Magnetic feed system for developer mix

A sumpless magnetic brush apparatus for mixing and applying developing material to electrostatic images in an electrostatic printing machine of the type utilizing a moving photoreceptor surface, comprising at least one magnetic developing brush roller with an internal magnetic means for establishing a north and south pole on an axis extending in a generally normal direction to a tangent plane at the intersection of said axis and the surface being developed, said pole at the surface being inboard, and the opposite pole being outboard, said roller having a periphery upon which bristles of magnetic developing material are adapted to be formed;

• a first mixer cylinder mounted adjacent to said brush roller with the axis thereof substantially parallel said brush roller, and with the surface thereof spaced from said brush roller a distance equal to the maximum depth of toner mix desired for said toner blanket;
• magnetic means for establishing a north and south pole in the first mixer cylinder with the poles positioned to place the pole of the first mixer cylinder which lies outboard and the outboard pole of the brush roller in the same polarity to thereby create a flux pattern dividing the flux of the mixer cylinder to create a projecting pattern of the roller pole and mixer cylinder outboard and a blanket flow pattern to the inboard pole of the brush roller;
• a second mixer cylinder mounted adjacent said first mixer cylinder, with means for establishing a north and south pole opposite to said first mixer cylinder with a flow flux pattern bridging the cylinders in a generally tangential direction;
• and
• means to turn said developer brush roller in a direction to impel toner mix from the mixer cylinders along said surface being developed, and the mixer cylinders in the opposite direction.