Patent GB-404653-A (GB)
Title: Improvements in or relating to light projector signals
IPC: B61L5/18
Filed: 1932-07-14
Abstract: 404,653. Railway &c. signal lamps. BRITISH POWER RAILWAY SIGNAL CO., Ltd., GLENN, S. L., and PIERCE, E. E., Windsor Works, Slough. July 14, 1932, No. 19981. [Classes 75 (ii) and 75 (iv).] Lantern shutters ; mounting reflectors on lamp casings :-In a railway or other signal lamp comprising an outer housing and a readily removable inner unit which includes a light projector system and a control mechanism therefor and which is normally locked in correct location within the housing, parts of the unit engage with parts on the inside of the housing when the unit is first introduced into the housing, and upon forward movement of the unit co-operating means on the unit and on the housing guide it into its correct location, other means being provided to assist said co-operating means in maintaining the unit in position. The lenses of the projector system may be carried partly by the housing and partly by the unit, or they may all be carried by one of these members and the other member closed by a cover glass. In the form shown, the inner unit 37 comprises an upper light projector portion 47 and a lower mechanism portion 48 which are dowelled and bolted together, the portion 47 being fitted with conical dowels 146 adapted to engage in corresponding recessed lugs on the inside of the outer housing 20, whilst a machined boss 148 on the portion 48 engages against a corresponding machined boss 149 on the housing. When being placed in position the unit 37 first rests upon its feet 150, and then short arms 160 on a pivoted handle 151 engage behind pins on the inside of the housing and lift the unit into position. Lugs 201 prevent the handle from fouling the terminal board 129 of the portion 48, and the handle may be retained in position by means of a head 158 on a rod 156 which is threaded through a transverse beam 154 on the housing. The latter is closed by a hinged door 200 through which freely passes a bar 164 having a bent-over portion 165 adapted to engage behind the beam 154 to prevent opening of the door, the bar being tightened against the beam by means of a nut 166 carrying a pivoted arm 167 which passes over a hasp 168 and is secured by means of a padlock. The portion 48 is provided with an inspection window 135 and a movable vane 50 carries colour filters 51 each of which is preferably of spherical form with its centre of curvature coincident with the focus of the lens system when in the operative position. A spring 70 presses an ellipsoidal reflector 57 against a thrust plate 69 which is removably secured to the front of a unit 56, the reflector being located axially by means of a flexible ring 72 in a groove near the mouth of the reflector. The unit 56 also carries an adjustable electric lamp bulb 58 and is removably mounted on an adaptor 61 by means of spring-pressed cone-faced locking members 62 on the adaptor engaging with bayonet slots in the unit 56, a lug on one part co-operating with a recess on the other part to ensure non-interchangeability of the position of the reflector. The adaptor 61 is formed integrally with a partition 75 having an aperture 83 and, in order to protect the relay mechanism in portion 47 from the atmosphere when the reflector unit is removed, this aperture is automatically closed by a shutter 76 mounted on a revolvable spindle 77 and operated by a spring 81. When the reflector unit is placed in position it engages one end 80 of a rack 79 which meshes with a pinion 78 on the spindle 77 and removes the shutter from the aperture. Forwardly directed light from the bulb 58 which does not fall on the reflector 57 may be intercepted by a concentrating lens or by a spherical recuperating reflector separate from the bulb or formed by silvering the front of the bulb. A part of the reflecting surface of the reflector 57 may be removed to form a backlight, or other means may be provided to form a backlight which may be controlled by duplicate colour filters operated by the relay mechanism. The front of the projector casing 47 is closed by an inner lens 52 provided with a truncated conical mask 53 whose apex approximates to the focus of the lens system. The retaining ring of the lens 52 is provided with a forwardly projecting flange 170 adapted to engage the mouth of a mask 171 so that, when the reflector unit is in position the inner and outer lenses 52, 40 are enclosed and protected from the atmosphere when the door of the lamp in opened for inspection purposes. The outer lens 40 is separately bolted to the outer housing 20 and preferably incorporates a sidelight sector as described in Specification 276,040, [Class 75 (ii), Lamp Chimneys &c.]. The unit 37 is fitted at its top and bottom with louvre or other ventilation apertures 145 fitted with air filters, each housing 20 is provided with upper and lower apertures 31, the uppermost and lowermost being closed by cover plates, and the doors 200 are fitted with screened ventilation apertures 245.