Patent GB-117170-A (GB)
Title: Improvements in Selective Signalling Systems and Selectively Operable Devices therefor.
IPC: H04L25/08
Filed: 1917-08-16
Abstract: 117,170. Western Electric Co., (Western Electric Co.). Aug. 16, 1917. Time-alarms.-Relates to signalling systems, particularly for train-dispatching systems, in which provision is made for sending standard time signals to all stations on a line. In the system described, step-by-step selectors are operated by polarized electro-magnets responsive to direct current impulses of alternate polarity, the polarized armatures being connected to the feed pawl in such a way that the ratchet-wheel carrying the contact member is moved a full step at each re versal of the line current. A holding-detent pre. vents release of the ratchet-wheel during the movement of the armature from one attracted position to the other, but in the neutral position of the armature, the detent is withdrawn so that the ratchet wheel is returned t6 normal by a spring, unless it has been set to a position in which it is held by the engagement of a pin on the wheel with a holding- member. In the system described, the selector at each station is brought to its first signalling position by a total of 15 impulses, divided into three sets, and the ratchet-wheel is provided with three pins, spaced apart by a number of teeth corresponding to the number of impulses in each set. The various stations are characterized by the division of the 15 impulses into the three sets ; thus different stations may be represented by the codes 3, 10, 2 ; 3, 9, 3; 3, 8, 4; 4, 9, 2; 4, 8, 3; and so on. In the case of the station represented by the codes 3, 10, 2, the three holding-pins would be placed 3, 13, and 15 steps from normal. Thus, after the sending of 3 impulses, all selectors having 3 as the first code digit would be held, the others being released. The next set of 10 impulses, say, would move the selectors of group 3 to their 13th position, but only those selectors having 3, 10 as the first two code digits would be held, the others being released. Similarly, a last set of 2 impulses would move all selectors of sub-groups 3, 10 two further steps, but only that one having the code 3, 10, 2 would be held with the contact arm in its circuit-closing position. In order that one of several signals may be given at the selected station, additional holding-pins are provided two, four, &c. steps from the first signalling position, corresponding signals being given at the station whose code number is 3, 10, 2 by sending sets of impulses 3, 10, 4; 3, 10, 6. All the stations in a group may be called simultaneously, thus all stations in group 3 may be called by sending 3 followed by 12 impulses. All the stations on the line may be called simultaneously by sending 15 impulses. Construction of selector. The polarized armature 6 of the electro-magnet 5 is secured to a member 8, Figs. 3 and 5, carrying two pins 9, 10, which engage upon opposite sides of the pawlcarrying lever 12, pivoted at 16, so that the lever 12 is moved to step the ratchet wheel 17 bv one of the pins 9 or 10 according to the direction of movement of the armature 6 from the neutral position shown in Fig. 5. A detent 40, also pivoted at 16, holds the ratchet-wheel during rapid oscillations of the armature, but when the latter comes to rest in the neutral position, a pin on the lower end of the lever 12 withdraws the detent so as to free the ratchet-wheel. The ratchetwheel, pawl, detent, and the armature are all arranged on a frame 14, 15, Fig. 1, removably mounted upon the support for the magnet windings. The axis of the ratchet-wheel carries a circular member 20 with a contact spring 53 adapted to engage the fixed contacts 22, 23, 24, 25, mounted on the frame member 15. The member 20 carries a holding-pin 29 in a position corresponding to fifteen steps from normal, and has a number of holes 54 adapted to receive interchangeable pins 27, 28, arranged according to the code of the station at which the selector is placed. The pins 27, 28, 29 co-operate with a spring holding-member 35, having a curved projection 38 adapted to engage and hold a pin as shown in Fig. 5, if the armature 6 comes to rest in its neutral position at a time when the pin is opposite the end of the spring 35. The pins 27, 28, 29 co-operate in the manner previously described to bring the contact 53 into engagement with the first signalling contact 22 in response only to the particular combination of impulses corresponding to the setting of the pins 27, 28. Additional holding-pins 60, 61 are provided on the member 20 to enable further signals to be given at the selected station as described above, these pins engaging the holding- member 35 when the contact spring 53 engages the contacts 23, 24 respectively. To provide for the receipt of time signals, the member 20 is formed with an elongated member 55 having a bent end which engages the holding-member 35 when the ratchet-wheel has been rotated twenty steps. In this position, the contact spring 53 lies between the contacts 24, 25, and in response to a further impulse given by the standard time signal, the spring 53 is caused momentarily to engage contact 25 so as to close a local bell circuit. At the end of the impulse, the spring 53 is moved back to its intermediate position so as to provide for repetition of the time signal, the bent end of the member 55 again engaging the holding-member 35 so as to prevent release of the ratchetwheel. Signalling system and construction of impulsesender. The magnets 5, Fig. 7, of the selectors are bridged across the line wires 70, 71, condensers 74, and inductances 75 being arranged as shown. A battery 85, normally disconnected from the line, is connected thereto by a relay 86 which is energised when any of the impulse-senders 89 - - 93 is operated. A relay 87,' energized when springs 96 pass over the raised portions of the impulse teeth, reverses the direction of the line current. The line impulses alternate in polarity, and owing to the connexion of the condensers 74 in series with the magnets 5, the latter respond only to impulses of current and de-energise when the line current is prolonged. The controlling-station is shown with five impulse-senders of the kind in which certain teeth are shielded by one or more adjustable cams. The senders 89, 90 which are used for calling individual stations, have two adjustable cams 94, 95 so arranged as to produce three sets of impulses separated by prolonged currents during the rotation of the sender. The sender 91 has only one cam, and is used to call a group of stations by sending three impulses followed by twelve. The sender 92 calls all stations simultaneously by sending fifteen impulses. The sender 93 prepares all stations to receive standard time signals by sending twenty impulses, after which the switch 107 is moved so as to bring the reversing-relay 87 under the control of a relay 105 in the standard time circuit. The spring 96 of each impulse-sender is normally out of engagement with the disk, but during rotation of the disk it continuously energises relay 86. As it passes over the raised parts of the teeth, the spring 96 engages spring 97 so as to energise the reversing-relay 87. As the spring 96 passes over the cam 94, the spring 97 energises relay 87 to send, say, a, negative current to line, but as the spring 96 passes over the second cam 95, a roller 98 on spring 97 engages a projection on the cam 95, thereby raising the spring 97 to prevent relay 87 energising, and thus sending a positive current to line. While the spring engages the part 100 of the disk, the local ringing-circuit is closed at the selected suit-station, and when it engages the part 101 a single impulse is sent to line to release the selector and stop ringing.