Patent GB-190820619-A (GB)
Title: Improvements in or relating to Railway Signalling Systems and Apparatus.
Inventor: ABRAHAM ROBERT MORRISON
Filed: 1908-09-30
Granted: 1909-07-01
Abstract: 20,619. Abraham, R. M., and Glenn, S. L. Sept. 30. Single - track systems ; interlocking.-A lock and block single-line signalling-system is arranged so that the starting-signal at the rear station, having once been automatically replaced at danger by a train operating a s l o t - controlling treadle, cannot again be lowered until the train has operated a treadle at the advance station and the signalman there has again operated his plunger to release the lever and to energize the slot. Further, only the first operation of the plunger at the advance station has any effect, and this operation cuts out the plunger at the rear station ; means are also provided whereby the advance signalman may cancel his permission to allow a train to proceed, provided that the train has not already entered the section. To allow a train to proceed from station A to station B, the signalman at A asks permission by the usual bell or telephone signals, and the signalman at B accepts by operating the plunger 1 whereby current flows from a battery 2, through the normally closed contact 3 of line relay 4, armature 5, armature 6 of relay 7, which normally closes contact 8, plunger 1, contact 9, plunger relay 10, back to battery 2. The relay 10 is thus energized and picks up its armatures 13, 21, 30, breaking the normally closed contact 29 and cutting the line relay 4 out of circuit. Current then passes through armature 13 and armature 15, and acts as a 'holding' circuit for the relay 10, which is thus kept energized after the plunger 1 is released, this circuit also passing through the armature 16 and the cancelling-key 19 which are in parallel. Current also passes through armature 21 and indicator 22, which is put to 'line clear' or similar indication, then dividing to pass through (1) the slot relay 24, which the current passing is not strong enough to energize (2) armatures 25, 26, whence it proceeds through the cancelling-relay 17 to the line-wire 28. The cancelling-relay 17 picks up its armature 16 and causes the full 'holding' current to pass through the cancelling-key 19, so that the signalman can, at this time, return the instruments to normal by breaking circuit at this key. The current from the line-wire flows through the relay 17 of instrument A, through armatures 26, 25, indicator 22, putting it to 'line clear,' armature 30, and line relay 4 to earth, a small part again passing through the relay 24. This current energizes relays 17, 4, lifting the armature 16 of the former and the three armatures of the latter, thus cutting out the plunger 1 ; current from the battery 2 thus flows through the armature 32, where it divides, part passing to the electric slot 40 of the signal 41 and to earth, and the other part through the armature 34 of the lock relay 35 to the lever lock 37, and back to the battery. The signalman at A is therefore at liberty to pull over his lever to place the signal 41 at safety, and by doing so he operates the arm 42 attached to the lever, to break the contact 43, which is in the normally closed holding circuit of the relay 35. The lock circuit is thus broken at contact 36, and the lever when once returned becomes automatically locked and remains so until the signalman at B again plunges. The train now passes the lowered signal at A, closing at the same time the contact 48 and completing the circuit of relay 7, which lifts its armatures 26, 15, 6, thus causing the whole line current to pass through the relay 24, and increasing the line resistance to such an extent that the relays 17 drop their armatures and render the cancelling-keys 19 inoperative. The full current now passing through the relay 24 causes it to lift the armatures 25, 38, thereby de-energizing the slot 40 and placing signal 41 at danger, where it is locked. On the train reaching the treadle 47 at station B, it closes the circuit of treadle relay 7 which lifts its armatures 26, 15, 6, thus breaking the 'holding' circuit of the relay 10, cutting off the line current, and putting both instruments to normal. The cancelling-key remains inoperative while the train is on the section since the line current continues to pass wholly through the relay 24, the alternative circuit being broken at the contact 23. The slot 40 at the station B cannot be energized after the plunger 1 has been operated, since the line relay 4 is cut out of circuit by the lifting of the armature 30. Any suitable apparatus (such as that used in the Phonophore system of simultaneous telegraphy and telephony) may be connected through the linewire 28 for giving the usual bell or telephone signals ; or any other method of communicating these signals may be employed. Separate treadles may be provided at each station for putting the instrument to normal and the signal to danger respectively, while the arrangements of contacts and armatures may be varied provided the same results are obtained. Instead of the relay 24 acting as a resistance, a separate resistance may be switched into the line when the relay 24 is energized ; or, again, an additional battery may be switched on to the line by such energization, in which case the cancelling-relay 17 is so wound that it cannot be energized until the additional battery is switched on, the circuits through the key 19 being reversed so that when the relay 17 is energized the contact 18 is closed and cancellation rendered impossible.