Image forming apparatus and cartridge

A cartridge for use in an image forming device including a belt unit including a looped belt that circularly moves, the looped belt having a first surface outside of the loop and a second surface inside of the loop, and being stretched to form a substantially straight portion on the loop that extends in a first direction;

• a plurality of photosensitive drums, each having a circumferential surface on which an electrostatic latent image is formable, each circumferential surface being opposed to the straight portion of the first surface, the plurality of photosensitive drums being held by the cartridge;
• a casing accommodating the belt unit and the plurality of photosensitive drums;
• and a first guide unit that guides the cartridge into a first predetermined position, the cartridge comprising:
• a cartridge body;
• and
• a first projection member that is guided by the first guide unit in order to guide the cartridge into a first predetermined position in the casing,
• wherein each circumferential surface of the plurality of photosensitive drums contacts the straight portion of the first surface when the cartridge is held at the first predetermined position, whereas each circumferential surface of the plurality of photosensitive drums moves apart from the straight portion of the first surface when the cartridge is detached from the first predetermined position.

A combination of a image forming device and a cartridge, wherein the image forming device comprises:

• a belt unit including a looped belt that circularly moves, the looped belt having a first surface outside of the loop and a second surface inside of the loop, and being stretched to form a substantially straight portion on the loop that extends in a first direction;
• a plurality of photosensitive drums, each having a circumferential surface on which an electrostatic latent image is formable, each circumferential surface being opposed to the straight portion of the first surface;
• a plurality of developing units disposed in one-to-one correspondence with the plurality of photosensitive drums, wherein each developing unit provides the circumferential surface of the corresponding photosensitive drum with developer in order to form a visible image thereon;
• a transfer unit opposed to the straight portion of the second surface, wherein the transfer unit transfers the visible image from the photosensitive drum into either the first surface of the looped belt or a recording medium mounted on the first surface;
• a casing accommodating the belt unit, the plurality of photosensitive drums, the plurality of developing units and the transfer unit, the casing having a base surface;
• a cartridge holding unit that holds the cartridge at a first predetermined position in the casing, wherein each circumferential surface of the plurality of photosensitive drums contacts the straight portion of the first surface when the cartridge is held by the cartridge holding unit at the first predetermined position;
• and
• a first guide unit that guides the cartridge into the first predetermined position, the first guide unit allowing the plurality of photosensitive drums to move apart from the straight portion of the first surface when the cartridge is detached from the first predetermined position, and
• wherein the cartridge comprising:
• a cartridge body;
• and
• a first projection member that is guided by the first guide unit in order to guide the cartridge into a first predetermined position in the casing,
• wherein each circumferential surface of the plurality of photosensitive drums contacts the straight portion of the first surface when the cartridge is held at the first predetermined position, whereas each circumferential surface of the plurality of photosensitive drums moves apart from the straight portion of the first surface when the cartridge is detached from the first predetermined position.