A vacuum circuit breaker insulating rod contact pressure self-adaptive regulating device

Abstract

The present invention belongs to the technical field of vacuum circuit breakers, and in particular to a pressure adaptive regulating device for insulating pull rod contacts of vacuum circuit breakers. Aiming at the problem that the moving and static contacts will have loose contact after multiple closing and touching in the prior art, the following scheme is proposed, including a support frame with an L-shaped structure in longitudinal section, the support frame includes a horizontal plate and a vertical plate, and the upper surface of the horizontal plate is provided with three equally distributed circuit breaker units, the circuit breaker unit includes a base tube fixed on the horizontal plate of the support frame, the top end of the base tube is plugged with an insulating tube body with an overall vertical tubular structure, and the circumferential outer wall of the insulating tube body is respectively reserved with through tubes near both ends. When the present invention is in use, after the closing operation is completed, the clamping mechanism is immediately controlled to operate, and then contact one and contact two are merged more tightly, thereby preventing the phenomenon of poor contact caused by loose contact due to long-term use.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum circuit breakers, and in particular to a vacuum circuit breaker insulating pull rod contact pressure self-adapting regulating device. Background Art

[0002] Vacuum circuit breaker is a kind of high voltage circuit breaker widely used in power system. Its main function is to protect electrical equipment from overload, short circuit and other faults. It uses vacuum as arc extinguishing medium. When a fault occurs, it quickly cuts off the circuit to prevent equipment damage and ensure the stable operation of the power grid.

[0003] As we all know, when closing the circuit breaker, the power mechanism will push the insulating pull rod and the moving contact at its shaft end to contact the static contact. After multiple closing and opening contacts, the contact tightness of the contacts will loosen, which will cause poor contact. Therefore, we need an adaptive adjustment device that can always keep the contact pressure normal to ensure that good contact is maintained after multiple contact and docking. Summary of the invention

[0004] In view of the technical problem in the prior art that the moving and static contacts may become loose after multiple closing contacts, the present invention adopts the following technical solution:

[0005] A vacuum circuit breaker insulating rod contact pressure self-adaptive regulating device, comprising a carrier frame with an L-shaped longitudinal section, the carrier frame comprising a horizontal plate and a vertical plate, and the upper surface of the horizontal plate is provided with three circuit breaker units distributed at equal distances, the circuit breaker unit comprises a base tube fixed on the horizontal plate of the carrier frame, the top end of the base tube is plugged with an insulating tube body with an overall vertical tubular structure, the circumferential outer wall of the insulating tube body is respectively reserved with through tubes whose axis lines are parallel to each other and symmetrical to each other near both ends, which are used to plug in and out the wire structure, and the circumferential inner wall of the insulating tube body is Annular retaining ring 1 and annular retaining ring 2 are reserved near the upper and lower ends respectively, and a fixed chuck is sealed and fixed in the annular retaining ring 1, a metal push rod is fixed in the fixed chuck, and a contact 1, i.e. a static contact, is fixed at the bottom end of the metal push rod 1; and an annular retaining ring 2 is provided with a movable push rod that slides up and down in a sealed manner, and a contact 2 is fixed at the top end of the movable push rod; an intermediate tube is reserved on the side of the middle of the insulating tube body away from the through tube, and a clamping mechanism is provided in the intermediate tube, and mutually symmetrical trapezoidal slot holes 1 and trapezoidal slot holes 2 are respectively opened on the side of the contact 1 and the contact 2 close to the clamping mechanism.

[0006] Furthermore, the contact one and the contact two are overall flat cylindrical structures with the same outer diameter, and the circumferential outer walls of the contact one and the contact two are provided with vertical sections on one side close to the middle tube, the trapezoidal slot hole one and the trapezoidal slot hole two are respectively provided on the corresponding vertical sections, and the inner ring diameter of the annular retaining ring one is larger than the outer diameter of the contact one.

[0007] Furthermore, plug sleeves are fixed at the openings of the two through tubes, and the two plug sleeves are respectively inserted with an input terminal iron and an output terminal iron for connecting electricity; the output terminal iron is located in the through tube at the top, and the end of the output terminal iron is fixed to the top of the metal support rod one by bolts; a soft wire is connected to one end of the input terminal iron close to the inside of the insulating tube body, and the other end of the soft wire is electrically connected to the outer wall of the moving top rod; it can play a dust-proof role, and with the soft wire in society, it can allow the contact two to have a larger range of movement.

[0008] Furthermore, the horizontal plates of the support frame are all provided with through holes just below the insulating tube body, and the through holes are all slidably connected with vertical insulating push rods, and the bottom end of the insulating push rod is provided with a driving mechanism, which can provide an upward force to the insulating push rod when the switch is closed; a spring support plate is fixed to the circumferential outer wall of the insulating push rod near the top, and three reset springs symmetrically distributed in the center are fixed to the upper surface of the spring support plate near the edge, and the top of the three reset springs are fixed with the same three-claw support seat, and the top of the three-claw support seat is fixed to the lower surface of the annular retaining ring 2; the circumferential inner wall of the annular retaining ring 2 is sealed with a guide tube, and sealing plug rings are fixed to the two end pipe openings of the guide tube, and the moving push rod is slidably connected between the two sealing plug rings; this can ensure that the inside of the moving push rod is in a vacuum state when it is moving.

[0009] Furthermore, the circumferential inner wall of the annular retaining ring 2 is provided with a plurality of annular grooves, and the circumferential outer wall of the guide tube is provided with a plurality of vertical V-shaped grooves near the annular grooves. By arranging the V-shaped grooves and annular grooves connected vertically and horizontally, the filler can more evenly stick the two together during plug-in installation, thereby improving the overall sealing effect.

[0010] Furthermore, the fixing chuck has a screw hole near the middle, and a one-way air extraction plug is provided in the screw hole, and a top cover is fixed to the top of the insulating tube body; this makes it easier to operate when regularly performing vacuum inspections on the device.

[0011] Furthermore, a sealing gasket is clamped on the lower surface of the fixed chuck near the circumferential edge, and the sealing gasket is located between the lower surface of the fixed chuck and the annular retaining ring, ensuring good sealing effect of the device at the fixed chuck.

[0012] Furthermore, the intermediate tube is located on one side of the vertical plate close to the support frame, and a folding mounting frame is fixed to the circumferential outer wall of the intermediate tube, and the other end of the folding mounting frame is detachably fixedly connected to the surface of the support frame; it plays an auxiliary fixing role for the single circuit breaker unit.

[0013] Furthermore, a sealing plug is fixedly connected to the port of the intermediate tube, and the sealing plug is slidably connected in the middle to a horizontally inwardly extending adjusting guide rod, the clamping mechanism includes a hinge seat fixed to the end of the adjusting guide rod, the hinge seat is an overall tilted T-shaped structure, and the hinge seat includes two symmetrical rotation positions, and the two rotation positions are respectively rotatably connected to mutually symmetrical clamping pointed rods, the tips of the two clamping pointed rods are respectively facing the corresponding trapezoidal slot hole one and contact two, and a clamping spring is fixed between the end of the two clamping pointed rods away from the tips and the hinge seat; the end of the adjusting guide rod away from the hinge seat is fixed with the same crossbeam connecting plate, and a tension spring is fixed between the crossbeam connecting plate and the sealing plug.

[0014] Furthermore, an electrically controlled positioning pin is fixed on one side of the lower surface of the folding mounting frame close to the beam connecting plate, and the top end of the output shaft of the electrically controlled positioning pin is fixed on the surface of the beam connecting plate. When the gate needs to be opened, the pin shafts of all the electrically controlled positioning pins can be controlled to be pushed out.

[0015] The beneficial effects of the present invention are:

[0016] 1. By providing contact 1 and contact 2 with trapezoidal slot 1 and trapezoidal slot 2, and cooperating with a clamping mechanism slidably connected in the middle tube, when the closing operation is completed, the clamping mechanism is immediately controlled to operate, and then contact 1 and contact 2 are combined more tightly, thereby preventing the phenomenon of poor contact caused by loose contact due to long-term use.

[0017] 2. By setting an annular retaining ring 1 with a diameter larger than that of contact 1 and cooperating with the setting of a fixing chuck, when installing contact 1 and contact 2, they only need to be inserted one by one from the top in sequence and then fixed accordingly.

[0018] 3. Through the clamping mechanism, when contact one and contact two are closed, it is only necessary to control the adjusting guide rod to move inward, and then the two clamping pointed rods can clamp the two to maintain a constant contact pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the overall structure of a vacuum circuit breaker insulating rod contact pressure self-adaptive regulating device after installation;

[0020] Figure 2 A side view of the vacuum circuit breaker insulating rod contact pressure self-adaptive regulating device after installation;

[0021] Figure 3 A top view of the vacuum circuit breaker insulating rod contact pressure self-adaptive regulating device after installation;

[0022] Figure 4A vacuum circuit breaker insulating rod contact pressure adaptive adjustment device proposed by the present invention Figure 3 Schematic diagram of the cross-sectional structure along line AA;

[0023] Figure 5 This is a schematic diagram of the overall structure of a single circuit breaker unit in a vacuum circuit breaker insulating rod contact pressure adaptive adjustment device proposed by the present invention;

[0024] Figure 6 A schematic cross-sectional view of a vacuum circuit breaker insulating rod contact pressure self-adaptive regulating device after opening the circuit breaker, as proposed by the present invention;

[0025] Figure 7 A vacuum circuit breaker insulating rod contact pressure adaptive adjustment device proposed by the present invention Figure 6 A schematic diagram of the enlarged structure at B in the middle;

[0026] Figure 8 An exploded diagram of a single circuit breaker unit of a vacuum circuit breaker insulating rod contact pressure adaptive adjustment device proposed by the present invention;

[0027] Fig. 9 The present invention is a schematic diagram of the assembly structure of contact 1 and contact 2 in a vacuum circuit breaker insulating pull rod contact pressure adaptive adjustment device proposed by the present invention.

[0028] In the figure: 1. support frame; 2. intermediate tube; 3. base tube; 4. inlet iron; 5. through tube; 6. outlet iron; 7. plug sleeve; 8. top cover; 9. insulating tube body; 901. annular retaining ring 1; 902. annular retaining ring 2; 10. folding mounting frame; 11. sealing plug; 12. contact 1; 121. trapezoidal slot hole 1; 13. contact 2; 131. trapezoidal slot hole 2; 14. insulating push rod; 15. reset spring; 16. three-claw support seat; 17. moving push rod; 18. adjustment guide rod; 19. crossbeam connecting plate; 20. electric control positioning pin; 21. metal push rod 1; 22. tension spring; 23. guide tube; 24. hinged seat; 25. clamping pointed rod; 26. fixed chuck. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] In this embodiment, refer to Figure 1-9A vacuum circuit breaker insulating rod contact pressure self-adaptive regulating device comprises a carrier frame 1 with an L-shaped longitudinal section, the carrier frame 1 comprises a horizontal plate and a vertical plate, and the upper surface of the horizontal plate is provided with three circuit-breaking units distributed at equal distances, the circuit-breaking unit comprises a base tube 3 fixed on the horizontal plate of the carrier frame 1, the top of the base tube 3 is plugged with an insulating tube body 9 with an overall vertical tubular structure, the circumferential outer wall of the insulating tube body 9 is respectively reserved with through tubes 5 whose axis lines are parallel to each other and symmetrical to each other near both ends, which are used to plug in and out of the wire structure, and the circumferential inner wall of the insulating tube body 9 is respectively reserved with annular retaining rings 9 near the upper and lower ends. 01 and an annular retaining ring 902, and a fixed chuck 26 is sealed and fixed in the annular retaining ring 901, a metal push rod 21 is fixed in the fixed chuck 26, and a contact 12, i.e., a static contact, is fixed at the bottom end of the metal push rod 21; and a movable push rod 17 that slides up and down in a sealed manner is provided in the annular retaining ring 902, and a contact 2 13 is fixed at the top end of the movable push rod 17; an intermediate tube 2 is reserved at the middle of the insulating tube body 9 away from the through tube 5, and a clamping mechanism is provided in the intermediate tube 2, and a mutually symmetrical trapezoidal slot hole 121 and a trapezoidal slot hole 2 131 are respectively opened on the side of the contact 12 and the contact 2 13 close to the clamping mechanism;

[0031] Specifically, by providing contact 12 and contact 2 13 with trapezoidal slot 1 121 and trapezoidal slot 2 131, and cooperating with a clamping mechanism slidably connected in the middle tube 2, when the closing operation is completed, the clamping mechanism is immediately controlled to operate, and then contact 1 12 and contact 2 13 are combined more tightly, thereby preventing the occurrence of poor contact due to loose contact caused by long-term use.

[0032] In the present invention, contact 1 12 and contact 2 13 are overall flat cylindrical structures with the same outer diameter, and the circumferential outer walls of contact 12 and contact 2 13 are provided with vertical sections on one side close to the intermediate tube 2, trapezoidal slot 1 121 and trapezoidal slot 2 131 are respectively provided on the corresponding vertical sections, and the inner ring diameter of annular retaining ring 1 901 is larger than the outer diameter of contact 1 12; by setting annular retaining ring 1 901 with a diameter larger than that of contact 1 12, in conjunction with the setting of a fixed chuck 26, the installation of contact 1 12 and contact 2 13 is more convenient.

[0033] Reference Figure 6 , plug sleeves 7 are fixed at the openings of the two through tubes 5, and the two plug sleeves 7 are respectively inserted with the input terminal iron 4 and the output terminal iron 6 for connecting electricity; the output terminal iron 6 is located in the through tube 5 at the top, and the end of the output terminal iron 6 is fixed to the top of the metal support rod 21 by bolts; the end of the input terminal iron 4 close to the inside of the insulating tube body 9 is connected with a soft wire, and the other end of the soft wire is electrically connected to the outer wall of the moving top rod 17; the plug sleeve 7 is set up, which can play a dust-proof role, and with the soft wire in society, it can allow the contact 2 13 to have a larger range of activities.

[0034] Reference Figure 6 , Figure 8 The horizontal plates of the support frame 1 are located directly below the insulating tube body 9 and are all perforated, and vertical insulating push rods 14 are slidably connected in the perforations. A driving mechanism is provided at the bottom end of the insulating push rod 14, and the driving mechanism can provide an upward force on the insulating push rod 14 when the switch is closed; a spring support plate is fixed to the circumferential outer wall of the insulating push rod 14 near the top, and three return springs 15 symmetrically distributed in the center are fixed to the upper surface of the spring support plate near the edge, and the top of the three return springs 15 is fixed to the same three-claw support seat 16, and the top of the three-claw support seat 16 is fixed to the lower surface of the annular retaining ring 902; the circumferential inner wall of the annular retaining ring 902 is sealed and clamped with a guide tube 23, and sealing plug rings are fixed at the two end pipe openings of the guide tube 23, and the dynamic push rod 17 is slidably connected between the two sealing plug rings; through such an arrangement, it can be ensured that the dynamic push rod 17 is in a vacuum state when it is active.

[0035] Reference Fig. 9 The circumferential inner wall of the annular retaining ring 902 is provided with a plurality of annular grooves, and the circumferential outer wall of the guide tube 23 is provided with a plurality of vertical V-shaped grooves near the annular grooves. By arranging the V-shaped grooves and annular grooves connected vertically and horizontally, the filler can more evenly stick the two together during plug-in installation, thereby improving the overall sealing effect.

[0036] Reference Fig. 9 A screw hole is opened near the middle of the fixed chuck 26, and a one-way exhaust plug is arranged in the screw hole, and a top cover 8 is fixed to the top of the insulating tube body 9; by setting the exhaust plug and the top cover 8, it is easier to operate when the device is regularly vacuum checked.

[0037] Reference Fig. 9 A sealing gasket is clamped on the lower surface of the fixed chuck 26 near the circumferential edge, and the sealing gasket is located between the lower surface of the fixed chuck 26 and the annular retaining ring 901; ensuring that the sealing effect of the device at the fixed chuck 26 is good.

[0038] Reference Figure 5-Figure 6 The middle tube 2 is located on one side of the vertical plate close to the supporting frame 1, and a folding mounting frame 10 is fixed to the circumferential outer wall of the middle tube 2, and the other end of the folding mounting frame 10 is detachably fixedly connected to the surface of the supporting frame 1; it plays an auxiliary fixing role for the single circuit breaker unit.

[0039] Reference Figure 6-Figure 8The port of the intermediate tube 2 is fixedly connected with a sealing plug 11, and the middle of the sealing plug 11 is slidably connected to the adjusting guide rod 18 extending horizontally inward. The clamping mechanism includes a hinge seat 24 fixed to the end of the adjusting guide rod 18. The hinge seat 24 is an overall tilted T-shaped structure, and the hinge seat 24 includes two symmetrical rotation positions, and the two rotation positions are respectively rotatably connected with mutually symmetrical clamping pointed rods 25, and the tips of the two clamping pointed rods 25 are respectively facing the corresponding trapezoidal slot 121 and contact 2. 13, and a pressing spring is fixed between the end of the two clamping pointed rods 25 away from the pointed end and the hinge seat 24; the same crossbeam connecting plate 19 is fixed to the end of the adjusting guide rod 18 away from the hinge seat 24, and a tension spring 22 is fixed between the crossbeam connecting plate 19 and the sealing plug 11; through the set clamping mechanism, when the contact 12 and the contact 2 13 are closed, it is only necessary to control the adjusting guide rod 18 to advance inward, and then the two clamping pointed rods 25 can clamp the two to maintain a constant contact pressure.

[0040] Reference Figure 6 and Figure 8 An electric control positioning pin 20 is fixed on one side of the lower surface of the folding mounting frame 10 close to the beam connecting plate 19, and the top end of the output shaft of the electric control positioning pin 20 is fixed on the surface of the beam connecting plate 19. When the gate needs to be opened, the pin shafts of all the electric control positioning pins 20 can be pushed out.

[0041] Working principle: When the device is in use, that is, when the switch is closed, contact one 12 and contact two 13 are in a tightly fitted state. At this time, the two clamping pointed rods 25 in the clamping mechanism are inserted into the corresponding trapezoidal slot one 121 and trapezoidal slot two 131 under the action of the adjusting guide rod 18, and cooperate with the action of the two clamping springs to tightly fit contact one 12 and contact two 13 together, and the pressure of the contacts changes with the advancement of the two clamping pointed rods 25; when the switch needs to be opened, the clamping mechanism is first removed, and then the driving mechanism removes the squeezing force on the insulating push rod 14 downward, and the contact two 13 is separated from the contact one 12 under the action of the three reset springs 15.

[0042] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A vacuum circuit breaker insulating rod contact pressure adaptive adjustment device, comprising a support frame (1) with an L-shaped longitudinal section, the support frame (1) comprising a horizontal plate and a vertical plate, and the upper surface of the horizontal plate is provided with three equidistantly distributed circuit breaking units, characterized in that: The circuit breaker unit comprises a base tube (3) fixed on a horizontal plate of a support frame (1), an insulating tube body (9) is inserted at the top end of the base tube (3), through tubes (5) are reserved near both ends of the circumferential outer wall of the insulating tube body (9), an annular retaining ring 1 (901) and an annular retaining ring 2 (902) are reserved near the upper and lower ends of the circumferential inner wall of the insulating tube body (9), and a fixed chuck (26) is sealed and fixed in the annular retaining ring 1 (901), and a metal support rod 1 (21) is fixed in the fixed chuck (26), so that A contact 1 (12) is fixed at the bottom end of the metal push rod 1 (21); a movable push rod (17) that slides up and down in a sealed manner is provided in the annular retaining ring 2 (902), and a contact 2 (13) is fixed at the top end of the movable push rod (17); an intermediate tube (2) is reserved in the middle of the insulating tube body (9) on a side away from the through tube (5), and a clamping mechanism is provided in the intermediate tube (2), and a symmetrical trapezoidal slot hole 1 (121) and a trapezoidal slot hole 2 (131) are respectively opened on the side of the contact 1 (12) and the contact 2 (13) close to the clamping mechanism; The contact 1 (12) and the contact 2 (13) are of a flat cylindrical structure as a whole and have the same outer diameter, and the circumferential outer walls of the contact 1 (12) and the contact 2 (13) are provided with vertical sections on one side close to the intermediate tube (2), the trapezoidal slot hole 1 (121) and the trapezoidal slot hole 2 (131) are respectively provided on the corresponding vertical sections, and the inner diameter of the annular retaining ring 1 (901) is larger than the outer diameter of the contact 1 (12); The intermediate tube (2) is located on one side of the vertical plate close to the support frame (1), and a folding mounting frame (10) is fixed to the circumferential outer wall of the intermediate tube (2), and the other end of the folding mounting frame (10) is detachably fixedly connected to the surface of the support frame (1); A sealing plug (11) is fixedly connected to the port of the intermediate tube (2), and the middle of the sealing plug (11) is slidably connected to an adjustment guide rod (18) extending horizontally inward. The clamping mechanism comprises a hinge seat (24) fixed to the end of the adjustment guide rod (18). The hinge seat (24) is an overall tilted T-shaped structure, and the hinge seat (24) comprises two symmetrical rotation positions, one above the other, and the two rotation positions are respectively rotatably connected to mutually symmetrical clamping pointed rods (25). The pointed heads of the two clamping pointed rods (25) are respectively oriented toward the corresponding trapezoidal slot hole 1 (121) and contact 2 (13), and a clamping spring is fixed between the ends of the two clamping pointed rods (25) away from the pointed heads and the hinge seat (24). The end of the adjustment guide rod (18) away from the hinge seat (24) is fixed to the same crossbeam connecting plate (19), and a tension spring (22) is fixed between the crossbeam connecting plate (19) and the sealing plug (11).

2. The device for self-adapting the pressure of insulating rod contact of vacuum circuit breaker according to claim 1, characterized in that: A plug sleeve (7) is fixed at the opening of the two through-tubes (5), and an incoming wire iron (4) and an outgoing wire iron (6) for connecting electricity are respectively inserted into the two plug sleeves (7); the outgoing wire iron (6) is located in the through-tube (5) at the top, and the end of the outgoing wire iron (6) is fixed to the top of a metal support rod (21) by means of bolts; one end of the incoming wire iron (4) close to the inside of the insulating tube body (9) is connected to a soft wire, and the other end of the soft wire is electrically connected to the outer wall of the movable push rod (17).

3. The device for self-adapting the pressure of insulating rod contact of vacuum circuit breaker according to claim 1, characterized in that: The horizontal plates of the support frame (1) are located directly below the insulating tube body (9) and are provided with through holes, and vertical insulating push rods (14) are slidably connected in the through holes, and a driving mechanism is provided at the bottom end of the insulating push rod (14); a spring support plate is fixed to the circumferential outer wall of the insulating push rod (14) near the top, and three return springs (15) are fixed to the upper surface of the spring support plate near the edge and are symmetrically distributed in the center, and the top ends of the three return springs (15) are fixed with the same three-claw support seat (16), and the top end of the three-claw support seat (16) is fixed to the lower surface of the annular retaining ring (902); the circumferential inner wall of the annular retaining ring (902) is sealed with a guide tube (23), and sealing plug rings are fixed at the two end pipe openings of the guide tube (23), and the dynamic push rod (17) is slidably connected between the two sealing plug rings.

4. The device for self-adapting the pressure of insulating rod contact of vacuum circuit breaker according to claim 3, characterized in that: The circumferential inner wall of the annular retaining ring 2 (902) is provided with a plurality of annular grooves, and the circumferential outer wall of the guide tube (23) is provided with a plurality of vertical V-shaped grooves near the annular grooves.

5. The device for self-adapting the pressure of insulating rod contact of vacuum circuit breaker according to claim 1, characterized in that: The fixing chuck (26) has a screw hole near the middle, and a one-way air extraction plug is provided in the screw hole. A top cover (8) is fixed to the top of the insulating tube body (9).

6. The device for self-adapting the pressure of insulating rod contact of vacuum circuit breaker according to claim 1, characterized in that: A sealing gasket is clamped on the lower surface of the fixed chuck (26) near the circumferential edge, and the sealing gasket is located between the lower surface of the fixed chuck (26) and the annular retaining ring (901).

7. The device for self-adapting the pressure of insulating rod contact of vacuum circuit breaker according to claim 1, characterized in that: An electric control positioning pin (20) is fixed to one side of the lower surface of the folding mounting frame (10) close to the cross beam connecting plate (19), and the top end of the output shaft of the electric control positioning pin (20) is fixed to the surface of the cross beam connecting plate (19).

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