GB123089A - Improvements in and relating to Explosive Mines. - Google Patents

Abstract

123,089. Duffie, J. J. Feb. 8, 1918, [Convention date]. Sounds, controlling and actuating apparatus by. -Consists of apparatus for automatically firing an explosive mine when a vessel approaches within a given distance, comprising a sound-responsive device which is adapted after it has been in operation for a predetermined continuous period to effect the action of the firing-device. The mine is preferably fired by electric means controlled by a thermal switch, but a mechanical connexion between the sound-responsive device and the firing- means may be employed, and where an electric firing-device is used, a circuit-closer operating in the desired manner may be provided. The apparatus shown comprises a microphone 2, Fig. 1, arranged on the mine A and connected in a battery-circuit including the primary 4 of an induction coil. The secondary winding 8 of the coil is connected to an electro-magnet 9, Fig. 2, mounted beneath a diaphragm 10 which carries a contact 11. This contact co-acts with a pivoted spring- regulated contact 12 so as normally to close a circuit through an electro-magnet 19, the armature of which is on a lever 23 carrying a contact 25 adapted to co-act with a fixed contact 27. When sound waves fall on the microphone 2, pulsations of current are thereby set up which cause the contacts 11, 12 to chatter. The spring-controlled armature-lever 23 is thus set in vibration, and a circuit comprising leads 35, 39 is thus intermittingly closed through contacts 25, 27 ; or the parts may be so adjusted that, during the operation of the microphone, the contacts 25, 27 are held together. The leads 35, 39 are in a circuit, shown in Fig. 3, comprising a variable resistance 37 and a thermal switch 28. This switch comprises a bimetallic or like coil which, when heated by the passage of current through a surrounding resistance-coil 28<1>, causes a contact-carrying hand 31 to approach and, after a predetermined movement, touch an adjustable contact-hand 33'. When this occurs, owing to the operation of the microphone 2 for a given time and the consequent passage of a current through the heating-coil 28<1> for a sufficient period, a current will flow through the firing-device of the mine, causing explosion. The firing- device shown is a heating-coil 42 connected to the battery 38 and to the contact-arm 33<1>.