Drawback device controlled by liquid surface tension, a switch incorporating such a device, and its use in magnetic relays

Claim 1

A switch comprising: an enclosure including a base defining a recess and a cover, said base and said cover each being internally treated to be mercury wettable; at least first and second electrical conductors extending through said base and being separated therefrom by insulation means; a fixed plate having a first plane of a dihedron-shaped component and a second plane integral with said base and insulated from said first and second conductors; a movable plate pivotally connected to said base for pivotal movement along an axis defined by the accommodation of an edge of said movable plate in said recess, said base being a third electrical conductor; a quantity of mercury placed between said fixed and movable plates which are wetted by said mercury which is held between said plates by capillarity action and applying a force to said two plates so as to bias said movable plate toward a first position in order to create an electrical contact between said movable plate and said first electrical conductor, said movable plate being movable in the presence of a magnetic field to a second position where it is in electrical contact with said second electrical conductor, and being drawn back to said first position by said liquid in the absence of a magnetic field; wherein said fixed plate defines an opening through which said movable plate passes, said axis about which said movable plate pivots being retained in said recess by said second plane.