An image forming apparatus includes a chassis having an opening, a cover, photosensitive members, an intermediate transfer belt, a primary-transfer member, a secondary-transfer roller, a cleaner device, an external-sheet inlet, a waste toner container, a connector, and a conveying roller, which is arranged within the feeding path to feed the recording sheet inserted through the external-sheet inlet in the feeding path. The conveying roller is mounted on the waste toner container and removable from the chassis along with the waste toner container.

A pressing device includes a cam member 120, a bearing 120a, a cam portion 120b, a cam engaging portion 120c of snap fit fashion. The bearing 102a is rotatably supported by a fixation frame 115. The cam portion 120b is provided on one side of the bearing 120a and contacts a pressing lever. The cam engaging portion 120c is provided on the other side of the bearing 120a and engages with a hole 123a formed on an outer surface of a cam shaft 123. The cam engaging portion 120c engages with the hole 123a at a position away from a maximum load portion of the cam portion 120b by not less than 90 degrees phase different.

An image forming apparatus includes, a main body of the image forming apparatus configured to form an image on a sheet, and provided with a stacking portion on which a sheet with an image formed thereon is stacked, a sheet conveyance device detachably attached to the stacking portion of the main body of the image forming apparatus, and provided with a conveyance path for conveying a sheet, a guide portion disposed in the sheet conveyance device, and configured to guide the conveyed sheet, a vertically extending wall portion disposed in the main body of the image forming apparatus, facing the stacking portion, and a restriction portion protruded from the wall portion, and configured to restrict a movement of the guide portion in a direction for opening the conveyance path.

A cleaning device includes a separation and contact mechanism that separates a web from a conveyance roller and brings the web into contact with the conveyance roller, and a controller. The controller includes a conveyed sheet number determination unit and a separation and contact control unit. The conveyed sheet number determination unit monitors a conveyed sheet number of both-surface image forming sheets where image forming processing is applied to both a first surface and a second surface with respect to the sheets conveyed by the conveyance roller, and determines whether or not a cumulative value of the conveyed sheet number has reached a predetermined threshold value. The separation and contact control unit controls the separation and contact mechanism so as to allow the web to be pressed to the conveyance roller by a pressing roller when the cumulative value of the conveyed sheet number has reached the threshold value.

A cleaning device includes a cleaning unit, a movement mechanism, and a positioning portion. The cleaning unit includes a cleaning part that has a contact surface extending along an axial direction of a conveyance roller and cleans the conveyance roller, and a cleaning housing that supports the cleaning part. The movement mechanism moves the cleaning unit between a cleaning position and a mounting and removing position. The movement mechanism allows the cleaning part to be brought into contact with the conveyance roller at the cleaning position, allows the cleaning part to be disposed below the conveyance roller in a separated manner at the mounting and removing position and allows the cleaning unit to be mounted on or removed from the apparatus body. The positioning portion restricts a relative position between the cleaning part and the conveyance roller by being brought into contact with the cleaning unit.

The cleaning device includes a cleaning unit. The cleaning unit includes a cleaning part having a contact surface brought into contact with a surface of a conveyance roller to clean the surface of the conveyance roller, and a housing that supports the cleaning part. The cleaning part includes a web of a strip shape, the web forming the contact surface that comes in contact with the conveyance roller, a pressing roller that presses the web against the conveyance roller, a feed-out roller that feeds out the web so as to cause a part of the web that comes in contact with the conveyance roller to shift, and a take-up roller that takes up the web. The housing has an opening that receives foreign matter dropping from the vicinity of a nip portion formed between the pressing roller and the conveyance roller.

A pressing device includes a cam member 120, a bearing 120a, a cam portion 120b, a cam engaging portion 120c of snap fit fashion. The bearing is rotatably supported by a fixing frame 115. The cam portion 120b is provided on one side of the bearing 120a and contacts a pressing lever. The cam engaging portion 120c is provided on the other side of the bearing 120a and engage with a hole 123a formed on the outer surface of a cam shaft 123. The cam engaging portion 120c engages with the hole 123a at a position away from maximum load portion of the cam portion 120b by not less than 90 degrees phase different.

An image forming apparatus includes an image forming unit, a storage portion to which a heating unit configured to heat the sheet stored in the storage portion is detachably attached, a conveyance unit, a detection unit configured to detect attachment of the heating unit to the storage portion, and a control unit configured to control the conveyance unit such that a standby time by which conveyance of the sheet fed from the storage portion is stopped is shorter when the detection unit detects the heating unit than when the detection unit does not detect the heating unit.

An image forming apparatus includes a chassis having an opening, a cover, photosensitive members, an intermediate transfer belt, a primary-transfer member, a secondary-transfer roller, a cleaner device, an external-sheet inlet, a waste toner container, a connector, and a conveying roller, which is arranged within the feeding path to feed the recording sheet inserted through the external-sheet inlet in the feeding path. The conveying roller is mounted on the waste toner container and removable from the chassis along with the waste toner container.

The invention provides a printing system and an extension unit that can transport media of any specified sizes appropriately.