A laser preheating system and a preheating method thereof

Abstract

The present application relates to the field of disposable hygiene products, in particular to a laser preheating system for preheating the waistband material of disposable hygiene products before welding, comprising: a light source module for emitting laser; a beam shaping module for adjusting the laser emitted by the light source module into a light spot with a preset energy distribution and geometric shape, and projecting it onto the surface of the waistband material to be preheated; a temperature feedback control module comprising a temperature sensor and a controller, the controller is configured to dynamically adjust the output power of the light source module according to the difference between the real-time temperature of the material surface collected by the temperature sensor and the preset target temperature, so as to maintain the preheating temperature of the material within a preset value range. It solves the technical problem that the waistband material of disposable hygiene products is in a normal temperature state when entering the welding station, resulting in poor welding performance. A laser preheating method is also proposed.

Description

Technical Field

[0001] This invention relates to the field of disposable hygiene products, and more particularly to a laser preheating system and its preheating method. Background Technology

[0002] In the production of disposable hygiene products (such as diapers and pull-up pants), waistband welding is a critical process. Elastic waistband materials are usually composed of multiple layers of nonwoven fabric combined with elastic film or elastic yarn, and the welding quality directly affects the connection strength and wearing comfort of the product.

[0003] Currently, the industry commonly uses two methods: heat sealing roller welding and ultrasonic welding.

[0004] Heat-sealing roller welding involves rolling and welding materials using heated rollers. This method requires high precision in the cutter holder, and the gap between the rollers is prone to drift after prolonged operation, necessitating frequent shutdowns for adjustment and impacting startup efficiency. Furthermore, the welded area becomes denser due to heat pressing, resulting in a harder feel and significantly reducing the softness and wearing comfort of the product's waistband.

[0005] Ultrasonic welding uses the high-frequency vibration of an ultrasonic welding head to generate heat through friction at the material interface, resulting in a relatively soft weld. However, its welding energy input is closely related to the contact time. As the machine speed increases, the time it takes for the material to pass through the welding head shortens, reducing the energy received at the weld joint. This can easily lead to insufficient weld strength, incomplete welds, or weld failure, thus limiting further increases in machine speed.

[0006] The root cause of the above problems is that the waistband material is not preheated before entering the welding station and is at room temperature. The welding station needs to complete all the energy input from room temperature to melting in a very short time. This inevitably requires the welding station to provide extremely high instantaneous energy density, thus exacerbating the contradiction between the high temperature dependence of the heat sealing roller and the insufficient energy of the ultrasonic waves.

[0007] Therefore, there is an urgent need for a technical solution that can preheat the waistband material before welding, so that the material enters the welding station in a near-molten activated state, thereby reducing the requirements for instantaneous energy input at the welding station and fundamentally taking into account the comprehensive needs of high-speed production, welding strength and wearing comfort. Summary of the Invention

[0008] Therefore, to address the aforementioned problems, this invention proposes a laser preheating system, which solves the technical problem that the disposable sanitary product waistband material is at room temperature when entering the welding station, resulting in poor welding performance. A laser preheating method is also proposed.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a laser preheating system for preheating disposable sanitary product waistband materials before welding, comprising: A light source module for emitting laser light; A beam shaping module is used to adjust the laser emitted by the light source module into a light spot with a preset energy distribution and geometry, and project it onto the surface of the waistband material to be preheated; A temperature feedback control module includes a temperature sensor and a controller. The controller is configured to dynamically adjust the output power of the light source module based on the difference between the real-time temperature of the material surface collected by the temperature sensor and a preset target temperature, so as to maintain the material preheating temperature within a preset value range.

[0010] Furthermore, it also includes: A beam transmission module is disposed between the light source module and the beam shaping module, and is used to change the laser transmission direction and guide the laser to the beam shaping module; A sealed protection module is used to form a closed channel in the optical path area between the light source module, the beam transmission module and the beam shaping module to prevent light leakage and optical path contamination. A thermal management module is provided for actively cooling the power supply and internal resonant cavity of the light source module.

[0011] Furthermore, the beam transmission module includes at least one reflector, and the beam shaping module includes at least one beam expander and at least one integrating mirror; The reflector, beam expander, and integrating mirror are respectively mounted on an adjustable mounting base with multi-directional adjustment margin.

[0012] Furthermore, the integrating mirror includes a focal length adjustment mechanism for adjusting the distance between the integrating mirror and the material to be heated, thereby changing the spot size and / or energy distribution.

[0013] Furthermore, the distance between the integrating mirror and the material to be heated is configured to be 80cm to 100cm to form a rectangular light spot with a length of 10cm to 14cm and a width of 2cm to 4cm.

[0014] Furthermore, the sealing and protection module is a tubular cylinder, which has a multi-segment connected structure.

[0015] Furthermore, the thermal management module includes a water chiller, which is connected to the power supply and the resonant cavity.

[0016] Furthermore, the temperature sensor is a non-contact infrared temperature sensor, whose detection area points to the heating area formed by the light spot on the material surface, and whose detection light spot falls within the geometric center range of the heating area.

[0017] A laser preheating method includes the following steps: The first step is to generate laser light in a light source module; The second step involves changing the laser direction through a beam transmission module and adjusting the laser into a spot with a preset energy distribution and geometry through a beam shaping module, which is then projected onto the surface of the waistband material traveling along the production line to preheat it. The third step is to obtain the temperature of the material surface in the preheating area in real time. The fourth step is to control the output power of the light source module in a closed loop based on the difference between the real-time temperature and the preset target temperature, so that the material reaches and is maintained within the preset temperature range before entering the welding station. The fifth step involves preheating the waistband material before it enters the downstream welding station for welding and sealing.

[0018] Furthermore, in the second step, the beam shaping module includes a beam expander and an integrating mirror. By adjusting the distance between the integrating mirror and the material surface, the beam spot is shaped into a rectangle with a distance of 80cm to 100cm, so as to form a rectangular beam spot with a length of 10cm to 14cm and a width of 2cm to 4cm. In the third step, the surface temperature of the material is obtained by a non-contact infrared temperature sensor, and its detection spot is aligned with the geometric center of the heating area of ​​the light spot.

[0019] By adopting the aforementioned technical solution, the beneficial effects of the present invention are: 1. A laser is emitted through a light source module, and the beam shaping module adjusts it into a light spot with a preset energy distribution and geometry, which is then projected onto the material surface. A temperature feedback control module dynamically adjusts the light source output power based on the difference between the real-time temperature and the preset target temperature. This solution fundamentally changes the traditional process where waistband materials are directly fed into the welding station at room temperature, preheating the material to a near-molten, activated state before welding. The resulting benefits are: significantly reduced instantaneous energy density required by the subsequent welding station in a very short time, ensuring sufficient fusion energy for ultrasonic welding even at high speeds, fundamentally resolving the contradiction between machine speed and insufficient welding strength; simultaneously, since the welding station no longer needs to handle all heating, it avoids material hardening problems caused by high-temperature dependence of the heat-sealing roller, maintaining a soft touch on the welded waistband, thus balancing the comprehensive needs of high-speed production, high welding strength, and good wearing comfort. Closed-loop temperature control ensures the accuracy and stability of the preheating temperature, effectively preventing material damage due to overheating or preheating failure due to insufficient temperature, providing reliable process assurance for continuous high-speed production lines.

[0020] 2. The beam transmission module can flexibly change the laser transmission direction, allowing the system layout to adapt to the space constraints of different production lines and improving the flexibility of equipment installation; the sealing and protection module forms a closed channel in the optical path area, which can effectively prevent dust, oil and other pollutants from the production environment from adhering to the surface of optical components, ensuring the long-term stability of laser transmission efficiency; the thermal management module actively cools the light source power supply and resonant cavity, which can ensure the power stability and service life of the light source module during long-term continuous operation, meeting the requirements of uninterrupted industrial production.

[0021] 3. Through multi-dimensional adjustment function, the laser optical path can be accurately calibrated so that the laser always passes through the center of each lens, minimizing energy loss and spot distortion, ensuring beam shaping quality, and reducing the difficulty of equipment assembly and debugging.

[0022] 4. The distance between the integrating mirror and the material surface can be flexibly adjusted according to different product specifications or material characteristics, thereby changing the spot size and energy distribution. This allows the same equipment to adapt to the switching needs of various waist sizes and production processes, improving the system's versatility and production changeover efficiency.

[0023] 5. This parameter range has been verified by the process and can form a rectangular uniform spot on the surface of the waistband material that is highly matched with the welding area. This ensures that the preheating area accurately covers the part to be welded, achieving ideal preheating uniformity and energy utilization, and providing a guarantee for stable and reliable subsequent welding.

[0024] 6. By using a multi-segmented tubular body, the reflector, beam expander, and integrating mirror can be installed on different segments of the tubular body, thus enabling convenient replacement, disassembly, and adjustment.

[0025] 7. Water cooling has high heat dissipation efficiency and stable temperature control, which can effectively suppress the temperature rise of the core components of the laser, avoid power attenuation or component damage caused by overheating, and ensure the reliability of the system under long-term high-load conditions.

[0026] 8. Non-contact temperature measurement avoids wear and interference caused by direct contact between the sensor and high-temperature or moving materials, and has a fast response speed; the centered detection spot can obtain the most representative temperature value of the heating area, providing accurate and real-time feedback signals for closed-loop control, and further improving temperature control accuracy.

[0027] 9. By organically combining the methods and steps, controllable preheating of waistband materials before welding was achieved, solving the problem of insufficient energy input under high-speed welding conditions from a process perspective. At the same time, closed-loop temperature control ensured the consistency and repeatability of the preheating process, providing reliable methodological support for large-scale industrial production.

[0028] 10. By adjusting specific parameters within a certain range, precise matching between the preheating spot and the welding area can be ensured; by centrally arranging the infrared thermography spot, the most accurate material surface temperature feedback can be obtained. These measures together guarantee the accuracy and consistency of the preheating method under different working conditions, enhancing the practicality and operability of the process plan. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the present invention.

[0030] Figure 2 This is a schematic diagram of the structure of the beam transmission module and the beam shaping module working together.

[0031] Figure label: 1. Light source module; 2. Beam transmission module; 3. Beam shaping module; 4. Sealing and protection module; 5. Adjustable mounting base; 21. Reflector; 31. Beam expander; 32. Integrator; 6. Welding device. Detailed Implementation

[0032] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0033] like Figure 1 , Figure 2 As shown, this embodiment provides a laser preheating system applied in the production line of disposable hygiene products (such as diapers and pull-up pants) to preheat the waistband material before it enters the welding station. The system mainly includes: a light source module 1, a beam transmission module 2, a beam shaping module 3, a sealing and protection module 4, an adjustable mounting base 5, a reflector 21, a beam expander 31, an integrating mirror 32, and a temperature feedback control module and a thermal management module (not separately labeled in the figures).

[0034] The light source module 1 can be an industrial-grade continuous-output carbon dioxide laser generator with a rated output power of 500W, used to emit the raw laser beam. This laser generator has an external control interface, capable of receiving analog or digital signals to achieve real-time adjustment of the output power. Of course, other laser generators can also be used.

[0035] The thermal management module includes a water chiller, which is connected to the power supply unit and the cooling interface of the internal resonant cavity of the light source module 1 via water pipes. After the water chiller is connected and tested, it can ensure that the temperature rise of the core components of the laser generator is effectively suppressed during long-term, high-load continuous operation, thus ensuring the long-term stability of the output power. Of course, the thermal management module can also have other structures, as long as it can achieve the cooling of the power supply unit and the internal resonant cavity of the light source module 1.

[0036] The beam transmission module 2 is disposed between the light source module 1 and the beam shaping module 3. In this embodiment, to adapt to the compact spatial layout of the production line, the optical path needs to be changed in the horizontal direction. Therefore, the beam transmission module 2 includes a reflector 21. After the laser beam is emitted horizontally from the light source module 1, it is reflected vertically downward by the reflector 21 and guided to the beam shaping module 3.

[0037] To prevent dust, oil, and other contaminants from the production environment from adhering to the surfaces of optical components such as the reflector 21, beam expander 31, and integrator 32, the system is equipped with a sealing and protection module 4. In this embodiment, the sealing and protection module 4 is a multi-segment connected tubular cylinder made of black opaque flexible material. This cylinder encloses the optical path area between the reflector 21, beam expander 31, and integrator 32 into a closed channel, effectively preventing light leakage and blocking external environmental pollution.

[0038] To achieve precise optical path calibration, the reflector 21, beam expander 31, and integrating mirror 32 are mounted on adjustable mounts 5 with multi-directional adjustment margins. Specifically, these adjustable mounts allow for fine-tuning of each lens in the horizontal direction and in the pitch angle. During system commissioning, adjusting these mounts ensures that the center of the laser beam passes precisely through the geometric center of each lens, thereby minimizing energy loss and beam distortion. The adjustable mounts 5 are a conventional technique in this field and will not be described in detail here.

[0039] The beam shaping module 3 includes a beam expander 31 and an integrating mirror 32. The beam expander 31 is used to increase the diameter of the laser beam to reduce its divergence angle. The integrating mirror 32 is used to homogenize and shape the Gaussian-distributed circular laser beam into a rectangular spot with a uniform energy distribution. The integrating mirror 32 is also equipped with a focus adjustment mechanism, such as a manual or electric lead screw slide, for precisely adjusting the vertical distance between the integrating mirror 32 and the surface of the waistband material to be preheated below. According to process verification, this distance is configured to 90cm in this embodiment. At this distance, the spot shaped by the integrating mirror 32 forms a rectangular uniform spot with a length of 12cm and a width of 3cm on the material surface. The size of this rectangular spot is highly matched to the waistband area to be welded at the downstream welding station. Depending on different product specifications and material characteristics, this distance can be adjusted within the range of 80cm to 100cm, correspondingly obtaining rectangular spots with a length of 10cm to 14cm and a width of 2cm to 4cm. The focus adjustment mechanism is also a conventional technique in this field.

[0040] Along the production line, a welding device 6 (such as an ultrasonic welding system or a heat-sealing roller system) is installed after the preheating station. The preheated waistband material then enters the welding device 6 for final welding and sealing.

[0041] The temperature feedback control module includes a non-contact infrared temperature sensor and a programmable logic controller (PLC). The infrared temperature sensor's detection lens is fixedly mounted so that its detection spot is precisely aligned with the geometric center of the rectangular light spot heating area formed by the integrating mirror 32. The sensor's response time is set to 10 milliseconds to capture the surface temperature of the material in rapid motion in real time. The controller is connected to the control interface signal of the light source module 1. The controller has a preset target temperature value (for example, for a typical composite waistband material, this value is 85% of the material's melting point). During operation, the controller reads the material surface temperature fed back by the temperature sensor in real time and compares it with the preset target temperature. If the real-time temperature is lower than the target value, the controller increases the power signal output to the light source module 1 proportionally; conversely, if the real-time temperature is higher than the target value, the output power is reduced. Through this closed-loop control method, the preheating temperature of the material surface is stably maintained within the preset value range (e.g., ±5℃), effectively preventing material damage due to overheating or subsequent welding failure due to insufficient preheating.

[0042] The laser preheating method of the present invention, in conjunction with the above system, is described in detail below, and includes the following steps: Step 1: Start all modules of the laser preheating system, including the water chiller of the thermal management module. After the water circulation is stable, start the light source module 1 and put it into standby mode.

[0043] Step 2: When the production line starts running and the waistband material moves continuously, the control system triggers the light source module 1 to emit a laser. The laser beam is first expanded by the beam expander 31, then its direction is changed by the reflector 21, and finally shaped by the integrating mirror 32 into a rectangular uniform spot of a preset size (e.g., 120mm × 30mm), which is then projected onto the surface of the moving waistband material to continuously preheat the specific area to be welded.

[0044] Step 3: The non-contact infrared temperature sensor in the temperature feedback control module acquires the temperature of the material surface in the preheating area in real time and sends the temperature signal to the controller.

[0045] Step 4: The controller calculates the difference between the real-time temperature and the internally stored preset target temperature value. Based on the calculation result, the controller dynamically adjusts the output power of the light source module 1. For example, when the real-time temperature is lower than the target value, the output power is increased; when the real-time temperature is higher than the target value, the output power is decreased. Through this closed-loop control, it is ensured that before the waistband material leaves the preheating station and enters the downstream welding station, its entire area to be welded has uniformly and stably reached and maintained within the preset, near-molten temperature range.

[0046] Step 5: After preheating, the waistband material enters the working area of ​​the downstream welding device 6. Since the material already has a high initial temperature, the welding device 6 only needs to provide a small amount of instantaneous energy to achieve a high-quality weld seal. This greatly reduces the sensitivity of ultrasonic welding to the action time, ensuring weld strength even when the machine is running at high speed. At the same time, it avoids the product hardening problem caused by the high-temperature dependence of the heat-sealing roller, resulting in a soft feel and comfortable wear for the welded waistband.

[0047] Further optimizations are made based on the above embodiments, with the main differences being: the configuration of the temperature feedback control module and the energy distribution adjustment capability of the beam shaping module.

[0048] The temperature feedback control module includes an array-type non-contact temperature sensor and a programmable logic controller. In this embodiment, the array-type temperature sensor is a linear infrared sensor, which can be a microbolometer array with 16×1 or 32×1 pixels, a conventional technique in the field. Its detection area covers the entire rectangular heating area along the width of the waistband material, i.e., perpendicular to the material's direction of travel. This linear sensor can simultaneously acquire the real-time temperature values ​​of multiple sub-regions distributed along the width of the heating area; in this embodiment, there are 16 sub-regions.

[0049] The beam shaping module also includes a programmable micromirror array before the integrating mirror. This array can be installed in the optical path between the beam expander and the integrating mirror. The micromirror array consists of multiple independently controllable micromirrors, each corresponding to a sub-region along the width of the heating area. By adjusting the tilt angle or duty cycle of each micromirror, the controller can independently change the laser energy density projected onto the corresponding sub-region, thereby achieving energy distribution modulation of the beam spot along the width of the beam.

[0050] The controller internally stores preset target temperature values ​​corresponding to each sub-region. These target temperature values ​​can be the same, for example, all 85% of the material's melting point; or they can be set to different values ​​according to the lateral characteristics of the waistband material. For example, considering the material characteristics of a higher density of elastic yarns in the middle region and a thicker nonwoven fabric in the edge regions, the target temperature of the middle sub-region can be set slightly lower than that of the two side sub-regions to prevent the elastic yarns from overheating and melting. In this embodiment, for the application of baby diaper waistband material, the density of elastic yarns in the middle region is greater than that on the sides, therefore the target temperature of the middle sub-region is set lower than that of the two side sub-regions.

[0051] The working process of this embodiment is as follows: When the production line is running, array-type temperature sensors acquire the surface temperature of each sub-region in real time and send it to the controller. The controller compares the real-time temperature of each sub-region with its corresponding preset target temperature and calculates the temperature difference between the sub-regions. Based on the magnitude and direction of the temperature difference, the controller adjusts the reflection angle or duty cycle of the corresponding micromirrors in the programmable micromirror array: for sub-regions with lower temperatures, the corresponding laser energy allocation ratio is increased; for sub-regions with higher temperatures, the corresponding laser energy allocation ratio is decreased. This adjustment process continues in a closed-loop manner, ensuring that the temperature of each sub-region in the width direction within the entire rectangular laser spot heating area tends to be consistent and stabilized within its respective preset range.

[0052] With the above-mentioned zoned temperature control scheme in the width direction, even if the waistband material has uneven density, thickness or composition in the lateral direction, the present invention can ensure that the surface temperature of the material is uniformly distributed, effectively avoiding local overheating that could lead to breakage of elastic wires or insufficient local preheating that could affect the subsequent welding quality. It is especially suitable for the preheating process of high elasticity, multi-layer composite waistband materials.

[0053] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A laser preheating system for preheating disposable sanitary product waistband materials before welding, characterized in that, include: A light source module for emitting laser light; A beam shaping module is used to adjust the laser emitted by the light source module into a light spot with a preset energy distribution and geometry, and project it onto the surface of the waistband material to be preheated; A temperature feedback control module includes a temperature sensor and a controller. The controller is configured to dynamically adjust the output power of the light source module based on the difference between the real-time temperature of the material surface collected by the temperature sensor and a preset target temperature, so as to maintain the material preheating temperature within a preset value range.

2. The laser preheating system according to claim 1, characterized in that, Also includes: A beam transmission module is disposed between the light source module and the beam shaping module, and is used to change the laser transmission direction and guide the laser to the beam shaping module; A sealed protection module is used to form a closed channel in the optical path area between the light source module, the beam transmission module and the beam shaping module to prevent light leakage and optical path contamination. A thermal management module is provided for actively cooling the power supply and internal resonant cavity of the light source module.

3. The laser preheating system according to claim 2, characterized in that, The beam transmission module includes at least one reflector, and the beam shaping module includes at least one beam expander and at least one integrating mirror. The reflector, beam expander, and integrating mirror are respectively mounted on an adjustable mounting base with multi-directional adjustment margin.

4. The laser preheating system according to claim 3, characterized in that, The integrating mirror includes a focal length adjustment mechanism for adjusting the distance between the integrating mirror and the material to be heated, thereby changing the spot size and / or energy distribution.

5. The laser preheating system according to claim 4, characterized in that, The distance between the integrating mirror and the material to be heated is configured to be 80cm to 100cm to form a rectangular light spot with a length of 10cm to 14cm and a width of 2cm to 4cm.

6. The laser preheating system according to claim 2, characterized in that, The sealing and protection module is a tubular cylinder, which has a multi-segment connected structure.

7. The laser preheating system according to claim 2, characterized in that, The thermal management module includes a water chiller, which is connected to the power supply and the resonant cavity.

8. The laser preheating system according to claim 1, characterized in that, The temperature sensor is a non-contact infrared temperature sensor, whose detection area points to the heating area formed by the light spot on the material surface, and whose detection spot falls within the geometric center range of the heating area.

9. A laser preheating method, applied to the laser preheating system according to any one of claims 1 to 8, characterized in that, Includes the following steps: The first step is to generate laser light in a light source module; The second step involves changing the laser direction through a beam transmission module and adjusting the laser into a spot with a preset energy distribution and geometry through a beam shaping module, which is then projected onto the surface of the waistband material traveling along the production line to preheat it. The third step is to obtain the temperature of the material surface in the preheating area in real time. The fourth step is to control the output power of the light source module in a closed loop based on the difference between the real-time temperature and the preset target temperature, so that the material reaches and is maintained within the preset temperature range before entering the welding station. The fifth step involves preheating the waistband material before it enters the downstream welding station for welding and sealing.

10. The laser preheating method according to claim 9, characterized in that, In the second step, the beam shaping module includes a beam expander and an integrating mirror. By adjusting the distance between the integrating mirror and the material surface, the light spot is shaped into a rectangle with a distance of 80cm to 100cm, so as to form a rectangular light spot with a length of 10cm to 14cm and a width of 2cm to 4cm. In the third step, the surface temperature of the material is obtained by a non-contact infrared temperature sensor, and its detection spot is aligned with the geometric center of the heating area of ​​the light spot.

Images