Abstract:
The present disclosure relates to a variable diameter electromagnetic coil. The coil may include a coil winding containing inner and outer winding layers. The coil may incorporate a first hub including one or a plurality of inner supports, one of the inner supports connected to a location on the inner winding layer. A second hub may then be provided including one or a plurality of outer supports, one of the outer supports connected to a location on the outer winding layer. One of the first or second hubs may be capable of rotating to cause the coil winding to wind or unwind. An interconnect hub may then be provided which may be capable of providing electrical connection to the coil winding.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Applications 60/805,669 and 60/805,697, both filed Jun. 23, 2006 whose teachings are incorporated herein by reference in their entirety. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   This invention was made with United States Government support under Government Contract No. DTRS 56-02-T-0001 awarded by the U.S. Department of Transportation. The Government has certain rights in this invention. 

   FIELD OF THE INVENTION 
   This disclosure pertains to variable diameter electromagnetic coils that may be used for generating electromagnetic fields. 
   BACKGROUND 
   Electromagnetic coils are used in numerous applications to generate alternating or static magnetic fields. In most applications, it may be sufficient for the coils to be of a fixed diameter. Fixed diameter coils may therefore be used, e.g., in a variety of applications that require a magnetic field, such as solenoid actuators, conventional electrical motors, transformers, etc. One example of what is termed a collapsible coil for inspection of pipelines is described in U.S. Pat. No. 7,154,264. As discussed therein, a collapsible excitation coil includes a plurality of electrically interconnected collapsible excitation coil segments connected to a first end of what is described as an inspection pig structure along with inspection of pipelines that have obstructions which were said to prevent conventional inspection pigs from passing the obstructions. 
   SUMMARY 
   In one exemplary embodiment, the present disclosure relates to an electromagnetic coil. The coil may include a coil winding containing inner and outer winding layers wherein the coil is wound in a first direction. The coil may incorporate a first hub including one or a plurality of inner supports, one of the inner supports connected to a location on the inner winding layer. A second hub may then be provided including one or a plurality of outer supports, one of the outer supports connected to a location on the outer winding layer. One of the first or second hubs may be capable of rotating to cause the coil winding to wind or unwind. An interconnect hub may then be provided that may be capable of providing electrical connection to the coil winding. 
   In a second exemplary embodiment, the present disclosure again relates to an electromagnetic coil. The coil may again include a coil winding containing inner and outer winding layers wherein the coil is wound in a first direction. A first hub may then be supplied including one or a plurality of inner supports, one of the inner supports connected to a location on the inner winding layer which inner support is capable of extending or retracting in a radial direction. A second hub may then be supplied including one or a plurality of outer supports, one of the outer supports connected to a location on the outer winding layer which outer support is also capable of extending or retracting in a radial direction. One of the first or second hubs is capable of rotating to cause the coil winding to wind or unwind. An inner interconnect cable and an outer interconnect cable may then be supplied, both attached to the coil winding and to an interconnect hub wherein one of the inner or outer interconnect cables is capable of winding about the interconnect hub in a second direction that is either equal to or opposite to the coil winding first direction. 
   In a third exemplary embodiment, the present disclosure relates to a method for manufacturing a variable diameter electromagnetic coil. The method includes forming a coil winding containing inner and outer winding layers wherein the coil is wound in a first direction. This may then be followed by positioning a first hub including one or a plurality of inner supports within the coil winding, one of the inner supports connected to a location on the inner winding layer. This may then be followed by positioning a second hub within the coil including one or a plurality of outer supports, one of the outer supports connected to a location on the outer winding layer. One of the first or second hubs is also capable of rotating to cause the coil winding to wind or unwind. This may then be followed by attachment of an inner interconnect cable and an outer interconnect cable to the coil winding and to an interconnect hub wherein one of the inner or outer interconnect cables is capable of winding about the interconnect hub. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The detailed description below may be better understood with reference to the accompanying figures which are provided for illustrative purposes and are not to be considered as limiting any aspect of the invention. 
       FIG. 1A  depicts an exemplary variable diameter coil at a first diameter; 
       FIG. 1B  depicts a cross-section of an exemplary variable diameter coil winding illustrating a configuration of substantially parallel conductors and insulation. 
       FIG. 2  depicts an exemplary variable diameter coil at a second diameter; 
       FIG. 3  depicts an exemplary variable diameter coil at a first (e.g., decreased) diameter including exemplary electrical connections to the coil winding; 
       FIG. 4  depicts an exemplary variable diameter coil at a second (e.g., increased) diameter including exemplary electrical connections to the coil winding; 
       FIGS. 5A and 5B  depict exemplary coil conductor interconnecting wiring configurations in a series arrangement and a parallel arrangement, respectively. 
   

   DETAILED DESCRIPTION 
   Attention is directed to  FIG. 1A  which illustrates an exemplary embodiment of a variable diameter electromagnetic coil  100  at a first diameter. The coil  100  may include a coil winding  110  and a first hub  120  that may include one or a plurality of inner supports  140 . The inner supports  140  may include a head portion  142  that may provide a curved surface portion that may contact and accommodate all or a portion of the curvature of an inner winding layer  160 . The inner supports may include a shaft  144 , one end of which may be engaged to the first hub  120  and the other end of which may be pivotably engaged to the head portion  142 . 
   The coil  100  may further include a second hub  130  that may include one or a plurality of outer supports  150  which may also include a shaft  152  and head portion  154 . A first hub may therefore be understood as any structure which may accommodate an inner support and a second hub may be understood as any structure that may accommodate an outer support. The coil diameter D may be adjusted by winding and/or unwinding the coil winding  110 . This may allow the coil  100  to have a continuously variable diameter D over a wide range and may allow the coil  100  to function electromagnetically at any diameter within the range. 
   Winding or unwinding the coil winding  110  may be accomplished by rotating the first hub  120 . An inner support  140 ′, which may be connected to the first hub  120 , may also be connected to a location on an inner winding layer  160 . An inner support may therefore be understood as any structure which supports the inner winding layer. An outer support  150 ′, which may be connected to the second hub  130 , may also be connected to a location on an outer winding layer  170 . An outer support may therefore be understood as any structure which may support an outer winding layer. 
   The inner supports  140  and the outer supports  150  may each be configured to extend and retract in the radial direction as the first hub  120  may be rotated. The inner supports  140  may also be configured to rotate along with the first hub  120 . The outer support  150 ′ that may be connected to a location on the outer winding layer  170  may be configured to fix the outer winding layer  170 . The supports  140 ,  150  may be configured to extend or retract in proportion to the rotation of the first hub  120 . Winding the coil winding  110  may be accomplished by rotating the first hub  120  in the clockwise direction, in the sense of  FIG. 1A . Unwinding the coil winding  110  may be accomplished by rotating the first hub  120  in the counterclockwise direction, again in the sense of  FIG. 1A . Winding the coil winding  110  may then reduce the coil diameter D and unwinding the coil winding  110  may increase the coil diameter D. 
   Attention is directed to  FIG. 1B  which illustrates an exemplary cross section  110 ′ of a coil winding  110  showing conductors  125  and insulation  135  that may be arranged in layers  115  of the coil winding  110 . The coil winding  110  may be formed of one or a plurality of conductors  125 . The conductors  125  may be spaced by insulating material  135 . The conductors may be joined as illustrated and may be in a substantially parallel configuration. It may be appreciated that the number of conductors  125  and number of layers  115  may be varied. A coil winding  110  may therefore be understood as one or a plurality of layers  115 . A layer  115  may be understood to mean all or a portion of a revolution of one or a plurality of joined conductors  125 , separated and/or surrounded by insulation  135 . A conductor may be understood to mean a wire or other structure constructed of a material having a resistivity value less than about 10 −4  ohm-centimeters at 20° C. It may be appreciated that winding a coil winding  110  may increase the number of layers  115  while unwinding may decrease the number of layers  115 . 
   As noted, the conductors  125  may be separated by, and may be surrounded by, a region of insulating material  135 . Insulating material may be understood to mean material with a resistivity value exceeding about 10 10  ohm-centimeters at 20° C. The conductor material and insulating material may provide a compliant-like characteristic when wound that may allow the coil winding  110  to expand or contract. 
   Attention is directed to  FIG. 2  which illustrates in exemplary embodiment of a variable diameter electromagnetic coil  200  at a second (e.g., increased) diameter. The coil  200  may again include a coil winding  210 , a first hub  220 , a second hub  230 , one or a plurality of inner supports  240 , and one or a plurality of outer supports  250 . The coil diameter D may again be adjusted by winding and/or unwinding the coil winding  210 . As noted above, the first hub  220  may rotate and the second hub  230  may be fixed, to provide winding and unwinding of the coil  210 . In addition, it may now be appreciated that the coil  200  may also be configured so that the first hub  220  may be fixed and the second hub  230  may rotate. In this configuration, at least one of the inner supports (e.g.,  240 ′) may be fixed to a location on the coil inner winding layer  260  and the outer supports  250  may rotate with the second hub  230 . An outer support  250 ′ may then be connected to a location on the outer winding layer  270 . The inner supports  240  (which include shaft  244  and head portion  242 ) and the outer supports  250 , may be configured to extend and retract in the radial direction as the second hub  230  may be rotated. The outer supports  250  may also rotate along with the second hub  230 . At least one of the inner supports (e.g.,  240 ′) may be connected to a location on the inner winding layer  260  to fix the inner winding layer  260  at such location. The supports  240 ,  250  may be configured to extend or retract in proportion to the rotation of the second hub  220 . Winding the coil winding  210  may be accomplished by rotating the second hub  230  in the counterclockwise direction, in the sense of  FIG. 2 . Unwinding the coil winding  210  may be accomplished by rotating the second hub  230  in the clockwise direction, in the sense of  FIG. 2 . 
   Attention is directed to  FIGS. 3 and 4  which depict exemplary embodiments of variable diameter electromagnetic coils  300 ,  400  at a first (e.g., decreased) and a second (e.g., increased) diameter, respectively. Similar to the coils disclosed above, the variable diameter coils shown in  FIGS. 3 and 4 , may include a coil winding  310 ,  410 , a first hub  320 ,  420 , a second hub  330 ,  430 , inner supports  340 ,  440 , and outer supports  350 ,  450 . The coil winding  310 ,  410  may also include an inner winding layer  360 ,  460  and an outer winding layer  370 ,  470 . 
   As shown in  FIG. 3 , the coil  300  may also include an interconnect hub  325 , an inner interconnect cable  335 , and an outer interconnect cable  345 . The inner interconnect cable  335  may be connected to the interconnect hub  325 . The inner interconnect cable  335  may also be connected to an inner connector  355  that may be connected to an end of the inner winding layer  360 . Similarly, the outer interconnect cable  345  may be connected to the interconnect hub  325 . The outer interconnect cable  345  may also be connected to an outer connector  365  that may be connected to an end of the outer winding layer  370 . The interconnect hub  325  may provide for electrical connections between the electromagnetic coil  300  and an external power supply (not shown). In this manner, power may be supplied to the electromagnetic coil winding  310  that may cause current to flow in the coil winding  310 . Current flowing in the coil winding  310  may then produce a magnetic field. The supplied power may be AC or DC. An electromagnetic coil that may be supplied by an AC power source may be used as part of a system for testing pipe wall integrity that may rely on remote field eddy currents. An example of such is supplied in U.S. Appl. 60/805,697, whose teachings are incorporated by reference. 
   It may be appreciated that the variable diameter electromagnetic coil  300  may be energized at any diameter D within a range of diameters. Thus, the coil  300  may function electromagnetically at any diameter D within this range. 
   The diameter D of the coil  300  may be increased by unwinding the coil winding  310  and may be decreased by winding the coil winding  310 . Winding or unwinding the coil winding  310  may be accomplished once again according to the description above with respect to  FIG. 1A . 
   The interconnect hub  325  itself may not rotate. The inner interconnect cable  335  may be wound about the interconnect hub  325  as the coil winding  310  may be wound. The inner interconnect cable  335  may be unwound as the coil winding  310  may be unwound. In order to achieve such coordinated winding and unwinding of the coil winding  310  along with the inner interconnect cable  335 , at initial assembly, the coil winding  310  may be wound about the inner supports  340  in the counterclockwise direction. Also at initial assembly, the inner interconnect cable  335  may be wound about the interconnect hub  325  in the clockwise direction. In addition, it may be appreciated that the coil winding  310  may be wound about the inner supports  340  in a clockwise direction and the inner interconnect cable  335  may be wound about the interconnect hub  325  in the counterclockwise direction. It may also be appreciated that the outer interconnect cable  345  may itself not wind about the interconnect hub  325 . An end of the outer interconnect cable  345  may be connected to the outer connector  365  and may extend or retract as the coil winding  310  may be unwound or wound. 
   Attention is directed to  FIG. 4  which illustrates an exemplary embodiment of a variable diameter coil  400  at an increased diameter. As shown in  FIG. 4 , the coil  400  may also include an interconnect hub  425 , an inner interconnect cable  435 , and an outer interconnect cable  445 . The interconnect hub  425  may include a first portion  423  and a second portion  424 . The first portion  423  and the second portion  424  may be capable of rotating relative to one another. More specifically, the interconnect hub  425  may provide the ability to form an electrical connection through such rotating assembly. Such electrical connection may include connection between an end of the inner coil winding layer  460  and an end of the outer coil winding layer  470 . It may also provide electrical connection to a power source (not shown for clarity). More specifically, the interconnect hub may include what is known as a slip ring which may include a conductive circle or band mounted on a shaft and appropriately insulated. It may be appreciated that in the case of such an interconnect hub, either the inner or outer interconnect cable may avoid the need to wind onto the interconnect hub when varying the coil diameter. 
   The inner interconnect cable  435  may be connected to the interconnect hub  425 , e.g. the first portion  423 . The inner interconnect cable  435  may also be connected to an inner connector  455  that may be connected to an end of the inner winding layer  460 . Similarly, the outer interconnect cable  445  may be connected to the interconnect hub  425 , e.g. the second portion  424 . The outer interconnect cable  445  may also be connected to an outer connector  465  that may be connected to an end of the outer winding layer  470 . The interconnect hub  425  may provide for electrical connections between the electromagnetic coil  400  and an external power supply (not shown). In this manner, power may be supplied to the electromagnetic coil winding  410  that may cause current to flow in the coil winding  410 . Current flowing in the coil winding  410  may then produce a magnetic field. In addition, the diameter D of the coil  400  may be increased or decreased according to the discussion above with respect to  FIG. 2 . 
     FIG. 4  also illustrates that situation wherein, unlike  FIG. 3 , the outer interconnect cable  445  may be wound about the interconnect hub  425  (which again may not rotate) as the coil winding  410  may be wound. The outer interconnect cable  445  may then be unwound as the coil winding  410  may be unwound. In order to achieve such coordinated winding and unwinding of the coil winding  410  and the outer interconnect cable  445 , at initial assembly, the coil winding  410  may be wound about the inner supports  440  in the counterclockwise direction. Likewise, also at initial assembly, the outer interconnect cable  445  may also be wound about the interconnect hub  425  in the counterclockwise direction. In addition, it may be appreciated that the coil winding  410  may be wound about the inner support  440  in the clockwise direction and the outer interconnect cable  445  may be wound about the interconnect hub  425  in the clockwise direction. As may also be appreciated, the inner interconnect cable  435  may not wind about the interconnect hub  325 . An end of the inner interconnect cable  435  may be connected to the inner connector  455  and may extend or retract as the coil winding  410  may be unwound or wound. 
   Attention is directed to  FIGS. 5A and 5B  which illustrate two exemplary electrical interconnection configurations  500 ,  500 ′ for a coil winding.  FIGS. 5A and 5B  depict only a first end  510  and a second end  520  of a coil winding and electrical interconnections  550 ,  530 ,  535  for clarity. As discussed above, a coil winding may include one or a plurality of conductors  1  through n. The coil winding may be configured similar to ribbon cable, meaning the conductors  1  through n may be substantially parallel and may be separated and/or surrounded by an insulating material  540 . 
     FIG. 5A  shows what may be termed series type interconnections  550 . The coil winding includes one or a plurality of conductors  1  through n separated and/or surrounded by an insulating material  540 . For a series interconnection configuration  500 , a first end  515 - 1  of a first conductor  1  may be configured to be connected to a first port  560  of a power source (not shown). A second end  525 - 1  of the first conductor  1  may be connected to a first end  515 - 2  of a second conductor  2  by interconnection  550 - 1 . A second end  525 - 2  of the second conductor  2  may be connected to a first end  515 - 3  of a third conductor  3  by interconnection  550 - 2 . These connections may be continued for n conductors and m interconnections. Interconnection m may be between a first end  515 - n  of conductor n and a second end  525 -(n- 1 ) of conductor n- 1 . A second end  525 - n  of the conductor n may be configured to be connected to a second port  565  of a power source (not shown). 
     FIG. 5B  shows parallel type interconnections  530 ,  535 . The coil winding includes one or a plurality of conductors  1  through n separated and/or surrounded by an insulating material  540 . The first ends  515 - 1  through  515 - n  of each conductor may be connected together by one or a plurality of interconnections  530 . The second ends  525 - 1  through  525 - n  may be connected together by one or a plurality of interconnections  535 . Interconnection  530  may also be connected to a first port  560 ′ of a power supply (not shown) and interconnection  535  may likewise be connected to a second port  565 ′ of the power supply. 
   Although illustrative embodiments and methods have been shown and described, a wide range of modifications, changes, and substitutions is contemplated in the foregoing disclosure and in some instances some features of the embodiments or steps of the method may be employed without a corresponding use of other features or steps. Accordingly, it is appropriate that the claims be construed broadly and in a manner consistent with the scope of the embodiments disclosed herein.