Large-diameter pneumatic reverse circulation reaming down-the-hole hammer

Abstract

The invention relates to a large-diameter pneumatic reverse circulation reaming down-the-hole hammer, which belongs to the technical field of geotechnical engineering drilling equipment and comprises a centralizing joint, a check valve, an air distribution seat, an outer cylinder, an inner cylinder, an adapter pipe, a collecting pipe, a piston, a lining, a clamping and nesting sleeve, a drill bit and a wear-resistant sleeve. The centralizing connector and the clamping and nesting sleeve are fixed to the two ends of the outer cylinder respectively, the drill bit is fixed in the clamping and nesting sleeve, the clamping and nesting sleeve is sleeved with the abrasion-resistant sleeve, and the check valve, the air distribution seat, the inner cylinder, the piston and the lining are sequentially arranged in the outer cylinder. The adapter pipe penetrates through the centralizing connector, the collecting pipe penetrates through the air distribution seat and the piston, one end of the collecting pipe is communicated with the adapter pipe, and the other end of the collecting pipe is communicated with a discharging hole in the drill bit. The abrasion-resistant sleeve is arranged, the outer edge of the abrasion-resistant sleeve is attached to the inner wall of the drill hole, a gap between the drill bit and the hole wall is effectively isolated, abnormal abrasion of the drill bit is greatly reduced, and the service life of the drill bit is prolonged.

Description

Technical Field

[0001] This application relates to the technical field of drilling equipment for geotechnical engineering, and in particular to a large-diameter pneumatic reverse circulation down-the-hole hammer for hole reaming. Background Technology

[0002] The reverse circulation down-the-hole hammer is a high-efficiency rock and soil drilling equipment that integrates impact crushing and reverse circulation slag removal. It is widely used in geotechnical engineering exploration, mining, pile foundation construction, geothermal drilling and other fields, and is especially suitable for drilling operations in complex strata such as hard rock and gravel layers.

[0003] In existing reverse circulation down-the-hole hammer drills used for large-diameter drilling, gaps easily form between the borehole wall and the drill bit due to the large borehole diameter. When rock cuttings enter these gaps, the rotating drill bit experiences significant friction with the cuttings. Rock cuttings with sharp edges can scratch the drill bit's sidewalls, affecting the overall stress distribution. This not only increases wear on the drill bit's sidewalls but also affects its normal operating condition, thus reducing its service life.

[0004] Therefore, there is an urgent need for a new large-diameter reverse circulation down-the-hole hammer. Summary of the Invention

[0005] To address the problem that existing down-the-hole hammers tend to have a short lifespan when drilling large-diameter holes, this application provides a large-diameter pneumatic reverse circulation down-the-hole hammer for reaming.

[0006] This application provides a large-diameter pneumatic reverse circulation down-the-hole hammer for hole reaming, which adopts the following technical solution: A large-diameter pneumatic reverse circulation down-the-hole hammer includes: a centralizing connector, a check valve, a valve seat, an outer cylinder, an inner cylinder, an adapter tube, a collection tube, a piston, a bushing, a retaining clip, a drill bit, and a wear-resistant sleeve. The centralizing connector has a first end connected to an external drilling rig, and a second end inserted into and connected to the outer cylinder. The centralizing connector has a first through hole, the adapter tube passes through the first through hole, the check valve is located within the first through hole and sleeved outside the adapter tube, and the check valve can block the first through hole after movement. The valve seat is located inside the outer cylinder and contacts the second end of the adapter tube. The inner cylinder passes through the outer cylinder, with its first end abutting the second end of the centralizing connector. The inner cylinder is sleeved outside the valve seat, and a first gap exists between a portion of the outer edge of the inner cylinder and the inner wall of the outer cylinder. The piston is slidably disposed within the outer cylinder. A second gap exists between the inner cylinder and the outer cylinder. The bushing passes through the outer cylinder. The locking sleeve is fitted onto the drill bit. The locking sleeve passes through the second end of the outer cylinder. The piston reciprocates between the first end of the drill bit and the second end of the air distribution seat. A discharge hole is provided on the drill bit. The collection tube is located inside the outer cylinder and passes through the piston and the air distribution seat. A third gap exists between the piston and the collection tube. The two ends of the collection tube are respectively connected to the discharge hole and the adapter tube. The wear-resistant sleeve is fitted onto the outside of the locking sleeve and its outer edge is attached to the inner wall of the borehole. A rear air chamber is formed between the inner cylinder, the air distribution seat, the piston, the drill bit, and the collection tube. A front air chamber is formed between the outer cylinder, the piston, and the bushing. An exhaust channel is provided on the locking sleeve. The exhaust channel is connected to the front air chamber. After the high-pressure gas flows out from the exhaust channel, it carries rock cuttings into the discharge hole.

[0007] By adopting the above technical solution, and by setting a wear-resistant sleeve and having its outer edge fit against the inner wall of the borehole, the annular gap between the borehole and the down-the-hole hammer can be effectively sealed, preventing rock cuttings from entering the gap and causing wear on the drill bit sidewall. At the same time, the reverse circulation airflow enters the borehole space through the exhaust channel and carries rock cuttings out through the discharge hole, collection pipe and adapter pipe, realizing real-time cleaning of the area around the drill bit during drilling, reducing wear of the drill bit by rock cuttings, and thus significantly improving the service life and working stability of the drill bit in large-diameter boreholes.

[0008] Optionally, a retaining ring is also included, which is sleeved on the drill bit and passes through the retaining nest, with the first end of the retaining ring contacting the second end of the bushing.

[0009] By adopting the above technical solution and setting a retaining ring, the sealing performance and structural stability between the retaining ring and the bushing can be further enhanced, gas leakage can be prevented, and the installation and positioning accuracy of the drill bit can be improved.

[0010] Optionally, a check spring is also included, which is sleeved on the outside of the adapter tube, with a first end of the check spring contacting the check valve and a second end of the check spring contacting the gas distribution seat.

[0011] By adopting the above technical solution, the setting of the check spring can automatically control the opening and closing of the check valve, ensure the unidirectional flow of high-pressure gas, and prevent rock cuttings or mud from flowing back into the gas circuit system.

[0012] Optionally, a washer is also included, which is located between the straightening connector and the outer cylinder, and also between the outer cylinder and the locking nest.

[0013] By adopting the above technical solution, the gasket can improve the connection stability between the straightening joint and the outer cylinder, and between the outer cylinder and the clip, and also improve the durability and sealing performance of the connection.

[0014] Optionally, the outer surface of the piston contacts a portion of the inner surface of the bushing and a portion of the inner surface of the inner cylinder.

[0015] By adopting the above technical solution, the piston maintains contact with the bushing and the inner cylinder respectively, which can improve the guiding accuracy and sealing of the piston movement, and enhance the impact efficiency and working stability.

[0016] Optionally, the straightening connector and the outer cylinder are connected by a thread, and the snap-fit ​​fitting and the outer cylinder are connected by a thread.

[0017] By adopting the above technical solution and using a threaded connection, the assembly and disassembly of the down-the-hole hammer are facilitated, improving maintenance and replacement efficiency. At the same time, the structure is compact and the connection is firm.

[0018] Optionally, a disc spring is also included, which is located between the inner cylinder and the centering joint.

[0019] By adopting the above technical solution, the disc spring can provide elastic preload between the inner cylinder and the centering joint, absorb vibration and shock, prevent the threads from loosening, and avoid wear caused by direct contact between the inner cylinder and the centering joint.

[0020] Optionally, the internal bore of the piston is a stepped bore, with the larger diameter of the stepped bore facing the valve seat and the smaller diameter of the stepped bore facing the drill bit.

[0021] By adopting the above technical solution, the piston's internal stepped hole structure can optimize the airflow channel, improve gas flow efficiency, and enhance the piston's motion response speed and impact force transmission effect.

[0022] Optionally, the discharge hole includes a small discharge hole and a large discharge hole. There are multiple small discharge holes, all of which are connected to the large discharge hole. The large discharge hole is connected to the collection tube, and the inlet end of the small discharge hole is connected to the surface of the drill bit.

[0023] By adopting the above technical solution, the discharge hole is composed of a combination of discharge small holes and discharge perforations, and there are multiple discharge small holes, which can expand the rock cuttings collection range, improve the slag discharge efficiency, prevent blockage, and ensure smooth reverse circulation.

[0024] Optionally, the inner diameter of the collection tube is the same as the inner diameter of the adapter tube.

[0025] By adopting the above technical solution, the inner diameter of the collection tube and the adapter tube are consistent, which can ensure the continuity and smoothness of the airflow and rock cuttings transport channel, reduce resistance loss, and improve reverse circulation efficiency.

[0026] In summary, this application includes at least one of the following beneficial technical effects: By setting a wear-resistant sleeve and fitting its outer edge to the inner wall of the borehole, the gap between the drill bit and the borehole wall is effectively isolated, preventing rock cuttings from entering and abrading the drill bit sidewall. At the same time, airflow flows into the drilling space formed between the wear-resistant sleeve and the borehole wall, and blows the rock cuttings in the drilling space into the collection tube and adapter tube, clearing the rock cuttings around the drill bit in real time, greatly reducing abnormal wear of the drill bit and extending its service life.

[0027] The high-frequency impact drill bit, which uses alternating front and rear air chambers to drive the piston, delivers impact force directly and has high energy utilization. In addition, the high-pressure airflow enters the drilling space through the exhaust channel, carrying rock cuttings and discharging them in real time through the discharge hole and collection pipe inside the drill bit, which significantly improves the drilling efficiency and hole formation speed of large-diameter hard rock formations.

[0028] The connection parts adopt threaded fit and elastic seals (such as gaskets, disc springs, O-rings, etc.), which ensures air circuit sealing and prevents pressure leakage, while also having good vibration resistance and buffering performance; the overall modular design supports quick assembly and disassembly, facilitates on-site replacement of vulnerable parts, reduces maintenance costs, and improves equipment applicability and engineering practicality. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a large-diameter pneumatic reverse circulation hole-reaming down-the-hole hammer provided in this application; Figure 2 yes Figure 1 A schematic diagram of a portion of the structure; Figure 3 yes Figure 1 A schematic diagram of another part of the structure.

[0030] In the diagram, 1. Straightening connector; 2. Check valve; 3. Gas distribution seat; 4. Outer cylinder; 5. Inner cylinder; 6. Adapter tube; 7. Collection tube; 8. Piston; 9. Bushing; 10. Snap ring; 11. Drill bit; 12. Wear-resistant sleeve; 13. Snap ring; 14. Check spring; 15. Washer; 16. Disc spring; 17. Snap ring; 18. O-ring. Detailed Implementation

[0031] The following is in conjunction with the appendix Figures 1-3 This application will be described in further detail.

[0032] This application discloses a large-diameter pneumatic reverse circulation down-the-hole hammer for expanding boreholes.

[0033] refer to Figure 1 A large-diameter pneumatic reverse circulation borehole reamer / down-the-hole hammer includes a straightening connector 1, a check valve 2, an air distribution seat 3, an outer cylinder 4, an inner cylinder 5, an adapter tube 6, a collection tube 7, a piston 8, a bushing 9, a retaining clip 10, a drill bit 11, and a wear-resistant sleeve 12.

[0034] refer to Figure 2 and Figure 3 The outer cylinder 4 has a first end connected to a centering connector 1 and a second end connected to a retaining clip 10. The outer diameter of the outer cylinder 4 is the same as that of the centering connector 1. The drill bit 11 is inserted into the retaining clip 10. A wear-resistant sleeve 12 is fitted onto the outside of the retaining clip 10. The outer diameter of the wear-resistant sleeve 12 is larger than that of the retaining clip 10 and the outer diameter of the outer cylinder 4. The outer edge of the wear-resistant sleeve 12 fits against the inner wall of the borehole, forming a certain seal between the wear-resistant sleeve 12 and the inner wall of the borehole. This prevents gas inside the down-the-hole hammer from flowing away along the gap between the down-the-hole hammer and the borehole, reducing the effectiveness of cuttings removal. The wear-resistant sleeve 12 is usually made of wear-resistant metal. The card nest 10 is equipped with an exhaust channel, which can blow the gas of the down-the-hole hammer into the drilling space between the card nest 10 and the inner wall of the borehole. Since rock cuttings will be generated in the drilling space, and the discharge hole on the drill bit 11 is connected to the drilling space, the rock cuttings will enter the discharge hole in the flow of gas, and finally flow to the outside through the collection pipe 7 and the adapter pipe 6.

[0035] The inner cylinder 5 is inserted inside the outer cylinder 4. One end of the inner cylinder 5 abuts against the straightening connector 1, and the other end abuts against the inner wall of the outer cylinder 4. When the straightening connector 1 is installed on the outer cylinder 4, the straightening connector 1 can hold the inner cylinder 5 in place, thereby fixing the inner cylinder 5 in the direction of the downhole hammer axis.

[0036] refer to Figure 1The straightening connector 1 has a first through hole. Part of the adapter tube 6 passes through the first through hole of the straightening connector 1, and the other part passes through the outer cylinder 4. The collection tube 7 is located inside the outer cylinder 4, and the end of the collection tube 7 passes into the interior of the adapter tube 6. The inner diameter of the collection tube 7 is the same as the inner diameter of the adapter tube 6. The check valve 2 is sleeved on the outside of the adapter tube 6 and located in the first through hole. The gas distribution seat 3 has a second through hole and is sleeved on the outside of the collection tube 7. A sealing protrusion is provided inside the first through hole. The check valve 2 abuts against the sealing protrusion. At the same time, the check spring 14 is located between the check valve 2 and the gas distribution seat 3. Since there is a corresponding air passage between the adapter tube 6 and the first through hole, when external pressurized gas enters the air passage formed between the inner wall of the adapter tube 6 and the first through hole, the gas will push the check valve 2, and the check spring 14 will be squeezed. The check valve 2 will separate from the sealing protrusion in the first through hole, so that the check valve 2 can avoid the pressurized gas.

[0037] refer to Figure 1 The corresponding valve seat 3 is also provided with a valve passage, and the inner cylinder 5 is provided with an inner passage. The air passage formed between the valve passage and the inner passage connects to the first gap between the inner cylinder 5 and the outer cylinder 4.

[0038] refer to Figure 2 and Figure 3 The piston 8 is sleeved outside the collection tube 7, and there is a third gap between the piston 8 and the collection tube 7, which reduces the frictional force on the reciprocating movement of the piston 8. The piston 8 is located inside the outer cylinder 4, and there is a second gap between the piston 8 and the outer cylinder 4. When the piston 8 moves to the left, it will hit the inner cylinder 5, and when it moves to the right, it will hit the end of the drill bit 11.

[0039] refer to Figure 3 The bushing 9 is inserted into the outer cylinder 4, with its left end abutting against the protrusion on the inner wall of the outer cylinder 4, and its right end contacting the retaining clip 10. First, the bushing 9 is inserted into the right end of the outer cylinder 4, and then the retaining clip 10 is installed. When the retaining clip 10 is in place, the bushing 9 is compressed. When the retaining clip 10 can no longer move, the position of the drill bit 11 can be locked through the positioning function of the bushing 9. In addition, the bushing 9 also serves a sealing function. When the piston 8 contacts the drill bit 11, a portion of the left end of the bushing 9 contacts the outer wall of the piston 8, thus forming a front air chamber between the bushing 9 and the piston 8. External gas enters the front air chamber first, and then the piston 8 is pushed by the gas, causing the piston 8 to move to the left. Once the piston 8 moves to the left, some gas flows into the drilling space through the air passage between the bushing 9 and the drill bit 11.

[0040] The external pipe is divided into an inner pipe and an outer pipe. The outer pipe is connected to the straightening connector 1, and the inner pipe is connected to the end of the adapter pipe 6. High-pressure gas flows into the downhole hammer between the outer pipe and the inner pipe, and after circulating in the drilling space, it flows into the collection pipe 7, the adapter pipe 6 and the inner pipe.

[0041] refer to Figure 3 The discharge holes of the drill bit 11 are a small discharge hole and a large discharge hole. The left end of the large discharge hole is connected to the collection tube 7. There are multiple small discharge holes that are not connected to the drilling space outside the drill bit 11.

[0042] It should be noted that, in order to allow gas to pass smoothly through the second gap between the piston 8 and the outer cylinder 4, and to allow gas to pass smoothly through the first gap between the inner cylinder 5 and the outer cylinder 4, corresponding grooves or protrusions are formed on the inner wall of the outer cylinder 4, the outer wall of the piston 8, or the outer wall of the inner cylinder 5, to achieve connectivity or closure of the first or second gap when necessary. In other words, the first and second gaps can be in a connected state or a closed state.

[0043] refer to Figure 2 and Figure 3 A rear air chamber is formed between the air distribution seat 3, inner cylinder 5, piston 8, and collection pipe 7, while a front air chamber is formed between piston 8, outer cylinder 4, and bushing 9. Pressurized gas first enters the front air chamber, and then piston 8 moves to the left, splitting the gas into two parts: one part enters the rear air chamber, and the other part enters the drilling space. The gas entering the rear air chamber pushes piston 8 to impact drill bit 11, while the gas entering the drilling space carries rock cuttings into the discharge hole, collection pipe 7, and adapter pipe 6. When piston 8 moves to the right, the rear air chamber is blocked, and a closed front air chamber is formed between piston 8 and bushing 9, pushing piston 8 to the left again. During the reciprocating movement of piston 8, drill bit 11 is continuously impacted by piston 8. From the outside of the down-the-hole hammer, the down-the-hole hammer continuously vibrates at a high frequency, which, combined with the low-speed rotation of the down-the-hole hammer, enables efficient drilling.

[0044] To enable quick and easy installation and disassembly of the down-the-hole hammer, the straightening connector 1 and the outer cylinder 4 are connected by threads, as are the retaining clip 10 and the outer cylinder 4. Furthermore, to improve the reliability of the threaded connections, washers 15 (or gaskets) are placed between the straightening connector 1 and the outer cylinder 4, and also between the outer cylinder 4 and the retaining clip 10, in order to facilitate the installation and disassembly of the down-the-hole hammer.

[0045] Since the inner cylinder 5 needs to be fixed by the straightening connector 1, a disc spring 16 is installed between the ends of the inner cylinder 5 and the straightening connector 1 to avoid wear between them. The disc spring 16 has a certain elasticity, which allows for indirect contact between the inner cylinder 5 and the straightening connector 1, and also allows the straightening connector 1 to be subjected to a certain preload, thereby improving the reliability of the threaded connection between the straightening connector 1 and the outer cylinder 4. In addition, to improve the sealing between the straightening connector 1 and the valve seat 3, a rubber gasket is installed between them. The rubber gasket contacts the straightening connector 1, the valve seat 3, and the disc spring 16 simultaneously.

[0046] refer to Figure 3 To improve the sealing of the threaded connection between the outer cylinder 4 and the retaining 10, a retaining ring 13 is installed between the bushing 9 and the drill bit 11. The retaining ring 13 is made of elastic material, and its outer wall contacts both the inner wall of the bushing 9 and the inner wall of the retaining 10. The deformed retaining ring 13 will seal the contact point between the bushing 9 and the retaining 10, thereby preventing gas from escaping from this location.

[0047] refer to Figure 2 The valve seat 3 has a notch at the end facing the piston 8, which, together with the inner cylinder 5 and the piston 8, can form a large rear air chamber. When the rear air chamber is large, the piston 8 is subjected to a large thrust, and the impact causes the drill bit 11 to have a large vibration effect.

[0048] refer to Figure 3 In order to improve the sealing effect inside the down-the-hole hammer, an O-ring 18 is installed between the inner wall of the bushing 9 and the outer cylinder 4, an O-ring 18 is installed between the air distribution seat 3 and the collection pipe 7, an O-ring 18 is installed between the collection pipe 7 and the adapter pipe 6, an O-ring 18 is installed between the outer cylinder 4 and the straightening connector 1, and an O-ring 18 is installed between the outer cylinder 4 and the clip nest 10.

[0049] refer to Figure 2 To prevent the adapter tube 6 from moving arbitrarily along its axis, a retaining ring 17 is installed inside the first through hole. The retaining ring 17 contacts a protrusion on the inner wall of the adapter tube 6, and a corresponding vent hole is formed on the protrusion on the inner wall of the adapter tube 6. The vent hole is used to allow high-pressure gas to pass through. The retaining ring 17 is used to achieve axial positioning of the adapter tube 6.

[0050] The implementation principle of a large-diameter pneumatic reverse circulation down-the-hole hammer according to this application embodiment is as follows: During operation, high-pressure gas is delivered via an external drilling rig to the annular air passage between the centering connector 1 and the adapter pipe 6. The gas first pushes open the check valve 2 and compresses the check spring 14, entering the front air chamber (composed of an outer cylinder 4, a piston 8, and a bushing 9). Under the action of air pressure, the piston 8 moves to the left. During the leftward movement of the piston 8, part of the gas enters the space between the wear-resistant sleeve 12, the drill bit 11, and the inner wall of the borehole through the exhaust channel on the retaining sleeve 10, forming a drilling space. The other part enters the rear air chamber (composed of an inner cylinder 5, an air distribution seat 3, a piston 8, a drill bit 11, and a collection pipe 7) through the air passage on the air distribution seat 3 and the inner cylinder 5. The air pressure in the rear air chamber pushes the piston 8 to the right, violently impacting the left end of the drill bit 11, achieving continuous high-frequency impact on the drill bit 11.

[0051] When gas enters the drilling space, it carries the broken rock cuttings into the discharge hole of drill bit 11, and then discharges them out of the hole through the continuous channel formed by the collection pipe 7 and the adapter pipe 6, achieving true reverse circulation continuous cuttings discharge. Because the wear-resistant sleeve 12 always fits against the hole wall, it effectively isolates the annular rock cuttings, preventing them from entering the drill string gaps and causing wear. Throughout the process, the reciprocating motion of piston 8, the gas distribution, and the discharge of rock cuttings are synchronized, thus achieving efficient impact rock breaking while ensuring a clean working environment for drill bit 11, significantly improving its service life and operational reliability in large-diameter drilling.

[0052] When it is necessary to specify, when the down-the-hole hammer in this application is drilling, the "left end" mentioned in this application refers to the upper end or top end when drilling, and the "right end" refers to the lower end or bottom end when drilling.

[0053] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A large-diameter pneumatic reverse circulation down-the-hole hammer for reaming, characterized in that, include: The system comprises a centralizing connector (1), a check valve (2), a gas distribution seat (3), an outer cylinder (4), an inner cylinder (5), an adapter tube (6), a collection tube (7), a piston (8), a bushing (9), a retaining sleeve (10), a drill bit (11), and a wear-resistant sleeve (12). The centralizing connector (1) has its first end connected to an external drilling rig, and its second end inserted into and connected to the outer cylinder (4). The centralizing connector (1) has a first through hole, the adapter tube (6) is inserted into the first through hole, and the check valve (2) is located within the first through hole and fitted onto the inner cylinder. Outside the adapter tube (6), the check valve (2) can block the first through hole after movement. The valve seat (3) is located inside the outer cylinder (4) and contacts the second end of the adapter tube (6). The inner cylinder (5) passes through the outer cylinder (4). The first end of the inner cylinder (5) abuts the second end of the straightening connector (1). The inner cylinder (5) is sleeved outside the valve seat (3). A first gap exists between a portion of the outer edge of the inner cylinder (5) and the inner wall of the outer cylinder (4). The piston (8) is slidably disposed inside the outer cylinder (4). The piston (8) and the outer cylinder... (4) There is a second gap between them. The bushing (9) passes through the outer cylinder (4). The retaining clip (10) is fitted on the drill bit (11). The retaining clip (10) passes through the second end of the outer cylinder (4). The piston (8) slides back and forth between the first end of the drill bit (11) and the second end of the air distribution seat (3). The drill bit (11) has a discharge hole. The collection tube (7) is located in the outer cylinder (4) and passes through the piston (8) and the air distribution seat (3). There is a third gap between the piston (8) and the collection tube (7). (7) is connected to the discharge hole and the adapter tube (6) at both ends respectively. The wear-resistant sleeve (12) is sleeved on the outside of the card nest (10) and its outer edge is attached to the inner wall of the borehole. A rear air chamber is formed between the inner cylinder (5), the air distribution seat (3), the piston (8), the drill bit (11) and the collection tube (7). A front air chamber is formed between the outer cylinder (4), the piston (8) and the bushing (9). The card nest (10) is provided with an exhaust channel. The exhaust channel is connected to the front air chamber. After the high-pressure gas flows out from the exhaust channel, it will carry rock cuttings into the discharge hole.

2. The large-diameter pneumatic reverse circulation down-the-hole hammer according to claim 1, characterized in that: It also includes a retaining ring (13), which is sleeved on the drill bit (11) and passes through the retaining nest (10), with the first end of the retaining ring (13) contacting the second end of the bushing (9).

3. The large-diameter pneumatic reverse circulation down-the-hole hammer according to claim 2, characterized in that: It also includes a check spring (14), which is sleeved on the outside of the adapter tube (6). The first end of the check spring (14) contacts the check valve (2), and the second end of the check spring (14) contacts the gas distribution seat (3).

4. The large-diameter pneumatic reverse circulation down-the-hole hammer according to claim 3, characterized in that: It also includes a washer (15) located between the straightening connector (1) and the outer cylinder (4), and the washer (15) is also located between the outer cylinder (4) and the snap-fit ​​(10).

5. A large-diameter pneumatic reverse circulation down-the-hole hammer according to any one of claims 1-4, characterized in that: The outer surface of the piston (8) contacts a portion of the inner surface of the bushing (9) and a portion of the inner surface of the inner cylinder (5).

6. A large-diameter pneumatic reverse circulation down-the-hole hammer according to any one of claims 1-4, characterized in that: The straightening connector (1) and the outer cylinder (4) are connected by a thread, and the snap-fit ​​nest (10) and the outer cylinder (4) are connected by a thread.

7. A large-diameter pneumatic reverse circulation down-the-hole hammer according to any one of claims 1-4, characterized in that: It also includes a disc spring (16) located between the inner cylinder (5) and the centering joint (1).

8. A large-diameter pneumatic reverse circulation down-the-hole hammer according to any one of claims 1-4, characterized in that: The piston (8) has a stepped hole inside, with the larger diameter of the stepped hole facing the gas distribution seat (3) and the smaller diameter of the stepped hole facing the drill bit (11).

9. A large-diameter pneumatic reverse circulation down-the-hole hammer according to any one of claims 1-4, characterized in that: The discharge hole includes a small discharge hole and a large discharge hole. There are multiple small discharge holes, all of which are connected to the large discharge hole. The large discharge hole is connected to the collection tube (7). The inlet end of the small discharge hole is connected to the surface of the drill bit (11).

10. A large-diameter pneumatic reverse circulation down-the-hole hammer according to any one of claims 1-4, characterized in that: The inner diameter of the collection tube (7) is the same as the inner diameter of the adapter tube (6).

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