An overhauling support device and a method for overhauling a threshold strip

Abstract

The application relates to a maintenance supporting device and a threshold strip maintenance method, which comprise a bearing shell matched with a gap to be maintained, the bearing shell being capable of being longitudinally inserted into and fitted to the gap to be maintained; the bearing shell is arranged along a first direction and has a containing cavity; a power input unit comprises an input end and a transmission shaft; the transmission shaft has a first end and a second end along the first direction, and the first end is connected with the input end; a transmission unit comprises a driving gear and a driven gear which are engaged with each other, the driving gear is coaxially connected with the second end, the axial direction of the driving gear is consistent with the first direction, the axial direction of the driven gear is a second direction, and the second direction is perpendicular to the first direction; the application can be applied to the maintenance supporting work of narrow gaps and can realize a variable direction jacking operation, so as to solve the problem that the existing technology is difficult to provide stable and adjustable supporting force in a narrow blind area.

Description

Technical Field

[0001] This invention relates to the field of rail transit vehicle maintenance and mechanical tooling equipment technology, and in particular to a maintenance support device and a door sill maintenance method. Background Technology

[0002] During the overhaul or major repair of urban rail transit vehicles, the maintenance of the car door sill strips and their internal components is a common and critical process. The door sill strips are located in the transition area between the car entrance / exit and the platform, and they contain embedded wear strips (also known as wear-resistant rubber strips or sealing strips). These wear strips bear the combined loads of passenger footsteps, luggage rolling, and the reciprocating vibrations of the doors during long-term vehicle operation, serving to buffer, seal, and protect the door sill substrate. With increasing operating mileage and years, the wear strips may experience material aging and adhesive failure. If not repaired promptly, the raised wear strips may jam the door mechanism or expose the door sill substrate directly to external corrosion, accelerating structural corrosion. This requires appropriate maintenance. Since door sill strips are typically connected to the vehicle chassis via countersunk screws or welded studs, and integrate dustproof sealing strips, door sill edge pressing, and door sliding grooves, complete disassembly can take 2-4 hours per operation, increasing the risk of fastener stripping, seal damage, and noise. Therefore, on-site maintenance employs an in-situ repair process without removing the door sill strip itself. During maintenance, the narrow gap between the door sill strip and the internal profile (typically only 3-8 mm wide and 15-30 mm deep, forming a long, narrow blind groove structure) is cleaned. Then, adhesive is reapplied and a new wear strip is embedded. During adhesive curing, continuous and even lateral pressure must be applied to the newly bonded wear strip to ensure a secure bond.

[0003] The limitations of existing technology are that conventional clamps or support tools are too large to fit into the narrow gap; even if a support (such as a wooden block or rubber plug) can be inserted, it cannot provide a stable and precisely adjustable clamping force, resulting in inconsistent bonding quality; in addition, existing tooling is single-function and is often designed only for gaps of a specific size. Once the vehicle model or repair project is changed (the gap width changes), the tooling becomes unusable, thus lacking versatility. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a maintenance support device and maintenance method that can be applied to maintenance support work in narrow gaps and can realize directional jacking operation, so as to solve the problem that the tooling in the prior art is difficult to provide stable and adjustable support force in narrow blind areas, and can also solve the problem of poor versatility of the existing tooling.

[0005] To solve the above-mentioned technical problems, the present invention provides a maintenance support device, comprising, A support housing adapted to the gap to be inspected, the support housing being able to be inserted longitudinally and fit against the gap to be inspected; the support housing extends along a first direction, and the support housing has an accommodating cavity inside; A power input unit includes an input end and a drive shaft. The input end is installed at one end of the bearing housing, and the drive shaft is disposed inside the bearing housing along a first direction. The drive shaft has a first end and a second end along the first direction, and the first end is connected to the input end. The input end is used to receive torque input and output power through the drive shaft. The transmission unit includes a driving gear and a driven gear that mesh with each other. The driving gear is coaxially connected to the second end. The axial direction of the driving gear is consistent with the first direction. The axial direction of the driven gear is the second direction, which is perpendicular to the first direction. The stroke output unit includes a push rod assembly, which includes a push rod extending along the second direction and coaxially and rotatably connected to the driven gear. The bearing housing has a clearance opening to allow the push rod assembly to pass through. During operation, power is input to the power input unit and transmitted through the transmission unit, causing the push rod assembly to output thrust along the second direction to support the gap to be inspected.

[0006] In one embodiment of the present invention, the power input unit further includes a bearing assembly, which is sleeved on the drive shaft; the bearing assembly includes a radial bearing and a thrust bearing, a limiting block is provided in the bearing housing, and a limiting through hole is formed on the limiting block along a first direction, the thrust bearing is limited in the limiting through hole; the inner ring of the thrust bearing is tightly fitted with the drive shaft.

[0007] In one embodiment of the present invention, the push rod assembly further includes a force-applying block, which is installed at the end of the push rod; the force-applying block has a contact surface on the side away from the push rod; the contact surface is parallel to the first direction; and a rubber or polyurethane gasket is provided on the surface of the force-applying block.

[0008] In one embodiment of the present invention, the bearing housing is further provided with a positioning protrusion, which is disposed opposite to the end of the push rod away from the force-applying block, so as to limit the axial retraction stroke of the push rod to the limit position.

[0009] In one embodiment of the present invention, the center hole of the driven gear is provided with an internal thread, and the push rod is configured as a lead screw with an external thread, the push rod threaded through the center hole of the driven gear; the bearing housing is provided with a circumferential limiting structure, the circumferential limiting structure cooperates with the push rod to limit the circumferential rotation of the push rod, so that when the driven gear rotates, it drives the push rod to move linearly axially along the second direction.

[0010] In one embodiment of the invention, the thread helix angle of the lead screw is configured to be less than the equivalent friction angle.

[0011] In one embodiment of the present invention, the input terminal includes an operation knob.

[0012] In one embodiment of the present invention, the transmission ratio of the driving gear and the driven gear is 1:1.

[0013] In one embodiment of the present invention, the driving gear is a bevel gear; the driven gear is a bevel gear.

[0014] This invention also discloses a method for inspecting door sills, which utilizes an inspection support device as described above to support the gap of the door sill to be inspected. The inspection method includes... Step S1: Insert the maintenance support device into the maintenance gap of the sill strip; Step S2: Input torque to the power input unit, control the push rod assembly to move along the second direction, move to abut against the gap to be inspected, and apply thrust to the wear strip to be bonded inside the sill strip to form a pressure-holding support in the gap to be inspected; Step S3: Perform the specified maintenance operation on the gap to be inspected; Step S4: After the maintenance is completed, a reverse torque is input to the power input unit to retract the push rod assembly to its initial position, and then the maintenance support device is moved out of the gap to be maintained.

[0015] The technical solution of the present invention has the following advantages over the prior art: This invention discloses a maintenance support device that provides stable support for the gap in a door sill, facilitating maintenance operations. The device includes a bearing housing, a power input unit, a transmission unit, and a stroke output unit. The bearing housing is adapted to the gap to be maintained, allowing it to be inserted longitudinally and fitted into the gap, enabling the device to perform maintenance support tasks in confined areas where direct operation is difficult. Furthermore, through meshing drive and driven gears, the input torque along the length of the equipment is converted into a thrust output along the width of the gap. This allows the operator to conveniently apply rotational power from outside the equipment, while the supporting force acts perpendicularly to the original direction within the gap, facilitating operation. The transmission shaft is located inside the bearing housing, and the push rod assembly extends through a clearance opening on the housing. The overall structure is compact, requiring no additional external transmission mechanism, which is beneficial for maintenance in confined spaces. The design is confined to a limited space; it employs gear meshing transmission, resulting in minimal power loss and smooth transmission. The driving gear is coaxial with the drive shaft, and the driven gear is coaxial with the push rod, ensuring uniform force distribution during push rod output, minimizing uneven load distribution, and ensuring smooth and reliable power transmission. Furthermore, the gear transmission outputs thrust in a fixed ratio between the input torque and output thrust, facilitating estimation of support force based on the input torque. The gear transmission also possesses a certain self-locking capability, maintaining the support state even after input stops, enhancing safety. Operators can drive the input end from a location away from the gap opening using hand cranks or power tools, utilizing the gear reduction and force amplification effect to obtain a larger push rod thrust, achieving effortless support. The push rod outputs thrust through the clearance opening, while the main body of the supporting housing remains within or at the edge of the gap, without occupying additional external operating space, facilitating other maintenance operations and reducing maintenance space requirements. Attached Figure Description

[0016] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the overall structure of the maintenance support device and the door sill strip in a preferred embodiment of the present invention.

[0018] Figure 2 yes Figure 1 A side view diagram.

[0019] Figure 3 yes Figure 1 Front view diagram.

[0020] Figure 4 This is a schematic diagram of the overall structure of the maintenance support device according to a preferred embodiment of the present invention.

[0021] Figure 5 This is a partial structural schematic diagram of the maintenance support device according to a preferred embodiment of the present invention.

[0022] Figure 6 This is a schematic diagram of the structure of the power input unit and the drive gear in a preferred embodiment of the present invention.

[0023] Figure 7 This is a schematic diagram of the driven gear according to a preferred embodiment of the present invention.

[0024] Figure 8 This is a schematic diagram of the push rod assembly according to a preferred embodiment of the present invention.

[0025] Figure 9 This is a schematic diagram of the internal structure of the bearing housing of the maintenance support device according to a preferred embodiment of the present invention.

[0026] Figure 10 This is an exploded view of the maintenance support device according to a preferred embodiment of the present invention.

[0027] Explanation of reference numerals on the accompanying drawings: 1. Bearing housing; 10. Threshold strip; 100. Maintenance gap; 11. Limiting block; 12. Positioning protrusion; 13. Circumferential limiting structure; 2. Power input unit; 20. Input end; 21. Drive shaft; 22. Radial bearing; 23. Thrust bearing; 3. Transmission unit; 30. Driving gear; 31. Driven gear; 4. Stroke output unit; 40. Push rod; 41. Force application block. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention. Example 1

[0029] Reference Figures 1 to 10 As shown, the present invention discloses a maintenance support device for supporting the gap of the sill strip 10, so as to facilitate the operator to carry out maintenance operations on the gap of the sill strip.

[0030] The maintenance support device includes a bearing housing 1, which is adapted to the gap to be maintained. The bearing housing 1 can be inserted into and fit against the gap 100 to be maintained along its longitudinal direction. Specifically, the bearing housing 1 adopts a slender structure, which serves as both a mounting carrier for internal parts and a support body for reverse contact during operation.

[0031] The supporting housing 1 extends along a first direction, and the supporting housing 1 has an accommodating cavity inside; The maintenance support device also includes a power input unit 2, which includes an input end 20 and a drive shaft 21. The input end 20 is installed at one end of the bearing housing 1, and the drive shaft 21 is arranged inside the bearing housing 1 along the first direction. Specifically, the drive shaft 21 has a first end and a second end along the first direction. The first end is connected to the input end 20. The input end 20 is used to receive torque input and transmit torque downward through the drive shaft 21. The maintenance support device also includes a transmission unit 3, which includes a driving gear 30 and a driven gear 31 that mesh with each other. The driving gear 30 is coaxially connected to the second end. The axial direction of the driving gear 30 is consistent with the first direction. The axial direction of the driven gear 31 is the second direction. It should be noted that the second direction is perpendicular to the first direction. The width direction of the gap to be inspected 100 is consistent with the second direction.

[0032] The maintenance support device further includes a stroke output unit 4, which includes a push rod assembly. The push rod assembly includes a push rod 40, which extends along the second direction and is coaxially and rotatably connected to the driven gear 31. In addition, the bearing housing 1 is provided with a clearance opening to allow the push rod assembly to pass through; During operation, torque is input to the power input unit 2 and transmitted through the transmission unit 3, causing the push rod assembly to output thrust in the second direction to support the gap to be inspected.

[0033] Therefore, it can be understood that the maintenance support device protected by this invention can stably support the gap of the sill strip, facilitating maintenance operations on the gap by operators. This maintenance support device includes a bearing housing, a power input unit, a transmission unit, and a stroke output unit. The bearing housing is adapted to the gap to be maintained, allowing it to be inserted longitudinally and fit snugly into the gap, enabling the device to complete maintenance support tasks in confined areas where direct operation is difficult. Furthermore, through the meshing of the driving and driven gears, the input torque along the length of the equipment is converted into a thrust output along the width of the gap. This allows the operator to conveniently apply rotational power from outside the equipment, while the supporting force acts perpendicularly to the original direction within the gap, facilitating operation. The transmission shaft is located inside the bearing housing, and the push rod assembly extends through a clearance opening on the housing. The overall structure is compact and requires no additional external transmission mechanism. It is advantageous for arrangement within a limited space; the gear meshing transmission results in low power loss and smooth transmission, and the coaxiality of the driving gear and drive shaft, as well as the driven gear and push rod, ensures uniform force distribution when the push rod outputs thrust, preventing uneven load distribution and ensuring smooth and reliable power transmission; in addition, the input torque and output thrust are in a fixed ratio through gear transmission, making it easy to estimate the support force based on the input torque; at the same time, the gear transmission has a certain self-locking capability, which can maintain the support state after the input stops, improving safety; the operator can drive the input end from a position away from the gap opening by hand crank, power tool, etc., and use the gear reduction and force amplification effect to obtain a larger push rod thrust, achieving labor-saving support; the push rod outputs thrust through the clearance opening, and the main body of the supporting housing is still located within the gap or at the edge of the gap, without occupying additional external operating space, facilitating other maintenance operations and reducing the occupation of maintenance space.

[0034] Furthermore, the power input unit 2 also includes a bearing assembly, which is sleeved on the drive shaft. The bearing assembly includes a radial bearing 22 and a thrust bearing 23. A limiting block 11 is provided inside the bearing housing 1. A limiting through hole is formed on the limiting block 11 along the first direction, and the thrust bearing 23 is limited in the limiting through hole. The inner ring of the thrust bearing 23 is tightly fitted with the drive shaft 21. With this arrangement, the radial bearing 22 can ensure the coaxiality of the rotation of the drive shaft 21. The thrust bearing 23 can ensure the stability and reliability of the drive shaft 21. When the push rod assembly applies a supporting force along the second direction, the thrust bearing 23 can absorb the upward axial reaction force, thereby preventing the shaft system from moving in a confined space.

[0035] In a preferred embodiment, the push rod assembly further includes a force-applying block 41, which is installed at the end of the push rod 40. The force-applying block 41 has a contact surface on the side away from the push rod 30. Preferably, the contact surface is flush with the first direction to ensure stability and uniform force application when the contact surface contacts the gap 100 to be inspected. With this configuration, the force-applying block 41 serves as a terminal actuator, and its stroke is infinitely adjustable through the extension and retraction of the push rod 40, thereby adapting to different widths of the sill strip 10 gap.

[0036] To increase contact friction and prevent scratching the bonded surfaces, a rubber or polyurethane gasket is provided on the surface of the pressure block 42. Preferably, the rubber or polyurethane gasket is attached to the pressure block 42 by adhesive bonding.

[0037] In a preferred embodiment, the driven gear 31 has an internal thread in its central hole, and the push rod 40 is configured as a lead screw with an external thread, the push rod 40 cooperating with the driven gear 31. The bearing housing 1 has a groove or guide key to limit the lead screw in the circumferential direction.

[0038] In some other embodiments, the driven gear 31 may also be coaxially connected to an internally threaded sleeve, and screwed to the lead screw through the internally threaded sleeve. The lead screw passes through the central hole of the driven gear 31, and the lead screw is circumferentially limited by a groove or guide key on the bearing housing 1. In this way, when the driven gear 31 rotates in place, because the rotational freedom of the lead screw is restricted, the relative motion of the threaded pair forces the lead screw to only perform linear extension and retraction along the transverse axis.

[0039] The bearing housing 1 is provided with a circumferential limiting structure 13, which cooperates with the push rod 40 to restrict the circumferential rotation of the push rod 40.

[0040] Furthermore, the housing 1 is provided with a positioning protrusion 12, which is disposed opposite to the end of the push rod 40 away from the driven gear 31, so as to position the stroke of the push rod 40 along the second direction.

[0041] In a preferred embodiment, the helix angle of the lead screw is configured to be less than the equivalent friction angle, thereby forming a mechanical self-locking mechanism. This means that the lead screw can only be driven forward and backward by the driving gear 30, and the external reaction force on the pressure block 41 at the front end cannot force the system to retract, effectively achieving the self-locking function. It should be noted that the equivalent friction angle is an angular parameter used to represent complex contact surface friction problems as an inclined plane slider model. The equivalent friction angle is the friction angle in the lead screw thread. In the lead screw thread pair, the thread surface has an inclination angle. Since the helix angle of the lead screw is configured to be less than its equivalent friction angle, when the pressure block 41 at the end receives an external reverse thrust, this reverse force cannot overcome the frictional resistance torque inside the thread pair, thus preventing the reverse drive of the lead screw and driven gear. The inherent mechanical self-locking characteristic of this mechanism ensures that the tooling can maintain a stable pressure-holding support state even after the external input torque is removed.

[0042] Preferably, the input terminal 20 includes an operating knob that an operator can rotate to apply torque to the drive shaft 21; of course, in some other embodiments, a drive unit can also be connected to the input terminal 20 to input torque to the input terminal 20.

[0043] In a preferred embodiment, the transmission ratio between the driving gear 30 and the driven gear 31 is 1:1. Of course, in other embodiments, depending on the specific pressure holding requirements, the driving gear 30 and the driven gear 31 may also adopt a reduction design with a small gear driving a large gear.

[0044] Preferably, the driving gear 30 is a bevel gear; the driven gear 31 is a bevel gear.

[0045] In summary, the maintenance support device of the present invention overcomes the physical limitation that the hands cannot directly operate in a narrow space. As a result, the operator can rotate the torque in an open space above, and through the cooperation of the transmission shaft 21 and the transmission unit 3, output a lateral linear pushing force in the narrow blind area at the bottom, thus solving the problem of pressure holding of the internal bonding of the door sill strip. Because the end output uses a screw thread drive, its lateral ejection stroke can be continuously adjusted steplessly within the effective length of the screw. This makes the device not only suitable for specific models of urban rail vehicles, but also compatible with other rail vehicle models with different gap widths, greatly improving the versatility of the equipment and making it suitable for a variety of application scenarios. It enables in-situ non-destructive repair, thus eliminating the time-consuming process of disassembling complex door sill strip structures; it provides stable and uniform mechanical support force, avoiding the safety hazards of poor adhesive strip bonding and subsequent detachment, improving repair quality, and reducing maintenance costs. The screw thread transmission structure has a reverse self-locking characteristic. After the set tightening force is reached, even if the operator's input torque is removed, the pressure block can maintain a constant pressure state and will not loosen due to slight vibration, making it safe and reliable. Example 2

[0046] The present invention also discloses a method for inspecting a door sill strip, which utilizes an inspection support device as described in Embodiment 1 to support the gap 100 to be inspected in the door sill strip 10. The inspection method includes, Step S1: Insert the maintenance support device into the maintenance gap 100 of the sill strip 10; Step S2: Input torque to power input unit 2, control push rod assembly to move along the second direction, move to abut against the gap to be inspected 100, apply thrust to the wear strip to be bonded in the sill strip 10, so as to form pressure support in the gap to be inspected 100. Step S3: The operator performs the specified maintenance operation on the gap to be inspected 100; Step S4: After the maintenance is completed, a reverse torque is input to the power input unit 2 to retract the push rod assembly to its initial position, and then the maintenance support device is moved out of the maintenance gap 100.

[0047] Therefore, it can be seen that by using the aforementioned maintenance support device, maintenance support work can be carried out in narrow gaps. It can be inserted into the narrow blind groove of the door sill strip, provide a continuous, uniform and precisely adjustable lateral clamping force, and adapt to different gap widths to achieve in-situ clamping. This facilitates maintenance operations for operators and effectively solves problems such as unstable bonding quality and poor tooling adaptability in existing maintenance work.

[0048] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0049] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0050] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A maintenance support device, characterized in that: include, A support housing adapted to the gap to be inspected, the support housing being able to be inserted longitudinally and fit against the gap to be inspected; The supporting housing extends along a first direction and has a receiving cavity inside; A power input unit includes an input end and a drive shaft. The input end is installed at one end of the bearing housing, and the drive shaft is disposed inside the bearing housing along the first direction. The drive shaft has a first end and a second end along the first direction, and the first end is connected to the input end. The input terminal is used to receive torque input and output power through the drive shaft; The transmission unit includes a driving gear and a driven gear that mesh with each other. The driving gear is coaxially connected to the second end. The axial direction of the driving gear is consistent with the first direction. The axial direction of the driven gear is the second direction, which is perpendicular to the first direction. A stroke output unit includes a push rod assembly, the push rod assembly including a push rod extending along the second direction, the push rod being coaxial with and rotatably connected to the driven gear; The bearing housing has an opening to allow the push rod assembly to pass through; during operation, power is input to the power input unit and transmitted through the transmission unit, causing the push rod assembly to output thrust in the second direction to support the gap to be inspected.

2. The maintenance support device according to claim 1, characterized in that: The power input unit further includes a bearing assembly, which is sleeved on the drive shaft; the bearing assembly includes a radial bearing and a thrust bearing, and a limiting block is provided in the bearing housing. A limiting through hole is formed on the limiting block along a first direction, and the thrust bearing is limited in the limiting through hole; the inner ring of the thrust bearing is tightly fitted with the drive shaft.

3. The maintenance support device according to claim 1, characterized in that: The push rod assembly further includes a force-applying block, which is installed at the end of the push rod; the force-applying block has a contact surface on the side away from the push rod; the contact surface is parallel to the first direction; and a rubber or polyurethane gasket is provided on the surface of the force-applying block.

4. The maintenance support device according to claim 3, characterized in that: The bearing housing is also provided with a positioning protrusion, which is positioned opposite to the end of the push rod away from the force-applying block, so as to limit the axial retraction stroke of the push rod to the extreme position.

5. The maintenance support device according to claim 1, characterized in that: The driven gear has an internal thread in its central hole, and the push rod is configured as a lead screw with an external thread. The push rod thread passes through the central hole of the driven gear. The bearing housing has a circumferential limiting structure, which cooperates with the push rod to limit the circumferential rotation of the push rod, so that when the driven gear rotates, it drives the push rod to move linearly axially along the second direction.

6. A maintenance support device according to claim 5, characterized in that: The thread helix angle of the lead screw is configured to be less than the equivalent friction angle.

7. The maintenance support device according to claim 1, characterized in that: The input terminal includes an operation knob.

8. A maintenance support device according to claim 1, characterized in that: The transmission ratio between the driving gear and the driven gear is 1:

1.

9. A maintenance support device according to any one of claims 1-8, characterized in that: The driving gear is a bevel gear; the driven gear is a bevel gear.

10. A method for inspecting door sill strips, characterized in that: Using a maintenance support device as described in any one of claims 1-9, the gap to be inspected in the door sill strip is supported, and the maintenance method includes, Step S1: Insert the maintenance support device into the maintenance gap of the sill strip; Step S2: Input torque to the power input unit, control the push rod assembly to move along the second direction, move to abut against the gap to be inspected, and apply thrust to the wear strip to be bonded inside the sill strip to form a pressure-holding support in the gap to be inspected; Step S3: Perform the specified maintenance operation on the gap to be inspected; Step S4: After the maintenance is completed, a reverse torque is input to the power input unit to retract the push rod assembly to its initial position, and then the maintenance support device is moved out of the gap to be maintained.

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