Patent GB-306147-A (GB)
Title: Improvements relating to despatcher control systems for railway traffic
IPC: B61L7/08
Filed: 1929-02-15
Abstract: 306,147. Westinghouse Brake &. Saxby Signal Co., Ltd., (Assignees of Snavely, C. S.). Feb. 16, 1928, [Convention date]. Selective distant-control systems; tell-tale apparatus.-In a despatching system in which signals and points apparatus at distant points are controlled from a central station and the position of such apparatus is indicated in the central station bv code currents transmitted over a pair of line wires common to the whole of the controlled apparatus, the transmitting apparatus comprises means for storing the actions of the operator for transmitting the various code signals until the transmission wires are free from other code currents and for preventing access of other code currents to the line wires until a transmission is completed. The coding device of the transmission apparatus at each point comprises a number of coding units G<4> and a checking unit G‹, a slowreleasing motor-relay m and a slow-releasing triprelay and a motor M driving a shaft through a gear 23, 26 and provided with a governor h which cuts in or out a short circuit across resistance 123 in series with the field windings. Each coding unit comprises a storing magnet r and a delivery magnet d and a coding disc D<4> carrying a notched disc 29 which is normally locked by the latch 42 connected to the armature of the magnet d. When a code current is to be transmitted from the central station, Fig. 1<a>, the operator closes the appropriate key of the series K - - K<8>, thus energizing the storing magnet r of the corresponding coding unit. Any number of keys K<1> &c. may be depressed in succession and the codes are then transmitted later in a predetermined order. If the transmission lines 66, 66a are not energized the armatures of the code repeater relay E<A> are in the normal position shown and when a storing relay is energized a circuit is completed from battery L<A>, contact 75, contact 87 or slow-release relay F'A, which is opened only when the relay EA is energized by code currents, contact 38 of the check unit G‹ relay m and contact of the energized storing relay r. The armature of the storing relay is latched by the catch 45 to keep its contacts closed until after energization and subsequent de-energization of the delivery magnet d. Relay m fulfils several functions. First, the pole changer relay H<A> is energized if all coding units are at rest and a locking impulse is sent from battery gA to the line wires 66, 66a and locks up all repeating relays at other stations. Secondly, the motor M is put in operation and drives the shaft 27 on which the discs 28 are frictionally mounted. Thirdly, the circuit to the storing relay r of the check unit G‹ is closed and the armature locked. Fourthly, a circuit is closed over contacts 56 on the governor h, and the back contacts of the delivery magnets d of all the coding units to the trip magnet t, which is thus energized and completes the circuit of the delivery magnet d of the check unit G‹, which withdraws the latch from the corresponding coding disc on the shaft 27 and releases latch 45 but itself holds the armature of the storing magnet until the disc D‹ has completed a revolution. Contacts 38 on the check unit are opened and relay m is de-energized momentarily and connects relay E<A> to the line wires and tests whether a code is being delivered from another station in which case the relay E<A >is energized and prevents re-energization of relay m to close the motor circuit for further operation. If the lines are free, the motor continues running and the trip magnet t is energized over the back contacts of all the delivery magnets and the delivery magnet associated with the first, in a predetermined order, of the energized storing magnets is energized and its code-wheel is put in operation and makes a complete revolution, opening and closing contact 36 in accordance with the code represented by the arrangement uf teeth on its periphery, causing the relay HA to lift and drop its armature 113 and send alternately reversed currents to the line wines. At the end of the revolution of one disc, the next coding unit of which the storing magnet is energized becomes effective, and its code is transmitted. After the last of the stored codes has been transmitted relays m, H<A> are de-energized and, the latter, opening quickly, sends an impulse to the line to energize the code-repeating relays at all stations; relay m re-connects relay EA to the line wires so that the station is then in condition to receive signals. Fig. 1<b> shows an example of a distant station with receiving selectors S<1> - - S<5> controlling the signals T<1>, T<2> T<3>, and the points 16 at a siding, with provision also, for indicating the position of the operated devices in the central station. The points are operated by a motor Q<B>, the circuits of which are controlled by a track relay R and by a two-coil relay JB, the coils of which are energized over contacts of the selector S<3>, S<1>, for normal and reverse operation respectively. Signal T<1> is controlled by selector S<2> in conjunction with detector contacts 157 at the points and signals T<2>, T<3> are controlled bv selector S<3> and alternative detector contacts 158 at the points. All the signals are reset to danger under control of selector S<1>. The position occupied by the signals is indicated to the central station by a coding device A<B> the storing magnets of the coding units being energized momentarily as the signals move towards their extreme positions. The passage of a train into and out of the section is indicated by two coding units controlled by contacts of the track relav R in series with contacts of a slowreleasing relay P controlled by the relay R. The corresponding receivers in the central station S<9> .. S<14> control lamps 191, 197 'through relays U, V, W. In order that several stations may not begin simultaneously to transmit stored codecurrents to the line wires as soon as the lines are set free by an operative station provision is made to give precedence to all the stations in a predetermined order by providing on the discs 28 of the checking unit at each station notches in different relative positions at each station so that the contacts 36 on the checking unit G‹ at each station are opened in predetermined order of precedence and the locking impulse is sent from the first station at which a storing magnet is energized thereby preventing all other stations from transmitting impulses to the line wires until all stored codes have been sent from that station. At the end of each transmission, the checking units of all stations are driven one revolution and the first in order of precedence which has stored signals for transmission becomes operative. Thus signals from the central station are always transmitted in preference to all signals to that station, although they may have been stored only during the transmission from the last operative station. In the case of two coding units in a station controlling related functions, which may cancel one another, the latch 45 of one coding unit may be released by an electromagnet in parallel with the storing magnet of the other, so that the last unit set is the only one effective for transmitting a signal. Specification 304,830 is referred to.