High-precision chute checkweigher

Abstract

A high-precision sliding groove weight checking scale comprises a control cabinet, a mounting base, a strain type weighing sensor and a weighing sliding groove, the weighing sliding groove is connected with the bearing end of the strain type weighing sensor located below the weighing sliding groove, the fixed end of the strain type weighing sensor is connected with a mounting bottom plate located below the strain type weighing sensor, and the strain type weighing sensor is electrically connected with the control cabinet. The weighing chute is a long-strip linear smooth chute body, the strain type weighing sensor is used for compensation, the weighing chute is used for compensation, and the weighing chute is connected with the bearing end of the strain type weighing sensor which is located below the weighing chute and is used for compensation. The fixed ends of the strain type weighing sensors for compensation are connected with the mounting bottom plate positioned below the strain type weighing sensors, the strain type weighing sensors for compensation are electrically connected with the control cabinet, and the strain type weighing sensors for compensation and the strain type weighing sensors for compensation are arranged in a close-range, side-by-side and parallel manner; and the weighing chute for compensation and the weighing chute for compensation are also arranged in a close distance, side by side and in parallel.

Description

Technical Field

[0001] This solution relates to a high-precision slide rail checkweigher, especially for high-precision slide rail checkweighers for standard items such as capsules, tablets, pills, syringes, medicine bottles, soft bags, and medicine boxes in the pharmaceutical and food industries. Background Technology

[0002] In the mass production of capsules, tablets, pills, and small medicine bottles in the pharmaceutical, health product, food, and industrial standard parts industries, it is often necessary to weigh each individual item individually. After weighing, items that do not meet the weight requirements must be discarded. Many of these processes utilize chute weighing technology, where the object is weighed as it slides along a chute. Specifically, a long, smooth, straight chute is connected to the load-bearing end of a strain gauge load cell located below it, effectively turning the chute into a weighing platform. The length of the chute is perpendicular to the force direction of the strain gauge load cell. The fixed end of the strain gauge load cell is connected to the mounting base plate below it, so that the length direction of the chute is perpendicular to the plane of the force direction of the bearing end of the strain gauge load cell and the horizontal plane. In this way, since the chute can be made very light, a high-resolution, high-precision strain gauge load cell with a small range can be selected. Since the object being tested slides automatically and smoothly on the chute, compared with other belt checkweighers that use conveyor belts as weighing mechanisms and require a large range sensor, the chute checkweigher can obtain higher accuracy weighing results and higher weighing efficiency.

[0003] The cross-section of the weighing chute can be U-shaped, and the bottom of the U-shaped chute can be a large V-shaped bottom or a flat bottom. The cross-section of the weighing chute can also be V-shaped or flat.

[0004] If the length of the chute is parallel to the horizontal plane, it is called a horizontal chute checkweigher. When in use, the object to be tested is moved horizontally at high speed by the feeding mechanism in front of the chute and slides across the chute weighing platform.

[0005] More often, the design involves adjusting the angle of the base relative to the horizontal plane, allowing the length of the chute to tilt at a sufficient angle relative to the horizontal plane. This is called an inclined chute checkweigher. In use, the objects to be checked are fed one by one by the feeding mechanism in front of the chute. The objects to be checked slide down autonomously under their own weight and pass through the entire chute weighing platform.

[0006] The strain gauge load cell is electrically connected to the control cabinet. When the object being weighed is pressed onto the weighing slide (weighing platform), the strain gauge load cell generates an electrical signal that is transmitted to the control cabinet. The control cabinet then uses a certain algorithm to calculate the weight of the object being weighed.

[0007] However, vibrations in the foundation can also cause the strain gauge load cell to output a signal through its fixed end. Light winds or air currents can also cause the strain gauge load cell to output a signal by acting on the surface of the weighing chute. The operator's touching of the mounting plate or the horizontal translational mechanical vibration or horizontal torsion of various other equipment connected to the chute checkweigher can also cause the strain gauge load cell to output a strain simulation signal through its mounting plate. These signals are not the actual weight signals of the object being weighed; they are all interference signals. Moreover, these interferences cannot be avoided on-site. They greatly reduce the actual accuracy of the checkweigher in the field and significantly narrow the scope of its application.

[0008] Because it is a dynamic slide checkweigher, to ensure weighing accuracy, the object being weighed must have sufficient time to rest on the weighing platform. Therefore, the length of the weighing slide must be designed to be sufficiently long, taking into account the length of the object being weighed, its sliding speed, and the required accuracy. Generally, the length of the weighing slide is more than 10 times its width. For long, narrow weighing slides (platforms), the opening faces upwards, making them prone to draft and having a large wind-receiving area. This results in significant interference from airflow with the strain gauge load cells. Furthermore, due to the large moment of inertia relative to the load cell's mounting end, external operations and contact causing torsional motion on the load cell's mounting plate significantly interfere with the load cell's output.

[0009] Because the length of the weighing chute is relatively long compared to the length of the object being weighed, and is generally more than 10 times its width, the moment of inertia of the weighing chute relative to the mounting point of the strain gauge load cell is not negligible. When the mounting base undergoes torsional motion, the output of the strain gauge load cell mounted on it becomes very large.

[0010] Many workshops requiring checkweighing are located on high floors, where floor vibrations are intense. Many checkweighers need to be connected to large equipment, such as capsule filling machines and tablet presses, for online testing, and these machines also cause significant floor vibrations. When used offline, chute checkweighers require frequent feeding. Frequent operation of the checkweigher's touchscreen, feeding hopper, and rejection hopper results in frequent contact with the checkweigher. Furthermore, the rejection action of the checkweigher in removing defective products generates a reaction force on the mounting plate of the strain gauge load cell, causing significant vibration to the strain gauge load cell.

[0011] All of these factors severely reduce the actual detection accuracy of checkweighers, making existing chute checkweighers ineffective for use in line testing with production equipment such as filling machines and tablet presses, and rendering them unusable in many high-rise workshops and temperature-controlled air-conditioned rooms.

[0012] To solve this problem, common solutions include installing vibration-damping or shock-absorbing feet on the checkweigher, preventing mechanical contact between the checkweigher and other equipment, or sealing the checkweigher chute (platform) to prevent airflow. These measures are cumbersome, costly, and ineffective. Utility Model Content

[0013] This solution proposes a high-precision slide rail checkweigher to address the shortcomings of existing technologies.

[0014] The technical measures adopted in this solution are as follows: a high-precision slide checkweigher, comprising a control cabinet, a mounting base, a strain gauge load cell, and a weighing slide. The weighing slide is connected to the bearing end of the strain gauge load cell located below it, and the fixed end of the strain gauge load cell is connected to the mounting base plate located below it. The strain gauge load cell is electrically connected to the control cabinet. The weighing slide is a long, straight, smooth trough. It also includes a compensating strain gauge load cell and a compensating weighing slide. The compensating strain gauge load cell is completely integrated with the strain gauge load cell. The same type of sensor is used for compensating the weighing chute, which is made of the same material, shape, size, and weight as the weighing chute. The compensating weighing chute is connected to the bearing end of the compensating strain gauge load cell located below it. The fixed end of the compensating strain gauge load cell is connected to the mounting base plate located below it. The compensating strain gauge load cell is electrically connected to the control cabinet. The compensating strain gauge load cell and the strain gauge load cell are arranged close together, side by side, and parallel to each other. The compensating weighing chute and the weighing chute are also arranged close together, side by side, and parallel to each other.

[0015] Another specific feature of this solution is that the length of the weighing chute is more than 10 times its width. When the checkweigher is working, there are never any capsules, tablets or other objects being tested on the weighing chute used for compensation. It is only used to sense various external interferences.

[0016] It also includes a feed chute that is parallel to the weighing chute and connected to the feeding end of the weighing chute.

[0017] It also includes a time-delay chute parallel to the weighing chute and connected to the discharge end of the weighing chute, with a rejection mechanism connected to the discharge end of the time-delay chute.

[0018] The line connecting the inlet end of the weighing chute and the compensating weighing chute is parallel to the horizontal plane.

[0019] The feeding chute, weighing chute, and delay chute are all inclined downwards, and the weighing chute used for compensation is also inclined downwards.

[0020] The mounting base plate is connected to the rotating vertical plate, and the rotating vertical plate is connected to the machine base.

[0021] The high-precision slide checkweigher also includes multiple sets of parallel strain gauge load cells and weighing slides, sharing a single strain gauge load cell and weighing slide for compensation. The weighing slide and strain gauge load cell for compensation are located in the middle of all working weighing slides and strain gauge load cells, or all sets of working weighing slides and strain gauge load cells are symmetrically distributed on both sides of the weighing slide and strain gauge load cell for compensation.

[0022] The high-precision chute checkweigher also includes multiple parallel material guide chutes connected to the inlet of the parallel weighing chutes.

[0023] The beneficial effects of this solution are: This utility model significantly improves the actual working accuracy of existing slide checkweighers using long slide platform under actual working conditions, enabling them to be truly applied to the precision weighing of extremely lightweight products such as capsules and tablets, thus solving a major problem for the online safety standard production of capsules and tablets in the pharmaceutical industry. 1. Because the strain gauge load cells used for compensation are exactly the same as those used for actual weighing, and the weight of the weighing platform used for compensation is exactly the same as that of the weighing chute used for actual weighing, the frequency response characteristics of the elastic mechanical system composed of the working strain gauge load cells and the weighing chute are consistent with those of the compensation strain gauge load cells and the weighing platform. This allows for effective subtraction of analog electrical signals without any adverse reaction. Furthermore, the two systems are very close to each other. Therefore, all interference—including vertical vibrations from the foundation, horizontal linear interference from equipment operation or nearby equipment contact, and the back-seat force interference from the rejection action—outputs the same signal to both strain gauge load cells used for different purposes. Only the output signal of the strain gauge load cell used for weighing contains the output signal of the object being weighed. Therefore, subtracting the analog electrical signals from the two strain gauge load cells leaves only the signal of the object being weighed, and this process is extremely fast. Compared to digital signal subtraction, analog signal subtraction is much faster. 1. The analog electrical signal of a strain gauge load cell is a direct, instantaneous signal proportional to the deformation caused by the applied force. It is not an indirect, delayed signal that may lose its strict proportional relationship due to various physical quantity conversions. 2. Because the shape, size, and moment of inertia of the chute weighing platform used for compensation and the long, narrow weighing chute used for actual weighing are exactly the same, and they are very close to each other, all interferences, whether from equipment operation or contact with nearby equipment, or from airflow, will output the same signal to both strain gauge load cells used for different purposes. Only the output signal of the strain gauge load cell used for weighing contains the output signal of the object being weighed. Therefore, subtracting the signals from the two strain gauge load cells leaves only the signal of the object being weighed. This eliminates various external and internal interferences, significantly improves the on-site working accuracy of the chute checkweigher, and solves the problem of severely reduced checkweigher accuracy under on-site conditions. Attached Figure Description

[0024] Figure 1 This is a top view of the front right side of this utility model. Figure 2 for Figure 1 The top view of the rear left side. Figure 3 This is a schematic diagram of the present invention with a rotating upright plate. Figure 4 A schematic diagram showing how multiple weighing chutes share a single weighing chute used for compensation.

[0025] In the figure, 1-material conveying chute, 2-weighing chute, 3-delay chute, 4-transition bracket, 5-strain gauge load cell, 6-mounting base plate, 7-rotating vertical plate, 12-weighing chute for compensation, 14-compensation transition component, 15-strain gauge load cell for compensation. Detailed Implementation

[0026] Example 1: A high-precision slide rail checkweigher, see Figure 1-3 It includes a control cabinet, a mounting base 6, a strain gauge load cell 5, and a weighing chute 2. The weighing chute 2 is connected to the bearing end of the strain gauge load cell 5 located below it. The fixed end of the strain gauge load cell 5 is connected to the mounting base 6 located below it. The strain gauge load cell 5 is electrically connected to the control cabinet. The weighing chute 2 is a long, straight, smooth chute, and its length is more than 10 times its width. It also includes a strain gauge load cell 15 for compensation and a weighing chute 12 for compensation. The strain gauge load cell 15 for compensation is identical in shape and size to the strain gauge load cell 5. The sensors have the same weight. The weighing slide 12 used for compensation is exactly the same as the weighing slide 2. The weighing slide 12 used for compensation is connected to the bearing end of the strain gauge load cell 15 used for compensation located below it. The fixed end of the strain gauge load cell 15 used for compensation is connected to the mounting base plate 6 located below it. The strain gauge load cell 15 used for compensation is electrically connected to the control cabinet. The strain gauge load cell 15 used for compensation and the strain gauge load cell 5 are arranged close together, side by side and parallel. The weighing slide 12 used for compensation and the weighing slide 2 are also arranged close together, side by side and parallel.

[0027] It also includes a parallel material guide chute 1 that is connected to the loading end of the weighing chute 2. The object being tested can be adjusted on the parallel material guide chute 1 to move onto the weighing chute 2 with minimal impact on the strain gauge load cell 5, so as to improve the weighing accuracy.

[0028] It also includes a time-delay chute 3 that is parallel to the weighing chute 2 and is connected to the discharge end of the weighing chute 2. A rejection mechanism is connected to the discharge end of the time-delay chute 3. During the process of the object being measured sliding on the time-delay chute 3, the control cabinet calculates the weight of the object being weighed and sends an action signal to the rejection mechanism.

[0029] The line connecting the inlet end of the weighing chute 2 and the weighing chute 12 used for compensation is parallel to the horizontal plane.

[0030] The feeding chute 1, weighing chute 2, and delay chute 3 are all inclined downwards, and the weighing chute 12 used for compensation is also inclined downwards.

[0031] To verify the actual effect of this utility model, the following comparative experiment was conducted. The test method was to take 20 capsules of the same material, shape and weight and pass them through the weighing chute at the same time interval and speed. No two or more capsules could be on the weighing chute at the same time. The standard deviation of the 20 weighing results was calculated using a probability and statistics formula.

[0032] A chute checkweigher for testing capsules was placed next to the capsule filling machine in the second-floor workshop. Its weighing platform has a chute width of 9.5mm, a side height of 8mm, a length of 200mm, and a weight of 25g. In the comparative test, the same #0 capsules with gelatin shells (total weight 600mg) were used, along with the same feeding method and equal time intervals. The weighing speed of each weighing channel was 100 capsules per minute, and the same dynamic checkweighing algorithm for the chute was used. Normal windproof and shockproof measures were taken. However, due to the large number of capsules that need to frequently enter and exit the weighing platform channel, the checkweigher could not achieve absolute airtightness and windproofness. The air conditioning air from the upper and lower circulation of the workshop still affected the weighing accuracy.

[0033] First, using the aforementioned chute checkweigher without a compensated strain gauge load cell and corresponding chute platform—that is, the existing technology—with the filling machine stopped, the air conditioning off, no feeding action, no impact on the ball at the end of the strain gauge load cell mounting base, and no rejection of defective products, the chute checkweigher's three-times standard deviation is 2.0 mg. This is the ideal accuracy in the laboratory.

[0034] The following tests the working accuracy of the above-mentioned chute checkweigher under actual working conditions by introducing only one interference, but not all at the same time:

[0035] 1. With the checkweigher positioned below the air conditioning vent in the workshop and the airflow constant, a 3x standard deviation results in a reading of 3.8 mg. The air conditioning airflow has a 90% impact on accuracy reduction.

[0036] 2. The filling machine is turned on and operating at normal speed. Three times the standard deviation is 3.2mg. The ground vibration caused by the filling machine has an impact of 60% on the accuracy.

[0037] 3. When a person at a height of 0.3 meters feeds material intermittently into the hopper of the chute checkweigher without contact, the result is 2.8 mg three times the standard deviation. The material feeding affects the accuracy by 40%.

[0038] 4. When the ball impacts one end of the mounting base of the strain gauge load cell at a certain speed, the long scale groove undergoes torsional vibration. The error is 3.6 mg three times the standard deviation. The addition of material affects the accuracy by 80%.

[0039] 5. Under the same frequency and time interval for rejecting non-conforming products, three times the standard deviation is 2.5 mg, and rejection affects the accuracy by 25%.

[0040] Given that strong impacts on the mounting base of the strain gauge load cell can be avoided in actual working conditions, four additional interferences are introduced simultaneously during the use of the aforementioned chute checkweigher. These interferences occur concurrently as follows: the chute checkweigher is located below the air conditioning vent in the workshop, with a constant airflow; the filling machine is running at normal speed; a person intermittently adds material to the chute checkweigher's hopper from a height of 0.3 meters without direct contact; and defective products are rejected at the same frequency and time interval. When all four interferences occur simultaneously, the aforementioned chute checkweigher, without a compensated strain gauge load cell and corresponding chute platform, under existing technology, yields a test result of 4.4 mg (3 times the standard deviation) under actual working conditions. The simultaneous occurrence of these four interferences affects accuracy by 120%.

[0041] Then, in the aforementioned existing chute checkweigher, the compensation device of this invention is adopted. A strain gauge load cell, identical to the working strain gauge load cell and the long chute load cell, is arranged parallel to the existing chute platform at a distance of 20mm as interference compensation. The signal of the working strain gauge load cell is subtracted from the signal of the compensation strain gauge load cell. Then, under the same chute dynamic weighing algorithm as before, the above-mentioned interference, i.e., the accuracy test under actual working conditions, is repeated. The results are as follows: 1. When the chute checkweigher is located under the air conditioner outlet in the workshop, with a constant airflow, the standard deviation is 2.2mg (3 times). The air conditioner airflow only reduces the accuracy by 10%. Compared with the prior art, the accuracy of the chute checkweigher of this invention is improved by 80%. 2. When the filling machine is turned on and operating at normal speed, the standard deviation is 2.2mg (3 times). The ground vibration caused by the filling machine reduces the accuracy by 10%. Compared with the prior art, the accuracy of the chute checkweigher of this invention is improved by 50%. 3. Manual, intermittent feeding from a height of 0.3 meters into the chute checkweigher without direct contact results in a 3-times standard deviation of 2.1 mg, affecting accuracy by 5%. Compared to existing technologies, this new chute checkweigher improves accuracy by 35%. 4. A ball impacts one end of the strain gauge load cell mounting base at a certain speed, causing torsional vibration in the elongated weighing trough. This results in a 3-times standard deviation of 2.3 mg, affecting accuracy by 15%. Compared to existing technologies, this new chute checkweigher improves accuracy by 65%. 5. Under the same frequency and time interval for rejecting defective products, the 3-times standard deviation is 2.1 mg, affecting accuracy by 5%. Compared to existing technologies, this new chute checkweigher improves accuracy by 20%. 6. When the aforementioned four interferences occur simultaneously, the 3-times standard deviation is 2.6 mg. Therefore, compared to no interference, the accuracy of the new chute checkweigher using this new technology decreases by only 30% under the simultaneous action of the four interferences. However, compared to the existing technology where the accuracy decreases by 120% under the simultaneous action of four interferences, the accuracy of the slide groove checkweigher of this utility model is improved by 90%.

[0042] Comparative test results show that by using this utility model patent, that is, by adding a compensating strain gauge load cell and a compensating slide, and by subtracting the signal of the compensating strain gauge load cell from the signal of the working strain gauge load cell, the existing slide checkweigher has significantly enhanced anti-interference capability, greatly improved actual working accuracy, and achieved remarkable compensation effect by using the same sliding checkweighing algorithm.

[0043] Example 2: A high-precision slide rail checkweigher, similar to Example 1 (details omitted), the difference being... (See...) Figure 3 The mounting base 6 is connected to the rotating vertical plate 7, which is connected to the machine base. Rotating the rotating vertical plate 7 can adjust the angle of the weighing slide 2 relative to the horizontal plane, thereby adjusting the weighing speed or weighing accuracy. Example

[0044] A high-precision slide rail checkweigher, similar to Example 1, will not be repeated here; the difference is that... (See...) Figure 4 It includes multiple sets of parallel strain gauge load cells 5 and weighing chutes 2, which share a compensating strain gauge load cell 15 and a compensating weighing chute 12. The compensating weighing chute 12 and the compensating strain gauge load cell 15 are located in the middle of all sets of working weighing chutes 2 and strain gauge load cells 5, or all sets of working weighing chutes 2 and strain gauge load cells 5 are symmetrically distributed on both sides of the compensating weighing chutes 12 and the compensating strain gauge load cell 15. It also includes multiple parallel feed chutes 1 connected to the feed inlets of the parallel weighing chutes 2.

Claims

1. A high-precision slide checkweigher, comprising a control cabinet, a mounting base, a strain gauge load cell, and a weighing slide, wherein the weighing slide is connected to the bearing end of the strain gauge load cell located below it, the fixed end of the strain gauge load cell is connected to the mounting base plate located below it, the strain gauge load cell is electrically connected to the control cabinet, and the weighing slide is a long, straight, smooth trough, characterized in that: It also includes a strain gauge load cell for compensation and a weighing chute for compensation. The strain gauge load cell for compensation is exactly the same as the strain gauge load cell. The weighing chute for compensation is exactly the same as the weighing chute in terms of material, shape, size, and weight. The weighing chute for compensation is connected to the bearing end of the strain gauge load cell for compensation located below it. The fixed end of the strain gauge load cell for compensation is connected to the mounting base plate located below it. The strain gauge load cell for compensation is electrically connected to the control cabinet. The strain gauge load cell for compensation and the strain gauge load cell are arranged close together, side by side, and parallel to each other. The weighing chute for compensation and the weighing chute are also arranged close together, side by side, and parallel to each other.

2. The high-precision slide rail checkweigher according to claim 1, characterized in that, The length of the weighing chute is more than 10 times its width.

3. The high-precision slide rail checkweigher according to claim 1, characterized in that, It also includes a feed chute that is parallel to the weighing chute and connected to the feeding end of the weighing chute.

4. A high-precision slide rail checkweigher according to claim 1, characterized in that, It also includes a time-delay chute parallel to the weighing chute and connected to the discharge end of the weighing chute, with a rejection mechanism connected to the discharge end of the time-delay chute.

5. A high-precision slide rail checkweigher according to claim 1, characterized in that, The line connecting the inlet end of the weighing chute and the compensating weighing chute is parallel to the horizontal plane.

6. A high-precision slide rail checkweigher according to claim 1, characterized in that, The weighing chute is tilted downwards, and the compensating weighing chute is also tilted downwards.

7. A high-precision slide rail checkweigher according to claim 1, characterized in that, The mounting base plate is connected to the rotating vertical plate, and the rotating vertical plate is connected to the machine base.

8. A high-precision slide rail checkweigher according to claim 1, characterized in that, The high-precision slide checkweigher also includes multiple sets of parallel strain gauge load cells and weighing slides. They share a set of strain gauge load cells and weighing slides used for compensation. All sets of working weighing slides and strain gauge load cells are symmetrically distributed on both sides of the weighing slides and strain gauge load cells used for compensation.

9. A high-precision slide rail checkweigher according to claim 8, characterized in that, It also includes multiple parallel feed chutes connected to the feed inlets of parallel weighing chutes.

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