PDC bit with self-adapting retractable device

Abstract

The application provides a PDC drill bit with a self-adapting telescopic device, comprising a drill bit body, a main cutting structure and a secondary cutting structure; the main cutting structure is installed on the drill bit body, and the main cutting structure comprises a drill bit base and a plurality of first cutting teeth which are arranged at intervals on the outer periphery of the drill bit base; a receiving groove is formed on the top end surface of the drill bit base, and the first cutting teeth are used for crushing the outer periphery of the stratum; the secondary cutting structure is inserted into the drill bit base and comprises a crushing disc and a telescopic assembly connected to the bottom of the crushing disc; the crushing disc is movably embedded in the receiving groove, the telescopic assembly is used for driving the crushing disc to move up and down in the receiving groove, and a plurality of second cutting teeth for crushing the center of the stratum are arranged on the side of the crushing disc away from the telescopic assembly. The telescopic assembly in the secondary cutting structure of the application can drive the crushing disc to move up and down, so that the crushing disc can adapt to different hardness strata, thereby realizing the self-adaptation of efficient rock breaking.

Description

Technical Field

[0001] This invention belongs to the field of mechanical drilling technology, and particularly relates to a PDC drill bit with an adaptive telescopic device in the core. Background Technology

[0002] As oil exploration and development continue to deepen, shallow and easily exploitable oil and gas resources are becoming increasingly scarce. Seeking oil and gas resources in deep strata and under complex geological conditions is gradually becoming a crucial task in both onshore and offshore exploration and development. Deep hard rocks typically exhibit properties such as high strength, high hardness, strong abrasiveness, severe heterogeneity, and poor drillability during drilling. Existing rock-breaking tools and drilling methods generally suffer from slow drilling speeds, short drill bit lives, long drilling cycles, and high drilling costs, directly restricting the drilling speed of deep and ultra-deep wells and the overall efficiency of exploration and development.

[0003] PDC drill bits are primarily used in soft to medium-hard formations, but their adaptability in hard formations is poor, easily leading to tooth breakage, chipping, and severe wear. In recent years, continuous improvements and innovations have been made to the cutting teeth, blade shape and structure, and hydraulic design of PDC drill bits, which have increased drilling speed in hard formations to some extent. However, these improvements still fall short of meeting the requirements for efficient rock breaking and increased rotational speed. Because the cutting ability differs from the center to the edge of the drill bit, the tooth density in the center is relatively low, resulting in a slower rock-breaking speed at the center and thus limiting the overall rock-breaking speed. Summary of the Invention

[0004] The main objective of this invention is to propose a PDC drill bit with an adaptive telescopic device in the core, which aims to solve the technical problem of poor adaptability of conventional PDC drill bits in complex formations with alternating soft and hard surfaces and complex directional well operations.

[0005] To achieve the above objectives, the present invention provides a PDC drill bit with an adaptive telescopic device in the core, comprising: Drill bit body; The main cutting structure, mounted on the drill bit body, includes a drill bit base and a plurality of first cutting teeth spaced apart on the outer periphery of the drill bit base. A receiving groove is formed on the top surface of the drill bit base. The first cutting teeth are used to break up the outer periphery of the formation's center. The secondary cutting structure is inserted into the drill bit body and includes a breaker disc and a telescopic assembly connected to the bottom of the breaker disc. The breaker disc is movably embedded in the receiving groove. The telescopic assembly is used to drive the breaker disc to move up and down in the receiving groove. The side of the breaker disc opposite to the telescopic assembly is provided with multiple second cutting teeth for breaking the center of the formation.

[0006] In an embodiment of the present invention, the telescopic component includes: Gear set; Screw; The nut is located between the screw and the gear set. The nut is threaded onto the outer circumference of the screw, and the nut and the gear set are connected for transmission. A rotary drive component used to drive the gear set to rotate.

[0007] In an embodiment of the present invention, the telescopic assembly further includes a planetary carrier, the planetary carrier and the nut are arranged coaxially, the inner peripheral wall of the planetary carrier and the outer peripheral wall of the nut are movably engaged, and the gear set is supported and installed on the planetary carrier.

[0008] In an embodiment of the present invention, the planetary carrier includes a central body and a plurality of support arms disposed on the periphery of the central body, and the gear set includes: The internal gear ring has a first gear tooth on its inner peripheral wall and is embedded in the inner wall of the drill bit body. The sun gear has a second tooth on its outer peripheral wall; and Multiple pinions are coaxially mounted on the support arm, one-to-one, and the pinions mesh with the internal gear ring and the sun gear.

[0009] In an embodiment of the present invention, the central axes of the sun gear, the nut, and the central body coincide. A first through hole is provided in the center of the central body. The nut includes a large-diameter portion and a small-diameter portion. The small-diameter portion is inserted into the first through hole, and the large-diameter portion is inserted into the sun gear. The top surface of the large-diameter portion is flush with the top surface of the sun gear.

[0010] In an embodiment of the present invention, a friction ring is provided between the inner peripheral wall of the sun gear and the outer peripheral wall of the large diameter portion.

[0011] In an embodiment of the present invention, the top surface of the receiving groove is open, the bottom wall of the receiving groove is provided with a second through hole for the screw to move through, and the drill bit body is also provided with a cavity for accommodating the planetary carrier, the cavity and the second through hole are connected.

[0012] In an embodiment of the present invention, the telescopic assembly further includes a sealing disc and a rubber ring disposed on the sealing disc, the sealing disc being disposed at the bottom of the nut and embedded in the central body.

[0013] In an embodiment of the present invention, the screw includes a smooth portion and a threaded portion integrally formed in the axial direction, wherein the height of the threaded portion is greater than the depth of the receiving groove.

[0014] In an embodiment of the present invention, the second cutting tooth has a conical structure, and the conical end of the second cutting tooth extends away from the crushing disc.

[0015] Through the above technical solution, the PDC drill bit with an adaptive telescopic device in the core provided by the embodiments of the present invention has the following beneficial effects: This application incorporates a main cutting structure and a secondary cutting structure on the drill bit body. The main cutting structure is mounted on the drill bit body, and a receiving groove is formed on the top surface of the drill bit base of the main cutting structure, within which the secondary cutting structure is housed. During drilling, the main cutting structure is used to break the outer periphery of the formation's center. The secondary cutting structure is inserted into the drill bit base and includes a breaking disc and a telescopic assembly connected to the bottom of the breaking disc. The breaking disc is movably embedded in the receiving groove, and the telescopic assembly drives the breaking disc to move up and down within the groove. Multiple second cutting teeth are provided on the side of the breaking disc opposite to the telescopic assembly for breaking the center of the formation. During drilling, the first cutting teeth on the main cutting structure first shear and grind the bottom of the well to form a convex bottom. Then, the telescopic assembly in the secondary cutting structure of this application drives the breaking disc to move up and down, enabling the breaking disc to adapt to formations of varying hardness, thereby achieving efficient rock breaking.

[0016] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of a PDC drill bit with an adaptive telescopic device in the core when the breaker disc extends according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a PDC drill bit with an adaptive telescopic device in the core retracting when the breaker disc is retracted, according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the secondary cutting structure of a PDC drill bit with an adaptive telescopic device in the core according to the present invention; Figure 4 This is a front view of a PDC drill bit with an adaptive telescopic device in the core, according to an embodiment of the present invention; Figure 5 yes Figure 4 A cross-sectional view of the AA section; Figure 6 This is a schematic diagram of the planetary carrier in the PDC drill bit with an adaptive telescopic device in the core of the present invention.

[0018] Explanation of reference numerals in the attached figures Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0020] The following description, with reference to the accompanying drawings, describes a PDC drill bit with an adaptive telescoping device in the core according to the present invention.

[0021] like Figure 1 and Figure 2 As shown, to address the poor adaptability of conventional PDC drill bits in complex formations with alternating soft and hard surfaces and complex directional well operations, this invention provides a PDC drill bit with an adaptive telescopic device in the core, comprising a drill bit body 10, a main cutting structure 20, and a secondary cutting structure 30. The main cutting structure 20 is mounted on the drill bit body 10 and includes a drill bit base 21 and a plurality of first cutting teeth 22 spaced apart on the outer periphery of the drill bit base 21. A receiving groove 33 is provided on the top surface of the drill bit base 21, and the first cutting teeth 22 are used to break the outer periphery of the center of the formation. The secondary cutting structure 30 is inserted into the drill bit base 21 and includes a breaking disc 31 and a telescopic component connected to the bottom of the breaking disc 31. The breaking disc 31 is movably embedded in the receiving groove 33, and the telescopic component is used to drive the breaking disc 31 to move up and down within the receiving groove 33. A plurality of second cutting teeth 32 for breaking the center of the formation are provided on the side of the breaking disc 31 away from the telescopic component.

[0022] The main cutting structure 20 is the primary rock-breaking structure of the PDC drill bit. During drilling, the first cutting tooth 22 on the main cutting structure 20 first shears and grinds the bottom of the well to form a convex bottom. Then, the telescopic component in the secondary cutting structure 30 can drive the breaking disc 31 to move up and down, thereby enabling the breaking disc 31 to adapt to formations of different hardness, thus achieving efficient rock breaking.

[0023] The PDC drill bit of this application, equipped with an adaptive telescoping device in its core, exhibits excellent adaptability to formations of varying hardness. When drilling into softer formations, the rock column recessed in the center of the drill bit body 10 is short, releasing corresponding stress at the bottom of the well. This makes the rock in the central part of the drill bit body 10 easier to break, thereby improving the overall rock-breaking efficiency of the drill bit. When encountering hard formations, the rock is not easily broken. Under the action of huge drilling pressure and counter-torque, the breaker disk 31 is compressed back, resulting in a longer central rock column during rock breaking. The stress released at the bottom of the well is greater, making the hard rock in the drill bit core easier to break, thus improving the rock breaking efficiency in hard formations. The rock-breaking structure of this application allows the PDC drill bit to adapt well to formations of different hardness, increasing drilling speed while making the drilling rate more stable. This innovation is of great significance for my country's development of deep oil and gas resources and ensuring national energy security.

[0024] Furthermore, in the actual manufacturing process, the secondary cutting structure 30 and the drill body 10 of this application can be manufactured separately and then connected by welding, which is suitable for industrial production applications.

[0025] It should be noted that the first cutting tooth 22 can be, but is not limited to, other tooth shapes such as conical teeth and axe-shaped teeth, and the second cutting tooth 32 can be a tooth shape structure of conical teeth, axe-shaped teeth, or a combination of both. Multiple first cutting teeth 22 are arranged sequentially and at intervals along the outer periphery of the drill bit base 21. Each first cutting tooth 22 includes multiple sequentially and at intervals cutting portions. The arrangement direction of the multiple first cutting teeth 22 is perpendicular to the arrangement direction of the multiple cutting portions in each cutting tooth.

[0026] like Figure 3 As shown, the telescopic assembly includes a gear set, a screw 34, a nut 35, and a rotary drive component. The nut 35 is located between the screw 34 and the gear set, and is threadedly connected to the outer circumference of the screw 34. The nut 35 and the gear set are connected in a transmission manner. The rotary drive component drives the gear set to rotate. When the rotary drive component drives the gear set to rotate, it can cause the nut 35 and the screw 34 to rotate relative to each other. Since the nut 35 and the screw 34 are threadedly connected, this enables the screw 34 to extend and retract vertically relative to the plane containing the nut 35. The rotary drive component can be a conventional rotary motor or other components capable of rotary drive.

[0027] Furthermore, to prevent relative movement of the nut 35, the telescopic assembly also includes a planetary carrier 36 installed within the drill bit base 21. The planetary carrier 36 transmits torque and secures the nut 35 and the gear set. The planetary carrier 36 and the nut 35 are coaxially arranged, with the inner peripheral wall of the planetary carrier 36 and the outer peripheral wall of the nut 35 in a movable fit. The gear set is supported and installed on the planetary carrier 36, ensuring that the entire planetary carrier 36, gear set, and nut 35 remain in the same position relative to the drill bit base 21.

[0028] like Figure 6 As shown, the planetary carrier 36 includes a central body 361 and multiple support arms 363 located on the outer periphery of the central body 361. The gear set includes an internal gear ring 37, a sun gear 38, and multiple pinions 39. The inner peripheral wall of the internal gear ring 37 has first gear teeth, and the internal gear ring 37 is embedded in the inner wall of the drill bit base 21. The outer peripheral wall of the sun gear 38 has second gear teeth. The multiple pinions 39 are coaxially mounted on the support arms 363 one-to-one through a rotating shaft, and the pinions 39 mesh with both the internal gear ring 37 and the sun gear 38.

[0029] When the rotary drive drives the internal gear ring 37 to rotate, it can drive the sun gear 38 and the pinion 39 to rotate simultaneously. Since the nut 35 is coaxially embedded in the planet carrier 36, it can drive the nut 35 to move relative to the screw 34. The entire planet carrier 36 is fixed on the central body 361, so the nut 35 and the gear set will only rotate radially and will not move up and down in the axial direction. Since the nut 35 and the screw 34 are threadedly connected, the screw 34 moves up and down relative to the nut 35, thereby driving the crushing disc 31 to move axially and extend and retract in the receiving groove 33.

[0030] like Figure 4 and Figure 5 As shown, the central axes of the sun gear 38, the nut 35, and the central body 361 coincide. The center of the central body 361 has a first through hole 362. The nut 35 includes a large diameter part and a small diameter part. The small diameter part is inserted into the first through hole 362, and the large diameter part is inserted into the sun gear 38. The top surface of the large diameter part is flush with the top surface of the sun gear 38.

[0031] In addition, in order to reduce the friction between the center body 361 and the nut 35, a bearing is provided between the small diameter portion of the center body 361 and the nut 35, and a bearing is also provided between the large diameter portion of the center body 361 and the nut 35 to realize the relative rotation between the center body 361 and the nut 35. This will prevent the nut 35 from becoming unable to rotate due to excessive friction under excessive drilling pressure.

[0032] In an embodiment of the present invention, a friction ring is provided between the inner peripheral wall of the sun gear 38 and the outer peripheral wall of the large diameter portion.

[0033] The choice of friction rings can be tailored to different drilling locations, allowing for the selection of friction pads with varying coefficients of friction. Different friction rings with different coefficients can be installed for different regions, thereby improving the adaptability of the PDC drill bit to various rock formations and extending the overall lifespan of the drill bit.

[0034] When the drill bit rotates, it drives the internal gear ring 37 to rotate, which in turn drives three planetary gears to rotate. These planetary gears then drive the central sun gear 38 to rotate, which in turn drives the friction ring to rotate. A threaded nut 35 is mounted at the center of the sun gear 38, and the friction ring is located between the nut 35 and the sun gear 38. The rotation of the friction ring by the sun gear 38, under the action of friction, causes the central nut 35 to rotate. The nut 35 then engages with the central screw 34, allowing the screw 34 to extend and retract vertically. The top of the screw 34 is connected to a breaker disc 31, which is equipped with several second cutting teeth 32. These second cutting teeth 32 achieve both impact rock breaking and a certain degree of cutting rock breaking. When encountering soft strata, the extension and retraction length of the screw 34 is longer, resulting in a shorter rock column formed by the drill bit. When encountering hard strata, the upward extension and retraction of the screw 34 is shorter, resulting in a taller rock column. When encountering formations with alternating soft and hard surfaces, the screw 34 extends and retracts when drilling into soft formations, but retracts due to the immense drilling pressure when drilling into hard formations. This is because the torque experienced by the screw 34 is significant when encountering hard formations. When this torque exceeds the torque between the friction ring and the nut 35, relative rotation occurs between the nut 35 and the sun gear 38. Under this immense drilling pressure, the nut 35 is forced to reverse, causing the screw 34 to move downwards. Meanwhile, the gear ring, sun gear 38, planetary gears, etc., continue their original movement. The cutting teeth of the PDC drill bit, equipped with an adaptive extension device in the core, first contact the formation and break the rock through shearing and plowing, forming a rock protrusion at the center of the drill bit. Subsequently, the hammer disc at the center of the drill bit crushes the central rock protrusion through impact crushing. The higher the protrusion, the greater the stress released in the core at the bottom of the well, which helps to break hard rocks. This type of drill bit achieves relatively stable torque and lateral vibration fluctuations during rock breaking, which is beneficial for improving drill bit stability and service life. By enhancing the drill bit's adaptability to formations of varying hardness, the mechanical drilling rate of the drill bit becomes more stable during drilling, thereby increasing the drilling rate and extending the life of the drill bit.

[0035] In an embodiment of the invention, the top surface of the receiving groove 33 is open, and the bottom wall of the receiving groove 33 has a second through hole through which the screw 34 moves. The drill bit base 21 also has a cavity for accommodating the planetary carrier 36, and the cavity is connected to the second through hole. Since the screw 34 passes through the second through hole axially, the second through hole acts as a guide to prevent the screw 34 from deviating from its position during axial movement. The planetary carrier 36 is placed in the cavity, and the outer peripheral wall of the internal gear ring 37 is embedded in the inner wall of the cavity, thereby achieving the fixed installation of the sun gear 38 and multiple pinions 39.

[0036] In an embodiment of the present invention, the telescopic assembly further includes a sealing disc and a rubber ring disposed on the sealing disc. The sealing disc is located at the bottom of the nut 35 and embedded within the central body 361. The rubber ring serves a sealing function to prevent drilling fluid from entering the bearing. In addition to its sealing function, the sealing disc also serves to fix the bearing. The sealing disc is connected to the planetary carrier 36 via a threaded connection.

[0037] In an embodiment of the present invention, the screw 34 includes a smooth portion and a threaded portion integrally formed in the axial direction, with the height of the threaded portion being greater than the depth of the receiving groove 33. The screw 34 includes a smooth portion and a threaded portion connected sequentially from top to bottom. When the threaded portion rotates relative to the nut 35, the screw 34 drives the crushing disc 31 to move up and down within the receiving groove 33. Because the height of the threaded portion is greater than the depth of the receiving groove 33, the threaded portion design of the screw 34 can meet the limit distance of the expansion and contraction of the crushing disc 31. Furthermore, the thread friction coefficient of both the threaded portion and the nut is very low, because if the friction coefficient is high, the resistance to the vertical expansion and contraction of the screw 34 will be large, which is detrimental to the function of the mechanism.

[0038] In an embodiment of the invention, the second cutting tooth 32 has a conical structure, with its conical end extending away from the breakup disk 31. The arrangement of the second cutting teeth 32 on the central breakup disk 31 increases the tooth density in the center of the drill bit, thereby improving the rock column breaking efficiency. During drilling, the pointed tip of the second cutting tooth 32 drills towards the center of the formation, thus forming a rock column similar in shape to the breakup disk 31 at the center of the formation. Through the combined action of the second cutting tooth 32 and the first cutting tooth 22, it is possible to adapt to formations of varying hardness while increasing drilling speed.

[0039] In addition, a drill bit nozzle is provided on the outer wall of the drill bit body 21, from which coolant can be sprayed onto the inner wall of the well to cool and lubricate the drill bit and clean the rock cuttings at the bottom of the well.

[0040] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0043] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A PDC drill bit with an adaptive telescopic device in its core, characterized in that, include: Drill bit body (10); The main cutting structure (20) is installed on the drill bit body (10). The main cutting structure (20) includes a drill bit base (21) and a plurality of first cutting teeth (22) spaced apart on the outer periphery of the drill bit base (21). The top surface of the drill bit base (21) is provided with a receiving groove (33). The first cutting teeth (22) are used to break the outer periphery of the center of the formation. and The secondary cutting structure (30) is inserted into the drill bit body (21) and includes a breaking disc (31) and a telescopic assembly connected to the bottom of the breaking disc (31). The breaking disc (31) is movably embedded in the receiving groove (33). The telescopic assembly is used to drive the breaking disc (31) to move up and down in the receiving groove (33). The breaking disc (31) has a plurality of second cutting teeth (32) on the side away from the telescopic assembly for breaking the center of the formation. The telescopic component includes: Gear set; Screw (34); A nut (35) is located between the screw (34) and the gear set. The nut (35) is threaded onto the outer periphery of the screw (34). The nut (35) and the gear set are connected in a driving connection. The nut (35) includes a large-diameter portion and a small-diameter portion. A rotary drive component is used to drive the gear set to rotate; Planetary carrier (36), the planetary carrier (36) and the nut (35) are arranged coaxially, the inner peripheral wall of the planetary carrier (36) and the outer peripheral wall of the nut (35) are movably fitted, and the gear set is supported and installed on the planetary carrier (36); The planetary carrier (36) includes a central body (361) and a plurality of support arms (363) disposed on the outer periphery of the central body (361), and the gear set includes: An internal gear ring (37) has a first gear tooth on its inner peripheral wall, and the internal gear ring (37) is embedded in the inner wall of the drill bit base (21); Sun gear (38), with a second tooth on its outer peripheral wall; and Multiple pinions (39) are coaxially mounted on the support arm (363) in a one-to-one correspondence. The pinions (39) mesh with the internal gear ring (37) and the sun gear (38). A friction ring is provided between the inner peripheral wall of the sun gear (38) and the outer peripheral wall of the large diameter portion. When the torque is greater than the torque of the friction ring and the nut (35), the nut (35) and the sun gear (38) rotate relative to each other. Under the huge drilling pressure, the nut (35) will be pressed and reversed, and the screw (34) will move downward, thereby realizing the adaptive extension and retraction function.

2. The PDC drill bit with an adaptive telescopic device in the core according to claim 1, characterized in that, The central axes of the sun gear (38), the nut (35) and the central body (361) coincide. The center of the central body (361) has a first through hole (362). The small diameter part is inserted into the first through hole (362), and the large diameter part is inserted into the sun gear (38). The top surface of the large diameter part is flush with the top surface of the sun gear (38).

3. The PDC drill bit with an adaptive telescopic device in the core according to claim 1, characterized in that, The top surface of the receiving groove (33) is open, and the bottom wall of the receiving groove (33) is provided with a second through hole for the screw (34) to pass through. The drill bit base (21) is also provided with a cavity for accommodating the planetary carrier (36), and the cavity is connected to the second through hole.

4. The PDC drill bit with an adaptive telescopic device in the core according to any one of claims 1 to 3, characterized in that, The telescopic assembly also includes a sealing disc and a rubber ring disposed on the sealing disc, the sealing disc being disposed at the bottom of the nut (35) and embedded in the central body (361).

5. The PDC drill bit with an adaptive telescopic device in the core according to any one of claims 1 to 3, characterized in that, The screw (34) includes a smooth part and a threaded part integrally formed in the axial direction, the height of which is greater than the depth of the receiving groove (33).

6. The PDC drill bit with an adaptive telescopic device in the core according to any one of claims 1 to 3, characterized in that, The second cutting tooth (32) has a conical structure, and the conical end of the second cutting tooth (32) extends away from the crushing disc (31).

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