Abstract:
A machine is provided for stripping the ground wall insulation from a stator bar quickly and in such a manner that the copper strands will not be damaged. The apparatus of the invention includes a power driven cutting tool for milling or routing the insulation from a portion of the insulated bar, a sensing device for detecting the location of the copper strands and a height adjustment assembly for determining a disposition of the bar with respect to the cutting tool. In an exemplary embodiment, the height adjustment assembly is adjusted in accordance with the location of the copper strands as detected by the sensing device to substantially prevent the cutting tool from making damaging contact with the copper strands.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a machine and method for mechanically stripping the insulation from an insulated stator bar without damage to the copper strands of the bar, so that the bar can be reinsulated for use in a stator winding. 
     During the factory production of stator bars, occasionally a stator bar is rejected because the cross-sectional dimensions of the insulated bar are out of prescribed tolerance limits or because it fails at the electrical proof test. Occasionally, in generators in power plants, the stator bar insulation fails in service or during electrical tests, making the bar unsuitable for continued service. In these instances, the lead time required to manufacture a replacement bar starting from raw materials is long and is unacceptable for meeting the schedule for shipment of a new generator from the factory or for returning the generator to service. Accordingly, conventionally, the ground wall insulation from the rejected and/or failed bar is stripped down to the bare bar and the bar is reinsulated for assembly in the stator. 
     Conventionally, the insulation is stripped manually, using hand tools. This method is slow and has the potential for damaging the copper strands of the bar, rendering it unsuitable for reuse. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a machine and method for stripping the ground wall insulation from a stator bar quickly and in such a manner that the copper strands will not be damaged. The apparatus of the invention includes a power driven cutting tool for milling or routing the insulation from a portion of the insulated bar, a sensing device for detecting the location of the copper strands and a height adjustment assembly for determining a disposition of the bar with respect to the cutting tool. In an exemplary embodiment, the height adjustment assembly is adjusted in accordance with the location of the copper strands as detected by the sensing device to substantially prevent the cutting tool from making damaging contact with the copper strands. 
     In an exemplary embodiment, the machine or apparatus is mounted to an insulated stator bar to be stripped and is driven longitudinally of the stator bar to cut the insulation along the length of the stator bar. 
     Accordingly, the invention is embodied in a stator bar stripping machine for removing insulation from a portion of an insulated stator bar, that comprises a power driven tool, including a cutter for milling the insulation from a portion of the insulated stator bar; a housing for at least partly enclosing the power driven tool; a support assembly for supporting the housing with respect to the stator bar; a sensing device for detecting a location of copper strands of the stator bar; and an adjusting mechanism for adjusting a disposition of the housing with respect to the stator bar so as to adjust a cutting depth of the power driven tool into a surface of the stator bar. 
     In an alternate embodiment of the invention, first and second power driven cutting tools are provided for simultaneously cutting spaced portions of the insulating material to thereby facilitate removal of the insulation from the copper strands following a single pass with the machine. 
     The invention is further embodied in a method of stripping insulation from a stator bar that comprises providing an insulation stripping machine including a power driven tool generally as described above, mounting the stripping machine to a stator bar by receiving the stator bar into the housing; and actuating the power driven tool to mill insulation from a portion of the insulated stator bar. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These as well as other objects and advantages of this invention will be more completely understood and appreciated by careful study of the following more detailed description of the presently preferred exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a rear left perspective view from above of an insulation stripping machine embodying the invention; 
     FIG. 2 is a top plan view of the stripping machine of FIG. 1, omitting the control line and vacuum line of FIG. 1; 
     FIG. 3 is a right side elevational view of the stripping machine; 
     FIG. 4 is a left side elevational view, partly in cross-section, showing the height adjustment mechanism, sensor device and support assembly of the stripping machine; 
     FIG. 5 is a rear elevational view of the stripping machine, partly in cross-section; 
     FIG. 6 is a front elevational view of the stripping machine, partly in cross-section and with some parts omitted for clarity; and 
     FIG. 7 is a view of the stripping machine taken generally along line  7 — 7  of FIG. 4, partly in cross section and with some parts omitted for clarity. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An insulation stripping machine  10  provided as an embodiment of the invention is schematically shown in FIG.  1 . In the illustrated embodiment, the machine is provided as a self contained unit that is mounted to the stator bar  12  and is driven along the bar to sever a portion of the insulation disposed on the outer periphery of the bar. Thus, in a preferred embodiment, a support assembly is provided for supporting the stripping machine upright on the stator bar. Furthermore, in the presently preferred embodiment, the stripping machine is driven longitudinally of the stator bar to cut the insulation along the length of the stator bar. Accordingly, in the presently preferred embodiment, the support assembly includes a driving mechanism for driving the stripping machine relative to the stator bar. 
     The support assembly of the invention can be best be seen in FIGS. 4-6. The stripping machine  10  is desirably supported with respect to the upper and lower surfaces of the associated stator bar  12 . In the illustrated embodiment, a pivot link roller  14  is disposed adjacent the leading end or forward end wall  16  of the stripping machine and a drive roller  18  is disposed adjacent the rearward end wall  20  of the stripping machine  10 . Each of the pivot link roller  14  and drive roller  18  engage the upper flat surface  22  of the stator bar  12 . The bottom surface  24  of the stator bar is engaged by a bottom roller  26 . As can be appreciated, because the stripping machine  10  is adapted to be driven along the length of the stator bar and because the bulk of the weight of the stripping machine is disposed in the top portion of the stripping machine, the stripping machine essentially rests on the pivot link roller  14  and drive roller  18  and is clamped with respect to the bar by the bottom roller  26 . 
     The drive roller  18  is mounted to a drive roller shaft  28  and supported with respect to side cover  30  and side wall  32  of the stripping machine housing main body  34  with suitable bearing structures  36 , 38  at each longitudinal end thereof as shown in FIG.  5 . At one end of the drive roller shaft, a drive roller gear  40  is provided for meshing with a motor gear  42  mounted to the shaft  44  of the drive motor  46  disposed in parallel to the drive roller shaft  28 . As shown in FIG. 5, in the illustrated embodiment, both the drive motor  46  and drive roller  18  are housed within the stripping machine housing main body  34 . 
     The bottom roller  26  is best seen and understood with reference to FIGS. 3,  5  and  6 . The bottom roller is mounted to a bottom roller shaft  48  that is rotatably supported by a bottom roller mount  50 . In the illustrated embodiment, the bottom roller shaft  48  is fixedly secured to the bottom roller mount  50  and the bottom roller  26  is rotatably mounted with respect to the bottom roller shaft by suitable bearings as shown at  52  and  54 . It is to be understood that in the alternative, the bottom roller can be fixedly mounted to the bottom roller shaft and the bottom roller shaft rotatably mounted by the bearings to the bottom roller mount. 
     The bottom roller mount is positioned with respect to the stripping machine housing main body  34  with an air cylinder  56  that resiliently urges the bottom roller  26  to a bar engaging and elevating disposition to clamp the same against the drive roller and pivot link roller. As shown in FIG. 4, in the illustrated embodiment, a toggle valve/switch  57  is provided to activate the air cylinder  56 . 
     The bottom roller is guided in its movement by guide shaft(s)  58 , 60  that are disposed through respective apertures  62 , 64  in the air cylinder mount  66 . The air cylinder mount is secured to the housing main body  34  by a series of brackets and mounts. In the illustrated embodiment, a cylinder mount bracket  68  is secured to the cylinder mount  66  and to a depending sidewall  70  of the housing main body  34  via bolts  69  and  71 , respectively. In the illustrated embodiment, the vertical position of the bottom roller  26  with respect to, e.g., the drive roller  18  is grossly adjusted by loosening bolts  71  and displacing the cylinder mount up or down with the bolts  71  sliding in slots  73  in side wall  70 . This relative displacement facilitates insertion and removal of the stator bar, as described in greater detail below, but may not be necessary for bar  12  insertion. 
     The pivot link roller  14  in the illustrated embodiment is rotatably mounted via suitable bearings  72  to a pivot roller shaft  74  that is fixedly secured to a pivot link  76 , as best shown in FIG.  7 . The pivot link is pivotally mounted via a pivot link shaft  78  to a sensor mount  80  that is secured to the front-end wall  16  of the housing main body  34 . As illustrated in FIG. 7, the sensor mount  80  includes the transverse sensor mount portion  82  and a generally longitudinally extending sensor support  84 . An inductive gauging sensor  86  is mounted to the rearward end of the sensor support  84  for being disposed in opposed facing relation to the stator bar  12  as described in greater detail below. In the illustrated embodiment, a bolt clamp assembly  88  is provided at the rearward end of the sensor support  84  for mounting and demounting, and controlling a vertical position of the sensor in the stripping machine. As will be understood from the fixed attachment of the sensor mount  80  to the forward wall  16  of the stripping machine, the sensor  86  mounted to the sensor support is fixedly disposed with respect to the stripping machine housing main body  34 . 
     The pivot link  76  further includes a rearwardly projecting adjustment assembly  90  including a screw block  92  for threadably engaging the screw thread defined on the shaft  94  of a height adjustment motor  96  as described in greater detail below. In the illustrated embodiment, actuation of the height adjustment motor rotates its threaded shaft which is engaged with threaded block  92 , which will in turn move upwardly or downwardly relative to the threaded shaft. The screw adjuster block  92  is rotatably or pivotally attached, as by shaft  91 , to the rearward projecting portion  90  of the pivot link  76 . Thus, actuation of the height adjustment mechanism will move the pivot link rearward end  90  upwardly or downwardly with respect to the pivot link shaft  78 . Because the pivot link roller  14  is engaged with the upper surface  22  of the stator bar  12 , relative downward movement of the pivot link roller  14  (part clockwise about shaft  78  in FIG. 4) will raise the forward end wall  16  of the stripping machine with respect to the top of the stator bar  12 . Conversely, movement of the screw adjuster block  92  upwardly towards the motor  96  to raise the pivot link roller  14  (counter clockwise in FIG. 4) will lower the forward end wall  16  of the stripping machine with respect to the stator bar. Thus, by adjusting the height of the rearward end of the pivot link and in turn the height of the pivot link roller  14 , a milling depth of the power driven cutting tool (described in greater detail below) with respect to the stator bar installation is adjusted. The inductive gauging sensor  86  detects the depth of the copper strands of the stator bar  12 . Thus, depending upon the depth of the copper strands as detected by the inductive gauging sensor, the height adjusting motor  96  is actuated to raise or lower the pivot link  76  and roller  14  mounted thereto to respectively increase or decrease the cutting depth of the milling tool. This minimizes the risk of the copper strands being undesirably cut by the cutting tool during the milling operation. 
     To further support the stripping machine with respect to the stator bar, steady rollers  98 , 100  and side rollers  102 , 104  are preferably provided in accordance with an embodiment of the invention, although some or all of these rollers are omitted from some of the illustrations for clarity. As best shown in FIG. 4, the steady rollers  98 , 100  are rotatably mounted to respective shafts  106 , 108  of respective steadies  110 , 112 . As can be seen from FIG. 5, in the presently preferred embodiment, the steadies are mounted to the front and rear walls  16 , 20  of the housing main body  34  to engage the left side wall  25  of the stator bar  12 . By loosening the thumb screws  114 , 116  to release the steady clamp plates  118 , 120  and the steady  110 , 112  for movement relative to the housing main body front and rear walls  16 , 20 , the steady rollers can be pivoted as shown by arrow A to a horizontal disposition so that the stator bar  12  can be laterally inserted and removed from the stripping machine (See, e.g., FIG.  6 ). 
     Thus, to mount the stator bar within the stripping machine, if necessary, bolts  71  are loosened and cylinder mount  66  is lowered to facilitate insertion of the bar  12 . Further, the steady  110  mounted to the front end wall  16  is loosened with respect to the housing by loosening the thumb screw  114  and then rotating the steady through about 90 degrees so that it is projecting to the left side of the housing. Similarly, the steady  112  provided at the rear end of the stripping machine is loosened with respect to the rear end wall  20  by loosening the associated thumb screw  116  and then it too is rotated through about 90 degrees. The thumb screws  114 , 116  may be temporarily retightened to hold the steadies in their horizontal disposition. 
     The stator bar  12  may then be inserted until its right sidewall abuts the side rollers  102 , 104  provided adjacent at the forward and rearward ends of the stripping machine  10 . Once the stator bar is abutted against the side rollers, the steady rollers are released by releasing their respective thumb screws  114 , 116  and pivoted or rotated to the configuration shown in FIG. 4 to engage the left side wall  25  of the stator bar  12 . The air cylinder mount  66  is then lifted and bolts  71  tightened to clamp the stator bar within the housing main body  34 . Thus, in the illustrated embodiment, the support assembly includes not only the pivot link roller  14 , drive roller  18  and bottom roller  26 , but also the steady rollers  98 , 100  and side rollers  102 , 104 , so that the machine  10  is supported with respect to all four sides of the stator bar  12 . 
     A power driven cutting tool is provided in accordance with the preferred embodiment of the invention for stripping the insulation from the stator bar. The insulation removing bit  121 , which may be characterized as a router-type bit, is in the presently preferred embodiment a carbide end mill mounted to a suitable end mill holder  122  that is rotatably mounted via upper and lower bearings  124 , 126  within the motor housing  128 . In the illustrated embodiment, the motor housing  128  is defined by a lower motor housing  130 , an upper motor housing  132  and a motor housing cover  134 . A bearing spacer  136  is disposed between the upper and lower bearings  124 , 126 . In the illustrated embodiment, a spindle gear  138  is secured to the upper end of the end mill holder for being driven to drive the end mill holder. 
     In the presently preferred embodiment, a nose mount air gear motor  140  is provided for driving the end mill holder  122 . The nose mount air gear motor can best be seen in FIGS. 4 and 5. A shaft  142  projects upwardly from the motor and has an air motor gear  144  fixedly secured thereto. The air motor gear meshes with the spindle gear  138  of the end mill holder  122  to translate rotation of the motor shaft  142  to rotation of the end mill holder  122  and in turn to rotation of the carbide end mill  121  for removing insulation from the stator bar  12 . The end mill/end miller holder  121 , 122  and air motor  140  operatively coupled thereto thus together define, in an exemplary embodiment of the invention, a power driven tool for milling or routing the insulation from a portion of the insulated bar. 
     In FIG. 7 an air input tube  146  for the nose mount air gear motor  140 , and an air exhaust tube  148  can be seen. More specifically, in the illustrated embodiment, an air input block  150  is mounted to the right side of the housing for coupling by nipple  152  to a suitable compressed air source. The compressed air is fed by air input tube  146  to the nose mount air gear motor  140 . The air exhaust tube  148  is mounted to extend from the nose mount air gear motor  140  and is desirably provided with a muffler  154  (shown only in FIG. 7 for clarity). 
     In use, it may be desirable to actuate the carbide end mill  121  to rotate during lifting of the air cylinder  56  to clamp the machine  10  to the stator bar  14 , to rout the stator bar insulation  156  to facilitate the full seating of the bar in the machine and to allow the subsequent longitudinal insulation removal following attachment of the stripping machine  10  to the stator bar  12 . 
     A vacuum hose is further desirably attached to the housing to evacuate debris resulting from the milling of the stator bar  12  with the end mill  121 . In the illustrated embodiment, a side vacuum port  172  is provided as best seen in FIGS. 2 and 7. In addition, or in the alternative, the vacuum port may be disposed on the housing main body  34  as shown in phantom lines at  174  in FIG.  2  and as illustrated by the vacuum tube  170  in the perspective view of FIG.  1 . 
     As noted above, the inductive gauging sensor detects the location of the copper strands to determine the position of the stator bar relative to the power driven tool. Suitable computer feedback control based upon the depth of the copper strands detected by the inductive gauging sensor is achieved by a control cable  178  as shown in FIG. 1, attached in an exemplary embodiment to a 14 pin male receptacle  180 . As disclosed herein above, the height adjustment motor in connection with the pivot link and pivot link roller  14  adjusts the position of the stripping machine with respect to the stator bar to determine the milling depth of the power driven end mill  121 . By suitably programming the control system, once the distance of the copper strands from the sensor has been detected a suitable height adjustment can be determined to ensure that the milling cutter cuts substantially to but not into the copper strands of the insulated bar. Thus, in the presently preferred embodiment, the height adjustment mechanism is actuated in response to the copper strand position detected by the sensing device. 
     In the exemplary embodiment illustrated in FIGS. 4-7, a single milling cutter is provided for removing insulation to a depth as determined by the height adjustment mechanism and to a width determined by the width of the end mill  121  and its lateral position with respect to the stator bar. Thus, as shown for example in FIG. 6, because the milling cutter is laterally offset with respect to a vertical plane of symmetry of the stator bar, the milling cutter removes a corner of the insulation disposed on the stator bar. Thus, in order to remove the insulation from each of two corners of the stator bar to facilitate removal of the insulation from the stator bar, the machine is passed twice along the stator bar, once longitudinal from one end to the other and then longitudinally from the other end to the one end. After such milling/stripping passes, the insulation may be rather readily removed from the stator bar. 
     In an alternate embodiment of the invention (not shown) a second end mill is provided for cutting the opposite corner of the stator bar so that the insulation can be suitably stripped following a single pass of the stripping machine. 
     The motor is desirably centered with respect to the housing to provide a stripping machine that is weight balanced for mounting to the stator bar. Because the milling cutter is preferably laterally offset with respect to the center of the stator bar, the end mill holder is provided as a separate structure from the motor and laterally offset with respect thereto. For that reason, the longitudinally and laterally offset end mill holder and gear are provided in the illustrated embodiment, operatively coupled with the air motor gear as shown in FIGS. 4-6. 
     In use, once the machine is clamped on the bar, the downstream roller(s), more specifically, the drive roller, drives the machine down the bar. The height adjusting mechanism, more specifically, the leading roller (in the illustrated embodiment the pivot link roller) adjusts the disposition of the bar so that the end mill will travel down the bar at a predetermined distance above the determined surface of the copper strands and to a side thereof. In order to adjust the height adjusting mechanism to control the milling depth, the inductive distance gauge is used to read the position of the copper through the insulation. Knowing where the copper is allows the cutter height to be adjusted automatically to effect the desired milling operation. 
     A number of pneumatically operated stands (not shown) are desirably provided to support the bar while the cutting operation is in progress. Each of these stands is desirably provided with a sensor to sense the approach of the cutting machine so that the support may be retracted as necessary or desirable to allow the machine to pass. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.