| 摘要 |
1,184,565. Rear illuminated signs. IMPERIAL CHEMICAL INDUSTRIES Ltd. 18 March, 1968 [30 March, 1967], No. 14594/67. Heading G5C. [Also in Division G2] A sign has a housing 51, a Fresnel lens 54 consisting of an inner circular prismatic lens and an outer annular prismatic lens, a tungsten filament lamp 52 located at the focal point of the inner lens and a toroidal shaped fluorescent lamp 53 located in the focal circle of the annular lens and a legend bearing sheet 56 located between the lenses and the lamps. The focal lengths of the lenses preferably lies between ¢ to ¥ of the diameter of the inner circular lens. The lenses are made of polymethyl methacrylate either by machining a flat sheet or by moulding using a flat sheet or moulding powder. The legend bearing sheet is made of a black material so that the legend is only visible when the lamps are lit. |
