Patent Publication Number: US-2021187650-A1

Title: Stud welding gun

Description:
TECHNICAL FIELD 
     In general terms, the invention relates to a fastening system for welding a welding stud to a substrate in a welding direction. 
     PRIOR ART 
     There are numerous known devices and methods by which various studs are fastened to a substrate in different applications. For example, a stud is brought into contact with the substrate and an electric current is applied to it. For this purpose, the stud is held by an electrically conductive stud holder. 
     As soon as the electric current flows between the stud and the substrate, the stud is lifted off the substrate to form an arc. The energy that is released causes the material of the stud and the substrate to be partially liquefied. The electric current is then switched off and the stud is immersed in the liquefied material while this material cools down and becomes solid. The stud is then connected to the substrate in an integrally bonded manner. 
     In order to provide the necessary energy for liquefying the material of the stud and the substrate in a sufficiently short time, there are known devices that generate an electric current of a very high intensity and use a correspondingly rated electric cable to feed it to the stud. To avoid oxidizing of the liquefied material, it is known to surround the area of contact between the stud and the substrate with an inert gas. 
     In the case of applications in building construction or shipbuilding for example, threaded studs of various sizes to which an item is screwed are used in order to fasten the item to the substrate. Some parameters of the fastening method, such as for example the duration and electrical power of the electric current, are to be set by a user on the device and are to be adapted to the stud that is used. The user finally assesses the quality of the connection between the stud and the substrate by means of a visual inspection. The quality of the connection consequently also depends on the experience and capabilities of the user. While the stud is being placed against the substrate, the stud is not visible to the user. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a device and/or a method with which fastening of a stud to a substrate is made easier and/or improved. 
     This object is achieved in the case of a fastening system for welding a welding stud in a welding direction to a substrate, comprising a welding gun, which defines the welding direction, and the welding stud, wherein the welding gun has a holding device for holding the welding stud during a welding process and an outer contour, wherein the welding stud comprises a contact surface, which is provided for making contact with the substrate before and/or during the welding process, and wherein, starting from the contact surface, a tangent can be applied to the outer contour, which encloses an angle of less than 60°, preferably less than 45°, particularly preferably less than 30°, with the welding direction when the welding stud is held by the holding device and the contact surface is in contact with the substrate. The welding gun preferably has a housing, which defines the outer contour or part of the outer contour. 
     An advantageous embodiment is characterized in that the welding gun has a holding spring, which acts on the holding device, and a bearing element having a bearing surface, and in that the holding device together with the welding stud can be moved relative to the bearing element counter to the welding direction, against a spring force of the holding spring, until the contact surface of the welding stud and the bearing surface are arranged at the same height in the welding direction. 
     An advantageous embodiment is characterized in that the welding gun has a contact pressure element having a contact pressure surface and a contact pressure spring, which acts on the contact pressure element, and wherein the contact pressure element can be moved relative to the bearing element counter to the welding direction, against a spring force of the contact pressure spring, until the contact surface of the welding stud and the contact pressure surface are arranged at the same height in the welding direction. The contact pressure surface, as viewed in the welding direction, is preferably arranged between the contact surface and the bearing surface. 
     Another aspect of the application is characterized in that the bearing element is substantially closed in a circumferential direction in relation to the welding direction and has a curved outlet channel. The outlet channel preferably has multiple curves. 
    
    
     
       EXEMPLARY EMBODIMENTS 
       The invention will be explained in more detail below on the basis of exemplary embodiments with reference to the drawings. In the drawings: 
         FIG. 1  schematically shows a welding device, 
         FIG. 2  shows a welding assembly in a partial longitudinal sectional view, 
         FIG. 3  shows a welding assembly in a partial longitudinal sectional view, 
         FIG. 4  shows a fastening system, and 
         FIG. 5  shows a bearing element. 
     
    
    
     In  FIG. 1 , a welding device  10  for welding a welding stud  20  to a substrate  30  is schematically represented. A material of the welding stud  20  and a material of the substrate  30  are electrically conductive, in particular metallic. The welding device  10  comprises a welding gun  40  with a trigger switch  41 , formed as a pushbutton switch, a welding unit  50 , a first electric cable  61 , a second electric cable  62  with a connection terminal  63 , an electric supply cable  64 , formed for example as a power cable, an electrical communication line  65 , a gas reservoir  70 , formed as a gas cylinder, a tubular gas supply line  71  and a gas hose  72 . 
     The first cable  61  serves for supplying the welding stud  20  with electric current through the welding unit  50 . The second cable  62  serves for electrically connecting the substrate  30  to the welding unit  50  when the connection terminal  63  is clamped to the substrate  30 . When the welding stud  20  comes into contact with the substrate  30 , a circuit closes, so that welding current, for example in the form of direct current or alternating current, can be applied to the welding stud  20  by the welding unit  50 . For this purpose, the welding gun  40  comprises a welding-current contact element that is not shown in  FIG. 1 . The welding unit  50  comprises a device that is not shown for converting electric current from the supply cable  64  into welding current, which comprises for example an electrical capacitor, a thyristor, a bipolar transistor with an isolated gate electrode or other components from power electronics and also an associated control unit with a microprocessor, in order to provide the welding current at the desired voltage and current intensity. 
     The gas supply line  71  and the gas hose  72  serve for supplying a contact region between the welding stud  20  and the substrate  30  with an inert gas from the gas reservoir  70 , in order to protect the contact region from oxidation due to oxygen from a surrounding area during a welding operation. For controlling a gas flow to the contact region, the gas reservoir  70 , the gas supply line  71 , the welding unit  50 , the gas hose  72  or the welding gun  40  comprises a valve, in particular a controllable valve, that is not shown. 
     The welding unit  50  has an input device  51  with actuating elements  52  and also an output device  53  with a visual display element  54  and a wireless transmission unit. The input device  51  serves for inputting parameters of a welding method to be carried out with the welding device  10 , such as for example the electrical voltage, current intensity, power and time duration of the welding current, position and speed of the stud and so on, by a user of the welding device  10 . The output device  53  serves for outputting information to the user, such as for example information on parameters of the welding method, information on detected emissions of the welding method or other variables, information on a quality of the welding operation, information on measures for improving the welding operation, information on detected characteristics of the welding stud or information derived from the aforementioned variables, and/or recommendations or instructions for cleaning and/or maintaining the welding device  10 , in particular the welding gun  40 . 
     The communication line  65  serves for communication between the welding gun  40 , in particular a control device of the welding gun  40  that is not shown in  FIG. 1 , and the welding unit  50 , in particular the control unit and/or the input device  51  and/or the output device  53 . By means of this communication, for example, an exchange of information about the parameters of a welding operation is accomplished, in order for example to achieve or facilitate a synchronization of the welding current with a movement of the welding stud  20 . In the case of exemplary embodiments that are not shown, the communication between the welding gun and the welding unit takes place wirelessly, by radio or by means of the first electric cable, which carries the welding current. 
     The welding gun  40  has a housing  42  with an opening  46 , from which housing a handle  43  with the trigger switch  41  protrudes. The welding gun  40  also has a stud holder  44 , on which the welding stud  20  is held during a welding operation. For this purpose, the stud holder comprises for example two, three, four or more resilient arms that are not shown in detail, between which the welding stud  20  is inserted and held by means of a clamping fit. The welding gun  40  also has, for applying a welding current to the welding stud  20 , a welding-current contact element which is integrated in the stud holder  44 , for example in the form of one or more of the resilient arms. 
     The welding gun  40  also has a control device  99  for controlling the various components and devices of the welding gun and of the welding unit  50 . The control device  99  is intended for controlling one or more parameters of the welding operation. For this purpose, the control device  99  comprises various electronic components, such as for example one or more microprocessors, one or more temporary or permanent data memories, and the like. 
     The welding gun  40  also has a stud lifting device, which is formed as a first lifting magnet, which acts on the stud holder  44  with a force away from the opening  46  to the rear (upwardly in  FIG. 1 ) when the stud lifting device is activated. Via a signal line that is not shown, the control device  99  communicates with the stud lifting device in order to control the stud lifting device, in particular to activate and deactivate it. 
     The welding gun  40  also has a stud immersing device, formed as a spring element or as a second lifting magnet, which acts on the stud holder  44  forwardly with a force toward the opening  46  (downwardly in  FIG. 1 ) when the stud immersing device is activated. Via a signal line that is not shown, the control device  99  communicates with the stud immersing device in order to control the stud immersing device, in particular to activate and deactivate it. If the stud immersing device takes the form of a spring element, this spring element is preferably tensioned when the stud holder is moved by the stud lifting device to the rear, with the result that the spring element moves the stud holder forward as soon as the stud lifting device is deactivated. 
     In a welding process with the welding apparatus  10 , at first the substrate  30  and the stud  20  are provided. In a further step, information, for example about desired parameters of the following welding operation, are input by a user via the input device. In a further step, a welding current between the welding stud  20  and the substrate  30  is applied to the welding stud  20  by the welding unit  50  by means of the first cable  61  and the second cable  62 . In a further step, the welding stud  20  is lifted off the substrate by means of the stud lifting device while maintaining the welding current flowing between the welding stud  20  and the substrate  30 , with an arc being formed between the welding stud  20  and the substrate  30 . Particularly on account of the heat generated by the arc, a material of the welding stud  20  and/or of the substrate  30  is then partially liquefied. In a further step, the welding stud  20  is immersed by means of the stud immersing device in the liquefied material of the welding stud  20  or of the substrate  30 . The liquefied material of the welding stud  20  or of the substrate  30  then solidifies such that the welding stud  20  is connected to the substrate  30  in an integrally bonded manner. 
       FIG. 2  illustrates a welding assembly  200  with a welding stud  220  and a stud holder  244 . The welding stud  220  has a shank  240 , which defines a longitudinal direction  230  and which is provided with an attachment means  250  designed as an external thread, a welding region  260  at the end, which is provided for liquefaction during a welding process, and a holding means  270 , which is designed as a depression, preferably a groove, running around in a circle, and which is arranged between the welding region  260  and the attachment means  250  in the longitudinal direction  230 . The stud holder  244  has a holding device  280 , which is designed as a projection which runs around in a circle and with which the holding means  270  is in engagement in order to hold the welding stud  220  during a welding process, e.g. using the welding device  10  ( FIG. 1 ). 
     The stud holder  244  is part of a welding gun (not shown specifically) for welding the welding stud  220  to a substrate, which is of similar design to the welding gun  40  ( FIG. 1 ), for example. The holding device  280  is arranged at a front end of the welding gun, with the result that the welding stud  220  is moved forward toward the substrate when the stud holder  244  is moved forward by a stud immersing device, for example. Behind the holding device  280 , the welding gun, in particular the stud holder  244 , has a socket  290 , designed substantially as a cavity, for the attachment means  250  of the welding stud. 
     By means of this arrangement, on the one hand, the attachment means  250  is protected from damage by the holding device  280  and, on the other hand, it is ensured that the holding device  280  holds the welding stud in the desired position, irrespective of a length of the shank  240  thereof and/or of the attachment means  250 . Moreover, it is possible to use a single stud holder for welding studs with different attachment means, in particular attachment means of different sizes. 
       FIG. 3  illustrates a second welding assembly  300  having a second welding stud  320  and the stud holder  244  from  FIG. 2 . The second welding stud  320  likewise has a shank  340 , which defines a longitudinal direction  330  and which is provided with an attachment means  350  designed as an external thread, a welding region  360  at the end, which is provided for liquefaction during a welding process, and a second holding means  370 , which is designed as a recess that runs around in a circle, is arranged between the welding region  360  and the attachment means  350  in the longitudinal direction  330  and has the same shape and the same dimensions as the holding means  270  of the welding stud  220  shown in  FIG. 2 . 
     The attachment means  350  of welding stud  320  has a smaller diameter than the attachment means  250  of welding stud  220  and is therefore likewise received in the socket  290  when welding stud  350  is held by the holding device  280  in engagement with the holding means  370 . Welding stud  220  and the second welding stud  320  are thus part of a fastening system according to this application. Here, the welding region  260  of welding stud  220  is the same as the welding region  360  of the second welding stud  320  in shape and dimensions. This makes it possible to weld welding studs with different attachment means, in particular attachment means of different sizes, to the substrate using the same welding parameters, such as welding current intensity, electric voltage, welding current duration and the like. 
       FIG. 4  illustrates a fastening system  400  which is provided for welding a welding stud  420  to a substrate  430  in a welding direction  410 . In addition to the welding stud  420 , the fastening system  400  comprises a welding gun  440 , which defines the welding direction  430  and has a housing  450  and a handle  460 . The welding gun has a holding device  444 , which is designed as a stud holder and which has a stud socket (not shown specifically) for holding the welding stud  420  during a welding process, into which the welding stud  420  can be inserted and is preferably held with a clamping action. A contact surface  425  of the welding stud  420  makes contact with the substrate  430  before and/or during the welding process. Starting from the contact surface  425 , a tangent  460  can be applied to an outer contour of the welding gun  440 , which encloses an angle of 20° with the welding direction  410 . This enables a user of the fastening system  400  to clearly see the contact point of the welding stud  420  with the substrate  430 , at least until the contact surface  425  makes contact with the substrate  430 . 
     The welding gun  440  has a holding spring  470 , which acts on the holding device  444  in the welding direction  410 , and a bearing element  480  having a bearing surface  481  facing in the welding direction  410 . The holding device  444  together with the welding stud  420  can be moved relative to the bearing element  480  counter to the welding direction  410 , against a spring force of the holding spring  470 , by a contact pressure travel A until the contact surface  425  of the welding stud  420  and the bearing surface  481  are arranged at the same height in the welding direction  410 . The contact pressure travel A is the distance by which the welding gun  440  still has to be moved in the welding direction  410  from the time when the contact surface  425  makes contact with the substrate  430  before a welding process begins. 
     The welding gun has a contact pressure element  490 , which has a guide ring  491  surrounding the bearing element  480 , and two, three or more contact pressure arms  492 , each having a contact pressure surface  493 . The contact pressure arms  492  are connected rigidly to the guide ring  491 , which can be moved in the welding direction  410  and, during this process, is guided by the bearing element  480 . The welding gun furthermore has at least one contact pressure spring  495 , in the example under consideration two such springs, which subject the contact pressure element  490 , in the example under consideration the guide ring  491 , to a spring force in the welding direction  410 . 
     The contact pressure element  490  can be moved relative to the bearing element  480  against the welding direction  410 , counter to the spring force of the contact pressure springs  495 , until the contact surface  425  of the welding stud  420  and the contact pressure surfaces  493  are arranged at the same height in the welding direction  410 . The contact pressure surfaces  493 , as viewed in the welding direction  410 , are arranged between the contact surface  425  and the bearing surface  481 . This ensures that, during the placement of the fastening system  400  on the substrate  430 , the contact surface  425  of the welding stud  420  makes contact with the substrate  430  first, followed by the contact pressure surfaces  493  of the contact pressure element  490  and finally by the bearing surface  481  of the bearing element  480 . As soon as the bearing element  480  is resting on the substrate  430 , a user can initiate a welding process by means of a triggering element  498 . 
     The visibility of the welding stud  420  makes it easier for a user to place the contact surface  425  on the substrate  430  at the desired welding point or to correct the position of the contact surface  425  by means of the welding gun  440 , in particular the handle  460  thereof. Since the user can see between the contact pressure arms  492 , the tangent decisive for the viewing angle, can be applied to the bearing element  480  or, as in the example under consideration, to the guide ring  491 , starting from the contact surface  425 . As soon as the contact pressure surfaces  493  are resting on the substrate  430 , the welding gun  440  is supported in the desired position, in particular against slipping. For this purpose, the contact pressure surfaces  493  are preferably composed of an elastomer. 
     The contact pressure springs  495  serve to reset the contact pressure element  490  after the welding gun  440  has been raised from the substrate  430 , e.g. after a welding process. The holding spring  470  serves to reset the holding device  444  after the welding gun  440  has been raised from the substrate and/or during the welding process as an immersion device, which makes the welding stud previously moved away from the substrate by a lifting device  499  designed as a lifting magnet dip into a molten weld pool. 
       FIG. 5  illustrates a bearing element  500  with a bearing surface  581  for bearing on a substrate  530 . The bearing element  500  is part of a welding gun (not shown further) for welding a welding stud  520  to the substrate  530  in a welding direction  510 . The bearing element  500  is substantially closed in a circumferential direction in relation to the welding direction  510  and has an outlet channel  540 , e.g. for a shielding gas flowing around the welding stud  520 .  FIG. 5  shows that the outlet channel  540  has two bends, thus reducing, in particular avoiding, a risk of escaping heat radiation or escaping hot material. The outlet channel  540  has a supporting foot  550  for support on the substrate  530 , which comprises an elastomer or is composed of an elastomer, for example. 
     The invention has been described on the basis of examples of a system for fastening a first item to a second item and of a welding gun. In this case, the features of the described embodiments can also be combined as desired with one another within a single fastening device. It should be noted that the device according to the invention is also suitable for other purposes.