US 4,391,503 AGranted

Magnetic brush developer unit for photocopier

AssigneeGestetner Manufacturing Limited

InventorRobert J. Pugh

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Abstract

A magnetic brush developer unit has a toner sump below the level of the magnetic brush supporting roller-shell combination and a magnetic pump rotor rotatable in the bottom of the sump to agitate toner and to return toner to a location from which it is attracted onto the shell of the magnetic brush roller. A scraper blade is effective to remove substantially all the circulating brush-forming toner from the shell and to cause at least a part of the removed toner to fall into the sump to be pumped back up by the magnetic pump rotor. An optional second scraper blade, directed in the opposite direction from that of the first scraper blade, removes any lumps of agglomerated toner which may be moving countercurrent to the main magnetic brush-forming toner mass.

Claims9

Dependent claims

In a magnetic brush developer unit for a photocopier, comprising:

(a) a developer shell for supporting a magnetic brush of single component toner in use of the developer unit;
(b) a housing defining a sump below the level of said developer shell to contain toner for forming a magnetic brush of toner on said shell;
(c) aperture means to said housing defining a development zone at which the magnetic brush can project from the housing;
(d) a magnetic roller within the developer shell, setting up a magnetic field around the developer shell;
(e) means operable to drive at least one of the developer shell and the roller for rotation about a longitudinal axis;
(f) a scraper blade positioned in said housing and directed so as to remove toner from said developer shell after the toner has been carried past said development zone on the developer shell;
(g) a rotatable magnetic member positioned within the housing below the level of said developer shell;
and
(h) means for driving said rotatable magnetic member in use of the developer unit, for rotation to entrain toner received from said scraper blade;
the improvement wherein:
(i) said rotatable magnetic member includes magnet means for magnetically attracting and holding toner on a surface of said rotatable magnetic member so that a clump of loosely held toner is formed on the surface of said magnetic member, the clump being movable through said sump along a circular path in contact with the toner in said sump, to carry said toner upwardly to join a stream of toner being applied to said developer shell, said toner being conveyed to a location wherein the magnetic field around said developer shell magnetically attracts toner from exterior portions of the clump, thereby avoiding mechanical agitation and coagulation of said toner.

8 more elements

Dependencies are inferred from the claim text.