Hollow platform belt checkweigher

Abstract

A hollow platform belt checkweigher includes a control cabinet, a frame, a feeding unit mounted on the frame, and a weighing unit. The feeding unit is connected to the weighing unit. The weighing unit includes a load cell, a force transmission connector, and a belt conveyor. The fixed end of the load cell is fixed to the frame, and the bearing end of the load cell is fixed to the force transmission connector. The belt conveyor includes a belt support, a drive roller, a driven roller, and a motor mounted on the belt support. The belt support is connected to the force transmission connector. Two weighing belts are arranged on the belt support, wrapped around the drive roller and the driven roller. The weighing belts are spaced apart, with (B-0.5×K)≥L≥K. A weighing belt support plate is arranged on the belt support, with the bottom surface of the upper half of each weighing belt corresponding to the top surface of the weighing belt support plate. The motor drives the drive roller to rotate through the transmission belt, thereby synchronously driving the two weighing belts to slide on the upper surface of the weighing belt support plate. The weighing belt support plate has a hollow structure.

Description

Technical Field

[0001] This solution relates to a belt checkweigher for the pharmaceutical, food, and health product industries, especially a high-precision belt checkweigher for lighter packaged goods on high-speed packaging production lines. Background Technology

[0002] Belt checkweighers are often used in the production and packaging of large-volume, lightweight, and standardized products in the pharmaceutical, health product, and food industries. They are used to check whether the quantity or weight of the standard packaging is up to standard, or to check whether the standard packaging is missing instructions or other independent separate contents.

[0003] A belt checkweigher typically includes a frame, control cabinet, feeding belt conveyor, weighing unit, and rejection unit. In existing technology, the weighing unit of a belt checkweigher includes a load cell, a force transmission connector, and a belt conveyor. The belt conveyor includes a belt support and a drive roller and a driven roller mounted on the belt support. A single, smooth, and flat belt support plate is placed between the drive roller and the driven roller. A wide weighing belt wraps around the drive roller and the driven roller and slides on the surface of the belt support plate. The object to be weighed is dragged by the wide weighing belt and moves relative to the belt support plate. The weighing platform refers to all parts mounted on the load cell that support the object to be weighed, including the belt support plate, weighing belt, rollers, and belt support. The feeding belt conveyor is mounted on a frame and includes a feeding belt support and a feeding drive roller and a feeding driven roller mounted on the feeding belt support. A feeding belt support plate with a smooth and flat upper surface is set between the feeding drive roller and the feeding driven roller. A wide feeding belt wraps around the feeding drive roller and the feeding driven roller and slides on the upper surface of the feeding belt support plate. The object to be weighed is dragged by the wide feeding belt and moves relative to the feeding belt support plate.

[0004] Existing belt checkweighers, when inspecting objects on high-speed production lines, show decreasing accuracy with increasing inspection speed. For lighter packaged goods, high accuracy is generally required. Therefore, when inspecting high-speed, lightweight packaged goods, especially cardboard boxes, the impact of various mechanical factors, environmental conditions, and the response time and resolution of weighing sensors on checkweighing accuracy becomes crucial. To improve checkweighing accuracy, many methods have been employed, such as improving the machining and dynamic balancing accuracy of moving parts of the weighing belt conveyor (including drive motors, rollers, weighing belts, and transmission devices), reducing the influence of rotating imbalances on weighing sensors, adding windproof covers to the weighing unit to prevent interference from external airflow, and improving software algorithms to adapt to extremely short weighing times. However, the overall results have remained unsatisfactory.

[0005] For example, for a high-speed belt checkweigher using a low-cost, simple strain gauge load cell, a medicine box with dimensions of approximately 60mm x 100mm x 20mm (length x width x height) containing a capsule blister pack and an instruction manual (instruction manual weighing 1g), and a total weight of 10.0g including all contents, can only achieve an accuracy of ±0.60g at a rate of 600 boxes per minute. Since the total weight of medicine boxes within the acceptable range itself has a ±0.1g deviation, with a checkweighing accuracy of 0.6g, to ensure that medicine boxes lacking instructions are rejected, the rejection threshold must be higher than 9.70g. Otherwise, assuming a rejection threshold of 9.69g, medicine boxes lacking instructions and having a weight deviation would weigh 9.10g. A 10.00g medicine box might be mistakenly judged as qualified and pass through the inspection due to a 0.60g error in weighing, resulting in a total weight of 9.70g, which is greater than the rejection threshold of 9.69g. Obviously, to ensure that no unqualified medicine boxes pass through, the rejection threshold must be set higher than 9.70g. Assuming the rejection threshold is set to 9.71g, a perfectly qualified 10.00g medicine box would be judged as unqualified and rejected because it is 0.60g lighter, with a weighing display of 9.40g, which is less than 9.71g. Therefore, this would lead to many qualified products being mistakenly rejected. Thus, this belt checkweigher is not capable of checking the weight of 1.0g instruction manuals on a production line of 600 boxes per minute.

[0006] In addition, many production lines are located in high-rise factory buildings or are near equipment that causes severe vibrations and impacts on the ground, which can also greatly affect weighing accuracy.

[0007] The market urgently needs a high-precision, high-speed checkweigher with a simple structure that can be improved upon existing technology, and it also needs to be able to adapt to environments with ground vibration. Utility Model Content

[0008] This solution addresses the shortcomings of existing technologies by proposing a simple, high-precision belt checkweigher suitable for weighing lightweight packaged goods on high-speed packaging production lines.

[0009] The technical measures adopted in this solution are as follows: a hollow platform belt checkweigher, which includes a control cabinet, a frame, a feeding unit and a weighing unit mounted on the frame. The feeding unit is connected to the weighing unit. The weighing unit includes a load cell, a force transmission connector, and a belt conveyor. The fixed end of the load cell is fixed to the frame, and the bearing end of the load cell is fixed to the force transmission connector. The belt conveyor includes a belt support, a drive roller, a driven roller, and a motor mounted on the belt support. The belt support is connected to the force transmission connector. The load cell and the motor are electrically connected to the control cabinet. The motor and the drive roller are connected via a transmission belt. Next, two weighing belts are installed on the belt support, wrapped around the driving roller and the driven roller. The weighing belts are spaced apart. The dimension of the bottom surface of the object being weighed, perpendicular to the length of the weighing belt, is B. The sum of the widths of the two weighing belts is K. The inner distance between the two weighing belts is L, and (B-0.5×K)≥L≥K. The weighing belt support plate is arranged on the belt support, above the bottom surface of the upper half of each weighing belt. The motor drives the driving roller to rotate through the transmission belt, thereby synchronously driving the two weighing belts to slide on the upper surface of the weighing belt support plate. The weighing belt support plate has a hollow structure.

[0010] The feeding unit is a feeding belt conveyor, which includes a feeding belt support, a feeding drive roller shaft and a feeding driven roller shaft mounted on the feeding belt support, a feeding motor, two feeding belts surrounding the feeding drive roller shaft and the feeding driven roller shaft, and a feeding belt support plate set on the feeding belt support and located below the feeding belts. The feeding motor drives the feeding drive roller shaft through the feeding transmission device, thereby causing the two feeding belts to slide on the upper surface of the feeding belt support plate, and the object to be weighed is dragged and moved by the two feeding belts.

[0011] The dimension of the bottom surface of the object being weighed along the length of the weighing belt is A, and the sum of the diameter of the roller at the discharge end of the feeding belt conveyor and the diameter of the roller at the feed end of the weighing unit is D, where A≥D.

[0012] Each feeding conveyor belt has a corresponding feeding conveyor support plate. The space between the two feeding conveyor support plates is a hollow structure that allows air to flow freely up and down between them.

[0013] A compensating load cell is also installed on the frame. The compensating load cell is arranged in parallel with the load cell and is used for compensation, just like the load cell of the weighing unit. A compensation block is installed on the compensating load cell. The compensation block is located between the adjacent weighing belt support plates and is lower than the weighing belt. The sum of the weights of all parts on the compensating load cell, including the compensation block, is the same as the sum of the weights of all parts on the load cell of the weighing unit.

[0014] The drive belt is a synchronous belt or a synchronous toothed belt, which can be located on the outside of two weighing belts or between two weighing belts.

[0015] The beneficial effects of this solution are: 1. By setting up two narrow weighing belts from a single wide weighing belt, and further dividing the single wide belt support plate under each weighing belt into corresponding support plates for each belt, and using flat, uniformly thin belts, the belt support becomes a hollow structure between adjacent weighing belt support plates. This unexpectedly and significantly improves the weighing accuracy. It was found that the most significant contributor to high-speed weighing errors is the pressure imbalance of air on the upper and lower surfaces of the weighing platform. This meets the weighing requirements of packaged products such as medicine boxes on high-speed packaging production lines, for example, the weighing of 1.0g instruction manuals on a production line of 300-600 boxes per minute. Specifically: 1) The inner distance between the two weighing belts should be ≤ (the dimension of the bottom surface of the object being weighed perpendicular to the length of the weighing belt - (half the sum of the widths of the two weighing belts)) to ensure that the object being weighed can be stably supported on each weighing belt for at least half the belt width. The high-speed movement of the object being weighed, supported by two narrow weighing belts at both ends, is smoother than the high-speed movement supported by three or more weighing belts, resulting in higher weighing accuracy. This is because, assuming there are three parallel weighing belts (a, b, and c) arranged sequentially on the weighing platform, the medicine box may initially only contact a and b, and later only b and c. This will cause slight fluctuations in the center of gravity of the medicine box, leading to an increase or decrease in weight on the weighing platform, thus contributing to the weighing error. If there are only two belts (a and c), the medicine box will not experience slight fluctuations throughout its movement on the weighing platform, preventing any increase or decrease in weight and contributing to the weighing error.

[0016] 2) There are only two belt rollers on the belt support that are in contact with the weighing belt. The belt tension is achieved by the relative movement of the bearing seats of the rollers. There are only two belt rollers rotating at high speed, which limits the eccentric mass and avoids affecting the weighing accuracy.

[0017] 3) Compared to the need to adjust multiple rollers when two weighing belts wrap around three or more different rollers, two weighing belts only wrap around the same two rollers. The flatness, parallelism and synchronization between the two weighing belts can be easily adjusted and guaranteed by adjusting the parallelism of the two rollers. This will not cause the medicine box to be unstable when running at high speed on the weighing belt, thus affecting the checkweighing accuracy.

[0018] 4) The weighing belt is a flat, thin, and narrow belt with uniform thickness. The diameter of the roller can be made smaller. The belt can surround the roller well and generate stable friction torque without a large tension. At the same time, it avoids the unbalanced mass of the roller at high speed caused by a large roller diameter. The belt runs more smoothly and will not cause the thick belt to jump at the roller due to the inconsistency of thickness, weight or hardness, which will affect the weighing accuracy.

[0019] Because the object being weighed is lightweight, the friction between the weighing belt and the belt support is very small. Therefore, the required tension on the weighing belt from the rollers is low, allowing for the use of a low-power motor. This results in a lighter total mass on the load cell and higher weighing accuracy. The likelihood of a drastic change in tension or even motor torque due to frictional variations causing significant interference with the load cell and ultimately degrading weighing accuracy is extremely low.

[0020] 5) The inner spacing between the two weighing belts is greater than or equal to the sum of the widths of the two weighing belts. This ensures that the hollow weighing platform structure allows the air in front of the high-speed moving medicine box to flow freely up and down, and that air pressure can be transmitted and conducted quickly and instantaneously. This effectively and quickly balances the bidirectional interference of the air or air pressure above and below the weighing platform on the weighed object itself and the upper and lower surfaces of the annular weighing belt wrapped around the roller shaft. It reduces the unidirectional downward influence of the air or air pressure above the weighing platform on the entire weighing belt support plate in the prior art. This truly solves the problem that previous methods, such as controlling machining precision, controlling ambient airflow, optimizing checkweighing algorithms, and replacing weighing sensors with high-response-speed ones, failed to significantly improve checkweighing accuracy at high speeds.

[0021] 2. Strictly speaking, the bottom surface of the objects being weighed, such as medicine boxes, is curved. The thickness of the entire wide belt on the feeding conveyor is inconsistent in different parts, making it a curved surface. The belt support plate below it is also curved. Therefore, the distribution of contact points between the bottom surfaces of different medicine boxes and the feeding conveyor is highly random. The two points on the bottom of the medicine box that contact the discharge end of the feeding conveyor are mostly not the two points on the bottom of the medicine box that contact the inlet end of the weighing conveyor. Therefore, when the medicine box is loaded from the entire feeding belt onto the weighing belt, it is mostly thrown over, resulting in a large impact. The feeding belt is divided into two flat, uniformly thick, thin narrow belts. The two points on the bottom of the medicine box that contact the discharge end of the feeding belt conveyor are the highest points of the two feeding narrow belts. Similarly, the two points on the bottom of the medicine box that contact the inlet end of the weighing belt conveyor are the highest points of the two weighing narrow belts. The two feeding narrow belts are aligned with the two weighing narrow belts, with the two highest points aligned with the two highest points. Height adjustment is extremely convenient and the alignment is precise. The two points on the bottom of the medicine box that contact the discharge end of the feeding belt conveyor are precisely the two points on the bottom of the medicine box that contact the inlet end of the weighing belt conveyor. This ensures that the medicine box is fed smoothly onto the weighing platform, without impact bounce, parabolic landing, or lateral swaying. This minimizes impact on the weighing sensor and significantly improves weighing accuracy. The medicine box is smoothly dragged by the two feeding narrow belts at both ends and then smoothly received by the two narrow belts of the weighing unit, minimizing impact on the weighing sensor and further improving accuracy.

[0022] The dimension of the bottom surface of the object being weighed along the length of the weighing belt is greater than or equal to twice the sum of the diameter of the roller at the discharge end of the feeding belt conveyor and the diameter of the roller at the feed end of the weighing unit. This ensures that the medicine box can smoothly cross from the feeding belt onto the weighing belt without impacting the weighing platform by bumping or tilting its head.

[0023] 3. The feeding belt conveyor also adopts the same hollow structure as the weighing belt conveyor, that is, the space between the narrow belt support plates of adjacent feeding belt conveyors is hollow. The air pushed by the high-speed medicine box can flow up and down in advance, and the air pressure can be balanced on the upper and lower surfaces of the belt as early as possible. In this way, when the medicine box is put on the weighing platform, there will be no sudden air splitting or abrupt changes in air pressure on the feeding belt. This reduces the interference of rapid and drastic changes in airflow or air pressure on the randomness and amplitude of the weight signal output, and greatly improves the weighing accuracy.

[0024] 4. Set up a load cell identical to the load cell of the weighing unit for compensation, called the compensation load cell. It is arranged in parallel with the load cell and also installed on the frame. A compensation block is installed on the compensation load cell. The compensation block is located between the adjacent weighing belt support plates and is lower than the weighing belt. The sum of the weights of all parts on the compensation load cell, including the compensation block, is the same as the sum of the weights of all parts on the load cell of the weighing unit.

[0025] The upward wind-receiving area and shape of the compensation block are specially designed to ensure that the compensation block does not affect the airflow and air pressure transmission between the upper and lower parts of the weighing platform. By subtracting the output signal of the compensation sensor under the compensation block from the output signal of the weighing unit's load cell, the interference of foundation vibration on the load cell on the frame can be reduced. This achieves the suppression and compensation of vibration of the foundation or frame, making the high-speed checkweigher of this solution suitable for various production lines with ground vibration.

[0026] 5. This technology is also suitable for weighing lightweight objects that travel at low speeds and have a large frontal area (the area perpendicular to the upper surface of the weighing belt and directly in front of the object's path).

[0027] 6. Compared with existing technologies, this technology only requires simple modifications to the belt pallets and belts of the weighing belt conveyor and the feeding belt conveyor, which has greatly improved the accuracy of the existing belt checkweigher. The structure is extremely simple, easy to implement, and has low improvement costs, thus expanding its applicable scenarios. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the high-speed belt checkweigher in this solution. Figure 2 This is a schematic diagram of the hollow weighing platform structure in this scheme. Figure 3 for Figure 2 Enlarged view of part I in the middle. Figure 4 This diagram illustrates that the feeding conveyor belt in this design consists of two narrow belts. Figure 5 This diagram illustrates the hollow structure of the feeding conveyor belt used in this design. Figure 6 This is a structural diagram of a high-speed belt checkweigher based on existing technology. Figure 7 This is a schematic diagram illustrating how a single weighing belt can be replaced with multiple narrow belts in a high-speed belt checkweigher of existing technology.

[0029] In the diagram, 1-weighing belt, 2-weighing belt support plate, 3-drive roller, 4-driven roller, 5-belt bracket, 6-force transmission connector, 7-bearing seat, 8-roller protrusion, 9-medicine box, 10-wide feeding belt, 11-feeding belt, 12-wide feeding belt support plate, 13-feeding driven roller, 14-feeding drive roller, 16-feeding belt support plate, 20-wide belt support plate, 21-control cabinet, 22-frame, 23-feeding unit, 24-weighing unit, 25-weighing sensor, 26-rejection unit, 42-gear, 43-toothed belt, I-enlarged view of belt support plate and roller protrusion, arrows indicate the direction of movement of the weighed object. Detailed Implementation

[0030] Example 1: A hollow platform belt checkweigher, see Figure 1-2It includes a control cabinet 21, a frame 22, a feeding unit 23 mounted on the frame 22, and a weighing unit 24. The feeding unit 23 is connected to the weighing unit 24. The weighing unit 24 includes a weighing sensor 25, a force transmission connector 6, and a belt conveyor. The fixed end of the weighing sensor 25 is fixed to the frame 22, and the bearing end of the weighing sensor 25 is fixed to the force transmission connector 6. The belt conveyor includes a belt support 5, a drive roller 3, a driven roller 4, and a motor mounted on the belt support 5. The belt support 5 is connected to the force transmission connector 6. The weighing sensor 25 and the motor are electrically connected to the control cabinet. The motor and the drive roller 3 are connected via a transmission belt. The belt support has a drive roller, a driven roller, and two weighing belts wrapped around the drive roller and the driven roller, except for the motor shaft. In addition, there are only two rollers on the belt support 5, namely the driving roller 3 and the driven roller 4. The weighing belts are arranged at intervals, and the distance between the inner sides of the two weighing belts is greater than or equal to the sum of the widths of the two weighing belts. The weighing belt support plates 2 are arranged at intervals on the belt support, corresponding to the bottom surface of the upper half of each weighing belt above the weighing belt support plate. The motor drives the driving roller to rotate through the transmission belt, thereby synchronously driving the upper half of the two weighing belts to slide on the upper surface of the weighing belt support plate. The two weighing belt support plates 2 are hollow structures that are open at the top and bottom, allowing air to flow freely on the weighing platform or air pressure to be quickly transmitted on the weighing platform. The object being weighed is dragged and moved by the two weighing belts.

[0031] Obviously, the high-speed movement of the weighed object, medicine box 9, supported by two weighing belts 1 at both ends is more stable than the high-speed movement supported by three or more belts.

[0032] See Figure 3 The transmission belt can be a toothed belt, a V-belt, or a trapezoidal belt.

[0033] The accuracy of all belt checkweighers described in this article is defined by statistical means as three times the standard deviation of the results from 20 test boxes.

[0034] Using this solution, see Figure 2 Only a 20mm wide weighing belt support plate 2 is retained under each weighing belt 1, and the belt is... Figure 7The portion of the original wide belt support plate 20 corresponding to the two weighing belts 1 is removed, meaning the other parts of the wide belt support plate 20 between the two weighing belt support plates 2 are hollowed out. Air can freely flow up and down in the 70mm wide gap between the two weighing belt support plates 2, and air pressure can be rapidly transmitted up and down the weighing platform. This makes the upward pressure of the air caused by the high-speed incoming medicine box 9 on the weighed object (i.e., the medicine box 9) and on the portion of the annular weighing belt 1 below the weighing support 5 more balanced with the downward pressure on the portion above the weighing support 5. Other configurations, such as the feeding unit 23, are exactly the same as in existing belt checkweighers. The same optimal checkweighing algorithm was used, and the test results are as follows: The accuracy of testing 20 boxes of the same weight at a rate of 300 boxes per minute was 0.21g.

[0035] At a rate of 600 boxes per minute, the accuracy of testing 20 boxes of the same weight (box 9) is 0.35g. If we disregard any potential weight deviation in qualified boxes 9, and ensure that boxes lacking instructions are rejected, the rejection threshold can be set at 9.36g. This way, a 9g box lacking 1g of instructions, even with a maximum weighing error of 0.35g, will weigh at most 9.35g, and will definitely be rejected if it's below 9.36g; in other words, defective products lacking instructions will definitely be rejected. Conversely, qualified boxes with instructions, even with a maximum weighing error of 0.35g, will weigh 9.65g, which is higher than the rejection threshold of 9.36g, and therefore will not be mistakenly rejected; that is, even if the checkweigher has its maximum error, qualified products will not be mistakenly rejected.

[0036] This solution significantly improves checkweighing accuracy, especially at high speeds, meeting the technical requirement that qualified products should not be mistakenly rejected while non-conforming products must be removed. Moreover, the structure is very simple.

[0037] Compared with the prior art shown in Example 6, it can be seen from the effect of this solution that the hollow structure of the weighing platform plays a decisive and important role in improving accuracy.

[0038] Example 2: A hollow platform belt checkweigher, similar to Example 1, will not be repeated here. The difference is that... (See...) Figure 4The feeding unit 23 is a feeding belt conveyor, which includes a feeding belt support, a feeding drive roller 14 mounted on the feeding belt support, a feeding driven roller 13, and a feeding motor. It also includes a flat, uniformly thick, thin feeding belt 11 that wraps around the feeding belt support, the feeding drive roller 14, and the feeding driven roller 13, corresponding one-to-one with the positions of the two weighing belts 1 of the weighing unit 24, and a planar wide feeding belt support plate 12 set on the upper surface of the feeding belt support. The feeding motor drives the feeding drive roller 14 through the feeding transmission device, thereby causing the two feeding belts 11 to slide on the upper surface of the wide feeding belt support plate 12, and the object to be weighed is dragged and moved by the two feeding belts 11.

[0039] The dimension of the bottom surface of the object being weighed along the length of the weighing belt is greater than or equal to the sum of the diameter of the roller at the discharge end of the feeding belt conveyor and the diameter of the roller at the feed end of the weighing unit. Using this solution, the feeding belt 11 is also a flat, uniformly thick 0.3mm thin belt. Below the two narrow feeding belts 11 is a single, wide feeding belt support plate 12. Other configurations are identical to the feeding unit 23 of the existing belt checkweigher. This results in a smoother loading of the medicine boxes 9 onto the weighing belt conveyor, with less impact on the weighing sensor 25. Test results are as follows: at a speed of 300 boxes per minute, the accuracy for testing 20 medicine boxes of the same weight is 0.19g. At a speed of 600 boxes per minute, the accuracy is 0.32g. It is evident that this solution effectively improves the checkweighing accuracy compared to Example 1.

[0040] Example 3: A hollow platform belt checkweigher, similar to Example 2, will not be repeated here. The difference is that... (See...) Figure 5 Each feeding belt 11 corresponds to an independent feeding belt support plate 16, instead of a single wide feeding belt support plate 12. The two feeding belt support plates 16 are connected by a hollow structure that allows air to flow freely between them.

[0041] Using this solution, because the weighing unit following the feeding unit is also a hollow structure, air can freely flow up and down, and air pressure can be rapidly transferred up and down. Therefore, when the objects being weighed, such as medicine boxes 9, cross from the feeding conveyor belt to the weighing conveyor belt, the influence of air is more constant and without abrupt changes. The movement posture and trend of the weighed objects are more stable, resulting in less interference with the weighing sensor 25. The test results are as follows: at a speed of 300 boxes per minute, the accuracy for testing 20 boxes of the same weight (9) is 0.17g. At a speed of 600 boxes per minute, the accuracy is 0.28g. It is evident that this solution further improves the checkweighing accuracy compared to Example 2.

[0042] Example 4: A hollow platform belt checkweigher, which is the same as Example 1 and will not be repeated here. The difference is that a weighing sensor, which is the same as the weighing sensor 25 of the weighing unit 24, is set up for compensation. It is called a compensation weighing sensor. It is arranged in parallel with the weighing sensor 25 and is also installed on the frame 22. A compensation block is installed on the compensation weighing sensor. The compensation block is located between the adjacent weighing belt support plates and is lower than the weighing belt. The sum of the weights of all parts on the compensation weighing sensor, including the compensation block, is the same as the sum of the weights of all parts on the weighing sensor of the weighing unit.

[0043] The signal of the weighing sensor 25 in the weighing unit 24 is subtracted from the signal of the compensation sensor below the compensation block. When there is no ground vibration, the noise is increased due to the subtraction of the two signals, which slightly reduces the detection accuracy. However, when there is a large foundation vibration, most of the interference of the foundation vibration on the weighing sensor 25 can be eliminated, achieving vibration suppression compensation and basically maintaining the original accuracy.

[0044] In the original embodiment 1, the accuracy of the scheme at a rate of 600 boxes per minute was only 0.44g when there was ground vibration interference.

[0045] The test results for this scheme are as follows: Without ground vibration, the accuracy is only 0.39g at a rate of 600 boxes per minute. With ground vibration, the accuracy is 0.41g at a rate of 600 boxes per minute.

[0046] It can be seen that the accuracy of this solution is slightly worse than that of Example 1 when there is no ground vibration, but it is still significantly improved compared to the prior art; however, the checkweighing accuracy can remain basically stable when there is ground vibration, making the high-speed checkweigher suitable for industrial occasions such as high-rise factories or large equipment in the vicinity that have a strong impact on the ground.

[0047] Example 5: A hollow weighing platform belt checkweigher, which is the same as Example 1 and will not be repeated. The difference is that the transmission belt is a synchronous belt or a synchronous toothed belt, which can be located on the outside of the two narrow weighing belts, thus simplifying the processing of the drive roller; or it can be located between the two narrow weighing belts, thus allowing for a smaller weighing frame width and a motor center of gravity closer to the center of the weighing platform, resulting in less impact from the deviation of the weighing sensor.

[0048] Example 6 (Comparative Example): See Figure 6 and Figure 7 The existing belt checkweigher, for a batch of standard paper medicine boxes 9 (length, width, and height approximately 60mm x 100mm x 20mm, containing one blister pack of capsules and one instruction manual, the instruction manual weighing 1g, the total weight of qualified medicine boxes 9 including all contents is 10.00g, the dimension B of the bottom surface of the medicine box perpendicular to the length of the weighing belt is 100mm wide, and the dimension A of the bottom surface of the medicine box along the length of the weighing belt is 60mm long), see [link to relevant documentation]. Figure 6 and Figure 7 A conventional belt checkweigher has a weighing belt support with an external dimension of approximately 190mm in length and 130mm in width. It features a single wide belt support plate 20 with a width matching the width of the weighing belt support. Four weighing belts 1, each 20mm wide, are wrapped around two rollers. Adjacent weighing belts 1 are evenly spaced at 10mm intervals. The distance from the outer edge of one weighing belt 1 at one end to the outer edge of the other weighing belt 1 on each roller is 110mm. The feeding unit is a feeding belt conveyor with only one wide feeding belt 10 (approximately 110mm wide) for conveying the weighed objects, such as medicine boxes 9. The roller diameter of the feeding unit 23 is the same as that of the weighing unit 24. Similar to the previous method, only when a medicine box 9 with a length of 60mm along the belt running direction crosses from the wide feeding belt 10 onto the weighing belt, the approximately 16mm gap between adjacent rollers will not affect the smoothness of the movement of the medicine box 9. Below the wide feeding belt 10 is a single wide feeding belt support plate 12. A weighing sensor with a range of less than 7.5kg is selected. Since the weight of the object being weighed is relatively light, usually less than 100 grams, the sensor itself is required to have high weighing resolution and high response frequency in order to effectively perform dynamic weighing. The existing technology test results are: the accuracy of testing 20 medicine boxes 9 of the same weight at a speed of 300 boxes per minute is 0.27g. The accuracy of the checkweigher at a speed of 600 boxes per minute is 0.60g. To ensure that at a speed of 600 boxes, medicine boxes 9 without instructions must be rejected. Without considering that there is still a certain weight deviation in qualified medicine boxes 9, the rejection limit should be higher than 9.60g, which will lead to many qualified products being mistakenly rejected.

[0049] According to existing technology, the diameter of the part of the two rollers on the weighing platform that contacts the weighing belt 1 is 16mm. For the same batch of standard paper medicine boxes 9 weighing 10.00g, compared with the previous weighing belt conveyor, only one weighing belt 1 is retained near each end of the roller. The thickness of the weighing belt 1 is 0.3mm. The flat, uniformly thin weighing belt 1 has better wrapping contact with the roller. Under the same tension, it can generate greater frictional torque on the 16mm diameter roller. The distance between these two weighing belts 1 is 70mm, but a wide belt support plate 20 with a width adapted to the width of the weighing belt support is still retained. The test results are: at a speed of 300 boxes per minute, the accuracy when testing 20 boxes of the same weight of medicine boxes 9 is 0.26g. At a speed of 600 boxes per minute, the accuracy when testing 20 boxes of the same weight of medicine boxes 9 is 0.57g, which still cannot meet the technical requirements of the 1g instruction manual.

[0050] Example 7: A hollow platform belt checkweigher, which is the same as Example 1 and will not be repeated here. The difference is that the transmission belt is a synchronous belt or a synchronous toothed belt, which can be located on the outside of the two narrow belts, so that the processing of the drive roller is simple; or it can be located between the two narrow belts, so that the width of the weighing frame can be smaller, the center of gravity of the motor is closer to the center of the platform, and the influence of the deviation of the weighing sensor is smaller.

Claims

1. A hollow platform belt checkweigher, comprising a control cabinet, a frame, a feeding unit mounted on the frame, and a weighing unit, wherein the feeding unit is connected to the weighing unit, the weighing unit includes a load cell, a force transmission connector, and a belt conveyor, the fixed end of the load cell is fixed to the frame, the bearing end of the load cell is fixed to the force transmission connector, the belt conveyor includes a belt support, a drive roller, a driven roller, and a motor mounted on the belt support, the belt support is connected to the force transmission connector, the load cell and the motor are electrically connected to the control cabinet, and the motor is connected to the drive roller via a transmission belt, characterized in that: Two weighing belts are installed on the belt support, wrapped around the driving roller and the driven roller. The weighing belts are spaced apart. The dimension of the bottom surface of the object being weighed, perpendicular to the length of the weighing belt, is B. The sum of the widths of the two weighing belts is K. The inner distance between the two weighing belts is L, and (B-0.5×K)≥L≥K. The weighing belt support plate is arranged on the belt support, with the bottom surface of the upper half of each weighing belt above the weighing belt support plate. The motor drives the driving roller to rotate through the transmission belt, thereby synchronously driving the two weighing belts to slide on the upper surface of the weighing belt support plate. The weighing belt support plate has a hollow structure.

2. The hollow weigh- platform belt checkweigher according to claim 1, characterized in that The feeding unit is a feeding belt conveyor, which includes a feeding belt support, a feeding drive roller shaft and a feeding driven roller shaft mounted on the feeding belt support, a feeding motor, two feeding belts surrounding the feeding drive roller shaft and the feeding driven roller shaft, and a feeding belt support plate set on the feeding belt support and located below the feeding belts. The feeding motor drives the feeding drive roller shaft through the feeding transmission device, thereby causing the two feeding belts to slide on the upper surface of the feeding belt support plate, and the object to be weighed is dragged and moved by the two feeding belts.

3. The hollow weigh- platform belt checkweigher according to claim 2, characterized in that The dimension of the bottom surface of the object being weighed along the length of the weighing belt is A, and the sum of the diameter of the roller at the discharge end of the feeding belt conveyor and the diameter of the roller at the feed end of the weighing unit is D, where A≥D.

4. The hollow weigh- platform belt checkweigher according to claim 2, characterized in that Each feeding conveyor belt has a corresponding feeding conveyor support plate. The space between the two feeding conveyor support plates is a hollow structure that allows air to flow freely up and down between them.

5. The hollow platform belt checkweigher according to claim 1, characterized in that, A compensating load cell is also installed on the frame. The compensating load cell is arranged in parallel with the load cell and is used for compensation, just like the load cell of the weighing unit. A compensation block is installed on the compensating load cell. The compensation block is located between the adjacent weighing belt support plates and is lower than the weighing belt. The sum of the weights of all parts on the compensating load cell, including the compensation block, is the same as the sum of the weights of all parts on the load cell of the weighing unit.

6. The hollow weigh- platform belt checkweigher according to claim 1, characterized in that The drive belt is a synchronous belt or a synchronous toothed belt, which can be located on the outside of two weighing belts or between two weighing belts.

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