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US 4,067,296 AGranted
Magnetic roller
AssigneeOce-van der Grinten N.V.
InventorBernardus Wilhelmus L. M. Sessink
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AssigneeOce-van der Grinten N.V.
InventorBernardus Wilhelmus L. M. Sessink
Estimating the term…
A magnetic roller comprising a diamagnetic cylinder rotatable about magnets extending axially inside the cylinder is made to inhibit escape of magnetically attractable powder particles from the surface of the cylinder by providing the magnets, or a cylindrical magnet composed of several of them, with means which form in the magnetic field near each end of the cylinder a spirally extending bandlike field range which deviates in field strength from that existing in other regions of the cylinder surface. The bandlike ranges preferably have a reduced field strength and are formed by grooves made in the surface of the magnets and/or by applied strips of material having a greater magnetic permeability than air. They preferably extend from the extremities of the magnets spirally inward in the direction of the rotation of the cylinder, so that powder particles will be displaced inwardly from them as the cylinder rotates.
In a magnetic roller comprising a rotatable diamagnetic cylinder and magnet means inside the cylinder for generating a magnetic field throughout an elongate region extending axially of the cylinder over at least a part of its circumference, the improvement which comprises means associated with said magnet means for forming in said magnetic field near each extremity of said region a spirally extending bandlike field range in which the field stength at any point deviates from the field strength at any point lying on the same descriptive in the part of said region between the bandlike ranges.
In a magnetic roller comprising a rotatable cylinder of diamagnetic material and a cylindrical magnet extending axially inside said cylinder so as to generate a magnetic field about said cylinder, said magnet comprising a plurality of axially extending arcuate segments joined together and forming circumferentially of said magnet a series of permanently magnetized regions alternating in polarity, the improvement which comprises said magnet having in its outer surface near each extremity thereof a groove extending spirally inward in the direction of rotation of said cylinder, each said groove forming about the outer surface of said cylinder a spirally extending bandlike magnetic field range of reduced field strength whereby magnetically attractable particles at said cylinder surface will be attracted preferentially to regions of the cylinder surface inward of said grooves.
Dependencies are inferred from the claim text.