Gas extraction device with borehole mouth protection

Abstract

The present application belongs to the technical field of gas drainage drilling, and in particular to a gas drainage device with a drilling hole opening protection, comprising a first shaft sleeve sleeved on the outside of a drill rod and a plurality of combined enclosure sealing plates rotatably arranged on the outside of the first shaft sleeve, the side end of the sealing plate being provided with an inflatable air cushion, the first shaft sleeve being provided with a cleaning brush, the outside of the drill rod being provided with a key strip selectively matched with an inner recess on the inside of the first shaft sleeve to establish a key shaft connection, so that the cleaning brush sweeps the mine wall while rotating with the drill rod; the back end of the sealing plate is connected to a second shaft sleeve through a connecting rod mechanism, the second shaft sleeve is connected to a hollow hydraulic cylinder through a thrust bearing, and the sealing plate is driven to open and adhere to the mine wall by the hydraulic cylinder. The present application realizes a complete operation closed loop of cleaning first and then sealing, and drainage first and then detection, through the cooperative matching of pre-cleaning and flexible sealing, the linkage of hydraulic driving and connecting rods, and the dynamic and static separation structure, and has the characteristics of reliable sealing, simple operation and intelligent monitoring.

Description

Technical Field

[0001] This invention relates to the field of borehole gas drainage technology, specifically a gas drainage device with borehole opening protection. Background Technology

[0002] Gas drainage is the main technical means of gas control in coal mines, which involves drilling holes in the coal seam and connecting them to drainage pipelines to release gas. During drilling and drainage, wellhead protection is a crucial aspect of ensuring operational safety. Currently, commonly used wellhead protection devices in coal mines mainly include components such as wellhead pipes, blowout preventers (BOPs), four-way valves, sealing components, and gas-water separators, which are fixed and sealed to the borehole wall after being connected by flanges. Based on this, some improved solutions employ fully enclosed negative pressure continuous drainage BOP devices, achieving multiple layers of protection through a multi-seal process of "wellhead-BOP-separation box"; other solutions use normally closed BOP systems, achieving automatic power-off and sealing functions through electro-hydraulic combined control; still others install pressurized, sealed hollow rubber gaskets on the outside of the BOP, using inflation to achieve a tight seal.

[0003] However, the existing technologies still have the following shortcomings: First, most wellhead sealing devices are fixed structures, and the sealing surface cannot be cleaned before drilling. Coal dust, slag, and other debris adhering to the surface of the mine wall can easily cause the seal to not fit tightly with the mine wall, forming a leakage channel. At the same time, sharp stones may puncture the flexible seal, affecting the sealing reliability. Second, the sealing plates or baffles of the existing devices are mostly rigid structures, which cannot completely cover the irregular surface of the mine wall around the borehole after being unfolded. There is a lack of effective flexible filling means at the joints between the seals, resulting in limited sealing effect. Third, the installation, unfolding, and retraction of existing blowout preventers mostly rely on manual on-site operation. Frequent disassembly and assembly and large-angle installation affect construction efficiency and increase the labor intensity of workers. In addition, the devices do not have self-cleaning functions and intelligent monitoring capabilities, making it difficult to detect and warn of residual gas at the wellhead after the drainage is completed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a gas drainage device with borehole opening protection, which solves the problems of existing borehole opening protection devices, such as the lack of pre-cleaning treatment on the mine wall surface leading to poor adhesion between the seal and the rough coal wall, the inability of the rigid sealing plate to adaptively cover the irregular mine wall around the borehole, the lack of flexible filling means at the joints of the seals, and the reliance on manual operation for device deployment and retraction without self-cleaning and intelligent monitoring functions.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a gas drainage device with borehole opening protection, comprising a drill rod, and further comprising: A first bushing is fitted onto the outside of the drill rod. The first bushing has a bearing ring inside, which allows the first bushing to move along the axial direction of the drill rod and is rotationally isolated from the drill rod. The sealing plate is a multi-group enclosed structure, which is rotatably set on the outside of the first bushing through the connecting seat and the support platform. The sealing plate can rotate to open or close around the central axis of the support platform. When opened, several groups of sealing plates form a circular covering surface that spreads outward with the center of the drill hole as the reference. An air cushion is fixedly installed on the side end of the sealing plate. After being inflated, the air cushion expands and covers the gap between the sealing plates. A cleaning brush extends radially and is disposed on the outside of the first bushing; A key bar is provided on the outside of the drill rod; an inner groove is provided on the front section of the inner side of the first bushing. After the first bushing moves toward the mine wall, the key bar can be inserted into the inner groove to establish a key shaft connection, so that the first bushing and the cleaning brush rotate with the drill rod. An axial pressure mechanism includes a second bushing, a bearing bracket, a connecting rod, a linkage shaft, a swing arm, a hollow hydraulic cylinder, a pusher, and a thrust bearing. The second bushing is sleeved on the outside of the drill rod and can move axially along the drill rod. The bearing bracket is installed on the outside of the second bushing. The connecting rod is installed on the back end of the sealing plate. The linkage shaft passes between the connecting rods on both sides. One end of the swing arm is rotatably connected to the linkage shaft, and the other end is rotatably connected to the bearing bracket. The pusher is installed inside the hollow hydraulic cylinder. The pusher is connected to the second bushing through the thrust bearing. The hollow hydraulic cylinder drives the second bushing to move axially through the pusher and the thrust bearing, thereby driving the connecting rod, the linkage shaft, and the swing arm to apply pressure or pull back on the sealing plate. A gas monitoring sensor and an audible and visual alarm are embedded in the side of the sealing plate.

[0006] In some embodiments, the sealing plate adopts a multi-group enclosed structure, and several groups of the sealing plates form a circular covering surface that spreads outward from the center of the drill hole; the air cushion is fixedly set on the side end of the sealing plate by fastening strips, the air cushion is soft around its periphery, and the part that expands after inflation evenly covers the gap between the sealing plates.

[0007] In some embodiments, an inflation tube and a pneumatic rotary joint are also included; the inflation tube is disposed on the back end of the sealing plate and inserted into the gap of the first bushing; one end of the inflation tube is connected to the air inlet of the air cushion, and the other end is connected to the internal channel of the rotating end of the pneumatic rotary joint; the pneumatic rotary joint is fixedly installed on the rear end of the first bushing, its rotating end rotates together with the first bushing, and its stationary end is connected to the air supply line of the external inflation device, so that the gas pumped by the external inflation device is delivered to each of the air cushions through the pneumatic rotary joint, and the external air supply line remains stationary and does not rotate with the drill rod.

[0008] In some embodiments, the cleaning brush is disposed in the gap between the two air cushions; when the air cushions are inflated, the cleaning brush is blocked by the air cushions; the cleaning brush rotates with the first bushing and is used to rotate and sweep the dust and debris on the mine wall when it comes into contact with the mine wall around the borehole.

[0009] In some embodiments, the connecting rod is mounted on the side end of the back end of the sealing plate, the linkage shaft is inserted between the two connecting rods, and the swing arm is rotatably connected to the linkage shaft; the shaft seat is detachably mounted on the outside of the second bushing by bolts, and the other end of the swing arm is rotatably connected to the shaft seat.

[0010] In some embodiments, the hollow hydraulic cylinder is prevented from being rotated by the thrust bearing, and the cylinder body of the hollow hydraulic cylinder is fixed to the frame of an external drilling rig by a mounting base.

[0011] In some embodiments, the first bushing is provided with a bearing ring inside, and the first bushing, the outer sealing plate, and the air cushion can move along the axial direction of the drill rod to adjust the distance from the drill hole; when the drill rod is connected to the drill bit for drilling, the bearing ring will not affect the rotation of the drill rod.

[0012] In some embodiments, the gas monitoring sensor and the audible and visual alarm are embedded in the side of the sealing plate; when the sealing plate is opened and sealed, the gas monitoring sensor is hidden inside and protected; when the sealing plate is pulled back and flipped over, the gas monitoring sensor measures the borehole opening, and the audible and visual alarm sounds an alarm when the gas concentration is abnormal.

[0013] In some embodiments, the sealing plate has a retracted state and an open state; in the retracted state, the sealing plate is in the retracted position through the rotatable connection between the connecting seat and the support platform, and is sent into the borehole opening position together with the drill rod; in the open state, the sealing plate is tightly attached to the cleaned mine wall surface.

[0014] Compared with the prior art, the present invention provides a gas drainage device with borehole orifice protection, which has the following beneficial effects: Before the sealing plate is attached to the mine wall, the area around the borehole is cleaned by rotating a cleaning brush to remove coal dust and sharp debris from the surface of the mine wall, providing a clean and flat surface for the air cushion seal. Then, multiple sets of enclosed sealing plates are used in conjunction with an inflatable air cushion. After the sealing plates are in place, they are inflated and expand to evenly cover the gaps between the sealing plates. The adaptive deformation characteristics of the flexible material are used to fill the micro-unevenness of the irregular surface of the mine wall, realizing the synergistic cooperation between the rigid sealing plate and the flexible air cushion, thereby greatly improving the sealing reliability. Furthermore, the opening and closing of each sealing plate is synchronously controlled by a single hollow hydraulic cylinder driving a linkage mechanism. When the sealing plate flips and closes, it naturally drives the embedded gas monitoring sensor from a hidden state to a detection position facing the borehole opening. This allows for immediate gas concentration detection and audible and visual alarms after extraction without the need for additional drive devices, forming a complete linkage chain of hydraulic drive, linkage transmission, sealing plate flipping, and sensor positioning. At the same time, the bearing ring inside the first bushing isolates the rotation from the drill rod, the thrust bearing isolates the rotational movement between the hollow hydraulic cylinder and the second bushing, and the pneumatic rotary joint enables the static-dynamic conversion of the air filling pipe. This ensures that each component operates independently without interference when the drill rod is rotating at high speed, thus achieving a complete closed-loop operation of cleaning before sealing and extraction before detection. This effectively improves the safety, reliability, and automation level of borehole opening protection. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the overall structure of one side of the back end of the sealing plate of the present invention; Figure 3 This is a schematic diagram of the side structure of the air cushion and sealing plate of the present invention; Figure 4 This is a schematic diagram of the connection position of the sealing plate and connecting rod of the present invention; Figure 5 This is a schematic diagram of the connection position structure of the first bushing and key strip of the present invention; Figure 6 This is a schematic diagram showing the installation position of the hollow hydraulic cylinder and the positional relationship between the pusher and the second bushing of the present invention; Figure 7 This is a schematic diagram of the overall structure of the sealing plate and air cushion in the controlled closing state under the pull-back state of the second bushing of the present invention.

[0016] In the diagram: 1. Drill rod; 2. Sealing plate; 3. First bushing; 4. Connecting seat; 5. Air cushion; 6. Connecting rod; 7. Linkage shaft; 8. Swing arm; 9. Second bushing; 10. Shaft support frame; 11. Hollow hydraulic cylinder; 12. Push cylinder; 13. Thrust bearing; 14. Cleaning brush; 15. Gas monitoring sensor; 16. Key strip; 17. Support platform; 18. Audible and visual alarm; 19. Fastening strip; 20. Air inflation pipe. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] Please see Figure 1-7 In this embodiment: a gas drainage device with borehole opening protection includes a drill rod 1 for drilling and gas extraction. A first bushing 3 is sleeved on the outside of the drill rod 1, and a sealing plate 2 is rotatably installed on the outside of the first bushing 3. A connecting seat 4 and a support platform 17 (e.g., ...) are provided between the sealing plate 2 and the first bushing 3. Figure 3 and Figure 5 As shown, the sealing plate 2 (as shown) is connected to the support platform 17 via a rotatable connection between the connecting seat 4 and the support platform 17, allowing the sealing plate 2 to rotate around the central axis of the support platform 17. When the sealing plate 2 opens ( Figure 2(As shown in the diagram), the surrounding mine wall of the drill hole into which drill rod 1 is inserted can be sealed and protected in a planar manner.

[0021] The sealing plate 2 adopts a multi-group enclosed structure, with several groups of sealing plates 2 forming a circular covering surface that spreads outward from the center of the drill hole.

[0022] To prevent gas from escaping from the gap between the sealing plates 2, an inflatable air cushion 5 is fixedly installed on the side of the sealing plate 2. The air cushion 5 is soft around its perimeter, so that even if the edges are squeezed together, there will be no hard contact. After inflation, the extended and expanded part can evenly cover the gap between the sealing plates 2, thereby improving the sealing performance.

[0023] The first bushing 3 has a bearing ring inside, so that the first bushing 3 and the outer sealing plate 2, air cushion 5 and other auxiliary structures can move along the axial direction of the drill rod 1, thereby adjusting the distance from the drill hole. The bearing setting also ensures that the drill rod 1 will not be affected when connected to the drill bit for drilling.

[0024] An inflation tube 20 is provided on the back end of the sealing plate 2 and inserted into the gap of the first bushing 3. The inflation tube 20 rotates with the first bushing 3. The inflation tube 20 passes through the internal gap and is connected to the external inflation device to pump gas to the air cushion 5.

[0025] It is important to note that the inflation pipe 20 is not directly and rigidly connected to the external inflation equipment. Instead, it achieves dynamic-to-static conversion through a pneumatic rotary joint. The rotary joint is fixedly installed at the rear end of the first bushing 3, and its rotating end rotates with the first bushing 3, while its stationary end is connected to the air supply line of the external inflation equipment. One end of the inflation pipe 20 is connected to the air inlet of the air cushion 5 on the side of the sealing plate 2, and the other end is connected to the internal channel of the rotating end of the rotary joint. The gas pumped by the external inflation equipment enters through the stationary end of the rotary joint, exits through the rotating end to the inflation pipe 20, and is then delivered to each air cushion 5. The rotary joint is equipped with precision bearings and a dynamic sealing structure, which ensures that the gas channel remains unobstructed and reliably sealed even when the drill rod 1 is rotating at high speed. At the same time, the inflation pipe 20 and the external air supply line remain stationary and do not rotate with the drill rod 1. Since the rotary joint technology is a commonly used technology, it will not be described in detail below.

[0026] In order to ensure that the sealing plate 2 can press against the surrounding mine wall of the borehole, a hollow hydraulic cylinder 11 is provided on the outside of the drill rod 1 to provide axial pressure drive; A connecting rod 6, a linkage shaft 7, and a swing arm 8 are provided on the back end of the sealing plate 2. The connecting rod 6 is installed on the side end of the sealing plate 2, while the linkage shaft 7 passes between the two connecting rods 6. The swing arm 8 is rotatably connected to the linkage shaft 7. The connecting rod 6, linkage shaft 7, and swing arm 8 are all used to transmit the axial pressure of the hollow hydraulic cylinder 11. To ensure a complete pressure transmission path, a second bushing 9 is provided on the outside of the drill pipe 1 (e.g., ...). Figure 6As shown, the second bushing 9 has the same internal structure as the first bushing 3 and can move axially along the drill rod 1. The bearing bracket 10 is detachably mounted on the outside of the second bushing 9 by bolts, and the other end of the swing arm 8 is rotatably connected to the bearing bracket 10. Thus, by simply pushing the second bushing 9, pressure can be transmitted to the sealing plate 2 through the connecting rod 6, the linkage shaft 7, and the swing arm 8, and the sealing plate 2 can be stably pressed against the mine wall.

[0027] A push cylinder 12 is installed inside the hollow hydraulic cylinder 11, and a thrust bearing 13 is installed between the push cylinder 12 and the second bushing 9 as a connecting member. Thus, the axial movement of the second bushing 9 is entirely driven and controlled by the hollow hydraulic cylinder 11. The specific operating steps are as follows: After drill rod 1 is inserted into the borehole, hollow hydraulic cylinder 11 controls pusher 12 to apply axial pressure. Under pressure, second bushing 9 drives connecting rod 6, linkage shaft 7, and swing arm 8 to press against sealing plate 2 until sealing plate 2 is tightly pressed against the mine wall. After gas extraction is complete, the operation is reversed, and sealing plate 2 is pulled back and retracted (e.g., ...). Figure 7 (The state shown).

[0028] It should be noted that the hollow hydraulic cylinder 11 is prevented from being rotated by the thrust bearing 13, and the cylinder body of the hollow hydraulic cylinder 11 is fixed to the frame of the external drilling rig by the mounting base.

[0029] A radially extending cleaning brush 14 is also provided on the outer side of the first bushing 3 (e.g., Figure 2 and Figure 7 As shown), the cleaning brush 14 is located in the gap between the air cushions 5 on both sides, and will be blocked when the air cushions 5 are inflated. The cleaning brush 14 rotates with the first bushing 3 and is used to rotate and clean the dust and debris on the mine wall when it comes into contact with the surrounding mine wall before drilling, so as to prevent the air cushions 5 from being punctured by sharp rocks after inflation.

[0030] To allow the cleaning brush 14 and the first bushing 3 to rotate and clean in a controlled manner, an inner groove is formed on the front inner side of the first bushing 3, and a keyway 16 is provided on the outer side of the drill rod 1 (e.g., Figure 5 As shown in the diagram, after the freely rotating first bushing 3 is pushed towards the mine wall, workers need to assist in adjusting its position so that the key bar 16 is inserted into the inside of the first bushing 3 to establish a key shaft connection. At this time, the first bushing 3 and the cleaning brush 14 can rotate with the help of the drill rod 1 and clean the mine wall before the air cushion 5 is inflated. Therefore, the overall operation steps are as follows: The sealing plate 2 moves towards the mine wall in a controlled manner—the first bushing 3 and the drill rod 1 are connected and rotate accordingly—the cleaning brush 14 cleans the mine wall—the hollow hydraulic cylinder 11 pressurizes to make the sealing plate 2 fit tightly against the mine wall—the air cushion 5 is inflated to fill the gaps and ensure a seal.

[0031] A gas monitoring sensor 15 and an audible and visual alarm 18 are also installed on the side of the sealing plate 2 (e.g., Figure 4As shown), it adopts an embedded installation, embedded inside the side end of the sealing plate 2, and its orientation is controlled by following the rotation of the sealing plate 2. When the sealing plate 2 is pulled back and flipped over (as shown), Figure 7 (As shown in the diagram) precise measurements can be taken directly at the borehole. During the borehole sealing phase, the sensor is hidden inside and protected.

[0032] In this embodiment: Before drilling, the sealing plate 2 is in a retracted state via the rotatable connection between the connecting seat 4 and the support platform 17 (e.g., Figure 7 The drill rod 1 is fed into the borehole opening along with the drill rod 1. After reaching the predetermined position, the first bushing 3 moves axially towards the mine wall along the drill rod 1, so that the key bar 16 on the outer side of the drill rod 1 is inserted into the inner groove of the front section of the first bushing 3 to establish a key shaft connection. At this time, the cleaning brush 14 on the first bushing 3 and the sealing plate 2 can rotate with the rotational power of the drill rod 1 to rotate and clean the mine wall around the borehole, removing dust and debris attached to the surface of the mine wall, and providing a clean surface for subsequent sealing. After cleaning is completed, the hollow hydraulic cylinder 11 is started, and the pusher 12 pushes the second bushing 9 to move axially along the drill rod 1 through the thrust bearing 13. The second bushing 9 drives the bearing bracket 10, the swing arm 8, the linkage shaft 7, and the connecting rod 6 to transmit axial pressure to the sealing plate 2, causing the sealing plate 2 to open (e.g., Figure 2 (As shown) and tightly adheres to the cleaned mine wall surface; subsequently, an external air-filling device pumps gas to the air cushion 5 on the side of the sealing plate 2 through a pneumatic rotary joint and air-filling pipe 20. After the air cushion 5 is inflated, it evenly covers the gap between the sealing plates 2, ensuring that there is no gas escape channel on the overall sealing surface. During drilling and drainage operations, the gas monitoring sensor 15 embedded in the side of the sealing plate 2 is in a hidden state and protected by the sealing plate 2. After the drainage is completed, the air cushion 5 is depressurized, and the hollow hydraulic cylinder 11 is driven in reverse, pulling the connecting rod mechanism through the push cylinder 12, thrust bearing 13 and second bushing 9 to pull the sealing plate 2 backward and flip it to close (as shown). Figure 7 As shown in the diagram, at this time, the gas monitoring sensor 15 rotates with the sealing plate 2 and is positioned directly in front of the borehole opening for precise measurement. If the gas concentration is abnormal, the audible and visual alarm 18 will automatically sound an alarm. After the drill retraction releases the connection between the key strip 16 and the first bushing 3, the entire device is withdrawn from the borehole along with the drill rod 1. In the above actions, the first bushing 3 is isolated from the rotation of the drill rod 1 through its internal bearing ring, the hollow hydraulic cylinder 11 is isolated from the rotational movement of the second bushing 9 through the thrust bearing 13, and the air inlet pipe 20 of the air cushion 5 is switched between static and dynamic states through a pneumatic rotary joint, ensuring that each component works independently without interfering with each other.

[0033] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A gas drainage device with borehole opening protection, comprising a drill rod (1), characterized in that, Also includes: The first bushing (3) is sleeved on the outside of the drill rod (1). The first bushing (3) has a bearing ring inside, so that the first bushing (3) can move along the axial direction of the drill rod (1) and is rotatably isolated from the drill rod (1). The sealing plate (2) is a multi-group enclosed structure. It is rotatably set on the outside of the first bushing (3) through the connecting seat (4) and the support platform (17). The sealing plate (2) can rotate to open or close around the central axis of the support platform (17). When opened, several groups of the sealing plates (2) form a circular covering surface that spreads outward with the center of the borehole as the reference. An air cushion (5) is fixedly installed on the side of the sealing plate (2). After the air cushion (5) is inflated, it expands and covers the gap between the sealing plates (2). A cleaning brush (14) extends radially and is disposed on the outside of the first bushing (3); A key bar (16) is provided on the outside of the drill rod (1); the front section of the inner side of the first bushing (3) is provided with an inner groove. After the first bushing (3) moves towards the mine wall, the key bar (16) can be inserted into the inner groove to establish a key shaft connection, so that the first bushing (3) and the cleaning brush (14) rotate with the drill rod (1). The axial pressure mechanism includes a second bushing (9), a bearing bracket (10), a connecting rod (6), a linkage shaft (7), a swing arm (8), a hollow hydraulic cylinder (11), a push cylinder (12), and a thrust bearing (13). The second bushing (9) is sleeved on the outside of the drill rod (1) and can move axially along the drill rod (1). The bearing bracket (10) is installed on the outside of the second bushing (9). The connecting rod (6) is installed on the back end of the sealing plate (2). The linkage shaft (7) is inserted between the connecting rods (6) on both sides. The swing arm (8) is... One end is rotatably connected to the linkage shaft (7), and the other end is rotatably connected to the bearing bracket (10); the hollow hydraulic cylinder (11) is equipped with the push cylinder (12), and the push cylinder (12) is connected to the second bushing (9) through the thrust bearing (13). The hollow hydraulic cylinder (11) drives the second bushing (9) to move axially through the push cylinder (12) and the thrust bearing (13) so as to drive the connecting rod (6), the linkage shaft (7) and the swing arm (8) to apply pressure or pull back on the sealing plate (2); A gas monitoring sensor (15) and an audible and visual alarm (18) are embedded in the side of the sealing plate (2).

2. A gas drainage device with borehole opening protection according to claim 1, characterized in that: The sealing plate (2) adopts a multi-group enclosed structure. Several groups of the sealing plates (2) form a circular covering surface that spreads outward from the center of the drill hole. The air cushion (5) is fixedly set on the side end of the sealing plate (2) by fastening strip (19). The air cushion (5) is soft around the periphery. After being inflated, the extended and expanded part evenly covers the gap between the sealing plates (2).

3. A gas drainage device with borehole opening protection according to claim 1, characterized in that: It also includes an inflation tube (20) and a pneumatic rotary joint; the inflation tube (20) is set on the back end of the sealing plate (2) and inserted into the gap of the first bushing (3); one end of the inflation tube (20) is connected to the air inlet of the air cushion (5), and the other end is connected to the internal channel of the rotating end of the pneumatic rotary joint; the pneumatic rotary joint is fixedly installed on the rear end of the first bushing (3), its rotating end rotates together with the first bushing (3), and its stationary end is connected to the air supply pipeline of the external inflation equipment, so that the gas pumped by the external inflation equipment is delivered to each of the air cushions (5) through the pneumatic rotary joint, and the external air supply pipeline remains stationary and does not rotate with the drill rod (1).

4. A gas drainage device with borehole opening protection according to claim 1, characterized in that: The cleaning brush (14) is located in the gap between the air cushions (5) on both sides; when the air cushions (5) are inflated, the cleaning brush (14) is blocked by the air cushions (5); the cleaning brush (14) rotates with the first bushing (3) and is used to rotate and clean the dust and debris on the mine wall when it comes into contact with the surrounding mine wall of the borehole.

5. A gas drainage device with borehole opening protection according to claim 1, characterized in that: The connecting rod (6) is installed on the side of the back end of the sealing plate (2), the linkage shaft (7) is inserted between the two connecting rods (6), and the swing arm (8) is rotatably connected to the linkage shaft (7); the shaft seat (10) is detachably installed on the outside of the second bushing (9) by bolts, and the other end of the swing arm (8) is rotatably connected to the shaft seat (10).

6. A gas drainage device with borehole opening protection according to claim 1, characterized in that: The hollow hydraulic cylinder (11) is prevented from being rotated by the thrust bearing (13), and the cylinder body of the hollow hydraulic cylinder (11) is fixed to the frame of the external drilling rig by the mounting seat.

7. A gas drainage device with borehole opening protection according to claim 1, characterized in that: The first bushing (3) is provided with a bearing ring inside. The first bushing (3), the sealing plate (2) on the outside, and the air cushion (5) can move along the axial direction of the drill rod (1) to adjust the distance from the drill hole. When the drill rod (1) is connected to the drill bit for drilling, the first bushing (3) will not affect the rotation of the drill rod (1).

8. A gas drainage device with borehole opening protection according to claim 1, characterized in that: The gas monitoring sensor (15) and the audible and visual alarm (18) are embedded in the side of the sealing plate (2). When the sealing plate (2) is opened and sealed, the gas monitoring sensor (15) is hidden inside and protected. After the sealing plate (2) is pulled back and flipped, the gas monitoring sensor (15) measures the borehole opening. When the gas concentration is abnormal, the audible and visual alarm (18) sounds an alarm.

9. A gas drainage device with borehole opening protection according to claim 1, characterized in that: The sealing plate (2) has a retracted state and an open state; in the retracted state, the sealing plate (2) is in the retracted position through the rotatable connection of the connecting seat (4) and the support platform (17), and is sent into the borehole opening position together with the drill rod (1); in the open state, the sealing plate (2) is tightly attached to the cleaned mine wall surface.

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