GB829578A - Improvements in and relating to indicator instruments - Google Patents

Abstract

829,578. Indicating-apparatus. KELVIN & HUGHES Ltd. Nov. 12, 1957 [Nov. 16, 1956], No. 35159/56. Class 106 (4). Indicating-apparatus comprises a dial or indicator 20 behind a transparent or translucent cover 13 having a convex surface adjacent the dial or indicator 20 and, near the periphery of the cover 13, lamps 18 to illuminate the dial or indicator 20 both directly and by reflection from the convex surface of the cover 13. An aircraft attitude indicator comprises an artificial horizon 25 marked on a roller blind 20 as the line of demarcation between a lower black region and an upper white region. The blind is wound up and down in accordance with the pitch of the aircraft and is rotated as a whole in dependence upon the angle of bank. Angle of bank marks 23 and pitch circles 24 are carried by a circular glass cover-plate 13 of uniform thickness, curved convexly towards the blind 20. A square opaque backing-plate 16 carries four lamps 18 protected by covers 19 carried by a front plate 11 and the lamps 18 illuminate the blind 20 directly and by reflection from the convex surface of plate 13 and also the marks 23, 24 by multiple internal reflections. A further mark 26 on the blind 20 appears when the aircraft is climbing almost vertically. The pitch circles 24 are each formed as a white region between two black regions so as to show up against a black and a white background.