Patent GB-569213-A (GB)
Title: Improvements in or relating to speed controls, particularly for synchronizing a number of power units
IPC: F02D25/02
Filed: 1943-01-16
Abstract: 569,213. Automatic control systems for prime movers. STEVENS, A. H. (Woodward Governor Co.). Jan 16, 1943, No. 832. [Class 38 (iv)] [Also in Groups XXVI and XXXVIII] Speed.-A system for maintaining synchronism of one or more rotary power units with another has means whereby the system can be instantly disabled and the prime movers caused each to develop its maximum speed. Each engine A ... D has a governor 5, the speed setting of which is controlled by an electric step-by-step motor 51 which operates through a high reduction gearing 81, Fig. 2, and a planetary gear mechanism 83 upon a member 86 which adjusts the compression of a spring 15 in opposition to the action of a second spring 87. The reaction member of the gear is normally restrained by a pawl 97 which can be disengaged by energizing a solenoid 102, whereupon the spring 87, which is adjustable by a screw 88, drives the member 86 to a high speed position determined by an adjustable screw 92. As shown, the governor controls fluid pressure means for adjusting the pitch of the propeller blades 6 of an aircraft engine, the servomotor 7 of which may also be actuated to feather the blades by energizing the motor 40 of a high pressure oil pump. The electric motors 51, Fig. 4, have a permanent magnet rotor the poles of which are each opposed by five pole faces of a twelve-pole stator; the stator has twelve overlapping coils each of which embraces two adjacent pole faces and these coils are connected in three series groups in delta to three plates of a disc commutator 68, Fig. 1, the face of which is engaged by two pairs of brushes. The brushes of each pair are interconnected and make contact with the disc at points 30 degrees apart so that as the commutator is turned by a shaft 63 the polar axis of the stator is turned likewise. When the energizing current is disconnected the rotor is held by its magnetic field in the position to which it has been moved. A system for controlling four prime movers in which any one may be selected as a. speed master by adjusting an indicator 117 is shown in Fig. 1. The shafts 63 of the commutators are coupled to selsyn rotors 107. The stators and the selsyns are connected by switches 111 to a small three-phase generator 109 driven by the selected master engine and the rotors of the selsyns of the remaining engine governors are connected each to a like generator 109 on the rotated engine by switches 112. A similar switch 180 controls lamps] 176 which indicate the master engine. All switches 111, 112, 180 are coupled to rotate in unison on a shaft 113 carrying the indicator 117. Any deviation from synchronous speed will cause the selsyn of the engine concerned to turn and adjust its governor progressively to lower or raise the speed setting until synchronism is restored. The shaft 113 is housed in a control box shown in section in Fig. 6 and in elevation in Fig. 3. It is indexed by a spring stud 153 which also moves it longitudinally to a position in which all switches are disengaged from their contacts. When the indicator 117 has boon moved to select the desired master engine the shaft is pressed in to establish synchronism control and held by a latch 148 which can be instantly released to disable the control either by pressing a knob 157 or energizing a solenoid 161, Figs. 1 and 6. The latter occurs when a manual switch 209 is closed to feather the propeller of the master engine (the switch 180 controlling this in part) or when the pilot puts his engines to full throttle striking thereby a bail to close a switch 185 ; a switch 188 in parallel to the latter may be arranged on the control panel. Any one of the selsyns may be disabled to permit independent speed control of the related engine by operating its switch 170 by a knob 210 on the panel; the spindle 63 of each commutator switch is manually operable for this purpose by a hand wheel 200 and, by drawing out knobs 203 whereby interconnecting gearing is engaged, two or more engines may be speedcontrolled in common by a single hand wheel. Each governor has a rheostat 193 coupled to the element 86 whereby an electrical indication representative of the speed of that engine may be obtained on an instrument 192 on the panel. A simplified system in which one engine alone may be the master engine is shown in Fig. ]3. A switch 228 and a switch 230 operated on disablement of the manual control of the governor settings may be actuated to energize a coil 226 which actuates switches to connect one generator to the stators of the selsyns of all controlled engines and to connect the rotors to the respective engines. The coil 226 also oloses a sealing circuit for itself through a switch 233, which is operated when a switch 185 is actuated to disable the governor adjusting motors, and a switch 234 operable at will.