Air inlet silencer mounting structure of energy-saving compressor

Through the automatic connection mechanism and sealing components, the problem of cumbersome disassembly and installation of the compressor air intake muffler is solved, and the rapid replacement of the muffler and the sealing guarantee are achieved, which improves the working efficiency of the compressor and environmental noise control.

CN120487572AInactive Publication Date: 2025-08-15SHANDONG BROADCONTROL ELECTROMECHANICAL
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Patent Information

Application Number
CN202510469958.3
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2025-04-15
Publication Date
2025-08-15
Estimated Expiration
Not applicable · inactive patent

AI Technical Summary

Technical Problem

The disassembly and installation process of existing compressor air intake mufflers is cumbersome, and it is easy to lead to a reduction in sealing, affecting working efficiency and environmental noise control.

Method used

The automatic connection mechanism and sealing assembly are adopted to automatically connect and disconnect the muffler from the intake pipe and the air supply pipe by driving the motor. Combined with the limiting assembly and clamping assembly, it ensures that the muffler is sealed and connected when the compressor is working, and can be quickly disconnected when it stops working, simplifying the replacement process.

Benefits of technology

It realizes rapid replacement of mufflers, reduces compressor downtime, improves replacement efficiency, and ensures connection effect and ambient noise control.

✦ Generated by Eureka AI based on patent content.

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Abstract

The invention belongs to the technical field of compressors, and particularly relates to an energy-saving compressor air inlet silencer mounting structure which comprises a mounting plate and a compressor body mounted on the mounting plate, and is characterized in that the air inlet end of the compressor body is communicated with an air inlet pipe, and air conveying pipes are arranged below the air inlet pipe at intervals; a silencer is arranged between the air inlet pipe and the air conveying pipe and communicated with the air inlet pipe and the air conveying pipe through an automatic connecting mechanism, a rotating mechanism is arranged on the mounting plate and comprises a positioning disc fixedly connected to the mounting plate, and the upper end of the positioning disc is rotationally connected with a rotating column concentric with the positioning disc. And the upper end of the rotating column is fixedly connected with two fixing plates which are symmetrically arranged left and right. In the work of replacing the silencer, the downtime of the compressor body is shortened, the replacement efficiency of the silencer is improved, disassembly and assembly of bolts are not needed, and the connection effect is guaranteed.
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Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and in particular to an energy-saving compressor intake muffler installation structure. Background Art

[0002] The compressor is a driven fluid machine that boosts low-pressure gas to high-pressure gas and is the heart of the refrigeration system. It draws in low-temperature, low-pressure refrigerant gas from the intake pipe, compresses it, and then discharges high-temperature, high-pressure refrigerant gas into the exhaust pipe, providing power for the refrigeration cycle. The compressor generates considerable noise during operation, which not only affects the quality of the working environment but may also have adverse effects on the health of workers. Therefore, installing a muffler on the compressor intake pipe to absorb noise can effectively reduce the noise level of the compressor and provide a quieter working environment. In the prior art, the intake muffler of the compressor is usually installed on the intake pipe through a flange structure seal. However, after the muffler has been working for a long time, the performance degradation of the muffler material and the accumulation of oil and dirt will require the replacement or cleaning of the muffler filter element, which requires the staff to manually remove the muffler from the pipe. The flange sealing structure is not only cumbersome and time-consuming during the disassembly and installation process, but also prone to bolt damage, which can easily lead to reduced sealing.

[0003] In order to solve the above problems, we proposed an energy-saving compressor intake muffler installation structure. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the background technology and to propose an energy-saving compressor intake muffler installation structure.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: an energy-saving compressor intake muffler mounting structure, comprising a mounting plate and a compressor body mounted on the mounting plate, characterized in that the intake end of the compressor body is connected to an intake pipe, an air supply pipe is arranged at intervals below the intake pipe, a muffler is provided between the intake pipe and the air supply pipe, the muffler is connected to the intake pipe and the air supply pipe through an automatic connecting mechanism, a rotating mechanism is provided on the mounting plate, the rotating mechanism comprises a positioning plate fixedly connected to the mounting plate, the upper end of the positioning plate is rotatably connected to a rotating column arranged concentrically therewith, the upper end of the rotating column is fixedly connected to two fixed plates arranged symmetrically on the left and right, and a limiting assembly and a clamping assembly are provided on the side away from the two fixed plates, and the muffler is fixed by the limiting assembly and the clamping assembly located on the left.

[0006] In the above-mentioned energy-saving compressor intake muffler installation structure, the automatic connection mechanism includes two connecting pipe heads connected to the intake end and the outlet end of the muffler, and the two connecting pipe heads are coaxially arranged close to the ends of the intake pipe and the air delivery pipe respectively. The intake pipe and the air delivery pipe are both provided with a sliding sleeve, and the end of the connecting sleeve close to the muffler is sleeved on the corresponding connecting pipe head, and a sealing assembly is provided in the connecting sleeve. The upper end of the mounting plate is fixedly connected to a vertical plate, and the right end of the vertical plate is fixedly connected to two end plates spaced apart up and down. A first bidirectional screw is connected to the two end plates in a common rotation, and two threaded sleeves symmetrically distributed up and down are threadedly sleeved on the first bidirectional screw. The right ends of the two threaded sleeves are fixedly connected to a connecting block, and the two connecting blocks are respectively fixedly connected to the two connecting sleeves, and a driving motor that drives the first bidirectional screw to rotate is fixedly installed on the vertical plate.

[0007] In the above-mentioned energy-saving compressor intake muffler installation structure, the sealing assembly includes an annular first arc groove opened on the two connecting pipe heads, and an annular second arc groove is opened on the intake pipe and the air delivery pipe. Two annular air bags spaced apart up and down are installed on the inner walls of the two connecting sleeves. The two annular air bags located in the same connecting sleeve are respectively stuck in the corresponding first arc groove and second arc groove in the expanded state. Air pumps are fixedly installed on the two connecting blocks, and the two air pumps are respectively connected to the two annular air bags located on the same side.

[0008] In the above-mentioned energy-saving compressor intake muffler installation structure, the limit assembly includes four rectangularly distributed limit plates fixedly connected to the fixed plate, and the four limit plates are respectively affixed to the upper and lower end surfaces of the muffler. Two contact blocks are fixedly connected to the limit plate and spaced apart in an upper and lower manner. The end of the contact block close to the muffler is an arc-shaped surface and is affixed to the outer peripheral surface of the muffler.

[0009] In the above-mentioned energy-saving compressor intake muffler mounting structure, the clamping assembly includes a second bidirectional screw rotatably connected between the two contact blocks, and the second bidirectional screw is provided with a sliding rod parallel to the front and rear positions, and the two sliding rods are fixedly connected to the two contact blocks respectively, and the second bidirectional screw is threadedly sleeved with two threaded sleeves spaced apart above and below, and the two sliding rods pass through the corresponding threaded sleeves and are slidably connected thereto, and the front and rear ends of the two threaded sleeves are rotatably connected to a connecting rod, and the two connecting rods on the same side are coaxially rotatably connected to a shaft rod at one end away from the threaded sleeve, and the shaft rod is fixedly connected to the connecting plate, and one end of the two connecting plates is fixedly connected to the clamping block, and the two clamping blocks are respectively located at the front and rear positions of the muffler and the end face close to the muffler is an arc concave surface, and the lower end of the second bidirectional screw extends to the bottom of the fixed plate and is fixedly connected to the rotating block.

[0010] In the above-mentioned energy-saving compressor intake muffler installation structure, two rotating plates symmetrically distributed front and back are fixedly connected to the outer circumference of the rotating column, and a moving rod is vertically penetrated and slidably connected to the two rotating plates. An end cap is fixedly connected to the moving rod, and a spring is fixedly connected between the end cap and the corresponding upper end surface of the rotating plate. A ball is installed at the lower end of the moving rod, and an annular groove is provided on the upper end surface of the positioning plate. The lower ends of the two moving rods slide in the annular groove through the ball, and a positioning slot is provided in the annular groove. The lower end of the moving rod located at the front is inserted into the positioning slot.

[0011] Compared with the existing technology, the advantages of the present invention are: By setting up an automatic connection mechanism and a sealing assembly, the connection between the muffler and the air intake pipe and the air supply pipe can be automatically completed by driving the motor. The sealing assembly controls the expansion and contraction of the annular airbag according to the state of the compressor body, so that the sealing assembly can effectively seal when the compressor body is working. When the compressor body stops working, the connection between the muffler and the air intake pipe and the air supply pipe can be directly disconnected through the automatic connection mechanism without the need to disassemble and assemble the bolts, and the connection effect is guaranteed.

[0012] By setting up a rotating mechanism, a limit assembly and a clamping assembly, the position of the muffler can be fixed so that it can be stably maintained in an aligned state with the intake pipe and the air delivery pipe, and two mufflers can be fixed at the same time. Then, when installing and removing the new and old mufflers, the position of the new muffler can be fixed before removing the muffler. Then, after stopping the compressor body, the old muffler can be directly disconnected and the new muffler can be rotated to the connection position, thereby quickly completing the replacement work, greatly reducing the downtime of the compressor body and improving the replacement efficiency of the muffler. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A three-dimensional diagram of an energy-saving compressor intake muffler installation structure proposed by the present invention; Figure 2 A three-dimensional diagram of the energy-saving compressor intake muffler installation structure proposed by the present invention from another perspective; Figure 3 This is a schematic diagram of an automatic connection mechanism in an energy-saving compressor intake muffler installation structure proposed by the present invention; Figure 4 This is a partial schematic diagram of an automatic connection mechanism in an energy-saving compressor intake muffler installation structure proposed by the present invention; Figure 5 This is a structural schematic diagram of a muffler in an energy-saving compressor intake muffler installation structure proposed by the present invention; Figure 6This is a schematic diagram of a rotating mechanism in an energy-saving compressor intake muffler installation structure proposed by the present invention; Figure 7 This is a schematic diagram of a clamping assembly in an energy-saving compressor intake muffler installation structure proposed by the present invention; Figure 8 This is a three-dimensional diagram of the positioning plate in the energy-saving compressor intake muffler installation structure proposed by the present invention.

[0014] In the figure: 1 mounting plate, 2 compressor body, 3 intake pipe, 4 air delivery pipe, 5 muffler, 6 vertical plate, 7 first bidirectional screw, 8 threaded sleeve, 9 connecting block, 10 connecting sleeve, 11 drive motor, 12 connecting pipe head, 13 first arcuate groove, 14 second arcuate groove, 15 annular airbag, 16 air pump, 17 positioning plate, 18 rotating column, 19 fixing plate, 20 limiting plate, 21 contact block, 22 second bidirectional screw, 23 threaded sleeve, 24 connecting rod, 25 connecting plate, 26 clamping block, 27 rotating block, 28 rotating plate, 29 moving rod, 30 end cap, 31 spring, 32 annular slide groove, 33 positioning card slot. DETAILED DESCRIPTION

[0015] The following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0016] Reference Figures 1-8 An energy-saving compressor intake muffler mounting structure includes a mounting plate 1 and a compressor body 2 mounted on the mounting plate 1. The intake end of the compressor body 2 is connected to an intake pipe 3, and an air supply pipe 4 is spaced below the intake pipe 3. A muffler 5 is provided between the intake pipe 3 and the air supply pipe 4. The air supply pipe 4, muffler 5, and intake pipe 3 constitute the intake pipeline of the compressor body 2. The muffler 5 is connected to the intake pipe 3 and the air supply pipe 4 via an automatic connection mechanism, which can automatically complete the connection between the muffler 5, the intake pipe 3 and the air supply pipe 4.

[0017] The automatic connection mechanism includes two connecting pipe heads 12 connected to the air inlet end and the air outlet end of the muffler 5. The two connecting pipe heads 12 are coaxially arranged close to the ends of the air inlet pipe 3 and the air supply pipe 4 respectively. The close end surfaces are both smooth surfaces, which are convenient for docking and contact translation. A connecting sleeve 10 is slidably provided on the air intake pipe 3 and the air delivery pipe 4. The end of the connecting sleeve 10 close to the muffler 5 is sleeved on the corresponding connecting pipe head 12. A sealing assembly is provided in the connecting sleeve 10. The sealing assembly includes an annular first arc groove 13 provided on the two connecting pipe heads 12. An annular second arc groove 14 is provided on the air intake pipe 3 and the air delivery pipe 4. Two annular air bags 15 spaced apart from each other are installed on the inner walls of the two connecting sleeves 10. The two annular air bags 15 located in the same connecting sleeve 10 are respectively stuck in the corresponding first arc groove 13 and second arc groove 14 in the expanded state. An air pump 16 is fixedly installed on the two connecting blocks 9. The two air pumps 16 are respectively connected to the two annular air bags 15 located on the same side. The air pump 16 can pump gas into or extract gas from the corresponding two annular air bags 15.

[0018] Specifically, when the compressor body 2 is started, the air pump 16 inflates the corresponding two annular airbags 15, causing the annular airbags 15 to expand and smoothly fit into the corresponding first arc-shaped groove 13 and second arc-shaped groove 14. In this state, the two annular airbags 15 in the connecting sleeve 10 form a sealed space between the annular grooves, thereby ensuring the connection and sealing between the muffler 5 and the intake pipe 3 and the gas delivery pipe 4. The arrangement of the annular airbags 15 can effectively reduce the vibration noise generated by the conveying gas of the intake pipe 3 and the gas delivery pipe 4. When the compressor body 2 stops working, the air pump 16 can pump out the air in the corresponding two annular airbags 15, causing the annular airbags 15 to shrink. The annular airbags can no longer be stuck in the first arc-shaped groove 13 and the second arc-shaped groove 14, making it easier to move the connecting sleeve 10 and replace the muffler 5.

[0019] The upper end of the mounting plate 1 is fixedly connected to a vertical plate 6, and the right end of the vertical plate 6 is fixedly connected to two end plates spaced apart up and down. A first bidirectional screw 7 is rotatably connected between the two end plates, and two threaded sleeves 8 symmetrically distributed up and down are threadedly sleeved on the first bidirectional screw 7. The right ends of the two threaded sleeves 8 are fixedly connected to a connecting block 9, and the two connecting blocks 9 are fixedly connected to the two connecting sleeves 10 respectively. A driving motor 11 for driving the first bidirectional screw 7 to rotate is fixedly installed on the vertical plate 6. When the compressor body 2 stops working, the first bidirectional screw 7 can be driven to rotate by the driving motor 11, thereby driving the two connecting sleeves 10 to move relative to each other, so that they are disengaged from the corresponding connecting pipe heads 12, and the muffler 5 can be disconnected from the air intake pipe 3 and the air delivery pipe 4. On the contrary, the driving motor 11 can control the reversal of the first bidirectional screw 7 to sleeve the two connecting sleeves 10 on the corresponding connecting pipe heads 12. Starting the compressor body 2 can complete the connection work of the muffler 5.

[0020] A rotating mechanism is provided on the mounting plate 1, and the rotating mechanism includes a positioning plate 17 fixedly connected to the mounting plate 1, and the upper end of the positioning plate 17 is rotatably connected to a rotating column 18 arranged concentrically therewith, and the upper end of the rotating column 18 is fixedly connected to two fixed plates 19 arranged symmetrically on the left and right. The two fixed plates 19 are provided with a limiting assembly and a clamping assembly on the side away from each other. The muffler 5 is fixed by the limiting assembly and the clamping assembly on the left side, and the limiting assembly and the clamping assembly on the right side can complete the fixing and clamping work of the new muffler 5 before releasing the connection of the muffler 5 on the left.

[0021] The limit assembly includes four rectangular limit plates 20 fixedly connected to the fixed plate 19. The four limit plates 20 are respectively attached to the upper and lower end surfaces of the muffler 5, and the attached end surfaces are smooth surfaces. They serve to limit the upper and lower positions of the muffler 5, so that it maintains a certain position height. Two contact blocks 21 are fixedly connected to the limit plates 20, and the ends of the contact blocks 21 closest to the muffler 5 are curved and are attached to the outer peripheral surface of the muffler 5. When installing a new muffler 5 on the right side, the muffler 5 can be pushed to contact the contact blocks 21 to determine whether it is in the specified position.

[0022] The clamping assembly includes a second bidirectional screw 22 rotatably connected between the two contact blocks 21. The second bidirectional screw 22 is provided with a sliding rod parallel to the front and rear positions. The two sliding rods are fixedly connected to the two contact blocks 21 respectively. The second bidirectional screw 22 is threadedly sleeved with two threaded sleeves 23 spaced apart from each other. The two sliding rods pass through the corresponding threaded sleeves 23 and are slidably connected thereto. The front and rear ends of the two threaded sleeves 23 are rotatably connected to a connecting rod 24. The two connecting rods 24 on the same side are coaxially rotatably connected to a shaft at one end away from the threaded sleeve 23. The shaft is fixedly connected to the connecting plate 25. One end of each of the two connecting plates 25 is fixedly connected to a clamping block 26. The two clamping blocks 26 are respectively located in the front and rear positions of the muffler 5 and the end faces close to the muffler 5 are arc-shaped concave surfaces. The lower end of the second bidirectional screw 22 extends to the bottom of the fixed plate 19 and is fixedly connected to a rotary block 27. The second bidirectional screw 22 can be rotated by the rotary block 27, thereby driving the two threaded sleeves 23 to move relative to each other. When the two threaded sleeves 23 move away from each other, the two clamping blocks 26 are brought close to each other for clamping. When the two threaded sleeves 23 move close to each other, the two clamping blocks 26 are moved away from each other, and the clamping of the muffler 5 is released.

[0023] Specifically, when replacing the new muffler 5, after pushing the new muffler 5 into the limit assembly on the right, the clamping assembly can be controlled by the rotary block 27 to clamp the new muffler 5, thereby completing the position fixation. After releasing the connection of the muffler 5 on the left, the new muffler 5 can be rotated to the left through the rotating mechanism, and then the connection work is completed through the automatic connection mechanism.

[0024] Two rotating plates 28 symmetrically distributed front and back are fixedly connected to the outer circumference of the rotating column 18 . The rotating column 18 can be easily rotated by the rotating plates 28 to replace the two new and old mufflers 5 . The two movable rods 29 are vertically penetrated and slidably connected to the two rotating plates 28, and the movable rods 29 are fixedly connected to the end caps 30. The end caps 30 are fixedly connected to the corresponding upper end surfaces of the rotating plates 28 by springs 31. The lower ends of the movable rods 29 are equipped with balls, and the upper end surface of the positioning plate 17 is provided with an annular slide groove 32. The lower ends of the two movable rods 29 slide in the annular slide groove 32 through the balls, and the annular slide groove 32 is provided with a positioning slot 33. The setting of the positioning slot 33 plays a role in positioning the rotating column 18. Whenever a movable rod 29 moves to the position of the positioning slot 33, it can be inserted into the positioning slot 33 under the elastic action of the corresponding spring 31. At this time, the rotating column 18 cannot rotate, and the muffler 5 also maintains the corresponding position connected to the intake pipe 3 and the air supply pipe 4. When the rotating column 18 needs to be rotated again, the end cap 30 at the upper end of the moving rod 29 at the front is lifted upward to move the moving rod 29 out of the positioning slot 33, and the rotating column 18 can be rotated to replace the muffler 5.

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An energy-saving compressor intake muffler mounting structure, comprising a mounting plate (1) and a compressor body (2) mounted on the mounting plate (1), characterized in that: The air inlet end of the compressor body (2) is connected to an air inlet pipe (3), an air delivery pipe (4) is arranged at intervals below the air inlet pipe (3), a muffler (5) is arranged between the air inlet pipe (3) and the air delivery pipe (4), and the muffler (5) is connected to the air inlet pipe (3) and the air delivery pipe (4) through an automatic connection mechanism, and a rotating mechanism is provided on the mounting plate (1), the rotating mechanism includes a positioning plate (17) fixedly connected to the mounting plate (1), the upper end of the positioning plate (17) is rotatably connected to a rotating column (18) arranged concentrically therewith, and the upper end of the rotating column (18) is fixedly connected to two fixed plates (19) arranged symmetrically on the left and right, and a limiting assembly and a clamping assembly are provided on the side away from each other of the two fixed plates (19), and the muffler (5) is fixed by the limiting assembly and the clamping assembly located on the left.

2. The energy-saving compressor intake muffler installation structure according to claim 1 is characterized in that: The automatic connection mechanism comprises two connecting pipe heads (12) connected to the air inlet end and the air outlet end of the muffler (5), the two connecting pipe heads (12) are respectively coaxially arranged close to the ends of the air inlet pipe (3) and the air delivery pipe (4), the air inlet pipe (3) and the air delivery pipe (4) are both slidably sleeved with connecting sleeves (10), the ends of the connecting sleeves (10) close to the muffler (5) are sleeved on the corresponding connecting pipe heads (12), a sealing component is provided in the connecting sleeves (10), and the upper end of the mounting plate (1) is fixedly connected to the vertical plate ( 6), the right end of the vertical plate (6) is fixedly connected to two end plates spaced apart in an upper and lower direction, a first bidirectional screw (7) is rotatably connected between the two end plates, two threaded sleeves (8) symmetrically distributed in an upper and lower direction are threadedly sleeved on the first bidirectional screw (7), the right ends of the two threaded sleeves (8) are fixedly connected to a connecting block (9), the two connecting blocks (9) are respectively fixedly connected to two connecting sleeves (10), and a driving motor (11) for driving the first bidirectional screw (7) to rotate is fixedly installed on the vertical plate (6).

3. The energy-saving compressor intake muffler installation structure according to claim 2 is characterized in that: The sealing assembly includes an annular first arc groove (13) provided on two connecting pipe heads (12), an annular second arc groove (14) provided on both the air inlet pipe (3) and the air delivery pipe (4), two annular air bags (15) spaced apart from each other are installed on the inner walls of the two connecting sleeves (10), and the two annular air bags (15) located in the same connecting sleeve (10) are respectively inserted into the corresponding first arc groove (13) and second arc groove (14) in the expanded state, and an air pump (16) is fixedly installed on the two connecting blocks (9), and the two air pumps (16) are respectively communicated with the two annular air bags (15) located on the same side.

4. The energy-saving compressor intake muffler installation structure according to claim 1 is characterized in that: The limiting assembly comprises four limiting plates (20) which are fixedly connected to a fixing plate (19) and are distributed in a rectangular shape. The four limiting plates (20) are respectively fitted on the upper and lower end surfaces of the muffler (5). Two contact blocks (21) which are spaced apart from each other are fixedly connected to the limiting plate (20). An end of the contact block (21) close to the muffler (5) is an arcuate surface and is fitted on the outer peripheral surface of the muffler (5).

5. The energy-saving compressor intake muffler installation structure according to claim 4 is characterized in that: The clamping assembly includes a second bidirectional screw (22) rotatably connected between the two contact blocks (21), and a sliding rod arranged parallel to the second bidirectional screw (22) is provided at the front and rear positions of the second bidirectional screw (22), and the two sliding rods are fixedly connected to the two contact blocks (21) respectively. The second bidirectional screw (22) is threadedly sleeved with two threaded sleeves (23) spaced apart from each other, and the two sliding rods pass through the corresponding threaded sleeves (23) and are slidably connected thereto. The front and rear ends of the two threaded sleeves (23) are rotatably connected. A connecting rod (24) is connected, and one end of the two connecting rods (24) located on the same side away from the threaded sleeve (23) is coaxially connected to a shaft, and the shaft is fixedly connected to the connecting plate (25). One end of the two connecting plates (25) is fixedly connected to a clamping block (26), and the two clamping blocks (26) are respectively located in front and behind the muffler (5) and the end surface close to the muffler (5) is an arc-shaped concave surface. The lower end of the second bidirectional screw (22) extends to the bottom of the fixed plate (19) and is fixedly connected to a rotating block (27).

6. The energy-saving compressor intake muffler installation structure according to claim 1, characterized in that: Two rotating plates (28) symmetrically distributed front and back are fixedly connected to the outer circumference of the rotating column (18), and a moving rod (29) is vertically penetrated and slidably connected to the two rotating plates (28). An end cap (30) is fixedly connected to the moving rod (29), and a spring (31) is fixedly connected between the end cap (30) and the upper end surface of the corresponding rotating plate (28). A ball is installed at the lower end of the moving rod (29), and an annular groove (32) is provided on the upper end surface of the positioning plate (17). The lower ends of the two moving rods (29) slide in the annular groove (32) through the ball, and a positioning groove (33) is provided in the annular groove (32). The lower end of the moving rod (29) located at the front is inserted into the positioning groove (33).