A negative pressure duct connection valve and a filter rod making machine

Abstract

This invention discloses a negative pressure duct connection valve and a filter rod forming machine, relating to the field of cigarette manufacturing technology. The negative pressure duct connection valve includes a valve body with a duct connection portion and a fan connection portion, which are connected by a communicating cavity within the valve body. The duct connection portion includes multiple duct connectors, the inner cavity of which communicates with the communicating cavity. Each duct connector has an insertion hole for inserting a negative pressure duct. The insertion hole contains a radial locking structure and an axial sealing limiting structure arranged sequentially along the insertion direction. The radial locking structure applies a radial locking force to the outer wall of the inserted negative pressure duct, while the axial sealing limiting structure abuts against the end face of the inserted negative pressure duct to limit its axial position and form a seal. This negative pressure duct connection valve achieves a stable sealed connection between the vacuum fan and the negative pressure duct, ensuring continuous and stable operation of the filter rod forming machine; it is also easy to disassemble and assemble, facilitating cleaning and maintenance.

Description

Technical Field

[0001] This invention relates to the field of cigarette manufacturing technology, and in particular to a negative pressure duct connecting valve and a filter rod forming machine. Background Technology

[0002] In the filter rod forming machine, the suction guide rail is installed between the cutting disc and the acceleration wheel. Several negative pressure holes are distributed on the arc surface of the guide rail. The negative pressure holes are connected to the vacuum fan through the negative pressure air pipe to form a negative pressure air film to adsorb and stably transport the filter rod.

[0003] In current production processes, multiple negative pressure ducts are often combined and connected to a vacuum blower. The common connection method involves using clips to tighten the ducts to the blower interface, followed by sealing with tape. This connection structure reveals the following problems in actual operation: First, the sealing method of clips and tape is unreliable, easily leading to air leakage at the interface. This causes fluctuations in adsorption force, resulting in filter rod vibration, misalignment, or poor track alignment during high-speed movement, severely affecting molding quality and failing to meet the requirements for long-term continuous and stable operation of the molding machine. Second, dust, debris, and other impurities generated during production are easily sucked into the negative pressure holes and enter the ducts, causing blockages and requiring frequent disassembly and cleaning. The aforementioned connection structure is cumbersome to disassemble and reassemble, making it impossible to independently disassemble a single blocked duct; the entire junction connection must be untied, resulting in low maintenance efficiency, poor reusability, and high cleaning costs. Furthermore, the simple junction connection makes it difficult to rationally distribute airflow across multiple ducts, and the uniformity of negative pressure in each guide section is not easily guaranteed, further exacerbating transmission stability problems such as filter rod misalignment and poor track alignment. Summary of the Invention

[0004] The purpose of this invention is to provide a negative pressure duct connecting valve and a filter rod forming machine to achieve a stable and sealed connection between the vacuum fan and the negative pressure duct, ensuring the continuous and stable operation of the filter rod forming machine; at the same time, it is easy to disassemble and assemble, and easy to clean and maintain.

[0005] To achieve this objective, the present invention adopts the following technical solution: A negative pressure duct connection valve includes a valve body, the valve body having a duct connection part and a fan connection part, the duct connection part and the fan connection part being connected through a communicating cavity inside the valve body; The duct connection includes multiple duct connectors, the inner cavity of each duct connector is connected to the communicating cavity, and each duct connector is provided with a insertion hole for inserting a negative pressure duct. The insertion hole is provided with a radial locking structure and an axial sealing limiting structure in sequence along the insertion direction. The radial locking structure can apply a radial locking force to the outer wall of the inserted negative pressure duct, and the axial sealing limiting structure is used to abut against the end face of the insertion end of the negative pressure duct to limit the axial position of the negative pressure duct and form a seal.

[0006] As an optional solution for the negative pressure duct connection valve, the radial locking structure includes multiple elastic retaining members arranged circumferentially along the insertion hole, which can elastically lock the outer wall of the negative pressure duct when it is inserted.

[0007] As an optional solution for the negative pressure duct connection valve, the elastic retaining member is an elastic internal toothed thrust plate extending from the inner wall of the insertion hole towards the center. The elastic internal toothed thrust plate is inclined towards the insertion direction, and the width of the elastic internal toothed thrust plate gradually decreases towards the center.

[0008] As an optional solution for the negative pressure duct connection valve, the axial sealing and limiting structure is an annular retaining ring located at the inner end of the insertion hole, and the inner diameter of the annular retaining ring is the same as the inner diameter of the negative pressure duct.

[0009] As an optional solution for the negative pressure duct connection valve, it also includes an unlocking cylinder, which can be inserted into the gap between the insertion hole and the negative pressure duct, and push the radial locking structure to release the radial locking force of the radial locking structure on the negative pressure duct.

[0010] As an optional solution for the negative pressure duct connection valve, the fan connection part is provided with a connecting cylinder, which is connected to the inner cavity of multiple duct connectors through the communicating cavity.

[0011] As an optional embodiment of the negative pressure duct connection valve, the connecting cavity is configured as a conical cavity, and the cross-sectional area of ​​the conical cavity gradually increases from the fan connection part to the duct connection part.

[0012] As an optional embodiment of the negative pressure duct connection valve, the valve body includes a first valve body and a second valve body that are detachably connected, the duct connection part is located in the first valve body, and the fan connection part and the communicating cavity are located in the second valve body.

[0013] As an alternative to the negative pressure duct connection valve, the first valve body and the second valve body are threaded together.

[0014] A filter rod forming machine includes a suction guide rail and a negative pressure duct connecting valve as described in any of the above embodiments. The suction guide rail is provided with a plurality of negative pressure holes, and the negative pressure holes are connected to the duct connector through a negative pressure duct.

[0015] The beneficial effects of this invention are: The present invention provides a negative pressure duct connection valve and a filter rod forming machine. The valve body has a duct connection part for connecting to a negative pressure duct and a fan connection part for connecting to a vacuum fan. The duct connection part includes multiple duct connectors, and the inner cavities of the multiple duct connectors are all connected to the fan connection part through a connecting cavity to realize the connection between multiple negative pressure ducts and the vacuum fan, while providing uniform and stable negative pressure to the multiple negative pressure ducts. By sequentially setting a radial locking structure and an axial sealing limiting structure in the insertion hole of the duct connector along the insertion direction, the radial locking structure applies a radial locking force to the outer wall of the negative pressure duct to achieve quick insertion and reliable fixation, and the axial sealing limiting structure abuts against the end face of the insertion end of the negative pressure duct to form an end face seal, improving the connection sealing performance, thereby providing stable negative pressure and solving the problem of filter rod shaking and displacement caused by air leakage. Meanwhile, each duct connector corresponds independently to a negative pressure duct. The releasability of the radial locking structure enables quick assembly and disassembly of a single duct without having to completely untangle the manifold. This makes cleaning and maintenance of clogged negative pressure ducts simple and efficient, reducing cleaning costs. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the working principle of the suction guide rail of the filter rod forming machine provided in the embodiment of the present invention; Figure 2 This is a schematic diagram of the negative pressure duct connection valve provided in an embodiment of the present invention; Figure 3 This is a front view of the negative pressure duct connection valve provided in an embodiment of the present invention; Figure 4 yes Figure 3 Sectional view along line AA; Figure 5 This is a cross-sectional schematic diagram of the negative pressure duct connection valve provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the connection between the duct connector and the negative pressure duct provided in an embodiment of the present invention; Figure 7 This is a top view of the connection between the duct connector and the negative pressure duct provided in this embodiment of the invention; Figure 8 yes Figure 7 Sectional view along the BB direction; Figure 9 This is a schematic diagram simulating the negative pressure wind velocity distribution within a connected cavity, provided in an embodiment of the present invention.

[0017] In the picture: 100. Suction guide rail; 101. Negative pressure hole; 200. Negative pressure air duct; 300. Vacuum blower; 400. Negative pressure duct connection valve; 1. Valve body; 11. First valve body; 111. Duct connector; 1111. Insertion hole; 1112. Elastic internal toothed thrust plate; 1113. Annular retaining ring; 1114. Connecting hole; 112. External threaded connector; 12. Second valve body; 121. Connecting cylinder; 122. Connecting cavity; 2. Unlock the pressure cylinder; 21. Flange. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0019] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, 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 the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0020] Unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and connections within two components or interactions between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0021] Unless otherwise expressly specified and limited, "above" or "below" a 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 a 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" of a 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.

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] The suction guide rail of the filter rod forming machine is installed between the cutting disc and the acceleration wheel. The suction guide rail includes an arc-shaped working surface and negative pressure holes on the arc-shaped working surface. The negative pressure holes are connected to a vacuum fan via negative pressure ducts. During production, the vacuum fan generates negative pressure, which is transmitted to the negative pressure holes through the negative pressure ducts, forming a thin and uniform negative pressure air film between the filter rod and the suction guide rail. This film firmly adheres to the filter rod, maintaining its straightness, while preventing scratches on the filter rod surface caused by hard contact. Simultaneously, during high-speed movement, the airflow carries away some heat, stabilizing the filter rod's properties until it enters the acceleration wheel. The suction guide rail has six negative pressure holes distributed along its length. These six holes generate uniform suction, stably adhering the cut filter rod to the arc-shaped working surface, reducing filter rod offset and vibration during high-speed movement, and precisely transferring the filter rod so that it can stably enter the acceleration wheel, minimizing downtime caused by insufficient filter rod transfer stability.

[0024] In existing technology, six negative pressure ducts are connected to the vacuum blower's connecting pipes using locking clips and sealed with tape. This method has poor sealing performance and even poses a risk of air leakage, causing filter rod vibration and unstable forming, which cannot meet the requirements of long-term operation of the filter rod forming machine. Furthermore, the simple convergence of the six negative pressure ducts cannot ensure uniform and reasonable negative pressure across the suction guide rail, easily causing filter rod misalignment and vibration during transport, severely affecting the quality of filter rod forming. Dust, debris, and other impurities generated during production are easily sucked into the negative pressure holes and enter the negative pressure ducts, causing blockages. Loosening the overall convergence connection results in low maintenance efficiency, poor reusability, and high cleaning costs.

[0025] For the suction guide rail and negative pressure air duct connection of the filter rod forming machine, such as Figure 1 As shown, this embodiment provides a filter rod forming machine, including a suction guide rail 100 and a negative pressure air duct connecting valve 400. The suction guide rail 100 is provided with a plurality of negative pressure holes 101. The negative pressure holes 101 are connected to the negative pressure air duct connecting valve 400 through a negative pressure air duct 200. The negative pressure air duct connecting valve 400 is connected to the connecting pipeline of a vacuum fan 300, which can achieve reliable sealing, uniform flow distribution and easy independent disassembly and maintenance.

[0026] like Figures 2-5As shown, this embodiment also provides a negative pressure duct connection valve 400, applied to the filter rod forming machine described above. The negative pressure duct connection valve 400 includes a valve body 1, which has a duct connection part and a fan connection part. The duct connection part and the fan connection part are connected through a connecting cavity 122 inside the valve body 1. The duct connection part includes multiple duct connectors 111. The negative pressure duct 200 is connected to the duct connectors 111, and the connecting pipe of the vacuum fan 300 is connected to the fan connection part. During production, the vacuum fan 300 is started, and the generated negative pressure enters the connecting cavity 122 through the fan connection part. Then, the connecting cavity 122 evenly distributes the negative pressure to each duct connector 111, ultimately forming a thin and uniform negative pressure air film between the arc-shaped working surface of the suction guide rail 100 and the filter rod. This film stably adsorbs and accurately transfers the filter rod, avoiding deviation and shaking during high-speed movement. At the same time, the airflow can carry away some heat, ensuring the quality of the filter rod forming.

[0027] The inner cavity of the duct connector 111 is connected to the connecting cavity 122. The duct connector 111 is provided with a insertion hole 1111 for inserting a negative pressure duct 200. A radial locking structure and an axial sealing limiting structure are sequentially arranged within the insertion hole 1111 along the insertion direction. The radial locking structure applies a radial locking force to the outer wall of the inserted negative pressure duct 200, and the axial sealing limiting structure abuts against the end face of the inserted negative pressure duct 200 to limit the axial position of the negative pressure duct 200 and form a seal. By sequentially arranging a radial locking structure and an axial sealing limiting structure within the insertion hole 1111 of the duct connector 111 along the insertion direction, the radial locking structure applies a radial locking force to the outer wall of the negative pressure duct 200, achieving quick insertion and reliable fixation. The axial sealing limiting structure abuts against the end face of the inserted negative pressure duct 200 to form an end face seal, improving the connection sealing performance, thereby providing stable negative pressure and solving the problem of filter rod vibration and displacement caused by air leakage. Meanwhile, each duct connector 111 corresponds independently to a negative pressure duct 200. The releasability of the radial locking structure enables quick disassembly and assembly of a single duct without the need to completely untangle the manifold, making the cleaning and maintenance of the blocked negative pressure duct 200 simple and efficient, and reducing cleaning costs.

[0028] In one embodiment, the valve body 1 includes a detachably connected first valve body 11 and second valve body 12. A duct connection is located on the first valve body 11, and a fan connection and a connecting cavity 122 are located on the second valve body 12. Since the duct connection directly faces dust, debris, and other impurities generated during filter rod production, it is a high-risk area for clogging. By dividing the valve body 1 into a first valve body 11 and a second valve body 12, when clogging occurs requiring deep cleaning, only the first valve body 11 with the duct connection 111 needs to be removed for cleaning or replacement. The second valve body 12 with the fan connection can remain connected to the vacuum fan 300, avoiding large-scale downtime and reconnection caused by complete disassembly and reassembly, shortening maintenance time, and reducing maintenance costs.

[0029] When the filter rod forming machine needs to adapt to the production of filter rods of different specifications, there may be different requirements for the number, diameter, or layout of the negative pressure holes 101 on the suction guide rail 100. The split design allows for quick matching of new working conditions by simply replacing the first valve body 11 with different numbers, arrangements, or specifications of duct connectors 111, while the connection pipeline between the second valve body 12 and the vacuum fan 300 can be retained as a universal module, improving the flexibility of the equipment and its adaptability to different production scenarios.

[0030] Specifically, the first valve body 11 has six duct connectors 111 corresponding to the six negative pressure holes 101 on the suction guide rail 100. Each duct connector 111 has a radial locking structure and an axial sealing and limiting structure inside. The second valve body 12 has a fan connection part and a connecting cavity 122 integrally formed. The connecting cavity 122 is located inside the second valve body 12, with one end communicating with the fan connection part and the other end open.

[0031] In some alternative embodiments, the first valve body 11 and the second valve body 12 are threadedly connected. Specifically, the rear end of the first valve body 11 is provided with an external threaded connector 112 whose outer diameter is smaller than the outer diameter of the front end of the first valve body 11, and the front end of the second valve body 12 is provided with an internal threaded interface, which communicates with the connecting cavity 122. During assembly, the external threaded connector 112 of the first valve body 11 is screwed into the internal threaded interface of the second valve body 12, thereby achieving a stable connection between the two valve bodies 1 and a sealed connection of the internal airflow channel.

[0032] In other alternative embodiments, the first valve body 11 and the second valve body 12 may also adopt other detachable connection methods such as quick-release buckles, flanges with sealing rings and bolt fastening.

[0033] like Figures 5-8 As shown, in one embodiment, the radial locking structure includes multiple elastic retaining members arranged circumferentially along the insertion hole 1111, which elastically clamp the outer wall of the negative pressure duct 200 when it is inserted. When the negative pressure duct 200 is inserted, the elastic retaining members undergo elastic deformation under the pressure of the outer wall of the negative pressure duct 200, and tightly clamp the outer wall of the negative pressure duct 200 by relying on the rebound force of the material itself, realizing a one-way quick connection that can be plugged in and locked without the need for additional locks, tapes or tools, making installation extremely convenient. At the same time, the multiple circumferentially distributed elastic retaining members apply uniform radial locking force from different directions, avoiding the skewing or local deformation of the negative pressure duct 200 caused by single-point force, ensuring a stable and reliable locking.

[0034] Specifically, the elastic retaining element is an elastic internal toothed thrust plate 1112 extending from the inner wall of the insertion hole 1111 towards the center. The elastic internal toothed thrust plate 1112 is inclined towards the insertion direction, and its width gradually decreases towards the center. Multiple elastic retaining elements are inclined towards the insertion direction, forming barbs or a backlash effect. When the negative pressure duct 200 is inserted, the elastic retaining elements open to make way; once the negative pressure duct 200 is inserted into place or has a tendency to be pulled out in the opposite direction, the elastic retaining elements will further embed or clamp into or tighten the outer wall of the negative pressure duct 200 under the combined action of elastic restoring force and friction, providing axial backlash prevention force.

[0035] In this embodiment, the elastic retaining element is composed of multiple elastic internal toothed thrust plates 1112, which provide a balanced and reliable radial locking effect. The number of elastic internal toothed thrust plates 1112 is 10 to 18, evenly distributed along the same circumferential cross-section of the insertion hole 1111. Each elastic internal toothed thrust plate 1112 extends from the inner wall of the insertion hole 1111 towards the center of the hole, forming a cantilever shape. It is preferably integrally injection molded with the valve body 1 using an engineering plastic with certain elasticity and wear resistance, or injection molded from a thin metal insert. This integral molding design reduces the number of parts and improves structural consistency and reliability.

[0036] The elastic internal toothed thrust plate 1112 is inclined towards the insertion direction of the insertion hole 1111 and the negative pressure duct 200. Its thickness gradually decreases from the root to the end to optimize its elastic deformation capacity and the distribution of the holding force. The end of the elastic internal toothed thrust plate 1112 has an acute angle or a small barbed holding edge. When the negative pressure duct 200 is inserted into the insertion hole 1111 in the insertion direction, its outer wall first pushes against the inclined elastic internal toothed thrust plate 1112, forcing the elastic internal toothed thrust plate 1112 to overcome its own elastic force and move outward. After the negative pressure duct 200 is inserted into place, under the action of elastic restoring force, the holding edge of the elastic internal toothed thrust plate 1112 will tightly press against and embed into the outer wall of the negative pressure duct 200, forming a multi-point, evenly distributed radial locking. At this time, if the negative pressure duct 200 tends to pull outward, the inclined anti-pull structure of the elastic internal tooth thrust plate 1112 will provide stronger biting resistance, effectively preventing the negative pressure duct 200 from loosening under negative pressure conditions or mechanical vibration.

[0037] Furthermore, the negative pressure duct connection valve 400 also includes an unlocking cylinder 2, which can be inserted into the gap between the insertion hole 1111 and the negative pressure duct 200, and push the radial locking structure to release the radial locking force of the radial locking structure on the negative pressure duct 200. When it is necessary to unlock the negative pressure duct 200, the axial force is applied by the unlocking cylinder 2 to overcome the elastic holding force, or the negative pressure duct 200 can be quickly disassembled by means of rotation unlocking.

[0038] The unlocking cylinder 2 is a thin-walled cylinder with a flange 21 at one end. The inner diameter of the thin-walled cylinder is slightly smaller than the outer diameter of the negative pressure duct 200, and the outer diameter is slightly smaller than the inner diameter of the insertion hole 1111. When it is necessary to disassemble the negative pressure duct 200, the unlocking cylinder 2 is axially pushed in along the annular gap between the negative pressure duct 200 and the insertion hole 1111. Its front end face will simultaneously push against all the elastic internal toothed thrust plates 1112, forcing them to expand and deform outward, thereby releasing the locking of the elastic internal toothed thrust plates 1112 to the outer wall of the negative pressure duct 200. At this time, the negative pressure duct 200 can be easily pulled out of the insertion hole 1111. The whole process does not damage the structure of the negative pressure duct 200 and the valve body 1.

[0039] In one embodiment, the axial sealing limiting structure is an annular retaining ring 1113 located at the inner end of the insertion hole 1111, the inner diameter of which is the same as the inner diameter of the negative pressure duct 200. When the negative pressure duct 200 is inserted into place, the inner wall of the negative pressure duct 200 and the inner wall of the annular retaining ring 1113 form a flush, seamless, continuous flow channel at the interface, ensuring smooth airflow through the interface and minimizing interference with the airflow. This helps maintain a stable and consistent negative pressure value across all sections of the suction guide rail 100. The annular retaining ring 1113, located at the inner end of the insertion hole 1111, provides an end-face sealing surface perpendicular to the insertion direction. Under the axial force or external thrust applied by the radial locking structure, the insertion end face of the negative pressure duct 200 is tightly pressed against the end face of the annular retaining ring 1113, forming a reliable end-face contact seal.

[0040] Specifically, the duct connector 111 also has a connecting hole 1114 coaxially arranged with the insertion hole 1111. An annular retaining ring 1113 is located between the insertion hole 1111 and the connecting hole 1114, separating the two. The annular retaining ring 1113 is flange-shaped and protrudes towards the center of the hole, and its inner ring center hole is the airflow channel. The connecting hole 1114 passes through the rear end of the first valve body 11 and communicates with the connecting cavity 122.

[0041] like Figure 4 and Figure 9 As shown, the fan connection part is provided with a connecting cylinder 121, which is connected to the inner cavity of multiple air duct connectors 111 through a connecting cavity 122. One end of the connecting cylinder 121 is used to connect to the connecting pipe of the vacuum fan 300, and the other end is connected to the inlet end of the connecting cavity 122, thereby distributing the negative pressure generated by the vacuum fan 300 during startup to each air duct connector 111 through the connecting cavity 122.

[0042] Specifically, the connecting cavity 122 is configured as a conical cavity, with its cross-sectional area gradually increasing from the fan connection to the duct connection. The connecting cavity 122 employs this conical expansion structure, which provides a dual effect during negative pressure airflow transmission. First, the conical cavity wall provides a continuous and gentle expansion channel for the airflow, allowing it to flow along the cavity wall without separation or impact, eliminating local resistance and energy loss caused by abrupt changes in the flow path, reducing the ineffective energy consumption of the vacuum fan 300, and achieving efficient negative pressure delivery. Second, as the negative pressure airflow flows along the gradually increasing cross-sectional area of ​​the conical cavity, sufficient pressure diffusion and velocity field reorganization are completed, effectively eliminating local pressure differences within the cavity, ultimately forming a uniform static pressure field in the conical cavity outlet region. Each duct connector 111 draws negative pressure from the same stable pressure source, ensuring that the negative pressure value obtained by each negative pressure duct 200 is precisely equal, thereby ensuring uniform suction force of each negative pressure hole 101 along the length of the suction guide rail 100.

[0043] The above description is only a preferred embodiment of the present invention. For those skilled in the art, there will be changes in the specific implementation and application scope based on the ideas of the present invention. The content of this specification should not be construed as a limitation of the present invention.

Claims

1. A negative pressure duct connection valve, characterized in that, Includes a valve body (1), the valve body (1) having a duct connection part and a fan connection part, the duct connection part and the fan connection part being connected through a communicating cavity (122) inside the valve body (1); The duct connection includes multiple duct connectors (111). The inner cavity of the duct connector (111) is connected to the communicating cavity (122). The duct connector (111) is provided with a insertion hole (1111) for inserting a negative pressure duct (200). The insertion hole (1111) is provided with a radial locking structure and an axial sealing limiting structure in sequence along the insertion direction. The radial locking structure can apply a radial locking force to the outer wall of the inserted negative pressure duct (200). The axial sealing limiting structure is used to abut against the end face of the insertion end of the negative pressure duct (200) to limit the axial position of the negative pressure duct (200) and form a seal.

2. The negative pressure duct connection valve according to claim 1, characterized in that, The radial locking structure includes a plurality of elastic retaining members arranged circumferentially along the insertion hole (1111) and capable of elastically locking the outer wall of the negative pressure duct (200) when the negative pressure duct (200) is inserted.

3. The negative pressure duct connection valve according to claim 2, characterized in that, The elastic retaining member is an elastic internal toothed thrust plate (1112) extending from the inner wall of the insertion hole (1111) towards the center. The elastic internal toothed thrust plate (1112) is inclined toward the insertion direction, and the width of the elastic internal toothed thrust plate (1112) gradually decreases toward the center.

4. The negative pressure duct connection valve according to claim 1, characterized in that, The axial sealing and limiting structure is an annular retaining ring (1113) located at the inner end of the insertion hole (1111), and the inner diameter of the annular retaining ring (1113) is the same as the inner diameter of the negative pressure air duct (200).

5. The negative pressure duct connection valve according to claim 1, characterized in that, It also includes an unlocking cylinder (2), which can be inserted into the gap between the insertion hole (1111) and the negative pressure duct (200) and push the radial locking structure to release the radial locking force of the radial locking structure on the negative pressure duct (200).

6. The negative pressure duct connection valve according to claim 1, characterized in that, The fan connection part is provided with a connecting cylinder (121), and the connecting cylinder (121) is connected to the inner cavity of a plurality of air duct connectors (111) through the connecting cavity (122).

7. The negative pressure duct connection valve according to claim 1, characterized in that, The connecting cavity (122) is configured as a conical cavity, and the cross-sectional area of ​​the conical cavity gradually increases from the fan connection part to the duct connection part.

8. The negative pressure duct connection valve according to any one of claims 1-7, characterized in that, The valve body (1) includes a first valve body (11) and a second valve body (12) that are detachably connected. The duct connection part is located in the first valve body (11), and the fan connection part and the communicating cavity (122) are located in the second valve body (12).

9. The negative pressure duct connection valve according to claim 8, characterized in that, The first valve body (11) and the second valve body (12) are threaded together.

10. A filter rod forming machine, characterized in that, It includes a suction guide rail (100) and a negative pressure duct connection valve as described in any one of claims 1-9. The suction guide rail (100) is provided with a plurality of negative pressure holes (101), and the negative pressure holes (101) are connected to the duct connector (111) through a negative pressure duct (200).

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