Laser welding head and laser welding device

Abstract

The invention provides a laser welding head and a laser welding device, and relates to the field of laser welding. The laser welding head comprises a barrel and a focusing structure, a first cavity is formed in the barrel, and a light outlet communicated with the first cavity is formed in one end of the barrel; the focusing structure comprises a movable sleeve and a plurality of focusing lenses, the movable sleeve is arranged in the first cavity, and the plurality of focusing lenses are arranged in the movable sleeve and used for focusing laser transmitted from the interior of the cylinder to the exterior of the light outlet; the movable sleeve can slide in the first cavity in the first direction and drive the multiple focusing lenses to slide synchronously so as to adjust the focus point positions of the focusing lenses after focusing. The movable sleeve capable of sliding is arranged to drive the focusing lens to move synchronously, the position of a focusing point of the focusing lens is conveniently adjusted, and the problem that an existing welding head is difficult to adapt to welding of workpieces with different thicknesses due to structural limitation is solved.

Description

Technical Field

[0001] This invention belongs to the field of laser welding technology, and in particular relates to a laser welding head and a laser welding device. Background Technology

[0002] Laser plastic welding is a solderless joining process. Compared with traditional welding methods, it has significant advantages such as fast welding speed, small heat-affected zone, high weld strength, and minimal damage to the welding material. Therefore, it has been widely used in many fields such as automobile manufacturing, electronic equipment, and medical devices.

[0003] However, in practical applications, the required focal point varies depending on the material thickness. Existing laser welding head structures are too simple and cannot meet the welding requirements of workpieces with different materials and thicknesses. Summary of the Invention

[0004] In view of this, the present invention provides a laser welding head and a laser welding device, which aims to solve the problem that existing laser welding heads are difficult to adapt to the welding needs of workpieces with different materials and / or thicknesses.

[0005] The technical solution of this invention is implemented as follows: This invention provides a laser welding head, including a cylindrical body and a focusing structure. The cylindrical body has a first cavity inside, and one end of the cylindrical body has a light outlet communicating with the first cavity. The focusing structure includes a movable sleeve and a plurality of focusing lenses. The movable sleeve is disposed within the first cavity, and the plurality of focusing lenses are disposed within the movable sleeve for focusing the laser transmitted from the cylindrical body to the light outlet. The movable sleeve can slide along a first direction within the first cavity, causing the plurality of focusing lenses to slide synchronously, thereby adjusting the focal point position after focusing. In one embodiment, the plurality of focusing lenses includes a first focusing lens and a second focusing lens arranged at intervals along the first direction. The optical axes of the first focusing lens and the second focusing lens are collinear and parallel to the first direction.

[0006] In one embodiment, the plurality of focusing lenses includes a first focusing lens and a second focusing lens arranged at intervals along a first direction, wherein the optical axes of the first focusing lens and the second focusing lens are collinear and parallel to the first direction.

[0007] In one embodiment, the focusing structure further includes an adjusting member, one end of which is connected to the movable sleeve, and the other end of which extends out of the side wall of the cylinder.

[0008] In one embodiment, the side wall of the cylinder is provided with an elongated hole extending along the first direction; the adjusting member is a screwed member, the stud of the screwed member passes through the elongated hole and is screwed to the movable sleeve, and the nut of the screwed member is pressed against the outside of the cylinder.

[0009] In one embodiment, a stepped surface is formed inside the elongated hole, and the nut of the screw connector is pressed against the stepped surface, with the top surface of the nut flush with the edge of the elongated hole.

[0010] In one embodiment, a filter lens is further included in the cylinder body. The filter lens is disposed on the side of the focusing structure near the light outlet and covers the light outlet in the first direction. The optical axis of the filter lens is collinear with the optical axis of the focusing lens.

[0011] In one embodiment, a spherical lens is further disposed within the light outlet, and the spherical lens is rotatable within the light outlet.

[0012] In one embodiment, the filter lens and the spherical lens are spaced apart in the first direction, and a buffer cavity is formed between the filter lens and the spherical lens; the laser welding device further includes an air blowing device, which includes an air pump and an air guide pipe, one end of the air guide pipe is connected to the buffer cavity, and the other end passes through the side wall of the cylinder and extends out of the cylinder to be connected to the air pump.

[0013] In one embodiment, a temperature compensation ring is provided between the first focusing lens and the second focusing lens; the temperature compensation ring is made of a ring-shaped shape memory alloy and can expand and contract along the first direction according to the temperature change in the first cavity; the movable sleeve has a first end near the light outlet, and a compression spring is provided between the first end and the first focusing lens.

[0014] This invention provides a laser welding apparatus, which includes a laser welding head and a laser generator. The laser generator generates and outputs laser light. The laser generator is connected to one end of the laser welding head away from the light output port of the laser welding head via an optical fiber to transmit the laser light into a first cavity of the laser welding head.

[0015] The laser welding head provided in this invention includes a cylindrical body and a focusing structure. A first cavity is formed inside the cylindrical body, and one end of the cylindrical body has a light-emitting port communicating with the first cavity. The focusing structure includes a movable sleeve and several focusing lenses. The movable sleeve is disposed within the first cavity, and the several focusing lenses are disposed within the movable sleeve, used to focus the laser transmitted from inside the cylindrical body to the outside of the light-emitting port. The movable sleeve can slide along a first direction within the first cavity, driving the several focusing lenses to slide synchronously, thereby adjusting the position of the focal point after focusing. This invention, by setting a slidable movable sleeve to drive the synchronous movement of the focusing lenses, achieves convenient adjustment of the focal point position, solving the problem that existing welding heads are difficult to adapt to workpieces of different thicknesses due to structural limitations. Specifically, by sliding the movable sleeve along the first direction, the distance between the focal point and the light-emitting port can be flexibly changed. When dealing with thicker workpieces, the movable sleeve is slid towards the light-emitting port, allowing the focal point to penetrate deep into the weld; when processing thinner workpieces, the movable sleeve is slid in the opposite direction, allowing the focal point to accurately fall on the weld surface. This meets diverse welding needs without disassembling or replacing parts, significantly improving the flexibility and efficiency of welding operations. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 This is an overall appearance view of the first laser welding head provided by the present invention; Figure 2 An overall cross-sectional view of the first laser welding head provided by the present invention; Figure 3 An exploded view of the first laser welding head provided by the present invention; Figure 4 for Figure 1 Enlarged view of point C in the middle; Figure 5 This is an overall cross-sectional view of the second type of laser welding head provided by the present invention; Figure 6 An exploded view of the second type of laser welding head provided by the present invention; Figure 7 for Figure 5 Enlarged view of point D in the middle.

[0018] Explanation of reference numerals in the attached figures: 100 / 100' Laser welding head; 1. Cylinder; 11. First cavity; 12. Light outlet; 13. Elongated hole; 131. Stepped surface; 2. Focusing structure; 21. Movable sleeve; 22. Focusing lens; 22A. First focusing lens; 22B. Second focusing lens; 23. Adjusting component / screw connector; 231. Stud; 232. Nut; 2321. Slot; 24. Temperature compensation ring; 25. Compression spring; 3. Filter lens; 4. Spherical lens; 5. Buffer cavity; 6. Air blowing device; 61. Air guide tube. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0021] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. "Multiple" refers to two or more. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0022] Laser plastic welding is a solderless joining process. Compared with traditional welding methods, it has significant advantages such as fast welding speed, small heat-affected zone, high weld strength, and minimal damage to the welding material. Therefore, it has been widely used in many fields such as automobile manufacturing, electronic equipment, and medical devices.

[0023] However, in practical applications, the required focal point varies depending on the material thickness. The existing laser welding head 100 structure is too simple and cannot meet the welding requirements of workpieces with different materials and thicknesses.

[0024] In view of this, the present invention provides a laser welding head 100 / 100', which aims to solve the problem that the existing laser welding head 100 is difficult to adapt to the welding needs of workpieces with different materials and / or thicknesses.

[0025] Please see Figure 1 , Figure 2 and Figure 3 The laser welding head 100 / 100' includes a cylindrical body 1 and a focusing structure 2. A first cavity 11 is formed inside the cylindrical body 1, and a light outlet 12 communicating with the first cavity 11 is provided at one end of the cylindrical body 1, through which the laser can be directed toward the workpiece to be welded.

[0026] The focusing structure 2 includes a movable sleeve 21 and several focusing lenses 22. The movable sleeve 21 is disposed within the first cavity 11, and the several focusing lenses 22 are installed within the movable sleeve 21. Their function is to focus the laser light transmitted from inside the cylinder 1 to the light outlet 12. Figure 2 (Represented by dashed line 'a') slides within the first cavity 11, causing several focusing lenses 22 to move synchronously during the sliding process, thereby changing the position of the focal point after focusing by the focusing lenses 22 to adapt to the welding requirements of workpieces of different thicknesses. Here, "several focusing lenses 22" can be understood as at least one focusing lens 22; when there are multiple focusing lenses 22, the focal lengths of the focusing lenses 22 can be the same or different.

[0027] The focusing principle of the focusing structure 2 is as follows: The sliding of the movable sleeve 21 within the first cavity 11 along a first direction causes the focusing lens 22 within the movable sleeve 21 to move synchronously, thus changing the distance between the focal point of the laser beam after passing through the focusing lens 22 and the light exit port 12. When the movable sleeve 21 slides closer to the light exit port 12, the focal point moves forward, allowing it to move from the surface of the weld to the depth of the weld, suitable for welding thicker workpieces. When the movable sleeve 21 slides away from the light exit port 12, the focal point moves backward, allowing it to move from the depth of the weld to the surface of the weld, suitable for welding thinner workpieces. In this way, there is no need to replace the welding head or adjust the overall position of the welding device; the focal point position can be quickly adjusted simply by sliding the movable sleeve 21, greatly improving the adaptability of the welding head to workpieces of different thicknesses.

[0028] The laser welding head 100 / 100' provided in this embodiment of the invention includes a cylindrical body 1 and a focusing structure 2. A first cavity 11 is formed inside the cylindrical body 1, and one end of the cylindrical body 1 is provided with a light outlet 12 communicating with the first cavity 11. The focusing structure 2 includes a movable sleeve 21 and a plurality of focusing lenses 22. The movable sleeve 21 is disposed within the first cavity 11, and the plurality of focusing lenses 22 are disposed within the movable sleeve 21, used to focus the laser transmitted from inside the cylindrical body 1 to outside the light outlet 12. The movable sleeve 21 can slide along a first direction within the first cavity 11, driving the plurality of focusing lenses 22 to slide synchronously, thereby adjusting the focal point position after focusing by the focusing lenses 22. This embodiment of the invention, by setting a slidable movable sleeve 21 to drive the focusing lenses 22 to move synchronously, achieves convenient adjustment of the focal point position, solving the problem that existing welding heads are difficult to adapt to workpieces of different thicknesses due to structural limitations. Specifically, by sliding the movable sleeve 21 along the first direction, the distance between the focal point and the light outlet 12 can be flexibly changed. When dealing with thicker workpieces, the movable sleeve 21 is slid towards the light outlet 12 to make the focal point penetrate into the weld. When dealing with thinner workpieces, the movable sleeve 21 is slid in the opposite direction to make the focal point accurately fall on the weld surface. This can meet diverse welding needs without disassembling or replacing parts, significantly improving the flexibility and efficiency of welding operations.

[0029] In some embodiments, please refer to Figure 2 and Figure 3 To improve laser focusing accuracy and adjustment flexibility, multiple focusing lenses 22 are used. Specifically, the multiple focusing lenses 22 include a first focusing lens 22A and a second focusing lens 22B arranged at intervals along a first direction, with their optical axes collinear and parallel to the first direction.

[0030] The focusing methods of the two focusing lenses 22 are as follows: the first focusing lens 22A can first converge the diverging laser beam and compress the beam diameter to improve the energy concentration; the second focusing lens 22B then performs secondary focusing on this basis. By precisely controlling the distance and focal length matching of the two lenses, a light spot with uniform energy distribution can be formed at different focal point positions.

[0031] This graded focusing method offers a wider focusing adjustment range compared to a single lens. When the movable sleeve 21 moves the two lenses synchronously, it can maintain the energy stability of the focal point over a greater depth range. For example, for thicker polycarbonate workpieces, a higher energy density at the focal point is required to ensure welding depth; while for thin polyethylene workpieces, the energy density needs to be appropriately reduced to avoid overheating of the material. By optimizing the optical path difference, the dual-lens combination can achieve focusing at different adjustment positions, thus simultaneously meeting the welding needs of workpieces with different materials and thicknesses, further expanding the applicability of the 100 / 100' laser welding head.

[0032] In some embodiments, in order to improve the energy density of the focal point, the first focusing lens 22A is positioned closer to the light outlet 12 than the second focusing lens 22B, and the focal length of the first focusing lens is smaller than the focal length of the second focusing lens 22B.

[0033] From an optical path design perspective, the second focusing lens 22B (far from the light exit port 12, with a long focal length) first receives the diverging laser beam transmitted within the cylinder 1. Its long focal length characteristic smoothly compresses the divergence angle of the beam, initially converging the originally dispersed laser energy into a quasi-parallel beam with a more concentrated energy distribution. This pre-focusing process reduces energy loss during laser transmission, laying the foundation for subsequent precise focusing. Meanwhile, the first focusing lens 22A (closer to the light exit port 12, with a short focal length) utilizes its strong converging capability to further compress the pre-focused beam, ultimately forming a focal point with extremely high energy density on or inside the workpiece surface.

[0034] This combination of long-focal-length pre-focusing and short-focal-length fine-focusing significantly improves focusing efficiency compared to a single lens or a reverse focal length design. The long-focal-length second focusing lens 22B avoids energy waste caused by instantaneous beam convergence, while the short-focal-length first focusing lens 22A can quickly achieve final focusing near the workpiece, reducing beam propagation loss in the air. For laser plastic welding, higher energy density means that the plastic can reach its melting temperature in a shorter time, which not only increases welding speed but also reduces the heat-affected zone. For example, when welding thick PVC pipes, high energy density ensures that the focal point penetrates deep into the weld for effective fusion; while when welding thin PE films, after adjusting the focal point position through the movable sleeve 21, the short-focal-length lens can still ensure that the focal point energy is concentrated and controllable, avoiding film burn-through caused by excessive energy diffusion.

[0035] In some embodiments, please continue reading Figure 2 and Figure 3 To facilitate convenient control of the sliding of the movable sleeve 21, an adjusting component 23 is added to the focusing structure 2. Specifically, one end of the adjusting component 23 is connected to the movable sleeve 21, and the other end extends out of the side wall of the cylinder 1.

[0036] This design allows operators to directly drive the movable sleeve 21 to slide along the first direction via the external adjusting component 23 without needing to contact the internal structure of the cylinder 1, greatly simplifying the adjustment process of the focal point position. The connection between the adjusting component 23 and the movable sleeve 21 adopts a rigid fixing method (such as screw connection or integral molding) to ensure the synchronization of their movements and avoid adjustment lag or deviation caused by loosening.

[0037] The adjusting component 23 extending from the side wall of the cylinder 1 can be designed as a rod-shaped, plate-shaped, or knob-shaped structure according to operational requirements: the rod-shaped adjusting component 23 is easy to push and pull manually, suitable for scenarios requiring rapid coarse adjustment; the knob-shaped adjusting component 23 can be used with a threaded transmission structure to achieve a slight sliding of the movable sleeve 21 through rotation, meeting high-precision adjustment requirements (such as welding positioning of thin-walled plastic parts in electronic equipment). In addition, a guide structure (such as a linear bearing or sliding guide rail) can be set at the penetration point between the adjusting component 23 and the side wall of the cylinder 1, which not only ensures the smooth sliding of the adjusting component 23, but also restricts its rotation in the circumferential direction, ensuring that the optical axis of the focusing lens 22 is always consistent with the first direction, avoiding focusing deviation caused by lens offset.

[0038] With this structure, the operator can intuitively control the sliding distance of the adjusting component 23 according to the workpiece thickness. Combined with the preset adjustment amount and the correspondence between the focal point position, the focal point can be quickly positioned to the ideal position, which significantly improves the operating efficiency and adjustment accuracy of the welding head.

[0039] In some embodiments, please continue reading Figure 2 and Figure 3 In order to achieve the positioning and locking of the movable sleeve 21, an elongated hole 13 extending in the first direction is provided on the side wall of the cylinder 1; and the adjusting member 23 is a screwed member, the stud 231 of the screwed member passes through the elongated hole 13 and is screwed to the movable sleeve 21, and the nut 232 of the screwed member is pressed against the outside of the cylinder 1.

[0040] The elongated hole 13 not only provides a sliding channel for the screw connector along the first direction, but its hole wall can also guide the movement trajectory of the screw connector, preventing circumferential displacement when the screw connector drives the movable sleeve 21 to slide, so that the movable sleeve 21 always moves smoothly along the first direction, thereby ensuring the coaxiality of the optical axis of the focusing lens 22 and the laser transmission path, and preventing focusing deviation caused by lens displacement.

[0041] The stud 231 and nut 232 of the screw connector simultaneously achieve the dual functions of transmission and locking: During the adjustment stage, after loosening the nut 232, the operator can push or pull the screw connector, and drive the movable sleeve 21 to slide synchronously through the rigid connection between the stud 231 and the movable sleeve 21. At this time, the guiding role of the elongated hole 13 is to make the adjustment process stable and controllable; During the positioning stage, when the movable sleeve 21 slides to the target position (i.e. the focal point reaches the ideal welding depth), tighten the nut 232 to make the nut 232 tightly press against the outer wall of the cylinder 1, and use the friction between the two to fix the screw connector, thereby locking the position of the movable sleeve 21 and the focusing lens 22, avoiding the displacement of the movable sleeve 21 due to equipment vibration or airflow impact during the welding process, and ensuring welding stability.

[0042] Furthermore, the edge of the elongated hole 13 can be marked with graduations, the graduation values ​​corresponding to the focal point position or workpiece thickness. Operators can quickly read the sliding position of the movable sleeve 21 by aligning the edge of the nut 232 with the graduations, thus achieving quantitative adjustment of the focal point. For example, when the graduation is 5mm, the focal point is 125mm from the light outlet, suitable for welding ABS plastic workpieces with a thickness of approximately 1-3mm; while a graduation of 2mm corresponds to welding thinner workpieces of 0-1mm. This visual graduation design, combined with the locking function of the screw connection, further improves the accuracy of adjustment and the convenience of operation, making it particularly suitable for batch production scenarios requiring frequent changes in workpiece type.

[0043] In some embodiments, please refer to Figure 4 To facilitate tightening and loosening of the threaded connection, a slot 2321 is provided on the top surface of the nut 232. This slot 2321 is compatible with common screwdrivers or wrenches; operators can easily tighten or loosen the nut 232 by inserting the tool into the slot and applying torque. The slot 2321 can be designed in a straight line shape (e.g.,...). Figure 1 (As shown), cross-shaped or hexagonal slots are available to be compatible with different types of tools: the flat slot allows for quick manual adjustment and is suitable for temporary positioning scenarios where locking force is not required; the cross-shaped or hexagonal slots provide more stable torque transmission, ensuring that the nut 232 remains reliably locked under long-term vibration and preventing accidental shift of the focal point position.

[0044] In some embodiments, a stepped surface is formed in the elongated hole 13 to make the overall appearance flat. Furthermore, the nut 232 of the screw connector 23 is pressed against the stepped surface 131, and the top surface of the nut 232 is flush with the edge of the elongated hole 13.

[0045] This design effectively avoids the risk of impact caused by the nut 232 protruding from the surface of the cylinder 1, while making the external structure of the laser welding head simpler and more compact, facilitating welding operations in confined spaces. The fit between the stepped surface 131 and the nut 232 also provides additional positioning, preventing the nut 232 from being excessively screwed into the cylinder 1 during tightening, ensuring that the sliding stroke of the movable sleeve 21 is not affected.

[0046] In some embodiments, please refer to Figure 2 and Figure 3 In order to selectively filter stray light or specific wavelength components in the laser, a filter lens 3 is added to the laser welding head 100 / 100'. Specifically, the filter lens 3 is disposed inside the cylinder 1, on the side of the focusing structure 2 near the light outlet 12, and covers the light outlet 12 in the first direction; the optical axis of the filter lens 3 is collinear with the optical axis of the focusing lens 22.

[0047] The core function of the filter lens 3 is to precisely control the laser spectrum: the original beam output by the laser generator may contain a small amount of stray light (such as frequency-doubled light or scattered light) that deviates significantly from the target wavelength. This stray light not only cannot be effectively absorbed by the welding material, but may also form interfering heat sources on the workpiece surface, causing thermal damage to non-welding areas. By placing the filter lens 3 between the focusing structure 2 and the light outlet 12, the optical selectivity of its coating layer can be utilized to allow only specific wavelengths of laser light (such as the 1064nm near-infrared light commonly used in plastic welding) to pass through efficiently, while reflecting or absorbing stray light, thereby purifying the spectral composition of the laser beam.

[0048] This selective filtering capability is more targeted for plastic workpieces of different materials: for example, when welding black PBT plastic reinforced with glass fiber, the filter lens 3 can filter out short-wavelength components that are easily scattered by glass fiber particles, and retain long-wavelength laser to enhance the penetration depth; while when welding composite workpieces of transparent PC plastic and black ABS plastic, the filter lens 3 can select wavelengths that can be efficiently absorbed by ABS and are not easily reflected by PC, ensuring that the laser energy mainly acts on the interface between the two materials and improves the welding strength.

[0049] Furthermore, the design of the filter lens 3 covering the light outlet 12 enables uniform filtering of the entire laser beam cross-section, avoiding uneven energy distribution caused by spectral shift at the beam edge; the collinear optical axis arrangement ensures that the filtered laser still focuses along the original path, without changing the positional accuracy of the focal point. This structural design optimizes the energy utilization efficiency of the laser and reduces the interference of stray light on the welding quality, allowing the laser welding head 100 to better adapt to the differences in optical properties of different plastic materials, thus broadening its application scenarios.

[0050] In some embodiments, please continue reading Figure 2 and Figure 3 To enhance the focusing of the laser, a spherical lens 4 is added. Specifically, the spherical lens 4 is disposed inside the light outlet 12 and can rotate within the light outlet 12.

[0051] The spherical curvature of the spherical lens 4 has unique optical converging characteristics, and its 360° uniform curved surface structure can form an all-round focusing enhancement for the incident laser. Compared with ordinary convex lenses, the spherical lens 4 can focus the laser beam from more angles to the same point. In particular, after the laser beam is initially focused by the focusing lens 22 of the focusing structure 2, the spherical lens 4 can further compress the beam diameter, thereby increasing the energy density at the focal point and enhancing the melting ability of high melting point plastics (such as PPS and PEEK).

[0052] The rotatable nature of the spherical lens 4 allows it to roll on the workpiece surface and achieve pressing. During welding, the outer surface of the spherical lens 4 directly contacts the surface of the plastic workpiece to be welded. As the welding head moves along the weld seam trajectory, the spherical lens 4 rotates synchronously within the light outlet 12, serving both a guiding function and applying continuous and uniform pressure to the welding area. This rolling pressing design offers dual advantages: firstly, the pressure eliminates micro-bubbles generated during plastic melting, promoting full bonding of the molten material and significantly improving weld strength. Secondly, the rolling contact between the spherical lens 4 and the workpiece surface reduces relative friction, lowering the risk of scratches on the workpiece surface, making it particularly suitable for medical device plastic parts requiring high surface finish (such as syringe housings and infusion set interfaces).

[0053] Meanwhile, the spherical optical properties of the spherical lens 4 remain stable during rotation, ensuring that the laser beam can be precisely focused on the weld area after passing through the spherical lens 4. Even if there are minor flatness deviations on the workpiece surface (such as slight warping after injection molding of plastic parts), the rolling pressing of the spherical lens 4 can adaptively adjust the contact angle through its own rotation, ensuring that the laser focus point is always in contact with the weld, avoiding welding leaks or energy shifts caused by uneven workpiece surfaces, and improving the weld formation quality.

[0054] In some embodiments, please continue reading Figure 2 and Figure 3 To ensure that the spherical lens 4 can continuously roll and maintain a stable focusing depth when pressing the workpiece, an air blowing device 6 is added. Specifically, the air blowing device 6 includes an air pump and an air guide pipe 61. The filter lens 3 and the spherical lens 4 are spaced apart in the first direction, and a buffer cavity 5 is formed between the filter lens 3 and the spherical lens 4. One end of the air guide pipe 61 is connected to the buffer cavity 5, and the other end passes through the side wall of the cylinder 1 and extends to the outside of the cylinder 1 to connect with the air pump.

[0055] The buffer chamber 5, in conjunction with the air blowing device 6, creates a stable positive pressure environment. Specifically, gas generated by the air pump is continuously injected into the chamber through the air guide pipe 61, making the air pressure inside the buffer chamber 5 higher than the air pressure in the external welding area. This positive pressure applies a uniform thrust to the ball lens 4 along the first direction (towards the workpiece). This thrust counteracts the reaction force generated by the slight vibration of the workpiece and the shrinkage of the molten plastic during welding, ensuring that the ball lens 4 is always pressed against the workpiece surface with a constant pressure, avoiding changes in the distance between the ball lens 4 and the workpiece due to fluctuations in contact pressure. Since the laser focusing depth is directly related to the distance between the ball lens 4 and the workpiece (too large a distance will cause the focal point to shift to the outside of the workpiece, while too small a distance will cause the focal point to penetrate too deeply into the workpiece), the constant contact distance maintained by the buffer chamber 5 ensures that after the laser passes through the ball lens 4, the focal point always falls precisely at the preset weld depth (such as the joint surface of two plastic parts), preventing problems such as the focal point being too shallow, too deep, or shifted due to the positional deviation of the ball lens 4.

[0056] In some embodiments, please refer to Figure 5 and Figure 6 (Second type of laser welding head), and Figure 7 Considering that the first focusing lens 22A and the second focusing lens 22B are gradient refractive index lenses, and the refractive index distribution of gradient refractive index lenses is easily affected by temperature, when the temperature inside the cylinder 1 rises during the welding process (such as heat accumulation caused by prolonged laser operation), the thermal expansion of the lens material will cause a change in the refractive index gradient, resulting in a shortening of the actual focal length; conversely, when the temperature decreases, the focal length will correspondingly lengthen. To ensure that the welding head maintains stable focusing performance under high-temperature operating conditions, a temperature compensation ring 24 is provided between the first focusing lens 22A and the second focusing lens 22B. The temperature compensation ring 24 is made of a ring-shaped shape memory alloy and can expand and contract along a first direction according to the temperature change inside the cylinder 1 to compensate for the focal length drift of the gradient refractive index lens caused by temperature changes. Furthermore, the movable sleeve 21 has a first end near the light outlet, and a compression spring 25 is provided between the first end and the first focusing lens 22A.

[0057] The temperature compensation principle of the focusing lens 22 is as follows: the annular shape memory alloy material of the temperature compensation ring 24 has a specific phase transition temperature. When the temperature inside the cylinder 1 deviates from the preset operating temperature (e.g., 25°C), the alloy will shift along the first direction by expanding or contracting: when the temperature rises, the compensation ring expands and pushes the first focusing lens 22A along the first direction closer to the light outlet 12 to offset the shortening of the focal length; when the temperature drops, the compensation ring contracts and pulls the first focusing lens 22A along the first direction away from the light outlet 12 to offset the lengthening of the focal length. This dynamic compensation mechanism ensures that the actual focal length of the focusing lens 22 remains near the design value (e.g., within ±0.05mm) under temperature fluctuations, avoiding the shift of the focal point position due to temperature changes. The compression spring 25 can push the first focusing lens 22A and the second focusing lens 22B to move together along the first direction as the temperature compensation ring 24 moves along the first direction.

[0058] This invention also provides a laser welding apparatus.

[0059] Please see Figure 1 , Figure 2 and Figure 3 The laser welding device includes a laser welding head 100 / 100' and a laser generator. The laser generator is used to generate and output laser light. The laser generator is connected to the end of the laser welding head 100 / 100' away from the light output port 12 via an optical fiber to transmit the laser light into the first cavity 11 of the laser welding head 100 / 100'.

[0060] The working process of the laser welding device is as follows: After the laser generator is started, the laser is transmitted through the optical fiber to the rear end of the laser welding head 100 and enters the first cavity 11 of the cylinder 1. In the cavity, the laser passes through the focusing lens 22 (such as the first and second focusing lenses 22B) of the focusing structure 2 for graded focusing, then passes through the filter lens 3 to filter stray light, and finally passes through the ball lens 4 to achieve precise focusing and be directed towards the workpiece to be welded. During the welding process, the moving sleeve 21 can be driven by the adjusting component 23 to slide and change the position of the focal point. With the help of the air blowing device 6, the positive pressure environment formed in the buffer cavity 5 ensures that the ball lens 4 stably presses the workpiece and maintains the focusing depth, ensuring the continuous and stable operation of the optical system.

[0061] The above are merely exemplary embodiments of the present invention and do not limit the scope of the patent of the present invention. All equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of patent protection of the present invention.

Claims

1. A laser welding head, characterized in that, include: The cylindrical body has a first cavity inside, and one end of the cylindrical body is provided with a light outlet communicating with the first cavity; The focusing structure includes a movable sleeve and several focusing lenses. The movable sleeve is disposed in the first cavity, and the several focusing lenses are disposed in the movable sleeve for focusing the laser transmitted from the cylinder to the light outlet. The movable sleeve can slide along a first direction within the first cavity, and drive the plurality of focusing lenses to slide synchronously, so as to adjust the position of the focal point after the focusing lenses are focused.

2. The laser welding head according to claim 1, characterized in that, The plurality of focusing lenses includes a first focusing lens and a second focusing lens arranged at intervals along a first direction, wherein the optical axes of the first focusing lens and the second focusing lens are collinear and parallel to the first direction.

3. The laser welding head according to claim 1, characterized in that, The focusing structure also includes an adjusting component, one end of which is connected to the movable sleeve, and the other end of which extends out of the side wall of the cylinder.

4. The laser welding head according to claim 3, characterized in that, The side wall of the cylinder is provided with an elongated hole extending along the first direction; the adjusting component is a screwed component, the stud of the screwed component passes through the elongated hole and is screwed to the movable sleeve, and the nut of the screwed component is pressed against the outside of the cylinder.

5. The laser welding head according to claim 4, characterized in that, A stepped surface is formed inside the elongated hole, and the nut of the screw connector is pressed against the stepped surface, with the top surface of the nut flush with the edge of the elongated hole.

6. The laser welding head according to claim 1, characterized in that, It also includes a filter lens disposed inside the cylinder, the filter lens being disposed on the side of the focusing structure near the light outlet and covering the light outlet in the first direction; The optical axis of the filter lens is collinear with the optical axis of the focusing lens.

7. The laser welding head according to claim 6, characterized in that, It also includes a spherical lens disposed within the light outlet, the spherical lens being rotatable within the light outlet.

8. The laser welding head according to claim 7, characterized in that, The filter lens and the spherical lens are spaced apart in the first direction, and a buffer cavity is formed between the filter lens and the spherical lens; The laser welding apparatus also includes an air blowing device, which includes an air pump and an air guide pipe. One end of the air guide pipe is connected to the buffer chamber, and the other end passes through the side wall of the cylinder and extends out of the cylinder to be connected to the air pump.

9. The laser welding head according to claim 2, characterized in that, A temperature compensation ring is provided between the first focusing lens and the second focusing lens; the temperature compensation ring is made of a ring-shaped shape memory alloy and can expand and contract along the first direction according to the temperature change in the first cavity; The movable sleeve has a first end near the light outlet, and a compression spring is provided between the first end and the first focusing lens.

10. A laser welding apparatus, characterized in that, include: The laser welding head as claimed in any one of claims 1-9; A laser generator is used to generate and output laser light. The laser generator is connected to the end of the laser welding head away from the light output port of the laser welding head via an optical fiber, so as to transmit the laser light into the first cavity of the laser welding head.

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