CN214641406U

CN214641406U - Underframe welding tool

Info

Publication number: CN214641406U
Application number: CN202120738756.1U
Authority: CN
Inventors: 张孝然; 李宝旺; 王波; 吴素艳; 闫石磊; 单晖
Original assignee: CRRC Tangshan Co Ltd
Current assignee: CRRC Tangshan Co Ltd
Priority date: 2021-04-12
Filing date: 2021-04-12
Publication date: 2021-11-09
Anticipated expiration: 2031-04-12

Abstract

The utility model provides an underframe welding tool, which relates to the technical field of welding tools and comprises a platform and two bearing rotating mechanisms, wherein each bearing rotating mechanism comprises two bases, a rotating ring component and a pressing component, and the bases are provided with rollers and rotary driving pieces; the rotating ring assembly comprises a lower ring seat and rotating opening and closing parts, and the extending ends of the two rotating opening and closing parts are connected through a connecting piece; the compressing assembly is arranged on the inner side of the rotating ring assembly. The utility model provides a chassis welding frock, it is rotatory to utilize the both ends that two bearing rotary mechanism drive the chassis, the rotatory chassis that drives the swivel subassembly and be located the swivel subassembly of gyro wheel on the base rolls, realize the change of chassis angle, it can fix the chassis in the swivel subassembly to compress tightly the subassembly, make chassis and swivel subassembly synchronous motion, two rotate the portion of opening and shutting and can rotate to the one side that deviates from the lower ring seat, the putting into of the chassis of being convenient for, this frock space occupies for a short time, be convenient for carry out the adjustment of chassis angle.

Description

Underframe welding tool

Technical Field

The utility model belongs to the technical field of the welding frock, more specifically say, relate to an chassis welding frock.

Background

In the manufacturing process of the railway vehicle, the vehicle body underframe needs to be assembled through welding. As an essential procedure in the process of welding the underframe, the underframe needs to be transversely turned over, and good welding accessibility of welding seams at different positions such as the side surface and the bottom surface of the underframe is ensured. Due to the fact that the underframe of the railway vehicle is heavy (about 18 tons at most) and the size change range of the length and the width is large, the difficulty in adjusting the angle and the position of the underframe is large, the welding space of the underframe is limited, and the welding angle is not ideal.

In the prior art, the installation and clamping of the underframe are mostly carried out by means of a tool installed on a positioner, and then the rotation end of the positioner is utilized to rotate to drive the tool and the underframe to synchronously overturn. But above-mentioned equipment has with high costs and occupies the big problem of room area, and the suitability of frock is relatively poor.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a chassis welding frock can carry out the upset of chassis with the help of rotating assembly, and frock occupation space is little, the degree of flexibility is high.

In order to achieve the above object, the utility model adopts the following technical scheme: the chassis welding tool comprises a platform and two bearing rotating mechanisms which are arranged on the platform and used for driving the chassis to rotate, wherein each bearing rotating mechanism comprises two bases, a rotating ring assembly and a pressing assembly; the swivel assembly is arranged between the two bases, the peripheral wall of the swivel assembly is in rolling fit with the roller, the swivel assembly is used for being sleeved on the periphery of the underframe and rotating under the driving of the roller and comprises a lower ring seat and two rotating opening and closing parts which are respectively and rotatably connected to the two upper ends of the lower ring seat, the two rotating opening and closing parts have rotating freedom degrees in the horizontal direction and can rotate to reach the extending ends of the two rotating opening and closing parts to be connected with the lower ring seat in a surrounding mode to form a closed ring, and the two extending ends are connected through a connecting piece; the pressing assembly is arranged on the inner side of the rotating ring assembly and used for clamping and fixing the underframe to the rotating ring assembly.

In a possible implementation mode, two ends of the lower ring seat are respectively provided with an extending shaft extending upwards, the rotating opening and closing part is provided with a shaft hole in rotating fit with the extending shaft, and the extending shaft is further sleeved with a thrust bearing positioned between the rotating opening and closing part and the lower ring seat.

In some embodiments, the upper end of one of the rotary opening and closing parts is provided with a first connecting part extending along the tangential direction; the upper end of the other rotating opening and closing part is provided with a second connecting part which extends along the tangential direction and is stacked below the first connecting part, and the connecting part is a pin shaft which runs through the first connecting part and the second connecting part.

In some embodiments, the outer end of the first connecting portion is provided with a first hook extending toward one side of the axis of the lower ring seat, the outer end of the second connecting portion is provided with a second hook extending away from one side of the axis of the lower ring seat, and the first hook and the second hook are in snap fit to limit the relative positions of the two rotating opening and closing portions.

In some embodiments, the platform is provided with a slide rail extending along the axial direction of the rotating ring assembly and located below the base, and one end of the slide rail is provided with a sliding driving piece for driving the base to slide along the slide rail.

In a possible implementation mode, an auxiliary rotating mechanism positioned between the two supporting rotating mechanisms is further arranged on the platform, the auxiliary rotating mechanism comprises two supporting seats and an auxiliary rotating ring, the two supporting seats are symmetrically arranged on two sides of the underframe, and driven wheels are respectively arranged on adjacent side surfaces of the two supporting seats; the auxiliary rotating ring is arranged between the two bearing seats, is matched with the driven wheel in a rolling manner, is used for bearing and positioning the middle part of the chassis, and the axis of the auxiliary rotating ring is superposed with the axis of the rotating ring component.

In a possible implementation mode, the base is provided with limiting wheel sets which are respectively positioned at the two sides of the rotating ring assembly to limit the axial position of the rotating ring assembly, and the limiting wheel sets are provided with a plurality of groups at intervals in the circumferential direction of the rotating ring assembly.

In a possible implementation mode, a limiting groove is formed in the circumferential wall of the roller and located in the axial middle of the roller, and a limiting convex ring which is in rolling fit with the limiting groove to limit the axial position of the rotating ring assembly is arranged on the periphery of the rotating ring assembly.

In one possible implementation manner, two groups of pressing components are arranged and are respectively positioned between the two rotary opening and closing parts and the lower ring seat, each pressing component comprises a first positioning block and a second positioning block, and the first positioning blocks are arranged on the inner peripheral wall of the lower ring seat and used for supporting the bottom surface of the underframe; the second positioning block is arranged on the inner peripheral wall of the rotary opening and closing part and used for being arranged above the underframe to be matched with the first positioning block to limit the underframe.

In some embodiments, the pressing assembly further includes two tightening bolts respectively screwed to the first positioning block and the second positioning block, and the tightening bolts abut against the top surface or the bottom surface of the chassis to lock the chassis.

The shown scheme of this application embodiment, compared with the prior art, the chassis welding frock that this embodiment provided, it is rotatory to utilize two bearing rotary mechanism to drive the both ends of chassis, the rotatory chassis that drives the swivel subassembly and be located the swivel subassembly on the base rolls, realize the change of chassis angle, it can fix the chassis in the swivel subassembly to compress tightly the subassembly, make chassis and swivel subassembly synchronous motion, two rotate the portion of opening and shutting and can rotate to the one side that deviates from the lower ring seat, the putting into of the chassis of being convenient for, this frock space occupies for a short time, high durability and convenient use, the adjustment of chassis angle is carried out in the welding process of being convenient for.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments or the prior art descriptions will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive labor.

Fig. 1 is a schematic structural diagram of an underframe welding tool provided in an embodiment of the present invention;

fig. 2 is a schematic view of a partially enlarged structure of the chassis welding tool in the embodiment of the present invention in fig. 1;

fig. 3 is a schematic structural view of the base in fig. 1 according to an embodiment of the present invention;

fig. 4 is a schematic structural view of the supporting seat in fig. 1 according to an embodiment of the present invention;

fig. 5 is a schematic partial sectional structure view of the rotary opening and closing part, the clamping assembly and the lower ring seat in fig. 1 according to the embodiment of the present invention;

fig. 6 is an enlarged schematic structural diagram of a connection node of two rotating opening and closing portions in fig. 1 according to the embodiment of the present invention.

Wherein, in the figures, the respective reference numerals:

1. a platform; 11. a slide rail; 12. a sliding drive member; 2. a base; 21. a roller; 22. a rotary drive member; 23. a limiting wheel set; 231. a limiting groove; 3. a swivel assembly; 31. a lower ring seat; 311. an extension shaft; 312. a thrust bearing; 32. rotating the opening and closing part; 321. a limit nut; 33. a first connection portion; 331. a first hook; 34. a second connecting portion; 341. a second hook; 35. a pin shaft; 36. a limit convex ring; 4. a compression assembly; 41. a first positioning block; 42. a second positioning block; 43. jacking the bolt; 5. an auxiliary rotating mechanism; 51. a bearing seat; 52. auxiliary rotating rings; 521. a driven wheel.

Detailed Description

In order to make the technical problem, technical solution and advantageous effects to be solved by the present invention more clearly understood, the following description is given in conjunction with the accompanying drawings and embodiments to illustrate the present invention in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or be indirectly on the other element. It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "top," "bottom," "inner," "outer," and the like are used in the orientation or positional relationship indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention. The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically limited otherwise.

Referring to fig. 1 and fig. 6, the present invention will now be described with reference to the following embodiments. The chassis welding tool comprises a platform 1 and two supporting and rotating mechanisms which are arranged on the platform 1 and used for driving the chassis to rotate, wherein each supporting and rotating mechanism comprises two bases 2, a rotating ring assembly 3 and a pressing assembly 4, and the adjacent side surfaces of the two bases 2 are respectively provided with a roller 21 and a rotary driving piece 22 used for driving the roller 21 to rotate; the swivel assembly 3 is arranged between the two bases 2, the peripheral wall of the swivel assembly 3 is in rolling fit with the roller 21, the swivel assembly 3 is used for being sleeved on the periphery of the underframe and is driven by the roller 21 to rotate, the swivel assembly 3 comprises a lower ring seat 31 and two rotating opening and closing parts 32 which are respectively and rotatably connected to the two upper ends of the lower ring seat 31, the two rotating opening and closing parts 32 have rotating freedom degrees in the horizontal direction and can rotate to the state that the extending ends of the two rotating opening and closing parts 32 are connected with each other to be matched with the lower ring seat 31 to form a closed ring shape, and the two extending ends are connected with each other through a connecting piece; a hold-down assembly 4 is provided inside the swivel assembly 3 for clamping and securing the undercarriage to the swivel assembly 3.

In this embodiment, the lower ring seat 31 can also adopt the form of two rotation opening and closing portions 32, when the chassis is welded, after the front welding part is welded, the swivel assembly 3 is utilized to drive the chassis to rotate to the back face upwards, then the back face is welded, after the welding is completed, the tool does not need to rotate to the position of the front face upwards, and the chassis can be conveniently detached by opening the two rotation opening and closing portions 32 of the lower ring seat 31. The two rotary opening and closing parts 32 respectively occupy a quarter of radian in the circumferential direction, and can be spliced together with the lower ring seat 31 to form a ring for mounting the underframe.

The chassis welding frock that this embodiment provided, compared with the prior art, the chassis welding frock that this embodiment provided, it is rotatory to utilize two bearing rotary mechanism to drive the both ends of chassis, the rotatory chassis that drives swivel subassembly 3 and be located swivel subassembly 3 on the base 2 rolls, realize the change of chassis angle, it can fix the chassis in swivel subassembly 3 to compress tightly subassembly 4, make chassis and 3 synchronous motion of swivel subassembly, two rotate the portion of opening and shutting 32 can rotate to the one side that deviates from lower ring seat 31, the putting into of the chassis of being convenient for, this frock space occupies for a short time, high durability and convenient use, the adjustment of chassis angle is carried out in the welding process of being convenient for.

In some possible implementations, the lower ring seat 31 has the structure shown in fig. 5. Referring to fig. 5, two ends of the lower ring seat 31 are respectively provided with an extending shaft 311 extending upward, the rotating opening and closing portion 32 is provided with a shaft hole rotatably matched with the extending shaft 311, and the extending shaft 311 is further sleeved with a thrust bearing 312 positioned between the rotating opening and closing portion 32 and the lower ring seat 31. In addition, a stopper nut 321 for preventing the rotation opening and closing portion 32 from coming off the extension shaft 311 is provided at the upper end of the extension shaft 311.

The periphery wall of lower ring seat 31 contacts with base 2, and the terminal surface at the both ends of lower ring seat 31 is gone up to be put ascending extension axle 311, is provided with the shaft hole on the lower terminal surface of rotation portion of opening and shutting 32, and extension axle 311 penetrates the shaft hole, realizes lower ring seat 31 and the normal running fit who rotates portion of opening and shutting 32, and stop nut 321 will rotate the relative position locking of portion of opening and shutting 32 and lower ring seat 31, avoids breaking away from between the two. When the underframe is installed, the rotary opening and closing part 32 is rotated to the outer side far away from the lower ring seat 31, the underframe can be conveniently installed in the opening of the lower ring seat 31, then the rotary opening and closing part 32 is rotated to the position capable of being connected, and the extending ends of the rotary opening and closing part 32 are connected and fixed through the connecting piece, so that the installation of the underframe is completed.

Further, the extension shaft 311 is sleeved with a thrust bearing 312, the lower end surface of the rotary opening and closing part 32 is located on the top surface of the reasoning bearing, and the reasoning bearing can reduce friction generated in the process that the rotary opening and closing part 32 rotates around the extension shaft 311, so that the smoothness in the rotation of the rotary opening and closing part 32 is improved.

In some embodiments, the above-described feature of the rotary shutter 32 may be configured as shown in fig. 6. Referring to fig. 6, an upper end of one of the rotation opening and closing portions 32 is provided with a first connecting portion 33 extending in a tangential direction; the upper end of the other rotary opening and closing part 32 is provided with a second connecting part 34 which extends along the tangential direction and is stacked below the first connecting part 33, and the connecting part is a pin shaft 35 which penetrates through the first connecting part 33 and the second connecting part 34. The two rotary opening and closing portions 32 are connected by a first connecting portion 33 and a second connecting portion 34, and are connected by a connecting member, i.e., a pin 35. The first connecting portions 33 and the second connecting portions 34 are disposed in a staggered manner in the vertical direction, and the pin shaft 35 can penetrate through the first connecting portions and the second connecting portions to fix the two rotary opening and closing portions 32.

Referring to fig. 6, it should be noted that, in order to effectively limit the relative positions of the first connecting portion 33 and the second connecting portion 34, a first hook 331 extending toward one side of the axial center of the lower ring seat 31 may be further disposed at the outer end of the first connecting portion 33, a second hook 341 extending away from one side of the axial center of the lower ring seat 31 is further disposed at the outer end of the second connecting portion 34, and the first hook 331 and the second hook 341 are engaged with each other to limit the relative positions of the two rotation opening and closing portions 32.

The first hook 331 arranged at the outer end of the first connecting portion 33 and the second hook 341 arranged at the outer end of the second connecting portion 34 can be mutually clamped, so that the relative positions of the two rotating opening and closing portions 32 can be effectively locked, and the two positions can be effectively locked by the pin shaft 35 penetrating through the first connecting portion 33 and the second connecting portion 34, thereby facilitating the reliable limitation of the chassis in the swivel assembly 3.

As shown in fig. 1 and 2, on the basis of being supported by the platform 1, the platform 1 is provided with a slide rail 11 extending along the axial direction of the rotating ring assembly 3 and located below the base 2, and one end of the slide rail 11 is provided with a sliding driving member 12 for driving the base 2 to slide along the slide rail 11.

The relative positions of the two bases 2 can be adjusted to suit the needs of chassis of different length dimensions. Set up slide rail 11 in the below of base 2, through the drive of the driving piece 12 that slides that links to each other with base 2, can make base 2 slide along slide rail 11, realize quick regulation effect, make the frock have better suitability.

As shown in fig. 1, on the basis that the rotating ring assembly 3 is used to drive the underframe to rotate, the underframe welding tool further comprises an auxiliary rotating mechanism 5 located between the two supporting rotating mechanisms, the auxiliary rotating mechanism 5 comprises two supporting seats 51 and an auxiliary rotating ring 52, the two supporting seats 51 are symmetrically arranged on two sides of the underframe, and driven wheels 521 are respectively arranged on adjacent side surfaces of the two supporting seats 51; the auxiliary rotating ring 52 is arranged between the two bearing seats 51, is in rolling fit with the driven wheel 521, and is used for bearing and positioning the middle part of the underframe, and the axis of the auxiliary rotating ring 52 is superposed with the axis of the rotating ring component 3.

The auxiliary rotating mechanism 5 is arranged between the two supporting rotating mechanisms and can support the axial middle part of the underframe. The chassis with larger length has better supporting effect and can be matched with the chassis to rotate. The auxiliary rotating mechanism 5 is not provided with a component having a driving function, and the driven wheel 521 arranged on the bearing seat 51 can cooperate with the rotating function, so that the auxiliary rotating ring 52 and the underframe rotate synchronously.

In some possible implementations, the above-mentioned feature base 2 adopts the structure shown in fig. 3. Referring to fig. 3, the base 2 is provided with a plurality of limiting wheel sets 23 respectively located at two sides of the swivel assembly 3 for limiting the axial position of the swivel assembly 3, and the limiting wheel sets 23 are arranged at intervals in the circumferential direction of the swivel assembly 3.

In order to ensure the position stability of the swivel assembly 3 in the axial direction and avoid driving the chassis to generate axial movement, the base 2 is provided with the limiting wheel sets 23, each limiting wheel set 23 comprises two wheel bodies, and the two wheel bodies are respectively matched with the two side walls of the swivel assembly 3 in a rolling manner to realize the axial limiting of the swivel assembly 3.

Furthermore, the limiting wheel set 23 can be provided with a plurality of sets in the circumferential direction of the rotating ring assembly 3, so that different positions in the circumferential direction of the rotating ring assembly 3 can be limited, and the axial displacement of the rotating ring assembly 3 is avoided.

In some possible implementations, the roller 21 is configured as shown in fig. 2. Referring to fig. 2, the circumferential wall of the roller 21 is provided with a limiting groove 231 located at the axial middle portion thereof, and the outer periphery of the rotating ring assembly 3 is provided with a limiting convex ring 36 which is in rolling fit with the limiting groove 231 to limit the axial position of the rotating ring assembly 3.

Correspondingly, an inward concave limiting groove 231 is arranged on the roller 21 along the circumferential direction, and a limiting convex ring 36 matched with the limiting groove 231 is arranged on the periphery of the rotating ring component 3. In the process that the idler wheel 21 drives the rotating ring component 3 to rotate, the axial position of the rotating ring component 3 is effectively limited, and the axial movement of the rotating ring component 3 and the chassis is avoided by combining the action of the limiting wheel set 23.

In some possible implementations, the above-described feature pressing assembly 4 adopts a structure as shown in fig. 5. Referring to fig. 5, two groups of pressing components 4 are respectively located between the two rotary opening and closing portions 32 and the lower ring seat 31, each pressing component 4 includes a first positioning block 41 and a second positioning block 42, and the first positioning blocks 41 are arranged on the inner peripheral wall of the lower ring seat 31 and used for supporting the bottom surface of the chassis; the second positioning block 42 is disposed on the inner peripheral wall of the rotary opening and closing portion 32, and is disposed above the chassis to limit the chassis by cooperating with the first positioning block 41.

The pressing assembly 4 is arranged between the rotating opening and closing part 32 and the lower ring seat 31, the top surface and the bottom surface of the underframe are limited respectively, and the relative rotation between the underframe and the rotating ring assembly 3 in the rotating ring assembly 3 is avoided.

In order to ensure the limiting effect of the first positioning block 41 and the second positioning block 42 on the chassis, the pressing assembly 4 further includes two tightening bolts 43 respectively screwed on the first positioning block 41 and the second positioning block 42, and the tightening bolts 43 are abutted to the top surface or the bottom surface of the chassis to lock the chassis. Adjusting the puller bolt 43 makes its top surface or the bottom surface butt of overhanging end and chassis, realizes the limiting displacement to the chassis, and then makes chassis and swivel subassembly 3 synchronous revolution, is convenient for carry out welding operation.

The above description is only exemplary of the present invention and should not be construed as limiting the present invention, and any modifications, equivalents and improvements made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

1. Chassis welding frock, its characterized in that sets up on the platform and is used for driving the rotatory bearing rotary mechanism of chassis, every including platform and two bearing rotary mechanism all includes:

the adjacent side surfaces of the two bases are respectively provided with a roller and a rotary driving piece for driving the roller to rotate;

the rotating ring assembly is arranged between the two bases, the peripheral wall of the rotating ring assembly is in rolling fit with the roller, the rotating ring assembly is used for being sleeved on the periphery of the underframe and is driven by the roller to rotate, the rotating ring assembly comprises a lower ring seat and two rotating opening and closing parts which are respectively and rotatably connected to the two upper ends of the lower ring seat, the two rotating opening and closing parts have rotating freedom degrees in the horizontal direction and can rotate to the state that the extending ends of the two rotating opening and closing parts are connected with each other to be matched with the lower ring seat to form a closed ring, and the two extending ends are connected with each other through a connecting piece;

and the pressing assembly is arranged on the inner side of the rotating ring assembly and is used for clamping and fixing the underframe to the rotating ring assembly.

2. The chassis welding tool according to claim 1, wherein two ends of the lower ring seat are respectively provided with an extending shaft extending upwards, the rotating opening and closing portion is provided with a shaft hole in rotating fit with the extending shaft, and the extending shaft is further sleeved with a thrust bearing located between the rotating opening and closing portion and the lower ring seat.

3. The chassis welding tool according to claim 2, wherein a first connecting portion extending in a tangential direction is arranged at an upper end of one of the rotary opening and closing portions; the upper end of another rotation portion of opening and shutting is equipped with along the tangential extension, and range upon range of in the second connecting portion of first connecting portion below, the connecting piece is for running through first connecting portion with the round pin axle that the second connecting portion set up.

4. The chassis welding tool according to claim 3, wherein an outer end of the first connecting portion is provided with a first hook extending to one side of an axis of the lower ring seat, an outer end of the second connecting portion is provided with a second hook extending to one side of the axis of the lower ring seat, and the first hook and the second hook are in clamping fit to limit relative positions of the two rotating opening and closing portions.

5. The underframe welding tool according to claim 1, wherein a slide rail extending in the axial direction of the swivel assembly and located below the base is provided on the platform, and a slide driving member for driving the base to slide along the slide rail is provided at one end of the slide rail.

6. The underframe welding tool according to any one of claims 1-5, wherein an auxiliary rotating mechanism is further disposed on the platform between the two supporting rotating mechanisms, and the auxiliary rotating mechanism comprises:

the two bearing seats are symmetrically arranged on two sides of the underframe, and driven wheels are respectively arranged on the adjacent side surfaces of the two bearing seats;

and the auxiliary rotating ring is arranged between the two bearing seats, is matched with the driven wheel in a rolling manner, is used for bearing and positioning the middle part of the chassis, and the axis of the auxiliary rotating ring is superposed with the axis of the rotating ring component.

7. The underframe welding tool according to any one of claims 1-5, wherein the base is provided with limiting wheel sets respectively located on two sides of the swivel assembly to limit the axial position of the swivel assembly, and the limiting wheel sets are arranged in a plurality of groups at intervals in the circumferential direction of the swivel assembly.

8. The underframe welding tool according to any one of claims 1-5, wherein a limiting groove is formed in the circumferential wall of the roller at the axial middle part of the roller, and a limiting convex ring is arranged on the periphery of the rotating ring assembly and is in rolling fit with the limiting groove to limit the axial position of the rotating ring assembly.

9. The chassis welding tool according to any one of claims 1 to 5, wherein two sets of the pressing assemblies are provided and are respectively located between the two rotary opening and closing portions and the lower ring seat, and the pressing assemblies comprise:

the first positioning block is arranged on the inner peripheral wall of the lower ring seat and used for supporting the bottom surface of the underframe;

and the second positioning block is arranged on the inner peripheral wall of the rotary opening and closing part and is used for being arranged above the underframe to be matched with the first positioning block to limit the underframe.

10. The chassis welding tool of claim 9, wherein the hold-down assembly further comprises two tightening bolts respectively screwed to the first positioning block and the second positioning block, and the tightening bolts abut against the top surface or the bottom surface of the chassis to lock the chassis.