Developer supply apparatus for a wet electrographic printer

Abstract: A developer supplying apparatus for a wet electrographic printer, including a reservoir (40) for storing a developer obtained by mixing a liquid carrier with an ink and a process tank (50) for storing the developer drained from the reservoir (40) through a developer draining path to enable accurate control of the level and concentration of the developer in the reservoir (40). The developer supply apparatus also includes a carrier cartridge (10) for supplying the liquid carrier to the reservoir through the carrier supplying path, an ink cartridge (20) for supplying the ink to the reservoir through an ink supplying path, and a developing unit (30) for receiving the developer of the reservoir through the developer supplying path to develop an electrostatic latent image.

Description: The present invention relates to a wet electrographic printer, and more particularly, to a developer supply apparatus for a wet electrographic printer, capable of controlling the concentration and level of the developer. US-A-3,789,794 discloses an apparatus for developing electrostatic images which includes means to recirculate developer comprising a diluent carrier and a tacky toner, between a developer supply tank and a developer station. In general, a wet electrographic printer is an apparatus for developing an electrostatic latent image, formed on a photosensitive medium such as a photosensitive belt, with a developer of a predetermined color and transferring the developed image to then print a desired image on a substrate such as a paper sheet. The wet electrographic printer includes a developing unit for developing an image by supplying the developer to the photosensitive medium, and a developer supply apparatus for constantly supplying developer of a predetermined density to the developing unit. The developer is a mixture of a condensed ink, containing a powdery toner, with a liquid carrier, in which the toner is diluted to approximately 2 - 4 wt%. Hereinafter, the concentration of the developer is defined by the wt% of toner. Meanwhile, the developer supply apparatus includes an ink cartridge for storing the condensed ink, a carrier cartridge for storing the liquid carrier, and a reservoir for storing the developer obtained by mixing the condensed ink with the liquid carrier at a predetermined ratio. Also, agitators for preventing the toner from settling out of the solution may be installed in the ink cartridge and the reservoir. In such a developer supply apparatus, the amount of developer stored in the reservoir is reduced by the amount used to develop the electrostatic latent image of the photosensitive medium, so that the condensed ink and the liquid carrier must be supplied to the reservoir to maintain the developer at a constant concentration. Also, it is desired to maintain the level of developer stored in the reservoir at a constant level. The consumption of toner and liquid carrier may vary according to the images to be printed. That is, more liquid carrier than toner is consumed to print a simple image or a small image, and more toner than liquid carrier is required to print a complicated image. Thus, in order to maintain the concentration of the developer at the predetermined concentration, it is necessary to appropriately supply the toner and the developer to the reservoir in accordance with the consumption of the toner and the liquid carrier. The known developer supply apparatus cannot control both the concentration of the developer stored in the reservoir and the level thereof. That is, if a lot of the liquid carrier is supplied to maintain a predetermined concentration of the developer in the reservoir, the level of the developer changes and thus undesired operating conditions may develop. On the other hand, if the level of the developer is controlled, the concentration of the developer may not be maintained at a constant level. It is an aim of the present invention to provide a developer supply apparatus for a wet electrographic printer, capable of properly controlling the concentration and level of the developer. According to the present invention there is provided a developer supply apparatus for a wet electrographic printer as set forth in claim 1 appended hereto. In a preferred aspect of the present invention the developer supply apparatus has a reservoir for storing developer and is characterised by a process tank for receiving developer drained from the reservoir through a developer draining path. Further preferred features of the present invention will be apparent from the claims appended hereto and the following description. For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic diagram of a developer supply apparatus of a wet electrographic printer employing a developer supply method according to an embodiment of the present invention; Figure 2 is a flowchart of a developer supply method according to an embodiment of the present invention; Figure 3 is a schematic diagram of a developer supply apparatus of a wet electrographic printer employing a developer supply method according to another embodiment of the present invention; and Referring to Figure 1, showing the structure of a developer supply apparatus of a wet electrographic printer according to an embodiment of the present invention, liquid carrier is stored in a carrier cartridge 10, and condensed ink is stored in an ink cartridge 20. The carrier cartridge 10 and the ink cartridge 20 are suitably replaceable. The carrier cartridge 10 and the ink cartridge 20 are connected to a first valve 53 such as a solenoid two-way valve through a carrier supply path 11 and an ink supply path 21 respectively. The first valve 53 selectively opens and closes the carrier supply path 11 and the ink supply path 21, so that ink and liquid carrier are supplied to a reservoir 40 through an ink/carrier supply path 54 by the driving force of a first pump 55. A level sensor 42 for sensing the level of the developer in the reservoir 40, and a concentration sensor 44 for sensing the concentration thereof, are installed in the reservoir 40. The reservoir 40 supplies the developer obtained by mixing the ink with the liquid carrier to a developing unit 30 through a developer supply path 34 by the driving force of a second pump 32. The developing unit 30 develops an electrostatic latent image formed on a photosensitive belt 70 using the developer supplied from the reservoir 40. A second valve 33 such as a solenoid two-way valve is installed in the developer supply path 34, and the second valve 33 selectively blocks the developer supply path 34 and a developer drain path 35, to direct the developer to the developer unit 30 and a process tank 50 through the developer supply path 34 and the developer drain path 35, respectively. Reference numeral 60 denotes a drying unit for recovering liquid carrier adhering to the electrostatic latent image of the photosensitive belt 70, where the collected liquid carrier returns to the carrier cartridge 10 along a collection pipe 61. The operation of the developer supply apparatus having the above structure will be described as follows. When the power of a printer is turned on, the liquid carrier and ink are supplied to the reservoir 40. That is, the first valve 53 selectively opens the ink supply path 21 and the carrier supply path 11 to supply ink and liquid carrier from the ink cartridge 20 and the carrier cartridge 10 to the reservoir 40 through the ink/carrier supply path 54. The supplied ink and liquid carrier are mixed to be useable for printing, with the developer having a predetermined concentration and level. The developer in the reservoir 40 is supplied to the developing unit 30 along the developer supply path 34 by the driving force of the second pump 32. At this time, the developer drain path 35 is closed by the second valve 33. Thus, the electrostatic latent image formed on the photosensitive belt 70 is developed using the supplied developer. At this time, excess developer supplied to the photosensitive belt 70 is eliminated by collection means such as a squeegee roller (not shown), to be collected in the reservoir 40 through the path 31. Where the amount of consumed ink is different from that of consumed carrier due to the above-described printing conditions during printing, the concentration of the developer collected through the path 31 may be different from that of the developer supplied through the developer supply path 34, so that the concentration of the developer stored in the reservoir 40 changes. Here, a concentration sensor 44 senses and measures the abnormal concentration of the developer to transmit a sensing signal to a controller (not shown). The controller stops the printing according to the sensing signal, and operates the second valve 33 to block the developer supply path 34 and open the developer drain path 35. Thus, the developer in the reservoir is drained to the process tank 50 by the second pump 32. This ensures sufficient room in the reservoir 40 into which to supply new ink and liquid carrier. The amount of developer drained from the reservoir (40) is appropriately controlled. Subsequently, the first valve 53 operates to supply liquid carrier and/or ink to the reservoir 40 such that the developer reaches an appropriate level and concentration. According to the above apparatus, if the concentration or level of the developer are inappropriate, the developer in the reservoir 40 is partially drained to the process tank 50, to thereby ensure sufficient room for supplying new ink and liquid carrier. Thus, the concentration and level of the developer can be relatively easily controlled. The structure of the developer supplying apparatus according to another embodiment of the present invention is shown in Figure 2. The same reference numerals represent the same elements having the same functions as those shown in Figure 1. According to the second embodiment, the process tank 50 is connected to a third valve 53a such as a solenoid three-way valve by a recycle path 51. Thus, the developer in the process tank 50 is supplied to the reservoir 40 by the recycle path 51 and the third valve 53a, to be reused. A concentration sensor 56 installed in the process tank 50 measures the concentration of the developer in the process tank 50 to determine the amount of developer to be supplied to the reservoir 40. In the operation of the developer supplying apparatus according to the second embodiment of the present invention, if the developer of a predetermined level drained from the reservoir 40 is stored in the process tank 50, the concentration of the developer is measured by the concentration sensor 56, and thus an information signal thereof is transferred to the controller (not shown). Subsequently, the controller drives the third valve 53a and this selectively opens a carrier supplying path 11, an ink supplying path 21 and the recycle path 51, to thereby supply the developer in the process tank 50 together with the liquid carrier and the ink to the reservoir 40. At this time, the controller appropriately controls the amount of the ink and the liquid carrier supplied according to the concentration information of the transferred developer, to thereby maintain the final developer in the reservoir 40 at an appropriate concentration and level. The structure of the developing supplying apparatus according to the third embodiment of the present invention is shown in Figure 3. The same reference numerals and the same elements indicate the same members having the same functions shown in Figures 1 and 2. According to the third embodiment of the present invention, when the used-up ink cartridge 20 is replaced with a new one, the developer containing undesired impurities in the reservoir 40 and the developing unit 30 can be drained to the used-up ink cartridge 20 to be thereby discarded together with the used-up ink cartridge 20. That is, the ink cartridge 20 is connected to a fourth valve 33a such as the solenoid three-way valve via a developer removing path 36. The fourth valve 33a selectively opens and closes a developer supplying path 34, a developer draining path 35 and a developer removing path 36. A level sensor 22 is installed in the ink cartridge 20, which detects whether the ink in the ink cartridge 20 is used up. If the ink in the ink cartridge 20 is used up during printing, a signal from the level sensor 22 is transmitted to the controller (not shown). Then, the controller temporarily stops the printing, and operates the fourth valve 33a to block the developer supplying path 34 and the developer draining path 35 and open the developer removing path 36. Thus, the developer stored in the reservoir 40 is drained to the ink cartridge 20 through the developer removing path 36. Also, in order to remove the developer in the process tank 50, the third valve 53a is driven by the controller to first supply the developer to the reservoir 40 through the recycle path 51 and the ink/carrier supplying path 54, and then the fourth valve 33a is driven to drain the developer to the ink cartridge 20 through the developer removing path 36. Subsequently, the new ink cartridge is replaced, and then the ink and the liquid carrier are supplied to the reservoir 40 to restart the printing in the same manner as the above. According to the above apparatus, a separate process tank allows the developer in the reservoir to be easily drained, so that the concentration of the developer and the level thereof can be easily controlled. Also, the developer in the process tank can be reused without variation in the concentration of the developer. Further, during replacement the ink cartridge, the developer of a low quality or containing impurities can be removed. In the specification, the developer supplying apparatus for one developing unit is disclosed. However, the above developer supplying apparatus may be employed in an electrographic color printer having a plurality of developing units corresponding to colors of, for example, yellow, magenta, cyan and black. Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

Claims: A developer supplying apparatus for a wet electrographic printer comprising: a reservoir (40) for storing a developer obtained by mixing a liquid carrier with an ink; a carrier cartridge (10) for supplying the liquid carrier to the reservoir (40) through a carrier supplying path (11), an ink cartridge (20) for supplying the ink to the reservoir (40) through an ink supplying path (21); and a process tank (50) for storing the developer drained from the reservoir (40) through a developer draining path: a level sensor (42) for sensing the level of developer in the reservoir (40); characterised by the reservoir (40) comprising: a concentration sensor (44) for sensing the concentration of the developer in the reservoir (40). The apparatus of claim 1, further comprising a developing unit (30) for receiving the developer of the reservoir through a developer supplying path (34) to develop an electrostatic latent image. The apparatus of claim 1 or 2, further comprising a developer draining path (35) for allowing the developer in the reservoir (40) to drain to the process tank (50) if the concentration sensor (44) senses that the developer is not within a predetermined concentration range. The apparatus of claim 3, further comprising a valve (33) for selectively opening or closing the developer draining path (35) and the developer supplying path (34). The apparatus of claim 4, wherein the valve (33) is arranged for closing the developer supplying path (34) and opening the developer draining path (35) if the concentration of the developer sensed by the concentration sensor (44) is not within a predetermined range. The apparatus of claim 1 or 2, further comprising a recycle path (51) for supplying the developer in the process tank (50) to the reservoir (40). The apparatus of claim 6, further comprising a valve (53a) for selectively opening and closing the ink supplying path (21), the carrier supplying path (11) and the recycle path (51). The apparatus of claim 7, further comprising a concentration sensor (56) for sensing the concentration of the developer in the process tank, wherein the valve (53a) selectively opens and closes the ink supplying path (21), the carrier supplying path (11) and the recycle path (51) according to the concentration of the developer measured by the concentration sensor to control the amount of the ink, the liquid carrier and the recycled developer supplied to the reservoir (40), respectively. The apparatus of claim 1 or 2, further comprising a developer removing path (36) for supplying the developer in the reservoir (40) and/or the process tank (50) to the ink cartridge (20). The apparatus of claim 9, further comprising a valve (33a) for selectively opening and closing the developer supplying path (34), the developer draining path (35) and the developer removing path (36). The apparatus of claim 10, further comprising a level sensor (22) for measuring the amount of ink in the ink cartridge (20), wherein if the ink in the ink cartridge is used up, the developer supplying path (34) is closed and the developer removing path (36) is opened by the valve (33a).

Inventors: LEE HYONG-GU, LEE, HYONG-GU
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1998
Main classification: G03G15
IPC codes: G03G15