An imaging system comprises a stirring-conveyance member to supply developer to a developing roller. The stirring-conveyance member includes a spiral structure to convey the developer and a reverse spiral structure disposed downstream the spiral structure in a conveying direction of the developer. The reverse spiral structure has a maximum outer diameter at an upstream end in the conveying direction and a minimum outer diameter at a downstream end in the conveying direction. The minimum outer diameter is approximately ⅗ or less, of the maximum outer diameter.

A powder supply device includes: a storage unit that stores a mixed agent including a functional material-containing powder and magnetic powder, the storage unit being provided with a discharge port through which a part of the stored mixed agent is discharged; a supply unit that holds the mixed agent and supplies the functional material-containing powder from the storage unit; and a magnetic body that covers at least a part of the discharge port and forms a nap of the mixed agent to prevent the mixed agent that is dispersed in air from flowing out through the discharge port.

A powder supply device includes: a storage unit that stores a mixed agent including a functional material-containing powder and magnetic powder, the storage unit being provided with a discharge port through which a part of the stored mixed agent is discharged; a supply unit that holds the mixed agent and supplies the functional material-containing powder from the storage unit; and a magnetic body that covers at least a part of the discharge port and forms a nap of the mixed agent to prevent the mixed agent that is dispersed in air from flowing out through the discharge port.

A developing device includes a developer bearer and a stirring conveyor. The stirring conveyor includes a first conveying chamber including a conveying member and a second conveying chamber to receive the developer from an end of the first conveying chamber. The conveying member includes a forward winding blade, a reverse winding blade, and a shaft portion on which the forward winding blade and the reverse winding blade are mounted with a space therebetween. A circumferential phase of the conveying member at a start position of the reverse winding blade is different from a circumferential phase of the conveying member at an end position of the forward winding blade. The conveying member is disposed in the first conveying chamber so that the space is opposite a portion at which the second conveying chamber receives the developer from the end of the first conveying chamber.

A developing device includes: a housing having a first transport path through which developer is supplied, a second transport path adjoining the first transport path with a first partition wall therebetween, and a first communication path communicating with the second transport path on a downstream side in a developer transport direction in the first transport path; a first transport member disposed in the first transport path and having an axially rotatable first rotary shaft and a first spiral blade projecting from an outer circumferential surface of the first rotary shaft; a second transport member disposed in the second transport path and having an axially rotatable second rotary shaft and a second spiral blade projecting from an outer circumferential surface of the second rotary shaft; and a first blade member projecting from the outer circumferential surface of the first rotary shaft, at a position facing the first communication path, the blade member discharging the developer onto the second transport path from above the first rotary shaft in the first transport path with the rotation of the first rotary shaft.

A developing device includes first and second chambers, a developing roller, first and second mixers, and one or more removable seals. The developing roller is in the first chamber. The first mixer is in the first chamber and configured convey developer in a first direction along a rotational axis of the developing roller. The second chamber is connected to the first chamber via a first port and a second port that are spaced apart from each other in the first direction. The second mixer is in the second chamber and configured to convey developer in a second direction opposite to the first direction. The one or more removable seals cover the first and second ports. A developer is contained in one of the first or second chambers. A developer discharge port is provided on the other one of the first or second chambers.

A transporting member includes a rotating shaft and plural helical blades that helically extend around the rotating shaft and that transport a transport object in a direction of the rotating shaft as the rotating shaft rotates, each helical blade including a downstream side surface at a downstream side in a transporting direction and an upstream side surface at a side opposite to the downstream side surface. A portion of at least one of the helical blades has a gap that enables the transport object to move in the direction of the rotating shaft, and the at least one of the helical blades includes an upstream section that extends upstream in a rotating-shaft rotation direction, in which the rotating shaft rotates, from the gap. The upstream section includes a portion in which an inclination angle of the downstream side surface is less than an inclination angle of the upstream side surface.

An image forming apparatus includes an insertable developing apparatus having a developer container, a developer discharging portion, and a shutter movably arranged between a closing position and an opening position. A first spring joins with the shutter and urges the shutter in an insertion direction in which the developing apparatus is inserted to the image forming apparatus so the shutter is maintained at the closing position, and a fixing member is detachably attached to the developing apparatus and fixes the shutter at the closing position. An attachment portion in the developing apparatus attaches to the fixing member, an engagement member engages with the shutter, and a second spring joins with the engagement member and urges the engagement member in a direction opposite to the insertion direction.

A developing device includes first and second chambers, a developing roller, first and second mixers, and one or more removable seals. The developing roller is in the first chamber. The first mixer is in the first chamber and configured convey developer in a first direction along a rotational axis of the developing roller. The second chamber is connected to the first chamber via a first port and a second port that are spaced apart from each other in in the first direction. The second mixer is in the second chamber and configured to perform convey developer in a second direction opposite to the first direction. The one or more removable seals cover the first and second ports. A developer is contained in one of the first or second chambers. A developer discharge port is provided on the other one of the first or second chambers.

A conveying screw configured to convey a toner in an axial direction includes a conveying shaft part and a conveying blade. The conveying shaft part is configured to be rotated around an axis. The conveying blade is spirally formed around an outer circumferential face of the conveying shaft part and configured to convey a toner in a replenishment path. At least one spiral of the conveying blade is formed by two semicircular blade plates which are coupled to in postures inclined in opposite directions to each other. A through hole through which the toner is passed in the axial direction is formed in an area surrounded by the conveying shaft part and the two blade plates.