Underreaming drilling bucket for rotary drilling rig

Abstract

The utility model belongs to the technical field of rotary drilling rigs, and particularly relates to an expanded-base drilling bucket for a rotary drilling rig. The drill rod connecting mechanism is connected with a power end of the rotary drilling rig; the top end of the drilling bucket box is fixedly connected with the drilling rod connecting mechanism, and an axial sliding cavity is formed in the drilling bucket box; the sliding piece is axially arranged in the sliding cavity in a sliding manner, and an accommodating cavity is formed in the sliding piece; the drilling bucket base is axially arranged in the accommodating cavity in a sliding manner; the bottom expanding mechanism comprises an upper swing arm and a lower swing arm, one end of the lower swing arm is hinged to the bottom of the upper swing arm; according to the limiting mechanism, a first limiting piece is arranged on the lower portion of the inner wall of a drilling bucket box; the second limiting piece is arranged at the top of the sliding piece and abuts against the first limiting piece when folded; the third limiting piece is arranged at the bottom of the sliding piece, abuts against the upper end face of the drilling bucket base when moving downwards and abuts against the lower end face of the drilling bucket box when moving upwards. Through cooperation of the drilling bucket box body, the sliding piece, the drilling bucket base and the limiting mechanism, accurate positioning of the bottom expanding mechanism is achieved, the bottom expanding height is dynamically adjusted to control the pile body shape, and concrete is prevented from exceeding the square shape.

Description

Technical Field

[0001] This utility model belongs to the field of rotary drilling rig technology, specifically a bottom-expanding drill bucket for rotary drilling rigs. Background Technology

[0002] In the field of pile foundation engineering, although conventional cylindrical piles formed by rotary drilling rigs have sufficient bearing capacity, their pull-out resistance is insufficient for applications such as high-speed rail, which have extremely high requirements for the pull-out resistance of pile foundations. To improve pull-out resistance, it is usually necessary to form an enlarged base structure (such as a frustum shape) at the bottom of the pile, and this process requires the use of enlarged-base drilling buckets.

[0003] However, traditional underreaming drill buckets have serious drawbacks: First, there is the problem of uncontrolled pile shape. Due to the rigid structural design, the underreaming mechanism (upper swing arm and lower swing arm) and the length of the drill bucket box are fixed in traditional drill buckets. When the underreaming ratio increases, the length of the upper swing arm and the height of the matching drill bucket box will inevitably increase, resulting in a "tall and thin" shape in the formed underreaming pile. Figure 1 First, the effective pull-out area of ​​the pile body is reduced. Second, excessive concrete volume is wasted: the deviation between the "tall and thin" pile shape and the design requirements ("short and fat" shape) directly leads to excessive concrete pouring, resulting in material waste and economic losses. Third, failure occurs in multi-fold diameter expansion conditions: when achieving large-scale diameter expansion (such as more than 3 times), the excessively long drill bucket box structure causes the drill bucket's center of gravity to shift, resulting in poor structural stability and the inability to form a compact "short and fat" expanded bottom shape.

[0004] Existing technology discloses a combined guided underreaming drill bit, as detailed in Chinese utility model patent CN213573911U. While this design achieves enlargement of different pile hole diameters by replacing a few parts, reducing customer procurement costs, its underreaming mechanism is driven by a fixed-length guide tube, making it impossible to dynamically adjust the underreaming height according to pile type requirements. This is particularly problematic as it fails to address the core contradiction between large underreaming ratios and short, wide pile types. Therefore, a novel underreaming drill bit structure is urgently needed to control the underreaming height and prevent excessive concrete volume. Utility Model Content

[0005] The purpose of this application is to provide an enlarged bottom drill bucket for rotary drilling rigs, which has the advantages of precisely controlling the enlarged bottom height, avoiding excessive concrete volume, and having structural stability.

[0006] This utility model adopts the following technical solution: a bottom-expanding drill bucket for a rotary drilling rig, including a drill rod connecting mechanism for connecting the power output end of the rotary drilling rig; a drill bucket box, the top of which is fixedly connected to the drill rod connecting mechanism, and an axially extending sliding cavity is provided inside; a sliding member, which is axially slidably disposed in the sliding cavity, and the sliding member has a receiving cavity inside; a drill bucket base, which is axially slidably disposed in the receiving cavity; a bottom-expanding mechanism, including: an upper swing arm, which is provided with a cutting element and whose top end is rotatably connected to the drill bucket box; a lower swing arm, one end of which is rotatably connected to the bottom of the upper swing arm, and the other end of which is rotatably connected to the drill bucket base; a limiting mechanism, including: a first limiting member, disposed in the lower part of the inner wall of the drill bucket box; a second limiting member, disposed in the top of the sliding member, which abuts against the first limiting member when the bottom-expanding mechanism is retracted; and a third limiting member, disposed in the bottom of the sliding member, which abuts against the upper end face of the drill bucket base when the sliding member moves downward, and abuts against the lower end face of the drill bucket box when the sliding member moves upward.

[0007] Furthermore, the sliding cavity of the drill bucket box has a polygonal cross-section, which is formed by the side plates. On the outer surfaces of the two oppositely arranged side plates, two axially extending support ribs are symmetrically arranged on each side, and an accommodating space is formed between the support ribs on the same side. The bottom expansion mechanism includes at least two upper swing arms, each upper swing arm being located in an accommodating space. A transverse limiting plate is fixedly connected between the two support ribs on the same side, which abuts against the back of the upper swing arm when the bottom expansion mechanism is in the retracted state.

[0008] Furthermore, the outer contour of the sliding component is adapted to the shape of the sliding cavity of the drill bucket housing.

[0009] Furthermore, the first limiting component includes multiple limiting plates, which are respectively fixed to the lower part of the inner wall of the side plate of the drill bucket box.

[0010] Furthermore, the second limiting member is a first limiting frame fixed to the top of the slider, located above the first limiting member.

[0011] Furthermore, the third limiting component is a second limiting frame fixed to the bottom of the sliding component, and its outer diameter is not less than the outer diameter of the side plate of the drill bucket box.

[0012] Furthermore, the drill bit base includes a support base and a centrally located protrusion, which slides in conjunction with the receiving cavity of the sliding member; symmetrical hinge seats that are hinged to the lower swing arm are provided on both sides of the protrusion, and the third limiting member abuts against the upper surface of the hinge seat when the sliding member moves down.

[0013] Furthermore, the lower control arm includes a first connecting arm and a second connecting arm connected at an acute angle; the top end of the second connecting arm is hinged to the upper control arm, and the bottom end of the second connecting arm is hinged to the hinge seat.

[0014] Furthermore, the upper swing arm is hinged to the support rib via a first pin and to the lower swing arm via a second pin; the lower swing arm is hinged to the hinge seat via a third pin.

[0015] Furthermore, when the bottom-expanding mechanism is in the retracted state, the axis of the third pin is located inside the straight line connecting the projection points of the first pin axis and the second pin axis, and this inside side is the side facing the central axis of the bottom-expanding drill bucket.

[0016] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0017] (1) This utility model achieves precise positioning of the expansion mechanism during the expansion process through the coordinated cooperation of the drill bucket box, sliding parts, drill bucket base and limiting mechanism. At the same time, the expansion height is dynamically adjusted by the axial sliding parts, thereby precisely controlling the expansion height and forming a "short and fat" expansion shape at the bottom of the pile. It has the advantages of avoiding excessive concrete volume and structural stability.

[0018] (2) This utility model sets a transverse limiting plate between the two supporting ribs so that the upper swing arm contacts and constrains the transverse limiting plate when it is retracted, thus preventing the upper swing arm from being over-retracted and affecting its re-expansion. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A front view schematic diagram of the pile type after bottom enlargement operation using a traditional bottom enlargement drill bit;

[0021] Figure 2 This is a front view structural diagram of the expanded bottom drill bucket of the present invention in the retracted state of a rotary drilling rig;

[0022] Figure 3 This is an exploded structural diagram of the enlarged bottom drill bucket of the present invention used in rotary drilling rigs;

[0023] Figure 4 This is a cross-sectional schematic diagram of the expanded bottom drill bucket of the present invention in the retracted state of a rotary drilling rig.

[0024] Figure 5 This is a front view schematic diagram of the expanded bottom mechanism of the expanded bottom drill bucket after being subjected to force.

[0025] Figure 6 This is a schematic diagram of the main structure of the bottom-expanding mechanism of the bottom-expanding drill bit after being subjected to force;

[0026] Figure 7 This is a front view schematic diagram of the pile type after the bottom-expanding operation of the bottom-expanding drill bit of this utility model;

[0027] Wherein: 1-Drill rod connecting mechanism, 2-Drill bucket box, 21-Sliding cavity, 22-Side plate, 23-Top plate, 24-Bottom plate, 25-Supporting rib, 26-Transverse limiting plate, 3-Sliding component, 31-Accommodating cavity, 4-Drill bucket base, 41-Supporting base, 42-Protrusion, 43-Hinge seat, 5-Expanding bottom mechanism, 51-Upper swing arm, 510-Cutting element, 52-Lower swing arm, 520-First connecting arm, 521-Second connecting arm, 53-First pin, 54-Second pin, 55-Third pin, 6-Limiting mechanism, 61-First limiting component, 610-Limiting plate, 611-Plug welding hole, 62-Second limiting component, 620-First limiting frame, 63-Third limiting component, 630-Second limiting frame. Detailed Implementation

[0028] The technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0029] The following is in conjunction with the appendix Figure 2 To be continued Figure 7 The present invention will be described in detail with reference to specific embodiments.

[0030] This utility model provides a bottom-expanding drill bucket for a rotary drilling rig, including a drill rod connecting mechanism 1 for connecting to the power output end of the rotary drilling rig; a drill bucket housing 2, the top of which is fixedly connected to the drill rod connecting mechanism 1, and has an axially extending sliding cavity 21 inside; a sliding member 3, which is axially slidably disposed in the sliding cavity 21, and has a receiving cavity 31 inside; a drill bucket base 4, which is axially slidably disposed in the receiving cavity 31; and a bottom-expanding mechanism 5, including: an upper swing arm 51, which is provided with a cutting element 510 and whose top end is connected to the bottom-expanding mechanism 1. The drill bucket housing 2 is rotatably connected; the lower swing arm 52 is rotatably connected at one end to the bottom of the upper swing arm 51 and at the other end to the drill bucket base 4; the limiting mechanism 6 includes: a first limiting member 61, which is disposed on the lower part of the inner wall of the drill bucket housing 2; a second limiting member 62, which is disposed on the top of the sliding member 3 and abuts against the first limiting member 61 when the bottom expansion mechanism 5 is closed; and a third limiting member 63, which is disposed on the bottom of the sliding member 3 and abuts against the upper surface of the drill bucket base 4 when the sliding member 3 moves down and abuts against the lower surface of the drill bucket housing 2 when the sliding member 3 moves up.

[0031] The drill rod connection mechanism 1 is a mechanical interface used to transmit torque and apply pressure to the rotary drilling rig, and its rigid connection with the drill bucket housing 2 ensures effective power transmission. The sliding cavity 21 of the drill bucket housing 2 is a guide structure that accommodates the sliding element 3, providing a precise axial displacement path for the sliding element 3. The accommodating cavity 31 of the sliding element 3 is an internal space used to accommodate the drill bucket base 4, allowing the drill bucket base 4 to achieve relative displacement within the sliding element 3.

[0032] Specifically, such as Figure 2 , Figure 5 and Figure 6 As shown, firstly, the rotary drilling rig drives the underreaming bucket into the pile body where underreaming is required. At this time, the underreaming bucket is in a retracted state, and the sliding member 3, under its own weight, causes the second limiting member 62 to abut against the first limiting member 61. When the bucket base 4 contacts the bottom of the pile body, the bucket base 4 stops moving, and the rotary drilling rig drives the bucket box 2 to press down and rotate. The sliding member 3 moves down synchronously with the bucket box 2. At the same time, as the distance between the bucket box 2 and the bucket base 4 continuously decreases, the upper swing arm 51 drives the lower swing arm 52 to partially unfold outward, cutting... The cutting element 510 expands outward to perform a rotating bottom-expanding operation; when the drill bucket box 2 pushes the sliding member 3 to continue moving downward until the third limiting member 63 abuts against the upper end face of the drill bucket base 4, the sliding member 3 also stops moving downward, and the drill bucket box 2 continues to move downward, forcing the upper end of the sliding member 3 to slide into the sliding cavity 21. During this process, the upper swing arm 51 continues to drive the lower swing arm 52 to unfold outward until the third limiting member 63 abuts against the lower end face of the drill bucket box 2. At this time, the drill bucket box 2 stops moving downward, and the bottom-expanding mechanism 5 reaches the fully unfolded angle, completing the bottom-expanding operation.

[0033] like Figure 7 As shown, by adjusting the stroke distance of the sliding member 3, the unfolding angle of the upper swing arm 51 and the lower swing arm 52 is changed, thereby precisely controlling the enlargement height and forming a "short and stout" enlargement shape at the bottom of the pile. At the same time, in the retracted state, the position of the locking mechanism is achieved by the abutment of the second limiting member 62 and the first limiting member 61. In the working state, the stroke range of the sliding member 3 is limited by the third limiting member 63, so that the enlargement height is independent of the length of the drill bucket box 2, realizing bidirectional stroke control and preventing structural instability caused by over-expansion.

[0034] Through the above technical solution, this application achieves dynamic adjustment of the enlarged base height. The cooperation between the sliding member 3 and the limiting mechanism 6 effectively controls the unfolding angle of the enlarged base mechanism 5, avoiding the generation of tall and thin piles and reducing the concrete over-cubic-meter ratio. At the same time, the bidirectional limiting structure ensures the stability of the mechanism under multiple diameter enlargement conditions and prevents mechanical failures caused by excessive sliding.

[0035] For details, please refer to Figures 2 to 6In this embodiment, the sliding cavity 21 of the drill bucket box 2 has a polygonal cross section and is formed by the side plate 22. The top plate 23 is fixedly connected to the top of the side plate 22, and the bottom plate 24 is sleeved on the outer side of the bottom. On the outer surface of the two oppositely arranged side plates 22, two axially extending support ribs 25 are symmetrically arranged on each side, and an accommodating space is formed between the support ribs 25 on the same side. The bottom expansion mechanism 5 includes at least two upper swing arms 51, and each upper swing arm 51 is arranged in an accommodating space. The transverse limiting plate 26 is fixedly connected between the two support ribs 24 on the same side, and abuts against the back of the upper swing arm 51 when the bottom expansion mechanism 5 is closed.

[0036] In this embodiment, the sliding cavity 21 has a polygonal cross-section, meaning its cross-sectional shape has three or more sides and is either regular or irregular, such as a rectangle or a regular hexagon. Specifically, it can be formed by welding or bolting multiple side plates together to provide stable guiding constraints and prevent circumferential deflection of the sliding component 3 during axial movement. Preferably, in this embodiment, the sliding cavity 21 has a square cross-section. The support rib 25 is a plate-shaped reinforcing structure extending longitudinally along the outer surface of the side plate 22. Specifically, it can be formed by welding steel plates of the same height as the side plates, with the distance between two support ribs 25 on the same side greater than the width of the upper swing arm 51. The transverse limiting plate 26 is a plate-shaped structure perpendicular to the support rib 25. Specifically, it can be fixed to the inner side of the support rib 25 by welding, and its height corresponds to the back position of the upper swing arm 51 when it is retracted. By contacting and constraining the retracted posture of the upper swing arm 51, it prevents the upper swing arm 51 from excessively contracting and affecting its subsequent unfolding.

[0037] Specifically, when the drill bit base 4 contacts the bottom of the pile, the drill bit box 2 moves downward, and the upper swing arm 51 swings outward with the supporting rib 25 as the fulcrum. The drill bit base 4 first slides into the receiving cavity 31, and then the sliding member 3 slides into the sliding cavity 21. Thus, under the same underreaming ratio, the length of the upper swing arm 51 can be shortened, and there is no need to increase the axial length of the drill bit box 2. This allows the underreaming mechanism 5 to be compressed into a smaller axial space when unfolded, reducing the pile height and forming a compact "short and stout" underreaming pile shape. This reduces the amount of excess concrete and also enhances the pull-out resistance of the pile foundation.

[0038] For details, please refer to Figures 2 to 6In this embodiment, the outer contour of the sliding member 3 is adapted to the shape of the sliding cavity 21 of the drill bucket box 2. The outer contour refers to the geometric shape of the outer surface of the sliding member 3, and its dimensional tolerance is controlled within the clearance range of the cavity wall of the sliding cavity 21, thus forming a sliding fit. When the drill rod connecting mechanism 1 drives the drill bucket box 2 to move downwards, the geometric constraint between the outer contour of the sliding member 3 and the sliding cavity 21 prevents radial wobble, allowing only axial movement. Simultaneously, the sliding cavity 21 adopts a polygonal structure, which can effectively suppress circumferential deflection caused by torque transmission during drilling, ensuring that the bottom diameter of the enlarged pile is consistent with the design parameters, and avoiding problems such as excessive pile diameter height or insufficient diameter due to the swaying of the sliding member 3.

[0039] For details, please refer to Figures 2 to 6 In this embodiment, the first limiting component 61 includes multiple limiting plates 610, which are respectively fixed to the lower part of the inner wall of the drill bucket box 2. The limiting plates 610 refer to multiple independently distributed plate-like structures, which can be fixed to the lower part of the inner wall of the drill bucket box by welding, forming multiple spaced constraint points. Preferably, the limiting plate 610 has a capsule-shaped plug welding hole 611 in the center. Welding at this point can strengthen the connection between the limiting plate 610 and the inner wall of the drill bucket box 2. Through this multi-support point layout, the contact load transmitted by the sliding component 3 can be dispersed, reducing the risk of local stress concentration.

[0040] Specifically, when the expanding mechanism 5 is in the retracted state, the second limiting member 62 at the top of the sliding member 3 simultaneously contacts multiple limiting plates 610. These multiple limiting plates 610 are evenly distributed circumferentially along the drill bucket housing 2, for example, four limiting plates spaced at 90-degree intervals. Each limiting plate 610 independently bears the load transmitted by the sliding member 31, avoiding localized deformation or swaying caused by single-point contact. When the drill bucket is subjected to lateral forces, the multiple limiting plates 610 provide torsional stiffness through distributed support, preventing relative rotation between the sliding member 31 and the drill bucket housing 2.

[0041] For details, please refer to Figure 3 In this embodiment, the second limiting member 62 is a first limiting frame 620 fixed to the top of the sliding member 3, located above the first limiting member 61. The second limiting member 62 is a rigid structure used to restrict the axial movement of the sliding member 3. Its function is to form rigid contact with the first limiting member 61 on the drill bucket box 2, and constrain the upper limit position of the sliding member 3 in the retracted state.

[0042] Specifically, when the bottom-expanding mechanism 5 is in the retracted state, the contact surface between the first limiting frame 620 and the first limiting member 61 forms a mechanical stop, preventing the sliding member 3 from continuing to fall off. During the bottom-expanding operation, the drill bucket base 4 remains stationary in contact with the bottom of the pile. When the third limiting member 63 on the sliding member 3 abuts against the upper surface of the drill bucket base 4, the sliding member 3 remains stationary, the drill bucket box 2 continues to move downward, and the first limiting frame 620 and the first limiting member 61 disengage from the limiting constraint. At this time, the separation distance between the first limiting frame 620 and the first limiting member 61 is converted into the unfolding angle of the upper swing arm 51. This solution, through rigid contact limiting, can maintain limiting accuracy during repeated operations, avoid displacement deviation of the sliding member 3 caused by vibration, and simplify the maintenance requirements of the limiting structure 6.

[0043] For details, please refer to Figures 2 to 6 In this embodiment, the third limiting member 63 is the second limiting frame 630 fixed to the bottom of the sliding member 3, and its outer diameter is not less than the outer diameter of the side plate 22 of the drill box 2.

[0044] The outer diameter of the second limiting frame 630 is set to be equal to or slightly larger than the outer diameter of the frame formed by the side plates 22 of the drill bucket housing 2. This structural feature allows the outer edge of the second limiting frame 630 to form a stable surface contact with the lower end face of the drill bucket housing 2 when the sliding member 3 moves upward. When the sliding member 3 slides into the sliding cavity 21 of the drill bucket housing 2 to its limit position, the second limiting frame 630 forcibly stops the sliding member 3 from moving upward. At this time, the unfolding angle of the bottom expander 5 is limited to a predetermined range, forming a "short and stout" bottom expander shape that meets the design requirements.

[0045] For details, please refer to Figures 2 to 4 In this embodiment, the drill base 4 includes a support base 41 and a centrally located protrusion 42. The protrusion 42 is slidably engaged with the receiving cavity 31 of the sliding member 3. The two sides of the protrusion 42 are symmetrically provided with hinge seats 43 that are hinged to the lower swing arm 52. The third limiting member 63 abuts against the upper surface of the hinge seat 43 when the sliding member 3 moves down.

[0046] The support base 41 is a flat plate structure that bears the working load of the bottom expansion mechanism 5. Its outer contour matches the inner diameter of the pile hole to ensure the stability of contact with the bottom of the pile during the bottom expansion operation. The protrusion 42 is a columnar structure extending upward from the center of the support base 41. In this embodiment, a square columnar structure adapted to the shape of the accommodating cavity 31 is adopted. Its height is the length of the accommodating cavity 31 of the sliding member 3. The axial sliding guidance of the drill bucket base 4 is achieved through the clearance fit with the accommodating cavity 31. The hinge seat 43 is an ear plate structure set on both sides of the protrusion 42. Specifically, it can be made of two parallel steel plates welded and fixed. The distance between the two ear plates is 1.05-1.2 times the thickness of the connecting end of the lower swing arm 52. The axis of the ear plate pin hole is perpendicular to the axis of the drill bucket to ensure that the hinge points of the lower swing arm 52 are symmetrically distributed on both sides of the axis of the drill bucket during the bottom expansion operation.

[0047] Specifically, during the reaming operation, the drill bit base 4 achieves linear axial movement guidance through the clearance fit between the protrusion 42 and the receiving cavity 31 of the sliding member 3, eliminating the skew phenomenon caused by uneven force. When the sliding member 3 moves downward under driving force, the third limiting member 63 forms a hard contact limit with the upper end face of the hinge seat 43, precisely limiting the maximum unfolding height of the reaming mechanism 5 by controlling the downward stroke of the sliding member 3. The hinge seats 43 symmetrically arranged on both sides of the protrusion 42 ensure that the hinge points of the lower swing arm 52 are concentrated near the drill bit axis. During the unfolding of the reaming mechanism 5, the force is evenly transmitted to the support base 41 through the hinge seats 43, avoiding structural deformation caused by stress concentration on one side.

[0048] For details, please refer to Figures 2 to 6 In this embodiment, the lower swing arm 52 includes a first connecting arm 520 and a second connecting arm 521 connected at an acute angle; its top end is hinged to the upper swing arm 51, and the bottom end of the second connecting arm 521 is hinged to the hinge seat 43. The acute-angle connection of the first connecting arm 520 and the second connecting arm 521 refers to the two arms being fixedly connected at an angle of less than 90 degrees, which can be achieved through welding or integral molding. This structure can form a stable triangular support when deployed, avoiding bending deformation caused by excessive length of a single arm.

[0049] Specifically, during the bottom enlargement process, the sliding member 3 moves downward, and the drill bucket base 4 slides upward relative to the sliding member 3 along the receiving cavity 31. The upper swing arm 51 drives the first connecting arm 520 to unfold outward around the hinge point, which in turn drives the second connecting arm 521 to rotate outward around the hinge seat 43 around the hinge point. After the bottom enlargement operation is completed, the rotary drilling rig drives the drill bucket box 2 to move upward. Under the action of gravity, the upper swing arm 51 moves upward and folds inward, while also driving the first connecting arm 520 to fold inward, completing the retraction of the bottom enlargement mechanism 5.

[0050] For details, please refer to Figures 1-2 , Figures 5-6 In this embodiment, the upper swing arm 51 is hinged to the support rib plate 24 via the first pin 53 and to the lower swing arm 52 via the second pin 54; the lower swing arm 52 is hinged to the hinge seat 43 via the third pin 55.

[0051] For details, please refer to Figures 2 to 3 In this embodiment, when the bottom-expanding mechanism 5 is in the retracted state, the axis of the third pin 55 is located inside the straight line L connecting the projection points of the axis of the first pin 53 and the axis of the second pin 54, and this inside side is the side facing the central axis of the bottom-expanding drill bucket.

[0052] Specifically, since the projection point of the third pin 55 axis is located inside the line L, when the drill bucket base 4 contacts the bottom of the pile, the drill bucket box 2 moves downward, the upper swing arm 51 moves downward, and applies a thrust to the lower swing arm 52 through the second pin 54, driving the lower swing arm 52 to unfold. When the bottom enlargement is completed and the bottom enlargement drill bucket needs to be pulled out, the power output end of the rotary drilling rig drives the drill bucket box 2 to move upward. The upper swing arm 51 and the lower swing arm 52 generate an unlocking force under the action of gravity and downward inertia. Because the third pin 55 is located inside the straight line L, the upper swing arm 51 and the lower swing arm 52 are always in a non-self-locking position and retract without jamming.

[0053] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the substance and scope of the present invention. Various modifications made by those skilled in the art to the above embodiments after reading this specification are all within the scope of protection of the present invention.

Claims

1. A shoe for a rotary drilling rig, characterized by: include: The drill rod connection mechanism is used to connect the power output end of the rotary drilling rig; The drill bucket box is fixedly connected to the drill rod connecting mechanism at its top end, and has an axially extending sliding cavity inside. A sliding member is axially slidably disposed within the sliding cavity, and the sliding member has an accommodating cavity inside; The drill bit base is axially slidably disposed within the accommodating cavity; Expansion mechanisms include: The upper swing arm is equipped with a cutting element and its top end is rotatably connected to the drill bucket box; The lower swing arm is rotatably connected at one end to the bottom of the upper swing arm and at the other end to the drill bucket base; Limiting mechanisms include: The first limiting member is disposed on the lower part of the inner wall of the drill bucket box; The second limiting member is located at the top of the sliding member and abuts against the first limiting member when the bottom expansion mechanism is in the closed state. The third limiting member is located at the bottom of the sliding member; it is used to abut against the upper end face of the drill bucket base when the sliding member moves down, and to abut against the lower end face of the drill bucket box when the sliding member moves up.

2. The underreamer for a rotary drill rig of claim 1, wherein, The sliding cavity of the drill bit box has a polygonal cross-section and is enclosed by side plates. On the outer surfaces of the two oppositely arranged side plates, two axially extending support ribs are symmetrically arranged on each side, and an accommodating space is formed between the support ribs on the same side. The bottom expansion mechanism includes at least two upper swing arms, each of which is located in one of the accommodating spaces. A transverse limiting plate is fixedly connected between the two support ribs on the same side, and abuts against the back of the upper swing arm when the bottom expansion mechanism is in the retracted state.

3. The underreamer for a rotary drill rig of claim 1, wherein: The outer contour of the slider is adapted to the shape of the sliding cavity of the drill box.

4. The underreamer bit for a rotary drill rig of claim 2, wherein: The first limiting component includes multiple limiting plates, which are respectively fixed to the lower part of the inner wall of the side plate of the drill bucket box.

5. The underreamer for a rotary drill rig of claim 1, wherein: The second limiting member is a first limiting frame fixed to the top of the slider, located above the first limiting member.

6. The underreamer bit for a rotary drill rig of claim 2, wherein: The third limiting member is a second limiting frame fixed to the bottom of the sliding member, and its outer diameter is not less than the outer diameter of the side plate of the drill bucket box.

7. The underreaming drill bucket for a rotary drilling rig according to claim 2, characterized in that: The drill bit base includes a support base and a centrally located protrusion, which slides in conjunction with the receiving cavity of the sliding member; symmetrical hinge seats that are hinged to the lower swing arm are provided on both sides of the protrusion, and the third limiting member abuts against the upper surface of the hinge seat when the sliding member moves down.

8. The underreaming drill bucket for a rotary drilling rig according to claim 7, characterized in that: The lower swing arm includes a first connecting arm and a second connecting arm connected at an acute angle; the top end is hinged to the upper swing arm, and the bottom end of the second connecting arm is hinged to the hinge seat.

9. The underreamer bit for a rotary drill rig of claim 7, wherein: The upper swing arm is hinged to the support rib via a first pin and to the lower swing arm via a second pin; the lower swing arm is hinged to the hinge seat via a third pin.

10. The underreaming drill bucket for a rotary drilling rig according to claim 9, characterized in that: When the bottom-expanding mechanism is in the retracted state, the axis of the third pin is located inside the straight line connecting the projection points of the first pin axis and the second pin axis, and this inside side is the side facing the central axis of the bottom-expanding drill bucket.

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