Patent GB-783575-A (GB)
Title: Railway points control system
IPC: B61L19/06
Filed: 1955-08-05
Abstract: 783,575. Railway points control. STANDARD TELEPHONES & CABLES, Ltd. Aug. 5, 1955 [Aug. 11, 1954], No. 22559/55. Class 104 (1). Points in a set-up railway route locked by respective points - lock relays are released sequentially each as soon as the releasing track section and the immediately preceding track section have been vacated by the train, by a first release relay operated by the releasing section track relay when the section is occupied and a second release relay operated when the track relay of the preceding track section is operated, the section being then vacated, and when the track relay of the succeeding section is dropped away, the section being then occupied, the points - lock relay of the releasing section being released when both release relays are operated and the track relay of the releasing section has re-operated, that section having been vacated. As shown, for releasing the section containing the points W2 in the set-up route A-B, Fig. 1, including sections with points W1, W2, W3a/W3b, W5, the section 4 not including points, the points locking latch relays V1, V2, &c., Fig. 3, are in their operated positions and as the train enters section W2, track relay G2 drops away closing contacts G21, Fig. 2, in the pick-up circuit of the second release relay H3 of section W3a/W3b and the lower winding of second release relay H1 of section Wl. The windings of the H relays oppose each other so that with one winding energized, the relay operates but with both windings energized the relay drops away. Relay G2 also closes contacts G22 in the energizing circuit of the first releasing relay P2, Fig. 3, of section W2 and opens contacts G23 in the energizing circuit of the points-locking relay V2 of points W2. Relay H2 has previously operated when the train entered section W1, when the track relay G1 was released and closed contacts G11 in the circuit of the upper winding of relay H2. Thus, relay P2 cannot pull up because contact H23 is open. As the first track section is vacated, track relay G1 re-operates and contacts G12, Fig. 3, open and slow-to-release relay P1 releases, and during the release period the release winding of points-lock relay VI is energized momentarily, the circuit being opened eventually at contact P12. If the train is shorter than section W2, relay G1 will reoperate and at contacts G11 relay H2 is released. If the train is longer than section W2 then the section W3a/W3b is occupied while relay H2 is operated. Track relay G3 releases and at back contact G31 energizes the lower winding of relay H2 and so releases this relay. In either case when section W2 is occupied contact H23, Fig. 3, is closed and relay P2 pulls up and sticks over its front contact P21. Relay H2 is pulled up over its lower winding as soon as section Wl is vacated and section W3a/W3b is occupied and the circuit over the upper winding is interrupted at contact G11. When the second section W2 is vacated, points-lock relay V2 is released in the same manner as relay V1, contacts G22 opening to release relay P2 and latch relay V2 being momentarily energized over contacts G23, H24 and P22 for release. It will be observed that some of the second release relays H, e.g. H2 include contacts such as W21, the position of which depends upon the position of the associated points, viz. W2, the contacts W21 connecting the winding of the H relay to a contact of the track relay, e.g. contacts G61 of track relay G6, or contacts G11 of track relay G1 of an adjacent section. The H relays may have windings of different strengths, the relay being held operated by the difference between the strengths if the stronger winding is energized first, and for a penultimate track section W5 of a route the stronger winding of the relay H5 is controlled by a contact G71 of the track relay G7 of the last section of the route and section W5 being adjacent a non-track circuited section. The H5 relay has the lower winding energized by the occupation of its own track section, i.e. over contact P53.