An adjustable drill bit suitable for positive and negative pressure combined sampling

Abstract

The present invention discloses an adjustable drill bit suitable for positive and negative pressure combined sampling, including: a drilling platform, a drill rod holder is installed on the top of the drilling platform, a double-walled drill rod is rotatably transmitted in the drill rod holder, an adjustable pressure blower is arranged on one side of the drilling platform, a drill bit is detachably installed at the end of the double-walled drill rod, an airflow piece is arranged in the drill bit, a plurality of the airflow pieces are circumferentially distributed on the inner wall of the drill bit, the inner tube of the double-walled drill rod is connected to the center of the drill bit, a capsule with a bearing is arranged between the double-walled drill rod and the borehole; and a sample collector is also arranged outside the drilling platform, an adjustable exhaust fan is connected to the outside of the sample collector, and a blocking mechanism is also arranged in the drill bit. The present invention mainly aims at internal transmission in the drill bit in an intermittently arranged transmission mode during coal sampling, so as to avoid internal blockage of coal samples, wherein the airflow piece further assists the transmission of coal samples at the drill bit, keeps the coal samples moving, and prevents end blockage.

Description

Technical Field

[0001] The invention belongs to the technical field of downhole sampling, and in particular relates to an adjustable drill bit suitable for positive and negative pressure combined sampling. Background Art

[0002] The determination of gas content requires fixed-point sampling. Domestic and foreign researchers have conducted extensive and in-depth research on underground sampling. The current sampling methods include: negative pressure injection coal sampling, twisted drill pipe, core tube sampling, etc. The positive and negative pressure combined sampling process is mainly based on the original compressed air reverse circulation sampling process, adding negative pressure at the sampling end to absorb coal samples, forming a positive pressure at the air inlet end to send the cut coal powder to the front end of the drill bit by compressed air, and using an adjustable fan (or vacuum pump) at the sampling end to pump the center tube of the drill pipe into negative pressure; however, the existing sampling drill bits are frequently wet due to the water-coal powder in the borehole, and the resistance is too large, which causes the coal samples to easily accumulate and clog in the drill bit and the drill pipe, affecting the sampling progress; therefore, it is necessary to provide an adjustable drill bit suitable for positive and negative pressure combined sampling to solve the problems raised in the above background technology. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides an adjustable drill bit suitable for positive and negative pressure combined sampling, which solves the problem that the existing sampling drill bits are frequently blocked by coal samples in the drill bit and drill rod due to moisture in the water-coal powder in the borehole and excessive resistance, thus affecting the sampling progress.

[0004] A kind of adjustable drill bit suitable for positive and negative pressure combined sampling, comprising: a drilling platform, a drill rod holder is installed on the top of which a double-walled drill rod is rotatably transmitted in the drill rod holder, an adjustable pressure fan is arranged on one side of the drilling platform, the adjustable pressure fan sends compressed air into the annular cavity of the double-walled drill rod through a double-channel air and water tap, a drill bit is detachably installed on the end of the double-walled drill rod, an air flow piece is arranged in the drill bit, a plurality of the air flow pieces are circumferentially distributed on the inner wall of the drill bit, and are used to discharge compressed air into the borehole to form an annular air curtain, the inner tube of the double-walled drill rod is connected to the center of the drill bit, and a sealing capsule with a bearing is arranged between the double-walled drill rod and the borehole; and a sample collector is also arranged outside the drilling platform, and an adjustable exhaust fan is connected to the outside of the sample collector, so that the adjustable exhaust fan is connected to the inner tube of the double-walled drill rod through the sample collector, and a blocking mechanism is also arranged in the drill bit.

[0005] Furthermore, the airflow component includes: a rotor shaft, which is arranged on the inner wall of the drill bit, the inner wall of the drill bit is provided with a mounting groove, the rotor shaft can be relatively rotatably assembled in the mounting groove, a sealing ring is wrapped around the side wall of the rotor shaft through a guide groove, and is used for sealing contact with the inner wall of the mounting groove, an airflow channel is opened in the drill bit, and a guide hole is provided in the rotor shaft, the airflow channel is connected to the guide hole, and an air sleeve is fixed outside the rotor shaft.

[0006] Furthermore, an arc-shaped notch is provided on the rotor shaft, and an inner lining member perpendicular to the arc-shaped notch of the rotor shaft is fixed on the inner wall of the drill bit at the end of the air flow channel, one end of the inner lining member is in sealing contact with the inner wall of the arc-shaped notch, and cooperates with the rotor shaft to form an air pressure chamber, and an inner spring is connected between the inner lining member and the rotor shaft.

[0007] Furthermore, the rotor shaft is vertical to the drill bit axis without external force, and when the air pressure in the air flow channel is higher than 0.02 MPa, the inner spring is elastically compressed, and the rotor shaft deflects within the range of 0° to 50°.

[0008] Furthermore, one or more of the rotor shafts are turned toward a side close to the double-wall drill pipe, and the remaining rotor shafts are deflected and turned toward a side away from the double-wall drill pipe.

[0009] Furthermore, the blocking mechanism comprises: an inner shaft cylinder, coaxially fixed in the drill bit, a plurality of guide rods are circumferentially distributed on the inner shaft cylinder, the guide rods are all slidably connected to the inner shaft cylinder, the guide rods are all sleeved with connecting springs, and the ends of the guide rods are all fixed with cutouts;

[0010] A sleeve is rotatably sleeved on the outside of the inner shaft tube in the drill bit, and a push column is fixed to the end of each guide rod away from the cutter body. One side end surface of the push column is set as a slope structure, and the inner wall of the sleeve is provided with an inner convex edge. The inner convex edge gradually contacts the outer slope of the push column during the rotation of the sleeve, and pushes the guide rod radially toward the axis center.

[0011] Furthermore, a partition chamber is sealed and fixed on one side of the double-wall drill pipe near the drill bit, a turbofan blade is rotatably arranged in the partition chamber, a coupling sleeve is rotatably sleeved on the inner tube of the double-wall drill pipe, the turbofan blade is fixed to the coupling sleeve, and one end of the coupling sleeve is clamped and fixed to the shaft sleeve;

[0012] An L-shaped channel is provided on the separation chamber for delivering the compressed air in the double-wall drill pipe into the separation chamber, and the end of the L-shaped channel is arranged tangentially to the rotation direction of the turbofan blade.

[0013] Furthermore, the partition cavity is also provided with a plurality of air flow holes distributed circumferentially.

[0014] Furthermore, the guide hole is a V-shaped channel, and the guide hole V-shaped channel is provided with an acute-angle channel and an obtuse-angle channel.

[0015] Furthermore, the blocking mechanism is arranged on the inner side of the air flow channel.

[0016] The beneficial effects of the present invention are as follows: the present invention mainly aims at internal transmission in the drill bit in the intermittent arrangement during coal sampling, thereby avoiding internal blockage of coal samples, wherein the airflow component further assists the transmission of coal samples at the drill bit, maintains the movement of coal samples, and prevents blockage at the end. The setting of the airflow component can discharge compressed air into the borehole to form an annular air curtain, and the coal sample transmission can be intermittently cut off by the blocking mechanism, one section of coal sample - one section of compressed air, and at the same time, the sample outlet uses an adjustable fan (or vacuum pump) to pump the drill pipe center tube into negative pressure, increase the pressure difference between the sample outlet end and the front end of the drill bit, and allow the coal sample to be smoothly discharged to the sample outlet through the borehole center tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention;

[0018] Figure 2 It is a schematic diagram of the structure of the airflow member in the present invention;

[0019] Figure 3 It is a schematic diagram of the structure of the separation cavity in the present invention;

[0020] Figure 4 It is a structural schematic diagram of the blocking mechanism in the present invention;

[0021] Figure 5 It is a schematic diagram of the compressed air flow after the airflow member in the drill bit is adjusted in the present invention;

[0022] Figure 6 It is a schematic diagram of the effect of compressed air transmission of the airflow component on the coal sample in the present invention;

[0023] In the figure: 1. Drilling rig; 11. Dual-channel air and water tap; 12. Adjustable pressure fan; 13. Capsule with bearing sealing hole; 14. Sample collector; 2. Double-wall drill pipe; 3. Drill bit; 31. Lining part; 4. Air flow part; 41. Rotor shaft; 42. Air flow channel; 43. Guide hole; 44. Air set kit; 45. Inner spring; 46. Air pressure chamber; 5. Blocking mechanism; 51. Inner shaft cylinder; 52. Guide rod; 53. Connecting spring; 54. Cutting body; 55. Bushing; 56. Top column; 6. Partition chamber; 61. Turbofan blade; 62. Connecting sleeve; 63. Air flow hole. DETAILED DESCRIPTION

[0024] In order to better explain the present invention and facilitate understanding, the technical solutions and effects of the present invention are described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0025] See also Figure 1-4In an embodiment of the present invention, an adjustable drill bit suitable for positive and negative pressure combined sampling includes: a drilling platform 1, a drill rod holder is installed on the top of the drilling platform, a double-walled drill rod 2 is rotatably transmitted in the drill rod holder, an adjustable pressure fan 12 is arranged on one side of the drilling platform 1, and the adjustable pressure fan 12 sends compressed air into the annular cavity of the double-walled drill rod 2 through a pipeline equipped with a dual-channel air and water tap 11, a drill bit 3 is detachably installed on the end of the double-walled drill rod 2, an airflow member 4 is arranged in the drill bit 3, and a plurality of the airflow members 4 are circumferentially distributed on the inner wall of the drill bit 3, which are used to discharge the compressed air into the borehole and thus form an annular air curtain, the inner tube of the double-walled drill rod 2 is connected to the center of the drill bit 3, and a bearing sealing capsule 13 is arranged between the double-walled drill rod 2 and the borehole, and the bearing sealing capsule 13 can stabilize the double-walled drill rod 2 in the borehole, thereby fixing the double-walled drill rod 2 to prevent drilling cuttings The effect of large-scale outflow; a sample collector 14 is also arranged outside the drilling rig 1, and the sample collector 14 is connected to the double-wall drill pipe 2 through an inner tube, and an adjustable exhaust fan (not shown in the figure) is connected to the outside of the sample collector 14, so that the adjustable exhaust fan is connected to the inner tube of the double-wall drill pipe 2 through the sample collector 14, and the adjustable exhaust fan can generate a certain intensity of wind flow. The wind flow can bring the taken coal powder through the inner tube of the double-wall drill pipe 2 to the sample collector 14. A blocking mechanism 5 is also arranged in the drill bit 3, that is, the compressed air enters the annular space between the inner and outer walls of the double-wall drill pipe 2 through the dual-channel air and water tap 11, and reaches the internal annular space of the drill bit 3. When the compressed air contacts the borehole wall, under the obstruction of the borehole wall, a part of the airflow flows out of the borehole from the space between the drill pipe and the borehole wall, and the other part reaches the front end of the borehole carrying the coal powder cut off by the drill bit 3 and flows into the inner tube of the drill bit 3. As the drill bit 3 rotates, the compressed air forms a vortex at the bottom of the hole. The inner tube of the drill bit 3 at the center of the vortex is a low-pressure area. Due to the pressure difference, the compressed air carries the coal powder into the inner tube of the drill bit 3, forming a reverse circulation. At the same time, the sample outlet end uses the adjustable exhaust fan outside the sample collector 14 to draw the drill pipe center tube into a negative pressure, increasing the pressure difference between the sample outlet end and the front end of the drill bit 3, so that the coal sample can be smoothly discharged to the sample outlet end through the borehole center tube. Specifically, the drilling rig 1, double-walled drill pipe 2, drill pipe clamp, adjustable compressed air fan 12, sample collector 14, channel air faucet 11, and bearing-sealed capsule 13 in this embodiment are all implemented using existing technologies.

[0026] like Figure 1 and Figure 2As shown, in this embodiment, the airflow member 4 includes: a rotor shaft 41, which is arranged on the inner wall of the drill bit 3, and the inner wall of the drill bit 3 is provided with a mounting groove. The rotor shaft 41 can be relatively deflected and assembled in the mounting groove. A sealing ring is wound around the side wall of the rotor shaft 41 through a guide groove, which is used for sealing contact with the inner wall of the mounting groove. An airflow channel 42 is opened in the drill bit 3, and a guide hole 43 is provided in the rotor shaft 41. The guide hole 43 is a V-shaped channel, and the V-shaped channel of the guide hole 43 is set as an acute angle channel and an obtuse angle channel; the airflow channel 42 is connected with the guide hole 43, and an air sleeve 44 is fixed outside the rotor shaft 41, and the through hole of the air sleeve 44 is connected with the guide hole 43, so that the compressed air in the double-wall drill pipe 2 can enter the air sleeve 44 through the airflow channel 42, and the compressed air is discharged directionally by the air sleeve 44. As a preferred embodiment, an arc-shaped notch is provided on the rotor shaft 41, and an inner lining 31 perpendicular to the arc-shaped notch of the rotor shaft 41 is fixed on the inner wall of the drill bit 3 at the end of the air flow channel 42, one end of the inner lining 31 is in sealing contact with the inner wall of the arc-shaped notch, and cooperates with the rotor shaft 41 to form an air pressure chamber 46, and an inner spring 45 is connected between the inner lining 31 and the rotor shaft 41. In this embodiment, the rotor shaft 41 is vertical to the axis of the drill bit 3 without external force, and when the air pressure in the air flow channel 42 is higher than 0.02Mpa, the inner spring 45 is elastically compressed, and the rotor shaft 41 deflects within the range of 0° to 50°, that is, when the air pressure in the air flow channel 42 is higher than 0.02Mpa, the air intake in the air flow channel 42 is much greater than the air discharge from the air set 44 outlet, so that the compressed air volume in the air pressure chamber 46 surges, the air volume of the air pressure chamber 46 increases, and the rotor shaft 41 deflects.

[0027] like Figure 5 , Figure 6 As shown, in this embodiment, one or more of the rotor shafts 41 turn toward the side close to the double-wall drill pipe 2 (i.e., forward rotation), and the remaining rotor shafts 41 deflect toward the side away from the double-wall drill pipe 2 (i.e., reverse rotation). It should be noted that the number of rotor shafts 41 rotating in the forward direction is greater than the number of rotor shafts 41 rotating in the reverse direction (at least three). In compressed air and normal pressure transportation, each rotor shaft 41 is perpendicular to the axis of the drill bit 3. At this time, the negative pressure pumping of the inner tube of the double-wall drill pipe 2 is coordinated, and the double-wall drill pipe 2 is continuously rotated. The downward pressure wind can form an annular vortex, thereby evenly transmitting the coal sample to the inner tube of the double-wall drill pipe 2; and especially in the compressed air high-pressure transmission, each rotor shaft 41 produces relative deflection. At this time, each rotor shaft 41 rotating in the forward direction forms external extrusion wind under the rotation of the double-wall drill pipe 2, which is used to tangentially discharge the coal sample near the inner wall of the drill bit 3 out of the drill bit 3, while each rotor shaft 41 rotating in the reverse direction forms internal extrusion wind. At this time, the negative pressure pumping of the inner tube of the double-wall drill pipe 2 can transport the coal sample to the inner tube of the double-wall drill pipe 2, avoiding blockage of the coal sample at the drill bit 3.

[0028] like Figure 3and Figure 4 As shown, in this embodiment, the blocking mechanism 5 is arranged on the inner side of the airflow channel 42 to avoid affecting the airflow channel 42. The blocking mechanism 5 includes: an inner shaft cylinder 51, which is coaxially fixed on the inner wall of the drill bit 3 close to the double-wall drill pipe 2. A plurality of guide rods 52 are circumferentially distributed on the inner shaft cylinder 51. The guide rods 52 are radially slidably connected to the inner shaft cylinder 51. The guide rods 52 are sleeved with connecting springs 53, which have a stable buffering effect, and the ends of the guide rods are fixed with cutters 54; a sleeve 55 is rotatably sleeved outside the inner shaft cylinder 51 in the drill bit 3, and each of the guide rods 52 is sleeved with a sleeve 55, and each of the guide rods 52 is sleeved with a sleeve 55. 2 is fixed with a top column 56 at one end away from the cut body 54, and one side end face of the top column 56 is set as an inclined surface structure, and the inner wall of the sleeve 55 is provided with an inner convex edge, and the inner convex edge gradually contacts with the outer inclined surface of the top column 56 during the rotation of the sleeve 55, and pushes the guide rod 52 radially toward the axis center, that is, under the continuous rotation of the sleeve 55, each cut body 54 can intermittently converge to the center of the drill bit 3, thereby forming a truncation effect on the transmission of the coal sample, so that a section of coal sample-a section of compressed air is formed in the inner tube of the double-wall drill pipe 2, thereby avoiding the blockage of the coal sample in the double-wall drill pipe 2.

[0029] like Figure 3 As shown, as a preferred embodiment, a partition chamber 6 is sealed and fixed on one side of the double-wall drill pipe 2 near the drill bit 3, and a turbofan blade 61 is rotatably arranged in the partition chamber 6. A coupling sleeve 62 is rotatably sleeved on the inner tube of the double-wall drill pipe 2, and the turbofan blade 61 is fixed to the coupling sleeve 62, and one end of the coupling sleeve 62 is clamped and fixed to the shaft sleeve 55. The rotation of the turbofan blade 61 drives the coupling sleeve 62 to rotate, thereby rotating the shaft sleeve 55; an L-shaped channel is provided on the partition chamber 6 for sending the compressed air in the double-wall drill pipe 2 into the shaft sleeve 55. The end of the L-shaped passage is arranged tangentially toward the rotation direction of the turbofan blade 61, that is, the compressed air can drive the turbofan blade 61 to rotate at a low speed during normal pressure transportation. At this time, each cutter 54 can converge and cut off at a low frequency to form a small number of coal sample transmission sections in the inner tube of the double-wall drill pipe 2; and when the compressed air is conveyed under high pressure, each cutter 54 can converge and cut off at a high frequency to form multiple small numbers of coal sample transmission sections in the inner tube of the double-wall drill pipe 2, especially for coal samples with high humidity and high viscosity, which can effectively avoid transmission blockage.

[0030] In this embodiment, a plurality of air flow holes 63 are circumferentially distributed on the partition cavity 6 so that the compressed air can evenly enter the air flow channel 42 in the drill bit 3 .

[0031] Specifically, the drill bit 3 drills into the coal seam along with the double-wall drill pipe 2. After the compressed air enters the annular space between the inner and outer walls of the double-wall drill pipe 2 through the dual-channel air and water tap 11, it reaches the internal annular space of the drill bit 3 and is discharged from the through hole of the air sleeve 44 of the drill bit 3 into the borehole to form an annular air curtain, wherein the compressed air pumping pressure is adjusted according to different sampling environmental conditions, and the compressed air is directionally discharged through the air sleeve 44 in the drill bit 3, and the blocking mechanism 5 can intermittently cut off the transmission of the coal sample, so that a section of coal sample and a section of compressed air are formed in the inner tube of the double-wall drill pipe 2. At the same time, the sample outlet end uses an adjustable fan (or vacuum pump) to draw the drill pipe center tube into negative pressure, thereby increasing the pressure difference between the sample outlet end and the front end of the drill bit 3, so that the coal sample can be smoothly discharged to the sample outlet end through the borehole center tube.

Claims

1. An adjustable drill bit suitable for positive and negative pressure combined sampling, characterized in that: include: A drilling rig (1) is provided with a drill rod holder on the top thereof, a double-walled drill rod (2) is rotatably transmitted in the drill rod holder, an adjustable pressure fan (12) is provided on one side of the drilling rig, the adjustable pressure fan (12) sends compressed air into the annular cavity of the double-walled drill rod (2) through a dual-channel air and water tap (11), a drill bit (3) is detachably installed at the end of the double-walled drill rod (2), an airflow component (4) is provided in the drill bit (3), a plurality of the airflow components (4) are circumferentially distributed on the inner wall of the drill bit (3), and are used to discharge compressed air into a drill hole to form an annular air curtain, the inner tube of the double-walled drill rod (2) is connected to the center of the drill bit (3), and the double-walled drill rod (2) is connected to the drill bit (3). A sealing capsule (13) with a bearing is provided between the boreholes; and a sample collector (14) is also provided outside the drilling platform (1), and an adjustable exhaust fan is connected to the outside of the sample collector (14), so that the adjustable exhaust fan is connected to the inner tube of the double-wall drill pipe (2) through the sample collector (14); a blocking mechanism (5) is also provided inside the drill bit (3), and the blocking mechanism (5) comprises: an inner shaft cylinder (51) coaxially fixed inside the drill bit (3); a plurality of guide rods (52) are circumferentially distributed on the inner shaft cylinder (51); the guide rods (52) are all radially slidably connected to the inner shaft cylinder (51); the guide rods (52) are all sleeved with connecting springs (53), and their ends A cutter body (54) is fixed to each of the two guide rods (52); a sleeve (55) is rotatably sleeved on the outside of the inner shaft cylinder (51) in the drill bit (3); a top column (56) is fixed to one end of each guide rod (52) away from the cutter body (54); one end surface of the top column (56) is arranged as an inclined surface structure; an inner convex edge is arranged on the inner wall of the sleeve (55); the inner convex edge gradually contacts the outer inclined surface of the top column (56) during the rotation of the sleeve (55), and pushes the guide rod (52) radially toward the axis; a partition chamber (6) is sealed and fixed to one side of the double-wall drill rod (2) close to the drill bit (3); a turbofan blade (61) is rotatably arranged in the partition chamber (6); and the double-wall drill rod (2) is provided with a plurality of spacers (61) disposed in a plurality of spacers (61) disposed in a plurality of spacers (6). A connecting sleeve (62) is rotatably sleeved on the inner tube of the double-wall drill pipe (2); the turbofan blades (61) are fixed to the connecting sleeve (62), and one end of the connecting sleeve (62) is fixedly engaged with the shaft sleeve (55); an L-shaped channel is provided on the separation chamber (6) for sending the compressed air in the double-wall drill pipe (2) into the separation chamber (6); the end of the L-shaped channel is arranged tangentially to the rotation direction of the turbofan blades (61); the compressed air can drive the turbofan blades (61) to rotate, drive the connecting sleeve (62) to rotate, and thus drive the shaft sleeve (55) to rotate. Under the continuous rotation of the shaft sleeve (55), each cutter body (54) can intermittently converge to the center of the drill bit (3), thereby forming a cutoff of the coal sample transmission.

2. The adjustable drill bit suitable for positive and negative pressure combined sampling according to claim 1, characterized in that: The airflow component (4) comprises: a rotor shaft (41) arranged on the inner wall of a drill bit (3); a mounting groove is provided on the inner wall of the drill bit (3); the rotor shaft (41) can be relatively rotatably mounted in the mounting groove; a sealing ring is wound around the side wall of the rotor shaft (41) through a guide groove, and is used for sealing contact with the inner wall of the mounting groove; an airflow channel (42) is opened in the drill bit (3); a guide hole (43) is provided in the rotor shaft (41); the airflow channel (42) is communicated with the guide hole (43); and an air sleeve (44) is fixed outside the rotor shaft (41).

3. The adjustable drill bit suitable for positive and negative pressure combined sampling according to claim 2, characterized in that: The rotor shaft (41) is provided with an arc-shaped notch, and an inner lining member (31) perpendicular to the arc-shaped notch of the rotor shaft (41) is fixed on the inner wall of the drill bit (3) at the end of the air flow channel (42), one end of the inner lining member (31) is in sealing contact with the inner wall of the arc-shaped notch, and cooperates with the rotor shaft (41) to form an air pressure chamber (46), and an inner spring (45) is connected between the inner lining member (31) and the rotor shaft (41).

4. The adjustable drill bit suitable for positive and negative pressure combined sampling according to claim 3, characterized in that: The rotor shaft (41) is vertically aligned with the axis of the drill bit (3) in the absence of external force. When the air pressure in the air flow channel (42) is higher than 0.02 MPa, the inner spring (45) is elastically compressed, and the rotor shaft (41) deflects within a range of 0° to 50°.

5. The adjustable drill bit suitable for positive and negative pressure combined sampling according to claim 4, characterized in that: One or more of the rotor shafts (41) are turned toward a side close to the double-wall drill pipe (2), and the remaining rotor shafts (41) are deflected toward a side away from the double-wall drill pipe (2).

6. The adjustable drill bit suitable for positive and negative pressure combined sampling according to claim 1, characterized in that: The partition cavity (6) is also provided with a plurality of air flow holes (63) distributed circumferentially.

7. The adjustable drill bit suitable for positive and negative pressure combined sampling according to claim 2, characterized in that: The guide hole (43) is a V-shaped channel, and the V-shaped channel of the guide hole (43) is provided with an acute-angle channel and an obtuse-angle channel.

8. The adjustable drill bit suitable for positive and negative pressure combined sampling according to claim 1, characterized in that: The blocking mechanism (5) is arranged on the inner side of the air flow channel (42).

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