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 thriugh 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  
       [0001]    This Patent Application is a continuation-in-part of patent application Ser. No.: 09/419,140 filed Oct. 15, 1999 and 09/467,599 filed Dec. 20, 1999, pending payment of Issue Fee. 
     
    
     
       BACKGROUND ART  
         [0002]    Tesla 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.  
           [0003]    The preferred pick-up assembly to date is a pot-core half with a pick-up coil of many turns of small guage magnet wire e.g. 42 ga., wound around the central pole, filling the annular coil space. 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.  
           [0004]    Alternately multiple parallel smaller gauge magnet wires e.g. 46 gauge, may be used.  
           [0005]    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 Pat. No. 5,909,118. As taught in Logue application Ser. No. 09/467,599 a polar coordinates sensor may be reduced to a ferrite pot-core core (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 sine-cosine excitation windings wound through mounting hole (now a winding hole)  184 , in FIG. 1. The pot-core half must be segment-less (no lead slots).  
           [0006]    Oscillatory Signal Build-up  
           [0007]    The polar coordinates signal disclosed in the asending Logue patents is actually formed by succesive revolutions of the hemispherical driving field acceleration; the axis of which is displaced by an asymmetry (flaw) in the eddy current reflection.  
           [0008]    This is a rotary type of parametric pumping. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a sectional-perspective viewof eddy current probe PS 1  spatially illustrating the disclosed methods of increasing resolution.  
         [0010]    [0010]FIG. 2, is a block-circular diagram of the preferred excitation/connection method for probe PS 1  in FIG. 1.  
         [0011]    [0011]FIG. 3, is a perspective-quadrant view of an eddy current probe utilizing concentric integral driving-sensing pot-cores on increasing radii. 
     
    
     OBJECTS OF THE DISCLOSURE  
       [0012]    A primary object of this disclosure is pursuant to the benefit of the filing date of pending Logue application Ser. No. 09/467,599 pertaining to a coil wound in the annular groove formed in a toroidal core i.e. a pot-core half (element  188  in FIG. 1). The referred benefit is found in Section 201.08 (MPEP). In the cited application Ser. No. 09/467,599 described the dual/alternate functions of a coil ( 190 , FIG. 1) wound in the annular groove ( 179 , FIG. 1) were: 1, poloid axis excitation, 2) as an auxiliary pick-up coil for detecting an asymmetry in the hemispherical probe driving field (flaw in a conducting workpiece,) A claim covering this alternate utility was inadvertently left out of application Ser. No., 09/467,599 by the Applicant.  
       DETAILED DESCRIPTION  
       [0013]    A second object of the disclosure is an improved method of fitting a Lenz lens/caseing  177 , in FIG. 1, (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 copper Lenz lens left a concentric air gap between driving-sensing core and subject high cross-section Lenz lens  177 .  
         [0014]    To prevent any cutting of magnet wire insulation Lenz lens is covered with a hard insulating coating.  
         [0015]    Another object of the disclosure is to teach a method of assembling a simple/robust eddy current probe comprising: a pot-core of high permeability, a Lenz reflecting lens and encompassing x-y axes excitation winding distributions. 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 .  
         [0016]    An object of the disclosure is to teach a simple method of signal nulling e.g. 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, and set in a potting compound (a thin layer covering the annular sensing face  166 .)  
         [0017]    An object of the invention is an improved method of sine-cosine excitation connection configuration (including series resistors in each lead to a bipolar excitation source (FIG. 2)  
         [0018]    Preferred Core Materials 1) Integral driving/sensing toroids: Square Permally  80 , Supermalloy (tape wound), from MAGNETICS* Butler, Pa.  
         [0019]    2) Pot-core half: Ferrite part no. 5578000721i, from Fair-Rite Products Corp. Wallkill, N.Y.  
         [0020]    Method of Driving Excitation and Connections  
         [0021]    [0021]FIG. 2, digrammatically illustrates a preferred method of: 1) sine-cosine excitation windings  162   a , FIG. 1, (connections in the probe case and to the excitation source EXx.) The preferred method of connecting configuration of poly-phase excitation windings  162   a , FIG. 1, is a mesh-connected (a single winding  62   a , 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 increasing eddy current resolution and also allowing a greater probe tilt angle (signal has less tilt noise). Referring again to FIG. 2, Current Lo 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. a probe tilt toward quadrant Qa, results in an increase of eddy current reflection in quadrant Qa. The gramme-ring, being 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 of exitation currents. 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.  
         [0022]    Concentric Pot-core Halves  
         [0023]    The light of cited Logue application Ser. No. 09/467,599 combined with the present teachings on integral driving-sensing pot-cores wound according to the discription, obviously pot-cores of increasing radii may be disposed concentrically as shown in FIG. 3 (a perspective-quadrant view of probe PS 2 ). Eddy current probe PS 2 , includes in the outer radius 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. Polyphase windings  262   b  are wound around core  255   b.    
         [0024]    Contemplated Excitation Methods  
         [0025]    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 subjec As part of this disclosure, an eddy current scan pattern similar to 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 cylinder and planar workpieces). It is contemplated the preceding methods would be useful for detecting aircraft flaws.