Vacuum table with gettering thimble and optical detection apparatus having the same

Abstract

The utility model discloses a vacuum work platform with aspirating ejector pin and optical detection equipment with same, vacuum work platform includes base, aspirating ejector pin executing mechanism and work platform surface, wherein, aspirating ejector pin executing mechanism includes jacking frame, aspirating ejector pin, cylinder and vacuum generator, and aspirating ejector pin sets up on jacking frame, be equipped with with jacking frame cooperation's vertical guide rail on base, and cylinder is fixed on base, work platform surface is fixed on base, and work platform surface is equipped with with the through -hole cooperation of aspirating ejector pin, under the drive of cylinder, jacking frame is with aspirating ejector pin and makes upward movement to make the upper end of aspirating ejector pin by retracted state to explore the jacking state of work platform surface, and the lower surface of plate material placed on work platform surface is adsorbed to the upper end of aspirating ejector pin, and drives plate material to separate work platform surface, the vacuum work platform of the utility model can reliably fix the plate material to be measured stably, and can realize the work platform device of protecting plate surface from being damaged.

Description

Technical Field

[0001] This utility model relates to the field of printing plate processing and testing equipment, and in particular to a vacuum worktable with suction pin and an optical testing device having thereon. Background Technology

[0002] Printed circuit boards (PCBs), as the core carrier for electrical connections of electronic components, directly determine the performance and stability of electronic devices due to their manufacturing precision, playing an irreplaceable role in consumer electronics, industrial control, and communication technology. With the rapid development of electronic devices towards miniaturization, high density, and high integration, the circuit density of PCBs is constantly increasing, and the size of fine lines and pads is continuously shrinking, placing stringent demands on the precision and stability of production, processing, and inspection processes. Among these, optical inspection (such as automated optical inspection, AOI) is a key process in PCB quality control, requiring the precise and stable fixing of the PCB on the worktable to avoid scanning deviations caused by board movement during inspection, ensuring the accuracy of defect identification.

[0003] Currently, the industry commonly uses vacuum adsorption workbenches to fix PCB boards. The core principle is to generate negative pressure through vacuum suction holes on the workbench surface, using atmospheric pressure to firmly adhere the PCB board to the surface. This method has the advantages of simple structure and reliable fixation, and is widely used in mass production. However, this traditional vacuum adsorption workbench has significant technical drawbacks: after inspection, a tight negative pressure seal forms between the PCB board and the workbench surface, and molecular adhesion forces develop between the board surface and the workbench surface, making it difficult to separate the PCB board from the workbench. In actual production, operators often need to use tools to pry or pull the PCB board to remove it, which not only severely reduces production efficiency but also easily causes damage such as scratches on delicate circuits and solder pad detachment, directly affecting product yield and increasing production costs.

[0004] To address the difficulty of board removal, improved worktables with lifting pins have gradually emerged in existing technologies. The design concept is that after inspection, the lifting pin extends from a through-hole or edge on the bottom of the PCB board, lifting it off the table surface for easy handling by robotic arms or manual labor. However, this improvement still has functional limitations: the lifting pin only has a single lifting function and lacks auxiliary positioning and stabilization mechanisms. During the initial lifting stage, when the vacuum on the worktable is suddenly released, the PCB board loses its negative pressure constraint and is prone to slight displacement or vibration due to uneven force. Especially for PCB boards that have already been precisely positioned, this slight displacement can lead to deviations in subsequent pick-and-place positions, affecting the processing accuracy of the next process. Furthermore, some lifting pins use a rigid contact design, and the hard collision with the bottom of the PCB board during lifting may cause hidden damage, failing to meet the "damage-proof" production requirements of high-precision PCB boards.

[0005] In summary, existing PCB board worktables face technical challenges in practical applications, such as the difficulty in balancing stable and reliable fixing with convenient board removal, and the susceptibility to displacement and damage during the lifting process. These limitations prevent them from fully meeting the core production requirements of the PCB industry, which demand high precision, high cleanliness, automation, and damage prevention. Therefore, developing a worktable device that can both stably and reliably fix PCB boards and prevent displacement and damage during board removal while ensuring production efficiency has become a pressing technical problem to be solved in the current PCB processing and testing equipment field.

[0006] The disclosure of the above background technical content is only for the purpose of assisting in understanding the concept and technical solution of this application, and does not necessarily provide technical instruction. Utility Model Content

[0007] The purpose of this invention is to provide a vacuum worktable with suction pins that can stably and reliably fix PCB boards while protecting the board surface from damage.

[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0009] A vacuum worktable with a suction pin includes a base, a suction pin actuator and a worktable surface, wherein the suction pin actuator includes a lifting frame, a suction pin, a cylinder and a vacuum generator, and the suction pin is disposed on the lifting frame;

[0010] The base is provided with a vertical guide rail that cooperates with the lifting frame, and the cylinder is fixed on the base.

[0011] The worktable is fixed on the base, and the worktable is provided with a through hole that cooperates with the suction pin. Under the drive of the cylinder, the lifting frame moves the suction pin upward so that the upper end of the suction pin changes from a retracted state to a lifted state that protrudes from the worktable.

[0012] The suction pin has an airflow channel extending through its upper end, which is connected to the vacuum generator. When the vacuum generator is in vacuum operation and the cylinder drives the lifting frame upward, the upper end of the suction pin adsorbs the lower surface of the plate placed on the worktable and drives the plate to detach from the worktable.

[0013] Furthermore, following any one or a combination of the aforementioned technical solutions, the number of suction pins is multiple, which are vertically distributed on the lifting frame, and the suction pins are connected to the air passage through pipe joints provided in the workbench.

[0014] Furthermore, following any one or a combination of the aforementioned technical solutions, several of the suction pins are arranged on the same ventilation module so that the air passages of the suction pins on the same ventilation module are connected, and different ventilation modules are connected by ventilation connectors.

[0015] Furthermore, following any one or a combination of the aforementioned technical solutions, multiple ventilation modules are sequentially connected to form an airflow branch, and one end of the airflow branch is blocked, while the other end is configured to communicate with the vacuum generator.

[0016] The number of airflow branches is multiple, and flexible suction nozzles are distributed on the lifting frame.

[0017] Furthermore, based on any or a combination of the aforementioned technical solutions, the upper end of the suction pin is provided with a flexible suction nozzle, which protrudes from the workbench surface in the lifted state and is used to contact the bottom of the plate placed on the workbench surface.

[0018] Furthermore, in accordance with any or a combination of the aforementioned technical solutions, the flexible suction nozzle is made of silicone rubber, and the upper surface of the flexible suction nozzle is a flat and smooth contact surface. The lower diameter of the flexible suction nozzle is adapted to the diameter of the suction pin rod. During the adsorption or lifting of the plate, the flexible suction nozzle forms a sealing surface contact with the lower surface of the plate.

[0019] Furthermore, following any one or a combination of the aforementioned technical solutions, a vacuum adsorption mechanism is also included. The vacuum adsorption mechanism includes a vacuum pump, a vacuum inlet assembly, and a vacuum channel. The vacuum channel is located inside the workbench, and the vacuum inlet assembly is connected to the vacuum pump and the vacuum channel respectively, for providing negative pressure to the workbench surface.

[0020] Furthermore, following any one or a combination of the aforementioned technical solutions, the worktable is provided with a plurality of adsorption holes, each of which is connected to a vacuum channel in a one-to-one correspondence, and the adsorption holes are arranged to avoid the distribution position of the suction pins.

[0021] Furthermore, in accordance with any or a combination of the aforementioned technical solutions, a control module is also included, wherein the control module is respectively connected to the cylinder, the vacuum pump, and the vacuum generator.

[0022] Furthermore, based on any or a combination of the aforementioned technical solutions, the Z-axis stroke of the cylinder is 40mm, driving the suction pin to lift the plate to a height of not less than 38mm.

[0023] According to another aspect of the present invention, an optical inspection device is provided, including a vacuum stage with a suction pin as described above. The vacuum stage is disposed on a horizontal slide rail of the optical inspection device, and the horizontal slide rail provides guidance for the vacuum stage to move to the inspection device of the optical inspection device.

[0024] The beneficial effects of the technical solution provided by this utility model are as follows:

[0025] a. The suction pin actuator and the vacuum adsorption mechanism work together through the control module to form a closed-loop process of "pin adsorption - loading - table adsorption - detection - pin lifting - unloading"; four linear guides and dual cylinder drive ensure smooth lifting and lowering, greatly reduce manual intervention and match the rhythm of automated production.

[0026] b. The suction pin tip uses a flexible silicone rubber nozzle to avoid hard contact with the board under test, which could damage delicate circuits or pads. At the same time, the pin integrates a vacuum adsorption function, which stabilizes the board under test through negative pressure during the lifting process. This solves the problem of board displacement and shaking caused by the sudden release of vacuum in traditional lifting pins, ensuring positioning accuracy and board surface cleanliness. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application 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 recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of the suction pin actuator structure provided for an exemplary embodiment of the present invention;

[0029] Figure 2 A top view of a vacuum worktable with a suction pin, provided as an exemplary embodiment of the present invention;

[0030] Figure 3 A schematic diagram of the retracted state of the suction pin actuator provided as an exemplary embodiment of the present invention;

[0031] Figure 4 A schematic diagram of the lifting state of the suction pin actuator provided as an exemplary embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of a single unit structure of a ventilation module consisting of three suction pins, which is provided as an exemplary embodiment of the present invention.

[0033] Among them, 100-base, 200-suction ejector mechanism, 300-worktable, 10-suction ejector, 20-cylinder, 30-lifting frame, 40-linear guide rail, 201-suction nozzle, 301-vacuum inlet, 302-adsorption hole. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0036] In one embodiment of this utility model, such as Figure 1-2 As shown, a vacuum stage with a suction pin is provided, which can be applied to optical inspection equipment. The vacuum stage is set on a horizontal slide rail of the optical inspection equipment (AOI equipment). The horizontal slide rail provides guidance for the vacuum stage to move to the inspection device of the optical inspection equipment. It includes a base 100, a suction pin actuator 200 and a worktable 300. The suction pin actuator 200 includes a lifting frame 30, a suction pin 10, a cylinder 20 and a vacuum generator. The suction pin 10 is set on the lifting frame 30.

[0037] The base is provided with a vertical guide rail 40 that cooperates with the lifting frame, and the cylinder 20 is fixed on the base 100;

[0038] The worktable surface 300 is fixed on the base 100, the worktable surface 300 is provided with through holes matching the suction thimbles, and under the drive of the air cylinder 20, the lifting frame 30 moves upward together with the suction thimbles 10, so that the upper end portions of the suction thimbles 10 switch from the retracted state to the lifting state protruding out of the worktable surface 300;

[0039] The suction thimble 10 has an air flow channel penetrating through its upper end, the air flow channel is in communication with the vacuum generator. When the vacuum generator is in the vacuumizing working state and the air cylinder drives the lifting frame upward, the upper end of the suction thimble adsorbs the lower surface of the plate material placed on the worktable surface, and drives the plate material to separate from the worktable surface.

[0040] It can be understood that the up-and-down movement of the lifting frame 30 along the Z direction takes the plane formed by the lifting frame 30 as the reference plane, and the Z direction is perpendicular to the plane.

[0041] The vacuum workbench with suction thimbles 10 provided by the present utility model has a compact structural design and coordinated functions. It conceals the suction thimble actuator 200 below the worktable surface 300, and forms a stable transmission system through the air cylinder 20, the lifting frame 30 and the linear guide rail 40, which can realize precise lifting of the Z-direction stroke and adapt to the picking and placing requirements of automated manipulators; the vacuum workbench mechanism is connected to a vacuum pump (not shown in the figure) through the vacuum access port assembly, the vacuum channels are distributed in the middle avoiding the suction thimbles, and form a uniform negative pressure in cooperation with the adsorption holes on the worktable surface, so as to ensure that the plate to be tested is stably fixed during detection; the whole structure not only solves the problem of difficult plate picking of traditional vacuum workbenches, but also avoids the displacement deviation caused by common lifting pins, which fully meets the high-precision production requirements of the PCB industry.

[0042] In one embodiment of the present utility model, as Figure 1 shown, the suction thimble actuator 200 adopts a "rectangular frame-shaped" lifting frame as the core support structure, which has both light weight and high stability. Two sets of air cylinders are symmetrically installed on the left and right frames, and the air cylinders are specifically arranged at the head positions on both sides of the middle frame to ensure uniform transmission of driving force. Four linear guide rails are fixed at the four corners of the lifting frame, the linear guide rails are vertically connected downward to the bottom of the workbench, and the lifting frame is slidably matched with the linear guide rails through sliding blocks to realize precise lifting along the Z direction.

[0043] As Figure 1 shown, 21 suction thimbles 10 are evenly distributed on the upper, middle and lower frames of the lifting frame, and the suction thimbles 10 are detachably connected with the lifting frame, which is convenient for later maintenance and replacement. The 21 suction thimbles 10 are grouped into 7 ventilation modules 12 with three in each group, as Figure 5as shown, the ventilation modules 12 are connected in sequence to form airflow branches, the number of said airflow branches is multiple, and they are distributed on the lifting frame, one end of each said airflow branch is in a blocked state, and the other end is configured to communicate with the vacuum generator; in a specific embodiment, Figure 1 the ventilation module in the middle of the lifting frame 30 independently forms one airflow branch, and each of the two sides of the lifting frame 30 is formed by three ventilation modules connected in sequence to form an airflow branch, in this way, the three airflow branches are connected in parallel: one end of each is in a blocked state, and the other end of each is in a connected state with the vacuum generator.

[0044] The suction thimbles 10 are vertically distributed on the lifting frame 30. The suction thimbles 10 adopt a grouping design with three sets as one unit. The suction thimbles 10 in the same group can communicate with each other through the air passages inside the workbench, and the groups are connected in series through the main air passage, and finally realize the air path connection with the vacuum generator through the pipe joint arranged in the workbench. Among them, 3 sets of suction thimbles 10 are respectively arranged on the upper frame and the lower frame of the "ri" shaped structure, and 1 set of suction thimbles 10 is arranged on the middle frame. This distribution method adapts to the support requirements of PCB boards of different sizes, and ensures that the plate is evenly stressed during the lifting process.

[0045] As shown in Figure 1 , 3 -4, the end of the suction thimble 10 is equipped with a flexible suction nozzle 101 (exemplarily made of silica gel). The flexible suction nozzle 201 has good elasticity and sealing performance, the upper end surface of the flexible suction nozzle 201 is a flat and smooth contact surface, the diameter of the lower end of the flexible suction nozzle is adapted to the diameter of the suction thimble rod body, and during the process of sucking or lifting the plate, the flexible suction nozzle forms a sealing surface contact with the lower surface of the plate. When the flexible suction nozzle 101 contacts the plate to be tested, it can avoid circuit scratches or pad falling off caused by hard collision, and at the same time improve the suction stability. The Z-direction stroke of the air cylinder is set to 40mm. When the air cylinder 20 is fully extended, it can drive the suction thimble 10 to drive the plate to be tested to a lifting height of 38mm, which is sufficient to meet the pick-and-place space requirement of the automated manipulator.

[0046] In one embodiment of the present utility model, the vacuum suction mechanism includes a vacuum pump, a vacuum access port assembly and a vacuum channel. The vacuum channel is opened inside the workbench, the vacuum access port assembly includes a vacuum air inlet 301. To avoid the installation position of the suction thimble 10, the vacuum channel is distributed in a mesh shape along the middle area of the suction thimble 10. A plurality of suction holes 302 are opened on the workbench surface 300, the suction holes 302 communicate with the vacuum channels in one-to-one correspondence, and the suction holes 302 are evenly distributed in the non-suction thimble area of the table surface, so as to ensure uniform stress when the plate to be tested is sucked and avoid plate deformation caused by local stress. The vacuum access port assembly is fixed on the side of the workbench, one end of which is connected with the vacuum pump through a pipeline, and the other end is communicated with the vacuum channel to realize stable transmission of negative pressure.

[0047] The worktable also includes a control module, which is connected to the cylinder 20, vacuum pump, and vacuum generator via signal lines. The control module has a built-in preset control program that enables the coordinated actions of each actuator. The control module can precisely control the extension and retraction speed and stroke of the cylinder, while simultaneously adjusting the start and stop timing of the vacuum pump and vacuum generator to ensure precise coordination between the "vacuum opening-lifting-vacuum closing-lowering" action of the suction pin and the adsorption and depressurization actions of the worktable.

[0048] In one embodiment of this utility model, such as Figure 3-4 As shown, the suction pin actuator 200 includes a lifting state and a retracted state;

[0049] The cylinder 20 drives the linear guide rail 40, which in turn drives the lifting frame 30 to move the suction pin 10 upward, so that the suction pin actuator 200 is in a lifting state; the cylinder 20 drives the linear guide rail 40, which in turn drives the lifting frame 30 to move the suction pin 10 downward, so that the suction pin actuator 200 is in a retracted state; in the retracted state, the suction pin actuator 200 is either below or flush with the worktable surface 300.

[0050] Retracted state: When the cylinder 20 is fully retracted, the lifting frame 30 moves downward along the linear guide rail 40, causing the suction pin 10 to retract synchronously. At this time, the flexible suction nozzle 101 of the suction pin 10 is flush with or lower than the worktable surface 300, ensuring that the plate can be stably attached to the worktable surface for testing.

[0051] Lifting state: When the cylinder 20 extends, it drives the lifting frame 30 to move upward along the linear guide rail 40. The suction pin extends out of the table, and the flexible suction nozzle 201 protrudes from the table and contacts the bottom of the test plate. Under the action of the vacuum generator, a negative pressure is generated to adsorb the test plate, thus achieving stable lifting.

[0052] For example, the overall workflow of the vacuum stage is as follows:

[0053] The control module issues a command, the vacuum generator starts to generate negative pressure in the suction pin, and at the same time the cylinder moves to drive the suction pin to rise to the lifting state.

[0054] When the automated robotic arm starts suction, it moves the board to be tested to the top of the worktable. After aligning the board with the flexible nozzle of the suction pin, the robotic arm stops suction, and the board to be tested is adsorbed onto the flexible nozzle.

[0055] The vacuum pump starts, and the vacuum adsorption mechanism generates negative pressure through the adsorption holes;

[0056] The cylinder retracts to drive the suction pin to descend. When the pin descends to a certain stroke, the control module controls the vacuum generator to shut down, and the suction pin releases the test material.

[0057] The suction pin continues to descend to the retracted state, and the test plate is completely attached to the workbench surface. It is firmly fixed under the negative pressure of the suction hole, and then the AOI inspection equipment scans and inspects the test plate.

[0058] After the test is completed, the vacuum pump stops working and the vacuum adsorption mechanism is depressurized.

[0059] The vacuum generator restarts, the suction pin generates negative pressure, and at the same time the cylinder moves to drive the suction pin to rise, lifting the test plate off the table.

[0060] When the test plate is lifted to a height of 38mm, the vacuum generator is turned off and the test plate is released.

[0061] The automated robotic arm starts suction, grabs the test material and transfers it to the next process, and then the robotic arm stops suction.

[0062] The cylinder retracts, driving the suction pin back to the retracted state. The vacuum generator remains on and ready to operate. The device returns to its initial state, waiting for the loading of the next test plate, and begins the cycle.

[0063] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0064] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A vacuum worktable with a suction pin, characterized in that, include: The system includes a base, a suction pin actuator, and a worktable. The suction pin actuator includes a lifting frame, a suction pin, a cylinder, and a vacuum generator. The suction pin is mounted on the lifting frame. The base is provided with a vertical guide rail that cooperates with the lifting frame, and the cylinder is fixed on the base. The worktable is fixed on the base, and the worktable is provided with a through hole that cooperates with the suction pin. Under the drive of the cylinder, the lifting frame moves the suction pin upward so that the upper end of the suction pin changes from a retracted state to a lifted state that protrudes from the worktable. The suction pin has an airflow channel extending through its upper end, which is connected to the vacuum generator. When the vacuum generator is in vacuum operation and the cylinder drives the lifting frame upward, the upper end of the suction pin adsorbs the lower surface of the plate placed on the worktable and drives the plate to detach from the worktable.

2. The vacuum worktable with suction pin according to claim 1, characterized in that, There are multiple suction pins, which are vertically distributed on the lifting frame. The suction pins are connected to the air passage through pipe joints provided in the workbench.

3. The vacuum worktable with suction pin according to claim 1 or 2, characterized in that, Several suction pins are arranged on the same ventilation module so that the suction pins on the same ventilation module are connected by air passages, and different ventilation modules are connected by ventilation connectors.

4. The vacuum worktable with suction pin according to claim 3, characterized in that, Multiple ventilation modules are connected in sequence to form an airflow branch, with one end of the airflow branch being blocked and the other end being configured to communicate with the vacuum generator; There are multiple airflow branches, which are distributed on the lifting frame.

5. The vacuum worktable with suction pin according to claim 3, characterized in that, The upper end of the suction pin is provided with a flexible suction nozzle. In the lifted state, the flexible suction nozzle protrudes from the workbench surface and is used to contact the bottom of the plate placed on the workbench surface.

6. The vacuum worktable with suction pin according to claim 5, characterized in that, The flexible nozzle is made of silicone rubber, and the upper surface of the flexible nozzle is a flat and smooth contact surface. The lower diameter of the flexible nozzle is adapted to the diameter of the suction pin rod. During the adsorption or lifting of the plate, the flexible nozzle forms a sealing surface contact with the lower surface of the plate.

7. The vacuum worktable with suction pin according to claim 1, characterized in that, It also includes a vacuum adsorption mechanism, which includes a vacuum pump, a vacuum inlet assembly, and a vacuum channel. The vacuum channel is located inside the workbench, and the vacuum inlet assembly is connected to the vacuum pump and the vacuum channel to provide negative pressure to the workbench surface.

8. The vacuum worktable with suction pin according to claim 7, characterized in that, The worktable is provided with multiple adsorption holes, each of which is connected to a vacuum channel in a corresponding manner, and the adsorption holes are arranged to avoid the distribution position of the suction pins.

9. The vacuum worktable with suction pin according to claim 7 or 8, characterized in that, It also includes a control module, which is connected to the cylinder, the vacuum pump, and the vacuum generator via signals.

10. The vacuum worktable with suction pin according to claim 1, characterized in that, The cylinder has a Z-axis stroke of 40mm, which drives the suction pin to lift the plate to a height of not less than 38mm.

11. An optical inspection device, characterized in that, The device includes a vacuum stage with a suction pin as described in any one of claims 1 to 10, wherein the vacuum stage is disposed on a horizontal slide rail of the optical inspection equipment, and the horizontal slide rail provides guidance for the vacuum stage to move to the inspection device of the optical inspection equipment.

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