Abstract:
An axial direction groove is formed in a high permeability toroidal core taking the form of a pot core half with a mounting hole, a high cross-section ratio copper casing being tightly fit around core circumference, having poly-phase excitation windings shuttled through the mounting hole to encompass both the copper casing and the pot-core, forming an integral driving-sensing eddy current probe. A naked pot-core is wound as an integral driving-sensing probe. Poly-phase excitation of the probe is mesh-connected as a gramme-ring.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Patent Application is a continuation-in-part of patent application Ser. Nos.: Ser. No. 09/419,140 filed Oct. 15, 1999 now U.S. Pat. No. 6,271,664B1 and Ser. No. 09/467,599 filed Dec. 20, 1999 now U.S. Pat. No. 6,265,871B1. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Earlier Logue patents refer to the related devices as “polar coordinates sensor” i.e. a hemispherical rotating field generator. 
     This invention employs a toroidal wound pot-core half generating a rotating magnetic field fringing through the excitation turns. 
     2. Related Art 
     Tesla U.S. Pat. No. 382,280 disclosed a ring built up of insulated annular iron plates and wound with poly-phase distributions forming an early rotating field stator for generator/motor use. Field utility was limited to the winding window of the toroidal stator. In the cited Logue patent applications the rotating hemispherical flux fringing from the plane of this toroidal stator (pot-core half) was utilized for inducing eddy currents in conducting workpieces e.g. aircraft splice joints. The driving flux is directly coupled from the toroidal plane to the workpiece through the poly-phase excitation turns. 
     Oscillatory Signal Build-up 
     The polar coordinates signal disclosed in the ascending Logue patents is actually formed by successive revolutions of the hemispherical driving field acceleration; the axis of which is displaced by an asymmetry (flaw) in the eddy current reflection. This is a rotary type of parametric pumping. Acceleration of the driving field revolutions is explained and illustrated in Logue U.S. Pat. No. 5,909,118 (obviously frequency modulation). 
     SUMMARY OF THE INVENTION 
     A primary object of the invention is a tighter focusing of the probe pattern fringing from the toroidal driving plane. Tightly fitting a copper toroid concentrically around a pot-core half eliminates the flux spilling gap resulting from a previous method of winding the excitation distributions around the pot-core first (Logue U.S. Pat. No. 6,265,871). An all encompassing toroidal excitation winding method is show in FIG. 1, in which the poly-phase distributions thread through the toroidal window, encircling the pick-up coil, driving toroid and the mentioned thick copper toroid (a Lenz lens). A second object of the invention is an arrangement of concentric pot-core halves on increasing radii for generating at least two radii of concentric eddy current hemispheres in a conducting workpiece, the pick-up coil of each pot-core generating a flaw signal in response to a flux asymmetry. This increasing driving\sensing radii equals differing depths of eddy current excitation\reflection. As taught in Logue U.S. Pat. No. 6,265,871 individuality of predetermined angular velocities is provided between concentric toroidal cores (radii isolation of excitation current phase/amplitude is obviously possible). A further object of the disclosure is an excitation method similar to well known television picture tube electron beam/s deflection by a predetermined current modulation of the toroidal yoke windings (toroidal probe) i.e the x-y excitation axes of a resultant vectorial fringing magnetic field. In the light of television, radar and Logue U.S. Pat. Nos. 6,265,871 6,229,305 6,271,664 6,271,664 the underling principles of this method are understood. 
     The preferred pick-up assembly to date is a pot-core half with a pick-up coil having many turns of small guage magnet wire e.g. 42 ga., wound around the central pole ( 184 , FIG. 1) filling the annular coil space  179 . For more complete annular space filling of the pick-up core, flat small guage magnet wire may be spool-less wound, using H. P. Reid Co (trademark). adhesive pre-coated voice-coil wire. Alternately multiple parallel smaller gauge magnet wires e.g. 46 gauge, may be used. 
     This high-density method of pick-up coil winding accentuates the z-axis permeability modulation of the pot-core half, increasing ramping signal build-up re: Logue U.S. Pat. No. 5,909,118 (see Oscillatory Signal Build-up above). As taught in Logue application Ser. No. 09/467,599 a polar coordinates sensor may be reduced to a ferrite pot-core half (integral x-y-z axes of permeability) having a pick-up coil of many turns wound around the central pole  284  (FIG.  1 ), combined with a rotating driving field generated by sine-cosine currents flowing in sine-cosine excitation windings wound through mounting hole  193  (now winding hole  193 ) in FIG.  1 . The pot-core half must be segment-less (no lead slots) 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional-perspective view of eddy current probe PS 1  spatially illustrating the disclosed methods of increasing resolution. 
     FIG. 2, is a block-circular diagram of a excitation/connection method for probe PS 1  in FIG.  1 . 
     FIG. 3, is a perspective-quadrant view of an eddy current probe utilizing concentric integral driving-sensing pot-core halves on increasing radii. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, illustrates an improved method of fitting a Lenz lens/caseing  177  (a higher cross-section ratio than formerly utilized) around integral driving/sensing core  188 , for tighter focusing of the driving field. Previously, (cited Logue application Ser. No. 09/467,599), the prior copper Lenz lens disposition left a concentric air gap between driving-sensing core  188  and subject high cross-section Lenz lens  177 . 
     To prevent any cutting of magnet wire insulation, Lenz lens  177  is covered with a hard insulating coating. 
     Another object of the disclosure is to teach a method of assembling a simple/robust eddy current probe comprising: a pot-core  188  of high permeability, a Lenz reflecting lens  177  and encompassing the x-y axes excitation winding distributions  162   t . This novel winding method as illustrated in FIG. 1, x-y axes excitation windings  162   a , (show in partial i.e. one quadrant represents all four quadrants) are wound through winding hole  193 , encompassing integral driving-sensing pot-core  188 , Lenz lens  177 , and pick-up coil  190 . Winding connections to all four quadrants are symbolized by leads Ea.  162   a  are. An alternate method of excitatation winding  162   b  (drawn in partial by dashed lines), which is toroidal wound through mounting hole  193  having leads Eb. For signal nulling pick-up coil  190  (having leads SIG. a) is precision wound around cylindrical pole  184  filling annular space  179 . Pot-core half  188  has a base portion  185  and an open annular sensing face  166 . 
     An object of the disclosure is to teach a simple method of signal nulling i.e. under dynamic conditions, the all encompassing excitation winding turns  162   t , are individually adjusted (angularly shifted slightly) for a near flat-line null on an oscilliscope, and then glued in place. Further the described probe assembly may be encased in a cylindrical metal/plastic housing (not shown) and set in a potting compound (a thin layer covering the annular sensing face  166 .) 
     An object of the invention is a method of sine-cosine excitation connection (including series resistors in each lead to a bipolar excitation source (FIG. 2) 
     Preferred Core Materials 
     1) Integral driving/sensing toroids: Square Permally  80 , Supermalloy (tape wound), from MAGNETICS* Butler, Pa. 
     2) Pot-core half: Ferrite part no. 5578000721, from Fair-Rite Products Corp. Wallkill, N.Y. 
     Method of Driving Excitation Connections FIG. 2, digrammatically illustrates a method of: 1) sine-cosine excitation windings  162   a , FIG. 1, (connections in the probe case and to the excitation source EXx.) FIG. 1, illustrates a mesh-connection (a single winding  62   a  in FIG. 2, is continously wound the circumference of toroid  88   a ) being tapped at each quadrant (x-axis taps are LXa, LXb, and y-axis taps are LYa, LYb.) This method allows the currents flowing through windings  162   a , FIG. 1, to circularly equalize as in a gramme-ring GR (FIG.  2 ). Referring again to FIG. 2, Current to the quadrant taps LXa, LXb, LYa, LYb, are respectively fed through series resistors XRa, XRb, YRa, YRb, for enhanced differential x-y axes tilt-ability e.g. probe tilt toward quadrant Qa results in an increase of eddy current reflection in in quadrant Qa. 
     The gramme-ring GR, shown as a series circuit allows a differential (diametric) current-shift toward quadrant Qb. Quadrants Qc, Qd, respond to tilt in their directions in a likewise redistribution od excitation currents. 
     Excitation Generation 
     Referring again to FIG.  2 . Digital values of the predetermined poly-phase sinusoidal wave shapes are loaded into the HOST COMPUTER on bus  05 . The computer generated digital values are fed to plural digital-to-analog converters DAC (PLURAL) by bus  06 . The analog waveforms are carried by buses  01 - 04  to the x-y axes amplifiers Xa, Xb, Ya, Yb, and from there to the respective series resistors XRa, XRb, YRa, YRb. 
     Other Excitation Methods 
     Just as a toroidal deflection yoke around the neck of a TV picture tube magnetically moves the electron beam/s to any location on the screen according to a predetermined program, so also the subject method moves the eddy current on (horizonal-vertical) x-y coordinates (FIG.  1 ). 
     As part of this disclosure, an eddy current scan pattern similar to a television raster may be generated in a planar workpiece by the polar coordinates probe utilizing a programable (software) method. Radar display type scans e.g. plan-position indicator (PPI) is also covered as a programable method of eddy current excitation for extending resolution (both cylindrical and planar workpieces). It is contemplated these excitation methods would be useful for detecting aircraft flaws. 
     Concentric Pot-core Halves 
     In light of cited Logue U.S. Pat. No. 6,265,871B1 combined with the present teachings on integral driving-sensing pot-core halves wound according to this discription, obviously pot-core halves of increasing radii may be disposed concentrically as shown in FIG. 3 (a perspective-quadrant view of probe PS 2 ). The concentric probe in Logue U.S. Pat. No. 6,265,871B1 utilized a plurality of toroid cores, whereas the present concentric probe PS 2  employs a plurality of concentric pot-core halves  255   a ,  255   b.    
     Eddy current probe PS 2 , includes in the outer radius, a wound integral driving-sensing toroidal core  255   a , (a pot-core of enlarged diameter.) Core  255   a  is fully circumferentially wound with poly-phase excitation windings  262   a , (leads not drawn) and is formed of a high permeability material with an annular pick-up coil groove  279   a.    
     Core  255   a  has outer and central poles  286   a ,  284   a.    
     Pick-up coil  290   a  in concentrically disposed in groove  279   a  (leads not shown) generating a first flaw signal. Integral driving-sensing pot-core  255   b , is formed of a high permeability material, having outer and central poles  286   b ,  284   b , leaving an annular pick-up coil space  279   b . A pick-up coil  290   b  is wound within groove  279   b  for generating a second flaw signal. Poly-phase windings  262   b  are wound around core  255   b . Ascending. reference number  277  (the lesser reference number  177  in FIG. 1, being the precedent) represents a concentrically interposed Lenz lens between cores  255   a ,  255   b.