Coal sample spreading device

Abstract

The utility model belongs to coal sample spreading technical field discloses a coal sample spreading device, including mounting seat, first spreading subassembly, second spreading subassembly and third driving part. The mounting seat is located one side of sample tray, first spreading subassembly includes first driving part and first scraping piece, second spreading subassembly includes second driving part and second scraping piece, and first driving part and second driving part are connected to the opposite sides of mounting seat respectively, and its output end is connected to first scraping piece and second scraping piece respectively, can drive first scraping piece and second scraping piece to rotate in horizontal plane respectively. The output end of third driving part is connected mounting seat, can drive mounting seat to rotate in horizontal plane, make one of first scraping piece and second scraping piece close sample tray and be located above sample tray, and the other is away from sample tray. The coal sample spreading device can make coal sample material heat evenly, and the accuracy of coal sample material moisture content detection and other analysis results is high, and the spreading effect is good and the working efficiency is high.

Description

Technical Field

[0001] This utility model relates to the field of coal sample leveling technology, and in particular to a coal sample leveling device. Background Technology

[0002] A coal sample leveling device is a specialized piece of equipment used in the coal testing and preparation process. It is mainly used to evenly spread coal samples in a container (such as a sample pan or crucible). The uniformity of the leveling directly affects the efficiency and accuracy of subsequent coal drying, weighing, and testing, and is particularly crucial for key indicators such as moisture content determination and calorific value analysis.

[0003] However, existing coal sample leveling devices use a unidirectional rotating scraping method. Under centrifugal force, the material tends to accumulate at the edge of the sample tray, forming a "crater" phenomenon with a thin center and thick edges. This results in uneven heating of the sample and seriously affects the accuracy of analytical results such as moisture detection. Furthermore, they are usually equipped with a single-size scraper, which cannot efficiently process materials with different particle sizes (such as 13mm coarse coal and 6mm fine coal) or different physical properties at the same time. This leads to poor leveling effect and requires frequent manual tool replacement, resulting in low efficiency.

[0004] Therefore, there is an urgent need to develop a coal sample leveling device to solve the above problems. Utility Model Content

[0005] The purpose of this utility model is to provide a coal sample leveling device that can level coal sample materials from both the front and back directions, making the coal sample materials more uniform and thus heating more evenly, resulting in high accuracy of analysis results such as coal sample moisture detection; it can simultaneously and efficiently process coal sample materials with different particle sizes or different physical properties using two specifications of scraping blades, with good leveling effect and high working efficiency.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] The coal sample leveling device includes:

[0008] Mounting base, the mounting base being located on one side of the sample tray;

[0009] A first leveling component and a second leveling component, wherein the first leveling component includes a first driving component and a first scraping component, and the second leveling component includes a second driving component and a second scraping component, wherein the first driving component and the second driving component are respectively connected to opposite sides of the mounting base, and the output ends of the first driving component and the second driving component are respectively connected to the first scraping component and the second scraping component, and are capable of driving the first scraping component and the second scraping component to rotate in the forward and reverse directions in the horizontal plane respectively;

[0010] The third driving component, whose output end is connected to the mounting base, is capable of driving the mounting base to rotate in the horizontal plane, so that one of the first scraping component and the second scraping component is close to the sample plate and located above the sample plate, while the other is away from the sample plate.

[0011] As an optional technical solution for the coal sample leveling device, the first leveling component further includes a first fixing plate, and the second leveling component further includes a second fixing plate. One end of the first fixing plate and the second fixing plate are respectively connected to the opposite sides of the mounting base, and the first driving member and the second driving member are respectively fixed to the first fixing plate and the second fixing plate.

[0012] As an optional technical solution for the coal sample leveling device, the coal sample leveling device further includes a first lifting component and a second lifting component. The first lifting component and the second lifting component are respectively fixed on both sides of the mounting base, and their output ends are respectively connected to the first fixing plate and the second fixing plate, which can drive the first fixing plate and the second fixing plate to move in the vertical direction.

[0013] As an optional technical solution for the coal sample leveling device, the first lifting assembly includes a first pushing member, a first guide rail, and a first slider. The second lifting assembly includes a second pushing member, a second guide rail, and a second slider. The first pushing member and the second pushing member are located on opposite sides of the top of the mounting base, and their output ends are respectively connected to the first fixed plate and the second fixed plate. The first guide rail and the second guide rail are located on opposite sides of the mounting base and extend along the vertical direction. One end of the first slider is slidably connected to the first guide rail, and the other end is fixedly connected to the first fixed plate. One end of the second slider is slidably connected to the second guide rail, and the other end is fixedly connected to the second fixed plate.

[0014] As an optional technical solution for the coal sample leveling device, the first lifting assembly further includes a first floating joint, the two ends of which are respectively connected to the output end of the first pusher and the first fixed plate; the second lifting assembly further includes a second floating joint, the second floating joint being connected to the output end of the second pusher and the second fixed plate.

[0015] As an optional technical solution for the coal sample leveling device, both the first floating joint and the second floating joint are active buffer elements, and both have integrated pressure sensors inside.

[0016] As an optional technical solution for the coal sample leveling device, the coal sample leveling device also includes two industrial cameras, which are respectively fixed to the first fixed plate and the second fixed plate, for identifying the material on the sample tray.

[0017] As an optional technical solution for the coal sample leveling device, the bottom of the first fixing plate is provided with a first baffle, which extends along the outer periphery of the sample plate and is arranged in a closed loop; the bottom of the second fixing plate is provided with a second baffle, which extends along the outer periphery of the sample plate and is arranged in a closed loop.

[0018] As an optional technical solution for the coal sample leveling device, the first leveling component further includes a first connecting shaft, one end of which is connected to the output end of the first driving component, and the other end of which is connected to the first scraping component; the second leveling component further includes a second connecting shaft, one end of which is connected to the output end of the second driving component, and the other end of which is connected to the second scraping component.

[0019] As an optional technical solution for the coal sample leveling device, the lower end of the first scraper is provided with a first trapezoidal notch, the width of which is in the range of 13mm-15mm; the lower end of the second scraper is provided with a second trapezoidal notch, the width of which is in the range of 7mm-9mm.

[0020] The beneficial effects of this utility model are:

[0021] The coal sample leveling device provided by this utility model includes a mounting base, a first leveling component, a second leveling component, and a third driving component. The mounting base is located on one side of the sample tray and serves as a fixed support. The first leveling component includes a first driving component and a first scraping component, and the second leveling component includes a second driving component and a second scraping component. The first driving component and the second driving component are respectively connected to opposite sides of the mounting base, and their output ends are respectively connected to the first scraping component and the second scraping component. This allows the first scraping component and the second scraping component to rotate in opposite directions in the horizontal plane, thus leveling the coal sample material from both directions. This makes the coal sample material on the sample tray more uniform, thereby ensuring uniform heating of the coal sample material and improving the accuracy of analytical results such as coal sample moisture detection. The output end of the third drive unit is connected to the mounting base, which can drive the mounting base to rotate in the horizontal plane. This causes one of the first and second scraping components to approach the sample plate and be located above it, while the other moves away from the sample plate. In other words, one of the two components switches to the working position, and the other switches to the non-working position. This allows two types of scraping blades to simultaneously and efficiently process coal samples with different particle sizes or different physical properties, resulting in good leveling effect and high working efficiency. Attached Figure Description

[0022] Figure 1 This is a first structural schematic diagram of the coal sample leveling device provided in this embodiment of the utility model;

[0023] Figure 2 This is a schematic diagram of the second structure of the coal sample leveling device provided in this embodiment of the utility model.

[0024] In the picture:

[0025] 100, Mounting base; 210, First driving component; 220, First scraping component; 230, First fixing plate; 231, First baffle; 310, Second driving component; 320, Second scraping component; 330, Second fixing plate; 331, Second baffle; 400, Third driving component; 510, First pushing component; 520, First guide rail; 530, First slider; 540, First floating joint; 610, Second pushing component; 620, Second guide rail; 630, Second slider; 640, Second floating joint. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.

[0027] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0028] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0029] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0030] This embodiment provides a coal sample leveling device that can level coal sample materials from both the front and back directions, making the coal sample materials more uniform and thus heating more evenly, resulting in high accuracy of analysis results such as coal sample moisture detection; it can simultaneously and efficiently process coal sample materials with different particle sizes or different physical properties using two specifications of scraping blades, with good leveling effect and high working efficiency.

[0031] Specifically, such as Figure 1 and Figure 2 As shown, the coal sample leveling device includes a mounting base 100, a first leveling assembly, a second leveling assembly, and a third driving component 400. The mounting base 100 is located on one side of the sample tray. The first leveling assembly includes a first driving component 210 and a first scraper 220, and the second leveling assembly includes a second driving component 310 and a second scraper 320. The first driving component 210 and the second driving component 310 are respectively connected to opposite sides of the mounting base 100, and their output ends are respectively connected to the first scraper 220 and the second scraper 320. The first driving component 210 and the second driving component 310 can drive the first scraper 220 and the second scraper 320 to rotate in opposite directions in the horizontal plane. The output end of the third driving component 400 is connected to the mounting base 100 and can drive the mounting base 100 to rotate in the horizontal plane, so that one of the first scraper 220 and the second scraper 320 is close to the sample tray and located above the sample tray, while the other is away from the sample tray.

[0032] Based on the above design, the mounting base 100 is located on one side of the sample tray, serving as a fixed support. The first leveling component includes a first driving component 210 and a first scraping component 220, and the second leveling component includes a second driving component 310 and a second scraping component 320. The first driving component 210 and the second driving component 310 are respectively connected to opposite sides of the mounting base 100, and their output ends are respectively connected to the first scraping component 220 and the second scraping component 320. This allows the first scraping component 220 and the second scraping component 320 to rotate in opposite directions in the horizontal plane, thus leveling the coal sample material from both directions. This prevents the coal sample material from accumulating towards the edge due to centrifugal force in the same direction for a long time, making the coal sample material on the sample tray more uniform, thereby ensuring uniform heating of the coal sample material and improving the accuracy of analytical results such as coal sample moisture detection. The output end of the third driving component 400 is connected to the mounting base 100, which can drive the mounting base 100 to rotate in the horizontal plane, so that one of the first scraper 220 and the second scraper 320 is close to the sample plate and located above the sample plate, while the other is away from the sample plate. That is, one of the two is switched to the working position and the other is switched to the non-working position, so that the two scraper blades of different specifications can simultaneously and efficiently process coal sample materials with different particle sizes or different physical properties, with good leveling effect and high working efficiency.

[0033] Optionally, the mounting base 100 is a column vertically arranged on one side of the sample tray, the third drive unit 400 is located at the top of the column, the first leveling component and the second leveling component are located on opposite sides of the column, and the third drive unit 400 can drive the column to rotate 180 degrees, so that the first leveling component and the second leveling component can switch between the working position (located above the sample tray) and the non-working position.

[0034] In this embodiment, the third driving component 400 can be a drive motor.

[0035] Optionally, the first leveling assembly further includes a first connecting shaft, one end of which is connected to the output end of the first drive member 210, and the other end of which is connected to the first scraper member 220. The first scraper member 220 is connected to the first drive member 210 via the first connecting shaft, which facilitates the installation of the first scraper member 220. The second leveling assembly further includes a second connecting shaft, one end of which is connected to the output end of the second drive member 310, and the other end of which is connected to the second scraper member 320. The second scraper member 320 is fixed to the output end of the second drive member 310 via the second connecting shaft, which facilitates the installation of the second scraper member 320.

[0036] Furthermore, the first scraper 220 and the second scraper 320 are detachably connected to the first connecting shaft and the second connecting shaft, respectively, to facilitate the replacement of the first scraper 220 and the second scraper 320.

[0037] The quick-change interface may also be equipped with an identification module for identifying the first scraper 220 and the second scraper 320, and the first connecting shaft and the second connecting shaft are respectively equipped with an identification reader for reading the identification module.

[0038] For example, the first scraper 220 and the second scraper 320 can be connected to the first connecting shaft and the second connecting shaft respectively via quick-change interfaces such as threads.

[0039] In this embodiment, the first driving component 210 and the second driving component 310 can be servo motors or stepper motors, which can drive the first scraper 220 and the second scraper 320 to alternately rotate in the forward and reverse directions to perform a leveling operation, thereby preventing the coal sample material from accumulating at the edge due to centrifugal action in the same direction for a long time.

[0040] Optionally, the lower end of the first scraper 220 is provided with a first trapezoidal notch, the width of which is in the range of 13mm-15mm. For example, the width of the first trapezoidal notch can be 13mm, 14mm or 15mm to process coal sample materials with coarser particles; the lower end of the second scraper 320 is provided with a second trapezoidal notch, the width of which is in the range of 7mm-9mm. For example, it can be 7mm, 8mm or 9mm to process coal sample materials with finer particles.

[0041] Optionally, the first leveling component further includes a first fixing plate 230, and the second leveling component further includes a second fixing plate 330. One end of the first fixing plate 230 and the second fixing plate 330 are respectively connected to opposite sides of the mounting base 100. The first driving member 210 and the second driving member 310 are respectively fixed to the first fixing plate 230 and the second fixing plate 330. The first fixing plate 230 and the second fixing plate 330 are respectively used to support the first driving member 210 and the second driving member 310, and to keep the first driving member 210 and the second driving member 310 at a certain distance from the mounting base 100, so as to avoid the first scraping member 220 and the second scraping member 320 rotating and scraping the mounting base 100, and also to leave a certain space for the installation of the first scraping member 220 and the second scraping member 320.

[0042] In this embodiment, the first fixing plate 230 and the second fixing plate 330 are both horizontally arranged, and the first driving member 210 and the second driving member 310 are respectively located at the ends of the first fixing plate 230 and the second fixing plate 330 away from the mounting base 100.

[0043] Optionally, the bottom of the first fixing plate 230 is provided with a first baffle 231, which extends along the outer periphery of the sample tray and is arranged in a closed loop; the bottom of the second fixing plate 330 is provided with a second baffle 331, which extends along the outer periphery of the sample tray and is arranged in a closed loop, to prevent coal samples in the sample tray from splashing during the leveling operation.

[0044] Furthermore, the coal sample leveling device also includes a first lifting component and a second lifting component. The first lifting component and the second lifting component are respectively fixed on both sides of the mounting base 100, and their output ends are respectively connected to the first fixed plate 230 and the second fixed plate 330, which can drive the first fixed plate 230 and the second fixed plate 330 to move vertically, thereby driving the first scraper 220 and the second scraper 320 to move vertically. In actual leveling operation, at the beginning of leveling, the first lifting component (second lifting component) drives the first fixed plate 230 (second fixed plate 330) to drive the first scraper 220 (second scraper 320) to move downward, and the first driving component 210 (second driving component 310) drives the first scraper 220 (second scraper 320) to rotate and level the coal sample material; at the end of leveling, the first lifting component (second lifting component) drives the first fixed plate 230 (second fixed plate 330) to drive the first scraper 220 (second scraper 320) to rise, that is, to move upward.

[0045] Furthermore, the first lifting assembly includes a first pusher 510, a first guide rail 520, and a first slider 530, and the second lifting assembly includes a second pusher 610, a second guide rail 620, and a second slider 630. The first pusher 510 and the second pusher 610 are located on opposite sides of the top of the mounting base 100, and their output ends are respectively connected to the first fixing plate 230 and the second fixing plate 330. The first guide rail 520 and the second guide rail 620 are located on opposite sides of the mounting base 100 and extend vertically. One end of the first slider 530 is slidably connected to the first guide rail 520, and the other end is fixedly connected to the first fixing plate 230. One end of the second slider 630 is slidably connected to the second guide rail 620, and the other end is fixedly connected to the second fixing plate 330. The first pusher 510 pushes the first fixed plate 230 to slide on the first guide rail 520 via the first slider 530, thereby realizing the downward movement and lifting of the first scraper 220; the second pusher 610 pushes the second fixed plate 330 to slide on the second guide rail 620 via the second slider 630, thereby realizing the downward movement and lifting of the second scraper 320. The guide rail slider structure is simple and easy to operate.

[0046] Of course, in other embodiments, the first lifting assembly may include a first pusher 510, a first magnetic strip, and a first magnetic block, and the second lifting assembly may include a second pusher 610, a second magnetic strip, and a second magnetic block. The first pusher 510 and the second pusher 610 are located on opposite sides of the top of the mounting base 100, and their output ends are respectively connected to the first fixing plate 230 and the second fixing plate 330. The first magnetic strip and the second magnetic strip are located on opposite sides of the mounting base 100 and extend vertically. One end of the first magnetic block is magnetically attracted to the first magnetic strip, and the other end is fixedly connected to the first fixing plate 230. One end of the second magnetic block is magnetically attracted to the second magnetic strip, and the other end is fixedly connected to the second fixing plate 330.

[0047] Furthermore, the first lifting assembly also includes a first floating joint 540, the two ends of which are respectively connected to the output end of the first pusher 510 and the first fixed plate 230. The first floating joint 540 provides a certain buffering effect when the first pusher 510 pushes the first fixed plate 230 to drive the first scraper 220 downwards and approaches the coal sample material, thus preventing the first scraper 220 from impacting the coal sample material with an excessive amplitude and creating a "large pit" in the coal sample material. The second lifting assembly also includes a second floating joint 640, the second floating joint 640 being connected to the output end of the second pusher 610 and the second fixed plate 330. The second floating joint 640 provides a certain buffering effect when the second pusher 610 pushes the second fixed plate 330 to drive the second scraper 320 downwards and approaches the coal sample material, thus preventing the second scraper 320 from impacting the coal sample material with an excessive amplitude and creating a "large pit" in the coal sample material.

[0048] It should be noted that both the first floating joint 540 and the second floating joint 640 are active buffer elements, and both have integrated pressure sensors inside.

[0049] In this embodiment, the first pusher 510 and the second pusher 610 may be the same or different, and may be a cylinder, an electric push rod or a servo electric cylinder, etc.

[0050] Optionally, the coal sample leveling device also includes two industrial cameras, which are fixed to the first fixed plate 230 and the second fixed plate, respectively, to identify the material on the sample tray and adaptively adjust the leveling strategy (such as scraping depth, speed, and direction) according to the real-time status of the coal sample material (such as stacking height and distribution), thereby improving the coal sample leveling device's ability to cope with complex working conditions.

[0051] To enhance the intelligence of the coal sample leveling device, it further includes a central controller. The central controller is electrically connected to the first drive unit 210, the second drive unit 310, the third drive unit 400, the first lifting assembly, the second lifting assembly, an industrial camera, a pressure sensor, and an identification reader. Specifically, the central controller is configured to receive image information acquired by the industrial camera, and based on this image information, identify the accumulation height and distribution uniformity of the coal sample material. It then adaptively plans the downward speed and stroke of the first or second lifting assembly, as well as the rotational speed and forward / reverse cycle of the first or second drive unit 210.

[0052] The central controller is also configured to receive feedback signals from the pressure sensor in real time, and when the pressure value exceeds the preset safety threshold, immediately control the first or second lifting component to stop descending or perform a lifting action.

[0053] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make various obvious changes, readjustments, and substitutions without departing from the protection scope of this utility model. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A coal sample leveling device, characterized in that, include: Mounting base (100), said mounting base (100) is located on one side of the sample plate; A first leveling component and a second leveling component, the first leveling component including a first driving member (210) and a first scraping member (220), the second leveling component including a second driving member (310) and a second scraping member (320), the first driving member (210) and the second driving member (310) are respectively connected to opposite sides of the mounting base (100), and the output ends of the first driving member (210) and the second driving member (310) are respectively connected to the first scraping member (220) and the second scraping member (320), which can drive the first scraping member (220) and the second scraping member (320) to rotate in opposite directions in the horizontal plane respectively; A third driving member (400) has its output end connected to the mounting base (100) and is capable of driving the mounting base (100) to rotate in the horizontal plane, so that one of the first scraper (220) and the second scraper (320) is close to the sample plate and located above the sample plate, while the other is away from the sample plate.

2. The coal sample leveling device according to claim 1, characterized in that, The first leveling component further includes a first fixing plate (230), and the second leveling component further includes a second fixing plate (330). One end of the first fixing plate (230) and the second fixing plate (330) are respectively connected to opposite sides of the mounting base (100), and the first driving member (210) and the second driving member (310) are respectively fixed to the first fixing plate (230) and the second fixing plate (330).

3. The coal sample leveling device according to claim 2, characterized in that, The coal sample leveling device further includes a first lifting component and a second lifting component. The first lifting component and the second lifting component are respectively fixed on both sides of the mounting base (100), and their output ends are respectively connected to the first fixing plate (230) and the second fixing plate (330), which can drive the first fixing plate (230) and the second fixing plate (330) to move in the vertical direction.

4. The coal sample leveling device according to claim 3, characterized in that, The first lifting assembly includes a first pusher (510), a first guide rail (520), and a first slider (530). The second lifting assembly includes a second pusher (610), a second guide rail (620), and a second slider (630). The first pusher (510) and the second pusher (610) are located on opposite sides of the top of the mounting base (100), and their output ends are respectively connected to the first fixing plate (230) and the second fixing plate (330). The first guide rail (520) and the second guide rail (620) are located on opposite sides of the mounting base (100) and extend along the vertical direction. One end of the first slider (530) is slidably connected to the first guide rail (520), and the other end is fixedly connected to the first fixing plate (230). One end of the second slider (630) is slidably connected to the second guide rail (620), and the other end is fixedly connected to the second fixing plate (330).

5. The coal sample leveling device according to claim 4, characterized in that, The first lifting assembly further includes a first floating joint (540), the two ends of which are respectively connected to the output end of the first pusher (510) and the first fixed plate (230); the second lifting assembly further includes a second floating joint (640), the second floating joint (640) being connected to the output end of the second pusher (610) and the second fixed plate (330).

6. The coal sample leveling device according to claim 5, characterized in that, Both the first floating connector (540) and the second floating connector (640) are active buffer elements, and both have integrated pressure sensors inside.

7. The coal sample leveling device according to claim 2, characterized in that, The coal sample leveling device also includes two industrial cameras, which are respectively fixed to the first fixed plate (230) and the second fixed plate, for identifying the material in the sample tray.

8. The coal sample leveling device according to claim 2, characterized in that, The bottom of the first fixing plate (230) is provided with a first baffle (231), which extends along the outer periphery of the sample plate and is arranged in a closed loop; the bottom of the second fixing plate (330) is provided with a second baffle (331), which extends along the outer periphery of the sample plate and is arranged in a closed loop.

9. The coal sample leveling device according to any one of claims 1-8, characterized in that, The first leveling component further includes a first connecting shaft, one end of which is connected to the output end of the first drive member (210), and the other end is connected to the first scraper member (220); the second leveling component further includes a second connecting shaft, one end of which is connected to the output end of the second drive member (310), and the other end is connected to the second scraper member (320).

10. The coal sample leveling device according to any one of claims 1-8, characterized in that, The lower end of the first scraper (220) is provided with a first trapezoidal notch, the width of which is in the range of 13mm-15mm; the lower end of the second scraper (320) is provided with a second trapezoidal notch, the width of which is in the range of 7mm-9mm.

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