A full-bore straight-through emergency disconnect device

Abstract

The present invention discloses a full-bore through-type emergency disconnect device, belonging to the technical field of safety connection equipment. It includes valve body a and valve body b. Valve body a and valve body b have a left-right symmetrical structure and are fixed by a clamp-type holder. A connection end a of flange a is provided on valve body a, and a flange b and a connection end b are provided on the right side of valve body b. A groove a and a protrusion are provided on connection end a, and a groove b and a recess are provided on connection end b. The protrusion corresponds to and engages with the groove. Spring rack drive assemblies a and b are respectively installed on valve body a and valve body b. Spring rack drive assemblies a and b are symmetrical structures and respectively cooperate with the spool assembly to form conduction or sealing. A limiting ejector rod and a limiting spacer sleeve are provided between spring rack drive assemblies a and b, solving the technical problems of high cost and large flow resistance of existing equipment, and are mainly applied to liquid transportation.

Description

Technical Field

[0001] The present invention belongs to the technical field of safety connection devices, and particularly relates to a full-bore straight-through emergency disconnect device. Background Art

[0002] Liquid petroleum products and liquid chemical raw materials are widely transported by tanker trucks for inland transportation. The filling process involves the loading and unloading of materials. At present, loading and unloading arms are generally used as material conveying equipment when loading and unloading tank trucks in China. The loading and unloading arm, commonly known as a swivel arm, is a foldable and rotatable pipeline, which is connected into multiple sections through a rotary joint, elbows, and straight pipes. When in use, the discharge or feed port at the end of the loading and unloading arm is connected to the interface or tank opening on the tank truck.

[0003] Since most petrochemical raw materials are flammable and toxic, in order to prevent accidental leakage of materials from causing explosion accidents and environmental pollution, it is required to do a good job in safety protection during the loading and unloading process. Article 5.3.14 of the national standard GB51142 "Code for Design of Liquefied Petroleum Gas Supply Engineering" mentions that "a breakaway valve with a breaking force of 800N - 1400N should be installed on the loading and unloading pipe section". Many loading and unloading arms are required to install an emergency disconnect device, that is, what we commonly call a breakaway valve. Its function is to avoid situations where the tank truck fails to disconnect from the loading and unloading arm in case of an emergency during loading and unloading, or the operator forgets to disconnect the tank truck from the loading and unloading arm, or the tank truck slips away, etc., and the tank truck drives away from the site, thus damaging the loading and unloading arm and causing a leakage safety accident. The breakaway valve can be broken into two parts under external force, and the two disconnected parts can be self-sealed to seal the medium.

[0004] In addition, in order to achieve the purpose of truncation after separation, the breakaway valve has a valve structure inside. Currently, the breakaway valves used for loading and unloading arms on the market generally adopt the truncation method of rotating flaps or moving valve discs. Since these structures are located in the pipeline and occupy the flow passage, they will cause throttling to the medium transportation, with a large flow resistance and pressure loss, seriously affecting the flow rate. Due to the limitation of the unloading pressure, this impact is particularly obvious for the unloading operation. Before and after the installation of the breakaway valve, the unloading time increases by 20 to 40 minutes, resulting in a waste of time and a reduction in work efficiency.

[0005] In order to achieve safety purposes, a variety of emergency disconnect devices installed on loading and unloading arms have been disclosed in the prior art.

[0006] Patent Application No.: CN201620519258.7 discloses a bolt-breakable breakaway valve. Its inner cavity is provided with a moving valve disc to achieve the shut-off of the valve. Its principle is that when the breakaway valve is stressed to a certain value, the breakable bolt first breaks, and the breakaway valve without restraint breaks into two parts from the middle. At the same time, the valve disc in the inner cavity moves under the action of the spring force to seal the valve.

[0007] However, the flow passage of this breakaway valve is largely occupied by the valve flap, resulting in a large flow resistance, seriously affecting the loading and unloading speed of the vehicle. After the break-off bolt is disconnected, it cannot be reused and needs to be replaced with a new one. Moreover, during the operation of the loading and unloading arm, the break-off bolt is prone to accidental breakage.

[0008] Patent Application No.: CN201620961742.5 discloses a breakaway valve with low flow resistance characteristics. Its inner cavity is provided with structures such as a fixed seat, a rotating flap, and a return spring for realizing the on-off of the valve. Although this shut-off structure reduces the cross-sectional area of the medium flow direction and has a certain effect on reducing the flow resistance, there is still a relatively large flow resistance. In addition, it also adopts a break-off bolt trigger mechanism, and the disadvantages are the same as the above content.

[0009] Patent Application No.: CN202221320105.1 discloses a marine full-bore breakaway valve, belonging to the field of flammable and explosive liquid transportation. It includes two valve bodies connected in series on the pipeline. There is a docking flange at the connection of the valve bodies. The two valve bodies are connected by a number of break-off bolts installed along the circumferential direction of the docking flange. Inside the valve body, two inner shells that can allow the medium to pass through unobstructed are slidably installed. A connecting sleeve is installed at the connection of the two inner shells; between the inner wall of the valve body and the outer wall of the inner shell, there are two rotary valve plate closing devices for closing the pipeline opening; the rotary valve plate closing device includes a rotary valve plate arranged along the central axis direction of the inner shell. Between the rotary valve plate and the inner wall of the valve body, there is a driving arm that drives the rotary valve plate to close the pipeline port when the inner shell slides out of the valve body. There is a fixed block on the valve body. One end of the driving arm is fixedly installed on the rotary valve plate, and the other end is hinged on the fixed block. The driving arm drives the rotary valve plate to close the pipeline port with the hinge point on the fixed block as the rotation axis. Although this patent can achieve full flux, in the actual production process, due to the adoption of the inner shell structure, during the break-off process, the entire inner shell cannot be quickly and timely detached from the outer shell, thus affecting the safety of equipment use. In addition, by adopting the inner shell and flipping structure, the production cost of the entire equipment is increased, which is not conducive to the product maintaining good competitiveness.

[0010] Patent Application Number: CN200910183100.1 discloses an emergency disconnection device for liquid transportation, which includes upper and lower valve bodies and a locking assembly. The clamping plate seat of the locking assembly is arranged on the side of the upper valve body. The valve core rotating rods of the upper and lower valve bodies are arranged on the front of the upper and lower valve bodies. Transmission gears are installed at the ends of the valve core rotating rods. A transmission block driven by an oil cylinder is arranged between the two transmission gears. The transmission block is provided with upper and lower racks that cooperate with the two transmission gears. The locking rod is provided with an extended push rod. The oil cylinder is vertically arranged with the extended push rod of the locking rod. Synchronous gears that mesh with each other are installed on the hinge shaft between the front and rear clamping plates and the clamping plate seat. It pushes the locking rod through the oil cylinder, and then pushes the clamping plate, so that the front and rear clamping plates are forcibly opened synchronously from the valve body. Then, under the action of the tension spring and through the transmission of the synchronous gears, the two clamping plates are rotated outward synchronously, making the separation of the two valve bodies complete, safe and reliable. In addition, the opening and closing of the valve are all completed by the oil cylinder, which is convenient for installation and debugging, has low labor intensity and high work efficiency. The above-mentioned device uses the force of the oil cylinder to push the locking rod and then push the clamping plate. Under the action of the synchronous gears, the front and rear clamping plates are forcibly opened synchronously from the valve body, and the success rate of opening is 100%. The safety and reliability are very good. After the front and rear clamping plates are forcibly opened from the valve body, the two clamping plates are rotated outward synchronously under the action of the tension spring and through the transmission of the synchronous gears, and there will be no phenomenon of incomplete separation. In addition, the opening and closing of the valve are all completed by the power of the oil cylinder, without the need for human physical strength, reducing the labor intensity of workers and improving work efficiency. The oil cylinder is fixed on the clamping plate, so the structure is compact and the overall sense is strong, and it is convenient for installation and debugging. However, the above-mentioned device has the following defects: Since it adopts an oil cylinder control structure, as well as a locking rod structure, the entire device needs to transmit signals to the oil cylinder for control, so the control system needs to intervene in the working process, which will inevitably lead to higher production costs, and the entire device has a complex structure and is not suitable for comprehensive promotion and application.

[0011] The applicant has been focusing on the research of emergency disconnection devices for several years. Currently, multiple patents for emergency disconnection devices have been applied. After long-term research, the applicant finally developed an emergency disconnection device with low production cost, good sealing effect, easy control and capable of ensuring full-bore liquid transportation. Summary of the Invention

[0012] In order to solve the technical problems proposed in the background art, the present invention provides a full-bore straight-through emergency disconnection device, and the technical solutions adopted are as follows:

[0013] A full-bore through-type emergency disconnect device, comprising valve body a and valve body b. Valve body a and valve body b are symmetric structures on the left and right and are fixed by a hoop-type gripper. The materials of valve body a and valve body b are metal materials. On the left side of valve body a, there is a flange a, and on the right side of valve body b, there is a flange b. The material of the flange is a metal material. On the right side of valve body a, there is a connection end a, and on the left side of valve body b, there is a connection end b. The material of the connection end is a metal material. On the connection end a, there are a groove a and a protrusion, and on the connection end b, there are a groove b and a groove. The protrusion corresponds to and engages with the groove. The diameters of groove a and groove b are the same and are sealed in the middle by a sealing ring.

[0014] The improvement of the present invention lies in that a spring rack drive assembly a and a spring rack drive assembly b are respectively installed on valve body a and valve body b. The spring rack drive assembly a and the spring rack drive assembly b are symmetric structures and respectively cooperate with the spool assembly to form conduction or sealing. Between the spring rack drive assembly a and the spring rack drive assembly b, there are a limit ejector rod and a limit spacer sleeve.

[0015] The spool assembly is the core component of the present invention. The spool assembly includes a rotating shaft valve rod, a gear, and a spherical spool. The spherical spool is located in valve body a and is sealed on both sides by a sphere sealing ring a and a sphere sealing ring b respectively. The upper part of the spherical spool is fixedly connected to the rotating shaft valve rod. The upper part of the rotating shaft valve rod is fixedly connected to the gear. From bottom to top, a valve rod lower sealing ring, a valve rod upper sealing ring, a sealing packing, and a packing gland are successively arranged at the connection of the rotating shaft valve rod and valve body a. The sealing ring and the sealing packing are used to ensure the sealing of the connection. The upper part of the rotating shaft valve rod is connected to the gear and fixed by a nut. A thrust bearing is arranged at the connection of the gear and the rotating shaft valve rod. The thrust bearing is used for the rotation of the rotating shaft valve rod. A limit pin is arranged at the lower part of the gear, and a stop block is arranged on a. The stop block cooperates with the limit pin, that is, the opening and closing of the spherical spool are controlled by the limit pin and the stop block.

[0016] The spring rack drive assembly is the core assembly of the present invention. The spring rack drive assembly a includes a sleeve and a special-shaped rack. A compression spring is arranged in the sleeve. A strip-shaped hole is arranged on the sleeve. On the right side of the compression spring, there is a special-shaped rack. The special-shaped rack includes a cylindrical guide body. A rack and an internal thread connection end are arranged on the cylindrical guide body. The rack slides left and right in the strip-shaped hole. Connection pieces a and b are arranged on the sleeve. Connection pieces a and b are connected to the valve body. The rack meshes with the gear.

[0017] The reset device of the present invention is provided with a reset screw rod and a reset nut. A through hole is arranged on the left side of the sleeve. The reset screw rod and the reset nut are threadedly connected. The right side of the reset screw rod is connected to the internal thread connection end for reset.

[0018] The hoop clamp type gripper is the core component of the present invention, including symmetrical hoop clamps, namely hoop clamp a and hoop clamp b. The left sides of hoop clamp a and hoop clamp b are connected by a right and left hand nut. The upper and lower parts of the right and left hand nut are respectively a reverse thread union bolt and a right hand thread union bolt. The right sides of the said hoop clamp a and hoop clamp b are connected by a breaking device. The said breaking device includes a pull ring, a lock cover, a top cone and a pull rod. A top cone hole is provided on the said top cone, and a breaking pin is provided in the said top cone hole. A trapezoidal inclined groove, a connection hole, a convex platform and a tapered countersunk hole are provided on the said hoop clamp a. The top cone is located in the tapered countersunk hole, the lock cover is sleeved on the convex platform, and the trapezoidal inclined groove is engaged with the connection end to form a seal.

[0019] The present invention has the following beneficial effects: Through the structural transformation of the present invention, full-bore flow can be achieved, and the production cost of the entire equipment is relatively low. There is no throttling effect on the pipeline, the flow resistance is extremely small, the flow velocity is fast, and the loading and unloading vehicle speed is not affected. The structure is simple, the breaking force value is stable, the action is rapid, it is easy to recombine after breaking, no parts need to be replaced, and it can be used repeatedly, which is suitable for comprehensive promotion and application. Description of the Drawings

[0020] Figure 1 is the three-dimensional view of the present invention;

[0021] Figure 2 is the top view of the present invention;

[0022] Figure 3 is the internal structure diagram of the spring rack drive mechanism of the present invention before separation;

[0023] Figure 4 is the internal structure diagram of the spring rack drive mechanism of the present invention after separation;

[0024] Figure 5 is the cross-sectional view of the present invention when not broken;

[0025] Figure 6 is the cross-sectional view of the present invention when broken;

[0026] Figure 7 is the structure diagram of the hoop clamp type gripper of the present invention;

[0027] Figure 8 is the structure diagram of the fixing part of the present invention;

[0028] Figure 9 is the structure diagram of the top cone of the present invention;

[0029] Figure 10 is the structure diagram of the clamping component of the present invention;

[0030] Figure 11 is the three-dimensional view of the spring rack drive component of the present invention;

[0031] Figure 12 Cross-sectional view of the spring rack drive assembly of the present invention;

[0032] Figure 13 Three-dimensional view of the special-shaped rack structure of the present invention. Detailed implementation manners

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Embodiment 1

[0035] As Figures 1 - 13 shown:

[0036] A full-bore through-type emergency disconnect device, comprising valve body a7 and valve body b8. Valve body a7 and valve body b8 are symmetric structures on the left and right and are fixed by a clamp-type holder 1. On the left side of valve body a7, there is a flange a7-15. On the right side of valve body b8, there is a flange b8-4. On the right side of valve body a7, there is a connection end a7-12. On the left side of valve body b8, there is a connection end b8-1. The connection end a7-12 is provided with a groove a7-12-1 and a protrusion 7-13. The connection end b8-1 is provided with a groove b8-2 and a groove 8-3. The protrusion 7-13 corresponds to and engages with the groove 8-3. The diameters of the groove a7-12-1 and the groove b8-2 are the same and are sealed in the middle by a sealing ring 9. A spring rack drive assembly a and a spring rack drive assembly b are respectively installed on valve body a7 and valve body b8. The spring rack drive assembly a and the spring rack drive assembly b are symmetric structures and respectively cooperate with the valve core assembly to form conduction or sealing. A limiting ejector rod 5 and a limiting spacer 6 are provided between the spring rack drive assembly a and the spring rack drive assembly b. The valve core assembly includes a rotating shaft valve stem 7-1, a gear 7-2, and a spherical valve core 7-5. The spherical valve core 7-5 is located inside valve body a7 and is sealed on both sides by a sphere sealing ring a7-6 and a sphere sealing ring b7-7 respectively. The upper part of the spherical valve core 7-5 is fixedly connected to the rotating shaft valve stem 7-1. The upper part of the rotating shaft valve stem 7-1 is fixedly connected to the gear 7-2. From bottom to top, a valve stem lower sealing ring 7-10, a valve stem upper sealing ring 7-9, a packing 7-8, and a packing gland 7-4 are provided at the connection of the rotating shaft valve stem 7-1 and valve body a7. The upper part of the rotating shaft valve stem 7-1 is connected to the gear 7-2 and fixed by a nut 7-16. A thrust bearing 7-3 is provided at the connection of the gear 7-2 and the rotating shaft valve stem 7-1. A limiting pin 7-11 is provided at the lower part of the gear 7-2. A stop block 7-14 is provided on a7, and the stop block 7-14 cooperates with the limiting pin 7-11. The spring rack drive assembly a includes a sleeve 4 and a special-shaped rack 3. A compression spring 4-1 is provided inside the sleeve 4. A strip-shaped hole 4-7 is provided on the sleeve 4. On the right side of the compression spring 4-1, there is a special-shaped rack 3. The special-shaped rack 3 includes a cylindrical guide body 3-1. A rack 3-2 and an internal thread connection end 3-3 are provided on the cylindrical guide body 3-1. The rack 3-2 slides left and right inside the strip-shaped hole 4-7. Connecting parts a4-4 and b4-5 are provided on the sleeve 4, and the connecting parts a4-4 and b4-5 are connected to the valve body. The rack 3-2 meshes with the gear 7-2. A reset screw rod 4-4 and a reset nut 4-2 are also provided. A through hole 4-6 is provided on the left side of the sleeve 4. The reset screw rod 4-4 and the reset nut 4-2 are threadedly connected, and the right side of the reset screw rod 4-4 is connected to the internal thread connection end 3-3 for reset. The clamp-type holder 1 includes symmetric clamps.They are respectively the hoop a1-4 and the hoop b1-5. The left sides of the hoop a1-4 and the hoop b1-5 are connected by a positive and reverse thread nut 1-1. The upper and lower parts of the positive and reverse thread nut 1-1 are respectively a reverse thread union bolt 1-2 and a positive thread union bolt 1-3. The right sides of the hoop a1-4 and the hoop b1-5 are connected by a breaking device 2. The breaking device 2 includes a pull ring 2-1, a lock cover 2-2, a top cone 2-3 and a pull rod 2-4. A top cone hole 2-3-1 is provided on the top cone 2-3, and a breaking pin 2-5 is provided in the top cone hole 2-3-1. A trapezoidal inclined groove 1-4-4, a connection hole 1-4-1, a convex platform 1-4-2 and a countersunk conical hole 1-4-3 are provided on the hoop a1-4. The top cone 2-3 is located in the countersunk conical hole 1-4-3. The lock cover 2-2 is sleeved on the convex platform 1-4-2. The trapezoidal inclined groove 1-4-4 is engaged with the connection end to form a seal.

[0037] The working principle of the present invention is as follows: During the use of the present invention, a pull rope is fixed on the loading and unloading arm, and the other end of the pull rope is fixed on the pull ring 2-1 of the hoop type gripper. When the loading and unloading arm swings beyond the set movement range, the pull rope will be tightened. The tightened pull rope will pull the pull ring 2-1, and then the pull ring 2-1 will pull the pull rod 2-4. The pull rod 2-4 cuts off the breaking pin 2-5. The pull rod 2-4 continues to move under tension. The pull rod 2-4 drives the lock cover 2-2 to disengage from the convex platform 2-4-2 of the hoop type gripper. The pull rod 2-4 continues to move under tension and will pull the top cone 2-3. The conical surface of the top cone 2-3 will spread the two hoops to both sides, realizing the separation of the hoop from the valve body. At this time, the limit ejector rod 5 and the limit spacer 6 fall off, and the compression spring 4-1 starts to reset and drives the rack 3-2 to move closer to the middle. At this time, the rack 3-2 respectively drives the gear 7-2 to rotate. The gear 7-2 drives the rotating shaft valve stem 7-1 to rotate. The rotating shaft valve stem 7-1 drives the spherical valve core 7-5 to rotate and completes the closing of the valve body under the action of the limit pin 7-11. The limit pin 7-11 is used to restrict the rotation angle range of the gear 7-2.

[0038] The reset screw rod 4-3 and the reset nut 4-2 of the spring rack drive mechanism are used to reset the closed ball valve after disconnection to the open state, and also facilitate the reset of the breaking valve after the breaking separation. The hoop type gripper 1 is reinstalled and reused. The limit ejector rod 5 is used to maintain the compressed state of the spring and the position of the special-shaped rack, and maintain the open state of the ball valve. The hoop type gripper 1 is used to serially fix two valve bodies and the main sealing ring 9.

[0039] In addition, it should be understood that although this specification is described according to the embodiments, not each embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A full-bore through-type emergency disconnect device, comprising valve body a (7) and valve body b (8). Valve body a (7) and valve body b (8) are symmetric structures on the left and right and are fixed by a clamp-type holder (1). On the left side of valve body a (7), there is a flange a (7-15). On the right side of valve body b (8), there is a flange b (8-4). On the right side of valve body a (7), there is a connection end a (7-12). On the left side of valve body b (8), there is a connection end b (8-1). On the connection end a (7-12), there are a groove a (7-12-1) and a protrusion (7-13). On the connection end b (8-1), there are a groove b (8-2) and a groove (8-3). The protrusion (7-13) corresponds to and engages with the groove (8-3). The diameters of the groove a (7-12-1) and the groove b (8-2) are the same and are sealed in the middle by a sealing ring (9). It is characterized in that, Spring rack drive assemblies a and b are respectively installed on valve body a (7) and valve body b (8). The spring rack drive assemblies a and b are symmetric structures and respectively cooperate with the spool assembly to form conduction or sealing. A limit ejector rod (5) and a limit spacer sleeve (6) are provided between the spring rack drive assemblies a and b; The spool assembly includes a rotating shaft valve stem (7-1), a gear (7-2), and a spherical spool (7-5); The upper part of the spherical spool (7-5) is fixedly connected to the rotating shaft valve stem (7-1), and the upper part of the rotating shaft valve stem (7-1) is fixedly connected to the gear (7-2); The spring rack drive assembly a includes a sleeve (4) and a special-shaped rack (3). A compression spring (4-1) is provided inside the sleeve (4). A strip hole (4-7) is provided on the sleeve (4). On the right side of the compression spring (4-1), there is a special-shaped rack (3). The special-shaped rack (3) includes a cylindrical guide body (3-1). On the cylindrical guide body (3-1), there are a rack a (3-2) and an internal thread connection end (3-3). The rack a (3-2) slides left and right in the strip hole (4-7). Connecting pieces a (4-4) and b (4-5) are provided on the sleeve (4). The connecting pieces a (4-4) and b (4-5) are connected to valve body a (7). The rack a (3-2) meshes with the gear (7-2).

2. The all - through direct - through emergency disconnection device according to claim 1, characterized in that, The described spherical valve core (7-5) is located inside the valve body a (7) and is sealed on both sides by a spherical seal ring a (7-6) and a spherical seal ring b (7-7) respectively. At the connection between the rotating shaft valve stem (7-1) and the valve body a (7), a valve stem lower seal ring (7-10), a valve stem upper seal ring (7-9), a sealing packing (7-8), and a packing gland (7-4) are provided successively from bottom to top. The upper part of the rotating shaft valve stem (7-1) is connected to a gear (7-2) and fixed by a nut (7-16). A thrust bearing (7-3) is provided at the connection between the gear (7-2) and the rotating shaft valve stem (7-1). A limit pin (7-11) is provided at the lower part of the gear (7-2). A stop block (7-14) is provided on the valve body a (7), and the stop block (7-14) cooperates with the limit pin (7-11).

3. The all-bore straight-through emergency disconnection device according to claim 2, characterized in that, A reset screw rod (4-3) and a reset nut (4-2) are also provided. A through hole (4-6) is provided on the left side of the sleeve (4). The reset screw rod (4-3) and the reset nut (4-2) are threadedly connected, and the right side of the reset screw rod (4-3) is connected to an internally threaded connection end (3-3) for resetting.

4. The all-through straight-through emergency release device according to claim 1, characterized in that, The described hoop-type gripper (1) includes symmetrical hoops, namely hoop a (1-4) and hoop b (1-5). The left sides of hoop a (1-4) and hoop b (1-5) are connected by a positive and negative thread nut (1-1). The upper and lower parts of the positive and negative thread nut (1-1) are respectively a reverse thread union bolt (1-2) and a positive thread union bolt (1-3). The right sides of hoop a (1-4) and hoop b (1-5) are connected by a breaking device (2). The breaking device (2) includes a pull ring (2-1), a lock cover (2-2), a top cone (2-3), and a pull rod (2-4). A top cone hole (2-3-1) is provided on the top cone (2-3). A breaking pin (2-5) is provided in the top cone hole (2-3-1). A trapezoidal inclined groove (1-4-4), a connection hole (1-4-1), a boss (1-4-2), and a tapered counterbore (1-4-3) are provided on hoop a (1-4). The top cone (2-3) is located in the tapered counterbore (1-4-3). The lock cover (2-2) is sleeved on the boss (1-4-2). The trapezoidal inclined groove (1-4-4) is respectively engaged with the connection end a (7-12) and the connection end b (8-1) to form a seal.

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