A direct drive pre-tension mechanical joint, a precast concrete pile and a connecting method

Abstract

The application discloses a kind of direct drive pre-tightening mechanical joint, precast concrete pile and connecting method, wherein the joint includes, the plug-in rod with plug;With accommodating cavity big nut is equipped;And with big nut thread connection pre-tightening nut;It is equipped in pre-tightening nut and clamping mechanism;And setting is in pre-tightening nut and is located on the outside portion of accommodating cavity, for after plug is inserted into the insertion cavity of pre-tightening nut and is clamped with clamping mechanism, by driving part from the lateral drive of pre-tightening nut, so that pre-tightening nut rotates and moves along the axial direction of the big nut, to drive structure for locking plug and clamping mechanism in the axial direction of the big nut.The pre-tightening mechanical joint disclosed in the application effectively eliminates the gap between the plug and the pre-tightening nut, so that when the precast concrete pile is connected using the mechanical joint, the connection of the precast concrete pile will not crack and crack when subjected to pulling force, shear force or bending force.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of prefabricated components, in particular to a direct-drive pre-tightening mechanical joint, a prefabricated concrete pile and a connecting method. BACKGROUND

[0002] Generally, engineering piles (prefabricated piles) are multi-section piles, and the existing prefabricated concrete pile ends are generally connected between piles by mechanical joints.

[0003] In the Technical Standard for Prestressed Concrete Pipe Pile JGJ / T406-2017, Article 5.1.7 provides that for prestressed pipe piles with strict requirements for no cracks, the crack control level should be first grade; Article 5.1.8 provides that when the pipe pile shaft is in tension, the crack control level is first grade; when the pipe pile shaft is in bending, the crack control level of the pipe pile in weak corrosion environment and above is second grade, and the crack control level of the pipe pile in medium and strong corrosion environment and above is first grade.

[0004] In the Code for Design of Concrete Structures GB50010-2015, Article 3.4.4 provides that the stress crack control level of the normal section of a structural member is divided into three grades, and the grade division and requirements should comply with the following provisions:

[0005] First grade - members with strict requirements for no cracks, when calculated according to load standard combination, the tensile edge concrete of the member should not produce tensile stress.

[0006] Second grade - members with general requirements for no cracks, when calculated according to load standard combination, the tensile stress of the tensile edge concrete of the member should not be greater than the standard value of the tensile strength of the concrete.

[0007] Third grade - members allowed to have cracks: for reinforced concrete members, when calculated according to load quasi-permanent combination considering the influence of long-term action, the maximum crack width of the member should not exceed the maximum crack width limit value specified in Table 3.4.5 of the present specification. For prestressed concrete members, when calculated according to load standard combination and considering the influence of long-term action, the maximum crack width of the member should not exceed the maximum crack width limit value specified in Table 3.4.5 of the present specification; for prestressed concrete members in Class 2a environment, they should also be calculated according to load quasi-permanent combination, and the tensile stress of the tensile edge concrete of the member should not be greater than the standard value of the tensile strength of the concrete. In the provisions of Table 3.4.5 of the present specification, it is specified that the crack control level of prestressed concrete structures in Class 3a and 3b environments is first grade, and the crack control level in Class 2b environment is second grade. In the first and second crack control levels, no cracks are allowed to occur. In Class 2a environment, the crack control level is third grade, and the maximum crack width limit is 0.1mm. In Class 1 environment, the crack control level is third grade, and the maximum crack width limit is 0.2mm.

[0008] As Figure 31 The first structure of the existing mechanical joint is shown in the figure, which includes a large nut 2, a small nut 21, a plug rod 1 and a connecting piece 90; one end of the plug rod is threadedly connected with the small nut, and the other end is provided with a plug; the connecting piece is threadedly connected with the large nut, and one end of the connecting piece placed in the large nut is provided with a plurality of elastic clamping pieces; the plug is inserted from one end of the connecting piece and can abut against the elastic clamping pieces, thereby achieving the clamping connection of the plug rod and the connecting piece, so that the mechanical joint can realize the quick connection of two sections of precast concrete piles. However, the mechanical joint for connecting precast concrete piles has the following disadvantages: 1. When the mechanical joint is used to connect precast concrete piles, the plug rod may be over-inserted into the connecting piece due to the inclination of the pile end face and other reasons. When the plug rod is over-inserted into the connecting piece, the entire or partial mechanical joint at the connecting end face of the precast concrete pile will produce an axial gap under the action of pulling force, shearing force or bending force, thereby causing the connecting end face of the precast concrete pile to also produce an axial gap, resulting in cracks in the mechanical joint connection of the precast concrete pile. Specifically, as Figure 31 When the plug rod is over-inserted into the connecting piece, an axial gap Δh will be formed between the end of the elastic clamping piece and the blocking surface of the plug, so that under the action of external force, the connecting end face of the precast concrete pile will also produce a corresponding axial gap, making it unable to meet the requirements of the "Technical Standard for Prestressed Concrete Pipe Piles" JGJ / T406-2017, which stipulates that the crack control level of prestressed pipe piles with strict requirements should be first level according to article 5.1.7; the crack control level of pipe pile shaft under axial tension is first level according to article 5.1.8; the crack control level of pipe pile shaft under bending is second level in weak corrosion environment and above, and first level in medium and strong corrosion environment and above; 2. Since the large nut and the connecting piece are connected by threads, and the small nut and the plug rod are also connected by threads, there will be a certain axial gap in the threaded connection, which will also cause the connecting end face of the precast concrete pile to produce a corresponding axial gap under the action of pulling force on the mechanical joint, further increasing the size of the cracks in the connection of the precast concrete pile, making it unable to meet the crack control requirements in the "Technical Standard for Prestressed Concrete Pipe Piles"; 3. As shown in Figure 32 When the mechanical joint is used to connect precast concrete piles, there is also a problem of under-insertion of the plug of the plug rod into the connecting piece, i.e. when the plug rod is inserted into the connecting piece, the end of the elastic clamping piece does not enter the ring groove of the plug rod, so the plug rod and the connecting piece cannot be clamped, thereby causing the connection of the pile to fail.

[0009] As Figure 33The second structure of the existing mechanical joint is shown, which comprises a large nut 2, a small nut 21, a plug rod 1, an intermediate nut 91, an elastic member 92 and a card 93. One end of the plug rod is threadedly connected with the small nut, the other end is provided with a plug, the intermediate nut is threadedly connected with the large nut, the intermediate nut is arranged at one end of the large nut and is provided with a tapered clamping surface, the elastic member and a plurality of cards are arranged in the accommodating cavity of the large nut, the elastic member abuts the plurality of cards on the tapered clamping surface of the intermediate nut, the plug is inserted into one end of the intermediate nut and can compress the elastic member, so that the plug passes through the space surrounded by the plurality of cards to be clamped between the intermediate nut and the plug, so as to realize the rapid connection of two sections of precast concrete piles. However, the following problems exist in the connection of the precast concrete piles by using the mechanical joint: 1. During the process of inserting the plug rod into the intermediate nut, the central axis x-x of the plug rod is different from the central axis y-y of the intermediate nut, so that, as shown in Figure 33 、 Figure 34 and Figure 35 , during the process of inserting the plug rod into the intermediate nut, the card close to the axis of the plug rod is first contacted with the plug, and the card far away from the axis of the plug rod is contacted with the plug later, the lower card is first contacted with the plug and is compressed by the spring under the action of the plug, and the upper card is contacted with the plug later, so that, as shown in Figure 33 , one side of the card enters between the plug and the intermediate nut, and the other side of the card cannot enter between the plug and the intermediate nut; or, as shown in Figure 34 , the clamping positions of the plurality of cards and the plug and the intermediate nut are different, thereby causing the pile connection failure or the low connection strength of the mechanical joint, so that, when the precast concrete pile is subjected to the pulling force, the shearing force or the bending force, the axial slip occurs between the plug rod and the card of the mechanical joint, thereby causing the axial gap of the whole or part of the mechanical joint at the pile connection end surface, and the cracking of the mechanical joint connection of the precast concrete pile; 2. After the plug is inserted into the intermediate nut and clamped with the card, the plug, the card and the intermediate nut do not form the complete fitting of the wedge surface (the force between the plug and the card is very small), so that, when the plug rod is subjected to the pulling force, the shearing force or the bending force, the plug of the plug rod will extrude the card, thereby causing the axial slip of the card relative to the plug, so that, when the precast concrete pile is connected by using the mechanical joint, the axial gap of the whole or part of the mechanical joint at the pile connection end surface will be caused when the precast concrete pile is subjected to the pulling force, the shearing force or the bending force, thereby causing the axial gap of the precast concrete pile connection, and the cracking of the mechanical joint connection of the precast concrete pile; 3. As shown in Figure 35 , the clamping surfaces of the card and the plug are both tapered cylindrical surfaces, and the clamping positions of the card and the plug are uncertain, so that, when the card is clamped with the plug, the clamping surfaces of the card and the plug do not completely fit. As shown in Figure 36As shown in the figure, Q1 to Q5 curves represent the cross-sectional radius curves of the clamping surface of the plug at different positions, and J curve represents the cross-sectional radius curve of the card at a certain position. As shown in the figure, when J curve is at Q1 position, J curve completely matches Q1, and when J curve is at Q2 to Q5, the gap between J curve and Q curve gradually increases, that is, when the card is at different positions of the plug, the clamping state of the card and the plug is different, that is, it cannot be guaranteed that the clamping surface of the card completely matches the clamping surface of the plug. That is, the card and the plug are in line contact, and when the mechanical joint is subjected to pulling force, shearing force or bending force, axial slip occurs between the card and the plug or the card is partially embedded into the plug (or the card is deformed under force), thereby causing axial gap of the mechanical joint. That is, when the mechanical joint is used for connecting precast concrete piles and subjected to pulling force, shearing force or bending force, axial gap also occurs between the connecting end surfaces of the precast concrete piles, causing cracks at the connecting position of the mechanical joint of the precast concrete piles; 4. Since the large nut and the intermediate nut are connected by threads, and the small nut and the plug are connected by threads, the threaded connection also has a certain axial gap, and when the mechanical joint is subjected to pulling force, shearing force or bending force, the axial gap of the threaded connection also causes the axial gap between the connecting end surfaces of the precast concrete piles, causing cracks at the connecting position of the mechanical joint of the precast concrete piles. The mechanical structure has the above-mentioned multiple deficiencies, therefore, when the mechanical joint is used for connecting precast concrete piles, it is easy to cause the precast concrete pile connection to fail to meet the requirements of "Prestressed Concrete Pipe Pile Technical Standard" JGJ / T406-2017, which stipulates that the crack control level of prestressed pipe piles with strict requirements should be first level; the crack control level of pipe piles under axial tension is first level; the crack control level of pipe piles under bending is second level in weak corrosion environment and above; the crack control level of pipe piles in medium and strong corrosion environment and above is first level.

[0010] The existing mechanical joint has the problem of axial gap, which causes the precast concrete pile connection to have a gap when subjected to pulling force, shearing force and / or bending force, thereby causing cracks at the joint of the precast concrete pile. The precast pile foundation is a hidden underground project, and the precast pile itself cannot be repaired.

[0011] Safety hazards of concrete precast pile joints:

[0012] When the precast concrete pile bears the bending resistance and the shearing force, the axial gap of the mechanical joint will cause cracks at the joint of the precast concrete pile, and further cause the pile and the pile not to be on the same axis, so that the local eccentric force is generated on the connecting end surface of the pile; the concrete at the end surface of the pile is damaged or cracked, and the building pile foundation has a safety hazard.

[0013] When the precast concrete pile bears the tension, the axial gap generated by the mechanical joint cannot be ensured to be completely consistent, and the axial tensile bearing capacity design value of the precast pile is considered according to the number of main reinforcement (the number of mechanical joints); when the mechanical joint bears the tension, it will be broken one by one, and the building pile foundation has a safety hazard.

[0014] When the precast concrete pile bears the bending resistance, the shearing force and the tension, the axial gap at the joint of the precast concrete pile causes cracks at the joint, which can cause underground water to corrode the mechanical connecting piece and / or the main reinforcement of the precast pile, so that the durability of the precast pile is difficult to guarantee. According to the annual corrosion rate of steel pile in Table 4.1.18 of JGJ94-2008, when the steel pile is above the ground and in the environment without corrosive gas or corrosive volatile medium, the single-side corrosion rate is 0.05-0.1mm / y; when the steel pile is below the ground and above the water level, the single-side corrosion rate is 0.05mm / y; when the steel pile is below the ground and below the water level, the single-side corrosion rate is 0.03mm / y; when the steel pile is below the ground and in the water level fluctuation area, the single-side corrosion rate is 0.1-0.3mm / y; therefore, when the precast concrete pile has cracks due to the axial gap of the mechanical joint, the mechanical joint and / or the main reinforcement will be rapidly corroded, so that the durability of the precast pile is difficult to guarantee, and the severity of the harm is self-evident. SUMMARY

[0015] The present application aims at the problem that the axial gap of the existing mechanical joint connection mechanism causes cracks at the joint of the precast concrete pile, and the main reinforcement and / or the mechanical joint are corroded, and the end surface of the pile is locally pressed, and proposes a direct-drive pre-tightening mechanical joint to solve the problem of the safety hazard caused by the axial gap of the existing mechanical joint connection.

[0016] The technical means adopted by the present application are as follows:

[0017] The direct drive pre-tightening mechanical joint comprises a plug rod, one end of the plug rod being a plug; a large nut, the large nut being provided with a containing cavity; a pre-tightening nut, the pre-tightening nut being arranged at one end of the containing cavity and being threadedly connected with the large nut, and part of the pre-tightening nut being located outside the containing cavity, the pre-tightening nut being provided with an insertion cavity; a clamping mechanism, the clamping mechanism being arranged in the containing cavity; and a transmission structure, the transmission structure being arranged on the part of the pre-tightening nut located outside the containing cavity, and being used for driving the pre-tightening nut to rotate and move axially along the large nut after the plug is inserted into the insertion cavity of the pre-tightening nut and clamped with the clamping mechanism, so as to lock the plug and the clamping mechanism in the axial direction of the large nut.

[0018] Further, the transmission structure is a clamping or pushing structure arranged on the outer wall or end of the pre-tightening nut away from the end threadedly connected with the large nut.

[0019] Further, the clamping or pushing structure is a clamping tooth, a pushing groove, a pushing protrusion or a bevel gear.

[0020] Further, the outer wall of the pre-tightening nut away from the end threadedly connected with the large nut is provided with a pushing groove, the driving component is a toothed rod, one end of the toothed rod is provided with a driving tooth, the driving tooth of the toothed rod can be clamped with the pushing groove from the side of the pre-tightening nut and drive the pre-tightening nut to rotate in the process of pushing and pulling of the toothed rod; or, the driving component is a driving rod, one end of the driving rod can be inserted into the pushing groove from the side of the pre-tightening nut and drive the pre-tightening nut to rotate in the process of pushing and pulling of the driving rod; or,

[0021] The outer wall of the pre-tightening nut away from the end threadedly connected with the large nut is provided with a first pushing protrusion, the driving component is a pushing rod, the pushing rod can be inserted between two adjacent first pushing protrusions from the side of the pre-tightening nut and drive the pre-tightening nut to rotate in the process of rotation of the pushing rod; or,

[0022] The end of the pre-tightening nut away from the end threadedly connected with the large nut is provided with a first bevel gear, the driving component is a bevel gear driving rod, one end of the bevel gear driving rod is provided with a second bevel gear, the second bevel gear of the bevel gear driving rod can be clamped with the first bevel gear from the side of the pre-tightening nut and drive the pre-tightening nut to rotate in the process of rotation of the bevel gear driving rod; or,

[0023] The second driving protrusion is arranged on the end of the pre-tightening nut away from the end threadedly connected with the large nut, the driving component is a bevel gear driving rod, the second bevel gear is arranged on one end of the bevel gear driving rod, and the second bevel gear of the bevel gear driving rod can engage with the second driving protrusion of the pre-tightening nut laterally and drive the pre-tightening nut to rotate in the rotation process of the bevel gear driving rod.

[0024] Further, the positioning sleeve is arranged in the accommodating cavity and used for correcting the plug rod during insertion of the plug rod into the accommodating cavity.

[0025] Further, the positioning sleeve is arranged between the end of the pre-tightening nut arranged in the large nut and the bottom surface of the accommodating cavity, the positioning sleeve is provided with a positioning hole, after the plug is inserted into the insertion cavity of the pre-tightening nut and radially clamped with the clamping mechanism, part of the plug is inserted into the positioning hole, and the radial gap between the plug and the positioning hole is smaller than the radial gap between the clamping mechanism and the pre-tightening nut or the radial gap between the plug and the positioning hole is smaller than the radial gap between the clamping mechanism and the plug.

[0026] Further, the clamping mechanism is a plurality of elastic clamping pieces arranged on the end of the pre-tightening nut arranged in the large nut, the pre-tightening nut rotates and moves axially along the large nut, the clamping surfaces at the ends of the plurality of elastic clamping pieces can abut against the clamping surfaces on the plug to lock the plug and the pre-tightening nut in the axial direction of the large nut.

[0027] Further, the clamping mechanism is a plurality of elastic clamping pieces arranged on the end of the pre-tightening nut arranged in the large nut, the first teeth are arranged on the inner wall of the elastic clamping piece, the second teeth are arranged on the outer wall of the plug, the first teeth and the second teeth are clamped with each other, and the tooth surfaces of the first teeth and the second teeth can abut against each other to lock the plug and the pre-tightening nut in the axial direction of the large nut during rotation and axial movement of the pre-tightening nut along the large nut.

[0028] Further, the insertion cavity of the pre-tightening nut is provided with a clamping piece accommodating groove, the clamping mechanism is a clamping piece arranged in the clamping piece accommodating groove, the inner wall of the side of the clamping piece accommodating groove close to the plug insertion end of the pre-tightening nut is a first clamping surface, and the plug is provided with a second clamping surface.

[0029] When the plug is inserted into the insertion cavity of the pre-tightening nut and connected with the card, the card is located between the first and second connecting surfaces; the pre-tightening nut rotates and moves axially along the large nut, so that the first connecting surface moves towards the side of the card and the first and second connecting surfaces abut against the card respectively, thereby locking the plug and the pre-tightening nut in the axial direction of the large nut.

[0030] Further, the card accommodating groove is directly machined on the inner wall of the insertion cavity of the pre-tightening nut; or,

[0031] The insertion cavity of the pre-tightening nut is provided with a blocking ring, and the blocking ring and the connecting surface in the insertion cavity form the card accommodating groove.

[0032] Further, before the plug and the connecting mechanism are locked in the axial direction of the large nut, the threaded connection between the pre-tightening nut and the large nut is a loose threaded connection.

[0033] Further, after the plug and the connecting mechanism are locked in the axial direction of the large nut, the tensile strength of the connection between the plug and the connecting mechanism is greater than or equal to the tensile strength of any of the main reinforcement, the large nut and the small nut.

[0034] Further, it further comprises a small nut for connecting with the insertion rod base of the insertion rod.

[0035] A precast concrete pile comprises a precast concrete pile body, a main reinforcement and the direct drive pre-tightening mechanical joint.

[0036] The main reinforcement is arranged in the precast concrete pile body, one end of the precast concrete pile body is provided with the large nut, and the large nut is provided with the connecting mechanism and the pre-tightening nut.

[0037] The other end of the precast concrete pile body is provided with the insertion rod.

[0038] The end of the precast concrete pile body is provided with a drive component accommodating groove.

[0039] When two adjacent precast concrete piles are connected, one end of the drive component accommodating groove communicates with the outer wall of the precast concrete pile body, and the other end extends to the end of the pre-tightening nut, so that after the drive component is inserted into the drive component accommodating groove from the outer wall of the precast concrete pile body, the drive component can interact with the transmission structure arranged on the pre-tightening nut, so that the pre-tightening nut rotates and moves axially along the large nut, thereby locking the plug and the connecting mechanism in the axial direction of the large nut.

[0040] Further, the end of the precast concrete pile body provided with the inserting rod is also provided with a small nut, one end of the large nut and the small nut is connected with two ends of the main reinforcement respectively, and the other end of the inserting rod is threadedly connected with the small nut.

[0041] Further, after the driving component drives the pre-tightening nut to rotate radially and locks the plug and the clamping mechanism in the axial direction of the large nut, the driving component remains in or moves out of the driving component accommodating groove.

[0042] Further, the connecting end face of the precast concrete pile body and the direct drive pre-tightening mechanical joint are also injected with structural glue.

[0043] A connecting method of the precast concrete pile, comprising the following steps:

[0044] The end of the precast concrete pile provided with the inserting rod is moved to the end of the adjacent precast concrete pile provided with the pre-tightening nut, and the plug of the inserting rod is inserted into the inserting cavity of the pre-tightening nut to realize the clamping of the plug and the clamping mechanism;

[0045] The driving component is inserted from the outer wall of the precast concrete pile, and the driving component drives the transmission structure, so that the pre-tightening nut rotates and moves in the axial direction of the large nut, thereby locking the plug and the clamping mechanism in the axial direction of the large nut.

[0046] Compared with the prior art, the direct drive pre-tightening mechanical joint has the following beneficial effects: the direct drive pre-tightening mechanical joint disclosed by the application is provided with a transmission structure, after the plug is inserted into the cavity and is radially clamped with the clamping mechanism, the pre-tightening nut is driven from the side by the driving part, so that the pre-tightening nut moves in the axial direction of the large nut, thereby locking the plug and the clamping mechanism in the axial direction of the large nut, and effectively eliminating the axial gap between the plug, the clamping mechanism and the pre-tightening nut. Further, the pre-tightening nut, the plug and the clamping mechanism are locked in the axial direction, and a certain axial force (tightening force) is generated in the locking process, under the action of the axial force, the axial gap between the pre-tightening nut, the plug, the large nut, the clamping mechanism and the small nut can be effectively eliminated, so that when the precast concrete pile connected by the mechanical joint is subjected to pulling force, shearing force or bending force, the connected part of the precast concrete pile will not crack and generate cracks, and the precast concrete pile connected by the mechanical joint can meet the relevant requirements of the crack grade control in the Technical Standard for Prestressed Concrete Pipe Pile JGJ / T 406-2017, and the problem that the existing mechanical joint connection mechanism generates a gap, causing cracks at the joint of the precast concrete pile and causing safety hazards of the building pile foundation is eliminated. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 It is a front view of the first embodiment of the direct drive pre-tightening mechanical joint disclosed by the application, and the transmission structure adopts a bevel gear form;

[0048] Figure 2 It is an axial view of the first embodiment of the direct drive pre-tightening mechanical joint disclosed by the application;

[0049] Figure 3 It is a sectional view of the first embodiment of the direct drive pre-tightening mechanical joint disclosed by the application, and the clamping mechanism adopts an elastic card form, and the state diagram when the plug and the pre-tightening nut are not axially locked;

[0050] Figure 4 It is a state diagram of the first embodiment of the direct drive pre-tightening mechanical joint disclosed by the application after the plug is inserted into the pre-tightening nut and the plug and the clamping mechanism are axially locked;

[0051] Figure 5 It is a structure diagram of the pre-tightening nut of the first embodiment of the direct drive pre-tightening mechanical joint disclosed by the application;

[0052] Figure 6 It is a diagram of the driving part in the application, and the driving part is a bevel gear driving rod;

[0053] Figure 7 Structure diagram of the plug-in rod in the first embodiment of the direct-drive pre-tightening mechanical joint disclosed in the present application;

[0054] Figure 8 Front view of the second embodiment of the direct-drive pre-tightening mechanical joint disclosed in the present application, in which the transmission structure adopts the form of bevel gears and protrusions;

[0055] Figure 9 Axial view of the second embodiment of the direct-drive pre-tightening mechanical joint disclosed in the present application;

[0056] Figure 10 Front view of the third embodiment of the transmission structure of the direct-drive pre-tightening mechanical joint disclosed in the present application, in which the transmission structure adopts the form of a pushing groove and a toothed rod;

[0057] Figure 11 Front view of the fourth embodiment of the transmission structure of the direct-drive pre-tightening mechanical joint disclosed in the present application, in which the transmission structure adopts the form of a pushing groove and a driving rod;

[0058] Figure 12 Front view of the fifth embodiment of the transmission structure of the direct-drive pre-tightening mechanical joint disclosed in the present application, in which the transmission structure adopts the form of a pushing groove and a screw rod;

[0059] Figure 13 Front view of the sixth embodiment of the transmission structure of the direct-drive pre-tightening mechanical joint disclosed in the present application, in which the transmission structure adopts the form of a wavy rod and protrusions;

[0060] Figure 14 Top view of the positioning sleeve of the direct-drive pre-tightening mechanical joint disclosed in the present application;

[0061] Figure 15 Axial view of the positioning sleeve of the direct-drive pre-tightening mechanical joint disclosed in the present application;

[0062] Figure 16 Second embodiment of the clamping mechanism of the direct-drive pre-tightening mechanical joint disclosed in the present application, in which the clamping mechanism adopts the form of elastic clamping pieces provided with clamping teeth;

[0063] Figure 17 Partial enlarged view of the state of the first tooth and the second tooth in the second embodiment of the clamping mechanism of the direct-drive pre-tightening mechanical joint disclosed in the present application when the plug-in rod and the locking nut are not axially locked;

[0064] Figure 18 Partial enlarged view of the state of the first tooth and the second tooth in the second embodiment of the clamping mechanism of the direct-drive pre-tightening mechanical joint disclosed in the present application when the plug-in rod and the locking nut are axially locked;

[0065] Figure 19This is a third embodiment of the snap-fit ​​mechanism for the direct-drive pre-tightening mechanical joint disclosed in this invention. The snap-fit ​​mechanism adopts a snap ring structure, and the insertion rod and the locking nut are not axially locked in the figure.

[0066] Figure 20 This is a third embodiment of the snap-fit ​​mechanism for the direct-drive pre-tightening mechanical joint disclosed in this invention. The snap-fit ​​mechanism adopts a snap ring structure, and the insertion rod and the locking nut are axially locked in the figure.

[0067] Figure 21 This is a structural diagram of the preload nut in the third embodiment of the snap-fit ​​mechanism of the direct-drive preload mechanical joint disclosed in this invention;

[0068] Figure 22 This is a front view of the retaining ring in the third embodiment of the snap-fit ​​mechanism of the direct-drive pre-tightening mechanical joint disclosed in this invention;

[0069] Figure 23 This is an axial view of the retaining ring in the third embodiment of the snap-fit ​​mechanism of the direct-drive pre-tightening mechanical joint disclosed in this invention;

[0070] Figure 24 This is the fourth embodiment of the snap-fit ​​mechanism for the direct-drive pre-tightening mechanical joint disclosed in this invention. The snap-fit ​​mechanism adopts a snap ring structure, and the snap ring receiving groove is formed by a retaining ring and a pre-tightening nut. In the figure, the insert rod and the locking nut are not axially locked.

[0071] Figure 25 This is the fourth embodiment of the snap-fit ​​mechanism of the direct drive pre-tightening mechanical joint disclosed in this invention. In the figure, the insert rod and the locking nut are axially locked.

[0072] Figure 26 This is a schematic diagram of a precast concrete pile connection with the direct-drive pre-tightening mechanical joint disclosed in this invention. The number of piles in the diagram is two sections.

[0073] Figure 27 A cross-sectional view of a precast concrete pile connection having the direct-drive pre-tightening mechanical joint disclosed in this invention.

[0074] Figure 28 for Figure 27 A magnified view of a section at point D;

[0075] Figure 29 A view of the connection end of a precast concrete pile having the direct-drive pre-tightening mechanical joint disclosed in this invention;

[0076] Figure 30 for Figure 29 A magnified view of a section at point F in the middle;

[0077] Figure 31 This is a structural diagram of the first type of existing mechanical connector, with the plug in an over-insertion state.

[0078] Figure 32 This is a structural diagram of the first type of existing mechanical connector, with the plug in a partially inserted state.

[0079] Figure 33 This is a structural diagram of the existing second type of mechanical connector, showing the insertion process when the axis of the insertion rod and the axis of the intermediate nut are not collinear.

[0080] Figure 34 The diagram shows the structure of the second type of mechanical connector. In the diagram, the plug of the insertion rod contacts the lower card first, preventing the lower card from entering between the plug and the middle nut.

[0081] Figure 35 This is a structural diagram of the existing second type of mechanical connector, in which multiple clips are held at different positions between the plug and the intermediate nut;

[0082] Figure 36 This is a schematic diagram showing the contact state between the card and the plug contact surface of the existing second type of mechanical connector;

[0083] In the diagram: 1. Insert rod; 10. Plug; 11. Insert rod connecting part; 12. Insert rod base; 13. Second snap-fit ​​surface; 2. Large nut; 20. Receiving cavity; 21. Small nut; 4. Pre-tightening nut; 40. Insertion cavity; 41. Elastic card; 42. First tooth; 43. Card receiving slot; 44. Card; 45. First snap-fit ​​surface; 46. Retaining ring; 47. Pre-tightening nut connecting part; 48. Pre-tightening nut driving part; 480. Pushing groove; 481. Engaging tooth; 48 2. First actuating protrusion; 483. First conical tooth; 484. Second actuating protrusion; 6. Driving component; 60. Toothed rod; 600. Driving tooth; 61. Driving rod; 62. Actuating rod; 63. Conical tooth driving rod; 630. Second conical tooth; 7. Positioning sleeve; 70. Positioning hole; 8. Precast concrete pile; 80. Precast concrete pile body; 81. Main reinforcement; 82. Driving component receiving groove; 90. Connector; 91. Intermediate nut; 92. Elastic element; 93. Card. Detailed Implementation

[0084] like Figure 1 and Figure 2 The image shows a direct-drive preload mechanical joint disclosed in this invention, comprising:

[0085] Insert rod 1, one end of which is a plug 10; large nut 2, which has a receiving cavity 20; preload nut 4, which is disposed at one end of the receiving cavity 20 and threadedly connected to the large nut 2, with part of the preload nut 4 located outside the receiving cavity 20, and the preload nut 4 has an insertion cavity 40; snap-fit ​​mechanism, which is disposed inside the receiving cavity 20;

[0086] The transmission structure is arranged on the outer side of the pre-tightening nut 4 in the accommodating cavity 20, and is used to drive the pre-tightening nut 4 from the side by the driving component 6 after the plug 10 is inserted into the insertion cavity 40 of the pre-tightening nut 4 and is clamped with the clamping mechanism, so that the pre-tightening nut 4 rotates and moves axially along the large nut 2, thereby locking the plug 10 and the clamping mechanism in the axial direction of the large nut 2.

[0087] The pre-tightening mechanical joint disclosed in the present application has the advantages of Figure 1 、 Figure 2 、 Figure 3 and Figure 4 Since the pre-tightening nut is provided with the transmission structure, the transmission structure can drive the pre-tightening nut 4 from the side by the driving component 6 after the plug 10 of the insertion rod 1 is inserted into the insertion cavity 40 of the pre-tightening nut 4 and is clamped with the clamping mechanism arranged in the accommodating cavity 20, so that the pre-tightening nut 4 rotates and moves axially along the large nut 2, thereby locking the plug 10 and the clamping mechanism in the axial direction of the large nut 2, that is, after the plug 10 of the insertion rod 1 is clamped with the clamping mechanism, the pre-tightening nut 4 can move in the axial direction of the large nut 2 under the driving of the driving component 6, thereby eliminating the axial gap L between the plug 10, the clamping mechanism and the pre-tightening nut 4 (the distance between the end of the elastic clamping piece and the clamping surface of the plug in the pre-tightening nut 4). Figure 3 Further, since the pre-tightening nut, the insertion rod and the clamping mechanism are locked in the axial direction, a tightening torque (tightening force) is generated between the pre-tightening nut and the large nut during the locking process, which generates a certain axial force in the axial direction of the pre-tightening nut, the insertion rod, the large nut, the clamping mechanism and the small nut, and the axial gap between the components, such as the axial gap of the threaded connection between the pre-tightening nut and the large nut (the threaded connection in the area of E2 shown in the pre-tightening nut 4), the axial gap of the threaded connection between the insertion rod base of the insertion rod and the small nut, and the axial gap of the threaded connection between the clamping mechanism and the small nut, can be effectively eliminated. Figure 4 Figure 4 ​The mechanical joint disclosed in this invention, which addresses issues such as the axial clearance of the threaded connection in area E1 and the clearance between the plug and the locking mechanism of the insertion rod, ensures that when using this mechanical joint for precast concrete pile connections, the connection will not crack under tensile, shear, or bending forces. This means that the mechanical joint provides high tensile, bending, and shear resistance at the pile connection, meeting the crack level control requirements of the "Technical Standard for Prestressed Concrete Pipe Piles" JGJ / T406-2017. Furthermore, it eliminates the problem of gaps in existing mechanical joint connections causing cracks at the precast concrete pile joints, which could lead to safety hazards in the building pile foundation.

[0088] Further, the transmission structure is an engagement or pushing structure located on the outer wall or end of the preload nut 4 away from the end threadedly connected to the large nut 2. The engagement or pushing structure can be an engagement tooth, a pushing groove, a shifting protrusion, or a conical tooth. Specifically, for example... Figures 1 to 6 The first embodiment of the transmission structure of the present invention is shown. In this embodiment, the end of the pre-tightening nut drive part 48 of the pre-tightening nut is provided with a first bevel tooth 483, the drive component 6 is a bevel tooth drive rod 63, and one end of the bevel tooth drive rod 63 is provided with a second bevel tooth 630. The second bevel tooth 630 of the bevel tooth drive rod 63 can engage with the first bevel tooth 483 from the side of the pre-tightening nut 4 and drive the pre-tightening nut to rotate during the rotation of the bevel tooth drive rod 63, thereby realizing the rotation of the pre-tightening nut and its movement along the axial direction of the large nut, thereby locking the plug and the snap-fit ​​mechanism in the axial direction of the large nut.

[0089] like Figure 8 and Figure 9 The following is a second embodiment of the transmission structure of the present invention. In this embodiment, the end of the preload nut drive part 48 of the preload nut 4 is provided with a second actuating protrusion 484. The drive component 6 is a bevel gear drive rod 63. One end of the bevel gear drive rod 63 is provided with a second bevel tooth 630. The second bevel tooth 630 of the bevel gear drive rod 63 can engage with the second actuating protrusion 484 from the side of the preload nut 4 and drive the preload nut to rotate during the rotation of the bevel gear drive rod 63.

[0090] like Figure 10 The image shows a third embodiment of the transmission structure of the present invention. In this embodiment, the engagement or pushing structure is a pushing groove, specifically as follows: Figure 10As shown, in this embodiment, the outer wall of the preload nut 4 is provided with a preload nut connecting part 47 and a preload nut driving part 48. The preload nut connecting part 47 is provided with an external thread for threaded connection with the large nut 2, and the preload nut driving part 48 is provided with a pushing groove 480. When the preload nut 4 is placed in the receiving cavity 20 and threadedly connected with the large nut 2, at least part of the preload nut driving part 48 is placed outside the receiving cavity 20. The driving component 6 is a toothed rod 60, which is a long column structure. The front end of the long column has multiple protrusions along the axial direction of the rod to form driving teeth 600. The moving tooth 600 is adapted to the pushing groove 480. The driving tooth 600 of the toothed rod 60 can engage with the pushing groove 480 from the side of the preload nut 4. During the reciprocating push and pull of the toothed rod 60, the preload nut 4 can be rotated. (When pulling the toothed rod, the toothed rod can be rotated at a certain angle to separate the driving tooth from the pushing groove. After the toothed rod is pulled out, the toothed rod is rotated again to make the driving rod engage with the pushing groove and push the toothed rod.) This enables the preload nut to rotate and move along the axial direction of the large nut, thereby locking the plug and the snap-fit ​​mechanism in the axial direction of the large nut.

[0091] like Figure 11 The image shows a fourth embodiment of the transmission structure in this invention. In this embodiment, a pushing groove 480 is provided on the outer wall of the pre-tightening nut drive part 48, and the drive component 6 is a drive rod 61. The drive rod is a long column structure, and the front end of the long column can be inserted into the pushing groove from the side of the pre-tightening nut 4 in an inclined direction. The reciprocating push of the push rod can make the pre-tightening nut rotate, thereby realizing the movement of the pre-tightening nut along the axial direction of the large nut, thereby locking the plug and the pre-tightening nut in the axial direction of the large nut.

[0092] like Figure 12 The fifth embodiment of the transmission structure of the present invention is shown. In this embodiment, the preload nut drive part 48 of the preload nut 4 is provided with a push groove 480 on the outer wall. The drive component 6 is a toothed rod 60. One end of the toothed rod 60 is provided with continuous drive teeth 600. The drive teeth 600 of the toothed rod 60 can engage with the push groove from the side of the preload nut 4 and drive the preload nut to rotate during the rotation of the toothed rod 60.

[0093] like Figure 13The sixth embodiment of the transmission structure in the application is shown, in which the outer wall of the pre-tightening nut driving part 48 of the pre-tightening nut is provided with a first poking protrusion 482, the driving part 6 is a poking rod 62, the poking rod 62 can be inserted between two adjacent first poking protrusions 482 from the side of the pre-tightening nut 4 and drive the pre-tightening nut to rotate in the process of rotating the poking rod 62; specifically, a plurality of protrusion structures are uniformly arranged on the outer wall of the pre-tightening nut in the circumferential direction to form poking protrusions, the driving part is a poking rod 62, the poking rod is a long rod body structure, the front end of the long column body is a flat structure and can be inserted between two adjacent poking protrusions, as shown in the figure, the poking rod can be rotated under the driving of an external tool, in the process of rotating the poking rod, the front end face of the poking rod on one side is in contact with the poking protrusion on the corresponding side and drives the pre-tightening nut to rotate, when the poking rod rotates one circle, the front end face of the poking rod is in contact with the other adjacent poking protrusion and continues to drive the pre-tightening nut to rotate, that is, the rotation of the poking rod can drive the pre-tightening nut to rotate and move axially along the large nut, so as to lock the plug and the pre-tightening nut (clamping mechanism) in the axial direction of the large nut, the poking rod can use a structure such as a Phillips screwdriver.

[0094] The transmission structure of the application is not limited to the above-described several specific structures, any structure that can realize the function of driving the pre-tightening nut to rotate from the side is within the protection scope of the patent, and the specific structures that can realize the function will not be described one by one.

[0095] Further, the positioning sleeve 7 for correcting the plug rod 1 in the process of inserting the plug rod 1 into the accommodating cavity 20 is arranged in the accommodating cavity 20. By arranging the positioning sleeve 7 for correcting the plug rod 1 in the process of inserting the plug rod 1 into the accommodating cavity 20 in the accommodating cavity 20, it can be ensured that the axis of the plug rod 1 is substantially coincident with or substantially parallel to the axis of the large nut 2, thereby reducing or eliminating the contact between the plug rod 1 and the pre-tightening nut 4 in the radial direction in the process of inserting the plug rod 1 into the pre-tightening nut 4 and / or after the plug rod 1 is inserted into the pre-tightening nut 4, that is, reducing the acting force between the plug rod 1 and the pre-tightening nut 4, so as to drive the pre-tightening nut 4 to rotate and move axially along the large nut 2, thereby locking the plug 10 and the clamping mechanism in the axial direction of the large nut 2.

[0096] Further, as Figure 14 and Figure 15As shown, the positioning sleeve 7 is arranged between the end of the pre-tightening nut 4 placed in the large nut and the bottom surface of the accommodating cavity 20, and the positioning sleeve 7 is provided with a positioning hole 70. After the plug 10 is inserted into the insertion cavity 40 of the pre-tightening nut 4 and radially clamped with the clamping mechanism, part of the plug is inserted into the positioning hole, and the radial gap between the plug and the positioning hole is smaller than the radial gap between the clamping mechanism and the pre-tightening nut or the radial gap between the plug and the positioning hole is smaller than the radial gap between the clamping mechanism and the plug.

[0097] Further, the positioning sleeve 7 is arranged between the end of the pre-tightening nut 4 placed in the large nut and the bottom surface of the accommodating cavity 20, and the positioning sleeve 7 is provided with a positioning hole 70. After the plug 10 is inserted into the insertion cavity 40 of the pre-tightening nut 4 and radially clamped with the clamping mechanism, part of the plug 10 is inserted into the positioning hole 70, and the radial gap between the plug 10 and the positioning hole 70 is smaller than the radial gap between the clamping mechanism and the pre-tightening nut 4 or the radial gap between the plug 10 and the positioning hole 70 is smaller than the radial gap between the clamping mechanism and the plug 10. Specifically, in the embodiment, as shown in Figure 14 and Figure 15As shown, the positioning sleeve 7 is in a circular ring structure, and preferably the positioning sleeve 7 is a circular ring metal sheet. The outer diameter of the positioning sleeve 7 is provided with a threaded structure, and the positioning sleeve 7 can be screwed into the accommodating cavity of the large nut 2. The large nut is provided with an accommodating cavity 20, and the inner wall of the accommodating cavity 20 is provided with an internal thread. One end of the large nut can be fixedly connected with the main rib, and the other end is connected with the pre-tightening nut through the internal thread. Preferably, the positioning sleeve 7 can be screwed into the root of the internal thread of the large nut. The inner diameter hole of the positioning sleeve 7 is a positioning hole 70. During the process of inserting the plug 10 into the insertion cavity 40 of the pre-tightening nut 4 or after the radial clamping of the clamping mechanism, part of the plug 10 is inserted into the positioning hole 70. Preferably, the hole diameter of the positioning hole is matched with the outer diameter of the plug, so that the radial gap between the plug 10 and the positioning hole 70 is smaller than the radial gap between the clamping mechanism and the pre-tightening nut 4, or the radial gap between the plug 10 and the positioning hole 70 is smaller than the radial gap between the clamping mechanism and the plug 10. Because the radial gap between the plug 10 and the positioning hole 70 is smaller than the radial gap between the clamping mechanism and the pre-tightening nut or the radial gap between the clamping mechanism and the plug, the positioning hole 70 can limit and guide the insertion rod 1 during the process of inserting the insertion rod 1 into the pre-tightening nut 4 and / or after the insertion rod 1 is inserted into the pre-tightening nut 4, so that the insertion rod 1 and the pre-tightening nut 4 have a gap (no contact) in the radial direction, that is, the acting force between the insertion rod and the pre-tightening nut is reduced or eliminated, so as to facilitate the rotation of the pre-tightening nut, so that the pre-tightening nut moves axially along the large nut, thereby locking the plug and the pre-tightening nut in the axial direction of the large nut. Preferably, the positioning hole 70 of the positioning sleeve 7 is a polygonal hole, and the diameter of the inscribed circle of the polygon is greater than or equal to the maximum outer diameter of the plug 10 and less than the inner diameter of the insertion cavity 40 of the pre-tightening nut 4. In the figure, it is an octagonal hole. The positioning hole is a polygonal hole, which is convenient for inserting a hexagonal wrench or other tools into the positioning hole to screw the positioning sleeve into the large nut.

[0098] The receiving cavity 20 of the large nut 2 can also be a stepped hole. The diameter of the stepped hole near the bottom surface of the receiving cavity is smaller, and the diameter of the stepped hole near the opening end is larger. An internal thread for threaded connection with the preload nut 4 is machined on the inner wall of the receiving cavity 20 of the large nut 2 (at the stepped hole with the larger diameter near the opening end). A positioning sleeve mounting hole is provided at the root of the internal thread (i.e., the end of the internal thread facing the bottom surface of the receiving cavity). The diameter of the positioning sleeve mounting hole is larger than the diameter of the hole near the bottom surface of the receiving cavity and smaller than the diameter of the stepped hole near the opening end. The positioning sleeve 7 is a ring-shaped structure, preferably a ring-shaped metal sheet. The outer diameter of the positioning sleeve 7 is interference-fitted with the positioning sleeve mounting hole. The positioning sleeve 7 is inserted into the positioning sleeve mounting hole under external force. The inner diameter hole of the positioning sleeve 7 is a positioning hole 70, and the inner diameter of the positioning hole 70 is larger than... The plug 10 has a maximum outer diameter that is smaller than the inner diameter of the insertion cavity 40 of the pre-tightening nut 4. After the plug 10 of the plug rod 1 passes through the insertion cavity 40 of the pre-tightening nut 4, the plug 10 is inserted into the positioning hole 70. Since the radial gap between the plug 10 and the positioning hole 70 is smaller than the radial gap between the snap-fit ​​mechanism and the pre-tightening nut or between the snap-fit ​​mechanism and the plug, the positioning hole 70 limits and guides the plug rod 1 during the insertion of the pre-tightening nut 4 and / or after the plug rod 1 is inserted into the pre-tightening nut 4. This results in a gap (no contact) between the plug rod 1 and the pre-tightening nut 4 in the radial direction, which reduces or eliminates the force between the plug rod and other components and the pre-tightening nut, so as to drive the pre-tightening nut to rotate and move the pre-tightening nut along the axial direction of the large nut, thereby locking the plug and the snap-fit ​​mechanism in the axial direction of the large nut.

[0099] like Figure 3 , Figure 4 and Figure 5 The diagram shows a first embodiment of the snap-fit ​​mechanism of the present invention. In this embodiment, the snap-fit ​​mechanism consists of multiple elastic clips 41 disposed on one end of the pre-tightening nut 4 inside the large nut 2. The elastic clips 41 are integral with the pre-tightening nut, i.e., multiple grooves are machined circumferentially at one end of the pre-tightening nut, and an elastic clip is formed between two adjacent grooves. The ends of the elastic clips 41 contract radially toward the center, and the elastic clips can open or close radially. The ends of the elastic clips form snap-fit ​​surfaces 410. The plug 10 of the insertion rod 1 is provided with a second snap-fit ​​surface 13, such as... Figure 4The schematic representation of its movement process is shown in the drawings. Specifically, after the plug is inserted into the pre-tightening nut, the end clamping surface of the elastic card has a certain axial gap L with the clamping surface of the plug. When the driving part drives the pre-tightening nut 4 to rotate (indicated by the arrow B in the drawing) and move axially along the large nut 2 (indicated by the arrow C in the drawing), the axial gap L between the plug and the elastic card gradually decreases, and finally the clamping surface 410 at the end of the plurality of elastic cards can abut against the second clamping surface 13 on the plug 10 (the plug rod includes a plug rod base 12, a plug rod connecting part 11 and a plug 10, the diameter of the plug rod connecting part is smaller than that of the plug, and the transition surface between the plug rod connecting part and the plug is the second clamping surface) to realize the locking of the plug 10 and the pre-tightening nut 4 in the axial direction of the large nut 2, that is, the axial gap between the first clamping surface and the second clamping surface after the plug is inserted into the pre-tightening nut is effectively eliminated, and the axial gap between the threaded connection of the pre-tightening nut and the large nut and the threaded connection between the plug rod and the small nut also exists. The clamping form of the elastic card has the advantages of simple structure, small number of components, easy processing and installation, etc. In this embodiment, as shown in Figure 3 the positioning hole of the positioning sleeve has a radial gap with the plug, which is smaller than the radial gap between the elastic card (in a free state) and the plug rod connecting part, so that the positioning hole 70 limits and guides the plug rod 1 during the process of inserting the plug rod 1 into the pre-tightening nut 4 and / or after the plug rod 1 is inserted into the pre-tightening nut 4, and thus the plug rod 1 and the pre-tightening nut 4 have a gap (no contact) in the radial direction, that is, the force between the plug rod and the pre-tightening nut is reduced or eliminated, so as to facilitate the rotation of the pre-tightening nut and the axial movement of the pre-tightening nut along the large nut, thereby locking the plug and the clamping mechanism in the axial direction of the large nut.

[0100] As shown in Figure 16 , Figure 17 and Figure 18 , it is a second embodiment of the clamping mechanism in the present application. In this embodiment, the clamping mechanism is a plurality of elastic cards 41 arranged at one end of the large nut 2. The formation of the elastic card is the same as that of the elastic card in embodiment 1. In this embodiment, the inner wall of the elastic card 41 is further provided with first teeth 42, and the outer wall of the plug 10 is provided with second teeth 14. The first teeth 42 and the second teeth 14 are clamped with each other. When the plug rod and the pre-tightening nut are just clamped, there is a certain axial gap between the first teeth and the second teeth (as shown in Figure 17 When the pre-tightening nut 4 rotates and moves axially along the large nut 2, the tooth surfaces of the first teeth 42 and the second teeth 14 can abut against each other to realize the locking of the plug 10 and the pre-tightening nut 4 in the axial direction of the large nut 2 (as shown in Figure 18(As shown). In this embodiment, the locking tooth structure allows the insert rod to engage with the preload nut, reducing the axial clearance before the insert rod and preload nut are axially locked. In this embodiment, before the insert rod and preload nut are axially locked, the axial clearance between the insert rod and preload nut is less than or equal to 0.5 times the tooth pitch, which is much smaller than the axial clearance in Embodiment 1. Therefore, when driving the preload nut to rotate, the preload nut only needs to move a small axial distance to achieve the tooth surfaces of the first and second teeth abutting each other, thereby achieving rapid axial locking between the preload nut and the insert rod. Simultaneously, in this embodiment, the insert rod and preload nut have a large axial contact length after axial locking, improving bending and shear resistance. In this embodiment, as... Figure 16 As shown, a positioning sleeve 7 is also provided inside the large nut 2. The radial gap between the positioning hole of the positioning sleeve and the plug is smaller than the radial gap between the tooth tip of the first tooth and the tooth root of the second tooth. This allows the positioning hole 70 to limit and guide the insertion rod 1 during the insertion of the insertion rod 1 into the pre-tightening nut 4 and / or after the insertion rod 1 is inserted into the pre-tightening nut 4. This results in a gap (no contact) between the insertion rod 1 and the pre-tightening nut 4 in the radial direction, which reduces or eliminates the force between the insertion rod and other components and the pre-tightening nut. This facilitates the rotation of the pre-tightening nut, causing it to move axially along the large nut, thereby locking the plug and the locking mechanism in the axial direction of the large nut.

[0101] like Figure 19 and Figure 20 The image shows a third embodiment of the snap-fit ​​mechanism in this invention. In this embodiment, as shown... Figure 21 As shown, the insertion cavity 40 of the preload nut 4 is provided with a card receiving groove 43, and the snap-fit ​​mechanism is a card 44 disposed in the card receiving groove 43, and the snap-fit ​​ring 44 is as follows: Figure 22 and Figure 23The metal elastic ring structure shown is a one-side opening structure, and can also be other structures, such as a plurality of clamping ring petals formed by a spring clamp, and the card can be expanded or contracted in the card accommodating groove, and the card accommodating groove 43 is a first clamping surface 45 on the inner wall of one side of the plug insertion end 45 of the pre-tightening nut 4, and the plug 10 is provided with a second clamping surface 13; when the plug is inserted into the pre-tightening nut, the card can be radially expanded and clamped at the plug rod connecting portion to achieve clamping of the card and the plug rod; when the plug 10 is inserted into the insertion cavity 40 of the pre-tightening nut 4 and clamped with the card 44, the card 44 is located between the first clamping surface 45 and the second clamping surface 13; the driving component drives the pre-tightening nut 4 to rotate and move axially along the large nut 2, so that the first clamping surface 45 moves towards the side of the card 44 and the first clamping surface 45 and the second clamping surface 13 abut the two sides of the card 44 respectively, so as to lock the plug 10 and the pre-tightening nut 4 in the axial direction of the large nut 2. In this embodiment, since the card accommodating groove is provided on the inner wall of the insertion cavity of the pre-tightening nut, the clamping mechanism adopts a card, so that the card can be directly installed in the card accommodating groove of the pre-tightening nut, so that the two components form an assembly, thereby facilitating the installation of the subsequent mechanical joint, reducing the installation difficulty and saving the cost. At the same time, the structure of the card and the pre-tightening nut is simple, which further reduces the cost. The end of the plug is hemispherical, parabolic or circular truncated conical, so as to facilitate the radial expansion of the card. In this embodiment, as shown in Figure 19 the positioning hole of the positioning sleeve is smaller than the radial gap between the plug and the insertion cavity of the pre-tightening nut, that is, the positioning hole is smaller than the diameter of the insertion cavity, so that the positioning hole 70 limits and guides the plug rod 1 during the insertion of the plug rod 1 into the pre-tightening nut 4 and / or after the insertion of the plug rod 1 into the pre-tightening nut 4, thereby allowing the plug rod 1 and the pre-tightening nut 4 to have a gap (not in contact) in the radial direction, that is, reducing or eliminating the force between the plug rod and the pre-tightening nut, so as to drive the pre-tightening nut to rotate by the driving component, so that the pre-tightening nut moves axially along the large nut, thereby locking the plug and the clamping mechanism in the axial direction of the large nut. Preferably, the side wall of the card accommodating groove 43 is inclined to the plug insertion end side of the pre-tightening nut 4, that is, the shape of the inner side wall of the card accommodating groove 43 is generally conical, when the plug is inserted into the card, the plug abuts in the inner hole of the card and generates a downward force on the card to the bottom of the accommodating cavity, the inner side wall of the card accommodating groove will give the card a radial outward force, so that the card is more easily expanded, and after the plug is inserted, the first clamping surface of the pre-tightening nut gives the card a radial inward force, so that the card and the plug are tightly matched to form a self-locking structure, thereby enhancing the anti-pulling-off performance.

[0102] Figure 24 and Figure 25 ​The fourth embodiment of the clamping mechanism is shown. The difference between the fourth embodiment and the third embodiment is that the clamping mechanism of the third embodiment is directly machined on the inner wall of the insertion cavity 40 of the pre-tightening nut 4, while the insertion cavity of the pre-tightening nut of the fourth embodiment is a stepped hole, the transition surface of the stepped hole is the clamping surface, and the clamping surface is preferably a tapered surface. A retaining ring 46 is arranged at one end of the pre-tightening nut, and the retaining ring 46 and the clamping surface in the insertion cavity 40 form the card accommodating groove 43. The split structure is more convenient for processing.

[0103] Further, the threaded connection between the pre-tightening nut 4 and the large nut 2 is a loose threaded connection before the plug 10 and the clamping mechanism are locked in the axial direction of the large nut 2. Specifically, the tolerances of the internal threads on the inner wall of the accommodating cavity of the large nut and the external threads on the outer wall of the pre-tightening nut can be reasonably selected according to the needs, so that the threaded connection between the pre-tightening nut and the large nut is a loose threaded connection. Since the threaded connection between the pre-tightening nut and the large nut is a loose threaded connection, the force between the pre-tightening nut and the large nut is relatively small before the plug and the clamping mechanism are locked, thereby facilitating the driving component to drive the pre-tightening nut to rotate and move the pre-tightening nut in the axial direction of the large nut, thereby locking the plug and the clamping mechanism in the axial direction of the large nut.

[0104] Further, after the plug 10 is locked with the clamping mechanism in the axial direction of the large nut 2, the tensile strength of the connection between the plug and the clamping mechanism is greater than or equal to the tensile strength of any of the main reinforcement, the large nut, and the small nut. After the plug 10 is locked with the clamping mechanism in the axial direction of the large nut 2, the connection between the plug and the clamping mechanism does not have ductile deformation when subjected to a pulling force of 11.7 MPa. In the present application, because the tensile strength of the connection between the plug and the clamping mechanism after the plug is locked with the clamping mechanism in the axial direction of the large nut 2 is greater than or equal to the tensile strength of any of the main reinforcement, the large nut, and the small nut, and the connection between the plug and the clamping mechanism does not have ductile deformation when subjected to a pulling force of 11.7 MPa, the precast concrete pile with the disclosed pre-tightening mechanical joint can not have ductile deformation of the large nut, the small nut, the plug, the clamping mechanism, and the pre-tightening nut before the main reinforcement has ductile deformation, so that no cracks or gaps are generated between the connecting end faces of the two precast piles, and the disclosed pre-tightening mechanical joint can be reliably connected without being damaged before the main reinforcement has ductile deformation and is pulled apart, further ensuring the connection performance of the precast concrete pile connected by the disclosed pre-tightening mechanical joint. Specifically, the relationship between the pile type and the pre-stressed main reinforcement is specified in detail in the pre-stressed concrete square pile reinforcement and mechanical performance table in the national building standard design drawing set "Precast Concrete Square Pile" drawing set number: 20G361), for example, it is specified that the pre-stressed main reinforcement of a pile with a pile cross section of 600x600 is 24Φ D 12.6; the relationship between the pile cross section type and the pile shaft tensile bearing capacity design value NtkN) is specified in detail in the pre-stressed concrete square pile shaft axial compressive force and normal section bending bearing capacity, and in the table, it is specified that the pile shaft tensile bearing capacity design value of a B-shaped pile with a pile cross section of 600x600 is 2544 kN. From the above data, it can be calculated that the tensile bearing capacity design value of the precast pile pre-stressed main reinforcement is 2544 / 24=10.6 kN; 10.6x1.1=11.66≈11.7 kN, i.e., the disclosed pre-tightening mechanical joint can withstand a pulling force of 11.7 kN without ductile deformation of the precast concrete pile main reinforcement and the pre-tightening mechanical joint, and no slip between the components of the mechanical joint, so that no gap is generated between the connecting end faces of the precast concrete pile, thereby ensuring the connection performance of the precast concrete pile.

[0105] Further, a small nut 21 is further included for connecting with the insertion rod base 12 of the insertion rod 1. Specifically, in the embodiment, the insertion rod 1 is fixed at one end of the precast concrete pile through the small nut 21, and the large nut 2 is fixed at the other end of the precast concrete pile. The large nut 2 and the small nut 21 are respectively fixedly connected with both ends of the main reinforcement in the precast concrete pile. The large nut is provided with a positioning sleeve, a pre-tightening nut and other components. Adjacent two sections of the precast concrete pile can be quickly connected through the pre-tightening mechanical joint disclosed in the application.

[0106] Embodiment 2

[0107] As shown in Figure 26 , Figure 27 , Figure 28 , Figure 29 and Figure 30 , the precast concrete pile disclosed in the application comprises a precast concrete pile body 80, a main reinforcement 81 and the direct-drive pre-tightening mechanical joint. The main reinforcement 81 is arranged in the precast concrete pile body 80. One end of the precast concrete pile body 80 is provided with the large nut 2. The large nut 2 is provided with the clamping mechanism and the pre-tightening nut 4. The other end of the precast concrete pile body 80 is provided with the insertion rod 1. The end of the precast concrete pile body 80 is provided with a drive component accommodating groove 82. When two adjacent sections of the precast concrete pile are connected, one end of the drive component accommodating groove 82 is in communication with the outer wall of the precast concrete pile body 80, and the other end extends to the end of the pre-tightening nut 4. After the drive component 6 is inserted into the drive component accommodating groove 82 from the outer wall of the precast concrete pile 80, the drive component 6 can interact with the transmission structure arranged on the drive part of the pre-tightening nut, so that the pre-tightening nut 4 rotates and moves axially along the large nut 2, thereby locking the plug 10 and the clamping mechanism in the axial direction of the large nut 2.

[0108] The pre-tightening mechanical joint disclosed in the application is provided with a transmission structure on the pre-tightening nut driving part. After the plug of the inserting rod is inserted into the insertion cavity of the pre-tightening nut and is radially clamped with the clamping mechanism arranged in the containing cavity, the driving part drives the pre-tightening nut from the side of the pre-tightening nut, so that the pre-tightening nut is driven to rotate and move axially along the large nut, thereby locking the plug and the pre-tightening nut in the axial direction of the large nut. That is, after the plug of the inserting rod is clamped with the clamping mechanism, the pre-tightening nut can move in the axial direction of the large nut under the driving of the transmission structure and the driving part, thereby eliminating the axial gap among the plug of the inserting rod, the clamping mechanism and the pre-tightening nut through the axial movement of the pre-tightening nut. Further, since the pre-tightening nut, the inserting rod and the clamping mechanism are locked in the axial direction, a certain axial force is generated in the axial direction of the pre-tightening nut, the inserting rod and the clamping mechanism during the locking process. Under the action of the axial force, the axial gaps among the pre-tightening nut, the inserting rod, the large nut, the clamping mechanism and the small nut, such as the gap between the pre-tightening nut and the large nut in the threaded connection, the gap between the inserting rod base of the inserting rod and the small nut in the threaded connection, the gap between the plug of the inserting rod and the clamping mechanism, etc., can be effectively eliminated. Therefore, when the mechanical joint disclosed in the application is used for connecting the precast concrete piles, the connection of the precast concrete piles will not crack and generate cracks under the action of pulling force, shearing force or bending force, that is, the connection of the precast concrete piles using the mechanical joint disclosed in the application has high anti-pulling, anti-bending and anti-shearing performance, so that the connection of the precast concrete piles using the mechanical joint disclosed in the application can meet the relevant requirements of the crack grade control in the Technical Standard for Prestressed Concrete Pipe Piles JGJ / T 406-2017. The problem of the cracks in the connection of the precast concrete piles caused by the gap generated by the connection mechanism of the existing mechanical joint is also eliminated.

[0109] Further, the precast concrete pile body 80 is provided with the small nut 21 at one end of the inserting rod 1. The large nut 2 and the small nut 21 are respectively connected to the two ends of the main reinforcement 81, and the inserting rod 1 is threadedly connected to the other end of the small nut 21. That is, the mechanical joint is arranged at the two ends of the main reinforcement, so that the main reinforcement and the mechanical joint are coaxial, and thus the main reinforcement and the mechanical joint are on the same axis when they are subjected to stress, thereby improving the anti-pulling performance of the pile. The driving part containing groove 82 can also be arranged at the end of the precast concrete pile provided with the small nut. When the driving part containing groove 82 is arranged at the end of the precast concrete pile provided with the small nut, the end of the end of the precast concrete pile provided with the small nut is provided with a pre-tightening nut containing hole, so that the upper part of the pre-tightening nut is arranged in the hole when the upper and lower precast piles are connected. The one end of the driving part containing groove 82 is in communication with the precast concrete pile, and the other end is in communication with the driving part containing groove 82, thereby enabling the driving part to drive the pre-tightening nut to rotate.

[0110] Further, the driving component 6 drives the pre-tightening nut 4 to rotate radially and locks the plug 10 and the clamping mechanism in the axial direction of the large nut 2, and then the driving component 6 remains in or moves out of the driving component accommodating groove 82.

[0111] Specifically, in the connection of the specific precast concrete pile, a driving component can be used to drive a plurality of pre-tightening nuts on the precast concrete pile to rotate radially, so as to realize the axial locking of all mechanical joints, eliminate the axial gap, improve the anti-pulling capacity of the pile, and the driving component can be reused, thereby saving the use cost. In the connection of the precast concrete pile, each mechanical joint can be driven by a driving component, and when the driving component drives the pre-tightening nut to rotate and realizes the axial locking, the driving component remains in the driving component accommodating groove, that is, the driving component is not taken out of the driving component accommodating groove. Since a plurality of driving component structures are arranged between the two sections of the precast concrete pile, the compression resistance of the end of the precast pile is further improved.

[0112] Further, the connecting end face of the precast concrete pile body 80 and the direct driving pre-tightening mechanical joint are also filled with structural glue. The structural glue can fill, bond and seal various grooves of the connecting end face, the mechanical joint and the end face, and further improve the connection performance and corrosion resistance between the piles.

[0113] Embodiment 3

[0114] A connection method of the precast concrete pile according to the present application, comprising the following steps: moving the end of the precast concrete pile provided with a plug rod and the end of the adjacent precast concrete pile provided with a pre-tightening nut relative to each other, and inserting the plug of the plug rod into the insertion cavity of the pre-tightening nut to realize the clamping of the plug and the clamping mechanism;

[0115] The driving component is inserted into the outer wall of the precast concrete pile, and the driving component drives the transmission structure, so that the pre-tightening nut rotates and moves axially along the large nut, thereby locking the plug and the clamping mechanism in the axial direction of the large nut.

[0116] The use of the mechanical joint disclosed in the present application for precast concrete pile connection can provide the pile connection with high anti-pulling, bending and shearing performance, so that the use of the mechanical joint disclosed in the present application for precast concrete pile connection can meet the relevant requirements of the crack grade control in the Technical Standard for Prestressed Concrete Pipe Pile JGJ / T 406-2017. The problem of cracks at the joint of the precast concrete pile caused by the gap generated by the connection mechanism of the existing mechanical joint is eliminated, and the safety hazard of the building pile foundation is avoided.

[0117] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A direct-drive pre-tightening mechanical joint for end connection between precast concrete piles, characterized in that: include, Insert rod (1), one end of which is a plug (10); Large nut (2), the large nut (2) is provided with a receiving cavity (20); A pre-tightening nut (4) is provided at one end of the receiving cavity (20) and is threadedly connected to the large nut (2). Part of the pre-tightening nut (4) is located outside the receiving cavity (20). An insertion cavity (40) is provided on the pre-tightening nut (4). A snap-fit ​​mechanism is disposed within the receiving cavity (20); The transmission structure is located on the outer part of the pre-tightening nut (4) located in the receiving cavity (20). After the plug (10) is inserted into the insertion cavity (40) of the pre-tightening nut (4) and engaged with the locking mechanism, the driving component (6) drives the pre-tightening nut (4) from the side, causing the pre-tightening nut (4) to rotate and move axially along the large nut (2), thereby eliminating the gap between the plug (10) and the locking mechanism in the axial direction of the large nut (2) and locking the plug (10) and the locking mechanism in the axial direction of the large nut (2).

2. The direct-drive pre-tightening mechanical joint according to claim 1, characterized in that: The transmission structure is an engagement or pushing structure located on the outer wall or end of the preload nut (4) away from the end that is threadedly connected to the large nut (2).

3. The direct-drive pre-tightening mechanical joint according to claim 2, characterized in that: The engagement or pushing structure is a pushing groove, a prying protrusion, or a conical tooth.

4. The direct-drive pre-tightening mechanical joint according to claim 3, characterized in that: The preload nut (4) has a pushing groove (480) on the outer wall of the end away from the threaded connection with the large nut (2). The driving component (6) is a toothed rod (60), one end of which is provided with driving teeth (600). The driving teeth of the toothed rod (60) can engage with the pushing groove (480) from the side of the preload nut (4) and drive the preload nut (4) to rotate during the pushing and pulling process of the toothed rod (60); or, the driving component (6) is a driving rod (61), one end of which can be inserted into the pushing groove (480) from the side of the preload nut (4) and drive the preload nut (4) to rotate during the pushing and pulling process of the driving rod; or, The preload nut (4) has a first actuating protrusion (482) on the outer wall of the end away from the threaded connection with the large nut (2). The driving component (6) is an actuating rod (62). The actuating rod (62) can be inserted laterally from the preload nut (4) between two adjacent first actuating protrusions (482) and drive the preload nut (4) to rotate during the rotation of the actuating rod (62); or, The preload nut (4) has a first bevel tooth (483) at the end away from the threaded connection with the large nut (2). The driving component (6) is a bevel tooth drive rod (63). One end of the bevel tooth drive rod (63) has a second bevel tooth (630). The second bevel tooth (630) of the bevel tooth drive rod (63) can engage with the first bevel tooth (483) from the side of the preload nut (4) and drive the preload nut (4) to rotate during the rotation of the bevel tooth drive rod (63); or, The preload nut (4) has a second actuating protrusion (484) at the end away from the threaded connection with the large nut (2). The driving component (6) is a bevel drive rod. One end of the bevel drive rod (63) has a second bevel tooth (630). The second bevel tooth (630) of the bevel drive rod (63) can engage with the second actuating protrusion (484) from the side of the preload nut (4) and drive the preload nut (4) to rotate during the rotation of the bevel drive rod (63).

5. The direct-drive pre-tightening mechanical joint according to claim 1, characterized in that: It also includes a positioning sleeve (7) disposed in the receiving cavity (20) for correcting the insert (1) during the insertion of the insert (1) into the receiving cavity (20).

6. The direct-drive pre-tightening mechanical joint according to claim 5, characterized in that: The positioning sleeve (7) is disposed between the end of the pre-tightening nut (4) placed inside the large nut and the bottom surface of the receiving cavity (20). The positioning sleeve (7) is provided with a positioning hole (70). After the plug (10) is inserted into the insertion cavity (40) of the pre-tightening nut (4) and radially engaged with the snap-fit ​​mechanism, part of the plug (10) is inserted into the positioning hole (70). The radial gap between the plug (10) and the positioning hole (70) is smaller than the radial gap between the snap-fit ​​mechanism and the pre-tightening nut (4) or the radial gap between the plug (10) and the positioning hole (70) is smaller than the radial gap between the snap-fit ​​mechanism and the plug (10).

7. The direct-drive pre-tightening mechanical joint according to claim 1, characterized in that: The locking mechanism consists of multiple elastic clips (41) disposed on one end of the pre-tightening nut (4) inside the large nut (2). The pre-tightening nut (4) rotates and moves axially along the large nut (2). The locking surfaces at the ends of the multiple elastic clips (41) can abut against the second locking surface (13) on the plug rod (1) to lock the plug (10) and the pre-tightening nut (4) in the axial direction of the large nut (2).

8. The direct-drive preload mechanical joint according to claim 1, characterized in that: The locking mechanism consists of multiple elastic clips (41) disposed on one end of the pre-tightening nut (4) inside the large nut (2). The inner wall of the elastic clip (41) is provided with a first tooth (42), and the outer wall of the plug (10) is provided with a second tooth (14). The first tooth (42) and the second tooth (14) engage with each other. When the pre-tightening nut (4) rotates and moves along the axial direction of the large nut (2), the tooth surfaces of the first tooth (42) and the second tooth (14) can abut against each other to lock the plug (10) and the pre-tightening nut (4) in the axial direction of the large nut (2).

9. The direct-drive preload mechanical joint according to claim 1, characterized in that: The insertion cavity (40) of the pre-tightening nut (4) is provided with a card receiving groove (43), and the snap-fit ​​mechanism is a card (44) provided in the card receiving groove (43). The inner wall of the card receiving groove (43) near the plug insertion end of the pre-tightening nut (4) is a first snap-fit ​​surface (45), and the plug (10) is provided with a second snap-fit ​​surface (13). When the plug (10) is inserted into the insertion cavity (40) of the pre-tightening nut (4) and engages with the card (44), the card (44) is located between the first engaging surface (45) and the second engaging surface (13); the pre-tightening nut (4) rotates and moves axially along the large nut (2), causing the first engaging surface (45) to move toward the card (44) and causing the first engaging surface (45) and the second engaging surface (13) to abut against the card (44) respectively, so as to lock the plug (10) and the pre-tightening nut (4) in the axial direction of the large nut (2).

10. The direct-drive preload mechanical joint according to claim 7, characterized in that: The card receiving groove is directly machined into the inner wall of the insertion cavity of the pre-tightening nut; or, The insertion cavity of the pre-tightening nut is provided with a retaining ring, and the retaining ring and the snap-fit ​​surface in the insertion cavity form the card receiving groove.

11. The direct-drive preload mechanical joint according to claim 1, characterized in that: Before the plug (10) and the pre-tightening nut (4) are locked in the axial direction of the large nut (2), the threaded connection between the pre-tightening nut (4) and the large nut (2) is a loose-fit threaded connection.

12. The direct-drive preload mechanical joint according to claim 1, characterized in that: After the plug (10) and the snap-fit ​​mechanism are locked in the axial direction of the large nut (2), the tensile strength of the connection between the plug and the snap-fit ​​mechanism is greater than or equal to the tensile strength of any one of the main rib, the large nut and the small nut.

13. The direct-drive preload mechanical joint according to claim 1, characterized in that: It also includes a small nut (21) for connecting to the insert base (12) of the insert (1).

14. A precast concrete pile, characterized in that: Includes a precast concrete pile body (80), main reinforcement (81), and the direct drive pre-tightening mechanical joint as described in any one of claims 1 to 13; The main reinforcement (81) is set inside the precast concrete pile body (80), and the precast concrete pile body (80) is provided with the large nut (2) at one end. The large nut (2) is provided with the snap-fit ​​mechanism (3) and the pre-tightening nut (4). The other end of the precast concrete pile body (80) is equipped with the insertion rod (1); the end of the precast concrete pile body (80) is provided with a drive component receiving groove (82). When two adjacent precast concrete piles are connected, one end of the drive component receiving groove (82) is connected to the outer wall of the precast concrete pile body (80), and the other end extends to the end of the pre-tightening nut (4). After the drive component (6) is inserted into the drive component receiving groove (82) from the outer wall of the precast concrete pile body (80), the drive component (6) can interact with the transmission structure (5) provided on the pre-tightening nut (4), so that the pre-tightening nut (4) rotates and moves along the axial direction of the large nut (2), thereby locking the plug (10) and the snap-fit ​​mechanism (3) in the axial direction of the large nut (2).

15. The precast concrete pile according to claim 14, characterized in that: The precast concrete pile body (80) is provided with a small nut (21) at one end of the insert rod (1). One end of the large nut (2) and the small nut (21) are respectively connected to the two ends of the main reinforcement (81). The insert rod (1) is threadedly connected to the other end of the small nut (21).

16. The precast concrete pile according to claim 14, characterized in that: After the drive component (6) drives the preload nut (4) to rotate radially and locks the plug (10) and the snap-fit ​​mechanism in the axial direction of the large nut (2), the drive component (6) remains in or is removed from the drive component receiving groove (82).

17. The precast concrete pile according to claim 14, characterized in that: Structural adhesive is also injected into the connecting end face of the precast concrete pile body (80) and the direct drive pre-tightening mechanical joint.

18. A method for connecting precast concrete piles according to any one of claims 14 to 17, characterized in that: The steps include: moving the end of the precast concrete pile with the insert rod and the end of the adjacent precast concrete pile with the pre-tightening nut relative to each other, and inserting the plug of the insert rod into the insertion cavity of the pre-tightening nut to achieve the snap-fit ​​between the plug and the snap-fit ​​mechanism; A drive component is inserted into the outer wall of a precast concrete pile, and the drive component drives the transmission structure, thereby causing the preload nut to rotate and move axially along the large nut, thereby locking the plug and the snap-fit ​​mechanism in the axial direction of the large nut.

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