Patent GB-521000-A (GB)
Title: Synchronising mechanism for multi-engined aircraft
IPC: F02D25/02
Filed: 1938-11-07
Abstract: 521,000. Synchronizing mechanism for multiengined aircraft ALGARSSON, G. Nov. 7, 1938, Nos. 32241 and 32242. Convention dates, Nov. 6, 1937, and Feb. 7, 1938, [Class 135] [Also in Group XXVI] A synchronising mechanism for multi-engined aircraft has a synchronising device associated with each engine furnishing a direct drive from the fastest engine to a transmission connecting all the synchronising devices, each of which is adapted to use any lag of its engine with respect to the transmission to effect an increase in the speed of its engine to achieve synchronisation. Figs. 1 and 3, show the invention applied to a twin engine aircraft in which each airscrew is provided with an hydraulic brake 28 for decreasing its pitch setting and relieving the load thereon and consequently increasing the speed of the corresponding engine 15, the brake being controlled by a valve 40. The valves 40 are mounted in a common casing 21 and each comprises concentric sleeves 20, 22 formed with ports 25, 26 respectively, the sleeve 20 being rotated by the engine through a shaft 17 and gears 18, 19, and the sleeve 22 by geared wheels 23, 23 which are rotated by the faster of the 'two sleeves 20 through the engagement of a lug 27 on the relevant sleeve 20 with the edge of the port 26 on its sleeve 22. The arrangement is such that should, for example, the left-hand or port engine lag behind the other, relative rotation of the sleeves 20, 22 of the port valve will be effected to close the. ports 25, 26 and cause the brake 28 associated therewith to adjust its associated airscrew. The apparatus may also include hydraulic brakes 32 for increasing the pitch setting of the airscrews in combination with a constant speed governor 34 which is driven by the gears 23 at the speed of the faster engine. The governor 34 is adapted on increase of speed to close a valve 36 in a common pipe 33 leading from the brakes 32 to effect an increase in pitch setting and a corresponding decrease in speed, and, on decrease in speed, to close a valve 37 in a common pipe 30 leading from the valves 40 of the brakes 28 and increase the speed, without affecting the functioning of the synchronising mechanism. In a modification, Fig. 4, each airscrew is provided with mechanism (not shown) for decreasing or increasing the pitch setting, the said mechanism being actuated by fluid delivered by a pump 118, driven by a shaft 116 coupled to the engine 115, under the control of a piston valve 123, the valve 123 permitting oil to be pumped from a tank 120 to the pitch-setting mechanism through pipes 122, 124 or permitting oil to return therefrom through pipes 124, 125. As shown the valve is controlled by a rod 133 which is driven through a lag drive 131, Fig. 6, located between a shaft 150 and a shaft 132 common to both engines and by a governor 126, driven from each shaft 116, connected to a floating lever 147 between the rod 133 and the rod 146 of the corresponding valve 123. In a modification, a single common governor, driven from the shaft 132, is connected to both floating levers 147. The lag drive 131 comprises-a casing 134 in which the shafts 150, 132 are journalled, the said shafts terminating in gears 135, 136 which engage further gears 137, 138, the gear 137 being screw threaded 'to receive a threaded portion 140 of a rod 141 pivotally coupled to the rod 133 and the gear being internally splined at 143 to receive splines 142 on the end of said rod 141. The portion 140 is backed by a spring 145, and'the arrangement s such that a difference in speed between the two shafts 150, 132 will effect an axial movement of the rod 141 to the left or right to actuate the piston valve 123. The shaft 132 may be replaced by a closed hydraulic circuit including two gear-pump-motors coupled to 'the members 131. Specification 522,249, [Group XXXIII], is referred to.