Light-weight pressure-maintaining and gas-maintaining coring device for deep coal mine and using method

Abstract

The invention relates to a light-weight pressure-maintaining gas-maintaining coring device for a deep coal mine and a using method, the coring device comprises an outer pipe, a center rod, a core barrel, a pressure-maintaining controller, a clamp spring and a core falling prevention device, the lower end of the outer pipe is connected with a coring drill bit, the lower end of the center rod is connected with the core barrel, and the core falling prevention device and the clamp spring are installed at the lower end of the core barrel; the core falling prevention device is positioned below the clamp spring and above the coring drill bit; the core falling prevention device comprises a plurality of discs arranged in the circumferential direction and an elastic piece used for driving the multiple discs to be folded and closed towards the middle. The core falling prevention device is added, so that the equipment has a core falling prevention function, and when the rock core is broken by the snap spring, the core falling prevention device can effectively prevent a coal sample from falling out of the rock core barrel, and the heart taking rate is increased.

Description

Technical Field

[0001] This invention relates to the field of pressure-maintaining coring technology, and in particular to a lightweight pressure-maintaining and gas-preserving coring device for deep coal mines and its usage method. Background Technology

[0002] Accurate determination of gas content is crucial for coal mine gas disaster prevention and control and coalbed methane resource development. Direct sampling, due to its simplicity and ease of operation—obtaining samples directly from the coal seam—is widely used in gas measurement in major coal mines. The direct method is further divided into open sampling and closed sampling. Open sampling obtains samples directly at the borehole opening, but it cannot prevent gas loss during the transfer of samples from the bottom of the borehole to the closed desorption tank; this loss is called gas loss. Gas loss can usually be estimated using empirical formulas, but the accuracy of the estimation depends on the degree of matching between the formula parameters and the actual conditions at the coal mine, resulting in unavoidable estimation errors.

[0003] Chinese patent document CN113958279A discloses a simple magnetically triggered multi-directional pressure-holding coring device and a rock sample extraction method. This device allows for bottom-hole sampling, in-situ pressure-based storage and transfer of samples, reducing the escape of methane gas from the samples into open spaces. Furthermore, because storage occurs under pressure, it effectively prevents the conversion of large amounts of adsorbed methane into free methane due to drastic environmental pressure changes, thus contributing to the stability of the coal sample's methane storage state. However, when this pressure-holding coring device is used for coring soft coal seams, the low strength and fragility of the core lead to core breakage. When the core enters the core cylinder and the retaining spring breaks it, core fragments easily fall out of the core cylinder, resulting in a low coring rate. Summary of the Invention

[0004] To solve the above-mentioned technical problems, this invention provides a lightweight pressure-maintaining and gas-preserving coring device for deep coal mines and its usage method.

[0005] This invention is achieved through the following technical solution:

[0006] A lightweight pressure-maintaining and gas-preserving coring device for deep coal mines includes an outer tube, a central rod, a core cylinder, a pressure-maintaining controller, a retaining spring, and an anti-core-dropping device. The lower end of the outer tube is connected to the coring drill bit, and the lower end of the central rod is connected to the core cylinder. The anti-core-dropping device and the retaining spring are installed at the lower end of the core cylinder. The anti-core-dropping device is located below the retaining spring and above the coring drill bit. The anti-core-dropping device includes multiple discs arranged in a circumferential direction and a spring element for driving the multiple discs to retract and close towards the center.

[0007] Optionally, one end of the disc is rotatably connected to the core cylinder via a pin, and an elastic element is provided between the disc and the core cylinder. Under the action of the elastic element, multiple discs tend to close.

[0008] Alternatively, the anti-core-fall device may also include a mounting ring, which is fixed to the core cylinder. One end of the disc is rotatably connected to the mounting ring via a pin. An elastic element is provided between the disc and the mounting ring. Under the action of the elastic element, multiple discs tend to close.

[0009] Optionally, the elastic element is a torsion spring.

[0010] Optionally, the end of the core tube has a first conical surface, which can be used to house the anti-core-fall device.

[0011] Optionally, the lightweight pressure-maintaining and gas-preserving coring device for deep coal mines has a length of 1.9m and an outer diameter of 90mm.

[0012] Optionally, an air collection port is provided on the side wall of the outer pipe.

[0013] Optionally, a central rod guide tube is installed on the outer tube, with the central rod installed inside the central rod guide tube and fitted with it with clearance.

[0014] Optionally, the pressure holding controller is a magnetic pressure holding controller.

[0015] The method of using the lightweight pressure-maintaining and gas-preserving coring device for deep coal mines provided in this application includes the following steps:

[0016] The core drill bit is driven in to obtain the core. The core pushes open the previously closed discs and enters the core cylinder. After drilling is completed, the retaining spring breaks the core.

[0017] Lift the center rod to move the core cylinder. When the core located below the snap ring no longer presses against the disc, the disc closes again.

[0018] As the center rod moves to the predetermined position, the core tube moves to the valve cover above the pressure holding controller. The core tube releases its limit on the valve cover, and the valve cover closes under the action of magnetic force, forming a seal at the lower end of the pressure holding chamber.

[0019] Compared with the prior art, this application has at least the following beneficial effects:

[0020] 1. This application adds an anti-core-drop device to give the equipment an anti-core-drop function. When the snap ring breaks the core, the anti-core-drop device can effectively prevent the coal sample from falling out of the core tube and improve the core sampling rate.

[0021] 2. This application utilizes magnetic force to trigger the pressure-holding action, which differs from the sealing method that uses gravity. It can achieve sealing triggering at any angle. Magnetic force can ensure stable sealing in vertical, horizontal, and inclined wells, and can achieve multi-directional pressure-holding coring.

[0022] 3. Existing methods based on orifice sampling involve a certain period of coal sample exposure, resulting in some gas escaping into the open space. This escaping amount is estimated using empirical formulas, which are significantly affected by the similarity between the formulas and the characteristics of the coal sample in the field. The coal sample in this application is directly sealed and stored at the bottom of the orifice, avoiding contact with air and ensuring that no gas escapes during the transfer of the coal sample from the bottom of the orifice to the coal sample container. This eliminates the need for empirical formulas to estimate losses and results in high accuracy in gas content determination. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the lightweight pressure-maintaining and gas-preserving core sampler for deep coal mines in the embodiment.

[0025] Figure 2 for Figure 1 A magnified view of a section at point A in the middle;

[0026] Figure 3 for Figure 1 A magnified view of a section at point B in the middle;

[0027] Figure 4 for Figure 1 Sectional view at CC;

[0028] Figure 5 for Figure 4 A magnified view of a section at point D;

[0029] Figure 6 This is a partial schematic diagram of the retaining spring when the anti-drop device is activated in the embodiment;

[0030] Figure 7 Isometric view of snap ring 5 with notch;

[0031] Figure 8 This is a schematic diagram of the structure after core extraction according to the present invention;

[0032] Figure 9 for Figure 8 A magnified view of a section at point E in the middle;

[0033] Figure 10 This is a schematic diagram of the structure before core removal in this invention;

[0034] Figure 11 for Figure 10 A magnified view of a section at point F. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. It should also be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0037] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are used only for the convenience of describing this invention and 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, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0038] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] like Figures 1-3 As shown, the lightweight pressure-maintaining and gas-maintaining coring device for deep coal mines disclosed in this embodiment includes an outer tube 1, a central rod 2, a core cylinder 3, a pressure-maintaining controller 4, a retaining spring 5, and an anti-core-dropping device 6. The lower end of the outer tube 1 is connected to the coring drill bit 7, and the side wall of the outer tube 1 is provided with a gas collection port 11.

[0040] A central rod guide tube 8 is installed on the outer tube 1. The central rod 2 is installed inside the central rod guide tube 8 and is fitted with it with a clearance. The lower end of the central rod 2 is connected to the core tube 3, and the upper end of the central rod 2 is connected to the spearhead 21.

[0041] The pressure holding controller 4 includes a valve seat 41 and a valve cover 42, with one side of the valve cover 42 movably connected to the upper end of the valve seat 41 via a shaft 43. In an exemplary embodiment, the pressure holding controller 4 is a magnetic pressure holding controller, which can drive the valve cover 42 to close under the action of magnetic force to achieve the sealing of the internal pressure chamber. The magnetic force can ensure stable sealing in vertical, horizontal, and inclined shafts.

[0042] The anti-drop device 6 and the retaining ring 5 are installed at the lower end of the core cylinder 3. The anti-drop device 6 is located below the retaining ring 5 and above the core drill bit 7.

[0043] The anti-fall-off device 6 includes multiple discs 61 arranged along the circumference and a spring member 63 for driving the multiple discs 61 to close together in the middle.

[0044] In some embodiments, such as Figure 4 , 5 As shown, the anti-core-drop device 6 also includes a mounting ring 60, which is fixed to the core cylinder 3. One end of the disc 61 is rotatably connected to the mounting ring 60 via a pin 62. An elastic element 63 is provided between the disc 61 and the mounting ring 60. Under the action of the elastic element 63, multiple discs 61 tend to close. When the retaining spring 5 breaks the core, the anti-core-drop device 6 can effectively prevent the coal sample from falling out of the core cylinder 3 and improve the core sampling rate.

[0045] In other embodiments, one end of the disc 61 is rotatably connected to the core cylinder 3 via a pin 62. An elastic element 63 is provided between the disc 61 and the core cylinder 3. Under the action of the elastic element 63, multiple discs 61 tend to close. When the retaining spring 5 breaks the core, the anti-core-drop device 6 can effectively prevent the coal sample from falling out of the core cylinder 3 and improve the core sampling rate.

[0046] In some embodiments, the elastic element 63 is a torsion spring.

[0047] It should be understood that the number of discs 61 is reasonably set as needed. In an exemplary embodiment, the anti-drop device 6 has 6 discs 61.

[0048] During core drilling, the core pushes aside the disc 61 before entering the core cylinder 3, and the disc 61 then rests against the first conical surface 31 inside the end of the core cylinder 3. Since the torque provided by the elastic element 63 is small and the surface of the disc 61 is smooth, it does not generate significant resistance to the core.

[0049] like Figure 3 , Figure 4 As shown, initially, the discs 61 can close by mutual contact and gravity (they can only enter from the outside, not from the inside), the torsion springs are not deformed, and only a small gap remains between the closed discs 61.

[0050] In some embodiments, the gap between two adjacent discs 61 is 0.15 mm.

[0051] In some embodiments, after the disc 61 is closed, the diameter of the central gap 64 of the anti-core-fall device 6 is 0.5 mm to prevent the core from falling out.

[0052] In some embodiments, the angle between the first conical surface 31 and the horizontal plane is 86°, and the disc 61 can open upwards by 86°.

[0053] In some embodiments, both the disc 61 and the pin 62 are made of 316L stainless steel.

[0054] It should be understood that the elastic force provided by the elastic element 63 is greater than the torque provided by the gravity of a single disc 61. Therefore, all discs 61 can also ensure closure in vertical, horizontal, and inclined shafts.

[0055] In some embodiments, the torque provided by the elastic element 63 is 1.6 N*mm. The torque provided by the gravity of a single disc 61 is 0.33 N*mm.

[0056] In some embodiments, the elastic element 63 is a torsion spring made of 40Mn carbon steel.

[0057] In some embodiments, such as Figure 6 As shown, the core tube 3 has a second conical surface 32 at its end, which is located above the first conical surface 31. The retaining spring 5 can move up and down along the second conical surface 32 to open and close. The upper end of the second conical surface 32 has an upper step 33 to limit the displacement of the retaining spring 5.

[0058] Existing pressure-maintaining coring technology is bulky and unsuitable for operations in confined underground spaces. Furthermore, its complex internal structure requires a larger drill bit diameter, resulting in a large amount of pre-drilling work. In some embodiments, a lightweight pressure-maintaining and gas-maintaining coring device for deep coal mines has an overall length of approximately 1.9m, is lightweight, and is suitable for underground coring operations. Preferably, the device has an outer diameter of 90mm, and the coring drill bit 7 has a diameter of 95mm.

[0059] This type of pressure-maintaining and gas-maintaining coring tool, through its precise internal structural design, can obtain a 40mm diameter core sample with a coring tool outer diameter of 90mm. The entire system is 1.9m long, with a sample diameter of 40mm, an equipment outer diameter of 90mm, and a matching coring drill bit diameter of 95mm. Its lightweight design facilitates use in confined downhole spaces and effectively reduces worker workload and pre-drilling requirements. Firstly, it eliminates the conventional method of using an external drill string and an internal coring tool, directly installing the coring drill bit at the end of the pressure-maintaining coring tool. Therefore, the borehole diameter can be reduced from 122 / 144mm (common external drill string dimensions) to 90 / 95mm (coring tool outer tube size / coring drill bit size).

[0060] Generally, the high-strength external structure of a core extractor requires a certain wall thickness, and the complex internal water channel-sealing design also requires a certain wall thickness, leaving very little space for core storage. For example... Figure 8-11 As shown, this application designs a rotary dynamic seal with sealing and water passage functions, and a magnetic pressure holding controller with water passage function. The rotary dynamic seal includes multiple sealing grooves 22 arranged axially on the outer periphery of the middle part of the central rod 2. Sealing rings 23 are provided within the sealing grooves 22. Before core sampling, there is a gap between the sealing rings 23 and the lower inner wall of the outer tube 1. After core sampling, the central rod 2 moves upward, and the sealing rings 23 and the upper inner wall of the outer tube 1 form a sealing pair through sealing contact. Because the rotational freedom of this structure is not restricted, it is called a rotary dynamic seal. Therefore, it is possible to obtain a 40mm diameter pressure-holding core with a 90mm outer tube diameter for the core sampler.

[0061] Based on the rotary dynamic seal design, this application features a meticulously designed internal water passage: In the past, the external drill string + internal corer solution allowed drilling fluid to reach the core bit through the annular gap between the external drill string and the corer, achieving cooling and cuttings removal functions. In this application, the water passage is designed inside the corer, which needs to simultaneously meet the water flow requirements during core extraction (drilling fluid flow) and the sealing requirements during pressure storage. This places high demands on the internal structural design. Specifically, before core extraction, a gap exists between the central rod 2 and the outer tube 1. Drilling fluid and other liquids flow from this gap from the retrieval tip 21 towards the core bit 7 and out of the system's design.

[0062] In some embodiments, it exhibits high wear resistance, corrosion resistance, and pressure resistance: it is made of 42CrMo material, and the outer tube 1 adopts a multi-segment structure with high-strength threaded connections. All outer tubes of the core extractor are made of high-strength materials (such as 42CrMo) and have undergone surface treatment to improve wear resistance and corrosion resistance.

[0063] In some embodiments, the outer tube 1 has the thinnest wall at the mounting position 10 of the pressure holding controller 4. Optionally, the wall thickness of the outer tube 1 at the mounting position 10 is 6 mm. This ensures the pressure-bearing performance, load-bearing capacity, and impact resistance of the equipment, achieving a pressure holding capacity of 30 MPa. The sealing structure is designed according to high-pressure vessel design standards. After processing, a pressure holding capacity test is conducted using a pressure testing platform. The test procedure is as follows: the pressure holding gas core extractor is adjusted to the pressure holding state, the core extractor is connected to the pressure pump (ultimate pressure 100 MPa), and pressure (water pressure) is applied to the inside of the core extractor, increasing by 5 MPa every 20 minutes, to test the ultimate pressure resistance of the equipment. After testing, it is verified that the equipment can stably hold pressure at 30 MPa.

[0064] Instructions for using lightweight pressure-maintaining and gas-preserving coring devices in deep coal mines:

[0065] S1, the core drill bit 7 drills in to obtain the core. The core pushes open the originally closed six discs 61 and enters the core cylinder 3. After drilling is completed, the retaining spring 5 slides down along the second conical surface 32 at the end of the core cylinder 3 and locks the core. Figure 7 As shown, the retaining ring 5 has an opening. During the process of the core entering the core cylinder 3, the core pushes the retaining ring 5 upwards along the second conical surface 32. At this time, the opening width of the retaining ring 5 increases, and the diameter of the retaining ring 5 increases. When the upper end of the retaining ring 5 reaches the upper step 33 at the upper end of the second conical surface 32, it will be restricted by the upper step 33, at which point the retaining ring 5 reaches its highest point. After drilling is completed, the retaining ring 5 moves downwards along the second conical surface 32. At this time, the opening width of the retaining ring 5 decreases, and the diameter of the retaining ring 5 decreases. Finally, the retaining ring 5 will break the core, at which point the lower end of the retaining ring 5 reaches the lower end of the second conical surface 32, and the retaining ring 5 reaches its lowest point.

[0066] S2, by lifting the central rod 2, the core cylinder 3 is moved, and the sample inside the core cylinder 3 also moves upwards; as the core extraction tool is raised, when the core located below the retaining spring 5 no longer presses against the discs 61, the six discs 61 close again under the action of gravity and / or the elastic element 63. Even if a loose core falls out of the retaining spring 5 during the drilling process, the closed discs 61 can effectively prevent it from falling.

[0067] S3, as the central rod 2 moves to the predetermined position, the core cylinder 3 moves above the opened valve cover 42, releasing the restriction of the core cylinder 3 on the valve cover 42. Under the action of magnetic force, the valve seat 41 of the valve cover 42 closes, forming a lower seal of the pressure chamber. The core cylinder 3 and the inner wall of the outer tube 1 achieve the required sealing gap, forming an upper seal of the pressure chamber. The side wall seal of the pressure chamber section is achieved by the sealing structure of the corer's outer tube. Therefore, the sample can be stored and transferred in a sealed state. This is a conventional technique in the field and will not be elaborated further here.

[0068] S4. The core sampler is moved to the ground and connected to the gas collection port 11 of the outer pipe 1 via the gas collection device, allowing for the measurement of methane gas content. No methane leakage occurs during the transfer of the coal sample from the bottom of the borehole to the testing device.

[0069] The gas content measurement results in this embodiment are accurate. This embodiment is based on pressure-holding coring technology, and there is no gas leakage in the entire coal sample transfer and testing process. The gas content can be directly measured without relying on empirical formulas, and there is no estimation error.

[0070]

[0071] The technical solution of this invention is based on pressure-maintaining coring technology. While ensuring the core diameter as much as possible, it minimizes the outer diameter of the equipment and the overall mass, thus making it suitable for coring operations in confined spaces downhole, reducing the amount of drilling work, and increasing the coring rate and efficiency.

[0072] Existing pressure-holding coring methods can effectively determine gas content, but due to their complex internal structure, they require a large volume, which is not conducive to operation in the confined spaces of underground coal mines. Furthermore, the larger diameter increases the drilling workload and the labor intensity for workers. A comparison of the parameters of existing pressure-holding coring devices and the pressure-holding coring device of this invention is shown in Table 1:

[0073] A parameter can be proposed: "Equipment integration degree = diameter of pressure-holding core / diameter of core drilling hole". Combining this with the parameters in Table 1, the equipment integration degree of multiple devices in Table 1 can be obtained. It can be seen that the equipment integration degree parameter proposed in this invention is the highest, reflecting the refined structural design within the equipment, enabling the acquisition of larger pressure-holding cores with a smaller drilling hole diameter (core drill bit diameter).

[0074] Table 1: Parameter Table

[0075]

[0076] Advantages of Confined Downhole Working Spaces: Downhole transportation work is mostly done manually, and in some narrow working tunnels / areas (working radius less than 2m), if the equipment is too long or too heavy, it becomes very inconvenient during transportation / installation. Therefore, this application reduces the core sampler diameter to 95mm, which is lighter and more suitable for downhole use compared to a 122mm core sampler. Furthermore, reducing the borehole diameter from 122mm to 95mm allows for estimation of the drilling workload based on the borehole cross-sectional area, saving approximately 40% of the earthwork.

[0077] Earthwork saved = 1 - cross-sectional area of ​​large borehole / cross-sectional area of ​​small borehole = 1 - 3.14 x (95 / 2) 2 / [3.14x(122 / 2) 2 =0.40

[0078] This application, through meticulous internal structural design, reduces structural redundancy, maximizes the core diameter, and minimizes the equipment's outer diameter. Furthermore, the lightweighting process enhances equipment strength, including torsional resistance during drilling and internal pressure-bearing capacity during pressure-holding and storage.

[0079] This equipment is mainly used to obtain and accurately measure the gas content of pressurized coal samples, providing accurate and reliable parameters for gas disaster prevention and resource development.

[0080] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lightweight, pressure-maintaining, and gas-preserving coring device for deep coal mines, characterized in that: It includes an outer tube (1), a central rod (2), a core cylinder (3), a pressure holding controller (4), a retaining ring (5), and an anti-core-dropping device (6); The lower end of the outer tube (1) is connected to the core drill bit (7), the lower end of the center rod (2) is connected to the core cylinder (3), the anti-drop device (6) and the snap ring (5) are installed at the lower end of the core cylinder (3), the anti-drop device (6) is located below the snap ring (5) and above the core drill bit (7); The anti-fall-out device (6) includes multiple discs (61) arranged in a circumferential direction and an elastic element (63) for driving the multiple discs (61) to close together in the middle; the outer tube (1) has an air collection port (11) on its side wall.

2. The lightweight pressure-maintaining and gas-preserving coring device for deep coal mines according to claim 1, characterized in that, One end of the disc (61) is rotatably connected to the core cylinder (3) via a pin (62). An elastic element (63) is provided between the disc (61) and the core cylinder (3). Under the action of the elastic element (63), multiple discs (61) tend to close.

3. The lightweight pressure-maintaining and gas-preserving coring device for deep coal mines according to claim 1, characterized in that, The anti-core-drop device (6) also includes a mounting ring (60), which is fixed to the core cylinder (3). One end of the disc (61) is rotatably connected to the mounting ring (60) via a pin (62). An elastic element (63) is provided between the disc (61) and the mounting ring (60). Under the action of the elastic element (63), multiple discs (61) tend to close.

4. The lightweight pressure-maintaining and gas-preserving coring device for deep coal mines according to claim 1, characterized in that, The elastic element (63) is a torsion spring.

5. The lightweight pressure-maintaining and gas-preserving coring device for deep coal mines according to claim 1, characterized in that, The core tube (3) has a first conical surface (31) at its end.

6. The lightweight pressure-maintaining and gas-preserving coring device for deep coal mines according to claim 1, characterized in that, The center rod (2) has one or more sealing grooves (22) along the axial direction on the outer periphery of the middle part. A sealing ring (23) is provided in the sealing groove (22). There is a gap between the sealing ring (23) and the lower inner wall of the outer tube (1). The sealing ring (23) and the upper inner wall of the outer tube (1) are connected in a sealing contact to form a sealing pair.

7. The lightweight pressure-maintaining and gas-preserving coring device for deep coal mines according to claim 1, characterized in that, A central rod guide tube (8) is installed on the outer tube (1), and the central rod (2) is installed inside the central rod guide tube (8) and is fitted with it with clearance.

8. The lightweight pressure-maintaining and gas-preserving coring device for deep coal mines according to claim 1, characterized in that, The pressure holding controller (4) is a magnetic pressure holding controller.

9. The lightweight pressure-maintaining and gas-preserving coring device for deep coal mines according to claim 1 or 5, characterized in that, The core tube (3) has a second conical surface (32) at its end. The retaining spring (5) can move up and down along the second conical surface (32) to open and close.

10. The method of using the lightweight pressure-maintaining and gas-preserving coring device for deep coal mines as described in any one of claims 1-9, characterized in that, Includes the following steps: The core drill bit (7) drills in to obtain the core. The core pushes open the originally closed discs (61) and enters the core tube (3). After drilling is completed, the retaining spring (5) snaps the core. Lift the center rod (2) to move the core cylinder (3). When the core located below the snap ring (5) no longer presses against the disc (61), the disc (61) closes again. As the center rod (2) moves to the predetermined position, the core tube (3) moves to the valve cover (42) above the pressure holding controller (4). The limit of the core tube (3) on the valve cover (42) is released, and the valve seat (41) of the valve cover (42) closes under the action of magnetic force, forming a lower end seal of the pressure holding chamber.

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