Patent GB-440847-A (GB)
Title: Electrical safety system for railway crossings
IPC: B61L29/28
Filed: 1934-11-30
Abstract: 440,847. Level - crossing signals. LORENZ AKT.-GES., C., 1, Lorenzweg, Tempelhof, Berlin. Nov. 30, 1934, Nos. 34405 and 34406. Convention dates, Dec. 1, 1933 and Jan. 23, 1934. [Class 105] A level-crossing signal is controlled by short insulated rail lengths and a relay, at each end of the stretch of track, so arranged and connected that the relay is de-energized when a train enters and is re-energized if the train backs out. In the arrangement shown, the insulated lengths C, D and U, T in the two rails of each short end section are unequal so that a train entering the stretch will short-circuit a relay A by connecting the length D to the earthed rail E. This relay normally is energized by a stick circuit over its own front contact a<1> so that it now remains dropped until the train on reaching the insulated length R just beyond the crossing energizes a relay K over the back contact a<3>. The relay A is then picked up over a front contact k' and remains energized over its stick circuit. The warning signal L<r> is energized first over a back contact a<4> and later over a front k<6> so that this signal continues until the last vehicle has left the crossing. When the train leaves the stretch a relay B is at first dropped during the time the train joins the insulated length T to the earthed rail E, but is picked up over its back contact b<1> when later the length T is joined only to length U and thereafter remains energized by its stick circuit. To prevent the warning signal coming into action during the time the relay B is dropped by a leaving train there are provided relays X, Y. Relay Y is picked up when the train at the crossing has energized the relays A, K and closed front contacts a<5>, k<7> and the relay Y then remains energized by a stick circuit over front contact g<2> and a back contact x<3>. As the train leaves the stretch the relay B, at first, closes its back contact b<2> whereby the relay X is picked over front contact y<1> and sticks over its own contact x<1> and back contact b<2>. The relay X breaks the stick circuit of the relay Y at x<3> while at its front contact x<2> it maintains the clear signal L<w> lit notwithstanding that the back contact b<4> is making. When the leaving train joins the length T to the length U only, the relay B picks up and the apparatus returns to the normal state. If a train should enter and back out before reaching the crossing the warning signal would be cancelled by the relay A being re-energized in the manner described for the relay B. If the train backs out after reaching the insulated length R at the crossing then the warning signal is cancelled as soon as the insulated length G is vacated, the relays X, Y acting in the manner already described to prevent the warning signal coming into operation during the backward passage of the train over the insulated length D. A recording-apparatus, Fig. 2, has its stylus S actuated only during the actual lighting periods of a flashing signal; all the lamps L<r> must be alight as otherwise the voltage tapped off the resistance W is insufficient to actuate the armature r<1>. The flashing magnet M and control contact B are set into operation by a relay K<1> which takes the place of the warning lamp L<r> of Fig. 1.