Patent GB-339594-A (GB)
Title: Improvements in electric signalling systems particularly adapted for controlling traffic
IPC: G08G1/085
Filed: 1929-09-02
Abstract: 339,594. Siemens &. General Electric Railway Signal Co., Ltd., and Boot, J. Sept. 2, 1929. Road-traffic signals.-Electric signalling apparatus for the control of traffic at intersecting routes comprises an electrically impulsed rotary switch which actuates switching means such as a relay controlling the " stop " and " proceed " circuits for at least two directions, a second switching means, for example, a relay, controlling the circuits to the caution indicators and to the proceed indicators whereby when the " caution " circuits are closed the circuit of the proceed indicator previously showing is opened. The rotary switch, driven by a motor actuated intermittently by means of a bi-metallic strip switch as described in Specification 325,296, [Class 38 (v), Electric switches &c.], consists of conducting segments a, a<1>, fixed wipers b, b<1>, and a wiper g mounted on a spindle h concentric with and rotatable with respect to the spindle of the switch. In the position of the switch shown, with the springs b, b above the air gaps the relays A, B are de-energized, and the yellow lamps Y of both signals S1, S2, corresponding to North- South and East-West roads at an intersection are illuminated over the contact j. On the next step of the rotary switch a circuit is made over + ve. coils d, e, e<1>, relay B, spring g, segment a, spring b<1>, winding c<1> to - ve. The relays do not operate, however, owing to the high resistances e, e<1> and the Y lamps remain operative until the heating element d has closed the bi-metallic contacts m. The relays B and A now operate. Closure of contact k breaks the circuit of the Y lamps and provides an alternative " stick " circuit to the relays B, A. Energization of coil c<1> has changed over the contacts n, n<1> and contact p being closed the green lamp G of Sl and the red lamp R of S2 are illuminated. These conditions remain until advancement of the rotary switch causes one of the brushes g, b, or b<1> to come over an air gap when the Y lamps are illuminated, the next step of the rotary switch and closure of contacts m resulting in energization of relay c and illumination of the red lamp of S1 and the green lamp of S2. Overlapping. When the relays A and B are inoperative and the Y lamps illuminated over contact j i as in Fig. 1, the red lamp of S1 remains illuminated over contact n, to give a caution signal, until the operation of coil c<1> changes the signal to green. Thus the sequence of lighting for each signal is red, red and yellow, green, yellow, red, &c. Modifications; time control. The duration of the red and green signals may be varied by rotation of the spindle h, the position of which may be indicated by a pointer integral with the spindle, and moving over a graduated dial. Various ways of controlling the times of operation of the thermal devices d, m and of that actuating the driving motor are also described. At night or in times of slack traffic the " stick " circuit at contact k, and the spring g are disconnected, - ve being applied to the.connection o when the Y lamps will flash synchronously with the operation of the thermal switch d, m. Manual operation. A five-position drum switch is provided, Fig. 2, for this purpose. In the position A (automatic) the apparatus functions as above; in position NS the relays B and c are energized; position Y, the yellow lamps are illuminated; position EW indications opposite to those of the NS position are given and in position FY, a flashing yellow signal is given.