Print head for electrostatic printing

Abstract

Print head for electrostatic printing of documents in accordance with the so called aperture technique (DFC=Digital Control Filter) comprising means ( ) for charging toner particles ( ) with a certain polarity, a toner depositing matrix ( ), which is provided with a number of toner depositing apertures ( ), through which toner particles ( ) are able to pass, means ( ) for controlling the deposit of toner particles to certain predetermined deposit positions, and means for feeding a document ( ) to be printed below the toner deposit matrix ( ). The means for charging the toner particles ( ) with a certain polarity comprise two co-operating brushes, viz. a feeding brush ( ) and a flipping brush ( ) to bring the toner particles ( ) to be charged by the fibers rubbing against the toner particles, and a flipper blade ( ) is situated adjacent to the exit for the flipping brush ( ), which blade flips toner particles ( ) from the brush fibers ( ) so that there is created a cloud of charged toner particles ( ), which are attracted against the aperture matrix ( ) and by electric attraction are controlled by an individual blocking field ( ) for every aperture ( ) in the aperture matrix ( ), which blocking field is arranged to open and close, respectively, the toner deposit apertures ( ) individually in an electric manner.