Mechanical multistage large-diameter hole-digging penetration device

Abstract

The application discloses a mechanical multistage large-diameter hole-digging and permeability-increasing device, which comprises a guiding mechanism, a cutting connecting rod mechanism and a rear joint which are sequentially connected in an axial direction; the guiding mechanism comprises a guiding pipe, and a guiding ball head is inserted into an axial front end of the guiding pipe; the cutting connecting rod mechanism comprises coaxially arranged inner and outer pipes, a first ring cavity is formed between the inner and outer pipes, and axial front ends of the inner and outer pipes are fixedly connected with a rear end of the guiding pipe; four-stage moving cutting mechanisms are arranged, the cutting radius of the moving cutting wings of the moving cutting mechanisms is gradually increased, the bending moment load borne by the moving cutting wings is dispersed, the problems of deformation and fracture of the moving cutting wings caused by large bending moment are effectively avoided, the purpose of large-diameter hole-digging and drilling is achieved, and the technical problem of limited hole-digging and drilling diameter in the prior art is solved.

Description

Technical Field

[0001] This invention belongs to the field of underground drilling technology in coal mines, and relates to a drilling device, specifically a mechanical multi-stage large-diameter drilling and permeability enhancement device. Background Technology

[0002] The technique of enlarging and hollowing out sections of cross-layer boreholes to enhance permeability is an effective method for solving the gas drainage problem in low-permeability coal seams. By selectively enlarging and hollowing out sections of the cross-layer borehole, the diameter of the gas drainage borehole is increased, making the coal seam more prone to collapse and destructive fractures. This increases the exposed area of ​​the coal seam and the range of pressure relief damage from the borehole, thereby improving gas drainage efficiency. The gas drainage effect is mainly affected by factors such as borehole diameter, drainage time, and sealing quality. The size of the pressure relief area around the borehole is directly proportional to the borehole diameter. When the borehole diameter increases to a certain extent, the pressure relief radius of the borehole can be greatly increased, expanding the exposed surface area of ​​the coal seam, thus increasing the permeability of the coal seam. Especially for low-permeability non-outburst coal seams and outburst coal seams after regional outburst mitigation measures have been implemented, the larger the diameter of the gas drainage borehole, the better the effect on improving coal seam permeability.

[0003] Currently, commonly used mechanical hole-cutting devices typically feature a single or symmetrical double cutter blade on the drill bit body, with gear and rack control for blade opening and closing. Because the cutter blades bear significant bending moments during hole-cutting operations, they are prone to deformation or even breakage, leading to difficulties in blade retraction or hole-cutting failure. To avoid these risks, short cutter blades are commonly used. By shortening the blades and reducing the lever arm length, bending moments are reduced, and the blades are actively protected. However, this results in limited hole-cutting diameter and only moderate improvement in coal seam permeability. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a mechanical multi-stage large-diameter hole-drilling and permeability-enhancing device to solve the technical problem of limited hole diameter in the existing technology.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A mechanical multi-stage large-diameter cavity-expanding and permeability-enhancing device includes a guide mechanism, a cutting linkage mechanism, and a rear connector connected sequentially along the axial direction;

[0007] The guiding mechanism includes a guide tube, and a guide ball head is inserted into the axial front end of the guide tube;

[0008] The cutting linkage mechanism includes an inner tube and an outer tube arranged coaxially, with a first annular cavity formed between the inner tube and the outer tube, and the axial front ends of the inner tube and the outer tube are fixedly connected to the rear end of the guide tube.

[0009] The cavity of the inner tube comprises a first cavity and a second cavity with different pore sizes, an annular groove is arranged on the axial rear end of the inner wall of the second cavity, and a snap spring is arranged in the annular groove; a piston structure is arranged in the second cavity on the axial front side of the snap spring, the piston structure comprises a piston rod, and the axial front end of the piston rod extends into the first cavity; a spring distributed in the axial direction is arranged in the second annular cavity between the piston rod and the inner wall of the inner tube; four first strip-shaped through holes distributed in the axial direction are arranged on the outer wall of the inner tube in the second cavity at equal intervals in the circumferential direction, the four first strip-shaped through holes are sequentially delayed in the axial direction on the outer wall of the inner tube, and a central through hole communicating the first cavity and the second cavity is arranged at the center of the end face of the piston rod; a first blind hole is further arranged on the outer wall of the inner tube on the axial front side of each first strip-shaped through hole, and a fixed block with a hole arranged in the axial direction at the center is fixedly installed in the first blind hole; a water eye communicating the first cavity and the first annular cavity is arranged on the outer wall of the inner tube in the first cavity,

[0010] Four moving cutting structures are arranged in the first annular cavity, and the four moving cutting structures correspond to the four first strip-shaped through holes in the axial and circumferential directions respectively; the moving cutting structure comprises an L-shaped moving guide rod extending into the first strip-shaped through hole and fixedly installed on the piston rod, one end of an L-shaped moving guide rod is arranged on the other end of the L-shaped moving guide rod and is hingedly connected with one end of a moving cutting wing, the other end of the moving cutting wing is hingedly connected with one end of a supporting rocker, and the other end of the supporting rocker is hingedly connected to the fixed block; PDC cutting teeth are arranged on the moving cutting wing and the supporting rocker;

[0011] The lengths of the four moving cutting wings increase, the lengths of the four supporting rockers increase, and the lengths of the four supporting rockers are greater than the lengths of the moving cutting wings in the corresponding moving cutting structures respectively;

[0012] The axial rear end of the outer tube is provided with a convex ring inward in the radial direction, four second strip-shaped through holes are arranged on the outer tube at equal intervals in the circumferential direction and are arranged in a staggered manner with the first strip-shaped through holes, and each second strip-shaped through hole is equidistant from the corresponding first strip-shaped through hole in the axial direction; the length of each second strip-shaped through hole is greater than the length of the supporting rocker in the corresponding moving cutting structure;

[0013] The center of the end face of the rear joint is provided with a water inlet hole communicating the second cavity and the outside.

[0014] The present application also comprises the following technical features:

[0015] Three annular grooves distributed at equal intervals in the axial direction are arranged at the contact position of the piston rod and the inner tube in the second cavity, and a sealing ring is arranged in the annular groove.

[0016] The three annular grooves form four protrusions, and each of the four protrusions is provided with a second blind hole, and the four second blind holes correspond to the four first strip-shaped through holes in the circumferential direction one by one, and one end of each of the four L-shaped moving guide rods is fixedly installed in the four second blind holes.

[0017] The outer wall of the inner tube on the axial rear side of the first strip-shaped through hole is provided with four protrusions at equal intervals in the circumferential direction; and the inner wall of the protruding ring is provided with four grooves matched with the protrusions.

[0018] The moving cutting wings are uniformly provided with complete PDC cutting teeth, and the supporting rocker arms are uniformly provided with half PDC cutting teeth. The guide ball head is provided with a first through cavity and a second through cavity with different hole diameters distributed in the axial direction at the radial center of the guide ball head, and the second through cavity is in communication with the guide tube.

[0019] The outer wall of the guide ball head is provided with two mutually perpendicular cutting alloys.

[0020] The outer wall of the guide tube is provided with a plurality of protrusions spirally distributed at equal intervals in the circumferential direction, and the protrusions are uniformly provided with a plurality of columnar gauge alloys.

[0021] The included angle between the four moving cutting wings after being opened and the inner tube in the axial direction is in the range of 70°-90°.

[0022] Compared with the prior art, the beneficial technical effects of the present application are:

[0023] (I) The four-stage moving cutting mechanism is provided, and the cutting radius of the moving cutting wings of each stage of the moving cutting mechanism is increased step by step, which helps to disperse the bending moment load received by each stage of the moving cutting wing, effectively avoids the problems of deformation and fracture of the moving cutting wing caused by bearing a large bending moment, realizes the purpose of large-diameter hole drilling, and solves the technical problem of limited hole drilling diameter in the prior art.

[0024] (II) The four-stage moving cutting wings in the present application are ladder-shaped hole drilling, which helps to release the coal seam stress step by step, reduces the disturbance to the coal body, and avoids the dynamic phenomenon of drill jamming and hole spraying. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a sectional view of the overall structure of the present application;

[0026] Figure 2 is a sectional view of the overall structure of the present application during operation

[0027] Figure 3 is a front view of the local structure of the present application;

[0028] Figure 4 A three-dimensional schematic view of the local structure of the present application;

[0029] Figure 5 A schematic view of the cutting link mechanism in the present application;

[0030] Figure 6 A schematic view of the cutting link mechanism in the present application; Figure 5 A sectional view of A-A in the present application;

[0031] Figure 7 A schematic view of the inner tube in the present application;

[0032] Figure 8 A sectional view of A-A in the present application; Figure 7 A sectional view of A-A in the present application;

[0033] Figure 9 A schematic view of the piston rod in the present application;

[0034] Figure 10 A schematic view of the moving cutting structure in the present application when retracted;

[0035] Figure 11 A schematic view of the moving cutting structure in the present application when extended;

[0036] Figure 12 A schematic view of the cutting link mechanism in the present application;

[0037] Figure 13 A sectional view of A-A in the present application; Figure 12 A sectional view of A-A in the present application.

[0038] Meaning of each reference numeral in the drawing: 1 - guide mechanism, 2 - cutting link mechanism, 3 - rear joint, 4 - water inlet hole;

[0039] 101 - guide tube, 102 - guide ball head;

[0040] 10101 - convex rib, 10102 - path-keeping alloy;

[0041] 10201 - first through cavity, 10202 - second through cavity, 10203 - cutting alloy;

[0042] 201 - inner tube, 202 - outer tube, 203 - first ring cavity, 204 - snap spring, 205 - piston structure, 206 - fixed block, 207 - moving cutting structure;

[0043] 20101 - first cavity, 20102 - second cavity, 20103 - first ring groove, 20104 - first strip-shaped through hole, 20105 - first blind hole, 20106 - water eye, 20107 - convex block;

[0044] 20201 - convex ring, 20202 - second bar-shaped through hole, 20203 - groove;

[0045] 20501 - piston rod, 20502 - second ring cavity, 20503 - spring, 20504 - second ring groove, 20506 - sealing ring, 20507 - protrusion, 20508 - second blind hole, 20509 - central through hole;

[0046] 20701 - L-shaped moving guide rod, 20702 - moving cutting wing, 20703 - supporting rocker, 20704 - PDC cutting tooth.

[0047] The specific content of the present application is further explained in detail in combination with the following embodiments. DETAILED DESCRIPTION

[0048] It should be noted that all parts in the present application, in the absence of special instructions, adopt parts known in the art.

[0049] The following gives specific embodiments of the present application, it should be noted that the present application is not limited to the following specific embodiments, any equivalent transformation made on the basis of the technical solutions of the present application falls within the protection scope of the present application.

[0050] The present application gives a mechanical multi-stage large-diameter hole-digging and permeability-increasing device, as shown in Figures 1 to 13 The device comprises a guide mechanism 1, a cutting connecting rod mechanism 2 and a rear joint 3 connected in sequence along the axial direction.

[0051] The guide mechanism 1 comprises a guide pipe 101, and a guide ball head 102 is inserted into the axial front end of the guide pipe 101.

[0052] The cutting connecting rod mechanism 2 comprises an inner pipe 201 and an outer pipe 202 coaxially arranged, and a first ring cavity 203 is formed between the inner pipe 201 and the outer pipe 202.

[0053] The cavity of the inner tube 201 comprises a first cavity 20101 and a second cavity 20102 with different hole diameters, a first ring groove 20103 is arranged at the axial rear end of the inner wall of the second cavity 20102, and a snap spring 204 is arranged in the first ring groove 20103; a piston structure 205 is arranged in the second cavity 20102 at the axial front side of the snap spring 204, the piston structure 205 comprises a piston rod 20501, the axial front end of the piston rod 20501 extends into the first cavity 20101; a spring 20503 distributed in the axial direction is arranged in a second ring cavity 20502 between the piston rod 20501 and the inner wall of the inner tube 201, a central through hole 20509 communicating the first cavity 20101 and the second cavity 20102 is arranged at the center of the end face of the piston rod 20501; four first strip-shaped through holes 20104 distributed in the axial direction are equidistantly arranged on the outer wall of the inner tube 201 in the circumferential direction, and the four first strip-shaped through holes 20104 are sequentially delayed in the axial direction on the outer wall of the inner tube 201; a first blind hole 20105 is further arranged on the outer wall of the inner tube 201 at the axial front side of each first strip-shaped through hole 20104, and a fixed block 206 with a hole arranged at the center in the axial direction is fixedly installed in the first blind hole 20105; a water eye 20106 communicating the first cavity 20101 and the first ring cavity 203 is arranged on the outer wall of the inner tube 201 where the first cavity 20101 is located;

[0054] Four moving cutting structures 207 are arranged in the first ring cavity 203, and the four moving cutting structures 207 correspond to the four first strip-shaped through holes 20104 in the axial and circumferential directions; the moving cutting structure 207 comprises an L-shaped moving guide rod 20701 extending into the first strip-shaped through hole 20104 and fixedly installed on the piston rod 20501, the other end of the L-shaped moving guide rod 20701 penetrates the fixed block 206 and is hingedly connected with one end of a moving cutting wing 20702, the other end of the moving cutting wing 20702 is hingedly connected with one end of a supporting rocker 20703, and the other end of the supporting rocker 20703 is hingedly connected to the fixed block 206; PDC cutting teeth 20704 are arranged on the moving cutting wing 20702 and the supporting rocker 20703;

[0055] The lengths of the four moving cutting wings 20702 increase, the lengths of the four supporting rockers 20703 increase, and the lengths of the four supporting rockers 20703 are greater than the lengths of the moving cutting wings 20702 in the corresponding moving cutting structures 207, respectively;

[0056] The outer tube 202 has a radially inwardly convex ring 20201 at its axial rear end. The outer tube 202 has four second strip-shaped through holes 20202 that are circumferentially staggered with the first strip-shaped through hole 20104. Each second strip-shaped through hole 20202 is equidistant from its corresponding first strip-shaped through hole 20104 in the axial direction. The length of each second strip-shaped through hole 20202 is greater than the length of the support rocker arm 20703 in its corresponding moving cutting structure 207.

[0057] A water inlet hole 4 is provided at the center of the end face of the rear connector 3, which connects the second cavity 20102 and the outside.

[0058] In the above technical solution, when the mechanical multi-stage large-diameter hole-expanding and permeability-enhancing device is delivered to the coal seam section requiring hole expansion and hole excavation, high-pressure water is first introduced into the water inlet hole, pushing the piston rod 20501 to move axially forward and compressing the spring 20503. This causes the four L-shaped moving guide rods 20701 fixed on the piston rod 20501 to move axially forward along the first strip-shaped through hole 20104 until one end of the L-shaped moving guide rod 20701 reaches the inner wall of the axial front end of the first strip-shaped through hole 20104, at which point the movement stops. At this time, the piston rod 20501 also stops moving. During the entire movement process, the four L-shaped moving guide rods 20701 move the same distance. .

[0059] Simultaneously, as the four L-shaped movable guide rods 20701 move, the four movable cutting wings 20702 slowly open radially, passing through the second strip-shaped through hole 20202 on the outer tube 202 until the limit state, to carry out the staged hole expansion and cavitation operation.

[0060] At this time, the high-pressure water pushes the piston rod 20501 to compress the spring 20503, and sprays out from the water eye 20106 on the inner tube 201 through the central through hole 20509 of the piston rod 20501, washing the four moving cutting structures 207 and carrying coal powder out of the hole.

[0061] By setting up a four-stage moving cutting structure 207, the cutting radius of the moving cutting wings 20702 of each stage of the moving cutting structure 207 increases progressively, which helps to disperse the bending moment load on each stage of the moving cutting wings 20702. This effectively avoids problems such as deformation and fracture of the moving cutting wings 20702 due to large bending moments, and achieves the purpose of large-diameter hole drilling, solving the technical problem of limited hole drilling diameter in the prior art.

[0062] In the above technical solution, the selection method for spring 20503 is as follows:

[0063] Assuming in Within a time period, there is a mass of The water jet impacts and pushes the piston rod 20501, causing the water jet, piston rod 20501, and moving cutting structure 207 to move at the same speed. Simultaneously, the compression spring 20503 is moved axially forward, and the mass of the water column... for:

[0064] (1)

[0065] In the formula:

[0066] The mass of the water column is expressed in kg.

[0067] The final velocity of the water column before it impacts the piston rod is in m / s;

[0068] The density of water is kg / m³. 3 ;

[0069] The duration of action is measured in seconds (s).

[0070] Let be the cross-sectional area of ​​the water column, in m². It can be represented as:

[0071] (2)

[0072] In the formula:

[0073] The outer diameter of the axial rear end face of piston rod 20501 is in meters (m).

[0074] The diameter of the central through hole 20509 inside the piston rod 20501 is in meters (m).

[0075] The final velocity of the water jet impacting the piston It can be represented as:

[0076] (3)

[0077] In the formula:

[0078] m is the flow rate of water. 3 / s.

[0079] According to the principle of conservation of momentum, we have:

[0080] (4)

[0081] In the formula:

[0082] The total weight of piston rod 20501 and moving cutting structure 207 is in kg;

[0083] Let be the moving speed of the piston rod after the impact, in m / s;

[0084] Taking the water column as the object of study, according to the momentum theorem, we have:

[0085] (5)

[0086] In the formula: Let N be the impact force of the water column on the piston rod.

[0087] According to equations (1) to (5), the impact force of the water column on the piston rod can be obtained. for:

[0088] (6)

[0089] The elastic force experienced by the spring 20503 during deformation is... According to Hooke's Law, we have:

[0090] (7)

[0091] In the formula:

[0092] The spring constant of spring 20503;

[0093] The compression displacement of spring 20503 is the limit displacement of the L-shaped moving guide rod moving towards the axial front end, in meters.

[0094] according to and This allows us to determine the spring constant of spring 20503, thus enabling us to select the appropriate spring type.

[0095] Among them, the compression displacement of spring 20503 The calculation method is as follows:

[0096] like Figure 10 As shown, in the initial state, the distance between the axial rear end of the L-shaped moving guide rod 20701 and the rivet hole of the fixing block 206 is... The distance between the rivet hole at one end of the moving cutting wing 20702 and the rivet hole of the fixing block 206 .like Figure 11 As shown, when the movable cutting wing 20702 is opened to its limit, the distance between the rivet holes at both ends of the L-shaped movable guide rod 20701 is... The distance between the rivet holes at both ends of the moving cutting wing 20702 The distance between the rivet holes at both ends of the support rocker arm 20703 To ensure the normal operation of the moving cutting structure 207, the following requirements must be met. At this time, the opening angle of the moving cutting blade 20702 is:

[0097] (8)

[0098] To ensure the optimal working condition of the moving cutting blade 20702, It should meet the following requirements:

[0099] (9)

[0100] That is, when the L-shaped moving guide rod 20701 moves a distance axially to the rear end... At that time, the opening angle of the moving cutting blade 20702 It should be between 70° and 90°.

[0101] According to equations (8) and (9), the distance between the rivet holes at both ends of the L-shaped moving guide rod 20701 in the extreme state of the moving cutting wing 20702 being open is:

[0102] (10)

[0103] Therefore, under the action of high-pressure water, the distance that the L-shaped moving guide rod 20701 moves is:

[0104] (11)

[0105] According to formulas (9) to (11), the distance that the L-shaped moving guide rod 20701 moves can be calculated. That is, the compression displacement of spring 20503 Substituting it into formulas (6) to (7), the spring constant of spring 20503 can be obtained, thereby assisting in the selection of spring 20503.

[0106] Specifically, three second annular grooves 20504 are provided at the contact point between the piston rod 20501 and the inner tube 201 where the second cavity 20102 is located. A sealing ring 20506 is provided in the second annular groove 20504 to prevent liquid from entering the second annular cavity 20502 between the piston rod 20501 and the wall of the inner tube 201.

[0107] Specifically, the three second annular grooves 20504 form four protrusions 20507, and each of the four protrusions 20507 is provided with a second blind hole 20508. The four second blind holes 20508 correspond one-to-one with the four first strip-shaped through holes 20104 in the circumferential direction. One end of each of the four second blind holes 20508 is fixedly installed in the corresponding hole.

[0108] Specifically, four protrusions 20107 are provided at equal intervals along the circumference on the outer wall of the inner tube 201 on the axial rear side of the first strip-shaped through hole 20104; four grooves 20203 are provided on the inner wall of the convex ring 20201 to cooperate with the protrusions 20107, so that the protrusions 20107 of the inner tube 201 and the grooves 20203 of the outer tube 202 can mesh with each other, further ensuring that the torque on the outer tube 202 is transmitted to the inner tube 201 during the hole-making process.

[0109] Specifically, the movable cutting wing 20702 is uniformly provided with complete PDC cutting teeth 20704, and the support rocker arm 20703 is uniformly provided with half of the PDC cutting teeth 20704, which is used to prevent coal powder from hindering the recovery of the movable cutting wing.

[0110] Specifically, the guide ball head 102 has a first cavity 10201 and a second cavity 10202 with different diameters distributed sequentially along the axial direction at its radial center. The second cavity 10202 is connected to the guide tube 101.

[0111] Specifically, the outer wall of the guide ball head 102 is provided with two mutually perpendicular cutting alloys 10203 to ensure that the guide ball head 102 is well guided into the collapsed hole, and also has an auxiliary cutting function.

[0112] Specifically, the outer wall of the guide tube 101 has multiple convex ribs 10101 that are equally spaced and spirally distributed along the circumference. Multiple columnar gauge-maintaining alloys 10102 are evenly distributed on the convex ribs 10101, which can effectively prevent the hole deviation caused by the large accumulation of rock powder at the front end of the drill bit, and also have an auxiliary gauge-maintaining function.

[0113] Specifically, the angle between the four movable cutting wings 20702 and the axial direction of the inner tube 201 after opening is all within the range of 70°~90°.

Claims

1. A mechanical multi-stage large-diameter cavity-digging permeability enhancement device, characterized in that, It includes a guide mechanism (1), a cutting linkage mechanism (2), and a rear connector (3) that are connected sequentially along the axial direction. The guiding mechanism (1) includes a guide tube (101), and a guide ball head (102) is inserted into the axial front end of the guide tube (101). The cutting linkage mechanism (2) includes an inner tube (201) and an outer tube (202) arranged coaxially, and a first annular cavity (203) is formed between the inner tube (201) and the outer tube (202). The axial front ends of the inner tube (201) and the outer tube (202) are fixedly connected to the rear end of the guide tube (101). The inner tube (201) has a cavity comprising a first cavity (20101) and a second cavity (20102) with different apertures. A first annular groove (20103) is formed at the axial rear end of the inner wall of the second cavity (20102), and a retaining ring (204) is provided in the first annular groove (20103). A piston structure (205) is provided in the second cavity (20102) axially forward of the retaining ring (204). The piston structure (205) includes a piston rod (20501), the axial front end of which extends into the first cavity (20101). A spring (20503) is provided in the second annular cavity (20502) between the piston rod (20501) and the inner wall of the inner tube (201). A spring (20503) distributed axially is provided in the second annular cavity (20502) between the piston rod (20501) and the inner wall of the inner tube (201). A connection to the first cavity is formed at the center of the end face of the piston rod (20501). The body (20101) and the second cavity (20102) have a central through hole (20509); four first strip-shaped through holes (20104) are equally spaced along the circumference on the outer wall of the inner tube (201) where the second cavity (20102) is located, and the four first strip-shaped through holes (20104) are sequentially extended along the axial direction on the outer wall of the inner tube (201); a first blind hole (20105) is also opened on the outer wall of the inner tube (201) on the axial front side of each of the first strip-shaped through holes (20104), and a fixing block (206) with a hole in the center along the axial direction is fixedly installed in each of the first blind holes (20105); a water eye (20106) connecting the first cavity (20101) and the first annular cavity (203) is opened on the outer wall of the inner tube (201) where the first cavity (20101) is located. The first annular cavity (203) is provided with four movable cutting structures (207), which correspond to four first strip-shaped through holes (20104) in the axial and circumferential directions, respectively. Each movable cutting structure (207) includes an L-shaped movable guide rod (20701) with one end extending into the first strip-shaped through hole (20104) and fixedly mounted on the piston rod (20501). The other end of the L-shaped movable guide rod (20701) passes through the fixed block (206) and is hinged to one end of a movable cutting wing (20702). The other end of the movable cutting wing (20702) is hinged to one end of a support rocker arm (20703), and the other end of the support rocker arm (20703) is hinged to the fixed block (206). Both the movable cutting wing (20702) and the support rocker arm (20703) are provided with PDC cutting teeth (20704). The lengths of the four movable cutting wings (20702) increase progressively, the lengths of the four supporting rockers (20703) increase progressively, and the lengths of the four supporting rockers (20703) are respectively greater than the lengths of the movable cutting wings (20702) in the corresponding movable cutting structure (207); The outer tube (202) has a radially inwardly convex ring (20201) at its axial rear end. The outer tube (202) has four second strip-shaped through holes (20202) that are circumferentially staggered with the first strip-shaped through hole (20104). Each second strip-shaped through hole (20202) is equidistant from its corresponding first strip-shaped through hole (20104) in the axial direction. The length of each second strip-shaped through hole (20202) is greater than the length of the support rocker arm (20703) in its corresponding moving cutting structure (207). The rear connector (3) has a water inlet (4) at the center of its end face that connects the second cavity (20102) and the outside.

2. The mechanical multi-stage large-diameter cavity-digging permeability enhancement device as described in claim 1, characterized in that, The piston rod (20501) and the inner tube (201) where the second cavity (20102) is located are provided with three second annular grooves (20504) that are equally spaced along the axial direction, and a sealing ring (20506) is provided in the second annular groove (20504).

3. The mechanical multi-stage large-diameter cavity-expanding permeability enhancement device as described in claim 2, characterized in that, The three second annular grooves (20504) form four protrusions (20507), and each of the four protrusions (20507) is provided with a second blind hole (20508). The four second blind holes (20508) correspond one-to-one with the four first strip-shaped through holes (20104) in the circumferential direction. One end of each of the four second blind holes (20508) is fixedly installed in the corresponding hole.

4. The mechanical multi-stage large-diameter cavity-expanding and permeability-enhancing device as described in claim 1, characterized in that, The outer wall of the inner tube (201) on the axial rear side of the first strip-shaped through hole (20104) is provided with four protrusions (20107) at equal intervals along the circumference; the inner wall of the convex ring (20201) is provided with four grooves (20203) that cooperate with the protrusions (20107).

5. The mechanical multi-stage large-diameter cavity-digging permeability enhancement device as described in claim 1, characterized in that, The movable cutting wing (20702) is uniformly provided with complete PDC cutting teeth (20704), and the support rocker (20703) is uniformly provided with half of the PDC cutting teeth (20704).

6. The mechanical multi-stage large-diameter cavity-digging permeability enhancement device as described in claim 1, characterized in that, The guide ball head (102) has a first cavity (10201) and a second cavity (10202) with different diameters distributed sequentially along the axial direction at its radial center. The second cavity (10202) is connected to the guide tube (101).

7. The mechanical multi-stage large-diameter cavity-expanding and permeability-enhancing device as described in claim 1, characterized in that, The outer wall of the guide ball head (102) is provided with two mutually perpendicular cutting alloys (10203).

8. The mechanical multi-stage large-diameter cavity-expanding and permeability-enhancing device as described in claim 1, characterized in that, The outer wall of the guide tube (101) has multiple convex ridges (10101) that are equally spaced and spirally distributed along the circumference, and multiple columnar diameter-maintaining alloys (10102) are evenly distributed on the convex ridges (10101).

9. The mechanical multi-stage large-diameter cavity-expanding and permeability-enhancing device as described in claim 1, characterized in that, The angle between the four movable cutting wings (20702) and the axial direction of the inner tube (201) after opening is in the range of 70°~90°.

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