GB431422A - Improvements in and relating to means electrically responsive to the establishment of a contact of short duration - Google Patents

Abstract

431,422. Electromagnetic switches. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. April 5, 1934, No. 10364. Convention date, April 5, 1933. [Class 38 (v)] In an arrangement for the indication of or response to a contact of short duration, means such as a relay has included in its energizing circuit a condenser and a seriesconnected saturable inductance, the supply to this circuit being so adjusted that when in response to the establishment of the transient controlling contact a small change of voltage is set up in this circuit, the circuit is caused to " silt " and a relatively large change of current in the controlled circuit occurs. In the circuit shown in Fig. 2, the relay winding R is normally in series circuit with a saturable inductance D and condenser C and also with an additional impedance Z across which is connected a contacting member K. Normally when the contacts of K are disengaged the voltage across the members C, D is of a value E3, Fig. 1, below the value E1 at which a sudden rise of current occurs. If, however, the contacts K are closed even momentarily, short-circuiting the impedance Z, the voltage rises slightly above E1 so that a rapid rise of current occurs immediately and the relay R is operated. On re-opening of the contacts the relay R is maintained operated as the fall of voltage to E3 is not sufficient to cause the sudden fall of current shown in the upper curve for falling voltages. This sudden diminution is, however, produced by the subsequent opening of a switch W normally short-circuiting a resistance Z which reduces the voltage across C, D to a value below E2 and thus causes the opening of the relay R. The initial condition of the circuit may then be restored by reclosure of the switch W. The Specification as open to inspection under Sect. 91 also describes a similar but modified arrangement (Fig. 3, cancelled, not shown), designed to operate a relay in response to the movement of a cage in a mine shaft, variations of voltage in the controlling circuit being produced by variation of the reluctance of inductive chokes due to the movement past them of a body of magnetic material carried by the cage. This subject-matter does not appear in the Specification as accepted.