Abstract:
Fabricating an implantable stimulation lead by advancing work material to be wrapped with wire conductors, then, operating a plurality of payout carriers to let out the wire conductors, rotating the plurality of payout carriers to wrap the wire conductors about the work material, providing an amount of twist to each wire conductor as the wire conductors are let out, forming a lead body using the wrapped conductors, and fabricating a plurality terminals on the lead body, wherein the plurality of terminals are electrically connected to the conductive wires.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 12/763,021, filed Apr. 19, 2010, pending, which was a continuation of U.S. application Ser. No. 11/869,844, filed Oct. 10, 2007, now U.S. Pat. No. 7,698,883, which was a continuation of U.S. application Ser. No. 11/285,826, filed Nov. 22, 2005, now U.S. Pat. No. 7,287,366, which claims the benefit of U.S. Provisional Application No. 60/630,323, filed Nov. 23, 2004, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Bioelectrical stimulus leads in general and pain management leads in particular have proven to be an important addition to mankind&#39;s set of tools for addressing bodily malfunction. Unfortunately, heretofore these leads have been made one at a time in a fairly expensive operation that included the use of a lathe to turn a set of insulated wires together about a mandrel and then the application of heat and pressure to fuse the insulation of the wires together. Additionally, at least in part because the lathe wrapping process results in a lead body having a varying outer diameter and insulation thickness, the previous method has encountered a fairly high defect rate, driving up the price for correctly manufactured leads. Later operations, in which electrodes are created in the lead body require a uniform outer diameter and insulation thickness to avoid frequent accidental damage to the lead bodies, due to an uncertain amount of insulation removal needed to reach the underlying wire. This uncertainty has made it impractical to automate the process. 
     A separate problem that occurs when helically winding wires about a mandrel is that of residual stress being imparted to the wires. In the prior art, two basic options are available for this kind of wire wrapping. In both options, a set of payout carriers are mounted on a turn table having a central aperture through which the core being wrapped is advanced. The turntable is rotated about this mandrel and the payout carriers let out wire, which helically wraps the mandrel. In a first option, known as a planetary system, the payout carriers are maintained in a stationary orientation relative to an absolute coordinate system. In the second option, the payout carriers are maintained in a stationary orientation relative to the turntable (“stationary re turntable” case). For each option, however, residual stress is imparted to wires as they are wrapped because the ideal amount of payout carrier rotation falls in between the planetary case and the stationary re turntable case. 
     Also, some references show a lead being made by taking a group of insulated wires and binding them together with an additional application of curable insulation. Although this is a workable method, the step of applying an additional coat of insulation requires some time for the insulated wires to be dipped into the curable insulating material, and then requires some time for that material to be cured. It would be advantageous to find some other way of binding a set of insulated wires together. 
     BRIEF SUMMARY 
     In a first separate aspect, the present invention is a method of producing a plurality of multi-electrode leads that uses a set of insulated wires. These wires are continuously stranded together, thereby forming a stranded portion. Then the wires of the stranded portion are continuously fused together, thereby creating a fused portion. 
     In a second separate aspect, the present invention is a length of working material, more than two meters (six feet) long, comprising a flexible central mandrel and insulated wires helically wrapped about the central mandrel and fused together. 
     In a third separate aspect, the present invention is a production facility for producing multi-electrode leads. The facility includes a wire wrapping device adapted and configured to wrap a mandrel with insulated wires and a radiant energy application device, located so as to continuously receive the wrapped mandrel, the radiant energy application device being adapted to apply radiant energy to the wrapped mandrel, sufficient to fuse the insulated wires together. 
     In a first separate aspect, the present invention is a helically wrapped wire device wherein a set, of wires are arranged helically about a core region and wherein each wire defines a central axis and wherein each wire goes through less than 0.1 rotations about its central axis for every complete rotation about the core region. 
     In a second separate aspect, the present invention is a wire wrapping device that includes a turntable assembly that is made up of a turntable and a driver adapted to rotate the turntable. Also, a set of payout carriers are mounted on the turntable, each payout carrier adapted to let out wire to be wrapped. A driver is adapted to turn each payout carrier relative to the turn table, the driver being user adjustable to turn each payout carrier by a selectable amount, per each complete rotation of the turntable. 
     In a third separate aspect, the present invention is a method of wrapping a central mandrel with flexible longitudinal elements. In the method a set of payout carriers are revolved about the central mandrel as the central mandrel is moved along its length and the payout carriers payout the flexible longitudinal elements, thereby helically wrapping the mandrel with the flexible longitudinal elements. Also, the payout carriers are rotated a user-selected amount per rotation of the turntable. 
     In a first separate aspect, the present invention is a method of making a multi-electrode probe, that starts with a length of a working material comprising a set of insulated wires arranged so that they are touching along their lengths. The working material is moved continuously in a lengthwise manner through a radiant energy application zone, where radiant energy is applied to the working material, thereby heating the working material to soften a portion of the insulation and render it adhesive. The softened insulation is permitted to adhere together and re-cool, thereby fusing together the insulated wires. 
     In a second separate aspect, the present invention is a reflow assembly, comprising a radiant energy application device, adapted to create plural radiant energy application zones, the plural radiant energy application zones being longitudinally and angularly displaced from each other. In addition, a movement assembly is adapted to move a continuous length of working material through the radiant energy application zones. 
     In a first separate aspect, the present invention is a helically wrapped wire device wherein a set of wires, insulated from one another and each having a wire central axis, are arranged helically about a core region defining a device central axis, and wherein at each point along each wire a radial distance may be defined between the wire central axis and the device central axis, and wherein the radial distances, over the entirety of the device do not vary by more than 100 microns. 
     In a second separate aspect, the present invention is a method of producing a multi-electrode probe, starting with a wrapped wire work piece having a set of wires, each surrounded by insulation which is fused together into a unitary mass and each having a most radially outward surface, which is radially outward relative to the work piece, the work piece defining a work piece central axis, and wherein at each point along each wire a radial distance may be defined between the work piece central axis and the most radially outward surface of the wire. Also, at least one prospective electrode point is defined along the most radially outward surface of each wire, each prospective electrode point having an actual radial distance that is within 100 micrometers of an ideal predetermined radial distance for the prospective electrode point. An energy beam is used to create an aperture through the insulation at each prospective electrode point, the application of the energy beam being facilitated by the actual radial distance being within 100 micrometers of the ideal radial distance. 
     In a first separate aspect, the present invention is a wire wrap device, comprising a turntable and a set of payout carrier assemblies positioned on the turntable. Each payout carrier includes, a spool bearing wire, an electric motor operatively connected to the spool; and an electric motor control assembly adapted to control the electric motor to maintain a selected tension on the wire. 
     In a second separate aspect, the present invention is a method of wrapping a central mandrel with flexible longitudinal elements. The method includes revolving a set of payout carriers about the central mandrel as the central mandrel is slowly moved along its length and the payout carriers payout the flexible longitudinal elements, thereby helically wrapping the mandrel with the flexible longitudinal elements. In addition, each payout carrier has a spool that is turned by an electric motor and also has a longitudinal element tension measurement device. The tension is regulated by controlling the electric motor in response to the tension measurement device. 
     In a first separate aspect, the present invention is a wire wrap device, comprising a turntable assembly that, in turn, includes a turntable that defines a central aperture, and payout carriers mounted on the turntable. In addition a payout assembly is adapted to payout flexible mandrel and a flexible mandrel guide assembly is adapted to guide the flexible mandrel through the aperture and to maintain the flexible mandrel in a constant rotational orientation. 
     In a second separate aspect, the present invention is a helically wrapped wire work piece, comprising a mandrel and a set of insulated wires, wrapped about the mandrel. The mandrel is not twisted anywhere over its length at a twist rate of more than one complete rotation per one meter of mandrel. 
     The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the preferred embodiment(s), taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a preferred manufacturing process according to the present invention. 
         FIG. 2  is a side view of a continuous work piece at a first stage in the process of  FIG. 1 . 
         FIG. 3  is a side view of the work piece of  FIG. 2  at a later stage in the process of  FIG. 1 . 
         FIG. 4A  is a cross-sectional view of the working material of  FIG. 3 . 
         FIG. 4B  is a cross-sectional view of the working material of  FIG. 7 . 
         FIG. 4C  is a cross-sectional view of a working material according to an alternative embodiment, including a second layer of wires. 
         FIG. 5  is a side view of the work piece of  FIG. 3  at a first sub-stage of a further stage in the process of  FIG. 1 . 
         FIG. 6  is an illustration of an optional step in the process of  FIG. 1 . 
         FIG. 7  is a side view of an individual work piece in a further stage of the process of  FIG. 1 . 
         FIG. 8  is a side view of a finished product of the process of  FIG. 1 . 
         FIG. 9  is a block diagram of a wire wrap process that forms a portion of the process illustrated in  FIG. 1 . 
         FIG. 10  is a front view of a wire wrapping device according to the present invention. 
         FIG. 11  is a partial front of the wire wrapping device of  FIG. 10 , showing some features obscured from view by the front panel shown in  FIG. 9 . 
         FIG. 12  is a partial top view of the wire, wrapping device of  FIG. 10 , showing the payout carrier gears. 
         FIG. 13  is a perspective view of a portion of the wire wrapping device of  FIG. 10 , showing the payout carrier turntable. 
         FIG. 14  is a perspective view of a single one of the payout carriers of the wire wrap device of  FIG. 10 . 
         FIG. 15  is an alternative perspective view of a single one of the payout carriers of the wire wrap device of  FIG. 10 . 
         FIG. 16  is a block diagram of the insulation fusing portion of the lead production process of  FIG. 1 . 
         FIG. 17  is a perspective view of a reflow oven according to the present invention. 
         FIG. 18  is a sectional view of the reflow oven of  FIG. 17  taken along line  18 - 18  of  FIG. 17 . 
         FIG. 19  is an illustration of an alternative preferred embodiment of the reflow process. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 through 8 , the following text describes a preferred method of the present invention in schematic overview. A more detailed discussion of the critical steps follows. 
     A preferred method for practicing the present invention begins with a continuous working material  10 , which at the process beginning is only a poly tetrafluoroethylene coated stainless steel mandrel wire  12 . The working material  10  is then helically wrapped with a set of four insulated wires  14   a ,  14   b ,  14   c  and  14   d  (collectively  14 ) at a wire wrapper  15 . Each of the wires  14  includes a layer of insulation  16 . While four insulated wires are used in one embodiment, those skilled in the art will recognize that any suitable number of wires may be wrapped onto mandrel  12 , using the methods of the present invention. The use of four wires in particular is not intended to be part of the invention. Referring to  FIG. 4   c , in one embodiment, one or more additional layers of wires are wound in helices over the initial layer of wires  14 . Typically, each additional layer of wires would be wound in the opposite direction to the layer immediately below. 
     Working material  10 , now comprising mandrel  12  and helically wrapped insulated wires  14  ( FIG. 4 ) may now be spooled and later unspooled (not shown) or fed directly to the next step in the process. In this next step, working material  10  may be selectively and repeatedly heated in a multistage reflow oven  18  ( FIG. 1 ). The wires  14  are heated to a temperature that causes the insulation  16  of insulated wires  14  to approach or achieve a phase change, thereby becoming soft and adherent and ultimately fusing together, by heating, melting and re-solidifying, in a set of angular regions  17  ( FIG. 5 ). This process is preferably repeated, by feeding working material  10  through additional stages of reflow oven  18 , until the insulation  16  is fused together over its entire angular extent. 
     In an alternative embodiment, the insulation of each wire  16  is chosen so that its phase transition temperature, T g , is different from the T g  of the insulation  16  of the neighboring wires  14 . In particular, one or more wires  14  may have insulation  16  having a T g  that is high enough so that it does not undergo a phase change in the reflow oven  18 , and emerges intact to lend desired physical characteristics (such as enhanced stiffness) to the working material  10 . In another alternative preferred embodiment (not shown), spacers may be used to impart desired physical characteristics, such as stiffness, to the overall working material  10 . 
     At this point, the working material  10 , now comprising mandrel  12  having insulated wires  14  at least partially fused about it, may now be spooled onto a spool  20  and stored for later work (optional step  19  in  FIG. 1 , shown in  FIG. 6 ). Alternatively, step  19  is not performed and working material  10  proceeds directly to the remaining steps. Continuous working material  10  is cut (step  24 ) into individual lead bodies  21 . Each individual lead body  21  may have a length of from about 10 cm (4 in) to about 150 cm (60 in). 
     After the lead bodies  21  have been cut to length, mandrel  12  must be removed from within in a mandrel removal step  28 . This task may be facilitated by a coating of mandrel  12  that will ease removal, such as a PTFE coating. The mandrel removal step  28  may be a simple hand operation by a human worker. 
     Next, in an electrode creation step  30  a proximal aperture  38   a  ( FIG. 7 ) and a distal aperture  38   b  are created through insulation  16  for each one of wires  14 . This task is performed by a laser machining station, preferably equipped with four (4) nd:YAG frequency multiplied lasers or other ultraviolet light lasers. Other removal steps may be used such as that disclosed in U.S. Pat. No. 6,952,616 is incorporated by reference as if fully set forth herein. 
     In a ring attachment step  32 , a power source ring connector  40   a  is attached at each proximal aperture  38   a  and a tissue stimulating ring electrode  40   b  is attached at each distal aperture  38   b . This may be done by constructing a column of conductive material and laser welding ring  40   a  or  40   b  to this column. One preferred method of attaching ring electrodes is described in patent application Ser. No. 10/700,110 filed on Nov. 3, 2003, which is assigned to the same assignee as the current application and is incorporated by reference as if fully set forth herein. 
     In one preferred embodiment mandrel  12  has an outer diameter of 330 microns (13 mils) and insulated wires  14  each have a diameter of 273 microns (10.75 mils), which after some compression results in an individual lead bodies  21  having an diameter of about 711 microns (28 mils). 
     Throughout the process as described above and in greater detail below, great care is taken to create a lead body  21  having uniform insulation thickness. It is in the creation of the apertures  38   a  and  38   b  through insulation  16  that this effort bears fruit, because it is far easier, and less prone to error, to laser machine a lead body having a uniform outer diameter (and therefore uniform laser range) then a non-uniform lead body. Particularly troubling is the case in which the range is too close, and too much insulation is removed, potentially ruining the entire end product. 
     FIGS.  9  and  10 - 15  describe the wire wrap process and the wire wrapper  15  used for helically wrapping the mandrel or core in greater detail. Referring to  FIG. 10  for a high level depiction of the wire wrapper  15 , the wire wrap process begins with a mandrel payout assembly  80  and a working material take up assembly  86  that together maintain working material  10  in well regulated motion and tension along its path. Simultaneously a controls and displays assembly  88  controls a power and linkage assembly  82 , which powers a wire payout assembly  84 . Although one preferred embodiment permits the use of a keyboard for user input of control parameters, as indicated in  FIG. 10 , an alternative embodiment provides a simple set of manual controls, such as knobs, for controls and display assembly  82 . 
     Assembly  84  includes a turntable  114  upon which a set of payout carriers  112  are supported. Wire wrapper  15  is configured to permit a variable degree of back twist compensation, which is implemented by rotating carriers  112  relative to turntable  114  at an operator specified rate. In one embodiment an operator manipulates controls and displays assembly  88  to place the right amount of back twist compensation onto wires  14 . In an alternative embodiment, the operator enters the wire and mandrel dimensions and the pitch at which the wires are to be wrapped and assembly  88  computes the degree of back twist compensation necessary to prevent residual stress being placed onto wires  14 . 
     Avoiding the placement of residual stress on wires  14  is necessary so that this stress does not cause the wires to move spontaneously later in the process, causing a deformation in the final shape of the lead body  10 , or inconsistent wire locations. After wrapping is complete, wrapped mandrel is spooled by working material take up assembly  86 , which maintains a constant tension to avoid deforming the working material  10 . In an alternative preferred embodiment, working material  10  is not spooled but progresses immediately to the next stage of processing. 
     In greater detail, the progress of working material  10  is maintained by the payout assembly  80  and the take up assembly  86 . The payout assembly  80  includes a mandrel payout spool  100 , a payout motor  102  and a dancer arm tension measurement device (not shown). Motor  102  is responsive solely to the tension measurement, thereby maintaining constant tension on working material  10 . In take up assembly  86 , working material take up spool  105  is also motor driven (not shown) and solely responsive to tension measurement dancer arm  103 . Take up spool  105  is moved cyclically into and out of the plane of  FIG. 10 , thereby causing working material  10  to spool in a repeated pattern. The tension placed on working material  10  can be changed by changing the weighting on either dancer arm  103  or the payout assembly  80  dancer arm (not shown). 
     An additional portion of take up assembly  86  is the capstan  106 , which includes an equal-diameter pair of wheels  108  and  110 , about which working material  10  is looped several times. Each wheel  108  and  110  bears several grooves along its exterior rim, to permit this looping while preventing the working material  10  from ever rubbing against itself. Capstan  106  is driven by an electric motor (not shown) and serves the function of stabilizing working material  10  as it exits wrapping guide plate  169  ( FIG. 11 ). 
     Referring to  FIG. 9 , for a more complete description of the control scheme of wrapper  15 , the wire wrap pitch  92 , which in practice is the ratio between the capstan  106  rotation rate and the turntable  114  rotation rate  96  (which equals the rotation rate of a turntable drive motor  132  [ FIG. 11 ]) may be set prior to beginning a wire wrapping run. Likewise the backtwist compensation ratio  96 , which is the ratio of a payout carrier drive motor  134  rate [ FIG. 11 ] to the turntable drive motor  132  rate, may be set at the same time. Then, during a run, the speed of the entire process may be changed by changing the turntable rotation rate command  94 , which changes the capstan  106  turn rate and payout carrier drive motor  134  rate, automatically. In other words, during operation, the capstan  106  drive and the payout carrier drive motor  134  are slaved to the turntable drive motor  132 . The rate of capstan  106  effectively controls the turn rate of take up spool  105  ( FIG. 10 ) and pay out spool  100  ( FIG. 10 ) as both these spools are controlled to place a fixed tension on working material  10 , and this can only be accomplished if they turn at the same average rate as capstan  106 . 
     Referring to  FIG. 11 , power and linkage assembly  82  ( FIG. 10 ) includes an inner shaft  122  which drives the turntable  114 , and an outer shaft  124  which drives the payout carriers  112 , by way of a system of gears  126 . Inner shaft and outer shaft are driven by a first pulley  128  and a second pulley  130 , respectively. Each of these pulleys  128 ,  130  are driven by a belt  129  and  131 , respectively, that is in turn driven by the turntable motor  132  and the payout carrier motor  134 , respectively. 
     The two motors  132  and  134  are managed by the control assembly  88  ( FIG. 10 ), which regulates their relative speed within a range of relative speeds. As noted previously, the turn rate ratio of these two motors is set before a production run is begun. In one preferred embodiment this range extends from equal speed (payout carriers  112  stationary relative to the turntable  114 ) to the case where the outer shaft rotates at one half the speed of the inner shaft (payout carriers  112  stationary relative to an absolute frame of reference). 
     A number of features shown in  FIGS. 11 and 13  facilitate the workings of the embodiment. A slip ring  140  permits electric power to be transmitted to the rotating inner assembly that includes shafts  122  and  124 . On turn table  114 , each payout carrier  112  includes a slip ring  142  near its base for supplying electricity to the payout carrier  112 . Each payout carrier  112  includes an electric wire tension control assembly  144  that maintains a constant tension on the insulated wire  14  that is being threaded onto working material  10 . Bearing assemblies  150 ,  152 ,  154  and  156  facilitate the rotation of shafts  122  and  124 . Plates  160  and  162  support power and linkage assembly  82 . A spider  164  supports a wire guide wheel  166  for each payout carrier  112 , to further restrain the wires  14  as turntable  114  rotates. A first pair of pinch wheels  168  acts as an anti-rotation device for mandrel  12 , to prevent it from being twisted by the torque imparted by wires  14 , as they are being wrapped. In addition, a guide plate  169  defines an aperture that helps stabilize mandrel  12  and wires  14  at the point that the actual wrapping takes place. Finally, a second pair of pinch wheels  171  act to further stabilize the mandrel  12 . Together pinch wheel pairs  168  and  171  form a guide path for and prevent rotation of mandrel  12 . 
     Referring to  FIGS. 12 ,  14  and  15 , each electric wire tension control assembly  144  includes an electric motor  170  that drives a spool  172 , both of which are mounted on a payout carrier frame  173 . A wire  14  follows a path defined by a dancer arm  174  which is rotatably mounted by way of an axle  175  to frame  173 . Dancer arm  174  has a first dancer arm guide wheel  176  and a second dancer arm guide wheel  178  about which wire  14  is threaded in an “S-pattern.” Wire  14  proceeds about a frame guide wheel  180  and through a payout carrier exit guide  182 . A dancer arm position measurement unit  184  monitors the position of arm  174  and sends this information to an electric motor controller  186 . Controller  186  commands the rate at which electric motor  170  turns. This arrangement permits control of the tension in wire  14  to an accuracy of about +1%. 
     Referring to  FIG. 12 , a system of gears  126  links the motion of outer shaft  124  with that of the payout carriers  112 . An outer shaft gear  190 , rigidly attached to outer shaft  124 , causes a set of intermediate gears  192  to counter rotate. Each gear  192  causes a pair of payout carrier gears  194  to rotate in the same direction as gear  190 . The size of gears  192  is chosen simply to permit each gear  192  to mesh with two gears  194 . The number of teeth of gear  192  is transparent to the turning ratios of gears  190  and  194 . Gears  194  have half the number of teeth of gear  190 , so that a half counter rotation of gear  190 , relative to turntable  114 , causes each gear  194  to go through a complete counter rotation relative to turntable  114 . Accordingly, if the outer shaft is turning at half the speed of the inner shaft, each payout carrier  112  undergoes a complete counter rotation per rotation of turntable  114 , thereby remaining stationary relative to a fixed frame of reference. If outer shaft  124  turns at the same rate as inner shaft  122 , there is no relative rotation between any of the gears  190 ,  192  and  194 , which causes the payout carriers  112  to remain stationary relative to the turn table  114 . 
     Referring to  FIG. 16 , the fusing of wires  14  about mandrel  12  is shown in schematic overview.  FIGS. 17-18  show a physical representation of one embodiment of a reflow oven for accomplishing that task. The fusing process includes the progressive remelting of the insulation of wires  14  in reflow zones  200 ,  201 ,  202  and  203  (collectively forming a reflow oven  28 ). Each reflow zone remelts insulation  16  over a mutually distinct angular portion  17  ( FIG. 5 ) of working material  10  so that wires  14  are held in place in the area of melted insulation, by the nearby unmelted insulation  16 . 
     Among the critical adjustments that are made in the process is a speed adjustment  204  for the working material as it passes through the remelt zones, a working material centering adjustment  205 , and an intensity and distance adjustment  206  for each radiant energy application device. A visual inspection system  207  aids an operator in adjusting the reflow oven  28  to achieve the best results. 
       FIGS. 17-19  show a stage  210  of a reflow oven assembly  28  through which the working material  10  is passed in order to briefly melt the insulation about wires  14 , sequentially in localized angular extents, to fuse insulated wires  14  together. Skilled persons will recognize that an additional stage or stages could be placed after stage  210 , the first one rotated by 90.degree. Stage  210  includes two reflow zones, such as zones  200  and  201 . 
     On either end of stage  210  is a wire guide assembly  212 . Assembly  212  includes a 45.degree. guide plate  214 , and a wire guide micrometer stage  216  that pushes on a slide block  222  that supports guide plate  214 . By turning stage  216  guide plate  214  is moved, causing the working material  10  to be moved relative to stage  210 . Two cartridge heater assemblies  230 , each including a cartridge heater  232 , and a heater micrometer stage  238 , for moving block  240 , which supports cartridge heater  232 . By moving stage  238  heater  232  is moved closer to or further away from a small window  236  that permits heat to radiate to working material  10 . In one embodiment a filament heater is used in place of cartridge heater  232 , having a filament made of “Kanthol D” available from Duralite corporation and having a resistance per meter for the 0.254 mm diameter wire of 26.7 ohms. A mirror  242  permits inspection of the reflow process and may be used by itself or in conjunction with a video camera (not shown). 
     In an alternative preferred embodiment ( FIG. 19 ), working material  10  is fused together by a laser  250 . A laser beam  252  is split and reflected by a sequence of beam splitter/mirrors  254  to be reflected onto working material  10  at a number of places, thereby remelting the insulation  16  of material  10 . 
     The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation. There is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow. In particular, although the case of a four wire lead has been discussed, leads having some other number of insulated wires could be used, including but not limited to 8, 12, 16, 24 or 36. In this application the term “continuous” does not mean “continuous in time” but rather refers to a process that may be brought to completion without reloading the machinery involved. The term “fused” means “joined together as by melting.”