Electrographic apparatus, method and system employing image development adjustment

Claim 1

In electrographic apparatus of the type wherein an imaging member bearing an electrostatic image pattern to be developed is moved at a predetermined linear velocity through a development zone whereat developer is applied and which has a development system including: (a) a supply of dry developer mixture including electrically insulative toner marking particles and hard magnetic carrier particles, both of average particle size less than about 100μ; (b) a non-magnetic cylindrical shell that is rotatable on an axis for transporting said developer mixture between said supply and said development zone; (c) a magnetic core that includes a plurality of magnetic pole portions arranged around the core periphery in alternating magnetic polarity relation and is rotatable on an axis within said shell; and (d) means for rotating said shell and said core so that developer is transported through said development zone in a direction co-current with the imaging member direction and at an operative linear velocity that is generally equal to said imaging member's linear velocity, the improvement comprising: (e) development adjustment means for varying the rotational rate of said shell and said core cooperatively to adjust developed image density and/or contrast while maintaining said operative developer velocity and direction.

Claim 9

A method of developing an electrographic image member bearing an electrostatic image pattern, said method comprising: (a) moving said image member through a development zone at a predetermined linear velocity; and (b) transporting electrographic developer, including hard magnetic carrier particles and electrically insulative toner particles, through said development zone in developing relation with the charge pattern of such moving imaging member, by: (1) rotating a non-magnetic shell around a path, between a supply of such developer and said development zone; (2) rotating an alternating-pole magnetic core within said shell; (3) controlling the directions and speeds of said shell and core rotations so that developer flows through said development zone in a direction co-current with the direction of image member movement and at an operative linear velocity that is generally equal to the linear velocity of said image member; and (4) varying said shell and core speeds cooperatively to adjust developed image density and/or contrast while maintaining said operative developer velocity and direction.

Claim 10

A method of developing an electrographic image member bearing an electrostatic image pattern, said method comprising: (a) moving said image member through a development zone at a predetermined linear velocity; and (b) transporting electrographic developer, including hard magnetic carrier particles and electrically insulative toner particles, through said development zone in developing relation with the charge pattern of such moving imaging member, by: (1) rotating a non-magnetic shell around a path, between a supply of such developer and said development zone; (2) rotating an alternating-pole magnetic core within said shell; (3) controlling the directions and speeds of said shell and core rotations so that developer flows through said development zone in a direction co-current with the direction of image member movement and at an operative linear velocity that is generally equal to the linear velocity of said image member; and (4) varying said shell and core speeds cooperatively to adjust developed image density and/or contrast while maintaining said operative developer velocity and direction.