Patent GB-191409134-A (GB)
Title: Improvements in Electrically Controlled Block Systems for Railways.
Inventor: SAYERS JOSIAH
IPC: B61L23/12
Filed: 1914-04-11
Granted: 1915-04-01
Abstract: 9134. Sayers, J., Acfield, W. C., Salt, G., and Cooke, B. W. April 11. Combined electrical and mechanical systems, non-automatic; signalling-instruments; locking signals. A three-position instrument is lockedagainst backward movement, except that, when in ' line clear ' position, if the signal at the entrance to the block is at ' danger,' the operators at the two ends may remove the lock by pressing cancellation buttons simultaneously. The instrument is locked at ' train on line ' until the train passes over a releasing-treadle in going out of the section, and is locked at ' line blocked ' until the signal for entry into the next block has been returned to danger. The instrument at ' line blocked ' and at a position between line clear ' and ' train on line ' makes the tapper circuit through the single line-wire between the instruments. The starting signal-lever lock is such that the signal cannot be put to ' safety ' until the current that released it for the previous operation has ceased and a further releasing-current has been received. The three-position instrument B is used by the receiving-signalman in conjunction with a non-pegging instrument A used by the dispatching-signalman. In the Figure, portions of the main spindle 2 of the instrument are shown separated at I, J, K, L, M. With the instrument A in the ' line blocked position, as shown, the tappers 75, 93 are in circuit. Signalling- currents are received at B from the line-wire by way of spindle 2, arm 4, contact 6<a>, springs 95, 94, and bridging-piece 99, and signalling- currents are sent from B by means of the tapper 93 by way of contacts 21, 22 which are connected by a contact-piece 17 on the instrument spindle 2. Movement of the tapper arm 20 breaks the receiving-circuit at either 94 or 95 and puts one of the oppositely-arranged batteries 82, 83 into circuit by way of contact 97 or 98. Signalling- currents pass round a magnet 84 at A and prevent the operation of the tapper 75 there when that at B is sending current. Signalling-currents from B pass also round magnets 34, but are not sufficiently strong to remove the lock 35. When tapper 75 at A is turned, contact 71 engages one of the springs 69, 70 and moves it out of contact with the block 72, and 72<a> contacts with 73. This puts a battery 81 into the line-wire circuit, and an arm 76, by permitting one of the springs 26, 27 to contact with a contact 78, cuts the magnets 34 out of the circuit. Opposite movements of the tapper couple opposite poles of the battery 81 to the line-wire. With the instrument at B in ' line clear ' position, the arm 4 is upon contact 5, and batteries 83, 85 are in series in the circuit of the magnets 34 at A, so that a current passes of sufficient strength to remove the lock 35 from the tappet bar 29 of the starting signal at A. In moving the instrument to ' line clear ' position, the batteries 83, 85 are first put into circuit by the contact of segment 10 on the instrument spindle 2 with a spring 11, and at the instant this takes place, a pawl 9 falls behind a tooth a of a ratchet-wheel 8 on the spindle 2 and prevents any backward movement of the instrument. In moving the instrument forward from the ' line clear ' position, the batteries 83, 85 are maintained in circuit after the contact 4, 5 is broken, by means of a tooth b on the wheel 8 which engages the pawl 9 and thereby lifts the spring 11 into contact with a spring 11<a>. When the pawl 9 falls behind the tooth b, it simultaneously breaks the circuit of batteries 83, 85 and locks the instrument against backward movement. When the instrument is in ' line clear ' position, contacts 43, 44 are bridged by a contact 43<a> on the instrument spindle 2, so that if the starting signal is at ' danger ' and thereby contacts 50 are closed, the signalmen, by simultaneously pressing cancellation keys 46 at B and 47 at A, may complete the circuit of a magnet 91 and remove the locking-pawl 9 from the spindle 2. Between the ' line clear ' and ' train on line ' positions, the arm 4 moves on to contact 6, and the tapper circuits are remade. When the instrument is moved to ' train on line ' position. arm 4 is upon contact 7, and the battery 82 is put in circuit, giving dial signals at 86 at B and 88 at A. In this position, the instrument is locked against further movement by the engagement of an arm 49 with a lever 15, which is raised to release the instrument when the circuit of a magnet 48 is closed by the outgoing train at the treadle 16. When the lever 15 is raised, a latch 14, which having been previously freed from the segment 12 had rested against the projection 15<a>, falls into engagement with that projection and holds the lever 15 raised. As the arm 4 is moved into the ' line blocked ' position, the segment 12 removes the latch 14, but at the same time, a holding-circuit for the magnet 48 is closed by the contact 70<a> on the instrument spindle, and thereby the instrument is locked in that position until the signal at B is put to ' danger ' and consequently the holding-circuit is broken at contacts 69<a>. A handlever 100 may be used for raising the lever 15. The lock on the tappet bar 29 includes a pivoted segment 30 having a pair of spring catches 32. When the arm 33 is raised and the tappet bar is being moved from left to right into the position shown, the catches 32 snap over projections 38 on the arm 33 and prevent the segment from being moved again to the left until the arm 33 is lowered. By this means, when the bar 29 has been moved into the danger position, it cannot be moved into the safety position again until the magnets 34 have been de-energized, permitting the arm 33 to fall and releasing the segments 30, and have been again energized to lift the arm 33 and remove the lock 3.5. The home signal at A is controlled by a track relay circuit between the home and starting signals, so that the home signal cannot be put to safety when that portion of the track is occupied.