Electric motor cooling means

Claim 1

AN ELECTRIC MACHINE HAVING AN OUTER CASING WHICH DEFINES AN AIR INLET AT ONE END AND AN AIR OUTLET AT THE SAME END AND IS IMPERVIOUS TO AIR EXCEPT AT SAID INLET AND SAID OUTLET, A STATOR, A ROTOR WITHIN THE CASING MOUNTED FOR ROTATION ABOUT A LONGITUDINAL AXIS, FOR ELECTRICAL COOPERATION WITH THE STATOR, AN IMPELLER MOUNTED WITHIN THE CASING COAXIALLY WITH THE ROTOR AT ONE END THEREOF AND FOR ROTATION THEREWITH, SAID IMPELLER COMPRISING A SERIES OF BLADES DISPOSED LONGITUDINALLY OF THE ROTOR AXIS AND ARRANGED IN A RING THEREABOUT TO DEFINE AN INTERIOR SPACE, GUIDE MEANS WITHIN THE CASING COOPERATING WITH THE IMPELLER ON ROTATION THEREOF IN A PREDETERMINED DIRECTION TO INDUCE A FLOW OF AIR FROM AN ENTRY SIDE OF THE IMPELLER THROUGH THE PATH OF THE ROTATING BLADES TO SAID INTERIOR SPACE AND THENCE AGAIN THROUGH THE PATH OF THE ROTATING BLADES TO AN EXIT SIDE OF THE IMPELLER, AND MEANS DEFINING AT LEAST A PAIR OF LONGITUDINAL DUCTS WITHIN AND CASING INCLUDING AN INFLOW DUCT FOR AIR FLOW FROM SAID ONE TO SAID OTHER END OF THE CASING AND AN UTFLOW DUCT FOR AIR FLOW FROM SAID OTHER TO SAID ONE END OF THE CASING, THE IMPELLER BEING ARRANGED IN SERIES WITH THE INFLOW AND OUTFLOW DUCTS BETWEEN THE INLET AND THE OUTLET WHEREBY ON ROTATION OF THE ROTOR AND IMPELLER THE LATTER SETS UP A FLOW OF AIR, ALL OF SAID FLOW PASSING FROM THE INLET TWICE ALONG THE LENGTH OF THE CASING TO THE OUTLET.