Magnetic drive systems

Claim 1

A HYSTERESIS COUPLING COMPRISING A STATIONARY D.C. FIELD WINDING, A FIRST ROTARY MEMBER, A SECOND ROTARY MEMBER ROTATABLE RELATIVE TO THE FIRST MEMBER AND TO SAID FIELD WINDING, SAID MEMBERS CONTITUTING TWO COUPLABLE PARTS OF SAID COUPLING, WHEREIN ONE OF SAID MEMBERS HAS A PLURALITY OF INTERDIGITATING POLE PIECES WHICH ARE INSULATED MAGNETICALLY FROM ONE ANOTHER AND MAGNETIZABLE IN TWO GROUPS OF OPPOSITE POLARITY LOCATED BETWEEN THE FIELD WINDING AND THE OTHER MEMBER, SAID POLE PIECES EXTENDING TOWARDS THE OUTER PERIPHERY OF THE OTHER MEMBER, SAID OTHER MEMBER HAVING AN OUTER SURFACE LAYER IS PROVIDED BY A LAYER OF HIGH HYSTERESIS MATERIAL ADAPTED TO COMPLETE A MAGNETIC CIRCUIT WHICH EXTENDS THROUGH THE POLE PIECES AND TO EXPERIENCE A TORQUE DEPENDENT UPON THE HYSTERESIS EFFECTS IN SAID OUTER SURFACE LAYER, SAID OUTER SURFACE LAYER BEING FORMED WITH AT LEAST ONE NON-HOMOGENEOUS PORTION WHICH EFFECTS A VARIATION IN THE RELUCTANCE, THEREBY EFFECTING CHANGES IN THE MAGNETIC FLUX OF THE MAGNETIC CIRCUIT WHEN SLIP OCCURS; A DETECTING MEANS DETECTING THE ELECTRICAL SIGNAL GENERATED DUE TO THE SAID FLUX CHANGES AND AN INDICATOR RESPONSIVE TO SAID DETECTION MEANS.