GB902260A - Illuminated indicator means for instruments - Google Patents

Abstract

902,260. Indicating-apparatus. BLACKWELL, D. J., and ZAWACKI, E. F. Dec. 11, 1958, No. 39984/58. Class 106 (4). In indicating - apparatus having a source of light 27 behind a dial plate 20 directly illuminating indicia and graduation marks therein from the rear, a light-conducting member 56 passes through a central hole in the dial 20 with sufficient clearance for an arm 47 to turn in the annular gap and the member 56 directs light forward on to a surface 61 of a pointer 46 carried by the arm 47, the surface 61 being at an angle to both axis and radius so that light is reflected through the pointer 46 to illuminate its tip 62. In the sealed aircratf instrument shown, the plate 20 is made of a translucent plastic, the marks thereon are of a white translucent substance and the rest of the surface is by contrast made opaque or slightly translucent to provide background illumination. The lamps 27 or the plate 20 may be coloured, e.g. red, so that the marks appear red when lit from behind and white by daylight. Minute lamps of very small mass are used, supported by their terminal wires connected to bus-rings of highly reflecting material, e.g. chrome plated or silver. The pointer 46 and light-conducting member 56 are of clear plastic, the latter being formed as a lens 58 at the front to concentrate light from a lamp 50 on to the pointer, which is coated white on its front surface. The lamp 50 or the member 56 may be coloured or a colour filter 64 may colour the illumination. Light shields in the form of an opaque disc 66 and opaque cylinders 68, 70 are provided. The lamp 50 may be supplemented by a further lamp offset radially therefrom and provided with a radially disposed light-conducting cylinder to direct light on to a part of the rear surface of the member 56 which is angularly offset to reflect light forward, while the remaining part receives light direct from the lamp 50 and passes it forward. Alternatively, the lamp 50 may be eliminated by using a diametrically opposed pair of lamps 27 and making the rear part of the member 56 of square cross-section with two angularly offset rear parts to deflect both sets of radial rays axially. In forming the indicia, Fig. 7, the plate 20 may be coated with a nearly opaque substance over the area 25 leaving the shapes 90 defined thereby and these shapes may be covered with white translucent material overlapping the area 25 to the larger outline 92 so that the marks appear white and wide by daylight, red and fine-drawn by night.