A tooling for assembling a gas meter movement

Abstract

The present invention provides a tool for assembling a gas meter movement, belonging to the field of mechanical technology. It solves the problems of low assembly efficiency and frequent operation errors in the assembly of an existing gas meter movement. This tool for assembling a gas meter movement includes a bottom plate and a positioning seat fixedly connected to the bottom plate. One end of the positioning seat is provided with a positioning component for placing the gas meter movement, and the other end of the positioning seat is provided with a lifting seat. A feeding block capable of reciprocating horizontally and laterally is arranged on the lifting seat. A positioning groove is arranged at the inner end of the feeding block, and a first return spring is arranged between the outer end of the feeding block and the lifting seat. The outer end of the feeding block has a clamping portion. An installation seat is fixedly connected to the side of the lifting seat, and a hook plate is arranged on the installation seat. After the feeding block moves inward, the clamping portion can be clamped with the hook plate, and the clamping portion can be disengaged from the hook plate when the feeding block descends with the lifting seat. This tool for assembling a gas meter movement has the advantages of high assembly efficiency and precise assembly of the gas meter movement.

Description

Technical Field

[0001] The present invention belongs to the technical field of machinery, and relates to a tooling, in particular to a tooling for assembling a gas meter movement. Background Art

[0002] As a metering instrument, a diaphragm gas meter belongs to the metering instrument for trade settlement, and the accuracy thereof is directly related to the fairness of transactions. The movement is the core component of the gas meter, and the key components determining the accuracy are all installed on the movement. Its working principle is that natural gas enters the shell from the air inlet, then enters through the chamber on the movement, pushes the diaphragm to move, the gas inside the diaphragm is discharged from another chamber to the air outlet, and as the diaphragm swings, it drives the diaphragm linkage arm and the driving arm to swing. The swing amplitude of the diaphragm is limited by the included angle between the diaphragm linkage arm and the driving arm. One swing back and forth of the diaphragm is a revolution volume, and one revolution volume corresponds to one circle of the first wheel of the digit wheel. The larger the angle of the diaphragm linkage arm, the larger the swing amplitude of the diaphragm, the larger the revolution volume, and the negative deviation of the error value; conversely, the positive deviation of the error value. To make the actual revolution volume conform to the designed revolution volume size, it is necessary to ensure that the included angle between the diaphragm linkage arm and the driving arm conforms to the designed dimensions. Therefore, higher requirements are imposed when installing the diaphragm linkage arm and the driving arm.

[0003] The assembly of the gas meter movement is mostly manual operation. Generally, it is required to select experienced and skilled workers for assembly. Therefore, its assembly efficiency is low and operation errors often occur. Summary of the Invention

[0004] The purpose of the present invention is to address the above problems existing in the prior art, and propose a tooling for assembling a gas meter movement with high assembly efficiency and high assembly precision.

[0005] The purpose of the present invention can be achieved by the following technical solutions: A tooling for assembling a gas meter movement, including a bottom plate and a positioning seat fixedly connected to the bottom plate. One end of the positioning seat is provided with a positioning component for placing the gas meter movement. It is characterized in that the other end of the positioning seat is provided with a lifting seat capable of reciprocating up and down relative to the positioning seat. A feeding block capable of reciprocating horizontally and transversely is provided on the lifting seat. A positioning groove for placing the diaphragm linkage arm is provided at the inner end of the feeding block. A first return spring is provided between the outer end of the feeding block and the lifting seat. A clamping portion is provided at the outer end of the feeding block. An installation seat is fixedly connected to the side of the lifting seat. A hook plate is provided on the installation seat. After the feeding block moves inward, the clamping portion can be engaged with the hook plate, and when the feeding block can descend with the lifting seat, the clamping portion can disengage from the hook plate.

[0006] This tooling is set on the automatic assembly line of the gas meter movement. During assembly, the gas meter movement is placed on the positioning component, and this tooling drives the gas meter movement to move to the next process; the robot places the diaphragm linkage arm into the positioning groove of the feeding block, and the robot moves the feeding block by pushing, so that the diaphragm linkage arm reaches the corresponding position of the movement. The manipulator grabs the long shaft, sleeves the sealing ring onto the long shaft, and then inserts the long shaft into the corresponding position of the movement, and continues to move to the next process; the robot places the driving arm and the central shaft into the corresponding positions of the movement, and then presses the long shaft, the central shaft and the driving arm, so that the upper and lower ends of the long shaft are respectively inserted into the driving arm and the diaphragm linkage arm and are fixedly connected, and then the valve cover is placed on the central shaft of the movement. After the diaphragm linkage arm is placed into the positioning groove of the feeding block, the first driving part pushes the feeding block to move inwards, so that the clamping part is clamped with the hook plate, and the connecting hole of the long shaft and the diaphragm linkage arm is coaxially arranged. When the lower end of the long shaft is pressed into the connecting hole of the diaphragm linkage arm, the second driving part presses down the lifting seat to move the lifting seat downwards, so that the diaphragm linkage arm is separated from the positioning groove of the feeding block, and at the same time presses down the hook plate, so that the clamping part of the feeding plate is separated from the hook plate, and under the elastic force of the first return spring, the feeding plate resets. Using this tooling to assemble the gas meter movement has the advantages of high assembly accuracy, high assembly efficiency and simple and reliable structure. The first driving part and the second driving part adopt cylinders or oil cylinders.

[0007] In the above-mentioned tooling for assembling a gas meter movement, a vertically arranged connecting column is fixedly connected to the lifting seat, and a horizontally arranged first guiding column is penetrated and fixedly connected to the middle of the connecting column, and the first guiding column passes through the feeding block. The first guiding column passes through the feeding block, which has a good guiding effect on the horizontal movement of the feeding block and can make the feeding block feed accurately.

[0008] In the above-mentioned tooling for assembling a gas meter movement, a limiting sleeve is sleeved on the first guiding column, one end of the limiting sleeve can abut against the connecting column, the other end of the limiting sleeve is for the side wall of the feeding block to abut against, and the first return spring is sleeved on the outside of the limiting sleeve. By setting the above-mentioned limiting sleeve, it plays a limiting role in the movement of the feeding block and improves the accuracy of feeding.

[0009] In the above-mentioned tooling for assembling a gas meter movement, a slider is fixedly connected to the lower side of the outer end of the feeding block, a horizontally arranged guide rail is fixedly connected to the lifting seat, the guide rail is arranged in parallel with the first guiding column, and the guide rail is embedded in the sliding groove of the corresponding slider. Through the guiding action of the slider and the guide rail, the movement of the feeding block relative to the lifting seat has a good guiding effect and improves the reliability of the work.

[0010] In the above-mentioned tooling for assembling a gas meter movement, one end of the hook plate is hinged to the mounting seat, and a second return spring is provided between the other end of the hook plate and the mounting seat. When the feeding plate moves inward, the clamping portion pushes the other end of the hook plate to swing downward and compress the second return spring. After the feeding plate moves into place, the second return spring pushes the other end of the hook plate to reset, causing the clamping portion to be clamped to the hook plate, which has the advantages of simple structure and reliable operation.

[0011] In the above-mentioned tooling for assembling a gas meter movement, the outer end of the hook plate is a pressing portion, a first groove is provided on the mounting seat, and a second groove is provided on the lower end surface of the pressing portion. The upper and lower ends of the second return spring are embedded in the first groove and the second groove. With the above arrangement, the second return spring has the advantages of good positioning effect and not being easily detached.

[0012] In the above-mentioned tooling for assembling a gas meter movement, a protruding head is provided on the upper side of the other end of the hook plate.

[0013] In the above-mentioned tooling for assembling a gas meter movement, an inclined guiding surface is provided on the outer side of the protruding head. By providing the guiding surface, the clamping portion slides along the guiding surface and is clamped to the protruding head, which has the advantage of smooth and reliable operation.

[0014] In the above-mentioned tooling for assembling a gas meter movement, the lifting seat is square, and a number of second guiding columns are vertically fixed to the lifting seat. A number of linear bearings are fixed to the front end of the positioning seat, and the second guiding columns pass through the corresponding linear bearings. The second guiding columns passing through the linear bearings provide a good guiding effect for the lifting of the lifting seat and improve the stability of the operation.

[0015] In the above-mentioned tooling for assembling a gas meter movement, the positioning assembly includes a positioning groove provided at one end of the positioning seat for the lower end of the gas meter movement to be embedded. Support columns I and II are provided on the positioning seat, and support columns I and II are located on both sides of the positioning groove. Limiting grooves are provided at the upper ends of support columns I and II. The lower end of the gas meter movement is embedded in the positioning groove, and the upper ends of the front and rear sides of the gas meter movement are respectively embedded in the limiting grooves of support columns I and II, which has the advantages of stable positioning of the gas meter movement and not being easily deflected.

[0016] In the above-mentioned tooling for assembling a gas meter movement, a vertically arranged stop block is provided on the lifting seat. The stop block is located outside the feeding block, and the feeding block can abut against the stop block. By providing the above-mentioned stop block for the feeding block to abut against, the feeding block can be limited.

[0017] In the above-mentioned tooling for assembling the movement of a gas meter, a vertically arranged guide column three is fixedly connected to the middle part of the lifting seat, the lower end of the guide column three passes through the positioning seat, and a return spring three is sleeved on the outer side of the guide column three, and the two ends of the return spring three respectively abut against the lifting seat and the positioning seat.

[0018] In the above-mentioned tooling for assembling a gas meter movement, two sets of feed blocks, a return spring and a hook plate are provided on the lifting seat, and the two sets of feed blocks, a return spring and a hook plate are symmetrically arranged on both sides of the lifting seat.

[0019] Compared with the prior art, the tooling for assembling the movement of a gas meter has the following advantages:

[0020] 1. After the diaphragm linkage arm is placed into the positioning groove of the feed block, the driving member 1 pushes the feed block to move inward, so that the clamping part is clamped with the hook plate, and the long axis and the connecting hole of the diaphragm linkage arm are coaxially arranged. When the lower end of the long axis is pressed into the connecting hole of the diaphragm linkage arm, the driving member 2 presses down the lifting seat to move the lifting seat downward, so that the diaphragm linkage arm is separated from the positioning groove of the feed block, and at the same time presses down the hook plate, so that the clamping part of the feed plate is separated from the hook plate. Under the elastic force of the reset spring 1, the feed plate is reset. The use of this tooling to assemble the gas meter movement has the advantages of assembly accuracy, high assembly efficiency, simple and reliable structure;

[0021] 2. A set of guide columns is provided with a limit sleeve, one end of which can abut against the connecting column, and the other end of the limit sleeve abuts against the side wall of the feeding block. A set of return springs is arranged on the outside of the limit sleeve to limit the movement of the feeding block, thereby improving the accuracy of feeding;

[0022] 3. An inclined guide surface is provided on the outside of the clamp head, so that the clamping part slides along the guide surface and clamps with the clamp head, which has the advantages of smooth and reliable operation;

[0023] 4. A vertically arranged stopper is provided on the lifting seat. The stopper is located on the outside of the feeding block and the feeding block can be abutted against the stopper, which can limit the feeding block. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The utility model is a three-dimensional schematic diagram of a tooling for assembling a gas meter movement.

[0025] Figure 2 The utility model is a top view schematic diagram of a tooling for assembling a gas meter movement.

[0026] Figure 3 yes Figure 2 AA cross-sectional view of .

[0027] Figure 4 yes Figure 2Schematic diagram of the B-B cross-section.

[0028] Figure 5 is Figure 2 Schematic diagram of the C-C cross-section.

[0029] Figure 6 is the working schematic diagram of a tooling for assembling a gas meter movement.

[0030] Figure 7 is the three-dimensional schematic diagram of the gas meter movement.

[0031] In the figure, 1 is the bottom plate; 2 is the positioning seat; 2a is the positioning groove; 3 is the positioning component; 3a is the first support column; 3b is the second support column; 3c is the limiting groove; 4 is the lifting seat; 5 is the feeding block; 5a is the positioning groove; 5b is the clamping part; 6 is the first return spring; 7 is the mounting seat; 7a is the first groove; 8 is the hook plate; 8a is the clamping head; 8b is the pressing part; 8c is the second groove; 8d is the guiding surface; 9 is the connecting column; 10 is the first guiding column; 11 is the limiting sleeve; 12 is the slider; 13 is the guide rail; 14 is the second return spring; 15 is the second guiding column; 16 is the linear bearing; 17 is the stop block; 18 is the third guiding column; 19 is the third return spring; 20 is the gas meter movement; 21 is the diaphragm linkage arm; 22 is the long shaft; 23 is the central shaft; 24 is the driving arm; 25 is the striker. Specific embodiments

[0032] The following are specific embodiments of the present invention and in combination with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

[0033] As Figures 1 to 7 shown, a tooling for assembling a gas meter movement includes a bottom plate 1 and a positioning seat 2 fixedly connected to the bottom plate 1. One end of the positioning seat 2 is provided with a positioning component 3 for placing the gas meter movement 20. The positioning component 3 includes a positioning groove 2a provided at one end of the positioning seat 2, and the positioning groove 2a is for the lower end of the gas meter movement 20 to be embedded. Exhaust grooves 2b are provided on both sides of the positioning groove 2a to facilitate the placement of the gas meter movement 20. The positioning seat 2 is provided with a first support column 3a and a second support column 3b. The first support column 3a and the second support column 3b are located on both sides of the positioning groove 2a, and the upper ends of the first support column 3a and the second support column 3b are provided with a limiting groove 3c. The bottom plate 1 is square, and four strikers 25 are provided on the upper end surface of the bottom plate 1. The four strikers 25 are located at the four corner ends of the bottom plate.

[0034] At the other end of the positioning seat 2, there is a lifting seat 4 that can reciprocate up and down relative to the positioning seat 2. On the lifting seat 4, there is a feeding block 5 that can reciprocate horizontally. At the inner end of the feeding block 5, there is a positioning groove 5a for placing the diaphragm linkage arm 21. Between the outer end of the feeding block 5 and the lifting seat 4, there is a first return spring 6. The outer end of the feeding block 5 has a clamping portion 5b. On the side of the lifting seat 4, there is a fixedly connected mounting seat 7. On the mounting seat 7, there is a hook plate 8. After the feeding block 5 moves inward, the clamping portion 5b can be clamped with the hook plate 8. When the feeding block 5 can descend with the lifting seat 4, the clamping portion 5b can be disengaged from the hook plate 8.

[0035] On the lifting seat 4, there is a vertically arranged connecting column 9 fixedly connected. In the middle of the connecting column 9, there is a horizontally arranged first guiding column 10 passing through and fixedly connected. The first guiding column 10 passes through the feeding block 5, which has a good guiding effect on the horizontal movement of the feeding block 5 and can enable the feeding block 5 to feed accurately. The first guiding column 10 is sleeved with a limiting sleeve 11. One end of the limiting sleeve 11 can abut against the connecting column 9, and the other end of the limiting sleeve 11 is for the side wall of the feeding block 5 to abut against. The first return spring 6 is sleeved outside the limiting sleeve 11, which plays a limiting role in the movement of the feeding block 5 and improves the accuracy of feeding.

[0036] At the lower side of the outer end of the feeding block 5, there is a slider 12 fixedly connected. On the lifting seat 4, there is a horizontally arranged guide rail 13 fixedly connected. The guide rail 13 is arranged parallel to the guiding column, and the guide rail 13 is embedded in the corresponding sliding groove of the slider 12.

[0037] One end of the hook plate 8 is hinged on the mounting seat 7. Between the other end of the hook plate 8 and the mounting seat 7, there is a second return spring 14. The outer end of the hook plate 8 is a pressing portion 8b. On the mounting seat 7, there is a first groove 7a. On the lower end surface of the pressing portion 8b, there is a second groove 8c. The upper and lower ends of the second return spring 14 are embedded in the first groove 7a and the second groove 8c, which has the advantages of good positioning effect on the second return spring 14 and not easy to fall off. On the upper side of the other end of the hook plate 8, there is a protruding clamping head 8a, and on the outside of the clamping head, there is an inclined guiding surface 8d.

[0038] The lifting seat 4 is square. On the lifting seat 4, there are four vertically fixedly connected second guiding columns 15. The four second guiding columns 15 are symmetrically arranged in pairs. At the front end of the positioning seat 2, there are four linear bearings 16 and the second guiding columns 15 pass through the corresponding linear bearings 16, which enables the lifting of the lifting seat 4 to have a good guiding effect and improves the stability of the work.

[0039] On the lifting seat 4, there is a vertically arranged stop block 17. The stop block 17 is located outside the feeding block 5 and the feeding block 5 can abut against the stop block 17, which can play a limiting role on the feeding block 5.

[0040] A vertically arranged third guide post 18 is fixedly connected to the middle of the lifting seat 4. The lower end of the third guide post 18 passes through the positioning seat 2. A third return spring 19 is sleeved outside the third guide post 18, and both ends of the third return spring 19 respectively abut against the lifting seat 4 and the positioning seat 2.

[0041] Two groups of feeding blocks 5, a first return spring 6 and a hook plate 8 are arranged on the lifting seat 4, and the two groups of feeding blocks 5, the first return spring 6 and the hook plate 8 are symmetrically arranged on both sides of the lifting seat 4.

[0042] This tooling is arranged on the automatic assembly line of the gas meter movement 20. During assembly, the gas meter movement 20 is placed on the positioning assembly 3, so that the lower end of the gas meter movement 20 is embedded in the positioning groove 2a, and the upper ends of the front and rear sides of the gas meter movement 20 are respectively embedded in the limit grooves 3c of the first support column 3a and the second support column 3b.

[0043] This tooling drives the gas meter movement 20 to move to the next process; the robot places the diaphragm linkage arm 21 into the positioning groove 5a of the feeding block 5. The robot moves the feeding block 5 by pushing, so that the diaphragm linkage arm 21 reaches the corresponding position of the movement. The manipulator grabs the long shaft 22, sleeves the sealing ring onto the long shaft 22, then inserts the long shaft 22 into the corresponding position of the movement, and continues to move to the next process; the robot places the driving arm 24 and the central shaft 23 into the corresponding positions of the movement, and then presses the long shaft 22, the central shaft 23 and the driving arm 24, so that the upper and lower ends of the long shaft 22 are respectively inserted into the driving arm 24 and the diaphragm linkage arm 21 and are fixedly connected, and then the valve cover (not shown in the instruction drawings) is placed on the central shaft 23 of the movement. When the diaphragm linkage arm 21 is placed into the positioning groove 5a of the feeding block 5, the first driving part pushes the feeding block 5 to move inwards, the clamping part 5b pushes the other end of the hook plate 8 to swing downwards and compresses the second return spring 14, the clamping part 5b slides along the guiding surface 8d and is clamped with the clamping head 8a. At this time, the side part of the feeding block 5 abuts against the outer end surface of the limit sleeve 11. At this time, the connection holes of the long shaft 22 and the diaphragm linkage arm 21 are coaxially arranged. When the lower end of the long shaft 22 is pressed into the connection hole of the diaphragm linkage arm 21, the second driving part presses down the lifting seat 4 to move the lifting seat 4 downwards, so that the diaphragm linkage arm 21 disengages from the positioning groove 5a of the feeding block 5, and at the same time presses down the pressing part 8b of the hook plate 8, so that the clamping part 5b of the feeding plate disengages from the clamping head 8a of the hook plate 8. Under the elastic force of the first return spring 6, the feeding plate moves outwards to the baffle, and at this time the feeding plate is reset. Using this tooling to assemble the gas meter movement 20 has the advantages of high assembly accuracy and high assembly efficiency. The first driving part and the second driving part adopt cylinders or oil cylinders.

[0044] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar means for substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0045] Although terms such as base plate 1, positioning seat 2, positioning groove 2a, positioning assembly 3, first support column 3a, second support column 3b, limiting groove 3c, lifting seat 4, feeding block 5, positioning groove 5a, clamping portion 5b, first return spring 6, mounting seat 7, first groove 7a, hook plate 8, clamping head 8a, pressing portion 8b, second groove 8c, guiding surface 8d, connecting column 9, first guiding column 10, limiting sleeve 11, slider 12, guide rail 13, second return spring 14, second guiding column 15, linear bearing 16, stop block 17, third guiding column 18, third return spring 19, gas meter movement 20, diaphragm linkage arm 21, long shaft 22, central shaft 23, driving arm 24 are used more frequently herein, the possibility of using other terms is not excluded. The use of these terms is only for more convenient description and explanation of the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A tooling for assembling a gas meter movement, comprising a bottom plate (1) and a positioning seat (2) fixedly connected to the bottom plate (1). One end of the positioning seat (2) is provided with a positioning component (3) for placing the gas meter movement (20), characterized in that, The other end of the positioning seat (2) is provided with a lifting seat (4) capable of reciprocating up and down relative to the positioning seat (2). A feeding block (5) capable of reciprocating horizontally is provided on the lifting seat (4). A positioning groove (5a) for placing the diaphragm linkage arm (21) is provided at the inner end of the feeding block (5). A first return spring (6) is arranged between the outer end of the feeding block (5) and the lifting seat (4). The outer end of the feeding block (5) has a clamping portion (5b). A mounting seat (7) is fixedly connected to the side of the lifting seat (4). A hook plate (8) is provided on the mounting seat (7). After the feeding block (5) moves inward, the clamping portion (5b) can be clamped with the hook plate (8). When the feeding block (5) can descend with the lifting seat (4), the clamping portion (5b) can be disengaged from the hook plate (8). One end of the hook plate (8) is hinged to the mounting seat (7). A second return spring (14) is arranged between the other end of the hook plate (8) and the mounting seat (7). The outer end of the hook plate (8) is a pressing portion (8b). A first groove (7a) is provided on the mounting seat (7). A second groove (8c) is provided on the lower end surface of the pressing portion (8b). The upper and lower ends of the second return spring (14) are embedded in the first groove (7a) and the second groove (8c).

2. The tooling for assembling a gas meter movement according to claim 1, characterized in that, A vertically arranged connecting column (9) is fixedly connected to the lifting seat (4). A horizontally arranged first guiding column (10) is penetrated and fixedly connected to the middle of the connecting column (9). The first guiding column (10) penetrates through the feeding block (5).

3. The tooling for assembling a gas meter movement according to claim 2, characterized in that, A limiting sleeve (11) is sleeved on the first guiding column (10). One end of the limiting sleeve (11) can abut against the connecting column (9). The other end of the limiting sleeve (11) is for the side wall of the feeding block (5) to abut against. The first return spring (6) is sleeved on the outside of the limiting sleeve (11).

4. The tool for assembling a gas meter movement according to claim 2, characterized in that, A slider (12) is fixedly connected to the lower side of the outer end of the feeding block (5). A horizontally arranged guide rail (13) is fixedly connected to the lifting seat (4). The guide rail (13) is arranged parallel to the first guiding column (10). The guide rail (13) is embedded in the sliding groove of the corresponding slider (12).

5. A tool for assembling a gas meter movement according to claim 1 or 2 or 3 or 4, characterized in that, An upwardly protruding clamping head (8a) is provided on the upper side of the other end of the hook plate (8). An inclined guiding surface (8d) is provided on the outside of the clamping head (8a).

6. A tool for assembling a gas meter movement according to claim 1 or 2 or 3 or 4, characterized in that, The lifting seat (4) is square. A plurality of second guiding columns (15) are vertically and fixedly connected to the lifting seat (4). A plurality of linear bearings (16) are fixedly connected to the positioning seat (2) and the second guiding columns (15) penetrate through the corresponding linear bearings (16).

7. A tool for assembling a gas meter movement according to claim 1 or 2 or 3 or 4, characterized in that, The positioning component (3) described above includes a positioning groove (2a) provided at one end of the positioning seat (2), and the lower end of the gas meter movement (20) is embedded in the positioning groove (2a). A first support column (3a) and a second support column (3b) are provided on the positioning seat (2). The first support column (3a) and the second support column (3b) are located on both sides of the positioning groove (2a). The upper ends of the first support column (3a) and the second support column (3b) are provided with a limit groove (3c).

8. A tool for assembling a gas meter movement according to claim 1 or 2 or 3 or 4, characterized in that, A vertically arranged stop block (17) is provided on the lifting seat (4). The stop block (17) is located outside the feeding block (5), and the feeding block (5) can abut against the stop block (17).

9. A tool for assembling a gas meter movement according to claim 1 or 2 or 3 or 4, characterized in that A vertically arranged third guide post (18) is fixedly connected to the middle of the lifting seat (4). The lower end of the third guide post (18) passes through the positioning seat (2). A third return spring (19) is sleeved outside the third guide post (18), and both ends of the third return spring (19) respectively abut against the lifting seat (4) and the positioning seat (2).

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