Patent GB-190109284-A (GB)
Title: Improvements in Electrical Instruments for Signalling on Railways.
Inventor: TYER EDWARD
Filed: 1901-05-04
Granted: 1902-05-01
Abstract: 9284. Tyer, E., Hollins, F. T., and Leake, F. W. May 4. Signalling-instruments; crossing-gate aignals.- Relates to electrical signalling - instruments, which are worked by momentary currents through a single line-wire with earth return. The instruments are arranged to give, in addition to the usual two indications, such as "Line clear" and "Train on line," a third signal for "Train out "of section or " Line blocked," which is usually given by beats on the bell. As shown in Fig. 1, the index a is provided with an arm having a stud c, working in conjunction with a pivoted latch and a pawl d on the pivoted arm t supported by the armature f of the electromagnet e. The index a is operated to the right or left in the usual way by a positive or negative current through the magnets b. When the index is moved to the right, the pin c raises the pawl d, and the pin g on the pawl raises the latch j, so that the pin c passes the pawl and latch, and the index moves to its extreme position. On the return movement of the index by a reverse current, the pin c raises and passes the latch j, but is then stopped by the pawl d, this position, with the two extreme positions to right and left, giving the three indications. The magnet e is in circuit with the coils b, but the normal current through it is insufficient to raise the armature f and pawl d, the release of the pawl being effected by additional battery powers &c. In order to give indications to the gateman or attendant at level crossings &c., a relay k, Fig. 2, and two indicators a operated respectively from the up and down stations, are introduced into the line-wire L at the gate cabin &c. The indicators are connected respectively to the up and down line-wires, and both are connected to the earth return l, m, E. When a current is transmitted from either end of the section, the corresponding indicator is operated, and is then short-circuited by the contact o on the armature n of the electromagnet k, the contact o also connecting the up and down lines for the transmission of the signal through to the other end of the section. The armature n, when operated, also breaks the earth connection of the instruments at the contact m, and completes at the contact p a circuit through the battery q and bell r to give an audible signal to the attendant. The indicators may be provided with midway detents similar to those shown in Fig. 1, and these detents may be released by local currents transmitted when the train passes over rail contacts at suitable distances on each side of the crossing, or they may be in circuit with the indicators and operated by additional battery power. When the indicators are employed in the signal box, the latch may be dispensed with, the index having no tendency to return to the right, but, in the arrangement shown in Fig. 2, the latch is necessary to prevent the operative current of one indicator from acting on the other. The Provisional Specification also states that the indicator may be arranged to be held in mid position by a weight or spring, and to be moved on from that position by additional battery power, and that the third indication might be obtained by a superimposed indicator operated only by additional power.