Liquid level detector

Claim 1

A liquid-level detector, comprising, a float adapted to be placed in the liquid so as to rise and lower with the change in level thereof, and a sensing device adapted to be fixed in position at the level to be detected for sensing the movement of the float with respect thereto, said sensing device comprising a non-magnetic housing, a magnetically-actuated switch disposed within the housing and having two operating conditions, a fixed permanent magnet disposed within the housing and located with respect to said switch such that its magnetic field causes the switch to normally assume one operating condition, a passageway formed in said housing, a movable permanent magnet disposed within the housing passageway and movable therein from a first position wherein it exerts no significant influence on the magnetic field of said fixed magnet with respect to the switch, to a second position wherein it influences the magnetic field of said fixed magnet with respect to the switch to cause the switch to assume its other operating condition, and a float magnet carried by said float and moving said movable magnet with it from said first to said second position or from said second to said first position, as the float rises and lowers with the change in level of the liquid, said movable magnet being retained in its moved position until returned by said float magnet, said passageway being at least twice the length of said movable magnet with the top of the passageway being substantially coextensive with the top of said fixed magnet, said first position of the movable magnet being completely below the fixed magnet and said second position of the movable magnet being sustantially coextensive with the fixed magnet, the ends of the fixed and movable magnets being oppositely polarized causing the movable magnet to move with a snap-action from said first to said second position, and from said second to said first position.