Patent GB-496521-A (GB)
Title: Improvements in or relating to electric indicating systems in or on aircraft
IPC: B64D45/00
Filed: 1937-09-15
Abstract: 496,521. Electric signalling systems. SPERRY GYROSCOPE CO., Inc. Sept. 15, 1937, No. 25109. Convention date, Sept. 17,1936. [Class 40 (i)] [Also in Group XX] In an aircraft the information given by a number of instruments is simultaneously indicated on a single dial, control potentials from each instrument being applied to the deflecting plates or coils of an oscillograph. Fig. 1 shows a view of a cathode-ray tube screen when the aircraft is on its course, spot 7 giving the compass bearings, line 8 the horizon, circle 11 indicating whether the aircraft is on a radio beam, while the deviation of line 9 indicates that the aircraft is turning. Alternating current from a transformer 26, Fig. 2, is supplied to the energizing coils 28, 29, 30 of the directional gyro, the gyro horizon and the turn indicator. The energizing coil 28 and the pick-up coils 32, 321, 34, 341 are mounted in an iron core having five limbs, a plate 36 of magnetizable material being eccentrically mounted in the direction gyro so that the flux through the coils is varied as the gyro rotates relative to the aircraft. Opposite pick-up coils are connected in series to transformers 33, 35 feeding double triode valves 40, 41 fed through resistances 46, 46<1> from secondaries on the transformer 26. With no input on the grids, the anode potentials are the same, but upon the application of an A.C. voltage, the D.C. potential of the anodes changes, smoothing condensers 57 being provided. The anodes 48<1>, 62 are connected together and to the deflecting plates 441, 45<1> of a cathode-ray tube 3 while the anodes 48, 62<1> are connected through plates A and commutators 50, 55 to the remaining plates 44, 45 of the tube. Owing to the eccentric mount- .ing of the plate 36 the spot on the screen will describe a circle around the periphery of the tube as the direction gyro moves relative to the aircraft. The pick-up coils 63, 63<1>, 78, 78<1> on the horizon gyro are similarly mounted but the limbs are shaped at their ends to allow the spherical segment 67 to move about a central point. Pick-up coils 63, 63<1> feed a transformer 70 and thus valve 71, producing a D.C. voltage across points 72, 72<1> when the flux through these coils is unequal due to a tilt in the craft. This voltage is applied, through the secondaries of transformers 76, 73, and segments D of commutator 50 to the vertical plates 44, 44<1> of the C.R. tube. A sweep voltage applied to the horizontal plates is derived from transformer 26 through segment D on commutator 55, the commutators 50, 55, 125 being driven on one shaft by the synchronous motor 60. In order to incline the line to show the sideways tilt of the craft, coils 78, 78<1> feed the valve 80 acting as an amplifier, A.C. potentials appearing across the secondary of the transformer 76 and being added to the D.C. voltage giving the vertical shift. Since they are in phase with the horizontal sweep voltage the line will become inclined when segment 67 covers more of one of the coils 78, 78<1> than the other. The turn indicator is provided with coils 95, 95<1> giving a variable D.C. voltage across points 102, 1021 fed through segment B to the plates 45, 451. The vertical sweep voltage is supplied through segment B from the transformer 26. Should the air speed fall below a certain value contact 104 closes and an extra A.C. voltage is introduced into the voltage on the plates 44, 441 when segment D is connected, the voltage being shifted in phase by network 107 so that the line becomes an ellipse. When the segments C are connected, a circle appears on the screen due to the use of A.C. voltages, shifted in phase by 90‹ applied to the plates. The outputs from receivers of the radio course and landing beams are fed to valves 115, 118 which add D.C. components to the A.C. voltages forming the circle so that it is displaced horizontally and vertically when off course. A paralyzing bias is given to the control grid of the C.R. tube by means of commutator 125 while the commutator arms 50, 55 are changing from one segment to the next in order to remove the back-trace of the beam. In a modification, Fig. 9, an H.F. oscillator 157 fed from transformer 26<1> is coupled to tuned circuits associated with the indicators. Trimmers 151 tune coils 148, 148<1> half-way up the resonance curves so that as the earthed plate on the direction gyro rotates, the A.C. voltage fed to the grids of the valve 159 varies and the anode potentials change, giving a variable D.C. voltage which is fed to the C.R. tube as before, the turn indicator acting in a similar manner. The horizon gyro is provided with an earthed plate 67<1>, the longitudinal axis of the aircraft being along 1631, 163, the associated circuits and valve 165 provide the D.C. shift while the plates 164, 164<1> alter the input to the valve 172 acting as a demodulator and providing a varying low-frequency A.C. to the transformer secondary 167 which is fed to the C.R. tube in series with the D.C. voltage to incline the line to show tilt of the craft. Bellows 180 connected to a pilot tube close the contact 181 if the air speed falls below a safe minimum. Upon switch 15 being rotated, Fig. 1, solenoid 131, Fig. 3, is energized, moving the core 132 to the right, and the core moving gear 135 into mesh with gear 136. A conical recess 137 centralizes pin 138, raising collar 139, pin 140 and locking arm 141. Upon further rotation of switch 15, motor 143 is started which rotates the ring 136 through the gearing. When the position of the spot 7 corresponds to the magnetic compass, 15 is switched off.