Abstract: The present application is directed to methods for transitioning between color printing and black-only printing in an image forming device. A cartridge is moved between a first position in which color printing may occur and a second position in which black-only printing may occur. In the first position, a color developer unit may be in contact with a color photoconductor unit. The color developer unit may be spaced from the color photoconductor unit in the second position. During the transition, a voltage supplied to the cartridge and a speed of a drive motor driving the cartridge may be adjusted.

Abstract: The present application is directed to methods for transitioning between color printing and black-only printing in an image forming device. A cartridge is moved between a first position in which color printing may occur and a second position in which black-only printing may occur. In the first position, a color developer unit may be in contact with a color photoconductor unit. The color developer unit may be spaced from the color photoconductor unit in the second position. During the transition, a voltage supplied to the cartridge and a speed of a drive motor driving the cartridge may be adjusted.

Abstract: The presence of a photoconductor drum in a laser printer may be determined by making electrical measurements without directly sensing drum presence. In some embodiments, this may be done without using any added printer components.

Abstract: Rubber charge roller cores are coated with loose particulate silicon carbide. Excess powder is removed, and the rollers are used in normal operation without an additional outer layer. Consistent, long-life operation of the charge roller is realized.

Abstract: An improved electrophotographic printer is provided in which the voltage applied to the charge roller is automatically adjusted to compensate for its changing characteristics over its life span. A high voltage DC power supply includes an output that is connected to the charge roller, and the input side of this high voltage DC power supply is controlled by a microprocessor of the print engine. The print engine controls the output voltage of the high voltage DC power supply by changing the duty cycle of the pulse-width modulated control signal that is supplied to the input of the high voltage DC power supply. A look-up table contains the correct duty cycle for the pulse-width modulated control signal with respect to the number of prints that have been made. The result of the inspection of the look-up table is used by the microprocessor of the print engine to control the correct duty cycle for the pulse-width modulated signal.

Abstract: A flexible doctor blade having a radiused surface or nub for contacting a developer roll. The blade geometry which includes a cantilevered support for the nub provides lower torque in the developer, compliance to compensate for developer imperfections, and less tendency for streaking due to toner packing and filming.

Abstract: A toner cartridge (1) has a cylindrical toner hopper (61) with a rear wall (61a) defining an output opening well above the lower part of the hopper. A paddle (63) is rotated in the hopper. The exit surface (61aaa) declines downward to form a chamber for the toner adder roller (45) and developer roller (43). This configuration discourages toner from returning to the hopper after it has been electrically charged.To improve movement of toner past the opening an agitator bar (65) extends across the cartridge near the exit surface. The bar is pivoted at both ends and has a portion (65a) which extends into the path of the paddle. As the paddle rotates, it moves the agitator upward until the curved paths of the two members reach separation, at which time the bar drops by gravity. The bar jars toner loose and eliminates jams of toner. The flat surface of the bar, when it has been moved up, partially blocks the exit opening, which desirably limits toner flow.