Technical Field of Invention

The invention relates to clamping device for welding system, method of fixing welded material sheets and method of arc welding for thin and very thin sheets.

Background of Invention

Today, in all electrical and electronic devices (such as phones, computers), high-speed trains, cars, airplanes, spacecraft etc. There are many parts/members such as coolant tankjack, connector, magnetic frame of transformer, core of electric motor, lithium battery, microprocessor chip etc., fabricated from thin and very thin bars/sheets (from a few micrometers to several hundred micrometers). In production lines, material sheets are often used in form of rolls with lengths of each roll to hundreds, even thousands of meters. After going through an automatic continuous punching, stamping, cutting, bending and straightening process controlled by different laser sensors and surveillance cameras to ensure the thickness, size, shape, etc. and a surface plating process will output the above-mentioned parts/members which can be used directly in the devices as described above.

Thus, it can be said that a continuous automatic production process from billet feeding - checking material size and shape - continuous punching and deformation process - checking details is provided to - coating metal or alloy on the surface - packaging - used for other stages is being used to manufacture details and parts to serve all industries manufacturing high-tech equipment.

In present manufacturing plants, after a material roll is used up, it is replaced with a new material roll. Due to the characteristics of present traditional production lines, each material roll cannot be used up all, but both ends will be cut off to either avoid defects or being rejected because of the speed change of punching system when stopping the machine to change the material rolls. According to the inventors’ survey at factories, about 20 meters of material at the beginning of both ends of each roll will not be used for the above reasons. This causes waste of materials, increases production costs, and is costly to dispose of this solid waste. Furthermore, stopping the machine to replace each roll of material takes about 60 minutes on average. This is an unnecessary waste of time and can be completely overcome by new technological solutions that contribute to improving the efficiency of the production process. On the other hand, welding thin and very thin sheet is a very difficult problem because thin sheets are capable of rapid thermal deformation, high heat transfer rate, sensitive to the change of heat source, easy to bum or drop down leading to damage to the part welded. Therefore, although a lot of effort has been made to solve this problem with the introduction of modem welding technologies such as micro-TIG (Tungsten inner gas), micro-Plasma, or high energy density welding processes such as laser welding and electron beam welding. However, so far, though, soldering thin and very thin sheets has not achieved the desired results. That is to say, current welding technologies cannot meet the requirements of factories and automated production lines. Therefore, the automatic production lines as mentioned above do not use welding operations.

CN210756086 U discloses a sheet metal welding jig. The device includes a fixed bottom plate 1 and a fixed vertical plate, translation cylinder (2) is fixedly connected to the middle of the upper end of a fixed bottom plate (1) through bolts, slide rails (3) are fixedly connected to the left portion and the right portion of the upper end of the fixed bottom plate, linear bearings (11) are movably connected to the outer surfaces of the jacking upright rods, a jig plate (9) is fixedly connected to the surfaces of the linear bearings, a positioning mechanism (8) is arranged inside the jig plate (9), and an upper pressing mechanism (7) is fixedly connected to, the lower end of the fixed vertical plate. This solution involves a thin plate soldering fixture. However, it does not solve the above problems.

Stemming from that urgent demand, the inventors of the present invention provide provide a new solution to weld these thin and very thin sheets of material. Specifically, the inventors have intensively researched the jig assembly system for thin sheet welding to weld the material rolls together in order to limit machine downtime in automatic production lines. That is, when a roll of input material (reel in use) is almost empty, a new roll of material is prepared. One end of the new roll of material will be welded to the end of the existing roll of material. At this time, the equipment system in the production line is still working. This makes the production process uninterrupted, without having to stop the machine for replacement; at the same time make maximum usage and save production materials. This solution will reduce material waste, increase production time, improve productivity, thereby reducing production costs, lowering product costs and increasing competitiveness for businesses. Moreover, this solution will also minimize the amount of solid waste caused by material removal as mentioned.

Summary of Invention

Therefore, the purpose of invention is to provide a clamping device for welding system, thin and very thin sheet. First aspect, the present invention provides a clamping device for welding system, including: working table can move up and down in vertical direction, in which the working table is provided with three-dimentional concave cavity having the same size as that of lower jig for fixing lower jig; jig assembly includes upper jig and lower jig; the first pair of claims in operating state will create pressure on upper jig for fixing upper jig and clamp welded material with working table; second pair of clamps can move up and down in vertical direction, when going down, the second pair of clamps create pressure on welded material for fixing welded material sheet on the surface of working table; and at least two pairs of locating pins for locating welded material are provided on working table, in which one of the pairs of locating pins is slidable along parallel grooves according to the width of welded material sheet, which are provided on working table, parallel and located on either side of the concave cavity depending on the width of welded material.

Tn second aspect, clamping device according to first aspect, in which the device further includes auxiliary clamping member provided between two the second pair of clamps and fixed on working table.

In third aspect, clamping device according to first aspect, in which lower jig has a gap including welding gap and adjusting gap communicated with each other.

In fourth aspect, clamping device according to first aspect, in which welding gaps of upper jig and lower jig have the same width.

In fifth aspect, clamping device according to fourth aspect, in which the cross- sectional shape of welding gap of the upper jig is in form of the letter V.

In sixth aspect, clamping device according to fourth aspect, in which the welding gap width is from 0,4mm to 4mm.

In seventh aspect, clamping device according to fourth aspect, in which the welding gap width of 0,4mm is used for material with thickness of 0,03mm to 0,05mm.

In eighth aspect, clamping device according to fourth aspect, in which the welding gap width of 0,5mm is used for matterial with thickness more than 0,05mm and less than or equal to 0,07mm.

In nineth aspect, clamping device according to fourth aspect, in which the welding gap width of 1mm is used for matterial with thickness more than 0,07mm and less than or equal to 0,12mm.

In tenth aspect, clamping device according to fourth aspect, in which the welding gap width of 1,5mm is used for matterial with thickness more than 0,12mm and less than or equal to 0,175mm. In eleventh aspect, clamping device according to fourth aspect, in which the welding gap width of 2,0 mm is used for matterial with thickness more than 0,175mm and less than 0,4mm.

In twelfth aspect, clamping device according to fourth aspect, in which the welding gap width of 4,0mm is used for matterial with thickness more than or equal to 0,4mm and less than or equal to 0,8mm.

In thirteenth aspect, clamping device according to fourth aspect, in which the welding gap widths of the upper jig and lower jig are adjustable according to the thickness of welded material sheet.

In fourteenth aspect, clamping device according to first aspect, in which the clamps of the first pair of clamps when inserting is in form of the letter V.

In fifteenth aspect, clamping device according to fourteenth aspect, in which at least one of the clamps of the first pair of clamps comprise elastic member to adjust clamping force when the two welded material sheets have different thickness.

In sixteenth aspect, clamping device according to first aspect, in which working table further provided with guide pins for guiding welded material.

In seventeenth aspect, clamping device according to first aspect, in which working table is further provided with auxiliary jig in contact with welded material in the middle of the first butt-welding position of the welded material sheets.

In eighteenth aspect, clamping device according to first aspect, in which the device further includes setting plate, when the device operating, setting plate is inserted via adjusting gap and welding gap for adjusting the postion of butt-welding of the two welded material sheets.

In nineteenth aspect, the invention provides a method of fixing welded material sheets using clamping device according to first aspect, including steps: passing setting plate through the gap of lower jig in the upward direction; placing the first welded material sheet in the direction perpendicular to setting plate so that one side of the welded material sheet comes in contact with setting plate at the postion of butt-welding; controlling one of clamps of second pair of clamps to move down to clamp the first welded material sheet with working table; pull out the setting plate; placing a planar sheet on the first welded material sheet so that it covers the welding position; placing the second welded material sheet in horizontal direction and under planar sheet so that one side of the welded material sheet in contact with the one side of the first welded material sheet at butt-welding position; controlling the other clamp of second pair of clamps to move down to clamp the second welded material sheet with the working table; removing the planar sheet from welded material sheets; inserting the upper jig on welded materials nho cac cap locating pin; controlling the first pair of clamps to come to working position; moving the working table in upward direction so that the first pair of claims in contact with upper jig and providing pressing force to clamp the upper jig with welded material sheets with working table.

In twentieth aspect, the method according to nineteenth aspect, in which the welding gap widths of the upper jig and lower jig are adjustable according to the thickness of welded material sheet.

In twenty- first aspect, the method according to in twentieth aspect, in which the welding gap width is from 0,4mm to 4mm.

In twenty-second aspect, the method according to in twentieth aspect, in which the welding gap width of 0,4mm is used for material with thickness of 0,03mm to 0,05mm.

In twenty-third aspect, the method according to in twentieth aspect, in which the welding gap width of 0,5mm is used for matterial with thickness more than 0,05mm and less than or equal to 0,07mm.

In twenty-fourth aspect, the method according to in twentieth aspect, in which the welding gap width of 1mm is used for matterial with thickness more than 0,07mm and less than or equal to 0,12mm.

In twenty- fifth aspect, the method according to in twentieth aspect, in which the welding gap width of 1,5mm is used for matterial with thickness more than 0,12mm and less than or equal to 0,175mm.

In twenty-sixth aspect, the method according to in twentieth aspect, in which the welding gap width of 2,0 mm is used for matterial with thickness more than 0,175mm and less than 0,4mm.

In twenty-seventh aspect, the method according to in twentieth aspect, in which the welding gap width of 4,0mm is used for matterial with thickness more than or equal to 0,4mm and less than or equal to 0,8mm.

In twenty-eighth aspect, the method according to nineteenth aspect, the method further includes adjusting the pair of locating pins movable along the width of the welded material sheets to keep the welded material from being deformed after welding.

In twenty-nineth aspect, the method according to nineteenth aspect, the method further includes letting the auxiliary clamping member clamp upper jig with welded material sheets by inserting welded materials under auxiliary clamping member, then inserting the upper jig jig under auxiliary clamping member.

In thirtieth aspect, the invention also provides a method of arc welding for very thin sheet, including steps: passing setting plate through the gap of lower jig in the upward direction; placing the first welded material sheet in the direction perpendicular to setting plate so that one side of the welded material sheet comes in contact with setting plate at the postion of butt-welding; controlling one of clamps of second pair of clamps to move down to clamp the first welded material sheet with working table; pull out the setting plate; placing a planar sheet on the first welded material sheet so that it covers the welding position; placing the second welded material sheet in horizontal direction and under planar sheet so that one side of the welded material sheet in contact with the one side of the first welded material sheet at butt-welding position; controlling the other clamp of second pair of clamps to move down to clamp the second welded material sheet with the working table; removing the planar sheet from welded material sheets; inserting the upper jig on welded materials nhd cac cap locating pin; controlling the first pair of clamps to come to working position; moving the working table in upward direction so that the first pair of clamps in contact with upper jig and providing pressing force to clamp the upper jig with welded material sheets with working table; controlling welding torch into the working position; adjusting and determining arc length; placing auxiliry jig in contact with the first butt-welding position of the welded material sheets; controlling the welding torch to discharge arc on the surface of auxiliary jig prior to the welding torch move the full length of butt welding of the welded material sheets.

In thirty-first aspect, the method according to thirtieth aspect, in which auxiliary jig is made from solid metal.

In thirty-second aspect, the method according to thirty-first aspect, in which auxiliary jig is made of copper alloy.

In thirty-third aspect, the method according to thirty-first aspect, in which the welding gap width is from 0,4mm to 4mm.

In thirty- fourth aspect, the method according to thirty-second aspect, in which the welding gap width of 0,4mm is used for material with thickness of 0,03mm to 0,05mm. In thirty-fifth aspect, the method according to thirty-second aspect, in which the welding gap width of 0,5mm is used for matterial with thickness more than 0,05mm and less than or equal to 0,07mm.

In thirty-sixth aspect, the method according to thirty-second aspect, in which the welding gap width of 1mm is used for matterial with thickness more than 0,07mm and less than or equal to 0, 12mm.

In thirty-seventh aspect, the method according to thirty-second aspect, in which the welding gap width of 1,5mm is used for matterial with thickness more than 0, 12mm and less than or equal to 0, 175mm.

In thirty-eighth aspect, the method according to thirty-second aspect, in which the welding gap width of 2,0 mm is used for matterial with thickness more than 0,175mm and less than 0,4mm.

In thirty-nineth aspect, the method according to thirty-second aspect, in which the welding gap width of 4,0mm is used for matterial with thickness more than or equal to 0,4mm and less than or equal to 0,8mm.

In fortieth aspect, the method according to thirty-first aspect, the method further includes adjusting the pair of locating pins movable along the width of the welded material sheets to keep the welded material from being deformed after welding.

In forty-first aspect, the method according to fortieth aspect, the method further includes letting the auxiliary clamping member clamp upper jig with welded material sheets by inserting welded materials under auxiliary clamping member, then inserting the upper jig jig under auxiliary clamping member.

In forty-second aspect, the method according to forty- first aspect, the method further includes using upper jig provided with parallel grooves along the length of upper jig and symestrical through welding gap, characterized in that, one side of the edge along the width of upper jig is provided concave parts so that when inserting the upper jig then the concave parts fit the pair of locating pins for the welded material sheets on working table and the upper jig is placed under auxiliary clamping member.

In forty-third aspect, the method according to forty- first aspect, in which and the upper jig is used for welded material sheet with thickness more than or equal to 0,06mm.

In forty- fourth aspect, the method according to forty-third aspect, the method further includes using upper jig is a solid metal bar consisting of two parts, one part for clamping welded materials, the other part is provided with protrusion as guiding ledges on the both edges along the length of upper jig parallel and symetrical through welding gap of upper jig, so that when inserting the guiding ledges, it is in contact with the inner groove edges of locating pins for the welded material sheets. In forty-fifth aspect, the method according to forty- fourth aspect, in which and the upper jig is used for welded material sheet with thickness less than 0,06mm

Advantageous effect of the invention

Welding system of the present invention is capable of welding a various types of material sheets with different width and thickness. Another effect of the welding system of the present invention is that because the control of the heat supplied to the weld is mainly by the gap of the fixture, the welding method using this clamping device can weld at the welding current and welding speed is pushed up higher than current thin plate welding solutions/technology. This ensures both manufacturing productivity increased due to high welding speed and stability and weld quality thanks to the use of high welding current (present technologies arid solutions for welding thin sheet is preferred to reduce the welding current to the lowest level as possible so that the minimum amount of heat supplied to the weld is desired, But in fact, the smaller the welding current, the more difficult for discharging arc and the welding arc process and the arc is easily destabilized. This stability will be better if the welding process uses higher welding current). This ensures the stability of welding arc, sag- free weld, reducing defects due to burning or reducing defects due to burning or without weld penetration to thin and very thin sheets.

Brief Description of Drawings

Fig.l is a drawing showing the welding system of thin and very thin sheet.

Fig.2 is a drawing showing alignment steps of welded material sheet of method for clamping material.

Fig. 3 is a drawing showing alignment steps of welded material sheet of method for clamping material.

Fig.4 is a plan view of a part of clamping device for welding system according to an embodiment of the invention.

Fig.5 is a front view of a part of welding system including first pair of clamps and welding torch 6.

Fig.6a showing cross-sectional drawing of auxiliary jig inserted on working table I .

Fig.6b showing plan view of auxiliary jig inserted on working table.

Fig.7a is a drawing showing upper jig according to an embodiment of the invention.

Fig.7b is a drawing showing upper jig according to another of embodiment of the invention. Fig.7c is a drawing showing lower j ig.

Fig.8a is an image showing the weld when applying the invention having high quality and stable butt welding.

Fig.8b is an image showing defects at the postion of butt-welding with thermal deformation or burned when not applied the invention.

Detailed Description

The invention will be described in more detail on the basis of the description of the specific embodiment below by reference to the drawings, and these embodiments do not limit the scope of the invention, modifications of the invention are made within the scope of the invention without separation from the spirit of the invention.

The invention relates to clamping device for welding system, as shown in Fig. 1, the device includes working table 1 can move up and down in vertical direction owing to the system of four pneumatic cylinders arranged at the four comers below working table 1. Working table 1 is provided with three-dimentional concave cavity having the same size as that of lower jig 43 for fixing lower jig 43 so that the surface of lower jig 43 located in the working table 1, surface of lower jig 43 is coplanar with that of working table 1.

According to the present invention, co at least two pairs of locating pins for locating welded material sheet are provided on working table 1, in which one of pairs of locating pins is movable in the width direction of welded material sheet.

According to another embodiment, working table 1 further provided with guide pin 34 for guiding welded material sheets. Reffering to Fig. 1, guiding pin 34 is provided at the input of the first welded material sheet 21. This pin is movable in respective grooves provided on the surface of working table 1 perpendicular to the direction of displacement of the welded material sheets.

According to an embodiment of the invention, the surface of working table 1 on which two parallel guiding grooves 12 of upper jig 42 are provided on the either side of the concave cavity containing lower jig 43 in which pins 33 are provided to keep welded material sheet not being defomed when welded. Pins 33 are slidable along cac ranh 12 and are adjusted according to the width of welded material sheets.

Jig assembly welding system of the present invention includes upper jig 41 and lower jig 43. Lower jig 43 is inserted on working table 1 as described above, in operating state, lower jig 43 is under welded material sheets. Lower jig 43 is made of solid metal. As shown in Fig.1 and Fig. 7, lower jig 43 includes welding gap and adjusting gap communicated with each other, in which the width of welding gap w’ is greater than that of adjusting gap. These gaps are provided along the length of lower jig 43. When inserting it into working table 1, these gaps are communicated with adjusting gap of working table 1. Upper jig 41 as shown in Fig.1 and Fig. 7a is also made of solid metal, in operating state, upper jig 41 nam tren welded material sheets and clamp welded material sheets voi lower jig 43. Upper jig 41 is provided with welding gap along the length of upper jig 41.

According to an embodiment of the invention, when welded material sheet with thickness more than or equal to 0,06mm, upper jig 41 is provided with openings 412 in parallel along the length of upper jig 41 and symestrical through welding gap of the upper jig 41. When inserting upper jig 41, locating pins for the welded material sheets on working table 1 are inserted and slidable along the openings. At the one side of the edge along the width of upper jig 41 is provided positioning reccesses 411 so that when inserting upper jig 41 then the positioning reccesses 411 fit the pair of locating pins for the other welded material sheets on working table 1. In addition, working table 1 is further provided with a pair of locating pins for upper jig 41 for locating and guiding upper jig 41 when inserting it on working table 1.

According to another of embodiment of the invention, when welded materials with thickness less than 0,06mm. As shown in Fig. 7b upper jig 41 is a solid metal bar consisting of two parts, clamping portion for welded materials 421, the other part is provided with protrusion which is so-called la guiding ledges 422 on the both edges along the length of upper jig 41 parallel and symetrical through welding gap of the upper jig 41. When inserting upper jig 41, guiding ledges 422 are in contact with inner ledges of guiding grooves 12 of locating pins for the welded material sheets. The reason why when the material with thickness is less than 0.06 mm, the upper plate must be replaced like this. This is associated with the accuracy when upper jig 41 is installed. If using a big upper jig with large width such as the upper jig with thickness more than or equal to 0,06 mm then the contact area of upper jig and welded material is greater. This makes it difficult to ensure clamping with high accuracy. Futhermore, when the upper jig with wide and large slab needs to be inserted, it should be inserted between auxiliary clamping member 53 and welded material sheets. This insertion step easily leads to the displacement of the welded material, the loss of the correlation accuracy between the two welded materials and the welding step will not give good results. Further, small types of upper jig as mentioned herein when inserting will not come into contact with auxiliary clamping member 53. When inserting,the upper jig is brought from an elevated position and then gently engages the two ridges-groove inside the pin that holds the welded material sheets. Its upper end is in direct contact with the cylindrical edge of auxiliary jig 44. This ensures that the welded material installed is not displaced. Thus, it ensures a welding process with higher accuracy and stability. The thinner the welded material sheet, the higher the clamping accuracy is required and the less error is large, so the jig assembly needs to be more sophisticated and stable.

As shown in Fig. 7a, the cross section of welding gap width w of upper jig 41 is in form of the letter V.

According to an embodiment of present invention, the welding gap width w of upper jig 41 and the welding gap width w’ of lower jig 43 are the same when used.

The welding of thin and very thin sheet is very difficult due to the possibility of controlling heat source for weld. For butt welding of thin and very thin sheets, controlling the amount of heat involved in the weld becomes very important.

It is required high accuracy and stability. In present welding technology solutions, the controlling of heat mainly focuses on changing welding technology parameters such as welding current, welding voltage, pulse frequency of current, welding speed, etc. This is also the most common and popular measure that welding technology engineers and manufacturers of welding equipment around the world are trying to implement.

However, this control will not be enough to ensure that thin and very thin sheets can be welded stably with high quality.

Futhermore, Thin and very thin sheets are often deformed very quickly when impacted by a heat source with an energy of several thousand to several tens of thousands of degrees. When such deformation occurs, it is very difficult to keep the two edges of the butt- welded sheets from deviating so that they are always coplanar.

At this point, the solution is to control the amount of heat just enough to meet the welded material with a specific thickness of welded material. This control should be done in combination with the jig assembly for welding system that we are developing with the welding specifications as mentioned above. For welding sheets with a thickness of a few millimeters or more up to a few tens of centimeters or even a few hundreds of centimeters, the degree of warping and deformation of the object to be welded is not large and not much compared to the thickness of the object to be welded, basically, the clamping of welded material is simple and easy to do by clamping bars at four different angles on either side of the welded material.

However, for thin and very thin sheets this ratio is very large and it will be difficult to guarantee a stable weld quality. The different thickness of welded material and different type of welded material will result in different gap of the jig assembly. The gap of the jig assembly is the place to control the amount of heat applied to the weld. If the gap is large, the amount of heat supplied to the weld will be high, combined with the optimal welding parameters of the welding equipment that thicker sheets will be able to welded.

If the gap of the jig assembly for welding becomes narrower, the amount of heat passing through this gap will become smaller and therefore, thinner material sheets is able to be welded with high and stable quality. The residual heat - excess that cannot pass through the gap jig assembly for welding is directly transferred to the jig assembly for welding and jig assembly for welding will absorb heat and dissipate heat quickly.

In order to absorb and dissipate heat quickly, jig assembly is made of cooper and cooper alloy in case of copper soldering. And the same for other material types.

When welding a very thin sheet that the gap of jig assembly for welding is large, it will lead to overheat of the weld, the welding bath will drop, the liquid metal falls out of the welding bath forming holes that are called bum-through in arc welding.

Therefore, the invention was found by conducting a lot of tests to find out the optimal range for jig assembly for welding.

According to the present invention, it only needs to change the welding gap width of jig assembly, it is possible to weld material sheets of different thickness with high and stable quality. According to an embodiment of the invention, the welding gap of jig assembly has a width ranging from 0,4mm to 4mm. The welding gap width of the upper jig 41 and lower jig 43 is adjustable according to the thickness of welded material sheet.

Thus, if thin and very thin welded material sheets with thickness is from 0,03 mm to 0,8 mm then jig assembly with suitable welding gap width shall be used.

According to an embodiment of the invention, with the thickness is from 0,03mm to 0,05mm, jig assembly has a gap width of 0,4 mm

According to another of embodiment of the invention, a welded material sheet with thickness is greater than 0,05mm and less than or equal to 0,07mm, the gap width of jig assembly is 0,5 mm

According to another of embodiment of the invention, a welded material sheet with thickness is greater than 0,07mm and less than or equal to 0,12mm, the gap width of jig assembly is 1,0 mm According to another of embodiment of the invention, a welded material sheet with thickness is greater than 0,12mm and less than or equal to 0,175mm, the gap width of jig assembly is 1,5 mm

According to another of embodiment of the invention, a welded material sheet with thickness is greater than 0,175mm and less than 0,4mm, the gap width of jig assembly is 2,0 mm

According to another of further embodiment of the invention, a welded material sheet with thickness is greater than or equal to 0,4mm and less than or equal to 0,8mm, the gap width of jig assembly is 4,0 mm.

As shown in Fig. 1, first pair of clamps in operating state will create pressure on upper jig 41 for fixing upper jig 41 and clamp welded material with working table 1. Second pair of clamps can move up and down in vertical direction, when going down, second pair of clamps create pressure on welded material sheet for fixing welded material sheet on the surface of working table 1.

As shown in Fig.l and Fig.5, the clamps of the first pair of clamps when inserting is in form of the letter V. Each clamp of the pair of clamp consists of two parts, V-shaped bar 5124 whose lower end creates pressure directly on upper jig 41 in operating state, and pressure block 5123 which creates pressure on the upper end of V-shaped bar 5124. According to the present invention, at least one of clamps of first pair of clamp further includes elastic member 5122 between V-shaped bar 5124 and pressure block 5123 for adjusting pressing force on upper jig 41 if the two welded material sheets have different thickness. According to an embodiment, one of clamps is provided with at least one spring, preferably two springs, more preferable 3 springs. The tightness of a clamp of first pair of clamps are adjusted by bolts 5121 connecting V-shaped bar 5124 and pressure block 5123. When tightening bolts 5121, V-shaped bar 5124 moves upward and decrease the tightness of the clamp. In contrast, when loosening bolts 5121 V-shaped bar 5124 moves downward and increase pressing force. Thanks to this mechanism, the present invention is possible to apply the welding to material shees with different thickness. Simultaneously, due to the ability to rotate and move around 5121 so when jig assembly and working table are pushed up to clamp, V-shaped bar of a clamp of first pair of clamps has the effect of both clamping the welded sheet on the same side as it and self-adjusting the appropriate height and pushing the welded material sheet into contact with the other one and minimizing the clearance and warping between the two welded material sheets when inserting.

As a result, a perfect solution for welding two material sheets with different or same thickness is achieved In fact, the position clamps of welded material clamp are quite far from each other, which leads to the position of the welded material sheets when clamping, especially for materials with very thin thickness of several tens of micrometers, which will easily be displaced at butt-welding position. Difficulty in adjusting during clamping process is inevitable. As a result, the product after welding is prone to defects due to gaps or misalignment of welded edges. In order to solve this problem, according to an embodiment of the invention, as shown in Fig. 4, the present invention provides auxiliary clamping member 53 is fixed on working table 1, which is positioned between second pair of clamps. The auxiliary clamping member is in form of letter U whose ends are curved upwards to facilitate inserting welded material sheets as well as upper jig 41 under auxiliary clamping member 53 nay when installing. The surface of the two sides of U-shaped clamp on which provided openings 531 are provided so that when inserting auxiliary clamping member 53 on working table 1, pair of locating pins 31 are inside openings 531.

Another feature is due to the characteristics of the TIG arc welding source, when starting to discharging arc, the welding current in a very short period increase from the smallest value suddenly up to a very large value of about 80 A, then due to the setting of the welding current, this welding current will be quickly reduced to the set steady value again. This time is the stage where the welding process often occurs defects due to the sudden increase in current leading to a sudden increase in the amount of heat supplied to the welding bath. This leads to burn-through due to overheating as explained above. It is very important for thin and very thin sheets. Thus, the inventors researched a solution auxiliary jig 44 which comes in contact with welded material in the center of butt-welding position. So that when the arc is discharged on the surface of auxiliary jig 44, after the arc becomes stable, the welding torch 6 begins to move to weld the full length of the welded material. According to an embodiment of the invention, as shown in Fig. 4, Fig. 6a and Fig. 6b, auxiliary jig 44 is arranged in contact with welded material in the center of the first butt-welding position of the welded material sheets. Auxiliary jig 44 is made of solid metal. As shown in Figs. 6a and 6b, auxiliary jig 44 in shape of cylinder is inserted inside of working table 1 so that the height of the protrusion of auxiliary jig 44 protruding from the surface of working table 1 is 0.3mm. The protrusion that protrudes from the surface of the working table as mentioned above is used to prevent welded material sheets from sliding on top of each other. Khi welded material sheets are installed, the protrusion and setting plate 42 and guiding pins 34 create a combination at the same time to help the installation of welding material sheets to be as accurate as possible. According to an embodiment, auxiliary jig 44 is made of copper alloy, preferably copper-molybdenum alloy. In addition, clamping device of the present invention further includes setting plate 23, when the device operating, setting plate 23 is inserted via adjusting gap and welding gap for adjusting the postion of butt-welding of the two welded material sheets.

Futhermore, the invention provides a method of fixing welded material sheets using clamping device as described above, including steps: passing setting plate 23 through the gap of lower jig 43 in the upward direction; placing the first welded material sheet 21 in the direction perpendicular to setting plate 23 so that one side of the welded material sheet comes in contact with setting plate 23 at the postion of butt-welding; controlling one of clamps of second pair of clamps to move down to clamp the first welded material sheet 21 with working table 1 ; pull out setting plate 23; placing planar sheet 24 on the first welded material sheet so that it covers the welding position; placing the second welded material sheet 22 in horizontal direction and under planar sheet 24 so that one side of the welded material sheet in contact with the one side of the first welded material sheet 21 at butt-welding position; controlling the other clamp of second pair of clamps to move down to clamp the second welded material sheet 22 vol working table 1 ; removing planar sheet 24 from welded material sheets; inserting the upper jig on welded material sheets; controlling the first pair of clamps to come to working position; moving working table 1 in the upward direction so that the first pair of clamps in contact with upper jig 41 and providing pressing force to clamp upper jig 41 with welded material sheets with working table 1.

According to an embodiment, the method of fixing welded material sheets of the present invention further includes adjusting the pair of locating pins movable along the width of the welded material sheets to keep the welded material from being deformed after welding.

For fixing welded material sheet, the method of the present invention further includes a step for auxiliary clamping member 53 clamping upper jig 41 with welded material sheets by inserting welded material sheets under auxiliary clamping member 53, then inserting the upper jig jig 41 under auxiliary clamping member 53.

In addition, the invention provides method of arc welding for very thin sheet using clamping device and a method of fixing welded material, including steps: passing setting plate 23 through the gap of lower jig 43 in the upward direction; placing the first welded material sheet 21 in the direction perpendicular to setting plate 23 so that one side of the welded material sheet comes in contact with setting plate 23 at the postion of butt-welding; controlling one of clamps of second pair of clamps to move down to clamp the first welded material sheet 21 vdi working table 1 ; pull out setting plate 23 ; placing a planar sheet 24 on the first welded material sheet so that it covers the welding position; placing the second welded material sheet 22 in horizontal direction and under planar sheet 24 so that one side of the welded material sheet in contact with the one side of the first welded material sheet 21 at butt-welding position; controlling the other clamp of second pair of clamps to move down to clamp the second welded material sheet 22 vdi working table 1; removing planar sheet 24 from the welded material sheets; inserting upper jig 41 on the welded material sheets; controlling the first pair of clamps to come to working position; moving working table 1 in the upward direction so that the first pair of clamps in contact with upper jig 41 and providing pressing force to clamp upper jig 41 with welded material sheets with working table 1; controlling welding torch 6 into the working position; adjusting and determining arc length; placing auxiliry j ig 44 in contact with the first butt-welding position of the welded material sheets; controlling the welding torch 6 to discharge arc on the surface of auxiliary jig 44 prior to the welding torch 6 move the full length of butt welding of the welded material sheets.

According to another embodiment, method of arc welding thin and very thin sheet further includes adjusting the pair of locating pins movable along the width of the welded material sheets to keep the welded material from being deformed after welding.

According to further embodiment, the method of arc welding thin and very thin sheet further includes a step for auxiliary clamping member 53 clamping upper jig 41 with welded material sheets by inserting welded material sheets under auxiliary clamping member 53, then inserting the upper jig jig 41 under auxiliary clamping member 53.

Method of arc welding is described in details as follows. As shown in Fig. 2, for adjusting welded material sheet to the center of welding gap of lower jig 43, setting plate 23 is passed through adjusting gap and welding gap of lower jig, then the first welded material sheet 21 is brought into contact with setting plate 23. Controlling first clamp 521 of second pair of clamps on the same side as the first welded material sheet 21 to move down to clamp the welded material sheet with working table 1. After fixing the first welded material sheet 21, pull out setting plate 23 through adjusting gap, the second welded material sheet 22 is brought into the position of butt-welding to contact the first welded material sheet 21 so that the two sheets are coplanar by placing planar sheet 24 on the two sheets. Planar sheet 24 prevents the second welded material sheet 22 from sliding on the surface of the first welded material sheet 21. Controlling second clamp 522 of second pair of clamps to clamp the second welded material sheet 22 with working table 1. Then removing planar sheet 24 from welding system.

According to an embodiment of the invention, when welded material sheet with thickness more than or equal to 0,06mm, the present invention provides to use upper jig 41 as shown in Fig.7a, upper jig 41 is inserted to clamping position by the guiding of locating- guiding pins 32 which are provided on working table 1 in the input of inserting direction of upper jig 41, at the same time when installed into the system, upper jig 41 is located by pair of locating pins 24 which are inside openings 531 of auxiliary clamping member 53. Pair of locating pins 24 engages with positioning recesses 411 at the end along the width of upper jig 41 nay, upper jig 41 is inserted under auxiliary clamping member 53.

According to another of embodiment of the invention, when welded material sheet with thickness less than 0,06mm, the present invention provides the using of upper jig 42 as shown in Fig.7b, when inserting, upper jig 42 is brought from an elevated position and then gently engages the two ridges-groove inside the pins that holds the welded material sheet. The upper end of clamping portion for welded material is in direct contact with the cylindrical edge of auxiliary jig 44. In this embodiment, clamping portion for welded materials 421 of upper jig 42 is located between the two U-sides of auxiliary clamping member 53. This ensures that the welded material installed is not displaced. Thus, it ensures a welding process with higher accuracy and stability.

Depending on the thickness of the welded material sheet, the invention includes embodiments for selecting a jig assembly with a suitable welding gap.

According to an embodiment of the invention, with the thickness is from 0,03mm to 0,05mm the gap width of jig assembly is 0,4 mm. According to another of embodiment of the invention, with thickness is greater than 0,05mm and less than or equal to 0,07mm the gap width of jig assembly is 0,5 mm.

According to another of embodiment of the invention, with thickness is greater than 0,07mm and less than or equal to 0, 12mm, the gap width of jig assembly is 1,0 mm.

According to another of embodiment of the invention, with thickness is greater than 0,12mm and less than or equal to 0,175mm, the gap width of jig assembly is 1,5 mm.

According to another of embodiment of the invention, with thickness is greater than 0,175mm and less than 0,4mm, the gap width of jig assembly is 2,0 mm.

According to another of further embodiment of the invention, with thickness is greater than or equal to 0,4mm and less than or equal to 0,8mm, the gap width of jig assembly is 4,0 mm.

Following the above steps, cluster including the clamps of the first pair of clamps move from the inner of welding system goes to the place where the welded material sheets in standby state. System of four pneumatic cylinders at the four comers under working table 1 pushes working table 1 upward so that the lower end of first pair of clamps in contact with upper jig and clamp the entire upper jig- welded material-lower jig with working table 1. Then welding torch 6 goes out from welding system to the working position. The system that automatically adjusts the arc length will now work to adjust and determine the exact arc length to be adjusted. Then welding torch 6 discharges arc on auxiliary jig 44 and starts the welding process. After the welding process is finished, welding torch 6 comes back inside of the system, four cylinders release clamping, two cylinders controlling second pair of clamps release clamping as well, upper jig comes back the initial position to finish the welding process.

According to traditional welding methods, the thinner the welded material sheet, the smaller the welding current should be and the welding speed should be controlled accordingly. However, a distinctive and excellent features of the method of arc welding of the present invention compared to traditional methods is when welding thin and very thin sheets, the invention uses high welding current so that it is stable and easy to weld. Because the control of the amount of heat supplied to the welding bath is mainly by the gap of the jig assembly, the welding current and welding speed in the welding method using the jig assembly of the present invention are often pushed higher than in the traditional methods, but still ensure the penetration depth, stability and weld width is highly stable.

At the end of the welding plate when the arc is turned off, in present welding equipment/technology, it is common to control the arc heat source at this time, the time from when the current decreases from a stable value to the minimum value is usually considered and controlled at the same time as the stopping motion of the welding torch or welded material sheets. In case of welded material sheets is thick, doing so is perfectly fine and reasonable. However, in case of thin and very thin sheets, this often occurs defects such as too large size for the weld at the end position and more seriously, the burnt-through of welded material sheet due to the accumulation of arc energy at the end of welding when the welding torch stops moving and the welding current decreases to its lowest value requiring a certain small amount of time. In order to solve this problem, the invention has developed to meet this requirement which is to reduce the current and turn off the arc about 2mm before the end position of the weld while the welding torch or welded material sheet is still move at a steady speed. Thus the invention achieves the desired result.

From the combination of all solutions and technological factors as mentioned above, the welding system using the method of arc welding of the present invention has improved the welding efficiency up to 6000mm/min, while the method of arc welding is normally lOOOmm/min.

As shown in Table 1 and Table 2, the comparison between some typical welding cases with using clamping device and welding method of the present invention and without using clamping device and welding method of the present invention. Thus, the present invention demonstrates excellence compared to traditional methods. Specifically, Fig. 8b shows the phenomenon of warping, deformation and defects at the postion of butt-welding when not using clamping device and welding method of the present invention, Fig. 8a shows a high quality and stable weld when applying the invention.

Table 1. Assessment of weld result when applying the invention (see Fig. 8a) Table 2. Assessment of weld result when not applying the invention (see Fig. 8b)

LIST OF REFERENCE SIGNS

Working table: 1;

Welding torch: 6;

Guiding grooves (of the upper jig 42): 12;

The first welded material sheet: 21

The second welded material sheet: 22;

Setting plate: 23;

Planar sheet: 24

Pair of locating pins (for upper jig 41): 31 ;

The guiding of locating-guiding pins (for upper jig 41): 32;

Pins: 33;

Guiding pins 34 (when inserting the first welded material sheet 21);

Lower jig: 43;

Auxiliary jig: 44;

Auxiliary clamping member:53

Positioning recesses : 411 ; Openings (of upper jig 41 according embodiment 1): 412;

Clamping portion for welded materials (of upper jig 41 according to embodiment 2): 4;

Guiding ledges (of upper jig 41 according to embodiment 2):422

The first clamp of the first pair of clamps: 511

The second clamp of the first pair of clamps:512

The first clamp of the second pair of clamps: 521

The second clamp of the second pair of clamps: 522

Openings (of auxiliary clamping member): 531

Bolts: 5121

Elastic member: 5122

Pressure block: 5123

V-shaped bar V: 5124