GB957573A - Improvements in pneumatic constant speed drives - Google Patents

Abstract

957,573. Epicyclic change-speed gear control. H. M. HOBSON Ltd. April 25, 1963 [March 23, 1962], No. 11276/62. Heading F2D. [Also in Division F1] The torque reaction member of an epicyclic gear, between an aircraft jet engine and an alternator to be driven at constant speed, is controlled by an air turbine at engine speeds from zero to above idling speed and by a positive displacement pneumatic machine above these speeds. A ring gear 20 is driven from the engine and the alternator is driven from the planet carrier 21, torque reaction being supplied by an air turbine 26 coupled by gears 25 to the sun gear 23. The sun gear 23 is connected through a free-wheel 46 to a gear 27 meshing with a gear 28 drivingly connected to a Rootes blower 30 and a ring gear 31 connected by free-wheel 27 to the ring gear 20. At zero engine speed, the alternator is driven from the turbine 26 by air from an auxiliary supply through pipe 40, an output shaft governor 15 maintaining the alternator speed constant by control of a valve 38 and turbine guide vanes 39. When the engine starts, interconnected controls 35, 37, 38 permit running of the turbine from the final stage of the engine compressor until the engine speed rises to a point between idling and aircraft stand-off speed, at which point the blower 30 provides reaction by acting as a compressor and the turbine commences to act as a compressor. For engine starting the blower 30 is run as a motor from auxiliary air supply and, in the event of engine failure, the turbine is fed from an air supply from another engine through pipe 42 to drive the alternator. Specification 871,576 is referred to.