Patent GB-497930-A (GB)
Title: Improved indicating instrument more especially for aircraft
IPC: G01P3/62
Filed: 1937-05-25
Abstract: 497,930. Indicating-instruments. CRANE, C. J., and NESBITT, F. G. May 25, 1937, No. 14514. Convention date, May 26, 1936. [Classes 106 (ii) and 106 (iv)] A plurality of sensitive elements responsive to factors contributing to maintenance of a desired condition actuate a plurality of pointers moving over a single dial, means being provided for setting the pointers so that they occupy a predetermined relative position on the dial whilst the condition is maintained so that departure therefrom is easily recognized. The mechanism is formed as a unit that can be inserted in a casing and is carried by a framework comprising three plates 11, 12, 13 distanced apart by studs 14, 15, 16. The speedometer comprises a diaphragm 21 exposed to the differential pressures of a Pitot tube device and is carried by the stud 14. A central stirrup 29 on the diaphragm conveys its movement to a crank 30 which turns a spindle 27 on which is an arm 31 engaging a pin 32 on a sector 33 pivoted at 35, the pin extending through a slot in the plate 12. The rack 33 engages a pinion 36 on a hollow shaft 37 which through gears 39, 40 and 47, 48 transfers the movement to a second hollow shaft 49 carrying a pointer 50. The planet wheels 40, 47 are carried on a spindle journalled in a bracket 42 secured to the plate 43. The rate of climb device comprises a diaphragm 60 mounted on a bracket 63 supported by studs 15, 16. It is carried by a post 61 extending through the bracket, and its inside is connected to a heat-insulated tank (not shown) by means of a conduit 64. A capillary tube 68 leads from the coupling 66, 67, the free end of the tube ending inside the casing 9, this casing being connected to the static pressure by means of a connection 70 to the static tube of the Pitot tube device. The movement of the diaphragm 60 is transmitted by crank 74 and link 75 to a sector 78 and wheel 81 which is on a shaft 82 passing through the shafts 37, 49 and carrying a pointer 83. The latter moves over a scale 84 on a fixed plate 45. Journalled on a shoulder on the plate 45 is a toothed plate 52 carrying the speed scale. The plate 52 may be turned and pointer 50 brought to a horizontal position pointing to the desired cruising speed. A wheel 91 on the shaft 88 meshes with a pinion on a parallel shaft, the pinion meshing with gear plate 43. When the button 87 is turned the plate 43 turns and the bracket 42 which it carries, the gear 40 rotating the pointer 50. On the parallel shaft is another pinion gearing with plate 52. The gears are such that pointer 50 and scale plate move in unison. If the shaft 88 is pushed in against the influence of spring 89, a gear 96 is brought to gear with a wheel 97 and the shaft 98 may be turned from button 87. A cam 100 on this shaft lifts the diaphragm 60 bodily and thus moves through the transmission gear the pointer 83. The pointers may thus be in line and any variation from the cruising speed or climb or fall indicated by the pointers taking an angular position. The parallel shaft referred to above may be turned by remote control, a flexible shaft moved from the navigator's or bomber's cockpit an indicator driven by worm gear from the flexible shaft being located in that pit.