Eddy current tachometer indicator assembly for indicating revolutions per minute

Claim 1

AN EDDY CURRENT TACHOMETER INDICATOR ASSEMBLY FOR INDICATING REVOLUTIONS PER MINUTE, HAVING A MINIMUM STARTING AND OPERATING TORQUE, COMPRISING A DIRECT CURRENT GALVANOMETER INDICATING INSTRUMENT HAVING A POINTER ACTUATED BY A DIRECT CURRENT COIL ALONG A SCALE CALIBRATED IN REVOLUTIONS PER MINUTE, A POTENTIOMETER COMPRISING A RESISTANCE WIRE OF SIMPLE CIRCULAR FORM CARRIED BY A FIXED INSULATING DISC ON THE PERIPHERY THEREOF, AND HAVING ITS TERMINALS CONNECTED TO A DIRECT CURRENT ENERGIZING CIRCUIT, SAID GALVANOMETER COIL HAVING ONE TERMINAL CONNECTED TO ONE END OF SAID RESISTANCE WIRE AND THE OTHER TERMINAL OF THE GALVANOMETER BEING CONNECTED TO A CONTACT, HAVING SLIDING ENGAGEMENT WITH SAID RESISTANCE WIRE, A TACHOMETER BODY COMPRISING A FIXED CYLINDRICAL HOUSING HAVING A BEARING SLEEVE CARRIED BY ONE END OF SAID BODY AND EXTENDING AXIALLY FROM SAID BODY, A FIRST SHAFT ROTATABLY MOUNTED IN SAID SLEEVE AND PROJECTING THEREFROM TO BE DRIVEN BY A ROTATING SHAFT, THE ROTATING SPEED OF WHICH IS TO BE INDICATED, A MAGNET CLAMP CARRIED BY THE INNER END OF SAID SHAFT AND COMPRISING A NON-MAGNETIC CYLINDRICAL BODY HAVING A RECTANGULAR SLOT RECESS EXTENDING AXIALLY INTO SAID BODY FOR RECEIVING A COMPLEMENTARY RECTANGULAR MAGNET BLOCK, A MAGNET ASSEMBLY COMPRISING A RECTANGULAR MAGNETIC BLOCK OF PARAMAGNETIC MATERIAL OF HIGH COERCIVE FORCE, POLARIZED TRANSVERSELY TO SAID SLOT IN SAID CLAMP AND FITTING IN SAID SLOT, AND SAID MAGNETIC BLOCK BEING PROVIDED WITH A PAIR OF PARTIALLY CYLINDRICAL SOFT IRON POLE SHOES SECURED TO THE POLARIZED ENDS OF SAID MAGNET AND FORMING WITH THE MAGNET AND CLAMP, A CYLINDRICAL MAGNET AND CLAMP ASSEMBLY, AN END PLATE SECURED TO SAID MAGNET CLAMP ABOUT SAID FIRST SHAFT, SAID END PLATE SUPPORTING AN AXIALLY EXTENDING CYLINDRICAL POLE SHOE OF PARAMAGNETIC MATERIAL, CONCENTRICALLY TO THE OUTER CYLINDRICAL SURFACE OF SAID MAGNET AND CLAMP ASSEMBLY, FORMING A CYLINDRICAL AIR GAP, A PARTITION IN SAID HOUSING AND HAVING A SECOND BEARING ALIGNED WITH SAID FIRST SHAFT, A SECOND SHAFT IN SAID SECOND BEARING AND SUPPORTING ON ITS INNER END, A CYLINDRICAL ARMATURE SLEEVE OF NON-MAGNETIC METAL, ROTATABLY MOUNTED IN SAID AIR GAP BY SAID SECOND SHAFT, AN INSULATING CONTACT BLOCK CARRIED BY SAID SECOND SHAFT AND SUPPORTING SAID CONTACT IN SLIDING ENGAGEMENT WITH SAID RESISTANCE WIRE, A SPRING CONNECTING SAID SECOND SHAFT AND SAID INSULATING DISC WHICH SUPPORTS SAID RESISTANCE WIRE FOR RESISTING ROTATIVE MOVEMENT OF SAID SECOND SHAFT AND URGING SAID ARMATURE SLEEVE TO A ZERO POSITION OF SAID SLIDING CONTACT, THE ROTATION OF SAID FIRST SHAFT ROTATING THE MAGNET AND CLAMP ASSEMBLY AND THE ARMATURE SLEEVE WITH THE FLUX GENERATED BY SAID MAGNET IN SAID AIR GAP, THE LINES OF FLUX ROTATING WITH SAID MAGNET AND ARMATURE SLEEVE AND THE LINES OF FLUX CUTTING LONGITUDINAL LINES OF CONDUCTIVITY IN SAID ARMATURE SLEEVE AND INCLUDING EDDY CURRENTS IN SAID ARMATURE SLEEVE, WHICH CUTTING PRODUCES MAGNETIC FLUX IN THE AIR GAP, COACTING WITH THE ROTATING FLUX OF THE MAGNET AND TENDS TO ROTATE THE ARMATURE SLEEVE, THE SLIDING CONTACT TAKING A POSITION PROPORTIONAL TO THE SPEED OF ROTATION OF THE FIRST SHAFT, AND THE POINTER INDICATING THE CORRESPONDING SPEED IN REVOLUTIONS PER MINUTE ON THE SCALE.