An emergency flameout device for vehicle throttle overtravel

Abstract

The present application relates to the technical field of vehicle safety equipment, in particular to a vehicle throttle overstroke emergency flameout device, which comprises a shell, a seat block, a throttle controller, a maximum throttle warning light and an emergency switch arranged on a vehicle operating platform, the seat block is installed in the shell, two wire passing steel wheels are arranged in the seat block, an engine throttle pull wire is wound on the two wire passing steel wheels, a reset mechanism is arranged at one end of the engine throttle pull wire, a seat plate is connected with the throttle controller through a throttle controller pull wire, the seat plate is connected with the wire passing steel wheels through a lead screw, a return tension spring is connected between the seat plate and the lower part of the seat block, and a normally open stroke switch is arranged on the upper part of the seat block, the emergency response time is greatly shortened, and the requirements of safety and reliability in the vibration working environment of engineering machinery are met.

Description

Technical Field

[0001] This invention relates to the field of vehicle safety equipment technology, specifically to an emergency engine shutdown device for vehicle throttle overtravel. Background Technology

[0002] The vehicle throttle system is the core structure controlling the engine's power output. During vehicle operation, emergencies such as engine runaway, hydraulic system failure, or malfunction of working devices may occur, requiring a rapid cutoff of engine power for emergency shutdown. This can lead to continuous acceleration and loss of control, causing serious traffic accidents such as rear-end collisions and impacts, posing a significant threat to the safety of passengers and road traffic. Currently, various engine emergency shutdown technologies exist on the market.

[0003] However, existing technologies still have the following shortcomings: First, existing engine shutdown systems for engineering vehicles mostly use independently installed switches or pull cords. In emergencies, drivers need to shift their gaze to find the switch location, resulting in a long reaction time, which does not conform to the ergonomic principles of emergency operation.

[0004] Secondly, some throttle linkage schemes set the engine shutdown trigger point within the normal operating stroke of the throttle. The working environment of engineering vehicles is subject to great vibration. During normal operation, the engine may be accidentally triggered by bumps or operating inertia, resulting in a sudden loss of pressure in the working device and causing a secondary accident.

[0005] Third, existing solutions are mainly designed for passenger cars or small agricultural machinery, without taking into account the special characteristics of micro-engineering vehicles, such as the hand throttle operation method, the requirements for preventing accidental touch in high vibration environments, and the dependence of the hydraulic system on engine power.

[0006] Fourth, the electronic control scheme completely fails when the controller malfunctions or the power supply fails, which cannot meet the high reliability requirements for functional safety of micro-engineering machinery.

[0007] Therefore, there is an urgent need to design a vehicle throttle overtravel emergency shutdown device with overtravel warning and emergency shutdown functions, stable structure, and wide adaptability. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies, such as excessively long operation response time, insufficient safety and reliability, and inability to be applied to the vibration working conditions of engineering vehicles, and to provide a vehicle throttle overtravel emergency shutdown device.

[0009] This invention is achieved through the following technical solution: An emergency engine shutdown device for vehicle throttle overtravel includes a housing, a base block, and a throttle controller, a maximum throttle warning light, and an emergency switch mounted on the vehicle's control panel. The base block is installed inside the housing and has two cable guide rollers. An engine throttle cable is wound around the two cable guide rollers. One end of the engine throttle cable has a reset mechanism, which includes a limit ball, a reset handle, and an electromagnetic expansion joint. The engine throttle cable passes through the limit ball, and the end of the engine throttle cable has a reset handle. The electromagnetic expansion joint is installed at the bottom of the base block. The front end of the electromagnetic expansion rod of the electromagnetic expansion joint has an electromagnetic latch with a notch through which the engine throttle cable passes. The other end of the engine throttle cable is connected to the throttle of the vehicle's engine. The throttle controller is connected to a base plate via a throttle controller cable. The base plate is connected to a guide steel wheel via a lead screw. A return spring connects the base plate to the lower part of the base block. Two normally open limit switches with different installation heights are installed on the upper part of the base block. The one with the lower installation height is normally open limit switch one, and the one with the lower installation height is normally open limit switch two. The maximum throttle warning light is connected in series with the vehicle's battery and normally open limit switch one. The emergency switch and normally open limit switch two are connected in parallel and then connected in series with the vehicle's battery and electromagnetic expansion joint.

[0010] Using "throttle overtravel" as a trigger signal, the driver can instantly trigger the engine shutdown through instinctive action without having to search for a separate switch, reducing the emergency response time to less than 0.5 seconds. By setting an "overtravel zone" at the end of the normal throttle travel and increasing the trigger resistance, the driver can clearly distinguish between normal throttle control and emergency engine shutdown operations, preventing accidental engine shutdown due to road bumps or operational inertia. The emergency mechanism is adapted to the special working conditions of mini engineering vehicles (mini excavators, mini loaders), and can maintain residual pressure in the working device (hydraulic system) when triggering shutdown. Combined with the posture judgment logic, it can prevent the bucket or boom from falling due to sudden pressure loss. In extreme cases such as main controller failure or complete power failure, the engine can still be triggered by physical contact, meeting the high reliability requirements of functional safety for engineering machinery.

[0011] Further preferably, the throttle controller is a push-rod type or a pedal type. This invention is applicable to both foot throttle pedals and hand throttle levers, thus having a wide range of applications.

[0012] Further preferably, a cable guide tube is installed inside the top of the housing, through which the throttle controller cable passes; A cable guide tube is installed inside the top of the housing, through which the engine throttle cable passes. During the up-and-down movement of the engine throttle cable and throttle controller cable, the cable guide tube and cable guide tube provide excellent protection and guidance for the engine throttle cable and throttle controller cable.

[0013] Further optimization reveals that the seat block has an open, hollow internal structure with two slotted holes. Two lugs are integrally mounted on the top of the seat block, and two normally open strokes are installed on these lugs. The seat block's specific structural design is reasonable and reliable, facilitating assembly and connection with other components.

[0014] Further optimization involves installing two pressure plates at the front and rear of the through block. Both ends of the pressure plates are threaded onto the lead screw and tightened with nuts. The engine throttle cable passes through the gap between the pressure plates and the cable guide wheel. The pressure plates limit and tighten the engine throttle cable, preventing accidental slippage.

[0015] Further optimization involves installing an axle within each of the two guide rollers. The lower end of the lead screw passes through the axle and is locked with a nut, while the upper end of the lead screw is connected to the base plate and locked with a nut. The connection between the lead screw and the guide rollers is secured with a nut, and the tension of the return spring can be adjusted by turning the nut, making operation convenient.

[0016] Compared with the prior art, the beneficial effects of this invention are: The beneficial effects of this invention are as follows: 1. Solve the problem of slow operation response in emergency situations: By using "throttle overtravel" as a trigger signal, the driver can instantly trigger the engine to shut off without having to find a separate switch, thus shortening the emergency response time to less than 0.5 seconds.

[0017] 2. Solve the safety problem of accidental triggering during normal operation: By setting an "overtravel zone" at the end of the normal throttle travel and increasing the trigger resistance, the driver can clearly distinguish between normal throttle control and emergency shutdown operation, preventing accidental stalling caused by road bumps or operating inertia.

[0018] 3. Optimized for engineering vehicle working conditions: An emergency mechanism adapted to the special working conditions of mini engineering vehicles (mini excavators, mini loaders) can maintain the residual pressure of the working device (hydraulic system) when the engine is triggered to shut down. Combined with the attitude judgment logic, it can prevent the bucket or boom from falling due to sudden pressure loss.

[0019] 4. Achieve control redundancy and high reliability: In extreme cases such as main controller failure or complete vehicle power failure, the engine can still be shut down by physical contact, meeting the high reliability requirements of engineering machinery for functional safety. Attached Figure Description

[0020] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a structural schematic diagram of a specific embodiment of the present invention (first perspective).

[0022] Figure 2 This is a structural schematic diagram of a specific embodiment of the present invention (second perspective).

[0023] Figure 3 This is a structural schematic diagram of the hidden outer shell (first view) in a specific embodiment of the present invention.

[0024] Figure 4 This is a structural schematic diagram of the hidden outer shell (second view) in a specific embodiment of the present invention.

[0025] Figure 5 This is a structural schematic diagram of a specific embodiment of the present invention, showing the hidden outer shell and partially separated parts (first view).

[0026] Figure 6 This is a structural schematic diagram of a specific embodiment of the present invention, showing the hidden outer shell and partially separated parts (second view).

[0027] Figure 7 This is a schematic diagram of the outer shell (first view) in a specific embodiment of the present invention.

[0028] Figure 8 This is a schematic diagram of the outer shell (second view) in a specific embodiment of the present invention.

[0029] Figure 9 for Figure 3 A magnified schematic diagram of the structure at point A in the middle.

[0030] Figure 10 This is a schematic diagram of the circuit principle of a normally open limit switch connected in series with the maximum throttle warning light in a specific embodiment of the present invention.

[0031] Figure 11 This is a schematic diagram of the circuit principle of a normally open limit switch two connected in parallel with an emergency switch and then connected in series with an electromagnetic expansion joint in a specific embodiment of the present invention.

[0032] In the diagram: 1. Seat block; 2. Cable guide wheel; 3. Bearing; 4. Axle; 5. Seat plate; 6. Lead screw; 8. Pressure plate; 9. Return spring; 10. Upper hook of spring; 11. Normally open limit switch one; 12. Electromagnetic telescopic block; 13. Reset handle; 14. Normally open limit switch two; 15. Housing; 16. Cable guide tube; 17. Engine throttle cable; 18. Limit ball; 19. Throttle controller; 20. Cable guide tube; 21. Maximum throttle warning light; 22. Emergency switch; 23. Throttle controller cable; 24. Electromagnetic latch; 25. Lower hook of spring; 26. Shaft retaining ring; 27. U-shaped bracket; 28. Electromagnetic lock body; 29. ​​Electromagnetic telescopic rod; 30. Base; 31. Ear plate; 32. Strip hole. Detailed Implementation

[0033] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0034] like Figures 1 to 11 An emergency engine shutdown device for vehicle throttle overtravel, as shown, includes a housing 15, a base block 1, and a throttle controller 19, a maximum throttle warning light 21, and an emergency switch 22 mounted on the vehicle's control panel. The maximum throttle warning light 21 is equipped with a buzzer. The throttle controller 19 is either a push rod type or a pedal type. The base block 1 is installed inside the housing 15 and has two cable guide wheels 2 inside. An engine throttle cable 17 is wound around the two cable guide wheels 2. One end of the engine throttle cable 17 is equipped with a reset mechanism, which includes a limiting steel ball 18, a reset handle 13, and an electromagnetic telescopic device. The engine throttle cable 17 passes through the limiting steel ball 18, and the end of the engine throttle cable 17 is equipped with a reset handle 13. The electromagnetic telescopic device is installed at the bottom of the base block 1. The front end of the electromagnetic telescopic rod 29 of the electromagnetic telescopic device is equipped with an electromagnetic locking tongue 24. The electromagnetic locking tongue 24 has a notch through which the engine throttle cable 17 passes. The other end of the engine throttle cable 17 is connected to the throttle of the vehicle's engine. The throttle controller 19 is connected to the seat plate 5 via the throttle controller cable 23. The seat plate 5 is connected to the cable guide wheel 2 via the lead screw 6. A return spring 9 is connected between the seat plate 5 and the lower part of the seat block 1. The upper part of the seat block 1 is equipped with two normally open limit switches with different installation heights. The one with the lower installation height is normally open limit switch 11, and the one with the lower installation height is normally open limit switch 2 14. The maximum throttle warning light 21 is connected in series with the vehicle's battery and normally open limit switch 11. The emergency switch 22 is connected in parallel with normally open limit switch 14 and then connected in series with the vehicle's battery and electromagnetic expansion joint.

[0035] The throttle controller 19, fixed to the control panel, raises the seat plate 5 via the cable 23. During the raising process, the seat plate 5 triggers normally open limit switches 11 and 14. The first stroke is from the initial position to normally open limit switch 11, and the second stroke is from normally open limit switch 11 to normally open limit switch 14. The first stroke corresponds to the normal engine speed range controlled by wire, and the second stroke is located at the end of the first stroke, forming an overtravel emergency trigger zone.

[0036] The handle of the throttle controller 19 pulls the seat plate 5 upwards via the throttle controller cable 23. The seat plate 5 is connected to two wire guide steel wheels 2 via the lead screw 6. The seat plate 5 drives the engine throttle cable 17 to rise, thereby increasing the engine throttle. When the seat plate 5 continues to rise and touches the contact of the normally open limit switch 11, the circuit is closed, the maximum throttle warning light 21 lights up, and the buzzer sounds a warning sound at the same time. The operator can release the throttle appropriately until the maximum throttle warning light 21 goes out and the buzzer is turned off. If the operator does not stop the throttle controller 19 handle from increasing the throttle after the maximum throttle warning light 21 is activated, the seat plate 5 continues to rise and touches the contact of the normally open limit switch 2 14. After the electromagnetic expansion joint is energized, it retracts, the limit ball 18 rises to the bottom of the seat block 1, the reset handle 13 rises to the bottom of the outer casing 15, the engine throttle cable 17 retracts, and the engine shuts off.

[0037] In case of an emergency, the operator can choose based on the ease of triggering: 1. Press the emergency switch 22 with both hands. The seat plate 5 continues to rise and touches the contact of the normally open limit switch 14. After the electromagnetic expansion joint is energized, it retracts. The limit ball 18 rises to the bottom of the seat block 1, the reset handle 13 rises to the bottom of the outer shell 15, the engine throttle cable 17 retracts, and the engine shuts off.

[0038] 2. Continue to increase the throttle directly to the over-range position, continue to increase the range of motion of the throttle controller 19 handle, increase the throttle action, the seat plate 5 continues to rise, triggering the contact of the normally open limit switch 14, the electromagnetic expansion joint is energized and retracts, the limit ball 18 rises to the bottom of the seat block 1, the reset handle 13 rises to the bottom of the outer casing 15, the engine throttle cable 17 retracts, and the engine shuts off.

[0039] Release the throttle controller 19 handle back to its initial position and turn the emergency switch 22 to reset. The return spring 9 drives the seat plate 5, lead screw 6, and cable guide wheel 2 to reset. The normally open limit switch 11 and normally open limit switch 24 return to their normally open state, the electromagnetic expansion joint resets, the engine throttle cable 17 loosens, and the reset handle 13 is pulled, which simultaneously drives the limit ball 18 and the engine throttle cable 17 to reset.

[0040] like Figure 1 , 2As shown, a cable guide tube 16 is installed inside the top of the housing 15, and the throttle controller cable 23 is arranged to pass through the cable guide tube 16; A cable guide spool 20 is installed inside the top of the outer casing 15, through which the engine throttle cable 17 passes. During the up-and-down movement of the engine throttle cable 17 and the throttle controller cable 23, the cable guide tube 16 and the cable guide spool 20 provide good protection and guidance for the engine throttle cable 17 and the throttle controller cable 23.

[0041] like Figure 7 , 8 As shown, the seat block 1 has an open hollow structure inside. There are two strip holes 32 on the seat block 1, and two ear plates 31 are integrally provided on the top of the seat block 1. The two normally open strokes are installed on the two ear plates 31. The specific structural design of the seat block 1 is reasonable and reliable, and it is easy to assemble and connect with other components.

[0042] like Figure 1-7 As shown, two pressure plates 8 are installed at the front and rear of the through block 1. The two ends of the pressure plates 8 are threaded onto the lead screw 6 and tightened with nuts. The engine throttle cable 17 passes through the gap between the pressure plate 8 and the cable guide wheel 2. The pressure plate 8 limits and tightens the engine throttle cable 17 to prevent it from slipping off accidentally.

[0043] Each of the two guide rollers 2 has a shaft 4. The lower end of the lead screw 6 passes through the shaft 4 and is locked with a nut. The upper end of the lead screw 6 is connected to the base plate 5 and locked with a nut. The connection between the lead screw 6 and the guide roller 2 is locked with a nut. The tension of the return spring 9 can be adjusted by turning the nut, making the operation convenient.

[0044] The lower part of the seat block 1 is provided with a tension spring hook 25, the bottom of the seat plate 5 is provided with two tension spring hooks 10, and the return tension spring 9 is installed between the tension spring hooks 10 and the tension spring hooks 25.

[0045] The base 30 is integrally provided at the bottom of the seat block 1. A U-shaped bracket 27 is installed on the base 30. The electromagnetic lock body 28 of the electromagnetic telescopic device is installed inside the U-shaped bracket 27. The electromagnetic lock tongue 24 passes through the U-shaped bracket 27.

[0046] like Figure 6 , 9 As shown, a bearing 3 is pressed into the wire guide wheel 2, and the two ends of the wheel axle 4 are fixed in the seat block 1 by axle snap rings 26. The wire guide wheel 2, bearing 3 and wheel axle 4 are placed together in the internal space of the seat block 1, and the two ends of the wheel axle 4 extend out from the strip hole 32.

[0047] Working principle: The throttle controller 19, fixed to the control panel, raises the seat plate 5 via the cable 23. During the raising process, the seat plate 5 triggers normally open limit switches 11 and 14. The first stroke is from the initial position to normally open limit switch 11, and the second stroke is from normally open limit switch 11 to normally open limit switch 14. The first stroke corresponds to the normal engine speed range controlled by wire, and the second stroke is located at the end of the first stroke, forming an overtravel emergency trigger zone.

[0048] The handle of the throttle controller 19 pulls the seat plate 5 upwards via the throttle controller cable 23. The seat plate 5 is connected to two wire guide steel wheels 2 via the lead screw 6. The seat plate 5 drives the engine throttle cable 17 to rise, thereby increasing the engine throttle. When the seat plate 5 continues to rise and touches the contact of the normally open limit switch 11, the circuit is closed, the maximum throttle warning light 21 lights up, and the buzzer sounds a warning sound at the same time. The operator can release the throttle appropriately until the maximum throttle warning light 21 goes out and the buzzer is turned off. If the operator does not stop the throttle controller 19 handle from increasing the throttle after the maximum throttle warning light 21 is activated, the seat plate 5 continues to rise and touches the contact of the normally open limit switch 2 14. After the electromagnetic expansion joint is energized, it retracts, the limit ball 18 rises to the bottom of the seat block 1, the reset handle 13 rises to the bottom of the outer casing 15, the engine throttle cable 17 retracts, and the engine shuts off.

[0049] In case of an emergency, the operator can choose based on the ease of triggering: 1. Press the emergency switch 22 with both hands. The seat plate 5 continues to rise and touches the contact of the normally open limit switch 14. After the electromagnetic expansion joint is energized, it retracts. The limit ball 18 rises to the bottom of the seat block 1, the reset handle 13 rises to the bottom of the outer shell 15, the engine throttle cable 17 retracts, and the engine shuts off.

[0050] 2. Continue to increase the throttle directly to the over-range position, continue to increase the range of motion of the throttle controller 19 handle, increase the throttle action, the seat plate 5 continues to rise, triggering the contact of the normally open limit switch 14, the electromagnetic expansion joint is energized and retracts, the limit ball 18 rises to the bottom of the seat block 1, the reset handle 13 rises to the bottom of the outer casing 15, the engine throttle cable 17 retracts, and the engine shuts off.

[0051] Release the throttle controller 19 handle back to its initial position and turn the emergency switch 22 to reset. The return spring 9 drives the seat plate 5, lead screw 6, wire pressure plate 8, and wire guide wheel 2 to reset. The normally open limit switch 11 and normally open limit switch 2 14 return to their normally open state, the electromagnetic expansion joint resets, the engine throttle cable 17 loosens, and the reset handle 13 is pulled, which simultaneously drives the limit ball 18 and the engine throttle cable 17 to reset.

[0052] The beneficial effects of this invention are as follows: 1. Solve the problem of slow operation response in emergency situations: By using "throttle overtravel" as a trigger signal, the driver does not need to find a separate switch. The engine can be instantly shut off by instinctively stepping on the pedal, reducing the emergency response time to less than 0.5 seconds.

[0053] 2. Solve the safety problem of accidental triggering during normal operation: By setting an "overtravel zone" at the end of the normal throttle travel and increasing the trigger resistance, the driver can clearly distinguish between normal throttle control and emergency shutdown operation, preventing accidental stalling caused by road bumps or operating inertia.

[0054] 3. Optimized for engineering vehicle working conditions: An emergency mechanism adapted to the special working conditions of mini engineering vehicles (mini excavators, mini loaders) is applicable to both foot accelerator pedal and hand accelerator lever. It can maintain residual pressure of the working device (hydraulic system) when the engine is triggered to shut off, and with the attitude judgment logic, it can prevent the bucket or boom from falling due to sudden pressure loss.

[0055] 4. Achieve control redundancy and high reliability: In extreme cases such as main controller failure or complete vehicle power failure, the engine can still be shut down by physical contact, meeting the high reliability requirements of engineering machinery for functional safety.

[0056] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0057] The terms “upper,” “lower,” “outer,” and “inner” in the specification, claims, and accompanying drawings of this invention are used, if present, to distinguish relative positional relationships and are not necessarily qualitative. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion.

[0058] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A vehicle throttle overtravel emergency shutdown device, characterized in that, The device includes a housing (15), a seat block (1), and a throttle controller (19), a maximum throttle warning light (21), and an emergency switch (22) installed on the vehicle control panel. The seat block (1) is installed inside the housing (15). The seat block (1) has two wire guide wheels (2) inside. The two wire guide wheels (2) are wound with an engine throttle cable (17). One end of the engine throttle cable (17) is provided with a reset mechanism. The reset mechanism includes a limit ball (18), a reset handle (13), and an electromagnetic telescopic device. The engine throttle cable (17) passes through the limit ball (18). The end of the engine throttle cable (17) is provided with a reset handle (13). The electromagnetic telescopic device is installed at the bottom of the seat block (1). The front end of the electromagnetic telescopic rod (29) of the electromagnetic telescopic device is provided with an electromagnetic latch (24). The electromagnetic latch (24) has a notch. The engine throttle cable (17) passes through the notch. The other end of the engine throttle cable (17) is connected to the throttle of the vehicle engine. The throttle controller (19) is connected to the seat plate (5) via the throttle controller cable (23). The seat plate (5) is connected to the wire guide wheel (2) via the lead screw (6). A return spring (9) is connected between the seat plate (5) and the lower part of the seat block (1). The upper part of the seat block (1) is provided with two normally open limit switches with different installation heights. The one with the lower installation height is normally open limit switch one (11), and the one with the lower installation height is normally open limit switch two (14). The maximum throttle warning light (21) is connected in series with the vehicle's battery and normally open limit switch one (11). The emergency switch (22) is connected in parallel with normally open limit switch two (14) and then connected in series with the vehicle's battery and electromagnetic expansion joint.

2. The vehicle throttle overtravel emergency shutdown device according to claim 1, characterized in that, The throttle controller (19) is either a push rod type or a pedal type.

3. The vehicle throttle overtravel emergency shutdown device according to claim 1, characterized in that, A cable guide tube (16) is installed inside the top of the housing (15), through which the throttle controller cable (23) passes; A cable reel (20) is installed inside the top of the housing (15), through which the engine throttle cable (17) passes.

4. The vehicle throttle overtravel emergency shutdown device according to claim 1, characterized in that, The seat block (1) has an open hollow structure inside. Two strip holes (32) are opened on the seat block (1). Two ear plates (31) are integrally provided on the top of the seat block (1). Two normally open strokes are installed on the two ear plates (31).

5. The vehicle throttle overtravel emergency shutdown device according to claim 1, characterized in that, Two pressure plates (8) are installed at the front and back of the through block (1). The two ends of the pressure plates (8) are threaded onto the lead screw (6) and tightened with nuts.

6. The vehicle throttle overtravel emergency shutdown device according to claim 1, characterized in that, Each of the two wire guide wheels (2) has a wheel axle (4). The lower end of the lead screw (6) passes through the wheel axle (4) and is locked with a nut. The upper end of the lead screw (6) is connected to the seat plate (5) and locked with a nut.

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