Abstract: Pressure rolls useful in printing, embossing, coating, calendering, conveying, and fixing images to substrates. The pressure rolls comprise a cylindrical core provided with an array of axial slots, a heating element disposed in the slots, and a shell around the core. The pressure rolls may be employed in apparatus for fixing a toner material image pattern on a substrate such as a paper sheet. The pressure contact between the sheet and the pressure rolls is established by a hydrostatic assembly which may be pre-set.

Abstract: Pressure rolls useful in printing, embossing, coating, calendering, conveying, and fixing images to substrates. The pressure rolls are prepared by cryogenically cooling a core component to about the temperature of liquid nitrogen, removing the core component therefrom and inserting a sleeve component over the core component. The composite roll is allowed to warm to ambient temperature whereby during warming the core component thermally expands and secures the sleeve component to the core component. Also disclosed is apparatus and a method for fixing a toner material image pattern on a substrate such as a paper sheet.

Abstract: A magnetic brush developing system for electrostatic duplication uses a developer having a magnetic carrier and non-magnetic toner which is transferred by the brush to an electrostatic image. A analog signal is derived using a Hall sensor in contact with the brush and adjacent to a magnet of the brush. The location of the sensor after and downstream of the transfer point provides information in the signal both as to the absolute value of the concentration (ratio of toner to carrier by weight) as well as the rate of transfer of the toner to the electrostatic image. These signals are used to control the supplying of replenishment toner to the developer only when the concentration of toner drops below a predetermined desired value and then at a rate commensurate with the rate of transfer of toner to the electrostatic image.