A quality detection method for invisible ink-jet code based on the same position blowing solidification

Abstract

The application discloses a kind of based on the quality detection method of invisible code of same station blowing solidification, comprising: solidification device and detection device are installed in the same station of transparent paper conveying channel;Adjust the working direction of solidification device to make solidification effect area overlap with code spraying area, and set solidification energy temperature lower than the initial shrinkage temperature of transparent paper;Control module obtains packaging machine operating phase and presets detection phase interval;When transparent paper reaches the station, solidification and detection are started simultaneously, and the detection device collects code spraying signal and converts it into detection signal;Control module judges whether code spraying is missing according to the state of detection signal in detection phase interval, judges whether code spraying is offset according to the comparison of detection signal characteristic phase value and preset standard phase value, and marks abnormality;Output rejection signal for abnormal products, and stop when continuous abnormality reaches threshold value.The application realizes the integration of solidification detection in the same station and the synchronous discrimination of code spraying missing and offset.

Description

Technical Field

[0001] This application relates to the technical field of packaging equipment in the tobacco industry, specifically to a method for detecting the printing quality of fluorescent invisible inkjet printing on transparent paper for small boxes. Background Technology

[0002] Currently, fluorescent invisible coding in cigarette factories primarily uses natural drying curing, meaning the ink evaporates and dries naturally in the air after coding. However, with packaging machine production speeds increasing to 600 packs per minute, the dwell time of the transparent paper within the effective conveying distance after coding is insufficient for the ink to fully dry and cure.

[0003] Incompletely cured inkjet printing is prone to problems such as scratches and code loss when passing through contact parts such as rollers and guide plates during subsequent transportation. This results in incomplete inkjet characters, affecting the accurate reading of product traceability information and the company's image.

[0004] Existing technologies also include technical solutions that arrange UV curing devices and inkjet printers sequentially along the conveying direction. However, this type of solution is for QR code printing and curing on cigarette cartons. It uses UV curing, which is suitable for UV ink systems but not for fluorescent invisible inks. Furthermore, the curing device and the detection device are arranged separately, which takes up a lot of space and is not suitable for the installation requirements of compact packaging machines.

[0005] Furthermore, existing invisible code detection devices for cigarette packaging only have a single detection function and do not integrate drying or curing devices. They cannot cure the inkjet code before detection and can only detect the presence or absence of inkjet code, but cannot identify missing characters or positional offsets. Summary of the Invention

[0006] To address the aforementioned issues, this application provides a method for detecting the quality of invisible inkjet printing based on simultaneous blow-drying and curing at the same workstation. This method simultaneously completes blow-drying and quality detection at the same workstation. Before detection, curing parameters (blow-drying angle and heating temperature) are configured. The continuity of sensor level signals within the phase interval is used to determine inkjet printing defects, and the rising edge phase positioning is used to determine inkjet printing offsets. This enables comprehensive and accurate detection of invisible inkjet printing quality under high-speed production conditions.

[0007] This application provides a method for quality inspection of invisible inkjet printing based on in-station blow-curing. The method is implemented under the condition of having the necessary prerequisites. Taking a blow-pipe as the curing device as an example, the details are as follows:

[0008] First, deploy the curing device and configure the curing parameters at the same workstation. Install the curing device and the detection device at the same workstation in the transparent paper conveying channel, so that their effective ranges overlap in the direction of transparent paper feeding. Adjust the working direction of the curing device according to the installation space and the location of the coding area, so that the curing area overlaps with the coding area; at the same time, set the curing parameters according to the thermal characteristics of the transparent paper material, so that the temperature when the curing energy acts on the coding area is lower than the initial shrinkage temperature of the transparent paper.

[0009] The control module acquires the phase signal of the packaging machine's operation and presets a detection phase interval based on the physical distance of the same workstation relative to the zero point of the packaging machine. When the transparent paper is conveyed to the same workstation, the control module synchronously starts the curing device for curing and activates the detection device for detection. The detection device collects the inkjet coding signal within the detection phase interval and converts it into a detection signal. The control module determines whether there is missing inkjet coding based on the state of the detection signal within the detection phase interval, and determines whether there is offset inkjet coding based on the comparison between the characteristic phase value of the detection signal and the preset standard phase value. Transparent papers with missing or offset inkjet coding are marked as abnormal. Subsequently, the control module outputs a rejection signal for the marked abnormal transparent papers, and outputs a stop signal when the number of consecutive abnormalities reaches a preset threshold.

[0010] As a further refinement of the above technical solution, the curing device can be implemented using a blowpipe. The blowpipe has multiple nozzles facing the transparent paper, and heats and cures the coding area by blowing hot air. The operating direction is achieved by adjusting the blowing angle of the blowpipe, which is adjusted in both positive and negative directions with a reference angle of 0°. The adjustment range is ±30°, and it can be manually adjusted or driven by a motor or other drive mechanism for stepless automatic adjustment. The temperature of the hot air emitted from the blowpipe is lower than the initial shrinkage temperature of the transparent paper, thus preventing the transparent paper from shrinking and deforming due to heat while rapidly drying the coding.

[0011] To further refine the detection process, the detection device can employ a stealth code detection sensor, whose output detection signal is a level signal. A continuous high level output within the detection phase interval indicates complete coding, while a low level indicates missing or incomplete coding. The characteristic phase value is the phase value at the rising edge of the level, from low to high. The preset standard phase value is the phase value corresponding to the standard appearance position of the first character of the coding within the detection phase interval. By comparing these two values, it can be determined whether there is a positional offset in the coding.

[0012] To further ensure system reliability, the control module includes an energy efficiency detection phase outside the detection phase range. Within this phase, it monitors whether the detection device outputs abnormal signals. If multiple abnormal outputs occur consecutively, a shutdown signal is output and a detection failure alarm is displayed, thus enabling online self-diagnosis of the detection device. The control module can obtain the aforementioned phase signals from the packaging machine's spindle encoder.

[0013] As a further improvement of the present invention, an energy efficiency detection phase is set outside the detection phase interval to monitor whether the sensor outputs an abnormal high level. If a high level is detected within the energy efficiency detection phase, a count is performed and the corresponding cigarette pack is removed. When a high level is detected multiple times in a row, the control module outputs a shutdown signal and displays a detection failure alarm, thereby realizing the sensor's self-diagnosis function.

[0014] The present invention has the following beneficial effects:

[0015] The simultaneous spray drying at the same workstation provides a stable signal foundation for detection. Spray drying and detection are carried out synchronously at the same workstation. The inkjet code is instantly cured and set before detection, eliminating the signal distortion and misjudgment problems caused by drying lag (incomplete curing due to insufficient natural drying time) in traditional solutions. This ensures that the detection sensor reads the real inkjet code signal after curing and setting, rather than a random signal affected by the state of the ink.

[0016] Based on the installed angle, i.e., with the working direction taking the installation reference of the blow pipe as 0°, the blowing angle can be continuously and steplessly adjusted within ±30° by manual means or motor drive, which can adapt to different installation spaces and coding area positions, ensuring that the hot airflow accurately covers the coding area; when using motor drive, it can be connected to an automated control system to realize online automatic adjustment and precise control of the blowing angle, further reducing the intensity of manual operation.

[0017] The heating temperature is set according to the heat-affected characteristics of the transparent paper. While ensuring that the ink dries quickly (e.g., solvent evaporation is completed within 0.3 to 0.5 seconds), the heating temperature is always lower than the initial shrinkage temperature of the transparent paper. This achieves a balance between drying effect and substrate protection, and avoids the transparent paper shrinking and deforming due to heat, which would affect the integrity of the inkjet pattern and the quality of the packaging appearance.

[0018] Simultaneously, it achieves triple detection of inkjet printing presence, character missingness, and positional offset. The detection depth and comprehensiveness are significantly better than existing technologies that can only detect presence or absence, effectively eliminating the quality risks of missing characters, incomplete codes, and offsets in inkjet printing.

[0019] The system uses sensors in conjunction with a control module to determine the phase range level, eliminating the need for complex vision equipment such as industrial cameras and image processing units. The system has a simple structure, low cost, and fast response speed, making it suitable for high-speed production scenarios of 600 packs / minute.

[0020] By enabling sensor self-diagnosis through energy efficiency detection, abnormal sensor output can be monitored outside the detection phase range, allowing for timely detection of sensor failure or interference, avoiding missed or false detections due to sensor malfunctions, and improving the overall robustness of the system.

[0021] Defective cigarette packs are automatically rejected, and the machine automatically stops and alarms when there are consecutive defects. This eliminates the need for operators to monitor in real time and conduct frequent spot checks, reducing the workload of operators and effectively ensuring the quality of the company's products. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A flowchart illustrating a method for quality inspection of invisible inkjet printing based on in-station spray curing, provided in an embodiment of this application;

[0024] Figure 2 This is a schematic diagram of a device for spray curing at the same workstation;

[0025] Figure 3 This is a schematic diagram of the blowpipe;

[0026] Figure 4 This is a flowchart illustrating the implementation of the detection method.

[0027] In the diagram: 1. Feed roller; 2. Discharge roller; 3. Support frame; 4. Inkjet printer; 5. Inkjet detector; 6. Blow-out pipe; 7. Light-absorbing plate; 8. Blow-out nozzle; 9. Transparent paper; 31. Upper fork arm; 32. Lower fork arm. Detailed Implementation

[0028] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0029] In the following description, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The following description provides multiple embodiments of this application, which can be substituted or combined with each other. Therefore, this application can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then this application should also be considered to include embodiments containing one or more other possible combinations of A, B, C, and D, even if such embodiments are not explicitly described in the following text.

[0030] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of this application. Various processes or components may be appropriately omitted, substituted, or added to the examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

[0031] The detection method of the present invention is implemented based on the following hardware environment: such as Figure 2 , Figure 3 As shown, the hardware device for implementing this method is installed on the transparent paper conveying channel of the small box transparent paper packaging machine, including a feed roller 1 and a discharge roller 2 for conveying transparent paper 9, which runs between the feed roller 1 and the discharge roller 2; an inkjet printer 4 is provided between the feed roller 1 and the discharge roller 2 for printing invisible inkjet codes on the transparent paper 9; a support frame 3 is also provided between the feed roller 1 and the discharge roller 2, the support frame 3 having a fork arm (i.e., upper fork arm 31) located above the transparent paper 9, a blow pipe 6 mounted on the fork arm and suspended above the transparent paper 9, with multiple blow holes 8 on its wall facing the transparent paper 9; an inkjet detector 5 is also mounted on the fork arm and its detection direction is towards the inkjet area of ​​the transparent paper 9. The support frame 3 also has a lower fork arm 32 located below the transparent paper 9, a light-absorbing plate 7 is provided on the lower fork arm 32, the light-absorbing plate 7 is arranged opposite to the inkjet detector 5, and is used to absorb ambient interference light. The diameters of the feed roller 1 and the discharge roller 2 are different to adjust the difference in material feeding speed, ensuring that the transparent paper 9 runs smoothly between the two rollers. This hardware structure provides the physical basis for simultaneous blowing and inspection at the same station—the blowpipe 6 and the inkjet printer 5 are mounted on the same fork arm (upper fork arm 31) of the same support frame 3, and their effective ranges overlap in the material feeding direction of the transparent paper 9, allowing blowing curing and quality inspection to be completed at the same station. The blowpipe 6 is rotatably installed in the mounting hole of the upper fork arm 31. The initial angle position of the blowpipe 6 after installation in the mounting hole is taken as the 0° reference. The blowing angle can be adjusted in both positive and negative directions of this 0° reference, so that the orientation of the blowpipe 8 overlaps with the inkjet printing area. The control module is communicatively connected to the encoder of the packaging machine's main shaft, acquiring the phase signal of the packaging machine's operation in real time.

[0032] It should be noted that the drive motor and its transmission structure between the drive motor and the blowpipe are not shown in the attached drawings. This drive motor and its transmission structure are an optional improvement to this device, and their installation method and drive connection relationship are clearly described in the text of the specification. The omission of this part in the attached drawings does not affect the understanding of the blowpipe rotation adjustment structure by those skilled in the art.

[0033] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0034] See Figure 1 , Figure 1 This is a schematic flowchart of a method for quality inspection of invisible inkjet printing based on in-station blow-curing, according to an embodiment of this application. The embodiment includes the following steps:

[0035] S1: Install the curing device and the detection device at the same station in the transparent paper conveying channel so that their effective ranges overlap in the transparent paper feeding direction; adjust the working direction of the curing device according to the installation space and the position of the inkjet printing area so that the curing area overlaps with the inkjet printing area; set the curing parameters according to the heat characteristics of the transparent paper material so that the temperature when the curing energy acts on the inkjet printing area is lower than the initial shrinkage temperature of the transparent paper.

[0036] S2: The control module acquires the phase signal of the packaging machine operation and presets the detection phase interval according to the physical distance of the same workstation relative to the zero point of the packaging machine;

[0037] S3: When the transparent paper is conveyed to the same workstation, the control module synchronously starts the curing device to perform curing treatment and activates the detection device to perform detection; the detection device collects the inkjet coding signal within the detection phase interval and converts it into a detection signal; the control module judges whether there is missing inkjet coding based on the state of the detection signal within the detection phase interval, and judges whether there is offset inkjet coding based on the comparison between the characteristic phase value of the detection signal and the preset standard phase value, and marks the transparent paper with missing or offset as abnormal.

[0038] S4: The control module outputs a rejection signal for transparent paper marked as abnormal, and outputs a stop signal when the number of consecutive abnormalities reaches a preset threshold.

[0039] Taking the curing device as an example, specifically:

[0040] The blowpipe and the invisible code detection sensor are installed on the same set of brackets in the transparent paper conveying channel so that their effective ranges overlap in the transparent paper feeding direction; depending on the installation space and the location of the coding area, the blowing angle of the blowpipe is adjusted manually or by the drive mechanism so that the blowing hole faces the coding area, and the blowing angle is continuously adjustable within a range of ±30°; the heating temperature is set according to the heat characteristics of the transparent paper material so that the temperature of the hot air flow ejected by the blowpipe is lower than the initial shrinkage temperature of the transparent paper;

[0041] The control module acquires the phase signal of the packaging machine in real time through the encoder of the packaging machine spindle; it presets the detection start phase and the detection end phase, which together constitute the detection phase interval. This interval is calibrated according to the physical distance of the same workstation relative to the zero point of the packaging machine.

[0042] When the transparent paper is conveyed to the overlapping station of blowing and detection, the control module simultaneously starts the blowing pipe to spray hot air, instantly drying the invisible inkjet code and activating the detection sensor to enter the test state; the blowing duration covers the entire detection phase interval; the detection sensor continuously collects fluorescence signals and converts them into level signals within the detection phase interval; the sensor output level is monitored within the detection phase interval, and if a high level is continuously output, the inkjet code is determined to be complete; if a low level occurs at any moment, the inkjet code is determined to be missing or incomplete, and marked as abnormal; the specific phase value of the sensor level from low to high (i.e., the rising edge) is recorded, and this phase value is compared with the preset standard phase. If the deviation value is greater than or equal to the set threshold, the inkjet code is determined to have a positional offset and marked as abnormal;

[0043] For transparent paper marked as abnormal, the control module outputs a rejection signal to the rejection device of the packaging machine, which then rejects the defective cigarette packs at the subsequent workstation and records the number of rejections. When the number of continuously marked abnormal transparent paper reaches the preset shutdown threshold, the control module outputs a shutdown signal to the packaging machine to stop and displays an alarm message.

[0044] In step S3, the threshold for offset determination can be ±3° phase angle. During synchronous startup at the same workstation, the control module simultaneously activates the blowpipe to spray hot air and activates the detection sensor, with the blowpipe operating according to the configured blowing angle and heating temperature. If a low level is detected at any moment within the detection phase interval, the transparent paper is marked as abnormal and used as the basis for subsequent rejection. The specific phase value of the rising edge is recorded and compared with a preset standard phase. If the deviation is greater than or equal to the set threshold, it is determined as a positional offset, and the transparent paper is marked as abnormal.

[0045] In step S4, the shutdown threshold for continuous defect shutdown protection is preset and adjusted through parameters.

[0046] The heating temperature is set according to the heat-receiving characteristics of the transparent paper. Under the premise of ensuring rapid drying of the inkjet ink, the heating temperature is always lower than the initial shrinkage temperature of the transparent paper.

[0047] This method first involves configuring the curing parameters, specifically setting the working direction (blowing angle) and heating temperature.

[0048] Regarding the adjustment of the working direction, the blowpipe 6 is rotatably installed in the mounting hole of the upper fork arm 31. Taking the initial angle position of the blowpipe 6 after installation in the mounting hole as the 0° reference, the operator or drive mechanism drives the blowpipe 6 to rotate in the positive and negative directions of this 0° reference, adjusting the orientation of the blowhole 8 so that the direction of the hot airflow overlaps with the coding area. The adjustment range of the blowing angle is ±30°, that is, the blowpipe 6 can be continuously and steplessly adjusted within the range of 30° in the positive direction to 30° in the negative direction of the 0° reference.

[0049] This range ensures both the flexibility of the blowpipe 6 arrangement within the limited installation space and the effective coverage of the coding area by the hot airflow without significant dispersion. The blowing angle is adjusted manually or by a drive mechanism.

[0050] As an improvement to the curing device, the blowpipe 6 can also be connected to a drive motor. This drive motor is fixed to the upper fork arm 31, and its output shaft is directly connected to one end of the blowpipe 6 via gear transmission, synchronous belt transmission, or coupling. This drive motor drives the blowpipe 6 to rotate relative to the upper fork arm 31, automatically adjusting the blowing angle. A control module or independent controller outputs a control signal to the drive motor, driving the blowpipe 6 to automatically rotate to the target angle within a ±30° range, achieving online automatic adjustment and precise control of the blowing angle. In this embodiment, the drive motor and its transmission structure with the blowpipe are not shown in the accompanying drawings. The specific installation and transmission connection methods are conventional techniques in the art, and can be implemented by those skilled in the art based on the description in this specification. This does not affect their understanding and implementation of the blowpipe rotation adjustment structure.

[0051] When a motor is used as the drive mechanism, the motor is connected to the blowpipe 6 via a transmission. The control module outputs a control signal to the motor, driving the blowpipe 6 to rotate to the target angle, thus achieving automated and precise angle adjustment control. Specifically, the control module presets a target angle value and outputs a corresponding drive signal to the motor driver based on this preset value. The motor driver drives the motor to rotate, and the motor output shaft drives the blowpipe 6 to rotate until the blowpipe 6 reaches the target angle. During angle adjustment, an angle sensor can be set to detect the real-time rotation angle of the blowpipe 6 and feed it back to the control module, forming a closed-loop control to achieve precise positioning of the blowing angle. This motor-driven method allows the blowing angle to be adjusted online during equipment operation without the need for manual operation during shutdown, improving the continuity and automation level of equipment operation.

[0052] As an optional implementation, the blowpipe 6 can be located above and to the side of the coding area to perform lateral operation, and the blowhole 8 blows out hot air at an angle, with the hot air acting on the coding area at a certain angle.

[0053] As another alternative implementation, the blow pipe 6 can be located directly above the coding area to perform forward operation, and the blow hole 8 blows hot air downwards, with the hot air acting vertically on the coding area.

[0054] The two angle settings mentioned above can be selected according to the actual installation space and the location of the coding area.

[0055] The heating temperature setting must fully consider the heat-affected characteristics of the transparent paper 9. Transparent paper (especially heat-shrinkable BOPP film) has dimensional stability boundaries when heated. Taking Kunling SKS-22 (22μm) heat-shrinkable BOPP film as an example, the initial shrinkage temperature of this film is 105~110℃. Above this temperature, the film molecular chains begin to disorient and shrink. Above 130℃, it is prone to softening, sticking to rollers, wrinkling, or even breaking. Therefore, the temperature of the hot air jet from the blowpipe 6 should be lower than the initial shrinkage temperature of the transparent paper 9.

[0056] Specifically, the principle of temperature setting is to ensure that the heating temperature remains below the initial shrinkage temperature of the transparent paper 9 while ensuring rapid drying of the inkjet ink, so that both drying effect and substrate protection are simultaneously achieved. This temperature is achieved by adjusting the temperature of the high-temperature gas source (e.g., through a heater and a throttle valve), and the specific value can be set according to the actual transparent paper material and its heat characteristics. Taking Kunling SKS-22 film as an example, its initial shrinkage temperature is 105~110℃, so the hot air flow temperature is set to not exceed 100℃ (e.g., 90℃). At this temperature, the solvent in the inkjet ink can completely evaporate within 0.3~0.5 seconds, the inkjet printing is quickly cured and dried, and the transparent paper 9 does not shrink or deform.

[0057] After configuring the curing parameters, this method enters the real-time detection process. The control module acquires the phase signal of the packaging machine's operation in real time through the packaging machine's spindle encoder. This phase signal corresponds to the conveying position of the transparent paper 9. Based on the physical distance between the blowpipe 6 and the inkjet detector 5 at the same station and the zero point of the packaging machine, the control module presets the detection start phase and detection end phase. These two phases together constitute the detection phase interval, which corresponds to the phase range within the detection area of ​​the same station where the invisible inkjet code on a transparent paper 9 should appear.

[0058] When the current phase acquired by the control module enters the detection phase interval, it indicates that the transparent paper 9 has reached the overlapping position of blowing and detection. The control module simultaneously performs two operations: it activates the blowing pipe 6 to spray hot air (according to the configured blowing angle and heating temperature) to instantly dry the invisible inkjet code; and it activates the inkjet code detector 5 to enter the test standby state. The blowing duration covers the entire detection phase interval, ensuring that the inkjet code remains in a solidified and fixed state throughout the detection period.

[0059] Within the detection phase interval, the inkjet printer 5 continuously collects fluorescence signals and converts them into level signals. When the inkjet code is present and complete, the inkjet printer 5 continuously outputs a high level; when the inkjet code is missing, it outputs a low level in the corresponding phase. The control module monitors the output level of the inkjet printer 5 within the detection phase interval: if it continuously outputs a high level throughout the entire detection phase interval, it determines that the inkjet code on the transparent paper 9 is complete; if a low level is detected at any moment within the detection phase interval, it determines that the transparent paper 9 has missing or incomplete inkjet code, marks the transparent paper 9 as abnormal, and uses this as the basis for subsequent rejection. Since the inkjet code has been instantly dried and shaped at the same station, the detected signal loss indicates that the inkjet printer 4 did not spray or the printhead is blocked, rather than the code loss caused by subsequent friction, thus eliminating misjudgments caused by poor drying.

[0060] Meanwhile, the control module records the specific phase value of the inkjet detector 5 as the level rises from low to high (i.e., the rising edge). This rising edge corresponds to the moment when the first character of the inkjet is detected. The control module compares the measured rising edge phase value with the preset standard phase (i.e., the phase corresponding to the position where the first character of the inkjet should appear in the same station): if the deviation value is greater than or equal to the set threshold (e.g., ±3° phase angle), it is determined that there is a positional offset in the inkjet, and the transparent paper 9 is marked as abnormal. Since the blowing and detection are in the same station, the transparent paper 9 is pressed by the blowing airflow at this position, without serpentine oscillation interference. Therefore, the phase drift can accurately reflect the printing timing offset of the inkjet printer 4 itself, without the need for complex motion compensation algorithms.

[0061] For the transparent paper 9 marked as abnormal, the control module outputs a rejection signal to the rejection device of the packaging machine. The defective cigarette pack is then rejected at a subsequent station, and the number of rejections is recorded. When the number of consecutively marked abnormal transparent papers reaches a preset shutdown threshold, the control module outputs a shutdown signal to the packaging machine to stop and displays an alarm message. This shutdown threshold can be preset and adjusted via parameters to adapt to different production quality requirements.

[0062] In a preferred embodiment of the present invention, the method further includes an energy efficiency detection step (i.e., self-diagnosis of the detection device). An energy efficiency detection phase is set outside the detection phase interval to determine whether the inkjet printer 5 itself is malfunctioning or interfered with. The output level of the inkjet printer 5 is monitored within this energy efficiency detection phase (no inkjet printing reaches the detection area within this phase interval; normally it should be low). If a high level is detected within the energy efficiency detection phase, it indicates that the inkjet printer 5 is experiencing ambient light interference or sensor aging, leading to a false alarm. The control module counts and removes the corresponding cigarette packs. When a high level is detected multiple times consecutively (e.g., 3 times) within the energy efficiency detection phase, the control module outputs a shutdown signal and displays a detection failure alarm message, prompting the operator to check or replace the inkjet printer 5.

[0063] In the embodiments of this application, the configuration of the detection device offers multiple flexible options to adapt to different application scenarios and reliability requirements. The detection device includes at least one invisible code detection sensor, preferably an ultraviolet fluorescence detection sensor with a receiving wavelength of 425-550 nm. It determines the presence, integrity, and incompleteness of the inkjet code by receiving the fluorescence signal emitted after the inkjet code is excited by ultraviolet light. The ultraviolet fluorescence detection sensor has a response time in the millisecond range, enabling real-time acquisition of inkjet code signals under high-speed production conditions, and requires no external light source for auxiliary illumination (the ultraviolet excitation source is integrated inside the sensor), resulting in a compact system structure.

[0064] In the basic configuration, a single ultraviolet fluorescence detection sensor operates independently, positioned on the upper fork arm along the direction of the transparent paper's feed, downstream of the blowpipe, with the detection direction facing the coding area of ​​the transparent paper. In this configuration, the sensor continuously acquires fluorescence signals within the detection phase interval and converts them into electrical level signals—a continuous high level indicates the presence and integrity of the coding, while a low level indicates missing or incomplete coding. This configuration is the most streamlined and cost-effective, suitable for applications with limited installation space or cost-sensitive scenarios.

[0065] In applications requiring higher reliability, multiple ultraviolet fluorescence detection sensors can be used in a coordinated configuration. Each sensor is spaced apart along the direction of the transparent paper feed on the upper fork arm of the same station, with adjacent sensors spaced 10-20mm apart. Each sensor independently collects the fluorescence signal of the same inkjet code and outputs a separate level signal to the control module. The control module comprehensively judges the level output of each sensor within the same detection phase range. When all sensor outputs are consistent (both high or all low), the control module directly outputs the corresponding judgment result (complete or missing inkjet code). When some sensors output high levels and others output low levels, the control module outputs the majority result according to the majority voting principle, and simultaneously outputs a "detection abnormality" prompt, suggesting that the operator check whether the sensor surface is contaminated, whether the position is misaligned, or whether there is ambient light interference. This coordinated approach of multiple sensors effectively offsets single-sensor misjudgments caused by accidental factors such as surface dust obstruction, ambient light fluctuations, and device aging, significantly improving the fault tolerance and long-term operational reliability of the detection system.

[0066] As an alternative extended configuration, an ultraviolet fluorescence detection sensor can be combined with a miniature image sensor. The ultraviolet fluorescence detection sensor is responsible for rapid qualitative screening of the presence and integrity of the inkjet printing. It boasts a fast response time and low power consumption, enabling rapid judgment within the detection phase range of each pack of transparent paper. The miniature image sensor is responsible for image acquisition and refined analysis of the inkjet printing area, using image processing algorithms to accurately identify incomplete characters and precisely measure offsets. The detection results of the two sensors corroborate each other—if the ultraviolet fluorescence detection sensor determines the presence of inkjet printing but the image sensor's analysis indicates incomplete characters, the refined judgment of the image sensor prevails, and a "incomplete" result is output. If the judgment results of the two sensors seriously conflict (e.g., presence / absence are opposite), an alarm is triggered, prompting the operator to manually confirm the actual status of the inkjet printing and the working status of both sensors. This configuration offers wider detection coverage and higher accuracy, but also increases cost and system complexity.

[0067] As an alternative configuration, a combination of sensors of the same type but different sensitivities can be configured in the detection device. Specifically, two ultraviolet fluorescence detection sensors with different detection thresholds are set at the detection station—one using a conventional detection threshold (for routine presence / absence determination), and the other using a higher sensitivity threshold (for capturing weak signals and avoiding missed detections due to fluorescence signal attenuation). The control module comprehensively judges the outputs of the two sensors: when both sensors output a high level, the inkjet code is considered complete; when the high-sensitivity sensor outputs a high level while the conventional sensor outputs a low level, the inkjet signal strength is considered insufficient, possibly indicating low ink concentration or poor inkjet curing; when both sensors output a low level, the inkjet code is considered missing. This configuration does not require changing the inkjet ink formula or inkjet process parameters; differentiated detection of inkjet quality can be achieved through the inherent sensitivity differences of the sensors.

[0068] In all the above configurations, the energy efficiency detection function shares the same detection sensor as the inkjet printing quality detection function, eliminating the need for additional sensors. Within the energy efficiency detection phase set outside the detection phase interval, the control module determines whether the detection sensor is abnormally outputting a high level (no inkjet printing arrives within this interval; normally it should be a low level). This allows the module to determine whether the detection sensor is affected by ambient light interference, whether it is aging, or whether the receiving window is contaminated, thus enabling online self-diagnosis of the sensor.

[0069] Furthermore, the detection signal of the inkjet printer 5 can simultaneously cover multiple detection items such as the presence, integrity, and defects of the inkjet code. The continuity of the level signal is used to determine the presence and integrity of the inkjet code, while the waveform characteristics of the level signal (such as pulse width and the timing of the falling edge) can be used to assist in determining whether there are any partial defects in the inkjet characters. When multiple sensors work together, the control module comprehensively compares the level signals output by each sensor within the same phase interval. If the outputs of all sensors are consistent, the result is taken as the standard; if the outputs of all sensors are inconsistent, it is determined as a detection anomaly and an alarm is triggered, thereby effectively avoiding misjudgments caused by accidental factors from a single sensor.

[0070] Therefore, through flexible configuration of single sensor working independently or multiple sensors working in coordination, it supports the detection of multiple items such as the presence, integrity, and defects of inkjet printing. When multiple sensors work in coordination, the detection signals of each sensor are compared and verified with each other, effectively eliminating misjudgments caused by environmental interference, device aging, or accidental factors caused by a single sensor, which significantly improves the reliability and fault tolerance of the detection system. Using a combination of sensors with different principles can also achieve complementarity in detection dimensions, further expanding the detection coverage.

[0071] The configuration scheme of the detection device in this application can be flexibly selected according to actual needs—from a simplified configuration with a single sensor working independently, to a high-reliability configuration with multiple sensors working together, and then to a high-precision configuration with a combination of multiple types of sensors, forming a variety of optional schemes. The user can balance and make trade-offs between detection accuracy, cost, and system complexity according to their actual needs.

[0072] All of the above-mentioned detection device configurations are compatible with the phase interval judgment logic and missing / offset judgment algorithm in the detection method. No modification is required to the core logic of the detection method. It can be achieved simply by configuring the corresponding sensor quantity parameters and comprehensive judgment logic mode (consistency output mode, minority obeys majority mode, difference alarm mode, etc.) in the control module.

[0073] See Figure 4 The present invention will be explained and illustrated below with reference to a specific embodiment.

[0074] This method was implemented on a ZB416 packaging unit C800 small box transparent paper packaging machine, using Kunling SKS-22 (22μm) heat-shrinkable BOPP film as the transparent paper 9. The blowpipe 6 and the coding detector 5 were installed on the same set of supports (i.e., upper fork arm 31) in the transparent paper 9 conveying channel. The blowpipe 6 was positioned approximately 15mm above the transparent paper 9, with the blow holes 8 facing the coding area of ​​the transparent paper 9. The blowpipe 6 was approximately 400mm long, with 38 blow holes 8, each 3mm in diameter, arranged in a single row at equal intervals along the axial direction. One end of the blowpipe 6 was closed, and the other end was connected to a high-temperature gas source via a throttle valve.

[0075] Based on the installation space, with the initial angle position of the blowpipe 6 after installation in the mounting hole as the 0° reference, the blowpipe 6 is driven by a motor to maintain the 0° reference (i.e., forward operation, with the blowhole 8 facing directly downwards), so that the hot airflow acts vertically on the coding area. According to the heat characteristics of BOPP film (initial shrinkage temperature 105~110℃), the high-temperature air source temperature is adjusted to 90℃ by the cooperation of a heater and a throttle valve, so that the temperature of the hot airflow ejected by the blowpipe 6 is about 90℃, which is lower than the initial shrinkage temperature of the transparent paper 9.

[0076] The control module acquires phase signals in real time through the packaging machine's spindle encoder. Based on the physical distance of the same workstation relative to the packaging machine's zero point, the control module presets a detection start phase of 85° and a detection end phase of 105°, forming a detection phase interval. The preset standard phase (the standard position of the rising edge corresponding to the first character of the inkjet print) is 92°, and the offset judgment threshold is set to ±3° phase angle. The continuous abnormal shutdown threshold is set to 5 packages, and the continuous failure threshold for energy efficiency detection is set to 3 times.

[0077] Transparent paper 9 is continuously fed, and inkjet printer 4 prints invisible codes on the front and sides of transparent paper 9. When the control module detects that the current phase has entered the 85°~105° range, it simultaneously starts the blow pipe 6 to spray 90°C hot air and activates the inkjet detector 5. The blow continues to cover the entire detection phase range (85° to 105°).

[0078] In a certain test, the inkjet printer 5 continuously output a high level in the entire 85°~105° range, with the rising edge appearing at the 92.5° phase. The deviation from the standard phase of 92° was +0.5°, which was less than the ±3° threshold. Therefore, it was determined that the inkjet printing on the transparent paper 9 was complete and without offset, and it passed normally.

[0079] In another test, the inkjet printer 5 experienced a low-level interruption at the 95° phase (the rising edge was still 92°). The control module detected the low level within the interval and determined that the transparent paper 9 had missing inkjet printing. It was marked as abnormal and the defective cigarette pack was removed at the subsequent rejection station, and the rejection count was incremented by 1.

[0080] In another test, although the inkjet printer 5 continuously output a high level, the rising edge appeared at the 97° phase, which deviated from the standard phase of 92° by +5°, which is greater than the ±3° threshold. The control module determined that the inkjet had a positional offset, marked it as abnormal, and removed it.

[0081] When five consecutive packages are marked as abnormal, the control module outputs a stop signal, the packaging machine stops and displays an "inkjet printing fault" alarm message. The operator checks the status of inkjet printer 4 and then resumes production.

[0082] During energy efficiency testing, if a high-level output is detected from the inkjet printer 5 outside the detection phase range (e.g., 70° phase), the control module counts and removes the corresponding cigarette packs. If this occurs three times consecutively, the control module outputs a shutdown signal and displays a "detection failure" alarm message, prompting the operator to check the inkjet printer 5.

[0083] In this embodiment, the packaging machine runs at a speed of 600 packages / minute. The integrity rate of the inkjet printing after curing and testing by this method is 100%, the offset detection accuracy reaches within ±3° phase angle, the detection accuracy is significantly improved, and the frequency of operator spot checks is greatly reduced.

[0084] It is understood that the above temperature settings are for illustrative purposes only. In actual implementation, the settings should be selected or adjusted according to the actual situation to ensure that product quality is not affected.

[0085] In the above description of this specification, the embodiments of the drive motor and its transmission structure are not shown in the accompanying drawings, but are clearly described in the text of the specification, and those skilled in the art can implement them based on the description.

[0086] Furthermore, the blowpipe is rotatably installed in the mounting hole of the upper fork arm 31. Taking the initial angular position of the blowpipe after installation in the mounting hole as a 0° reference, the operator or drive mechanism rotates the blowpipe in both positive and negative directions around this 0° reference, adjusting the orientation of the blowpipe orifice 8 so that the direction of the hot airflow overlaps with the coding area. The adjustment range of the blowing angle is ±30°, meaning the blowpipe can be continuously and steplessly adjusted within a range of 30° clockwise to 30° counterclockwise from the 0° reference. This range ensures both the flexibility of the blowpipe's arrangement within a limited installation space and that the hot airflow effectively covers the coding area without significant dispersion.

[0087] When using a motor as the drive mechanism, the control module presets a target angle value. Based on this preset value, the control module outputs a corresponding drive signal (such as a pulse signal or analog signal) to the motor driver. The motor driver drives the motor to rotate, and the motor output shaft drives the blowpipe to rotate until the blowpipe reaches the target angle. During angle adjustment, an angle sensor (such as a potentiometer or encoder) can be used to detect the real-time rotation angle of the blowpipe and feed it back to the control module, forming a closed-loop control to achieve precise positioning of the blowing angle. This motor-driven method allows the blowing angle to be adjusted online during equipment operation without requiring manual intervention, improving the continuity and automation level of equipment operation.

[0088] It should be clarified that, in specific implementation, the preset adjustment range can be implemented based on operational requirements. When adjusting manually, avoid over-adjustment and adaptation to the width of the transparent paper. When adjusting electronically, the boundary range should be clearly defined to facilitate drive control and adaptation to the width of the transparent paper.

[0089] Specifically, it can be equipped with an angle sensor to record the starting position of the curing device and the angle of each adjustment. The reasonableness of each adjustment angle is judged by a preset adjustment range. If there is overshoot, it can be alerted and fed back through indicator lights, alarms, etc.

[0090] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0091] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0092] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, which may include: a flash drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc.

[0093] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of embodiments of this disclosure upon considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

Claims

1. A method for quality inspection of invisible inkjet printing based on in-station spray curing, characterized in that, Includes the following steps: S1: Install the curing device and the detection device at the same station in the transparent paper conveying channel so that their effective ranges overlap in the transparent paper feeding direction; adjust the working direction of the curing device according to the installation space and the position of the inkjet printing area so that the curing area overlaps with the inkjet printing area; set the curing parameters according to the heat characteristics of the transparent paper material so that the temperature when the curing energy acts on the inkjet printing area is lower than the initial shrinkage temperature of the transparent paper. S2: The control module acquires the phase signal of the packaging machine operation and presets the detection phase interval according to the physical distance of the same workstation relative to the zero point of the packaging machine; S3: When the transparent paper is delivered to the same workstation, the control module synchronously starts the curing device to perform curing treatment and activates the detection device to perform detection; the detection device collects the inkjet coding signal within the detection phase interval and converts it into a detection signal; the control module determines whether there is missing inkjet coding based on the state of the detection signal within the detection phase interval, and determines whether there is offset inkjet coding based on the comparison between the characteristic phase value of the detection signal and the preset standard phase value, and marks the transparent paper with missing or offset coding as abnormal; S4: The control module outputs a rejection signal for transparent paper marked as abnormal, and outputs a stop signal when the number of consecutive abnormalities reaches a preset threshold.

2. The method according to claim 1, characterized in that, The curing device is a blowpipe with multiple blow holes facing the transparent paper, which heat and cure the coding area by blowing hot air.

3. The method according to claim 2, characterized in that, The working direction is achieved by adjusting the blowing angle of the blow pipe; the blowing angle is based on the installation reference of the blow pipe as 0° reference, and an adjustment range is preset on the 0° reference, the adjustment range can be adjusted in both the positive and negative directions of the 0° reference.

4. The method according to claim 2, characterized in that, The temperature of the hot air stream ejected from the blowpipe is lower than the initial shrinkage temperature of the transparent paper.

5. The method according to claim 3, characterized in that, The blowing angle can be adjusted manually or by a drive mechanism; the drive mechanism is a motor, which enables stepless automatic adjustment.

6. The method according to claim 1, characterized in that, The detection device includes at least a stealth code detection sensor.

7. The method according to claim 1, characterized in that, The detection signal is a level signal. A continuous high level output within the detection phase interval indicates that the inkjet printing is complete, while a low level output within the detection phase interval indicates that the inkjet printing is missing or incomplete.

8. The method according to claim 1, characterized in that, The characteristic phase value of the detection signal is the phase value when the level rises from low to high, i.e., the rising edge. The preset standard phase value is the phase value corresponding to the standard occurrence position of the first character of the inkjet code within the detection phase interval.

9. The method according to claim 1, characterized in that, The control module also has an energy efficiency detection phase outside the detection phase interval. Within the energy efficiency detection phase, it monitors whether the detection device outputs abnormal signals. If there are multiple consecutive abnormal outputs, it outputs a shutdown signal and displays a detection failure alarm.

10. The method according to claim 1, characterized in that, The control module obtains the phase signal through the encoder of the packaging machine spindle.

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