Patent GB-190403211-A (GB)
Title: Improvements in and relating to Electric Railway Signalling Systems.
Inventor: BRADLEY HAROLD EMMONS
Filed: 1904-02-09
Granted: 1904-08-11
Abstract: 3211. Bradley, H. E., and Bowen, E. F. Feb. 9. Signalling between trains ; electric railways and tramways, signalling on; semaphore &c. signals; lamp signals; contacts, elctrie.-Relates to an automatic electric permissive block system for electric railways, described for a single line with trolley wire, in which cars entering a section set a "danger" signal at the distant end, the proper setting of which causes a "caution" signal to appear at the entering end. As the car leaves the section, it either clears the " danger" signal, or leaves the apparatus in such position that it will be cleared by the exit of the last car upon the section. In each of the similar signal mechanisms, there are two electromagnets B, D, Fig. 2, with pole-pieces b which attract a longitudinal armature E carried by the arm e pivoted at b<1> and normally held up by the spring e<1>. A U-shaped pawl E<1> can move through holes in the guides e<3>, e<6> under the control of springs e<4>, the upward motion of the arm and pawl being limited by stops g'. Upon the spindle F' are a detent-wheel H, against which the roller on the pivoted arm H<1> is held by the spring H<2>, two ratchet-wheels G, F, one of which is driven when either the right or left pawl is pulled down by its magnet, and an arm f, which normally presses the tappet G<6> to the left, and keeps the U-shaped conductor G<5> depressed into the mercury cups G<7>, whereby the electromagnet J is energized, and its armature J<3> pulled down so that the linkwork will raise the arm I<2>, pivoted at i<1>, and keep the target I in the raised or "line-clear" position indicated by dotted lines. The target I, with a red border and red glass centre, is displayed to trains just entering the section as a "danger" signal, and a second green banjo-shaped target, with green glass centre, is displayed in the opposite direction to trains leaving the section as a safety signal, the incandescent lamp I' being placed between the two targets. The "danger" signal is given when there are cars on the section moving in the opposite direction to a car entering at the signal, and a " caution " signal, by the switching-on of a green lamp n, when cars on the section are moving in the same direction as such entering car. As the trolley-pole passes each signal-mechanism, it makes contact between a swinging-arm P, Fig. 6, and one or other of the contact-studs p, p<3>. Fig. 4 shows the wiring for a section, the apparatus Y, Z being placed at opposite ends thereof. Contact made by an entering car at P p energizes the coil B at Z, and rotates the ratchet-wheel one tooth, thereby de-energizing the coil J, and setting the danger signal for oppositely-entering cars at Z. As the bent lever P falls, the contact at N which it controls is made, and the caution lamp n at Y energized, but, on the car leaving the section, it makes the corresponding contact, and energizes the coil D to effect the return of the ratchet-wbeel, and the energization of coil J to take off the danger signal and break the contact N. The ratchet gear ensures that if a number of cars are on the section at once, they must all pass off before " line clear" is shown. Current may be taken from the trolley wire.