Patent GB-152128-A (GB)
Title: Improvements relating to electrical transmission systems for use in speed controlling, measuring and/or indicating, in signalling by speed variation, and for analogous purposes
IPC: G01R1/20
Filed: 1919-07-10
Abstract: 152,128. Evershed & Vignoles, and Needham, J. C. July 10, 1919. Electric and magnetic speed indicat o r s ; revolutiondirection indicators. -Relates to electric systems for use in speed controlling, measuring, and/or indicating, in signalling by speed variation, and for analogous purposes, and consists in the employment of a condenser of constant capacity combined with a charging and discharging device or interrupter adapted to make and break alternately the circuit of the condenser. This arrangement acts as a resistance and the current passing through the circuit is dependent upon the number of alternations and is therefore proportional to the speed or number of revolutions. For indicating speed, as shown in Fig. 1, the condenser e and interrupter f, mounted on a shaft f<1> the speed of which is to be determined, are placed in the circuit of a coil x of an ohmmeter a, the other coil y of which is arranged in parallel and in circuit with a source of supply b. As shown applied to a speed telegraph and reply, Fig. 2, based on the principle of a Wheatstone bridge, the transmitting instrument comprises a resistance j forming two arms of the bridge, the ratio of which can be varied by a sliding contact g; the other arms are constituted by a resistance h and by the condenser e and interrupter f, the speed of which, after setting of the contact q, is regulated by the apparatus under control to restore balance in the indicating instruments i, i<1>. By suitably disposing and duplicating the parts orders can be transmitted to two or more sets of apparatus and differences of speed can be measured. To compare the speeds of two shafts a second condenser e, interrupter f, and a resistance h are substituted for the resistance and contact g, and by varying the resistances h or adjusting the condensers e any desired relation of speeds can be effected. The indicating instrument may be replaced by a motor actuated by a relay or other device which automatically operates upon the apparatus under control so as to change its speed when current passes through the motor. When employed as a signalling device for any kind of orders the interrupter acts as a transmitter and the order is made dependent on the speed thereof. This may be effected by a small motor, the speed of which can be controlled and indicated bv any known form of speed indicator on the dial of which the orders are engraved. To indicate the direction of revolution two resistances j, j', Fig. 6, are arranged in parallel and connected respectively to pairs of indicators i; i'. These indicators are connected by means of slip rings p, Fig. 7, to a commutator q and support t on the shaft f<1>, the support being arranged so that a certain amount of lost motion exists between it and the shaft by means of an arm s and pins u, u<1>. A modification is described in which a smaller condenser is used, and is so arranged that it can be alternately charged, discharged, recharged in opposite direction and discharged, another indicator being included in the circuit to enable a third person to ascertain the speed without disturbing the normal working of the circuit. Alternative arrangements are described having indicating instruments with moving coils and duplex windings.