A two-stage elastic sealing plunger tool

Abstract

This invention discloses a two-stage elastic sealing plunger tool, belonging to the technical field of downhole tools for gas well drainage and production. The plunger tool has a guide hole on its upper guide channel; a valve seal is located at the lower end of the upper guide channel; a lower guide channel is located at the lower end of the valve seal, and the lower guide channel also has a gas guide hole for gas from the lower end of the plunger to enter the lower guide channel; multiple flaps are evenly distributed outside the lower guide channel, with their upper ends connected to the valve seal and their lower ends connected to the lower guide channel; a pneumatic diaphragm is located between the outer wall of the lower guide channel and the flaps, and the lower guide channel has a pressure guide hole for allowing gas from the lower guide channel to enter the pneumatic diaphragm. The plunger tool of this invention balances sealing and throughput during reciprocating motion, while improving the plunger's service life while ensuring increased fluid production through plunger drainage.

Description

Technical Field

[0001] This invention relates to the field of downhole tools for gas well drainage and gas production, specifically to a two-stage elastic sealing plunger tool. Background Technology

[0002] Plunger gas lift drainage gas production is a method that uses a plunger as a mechanical sealing surface. The expansion of gas at the lower end of the plunger pushes the plunger and the liquid above it from the bottom of the well to the surface. During this lifting process, the gas at the lower end of the plunger will surge up through the gap between the plunger and the tubing to the upper end of the plunger. At the same time, the liquid column lifted at the upper end of the plunger will also slip off through the gap between the plunger and the tubing to the bottom of the well during the lifting process. To ensure the drainage effect of the plunger, it is necessary to minimize the upward surge of gas and the slippage of liquid.

[0003] Currently, the most commonly used plunger tool in gas wells is the cylindrical plunger. Its main structural feature is that it includes a continuous turbulent sealing groove. The maximum outer diameter is 59.5 mm, and the applicable gas well tubing inner diameter is 62 mm. The single-sided clearance of the annular cross-section between the plunger and the tubing is 1.25 mm. During the process of lifting the liquid upward, each stage of the sealing groove will change the sliding liquid into a turbulent flow state, thereby reducing the liquid slippage velocity.

[0004] In the process of plunger gas lift, the gas well is opened and closed at the wellhead through remote system control. This conventional plunger gas lift method has its own advantages and disadvantages during operation:

[0005] Advantages: The plunger has a simple structure with a retrieval head at the top. When the plunger is at the bottom of the well, it can be retrieved with a wire. The sealing effect is good during the fluid lifting process, and the multi-stage turbulent sealing groove structure facilitates the plunger's upward movement to the wellhead blowout preventer for capture.

[0006] Disadvantages: As the plunger moves up and down repeatedly, friction occurs between the outer wall and the tubing, causing a reduction in the outer diameter of the metal plunger. Generally, the reduction is 1mm / year. According to statistics from field applications, for every 1mm reduction in the outer diameter of the plunger, its lifting and drainage efficiency decreases by 10%. During the lifting process, some fluid will slip to the bottom of the well. If the plunger is kept running in the wellbore without being replaced, the lifting and drainage effect of the plunger will become increasingly worse.

[0007] Because the plunger is a solid structure, the liquid above the plunger can only slide down through the gap between the outer wall of the plunger and the inner wall of the tubing. Simultaneously, the compressed gas below the plunger can only rise through this gap, thus forming a liquid film between the outer wall of the plunger and the inner wall of the tubing. This makes it easier for the plunger to fall and rise under the lubrication of the liquid film. However, there are certain requirements regarding the size of the gap between the outer wall of the plunger and the inner wall of the tubing. If the axes of the plunger cylinder and the tubing cylinder coincide, it is considered a concentric rise or fall, in which case the liquid leakage above the plunger is relatively small. If the axes do not coincide, it is considered an eccentric rise or fall, in which case the liquid leakage above the plunger is relatively large. In actual production, eccentric motion occurs more frequently than concentric motion, making it difficult to simultaneously achieve both sealing and flowability of the plunger. Therefore, this invention provides a two-stage elastic sealing plunger tool that can balance sealing and flowability. Summary of the Invention

[0008] The purpose of this invention is to develop a two-stage elastic sealing plunger tool that balances sealing and flow during reciprocating motion, while increasing plunger service life while ensuring increased liquid discharge.

[0009] This invention provides a two-stage elastic sealing plunger tool, including an upper flow channel with a flow guide hole thereon;

[0010] A valve seal is located at the lower end of the upper flow channel;

[0011] A lower guide channel is provided at the lower end of the valve seal, and the lower guide channel is also provided with a gas guide hole for the gas at the lower end of the plunger to enter the lower guide channel;

[0012] Multiple petals are evenly distributed outside the lower guide channel, with their upper ends connected to the valve seal and their lower ends connected to the lower guide channel.

[0013] A pneumatic membrane is disposed between the outer wall of the lower guide channel and the flaps. The lower guide channel is provided with pressure guiding holes for allowing gas in the lower guide channel to enter the pneumatic membrane.

[0014] Preferably, the valve sealing part includes a valve sealing cover and an upper sealing ball seat, an upper sealing ball, a bidirectional ball seat, a lower sealing ball, and a lower sealing ball seat disposed inside the valve sealing cover. The upper sealing ball seat is connected to the upper flow guide channel. The upper sealing ball is located between the upper ends of the upper sealing ball seat and the bidirectional ball seat. The lower sealing ball is located between the lower end of the bidirectional ball seat and the lower sealing ball seat. The upper sealing ball seat is connected to the upper flow guide channel, and the lower sealing ball seat is connected to the lower flow guide channel.

[0015] Preferably, a turbulence sealing groove is provided on the outside of the upper guide channel.

[0016] Preferably, a buffer mechanism is also provided at the bottom of the lower guide channel.

[0017] Preferably, the pneumatic diaphragm is made of nitrile rubber that can withstand high temperatures of 120°C and high pressures of 20MPa.

[0018] Preferably, the buffer mechanism includes a buffer spring and an impact head disposed at the lower end of the buffer spring, the buffer spring being connected to the bottom end of the lower guide channel.

[0019] Preferably, the number of petals is 8.

[0020] Preferably, the pneumatic diaphragm is made of nitrile rubber that can withstand high temperatures of 120°C and high pressures of 20MPa.

[0021] Preferably, a retrieval unit is also connected to the top of the upper guide channel and the turbulent sealing groove.

[0022] Preferably, the upper and lower ends of the petals are further provided with limiting blocks to restrict the degree of opening of the petals.

[0023] Preferably, the upper and lower ends of the petals are provided with limiting blocks to restrict the degree of their opening.

[0024] Preferably, each petal has a strip-shaped groove in the middle along the opening direction of the petal, and the limiting block is located in the groove and is fixedly connected to the flow channel.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: The plunger tool of the present invention uses a threaded assembly connection for each component and is designed with a set screw snap-fit ​​structure to prevent disintegration due to loosening caused by vibration during operation. The device is designed with a pressure rating of 20MPa, or a higher pressure rating depending on the different gas collection methods in different blocks. The device adopts an integrated structural design, specifically designed for both sealing and unsealing states. The upward process allows for the simultaneous and full activation of both sealing structures, while the downward process rapidly reduces the pressure difference between the upper and lower ends of the plunger, solving two problems, as detailed below:

[0026] 1. Improved sealing performance. Due to the consideration of sealing performance, during the upward movement of the device, the hydraulic pressure in the upper guide channel firmly locks the liquid at the upper end of the valve seal by the sealing ball and sealing ball seat. Simultaneously, this hydraulic pressure prevents gas in the lower guide channel from passing through the valve seal section. Under the sealing effect of the valve seal, the gas pressure in the lower guide channel increases and acts on the pneumatic diaphragm through the pressure guide hole. Driven by this pressure, the pneumatic diaphragm expands outward, pushing the eight limiting sealing petals outward. Because the limiting sealing petals are designed with limit blocks at both ends, the maximum expansion outer diameter of the petals can only reach 61mm. Since the inner diameter of the 27 / 8” oil pipe is 62mm, the tool is only 1mm away from the inner wall of the oil pipe during concentric motion. This not only forms an effective liquid film, but also, through the combined action of the turbulent sealing groove section and the pneumatic limiting sealing petals, reduces liquid slippage above the tool, thus improving the sealing performance of the plunger tool.

[0027] 2. The problem of maneuverability has been solved. Because the tool of this invention has upper and lower guide channels, it functions bidirectionally. During the upward movement of the tool, the pressure of the upper liquid column presses down on the two-stage sealing balls, preventing the gas in the lower guide channel from passing through the valve seal section. Since the pneumatic diaphragm contains compressible gas, when it encounters the tubing clamp, the limiting sealing flap can retract moderately under localized external force, quickly returning to its original size after passing the diameter change position. Because the flap is metal, it resists shear at the tubing clamp platform. When the tool reaches the wellhead for fluid discharge, the pressure of the liquid column above the tool decreases rapidly. At this time, the gas in the lower guide channel quickly pushes up the two-stage sealing balls and passes through the upper guide channel. Simultaneously, the pressure in the lower guide channel decreases, and the pneumatic diaphragm and limiting sealing flap retract simultaneously, causing the pressure difference between the upper and lower ends of the tool to quickly balance, thus initiating its descent. During the descent, because the pressure difference between the upper and lower ends of the tool remains small, the tool can descend without shutting down the well. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the present invention;

[0029] Figure 2 This is a schematic diagram of the internal structure of the valve sealing part of the present invention;

[0030] Figure 3 This is a schematic diagram of the structure of the petals and the limiting block of the present invention.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Upper guide channel, 11. Guide hole, 2. Valve seal, 201. Valve seal cover, 202. Upper sealing ball seat, 203. Upper sealing ball, 204. Bidirectional ball seat, 205. Lower sealing ball, 206. Lower sealing ball seat, 3. Lower guide channel, 4. Air guide hole, 5. Flap, 6. Limiting block, 7. Pneumatic diaphragm, 8. Pressure guide hole, 9. Buffer mechanism, 901. Buffer spring, 902. Impact head, 10. Turbulent sealing groove, 12. Retrieval part. Detailed Implementation

[0033] The following is in conjunction with the appendix Figure 1-3 The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] This invention provides a two-stage elastic sealing plunger tool, comprising an upper flow channel 3 with a flow guide hole 11 thereon. Gas / liquid flows through the upper flow channel 3 to the upper end of the plunger through the flow guide hole 11, thereby balancing the pressure difference between the upper and lower ends of the plunger.

[0035] The valve sealing part 2 is located at the lower end of the upper guide channel 1;

[0036] The lower guide channel 3 is located at the lower end of the valve seal. The lower guide channel 3 is also provided with a gas guide hole 4 for the gas at the lower end of the plunger to enter the lower guide channel 3.

[0037] Multiple petals 5 are evenly distributed outside the lower guide channel 3. Their upper ends are connected to the valve sealing part 2, and their lower ends are connected to the lower guide channel 3. In this embodiment, there are preferably 8 petals 5. The upper ends are received by the sealing cover of the valve sealing part 2. When the pneumatic membrane 7 is supported, the 8 petals 5 that are tightly attached are pushed outward by force. The lower ends are in contact with the lower guide channel 3.

[0038] A pneumatic membrane 7 is disposed between the outer wall of the lower guide channel 3 and the leaflets 5. The lower guide channel 3 is provided with pressure guiding holes 8 for allowing gas in the lower guide channel 3 to enter the pneumatic membrane 7. The pressure guiding holes 8 are orifices designed in the middle of the lower guide channel 3, serving as channels for gas in the lower guide channel 3 to enter the pneumatic membrane 7. When gas enters the pressure guiding holes 8, it rapidly expands outward under the action of force, pushing the eight leaflets 5 to expand outward together.

[0039] like Figure 2As shown, the valve sealing part 2 includes a valve sealing cover 201 and an upper sealing ball seat 202, an upper sealing ball 203, a bidirectional ball seat 204, a lower sealing ball 205, and a lower sealing ball seat 206 disposed inside the valve sealing cover 201. The upper sealing ball seat 202 is connected to the upper guide channel 1. The upper sealing ball 203 is located between the upper ends of the upper sealing ball seat 202 and the bidirectional ball seat 204. The lower sealing ball 205 is located between the lower end of the bidirectional ball seat 204 and the lower sealing ball seat 206. The upper sealing ball seat 202 is connected to the upper guide channel 1, and the lower sealing ball seat 206 is connected to the lower guide channel 3.

[0040] Furthermore, a turbulent flow sealing groove 10 is provided on the outside of the upper flow channel 1. The structure of the turbulent flow sealing groove 10 is the same as that of the cylindrical plunger, but its length is half that of the cylindrical plunger. Its main function is to prevent liquid from slipping off its outer wall.

[0041] Furthermore, a buffer mechanism 9 is also provided at the bottom of the lower guide channel 3.

[0042] Furthermore, the buffer mechanism 9 includes a buffer spring 901 and an impact head 902 disposed at the lower end of the buffer spring 901. The buffer spring 901 is connected to the bottom end of the lower guide channel 3. The buffer spring 901 is used to buffer and decelerate the plunger as it falls onto the seat; the impact head 902 is used to contact and decelerate the plunger as it falls onto the seat.

[0043] Furthermore, the number of petals 5 is 8.

[0044] Furthermore, the pneumatic membrane 7 is made of nitrile rubber that can withstand high temperatures of 120°C and high pressures of 20MPa.

[0045] Furthermore, the top of the upper guide channel 1 and the turbulent sealing groove 10 is also connected to a retrieval part 12. The retrieval part 12 is mainly used for wireline retrieval. When the plunger is stuck in the tubing, it is pulled out of the wellhead by wireline. The size is 35mm, which is consistent with the cylindrical plunger.

[0046] like Figure 3 As shown, furthermore, the upper and lower ends of the petals 5 are provided with limiting blocks 6 for restricting the degree of opening of the petals 5. A strip-shaped groove is provided in the middle of each petal 5 along the opening direction of the petal 5, and the limiting blocks 6 are located within the grooves and are fixedly connected to the flow channel 3.

[0047] The functions of each component in this embodiment are as follows:

[0048] The 12 retrieval neck is mainly used for wireline retrieval. When the plunger is stuck in the tubing, it is pulled out of the wellhead by wireline. The size is 35mm, which is consistent with the cylindrical plunger.

[0049] The gas / liquid flows through the upper guide channel 1 through the guide hole 1 until it reaches the upper end of the plunger, so that the pressure difference between the upper and lower ends of the plunger is balanced.

[0050] The upper guide flow 1 has a guide hole 11 at the upper end and an upper sealing ball seat 202 at the lower end, serving as a flow channel for gas and liquid phases. When the plunger moves downward, the gas flowing through the lower upper sealing ball seat 202 passes through quickly and is discharged from the guide hole 11. When the plunger moves upward to lift the liquid, the liquid fills the space and creates pressure, causing the upper sealing ball 203 to sit on the upper end of the bidirectional ball seat 204.

[0051] Turbulent sealing groove 10 has the same structure as the cylindrical plunger, but its length is half that of the cylindrical plunger. Its main function is to prevent liquid from slipping off its outer wall.

[0052] The upper sealing ball seat 202 mainly functions with the upper sealing ball 203 to prevent the upper sealing ball 203 from entering the upper guide channel 1 when the plunger moves downward.

[0053] During the downward movement of the plunger, the upper sealing ball 203 is pushed up by the gas through the bidirectional ball seat 204, allowing the gas to quickly pass through the valve seal 201. During the upward movement of the plunger, it is seated on the upper end of the bidirectional ball seat 204 under the action of the liquid pressure in the upper guide channel, preventing the gas in the valve seal 201 from entering the upper guide channel 1.

[0054] The valve sealing part 2 integrates five parts: upper sealing ball seat 202, upper sealing ball 203, valve sealing cover 201, bidirectional ball seat 204, lower sealing ball 205, and lower sealing ball seat 206. The upper end is connected to the upper guide channel 1, and the lower end is connected to the lower guide channel 3.

[0055] The bidirectional ball 204 causes the upper sealing ball 203 and the lower sealing ball 205 to be seated on its upper and lower end surfaces.

[0056] During the downward movement of the plunger, the lower sealing ball 205 is lifted by the gas through the lower guide channel 3, allowing the gas and liquid to quickly pass through the valve seal 201. During the upward movement of the plunger, the liquid pressure in the valve seal 201 decreases, causing it to sit on the upper end of the lower sealing ball seat 206, preventing the gas in the lower guide channel 3 from leaking through. During the downward movement of the plunger, the gas in the lower guide channel 3 lifts it, allowing the gas to quickly pass through the valve seal 201 and enter the upper guide channel 1.

[0057] The lower sealing ball seat 206 is connected to the upper sealing ball 205 at the upper end and to the lower guide channel 3 at the lower end;

[0058] The lower guide channel 3 is connected to the lower sealing ball seat 206 at its upper end and to the buffer mechanism 9 at its lower end. Its outer wall is in contact with the pneumatic membrane 7 and the flap 5.

[0059] There are 8 petals 5 in total. The upper end is connected to the valve sealing cover 201. When the pneumatic membrane 7 is raised, the 8 petals 5 that are tightly attached are pushed outward by the force. The lower end is in contact with the lower guide channel 3.

[0060] The pressure guiding hole 8 is an opening designed in the middle of the lower guide channel 3, which is the channel for gas in the lower guide channel 3 to enter the pneumatic membrane 7;

[0061] The pneumatic diaphragm 7 is made of nitrile rubber that can withstand temperatures up to 120°C and pressures up to 20MPa. When gas enters through the pressure guide hole, it expands rapidly outward under the action of force, pushing the eight limiting sealing flaps 5 to expand outward together.

[0062] 4 is the gas guide hole, through which gas from the lower end of the plunger enters the lower guide channel 3, and is connected by the gas guide hole.

[0063] Buffer spring 901. The plunger falls onto the seat to buffer and decelerate the vehicle.

[0064] Impact head 902. The plunger falls onto the landing gear to act as a contact decelerator;

[0065] The plunger tool provided in this embodiment retains the same retrieval and sealing performance as a cylindrical plunger. The design of the upper and lower flow channels allows the tool to descend while the well is open. While retaining the elastic sealing structure of the liner-type plunger, it reduces the friction between the rubber sheet and the inner wall of the tubing, thus improving the tool's passability. By wrapping rubber around the sealing rubber sheet, the rubber only serves to transmit pressure, preventing friction and shearing between the rubber sealing section and the metal inner wall of the tubing, thereby making the rubber more durable.

[0066] This tool can not only replace the commonly used cylindrical plunger in well opening and closing operations, but can also be used in the well opening state of gas wells, greatly expanding the application range of the plunger technology.

[0067] In this embodiment, the plunger tool uses threaded assembly for all components and is designed with a set screw locking structure to prevent disintegration due to loosening caused by vibration during operation. The device is designed for a pressure rating of 20 MPa, or a higher rating depending on the different gas collection methods in different blocks. The device employs an integrated structural design with targeted designs for both sealing and unsealing states. The upward movement allows for the simultaneous and full activation of both sealing stages, while the downward movement rapidly reduces the pressure difference between the upper and lower ends of the plunger, solving two key problems, as detailed below:

[0068] 1. Improved sealing performance. Due to the consideration of sealing performance, during the upward movement of the device, the hydraulic pressure in the upper guide channel firmly locks the liquid at the upper end of the valve seal by the sealing ball and sealing ball seat. Simultaneously, this hydraulic pressure prevents gas in the lower guide channel from passing through the valve seal section. Under the sealing effect of the valve seal, the gas pressure in the lower guide channel increases and acts on the pneumatic diaphragm through the pressure guide hole. Driven by this pressure, the pneumatic diaphragm expands outward, pushing the eight limiting sealing petals outward. Because the limiting sealing petals are designed with limit blocks at both ends, the maximum expansion outer diameter of the petals can only reach 61mm. Since the inner diameter of the 27 / 8” oil pipe is 62mm, the tool is only 1mm away from the inner wall of the oil pipe during concentric motion. This not only forms an effective liquid film, but also, through the combined action of the turbulent sealing groove section and the pneumatic limiting sealing petals, reduces liquid slippage above the tool, thus improving the sealing performance of the plunger tool.

[0069] 2. The problem of maneuverability has been solved. Because the tool of this invention has upper and lower guide channels, it functions bidirectionally. During the upward movement of the tool, the pressure of the upper liquid column presses down on the two-stage sealing balls, preventing the gas in the lower guide channel from passing through the valve seal section. Since the pneumatic diaphragm contains compressible gas, when it encounters the tubing clamp, the limiting sealing flap can retract moderately under localized external force, quickly returning to its original size after passing the diameter change position. Because the flap is metal, it resists shear at the tubing clamp platform. When the tool reaches the wellhead for fluid discharge, the pressure of the liquid column above the tool decreases rapidly. At this time, the gas in the lower guide channel quickly pushes up the two-stage sealing balls and passes through the upper guide channel. Simultaneously, the pressure in the lower guide channel decreases, and the pneumatic diaphragm and limiting sealing flap retract simultaneously, causing the pressure difference between the upper and lower ends of the tool to quickly balance, thus initiating its descent. During the descent, because the pressure difference between the upper and lower ends of the tool remains small, the tool can descend without shutting down the well.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A two-stage elastic sealing plunger tool, characterized in that, include: The upper guide channel (1) is provided with a guide hole (11), and the upper guide channel (1) is provided with a turbulent sealing groove (10) on the outside. A valve sealing part (2) is provided at the lower end of the upper guide channel (1); The lower guide channel (3) is located at the lower end of the valve seal. The lower guide channel (3) is also provided with a gas guide hole (4) for the gas at the lower end of the plunger to enter the lower guide channel (3). There are multiple petals (5) evenly distributed outside the lower guide channel (3). The upper end of the petals (5) is connected to the valve seal (2), and the lower end is connected to the lower guide channel (3). The upper and lower ends of the petals (5) are also provided with limiting blocks (6) for limiting the degree of opening of the petals (5). A pneumatic membrane (7) is disposed between the outer wall of the lower guide channel (3) and the flap (5). The lower guide channel (3) is provided with a pressure guide hole (8) for allowing the gas in the lower guide channel (3) to enter the pneumatic membrane (7). Under the limiting action of the limiting block, the maximum expansion outer diameter of the flap reaches 61mm, and the inner diameter of the oil pipe is 62mm, so that the plunger tool is only 1mm away from the inner wall of the oil pipe in the concentric motion state, forming an effective liquid film.

2. The two-stage elastic sealing plunger tool as described in claim 1, characterized in that, The valve sealing part (2) includes a valve sealing cover (201) and an upper sealing ball seat (202), an upper sealing ball (203), a bidirectional ball seat (204), a lower sealing ball (205), and a lower sealing ball seat (206) disposed inside the valve sealing cover (201). The upper sealing ball seat (202) is connected to the upper guide channel (1). The upper sealing ball (203) is located between the upper end of the upper sealing ball seat (202) and the upper end of the bidirectional ball seat (204). The lower sealing ball (205) is located between the lower end of the bidirectional ball seat (204) and the lower sealing ball seat (206). The upper sealing ball seat (202) is connected to the upper guide channel (1), and the lower sealing ball seat (206) is connected to the lower guide channel (3).

3. The two-stage elastic sealing plunger tool as described in claim 1, characterized in that, The bottom of the lower guide channel (3) is also provided with a buffer mechanism (9).

4. The two-stage elastic sealing plunger tool as described in claim 3, characterized in that, The buffer mechanism (9) includes a buffer spring (901) and an impact head (902) located at the lower end of the buffer spring (901). The buffer spring (901) is connected to the bottom end of the lower guide channel (3).

5. The two-stage elastic sealing plunger tool as described in claim 1, characterized in that, The number of the lobes (5) is 8.

6. The two-stage elastic sealing plunger tool as described in claim 1, characterized in that, The pneumatic membrane (7) is made of nitrile rubber that can withstand high temperatures of 120°C and high pressures of 20MPa.

7. The two-stage elastic sealing plunger tool as described in claim 1, characterized in that, The top of the upper guide channel (1) and the turbulent sealing groove (10) is also connected to a retrieval part (12).

8. The two-stage elastic sealing plunger tool as described in claim 7, characterized in that, Each petal (5) has a strip-shaped through groove in the middle along the opening direction of the petal (5), and the limiting block (6) is located in the through groove and is fixedly connected to the guide channel (3).

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