Patent GB-457562-A (GB)
Title: Improved warning and indicating device particularly for use in aircraft
IPC: B64C25/28
Filed: 1935-09-13
Abstract: 457,562. Safety devices for aircraft; retractive switches. FAIREY AVIATION CO., Ltd., Cranford Lane, Hayes, Middlesex, LOBELLE, M. J. O., 298, Langley Road, Langley, Buckinghamshire, and VOSS, E., Bourne House, Dawley Road, Hayes, Middlesex. Sept. 13, 1935, No. 25456. [Class 4] [See also Group XXXVII] An aircraft having a retractable undercarriage is provided with an electrical indicating device comprising for each retractable element a pair of coloured lights or like visual indicating means, controlled by an " up " switch in series with a two-way "down" switch which switches are operated by the locking of the retractable member in the retracted and extended positions respectively, an audible warning switch coupled mechanically with the "down" switch, a double switch, both circuits of which can be controlled simultaneously by the throttle lever of the aircraft, the double switch by one of the circuits being in series with a horn or the like and with the audible warning switch and by the other circuit with an illuminable indicator so that the horn and indicator may be operated simultaneously. Fig. 1 shows the circuit diagram in the case of a single retractable member in which 11 is an illuminable indicator, 12 is a red and 13 a green lamp, and 14 is a horn. These devices are connected with a source of current 15 through switch means comprising a master switch 11, an "up" switch 20, a two-way "down" switch 21, a horn switch 26 and a double switch 28 operated by the throttle lever. When the craft is in the air with undercarriage locked in the retracted position and the throttle open, the position of the switches is as shown in Fig. 2, i.e. horn switch 26 closed, switch 21 in position to illuminate the red lamp 12 and "up" switch 20 open. Since both ways of switch 28 are open and switch 21 is open, lamp 12 and indicator 11 are not illuminated and horn 14 is silent. When the pilot closes the throttle prior to landing switch 28 is closed, indicator 11 is illuminated and horn 14 sounded. If the undercarriage is now lowered, " up " switch 20 is closed and red lamp 12 illuminated. When the undercarriage locks in the fully extended position, "down" switch 21 and horn switch 26 which are mechanically interconnected are actuated as shown in Fig. 3 to illuminate green lamp 13 and to switch off horn 14. Master switch 17 may then be opened. On taking off, master switch 17 is closed causing illumination of green lamp 13. Initiation of retraction of the undercarriage operates ''down" switch 21 to extinguish green lamp 13 and light red lamp 12 ; horn switch 12 is simultaneously closed, but since the throttle and hence double switch 28 are open the horn is not sounded. Red lamp 13 is only extinguished when locking of the undercarriage in the fully retracted position opens the "up " switch 20 (position of Fig. 2). Circuit diagrams are described for a system in which the position of three retractable elements, viz. port and starboard wheel carrying members and a tail wheel, are indicated by red and green lamps. One form of double switch 28 permitting of interruption of the horn circuit without interrupting that of the indicator during extension of the undercarriage is shown in Fig. 7. Operating lever 47 is urged to the "off" position by a spring 48 and is secured by a pin-and-slot connection to an arm 49 fixed to a shaft 52 on which is rotatably mounted a contact-carrying lever 54. A shoulder 54a formed on lever 54 engages a laterally extending pin 53 on arm 49. Pin 53 forms an abutment for a coiled spring 58 bearing on to underside of lever 54. Also rotatably mounted on the shaft is a contactcarrying lever 62 located between a fixed friction disc 64 and an axially movable spring- pressed friction disc 60. When the throttle is moved back to the closed position, operating lever 47 is moved to rotate shaft 52 causing contacts 55 and 63 carried by levers 54 and 62 respectively to engage fixed contacts 56, 57 establishing the indicator and horn circuits respectively. Further movement of the throttle lever merely increases the'tension of spring 58, but causes slipping of clutch plates 60, 64 relative to lever 62, thus very slight reverse movement of the throttle lever will cause reverse movement of lever 62, thus opening the horn circuit without affecting the position of lever 54 and hence without opening the indicator circuit. Figs. 8 and 9 show the two-way "down" switch 21 coupled with the horn switch 26. The switch comprises a contact block 77 movable between fixed contact blocks 72, 73. Block 77 carries electrically interconnected contacts 78, 80 adapted to engage contacts 74, 76 establishing the circuits of the red or green lamp. Block 77 also carries a contact, 79 adapted to engage a contact 75 and to enable establishment of the horn circuit when in the position shown in Fig. 9 in which contacts 74, 78 are in engagement closing the circuit to the red lamp. Movement of contact block 77 away from the position shown is effected by a plunger 85 adapted to be engaged by a moving part of the undercarriage. Plunger 85 is housed within a sleeve 83 upon which block 77 is 'mounted for limited axial movement. Movement of plunger 85 is transmitted to the sleeve by a spring 86 and in turn to block 77 by an external shoulder 84 formed on the sleeve. On release of plunger 85, block 77 is returned to the position shown by a spring 89. Switch 20 is of similar construction but comprises only one fixed contact block and a single pair of contacts. According to the Provisional Specification, the invention may be employed in connection with retractable bomb or torpedo carrying apparatus or retractable doors therefor.