Image forming apparatus having a toner recycling mechanism

An image forming apparatus having an electrostatic latent image support member rotatably mounted therein comprising:

• a developing unit accommodating developer for developing an electrostatic latent image formed on a surface of the electrostatic latent image support member;
• a cleaning unit for recovering developer remaining on the surface of the electrostatic latent image support member after development;
• a developer conveyor unit, connected to said developing unit and to said cleaning unit, for conveying the developer recovered by said cleaning unit to said developing unit, said developer conveyor unit including a conveyor pipe and a coil rotatably mounted therein;
• and
• a developer supply means, connected to said developer conveyor unit and to said developing unit, for supplying the developer from said developing unit to the recovered developer which is on the way to be conveyed to the developing unit.

An image forming apparatus having an electrostatic latent image support member rotatably mounted therein comprising:

• a developing unit accommodating developer for developing an electrostatic latent image formed on a surface of the electrostatic latent image support member;
• a cleaning unit for recovering developer remaining on the surface of the electrostatic latent image support member after development;
• a developer conveyor unit, connected to said developing unit and to said cleaning unit, for conveying the developer recovered by said cleaning unit to said developing unit, said developer conveyor unit including an impurity sorting unit for removing foreign substances contained in the developer recovered by said cleaning unit;
• and
• a developer supply means, connected to said developer conveyor unit and to said developing unit, for supplying the developer from said developing unit to the recovered developer which is on the way to be conveyed to the developing unit.

An image forming apparatus having an electrostatic latent image support member rotatably mounted therein comprising:

• a developing unit accommodating developer for developing an electrostatic latent image formed on a surface of the electrostatic latent image support member;
• a cleaning unit for recovering developer remaining on the surface of the electrostatic latent image support member after development;
• a developer conveyor unit, connected to said developing unit and to said cleaning unit, for conveying the developer recovered by said cleaning unit to said developing unit, said developer conveyor unit including an impurity sorting unit for removing foreign substances contained in the developer recovered by said cleaning unit;
• and
• a developer supply means, connected to said developer conveyor unit and to said developing unit, for supplying the developer from said developing unit to the recovered developer which is on the way to be conveyed to the developing unit;
• wherein said impurity sorting unit separates toner particles contained in the developer from foreign substances which have been charged so as to have a polarity opposite to the polarity of the toner particles by an application of a biasing voltage.

An image forming apparatus having an electrostatic latent image support member rotatably mounted therein comprising:

• a developing unit accommodating magnetic developer for developing an electrostatic latent image formed on a surface of the electrostatic latent image support member;
• a cleaning unit for recovering magnetic developer remaining on the surface of the electrostatic latent image support member after development;
• a developer conveyor unit, connected to said developing unit and to said cleaning unit, for conveying the magnetic developer recovered by said cleaning unit to said developing unit, said developer conveyor unit including an impurity sorting unit for removing foreign substances contained in the developer recovered by said cleaning unit;
• and
• a magnetic field generating means, disposed inwardly of a non-image region defined at one or more end portion of said electrostatic latent image support member, for generating a magnetic field to thereby magnetically hold the magnetic developer on the surface of said electrostatic latent image support member so that the magnetic developer is supplied from said developing unit to said cleaning unit.

An image forming apparatus having an electrostatic latent image support member rotatably mounted therein comprising:

• a developing unit accommodating magnetic developer for developing an electrostatic latent image formed on a surface of the electrostatic latent image support member;
• a cleaning unit for recovering magnetic developer remaining on the surface of the electrostatic latent image support member after development;
• a developer conveyor unit, connected to said developing unit and to said cleaning unit, for conveying the magnetic developer recovered by said cleaning unit to said developing unit;
• and
• a developer recycling unit comprising:
• a cylindrical recycling pipe;
• a magnetic sleeve having a plurality of belt-shaped magnetic poles extending along an outer peripheral surface of said recycling pipe;
• a developer supply pipe having one end connected to an upstream end of said recycling pipe in a direction of travel of the developer;
• a foreign substance discharge pipe having one end inserted into and connected to a downstream end of said recycling pipe in the direction of travel of the developer, an upper portion of said one end of said foreign substance discharge pipe being removed;
• a developer discharge portion formed at a portion of said downstream end of said recycling pipe;
• a developer conveyor means mounted in said developer supply pipe and said foreign substance discharge pipe;
• and a driving means for driving said magnetic sleeve.

An image forming apparatus having an electrostatic latent image support member rotatably mounted therein comprising:

• a developing unit accommodating magnetic developer for developing an electrostatic latent image formed on a surface of the electrostatic latent image support member;
• a cleaning unit for recovering magnetic developer remaining on the surface of the electrostatic latent image support member after development;
• a developer conveyor unit, connected to said developing unit and to said cleaning unit, for conveying the magnetic developer recovered by said cleaning unit to said developing unit;
• and
• a developer recycling unit comprising:
• a cylindrical recycling pipe;
• a magnetic sleeve having a plurality of belt-shaped magnetic poles spirally extending along an outer peripheral surface of said recycling pipe;
• a developer supply pipe having one end connected to an upstream end of said recycling pipe in a direction of travel of the developer;
• a foreign substance discharge pipe having one end inserted into and connected to a downstream end of said recycling pipe in the direction of travel of the developer, said one end of said foreign substance discharge pipe within said recycling pipe being spaced from an inner peripheral surface of said recycling pipe and an upper portion thereof being removed;
• a developer discharge portion formed at a portion of said downstream end of said recycling pipe;
• a developer conveyor means mounted in said developer supply pipe and said foreign substance discharge pipe;
• and a rotating means for rotating said magnetic sleeve, thereby rotating the developer supplied from said developer supply pipe along the inner peripheral surface of said recycling pipe and conveying the developer towards said foreign substance discharge pipe and said developer discharge portion.

In an image forming apparatus having a rotatable electrostatic latent image support member and a developing unit accommodating a magnetic developer to be supplied to an electrostatic latent image formed on a surface of said electrostatic latent image support member upon development, a method comprising the steps of:

• electrostatically holding the magnetic developer on an image region of the electrostatic latent image support member;
• magnetically holding the magnetic developer on a nonimage region of the electrostatic latent image support member;
• recovering the magnetic developer held on the image region of the support member and the developer held on the nonimage region of the support member after development;
• mixing the magnetic developer recovered from the image region of the support member and the magnetic developer recovered from the nonimage region of the support member;
• and
• resupplying the mixed developer to the developing unit.