Capture of paper moisture for aquatron replenishment

Abstract: An apparatus, printing machine and method for replenishing an aquatron liquid reservoir in an aquatron charging device. The print media (e.g. paper, vellum, etc.) releases liquid from the print media during fusing. A condenser creates condensate from the liquid released by the print media which is collected in a conduit and transported using air flow into a collection container. This collection container can be the aquatron liquid reservoir, or a separate collection container that pumps liquid to the aquatron liquid reservoir, thus, enabling replenishing the liquid supply of the aquatron liquid reservoir within the printing machine. Sensing devices measuring liquid concentration resistance in the aquatron liquid reservoir and/or the collection container control the liquid level of the reservoir and/or collection container.

Description: BACKGROUND OF THE INVENTION This invention relates generally to an electrostatographic printer and copier, and more particularly, concerns an apparatus for enabling ion transfer via ionic conduction through an ionically conductive liquid, primarily for use in electrostatographic applications, for example, for charging an imaging member such as a photoreceptor or a dielectric charge receptor. SUMMARY OF THE INVENTION Briefly stated, and in accordance with one aspect of the present invention, there is provided an electrostatographic printing machine comprising an apparatus for replenishing an aquatron liquid reservoir according to claim 1. Pursuant to another aspect of the present invention, there is provided a method for replenishing an aquatron liquid reservoir in a printing machine, comprising the steps of: condensing liquid being released by a print media during fusing by a fuser in the printing machine; collecting the condensing liquid in a collection member; and determining resistance of a liquid concentration in the aquatron liquid reservoir. Other features of the present invention will become apparent as the following description proceeds and upon reference to the drawings, in which: Figure 1 is an elevational schematic view of water condensing for transferring moisture condensate from fused paper to an aquatron reservoir; Figure 2 is a magnification of 2 in Figure 1; Figure 3 is a schematic of a circuit for controlling pumping of liquid from the sump to the aquatron; Figure 4 is a schematic of a sensor/control circuit for sensing liquid supply and controlling pumping of liquid from the sump to the aquatron; and Figure 5 is a schematic elevational view showing an electrophotographic copier employing the features of the present invention. DETAILED DESCRIPTION OF THE INVENTION For a general understanding of the features of the present invention, reference is made to the drawings wherein like reference numerals have been used throughout to designate identical elements. Referring initially to Figure 5 prior to describing the invention in detail, a schematic depiction of the various components of an exemplary electrophotographic reproducing apparatus incorporating the fluid media charging structure of the present invention is provided. Although the apparatus of the present invention is particularly well adapted for use in an automatic electrophotographic reproducing machine, it will become apparent from the following discussion that the present fluid media charging structure is equally well suited for use in a wide variety of electrostatographic processing machines and is not necessarily limited in its application to the particular embodiment or embodiments shown herein. In particular, it should be noted that the charging apparatus of the present invention, described hereinafter with reference to an exemplary charging system, may also be used in a transfer, detack, or cleaning subsystem of a typical electrostatographic apparatus since such subsystems also require the use of a charging device. The exemplary electrophotographic reproducing apparatus of Figure 5 employs a drum 10 including a photoconductive surface 12 deposited on an electrically grounded conductive substrate 14. A motor (not shown) engages with drum 10 for rotating the drum 10 to advance successive portions of photoconductive surface 12 in the direction of arrow 16 through various processing stations disposed about the path of movement thereof, as will be described. Initially, a portion of drum 10 passes through charging station A. At charging station A, a charging structure in accordance with the present invention, indicated generally by reference numeral 20, charges the photoconductive surface 12 on drum 10 to a relatively high, substantially uniform potential. This charging device will be described in detail hereinbelow. Once charged, the photoconductive surface 12 is advanced to imaging station B where an original document (not shown) is exposed to a light source for forming a light image of the original document which is focused onto the charged portion of photoconductive surface 12 to selectively dissipate the charge thereon, thereby recording an electrostatic latent image corresponding to the original document onto drum 10. One skilled in the art will appreciate that a properly modulated scanning beam of energy (e.g., a laser beam) may be used to irradiate the charged portion of the photoconductive surface 12 for recording the latent image thereon. After the electrostatic latent image is recorded on photoconductive surface 12, drum 10 is advanced to development station C where a magnetic brush development system, indicated generally by the reference numeral 30, deposits developing material onto the electrostatic latent image. The magnetic brush development system 30 includes a single developer roller 32 disposed in developer housing 34. Toner particles are mixed with carrier beads in the developer housing 34, creating an electrostatic charge therebetween which causes the toner particles to cling to the carrier beads and form developing material. The developer roller 32 rotates to form a magnetic brush having carrier beads and toner particles magnetically attached thereto. As the magnetic brush rotates, developing material is brought into contact with the photoconductive surface 12 such that the latent image thereon attracts the toner particles of the developing material, forming a developed toner image on photoconductive surface 12. It will be understood by those skilled in the art that numerous types of development systems could be substituted for the magnetic brush development system shown herein. After the toner particles have been deposited onto the electrostatic latent image for development thereof, drum 10 advances the developed image to transfer station D, where a sheet of support material 42 is moved into contact with the developed toner image via a sheet feeding apparatus (not shown). The sheet of support material 42 is directed into contact with photoconductive surface 12 of drum 10 in a timed sequence so that the developed image thereon contacts the advancing sheet of support material 42 at transfer station D. A charging device 40 is provided for creating an electrostatic charge on the backside of sheet 42 to aid in inducing the transfer of toner from the developed image on photoconductive surface 12 to a support substrate 42 such as a sheet of paper. While a conventional coronode device is shown as charge generating device 40, it will be understood that the fluid media charging device of the present invention can be substituted for the corona generating device 40 for providing the electrostatic charge which induces toner transfer to the support substrate materials 42. The support material 42 is subsequently transported in the direction of arrow 44 for placement onto a conveyor (not shown) which advances the sheet to a fusing station 52 which permanently affixes the transferred image to the support material 42 creating a copy or print for subsequent removal of the finished copy by an operator. Invariably, after the support material 42 is separated from the photoconductive surface 12 of drum 10, some residual developing material remains adhered to the photoconductive surface 12. Thus, a final processing station, namely cleaning station E, is provided for removing residual toner particles from photoconductive surface 12 subsequent to separation of the support material 42 from drum 10. Cleaning station E can include various mechanisms, such as a simple blade 50, as shown, or a rotatably mounted fibrous brush (not shown) for physical engagement with photoconductive surface 12 to remove toner particles therefrom. Cleaning station E may also include a discharge lamp 52 for flooding the photoconductive surface 12 with light in order to dissipate any residual electrostatic charge remaining thereon in preparation for a subsequent imaging cycle. From US-A-5 510 879 it was known to reclaim developing liquid of the fuser for re-use. The foregoing description should be sufficient for purposes of the present application for patent to illustrate the general operation of an electrophotographic reproducing apparatus incorporating the features of the present invention. As described, an electrophotographic reproducing apparatus may take the form of any of several well known devices or systems. Variations of the specific electrostatographic processing subsystems or processes described herein may be expected without affecting the operation of the present invention. Liquid charging (e.g. aquatron, as described in US-A 5,510,879 to Facci et al.) is an ozone-free contact charging technique that is based on electrification of a water or other liquid moistened contact pad on the photoreceptor surface. Its advantage over other contact charging techniques in that it provides excellent charging uniformity over a wide range of process speeds, e.g. to at least 50 ips and is DC-only. It is nearly 100% efficient, operating at near theoretical voltage and current levels. During the fusing of xerographic imaging, paper is heated with the expulsion of water vapor into the machine. In the 3030 and 3050 Xerox engineering copiers the water released from the fusing step is condensed onto a cooling surface and collected in a gallon 1 gallon is about 4.55 liter sized container. In the present invention, a similar condenser is used in order to collect liquid condensate as the supply for an aquatron charging unit, as the liquid in the device is depleted. A commercially available pump and sensor arrangement can be used to indicate when the aquatron needs to be resupplied with liquid. One of the main objectives of charging with an aquatron (a water based liquid charging device) is the management of the water supply. Evaporation of liquid during "off" times (i.e. machine is non-operable) can be managed by containment of the liquid reservoir and sealing or covering of the exposed moist charging element (applicator) which contacts the surface during the charging step to prevent evaporation of the charging liquid. In practice, a minute quantity of liquid is transferred to the photoreceptor during charging. Also some evaporation from the exposed applicator surfaces during charging is also unavoidable. At an experimentally determined depletion rate of about 1 microliter per page, 100 cc of water is consumed per 100,000 copies. While the depletion of water can be maintained at this or a lower level, it would be desirable to replenish water from time to time in order to extend the life of the device, especially if the process were not obvious to the customer to avoid customer/user intervention. In certain applications it is undesirable to expect the customer to replenish the liquid supply either because of the inconvenience or added supplies cost. By using an inherent supply of liquid (e.g. water) in the printer/copier, namely the liquid (e.g. water) vapor which is released from paper during the fusing step, the inconvenience and added cost, mentioned above, are prevented. In some copiers, the quantity of liquid which is expelled from paper is substantial. In the 3030 and 3050 Xerox engineering copiers, a gallon sized container is provided to capture the moisture vapor which is condensed onto a cooling surface. The surfaces onto which the vapor condenses are at the nominal internal temperature of the machine (about 40°C) and are not intentionally cooled. In the present invention, the moist air in the vicinity of the fuser is directed against such a condensing surface described above, in order to collect the moisture escaping from paper during fusing into liquid. The liquid is then drained into a sump. A schematic diagram of the present invention is shown in Figure 1. An interesting advantage of this process is that it produces distilled liquid (e.g. water). Antibiotic, anti-fungal and other additives may be added to the liquid collection sump to keep the liquid free of organic growths and odors while in storage before dispensing to the aquatron. Figure 1 shows an elevational schematic of liquid condensing. In the present invention moisture condensate is transferred from fused paper 100 to an aquatron reservoir. A print media 100 passes in between a fuser roll 110 and a back up roll 120. The direction of motion of the print media 100 is shown by arrow 101. The liquid condensing apparatus of the present invention is indicated by the magnification circle referencing Figure 2. In Figure 2, air flow 160 occurs between the solid or hollow condenser block 140 and the liquid collection conduit or trough 150. The air flow 160 transports the condensate along the conduit 150 to a collection container or sump 180 (see Figure 3). Figure 3 shows a block diagram of an integrated system for sensing the need for liquid and transferring the moisture condensate from a collection vessel (sump) 180 to the aquatron reservoir 170 via an inexpensive pump 190 that is currently used in the Xerox 3050 engineering copier to pump silicone oil. (It is also noted that the collection vessel could also be the aquatron reservoir, thus, eliminating the cost of a separate collection vessel and the step of moving the liquid to the aquatron reservoir 170 from the collection vessel 180.) A sensor or series of sensors 200 based on the measurement of resistance is used to indicate when the liquid concentration in the reservoir 170 or at the applicator medium contacting the image receptor reaches some lower critical threshold. The pump 190 is triggered on when either a sensor located in the water reservoir 170 or on the applicator reads a resistance higher than a threshold resistance. Testing has found that a value of about 1-2 Megohms (MΩ) is a good threshold. A resistance higher than this value indicates the need for replenishment of the aquatron. A similar sensor located in the sump is used to confirm that water is present in the sump when needed. A high voltage DC power supply 210 can be used for this apparatus. This power supply provides the high voltage to charge the photoreceptor. In some cases it is neither an inconvenience nor an excessive expense to the customer to add liquid directly to the sump, i.e. an external reservoir. The system shown in Figure 3 automatically monitors the correct level or concentration of liquid in the internal aquatron reservoir, the resistance of the liquid applicator and the presence of liquid in the sump when needed. In addition, the aquatron can be miniaturized to fit into confined areas. In these situations the engine design of the printer/copier could take advantage of the small footprint capability of the aquatron. This arrangement likely requires a remotely located source of liquid. The sensing and pumping arrangement of Figure 3 could therefore be used to supply liquid as needed to a miniature aquatron. A sensor or series of sensors based on the measurement of resistance can be used to indicate when the liquid or fluid concentration in the reservoir or a moist wick (i.e. an open cell foam or a bundle of fibers loosely twisted, braided or woven cord, tape or tube that by capillary action draws up a steady supply of charging liquid to the charging unit) reaches some lower critical threshold. The sensor/control circuit shown in Figure 4 was tested. When the applicator medium, in this case PVA (poly vinyl alcohol) foam, dries to below a threshold water concentration, corresponding to a foam resistance of about 1 Megohm (MΩ), the pump is turned on and water (e.g. liquid) from the sump is pumped into the reservoir. A commercially available pump which is used to pump silicone oil in reprographic equipment is used. The threshold resistance of the sensor is controlled by resistor 1 (R1). The pumping rate (number of strokes per second) is controlled by resistor 2 (R2) and the stroke length (volume of water pumped per stroke) is controlled by resistor 3 (R3). A slow pumping rate is desirable so that the applicator has time to become rewet, but not overshoot the correct wetness. By placing additional sensors in series with different set points the circuit can be made to shut off the pump when the internal resistance of the reservoir reaches a lower threshold value of about 100 kilohms. A sensor may also signal that the storage capacity of the sump has reached a maximum and should be emptied. In recapitulation, the present invention utilizes a device for charging photoconductive imaging members by ionic conduction through a fluid media charging device called an aquatron. The aquatron fluid supply must be replenished when the fluid supply decreases. The print media releases liquid from the print media during fusing in the printing machine. A condenser creates condensate from this liquid which is collected in a conduit and transported using air flow into a collection container. This collection container can be the aquatron reservoir or a separate collection container that pumps liquid to the aquatron reservoir, thus, enabling replenishing of the liquid supply of the aquatron reservoir within the printing machine. Sensing devices measuring liquid concentration resistance in the aquatron reservoir and/or the collection container control the liquid level of the reservoir and/or collection container.

Claims: An electrostatographic printing machine comprising an apparatus for replenishing an aquatron liquid reservoir, comprising: a fuser (110, 120) for permanently affixing an image onto a print media; a condenser device (140) for condensing liquid released by the print media during fusing at said fuser; a collection member (180) for collecting the condensing liquid; and a measuring device (200) for determining resistance of a liquid concentration. An electrostatographic printing machine as recited in claim 1, wherein said condenser device comprises: a condensing member; a conduit device (150) located adjacent to said condensing member to enable capture of condensed liquid from said condensing member; and air flow (160) that occurs between said condensing member and said conduit device, said air flow containing the condensed liquid for transport to the collection member. An electrostatographic printing machine according to claim 1 or 2, wherein said collection member comprises the aquatron liquid reservoir (170). An electrostatographic printing machine according to any of the preceding claims, wherein said measuring device comprises a sensor. An electrostatographic printing machine according to claim 4, further comprising a pump (190) being connected to said collection member (180) to remove liquid therefrom, said pump being activated when said sensor reads a resistance higher than a threshold resistance. An electrostatographic printing machine according to the combination of claim 3 and 5, wherein said sensor being located in the aquatron liquid reservoir (170) determines when resistance of a liquid concentration therein reaches a lower critical threshold. An electrostatographic printing machine according to claim 5, wherein said sensor being located at an applicator medium contacting an image receptor for determining when resistance of a liquid concentration reaches a lower critical threshold. An electrostatographic printing machine according to any of the preceding claims, wherein said collection member comprises a sump. An electrostatographic printing machine according to any of the preceding claims 4 to 8, wherein said sensor includes: a first sensor for determining resistance of liquid concentration in the aquatron liquid reservoir; and a second sensor for determining resistance of liquid concentration in said sump. An electrostatographic printing machine according to a combination of claims 8 and 4, further comprising a pump being connected to said sump and the liquid aquatron to transport liquid to and from said sump and the liquid aquatron reservoir, said pump being activated when said sensor reads a resistance higher than a threshold resistance. A method for replenishing an aquatron liquid reservoir in an electrostatographic printing machine, comprising the steps of: condensing liquid being released by a print media (100) during fusing by a fuser in the printing machine; collecting the condensing liquid in a collection member (180); and determining resistance of a liquid concentration in the aquatron liquid reservoir. An electrostatographic printing machine, according to any of claims 1 to 10, further comprising: a charge retentive surface (12), capable of movement, advancing past a charging station (A) for charging of said charge retentive surface; an exposure station (B) through which said charge retentive surface moves, said charge retentive surface having charged portions being exposed to a scanning device that discharges said charge retentive surface forming a latent image thereon; a development station (C) advancing toner particles into contact with the latent image on said charge retentive surface as said charge retentive surface moves through said development station; a transfer station (D) advancing a print media (42) for transfer of the toner particles adhered to the latent image onto the print media, the toner particles of the latent image being permanently affixed to the print media via fusing of the latent image of toner particles to the print media; and a cleaning station (E) for removal of the toner particles remaining on said charge retentive surface after transfer.

Inventors: FACCI JOHN S, LEVY MICHAEL J, MAMMINO JOSEPH, FACCI, JOHN S., LEVY, MICHAEL J., MAMMINO, JOSEPH
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1999
Main classification: G03G15
IPC codes: G03G15