Abstract: A coupling apparatus capable of being connected by sliding and transferring power when being connected . The apparatus has a first coupler having a plurality of first ribs protruding at an outer circumference of a body at a regular interval and a second coupler having a connection portion to embrace and be separated from the body of the first coupler, and a plurality of second ribs protruding at an inner circumference of the connection portion, the plurality of second ribs being connected between the plurality of first ribs, wherein each of front ends of the first ribs and the second ribs have sloping sides sloped in a predetermined direction, and the first ribs include a rib having a relatively longer length than the other ribs.

Abstract: A developing device of an electrophotographic printer includes a power transmitting gear, which is meshed with a photosensitive drum gear and is connected to a developing roller through a belt, and an idler gear, which is provided between the power transmitting gear and a feeding roller gear, to indirectly transmit driving force from the photosensitive drum gear to the feeding roller and to the developing roller gear. Accordingly, a predetermined nip is maintained between the respective rollers of the developing device, and the rollers are operated at a constant velocity.

Abstract: There is provided a fixing device heat shield apparatus in a printer having a fixing device and a developing device. A plurality of air holes are formed on a side surface of a body frame of the printer over the fixing device, for discharging heated air to the outside of the printer, and a heat shielding plate is located between the fixing device and the developing device, for blocking heat transfer from the fixing device.