Reservoir systems for administering multiple populations of particles

Various particle reservoir systems such as used in printing systems are described which utilize one or more traveling wave grids within a reservoir to selectively transport particles to a reservoir exit. The traveling wave grids serve to transport the particles by use of moving electrostatic fields that travel across the grids. The reservoir systems are adapted for use with a variety of print head configurations.

BACKGROUND

The present exemplary embodiment relates to the dispensing or administration of two or more populations of particles. It finds particular application in conjunction with the printing arts, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications such as the pharmaceutical processing of medication as in the “printing” of pills.

BRIEF DESCRIPTION

In accordance with one aspect of the present exemplary embodiment, a reservoir system adapted for use in a printing system is provided. The reservoir system comprises a reservoir body defining an interior hollow region adapted to store particles and a channel. The hollow region and the channel are in flow communication through a particle feed exit. The reservoir system also comprises a traveling wave grid assembly disposed within the interior hollow region. The traveling wave grid assembly is adapted to transport particles in the hollow region defined in the reservoir body to a location proximate the particle feed exit. The traveling wave grid assembly includes a non-planar traveling wave grid that serves to recirculate and provide a continuous, or nearly so, supply of particles to the location proximate the particle feed exit.

In accordance with another aspect of the present exemplary embodiment, a reservoir system is provided which is adapted for use in a printing system. The reservoir system comprises at least one member defining a hollow flow channel terminating at a channel exit. The reservoir system also comprises a collection of reservoir bodies, in which each reservoir body defines an interior hollow region adapted to store particles. The hollow region in the hollow flow channel are in flow communication through a particle feed exit. The reservoir system also comprises a collection of traveling wave grids. At least one of the collection of traveling wave grids is disposed within the interior hollow region of a corresponding reservoir body and positioned and configured to transport particles in the hollow region of the corresponding reservoir body to a location proximate the particle feed exit.

In accordance with yet another aspect of the present exemplary embodiment, a reservoir system adapted for use in a printing system is provided. The reservoir system comprises a collection of reservoir bodies, in which each body defines an interior hollow region adapted to store particles. The reservoir system also comprises a collection of corresponding gas channels. Each gas channel is dedicated to a respective reservoir body and in flow communication therewith through a particle feed exit. The reservoir system also comprises a collection of corresponding traveling wave grids. Each traveling wave grid is disposed in an interior hollow region defined within a respective reservoir body.

DETAILED DESCRIPTION

The exemplary embodiment provides systems and techniques for the storage, transport, and controlled distribution of small particles such as for example, toner particles. Although the exemplary embodiment is described in terms of the printing arts and transporting toner particles, it is to be understood that the exemplary embodiment includes other applications involving the storage, transport, or distribution of minute particles.

Several exemplary embodiment print head configurations are described herein. These print head configurations are particularly adapted for use in a powder ballistic aerosol marking (BAM) printer that can image onto an intermediate substrate or be used as a direct marking device. The exemplary embodiment print head configurations include single-shot color, two-shot color, and tandem color. A significant feature of the exemplary embodiment is the provision and incorporation of a multi-piece traveling wave grid for recirculating transport and cascade delivery of toner to one or more gating aperture arrays for on demand printing.

The term “traveling wave grid” as used herein collectively refers to a substrate, a plurality of traveling wave electrodes to which a voltage waveform is applied to generate the traveling wave(s), and one or more busses, vias, and electrical contact pads to distribute the electrical signals (or voltage potentials) throughout the grid. The term also collectively refers to one or more sources of electrical power, which provides the multi-phase electrical signal for operating the grid. The traveling wave grids may be in nearly any form, such as for example a flat planar form, or a non-planar form. Traveling wave grids, their use, and manufacture are generally described in U.S. Pat. Nos. 6,351,623; 6,290,342; 6,272,296; 6,246,855; 6,219,515; 6,137,979; 6,134,412; 5,893,015; and 4,896,174, all of which are hereby incorporated by reference.

Ballistic aerosol marking (BAM) is a technology being developed for high speed direct marking onto paper or onto an intermediate medium. BAM uses high-speed continuous gas jets to move small toner particles to the print medium. The toner is electrostatically gated on demand from apertures transverse to the gas channel. The print head is comprised of an array of individually controlled micro-channels, each of which is a Laval nozzle incorporating a Venturi structure (converging/diverging channel) to accelerate and focus the narrow gas jets. BAM is designed to be a true color CMYK printing system, whereby metered amounts of component colors for individual nozzles are injected on-demand into the jet stream at the same time to be conveyed to the print medium. A schematic of the process is shown inFIG. 1. Details and information relating to ballistic aerosol marking systems, components, and processes are described in the following U.S. Pat. Nos. 6,751,865; 6,719,399; 6,598,954; 6,523,928; 6,521,297; 6,511,149; 6,467,871; 6,467,862; 6,454,384; 6,439,711; 6,416,159; 6,416,158; 6,340,216; 6,328,409; 6,293,659; and 6,116,718; all of which are hereby incorporated by reference.

Specifically,FIG. 1illustrates a BAM printing apparatus100comprising a member110defining a hollow channel120. As noted, the channel120is in the form of a Laval type expansion pipe through which pressurized gas flows, as indicated by arrow140. The channel120includes a narrowed region130, which is upstream of one or more feed apertures described below. The channel120terminates at an exit150at which the exiting gas flow, indicated by arrow170, is discharged from the member110. The apparatus100further comprises one or more toner supply and administering devices designated for example as160a,160b,160c, and160dthrough which toner types C, M, Y, and K are administered, respectively. Referring to device160afor toner type C, for example, the toner is selectively delivered through a feed line162aand exits at a venturi toner feed or pressure forced feed exit164a. Control of toner through each of the devices160a,160b,160c, and160dcan be provided by an electrostatic toner gate. During operation of the apparatus100, a flow140of highly pressurized gas, for example CO2at 72 atmospheres, enters the channel120and specifically, the narrowed region130. Toner is entrained in the gas flow as the flow passes the various toner feed exits, for example164a. The pressure of the gas flow is reduced upon entering the expanded region of the channel120prior to the exit150. As the gas leaves the exit150, its pressure is for example, about 1 atmosphere. This is significant in that it results in the gas reaching its fully expanded volume. The exiting gas flow170is a focused, high velocity aerosol jet. Fusing of toner entrained in the flow can occur on impact with a substrate, such as180, or fusing may occur while toner is in flight.

Although a high pressure gas at 72 atmospheres is noted, the exemplary embodiment reservoir systems can utilize high pressure gas sources at pressures less than or greater than that noted.

This technology can utilize high viscosity inks to minimize inter-color bleed. Since it is designed as a single-pass print engine, there is no additional requirement for color registration. Images are formed when the individually controlled micro-channels combine to lay down the component image patterns. Although in theory toners may be designed for kinetic fusing on impact, a working compromise is to lower gas pressure and optimize toner morphology together with paper preheat or print medium surface treatments to minimize backscatter or bounce-back of the toner on impact.

Continuous line printing has been successfully demonstrated using an exemplary embodiment reservoir system. On demand gating into a 8× macro-channel and subsequent pixel printing has also been experimentally demonstrated using an exemplary embodiment reservoir system. In the latter, a re-circulating toner supply mechanism is fabricated using a traveling wave grid disposed on or about an Ultim roll for traveling wave transport and fluidization of the toner.FIG. 2shows a schematic view of a toner re-circulating flow cell200in accordance with the exemplary embodiment. Specifically, the cell200comprises a body or enclosure210for housing or otherwise retaining toner, designated as a toner sump220. The enclosure210also comprises an apertured plate230disposed along one of its faces. The cell additionally includes a member240, which in the exemplary embodiment depicted inFIG. 2is a cylindrical or roll member. The member240includes a region such as an outer circumferential surface about its periphery that includes a traveling wave grid250. The cell200also comprises, or can be adapted to interface with, a toner loading component260, such as a solenoid actuator that is configured to supply toner to the cell upon actuation of the solenoid. Upon operation of the cell200, the activation of the traveling wave grid250transports toner from the sump220toward the apertured plate230in the direction of arrow A, at which the toner can be withdrawn or otherwise deposited. Remaining toner on the grid250is returned as shown by arrow B to the sump220. The toner cloud resulting adjacent the traveling wave grid250in the cell200can be gated for example, using 2-φ voltage signals through electrodes providing 50 um apertures fabricated from a gold coated 2-mil Kapton film. The electrodes could be disposed in the plate230. A 4-phase circuit is used to drive the traveling wave. These parameters are representative in nature and variations can be utilized in the exemplary embodiment.

FIG. 3shows two cycles and representative voltage patterns for the traveling wave used in the exemplary embodiment. A 10 Hz wave frequency induces a toner wave velocity of 0.5 cm/s. The voltage pattern inFIG. 3was applied at a 90 degree phase separation, a percentage duty cycle (w/t) of 50%, a level of 400 V thereby producing a charge of −3.07 C, a density of 0.811 gm/cm3, and an electrode spacing of 2.9 μm. An experimental implementation has been demonstrated for three flow cells containing magenta (Majestyk), and black and cyan emulsion aggregation (EA) toner, all sharing a single traveling wave grid. Toner transport has been achieved on a non-planar traveling wave grid wrapped around an Ultim roll. Striations were observed of cyan EA toner on the conductive portions of the traveling wave grid, which is 8-mil pitch at 50% duty cycle. Additionally, gated toner was observed distributed around a 50 um aperture.

The incorporation of aperture arrays into flow cells enables the provision of print head architectures that may be suitable for a BAM printer. Various exemplary embodiments are described as follows: single-shot color, two-shot color, and tandem color.

An exemplary embodiment reservoir system for a single-shot color configuration is shown schematically inFIG. 4. In this embodiment, a single channel320utilizes four toner apertures, with two re-circulating toner cavities located on each side of the channel. Specifically,FIG. 4depicts a single-shot color print head300comprising a channel320in communication with a reservoir310a,310b,310c, and310d; and a toner feed exit312a,312b,312c, and312ddefined therein. Each of the feeds312a-dadminister toner to the channel320through which a stream of gas, designated by arrow A, flows. The channel320generally extends from a source of high pressure gas (not shown) to a channel exit322. The toner, carried or otherwise entrained in the flow A, is subsequently deposited on a print medium350, such as a drum or belt. Disposed within each reservoir is at least one traveling wave grid for transporting and in certain configurations, recirculating toner within the reservoir. The one or more traveling wave grids transport toner or other particulates from a hollow region within a reservoir to a location near a toner feed exit. For example, a first traveling wave grid314aand a second traveling wave grid316aare provided in reservoir310a. The first grid314atransports toner from a first region to a second region within the reservoir310a. The second grid316atransports toner within the reservoir310a, and ideally from the second region to the first region. During operation and transport of toner within a reservoir, a toner “cloud” typically forms in proximity to each grid, such as shown for example by clouds322aand324ainFIG. 4.

To accommodate this single-shot CMYK configuration, a channel length of about 4 mm is utilized. “Channel length” as described herein is generally the distance from the location in the channel at which toner feed is suitably mixed, to the substrate or surface to which the toner is applied. Referring toFIG. 5, a schematic of an alternate exemplary embodiment reservoir system for a single-shot print head400is shown. The print head400comprises a body405which defines a plurality of toner reservoirs such as reservoir410. A toner sump420is defined within the reservoir410. A traveling wave grid member430transports toner from the sump420to a channel440through which gas such as air flows. A source of high pressure445is provided upstream of the location in the channel440at which toner from a reservoir is fed. Toner exits the reservoir410through a feed412at which it enters the channel440. The toner is entrained or otherwise carried in the flowing gas stream in the channel440and subsequently deposited on a drum450. A time delay in aperture gating can be utilized to allow for color premixing within the channel. Therefore, a major advantage is that color registration is not a problem. The channel440can be oriented to print upwards, for example up to 30 degrees from vertical, as gravity may be a factor for toner cloud generation and thus transport of the toner along a traveling wave grid. Toner is electrostatically gated on-demand. The traveling wave grid430can be provided in two over-lapping sections. In such a multi-section configuration, unused toner falls back onto a lower grid to be transported back to an upper grid. Toner in the flow cell is refilled periodically from a main reservoir (not shown) using a controlled transport mechanism.

The channel through which a flowing gas or medium travels and entrains or otherwise receives particles such as toner, can be defined in the same member or body as is defined the hollow reservoir. Alternately, the channel can be defined in a separate component or body, apart from or different than the reservoir.

In a two-shot color print head configuration, a print head is utilized that corresponds to the single-shot color configuration previously described, but with two channels and one toner supply on each side of each channel. Each channel has two re-circulating toner cavities, with one on each side. Full color requires two channels or two passes. This configuration allows the use of 2 mm channel lengths, and half the number of high voltage drivers. The channel can be utilized to print upward, up to 30 degrees from vertical, as gravity may be a factor for toner cloud generation.

A portion of an exemplary embodiment reservoir system for a two-shot color configuration is shown schematically inFIG. 6. Referring toFIG. 6, one half of a two-shot color print head500is shown. The portion shown comprises one channel, having reservoirs510aand510b; and toner feed exits512aand512bdefined therein. The channel520extends from a source of high pressure gas (not shown) to a channel exit532. Each of the reservoirs include a toner supply cell with traveling wave grids for transporting toner from a sump to the feed exit. It will be understood that for full color, two of the assemblies shown inFIG. 6are utilized. Specifically, reservoir510aincludes a lower traveling wave grid514awhich transports toner to an upper traveling wave grid516a. Reservoir510bincludes a lower traveling wave grid514bwhich transports toner to an upper traveling wave grid516b. During operation of the grids, toner clouds522aand524areside on, and are generally transported on, grids514aand516a, respectively. Similarly, toner clouds522band524breside on, and are generally transported on, grids514band516b, respectively. Each of the feeds512aand512badminister toner to a channel520through which a stream of gas, designated by arrow A, flows. The toner, carried or otherwise entrained in the flow A, is deposited on a print medium550such as a drum or belt.

An exemplary embodiment reservoir system for a tandem color configuration is also provided. A tandem color configuration uses one re-circulating toner supply per channel, with one color per channel, and four tandem channels for single pass color.FIG. 7shows a quad print head arrangement. Time delay is incorporated into the gating to synchronize four color registration. Channel length may be 2 mm and the heads can print laterally or sideways. Referring toFIG. 7, a schematic of an alternate tandem color print head600is shown. The print head600comprises a body605which defines a plurality of toner reservoirs such as reservoir610. A toner sump620is defined within the reservoir610. A traveling wave guide member630transports toner from the sump620to a channel645through which gas such as air flows. A source of high pressure640is provided upstream of the location in the channel645at which toner from a reservoir is fed. The toner is entrained or otherwise carried in the flowing gas stream in the channel645and subsequently deposited on a drum650. Toner exits the channel645at exit or aperture612. The configuration of the other toner reservoirs generally corresponds to that of toner reservoir610.

FIG. 8is a more detailed view of an individual flow cell having upper fluidization and lower return traveling wave grids. Specifically,FIG. 8illustrates a print head700defining a reservoir710which defines a toner sump720. The print head700includes a body705, a channel745and pressure source740. Toner is delivered from the sump720via a traveling wave grid730to an exit712. Toner entrained in a flowing gas stream within the channel745is deposited upon a printing medium such as drum750. Specifically, the traveling wave grid730includes an upper toner delivery leg732and a lower toner return leg734.

In all of the exemplary embodiments described herein, a wide array of different configurations and arrangements of reservoir bodies, channels, high pressure gas sources, and traveling wave grids can be utilized. The systems described herein can employ one or more reservoirs in conjunction with a gas flow channel or member providing such. Alternately, each reservoir may be utilized with its own dedicated gas flow channel. Alternately, a plurality of sets of reservoirs and channels can be used. For example, two or more sets of a pair of reservoirs dedicated to a single channel can be used.FIG. 6illustrates a pair of reservoirs and a dedicated channel.

Generally, the exemplary embodiment traveling wave grid assemblies include a traveling wave grid that is non-planar. Examples of such geometry include but are not limited to arcuate, curved, or linearly alternating or stepped configurations. The non-planar grid is positioned within a reservoir such that upon operation of the grid, the grid serves to recirculate and provide a continuous supply of particulates or material to a desired location. A significant advantage of this configuration is that it can reduce, and in certain applications, entirely eliminate, mechanical moving parts, such as may otherwise be required.

Experiments with several planar and non-planar traveling wave grid arrangements have shown that toner re-circulating transport is possible for the designed flow cells. In addition, the electrostatic fields for transport of toner has been modeled and quantified. Electrodynamics of toner gating have also been modeled and optimized to successfully guide experiments.