CN214241266U

CN214241266U - Rodless aircraft tractor

Info

Publication number: CN214241266U
Application number: CN202120072112.3U
Authority: CN
Inventors: 李闯; 李川; 张智慧; 安静云; 李志磊
Original assignee: Xinxiang Pingyuan Aviat Technology Engineering Co ltd
Current assignee: Shaanxi Aircraft Industry Co Ltd
Priority date: 2021-01-12
Filing date: 2021-01-12
Publication date: 2021-09-21
Anticipated expiration: 2031-01-12

Abstract

The utility model relates to a rodless aircraft tractor. The rodless aircraft tractor comprises a frame, wheels and a bracket, wherein the bracket is used for supporting a nose landing gear of an aircraft; the bracket suspension mechanism comprises a cross beam and a suspension mechanism oil cylinder, the bracket comprises a bracket body and a spherical hinge structure arranged at the front end of the bracket body, the spherical hinge structure comprises a bracket body connecting seat and a spherical matching piece, and the spherical matching piece is movably matched with the bracket body connecting seat through a spherical surface; the front side of the frame body connecting seat is provided with a rotation stopping cylindrical surface which is tangent with the rotation stopping surfaces at the left side and the right side. The front landing gear is supported or put down by enabling the bracket to swing up and down, and the horizontal rotation stopping of the bracket can be realized through the rotation stopping cylindrical surface at the spherical hinge structure, so that the stability of the bracket is improved. The tractor simplifies the structure of a driving system by enabling the bracket to swing, and solves the technical problem that the existing rodless aircraft tractor adopts a plurality of groups of hydraulic cylinders to control the front end and the rear end of the bracket to lift simultaneously, so that the whole driving system is complex in structure and high in cost.

Description

Rodless aircraft tractor

Technical Field

The utility model relates to a rodless aircraft tractor.

Background

The aircraft tractor is important equipment for guaranteeing the ground movement of the aircraft, and is divided into rod traction and rodless traction according to different traction modes, wherein the rod traction means that the aircraft tractor is connected with a nose landing gear of the aircraft through a traction rod to realize the traction or pushing of the aircraft. The rodless tractor is an airplane tractor which carries the nose landing gear of the airplane, and the tractor and the airplane form a whole to realize the traction or pushing of the airplane. The rodless traction device is simple in operation, small in turning radius, few in guarantee personnel and good in universality.

A wheel holding clamping mechanism is arranged on the rodless aircraft tractor and used for clamping the front landing gear of the aircraft. Chinese patent with grant announcement number CN206750172U and grant announcement date 2017.12.15 discloses a rodless aircraft tractor, which comprises a main chassis bottom frame, wherein the main chassis bottom frame comprises a driving wheel assembly, a steering wheel assembly and a U-shaped frame, an interface connected with a wheel-clasping jacking mechanism is arranged in the main chassis bottom frame, the wheel-clasping jacking mechanism can be fixed in the main chassis bottom frame, and a support carrier is provided for the action of the wheel-clasping jacking mechanism.

Embrace wheel jacking mechanism and include main frame subassembly, sliding beam subassembly and main beam subassembly, main beam subassembly hinge is articulated with preceding supporting riser and back supporting riser, and main beam subassembly both ends are supported through two pneumatic cylinders, and the mount pad of pneumatic cylinder has three rotational degree of freedom, makes main beam subassembly rotate for main frame subassembly. The main frame assembly is connected with the rear connecting seat of the main frame through a pin shaft, the rear connecting seat of the main frame drives the rear connecting seat of the main frame to ascend and descend through a piston rod of a hinge connection hydraulic cylinder with three degrees of freedom, and meanwhile, the rear connecting seat of the main frame can move relative to the main frame at the bottom of the vehicle. The main beam assembly is lifted under the action of the hydraulic cylinders at the two ends, the main frame assembly can be driven to lift synchronously, and the rear end of the main frame assembly is lifted up and down under the action of the other hydraulic cylinder. The main frame assembly is a bracket for supporting the landing gear of the airplane, and the main beam assembly and the hydraulic cylinders at two ends form a bracket suspension mechanism for lifting the bracket. When the aircraft tractor rotates along the vertical axis, the main frame assembly rotates along with the tractor, and meanwhile, the main frame assembly can rotate around the hinge shaft of the upper supporting vertical plate of the tractor in a self-adaptive mode, so that additional torque on the aircraft undercarriage is avoided.

The aircraft tractor controls the front end and the rear end of the bracket to lift simultaneously by means of the three groups of hydraulic cylinders, so that the lifting and descending of the undercarriage of the aircraft are realized, and the whole driving system is complex in structure and high in cost.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a rodless aircraft tractor for solve present rodless aircraft tractor and adopt multiunit pneumatic cylinder control bracket around both ends lift simultaneously the complicated higher technical problem of cost of whole actuating system structure that causes.

The utility model discloses a no pole aircraft tractor adopts following technical scheme:

a rodless aircraft tractor comprising:

a frame;

a wheel;

a cradle for lifting a nose landing gear of an aircraft;

the bracket suspension mechanism comprises a cross beam and suspension mechanism oil cylinders positioned at two ends of the cross beam, wherein two ends of the cross beam are supported on the frame through the suspension mechanism oil cylinders, the middle part of the cross beam lifts the rear part of the bracket, the cross beam is hinged with the rear part of the bracket through a cross beam hinge shaft, and two ends of the cross beam can swing back and forth relative to the frame and can swing left and right relative to the frame;

the bracket comprises a bracket body and a spherical hinge structure arranged at the front end of the bracket body, the spherical hinge structure comprises a bracket body connecting seat and a spherical fitting piece which are connected with the bracket body, the spherical fitting piece is arranged on the frame, and the spherical fitting piece is movably matched with the bracket body connecting seat through a spherical surface, so that the bracket can swing up and down to support or put down the nose landing gear and can swing around the central axis of the beam hinged shaft;

a rotation stopping cylindrical surface is arranged on the front side of the frame body connecting seat, extends forwards and backwards and is coaxial with the beam hinged shaft; the frame is provided with rotation stopping surfaces at the left side and the right side of the rotation stopping cylindrical surface, and the rotation stopping cylindrical surface is tangent to the rotation stopping surfaces at the left side and the right side so as to realize rotation stopping matching of the bracket and the frame in the horizontal direction.

Has the advantages that: the utility model discloses a rodless aircraft tractor's bracket front end passes through ball pivot structural connection on the frame, holds up or puts down nose landing gear through making the bracket luffing motion, and through the face of cylinder that splines of ball pivot structure department, the level that can realize the bracket splines improves the stability of bracket, compares the mode through the whole lift bracket of pneumatic cylinder at present, the utility model discloses a tractor has simplified actuating system's structure through making the wobbling mode of bracket, solves the complicated higher technical problem of cost of the whole actuating system structure that both ends go up and down simultaneously caused around present rodless aircraft tractor adopts multiunit pneumatic cylinder control bracket.

Furthermore, the spherical hinge structure comprises a joint bearing, the inner ring of the bearing of the joint bearing forms the spherical mating piece, and the outer ring of the joint bearing is arranged on the frame body connecting seat. The knuckle bearing is good in stability as a standard component and low in cost.

Furthermore, a rotation stopping cylinder is fixed on the front side of the frame body connecting seat, and the outer peripheral surface of the rotation stopping cylinder forms the rotation stopping cylindrical surface. The cylinder is high in strength and can bear large torque.

Furthermore, the frame is provided with mounting plates arranged at intervals, and the opposite side surfaces of the mounting plates form the rotation stopping surfaces. The mounting plate structure is simpler, the assembly of being convenient for.

Further, a torque sensor is arranged between the frame body connecting seat and the frame body, and the torque sensor is used for measuring steering torque between the bracket and the frame in a horizontal plane; the rodless aircraft tractor further comprises a controller, wherein the controller is connected with the torque sensor, and the steering of the wheels is controlled according to the measured value of the torque sensor. The torque between the frame and the bracket in the horizontal plane can be measured by the torque sensor, in the steering process of the aircraft tractor, the controller can control the steering of the wheels according to the numerical value measured by the torque sensor, when the numerical value measured by the torque sensor is too large, the wheels can be controlled to rotate reversely or stop to continue increasing the rotating angle, and the nose landing gear is not easy to damage.

Further, the controller controls the wheel to rotate in a reverse direction after the measured value of the torque sensor reaches a set value. Further making the nose landing gear of the aircraft less susceptible to damage.

Further, torque sensor's upper and lower both ends all are equipped with flange, and torque sensor passes through the flange at both ends respectively with support body and support body connecting seat fixed connection. The sensor is convenient to mount, and the fixing effect is guaranteed.

Furthermore, the periphery of the oil cylinder of the suspension mechanism is sleeved with an oil cylinder seat, two coaxial oil cylinder hinged shafts extending front and back are fixed on a cylinder body of the oil cylinder of the suspension mechanism, the oil cylinder seat hinged shafts extending left and right are arranged on the oil cylinder seat, the oil cylinder seat hinged shafts are hinged on the frame, two ends of the cross beam swing front and back relative to the frame through the oil cylinder seat hinged shafts, and swing left and right relative to the frame through the oil cylinder hinged shafts. The oil cylinder seat is sleeved on the periphery of the oil cylinder of the suspension mechanism, so that the oil cylinder of the suspension mechanism is stressed more uniformly and has better stability.

Drawings

Fig. 1 is a schematic structural view of a specific embodiment 1 of the rodless aircraft tractor according to the present invention;

FIG. 2 is a schematic structural view of a bracket according to embodiment 1 of the rodless aircraft tractor of the present invention;

FIG. 3 is a schematic view of the vertical plane force analysis in the exemplary embodiment 1 of the rodless aircraft tractor according to the present invention;

fig. 4 is a schematic view of the force analysis of the horizontal plane in embodiment 1 of the rodless aircraft tractor according to the present invention;

fig. 5 is a schematic view of the installation structure of the torque sensor in embodiment 1 of the rodless aircraft tractor according to the present invention;

fig. 6 is a schematic view of another installation structure of the torque sensor in embodiment 1 of the rodless aircraft tractor according to the present invention;

fig. 7 is a schematic structural view of a spherical hinge structure in embodiment 1 of the rodless aircraft tractor according to the present invention;

fig. 8 is a schematic structural view of the connection between the bracket and the frame in embodiment 1 of the rodless aircraft tractor according to the present invention;

in the figure: 1. a frame; 11. mounting a plate; 111. a rotation stopping surface; 2. a bracket; 21. a rear door shield; 22. front holding clamp; 23. a frame body; 24. a frame body connecting seat; 241. connecting lugs; 242. fixing the step; 25. a knuckle bearing; 251. a bearing inner race; 26. installing a shaft; 27. a rotation stopping cylinder; 271. a rotation stopping cylindrical surface; 3. a wheel; 4. a nose landing gear; 5. a bracket suspension mechanism; 51. a cross beam; 52. a suspension mechanism cylinder; 521. a piston rod; 522. a suspension mechanism cylinder; 523. a hinge shaft of the oil cylinder; 53. a beam hinge shaft; 54. a cylinder block; 541. a hinged shaft of the oil cylinder seat; 6. a torque sensor; 61. an upper connecting flange; 62. and a lower connecting flange.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention, i.e., the described embodiments are only some, but not all embodiments of the invention. The components of embodiments of the present invention, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the accompanying drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiment of the present invention, all other embodiments obtained by the person skilled in the art without creative work belong to the protection scope of the present invention.

It is noted that relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The features and properties of the present invention are described in further detail below with reference to examples.

The utility model discloses concrete embodiment 1 of rodless aircraft tractor:

as shown in fig. 1 to 6, the rodless aircraft tractor comprises a frame 1 and a bracket 2, and wheels 3, a driving system and a steering system are mounted on the frame 1, wherein the driving system and the steering system are both in the prior art, and detailed description is omitted in this embodiment.

The bracket 2 is used for supporting a nose landing gear 4 of the airplane so that the rodless airplane tractor can pull the airplane to move. In this embodiment, the frame 1 is a U-shaped frame, the rear end of the frame 1 has an opening for the nose landing gear 4 to enter, the bracket 2 is provided with a rear door stop 21 and a front holding clamp 22, wherein the structure for holding the nose landing gear 4 by the bracket 2 is the prior art, and is the same as the structure of the wheel holding jacking mechanism disclosed in the chinese patent document with the publication number CN206750172U, and a detailed explanation is not provided here, and the embodiment mainly develops in detail for the improved part of the prior art.

The rear end of the bracket 2 is hung on the frame 1 through the bracket hanging mechanism 5, as shown in fig. 2, the bracket hanging mechanism 5 comprises a cross beam 51 and hanging mechanism oil cylinders 52 at two ends of the cross beam 51, two ends of the cross beam 51 are supported on the frame 1 through the hanging mechanism oil cylinders 52, the middle part of the cross beam 51 is hung up at the rear part of the bracket 2, the cross beam 51 is hinged with the rear part of the bracket 2 through a cross beam hinge shaft 53, two degrees of freedom are provided between an oil cylinder seat 54 of the hanging mechanism oil cylinder 52 and the frame 1, and the cross beam 51 is hinged at the top of a piston rod 521 of the hanging mechanism oil cylinder 52, so that two ends of the cross beam 51 can swing back and forth relative to the frame 1 and can swing left and right relative to the frame 1. The cylinder base 54 in this embodiment is sleeved on the suspension cylinder 52, but in other embodiments, the connection form between the suspension cylinder and the frame may also be the one disclosed in the publication No. CN 206750172U.

As shown in fig. 2, two cylinder hinge shafts 523 extending back and forth are fixed on a suspension cylinder body 522 of the suspension cylinder 52, the cylinder base 54 is sleeved outside the suspension cylinder 52, a cylinder base groove for matching the cylinder hinge shafts 523 is arranged on the cylinder base 54, two cylinder base hinge shafts 541 coaxial left and right are further arranged on the outer side surface of the cylinder base 54, and the cylinder base hinge shafts 541 are hinged on the frame 1.

In this embodiment, the bracket 2 includes support body 23 and the spherical hinge structure that sets up at support body 23 front end, and the spherical hinge structure includes support body connecting seat 24 be connected with support body 23 and passes through sphere clearance fit's sphere fitting piece with support body connecting seat 24, and in this embodiment, the spherical hinge structure includes joint bearing 25, and joint bearing 25's bearing inner race 251 constitutes the sphere fitting piece, and joint bearing 25's outer lane is fixed on support body connecting seat 24. The bearing inner race 251 is fixed to the mounting shaft 26, and the mounting shaft 26 extends left and right and is mounted on the frame 1.

The front side of the frame body connecting seat 24 is fixed with a rotation stopping cylinder 27, the outer peripheral surface of the rotation stopping cylinder 27 forms a rotation stopping cylinder surface 271, the rotation stopping cylinder surface 271 is coaxial with the beam hinge shaft 53, the frame 1 comprises two mounting plates 11 which are opposite to each other at the left and the right, two ends of the mounting shaft 26 are respectively assembled on the mounting plates 11, the opposite side surfaces of the two mounting plates 11 form a rotation stopping surface 111 which is tangent with the rotation stopping cylinder surface 271, the rotation stopping surface 111 is a plane which extends forwards and backwards and is vertically arranged, the rotation stopping surface 111 is tangent with the rotation stopping cylinder surface 271, so that the bracket 2 is matched with the frame 1 in a rotation stopping way in the horizontal direction, the bracket 2 can swing up and down to accommodate the up and down movement of the undercarriage relative to the frame 1, and the frame 1 can swing around the central axis of the rotation stop cylindrical surface 271, so that the bracket 2 can swing around the axis of the cross beam hinge shaft 53 relative to the frame 1 to accommodate the inclination of the undercarriage during turning. In order to keep the frame 1 from interfering with the rotation-stopping cylinder 27, the space between the two mounting plates 11 is provided for the rotation-stopping cylinder 27 to move, and a space is provided between the front side of the rotation-stopping cylinder 27 and the frame 1. In other embodiments, the frame can also be provided with two longitudinal beams, the rotation stopping cylinder is arranged between the two longitudinal beams, and the rotation stopping surface is arranged on the longitudinal beams.

The joint bearing 25 and the rotation-stopping cylinder 27 can simplify the connection structure of the frame 1 and the front end of the bracket, and are convenient to install and maintain.

The bracket 2 is connected with the frame 1 by a bracket suspension mechanism 5 at the rear part and a spherical hinge structure at the front end, and the lifting of the bracket 2 is realized by a suspension mechanism oil cylinder 52 of the bracket suspension mechanism 5, so that the lifting of the nose landing gear 4 is controlled. In this embodiment, the rear portion of the carrier 2 swings up and down to raise and lower the nose landing gear 4.

When rodless aircraft tractor turned to, there was the steering torque between rodless aircraft tractor and the nose landing gear 4, in order to avoid the too big damage nose landing gear 4 of steering torque, the utility model discloses a 2 front portions of bracket are provided with torque sensor 6, and torque sensor 6 sets up between the support body connecting seat 24 of bracket 2 and ball pivot structure, and torque sensor 6 includes flange 61 and lower flange 62, goes up flange 61 and is fixed with bracket 2, and lower flange 62 is fixed with support body connecting seat 24.

As shown in fig. 7 and 8, the frame body coupling seat 24 includes a coupling lug 241 at a front end, the coupling lug 241 is used for mounting the outer ring of the joint bearing 25 and the rotation stopping cylinder 27, and the rotation stopping cylinder 27 is fixed with the coupling lug 241. The frame body coupling seat 24 is provided at the rear side thereof with a fixing step 242, and the lower coupling flange 62 is fixed to the fixing step 242 by bolts. The upper connecting flange 61 is fixed to the frame body 23 by bolts.

As shown in the figure, since the crossbeam 51 can move back and forth, left and right, and only provides the vertically upward acting force for the bracket 2, the force of the tractor is balanced in the vertical plane, the tractor is subjected to the steering force of the front wheel of the tractor in the horizontal plane, and the torque generated by the torque sensor 6 is the product of the steering force provided by the front wheel of the rodless aircraft tractor and the moment arm.

The controller of the rodless aircraft tractor is connected with the torque sensor 6, the controller controls the steering of the wheels 3 according to the numerical value measured by the torque sensor 6, and when the numerical value of the torque sensor 6 exceeds a set value, the wheels 3 are controlled to rotate reversely, so that the damage to the nose landing gear 4 is avoided. In other embodiments, the torque sensor may not be provided on the bracket when the use condition is good.

The utility model discloses a rodless aircraft tractor during operation, the piston rod 521 withdrawal of suspension mechanism hydro-cylinder 52, crossbeam 51 descends, and bracket 2's rear portion descends, and the back door shield 21 of bracket 2 rear end is opened, and the forebay gear 4 removes to bracket 2 and goes up the back, and the back door shield 21 is closed, and the wheel of forebay gear 4 is held tightly to preceding armful clamp 22 on the bracket 2, then suspension mechanism hydro-cylinder 52 raises, and rodless aircraft tractor can pull the aircraft and remove the steering this moment. During the moving steering process, the bracket 2 can swing around the beam hinge shaft 53 and can swing up and down, so that the additional torque of the aircraft landing gear is reduced. For the steering torque received by the aircraft landing gear in the steering process, the controller can control the steering of the rodless aircraft tractor according to the steering torque, and after the torque received by the current landing gear 4 exceeds a set value, the controller controls the rodless aircraft tractor to reversely steer. To the nose-gear 4 of different grade type and different road conditions, the utility model discloses a steering torque that no pole aircraft tractor can real time monitoring nose-gear 4 receive avoids nose-gear 4 impaired.

The utility model discloses a concrete embodiment 2 of rodless aircraft tractor, the structure of rodless aircraft tractor in this embodiment only lies in with the difference among the above-mentioned rodless aircraft tractor concrete embodiment 1: in the embodiment, the torque sensor is arranged in the middle of the bracket, and the steering torque of the nose landing gear is obtained through conversion.

The utility model discloses a concrete embodiment 3 of rodless aircraft tractor, the structure of rodless aircraft tractor in this embodiment only lies in with the difference among the above-mentioned rodless aircraft tractor concrete embodiment 1: the torque sensor is arranged between the hinge structure and the frame in this embodiment.

The utility model discloses a concrete embodiment 4 of rodless aircraft tractor, the structure of rodless aircraft tractor in this embodiment only lies in with the difference among the above-mentioned rodless aircraft tractor concrete embodiment 1: the cylinder base of the suspension mechanism cylinder may be disposed at the bottom of the cylinder.

The utility model discloses a concrete embodiment 5 of rodless aircraft tractor, the structure of rodless aircraft tractor in this embodiment only lies in with the difference among the above-mentioned rodless aircraft tractor concrete embodiment 1: in this embodiment, a circular tube is used instead of the rotation stopping cylinder, and the outer peripheral surface of the circular tube forms a rotation stopping cylindrical surface. In other embodiments, the anti-rotation cylinder or tube may be rotatably mounted to the frame to reduce friction.

The utility model discloses a concrete embodiment 6 of rodless aircraft tractor, the structure of rodless aircraft tractor in this embodiment only lies in with the difference among the above-mentioned rodless aircraft tractor concrete embodiment 1: the frame body connecting seat is provided with a ball head, a spherical matching piece matched with the ball head is fixed on the frame, and the rotation stopping cylinder is fixed on the ball head.

The above description is only for the preferred embodiment of the present invention, and the present invention is not limited thereto, the protection scope of the present invention is defined by the claims, and all structural changes equivalent to the contents of the description and drawings of the present invention should be included in the protection scope of the present invention.

Claims

1. A rodless aircraft tractor comprising:

a frame;

a wheel;

a cradle for lifting a nose landing gear of an aircraft;

the front undercarriage lifting device is characterized in that the bracket comprises a bracket body and a spherical hinge structure arranged at the front end of the bracket body, the spherical hinge structure comprises a bracket body connecting seat connected with the bracket body and a spherical fitting piece, the spherical fitting piece is arranged on the frame, and the spherical fitting piece is movably matched with the bracket body connecting seat through a spherical surface, so that the bracket can swing up and down to support or put down the front undercarriage and can swing around the central axis of the cross beam hinge shaft;

2. The rodless aircraft tractor of claim 1 wherein the ball joint structure includes a knuckle bearing, an inner race of the knuckle bearing forming the spherical mating element, and an outer race of the knuckle bearing mounted on the frame attachment base.

3. The rodless aircraft tractor according to claim 1 or 2, wherein a rotation-stopping cylinder is fixed to a front side of the frame body connecting seat, and an outer circumferential surface of the rotation-stopping cylinder forms the rotation-stopping cylindrical surface.

4. The rodless aircraft tractor according to claim 1 or 2, wherein the frame has spaced apart mounting plates, opposite sides of the mounting plates forming the anti-roll surfaces.

5. The rodless aircraft tractor according to claim 1 or 2, wherein a torque sensor is disposed between the frame connecting base and the frame, the torque sensor being configured to measure a steering torque between the bracket and the frame in a horizontal plane; the rodless aircraft tractor further comprises a controller, wherein the controller is connected with the torque sensor, and the steering of the wheels is controlled according to the measured value of the torque sensor.

6. The rodless aircraft tractor of claim 5 wherein the controller controls the wheels to rotate in reverse after the measurement from the torque sensor reaches a set value.

7. The rodless aircraft tractor according to claim 5, wherein the torque sensor has connecting flanges at upper and lower ends thereof, and the torque sensor is fixedly connected to the frame body and the frame body connecting seat through the connecting flanges at the two ends.

8. The rodless aircraft tractor according to claim 1 or 2, wherein a cylinder base is sleeved on the periphery of the suspension mechanism cylinder, two cylinder hinge shafts extending front and back and coaxial are fixed on a cylinder body of the suspension mechanism cylinder, a cylinder base hinge shaft extending left and right is arranged on the cylinder base, the cylinder base hinge shaft is hinged to the frame, two ends of the cross beam swing back and forth relative to the frame through the cylinder base hinge shaft, and swing left and right relative to the frame through the cylinder hinge shaft.