Patent GB-270917-A (GB)
Title: Improvements relating to railway signalling
IPC: B61L23/16
Filed: 1926-07-12
Abstract: 270,917. Larry, E. C. July 12, 1926. Electric systems, automatic; lamp signals.- In an electric lamp signalling system a relay is connected in the circuit of the lamp under danger conditions whereby, if the lamp fails at any time when it should be indicating danger, the signal of the section to the rear is automatically caused to indicate danger. The invention is described as applied to colour light signals, but is applicable also to position light signals. The track rails are divided into insulated sections H, I, J. Each section has a three-position track relay T, T' bridging the rails at the entrance end, slowacting relays SR, SR<1>, CR, CR<1> and signal S with danger, caution, and clear lamps R, Y, G. The local windings of the three relays T, SR, CR are energized in parallel from the secondary of a transformer 6, the primary of which is supplied from a transformer 4 connected to the supply mains 3. The other winding of transformer T is energized from the secondary of transformer 7' of the section J ahead over front contacts 10', 15<1> of the relay CR<1>. The primary of transformer 7<1> is supplied from the secondary of transformer 4<1> over pole-changing contacts (back or front) 20<1>, 24<1> of relay SR<1> so that the instantaneous polarity of current supplied to the winding of relay T depends upon whether relay SR<1> is energized or de-energized. Contacts 30, 51 of relay T occupy one or other of the extreme position indicated according to the polarity of the track current so that, when the relay T is energized either way a circuit is closed from the secondary of transformer 6 over contact 30, wire 32 and winding of relay SR, which is thus energized when relay T is energized. With the track clear, the conditions are as shown, a circuit being closed to light clear lamp G from transformer 6 over contact 53 of relay SR, contact 51 of relay T, lamp G and wires 48, 38. A pick-up circuit is also closed from transformer 6 over wires 38, 39, relay winding CR, resistance 42 and contact 44 of relay SR, so that current of normal polarity is supplied over contact 10, 15 to the track-section H owing to front contacts 20, 24 being closed. When section I becomes occupied, relay T is de-energized with consequent de-energization of relay SR. Lamp G is thus extinguished at contact 51, and a stick circuit is closed from transformer 6 over back contact 53, contact 59 of relay CR, danger lamp R, winding of relay CR and wires 39, 38. Lamp R and relay CR being thus in series, failure of lamp R would de-energize relay CR, and owing to inclusion of the contact 59, a momentary failure would be sufficient to effect this. Contacts 10, 15 would thus be opened, cutting off current supply to the rails of section H, so that a danger signal would be given at the entrance to that section. With lamp R intact, contacts 10, 15 remain closed, and a current of reversed polarity is supplied to section H owing to back contacts 20, 24 of de-energized relay SR being closed. Relay CR is sluggish to ensure that its contacts 59 shall not open in the short period between breaking the pick-up circuit and closing the stick circuit at contacts 44, 53. Contacts 44, 53 may be adjusted so that one or other is always closed, in which case relay CR need not be sluggish. When the train passes on to section J, a similar operation to that described above occurs, a danger signal being given at that section, and current of reversed polarity supplied to the rails of section I. Relay T is thus re-energized with its contacts 30, 51 thrown to dotted-line position. Relay SR is thus re-energized, restoring the pick-up circuit of relay CR, and closing front contacts 20, 24 to supply normal current to section H. At the same time a circuit is closed from transformer 6 over front contact 53, contact 51, wire 61, caution lamp Y, and wires 48, 38. When the train leaves section J, a caution signal is given in that section and normal current is supplied to section I, so that the clear conditions shown are restored. Relay SR is made sluggish so that its contacts do not open when its circuit is momentarily broken as the contacts of relay T move from right to left in changing from caution to clear, so that no false indications are given. Specification 273,201 is referred to.