A high-reliability rigid-flexible sealing connection structure

Abstract

The application discloses a high-reliability rigid-flexible sealing connection structure capable of being repeatedly disassembled, and belongs to the technical field of structure design. The structure comprises a flexible film structure, a sealing ring and a fastener. The flexible film structure is a composite layer, and from inside to outside of the metal cabin, the composite layer comprises a pressure-bearing layer, an air-tight layer and a fire-retardant layer. Each layer is independently connected to the metal cabin. The metal cabin is provided with a ring of uniformly distributed hooks and a ring frame in the circumferential direction. The ring frame is located above the hooks. A sealing groove and a plurality of screw holes are arranged on the end face of the ring frame. The air-tight layer is pressed against the ring frame through the sealing ring placed in the sealing groove. The air-tight layer and the fire-retardant layer are connected to the screw holes through the fastener. The application has the advantages of high reliability and repeatability of disassembly and assembly, and is particularly suitable for large-size rigid-flexible sealing cabin structures.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-reliability rigid-flexible sealing connection structure which can be disassembled and assembled repeatedly, and belongs to the technical field of structure design. BACKGROUND

[0002] With the increasing complexity of space exploration tasks and the increasing distance of exploration targets, the demand for lightweight aircraft is more urgent. Using flexible film sealing structure to replace metal sealing cabin structure is an effective lightweight approach and has broad application prospects in the future.

[0003] Flexible sealing structure can be applied to full-flexible sealing cabin structure and rigid-flexible mixed sealing cabin structure. Full-flexible sealing cabin structure inevitably has transition connection with rigid structure due to opening and equipment connection, and rigid-flexible mixed sealing cabin structure is a more efficient structure form in some exploration tasks, and rigid structure and flexible sealing need to be connected. The rigid-flexible connection structure needs to have long service life, high-reliability bearing and sealing performance, and these connections are prone to become weak links due to stiffness mutation, long-term wear and other reasons, which are the key points and difficulties of flexible sealing cabin structure design.

[0004] Chinese patent CN104058103A discloses a rigid-flexible connection structure for a spacecraft flexible inflatable deployment structure, and a double O-ring seal is added between the rigid-flexible structure to achieve air-tight connection. The document "Flexible Cabin O-ring Seal Performance Analysis" introduces a rigid-flexible sealing connection structure. The technical solutions of these two methods are to realize sealing by generating a large local sealing contact stress after the O-ring seal is compressed. The disadvantage is that the air-tight film may slip from the compressed position under the action of internal pressure load, resulting in failure of bearing and sealing functions.

[0005] Patent CN106287101B discloses a bonding method and sealing tool for solid rocket engine nozzle and flexible plug, and the document "Inflatable Structures Technology Handbook" introduces a method of bonding flexible film and metal parts with adhesive to realize rigid-flexible air-tight connection. These two methods bond the rigid-flexible structure at the connection position to ensure air-tightness and prevent the flexible air-tight film from slipping at the connection position. The disadvantage of these two methods is that once bonded, the structure cannot be disassembled, and the structure cannot be repaired and replaced. In addition, the sealing performance is greatly affected by the bonding process and is difficult to accurately control. SUMMARY

[0006] The technical problem solved by the present application is to overcome the shortcomings of the prior art and provide a high-reliability rigid-flexible sealing connection structure which can be disassembled and assembled repeatedly, has high-reliability bearing and sealing functions, and can be repeatedly disassembled and assembled, especially suitable for large-size rigid-flexible mixed sealing cabin structure.

[0007] The technical solution of the present application is:

[0008] A high-reliability rigid-flexible sealing connection structure for connecting metal cabins, comprising a flexible film structure, a sealing ring and a fastener.

[0009] The flexible film structure is a composite layer, which comprises, from inside to outside of the metal cabin, a pressure-bearing layer, an airtight layer and a fire-retardant layer, each layer being independently connected to the metal cabin; the pressure-bearing layer is used to support the airtight layer and bear and transfer the internal pressure load, the airtight layer is used for sealing, and the fire-retardant layer is used for fire-retardant of the metal cabin.

[0010] The metal cabin is uniformly provided with a plurality of hooks along the ring direction, the hooks serve as the interface between the metal cabin and the pressure-bearing layer, and the pressure-bearing layer is hung on each hook; the metal cabin is provided with a ring frame along the ring direction, and the ring frame is located above the hooks; a sealing groove and a plurality of uniformly distributed screw holes are arranged on the end face of the ring frame, the airtight layer is pressed by the sealing ring placed in the sealing groove, and the screw holes are connected to the airtight layer and the fire-retardant layer through the fastener, thereby realizing the connection between the metal cabin and the airtight layer and the connection between the metal cabin and the fire-retardant layer.

[0011] Further, the pressure-bearing layer is a film structure made of nylon-polyurethane coated fabric through cutting and heat sealing, and a plurality of hanging holes are uniformly arranged on the outer periphery, the shape, size and distribution of the hanging holes are the same as those of the hooks, and the hanging holes and the hooks are one-to-one corresponding and adopt a tight fit, so that the pressure-bearing layer is hung on each hook.

[0012] Further, a screw hole is formed on each hook, and the screw hole is used for installing an anti-extraction screw to prevent the pressure-bearing layer from being extracted from the hook, one end of the anti-extraction screw is flush with the side surface of the hook, and the other end is not allowed to be in contact with the cabin wall of the metal cabin.

[0013] Further, the airtight layer is formed by bonding an airtight film and a second bonding ring, the airtight film is a film structure made of polyurethane film through cutting and heat sealing, and the second bonding ring is a circular ring plate structure, the second bonding ring is tightly sealed with the ring frame through the sealing ring; a plurality of nail holes are uniformly formed on the second bonding ring in the ring direction, the number and distribution of the nail holes are the same as those of the screw holes on the ring frame, and the airtight layer is fixedly connected to the metal cabin by the fastener passing through the nail holes and the corresponding screw holes.

[0014] Further, the material of the second bonding ring is preferably lightweight aluminum alloy, fiber-reinforced composite laminate or plastic, one side of the second bonding ring that is in contact with the sealing ring is a sealing surface, and the roughness is less than 1.6.

[0015] Further, the surface of the ring frame facing the outside of the cabin is designed as an inclined surface, and the roughness of each surface of the sealing groove is less than 1.6.

[0016] Furthermore, the flame-retardant layer includes a flame-retardant cloth and a first adhesive ring. The first adhesive ring has a circular plate structure, and the outer periphery of the flame-retardant cloth is bonded to the first adhesive ring. The first adhesive ring has a plurality of through holes evenly opened along the circumferential direction. The number and distribution of the through holes are the same as the number and distribution of the screw holes. The airtight layer and the metal compartment are fixedly connected by fasteners passing through the through holes and the corresponding screw holes. The material of the first adhesive ring is preferably lightweight aluminum alloy, fiber-reinforced composite laminate, or plastic.

[0017] Furthermore, multiple soft pads are placed between the pressure-bearing layer, the airtight layer, and the bulkhead of the metal compartment to fill the gaps between the ring frame, the metal bulkhead, the hooks, the airtight layer, and the pressure-bearing layer, in order to support and protect the airtight layer.

[0018] Furthermore, the soft pads are made of lightweight foam or sponge, and are divided into multiple sections around the metal cabin wall; the soft pads are machined with embedded grooves, which are tightly fitted between the ring frame and the hook.

[0019] Methods for assembling highly reliable rigid-flexible sealing connection structures include:

[0020] Step 1: Install the sealing ring into the sealing groove;

[0021] Step 2: Set quadrant markings on the pressure-bearing layer, airtight layer, flame-retardant layer, and metal compartment. Align the quadrant markings on the pressure-bearing layer with the quadrant markings on the metal compartment, and hang the hanging holes of the pressure-bearing layer on the hooks of the metal compartment.

[0022] Step 3: Install the anti-detachment screw. One end of the anti-detachment screw should be flush with the side of the hook, and the other end should not touch the metal cabin wall.

[0023] Step 4: Install multiple soft pad blocks;

[0024] Step 5: Align the quadrant markings on the airtight layer with the quadrant markings on the metal compartment, place the second adhesive ring with the airtight membrane attached above the ring frame and the sealing ring, and install at least 4 fasteners to temporarily fix the airtight layer.

[0025] Step 6: Align the quadrant markings on the flame-retardant layer with the quadrant markings on the metal compartment, and place the first adhesive ring with the flame-retardant cloth attached onto the second adhesive ring.

[0026] Step 7: Remove the fasteners that temporarily fix the airtight layer, and reinstall each fastener to connect the screw holes to the airtight layer and flame retardant layer. Install the fasteners diagonally and apply pre-tightening force in multiple stages to ensure that the product is stressed evenly. Seal the screw heads with glue during the last installation.

[0027] The advantages of this invention compared to the prior art are:

[0028] (1) In the rigid-flexible connection structure proposed in this invention, the connections between each functional layer (pressure-bearing layer, airtight layer, and flame-retardant layer) and the metal compartment are independent, resulting in high connection reliability. The pressure-bearing layer is hung on the compartment hooks through hanging holes, forming a multi-point distributed connection. Under internal pressure, each point evenly distributes and transfers the load of the pressure-bearing layer to the metal compartment, and the joint can withstand a large load. The airtight layer's connection with the metal compartment is for airtightness and does not bear internal pressure load. The airtight layer is bonded to the adhesive ring, forming the first sealing link. The adhesive ring is pressed against the compartment ring frame by a sealing ring, forming the second sealing link. Both sealing links have highly reliable sealing performance and allow the connection between the airtight layer and the compartment to be detachable. The flame-retardant layer is bonded to another adhesive ring and connected to the metal compartment ring frame by fasteners. Soft pads are filled between the airtight layer, the pressure-bearing layer, and the metal compartment to support and protect the airtight membrane. Each layer is independently connected and independently achieves different functions, resulting in high connection reliability.

[0029] (2) The rigid-flexible connection structure proposed in this invention can be repeatedly disassembled and assembled. The pressure-bearing layer is hooked to the metal compartment, and the airtight layer and flame-retardant layer are mechanically connected to the metal compartment through adhesive rings. The connection of each functional layer can be repeatedly disassembled and assembled, which is convenient to operate.

[0030] (3) The rigid-flexible connection structure proposed in this invention is lightweight, making it particularly suitable for large-size rigid-flexible hybrid sealing chambers. A reliable airtight connection can be achieved with a relatively weak adhesive ring, avoiding the weight increase caused by rigid connection flanges; the hook and metal chamber are integrated, eliminating the need for a transition structure and saving structural weight. For large-size rigid-flexible hybrid sealing chamber structures, the weight advantage of the rigid-flexible connection structure proposed in this invention is even more significant. Attached Figure Description

[0031] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0032] Figure 1 This is an assembly diagram of the rigid-flexible connection structure according to an embodiment of the present invention;

[0033] Figure 2(a) is an overall schematic diagram of the metal compartment interface according to an embodiment of the present invention; Figure 2(b) is a cross-sectional view of the metal compartment interface according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the hanging holes in the pressure-bearing layer according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the airtight layer interface according to an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the flame-retardant layer interface in an embodiment of the present invention;

[0037] Figure 6(a) is a schematic diagram of the overall soft pad block according to an embodiment of the present invention; Figure 6(b) is a schematic diagram of the cross-section of the soft pad block according to an embodiment of the present invention. Detailed Implementation

[0038] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0039] This invention proposes a highly reliable rigid-flexible sealing connection structure that can be disassembled and reassembled multiple times, such as... Figure 1 As shown, it includes a flexible membrane structure, a clamping screw 2, a gasket 3, a sealing ring 6, an anti-loosening screw 9, and a soft pad 12.

[0040] The flexible membrane structure consists of a pressure-bearing layer 13, an airtight layer, and a flame-retardant layer, arranged sequentially from the inside to the outside of the cabin. These layers are bonded together with adhesive to form a composite layer. The flame-retardant layer is mainly used for flame retardancy inside the cabin, the airtight layer is mainly used for sealing, and the pressure-bearing layer 13 is mainly used to support the airtight layer and bear and transmit internal pressure loads.

[0041] The pressure-bearing layer 13, the airtight layer, and the flame-retardant layer are independently connected to the metal compartment 1. The metal compartment 1 is equipped with connection interfaces that mate with the pressure-bearing layer interface, the airtight layer interface, and the flame-retardant layer interface, such as... Figure 2(a) , 2(b) As shown, the specific configuration is as follows: a ring frame 7 is arranged circumferentially along the metal compartment 1, with rounded edges on all sides; a sealing groove 15 and several evenly distributed clamping screw holes 14 are provided on the end face of the ring frame 7 near the interior of the compartment. The surface roughness of each surface of the sealing groove should be less than 1.6. The specifications of the screw holes 14 and the spacing between adjacent screw holes 14 are determined by the clamping force requirements of the sealing ring. Several evenly distributed hooks 8 are arranged circumferentially along the metal compartment below the ring frame 7 (pointing outwards from the bottom). In this embodiment, 180 hooks are provided, and the spacing between adjacent hooks 8 is determined by the hanging point load and the manufacturer's processing capability. The edges of the hooks 8 are rounded, and the ring frame 7 and hooks 8 are integrated with the metal compartment 1. A screw hole 16 is machined on each hook 8 for installing an anti-loosening screw 9. The ring frame 7 and hooks 8 are as close as possible. To ensure processing space for the hooks 8, the lower surface of the ring frame 7 (pointing outwards from the bottom) is designed as a slope. The screw holes 16 are used to install the anti-loosening screws 9.

[0042] The pressure-bearing layer 13 is a membrane structure made of nylon-polyurethane coated fabric through cutting and heat sealing, with several evenly distributed hanging holes 17 on its outer periphery, such as... Figure 3As shown, the number, size, and distribution of the hanging holes 17 are the same as those of the hooks 8 in the metal compartment. The hooks 8 in the metal compartment 1 are attached via these holes, and each hook 8 is equipped with an anti-detachment screw 9 to prevent the pressure-bearing layer 13 from detaching from the hook 8. Specifically, multiple hooks 8 are evenly distributed around the circumference of the metal compartment 1, with the spacing between adjacent hooks determined based on the load at the attachment point and the manufacturer's processing capabilities. Multiple evenly distributed hanging holes 17 are provided around the outer periphery of the pressure-bearing layer 13. The hanging holes 17 are tightly fitted to the hooks 8, and their distribution is consistent with that of the hooks 8. This ensures that the pressure-bearing layer 13 is smoothly attached to the hooks 8 and prevents it from detaching from the hooks 8. With this connection method, the pressure-bearing layer 13 should have sufficient connection strength at the hanging holes 17 to prevent damage to the hanging holes 17 under internal pressure loads.

[0043] The airtight layer is formed by bonding the airtight membrane 10 and the second bonding ring 5 together with an adhesive. The airtight membrane is a membrane structure made of polyurethane membrane through cutting and heat sealing. A high-strength and tough adhesive should be selected. The second bonding ring 5 is a circular thin plate structure, made of lightweight aluminum alloy, fiber-reinforced composite laminate, plastic, etc. The surface of the second bonding ring 5 that presses the sealing ring is the sealing surface, and its roughness should be less than 1.6. After the airtight membrane 10 and the second bonding ring 5 are bonded together, several evenly distributed through-holes 18 are drilled around the second bonding ring 5. Figure 4 As shown, the number and distribution of the through-holes 18 and the screw holes 14 in the metal compartment 1 are equal. Then, it is connected to the ring frame 7 of the metal compartment 1 by clamping screws 2, which clamp the sealing ring 6. The clamping screws 2 are used to install the airtight layer and the flame-retardant layer and provide the clamping force required to tighten the sealing ring. The bonding surface between the airtight membrane 10 and the second adhesive ring 5 forms the first sealing link, and the second adhesive ring 5 clamping the sealing ring 6 forms the second sealing link, thus achieving a seal.

[0044] Multiple sections of shaped soft pads 12 are installed between the pressure-bearing layer 13, the airtight membrane 10, and the bulkhead of the metal compartment 1 to fill the gaps between the ring frame 7, the metal bulkhead, the hook 8, the airtight layer, and the pressure-bearing layer 13. Figure 6(a) , 6(b) As shown, the soft pad 12 is tightly fitted to the cabin body, serving to support and protect the airtight membrane 10 from damage to the metal structure. The soft pad 12 is made of lightweight foam or sponge and is divided into multiple sections around the circumference of the metal cabin 1. Embedded grooves 20 are machined into the soft pad 12, which are tightly fitted between the ring frame 7 and the hook 8.

[0045] The flame-retardant layer is formed by bonding a flame-retardant fabric 11 and a first adhesive ring 4. The flame-retardant fabric 11 is made of Nomex flame-retardant fabric or other flame-retardant fabrics sewn together. The first adhesive ring 4 is a circular thin-plate structure made of lightweight aluminum alloy, fiber-reinforced composite laminate, plastic, etc. After the flame-retardant fabric 11 is bonded to the first adhesive ring 4, several evenly distributed through-holes 19 are machined around the circumference of the first adhesive ring 4.Figure 5 As shown, the number of through holes 19 and screw holes 14 are equal and the same. The through holes 19 are connected to the ring frame 7 of the metal compartment 1 by screws 2.

[0046] The assembly process of a highly reliable rigid-flexible sealing connection structure that can be disassembled and reassembled multiple times involves the following steps when assembling the flexible membrane structure and the metal chamber 1: sealing ring 6, pressure-bearing layer 13, anti-loosening screw 9, soft pad 12, airtight layer, and flame-retardant layer. The disassembly process is the reverse of the assembly process. The specific assembly process is as follows:

[0047] Step 1: Place the sealing ring 6 into the sealing groove 15;

[0048] Step 2: Set quadrant markings on the pressure-bearing layer 13, the airtight membrane of the airtight layer, the flame-retardant cloth of the flame-retardant layer, and the metal cabin to facilitate installation and positioning; transfer the flexible membrane structure from the opening of the metal cabin 1 into the metal cabin 1.

[0049] Step 3: Align the quadrant markings on the pressure-bearing layer 13 with the quadrant markings on the metal compartment 1, and attach the hanging holes of the pressure-bearing layer 13 to the hooks on the metal compartment 1.

[0050] Step 4: Install the anti-detachment screw 9. Install the anti-detachment screw 9 into the screw hole 16, ensuring that one end of the anti-detachment screw 9 is flush with the side of the hook 8, and the other end does not touch the wall of the metal compartment 1. Seal the threads with adhesive during the final installation of the flexible membrane structure.

[0051] Step 5: Install the multi-segment soft pad 12.

[0052] Step 6: Align the quadrant markings on the airtight layer with the quadrant markings on the metal compartment 1, place the adhesive ring 5 with the airtight membrane 10 attached above the ring frame 7 and the sealing ring 6, and install at least 4 screws 2 and 4 washers 3 to temporarily fix the airtight layer.

[0053] Step 7: Align the quadrant markings on the flame-retardant layer with the quadrant markings on the metal compartment 1, and place the first adhesive ring 4 with the flame-retardant cloth attached onto the second adhesive ring 5.

[0054] Step 8: Remove screw 2 and washer 3 from the temporary airtight layer, install screw 2 and washer 3, screw 2 should be installed diagonally, apply pre-tightening force in multiple stages to make the product evenly stressed, and seal the screw heads with glue during the last installation.

[0055] The disassembly process of a rigid-flexible connection structure is the reverse process of the assembly process.

[0056] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A highly reliable rigid-flexible sealing connection structure that can be disassembled and reassembled multiple times, used for connecting a metal compartment, characterized in that, This includes flexible membrane structures, sealing rings, and fasteners; The flexible membrane structure is a composite layer, consisting of a pressure-bearing layer, an airtight layer, and a flame-retardant layer from the inside to the outside of the metal cabin. Each layer is independently connected to the metal cabin. The pressure-bearing layer is used to support the airtight layer and bear and transmit the internal pressure load. The airtight layer is used for sealing. The flame-retardant layer is used to retard the metal cabin. The metal compartment is uniformly provided with several hooks along the circumference. The hooks serve as the interface between the metal compartment and the pressure-bearing layer, and the pressure-bearing layer is hooked onto each hook. The metal compartment is provided with a ring frame along the circumference, which is located above the hooks. A sealing groove and several evenly distributed screw holes are provided on the end face of the ring frame. The airtight layer and the ring frame are pressed together by a sealing ring placed in the sealing groove. The screw holes are connected to the airtight layer and the flame-retardant layer by fasteners, thereby realizing the connection between the metal compartment and the airtight layer, and between the metal compartment and the flame-retardant layer. The pressure-bearing layer is a membrane structure made of nylon-polyurethane coated fabric by cutting and heat sealing. It has several hanging holes evenly distributed on its outer periphery. The shape, size and distribution of the hanging holes are the same as the shape, size and distribution of the hooks. The hanging holes and hooks correspond one-to-one and are tightly fitted so that the pressure-bearing layer can be hung on each hook. The airtight layer is formed by bonding an airtight membrane and a second adhesive ring. The airtight membrane is a membrane structure made of polyurethane membrane by cutting and heat sealing. The second adhesive ring is a circular plate structure. The second adhesive ring and the ring frame are pressed and sealed by a sealing ring. The second adhesive ring has a number of through holes evenly opened in the circumferential direction. The number and distribution of the through holes are the same as the number and distribution of the screw holes on the ring frame. The airtight layer and the metal compartment are fixedly connected by fasteners passing through the through holes and the corresponding screw holes. The flame-retardant layer includes a flame-retardant cloth and a first adhesive ring. The first adhesive ring has a circular plate structure, and the outer periphery of the flame-retardant cloth is bonded to the first adhesive ring. The first adhesive ring has a plurality of through holes evenly distributed along the circumferential direction. The number and distribution of the through holes are the same as the number and distribution of the screw holes. Fasteners pass through the through holes and the corresponding screw holes to achieve a fixed connection between the airtight layer and the metal compartment. The material of the first adhesive ring is lightweight aluminum alloy, fiber-reinforced composite laminate, or plastic. Multiple soft pads are placed between the pressure layer, the airtight layer and the bulkhead of the metal compartment to fill the gaps between the ring frame, the metal bulkhead, the hooks, the airtight layer and the pressure layer, in order to support and protect the airtight layer. The soft pads are made of lightweight foam or sponge and are divided into multiple sections around the metal cabin wall. The soft pads are machined with embedded grooves and are tightly fitted between the ring frame and the hook.

2. The highly reliable rigid-flexible sealing connection structure that can be disassembled and reassembled multiple times, as described in claim 1, is characterized in that... Each hook has a screw hole for installing an anti-detachment screw to prevent the pressure layer from coming off the hook. One end of the anti-detachment screw is flush with the side of the hook, and the other end is not allowed to touch the metal cabin wall.

3. The highly reliable rigid-flexible sealing connection structure that can be disassembled and reassembled multiple times, as described in claim 1, is characterized in that... The material of the second adhesive ring is lightweight aluminum alloy, fiber-reinforced composite laminate, or plastic. The side of the second adhesive ring that presses against the sealing ring is the sealing surface, with a roughness of less than 1.

6.

4. The highly reliable rigid-flexible sealing connection structure that can be disassembled and reassembled multiple times, as described in claim 1, is characterized in that... The surface of the ring frame facing outwards from the cabin is designed as a slope, and the roughness of each surface of the sealing groove is less than 1.

6.

5. A method for assembling the high-reliability rigid-flexible sealing connection structure as described in claim 1, characterized in that, include: Step 1: Install the sealing ring into the sealing groove; Step 2: Set quadrant markings on the pressure-bearing layer, airtight layer, flame-retardant layer, and metal compartment. Align the quadrant markings on the pressure-bearing layer with the quadrant markings on the metal compartment, and hang the hanging holes of the pressure-bearing layer on the hooks of the metal compartment. Step 3: Install the anti-detachment screw. One end of the anti-detachment screw should be flush with the side of the hook, and the other end should not touch the metal cabin wall. Step 4: Install multiple soft pad blocks; Step 5: Align the quadrant markings on the airtight layer with the quadrant markings on the metal compartment, place the second adhesive ring with the airtight membrane attached above the ring frame and the sealing ring, and install at least 4 fasteners to temporarily fix the airtight layer. Step 6: Align the quadrant markings on the flame-retardant layer with the quadrant markings on the metal compartment, and place the first adhesive ring with the flame-retardant cloth attached onto the second adhesive ring. Step 7: Remove the fasteners that temporarily fix the airtight layer, and reinstall each fastener to connect the screw holes to the airtight layer and flame retardant layer. Install the fasteners diagonally and apply pre-tightening force in multiple stages to ensure that the product is stressed evenly. Seal the screw heads with glue during the last installation.

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