Switchable permanent magnetic device

A switchable magnetic device comprising a housing, a first permanent magnet, a second permanent magnet, said first and second permanent magnets being essentially cylindrically shaped, said first and second permanent magnets being diametrically polarized, said first and second permanent magnets being mounted within the housing such that the first and second permanent magnets are rotatable relative to each other, and actuation means for causing relative rotation of the first and second permanent magnets, wherein said device presents a relatively strong external magnetic field when said first and second permanent magnets are positioned relative to each other such that a north and south poles of the first magnet are in substantial alignment with respective north and south poles of the second magnet, and the device presents a relatively weak external magnetic field when the first and second magnets are positioned relative to each other such that the north pole of the first magnet is in substantial alignment with the south pole of the second magnet and vice versa, wherein the housing comprises two pole pieces.

A switchable magnetic device of the kind including a housing, a first permanent magnet, a second permanent magnet, the first and second permanent magnets being mounted within the housing such that the first and second magnets are rotatable relative to each other, and actuation means for causing relative rotation of the first and second magnets, wherein in a “fully off” position the north pole of the first magnet is in substantial alignment with the south pole of the second magnet and vice versa such that the device presents a relatively weak external magnetic field and relative rotation of the magnets by 180° moves the magnet to a “fully on” position in which the north pole of the first magnet is positioned in alignment with the north pole of the second magnet such that the device presents a relatively strong external magnetic field, wherein a biasing means is operatively associated with said actuation means to bias said magnets away from the fully off position and wherein placing said device on or in close proximity to a ferromagnetic material causes the first and second magnets to switch to a relative orientation such that the device presents a relatively strong external magnetic field.

A switchable magnetic device of the kind including a housing, a first permanent magnet, a second permanent magnet, the first and second permanent magnets being mounted within the housing such that the first and second magnets are rotatable relative to each other, and actuation means for causing relative rotation of the first and second magnets wherein in a “fully off” position the north pole of the first magnet is in substantial alignment with the south pole of the second magnet and vice versa such that the device presents a relatively weak external magnetic field and relative rotation of the magnets by 180° moves the magnets to a “fully on” position in which the north pole of the first magnet is positioned in alignment with the north pole of the second magnet such that the device presents a relatively strong external magnetic field, characterized in that wherein said device further includes rotation limiting means preventing said magnets from reaching the “fully on” position.

A switchable magnetic device of the kind including a housing, a first permanent magnet, a second permanent magnet, the first and second permanent magnets being mounted within the housing such that the first and second magnets are rotatable relative to each other, and actuation means for causing relative rotation of the first and second magnets, wherein in a “fully off” position the north pole of the first magnet is in substantial alignment with the south pole of the second magnet and vice versa such that the device presents a relatively weak external magnetic field and relative rotation of the magnets by 180° moves the magnet to a “fully on” position in which the north pole of the first magnet is positioned in alignment with the north pole of the second magnet such that the device presents a relatively strong external magnetic field, wherein said actuation means includes a flexible portion that deforms if the actuation means is actuated in the absence of an external magnetic circuit to thereby limit relative rotation of said magnets, said flexible portion having sufficient yield strength to substantially avoid deformation during actuation of said actuation means in the presence of an external magnetic circuit.

A coupling comprising a first magnetic device and a second magnetic device, the first magnetic device being a switchable magnetic device comprising a first permanent magnet and a second permanent magnet, said first and second permanent magnets being movable relative to each other and actuation means for effecting relative movement between the first and second magnets wherein said first magnetic device presents a relatively strong external magnetic field when the first and second magnets are positioned relative to each other such that north and south poles of the first magnet are in substantial alignment with respective north and south poles of the second magnet and the first magnetic device presents a relatively weak external magnetic field when the north pole of the first magnet is in substantial alignment with the south pole of the second magnet and vice versa, said first magnetic device and said second magnetic device being arranged relative to each other such that said second magnetic device attracts the first magnetic device when the first magnetic device presents a relatively weak external magnetic field and said second magnetic device repels said first magnetic device when said first magnetic device presents a relatively strong external magnetic field.

A switchable magnetic device comprising a housing, a first permanent magnet, a second permanent magnet, said first and second permanent magnets being essentially cylindrically shaped, said first and second permanent magnets being diametrically polarized, said first and second permanent magnets being mounted within the housing such that the first and second permanent magnets are rotatable relative to each other, and actuation means for causing relative rotation of the first and second permanent magnets, wherein said device presents a relatively strong external magnetic field when said first and second permanent magnets are positioned relative to each other such that a north and south poles of the first magnet are in substantial alignment with respective north and south poles of the second magnet, and the device presents a relatively weak external magnetic field when the first and second magnets are positioned relative to each other such that the north pole of the first magnet is in substantial alignment with the south pole of the second magnet and vice versa, wherein the actuation means includes torque limiting means such that a torque in excess of a predetermined torque cannot be applied to the magnets to cause relative rotation thereof.