Patent GB-258010-A (GB)
Title: Improvements relating to route indicators for railways and the like
IPC: B61L17/02
Filed: 1925-06-12
Abstract: 258,010. Challans, E. W., Peter, L. H., and Westing-house Brake & Saxby Signal Co., Ltd. June 12, 1925. Selective signalling apparatus.-Railway route indications are given by optical projection devices 2, 3, 4 selectively operated in conjunction with the points and usual signal, and throwing the indication on a to a screen 9 common to a number of units, three being shown and corresponding with a straight track and two side tracks. The indicator is described in conjunction with a light signal the arrangement being such that a " clear signal cannot be given unless a route indication is also being given. The projection units comprise lamps 5, 28, 29 each with condenser 6, stencil &c. 8 and projecting lens 7, arranged in a casing 1 which may be mounted on the same support as the usual signal. The screen 9 may be protected from direct sunlight by a hood, not shown. The points leading to one side track are controlled by a lever 19 which also operates contacts 22, 23, the points to the other side track being controlled by lever 20 with contacts 24, 25. The light signal 10 comprises a "danger" lamp 11 and " clear " lamp 12 respectively connected in the secondaries of transformers 39, 40 the primary circuits of which are controlled by a signal lever 21 operating contacts 26, 27. As shown, the circuits are closed for a " clear " signal for the straight road, numbered 2, but in normal or danger conditions contact 23, 24 are closed, contacts 22, 25 open, contact 26 open and contact 27 closed. The indicator circuits from supply terminal 41 through contact 26, conductors 30, 31 or 32 and lamps 5, 28, 29, common return 33, relay 34 to supply terminal 42 are broken at contact 26 and no route indication is given. At the same time the circuit from supply terminal 41 over contact 26 and contact of relay 34 to relay 36 and terminal 47 is broken, so that contacts 37, 38 are dropped. A circuit is thus completed from terminal 45 over contact 38 and primary of transformer 39 to terminal 43 so that the danger lamp 11 is lit. With the points set for the straight track contacts 23, 24 are closed, preparing the circuit through lamp 28, but no route indication is given until lever 21 is operated to give a " clear " signal, closing contact 26. Lamp 28 is thus lit, showing route 2 on screen 9 and relay 34 is energized, its contact closing the circuit of relay 36. Contact 38 then breaks the circuit of transformer primary 39 and contact 40 closes the circuit of transformer primary 40, whereby the " clear " signal lamp 12 is lit. When lever 19 is operated to set the points for one side track contact 23 is opened and contact 22 closed to prepare a circuit through lamp 5. When lever 20 is operated to set the points for the other side track, contact 24 is opened and contact 25 closed to prepare a circuit through lamp 29. In each case the route indication lamp is lit only when contact 26 is closed by the signal lever when operated to give a " clear" signal, and the clear signal is only given if relay 34 is effectively energized. The route and signal indications may be repeated in the signal cabin by a miniature indicator 48 the lamps of which are bridged across resistances in tha corresponding main circuits as shown. A modified indicator is described for a larger number of routes in which each projection unit comprises a lamp, and a projecting lens and stencil mounted independently of the lampholder. Distortion of the indication on the screen from some of the units due to oblique projection is corrected by using a suitably distorted stencil. A further modification for giving a longer projection path in compact form with correspondingly larger screen image uses reflecting mirrors angularly disposed in the paths of projection.