Patent GB-523539-A (GB)
Title: Improvements in or relating to electric indicating and positional control systems
IPC: F41G5/12
Filed: 1939-01-03
Abstract: 523,539. Electric control systems. SPERRY GYROSCOPE CO., Inc. Jan. 3, 1939, No. 158. Convention date, Jan. 3, 1938. [Class 40 (i)] In a system for controlling a body such as a searchlight in accordance with the movements of a sound locator from a station remote from the locations of the searchlight and sound locator, an A.C. transmission system. of the "Selsyn" or rotary transformer type is employed for comparing the relative positions of the searchlight and locator, and indicators at the' control station are supplied with the comparison data to enable the searchlight to be controlled. As shown the searchlight 9 is controlled in elevation and azimuth by step-by-step motors 29. 29<SP>1</SP> operated by manually controlled transmitters 26, 28, 26<SP>1</SP>, 281 located at a control station 22. Zero-reading indicators 21, 21<SP>1</SP> are provided at the control station for comparing the positions of the searchlight and a sound locator 1 both in azimuth and elevation. The locator controls "Selsyn" type transmitters 3, 3<SP>1</SP> which produce fields in the stators of the "Selsyn" receivers 7, 7<SP>1</SP> the directions of which correspond to the positions of the rotors of the transmitters. The rotors of the receivers are mechanically coupled to the searchlight and are connected to bridge connected rectifier arrangements 12, 12<SP>1</SP> which supply the indicators 21, 211 In order to maintain the'searchlight in positional agreement with the locator; the searchlight is operated from the control station to maintain the receiver rotors in positions at right angles to the stator fields and thereby maintain the induced current in the indicator circuits at zero. Resistances 24, 24<SP>1</SP> are provided to facilitate oscillatory searching movements of the searchlight beam without affecting the indications. As shown in Fig. 2, depression of a handle 31 closes contacts 33 and switches on a motor 34 which, through a crank disc 37, oscillates a sector plate 40 to which is geared a differential gear controlled by the control handle 26 and thereby introduces an oscillatory control of the " elevation " transmitter 28. The plate 40 also oscillates the contact arm 44 of the resistance 24 to introduce into the indicating circuit a voltage which compensates the oscillatory movements of the " elevation " receiver rotor operated by the searchlight. To provide oscillatory movements of the searchlight beam in azimuth the handle 31 and contact 441 of resistance 241 are oscillated slowly and the control transmitter 281 is operated correspondingly to maintain the indicator 21<SP>1</SP> at zero. Corrections for lag or lead in the locator data may be introduced by rotary adjustment of the handle 31. The rectifier bridges may be located at the control station and in this case the resistance of the bridges may replace the potentiometer 24, 24<SP>1</SP>. In a modification, an electric differential having a threephase stator and rotor is connected between the transmitter 3 and receiver 7 and is located at the control station. Compensation for the searching movements for the searchlight is then effected by oscillating the rotor of the differential by a sector plate such as 40. In a further modification, searching movements are produced by an auxiliary motor which oscillates the searchlight through differential gear also associated with the control step-by-step motor. A second differential gear is introduced between the searchlight and the receiver rotor in order to cancel out the oscillatory motion in the rotor.