Three-proof display screen with good anti-vibration performance

Abstract

The utility model belongs to display screen technical field, and disclose a three -proof display screen that anti -vibration performance is good, aims at solving the problem that the display screen of monitoring near powder unloading equipment is easy to be damaged because of low frequency vibration. It includes metal shell, transparent resin front protective layer, branch, detachable base and damping protection structure. Metal shell adopts anticorrosive alloy to make, inside cover flexible silica rubber inner protection part and wrap display screen panel, and transparent resin front protective layer forms secondary protection with waterproof glue liquid through staggered table clamping, realizes waterproof and dustproof. Damping protection structure is located in the middle of the branch, is composed of disc -shaped elastic member and rubber vibration isolation ring, cooperates with anti -drop pole and anti -drop groove limit, can absorb and dissipate low frequency vibration energy, bears and damps simultaneously. The base can adapt to different installation environment, and is stably connected through bolt. The display screen can adapt to high dust, many vibration powder unloading scene, long service life, can guarantee equipment operation monitoring stability.

Description

Technical Field

[0001] This utility model relates to the field of display screen technology, specifically a ruggedized display screen with good vibration resistance. Background Technology

[0002] In industrial production, powder feeding equipment is one of the core pieces of equipment in industries such as grain processing, chemical production, and building materials manufacturing. Its feeding efficiency and stability directly determine the operational quality of the entire production line. To monitor key parameters such as equipment speed, feeding volume, and blockage warnings in real time, the industry commonly installs dedicated monitoring displays near powder feeding equipment. Through data visualization, dynamic control of equipment operation status is achieved, ensuring the continuity and safety of the production process.

[0003] However, during the conveying and feeding process, powder materials are prone to accumulation and blockage in key areas such as hoppers and conveying pipelines due to differences in adsorption, friction, and flowability between particles. Once blockage occurs, it not only leads to interrupted feeding but can also trigger a chain reaction of malfunctions, such as equipment overload and powder deterioration due to moisture, severely impacting production efficiency. To address this issue, the mainstream technical solution currently involves installing vibrators on the outer wall of the hopper or pipeline of the powder feeding equipment. The periodic vibrations generated by the vibrators disrupt the powder's accumulation structure, promoting smooth powder flow and effectively preventing and mitigating blockage problems.

[0004] However, while the aforementioned anti-clogging solutions ensure smooth material feeding, they also pose a significant challenge to the stable operation of the display screen. Because the vibrator generates low-frequency vibrations typically between 10-50Hz, and powder feeding equipment is mostly a rigid structure made of metal, vibration energy is rapidly transmitted to the nearby display screen through the equipment body, mounting brackets, and surrounding ground. Existing ruggedized display screens for monitoring primarily focus on basic display functions and durability, without specific optimization for low-frequency vibration environments: their internal circuit boards, component solder joints, cable interfaces, and other circuit structures generally use conventional fixing methods.

[0005] Under prolonged low-frequency vibration, the internal circuit structure of the display screen will continuously endure periodic vibration stress. On the one hand, the solder joints between the circuit board and components are prone to fatigue damage due to repeated micro-displacements, gradually leading to poor soldering and desoldering, resulting in poor circuit contact. This manifests as screen flickering, garbled data, or even a black screen, resulting in a short service life and potentially affecting production operations. Utility Model Content

[0006] To address the shortcomings of existing technologies, this utility model provides a three-proof display screen with good vibration resistance, thereby solving the problems mentioned in the background art, such as the reduced service life of the display screen caused by vibration-based anti-clogging in some powder feeding equipment.

[0007] To achieve the above-mentioned objectives, this utility model provides the following technical solution: a ruggedized display screen with good vibration resistance, comprising: A metal casing, comprising a front casing and a rear casing, with a display panel disposed between the front casing and the rear casing; A transparent resin front protective layer is disposed on the front shell corresponding to the front side of the display panel; Support rod, the support rod being disposed at the bottom of the front housing; At least one set of bases, the bases having multiple sets of fixing holes, the bases having plug rods, the support rods having plug slots corresponding to the plug rods, the plug rods and plug slots having through fixing screw holes, and the bases being detachably fixed to the bottom of the support rods by bolts; A vibration damping and protection structure is located in the middle of the support rod, dividing the support rod into upper and lower sections. The vibration damping structure includes a disc-shaped spring and a rubber vibration isolation ring. A small protrusion is provided at the top of the lower section of the support rod, and a mating groove is provided at the bottom of the upper section of the support rod. The small protrusion is inserted into the mating groove, and a disc-shaped spring is provided between the small protrusion and the mating groove. A rubber vibration isolation ring is provided on the outside of the small protrusion, and the two sides of the rubber vibration isolation ring abut against the upper and lower ends of the support rod, respectively. Multiple anti-detachment rods are provided at the bottom of the upper section of the support rod, and an anti-detachment groove corresponding to the anti-detachment rod is opened in the lower section of the support rod. The anti-detachment rod is snapped into the anti-detachment groove.

[0008] Preferably, the transparent resin front protective layer has a mating stagger on the side edge opposite to the display panel, and the inner wall of the front shell has a stagger groove corresponding to the transparent resin front protective layer. The mating stagger and the stagger groove are engaged, and the gap between the mating stagger and the stagger groove is filled with waterproof adhesive.

[0009] Preferably, the rear shell has a rear shell flange on the side adjacent to the front shell, and the rear shell and the front shell are fixedly connected by adhesive or bolts.

[0010] Preferably, a waterproof sealing strip is provided on the front shell at the protruding edge corresponding to the rear shell.

[0011] Preferably, the outer side of the display panel is fitted with an inner protective component, which is made of flexible silicone rubber.

[0012] Preferably, the lower section of the support rod is provided with a pressure balance air hole that communicates with the anti-detachment groove.

[0013] Compared with the prior art, this utility model provides a ruggedized display screen with good vibration resistance, and has the following beneficial effects: This ruggedized display screen boasts excellent vibration resistance and is equipped with a metal casing, display panel, transparent resin front protective layer, support rod, base, and vibration damping protection structure. The metal casing provides strong protection for the display panel, and the base can be replaced with a shape suitable for the installation environment. The entire display screen can be bolted to be installed near industrial equipment. The vibration damping protection structure absorbs and reduces low-frequency vibrations generated by equipment operation, significantly extending the lifespan of the display screen. It is waterproof, dustproof, drop-proof, and vibration-resistant, making it suitable for industrial environments with high dust levels or long-term vibration, especially for monitoring powder feeding equipment. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a schematic diagram of the metal shell structure of this utility model; Figure 3 This is an exploded view of the overall structure of this utility model; Figure 4 This is a schematic diagram of the support rod and base structure of this utility model; Figure 5 This is a schematic diagram of the vibration reduction and protection structure of this utility model; Figure 6 This is a schematic diagram of the vibration reduction and protection structure of this utility model.

[0015] In the diagram: 1. Metal outer shell; 2. Front shell; 3. Rear shell; 4. Display panel; 5. Transparent resin front protective layer; 6. Support rod; 7. Base; 8. Disc-shaped spring; 9. Rubber vibration damping ring; 10. Small protrusion; 11. Docking groove; 12. Anti-detachment rod; 13. Anti-detachment groove; 14. Misalignment; 15. Misalignment groove; 16. Rear shell protrusion; 17. Waterproof sealing strip; 18. Inner protective component; 19. Pressure balance vent; 20. Connecting rod; 21. Connecting groove; 22. Fixing screw hole. Detailed Implementation

[0016] 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.

[0017] Please see Figure 1-6 This utility model provides a technical solution: A ruggedized display screen with good vibration resistance includes: The metal casing 1 includes a front casing 2 and a rear casing 3, with a display panel 4 disposed between the front casing 2 and the rear casing 3. The metal casing has good mechanical properties and can meet the usage requirements. It is recommended to use a corrosion-resistant alloy.

[0018] Transparent resin front protective layer 5 is disposed on the front shell 2 on the front side corresponding to the front of the display panel 4. Support rod 6 is located at the bottom of front shell 2; support rod 6 is also made of metal and is welded to or integrally machined with front shell 2.

[0019] At least one set of bases 7, with multiple sets of fixing holes on the bases 7, and a plug-in rod 20 on the bases 7. The support rod 6 is provided with a plug-in groove 21 corresponding to the plug-in rod 20. The plug-in rod 20 and the plug-in groove 21 are provided with through fixing screw holes 22. The bases 7 are detachably fixed to the bottom of the support rod 6 by bolts. The bases 7 can be provided with different models and sizes to cope with different installation environments. They can be directly connected to the flange seat by bolts, and the connection is very firm. At the same time, it is used for equipment operation monitoring and does not need to be moved. This fixing method has no impact on use.

[0020] A vibration damping and protection structure is located in the middle of the support rod 6, dividing the support rod 6 into upper and lower sections. The vibration damping structure includes a disc-shaped spring 8 and a rubber vibration isolation ring 9. A small protrusion 10 is provided at the top of the lower section of the support rod 6, and a mating groove 11 is provided at the bottom of the upper section. The small protrusion 10 and the mating groove 11 are inserted into each other, and a disc-shaped spring 8 is provided between the small protrusion 10 and the mating groove 11. A rubber vibration isolation ring 9 is provided on the outer side of the small protrusion 10, with both sides of the rubber vibration isolation ring 9 abutting against the upper and lower ends of the support rod 6. Multiple anti-detachment rods 12 are provided at the bottom of the upper section of the support rod 6, and an anti-detachment groove 13 corresponding to the anti-detachment rod 12 is provided in the lower section of the support rod 6. The anti-detachment rod 12 is engaged within the anti-detachment groove 13. The anti-detachment rod 12 and the anti-detachment groove 13 can use a traditional male-female groove and female-female ring structure. The disc-shaped spring 8 has a structure similar to a disc spring, possessing the same low-frequency vibration absorption capability as a disc spring. It can significantly reduce the low-frequency vibration transmission rate, but its damping is small. Therefore, it is used in conjunction with a rubber vibration isolator 9. The rubber vibration isolator 9 utilizes the viscoelasticity of rubber material to reduce vibration. It has high damping and good resonance suppression effect, but the load-bearing capacity of the rubber vibration isolator 9 is weak. The disc-shaped spring 8 provides a stronger load-bearing capacity. The combination of the disc-shaped spring 8 and the rubber vibration isolator 9 can significantly eliminate low-frequency vibration and support the weight of the display screen (the metal casing 1 results in high mass), which can significantly improve the service life of the display screen.

[0021] Furthermore, a mating stud 14 is provided on the side edge of the transparent resin front protective layer 5 away from the display panel 4, and a stud groove 15 is provided on the inner wall of the front shell 2 corresponding to the transparent resin front protective layer 5. The mating stud 14 and the stud groove 15 are engaged and fitted together, and the gap between the mating stud 14 and the stud groove 15 is filled with waterproof adhesive.

[0022] Furthermore, a rear shell flange 16 is provided on the side of the rear shell 3 adjacent to the front shell 2, and the rear shell 3 and the front shell 2 are fixedly connected by adhesive or bolts. The rear shell flange 16 serves as a base for bearing the adhesive or bolts.

[0023] Furthermore, a waterproof sealing strip 17 is provided on the front shell 2 at the location corresponding to the rear shell protrusion 16. Since the gap between the front shell 2 and the rear shell 3 is difficult to control, the waterproof sealing strip 17 is used to improve the sealing performance and prevent liquid and moisture from seeping in.

[0024] Furthermore, an inner protective component 18 is fitted on the outer side of the display panel 4, and the inner protective component 18 is made of flexible silicone rubber.

[0025] Furthermore, a pressure balance vent 19 is provided on the lower section of the support rod 6, which communicates with the anti-detachment groove 13. The pressure balance vent 19 is connected to the air pressure inside the anti-detachment groove 13 to prevent air pressure from affecting the movement of the anti-detachment rod 12.

[0026] Structural Description: Metal casing 1: Composed of front casing 2 and rear casing 3, it is a rigid protective body made of corrosion-resistant alloy, used to wrap and protect internal components such as display panel 4, resist external impact and form a closed space. Front shell 2: A component of the metal shell 1, with a support rod 6 at the bottom, a staggered groove 15 on the inner wall corresponding to the transparent resin front protective layer 5, and a waterproof sealing strip 17 corresponding to the rear shell protrusion 16. It is connected to the rear shell 3 by adhesive or bolts, providing a basis for the installation and mating of related components. Rear shell 3: A component of the metal outer shell 1, with a rear shell protrusion 16 on the side adjacent to the front shell 2, which is fixedly connected to the front shell 2 by adhesive or bolts, forming a closed space together with the front shell 2 to protect the internal display panel 4. Display panel 4: Located between the front shell 2 and the rear shell 3, with an inner protective component 18 on the outside, used to display the operating parameters of the powder feeding equipment such as the rotation speed and feeding amount, so as to realize the visual monitoring of the equipment status; Transparent resin front protective layer 5: It is set on the front side of the front shell 2 corresponding to the front of the display panel 4. The edge is provided with a mating step 14, which is engaged with the mating groove 15 and the gap is filled with waterproof glue. It can protect the display panel 4 and ensure display clarity, while forming a secondary seal. Support rod 6: A metal component located at the bottom of the front shell 2, which is welded to or integrally machined with the front shell 2. It has a vibration damping protection structure in the middle and is divided into upper and lower sections. The lower section has a small protrusion 10, an anti-detachment groove 13, and a pressure balance air hole 19. The upper section has a docking groove 11 and an anti-detachment rod 12. The bottom has an insertion groove 21, which is used to connect the front shell 2 and the base 7 and to transmit and filter vibration. Base 7: Located at the bottom of support rod 6, it has multiple sets of fixing holes, and is equipped with plug rod 20 and fixing screw hole 22. It can be detachably fixed to support rod 6 by bolts. Different models can be replaced to adapt to the installation environment. It can be connected to industrial equipment or flange seat by bolts to transmit vibration to support rod 6. Disc-shaped spring 8: Located between the small protrusion 10 and the docking groove 11 in the upper and lower sections of the support rod 6, similar to a disc spring, it can absorb low-frequency vibration energy and convert it into elastic potential energy through axial compression and rebound, reduce vibration transmission rate, and provide load-bearing capacity to support the weight of the display screen. Rubber vibration isolation ring 9: It is sleeved on the outside of the small protrusion 10, and abuts against the upper and lower ends of the support rod 6 on both sides. It uses the viscoelasticity of rubber to dissipate the remaining vibration energy through intramolecular friction, which makes up for the insufficient damping of the disc spring 8 and suppresses resonance. Small protrusion 10: Located at the top of the lower section of the support rod 6, it is inserted into the mating groove 11, with a rubber vibration isolation ring 9 on the outside and a disc-shaped spring 8 installed inside, providing an installation position for the vibration damping components and realizing the guiding fit between the upper and lower sections of the support rod; The docking groove 11 is located at the bottom of the upper section of the support rod 6 and is inserted into the small protrusion 10. The disc-shaped spring 8 is placed inside to provide insertion space for the small protrusion 10, so as to realize the connection between the upper and lower sections of the support rod and the vibration reduction function. Anti-detachment rod 12: Located at the bottom of the upper section of the support rod 6, it is snapped into the anti-detachment groove 13 and can extend and retract freely with vibration. It is used to prevent the upper and lower sections of the support rod 6 from separating during vibration and plays a mechanical limiting role. Anti-detachment groove 13: It is opened in the lower section of the support rod 6, corresponding to the anti-detachment rod 12 and connected to the pressure balance air hole 19, to provide the anti-detachment rod 12 with a space for movement, and to prevent the upper and lower sections of the support rod from separating in conjunction with the anti-detachment rod 12; Matching misalignment 14: Located on the side edge of the transparent resin front protective layer 5 away from the display panel 4, it engages with the misalignment groove 15, and the gap is filled with waterproof adhesive to achieve a stable connection between the transparent resin front protective layer 5 and the front shell 2 and to assist in sealing. Misalignment groove 15: It is opened on the inner wall of the front shell 2 at the location corresponding to the transparent resin front protective layer 5, and is engaged with the mating misalignment 14. The gap is filled with waterproof adhesive, providing an installation groove for the mating misalignment 14 and assisting in forming a secondary seal. Rear shell protrusion 16: Located on the side of the rear shell 3 adjacent to the front shell 2, serving as a base for bearing adhesive or bolts when the rear shell 3 is connected to the front shell 2, and assisting the front and rear shells in forming a closed space; Waterproof sealing strip 17: Located on the front shell 2 at the corresponding rear shell protrusion 16, it is used to improve the sealing performance of the connection gap between the front shell 2 and the rear shell 3, and to prevent dust and liquid from entering the equipment. Inner protective component 18: A flexible silicone rubber component fitted on the outside of the display panel 4, which can buffer the local vibration transmitted by the shell and prevent the display panel 4 from being directly subjected to force and thus breaking. Pressure balancing vent 19: Located in the lower section of the support rod 6 and connected to the anti-detachment groove 13, it is used to balance the air pressure in the anti-detachment groove 13 and ensure that the anti-detachment rod 12 is not affected by air pressure resistance when it freely extends and retracts with vibration. Plug-in rod 20: Located on the base 7, it is plugged into the plug-in slot 21 of the support rod 6. It has a through fixing screw hole 22 to provide positioning for the connection between the base 7 and the support rod 6, and can be rigidly locked with bolts. Insertion slot 21: It is opened on the support rod 6 and is inserted into the corresponding insertion rod 20 of the base 7. It has a through fixing screw hole 22 to provide insertion space for the insertion rod 20, so as to realize the detachable connection between the base 7 and the support rod 6. Fixed screw hole 22: Through the insertion rod 20 and the insertion slot 21, for bolts to pass through, so as to detachably fix the base 7 to the bottom of the support rod 6 and ensure that the connection between the two is stable.

[0027] Working Principle: The metal casing 1 adopts a combination design of front casing 2 and rear casing 3. A rigid protective body is constructed using corrosion-resistant alloy material, utilizing the excellent mechanical properties of metal to resist external impacts. Simultaneously, a sealed space is formed by the adhesive or bolt connection between the rear casing's protruding edge 16 and the front casing 2. This, along with the waterproof sealing strip 17 on the edge of the front casing 2, blocks the intrusion path of dust and liquid. The display panel 4 is encased between the front casing 2 and the rear casing 3. A flexible silicone rubber inner protective component 18 on the outer side buffers minor vibrations transmitted by the casing, preventing the panel from breaking due to direct force. The transparent resin front protective layer 5 installed at the front end of the front casing 2 is fixed by a snap-fit ​​structure that engages with the misalignment 14 and misalignment groove 15. The waterproof adhesive filling the gaps forms a secondary sealing barrier, preventing powder particles and moisture from seeping into the internal circuitry through the panel edges.

[0028] The core vibration reduction function of the equipment is achieved by the vibration damping protection structure in the middle of the support rod 6. This structure divides the support rod 6 into upper and lower sections. The small protrusion 10 at the top of the lower section and the mating groove 11 at the bottom of the upper section form a guide insertion fit. The disc-shaped spring 8 between them utilizes the elastic deformation characteristics similar to a disc spring to absorb low-frequency vibration energy. When the vibration is transmitted to the lower section of the support rod 6 through the base 7, the disc-shaped spring 8 converts the vibration energy into elastic potential energy through axial compression and rebound, significantly reducing the transmission efficiency of low-frequency vibration. At the same time, the rubber vibration isolation ring 9 on the outside of the small protrusion 10 is tightly attached to the ends of the upper and lower sections of the support rod 6. The viscoelasticity of its rubber material dissipates the remaining vibration energy through intramolecular friction, making up for the insufficient damping of the disc-shaped spring 8 and effectively suppressing resonance. To prevent the upper and lower sections of the support rod 6 from separating during vibration, the anti-detachment rod 12 at the bottom of the upper section is inserted into the corresponding anti-detachment groove 13 of the lower section to form a mechanical limit. Meanwhile, the pressure balance air hole 19 of the lower section of the support rod 6 can balance the air pressure in the anti-detachment groove 13, ensuring that the anti-detachment rod 12 is not affected by air pressure resistance when it freely extends and retracts with vibration.

[0029] The base 7 is positioned by the insertion slot 21 of the support rod 6 via the insertion rod 20, and is rigidly locked by the bolts in the fixing screw hole 22. Different models of base 7 can be replaced according to the installation environment to ensure that the equipment is firmly connected to industrial equipment or flange seats through the fixing holes. When the vibrator of the powder feeding equipment is working, the vibration energy is first transmitted to the lower section of the support rod 6 through the base 7. After being filtered by the disc-shaped spring 8 and the rubber vibration isolation ring 9 of the vibration damping structure, only weak vibrations are transmitted to the upper section of the support rod 6 and the metal shell 1, avoiding severe vibration stress on the internal circuit of the display screen. This composite vibration damping design retains the high load-bearing capacity of the disc-shaped spring 8 to support the weight of the metal shell 1, and utilizes the high damping characteristics of the rubber vibration isolation ring 9 to suppress resonance, significantly reducing the risk of circuit solder joint desoldering and loosening of ribbon cables.

[0030] The overall structure provides comprehensive protection for the display screen in high-dust, high-vibration powder feeding environments through the rigid protection of the metal shell 1, the waterproof and dustproof capabilities of the multi-layer sealing design, and the low-frequency vibration isolation effect of the composite vibration reduction structure. This fundamentally solves the problem of short service life of traditional monitoring display screens due to vibration damage and environmental erosion.

[0031] 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 ruggedized display screen with good vibration resistance, characterized in that, include: Metal casing (1), the metal casing (1) includes a front shell (2) and a rear shell (3), and a display panel (4) is provided between the front shell (2) and the rear shell (3). A transparent resin front protective layer (5) is disposed on the front shell (2) on the front side corresponding to the display panel (4); Support rod (6), the support rod (6) is disposed at the bottom of the front shell (2); At least one set of bases (7) are provided, the bases (7) have multiple sets of fixing holes, the bases (7) are provided with plug rods (20), the support rods (6) are provided with plug grooves (21) corresponding to the plug rods (20), the plug rods (20) and the plug grooves (21) are provided with through fixing screw holes (22), and the bases (7) are detachably fixed to the bottom of the support rods (6) by bolts; The vibration damping protection structure is located in the middle of the support rod (6) and divides the support rod (6) into upper and lower sections. The vibration damping structure includes a disc-shaped spring (8) and a rubber vibration isolation ring (9). A small protrusion (10) is provided at the top of the lower section of the support rod (6), and a mating groove (11) is provided at the bottom of the upper section of the support rod (6). The small protrusion (10) and the mating groove (11) are inserted into each other, and the small protrusion (10) and the mating groove (11) are mated together. 1) A disc-shaped spring (8) is provided between them. A rubber vibration isolation ring (9) is provided on the outside of the small protrusion (10). The two sides of the rubber vibration isolation ring (9) abut against the upper and lower ends of the support rod (6). Multiple anti-detachment rods (12) are provided at the bottom of the upper section of the support rod (6). An anti-detachment groove (13) corresponding to the anti-detachment rod (12) is opened in the lower section of the support rod (6). The anti-detachment rod (12) is snapped into the anti-detachment groove (13).

2. The three-proof display screen with good vibration resistance according to claim 1, characterized in that, The transparent resin front protective layer (5) has a mating platform (14) on one side edge away from the display panel (4), and the inner wall of the front shell (2) has a mating groove (15) corresponding to the transparent resin front protective layer (5). The mating platform (14) and the mating groove (15) are engaged, and the gap between the mating platform (14) and the mating groove (15) is filled with waterproof adhesive.

3. A ruggedized display screen with good vibration resistance according to claim 1, characterized in that, The rear shell (3) is provided with a rear shell flange (16) on the side adjacent to the front shell (2), and the rear shell (3) and the front shell (2) are fixedly connected by adhesive or bolts.

4. A ruggedized display screen with good vibration resistance according to claim 3, characterized in that, A waterproof sealing strip (17) is provided on the front shell (2) at the corresponding rear shell protrusion (16).

5. A ruggedized display screen with good vibration resistance according to claim 1, characterized in that, The display panel (4) is fitted with an inner protective component (18) on the outside, and the inner protective component (18) is made of flexible silicone rubber.

6. A ruggedized display screen with good vibration resistance according to claim 1, characterized in that, The lower section of the support rod (6) is provided with a pressure balance air hole (19) that communicates with the anti-detachment groove (13).

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