Apparatus for detecting longitudinal and transverse imperfections in elongated ferrous workpieces

Mechanism for detecting the presence and location of an imperfection in an elongated ferrous workpiece, comprising

• magnet means for establishing a first localized magnetic field which is extremely small relative to the workpiece as a whole and which is restricted to only a portion of said workpiece and of a size expected to contain the imperfection sought to be detected,
• means for moving said first localized magnetic field relative to said workpiece and to said imperfection to create a distortion in said field which is functionally proportional to said imperfection and which is large relative to the size of said field,
• coil means for generating a first electric current responsive and proportional to said distortion resulting from the presence of said imperfection in said first localized field,
• second magnet means for establishing a second localized magnetic field which is extremely small relative to the workpiece as a whole and which is restricted to only a portion of said workpiece and of a size expected to contain the imperfection sought to be detected,
• second means for moving said workpiece relative to said second field to create a distortion in said second field which is functionally proportional to said imperfection and which is large relative to the size of said second field,
• second coil means for generating a second electric current responsive and proportional to said distortion in said second field resulting from the presence of said imperfection in said second field,
• said first coil means being disposed in a direction transverse to the axis of the workpiece, said second coil means being disposed parallel to the axis of the workpiece,
• amplifier circuit means having the input thereof coupled to both said coil means and amplifying the electromotive force signals received at said input,
• signal display means being coupled to said amplifier circuit means and rendering a display that is responsive to the electrical signals received from said amplifier circuit means,
• said signal display means including a galvanometer mechanism capable of relating electrical signals into mechanical form,
• printing apparatus being connected to said galvanometer and providing a printed display of said electrical signals in graphical form,
• graph means being located adjacent said galvanometer and being contacted by said printing apparatus, said printing apparatus printing a graphical display of said electrical signals on said graph means,
• said galvanometer mechanism comprising
• a circuit board having an electrical circuit printed thereon and defining a plug portion,
• a plurality of electrical contacts being defined on said plug portion of said circuit board and being electrically connected to said printed electrical circuit, said plug portion being adapted for insertion into a galvanometer control console receptacle for connection to appropriate galvanometer actuating circuitry,
• a magnet being fixed to said circuit board and having a pair of spaced legs defining the poles of the magnet,
• a torsion bar being secured between the legs of said magnet,
• electrical coil means connected to said printed electrical circuit, said coil means being supported by said torsion bar and being rotated against the restraining force of said torsion bar responsive to the electrical signal being applied to said coil, and
• said printing apparatus being operatively connected to said coil means for movement in response to said electrical signal and being positioned relative to print receiving apparatus by said coil means.