Roller screen for coal
By setting up a pre-screening device and material guide components in the roller screen to pre-screen and uniformly guide the coal, the problem of excessive load of the roller screen when dealing with wet coal is solved, and the screening efficiency and equipment stability are improved.
Patent Information
- Application Number
- CN202422112122.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-29
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2034-08-29
AI Technical Summary
When the roller screen treats coal with large humidity and different particle sizes, the load on the screen shaft and screen disc is too large, resulting in poor screening, damage to the screen shaft and excessive motor load, affecting the safe and stable operation of the unit.
The pre-sieve device and a material guide assembly are arranged in the sealed box. The material is initially separated through the pre-sieve device to reduce the screening load, and the material flows evenly to the screening area composed of the screen shaft and the screening plate through the material guide assembly.
It effectively reduces the workload of the screen shaft and screen disc, improves the screening efficiency, reduces the equipment failure rate and maintenance costs, and improves the quality of material processing.
Smart Images
Figure CN223145316U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of screening equipment, and particularly relates to a roller screen for coal. Background Art
[0002] A roller screen is a special screening machine mainly used for the conveying and separation of materials. Its working principle is to push the materials forward by multiple rotating screening shafts for screening, and it is suitable for coarse screening. The screening surface of the roller screen consists of multiple screening shafts arranged in parallel, and screening plates are staggered on each screening shaft. The rollers rotate through chain wheels or gears, and their rotation direction is the same as the material flow direction. The design concept of the roller screen includes single-machine rotation, the screening shafts are arranged according to the equal-thickness principle, and the screening plates are made of high-strength wear-resistant materials, etc. These designs make the roller screen have the characteristics of high screening efficiency, low noise, and stable operation. For example, the roller screen can screen out materials larger than the screen holes and send them into the coal crusher for crushing, while the materials smaller than the screen holes directly fall by their own gravity and enter the system. As an efficient and reliable screening equipment, the roller screen can be applied to the screening of various coarse-grained materials and is widely used in the coal conveying systems of thermal power plants and thermoelectric power plants.
[0003] When the roller screen is applied to the coal conveying systems of each power plant, when a coal flow with a certain humidity and different particle sizes moves in the roller screen, it will cause problems such as poor screening, damage to the screening shafts, and excessive motor load inside the roller screen, which will affect the safe and stable operation of the unit. Utility Model Content
[0004] This application provides a roller screen for coal, which can effectively reduce the loads on the screening shafts and screening plates inside the roller screen.
[0005] The above object of this application is achieved through the following technical solutions:
[0006] A roller screen for coal includes a sealed box. Inside the sealed box, there are multiple screening shafts arranged in parallel and connected to power equipment. Screening plates are installed on each screening shaft. A baffle plate is installed at the feeding port of the sealed box, and the baffle plate inclines downward from top to bottom towards the screening area composed of the multiple screening shafts and screening plates;
[0007] There is a gap between the lower end of the baffle plate and the screening shaft on the side close to the feeding port of the sealed box. A pre-screening device is arranged in this gap. One end of the pre-screening device is located below the lower end of the baffle plate, and the other end of the pre-screening device is located above the screening shaft on the side close to the feeding port of the sealed box;
[0008] A material guiding component is installed on the pre-screening device, and the material guiding component can make the coal materials discharged by the pre-screening device evenly flow towards the screening area composed of the multiple screening shafts and screening plates.
[0009] Furthermore, the pre-screening device includes a plurality of comb teeth arranged in parallel, and the plurality of comb teeth are equidistantly arranged along the width direction of the sealed box in the sealed box. One end of the plurality of comb teeth close to the lower part of the baffle plate is connected to the sealed box through the same first fixed-end shaft, and one end of the plurality of comb teeth far from the baffle plate is connected to the sealed box through the same second fixed-end shaft; and the height of the first fixed-end shaft is higher than the height of the second fixed-end shaft.
[0010] Furthermore, the comb teeth are cylindrical rods.
[0011] Furthermore, the diameter of the first fixed-end shaft is larger than the diameter of the comb teeth. The first fixed-end shaft sequentially penetrates through the central positions of one end of the plurality of comb teeth close to the baffle plate along the width direction of the sealed box and fixedly connects them together, and the first fixed-end shaft is located below the lower end of the baffle plate.
[0012] Furthermore, an arc-shaped connecting plate is fixedly connected to the lower part directly below one end of the comb teeth far from the baffle plate; the second fixed-end shaft sequentially penetrates through the arc-shaped connecting plates below the plurality of comb teeth along the width direction of the sealed box and fixedly connects them together.
[0013] Furthermore, the material guiding assembly includes an arc-shaped main material distribution plate, and the arc-shaped main material distribution plate is arranged at the middle position of the upper end of the pre-screening area formed by the plurality of comb teeth, and the open end of the arc-shaped main material distribution plate faces downward;
[0014] An arc-shaped secondary material distribution plate is respectively arranged below both sides of the open end of the arc-shaped main material distribution plate. The open end of the arc-shaped secondary material distribution plate faces the same direction as the open end of the arc-shaped main material distribution plate, and the arc-shaped secondary material distribution plate is fixedly installed on the pre-screening area formed by the plurality of comb teeth.
[0015] Furthermore, an inclined guiding side plate is respectively arranged on a relative side of the arc-shaped main material distribution plate along the width direction of the sealed box. Both of the guiding side plates are fixedly installed at the pre-screening area formed by the plurality of comb teeth, and both of the guiding side plates are inclined gradually downward to the middle position of the sealed box.
[0016] In summary, the present application includes at least one of the following beneficial technical effects:
[0017] In this application, a pre-screening device is added between the material baffle in the box body and the screening area composed of the screening shaft and the screening plate. The materials waiting to be screened for coal are added from the feeding port of the sealed box and will fall on the baffle. Then, before flowing to the screening area along the baffle, they will first come into contact with the pre-screening device. The pre-screening device of this application can separate and intercept some impurities in the materials in advance. These materials will flow to the screening area composed of the screening shaft and the screening plate only after being pretreated by the pre-screening device. Compared with the prior art, the screening pressure of the screening shaft and the screening plate in the roller screen of this application is significantly reduced, and the corresponding material screening efficiency is also improved. Moreover, due to the reduction of the screening load of the screening shaft and the screening plate, the failure rate of devices such as the screening shaft and the motor in the power equipment will also be reduced accordingly, saving the maintenance cost. Brief Description of the Drawings
[0018] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0019] Figure 1 is the overall structural schematic diagram of this application;
[0020] Figure 2 is the structural schematic diagram after cutting open the sealed box part of this application;
[0021] Figure 3 is the structural schematic diagram of the pre-screening device of this application and the material guiding assembly thereon;
[0022] Figure 4 is the structural schematic diagram of installing springs at both ends of the first fixed end shaft and the second fixed end shaft of this application, and installing a vibration motor in the pre-screening area.
[0023] Reference Numerals: 1, sealed box; 2, screening shaft; 3, screening plate; 4, baffle; 5, pre-screening device; 51, comb teeth; 52, first fixed end shaft; 53, second fixed end shaft; 6, material guiding assembly; 61, arc-shaped main material distributing plate; 62, arc-shaped secondary material distributing plate; 7, arc-shaped connecting plate; 8, guiding side plate; 9, spring; 10, vibration motor. Detailed Description of the Embodiment
[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following describes the technical solutions in the embodiments of this application clearly and completely. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts also belong to the scope of protection of this application.
[0025] As Figure 1 and Figure 2 shown, a roller screen for coal disclosed in this application includes a sealed box 1. Inside the sealed box 1, there are multiple sieve shafts 2 arranged in parallel and connected to power equipment. Sieve trays 3 are installed on the sieve shafts 2. A baffle 4 is installed in the feeding port of the sealed box 1. The baffle 4 inclines downward to the screening area composed of multiple sieve shafts 2 and sieve trays 3; there is a gap between the lower end of the baffle 4 and the sieve shaft 2 on the side close to the feeding port of the sealed box 1. A pre-screening device 5 is provided in this gap. One end of the pre-screening device 5 is located below the lower end of the baffle 4, and the other end of the pre-screening device 5 is located above the sieve shaft 2 on the side close to the feeding port of the sealed box 1; a material guiding assembly 6 is installed on the pre-screening device 5, and the material guiding assembly 6 can make the coal materials discharged from the pre-screening device 5 flow evenly to the screening area composed of multiple sieve shafts 2 and sieve trays 3.
[0026] In the above embodiments, the baffle 4 provided by this application below the feeding port of the sealed box 1 can play a buffering and guiding role for the materials after the coal materials to be screened are added into the sealed box 1. The pre-screening device 5 of this application is located between the baffle 4 and the screening area composed of multiple sieve shafts 2 and sieve trays 3. In this way, the materials to be screened will flow onto the pre-screening device 5 along the guidance of the baffle 4 before reaching the screening area composed of multiple sieve shafts 2 and sieve trays 3. The materials to be screened will flow to the screening area composed of multiple sieve shafts 2 and sieve trays 3 in the sealed box 1 after completing the pre-screening treatment on the pre-screening device 5. Compared with the prior art, since the pre-screening device 5 of this application has carried out pre-screening treatment before the materials to be screened reach the screening area composed of sieve shafts 2 and sieve trays 3, the amount of materials actually reaching the screening area composed of sieve shafts 2 and sieve trays 3 will be significantly reduced, thereby reducing the working load of the sieve shafts 2 and sieve trays 3. In this way, the screening efficiency of the entire equipment can be effectively improved, and the probability of the sieve shafts 2 and other equipment failing due to large screening load can be reduced. Accordingly, the maintenance cost can also be effectively reduced.
[0027] The material guiding assembly 6 provided on the pre-screening device 5 can make the pre-screened materials flow evenly into the screening area composed of sieve shafts 2 and sieve trays 3, so as to avoid the accumulation of materials in the middle area of the screening area composed of sieve shafts 2 and sieve trays 3, which affects the screening efficiency and the material moving speed.
[0028] Further, asFigure 2 and Figure 3 As shown in Figure 3 , the pre-screening device 5 includes a plurality of comb teeth 51 arranged in parallel, and the plurality of comb teeth 51 are equidistantly arranged along the width direction of the sealed box 1 inside the sealed box 1. One end of the plurality of comb teeth 51 close to the lower part of the baffle plate 4 is connected to the sealed box 1 through the same first fixed-end shaft 52, and one end of the plurality of comb teeth 51 far from the baffle plate 4 is connected to the sealed box 1 through the same second fixed-end shaft 53; and the height of the first fixed-end shaft 52 is higher than the height of the second fixed-end shaft 53.
[0029] In the above embodiments, the gaps between the plurality of comb teeth 51 of the present application can separate and intercept the materials in the materials whose particles conform to the gap size between the comb teeth 51 when the materials to be screened pass by, and the remaining materials will gradually flow along the plurality of comb teeth 51 to the screening area composed of the sieve shaft 2 and the sieve plate 3. Since the gaps between adjacent comb teeth 51 are equal, when the logistics flows along the plurality of comb teeth 51, the gaps between the plurality of comb teeth 51 can work simultaneously to achieve the preliminary screening effect of the materials, effectively improving the screening efficiency.
[0030] The plurality of comb teeth 51 can be firmly installed in the sealed box 1 through the first fixed-end shaft 52 and the second fixed-end shaft 53, and a stable integral structure is formed between them, so as to ensure the stability of their operation process. The first fixed-end shaft 52 of the present application is higher than the second fixed-end shaft 53, and the corresponding end of the comb tooth 51 connected to the first fixed-end shaft 52 is also higher than the end connected to the second fixed-end shaft 53. In this way, when the materials to be screened fall on the plurality of comb teeth 51, it is convenient for them to flow to the screening area composed of the sieve shaft 2 and the sieve plate 3 under their own weight.
[0031] Further, as Figure 2 and Figure 3 shown, the comb teeth 51 are cylindrical rods.
[0032] In the above embodiments, compared with setting the comb teeth 51 as rectangular rods, the cylindrical comb teeth 51 can avoid the accumulation of materials at their end faces during the process of conveying materials, increasing the subsequent cleaning burden.
[0033] Further, as Figure 2 and Figure 3 shown, the diameter of the first fixed-end shaft 52 is larger than the diameter of the comb teeth 51. The first fixed-end shaft 52 sequentially penetrates the central positions of one end of the plurality of comb teeth 51 close to the baffle plate 4 along the width direction of the sealed box 1 and fixedly connects them together, and the first fixed-end shaft 52 is located below the lower end of the baffle plate 4.
[0034] In the above embodiments, the first fixed-end shaft 52 of the present application fixedly connects the upper ends of the plurality of comb teeth 51 in the above-mentioned manner, which can not only improve the firmness of the connection of the plurality of comb teeth 51, but also increase the contact area between the first fixed-end shaft 52 with a larger diameter and the sealing box 1, thus providing a better installation support effect for the plurality of comb teeth 51. Since the diameter of the first fixed-end shaft 52 is larger than that of the comb teeth 51, if the material directly falls from the side of the first fixed-end shaft 52 far from the second fixed-end shaft 53, the upward protruding part of the first fixed-end shaft 52 may hinder the downward flow of the material. Therefore, the present application arranges the first fixed-end shaft 52 below the lower end of the baffle plate 4, so that the material falling from the baffle plate 4 will cross the first fixed-end shaft 52 and directly fall on the part of the plurality of comb teeth 51 between the first fixed-end shaft 52 and the second fixed-end shaft 53, effectively avoiding the larger-diameter first fixed-end shaft 52 from affecting the flow effect of the material on the comb teeth 51.
[0035] Further, as Figure 2 and Figure 3 shown, an arc-shaped connecting plate 7 is fixedly connected to the lower end of the comb teeth 51 directly below the end far from the baffle plate 4; the second fixed-end shaft 53 sequentially penetrates through the arc-shaped connecting plates 7 below the plurality of comb teeth 51 along the width direction of the sealing box 1 and fixedly connects them together.
[0036] In the above embodiments, if the second fixed-end shaft 53 is arranged above the lower ends of the plurality of comb teeth 51, the material may be hindered when flowing along the comb teeth 51 to the screening area composed of the screening shaft 2 and the screening plate 3. Therefore, the present application arranges the second fixed-end shaft 53 below the lower ends of the plurality of comb teeth 51, so that the upper part of the lower ends of the plurality of comb teeth 51 is smooth and will not be interfered by the second fixed-end shaft 53 when the material flows to the screening area.
[0037] The arc-shaped connecting plate 7 provided at the lower end of the comb teeth 51 in the present application facilitates the second fixed-end shaft 53 to sequentially penetrate and connect them in series, thereby making the overall structure integrity and stability of the plurality of comb teeth 51 better.
[0038] Further, as Figure 2 and Figure 3 shown, the material guiding assembly 6 includes an arc-shaped main material distributing plate 61, which is arranged at the middle position of the upper end of the pre-screening area composed of the plurality of comb teeth 51, and the open end of the arc-shaped main material distributing plate 61 faces downward;
[0039] On both sides below the open end of the arc-shaped main material distributing plate 61, there is respectively an arc-shaped secondary material distributing plate 62, the open end of the arc-shaped secondary material distributing plate 62 faces the same direction as the open end of the arc-shaped main material distributing plate 61, and the arc-shaped secondary material distributing plate 62 is fixedly installed on the pre-screening area composed of the plurality of comb teeth 51.
[0040] In the above embodiments, since the material to be screened is generally directly poured into the middle area of the feed port of the sealed box 1, during the subsequent screening process, these materials are likely to accumulate in the middle position of the screening area composed of the screening shaft 2 and the screening plate 3. In this way, the load on both sides during the operation of the screening shaft 2 and the screening plate 3 is relatively small, while the load in the middle area is too large.
[0041] In this application, an arc-shaped main material distribution plate 61 is arranged at the middle position above the pre-screening area composed of multiple comb teeth 51 to receive the material to be screened flowing down from the baffle plate 4. After contacting the arc-shaped main material distribution plate 61, these materials to be screened will be divided into two parts by the arc-shaped main material distribution plate 61 and continue to flow downward from its left and right sides. In this application, an arc-shaped secondary material distribution plate 62 is respectively arranged below both sides of the open end of the arc-shaped main material distribution plate 61. When the materials flowing down from both sides of the open end of the arc-shaped main material distribution plate 61 contact the two arc-shaped secondary material distribution plates 62, they will be divided again, generating four material flows flowing towards the screening area composed of the screening shaft 2 and the screening plate 3. In this way, the pre-screened materials can be evenly flowed into the screening area composed of the screening shaft 2 and the screening plate 3, avoiding the problem that the materials in the middle part of the screening area composed of the screening shaft 2 and the screening plate 3 are too concentrated while there are very few materials in the two side areas, resulting in too large a load in the middle area and prone to accumulation and blockage.
[0042] The arc-shaped main material distribution plate 61 and the arc-shaped secondary material distribution plate 62 of this application can buffer and adjust the moving speed of the materials, making the materials flow evenly and slowly towards the screening area composed of the screening shaft 2 and the screening plate 3, thereby improving the screening efficiency. In actual use, the types and particle sizes of the materials used by different enterprises or in different usage scenarios may vary. To ensure that the two arc-shaped secondary material distribution plates 62 can evenly guide the materials towards the screening area, the user can adaptively adjust the distance between the two arc-shaped secondary plates according to the actual situation.
[0043] Furthermore, as Figure 3 shown, an inclined guiding side plate 8 is respectively arranged on a relative side of the arc-shaped main material distribution plate 61 along the width direction of the sealed box 1. Both guiding side plates 8 are fixedly installed at the pre-screening area composed of multiple comb teeth 51, and both guiding side plates 8 are inclined gradually from top to bottom towards the middle position of the sealed box 1.
[0044] In the above embodiments, when adding materials from the feed port of the sealed box 1, although most of the materials will fall towards the arc-shaped main material distribution plate 61 along the middle area of the baffle plate 4, there will still be a part of the materials scattered towards both sides during the falling process. The two guiding side plates 8 arranged on both sides of the arc-shaped main material distribution plate 61 in this application can gather and guide these materials, so that they flow towards the two arc-shaped secondary material distribution plates 62 below together with the materials separated by the arc-shaped main material distribution plate 61.
[0045] In actual use, when the moisture content of the material to be screened is relatively high, during the process of moving downward along the pre-screening area, due to the settings of the material guiding component 6 and the guiding side plate 8, the downward movement effect is affected. For example Figure 4 As shown, technicians can connect both ends of the first fixed-end shaft 52 and both ends of the second fixed-end shaft 53 to the inner wall of the sealing box 1 through springs 9, and install a vibration motor 10 on the side of the guiding side plate 8 away from the arc-shaped main material distributing plate 61. In this way, during pre-screening, the vibration motor 10 can drive the pre-screening area composed of multiple comb teeth 51 to generate a certain vibration in the sealing box 1 (the working principle of the vibration is similar to that of the vibrating screen in the prior art). In this way, even for the material to be screened with a slightly higher moisture content, the present application can also perform better pre-screening treatment and enable the pre-screened material to smoothly flow to the screening area.
[0046] The implementation principle of this embodiment is as follows: During use, the material to be screened first falls on the baffle plate 4 from the feed port of the sealing box 1, and then flows along the baffle plate 4 to the pre-screening area composed of multiple comb teeth 51. This area is designed with a special inclination angle (for example, the inclination angle of the pre-screening area composed of multiple comb teeth 51 in the sealing box is 30°), so that before the material enters the screening area composed of the screening shaft 2 and the screening disc 3, some impurities in the material are separated and intercepted in the pre-screening area. These materials will flow to the screening area composed of the screening shaft 2 and the screening disc 3 only after being pretreated by the pre-screening device 5, and during this process, the material guiding component 6 provided in the pre-screening area of the present application can make the material flow evenly to the screening area. Next, the pre-screened material enters the screening area composed of the screening shaft 2 and the screening disc 3 for further screening treatment.
[0047] Compared with the prior art, the present application significantly improves the screening efficiency and the material processing quality, and reduces the failure rate of the equipment by adding a pre-screening device 5 and a material guiding component 6 in the sealing box 1. It has a wide application prospect in the field of material screening and can bring higher benefits and values to industrial production.
[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A roller screen for coal, comprising a sealed box (1), wherein a plurality of sieve shafts (2) arranged in parallel and connected to a power device are provided in the sealed box (1), and sieve trays (3) are installed on the sieve shafts (2). It is characterized in that: A baffle plate (4) is installed at the feeding port of the sealed box (1), and the baffle plate (4) inclines downward from top to bottom towards the screening area composed of the plurality of screening shafts (2) and the screening trays (3); There is a gap between the lower end of the baffle plate (4) and the screening shaft (2) close to the feeding port side of the sealed box (1), and a pre-screening device (5) is arranged in this gap. One end of the pre-screening device (5) is located below the lower end of the baffle plate (4), and the other end of the pre-screening device (5) is located above the screening shaft (2) close to the feeding port side of the sealed box (1); A material guiding assembly (6) is installed on the pre-screening device (5), and the material guiding assembly (6) can make the coal materials discharged from the pre-screening device (5) flow evenly towards the screening area composed of the plurality of screening shafts (2) and the screening trays (3).
2. The roller screen for coal according to claim 1, wherein: The pre-screening device (5) includes a plurality of comb teeth (51) arranged in parallel, and the plurality of comb teeth (51) are arranged at equal intervals along the width direction of the sealed box (1) in the sealed box (1). The lower ends of the plurality of comb teeth (51) close to the baffle plate (4) are connected to the sealed box (1) through the same first fixed-end shaft (52), and the ends of the plurality of comb teeth (51) far from the baffle plate (4) are connected to the sealed box (1) through the same second fixed-end shaft (53); and the height of the first fixed-end shaft (52) is higher than the height of the second fixed-end shaft (53).
3. The roller screen for coal according to claim 2, wherein: The comb teeth (51) are cylindrical rods.
4. The roller screen for coal according to claim 3, wherein: The diameter of the first fixed-end shaft (52) is larger than the diameter of the comb teeth (51). The first fixed-end shaft (52) sequentially penetrates through the central positions of the ends of the plurality of comb teeth (51) close to the baffle plate (4) along the width direction of the sealed box (1) and fixedly connects them together, and the first fixed-end shaft (52) is located below the lower end of the baffle plate (4).
5. The roller screen for coal according to any one of claims 2 to 4, characterized in that: An arc-shaped connecting plate (7) is fixedly connected to the lower side directly below the end of the comb teeth (51) far from the baffle plate (4); the second fixed-end shaft (53) sequentially penetrates through the arc-shaped connecting plates (7) below the plurality of comb teeth (51) along the width direction of the sealed box (1) and fixedly connects them together.
6. The roller screen for coal according to any one of claims 2 to 4, characterized in that: The material guiding assembly (6) includes an arc-shaped main material distribution plate (61), and the arc-shaped main material distribution plate (61) is arranged at the middle position at the upper end of the pre-screening area composed of the plurality of comb teeth (51), and the open end of the arc-shaped main material distribution plate (61) faces downward; An arc-shaped secondary material distribution plate (62) is respectively arranged below both sides of the open end of the arc-shaped main material distribution plate (61). The open end of the arc-shaped secondary material distribution plate (62) faces the same direction as the open end of the arc-shaped main material distribution plate (61), and the arc-shaped secondary material distribution plate (62) is fixedly installed on the pre-screening area composed of the plurality of comb teeth (51).
7. The roller screen for coal according to claim 6, wherein: On one opposite side of the arc-shaped main material distribution plate (61) along the width direction of the sealing box (1), an inclined guiding side plate (8) is respectively provided. Both of the two guiding side plates (8) are fixedly installed at the pre-screening area composed of a plurality of the comb teeth (51), and the two guiding side plates (8) are gradually inclined towards the middle position of the sealing box (1) from top to bottom.