Patent GB-191325006-A (GB)
Title: Improved Three Position Block Instrument for Railway and Tramway Purposes.
IPC: B61L23/12
Filed: 1913-11-03
Granted: 1914-11-03
Abstract: 25,006. McKenzie & Holland, and Edmonds, C. H. W. Nov. 3. Signalling instruments.-In the receiving portion of a three-position one-wire block instrument, visual indications of the state of the line are given by a mechanical connexion with the armatures of an electro-magnetic device which is directly energized by currents differing in strength and polarity according to the indication in the transmitting-device at the other end of the line wire. Means are provided for ensuring the transmission of the signals in the correct order, and for masking the signal in the transmitting-device until the signal has actually been transmitted. The instrument at each station A, B comprises a transmitting-device which displays the signal sent at an aperture 14, Fig. 2, and a receiving-device which displays the received signal at an aperture 47. The transmitter includes a tapper key 2, and an indicatorplate 13 mounted on a spindle 10, which carries a commutator 15 supporting contacts 16, 17, 18, 19, 20 adapted to co-operate in connected pairs as shown in Fig. 8 with spring contacts 21, 22, 23, 24. A masking-device 27, Fig. 1, is carried by one arm 26, Fig. 6, of a bell-crank, the second arm 28 of which carries a locking piece 30. When the masking-arm 26 is swung into operative position by its engagement with a stud 31, 32, or 33 carried by the indicator disk 13, the arm 28 swings over the end of a pawl 37, and is thereby held in such a position that the locking-piece 30 obstructs the path of a stud 36, 34, or 35 and locks the disk 13 against further forward movement. Backward movement of the disk 13 is simultaneously prevented by the stud 34, 35, or 36 being obstructed by the end of the arm 26. The receiving- apparatus comprises two electro-magnetic devices 41, 42 adapted to operate pivoted armatures 48 which are arranged in the fields of permanent magnets 50, 51 and are mounted on spindles 52, 53 carrying flags 44, 45 indicating ' line closed ' and ' train on ' respectively. The flag 45 can be moved so as to cover the fixed ' line clear ' indicator, and the flag 44 can similarly .he moved so as to cover the flag 45. The electro-magnets 41, 42 are arranged in series, and so constructed that a stronger current is required to operate the magnet 41. Assuming a train is to be sent from B to A, Fig. 8, the signalman A, after the usual block bell signals, turns the handle 11 of his transmitter until the pointer indicates line clear,' in which position the same indication on the plate 13 registers with the aperture 14, but is marked by the device 27 as explained above. The same rotation of the handle 11 changes the connexions of the commutator 15 and contacts 21, 17, 18, 24 are made. so that a strong positive battery BP is placed in circuit, and on A depressing his key 2, the following circuit is completed:-Battery BP, contacts 24, 18, 17, 21, wire 62, magnet 40, wire 63, contact 7, key 2, wire 64, lightning- arrester 60 at A, line wire 61, lightning-arrester at B, wire 64, key 2, contact 6, wire 65, coils 42, wire 66, coils 41, wire 67, and lightning-arrester 60 to earth and via earth back to battery BP. The coils 41, 42 at B will thus both be energized and the flags 44, 45 moved away so as to uncover the indication line clear' at B. The energizing at the same time of the magnet 40 at A causes its armature 39 to be attracted and the connected pawl 37 to be rocked so as to free the lever 28, which swings the masking device 27 away from the opening 14 at A and discloses 'line clear' on the plate 13. On the train leaving B, the signalman at B informs the signalman at A on the block bell, and the latter signalman rotates the handle 11 to the ' train on line ' indication, which will be masked as above described, and the commutator 15 makes the contacts 23, 20, 19, 21 and places the weak negative battery. SN into circuit. On the signalman A depressing his key 2, the weak negative current only suffices to energize the coil 42 at B and move the flag 45 into position. The sending of this current also energizes the releasing-magnet 40 and frees A's commutator 15 and handle 11. On the train arriving at A, the signalman at A further rotates his handle 11 to line closed,' and the contacts 22, 16, 21 are made, and the strong negative battery BN is placed in circuit, so that when the signalman A depresses his key 2, the flag 44 at B is moved into position in front of the flag 45, and the releasing-devices at A are operated. To prevent jamming of the locking-piece 30 and the studs 34, 35, 36, the depression of the key 2 is arranged to operate a lever 68 having a projection 70 adapted to engage one or other of the studs 31, 32, 33 and move the disk 13 into the correct position.