| 摘要 |
1,071,697. Rollers. KALLE A.G. Dec. 17, 1964 [Dec. 18, 1963], No. 51423/64. Heading F2U. [Also in Division G2] A magnetic roller, for use in developing electrostatic images, has pole shoes 1 of soft iron separated by strips 2 of non-magnetic material forming a tubular shell. A core formed by a round bar 3 of soft iron, has permanent magnets 4 magnetized, so that the poles facing the shell are of alternate N and S polarity, the magnets being spaced apart by non-magnetic material. The core is rotatable relatively to the shell. In the position shown, a permanent magnet is positioned under each shoe 1, such that the lines of force 6 extend outside the shoes, thereby attracting developer having a magnetic carrier. In the Fig. 2 (not shown) position, the magnets 4 are each opposite a strip 2 and the roller does not attract developer. The relative rotation between the core and shell may be effected automatically e.g. as a result of movement of an image carrying surface. In a modification, Fig. 3 (not shown) a curved sheet (12) of highly permeable metal is held in a fixed position, so that adjacent pole shoes are not magnetized. The cores may alternatively be formed by a sleeve (17), Fig. 4 (not shown) magnetized radially or by a rod (18), Fig. 5 (not shown) circumferentially magnetized.
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