Paper-plastic packaging box for oral use

Abstract

The utility model discloses a paper-plastic packaging box for oral tobacco, which comprises a box body with a containing cavity and a cover body for opening and closing the containing cavity. The cover body has a plugging head partially inserted into the containing cavity when the cover body closes the containing cavity. The plugging head is provided with a sealing ring for interference fit with the containing cavity. The cavity wall surface of the containing cavity and the surface of the plugging head are each coated with a high-barrier environmental protection coating. The paper-plastic packaging box for oral tobacco has the advantages of good experience and good moisture-proof and waterproof effects.

Description

Technical Field

[0001] This utility model relates to the field of packaging technology for oral cigarettes, and in particular to a paper-plastic packaging box for oral cigarettes. Background Technology

[0002] Currently, commercially available paper-plastic packaging containers used for sealing cigarettes typically employ lamination or simple waterproof coating processes, which can only prevent liquid water penetration for a short period. However, systematic research and optimization of water vapor transmission rate (MVTR) have not been conducted. Due to the porous nature of paper-plastic fibers, moisture can permeate the material in a relatively short time, causing the cigarette inside to become damp and deteriorate. This is particularly evident in multi-piece paper-plastic packaging applications, where the overall barrier properties of individual components and the entire package cannot be achieved, making the insufficient barrier performance especially apparent.

[0003] Therefore, there is an urgent need for a paper-plastic packaging box for mouth-held cigarettes to overcome one or more of the above-mentioned defects. Utility Model Content

[0004] The purpose of this utility model is to provide a paper-plastic packaging box for oral cigarettes that offers a good user experience and excellent moisture and water resistance.

[0005] To achieve the above objectives, the present invention provides a paper-plastic packaging box for oral cigarettes, comprising a box body having a holding cavity and a cover for opening and closing the holding cavity. The cover has a sealing head that partially extends into the holding cavity when the cover is closed. The sealing head is fitted with a sealing ring for interference fit with the holding cavity. The cavity wall and the surface of the sealing head are each coated with a high-barrier, environmentally friendly coating.

[0006] Compared with existing technologies, this invention achieves a double protective effect by coating the cavity wall and the sealing head with a high-barrier, environmentally friendly coating, and by fitting the sealing head with a sealing ring for an interference fit with the cavity. This results in excellent moisture and water resistance for the oral cigarette packaging box. Because the sealing head and cavity are sealed through the interference fit of the sealing ring, a uniform pressure is formed between the lid and the box body, providing a clear opening and closing feel. Furthermore, repeated opening and closing does not affect the sealing performance, resulting in a superior user experience.

[0007] Preferably, the high-barrier environmentally friendly coating is a nano-modified polyvinylidene chloride coating.

[0008] Preferably, the thickness of the high-barrier environmentally friendly coating is any value between 3 micrometers and 15 micrometers.

[0009] Preferably, the sealing head has an embedded recessed groove extending in the circumferential direction, and the sealing ring is an elastomeric sealing ring that is elastically tensioned and fitted into the embedded recessed groove.

[0010] Preferably, the sealing ring is a biodegradable rubber sealing ring or a thermoplastic elastomer sealing ring.

[0011] Preferably, the cover body includes an upper outer cover and an upper inner cover that is stacked and fixed to the upper outer cover. The sealing head is located on the upper inner cover. The middle of the sealing head is bent upward to form an arched structure that is concave downward and convex upward. The arched structure has an adhesive end face for the upper outer cover to be glued and fixed to support the upper outer cover.

[0012] Preferably, the box body includes a cylindrical lower outer shell, a cylindrical lower inner box, and a disc-shaped intermediate sleeve. The bottom of the lower outer shell is bent upward at the middle to form a support structure with a concave bottom and a convex top. The lower inner box is located inside the lower outer shell, and the bottom of the lower inner box is also glued to the support structure. The intermediate sleeve is fixedly fitted onto the lower inner box, and the intermediate sleeve also has a clearance through hole to avoid the support structure. The holding cavity is located on the lower inner box.

[0013] Preferably, the intermediate sleeve, which defines the position of the clearance through hole, is adhesively fixedly stacked below the bottom of the lower inner box.

[0014] Preferably, the box body further includes a bottom shell that is partially embedded in the support structure from below and is in the shape of an inverted disc. The middle of the bottom shell is bent downward to form an inverted frustum structure that is concave at the top and convex at the bottom. The bottom shell is also glued to the bottom of the lower outer shell.

[0015] Preferably, the bottom of the lower outer shell is further bent upward to form an annular structure that is concave at the bottom and convex at the top. The annular structure is separated from the supporting structure and is arranged around the supporting structure from the outside.

[0016] Preferably, the paper-plastic packaging box for oral cigarettes of this utility model further includes a pivot module for opening and closing the holding cavity by flipping the cover relative to the box body, a first reinforcing ring clamped and fixed by the upper outer cover and the lower inner cover, and a second reinforcing ring clamped and fixed by the intermediate sleeve and the lower inner box; the lower inner cover has a cover hinge area for partially exposing the first reinforcing ring, and the lower outer cover and the lower inner box also have a box hinge area for partially exposing the second reinforcing ring and located beside the holding cavity; the pivot module includes a first hinge seat located in the cover hinge area, a second hinge seat located in the box hinge area, and a pivot for hinged between the second hinge seat and the first hinge seat, the first hinge seat and / or the second hinge seat having a shaft hole for micro-clear clearance fitting with the pivot, the first hinge seat being fixed at the position where the first reinforcing ring is exposed from the cover hinge area, and the second hinge seat being fixed at the position where the second reinforcing ring is exposed from the box hinge area.

[0017] Preferably, the first hinge seat and / or the second hinge seat are provided as a collar structure that defines the position of the shaft hole as being open at both ends in the circumferential direction. Attached Figure Description

[0018] Figure 1 This is a top-down plan view of the paper-plastic packaging box for oral cigarettes according to this utility model.

[0019] Figure 2 It is along Figure 1 Internal view of the section cut along the BB line.

[0020] Figure 3 yes Figure 2 Enlarged view of section C.

[0021] Figure 4 This is a perspective view of the paper-plastic packaging box for oral cigarettes of this utility model when the lid is flipped open to a preset angle.

[0022] Figure 5 yes Figure 4 Enlarged view of section D.

[0023] Figure 6 yes Figure 4 The image shows the interior of a paper-plastic packaging box for oral cigarettes after being cut by a plane passing through the center line of the box and perpendicular to the axis of rotation.

[0024] Figure 7 yes Figure 4 An exploded perspective view of a paper-plastic packaging box for oral cigarettes, as shown.

[0025] Figure 8 yes Figure 7 A further exploded 3D diagram.

[0026] Figure 9 yes Figure 4 A 3D view showing the lid and box body hidden. Detailed Implementation

[0027] To explain the technical content and structural features of this utility model in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0028] Please see Figure 1 The paper-plastic packaging box 100 for mouth-held cigarettes of this utility model is used for packaging and sealing mouth-held cigarettes to prevent them from absorbing moisture and becoming damp, thereby affecting the taste of the mouth-held cigarettes.

[0029] Combined Figure 2 , Figure 4 and Figure 6The present invention relates to a paper-plastic packaging box 100 for oral cigarettes, comprising a box body 10 and a lid 20. The box body 10 has a holding cavity 11 for holding oral cigarettes; optionally, it is further... Figure 4 , Figure 7 and Figure 8 In this example, the container cavity 11 is circular to facilitate the manufacture of the box body 10. Obviously, depending on actual needs, the container cavity 11 can also be other shapes well known in the art, so it is not considered a perfect example. Figure 4 , Figure 7 and Figure 8 The above is for reference only; additionally, at [date / time], Figure 4 , Figure 7 and Figure 8 In this example, the outer contour of the box 10 in the circumferential direction is an outer circle to facilitate the manufacture of the box 10. Obviously, depending on actual needs, the outer contour of the box 10 in the circumferential direction can also be other shapes well known in the field, so it is not considered... Figure 4 , Figure 7 and Figure 8 The above is the limit.

[0030] The cover 20 is used to open and close (i.e., open or close) the holding cavity 11 to meet the needs of the operator to put or remove a mouth-held cigarette into the holding cavity 11; alternatively, it is used for... Figure 1 In this example, the outer contour of the cover 20 in its circumferential direction is circular to facilitate the manufacture of the cover 20; obviously, depending on actual needs, the outer contour of the cover 20 in its circumferential direction can also be other shapes well known in the art, therefore it is not considered as such. Figure 1 The description is limited to what is shown. Additionally, the cover 20 has a sealing head 21 that partially extends into the holding cavity 11 when the cover 20 is closed. The sealing head 21 is fitted with a sealing ring 22 for an interference fit with the holding cavity 11, thereby achieving a seal between the sealing head 21 and the box body 10. Furthermore, the surface of the sealing head 21 is coated with a high-barrier environmentally friendly coating 213, and the cavity wall surface of the holding cavity 11 is coated with a high-barrier environmentally friendly coating 111; so that the paper-plastic packaging box 100 for oral cigarettes of this invention provides a double sealing effect for the oral cigarettes within the holding cavity 11. Specifically, in Figure 3 As an example, the high-barrier environmentally friendly coatings 111 and 213 are nano-modified polyvinylidene chloride coatings. On the one hand, this gives the oral cigarette packaging box 100 of this invention a low water vapor transmittance (MVTR < 5 g / m²·24h), providing long-lasting water vapor barrier. On the other hand, it avoids the degradation problems associated with traditional PE or EVOH composite films, aligning with the trend of green packaging development. Furthermore, the thickness of the high-barrier environmentally friendly coatings 111 and 213 is any value between 3 micrometers and 15 micrometers, for example, 3 micrometers, 5 micrometers, 7 micrometers, 9 micrometers, 11 micrometers, 13 micrometers, or 15 micrometers. More specifically, see the description below.

[0031] like Figure 2 , Figure 3 and Figure 6 As shown, as an example, the sealing head 21 has an embedded recessed groove 211 extending in the circumferential direction. In this case, the sealing ring 22 is an elastomeric sealing ring, which is elastically tensioned and fitted into the embedded recessed groove 211. This design makes the sealing performance between the sealing ring 22 and the sealing head 21 better. Alternatively, as an example, the sealing ring 22 can be a biodegradable rubber sealing ring or a thermoplastic elastomer sealing ring, thus making the oral cigarette paper-plastic packaging box 100 of this utility model more environmentally friendly.

[0032] like Figure 2 and Figure 6 As shown, as an example, the cover 20 includes an outer cover 20a and an inner cover 20b stacked and fixed to the outer cover 20a. A sealing head 21 is located on the inner cover 20b. The middle of the sealing head 21 is bent upwards to form an arched structure 21a, making the sealing head 21 concave downwards and convex upwards. The arched structure 21a has an adhesive end face 212 for the outer cover 20a to be glued and fixed to support it. Therefore, the arched structure 21a increases the structural strength of the cover 20 and also increases the adhesive area between the outer cover 20a and the inner cover 20b. Specifically, in conjunction with... Figure 2 , Figure 4 and Figures 6 to 8 As an example, the arched structure 21a is frustum-shaped to facilitate the fabrication of the inner cover 20b; obviously, depending on actual needs, the arched structure 21a can also be other shapes well known in the art, therefore... Figure 2 , Figure 4 and Figures 6 to 8 The above is the limit.

[0033] For example Figure 2 and Figure 6 As shown, as an example, the box body 10 includes a cylindrical lower outer shell 10a, a cylindrical lower inner box 10b, a disc-shaped intermediate sleeve 10c, and a bottom shell 10d in the shape of an inverted disc. The bottom of the lower outer shell 10a is bent upward at the middle, so that the bottom 10a1 has a concave-convex support structure 12. Optionally, in Figure 2 and Figure 6 In the example shown, the support structure 12 is cylindrical to facilitate the fabrication of the lower outer shell 10a. Obviously, the support structure 12 can also be other shapes depending on actual needs, so it is not considered a perfect example. Figure 2 and Figure 6As shown, the lower inner box 10b is located inside the lower outer shell 10a, and the bottom 10b1 of the lower inner box 10b is also glued to the support structure 12. The intermediate sleeve 10c is fixedly fitted onto the lower inner box 10b, and the intermediate sleeve 10c also has a clearance through hole 13 to avoid the support structure 12. The bottom shell 10d is partially embedded in the support structure 12 from below, and the middle of the bottom shell 10d is bent downward to form an inverted frustum structure 14 with a concave upper and convex lower section to increase the structural strength of the bottom shell 10d; the bottom shell 10d is also glued to the bottom 10a1 of the lower outer shell 10a; and the holding cavity 11 is located on the lower inner box 11b. Specifically, in Figure 2 and Figure 6 In this example, the intermediate sleeve 10c is used to define the position 10c1 of the clearance through hole 14 and is adhesively fixedly stacked below the bottom 10b1 of the lower inner box 10b; this increases the stability between the intermediate sleeve 10c and the lower inner box 10b; furthermore, in Figure 2 and Figure 6 In this example, both the lower inner box 10b and the intermediate sleeve 10c have horizontally extending rings 10b2 (10c2) at their tops, with the horizontally extending ring 10c2 of the intermediate sleeve 10c located directly below the horizontally extending ring 10b2 of the lower inner box 10b; furthermore, in Figure 2 and Figure 6 As an example, the bottom 10a1 of the lower outer shell 10a is bent upward to form an annular structure 15 that makes the bottom 10a1 concave downward and convex upward. The annular structure 15 is separated from the supporting structure 12 and is arranged around the supporting structure 12 from the outside. Therefore, the bottom shell 10d is recessed into the lower outer shell 10a by means of the annular structure 15, so the bottom shell 10d will not bulge outward from the bottom 10a1 of the lower outer shell 10a. It should be noted that, although Figure 2 and Figure 6 The diagram shows that the box 10 includes a lower outer shell 10a, a lower inner box 10b, an intermediate sleeve 10c, and a bottom shell 10d. Obviously, depending on actual needs, the box 10 can also be made without the bottom shell 10d; therefore, it is not considered a separate case. Figure 2 and Figure 6 The above is the limit.

[0034] In order to enable the lid 20 to flip relative to the box 10 to open and close the holding cavity 11, and to improve the structural strength of the lid 20 and the box 10, combined with Figure 2 and Figures 4 to 9As an example, the paper-plastic packaging box 100 for oral cigarettes of this utility model also includes a pivot module 30 for opening and closing the holding cavity 11 by flipping the cover 20 relative to the box body 10, a first reinforcing ring 40 clamped and fixed by the upper outer cover 20a and the lower inner cover 20b, and a second reinforcing ring 50 clamped and fixed by the intermediate sleeve 10c and the lower inner box 10b. Optionally, as an example, the first reinforcing ring 40 is a metal ring; obviously, depending on actual needs, other structures with a hardness greater than that of the cover 20 can also be selected. Similarly, the second reinforcing ring 50 is a metal ring; obviously, depending on actual needs, other structures with a hardness greater than that of the box body 10 can also be selected. Furthermore, the lower inner cover 20b has a cover hinge area 23 on which the first reinforcing ring 40 is partially exposed (see state). Figure 7 and Figure 8 As shown), under the action of the hinge area 23, the need for assembly connection between the pivot module 30 and the first reinforcing ring 40, which is clamped and fixed by the upper outer cover 20a and the lower inner cover 20b, is met. In addition, the lower outer shell 10a and the lower inner box 10b are both provided with a box hinge area 16 (see state) for the second reinforcing ring 50 to be partially exposed and located on the side of the container cavity 11. Figure 7 and Figure 8 (As shown); Therefore, under the action of the hinge area 16 of the box, the need for the rotating shaft module 30 to be assembled and connected with the second reinforcing ring 50 which is clamped and fixed by the intermediate sleeve 10c and the lower inner box 10b is met.

[0035] Meanwhile, the hinge module 30 includes a first hinge seat 31 located in the hinge area 23 of the cover, a second hinge seat 32 located in the hinge area 16 of the box, and a hinge 33 for hinged between the second hinge seat 32 and the first hinge seat 31. The first hinge seat 31 is fixed at the position 41 where the first reinforcing ring 40 protrudes from the hinge area 23 of the cover, and the second hinge seat 32 is fixed at the position 51 where the second reinforcing ring 50 protrudes from the hinge area 16 of the box, as shown in the diagram. Figure 8 As shown. Additionally, the first hinge seat 31 has a shaft hole 311 for a slight clearance fit with the rotating shaft 33, and the second hinge seat 32 has a shaft hole 321 for a slight clearance fit with the rotating shaft 33. Obviously, depending on actual needs, the first hinge seat 31 can also have a shaft hole 311 for a slight clearance fit with the rotating shaft 33, or the second hinge seat 32 can have a shaft hole 321 for a slight clearance fit with the rotating shaft 33; alternatively, in... Figure 8 In this example, the first hinge seat 31 defines the position of the shaft hole 311 as a collar structure 312 that is open at both ends in the circumferential direction. Therefore, through the collar structure 312 that is open at both ends in the circumferential direction, the operator can flexibly adjust the fit clearance between the shaft hole 311 and the rotating shaft 33 according to actual needs, thereby obtaining different rotational damping effects, and thus allowing the cover 20 to obtain different controlled angles; furthermore, in Figure 8In this example, the second hinge seat 32 defines the position of the shaft hole 321 as a collar structure 322 that is open at both ends in the circumferential direction. Therefore, by means of the collar structure 322 that is open at both ends in the circumferential direction, the operator can flexibly adjust the fitting clearance between the shaft hole 321 and the rotating shaft 33 according to actual needs, thereby obtaining different rotational damping effects, and thus causing different controlled angles for the cover 20 to flip open relative to the box 10. More specifically, see the description below.

[0036] like Figure 5 As shown, as an example, the micro-gap ranges from 0.01 mm to 0.05 mm. For example, the micro-gap is 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, or 0.05 mm. Therefore, by adjusting the size of the micro-gap, the rotational damping effect of the cover 20 relative to the box 10 can be adjusted, thereby flexibly changing the controlled angle at which the cover 20 flips open relative to the box 10. Furthermore, when the lid 20 is flipped open relative to the box 10 to a preset angle, the gravitational torque of the lid 20 relative to the axis 331 of the rotating shaft 33 is equal to the frictional torque of the rotating shaft 33 relative to the axis 331 of the rotating shaft 33 caused by the frictional force of the first hinge seat 31 and / or the second hinge seat 32. This allows the lid 20 to have a controlled hovering function at the preset angle. Combined with the circumferentially open collar structure 312 and collar structure 322, the size of the micro-gap can be adjusted more flexibly, thereby flexibly changing the balance between the gravitational torque of the lid 20 relative to the axis 331 of the rotating shaft 31 and the frictional torque of the rotating shaft 33 relative to the axis 331 of the rotating shaft 33 caused by the frictional force of the first hinge seat 31 and / or the second hinge seat 32. Thus, the preset angle at which the lid 20 is flipped open relative to the box 10 and controlled can be flexibly adjusted. Alternatively, as an example, the preset angle is any value between 30 and 90 degrees, such as 30, 60, or 90 degrees.

[0037] Compared with existing technologies, the paper-plastic packaging box 100 for oral cigarettes is made of this invention by coating the cavity wall of the holding cavity 11 and the surface of the sealing head 21 with a high-barrier environmentally friendly coating 111 (213), and by covering the sealing head 21 with a sealing ring 22 for interference fit with the holding cavity 11, achieving a double protection effect. This makes the paper-plastic packaging box 100 for oral cigarettes of this invention have good moisture and water resistance. Because the sealing head 21 and the holding cavity 11 are sealed by the interference fit between the sealing ring 22 and the holding cavity 11, a uniform pressing force can be formed between the cover 20 and the box body 10. The opening and closing feel is clear, and the sealing performance can be affected by multiple opening and closing, thus providing a good user experience.

[0038] In summary, the advantages of the oral cigarette paper-plastic packaging box 100 of this utility model are as follows: (i) Super strong barrier properties: Through the high barrier environmental protection coating 111 (213), it has the performance of low MVTR (<5 g / m²·24h) and can effectively block water vapor for a long time.

[0039] (ii) Completely moisture-proof and waterproof: With the help of the sealing ring 22, the box body 10 and the cover body 20 are sealed, completely eliminating the problem of seepage through the joint gap.

[0040] (iii) Modular application: It is suitable for single and multi-piece packaging box structures. Whether stored independently or used in combination, it can ensure the overall moisture-proof effect.

[0041] (iv) Environmental protection and biodegradability: The high-barrier environmental protection coating 111 (213) uses environmentally friendly materials to avoid the degradation problems caused by traditional PE or EVOH composite films, which is in line with the development trend of green packaging.

[0042] (v) Excellent user experience: Through the interference fit between the sealing ring 22 and the container cavity 11, a uniform clamping force can be formed when closed. In particular, the sealing ring 22 is elastically tensioned and fitted in the embedded concave ring groove 211, the opening and closing feel is clear, and it can be opened and closed multiple times without affecting the sealing performance.

[0043] It should be further noted that when the intermediate sleeve 10c is provided with a horizontal extension ring 10c2 and the lower inner box 10b is provided with a horizontal extension ring 10b2, the second reinforcing ring 50 is clamped and fixed by the horizontal extension rings 10c2 and 10b2, and the second reinforcing ring 50 is arranged around the lower inner box 10b from the outside, as shown in the figure. Figure 2 and Figure 6 As shown; the first reinforcing ring 40 is arranged around the support structure 21a from the outside and is separated from the support structure 21a, as shown in the figure. Figure 2 and Figure 6 As shown.

[0044] The above-disclosed examples are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Therefore, any equivalent variations made in accordance with the claims of the present utility model shall fall within the scope of the present utility model.

Claims

1. A paper-plastic packaging box for oral cigarettes, comprising a box body having a holding cavity and a lid for opening and closing the holding cavity, characterized in that, The cover has a sealing head that partially extends into the container cavity when the cover is closed. The sealing head is fitted with a sealing ring for interference fit with the container cavity. The cavity wall and the surface of the sealing head are each coated with a high-barrier environmentally friendly coating.

2. The paper-plastic packaging box for oral cigarettes according to claim 1, characterized in that, The high-barrier environmentally friendly coating is a nano-modified polyvinylidene chloride coating; the thickness of the high-barrier environmentally friendly coating is any value between 3 micrometers and 15 micrometers.

3. The paper-plastic packaging box for oral cigarettes according to claim 1, characterized in that, The sealing head has an embedded recessed groove extending in the circumferential direction, and the sealing ring is an elastic sealing ring that is elastically tensioned and fitted into the embedded recessed groove.

4. The paper-plastic packaging box for oral cigarettes according to claim 3, characterized in that, The sealing ring is a biodegradable rubber sealing ring or a thermoplastic elastomer sealing ring.

5. The paper-plastic packaging box for oral cigarettes according to any one of claims 1 to 4, characterized in that, The cover includes an outer cover and an inner cover that is stacked and fixed to the outer cover. The sealing head is located on the inner cover. The middle of the sealing head is bent upward to form an arched structure that is concave at the bottom and convex at the top. The arched structure has an adhesive end face for the outer cover to be glued and fixed to support the outer cover.

6. The paper-plastic packaging box for oral cigarettes according to claim 5, characterized in that, The box body includes a cylindrical lower outer shell, a cylindrical lower inner box, and a disc-shaped intermediate sleeve. The bottom of the lower outer shell is bent upward at the middle to form a concave-convex support structure. The lower inner box is located inside the lower outer shell, and the bottom of the lower inner box is also glued to the support structure. The intermediate sleeve is fixedly fitted onto the lower inner box, and the intermediate sleeve also has a clearance through hole to avoid the support structure. The holding cavity is located on the lower inner box.

7. The paper-plastic packaging box for oral cigarettes according to claim 6, characterized in that, The intermediate sleeve, which defines the position of the clearance through hole, is adhesively and fixedly stacked below the bottom of the lower inner box.

8. The paper-plastic packaging box for oral cigarettes according to claim 6, characterized in that, The box body also includes a bottom shell that is partially embedded in the support structure from below and is in the shape of an inverted disc. The middle part of the bottom shell is bent downward to form an inverted frustum structure that is concave at the top and convex at the bottom. The bottom shell is also glued to the bottom of the lower outer shell.

9. The paper-plastic packaging box for oral cigarettes according to claim 8, characterized in that, The bottom of the lower outer shell is also bent upward to form an annular structure that is concave at the bottom and convex at the top. The annular structure is separated from the supporting structure and is arranged around the supporting structure from the outside.

10. The paper-plastic packaging box for oral cigarettes according to claim 6, characterized in that, It also includes a pivot module for opening and closing the holding cavity by flipping the cover relative to the box body, a first reinforcing ring clamped and fixed by the upper outer cover and the lower inner cover, and a second reinforcing ring clamped and fixed by the intermediate sleeve and the lower inner box; the lower inner cover has a cover hinge area for partially exposing the first reinforcing ring, and the lower outer cover and the lower inner box also have box hinge areas for partially exposing the second reinforcing ring and located beside the holding cavity; the pivot module includes a first hinge seat located in the cover hinge area and a second hinge seat located in the box body hinge area. The body hinge area includes a second hinge seat and a rotating shaft for hinged connection between the second hinge seat and the first hinge seat. The first hinge seat and / or the second hinge seat are provided with shaft holes for micro-clear clearance fit with the rotating shaft. The first hinge seat is fixed at the position where the first reinforcing ring is exposed from the hinge area of ​​the cover body, and the second hinge seat is fixed at the position where the second reinforcing ring is exposed from the hinge area of ​​the box body. The first hinge seat and / or the second hinge seat are provided to define the position of the shaft hole as a collar structure that is open at both ends in the circumferential direction.

Images