A nuclear power plant gate valve disc disassembly tool

Abstract

The utility model relates to a nuclear power plant gate valve disc disassembly tool, including a positioning support assembly and a tension assembly, wherein the positioning support assembly is used to cooperate with the valve body of the gate valve for positioning; the tension assembly includes a tension driving rod, a tension disk and a tension arm, the tension driving rod is reciprocatably arranged on the positioning support assembly, a plurality of tension arms are circumferentially spaced on the tension disk, and the tension arm is rotatably connected to the tension disk, the tension disk is reciprocatably arranged on the tension driving rod, a transmission mechanism is arranged between the tension driving rod and each tension arm, and the transmission mechanism is used to convert the reciprocating movement of the tension driving rod relative to the tension disk into the rotation of the tension arm relative to the tension disk. The nuclear power plant gate valve disc disassembly tool can realize on-site replacement of the valve disc without replacing the entire gate valve, reducing the difficulty of maintenance, improving the gate valve maintenance efficiency and reducing maintenance costs, protecting the property safety of operators, and ensuring the smooth operation of the pipeline network.

Description

Technical Field

[0001] The utility model relates to the technical field of nuclear power station gate valve maintenance, in particular to a nuclear power station gate valve disc disassembly tool. Background Art

[0002] Most of the valves used in nuclear power plant pipelines are gate valves. After long-term use, the valve disc and valve stem are prone to fall off, causing the valve disc to fall into the valve seat and cannot be removed. Since most valves are installed in the valve well, the working space is small, which increases the difficulty of valve disc removal and the risk of accidental injury to operators. Therefore, there is an urgent need for a special tool that facilitates valve disc removal, reduces maintenance difficulty, shortens maintenance time, protects the property safety of operators, and ensures the smooth operation of the pipeline network. Utility Model Content

[0003] The utility model aims to provide a nuclear power station gate valve disc disassembly tool, so as to facilitate the removal of the disc, reduce the difficulty of maintenance, shorten the maintenance time, protect the property safety of operators, and ensure the smooth operation of the pipeline network.

[0004] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0005] A nuclear power station gate valve disc disassembly tool, comprising:

[0006] A positioning support assembly, the positioning support assembly is used to cooperate with the valve body of the gate valve for positioning;

[0007] A tension assembly, the tension assembly comprising a tension driving rod, a tension disk and a tension arm, the tension driving rod being reciprocatably disposed on the positioning support assembly, a plurality of tension arms being circumferentially spaced on the tension disk, and the tension arms being rotatably connected to the tension disk, the tension disk being reciprocatably disposed on the tension driving rod, a transmission mechanism being disposed between the tension driving rod and each of the tension arms, the transmission mechanism being used for converting the reciprocating movement of the tension driving rod relative to the tension disk into the rotation of the tension arm relative to the tension disk.

[0008] In one embodiment of the present application, the tension arm includes a mounting portion, a connecting portion and a clamping portion which are connected in sequence, the connecting portion is rotatably connected to the tension disk, the clamping portion is used to extend into the screw hole of the valve disc of the gate valve and be clamped with the valve disc of the gate valve, and the connecting portion is inclined relative to the mounting portion and the clamping portion.

[0009] In one embodiment of the present application, the clamping portion is provided with a clamping boss, and the clamping boss extends from one end of the mounting portion away from the connecting portion toward the connecting portion, and the cross-section of the clamping boss gradually expands from the mounting portion to the connecting portion, and the end of the clamping boss close to the connecting portion forms a clamping surface for clamping with the valve disc of the gate valve.

[0010] In one embodiment of the present application, the positioning support assembly includes:

[0011] A support body, the support body comprising a central portion and a plurality of beam portions circumferentially spaced around the central portion, the central portion being provided with a first through hole for the tension driving rod to pass through;

[0012] A support leg is provided on the beam portion so as to be reciprocatingly slidable along the beam portion, and a matching portion for matching with a valve body of a gate valve is provided at one end of the support leg away from the beam portion.

[0013] In one embodiment of the present application, a locking mechanism is arranged between the supporting leg and the beam portion, the supporting leg is provided with a second through hole for the beam portion to pass through, the locking mechanism includes a threaded locking member and a threaded hole arranged on the supporting leg, the threaded hole is connected to the second through hole, the threaded locking member is threadedly matched with the threaded hole and is tightened against the beam portion.

[0014] In one embodiment of the present application, the matching portion is a positioning column used to match with the diagonal bolt hole of the valve body of the gate valve.

[0015] In one embodiment of the present application, the tension driving rod includes a rod body, a rotating handle and a fixing nut, the rod body includes a threaded rod segment and a smooth rod segment, the threaded rod segment is threadedly engaged with the tension disk, the smooth rod segment passes through the positioning support assembly, the rotating handle is arranged on the smooth rod segment, and the fixing nut is threadedly engaged with the threaded rod segment on a side of the positioning support assembly away from the tension disk.

[0016] In one embodiment of the present application, the transmission mechanism includes a driving block disposed at one end of the threaded rod segment away from the smooth rod segment, the driving block is located between the tension arms, and the driving block is in contact with and cooperates with the tension arms.

[0017] In one embodiment of the present application, an elastic preload is provided between the tension arm and the tension disk, and the elastic preload is used to keep the end of the tension arm away from the tension disk in a tendency to converge with each other.

[0018] In one embodiment of the present application, the transmission mechanism includes a worm gear disposed at one end where the tension arm is connected to the tension disk, and the worm gear cooperates with the threaded rod segment to form a worm gear transmission mechanism.

[0019] It can be seen from the above technical scheme that the utility model discloses a nuclear power plant gate valve disc removal tool, which includes a positioning support assembly and a tension assembly, wherein the positioning support assembly is used to cooperate with the valve body of the gate valve for positioning; the tension assembly includes an tension driving rod, an tension disk and an tension arm, the tension driving rod is reciprocatingly arranged on the positioning support assembly, a plurality of tension arms are circumferentially spaced on the tension disk, and the tension arm is rotatably connected to the tension disk, the tension disk is reciprocatingly arranged on the tension driving rod, and a transmission mechanism is arranged between the tension driving rod and each tension arm, and the transmission mechanism is used to convert the reciprocating movement of the tension driving rod relative to the tension disk into the rotation of the tension arm relative to the expansion disk.

[0020] When in use, first remove the upper valve cover of the gate valve to be repaired, position the nuclear power plant gate valve disc removal tool on the valve body of the gate valve through the positioning support component, and then insert each tension arm into the valve disc screw hole. After being inserted into place, the action of the tension driving rod will make the ends of each tension arm away from the tension disk move away from each other, so that each tension arm is tightened in the valve disc screw hole, and then the tension driving rod is pulled out of the valve body of the gate valve, and the valve disc can be taken out, and finally a new valve disc is replaced, the gate valve is assembled, and the gate valve repair is completed. The above-mentioned nuclear power plant gate valve disc removal tool can be used for removing valve discs of gate valves of various specifications, has a wide range of applications, and can realize on-site replacement of valve discs without replacing the entire gate valve, reducing the difficulty of maintenance, improving the gate valve maintenance efficiency and reducing maintenance costs, protecting the property safety of operators, and ensuring the smooth operation of the pipeline network. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic diagram of the structure of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0023] Figure 2 A front view of a tension arm of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0024] Figure 3 A side view of a tension arm of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0025] Figure 4A top view of a tension arm of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0026] Figure 5 A top view of a tension plate of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0027] Figure 6 A front view of a tension plate of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0028] Figure 7 A front view of a support body of a positioning support assembly of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0029] Figure 8 A top view of a support body of a positioning support assembly of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0030] Fig. 9 A side view of a support body of a positioning support assembly of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0031] Fig.10 A front view of a support leg of a positioning support assembly of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0032] Fig.11 A side view of a support leg of a positioning support assembly of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0033] Fig.12 A top view of the support legs of the positioning support assembly of the nuclear power plant gate valve disc removal tool provided by the embodiment of the utility model;

[0034] Fig.13 A bottom view of the support legs of the positioning support assembly of the nuclear power plant gate valve disc removal tool provided by the embodiment of the utility model;

[0035] Fig.14 A front view of a rod body of an expansion drive rod of a nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model;

[0036] Fig.15 A side view of the rod body of the tension driving rod of the nuclear power plant gate valve disc removal tool provided by an embodiment of the utility model.

[0037] In the figure:

[0038] 1 is a positioning support assembly; 110 is a support body; 111 is a central portion; 112 is a beam portion; 113 is a first through hole; 120 is a support leg; 130 is a matching portion; 140 is a threaded locking member; 150 is a second through hole; 2 is an expansion assembly; 210 is an expansion drive rod; 211 is a rod body; 2111 is a threaded rod section; 2112 is a bare rod section; 2113 is a third through hole; 212 is a rotating handle; 213 is a fixing nut; 220 is an expansion disk; 221 is a disk body; 222 is a mounting arm; 223 is a threaded hole; 224 is a mounting groove; 225 is a first pin hole; 230 is an expansion arm; 231 is a mounting portion; 232 is a connecting portion; 233 is a clamping portion; 234 is a clamping boss; 235 is a second pin hole; 240 is a driving block. DETAILED DESCRIPTION

[0039] The core of the utility model is to provide a nuclear power plant gate valve disc disassembly tool. The structural design of the nuclear power plant gate valve disc disassembly tool makes it easy to remove the valve disc, reduce the difficulty of maintenance, shorten the maintenance time, protect the property safety of operators, and ensure the smooth operation of the pipeline network.

[0040] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0041] See also Figure 1 , Figure 1 A schematic structural diagram of a nuclear power plant gate valve disc removal tool provided in an embodiment of the utility model.

[0042] The utility model discloses a nuclear power station gate valve disc disassembly tool in an embodiment. The nuclear power station gate valve disc disassembly tool comprises a positioning support component 1 and a tension component 2.

[0043] Among them, the positioning support component 1 is used to cooperate with the valve body of the gate valve for positioning. The positioning support component 1 can be adapted to the holes, grooves, edge bosses and other structures of the valve body of the gate valve to position the nuclear power plant gate valve disc removal tool relative to the valve body of the gate valve.

[0044] The tension assembly 2 includes a tension driving rod 210, a tension disk 220 and a tension arm 230. The tension driving rod 210 is reciprocatably arranged on the positioning support assembly 1. Multiple tension arms 230 are circumferentially spaced on the tension disk 220, and the tension arms 230 are rotatably connected to the tension disk 220. The tension disk 220 is reciprocatably arranged on the tension driving rod 210. A transmission mechanism is arranged between the tension driving rod 210 and each tension arm 230. The transmission mechanism is used to convert the reciprocating movement of the tension driving rod 210 relative to the tension disk 220 into the rotation of the tension arm 230 relative to the tension disk 220.

[0045] Compared with the prior art, the nuclear power plant gate valve disc removal tool provided by the embodiment of the utility model is used. First, the upper valve cover of the gate valve to be repaired is removed, and the nuclear power plant gate valve disc removal tool is positioned on the valve body of the gate valve through the positioning support assembly 1. Then, each tension arm 230 is inserted into the valve disc screw hole. After being inserted into place, the action of the tension driving rod 210 will make the ends of each tension arm 230 away from the tension disk 220 move away from each other, so that each tension arm 230 is tightened in the valve disc screw hole, and then the tension driving rod 210 is pulled out of the valve body of the gate valve, and the valve disc can be taken out. Finally, a new valve disc is replaced, the gate valve is assembled, and the gate valve repair is completed. The above-mentioned nuclear power plant gate valve disc removal tool can be used for removing valve discs of gate valves of various specifications, has a wide range of applications, and can realize on-site replacement of valve discs without replacing the entire gate valve, reducing the difficulty of maintenance, improving the gate valve maintenance efficiency and reducing the maintenance cost, ensuring the property safety of operators, and ensuring the smooth operation of the pipeline network.

[0046] like Figures 2 to 4 As shown, in an embodiment of the utility model, the tension arm 230 includes a mounting portion 231, a connecting portion 232 and a clamping portion 233 which are connected in sequence. The connecting portion 232 is rotatably connected to the tension disk 220. The clamping portion 233 is used to extend into the screw hole of the valve disc of the gate valve and to be clamped with the valve disc of the gate valve. The connecting portion 232 is tilted relative to the mounting portion 231 and the clamping portion 233. By tilting the connecting portion 232 relative to the mounting portion 231 and the clamping portion 233, the clamping portions 233 can be made to fit closely together when one end of the tension arm 230 away from the tension disk 220 is gathered together, so that each clamping portion 233 can enter the screw hole of the valve disc more easily.

[0047] Furthermore, in order to make each clamping part 233 fit more closely, the cross-section of each clamping part 233 is trapezoidal or triangular, so that two adjacent clamping parts 233 can fit tightly, reducing the cross-sectional size of each clamping part 233 after fitting, so that each clamping part 233 can extend into the valve disc screw hole.

[0048] like Figure 2 and Figure 3As shown, the above-mentioned clamping portion 233 is provided with a clamping boss 234, and the clamping boss 234 extends from one end of the mounting portion 231 away from the connecting portion 232 toward the connecting portion 232. The cross-section of the clamping boss 234 gradually expands from the mounting portion 231 to the connecting portion 232. The end of the clamping boss 234 close to the connecting portion 232 forms a clamping surface for clamping with the valve disc of the gate valve. The clamping boss 234 and the clamping surface can make the clamping portion 233 form a hook-shaped structure, so that the clamping portion 233 can hook the other side surface of the valve disc after passing through the valve disc screw hole, thereby preventing the clamping portion 233 from being separated from the valve disc when the valve disc is pulled out of the valve body.

[0049] Corresponding to the above-mentioned tension arm 230, as Figure 5 and Figure 6 As shown, in an embodiment of the utility model, the tension disk 220 includes a disk body 221 and a mounting arm 222 circumferentially spaced apart on the disk body 221, the disk body 221 is provided with a threaded hole 223 for threadedly mating with the threaded rod segment 2111 of the rod body 211 of the tension driving rod 210 described below, an mounting groove 224 for mounting the tension arm 230 is provided at one end of the mounting arm 222 away from the disk body 221, a first pin hole 225 is provided on the groove walls on both sides of the mounting groove 224, a second pin hole 235 is provided on the mounting portion 231 of the tension arm 230, the mounting pin passes through the first pin hole 225 on the groove walls on both sides of the mounting groove 224 and the second pin hole 235 on the mounting portion 231 of the tension arm 230 to rotatably connect the tension arm 230 with the tension disk 220.

[0050] The number of mounting arms 222 is the same as the number of tension arms 230 , and the number of tension arms 230 and mounting arms 222 is at least two. In the embodiment of the utility model, three tension arms 230 are provided, and correspondingly, three mounting arms 222 are provided, and the mounting arms 222 are evenly distributed along the circumference of the disk body 221 .

[0051] like Figures 7 to 13 As shown, in an embodiment of the utility model, the positioning support assembly 1 includes a support body 110 and a support leg 120, wherein the support body 110 includes a central portion 111 and a plurality of beam portions 112 circumferentially spaced around the central portion 111, the support body 110 is provided with at least two beam portions 112, the central portion 111 is provided with a first through hole 113 for the tension driving rod 210 to pass through, the first through hole 113 is a light hole, and the tension driving rod 210 can reciprocate along the first through hole 113; the support leg 120 can be reciprocatingly slidably arranged on the beam portion 112 along the beam portion 112, so as to adjust the position of the support leg 120 according to different models and specifications of gate valves, so as to facilitate the positioning support assembly 1 to adapt thereto, and the end of the support leg 120 away from the beam portion 112 is provided with a mating portion 130 for mating with the valve body of the gate valve.

[0052] like Fig.10 and Fig.11 As shown, a locking mechanism is provided between the support leg 120 and the beam 112 to fix the support leg 120 and the beam 112 relatively to avoid misalignment between the valve disc removal tool of the nuclear power plant gate valve and the valve body of the gate valve during the process of pulling out the valve disc. Specifically, the support leg 120 is provided with a second through hole 150 for the beam 112 to pass through, and the locking mechanism includes a threaded locking member 140 and a threaded hole 223 provided on the support leg 120, the threaded hole 223 is connected to the second through hole 150, and the threaded locking member 140 is threadedly matched with the threaded hole 223 and is tightened against the beam 112.

[0053] like Fig.10 , Fig.11 as well as Fig.13 As shown, the matching portion 130 is a positioning column used to match the diagonal bolt holes of the valve body of the gate valve. When in use, the positioning column is inserted into any group of diagonal bolt holes on the upper end of the valve body of the gate valve, thereby realizing the positioning of the positioning support assembly 1 on the valve body of the gate valve.

[0054] like Figure 1 , Fig.14 and Fig.15 As shown, in an embodiment of the utility model, the tension driving rod 210 includes a rod body 211, a rotating handle 212 and a fixing nut 213. The rod body 211 includes a threaded rod segment 2111 and a bare rod segment 2112. The threaded rod segment 2111 is threadedly matched with the tension disk 220. The bare rod segment 2112 passes through the positioning support assembly 1. The rotating handle 212 is arranged on the bare rod segment 2112. The fixing nut 213 is threadedly matched with the threaded rod segment 2111 on the side of the positioning support assembly 1 away from the tension disk 220. The fixing nut 213 is used to lock and fix the tension driving rod 210 to the positioning support assembly 1.

[0055] Specifically, a third through hole 2113 is provided on the bare rod segment 2112 , and the rotating handle 212 passes through the third through hole 2113 .

[0056] like Figure 1 , Fig.14 and Fig.15 As shown, the transmission mechanism includes a driving block 240 arranged at one end of the threaded rod section 2111 away from the smooth rod section 2112, the driving block 240 is located between each tension arm 230, and the driving block 240 is in contact and cooperate with each tension arm 230. When the driving block 240 moves along with the rod body 211 relative to the tension disk 220 in a direction away from the tension disk 220, the driving block 240 drives the ends of each tension arm 230 away from the tension disk 220 to move away from each other, and the surface of the side of the driving block 240 away from the tension disk 220 is a conical surface.

[0057] To further optimize the above technical solution, in the above embodiment, an elastic preload is arranged between the tension arm 230 and the tension disk 220, and the elastic preload is used to make the end of the tension arm 230 away from the tension disk 220 maintain a tendency to gather together, so that when the driving block 240 moves along with the rod body 211 relative to the tension disk 220 in a direction close to the tension disk 220, the end of each tension arm 230 away from the tension disk 220 can gather together under the action of the elastic preload.

[0058] Of course, the transmission mechanism is not limited to the above structure. In another embodiment of the present invention, the transmission mechanism includes a worm gear arranged at one end where the tension arm 230 is connected to the tension disk 220. The worm gear cooperates with the threaded rod segment 2111 to form a worm gear transmission mechanism. When the rod body 211 is spirally fed relative to the tension disk 220, the threaded rod segment 2111 of the rod body 211 can simultaneously drive the worm gear to realize the rotation of the tension arm 230 relative to the tension disk 220, thereby realizing the convergence or separation of the ends of each tension arm 230 away from the tension disk 220.

[0059] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0060] This article uses specific examples to illustrate the principles and implementation methods of the utility model. The above examples are only used to help understand the core idea of ​​the utility model. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the utility model.

Claims

1. A nuclear power plant gate valve disc removal tool, characterized in that: include: A positioning support assembly, the positioning support assembly is used to cooperate with the valve body of the gate valve for positioning; A tension assembly, the tension assembly comprising a tension driving rod, a tension disk and a tension arm, the tension driving rod being reciprocatably disposed on the positioning support assembly, a plurality of tension arms being circumferentially spaced on the tension disk, and the tension arms being rotatably connected to the tension disk, the tension disk being reciprocatably disposed on the tension driving rod, a transmission mechanism being disposed between the tension driving rod and each of the tension arms, the transmission mechanism being used for converting the reciprocating movement of the tension driving rod relative to the tension disk into the rotation of the tension arm relative to the tension disk.

2. The nuclear power plant gate valve disc removal tool according to claim 1 is characterized in that: The tension arm includes a mounting portion, a connecting portion and a clamping portion which are connected in sequence. The connecting portion is rotatably connected to the tension disk. The clamping portion is used to extend into the screw hole of the valve disc of the gate valve and be clamped with the valve disc of the gate valve. The connecting portion is inclined relative to the mounting portion and the clamping portion.

3. The nuclear power plant gate valve disc removal tool according to claim 2, characterized in that: The clamping portion is provided with a clamping boss, which extends from an end of the mounting portion away from the connecting portion toward the connecting portion, and a cross-section of the clamping boss gradually expands from the mounting portion to the connecting portion. An end of the clamping boss close to the connecting portion forms a clamping surface for clamping with a valve disc of the gate valve.

4. The nuclear power plant gate valve disc removal tool according to any one of claims 1 to 3, characterized in that: The positioning support assembly comprises: A support body, the support body comprising a central portion and a plurality of beam portions circumferentially spaced around the central portion, the central portion being provided with a first through hole for the tension driving rod to pass through; A support leg is provided on the beam portion so as to be reciprocatingly slidable along the beam portion, and a matching portion for matching with a valve body of a gate valve is provided at one end of the support leg away from the beam portion.

5. The nuclear power plant gate valve disc removal tool according to claim 4, characterized in that: A locking mechanism is arranged between the supporting leg and the beam portion. The supporting leg is provided with a second through hole for the beam portion to pass through. The locking mechanism includes a threaded locking member and a threaded hole arranged on the supporting leg. The threaded hole is connected to the second through hole. The threaded locking member is threadedly matched with the threaded hole and is tightened against the beam portion.

6. The nuclear power plant gate valve disc removal tool according to claim 4, characterized in that: The matching portion is a positioning column used to match with the diagonal bolt hole of the valve body of the gate valve.

7. The nuclear power plant gate valve disc removal tool according to any one of claims 1-3, 5 and 6, characterized in that: The tension driving rod includes a rod body, a rotating handle and a fixing nut. The rod body includes a threaded rod segment and a smooth rod segment. The threaded rod segment is threadedly engaged with the tension disk. The smooth rod segment passes through the positioning support assembly. The rotating handle is arranged on the smooth rod segment. The fixing nut is threadedly engaged with the threaded rod segment on a side of the positioning support assembly away from the tension disk.

8. The nuclear power plant gate valve disc removal tool according to claim 7, characterized in that: The transmission mechanism comprises a driving block arranged at one end of the threaded rod section away from the polished rod section, the driving block is located between the tension arms, and the driving block is in contact with and cooperates with the tension arms.

9. The nuclear power plant gate valve disc removal tool according to claim 8, characterized in that: An elastic preload is provided between the tension arm and the tension disk, and the elastic preload is used to keep the ends of the tension arm away from the tension disk in a tendency to converge with each other.

10. The nuclear power plant gate valve disc removal tool according to claim 7, characterized in that: The transmission mechanism comprises a worm gear arranged at one end where the tension arm is connected to the tension disk, and the worm gear cooperates with the threaded rod segment to form a worm gear transmission mechanism.

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