Month in the Patent Office

A propeller 1 in a stationary tubular casing 2 rotates inside a guard ring 3 which is mounted for free rotation inside the casing on bearings 4, the free flow of air between the blade tips and the guard ring being reduced to a minimum by reducing the clearance between tips and rings and shaping the blade ends to conform with the interior of the ring. The flow of air through the casing is regulated by a ring 5 adjustably mounted in front of the casing to form an adjustable slat and controllable gills or flaps 7 at the rear. The inlet is provided with a fixed ‘cone’ 13; annular deflectors 14 ensure a homogeneous distribution of the air flow; the outlet is profiled at 15. The air compressed by the propeller is heated by engine cooling, exhaust gases, and/or burners for the purpose of increasing thrust. The propeller may be driven by an internal combustion engine or a turbine motor. The rotatable guard ring 3 may be replaced by fixed baffle plates.