Abstract: A continuous purification method for removing neutral, as well as ionic, contaminants from liquid toner in an electrostatic printing system is disclosed. This method involves circulating liquid toner from a toner supply tank through a common volume which includes the toning applicator. The liquid toner is introduced to solid and ionic contaminants in the common volume and as the toner is circulated back to the toner supply tank for each toning pass, some contaminants and toner are left in the common volume. Next a wash fluid from a wash fluid supply tank is circulated through the common volume after each toning pass, the wash fluid mixing with the toner and the contaminants. This mixture is then passed through an electrophoretic purifier to remove the contaminants. Then the mixture passes through a porous particulate filter to remove any remaining contaminants before it returns back to the wash fluid supply tank.

Abstract: An electrostatic recorder or copier that includes a vise which provides a variable clamping force to a recording medium, thereby capable of squeezing it between an applicator and a backplate. The vise is an expandable bladder expanding and retracting in response to fluid pressure. In this manner, movement of the recording medium may be prevented while purging toner from the applicator. A cross member is provided that is spaced apart from the applicator and the bladder is attached to it. The bladder includes a metal surface, which faces the applicator, capable of conforming to the profile, or irregularities, of the toning surface. The metal surface may be connected as an electrically grounded electrode and may include a single sheet of thin metal or a plurality of segmented metal sheets or plates.

Abstract: An electrophoretic purifying system employing a gas/bubble filter is described, with the gas/bubble filter disposed in the path of a single phase liquid flow moving toward an electrophoretic purifier. The gas/bubble filter prevents bubbles, having a predetermined diameter, from entering the electrophoretic purifier. A rotating drum electrophoretic purifier is employed in which a rotating drum is in close proximity to a repelling electrode, defining a gap therebetween. The repelling electrode may be shaped as a cylindrical trough which houses an arcuate portion of the drum. Alternatively, the interior surface of the cylindrical trough may comprise of a repelling electrode. The gap is in fluid communication with a fluid outlet of a supply tank containing liquid having contaminants. The gas/bubble filter is disposed proximate to the fluid outlet, and the liquid flows therethrough to be purified.

Abstract: A dual separator purification system and method for removing particulate as well as ionic contaminants from liquids is disclosed. The present invention is particularly useful in the electrostatic printing industry. The system comprises two disparate separators connected in series. The first separator has a repelling electrode and a rotating drum which collects charged particulate contaminants and debris. A liquid such as spent liquid toner is passed through a gap between the repelling electrode and the rotating drum. The contaminants, including colored toner particles and paper debris, move electrophoretically through the gap and adhere to the rotating drum. Upward motion of the drum surface brings the accumulated deposit out of the gap region and to a scraper blade which removes the deposit from the drum for subsequent disposal. The partially purified liquid is collected and then passed through a second separator which has a spirally-wound laminate of porous and electrically conductive layers.

Abstract: An electrostatic recorder or copier having a toning shoe that includes a plurality of fluid supply channels in a bifurcation means for separating fluids, to avoid back pressure in the toning shoe. The bifurcation means substantially separates a flow of return air from a flow of return toner in the toning shoe by defining a plurality of fluid return channels. The electrostatic recorder or copier also includes a backing support spaced apart from the applicator so as to flexibly retain a recording medium in close proximity to a toning surface of the toning shoe.

Abstract: A method and apparatus for a continuous developing system for electrostatic printing in which a mixing means is disposed within a tank containing developer concentrate in order to maintain the concentrate in an homogenous solution. This mixing allows a concentration of dissolved charge agent in the concentrate to be greatly reduced, as the higher concentration of charge agent is no longer needed to prevent toner particles within the concentration from agglomerating. The lower concentration of charge agent facilitated by the concentrate mixing allows the concentrate to have a charge agent concentration as low as that favorable for the developing solution. The concentrate can therefore be combined with a carrier liquid to form a developer immediately before printing, rather than using premixed developer.

Abstract: An electrostatic color printer or copier having a single toner applicator with a system for continuous toner purification. The single applicator is used for each color sequentially and as toning of one color is completed a volume of spent or contaminated toner fluid is left behind in the applicator. This volume is removed with clean wash fluid and sent to a wash fluid tank. Dirty wash fluid is continuously purified either before or after return to a wash fluid supply tank. In the latter case, the wash fluid supply becomes contaminated but is purified as wash fluid is withdrawn or while still in the tank. Continuous purification of dirty wash fluid allows a small volume purifier to be used without need for spent toner disposal.

Abstract: An electrostatic color printer or copier having a print medium supplied from a supply roll to a takeup roll, requiring close registration for multiple printing passes over the same portion of the medium. The supply and takeup rolls are mounted in a closed housing which is airtight. The writing head and toner applicator are located in the housing. In another embodiment a limited air exchange capability through air filtration ports is provided, but the ports are shielded from the main housing for the medium so that air exchange near the print medium is limited.

Abstract: An apparatus for retaining a recording medium in close proximity to a toner applicator using a segmented backing support, wherein the backing support is comprised of several closely spaced backing segments. Each of the segments is elastically mounted above the recording medium such that the segments are pushed against the recording medium. The downward force exerted on the recording medium by the backing segments is sufficient to overcome the upward force generated on the recording medium by air and toner expelled from the surface of the toner applicator. As a result, the recording medium is kept close enough to the toner applicator such that air does not leak excessively from between the toner applicator and the recording medium. A plurality of the backing segments are arranged closely together such that the recording medium is pressed against the toner applicator along the entire surface of the toner applicator.

Abstract: In electrostatic liquid toning, an apparatus for removing excess liquid toner from a recording medium using an air knife integrated with a toner applicator into a single mechanical structure. The toner applicator contains a toning channel and an air channel adjacent to a toner drain channel. The recording medium carrying a latent electrostatic image is directed past the toning channel in the toner applicator. The toning channel in the applicator contains toner and is in fluid communication with the recording medium. Air under pressure is expelled through the air channel and against the recording medium such that excess toner deposited onto the surface of the recording medium is directed into the toner drain channel.

Abstract: A method and apparatus for applying liquid toner to a recording medium using a toner applicator, wherein the applicator contains a channel for toner flow peripherally surrounded by an air channel. The recording medium carrying a latent electrostatic image is directed past the channel in the toner applicator. The channel in the applicator contains toner and is in fluid communication with the recording medium. Air under pressure is introduced into the air channel surrounding the toning channel thus providing a barrier around the toning channel, such that the toner is confined within the channel, thereby preventing unwanted leakage of liquid toner from the channel.

Abstract: An electrostatic color printer or copier which uses a single pump for controlling fluid toner at low flow velocities and a separate pump or blower for an air jet used to expel fluid from common passages between applications of different colors. A full width toning applicator admits toner and air in a manner so that air limits flow of toner beyond the applicator. During a purging cycle, more air is admitted, forming an air jet which blasts surfaces and passages clear of liquid.

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.