Patent Publication Number: US-7220942-B2

Title: Feeder for endless welding wire

Description:
The present invention relates to the art of electric arc welding and more particularly to a feeder device for feeding an endless welding wire to an arc welding station. 
   INCORPORATION BY REFERENCE 
   The welding wire feeding device of the present invention relates to the concept of using a continuous welding wire from successive drums containing coiled wire with a feed end and a trailing end, both of which ends are exposed from the top of the drum with the trailing end of the coil being fed to the welding station butt welded to the feed end of the next coiled welding wire. This high production technology is becoming quite popular with mass production lines such as used in automobile production. One feeder suggested for commercial application is described in PCT application WO 02/094493 where the spaced drums incorporate a wire feeder using an upper guide tube only. This application is incorporated by reference herein as background information regarding the technology to which the present invention is directed. 
   In accordance with the invention, a feeding grommet is moved over the drums to accommodate feeding of a coil from each of the spaced containers. The grommet of the invention is mounted to be moved in a given path by a rodless cylinder. A catalog for a rodless cylinder by Bimba Manufacturing is incorporated by reference herein as background information. The cylinder is also disclosed in Clark U.S. Pat. No. 5,739,704 and Yarnall U.S. Pat. No. 5,491,737. These patents are incorporated by reference. 
   BACKGROUND OF INVENTION 
   For high production electric are welding, especially in the automobile industry, there is substantial development work directed to providing endless welding wire from a continuous supply of wire by butt welding the ends of wire in coils of adjacent packages, such as drums. The use of endless welding wire reduces the down time associated with package change over in automatic and robotic welding. Endless welding wire involves welding wire coiled in two adjacent packages butt welded together so that as one coil is exhausted, the second coil automatically provides welding wire. To continue the supply of endless welding wire, an empty container is replaced by a new container having a first wire end forming the normal feed wire end and an exposed trailing end from the bottom of the new coil. The feed end is then butt welded to the exposed trailing end of the previous wire coil to continue providing welding wire. This technique is well known; however, it is seldom used because of the difficulty in feeding the wire from one coil and then the next coil by a single wire feeding device capable of accommodating wire from one drum and then wire from the next drum. The common wire feeding mechanism is a feeding grommet spaced substantially above and generally between the two containers or drums so that the wire from one drum is pulled through the vertically spaced grommet and then wire from the second drum is pulled through the same grommet. To prevent tangles and sharp bends, the vertically spaced feed grommet must be substantially above the two adjacent containers or drums. This typical feeding device for endless welding wire has two major disadvantages. First, the feed grommet is over 2 feet above the top of the adjacent containers. This creates interference with associated mechanisms and structures adjacent the wire feeder. Consequently, the two drums and the wire feeder must be spaced away from the welding station or robot so that it is in an area having a vertical clearance. In some factories, such clearance is not available, thus, causing rejection of this feeder for an endless welding wire. Furthermore, the welding wire is normally at the open circuit voltage of the welding operation. Thus, the wire extending from the packages to the grommet exposes high voltage, requiring some type of protective guard around the feeding operation. Such guard presents another obstacle to using the standard feeding device for endless welding wire. In an effort to reduce the height necessary for the feeding grommet it has been proposed that the feeding grommet be mounted on a swinging arm that pivots from the center of one welding wire coil to the center of the adjacent welding wire coil, as the first coil is exhausted and the second coil replaces the first coil. This swinging arm allows the endless welding wire from the first coil to be pulled through the feeding grommet directly above the coil. As the next coil is used, the arm pivots to a position above the second coil. This mechanism reduces the height of the feeding grommet and the length of bare wire exposed during the welding operation. To assure proper orientation of the feeding grommet, the swinging arm carrying the grommet has two arcuate positions, normally locked in place by a spring biased detent. This swinging arm feeding device does reduce the height of the mechanism, but not to any great extent. The swinging action from one coil to the other coil of the endless welding wire must avoid sharp bends in the wire. Thus, the vertical height remained a spatial problem. Furthermore, the pivoting arm, not only caused certain difficulties when shifting from one coil to the next coil, but also maintained a large length of exposed, bare welding wire with open circuit voltage. The high fixed feeding grommet and swinging arm feeding grommet constitute background technology to which the present invention is directed. They both have the problem of excessive height requiring vertical clearance for the area containing the two welding wire packages and result in a substantial length of exposed wire. Furthermore, the swinging arm feeding device promotes tanglements, as the arm swung from one coil supply to the next coil supply at changeover. The present invention relates to an improved feeding device for an endless welding wire that overcomes the disadvantages associated with prior attempts in this technical area. 
   PRESENT INVENTION 
   The present invention solves the problems associated with prior devices for endless welding wire installations. Such installations involve two specially wound supplies or coils of welding wire, wherein each supply has an exposed end of welding wire, which is the initial feed end for the coiled wire. The wire package also includes the trailing end of the wire on the coil, which end extends along the outside of the coil and is exposed at the open end of the container. The container is normally a drum, but could be a cardboard box. Two containers are mounted together at the endless welding wire installation. The feeding end of the first wire coil is directed through the upper guide grommet of the feeding device, which device is connected to the welding station by a guide tube normally a plastic sheath. A butt welding mechanism not forming a part of the present invention is then actuated to butt weld the exposed trailing end of the first welding wire coil with the feed end of the adjacent welding wire coil. The butt welder pushes the two ends together and directs an electric current for I 2 R heating the butt junction. This upsets the end surfaces and welds the two welding wires together. Then, the butt joint with its flash is hand filed or passed through a sizing stripper. Thus, the two supplies of welding wire are joined together to form what is termed an “endless welding wire.” The endless wire is pulled through the upper guide grommet and directed to the welding station from the first coiled supply of welding wire. When this welding wire coil is exhausted, the second coil is then used for welding. At that time, the second package is either shifted to the first position or the next package replaces the first exhausted package. This next package has a coil of welding wire with an exposed normal feed end and has an exposed trailing end. The butt welding procedure is repeated to join the next coil of welding wire to the welding wire coil being used in the welding operation. This procedure of providing replacement welding wire packages and connecting the new package with the trailing end of the package being used is an endless welding wire installation. Such installation uses the present invention. 
   In accordance with the present invention, there is provided a device for feeding, toward a welding station, welding wire coiled in two separate containers and joined together into an “endless welding wire”, as this term is employed in the electric arc welding field. By using the present invention, the height of the guide grommet is reduced. Indeed, the grommet essentially floats into a balanced position dictated by the welding wire being fed to the welding station. Consequently, the feed grommet seeks the appropriate position above the spaced containers. Thus, it can be located quite close to the top of the containers, thereby drastically reducing the head room necessary for the endless welding wire installation. 
   The novel feeding device of the present invention comprises a track element extending in a path generally including vertical axes of the spaced wire coils butt welded together into an endless welding wire. The track element extends above the coils in a given direction. It carries a grommet with a wire receiving guide opening surrounding a wire guide axis and a generally lower entrant end. The invention involves a carrier mounting the grommet on the track element for movement of the grommet above the coils and along the path determined by the track element. The grommet glides along the track so the trajectory of the wire coming from the coiled supplies determines the position of the wire as it is pulled from the respective coils. In essence, the grommet floats above the containers to match the upwardly moving wire; however, the invention also involves a servo mechanism having an input sensor mounted on the carrier and spaced below the grommet entrant end a distance defining a gap below the grommet. The servo mechanism senses the displacement of the welding wire in the extended direction of the track and creates a feedback signal that is used by a motion device of the servo mechanism to move the grommet to the desired location so the welding wire continues to be vertically oriented in the gap prior to entering the grommet. As the wire pulls in one direction or the other, the servo mechanism moves the grommet to be directly above the vertical orientation of the endless wire. 
   In the preferred embodiment, the path of movement of the grommet on the track element is linear so the track element extends in a direction or path intersecting generally the center axis of the two spaced coils butt welded together into an endless welding wire. As the wire is pulled from either coil the grommet is moved by the servo mechanism to be vertically aligned with the trajectory of the wire. Thus, the possibility of e-script tangles and bird nesting is reduced. Furthermore, the track element and movable carrier are closely spaced from the top of the containers, so the head room for the endless welding wire installation is less than a distance, such as 2 feet. This drastically increases the locations that will accommodate the installation. 
   The carrier is moved by the servo mechanism so it generally has a floating action above the natural trajectory of the upwardly directed endless welding wire. The only position constraint is that the floating action of the carrier is in the direction determined by the path of the track element supporting the carrier. This path is generally above the center of the two spaced containers providing the endless welding wire. A rodless cylinder is used. This track member is made by Bimba Manufacturing and is generally shown in Yarnall U.S. Pat. No. 5,491,737. One parallel rod of the track element has an internal, movable magnetic element that is pushed one way or the other according to the sensed displacement of the natural trajectory of the wire moving upwardly into the guide grommet. This centering action is performed by a pneumatic circuit, where the sensing device is moved by the incoming wire and determines the air supplied on one or the other side of the movable magnetic element of piston. When the air is released, the piston stays in its new adjusted position. A magnetic coupling is on the carrier and surrounding the rodless cylinder. It moves with the internal movable magnetic element to position the guide grommet in the desired location determined by natural trajectory of the upwardly moving endless wire. 
   In accordance with the invention, the grommet is spaced above the containers a short distance, preferably less than about 2 feet. In practice, this spacing is about 1–2 feet. In this manner, the needed head room of the installation is decreased and the exposed length of energized wire is decreased. Thus, there is no need for shielding, as is often required by other endless wire feeding devices. 
   In accordance with the invention, there is provided a carrier for guiding wire to a welding station. This carrier includes a grommet with a vertical wire receiving guide opening surrounding a guide axis and having a lower entrant end. A pair of passageways in the carrier allows movement of the carrier along two parallel rods extending between the wire supplies joined together to form an endless welding wire. A sensor is mounted on the carrier below the entrant end of the guide grommet to determine any displacement of the upwardly moving welding wire from the vertical axis of the guide grommet. 
   Furthermore, the invention involves a method of feeding a welding wire from a first and second container of wire, with each container including a coil of wire with a feed end and a trailing end. The trailing end of one container is butt welded to the feed end of the second container to provide an endless welding wire. This method involves providing a wire guide grommet with an entrant end, passing the wire from the feed end to the trailing end through the grommet and then moving the grommet across the containers in a given path according to the vertical orientation of the upwardly moving wire with respect to the entrant end of the grommet. In this method, the path of the moving grommet is less than about 2 feet above the containers having the coiled welding wire. The containers are preferably drums, but may be square boxes. 
   The novel device for feeding endless welding wire has been defined above; however, it could be further described as a device that also includes a butt welder to join the exposed trailing end of the wire in the first container to the feed end of wire in the second container to create what is called an endless welding wire. A grommet with a vertical wire receiving opening floats above the container in a given path determined by a track element slidably receiving the floating grommet. The path is generally linear and the containers are normally drums. The floating grommet is preferably moved by a servo mechanism responding to the natural position of the wire below the opening of the grommet. The track element includes first and second parallel rods. A carrier mounts the floating grommet and moves along the first rod. A guide passage in the carrier receives the second rod. The first rod is a rodless cylinder of the type sold by Bimba Manufacturing. There is a guide sleeve or sheath above the grommet for directing the welding wire from the floating or movable grommet to the welding station. 
   The primary object of the present invention is the provision of a feeding device for use in an endless welding wire installation, which feeding device has a reduced head room and reduces tangles and other physical problems associated with wore feeders for endless welding wire installations used in high production welding operations. 
   Another object of the present invention is the provision of a feeding device, as defined above, which feeding device involves a guide grommet movable along a path above the spaced coils constituting the butt welded coils of welding wire in an endless welding wire installation. 
   Still a further object of the present invention is the provision of a feeding device, as defined above, which device can be used with any endless welding wire installation having various types of welding wire containers. 
   Still another object of the present invention is the provision of a method for feeding an endless welding wire to a welding station, which method effectively feeds the endless wire to the welding station and effectively changes from one welding wire coil to the other by using the natural trajectory of the upwardly moving welding wire as it is pulled toward the welding station. 
   These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a block diagram illustrating a manufacturing layout to which the present invention is directed; 
       FIG. 2  is a side elevational view of a prior art wire feeder for an endless welding wire installation illustrating the required head room; 
       FIG. 3  is a top schematic view of a further prior art endless wire feeder for two spaced drums constituting an endless welding wire installation; 
       FIGS. 3A–3C  are schematic side elevational views of an endless welding wire installation using the basic aspect of the present invention and illustrating the reduced head room obtained by using the present invention; 
       FIG. 4  is a schematic pictorial view of a common butt welding device used for connecting the ends of adjacent wire coils to produce an endless welding wire for electric arc welding; 
       FIG. 5  is an enlarged schematic view illustrating the concept of sizing the butt welded joint between the ends of two adjacent wire coils to produce an endless welding wire for electric arc welding; 
       FIGS. 6A and 6B  are side elevational views similar to the views shown in  FIGS. 3A–3C  illustrating the broad concept of the preferred embodiment of the present invention; 
       FIG. 7  is a top elevational view of the feeding device shown in  FIGS. 6A–6B  used with adjacent drums constituting the containers for the endless welding wire; 
       FIG. 8  is a top plan view similar to  FIG. 7  illustrating the use of the present invention with adjacent square boxes instead of the preferred round drums, as shown in  FIG. 7 ; 
       FIG. 8A  is a top plan view similar to  FIG. 8  illustrating the concept of providing a non-linear track element for use in practicing the present invention; 
       FIG. 9  is a partial top view of the preferred embodiment of the present invention; 
       FIG. 10  is a schematic side elevational view of the preferred embodiment of the present invention, illustrating the general concept of a servo mechanism; 
       FIG. 11  is a pictorial view of the preferred embodiment of the present invention; 
       FIG. 12  is a front view partially in cross-section of the preferred embodiment of the present invention illustrated in  FIG. 11 ; 
       FIG. 13  is an enlarged cross-sectional view taken generally along line  13 — 13  of  FIG. 12 ; 
       FIG. 14  is a partial cross-sectional view taken generally along line  14 — 14  of  FIG. 13 ; 
       FIG. 15  is a partial top elevational view illustrating the displacement sensor of the servo mechanism used in the preferred embodiment of the present invention; 
       FIG. 16  is a top elevational view with a superimposed pneumatic circuit employed in the servo mechanism of the preferred embodiment of the present invention; 
       FIG. 17  is a view similar to  FIG. 16  illustrating movement of the carrier for the guide grommet utilizing the pneumatic servo mechanism of the preferred embodiment; and, 
       FIG. 18  is a top plan view illustrating optional mechanisms to be applied to the preferred embodiment of the present invention. 
   

   PREFERRED EMBODIMENT 
   The present invention relates to a wire feeder for an endless welding wire installation such as installation  10  in production or assembly line A shown in  FIG. 1 . The welding cell using an endless welding wire is part of several manufacturing operations, indicated generally as processes  12 ,  14  and  16 . A component or part enters at input  20  and is processed successively by the welding cell in series with several distinct processing operations to produce a completed part or assembly  22 . This type of assembly line, or production line, is a “just in time” manufacturing system. Consequently, an endless welding wire for welding cell  10  is advantageous so the welding wire is never exhausted; therefore, cell  10  need not be shut down for changing the supply of wire.  FIG. 1  illustrates that a shut down to replace an empty supply of welding wire with the next supply of welding wire has the effect of shutting down all of the processes  12 ,  14  and  16 . This interruption of flow drastically affects the efficiency and operating costs of manufacturing. Thus, it is desirable to use an endless welding wire for any welding cell in a manufacturing facility. However, attempts to use an endless welding wire installation has met with limited success. Some problems of feeding the endless wire from the wire supply containers to the welding operation of cell  10  have defied solution. For instance, prior feeding devices as shown in  FIGS. 2 and 3  have been proposed to feed the endless wire from containers C′, C″ to a welding operation or station. In  FIG. 2 , the wire feeder for an endless welding wire installation includes a fixed upper guide grommet  32  spaced from the top of containers C′, C″ by distance y, which distance is substantially greater than 2 feet. Containers C′, C′ rest on a support surface  30 . Fixed grommet  32  is mounted on a vertically spaced member  34  for guiding endless wire W into and through plastic sheath  36 , through which the wire is pulled to perform a welding operation in an adjacent welding station. Endless wire W includes a first coiled supply  40  and a second coiled supply  42 , with feed end  40   a  pulled from container C′ until the container is empty. The trailing end  40   b  is pulled upwardly through grommet  32 . Since end  40   b  is butt welded to feed end  42   a  of coiled supply  42  by butt weld B, exhaustion of coiled supply  40  merely transfers the supply of endless welding wire from container C′ to container C″. The second container has an exposed trailing end  40   b  for attachment to the feed end of the next container that replaces empty container C′ in accordance with standard procedure. The coiled wire supplies  40 ,  42  are called “coils” and include parallel spaced vertical axes  40   c ,  42   c , which axes are generally equally spaced from center vertical axis  32   a  of grommet  32 . By using this prior art structure, height y of grommet  32  must be great enough to accommodate pulling wire from one side of container C′ to the remote opposite side of container C″, without moving grommet  32 . This restricted action dictates a substantial height y for grommet  32 . 
   To accommodate the requirement of pulling wire from coils having spaced axes  40   c ,  42   c , it has been suggested that grommet  32  be mounted on a pivoted or swinging arm  50 , as shown in  FIG. 3 . Arm  50  is pivoted about pin  52  on fixed support  34  between the solid line position and the phantom line position shown in  FIG. 3 . Guide grommet  60  on the outer end of arm  50  is movable between a position generally above axis  40   c  to a position generally above axis  42   c . This mechanism for feeding endless wire W does allow the normal feeding from the center of coils  40 ,  42  as in normal electric arc welding with a single container or drum. However, even with pivot arm  50  carrying sheath  36  and guide grommet  60 , the pivot arm still must remain substantially above containers C′ and C″. Furthermore, the endless welding wire feeding  5  installation requires accommodation of the spacing x between containers C′, C″ and fixed support structure  34  for pivot arm  50 . Thus, adoption of the swinging pivot arm to reduce the head room of feeding device introduced further spatial constraints for the endless wire installation. Prior art feeders as shown in  FIGS. 2 and 3  are the wire feeders having the disadvantages corrected and overcome by the present invention. 
   Operation of the present invention is generally described with respect to the schematic presentations of  FIGS. 3A ,  3 B and  3 C wherein guide grommet  100  is movable in a path P over the top of spaced containers C′, C″ that are resting on support surface  30 . The containers of  FIG. 3A  are essentially the same as containers shown in the prior art feeders of  FIGS. 2 and 3 . Guide grommet  100  is closely spaced from the top of containers C′, C″ by a distance x, which distance is less than about 2 feet to reduce the head room requirement for the wire feeder used to feed endless wire W first from container C′ and then from container C″. Transition of floating grommet  100  movable along path P from the empty container C′ to the full container C″ is illustrated in  FIG. 3B . When container C′ is empty, grommet  100  is moved along path P to a location determined by the natural vertical trajectory of wire W, which trajectory is generally above axis  42   c  of container C″. When container C′ is empty, it is removed along path R′ and replaced by a full container or drum  110  moved in the replacement path indicated by arrow R″. As wire W is being pulled through sheath  36  and through floating grommet  100  from container C″, the coiled supply or coil  120  of welding wire in container  110  is butt welded at B′ so that the feed end  120   a  of coil  120  is connected to the trailing end  42   b  of coil  42 . Trailing end  120   b  is exposed at the upper end of container  110  for joining to the next successive leading end of the drum to replace drum  110  as it is exhausted. A basic novel concept of the present invention is illustrated in  FIGS. 3A ,  3 B and  3 C wherein grommet  110  floats along a path P closely spaced above the welding wire containers between the position for guiding endless wire W from one container and then the new position for guide wire from the next successive container. Details of the preferred embodiment of the invention for floating and moving grommet  100  along path P is shown in detail in  FIGS. 11–17 . 
   Any type of butt welder can be used for joining the ends of the wire in spaced containers C′, C″ to produce an endless welding wire W. A schematically illustrated butt welding mechanism  130  is schematically illustrated in  FIGS. 4 and 5  wherein wire ends  40   b  and  42   a  are gripped by movable vice members  132 ,  134  and jammed together by force devices not shown, but illustrated as arrows  140 ,  142 . As the ends  40   b ,  42   a  are forced together electric current is passed between the wires by a low frequency power source mounted on or in platform  136 . Thus, the two ends  40   b  and  42   a  are butt welded to produce the butt weld B shown in  FIG. 5 . To remove the upset portion of butt weld B, stripper jaws  150 ,  152  are mounted on movable support  156  and fixed support  158 , respectively, and are forced around the welding wire W by lever  170 . Spring  154  controls the force between the jaws. End  42   a  is pulled by drive rolls  160 ,  162  by a motor also mounted in platform  136  and not shown. Wire W is pulled through the stripping jaws  150 ,  152  to remove the upset portion of the butt weld. Lever  170  moves the drive rolls and stripping jaws against the wire for pulling the butt welded wire through the gripping jaws. To release the mechanism, lever  170  is moved in the opposite direction. The mechanism schematically illustrated in  FIGS. 4 and 5  is only representative to show that the invention is used for an endless wire installation. Details of the butt welder and wire stripping mechanism do not form a part of the present invention. It is illustrated only for general showing of a device now used in some endless welding wire installations. 
   The schematic illustration of movable grommet  100  in  FIGS. 3A ,  3 B and  3 C is expanded in  FIGS. 6A ,  6 B. A structure is provided for controlling movement of spool  100 . This structure is a linear track element  200  extending horizontally over the tops of container C′, C″ a distance x. Track  200  controls movement of carrier  202  that supports and moves guide grommet  100  as it is shifted along path P. A top view of the installation as shown in  FIGS. 6A ,  6 B is illustrated in  FIG. 7 . Path P extends generally between axes  40   c ,  42   c .  FIGS. 8 and 8A  are presented to illustrate certain modifications of the invention. For instance,  FIG. 8  replaces cylindrical drums C′, C″ with cardboard boxes  210 ,  212  having the standard octagonal liners  214 ,  216 , respectively. By use of boxes, the containers can be aligned by merely placing the two boxes together as shown in  FIG. 8 . In  FIG. 8A , linear track element  200  need not be exactly straight. A somewhat curvilinear track  200 ′ can perform the invention. Floating guide grommet  100  is moved from a position over axis  40   c  to a position over axis  42   c . The exact configuration of path P, which is preferably linear can be somewhat non-linear such as path P′.  FIGS. 8 and 8A  reveal how the basic concepts of the present invention can be modified by using the equivalent structures and concepts. 
   The preferred embodiment of the present invention involves moving carrier  202  along track element  200  by a servo mechanism as schematically illustrated in  FIGS. 9 and 10 . Servo mechanism SV includes a sensor  220  to sense displacement of wire W at position  222  below the lower entrant end  230  of grommet  100 . The space between entrant end  230  and position  222  defines a gap g in which wire W is intended to be substantially vertical and aligned with the central axis of grommet  100 . Sensor  220  detects if wire W is deflected in the direction of path P to position  222   a  in one direction and position  222   b  in the opposite direction. These two directions are along path P, as shown in  FIG. 9 . If the wire is displaced to a position  222   a , sensor  220  creates a signal in line  240 , which signal is directed to motion device  242 . This signal causes output drive element  244  to move carrier  202  to the right for vertical orientation or alignment of wire W. In a like manner, if wire W is displaced to the left position  222   b , a reverse signal is provided at output  240  of sensor  220  forcing motor device  242  to drive element  244  in the opposite direction moving carrier  202  to the left. Thus, grommet  100  is aligned with the desired or natural vertical feeding trajectory of wire W to facilitate feeding of wire W through grommet  100  and sheath  36 . Sensor  220  is mounted on carrier  202  so it senses displacement of wire W in one direction or the other with respect to path P as grommet  100  moves between spaced containers C′, C″ of the endless welding wire installation. Various servo mechanisms can be provided, as well as various track elements  200 ; however, the preferred implementation of the present invention has specific structural details for these elements as shown in  FIGS. 11–17 . 
   The mechanical features of the practical embodiment are best described in  FIGS. 11–14 . Track element  200  is mounted on support stanchion  300  having a horizontal arm  302  and a fixed back plate  304  with spaced facing ends or caps  306 ,  308 . Track element  200  includes a center rodless cylinder  310  which is a previously described commercial product. Guide rods  312 ,  314  are assembled between ends  306 ,  308  by bolts  316  and are parallel to rodless cylinder  310 . These parallel rods define the path of movement of carrier  202 . Carrier  202  includes housing  320  with parallel guide passageways  322 ,  324  for slidably receiving in cylindrical bearings guide rods  312 ,  314 , respectively. Front mounting plate  330  is affixed to housing  320  by bolts  332 . Lower extension  334  has clearance slot  336  to allow pivoting action of the sensor elements  350 . Upper gudgeon block  340  positions guide grommet  100 . A round opening in the grommet has a low friction surface, such as a TEFLON (Polytetrafluoroethylene) sleeve that surrounds its vertical axis and defines lower entrant end  230 . On mounting plate  330  below entrant end  230  is a pivoted sensor element  350  spaced from grommet  100  by gap g. Sensor element  350  is pivotally mounted in clearance slot  336  of lower extension  334  by pivot pin  352 . A rearwardly extending arm  354  is movable in slot  336 . Circular opening  356  of sensor element  350  receives wire W. Sensor element  350  pivots about pin  352  as wire W is displaced to the right or to the left. Extending from arm  354  are two spaced, angled cutoff surfaces  360 ,  362 . These surfaces coact with vent orifices  370 ,  372  for controlling the servo mechanism best shown in  FIGS. 15–17 . 
   Carrier  220  slides on commercially available rodless cylinder  310 . The details of this rod are best shown in  FIG. 14 . A central passage  400  slidably receives cylindrical piston  402  to define air volumes  404 ,  406  on opposite sides of the piston. Volume  404  is connected to air line  400   a  and, in a like manner, volume  406  is connected to line  400   b . Within piston  402  there is a strong permanent magnet element  410  that coacts with cylindrical magnet carrier element  420  surrounding rodless cylinder  310  and held into bore  422  of housing  320  by snap rings  420   a ,  420   b . Central passage  424  allows a sliding action of element  420  on rod  310 . Within ring or element  420  are spaced permanent magnets  426 ,  428  facing the poles of magnet  410  in floating piston  402 . Carrier  420  is pulled axially along rods  312 ,  314  by movement of piston  402  caused by the difference in pressure in volumes  404 ,  406 . Coupling of element  420  with piston  402  is by magnetic force between magnet  410  and magnets  426 ,  428 . Thus, movement of piston  402  pulls carrier  420 ; however, there is no physical connection so it is possible to break the coupling with a relatively small force. In this manner, wire W can not be forced into an unnatural location or can not cause tangles by improper movement of cylinder  402 . Pivoting element  350  is the sensing member for the servo mechanism, which member provides a signal when displacement of wire W pivots element  350  a distance covering either vent orifice  370  or vent orifice  372 . Such displacement of the wire controls air in volumes  404 ,  406  to move carrier  202  along cylinder  310  so wire W between opening  356  and grommet  100  is generally aligned with the vertical axis of the grommet. In this manner, the grommet is moved or floats along path P to maintain a vertical orientation of wire Win gap g. 
   The pneumatic system  500  operates in response to the position of sensor element  350 , best shown in  FIG. 15 . The hydraulic system can have a variety of configuration. Indeed, the servo mechanism can be mechanical or electrical. In the preferred embodiment it is pneumatic using system  500  shown in  FIGS. 16 and 17 . Air supply  502  directs pressurized air in lines  504 ,  506  and  508 . Lines  400   a ,  400   b  are connected to piston balancing lines  512   514  through control valves  516 ,  518  allowing pressure to bleed from volumes  404 ,  406 , but preventing rapid movement of the piston in either direction. The basic features of system  500  involves the operation of bypass valves  520 ,  530 . Bypass  520  includes a primary outlet line  522  and pressure control line  524 . Line  522  is used in conjunction with spring  526  in chamber  526   a . In a like manner, bypass valve  530  includes a primary outlet line  532  and pressure control line  534 . Line  532  acts in unison with spring  536  in chamber  536   a . Slide valve  540  includes three sections  542 ,  544  and  546 . Exhaust lines  550 ,  554  are aligned with the valve sections  542 ,  544  and  546  as they are moved into the center position. In  FIG. 16 , the position of carrier  202  is stabilized with opening  356  aligned with the vertically spaced guide grommet  100 . Pressure is maintained on line  512 ,  516  to maintain the axial position of piston  402  and thus carrier  202  magnetically coupled to this piston. As long as the wire moves vertically through opening  356 , system  500  is balanced as shown in  FIG. 16 . Assume that there is displacement of wire W to the right as shown in  FIG. 17 . This happens when wire W converts from coil  40  to coil  42 . Element  350  pivots counterclockwise, with surface  362  closing vent orifice  372 . There is a pressure buildup in line  524  so that this line can not vent bypass valve  520 . Thus, the pressure in line  506  is directed to the chamber  526   a  of spring  526  to move slide valve  540  to the right. Thus, pressurized line  504  is connected through valve portion  544  to line  512  and line  514  is vented. Air is directed through valve  516  into volume  404  moving piston  402  to the right forcing carrier  202  to the right. This compensates for the deflection of wire W to the right. This action will continue until wire W is vertically aligned with the axis of grommet  100  by being above coil  42 . When that happens, surface  362  is pivoted away from vent orifice  372  to vent the pressure in line  524 . This removes pressure from line  522  causing springs  526  and  536  to center slide valve  540 . Springs  526 ,  536  are selected to maintain valve  540  centered when vents  370 ,  372  are opened. When sensor element  350  pivots clockwise, the reverse action illustrated in  FIG. 17  takes place. Thus, carrier  220  is moved by system  500  to maintain the upper guide grommet  100  directly above the trajectory that wire W wants to follow as it is being pulled from the containers. When the first container is exhausted and the second container is operated, element  350  is held in the position shown in  FIG. 17  until carrier  202  moves above coiled wire  42  where it is again stabilized. In this manner, the guide grommet moves or floats back and forth as schematically illustrated and described with respect to  FIGS. 3A ,  3 B,  3 C,  6 A,  6 B and  7 – 10 . However, the preferred and practical implementation of the present invention is illustrated in  FIGS. 11–17 . 
   A slight modification of the present invention is illustrated in  FIG. 18 , wherein containers in the form of boxes  210 ,  212  are moved together and then positioned against a fixed surface  600 . In this embodiment, the alignment of track element  200  over the axes  40   c ,  42   c  is automatic and controlled by a device to transfer track element  200  laterally. This automatic transfer device is schematically illustrated as a fixed channel  610  slidably receiving rod  612  to slide horizontally under the control of a rack  620  driven by pinion  622 . Rod  612  having a horizontal arm  302   a  to at least partially support transfer track element  200 . Sensor device  630  includes feeler  632  for engaging the front face of boxes  210 . The position of the box produces a signal in line  634  driving motor  640  connected to pinion  622  by a shaft  642 . Thus, by merely moving the boxes  210 ,  212  together against surface  600 , feelers  632  move track element  200  to the proper lateral position above the matched boxes. This showing merely illustrates a device for adjusting the lateral position of track element  200  over wire coils  40 ,  42 . Consequently, the containers themselves need not be accurately positioned in the endless wire installation. The track member can be adjusted either manually or automatically to the proper position over the center of the coils.