A drying machine for cardboard box production

Abstract

This utility model discloses a cardboard box drying machine, including a drying shell with a conveyor at the lower end of the interior of the drying shell, and a drying mechanism. The drying mechanism includes a telescopic rod, an inner shell, a first fixed seat, an upper pipe, a lower pipe, an air pipe, a circulation component, and a lifting component. The inner shell is mounted on the top wall of the drying shell via symmetrically distributed telescopic rods. The front and rear ends of the top wall of the inner shell are provided with upper pipes via symmetrically distributed first fixed seats, and the front and rear walls of the drying shell are provided with lower pipes via second fixed seats. This cardboard box drying machine, through the support component, creates a certain vertical gap between the cardboard board and the conveying unit, facilitating the effective drying of the bottom of the cardboard board by hot air. At the same time, the device uses hot air circulation to dry the cardboard board, reducing the energy consumption of drying the cardboard board. During the hot air circulation process, a dehumidifying element removes the moisture carried in the hot air.

Description

Technical Field

[0001] This utility model relates to the field of cardboard box production technology, specifically a cardboard box drying machine. Background Technology

[0002] A cardboard box is a container typically made of cardboard or corrugated cardboard, used for packaging goods for storage, transportation, and distribution. During the production process, the cardboard boards are dried using a dryer to keep the produced cardboard boxes in a dry state. In the prior art, patent publication number CN 221518938 U discloses a drying and conveying structure for producing packaging cardboard boards, including a support frame. Mounting blocks are fixed to both ends of the upper surface of the support frame, and a conveyor belt mechanism is fixed between the two mounting blocks. A box body is fixed to the upper surface of the mounting blocks. A connecting plate is fixed between the left and right side walls of the inner side of the support frame. A drying mechanism is provided on the connecting plate. The drying mechanism includes a fan fixed to the upper surface of the connecting plate. The output end of the fan is connected to a connecting pipe. A filter box is fixed to the end of the connecting pipe away from the fan, and a filter screen is fixed between the upper and lower side walls of the inner cavity of the filter box. This packaging carton board drying and conveying structure is equipped with a drying mechanism. When the packaging carton board needs to be dried, the top and bottom of the packaging carton board on the conveyor belt mechanism with through holes and the drying mechanism can be dried simultaneously, thereby drying the packaging carton board quickly and improving its practicality. However, during the drying process of the carton board, the bottom of the carton board is in contact with the conveyor belt, which makes it difficult for the drying airflow to enter, resulting in an unsatisfactory drying effect. At the same time, the hot air after drying the carton board is exposed to the outside of the device, resulting in a large amount of heat waste. Therefore, we propose a dryer for carton production. Utility Model Content

[0003] The technical problem to be solved by this utility model is to overcome the existing defects and provide a dryer for carton production. The device uses a support component to create a certain vertical gap between the carton board and the conveying unit, which facilitates the passage of hot air to effectively dry the bottom of the carton board. At the same time, the device uses hot air circulation to dry the carton board, reducing the energy consumption of carton board drying. Furthermore, during the hot air circulation process, a dehumidification element removes the moisture carried in the hot air, which can effectively solve the problems in the background art.

[0004] To achieve the above objectives, this utility model provides the following technical solution: a drying machine for carton production, comprising a drying shell, wherein a conveyor is provided at the lower end of the interior of the drying shell, and a drying mechanism is also included; The drying mechanism includes a telescopic rod, an inner shell, a fixed base, an upper pipe, a lower pipe, an air pipe, a circulation component, and a lifting component. The inner shell is mounted on the top wall of the drying shell via symmetrically distributed telescopic rods. Upper pipes are located at both ends of the top wall of the inner shell via symmetrically distributed fixed bases. Lower pipes are located on both the front and rear walls of the drying shell via fixed bases. Horizontally evenly distributed air pipes penetrate the inner walls of both the lower and upper pipes. The rear ends of the air pipes on the front lower pipe pass through the front wall of the conveyor. A circulation component is located between the upper and lower pipes and the drying shell. A lifting component is located between the inner shell and the drying shell. The device, through the support component, creates a vertical gap between the cardboard and the conveying unit, facilitating the effective drying of the bottom of the cardboard by hot air. Simultaneously, the device uses hot air circulation to dry the cardboard, reducing energy consumption. Furthermore, a dehumidifying element removes moisture carried in the hot air during the hot air circulation process.

[0005] Furthermore, it also includes a microcontroller, which is located outside the drying shell. The input terminal of the microcontroller is electrically connected to an external power supply, and the output terminal of the microcontroller is electrically connected to the input terminal of the conveyor, which facilitates the control of electrical components within the device.

[0006] Furthermore, the circulation assembly includes a hot air blower, a steam-water separator, a hose, connecting pipe one, connecting pipe two, a three-way pipe, connecting pipe three, and connecting pipe four. The hot air blower and the steam-water separator are respectively located on the upper side of the drying shell. The input end of the hot air blower is electrically connected to the output end of the microcontroller. The right end of the upper pipe is connected to connecting pipe one through a hose, and the right end of the lower pipe is connected to connecting pipe two. Connecting pipe two and the vertically adjacent connecting pipe one are connected to connecting pipe three through a three-way pipe. The middle parts of connecting pipe two and connecting pipe one pass through the wall of the drying shell. The air outlet one of the hot air blower is connected to the upper end of connecting pipe three on the front side. The air inlet one of the hot air blower is connected to the air outlet two of the steam-water separator through connecting pipe four. The air inlet two of the steam-water separator is connected to the upper end of connecting pipe three on the rear side. The cardboard is dried by hot air circulation drying, reducing the energy consumption of cardboard drying.

[0007] Furthermore, the circulation component also includes temperature sensors, which are evenly arranged in the upper wall of the front connecting pipe three. The temperature sensors are all bidirectionally electrically connected to the microcontroller to detect and upload the temperature of the hot air used for drying the cardboard in the carton production dryer.

[0008] Furthermore, the lifting assembly includes an electro-hydraulic actuator and a laser sensor. The electro-hydraulic actuator is located on the upper side of the drying shell. The input end of the electro-hydraulic actuator is electrically connected to the output end of the microcontroller. The telescopic end of the electro-hydraulic actuator is fixedly connected to the upper side of the inner shell. A laser sensor is provided on the upper side of the inner shell. The laser sensor is bidirectionally electrically connected to the microcontroller to regulate the vertical space for drying cardboard boards inside the cardboard drying machine.

[0009] Furthermore, the conveyor belt is provided with evenly distributed ventilation holes, allowing the drying gas from the carton production dryer to enter the conveyor.

[0010] Furthermore, the outer arc surface of the conveyor belt is provided with longitudinally symmetrically distributed rubber rings, and the interior of each rubber ring is provided with uniformly distributed annular ventilation holes, so that there is a drying gap between the carton board of the carton production dryer and the conveying unit.

[0011] Compared with the prior art, the beneficial effects of this utility model are as follows: This carton drying machine has the following advantages: 1. When using a carton drying machine, the device uses a support assembly to create a vertical gap between the carton board and the conveying unit, which facilitates the passage of hot air and thus effectively dries the bottom of the carton board.

[0012] 2. When using a dryer for cardboard box production, the device uses hot air circulation through a circulation component and corresponding pipes to dry the cardboard boards. By recycling heat, the energy consumption for drying the cardboard boards is reduced. During the hot air circulation process, a dehumidification element removes moisture carried in the hot air, preventing moisture from interfering with the hot air circulation and drying of the cardboard boards. At the same time, the device can vertically adjust the hot air drying space of the cardboard boards according to the thickness of the cardboard boards through control elements, thereby reducing the hot air overflow caused by excessive drying space, further reducing the energy consumption for drying the cardboard boards. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a schematic diagram of the internal structure of this utility model; Figure 3 This is an enlarged structural diagram of point A in this utility model.

[0014] In the diagram: 1. Drying shell, 2. Microcontroller, 3. Conveyor, 4. Drying mechanism, 41. Telescopic rod, 42. Inner shell, 43. Fixed base one, 44. Upper pipe, 45. Lower pipe, 46. Air pipe, 47. Circulation assembly, 471. Hot air blower, 472. Steam-water separator, 473. Hose, 474. Connecting pipe one, 475. Connecting pipe two, 476. T-connector, 477. Connecting pipe three, 478. Connecting pipe four, 479. Temperature sensor, 48. Lifting assembly, 481. Electro-hydraulic actuator, 482. Laser sensor, 5. Vent one, 6. Rubber ring, 7. Vent two. Detailed Implementation

[0015] 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.

[0016] Please see Figure 1-3 This embodiment provides a technical solution: a dryer for carton production, including a drying shell 1, a conveyor 3 located at the lower end of the interior of the drying shell 1, and a microcontroller 2 located outside the drying shell 1. The input end of the microcontroller 2 is electrically connected to an external power source, and the output end of the microcontroller 2 is electrically connected to the input end of the conveyor 3. The conveyor 3 has evenly distributed ventilation holes 5 inside its belt. When drying the carton boards during the carton production process, the microcontroller 2 starts the conveyor 3 to provide power for drying and conveying the carton boards. The dryer also includes a drying mechanism 4. Drying mechanism 4 includes telescopic rods 41, inner shell 42, fixed base 43, upper pipe 44, lower pipe 45, air pipe 46, circulation assembly 47, and lifting assembly 48. The inner shell 42 is mounted on the top wall of the drying shell 1 via symmetrically distributed telescopic rods 41. Upper pipes 44 are provided at both the front and rear ends of the top wall of the inner shell 42 via symmetrically distributed fixed bases 43. Lower pipes 45 are provided on both the front and rear walls of the drying shell 1 via fixed bases 2. Horizontally evenly distributed air pipes 46 penetrate the inner walls of both the lower pipes 45 and the upper pipes 44. The rear ends of the air pipes 46 on the front lower pipe 45 pass through the front wall of the conveyor 3. A circulation assembly 47 is provided between the upper pipes 44, lower pipes 45, and the drying shell 1. A lifting assembly 48 is provided between the inner shell 42 and the drying shell 1. Component 48, the circulation assembly 47 includes a hot air blower 471, a steam-water separator 472, a hose 473, a connecting pipe 1 474, a connecting pipe 2 475, a three-way pipe 476, a connecting pipe 3 477, and a connecting pipe 478. The hot air blower 471 and the steam-water separator 472 are respectively located on the upper side of the drying shell 1. The input end of the hot air blower 471 is electrically connected to the output end of the microcontroller 2. The right end of the upper pipe 44 is connected to the connecting pipe 1 474 via the hose 473, and the right end of the lower pipe 45 is connected to the connecting pipe 2 475. The connecting pipe 2 475 and the vertically adjacent connecting pipe 1 474 are connected to the connecting pipe 3 477 via the three-way pipe 476. The middle parts of the connecting pipe 2 475 and the connecting pipe 1 474 pass through the wall of the drying shell 1. The air outlet of the hot air blower 471 is connected to the front connecting pipe 3 477. The upper end is connected to the hot air blower 471. The air inlet 1 of the hot air blower 471 is connected to the air outlet 2 of the steam-water separator 472 through the connecting pipe 478. The air inlet 2 of the steam-water separator 472 is connected to the upper end of the connecting pipe 3 477 on the rear side. The circulation component 47 also includes a temperature sensor 479. The temperature sensors 479 are evenly distributed in the upper wall of the connecting pipe 3 477 on the front side. The temperature sensors 479 are all bidirectionally electrically connected to the microcontroller 2. When the cardboard enters the device, the microcontroller 2 starts the hot air blower 471. The hot air blower 471 consists of a fan and an electric heating wire. When the fan runs, the gas in the connecting pipe 478 enters through its own air inlet 1. At the same time, the electric heating wire runs, thereby heating the gas that enters. Then the hot air in the hot air blower 471 flows along the upper end of the connecting pipe 478 on the front side. Pipe 477, T-connector 476, connecting pipe 475, connecting pipe 474, and flexible hose 473 enter the upper pipe 44 and lower pipe 45 on the front side. The hot air in the upper pipe 44 is ejected through the corresponding air pipe 46 (all air pipes 46 in the upper pipe 44 are arranged at a downward angle), thereby drying the upper surface of the cardboard. The hot air in the lower pipe 45 enters the conveyor 3 through the corresponding air pipe 46 and is ejected through the vent 5 on the belt of the conveyor 3, thereby drying the lower surface of the cardboard. The drying gas on the lower surface of the cardboard is discharged through the gaps between the cardboard boards and the second through hole 7. The hot air after the cardboard is dried, carrying moisture, enters through the air pipes 46 of the upper and lower pipes on the rear side.The air enters the inlet of the steam-water separator 472 via the corresponding hoses 473, 474, 475, 476, and 477. The steam-water separator 472 dehumidifies the air through physical barriers and gravity separation. For example, a cyclone structure separates and discharges moisture using centrifugal force and gravity. The dehumidified hot air flows back to the hot air blower 471 through the outlet 2 of the steam-water separator 472 and the connecting pipe 478, thus achieving hot air recycling for drying the cardboard in the dryer and reducing energy consumption. Simultaneously, during the cardboard drying process, the microcontroller 2 activates the temperature sensor 479. The temperature sensor 479 operates by using a thermistor to detect temperature changes. The change in resistance value detects the temperature of the hot air inside the connecting pipe 477, and transmits the detection result to the microcontroller 2 as an electrical signal. Multiple temperature sensors 479 are installed inside the connecting pipe 477, distributed at different positions on the upper part of each sensor. The multiple temperature sensors 479 improve the accuracy of temperature detection of the hot air inside the connecting pipe 477. Based on the detection results, the microcontroller 2 adjusts the power of the heating wire in the hot air blower 471, thereby regulating the temperature of the hot air used for drying the cardboard. This device uses hot air circulation to dry the cardboard, reducing energy consumption. Furthermore, during the hot air circulation process, a dehumidifying element removes moisture carried in the hot air. The lifting assembly 48 includes an electro-hydraulic actuator 481 and a laser sensor 482. The electro-hydraulic actuator 481 is located on the upper side of the drying shell 1. The input end of the electro-hydraulic actuator 481 is electrically connected to the output end of the microcontroller 2. The telescopic end of the electro-hydraulic actuator 481 is fixedly connected to the upper side of the inner shell 42. The upper side of the inner shell 42 is equipped with a laser sensor 482, which is bidirectionally electrically connected to the microcontroller 2. During the carton drying process, the microcontroller 2 can activate the electro-hydraulic actuator 481 according to the overall height of the carton, causing its telescopic end to move the inner shell 42 vertically downward. The inner shell 42, through the fixed seat 43, drives the upper pipe 44 and lower pipe 45 on the upper side to move vertically downward simultaneously. By reducing the vertical space for hot air drying of the carton, the total amount of hot air overflow during the hot air circulation process is reduced, further reducing the energy consumption of carton drying. During this process, the microcontroller 2 activates the laser sensor 482. 82. The laser sensor 482 emits a light signal that irradiates the top wall of the drying shell 1 and reflects back to the initial position. Based on the propagation time and speed of the light signal, the vertical movement distance of the inner shell 42 is obtained. Subsequently, the laser sensor 482 transmits the detection result to the microcontroller 2 in the form of an electrical signal. The microcontroller 2 adjusts the extension end of the electro-hydraulic push rod 481 according to the detection result, thereby realizing the control of the vertical movement position of the inner shell 42. During the vertical movement of the inner shell 42, the extension end of the extension rod 41 moves vertically synchronously with the inner shell 42. Through the sliding connection between the extension end and the fixed end of the extension rod 41, the vertical movement stability of the inner shell 42 is improved. The device can vertically adjust the hot air drying space of the carton board according to the thickness of the carton board through the control element, thereby reducing the hot air overflow phenomenon caused by the excessive drying space of the carton board, and further reducing the drying energy consumption of the carton board. The outer arc surface of the conveyor belt of the conveyor 3 is provided with longitudinally symmetrically distributed rubber rings 6. Each rubber ring 6 has a ring of evenly distributed ventilation holes 7 inside. The conveyor 3 moves synchronously with the rubber rings 6 through its own belt. The rubber rings 6 move the carton board from left to right through the contact friction between themselves and the carton board. The rubber rings 6 create a certain gap between the carton board and the conveyor belt of the conveyor 3, which facilitates the subsequent drying operation. The device, through the support component, creates a certain vertical gap between the carton board and the conveying unit, which facilitates the hot air to pass through and effectively dry the bottom of the carton board.

[0017] The working principle of the carton drying machine provided by this utility model is as follows: When drying the carton boards during the carton production process, the microcontroller 2 starts the conveyor 3. The conveyor 3 drives the rubber ring 6 to move synchronously through its own belt. The rubber ring 6 moves the carton board from left to right due to the contact friction between itself and the carton board. The rubber ring 6 creates a certain gap between the carton board and the belt of the conveyor 3, which facilitates the subsequent drying operation. As the carton board enters the device, the microcontroller 2 starts the hot air fan 471. The hot air fan 471 consists of a fan and an electric heating wire. When the fan runs, the gas in the connecting pipe 478 enters through its own air inlet. At the same time, the electric heating wire runs, thereby purifying the incoming gas. After heating, hot air from the hot air blower 471 enters the upper and lower pipes 44 and 45 along the connecting pipes 477, 476, 475, 474, and 473. The hot air in the upper pipe 44 is ejected through the corresponding air pipes 46 (all air pipes 46 in the upper pipe 44 are arranged at a downward angle), thus drying the upper surface of the cardboard. The hot air in the lower pipe 45 enters the conveyor 3 through the corresponding air pipes 46 and is ejected through the vent 5 on the conveyor belt, thus drying the lower surface of the cardboard. The drying gas from the lower surface of the cardboard is discharged through the gaps between the cardboard boards and the second through-hole 7. The hot air from the dried cardboard, carrying moisture, enters through the air pipe 46 of the upper and lower pipes on the rear side, and then enters the air inlet of the steam-water separator 472 along the corresponding flexible hose 473, connecting pipe one 474, connecting pipe two 475, three-way pipe 476, and connecting pipe three 477. The steam-water separator 472 dehumidifies the air through physical barriers and gravity separation. For example, a cyclone structure separates and discharges moisture through centrifugal force and gravity. The dehumidified hot air flows back to the hot air blower 471 through the second air outlet of the steam-water separator 472 and the fourth connecting pipe 478, thus realizing the recycling of hot air from the cardboard drying machine and reducing energy consumption. At the same time, during the cardboard drying process, the microcontroller 2 activates the temperature sensor 479, and the temperature sensor 4... The system operates by detecting the temperature of the hot air inside the connecting pipe 477 by measuring the resistance change of a thermistor as the temperature changes. The detection result is transmitted to the microcontroller 2 as an electrical signal. Multiple temperature sensors 479 are located at different positions on the upper part of the connecting pipe 477, improving the accuracy of hot air temperature detection. Based on the detection results, the microcontroller 2 adjusts the power delivery of the heating wire in the hot air blower 471 to regulate the temperature of the hot air used for drying the cardboard. Simultaneously, during the cardboard drying process, the microcontroller 2 can activate the electro-hydraulic actuator 481, according to the overall height of the cardboard, causing its extension end to move the inner shell 42 vertically downwards.The inner shell 42, via the fixed base 43, drives the upper pipe 44 and lower pipe 45 to move vertically downwards synchronously. By reducing the vertical space for hot air drying of the cardboard, the total amount of hot air overflow during hot air circulation is reduced, further reducing the energy consumption of cardboard drying. During this process, the microcontroller 2 activates the laser sensor 482, which emits a light signal that illuminates the top wall of the drying shell 1 and reflects back to the initial position. Based on the propagation time and speed of the light signal, the vertical movement distance of the inner shell 42 is obtained. Subsequently, the laser sensor 482 transmits the detection result to the microcontroller 2 as an electrical signal. The microcontroller 2 adjusts the extension end of the electro-hydraulic push rod 481 according to the detection result, thereby controlling the vertical movement position of the inner shell 42. During the vertical movement of the inner shell 42, the extension end of the telescopic rod 41 moves vertically synchronously with the inner shell 42. Through the sliding connection between the extension end and the fixed end of the telescopic rod 41, the vertical movement stability of the inner shell 42 is improved.

[0018] It is worth noting that the microcontroller 2 disclosed in the above embodiments can be an MSP430, the conveyor 3 can be a DTL series belt conveyor, the hot air blower 471 can be a HAG-R10A-31, the temperature sensor 479 can be a PT100, the electro-hydraulic actuator 481 can be a DYTZB1000-500, and the laser sensor 482 can be a CD33-30N-422. The microcontroller 2 controls the operation of the conveyor 3, the hot air blower 471, the temperature sensor 479, the electro-hydraulic actuator 481, and the laser sensor 482 using methods commonly used in the prior art.

[0019] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made based on the content of this utility model specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. A drying machine for cardboard box production, comprising a drying shell (1), wherein a conveyor (3) is provided at the lower end of the interior of the drying shell (1), characterized in that: It also includes a drying mechanism (4); Drying mechanism (4): It includes telescopic rod (41), inner shell (42), fixed seat one (43), upper pipe (44), lower pipe (45), air pipe (46), circulation component (47) and lifting component (48). The inner shell (42) is set on the top wall of the drying shell (1) through the telescopic rod (41) which is symmetrically distributed laterally. The upper pipe (44) is provided at both the front and rear ends of the top wall of the inner shell (42) through the fixed seat one (43) which is symmetrically distributed laterally. The lower pipe (45) is provided at both the front and rear walls of the drying shell (1) through the fixed seat two. The inner walls of the lower pipe (45) and the upper pipe (44) are provided with air pipes (46) which are evenly distributed laterally. The rear end of the air pipe (46) on the lower pipe (45) on the front side passes through the front wall of the conveyor (3). The circulation component (47) is provided between the upper pipe (44), the lower pipe (45) and the drying shell (1). The lifting component (48) is provided between the inner shell (42) and the drying shell (1).

2. The cardboard box drying machine according to claim 1, characterized in that: It also includes a microcontroller (2), which is located outside the drying shell (1). The input end of the microcontroller (2) is electrically connected to an external power supply, and the output end of the microcontroller (2) is electrically connected to the input end of the conveyor (3).

3. A drying machine for cardboard box production according to claim 2, characterized in that: The circulation component (47) includes a hot air blower (471), a steam-water separator (472), a hose (473), a connecting pipe one (474), a connecting pipe two (475), a three-way pipe (476), a connecting pipe three (477), and a connecting pipe four (478). The hot air blower (471) and the steam-water separator (472) are respectively located on the upper side of the drying shell (1). The input end of the hot air blower (471) is electrically connected to the output end of the microcontroller (2). The right end of the upper pipe (44) is provided with a connecting pipe one (474) through the hose (473), and the right end of the lower pipe (45) is provided with a connecting pipe. The second (475) and the vertically adjacent first (474) are connected by a third (477) through a three-way pipe (476). The middle parts of the second (475) and the first (474) pass through the wall of the drying shell (1). The outlet of the hot air blower (471) is connected to the upper end of the third (477) on the front side. The inlet of the hot air blower (471) is connected to the outlet of the steam-water separator (472) through the fourth (478). The inlet of the steam-water separator (472) is connected to the upper end of the third (477) on the rear side.

4. A cardboard box drying machine according to claim 3, characterized in that: The circulation component (47) also includes a temperature sensor (479), which is evenly arranged in the upper wall of the front connecting pipe (477). The temperature sensor (479) is bidirectionally electrically connected to the microcontroller (2).

5. A drying machine for cardboard box production according to claim 2, characterized in that: The lifting assembly (48) includes an electro-hydraulic actuator (481) and a laser sensor (482). The electro-hydraulic actuator (481) is located on the upper side of the drying shell (1). The input end of the electro-hydraulic actuator (481) is electrically connected to the output end of the microcontroller (2). The telescopic end of the electro-hydraulic actuator (481) is fixedly connected to the upper side of the inner shell (42). The upper side of the inner shell (42) is provided with a laser sensor (482). The laser sensor (482) is bidirectionally electrically connected to the microcontroller (2).

6. A drying machine for cardboard box production according to claim 1, characterized in that: The conveyor (3) has evenly distributed ventilation holes (5) inside its belt.

7. A drying machine for cardboard box production according to claim 1, characterized in that: The conveyor (3) has longitudinally symmetrically distributed rubber rings (6) on the outer arc surface of the belt, and the interior of each rubber ring (6) is provided with uniformly distributed annular ventilation holes (7).

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