GB974220A - Improvements in or relating to composite constant-speed drives - Google Patents

Abstract

974,220. Variable-speed gear. PLESSEY CO. Ltd. Feb. 17, 1961 [Feb. 19, 1960], No. 5954/60. Heading F2D. [Also in Division F1] Constant speed of an electric alternator 2 driven through variable ratio planet gearing 3 by a variable input 1 is obtained by controlling an air motor 12 in response to variations in output speed sensed by a governor 21 which operates a valve 20 in both the inlet and outlet lines of the motor 12 which drives or is driven by a reaction planet carrier 7 of the planet gear, to permit the carrier to run in either direction at the varying speeds necessary to result in constant output speed as the input speed varies, and the motor 12 may be driven in the reverse direction whilst the output is held by a one-way brake 46 for starting the engine. The gear train comprises input and output suns 4, 5 which mesh stepped planets 8, 9 the reaction carrier 7 of which is geared to the output shaft of the motor 12. In operation when the output speed is low the valve 20 is moved right by a spring 49 to connect the motor input line 15 with an engine compressor bleed air line 24, and the pressure air drives the motor 12 and planet carrier 7 in the same direction as the engine 1 with consequential increase of output speed. As the input speed increases the valve 20 moves left, throttling pressure air to the inlet 15 until the valve lands 31, 32 block both the inlet 15 and outlet 16 of the motor 12 whereupon the engine alone drives the alternator 2. On further increase of input speed the valve 20 moves further left to connect the line 15 with an exhaust line 29 whereupon the reaction planet carrier 7 drives the motor 12 in reverse which latter draws air from an atmospheric inlet 33 past a one-way valve 34 and exhausts it through lines 15, 29 against a resistance produced by the throttling action of the land 31. On further increase of input speed the valve 18 connects the engine compressor bleed air line 24 to the line 16, and the pressure air drives the motor 12 and planet carrier 7 in the reverse direction. Suction in the line 29 may also be provided in a manner described in Specification 952,982. For starting the engine, the motor 12 is driven in reverse whilst the output sun 5 of the gear 3 is held stationary by a one-way brake 46 on the alternator shaft. As the engine is stationary the bleed air pressure is zero and a pressure sensitive valve 42 moves right to connect an auxiliary pressure line 26 through lines 39, 40, a manually operated starter valve 38 and line 36 to the right-hand side of a servo 35 which moves the valve 20 to its extreme left-hand position to connect the auxiliary pressure supply to the line 16 which air drives the motor in reverse to start the engine. One-way valves 25, 27 are provided in the engine compressor bleed air line 24 and auxiliary air line 26 respectively. For testing, the engine and alternator may be driven in the correct direction by locking the gear 3 with a pin clutch 47 and driving the motor in the normal direction.