A pneumatic impact drill bit

Abstract

A pneumatic impact drill bit includes an outer tube, an inner tube, and a hard extrusion head. The outer tube is sequentially divided into a drilling part, a reaming part, an exhaust part, and a connection part from front to back. Both the drilling part and the exhaust part are frustum structures. The large-diameter ends of the drilling part and the exhaust part are smoothly connected to the two ends of the reaming part respectively. The reaming part is provided with a sizing ring for determining the hole diameter of the formed hole. The hard extrusion head is fixed to the small-diameter end of the drilling part. A plurality of exhaust slits are circumferentially formed on the conical surface of the exhaust part. One end of the connection part is smoothly connected to the small-diameter end of the exhaust part, and the other end is connected to the impactor. The inner tube is fixed in the lumen of the outer tube. The front end of the inner tube is in a closed state, and the rear end is communicated with the air circuit of the impactor through the connection part. A plurality of ventilation holes are formed on the tube wall of the inner tube to communicate the lumen of the inner tube and the outer tube. While the drilling efficiency of the present invention is improved, the structure of the drill bit is simpler, and its cost is lower, so it has a higher cost performance.

Description

Technical Field

[0001] The present invention belongs to the field of drilling and hole-forming equipment, and particularly relates to an impact drill bit installed at the front end of a pneumatic impactor. Background Art

[0002] At present, the main forms of deep foundation pit support include: soil nailing wall support, steel sheet pile support, cement soil wall support, row pile internal support support, row pile soil anchor support, and diaphragm wall support. Among them, the soil nailing wall support has the advantages of low cost, fast construction, and reliable performance, and is widely used.

[0003] The soil nailing wall is an in-situ soil reinforcement technology. It is a slope reinforcement support construction method that combines the foundation pit slope reinforced by soil nails made of steel bars, a steel mesh laid on the slope surface, and a layer of concrete surface layer sprayed on the soil slope. Its structure is a composite body formed by the reinforcement members (i.e., soil nails or anchor rods) arranged in the slope body firmly bonded with the surrounding soil, and a support structure similar to a gravity retaining wall formed by the surface layer.

[0004] The soil nailing wall has various forms, such as the drilled grouting type, the direct driving type, and the driving grouting type. Among them, for the drilled grouting type, mechanical equipment such as a drill is first used to drill holes in the soil. After the holes are formed, the rod bodies (generally made of HRB335 ribbed steel bars) are inserted, and then cement slurry is injected along the entire length. The drilled grouting type is suitable for almost all soil layers, has a relatively high pull-out resistance, reliable quality, and low cost, and is the most commonly used type of soil nailing wall.

[0005] At present, the drill bits used for hole formation during the construction of soil nailing walls include pneumatic down-the-hole drill bits and drill bits with threaded teeth.

[0006] For down-the-hole drill bits, they are generally more suitable for rock formations. For soil layers, it is very difficult to use them normally. The reason is that the down-the-hole drill bit needs to be connected to a pneumatic impactor and the air path needs to be kept unobstructed to ensure the normal operation of the pneumatic impactor. However, the front end of the down-the-hole drill bit is provided with exhaust holes. When operating in soil layers, on the one hand, it is easily blocked by soil, and on the other hand, the soil residues drilled out of the hole will block between the drill bit and the hole wall, making the air discharged from the front of the drill bit unable to be discharged backward. As a result, the pneumatic impactor cannot operate normally, and the down-the-hole drill bit cannot drill normally. In addition, the cost of the down-the-hole drill bit is also very high, which will undoubtedly increase the construction cost.

[0007] For drill bits with threaded teeth, although their cost is low, when drilling, they need to rotate for drilling, and the resistance is relatively large, resulting in a relatively low drilling efficiency. For example, for a single-head drilling rig using this type of drill bit, the daily drilling length is only 300 m, which is difficult to meet the requirements of the construction party. Summary of the Invention

[0008] The object of the present invention is to provide a pneumatic impact drill bit. Through the overall optimization of the drill bit structure, the drilling efficiency is greatly improved, and the manufacturing cost of the drill bit is much lower than that of the pneumatic down-the-hole drill bit. Therefore, it has excellent comprehensive performance.

[0009] To achieve the above object, the technical solution adopted by the present invention is: a pneumatic impact drill bit, including an outer tube, an inner tube and a hard extrusion head. The outer tube is sequentially divided into a drilling part, an expanding part, an exhaust part and a connecting part from front to back. Both the drilling part and the exhaust part are frustum structures. The large-diameter ends of the drilling part and the exhaust part are respectively and smoothly connected to both ends of the expanding part. The position of the maximum outer diameter of the expanding part is a sizing ring for determining the hole diameter of the formed hole. The hard extrusion head is fixed at the small-diameter end of the drilling part. A plurality of exhaust slits are circumferentially provided on the conical surface of the exhaust part. One end of the connecting part is smoothly connected to the small-diameter end of the exhaust part, and the other end of the connecting part is used to connect to a pneumatic impactor; the inner tube is fixed in the lumen of the outer tube. The front end of the inner tube is in a closed state. The rear end of the inner tube is fixed on the inner wall of the connecting part or the exhaust part and is communicated with the air circuit of the impactor through the channel of the connecting part. A plurality of ventilation holes are provided on the tube wall of the inner tube to communicate the lumen of the inner tube and the lumen of the outer tube.

[0010] The hard extrusion head is welded to the small-diameter end of the drilling part.

[0011] The hard extrusion head is a steel ball head.

[0012] A part of the spherical surface of the steel ball head is located in the lumen of the outer tube, and the rest of the spherical surface is located outside the outer tube. And the depth of the steel ball head entering the outer tube is less than the radius of the steel ball head itself.

[0013] The front end of the inner tube is welded to the spherical surface of the steel ball head entering the lumen of the outer tube to achieve the closure of the front end of the inner tube.

[0014] The inner tube is a cylindrical tube.

[0015] The generatrix length of the conical surface of the drilling part is greater than the generatrix length of the conical surface of the exhaust part.

[0016] The length of the exhaust slit is not greater than the generatrix length of the conical surface of the exhaust part.

[0017] The expanding part is cylindrical or drum-shaped.

[0018] The connecting part is provided with an internal thread hole for connecting a pneumatic impactor.

[0019] The beneficial effects of the present invention are as follows: First, the shape of the drill bit of the present invention is set to be frustum-shaped at the front and rear, and the middle section is an enlarged diameter part that is cylindrical or drum-shaped. In this way, no matter whether it is advanced by rotation or linearly, the conical surface at the front end of the drill bit extrudes and drills into the soil layer. Therefore, less soil residue is generated and the exhaust holes will not be blocked. Moreover, the exhaust holes of the present invention are arranged on the exhaust part which is also a conical surface, and backward exhaust can be realized. During drilling, since the rear part of the drill bit is in the drilled hole after hole formation, it can be connected to the outside through the hole opening. Therefore, the air path between the impactor and the drill bit can always be kept unobstructed. In addition, the working ring at the maximum outer diameter of the enlarged diameter part of the present invention is in close contact with the hole wall. Therefore, even a small amount of soil residue generated will be enclosed at the front end of the drill bit by the working part and will not block the exhaust holes at the rear end of the drill bit. In this way, the problem that the air path of the down-the-hole drill bit is easily blocked after hole formation in the soil layer in the prior art can be solved. In addition, the present invention uses exhaust slits as exhaust holes, which can effectively increase the exhaust area. After setting the slits, the air flow velocity increases, further ensuring the unobstructed air path from the impactor to the drill bit and then to the drilled hole. However, while the performance is improved, the structure of the drill bit is simpler and its cost is lower. Therefore, it has a high cost performance.

[0020] Second, there are no thread teeth or the like on the outer tube of the present invention, but it is smooth throughout. During hole formation, the hole is formed by extruding the soil mass, and a sizing ring is provided on the outer tube. The purpose of the sizing ring is to determine and stabilize the hole diameter of the drilled hole, and at the same time, it can also reduce the contact area between the drill bit and the soil layer. Especially when the working part of the drill bit is drum-shaped, the frictional resistance between the drill bit and the soil layer is greatly reduced. Therefore, compared with the drill bit with thread teeth, the present invention can increase the drilling efficiency by several times. According to the comparative test, when the hole formation diameter is the same, a drill bit with thread teeth can drill 300 meters per day, while after using the drill bit of the present invention, it can drill 1500 meters per day.

[0021] Third, when the present invention is in use, it is still installed on a traditional pneumatic impactor. Therefore, there is no installation and use threshold, and this drill bit can not only be used for drilling in soil layers (hard soil, soft soil), but also in sandy gravel geology. Therefore, it has good versatility. Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of the outside of the present invention;

[0023] Figure 2 is a schematic structural diagram of the inside of the present invention;

[0024] Reference numerals in the figure: 1. Outer tube, 2. Inner tube, 3. Ball head, 4. Front conical part, 5. Working part, 6. Rear conical part, 7. Connecting part, 8. Exhaust slit. Detailed Embodiments

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but it shall not be used as a basis for any limitation to the invention.

[0026] As shown in the accompanying drawings, a pneumatic impact drill bit is used to connect with a pneumatic impactor to achieve drilling operations in foundation pit support. The drill bit includes an outer tube, an inner tube, and a hard extrusion head.

[0027] According to different functions in drilling, the outer tube can be sequentially divided into the following sections from front to back: a drilling section, a diameter-expanding section, an exhaust section, and a connecting section, and the connection between the above sections is smooth. The drilling section is used to extrude the soil to form a hole, so the drilling section adopts a frustum structure, and its pipe wall is a conical surface. The small-diameter end of the drilling section is the front end of the outer tube and is fixedly connected to the hard extrusion head, and the large-diameter end of the drilling section is smoothly connected to one end of the diameter-expanding section. The diameter-expanding section is mainly used to determine the aperture of the hole drilled by the drilling section. The diameter-expanding section is provided with a positioning ring for determining the aperture. The diameter-expanding section can be cylindrical or drum-shaped. For the cylindrical shape, its positioning ring is a cylindrical surface; for the drum-shaped shape, since the side surface of the drum is an arc surface protruding in the middle, the maximum diameter of the drum is the positioning ring, and the outer diameter of the positioning ring is the aperture of the drilling hole. The exhaust section is mainly used to discharge the air inside the drill bit to ensure the smoothness of the air path inside the drill bit and the air path of the pneumatic impactor, and thus ensure the smooth progress of the pneumatic operation. Therefore, the exhaust section needs to be set as a frustum structure, that is, the pipe wall at the exhaust section is a conical surface, and the large-diameter end of the exhaust section is connected to the other end of the diameter-expanding section, and the small-diameter end of the exhaust section is connected to the connecting section. In this way, the exhaust section and the drilling section are respectively located at the axial two ends of the diameter-expanding section. A plurality of exhaust slits are evenly distributed along the circumferential direction on the conical surface of the exhaust section. Therefore, the exhaust direction of the exhaust slits is backward, that is, towards the drilling hole mouth, which is conducive to smooth exhaust, and the soil slag during drilling will not block the exhaust slits. The connecting section is provided with an internal thread hole for connecting the drill bit and the pneumatic impactor, and the connecting section is also provided with a gas channel to connect the air path of the pneumatic impactor and the air path inside the drill bit.

[0028] The hard extrusion head adopts a steel ball head, which is welded to the small-diameter end of the drilling section, and a part of the spherical surface of the steel ball head is located inside the lumen of the outer tube, and the rest of the spherical surface is located outside the outer tube, and the depth of the steel ball head entering the outer tube is less than the radius of the steel ball head itself.

[0029] The inner tube is a cylindrical hollow tube. The front end of the inner tube is welded to the steel ball head to form a closed front end of the inner tube. The pipe wall at the rear end of the inner tube is welded to the inner wall of the outer tube, and the welding part can be on the inner wall of the connecting section or the exhaust section, but it is necessary to ensure that the port at the rear end of the inner tube is connected to the gas channel inside the connecting section, and the purpose is to allow the air of the pneumatic impactor to enter the drill bit along the inner tube. A plurality of ventilation holes are provided on the pipe wall of the inner tube to connect the lumen of the inner tube and the lumen of the outer tube.

[0030] Furthermore, the generatrix length of the conical surface of the drilling part is greater than that of the conical surface of the exhaust part to reduce the drilling resistance and improve the drilling efficiency.

[0031] Moreover, the length of the exhaust slit is not greater than the generatrix length of the conical surface of the exhaust part to ensure that air can be exhausted backward.

[0032] When the present invention is in use, it is connected to a pneumatic impactor through the internal thread hole of the connecting part. During the drilling process, the front drilling part advances forward by extruding the soil layer through the conical surface, and the sizing ring of the diameter-expanding part can stabilize the diameter of the drilled hole. As Figure 2 shown, the air in the pneumatic impactor enters the inner tube through the gas passage of the connecting part, then enters the lumen of the outer tube through the ventilation holes on the inner tube, and then is discharged from the exhaust slit of the exhaust part. Since no exhaust holes are provided at the front end of the drill bit, the exhaust slit of the exhaust part is always located inside the drilled hole after the hole is formed and does not contact the hole wall. Therefore, soil residues during drilling will not block the air path, thus ensuring the smooth progress of drilling.

[0033] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Those of ordinary skill in the art should understand that the specific implementation manners of the present invention can be modified or equivalently replaced with reference to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the protection scope of the claims pending for approval.

Claims

1. A pneumatic impact drill bit, used for drilling holes in soil layers or sandy gravel geology, characterized in that: It includes an outer tube, an inner tube and a rigid extrusion head. The outer tube is sequentially divided into a drilling part, an expanding part, an exhaust part and a connecting part from front to back. Both the drilling part and the exhaust part are frustum structures. The large-diameter ends of the drilling part and the exhaust part are smoothly connected to the two ends of the expanding part respectively. The position of the maximum outer diameter of the expanding part is a sizing ring for determining the hole diameter of the formed hole. The rigid extrusion head is fixed at the small-diameter end of the drilling part. A plurality of exhaust slits are circumferentially formed on the conical surface of the exhaust part, and the exhaust direction of the exhaust slits is backward. One end of the connecting part is smoothly connected to the small-diameter end of the exhaust part, and the other end of the connecting part is used to connect to a pneumatic impactor. The inner tube is fixed in the lumen of the outer tube. The front end of the inner tube is in a closed state. The rear end of the inner tube is fixed on the inner wall of the connecting part or the exhaust part and is communicated with the air circuit of the impactor through the channel of the connecting part. A plurality of ventilation holes are formed on the tube wall of the inner tube to communicate the lumen of the inner tube and the lumen of the outer tube. The expanding part is drum-shaped, the side surface of the drum is an arc surface protruding in the middle, and the position of the maximum diameter on the drum is the sizing ring mentioned above.

2. The pneumatic impact drill bit according to claim 1, characterized in that: The rigid extrusion head is welded to the small-diameter end of the drilling part.

3. The pneumatic impact drill bit according to claim 1, wherein: The rigid extrusion head is a steel ball head.

4. The pneumatic impact drill bit according to claim 3, characterized in that: A part of the spherical surface of the steel ball head is located in the lumen of the outer tube, and the rest of the spherical surface is outside the outer tube. The depth of the steel ball head entering the outer tube is less than the radius of the steel ball head itself.

5. The pneumatic impact drill bit according to claim 1, characterized in that: The front end of the inner tube is welded to the spherical surface of the steel ball head entering the lumen of the outer tube to achieve the closure of the front end of the inner tube.

6. The pneumatic impact drill bit according to claim 1, characterized in that: The inner tube is a cylindrical tube.

7. The pneumatic impact drill bit according to claim 1, characterized in that: The generatrix length of the conical surface of the drilling part is greater than the generatrix length of the conical surface of the exhaust part.

8. The pneumatic impact drill bit according to claim 1, wherein: The length of the exhaust slit is not greater than the generatrix length of the conical surface of the exhaust part.

9. The pneumatic impact drill bit according to claim 1, wherein: The connecting part is provided with an internal thread hole for connecting a pneumatic impactor.

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