Patent GB-759893-A (GB)
Title: Drum indicator system
IPC: G01S1/02
Filed: 1954-10-21
Abstract: 759,893. Electric selective signalling systems. BENDIX AVIATION CORPORATION. Oct. 21, 1954 [Oct. 30, 1953], No. 30354/54. Class 40(1) [Also in Group XIX] The inventon relates to indicating systems of the type comprising a counter which is actuated at a distance from a main indicator, and consisting of a set of drums corresponding to digits of successive numerical order, each drum being independently driven by its own electrically operated direct drive. As applied to a known system of automatic distance indication for aircraft a receiver and distance computer 10, Fig. 1, operate through a shaft 11 a standard type of counter 12. In the event of a power failure, or weakness or lack of signals, a strip 20 pivoted on the shaft 22 of the indicator 12, is swung into position in line with the visible numerals as a warning signal, the strip being normally held out of view by a solenoid 30 energized from the receiver 10. A remote indicator 37 comprising a units drum 38, a tens drum 39 and a hundreds drum 40, corresponding to, the drums of the main indicator 12, is provided with a drive at the main indicator consisting of syncros 41, 42, 43, driven from the shaft 11 through gearing 44, 46. The drive for the units drum 38 is a synchro 4m7, Fig. 6, coaxial with and extending into the drum 38, the transverse flange 49 of the drum 38 being attached to the shaft 50 of the synchro. The tens drive synchro 51 is similarly mounted, the central flange 52 of the tens drum 39 being attached to the shaft 53 of the synchro 51. The hundreds drum 40 has an apertured end flange 54, rotates around a cylindrical bearing 57, and is driven by synchro 58 through gearing 55, 59. A warning signal comprising a pivoted strip 62 is operated by a solenoid 73 connected in parallel with the solenoid 30 at the main indicator. Where only a limited number of digits, e.g. one, will ever be used on the hundreds drum the synchro 43 may be replaced by a rotary switch 87 and the synchro 58 by solenoid actuated gearing, Figs. 7 and 8. The ring gear 55 on the drum 40 co-operates with a spring-loaded gear sector 78 on an arm 79 pivoted at 81, and when the solenoid 84 is energized, the gear sector 78 is rocked to bring the digit 1 on the drum 40 into view. The switch 87 for energizing the solenoid 84 is driven through gearing 46<SP>1</SP> and comprises metal conducting strips 89, 90 co-operating with brushes 93, 94, 95, brushes 93 and 94 being attached to the shaft 53 of the synchro 51. The hundreds drum 40 has an apertured end flange 54, rotates around a cylindrical bearing 57, and is driven by synchro 58 through gearing 55, 59. A warning signal comprising a pivoted strip 62 is operated by a solenoid 73 connected in parallel with the solenoid 30 at the main indicator. Where only a limited number of digits, e.g., one, will ever be used on the hundreds drum the synchro 43 may be replaced by a rotary switch 87 and the synchro 58 by solenoid actuated gearing, Figs. 7 and 8. The ring gear 55 on the drum 40 co-operates with a spring-loaded gear sector 78 on an arm 79 pivoted at 81, and when the solenoid 84 is energized, the gear sector 78 is rocked to bring the digit 1 on the drum 40 into view. The switch 87 for energizing the solenoid 84 is driven through gearing 46<SP>1</SP> and comprises metal conducting strips 89, 90 co-operating with brushes 93, 94, 95, brushes 93 and 94 being connected to a D.C. source 96 as shown in dotted lines. In an alternative arrangement, Fig. 8, the drum 40 is rotated by a synchro 58 controlled by the switch 87. The ends of the secondary winding of a transformer 98, energized from A.C. source 99, are connected to brushes 93 and 94. The winding 101 of the synchro 58 is grounded, the winding 102 is connected to a tapping 103 on the transformer secondary, and the winding 104 is connected to the brush 95, and under these conditions the rotor 105 and drum 40 will alternate between two positions, the tap 103 being so selected that the positions are 90 degrees apart. If four positions are required a cam 108 is provided on the switch 87 which engages a plunger-actuated switch 110 to reverse the phase of the voltage applied to the rotor 105 after the first step, the switch 87 having four equal contact-teeth 91 and rotating through 90 degrees for each revolution of the tens drum 39. In a further arrangement, Fig. 11, for locating drum 40 in ten successive equally spaced positions, a stationary switch disc 115 is provided with contact arms 133, 136, attached to a shaft 116 and driven by standard ten step gearing. The arm 133 carries a brush 134 engaging sectors 119, and a brush 135 engaging contact ring 117 and connected to brush 134, and the arm 136 through a brush 137 engages sectors 119 and through bush 138 engages contact ring 118, the brushes 137 and 138 being electrically connected. Sectors 120, 122, 123, 124 and 128 are connected to appropriate points on the secondary of a transformer 98 connected to an A.C. supply, and sectors 132, 131 and 130 are cross-connected to sectors 122, 123, and 124 respectively, the ring 117 being connected to stator winding 102 and the ring 118 to stator winding 104. Curves showing the voltage relationship in the stator coils for the ten positions are given in Fig. 10 (not shown).