Patent ID: 7103291
Filing Date: 2006-09-05
Classification: G03G

Abstract:
1. A printing device comprising: an electrostatic latent image forming unit that is configured to form an electrostatic latent image of an image to be printed; a developing unit that is configured to develop the electrostatic latent image formed by the electrostatic latent image forming unit using retaining toner while being supplied with toner; a toner concentration sensor that is configured to detect the concentration of the toner retained in the developing unit; a cartridge type toner supply unit detachably attached to the printing device, the toner supply unit comprising: a controller that is configured to selectively perform first and second operations based on the toner concentration detected by the toner concentration sensor, wherein the first operation includes driving the first toner supply mechanism to feed the toner stored in the first toner storage room to the developing unit, wherein second operation includes driving the second toner supply mechanism to feed the toner stored in the second toner storage room to the first toner storage room, and wherein the toner concentration sensor is disposed externally of the developing unit.