Abstract: A latent electrostatic image developing device. A developer agitating/conveying mechanism is disposed in a development housing and has an agitating/conveying member for conveying a developer, while agitating it, along a developer application. A toner concentration detector is disposed in the bottom wall of the development housing to oppose the agitating/conveying member. The upper surface and the side surface of a detector portion of the toner concentration detector are connected by an arcuate surface or a chamfered surface. The toner concentration detector is fitted into an opening formed in the bottom wall of the development housing, and the upper surface of the detector portion protrudes from the inner surface of the bottom wall of the development housing by an amount nearly corresponding to the radius of the arcuate surface or the height of the chamfer of the chamfered surface.

Abstract: A developer agitating/conveying device having at least one partition wall disposed within a housing with a developer transfer port at the central portion thereof; a first agitating/conveying member disposed along the partition wall on one side of the partition wall for conveying the developer from the opposite end portions toward the central portion thereof, the first agitating/conveying member having a first helical blade and a second helical blade; and a second agitating/conveying member disposed along the partition wall on the other side of the partition wall for conveying the developer from the central portion toward the opposite end portions thereof, the second agitating/conveying member having a first helical blade and a second helical blade.

Abstract: A latent electrostatic image developing device using a developer including a toner and carrier particles has a development housing, in which an upstream agitating/conveying device, a midstream agitating/conveying device, and a downstream agitating/conveying device are disposed. The upstream agitating/conveying device conveys the developer from the central portion in the widthwise direction toward the opposite end portions in the widthwise direction while agitating it, the midstream agitating/conveying device conveys the developer from the opposite end portions in the widthwise direction toward the central portion in the widthwise direction while agitating it, and the downstream agitating/conveying device conveys the developer from the central portion in the widthwise direction toward the opposite end portions in the widthwise direction while agitating it.