Abstract: A simplified color printing system and method is disclosed in which the printing system has a single applicator that is supplied with toner fluids or inks of different colors. The printing system is simplified by having a single pump employed in association with the applicator. Use of a single pump is made possible, because during a color change the pump and applicator are purged with air both before and after a wash fluid is circulated. The single pump is used to pump both the imaging fluids and the air. The present invention has application in both color electrostatic printers and copiers, and in color ink-jet printers.

Abstract: A system and method for recovering charge-bearing solid pigment particles from a fluid dispersant in a liquid toner, wherein the system includes a particle-accumulating surface spaced apart from a complementary electrically biased electrode surface to define a channel therebetween. The channel has a mouth in gravity-feed relation to an outlet. Liquid toner is introduced at the mouth to cause flow within the channel. The bias of the electrode, however, sets up an electric field in the channel directing charge-bearing solid pigment particles away from the electrode surface so that only substantially particle-free fluid dispersant reaches the outlet. A slime rich in charge-bearing solid pigment particles collects on the particle-accumulation surface which is moved in a direction opposite of toner flow. At a location remote from the electrode, the solid pigment particles are removed from the particle-accumulating surface and are stored for later remixing with the fluid dispersant to form fresh toner.

Abstract: A writing apparatus for forming an electrostatic latent image on a charge-retentive image carrier in which the writing head is biased by a force so that the writing head tends to contact the image carrier, thereby blocking a gas opening operatively associated with the writing head. A stream of pressurized gas is projected from the gas opening and the escaping air provides a counterforce which moves the writing head away from the image carrier until an equilibrium position is reached in which the writing head is preferably spaced apart from the image carrier by a predetermined very small distance. Typically, the image carrier is a sheet of paper supported on a rotatable drum, but the image carrier may be paper drawn from a roll of paper and resiliently biased against the writing head. The latent image is written by a plurality of selectively energized charging elements that terminate at an outlet side of the writing head.

Abstract: A method of cleaning a circulation path of an image developing apparatus using liquid toners. Liquid dispersant is continuously circulated from its supply tank by a pump along lines to a toner applicator then back to the supply tank. Color concentrates containing charge bearing solid pigment particles are selectively injected and mixed with the dispersant by means of pumps or valves to form liquid toner only when developing a latent image is desired. When toner application is completed, the injection of color concentrate into the dispersant is stopped, and the liquid dispersant then automatically rinses the liquid toner out of the circulation path.

Abstract: A drying apparatus for printers and copiers using liquid developers or toners having an air bar which is resiliently biased into contact with a supported surface having a developed image. The air bar has an air-release side that includes a bearing surface and a wedge edge spaced apart from the bearing surface by a plenum slit. The release of pressurized gas, preferably air, through the plenum slit overcomes the bias of the air bar against the surface until an equilibrium position is reached wherein the air bar is spaced apart from the tensioned surface by a predetermined slight distance. Gas escaping between the bearing surface and tensioned surface acts as an air bearing, while the portion of the gas which escapes between the wedge edge and tensioned surface provides a high velocity shearing stress in a slug flow fluid low mode which removes the excess liquid from the tensioned surface. The escaping pressurized gas is then captured and recycled for return to the air bar.

Abstract: An electrostatic drum printer having a linear array of charging elements scanning a sheet of paper with a helical stripe pattern. The head is supported on a lead screw which advances the head as the drum rotates. The head writes an electrostatic latent image of digital words which visually appear as adjacent columns once the sheet is toned and laid flat. A toning shoe assembly is carried along with the head, with a single toning shoe, having a toner of a specified color, adjacent the head. When the head reaches the end of a scan, the head and shoe assembly is retracted for fly back to a starting position. A new toning shoe, having a toner of another color, may be indexed into position near the head. The retracted elements are pushed forward for starting another scan. With several scans, a color image may be recreated.

Abstract: A toning shoe for applying fluid developer to a latent image on a supported sheet. A drum is the preferred support, with the toning shoe having raised upstream and downstream support rims contacting the sheet, opposed lateral insulating rims spaced very slightly from the sheet and a recessed electrode further spaced from the sheet. Fluid developer is injected through a slit into the shoe, flows as a thin film between the electrode and the sheet and then passes through a drain for collecting and recycling. The shoe moves laterally as the drum rotates so that development occurs in a helical stripe pattern.

Abstract: A toner recycling system having separate supply tank of clear liquid dispersant and tanks of color concentrate. The liquid dispersant is continuously circulated from its supply tank by a pump along lines to a toner applictor then back to the supply tank. Color concentrate containing charge bearing solid pigment particles are selectively injected and mixed with the dispersant by means of pumps or valves to form liquid toner whenever developing a latent image is desired. The excess toner is collected and sent to a solids separator, either dedicated to a particular color of toner or common to all toners, where an electrically biased electrode repels the solid pigment particles toward a particle accumulating surface, thereby separating the particles from the dispersant. The dispersant is returned to the supply tank, while the particles which have accumulated on the surface of either a drum or belt as a layer of concentrate is scraped off by a blade and returned to the appropriate tank.

Abstract: A toning shoe for applying fluid developer to a latent image on a supported sheet. A drum is the preferred support, with the toning shoe having raised upstream and downstream support rims contacting the sheet, opposed lateral insulating rims spaced very slightly from the sheet or conducting rims contacting the sheet and a recessed multi-segmented electrode further spaced from the sheet. Fluid developer is injected through slits at leading edges of the electrode segments, flows as a thin film between the electrode segments and the sheet and then passes through drains at trailing edges of the electrode segments for collecting and recycling. The shoe moves laterally as the drum rotates so that development occurs in a helical stripe pattern.

Abstract: An electrostatic color printer method using a single toning shoe for successively and sequentially applying color liquid developers to a color latent image overlay to a sheet disposed against a rotating drum. An electrostatic head scans the sheet in a helical pattern of abutting stripes and forms the latent image on the sheet. A toning shoe assembly follows the head and applies one of the color developers to the sheet. A drain selector foot, pivotable beneath the toning shoe, brings an appropriate developer recycling tube into communication with a drain in the toning shoe assembly for returning used developer to the correct supply tank. After scanning the sheet, the toning shoe is rinsed with a solvent at a cleaning station past the end of the drum. The toning shoe has a plurality of pressure responsive reed valves, each communicating with one of a plurality of channels in the shoe for selecting sequential color developers until the entire image is toned in repeated passes of the single toning shoe.

Abstract: An electrostatic color picture having a single toning shoe for successively and sequentially applying color liquid developers to a color latent image overlay to a sheet disposed against a rotating drum. An electrostatic head scans the sheet in a helical pattern of abutting stripes and forms the latent image on the sheet. A toning shoe assembly follows the head and applies one of the color developers to the sheet. A drain selector foot, pivotable beneath the toning shoe, brings an appropriate developer recycling tube into communication with a drain in the toning shoe assembly for returning used developer to the correct supply tank. After scanning the sheet, the toning shoe is rinsed with a solvent at a cleaning station past the end of the drum. The toning shoe has a plurality of pressure responsive reed valves, each communicating with one of a plurality of channels in the shoe for selecting sequential color developers until the entire image is toned in repeated passes of the single toning shoe.

Abstract: A toner applicator assembly for electrostatic drum printers featuring a toning shoe with a biasing mechanism in which the toning shoe is biased only at a single point. The toning shoe scans a sheet having an electrostatic latent image supported on a rotating drum, in a helical path, and applies liquid developer to the sheet to develop the latent image. The toning shoe has a normal orientation which is skewed with respect to the drum's rotation axis so as to follow a helical path. The toning shoe is movable with respect to three degrees of freedom relative to the normal orientation so as to automatically adjust its orientation to match the orientation of the sheet. The biasing mechanism comprises a base fixed relative to the drum, a lever body pivotally mounted to the base, a pin mounted on an end of the lever body and engaging a detent in the back of the shoe, and a spring connected to both the base and the end of the lever body opposite from the pin.

Abstract: A toning shoe for applying fluid developer to a latent image on a supported sheet. A drum is a preferred support, with a toning shoe having raised edges, a central recessed area contacting the sheet and a drain. Fluid developer is injected into the shoe under pressure from an opening and flows to the drain, contacting the sheet between the opening and the drain, and then is collected and recycled back to the shoe. The shoe is moved laterally as the drum rotates so that development occurs in a stripe pattern.