Patent GB-446589-A (GB)
Title: Improvements relating to block signalling systems for railways and the like
IPC: B61L23/10
Filed: 1934-11-24
Abstract: 446,589. Railway signalling instruments. LASCELLES, T. S., and SYKES INTERLOCKING SIGNAL CO., Ltd., W. R., 26, Voltaire Road, Clapham, London. Nov. 24, 1934, No. 33833. [Class 105] [See also Group XXXVIII] Block signalling instruments of the type with indicators giving " line blocked," " line clear," and " train on line" indications are operated at least in part by electric current impulses forming code signals and such block signals, which in certain cases also serve as train descriptions, are selectively received and recorded, for example, being printed on a tape together with the time and exposed at a window in the instrument. The entire signalling operations may be effected by code transmissions and recorded at both instruments, the threeposition needle indicators being selectively operated by the codes, but in the arrangement shown, the block signalling from the accepting instrument B is effected by weak and strong negative and positive currents. The traindescription transmission and printing mechanism may be of the form described in Specification 353,901. The instrument A at the entrance end comprises a three-position block indicator a operated from the distant instrument B when appropriate keys 29, 30, 31 are depressed. The instrument A transmits a code signal when the handle 8 is appropriately set and a plunger 13 is depressed, the positions 12 giving emergency signals, the positions 10 giving train descriptions which also serve as the " is line clear" signal to the distant instrument B, and the position 11, which is reached by a reverse movement, giving the " train on line " signal to the distant instrument B. At the distant instrument B the train description or block signal is printed on a tape and exposed at a window 34. Figs. 2 and 3 show the arrangements at the instruments A and B respectively. The handle 8 is normally locked, but is released on depressing a key 7 which energizes lock magnets 15, 16 to permit the setting of the handle 8 and of the transmitter member which is coupled therewith. If a contact 17, closed only in the " line blocked" condition, is open, the magnet 16 remains de-energized and prevents the handle 8 being moved beyond the emergency signal positions 12. When the plunger 13 is depressed a contact 19 is closed to energize a relay 20 which then sticks by a circuit over its own contact 51 and a contact 18 which is closed so long as the transmitter is not in the zero position. The depression of the plunger 13 uncouples the transmitter member which in returning under the action of a spring to the zero position, pulses a contact 14 thereby to apply current pulses to the line wire 3. When the transmitter has returned to its zero position the contact 18 opens and the relay 20 drops so removing the current source from line 3 by opening the front contact 50. At the distant instrument B the line wire pulses repeatedly energize a relay 36 over unoperated key contacts 53, 54, 55, 56. The relay 36 at its vibrating contact 61 pulses a ratchet magnet 37 to drive a type wheel to the position corresponding to the code transmitted and on cessation of the code a slow relay 38 drops its contact 62 to apply current to a magnet 44 whereby the type wheel is moved into printing contact with the record tape. The magnet 44 is energized over a lefthand contact 60 of a relay 39, the winding 59 of which was energized by the line current pulses. The closure of a front contact 46 of the magnet 44 applied current to the other winding of the relay 39 so that the contact arm 60 moves to the right and so de-energizes the magnet 44. The type wheel is now released from its ratchet (and returns to the zero position) by the energization of a magnet 41 over a back contact 45 of the magnet 44 and a front contact 67 of a relay 40 which was picked up by the front contact 45 and which sticks up until the opening of a contact 66 which was closed by the movement of the type wheel to effect the printing. This printed train description serves as the " is line clear ? " block signal. The movement of an arm 47 of the type wheel on to a contact segment 49 acting in conjunction with front contact 46 of magnet 44 picked up a magnet 42 which sticks until the operator at B opens a contact 70 by depressing a key 30 to send a " line clear " signal to A ; a lamp 28 remains lit until such signal is sent. This " line clear signal consists of a positive current on the line wire 3 applied over depressed key contact 55. When the operator at A receives this signal on the indicator a he sets the handle 8 to position 11 and so transmits a " train on line " code which is printed on the record tape at B. The operator at B then depresses key 31 to send a negative current over depressed contact 53 to set the block indicator a at A to "train on line." When the train has passed beyond the point B, the operator sends a strong negative current by depressing key 29 to close depressed contact 54; this strong negative current causes relay 25 at A to lift and as the polar relay 24 sets its contact to the left the winding 21 at A is energized to set the indicator a to " line blocked." An emergency signal such as " stop and examine train " or " vehicle running away " is transmitted by the operator at A, setting the handle 8 to one of the positions 12 and depressing the plunger 13 ; it should be noted that energization of the magnet 16 is not necessary for this movement as the contact 17 operated by the block indicator may be open. At the instrument B such emergency signal is printed by the operation of the type wheel as before and as the arm 47 will be in contact with the segment 48 a relay 43 will be picked up and maintain lamps 4 and a bell 27 in operation until the operator depresses an acknowledging key 32. The operator at B may send an " obstruction danger " signal by breaking the seal of a key 33 ; depression of this key to close the depressed contact 56 sends a strong positive current to instrument A thereby causing the magnet 25 to lift its contacts and the polar relay 24 to set its contact 73 to the right and thus a relay 26 is picked up and will maintain lamps 4 and a bell 27 of the instrument A in operation until an acknowledging key 6 is operated. With this " obstruction danger " signal both the block indicators a, b are set to " train on line " by the local energization of the two windings 23. The closure of key contact 33 energized the printing magnet 44 to record the sending of this " obstruction danger " signal.