Longitudinal paper tube conveying device with negative pressure adsorption function

Abstract

The invention relates to the technical field of conveying devices, in particular to a negative pressure adsorption paper tube longitudinal conveying device which comprises a conveying frame, a conveying belt, a bottom plate and a first flow guide box, a protection plate is fixedly installed on the front face of the top of the bottom plate, and a back plate is fixedly installed on the back face of the bottom plate; and sound insulation plates are fixedly installed in the back plate and the protection plate, a sound insulation plate is fixedly installed between the back plate and the protection plate, an oscillation plate is installed between the back plate and the protection plate, and a motor is fixedly installed on one side of the back face of the back plate. A plurality of communicating pipes are mounted between a first communicating box and a second communicating box, so that an air pump can suck air in a first flow guide box and a second flow guide box at the same time, and the first flow guide box and the second flow guide box can generate a negative pressure adsorption effect on a conveying belt; and the functionality of the device is increased under the condition that the overall energy consumption of the device is not increased.

Description

Technical Field

[0001] The present invention relates to the technical field of conveying devices, and particularly to a longitudinal conveying device for paper tubes with negative pressure adsorption. Background Art

[0002] In modern industrial production, paper tubes, as a widely used packaging material and industrial raw material, their efficient and stable conveying is crucial. In industries such as papermaking, printing, and packaging, paper tubes need to be accurately transferred between different processes. And with the continuous progress of technology, due to its unique adsorption principle and advantages, the negative pressure adsorption technology has gradually emerged in the field of material conveying. Therefore, we propose a longitudinal conveying device for paper tubes with negative pressure adsorption.

[0003] The following defects still exist in the prior art during use: When the longitudinal conveying device for paper tubes in the prior art adsorbs and conveys paper tubes using the negative pressure adsorption principle, the functionality of the negative pressure adsorption structure is relatively single, which leads to an increase in the overall energy consumption of the device and a reduction in the environmental friendliness of the device; When the longitudinal conveying device for paper tubes in the prior art conveys paper tubes, during the production and conveying process of paper tubes, there will be debris of paper scraps remaining on the surface, and a large amount of paper scraps will get stuck inside the conveyor belt that is in direct contact with the paper tubes for a long time, thus affecting the air flow. This will not only form resistance to the rolling of the conveyor belt, but also affect the effect of negative pressure adsorption, and further affect the stability of the paper tubes during the conveying process.

[0004] In view of this, we propose a longitudinal conveying device for paper tubes with negative pressure adsorption to solve the existing problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a longitudinal conveying device for paper tubes with negative pressure adsorption to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A longitudinal conveying device for paper tubes with negative pressure adsorption, including a conveying frame, a conveyor belt, a bottom plate, and a first diversion box. A protective plate is fixedly installed on the front surface of the top of the bottom plate, a back plate is fixedly installed on the back of the bottom plate, sound insulation plates are fixedly installed inside both the back plate and the protective plate, and a sound insulation plate is fixedly installed between the back plate and the protective plate. An oscillating plate is installed between the back plate and the protective plate, and a motor is fixedly installed on one side of the back of the back plate; A conveyor belt is installed between the back plate and the protective plate. A number of ventilation holes are equidistantly arranged inside the conveyor belt. Two conveyor rollers are installed on the inner side of the conveyor belt, and one of the conveyor rollers is fixedly connected to the output shaft of the motor; The conveying frame is fixedly installed on the top of the back plate; A first diversion box is installed between the back plate and the protection plate. A first connection box is fixedly installed on the front of the first diversion box. A plurality of air inlets are formed in the top of the first diversion box, and the first diversion box is in contact with the upper part inside the conveyor belt. A second diversion box is installed below the first diversion box.

[0007] Preferably, the second diversion box has the same structure as the first diversion box, and the top of the second diversion box is in contact with the bottom of the conveyor belt. A second connection box is fixedly installed on the front of the second diversion box. A plurality of connecting pipes are fixedly installed between the first connection box and the second connection box. A connecting pipe is installed at the bottom of the second connection box through a plurality of connecting pipes. An air suction pipe is fixedly installed on one side of the bottom of the connecting pipe. One end of the air suction pipe away from the connecting pipe is fixedly installed with an air pump.

[0008] Preferably, a plurality of scraping teeth are arranged at the bottom of the oscillating plate, and the scraping teeth are of an elliptical curved surface structure.

[0009] Preferably, three groups of spiral springs are fixedly installed on the top of the oscillating plate. The top of the spiral spring is fixedly installed with a fixing frame, and the front and back of the fixing frame are fixedly connected to the protection plate and the back plate respectively.

[0010] Preferably, the air pump is fixedly connected to the top of the bottom plate, and a solenoid valve is fixedly installed at the connection position between the air pump and the air suction pipe.

[0011] Preferably, both the first diversion box and the second diversion box are of a hollow square structure, and the backs of the first diversion box and the second diversion box are of an open design.

[0012] Preferably, a main control box is fixedly installed on the left side of the front of the protection plate, and a plurality of support beams are fixedly installed between the protection plate and the back plate.

[0013] Preferably, a feeding belt is installed on the top of the conveying frame, and two driving rollers are installed inside the feeding belt. A conveying motor is fixedly installed on one side of the conveying frame, and the output shaft of the conveying motor is fixedly connected to the driving roller. A guide plate is fixedly installed on the front of the conveying frame. The guide plate is an arc-shaped object. The top of the guide plate is on the same horizontal plane as the feeding belt, and there is a distance of three to five centimeters between the bottom of the guide plate and the conveyor belt.

[0014] Preferably, a plurality of sound insulation holes are formed inside the sound insulation plate, and the aperture outside the sound insulation hole is twice that of the inner aperture.

[0015] Compared with the prior art, the beneficial effects of the present invention are: In the present invention, a number of connecting pipes are installed between the first connecting box and the second connecting box, enabling the air pump to simultaneously suck the air inside the first diversion box and the second diversion box, so that both the first diversion box and the second diversion box can generate a negative pressure adsorption effect on the conveyor belt, increasing the functionality of the device without increasing the overall energy consumption of the device.

[0016] In the present invention, an oscillating plate is installed above the second diversion box. The air pump can simultaneously suck the air inside the first diversion box and the second diversion box to form a negative pressure for adsorbing the conveyor belt. While the second diversion box adsorbs the paper scraps inside the conveyor belt, it drives the oscillating plate to perform reciprocating vertical movement, thereby discharging the paper scraps attached to the inside of the conveyor belt, avoiding a large amount of paper scraps being stuck inside the conveyor belt and affecting the rolling of the conveyor belt, and ensuring that the first diversion box can apply a sufficient large suction force to the paper tube, ensuring that the paper tube can be stably transported at the top of the conveyor belt in a vertical state. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic perspective front view structure diagram of the present invention; Figure 2 is a schematic front external structure diagram of the present invention; Figure 3 is a schematic front internal structure diagram of the present invention; Figure 4 is a schematic side sectional structure diagram of the present invention; Figure 5 is a schematic perspective rear view structure diagram of the present invention; Figure 6 is a schematic perspective front sectional structure diagram of the present invention; Figure 7 is a schematic partial perspective structure diagram of the present invention; Figure 8 is a schematic partial structure diagram of the oscillating plate of the present invention; Figure 9 is Figure 8 a partial enlarged structure diagram at A in Figure 10 is a schematic perspective bottom view structure diagram of the oscillating plate of the present invention.

[0018] In the figure: 1. Conveyor frame; 101. Feeding belt; 102. Conveyor motor; 103. Guide plate; 2. Transmission belt; 201. Transmission roller; 3. Bottom plate; 301. Back plate; 302. Support beam; 303. Main control box; 304. Sound insulation board; 305. Protection plate; 306. Oscillation plate; 3061. Fixed frame; 3062. Helical spring; 3063. Scraping teeth; 307. Motor; 4. First diversion box; 401. First connection box; 402. Connecting pipe; 403. Second connection box; 404. Second diversion box; 405. Connecting pipe; 406. Suction pipe; 407. Air pump. Detailed implementation mode

[0019] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0020] As Figures 1 - 10 shown, a longitudinal paper tube conveying device with negative pressure adsorption proposed by the present invention includes a conveyor frame 1, a transmission belt 2, a bottom plate 3 and a first diversion box 4. A protection plate 305 is fixedly installed on the front of the top of the bottom plate 3, and a back plate 301 is fixedly installed on the back of the bottom plate 3. Sound insulation boards 304 are fixedly installed inside both the back plate 301 and the protection plate 305, and a sound insulation board 304 is fixedly installed between the back plate 301 and the protection plate 305. An oscillation plate 306 is installed between the back plate 301 and the protection plate 305. A motor 307 is fixedly installed on one side of the back of the back plate 301. The bottom plate 3 can provide an installation position for the components on the top and support the components on the top to ensure the stability of the device. The protection plate 305 and the back plate 301 are used to provide an installation position for the surrounding components. The sound insulation board 304 can isolate the noise generated during the operation of the device without affecting the heat dissipation of the internal components of the device, thereby reducing the noise impact of the device on the surrounding environment. The oscillation plate 306 can irregularly jump inside the transmission belt 2 through the suction force applied by the second diversion box 404 and the elastic force applied by the helical spring 3062. Then, when contacting the transmission belt 2, the holes inside the transmission belt 2 are cleaned, so as to cooperate with the second diversion box 404 to improve the cleaning effect of the device on the paper scraps inside the transmission belt 2. The motor 307 adopts the YE3 - 500KW type. After the motor 307 is powered on and rotates, it drives one of the two transmission rollers 201 to rotate at a constant speed, and then the transmission belt 2 installed on the outside of the transmission roller 201 rolls at a constant speed; A conveyor belt 2 is installed between the back plate 301 and the protective plate 305. A plurality of air holes are opened at equal intervals inside the conveyor belt 2. Two conveyor rollers 201 are installed on the inner side of the conveyor belt 2, and one of the conveyor rollers 201 is fixedly connected to the output shaft of the motor 307. The conveyor roller 201 is fixedly connected to the output shaft of the motor 307, so that when the motor 307 is working, the conveyor roller 201 rotates synchronously with the rotation of the motor 307, and the conveyor belt 2 rolls synchronously with the conveyor roller 201. When the paper tube falls on the top of the conveyor belt 2, the conveyor belt 2 can be used to transport the paper tube in a horizontal direction, and the paper tube is transported to a designated position, so as to stably transport a large number of paper tubes between equipment in different processes, save manpower required for transportation during paper tube processing, and improve the efficiency of the overall paper tube processing process; A conveyor frame 1 is fixedly installed on the top of the back plate 301. The conveyor frame 1 can provide a mounting position for surrounding components, thereby facilitating the connection of the device with other equipment, transporting the processed paper tube to the top of the conveyor belt 2, and making the paper tube fall on the top of the conveyor belt 2 in a longitudinal state, so as to realize the longitudinal transmission of the paper tube; A first guide box 4 is installed between the back plate 301 and the protective plate 305, a first connecting box 401 is fixedly installed on the front of the first guide box 4, a plurality of air inlets are opened on the top of the first guide box 4, and the first guide box 4 is in contact with the upper inner side of the conveyor belt 2, a second guide box 404 is installed below the first guide box 4, the first guide box 4 can be connected to the first connecting box 401, the second guide box 404 can be connected to the second connecting box 403, and the first connecting box 401 and the second connecting box 403 are connected in series through the connecting pipe 402 and the connecting pipe 405, and the connecting pipe 405 is connected to the air pump 407 through the suction pipe 406, and the air inlet When the air pump 407 is powered on, it can apply suction to the conveyor belt 2 through the first guide box 4 and the second guide box 404. When the first guide box 4 applies suction to the conveyor belt 2, the paper tube can be stably conveyed in a longitudinal state on the top of the conveyor belt 2. When the second guide box 404 applies suction to the conveyor belt 2, on the one hand, it can directly suck out the paper scraps inside the conveyor belt 2, and on the other hand, it can apply suction to the oscillation plate 306 to promote irregular jumping of the oscillation plate 306, so that the oscillation plate 306 intermittently applies longitudinal pressure to the conveyor belt 2, shakes off the paper scraps stuck in the conveyor belt 2, and improves the cleaning effect of the device on the conveyor belt 2.

[0021] Furthermore, the second flow guiding box 404 has the same structure as the first flow guiding box 4, and the top of the second flow guiding box 404 is in contact with the bottom of the conveyor belt 2. A second communication box 403 is fixedly installed on the front surface of the second flow guiding box 404. A number of connecting pipes 402 are fixedly installed between the first communication box 401 and the second communication box 403. A connecting pipe 405 is installed at the bottom of the second communication box 403 through a number of connecting pipes 402. An air suction pipe 406 is fixedly installed on one side of the bottom of the connecting pipe 405. One end of the air suction pipe 406 far from the connecting pipe 405 is fixedly installed with an air pump 407. The tops of the first flow guiding box 4 and the second flow guiding box 404 are both flat surfaces, which can support the conveyor belt 2, so that the conveyor belt 2 always works in a horizontal state, and at the same time ensure that the paper tube on the top of the conveyor belt 2 is conveyed in a horizontal state. While applying suction force to the conveyor belt 2, the first flow guiding box 4 and the second flow guiding box 404 can prevent the conveyor belt 2 from deforming, thereby preventing a large gap from appearing between the conveyor belt 2 and the conveyor roller 201 and affecting the transmission efficiency of the conveyor belt 2. The connecting pipes 402 and the connecting pipe 405 can connect the first communication box 401 and the second communication box 403 in series, and facilitate the air suction pipe 406 and the air pump 407 to quickly suck the air inside the first flow guiding box 4 and the second flow guiding box 404. The air pump 407 adopts the XH1210H type. After being powered on, the air pump 407 starts to work, and can suck the air inside the connecting pipe 402 through the air suction pipe 406, so that the air inside the first flow guiding box 4 and the second flow guiding box 404 is all pumped out through the connecting pipe 405, so as to facilitate the formation of a negative pressure environment inside the first flow guiding box 4 and the second flow guiding box 404, and then use the first flow guiding box 4 and the second flow guiding box 404 to apply suction force to the conveyor belt 2, realizing the stable longitudinal transmission of the paper tube on the top of the conveyor belt 2.

[0022] Furthermore, a number of scraping teeth 3063 are provided at the bottom of the oscillating plate 306, and the scraping teeth 3063 are of an elliptical curved surface structure. The shape of the scraping teeth 3063 is the same as the shape of the holes inside the conveyor belt 2. When the conveyor belt 2 rolls, it can continuously contact a number of scraping teeth 3063, thereby discharging the paper scraps attached inside the conveyor belt 2. Cooperating with the suction force applied by the second flow guiding box 404 to the conveyor belt 2, the paper scraps can be quickly and effectively removed from the holes inside the conveyor belt 2, avoiding the blockage of the holes inside the conveyor belt 2 and affecting the suction force applied by the first flow guiding box 4 to the conveyor belt 2.

[0023] Further, three sets of helical springs 3062 are fixedly installed on the top of the oscillation plate 306. The top of the helical springs 3062 is fixedly installed with a fixing frame 3061. The front and back of the fixing frame 3061 are respectively fixedly connected to the protection plate 305 and the back plate 301. The helical springs 3062 can elastically connect the fixing frame 3061 and the oscillation plate 306 by using their own elastic force. During the operation of the oscillation plate 306, due to the suction force applied by the second diversion box 404, the oscillation plate 306 irregularly jumps on the top of the conveyor belt 2. As a result, a number of scraping teeth 3063 at the bottom of the oscillation plate 306 intermittently contact the conveyor belt 2, thereby discharging the paper scraps attached to the holes inside the conveyor belt 2. The fixing frame 3061 can be connected to the back plate 301 and the protection plate 305 to facilitate the installation of the helical springs 3062 and the oscillation plate 306. The oscillation plate 306 can irregularly jump on the top of the conveyor belt 2 by using the elastic force applied by the helical springs 3062 and the suction force applied by the second diversion box 404, and then clean the paper scraps on the conveyor belt 2.

[0024] Further, the air pump 407 is fixedly connected to the top of the bottom plate 3, and a solenoid valve is fixedly installed at the connection position between the air pump 407 and the suction pipe 406. The solenoid valve can control the opening and closing of the suction pipe 406, so that when the suction pipe 406 is opened, the air pump 407 can suck air through the suction pipe 406.

[0025] Further, both the first diversion box 4 and the second diversion box 404 are hollow square structures, and the back surfaces of the first diversion box 4 and the second diversion box 404 are both open-type designs. After the first diversion box 4 and the second diversion box 404 are connected by the connecting pipe 402, they are fixedly connected to the connecting pipe 405 through the connecting pipe 402, which facilitates the air pump 407 to suck the air inside the first diversion box 4 and the second diversion box 404.

[0026] Further, a main control box 303 is fixedly installed on the left side of the front surface of the protection plate 305, and a number of support beams 302 are fixedly installed between the protection plate 305 and the back plate 301. The main control box 303 can be electrically connected to the electronic components inside the device through wires, so as to facilitate the control of multiple electronic components to cooperate with each other to work. The support beams 302 can improve the connection stability between the back plate 301 and the protection plate 305.

[0027] Furthermore, a feeding belt 101 is installed at the top of the conveying rack 1, and two driving rollers are installed inside the feeding belt 101. A conveying motor 102 is fixedly installed on one side of the conveying rack 1, and the output shaft of the conveying motor 102 is fixedly connected to the driving roller. A guiding plate 103 is fixedly installed on the front of the conveying rack 1. The guiding plate 103 is an arc-shaped plate. The top of the guiding plate 103 is on the same horizontal plane as the feeding belt 101, and there is a distance of three to five centimeters between the bottom of the guiding plate 103 and the transmission belt 2. The feeding belt 101 can roll as the driving roller rotates, so as to transfer the paper tube to the top of the transmission belt 2. The conveying motor 102 adopts the YE3-100KW type. After the conveying motor 102 is powered on, it can rotate, and then drive the driving roller to rotate, so as to drive the feeding belt 101 to roll. The guiding plate 103 can change the paper tube at the top of the feeding belt 101 from horizontal to vertical, and then place the paper tube longitudinally on the top of the transmission belt 2 for transmission.

[0028] Furthermore, a number of sound insulation holes are provided inside the sound insulation board 304, and the aperture outside the sound insulation holes is twice that of the inner aperture. The sound insulation holes can facilitate the heat dissipation of the components inside the device. At the same time, the inner aperture of the sound insulation holes is smaller than the outer aperture, which can reduce the influence of the sound insulation holes on the sound insulation effect of the sound insulation board 304, so that the sound insulation holes can achieve sound insulation without affecting the heat dissipation inside the device.

[0029] Working principle: After the device is assembled, move the device to a specified position and fix it. Control the electronic components inside the device to be powered on and work through the main control box 303. The conveying motor 102 is powered on and rotates to drive the feeding belt 101 to roll. At the same time, the motor 307 is powered on and rotates to drive the transmission roller 201 to rotate at a constant speed, and then the transmission roller 201 rolls at a constant speed. After the air pump 407 is powered on, it pumps air into the first diversion box 4 and the second diversion box 404, so that the first diversion box 4 and the second diversion box 404 respectively apply suction to the transmission belt 2; When starting the transmission, the paper tube moves to the top of the transmission belt 2 in a horizontal position through the feeding belt 101 and changes from horizontal to vertical. The first diversion box 4 applies suction to the longitudinally arranged paper tube through the transmission belt 2. The paper tube is fixed on the top of the transmission belt 2 by the suction force and moves horizontally to the other side of the transmission belt 2 with the transmission belt 2 to complete the transmission of the paper tube; During the process of the transmission belt 2 rolling at a constant speed, when the air pump 407 pumps air into the first diversion box 4 and the second diversion box 404, the shock plate 306 is affected by the suction force applied by the second diversion box 404 and intermittently contacts the transmission belt 2, so that the scraping teeth 3063 intermittently contact the holes inside the transmission belt 2, knocking down the paper scraps attached to the inside of the transmission belt 2. Cooperating with the suction force applied by the second diversion box 404 to the paper scraps, the surface of the transmission belt 2 is kept clean, and the blockage of the holes inside the transmission belt 2 is avoided, which affects the suction force applied by the first diversion box 4 to the paper tube.

[0030] The above specific embodiments are merely several preferred embodiments of the present invention. Based on the technical solution of the present invention and the relevant revelations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A negative pressure adsorption paper tube longitudinal conveying device, comprising a conveying frame (1), a conveying belt (2), a bottom plate (3) and a first guide box (4), characterized in that: A protective plate (305) is fixedly mounted on the front of the top of the bottom plate (3), a back plate (301) is fixedly mounted on the back of the bottom plate (3), sound insulation plates (304) are fixedly mounted inside the back plate (301) and the protective plate (305), and a sound insulation plate (304) is fixedly mounted between the back plate (301) and the protective plate (305), an oscillation plate (306) is mounted between the back plate (301) and the protective plate (305), and a motor (307) is fixedly mounted on one side of the back of the back plate (301); A conveyor belt (2) is installed between the back plate (301) and the protective plate (305), a plurality of air holes are provided at equal intervals inside the conveyor belt (2), two conveyor rollers (201) are installed on the inner side of the conveyor belt (2), and one of the conveyor rollers (201) is fixedly connected to the output shaft of the motor (307); A conveying frame (1) is fixedly mounted on the top of the back plate (301); A first guide box (4) is installed between the back plate (301) and the protective plate (305); a first connecting box (401) is fixedly installed on the front of the first guide box (4); a plurality of air inlets are provided on the top of the first guide box (4); the first guide box (4) is in contact with the upper part of the inner side of the conveyor belt (2); and a second guide box (404) is installed below the first guide box (4).

2. A negative pressure adsorption paper tube longitudinal conveying device according to claim 1, characterized in that: The second flow guide box (404) has the same structure as the first flow guide box (4), and the top of the second flow guide box (404) contacts the bottom of the conveyor belt (2). A second connecting box (403) is fixedly installed on the front of the second flow guide box (404). A plurality of connecting tubes (402) are fixedly installed between the first connecting box (401) and the second connecting box (403). A connecting tube (405) is installed on the bottom of the second connecting box (403) through the plurality of connecting tubes (402). An air suction tube (406) is fixedly installed on one side of the bottom of the connecting tube (405), and an air pump (407) is fixedly installed on one end of the air suction tube (406) away from the connecting tube (405).

3. The negative pressure adsorption paper tube longitudinal conveying device according to claim 1, characterized in that: A plurality of scraping teeth (3063) are provided at the bottom of the oscillating plate (306), and the scraping teeth (3063) are elliptical curved surface structures.

4. A negative pressure adsorption paper tube longitudinal conveying device according to claim 1, characterized in that: Three groups of coil springs (3062) are fixedly mounted on the top of the oscillation plate (306), a fixing frame (3061) is fixedly mounted on the top of the coil springs (3062), and the front and back sides of the fixing frame (3061) are fixedly connected to the protective plate (305) and the back plate (301), respectively.

5. The negative pressure adsorption paper tube longitudinal conveying device according to claim 2, characterized in that: The air pump (407) is fixedly connected to the top of the bottom plate (3), and a solenoid valve is fixedly installed at the connection position between the air pump (407) and the air suction pipe (406).

6. A negative pressure adsorption paper tube longitudinal conveying device according to claim 1, characterized in that: The first flow guide box (4) and the second flow guide box (404) are both hollow square structures, and the backs of the first flow guide box (4) and the second flow guide box (404) are both open-type designs.

7. The negative pressure adsorption paper tube longitudinal conveying device according to claim 1, characterized in that: A main control box (303) is fixedly installed on the left side of the front side of the protection plate (305), and a plurality of support beams (302) are fixedly installed between the protection plate (305) and the back plate (301).

8. The negative pressure adsorption paper tube longitudinal conveying device according to claim 1, characterized in that: A feed belt (101) is installed on the top of the conveyor frame (1), and two driving rollers are installed on the inner side of the feed belt (101). A conveying motor (102) is fixedly installed on one side of the conveyor frame (1), and the output shaft of the conveying motor (102) is fixedly connected to the driving roller. A guide plate (103) is fixedly installed on the front of the conveyor frame (1), and the guide plate (103) is an arc-shaped plate. The top of the guide plate (103) and the feed belt (101) are on the same horizontal plane, and a distance of three to five centimeters is set between the bottom of the guide plate (103) and the conveyor belt (2).

9. The negative pressure adsorption paper tube longitudinal conveying device according to claim 1, characterized in that: The sound insulation board (304) is provided with a plurality of sound insulation holes inside, and the hole diameter outside the sound insulation hole is twice the hole diameter inside.

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