Magnetically coupled indicator means for control setting

Claim 1

In a magnetically coupled dial and pointer indicator adapted to reveal the rotary position of an instrument circuit control rotor concealed inside an instrument vessel mounted on a support and controlled in position by a rotatably adjustable shaft extending through a wall of the vessel, bar magnet means fixed on an end portion of said shaft, exteriorly of said vessel, said bar magnet means extending generally radially from opposite sides of said shaft and having outer extremities of respectively opposite polarity, said bar magnet means being configured and oriented to have a magnetic circuit producing a magnetic flux loop extending between said extremities and having an intermediate region thereof extending substantially unidirectionally transversely across the prolonged axis of said shaft, generally perpendicularly thereto, a non-magnetic indicator housing for said pointer indicator spacedly fixed with respect to said instrument vessel, with a back, and a transparent cover, said housing being positioned with its back facing said end portion of said shaft, said housing being so positioned relatively to said end portion of said shaft and said extremities of said bar magnet means that said intermediate region of said flux loop is substantially contained inside said housing, said pointer indicator comprising a longitudinally magnetized pointer in said housing, means on said housing mounting said pointer to rotate freely on an axis generally aligned with said shaft, and in a plane generally perpendicular to such axis, within said intermediate region of said flux loop, a fixed calibrated scale associated with said housing and cooperable with said pointer; and said pointer and housing having a passageway therethrough, aligned with said shaft, to provide for extending a tool therethrough to engage and rotate said shaft.