Provided, in one aspect, is a downhole magnetic debris removal apparatus. The downhole magnetic debris removal apparatus, in one aspect, includes a housing having a longitudinal axis, and a plurality of magnets arranged as one or more Halbach arrays of magnets coupled to the housing, the one or more Halbach arrays of magnets having a strong side and a weak side.

A method and apparatus for operating a debris removal tool. In one embodiment, the tool includes a cover assembly having a plurality of covers spaced from one another along the length of the assembly creating a gap between adjacent covers. A carrier disposed within the cover assembly is axial movable relative thereto and has a plurality of magnet groups spaced from one another along its length. In an unactuated position of the tool, each of the plurality of magnet groups is under one of the plurality of covers and in an actuated position, each of the plurality of magnets is in a gap between covers.

A switchable permanent magnetic unit is disclosed. The unit comprises: a housing, first and second permanent magnets, and a conductive coil. The first magnet is mounted within the housing and the second magnet is rotatable between first and second positions and mounted within the housing in a stacked relationship with the first magnet. The unit generates a first level of magnetic flux at a workpiece contact interface when the second magnet is in the first position and a second level of magnetic flux at the interface when the second magnet is in the second position, the second level being greater than the first level. The conductive coil is arranged about the second magnet and generates a magnetic field. A component of the conductive coil's magnetic field is directed from S to N along the second magnet's N-S pole pair when the second magnet is in the first position.

A magnet chuck has a piston assembly including a tube shaped permanent magnet and a core yoke able to move on the interior of a cylinder tube. The permanent magnet is provided on the outer periphery of the core yoke, is magnetized in the radial direction, and a magnetic sensor is attached to the side surface of the cylinder tube.

A magnet has a circular cylinder or circular tube shape and contains magnetic crystal grains, wherein an orientation of magnetization of the magnet is in a direction perpendicular to an axis of the circular cylinder or the circular tube, and directions of axes of easy magnetization of the magnetic crystal grains are isotropic.

Magnetic coupling devices are disclosed having magnetic field sensors. The magnetic coupling device may include degaussing coils wrapped about pole extension shoes of the magnetic coupling device.

Magnetic coupling devices are disclosed which may be configured in at least three states. The various states may be provided through one or more of altering a position of a permanent magnet relative to another permanent magnet and altering a current level in a coil surrounding a permanent magnet.

Magnetic coupling devices are disclosed which may be configured in at least three states. The various states may be provided through one or more of altering a position of a permanent magnet relative to another permanent magnet and altering a current level in a coil surrounding a permanent magnet.

A device to attract and hold microscopic items such as micro LEDs magnetically rather than by static electricity includes a substrate and a plurality of magnetic units on a surface of the substrate. The magnetic units are spaced apart from each other and are constrained in the size and direction of their individual magnetic fields. Each of the magnetic units includes a magnet and a cladding layer partially covering the magnet. The cladding layer is made of a magnetic material. A side of the magnet away from the substrate is exposed from the cladding layer to attract and hold one micro LED.

An adsorption device includes a substrate, a plurality of magnetic films, and a plurality of magnets. The substrate defines a plurality of receiving grooves spaced apart from each other. Each receiving groove defines a bottom wall and a side wall. Each magnetic film is in one receiving groove and covers the bottom wall and the side wall. The magnetic films are made of magnetic material. Each magnet is in one receiving groove. Each magnetic film is between the substrate and one magnet, a large number of magnetized LEDs of very small size are attracted on a one-to-one basis to the receiving grooves for transfer and placement of the LEDs onto a display panel which is in the course of being manufactured.