Patent GB-692866-A (GB)
Title: Improvements in or relating to apparatus for controlling the speed of a prime mover
Inventor: CHILMAN JOHN ALFRED
IPC: H02P5/50
Filed: 1950-03-02
Abstract: 692,866. Automatic speed control systems; induction motors. ROTOL, Ltd. March 2, 1951 [March 2, 1950], No. 5370/50. Classes 35 and 38 (iv). [Also in Group XXXVII] Selective manual control of speed setting and synchronization of multi-engined aircraft with variable pitch propellers is provided additionally in a synchronizing system such as that described in Specification 515,934, wherein a differential polyphase servomotor fed from engine-driven alternators alters the loading on centrifugal/hydraulic governors controlling the propeller pitch. Limits of synchronizing and manual adjustment are provided by a mechanical brake. As shown, Fig. 1, the control for each engine comprises a differential servomotor 21 with two stators (as described in Specification 515,934) drives an output shaft 26 through worm reduction gearing to adjust the loading on a centrifugal governor 34 controlling a hydraulic actuator to vary the propeller pitch, e.g. as described in Specification 657,792,[Group XXXIII]. More detailed construction of the servomotor and its limit switches and braking arrangements are given in Figs. 2, 3 and 6 ... 10 (not shown). Limit of travel arrangements.-Synchronous limits (Œ 100 r.p.m.) : a clutch 46 driven by the output shaft 26 is spring urged into engagement with a sleeve 41 carrying two pins 44, 45, co-operating with blade springs 50, 51 which carry detents 53, 54 to engage respectively projections 55, 56 (carried by a flange on the motor shaft) at the limits of adjustment. Alternatively, Fig. 2 (not shown), the pins 43, 44 may be replaced by a cam operating a contact to control the hold-off solenoid of a brake built in the motor housing, so that the solenoid is de-energized to stop the motor at the limits of adjustment. Limits of manual adjustment. During manual adjustment of r.p.m. the clutch solenoid 49 is energized so that the brake control sleeve is not driven by the shaft until cam 59 opens the limit contacts 60 to de-energize the clutch solenoid and drive the brake control sleeve. Feathering. The feathering switch shorts the range limit contacts allowing the output shaft 26 to be further revolved until the propeller is feathered and the feather limit contacts (not shown) are opened. These contacts (seen in detail, Fig. 10, not shown), may be operated by a further rise on the range limit cam 59. Selective control.-The clutch windings and servomotor stator connections for all engines are controlled by a common switchboard 66; (i) non-synchronous running: the two stator windings 22, 23 are energized in opposition from the engine alternator so that the rotor is locked; (ii) manual adjustment of r.p.m.: the requisite one of the stators is reversely connected so that the servomotor runs in the required direction as an induction motor, until switched off or stopped by the limit brake as described above ; (iii) synchronous running: the master servomotor remains locked as in (i) above but the " slave " servomotors have their stator windings differentially energized from the master alternator and their own engine alternators respectively, the clutch winding 49 being de-energized to impose the synchronous limits of adjustment. Circuits for a fourengine control system are given, Figs. 4, 11, 12 (not shown).