An anti-drop structure for a lifting sub and a hydraulic lifting clamp

Abstract

The present invention discloses an anti-drop structure for a lifting sub and a hydraulic lifting sub, belonging to the technical field of oil drilling. It includes a lifting sub body and a lifting sub. A drill string is clamped inside the lifting sub. It further includes: a lifting sub blocking mechanism installed on the lifting sub body for limiting the lifting sub, including a lock nut and a lock rod; and also includes: a drill string lowering speed adjustment system for adjusting the lowering speed of the drill string, including: a data acquisition module for collecting and detecting the state data of the drill string and the lock rod, the lowering speed of the drill string, and the impact load; a data processing module for analyzing the data obtained by the data acquisition module and then evaluating the safety state of the lock rod; a speed adjustment module for adjusting the lowering speed of the drill string according to the safety state of the lock rod output by the data processing module. The present invention can solve the problem of the lifting sub falling off and avoid the fracture of the lock rod by adjusting the lowering speed of the drill string.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil drilling, and particularly relates to an anti-drop structure for a lifting clamp insert and a hydraulic lifting clamp. Background Art

[0002] A lifting clamp is an essential tool for oil drilling operations. During the drilling operation, the lifting and lowering of the drill string must use a lifting clamp. During the tripping operation, the insert in the lifting clamp is used to hold the drill string. Due to the large force on the drill string during the lifting and lowering process, there is a risk of the insert falling off in the existing insert fixing structure, and there is a risk of the locking rod used to hold the insert breaking during the lowering process of the drill string. Summary of the Invention

[0003] In view of the deficiencies of the prior art, the present invention provides an anti-drop structure for a lifting clamp insert and a hydraulic lifting clamp, which solves the above problems.

[0004] To achieve the above objectives, the present invention is realized through the following technical solutions: An anti-drop structure for a lifting clamp insert and a hydraulic lifting clamp, including a lifting clamp body and an insert, the insert is installed on the lifting clamp body through a pin shaft, and a drill string is clamped inside the insert. It further includes:

[0005] An insert blocking mechanism, installed on the lifting clamp body, used for limiting the insert, including a lock nut and a locking rod. One end of the lock nut is embedded in a slideway opened on the lifting clamp body and is threadedly connected to the lifting clamp body. The locking rod passes through the lock nut and is slidably matched with the lock nut;

[0006] It further includes: A drill string lowering speed adjustment system, used for adjusting the lowering speed of the drill string, including:

[0007] A data acquisition module, used for collecting and detecting the state data of the drill string and the locking rod, the lowering speed of the drill string, and the impact load. The state data includes the temperature of the locking rod, the pressing force and the frictional force between the locking rod and the drill string;

[0008] A data processing module, analyzing the data obtained by the data acquisition module and then evaluating the safety state of the locking rod;

[0009] A speed adjustment module, adjusting the lowering speed of the drill string according to the safety state of the locking rod output by the data processing module.

[0010] Based on the above technical solutions, the present invention also provides the following optional technical solutions:

[0011] Further technical solution: The specific processing method of the data processing module is:

[0012] S101. Obtain the pressing force information of the locking rod on the bushing, the friction force information between the locking rod and the bushing, and the drill string lowering speed information. After dimensionless processing, import them into the pre-constructed real-time stress model to obtain the real-time total stress of the locking rod. The real-time stress model is expressed as:

[0013]

[0014] Among them, represents the real-time total stress, is the influence coefficient of speed on stress, is the influence coefficient of temperature on stress, is the static stress information of the superimposed dynamic load stress, reflecting the transient impact on the instantaneous overload risk of the locking rod. The expression of the static stress information is: is the current drill string lowering speed information, represents the current temperature, represents the reference temperature;

[0015] The static stress information includes the superposition of the dynamic stress generated by the impact load, reflecting the transient impact on the instantaneous overload risk of the locking rod. The expression of the static stress information is:

[0016]

[0017] Among them, is the static stress information of the superimposed dynamic load stress, represents the cross-sectional area of one end of the locking rod in contact with the bushing, represents the pressing force information, represents the friction force information, represents the contact area information between the locking rod and the bushing, represents the impact load;

[0018] S102. Based on the current temperature information of the locking rod and the allowable stress of the locking rod, construct a locking rod stress-temperature model. Import the allowable stress at the reference temperature, the current temperature information, and the reference temperature information into the constructed locking rod stress-temperature model to obtain the allowable stress of the locking rod at the current temperature. The locking rod stress-temperature model is expressed as:

[0019]

[0020] Among them, represents the allowable stress of the locking rod at the current temperature, represents the reference temperature the allowable stress of the locking rod at represents the temperature influence coefficient, represents the current temperature, represents the reference temperature;

[0021] S103. Compare the real-time total stress of the lock rod obtained with the allowable stress of the lock rod at the current temperature. If the real-time total stress of the lock rod is less than the allowable stress of the lock rod, it indicates that the lock rod is in a safe state, and the lowering speed of the drill string is maintained or increased. If the real-time total stress of the lock rod is greater than or equal to the allowable stress of the lock rod, it means that the lock rod is in a dangerous state, and the lowering speed of the drill string is reduced until the real-time total stress of the lock rod is less than the allowable stress of the lock rod.

[0022] Further technical solution: The specific processing method of the speed adjustment module is as follows:

[0023] If the lock rod is in a safe state, select and import the current lowering speed into the constructed first speed adjustment model to obtain the first target speed , where , where is the current lowering speed, is the speed increment, is the target speed;

[0024] If the lock rod is in a dangerous state, import the current lowering speed into the constructed second speed adjustment model to obtain the second target speed , and the expression of the second speed adjustment model is:

[0025]

[0026] where represents the second target speed, represents the current lowering speed, represents the adjustment coefficient, , represents the real-time total stress of the lock rod, represents the allowable stress of the lock rod at the current temperature.

[0027] Further technical solution: The insert core is embedded in the elevating body, and pin holes for cooperating with the pin shafts are provided on the elevating body.

[0028] Further technical solution: The pressing force is the static pressure of the lock rod on the insert core, usually determined by the pre-tightening force of the lock rod, and the calculation formula is: , is the stiffness coefficient of the lock rod, is the compression displacement of the lock rod.

[0029] Further technical solution: The frictional force is the resistance between the contact surfaces of the lock rod and the insert core, and the calculation formula is: , is the friction coefficient between the lock rod and the insert core.

[0030] Further technical solution: The impact load is calculated based on the acceleration of the drill string and the mass of the drill string, and its calculation formula is: , represents the impact load, represents the mass of the drill string, represents the acceleration information of the drill string.

[0031] Further technical solution: A chain is installed on the locking rod, and an elastic member is sleeved on the locking rod. The two ends of the elastic member respectively abut against the inner step surface of the locking rod and the inner side surface of the lock cap.

[0032] Beneficial effects

[0033] The present invention provides a structure for preventing the dropping of a lifting clamp insert and a hydraulic lifting clamp, which has the following beneficial effects compared with the prior art:

[0034] 1. In the present invention, the insert is installed on the lifting clamp body through a pin shaft. The insert blocking mechanism is used to prevent the insert from accidentally dropping during the application of the lifting clamp. A thread is processed on the lock cap in the insert blocking mechanism and is threadedly connected to the lifting clamp body. When it is necessary to install or remove the insert, the safety pin is pulled out and the chain is pulled. The locking rod moves outwards. At this time, the insert can be pressed on or removed. After the chain is released, the locking rod returns to its original position, blocking the up and down movement of the insert and preventing the insert from falling off in the pin shaft;

[0035] 2. Through the real-time force model, comprehensively considering the static pressing force, friction force, impact load and temperature-velocity influence coefficient, accurately calculate the total stress of the locking rod, capture the transient overload risk (such as the dynamic superposition effect of the impact load), avoid the fracture of the locking rod due to instantaneous overload. At the same time, a temperature compensation mechanism is set up, and the allowable stress threshold is dynamically adjusted based on the stress-temperature model to solve the misjudgment problem caused by the decrease in material strength in a high-temperature environment, ensure the accuracy of risk assessment, and at the same time adopt a dual-criterion trigger control. By comparing the real-time total stress with the temperature-corrected allowable stress in real time, quickly identify the dangerous state of the locking rod, and timely trigger the speed reduction instruction, significantly reducing the risk of equipment damage. Brief description of the drawings

[0036] Figure 1 is a three-dimensional structure schematic diagram of the present invention.

[0037] Figure 2 is a structural schematic diagram of the insert blocking mechanism of the present invention.

[0038] Figure 3 is a structural schematic diagram of the locking rod of the present invention.

[0039] Annotation of reference numerals: 1. Elevator body; 2. Die nipple; 3. Drill string; 4. Pin hole; 5. Pin; 6. Die nipple blocking mechanism; 601. Lock nut; 602. Lock rod; 603. Elastic member; 604. Nut; 605. Nut stop; 606. Safety pin; 607. Chain; 608. Pressure sensor. Detailed implementation manners

[0040] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] The following describes in detail the specific implementation of the present invention with reference to specific embodiments.

[0042] Please refer to Figures 1 to 3 , which is provided for an embodiment of the present invention, an anti-drop structure for a die nipple of an elevator and a hydraulic elevator, including an elevator body 1 and a die nipple 2. The die nipple 2 is embedded in the elevator body 1. The die nipple 2 is installed on the elevator body 1 through a pin 5. A pin hole 4 for cooperating with the pin 5 is formed on the elevator body 1. A drill string 3 is clamped in the die nipple 2. Further included are:

[0043] A die nipple blocking mechanism 6, installed on the elevator body 1, for limiting the die nipple 2, including a lock nut 601 and a lock rod 602. One end of the lock nut 601 is embedded in a slideway (not marked in the figure) formed on the elevator body 1 and is threadedly connected to the elevator body 1. The lock rod 602 passes through the lock nut 601 and is slidably matched with the lock nut 601. The other end of the lock nut 601 is sequentially installed with a nut 604 and a nut stop 605. The nut 604 is fixedly connected to the lock nut 601 by threading. The nut stop 605 is embedded in a slot (not marked in the figure) formed on the elevator body 1. The lock rod 602 is detachably installed on the lock nut 601 through a safety pin 606. Pin holes (not marked in the figure) for the safety pin 606 to pass through are formed on both the lock nut 601 and the lock rod 602. A chain 607 is installed on the lock rod 602. An elastic member 603 is sleeved on the lock rod 602. Two ends of the elastic member 603 respectively abut against the inner step surface of the lock rod 602 and the inner side surface of the lock nut 601;

[0044] In the embodiment of the present invention, the adapter bushing 2 is installed on the elevating sub body 1 through a pin shaft 5. The adapter bushing blocking mechanism 6 is used to prevent the accidental dropping of the adapter bushing 2 during the application of the elevating sub. A threaded portion is machined on the lock nut 601 of the adapter bushing blocking mechanism 6, which is threadedly connected to the elevating sub body. When it is necessary to install or remove the adapter bushing 2, the cotter pin 606 is pulled out, the chain 607 is pulled, and the locking rod 602 moves outwards. At this time, the adapter bushing 2 can be pressed on or removed. After releasing the chain, the locking rod 602 returns to its original position, blocking the up and down movement of the adapter bushing 2 and preventing the adapter bushing from falling off in the pin shaft.

[0045] As an embodiment of the present invention, in oil drilling operations, the locking rod 602 in the adapter bushing blocking mechanism 6 is prone to fracture due to the impact load (the impact load is the dynamic load generated during the lowering of the drill string 3 due to vibration, acceleration, or sudden stop. The impact load described in the embodiment of the present invention is the impact load generated by acceleration or sudden stop), the pressing force, and the frictional force during the lowering of the drill string 3. Especially in the case where the temperature has a great influence on the material properties, the faster the lowering speed of the drill string 3, the greater the impact load, and the higher the total stress of the locking rod 602; the slower the lowering speed of the drill string 3, the smaller the impact load, and the lower the total stress of the locking rod 602. Therefore, the drill string lowering speed adjustment model constructed based on the impact load, lowering speed, pressing force, frictional force of the drill string 3 during lowering, and the temperature of the locking rod 602 can real-time control the speed of the drill string 3, reduce the fracture risk of the locking rod 602, improve its service life, and improve the drilling operation efficiency at the same time.

[0046] It further includes: a drill string lowering speed adjustment system for adjusting the lowering speed of the drill string 3, including:

[0047] A data acquisition module for collecting and detecting the state data of the drill string and the locking rod 602, the lowering speed of the drill string 3, and the impact load. The state data includes the temperature of the locking rod 602, the pressing force between the locking rod 602 and the drill string, and the frictional force;

[0048] A data processing module for analyzing the data obtained by the data acquisition module and then evaluating and processing the safety state of the locking rod 602;

[0049] A speed adjustment module for adjusting the lowering speed of the drill string 3 according to the safety state of the locking rod 602 output by the data processing module.

[0050] The specific processing method of the data processing module is as follows:

[0051] S101. Obtain the pressing force information of the locking rod 602 on the adapter bushing 2, the frictional force information between the locking rod 602 and the adapter bushing 2, and the lowering speed information of the drill string 3, and import them into the pre-constructed real-time stress model, and then obtain the real-time total stress of the locking rod 602. The real-time stress model is expressed as:

[0052]

[0053] Among them, represents the real-time total stress, is the influence coefficient of speed on stress (indicating that for every 1 unit increase in the lowering speed of the drill string (such as 1 m / s), the total stress of the locking rod increases), is the influence coefficient of temperature on stress (indicating that for every 1°C increase in temperature, the total stress of the locking rod increases), is the static stress information of the superimposed dynamic load stress, is the current lowering speed information of the drill string, represents the current temperature, represents the reference temperature, , ;

[0054] The static stress information includes the superposition of the dynamic stress generated by the impact load, reflecting the risk of instantaneous overload of the locking rod caused by the transient impact. The expression of the static stress information is:

[0055]

[0056] Among them, is the static stress information of the superimposed dynamic load stress, represents the cross-sectional area of one end of the locking rod in contact with the bushing, represents the pressing force information, represents the friction force information, represents the contact area information between the locking rod and the bushing, represents the impact load;

[0057] Among them, the pressing force is the static pressure of the locking rod on the bushing 2, usually determined by the pre-tightening force of the locking rod 602. The calculation formula is: , is the stiffness coefficient of the locking rod 602, is the compression displacement of the locking rod 602;

[0058] Among them, the friction force is the resistance between the contact surfaces of the locking rod 602 and the bushing 2. The calculation formula is: , is the friction coefficient between the locking rod 602 and the bushing 2;

[0059] Among them, the impact load is calculated based on the acceleration of the drill string 3 and the mass of the drill string. The calculation formula is: , represents the impact load, represents the mass of the drill string 3, represents the acceleration information of the drill string 3;

[0060] S102. Based on the current temperature information of the lock rod 602 (the higher the temperature, the lower the allowable stress of the lock rod 602 and the higher the fracture risk), and the allowable stress of the lock rod 602, construct a lock rod stress-temperature model, and import the allowable stress at the reference temperature, the current temperature information, and the reference temperature information into the constructed lock rod stress-temperature model to obtain the allowable stress of the lock rod at the current temperature. The lock rod stress-temperature model is expressed as:

[0061]

[0062] Wherein, represents the allowable stress of the lock rod at the current temperature, represents the allowable stress of the lock rod at the reference temperature under the reference temperature, represents the temperature influence coefficient (reflecting the influence degree of temperature on the allowable stress, indicating the proportion of the decrease in the allowable stress of the material per 1°C increase in temperature (unit is ), for example , then for every 1°C increase in temperature, the allowable stress decreases by 0.2%), represents the current temperature, represents the reference temperature (usually normal temperature, such as 20 degrees Celsius);

[0063] S103. Compare the obtained real-time total stress of the lock rod with the allowable stress of the lock rod at the current temperature. If the real-time total stress of the lock rod is less than the allowable stress of the lock rod, it indicates that the lock rod 602 is in a safe state, and the lowering speed of the drill string 3 is maintained or increased. If the real-time total stress of the lock rod is greater than or equal to the allowable stress of the lock rod, it means that the lock rod is in a dangerous state, and the lowering speed of the drill string 3 is reduced until the real-time total stress of the lock rod is less than the allowable stress of the lock rod;

[0064] The specific processing method of the speed adjustment module is as follows:

[0065] If the lock rod 602 is in a safe state, the current lowering speed can be selected and imported into the constructed first speed adjustment model to obtain the first target speed , the , wherein, is the current lowering speed, is the speed increment, is the target speed, the ;

[0066] If the lock rod 602 is in a dangerous state, the current lowering speed is imported into the constructed second speed adjustment model to obtain the second target speed , and the expression of the second speed adjustment model is:

[0067]

[0068] Among them, represents the second target speed, represents the current lowering speed, represents the adjustment coefficient (the adjustment range of the drill string lowering speed when the stress of the locking rod exceeds the limit, the larger it is, the greater the speed reduction amplitude, the smaller it is, the smaller the speed reduction amplitude, and the specific value can be initially set according to the average value of past data ), , represents the total real-time stress of the locking rod, represents the allowable stress of the locking rod at the current temperature.

[0069] As an embodiment of the present invention, the data acquisition module includes:

[0070] A speed acquisition unit for detecting the acceleration and speed of the drill string 3, including an acceleration sensor and a speed sensor installed on the drill string 3;

[0071] A pressing force acquisition unit for detecting the pressing force of the drill string, including a pressure sensor 608 installed on the locking rod 602, and the pressure sensor 608 is located between two sections of the locking rod 602 and is fixedly connected to the two sections of the locking rod 602 at both ends.

[0072] In the embodiment of the present invention, through the real-time force model, the static pressing force, friction force, impact load and temperature-speed influence coefficient are comprehensively considered to accurately calculate the total stress of the locking rod, capture the transient overload risk (such as the dynamic superposition effect of the impact load), avoid the fracture of the locking rod due to instantaneous overload, and at the same time set a temperature compensation mechanism to dynamically adjust the allowable stress threshold based on the stress-temperature model, solve the misjudgment problem caused by the decrease of material strength in high-temperature environments, ensure the accuracy of risk assessment, and at the same time adopt a dual-criterion trigger control. By comparing the real-time total stress with the temperature-corrected allowable stress in real time, quickly identify the dangerous state of the locking rod, and timely trigger the speed reduction instruction, significantly reducing the risk of equipment damage.

[0073] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusively, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0074] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hydraulic elevating device with an anti - falling structure for elevating device insert, comprising an elevating device body (1) and an elevating device insert (2). The elevating device insert (2) is installed on the elevating device body (1) through a pin shaft (5). A drill string (3) is clamped inside the elevating device insert (2). It is characterized in that, Further included are: A bushing blocking mechanism (6), installed on the elevating collar body (1) for limiting the bushing (2), including a lock nut (601) and a lock rod (602). One end of the lock nut (601) is embedded in a slideway opened on the elevating collar body (1) and is threadedly connected to the elevating collar body (1). The lock rod (602) penetrates through the lock nut (601) and is slidably engaged with the lock nut (601); Further included is: A drill string lowering speed adjustment system for adjusting the lowering speed of the drill string (3), including: A data acquisition module for acquiring and detecting the state data of the drill string and the lock rod (602), the lowering speed of the drill string (3), and the impact load. The state data includes the temperature of the lock rod (602), the pressing force and the frictional force between the lock rod (602) and the drill string; A data processing module for analyzing the data obtained by the data acquisition module and then evaluating the safety state of the lock rod (602); A speed adjustment module for adjusting the lowering speed of the drill string (3) according to the safety state of the lock rod (602) output by the data processing module.

2. The hydraulic elevating bail according to claim 1, characterized in that The data acquisition module includes: A speed acquisition unit for detecting the acceleration and speed of the drill string (3), including an acceleration sensor and a speed sensor installed on the drill string (3); A pressing force acquisition unit for detecting the pressing force of the drill string, including a pressure sensor (608) installed on the lock rod (602). The pressure sensor (608) is located between two sections of the lock rod (602) and is fixedly connected to the two sections of the lock rod (602) at both ends.

3. The hydraulic elevating bail according to claim 1 or 2, characterized in that The specific processing method of the data processing module is: S101. Obtain the pressing force information of the lock rod (602) on the bushing (2), the frictional force information between the lock rod (602) and the bushing (2), and the lowering speed information of the drill string (3), perform non-dimensionalization processing, and then import them into a pre-constructed real-time stress model to obtain the real-time total stress of the lock rod (602). The real-time stress model is expressed as: Among them, represents the real-time total stress, is the influence coefficient of velocity on stress, is the influence coefficient of temperature on stress, is the static stress information of the superimposed dynamic load stress, is the current drill string lowering speed information, represents the current temperature, represents the reference temperature; The static stress information includes the superposition of the dynamic stress generated by the impact load, reflecting the instantaneous overload risk of the lock rod due to transient impact. The expression of the static stress information is: Among them, is the static stress information of the superimposed dynamic load stress, represents the cross-sectional area of one end where the locking rod contacts the bush, represents the pressing force information, represents the friction force information, represents the contact area information between the locking rod and the bush, represents the impact load; S102. Construct a lock rod stress-temperature model based on the current temperature information of the lock rod and the allowable stress of the lock rod (602), and import the allowable stress at the reference temperature, the current temperature information, and the reference temperature information into the constructed lock rod stress-temperature model to obtain the allowable stress of the lock rod at the current temperature. The lock rod stress-temperature model is expressed as: Among them, represents the allowable stress of the locking lever at the current temperature, represents the reference temperature and the allowable stress of the locking lever under it, represents the temperature influence coefficient, represents the current temperature, represents the reference temperature; S103. Compare the obtained real-time total stress of the lock rod with the allowable stress of the lock rod at the current temperature. If the real-time total stress of the lock rod is less than the allowable stress of the lock rod, it indicates that the lock rod (602) is in a safe state, and the lowering speed of the drill string (3) is maintained or increased. If the real-time total stress of the lock rod is greater than or equal to the allowable stress of the lock rod, it means that the lock rod is in a dangerous state, and the lowering speed of the drill string (3) is reduced until the real-time total stress of the lock rod is less than the allowable stress of the lock rod.

4. The hydraulic elevating bail according to claim 3, further comprising an anti-drop structure for the elevating bail insert, characterized in that, The specific processing method of the speed adjustment module is: If the locking lever (602) is in a safe state, selectively import the current lowering speed into the constructed first speed adjustment model to obtain the first target speed , the , is the current lowering speed, is the speed increment, is the target speed; If the locking lever (602) is in a dangerous state, the current lowering speed is introduced into the constructed second speed adjustment model to obtain the second target speed , and the expression of the second speed adjustment model is: Among them, represents the second target speed, represents the current lowering speed, represents the adjustment coefficient, , represents the total real-time stress of the locking rod, represents the allowable stress of the locking rod at the current temperature.

5. The hydraulic elevating bail according to claim 1, characterized in that, The reducing bushing (2) is embedded in the elevating bowl body (1), and a pin hole (4) for cooperating with the pin shaft (5) is formed in the elevating bowl body (1).

6. The hydraulic elevator slip according to claim 2, characterized in that The pressing force is the static pressure exerted by the locking rod on the bush (2), which is usually determined by the pre-tightening force of the locking rod (602). The calculation formula is as follows: , where is the stiffness coefficient of the locking rod (602), and is the compression displacement of the locking rod (602).

7. The hydraulic elevator slip according to claim 5, characterized in that, The frictional force is the resistance between the contact surfaces of the locking rod (602) and the bush (2), and the calculation formula is: , where μ is the friction coefficient between the locking rod (602) and the bush (2).

8. The hydraulic elevating bail according to claim 2, further comprising a structure for preventing the elevating bail insert from falling off, characterized in that The impact load is calculated based on the acceleration of the drill string (3) and the mass of the drill string, and its calculation formula is: , represents the impact load, represents the mass of the drill string (3), represents the acceleration information of the drill string (3).

9. The hydraulic elevating bowl with an anti-dropping structure for the elevating bowl reducing bushing according to claim 1, wherein a chain (607) is installed on the locking rod (602), an elastic member (603) is sleeved on the locking rod (602), and two ends of the elastic member (603) respectively abut against the inner step surface of the locking rod (602) and the inner side surface of the locking cap (601).

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