Abstract:
A system and method of feeding wire is provided using at least one roller which is biased towards the wire. The at least one roller is permitted to deflect a limited amount during the wire feeding operation. The roller is permitted to deflect 50% or less than the wire diameter during feeding to prevent tangling.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Devices, systems, and methods consistent with the invention relate to an improved wire drive design for a wire feeder. 
     2. Description of the Related Art 
     During welding, such as metal inert gas (MIG) welding, a welding electrode is typically fed to a welding torch by a wire feeder. The wire feeder usually has two or more rollers which are in frictional contact with the electrode and cause the electrode to be advanced to the welding torch. In a two roller configuration, one roller is fixed positionally while the other is biased towards the electrode to provide the frictional contact with the electrode. As the electrode is delivered to the torch there can be unexpected increases in downstream frictional forces and resistance in the feeding of the wire to the torch. These increases in resistance can cause the electrode to buckle at the rollers and this buckling can overcome the biasing force applied to the rollers, ultimately resulting in the electrode becoming tangled at the rollers. This is often referred to as “birdnesting.” Therefore, it is desirable to provide a wire feeder and roller configuration which inhibits or prevents this from occurring. 
     BRIEF SUMMARY OF THE INVENTION 
     An exemplary embodiment of the present invention is a wire feeder having at least one roller to be placed in frictional contact with a wire passing through the wire feeder. The roller is free to move in at least one direction normal to an axis of rotation of the roller. The wire feeder also has a supporting member supporting the roller, and a restricting portion which engages with at least one of the roller or the supporting member to limit the movement of the roller to a maximum deflection distance of G, where G is 50% or less of the diameter of the wire. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects of the invention will be more apparent by describing in detail exemplary embodiments of the invention with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates a diagrammatical representation of a wire feeder incorporating an exemplary embodiment of the present invention; 
         FIG. 2  illustrates a diagrammatical representation of an exemplary embodiment of the present invention; 
         FIG. 3  illustrates a diagrammatical representation of a further exemplary embodiment of the present invention; 
         FIG. 4  illustrates a diagrammatical representation of an additional exemplary embodiment of the present invention, and 
         FIG. 5  illustrates a diagrammatical representation of a wire feeding system in accordance with an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments of the invention will now be described below by reference to the attached Figures. The described exemplary embodiments are intended to assist the understanding of the invention, and are not intended to limit the scope of the invention in any way. Like reference numerals refer to like elements throughout. 
       FIG. 1  is a representative diagrammatical representation of wire feeder  100  incorporating aspects of the present invention. Specifically, the wire feeder  100  has a housing  101 , of any suitable construction, control electronics  103  and a wire roller module  200 . The control electronics  103  of the wire feeder  100  are electronics used to control the operation and functionality of the wire feeder  100  and a drive motor (not shown) within the wire feeder  100  which drives at least one, if not all, of the rollers  107 . Because these electronics are known by those of skill in the art, the electronics will not discussed in detail herein. 
     Within the wire feeder  100  is a wire roller module  200  (also shown in  FIG. 2 ). The module  200  has a support structure  105  upon which at least two wire rollers  107  are mounted. Although the depicted module only depicts two rollers  107 , the present invention is not limited to such a configuration, and can be used in embodiments using as few as one roller, or more than two rollers. For example, embodiments of the present invention can be used with a four roller configuration. In the exemplary embodiment shown in  FIGS. 1 and 2 , the bottom roller  107  is fixedly mounted to the support structure  105  with its shaft  109 . Thus, the roller  107  is free to rotate (or can be driven by a motor) its vertical and horizontal positioning relative to the support structure is fixed. However, the upper roller  107  is mounted to a pivot arm  111  which is also secured to the support structure  105  with a pivot shaft  113 . Thus, the pivot arm  111  can freely rotate about the shaft  113  allowing the upper roller  107  to be moved away from the electrode E. A biasing member  115 , which can be a spring or other biasing type device, provides a biasing force onto the pivot arm  111  and/or the upper roller  107  so as to apply a squeezing force onto the wire. This squeezing force increases the friction between the rollers  107  and the electrode E to aid in driving the electrode E to a welding torch. 
     Also coupled to the support  105  is a restricting member  117  which has a restricting portion  119 . The restricting member  117  is pivotally secured to the support  105  with the pivot  121 . With this structure the restricting portion  119  engages with the pivot arm  111  to restrict the movement of the pivot arm during the wire feeding operation. As explained previously, during operation it is possible that resistance in the feeding of the electrode E can cause the compression forces in the electrode E to exceed its columnar strength and cause buckling. This buckling causes the electrode E to exceed the bias strength of the biasing member  115  and move the upper roller  107  far enough away from the lower roller  107  so that the electrode will tangle within the wire feeder  100 . However, in this exemplary embodiment of the present invention the restraining portion  119  engages with the pivot arm  111  and prevents the pivot arm  111 , and thus the upper roller  107 , from moving too far away from the lower roller  107 . This restriction aids in preventing the above described tangling from occurring. Specifically, by restraining the upper roller  107 , embodiments of the present invention provide additional support to the electrode E to inhibit buckling. 
     As shown in  FIG. 2 , embodiments of the present invention have a gap G between the restraining portion  119  and the pivot arm  111  during normal operation. This gap G is to prevent the restraining portion  119  and member  117  from exerting excessive force onto the electrode E during operation—to avoid crushing the electrode E. During normal operation the biasing member  115  provides sufficient force for proper operation of the rollers. However, if the electrode E begins to buckle and push against the upper roller  107 , the pivot arm  111  will only deflect for the distance of the gap G and will prevent the buckling and tangling described above. 
     In an exemplary embodiment of the present invention, the gap G is 50% or less than the diameter of the electrode E. In a further exemplary embodiment of the present invention, the gap G is 5% or less than the diameter of the electrode. This ensures that the upper roller  107  has sufficient deflection for normal operation but will not deflect so as to permit the electrode E to buckle. 
     During operation, when an electrode E is to be inserted into the wire feeder  100  the restraining member  117  is pivoted away from the pivot arm  111  so that the upper roller  107  can be moved sufficiently to allow the electrode E to be properly positioned between the rollers  107 . The biasing member  115  will maintain contact between the rollers  107  and the electrode E during operation. Once the electrode E is positioned the restraining member  117  is positioned such that the restraining portion  119  is positioned to create the gap G with the pivot arm  111 . This positioning is maintained during normal operation of the wire feeder  100  so that tangling of the electrode E is reduced or eliminated. 
     In another exemplary embodiment, the restraining member  119  and/or the restraining portion  119  can have a flexible spacer (not shown in  FIG. 2 ) which bridges the gap G when the restraining member  119  is moved into its operational position. In this embodiment the spacer can provide additional biasing force, but is flexible to allow for at least some deflection of the upper roller  107  during operation. 
     In another exemplary embodiment of the present invention, the module  200  is easily removable and replaceable as an entire unit. In many existing wire feeders when the rollers are worn or need to be replaced because different electrode diameters are being used, it is necessary to remove and replace the rollers, which can be a cumbersome and time consuming process. However, with the modular aspects of the present invention, the module  200 , including its components, such as the support  105 , rollers  107 , etc. can be replaced as a single unit easily. Thus, when the rollers  107  need to be replaced, for whatever reason, the module  200  can be easily replaced. 
     In a further exemplary embodiment, the module  200  contains an identifier  201 . The identifier  201  identifies the module  200  to the wire feeder assembly  100 , so that wire feeder  100  recognizes the electrode sizing of the rollers  107 . For example, if the wire feeder  100  is to be use for a 0.045 inch electrode, the identifier  201  would identify to the wire feeder  100  that the module  200  is for 0.045 inch wire. In an exemplary embodiment, the wire feeder  100  and its control electronics can display information related to the module  200  on a display screen (not shown) of the wire feeder  100 . For example, the display screen can show the electrode diameter that the module  200  was designed for. Further, the control electronics can also display an error code if an incorrect module  200  is installed. 
     For example, if an operator desires to weld with a 0.045 inch electrode the operator inputs this information into the wire feeder controls (not shown). If the wrong module  200  is installed in the wire feeder  100  then an error or warning message will be displayed indicating to the operator that the wrong module  200  is installed. Similarly, if during a welding operation the module  200  needs to be replaced (because of wear) an error message would be shown if the wrong module  200  was placed in the wire feeder. In alternative embodiment, the control electronics would prevent operation of the wire feeder  100  until the proper module  200  was installed. 
     The identifier  201  can be any identifying mechanism which identifies characteristics of the module  200 , such as electrode diameter, to the wire feeder  100 . For example, the identifier  201  can be an RFID type tag, a bar code tag, or any other type of identifying component. The use of this technology is well known and understood and will not be discussed in detail herein. 
     In another exemplary embodiment, the module  200  contains a shut-off switch  203  which is coupled to the wire feeder  100  control electronics. The shut-off switch  203  can be a pressure switch or an electronic switch, which is activated if the arm  117  is moved past a threshold point. Specifically, if, during operation, the arm  117  is not in a proper position or is inadvertently moved during operation the switch  203  would shut-off operation of the wire feeder  100 . 
       FIG. 3  depicts a further exemplary embodiment of a module  300  in accordance with the present invention. In this exemplary embodiment, at least one of the rollers  107  is mounted to a shaft  109  which passes through an elongated or slotted groove  123  in the support  105  (or similar structure). During operation a biasing member  115 , also coupled to the shaft  109 , biases the upper roller  107  so as to provide the proper amount of frictional force to the electrode E for operation. However, because of the elongated hole  123  the upper roller  107  travel vertically a distance G. As explained previously, the distance G can be 50% or less of the diameter of the electrode, and in another embodiment is 5% or less of the diameter of the electrode E. Similar to the discussion above, the elongated hole  123  prevents the upper roller  107  from traveling too far, vertically, if an electrode E tangle occurs. In another exemplary embodiment of the present invention, the bottom roller  107  is also engaged with an elongated hole  123 . In such an embodiment, the distance G is divided the two rollers, such that each of the rollers  107  can move to accommodate the electrode E and any operational anomalies, but the rollers  107  would not move away from each other by more than the distance G. 
       FIG. 4  depicts yet another exemplary embodiment of the present invention. In this embodiment the shaft  109  of the upper roller  107  is secured to the structure  105  with a flexible o-ring or grommet  125 . The grommet  125  is made from a stiff but flexible material, such as rubber, for example, which is capable of deforming under a load. Similar to the embodiments described above, during operation the grommet  125  can compress, but no more than the gap distance G discussed above. In an exemplary embodiment of the present invention, the grommet  125 , shaft  109 , structure  105  and rollers  107  are designed such that there is at least some biasing of the rollers  107  against the electrode E during normal operation so as to provide the necessary frictional forces. Further, if a tangle occurs, or some other anomaly, the roller  107  can deflect the distance G because of the flexibility of the grommet. However, the grommet  125 , roller  107 , shaft  109  and support  105  are designed such that the maximum displacement of the roller  107  is the gap distance G. Further, as discussed above with respect to  FIG. 3 , in this embodiment, both rollers  107  can use a grommet  125  to provide the desired bias and displacement. 
     It is noted that the present invention is not limited to the specific embodiments described above and shown in  FIGS. 1 through 4 . Specifically, other types of components and configurations can be used to provide the desired compressive force between the rollers (to effect proper driving of the electrode E) and limit the movement of the rollers as described above. For example, V-springs, helical springs, canted coil springs, or other types of biasing components, can be used. 
     In a further exemplary embodiment, shown in  FIG. 5 , a torque sensor  301 , or similar device, is coupled to the drive motor  303  to measure the torque being applied by the motor  303  to the roller  107 . The torque sensor  301  is also coupled to the control electronics of the wire feeder  100  such that when the sensed torque on the motor  303  driving the roller  107  exceeds a threshold amount the control electronics stops operation of the wire feeder  100  to prevent tangling. When an electrode E begins to tangle in the wire feeder  100  there can be a rapid increase in the torque load in the motor  303  through the rollers  107 , which are trying to drive the electrode E. The control electronics recognizes this increase in the torque load as the beginning of a tangle and executes an emergency stop of the wire feeder  100 . In other embodiments a warning signal can be displayed on a display panel. Further, the shut down can be also communicated to other systems, such as a power supply, computer, etc. which is coupled to the wire feeder  100 , such as in a welding network or robotic welding cell. In other exemplary embodiments, the control electronics of the wire feeder  100  monitors the current and/or power of the motor  303  vie the use of a current and/or power sensor device or circuit  305  to determine of a tangle is occurring. Specifically, similar to the discussion above, as a tangle occurs the current and power in the motor  303  increases. Thus, the control electronics monitors the motor current and/or power and if either or both exceed a threshold, indicating the beginning of a tangle, then the control electronics signals the motor  303  to stop operation and/or provide a warning or error signal to an operator, for example through a display panel. The present invention is not limited by the circuitry, electronics and systems employed to monitor the motor torque, current and/or power as any know sensing mechanism or circuitry can be employed to provide the control electronics the desired feedback. Moreover, the torque, current and/or power threshold level employed by the control electronics to determine if a tangle has occurred can be either preset into the control electronics, or can be a function of the module  200  employed in the wire feeder. 
     Specifically, as described above the module  200  can have an identifier  201 . In an exemplary embodiment, when the identifier  201  identifies the module  200  to the control electronics of the wire feeder  100  the control electronics changes the threshold level of the torque, current and/or power based on the module  200 . For example, it is contemplated that the threshold level changes for different wire diameters, and the control electronics appropriately selects the desired threshold level based on the diameter of the electrode to be used in the welding operation. The control electronics can receive the electrode diameter information from either the user entry of the information, or from the identifier  201  associated with the module  200 . 
     It is noted that the present invention is not limited by the type of welding electrode to be utilized or the type of welding operation, but can be used in many different types of welding operations with many different types of welding electrodes and electrode combinations. Further, embodiments of the present invention are not limited to the welding industry, but can be used with any wire feeding operation where tangling during feeding can be an issue. 
     While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims.