Magnetic brush developer system

Claim 2

Apparatus for applying dry toner to a moving surface bearing an electrostatic image comprising a trough for holding a mixture of dry toner and magnetic carrier particles, said trough having a wall extending upwardly and progressively closer to said image surface, said wall being a continuous extension of the bottom portion of said trough and said wall having its upper end portion curved in a direction toward said image bearing surface, and said trough being filled to a level insufficient to be in contact with said image bearing surface, means for providing a magnetic field outside of said trough, and means for moving said magnetic-field means upwardly parallel to said wall for lifting a quantity of said mixture from said trough and carryinG it upwardly along said wall into progressively closer contact with said image surface, said magnetic field means being oriented with flux lines thereof approximately normal to said image surface while said quantity of mixture is in contact with said image surface.

Claim 3

Apparatus as defined in claim 1 including means within said trough for permitting said quantity of mixture lifted from said trough by said magnetic-field means to pass upwardly along said wall from a position of rest near the bottom of said trough, and for thereafter causing said quantity of mixture to pass downwardly along a path diverging from said wall.

Claim 4

Apparatus for applying dry toner to a surface bearing an electrostatic image to develop the image comprising means for moving said surface past a developing station in a given direction with said surface exposed for receiving toner from below, a trough at said station for holding a mixture of dry toner and carrier particles, said particles being of magnetic material separated in the triboelectric series from said toner, said trough being positioned below said surface and having a wall extending upwardly and outwardly in a direction opposite the direction of motion of said surface, said wall converging at its upper end portion toward but never in contact with said surface, said trough being made of non-magnetic material, a mixture in said trough, said trough being filled with said mixture to a level insufficient to be in contact with said image bearing surface, means for providing a magnetic field outside of said trough, and means for moving said magnetic field means upwardly and outwardly along a path substantially parallel to said wall of said trough in a direction opposite the direction of motion of said surface with flux lines of said field passing through said wall approximately normal to said wall, to thereby move a quantity of said mixture upwards along said wall and against said surface.

Claim 5

Apparatus for applying dry toner to a surface bearing an electrostatic image to develop the image comprising means for moving said surface past a developing station in a given direction with said surface exposed for receiving toner from below, a trough at said station for holding a mixture of dry toner and carrier particles, said particles being of magnetic material separated in the triboelectric series from said toner, said trough being positioned below said surface and having a wall extending upwardly and outwardly in a direction opposite the direction of motion of said surface, said wall converging at its upper end portion toward but never in contact with said surface, said trough being made of non-magnetic material, a mixture in said trough, said trough being filled with said mixture to a level insufficient to be in contact with said image bearing surface, means for providing a magnetic field outside of said trough, and means for moving said magnetic field means upwardly and outwardly along a path substantially parallel to said wall of said trough in a direction opposite the direction of motion of said surface with flux lines of said field passing through said wall approximately normal to said wall, to thereby move a quantity of said mixture upwards along said wall and against said surface.

Claim 6

Apparatus as defined in claim 3 including a substantially flat and rigid sheet of non-magnetic material disposed between said wall and said image bearing surface, means for supporting said sheet for rotation about an axis parallel to said wall and to the bottom of said trough at a distance from said wall to function as a gate, said sheet having its upper edge above said axis, means for causing said sheet to rotate to a position which places its upper edge away from said wall to allow said quantity of mixture to be moved upwardly along said wall as said magnetic field producing means moves upwardly and outwardly along said path substantially parallel to said wall, and for causing said sheet to rotate back to a position which places its upper edge proximate said wall after said quantity of mixture has cleared said upper edge as it is moved upwardly, thereby causing said mixture to be returned to the bottom of said trough on a side of said trough remote from said wall after said image has been developed.

Claim 7

Apparatus as defined in claim 4 wherein said wall of said trough includes a first substantially flat portion extending from near the bottom of said trough to a point near said surface, and a second portion curved upwardly to cause said wall to converge toward said surface, and wherein said means for moving said magnetic field producing means comprises means for guiding said magnetic field producing means along said path substantially parallel to said flat portion of said wall, and drive means for moving said field producing means upwardly on said guiding means and then downardly on said guiding means in synchronism with said image surface moving means.

Claim 8

Apparatus as defined in claim 5 wherein said means for guiding said magnetic field producing means includes a portion at the upper end thereof for guiding said field producing means slightly away from said surface along a curved path, thereby causing said magnetic field producing means to orient the flux lines thereof, and thereby orient carrier pArticles of said mixture more nearly normal to said surface for optimum transfer of toner to said electrostatic image after said quantity has come in contact with said surface.

Claim 9

Apparatus as defined in claim 6 wherein said image surface moving means includes a motor and gear means for coupling said image surface to said motor, and wherein said drive means for moving said field producing means includes means connected to said gear means for converting rotary motion to reciprocating linear motion, and means for translating said linear motion to said field producing means.

Claim 10

Apparatus as defined in claim 4 wherein said wall of said trough extending upwardly and outwardly has a complex curvature including a first curvature from near the bottom of said trough to near said surface, said first curvature having a fixed radius from a point outside of said trough, and a second curvature extending upwardly from said first curvature, the direction of said second curvature being toward said surface, said second curvature thus causing said wall to converge toward said surface, and wherein said means for moving said magnetic field producing means comprises support bars pivoted at said point of said radius of said first curvature, drive means for swinging said bars to cause said magnetic field producing means to move upwardly in an arc along said first curvature and to a position past the end of said first curvature, and means for synchronizing said drive means with motion of said surface.

Claim 11

Apparatus as defined in claim 8 wherein said image surface is the surface of a cylinder, and motion of said surface is produced by a motor coupled to said cylinder by gear means, and wherein said drive means for swinging said bars is synchronized with said cylinder through said gear means.

Claim 12

Apparatus for applying dry toner to a moving surface bearing an electrostatic image comprising a trough for holding a mixture of dry toner and magnetic carrier particles, said trough having a wall extending upwardly and progressively closer to said image surface, said wall extending both upwardly and outwardly, and having a complex curvature including a first curvature having a fixed radius from a point outside of said trough, and a second curvature extending upwardly from said first curvature, the direction of said second curvature being opposite said first curvature, and said trough being filled to a level insufficient to be in contact with said image bearing surface, means for providing a magnetic field outside of said trough, and means for moving said magnetic-field means upwardly parallel to said wall for lifting a quantity of said mixture from said trough and carrying it upwardly along said wall into progressively closer contact with said image surface, said magnetic field means being oriented with flux lines thereof approximately normal to said image surface while said quantity of mixture is in contact with said image surface.

Claim 13

Apparatus for applying dry toner to a moving surface bearing an electrostatic image comprising a trough for holding a mixture of dry toner and magnetic carrier particles, said trough having a wall extending upwardly and progressively closer to said image surface, said wall extending both upwardly and outwardly, and having a complex curvature including a first curvature having a fixed radius from a point outside of said trough, and a second curvature extending upwardly from said first curvature, the direction of said second curvature being opposite said first curvature, and said trough being filled to a level insufficient to be in contact with said image bearing surface, means for providing a magnetic field outside of said trough, and means for moving said magnetic-field means upwardly parallel to said wall for lifting a quantity of said mixture from said trough and carrying it upwardly along said wall into progressively closer contact with said image surface, said magnetic field means being oriented with flux lines thereof approximately normal to said image surface while said quantity of mixture is in contact with said image surface.