Outdoor high-brightness liquid crystal display sealing structure with demisting and moisture-proof functions

The outdoor LCD screen, with its double-layer shell and modular defogging design, solves the problems of poor sealing performance and the shortcomings of traditional defogging technology. It achieves efficient moisture-proof defogging, convenient disassembly and assembly, and stable operation, improving the reliability and clarity of the screen and extending its service life.

CN224190360UActive Publication Date: 2026-05-01SHENZHEN SENDAYUANSHANG TECHNOLOGY CO LTD
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Utility models(China)
Current Assignee / Owner
SHENZHEN SENDAYUANSHANG TECHNOLOGY CO LTD
Filing Date
2025-06-24
Publication Date
2026-05-01

AI Technical Summary

Technical Problem

Existing outdoor LCD screens have insufficient sealing performance under extreme weather conditions, making them susceptible to moisture intrusion, which can lead to short circuits and component damage. Furthermore, traditional defogging technologies are energy-intensive, have uneven heating, and are difficult to maintain, making it difficult to achieve long-term stable operation.

Method used

It adopts a double-layer shell design, combined with multiple seals and a modular defogging structure. It uses air ducts and hot air modules to generate uniform hot airflow to prevent water vapor condensation. It can be easily disassembled and assembled by rotating rods and fixing blocks, and the air ducts and shells slide and snap together for easy maintenance.

Benefits of technology

It effectively prevents moisture penetration, achieves efficient moisture-proof and defogging, reduces equipment maintenance costs, improves the reliability and clarity of the display screen in complex environments, and extends its service life.

✦ Generated by Eureka AI based on patent content.

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Abstract

The utility model relates to the field of liquid crystal display, and discloses an outdoor high-brightness liquid crystal display sealing structure with demisting and moisture-proof functions, which comprises a display screen, a left shell structure and a right shell structure, and the left shell structure and the right shell structure are assembled on the outer side of the display screen. The display screen comprises a left shell structure, a right shell structure, a plurality of groups of fixed clamping structures arranged between the left shell structure and the right shell structure and used for fixedly assembling the left shell structure and the right shell structure, a glass plate arranged between the left shell structure and the right shell structure and corresponding to a display surface of the display screen, and a demisting structure arranged on the left shell structure and the right shell structure, one face, corresponding to the display face of the display screen, of the left shell structure and one face, corresponding to the display face of the display screen, of the right shell structure are each provided with a demisting structure, and through the double-layer shell splicing, multi-sealing and modular demisting design, efficient damp-proof demisting, even heating, convenient and fast disassembly and assembly and stable operation are achieved.
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Description

A sealing structure for outdoor high-brightness LCD displays with defogging and moisture-proof properties. Technical Field

[0001] This utility model relates to the field of liquid crystal displays, specifically a sealing structure for outdoor high-brightness liquid crystal displays with defogging and moisture-proof properties. Background Technology

[0002] With the rapid development of intelligent transportation, outdoor advertising, and public information display, the application of outdoor high-brightness LCD display equipment is becoming increasingly widespread. However, in actual use, the complex and ever-changing outdoor environmental conditions, such as high humidity, temperature differences, and rain, have seriously affected the performance and lifespan of LCD screens.

[0003] Currently, most outdoor LCD displays on the market use a single sealing strip or a simple shell design, resulting in insufficient sealing performance under extreme weather conditions. This makes it easy for moisture to seep in, causing short circuits and component damage. When there are large temperature differences between day and night, condensation easily forms on the screen surface, affecting the display effect. Traditional defogging technology mainly relies on heating wires, which suffers from high energy consumption, uneven heating, and accelerated aging. Mechanical defogging devices are complex in structure, difficult to maintain, and prone to failure in low-temperature environments, making it difficult to achieve long-term stable operation of outdoor equipment. Therefore, we propose a sealing structure for outdoor high-brightness LCD displays that has defogging and moisture-proof properties. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a sealing structure for outdoor high-brightness LCD displays that features defogging and moisture protection, thus solving the aforementioned problems.

[0005] To achieve the above-mentioned objectives, this utility model provides the following technical solution: an outdoor high-brightness liquid crystal display sealing structure with defogging and moisture-proof properties, including a display screen, and further comprising:

[0006] The left and right shell structures are assembled on the outside of the display screen.

[0007] Multiple sets of fixing snap-fit ​​structures are disposed between the left shell structure and the right shell structure for fixing the left shell structure and the right shell structure together.

[0008] A glass plate is disposed between the left shell structure and the right shell structure, and the glass plate corresponds to the display surface of the display screen;

[0009] The defogging structures are provided on the left and right shell structures, and each of the left and right shell structures has a set of defogging structures on the side corresponding to the display surface of the display screen.

[0010] Preferably, the left shell structure includes a left outer shell and a slot. The left outer shell is a box-shaped structure and is fitted onto the left side of the display screen. The open end of the left outer shell has a slot, and the side of the left outer shell corresponding to the display surface of the display screen has a display hole.

[0011] Preferably, the right shell structure includes a right outer shell and a insert. The right outer shell is a box-shaped structure and is fitted onto the right side of the display screen. The open end of the right outer shell is fixedly connected to the insert, which corresponds to the slot and is inserted into the slot. The side of the right outer shell corresponding to the display surface of the display screen has a display hole.

[0012] Preferably, the sidewall of the slot that is in contact with the insert has a plurality of equally spaced square slots extending outward from the left outer shell, and each square slot has a strip-shaped slot extending outward from the left outer shell, the strip-shaped slot penetrating to the outside of the left outer shell.

[0013] Preferably, the side of the insert opposite to the square groove has a plurality of equally spaced strip holes, the number and distribution of which correspond to the square groove.

[0014] Preferably, the fixed snap-fit ​​structure includes a rotating rod and a fixed block. One end of the rotating rod is fixedly connected to the fixed block, which corresponds to the strip groove. The rotating rod is inserted into the strip groove and the square groove, and the fixed block is inserted into the strip hole. Each strip groove and strip hole has a set of fixed snap-fit ​​structures inserted into it.

[0015] Preferably, the opening ends of the left and right outer shells are provided with slots on the side with the display holes. The slots pass through the display holes of the left and right outer shells, and a glass plate is inserted into the slots of the left and right outer shells.

[0016] Preferably, the side of the card slot that is in contact with the front of the glass plate has a sealing groove, and a sealing strip is snapped into the sealing groove.

[0017] Preferably, the defogging structure includes an air duct, an exhaust port, and a hot air module. The air duct is a hollow structure with a C-shaped frame. Multiple equidistant exhaust ports are opened through the inner ring surface of the air duct. A hot air module is installed inside the air duct. One side of the air duct is fitted and corresponds to the front of the left and right outer shells.

[0018] Preferably, the left and right outer shells have trapezoidal protrusions connected to the upper and lower sides of the side that fits with the air duct. The short side of the trapezoidal protrusions is fixedly connected to the left and right outer shells. The side of the air duct corresponding to the trapezoidal protrusions has trapezoidal grooves on both sides of the symmetrical side. The trapezoidal grooves correspond to the trapezoidal protrusions and are slidably engaged with them.

[0019] Compared with the prior art, this utility model provides a sealing structure for outdoor high-brightness liquid crystal displays with defogging and moisture-proof properties, which has the following beneficial effects:

[0020] This outdoor high-brightness LCD display sealing structure, featuring defogging and moisture protection, effectively solves the problems of poor sealing performance, easy fogging due to moisture, and inconvenient maintenance of traditional outdoor displays through double-layer shell splicing, multi-seal and modular defogging design. It achieves efficient moisture and fog protection, uniform heating, convenient disassembly and assembly, and stable operation, significantly improving the reliability, display clarity and service life of outdoor displays in complex environments, and reducing equipment maintenance costs and energy consumption. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the structure of this utility model;

[0022] Figure 2 is an exploded view of the structure of this utility model;

[0023] Figure 3 is a cross-sectional schematic diagram of the left and right shell structures of this utility model;

[0024] Figure 4 is a magnified view of part A in Figure 3;

[0025] Figure 5 is a magnified view of part B in Figure 3.

[0026] In the diagram: 1. Left outer shell; 2. Glass plate; 3. Air duct; 4. Right outer shell; 5. Exhaust vent; 6. Rotating rod; 7. Hot air module; 8. Trapezoidal protrusion; 9. Display screen; 10. Strip groove; 11. Insert strip; 12. Strip hole; 13. Slot; 14. Sealing strip; 15. Trapezoidal groove; 16. Sealing groove; 17. Slot; 18. Square groove; 19. Fixing block. Detailed Implementation

[0027] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0028] Please refer to Figures 1-5. An outdoor high-brightness LCD display sealing structure with defogging and moisture-proof features includes a display screen 9, and further includes:

[0029] The left and right shell structures are assembled on the outside of the display screen 9.

[0030] Multiple sets of fixing snap-fit ​​structures are set between the left shell structure and the right shell structure to fix the left shell structure and the right shell structure in place.

[0031] The glass plate 2 is disposed between the left shell structure and the right shell structure, and the glass plate 2 corresponds to the display surface of the display screen 9;

[0032] Defogging structures are provided on the left and right shell structures, and a set of defogging structures is provided on the side of the left and right shell structures corresponding to the display surface of the display screen 9.

[0033] Furthermore, the left shell structure includes a left outer shell 1 and a slot 17. The left outer shell 1 is a box-shaped structure. The left outer shell 1 is fitted onto the left side of the display screen 9. The slot 17 is provided at the open end of the left outer shell 1. A display hole is provided on the side of the left outer shell 1 that corresponds to the display surface of the display screen 9. The left outer shell 1 is used to protect the left side of the display screen 9, and the slot 17 is used to install the right shell structure.

[0034] Furthermore, the right shell structure includes a right outer shell 4 and a plug 11. The right outer shell 4 is a box-shaped structure. The right outer shell 4 is fitted onto the right side of the display screen 9. The plug 11 is fixedly connected to the open end of the right outer shell 4. The plug 11 corresponds to the slot 17 and is inserted into the slot 17. The side of the right outer shell 4 that corresponds to the display surface of the display screen 9 has a display hole. The right outer shell 4 is used to protect the right side of the display screen 9. The plug 11 and the slot 17 assemble the left outer shell 1 and the right outer shell 4 into a whole.

[0035] Furthermore, the side wall of the slot 17 that is in contact with the insert 11 extends outward to the left outer shell 1 and is provided with a plurality of equally spaced square slots 18. Each square slot 18 extends outward to the left outer shell 1 and is provided with a strip groove 10. The strip groove 10 extends through to the outside of the left outer shell 1. The square slots 18 and the strip groove 10 are used to install and fix the snap-fit ​​structure.

[0036] Furthermore, the side of the insert 11 opposite to the square groove 18 is provided with a plurality of equally spaced strip holes 12. The number and distribution of the strip holes 12 correspond to the square groove 18. The strip holes 12 are used to snap and fix the snap-fit ​​structure to fix the insert 11 and the slot 17.

[0037] Furthermore, the fixed snap-fit ​​structure includes a rotating rod 6 and a fixing block 19. One end of the rotating rod 6 is fixedly connected to the fixing block 19, which corresponds to the strip groove 10. The rotating rod 6 is inserted into the strip groove 10 and the square groove 18, and the fixing block 19 is inserted into the strip hole 12. Each strip groove 10 and strip hole 12 has a set of fixed snap-fit ​​structures inserted into it. The fixing block 19 is inserted into the strip hole 12 to fix the insert 11 and the slot 17. By operating the rotating rod 6, the fixing block 19 is moved out of the strip hole 12 and into the square groove 18. The fixing block 19 is rotated and snapped into the square groove 18, so the left outer shell 1 and the right outer shell 4 can be easily disassembled.

[0038] Furthermore, both the left outer shell 1 and the right outer shell 4 have slots 13 on the side with the display hole at their open ends. The slots 13 pass through the display holes of the left outer shell 1 and the right outer shell 4. A glass plate 2 is inserted into the slots 13 of the left outer shell 1 and the right outer shell 4. The slots 13 are used to install the right outer shell 4.

[0039] Furthermore, a sealing groove 16 is provided on the side of the slot 13 that is in contact with the front of the glass plate 2. A sealing strip 14 is snapped into the sealing groove 16. The sealing groove 16 is used to install the sealing strip 14, and the sealing strip 14 is used to absorb water and prevent moisture.

[0040] Furthermore, the defogging structure includes an air duct 3, an exhaust port 5, and a hot air module 7. The air duct 3 is a hollow structure with a C-shaped frame. Multiple equidistant exhaust ports 5 are opened through the inner ring surface of the air duct 3. The hot air module 7 is installed inside the air duct 3. One side of the air duct 3 is attached to the front of the left outer shell 1 and the right outer shell 4. The air duct 3 is used to guide the direction of the hot air flow generated by the hot air module 7. The exhaust port 5 is used to blow the hot air flow in the air duct 3 evenly onto the surface of the glass plate 2.

[0041] Furthermore, trapezoidal protrusions 8 are connected to the upper and lower sides of the side of the left outer shell 1 and the right outer shell 4 that are in contact with the air duct 3. The short side of the trapezoidal protrusions 8 is fixedly connected to the left outer shell 1 and the right outer shell 4. Trapezoidal grooves 15 are opened on the two symmetrical sides of the side of the air duct 3 corresponding to the trapezoidal protrusions 8. The trapezoidal grooves 15 and the trapezoidal protrusions 8 are slidably engaged. The trapezoidal protrusions 8 and the trapezoidal grooves 15 are used to install the air duct 3 on the left outer shell 1 and the right outer shell 4, and are convenient for disassembly and assembly.

[0042] Structural Description:

[0043] Left outer shell 1: Box-shaped structure, fitted onto the left side of display screen 9, with a slot 17 at the open end and a display hole on the side corresponding to the display surface, used to protect the left side of the display screen and provide an installation interface for the right shell structure;

[0044] Glass plate 2: Flat plate, inserted into the slot 13 at the opening end of the left outer shell 1 and the right outer shell 4, corresponding to the display surface of the display screen 9, protecting the surface of the display screen, and at the same time cooperating with the sealing strip 14 to achieve sealing;

[0045] Air duct 3: The hollow structure of the C-shaped frame is attached to the front of the left and right outer shells on one side. Multiple exhaust holes 5 are opened on the inner ring surface. The hot air module 7 is installed inside to guide the hot air flow and blow it evenly onto the glass plate 2 to play a defogging role.

[0046] Right outer shell 4: Box-shaped structure, fitted onto the right side of display screen 9, with a fixed connecting strip 11 at the open end, a display hole on the side corresponding to the display surface, protecting the right side of the display screen, and spliced ​​together with the left outer shell 1 to form a whole;

[0047] Exhaust vent 5: Multiple equidistant circular holes are opened on the inner annular surface of the air duct 3 to evenly blow the hot airflow in the air duct 3 onto the surface of the glass plate 2 to achieve defogging;

[0048] Rotating rod 6: A rod-shaped structure with one end connected to the fixing block 19. It is inserted into the strip groove 10 and the square groove 18. By rotating, the fixing block 19 can be engaged or disengaged from the strip hole 12. It is used to fix and disassemble the left and right outer shells.

[0049] Hot air module 7: Installed inside air duct 3, its specific shape depends on the actual design. It generates hot airflow during operation to provide a heat source for demisting.

[0050] Trapezoidal protrusion 8: It is trapezoidal, with its short side fixedly connected to the left outer shell 1 and the right outer shell 4, and correspondingly engaged with the trapezoidal groove 15 of the air duct 3, which facilitates the installation and disassembly of the air duct 3.

[0051] Display screen 9: The core display component, the specific shape and size of which depend on product requirements, is used to display content;

[0052] Strip groove 10: It is formed on the left outer shell 1, extends from the square groove 18 to the outside of the left outer shell 1 and passes through it, and is used to insert the rotating rod 6, and cooperate with the fixed snap-fit ​​structure to realize the splicing and fixing of the outer shell;

[0053] Insert 11: A long strip structure, fixed at the opening end of the right outer shell 4, corresponding to the slot 17 of the left outer shell 1, inserted into the slot 17 to achieve the initial splicing of the left and right outer shells;

[0054] Strip-shaped hole 12: It is opened through the insert 11 and is distributed correspondingly to the square groove 18. It is used to snap the fixing block 19 and fix the insert 11 and the slot 17.

[0055] Card slot 13: It is opened on the side with the display hole at the opening end of the left outer shell 1 and the right outer shell 4, and passes through the display hole for inserting the glass plate 2;

[0056] Sealing strip 14: A strip-shaped structure that snaps into the sealing groove 16 and fits tightly against the glass plate 2, serving to absorb water and prevent moisture, and to seal the glass plate 2, preventing external moisture from entering.

[0057] Trapezoidal groove 15: It is opened on both sides of the air duct 3, corresponding to the trapezoidal protrusion 8, and the air duct 3 is connected and disassembled with the left and right outer shells by sliding snap-fit;

[0058] Sealing groove 16: A groove is formed on the side of the card slot 13 that is in contact with the front of the glass plate 2, and is used to install the sealing strip 14;

[0059] Slot 17: It is opened at the left outer shell 1 and corresponds to the insert 11. It is used to insert the insert 11 to realize the splicing of the left and right outer shells;

[0060] Square groove 18: It is formed on the side wall of slot 17, extends to the outside of the left outer shell 1, and communicates with strip groove 10 for installing and fixing snap-fit ​​structure;

[0061] Fixed block 19: Block structure, fixedly connected to one end of rotating rod 6, corresponding to strip groove 10, can be inserted into strip hole 12 to fix left and right outer shell, or can be rotated in square groove 18 to disassemble outer shell.

[0062] Working Principle: The left outer shell 1 and right outer shell 4 are respectively fitted onto the left and right sides of the display screen 9. Initial assembly is achieved through the insertion strip 11 and slot 17. Then, the rotating rod 6 of the fixing and snapping structure is inserted into the strip groove 10 and square groove 18. Rotating the rotating rod 6 causes the fixing block 19 to snap into the strip hole 12 of the insertion strip 11, thus firmly assembling the left and right outer shells into a single unit, providing stable external protection for the display screen 9. A glass plate 2 is inserted into the slot 13 at the opening end of the outer shell. The glass plate 2 corresponds to the display surface of the display screen 9, protecting the screen. Simultaneously, the sealing groove 16 in the slot 13 engages with the sealing strip 14, which tightly adheres to the glass plate 2, forming an effective sealing barrier to prevent external rainwater and moisture from entering the display screen, avoiding short circuits or component damage caused by moisture. When fogging occurs on the display screen surface, the defogging structure begins to function, and the hot air module 7 in the air duct 3 is activated. Guided by the air duct 3, the generated hot airflow is evenly blown onto the surface of the glass plate 2 through multiple exhaust holes 5 on the inner ring surface. The hot airflow can raise the temperature of the glass plate 2 to be higher than the ambient dew point temperature, thereby preventing water vapor from condensing into fog on the surface of the glass plate 2. At the same time, the water fog that has already formed evaporates and dissipates quickly under the action of the hot airflow, ensuring clear display of the screen. In addition, the air duct 3 is slidably engaged with the left and right outer shells through trapezoidal protrusions 8 and trapezoidal grooves 15. This design not only facilitates the installation of the air duct 3, but also allows for quick disassembly of the air duct 3 for inspection or replacement when the hot air module 7 malfunctions or needs maintenance, ensuring long-term stable operation of the defogging function. In terms of equipment maintenance, by operating the rotating rod 6, the fixing block 19 is moved out of the strip hole 12 and rotated into the square groove 18, which can easily disassemble the left outer shell 1 and the right outer shell 4 without damaging the overall sealing structure, making it convenient to inspect or replace parts of the display screen 9.

[0063] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A sealing structure for an outdoor high-brightness liquid crystal display with defogging and moisture-proof properties, comprising a display screen (9), characterized in that, Also includes: A left shell structure and a right shell structure are assembled on the outside of the display screen (9); multiple sets of fixing and snap-fit ​​structures are set between the left shell structure and the right shell structure for fixing the assembled left shell structure and the right shell structure; a glass plate (2) is set between the left shell structure and the right shell structure, and the glass plate (2) corresponds to the display surface of the display screen (9); a defogging structure is set on the left shell structure and the right shell structure, and a set of defogging structure is set on the side of the left shell structure and the right shell structure corresponding to the display surface of the display screen (9).

2. The outdoor high-brightness liquid crystal display sealing structure with defogging and moisture-proof properties according to claim 1, characterized in that, The left shell structure includes a left outer shell (1) and a slot (17). The left outer shell (1) is a box-shaped structure. The left outer shell (1) is fitted onto the left side of the display screen (9). The slot (17) is provided at the open end of the left outer shell (1). A display hole is provided on the side of the left outer shell (1) that corresponds to the display surface of the display screen (9).

3. The sealing structure for an outdoor high-brightness liquid crystal display with defogging and moisture-proof properties according to claim 2, characterized in that, The right shell structure includes a right outer shell (4) and a plug (11). The right outer shell (4) is a box-shaped structure. The right outer shell (4) is fitted onto the right side of the display screen (9). The plug (11) is fixedly connected to the open end of the right outer shell (4). The plug (11) corresponds to the slot (17). The plug (11) is inserted into the slot (17). The side of the right outer shell (4) that corresponds to the display surface of the display screen (9) has a display hole.

4. The outdoor high-brightness liquid crystal display sealing structure with defogging and moisture-proof properties according to claim 2, characterized in that, The side wall of the slot (17) that is in contact with the insert (11) extends outward to the left outer shell (1) with a plurality of equally spaced square slots (18). Each square slot (18) extending outward to the left outer shell (1) is provided with a strip slot (10). The strip slot (10) extends through to the outside of the left outer shell (1).

5. The outdoor high-brightness liquid crystal display sealing structure with defogging and moisture-proof properties according to claim 4, characterized in that, The insert (11) has multiple equally spaced strip holes (12) through it on the side opposite to the square groove (18), and the number and distribution of the strip holes (12) correspond to the square groove (18).

6. The outdoor high-brightness liquid crystal display sealing structure with defogging and moisture-proof properties according to claim 5, characterized in that, The fixed snap-fit ​​structure includes a rotating rod (6) and a fixing block (19). One end of the rotating rod (6) is fixedly connected to the fixing block (19). The fixing block (19) corresponds to the strip groove (10). The rotating rod (6) is inserted into the strip groove (10) and the square groove (18). The fixing block (19) is inserted into the strip hole (12). A set of fixed snap-fit ​​structures is inserted into each strip groove (10) and strip hole (12).

7. The outdoor high-brightness liquid crystal display sealing structure with defogging and moisture-proof properties according to claim 3, characterized in that, The left outer shell (1) and the right outer shell (4) each have a slot (13) on the side with the display hole. The slot (13) passes through the display hole of the left outer shell (1) and the right outer shell (4). A glass plate (2) is inserted into the slot (13) of the left outer shell (1) and the right outer shell (4).

8. The sealing structure for an outdoor high-brightness liquid crystal display with defogging and moisture-proof properties according to claim 7, characterized in that, The card slot (13) has a sealing groove (16) on the side that is in contact with the front of the glass plate (2), and a sealing strip (14) is snapped into the sealing groove (16).

9. The outdoor high-brightness liquid crystal display sealing structure with defogging and moisture-proof properties according to claim 3, characterized in that, The defogging structure includes an air duct (3), an exhaust port (5), and a hot air module (7). The air duct (3) is a hollow structure with a C-shaped frame. Multiple equidistant exhaust ports (5) are opened through the inner ring surface of the air duct (3). The hot air module (7) is installed inside the air duct (3). One side of the air duct (3) is attached to the front of the left outer shell (1) and the right outer shell (4).

10. The outdoor high-brightness liquid crystal display sealing structure with defogging and moisture-proof properties according to claim 9, characterized in that, The left outer shell (1) and the right outer shell (4) are fitted with trapezoidal protrusions (8) on both the upper and lower sides of the side that is in contact with the air duct (3). The short side of the trapezoidal protrusions (8) is fixedly connected to the left outer shell (1) and the right outer shell (4). The side of the air duct (3) corresponding to the trapezoidal protrusions (8) is provided with trapezoidal grooves (15) on both sides of the symmetrical side. The trapezoidal grooves (15) correspond to the trapezoidal protrusions (8) and are slidably engaged with the trapezoidal protrusions (8).