Patent GB-371315-A (GB)
Title: Improvements in and relating to railway signalling
IPC: B61L23/16
Filed: 1930-10-13
Abstract: 371,315. Automatic railway signalling systems. VEREINIGTE EISENBAHNSIGNALWERKE GES., Siemensstadt, Berlin. Oct. 13, 1930, No. 30603. Convention date, Oct. 19, 1929. Void [Published under Sect. 91 of the Acts]. [Class 105.] In an automatic railway signalling system using track relays and in which the track current is reversed to give the different signal indications, the clear signal can only be given if the polarity of the track currents is in the proper sequence. This prevents a clear signal being given in a rear section if the track relay in the occupied section fails to drop its armature. In the alternating current system shown in Fig. 1, a track relay R30 when de-energized closes a contact 30c to supply reverse current to the rear section through a transformer winding b3 and also closes a contact 30 to light a red signal lamp R0 ; when energized reversely it closes a contact 30i to pick up a sequence - controlled relay K3 and also closes contacts 30l, 30b to light a yellow signal lamp Ge and to supply normal current to the rear section through a transformer winding a3 ; when energized normally it closes a contact 30k in the stick circuit of the relay K3 and also closes contacts 30l, 30a to light a green lamp Gr (the relay K3 being energized and so closing a contact K33) and to supply normal current to the rear section. The green lamp Gr can therefore only be lit if the track relay R30 is first reversely energized so as to close the pick up circuit of relay K3 and is then energized normally ; also the red lamp continues to be lit over back contact K34 until the relay K3 is energized. Should the red lamp R0 burn out a relay F3 in series therewith drops its contact F31 and thereby cuts off current from the transformer b3 supplying the rear section so that the signal of the latter section gives a danger indication corresponding to that when a train occupies such section. In the system shown in Fig. 2 the relay K1 is used both as the lamp-failure relay and as the sequencecontrolled relay. When the track relay R10 is de-energized the relay K1 and red lamp R are energized since short circuits over the normal or reverse contacts 30k, 30i are broken. Should the relay R10 pass directly to the line clear position and therefore close the contact 30k the lamp and relay K1 would not be short-circuited, due to the armature K12 being in its attracted position; relay K1 and the lamp R therefore continue to be energized. With the correct sequence of track current the track relay first closes contact 30i and so short-circuits the red lamp R and relay K1 and thereafter when normal current is supplied to close the contact 30k the red lamp R and relay K1 are now short-circuited since the armature K12 has closed its back contact. The reverse current to the rear section is supplied by front contact K16 of relay K which closes a circuit to the transformer winding b<1>. Fig. 4 shows a mechanical device for preventing the clear signal being given unless the sequence is correct. The armature 26 of a three-position relay can move in the direction P to depress a lever 33 which withdraws a rack 28 by means of a toothed sector 29. The armature 26 can now move in the direction O since the sector 29, moving in the field of a magnet 30, only returns slowly and so the rack 28 cannot block the pin 31. If the armature were first stressed in the direction O the rack 28 would block the pin 31. In the system shown in Fig. 6 the track relay has a second winding 3 the supply of current to which takes place through reversing contacts L47 actuated by a step relay L48 which at each energization reverses its contacts, the contacts L46 reversing the supply of track current. A train in a section causes track relay contact R49 to drop and energize the step relay which reverses the current supply to the auxiliary winding 3 of its own track relay and to the rear track section. When the train leaves the section the track relay will only lift if the track current is reversed so that the currents in windings 3, 5 are similar, that is, only if the section ahead has acted properly to drop its track relay and actuate its step relay.