Patent GB-190400869-A (GB)
Title: Improvements in Relays for Recording Re-Transmitting and Controlling Currents of Electricity and in Apparatus therefor
Inventor: JOHNSTON WILLIAM EWART GLADSTO
Filed: 1904-01-13
Granted: 1904-12-15
Abstract: 869. Johnston, W. E. G. Jan. 13. Relays; telegraphs.-Relates to electric relays for use in combination as selectors for currents of different strengths, or for recording currents above or below a defined range, or for controlling an engine driving a dynamo, or for use as cutouts. By the use of these selective devices a telegraphic circuit can be used as a multiplex one if the various keys which transmit the currents of different strengths are so arranged that only one can be depressed at a time. Fig. 1 shows a simple form of relay or selector in which currents of two different strengths flowing in the line wire x, y actuate local receiving-instruments R, R<1> respectively. The letters N, N', S, S', &c. denote the polarity of the relay electromagnet A, controlling electromagnets K, C, and pivoted permanentmagnetsD,E. The controlling. electromagnets K,C are energized from batteries b<1>, b<2> through suitable regulating resistances. Normally, the magnets D, E are attracted by the poles N', S<2> and the relay tongues J, L make contact at F, I. If the weaker of the two currents to which the apparatus is to respond flows in the line, the magnet D is attracted to the pole N, and the circuit of the receiving or recording instrument R is closed through the contacts J, G and L, I. If the stronger of the two currents is flowing, both the magnets D, E are attracted, and the circuit of the other receiving instrument R' is closed through the contact H, L, one or other of the two instruments being thus selected according to the strength of the current. Mechanical adjustments are provided for the controlling electromagnets, and for the permanent magnets and their associated contacts. Permanent magnets properly aged may take the place of the controlling electromagnets. Similar connections may be established between the contacts of four relays, the eight pivoted magnets of which respond in succession to currents of eight different strengths. There are in this case eight local circuits and eight receiving-instruments. The local circuits may re-transmit currents to other line-wires. The regulation of a dynamo supplying the current in the line may be effected by causing the local circuits which are closed or opened in accordance with the current strength to act on the engine &c. driving the dynamo. A cut-out can similarly be under the control of a local circuit which is closed, or opened, when the current in the line ceases. Such a cut-out may be used as a safety device in the case of the snapping of an overhead trolley wire &c. In a modified form of relay, the pivoted magnet swings between the poles of a horse-shoe electromagnet differentially wound, so that its position depends on whether the line current or the local controlling-current is the stronger. In another form, the relay electromagnet and controlling electromagnet are both of horse-shoe type, and are placed with like poles opposed. The pivoted portion comprises two small permanent magnets DD, Fig. 5, carried by a non-magnetic frame D<1>, pivoted at d. The relay tongue J is also non-magnetic. In order that good contacts may be made when the moving parts are light and the forces small, the relay or selector may be exposed to electromagnetic radia. tion. To prevent mechanical coherence, a serrated wheel rotates in contact with a bar so as to subject the whole apparatus to vibration. When the main circuit carries a heavy current, adjustable springs may replace the controlling electromagnets.