MXPA00004517A - Development housing having improved toner emission control - Google Patents

Abstract

An electrophotographic printing machine of the type in which an electrostatic latent image recorded on a charge retentive surface is developed with toner particles to form a visible image thereof. A Hybrid Scavengeless Development (HSD) developer housing designed to control toner emission by employing two internal capture[JMC16], external exhaust manifolds. The location of the two manifolds are placed above and below the upper and lower donor rolls respectively. The manifolds are mounted in a position to improve emissions control as well as reductions in the flow needed to accomplish the task The upper and lower manifolds are able to control the loose toner emitted by the housing and lower powder cloud, they cannot collect the toner released by the upper powder cloud. To prevent toner accumulation in the middle regions of the wire module, a manifold is incorporated as an integral part of the wire module frame. Finally, toner released in the region between the two donor rolls near the mag roll surface may be controlled by inserting a baffle.

Description

DEVELOPMENT ACCOMMODATION WHICH HAS CONTROL OF IMPROVED ORGANIC PIGMENT CONTROL BACKGROUND OF THE INVENTION This invention relates generally to the development of electrostatic images, and more particularly relates to a design of the developer housing which allows a steady flow of air to the developer housing and prevents the emission of organic pigment thereof. Accordingly, a US Patent Application No. D / 99001Q related to the inventor, from the same patent holder, filed on the same date as this application, and entitled "DEVELOPMENT CONDITIONING CONTROLLED" is hereby incorporated by reference. EMISSION OF IMPROVED ORGANIC PIGMENT ". The invention can be used in the electrophotographic printing technique. Generally, the electrophotographic printing process includes sensitizing a photoconductive surface by charging it to a substantially uniform potential. The charge is selectively dissipated according to an activating radiation pattern corresponding to a desired image. The selective dissipation of REF .: .33107 the load of a latent load latent that is revealed by contacting a revealing material with it. This process forms an image of organic pigment powder on the photoconductive surface which is subsequently transferred to a copying house. Finally, the dust image is heated to permanently fix it to the copying file in the image configuration. Commonly, two component and one component developer materials are used. A typical two-component developer material comprises magnetic carrier granules having organic pigment particles that triboelectrically adhere to these. A single component developer material typically comprises organic pigment particles that have an electrostatic charge, so that they will be attracted to, and will adhere to, the latent image on the photoconductive surface. There are several known developing systems for bringing the organic pigment particles to a latent image on a photoconductive surface. The single-component developing systems use a donor roller to transport charged organic pigment to the development retention point defined by the donor roller and the Is £ §__r ~? ": * '? 5í __" _' * photoconductive surface. The organic pigment is developed on the latent image recorded on the photoconductive surface by a development combination without mechanical scanning. A scanning system without a scan uses a donor roller with a plurality of electrode wires spaced apart from one another in the development zone. An AC (Alternating Current) voltage is applied to the wires, releasing the organic pigment from the donor roller and forming a cloud of organic pigment powder in the developing zone. The electrostatic fields generated by the latent image attract organic pigment from the organic pigment cloud to reveal the latent image. In another type of system without sweeping, a magnetic development roller attracts the developer of a reservoir. The developer includes a carrier and organic pigment. The organic pigment is attracted from the carrier to the donor roller. The donor roller then carries the organic pigment close to the latent image. One method to control the emissions of organic pigment from the developer housings in the xerographic equipment is to release any positive pressure generated in the housing. Moving components such as magnetic brush rolls and mixing augers can pump air into the housing, producing slight positive pressures. These positive pressures can result in an air flow out of the housing via low impedance leak paths. This air that escapes from the housing contains trapped organic pigment and is a major potential source of dust within the xerographic system. A common method to release this pressure is through the use of a "collector sucker". In its simplest form the collector sucker is a door simple to the air space above the developer material in the housing. This lowers the pressure in the housing below the atmospheric pressure, therefore the air flows towards, rather than out of any air leakage path from ba to impedance inside the accommodation. This air charged with organic pigment is extracted through a collector assembly. A disadvantage of these systems is that a considerable amount of contamination is present by emission of organic pigment in the areas around the rollers donors in the developer's housing. Additionally, an excessive accumulation of organic pigment occurs above the characteristics of the tipping arrangement, and internal filtration is required to avoid waste percentages of excessive organic pigment. Filtration is subject to a frequent cleaning cycle to prevent plugging. As the speeds of the xerographic printing processes increase, a corresponding increase in the angular velocities of the developing roller is required to maintain the developing capacity of the appropriate donor. The problem with the escaping organic pigment has become more acute and under these conditions the emissions of organic pigment have increased and are considered a serious problem. BRIEF DESCRIPTION OF THE INVENTION In accordance with an object of the present invention, an improved developer housing design is provided which allows a steady flow of air to a developing housing and prevents the emission of organic pigment therefrom. An electrophotographic printing machine of the type in which a latent electrostatic image recorded on a charge retaining surface is developed with particles of organic pigment to form a visible image thereof, comprising; a housing having a supply of organic pigment and developer therein; a first donor member for transporting organic pigment from the housing to the developing zone; a second donor member, adjacent to the first donor member, for transporting organic pigment from the housing to the developing zone; a baffle between the first donor member and the second donor member, for controlling the organic pigment released in the region between the two donor rollers near the surface of the magnetic roller; a module of the support structure of the electrode wires of the developer between the first donor member and the second donor member, the module has means for generating a negative air flow to transport the organic pigment therein.

DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic elevation view of an illustrative electrophotographic printing machine incorporating a developer unit having the features of the present invention therein; FIGURE 2 is a schematic elevation view showing a mode of the developer unit used in the printing machine of FIGURE 1; FIGURE 3 is an amplified illustration of the present invention; tJS - FIGURE 4 is a top view of the wired module employed with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY OF THE INVENTION Although the present invention will be described in relation to a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims. Since the technique of electrophotographic printing is well known, the various process stations employed in the printing machine of FIGURE 1 will be shown here schematically below and their operation will be briefly described with respect to this. Referring micially to FIGURE 1, there is shown an illustrative electrophotographic printing machine incorporating the developing apparatus of the present invention therein. The electrophotographic printing machine employs a band 10 having a photoconductive surface 12 deposited on a conductive substrate. Preferably, the photoconductive surface 12 is made of selenium alloy. The conductive substrate is preferably made of an aluminum alloy which is electrically grounded. One skilled in the art will appreciate that any suitable photoconductive band can be used. The band 10 moves in the direction of arrow 16 to advance successive portions of the photoconductive surface 12 sequentially through the different process stations placed through the path of movement thereof. The motor 24 rotates the band 10 in the direction of the arrow 16. The roller 22 is coupled to the motor 24 by suitable means, such as a drive belt. Initially a portion of the band 10 passes through the charging station A. At the charging station A, a corona generating device, indicated generally by the reference numeral 26 loads the photoconductive surface 12 at a relatively high potential , substantially uniform. The high voltage power supply 28 is coupled to the corona generating device 26 for charging the photoconductive surface 12 of the strip 10. After the photoconductive surface 12 of the strip 10 is charged, the charged portion thereof is advanced through the exposure station B. In the exposure station B, an original document 30 is placed facing upwards on a transparent display glass 32. The lamp 34 shines rays of light on the original document 30. The rays of light reflected from the original document 30 are transmitted through lenses 36 to form a luminous image thereof. The lenses 36 focus this luminous image on the charged portion of the photoconductive surface 12 to selectively dissipate the charge thereon. This records a latent electrostatic image on the photoconductive surface 12 which corresponds to the information areas contained within the original document 30. After the latent electrostatic image has been recorded on the photoconductive surface 12, the band 10 advances the latent image to the developing station C. In the developing station C, a developer unit, indicated generally by the reference numeral 38, reveals the latent image recorded on the photoconductive surface. Preferably, the developer unit 38 includes donor rollers 40 and 41 and electrode wires 42. The wires of the electrode 42 are electrically biased relative to the donor rollers 40 and 41 to detach the organic pigment therefrom to form a cloud of organic pigment powder 43 in the space between the donor rolls and the photoconductive surface. The latent image attracts the organic pigment particles from the dust cloud of the organic pigment 43 forming an image of organic pigment powder thereon. The donor rolls 40 and 41 are mounted, at least partially, in the chamber of the developer housing. The chamber in the developer housing stores a supply of developer material. In one embodiment, the developer material is a single component particle development material of organic pigment, while in another embodiment, the developer material includes at least organic pigment and a carrier. Continuing with reference to FIGURE 1, after the latent electrostatic image is revealed, the web 10 advances the organic pigment powder image to the transfer station D. A copy sheet 70 is advanced until the transfer D by means of the sheet feeder apparatus 72. Preferably, the sheet feeder apparatus 72 'Xl-X includes a feed roller 74 in contact with the uppermost sheet of the stack 76 in a ramp 78. The ramp 78 directs the advance of the sheet of support material in contact with the photoconductive surface 12 of the band 10 in a synchronized sequence, so that the image of organic pigment powder developed therein comes in contact with the advancing sheet at the transfer station D. The transfer station D includes a device generating crown 80 which sprays ions on the back side of sheet 70. This attracts the image of organic pigment powder from photoconductive surface 12 to sheet 70. After transfer, sheet 70 continues to move in the direction of the arrow 82 on a conveyor machine (not shown) that advances the sheet 70 towards the fusion station E. The fusion station E includes a fuser assembly, generally indicated by the reference number 84, which permanently fixes the powder image transferred to the sheet 70. The fuser assembly 84 includes a hot fuser roll 86 and a support roll 88. The sheet 70 passes between the fuser roll 86 and the support roll 88 with the image of organic pigment powder in contact with the fuser roller- "86. In this way, the organic pigment powder image is permanently affixed to the sheet 70. After melting, the sheet 70 advances through the ramp 92 towards a capture tray 94 for the subsequent removal of the printing machine by the operator. After the copying sheet is separated from the photoconductive surface 12 of a strip 10, the residual organic pigment particles adhering to the photoconductive surface 12 are removed therefrom in the cleaning station F. The cleaning station F includes a fiber brush mounted rotatably 96 in contact with the photoconductive surface 12. The particles are cleaned from the photoconductive surface 12 by the rotation of the brush 96 in contact therewith. After cleaning, a discharge lamp (not shown) floods the photoconductive surface 12 with light 'to dissipate any residual electrostatic charge remaining on it before charging it for the next successive imaging cycle. It is believed that the above description is sufficient for the purposes of the present application to illustrate the general operation of an electrophotographic printing machine that incorporates the developing apparatus of the present invention therein.

Referring now to FIGURE 2, there is shown one embodiment of the present invention in greater detail. The developing system 38 includes donor rolls 40 and 41, electrode wires 42, and magnetic metering rolls 46. Roller 46 supplies organic pigment loaded to donor rolls 40 and 41. Donor rolls 40 and 41 can be rotated "in" or "against" the direction relative to the direction of movement of the band 10. The donor roller is shown rotating the direction of the arrow 41. The auger 88 and 86 mix developer material, which is supplied to the magnetic roller 46. The apparatus The developer 38 further has electrode wires 42 located in the space between the photoconductive surface 12 on the donor rollers 40 and 41. The wires of the electrode 42 include one or more thin metal wires which are placed lightly against the donor rollers 40 and 41. The distance between the wires 42 and the donor rolls is approximately the thickness of the organic pigment layer on the donor rolls. The ends of the wires are supported by modules of a rectangular frame (not shown) located around the periphery of each donor roller. An electrical deviation is applied to the electrode wires by means of a voltage source 48. The deviation establishes an electrostatic field between the wires 42 and the donor rolls, which is effective in detaching the organic pigment from the surface of the donor rolls. and forming a cloud of organic pigment 43 around the wires 42. The height of the cloud is such that it does not come into contact with the photoconductive surface 12. A DC (Direct Current) deviation supply 50 establishes an electrostatic field between the surface photoconductor 12 and donor rollers 40 and 41 to attract the organic pigment particles detached from the cloud surrounding the wires 42 to the latent image of the photoconductive surface 12. A deviation supply of CD 56 establishes an electrostatic field between the magnetic roller 46 and the donor rollers that cause the organic pigment particles to be attracted from the magnetic roller tico the donor roller. A portion of the doctor blade 100 can be placed very close adjacent the magnetic roller 46 to maintain the height of the compressed stack of the developer material on the magnetic roller 46 at the desired level. The magnetic roller 46 includes a tubular member or non-magnetic sleeve made preferably of aluminum having an outer circumferential surface thereof. An elongated multiple magnet is located inside of and separated from the tubular member. The elongated magnet is mounted on bearings and coupled to the motor. The sleeve can also be mounted on suitable bearings and coupled to the motor. The organic pigment particles are attracted from the carrier granules on the magnetic roller to the donor roller. A minimal magnetic field zone allows the bare carrier beads and the foreign developer material to fall away from the sleeve surface. When successive latent electrostatic images are revealed, the organic pigment particles within the developer material are depleted. The augers are mounted rotatably to mix fresh organic pigment particles with the remaining developer material, so that the resulting developer material there is substantially uniform with the concentration of organic pigment particles that are being optimized. Applicants have conducted extensive numerical simulation research for the trajectories of the organic pigment particles for organic pigment particles of a nominal diameter of 7 microns with the multiple 501 and 502 operating at 10 CFM each. The particles are released from two places; the region of arrangement 505 and region 506 between two donor rollers. As a result of extensive research on the flow patterns of the organic pigment in the developer housing studied; it has been found that the volume of pollution escaping from the 506 region with several key surfaces exposed to contamination. Predominantly, the surfaces of the supporting frames of the wire module 600 and 601 that form the walls of the air channels around the donor rolls and the photoconductor. Applicants have found that the location of the upper and lower manifolds 501 and 502 is a major factor in the reduction of contamination by organic pigment. Applicants have found that placing the upper and lower manifolds 501 and 502 with the center lines of the vacuum inlet impeller facing the donor rollers 40 and 41 at approximately 11 o'clock and 7 o'clock, respectively, resulting in a increase in collection performance at reduced volumetric air flows. The width of the channel formed by the surfaces of the inlet flanges of the impeller in relation to each of the respective donor rolls and the conductive surfaces, is such that the velocity of the contaminated air does not exceed the speed required to maintain the path of the average particle near the centerline of the inputs of the impeller. The altitude of the impeller openings and the reduction of the cross-sectional area in the direction of flow from the opening of the impeller to the transport pipeline, is such that the average particle path is maintained close to the centerline of the pipeline. This results in a significant reduction in the accumulation of organic pigment within the ducts, caused by the impact of the particles with the walls of the duct. The elimination of the space in the central portion 506 of the wire modules 600 and 601 is also a factor in reducing contamination by organic pigment. The numerical and experimental results indicate that the organic pigment particles leaving this region are deposited on the frameworks of the 600 and 601 wire modules in this area. To prevent the accumulation of organic pigment, a manifold was incorporated as an integral part of the wire module frame. The trajectory patterns of the particles and the experimental results reveal that the outer surfaces of the wire modules 600 and 601 are free from contamination by organic pigment. Applicants have found that "contoured wireframe support frames provide a uniform channel cross section for uniform velocity profiles (no deceleration), and channels of constant cross section with no deceleration flows improve transport of organic pigment and They eliminate the accumulation of organic pigment The trajectories of the particles, with the proposed location of a manifold, were calculated 10 CFM by multiple, the experimental results show that excellent results were obtained at 1 CFM per manifold. By operating the manifolds at 10 CFM each, an excess of organic pigment is pulled from the developer collector, increasing the percentage of organic pigment waste.

To remove the deposit of organic pigment on the bar of the array 100, the top cover is contoured to the magnetic brush. This constant separation also provides a high impedance path to minimize the removal of the organic pigment / air mixture from the back of the housing by the upper manifold. The inlet of the upper manifold impeller on the surface of the upper donor roller is also contoured to minimize the buildup of organic pigment on the walls due to the sudden interruption of the flow and path of the organic pigment particles. Finally, seals in the form of urethane lips 525 and 526 are used to reduce the output of organic pigment and developer of the applied areas. The seals also provide a high impedance path to minimize mixing of organic pigment / air to remove from the back of the developer housing. A baffle 700 is located in the space between the donor rollers 40 and 41. The deflector 700 has the contour of the rollers 40 and 41 on the respective sides thereof. It has been observed that the presence of this baffle 700 dramatically reduces the emissions of organic pigment and developer carried by the lower donor roll 40. As a recapitulation, an HSD developer housing designed to control the emission of organic pigment using two multiples of internal capture, external exhaustion. The location of the impeller inlets of the two manifolds is above and below the upper and lower donor rolls, respectively. The numerical predictions of the flow patterns, as well as the experimental results show an improved emission control as well as the reduction in the flow necessary to carry out the task. The region between the two donor rollers provides a particular challenge. Even when the multiple - upper and lower are able to control the loose organic pigment emitted by the housing and the lower dust cloud, they can not completely collect the organic pigment released by the upper dust cloud. To prevent the accumulation of organic pigment in the middle regions of the wire module, it is proposed that a manifold be incorporated as an integral part of the wire module frame. Finally, the organic pigment released in the region between the two donor rollers near the surface of the magnetic roller can be controlled by inserting a baffle. Therefore, it is evident that it has been provided, in accordance with the present invention, that which fully satisfies the objectives and advantages set forth hereinbefore. Although this invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to cover all those alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it refers.

Claims (4)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property. An electrophotographic printing machine of the type in which a latent electrostatic image is recorded on a surface that retains revealed charge with organic pigment particles to form a visible image thereof, characterized in that it comprises: a developing housing having a supply of organic pigment and developer in it; a first donor member for transporting organic pigment from the housing to the developing zone; a second donor member, adjacent to the first donor member, for transporting organic pigment from the housing to the developing zone; a baffle between the first donor member and the second donor member, for controlling the organic pigment released in the region between the two donor rollers near the surface of the magnetic roller; a module of the support structure of the electrode wires of the developer between the first donor member and the second donor member, the module has means
2. # < < • '• to generate a negative air flow to transport the organic pigment in it. The printing machine according to claim 1, characterized in that the deflector is a wedge having a first side facing the first donor member and a second side facing the second donor member.
3. 3. The printing machine according to claim 1, characterized in that the wire support module is a wedge having a first side facing the first donor member and a second side facing the second donor member.
4. 4. The printing machine according to claim 1, characterized in that the wire support module includes a manifold where the negative air flow flows therethrough.

   SUMMARY OF THE INVENTION An electrophotographic printing machine of the type in which a latent electrostatic image recorded on the surface that retains charge is revealed with 5 particles of organic pigment to form a visible image thereof. A developer housing without hybrid debugging (HSD) designed to control the emission of organic pigment using two internal capture manifolds [JMC16], and external exhaust. The location of

   The two multiples is above and below the upper and lower donor rollers, respectively. The manifolds are mounted in a position to improve the control of emissions as well as to reduce the flow necessary to carry out the task. The multiple

   As the upper and lower layers are able to control the loose organic pigment emitted by the housing and the lower dust cloud, they can not collect the organic pigment released by the upper dust cloud. To prevent the accumulation of organic pigment in the regions

   20 means of the wire module, a multiple is incorporated as an integral part of the wire module frame. Finally, the organic pigment released in the regions between the two donor rollers near the surface of the

   - & fiáü_k ~ ¿-_¿- ^ p ^ magnetic pillar can be controlled by inserting a baffle.