A multi-layer sealing based casing waterproof structure and method thereof

Abstract

The present application relates to the technical field of aviation machine shell assembly and waterproof sealing, in particular to a machine shell waterproof structure and method based on multi-layer sealing; comprising a machine shell positioning and bearing mechanism, a multi-layer sealing execution mechanism, a compression state recognition mechanism, a difference suppression mechanism and a controller; the system solves and forms a compression track by combining the screw angle, torque, sinking amount and outside contact state through the servo tightening head, compression displacement ruler and edge contact sheet; the core is that the controller dynamically adjusts the screw compression sequence according to the track, overcomes the local virtual compression and sealing material overpressure damage caused by the traditional single torque determination; the present application effectively adapts to the natural warping of the machine shell, reduces the probability of excessive compression, and significantly improves the uniformity and sealing consistency of the assembly.

Description

Technical Field

[0001] This invention relates to the field of aircraft housing assembly and waterproof sealing technology, specifically to a waterproof housing structure and method based on multi-layer sealing. Background Technology

[0002] When an aircraft is in the maintenance and assembly phase, the waterproof sealing of a thin-walled fuselage mainly relies on screws and sealing materials for splicing and pressing. To achieve waterproofing, existing solutions generally adopt a single torque control architecture, which applies a preset torque through a tool and directly determines the sealing completion based on this single torque value. Although this solution has a certain sealing capability under normal assembly conditions, its high dependence on a single torque ignores the natural warping state of the fuselage during assembly, resulting in the risk of localized false pressure and the outer side fitting first while the inner side is not sealed during the pressing process. In addition, this solution lacks multi-dimensional verification of pressing displacement and external contact state. Continuing to pressurize at a single point will lead to overpressure and damage to the sealing material, resulting in reduced sealing consistency between different fuselages.

[0003] Therefore, how to reduce the probability of local over-compression and improve the uniformity and accuracy of the multi-layer seal establishment process of the casing has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a waterproof casing structure and method based on multi-layer sealing. Specifically, this invention provides the following technical solution: On one hand, the present invention provides a waterproof housing structure based on multi-layer sealing, comprising: The aircraft fuselage positioning and bearing mechanism, multi-layer sealing actuator, compression state recognition mechanism, differential suppression mechanism, and controller are arranged around the edge where the upper and lower shells of the aircraft fuselage are joined. The housing positioning and bearing mechanism includes a frame base, an adjustable bracket, a bearing plate, a lower housing support plate, and a housing clamping and positioning component. The lower housing support plate is fixed on the bearing plate to support the edge of the lower housing and reinforcing ribs. The multi-layer sealing actuator includes a lower shell stepped sealing edge, an upper cover pressing edge, a multi-layer sealing strip, and a screw tightening mechanism. The lower shell stepped sealing edge is composed of an outer water guide slope, a middle pressure bearing platform, and an inner water-stopping ridge in sequence along the direction of external water flow. The upper cover pressing edge is provided with a drip lip, a sealing strip receiving groove, and an inner limiting plane. The multi-layer sealing strip is embedded in the sealing strip receiving groove and is composed of an outer lip, a middle belly, and an inner ridge in sequence. The clamping status recognition mechanism includes a servo tightening head, a clamping displacement gauge, and an edge contact plate; The controller is electrically connected to the servo tightening head, pressing displacement gauge, and edge contact plate. It is used to form a compression trajectory and adjust the screw tightening sequence based on the screw angle, torque, upper cover sinking amount, and outer contact state.

[0005] In one embodiment: the outer water guide slope is located outside the stepped sealing edge of the lower shell and slopes outward and downward, the intermediate pressure bearing platform is located inside the outer water guide slope, and the inner water stop ridge is located on the side close to the inner cavity of the housing; wherein, the top surface of the inner water stop ridge is higher than the intermediate pressure bearing platform, and the width of the top surface of the inner water stop ridge is smaller than the width of the intermediate pressure bearing platform.

[0006] In one embodiment: the drip lip is located outside the pressing edge of the upper cover and is opposite to the outer water guide slope. The drip lip and the outer water guide slope form a folding water channel after the upper cover and the lower shell are assembled. The sealing strip receiving groove is located in the middle of the upper cover pressing edge, and the bottom of the sealing strip receiving groove is provided with a shallow rough surface; the inner limiting plane is located on the inner side of the upper cover pressing edge and is arranged opposite to the inner water-stop ridge, and the inner limiting plane and the inner water-stop ridge maintain a gap at the end of the pressing.

[0007] In one embodiment: the outer lip is a slanted tongue-shaped outer lip, the tip of the outer lip facing the outer water guide slope; the middle belly is a hollow elliptical middle belly, the hollow cavity of the middle belly extends continuously along the circumference of the multi-layer sealing strip; the inner ridge is a narrow rectangular dome-shaped inner ridge; wherein, the outer lip, the middle belly and the inner ridge are continuously formed on the same sealing strip.

[0008] In one embodiment: the screw clamping mechanism includes a screw, a countersunk hole in the upper cover, a threaded bushing in the lower shell, and an annular limiting shoulder. The screw passes through the countersunk hole in the upper cover and engages with the threaded bushing in the lower shell. The annular limiting shoulder is disposed around the threaded bushing in the lower shell, and the upper surface of the annular limiting shoulder is lower than the top surface of the inner water-stop ridge.

[0009] In one embodiment: the servo tightening head is disposed above the upper cover, the output shaft of the servo tightening head is connected to the bit holder through a flexible coupling, and the lower end of the bit holder holds a bit that matches the screw head shape; the pressing displacement gauge is disposed above the outer edge of the upper cover, and the lower end of the measuring rod of the pressing displacement gauge contacts the measuring plane of the upper cover through a ball head; The edge contact piece is disposed in the outer region between the upper cover pressing edge and the lower shell stepped sealing edge. The edge contact piece is used to detect the contact state between the drip lip and the outer deflection layer in the corresponding region of the outer water guide slope.

[0010] In one embodiment: the difference suppression mechanism includes a symmetrical reference screw position, a corner pressure relief pad, and a temperature reference block; the symmetrical reference screw position is located at a geometrically symmetrical position of the housing; the corner pressure relief pad is located below the multi-layer sealing strip at the corner of the housing and covers the area between adjacent screws on both sides of the corner; The temperature reference block is fixed to the side of the lower shell support plate. The temperature reference block is provided with short templates of the same batch as the multi-layer sealing strip. The short templates are used to provide the controller with the correction basis for the current softness and hardness of the sealing material.

[0011] In one embodiment, it further includes a crossbeam, a vertical pressing compensation mechanism, a lateral shifting mechanism, and a whole-line communication scheduling unit; the vertical pressing compensation mechanism is disposed between the crossbeam and the servo tightening head, and is used to control the engagement pressure between the bit and the screw head; The lateral shifting mechanism is located above the housing and is used to drive the servo tightening head to move circumferentially along the housing to different screw positions; the whole line communication scheduling unit is connected to the controller and is used to output release, extended holding or manual verification instructions to the material feeding, curing or airtightness inspection station according to the pressing status.

[0012] On the other hand, the present invention further proposes a casing waterproofing method based on a multi-layer sealed casing waterproofing structure, comprising the following steps: S1: Position the lower shell on the lower shell support plate, keep the lower shell in a natural warped state, and place the multi-layer sealing strip into the sealing strip receiving groove with the outer lip facing outward, the middle belly centered, and the inner ridge facing inward; S2: Pre-connect the upper cover to the lower shell, perform a light touch pre-tightening on all screws, and use the light touch position as the starting point of the subsequent compression trajectory; S3: The controller establishes an initial pressing path based on the housing model, screw circumferential number, preset corner pressure relief zone parameters, preset limit shoulder position parameters, and sealing strip cross-section type; S4: After the servo tightening head moves along the circumference of the housing to different screw positions, the servo tightening head performs multiple rounds of small-step tightening on the screw group. The controller synchronously collects the screw angle, torque, upper cover sinking amount and edge contact state to form the compression trajectory of each screw position. S5: The controller determines the sequence of the outer lip contact, effective compression of the middle abdomen and the inner ridge approaching the limit according to the compression trajectory, and adjusts the screw position, rotation amount and holding time of the next round according to the circumferential continuity and symmetrical reference relationship. S6: When the edge contact plate outputs a contact signal, the upper cover sinks into the reference compression range, and the torque increment does not exceed the preset threshold, the final locking and holding is performed.

[0013] In one embodiment: In step S5, if the outer contact status shows that the outer lip has been in contact and the upper cover sinking amount has not entered the set reference compression range, and the compression lag of the middle abdomen is determined, then the corresponding area is determined to be the area with a gap greater than the first preset threshold. First, the adjacent area is compressed and then the small step compression is performed in the area with a gap greater than the first preset threshold. If the displacement change slows down rapidly and the torque increases rapidly after the middle abdomen is compressed, the corresponding area is determined to be an area where the gap is less than the second preset threshold or a local protrusion area. The next pressing amount of the corresponding area is reduced and the pressing action is transferred to the opposite area or the adjacent area. If the torque in the corner area reaches the preset early torque reference value, and the sinking of the upper cover on the adjacent straight edge does not enter the set reference compression range, then first press the middle section of the straight edge on both sides of the corner, then return to the corner to perform small-step final pressing, and perform a check on the diagonal position.

[0014] The present invention has the following beneficial effects: 1. This invention uses a servo tightening head, a pressing displacement gauge, and an edge contact plate in a pressing state recognition mechanism to form a compression trajectory by combining angle, torque, sinking amount, and outer contact state. The controller adjusts the screw tightening sequence according to this trajectory, overcoming the problems of local false pressure and overpressure damage to sealing materials caused by relying on a single torque determination. This method effectively adapts to the natural warping of the housing, reduces the probability of over-compression, and significantly improves the uniformity and consistency of assembly. 2. This invention establishes an outer deflection layer, a middle slow-release layer, and an inner blocking layer by using a stepped sealing edge on the lower shell in conjunction with a multi-layer sealing strip. Combined with controller logic, it ensures a phased response of outer lip contact, effective compression of the middle abdomen, and approach blocking of the inner ridge in sequence. This structure avoids the phenomenon of the outer side being bonded first while the inner side is not sealed, and prevents the single plane from being mistakenly judged as a complete seal when pressed, thus achieving a reliable waterproof effect. Attached Figure Description

[0015] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the device; Figure 2 This is a schematic diagram of the overall exploded structure of the device; Figure 3 This is a schematic diagram of the screw clamping mechanism of the device; Figure 4 This is a schematic diagram of the multi-layer sealing actuator structure of the device; Figure 5 It is a device Figure 4 Enlarged schematic diagram of structure A in the middle; Figure 6 The flowchart illustrates the logic control of the method provided in this embodiment of the invention.

[0016] In the diagram: 1. Frame base; 2. Adjustable bracket; 3. Bearing plate; 4. Lower shell support plate; 5. Shell clamping and positioning component; 6. Top cover; 7. Lower shell; 8. Shell positioning and bearing mechanism; 9. Lower shell stepped sealing edge; 10. Outer water guide slope; 11. Intermediate pressure bearing platform; 12. Inner water-stop ridge; 13. Top cover pressing edge; 14. Drip lip; 15. Sealing strip receiving groove; 16. Shallow rough surface; 17. Inner limiting plane; 18. Multi-layer sealing strip; 19. Outer lip; 20. Middle abdomen; 21. Inner ridge; 22. Multi-layer sealing actuator 23. Screw clamping mechanism; 24. Screw; 25. Upper cover countersunk hole; 26. Lower shell threaded bushing; 27. Annular limiting shoulder; 28. Clamping status recognition mechanism; 29. ​​Servo tightening head; 30. Flexible coupling; 31. Bit holder; 32. Bit; 33. Clamping displacement gauge; 34. Edge contact piece; 35. Differential suppression mechanism; 36. Symmetrical reference screw position; 37. Corner pressure relief pad; 38. Temperature reference block; 39. Short spline; 40. Vertical clamping compensation mechanism; 41. Lateral displacement mechanism; 42. Crossbeam. Detailed Implementation

[0017] 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 of the present invention. 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 scope of protection of the present invention.

[0018] Example 1: A waterproof housing structure based on multi-layer sealing, comprising: Combination Figure 1 and Figure 2 As shown, the aircraft housing is provided with a housing positioning and bearing mechanism 8, a multi-layer sealing actuator 22, a clamping state identification mechanism 28, a difference suppression mechanism 35, and a controller arranged around the splicing edge of the upper cover 6 and the lower shell 7. The housing positioning and bearing mechanism 8 includes a frame base 1, an adjustable bracket 2, a bearing plate 3, a lower shell support plate 4, and a housing clamping and positioning component 5. The lower shell support plate 4 is fixed above the bearing plate 3 and is used to support the edge of the lower shell 7 and the position of the reinforcing ribs. like Figure 4As shown, the multi-layer sealing actuator 22 includes a lower shell stepped sealing edge 9, an upper cover pressing edge 13, a multi-layer sealing strip 18, and a screw clamping mechanism 23. The lower shell stepped sealing edge 9 is formed by an outer water guide slope 10, a middle pressure bearing platform 11, and an inner water-stopping ridge 12 in sequence along the direction of external water flow. The upper cover pressing edge 13 is provided with a drip lip 14, a sealing strip receiving groove 15, and an inner limiting plane 17. The multi-layer sealing strip 18 is embedded in the sealing strip receiving groove 15 and is formed by an outer lip 19, a middle belly 20, and an inner ridge 21 in sequence. The clamping state recognition mechanism 28 includes a servo tightening head 29, a pressing displacement ruler 33, and an edge contact piece 34. The controller is electrically connected to the servo tightening head 29, the pressing displacement ruler 33, and the edge contact piece 34, and is used to form a compression trajectory and adjust the clamping sequence of the screws 24 based on the screw angle, torque, the sinking amount of the upper cover 6, and the outer contact state.

[0019] This embodiment is used to solve the problems that are easy to occur when thin-walled housings rely on a single torque for clamping, such as local false pressure, outer side fitting first but inner side not sealing, and overpressure damaging the sealing material; by providing a stable reference through the frame base 1, the adjustable bracket 2 adapting to different specifications of housings, and the lower shell support plate 4 providing load-bearing only for the edge and reinforcing rib areas, the lower shell 7 maintains a natural warp close to the assembly state. By establishing a correspondence between the lower shell stepped sealing edge 9, the upper cover pressing edge 13, and the multi-layer sealing strip 18, the outer water guide slope 10, drip lip 14, and outer lip 19 first form a flow deflection condition, the middle pressure bearing platform 11 and the middle belly 20 bear the main compression, and the inner water-stopping ridge 12 and inner ridge 21 form an end blockage; the compression state recognition mechanism 28 converts the angle, torque, displacement, and outer contact changes during the rotation of the screw 24 into a compression trajectory, and the controller changes the compression sequence according to the trajectory, thereby reducing the probability of local over-compression while the far end has not yet reached an effective compression state, and improving the sealing consistency between different housings; The compression trajectory refers to the phased record formed by connecting the screw 24 angle increment, torque change, upper cover 6 sinking amount, edge contact piece 34 on / off state and their occurrence sequence in time sequence during the continuous small-step tightening process. The controller takes the initial contact point during light pre-tightening as the zero point and, in conjunction with the reference range obtained from the pre-compression of the same model sample, divides the compression trajectory into three judgment segments: outer lip 19 contact, middle belly 20 effective compression, and inner ridge 21 approaching blockage. The reference range includes at least the displacement reference range and the torque reference range. Only when a judgment segment continuously crosses the corresponding reference range will the controller change the position, rotation amount, and holding time of the screw 24 in the next round. The controller's judgment logic includes four parts: trajectory acquisition, stage identification, circumferential comparison, and compaction command output. The trajectory acquisition part receives the screw angle and torque signals output by the servo tightening head 29, the upper cover 6 sinking signal output by the compaction displacement gauge 33, and the contact status signal output by the edge contact piece 34. The stage identification part uses the establishment of the contact state, the displacement entering the effective compression range, and the relationship between torque and displacement tending to the final compaction state as the basis for sequential judgment. The circumferential comparison section compares the current screw position 24 with the adjacent screw positions 24 and the symmetrical reference screw position 36, and updates the judgment range based on the material hardness correction provided by the temperature reference block 38; the aforementioned structure also includes a lateral shifting mechanism 41 and a vertical pressing compensation mechanism 40; the pressing command output section outputs the next round screw position 24, rotation amount and holding time to the lateral shifting mechanism 41, the servo tightening head 29 and the vertical pressing compensation mechanism 40 according to the comparison results; This logical process does not directly determine the sealing completion based on a single torque value. Instead, it cross-checks the rotational resistance reflected by the torque, the degree of pressing of the upper cover 6 reflected by the displacement, and the outer contact state reflected by the contact piece. This characterizes the force and flow relationship between the upper cover 6 and the lower shell 7 as they gradually establish contact, compression, and blocking from the outside in. Only when the stage sequence of the same screw position 24 and its adjacent areas is continuous and no overpressure characteristics appear at the end are they allowed to enter the next round of tightening or final locking. The controller can be implemented using an industrial programmable logic controller or a threshold determination program in an industrial control computer. The above trajectory acquisition, stage recognition and circumferential comparison are all based on the original electrical signals, displacement signals and contact on / off signals of the sensors. There is no need to introduce image recognition, deep learning or other high-dimensional algorithms that are unrelated to this assembly environment, so that the basis for adjusting the pressing sequence remains the structural and process quantities that can be directly measured and verified. The controller synchronously acquires the original electrical signal, displacement signal, and contact on / off signal at a fixed sampling period. The servo tightening head 29 outputs the screw 24 angle pulse and torque feedback value, the pressing displacement gauge 33 outputs the continuous or digital displacement value, and the edge contact piece 34 outputs the on / off value. The controller generates a tightening judgment in sequence according to the stage results of outer contact establishment, displacement entering the reference compression range, torque increment exceeding the preset threshold, and comparison of the results of adjacent screw 24 positions with the symmetrical reference screw position 36. It outputs the next screw 24 position number, target rotation angle, holding time, and whether to pause the control command of the current screw 24 position. When any judgment segment fails to enter the corresponding reference interval within two consecutive sampling periods, the controller maintains the original pressing sequence and only updates the sampling record of the current position. The above judgment process can be directly implemented by the sequential function chart or threshold comparison program in the programmable logic controller, so that a clear data closed loop is formed between the compression trajectory, stage identification and pressing sequence adjustment.

[0020] like Figure 5 As shown, the outer water guide slope 10 is located outside the lower shell stepped sealing edge 9 and slopes outward and downward. The middle pressure bearing platform 11 is located inside the outer water guide slope 10, and the inner water stop ridge 12 is located on the side close to the inner cavity of the casing. The top surface of the inner water stop ridge 12 is higher than the middle pressure bearing platform 11, and the width of the top surface of the inner water stop ridge 12 is smaller than the width of the middle pressure bearing platform 11.

[0021] In this embodiment, a layered force relationship is established through height and width differences; the outer water guide slope 10 is used to change the direction of water film flow, so that the liquid entering the vicinity of the splicing edge is discharged along the outer wall first, without directly impacting the sealing strip body; the middle pressure bearing platform 11 serves as the main pressure bearing surface, providing a stable compression foundation for the outer lip 19 and the middle belly 20; the inner water-stopping ridge 12 is higher than the middle pressure bearing platform 11, so that it forms an end blocking boundary close to the inner cavity after compression; Because the width of the water-stop ridge is smaller than the width of the intermediate pressure plate, stress concentration occurs at the end contact, causing the torque to rise rapidly. The controller can use this to identify whether the final pressure is close, thereby distinguishing between the three states of external flow deviation, intermediate slow release, and internal blockage, and avoiding misjudging a single plane compression as a complete seal.

[0022] The drip lip 14 is located on the outside of the upper cover pressing edge 13 and is opposite to the outer water guide slope 10. The drip lip 14 and the outer water guide slope 10 form a folded water channel after the upper cover 6 and the lower shell 7 are assembled. The sealing strip receiving groove 15 is located in the middle of the upper cover pressing edge 13. The bottom of the sealing strip receiving groove 15 is provided with a shallow rough surface 16. The inner limiting plane 17 is located on the inner side of the upper cover pressing edge 13 and is opposite to the inner water stop ridge 12. The inner limiting plane 17 and the inner water stop ridge 12 maintain a gap at the end of the pressing.

[0023] In this embodiment, a deflection water path is formed between the drip lip 14 and the outer guide slope 10, causing the external water flow to change direction before approaching the joint, reducing the possibility of it entering directly along the joint; the sealing strip receiving groove 15 is used to constrain the lateral displacement of the multi-layer sealing strip 18, and the shallow rough surface 16 at the bottom of the groove improves the stability of the sealing strip during the pre-pressing stage, preventing the sealing strip from sliding along the groove and causing stage judgment distortion; the inner limiting plane 17 is used to limit the final pressing boundary, so that there will be no rigid direct contact between metal parts at the end of the pressing, reducing structural damage; The above coordination allows the three functions of external water guiding, sealing strip positioning, and final pressure boundary to exist simultaneously. The controller can use whether the external water guiding path turns back, whether the sealing strip falls stably into the groove, and whether the internal side is close to the limit as the basis for phased judgment.

[0024] The outer lip 19 is a slanted tongue-shaped outer lip 19, with the tip of the outer lip 19 pointing towards the outer water guide slope 10; the middle belly 20 is a hollow elliptical middle belly 20, with the hollow cavity of the middle belly 20 extending continuously along the circumference of the multi-layer sealing strip 18; the inner ridge 21 is a narrow rectangular dome-shaped inner ridge 21; wherein, the outer lip 19, the middle belly 20 and the inner ridge 21 are continuously formed on the same sealing strip.

[0025] In this embodiment, the multi-layer sealing strip 18 is not a stack of multiple independent rubber strips, but rather three functional areas with different hardness and cross-section are set on the same sealing strip; the low-hardness outer lip 19 first contacts the water guide slope to form a smooth transition and reduce edge impact; the hollow elliptical middle belly 20 has measurable displacement deformation when under pressure, which can serve as the main compression area, making it easy for the controller to identify whether effective compression has been established. The high-hardness inner ridge 21 only enters a significant stress state near the final compression stage, and is used to form a blocking boundary near the inner cavity. Since the mechanical response of the three regions is different, the torque and displacement will not change synchronously. Based on this, the controller can distinguish between the three stages of contact, effective compression and near blocking, thereby providing a recognizable signal for adjusting the compression sequence.

[0026] like Figure 3 As shown, the screw clamping mechanism 23 includes a screw 24, a countersunk hole 25 in the upper cover, a threaded bushing 26 in the lower shell, and an annular limiting shoulder 27. The screw 24 passes through the countersunk hole 25 in the upper cover and engages with the threaded bushing 26 in the lower shell. The annular limiting shoulder 27 is disposed around the threaded bushing 26 in the lower shell, and the upper surface of the annular limiting shoulder 27 is lower than the top surface of the inner water-stop ridge 12.

[0027] In this embodiment, the screw 24 is circumferentially pressed by engaging with the threaded bushing 26 of the lower shell through the countersunk hole 25 of the upper cover. The annular limiting shoulder 27 is set around the threaded bushing to provide boundary constraints for local pressing. The height of the limiting shoulder is lower than the inner water-stop ridge 12, so that it will not interfere with the sealing function area before it, but can limit further pressing in the final pressing stage. The lower periphery of the countersunk hole 25 of the top cover serves as a restricted surface opposite to the annular limiting shoulder 27. The annular limiting shoulder 27 maintains a gap with the restricted surface during the initial pressing stage, and gradually approaches or contacts the restricted surface when the sealing strip is close to being compacted and the top cover 6 continues to sink and be restricted, so that the limiting effect occurs in the final stage rather than the initial pressing stage. When the servo tightening head 29 detects a rapid increase in torque and a slowing change in displacement, it can be determined that the sealing strip is close to the compaction zone. At this time, the limiting shoulder is used to suppress local overpressure caused by continued pressure increase. In this way, the mechanical limit and torque displacement judgment work together to reduce the damage to the sealing strip and local deformation of the top cover 6 caused by continued tightening at a single point. The rapid increase in torque and the gradual slowing of displacement change mean that during continuous tightening, when comparing two adjacent sampling points of the same screw 24, the torque increment of the later sampling point relative to the earlier sampling point is greater than the preset torque threshold, and the sinking increment of the upper cover 6 relative to the earlier sampling point is less than the preset displacement threshold, indicating that the sealing strip has entered the final compaction zone; in this state, the annular limiting shoulder 27 gradually approaches the peripheral restricted surface of the upper cover counterbore 25, and provides mechanical limiting when the preset approach amount is reached to prevent further pressure increase from causing local overpressure; The limiting function of the annular limiting shoulder 27 is based on the axial pressing of the corresponding screw 24 position. The amount of approach between the annular limiting shoulder 27 and the peripheral restricted surface of the upper cover countersunk hole 25 is confirmed by the pressing displacement gauge 33. The torque change of the servo tightening head 29 is only used to identify the sealing strip entering the final compaction zone, and is not used as a criterion for the annular limiting shoulder 27 to have made contact. When the proximity reaches the preset proximity range and the adjacent sampling points still show a combination of decreasing displacement increment and increasing torque increment, the controller reduces the subsequent rotation of the screw 24 or stops tightening, so that the annular limiting shoulder 27 restricts the local continued pressing, while the adjacent screw 24 bears the pressing of the unfinished area. Thus, a sequential relationship is formed between the annular limiting shoulder 27, the peripheral restricted surface of the upper cover counterbore 25, the pressing displacement gauge 33, and the servo tightening head 29, where compression is first generated by the sealing strip and then the overpressure is limited by the mechanical structure, thus avoiding misjudging the initial structural gap as the final pressure limit.

[0028] A servo tightening head 29 is positioned above the upper cover 6. The output shaft of the servo tightening head 29 is connected to a bit holder 31 via a flexible coupling 30. The lower end of the bit holder 31 holds a bit 32 that matches the head shape of the screw 24. A pressing displacement gauge 33 is positioned above the outer edge of the upper cover 6. The lower end of the measuring rod of the pressing displacement gauge 33 contacts the measuring plane of the upper cover 6 via a ball head. An edge contact piece 34 is positioned in the outer area between the pressing edge 13 of the upper cover and the stepped sealing edge 9 of the lower shell. The edge contact piece 34 is used to detect the contact state of the outer deflection layer in the area corresponding to the drip lip 14 and the outer water guide slope 10.

[0029] In this embodiment, the servo tightening head 29 is connected to the bit holder 31 through the flexible coupling 30, which can absorb axial deviation within the preset tolerance range and reduce torque noise caused by unstable mating between the bit 32 and the screw 24; the pressing displacement gauge 33 uses a ball head to contact the measuring plane of the cover 6, so that the measuring point is subjected to force at a single point, reducing the influence of surface coating and local deformation on the measurement results. One end of the edge contact piece 34 is fixed to the outside of the stepped sealing edge 9 of the lower shell or the mounting part connected thereto, and the other end extends toward the corresponding gap between the drip lip 14 and the outer water guide slope 10 with a low stiffness elastic contact end. The elastic contact end is only used to sense the contact or disengagement state and does not serve as a load-bearing limiter of the upper cover 6, so it will not change the main compression of the sealing strip. When the dripping lip 14 sinks with the upper cover 6 and approaches the corresponding area of ​​the outer water guide slope 10, causing the elastic contact end to undergo a predetermined deformation, the edge contact piece 34 outputs an outer contact signal. When it detaches, it returns to a non-contact signal. After the controller reads the torque, displacement and contact status at the same time, it can determine whether the outer lip 19 has established contact, whether the upper cover 6 has actually sunk, and whether the outer deflection layer is continuous, thereby avoiding misjudgment caused by relying solely on torque.

[0030] The differential suppression mechanism 35 includes a symmetrical reference screw position 36, a corner pressure relief pad 37, and a temperature reference block 38. The symmetrical reference screw position 36 is located at a geometrically symmetrical position on the housing. The corner pressure relief pad 37 is located below the multi-layer sealing strip 18 at the corner of the housing and covers the area between adjacent screws 24 on both sides of the corner. The temperature reference block 38 is fixed to the side of the lower housing support plate 4. The temperature reference block 38 is provided with short strips 39 of the same batch as the multi-layer sealing strip 18. The short strips 39 are used to provide the controller with the correction basis for the current softness and hardness of the sealing material.

[0031] In this embodiment, the symmetrical reference screw position 36 is used to compare the compression trajectory differences in the geometric symmetry direction of the housing to distinguish between overall material hardness changes and local warping deformation; the corner pressure relief pad 37 is located below the corner sealing strip and covers the corner transition area between adjacent screws 24. The corner pressure relief pad 37 is made of compressible elastic material, and its initial thickness and arrangement height are lower than the main force height of the corner sealing strip under normal compression, so that it does not push up the sealing strip in the initial compression stage, and generates compensating compression when the corner continues to sink or local force is concentrated; The two sides of the corner pressure relief pad 37 gradually transition to the adjacent straight edge area to avoid abrupt support at the edge of the pressure relief pad; a short spline 39 is set on the side of the temperature reference block 38. The short spline 39 is from the same batch as the multi-layer sealing strip 18 and can reflect the current changes in the softness and hardness of the material; after the controller combines the compression response correction stage threshold of the short spline 39, it can reduce misjudgments caused by temperature deviation, and suppress symmetry differences, corner overpressure tendency and changes in material softness and hardness respectively; The correction basis for the short spline 39 can be obtained by synchronously collecting the displacement increment and torque increment of the same pressing displacement gauge 33 and servo tightening head 29 during the pre-pressing process. The controller only uses the increment result as the correction amount of the reference range, without relying on independent high-precision thermal imaging, acoustic or complex material identification modules, so that the temperature compensation remains a simple correction logic based on the field measurable data.

[0032] The structure also includes a crossbeam 42, a vertical pressing compensation mechanism 40, a lateral shifting mechanism 41, and a whole-line communication scheduling unit. The vertical pressing compensation mechanism 40 is located between the crossbeam 42 and the servo tightening head 29 and is used to control the engagement pressure between the bit 32 and the screw head 24. The lateral shifting mechanism 41 is located above the housing and is used to drive the servo tightening head 29 to move circumferentially along the housing to different screw 24 positions. The whole-line communication scheduling unit is connected to the controller and is used to output release, extended holding, or manual verification instructions to the material feeding, curing, or airtightness inspection station according to the pressing status.

[0033] In this embodiment, the vertical pressing compensation mechanism 40 is used to keep the engagement pressure between the bit 32 and the screw head 24 within a set range, so that the torque signal mainly reflects the force change of the screw 24 and the sealing strip, rather than reflecting the unstable contact of the bit 32; the lateral shifting mechanism 41 is used to move between the positions of each screw 24 according to the pressing path output by the controller. The movement sequence can be adjusted according to the circumferential continuity and the state of the distortion area, rather than being fixed in a single direction. The whole-line communication scheduling unit is used to transmit the compaction result to the subsequent workstations. When the compaction status is stable, it outputs a release command; when it needs to be maintained after compaction, it outputs an extended holding command; and when there is a local abnormality, it outputs a manual review command. Thus, the sealing quality is not only used for judgment at this workstation, but also for the cycle control of the subsequent workstations. The entire line communication scheduling unit can communicate with the controller via industrial Ethernet, serial communication bus, or discrete input / output hardwired. The uploaded status information includes at least the workstation number, compaction stage code, holding requirement code, and abnormal flag. The received instruction information includes at least three types of control codes: release, extended holding, and manual review. Among them, the compaction stage code can be encoded according to waiting to be compacted, pre-tightened, mid-section 20 compression, final compaction, and abnormal, so that subsequent workstations can directly execute the corresponding actions without parsing the original torque and displacement data. The actions of the vertical pressing compensation mechanism 40 and the lateral shifting mechanism 41 are driven by digital quantities or bus commands output by the controller. The controller updates the status table in the communication scheduling unit according to the current 24-bit stage result of the screw, and then the status table determines whether to send a release or verification signal to the subsequent workstation, so as to keep the interaction between pressing data, equipment actions and the overall line cycle time clear.

[0034] Example 2: Please see Figure 6 A method for waterproofing a casing based on multi-layer sealing includes the following steps: S1: Position the lower shell 7 on the lower shell support plate 4, keep the lower shell 7 in a natural warped state, and put the multi-layer sealing strip 18 into the sealing strip receiving groove 15 with the outer lip 19 facing outward, the middle belly 20 in the center, and the inner ridge 21 facing inward. S2: Pre-connect the upper cover 6 and the lower shell 7, perform a light touch pre-tightening on all screws 24, and use the light touch position as the starting point of the subsequent compression trajectory; S3: The controller establishes the initial clamping path based on the housing model, the 24 circumferential screw numbers, the preset corner pressure relief zone parameters, the preset limit shoulder position parameters, and the sealing strip cross-section type. S4: After the servo tightening head 29 moves along the circumference of the housing to different screw positions 24, the servo tightening head 29 performs multiple rounds of small-step tightening on the screw group 24. The controller synchronously collects the screw angle, torque, upper cover 6 sinking amount and edge contact status to form the compression trajectory of each screw position 24. S5: The controller determines the sequence of stages of outer lip 19 contact, middle abdomen 20 effective compression and inner ridge 21 approaching the limit according to the compression trajectory, and adjusts the position, rotation amount and holding time of screw 24 in the next round according to the circumferential continuity and symmetrical reference relationship. S6: When the entire circle reaches the state where the edge contact piece 34 outputs a contact signal, the upper cover 6 sinks into the reference compression range, and the torque increment does not exceed the preset threshold, the final locking and holding is performed.

[0035] This embodiment is used to directly determine the sealing status using the compression trajectory during the assembly process, rather than relying on the single torque result after assembly is completed; the lower shell 7 retains natural warping during positioning so that the subsequent trajectory reflects the true deformation; after the sealing strip is placed in the direction of the outer lip 19, the middle belly 20, and the inner ridge 21, the compression direction is consistent with the water flow direction; the pre-hanging connection and light touch pre-tightening are used to unify the starting point of each screw 24 to avoid the difference in thread start affecting the judgment; The controller establishes an initial path based on the model information, screw number 24, corner pressure relief area, and limit shoulder position. Then, it collects angle, torque, displacement, and outer contact status through multiple rounds of small-step clamping to form a compression trajectory that can be used for stage identification. The controller adjusts the next round of clamping position, rotation amount, and holding time according to the stage sequence, circumferential continuity, and symmetrical reference relationship until the outer deflection, middle slow release, and inner blocking simultaneously meet the set conditions before entering the holding phase. The stage identification in step S5 can be completed by using a fixed threshold plus a sequence rule, that is, the next round of pressing path is changed only when the contact signal of the outer lip 19, the displacement increment of the middle belly 20 and the torque change continuously meet the preset combination conditions; the comparison of circumferential continuity and symmetrical reference relationship only involves the same set of sampled data of adjacent screw 24 and symmetrical screw 24, without the need to introduce an additional complex prediction model, so that the path adjustment can be stably achieved by a conventional controller; After each small-step clamping step in S4, the controller generates a clamping list for the next round. The clamping list includes at least the target screw position 24, the incremental rotation amount, the holding time, and the skip mark. The judgment in S5 is based on the changing trend of two adjacent sampling points. If the current screw position 24 has not yet entered the corresponding stage reference interval, only the record is updated and the final locking is not switched until the stage sequence of outer lip 19 contact, middle belly 20 effective compression, and inner ridge 21 approaching the limit is stably established in continuous sampling.

[0036] In step S5, if the outer contact status shows that the outer lip 19 has made contact and the upper cover 6 has not sunk into the set reference compression range, and the compression of the middle abdomen 20 is determined to be sluggish, then the corresponding area is determined to be the area with a gap greater than the first preset threshold. First, press the adjacent area and then return to the area with a gap greater than the first preset threshold to perform small-step compression. If the displacement change slows down and the torque increases rapidly after the middle abdomen 20 is compressed, the corresponding area is determined to be an area where the gap is less than the second preset threshold or a local protrusion area. The next pressing amount of the corresponding area is reduced and the pressing action is transferred to the opposite area or the adjacent area. If the torque in the corner area reaches the preset early torque reference value, and the sinking amount of the upper cover 6 on the adjacent straight edge does not enter the set reference compression range, then first press the middle section of the straight edge on both sides of the corner, then return to the corner to perform small-step final pressing, and perform a check on the diagonal position.

[0037] In this embodiment, the controller uses the combination of outer lip 19 contact, middle belly 20 compression and displacement change as the basis for gap judgment. If the outer lip 19 has already contacted but the middle belly 20 is sluggish, it indicates that the splicing gap in this area is too large or the groove is not fully settled. Therefore, the adjacent areas are first allowed to establish continuous pressure, and then the target area is returned to perform small-step pressure supplementation to reduce the risk of edge flipping caused by single-point strong pressure. If the displacement of the middle abdomen 20 slows down after compression while the torque increases rapidly, it indicates that the target area is closer to a local protrusion or the gap is too small. Therefore, reduce the amount of compression in the next step and transfer the compression action to the opposite side or adjacent area to avoid continuing to increase pressure at the high point. If the corner has an early high torque and the adjacent straight edge has not yet entered effective compression, prioritize establishing a continuous pressure zone in the middle section of the straight edge, then return to the corner to perform small-step final compression, and check the diagonal position to control the risk of over-compression at the corner and the risk of false sealing on the straight edge at the same time. Among them, the outer lip 19 has made contact while the middle belly 20 is under-compressed, which means that the edge contact piece 34 has output a contact signal but the pressing displacement ruler 33 shows that the corresponding sinking amount of the middle belly 20 has not entered the reference compression range; the displacement change is slowing down and the torque increase is accelerating, which means that in the process of two or more consecutive small-step pressing, the sinking increment of the upper cover 6 corresponding to each pressing gradually decreases and the torque increment corresponding to each pressing gradually increases; the early high torque in the corner area means that the corner screw 24 reaches the preset early torque reference value before the adjacent straight edge is effectively compressed; The controller uses the above states as the basis for judging whether the gap is too large, the gap is too small, or there is a tendency for local bulging or corner overpressure. The reference compression range and early torque reference value are corrected according to the housing model, the type of sealing strip cross section and the compression response of the short spline 39 of the temperature reference block 38, and the continuous sampling results are used as the basis for judgment, without directly changing the compression path based on a single sampling point. The corresponding combination relationship is the signal change relationship set in the previous text for gaps that are too large, gaps that are too small, or local protrusions and corner overpressure tendencies. When the outer lip 19 contact signal, the middle belly 20 displacement response and torque change maintain the corresponding combination relationship in adjacent sampling points, the controller confirms the gap state of the corresponding area. The setting logic of the first preset threshold and the second preset threshold is as follows: based on the standard deformation of the same model housing sealing strip under the effective compression state of the middle belly, the deviation value greater than the upper limit of the standard deformation value is set as the first preset threshold, and the deviation value less than the lower limit of the standard deformation value is set as the second preset threshold, so as to quantify the degree of gaps that are too large and gaps that are too small. For areas with large gaps, the controller first selects the screw 24 adjacent to the area that has not yet completed effective compression of the middle part 20 to establish a pressure transition, and then returns to compensate for the pressure with a rotation amount smaller than the normal step size; for areas with small gaps or local protrusions, the controller retains the current stage record of the area and transfers the clamping action, so that the surrounding area first forms continuous compression, and then performs a verification after the displacement response of the adjacent area tends to stabilize. Regarding the tendency of corner overpressure, the controller compares the stage sequence of the corner screw 24 with the two straight edge screws 24 and the diagonal reference screw position. Only when the middle section of the straight edge enters the middle belly 20 for effective compression and no abnormally high torque appears at the diagonal position is the corner allowed to enter the final pressure. Through the above data flow and judgment sequence, the outer lip 19 contact signal is used to confirm the initial contact, the displacement response is used to confirm whether the middle belly 20 has established effective compression, the torque change is used to identify local compaction or obstruction state, and the circumferential and symmetrical comparisons are used to distinguish between local gap differences and overall material state changes, thereby forming a corresponding causal relationship between the pressing action and the specific structural state.

[0038] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A waterproof casing structure based on multi-layer sealing, characterized in that, include: The aircraft housing positioning and bearing mechanism (8), multi-layer sealing actuator (22), compression state recognition mechanism (28), differential suppression mechanism (35), and controller are arranged around the splicing edge of the upper cover (6) and lower shell (7) of the aircraft housing. The housing positioning and bearing mechanism (8) includes a frame base (1), an adjustable bracket (2), a bearing plate (3), a lower housing support plate (4), and a housing clamping and positioning component (5). The lower housing support plate (4) is fixed on the bearing plate (3) to support the edge of the lower housing (7) and the reinforcing ribs. The multi-layer sealing actuator (22) includes a lower shell stepped sealing edge (9), an upper cover pressing edge (13), a multi-layer sealing strip (18), and a screw tightening mechanism (23). The lower shell stepped sealing edge (9) is composed of an outer water guide slope (10), a middle pressure bearing platform (11), and an inner water-stopping ridge (12) in sequence along the direction of external water flow. The upper cover pressing edge (13) is provided with a drip lip (14), a sealing strip receiving groove (15), and an inner limiting plane (17). The multi-layer sealing strip (18) is embedded in the sealing strip receiving groove (15) and is composed of an outer lip (19), a middle belly (20), and an inner ridge (21) in sequence. The clamping status recognition mechanism (28) includes a servo tightening head (29), a pressing displacement gauge (33), and an edge contact piece (34); The controller is electrically connected to the servo tightening head (29), the pressing displacement gauge (33), and the edge contact piece (34) to form a compression trajectory and adjust the screw (24) tightening sequence according to the screw (24) angle, torque, the sinking amount of the top cover (6), and the outer contact state.

2. The waterproof casing structure based on multi-layer sealing according to claim 1, characterized in that: The outer water guide slope (10) is located outside the lower shell stepped sealing edge (9) and slopes outward and downward. The intermediate pressure bearing platform (11) is located inside the outer water guide slope (10). The inner water stop ridge (12) is located on the side close to the inner cavity of the casing. The top surface of the inner water stop ridge (12) is higher than the intermediate pressure bearing platform (11), and the width of the top surface of the inner water stop ridge (12) is smaller than the width of the intermediate pressure bearing platform (11).

3. The waterproof casing structure based on multi-layer sealing according to claim 1, characterized in that: The drip lip (14) is located outside the upper cover pressing edge (13) and is opposite to the outer water guide slope (10). The drip lip (14) and the outer water guide slope (10) form a folding water channel after the upper cover (6) and the lower shell (7) are assembled. The sealing strip receiving groove (15) is located in the middle of the upper cover pressing edge (13), and the bottom of the sealing strip receiving groove (15) is provided with a shallow rough surface (16); the inner limiting plane (17) is located on the inner side of the upper cover pressing edge (13) and is arranged opposite to the inner water-stop ridge (12), and the inner limiting plane (17) and the inner water-stop ridge (12) maintain a gap at the end of the pressing.

4. The waterproof casing structure based on multi-layer sealing according to claim 1, characterized in that: The outer lip (19) is a slanted tongue-shaped outer lip (19), with the tip of the outer lip (19) facing the outer water guide slope (10); the middle belly (20) is a hollow elliptical middle belly (20), with the hollow cavity of the middle belly (20) extending continuously along the circumference of the multi-layer sealing strip (18); the inner ridge (21) is a narrow rectangular dome-shaped inner ridge (21); wherein, the outer lip (19), the middle belly (20) and the inner ridge (21) are continuously formed on the same sealing strip.

5. A waterproof casing structure based on multi-layer sealing according to claim 1, characterized in that: The screw clamping mechanism (23) includes a screw (24), a countersunk hole (25) on the upper cover, a threaded bushing (26) on the lower shell, and an annular limiting shoulder (27). The screw (24) passes through the countersunk hole (25) on the upper cover and engages with the threaded bushing (26) on the lower shell. The annular limiting shoulder (27) is located around the threaded bushing (26) on the lower shell, and the upper surface of the annular limiting shoulder (27) is lower than the top surface of the inner water-stop ridge (12).

6. The waterproof casing structure based on multi-layer sealing according to claim 1, characterized in that: The servo tightening head (29) is located above the upper cover (6). The output shaft of the servo tightening head (29) is connected to the bit holder (31) through a flexible coupling (30). The lower end of the bit holder (31) holds a bit (32) that matches the head shape of the screw (24). The pressing displacement gauge (33) is located above the outer edge of the upper cover (6). The lower end of the measuring rod of the pressing displacement gauge (33) contacts the measuring plane of the upper cover (6) through the ball head. The edge contact piece (34) is located in the outer area between the pressing edge (13) of the upper cover and the stepped sealing edge (9) of the lower shell. The edge contact piece (34) is used to detect the contact state of the outer deflection layer of the drip lip (14) and the corresponding area of ​​the outer water guide slope (10).

7. A waterproof casing structure based on multi-layer sealing according to claim 1, characterized in that: The differential suppression mechanism (35) includes a symmetrical reference screw position (36), a corner pressure relief pad (37), and a temperature reference block (38); the symmetrical reference screw position (36) is located at a geometrically symmetrical position of the housing; The corner pressure relief pad (37) is located below the multi-layer sealing strip (18) at the corner of the housing and covers the area between adjacent screws (24) on both sides of the corner; the temperature reference block (38) is fixed to the side of the lower shell support plate (4), and the temperature reference block (38) is provided with short strips (39) of the same batch as the multi-layer sealing strip (18). The short strips (39) are used to provide the controller with the correction basis for the current soft and hard state of the sealing material.

8. A waterproof casing structure based on multi-layer sealing according to claim 1, characterized in that: It also includes a crossbeam (42), a vertical pressing compensation mechanism (40), a horizontal shifting mechanism (41), and a whole-line communication scheduling unit; the vertical pressing compensation mechanism (40) is located between the crossbeam (42) and the servo tightening head (29), and is used to control the engagement pressure between the bit (32) and the screw (24) head; The lateral shifting mechanism (41) is located above the housing and is used to drive the servo tightening head (29) to move along the circumference of the housing to different screw (24) positions; the whole line communication scheduling unit is connected to the controller and is used to output release, extended holding or manual verification instructions to the material feeding, curing or airtightness inspection station according to the pressing status.

9. A casing waterproofing method using a multi-layer sealed casing waterproofing structure as described in any one of claims 1 to 8, characterized in that: Includes the following steps: S1: Position the lower shell (7) on the lower shell support plate (4) so ​​that the lower shell (7) is in a natural warped state, and place the multi-layer sealing strip (18) into the sealing strip receiving groove (15) with the outer lip (19) facing outward, the middle belly (20) centered, and the inner ridge (21) facing inward. S2: Pre-connect the upper cover (6) and the lower shell (7), perform light pre-tightening on all screws (24), and use the light-tightening position as the starting point of the subsequent compression trajectory; S3: The controller establishes an initial pressing path based on the housing model, the circumferential number of the screw (24), the preset corner pressure relief zone parameters, the preset limit shoulder position parameters, and the sealing strip cross-section type; S4: After the servo tightening head (29) moves along the circumference of the housing to different screw (24) positions, the servo tightening head (29) performs multiple rounds of small-step tightening on the screw (24) group. The controller synchronously collects the screw (24) angle, torque, upper cover (6) sinking amount and edge contact state to form the compression trajectory of each screw (24) position. S5: The controller determines the sequence of the outer lip (19) contact, the middle abdomen (20) effective compression and the inner ridge (21) approaching the limit according to the compression trajectory, and adjusts the position, rotation amount and holding time of the next screw (24) according to the circumferential continuity and symmetrical reference relationship. S6: When the entire circle reaches the state where the edge contact piece (34) outputs a contact signal, the upper cover (6) sinks into the reference compression range, and the torque increment does not exceed the preset threshold, the final locking and holding is performed.

10. The method for waterproofing a casing according to claim 9, characterized in that: In step S5, if the outer contact status shows that the outer lip (19) has been in contact and the upper cover (6) has not sunk into the set reference compression range, and the middle abdomen (20) is determined to be sluggish in compression, then the corresponding area is determined to be the area with a gap greater than the first preset threshold. First, press the adjacent area and then return to the area with a gap greater than the first preset threshold to perform small-step pressure replenishment. If the displacement change slows down and the torque increases rapidly after the middle abdomen (20) is compressed, the corresponding area is determined to be an area with a gap smaller than the second preset threshold or a local protrusion area. The next pressing amount of the corresponding area is reduced and the pressing action is transferred to the opposite area or the adjacent area. If the torque in the corner area reaches the preset early torque reference value, and the sinking amount of the upper cover (6) on the adjacent straight edge does not enter the set reference compression range, then first press the middle section of the straight edge on both sides of the corner, then return to the corner to perform small-step final pressing, and perform a check on the diagonal position.

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