Toilet lid locking and fastening device

Abstract

The utility model provides a toilet lid locking and fastening device which comprises a support, a pull-up bolt, a locking piece and a nut, the locking piece comprises a pair of side walls, a U-shaped bottom wall arranged at one ends of the side walls and a planar connecting wall arranged at the other ends of the side walls, and the connecting wall is integrally connected to the top of one end of each side wall; the bottom wall is integrally connected to the bottom of the other end of the side wall, and the U-shaped opening faces between the two side walls; the two side walls protrude out of the lower end of the connecting wall to form limiting walls, and a nut limiting groove used for containing a nut and limiting rotation of the nut is defined between the limiting walls and the bottom wall; the two side walls, the connecting wall and the bottom wall enclose to form a bolt limiting groove which is distributed along the length direction of the side walls and is used for a pull-up bolt to pass through. The locking piece structure is improved, so that the problems of insufficient strength and poor connecting stability of a locking piece in the prior art are effectively solved; and a more efficient, stable and durable solution is provided for installation of the closestool cover plate.

Description

Technical Field

[0001] The utility model relates to the technical field of toilet seat locking devices, in particular to an upper locking and fastening device for a toilet seat. Background Art

[0002] In the prior art, for the fixed installation of a toilet seat cover, especially considering the narrow installation space under the ceramic body of the toilet, a specific locking structure was designed. This structure mainly consists of an upper pull bolt, a rotatable locking member, and a nut, aiming to firmly fix the support of the cover on the ceramic body of the toilet. Specifically, when the upper pull bolt, the locking member, and the nut sequentially pass through the preset installation holes on the toilet ceramic, the locking member is urged to rotate to a horizontal position against the lower end face of the installation hole by the action of the upper pull bolt, and at the same time, the nut falls into the limiting groove at the lower end of the locking member. Subsequently, by rotating the bolt and cooperating with the limitation of the nut by the locking member, the effective locking of the support can be achieved.

[0003] In addition, an improvement measure was also mentioned in the existing technical solutions. As described in Chinese Patent Publication No. CN216143013U, by adding a fixing frame to limit and guide the locking member and the nut, the upper pull and locking process between the bolt and the nut is simplified, and the installation efficiency is improved.

[0004] However, although the above two solutions solve the problem of toilet seat cover installation to a certain extent, there are still the following deficiencies:

[0005] 1. In the first solution, the locking member is generally integrally formed by stamping, and its opening design is prone to deformation or damage due to excessive force during actual operation, resulting in the failure of the locking function, thus affecting the stable installation of the entire toilet seat cover and increasing the user's trouble in use.

[0006] 2. Although the second solution improves the installation convenience by introducing a fixing frame, due to the fixed size of the installation holes on the ceramic body of the toilet, in order to accommodate the additional fixing frame, the diameter of the bolt has to be reduced. This change directly reduces the mechanical strength of the connection part, affects the durability and reliability of the overall structure, and may pose a risk of loosening or breaking during long-term use.

[0007] In view of this, the inventor specifically designed an upper locking and fastening device for a toilet seat, and this case was thus generated. Summary of the Utility Model

[0008] In order to solve the above problems, the technical solution of the utility model is as follows:

[0009] A locking and fastening device for a toilet lid, comprising a support, an upward pull bolt, a rotatable locking member and a nut. The locking member is integrally die-cast to form a U-shaped integral body. The U-shaped integral body includes a pair of parallel side walls, a U-shaped bottom wall provided at one end of the side walls, and a planar connecting wall provided at the other end of the side walls. Among them:

[0010] The connecting wall is integrally connected to the top of one end of the side wall and forms a plane with the top surfaces of the two side walls that can be in flat contact with the inner wall of the ceramic mounting hole of the toilet bowl.

[0011] The bottom wall is integrally connected to the bottom of the other end of the side wall and its U-shaped opening faces towards the space between the two side walls.

[0012] At the lower end of the connecting wall, a limiting wall protrudes from both of the side walls. A nut limiting groove for accommodating the nut and restricting its rotation is formed by enclosing between the limiting wall and the bottom wall.

[0013] A bolt limiting groove for the upward pull bolt to pass through is formed by enclosing between the two side walls, the connecting wall and the bottom wall, and is distributed along the length direction of the side wall.

[0014] Preferably, one side of the bottom wall away from the connecting wall is flush with the end face of the side wall, and the other side extends along the length direction of the bottom of the side wall to a position close to the middle of the side wall.

[0015] Preferably, the extending distance of the limiting wall in the direction away from the connecting wall does not exceed the bottom of the bottom wall.

[0016] Preferably, an inclined guiding surface extending from the top of the side wall to the bottom of the limiting wall is provided on one side of the limiting wall away from the bottom wall.

[0017] Preferably, first arc-shaped guide corners are provided at the connection position between the guiding surface and the side wall and at the connection position between the guiding surface and the bottom surface of the limiting wall.

[0018] Preferably, second arc-shaped guide corners are provided at the contact positions between both sides of the connecting wall and the side wall.

[0019] Preferably, the extending distances of the limiting wall, the nut limiting groove and the bottom wall along the length direction of the side wall are such that the limiting wall, the nut limiting groove and the bottom wall trisect the side wall.

[0020] Preferably, in the opening area between the connecting wall and the top of the side wall and at a position close to the connecting wall, on both sides of this position, the top of the side wall horizontally protrudes towards the center position to form a pair of limiting edges. A clamping groove with a spacing smaller than the outer diameter of the upward pull bolt is formed between the two limiting edges.

[0021] Preferably, the extending distance of the limiting edge along the length direction of the side wall is such that the upward pull bolt is in a position opposite to the middle of the nut limiting groove when in movable contact with the clamping groove.

[0022] Preferably, a structural support portion integrally connected to the limiting edge is provided at the top of the inner side wall of the bolt limiting groove, and an arc-shaped transition surface is provided between the structural support portion and the inner side wall of the side wall.

[0023] Advantages of the present utility model:

[0024] Compared with the original stamping method, the U-shaped integral locking part formed by integral die-casting has an integrally die-cast connecting wall added on the opening side of the side wall, so that the two side walls on both sides of the opening form a whole, further strengthening its connection strength, avoiding deformation or damage of the opening side of the locking part due to excessive force during installation, effectively ensuring the normal operation of the locking function, and improving the installation stability of the toilet cover and the safety of users.

[0025] In addition, compared with the method of introducing a fixing bracket, the present utility model optimizes the structure of the locking part, overcomes the problem that the opening side is prone to bursting and deformation, does not require an additional fixing bracket, uses a larger diameter upper pull bolt, improves the mechanical strength of the connection part, and fully improves the durability and reliability of the overall structure, avoiding the risk of loosening or breaking during long-term use.

[0026] In addition, the two edges of the locking part protrude to form a limiting wall, which together with the bottom wall encloses a nut limiting groove, which not only provides a space for placing the nut, but also ensures that the nut will not move randomly when tightening the bolt by restricting the rotation of the nut, greatly improving the locking efficiency and accuracy.

[0027] In addition, the inclined guiding surface on the limiting wall enables the locking part to be inserted into the installation hole of the toilet ceramic more smoothly following the upper pull bolt, simplifies the installation steps, improves the installation efficiency, and at the same time reduces the problem of reduced connection strength that may be brought about by the introduction of additional components.

[0028] Particularly, the design of the clamping groove enables the locking part to be axially aligned with the upper pull bolt through the extrusion of the upper pull bolt and the clamping groove when the locking part rotates to be perpendicular to the upper pull bolt, so that the nut can be more easily clamped into the nut limiting groove during the process of lifting the upper pull bolt upward, greatly improving the simplicity of the fixing process of the support.

[0029] In summary, the present utility model effectively solves the problems of insufficient strength and poor connection stability of the locking part in the prior art by improving the structure of the locking part, and provides a more efficient, stable and durable solution for the installation of the toilet cover. Description of the Drawings

[0030] The accompanying drawings described herein are used to provide a further understanding of the present utility model, and constitute a part of the present utility model. The schematic embodiments of the present utility model and their descriptions are used to explain the present utility model, and do not constitute an improper limitation of the present utility model.

[0031] Among them:

[0032] Figure 1 is a schematic installation structure diagram of the first embodiment of the present utility model;

[0033] Figure 2 is a schematic overall exploded structure diagram of the first embodiment of the present utility model;

[0034] Figure 3 is one of the schematic installation structure diagrams of the first embodiment of the present utility model;

[0035] Figure 4 is the second schematic installation structure diagram of the first embodiment of the present utility model;

[0036] Figure 5 is one of the three-dimensional structure diagrams of the locking member in the first embodiment of the present utility model;

[0037] Figure 6 is the second three-dimensional structure diagram of the locking member in the first embodiment of the present utility model;

[0038] Figure 7 is the side view perspective structure diagram of the locking member in the first embodiment of the present utility model;

[0039] Figure 8 is the top view perspective structure diagram of the locking member in the first embodiment of the present utility model;

[0040] Figure 9 is the three-dimensional and partial cross-sectional structure diagram of the locking member in the first embodiment of the present utility model;

[0041] Figure 10 is the side view perspective structure diagram of the locking member in the second embodiment of the present utility model.

[0042] Reference numeral description:

[0043] 10, support; 11, adjustment hole; 12, insertion shaft; 20, upper pull bolt; 21, main body; 22, tightening end; 30, locking member; 31, side wall; 32, bottom wall; 33, connecting wall; 331, limiting edge; 332, clamping groove; 333, structural support part; 34, limiting wall; 35, nut limiting groove; 351, guiding wall surface; 36, bolt limiting groove; 37, guiding surface; 38, first arc-shaped chamfer; 39, second arc-shaped chamfer; 40, nut; 50, ceramic layer; 51, installation hole. Detailed implementation manners

[0044] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present utility model clearer and more understandable, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0045] Embodiment 1

[0046] Please refer to Figures 1 to 9 , which is a locking and fastening device for a toilet cover as the best embodiment of the present utility model, including a support 10, an upper pull bolt 20, a rotatable locking member 30 and a nut 40. In this embodiment, the outer peripheral side of the nut 40 is formed in a rectangular shape.

[0047] In the prior art, the toilet has a ceramic layer 50 for installing the support 10. A standard installation hole 51 is opened on the ceramic layer 50 for the fastening device to pass through. A waist-shaped adjustment hole 11 matching the upper pull bolt 20 is also opened on the support 10 to facilitate the penetration and locking of the upper pull bolt 20. An insertion shaft 12 for inserting into the toilet cover plate is provided at the upper end of the support 10. In order to realize the penetration of the fastening device, the size of the installation hole 51 is usually designed to be larger than the maximum outer diameter of the thread of the main body 21 of the upper pull bolt 20 and the extension distance of the locking member 30 in the width direction, so as to facilitate the locking member 30 and the nut 40 movably attached to the upper pull bolt 20 to be placed into the installation hole 51 together with the upper pull bolt 20. These are conventional components and settings and will not be elaborated here.

[0048] Specifically, the upper pull bolt 20 includes a main body 21 with an external thread and a tightening end 22 provided at the upper end of the main body 21. The tightening end 22 is in limit fit with the adjustment hole 11 of the support 10.

[0049] The locking member 30 is integrally die-cast into a U-shaped whole. The U-shaped whole includes a pair of parallel side walls 31, a U-shaped bottom wall 32 provided at one end of the side walls 31, and a flat connecting wall 33 provided at the other end of the side walls 31, wherein:

[0050] The connecting wall 33 is integrally connected to the top of one end of the side walls 31 and forms a plane with the top surfaces of the two side walls 31 that can be in flat contact with the inner wall of the ceramic installation hole 51 of the toilet;

[0051] The bottom wall 32 is integrally connected to the bottom of the other end of the side walls 31 and its U-shaped opening faces between the two side walls 31;

[0052] A limiting wall 34 protrudes from each of the two side walls 31 at the lower end of the connecting wall 33. A nut limiting groove 35 for accommodating the nut 40 and restricting its rotation is formed by enclosing between the limiting wall 34 and the bottom wall 32;

[0053] A bolt limiting groove 36 is formed by enclosing between the two side walls 31, the connecting wall 33 and the bottom wall 32, which is distributed along the length direction of the side wall 31 and through which the upward pulling bolt 20 passes.

[0054] In the structural composition of the above-mentioned locking member 30, it is integrally die-cast in a corresponding mold by melting zinc alloy material. Among them, the overall specific gravity of the bottom wall 32 is greater than that of the other end of the side wall 31. The above design is to enable the locking member 30 to automatically drop and flip to a horizontal state after following the upward pulling bolt 20 through the mounting hole 51. As Figure 3 shown, in the initial state, in order to facilitate the locking member 30 to pass through the mounting hole 51, it is restricted to a state where the whole is parallel to the upward pulling bolt 20. At this time, the upward pulling bolt 20 passes through the locking member 30 as a whole along the bolt limiting groove 36, and the nut 40 is then screwed onto the bottom of the upward pulling bolt 20 to form a limit and support for the lower end of the locking member 30, so that the whole maintains a relatively balanced state; as Figure 4 shown, after passing through the mounting hole 51, shake the upward pulling bolt 20 to make one side of the bottom wall 32 of the locking member 30 droop, and the connecting wall 33 side of the locking member 30 will flip upward, so that the connecting wall 33 side flips to the upper position. Lift the upward pulling bolt 20 to make the upper sides of the side wall 31 and the connecting wall 33 of the locking member 30 be in flat contact with the lower plane of the mounting hole 51. After the nut 40 is stuck into the nut limiting groove 35, rotate the upward pulling bolt 20. According to the friction between the upper end faces of the side wall 31 and the connecting wall 33 and the lower plane of the mounting hole 51, restrict the rotation of the nut 40, and then the main body 21 of the upward pulling bolt 20 can be rotated downward. When it is rotated to the lowest installation position of the support 10, the fixation of the support 10 can be realized. At this time, the ceramic layer 50 of the toilet bowl is limited between the support 10 and the locking member 30, and the fixation of the support 10 is completed.

[0055] Preferably, as Figure 5 、 6 shown, the side of the bottom wall 32 away from the connecting wall 33 is flush with the end face of the side wall 31, and the other side extends along the length direction of the bottom of the side wall 31 to a position close to the middle of the side wall 31.

[0056] Preferably, as Figure 7 shown, the extending distance H1 of the limiting wall 34 along the direction away from the connecting wall 33 does not exceed the extending distance H2 of the bottom of the bottom wall 32. The above design makes the overall specific gravity of the bottom wall 32 greater than that of the connecting wall 33 and the limiting wall 34, so that after the locking member 30 passes through the mounting hole 51, it can be flipped to the state where the connecting wall 33 is on the upper side, thus realizing the convenient connection between the locking member 30 and the ceramic layer 50.

[0057] Preferably, as Figure 7As shown, on the side of the limiting wall 34 away from the bottom wall 32, there is an inclined guiding surface 37 extending from the top of the side wall 31 to the bottom of the limiting wall 34. At the connection positions between the guiding surface 37 and the side wall 31 and between the guiding surface 37 and the bottom surface of the limiting wall 34, there are first arc-shaped guiding corners 38. At the contact positions between both sides of the connecting wall 33 and the side wall 31, there are second arc-shaped guiding corners 39.

[0058] In this embodiment, the guiding surface 37 enables the locking member 30 to form a guide with the opening and the inner side wall of the mounting hole 51 during the process of following the pull-up bolt 20 into the mounting hole 51, facilitating the overall positioning between the pull-up bolt 20 and the mounting hole 51, so that the process of the pull-up bolt 20 driving the nut 40 and the locking member 30 into the mounting hole 51 is more convenient and controllable.

[0059] Preferably, as Figure 7 shown, the extension distances of the limiting wall 34, the nut limiting groove 35, and the bottom wall 32 along the length direction of the side wall 31 trisect the side wall 31. Thus, the trisecting structure makes the proportion of the locking member 30 more balanced, making it more stable and controllable during rotation.

[0060] Preferably, as Figure 8 shown, in the opening area between the connecting wall 33 and the top of the side wall 31 and near the connecting wall 33, on both sides of this position, the top of the side wall 31 horizontally protrudes towards the center position to form a pair of limiting edges 331. A clamping groove 332 with a distance less than the outer diameter of the pull-up bolt 20 is formed between the two limiting edges 331. The extension distance of the limiting edges 331 along the length direction of the side wall 31 makes the pull-up bolt 20 in a position opposite to the middle of the nut limiting groove 35 when in active contact with the clamping groove 332. Thus, the design of the clamping groove 332 enables the nut limiting groove 35 of the locking member 30 to be axially aligned with the pull-up bolt 20 by the extrusion between the pull-up bolt 20 and the clamping groove 332 when the locking member 30 rotates to be perpendicular to the pull-up bolt 20. When the pull-up bolt 20 is lifted upwards, the nut 40 can be more easily caught in the nut limiting groove 35, greatly improving the simplicity of the installation and fixation process of the support 10.

[0061] Preferably, as Figure 8 、 9As shown, inside the bolt limiting groove 36 and at the top of the inner side wall of the side wall 31, there is a structural support portion 333 integrally connected to the limiting edge 331. There is an arc-shaped transition surface (not marked in the figure) between the structural support portion 333 and the inner side wall of the side wall 31. Thus, through the structural support portion 333, on the one hand, the overall structural strength of the limiting edge 331 can be further enhanced, and on the other hand, it can also serve as the rotation fulcrum of the locking member 30. After the locking member 30 passes through the mounting hole 51, the bolt 20 is jolted and pulled upwards, causing the side of the locking member 30 facing the bottom wall 32 to flip. At this time, as the protruding part inside the bolt limiting groove 36, the structural support portion 333 first contacts the pulled-up bolt 20, thus forming the support point for the locking member 30 to rotate around the pulled-up bolt 20. And due to the connection and transition relationship between the structural support portion 333 and the limiting edge 331, after the locking member 30 rotates completely, the pulled-up bolt 20 will be exactly positioned at the position where it contacts the edge of the limiting edge 331 (i.e., the opening position of the clamping groove 332). At this time, the pulled-up bolt 20 is exactly in the middle position close to the nut limiting groove 35. After the locking member 30 slides down along the pulled-up bolt 20, the nut 40 can be conveniently aligned with the nut limiting groove 35 and snapped into the nut limiting groove 35, facilitating the subsequent installation and fixing process.

[0062] Embodiment 2

[0063] Please refer to Figure 10 , which is a locking and fastening device for a toilet lid as the second embodiment of the present invention. The difference from the first embodiment is as follows:

[0064] In order to further facilitate the alignment and embedding process of the nut 40 with the nut limiting groove 35, inclined guiding wall surfaces 351 can be further provided on the limiting walls 34 and the bottom wall 32 on both sides of the nut limiting groove 35.

[0065] Advantages of the present invention:

[0066] Compared with the original stamping method, the U-shaped integral locking member 30 formed by integral die-casting in the present invention adds an integrally die-cast connecting wall 33 on the opening side of the side wall 31, so that the side walls 31 on both sides of the opening form an integral body, further enhancing its connection strength, avoiding deformation or damage of the opening side of the locking member 30 due to excessive force during the installation process, effectively ensuring the normal operation of the locking function, and improving the installation stability of the toilet cover and the safety of user use.

[0067] In addition, compared with the method of introducing a fixing frame, the present invention optimizes the structure of the locking member 30, overcomes the problem that the opening side is prone to burst and deform, does not need to introduce an additional fixing frame, uses a larger-diameter pulled-up bolt 20, improves the mechanical strength of the connection part, fully enhances the durability and reliability of its overall structure, and avoids the risk of loosening or breaking during long-term use.

[0068] In addition, the two edges of the locking piece 30 protrude to form a limiting wall 34, which together with the bottom wall 32 encloses a nut limiting groove 35, which not only provides a space for placing the nut 40, but also limits the rotation of the nut 40, ensuring that the nut 40 will not move at will when tightening the bolt, thereby greatly improving the locking efficiency and accuracy.

[0069] In addition, the inclined guide surface 37 on the limiting wall 34 allows the locking member 30 to follow the pull-up bolt 20 and be inserted into the installation hole 51 of the toilet ceramic more smoothly, which simplifies the installation steps, improves the installation efficiency, and also reduces the problem of reduced connection strength caused by the introduction of additional components.

[0070] In particular, the design of the locking groove 332 allows the nut limiting groove 35 of the locking member 30 to be axially aligned with the upper bolt 20 through the squeezing of the upper bolt 20 and the locking groove 332 when the locking member 30 is rotated to be perpendicular to the upper bolt 20, so that when the upper bolt 20 is lifted, the nut 40 can be more easily inserted into the nut limiting groove 35, which greatly improves the ease of installation and fixing of the support 10.

[0071] In summary, the utility model improves the structure of the locking piece 30, effectively solving the problems of insufficient strength and poor connection stability of the locking piece 30 in the prior art, and provides a more efficient, stable and durable solution for the installation of the toilet cover.

[0072] The utility model is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the utility model is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the utility model, or the concept and technical solution of the utility model are directly applied to other occasions without improvement, they are all within the protection scope of the utility model.

Claims

1. A toilet lid locking and fastening device, characterized in that: The invention comprises a support (10), a pull-up bolt (20), a reversible locking member (30) and a nut (40), wherein the locking member (30) is formed into a U-shaped integral body by integral die-casting, and the U-shaped integral body comprises a pair of parallel side walls (31), a U-shaped bottom wall (32) arranged at one end of the side wall (31), and a plane connecting wall (33) arranged at the other end of the side wall (31), wherein: The connecting wall (33) is integrally connected to the top of one end of the side wall (31) and forms a plane with the top surfaces of the two side walls (31) that can be in smooth contact with the inner wall of the ceramic installation hole (51) of the toilet; The bottom wall (32) is integrally connected to the bottom of the other end of the side wall (31) and its U-shaped opening faces between the two side walls (31); The two side walls (31) protrude from the lower end of the connecting wall (33) to form a limiting wall (34), and the limiting wall (34) and the bottom wall (32) enclose a nut limiting groove (35) for accommodating a nut (40) and limiting its rotation; The two side walls (31), the connecting wall (33) and the bottom wall (32) enclose a bolt limiting groove (36) distributed along the length direction of the side wall (31) and for the upper pull bolt (20) to pass through.

2. A toilet cover locking and fastening device according to claim 1, characterized in that: The side of the bottom wall (32) away from the connecting wall (33) is flush with the end surface of the side wall (31), and the other side thereof extends along the length direction of the bottom of the side wall (31) to a position close to the middle of the side wall (31).

3. A toilet cover locking and fastening device according to claim 2, characterized in that: The extension distance of the limiting wall (34) in the direction away from the connecting wall (33) does not exceed the bottom of the bottom wall (32).

4. A toilet cover locking and fastening device according to claim 3, characterized in that: A side of the limiting wall (34) away from the bottom wall (32) is provided with an inclined guide surface (37) extending along the top of the side wall (31) to the bottom of the limiting wall (34).

5. A toilet cover locking and fastening device according to claim 4, characterized in that: A first arc-shaped chamfer (38) is provided at the connection position between the guide surface (37) and the side wall (31) and at the connection position between the guide surface (37) and the bottom surface of the limiting wall (34).

6. A toilet cover locking and fastening device according to claim 5, characterized in that: Second arc-shaped chamfers (39) are provided at positions on both sides of the connecting wall (33) where the connecting wall (33) contacts the side wall (31).

7. A toilet lid locking and fastening device according to claim 2, characterized in that: The extending distance of the limiting wall (34), the nut limiting groove (35) and the bottom wall (32) along the length direction of the side wall (31) enables the limiting wall (34), the nut limiting groove (35) and the bottom wall (32) to divide the side wall (31) into three equal parts.

8. The toilet cover locking and fastening device according to claim 1, characterized in that: The opening area between the connecting wall (33) and the top of the side wall (31) is located close to the connecting wall (33), and the tops of the side walls (31) on both sides of the position protrude horizontally toward the center position to form a pair of limiting edges (331), and a positioning groove (332) with a spacing smaller than the outer diameter of the upper pull bolt (20) is formed between the two limiting edges (331).

9. A toilet cover locking and fastening device according to claim 8, characterized in that: The extension distance of the limiting edge (331) along the length direction of the side wall (31) enables the upper pull bolt (20) to be located opposite to the middle of the nut limiting groove (35) when it is in active contact with the locking groove (332).

10. A toilet cover locking and fastening device according to claim 8, characterized in that: A structural support portion (333) integrally connected to the limiting edge (331) is provided in the bolt limiting groove (36) and at the top of the inner wall of the side wall (31), and an arc-shaped transition surface is provided between the structural support portion (333) and the inner wall of the side wall (31).

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