Patent GB-784788-A (GB)
Title: Improvements in or relating to lanterns for signalling
IPC: H04B10/50
Filed: 1954-09-06
Abstract: 784,788. Signal lamps. GENERAL ELECTRIC CO., Ltd., and ADAMS, J. C. Dec. 6, 1955 [Sept. 6, 1954], No. 25856/54. Class 75(4) In a lantern for signalling of the kind including an electric lamp 8 with its light source at the focus of a concave mirror 4 and a movable shutter operated by control means, the shutter consists of a pair of plane plates 17, 18 each mounted for rotation about an axis which is perpendicular to the mirror axis and lies between the mirror and its focus on or close to the mirror axis and the control means rotates the plates simultaneously in opposite directions between a position in which the plates lie in a common plane perpendicular to the mirror axis to prevent the light from the lamp reaching the mirror and a position in which the plates lie parallel to the mirror axis to allow light from the lamp to reach the mirror. The shutter plates 17, 18 are semi-circular and their straight edges are attached to strips 19, 20 which pivot about a shaft 21 extending through and perpendicular to the mirror axis at a point nearer the mirror focus than the mirror. The lower ends of the strips 19, 20 have forwardly directed lugs 22, 23 which are linked by stout resilient wires 24, 25 to the moving arm 26 of a snap action mechanism operated by a trigger 38 pivoted on a butt 3 secured to the shell 1 of the lantern. The stout wires 24, 25 are resilient against spreading away from each other and thus tend to hold the shutter plates in both open and closed positions. The moving arm 26 of the snap action mechanism is pivoted on a carriage 33 arranged to slide along a bar 34 and a compression spring 36 acts between the head of the arm 26 and the bar 34. The with a lever arm 37 pivoted to the butt 3 and pressed forwardly by a spring 40. The trigger 38 when pressed rotates the lever 37 to slide the carriage rearwardly and the arm 26 snaps over a dead centre position of the spring 36 to fold the shutters 17, 18 together in the open position. When the trigger is released the spring 40 returns the lever 37 and in consequence the shutters move to their initial closed position. The lamp holder 7 is slidably mounted on rods 9 fixed to a plug 10 detachably closing a hole in a shallow trough 2 attached to the shell 1. The plug has outwardly extending terminal pins 11 connected to the terminals of the holder, one of the connections including contacts 12 insulatingly mounted on the plug and arranged to be bridged by a movable contact 13 carried on a pivoted arm 44 connected by a stout wire 43 to the upper end of a spring urged lever 41 pivoted to the butt 3. A shield 15 fits closely around one side of the lamp to prevent direct emission of light. The concave mirror 4 is attached to a spider 5 mounted on the base of the shell 1 on three adjustable screws 6. A mechanism adapted to move one or other of two coloured transparent discs 48, 49 to a position between the lamp 8 and the shutters 17, 18 is mounted in the front of the lantern and comprises a pair of arms 50, 51 carrying the discs 48, 49 and having circular ends loosely fitted on a shaft 52 extending perpendicularly through the trough 2 and connected to a handle 45 on the outside of the casing. The arms 50, 51 are biased into line with one another by a wire spring 55 coiled round the shaft 52 and bearing at each end against the arms. The rotation of the shaft is transmitted to one or other of the arms by a pin 57 secured to the shaft and adapted to engage shoulders 53, 54 on the arms. The operative positions of the coloured discs are determined by pins 60, 61 on a plate 59 keyed to the shaft abutting a stop 62 on the trough 2. A click indication of the positions of the discs is given by the engagement of balls 63 in the trough with holes formed in the plate 59, The handle 45 has coloured panels 58 to indicate the setting of the coloured discs. The light emitting end of the casing is closed by a glass plate 16. The internal surface of the casing and the shutters 17, 18 are given a dull black finish. Sights 46, 47 are attached to the top of the lantern.