Patent GB-472412-A (GB)
Title: Improvements in or relating to power plant for use on aircraft
IPC: B64D35/00
Filed: 1936-03-28
Abstract: 472,412. Driving dynamos. AIR-EQUIPMENT. March 28, 1936, No. 9276. Convention date, March 29, 1935. [Class 35] [Also in Groups XXVII and XXIV] A power plant for aircraft comprises a propelling engine 1, an auxiliary internalcombustion engine 2, and at least one accessory 3 such as an electric generator, normally driven through a transmission device from the propelling engine. The generator is also connected to the auxiliary engine by another transmission device and the apparatus is provided with means whereby, in the event of the stopping or slowing of the propelling engine, the auxiliary engine will be started by means of the kinetic energy of the generator or the propelling engine and will ensure the driving of the generator at the desired speed. The auxiliary engine is preferably also adapted to be used for starting the propelling engine. As shown in Fig. 1, the generator 2 is driven at constant speed from the shaft 1 of the main engine through gearing 4, 5, a free-wheel 7, and a friction clutch 8 transmitting a torque varied automatically in accordance with the speed of the driven member. The clutch 8 comprises a drum 9 secured to the shaft 6, and engaged by friction shoes 10, Fig. 2, pivoted on studs 11 on a disc 12 on the shaft of the generator 3 ; the shoes are pressed against the drum 9 by springs 15 connected to studs 16 on the disc 12 and to governor weights 13 tending to withdraw the shoes as the speed of the generator increases. The generator is also connected to the auxiliary engine 2 through a clutch 8<1> similar to the clutch 8 and comprising a drum 9<1> integral with gear wheels 22, 23 in engagement with gears 17, 18, which are connected to the shaft 19 of the engine 2 through oppositely directed free wheels 20, 21. When the engine 2 is started, it drives the generator 3 at constant speed through the gears 17, 22 and the clutch 8<1>. The engine 2 is then coupled to the main engine to start the latter, which overruns the free-wheel 7 and drives the generator 3 through the gearing 4, 5 and clutch 8. The generator is thereupon disconnected from the engine 2 by the clutch 8<1>, in which the studs 16<1>, Fig. 4, are carried by a sleeve on the shaft of the generator 3 and engage slots 25 in the disc 12<1>, so that the coupling capacity of the springs 15<1> is reduced on the generator 3 being driven from the engine 1. The engine 2 can then be stopped. If the engine 1 stops or slows down, the governor weights 131 will 're-engage the clutch drum 9<1> and the engine 2 will be restarted from the generator 3 through the clutch 8<1>, gears 23, 18 and free-wheel 21. In modification, Fig. 6, the generator 3, is driven from the main engine through the gearing 41, 5<1>, free-wheel 7<1>, and a frictiondisc clutch 8<11> controlled by governor weights 13<11> to keep the speed constant. The drive from the auxiliary engine 2 is through gearing 32, 31 and a free-wheel 33 adapted to gain in either direction of rotation and comprising clutch rollers in a frame 34 ; when the shaft 61 is driven from the main engine, governor weights 37 bring tongues 35 into engagement with the frame 34 and prevent the clutch rollers from jamming, so that the gear 31 is freed from the shaft 6<1>. When the main engine stops or slows down, the frame 34 is released and the free-wheel 33 then transmits starting torque through the gears 31, 32 to the engine 2. To enable the engine 2 to be started without driving the generator 3, the clutch 8<1> may be manually disengaged by means of a disc 30 acting on the governor weights 13". In another modification, Fig. 7, the transmission gearing is enclosed in a casing 55 on which the generator 3 and the auxiliary engine 2 are externally mounted. A gear wheel 40 on the shaft of the engine 2 carries a double planet pinion 47 meshing with a fixed toothed ring 48 and with a sun pinion 49 on the hub of a freely rotatable flywheel 50. The second set of teeth of the pinion 47 engages an internally toothed wheel 51 keyed to a clutch member 53 for coupling to the shaft 1 of the main engine. The wheel 40 engages a wheel 41 on a friction drum 43 connected by a free wheel 42 with the drum 9a of the clutch 8a, forming part of the transmission between the engine shaft 1 and the generator 3. The drum 43 is also connected to the shaft of the generator 3 by centrifugally controlled friction shoes 44 when the speed of the generator decreases owing to the stopping or slowing of the main engine, in order to enable the engine 2 to be started through the gearing 41, 40. In another modification, Fig. 8, of the constant-speed drive for the generator, a cone clutch 62 or a plate clutch between the shaft 59 of the generator and a wheel 63 geared to the auxiliary engine is controlled by a nut 61 movable between end stops on a screw-thread 60 on the shaft 59. The nut is connected by splines to the clutch member 62 and pivoted on the nut are governor weights 13b acted upon by a spring 15b to effect the engagement of the clutch. In a further modification, a multiple-plate clutch is controlled by centrifugally-acting weighted members which gradually relieve the clutch of the pressure of its springs as the engine speed increases. The weighted members act through rollers on the inclined face of a member mounted on the disc engaged by the clutch springs.