Abstract: A printer employing a scanning electrostatic print head includes a sensor to determine dimensional variations in a printable dielectric material, such as paper, on which a latent electrostatic image is disposed. A charge deposition delay circuit is in electrical communication with the scanning print head which allows properly positioning the electrostatic image on the dielectric material to compensate for the dimensional variations.

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: A power module including an RC circuit is uniquely associated with each of a plurality of electrodes of an electrostatic print head to individually control the rate of charge decay of a voltage disposed thereon. The resistor of the RC circuit is a potentiometer that may be manually adjusted to obtain an optimal decay rate. A paper supply roller and take-up roller accurately position dielectric material, such as a paper web, adjacent to the electrodes of the print head, which is located between the rollers. The electrodes are typically a plurality of wires. The print head moves across the width of paper web to dispose thereon a plurality of charge areas corresponding to a strip of a latent image. Control circuitry synchronizes the movement of the print head and the web to produce a plurality of abutting strips of charge areas, producing a complete latent image.

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: A toning method for electrostatic printers and copiers where paper is wound on a supply roll and moved toward a takeup roll. After a latent image of a first color is written and the image area is wound toward a takeup roll, toner of a first color is applied while rewinding the image bearing web toward the supply roll. After the image area passes the writing head, the web is stopped and reversed so that a latent image corresponding to a second color may be written. Once the image region passes toning stations, the web is stopped and again reversed. During reverse direction travel of the image region, toner of a second color is applied and the image region is again wound on the supply roll. The process continues for toning all colors during the rewind operation. Although the image area may move at variable speeds during image writing, the image area is moved at constant speed in the reverse direction for toning.

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.