Plastic molding process and zipper of a double-layer airtight zipper

Abstract

This invention relates to the field of zipper manufacturing, and more particularly to a plastic molding process for a double-layer airtight zipper, comprising the following steps: S1, zipper head molding; molding the zipper head into plastic using a zipper head molding device; S2, chain belt molding; sewing the chain teeth onto the chain fabric; S3, waterproof structure molding; molding a first waterproof structure and a second waterproof structure using a plastic molding device; S4, component assembly; embedding the newly molded first and second waterproof structures into a first through groove and a second through groove under high temperature, and then cooling the entire chain belt after embedding; S5, zipper head and chain belt assembly; assembling and assembling the zipper head and chain belt, thus solving the technical problem that existing airtight zippers are prone to chain belt bursting due to sharp external objects or internal sharp objects pressing against the chain belt.

Description

Technical Field

[0001] This invention relates to the field of zipper manufacturing, and more particularly to a plastic molding process for a double-layer airtight zipper and the zipper itself. Background Technology

[0002] Airtight zippers are high-performance zippers that completely block the penetration of gases and liquids through a precision toothed structure and high-sealing materials. They are widely used in scenarios with extremely high sealing requirements.

[0003] It mainly forms a continuous, gapless physical barrier through micron-level tooth-like interlocking and a special coating (such as TPU or PVC) covering the base strip. After closing, it can effectively prevent water vapor, air, and even fine particles from penetrating. Some high-end models can achieve a waterproof rating of IPX8 (waterproof for 1 hour at a depth of 10 meters). The airtight zippers currently on the market are mainly woven airtight zippers, which use nylon or polyester fiber as the base strip and are coated with a TPU / PVC waterproof layer. They are relatively inexpensive and suitable for mass-market products such as outdoor backpacks and rain jackets, with a unit price of about 10-30 yuan per zipper.

[0004] Conventional plastic molding equipment is ill-suited for molding specific double-layer airtight zippers. Chinese patent application number 202310691051.2 discloses a nylon airtight zipper, including a chain belt, a lower plate fixed to the lower end of the chain belt, an upper plate fixed to the upper end of the chain belt, and chain teeth blocks evenly installed on the chain belt; it also includes: an upper pull head disposed on the front side of the chain belt, a lower pull head disposed on the rear side of the upper pull head, the lower pull head and the upper pull head contacting the upper plate to achieve a sealing effect, and a guide plate fixed on both the lower pull head and the upper pull head; and a pull lock fixed to the front end face of the upper pull head, with a pull tab connected to the pull lock. This nylon airtight zipper, by splitting the separating teeth into separating rubber teeth and separating chain teeth, with the length of the separating rubber teeth being greater than the length of the separating chain teeth, forms an upper and lower, front and back separating mechanism, thereby improving the convenience of opening and closing the zipper. Furthermore, through the built-in top plate structure, it can function to press the chain teeth blocks when the zipper is closed, thus overcoming the constraint that the overall height of the chain body must be greater than the inner cavity of the pull head to prevent the chain from bursting. The main improvement to the zipper mentioned above addresses the necessity that the overall height of the zipper body must be greater than the inner cavity of the zipper head to prevent the zipper from bursting. However, in practical applications, zipper bursts are not solely caused by whether the zipper body height exceeds the inner cavity of the zipper head. There are many possible causes for zipper bursts. A common one is that sharp objects, either externally or internally, can impact the zipper teeth, causing the zipper to burst. For conventional zippers, the impact of a burst is relatively controllable, resulting in minimal damage. However, for airtight zippers, due to their waterproof and sealed nature, and the different items stored inside compared to conventional items, bursts in airtight zippers often result in significant losses. Summary of the Invention

[0005] Therefore, in view of the above problems, the present invention proposes a plastic molding process and zipper for a double-layer airtight zipper, which solves the technical problem that the existing airtight zipper is prone to chain breakage due to sharp objects from the outside or inside pressing against the chain.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a plastic molding process for a double-layer airtight zipper, comprising the following steps: S1. Slipper head forming; The slipper head of the zipper is formed into plastic using a slipper head forming device; S2. Chain forming; sewing the chain teeth onto the chain fabric; S3. Waterproof structure molding; The first and second waterproof structures are molded using a plastic molding device; S4. Component assembly: The newly formed first and second waterproof structures are embedded in the first and second through grooves under high temperature conditions. After the embedding is completed, the entire chain belt is cooled. S5. Slider head and chain assembly; Assemble the slider head and chain. The plastic molding device includes a working base, a support frame mounted on the working base, an upper molding template and a lower molding template mounted on the support frame. An upper molding cavity is provided on the side of the upper molding template closest to the lower molding template, and a lower molding cavity is provided on the side of the lower molding template closest to the upper molding template. The structures of the upper and lower molding cavities are symmetrical. Both the upper and lower molding cavities include a connecting surface and a molding surface. Cooling devices are integrated into both the upper and lower molding templates for cooling and demolding the upper and lower molding cavities. The molding surface is provided with intermittently spaced concave and convex molding portions. Each concave and convex molding portion includes a molding arc groove and an arc-shaped rotating plate rotatably mounted within the molding arc groove. The arc-shaped rotating plate has a bowl-shaped structure. When forming an airtight protrusion, the convex surface of the arc-shaped rotating plate faces into the molding arc groove; when forming an airtight recess, the convex surface of the arc-shaped rotating plate faces away from the molding arc groove.

[0007] Furthermore, a heating plate is provided on the connecting surface.

[0008] A double-layer airtight zipper, manufactured using a plastic molding process for double-layer airtight zippers, includes a chain belt and a zipper pull that cooperate with each other. The chain belt includes a first chain fabric, a second chain fabric, a first set of chain teeth disposed on the first chain fabric, a second set of chain teeth disposed on the second chain fabric, a first waterproof structure disposed on the first chain fabric, and a second waterproof structure disposed on the second chain fabric. When the chain belt is closed, the first set of chain teeth and the second set of chain teeth engage with each other, and the first waterproof structure and the second waterproof structure adhere to each other.

[0009] Furthermore, both the first and second chain fabrics are defined to include an upper surface layer and a lower surface layer. The first chain tooth group includes a first sub-chain tooth and a first mother chain tooth, and the second chain tooth group includes a second sub-chain tooth and a second mother chain tooth. The first sub-chain tooth and the first mother chain tooth are respectively disposed on the upper surface layer and the lower surface layer of the first chain fabric with the first chain fabric as the center of symmetry. The second sub-chain tooth and the second mother chain tooth are respectively disposed on the upper surface layer and the lower surface layer of the second chain fabric with the second chain fabric as the center of symmetry. When the chain is closed, the first sub-chain tooth and the second sub-chain tooth mesh with each other, and the first mother chain tooth and the second mother chain tooth mesh with each other.

[0010] Furthermore, a first through groove is naturally formed between the first sub-chain tooth and the first mother chain tooth, and a second through groove is naturally formed between the second sub-chain tooth and the second mother chain tooth. When the chain is closed, the first through groove and the second through groove are arranged opposite to each other. The first waterproof structure is disposed in the first through groove, and the second waterproof structure is disposed in the second through groove.

[0011] Furthermore, the first waterproof structure is made of flexible rubber and completely fills the first through groove; the second waterproof structure is also made of flexible rubber and completely fills the second through groove.

[0012] Furthermore, the first waterproof structure includes a first central support portion, a first elongated protrusion and a second elongated protrusion integrally formed on the first central support portion. The first central support portion has an elongated structure that extends through the first through groove. The first elongated protrusion and the second elongated protrusion are respectively disposed at the upper and lower ends of the first central support portion and extend through the first through groove along with the first central support portion. The second waterproof structure includes a second central support portion, a third elongated protrusion and a fourth elongated protrusion integrally formed on the second central support portion. The second central support portion has an elongated structure that extends through the second through groove. The third elongated protrusion and the fourth elongated protrusion are respectively disposed at the upper and lower ends of the second central support portion and extend through the second through groove along with the second central support portion. When the chain is closed, the first elongated protrusion and the third elongated protrusion are in contact with each other, and the second elongated protrusion and the fourth elongated protrusion are in contact with each other.

[0013] Furthermore, each of the first, second, third, and fourth elongated protrusions is provided with an airtight protrusion and an airtight groove at intervals. The specifications of the airtight protrusions and the airtight grooves correspond to each other. That is, when the first and third elongated protrusions are in contact with each other, the airtight protrusions and airtight grooves respectively provided on the first and third elongated protrusions are nested in each other. Similarly, when the second and fourth elongated protrusions are in contact with each other, the airtight protrusions and airtight grooves respectively provided on the second and fourth elongated protrusions are nested in each other.

[0014] Furthermore, when the chain is closed, the meshing of the first and second chain tooth groups will cause the first, second, third, and fourth elongated protrusions to move closer to the central axis of the chain. At this time, the first and third elongated protrusions are squeezed at their contact points, and the second and fourth elongated protrusions are squeezed at their contact points. The squeeze allowance generated by the two squeezes fills the gaps between the first and second elongated protrusions and between the third and fourth elongated protrusions, respectively.

[0015] By adopting the aforementioned technical solution, the beneficial effects of the present invention are: 1. This invention improves the structure of the zipper chain to give it waterproof and airtight properties. Compared with conventional waterproof and airtight zippers, the proposed solution is a double-layer structure. During use, the tight cooperation of the double-layer structure improves the overall waterproof and airtightness of the zipper. On the other hand, the double-layer structure ensures that the zipper will not burst. Specifically, as the zipper pull is pulled, the chain closes. The first and second sub-chain teeth mesh with each other, and the first and second female chain teeth mesh with each other, forming two protective barriers. Furthermore, the first and second waterproof structures set in the center of the chain achieve the waterproof and airtight effect. The first and second chain tooth groups not only achieve the locking function of a conventional zipper, but also work in conjunction with the first and second waterproof structures to maximize the waterproof and airtight properties of the zipper and the function of the burst-proof chain.

[0016] 2. When the chain is closed, because the first sub-chain teeth, first master chain teeth, second sub-chain teeth, and second master chain teeth on the first and second chain tooth groups are respectively located at the upper and lower ends of the first and second chain fabrics, simulating when the chain is bent or impacted by sharp objects, when a sharp object presses against the chain teeth from the outside, the outer side, as the frontal impact surface, will be concave and in a tightened defensive posture, while the inner side also maintains a locking state. At the same time, the locking state of the inner chain teeth can provide auxiliary protection for the outer chain teeth, preventing the chain from bursting. That is, because the inner and outer chain teeth are designed... Placed on the same chain, the inner chain teeth are tightly locked to prevent the outer chain teeth from bursting. When a sharp object is pressed against the chain teeth from the inside, the inner side, as the frontal impact surface, will be concave and in a tightened defensive posture, while the outer side also remains locked. At the same time, the locked state of the outer chain teeth can provide auxiliary protection for the inner chain teeth, preventing them from bursting. In other words, because the inner and outer chain teeth are set on the same chain, the outer chain teeth are tightly locked to ensure that the inner chain teeth will not burst. Therefore, no matter whether the chain is impacted from the outside or the inside, it can defend itself through its own structure.

[0017] 3. Simultaneously, the first and second waterproof structures of this invention are respectively disposed between the first and second through grooves. The principle is as follows: by being disposed between the first sub-chain tooth and the first mother chain tooth, and between the second sub-chain tooth and the second mother chain tooth, the chain teeth can provide protection for both when closed. Regardless of whether the impact is external or internal, the chain teeth provide protection for the waterproof structure. The waterproof structure is also a double-layered structure, consisting of a first waterproof structure and a second waterproof structure, working in conjunction with the first and second chain tooth groups. No matter where the impact comes from, the opposite side can continue to work unaffected and provide auxiliary defensive support to the impacted side. Furthermore, the first and second waterproof structures of this invention... The second waterproof structure also meets the impact resistance requirements. The first and second waterproof structures adopt a double-layer design. Regardless of whether the chain is subjected to external or internal impact, one side of the long strip protrusion is always in a contracted and closed state. When the chain is pressed and bent inward, the inner long strip protrusion is in a contracted and closed state while the outer long strip protrusion is in an open and relaxed state. When the chain is pressed and bent outward, the outer long strip protrusion is in a contracted and closed state while the inner long strip protrusion is in an open and relaxed state. In any case, one side is always in a contracted and closed state. This ensures that when one side is relaxed and open, resulting in air and water leakage, the other side is in a more tightly sealed state, providing the chain with safe waterproof and airtight performance.

[0018] 4. In this invention, the first, second, third, and fourth elongated protrusions are each provided with a matching airtight protrusion and an airtight groove. When the elongated protrusions are in contact with each other, the airtight protrusion and the airtight groove also cooperate with each other, so that when the chain bends outward or inward, there will always be one side of the elongated protrusion that cooperates more tightly, and the airtight protrusion and the airtight groove on that side will also cooperate more tightly to provide better waterproof and airtightness for the zipper.

[0019] 5. In addition, when the zipper is closed, the engagement between the long protrusions is similar to an interference fit in the mechanical field, driven by the zipper teeth. That is, the contact surfaces are not simply touching and touching, but rather in a compression fit. The excess material generated by the compression of the flexible rubber fills the gaps between the first and second long protrusions and between the third and fourth long protrusions, ensuring that when the zipper is closed, the long protrusions are always under the traction force of the zipper teeth and thus remain tightly fitted. The zipper teeth are like two hands pressing the long protrusions towards the center of the zipper belt.

[0020] 6. In the production process proposed in this invention, the waterproof structure is formed in one step. The corresponding plastic molding device is equipped with a concave-convex forming part. The concave-convex forming part flexibly forms the airtight protrusion and airtight groove, and the switching is convenient, requiring only rotation by an arc-shaped rotating plate. At the same time, a heating plate is provided on the connecting surface to ensure that the heating plate keeps heating the waterproof structure after molding, improving the plasticity of its end and facilitating good airtightness when assembling the first waterproof structure and the second waterproof structure later. Attached Figure Description

[0021] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a flowchart of the production process of the present invention; Figure 2 This is a schematic diagram of the plastic molding apparatus of the present invention; Figure 3 for Figure 2 Enlarged view of point A in the middle; Figure 4 This is a schematic diagram of the working state of the concave-convex forming part of the present invention; Figure 5 This is a schematic diagram of the zipper structure of the present invention; Figure 6 This is a schematic diagram of the outer structure of the chain belt of the present invention; Figure 7 This is a schematic diagram of the inner structure of the chain belt of the present invention; Figure 8 This is a schematic diagram of the side cross-sectional structure of the chain belt of the present invention; Figure 9 This is a schematic diagram of the chain belt of the present invention being subjected to impact. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0023] Please see Figures 1-9This invention provides a double-layer airtight zipper, comprising a chain belt 1 and a zipper pull 2 ​​that cooperate with each other. The chain belt 1 includes a first chain fabric 11, a second chain fabric 12, a first chain tooth group 3 disposed on the first chain fabric 11, a second chain tooth group 4 disposed on the second chain fabric 12, a first waterproof structure 5 disposed on the first chain fabric 11, and a second waterproof structure disposed on the second chain fabric 12. When the chain belt 1 is closed, the first chain tooth group 3 and the second chain tooth group 4 engage with each other, and the first waterproof structure and the second waterproof structure adhere to each other. The first chain fabric 11 and the second chain fabric 12 are defined to each include an upper surface layer and... In the lower layer, the first chain tooth group 3 includes a first sub-chain tooth 31 and a first female chain tooth 32, and the second chain tooth group 4 includes a second sub-chain tooth and a second female chain tooth. The first sub-chain tooth 31 and the first female chain tooth 32 are respectively disposed on the upper and lower layers of the first chain cloth 11 with the first chain cloth 11 as the center of symmetry. The second sub-chain tooth and the second female chain tooth are respectively disposed on the upper and lower layers of the second chain cloth 12 with the second chain cloth 12 as the center of symmetry. When the chain belt 1 is closed, the first sub-chain tooth 31 and the second sub-chain tooth mesh with each other, and the first female chain tooth 32 and the second female chain tooth mesh with each other.

[0024] A first through groove 33 is naturally formed between the first sub-chain tooth 31 and the first female chain tooth 32, and a second through groove is naturally formed between the second sub-chain tooth and the second female chain tooth. When the chain belt 1 is closed, the first through groove 33 and the second through groove are arranged opposite to each other. The first waterproof structure 5 is disposed in the first through groove 33, and the second waterproof structure is disposed in the second through groove. The first waterproof structure 5 is made of flexible rubber and completely fills the first through groove 33. The second waterproof structure is also made of flexible rubber and completely fills the second through groove. The first waterproof structure 5 includes a first central support portion 51, a first elongated protrusion 52 and a second elongated protrusion 53 integrally formed on the first central support portion 51. The first through groove 33 is a long strip structure. The first long strip protrusion 52 and the second long strip protrusion 53 are respectively disposed at the upper and lower ends of the first central support 51 and follow the first central support 51 through the first through groove 33. The second waterproof structure includes a second central support, a third long strip protrusion and a fourth long strip protrusion integrally formed on the second central support. The second central support has a long strip structure and passes through the second through groove. The third long strip protrusion and the fourth long strip protrusion are respectively disposed at the upper and lower ends of the second central support and follow the second central support through the second through groove. When the chain belt 1 is closed, the first long strip protrusion 52 and the third long strip protrusion are in contact, and the second long strip protrusion 53 and the fourth long strip protrusion are in contact.

[0025] Each of the first elongated protrusion 52, the second elongated protrusion 53, the third elongated protrusion, and the fourth elongated protrusion is provided with an airtight protrusion 521 and an airtight groove 531 at intervals. The specifications of the airtight protrusion 521 and the airtight groove 531 correspond to each other. That is, when the first elongated protrusion 52 and the third elongated protrusion are attached to each other, the airtight protrusion 521 and the airtight groove 531 respectively provided on the first elongated protrusion 52 and the third elongated protrusion are nested in each other. Similarly, when the second elongated protrusion 53 and the fourth elongated protrusion are attached to each other, the airtight protrusion 521 and the airtight groove 531 respectively provided on the second elongated protrusion 53 and the fourth elongated protrusion are nested in each other.

[0026] When the chain belt 1 is closed, the meshing of the first chain tooth group 3 and the second chain tooth group 4 will cause the first elongated protrusion 52, the second elongated protrusion 53, the third elongated protrusion, and the fourth elongated protrusion to move closer to the central axis of the chain belt 1. At this time, the first elongated protrusion 52 and the third elongated protrusion are squeezed at their joints, and the second elongated protrusion 53 and the fourth elongated protrusion are squeezed at their joints. The squeeze allowance generated by the two squeezes fills the gaps between the first elongated protrusion 52 and the second elongated protrusion 53, and between the third elongated protrusion and the fourth elongated protrusion, respectively.

[0027] This invention also proposes a manufacturing process for the aforementioned double-layer airtight zipper, a manufacturing process for producing a double-layer airtight zipper, comprising the following steps: S1. Slipper head forming; The zipper head 2 is plastic-formed using a slipper head forming device; S2. Chain forming; sewing the chain teeth onto the chain fabric; S3. Waterproof structure molding; The first and second waterproof structures are molded using a plastic molding device; S4. Component assembly: The newly formed first and second waterproof structures are embedded in the first and second through grooves under high temperature conditions. After the embedding is completed, the entire chain belt is cooled. S5. Slider head and chain assembly: Assemble the slider head and chain.

[0028] The plastic molding device includes a working base 6, a support frame 61 mounted on the working base 6, an upper molding template 8 and a lower molding template 7 mounted on the support frame 61. An upper molding cavity 81 is provided on the side of the upper molding template 8 closest to the lower molding template 7, and a lower molding cavity 71 is provided on the side of the lower molding template 7 closest to the upper molding template 8. The structures of the upper molding cavity 81 and the lower molding cavity 71 are symmetrical. Both the upper molding cavity 81 and the lower molding cavity 71 include a connecting surface 711 and a molding surface 713. Cooling devices are integrated within each plate 7 for cooling and demolding the upper forming cavity 81 and the lower forming cavity 71. The forming surface 713 is provided with spaced-apart concave-convex forming portions 9, each including a forming arc groove 91 and an arc-shaped rotating plate 92 rotatably disposed within the forming arc groove 91. The arc-shaped rotating plate 92 has a bowl-shaped structure. When forming an airtight protrusion 521, the convex surface of the arc-shaped rotating plate 92 faces into the forming arc groove 91; when forming an airtight groove 531, the convex surface of the arc-shaped rotating plate 92 faces away from the forming arc groove 91. A heating plate 712 is provided on the connecting surface 711.

[0029] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0030] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A plastic molding process for a double layer airtight zipper, characterized by: Includes the following steps: S1. Slipper head forming; The slipper head of the zipper is formed into plastic using a slipper head forming device; S2. Chain forming; sewing the chain teeth onto the chain fabric; S3, Waterproof structure molding; The first and second waterproof structures are formed using a plastic molding device. S4. Component assembly: The newly formed first and second waterproof structures are embedded in the first and second through grooves under high temperature conditions. After the embedding is completed, the entire chain belt is cooled. S5. Slider head and chain assembly; Assemble the slider head and chain. The plastic molding device includes a working base, a support frame mounted on the working base, an upper molding template and a lower molding template mounted on the support frame. An upper molding cavity is provided on the side of the upper molding template closest to the lower molding template, and a lower molding cavity is provided on the side of the lower molding template closest to the upper molding template. The structures of the upper and lower molding cavities are symmetrical. Both the upper and lower molding cavities include a connecting surface and a molding surface. Cooling devices are integrated into both the upper and lower molding templates for cooling and demolding the upper and lower molding cavities. The molding surface is provided with intermittently spaced concave and convex molding portions. Each concave and convex molding portion includes a molding arc groove and an arc-shaped rotating plate rotatably mounted within the molding arc groove. The arc-shaped rotating plate has a bowl-shaped structure. When forming an airtight protrusion, the convex surface of the arc-shaped rotating plate faces into the molding arc groove; when forming an airtight recess, the convex surface of the arc-shaped rotating plate faces away from the molding arc groove.

2. A plastic molding process for a dual layer air-tight zipper as defined in claim 1, wherein: A heating plate is provided on the connecting surface.

3. A double-layer airtight zipper, manufactured using the process described in claim 2, characterized in that: The invention includes a chain belt and a zipper pull that cooperate with each other, characterized in that: the chain belt includes a first chain cloth, a second chain cloth, a first chain tooth group disposed on the first chain cloth, a second chain tooth group disposed on the second chain cloth, a first waterproof structure disposed on the first chain cloth, and a second waterproof structure disposed on the second chain cloth; when the chain belt is closed, the first chain tooth group and the second chain tooth group engage with each other, and the first waterproof structure and the second waterproof structure adhere to each other.

4. A double-layer airtight zipper according to claim 3, characterized in that: Both the first and second chain fabrics are defined as having an upper surface and a lower surface. The first chain tooth group includes a first sub-chain tooth and a first mother chain tooth, and the second chain tooth group includes a second sub-chain tooth and a second mother chain tooth. The first sub-chain tooth and the first mother chain tooth are respectively disposed on the upper surface and the lower surface of the first chain fabric with the first chain fabric as the center of symmetry. The second sub-chain tooth and the second mother chain tooth are respectively disposed on the upper surface and the lower surface of the second chain fabric with the second chain fabric as the center of symmetry. When the chain is closed, the first sub-chain tooth and the second sub-chain tooth mesh with each other, and the first mother chain tooth and the second mother chain tooth mesh with each other.

5. A double-layer airtight zipper according to claim 4, characterized in that: A first through groove is naturally formed between the first sub-chain tooth and the first mother chain tooth, and a second through groove is naturally formed between the second sub-chain tooth and the second mother chain tooth. When the chain is closed, the first through groove and the second through groove are arranged opposite to each other. The first waterproof structure is disposed in the first through groove, and the second waterproof structure is disposed in the second through groove.

6. A double-layer airtight zipper according to claim 5, characterized in that: The first waterproof structure is made of flexible rubber and completely fills the first through groove. The second waterproof structure is also made of flexible rubber and completely fills the second through groove.

7. A double-layer airtight zipper according to claim 6, characterized in that: The first waterproof structure includes a first central support portion, a first elongated protrusion and a second elongated protrusion integrally formed on the first central support portion. The first central support portion has an elongated structure that extends through the first through groove. The first elongated protrusion and the second elongated protrusion are respectively disposed at the upper and lower ends of the first central support portion and follow the first central support portion through the first through groove. The second waterproof structure includes a second central support portion, a third elongated protrusion and a fourth elongated protrusion integrally formed on the second central support portion. The second central support portion has an elongated structure that extends through the second through groove. The third elongated protrusion and the fourth elongated protrusion are respectively disposed at the upper and lower ends of the second central support portion and follow the second central support portion through the second through groove. When the chain is closed, the first elongated protrusion and the third elongated protrusion are in contact with each other, and the second elongated protrusion and the fourth elongated protrusion are in contact with each other.

8. A double-layer airtight zipper according to claim 7, characterized in that: Each of the first, second, third, and fourth elongated protrusions is provided with an airtight protrusion and an airtight groove at intervals. The specifications of the airtight protrusions and the airtight grooves correspond to each other. That is, when the first and third elongated protrusions are in contact with each other, the airtight protrusions and airtight grooves respectively provided on the first and third elongated protrusions are nested in each other. Similarly, when the second and fourth elongated protrusions are in contact with each other, the airtight protrusions and airtight grooves respectively provided on the second and fourth elongated protrusions are nested in each other.

9. A double-layer airtight zipper according to claim 8, characterized in that: When the chain is closed, the meshing of the first and second chain tooth groups will cause the first, second, third, and fourth elongated protrusions to move closer to the central axis of the chain. At this time, the first and third elongated protrusions and the second and fourth elongated protrusions will be squeezed at their joints. The squeezed allowances from these two joints will fill the gaps between the first and second elongated protrusions and between the third and fourth elongated protrusions, respectively.

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