A paper feeding mechanism includes a feeding path, a driving motor, a bidirectional transmission mechanism, at least one feeding roller, a unidirectional transmission mechanism and at least one blocking roller. The driving motor is controllable to output a driving force towards a forward direction or a driving force towards a reverse direction. The bidirectional transmission mechanism is connected to the driving motor. The at least one feeding roller is mounted in the feeding path. The at least one feeding roller is connected to the bidirectional transmission mechanism. The unidirectional transmission mechanism is connected to the driving motor. The at least one blocking roller is mounted in the feeding path. The at least one blocking roller is disposed to a downstream of the at least one feeding roller. The at least one blocking roller is connected to the unidirectional transmission mechanism.

A paper feeding mechanism includes a feeding path, a driving motor, a bidirectional transmission mechanism, at least one feeding roller, a unidirectional transmission mechanism and at least one blocking roller. The driving motor is controllable to output a driving force towards a forward direction or a driving force towards a reverse direction. The bidirectional transmission mechanism is connected to the driving motor. The at least one feeding roller is mounted in the feeding path. The at least one feeding roller is connected to the bidirectional transmission mechanism. The unidirectional transmission mechanism is connected to the driving motor. The at least one blocking roller is mounted in the feeding path. The at least one blocking roller is disposed to a downstream of the at least one feeding roller. The at least one blocking roller is connected to the unidirectional transmission mechanism.

An image forming apparatus includes: a reconveying unit including a reconveying roller; and a second transmission mechanism. The second transmission mechanism transmits a drive force to the reconveying roller and includes: an input gear; an output gear; an intermediate gear including first and second gears; and first and second swinging gears. The first toothless part of the first gear and the second toothless part of the second gear are provided at such a position that, when the intermediate gear is rotated by a drive force transmitted from the input gear through the second swinging gear while the second swinging gear meshes with the second toothed part of the second gear and the output gear meshes with the first toothed part of the first gear, the first toothless part reaches a position confronting the output gear and then the second toothless part reaches a position confronting the second swinging gear.

A sheet transport device includes a transport roller, a drive source, and a gear train The transport roller transports a sheet. The gear train transmits rotating force from the drive source to the transport roller. The gear train includes a movable gear and a leaf spring. The movable gear is configured to move between a normal position where transmission of the rotating force to the transport roller is enabled, and a disengaged position where the transmission of the rotating force to the transport roller is interrupted, and also to move in an axial direction, and includes a helical gear that generates force to axially move in one direction, when the movable gear moves from the normal position to the disengaged position. The leaf spring buffers the movement of the movable gear in the one direction.

Provided is an image forming apparatus that together with being able to suppress rotation unevenness is capable of preventing unexpected downtime due to a broken belt. A guide member guides the swing of a swing gear on an arc that connects a first position where the swing gear is engaged with an idle gear, and a second position where the swing gear is not engaged with the idle gear. A transmission cutoff mechanism cuts off transmission of a drive force transmitted to a driven pulley via a belt to a driven shaft when a motor rotates in the reverse direction. A control unit, in a case where rotation unevenness meets a condition, causes the swing gear to swing to the first position by reverse rotation of the motor, which causes the drive force to be transmitted to the driven shaft.

A sheet transport device includes a transport roller, a drive source, and a gear train. The transport roller transports a sheet. The gear train transmits rotating force from the drive source to the transport roller. The gear train includes a movable gear and a leaf spring. The movable gear is configured to move between a normal position where transmission of the rotating force to the transport roller is enabled, and a disengaged position where the transmission of the rotating force to the transport roller is interrupted, and also to move in an axial direction, and includes a helical gear that generates force to axially move in one direction, when the movable gear moves from the normal position to the disengaged position. The leaf spring buffers the movement of the movable gear in the one direction.

A sheet conveyance device includes: a first conveyance path configured to allow a sheet to be conveyed along the first conveyance path; a second conveyance path that extends upward from a branch position in the first conveyance path; a third conveyance path that extends downward from the branch position; a first conveyance roller disposed in the second conveyance path and configured to rotate normally and reversely to convey the sheet; a first drive motor disposed below the branch position; and a first belt disposed in a drive transmission path from the first drive motor to the first conveyance roller and configured to transmit a driving force from the first drive motor to the first conveyance roller.

The invention which solves the relative speed problem between nips in a printing system is disclosed. The invention consists of a swing arm body that rotates about a pivot, an input drive gear, a forward swing arm gear, two reverse swing arm gears, a compound duplex drive gear, and a housing.

A sheet conveyance device includes: a first conveyance path configured to allow a sheet to be conveyed along the first conveyance path; a second conveyance path that extends upward from a branch position in the first conveyance path; a third conveyance path that extends downward from the branch position; a first conveyance roller disposed in the second conveyance path and configured to rotate normally and reversely to convey the sheet; a first drive motor disposed below the branch position; and a first belt disposed in a drive transmission path from the first drive motor to the first conveyance roller and configured to transmit a driving force from the first drive motor to the first conveyance roller.

Provided is an image forming apparatus that together with being able to suppress rotation unevenness is capable of preventing unexpected downtime due to a broken belt. A guide member guides the swing of a swing gear on an arc that connects a first position where the swing gear is engaged with an idle gear, and a second position where the swing gear is not engaged with the idle gear. A transmission cutoff mechanism cuts off transmission of a drive force transmitted to a driven pulley via a belt to a driven shaft when a motor rotates in the reverse direction. A control unit, in a case where rotation unevenness meets a condition, causes the swing gear to swing to the first position by reverse rotation of the motor, which causes the drive force to be transmitted to the driven shaft.