Patent GB-892845-A (GB)
Title: Improvements in or relating to electrical systems for synchronising rotary members
Inventor: CHILMAN JOHN ALFRED
IPC: B64C11/50
Filed: 1957-10-14
Abstract: 892,845. Automatic synchronizing control systems. DOWTY ROTOL Ltd. Oct. 9, 1958 [Oct. 14, 1957], No. 32086/57. Class 38 (4). Relates to a system in which the speed of a slave engine-propeller unit of a two-engined aircraft is equalized with the speed of a master unit, the slave unit then being brought into a desired phase relationship with the master unit. A motor 60 has stator windings supplied respectively from alternators driven by the master and slave units, and its rotor drives a pinion and .causes a lever 51 to operate a control linkage 50 of the slave engine. In this manner, the speed of the slave engine is made equal to that of the master engine after which the motor 60 ceases to operate. The engines are provided with electromagnetic pulse units each comprising a stationary core co-operating with two armatures rotating with the propellers. Pulses from the master and slave units are preamplified by valves 103, 104, a valve 133 producing signals from anodes 145, 146, respectively which are of duration depending on the difference in phase of the master and slave pulses. Thus, current flows to anode 145 when a master pulse reaches grid 131 and continues until a slave pulse reaches grid 132, whereupon the anode 146 becomes effective instead of the anode 145. If the master and slave pulses have a common frequency and a phase-difference of 180 degrees, then the signals from the anodes 145, 146, will have the same mean D.C. levels. An error in the phase-difference causes the mean D.C. levels of the outputs to become unequal. The signals from the valve 133 are smoothed and then passed to the grids of a double-triode valve 167 operating a magnetic amplifier 218 which in turn supplies a phasesynchronizing motor 19. A feed-back generator driven by this motor has its speed signal amplified by valves 177, 173, the combined outputs from valves 133, 173, being fed to the grids of valve 167. The valve 177 is connected to a phase-shift potentiometer 189, the valve 167 amplifying the combined signals from the feed-back generator and pulse units to feed them to the magnetic amplifier 218. This amplifier supplies one or other of the operating windings of the motor 19 depending on which anode of the valve 167 is providing current. The phasesynchronizing motor drives a worm gear which meshes with pinion 63 carrying a pivot for lever 52 which is coupled to control linkage 56 for the fuel valve of the slave propeller unit. The potentiometer 189 adjusts the phase relationship between the master and slave propellers. In an alternative arrangement a controller for the slave engine is coupled through differential gearing with a speed-equalizing motor and a phase-synchronizing motor, Fig. 10 (not shown). In a further embodiment, the slave engine unit comprises an hydraulic variable pitch propeller having a constant speed unit including a fluid pump driven by the engine and a relief valve for the pump. The motor 19 adjusts the setting of the relief valve. Variation of the relief valve blowoff pressure changes the output of the pump and varies the power loading of the slave engine whereby the phase relationship of the slave and master propellers is modified, Fig. 7 (not shown). A tachometer generator driven by the motor 60 may provide a signal proportional to the rateof-change of the phase-difference error signal for controlling the speed of the slave propeller unit through the motor 19. Specification 515,934 is referred to.