Tablet hardness measuring method and device

Abstract

The invention relates to the technical field of tablet detection, in particular to a tablet hardness measuring method and device, and aims to solve the problem that the result is inaccurate when the tablet hardness is measured. The tablet hardness measuring method provided by the invention comprises the following steps: measuring the pressure on a tablet by using a force sensor; and the first push plate applies gradually increasing thrust to the tablets to extrude the tablets, so that the pressure borne by the tablets measured by the force sensor and time form a linear increasing relationship. Compared with relatively gentle pressure change before the tablet is crushed when the tablet is extruded at a constant speed, the tablet hardness measuring method provided by the invention has the advantages that the pressure change before the tablet is crushed is linear, the pressure change is more obvious when the tablet is crushed, and the moment when the tablet is crushed and the peak pressure before the tablet is crushed can be clearly and accurately captured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tablet hardness measurement, and particularly relates to a tablet hardness measurement method and device. BACKGROUND

[0002] The existing method for measuring tablet hardness is to push the tablet by a lead screw until the tablet is crushed, so as to measure the maximum stress before the tablet is crushed. However, the existing tablet hardness tester is uniformly extruded during the whole extrusion process, so that the stress curve of the tablet is as shown in the following figure: Figure 6 The horizontal axis represents time, and the vertical axis represents stress value. When this measurement method is used, the pressure curve of the tablet before being crushed is more gentle. Since the time interval for sampling force by the force sensor is fixed, sufficient force data cannot be captured in a short time, and thus the peak stress before the tablet is crushed cannot be accurately captured, resulting in inaccurate measurement results.

[0003] Meanwhile, since the stress change before the tablet is crushed is not obvious, the sensor may not be able to capture the sudden drop of force in time, and thus the tablet is continuously extruded after being crushed, the tablet which has been crushed into two halves is secondarily crushed, the stress of the secondary crushing of the tablet is incorrectly taken as the tablet hardness, and thus the measurement result is inaccurate. SUMMARY

[0004] The present application aims to provide a tablet hardness measurement method and device to solve the problem of inaccurate hardness detection data.

[0005] To solve the above technical problems, the technical solution provided by the present application is as follows:

[0006] The present application provides a tablet hardness measurement method, which comprises the following steps:

[0007] measuring the pressure received by the tablet by using a force sensor;

[0008] the first push plate applies gradually increasing pushing force to the tablet to extrude the tablet, so that the pressure received by the tablet measured by the force sensor has a linear growth relationship with time.

[0009] Further, the time when the tablet is crushed is obtained according to the change of the torque of the motor driving the first push plate to extrude the tablet.

[0010] Further, a servo motor is used to drive the first push plate to extrude the tablet.

[0011] Further, the first push plate is driven by a motor to extrude the tablet;

[0012] the time when the tablet is crushed is obtained according to the change of the torque of the motor or the change of the pressure received by the tablet, and the time which first decreases among the two is taken as the time when the tablet is crushed.

[0013] Further, the tablet hardness measuring method further comprises the following steps:

[0014] The first push plate approaches and contacts the tablet and applies a push force not exceeding a preset value to the tablet, and then the first push plate continues to move and extrudes the tablet with gradually increasing push force.

[0015] In another aspect of the present application, a tablet hardness measuring device is provided, which adopts the tablet hardness measuring method described above and comprises an extrusion mechanism, wherein the extrusion mechanism comprises a force sensor, a first push plate, a motor and a first lead screw.

[0016] The force sensor and the first push plate are arranged on both sides of the tablet, and the motor drives the first lead screw to rotate so that the first lead screw drives the first push plate to move towards the force sensor.

[0017] Further, the motor is a servo motor, which is connected to the first lead screw through a shaft coupling.

[0018] Further, the tablet hardness measuring device further comprises a centering mechanism, wherein the centering mechanism comprises a first conveying assembly and a second conveying assembly, the first conveying assembly comprises at least one first conveying roller, and the second conveying assembly comprises at least one second conveying roller.

[0019] The conveying directions of the first conveying assembly and the second conveying assembly are opposite.

[0020] The first conveying assembly conveys materials to the second conveying assembly in a first direction, and the second conveying assembly conveys materials to the first conveying assembly in a second direction.

[0021] Further, the first conveying assembly comprises at least two first conveying rollers, and the rotational speeds of the first conveying rollers gradually decrease one by one in the first conveying direction.

[0022] The second conveying assembly comprises at least two second conveying rollers, and the rotational speeds of the second conveying rollers gradually decrease one by one in the second conveying direction.

[0023] Further, the adjacent first conveying rollers and second conveying rollers rotate in opposite directions and have equal linear speeds.

[0024] The technical effects that can be achieved by the present application are as follows:

[0025] The tablet hardness measuring method provided by the present application comprises the following steps: measuring the pressure received by the tablet using a force sensor; and applying gradually increasing push force to the tablet by a first push plate to extrude the tablet, so that the pressure received by the tablet measured by the force sensor has a linear growth relationship with time.

[0026] The tablet hardness measuring method provided by the present application measures the hardness of a tablet by applying a gradually increasing pushing force to the tablet so that the tablet is subjected to a linearly increasing pressure. When the tablet breaks, the pressure measured by the force sensor will obviously decrease, and the peak pressure before the tablet breaks is the hardness of the tablet. Compared with the relatively flat pressure change before the tablet breaks when the tablet is pressed at a constant speed, the pressure change before the tablet breaks in the tablet hardness measuring method provided by the present application is linear, and the pressure change when the tablet breaks is more obvious. At this time, the time when the tablet breaks and the peak pressure before the tablet breaks can be clearly and accurately captured.

[0027] Since the time acquisition has continuity, the pressure value acquired according to the linear relationship is also continuous. The peak pressure can be calculated from the breaking time according to the linear relationship. Thus, this method avoids the problem that the sampling time interval of the force sensor cannot continuously monitor the pressure change, and further causes inaccurate measurement results. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0029] Figure 1 It is a schematic diagram of the assembly of the pressing mechanism and the centering mechanism;

[0030] Figure 2 It is a schematic diagram of the structure of the pressing mechanism;

[0031] Figure 3 It is a schematic diagram of the structure of the centering mechanism;

[0032] Figure 4 It is a schematic diagram of the stress change curve of the tablet in the tablet hardness measuring method provided by the embodiment of the present application;

[0033] Figure 5 It is a stress change curve diagram when the tablet hardness measuring method provided by the embodiment of the present application is actually applied;

[0034] Figure 6 It is a schematic diagram of the stress change curve of the tablet in the prior art tablet hardness measuring method;

[0035] Figure 7 It is a top view of the tablet hardness measuring device provided by the embodiment of the present application;

[0036] Figure 8 It is a perspective view of the tablet hardness measuring device provided by the embodiment of the present application;

[0037] Figure 9 Fig. 1 is a structural schematic diagram of a first rotary disc;

[0038] Figure 10 Fig. 2 is a structural schematic diagram of a channel structure of a linear vibration feeder;

[0039] Figure 11 Fig. 3 is a structural schematic diagram of a thickness detection mechanism;

[0040] Figure 12 Fig. 4 is a structural schematic diagram of a second rotary disc;

[0041] Figure 13 Fig. 5 is a structural schematic diagram of a collection disc.

[0042] Fig. 1 is a structural schematic diagram of a first rotary disc; Fig. 2 is a structural schematic diagram of a channel structure of a linear vibration feeder; Fig. 3 is a structural schematic diagram of a thickness detection mechanism; Fig. 4 is a structural schematic diagram of a second rotary disc; Fig. 5 is a structural schematic diagram of a collection disc. Fig. 1 is a structural schematic diagram of a first rotary disc; Fig. 2 is a structural schematic diagram of a channel structure of a linear vibration feeder; Fig. 3 is a structural schematic diagram of a thickness detection mechanism; Fig. 4 is a structural schematic diagram of a second rotary disc; Fig. 5 is a structural schematic diagram of a collection disc. Fig. 1 is a structural schematic diagram of a first rotary disc; DETAILED DESCRIPTION

[0043] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0044] Some embodiments of the present application will be described below in detail with reference to the drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0045] The existing method for detecting the hardness of a tablet is to push the tablet by a screw rod until the tablet is crushed, so as to measure the maximum stress before the tablet is crushed. However, the existing tablet hardness tester is uniformly extruded during the whole extrusion process, so that the stress curve of the tablet is more gentle before the tablet is crushed, and the time interval for sampling the force by the force sensor is fixed, so that sufficient force data cannot be captured in a short time, and thus the peak stress before the tablet is crushed cannot be accurately captured, resulting in inaccurate measurement results.

[0046] Meanwhile, since the stress change before the tablet is crushed is not obvious, the sensor may not capture the sudden drop of the force in time, and thus the tablet is continuously extruded after being crushed, so that the tablet which has been crushed into two halves is secondarily crushed, the stress of the secondary crushing of the tablet is incorrectly taken as the hardness of the tablet, and thus the measurement result is inaccurate.

[0047] Therefore, the present application provides a tablet hardness measurement method, which comprises the following steps: measuring the pressure received by the tablet by using a force sensor 110; and applying a gradually increasing pushing force to the tablet by a first pushing plate 120 to extrude the tablet, so that the pressure received by the tablet measured by the force sensor 110 linearly increases with time.

[0048] The tablet hardness measurement method provided by the present application applies a gradually increasing pushing force to the tablet to make the pressure received by the tablet linearly increase, and when the tablet is crushed, the pressure received by the tablet measured by the force sensor 110 will obviously decrease, and the peak pressure before the tablet is crushed is the hardness of the tablet. Compared with the gentle pressure change before the tablet is crushed when the tablet is uniformly extruded, the pressure change before the tablet is crushed is linear according to the tablet hardness measurement method provided by the present application, and the pressure change is more obvious when the tablet is crushed, so that the time when the tablet is crushed and the peak pressure before the tablet is crushed can be clearly and accurately captured.

[0049] Since the time acquisition is continuous, the pressure value obtained according to the linear relationship is also continuous, and the peak pressure can be calculated from the crushing time according to the linear relationship. Therefore, this method avoids the problem that the sampling time interval of the force sensor 110 cannot continuously monitor the pressure change, and thus the measurement result is inaccurate.

[0050] The following will be described in detail Figures 1-6 The tablet hardness measurement method provided by the present embodiment will be described in detail.

[0051] In the present embodiment, the output torque of the first motor 130 is adjusted according to the data collected by the force sensor 110, so as to ensure that the force data collected by the force sensor 110 is linearly related to time.

[0052] In an optional solution of the embodiment, the time of tablet breaking is obtained according to the change of the torque of the first motor 130 driving the first push plate 120 to press the tablet. That is, when the torque of the first motor 130 suddenly decreases, it indicates that the tablet is broken at this time, and the resistance of the tablet to the movement of the first push plate 120 driven by the first motor 130 is significantly reduced.

[0053] In order to capture the change of the torque of the first motor 130 in real time and accurately, a servo motor is used to drive the first push plate 120 to press the tablet.

[0054] In an optional solution of the embodiment, the force sensor 110 is arranged and used to measure the pressure of the tablet while the first motor 130 drives the first push plate 120 to press the tablet. The force sensor 110 and the first push plate 120 are arranged along the moving direction of the first push plate 120 and located on both sides of the tablet.

[0055] At this time, the time of tablet breaking can be obtained according to the change of the torque of the first motor 130 or the change of the pressure of the tablet, and the time at which the first decrease occurs among the two is taken as the time of tablet breaking. That is, during the process of pressing the tablet, when the torque of the first motor 130 or the value detected by the force sensor 110 has a significant decrease, it indicates that the tablet is broken. Compared with only monitoring the change of the torque of the first motor 130, the time of tablet breaking can be obtained more accurately.

[0056] In the embodiment, the tablet hardness measurement method further includes the following steps: the first push plate 120 approaches and contacts the tablet, and applies a pushing force not exceeding a preset value to the tablet, and then the first push plate 120 continues to move and presses the tablet with a gradually increasing pushing force. Generally, the pushing force of the preset value does not exceed 10N, which can be detected by the force sensor 110. This step is used to ensure that the first push plate 120 can reliably contact the tablet without crushing the tablet.

[0057] In the embodiment, the tablet hardness measurement method further includes the following steps: before the first push plate 120 contacts the tablet, the first push plate 120 moves at a high speed to a position at a preset distance from the tablet to quickly approach the tablet to improve the detection speed. The preset distance can be set to 0.5mm-2mm, which slightly differs according to the standard size of the tablet. The larger the size of the tablet, the greater the preset distance.

[0058] Based on the tablet hardness measurement method provided in the embodiment, a tablet hardness measurement device is proposed, which adopts the above-mentioned tablet hardness measurement method. Specifically, the tablet hardness measurement device includes a pressing mechanism 100, which includes a force sensor 110, a first push plate 120, a first motor 130 and a first lead screw 140, as shown in Figure 2 .

[0059] Specifically, the force sensor 110 and the first push plate 120 are arranged on both sides of the tablet, the first motor 130 drives the first screw rod 140 to rotate to drive the first push plate 120 to move to the force sensor 110, so as to extrude the tablet between the force sensor 110 and the first push plate 120.

[0060] In the embodiment, the first motor 130 is a servo motor, and the servo motor is connected with the first screw rod 140 through a shaft coupling. In order to ensure accurate control of the position, the first motor 130 is selected as a servo motor with an absolute value encoder. The absolute value encoder can provide absolute position information of the rotating shaft of the first motor 130. When cooperating with the servo motor, the precise position data fed back by the absolute value encoder can be used to accurately control the movement of the servo motor, so that the servo motor can accurately reach the target position. In addition, the torque limitation of the servo motor can prevent the tablet from being excessively extruded.

[0061] In the embodiment, the extrusion mechanism 100 further comprises an extension rod 150, a sliding block 160 and a connecting frame 170. The first motor 130 is installed on the connecting frame 170, the first screw rod 140 is rotatably installed on the connecting frame 170, and the sliding block 160 is slidably installed on the connecting frame 170. The sliding block 160 is sleeved on the first screw rod 140 and is threadedly connected with the first screw rod 140. One end of the extension rod 150 is connected with the first push plate 120, and the other end of the extension rod 150 is connected with the sliding block 160. In order to ensure the stability of the first push plate 120, at least two extension rods 150 are provided. In operation, the first motor 130 drives the first screw rod 140 to rotate to drive the sliding block 160 to slide, and then the sliding block 160 drives the first push plate 120 to move to extrude the tablet.

[0062] The sliding block 160 and the connecting frame 170 can be connected through a linear guide rail, the sliding block of the linear guide rail is connected with the sliding block 160, and the guide rail of the linear guide rail is arranged in parallel with the first screw rod 140 and is installed on the connecting frame 170. The use of the linear guide rail is conducive to reducing friction, and a guide light rod can also be used. Specifically, the guide light rod is arranged in parallel with the first screw rod 140 and is installed on the connecting frame 170, and the guide light rod is inserted into the sliding block 160 and is slidably connected with the sliding block 160 to prevent the sliding block 160 from rotating with the first screw rod 140. Similarly, the connecting frame 170 itself can also limit the rotation of the sliding block 160, and at this time, one surface of the sliding block 160 is in contact with one surface of the connecting frame 170.

[0063] In the embodiment, the first motor 130, the first screw rod 140, the shaft coupling, the sliding block 160 and the connecting frame 170 can be integrated into a linear module to improve the integration degree and reduce the cost. The first screw rod 140 adopts a high-precision screw rod to ensure the operation precision. Specifically, the precision of the first screw rod 140 can be set to less than 0.012 mm in the stroke variation within any 300 mm stroke.

[0064] In the embodiment, the tablet hardness measuring device further comprises a centering mechanism 200, which comprises a first conveying assembly 210 and a second conveying assembly 220. The first conveying assembly 210 comprises at least one first conveying roller 211, and the second conveying assembly 220 comprises at least one second conveying roller 221, as shown in the figure. The conveying directions of the first conveying assembly 210 and the second conveying assembly 220 are opposite; the first conveying assembly 210 conveys the material to the second conveying assembly 220 in a first direction, and the second conveying assembly 220 conveys the material to the first conveying assembly 210 in a second direction. Figure 3

[0065] The centering mechanism 200 has the functions of supporting the tablet and adjusting the posture of the tablet. When the tablet is circular, no adjustment is needed; when the tablet is long-axis symmetric, such as ellipse, oblong, etc., the posture usually needs to be adjusted. Specifically, the axes of the adjacent first conveying roller 211 and the second conveying roller 221 are parallel, the rotating directions are opposite, and the linear velocities are equal, which are used to adjust the posture of the tablet. When measuring the hardness, the tablet is supported by the first conveying roller 211 and the second conveying roller 221. When the tablet is long-shaped, the reverse rotation of the first conveying roller 211 and the second conveying roller 221 can make the posture of the tablet adjusted to be parallel to the axial direction of the first conveying roller 211 and the second conveying roller 221. In actual use, the diameters of the first conveying roller 211 and the second conveying roller 221 are equal to reduce the control difficulty; different diameters and different rotating speeds can also be used, but the linear velocities are equal and a plane is formed at the upper end, that is, the vertex heights of the first conveying roller 211 and the second conveying roller 221 are equal to support the tablet.

[0066] Similarly, the multiple first conveying rollers 211 in the first conveying assembly 210 can adopt the mode of equal vertex heights and equal rotating speeds and different diameters to realize the step-by-step change of the linear velocities; or adopt the mode of equal diameters and different rotating speeds to realize the step-by-step change of the linear velocities. Obviously, the second conveying assembly 220 can also be provided in this way.

[0067] In the embodiment, the first conveying assembly 210 comprises at least two first conveying rollers 211, and the rotating speeds of the first conveying rollers 211 in the first conveying direction decrease step by step; the second conveying assembly 220 comprises at least two second conveying rollers 221, and the rotating speeds of the second conveying rollers 221 in the second conveying direction decrease step by step. Specifically, each first conveying roller 211 is sequentially numbered in the first conveying direction, and each second conveying roller 221 is sequentially numbered in the second conveying direction, and the rotating speeds of the first conveying roller 211 and the second conveying roller 221 with the same number are equal.

[0068] ​By providing multiple first and second conveyor rollers 211, 221 and gradually decreasing their rotational speeds along the conveying direction, the tablet begins adjusting its posture upon entering the first or second conveyor assembly 210, 220 of the centering mechanism 200, ultimately completing the adjustment at the hardness testing station. The hardness testing station, located adjacent to the first and second conveyor rollers 211, 221, shortens the adjustment time compared to performing adjustments upon arrival at the hardness testing station.

[0069] Specifically, such as Figure 3 As shown, the first conveyor rollers 211 are numbered 1-5 along the first conveying direction, and the second conveyor rollers 221 are numbered 1-5 along the second conveying direction. The adjacent first conveyor roller 211 (number 5) and second conveyor roller 221 (number 5) constitute the hardness testing station, where the two conveyor rollers jointly support the tablet for hardness testing. As the tablet passes from the first conveyor assembly 210 into the hardness testing station, if the length of the tablet is not parallel to the axis of the first conveyor roller 211, the two ends of the tablet will contact the two first conveyor rollers 211. For example, if the two ends of the tablet are respectively on first conveyor roller 211 (number 1) and first conveyor roller 211 (number 2), the slower speed of first conveyor roller 211 (number 2), which has a higher number, will block the tablet, causing it to oscillate in the horizontal plane. This speed difference causes the length of the tablet to oscillate parallel to the axis of the first conveyor roller 211.

[0070] In this embodiment, the squeezing mechanism 100 can measure the diameter and length of the tablet, and can also measure the hardness of the tablet.

[0071] It should be noted that the conveying roller of the centering mechanism 200 continues to rotate until the measurement is completed, so as to avoid the deviation of the tablets during the measurement process, thereby ensuring the accuracy of the measurement results.

[0072] After the tablets are broken, if the broken particles are smaller than the minimum gap between adjacent conveyor rollers, they can fall through the gap between the adjacent conveyor rollers. If the particle size is larger than the minimum gap between adjacent conveyor rollers and smaller than the maximum gap between the conveyor rollers, due to the opposite rotation directions or speed difference between the adjacent conveyor rollers, the particles will be squeezed by the two adjacent conveyor rollers and further broken into particles smaller than the minimum gap between the adjacent conveyor rollers. These particles then fall through the gap between the adjacent conveyor rollers and are discharged, preventing residual particles from affecting subsequent tablet inspection. If the particle size is larger than the maximum gap between adjacent conveyor rollers, the conveyor rollers can be rotated in the opposite direction to discharge the particles from the end of the centering mechanism 200 away from the transfer mechanism 600. This operation prevents the accumulation of broken tablet powder and affects the accuracy of subsequent measurements. It should be noted that the maximum gap between adjacent conveyor rollers is the distance between the vertices of the adjacent conveyor rollers.

[0073] Through detailed testing and simulation on the size and gap of the conveying rollers, the centering mechanism 200 can be applied to centering of all round and long axis symmetrical tablets with a size ranging from 5mm to 25mm, which basically covers the shapes and sizes of most tablets on the market. No manual adjustment is required during use, which improves the versatility of the equipment and reduces the workload of the equipment user. Specifically, the diameter of the conveying rollers is 3mm, the gap between the conveying rollers is 1.5mm, and the speed ratio of adjacent conveying rollers is 1.15-1.2.

[0074] In this embodiment, the centering mechanism 200 further includes a centering support 230, and the first conveying roller 211 and the second conveying roller 221 are both mounted on the centering support 230. The speed difference can be realized by changing the transmission ratio through gear transmission, synchronous belt transmission, etc. As shown in Figure 2 The pressing mechanism 100 further includes a sensor mounting plate 180, and the force sensor 110 is mounted on the sensor mounting plate 180, and the sensor mounting plate 180 is mounted on the centering support 230.

[0075] In this embodiment, the first conveying assembly 210 and the second conveying assembly 220 can be driven by the same power source, or can be driven respectively. The power source can be selected from a servo motor, a stepper motor or a constant speed motor, etc.

[0076] The centering mechanism 200 provided in this embodiment has a simple and reliable structure, and only has the rotation of the conveying rollers as the only action. Compared with the tablet posture adjusting device driven by pneumatic elements, it has the advantages of low equipment cost, high precision and stable operation, low failure rate and convenient maintenance.

[0077] Through detailed testing and simulation on the size and gap of the conveying rollers, the centering mechanism 200 can be applied to centering of all round and long axis symmetrical tablets with a size ranging from 5mm to 25mm, which basically covers the shapes and sizes of most tablets on the market. No manual adjustment is required during use, which improves the versatility of the equipment and reduces the workload of the equipment user. Specifically, the diameter of the conveying rollers is 3mm, the gap between the conveying rollers is 1.5mm, and the speed ratio of adjacent conveying rollers is 1.15-1.2.

[0078] The tablet hardness measurement method provided in this embodiment includes three stages: approaching the tablet, contacting the tablet, and pressing the tablet. The specific implementation process is as follows:

[0079] Approaching tablet stage: the control system calculates the displacement of the first push plate 120 from the initial position to approach the tablet according to the standard tablet size (diameter or length) input by the user, and converts the displacement into the number of turns of the first motor 130 driving the first lead screw 140. Then the servo motor with absolute value encoder drives the first lead screw 140 to rotate the corresponding number of turns at the maximum allowed speed, thereby driving the first push plate 120 to rapidly approach the tablet at a higher speed to a position slightly larger than the diameter or length of the tablet to reduce the time required for the first push plate 120 to approach the tablet as much as possible. Since the actual tablet extrusion stroke is only a displacement of zero point several millimeters, setting the standard size of the tablet in advance can avoid excessive extrusion of the tablet.

[0080] Contact tablet stage: the control system automatically adjusts the rotation speed of the servo motor during this stage, and adjusts the movement speed of the first push plate 120 to 1-5 mm / s through the high-precision lead screw. The movement speed is slightly different depending on the standard size of the tablet, and the larger the tablet size, the greater the movement speed. The first push plate 120 moves at a constant speed to approach and touch the tablet until the force sensor 110 captures a pressure of no more than 10 N or the servo motor captures an increase in torque, whichever comes first, thereby ensuring that the first push plate 120 reliably contacts the tablet without crushing the tablet and ensuring that the tablet is stable during extrusion to obtain accurate hardness. At this time, the diameter or length of the tablet can be measured.

[0081] Extruding tablet stage: the control system adjusts in real time according to the force data and torque data obtained by capturing the changes in force collected by the force sensor 110 and the changes in torque of the servo motor to achieve a linear increase in force over time during the extrusion process, ensuring that the force changes as close to a straight line as possible during the entire process of the tablet from bearing pressure to breaking, as shown in Figure 4 . Figure 5 The pressure change curve displayed on the screen of the industrial computer during actual testing is the stress change curve of the tablet.

[0082] When the tablet breaks, the pressure of the force sensor 110 and the torque of the servo motor will have a sudden drop, whichever comes first. Since the entire force measurement curve is approximately linear, the sudden drop in torque of the force sensor 110 and the first motor 130 will be clear and significant. By this method, the peak pressure before the tablet breaks, i.e. the hardness of the tablet, can be clearly and accurately captured.

[0083] The measurement method can quickly capture the force surge at the first time of tablet crushing, stop the continuous extrusion of the first push plate 120 on the tablet, prevent the tablet from being crushed again due to the secondary extrusion and cause the confusion of the peak pressure, thereby improving the accuracy of the tablet hardness measurement. When the force sensor 110 fails to capture the pressure at the time of tablet crushing due to the sampling time interval, but determines the tablet crushing time through the reduction of the torque of the first motor 130, the pressure of the tablet at the time of crushing can be determined according to the linear relationship between the pressure and the time, that is, the tablet hardness.

[0084] In contrast, the conventional measurement scheme using the first push plate 120 to move at a constant speed for extrusion, the stress change curve measured by the force sensor 110 is as shown in FIG. 2. Before the tablet is crushed, a segment of the curve is relatively flat and nonlinear, and the maximum pressure before crushing cannot be calculated according to the time of the torque surge, and the force surge is easy to be ignored, causing the tablet to be crushed again. In addition, due to the sampling time interval of the force sensor 110, the maximum pressure captured is difficult to be consistent with the actual pressure peak, and there is a large deviation between the measurement result and the actual pressure. Figure 6

[0085] In summary, the tablet hardness measurement method provided in the embodiment greatly improves the accuracy of tablet hardness measurement by optimizing the pressure curve in the tablet hardness measurement process.

[0086] The tablet hardness measurement device provided in the embodiment further includes a feeding mechanism 300, a weighing mechanism 400, a thickness detection mechanism 500, a transfer mechanism 600 and a collection mechanism 700.

[0087] The structure and shape of the tablet hardness measurement device provided in the embodiment will be described in detail below. Figures 1-13 The feeding mechanism 300 is used to feed the tablets into the weighing mechanism 400 one by one; the weighing mechanism 400 is used to weigh the tablets; the thickness detection mechanism 500 includes a second lead screw 510 and a second push plate 520, the second lead screw 510 drives the second push plate 520 to move in the vertical direction to make the second push plate 520 contact with the tablets; the transfer mechanism 600 is used to transfer the tablets from the thickness detection mechanism 500 to the centering mechanism 200.

[0088]

[0089] ​​The tablet hardness measuring device provided by the embodiment determines the tablet size by using the displacement difference of the push plate driven by the lead screw. Compared with the grating ruler, the device has better adaptability to the environment, avoids the interference caused by mechanical vibration and wind, and reduces the difficulty of assembly, installation, debugging and maintenance. The reason is that the tablet measuring device is usually placed at a lower position in the tablet press chamber, often near the return air outlet of the air conditioner, and is easily affected by the wind and the vibration of the tablet press. The measurement accuracy of the grating ruler is greatly affected by vibration and wind, so the installation and use environment is high. Specifically, the high-precision lead screw is selected to ensure the measurement accuracy, and the servo motor is used for control during use. The torque of the servo motor is limited to control the push plate to apply a certain range of pressure to the tablet, ensuring accurate measurement.

[0090] In the embodiment, the thickness detection mechanism 500 further comprises a second motor 530, which is a servo motor with an absolute value encoder, used to drive the second lead screw 510 to rotate around its own axis.

[0091] Further, the thickness detection mechanism 500 further comprises a linear guide rail, the slider of the linear guide rail is connected with the second push plate 520, and the guide rail of the linear guide rail is arranged in parallel with the second lead screw 510; the second lead screw 510 rotates around its own axis to drive the slider of the linear guide rail to move. Specifically, the structure of the thickness detection mechanism 500 can refer to the extrusion mechanism 100, and the mechanical structures of the two can be completely the same, which will not be repeated here. It should be noted that the thickness detection mechanism 500 further comprises a photoelectric sensing sensor, which is used to identify that the tablet reaches below the second push plate 520, so as to confirm that the thickness detection can be started.

[0092] In the optional scheme of the embodiment, the feeding mechanism 300 is arranged as a vibrating disc, which is used to output the tablets one by one to the weighing mechanism 400. A pair of photoelectric sensors are arranged at the outlet position of the vibrating disc, which are used to monitor the entire cross section of the channel, so as to confirm that the tablet passes through the outlet and enters the weighing mechanism 400, avoiding sending multiple tablets into the weighing mechanism 400. When one tablet is identified to fall down, the feeding mechanism 300 stops working, waits for the measurement and instruction of the weighing mechanism 400, and ensures that the tablet can accurately fall down one tablet at a time. In addition, a discharging port is arranged on the vibrating disc, which is used to discharge the dust falling off during the vibration of the tablet to the dust collection box below the vibrating disc, avoiding the influence of the dust on the weighing.

[0093] In the optional scheme of the embodiment, the weighing mechanism 400 comprises a weighing sensor 410 and a first turntable 420, as shown in Figure 8 The weighing sensor 410 is used to weigh the tablet, and the first turntable 420 is provided with a displacement ring 421. The first turntable 420 is arranged above the weighing sensor 410 and is configured to rotate around its own axis to make the displacement ring 421 rotate around the axis of the first turntable 420.

[0094] Further, the weighing mechanism 400 further comprises a linear vibration feeder 430. Specifically, the displacement ring 421 pushes the tablets into the linear vibration feeder 430, and the linear vibration feeder 430 sends the tablets under the second push plate 520.

[0095] In the embodiment, the first turntable 420 further comprises a discharge plate 422 and a brush, and the displacement ring 421, the discharge plate 422 and the brush are uniformly distributed around the axis of the first turntable 420. The discharge plate 422 is provided with an inclined plane for arranging the tablets into the collecting mechanism 700. As shown in the figure, the bending plate is used to install the brush, and the brush is used to clean the surface of the weighing sensor 410 to prevent dust and other residues from affecting the weighing accuracy. Figure 9

[0096] In an optional scheme of the embodiment, the transfer mechanism 600 comprises a second turntable 610, and the second turntable 610 is provided with a clamping groove 611. As shown in the figure, the clamping groove 611 is V-shaped and used to carry tablets 101 of different sizes. In the embodiment, three clamping grooves 611 are uniformly distributed around the axis of the second turntable 610. The second turntable 610 is configured to rotate around its own axis to make the clamping groove 611 drive the tablets located in the thickness detection mechanism 500 into the centering mechanism 200. Figure 12

[0097] In the embodiment, the first turntable 420 and the second turntable 610 can be driven by a servo motor cooperating with a transmission mechanism.

[0098] In an optional scheme of the embodiment, the collecting mechanism 700 comprises a collecting disc, and the collecting disc is configured to rotate around its own axis. Specifically, as shown in the figure, the collecting disc is provided with a plurality of first collecting grooves 711 and a second collecting groove 712 which are uniformly distributed around the axis of the collecting disc, and different collecting grooves are selected according to the required capacity and the type of tablets. Figure 13

[0099] The use process of the tablet hardness measuring device provided in the embodiment is as follows:

[0100] S100 weighing: The feeding mechanism 300 sends the tablets into the weighing mechanism 400 one by one. Specifically, the tablets fall onto the weighing sensor 410 and are located in the displacement ring 421. With the reciprocating rotation of the first turntable 420, the displacement ring 421 swings left and right to make the tablets located in the center position of the weighing sensor 410, so as to ensure the weighing accuracy. Among them, the weight of the tablet should be 0.5-1.5 times of the standard weight, otherwise it is considered that the tablet is a fragment or at least two tablets enter the weighing sensor 410, and the first turntable 420 is rotated to the left, the displacement ring 421 pushes the tablets to the discharge port, and the tablets fall into the collecting mechanism 700.

[0101] ​​​When the required number of tablets is detected, the first turntable 420 is turned to the position where the discharge plate 422 is in alignment with the outlet of the vibration plate. The tablets remaining in the vibration plate are fed into the discharge plate 422 by the vibration plate and fall into the collecting mechanism 700 under the action of gravity.

[0102] S200: Thickness measurement. After the tablets are weighed, the first turntable 420 is turned to the right, and the shift ring 421 pushes the tablets to the linear vibration feeder 430. After the tablets are weighed, the brush rotates with the first turntable 420 to the weighing sensor 410 and cleans the surface of the weighing sensor 410.

[0103] The tablets enter the thickness detection mechanism 500 through the V-shaped channel of the linear vibration feeder 430. After the photoelectric sensor detects the entry of the tablets, the thickness detection mechanism 500 starts to work. The second motor 530 drives the second push plate 520 to move downward to apply a pressure of not more than 10N, usually set to 5N-7N, to the tablets. At this time, the thickness of the tablets can be calculated according to the position of the second push plate 520. The pressure can be controlled by the torque of the second motor 530.

[0104] S300: Hardness measurement. The second turntable 610 rotates and brings the tablets to the centering mechanism 200. The tablets fall into the centering mechanism 200 and finally enter the hardness detection station. Then the extrusion mechanism 100 is started, and the first motor 130 drives the first push plate 120 to move to apply a pressure of not more than 10N, usually set to 5N-7N, to the tablets. At this time, the thickness of the tablets can be calculated according to the position of the first push plate 120. The pressure can be controlled by the torque of the first motor 130 or obtained by the force sensor 110.

[0105] Then the first push plate 120 continues to move and crushes the tablets to complete the detection of the hardness of the tablets. During this process, the torque of the first motor 130 is constantly adjusted by the data of the force sensor 110, so that the pressure on the tablets increases linearly. When the tablets are crushed, the torque of the first motor 130 or the value detected by the force sensor 110 will decrease significantly.

[0106] The tablet hardness measurement device provided in the embodiment uses a servo motor with an absolute value encoder to drive a high-precision slide rail to move the push plate, and calculates to realize the detection of the thickness, length or diameter of the tablets. Before measurement, the push plate will first move to contact the reference surface, and the reference surface is used as the zero position for size measurement. The reference surface is the surface on which the tablets are carried in the thickness detection mechanism 500 or the surface on which the force sensor 110 in the extrusion mechanism 100 contacts the tablets. When the push plate moves to contact the tablets, the difference between the distance moved by the push plate after leaving the reference surface and the distance moved by the push plate again to contact the tablets is calculated. This difference is the thickness, length or diameter of the tablets.

[0107] The tablet hardness measuring device provided by the embodiment utilizes the rotation number of the screw in the high-precision slide rail to make accurate counting, and multiplies the pitch of the screw to calculate the displacement of each push plate. The accuracy of the screw can easily reach the micron level, meeting the measurement requirements. At the same time, the absolute value encoder of the servo motor is used to ensure the accuracy of the servo motor in counting the rotation number of the screw each time, ensuring the measurement accuracy. The torque limit of the servo motor is used to ensure that the extrusion force of the push plate on the tablet is limited within 10N, so that the tablet will not be excessively extruded during the size measurement process.

[0108] The tablet hardness measuring device provided by the embodiment uses the calculation of the rotation number of the high-precision screw to perform size measurement, so the measurement accuracy will not be affected by vibration and wind. The installation, debugging, and maintenance difficulty is greatly reduced. The measurement accuracy is only related to the machining accuracy of the screw itself and will not be disturbed by other factors. At the same time, the load during use is very small, and the wear of the screw is extremely small, so the long-term stability of the single measurement accuracy and the repeatable measurement accuracy can be ensured.

[0109] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for measuring tablet hardness, characterized in that: The steps include: Using a force sensor (110) to measure the pressure exerted on the tablet; The first push plate (120) applies a gradually increasing push force to the tablet to squeeze the tablet, so that the pressure on the tablet measured by the force sensor (110) increases linearly with time.

2. The tablet hardness measuring method according to claim 1, characterized in that: The tablet crushing time is obtained according to the change of the torque of the first motor (130) that drives the first push plate (120) to squeeze the tablet.

3. The tablet hardness measuring method according to claim 2, characterized in that: A servo motor is used to drive the first push plate (120) to squeeze the tablet.

4. The tablet hardness measuring method according to claim 1, characterized in that: Using a first motor (130) to drive the first push plate (120) to squeeze the tablet; The tablet crushing time is obtained according to the change of the torque of the first motor (130) or the change of the pressure on the tablet, and the time when the first of the two decreases is the tablet crushing time.

5. The tablet hardness measuring method according to any one of claims 2 to 4, characterized in that: The following steps are also included: The first push plate (120) approaches the tablet and contacts the tablet, applying a pushing force not exceeding a preset value to the tablet, and then the first push plate (120) continues to move and squeezes the tablet with a gradually increasing pushing force.

6. A tablet hardness measuring device, using the tablet hardness measuring method according to any one of claims 1 to 5, characterized in that: The extrusion mechanism (100) includes the force sensor (110), the first push plate (120), a first motor (130), and a first lead screw (140); The force sensor (110) and the first push plate (120) are arranged on both sides of the tablet, and the first motor (130) drives the first screw (140) to rotate so that the first screw (140) drives the first push plate (120) to move toward the force sensor (110).

7. The tablet hardness measuring device according to claim 6, characterized in that: The first motor (130) is a servo motor, and the servo motor is connected to the first lead screw (140) via a coupling.

8. The tablet hardness measuring device according to claim 6, characterized in that: The centering mechanism (200) further comprises a first conveying assembly (210) and a second conveying assembly (220), wherein the first conveying assembly (210) comprises at least one first conveying roller (211), and the second conveying assembly (220) comprises at least one second conveying roller (221); The conveying directions of the first conveying component (210) and the second conveying component (220) are opposite; The first conveying component (210) conveys material toward the second conveying component (220) along a first direction, and the second conveying component (220) conveys material toward the first conveying component (210) along a second direction.

9. The tablet hardness measuring device according to claim 8, characterized in that: The first conveying assembly (210) comprises at least two first conveying rollers (211), and the rotational speeds of the first conveying rollers (211) decrease one by one along the first conveying direction; The second conveying assembly (220) comprises at least two second conveying rollers (221), and the rotational speeds of the second conveying rollers (221) decrease one by one along the second conveying direction.

10. The tablet hardness measuring device according to claim 9, characterized in that: The adjacent first conveying roller (211) and the second conveying roller (221) rotate in opposite directions and have the same linear speed.

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