A wall scraping type Venturi injection device

Abstract

The invention relates to the technical field of pneumatic conveying of powders, and discloses a wall-scraping Venturi injection device, comprising an ejector, the ejector comprising a jet tube, a powder falling tube, an air inlet tube and a coupling tube, one end of the jet tube is detachably mounted with an end sealing tube, the other end of the jet tube extends to a powder receiving point, the jet tube surface from the powder receiving point to one side of the end sealing tube is sequentially fixedly connected with the powder falling tube, the air inlet tube and the coupling tube, a driving assembly is arranged above the coupling tube, a transmission part of the driving assembly is transmission-connected with a transmission shaft of an inner cavity of the jet tube through a bevel gear set, the transmission shaft passes through a guide tube and a retractable assembly and is connected with a scraper assembly below the powder falling tube; the airflow forms an air flow after passing through the guide tube, and forms a negative pressure below the powder falling tube, when the powder starts to fall, the second bevel gear, the transmission shaft and the scraper assembly connected to the end thereof rotate coaxially, and the wall-adhering powder is scraped off in time through the rotation of the scraper head, so as to prevent the powder from being compacted and adhered, and improve the conveying efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of powder pneumatic conveying, and more specifically to a wall-scraping Venturi injection device. Background Art

[0002] At present, in the environmental protection industry, calcium-based dry desulfurization technology is the most novel and promising desulfurization technology for steel rolling heating furnaces and blast furnace hot blast furnaces. The desulfurization process mainly relies on the chemical reaction of calcium-based desulfurizers with sulfur dioxide in the flue gas to generate sulfates to remove pollutants. In this process, the calcium-based desulfurizer usually needs to be ground into an ultra-fine powder state (a type of powder with a particle size between 0.1um and 10um), which can significantly increase its surface area and improve the desulfurization efficiency. This ultra-fine powder can be transported by a positive pressure fan, and a negative pressure cavity is formed at the powder drop point using an ejector, so that the powder is sprayed forward into the powder spraying flue driven by high-speed airflow, thereby achieving efficient transportation of the powder.

[0003] However, during the pneumatic conveying of powders, although a certain negative pressure can be formed below the drop point, the effect of the negative pressure is limited. In addition, the large area of ​​the powder drop port causes a large vortex in the powder drop cavity, which easily leads to powder accumulation. In addition, the pipeline transportation distance is long, and the calcium-based dry powder easily absorbs water and becomes damp, sticks to the pipe wall, and adheres to the inner wall of the pipe, causing blockage.

[0004] Therefore, the present invention proposes a wall scraping type Venturi injection device to improve the stability of the powder conveying process, reduce the possibility of powder accumulation and pipeline blockage, and improve the conveying efficiency. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a wall-scraping Venturi injection device to solve the problem of preventing powder from adhering to the inner wall of the powder falling section pipe and causing compaction and blockage during pneumatic conveying of powder in the above-mentioned background technology.

[0006] The present invention provides the following technical solutions: a wall-scraping Venturi injection device, comprising an ejector, the ejector comprising a jet tube, a powder-dropping tube, an air inlet tube and a shaft-connecting tube, one end of the jet tube is detachably mounted with an end-sealing tube, the other end of the jet tube extends to a powder-receiving point, the surface of the jet tube from the powder-receiving point to the end-sealing tube side is sequentially fixedly connected with the powder-dropping tube, the air inlet tube and the shaft-connecting tube, a driving assembly is arranged above the shaft-connecting tube, the transmission part of the driving assembly is connected to the transmission shaft of the inner cavity of the jet tube through a bevel gear set, the transmission shaft passes through the guide tube and the retracting assembly and is connected to the scraping assembly below the powder-dropping tube;

[0007] The guide pipe includes a conical pipe, a throat pipe, a limit pipe and a plug, wherein the outer side of the conical pipe is fixedly sleeved with the limit pipe, the conical pipe is fixedly assembled in the jet pipe through the limit pipe, the limit pipe and the jet pipe are sealed, the side walls of the conical pipe and the limit pipe are provided with a connected exhaust passage, the exhaust passage is slidably connected with a plug, the end of the conical pipe is movably plugged with a throat pipe, and the throat pipe extends to the bottom of the powder falling pipe;

[0008] The scraper assembly includes a scraper head, a receiving seat, a first spring, a second spring and a pushing head, wherein the scraper head is formed by a piston rod and a scraper in one piece, a small rotation gap exists between the scraper of the scraper head and the inner wall of the jet tube, a first spring is arranged in the tube cavity of the receiving seat, so that the piston rod of the scraper head can be elastically extended and retracted in the tube cavity of the receiving seat, the tube cavity of the receiving seat is fixedly penetrated through the transmission shaft, the scraper end of the scraper head extends and touches the side wall of the limiting tube, and a receiving groove is arranged in the scraper of the scraper head, the receiving groove is provided with a second spring and a Pushing head, when the scraper of the scraper head is not aligned with the exhaust duct where the plug is located, the pushing head compresses the second spring and contacts the side wall of the limiting tube. At this time, the scraper head performs the powder scraping operation on the side wall of the jet tube. When the powder adhering to the scraper head needs to be cleaned, the scraper head is driven to shrink into the receiving seat through the retracting and releasing assembly until the pusher head set at the scraper end of the scraper head is aligned with the exhaust duct of the limiting tube, so that the scraper of the scraper head can obtain the high-pressure airflow directly blown on its surface, so as to realize automatic cleaning of the scraper until the scraper head's ability to scrape powder on the inner wall of the jet tube is restored.

[0009] Furthermore, the retractable assembly includes a turntable, a fixed tube, a pull-out rod, a convex head and a flat gear, wherein the turntable is rotatably connected in an annular groove on the inner wall of the throat and the surface of the transmission shaft, the fixed tube is fixedly installed on the transmission shaft and is located on one side of the turntable, and the other side of the turntable can engage with the flat gear, and a pull-out rod is movably inserted in the fixed tube, and the bottom end of the pull-out rod is fixedly connected to a convex head inserted in the arc-shaped groove of the side wall of the turntable, and the side wall of the fixed tube is provided with a through groove for the movement of the convex head. Through the forward and reverse rotation of the turntable, the arc-shaped groove on its surface can pull the convex head, so that the convex head carries the pull-out rod and pulls the scraper head connected to its top end to move, so as to adjust the distance between the convex head and the inner wall of the jet tube.

[0010] Furthermore, the retractable and extending assembly also includes a reversible motor and a connecting rod, wherein the output shaft of the reversible motor is fixedly sleeved with the plane gear, and the base of the reversible motor is fixedly mounted on the positioning member via the connecting rod.

[0011] Furthermore, a through hole for airflow to pass through is opened on the rotating disk, and the pulling rod is movably passed through the throat and fixedly connected with the scraper head.

[0012] Furthermore, the driving assembly includes a connecting shaft, a coupling, a servo motor and a fixed plate, wherein the slots at the top and bottom ends of the coupling are fixedly assembled with the output shaft and the connecting shaft of the servo motor through limit screws, respectively, the base of the servo motor is fixedly mounted on the fixed plate, and the fixed plate is bound to the supporting component, and the bottom end of the connecting shaft passes through the shaft seal and the connecting shaft tube and then extends into the jet tube.

[0013] Furthermore, the bevel gear set includes a first bevel gear and a second bevel gear, wherein the first bevel gear is fixedly assembled on the bottom end of the connecting shaft by a limiting screw, and the second bevel gear is fixedly assembled on the transmission shaft by a limiting screw, and the first bevel gear is perpendicular to the second bevel gear and the contact parts of the two are meshed.

[0014] Furthermore, the powder falling pipe is connected to a supply source of powder, the air inlet pipe is sealed to an exhaust end of the Roots blower, and the end of the jet pipe away from the end sealing pipe is a powder injection port.

[0015] Furthermore, the transmission shaft is horizontally arranged inside the jet tube, and its rear end passes through the positioning member and the second bevel gear in sequence and just enters the shaft sleeve inside the end sealing tube. The positioning member is composed of a fixed support rod and a fixed sleeve.

[0016] Technical effects and advantages of the present invention:

[0017] The present invention is provided with a transmission shaft, a scraper assembly, a guide tube and a retractable assembly, which is conducive to the formation of an air flow after the air flows through the guide tube, and forms a negative pressure under the powder falling tube. When the powder starts to fall, the second bevel gear, the transmission shaft and the scraper assembly connected to the end thereof rotate coaxially, and there is a small rotation gap between the scraper head and the inner wall of the jet tube. Through the rotation of the scraper head, the powder adhering to the wall is scraped off in time to prevent the powder from being compacted and adhered, and is transported to a designated position following the high-speed air flow; when the powder adhering to the scraper head needs to be cleaned, the scraper head is driven by the retractable assembly to shrink into the receiving seat until the push head arranged at the end of the scraper plate of the scraper head is aligned with the exhaust duct of the limiting tube, so that the scraper plate of the scraper head can obtain the high-pressure airflow directly blown on its surface, so as to realize automatic cleaning of the scraper plate, until the scraper head is restored to have the ability to scrape the powder of the inner wall of the jet tube, so as to improve the stability of the powder conveying process, reduce the possibility of powder accumulation and pipeline blockage, and improve the conveying efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0019] Figure 2 It is a schematic diagram of the overall structure of the present invention and its partial cross-section.

[0020] Figure 3 For the present invention Figure 2A further schematic cross-sectional view of the structure.

[0021] Figure 4 For the present invention Figure 3 Schematic diagram of the structure at point A in the middle.

[0022] Figure 5 For the present invention Figure 3 A further cross-sectional schematic diagram of the remaining structure without the drive assembly and bevel gear set.

[0023] Figure 6 For the present invention Figure 5 Schematic diagram of the structure at point B in the middle.

[0024] Figure 7 It is a schematic diagram of the connection structure of the transmission shaft, the scraper assembly, the guide pipe and the retractable assembly of the present invention.

[0025] Figure 8 For the present invention Figure 7 Schematic diagram of the structure at point C in the middle.

[0026] The accompanying drawings are marked as follows: 1. ejector; 101. ejector tube; 102. powder drop tube; 103. air inlet tube; 104. shaft connecting tube; 105. shaft seal; 2. end sealing tube; 3. drive assembly; 301. connecting shaft; 302. coupling; 303. servo motor; 304. fixing plate; 4. bevel gear set; 401. first bevel gear; 402. second bevel gear; 5. transmission shaft; 6. scraper assembly; 601. scraper Head; 602, receiving seat; 603, first spring; 604, second spring; 605, push head; 7, positioning piece; 8, guide tube; 801, tapered tube; 802, throat; 803, limit tube; 804, plug; 9, retractable assembly; 901, turntable; 902, fixed tube; 903, pull rod; 904, convex head; 905, flat gear; 906, reversible motor; 907, connecting rod; 10, shaft sleeve. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The wall-scraping Venturi injection device involved in the present invention is not limited to the various structures described in the following embodiments. All other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0028] Reference Figure 1-8The present invention provides a wall-scraping Venturi injection device, including an ejector 1, which includes a jet tube 101, a powder-dropping tube 102, an air inlet tube 103 and a connecting tube 104. One end of the jet tube 101 is detachably mounted with an end sealing tube 2 through a connecting flange, and the other end of the jet tube 101 extends to a powder receiving point. The surface of the jet tube 101 from the powder receiving point to the side of the end sealing tube 2 is sequentially fixedly connected to the powder-dropping tube 102, the air inlet tube 103 and the connecting tube 104. A driving assembly 3 is arranged above the connecting tube 104. The transmission part of the driving assembly 3 is connected to the transmission shaft 5 in the inner cavity of the jet tube 101 through a bevel gear set 4. The transmission shaft 5 passes through the guide tube 8 and the retractable assembly 9 and is connected to the scraping assembly 6 below the powder-dropping tube 102.

[0029] In this embodiment, it should be specifically explained that the powder falling pipe 102 is connected to the supply source of the powder, and the air inlet pipe 103 is sealed and connected to the exhaust end of the Roots blower, and the end of the jet pipe 101 away from the end sealing pipe 2 is a powder injection port. The gas blown out of the Roots blower enters the jet pipe 101 connected thereto through the air inlet pipe 103, and forms a high-speed air flow after passing through the guide pipe 8 set inside the jet pipe 101. The static pressure energy is converted into dynamic pressure energy, and a relatively high negative pressure is formed below the straight section in the powder falling pipe 102. The falling powder is sucked into the cavity of the jet pipe 101 and transported to the designated position along with the high-speed flowing air.

[0030] Reference Figure 2-4 The driving assembly 3 includes a connecting shaft 301, a coupling 302, a servo motor 303 and a fixing plate 304, wherein the slots at the top and bottom ends of the coupling 302 are fixedly assembled with the output shaft of the servo motor 303 and the connecting shaft 301 through limiting screws to achieve a stable connection, the base of the servo motor 303 is fixedly mounted on the fixing plate 304, and the fixing plate 304 is bound to the supporting component, wherein the supporting component can be a support such as a stand and a wall, and the bottom end of the connecting shaft 301 passes through the shaft seal 105 and the connecting shaft pipe 104 and then extends into the jet tube 101;

[0031] The bevel gear set 4 includes a first bevel gear 401 and a second bevel gear 402, wherein the first bevel gear 401 is fixedly assembled at the bottom end of the connecting shaft 301 through a limiting screw, and the second bevel gear 402 is fixedly assembled with the transmission shaft 5 through a limiting screw, the first bevel gear 401 is perpendicular to the second bevel gear 402 and the contact parts of the two are meshed, and then the output shaft of the servo motor 303 does not need to be arranged coaxially with the jet tube 101, reducing the requirements of this arrangement on the surrounding space environment;

[0032] The transmission shaft 5 is horizontally arranged inside the jet tube 101, and its rear end passes through the positioning member 7 and the second bevel gear 402 in sequence and just enters the shaft sleeve 10 inside the end sealing tube 2. The positioning member 7 is composed of a fixed support rod and a fixed sleeve. The specific fixed support rod is circumferentially distributed on the outside of the fixed sleeve and connected to the inner wall of the jet tube 101. The coaxial arrangement of the fixed sleeve and the shaft sleeve 10 defines the rotation center of the transmission shaft 5 and is used to carry the transmission shaft 5, so that the assembled transmission shaft 5 can rotate about the axis of the jet tube 101.

[0033] In this embodiment, it is necessary to specifically explain that the first bevel gear 401 and the second bevel gear 402 are close to the port where the jet tube 101 is connected to the end sealing tube 2. When it is necessary to inspect or replace the internal parts of the equipment, it is only necessary to loosen the connecting flange between the jet tube 101 and the end sealing tube 2, and then loosen the limiting screw on the bevel gear set 4 to remove the first bevel gear 401 and the second bevel gear 402. The transmission shaft 5 and the scraper assembly 6 connected to its end, the throat 802 and the turntable 901, the fixing tube 902, the pulling rod 903 and the protruding head 904 in the retracting assembly 9 can be taken out from the powder injection port, and the scraper assembly 6 can be taken out from it, which is convenient for disassembly, replacement or inspection.

[0034] Reference Figure 5-8 , the guide pipe 8 includes a tapered pipe 801, a throat pipe 802, a limit pipe 803 and a plug 804, wherein the limit pipe 803 is fixedly sleeved on the outer side of the tapered pipe 801, the tapered pipe 801 is fixedly assembled in the jet pipe 101 through the limit pipe 803, the limit pipe 803 and the jet pipe 101 are sealed, the side walls of the tapered pipe 801 and the limit pipe 803 are provided with a connected exhaust passage, and a plug 804 is slidably connected in the exhaust passage, when the plug 804 is not pushed by the push head 605, the airflow can press the plug 804 to seal and fit at the end of the exhaust passage to block the exhaust passage, so that the airflow is concentrated and discharged outward from the tapered pipe 801, and the end of the tapered pipe 801 is movably plugged with a throat pipe 802, and the throat pipe 802 extends to the bottom of the powder falling pipe 102;

[0035] The scraper assembly 6 includes a scraper head 601, a receiving seat 602, a first spring 603, a second spring 604 and a push head 605, wherein the scraper head 601 is formed by a piston rod and a scraper in one piece, and there is a small rotation gap between the scraper of the scraper head 601 and the inner wall of the jet tube 101 or the two are attached, and a first spring 603 is arranged in the tube cavity of the receiving seat 602, so that the piston rod of the scraper head 601 can be elastically extended and retracted in the tube cavity of the receiving seat 602, and the tube cavity of the receiving seat 602 is fixedly passed through the transmission shaft 5, and the distance between the receiving seat 602 and the jet tube 101 is set to at least prevent it from scraping powder, and the scraper end of the scraper head 601 extends and touches the side wall of the limiting tube 803, and a receiving groove is arranged in the scraper of the scraper head 601, and the receiving groove is provided with a second spring 604 and a pusher head 605 connected to the end of the second spring 604. When the scraper of the scraper head 601 is not aligned with the exhaust passage where the plug 804 is located, the pusher head 605 compresses the second spring 604 and contacts the side wall of the limiting tube 803. At this time, the scraper head 601 performs the powder scraping operation on the side wall of the jet tube 101. When the powder adhering to the scraper head 601 needs to be cleaned, the scraper head 601 is driven to shrink into the receiving seat 602 through the retracting assembly 9 until the pusher head 605 set at the end of the scraper of the scraper head 601 is aligned with the exhaust passage of the limiting tube 803, so that the scraper of the scraper head 601 can obtain the high-pressure airflow directly blown on its surface, so as to realize automatic cleaning of the scraper, until the scraper head 601 is restored to the powder scraping ability of the inner wall of the jet tube 101;

[0036] The retractable assembly 9 includes a turntable 901, a fixed tube 902, a draw rod 903, a convex head 904 and a flat gear 905, wherein the turntable 901 is rotatably connected in an annular groove on the inner wall of the throat 802 and the surface of the transmission shaft 5, the fixed tube 902 is fixedly mounted on the transmission shaft 5 and is located on one side of the turntable 901, and the other side of the turntable 901 can mesh with the flat gear 905, a draw rod 903 is movably inserted in the fixed tube 902, and the bottom end of the draw rod 903 is fixedly connected to a convex head 904 inserted in the arc-shaped groove on the side wall of the turntable 901, and the side wall of the fixed tube 902 is provided with a through groove for the convex head 904 to move, and the arc-shaped groove on its surface can pull the convex head 904 through the forward and reverse rotation of the turntable 901, so that the convex head 904 carries the draw rod 903 and pulls the scraper head 601 connected to its top to move, so as to adjust the distance between the convex head 904 and the inner wall of the jet tube 101;

[0037] The retractable assembly 9 also includes a reversible motor 906 and a connecting rod 907 , wherein the output shaft of the reversible motor 906 is fixedly sleeved with the flat gear 905 , and the base of the reversible motor 906 is fixedly mounted on the positioning member 7 via the connecting rod 907 to maintain the stable output of the reversible motor 906 .

[0038] In this embodiment, it should be specifically explained that the elastic potential energy of the second spring 604 on the push head 605 is greater than the wind pressure energy of the airflow through the exhaust duct on the plug 804, wherein the thrust provided by the spring can reach thousands of Newtons N to tens of thousands of Newtons N, and the thrust of the spring depends on multiple factors, including the material, wire diameter, effective number of turns and center diameter of the spring;

[0039] The turntable 901 is provided with a through hole for air flow to pass through, so that the air flow in the jet tube 101 can flow normally through the guide tube 8. In addition, the pull rod 903 movably passes through the throat 802 and is fixedly connected to the scraper head 601.

[0040] Working principle of the present invention:

[0041] The gas blown out by the Roots blower enters the jet pipe 101 connected thereto through the air inlet pipe 103, and forms a high-speed air flow after passing through the tapered pipe 801 and the throat pipe 802 installed inside the jet pipe 101. The static pressure energy is converted into dynamic pressure energy, and a high negative pressure is formed below the straight section in the powder falling pipe 102. The falling powder is sucked into the cavity of the jet pipe 101 and transported to the designated position along with the high-speed flowing air.

[0042] When the powder starts to fall, the servo motor 303 is turned on, and the output shaft of the servo motor 303 carries the coupling 302 assembled therewith to rotate, and then the rotating coupling 302 drives the connecting shaft 301 assembled therewith and the first bevel gear 401 installed at the bottom end thereof to coaxially rotate. Since the first bevel gear 401 is meshed and linked with the second bevel gear 402, the spinning first bevel gear 401 drives the second bevel gear 402, so that the second bevel gear 402, the transmission shaft 5 and the scraper assembly 6 connected to the end thereof rotate coaxially. There is a small rotation gap between the scraper head 601 in the scraper assembly 6 and the inner wall of the jet tube 101, or the two are attached to each other. Through the rotation of the scraper head 601, the powder adhering to the wall is scraped off in time to prevent the powder from being compacted and adhering.

[0043] When the powder adhered to the scraper head 601 needs to be cleaned, the transmission scraper assembly 6 is used to rotate it to a vertical state, that is, after the scraper head 601 and the receiving seat 602 are respectively located on the upper and lower sides of the transmission shaft 5, the servo motor 303 stops running and is switched to the reversible motor 906 for starting. The output shaft of the reversible motor 906 drives the plane gear 905 coaxially assembled therewith to rotate, and the rotating plane gear 905 drives the turntable 901 meshing therewith, so that the turntable 901 rotates along the annular groove on the inner wall of the throat 802, and the arc-shaped groove on the surface of the turntable 901 rotates to pull the convex head 904 inserted therein, and the convex head 904 subjected to this traction force carries the pulling rod 903 to the inside of the fixed tube 902 The cavity is shrunk, and the pulling rod 903 will simultaneously pull the scraper head 601 connected to its top end to move inward, that is, the piston rod of the scraper head 601 is shrunk toward the tube cavity of the receiving seat 602 by compressing the first spring 603, until the push head 605 set at the end of the scraper of the scraper head 601 is aligned with the plug 804, and the push head 605 pushes the plug 804 open under the elastic force of the second spring 604, so that the plug 804 is separated from the exhaust duct of the side wall of the limiting tube 803, and part of the air flow is discharged to the scraper of the scraper head 601 through the exhaust duct. At this time, the reversible motor 906 is suspended, so that the scraper of the scraper head 601 can obtain the high-pressure airflow directly blown on its surface, so as to realize automatic cleaning of the scraper;

[0044] After the scraper head 601 is completely cleaned, the output shaft of the reversible motor 906 is controlled to drive in reverse, and the pull rod 903 is adjusted to gradually withdraw from the inner cavity of the fixed tube 902, until the pull rod 903 pulls the scraper head 601 to approach the inner wall of the jet tube 101 again. The reversible motor 906 stops driving and switches to the servo motor 303 drive again to restore the scraper head 601's ability to scrape powder from the inner wall of the jet tube 101, so as to improve the stability of the powder conveying process, reduce the possibility of powder accumulation and pipeline blockage, and improve the conveying efficiency.

[0045] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent substitutions or modifications within the technical scope disclosed by the present invention; according to the technical plan and its improved conception of the present invention, all of which should be included under the protection of the present invention.

Claims

1. A scraping wall type Venturi injection device, comprising an ejector (1), characterized in that: The ejector (1) comprises an ejector tube (101), a powder falling tube (102), an air inlet tube (103) and a connecting tube (104); one end of the ejector tube (101) is detachably mounted with an end sealing tube (2); the other end of the ejector tube (101) extends to a powder receiving point; the surface of the ejector tube (101) from the powder receiving point to the end sealing tube (2) is sequentially fixedly connected to the powder falling tube (102), the air inlet tube (103) and the connecting tube (104); a driving assembly (3) is arranged above the connecting tube (104); a transmission part of the driving assembly (3) is connected to a transmission shaft (5) in the inner cavity of the ejector tube (101) through a bevel gear set (4); the transmission shaft (5) passes through the guide tube (8) and the retractable assembly (9) and is connected to a scraper assembly (6) below the powder falling tube (102); The guide pipe (8) comprises a conical pipe (801), a throat pipe (802), a limit pipe (803) and a plug (804), wherein the limit pipe (803) is fixedly sleeved on the outer side of the conical pipe (801), the conical pipe (801) is fixedly assembled in the jet pipe (101) through the limit pipe (803), the limit pipe (803) and the jet pipe (101) are sealed, a communicating exhaust duct is provided on the side walls of the conical pipe (801) and the limit pipe (803), a plug (804) is slidably connected in the exhaust duct, the throat pipe (802) is movably plugged at the end of the conical pipe (801), and the throat pipe (802) extends to the bottom of the powder dropping pipe (102); The scraper assembly (6) comprises a scraper head (601), a receiving seat (602), a first spring (603), a second spring (604) and a push head (605), wherein the scraper head (601) is formed by a piston rod and a scraper in one piece, a small rotation gap exists between the scraper of the scraper head (601) and the inner wall of the jet tube (101), a first spring (603) is arranged in the tube cavity of the receiving seat (602), so that the piston rod of the scraper head (601) can be elastically extended and retracted in the tube cavity of the receiving seat (602), the tube cavity of the receiving seat (602) is fixedly passed through the transmission shaft (5), the scraper end of the scraper head (601) extends and touches the side wall of the limiting tube (803), and a receiving groove is arranged in the scraper of the scraper head (601), the receiving groove is provided with a second spring (604) and a spring connected to the second spring (604) ) at the end thereof, when the scraper of the scraper head (601) is not aligned with the exhaust passage where the plug (804) is located, the pusher head (605) compresses the second spring (604) and contacts the side wall of the limiting tube (803), and at this time, the scraper head (601) performs a powder scraping operation on the side wall of the jet tube (101), and when the powder adhering to the scraper head (601) needs to be cleaned, the scraper head (601) is driven by the retracting assembly (9) to shrink into the receiving seat (602) until the pusher head (605) provided at the end of the scraper of the scraper head (601) is aligned with the exhaust passage of the limiting tube (803), so that the scraper of the scraper head (601) can obtain the high-pressure airflow directly blown on its surface, so as to realize automatic cleaning of the scraper, until the ability of the scraper head (601) to scrape the powder of the inner wall of the jet tube (101) is restored; The retractable assembly (9) comprises a rotating disk (901), a fixed tube (902), a pull rod (903), a convex head (904) and a flat gear (905), wherein the rotating disk (901) is rotatably connected to the inner wall of the throat (802) and the annular groove on the surface of the transmission shaft (5), the fixed tube (902) is fixedly mounted on the transmission shaft (5) and is located on one side of the rotating disk (901), and the other side of the rotating disk (901) is capable of meshing with the flat gear (905), and a movable plug in the fixed tube (902) is provided. A pull rod (903) is connected, and the bottom end of the pull rod (903) is fixedly connected to a convex head (904) inserted into the arc-shaped sliding groove of the side wall of the rotating disk (901), and the side wall of the fixed tube (902) is provided with a through groove for the convex head (904) to move. When the rotating disk (901) rotates forward and reverse, the arc-shaped sliding groove on its surface can pull the convex head (904), so that the convex head (904) carries the pull rod (903) and pulls the scraper head (601) connected to its top end to move, so as to adjust the distance between it and the inner wall of the jet tube (101).

2. A scraping wall type Venturi injection device according to claim 1, characterized in that: The retractable assembly (9) further comprises a reversible motor (906) and a connecting rod (907), wherein the output shaft of the reversible motor (906) is fixedly sleeved with the plane gear (905), and the base of the reversible motor (906) is fixedly mounted on the positioning member (7) via the connecting rod (907).

3. A scraping wall type Venturi injection device according to claim 1, characterized in that: The rotating disk (901) is provided with a through hole for air flow to pass through, and the pulling rod (903) is movably passed through the throat (802) and fixedly connected to the scraper head (601).

4. A scraping wall type Venturi injection device according to claim 1, characterized in that: The driving assembly (3) comprises a connecting shaft (301), a coupling (302), a servo motor (303) and a fixing plate (304), wherein slots at the top and bottom ends of the coupling (302) are fixedly assembled with the output shaft of the servo motor (303) and the connecting shaft (301) through limiting screws, respectively; the base of the servo motor (303) is fixedly mounted on the fixing plate (304), and the fixing plate (304) is bound to the supporting component; and the bottom end of the connecting shaft (301) passes through a shaft seal (105) and a connecting shaft tube (104) and then extends into the jet tube (101).

5. A scraping wall type Venturi injection device according to claim 4, characterized in that: The bevel gear set (4) comprises a first bevel gear (401) and a second bevel gear (402), wherein the first bevel gear (401) is fixedly assembled on the bottom end of the connecting shaft (301) via a limiting screw, and the second bevel gear (402) is fixedly assembled on the transmission shaft (5) via the limiting screw, and the first bevel gear (401) and the second bevel gear (402) are perpendicular to each other and their contact parts are meshed.

6. A scraping wall type Venturi injection device according to claim 1, characterized in that: The powder drop pipe (102) is connected to a powder supply source, the air inlet pipe (103) is sealedly connected to an exhaust end of a Roots blower, and the end of the jet pipe (101) away from the end seal pipe (2) is a powder injection port.

7. A scraping wall type Venturi injection device according to claim 1, characterized in that: The transmission shaft (5) is horizontally arranged inside the jet tube (101), and its rear end passes through the positioning member (7) and the second bevel gear (402) in sequence and then just enters the shaft sleeve (10) inside the end sealing tube (2). The positioning member (7) is composed of a fixed support rod and a fixed sleeve.

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