Dust removal device for TPV (thermoplastic vulcanizate) raw material mixing barrel

Abstract

The utility model relates to a dust removal device for a TPV raw material mixing barrel, and relates to the field of TPV production equipment.The mixing barrel comprises a mixing barrel support and a mixing barrel body, the mixing barrel body is supported on the mixing barrel support, a feeding port is formed in the upper portion of the mixing barrel body, a discharging port is formed in the lower portion of the mixing barrel body, the dust removal device is arranged on the periphery of the feeding port, and the dust removal device is arranged on the periphery of the discharging port. The dust removal device comprises a plurality of dust suction ports and a dust suction pipe, the plurality of dust suction ports are arranged on the mixing barrel body at the periphery of the feeding port at intervals, and the dust suction pipe is connected between the dust suction ports and an external negative pressure device; and dust pollution generated when TPV raw materials are added into the mixing barrel and the TPV raw materials in the mixing barrel are stirred can be reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the field of TPV production equipment, in particular to a TPV raw material mixing barrel dust removal device. BACKGROUND

[0002] Thermoplastic vulcanizate, abbreviated as TPV, is mainly composed of two parts, one is plastic as a continuous phase, and the other is rubber as a dispersed phase, which has excellent dynamic fatigue resistance, high tear resistance, excellent weather resistance, good wear resistance and excellent flame resistance and ultraviolet resistance, and has excellent corrosion resistance to water-based acid and alkali liquids and polar oil products, and is widely used in automobile parts, electronics and electrical appliances, sports equipment, wire and cable industries.

[0003] TPV is usually made of a mixture of ethylene-propylene-diene rubber (EPDM) and polypropylene (PP) materials and some auxiliary fillers such as filling powder and oil. When processing TPV elastomer, various raw materials are usually added to the mixing barrel first, and the stirring mechanism in the mixing barrel is used to stir the TPV raw materials, so that the different TPV raw materials are fully mixed in the mixing barrel. Then the mixed raw materials and vulcanizing agent are added to the double-screw extruder, heated to a molten state in the double-screw extruder, and vulcanized while mixing in the double-screw extruder to form TPV material. The TPV material is extruded through the extrusion hole on the extrusion die plate and cut by the granulator to form TPV elastomer particles.

[0004] The TPV raw materials are usually in the form of particles or powder, and a large amount of dust is usually generated during the process of adding TPV raw materials to the mixing barrel and mixing the TPV raw materials in the mixing barrel, causing dust pollution of the production environment. The existing TPV raw material mixing barrel usually uses a dust strip for dust isolation, which has poor dust prevention effect and cannot effectively prevent dust from escaping, resulting in serious dust pollution during production. CONTENT OF THE INVENTION

[0005] In order to reduce dust pollution during production, the application provides a TPV raw material mixing barrel dust removal device.

[0006] The TPV raw material mixing barrel dust removal device provided by the application, the mixing barrel includes a mixing barrel support and a mixing barrel body, the mixing barrel body is supported on the mixing barrel support, the upper part of the mixing barrel body is provided with a feeding port, and the lower part is provided with a discharging port, the periphery of the feeding port is provided with a dust removal device, the dust removal device includes a dust suction port and a dust suction pipe, the dust suction port is provided with a plurality of dust suction ports, the dust suction ports are arranged on the mixing barrel body around the discharging port, and the dust suction pipe is connected between the dust suction port and an external negative pressure device.

[0007] Further preferably, the dust suction port includes a first dust suction port and a second dust suction port, the dust suction pipe includes a first dust suction pipe and a second dust suction pipe, the first dust suction port is connected to the first dust suction pipe, the second dust suction port is connected to the second dust suction pipe, and the first dust suction pipe and the second dust suction pipe are both connected to the negative pressure device.

[0008] Furthermore, the top of the mixing barrel body is open to form the feeding port, the upper edge of the mixing barrel body is provided with a dust suction frame, the dust suction pipe is provided in the dust suction frame, and the dust suction port is provided on the dust suction frame.

[0009] Further preferably, the first dust suction port is arranged on the inner side of the dust suction frame, and the second dust suction port is arranged on the upper side of the dust suction frame.

[0010] Furthermore, a dust-isolating strip is provided on the upper side of the dust suction frame, and the dust-isolating strip is provided on the inner side of the second dust suction port.

[0011] Preferably, the mixing barrel further comprises a barrel cover, a barrel cover mounting strip is provided on the top of the mixing barrel body, the dust suction pipe is provided inside the barrel cover mounting strip, the dust suction ports are provided on both sides of the barrel cover mounting strip, the barrel cover is hinged on both sides of the barrel cover mounting strip, and can cover the feed port.

[0012] Further preferably, the first dust suction port is arranged at the lower part of both sides of the barrel cover mounting strip, and the second dust suction port is arranged at the upper part of both sides of the barrel cover mounting strip.

[0013] Furthermore, dust-proof strips are provided on both sides of the barrel cover mounting strip, and the dust-proof strips are provided between the first dust suction port and the second dust suction port.

[0014] Preferably, the dust removal device also includes a barrel cover sensing switch, a first solenoid valve is provided between the first dust suction pipe and the negative pressure device, a second solenoid valve is provided between the second dust suction pipe and the negative pressure device, and the barrel cover sensing switch is provided on both sides of the barrel cover mounting strip and is connected to the first solenoid valve and the second solenoid valve.

[0015] The TPV raw material mixing barrel dust removal device of the present application has at least one of the following beneficial technical effects:

[0016] 1. The dust removal device installed around the feed port of the mixing barrel can remove TPV raw material dust at the feed port when adding TPV raw materials to the mixing barrel and when the stirring mechanism in the mixing barrel stirs and mixes the TPV raw materials, preventing TPV raw material dust from drifting into the environment through the feed port and reducing dust pollution during the production process.

[0017] 2. By using multiple dust suction ports spaced apart in the area surrounding the feed port, TPV raw material dust can be removed at different locations around the feed port, effectively reducing the amount of dust escaping through the feed port. By using a dust suction pipe connected between the dust suction port and the external negative pressure device, the negative pressure generated by the external negative pressure device can be continuously transmitted to the dust suction port, forming a continuous dust suction effect. A dust filter collection device can also be set at the external negative pressure device to intercept and remove dust particles in the negative pressure airflow.

[0018] 3. By arranging the first dust suction port and the second dust suction port in different areas on the dust suction frame on the upper edge of the mixing barrel and the barrel cover mounting strip, a more effective negative pressure dust suction range can be formed in the feed port area, thereby improving the suction effect of the TPV raw material dust passing through the feed port and reducing dust pollution.

[0019] 4. The barrel cover induction switches arranged on both sides of the barrel cover mounting strip can control the connection status between the first and second vacuum pipes and the external negative pressure device according to the opening and closing of the barrel cover. While effectively preventing the escape of TPV raw material dust, it reduces the energy consumption of the negative pressure device, prevents unnecessary suction of TPV raw materials, and improves the utilization rate of TPV raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of an embodiment of the present application.

[0021] Figure 2 This is a cross-sectional view of a dust collection frame in one embodiment of the present application.

[0022] Figure 3 This is a cross-sectional view of the barrel cover mounting strip in one embodiment of the present application.

[0023] Explanation of the accompanying reference numerals: 1. Mixing barrel bracket; 2. Mixing barrel body; 21. Dust suction frame; 22. Barrel cover mounting strip; 23. Discharge pipe; 231. Discharge switch; 3. Dust removal device; 31. Dust suction port; 311. First dust suction port; 312. Second dust suction port; 32. Dust suction pipe; 321. First dust suction pipe; 322. Second dust suction pipe; 33. Dust barrier strip; 34. Barrel cover induction switch; 4. Barrel cover; 5. Stirring motor. DETAILED DESCRIPTION

[0024] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not intended to limit the present application.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0026] An embodiment of the TPV raw material mixing barrel dust removal device of the present application is as follows: Figures 1 to 3 As shown, the mixing barrel includes a mixing barrel bracket 1 and a mixing barrel body 2. The lower end of the mixing barrel bracket 1 is supported on the ground, and the upper end is fixedly supported on the mixing barrel body 2, and the mixing barrel body 2 is supported on the mixing barrel bracket 1 at a spatial position at a certain height above the ground.

[0027] The main portion of the mixing barrel 2 is in the shape of an inverted truncated cone with a slightly larger diameter at the top and a slightly smaller diameter at the bottom, with a smaller taper. The diameter of the bottom of the mixing barrel 2 decreases sharply, forming an inverted truncated cone-shaped support surface with a larger taper, and an inverted truncated cone-shaped mixing space is formed inside the mixing barrel 2. A feed port for adding TPV raw materials into the mixing barrel 2 is provided at the top of the mixing barrel 2, and a discharge port for discharging the mixed TPV raw materials from the mixing barrel 2 is provided at the bottom. The discharge port is usually provided on the inverted truncated cone-shaped support surface at the bottom of the mixing barrel 2, and a discharge pipe 23 is provided at the discharge port. The mixed TPV raw materials in the mixing barrel 2 are discharged into the packaging bag through the discharge pipe 23 to prevent the generation of TPV raw material dust during the discharge process. A discharge switch 231 is provided on the discharge pipe 23 adjacent to the discharge port. The discharge switch 231 can be a gate that can isolate the discharge port, or various electrically driven switch valves. The discharge switch 231 can control the opening and closing of the discharge port, thereby controlling whether the TPV raw materials in the mixing barrel 2 are discharged.

[0028] A stirring device is provided in the mixing barrel body 2, and a stirring motor 5 is provided on the outer side of the bottom surface of the mixing barrel body 2. The output shaft of the stirring motor 5 passes through the bottom wall of the mixing barrel body 2 and is connected to the stirring device, thereby driving the stirring device to rotate and stir and mix the TPV raw materials in the mixing barrel body 2.

[0029] A dust removal device 3 is provided around the feed port at the top of the mixing barrel 2. The dust removal device 3 can be any device capable of preventing the escape of TPV raw material dust from the mixing barrel 2, such as a negative pressure dust suction port, a dust suction air curtain, or a dust-proof soft curtain. The provision of the dust removal device 3 can prevent the escape of TPV raw material dust through the feed port during the process of adding TPV raw materials into the mixing barrel 2 through the feed port, and during the process of mixing the TPV raw materials in the mixing barrel 2 by the stirring device, thereby reducing the pollution of TPV raw material dust during the production process. The dust removal device 3 includes a dust suction port 31 and a dust suction pipe 32. A plurality of dust suction ports 31 are provided on the mixing barrel 2 around the feed port. The plurality of dust suction ports 31 are spaced apart on the mixing barrel 2, and are usually evenly spaced at the same intervals. The dust suction pipe 32 is arranged on the mixing barrel body 2 around the feed port along the setting path of multiple dust suction ports 31, or inside the cylindrical wall of the mixing barrel body 2. The multiple dust suction ports 31 are all connected to the tube cavity of the dust suction pipe 32, and are connected to the external negative pressure device through the dust suction pipe 32. The negative pressure generated by the external negative pressure device forms a negative pressure dust suction airflow at the dust suction port 31, which removes the TPV raw material dust at the feed port and prevents the dust in the mixing barrel body 2 from escaping through the feed port and causing dust pollution in the production environment.

[0030] A dust filter device such as a dust bag or a water filter dust removal device is usually provided between the dust suction pipe 32 and the external negative pressure device to remove dust in the negative pressure airflow and prevent the dust from affecting the normal operation of the external negative pressure device.

[0031] In a preferred embodiment of the TPV raw material mixing barrel dust removal device of the present application, as Figures 1 to 3 As shown, multiple dust suction ports 31 are divided into two groups of first dust suction ports 311 and second dust suction ports 312. The first dust suction ports 311 and the second dust suction ports 312 are respectively arranged at intervals around the feed port. Usually, the first dust suction port 311 is closer to the internal area of ​​the mixing barrel body 2, and the second dust suction port 312 is closer to the end area of ​​the mixing barrel body 2. The first dust suction port 311 and the second dust suction port 312 respectively perform negative pressure suction on the TPV raw material dust from different longitudinal depth areas of the feed port of the mixing barrel body 2, thereby effectively improving the suction effect of the TPV raw material dust.

[0032] Accordingly, the dust collection pipe 32 includes two different sets of pipes: a first dust collection pipe 321 and a second dust collection pipe 322. The first dust collection pipe 321 is connected to the plurality of first dust collection ports 311, and the second dust collection pipe 322 is connected to the plurality of second dust collection ports 312. The first dust collection pipe 321 and the second dust collection pipe 322 are respectively connected to an external negative pressure device, and the negative pressure generated by the external negative pressure device is transmitted to the first dust collection ports 311 and the second dust collection ports 312, respectively, to achieve a dust removal effect at the first dust collection ports 311 and the second dust collection ports 312.

[0033] As a specific embodiment of the TPV raw material mixing barrel dust removal device of the present application, Figure 1 and Figure 2 As shown, the opening at the top of the mixing barrel 2 is formed as the feed port of the mixing barrel 2. A dust collection frame 21 is provided on the upper edge of the barrel wall at the top opening of the mixing barrel 2. The dust collection frame 21 is usually a hollow frame made of profiles, and the dust collection frame 21 covers the entire opening edge of the mixing barrel 2.

[0034] A plurality of suction ports 31 are provided on the dust collection frame 21, and the plurality of suction ports 31 are evenly spaced on the dust collection frame 21 around the opening of the mixing barrel 2. A dust collection pipe 32 is provided on the inner wall of the dust collection frame 21 and is connected to the plurality of suction ports 31 through connecting pipes.

[0035] In a preferred embodiment of the TPV raw material mixing barrel dust removal device of the present application, as Figure 1 and Figure 2 As shown, the first dust suction port 311 is provided on the inner side surface of the dust suction frame 21 and is evenly spaced thereon. It is primarily used to remove dust generated during the addition of the TPV raw material into the mixing barrel 2. The second dust suction port 312 is provided on the upper side surface of the dust suction frame 21 and is evenly spaced thereon. When the stirring device in the mixing barrel 2 rotates to stir the TPV raw material, the opening of the mixing barrel 2 is usually covered. The second dust suction port 312 is primarily used to remove dust between the dust suction frame 21 and the covering to prevent dust generated during the stirring of the TPV raw material from escaping.

[0036] In a preferred technical solution of the TPV raw material mixing barrel dust removal device of the present application, as Figure 1 and Figure 2 As shown, a dust barrier strip 33 is further provided on the upper side of the dust collection frame 21. The dust barrier strip 33 is made of a dust-isolating material such as felt and is provided on the inner side of the second dust collection port 312 to prevent dust from passing through the gap between the opening of the mixing barrel 2 and the cover, thereby reducing dust pollution during the mixing process of the TPV raw materials.

[0037] In some embodiments of the TPV raw material mixing barrel dust removal device of the present application, such as Figure 1 and Figure 3As shown, a lid mounting strip 22 is provided in the middle of the opening at the top of the mixing barrel body 2. The lid mounting strip 22 spans the opening of the mixing barrel body 2 and is fixed to the mixing barrel body 2 on opposite sides of the mixing barrel body 2. A lid 4 is provided at the opening of the mixing barrel body 2 on both sides of the lid mounting strip 22. The lid 4 is rotatably connected to the lid mounting strip 22 via a hinge. By rotating the lid 4 relative to the lid mounting strip 22, the lid 4 can cover the dust collection frame 21, closing the opening of the mixing barrel body 2 on the side of the lid mounting strip 22, that is, the feed inlet on one side; or it can move away from the opening of the mixing barrel body 2 on the side of the lid mounting strip 22, so that the feed inlet on the side of the lid mounting strip 22 is open.

[0038] The barrel cover mounting strip 22 is made of a hollow profile, and a dust suction pipe 32 is arranged inside the barrel cover mounting strip 22. Dust suction ports 31 are arranged on both sides of the barrel cover mounting strip 22. The dust suction ports 31 on both sides of the barrel cover mounting strip 22 are respectively connected to the dust suction pipe 32 inside the barrel cover mounting strip 22, so that the dust at the feed port can be removed by negative pressure from both sides of the barrel cover mounting strip 22.

[0039] In a preferred embodiment of the TPV raw material mixing barrel dust removal device of the present application, as Figure 1 and Figure 3 As shown, the dust suction port 31 on the bucket cover mounting strip 22 includes a first dust suction port 311 evenly spaced at the lower portion of both sides of the bucket cover mounting strip 22, and a second dust suction port 312 evenly spaced at the upper portion of both sides of the bucket cover mounting strip 22. The dust suction pipe 32 inside the bucket cover mounting strip 22 includes a first dust suction pipe 321 and a second dust suction pipe 322. A first dust suction pipe 321 and a second dust suction pipe 322 are respectively provided on both sides of the bucket cover mounting strip 22. The first dust suction pipes 321 on both sides are respectively connected to the first dust suction port 311 on the same side, and are also connected to the first dust suction pipe 321 in the dust suction frame 21 on the same side; the second dust suction pipes 322 on both sides are respectively connected to the second dust suction port 312 on the same side, and are also connected to the second dust suction pipe 322 in the dust suction frame 21 on the same side, thereby being able to control the first dust suction port 311 and the second dust suction port 312 around the feed port on both sides of the bucket cover mounting strip 22 respectively, thereby optimizing the dust suction effect at the feed port.

[0040] In a preferred technical solution of the TPV raw material mixing barrel dust removal device of the present application, as Figure 1 and Figure 3 As shown, dust-proof strips 33 are provided on both sides of the barrel cover mounting strip 22. The dust-proof strips 33 are provided between the first dust suction port 311 and the second dust suction port 312. When the barrel cover 4 is in the closed state, the dust-proof strips 33 seal the gap between the barrel cover 4 and the barrel cover mounting strip 22, preventing dust in the mixing barrel body 2 from escaping through the gap between the mixing barrel body 2 and the barrel cover 4, further reducing dust pollution generated when the TPV raw materials are mixed.

[0041] In some embodiments of the TPV raw material mixing barrel dust removal device of the present application, such as Figures 1 to 3 As shown, the dust removal device 3 further includes a bucket cover sensor switch 34 provided on the bucket cover mounting strip 22. The bucket cover sensor switch 34 can be any electrical switch that can be triggered by the opening and closing of the bucket cover 4. In this embodiment, the bucket cover sensor switch 34 uses a single-pole double-throw push button switch. A bucket cover sensor switch 34 is provided on each side of the bucket cover mounting strip 22. Each bucket cover sensor switch 34 can be triggered when the bucket cover 4 on the same side is closed.

[0042] One end of the two first dust suction pipes 321 in the lid mounting strip 22 is respectively connected to the first dust suction pipes 321 in the dust suction frame 21 on the same side, and the other end passes through the lid mounting strip 22 to connect to the external negative pressure device. A first solenoid valve is provided between each of the two first dust suction pipes 321 and the negative pressure device. Similarly, one end of the two second dust suction pipes 322 in the lid mounting strip 22 is respectively connected to the second dust suction pipes 322 in the dust suction frame 21 on the same side, and the other end passes through the lid mounting strip 22 to connect to the external negative pressure device. A second solenoid valve is provided between each of the two second dust suction pipes 322 and the negative pressure device.

[0043] The barrel cover induction switches 34 on both sides of the barrel cover mounting strip 22 are respectively connected to the first solenoid valve on the first dust suction pipe 321 on the same side and the second solenoid valve on the second dust suction pipe 322 on the same side. When the barrel cover 4 on one side of the barrel cover mounting strip 22 is opened, the barrel cover induction switch 34 on the corresponding side is activated, causing the first solenoid valve on the same side to open and the second solenoid valve to close. At this time, the negative pressure generated by the negative pressure device is transmitted to the first dust suction port 311 on the corresponding side of the barrel cover mounting strip 22 and the first dust suction port 311 on the inner side of the dust suction frame 21 on the same side, forming a negative pressure airflow at the inner edge of the feed port on the same side, sucking away the dust raised by the addition of TPV raw materials, and preventing dust pollution during the feeding process. When the barrel cover 4 on one side of the barrel cover mounting strip 22 is closed, the barrel cover induction switch 34 on the corresponding side is triggered to operate, causing the first solenoid valve on the same side to close and the second solenoid valve to open. At this time, the negative pressure generated by the negative pressure device is transmitted to the second dust suction port 312 on the corresponding side of the barrel cover mounting strip 22 and the second dust suction port 312 on the inner side of the dust suction frame 21 on the same side, and a negative pressure airflow is formed between the barrel cover 4 and the barrel cover mounting strip 22 on the same side, and between the barrel cover 4 and the dust suction frame 21, which removes a small amount of dust passing through the dust barrier strip 33 from the dust generated by the stirring device in the mixing barrel 2 when stirring the TPV raw materials, or adding the TPV raw materials through the feed port on the opposite side. A better dust suction effect is produced by the smaller negative pressure airflow, which further prevents dust pollution during the feeding or stirring process while reducing the energy consumption of the external negative pressure device.

[0044] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A TPV raw material mixing barrel dust removal device, the mixing barrel comprising a mixing barrel support (1) and a mixing barrel body (2), the mixing barrel body (2) being supported on the mixing barrel support (1), the mixing barrel body (2) being provided with a feed port at the top and a discharge port at the bottom, characterized in that: A dust removal device (3) is provided around the feed port, and the dust removal device (3) includes a dust suction port (31) and a dust suction pipe (32). A plurality of dust suction ports (31) are provided, and the plurality of dust suction ports (31) are spaced apart and arranged on the mixing barrel (2) around the feed port. The dust suction pipe (32) is connected between the dust suction port (31) and an external negative pressure device.

2. The TPV raw material mixing barrel dust removal device according to claim 1, characterized in that: The dust suction port (31) comprises a first dust suction port (311) and a second dust suction port (312); the dust suction pipe (32) comprises a first dust suction pipe (321) and a second dust suction pipe (322); the first dust suction port (311) is connected to the first dust suction pipe (321); the second dust suction port (312) is connected to the second dust suction pipe (322); and both the first dust suction pipe (321) and the second dust suction pipe (322) are connected to the negative pressure device.

3. The TPV raw material mixing barrel dust removal device according to claim 2, characterized in that: The top of the mixing barrel (2) is open to form the feed port, a dust suction frame (21) is provided on the upper edge of the mixing barrel (2), the dust suction pipe (32) is provided in the dust suction frame (21), and the dust suction port (31) is provided on the dust suction frame (21).

4. The TPV raw material mixing barrel dust removal device according to claim 3, characterized in that: The first dust suction port (311) is arranged on the inner side of the dust suction frame (21), and the second dust suction port (312) is arranged on the upper side of the dust suction frame (21).

5. The TPV raw material mixing barrel dust removal device according to claim 4, characterized in that: A dust separation strip (33) is also provided on the upper side of the dust suction frame (21), and the dust separation strip (33) is provided on the inner side of the second dust suction port (312).

6. The TPV raw material mixing barrel dust removal device according to claim 3, characterized in that: The mixing barrel further comprises a barrel cover (4), a barrel cover mounting strip (22) is provided on the top of the mixing barrel body (2), the dust suction pipe (32) is provided inside the barrel cover mounting strip (22), the dust suction ports (31) are provided on both sides of the barrel cover mounting strip (22), and the barrel cover (4) is hinged on both sides of the barrel cover mounting strip (22) and can cover the feed port.

7. The TPV raw material mixing barrel dust removal device according to claim 6, characterized in that: The first dust suction port (311) is arranged at the lower portion of both sides of the barrel cover mounting strip (22), and the second dust suction port (312) is arranged at the upper portion of both sides of the barrel cover mounting strip (22).

8. The TPV raw material mixing barrel dust removal device according to claim 7, characterized in that: Dust-isolating strips (33) are also provided on both sides of the barrel cover mounting strip (22), and the dust-isolating strips (33) are provided between the first dust suction port (311) and the second dust suction port (312).

9. The TPV raw material mixing tank dust removal device according to any one of claims 6 to 8, characterized in that: The dust removal device (3) further comprises a barrel cover induction switch (34), a first solenoid valve is provided between the first dust suction pipe (321) and the negative pressure device, a second solenoid valve is provided between the second dust suction pipe (322) and the negative pressure device, and the barrel cover induction switch (34) is provided on both sides of the barrel cover mounting strip (22) and is connected to the first solenoid valve and the second solenoid valve.

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