Abstract:
A welding gun adapted to secure a contact tip within the welding gun without threading the contact tip and without the use of tools. The contact tip may be adapted to abut a surface of a first member disposed within the welding gun. The surface may be a surface of a gas diffuser. The surface may be adapted to abut the contact tip. The contact tip also may be adapted for abutment with a second member to urge the contact tip toward the first member. The second member may be a portion of a nozzle adapted to abut the contact tip to urge the contact tip toward the surface of the first member. A method of assembling a welding gun also is provided. The method may include disposing a contact tip between a first and a second member and capturing the contact tip between the first and second members.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/159,154, filed on Jan. 20, 2014, which is a continuation of U.S. patent application Ser. No. 11/971,743, filed on Jan. 9, 2008, and issued as U.S. Pat. No. 8,633,422 on Jan. 21, 2014, which is a continuation of U.S. patent application Ser. No. 11/514,416, filed on Sep. 1, 2006, and issued as U.S. Pat. No. 7,576,300 on Aug. 18, 2009, which is a divisional of U.S. patent application Ser. No. 10/215,811, filed on Aug. 9, 2002, and issued as U.S. Pat. No. 7,105,775 on Sep. 12, 2006, each of which is herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention relates generally to welding systems, and particularly to a wire-feed welding gun having a tip to guide wire through a nozzle of a welding gun. 
         [0003]    Welding is a method of joining, or separating, metal objects. Arc welding is a common type of welding. An arc welding system typically is comprised of a power supply coupled by an electrical cable to a welding gun housing an electrode. A ground cable is used to connect the metal object to the power supply. When the electrode is placed against the metal object, the electrode in the welding handle completes an electrical circuit between the power supply and the metal object, allowing electrical current to flow through the electrode and metal object. The electrical current produces an arc between the electrode and the metal object. The heat of the electric arc melts the metal object in the region surrounding the electric arc. A filler material may be added to the molten metal. For example, a wire may be placed against the molten portion of the object, melting the wire and allowing the molten wire to merge with the molten object. Once the electrode is drawn away from the metal object, the circuit is broken and the molten mass begins to cool and solidify, forming a weld. 
         [0004]    MIG (Metal Inert Gas) welding is one type of arc welding. MIG welding is also referred to as “wire-feed” or GMAW (Gas Metal Arc Welding). In MIG welding, a metal wire is used as the electrode. The wire is shielded by an inert gas and the metal wire acts as the filler for the weld. The inert gas is used to shield the molten metal from outside contaminants and gases that may react with the molten metal. Non-inert gases, such as CO2, may also be used in MIG welding. 
         [0005]    The wire and gas are coupled through a cable to a welding gun. A typical welding gun used in MIG welding and similar welding systems has a handle and a neck that extends from the handle. The wire and gas are directed through the neck towards a workpiece. The neck typically has a nozzle assembly that is secured to the neck to direct the flow of wire and gas towards the workpiece. The wire is directed through a contact tip housed within the nozzle assembly. The electrical current is coupled from the cable to the wire through the contact tip. In addition, the end of the nozzle assembly typically has a cone-shape to taper the flow of gas from the welding gun. A typical welding gun has a switch, or trigger, that is coupled to the wire feeder. When the trigger is operated, wire is fed through the tip and gas is directed through the nozzle towards a workpiece. 
         [0006]    Contact tips require frequent replacement during operation of the welding gun. Many contact tips are threaded into the welding gun. However, threadless contact tip designs also have been used. For example, threadless contact tip designs having a cam surface have been used. The cam surface is adapted to bind the contact tip against a stationary protrusion when the contact tip is rotated. 
         [0007]    Unfortunately, there are a number of problems associated with existing threadless contact tip designs. For example, the process of binding the contact tip against the protrusion produces a bending stress in the contact tip. In addition, variations in the distance between the contact tip and the exterior portion of the nozzle, known as the tip-nozzle recess, occur with existing threadless contact tip designs. A consistent tip-recess distance is critical in certain welding applications, especially robotic welding systems. In addition, molten spatter from the weld may deposit on the end of the nozzle, eventually requiring replacement of the nozzle. Consequently, nozzles having a nozzle body and a removable threaded end section have been developed. However, weld spatter may contaminate the threads or the threads may experience galling, requiring a tool, such as a wrench, to remove the threaded end section from the nozzle body. 
         [0008]    There exists then a need for a welding gun that utilizes a threadless contact tip design. Additionally, there is a need for a welding gun that enables a contact tip to be installed and removed without the use of tools. Furthermore, there exists then a need for a welding gun that utilizes a removable nozzle end section that may be secured and removed without threads or the use of tools. Finally, there exists a need for a nozzle assembly having a threadless contact tip design that produces a consistent tip-recess distance. 
       BRIEF DESCRIPTION 
       [0009]    The present technique provides a welding gun adapted to secure a contact tip within a nozzle assembly without threading the contact tip and without the use of tools. The contact tip may be captured by abutment between two members. The two members may be a gas diffuser and a portion of a nozzle. 
         [0010]    In some embodiments of the present technique, a gas diffuser that is adapted to receive the contact tip in abutment is provided. The gas diffuser may have a tapered surface adapted for sealing engagement with a tapered surface of the contact tip. Furthermore, in some embodiments of the present technique, a nozzle adapted to abut a portion of the contact tip. The nozzle may comprise an insert disposed within a nozzle body. The nozzle may also be adapted for threaded engagement with the gas diffuser. 
         [0011]    Another aspect of the present technique is a method of assembling a nozzle assembly of a welding gun. The method may comprise disposing a contact tip between two members of the nozzle assembly. The method may also comprise securing the nozzle to the gas diffuser to capture the contact tip between the gas diffuser and the nozzle. 
     
    
     
       DRAWINGS 
         [0012]    The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
           [0013]      FIG. 1  is a diagram of a MIG welding system, according to an exemplary embodiment of the present technique; 
           [0014]      FIG. 2  is a front elevational view of a MIG welding gun, according to an exemplary embodiment of the present technique; 
           [0015]      FIG. 3  is an exploded view of the nozzle assembly of the MIG welding gun of  FIG. 2 ; 
           [0016]      FIGS. 4 and 5  are cross-sectional views of the nozzle assembly, illustrating the assembly of the nozzle assembly, according to an exemplary embodiment of the present technique; 
           [0017]      FIG. 6  is an end view of the nozzle assembly of  FIG. 4 ; 
           [0018]      FIG. 7  is a cross-sectional view of an alternate embodiment of a nozzle assembly, according to an exemplary embodiment of the present technique; 
           [0019]      FIG. 8  is an exploded view of the alternate embodiment of a nozzle assembly; and 
           [0020]      FIG. 9  is an embodiment of a retaining ring for securing the detachable cone to the nozzle, according to an exemplary embodiment of the present technique. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Referring generally to  FIG. 1 , an exemplary metal inert gas (“MIG”) welding system  20  is illustrated. However, the present technique may be used in other wire feed welding systems, such as submerged arc welding. The illustrated MIG welding system  20  comprises a power source/wire feeder  22 , a gas cylinder  24  containing a gas  25 , a spool  26  of electrode wire  27 , a welding gun  28 , a welding cable  30 , a work clamp  34 , and a ground cable  32 . In the illustrated embodiment, the gas  25  and wire  27  are routed from the power source/wire feeder  22  to the welding cable  30 . The welding cable  30 , in turn, routes the gas  25  and the wire  27  to the welding gun  28 . The power source/wire feeder  22  also may be comprised of a separate power source and a separate wire feeder. 
         [0022]    The welding cable  30  also has conductors (not shown) for conveying large amounts of electric current from the power source/wire feeder  22  to the welding gun  28 . The power source/wire feeder  22  is operable to control the feeding of wire  27  to the welding gun  28 . In addition, the power source/wire feeder  22  also may be used to control the flow of gas  25  to the welding gun  28 . To assemble the system, a ground cable  32  having a clamp  34  is connected to the power source/wire feeder  22 . The clamp  34  is clamped onto a workpiece  36  to electrically couple the workpiece  36  to the power source/wire feeder  22 . The work clamp  34  and ground cable  32  electrically couple the power source/feeder  22  to the workpiece  36 . Additionally, the wire  27  within the MIG welding cable  30  may be electrically coupled to the power source/wire feeder  22 . 
         [0023]    The welding gun  28  is used to direct the wire  27  towards the workpiece  36 . When the wire is touched to the workpiece  36 , an electrical circuit between the workpiece  36  and power source/wire feeder  22  is completed. Electric current flows from the power source  22  through the welding cable  30 , the electrode wire  27 , the workpiece  36 , the work clamp  34 , and the ground cable  32  back to the power source  22 . An arc is produced between the electrode wire  27  and the workpiece  36 . The electric arc melts the workpiece  36  in a region surrounding the arc, forming a weld puddle. The heat of the arc melts the wire  27  along with the workpiece  36 , enabling the electrode wire  27  to act as a filler material for the weld puddle. The inert gas  25  forms a shield that prevents harmful chemical reactions from occurring at the weld puddle. When the arc is removed, the weld puddle solidifies, forming the weld. 
         [0024]    Referring generally to  FIGS. 1 and 2 , the welding gun  28  comprises a handle  38 , a trigger  40 , a neck  42 , and a nozzle assembly  44 . The neck  42  is secured to the handle  38  by a locking nut  46 . The MIG welding cable  30  also has an electrical cable (not shown) that is electrically coupleable to the trigger  40 . The trigger  40  enables a user to control the supply of electrode wire  27  and power from the power source/feeder  22 . A number of events occur when the trigger  40  is operated. One event is that the power source/wire feeder  22  draws in wire  27  from the wire spool  26  and feeds it though the MIG welding cable  30  to the welding gun  28 . Also, electric power from the power source/feeder  22  is supplied to the wire  27 . The welding gun may be adapted to enable the flow of gas  25  from the gas cylinder  24  to be controlled by the trigger  40 . The wire  27  and gas  25  are then fed through the neck assembly  42  towards the workpiece  36 . The nozzle assembly  44  directs the wire  27  and gas  25  towards the target  36 . When the trigger  40  is released, the wire  27  and electric current are no longer fed to the welding gun  28 . 
         [0025]    Referring generally to  FIG. 3 , the nozzle assembly  44  comprises a gas diffuser  48 , a tip  50 , and a nozzle  52 . Gas  25  flows from the welding cable  30  and the welding gun  28  to the gas diffuser  48 . The gas diffuser  48  is used to establish desired flow characteristics of the gas  25 . The nozzle  52  is used to direct the gas  25  from the gas diffuser  48  towards the workpiece  36 . The tip  50  is used to direct the wire  27  from the welding gun  28  and to conduct electric current from the welding cable  30  to the electrode wire  27 . The large amounts of electric current drawn from a typical power source/wire feeder  22  during welding could damage the electrode wire  27  if the electric current was conducted through the entire length of the electrode wire. Therefore, the welding cable  30 , rather than the electrode wire, is used to conduct most, if not all, of the electric current from the power source/wire feeder  22  to the welding gun  28 . The contact tip  50  is used to transfer the electric current flowing through the welding cable  30  to the electrode wire  27 . The contact tip  50  is electrically coupled to the welding cable  30  by the neck  42  and the gas diffuser  48 . 
         [0026]    In the illustrated embodiment, the contact tip  50  is secured within the welding gun  28  by abutment with the gas diffuser  48  and nozzle  52 , rather than by threading the tip  50  into the gas diffuser  48 . The contact tip  50  has a channel  54  that extends through the length of the contact tip  50  that is used to direct the electrode wire  27  through the contact tip  50 . In addition, the channel  54  is used to bring the electrode wire  27  into contact with the contact tip  50  so that electric current may be conducted from the contact tip  50  to the electrode wire  27 . In the illustrated embodiment, the channel  54  defines an axis extending linearly through the contact tip  50 , the gas diffuser, and the nozzle  52 . In addition, in this embodiment, the contact tip  50  is symmetrical about the axis. 
         [0027]    As best illustrated in  FIG. 4 , the contact tip  50  has an end surface  56  that is adapted to abut a seating surface  58  of the gas diffuser  48  and a shoulder  60  that extends around the contact tip  50  for engagement by the nozzle  52 . In the illustrated embodiment, the end surface  56  is uniform around the contact tip  50 . Preferably, the end surface  56  of the contact tip  50  and the seating surface  58  of the gas diffuser  48  are adapted for sealing engagement to prevent gas from escaping between the gas diffuser  48  and the contact tip  50 . In the illustrated embodiment, the end surface  56  and the seating surface  58  are tapered to have a generally conical shape. However, the end surface  56  and the seating surface  58  may be curved or otherwise configured for mutual abutment and/or for sealing engagement. In the illustrated embodiment, the shoulder  60  protrudes from the contact tip  50  and is adapted to be abutted. In this embodiment, the shoulder  60  is uniform around the contact tip  50 . 
         [0028]    In the illustrated embodiment, the nozzle  52  and the contact tip  50  are secured to the welding gun when the nozzle  52  is secured to the gas diffuser  48 . The nozzle  52  has a nozzle body  62 , a nozzle insert  64 , and a layer of insulation material  66  disposed between the nozzle insert  64  and the nozzle body  62 . In the illustrated embodiment, the nozzle body  62  has a conical portion  68  for directing the flow of gas  25  towards the workpiece  36 . The nozzle insert  64  has a threaded portion  70  that is adapted for threaded engagement with a threaded portion  72  of the gas diffuser  48 . In the illustrated embodiment, the nozzle insert  64  has an annular portion  74  that is adapted for engagement with the shoulder  60  of the contact tip  50 . The annular portion  74  has an opening  75  therethrough for enabling the contact tip  50  to extend through the nozzle insert  64 . The annular portion  74  may be a separate removable securing member, such as a retaining ring or snap ring. 
         [0029]    Preferably, the shoulder  60  extends around the entire circumference of the contact tip  50  and is transverse to the axis of the contact tip  50  so as to be in facing relationship with the annular portion of the nozzle insert  64 . The contact tip may be adapted with other types of protrusion, other than the shoulder  60  illustrated in the figures. For example, the contact tip may be adapted with a plurality of separate protrusions spaced at various locations around the circumference of the contact tip. In addition, a securing member, such as a retaining ring or snap ring, may be secured to the tip to act as a protrusion. 
         [0030]    The contact tip  50  is disposed between the gas diffuser  48  and the nozzle  52  prior to securing the nozzle  52  to the gas diffuser  48 . Because the illustrated embodiment is uniform about the axis of the contact tip  50 , the contact tip  50  may be disposed between the gas diffuser  48  and nozzle  52  in any rotational orientation. As illustrated, there is a gap  76  between the annular portion  74  and the shoulder  60  of the contact tip  50 . However, the contact tip  50  may be disposed through the nozzle insert  64  prior to disposing the contact tip  50  against the gas diffuser  48 . Consequently, the gap  76  may be between the gas diffuser  48  and the contact tip  50 , rather than between the contact tip  50  and the nozzle insert  64 . 
         [0031]    As best illustrated in  FIG. 5 , the nozzle  52  is drawn towards the gas diffuser  48  as the nozzle  52  is threaded onto the gas diffuser  48 , as represented by the arrow  77 . The annular portion  74  of the nozzle insert  64  abuts the shoulder  60  of the contact tip  50  and urges, or holds, the contact tip  50  axially against the gas diffuser  48 , bringing the end surface  56  of the contact tip  50  into abutment with the seating surface  58  of the gas diffuser  48  and thereby capturing the contact tip  50  between the gas diffuser  48  and the nozzle  52 . Preferably the annular portion  74  of the nozzle insert  64  extends around the inner portion of the nozzle  52 . 
         [0032]    Referring generally to  FIGS. 4-6 , gas  25  enters the gas diffuser  48  from the neck  42  via an entrance chamber  78 . In the illustrated embodiment, the gas diffuser has a plurality of exit holes  79  for the gas  25  to exit the gas diffuser  48 . In addition, the annular portion  74  of the nozzle  52  has a plurality of gas delivery holes  80 . The gas delivery holes may be round, or slots. The gas delivery holes  80  enable gas  25  to pass through the annular portion  74  and enter the conical portion  68  of the nozzle  52 . Contrary to previous nozzle embodiments, the gas delivery holes  80  of the illustrated embodiment extend in parallel to the contact tip  50 , thus improving the flow characteristics of the gas  25  flowing from the nozzle  52 . 
         [0033]    Referring generally to  FIGS. 7-9 , an alternative embodiment of a nozzle  82  is illustrated. In this embodiment, a detachable cone  84  is used. The detachable cone  84  is adapted to be secured to and removed from a nozzle body  86  without the use of a tool. In the illustrated embodiment, the detachable cone  84  comprises a conical portion  88 , a cylindrical portion  90 , and an annular ring portion  92 . The cylindrical portion  90  of the detachable cone  84  is disposed within the interior of the nozzle body  86 . The annular ring  92  limits the travel of the detachable cone  84  into the nozzle body  86 . In the illustrated embodiment, the cylindrical portion  90  has an external groove  94  and the nozzle body  86  has a corresponding internal groove  96 . However, the cylindrical portion  90  and the nozzle body  86  may be adapted conversely, i.e., the cylindrical portion  90  may have an internal groove  96  and the nozzle body  86  may have the external groove  94 . In addition, in this embodiment, a spring retaining ring  98  is disposed within the external groove  94  of the detachable cone  84  to secure the cone  84  to the nozzle body  86 . However, other devices, such as a snap ring, may be used to secure the detachable cone  84  to the nozzle body  86 . 
         [0034]    In the illustrated embodiment, the cylindrical portion  90  of the detachable cone  84  is pushed into the nozzle body  86  to secure the cone  84  to the nozzle body  86 . During installation of the cone  84 , the ring  98  is compressed as the cylindrical portion  90  of the cone  84  is inserted into the nozzle body  86 . A user may compress the retaining ring  98  or the ring  98  may be compressed by the nozzle body  86 . When the retaining ring  98  reaches the internal groove  96  in the nozzle body  86 , the retaining ring  98  expands outward into the internal groove  96 . In the illustrated embodiment, retaining ring  98  occupies a portion of the internal groove  94  of the cone  84  and the internal groove  96  of the nozzle body  86 , thereby obstructing displacement of the cone  84  and nozzle body  86  and securing the cone  84  to the nozzle body  86 . 
         [0035]    In the illustrated embodiment, the retaining ring  98  is strong enough to secure the cone  84  to the nozzle body  86 , but may be overcome by a user. To remove the detachable cone  84  from the nozzle body  86 , a user grabs the cone  84  and pulls the cone  84  away from the nozzle body  88 . The annular ring portion  92  assists a user in gripping the detachable cone  84 . A new detachable cone  84  and/or retaining ring  98  may then be secured to the nozzle body  86 . Thus, the detachable cone  84  may be secured to the nozzle  52  and removed without the use of tools. 
         [0036]    The above embodiments provide a contact tip and a detachable cone that are threadless. In addition, because the contact tip is secured by threading the relatively large diameter nozzle to the gas diffuser, rather than the contact tip, no tools are needed to secure the contact tip to or remove the contact tip from the nozzle assembly. In addition, the cone may be secured to and removed from the nozzle without the use of tools. Furthermore, as best illustrated in  FIGS. 5 and 7 , the embodiments provided above enable the tip-nozzle recess  100  between the end  102  of the tip  50  and the exit opening  104  of the conical portion  88  of the nozzle  52  to be consistent as contact tips and conical portions of the nozzle are replaced. 
         [0037]    While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown in the drawings and have been described in detail herein by way of example only. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.