or after coating process and calculating the film thickness of each tablet from the weight difference between the film-coated tablet and the uncoated tablet. There has also been known a technique of using a measuring apparatus which uses an optical sensor such as a near-infrared (NIR) sensor to measure tablets on a one-by-one basis. Further, as described in Patent Document 2, attempts have been made to provide a light-transmitting member at a part of a tablet coating apparatus and to use a sensor to perform measurements of tablets during coating process by way of the light-transmitting member. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: JP 2013-096717A 
     Patent Document 2: JP 2011-136311A 
     Patent Document 3: JP 2017-038908A 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, since the technique of using weight difference of tablets between before and after the coating process does not take measurements of tablets on an individual basis, it may pose lack in accuracy as a film thickness control scheme. On the other hand, the method of using an optical sensor, which is capable of individual-based tablet measurement, can output accurate measurements, but requires complex operations and hence is inefficient. Further, the system where a light-transmitting member is provided in a part of a tablet coating apparatus can manage real-time measurement; however, in the system, the distance between the tablet surface and the sensor is not constant, and besides, each tablet poses differently. For the above reasons, the system providing a light-transmitting member does not always give reliable measurement results. 
     Means for Solving the Problems 
     A tablet measuring apparatus according to the present invention is a tablet measuring apparatus for measuring physical properties of a tablet ejected from a tablet coating apparatus, characterized by comprising: a tablet receiving section to which a tablet is introduced; a measuring section for measuring physical properties of the tablet while conveying the tablet; a tablet feeding section for feeding the tablet introduced to the tablet receiving section to the measuring section; and a recovery section for returning the tablet whose physical properties have been measured to the tablet coating apparatus. The measuring section has an optical sensor capable of measuring the physical properties of the tablet in a non-contact manner. 
     In the present invention, the tablet receiving section receives a tablet from the tablet coating apparatus and the tablet feeding section passes the tablet over to the measuring section. The tablet delivered to the measuring section is concurrently conveyed and measured in terms of physical properties thereof. The tablet having undergone the measurement is fed back from the recovery section to the tablet coating apparatus. The tablet measuring apparatus so configured as described above enables to can sequentially take accurate physical property measurements of each tablet, to grasp the coating thickness and the like of the tablet precisely on a real-time basis, and to achieve improvement in product quality. 
     In the tablet measuring apparatus of the invention, the measuring section may include a sensor positioning mechanism capable of adjusting the distance between the optical sensor and the tablet. Thereby, the optical sensor can be adjusted to the best position suited for every individual tablet to be measured. Therefore, measurement can be carried out while keeping the distance from each individual tablet constant at all times, which enables to conduct reliable physical property measurements. Further, an NIR sensor can satisfactorily serve as the optical sensor. 
     Further, the measuring section may include a conveying unit that sucks/supports the tablet while conveying the tablet. In that case, as the conveying unit, a conveyance disk can be used, which has sucking portions formed circumferentially at its end face so as to suck the side face of the tablet, whereby the conveyance disk-can suck/support the side face of the tablet in such a way that the front and back faces of the tablet are fully exposed. It is also possible to employ a belt conveyor which conveys the tablet being sucked to it. 
     Meanwhile, the tablet measuring method of the present invention is a tablet measuring method for measuring physical properties of a tablet ejected from a tablet coating apparatus. This method is configured to convey the tablet and, at the same time, measure the absorbance of the tablet using an optical sensor, calculate physical properties of the tablet from calibration curves concerning the physical properties and the measured value of absorbance, and return the tablet having undergone the measurement to the tablet coating apparatus. 
     In the present invention, while the tablet is being conveyed, the absorbance of a tablet is measured by the optical sensor and physical properties of the tablet is calculated from calibration curves concerning the physical properties and the measured value of absorbance. This configuration makes it possible to sequentially take accurate physical property measurements of each tablet, grasp the coating thickness and the like of the tablet correctly on a real-time basis, and achieve improvement in product quality. 
     In the tablet measuring method, the calculation of physical properties may be executed under the condition of the tablet being hermetically sealed off from the exterior environment. In general, the sampling process in the physical property measurement of tablets makes it possible to acquire various data at that moment; however, the conditions of the tablets cannot be grasped sequentially in real time. Further, the sampling operation is not considered to be beneficial if the apparatus is adapted for containment system (seal-off of workpiece) to prevent cross-contamination and operators&#39; radiation exposure. In contrast, the tablet measuring apparatus and method of the present invention can perform containment-based physical property measurements, preventing product cross-contamination and operators&#39; radiation exposure from occurring. 
     Advantageous Effects of the Invention 
     The tablet measuring apparatus of the present invention includes a tablet receiving section to which a tablet is introduced, a measuring section for measuring physical properties of the tablet while conveying the tablet, a tablet feeding section for feeding the tablet introduced to the tablet receiving section to the measuring section, and a recovery section for returning the tablet whose physical properties have been measured to the tablet coating apparatus. This configuration makes it possible to sequentially take accurate physical property measurements of each tablet and hence grasp the coating thickness and the like of the tablet precisely on a real-time basis. 
     The tablet measuring method of the present invention is configured to convey a tablet and, at the same time, measure the absorbance of the tablet using an optical sensor, and calculate physical properties of the tablet from calibration curves concerning the physical properties and the measured value of absorbance. This configuration makes it possible to sequentially take accurate physical property measurements of each tablet, and hence grasp the coating thickness and the like of the tablet correctly on a real-time basis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory view illustrating the outer appearance of a tablet measuring apparatus according to an embodiment of the present invention; 
         FIG. 2  is an explanatory view illustrating the internal configuration of the tablet measuring apparatus illustrated in  FIGS. 1 ; and 
         FIG. 3  is an explanatory view illustrating a modification of the tablet measuring apparatus, where a tablet feed disk is provided as a tablet posture control unit between a measuring section and a tablet feeding section. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the present invention will be described. The embodiment described below aims to provide a tablet measuring apparatus and a tablet measuring method that can sequentially take accurate measurements of physical properties of individual tablets using an optical sensor.  FIG. 1  is an explanatory view illustrating the outer appearance of a tablet measuring apparatus  10  according to an embodiment of the present invention.  FIG. 2  is an explanatory view illustrating the internal configuration of the tablet measuring apparatus  10 . The tablet measuring method according to the present invention is implemented by the tablet measuring apparatus  10  illustrated in  FIG. 1 . The tablet measuring apparatus  10  is connected to a tablet coating apparatus (hereinafter abbreviated as “coating apparatus”) and performs a real-time measurement on the film-coating thickness and the like (physical properties) of each tablet  3  ejected from the coating apparatus. 
     As shown in  FIGS. 1 and 2 , the tablet measuring apparatus  10  has a housing  21  made of stainless steel, accommodating a measuring section  30  equipped with a conveyance disk  1  and an optical sensor  2 , a tablet feeding section  40  for feeding the tablets  3  to the measuring section  30 , and a recovery section  50  for returning the tablets  3  that have been measured to the coating apparatus. In the tablet measuring apparatus  10 , the measurement of physical properties of the tablets  3  is carried out in a condition where the tablets  3  are hermetically sealed off from outside of the apparatus (environmental containment). Therefore, the course of the tablets  3  physically traveling, namely the route from the coating apparatus to the tablet measuring apparatus  10 , respective components including the measuring section  30  within the tablet measuring apparatus  10  and the route from the tablet measuring apparatus  10  to the coating apparatus are all hermetically sealed off from the exterior environment in the airproof condition. 
     On the housing  21 , a computer (PC)  4  is disposed as control/measurement equipment. The computer  4  controls over the operation of the tablet measuring apparatus  10 , fetches physical property data of each tablet  3  in real time from the optical sensor  2 , and displays the fetched data as needed. Casters  22  are attached to the lower surface of the housing  21 , so that the tablet measuring apparatus  10  can be moved according to the needs. A tablet charging port  23 , as a tablet receiving section  20 , is opened in an upper surface  21   a  of the housing  21 . Any tablets  3  ejected from the coating apparatus are introduced into the tablet charging port  23 . A tablet recovery port  24  of the recovery section  50  is opened in a side surface  21   b  of the housing  21 . 
     The tablet feeding section  40  has a rotary feeder  41 . Into the rotary feeder  41 , the tablets  3  ejected from the not-shown coating apparatus are supplied through the tablet charging port  23 . A hopper may be provided between the tablet charging port  23  and the rotary feeder  41  to retain the tablets  3  therein and feed them to the rotary feeder  41 . The tablets  3  fed to the rotary feeder  41  are passed over to the conveyance disk  1  of the measuring section  30 . The conveyance disk  1  sucks the tablets  3  onto an end face la thereof and conveys them. Each tablet  3  being conveyed is measured by the optical sensor  2  in terms of the film-coating thickness and physical properties thereof including the contents of active ingredients. The measured data is sent to the computer  4 . The measured tablet  3  is collected at the recovery section  50  arranged in the position following the measuring section  30  and fed back to the not-shown coating apparatus through the tablet recovery port  24 . 
     In the tablet measuring apparatus  10 , as illustrated in  FIG. 2 , firstly a sampled tablet  3  is fed to the tablet feeding section  40  through the tablet charging port  23 . The rotary feeder  41  of the tablet feeding section  40  is a non-vibratory rotary parts feeder, and is constituted by coaxially forming a rotary disk  43  and an annular rotary plate  44  within a cylindrical casing  42 . The tablet  3  is fed through the tablet charging port  23  onto the rotary disk  43  while rotating. The tablet  3  on the rotary disk  43  moves in the circumferential direction by the rotation of the disk  44 , moving toward the annular rotary plate  44 . The tablet  3  on the annular rotary plate  44  then moves in the circumferential direction by the rotation of the rotary plate  44  so as to be delivered to a tablet acquiring part  45 . The tablet  3  delivered to the tablet acquiring part  45  is sucked onto the rotating conveyance disk  1  of the measuring section  30 . 
     The end face la of the conveyance disk  1  has suction holes (sucking portions)  31  connected with a suction device (not shown) such as a vacuum pump. A side face  3   c  of the tablet  3  is sucked to the suction hole  31  and hence the tablet  3  is held on to the end face la of the conveyance disk  1 . The tablet  3  is sucked to the end face la in a horizontal posture (that is, a state of a front face  3   a  and a back face  3   b  of the tablet  3  facing upward and downward in a perpendicular direction, respectively), and is conveyed in the circumferential direction without changing the posture, as rotation of the conveyance disk  1 . 
     Due to the rotation of the conveyance disk  1 , the tablet  3  sucked to the conveyance disk  1  is conveyed to the position of optical sensor  2  while keeping the horizontal posture, where physical properties of the tablet  3  such as the film-coating thickness and contents of active ingredients are measured. The optical sensor  2  is a NIR sensor that uses near-infrared rays as inspection light and takes the measurements of physical properties of the tablet  3  non-destructively in real time. The optical sensor  2  irradiates a near-infrared ray in a prescribed wavelength region (for example, about 800-3000 nm) and receives a light reflected from the tablet  3 . The data of the reflective light is sent to the computer  4 , where chemical properties of the tablet  3  such as the absorbance and transmittance of light are calculated. In the computer  4 , calibration curves concerning physical properties of the tablet  3 , including the absorbance, is stored in advance. The computer  4  calculates physical properties of the tablet  3  such as the film-coating thickness thereof, from the calibration curves and the measured values of e.g., absorbance. Alternatively, it is also possible that the optical sensor measures the surface of a tablet which is yet to be coated (uncoated tablet) and the data of reflected light on the tablet surface is stored in advance in the computer. Then, the data thus stored is compared with the data of reflected light measured by the optical sensor on the surface of the tablet having gone through the coating process, and through this comparison, the film-coating thickness of the tablet  3  can be predicted. 
     The tablet measuring apparatus  10  is provided with a height adjusting mechanism (sensor positioning mechanism)  32  which makes the height level of the optical sensor  2  adjustable in accordance with the thickness of the tablet  3  so that physical properties of various types of tablets  3  can be precisely measured. The height adjusting mechanism  32  causes the optical sensor  2  to move along X-direction (the direction perpendicular to the surfaces of the tablet) as indicated in  FIG. 2 , whereby the height level of the optical sensor  2  can be adjusted in accordance with the size of the tablet  3 . The height adjusting mechanism  32  is, e.g., comprised of a not-shown motor and a not-shown ball screw, and detects the height level of the optical sensor  2  using a position sensor including a rotary encoder or potentiometer. The data detected by the position sensor is sent to the computer  4 , where the distance between the optical sensor  2  and the tablet  3  is feedback controlled so as to take a desired value. This arrangement allows the distance between the table  3  and the optical sensor  2  to be held constant, independent of size variation of the tablet  3 . This makes it possible to perform the physical property measurement of different types of the tablets  3  under the best suited condition and hence to obtain measured data which is accurate and highly reliable. The optical sensor  2  shown in  FIG. 2  is placed above the horizontal surface of the conveyance disk to measure the upper surface of the tablet, although the optical sensor  2  may be placed below the horizontal surface of the conveyance disk to measure the lower surface of the tablet. The placement of the optical sensor above the conveyance disk can facilitate the maintenance in case of trouble, whereas the placement below the conveyance disk can make the housing compact. 
     In the tablet measuring apparatus  10 , the tablet  3  is fully exposed to the optical sensor  2  with the front face  3   a  or back face  3   b  thereof positioned vis-à-vis the optical sensor  2 . The apparatus  10 , therefore, can thoroughly measure the entire surface of the tablet  3 , allowing every corner of the tablet region to be measurable without fail. Therefore, in this respect as well, accurate and highly reliable measured data concerning the tablet  3  can be obtained. While  FIGS. 1 and 2  illustrate a configuration where the optical sensor  2  and the computer  4  are connected by a connection cable  33 , they can be connected by a wireless communication unit. 
     The tablet  3  whose physical properties have been measured by the optical sensor  2  is sent to the recovery section  50  arranged in a position following the measuring section  30 . In a position preceding the recovery section  50 , a defective product discharging section  60  is provided so as to eliminate the tablets  3  which are determined to be off-spec products (defective products) as a result of physical property measurement. In the defective product discharging section  60 , an excluder  61  is provided so as to remove defective products from the conveyance disk  1 . The excluder  61  is formed like a gear having a plurality of engaging projections  62  radially extending on the circumference thereof. Once a tablet  3  determined to be an out-of-spec product in terms of film-coating thickness or the like arrives at the defective product discharging section  60 , the excluder  61  starts rotating, causing the tablet  3  to fall off the conveyance disk  1  by the engaging projection  62 . The tablet  3  that fell off the conveyance disk  1  is excluded from the production line, while the tablet  3  which is non-defective is sent to the recovery section  50 . 
     The tablet  3  determined to be within the scope of a standard (non-defective product) is conveyed to a tablet dislodging part  34 , where the tablet  3  is released from the sucked state. Namely, the sucking action of the suction hole  31  is stopped, and hence the tablet  3  breaks away from the end face la of the conveyance disk  1 . The tablet  3  separated from the conveyance disk  1  is held within a recovery pipe  51  of the recovery section  50 . The recovery section  50  has a main body  52  connected with a not-shown ejector. The upstream side of the main body  52  is linked to the recovery pipe  51  and the downstream side thereof to the tablet recovery port  24 . The tablet  3  at the tablet dislodging part  34  is attracted to and sucked into the recovery pipe  51  and runs through the main body  52  to reach the tablet recovery port  24 . The tablet  3  having been brought to the tablet recovery port  24  is then returned to the coating apparatus by way of a not-shown conduit. 
     As described above, the tablet measuring apparatus  10  of the present invention uses the conveyance disk  1  to suck the tablets  3 , arranging the respective tablets  3  in a coordinated manner to send them to the measuring section  30 . At the measuring section  30 , the optical sensor  2  measures physical properties of each tablet  3  in a non-contact manner. At this time, the height adjusting mechanism  32  adjusts the position of the optical sensor  2  to the optimum height level that meets the size of the tablet, before the execution of the measurement. Accordingly, in the tablet measuring apparatus  10 , the entire surface of the tablet  3  can be measured at an equal distance constantly, which enables to make a reliable physical property measurement. In consequence, it is possible to sequentially and accurately measure the physical properties of each tablet, grasping the accurate film-coating thickness and the like of the tablet in real time, and hence improve the product quality. 
     Further, with respect to the tablets  3  measured in terms of physical properties, any defective products are eliminated at the defective product discharging section  60  and any non-defective products are returned from the recovery section  50  to the coating apparatus. Thus, the defective products are removed without fail, while the non-defective products are promptly returned to the processing apparatus. The tablet measuring apparatus  10  of the present invention is designed to perform speedy inspections of tablets and, therefore, it is possible to subject all of the tablets to inspection as well as picking up some of the tablets in process as samples for physical property measurement. Hence, the product quality can more reliably be improved without increasing the process time and the number of processes. 
     The present invention is by no means limited to the above embodiment and can be modified in various ways without departing from the scope of the invention. 
     In the above embodiment, for example, the processing target of the tablet measuring apparatus  10  is a circular tablet; however, the tablet measuring apparatus of the present invention can process various types of tablets such as oblong tablets, caplets and polygon-shaped tablets. Further, while, in the above embodiment, the non-vibratory rotary feeder  41  is arranged in the tablet feeding section  40 , a vibratory rotary feeder can also be applied. Further, the height adjusting mechanism  32  can take any alternative configuration other than the configuration of motor and ball screw; for instance, it is possible to adopt a pneumatic actuator or hydraulic actuator as the drive source, and a rack-and-pinion system as the power transmission mechanism. Note that not only the above-described rotary motor but also a linear motor is applicable as a motor. Moreover, for the optical sensor to be employed in the above-described 100% inspection, Raman scattered light or THz (terahertz) waves can be used in place of NIR. 
     Additionally, although the conveyance disk  1  is used to suck/convey the tablets  3  in the measuring section  30 , the conveyance unit for the tablets is not limited to this, and may be a conveyance unit using belt-conveyor system with suction holes which function to suck tablets during conveyance. Also, as illustrated in  FIG. 3 , as a tablet posture control unit, a tablet feeding disk  71  for sucking/conveying the tablets  3  may be provided between the conveyance disk  1  and the rotary feeder  41 . This configuration allows the tablets  3  to be sucked to the conveyance disk  1  while keeping its posture more stable. 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable not only to pharmaceutical tablets, but also to food products such as confectionary having a tablet shape. 
     REFERENCE SIGNS LIST 
     
         
           1 : Conveyance disk (conveyance unit) 
           1   a : End face 
           2 : Optical sensor 
           3 : Tablet 
           3   a : Front face 
           3   b : Back face 
           3   c : Side face 
           4 : Computer 
           10 : Tablet measuring apparatus 
           20 : Tablet receiving section 
           21 : Housing 
           21   a : Upper face 
           21   b : Side face 
           22 : Caster 
           23 : Tablet charging port 
           24 : Tablet recovery port 
           30 : Measuring section 
           31 : Suction hole 
           32 : Height adjusting mechanism (sensor positioning mechanism) 
           33 : Connection cable 
           34 : Tablet dislodging part 
           40 : Tablet feeding section 
           41 : Rotary feeder 
           42 : Casing 
           43 : Rotary disk 
           44 : Annular rotary plate 
           45 : Tablet acquiring part 
           50 : Recovery section 
           51 : Recovery pipe 
           52 : Main body 
           60 : Defective product discharging section 
           61 : Excluder 
           62 : Engaging projection 
           63 : Defective product discharge port 
           71 : Tablet feeding disk