Diameter-variable sidetracking reaming-while-drilling device

Abstract

The utility model discloses a diameter-variable sidetracking reaming-while-drilling device which comprises a mandrel, and a cutting mechanism is arranged on the outer wall of the mandrel. A diameter adjusting mechanism is arranged in the cutting mechanism, and a pressure sensing and transmitting mechanism is arranged in the mandrel. The diameter adjusting mechanism comprises a positioning rod and a sliding block, the positioning rod is connected with the cutting mechanism, the pressure sensing and transmitting mechanism penetrates through the mandrel to be connected with the sliding block, the sliding block is provided with a multi-gear clamping face, and the positioning rod is in contact fit with the multi-gear clamping face. A ball is not needed to be thrown when the reamer is started, the reaming diameter is started and adjusted by adjusting the injection flow of drilling fluid, the risk of blockage of the drilling fluid is reduced, the working condition adjusting capacity is high, multi-gear adjustment is achieved through the positioning rod and the multi-gear clamping face of the sliding block, and the reamer has the advantage of being high in stability.

Description

Technical Field

[0001] The utility model relates to the technical field of oil field drilling operations, in particular to a side-drilling while-drilling reaming device with variable diameter. Background Art

[0002] In the process of deep well oil development and drilling, as the drilling tools continue to penetrate the formation, the borehole size under the layers of casing becomes smaller and smaller, and the number of drill bit replacements increases. In this process, if the well wall is unstable and squeezed by the formation, it may cause the well wall to collapse, making it difficult to continue drilling. In serious cases, the drill may get stuck or the drill tool may fall, causing drilling accidents. Therefore, in order to solve the problems of reduced casing clearance and more tripping times during deep well drilling, various types of drilling-while-drilling reamers have emerged.

[0003] The blade opening angle of the traditional while-drilling reamer is a fixed value, and the reaming diameter is a fixed value that cannot be changed. The reamer needs to be retracted to the ground to reset the blade opening angle, which is prone to safety accidents such as wellbore instability. The traditional while-drilling reamer uses a ball-throwing pressure-holding method to start the blade opening of the reamer. The starting ball is dropped once and cannot be recovered during the drilling process, and the working condition adjustment ability is poor. After the ball is dropped, the drilling fluid can no longer flow from the inside of the core shaft, and can only continue to flow downward from the bypass hole. The bypass hole is narrow and easy to clog, and the drilling fluid flow is not smooth. When the blade is recovered, it needs to be operated again, which is complicated and difficult.

[0004] Publication (Announcement) No.: CN116556844A, discloses a wireless controlled electric-driven hydraulic reamer while drilling, transmits the reaming opening control command to the communication short section, and the active cavity of the power short section moves linearly or rotates to a predetermined position. A portion of the drilling fluid will flow into the piston and the nozzle from the flow channel hole after the active cavity is aligned with the lower cover, and the piston pushes the drive ring to move to the left together. The blade, driven by the drive ring, opens upward and outward along the slide groove on the shell, and the stop ring also moves upward to compress the upper spring until it contacts the shell. At this time, the blade 8 opens to the maximum stroke position, completing the reaming operation.

[0005] Publication (announcement) number: CN116291215A, discloses a self-locking reaming while drilling device and its application, wherein the telescopic reaming blade is extended out of the groove according to the drilling fluid displacement, the telescopic reaming blade is extended to the maximum reaming diameter, the self-locking component is triggered to self-lock, the retractable self-locking component is triggered to unlock, and the telescopic reaming blade is extended and retracted.

[0006] Publication (Announcement) Number: CN218716542U, which discloses a telescopic hole - reaming tool while drilling. When drilling, the drill bit contacts the bottom of the well. After adding the drilling pressure, the transmission shaft compresses the disc spring group and drives the guide shaft to move downward until the lower end face of the end cap contacts the upper end face of the lower sub. The guide shaft relies on the wedge - shaped guide surface to extrude the piston and the hole - reaming blade. The hole - reaming blade shears the pin and extends outwards to reach the required hole - reaming diameter, and cuts and enlarges the diameter of the drilled wellbore through the cutting teeth, thus achieving the effect of hole - reaming while drilling.

[0007] The above - mentioned prior art is different from the traditional hole - reaming device, which is controlled hydraulically, but neither can achieve multi - gear stable and controllable hole - reaming. There are only two sizes in the initial state and locked at the maximum stroke. The blade cannot stably stop before reaching the maximum stroke.

[0008] In summary, the technical solutions, the technical problems to be solved and the beneficial effects of the above - disclosed technologies are all different from those of the present utility model. For more technical features, technical problems to be solved and beneficial effects of the present utility model, there is no technical inspiration in the above - disclosed technical documents. Content of the Utility Model

[0009] Aiming at the above - mentioned defects existing in the prior art, the purpose of the present utility model is to provide a sidetracking hole - reaming device with variable diameter while drilling, which can stably adjust the length of the blade extending outwards in multiple gears.

[0010] In order to achieve the above - mentioned purpose, the present utility model adopts the following technical solutions:

[0011] A sidetracking hole - reaming device with variable diameter while drilling includes a mandrel. A cutting mechanism is arranged on the outer wall of the mandrel; a diameter - adjusting mechanism is arranged inside the cutting mechanism, and a pressure - sensing and transmitting mechanism is arranged inside the mandrel. The diameter - adjusting mechanism includes a positioning rod and a slider. The positioning rod is connected to the cutting mechanism, the pressure - sensing and transmitting mechanism passes through the mandrel and is connected to the slider. The slider is provided with multiple - gear engaging surfaces, and the positioning rod is in contact and cooperation with the multiple - gear engaging surfaces.

[0012] Furthermore, the cutting mechanism includes an upper blade baffle, a blade, a baffle, and a lower blade baffle;

[0013] Specifically, the upper blade baffle is connected to the mandrel through a second fixing pin, and the lower blade baffle is connected to the mandrel through a third fixing pin;

[0014] Specifically, the baffle is fixedly arranged between the upper blade baffle and the lower blade baffle;

[0015] Specifically, the blade is movably arranged outside the baffle;

[0016] Specifically, the diameter - adjusting mechanism is arranged inside the baffle and is connected to the blade.

[0017] Furthermore, the diameter adjusting mechanism includes a positioning rod, a positioning spring, a slider, and a return spring;

[0018] Specifically, the tail of the positioning rod passes through the baffle and is connected to the blade. A spring baffle is provided at the head of the positioning rod. The positioning rod is sleeved with a positioning spring. One end of the positioning spring is connected to the baffle, and the other end is connected to the spring baffle;

[0019] Specifically, the slider is arranged between the baffle and the mandrel. The multi-stage engaging surface of the slider is an inclined cone surface, which faces the blade. At least two positioning protrusions are provided on the inclined cone surface, and the head of the positioning rod can be engaged with the positioning protrusions;

[0020] Specifically, one end of the return spring is connected to the baffle on the blade, and the other end is connected to the slider. The upper end of the slider is connected to the pressure sensing and transmission mechanism.

[0021] Furthermore, the pressure sensing and transmission mechanism includes a first rotating shaft, a first connecting rod, a second connecting rod, and an induction target;

[0022] Specifically, the first rotating shaft is arranged at the upper end of the slider. A rotating shaft hole is provided on the wall of the mandrel. A third rotating shaft is rotatably arranged on the second connecting rod, and the third rotating shaft is fixedly connected to the side wall of the rotating shaft hole;

[0023] Specifically, the induction target is located at the axis position of the mandrel. The inner end of the second connecting rod is rotatably connected to the induction target, and the outer end of the second connecting rod is rotatably connected to the first connecting rod through a second rotating shaft;

[0024] Specifically, the first connecting rod is rotatably connected to the first rotating shaft.

[0025] Furthermore, the contact surfaces of the positioning rod and the positioning protrusions are both arc surfaces.

[0026] Furthermore, the positioning spring and the return spring are always in a compressed state.

[0027] Furthermore, there is a clearance fit between the outer wall of the slider and the inner wall of the baffle, and there is a clearance fit between the inner wall of the slider and the outer wall of the mandrel.

[0028] Furthermore, the upper baffle on the blade, the baffle, the lower baffle on the blade, and the slider are all of annular structures;

[0029] Specifically, the blade, the positioning rod, the positioning spring, the return spring, the first rotating shaft, the first connecting rod, the second connecting rod, and the rotating shaft hole are a set of adjustable quantity units. At least two sets of the adjustable quantity units are provided and are evenly distributed along the circumference of the mandrel.

[0030] Furthermore, the induction target is circular and elastic.

[0031] Furthermore, a positioning mechanism and a connecting mechanism are also sleeved on the outer wall of the mandrel.

[0032] Specifically, the positioning mechanism includes an upper positioning joint and a lower positioning joint.

[0033] Specifically, the lower end face of the upper positioning joint contacts the upper end face of the wing baffle, and the upper positioning joint is connected to the mandrel through a first fixing pin.

[0034] Specifically, the upper end face of the lower positioning joint contacts the lower end face of the wing baffle, and the lower positioning joint is connected to the mandrel through a fourth fixing pin.

[0035] Specifically, the connecting mechanism includes an upper joint and a lower joint.

[0036] Specifically, the lower end of the upper joint is threadedly connected to the upper end of the upper positioning joint.

[0037] Specifically, the upper end of the lower joint is threadedly connected to the lower end of the lower positioning joint.

[0038] The utility model has the following beneficial effects compared with the prior art:

[0039] 1. The utility model realizes multi-stage adjustment through the multi-stage engaging surfaces of the positioning rod and the slider, and has the advantage of high stability.

[0040] 2. The utility model adjusts the drilling fluid flow rate, senses the pressure of the drilling fluid through the induction target, transmits the force of the induction target through the connecting rod, and adjusts the outward extension length of the wing through the positioning rod, positioning spring, slider and positioning boss, so as to realize the function of changing the reaming diameter in real time.

[0041] 3. The utility model does not need to throw a ball to start the reamer, starts and adjusts the reaming diameter by adjusting the injection flow rate of the drilling fluid, reduces the risk of drilling fluid blockage, and has strong working condition adjustment ability. When the wing is retracted, the drilling fluid flow rate is reduced, and the return spring pushes the slider to reset, realizing the function of automatic wing recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a schematic structural diagram of a side-drilling reamer with variable diameter of the utility model;

[0043] Figure 2 is the utility model Figure 1 The enlarged schematic diagram at A in.

[0044] In the figure: upper joint 1, upper positioning joint 2, mandrel 3, fixing pin 1 4, upper baffle of cutter blade 5, fixing pin 2 6, cutter blade 7, baffle 8, positioning rod 9, positioning spring 10, slider 11, positioning boss 12, rotating shaft 1 13, connecting rod 1 14, rotating shaft 2 15, outer end of connecting rod 2 16, rotating shaft 2 17, connecting rod 2 18, induction target 19, return spring 20, lower baffle of cutter blade 21, fixing pin 3 22, lower positioning joint 23, fixing pin 4 24, lower joint 25, spring baffle 26. Detailed implementation mode

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0046] Embodiment 1:

[0047] Please refer to Figures 1 to 2 , a side drilling while-drilling reaming device with variable diameter provided by the present invention includes a mandrel 3. A cutting mechanism is arranged on the outer wall of the mandrel 3. A diameter adjusting mechanism is arranged in the cutting mechanism. A pressure sensing and transmitting mechanism is arranged in the mandrel 3. The pressure sensing and transmitting mechanism passes through the mandrel 3 and is connected to the diameter adjusting mechanism to control the diameter adjusting mechanism, and further control the diameter of the cutting mechanism.

[0048] The cutting mechanism includes an upper baffle of cutter blade 5, cutter blade 7, baffle 8, and lower baffle of cutter blade 21. The upper baffle of cutter blade 5 is connected to the mandrel 3 through a fixing pin 2 6. The lower baffle of cutter blade 21 is connected to the mandrel 3 through a fixing pin 3 22. The baffle 5 is fixedly arranged between the upper baffle of cutter blade 5 and the lower baffle of cutter blade 21. The cutter blade 7 is movably arranged outside the baffle. The diameter adjusting mechanism is arranged inside the baffle and is connected to the cutter blade 7.

[0049] The diameter adjusting mechanism includes a positioning rod 9, a positioning spring 10, a slider 11, and a return spring 20. The tail of the positioning rod 9 passes through the baffle 8 and is connected to the cutter blade 7. A spring baffle 26 is arranged at the head of the positioning rod 9. The positioning rod 9 is sleeved with a positioning spring 10. One end of the positioning spring 10 is connected to the baffle 8, and the other end is connected to the spring baffle 26. The slider 11 is arranged between the baffle 8 and the mandrel 3. The slider 11 is provided with an inclined cone surface facing the cutter blade 7. At least two positioning bosses 12 are arranged on the inclined cone surface. The head of the positioning rod 9 can be engaged with the positioning bosses 12. One end of the return spring 20 is connected to the upper baffle of cutter blade 5, and the other end is connected to the slider 11. The upper end of the slider 11 is connected to the pressure sensing and transmitting mechanism.

[0050] The pressure sensing and transmission mechanism includes a first rotating shaft 13, a first connecting rod 14, a second connecting rod 18, and an induction target 19; the first rotating shaft 13 is arranged at the upper end of the slider 11, a rotating shaft hole is formed in the wall of the core shaft 3, a third rotating shaft 17 is rotatably arranged on the second connecting rod 18, the third rotating shaft 17 is fixedly connected to the side wall of the rotating shaft hole, the induction target 19 is located at the axis position of the core shaft 3, the inner end of the second connecting rod is rotatably connected to the induction target 19, the outer end 16 of the second connecting rod is rotatably connected to the first connecting rod 14 through a second rotating shaft 15, and the first connecting rod 14 is rotatably connected to the first rotating shaft 13.

[0051] Wherein, the inclined cone surface of the slider 11 and at least two positioning bosses 12 form a multi-stage engaging surface, enabling the device to have the ability of multi-stage adjustment.

[0052] Wherein, the contact surfaces of the positioning rod 9 and the positioning boss 12 are both arc surfaces, enabling the slider 11 to smoothly move the positioning rod 9 under the action of an external force.

[0053] Wherein, the positioning spring 10 and the return spring 20 are always in a compressed state, enabling the positioning rod 9 to always closely adhere to the positioning boss 12, and enabling the slider 11 to always be subjected to a downward force.

[0054] Wherein, the outer wall of the slider 11 and the inner wall of the baffle 8 are in clearance fit, and the inner wall of the slider 11 and the outer wall of the core shaft 3 are in clearance fit, enabling the slider 11 to axially slide and be radially positioned at the same time.

[0055] Wherein, the upper baffle 5 of the blade, the baffle 8, the lower baffle 21 of the blade, and the slider 11 are all annular structures.

[0056] Wherein, the blade 7, the positioning rod 9, the positioning spring 10, the return spring 20, the first rotating shaft 13, the first connecting rod 14, the second connecting rod 18, and the rotating shaft hole are a set of adjustable quantity units, and at least two sets of the adjustable quantity units are provided and are evenly distributed along the circumferential direction of the core shaft 3.

[0057] Wherein, the induction target 19 is circular and elastic, and deforms and moves under the impact of the internal liquid flow of the core shaft 3, pulling the second connecting rod 18.

[0058] A positioning mechanism and a connecting mechanism are also sleeved on the outer wall of the core shaft 3;

[0059] The positioning mechanism includes an upper positioning joint 2 and a lower positioning joint 23; the lower end surface of the upper positioning joint 2 contacts the upper end surface of the upper baffle 5 of the blade, and the upper positioning joint 2 is connected to the core shaft 3 through a first fixing pin 4; the upper end surface of the lower positioning joint 23 contacts the lower end surface of the lower baffle 21 of the blade, and the lower positioning joint 23 is connected to the core shaft 3 through a fourth fixing pin 24.

[0060] The connecting mechanism includes an upper joint 1 and a lower joint 25; the lower end of the upper joint 1 is threadedly connected to the upper end of the upper positioning joint 2, and the upper end of the lower joint 25 is threadedly connected to the lower end of the lower positioning joint 23.

[0061] Embodiment 2:

[0062] Based on Embodiment 1, this embodiment provides a method for using a side drilling while-drilling reaming device with variable diameter:

[0063] S1. The drilling fluid flows downward inside the core shaft 3;

[0064] When the drilling fluid flows normally, there is a downward impact force on the induction target 19. Through the second connecting rod 18, the third rotating shaft 17, the second connecting rod 16, the second rotating shaft 15, the first connecting rod 14, and the first rotating shaft 13, the impact force is converted into an upward pulling force on the slider 11, and the slider 11 is subjected to the downward elastic force of the return spring 20.

[0065] When the drilling fluid flows normally, the upward pulling force on the slider 11 is small, and the downward elastic force on the slider 11 is greater than the upward pulling force. The slider 11 will not move, and the cutter blade 7 will not extend out.

[0066] The positioning spring 10 causes the end of the positioning rod 9 to generate pressure on the contacted positioning boss 12, thereby generating static friction to maintain the position of the slider 11, enabling the pressure inside the core shaft 3 to fluctuate. Only when the difference between the pulling force and the elastic force of the return spring 20 is greater than the static friction due to pressure increase or decrease can the slider 11 move, changing the position of the positioning rod 9.

[0067] S2. When the drilling reaches the position where reaming is required, increase the flow rate of the drilling fluid. The downward impact force of the drilling fluid on the induction target 19 increases, the induction target 19 moves downward, causing the second connecting rod 18 to rotate around the third rotating shaft 17, pulling the induction target 19 apart, and causing the first connecting rod 14 to move upward, converting the impact force into an upward pulling force on the slider 11. The pulling force is greater than the elastic force of the return spring 20 + the static friction between the positioning rod 9 and the slider 11 + gravity. The slider 11 moves upward, the positioning rod 9 is squeezed and moves to the left, pushing the cutter blade 7 to extend outward, and the end of the positioning rod 9 contacts the next positioning boss 12;

[0068] Similarly, when the flow rate of the drilling fluid continues to increase, the positioning rod 9 is further squeezed and moves to the left, pushing the cutter blade 7 to continue to extend outward, increasing the reaming diameter, and the end of the positioning rod 9 extends below the next positioning boss 12.

[0069] S3. After the hole is expanded, the flow rate of the drilling fluid is reduced, the downward impact force of the drilling fluid on the sensing target 19 is reduced, the sensing target 19 recovers, and the pulling force is reduced accordingly. The pulling force + the static friction between the positioning rod 9 and the slider 11 is less than the elastic force of the return spring 20 + gravity, the slider 11 moves downward, and the positioning rod 9 is moved to the right by the elastic force of the positioning spring 10, pushing the blade 7 to retract inward.

[0070] All components and connection methods of components not discussed in this application belong to the known technologies in this technical field and can be directly applied without further explanation.

[0071] In the present invention, the term "plurality" means two or more than two, unless otherwise clearly defined. The terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0072] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as "up", "down", "left", "right", "front" and "back" are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention.

[0073] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0074] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A diameter-variable sidetracking reaming device, comprising a mandrel, characterized in that: The outer wall of the mandrel is provided with a cutting mechanism; The cutting mechanism is provided with a diameter adjustment mechanism, and the mandrel is provided with a pressure sensing transmission mechanism; The diameter adjustment mechanism includes a positioning rod and a slider. The positioning rod is connected to the cutting mechanism. The pressure sensing transmission mechanism is connected to the slider through the core shaft. The slider is provided with multiple engaging surfaces. The positioning rod is in contact with the multiple engaging surfaces.

2. The variable diameter sidetracking reaming device according to claim 1, characterized in that: The cutting mechanism comprises a blade upper baffle, a blade, a baffle, and a blade lower baffle; The upper baffle plate of the blade wing is connected to the core shaft through a second fixing pin, and the lower baffle plate of the blade wing is connected to the core shaft through a third fixing pin; The baffle is fixedly arranged between the upper baffle of the blade wing and the lower baffle of the blade wing; The blade is movably arranged on the outside of the baffle; The diameter adjustment mechanism is arranged on the inner side of the baffle plate and is connected with the blade wing.

3. The variable diameter side drilling while drilling reaming device according to claim 2, characterized in that: The diameter adjustment mechanism includes a positioning rod, a positioning spring, a slider, and a return spring; The tail of the positioning rod passes through the baffle and is connected to the blade wing, the head of the positioning rod is provided with a spring baffle, the outer sleeve of the positioning rod is provided with a positioning spring, one end of the positioning spring is connected to the baffle, and the other end is connected to the spring baffle; The slider is arranged between the baffle and the core shaft, the multi-block engaging surface of the slider is an inclined conical surface, the inclined conical surface faces the blade, at least two positioning bosses are arranged on the inclined conical surface, and the head of the positioning rod can be engaged with the positioning bosses; One end of the return spring is connected to the upper baffle of the blade wing, and the other end is connected to the slider. The upper end of the slider is connected to the pressure sensing transmission mechanism.

4. The variable diameter side drilling while drilling reaming device according to claim 3, characterized in that: The pressure sensing transmission mechanism comprises a first rotating shaft, a first connecting rod, a second connecting rod, and a sensing target; The first rotating shaft is arranged at the upper end of the slider, a rotating shaft hole is opened on the core shaft wall, a third rotating shaft is rotatably arranged on the second connecting rod, and the third rotating shaft is fixedly connected to the side wall of the rotating shaft hole; The induction target is located at the center of the core shaft, the inner end of the second connecting rod is rotatably connected to the induction target, and the outer end of the second connecting rod is rotatably connected to the first connecting rod through the second rotating shaft; The connecting rod 1 is rotatably connected to the rotating shaft 1.

5. The variable diameter side drilling while drilling reaming device according to claim 3, characterized in that: The contact surfaces of the positioning rod and the positioning boss are both arc surfaces.

6. The variable diameter side drilling while drilling reaming device according to claim 3, characterized in that: The positioning spring and the return spring are always in a compressed state.

7. The variable diameter sidetracking reaming device according to claim 3, characterized in that: The outer wall of the slider is clearance matched with the inner wall of the baffle, and the inner wall of the slider is clearance matched with the outer wall of the core shaft.

8. The diameter-variable sidetracking reaming device according to claim 4, characterized in that: The upper baffle plate, baffle plate, lower baffle plate and slider of the blade wing are all annular structures; The blade, positioning rod, positioning spring, return spring, rotating shaft one, connecting rod one, connecting rod two, and rotating shaft hole form a group of adjustable quantity units, and the adjustable quantity units are arranged in at least two groups and are evenly distributed along the circumference of the core shaft.

9. The variable diameter side drilling while drilling reaming device according to claim 4, characterized in that: The induction target is circular and elastic.

10. A diameter-variable sidetracking reaming device according to any one of claims 2 to 9, characterized in that: The outer wall of the mandrel is also covered with a positioning mechanism and a connecting mechanism; The positioning mechanism comprises an upper positioning joint and a lower positioning joint; The lower end surface of the upper positioning joint contacts the upper end surface of the blade upper baffle plate, and the upper positioning joint is connected to the core shaft through a fixing pin 1; The upper end surface of the lower positioning joint contacts the lower end surface of the blade lower baffle, and the lower positioning joint is connected to the core shaft through a fixing pin four; The connecting mechanism comprises an upper joint and a lower joint; The lower end of the upper joint is threadedly connected to the upper end of the upper positioning joint; The upper end of the lower joint is threadedly connected to the lower end of the lower positioning joint.

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