Apparatus for sensing relative rotation between a pair of elements

Claim 1

IN A MAGNETIC TAPE RECORDING AND REPRODUCING MACHINE, A MOTION SENSOR FOR A REEL SHAFT, COMPRISING; A MEMBER MOUNTED FOR ROTATION ABOUT THE AXIS OF SAID SHAFT, SAID MEMBER HAVING A NORMAL POSITION INDICATING A STATIONARY CONDITION OF SAID SHAFT, A FIRST ARRAY OF DISPLACED POSITIONS WITH SAID MEMBER CIRCUMFERENTIALLY DISPLACED IN ONE ROTATIONAL DIRCTION WITH RESPECT TO SAID NORMAL POSITION INDICATING CONCURRENT ROTATION OF SAID SHAFT IN SAID ONE DIRECTION AT VARIOUS SPEEDS, AND A SECOND ARRAY OF DISPLACED POSITIONS WITH SAID MEMBER CIRCUMFERENTIALLY DISPLACED IN AN OPPOSITE ROTATIONAL DIRECTION WITH RESPECT TO SAID NORMAL POSITION INDICATING CONCURRENT ROTATION OF SAID SHAFT IN SAID OPPOSITE DIRECTION AT VARIOUS SPEEDS; A MAGNET MOUNTED ON SAID MEMBER AT THE PERIPHERY THEREOF; SPRING MEANS COUPLED TO SAID INDICATING MEMBER FOR URGING SAID MEMBER TOWARD SAID NORMAL POSITION; BALL BEARING MEANS BETWEEN SAID SHAFT AND MEMBER, SAID BEARING MEANS INCLUDING INNER AND OUTER RACES AND SEALING MEANS DEFINING THEREWITH A HOUSING FOR CONTAINING FLUID IN SAID BEARING MEANS SAID INNER RACE BEING ATTACHED TO SAID SHAFT AND SAID OUTER RACE BEING ATTACHED TO SAID INDICATING MEMBER; A VISCOUS FLUID DISPOSED IN SAID HOUSING BETWEEN SAID INDICATING MEMBER AND SAID SHAFT AND FORMING A VISCOUS COUPLING FOR CAUSING SAID MEMBER TO MOVE AWAY FROM SAID NORMAL POSITION UPON ROTATION OF SAID SHAFT, AND FOR PERMITTING RETURN OF SAID MEMBER TO SAID NORMAL POSITION UPON CESSATION OF SAID ROTATION; FIRST AND SECOND ARRAYS OF MAGNETIC SWITCHES POSITIONED AT SAID FIRST AND SECOND ARRAYS OF POSITIONS, RESPECTIVELY, FOR OPERATIVE MAGNETIC COUPLING WITH SAID MAGNET OF SAID INDICATING MEMBER, SAID SWITCHES EACH BEING BIASSED AGAINST OPERATION THEREOF; AND MEANSA COUPLED TO SAID SWITCHES FOR INDICATING THE DIRECTION OF AND DEGREE OF DISPLACEMENT OF SAID MEMBER AS A FUNCTION OF THE DIRECTION AND SPEED OF ROTATION OF SAID SHAFT.