Pneumatic mold clamping device for injection molding machines

Abstract

This invention relates to a pneumatic anti-sticking clamping device for injection molding machines, belonging to the field of injection molding machine technology. It includes a clamping mechanism and a separating mechanism. The clamping mechanism is disposed in the lower mold and is used to clamp the injection-molded round tube. The separating mechanism is disposed on the clamping surface of the clamping mechanism for rolling contact with the round tube. The separating mechanism includes a connecting shaft and several rotating balls. The connecting shaft is fixedly disposed in the clamping mechanism, and the rotating balls are rotatably connected to the connecting shaft. The rotating balls protrude from the clamping surface of the clamping mechanism and make rotatable contact with the round tube. The rotating balls of this invention not only achieve rotatable contact with the round tube, reducing friction and preventing damage during clamping, but also prevent adhesion between the round tube and the upper mold during rotation through the adsorption effect of the adsorption groove.

Description

Technical Field

[0001] This invention belongs to the field of injection molding machine technology, specifically relating to a pneumatic anti-stick mold clamping device for injection molding machines. Background Technology

[0002] A pneumatic anti-sticking mold clamping device for injection molding machines is disclosed. In the injection molding industry, the injection molding machine, as a core piece of equipment, undertakes the important task of injecting thermoplastic or thermosetting plastics into the mold cavity after heating and melting, and then cooling and solidifying them to obtain plastic products of various shapes. The mold, as a key component in the injection molding process, has several carefully designed molding cavities. The shape and size of these cavities precisely correspond to the appearance and structure of the final round tube product, and are the basic carrier for the formation of the round tube product.

[0003] In the injection molding process, after the molten plastic cools and solidifies within the mold cavity to form the desired round tube, the upper and lower molds separate according to a predetermined procedure. While this separation process is a necessary step designed to facilitate the removal of the molded round tube, it also introduces a significant problem: the parting force generated during mold separation acts on the molded round tube. If effective clamping measures are not taken at this time, the molded round tube can easily move along with the upper mold under the influence of the parting force, thus separating from the cavity. Once this happens, it not only leads to quality problems such as deformation and damage in the molded round tube, failing to meet production requirements and wasting raw materials and energy, but it also seriously affects the smooth progress of subsequent injection molding of round tubes, reducing production efficiency and increasing production costs.

[0004] However, although some clamping devices are used to clamp the finished round tube, the clamping devices are difficult to effectively clamp and fix the finished round tube in the lower mold when it is a round tube made of softer material.

[0005] Therefore, there is an urgent need for an anti-stick film clamping device for injection molding machines that can hold soft round tube finished products. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a pneumatic anti-sticking mold clamping device for injection molding machines. This device solves the problem that existing clamping devices struggle to balance the adhesion of the finished round tube as it moves with the upper mold after mold opening, as well as the clamping force of the clamping device to prevent damage to soft materials.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A pneumatic anti-sticking mold clamping device for an injection molding machine includes a clamping mechanism and a separating mechanism. The clamping mechanism is disposed in the lower mold and is used to clamp the injection-molded round tube product. The separating mechanism is disposed on the clamping surface of the clamping mechanism for rolling contact with the round tube product. The separating mechanism includes a connecting shaft and a plurality of rotating balls. The connecting shaft is fixedly disposed in the clamping mechanism, and the plurality of rotating balls are rotatably connected to the connecting shaft. The rotating balls protrude from the clamping surface of the clamping mechanism and are in rotatable contact with the round tube product.

[0009] Preferably, the rotating ball is provided with a plurality of adsorption grooves, and the center of the plurality of adsorption grooves is located on the side of the rotating ball perpendicular to the axis of the connecting shaft.

[0010] Preferably, the diameter of the rotating ball is smaller than the diameter of the finished circular tube.

[0011] Preferably, it further includes a negative pressure mechanism, which is disposed on the connecting shaft and is used to form a negative pressure adsorption cylindrical tube product. The negative pressure mechanism includes a first air passage, a second air passage, and an air supply pipe. The first air passage and the second air passage are coaxially disposed on the connecting shaft and are coaxial with the connecting shaft. The first air passage and the second air passage are spaced apart end to end, and the diameter of the first air passage is larger than the diameter of the second air passage. The air supply pipe communicates with the second air passage and is offset from the rotating ball. The air supply pipe is used to adsorb the airflow around the cylindrical tube product.

[0012] Preferably, the gas delivery pipe can also be installed on the rotating ball, and the gas delivery pipe is connected to the adsorption tank for directly adsorbing the finished round tube.

[0013] Preferably, the clamping mechanism includes a pair of grippers, an air inlet pipe, and an air extraction pipe; the pair of grippers are located on both sides of the finished round tube, the air inlet pipe is used to supply air to drive the pair of grippers closer to each other; the air extraction pipe is used to extract air to drive the pair of grippers further apart.

[0014] Preferably, it also includes a cylinder, and both the suction pipe and the supply pipe are connected to the cylinder, which is used to perform the supply and suction actions.

[0015] Preferably, it also includes a negative pressure air pipe, one end of which is connected to the first airway and the other end of which is connected to the cylinder, the cylinder being used to deliver high-pressure airflow to the negative pressure air pipe.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. This application increases the contact area between the rotating ball and the finished tube by making the diameter of the rotating ball smaller than the diameter of the finished tube. This allows the rotating ball to make rotational contact with the finished tube, reducing friction and preventing damage to the finished tube during clamping. It also prevents the finished tube from sticking to the upper mold during rotation by adsorbing the tube through the adsorption groove.

[0018] 2. The negative pressure adsorption of this application, through the action of airflow, can achieve adsorption and positioning of the round tube product without direct contact with the surface of the round tube product. It can balance the softness between the round tube products and the adhesion of the round tube products with the upper mold movement, avoiding the interference caused by mechanical clamping, so that the round tube products can maintain a stable posture during the mold opening process. Attached Figure Description

[0019] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0020] Figure 1 This is a front view schematic diagram of the clamping device provided in one embodiment of the present invention;

[0021] Figure 2 This is a schematic cross-sectional view of the injection molding state provided in one embodiment of the present invention;

[0022] Figure 3 This is a top view of the clamping mechanism provided in one embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the non-contact adsorption structure of the negative pressure mechanism provided in one embodiment of the present invention;

[0024] Figure 5 This is a top view of the structure of the gas delivery pipe provided in one embodiment of the present invention, which is arranged on the rotating sphere.

[0025] Figure 6 This is a schematic diagram of the connection structure between the rotating ball and the gas pipeline provided in one embodiment of the present invention;

[0026] Legend: 1. Clamping mechanism; 11. Gripper; 12. Air inlet pipe; 13. Air extraction pipe; 2. Separation mechanism; 21. Connecting shaft; 22. Rotating ball; 221. Adsorption tank; 3. Negative pressure mechanism; 31. First air passage; 32. Second air passage; 33. Air delivery pipe; 4. Cylinder; 5. Negative pressure air pipe; 61. Upper mold; 62. Lower mold; 7. Finished round tube. Detailed Implementation

[0027] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0028] In injection molding, after the mold opens, the finished round tube 7 often adheres to the upper mold. Due to its surface characteristics and material shrinkage, the injection-molded round tube 7 is prone to moving with the upper mold at the moment of mold opening, affecting subsequent processing steps and the quality of the finished round tube 7. Currently, most injection molding machine clamping devices on the market focus on clamping and fixing the finished round tube 7 to prevent displacement during transportation or processing. However, these traditional clamping devices often struggle to balance two key factors when facing the problem of the finished round tube 7 adhering to the upper mold: on the one hand, if the clamping force is insufficient, it cannot effectively overcome the adhesion between the finished round tube 7 and the upper mold, and the finished round tube 7 will still move with the upper mold; on the other hand, if the clamping force is too large, it can easily cause damage to the clamping part for some soft materials (such as silicone, rubber, etc.), affecting the integrity and performance of the finished round tube 7.

[0029] like Figures 1-6 As shown, a pneumatic anti-stick mold clamping device for an injection molding machine includes a clamping mechanism 1 and a separating mechanism 2. The clamping mechanism 1 is disposed on the lower mold 62 and is used to clamp the injection-molded round tube product 7. The separating mechanism 2 is disposed on the clamping surface of the clamping mechanism 1 for the round tube product 7 and is used to roll contact with the round tube product 7.

[0030] The separation mechanism 2 adopts a roller structure, with multiple rollers evenly distributed on the arc-shaped clamping surface of the clamping mechanism 1. The rollers are connected to the clamping mechanism 1 via rotating shafts and can rotate freely. When the mold opens, if the finished round tube 7 tends to adhere to the upper mold 61, the rollers of the separation mechanism 2 will first contact the finished round tube 7. Since the rollers can roll, under the action of the adhesion force between the finished round tube 7 and the upper mold 61, the rollers will roll, changing the sliding friction between the finished round tube 7 and the upper mold 61 into rolling friction. The friction force of rolling friction is much smaller than that of sliding friction, thereby greatly reducing the adhesion force between the finished round tube 7 and the upper mold 61, making it easier for the finished round tube 7 to separate from the upper mold 61 and be clamped and held in the lower mold 62 by the clamping mechanism 1.

[0031] The separation mechanism 2 includes a connecting shaft 21 and several rotating balls 22. The connecting shaft 21 is fixedly mounted on the clamping mechanism 1, and the rotating balls 22 are rotatably connected to the connecting shaft 21. The rotating balls 22 protrude from the clamping surface of the clamping mechanism 1 and rotatably contact the finished round tube 7. During the movement of the clamping mechanism 1, because the rotating balls 22 protrude from the clamping surface, they will first contact the finished round tube 7. As the clamping mechanism 1 continues to advance, the rotating balls 22 roll on the surface of the finished round tube 7, instead of generating sliding friction as in traditional clamping methods. Specifically, when the rotating balls 22 contact the finished round tube 7, because the rotating balls 22 are rotatably connected to the connecting shaft 21, under the action of the frictional force applied to the surface of the finished round tube 7, the rotating balls 22 will rotate around the connecting shaft 21, which can convert sliding friction into rolling friction. According to the principle of physics, rolling friction is much smaller than sliding friction, thus effectively reducing the frictional force between the finished round tube 7 and the separation mechanism 2. This reduces the clamping force on the finished round tube 7 through the rotating balls 22, avoiding damage.

[0032] In summary, for the round tube 7 made of soft material, excessive friction can easily lead to deformation. By reducing friction, the rolling contact between the rotating ball 22 and the round tube 7 can significantly reduce the lateral pressure on the round tube 7, thus reducing the possibility of deformation. Sliding friction can easily cause scratches on the surface of the round tube 7, affecting its appearance quality. The rolling contact of the rotating ball 22 avoids this direct, large-area sliding friction, reducing the hard contact between the surface of the round tube 7 and the clamping device, thereby effectively preventing surface scratches and improving the appearance quality of the round tube 7.

[0033] In one embodiment, the rotating ball 22 is provided with a plurality of adsorption grooves 221. The center of the plurality of adsorption grooves 221 is located on the side of the rotating ball 22 perpendicular to the axis of the connecting shaft 21. That is, the rotating ball 22 and the connecting shaft 21 are in rotational contact with the finished round tube 7 in a state of perpendicularity to the axis. The adsorption grooves 221 are located in the area where the rotating ball 22 is closest to the finished round tube 7, so that the rotating ball 22 is in full contact with the finished round tube 7 during rotation. In addition, when the rotating ball 22 is in full contact with the finished round tube 7, the adsorption grooves 221 can fit more tightly against the surface of the finished round tube 7, forming multiple independent adsorption points. These adsorption points cooperate with each other to more stably adsorb the finished round tube 7, reducing the shaking or displacement of the finished round tube 7 during the separation process.

[0034] In one embodiment, the diameter of the rotating ball 22 is smaller than the diameter of the finished cylindrical tube 7. This allows the rotating ball 22 to fully contact the finished cylindrical tube 7 during separation, effectively performing the separation function, without causing excessive compression or interference due to its large size. This size design is particularly effective for cylindrical tubes made of soft materials, preventing localized deformation or damage caused by an excessively large contact area. Specifically, the smaller diameter of the rotating ball 22 compared to the finished cylindrical tube 7 allows the adsorption groove 221 to better contact the finished cylindrical tube and generate a slight negative pressure within the adsorption groove 221, preventing the finished cylindrical tube 7 from moving upwards with the upper mold 61. Conversely, if the diameter of the rotating ball 22 is similar to the diameter of the finished cylindrical tube 7, the contact between the rotating ball 22 and the finished cylindrical tube 7 decreases during rotation, making it difficult for the adsorption groove 221 to achieve a slight adsorption effect on the finished cylindrical tube 7, and also failing to prevent the finished cylindrical tube 7 from moving with the upper mold 61. Therefore, by increasing the contact area between the rotating ball 22 and the finished tube 7 by making the diameter of the rotating ball 22 smaller than that of the finished tube, the rotating ball 22 can not only achieve rotational contact with the finished tube 7, reducing friction with the finished tube 7 and avoiding damage to the finished tube 7 during clamping, but also prevent the finished tube 7 from adhering to the upper mold 61 during rotation through the adsorption effect of the adsorption groove 221.

[0035] In one embodiment, a negative pressure mechanism 3 is also included. The negative pressure mechanism 3 is disposed on the connecting shaft 21 and is used to form a negative pressure adsorption circular tube finished product 7. The negative pressure mechanism 3 includes a first air passage 31, a second air passage 32, and an air delivery pipe 33. The first air passage 31 and the second air passage 32 are coaxially disposed on the connecting shaft 21 and are coaxial with the connecting shaft 21. The first air passage 31 and the second air passage 32 are spaced apart end to end, and the diameter of the first air passage 31 is larger than the diameter of the second air passage 32. The air delivery pipe 33 is connected to the second air passage 32 and is offset from the rotating ball 22. The air delivery pipe 33 is used to adsorb the airflow around the circular tube finished product 7.

[0036] Specifically, when the high-pressure airflow enters the second airflow 32 through the first airflow 31, since the first airflow 31 and the second airflow 32 are set at opposite ends, and the diameter of the first airflow 31 is larger than the diameter of the second airflow 32, according to the Venturi effect, the airflow velocity will increase sharply when passing through the narrow second airflow 32. According to Bernoulli's principle, while the airflow velocity increases, the air pressure in this area will decrease significantly.

[0037] The second air passage 32 is connected to the air supply pipe 33, which is offset from the rotating ball 22. When the air pressure in the second air passage 32 decreases to form a negative pressure area, the air pressure at the air supply pipe 33 will also decrease. At this time, a pressure difference is formed between the air supply pipe 33 and the surrounding environment of the finished circular tube 7. The air pressure around the finished circular tube 7 is relatively high. Driven by the pressure difference, the airflow around the finished circular tube 7 will be drawn into the second air passage 32 through the air supply pipe 33, and then discharged from the negative pressure mechanism 3 along with the mainstream high-pressure airflow.

[0038] At the moment the mold opens, the finished round tube 7 may be subject to the adhesive force of the upper mold 61 and tend to move with the upper mold 61. At this time, the negative pressure mechanism 3 is activated, forming a negative pressure adsorption area around the finished round tube 7. The adsorption force generated by this negative pressure adsorption area will act on the surface of the finished round tube 7, forming a relatively downward pulling force. This pulling force is balanced with the adhesive force of the upper mold 61 on the finished round tube 7. When the adsorption force is large enough, it can counteract the adhesive force of the upper mold 61, keeping the finished round tube 7 relatively stationary and preventing it from moving with the upper mold 61.

[0039] Unlike traditional mechanical clamping methods, negative pressure adsorption is a non-contact adsorption method. For finished round tubes 7, especially those made of soft materials, mechanical clamping may damage the surface of the finished tube 7 due to uneven or excessive clamping force, and may also interfere with the natural state of the finished tube 7. Negative pressure adsorption, through the action of airflow, can achieve adsorption and positioning of the finished round tube 7 without direct contact with its surface, avoiding the interference caused by mechanical clamping and allowing the finished round tube 7 to maintain a stable posture during mold opening.

[0040] In summary, negative pressure adsorption can quickly and effectively create an adsorption force around the finished round tube 7, causing it to rapidly separate from the upper mold 61. This reduces the movement of the finished round tube 7 with the upper mold 61. For the round tube 7 made of soft material, the non-contact negative pressure adsorption method can effectively reduce the direct force on the surface of the finished round tube 7, avoiding surface scratches, deformation, or even damage that may be caused by mechanical clamping. This ensures the appearance quality and structural integrity of the finished round tube 7 and improves the yield of the finished round tube 7.

[0041] In one embodiment, the separation mechanism 2 still includes a connecting shaft 21 and a plurality of rotating balls 22. The connecting shaft 21 is fixedly mounted on the clamping mechanism 1. The rotating balls 22 are rotatably connected to the connecting shaft 21 and protrude from the clamping surface of the clamping mechanism 1. The rotating balls 22 are provided with a plurality of adsorption grooves 221. The difference is that the gas supply pipe 33 is mounted on the rotating balls 22 and the gas supply pipe 33 is connected to the adsorption grooves 221.

[0042] As the clamping mechanism 1 drives the separating mechanism 2 to move toward the finished round tube 7, the rotating ball 22 first contacts the surface of the finished round tube 7. At this time, the rotating ball 22 and the finished round tube 7 are in rolling contact, and at the instant of contact, the rotating ball 22 begins to rotate around the connecting shaft 21;

[0043] When the injection mold is opened and the finished round tube 7 needs to be separated from the upper mold 61, the external high-pressure airflow source starts to work. The high-pressure airflow is guided to the rotating ball 22 through the first air passage 31 and the second air passage 32. Since the air supply pipe 33 is set on the rotating ball 22 and is connected to the second air passage 32 but not in contact, the high-pressure airflow directly enters the air supply pipe 33 inside the rotating ball 22.

[0044] During the rotation of the rotating ball 22, the adsorption tank 221, which is connected to the gas supply pipe 33, forms a dynamic contact area with the surface of the finished round tube 7 as the rotating ball 22 moves. Since a high-pressure airflow continuously passes through the gas supply pipe 33, a local low-pressure area is formed at the adsorption tank 221 according to the principle of airflow. This allows the adsorption tank 221 to directly adsorb the finished round tube 7. If the adhesion force of the finished round tube 7 is still greater than the adsorption force of the adsorption tank 221, the finished round tube 7 moves upward, causing the rotating ball 22 to rotate. During the rotation of the rotating ball 22, it will switch from the previous adsorption tank 221 to the next adsorption tank 221. Since each adsorption tank 221 is equipped with a gas supply pipe 33, the rotating ball 22 also adsorbs the finished round tube 7 when it rotates to the next adsorption tank 221, preventing the finished round tube 7 from adhering and moving with the upper mold 61. This process is repeated until the adhesion force of the upper mold 61 on the finished round tube 7 gradually decreases until the finished round tube 7 separates from the upper mold 61.

[0045] In one embodiment, the clamping mechanism 1 includes a pair of jaws 11, an air inlet pipe 12, and an air extraction pipe 13; the pair of jaws 11 are located on both sides of the finished round tube 7, the air inlet pipe 12 is used to supply air to drive the pair of jaws 11 to move closer to each other; the air extraction pipe 13 is used to extract air to drive the pair of jaws 11 to move away from each other.

[0046] To avoid interference between the clamping mechanism 1 and the upper mold 61, which would affect normal injection molding, the clamping mechanism 1 is located on the platform where the lower mold 62 is recessed downwards. When the upper mold 61 and the lower mold 62 are closed for injection molding, the clamping mechanism 1 and the upper mold 61 will not interfere. When the upper mold 61 and the lower mold 62 are open, the clamping claws 11 are driven to move closer to each other to clamp the finished round tube 7 after the upper mold 61 leaves the lower mold 62, thus preventing the finished round tube 7 from moving upwards with the upper mold 61. After the separation of the finished round tube 7 is completed, the pair of clamping claws 11 are driven to move relative to each other under the action of the air extraction pipe 13.

[0047] In one embodiment, a cylinder 4 is also included. A suction pipe 13 and a delivery pipe 33 are all connected to the cylinder 4. The cylinder 4 is used to perform gas delivery and suction operations. When the mold opens and the finished round tube 7 needs to be clamped, the control system sends a command to the cylinder 4 to open the valve connected to the delivery pipe 33. Simultaneously, other valve states may be adjusted according to design requirements. An external high-pressure gas source begins to supply high-pressure gas flow to the cylinder 4. The high-pressure gas enters the cylinder 4 through the delivery pipe 33, pushing the piston inside the cylinder 4 to move in a specific direction, providing power for the clamping mechanism 1 to move the grippers 11 closer together to clamp the finished round tube 7. After the separation, transfer, or other operations of the finished round tube 7 are completed, it needs to be released. At this time, the control system sends a command to close the valve connected to the delivery pipe 33 and simultaneously open the valve connected to the suction pipe 13. The suction pipe 13 is connected to an external suction device (such as a vacuum pump) to begin suction operations inside the cylinder 4. As the gas inside cylinder 4 is continuously extracted, the air pressure inside cylinder 4 gradually decreases, causing the grippers 11 to move away from each other, thereby releasing the grip on the finished round tube 7.

[0048] In one embodiment, a negative pressure air pipe 5 is also included. One end of the negative pressure air pipe 5 is connected to the first air passage 31, and the other end is connected to the cylinder 4. The cylinder 4 is used to deliver high-pressure airflow to the negative pressure air pipe 5. An air inlet valve is usually provided at the connection between the air supply pipe 33 and the cylinder 4. The air valve is precisely controlled by the control system. When non-contact adsorption of the round tube finished product 7 is achieved, the control system opens the air inlet valve, allowing an external high-pressure air source to deliver high-pressure airflow to the cylinder 4 through the air supply pipe 33, thereby achieving adsorption of the round tube finished product 7 by reducing the air pressure in the area of ​​the round tube finished product 7.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A pneumatic anti-stick mold clamping device for an injection molding machine, characterized in that, The device includes a clamping mechanism and a separating mechanism. The clamping mechanism is disposed in the lower mold and is used to clamp the injection-molded round tube. The separating mechanism is disposed on the clamping surface of the clamping mechanism for rolling contact with the round tube. The separating mechanism includes a connecting shaft and several rotating balls. The connecting shaft is fixedly disposed in the clamping mechanism, and the several rotating balls are rotatably connected to the connecting shaft. The rotating balls protrude from the clamping surface of the clamping mechanism and are in rotatable contact with the round tube. The rotating sphere is provided with a plurality of adsorption grooves, the centers of which are located on a side of the rotating sphere perpendicular to the axis of the connecting shaft. It also includes a negative pressure mechanism disposed on the connecting shaft, used to form a negative pressure adsorption cylindrical tube product. The negative pressure mechanism includes a first air passage, a second air passage, and an air supply pipe. The first and second air passages are coaxially disposed on and with the connecting shaft. The first and second air passages are spaced apart end-to-end, with the diameter of the first air passage being larger than that of the second air passage. The air supply pipe communicates with the second air passage and is offset from the rotating sphere, used to adsorb the airflow around the cylindrical tube product. The diameter of the rotating sphere is smaller than the diameter of the cylindrical tube product.

2. The pneumatic anti-sticking mold clamping device for an injection molding machine according to claim 1, characterized in that, The clamping mechanism includes a pair of jaws, an air inlet pipe, and an air extraction pipe; the pair of jaws are located on both sides of the finished round tube, the air inlet pipe is used to supply air to drive the pair of jaws to move closer to each other; the air extraction pipe is used to extract air to drive the pair of jaws to move away from each other.

3. The pneumatic anti-sticking mold clamping device for an injection molding machine according to claim 2, characterized in that, It also includes a cylinder, and both the suction pipe and the delivery pipe are connected to the cylinder, which is used to perform the actions of delivering and suctioning air.

4. The pneumatic anti-sticking mold clamping device for an injection molding machine according to claim 3, characterized in that, It also includes a negative pressure air pipe, one end of which is connected to the first air passage and the other end of which is connected to the cylinder. The cylinder is used to deliver high-pressure airflow to the negative pressure air pipe.

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