An adaptive screw-in double-buckle micro-injector

Abstract

The present invention relates to the field of syringes, and provides an adaptive screw-in double-clip micro-syringe. The purpose is to achieve multi-point, micro-volume, precise quantitative injection for the same patient, and to prevent a disposable self-destructive syringe from being reused. The main scheme includes a base, a jacket is fixedly arranged at the bottom end of the base, a nut seat mounting seat is fixedly arranged at the upper end of the base, a nut seat is rotatably connected to the nut seat mounting seat, a threaded core rod is arranged in the jacket, the threaded core rod passes through the central rectangular hole of the nut seat mounting seat and is gap-matched with the central rectangular hole, the thread of the threaded core rod is matched with the threaded hole of the nut in the nut seat, the nut includes two half nuts, the two half nuts are pressed against the threaded core rod by a spring, and the thread of the half nut is matched with the threaded core rod, the nut seat is rotated to drive the rotation between the nut and the threaded core rod, and the thread drives the threaded core rod through the thread, so that the threaded core rod moves in the axial direction of the threaded core rod.

Description

Technical Field

[0001] The invention relates to the field of syringes and provides an adaptive screw-in double-buckle micro-syringe. Background Art

[0002] Public syringes can transmit diseases, so they must be sterilized. However, sterilization equipment is expensive and time-consuming, so this method has been basically eliminated and disposable syringes have come into being.

[0003] Disposable syringes have been widely used throughout the world for many years. The most commonly used ordinary disposable syringes in medical institutions are composed of a syringe, a needle, a piston and a core rod assembled in the syringe.

[0004] However, the injection dose of an ordinary syringe is usually a one-time dose, that is, the drug solution is drawn once and injected at one time. Even if the drug solution may be drawn once and injected in multiple times, the injection dose is only determined by the operator through the scale printed on the syringe barrel. The syringe scale itself has errors, so there will be scale errors and human errors. Therefore, the stability and accuracy of the injection dose cannot be guaranteed. With the continuous development of treatment methods and drug efficacy, some diseases require multi-point injection of drugs for the same patient, and require micro-injection at each point, and the injection dose at each point is accurate and the same. The current minimum capacity of ordinary syringes is 0.1mL, which cannot meet the requirements of multiple, micro, and accurate and fixed injection doses each time.

[0005] The infusion pumps of the prior art can achieve micro- and precision injections, but due to their large size, they are not suitable for handheld operation. During injection, they need to be connected to a long hose, resulting in a lot of residual drug solution. Drugs that require micro- and precision quantitative injections often have small packaging specifications and are expensive. Therefore, infusion pumps are not suitable for micro- and precision quantitative injections of such drugs.

[0006] In addition, ordinary syringes cannot be destroyed after use, and there is a risk of reuse, which may cause cross-infection of pathogens and endanger life. Existing self-destructive syringes have a self-destruction function, but cannot complete micro-amount and precise quantitative injection. Therefore, there is a need for a syringe that can simultaneously achieve a single suction of liquid medicine, micro-amount and precise quantitative injection at multiple points on the same patient, and prevent secondary use.

[0007] At present, there are two types of syringes that can achieve quantitative and micro-injection functions: rotary and push-type. The rotary type drives the syringe core rod by rotating the thread or gear to complete the pumping and injection functions; the push-type uses the tooth buckle method to push the core rod by pressing to complete the injection function. The above methods have the following problems:

[0008] 1. Some structural designs are too complex, with numerous accessories and high precision requirements, complex assembly procedures and high assembly precision requirements, making it very difficult to achieve industrial mass production;

[0009] 2. Some structural designs look simple, but they are only feasible in theory. The accessories cannot be produced through conventional processes, the accessories cannot be assembled, etc., and industrial mass production cannot be achieved;

[0010] 3. The gear rotation structure can achieve micro-injection, but the suction of liquid and exhaust are limited by the structure, which is time-consuming, laborious, inefficient, time-consuming, and not operable;

[0011] 4. Some rotating structures have too large rotation angles and no limit, so they need to be operated by looking at the scale, which is time-consuming and laborious. The dosage control depends entirely on human judgment, which has a high probability of deviation and low accuracy.

[0012] 5. Some rotating structures use a method of dividing the nut into two halves. When in use, the two halves of the nut are closed and matched with the screw. However, when the two halves of the nut are closed, there is no buffer. When the threads of the nut and the screw are not completely aligned, the nut and the screw cannot be effectively engaged. Multiple alignments are required, which is very inconvenient to operate. In addition, the core rod is rotated, and it cannot be effectively positioned during rotation. The dosage control is difficult and the accuracy is low.

[0013] 6. Some structures do not have a self-destruct function and cannot effectively prevent secondary use. Summary of the invention

[0014] In order to solve the above technical problems, the present invention provides a technical solution for a syringe that can simultaneously achieve one-time suction of liquid medicine, multi-point, trace, and precise quantitative injection on the same patient, can prevent secondary use, has a simple structure, can be mass-produced with existing equipment and technology, is easy to operate for medical staff, has low production cost, and has high accuracy.

[0015] The technical solution of the present invention is as follows:

[0016] The invention discloses an adaptive screw-in double-clip micro-injector, comprising a base, a jacket fixedly arranged at the bottom end of the base, a nut seat mounting seat fixedly arranged at the upper end of the base, a nut seat rotatably connected to the nut seat mounting seat, a threaded core rod arranged in the jacket, the threaded core rod passes through the center hole of the nut seat mounting seat and is clearance-matched with the center hole, the thread of the threaded core rod is matched with the threaded hole of the nut in the nut seat, the nut comprises two half nuts, the two half nuts are pressed against the threaded core rod by a spring, the threads of the half nuts and the threaded core rod are adaptively matched, the nut seat is rotated to drive the nut and the threaded core rod to rotate, the thread drives the threaded core rod to move in the axial direction of the threaded core rod.

[0017] In the above technical solution, the threaded core rod adopts a rectangular threaded core rod.

[0018] In the above technical solution, the bottom end of the outer jacket is provided with a needle tip connecting portion and a needle tip protective cover.

[0019] In the above technical solution, the nut seat is covered with a nut cover, and the nut cover includes protrusions evenly distributed in the circumference of the central through hole.

[0020] In the above technical solution, a convex point is arranged on the joint surface between the base and the nut seat.

[0021] In the above technical solution, the nut seat mounting seat is composed of two half nut seat mounting seats, and the half nut seat mounting seat includes a nut seat mounting half cavity and a center half hole arranged at the center. The two seat mounting half cavities form a nut seat mounting cavity, and the two center half holes form a center hole.

[0022] In the above technical solution, a center through hole is arranged on the central axis of the nut seat, a rotating seat is arranged at the bottom end of the nut seat and is rotatably matched with the nut seat mounting cavity of the nut seat mounting seat, a nut groove is arranged at the upper end of the nut seat, limiting grooves are arranged on both sides of the nut groove, and a groove is arranged on the joint surface between the nut seat and the base.

[0023] In the above technical solution, a nut limiting fork is provided, and limiting protrusions cooperating with the limiting grooves are arranged on the outer sides of the two legs of the nut limiting fork, a spring limiting protrusion is arranged between the two legs of the nut limiting fork, and limiting strips are arranged on the inner sides of the two legs of the nut limiting fork, and a nut limiting protrusion is arranged at the end of the limiting strip.

[0024] In the above technical solution, a spring mounting hole is arranged at one end of the half nut, a half thread is arranged at the other end, and a limited long groove is arranged on the side between the spring mounting hole and the half thread.

[0025] In the above technical solution, a fixing boss for fixing the rubber plug is provided at the bottom end of the threaded core rod, a handle is provided at the top end, and a non-threaded empty groove and a core rod locking groove are provided at the top end position of the thread of the threaded rod of the threaded core rod. When the core rod is pushed to the bottom of the outer sleeve, the threads of the two half nuts fall into the non-threaded empty grooves of the threaded rod, and the convex feet of the nut cover are buckled into the core rod locking groove.

[0026] In the above technical solution, a mounting groove is provided on the inner side wall of the base, and the upward mounting protrusion on the nut seat mounting seat cooperates with the mounting groove to fix the nut seat mounting seat in the base.

[0027] In the above technical solution, a scale mark is provided on the base, and a corresponding reference mark is provided on the nut seat.

[0028] In the above technical solution, a nut cover fixing cavity is provided on the nut seat, a nut cover mounting leg of the nut cover is installed in the nut cover fixing cavity, and a protrusion on the mounting leg falls into a groove of the nut cover fixing cavity.

[0029] Because the present invention adopts the above technical solution, it has the following beneficial effects:

[0030] The nut position of the present invention can be in two states: in the initial state, the nut and the threaded core rod are in a thread-separated state, at which time the threaded core rod can be sucked and pushed back by the handle to complete the functions of pumping liquid and exhausting air;

[0031] After the pumping and exhausting are completed, the nut limit fork is moved to push the nut to cooperate with the thread of the threaded core rod. The elastic force of the spring presses the nut and the thread of the threaded core rod tightly. At this time, the thread of the nut may not be completely aligned with the thread of the core rod. During the rotation of the nut seat, under the action of the spring, the thread of the nut automatically engages with the thread of the core rod to realize the function of advancing the core rod. The setting of the spring enables the nut thread to adaptively cooperate with the thread of the core rod. The operator only needs to move the position of the nut limit fork once, which reduces the operating requirements and improves the operating efficiency.

[0032] During the injection process, the grooves on the base and the protrusions on the nut seat correspond to the scale markings on the base and the nut seat. During the rotation of the nut seat, the protrusions falling into the grooves can produce an obvious feel, so that the operator does not need to focus on the scale lines and can accurately grasp the injection dose, thereby reducing the operating intensity, improving efficiency and reducing deviations.

[0033] After the spring, nut limiting fork and half nut are assembled, the limiting long groove on the side of the nut falls into the limiting protrusion of the nut limiting fork, forming a stable accessory combination, which is beneficial to clamping, transfer, secondary assembly, etc. during the automated assembly process, and improves the stability and assembly efficiency of the automated assembly.

[0034] A variety of injection needle connection methods make it convenient for clinicians to choose according to their needs and meet various clinical needs.

[0035] After the injection is completed, the thread of the nut falls into the unthreaded empty groove at the end of the threaded core rod, the nut and the threaded core rod lose thread cooperation, and the nut can no longer drive the threaded core rod to move. At the same time, the convex foot of the nut cover buckles into the core rod locking groove, which again limits the movement of the core rod, realizes the self-destruction function, and effectively prevents the secondary use of the syringe. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the present invention;

[0037] Figure 2 It is a partial view of the base of the present invention;

[0038] Figure 3 , Figure 4 It is a schematic diagram of the cooperation between the base and the nut seat mounting seat of the present invention;

[0039] Figure 5This is a schematic diagram of installing a nut seat on the base of the present invention;

[0040] Figure 6 It is a schematic diagram of the cooperation between the nut seat and the nut limiting fork;

[0041] Figure 7 It is a schematic diagram of the cooperation between the nut limiting fork and the half nut;

[0042] Figure 8 This is a partial cross-sectional view without the nut cover installed;

[0043] Fig. 9 It is a partial cross-sectional view;

[0044] Fig.10 It is a schematic diagram of the nut seat;

[0045] Fig.11 , Fig.12 It is a schematic diagram of a half nut;

[0046] Fig.13 This is a schematic diagram of the nut cover;

[0047] Fig.14 It is a schematic diagram of the threaded core rod;

[0048] Fig.15 This is a cross-sectional view of the base;

[0049] Fig.16 A partial cross-sectional view after adding a needle tip protective cover;

[0050] Fig.17 It is a partial schematic diagram of the nut seat mounting seat;

[0051] Fig.18 It is a schematic diagram of a rotating structure technology, A1-outer sleeve, A2-limiting sleeve, A3-left nut clamp, A4-right nut clamp, A5-core rod.

[0052] Description of Reference Numerals

[0053] 1-jacket, 1-1-connecting part, 2-base, 2-1-mounting groove, 2-2-convex point, 3-nut seat, 3-1-rotating seat, 3-2-nut groove, 3-3-center through hole, 3-4-limiting groove, 3-5-groove, 3-6-nut cover fixing cavity, 3-7-groove of nut cover fixing cavity, 3-8-reference mark, 4-nut cover, 4-1-convex foot, 4-2-nut cover mounting leg, 4-3-protrusion on mounting leg, 5-nut seat mounting seat, 5-1-center half hole, 5-2-seat mounting half cavity, 5-3-fixed Fixed pin, 5-4-pin hole, 6-center hole, 7-nut limiting fork, 7-1-spring limiting protrusion, 7-2-limiting protrusion, 7-3-limiting strip, 7-4-nut limiting protrusion, 8-half nut, 8-1-spring mounting hole, 8-2-limiting strip groove, 8-3-half thread, 9-spring, 10-threaded core rod, 10-1-threaded rod, 10-2-unthreaded empty groove, 10-3-core rod locking groove, 10-4-handle, 10-5-rubber plug fixing boss, 11-rubber plug, 12-needle tip, 13-needle tip protection cover. DETAILED DESCRIPTION

[0054] The following is a detailed description of the embodiments of the present invention. Although the present invention will be described and illustrated in conjunction with some specific embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, modifications or equivalent substitutions made to the present invention should all be included in the scope of the claims of the present invention.

[0055] In addition, in order to better illustrate the present invention, numerous specific details are given in the following specific embodiments. It will be understood by those skilled in the art that the present invention can also be implemented without these specific details.

[0056] The main scheme includes a base, a jacket is fixedly arranged at the bottom end of the base, a nut seat mounting seat is fixedly arranged at the upper end of the base, a nut seat is rotatably connected to the nut seat mounting seat, a groove is arranged on the base and the nut seat joint surface, a convex point is arranged on the nut seat and the base joint surface, during the rotation of the nut seat, the convex point cyclically falls into the groove, a threaded core rod is arranged in the jacket, the threaded core rod passes through the center hole of the nut seat mounting seat and is gap-matched with the center hole of the nut seat mounting seat, the thread of the threaded core rod is matched with the threaded hole of the nut in the nut seat, and the nut It includes two half nuts, which are pressed against the threaded core rod by a spring to achieve adaptive thread matching between the half nuts and the threaded core rod. The nut seat is rotated to drive the nut and the threaded core rod to rotate, and the threaded core rod is driven to move in the axial direction of the threaded core rod through the thread. A nut cover is covered on the nut seat, and the nut cover includes convex feet evenly distributed in the circumference of the central through hole. The top end of the threaded rod of the threaded core rod is provided with a core rod locking groove at the end position of the thread. When the core rod is pushed to the bottom of the empty cylinder, the convex foot of the nut cover is buckled into the core rod locking groove.

[0057] The present invention further provides an adaptive screw-in double-snap micro-injector, comprising a base 2, a jacket 1 fixedly arranged at the bottom end of the base 2, a nut seat mounting seat 5 fixedly arranged at the upper end of the base 2, a nut seat 3 rotatably connected to the nut seat mounting seat 5, a threaded core rod 10 arranged in the jacket 1, the threaded core rod 10 passes through the center hole 6 of the nut seat mounting seat 5 and is clearance-matched with the center hole 6, the thread of the threaded core rod 10 is matched with the threaded hole of the nut in the nut seat 3, the nut comprises two half nuts 8, the two half nuts 8 are pressed against the threaded core rod 10 by a spring 9, so that the threads of the half nuts 8 and the threaded core rod 10 are adaptively matched, the nut seat 3 is rotated to drive the rotation between the nut and the threaded core rod 10, and the thread drives the threaded core rod 10 to move in the axial direction of the threaded core rod 10.

[0058] In the above technical solution, the bottom end of the outer sleeve 1 is provided with a needle tip 12 connecting device 1 - 1 and a needle tip protective sleeve 13 .

[0059] In the above technical solution, the nut seat 3 is covered with a nut cover 4, and the nut cover 4 includes protrusions 4-1 uniformly distributed in the circumferential direction of the central through hole.

[0060] In the above technical solution, a groove 2 - 2 is provided on the surface of the base 2 that is connected to the nut seat 3 .

[0061] In the above technical solution, the nut seat mounting seat 5 is composed of two half nut seat mounting seats, and the half nut seat mounting seat includes a nut seat mounting half cavity 5-2 and a center half hole 5-1 arranged at the center. The two seat mounting half cavities 5-2 form a nut seat mounting cavity, and the two center half holes 5-1 form a center hole 6.

[0062] In the above technical scheme, a central through hole 3-3 is provided on the central axis of the nut seat 3, a rotating seat 3-1 which is rotatably matched with the nut seat mounting cavity of the nut seat mounting seat is provided at the bottom end of the nut seat 3, a nut groove 3-2 is provided at the upper end of the nut seat 3, and limiting grooves 3-4 are respectively provided on both sides of the nut groove 3-2, and a convex point 3-5 is provided on the joint surface between the nut seat 3 and the base.

[0063] In the above technical solution, the nut limiting fork 7, the outer sides of the two legs of the nut limiting fork 7 are provided with limiting protrusions 7-2 that cooperate with the limiting grooves 3-4, a spring limiting protrusion 7-1 is provided between the two legs of the nut limiting fork 7, and the inner sides of the two legs of the nut limiting fork 7 are provided with limiting strips 7-3, and a nut limiting protrusion 7-4 is provided at the end of the limiting strip 7-3.

[0064] In the above technical solution, a spring mounting hole 8-1 is provided at one end of the half nut 8, a half thread 8-3 is provided at the other end, and a limited long groove 8-2 is provided on the side between the spring mounting hole 8-1 and the half thread 8-3.

[0065] In the above technical scheme, a rubber plug fixing boss 10-5 for fixing the rubber plug 11 is provided at the bottom end of the threaded core rod 10, and a handle 10-4 is provided at the top end. The top end of the threaded rod 10-1 of the threaded core rod 10 is provided with a non-threaded empty groove 10-2 and a core rod locking groove 10-3 at the end position of the thread. When the core rod is pushed to the bottom of the outer sleeve, the threads of the two half nuts 8 fall into the non-threaded empty groove 10-2 of the threaded rod 10-1, and the protrusion 4-1 of the nut cover 4 is buckled into the core rod locking groove 10-2.

[0066] In the above technical solution, a mounting groove 2 - 1 is provided on the inner wall of the base 2 , and an upward mounting protrusion on the nut seat mounting seat cooperates with the mounting groove 2 - 1 to fix the nut seat mounting seat in the base 2 .

[0067] In the above technical solution, scale marks 2 - 3 are provided on the base 2 , and corresponding reference marks 3 - 8 are provided on the nut seat 3 .

[0068] In the above technical solution, a nut cover fixing cavity 3-5 is provided on the nut seat 3, the nut cover mounting leg 4-2 of the nut cover 4 is installed in the nut cover fixing cavity 3-6, and the protrusion 4-3 on the mounting leg falls into the groove 3-7 of the nut cover fixing cavity.

[0069] Supplementary explanation of the above scheme:

[0070] The function of the center hole of the nut seat mounting seat is to limit the rotation of the threaded core rod, to ensure that when the nut rotates, the threaded core rod moves along the axial direction of the threaded core rod driven by the thread without rotating. Therefore, the shape of the center hole of the nut seat mounting seat cannot be a perfect circle, but can be other shapes besides a perfect circle, such as square, oval, special-shaped, etc. that can limit the rotation of the threaded core rod. The cross-sectional shape of the threaded core rod is the same as the shape of the center hole of the nut seat mounting seat.

[0071] The function of the thread is to drive the threaded core rod to move. Depending on the capacity of the syringe, the single injection volume, the expected injection resistance, etc., the thread can be a single-start thread, double-start thread, multi-start thread, coarse thread, fine thread, square thread, triangular thread and other forms of thread.

[0072] The function of the spring is to make the thread of the nut automatically match the thread of the threaded core rod. Therefore, as long as it can provide sufficient elastic force, the material of the spring can be metal, plastic or other materials, and the structure of the spring can be independent or connected.

[0073] Depending on the application scenario of the syringe, the connection between the outer sleeve and the needle tip can be fixed: the needle tip is directly bonded to the bottom end of the outer sleeve, or split: the needle tip is bonded to an independent needle seat, and the needle seat is then connected to the bottom end of the outer sleeve.

[0074] The function of the convex foot of the nut cover is to fit into the core rod locking groove to prevent the threaded core rod from moving, thereby realizing the self-destruction function of the syringe. As long as the function of preventing the threaded core rod from moving can be achieved, the convex foot of the nut cover can be set unilaterally or multilaterally, symmetrically or asymmetrically.

[0075] The nut seat and the base can be assembled by various methods other than snap-fitting, bonding, welding, etc.

[0076] The scale markings on the base and the nut seat can be integrally formed, or can be printed, labeled or other marking methods.

[0077] The nut cover and the nut seat can be assembled by various methods other than snap-fitting, bonding, welding, etc.

Claims

1. An adaptive screw-in double-buckle micro-injector, characterized in that: The invention comprises a base (2), a jacket (1) is fixedly arranged at the bottom end of the base (2), a nut seat mounting seat (5) is fixedly arranged at the upper end of the base (2), a nut seat (3) is rotatably connected to the nut seat mounting seat (5), a threaded core rod (10) is arranged in the jacket (1), the threaded core rod (10) passes through the center hole (6) of the nut seat mounting seat (5) and is clearance-matched with the center hole (6), the thread of the threaded core rod (10) is matched with the threaded hole of the nut in the nut seat (3), the nut comprises two half nuts (8), the two half nuts (8) are pressed against the threaded core rod (10) by a spring (9), so that the threads of the half nuts (8) and the threaded core rod (10) are adaptively matched, the nut seat (3) is rotated to drive the nut and the threaded core rod (10) to rotate, and the thread drives the threaded core rod (10) through the thread, so that the threaded core rod (10) moves in the axial direction of the threaded core rod (10); The nut seat mounting seat (5) is composed of two half nut seat mounting seats, the half nut seat mounting seat includes a seat mounting half cavity (5-2), a center half hole (5-1) arranged at the center of the seat mounting half cavity, the two seat mounting half cavities (5-2) form a nut seat mounting cavity, and the two center half holes (5-1) form a center hole (6); A central through hole (3-3) is provided on the central axis of the nut seat (3); a rotating seat (3-1) is provided at the bottom end of the nut seat (3) and is rotatably matched with the nut seat mounting cavity of the nut seat mounting seat; a nut groove (3-2) is provided at the upper end of the nut seat (3); limiting grooves (3-4) are respectively provided on both sides of the nut groove (3-2); and a groove (3-5) is provided on the joint surface between the nut seat (3) and the base; A nut limiting fork (7) is provided, wherein the outer sides of the two legs of the nut limiting fork (7) are provided with limiting protrusions (7-2) that cooperate with the limiting grooves (3-4), a spring limiting protrusion (7-1) is provided between the two legs of the nut limiting fork (7), and limiting strips (7-3) are provided inside the two legs of the nut limiting fork (7), and a nut limiting protrusion (7-4) is provided at the end of the limiting strip (7-3).

2. The self-adaptive screw-in double-buckle micro-injector according to claim 1, characterized in that: The nut seat (3) is covered with a nut cover (4), and the nut cover (4) comprises protruding feet (4-1) evenly distributed in the circumference of the central through hole.

3. The self-adaptive screw-in double-buckle micro-injector according to claim 1, characterized in that: A convex point (2-2) is provided on the surface of the base (2) that is joined to the nut seat (3).

4. The self-adaptive screw-in double-buckle micro-injector according to claim 1, characterized in that: A spring mounting hole (8-1) is provided at one end of the half nut (8), a half thread (8-3) is provided at the other end, and a limited long groove (8-2) is provided on the side between the spring mounting hole (8-1) and the half thread (8-3).

5. The self-adaptive screw-in double-buckle micro-injector according to claim 1, characterized in that: The bottom end of the threaded core rod (10) is provided with a fixing boss (10-5) for fixing the rubber plug (11), and the top end is provided with a handle (10-4). The top end of the threaded rod (10-1) of the threaded core rod (10) is provided with a non-threaded empty groove (10-2) and a core rod locking groove (10-3) at the end position of the thread. When the core rod is pushed to the bottom of the outer sleeve, the threads of the two half nuts (8) fall into the non-threaded empty groove (10-2) of the threaded rod (10-1), and the convex foot (4-1) of the nut cover (4) is buckled into the core rod locking groove (10-3).

6. The self-adaptive screw-in double-buckle micro-injector according to claim 1, characterized in that: An installation groove (2-1) is provided on the inner side wall of the base (2), and an upward installation protrusion on the nut seat installation seat cooperates with the installation groove (2-1) to fix the nut seat installation seat in the base (2).

7. The self-adaptive screw-in double-buckle micro-injector according to claim 1, characterized in that: The base (2) is provided with a scale mark (2-3), the nut seat (3) is provided with a corresponding reference mark (3-8), the nut seat (3) is provided with a nut cover fixing cavity (3-6), the nut cover mounting leg (4-2) of the nut cover (4) is mounted in the nut cover fixing cavity (3-6), and the protrusion (4-3) on the mounting leg falls into the groove (3-7) of the nut cover fixing cavity.

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