Developing device with retractable cutoff member

Claim 1

A developing device comprising: a developing sleeve rotatably provided in the vicinity of an electrostatic latent image support member; a supply means for supplying developer to the peripheral surface of said developing sleeve; a bristle height regulating member for regulating amount of the developer transported, according to rotation of said developing sleeve, on the peripheral surface of said developing sleeve towards a developing region where said developing sleeve confronts said electrostatic latent image support member; a removal means for removing from the peripheral surface of said developing sleeve the developer having passed through the developing region; a cutoff member for cutting off supply of the developer from said supply means to said developing sleeve, said cutoff member being so provided as to be retractably projected into a developer supply region defined between said developing sleeve and said supply means; and a magnet member which is fixedly provided in said developing sleeve and includes a developing magnetic pole confronting said electrostatic latent image support member, a first magnetic pole confronting said bristle height regulating member and a second magnetic pole confronting the developer supply region, said second magnetic pole having a polarity identical with that of said first magnetic pole such that the developer is continuously held in an erect state on said developing sleeve by said first and second magnetic poles.