Patent Publication Number: US-2023132563-A1

Title: Battery-powered electronic resistance welding machine for sheet metal repair

Description:
This invention is generally concerned with a battery-powered electronic resistance welding machine for sheet metal repair, particularly suitable for vehicle bodywork repair applications. 
     Multi-tool stations are still known today for repairs on steel and aluminium vehicle bodywork, using various tools and traction accessories on large dents in bonnets, doors, wheel boxes, etc., and on circumscribed areas (e.g. for hail dents). 
     This method involves, in particular, a first phase of paint stripping and cleaning the uneven area, the tacking or welding of a washer to couple the mass grip, tracing the location on the bodywork where a series of slotted washers will be aligned and preparing an electrode welding gun in sequence a series of slotted washers that are positioned aligned. 
     A lever is then inserted into the aligned slots of each washer and, in the case of repair on large areas or areas where distributed traction is required, a traction bar is used, equipped with articulated support feet and suction cups for the stable anchorage to the bodywork without the need for additional fastenings, which is placed at the uneven area and fixed to the traction bar using special hooks. 
     The uneven part is restored by successive adjustments and traction of the bar. 
     In case of repair on limited areas, where a distributed traction is required and where the positioning of the traction bar could be problematic, successive tacking and traction operations are normally carried out using special extractor kits (electrodes, multi-hooks, corrugated wires, etc.) and/or using a blowback mass, which is moved by hand, for the traction movements in order to raise and shape the sheet metal. 
     As said, the traditional multi-tool stations mentioned above comprise generators for capacitive discharge welding of pins and washers, at least one multi-function inductor for localised and controlled sheet metal heating and a series of specific accessories, such as hooks, pins, washers, etc., for sheet metal traction. 
     All the equipment is therefore extremely complex and cumbersome and above all, requires extensive and significant wiring, placed between the generator, powered by the mains power supply, and the welding gun, considering that this wiring must be prepared in order to allow the passage of extremely high intensity currents (such as those used in these applications, which are variable between 1,000 and 2,000 amperes). 
     The aim of the present invention is therefore to remedy the technical drawbacks indicated above and in particular, the main aim of the present invention is to create a battery-powered electronic resistance welding machine for sheet metal repair, in particular vehicle sheet metal, having relatively small dimensions and which at the same time, allows the welding and traction operations necessary for such repair to be carried out efficiently and rapidly. 
     Another aim of the present invention is to create an electronic resistance welding machine for sheet metal repair that is more manageable, reliable, safe, economical, battery-powered and with reduced weight and dimensions compared to the known art. 
     These and other aims which will emerge more fully below are achieved by an electronic welding machine for the repair of sheet metal, in particular of vehicles, according to the attached claim 1; further detailed features of the welding machine according to the invention are indicated in the following dependent claims. 
     Advantageously, the electronic welding machine, which is the object of the invention, comprises a machine unit inside which all the components necessary for operation are housed. 
     In practice, it is a rechargeable battery-powered tool, such as a lithium-polymer accumulator or other type of accumulator, which does not use mains power and which includes a microprocessor electronic circuit adapted to allow the user to select the energy and tacking power in order to weld the electrode point of slots, washers and/or pins used to repair the aforementioned sheet metal. 
     A digital panel, installed on board the machine, allows a user to automatically adjust the parameters according to the tool chosen and the material to be welded. 
    
    
     
       Further features and advantages of the present invention will emerge more fully from the description of a preferred, but non-limiting, embodiment of the electronic resistance welding machine for sheet metal repair according to the present invention, illustrated by way of non-limiting example in the accompanying drawings, in which: 
         FIG.  1    shows a prospective view of a non-limiting example embodiment of the electronic resistance welding machine for sheet metal repair according to the present invention; 
         FIG.  2    shows a circuit operation block diagram of the electronic resistance welding machine in  FIG.  1   , according to the present invention. With reference to the mentioned  FIGS.  1 ,  2   , the electronic welding machine, which is particularly useful for carrying out repairs on metal vehicle bodywork, as well as for extracting and flattening dents in sheet metal, comprises a machine unit  10  with a handle  12  near which at least one button  13  is positioned to activate the machine. 
     
    
    
     Inside the machine unit  10 , which includes the handle  12 , there is a rechargeable battery  11 , for example a lithium-polymer accumulator, which allows the machine to be powered without the need to use the mains power supply; the rechargeable battery  11  can also be of the extractable type. 
     The machine unit  10  comprises:
     at least one first rod  14 , constrained, in a sliding fashion (according to the direction of the arrows F in  FIG.  2   ), with one end and by means of a first elastic element  19 , to a terminal  15  of the machine unit  10 , which has, at the opposite free end, a ground electrode or tip  16  that comes into contact with a metal portion or sheet metal to create the electrical circuit,   and at least one second rod  17 , which is also constrained in a sliding fashion (according to the direction of the arrows F in  FIG.  2   ), with one end and by means of a second elastic element  19 , to the terminal  15  of the machine unit  10 , which has, at the opposite free end, a welding electrode or tip  18  which can be replaced if necessary in favour of fixing the repair accessories (eyelets, hooks, etc.).   

     The elastic elements  19  are compression loaded and are adapted to counteract the sliding of the rods  14 ,  17  towards the inside of the machine unit  10 . 
     The ground electrode  16  is preferably made of copper, while the welding electrode  18  preferably comprises a tip made of copper, iron or a slot holder accessory. 
     The ground electrodes or tips  16  and welding electrodes or tips  18  are constrained to the relative rods  14  and  17  in a removable or permanent fashion. 
     The ground rods  14  and welding rods  17  are both directly connected to a microprocessor electronic circuit  20 , which in turn is directly connected to the rechargeable battery  11  of the machine for its power supply. 
     Moreover, the microprocessor electronic circuit  20  is directly connected to an electronic device  21  for controlling the welding power and energy; the electronic control device  21  is associated with a digital panel  22 , installed on board the machine and available to a user to select the amount of energy and/or power, the duration of welding and the thickness of the sheet metal to be treated. 
     The ground rods  14  and welding rods  17  are partly housed in corresponding housings or guides of the terminal  15  and are arranged parallel to each other and facing each other at a certain distance. Furthermore, as mentioned, they slide elastically and axially in their respective housings, compared to the machine unit  10 , as well as independently of each other. 
     In order to insulate the ground rod  14  from the machine unit  10 , the aforementioned ground rod  14  slides in an insulating pipe with high thermal resistance, inserted in the relevant housing or guide, and in addition, the ground electrode or tip  16  is housed inside an insulating flange. 
     The welding rod  17  has preferably a polygonal section and is inserted in a guide bush, with a housing having shape corresponding to the section of the rod  17 , with anti-rotation function to carry out the traction operations and at the end of the cycle, detach the welding tip  18  from the metal portion on which it is working. 
     According to the present invention, it is also possible to directly exploit the blowback mass of the machine unit  10 , which also includes the weight of the rechargeable batteries  11  on board the machine, by elastically acting on the rods  14 ,  17  in order to shape the sheet metal and/or carry out the necessary traction operations. 
     In particular, according to the present invention, the traction operation can be carried out directly with the tip  18 , which, thanks to the use of the springs  19 , constitutes the traction element of the sheet metal during the repair. 
     When the springs  19  are loaded, they provide the necessary push to increase the effect of the blowback mass represented by the entire tool complete with rechargeable battery  11 . 
     Finally, the absence of long power supply cables is a considerable advantage from the point of view of energy efficiency, compared to similar products of the traditional type, since the current of 1,000 to 2,000 amperes flows from the battery  11  through the control device  21  only on the terminals of the rods  14 ,  17 , as well as on the tips  16 ,  18  and on the tip of the metal portion to be melted, which is the welding resistance of the electrical circuit in  FIG.  2   ; such a short current path, without long wiring, consequently results in a truly minimal dissipation. 
     Further innovative and advantageous features of the invention are the fact that it is possible to use only one tool (the welding gun) rather than a tack welding machine wired with an external generator (thus drastically reducing the overall dimensions and structural and functional complexity of the equipment) and to carry out up to 750 welding points and more (in any case sufficient to carry out the most common types of repairs on bodywork sheet metal) independently, by simply using the built-in rechargeable battery  11  and without the need to connect the machine to the mains power supply. 
     The characteristics of the electronic resistance welding machine for sheet metal repair, which is the object of this invention, are clear from the description provided, as are its advantages. 
     They are represented in particular by:
     control of the resistance tacking (welding) power;   use of a self-powered microprocessor electronic circuit to control the functions of the welding machine;   use of rechargeable batteries;   use of cushioned rods that favour the tacking and drawing action of the sheet metal;   the machine does not need a power supply;   operating autonomy of up to 750 welding spots and more;   drastic reduction of overall dimensions, compared to the known art;   lightweight structure (less than 3 kg), compared to the known art and by virtue of the advantages achieved;   energy efficiency due to the absence of long power cables.   

     The invention as it is conceived is susceptible to numerous modifications and variants, all falling within the scope of protection of the appended claims. 
     Moreover, all the details can be replaced by other technically-equivalent elements; in practice, the materials used, as well as the shapes and dimensions, can be varied according to the contingent requirements and the prior art. 
     Where the constructional and technical characteristics mentioned in the following claims are followed by signs or reference numbers, the signs or reference numbers have been used only with the aim of increasing the intelligibility of the claims themselves and, consequently, they do not constitute in any way a limitation to the interpretation of each element identified, purely by way of example, by the signs or reference numerals.