Abstract:
A welding wire dispensing assembly and apparatus for providing adjustment of rotational resistance in a spool comprises a spool support, an axle assembly, and a resistance adjustment assembly. The spool support is rotatably mounted to the welding wire dispensing assembly. The spool support has a first end and a second end and defines between the first end and the second end a surface around which a wire spool can be mounted. The axle assembly includes an axle and a first friction member with a friction surface. The resistance adjustment assembly comprises a second friction member, a force actuator, and a cam mechanism. Either the first friction member or the second friction member is substantially fixed with respect to either the spool support or the axle. The force actuator is adjustable between two positions. In a first position, the force actuator exerts a first level of interface force on one the first friction member or the second friction member, creating a first level of friction force between the first friction surface and the second friction surface. In a second position, the force actuator exerts a second level of interface force on one of the first friction member and the second friction member creating a second level of friction force between the first friction surface and the second friction surface. The cam mechanism comprises a cam channel and a cam follower. The cam follower is movable between a first stop and a second stop. Movement of the cam follower to a first location in the cam channel causes the cam mechanism to at least indirectly exert a force on the force actuator to move the force actuator to the first position, and movement of the cam follower to a second location in the cam channel causes the cam mechanism to at least indirectly exert a force on the force actuator to move the force actuator to the second position.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a mechanism for providing and adjusting rotational resistance in a spool and more particularly to a welding wire dispensing assembly and apparatus for retarding the rotation of a filler wire spool used to feed filler material to a welding torch such as an arc welding head or gun.  
           [0003]    2. Description of the Related Art  
           [0004]    In certain welding processes, a filler material, in the form of a coiled wire, such as steel or aluminum wire, is fed to a welding machine such as an arc welding gun. The wire filler material is typically fed to the welding site by motor driven rollers carried by the welding gun or by rollers mounted in a remote cabinet or both. During this feeding process, the level of tension on the wire should be regulated as the level of tension on the wire affects the column strength of the wire. Typically, a frictional drag force is applied to the wire spool in order to create the proper amount of rotational resistance in the spool and the proper amount of tension in the wire. Typically, the frictional drag force is created (1) between a spindle, rotatably mounted with the spool and a stationary axle member or (2) between a spring biased torsion arm and a rim of the spool.  
           [0005]    In welding wire support assemblies, the degree of frictional drag provided must frequently be adjusted. Welding wire support assemblies typically may hold wires made of one of many types of material, including steel, aluminum, and other materials. These materials have differing densities and, as such, have differing levels of inertia. Thus, for different wires, the rotational resistance needed to create the proper tension in the wire may be different.  
           [0006]    Typically, in devices relying on creating a frictional drag force, the frictional drag force is increased or decreased by rotating a nut about a bolt. In this way, more or less pressure is applied to a frictional pad such as a fabric washer. This prior art is inaccurate and inconsistent, because there exists no easily calculable method for determining when the appropriate setting has been achieved. Furthermore, methods for operating this prior art allow for too much operator error. Many operators adjust rotational resistance by sight, and rely on a trial and error method if their first estimate is incorrect. Other operators rotate the nut until it is as tight as possible, and then rotate the nut in the opposite direction a specified number of rotations based on the type of wire on the spool. For example, an operator may rotate the nut three rotations for one type of wire and five rotations for another type of wire. This method is subject to operator error and produces unpredictable and inaccurate results because no mechanism exists to indicate when the correct adjustment level is achieved.  
         SUMMARY OF THE INVENTION  
         [0007]    Thus, there exists a need for a welding wire dispensing assembly including an apparatus for quickly adjusting the rotational inertia provided by a spool in which the proper setting is easily detectable, is accurate, and is consistent. Described herein is a welding wire dispensing assembly that accomplishes those objectives.  
           [0008]    One aspect of the described welding wire dispensing assembly is a welding wire dispensing assembly comprising a spool support rotatably mounted to the welding wire dispensing assembly. The spool support has a first end and a second end and defines between the first end and the second end a surface around which a wire spool can be mounted. The welding wire dispensing assembly further has an axle assembly including an axle and a first friction member with a friction surface. The welding wire dispensing assembly further has a resistance adjustment assembly comprising a second friction member, a force actuator, and a cam mechanism. Either the first friction member or the second friction member is substantially fixed with respect to either the spool support or the axle. The force actuator is adjustable between two positions. In a first position, the force actuator exerts a first level of interface force on one the first friction member or the second friction member, creating a first level of friction force between said first friction surface and said second friction surface. In a second position, the force actuator exerts a second level of interface force on one of the first friction member and the second friction member creating a second level of friction force between the first friction surface and the second friction surface. The cam mechanism comprises a cam channel and a cam follower. The cam follower is movable between a first stop and a second stop. Movement of the cam follower to a first location in the cam channel causes the cam mechanism to at least indirectly exert a force on the force actuator to move the force actuator to the first position, and movement of the cam follower to a second location in the cam channel causes the cam mechanism to at least indirectly exert a force on the force actuator to move the force actuator to the second position.  
           [0009]    Another aspect of the welding wire dispensing assembly is that the force actuator or the cam mechanism may prevent the force actuator from moving in at least one direction beyond the first position. Similarly, either the force actuator or the cam mechanism prevents the force actuator from moving in at least one direction beyond the second position.  
           [0010]    Another aspect of the welding wire dispensing assembly is that the cam follower may be movable in opposite directions to move the force actuator between the first position and the second position.  
           [0011]    Another aspect of the welding wire dispensing assembly is that the first level of friction force is greater than the second level of the friction force.  
           [0012]    Another aspect of the welding wire dispensing assembly is that the welding wire dispensing assembly may further comprises a spool retainer releasably securable to the first end of the spool support. The spool retainer has a surface configured to cooperate with the spool support to prevent a spool from sliding off the first end of the spool support.  
           [0013]    Another aspect of the welding wire dispensing assembly is that the welding wire dispensing assembly may further comprise a spool retainer releasably securable to the first end of the spool support. The spool retainer has a surface configured to cooperate with the spool support to prevent a spool from sliding off the first end of the spool support. The spool retainer further defines gripping surface configured to at least indirectly exert force on the cam mechanism to move the cam follower so that the cam mechanism at least indirectly causes the movement of the force actuator between the first position and the second position.  
           [0014]    Another aspect of the welding wire dispensing assembly is that the retainer may further define a finger gripping surface configured to facilitate rotation of the retainer by fingers of a user.  
           [0015]    Another aspect of the welding wire dispensing assembly is that the retainer may further comprise visual indicia indicating the direction the retainer is to be moved to obtain the desired level of resistance when a spool of a given type of wire is mounted on the spool support.  
           [0016]    Another aspect of the welding wire dispensing assembly is that the welding wire dispensing assembly may comprise a frame, a spool support, an axle assembly, and a resistance adjustment assembly. The spool support has a first end and a second end and defines between the first end and the second end a surface around which a wire spool can be mounted. The axle assembly includes an axle and a first friction member with a friction surface. The resistance adjustment assembly comprises a second friction member, a force actuator, and a control. Either the first friction member or the second friction member is substantially fixed with respect to either the spool support or the axle. The force actuator is adjustable between two positions. In a first position, the force actuator exerts a first level of interface force on one the first friction member or the second friction member, creating a first level of friction force between said first friction surface and said second friction surface. In a second position, the force actuator exerts a second level of interface force on one of the first friction member and the second friction member creating a second level of friction force between the first friction surface and the second friction surface. The control defines a second adjustment surface. The force actuator is movable between the first position and the second position in response to interaction between the first adjustment surface and the second adjustment surface. Movement of the force actuator in at least one direction from said first position is subject to greater resistance than movement in the at least one direction toward the first position and movement of the force actuator in at least one direction from the second position is subject to greater resistance than movement in the at least one direction toward the second position.  
           [0017]    Another aspect of the welding wire dispensing assembly is that at least one of the force actuator and the control may prevent the force actuator from moving in at least one direction beyond the first position and at least one of the force actuator and the control may prevent the force actuator from moving in at least one direction beyond the second position.  
           [0018]    Another aspect of the welding wire dispensing assembly is that the control may be movable in opposite directions to move the force actuator between the first position and the second position.  
           [0019]    Another aspect of the welding wire dispensing assembly is that the first level of friction force may be greater than the second level of friction force.  
           [0020]    Another aspect of the welding wire dispensing assembly is that the welding wire dispensing assembly may further comprise a spool retainer releasably securable to the first end of the spool support. The spool retainer has a surface configured to cooperate with the spool support to prevent a spool from sliding off the first end of the spool support.  
           [0021]    Another aspect of the welding wire dispensing assembly is that the control may define a manipulation surface configured to be gripped to move the control so that the first adjustment surface and the second adjustment surface interact to move the force actuator between the first position and the second position.  
           [0022]    Another aspect of the welding wire dispensing assembly is that the welding wire dispensing assembly may further comprise a spool retainer releasably securable to the first end of said spool support. The spool retainer has a surface configured to cooperate with the spool support to prevent a spool from sliding off the first end of the spool support. The spool retainer further defines a gripping surface configured to exert force on the manipulation surface of the control to move the control so that the first adjustment surface and the second adjustment surface interact to move the force actuator between the first position and the second position.  
           [0023]    Another aspect of the welding wire dispensing assembly is that the retainer may further define a finger gripping surface configured to facilitate rotation of said retainer by fingers,of a user.  
           [0024]    Another aspect of the welding wire dispensing assembly is that the retainer may further comprise visual indicia indicating the direction the retainer is to be moved to obtain the desired level of resistance when a spool of a given type or size of wire is mounted on the spool support.  
           [0025]    Another aspect of the welding wire dispensing assembly is that either the force actuator or the control may define a cam surface which cooperates with a cam follower on the other of the force actuator and the control to move the force actuator from one of the first position and the second position to the other of the first position and the second position.  
           [0026]    Another aspect of the welding wire dispensing assembly is a welding wire dispensing assembly comprising a frame, a spool support, and an adjustment assembly. The spool support is rotatably mounted to the frame and has a first end and a second end. The spool support defines between the first end and the second end a surface around which a wire spool can be mounted. The resistance adjustment assembly comprises a force actuator and a spool retainer. The force actuator has a first adjustment surface, a first position configured to cause a first level of resistance, and a second position configured to cause a second level of resistance. The spool retainer is releasably securable to the first end of the spool support. The spool retainer has a surface configured to cooperate with the spool support to prevent a spool from sliding off the first end of the spool support. The spool retainer further defines a gripping surface configured to interact at least indirectly with the force actuator to cause the force actuator to assume either the first position or the second position.  
           [0027]    Another aspect of the welding wire dispensing assembly is that the spool retainer may further provide a first mode of operation to cause the force actuator to assume the first position and a second mode of operation to cause the force actuator to assume the second position.  
           [0028]    Another aspect of the welding wire dispensing assembly is that the spool retainer may further provide visual indicia illustrating the first mode of operation and the second mode of operation.  
           [0029]    Another aspect of the welding wire dispensing assembly is that the first mode of operation may be rotating the spool retainer in either a clockwise direction or a counter-clockwise direction. The second mode of operation may be rotating the spool retainer in the opposite direction.  
           [0030]    Another aspect of the welding wire dispensing assembly is a welding wire dispensing assembly comprising a frame, a spool support, a resistance adjustment assembly, and a tool. The spool support is rotatably mounted to the frame and has a first end and a second end. The spool support defines between the first end and the second end a surface around which a wire spool can be mounted. The resistance adjustment assembly comprises a force actuation having a first adjustment surface. The force actuator has a first position configured to cause a first level of resistance, and a second position configured to cause a second level of resistance. The tool defines a gripping surface configured to interact at least indirectly with the first adjustment surface of the force actuator to cause the force actuator to assume eiether the first position or the second position. The tool is rotatable in one direction to cause the force actuator to assume the first position and rotatable in an opposite direction to cause the force actuator to assume the second position. The tool includes visual indicia indicating the direction the tool is to be moved to obtain the desired level of resistance when a spool of a given type of wire is mounted on the spool support.  
           [0031]    Another aspect of the welding wire dispensing assembly is that the tool may be integrally formed into a component of the welding wire dispensing assembly.  
           [0032]    Another aspect of the welding wire dispensing assembly is that the tool may be attached to a component of the welding wire dispensing assembly.  
           [0033]    These and other aspects of the welding wire dispensing assembly are herein described in more detail with reference to the following drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]    [0034]FIG. 1 illustrates one embodiment of a welding wire dispensing assembly with an attached welding wire support assembly.  
         [0035]    [0035]FIG. 2 is an external view of an assembled welding wire support assembly.  
         [0036]    [0036]FIG. 3 is an exploded view of the components of the welding wire support assembly.  
         [0037]    [0037]FIG. 4 illustrates one position of a pin within a cam mechanism of the welding wire support assembly.  
         [0038]    [0038]FIG. 5 illustrates another position of a pin within a cam mechanism of a welding wire support assembly.  
         [0039]    [0039]FIG. 6 illustrates the relationship between cam positions, spring compression, and the size of a gap between a spacer and a tension knob when the tension knob is in a backed-off position.  
         [0040]    [0040]FIG. 7 illustrates the relationship between cam positions, spring compression, and the size of a gap between a spacer and a tension knob when the tension knob is in a forward position.  
         [0041]    [0041]FIG. 8 illustrates an advantageous embodiment in which a tension knob adjustment tool is integrally formed into the welding wire support assembly.  
         [0042]    [0042]FIG. 9 illustrates an advantageous embodiment in which a detached retainer is in a position to function as a tension knob adjustment tool. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0043]    [0043]FIG. 1 illustrates one embodiment of a welding wire dispensing assembly including a welding wire support assembly  10  upon which a welding wire spool is mounted. As illustrated, the welding wire support assembly  10  is located within a cabinet  12 . The support assembly has a proximal end adjacent to an inner wall  4  of the cabinet  12  to which the assembly is mounted and a distal end opposite the proximal end. Thus, the cabinet forms a frame for supporting the support assembly. During use of the welding device, wire wrapped around the spool (shown in phantom) is unrolled and fed through an opening  14  in the cabinet  12  by a first wire feed mechanism  16  mounted in the cabinet and a second wire feed mechanism which forms a part of a welding gun.  
         [0044]    Alternatively, the welding wire dispensing assembly may be a welding gun that defines a frame for mounting the welding wire support assembly  10 . For example, the welding wire dispensing assembly may be a welding gun as portrayed in U.S. Pat. No. 6,064,036, entitled “WELDING GUN FILLER WIRE SPOOL BRAKE AND WIRE POSITION REGULATOR,” issued May 16, 2000. Typically, a welding gun with a welding wire support assembly  10  has a proximal end and a distal end. During use of the welding gun, wire wrapped around the spool is unrolled and fed through the proximal tip of the welding gun.  
         [0045]    One of ordinary skill in the art will appreciate that many of the inventive aspects described herein relate to the welding wire support assembly  10  itself. As such, the welding wire dispensing assembly upon which the welding wire support assembly  10  is mounted may be modified without eliminating many of the inventive aspects of the welding wire support assembly  10 . The Claims cover any welding wire support assembly  10  as described in the Claims regardless of the type of welding wire dispensing assembly upon which the welding wire support assembly  10  is mounted, whether the welding wire dispensing assembly is a welding cabinet as shown in FIG. 1, a welding gun, or another type of welding wire dispensing assembly.  
         [0046]    Structure of the Welding Wire Support Assembly  
         [0047]    [0047]FIGS. 2 and 3 illustrate the welding wire support assembly  10 . The welding wire support assembly  10  includes an axle asembly  78 , a support or spindle assembly  80  that receives and retains the spool, and a rotational resistance assembly  82 .  
         [0048]    The Spindle Assembly  
         [0049]    The spindle assembly  80  comprises a spindle  18 , a plate back up ring  30 , a brake disk  26 , and a retainer  34 . The spindle comprises a generally disc-shaped face plate  20  and a generally cylindrical body  6 . The retainer  34  is detachably attached to the distal end of the spindle  18  for securing the spool to the spindle  18 . The body  6  defines a series of generally cylindrical support surfaces which cooperate with a mating cylindrical surface defined by the central inner wall of the wire spool. Though this series of generally cylindrical support surfaces need not be cylindrical, it is desirable that the surfaces cooperate with the inner wall of the spool so that the spool is secured so as to rotate in unison with the spindle. Alternatively, the retainer  34  and face plate  20  may be spaced to provide pressure on the spool sufficient to secure the spool so as to rotate in unison with the spindle. An axle  24 , describe in more detail below, protrudes from the proximal end of the spindle  18 . Abutting the face plate  20  of the spindle  18  is a brake disk  26 . A number of brake teeth  28  encircle the circumference of the brake disk  26 . The brake teeth  28  are adapted to receive a pawl  3  (FIG. 1), providing a means to brake the rotation of the welding wire support assembly  10 . Abutting the brake disk  26  is a plate back up ring  30 . In one embodiment, the face plate  20 , the brake disk  26 , and the plate back up ring  30  are secured to each other with springs  25 , washers  27 , and screws  29 . In one embodiment, three sets of springs  25 , washers  27 , and screws  29  are provided. The screws  29  extend through the washers  27 , springs  25 , face plate  20 , and brake disk  26 , and are received by holes  31  in the plate back up ring  30 . Alternatively, a different type and/or number of fasteners may be provided. In one preferred embodiment, a retainer  34  threadably attaches to the spindle  18  at the end opposite the face plate  20 . Alternatively, the retainer  34  may attach to the spindle  18  in another fashion, such as by providing on the retainer  34  a series of protrusions that snap into notches provided on distal end of the spindle  18 . Any manner of detachably securing the retainer  34  is within the scope of the inventive aspect.  
         [0050]    The Axle Assembly  
         [0051]    The axle assembly  78  comprises the axle  24 , and a bearing assembly  50 . The axle  24  includes a proximal portion  52 , a distal portion  54 , and an internal portion  53  that runs between the proximal portion  52  and the distal portion  54 . Located starting at the proximal portion  52  is a shaft  55 . The shaft may be approximately 4.5″ long and may have an approximate diameter of 0.625″. Located at the distal portion  54  is a smaller diameter connector section such as an externally threaded shaft  77 . The threaded connector section  77  may extend internally into the shaft  55 , and protrudes from the shaft  55 . The protruding portion of the connector section may have a length of approximately 1.125″ and a diameter of approximately 0.25″. The bearing assembly  50  is desirably cylindrical, and may have a length of approximately 1.5″ and a diameter of approximately 1″. The bearing assembly  50  includes an exposed planar annular friction surface, or rim  56 , and a series of internal ball bearings arranged so as to encircle the axle  24 . While other types of friction surfaces are possible, the planar annular rim  56  is desirable because it permits the apparatus to utilize an off the shelf bearing and is easily manufactured to the desired tolerance. In one embodiment, dual radial single race ball bearings are used. Any type of bearing may be used that effectively reduces friction between the bearing assembly  50  and the axle  24 .  
         [0052]    The axle  24  extends through the bearing assembly  50 . The proximal portion  52  of the axle  24  protrudes from the bearing assembly  50  and is secured to the wall  4  of the cabinet  12 . Desirably, the proximal portion  52  of the axle  24  is fixedly secured to the cabinet  12  such that the axle  24  does not rotate. In this embodiment, the bearing assembly  50  rotates about the axle  24 . Alternatively, the bearing assembly  50  may be fixed against rotation and the axle  24  may rotate with respect to the bearing assembly  50 . The internal portion  53  of the axle  24  is inside the bearing assembly  50 . The internal bearings encircle the internal portion  53  of the axle  24 , enabling the rotation of the axle  24  in relation to the bearing assembly  50  or the rotation of the bearing assembly  50  relative the axle  24 . The distal portion  54  of the axle  24  protrudes from the bearing assembly  50  on the opposite side of the proximal portion  52 . The distal portion  54  of the axle  24  includes a radially extending protrusion.  
         [0053]    The Rotational Resistance Assembly  
         [0054]    The rotational resistance assembly  82  comprises a leather washer  58 , a spacer  60 , a spring  66 , a cam  68 , and a tension knob  70 . The compressability of the leather washer  58  provides a degree of friction between the leather washer  58  and any surfaces that it contacts. Alternatively, any number of compressable materials or materials that provide a similar degree of friction may be used, such as, for example, fabric or rubber. The leather washer  58  abuts the spacer  60 . Formed into an inner wall of the spacer  60  is a notch  62  sized and shaped to receive and retain the protrusion. The distal end of the spacer forms an annular spring seat. The spring  66  abuts the spring seat of the spacer  60 . The cam  68 , has a cam barrel  67 , a cam channel or cam groove  69 , a bore  71  and a cam threaded shaft  73 . The cam  68  is received into the tension knob  70 . The bore is located at the proximal or bore end of the cam barrel  67  receives the threaded shaft  77  of the axle  24 . Opposite the bore end is a distal thread end, ending in the cam threaded shaft  73 . The diameter of the cam barrel  67  may be approximately 0.625″. The length of the cam barrel may be approximately 1.5″. Integrally formed into the cam barrel  67  at the thread end is the cam threaded shaft  73 , adapted to receive a hex nut  74 . The cam groove  69  is formed into the outer cylindrical wall of the cam barrel  67  and has a head at its proximal end and a tail  93  at its distal end. The head  91  may be located approximately 0.5″ from the bore end. The head  91  has three walls, configured such that a pin  90  (FIG. 4) received into the cam groove  69  is allowed to slide only toward the tail  93 . The head  91  may extend for approximately 0.125″, aligned generally perpendicular to the axis of the cam barrel  67 . The tail  93  extends from the head  91  to the thread end at an approximately 45° angle to the head  91  and the axis of the cam barrel  67 . The length of the tail  93  along the perimeter of the cam barrel  67  may be approximately 1.25″. The tail  93  has two walls, configured such that a pin  90  (FIG. 4) received into the cam groove  69  is allowed to slide either toward the head  91  or away from the head  91 . The tail  93  is open at the thread end, such that a pin  90  (FIG. 4) received into the cam groove  69  is not restrained, by the groove walls, from leaving the cam groove  69 . The depth of the cam groove  69  may be approximately 0.1″. The walls of the cam groove  69  are aligned generally perpendicular to the surface of the cam barrel  67 .  
         [0055]    The tension knob  70  has a cylindrical proximal portion  95  and a polygonal gripping portion  97  through which axially extend an inner bore. The proximal portion  95  may have a length of approximately 0.5″ and a diameter of approximately 1.0″. Embedded in the wall of the proximal portion  95  is a cam follower or pin  90  (FIG. 4) approximately 0.125″ in diameter. A portion of the pin  90  (FIG. 4) extends radially inward into the bore of the proximal portion  95  a distance slightly smaller than the depth of the cam groove  69 . Thus, when the pin  90  is received into the cam groove  69 , the pin  90  may slide freely along the cam groove  69  without scraping the floor of the cam groove  69 . The gripping portion  97  may have a length of approximately 0.875″. When the cam follower or pin  90  is received into the cam channel or cam groove  69 ; a cam mechanism comprising the cam follower or pin  90  and the cam channel or cam groove  69  is formed. As is described in more detail, in one embodiment the cam mechanism participates in the selection of a rotational resistance level.  
         [0056]    The gripping portion  97  generally defines a square having chamferred corners on its outside perimeter. The bore extending through the tension knob has a first proximal larger diameter portion and a second distal smaller diameter portion which cooperate to form a radially extending annular shoulder there between. The gripping portion  97  has a first cylindrical inner perimeter having a diameter of approximately 0.75″. Approximately 0.5″ from the end of the gripping portion  97  that is opposite the cylindrical portion  95 , the gripping portion has a second cylindrical inner perimeter having a diameter that is slightly smaller than the diameter of the first cylindrical inner perimeter. Thus, the second cylindrical inner perimeter forms a shoulder  99  inside the second cylindrical inner perimeter. The outside perimeter of the gripping portion  97  has 4 major sides  101  (FIG. 8) and 4 minor sides  103  (FIG. 8), arranged alternatively. The major sides  101  are aligned at approximately 90° angles from each other, and have a length of approximately 0.5″. The minor sides  103  are aligned at approximately 90° angles from each other, and approximately 45° angles from the major sides  101 , and have a length of approximately 0.375″. The length from one major side  101  to its parallel major side  101  is slightly smaller than the diameter of the cylindrical portion. Thus, a small shelf  105  is provided near the end of the gripping portion  97  that is adjacent to the cylindrical portion  95 .  
         [0057]    The threaded shaft  77  extends through the tension knob  70 , a spacer washer  107 , a stop or second washer  72 , and a fastener or hex nut  74  and is secured by the hex nut  74 . The spacer washer  107  and the washer  72  have diameters slightly larger than the diameter of the shoulder  99  formed internally in the tension knob  70 . Thus, when the spacer washer  107  and second washer  72  come into contact with the shoulder  99 , further forward motion of the cam barrel  67  with respect to the tension knob  70  is prevented. The size of the spacer washer  107 , the washer  72 , and the tightness of the hex nut  74  determine the precise position of the cam barrel  67  with respect to the tension knob  70  when further motion is prevented. Thus, by altering these parameters, one can adjust one position of the cam barrel  67  with respect to the tension knob  70 . A protective cap  76  covers the hex nut  74 .  
         [0058]    Structural Relationship Among the Three Assemblies  
         [0059]    The distal portion  54  of the axle  24  protrudes from the bearing assembly  50  and extends into the center of the body  6  of the spindle  18 . An external wall of the bearing assembly  50  is received snugly into an internal wall of the spindle  18  and is secured against rotation relative the spindle  18 . Thus, the bearing assembly  50  is secured such that it rotates in concert with the spindle  18 . The rim  56  of the axle assembly  78  is within the body  6  of the spindle  18 . The distal portion  54  of the axle  24  extends through the leather washer  58 , the spacer  60 , and the spring  66  of the rotational resistance assembly  82 . Thus, the rim  56  of the axle assembly  78  abuts the leather washer  58 . The bore  71  of the cam  68  threadably receives the threaded shaft  77  of the axle  24 . The notch  62  of the spacer  60  receives the protrusion  64  of the internal portion  53  of the axle assembly  78 . Thus, since the axle  24  is fixed, the spacer  60  is likewise fixed against rotation.  
         [0060]    Structural Relationship Between the Cam and the Tension Knob  
         [0061]    Referring to FIGS. 4 and 5, formed into the inner wall of the tension knob  70  is a pin  90  that is slidably received into the cam groove  69 . The cam groove  69 , tension knob  70 , spacer washer  107 , tension knob washer  72 , and tension knob hex nut  74  define a range of motion for the pin  90  along the cam groove  69 . The pin  90  may be temporarily located at any position along the cam groove  69 . Generally, however, the pin  90  assumes either a proximal or forward position  92  or a distal or backed-off position  94 . The two positions are at two lineal distances with respect to the distal end of the cam barrel  67 . FIG. 4 illustrates a forward position  92 , in which the location of the pin  90  within the cam groove  69  is lineally closer to the edge of the cam barrel  67 . A proximal or forward wall  109  of the cam groove  69  prevents the pin  90  from moving axially more forward than the forward wall  109 . In one embodiment, when the pin  90  is in the forward position  92 , the cam barrel  67  extends 0.375″ from the edge of the tension knob  70 .  
         [0062]    [0062]FIG. 5 illustrates a backed-off position  94 , in which the location of the pin within the cam  68  is lineally farther away from the distal end of the cam barrel  67 . In one embodiment, the internal shoulder  99  of the tension knob  70  contacts the combination of the spacer washer  107 , the second washer  72 , and the hex nut  74  at the point where the pin has reached the backed-off position  94 . In this embodiment, the spacer washer  107 , second washer  72 , and hex nut  74  combination determines the location of the backed-off position  94  of the pin  90 . The pin  90  could be located even farther back if it were not for the restraint imposed by the spacer washer  107 , the second washer  72 , and the hex nut  74 . Thus, a different backed-off position  94  may advantageously be established without replacing the cam  68  by changing the parameters of the spacer washer  107 , second washer  72 , and hex nut  74  combination. Alternatively, the cam groove  69  may provide a second terminal wall that constrains the movement of pin  90 . In one embodiment, when the pin  90  is in the backed-off position  94 , the cam barrel  67  extends 0.75″ from the edge of the tension knob  70 .  
         [0063]    Selecting a Rotational Resistance Setting Using the Tension Knob  
         [0064]    An operator selects one of two rotational resistance settings by manipulating the tension knob  70  such that the pin  90  assumes either the forward position  92  or the backed-off position  94 . The pin  90  assumes the forward position  92  upon a clockwise rotation of the tension knob  70 . The pin  90  assumes the backed-off position  94  upon a counter-clockwise rotation of the tension knob  70 . Alternatively, the rotational resistance assembly  82  may be configured such that the pin  90  assumes the forward position  92  upon a clockwise rotation of the tension knob  70 , and assumes the backed-off position  94  upon a counter-clockwise rotation of the tension knob  70 . Preferably, the degree of rotation of the tension knob  70  that is necessary to adjust the resistance setting is less than one full rotation. In one preferred embodiment, a change in resistance level occurs with an approximately one-quarter rotation of the tension knob  70 . Alternatively, the rotational resistance assembly  82  may be configured such that smaller or larger degrees of rotation are adequate for adjusting the resistance setting.  
         [0065]    The distance that the cam barrel  67  extends from the edge of the tension knob  70  corresponds to a gap between the spacer  60  and the tension knob  70 . As will be further explained, the size of this gap determines the degree of friction and thus rotational resistance that is created by the rotational resistance assembly  82 . As the gap between the spacer  60  and the tension knob  70  narrows, the spring  66  is compressed. The compression of the spring  66  against the spacer  60  exerts pressure on the spacer  60 , the leather washer  58 , and the rim  56 , respectively. Thus, as the gap between the spacer  60  and the tension knob  70  narrows and the spring  66  becomes more compressed, the frictional drag force exerted on the rim  56  increases, resulting in a higher level of rotational resistance on the spindle  18 .  
         [0066]    [0066]FIGS. 6 and 7 illustrate the relationship between the cam  68  positions, spring  66  compression, and the size of the gap between spacer  60  and tension knob  70 . FIG. 6 depicts this relationship when the tension knob  70  is in the forward position  92  with relation to the cam barrel  67 . As previously indicated, when the tension knob  70  is in the forward position  92 , the cam barrel  67  protrudes approximately 0.75″ from the tension knob  70 . Thus, in this embodiment, the forward gap  100  between the spacer  60  and the tension knob  70  is approximately 0.75″. Thus, in FIG. 6, the spring  66  is less compressed in this position relative the backed-off position  94  shown in FIG. 7.  
         [0067]    [0067]FIG. 7 depicts the relationship when the tension knob  70  is in the forward position  92  with relation to the cam barrel  67 . As previously indicated, when the tension knob  70  is in the forward position  92 , the cam barrel  67  protrudes approximately 0.375″ from the tension knob  70 . Since the gap between the spacer  60  and the tension knob  70  is approximately the length of the protruding portion of the cam barrel  67 , the backed-off gap  102  between the spacer  60  and the tension knob  70  is approximately 0.375″. Thus, in FIG. 7, the spring  66  is compressed.  
         [0068]    The differences in spring  66  compression caused by the differing gaps between spacer  60  and tension knob  70  result in differing levels of rotational resistance on the spindle  18 . The characteristics of the leather washer  58 , spring  66 , tension knob  70 , and cam  68 , are known. Furthermore, the two terminal positions  92  and  94  of the pin  90  (FIG. 4) consistently produce gaps between the spacer  60  and the tension knob  70  that are of known dimension. Advantageously, because all of these parameters are known, the rotational resistance at each of the two positions  92  and  94  of the tension knob  70  is calculable.  
         [0069]    Additionally, as illustrated in FIGS. 4 and 5, once the pin  90  reaches one of the two terminal positions  92  and  94 , the pin  90  is constrained such that it can only move toward the other terminal position. Thus, an operator is prevented from rotating the tension knob  70  too much, eliminating or reducing the potential for operator error. Furthermore, an operator may easily detect when the desired location has been reached. Therefore, unlike prior art devices using a frictional drag force, the use of the cam  68  enables an operator to reliably, repeatably, and accurately choose between two rotational resistance settings.  
         [0070]    Advantageously, the cam  68  also may enable an operator to adjust the rotational resistance of the spool with a nominal rotation of the tension knob  70 . As previously indicated, prior art rotational resistance adjustment mechanisms require an operator to rotate a nut about a bolt a number of rotations. The cam  68 , however, provides a nearly immediate displacement upon rotating the tension knob  70  enough to cause the tension knob  70  to switch from the forward position  92  to the backed-off position  94 , or vice-versa. In one preferred embodiment, the adjustment may be performed by an approximately one-quarter rotation of the tension knob  70 .  
         [0071]    Furthermore, the cam  68  of the present invention enables one of ordinary skill in the art to design a spool mechanism that can reliably provide any two arbitrary levels of rotational resistance. Different rotational resistance settings can be designed into a device by changing the characteristics of the spring  66 , the cam  68 , the tension knob  70  or other components. In one preferred embodiment, a setting for aluminum, and a setting for steel and other heavier metals are provided. For this embodiment, it has been determined that the characteristics and dimensions of the cam  68  previously described are advantageous. Additionally, it has been determined that the spring  66  advantageously may be composed of music wire, have an outside diameter of 0.85″, have an inside diameter of 0.69″, have a free length of 0.75″, have a rate of 67 pounds/inch, have a maximum deflection of 0.43″, have a maximum load of 29 pounds, have a solid height of 0.31″, have a wire diameter of 0.080″, and have 3.88 total coils. With these characteristics of a preferred embodiment, it has been determined that between 0.75 and 1.25 pounds of torque turn the axle  24  when the tension knob  70  is in the backed-off position  94  relative the cam  68 . It has been determined that between 2.5 and 3.5 pounds of torque turn the axle  24  when the tension knob  70  is in the forward position  92  relative the cam barrel  67 . These parameters have been determined to be adequate for typical aluminum and steel wire. Alternative parameters may be chosen and remain within the scope of the invention as described.  
         [0072]    An Integral Tension Knob Adjustment Tool  
         [0073]    [0073]FIG. 8 illustrates an advantageous embodiment in which a tension knob adjustment tool is integrally formed into the welding wire support assembly  10 . In a preferred embodiment, retainer  34  doubles as the tension knob adjustment tool  110  when detached from the end of the spindle  18 . As illustrated, one side of the retainer  34  provides external threads  112  that mate with internal threads in the distal end of the body  6  of the spindle  18  to enable the retainer  34  to perform one function of holding wire on the welding wire support assembly  10 . The other side of the retainer  34  is the tension knob adjustment tool  110 . In this embodiment, the retainer  34  is encircled by an adjustment grip  114 . The adjustment grip  114  provides an undulating series of crests  113  and troughs  115 . The troughs  115  are adapted to provide convenient finger holds for an operator. In one embodiment, 6 crests  113  and 6 troughs  115  are provided. An alternative number of crests  113  and troughs  115  may be provided.  
         [0074]    [0074]FIG. 9 illustrates the retainer  34  in the position it assumes when performing one function as a tension knob adjustment tool  110 . The outer shape of the tension knob  70  and the inner shape of the tension knob adjustment tool  110  , as illustrated, are configured such that the inner surface of the tension knob adjustment tool  110  snugly receives and surrounds the outer surface of the tension knob  70 . In one embodiment, the internal dimensions of the tension knob adjustment tool  110  are slightly larger than the external dimensions of the gripping portion  97  of the tension knob  70 . That is, the tension knob adjustment tool  110  provides a cutout that receives a polygonal shape with 4 major sides and 4 minor sides with dimensions as described in relation to the gripping portion  97  of the tension knob  70 . In the embodiment described, the outer shape of the tension knob  70  is similar to the shape of a hex nut (though more than  6  sides are provided). Other shapes may be employed that allow the tension knob  70  to be received snugly into the tension knob adjustment tool  110  and are within the scope of this inventive aspect.  
         [0075]    Advantageously, the tension knob adjustment tool  110  provides adjustment indicia  117  indicating the direction that an operator should rotate the tension knob adjustment tool  110  in order to achieve the desired setting. In one embodiment, the tension knob adjustment tool  110  is rotated counter-clockwise for a setting appropriate for small diameter aluminum wires, such as those that are up to 0.035″ in diameter, and is rotated clockwise for a setting appropriate for other wires. Alternatively, the rotational resistance assembly  82  may be configured such that these directions of rotation are reversed. In either case, the adjustment indicia  117  indicates the correct direction to rotate the tension knob  70 . In the embodiment illustrated, the adjustment indicia  117  comprise a left arrow  119  pointing toward the correct rotational direction, a label  121  indicating the type of wire that is to be loaded onto the welding wire support assembly  10 , and a right arrow  123  pointing toward the correct rotational direction. This double arrow arrangement, as described, is not necessary for this inventive aspect. Alternatively, a single arrow can be used. Furthermore, the label  121  can alternatively indicate a value of rotational resistance instead of a wire type. Any arrangement for indicating the direction that the tension knob  70  should be rotated to achieve a desired setting is within the scope of this inventive aspect.  
         [0076]    Advantageously, the adjustment indicia  117  is displayed on a convenient side of the retainer  34 . In one embodiment, shown in FIG. 9, the adjustment indicia  117  is displayed on the side that is most visible to the operator when the operator is making an adjustment. In this embodiment, the adjustment indicia  117  is not displayed on the opposite side of the retainer  34 . This embodiment aids the operator in determining which side of the retainer  34  should be used for making adjustments, because the adjustment indicia  117  should be visible when the retainer  34  is properly aligned to be used as an adjustment tool. Alternatively, indicia may be provided on the opposite side, or on both sides.  
         [0077]    Advantageously, the tension knob adjustment tool  110  is integrally formed into the welding wire support assembly  10 . An operator of a welding device may not have convenient access to non-integral adjustment tools. Furthemore, non-integral adjustment tools may become lost. Thus, it is particularly advantageous that the tension knob adjustment tool  110  of a preferred embodiment is integrally formed into a portion of the welding wire support assembly  10  that is normally expected to be present during welding operations. A welder is not likely to lose the retainer  34  because it is advantageous to operate the welding device with the retainer  34  attached, such that the wire does not fall off the body  6 . Alternatively, the integral adjustment tool  110  may be formed into another component of the welding wire support assembly  10 .  
         [0078]    One Method of Adjusting Rotational Resistance  
         [0079]    One of ordinary skill in the art will appreciate that the apparatus described above enables new and useful methods of operating a welding device. For example, an operator may quickly and effectively change rotational resistance settings when wire types or wire sizes change. When an operator decides to change wire sizes or types, he or she may remove the retainer  34 . Then, the operator removes the wire from the body  6 . Then, the operator places a new wire on the body  6 . The operator uses the tension knob adjustment tool  110  to rotate the tension knob  70  in a desired direction. The operator detects the correct setting by noticing the change in position of the cam  68 . The operator replaces the retainer  34 .  
         [0080]    The Above Embodiments are Exemplary Only  
         [0081]    The foregoing describes various illustrative embodiments of a welding wire dispensing assembly and apparatus for providing adjustment of rotational resistance in a spool. While various embodiments are described in detail, one of ordinary skill in the art will appreciate that the principles of the invention described herein are applicable to additional alternative embodiments. Thus, those additional alternative embodiments that apply the principles of the invention as described herein are within the scope of the invention to the extent they are within the Claims.