CN221116900U

CN221116900U - Safety supporting device of crawler scissor fork

Info

Publication number: CN221116900U
Application number: CN202322427182.8U
Authority: CN
Inventors: 刘维顺; 王云
Original assignee: Changsha Special Engineering Equipment Industrial Technology Research Institute Co ltd; Sunward Intelligent Equipment Co Ltd
Current assignee: Changsha Special Engineering Equipment Industrial Technology Research Institute Co ltd; Sunward Intelligent Equipment Co Ltd
Priority date: 2023-09-06
Filing date: 2023-09-06
Publication date: 2024-06-11
Anticipated expiration: 2033-09-06

Abstract

The utility model discloses a safety supporting device of a crawler scissor fork, which relates to the technical field of crawler scissor fork type lifting platforms, and comprises the following components: a chassis assembly; the shear fork assembly is arranged above the chassis assembly and is used for realizing lifting operation; the working platform is arranged above the scissor assembly; the safety support is detachably arranged on one side of the chassis assembly and is used for transversely propping up between the chassis assembly and the bottom of the lifting scissor assembly; the walking system is arranged below the chassis assembly and is used for realizing walking operation. The safety supporting device of the crawler scissor fork can effectively improve the use safety and the use range of the crawler scissor fork type lifting platform.

Description

Safety supporting device of crawler scissor fork

Technical Field

The utility model relates to the technical field of crawler scissor type lifting platforms, in particular to a safety supporting device of crawler scissor type lifting platforms.

Background

In the related art, a crawler scissor type lifting platform (hereinafter referred to as crawler scissor) is a lifting platform using a scissor structure as an extension mechanism, people, tools and materials are carried to a working position through the extension of the scissor structure, and the crawler mechanism walks and moves on various complex road conditions. The basic structure of the crawler scissor fork comprises a chassis assembly, an extending mechanism, a working platform and the like. Wherein, the battery is deposited in chassis assembly inside. Track assemblies are arranged on two sides of the chassis, and a battery has no access space; the door box at the front part of the chassis has limited length and no installation space for the battery; the rear side of the chassis is provided with a pedal staircase, and the battery has no access space; at the bottom of the chassis, battery access is difficult to operate, and under complex road conditions, battery packs are easy to damage, so that battery access is generally performed at the upper part of the chassis.

The crawler scissor is used as one of the movable lifting working platforms, and safety protection is an important design index. The safety support is a necessary component of each movable lifting working platform. When maintenance personnel carry out maintenance work at the bottom of the scissors, the scissors must be supported for safe support, so that the scissors are prevented from falling accidentally.

The traditional safety support is arranged on the connecting shaft of the scissor arm and can rotate around the connecting shaft. When the safety support is not in work, the safety support can be rotated to lean against the scissor arms, and the safety support is stored and protected; when the safety support is in operation, the safety support can be rotated and is erected on the connecting shaft of the adjacent shearing fork arms, so that the shearing fork structure falls off unnaturally, and the aim of safety support is fulfilled. However, the traditional safety support is limited in storage space, the length is generally 400-500mm, and the maintenance space at the upper part of the chassis is 100-200mm after the support is lifted. However, for battery access, repair, and maintenance of the track scissors, the required space height is greater than 350mm, and the conventional safety support cannot meet the requirements. And, traditional safety support's simple structure, intensity is not enough, often needs to set up a plurality of safety supports because of shearing fork level increases, and partial safety support installs on high-level shearing fork arm connecting axle, when supporting the operation, and the operation height is higher, uses inconveniently.

In summary, how to improve the use safety and the use range of the crawler scissor type lifting platform is a problem to be solved by those skilled in the art.

Disclosure of utility model

In view of the above, the present utility model aims to provide a safety support device for a crawler scissor fork, which can effectively improve the use safety and the use range of the crawler scissor fork type lifting platform.

In order to achieve the above object, the present utility model provides the following technical solutions:

a safety support device for a track scissor fork, comprising:

a chassis assembly;

the shear fork assembly is arranged above the chassis assembly and is used for realizing lifting operation;

The working platform is arranged above the scissor assembly;

The safety support is detachably arranged on one side of the chassis assembly and is used for transversely propping between the chassis assembly and the bottom of the lifted scissor assembly;

The walking system is arranged below the chassis assembly and is used for realizing walking operation.

Preferably, the chassis assembly comprises a welding chassis for accommodating a battery, support leg assemblies arranged at four corners of the welding chassis, and a battery cover plate for covering the battery.

Preferably, the scissors assembly comprises a first-stage inner fork, a second-stage inner fork, a third-stage inner fork, a fourth-stage inner fork, a lifting oil cylinder, a lower lifting oil cylinder and a first-stage outer fork, wherein the first-stage inner fork, the second-stage inner fork, the third-stage inner fork and the fourth-stage inner fork are sequentially arranged from bottom to top;

The lifting oil cylinder is arranged on the three-stage inner fork, the lower lifting oil cylinder is arranged on the one-stage inner fork, the one-stage outer fork and the one-stage inner fork are both arranged on the welding chassis, and the one-stage outer fork is positioned on the outer side of the one-stage inner fork.

Preferably, the safety support comprises a pedal staircase rotatably arranged at one side of the chassis assembly;

When the pedal escalator rotates to be distributed along the longitudinal direction of the chassis assembly, the pedal escalator is used as the pedal escalator, and when the pedal escalator rotates to be distributed along the transverse direction of the chassis assembly, the pedal escalator is used as a safety support to prevent the scissor assembly from falling.

Preferably, a pedal escalator is fixedly arranged on one side of the chassis assembly.

Preferably, the escalator comprises a lower mounting plate, an upper mounting plate arranged above the lower mounting plate, a supporting block arranged above the upper mounting plate, a right side vertical plate vertically distributed with the supporting block and a left side vertical plate parallelly distributed with the right side vertical plate;

The lower mounting plate and the upper mounting plate are both fixed on the chassis assembly.

Preferably, the safety support comprises a scissor support plate, two support beams which are distributed oppositely, an escalator support plate and a reinforcing plate, wherein the scissor support plate is vertically arranged at one end of the support beam, the support beam is vertically arranged at the other end of the support beam, and the reinforcing plate is used for connecting the support beam and the scissor support plate;

The scissors supporting plate is used for propping up the bottom of the scissors assembly, and the escalator supporting plate is placed on the supporting block to prop up the right side vertical plate and the left side vertical plate.

Preferably, a connecting beam is vertically arranged between the two supporting beams, a handle is arranged on the connecting beam, a hook is arranged on the supporting leg assembly, and the handle is hung on the hook.

Preferably, the safety support comprises two oppositely distributed support beams and a connecting beam vertically arranged between the two support beams;

One end of each supporting beam is aligned with the right vertical plate and the left vertical plate respectively, and the other ends of the supporting beams are used for being clamped with the bottoms of the scissor assemblies.

Preferably, the safety support comprises a telescopic part and a fixing part connected with the telescopic part, and the fixing part is rotatably arranged on one side of the chassis assembly;

the telescoping portion does not operate when the safety support is rotated to be longitudinally distributed along the chassis assembly, and the telescoping portion laterally telescopes when the safety support is rotated to be laterally distributed along the chassis assembly.

When the safety supporting device of the crawler scissor fork is used, when the working platform needs to be lifted, the scissor fork assembly can be controlled to lift along the vertical direction, then the safety support is transversely propped between the chassis assembly and the bottom of the lifted scissor fork assembly, and at the moment, the scissor fork thrust of the scissor fork assembly is transferred to the chassis assembly through the safety support so as to transversely support the bottom of the scissor fork assembly. Because when the scissors assembly lifts, the transverse displacement of the scissors assembly is far smaller than the longitudinal displacement of the scissors assembly, then the scissors assembly can be lifted to a higher height by the aid of the safety support through a smaller length, and further the maintenance operation space on the upper portion of the chassis assembly is enlarged, so that safety access of components such as a battery is guaranteed later, meanwhile, the taking and placing of the safety support are operated at a low position, and safety and convenience of using the safety support are improved.

When the working platform needs to be lowered, the safety support can be taken down, placed on one side of the chassis assembly, and then the scissor assembly is pressed down to reset. And the working platform can be moved to a required position by controlling the running of the running system.

In summary, the safety supporting device for the crawler scissor fork provided by the utility model can effectively improve the use safety and the use range of the crawler scissor fork type lifting platform.

Drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present utility model, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic view of a safety support device for a crawler scissor fork according to the present utility model;

FIG. 2 is an exploded view of the chassis assembly;

FIG. 3 is a schematic view of a structure of a scissor assembly;

fig. 4 is a schematic structural view of the escalator;

FIG. 5 is a schematic structural view of a safety support;

Fig. 6 is a schematic structural view of the safety support device of the crawler scissor fork when the safety support device is used.

In fig. 1-6:

The walking system comprises a chassis assembly 1, a welding chassis 11, a rear vertical plate 111, a guide rail panel 112, a pedal escalator 12, a lower mounting plate 121, an upper mounting plate 122, a supporting block 123, a right vertical plate 124, a left vertical plate 125, a flat washer 13, a spring washer 14, a bolt 15, a supporting leg assembly 16, a hook 161, a battery cover 17, a shearing fork assembly 2, a primary inner fork 21, a secondary inner fork 22, a tertiary inner fork 23, a quaternary inner fork 24, an ascending lifting cylinder 25, a lower lifting cylinder 26, a primary outer fork 27, a connecting shaft 271, a working platform 3, a safety support 4, a shearing fork supporting plate 41, a supporting beam 42, a connecting beam 43, an escalator supporting plate 44, a handle 45, a reinforcing plate 46 and a walking system 5.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

The utility model provides a safe supporting device of a crawler scissor fork, which can effectively improve the use safety and the use range of the crawler scissor fork type lifting platform.

Referring to fig. 1 to 6, fig. 1 is a schematic structural view of a safety supporting device of a crawler scissor according to the present utility model; FIG. 2 is an exploded view of the chassis assembly; FIG. 3 is a schematic view of a structure of a scissor assembly; fig. 4 is a schematic structural view of the escalator; FIG. 5 is a schematic structural view of a safety support; fig. 6 is a schematic structural view of the safety support device of the crawler scissor fork when the safety support device is used.

The embodiment provides a safe supporting device of crawler scissor fork, which comprises:

A chassis assembly 1;

The shear fork assembly 2 is arranged above the chassis assembly 1, and the shear fork assembly 2 is used for realizing lifting operation;

the working platform 3 is arranged above the scissor assembly 2;

A safety support 4 detachably provided at one side of the chassis assembly 1 for being laterally abutted between the chassis assembly 1 and the bottom of the raised scissor assembly 2;

And the walking system 5 is arranged below the chassis assembly 1 and is used for realizing walking operation.

The shape, the type, the position and the like of the chassis assembly 1, the scissor assembly 2, the working platform 3, the safety support 4 and the traveling system 5 can be determined according to actual conditions and actual requirements in the actual application process.

When the safety supporting device of the crawler fork provided by the utility model is used, when the working platform 3 needs to be lifted, the fork assembly 2 can be controlled to lift along the vertical direction, then the safety support 4 transversely pushes against the bottom of the chassis assembly 1 and the lifted fork assembly 2, and at the moment, the fork thrust of the fork assembly 2 is transferred to the chassis assembly 1 through the safety support 4 so as to transversely support the bottom of the fork assembly 2. Because when the scissor assembly 2 lifts, the transverse displacement of the scissor assembly 2 is far smaller than the longitudinal displacement of the scissor assembly 2, then the safety support 4 can ensure that the scissor assembly 2 lifts to a higher height by using a smaller length, so that the application range of a lifting platform is improved, and further the maintenance operation space on the upper part of the chassis assembly 1 is enlarged, so that the safety access of components such as a battery is guaranteed later, and meanwhile, the taking and placing of the safety support 4 are operated at a low position, so that the safety and convenience of using the safety support 4 are improved.

When the working platform 3 needs to be lowered, the safety support 4 can be taken down, placed on one side of the chassis assembly 1, and then the scissor assembly 2 is pressed down to reset. And, the working platform 3 can be moved to a desired position by controlling the running system 5 to run.

On the basis of the above embodiment, it is preferable that the chassis assembly 1 includes a welding chassis 11 for accommodating a battery, leg assemblies 16 provided at four corners of the welding chassis 11, and a battery cover 17 for covering the battery. Therefore, when the battery needs to be replaced, the scissor assembly 2 can be lifted and transversely propped between the chassis assembly 1 and the bottom of the lifted scissor assembly 2 by the safety support 4 so that the bottom of the scissor assembly 2 is far away from the top of the chassis assembly 1, and then the battery cover 17 can be opened, so that an operator can conveniently take out the battery from the upper part for replacement.

Preferably, the scissors assembly 2 comprises a first-stage inner fork 21, a second-stage inner fork 22, a third-stage inner fork 23, a fourth-stage inner fork 24, an upper lifting oil cylinder 25, a lower lifting oil cylinder 26 and a first-stage outer fork 27, wherein the first-stage inner fork 21, the second-stage inner fork 22, the third-stage inner fork 23 and the fourth-stage inner fork 24 are sequentially arranged from bottom to top; the upper lifting oil cylinder 25 is arranged on the three-stage inner fork 23, the lower lifting oil cylinder 26 is arranged on the one-stage inner fork 21, the one-stage outer fork 27 and the one-stage inner fork 21 are both arranged on the welding chassis 11, and the one-stage outer fork 27 is positioned on the outer side of the one-stage inner fork 21.

It should be noted that, the lifting cylinder 25 is used for driving the first-stage inner fork 21, the second-stage inner fork 22, the third-stage inner fork 23 and the fourth-stage inner fork 24 to lift upwards, and the lower lifting cylinder 26 is used for driving the first-stage inner fork 21, the second-stage inner fork 22, the third-stage inner fork 23 and the fourth-stage inner fork 24 to fall back downwards. Because the device adopts the safety support 4 to transversely prop between the chassis assembly 1 and the bottom of the lifted scissor assembly 2, low-level operation can be realized, the scissor assembly 2 does not need to be lifted or fall back by an operator to climb to a high place, and the device is beneficial to expanding the operable space of the chassis assembly 1 after the scissor assembly 2 is lifted.

Preferably, the safety support 4 comprises a escalator 12 rotatably arranged at one side of the chassis assembly 1; when the escalator 12 rotates to be longitudinally distributed along the chassis assembly 1, the escalator 12 serves as an escalator, and when the escalator 12 rotates to be transversely distributed along the chassis assembly 1, the escalator 12 serves as a safety support to prevent the scissor assembly 2 from falling down, so that maintenance safety is guaranteed. The longitudinal direction refers to a direction vertically distributed relative to a horizontal plane, and the transverse direction refers to a direction horizontally distributed relative to the horizontal plane.

Preferably, a escalator 12 is fixedly arranged on one side of the chassis assembly 1, i.e. an operator can reach the working platform 3 by stepping on the escalator 12.

Preferably, the escalator 12 comprises a lower mounting plate 121, an upper mounting plate 122 arranged above the lower mounting plate 121, a supporting block 123 arranged above the upper mounting plate 122, a right side vertical plate 124 vertically distributed with the supporting block 123 and a left side vertical plate 125 parallel to the right side vertical plate 124, and the structure is shown in fig. 4; the lower mounting plate 121 and the upper mounting plate 122 are both fixed to the chassis assembly 1. For example, the escalator 12 may have the lower and upper mounting plates 121, 122 mounted to the rear riser 111 of the chassis assembly 1 by means of flat washers 13, elastic washers 14, and bolts 15.

Preferably, the safety support 4 comprises a scissor support plate 41, two support beams 42, an escalator support plate 44 and a reinforcing plate 46, wherein the two support beams 42 are oppositely distributed, the scissor support plate 41 is vertically arranged at one end of the support beam 42, the support beam 42 is vertically arranged at the other end of the support beam 42, and the reinforcing plate 46 is used for connecting the support beam 42 and the scissor support plate 41; the scissor support plate 41 is used to bear against the bottom of the scissor assembly 2, and the escalator support plate 44 is placed on the support block 123 to bear against the right side riser 124 and the left side riser 125. Wherein the bottom of the reinforcing plate 46 may be flush with the bottom of the fork supporting plate 41 to increase the contact area between the fork supporting plate 41 and the fork assembly 2.

Preferably, a connecting beam 43 is vertically arranged between the two supporting beams 42, a handle 45 is arranged on the connecting beam 43, a hook 161 is arranged on the supporting leg assembly 16, and the handle 45 is hung on the hook 161. That is, when the safety support 4 is required to be used, an operator may hold the handle 45 to place the safety support 4 between the connection shaft 271 of the primary outer fork 27 of the chassis assembly 1 and the bottom of the raised scissor assembly 2. When the safety support 4 is not needed, the operator can hang the handle 45 on the hook 161 so as not to influence the resetting process of the scissor assembly 2.

In order to further explain the use method of the safety support device of the crawler scissor fork provided by the utility model, the safety support device is exemplified.

When the device is in operation, an operator can place the scissor support plates 41 of the safety support 4 on the rail panels 112 of the chassis assembly 1 and the escalator support plates 44 on the support blocks 123 of the escalator 12. The scissor support plate 41 of the safety support 4 abuts against the connecting shaft 271 of the primary outer fork 27, and the escalator support plate 44 abuts against the right side riser 124 and the left side riser 125. The two support beams 42 are aligned with the sides of the right and left side risers 124, 125, respectively, and the escalator 12 is mounted on the rear riser 111. The shearing thrust of the shearing assembly 2 is transmitted to the safety support 4 through the connecting shaft 271, then to the escalator 12 and finally to the rear vertical plate 111 of the chassis assembly 1.

When the device is in a non-working state, the safety support 4 is hung on the hook 161 of the support leg assembly 16 through the handle 45.

On the basis of the above embodiment, it is preferable that the safety support 4 includes two oppositely-distributed support beams 42 and a connection beam 43 vertically provided between the two support beams 42; one end of the two support beams 42 is aligned with the right side riser 124 and the left side riser 125, respectively, and the other end of the two support beams 42 is used for clamping the bottom of the scissor assembly 2. That is, two support beams 42 can be used alone to support the scissor assembly 2, and the structure of the safety support 4 is simpler and lighter.

Preferably, the safety support 4 comprises a telescopic part and a fixed part connected with the telescopic part, and the fixed part is rotationally arranged on one side of the chassis assembly 1; the telescoping sections do not run when the safety support 4 is rotated to be longitudinally distributed along the chassis assembly 1, and telescope laterally when the safety support 4 is rotated to be laterally distributed along the chassis assembly 1.

That is, when working is required, the safety support 4 can be placed transversely relative to the chassis assembly 1, and for maintenance of different components, the lifting heights of the scissor assemblies 2 are different, the operating spaces on the chassis assembly 1 are different, that is, the lifting heights of the scissor assemblies 2 are different, the sliding amounts of the connecting shafts 271 of the primary outer forks 27 are different, and the transverse total length of the safety support 4 can be adjusted by adjusting the telescopic amounts of the telescopic parts so as to match and support various components. When the device is not required to be used, the safety support 4 can be longitudinally placed relative to the chassis assembly 1, so that space is saved.

It should be noted that the orientation or positional relationship indicated by "up and down" and the like of the present utility model is based on the orientation or positional relationship shown in the drawings, and is merely for simplicity of description and ease of understanding, and does not indicate or imply that the apparatus or element to be referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present utility model.

In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. Any combination of all the embodiments provided in the present utility model is within the protection scope of the present utility model, and will not be described herein.

The safety support device of the crawler scissor fork provided by the utility model is described in detail above. The principles and embodiments of the present utility model have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present utility model and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the utility model can be made without departing from the principles of the utility model and these modifications and adaptations are intended to be within the scope of the utility model as defined in the following claims.

Claims

1. A safety support device for a track scissor fork, comprising:

A chassis assembly (1);

The scissor assembly (2) is arranged above the chassis assembly (1), and the scissor assembly (2) is used for realizing lifting operation;

the working platform (3) is arranged above the scissor assembly (2);

A safety support (4) detachably arranged on one side of the chassis assembly (1) and used for transversely propping between the chassis assembly (1) and the bottom of the lifted scissor assembly (2);

And the walking system (5) is arranged below the chassis assembly (1) and is used for realizing walking operation.

2. The safety support device of a crawler scissor fork according to claim 1, characterized in that the chassis assembly (1) comprises a welding chassis (11) for accommodating a battery, leg assemblies (16) provided at four corners of the welding chassis (11), and a battery cover plate (17) for covering the battery.

3. The safety support device of a crawler scissor fork according to claim 2, wherein the scissor assembly (2) comprises a primary inner fork (21), a secondary inner fork (22), a tertiary inner fork (23), a quaternary inner fork (24), an upper lifting cylinder (25), a lower lifting cylinder (26) and a primary outer fork (27), wherein the primary inner fork (21), the secondary inner fork (22), the tertiary inner fork (23) and the quaternary inner fork (24) are sequentially arranged from bottom to top;

The lifting oil cylinder (25) is arranged on the three-stage inner fork (23), the lower lifting oil cylinder (26) is arranged on the one-stage inner fork (21), the one-stage outer fork (27) and the one-stage inner fork (21) are both arranged on the welding chassis (11), and the one-stage outer fork (27) is arranged on the outer side of the one-stage inner fork (21).

4. A safety support device for a track scissor fork according to claim 2 or 3, characterized in that the safety support (4) comprises a foot rest (12) rotatably provided on one side of the chassis assembly (1);

When the escalator (12) rotates to be longitudinally distributed along the chassis assembly (1), the escalator (12) serves as an escalator, and when the escalator (12) rotates to be transversely distributed along the chassis assembly (1), the escalator (12) serves as a safety support to prevent the fork assembly (2) from falling down.

5. A safety support device for a crawler scissor fork according to claim 2 or 3, characterized in that a foot-operated escalator (12) is fixedly arranged on one side of the chassis assembly (1).

6. The safety support device of a crawler scissor fork according to claim 5, characterized in that the escalator (12) comprises a lower mounting plate (121), an upper mounting plate (122) arranged above the lower mounting plate (121), a support block (123) arranged above the upper mounting plate (122), a right side riser (124) distributed perpendicularly to the support block (123) and a left side riser (125) distributed parallel to the right side riser (124);

The lower mounting plate (121) and the upper mounting plate (122) are both fixed on the chassis assembly (1).

7. The safety support device of a crawler fork according to claim 6, characterized in that the safety support (4) comprises a fork support plate (41), two oppositely distributed support beams (42), an escalator support plate (44) and a reinforcing plate (46), the fork support plate (41) being vertically arranged at one end of the support beam (42), the support beam (42) being vertically arranged at the other end of the support beam (42), the reinforcing plate (46) being used for connecting the support beam (42) and the fork support plate (41);

the scissors supporting plate (41) is used for propping up the bottom of the scissors assembly (2), and the staircase supporting plate (44) is placed on the supporting block (123) to prop up the right side vertical plate (124) and the left side vertical plate (125).

8. The safety support device of a crawler scissor fork according to claim 7, characterized in that a connecting beam (43) is vertically arranged between two supporting beams (42), a handle (45) is arranged on the connecting beam (43), a hook (161) is arranged on the supporting leg assembly (16), and the handle (45) is hung on the hook (161).

9. The safety support device of a crawler scissor fork according to claim 6, characterized in that the safety support (4) comprises two oppositely distributed support beams (42) and a connecting beam (43) arranged vertically between the two support beams (42);

One end of each supporting beam (42) is aligned with the right vertical plate (124) and the left vertical plate (125), and the other end of each supporting beam (42) is used for being clamped with the bottom of the scissor assembly (2).

10. The safety support device of a crawler scissor fork according to claim 6, characterized in that the safety support (4) comprises a telescopic part and a fixed part connected with the telescopic part, the fixed part is rotatably arranged on one side of the chassis assembly (1);

the telescoping section does not run when the safety support (4) is rotated to be longitudinally distributed along the chassis assembly (1), and stretches laterally when the safety support (4) is rotated to be laterally distributed along the chassis assembly (1).