Patent GB-814615-A (GB)
Title: Multiple indicators
Inventor: EBEL FRANCIS LEONARD
IPC: G08B5/30
Filed: 1956-01-09
Abstract: 814,615. Multiple indicators on aircraft. FAIREY AVIATION CO. Ltd. Jan. 8, 1957 [Jan. 9, 1956], No. 727/56. Class 4. A visual indicator on an aircraft includes at least two individual indicators each arranged to indicate a different occurrence, and a common indicator arranged to indicate any one of the occurrences. There may also be means operative only after one of the occurrences for rendering the common indicator incapable of further indicating that occurrence but capable of indicating any other of the occurrences. In Fig. 1, a plurality of fault relay switches 20A, 20B, ... 20F are connected to a positive line 19 and over lines 21A, 21B ... 21F to corresponding indicator lamps 23A, 23B ... 23F having a common earth lead 24. Each line 21A, 21B ... 21F is connected through a rectifier such as 39A and relay contacts such as 40A, 41A to a common line 42 connected to a flasher unit 44 comprising a bi-metallic contact 51 and heater element 52. The flasher unit controls the operation of an indicator lamp 55 and an acoustic horn 56. Each relay such as 45A is strong enough when energized to hold its armature 41A in a contact breaking position against a spring 46A, but is not strong enough to move the armature from the contact making to the contact breaking position. To render the lamps dim or bright for day or night operation, a resistor 26 may be inserted into or shorted out from the earth line 24 according as one or other coil 28 or 29 of an electromagnet is energized by an armature 34 making contact 33 or 32 respectively. The resistance of resistor 26 varies with the current so as to tend to keep the lamps at a given illumination irrespective of how many are energized. Fig. 2 shows the indicator face, the lamps such as 23A being mounted behind windows 14 marked with the corresponding fault and surrounding a knob 13 which is rotatable to rotate the switch armature 34, Fig. 1, and houses lamp 55. The knob is also linked to a ring contact 48, connected to the positive line 19, and the knob and ring can be pressed inwardly, the ring making contacts 22A, 22B ... 22F to light all the lamps 23A, 23B ... 23F, and also pushing all the relay armatures such as 41A to the contact breaking position. In operation, if a fault develops, the appropriate contact, say contact 20A, is closed, lighting the lamp 23A and energizing the relay 45A which however is not strong enough to break contacts 40A, 41A. The flasher unit 44 is energized through rectifier 39A, rectifiers 39B ... 39F preventing energization of the other indicator circuits. Flasher unit 44 energizes lamp 55 and horn 56, the intermittent operation of which attracts the pilots' attention. He then presses knob 13, and contact 48 makes contacts 22A ... 22F, lighting all the lamps, and pushes all the armatures 41A ... 41F to the contact breaking position. On releasing the knob, only armature 41A is retained in the contact breaking position and only lamp 23A remains lit, coil 45A being energized. The lamp 55 and horn 56 are cut off, and since contacts 40A, 41A are open, cannot be re-operated by the same fault until line 21A is cleared by rectification of the fault, but are available to be operated by any different fault. The lamps 23A ... 23F can be rested by pressing knob 13, when they are energized by contact 48.