Abstract:
A securement member for securing a contact tip to a welding torch assembly is provided. A channel extends axially therethrough and has an internal shoulder that extends into this channel. This internal shoulder abuts against a shoulder on the contact tip, capturing the contact tip between the shoulder and a seating surface on the diffuser and securing the contact tip in the torch assembly. The contact tip is securely seated without threading engagement, facilitating quick release and installation. The exemplary securement member couples to the diffuser such that the egress of fluid from the diffuser is blocked when used for gasless welding. This blocking allows a user to leave the diffuser secured to the welding torch when a gasless electrode is in use.

Description:
BACKGROUND 
     The present invention relates generally to a tip assembly for a welding torch and, particularly, to a tip assembly for a wire feed welding system. 
     A common metal welding technique employs the heat generated by electrical arcing to transition a workpiece to a molten state, followed by addition of metal from a wire or electrode. One technique that employs this arcing principle is wire-feed welding. At its essence, wire-feed welding involves routing welding current from a power source into an electrode that is brought into close proximity with the workpiece. When the electrode is sufficiently close to the work piece, current arcs from the electrode to the workpiece, completing a circuit and generating sufficient heat to melt and weld the workpiece. Often, the electrode is consumed and becomes part of the weld itself. Thus, new wire electrode is advanced, continuously replacing the consumed electrode and maintaining the welding arc. If the welding device is properly adjusted, the wire-feed advancement and arcing cycle progresses smoothly, providing a good weld. One common type of wire-feed welding is metal inert gas or “MIG” welding. 
     In typical wire-feed systems, wire electrode is directed through a welding cable, into a torch assembly, and, lastly, into a contact tip housed within the nozzle assembly. Electrical current is routed from the cable to the wire electrode through the contact tip. When a trigger on the welding torch is operated, wire electrode is advanced toward the contact tip, at which point current is conducted from the contact tip into the egressing electrode. 
     Because of its proximity to the weld location, a contact tip is exposed to weld splatter and relatively high-levels of heat. Accordingly, contact tips require more frequent maintenance or replacement than other components of the welding system. To facilitate quick replacement of contact tips, present assemblies include certain “threadless” contact tip assemblies, in which the contact tip is not threaded with respect to the remainder of the torch assembly. 
     Unfortunately, there are a number of problems associated with existing threadless contact tip designs. As one example, the structures for binding the contact tip in the welding torch can impart bending stresses on the contact tip. As another concern, 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 highly desireable 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. 
     Furthermore, to prevent the ingress of impurities into the molten weld, a flow a shielding material is typically provided to the weld location when certain types of wire electrode are employed. By way of example, inert shielding gas is routed from a gas source, through a welding cable and welding torch, into a gas-diffuser that delivers the gas to the weld location via a nozzle. Welding systems that employ such shielding materials are often referred to in the industry as gas metal arc welding (GMAW) systems, or MIG systems, as mentioned above. 
     However, there are certain other types of wire electrodes that are employed without a shielding gas. Accordingly, when employing such “gasless” electrodes, the gas routed into the welding cable is blocked from egressing to the environment. In the past, this meant replacing the components at the terminal end of the welding torch with those that prevent the egress of gas. For example, when using gasless wire electrodes, the diffuser is replaced with a component or components that seat the contact tip, prevent the egress of gas from the cable, and electrically insulate a user from the operating current in the contact tip. 
     Unfortunately, when a welder desires to use both types of electrode, transitioning between these terminal components can be a time consuming task. Moreover, existing arrangements accommodating the different electrode systems generally require an operator to maintain a relatively large inventory of parts, thus increasing the costs of operation. 
     Therefore, there exists a need for improved contact tip assemblies for welding devices, particularly for facilitating the transition between gas shielded and gasless welding. 
     BRIEF DESCRIPTION 
     In accordance with certain embodiments, the present invention provides a securement member for securing a contact tip to a welding torch assembly. The exemplary securement member has a channel extending axially therethrough, and has an internal shoulder that extending into this channel. This internal shoulder abuts against a shoulder on the contact tip, capturing the contact tip between the shoulder and a seating surface on a diffuser, securing the contact tip in the torch assembly. The contact tip may thereby be securely seated without threading, facilitating quick release and installation. Moreover, the exemplary securement member couples to the diffuser such that the egress of fluid from the diffuser is blocked. This blocking allows a user to leave the diffuser secured to the welding torch when a gasless electrode is in use. 
     In accordance with certain other embodiments, the present invention provides a family of securement members for securing a contact tip with respect to a welding torch assembly. Each exemplary securement member is configured to engage a diffuser of the welding torch. However, one of the securement members is configured to direct fluids egressing from the diffuser toward a weld location, while the other blocks the egress of fluid from the diffuser. This interchangeability allows the for using essentially the same welding torch assembly for a gas-shielded wire electrode and a gasless wire electrode, leading to cost and time savings. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a diagrammatic representation of a welding system, in accordance with an embodiment of the present invention; 
         FIG. 2  is a diagrammatic representation of a welding torch assembly for use with the system of  FIG. 1 , in accordance with an embodiment of the present invention; 
         FIG. 3  is an exploded view of an exemplary contact tip securement assembly for the torch assembly shown in  FIG. 2 ; 
         FIG. 4A  is a cross-sectional representation taken along line  4 - 4  of  FIG. 2  of a contact tip securement assembly for a shielded wire electrode; 
         FIG. 4B  is a cross-section representation taken along line  4 - 4  of  FIG. 2  of a contact tip securement assembly for a gasless wire electrode; and 
         FIG. 5  is a perspective, exploded view of a securement member for the assembly, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As discussed in detail below, embodiments of the present invention provide a securement member for securing a contact tip with respect to a welding torch assembly. Advantageously, the securement member captures a contact tip to secure it with respect to torch assembly and, moreover, blocks the egress of shielding material from a diffuser to which the securement member is coupled. Accordingly, a welding torch assembly can be quickly adapted for use with a wire electrode that benefits from a shielding material or for use with a gasless wire electrode that does not employ a shielding material. 
       FIG. 1  illustrates an exemplary wire-feed welding system  10  that incorporates such a securement member. Prior to continuing, however, it is worth noting that the following discussion merely relates to exemplary embodiments of the present technique. As such, the appended claims should not be viewed as limited to those embodiments described herein. 
     The exemplary welding system  10  includes a welding torch  12  that defines the location of the welding operation with respect to a workpiece  14 . Placement of the welding torch  12  at a location proximate to the workpiece  14  allows electrical current, which is provided by a power source  16  and routed to the welding torch  12  via a welding cable  18 , to arc from the welding torch  12  to the workpiece  14 . In summary, this arcing completes an electrical circuit from the power source  16 , to the welding torch  12  via the welding cable  18 , to a wire electrode, to the workpiece  14 , and, at its conclusion, back to the power source  16 , generally to ground. This arcing generates a relatively large amount of heat causing the workpiece  14  and/or filler metal to transition to a molten state, facilitating the weld. 
     To produce electrical arcing, the exemplary system  10  includes a wire-feeder  20  that provides a consumable wire electrode to the welding cable  18  and, in turn, to the welding torch  12 . This wire-electrode can be of various types, including traditional wire electrode or gasless wire electrode. As discussed further below, the welding torch  12  conducts electrical current to the wire electrode via a contact tip  20  located in a neck assembly  22  and supported by securement member  24 , leading to arcing between the egressing wire electrode and the workpiece  14 . 
     To shield the weld area from contaminants during welding, to enhance arc performance, and to improve the resulting weld, the exemplary system  10  includes a shielding material source  26  that feeds an inert, shielding gas to the welding torch  12  via the welding cable  18 . It is worth noting, however, that a variety of shielding materials, including various fluids and particulate solids, may be employed to protect the weld location. However, certain wire electrodes, such as gasless wire electrodes, do not greatly benefit from a shielding material. Accordingly, when such wire electrodes are employed with the present system, a securement member  24  better suited for such electrodes is employed, as discussed further below. 
     Referring to  FIG. 2 , advancement of these welding resources (e.g., welding current, wire electrode, and shielding gas) is effectuated by actuation of a trigger  28  secured to a handle  30 . By depressing the trigger  28 , a switch (not shown) disposed within the trigger is closed, causing the transmission of an electrical signal that commands delivery of the welding resources into the welding cable  18 . 
     Turning to  FIG. 3  and  FIGS. 4A and 4B , these figures illustrate a family of securement members  24 A and  24 B. Each securement member is adapted to capture and secure a welding contact tip  20  with respect to a seating location  32  on a diffuser  34 . In the exemplary welding system, the diffuser  34  operates to receive the welding current, wire electrode, and shielding material. During operation, radially extending channels  36  in the diffuser  34  operate to direct shielding gas around an egressing wire electrode. Additionally, the conical shape of the seating location  32  corresponds with the conical shape of the contact tip end  38 , thus facilitating centering and engagement of the contact tip  20  with respect to the diffuser  34  and the welding torch as a whole. Such conically shaped diffusers and contact tips are described in U.S. Pat. No. 6,852,950 that issued on Feb. 8, 2005, and U.S. patent application Ser. No. 10/215,811 that was filed on Aug. 9, 2002, both of which are incorporated herein by reference. 
     To seat the contact tip  20  with respect to the diffuser  34 , the exemplary contact tip  20  includes a shoulder  40  that extends radially beyond the surface of the remainder of the contact tip  20 . This shoulder  40  is configured to interact with an internal shoulder of either of the securement members  24 A or  24 B. As illustrated, each securement member  24 A and  24 B includes a central channel  42 A and  42 B, respectively, extending axially therethrough. Additionally, each exemplary securement member  24 A and  24 B includes an internal shoulder  44 A and  44 B, respectively, that extends into the respective central channel  42 A and  42 B. 
       FIGS. 4A and 4B , which are discussed further below, better illustrate the capture of a contact tip  20  between the securement member  24  and the diffuser  34  when the given securement member is threaded onto the diffuser  34 . As generally illustrated in  FIG. 3 , the respective internal shoulders  44 A and  44 B are located at a corresponding axial location from an inboard end of the given securement member  24 A and  24 B. Thus, the securement members  24 A and  24 B can be interchangeably used with same contact tip  20  and the same diffuser  34 . In fact, the securement members  24 A and  24 B each have similar counterbores  46 A and  46 B to help seat the securement members  24 A and  24 B with the same diffuser  34 . Moreover, threads  48 A and  48 B on each securement member  24 A and  24 B (see  FIGS. 4A and 4B ) are matched, facilitating threaded engagement of the securement members  24 A and  24 B with the same diffuser  34 . Of course, other mechanisms for mechanically coupling the securement members  24 A and  24 B with the diffuser  34 , such as clamps or friction fit arrangements, may be envisaged. In summary, the securement members  24 A and  24 B define a family of securement members that can be interchangeably used with the same diffuser and torch assembly, the interchangeable nature facilitating operation of the welding system  10  with shielded wire electrodes and gasless wire electrodes. 
     Although there are similarities between the securement members  24 A and  24 B, there are also a number of differences. For example, the larger diameter securement member  24 A is designed for use with a wire electrode that benefits from a shielding gas. Accordingly, when the contact tip  20  is captured between the conical seating surface  32  of the diffuser  34  and the internal shoulder  44 A of the securement member  24 A, a pathway is provided for guiding the shielding material toward the weld location. Specifically, with regard to securement member  24 A, gas is routed through the radially extending diffuser channels  36 , as represented by arrow  50 . This shielding material then enters an interstitial space  52  defined by the exterior of the diffuser  34  and the interior surface of the securement member  24 A, which defines the channel  42 A. It is the inclusion of the interstitial space  52  that at least partially results in the diameter of the exemplary securement member  24 A being slightly larger than exemplary securement member  24 B. The shielding material is routed axially though the interstitial space  52  and into axial ports  54  extending through the internal shoulder  44 A. Subsequently, the shielding material is routed toward the weld location by the interior surface of the securement member  24 A, at the conclusion of which the shielding materials egresses from the member  24 A, shielding the egressing wire electrode. As illustrated, arrows  56  represent the flow of shielding material axially through the channel  42 A of the securement member  24 A. 
     Along with shielding material, the diffuser  34  also facilitates the routing of electrical current to the contact tip  20  and, ultimately, to the egressing wire electrode. This transmission of current is facilitated by the fact that the exemplary diffuser  34  and the contact tip  20  are formed of a conductive material, such as copper. To insulate the current-carrying members of the assembly, the exemplary securement member  24 A includes an insulative layer  60  that insulates the exposed external surface of the securement member from the possibly electrically conductive internal surfaces of the securement member  24 A. 
     Securement member  24 B is more particularly designed for use with wire electrodes that do not greatly benefit from shielding material (i.e., gasless operation). As illustrated, the exemplary securement member  24 B has a interior channel  44 B region that matches closely the diameter of the diffuser  34  where the radial channels  36  are located. When the securement member  24 B is threaded onto the diffuser  34 , the internal surface  62  of the securement member  24 B blocks the egress of shielding material from the channels  36 . That is, the exemplary securement member  24 B does not present an interstitial space for the flow of shielding material, thus preventing the egress of this material. Moreover, the securement member  24 B protects the channels  36  from clogging weld splatter, for instance, when a gasless wire electrode is employed. Advantageously, the body  66  of the securement member  24 B is formed of an electrically insulative material, such as plastic, with low heat retention properties. Thus, the body  66  also serves as an electrical insulating member. 
       FIG. 5  illustrates the exemplary securement member  24 B of  FIG. 4B  in an exploded view. As illustrated, the exemplary securement member  24 B includes a body portion  66  that defines the external surface of the securement member  24 B as well as much of the channel  42 B. As discussed above, the exemplary body  66  is formed of an electrically insulative material, which, to allow easier user operation, may have low heat retention properties. The exemplary securement member  24 B also includes an insert member  70  that defines the internal shoulder  44 B. As illustrated, the insert member  70  is a hollow member that has an external surface with a plurality of ribs  72  extending axially thereon. These ribs  72  facilitate a good engagement of the insert member  70  with the body  66  when the insert member  70  is inserted into the body  66 . The ribs  72  may plastically deform the body  66 , thus well securing the insert member  70  with respect to the body  66 . The exemplary insert member  70  is formed of a durable material, such as metal, to provide for a more robust construction. 
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.