Electromagnetic driving device with a movable permanent magnet

Claim 1

Electromagnetic driving device comprising a stator structure and a movable member including one or more parts magnetized perpendicularly to the direction of their movement, said magnetized part or parts being made from a material having a reversible permeability close to that of the air and having in the entire operating range a practically straight demagnetization characteristic and a straight recoil line practically coincident with this characteristic, said stator structure comprising at least one first magnetic circuit part made of a material of high magnetic permeability, said circuit part or parts having each two polar parts, said stator structure further comprising at least one electric energizing coil coupled with said first magnetic circuit part, the movable member or the stator structure comprising at least one second magnetic circuit part made of a material of high magnetic permeability and arranged so as to form with each of said polar parts an air-gap, all these air-gaps having the same substantially constant length measured perpendicularly to the faces of the polar parts, said first and second circuit parts forming together one or more closed magnetic circuits, the driving device being arranged so that said magnetized part or parts can move through said air-gaps, these magnetized parts having each a substantially constant length measured in the direction of magnetization, which length is shorter than the length of each air-gap by the mechanical clearance necessary to allow the movement of the movable member through said air-gaps, each magnetized part of the movable member having a width which does not exceed the sum of the width of a polar part and of the width of the space between the two polar parts of a same magnetic circuit, all these widths being measured in the direction of said movement, said magnetized parts of the movable member, in case said member comprises more than one of such parts, being all magnetized in the same direction, the material of the magnetized part or parts having a practically linear demagnetization characteristic up to temperatures at least equal to 100° C. and at least up to a negative value of the flux density substantially equal, in absolute value, to 0.5 times the remanence of said material, and said magnetic circuit or circuits and said magnetized part or parts being dimensioned so that the mean operating point of each magnetized part, in the absence of current in said coil or coils, lies at a flux density value smaller than 0.5 times the value of the remanence of said magnetic material.