A servo-driven knife pressing device, a packing machine, and a control method for the servo-driven knife pressing device.

Abstract

This application provides a servo pressure knife device, a strapping machine, and a control method for the servo pressure knife device, applied in the field of strapping machine technology. The pressure knife assembly applies clamping force to the strapping tape. The servo pressure cylinder structure integrates a high-precision pressure sensor and a drive unit, driving the pressure knife assembly to move and controlling its output pressure. The high-precision pressure sensor collects actual pressure data in real time; a tape thickness detector acquires the strapping tape thickness information; and a PLC control unit dynamically adjusts the output power or displacement of the drive unit based on preset pressure parameters, actual pressure data, and thickness information, so that the actual pressure data is maintained within the range allowed by the preset pressure parameters. This method has the advantage of achieving precise control and adaptive adjustment of the strapping tape clamping force, overcoming the shortcomings of traditional devices where spring pressure cannot accurately adapt, leading to strapping tape cracking or slippage, and low strapping quality and efficiency, thereby improving strapping quality and efficiency.

Description

Technical Field

[0001] This application relates to the field of packaging machine technology, and in particular to a servo pressing device, a packaging machine, and a control method for the servo pressing device. Background Technology

[0002] In the field of strapping machinery, the clamping quality of strapping directly affects the reliability and efficiency of strapping. Traditional strapping clamping devices typically use a motor-driven cam, which in turn drives a pressure knife structure. The pressure knife structure contains a mold spring, relying on the spring's elasticity to adapt to the strapping thickness and adjust the pressure. However, this structure has a significant drawback: when the strapping thickness changes, the spring pressure cannot accurately adapt, easily leading to two problems—either excessive pressure causing the strapping to crack, or insufficient pressure causing the strapping to slip during tightening. This directly results in low strapping quality and low strapping efficiency, severely restricting the production efficiency of strapping operations. There is an urgent need for a device capable of precise control and adaptive adjustment of strapping clamping force to overcome the shortcomings of traditional devices where the spring pressure cannot accurately adapt, leading to strapping cracking or slippage, and low strapping quality and efficiency, thereby improving both strapping quality and efficiency.

[0003] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0004] In view of the shortcomings of the prior art, this application provides a servo pressure knife device, a strapping machine, and a control method for the servo pressure knife device, which is applied to the field of strapping machine technology. It can achieve precise control and adaptive adjustment of the strapping clamping force, overcome the defects of traditional devices that cannot accurately adapt to spring pressure, resulting in strapping cracking or slippage, and low strapping quality and efficiency, thereby improving strapping quality and efficiency.

[0005] In a first aspect, a servo-driven tool pressing device, the device comprising:

[0006] The pressure knife assembly is used to contact and apply clamping force to the strapping.

[0007] The servo pressure cylinder structure integrates a high-precision pressure sensor and a drive unit. The drive unit is connected to the pressure knife assembly and is used to drive the pressure knife assembly to move and control its output pressure. The high-precision pressure sensor is used to collect the actual pressure data of the pressure knife assembly acting on the packing strap in real time.

[0008] A thickness detector is used to obtain the thickness information of the packing strap to be compressed;

[0009] The PLC control unit is electrically connected to the pressing knife assembly, the servo pressing cylinder structure, and the thickness detector. The PLC control unit is used to dynamically adjust the output power or displacement of the drive unit according to the preset pressure parameters, the actual pressure data, and the thickness information, so that the actual pressure data is maintained within the range allowed by the preset pressure parameters.

[0010] Furthermore, the PLC control unit includes:

[0011] The acquisition module is used to acquire the preset pressure parameters and the initial thickness information of the packing strap;

[0012] The first control module is used to control the drive unit to drive the pressure knife assembly to move toward the packing strap until the actual pressure data reaches the initial threshold corresponding to the preset pressure parameter.

[0013] The second control module is used to control the high-precision pressure sensor to collect the actual pressure data of the packing strap in real time, and to control the thickness detector to monitor the thickness change of the packing strap in real time.

[0014] The third control module is used to adjust the output pressure of the drive unit according to the thickness change direction, preset pressure parameters and actual pressure data when the thickness change exceeds the preset range, so that the actual pressure data is maintained within the allowable fluctuation range of the preset pressure parameters.

[0015] Specifically, when the third control module adjusts the output pressure of the drive unit, the magnitude of the pressure adjustment is positively correlated with the thickness change, and the magnitude of the pressure adjustment does not exceed ±20% of the preset pressure parameter.

[0016] Furthermore, the thickness detector includes, but is not limited to, a laser sensor, an infrared sensor, or a mechanical contact displacement sensor; the thickness detector is located at the feeding end of the pressing knife assembly and is used to collect the thickness information in advance before the packing strap is pressed and send it to the PLC control unit.

[0017] Furthermore, the drive unit includes a servo motor, a ball screw and a cylinder that are connected to the servo motor in a transmission manner, and the servo motor drives the output end of the cylinder to extend and retract through the ball screw; the high-precision pressure sensor is integrated at the end of the pressure knife assembly away from the servo motor, and is used to directly detect the actual pressure data of the pressure knife assembly acting on the packing strap.

[0018] Furthermore, the PLC control unit is preset with at least two sets of pressure parameters, each set of pressure parameters corresponding to a type of packing strap of a certain material or specification;

[0019] The PLC control unit is also used to call the pressure parameter that matches the current strapping type as the preset pressure parameter when changing the strapping type;

[0020] The PLC control unit is also connected to a human-machine interface unit, which is used to receive user-inputted custom pressure parameters and store the custom pressure parameters as a new pressure parameter group in the PLC control unit.

[0021] Furthermore, the pressure knife assembly includes at least a pressure knife body and a connecting seat, the connecting seat being rigidly connected to the output end of the drive unit; the working surface of the pressure knife body that contacts the packing strap is provided with anti-slip texture.

[0022] Furthermore, the PLC control unit also includes:

[0023] The first calculation module is used to continuously acquire multiple thickness information within a preset time window and calculate the statistical feature value of the thickness information;

[0024] The judgment module is used to determine whether the deviation between the statistical feature value and the current reference thickness exceeds a first preset deviation threshold.

[0025] The fourth control module is used to determine that the current thickness fluctuation is a valid thickness fluctuation when the deviation exceeds the first preset deviation threshold and the duration reaches a preset duration, and to update the preset pressure parameter according to the statistical feature value.

[0026] The fifth control module is used to determine that the current thickness fluctuation is surface noise interference when the deviation does not exceed the first preset deviation threshold, or when the deviation exceeds the first preset deviation threshold but the duration does not reach the preset duration, and to keep the current preset pressure parameter unchanged.

[0027] Furthermore, the PLC control unit also includes:

[0028] The second calculation module is used to calculate the thickness change rate of the thickness information within adjacent sampling periods;

[0029] The comparison module is used to compare the thickness change rate with a preset change rate threshold.

[0030] The sixth control module is used to activate a fast response mode when the thickness change rate is greater than the change rate threshold, calculate the feedforward compensation amount according to the thickness change rate, and add the feedforward compensation amount to the displacement control command of the drive unit in advance to offset the pressure fluctuation caused by the sudden change in thickness.

[0031] The seventh control module is used to adjust the output power of the drive unit based on the actual pressure data and the preset pressure parameters when the thickness change rate is less than or equal to the change rate threshold.

[0032] Secondly, a packaging machine includes any of the aforementioned servo pressing devices, and further includes a tape feeding mechanism, a tightening mechanism, and a welding mechanism arranged in sequence, wherein the servo pressing device is disposed at a pressing station between the tightening mechanism and the welding mechanism.

[0033] Thirdly, a control method for a servo-driven tool pressing device, the method being applied to any of the servo-driven tool pressing devices described above, the method comprising the steps of:

[0034] S1: Obtain the thickness information of the packing strap to be compressed;

[0035] S2: Real-time acquisition of actual pressure data of the pressure knife assembly acting on the packing strap;

[0036] S3: Based on the preset pressure parameters, the actual pressure data, and the thickness information, dynamically adjust the output power or displacement of the drive unit so that the actual pressure data is maintained within the preset threshold range.

[0037] Beneficial Effects: This application provides a servo pressure knife device, a strapping machine, and a control method for the servo pressure knife device. The pressure knife assembly applies clamping force to the strapping tape. The servo pressure cylinder structure integrates a high-precision pressure sensor and a drive unit, driving the pressure knife assembly to move and controlling its output pressure. The high-precision pressure sensor collects actual pressure data in real time; a tape thickness detector acquires the strapping tape thickness information; and the PLC control unit dynamically adjusts the output power or displacement of the drive unit based on preset pressure parameters, actual pressure data, and thickness information to maintain the actual pressure data within the allowable range of the preset pressure parameters. This method achieves precise control and adaptive adjustment of the strapping tape clamping force, overcoming the shortcomings of traditional devices where spring pressure cannot accurately adapt, leading to strapping tape cracking or slippage, and low strapping quality and efficiency. Therefore, it improves strapping quality and efficiency. Attached Figure Description

[0038] Figure 1 This application provides a structural diagram of a servo-driven knife pressing device.

[0039] Figure 2 This is a schematic diagram showing the installation position of the thickness detector in a servo pressing device provided in this application.

[0040] Figure 3 This is a schematic diagram showing another installation position of the thickness detector in the servo pressing device provided in this application.

[0041] Figure 4A flowchart of a control method for a servo-driven knife pressing device provided in this application.

[0042] Labeling explanations: 1. Pressure knife assembly; 2. Servo pressure cylinder structure; 3. Thickness detector; 4. Packing strap; 11. Pressure knife body; 12. Connecting seat. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and marked in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0044] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0045] In automated packaging production lines, the packing operation is a crucial step in ensuring that products remain intact and secure during transportation and storage. Traditional packing machines generally rely on a mechanical transmission structure consisting of a motor, cam, and springs to tighten the strapping. In this structure, the rotational motion of the motor is converted into the reciprocating motion of the pressure blade via the cam, and the pressure exerted by the pressure blade on the strapping mainly comes from the elastic force of the internal mold spring. While this design is simple in structure, it has revealed many insurmountable shortcomings in practical applications.

[0046] The core problem lies in the fact that the spring's pressure output is linearly related to its compression, resulting in very limited pressure adjustment range and precision. When faced with uneven thicknesses across different batches, specifications, or even the same roll of strapping, this fixed spring mechanism proves inadequate. When a thicker piece of strapping passes under the pressure cutter, the spring is over-compressed, potentially exceeding the strapping's tolerance limit momentarily. This can lead to indentations on the strapping surface, damage to the internal structure, or even cracking, resulting in ineffective packaging. Conversely, when a thinner piece of strapping passes through, the spring's compression is insufficient, generating too little clamping force to effectively secure the strapping. In subsequent tightening processes, the strapping may slip under the pressure cutter, causing tightening failure and resulting in loose and collapsed packages. These problems directly lead to low packaging quality pass rates. Frequent equipment downtime and manual intervention not only severely impact production efficiency but also waste packaging materials and increase operating costs for the company.

[0047] To address the aforementioned technical challenges, namely the cracking or slippage of strapping due to inaccurate pressure control during traditional strapping clamping processes, this application provides a servo-driven clamping device. The core idea of ​​this device is to abandon the traditional passive spring pressure structure and instead employ an active, precisely controllable servo drive system, combined with a real-time feedback mechanism, to achieve dynamic adaptive adjustment of the clamping force.

[0048] The device includes:

[0049] The pressure knife assembly 1 is used to contact and apply a clamping force to the packing strap 4;

[0050] The servo pressure cylinder structure 2 integrates a high-precision pressure sensor and a drive unit. The drive unit is connected to the pressure knife assembly 1 and is used to drive the pressure knife assembly 1 to move and control its output pressure. The high-precision pressure sensor is used to collect the actual pressure data of the pressure knife assembly 1 acting on the packing strap 4 in real time.

[0051] Thickness detector 3 is used to obtain the thickness information of the packing strap 4 to be compressed;

[0052] The PLC control unit is electrically connected to the pressure knife assembly 1, the servo pressure cylinder structure 2, and the thickness detector 3. The PLC control unit is used to dynamically adjust the output power or displacement of the drive unit according to the preset pressure parameters, actual pressure data, and thickness information, so that the actual pressure data is maintained within the range allowed by the preset pressure parameters.

[0053] The pressure knife assembly 1 is the actuating component that directly contacts the packing strap 4 and applies clamping force. It includes at least three pressure knives: a left pressure knife, a middle pressure knife, and a right pressure knife arranged side-by-side. See the appendix for details. Figure 1 As shown.

[0054] The servo pressure cylinder structure 2 integrates a high-precision pressure sensor and a drive unit. The drive unit is connected to the pressure knife assembly 1, responsible for driving the assembly to perform precise reciprocating movements and accurately controlling its output pressure. Simultaneously, the high-precision pressure sensor is configured to continuously collect the actual pressure data of the pressure knife assembly 1 acting on the packing strap 4 in real time, and uses this actual pressure data as a feedback signal.

[0055] Please refer to Figure 2 and Figure 3 The thickness detector 3 is used to obtain the thickness information of the packing strap 4 to be compressed before the packing strap 4 enters the compression area.

[0056] The PLC control unit establishes electrical signal connections with the pressure knife assembly 1, the servo pressure cylinder structure 2, and the thickness detector 3. The core logic of the PLC control unit is to perform comprehensive calculations and logical judgments based on the preset target pressure parameters, the actual pressure data fed back by the high-precision pressure sensor, and the thickness information of the packing tape 4 provided by the thickness detector 3. Then, it dynamically and in real time adjusts the output power or output displacement of the drive unit. The ultimate goal is to ensure that the actual pressure data is always accurately maintained within the fluctuation range allowed by the preset pressure parameters.

[0057] In a complete work cycle, the servo pressing device operates as follows: First, when a new strapping tape 4 is fed into the pressing station by the feeding mechanism, the tape thickness detector 3 located at the feeding end of the pressing assembly 1 measures the thickness of the incoming strapping tape 4 and sends the initial thickness information to the PLC control unit. Upon receiving this thickness information, the PLC control unit, combined with the preset pressure parameters corresponding to the current production task, generates initial control commands. Subsequently, the PLC control unit controls the drive unit in the servo pressing cylinder structure 2 to begin operation. The drive unit drives the pressing assembly 1 to descend rapidly, approaching the strapping tape 4. When the pressing assembly 1 contacts the surface of the strapping tape 4, the high-precision pressure sensor detects a pressure signal. The PLC control unit continuously monitors this pressure signal and controls the drive unit to continue applying pressure until the actual pressure data reaches an initial threshold set by the preset pressure parameters, completing the initial pressing. After this, the tightening mechanism of the strapping machine begins operation to tighten the strapping tape 4. Throughout the tightening process, the PLC control unit enters a high-frequency closed-loop control state. On one hand, the thickness detector 3 continuously monitors the thickness of the subsequently entering strapping 4 and transmits the thickness change information to the PLC in real time. On the other hand, the high-precision pressure sensor also monitors the actual pressure fluctuations caused by changes in the thickness or tension of the strapping 4 in real time. The PLC control unit calculates the deviation between the actual pressure data and the preset pressure parameters, as well as the change in the thickness of the strapping 4. Once the deviation exceeds its corresponding threshold, it indicates that the actual pressure has deviated from the preset range, or a significant thickness change is detected. The control unit immediately calculates the required adjustment amount and sends a fine-tuning command to the drive unit. By fine-tuning the output power or displacement of the drive unit, these changes are compensated, thereby ensuring that the clamping force is always precisely locked within the target range throughout the entire dynamic process, preventing the strapping 4 from slipping and avoiding cracking it.

[0058] By combining a closed-loop control strategy that integrates pre-detection, real-time feedback, and dynamic adjustment, the servo pressure knife device proposed in this application fundamentally overcomes the limitations of traditional spring pressure knives. It can actively adapt to the thickness changes of the packing tape 4, achieving precise and constant control of the clamping force, thereby significantly improving the stability of packing quality and the efficiency of production operations.

[0059] Furthermore, the PLC control unit includes:

[0060] The acquisition module is used to acquire preset pressure parameters and the initial thickness information of the packing strap 4;

[0061] The first control module is used to control the drive unit to drive the pressure knife assembly 1 to move toward the packing strap 4 until the actual pressure data reaches the initial threshold corresponding to the preset pressure parameter.

[0062] The second control module is used to control the high-precision pressure sensor to collect the actual pressure data of the packing strap 4 in real time, and to control the thickness detector 3 to monitor the thickness change of the packing strap 4 in real time.

[0063] The third control module is used to adjust the output pressure of the drive unit according to the direction of thickness change, preset pressure parameters and actual pressure data when the thickness change exceeds the preset range, so as to keep the actual pressure data within the allowable fluctuation range of the preset pressure parameters.

[0064] It should be noted that the initial threshold, the allowable range of the preset pressure parameter, and the limitation of not exceeding ±20% of the preset pressure parameter are all related to the currently activated preset pressure parameter group. Since the PLC control unit has multiple sets of pressure parameters corresponding to different materials or specifications, the aforementioned initial threshold, allowable fluctuation range, and maximum adjustment range are not globally fixed values, but rather variables that dynamically change with the currently invoked recipe.

[0065] Among them, when the third control module adjusts the output pressure of the drive unit, the magnitude of the pressure adjustment is positively correlated with the thickness change, and the magnitude of the pressure adjustment does not exceed ±20% of the preset pressure parameter.

[0066] The acquisition module's function is to read preset pressure parameters matching the current packaging task from memory at the beginning of each packaging cycle, and to acquire the initial thickness information of the packing tape 4 from the tape thickness detector 3. This information forms the benchmark and starting point for all subsequent control actions.

[0067] After receiving the reference information from the acquisition module, the first control module sends a command to the drive unit in the servo cylinder structure 2, driving the pressure knife assembly 1 to move towards the strapping 4 at a set speed. Once the pressure knife assembly 1 contacts the strapping 4 and begins applying pressure, the first control module continuously monitors the actual pressure data transmitted by the high-precision pressure sensor and compares it with preset pressure parameters. When the actual pressure data reaches an initial threshold corresponding to the preset pressure parameters, such as 90% of the target pressure, the first control module stops the rapid downward pressure of the pressure knife assembly 1. This step ensures that the pressure knife assembly 1 can safely and effectively press the strapping 4 with an initial pressure in the initial stage.

[0068] After the initial compression is completed, the second control module simultaneously controls a high-precision pressure sensor to monitor the actual pressure data applied to the strapping 4 in real time, and controls a thickness detector 3 to monitor the thickness change of the strapping 4 in real time. By simultaneously collecting these two key variables, pressure and thickness, the control system can comprehensively grasp the real-time status of the strapping 4 during the compression process, providing dual feedback for subsequent adaptive adjustments, and greatly improving the accuracy and robustness of the control.

[0069] The third control module continuously analyzes the thickness change data provided by the second control module. When the detected thickness change exceeds a preset range, such as exceeding 5% of the nominal thickness, the third control module first determines the direction of the thickness change, i.e., whether the packing strap 4 has thickened or thinned. Then, based on the direction and magnitude of the thickness change, it precisely adjusts the output pressure of the drive unit. During this process, a preset pressure parameter serves as a target value or reference range. The third control module compares the actual pressure data with this parameter to determine whether the actual pressure deviates from the allowable range. The preset pressure parameter is the basis for pressure adjustment. The actual pressure data serves as a feedback signal. The second control module collects this data in real time, reflecting the current output pressure status of the drive unit. The actual pressure data is the input for pressure adjustment. If the packing strap 4 thickens, the output pressure is appropriately reduced to prevent cracking; if the packing strap 4 thins, the output pressure is increased accordingly to prevent slippage. In this way, the actual pressure data is always maintained within the small fluctuation range allowed by the preset pressure parameter.

[0070] The third control module incorporates a preset linear mapping function. When the thickness change is within a preset range, the pressure adjustment increases synchronously with the thickness increase, or decreases synchronously with the thickness decrease. The specific mapping ratio is determined based on the material compression curve of the strapping 4. For polypropylene strapping 4, the pressure adjustment coefficient is set to 0.85. That is, when the thickness increases by 10%, the output pressure of the drive unit increases by 8.5% accordingly. This positive correlation adjustment logic ensures that regardless of the thickness of the strapping 4, the contact pressure between the pressure knife working surface and the strapping 4 remains within a stable range.

[0071] In practical applications, the magnitude of pressure adjustment is positively correlated with the amount of thickness change. This relationship means that the greater the thickness change of the strapping 4, the greater the pressure adjustment calculated by the PLC, thus more quickly and effectively offsetting the impact of thickness change on pressure stability. Furthermore, an upper limit is set for the pressure adjustment magnitude; specifically, it cannot exceed ±20% of the preset pressure parameter. This upper limit is set to prevent over-adjustment when facing extreme thickness changes, ensuring the overall stability of the clamping force and avoiding unnecessary damage to the strapping 4 or the equipment itself due to violent pressure fluctuations.

[0072] Furthermore, the thickness detector 3 includes, but is not limited to, a laser sensor, an infrared sensor, or a mechanical contact displacement sensor; the thickness detector 3 is set at the feeding end of the pressure knife assembly 1, and is used to collect thickness information in advance and send it to the PLC control unit before the strapping 4 is pressed.

[0073] In one specific embodiment, a laser sensor can be used as the thickness detector 3. This sensor consists of a laser emitter and a high-resolution image sensor. Laser sensors offer high measurement accuracy and fast response, making them suitable for applications with extremely high packaging quality requirements.

[0074] In another embodiment, considering the potential interference from dust, oil, and other contaminants in the production environment, an infrared sensor can be selected. Infrared sensors have strong anti-interference capabilities and good environmental adaptability.

[0075] In another embodiment, for greater economic efficiency and structural simplicity, a mechanical contact displacement sensor can also be used. Mechanical contact displacement sensors are reliable in structure, low in cost, and suitable for applications where measurement accuracy requirements are not particularly stringent.

[0076] Regardless of the type of sensor used, the thickness detector 3 is uniformly positioned at the feed end of the pressing assembly 1. This allows the thickness information of the strapping 4 to be pre-collected and sent to the PLC control unit before it is pressed by the pressing assembly 1. This pre-collection layout gives the control system a predictive capability. When a section of strapping 4 with abnormal thickness is still moving towards the pressing area, the PLC has already received this information and can calculate the required pressure adjustment amount in advance to prepare for compensation. Compared to detecting the thickness only during the pressing process, this method greatly shortens the system's response delay, making pressure adjustment more timely and accurate. This effectively avoids the problem of instantaneous pressure runaway caused by control lag, further improving the stability and efficiency of the pressing process.

[0077] Furthermore, the drive unit includes a servo motor, a ball screw and a cylinder connected to the servo motor, and the servo motor drives the output end of the cylinder to extend and retract through the ball screw; a high-precision pressure sensor is integrated at the end of the pressure knife assembly 1 away from the servo motor, and is used to directly detect the actual pressure data of the pressure knife assembly 1 acting on the packing strap 4.

[0078] Among them, the servo motor, as a power source, inherently possesses the characteristics of high-precision positioning, high dynamic response, and precise torque control.

[0079] The output shaft of the servo motor is connected to one end of the ball screw. The ball screw is a highly efficient transmission component that can convert rotary motion into linear motion with minimal friction and extremely high precision.

[0080] The ball screw nut is fixedly connected to the telescopic rod inside the cylinder. When the servo motor rotates, the ball screw rotates accordingly, driving the nut to move linearly along the axial direction, thereby causing the telescopic rod inside the cylinder to extend and retract. This transmission chain, from the electrical signal input of the servo motor to the linear displacement output of the cylinder, has extremely high rigidity and transmission efficiency, achieving micron-level precise control of the position and pressure of the pressure knife assembly 1.

[0081] Specifically, the high-precision pressure sensor can be a piezoelectric force sensor, which can convert the sensed mechanical signal into a precise electrical signal in real time and feed it back to the PLC control unit. The high-precision pressure sensor is installed at the end of the pressure knife assembly 1 to collect the actual pressure data exerted by the pressure knife assembly 1 on the strapping 4. This arrangement allows the pressure sensor to directly withstand and detect the reaction force exerted by the pressure knife assembly 1 on the strapping 4. When the pressure knife assembly 1 presses the strapping 4, the supporting force generated by the strapping 4 on the pressure knife assembly 1 is transmitted to the pressure sensor without attenuation.

[0082] Furthermore, the PLC control unit has at least two sets of pressure parameters preset, each set of pressure parameters corresponding to a type of packing strap of a certain material or specification.

[0083] The PLC control unit is also used to call the pressure parameter that matches the current type of strapping 4 as the preset pressure parameter when changing the type of strapping 4;

[0084] The PLC control unit is also connected to a human-machine interface unit, which receives user-inputted custom pressure parameters and stores them as a new pressure parameter group in the PLC control unit.

[0085] To improve the adaptability of the servo-driven clamping device to different types of strapping 4 and provide users with greater operational flexibility, at least two sets of pressure parameters are pre-set in the PLC control unit's memory. Each set of pressure parameters corresponds to a specific material or specification of strapping 4. For example, one set of parameters might be set for 0.8 mm thick polypropylene strapping 4, specifying the optimal clamping force, allowable fluctuation range, and response speed; while another set of parameters might be set for 1.2 mm thick polyester strapping 4, with completely different parameter values. By pre-setting multiple sets of such process parameter packages, the device can provide optimized clamping strategies for the physical characteristics of different strapping 4, thereby avoiding the limitation of using a single parameter that cannot adapt to various strapping 4, and greatly improving the device's versatility and applicability.

[0086] When the production line needs to switch to a different type of strapping strap (Type 4), the PLC control unit can retrieve the pressure parameters that match the current Type 4 strapping strap as the new preset pressure parameters. Operators no longer need to perform complex manual parameter adjustments; they simply select the type of Type 4 strapping strap to be used via the human-machine interface, and the system automatically loads the corresponding process parameter package. This function greatly simplifies the line changeover process, shortens equipment setup time, improves work efficiency, and effectively reduces packaging quality problems caused by manual setting errors.

[0087] In addition, the PLC control unit is connected to a human-machine interface (HMI). This HMI is typically a touchscreen display, providing operators with an intuitive graphical interface. Through this HMI, experienced technicians or operators can input custom pressure parameters based on actual packaging needs or the characteristics of special packaging materials. For example, they can fine-tune the target pressure value or adjust the allowable range of pressure fluctuations. These custom parameters can be saved as a new pressure parameter set and stored in the PLC control unit's recipe library. This design not only provides great flexibility for handling non-standard packaging tasks but also allows users to continuously optimize and iterate process parameters based on long-term production practice, solidifying these optimized experiences into new standard procedures. This continuously improves the performance and adaptability of the equipment, making it more intelligent and user-friendly.

[0088] Furthermore, the pressure knife assembly 1 includes at least a pressure knife body 11 and a connecting seat 12. There are three pressure knife bodies 11, which are rigidly connected to the output end of the corresponding drive unit. The connecting seat 12 is used to install the three pressure knife bodies 11 to ensure that the three pressure knife bodies 11 press down at the same time. The working surface of the pressure knife body 11 that contacts the packing strap 4 is provided with anti-slip texture.

[0089] The pressure knife body 11 is rigidly connected to the end of the telescopic rod of the servo pressure cylinder structure 2, which ensures that the precise displacement and pressure output by the drive unit can be transmitted to the pressure knife body 11 without loss or delay, thus ensuring the stability of the clamping force and the accuracy of the control.

[0090] The connecting seat 12 is located at the end of the pressure knife body 11 away from the drive unit, and is used to fix the three pressure knife bodies 11 to the same mounting plate, so that the three pressure knife bodies 11 can press down simultaneously during the process of pressing the packing strap.

[0091] The pressure cutter body 11 is the working part that directly contacts and applies pressure to the strapping 4. Its working surface in contact with the strapping 4 is provided with anti-slip textures. These anti-slip textures can significantly increase the coefficient of friction between the pressure cutter body 11 and the strapping 4. These anti-slip textures can be designed in various forms, such as fine knurled patterns, transverse V-shaped grooves, or dot-matrix raised patterns. When the pressure cutter body 11 presses down, the geometry of the anti-slip textures can effectively embed into the surface of the strapping 4, forming a mechanical interlocking effect, thereby greatly enhancing the gripping force on the strapping 4. This ensures that even under maximum tightening force, the strapping 4 can be firmly fixed, providing a reliable guarantee for subsequent welding processes.

[0092] Furthermore, the PLC control unit also includes:

[0093] The first calculation module is used to continuously acquire multiple thickness information within a preset time window and calculate the statistical characteristic values ​​of the thickness information.

[0094] The judgment module is used to determine whether the deviation between the statistical feature value and the current reference thickness exceeds the first preset deviation threshold.

[0095] The fourth control module is used to determine that the current thickness fluctuation is a valid thickness fluctuation when the deviation exceeds the first preset deviation threshold and the duration reaches the preset duration, and to update the preset pressure parameters according to the statistical characteristic values.

[0096] The fifth control module is used to determine that the current thickness fluctuation is surface noise interference when the deviation does not exceed the first preset deviation threshold, or when the deviation exceeds the first preset deviation threshold but the duration does not reach the preset duration, and to keep the current preset pressure parameters unchanged.

[0097] The function of the first calculation module is to continuously and frequently acquire multiple thickness data points within a preset time window, and then perform statistical processing on these acquired data to calculate their statistical characteristic values. Specifically, the process is as follows: First, the preset time window is 50 to 100 milliseconds. Then, 50 thickness sample points are collected within this time window. The five sample points with the highest and lowest values ​​are removed, and the arithmetic mean of the remaining forty sample points is calculated to obtain the statistical characteristic value. In this way, instantaneous measurement errors and random noise caused by sensor noise, minor surface imperfections of the packing tape 4, or dust particles in the air can be effectively smoothed out, thus obtaining a more stable value that better represents the true average thickness of the packing tape 4 within that time period.

[0098] The judgment module receives the statistical characteristic value calculated by the first calculation module and compares it with the reference thickness currently used by the system, calculating the deviation between the two. Then, the judgment module compares this deviation with a preset first deviation threshold. This threshold is set to filter out negligible thickness fluctuations within the normal process range. Only when the absolute value of the deviation exceeds this threshold is a meaningful thickness change considered to have occurred. Such a meaningful thickness change often indicates a switch to the 4-specification of the packing tape.

[0099] When the judgment module determines that the deviation exceeds the first preset deviation threshold, control is not immediately transferred to the fourth control module. The system also starts a timer to determine whether this over-threshold state can last for a preset duration. Only when the deviation exceeds the first preset deviation threshold and the duration of this state also reaches the preset duration, such as lasting more than 400 milliseconds, will the fourth control module be triggered. At this time, the system will determine that this fluctuation is a valid thickness fluctuation, which may indicate that the packing strap 4 has switched specifications and entered a new segment with a different thickness. Then, the fourth control module will calculate the corresponding new preset pressure parameters based on the latest statistical characteristic values, such as the new average thickness, through a lookup table method or a preset mathematical model, so that the clamping force can actively adapt to the actual thickness change of the packing strap 4, ensuring the subsequent packing quality. In the above embodiment, it has been mentioned that in order to improve the adaptability of the servo pressing device to different types of packing strap 4, at least two sets of pressure parameters are preset in the memory of the PLC control unit. Each set of pressure parameters corresponds to a specific material or specification of packing strap 4. Therefore, when the fourth control module determines that an effective thickness fluctuation has occurred, it can obtain the current actual thickness after the thickness fluctuation has stabilized, and query the corresponding mapping table in the memory of the PLC control unit according to the current actual thickness to determine the packing tape specification corresponding to the current actual thickness, thereby querying the corresponding preset pressure parameters to update the preset pressure parameters used before the effective thickness fluctuation occurred.

[0100] In contrast, the fifth control module handles all cases deemed invalid fluctuations. If the deviation does not exceed the first preset deviation threshold, or if the deviation exceeds the threshold but its duration does not reach the preset duration (e.g., a brief glitch signal), then the fifth control module will classify this fluctuation as surface noise interference. In this case, the system will choose to ignore the fluctuation and maintain the current preset pressure parameters unchanged.

[0101] This intelligent discrimination mechanism avoids unnecessary and frequent responses from the system to various transient and invalid interference signals, greatly improving the stability and anti-interference capability of the entire control system, preventing mechanical wear and energy waste caused by frequent pressure adjustments, and ensuring a smooth and stable packaging process.

[0102] To further enhance the PLC control unit's response to sudden changes in the thickness of the packing tape, achieve faster compensation, and implement differentiated control strategies based on different thickness change rates, a feedforward control mechanism is introduced into the control algorithm. Specifically, the PLC control unit also includes:

[0103] The second calculation module is used to calculate the thickness change rate of thickness information within adjacent sampling periods;

[0104] The comparison module is used to compare the thickness change rate with a preset change rate threshold.

[0105] The sixth control module is used to activate the fast response mode when the thickness change rate is greater than the change rate threshold, calculate the feedforward compensation amount based on the thickness change rate, and superimpose the feedforward compensation amount into the displacement control command of the drive unit in order to offset the pressure fluctuation caused by the sudden change in thickness in advance.

[0106] The seventh control module is used to adjust the output power of the drive unit based on actual pressure data and preset pressure parameters when the thickness change rate is less than or equal to the change rate threshold.

[0107] The core task of the second calculation module is to calculate the rate of change of thickness information within adjacent sampling periods in real time. By performing differential operations on the thickness data, this module can accurately quantify the speed and trend of the thickness change of the packing tape 4.

[0108] The formula for calculating the feedforward compensation is based on Hooke's Law for the packing strap 4. Let the detected thickness change rate within adjacent sampling periods be V, and the sampling period be T, where V = (h1 - h0) / T, where h1 is the thickness of the packing strap 4 detected by the sensor at the current moment, and h0 is the thickness of the packing strap 4 detected by the sensor at the previous moment. Then, the thickness change in the next sampling period can be predicted as Δh = V·T. To ensure that the pressure fluctuation caused by this thickness change is offset in the next sampling period, feedforward compensation is required for the displacement of the pressure knife assembly 1. The feedforward compensation amount Δx is calculated as follows: According to Hooke's Law, the pressure change requirement ΔF = k·Δh, where k is the equivalent stiffness coefficient of the packing strap 4, characterizing the linear relationship between pressure and deformation of the packing strap 4 in the pressing direction, and is determined by the specifications of the packing strap 4. Specifically, the process can be calibrated beforehand through experiments. A sample of the same material and specifications as the current packing strap 4 is placed between the pressure knife assembly 1 and the rigid platform. The drive unit is controlled to apply pressure in a step-increasing manner, while simultaneously recording the pressure knife displacement and pressure sensor readings. A pressure-compression curve is plotted, and the slope of its linear interval is taken as the equivalent stiffness coefficient k of the packing strap 4, which is then stored in the PLC control unit. To maintain a constant clamping force, the displacement compensation of the pressure knife assembly 1 should satisfy k·Δx=ΔF. Combining this equation with the pressure change requirement ΔF=k·Δh, we can obtain the feedforward compensation Δx: Δx=Δh=V·T.

[0109] The calculated feedforward compensation is directly superimposed on the displacement control command of the drive unit in the form of a pulse signal. This superposition method allows the servo motor to pre-compute displacement compensation based on thickness changes before receiving the pressure closed-loop adjustment command, thereby offsetting the response lag of the servo mechanism and suppressing the generation of pressure peaks.

[0110] The comparison module receives the thickness change rate calculated by the second calculation module and compares it with a preset change rate threshold. This threshold distinguishes between normal, slow thickness gradients and abnormal, rapid thickness abrupt changes. For example, a sudden thickness change could occur at the joint of a four-roll packing strap or due to severe manufacturing defects.

[0111] When the comparison module determines that the thickness change rate exceeds a preset threshold, it indicates that a sudden thickness change has been detected. At this point, the sixth control module immediately activates the fast response mode. In this mode, the system no longer relies solely on the feedback signal from the pressure sensor for adjustment, as this feedback adjustment has an inherent delay. Instead, the sixth control module quickly calculates the feedforward compensation amount based on the current large thickness change rate using the aforementioned calculation formula. This feedforward compensation amount directly corresponds to the displacement adjustment required for the pressure tool assembly 1 to offset this sudden thickness change. Then, this feedforward compensation amount is directly added to the displacement control command of the drive unit.

[0112] This means that the system can proactively adjust the position of the pressure cutter before the pressure fluctuates significantly due to sudden changes in thickness, thereby preemptively offsetting the impending pressure shock. This feedforward control mechanism greatly shortens the system's response time and effectively avoids instantaneous pressure overshoot or undershoot caused by hysteresis adjustment, thus reliably preventing the strapping 4 from being crushed or slipping at joints and other locations.

[0113] Conversely, when the comparison module determines that the thickness change rate is less than or equal to the preset change rate threshold, it indicates that the thickness change of the packing tape 4 is in a normal and gradual state. At this time, the seventh control module will maintain the conventional feedback control mode. In this mode, the system mainly adjusts the output power or torque of the drive unit based on the deviation between the actual pressure data collected in real time by the high-precision pressure sensor and the preset pressure parameters. This feedback control strategy is very suitable for handling normal, slow thickness changes, and can ensure that the clamping force is always maintained near the preset target value with extremely high steady-state accuracy. Through the intelligent switching between these two control modes, the servo clamping device constructs a complete adaptive adjustment system, which can not only calmly cope with gradual changes, but also quickly respond to sudden situations.

[0114] The servo pressure device described in this application can be integrated into a complete strapping machine to play its core role. Specifically, a strapping machine includes any of the above-mentioned servo pressure devices, and also includes a tape feeding mechanism, a tightening mechanism, and a welding mechanism arranged in sequence, with the servo pressure device disposed at the pressure station between the tightening mechanism and the welding mechanism.

[0115] The packaging process of this packaging machine is as follows: First, the feeding mechanism pulls the strapping tape 4 from the tray and wraps it around the item to be packaged along a preset track. Next, the tightening mechanism starts, forcefully pulling the wrapped strapping tape 4 taut to ensure it fits tightly against the object's surface. After the tightening force reaches a preset value, the servo pressure device starts working at the clamping station between the tightening and welding mechanisms. The servo pressure device applies precise and constant clamping force to the overlapping portion of the tightened strapping tape 4, firmly fixing it in place. Finally, the welding mechanism heats and melts the overlapping portion of the clamped strapping tape 4 and then cools and solidifies it, forming a strong joint. The precise clamping of the servo pressure device provides a crucial and stable foundation for the subsequent welding quality, ensuring high reliability and high quality throughout the entire packaging operation.

[0116] Please refer to Figure 4 Accordingly, this application also provides a control method for a servo-driven tool pressing device, which is applied to any of the servo-driven tool pressing devices described above. The method includes the following steps:

[0117] S1: Obtain the thickness information of the packing strap 4 to be compressed;

[0118] S2: Real-time acquisition of actual pressure data of the pressure knife assembly acting on the packing strap 4;

[0119] S3: Based on preset pressure parameters, actual pressure data, and thickness information, dynamically adjust the output power or displacement of the drive unit to keep the actual pressure data within the preset threshold range.

[0120] Specifically, in step S1, the thickness information of the strapping 4 to be compressed is acquired by the thickness detector 3. The thickness detector 3 can be understood as a sensor capable of non-contact or contact measurement of object thickness, such as a laser sensor, infrared sensor, or mechanical contact displacement sensor. This thickness detector 3 is typically located at the feed end of the pressure assembly 1 to collect the thickness information of the strapping 4 before it is compressed, and then send this information to the PLC control unit for processing. Its purpose is to provide important reference for subsequent pressure adjustment, enabling the system to predict and adjust based on the actual thickness of the strapping 4.

[0121] In step S2, the actual pressure data of the pressure knife assembly acting on the packing strap 4 is acquired in real time by a high-precision pressure sensor. This high-precision pressure sensor is integrated into the servo cylinder structure 2, for example, it can be integrated into the output end of the cylinder body, and is used to directly detect the actual pressure of the pressure knife assembly 1 acting on the packing strap 4. The purpose is to provide accurate real-time feedback, so that the PLC control unit can accurately understand the actual situation of the current clamping force and provide reliable input for dynamic adjustment.

[0122] In step S3, the PLC control unit dynamically adjusts the output power or displacement of the drive unit based on preset pressure parameters, actual pressure data, and thickness information. The preset pressure parameters are one or more target pressure values ​​pre-set for different materials or specifications of the strapping 4. For example, at least two sets of pressure parameters can be preset, each corresponding to a specific material or specification of strapping 4. The PLC control unit will call the matching preset pressure parameters according to the current type of strapping 4. Alternatively, the user can input and store custom pressure parameters through the human-machine interface. The drive unit typically includes a servo motor that drives the pressure knife assembly 1 to move via a ball screw and cylinder. The PLC control unit adjusts the output power or displacement of the servo motor to change the clamping force applied to the strapping 4 by the pressure knife assembly 1, thereby maintaining the actual pressure data within the range allowed by the preset pressure parameters. The purpose is to achieve closed-loop control of the clamping force, ensuring that the actual clamping force remains stable within the target range regardless of changes in the thickness of the strapping 4 during the packaging process.

[0123] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A servo-driven knife pressing device, characterized in that, The device includes: The pressure knife assembly is used to contact and apply clamping force to the strapping. The servo pressure cylinder structure integrates a high-precision pressure sensor and a drive unit. The drive unit is connected to the pressure knife assembly and is used to drive the pressure knife assembly to move and control its output pressure. The high-precision pressure sensor is used to collect the actual pressure data of the pressure knife assembly acting on the packing strap in real time. A thickness detector is used to obtain the thickness information of the packing strap to be compressed; The PLC control unit is electrically connected to the pressing knife assembly, the servo pressing cylinder structure, and the thickness detector. The PLC control unit is used to dynamically adjust the output power or displacement of the drive unit according to the preset pressure parameters, the actual pressure data, and the thickness information, so that the actual pressure data is maintained within the range allowed by the preset pressure parameters. The PLC control unit also includes: The first calculation module is used to continuously acquire multiple thickness information within a preset time window and calculate the statistical feature value of the thickness information; The judgment module is used to determine whether the deviation between the statistical feature value and the current reference thickness exceeds a first preset deviation threshold. The fourth control module is used to determine that the current thickness fluctuation is a valid thickness fluctuation when the deviation exceeds the first preset deviation threshold and the duration reaches a preset duration, and to update the preset pressure parameter according to the statistical feature value. The fifth control module is used to determine that the current thickness fluctuation is surface noise interference when the deviation does not exceed the first preset deviation threshold, or when the deviation exceeds the first preset deviation threshold but the duration does not reach the preset duration, and to keep the current preset pressure parameter unchanged.

2. The servo-driven tool pressing device according to claim 1, characterized in that, The PLC control unit includes: The acquisition module is used to acquire the preset pressure parameters and the initial thickness information of the packing strap; The first control module is used to control the drive unit to drive the pressure knife assembly to move toward the packing strap until the actual pressure data reaches the initial threshold corresponding to the preset pressure parameter. The second control module is used to control the high-precision pressure sensor to collect the actual pressure data of the packing strap in real time, and to control the thickness detector to monitor the thickness change of the packing strap in real time. The third control module is used to adjust the output pressure of the drive unit according to the thickness change direction, preset pressure parameters, and actual pressure data when the thickness change exceeds the preset range, so that the actual pressure data is maintained within the allowable fluctuation range of the preset pressure parameters; the thickness change direction indicates whether the packing tape becomes thicker or thinner. Specifically, when the third control module adjusts the output pressure of the drive unit, the magnitude of the pressure adjustment is positively correlated with the thickness change, and the magnitude of the pressure adjustment does not exceed ±20% of the preset pressure parameter.

3. The servo-driven tool pressing device according to claim 1, characterized in that, The thickness detector includes a laser sensor, an infrared sensor, or a mechanical contact displacement sensor; the thickness detector is located at the feeding end of the pressing knife assembly and is used to collect the thickness information in advance before the packing strap is pressed and send it to the PLC control unit.

4. The servo-driven tool pressing device according to claim 1, characterized in that, The drive unit includes a servo motor, a ball screw and a cylinder that are connected to the servo motor for transmission. The servo motor drives the output end of the cylinder to extend and retract through the ball screw. The high-precision pressure sensor is integrated at the end of the pressure knife assembly away from the servo motor and is used to directly detect the actual pressure data of the pressure knife assembly acting on the packing strap.

5. A servo-driven tool pressing device according to claim 1, characterized in that, The PLC control unit has at least two sets of pressure parameters preset, and each set of pressure parameters corresponds to a type of packing strap of a certain material or specification. The PLC control unit is also used to call the pressure parameter that matches the current strapping type as the preset pressure parameter when changing the strapping type; The PLC control unit is also connected to a human-machine interface unit, which is used to receive user-inputted custom pressure parameters and store the custom pressure parameters as a new pressure parameter group in the PLC control unit.

6. The servo-driven tool pressing device according to claim 1, characterized in that, The pressing knife assembly includes at least a pressing knife body and a connecting seat, the connecting seat being rigidly connected to the output end of the drive unit; the working surface of the pressing knife body that contacts the packing strap is provided with anti-slip texture.

7. A servo-driven tool pressing device according to claim 1, characterized in that, The PLC control unit also includes: The second calculation module is used to calculate the thickness change rate of the thickness information within adjacent sampling periods; The comparison module is used to compare the thickness change rate with a preset change rate threshold. The sixth control module is used to activate a fast response mode when the thickness change rate is greater than the change rate threshold, calculate the feedforward compensation amount according to the thickness change rate, and add the feedforward compensation amount to the displacement control command of the drive unit in advance to offset the pressure fluctuation caused by the sudden change in thickness. The seventh control module is used to adjust the output power of the drive unit based on the actual pressure data and the preset pressure parameters when the thickness change rate is less than or equal to the change rate threshold.

8. A packaging machine, characterized in that, The servo pressing device, including any one of claims 1-6, further includes a belt feeding mechanism, a tightening mechanism, and a welding mechanism arranged in sequence, wherein the servo pressing device is disposed at a pressing station between the tightening mechanism and the welding mechanism.

9. A control method for a servo-driven knife pressing device, characterized in that, The method is applied to the servo-driven tool pressing device as described in any one of claims 1-6, and the method includes the following steps: S1: Obtain the thickness information of the packing strap to be compressed; S2: Real-time acquisition of actual pressure data of the pressure knife assembly acting on the packing strap; S3: Based on the preset pressure parameters, the actual pressure data, and the thickness information, dynamically adjust the output power or displacement of the drive unit so that the actual pressure data is maintained within the preset threshold range.

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