Patent GB-1101881-A (GB)
Title: Speed control system
IPC: B61L23/16
Filed: 1965-06-30
Abstract: 1,101,881. Automatic train control. WESTINGHOUSE AIR BRAKE CO. 30 June, 1965 (14 July, 1964 (2)], No. 27667/65. Heading B7N. [Also in Divisions G3 and H1] In an automatic train control system for driverless trains, the track is divided into sections and trains are controlled either by a first coded tone at frequency F 1  applied to the end of a section, which also controls the track relay of the section, or by the first coded tone in conjunction with a second and/or third coded tone at frequencies f 2  and f 3  respectively applied at the end or intermediate the ends of the section. The tones are interruption coded at 180, 120 at 75 cycles/min. and four code patterns, Figs. 2-5 (not shown), are available comprising a first in which a signal at frequency f 1  is interrupted at a required code rate, a second comprising the first code pattern with the addition of a signal at frequency f 2  during the "off" periods of the first coded signal, a third similar to the second except that the added signal is at frequency f 3  and a fourth arrangement in which signals at frequencies f 2  and f 3  are applied alternately during the "off" periods of the first coded signal. The interruption frequency for each section is determined by the type of section e.g. stopping section and by the occupancy of the section in advance but the pattern of the coded signal received on the train can vary in the section as the train passes the points of application of the second and third frequency tones. The speed signalled to the train depends on the frequency of the interruption code and also on the code pattern, Fig. 6, the speed decreasing with code frequency and also with the number of signals applied. Assume a train entering section 2T, Fig. 10, and that the following stopping section IT is unoccupied, 180 code is applied from coding relay 180CT via f.c. (front contacts) a and b of track relay 1TR to a code follower relay 2CTP. During the period the contacts of this relay are in the normal (left) position a signal at frequency f 1  from terminal f 1  BX is applied to the end of track section 2T via terminals PA2 and when the contacts are in the reverse position (off period at frequency f 1 ) a signal at frequency f 2  is applied from terminal f 2  BX via b.c. (back contact) a of a coast relay CR (assumed deenergized), f.c.c. of relay 1TR and terminal PB21 to a point B21 intermediate the ends of the section. The train on picking up the signals at f 1  and f 2  is controlled to a speed of 55 m.p.h. until it reaches the point B21 when cut off of the signal at frequency f 2  reduces the controlled speed to 40 m.p.h. With section 3T unoccupied a code rate of 120 is selected for the stopping section IT and a signal at frequency f 1  interrupted at this rate is applied via the normal contact of code follower relay 1CTP and terminal PA1 to the end of the section. Contacts b of the code follower relay operate on a code halving circuit including relay 1CHR whereby alternately a signal of frequency f 2  is applied via normal contact d relay 1CHR, reverse contact d relay 1CTP and terminal PB11 to point B11 and a signal of frequency f 3 is applied via reverse contact c relay 1CHR, reverse contact c relay 1CTP and terminal PB12 to point B12 during the " off " periods of the signal at frequency f 1 . As a result on entry of the train into the section it receives signals at the three frequencies at code rate 120 and is further controlled to 40 m.p.h. until it reaches point B12 when drop away of the signal at frequency f 3  reduces the speed to 25 m.p.h., on passing point B11 the signal at frequency f 2 drops away and service braking is applied to bring the train to a stop at the station. Additionally a station stop servo control operated from a wayside loop as the train approaches the station may control the stopping of the train, the arrangement described only taking over if the servo control does not operate correctly. Fig. 14 (not shown) shows an arrangement for restricting the speed of the train on curves. On each train apparatus responsive to the code rate and the number of frequencies present operates on relay circuitry to set up a series of contacts indicative of the required speed via which, and a series of contacts actuated by the actual train speed the brake and power control circuits are operated (see Division G3). An automatically operated door control arrangement is also provided. The track sections may be insulated from each other or uninsulated in which case the signals can be applied to or received from the ends of the sections via a combined impedance band and transformer (see Division H1).