Reverse circulation casing-following drilling tool

Abstract

The reverse circulation casing-following drilling tool comprises a reamer bit, an air outlet channel and a slag discharging channel are arranged in the reamer bit, and the air outlet channel is arranged on the outer side of the slag discharging channel; the outer side of the rear end of the reamer bit is sleeved with the drill clamping sleeve, and a gas channel is formed between the drill clamping sleeve and the reamer bit; the blocking sleeve is arranged on the outer side of the drill rod clamping sleeve in a sleeving mode, and an air passing channel is formed between the blocking sleeve and the drill rod clamping sleeve and used for communicating the air channel with the air outlet channel; the protection pipe is arranged on the outer side of the reamer bit in a sleeving mode, the outer diameter of the reamer bit is variable, the maximum hole forming outer diameter of the reamer bit is larger than the maximum outer diameter of the protection pipe, and the minimum outer diameter of the reamer bit is smaller than the minimum inner diameter of the protection pipe. Compared with the prior art, the reverse circulation casing-following drilling tool provided by the utility model not only can effectively solve the problems of hole shrinkage, collapse and hole wall instability of a soft soil layer, but also is better in deslagging effect and higher in drilling efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of drilling in soil layers or rocks, and more specifically, to a reverse circulation pipe-following drill tool. Background Art

[0002] When drilling in soft rock and soil layers such as loose, poorly cemented, easily broken, and easily hydrated ones, the construction difficulty is great, and problems such as difficult core sampling, difficult hole formation, and hole wall collapse are often encountered, and the drilling effect is not ideal. The main reason is that during the construction process, the hole is prone to collapse while drilling, the amount of slag discharge is large, and accidents such as drill sticking, drill jamming, and drill burying may also occur, resulting in low drilling efficiency.

[0003] The down-the-hole hammer pipe-following drilling technology makes full use of the advantage of the high-efficiency impact of the down-the-hole hammer on rock breaking. While efficiently breaking the rock for drilling, the casing is inserted to protect the hole wall of the borehole. By using the rigid guiding effect of the casing, the bending of the borehole can be inhibited, and the straightness of the borehole can be ensured. Therefore, the pipe-following reaming drill tool is also widely used in engineering borehole construction in hard, broken, loose and other complex strata at home and abroad.

[0004] The existing pipe-following reaming drill tools mainly use positive circulation for slag discharge. However, when the hole diameter is large or the formation is complex, it is difficult to discharge slag by positive circulation, resulting in reduced drilling efficiency, shortened drill tool life, and increased drilling costs. Moreover, the drill bit is easily stuck by rock debris when the drill is lifted, which brings inconvenience to the drill lifting operation.

[0005] Therefore, there is an urgent need for a reverse circulation pipe-following drill tool, which can not only effectively solve the problems of hole shrinkage, collapse, and hole wall instability in soft soil layers, but also has better slag discharge effect and higher drilling efficiency. Summary of the Utility Model

[0006] To solve the above technical problems, the present application provides a reverse circulation pipe-following drill tool, which can not only effectively solve the problems of hole shrinkage, collapse, and hole wall instability in soft soil layers, but also has better slag discharge effect and higher drilling efficiency.

[0007] The technical solution provided by the present application is as follows:

[0008] A reverse circulation pipe-following drill tool, comprising:

[0009] A reaming bit, in which an air outlet channel and a slag discharge channel are arranged, and the air outlet channel is arranged outside the slag discharge channel;

[0010] A chuck sleeve sleeved on the outer side of the rear end of the reaming bit, and a gas channel is formed between the chuck sleeve and the reaming bit;

[0011] A plug sleeve sleeved on the outer side of the chuck sleeve, and a gas passing channel is formed between the plug sleeve and the chuck sleeve, and the gas passing channel is used to connect the gas channel and the air outlet channel;

[0012] A protective tube sleeved on the outside of the reaming bit, the outer diameter of the reaming bit being variable, the maximum hole-forming outer diameter of the reaming bit being greater than the maximum outer diameter of the protective tube, and the minimum outer diameter of the reaming bit being less than the minimum inner diameter of the protective tube.

[0013] Preferably, the protective tube includes:

[0014] A pipe shoe sleeved on the outside of the reaming bit, positioning blocks being provided on the inner wall of the pipe shoe, and bumps being provided on the outer circumferential surface of the reaming bit, the rear end face of the positioning block abutting against the front end face of the bump;

[0015] A following pipe sleeved on the outside of the rear end of the pipe shoe and fixedly connected to the pipe shoe.

[0016] Preferably, an external thread line is provided on the outer surface of the rear end of the pipe shoe, an internal thread line is provided on the inner surface of the front end of the following pipe, and the pipe shoe and the following pipe are fixedly connected by threads.

[0017] Preferably, the air passage includes:

[0018] A first passage provided between the plug sleeve and the chuck sleeve and used for communicating with the air outlet passage;

[0019] A second passage provided on the chuck sleeve and used for communicating the gas passage with the first passage.

[0020] Preferably, the front end of the plug sleeve abuts against the rear end of the installation part of the reaming bit, a plug block is provided at the rear end of the plug sleeve, a stop block is provided on the outside of the chuck sleeve, the stop block is provided at one end of the first passage far from the air outlet passage, and the rear end face of the stop block abuts against the front end face of the plug block.

[0021] Preferably, the slag discharge passage includes:

[0022] A slag discharge groove provided on the front end face of the reaming bit;

[0023] A first slag discharge passage provided in the reaming bit and extending along the axial direction of the reaming bit;

[0024] A second slag discharge passage for connecting the slag discharge groove and the first slag discharge passage, the included angle between the axial direction of the second slag discharge passage and the axial direction of the first slag discharge passage being greater than 90°.

[0025] Preferably, the reaming bit includes:

[0026] An installation part and an impact part connected to each other;

[0027] A slider group is provided at one end of the impact part away from the installation part. The slider group is slidably connected to the impact part so that the slider group has an open state and a retracted state.

[0028] When the slider group is in the open state, the maximum outer diameter of the slider group is greater than the maximum outer diameter of the protection tube. When the slider is in the retracted state, the maximum outer diameter of the slider group is less than the minimum inner diameter of the protection tube.

[0029] Preferably, the difference between the maximum hole-forming outer diameter of the reaming bit and the maximum outer diameter of the protection tube is 2 mm to 3 mm.

[0030] Preferably, it further includes:

[0031] An outer sleeve that is sleeved on the outside of the drill rod sleeve and fixedly connected to the drill rod sleeve;

[0032] An inner sleeve that is sleeved inside the outer sleeve. The front end of the inner sleeve is used to communicate with the slag discharge channel;

[0033] A piston that is movably arranged between the inner sleeve and the outer sleeve;

[0034] A joint assembly that is sleeved on the outside of the rear end of the inner sleeve and fixedly connected to the outer sleeve;

[0035] A high-pressure air channel is formed among the piston, the inner sleeve, the joint assembly and the outer sleeve. The outlet of the high-pressure air channel is communicated with the gas channel.

[0036] Preferably, the outer sleeve is connected to the drill rod sleeve and the outer sleeve is connected to the joint assembly by threads.

[0037] For the reverse circulation pipe-following drilling tool provided by the present invention, first, due to the provision of a reaming bit, a drill rod sleeve and a plug sleeve. Among them, a slag discharge channel and an air outlet channel are provided in the reaming bit. The slag discharge channel is used to discharge the rock slag during the drilling process, and the air outlet channel is arranged outside the slag discharge channel. The drill rod sleeve is arranged outside the rear end of the reaming bit. A gas channel is formed between the drill rod sleeve and the reaming bit. The plug sleeve is sleeved on the outside of the drill rod sleeve. An air passage is formed between the plug sleeve and the drill rod sleeve. The air passage is used to communicate the gas channel and the air outlet channel. High-pressure gas is discharged from the reaming bit through the gas channel, the air passage and the air outlet channel, and blows up the rock slag at the bottom of the hole, so that the rock slag is discharged from the slag discharge channel. Compared with the prior art in which high-pressure gas is discharged from the middle of the drill bit and the rock slag is discharged from the side, in the reverse circulation pipe-following drilling tool of the present application, since the rock slag is discharged from the drill bit, it will not cause the drill bit to be easily stuck by rock chips when the drill is lifted, and the slag discharge process is smoother, there is less dust during the drilling process, and the environment is more friendly.

[0038] Secondly, a protective pipe is also provided. The protective pipe is sleeved outside the reaming bit. The hole wall of the protective pipe can be supported by the protective pipe. For soft rock and soil layers such as loose, poor cementation, easy to break, and easy to hydrate, the situation of hole wall collapse during drilling can be avoided. In addition, in order to facilitate drill lifting, the outer diameter of the reaming bit in the embodiment of the present invention is variable. The maximum hole-forming outer diameter of the reaming bit is greater than the maximum outer diameter of the protective pipe, which is convenient for the reaming bit to drill holes. After drilling, the protective pipe can extend into the hole. The minimum outer diameter of the reaming bit is smaller than the minimum outer diameter of the protective pipe, and the reaming bit can be received into the protective pipe, so as to lift the drill. Furthermore, since the rock slag is discharged from the central channel of the reaming bit instead of being discharged between the reaming bit and the protective pipe, the situation that the reaming bit is stuck by the rock slag can also be avoided.

[0039] It can be seen that, compared with the prior art, the reverse circulation pipe - following drill tool in the embodiment of the present invention can not only effectively solve the problems of diameter reduction, collapse, and hole wall instability in soft soil layers, but also has better slag discharge effect and higher drilling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0041] Figure 1 is a schematic structural diagram (with a hammer) of the reverse circulation pipe - following drill tool provided by the embodiment of the present invention;

[0042] Figure 2 is a schematic structural diagram (without a hammer) of the reverse circulation pipe - following drill tool provided by the embodiment of the present invention;

[0043] Figure 3 is a schematic structural diagram (with a pipe shoe sleeved) of the reaming bit provided by the embodiment of the present invention;

[0044] Figure 4 is Figure 3 a schematic structural diagram of the left - view of.

[0045] Reference numerals: 1, reaming bit; 11, air - outlet channel; 12, slag - discharge channel; 13, installation part; 14, impact part; 15, slider group; 2, chuck sleeve; 21, gas channel; 3, plug sleeve; 51, pipe shoe; 52, pipe - following; 6, outer sleeve; 7, inner sleeve; 8, piston; 9, joint assembly; 41, first channel; 42, second channel. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0047] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly disposed on the other element; when an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0048] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to this application.

[0049] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, the meaning of "a plurality" and "several" is two or more, unless otherwise specifically and clearly defined.

[0050] It should be noted that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions under which this application can be implemented. Therefore, they do not have a technical essence. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that this application can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in this application.

[0051] The embodiments of the present utility model are written in a progressive manner.

[0052] As Figures 1 to 4 shown, Figure 1The direction of the single arrow is the direction of gas discharge, and the direction of the double arrow is the direction of slag discharge for the reverse circulation casing drill. An embodiment of the present invention provides a reverse circulation casing drill, including: a reaming bit 1, an air outlet channel 11 and a slag discharge channel 12 are arranged in the reaming bit 1, and the air outlet channel 11 is arranged outside the slag discharge channel 12; a chuck sleeve 2 sleeved outside the rear end of the reaming bit 1, a gas channel 21 is formed between the chuck sleeve 2 and the reaming bit 1; a plug sleeve 3 sleeved outside the chuck sleeve 2, an air passing channel is formed between the plug sleeve 3 and the chuck sleeve 2, and the air passing channel is used to connect the gas channel 21 and the air outlet channel 11; a casing sleeved outside the reaming bit 1, the outer diameter of the reaming bit 1 is variable, the maximum hole-forming outer diameter of the reaming bit 1 is greater than the maximum outer diameter of the casing, and the minimum outer diameter of the reaming bit 1 is less than the minimum inner diameter of the casing.

[0053] The existing casing reaming drill mainly uses positive circulation for slag discharge. However, when the hole diameter is large or the formation is complex, it is difficult to discharge slag by positive circulation, resulting in reduced drilling efficiency, shortened drill life, increased drilling costs, and the drill bit is easily stuck by cuttings when the drill is lifted, which brings inconvenience to the work of lifting the drill.

[0054] For the reverse circulation casing drill provided by the present invention, firstly, due to the provision of the reaming bit 1, the chuck sleeve 2 and the plug sleeve 3. Among them, a slag discharge channel 12 and an air outlet channel 11 are arranged in the reaming bit 1. The slag discharge channel 12 is used to discharge the cuttings during the drilling process, and the air outlet channel 11 is arranged outside the slag discharge channel 12. The chuck sleeve 2 is arranged outside the rear end of the reaming bit 1, and a gas channel 21 is formed between the chuck sleeve 2 and the reaming bit 1. The plug sleeve 3 is sleeved outside the chuck sleeve 2, and an air passing channel is formed between the plug sleeve 3 and the chuck sleeve 2. The air passing channel is used to connect the gas channel 21 and the air outlet channel 11. High-pressure gas is discharged from the reaming bit 1 through the gas channel 21, the air passing channel and the air outlet channel 11, and blows up the cuttings at the bottom of the hole, so that the cuttings are discharged from the slag discharge channel 12. Compared with the way in the prior art that high-pressure gas is discharged from the middle of the drill bit and the cuttings are discharged from the side, in the reverse circulation casing drill of the present application, since the cuttings are discharged from the drill bit, it will not cause the drill bit to be easily stuck by cuttings when the drill is lifted, and the slag discharge process is smoother, there is less dust during the drilling process, and the environment is more friendly.

[0055] Secondly, a protective pipe is also provided. The protective pipe is sleeved outside the reaming bit 1. Through the protective pipe, the hole wall of the protective pipe can be supported. For soft rock and soil layers such as loose, poorly cemented, easily broken, and easily hydrated ones, the situation of hole wall collapse during drilling can be avoided. In addition, in order to facilitate drill extraction, the outer diameter of the reaming bit 1 in the embodiment of the present utility model is variable. The maximum hole-forming outer diameter of the reaming bit 1 is greater than the maximum outer diameter of the protective pipe, which is convenient for the reaming bit 1 to drill holes. After drilling, the protective pipe can extend into the drilled hole. The minimum outer diameter of the reaming bit 1 is smaller than the minimum outer diameter of the protective pipe, and the reaming bit 1 can be received into the protective pipe, so as to extract the drill. Furthermore, since the rock slag is discharged from the central channel of the reaming bit 1 instead of being discharged between the reaming bit 1 and the protective pipe, the situation that the reaming bit 1 is stuck by the rock slag can also be avoided.

[0056] It can be seen that, compared with the prior art, the reverse circulation pipe-following drilling tool in the embodiment of the present utility model can not only effectively solve the problems of diameter reduction, collapse, and hole wall instability of soft soil layers, but also has better slag discharge effect and higher drilling efficiency.

[0057] The reaming bit 1 in this application is mainly used for drilling holes. The reaming bit 1 in the prior art for the positive circulation pipe-following drilling tool can also be used in this application. In this application, the specific structure of the reaming bit 1 is not limited. It only needs that the outer diameter of the reaming bit 1 is variable, the maximum hole-forming outer diameter of the reaming bit 1 is greater than the maximum outer diameter of the protective pipe during drilling, and the minimum outer diameter of the reaming bit 1 is smaller than the minimum outer diameter of the protective pipe during drill extraction.

[0058] It should be noted that the front end in this application refers to the end of the reaming bit 1 close to the bottom of the hole, and the rear end in this application refers to the end of the reaming bit 1 far from the bottom of the hole.

[0059] In the above structure, as one specific implementation manner, the protective pipe in the embodiment of the present utility model includes a pipe shoe 51 and a pipe-following part 52. Among them, the pipe shoe 51 is sleeved outside the reaming bit 1, and positioning blocks are provided on the inner wall of the pipe shoe 51. Protrusions are provided on the outer circumferential surface of the reaming bit 1, and the rear end face of the positioning block abuts against the front end face of the protrusion. In this way, when the reaming bit 1 is drilling, the reaming bit 1 extends out of the pipe shoe 51, and the axial position of the reaming bit 1 is positioned through the cooperation of the positioning block and the protrusion. When the reaming bit 1 is extracting the drill, the reaming bit 1 can retract into the pipe shoe 51 and the pipe-following part 52. The pipe-following part 52 is arranged at the rear end of the pipe shoe 51 and is used for fixedly connecting with the pipe shoe 51. The pipe-following part 52 and the pipe shoe 51 support the hole wall of the drilled hole to avoid the situation of hole collapse.

[0060] Further, as a specific implementation manner, an external thread is provided on the outer surface of the rear end of the pipe shoe 51 of the present utility model, and an internal thread is provided on the inner surface of the front end of the follow-up pipe 52. The pipe shoe 51 and the follow-up pipe 52 are fixedly connected by threads.

[0061] Further, as a specific implementation manner, the air passage in the embodiment of the present utility model includes a first passage 41 and a second passage 42. Among them, the first passage 41 is provided between the plug sleeve 3 and the drill rod sleeve 2, and the first passage 41 is used to communicate with the air outlet passage 11. The second passage 42 is provided on the drill rod sleeve 2, and the second passage 42 is used to communicate the gas passage 21 and the first passage 41. After the gas passage 21 passes through the second passage 42 and the first passage 41, it is discharged from the air outlet passage 11, so as to blow the slag on the bottom of the hole.

[0062] Further, in order to prevent high-pressure gas from flowing out from the rear end of the first passage 41, as a more preferred implementation manner, the front end of the plug sleeve 3 in the embodiment of the present utility model abuts against the rear end of the mounting portion 13 of the reaming bit 1. A blocking block is provided at the rear end of the plug sleeve 3, and a blocking block is provided on the outer side of the drill rod sleeve 2. The blocking block is provided at one end of the first passage 41 away from the air outlet passage 11, and the rear end surface of the blocking block abuts against the front end surface of the blocking block. Through the cooperation of the blocking block and the blocking block, the high-pressure gas can only enter the air outlet passage 11 unidirectionally from the first passage 41.

[0063] Further, as a more preferred implementation manner, a sealing member is provided between the connecting surfaces of the blocking block and the blocking block in the embodiment of the present utility model.

[0064] Further, as an implementation manner, the slag discharge passage 12 in the embodiment of the present utility model includes: a slag discharge groove provided on the front end surface of the reaming bit 1; a first slag discharge passage provided in the reaming bit 1, and the first slag discharge passage extends along the axial direction of the reaming bit 1; a second slag discharge passage for connecting the slag discharge groove and the first slag discharge passage, and the included angle between the axial direction of the second slag discharge passage and the axial direction of the first slag discharge passage is greater than 90°.

[0065] Specifically, after the high-pressure gas is discharged from the exhaust passage, there is a pressure difference between the slag discharge passage 12 and the bottom of the hole. Under the action of the pressure difference, the rock slag at the bottom of the hole enters the first slag discharge passage through the slag discharge groove and the second slag discharge passage, and is discharged through the inner sleeve 7 of the reverse circulation impactor.

[0066] In the above structure, as a specific implementation manner, the reaming bit 1 in the embodiment of the present utility model includes a mounting portion 13, an impact portion 14, and a slider group 15. The impact portion 14 is used for drilling. The mounting portion 13 is connected to the rear end of the impact portion 14. The slider group 15 is arranged at one end of the impact portion 14 away from the mounting portion 13. The slider group 15 is slidably connected to the impact portion 14, so that the slider group 15 has an open state and a retracted state. When the slider group 15 is in the open state, the maximum hole-forming outer diameter of the slider group 15 is greater than the maximum outer diameter of the casing pipe, which is convenient for the bit to drill. When the slider group 15 is in the retracted state, the minimum outer diameter of the slider group 15 is less than the minimum inner diameter of the casing pipe, which is convenient for lifting the reaming bit 1. When the front end of the impact portion 14 contacts the bottom of the hole, the slider group 15 is pushed to slide outwards and switches to the open state. When the front end of the impact portion 14 separates from the bottom of the hole, the slider group 15 retracts and switches to the retracted state.

[0067] As a specific implementation manner, the reaming bit 1 can be the reaming bit disclosed in CN212249842U.

[0068] In the above structure, as a specific implementation manner, the difference between the maximum outer diameter of the reaming bit 1 in the embodiment of the present utility model and the maximum outer diameter of the casing pipe is 2 mm to 3 mm. With such a setting, it is convenient for the casing pipe to extend into the drilled hole for support, and the gap between the hole wall and the casing pipe is small, which will not affect slag discharge.

[0069] In the above structure, as an implementation manner, the reverse circulation casing drill in the embodiment of the present utility model further includes an outer casing 6, an inner casing 7, a piston 8, and a joint assembly 9. Among them, the outer casing 6 is sleeved outside the chuck sleeve 2, and the outer casing 6 is fixedly connected to the chuck sleeve 2; the inner casing 7 is sleeved inside the outer casing 6, and the front end of the inner casing 7 is used to communicate with the slag discharge channel 12, and the rock slag is discharged through the inner casing 7; the piston 8 is movably arranged between the inner casing 7 and the outer casing 6; the joint assembly 9 is sleeved outside the rear end of the inner casing 7 and is fixedly connected to the outer casing 6; a high-pressure air passage is formed among the piston 8, the inner casing 7, the joint assembly 9 and the outer casing 6, and the outlet of the high-pressure air passage is communicated with the gas passage 21.

[0070] Specifically, the outer casing 6, the chuck sleeve 2, the inner casing 7, the reaming bit 1, and the joint assembly 9 form an accommodation cavity. The piston 8 is movably sleeved between the inner casing 7 and the outer casing 6, and divides the accommodation cavity into a first air chamber A and a second air chamber B. High-pressure gas alternately enters the first air chamber A and the second air chamber B from the joint assembly 9, so that there is a pressure difference between the first air chamber A and the second air chamber B, and the piston 8 is pushed to reciprocate along the inner casing 7, providing a pulsed force for the reaming bit 1. The excess exhaust gas enters the gas passage 21 through the high-pressure air passage and is discharged.

[0071] Further, as one specific implementation manner, between the outer sleeve 6 and the drill rod chuck sleeve 2, and between the outer sleeve 6 and the joint assembly 9 in the embodiments of the present utility model, they are all connected by threads.

[0072] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present utility model. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present utility model. Therefore, the present utility model will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An anti-circulation casing drill tool, characterized in that Comprising: A reaming bit (1), an air outlet channel (11) and a slag discharge channel (12) are arranged inside the reaming bit (1), and the air outlet channel (11) is arranged outside the slag discharge channel (12); A chuck sleeve (2) sleeved on the outer side of the rear end of the reaming bit (1), a gas channel (21) is formed between the chuck sleeve (2) and the reaming bit (1); A plug sleeve (3) sleeved on the outer side of the chuck sleeve (2), an air passing channel is formed between the plug sleeve (3) and the chuck sleeve (2), and the air passing channel is used for communicating the gas channel (21) and the air outlet channel (11); A protection tube sleeved on the outer side of the reaming bit (1), the outer diameter of the reaming bit (1) is variable, the maximum hole-forming outer diameter of the reaming bit (1) is greater than the maximum outer diameter of the protection tube, and the minimum outer diameter of the reaming bit (1) is less than the minimum inner diameter of the protection tube.

2. The reverse circulation pipe-following drilling tool according to claim 1, wherein The protection tube includes: A pipe shoe (51) sleeved on the outer side of the reaming bit (1), positioning blocks are arranged on the inner wall of the pipe shoe (51), convex blocks are arranged on the outer circumferential surface of the reaming bit (1), and the rear end surface of the positioning block abuts against the front end surface of the convex block; A pipe-following part (52) sleeved on the outer side of the rear end of the pipe shoe (51) and fixedly connected with the pipe shoe (51).

3. The reverse circulation pipe-following drilling tool according to claim 2, wherein External thread lines are arranged on the outer surface of the rear end of the pipe shoe (51), internal thread lines are arranged on the inner surface of the front end of the pipe-following part (52), and the pipe shoe (51) and the pipe-following part (52) are fixedly connected by threads.

4. The reverse circulation pipe-following drilling tool according to any one of claims 1 to 3, wherein The air passing channel includes: A first channel (41) arranged between the plug sleeve (3) and the chuck sleeve (2), and the first channel (41) is used for communicating with the air outlet channel (11); A second channel (42) arranged on the chuck sleeve (2) and used for communicating the gas channel (21) with the first channel (41).

5. The reverse circulation pipe-following drilling tool according to claim 4, wherein The front end of the plug sleeve (3) abuts against the rear end of the installation part of the reaming bit (1), a plug block is arranged at the rear end of the plug sleeve (3), a stop block is arranged on the outer side of the chuck sleeve (2), the stop block is arranged at one end of the first channel (41) far away from the air outlet channel (11), and the rear end surface of the stop block abuts against the front end surface of the plug block.

6. The reverse circulation pipe-following drilling tool according to any one of claims 1 to 3, 5, wherein The slag discharge channel (12) includes: A slag discharge groove arranged on the front end surface of the reaming bit; A first slag discharge channel arranged inside the reaming bit, and the first slag discharge channel extends along the axial direction of the reaming bit; A second slag discharge channel for connecting the slag discharge tank and the first slag discharge channel, the included angle between the axial direction of the second slag discharge channel and the axial direction of the first slag discharge channel being greater than 90°.

7. The reverse circulation casing drill according to any one of claims 1 to 3 and 5, characterized in that The reaming bit (1) includes: An installation part (13) and an impact part (14) connected to each other; A slider group (15) provided at one end of the impact part (14) away from the installation part (13), the slider group (15) being slidably connected to the impact part (14) so that the slider group (15) has an open state and a retracted state; When the slider group (15) is in the open state, the maximum outer diameter of the slider group (15) is greater than the maximum outer diameter of the casing, and when the slider group (15) is in the retracted state, the maximum outer diameter of the slider group (15) is less than the minimum inner diameter of the casing.

8. The reverse circulation casing drill according to any one of claims 1 to 3 and 5, characterized in that The difference between the maximum hole-forming outer diameter of the reaming bit (1) and the maximum outer diameter of the casing is 2 mm to 3 mm.

9. The reverse circulation casing drill according to any one of claims 1 to 3 and 5, characterized in that It further includes: An outer casing (6) sleeved on the outside of the chuck sleeve (2) and fixedly connected to the chuck sleeve (2); An inner casing (7) sleeved inside the outer casing (6), the front end of the inner casing (7) being used for communicating with the slag discharge channel (12); A piston (8) movably arranged between the inner casing (7) and the outer casing (6); A joint assembly (9) sleeved on the outside of the rear end of the inner casing (7) and fixedly connected to the outer casing (6); A high-pressure air passage is formed between the piston (8), the inner casing (7), the joint assembly (9) and the outer casing (6), and the outlet of the high-pressure air passage is communicated with the gas passage (21).

10. The reverse circulation casing drill according to claim 9, characterized in that Between the outer casing (6) and the chuck sleeve (2), and between the outer casing (6) and the joint assembly (9), they are all connected by threads.

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