Patent Publication Number: US-11654502-B2

Title: Method of rotating a welding torch during operation

Description:
RELATED APPLICATIONS 
     This application claims the benefit of the filing date of U.S. Utility patent application Ser. No. 15/813,932, filed on Nov. 15, 2017, entitled “Reduced Friction Rotating Coupler Assembly and quick disconnect for use with Welding devises” by Juan Solis, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     A. Field of Invention 
     The present invention is in the technical field of Welding devices. More particularly, the present invention is in the technical field of gas metal arc welding (GMAW) and metal inert gas (MIG) welding torches. 
     B. Description of Related Art 
     Prior art welding torches used in welding metallic materials together, such as MIG welding torches, have generally utilized a fixed or rotating conductor tube or goose neck mechanically and electrically connected to a unicable which generally supplies power, welding or shielding gas, and filler wire to the MIG torch. The unicable generally comprises a core tube for passage of the filler wire, welding/shielding gas, and liner, copper cabling for conducting the electrical current to the torch, and shielded lead wires for controlling the operation of the torch. The unicable is permanently attached to an end of a typical MIG torch, generally via a crimp or other permanent mechanical attachment. In MIG torches with a fixed goose neck the unicable will undergo bending and flexing as the MIG torch is moved and rotated. This bending and flexing cyclically stresses the unicable and after a finite number of cycles the unicable will fail. In human operated torches the time needed to reach the cycle life of an unicable is variable depending on the method of use by the operator. In robot operated torches the life a welding torch generally tends to be longer than a human operated torch due to the reduced range of movement experienced by the unicable in typical robotic welding applications. The service life of a MIG unicalble used in a robotic application can be extended by the use of a MIG torch that is rotatable versus a fixed torch, resulting in increased productivity due to the increase in the amount of time before the unicable requires replacement or service and the reduced movement required to perform certain operations. Rotating torches that can rotate a full 360 degrees or any amount less than 360 degrees, fully rotatable welding torches are more desirable than rotatable welding torches that are limited to ˜270 degrees or less. Prior attempts at a rotating welding torch have used various methods to accomplish rotation. Such as U.S. Pat. No. 7,665,996 by Jaeger et al. (hereinafter Jaeger) which uses a rotating power connector on the goose neck mating end of the unicable. 
     As seen in FIG. 2 of Jaeger, this design uses a connector pin 34 and rotating stud 40 that are in direct contact with each other inside the rotating power connector assembly. The rotating stud 40 has a bearing 62 at approximately half the axial length of the rotating stud 40 to facilitate rotation. The Jaeger design relies on multiple current paths to ensure an electrical connection between the unicable and the goose neck and uses a secondary contact ring 52 to accomplish this task. The secondary contact ring 52 of Jaeger is designed to act as a wedge between the rotating stud 40 and the inner housing 50. The electrical contact faces of the rotating stud 40 and connector pin 34 are horizontal faces that are pressed against one another by a spring (biasing member 58) that also pushes or wedges the contact ring 52 between the tapered surface 60 of the inner housing 50 and contact portions 54 of the contact ring 52. This wedging produces friction between the contact ring 52 and rotating stud 40 that increases the amount of torque required to turn the connector pin 34 about the rotating stud 40. As result, the amount of breakaway torque required to spin the connector pin 34 is ˜0.32624 N-m (2.89 inch-lbs), which is a significant amount if attempted by hand. The frictional force between the connector pin 34 and rotating stud 40 causes mechanical wear on the contact surfaces of the Jaeger invention which will eventually lead to the failure of the welding torch in accordance with Jaeger. As can be seen in FIG. 4 of Jaeger, the invention of Jaeger is permanently attached to the unicable 18 via an unlabeled mechanical crimp seen below the location of the label “18” near the proximal end of the figure. 
     Another side effect of the significant breakaway torque required by Jaeger and other prior art rotatable welding torches is the torsion and or minor rotation of the unicable at the mechanical attachment to the prior art torch. This results in visually observable movement, of the unicable relative to the robot arm, at the mechanical attachment to the prior art welding torch. The movement is not as significant as the movement that occurs in fixed head welding torches but does result in reduced service life of the unicable. 
     Typical power supplies for MIG welding torches can output between 0 and 800 amps. The unicable and all portions of the MIG welding torch that are part of the electrical circuit between the power supply and MIG welding torch are required to withstand the maximum current output of the power supply being used for any given application. 
     SUMMARY OF THE INVENTION 
     The present invention provides a rotating power connector that reduces the amount of torque required to spin the welding torch assembly about a central axis. The present invention reduces the amount of torque required to spin the rotating assembly by reducing the amount of axial force required to keep the rotating and contact elements of the assembly in electrical communication. The reduction in axial force is partially accomplished by using mating conical geometries (interlocking convex and concave surfaces) that use the cone angle of the mating surfaces to reduce the axial component of the contact force need to maintain electrical communication between the surfaces when compared to rotating connectors used in previous designs of rotating MIG Torches. Additionally the conical shape of the contact surfaces allows for increased surface area versus designs that use horizontal faces that are in contact in the axial direction, such as the invention of Jaeger. Additionally, the present invention allows for embodiments that can be quickly disconnected from the unicable while allowing for rotation of the goose neck and wear in the axial direction by the internal components of the rotating coupler assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Figures are not drawn to scale. The figures depict one or more embodiment of the present invention, additional embodiments are not illustrated. 
         FIG.  1    is a cross section of a welding torch assembly including an embodiment of the present invention; 
         FIG.  2    is a partial cross section detailing an embodiment of the present invention; 
         FIG.  3    is a cross section of the constant pressure apparatus used by one embodiment of the present invention; 
         FIG.  4    is a cross section of a rotating member used by one embodiment of the present invention; 
         FIG.  5    is a cross section of a second embodiment of the present invention that includes a quick disconnect from the unicable. 
         FIGS.  6   a  and  6   b    are cross sections of the receiving member and the male and female connections of the quick disconnect used by the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, embodiments of the invention shown. The present invention is a reduced friction rotating coupler assembly with or without quick disconnect from the unicable for use with welding torches. 
     A cross sectional view of an embodiment of the present invention can be seen in  FIG.  1   . The reduced friction rotating coupler assembly (hereinafter RCA)  1  is located inside the welding torch assembly  2 . The welding torch assembly  2  is mechanically attached to a robotic arm (not shown) via a flanged interface  3  located at the proximal end of the welding torch assembly  2 . The welding torch assembly  2  is rotated about a central axis  4  as the flanged interface  3  is rotated by the movement of the robotic arm (not shown). 
     As seen in  FIGS.  1  and  2   , the RCA  1  has an outer housing  5  that serves as an insulator and a means for positioning the RCA  1  via a interface between the proximal end of the RCA  1  and the proximal end of the main body  7  of the welding torch assembly  2 . A flange  6 , located at the proximal end of the substantially cylindrical outer housing  5  of the RCA  1  is positioned in a stepped recess located at the proximal end of the main body  7  of the welding torch assembly  2 . The flange  6  limits the radial movement of the proximal end of the RCA  1  inside the welding torch assembly  2 . The flange  6  is in mechanical communication with the main body  7  of the welding torch assembly  2  but not electrical communication due to the insulating properties of the outer housing  5  of the RCA  1 . 
     As seen in  FIG.  2   , the substantially cylindrical inner housing  8  is positioned within the outer housing  5  of the RCA  1  and extends for substantially the entire length of the RCA  1 . A substantially cylindrical rotating member  9  is positioned at the distal end of the RCA  1  along the central axis  4  within the inner housing  8  of the RCA  1 . The rotating member  9  is mechanically supported by at least one bearing  10 . The bearing(s)  10  are in mechanical communication with the inner housing  8  and rotating member  9 . The bearing(s)  10  are centered within the inner housing  8  and in turn center the rotating member  9  along the central axis  4 . The material selection for the bearing(s)  10  does not require a material that is electrically conductive, materials with low electrical conductivity or insulating qualities (i.e. ceramic bearings) are preferable as electrical conduction through the bearing(s)  10  would reduce the life of bearing(s)  10  by drying out the lubricant sealed within. 
     As seen in  FIG.  2   , the rotating member  9  has a first locking feature at the proximal end of the rotating member  9 , in this embodiment a flange  11 , is in mechanical communication with a bearing  10  thereby limiting the axial movement along the central axis  4  of the rotating member  9  within the RCA  1 . The rotating member  9  has a second locking feature at the distal end of the rotating member  9 , in this embodiment a threaded lock ring  12 . Threads  13  on the outer diameter of the distal end of the rotating member  9  are in mechanical communication with the threaded lock ring  12 . When installed the lock ring  12  and the flange  11  limit the axial movement of the rotating member  9  within the RCA  1 . 
     As seen in  FIG.  1 - 2   , a constant pressure apparatus  14  is installed in the proximal end of the RCA  1  within the inner housing  8  of the RCA  1 . As seen in  FIG.  3   , the constant pressure apparatus  14  comprises a receiving member  15  and a sliding member  16 . The receiving member  15  has threads  17  at the distal end of the receiving member  15  which engage the threaded proximal end of the inner housing  8 . A flange  18  of the receiving member  15  engages the step  19  at the proximal end of the inner housing  8  of the RCA  1 , thereby setting the axial location the receiving member  15  along the central axis  4 . As seen in  FIG.  1 - 2   , the inner diameter of sliding member  16  of the constant pressure apparatus  14  is in mechanical communication with the outer diameter of centering feature  20  of the rotating member  9  via a centering feature  22 , in this embodiment an o-ring, of the sliding member  16  located at the distal end of the sliding member  16 . The centering feature  22 , in this embodiment an o-ring, centers the proximal end of the rotating member  9  along the central axis  4  as well as acting as a pneumatic seal. The centering feature  20  of the rotating member  9  is designed to allow for the sliding member  16  to move towards to the distal end of the RCA  1  as the concave contact surface  23  of the sliding member  16  wears into convex contact surface  24  of the rotating member  9 . 
       FIG.  1    shows the rotating member  9  and the sliding member  16  are in electrical communication via a radial contact interface. In this embodiment radial contact interface comprises a concave contact surface  23  on the distal end of the sliding member  16  and a convex contact surface  24  on the proximal end of the rotating member  9  of the RCA  1 . The concave contact surface  23  and convex contact surface  24  are in mechanical and electrical communication with each other due to the force exerted by an axial force member  25 . In this embodiment the axial force member  25  is located in a recess in the proximal end of the sliding member  16 . When the receiving member  15  is seated in the step  19  located at the proximal end of the inner housing  8  of the RCA  1  the axial force member  25 , in this embodiment a spring, exerts an axial force against the receiving member  15  and sliding member  16 ; as the receiving member&#39;s  15  axial location is fixed by the flange  18  and step  19  of the inner housing  8 , the concave contact surface  23  of the sliding member  16  is pressed against the convex contact surface  24  of the rotating member  9  thereby creating an electrical conduction path between the sliding member  16  and the rotating member  9 . The sliding member  16  and receiving member  15  are designed to prevent rotation by the sliding member  16 , in this embodiment an anti rotation pin  29  is pressed into the receiving member  15  and slip fit into the sliding member  16 . 
     In some embodiments, an electrically conductive lubricant can be used to reduce friction between the contact surfaces of the sliding member  16  and rotating member  9 , including but not limited to oil or grease containing copper, silver, nickel, or other metal based or impregnated lubricant. The sliding member  16 , rotating member  9  and axial force member  25  are designed to allow between 1-5 mm of wear between the contact surfaces before electrical conduction between the sliding member  16  and rotating member  9  can no longer be maintained. The axial force member  25 , in this embodiment a spring, exerts an axial force between 44.48-111.20 N (10-25 lbf) on the sliding member  16  and the receiving member  15 . In one embodiment the initial spring load is  20  lbs, at this spring load the breakaway torque of the RCA  1  is measured to be ˜0.202 N-m (1.79 ft-lbs). The low breakaway torque required by the RCA  1  has the added benefit of allowing a welding torch in accordance with the present invention to rotate about a central axis  4  with zero to virtually no torsion or rotation translated to the unicable. While in operation, the unicable in a welding torch in accordance with the present invention will not be subjected to torsion loading or rotate as a result of rotation of the welding torch about the central axis  4 . 
     The inner diameter of the receiving member  15  is designed to accommodate at least one compressible electric contact member, in this embodiment a canted coil spring. The compressible contact member(s) (not shown) are seated in radial grooves  26  in the receiving member  15  and conduct electricity between the sliding member  16  and the receiving member  15  while allowing the sliding member  16  to move in the axial direction, along the central axis  4 , while maintaining electrical conduction between the sliding member  16  and the receiving member  15 . 
     The rotating member  9 , sliding member  16 , compressible contact member(s) (not shown), and receiving member  15  are manufactured out of electrically conductive materials (including but not limited to copper, brass, silver, and gold) and are in electrical communication. The inner housing  8  and lock ring  12  can be manufactured from the same material as the receiving member  15 , sliding member  16 , and or the rotating member  9  but do not need to be manufactured from electrically conductive materials as no secondary conduction path is needed by the present invention. 
     In one embodiment of the present invention the proximal end of the receiving member  15  is configured as a hose barb  27  that extends beyond the proximal end of the RCA  1  in the proximal direction about the central axis  4  and extends beyond the proximal end of the welding torch assembly  2  in the proximal direction about the central axis  4 . The hose barb  27  is mechanically connected to the core tube of an unicable (not shown). The hose barb  27  is crimped to the copper cabling of the unicable (not shown) creating a permanent mechanical and electrical connection between the receiving member  15  and the unicable. 
       FIG.  5    shows another embodiment of the present invention. In this embodiment the proximal end of this embodiment&#39;s receiving member  40  is configured as quick disconnect  30 . As seen in  FIGS.  6   a  and  6   b   , the quick disconnect  30  comprises a female connection  31  and male connection  32 . The proximal end of the male connection  32  is a hose barb  37  that is in mechanical and electrical communication with a unicable (not shown). The female connection  31  is designed to accommodate at least one compressible electric contact member (not shown), in this embodiment a canted coil spring. The female connection  31  has at least one radial groove  36  to accommodate a compressible electric contact member (not shown). The compressible electric contact member (not shown) conducts electricity between the female connection  31  and the male connection  32  without the use of a permanent mechanical connection, such as a crimp. The quick disconnect  30  functions in a similar fashion as the radial groove(s)  26  and compressible electric contact member(s) function as a slidable assembly in the RCA  1 ; the quick disconnect  30  allows for the male connection  32  to be inserted into the female connection  31  while allowing for the conduction of 0-800 amps of electric current. This embodiment of the present invention has the advantage of being capable of disconnection from the unicable in a quick and repeatable fashion. As a result, this embodiment also has the advantage of allowing the entire welding torch assembly  2  to be removed from the robotic arm (not shown) without having to remove the unicable (not shown) from robotic arm (not shown). A significant saving in time and labor are achieved by this embodiment because welding torch assembly  2  can be removed for maintenance without removal of the unicable, liner and filler material required for normal operation of a welding torch. 
     The female connection  31 , male connection  32 , and compressible contact member(s) are manufactured out of electrically conductive materials (including but not limited to copper, brass, silver, and gold) and are in electrical communication with each other and the RCA  1 . 
     The quick disconnect  30  can include an anti-rotation feature, such as an anti-rotation pin  29  seen in the RCA  1 . The quick disconnect  30  can include a releasable locking feature to prevent the removal of the male connection  32 , in the axial direction along the central axis  4 , after it has been inserted into the female connection  31  without the locking feature being released.