Layered reaming drilling tool for low-permeability coal seam

Abstract

The invention is suitable for the technical field of drilling tools, and provides a low-permeability coal seam layered reaming drilling tool. The mounting pipe is rotationally mounted on the supporting pipe, and a mounting seat is fixedly mounted at the bottom of the mounting pipe; the first drill bit and the second drill bits are arranged on the mounting seat, and the first drill bit and the second drill bits are used for drilling a low-permeability coal seam; the expanding and adjusting mechanism is assembled on the mounting seat and the plurality of second drill bits and is used for expanding and adjusting the transverse use of the second drill bits; the expanding adjustment mechanism comprises a plurality of installation rods installed on the installation base in a sliding mode, and the multiple installation rods are connected with the multiple second drill bits correspondingly. According to the layered reaming drilling tool for the low-permeability coal seam, drilling operation can be conducted on the low-permeability coal seam, the drilling requirements of different layer depths and different diameters of the low-permeability coal seam can be met, layered reaming operation is achieved, and the actual drilling requirements of the low-permeability coal seam are better met.

Description

Technical Field

[0001] This invention relates to the field of drilling tools, and in particular to a layered enlargement drilling tool for low-permeability coal seams. Background Technology

[0002] Low-permeability coal seams refer to coal seams with low permeability and poor gas (mainly methane) flow within them. Currently, the industry generally considers coal seams with a permeability below 0.1 millidarcy (mD) to be low-permeability coal seams. Some coal seams even have permeability below 0.01 mD, classifying them as "ultra-low permeability" or "super-low permeability" coal seams. In my country's high-gas and coal and gas outburst mines, low-permeability coal seams constitute the vast majority, accounting for approximately 70%-90% or more.

[0003] To ensure the efficiency and safety of gas extraction from low-permeability coal seams, drilling is required. This drilling rig uses appropriate drilling tools, which rotate the drill bit within the low-permeability coal seam. However, because low-permeability coal seams are like dense sponges, gas flow is extremely difficult, resulting in very low extraction efficiency. Therefore, it is necessary to artificially modify the low-permeability coal seam through engineering methods, establishing a channel system that can efficiently extract gas from deep within the coal seam and increase its permeability. Conventional drilling tools cannot adjust the borehole diameter, requiring multiple trips up and down the drill string and replacement of different sized tools, a cumbersome process that severely impacts drilling efficiency. Summary of the Invention

[0004] To address the technical problem mentioned in the background art that conventional drilling tools cannot adjust the diameter of the borehole, requiring multiple trips up and down the drill string and replacement of different sized drilling tools, which is cumbersome and seriously affects drilling efficiency, this invention provides a layered borehole enlargement drilling tool for low-permeability coal seams.

[0005] The low-permeability coal seam layered borehole enlargement drill bit provided by the present invention includes: a support pipe; an installation pipe rotatably mounted on the support pipe, wherein an installation seat is fixedly mounted at the bottom of the installation pipe; a first drill bit and a plurality of second drill bits disposed on the installation seat, wherein the first drill bit and the plurality of second drill bits are used for drilling operations in low-permeability coal seams; and an expansion adjustment mechanism assembled on the installation seat and the plurality of second drill bits, wherein the expansion adjustment mechanism is used for expanding and adjusting the lateral use of the second drill bits.

[0006] Preferably, the expansion mechanism includes: a plurality of mounting rods slidably mounted on the mounting base, the plurality of mounting rods being respectively connected to a plurality of second drill bits, and a connecting rod fixedly mounted on each of the plurality of mounting rods; a servo motor fixedly mounted in the mounting base; a mounting frame fixedly mounted in the mounting base, on which a lead screw is rotatably mounted, the output shaft of the servo motor being connected to the top end of the lead screw via a coupling; and a pressing rod threaded onto the lead screw, the pressing rod being used to press the plurality of connecting rods, and the end of the connecting rod near the pressing rod being inclined, and a reset mechanism being provided on the connecting rod and the mounting base, wherein when the pressing rod does not press the connecting rod, the connecting rod is reset by the reset mechanism.

[0007] Preferably, the reset mechanism includes: a crossbar fixedly installed in the mounting base, with a spring sleeved on the crossbar; and a compression plate fixedly installed on the connecting rod, the compression plate being slidably connected to the crossbar, the compression plate being used to compress the spring.

[0008] Preferably, a connecting block is fixedly installed on the second drill bit, and a connecting groove is provided on the mounting rod. Both the connecting block and the connecting groove are rectangular and are adapted to be connected. Connecting screws are assembled on the mounting rod and the connecting block, and the connecting block is fixedly connected to the mounting rod through the connecting screws.

[0009] Preferably, a limiting rod is fixedly installed on the extrusion rod, and the limiting rod is slidably connected to the mounting bracket. The limiting rod is used to limit the movement of the extrusion rod.

[0010] Preferably, a positioning sleeve is fixedly installed at the bottom of the mounting base, and a positioning block is fixedly installed at the top of the first drill bit. The positioning block and the positioning sleeve are adapted to each other, and positioning screws are provided on the positioning sleeve and the positioning block.

[0011] Preferably, a plurality of support blocks are fixedly installed inside the support tube, the mounting tube and the support blocks are rotatably connected, and the support blocks are used to support the mounting tube.

[0012] Preferably, the support pipe is provided with a vertical pipe, and multiple diversion pipes are connected to the vertical pipe. Each of the multiple diversion pipes is provided with a nozzle, and the nozzle is located above the mounting base.

[0013] Preferably, the support tube has multiple clearance openings, which are used to avoid multiple nozzles.

[0014] Compared with related technologies, the low-permeability coal seam layered borehole enlargement drill bit provided by the present invention has the following beneficial effects: This invention provides a layered borehole enlargement drill for low-permeability coal seams: A drilling rig drives an installation pipe to rotate on a support pipe. Simultaneously, the installation pipe drives a first drill bit and multiple second drill bits on a mounting base to rotate. The operator controls the drilling rig to bring the rotating first and second drill bits into contact with the low-permeability coal seam, drilling holes in the seam. At the same time, the drilling rig drives the support pipe and installation pipe deeper into the low-permeability coal seam, thus performing drilling operations. During drilling, when the drilling rig has penetrated the support and installation pipe to a certain depth within the low-permeability coal seam, the operator activates an expansion adjustment mechanism via a remote control. This mechanism expands and adjusts the lateral position of the multiple second drill bits. The rotating installation pipe then drives the laterally adjusted second drill bits to continue drilling into the low-permeability coal seam. This allows for drilling operations of different diameters at different depths within the low-permeability coal seam, meeting the drilling requirements for different depths and diameters in low-permeability coal seams, achieving layered borehole enlargement operations, and better satisfying the actual drilling needs of low-permeability coal seams. Attached Figure Description

[0015] Figure 1 This is a front view schematic diagram of a preferred embodiment of the low-permeability coal seam layered borehole enlargement drill bit provided by the present invention. Figure 2 This is a schematic diagram of the front sectional view of the present invention; Figure 3 for Figure 2 An enlarged structural diagram of part A shown in the figure; Figure 4 for Figure 3 An enlarged structural diagram of part B shown in the figure; Figure 5 for Figure 3 An enlarged structural diagram of section C shown in the figure; Figure 6 for Figure 3 An enlarged structural diagram of part D shown in the figure; Figure 7 for Figure 2 An enlarged structural diagram of part E shown in the figure; Figure 8 for Figure 2 An enlarged structural diagram of part F shown in the figure; Figure 9 This is a schematic diagram illustrating the usage of the present invention when drilling holes of different diameters in low-permeability coal seams.

[0016] The following are the labels in the diagram: 1. Support pipe; 2. Mounting pipe; 3. Mounting base; 4. First drill bit; 5. Second drill bit; 6. Connecting rod; 7. Servo motor; 8. Mounting bracket; 9. Lead screw; 10. Extrusion rod; 11. Mounting rod; 12. Compression plate; 13. Spring; 14. Crossbar; 15. Connecting block; 16. Connecting groove; 17. Connecting screw; 18. Limiting rod; 19. Positioning sleeve; 20. Positioning block; 21. Positioning screw; 22. Support block; 23. Vertical pipe; 24. Diverter pipe; 25. Nozzle; 26. Clearance opening. Detailed Implementation

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the specification and the foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification or the foregoing drawings of this application are used to distinguish different objects, not to describe a particular order; the terms "inner," "outer," "left," and "right" indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the 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 the invention.

[0018] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0019] This invention provides a layered borehole enlargement drill for low-permeability coal seams, such as... Figure 1-9 As shown, the low-permeability coal seam layered borehole enlargement drill includes: a support pipe 1; an installation pipe 2 rotatably mounted on the support pipe 1, with an installation base 3 fixedly mounted at the bottom of the installation pipe 2; a first drill bit 4 and a plurality of second drill bits 5 disposed on the installation base 3, the first drill bit 4 and the plurality of second drill bits 5 being used for drilling operations in the low-permeability coal seam; and an expansion adjustment mechanism assembled on the installation base 3 and the plurality of second drill bits 5, the expansion adjustment mechanism being used for expanding and adjusting the lateral use of the second drill bits 5.

[0020] In this embodiment, coalbed methane (mainly composed of methane) exists primarily in two states: Adsorbed state: The vast majority (about 80%-95%) of gas molecules are tightly adsorbed on the microporous surface inside the coal body, just like a magnet attracts iron filings; Free state: A small amount of gas exists in the cracks and larger pores of the coal body and can flow freely.

[0021] The core characteristics of low-permeability coal seams are extremely low permeability, complex pore structure, poor connectivity, strong adsorption capacity, and usually high gas content but poor mineability. This makes the coal seam a nearly closed high-pressure gas tank: gas cannot flow out - although the gas pressure is very high, there is a lack of "highways" or even "country roads" for gas flow, the flow resistance is huge, and the natural desorption and seepage rate is extremely slow; the pressure cannot be effectively released - the adsorption state of gas is controlled by pressure, and if the pressure does not drop, it is difficult for gas to be desorbed from the adsorbed state into a large amount of free state.

[0022] Drilling directly into the coal seam creates a huge, continuous "cavity" within the dense coal mass. This cavity instantly reduces the gas pressure at the borehole wall to atmospheric pressure, forming a massive "pressure funnel" within the coal seam. The pressure balance is broken, and free gas in the fissures closest to the borehole wall flows rapidly towards the borehole and is extracted. Therefore, the purpose of drilling is to improve the efficiency of gas extraction.

[0023] Moreover, boreholes are not only production channels for gas extraction, but also "life-saving projects" to ensure safety. Boreholes directly reduce gas content and pressure, eliminating the driving force of outbursts. The essence of coal and gas outbursts is the imbalance between ground stress, gas pressure, and coal strength. Among them, gas pressure is the key "ammunition" and "driving force". Therefore, eliminating the driving force of outbursts in coal seams through boreholes can effectively improve the safety of gas extraction and ensure safe and efficient production in coal mines.

[0024] Therefore, to ensure the efficiency and safety of gas extraction from low-permeability coal seams, drilling operations are required. When drilling, the entire drilling tool and corresponding drilling rig are first connected. The drilling rig drives the installation pipe 2 to rotate on the support pipe 1. At this time, the installation pipe 2 drives the first drill bit 4 and multiple second drill bits 5 on the mounting base 3 to rotate. Then, the operator controls the drilling rig to make the rotating first drill bit 4 and multiple second drill bits 5 contact the low-permeability coal seam, drilling through it. Simultaneously, the drilling rig drives the support pipe 1 and installation pipe 2 deeper into the low-permeability coal seam, thus performing the drilling operation. During drilling, when the drilling rig has penetrated the support pipe 1 and installation pipe 2 to a certain depth into the low-permeability coal seam, the operator uses a SIMATIC [type of drilling rig] to... The IPC647D's remote control activates the expansion mechanism, which adjusts the lateral positions of multiple second drill bits 5. Simultaneously, the rotating mounting tube 2 drives the second drill bits 5, now in their adjusted positions, to continue drilling into the low-permeability coal seam. This allows for drilling of different diameters at different depths within the low-permeability coal seam, meeting the drilling requirements for varying depths and diameters, and enabling layered expansion drilling. This better satisfies the actual drilling needs of low-permeability coal seams. Figure 9 The diagram shows the usage of the first drill bit 4 and the second drill bit 5 in drilling holes of different diameters in low-permeability coal seams. Figure 9 In this context, a, b, and c represent different diameters. By drilling into low-permeability coal seams, a huge, continuous "cavity" can be artificially created in the dense coal body, eliminating the driving force for outbursts in the coal seam, effectively improving the efficiency and safety of gas extraction, and ensuring safe and efficient production in coal mines.

[0025] In a further preferred embodiment of the present invention, the expansion adjustment mechanism includes: a plurality of mounting rods 11 slidably mounted on the mounting base 3, the plurality of mounting rods 11 being respectively connected to a plurality of second drill bits 5, and a connecting rod 6 being fixedly mounted on each of the plurality of mounting rods 11; a servo motor 7 fixedly mounted in the mounting base 3; a mounting frame 8 fixedly mounted in the mounting base 3, a lead screw 9 being rotatably mounted on the mounting frame 8, the output shaft of the servo motor 7 being connected to the top end of the lead screw 9 via a coupling; and a pressing rod 10 threaded onto the lead screw 9, the pressing rod 10 being used to press the plurality of connecting rods 6, and the end of the connecting rod 6 near the pressing rod 10 being inclined, and a reset mechanism being provided on the connecting rod 6 and the mounting base 3, wherein when the pressing rod 10 does not press the connecting rod 6, the connecting rod 6 is reset by the reset mechanism.

[0026] In this embodiment, when it is necessary to adjust the lateral position of the second drill bit 5 to achieve hole enlargement, the servo motor 7 is started by remote control. The output shaft of the servo motor 7 drives the lead screw 9 to rotate. Since the extrusion rod 10 is threaded on the lead screw 9, and under the limiting action of the limiting rod 18, the extrusion rod 10 will move along the lead screw 9 during the rotation of the lead screw 9. When the extrusion rod 10 moves down, it will evenly extrude multiple connecting rods 6. Because the end of the connecting rod 6 near the extrusion rod 10 is inclined, under the extrusion action of the extrusion rod 10, the connecting rod 6 will drive the mounting rod 11 to slide, thereby driving the second drill bit 5 to move laterally and achieve hole enlargement adjustment. When the extrusion rod 10 does not extrude the connecting rod 6, the connecting rod 6 can be reset under the action of the reset mechanism, thereby driving the second drill bit 5 to reset, which facilitates the next hole enlargement operation with different requirements. Overall, it realizes the hole enlargement requirements of different depths and diameters in low-permeability coal seams, improves the efficiency and adaptability of drilling operations, and effectively solves the drilling problem caused by special geological conditions in low-permeability coal seams.

[0027] In a further preferred embodiment of the present invention, the reset mechanism includes: a crossbar 14 fixedly installed in the mounting base 3, and a spring 13 sleeved on the crossbar 14; and a compression plate 12 fixedly installed on the connecting rod 6, the compression plate 12 and the crossbar 14 being slidably connected, the compression plate 12 being used to compress the spring 13.

[0028] In this embodiment, during the operation of the expansion mechanism, when the extrusion rod 10 extrudes the connecting rod 6, causing the second drill bit 5 to move laterally to expand the hole, the connecting rod 6 drives the compression plate 12 to move along the crossbar 14. During the movement, the compression plate 12 compresses the spring 13, causing the spring 13 to store elastic potential energy. When the extrusion rod 10 no longer applies extrusion force to the connecting rod 6, the spring 13 releases the stored elastic potential energy to return to its original state, generating a reverse thrust on the compression plate 12, pushing the compression plate 12 to move in the opposite direction along the crossbar 14, thereby driving the connecting rod 6 to reset, and finally resetting the second drill bit 5, facilitating the next expansion operation with different requirements.

[0029] In a further preferred embodiment of the present invention, a connecting block 15 is fixedly installed on the second drill bit 5, and a connecting groove 16 is provided on the mounting rod 11. Both the connecting block 15 and the connecting groove 16 are rectangular and are adapted to be connected. A connecting screw 17 is assembled on the mounting rod 11 and the connecting block 15, and the connecting block 15 is fixedly connected to the mounting rod 11 by the connecting screw 17.

[0030] In this embodiment, the connection between the connecting block 15 and the connecting groove 16 and the fixing of the connecting screw 17 achieves a stable, reliable and easy-to-disassemble connection between the second drill bit 5 and the mounting rod 11. This effectively prevents the second drill bit 5 from shaking or shifting relative to the mounting rod 11 during operation, ensuring the accuracy of drilling and reaming. This provides a solid foundation for drilling and reaming operations of low-permeability coal seam layered reaming drill bit at different depths and diameters, while also facilitating the disassembly and replacement of the second drill bit 5.

[0031] In a further preferred embodiment of the present invention, a limiting rod 18 is fixedly installed on the extrusion rod 10, the limiting rod 18 is slidably connected to the mounting bracket 8, and the limiting rod 18 is used to limit the movement of the extrusion rod 10.

[0032] In this embodiment, when the servo motor 7 drives the lead screw 9 to rotate, thereby causing the extrusion rod 10 to move along the lead screw 9, the limiting rod 18 will slide on the mounting frame 8 together with the extrusion rod 10. Due to the sliding connection between the limiting rod 18 and the mounting frame 8, it can restrict the extrusion rod 10 to move linearly only along the axial direction of the lead screw 9, effectively preventing the extrusion rod 10 from deviating, shaking, or rotating during the movement, ensuring that the extrusion rod 10 can accurately extrude the connecting rod 6, making the lateral expansion adjustment of the second drill bit 5 more accurate, thereby meeting the precise requirements of different depths of low-permeability coal seams for different borehole diameters and improving the drilling quality.

[0033] In a further preferred embodiment of the present invention, a positioning sleeve 19 is fixedly installed at the bottom of the mounting base 3, and a positioning block 20 is fixedly installed at the top of the first drill bit 4. The positioning block 20 and the positioning sleeve 19 are adapted to be connected, and positioning screws 21 are provided on the positioning sleeve 19 and the positioning block 20.

[0034] In this embodiment, after the positioning block 20 is embedded in the positioning sleeve 19 and completes the initial positioning, the positioning block 20 and the positioning sleeve 19 can be firmly fixed together by tightening the positioning screw 21, which further enhances the stability of the first drill bit 4 installation. Even when the drill bit rotates at high speed and is subjected to great resistance, the first drill bit 4 will not easily loosen or fall off, ensuring the continuity and stability of the drilling operation, and at the same time facilitating the disassembly and replacement of the first drill bit 4.

[0035] In a further preferred embodiment of the present invention, a plurality of support blocks 22 are fixedly installed inside the support tube 1, the mounting tube 2 and the support blocks 22 are rotatably connected, and the support blocks 22 are used to support the mounting tube 2.

[0036] In this embodiment, during the drilling process, the drilling rig drives the installation pipe 2, and the support block 22 provides stable support for the installation pipe 2, thereby improving the stability of the installation pipe 2 when it rotates.

[0037] In a further preferred embodiment of the present invention, a vertical pipe 23 is provided on the support pipe 1, and a plurality of diversion pipes 24 are connected to the vertical pipe 23. Each of the plurality of diversion pipes 24 is provided with a nozzle 25, and the nozzle 25 is located above the mounting base 3.

[0038] In this embodiment, during actual drilling operations, flushing water can be supplied to the vertical pipe 23 through an external liquid supply system. The flushing water flows into each branch pipe 24 through the vertical pipe 23 and is finally sprayed out from the nozzle 25, directly acting on the drilling area below the mounting base 3. The liquid sprayed from the nozzle 25 can promptly flush away coal dust, rock dust, and other debris generated during the drilling process from the drilling area, preventing these debris from accumulating in the borehole and avoiding serious problems such as blockage caused by debris affecting the drilling progress or even causing the drill to get stuck. This ensures the continuity and efficiency of the drilling operation. At the same time, the flushing water can effectively reduce the temperature of the drilling area and the first drill bit 4 and the second drill bit 5, extending the service life of the first drill bit 4 and the second drill bit 5 and reducing the operating cost.

[0039] In a further preferred embodiment of the present invention, the support tube 1 is provided with a plurality of clearance openings 26, which are respectively used to avoid the plurality of nozzles 25.

[0040] In this embodiment, the clearance opening 26 provides sufficient installation and movement space for the nozzle 25, enabling the nozzle 25 to be smoothly installed in the predetermined position and to freely and stably spray coolant or flushing fluid when the drill is working, precisely acting on the drilling area below the mounting base 3.

[0041] In summary, compared with related technologies, this drilling tool can be used to drill holes in low-permeability coal seams, and can meet the drilling requirements of different depths and diameters in low-permeability coal seams, realizing layered hole enlargement operations and better meeting the actual drilling needs of low-permeability coal seams.

[0042] It should be understood, in the several embodiments provided in this application, that the disclosed apparatus may be implemented in other ways.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. A low-permeability coal bed zonal reaming drill tool, characterized by, The utility model relates to a low permeability coal seam drilling device, including: Support pipe; Mounting pipe is rotatably installed on the support pipe, and the bottom of the mounting pipe is fixedly installed with a mounting seat; A first drill bit and a plurality of second drill bits are arranged on the mounting seat, and the first drill bit and the plurality of second drill bits are used for drilling operation on low permeability coal seam; A diameter expansion mechanism is assembled on the mounting seat and the plurality of second drill bits, and the diameter expansion mechanism is used for expanding adjustment of the transverse use of the second drill bit.

2. The underpressured coal seam separate zonal reaming drill tool of claim 1, wherein, The diameter expansion mechanism includes: A plurality of mounting rods are slidably installed on the mounting seat, the plurality of mounting rods are respectively connected with the plurality of second drill bits, and a connecting rod is fixedly installed on each of the plurality of mounting rods; A servo motor is fixedly installed in the mounting seat; A mounting bracket is fixedly installed in the mounting seat, a lead screw is rotatably installed on the mounting bracket, and the output shaft of the servo motor is connected with the top end of the lead screw through a shaft coupling; A pressing rod is threadedly installed on the lead screw, the pressing rod is used for pressing the plurality of connecting rods, one end of the connecting rod close to the pressing rod is obliquely arranged, and a reset mechanism is arranged on the connecting rod and the mounting seat, so that the connecting rod is reset through the reset mechanism when the pressing rod does not press the connecting rod.

3. The underpressured coal seam separate zonal reaming drill tool of claim 2, wherein, The reset mechanism includes: A cross rod is fixedly installed in the mounting seat, and a spring is sleeved on the cross rod; A compression plate is fixedly installed on the connecting rod, the compression plate is slidably connected with the cross rod, and the compression plate is used for compressing the spring.

4. The underpressured coal seam separate zonal reaming drill tool of claim 2, wherein, A connecting block is fixedly installed on the second drill bit, a connecting groove is formed in the mounting rod, the connecting block and the connecting groove are both rectangularly arranged, and the connecting block and the connecting groove are adaptively connected, a connecting screw is assembled on the mounting rod and the connecting block, and the connecting block is fixedly connected with the mounting rod through the connecting screw.

5. The underpressured coal seam separate zonal reaming drill tool of claim 2, wherein, A limiting rod is fixedly installed on the pressing rod, the limiting rod is slidably connected with the mounting bracket, and the limiting rod is used for limiting the movement of the pressing rod.

6. The underpressured coal bed zonal reamer of claim 1, wherein, A positioning sleeve is fixedly installed on the bottom of the mounting seat, a positioning block is fixedly installed on the top of the first drill bit, the positioning block and the positioning sleeve are adaptively connected, and a positioning screw is arranged on the positioning sleeve and the positioning block.

7. The underpressured coal seam separate zonal reaming drill tool of claim 1, wherein, A plurality of supporting blocks are fixedly installed in the support pipe, the mounting pipe is rotatably connected with the supporting blocks, and the supporting blocks are used for supporting the mounting pipe.

8. The underpressured coal seam separate zonal reaming drill tool of claim 1, wherein, A vertical pipe is arranged on the support pipe, a plurality of shunt pipes are connected with the vertical pipe, a plurality of nozzles are arranged on the plurality of shunt pipes, and the nozzles are located above the mounting seat.

9. The underpressured coal seam separate zonal reaming drill tool of claim 8, wherein, A plurality of avoiding openings are formed in the support pipe, and the plurality of avoiding openings are respectively used for avoiding the plurality of nozzles.

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