Developing chamber for electrostatic latent images

Claim 1

A developing chamber for electrostatic latent images provided with a device by which a developer consisting of electroscopic particles and a carrier material can be applied in the field of a magnet to a record carrier passed through the chamber, and can be carried along by the record carrier because of frictional forces, comprising: a magnet which produces a field; a chamber having walls comprising an electrically conductive material, and a rear wall portion comprising an electrically conductive material and having an inner surface, said rear wall portion being arranged such that a record carrier can be passed through said chamber along said surface through said magnet field, said magnet being external to the chamber; an auxiliary non-rotating electrode disposed in said chamber so as to extend across the entire width of a record carrier passing therethrough, said electrode being a slight distance from said record carrier such that developer between the electrode and the carrier is maintained at a same potential as developer in other parts of the chamber, and means for applying a bias voltage between said rear wall and said electrode, and for maintaining said chamber walls and said electrode at a same electric potential.