Patent GB-378242-A (GB)
Title: Improvements in engine synchronism indicators
IPC: G01P3/40
Filed: 1931-09-24
Abstract: 378,242. Comparison speed indicators. PIONEER INSTRUMENT CO., Inc., 754, Lexington Avenue, Brooklyn, New York, U.S.A. Sept. 24, 1931, No. 26672. Convention date, Sept. 27,1930. [Class 106 (iii).] Comprises stroboscopic apparatus for indicating the synchronism of aircraft engines or other mechanisms wherein a gas-discharge device for each engine is periodically illuminated at a frequency corresponding to its associated engine or a multiple of such frequency, the gasdischarge devices being simultaneously rotated at a speed corresponding to the speed of the revolving master mechanism so that when illuminated they appear to be stationary when the speed of the respective engines agrees with that of the master mechanism. The particular construction is such that the high frequency currents are generated close to the indicating device and thus interference with radio apparatus is avoided. The outboard engines 7, 9 are compared with the central engine 8 from which the neon lamps 12, 13 are rotated. The lamps are rotated by a self-starting synchronous motor 19 actuated by pulsations of current flowing through field coils 20, 21 adapted to energize a laminated field magnet 22 and arranged to change the polarity of the magnet as the coils are energized in sequence. The polepieces 23, 24 are divided into pairs, the diametrically opposite members being provided with shading coils to delay magnetization. A rotor 27 of preferably hardened steel is rotated by the rotating field, the shaft 28 of the rotor carrying the mounting member 14 for the neon tubes. The coils are alternately energized by an interrupter 31. Movable contacts 33, 34 are carried by arms 35, 36 operated by a cam disc 37 driven from the engine 8 to open and close alternately the circuit between the stationary contact 32 and contacts 33, 34. The contact 32 is connected by a lead 39 to a batterv 40 while contacts 33, 34 are connected by leads 41, 42 to the outer terminals of field coils 20, 21, the other ends of the field coils being connected with the other terminal of the battery by leads 43, 44. The means for illuminating the neon lamps 12, 13 periodically in accordance with the speed of the outboard motors 7, 9 by producing a spark discharge in the tubes once per revolution of their respective engines comprises a pair of interrupters 45, 46 and a pair of transformers 47, 48. The stationary contacts 49, 50 are connected by leads 61, 62 to one terminal of the battery 40 while movable contacts 53, 54 are connected by leads 63, 64 to the primary windings 65, 66 of the transformers 47, 48 which are located adjacent the casing of the indicating device whereby long high tension leads are eliminated. One end of the secondary 67 of transformer 47 is connected to the metallic ring 17 by means of lead 68, while one end of the secondary 69 of transformer 48 is connected to the metallic ring 18 by means of lead 70. The two transformers are connected together by a lead 71 to provide a return path for the primary windings to the battery 40 by means of leads 72, 44. The return of the secondaries is through the neon lamps 12, 13 and through mounting member 14 through leads 43, 72, the former being electrically connected with the magnet 22 at 73.