| 摘要 |
A magnetic brush developing apparatus is described which comprises a vertically positioned magnetic supply roll, a similarly positioned magnetic developer roll, and supply means such as a hopper for supplying magnetically attractable developer particles to the lower portion of the supply roll. The supply roll is provided with a magnetization pattern in which the magnetic poles are arranged in helical bands with respect to the roll axis. The developer roll has a symmetric magnetization pattern in which the magnetic poles are arranged in straight linear bands parallel to the roll axis. Developer particles move circumferentially and vertically upward on the surface of the supply roll and are transferred to the surface of the developer roll across a narrow vertical gap separating the two rolls. A doctor blade associated with the supply roll returns excess developer from the supply roll to the hopper. A second doctor blade associated with the developer roll, and positioned in proximity to the gap separating the supply roll from the developer roll, removes excess developer from the developer roll and allows the developer so removed to be magnetically attracted back to the supply roll. The developer is thus continually recirculated between the supply roll and developer roll, and between the supply roll and the supply hopper, with the net amount of developer removed from the hopper being equal to the amount transferred to the recording medium by the developer roll.
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