GB853022A - Improvements in and relating to lamp signalling apparatus - Google Patents

Abstract

853,022. Visible signalling apparatus. ERICSSON TELEPHONES Ltd. July 16, 1957 [July 4, 1956], No. 20751/56. Class 118 (2). [Also in Groups XI, XX, XL (a)] Lamp signalling apparatus includes a housing 1 enclosing a filament lamp 7 and an element 23 of indium antimonide, an ellipsoidal reflector 31 for directing visible light from the lamp 7 on to the element 23 to cause the emission of a beam of infra-red light, and means for signalling by interrupting the generation of the beam. The latter means can comprise a pivoted spring- controlled trigger 15 on which the element 23 is mounted, or the element 23 can be held in a fixed position and a shutter can be provided for substantially preventing visible light from reaching the element 23 when the trigger is in the " off " position. Adjustable screws 25 and 26 are provided to form stops for the trigger 15. The element 23 can be in the form of a solid cylinder, the cylindrical surface 32 and one end face 28 of which are polished to promote internal reflection of the infra-red light generated, and the other end face of which has mounted on it an f-ratio cone channel converter, the surface 33 of which is polished to promote multiple reflection and the end of which is ground to form a lens 30. The diameter of the cylinder 23 can be of the order of 0.01 inches and the length of the order of 0.1 inches. The element 23 and converter 29 can be made in one unit from indium antimonide or the converter 29 can be formed from silicon or antimony trisulphide glass both of which are transparent to infra-red light. The surfaces 28 and 33 can be coated with aluminium. In a modification the element 23 can be in the form of a thin layer on a support transparent to infra-red radiation. The housing 1 comprises two members fastened together by threaded bolts and can be made of a metal casting or a moulding of thermo-setting plastic. Dry cells 3 for energizing the lamp 7 are provided. The infra-red light issues through a conical metal screen 9, lens 10 and a glass window 12, held together by a threaded metal ring 13 and a ring 11 of natural rubber. The beam of infra-red light can be given a characteristic cross-sectional shape by a mask superimposed on the glass window 12. The lamp may be provided with sights for directing the beam towards a receiving station. According to the Provisional Specification the lamp 7 is provided with an upper concave reflector directing light downwardly on to a pivotallymounted mirror under the control of a slidably mounted trigger, light from the mirror passing to a lens system directing the light on to an element of indium antimonide in the form of a thin layer on a sheet of glass within a shroud. Sights are provided for directing the infrared beam on to a receiver such as a fluorescent screen. The layer of indium antimonide can have a thickness of approximately 0.005 inches and a mask can be superimposed on the supporting glass plate. A shutter can replace the mirror.