Submarine signalling device and fail-safe switch

Claim 1

For use in a submarine signalling device having a battery, a detonator, a pressure switch means operatively connected in a series electrical circuit, and a sea water switch comprising a housing means and an anode and a cathode in said housing means electrically connected to said electrical circuit and electrically interconnectable through an interspace floodable via orifices in said housing means: the improvement comprising a fail-safe switch comprising a container means having orifices, two electric terminals in said container means for electrical connection to said battery, a permanent magnet magnetically influencing said electric terminals to maintain them in nonoperative position, a spring-loading means urging said electrical terminals to an operative position, a plug means maintaining said magnet in said position, said plug means being constructed of a material which disintegrates upon contact with sea water over a specified time period, and a displacing means urging said magnet in the direction of said plug means whereby on immersion of the fail-safe switch water enters through said orifices in said container means and disintegrates said plug means over said specified time period thereby allowing displacement of said magnet by action of said displacing means and consequent translation of said electric terminals to an operative position under the action of said spring loading means.