Patent GB-737558-A (GB)
Title: Improvements in or relating to railway signalling systems
Inventor: BROWN ANDREW
IPC: B61L19/06
Filed: 1951-02-20
Abstract: 737,558. Railway route setting apparatus. STANDARD TELEPHONES & CABLES, Ltd. Feb. 15, 1952 [Feb. 20, 1951], No. 4142/51. Class 105. In a route setting apparatus, the signal governing the entrance to the route is only cleared when proof is had of the release of the approach locking relay and also when proof is had of all equipment having assumed the correct condition for the selected route, on the signal returning to danger due to any cause other than the passage of a train as when a signalman breaks down a previously set-up route, a predetermined time delay occurs before the operation of movable track equipment can take place. Release of the approach locking relay is proved by a back contact of that relay included in the operating circuit of the signal control relay in which circuit is also a front contact of an equipment check relay whose operating circuit includes contacts associated with the equipment appertaining to the selected route so as to be closed only when the equipment has assumed the correct condition for that route. The approach locking relay is released by the opening of a back contact of the equipment check relay which contact is included in two operating circuits of the approach locking relay, one of which operates the relay immediately the signal returns to danger on the passage of a train and the other operates the relay after a predetermined time delay when the signal returns to danger due to some other cause. The approach locking relay controls means for preventing the equipment from being operated unless this relay has operated so that a train approaching the signal can stop before the track points are moved. " Cross protection " of the signal relay is obtained by a change-over contact of the equipment check relay. The Figs. 1 and 3 (Comp.) show the circuiting for setting up a secondary running through route 4B3 comprising three partial routes, viz. (1) 4B3 from a signal 4, Fig. 1 (Prov.), ontrack 13T cross-over points 6 to track sections 6BT, 12T; (2) 4W1 comprising a track section 12T and (3) 4W2 comprising track sections 25T and 5T to a signal 35. Each partial route appears on a different sequence switch as described in Specification 719,133. The operating circuit, Fig. 1 (Comp.), of the equipment check relay 4BRC, which applies to route 4B3, includes camoperated contacts of sequence switches 4, 5 closed in positions for partial routes 4W1, 4W2 respectively and a cam-operated contact of sequence switch 11 closed in the position allotted to partial route 4B3, front contacts 11ZCP, 4ZCP and 5ZCP which are operated when sequence switches 11, 4, 5 respectively are properly positioned and other contacts appertaining to the partial routes and associated equipments. If all these contacts are closed there is no conflicting route or partial route in use and no conflicting track occupancy and it is thus safe to clear the signal 4 governing entrance to the route. Relay 4BRC thus operates to energize over a back contact of the approach locking relay 4/15NPS (Fig. 2 (Comp), not shown) the control relay of signal 4 by a changeover contact to remove negative battery from the supply side of the relay winding and apply positive battery to that side, thereby providing " cross protection " of the relay. If it is safe to clear the signal or reset the signal after use, this NPS relay is released and its back contact is closed. On operation the signal 4 control relay interrupts the operating circuit of a danger signal relay and completes the operating circuit of either the caution signal relay or the clear signal relay, depending upon the operation of the equipment check relay 4BRC. The circuitry of the approach locking relay 4/15NPS for signal 4 is shown in Fig. 3 (Comp.). On passage of a train past the signal, the operating circuit for the relay is from positive battery, front contacts 4NP, 15NP of signal repeat relays energized when the respective signals 4, 15 are at danger; back contacts of equipment check relays 4ARC, 4BRC and 4CRC and 15CRC appertaining to equipment associated with partial routes (not shown) 4A, 4B, 4C and 15C; back contact of track relay 13T, released when the track 13T is occupied as when a train passes signal 4; back contacts of time delay relay elements 4A/BFE and 4/15CTE, winding of relay 4/15NPS to negative battery. On operation of the relay NPS, back contact 13T is bridged by front contact 4/15NPS to provide a stick circuit for this relay.. The operating circuit of the time delay elements 4/15CTE and 4A/BTE is opened at back contact 4/15NPS and the circuit of signal 4 control relay is opened at a back contact of the NPS relay so that this signal 4 control relay releases and puts the signal at danger, immediately on a train passing the signal. Under normal circumstances the time element relays are released, thus indicating that a safe period has elapsed since the signal was last restored to danger. If the signal is restored to danger due to some cause other than the passage of a train, with the signal at danger and contact 4NP closed and the equipment check relay for that route released, so that contact of 4BRC is closed, relay 4/15NPS being released, a circuit is completed at front contact 13T assuming the track is clear, and back contact 4/15NPS for the time delay relay element 4/15CTE from positive battery over contacts including 15CRC, sequence switch 11 cam contact closed in position 8 allotted to route 4C4, winding of time delay relay 4/15CTE, back contact 4/15TES to negative battery. After the allotted time delay the relay 4/15CTE closes a contact to complete the operating circuit of time element stick relay 4/15TES and at back contact 4/15CTE opens the operating circuit of the approach locking relay 4/15NPS. On operation of relay 4/15TES at its back contact it opens the circuit of relay 4/15CTE and at front contacts it bridges out the relays 4/15CTE and 4A/BTE and bridges back contact 13T so that when relay 4/15CTE releases, at its back contact it completes the operating circuit for relay 4/15NPS which operates and at its front contact bridges the front contact 4/15TES and back contact 13T. Time delay relay 4A/BTE operates similarly. No equipment can be released until the approach locking relay has operated because, as described in Specification 719,133, until this relay operates the sequence switches controlling the route set cannot return to the rest position to effect the release. Specification 496,495 also is referred to.