GB1241427A - Control panel overlay - Google Patents

Abstract

1,241,427. Etching. GENERAL ELECTRIC CO. 15 Nov., 1968 [16 Feb., 1968], No. 54448/68. Heading B6J. [Also in Divisions C4 and G5] A control panel overlay comprises a thin, sheet-like metallic member 1 (e.g. Al which may be anodized) with first recessed area 8, second recessed area 7, within said first recessed area, indicia openings 2, flat transparent support member 6 seated in area 7 and electrolaminescent lamp 5 conforming to the shape of and seated in area 8. Additional recesses provide supporting recesses 4. Overlay 1 is metallic for non-flammability purposes such as required in air- and spacecraft vehicle cockpit applications and member 6, preferably zinc borosilicate glass due to its flexibility and high temperature resistance, may be tinted to control colour or brightness. In fabrication, the indicia may be mechanically engraved on one face of a metal blank to a depth less than the blank thickness and the Al may be then anodized to reduce glare and improve appearance. A chemical etch maskant is applied either to the whole blank, the areas to be etched being removed, or just to the blank except those areas to be etched, the maskant serving also to subsequently support the free or island indicia portions. Chemical etching with a sodium hydroxide etchant for example in one or more stages, exposes the indicia on the reverse side, forms recesses and possibly ribs. Maskant removal from the overlay front is hampered by epoxy cement bonding layer 6, so preferably a PVA parting layer and silicone rubber overcoat are applied to the reverse side of the etched indicia, maskant removed from the front, PVA and silicone rubber applied to same, first PVA- silicone rubber removed, and member 6 then bonded, the second PVA-silicone rubber coating being easily removed.