Self-holding electromagnetically driven device

Claim 1

A bistable electromagnetic device comprising: a pair of aligned permanent magnets with confronting ends of like polarity spaced apart along an axis; a pair of electromagnetic coils respectively surrounding said magnets and centered on said axis; an armature of magnetically permeable material axially movable between said confronting ends, said armature having a central body of a cross section substantially coextensive with that of said magnets provided with a peripheral rib in the midplane of said body projecting radially beyond said confronting ends, the spacing of said coils exceeding the axial length of said body; a pair of magnetically permeable sleeves respectively surrounding said coils and extending therebeyond toward each other on opposite sides of said rib, said sleeves having confronting terminations constituting abutments for said rib in two alternate positions of said armature in which said body closely adjoins the corresponding magnets; a pair of magnetically permeable end plates remote from said terminations forming part of a flux path from said magnets into said sleeves; an operating element connected with said armature for displacement thereby; and circuit means for the selective energization of either of said coils to reinforce temporarily the magnetic force of the respective magnet for attracting said armature toward same from a position adjacent the opposite magnet.