Patent GB-776393-A (GB)
Title: Improvements in or relating to light signals of the searchlight type
IPC: G08G1/095
Filed: 1955-02-28
Abstract: 776,393. Railway light signals. GENERAL RAILWAY SIGNAL CO. Feb. 28, 1955 [March 2, 1954], No. 5861/55. Class 105. [Also in Group XXXVII] The spectacle arm of a search-light type railway signal is operatively connected to and pivotally supported jointly by the pivoted armatures of two independently operated polarized electromagnetic relays which by their selective operation as by signal control relays bring the spectacle arm to any one of three positions, i.e. by energizing one or the other or neither of the relays. As shown, a spectacle arm S carries three roundels, Y (yellow), R (red) and G (green) near the focal point F of the reflector 4 of a signal lantern with an electric bulb 3 to project light through an aperture 11 in a ribbed cone 12 carried by a mechanism case MC having at its bottom side a mechanism mounting plate,P supported from the casing MC on shock-absorbing structures each comprising a shouldered stud 68, Fig. 1, and a spring 70 between the head of the stud and the plate P supported thereby and a spring 69 between the plate P and the support on the case MC for the stud 68, the two springs having different natural frequencies. The spectacle arm S of channel L-shape, Fig. 5, is supported at one side by a straight pin 18 passing through a bore 21 in the armature A1 of one polarized electromagnetic relay and received by bearings 20 in the arm S and at the other side by an eccentric pin 19 received in a bearing 22 with a horizontally elongated opening and passing through a bore 23 in the armature A2 of the other polarized relay and retained by a nut 29 at its slotted end by which it can be rotated to adjust the position of the arm S about the pin 18 to align the arm with the opening 11. The pin 18 is held axially by clips 24 secured on the armature. Lifting movement of the armature A1 rotates the arm S about pin 19 anticlockwise to bring roundel G, Fig. 2, opposite opening 11 and lifting of armature A2 rotates the arm S clockwise about pin 18 to bring the roundel Y opposite the opening 11. Lifting of both armatures together due to electrical or mechanical failure would raise the arm without any rotation so that the red roundel would still show through the opening 11. A rigid movable weight W, Fig. 5, is retained in the arm S to damp the movement of the arm and has a bevelled and slotted base 31 seated on a bearing block 32, the two upper longitudinal edges of which act as knife edge bearings, one or other or both supporting the weight at all times according to the position of the arm. The two relays are similar. The steel armature A1 pivots at one end about the upper edge of an opening 34, Fig. 5, in a plate 33 engaging in a groove in the armature, being retained in position by two helical springs 36, 37. The plate 33 is adjustably attached to the base-plate 41 by screws 42 and elongated holes 44. The free end of the armature rests on the head 45, Fig. 2, of a screw in a threaded bore in the base 41 and locked by a nut 46. The screw 45 adjusts the air gap between the armature and the poleshoes 47. A spring 48, Figs. 2, 5, on the pivot end of the armature exerts a force on the armature which reduces the energizing current requirements of the relay structure. The relay is polarized by permanent magnets M1, M2 acting on two cores 50 passed up through holes 51, Fig. 1, in the base-plate 41, the pole shoes 47 of the cores (riveted to the base-plate), through a leakage strip K, spring washers 52 and axial openings in windings G1, G2 and are held against the plate P by threaded bolts 53 with lock washers 54. Windings G, G2 are connected in series with a half-wave rectifier therebetween. Each armature operates a plurality of contacts 60 by means of arms 56 extending from contact pushers 57 made of insulating material. Specifications 379,776, 553,372 and 632,271, [Group XXXVII], are referred to.