Patent Document

BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of electrophotographic image forming, and more particularly to a seal design for cleaning assemblies of electrophotographic image forming apparatuses that helps prevent toner leakage. 
     In the electrophotographic printing process, an image forming apparatus, such as a laser printer, selectively exposes a uniformly charged image carrier known as a photoconductor to form a latent image. The latent image is made visible by toner, and the toner image is transferred to a recording medium so that the image may be rendered permanent. In such an apparatus, additional toner must be supplied each time the toner is used up, which may be inconvenient and messy. Also, the presence of toner outside its intended areas may make it necessary to perform maintenance on various parts of the apparatus. As such, significant emphasis is placed on preventing leakage of toner outside its intended areas in the electrophotographic printing process. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an end seal design that uses an array of ridges (or grooves) to urge toner inwardly so as to help prevent outward toner escape, and to cleaning assemblies in an electrophotographic image forming apparatus that employ such an end seal design. Because the end seal according to the present invention does more than merely create a passive barrier to toner, it also actively urges toner in the desired direction, the end seal may be referred to herein as a dynamic end seal. 
     In a first aspect of the invention, the inventive concept is used on an end seal for a cleaning assembly associated with a photoconductor, such as a common photoconductive drum. The cleaning assembly includes a photoconductive drum, a cleaning blade, one or more end seals, and an optional lower flexible seal. The end seals include a blade pocket for mating with the end portions of the cleaning blade and another portion having an array of ridges thereon. The ridges are angled inward and, when in contact with the photoconductive drum, urge any toner trapped therebetween inward towards the center of the photoconductive drum, where the toner can be directed to a waste reservoir in a normal fashion. This “snowplowing” action of the ridges helps prevent outward migration of the toner, thereby minimizing toner escape. The end seal may be composed of two layers—the layer closest to the photoconductive drum being a relatively firm low friction material, while the layer away from the photoconductive drum being compliant material such as foam. The compliant material helps bias the end seal against the photoconductive drum, the cleaning blade, and the lower flexible seal, and account for surface variations in the nearby housing. There may be, of course, one such end seal at each end of the cleaner blade. 
     In a second aspect of the invention, the inventive concept is used on an end seal for a cleaning assembly associated with an intermediate transfer medium, such as an intermediate transfer belt. The cleaning assembly includes an intermediate transfer medium, a cleaning blade, one or more end seals, and an optional lower flexible seal. The end seals include a blade pocket for mating with the end portions of the cleaning blade and another portion having an array of ridges thereon. The ridges are angled inward and, when in contact the intermediate transfer medium, urge any toner trapped therebetween inward towards the center of the intermediate transfer medium, where the toner can be directed to a waste reservoir in a normal fashion. This “snowplowing” action of the ridges helps prevent outward migration of the toner, thereby minimizing toner escape. The end seal may be composed of two layers—the layer closest to the intermediate transfer medium being a relatively firm low friction material, while the layer away from the intermediate transfer medium being compliant material such as foam. The compliant material helps bias the end seal against the intermediate transfer medium, the cleaning blade, and the lower flexible seal, and account for surface variations in the nearby housing. There may be, of course, one end seal at each end of the relevant cleaner blade. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 shows an image forming apparatus. 
     FIG. 2 shows perspective view of a photoconductive drum cleaning assembly employing one embodiment of the end seal according to the present invention. 
     FIG. 3 shows a more detailed view of the end seal of FIG. 2 in an undeflected state. 
     FIG. 4 shows the primary portion of the end seal of FIG.  3 . 
     FIG. 5 shows one possible profile for the ridges on the end seal of FIG.  4 . 
     FIG. 6 shows a perspective view of an ITM cleaning assembly employing one embodiment of the end seal according to the present invention. 
     FIG. 7 shows a front view of the cleaning assembly of FIG. 6 with the ITM removed. 
     FIG. 8 shows a side view of the cleaning assembly of FIG. 7 with the outboard wall removed to show the cleaning blade pocket. 
     FIG. 9 shows one possible profile for the ridges on the end seal of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As the present invention relates to the sealing within an electrophotographic image forming apparatus, an understanding of the basic elements of an electrophotographic image forming apparatus may aid in understanding the present invention. For purposes of illustration, a four cartridge color laser printer will be described; however one skilled in the art will understand that the present invention is applicable to other types of electrophotographic image forming apparatuses that use one or more toner colors for printing. Further, for simplicity, the discussion below may use the terms “sheet” and/or “paper” to refer to the recording media  5 ; this term is not limited to paper sheets, and any form of recording media is intended to be encompassed therein, including without limitation, envelopes, transparencies, postcards, and the like. 
     A four color laser printer, generally designated  10  in FIG. 1, typically includes a plurality of optionally removable toner cartridges  20  that have different toner color contained therein, an intermediate transfer medium  40 , a fuser  50 , and one or more recording media supply trays  80 . For instance, the printer  10  may include a black (k) cartridge  20 , a magenta (m) cartridge  20 , a cyan (c) cartridge  20 , and a yellow (y) cartridge  20 . Typically, each different color toner forms an individual image of a single color that is combined in a layered fashion to create the final multi-colored image, as is well understood in the art. Each of the toner cartridges  20  may be substantially identical; for simplicity only the operation of the cartridge  20  for forming yellow images will be described, it being understood that the other cartridges  20  may work in a similar fashion. 
     The toner cartridge  20  typically includes a photoconductor  22  (or “photoconductive drum” or simply “PC drum”), a charger  24 , a developer section  26 , a cleaning assembly  28 , and a toner supply bin  30 . The photoconductor  22  is generally cylindrically-shaped with a smooth surface for receiving an electrostatic charge over the surface as the photoconductor  22  rotates past charger  24 . The photoconductor  22  rotates past a scanning laser  70  directed onto a selective portion of the photoconductor surface forming an electrostatically latent image representative of the image to be printed. Drive gears (not shown) may rotate the photoconductor  22  continuously so as to advance the photoconductor  22  some uniform amount, such as {fraction (1/600)}th or {fraction (1/1200)}th of an inch, between laser scans. This process continues as the entire image pattern is formed on the surface of the photoconductor  22 . 
     After receiving the latent image, the photoconductor  22  rotates to the developer section  26  which has a toner bin  30  for housing the toner and a developer roller  27  for uniformly transferring toner to the photoconductor  22 . The toner is typically transferred from the toner bin  30  to the photoconductor  22  through a doctor blade nip formed between the developer roller  27  and the doctor blade  29 . The toner is typically a fine powder constructed of plastic granules that are attracted and cling to the areas of the photoconductor  22  that have been discharged by the scanning laser  70 . To prevent toner escape around the ends of the developer roller  27 , end seals may be employed, such as those described in U.S. patent application 09/833,888, filed Apr. 12, 2001, entitled “Dynamic End-Seal for Toner Development Unit,” which is incorporated herein by reference. 
     The photoconductor  22  next rotates past an adjacently-positioned intermediate transfer medium (“ITM”), such as belt  40 , to which the toner is transferred from the photoconductor  22 . The location of this transfer from the photoconductor  22  to the ITM belt  40  is called the first transfer point (denoted X in FIG.  1 ). After depositing the toner on the ITM belt  40 , the photoconductor  22  rotates through the cleaning section  28  where residual toner is removed from the surface of the photoconductor  22 , such as via a cleaning blade well known in the art. The residual toner may be moved along the length of the photoconductor  22  to a waste toner reservoir (not shown) where it is stored until the cartridge  20  is removed from the printer  10  for disposal. The photoconductor  22  may further pass through a discharge area (not shown) having a lamp or other light source for exposing the entire photoconductor surface to light to remove any residual charge and image pattern formed by the laser  70 . 
     As illustrated in FIG. 1, the ITM belt  40  is endless and extends around a series of rollers adjacent to the photoconductors  22  of the various cartridges  20 . The ITM belt  40  and each photoconductor  22  are synchronized by controller  60 , via gears and the like well known in the art, so as to allow the toner from each cartridge  20  to precisely align on the ITM belt  40  during a single pass. By way of example as viewed in FIG. 1, the yellow toner will be placed on the ITM belt  40 , followed by cyan, magenta, and black. The purpose of the ITM belt  40  is to gather the image from the cartridges  20  and transport it to the sheet  5  to be printed on. 
     The paper  5  may be stored in paper supply tray  80  and supplied, via a suitable series of rollers, belts, and the like, to the location where the sheet  5  contacts the ITM belt  40 . At this location, called the second transfer point (denoted Z in FIG.  1 ), the toner image on the ITM belt  40  is transferred to the sheet  5 . If desired, the sheet  5  may receive an electrostatic charge prior to contact with the ITM belt  40  to assist in attracting the toner from the ITM belt  40 . The sheet  5  and attached toner next travel through a fuser  50 , typically a pair of rollers with an associated heating element, that heats and fuses the toner to the sheet  5 . The paper  5  with the fused image is then transported out of the printer  10  for receipt by a user. After rotating past the second transfer point Z, the ITM belt  40  is cleaned of residual toner by an ITM cleaning assembly  45  so that the ITM belt  40  is clean again when it next approaches the first transfer point X. 
     A first aspect of the present invention addresses the problem of toner leakage proximate the cleaning assembly  28  associated with the photoconductor  22  (sometimes referred to as the “PC drum”). Referring to FIGS. 2-5, this cleaning assembly  28  may include a cleaning blade  90 , a flexible seal  98 , and one or more end seals  100 . The cleaning blade  90  is typically a rectangular polyhedron having a front surface  91 , a back surface  92 , an upstream surface  93  (with respect to the rotational direction of the photoconductor  22  about a longitudinal axis  22   a  thereof), and a downstream surface  94 . The upstream surface  93  includes cleaning edge  95  and a trailing edge  96 . The cleaning edge  95  typically contacts the photoconductor  22  so as to remove residual toner therefrom. The cleaning blade  90  may be held in place by any means known in the art, typically with the downstream portion of the cleaning blade  90  held fixedly, such as captured between a portion of the cartridge housing and a rigid plate (not shown) screwed into the cartridge housing. The upstream portion of the cleaning blade  90  should be left free to deflect while pressing against the photoconductor  22 . The cleaning blade  90  may be made from any suitable material, such as urethane or polyurethane. In general, numerous cleaning blades  90  and mounting approaches are known in the art, any one of which may be used, and the details of the cleaning blade  90  itself is not important to understanding the present invention. 
     The flexible seal  98  may be a thin strip of flexible material, such as polyethylene terephthalate. The flexible seal  98  extends from one end portion  22   e  (e.g., the left side) of the photoconductor  22  to the other. There is a gap between the cleaning blade  90  and the flexible seal  98  that allows residual toner removed from the photoconductor  22  to fall into a suitable capture reservoir, as is known in the art. In general, numerous flexible seals  98  are known in the art, any one of which may be used, and the details of the flexible seal  98  itself is not important to understanding the present invention. 
     The end seals  100  are disposed proximate the respective end portions  22   e  of the photoconductor  22  and generally disposed perpendicular to the longitudinal axis  22   a  of the photoconductor  22 . The end seals  100  may be substantially similar in construction and configuration, with the right end seal  100  being a left-to-right mirror image of the left end seal  100 . As such, the present description will focus on the left end seal  100  for clarity. The end seal  100  may include a blade portion  120 , a middle portion  140 , and an upstream portion  160 . The blade portion  120  includes a recess forming a blade pocket  130  with an upstream wall  132  and a downstream wall  134 . The blade pocket  130  is sized to mate with the corresponding end portion of the cleaning blade  90 . The middle portion  140  includes an array  150  of small angled ridges (or grooves)  152 . The ridges  152  extend inwardly at an acute angle α with respect to line L 1  (representing a plane perpendicular to the longitudinal axis of the photoconductor). This angle α may be in the general range of 5° to 45°, and preferably about 35° to 45°, such as 38.6°. The array  150  includes at least three ridges  152 , and more preferably ten or more, and the ridges  152  may substantially or entirely cover the surface of the middle portion  140  closest the photoconductor  22 . The ridges  152  are small, with a depth D typically in the range of 0.05 to 0.3 mm, such as approximately 0.1 mm, and narrow spacing, such as 0.08 mm. The relatively small size of the ridges  152  is selected so as to avoid creating an escape route for the toner, as may happen if the ridges  152  are 0.3 mm or larger. The ridges  152  may have any suitable profile, such as a generally triangular profile with a sharp leading edge. The size and shape of the ridges  152  is selected to allow the ridges  152  to “snowplow” toner off the photoconductor  22  and urge the removed toner inward away from the end portions  22   e . The upstream portion  160  may be an extension of the general plane of the middle portion  140 , but should not include the ridges  152 . This upstream portion  160  is intended to press against the backside of the flexible seal  98  and sandwich the flexible seal  98  between the upstream portion  160  of the end seal  100  and the photoconductor  22 . 
     The end seal  100  may advantageously be, but is not required to be, formed of two distinct elements  110 ,  180 , which are either readily separable or adhered together. The primary portion  110  of the seal  100  should be made from a hard, yet flexible material, with a low coefficient of friction, such as SANTOPRENE. This primary portion  110  is disposed closer to the photoconductor  22  and includes the blade pocket  130  and the ridge array  150 . The secondary portion  180  of the seal  100  may be made from any suitable cushion material known in the art, such as urethane foam or polyurethane foam. The secondary portion  180  of the end seal  100  is intended to be compressed against the nearby housing so as to urge the primary portion  110  against the cleaning blade  90 , the photoconductor  22 , and the flexible seal  98 ; as such, the geometry of the secondary portion  180  will depend somewhat on the geometry of the associated housing. The secondary portion  180  may include a channel  182  or cut that is disposed near the boundary between the blade portion  120  and the middle portion  140 , but is advantageously within the area of the middle portion  140 . This channel  182  runs generally radially outward from the perspective of the photoconductor  22  and helps provide stress relief so that the respective portions of the primary portion  110  are urged in the correct direction. The secondary portion  180  may include another channel  184  or cut that is disposed towards the downstream portion of the blade portion  120 . This channel  184  runs generally radially inward from the perspective of the photoconductor  22  and may help provide stress relief so that the respective portions of the primary portion  110  are urged in the correct direction. In addition, the channel  184  may help align the secondary portion  180  within the housing as necessary. To aid in aligning the primary portion  110  and the secondary portion  180 , the primary portion  10  may include an alignment flange  170  outboard of the secondary portion  180 . This flange  170  may also serve to strengthen the primary portion  110  in the upstream area of the blade pocket  130 . 
     The purpose of the end seals  100  is to help prevent toner from escaping around the end portions  22   e  of the photoconductor  22 . As discussed above, the cleaning blade  90  removes (e.g., scrapes) toner off the photoconductor  22 . The blade pocket  130  of the respective end seals  100  help seal the respective end portions of the cleaning blade  90 . In particular, the blade pocket  130  contacts at least a portion of the back surface  92  and the downstream surface  94  of the cleaning blade  90  so as to form a seal therebetween. The cleaning edge  95  of the upstream surface  93  of the cleaning blade  90  is deflected from its static position as shown in FIG. 3 when photoconductor  22  is installed, thereby flexing the cleaning blade  90 , the seal portions  110  and  180  and the flexible seal  98  as shown in FIG.  2 . The back surface  92  and the trailing edge  96  of the cleaning blade  90  is thus urged into contact against the black surface  130  of the blade pocket  120 . The ridge array  150  of the middle portion  140  of the end seal  100  is urged against the photoconductor  22  by the compression of the secondary portion  180 , thereby being dragged by the rotating photoconductor  22  so as to press the upstream wall  132  of the blade pocket  120  tightly against the upstream surface  93  of the cleaning blade  90 . Thus, toner is prevented from escaping around the ends of the cleaning blade  90 . The ridge array  150  of the middle portion  140  of the end seal  100  is urged against the photoconductor  22 . Any residual toner in the corresponding section of the photoconductor  22  is scraped off by the ridge array  150  and urged inwardly towards the gap between the cleaning blade  90  and the flexible seal  98 . These corresponding side areas of the photoconductor  22  are typically outside the “printable area” of the photoconductor  22  and may therefor have less toner adhered thereto. Indeed, most of the toner is this area may be “old” residual toner that somehow was not fully removed by the cleaning blade  90 . This “snowplow” action of the ridge array  150  is specifically designed to help prevent sideways migration of toner outside the end seals  100 , thereby helping to ensure that the waste toner is properly contained. 
     A second aspect of the present invention addresses the problem of toner leakage proximate the cleaning assembly  45  associated with the ITM  40 . For simplicity, the ITM  40  will be assumed to be in the form of a belt that rotates about a roller proximate the relevant cleaning assembly  45 . Referring to FIGS. 6-9, this cleaning assembly  45  may include a cleaning blade  200  and one or more end seals  220 . The cleaning blade  200  is typically a rectangular polyhedron having a front surface  202 , a back surface  204 , an upstream surface  206  (with respect to the rotational direction of the ITM belt  40  about a longitudinal axis of the roller), a downstream surface  208 , and respective side-end faces  214  (the side-end faces adjacent the other four surfaces). The upstream surface  206  includes cleaning edge  210  and a trailing edge  212 . The cleaning edge  210  typically contacts the ITM belt  40  so as to remove residual toner therefrom. The cleaning blade  200  may be held in place by any means known in the art, typically with the downstream portion of the cleaning blade  200  held fixedly, such as captured between a portion of the printer housing and a rigid plate (not shown) screwed into the printer housing. The upstream portion of the cleaning blade  200  should be left free to deflect while pressing against the ITM belt  40 . The cleaning blade  200  may be made from any suitable material, such as urethane or polyurethane. In general, numerous cleaning blades  200  are known in the art, any one of which may be used, and the details of the cleaning blade  200  itself is not important to understanding the present invention. 
     The optional flexible seal  218  may be a thin strip of flexible material, such as polyethylene terephthalate. The flexible seal  218  extends from one side of the ITM belt  40  to the other. There is a gap between the cleaning blade  200  and the flexible seal  218  that allows residual toner removed from the ITM belt  40  to fall into a suitable capture reservoir, as is known in the art. In general, numerous flexible seals  218  are known in the art, any one of which may be used, and the details of the flexible seal  218  itself is not important to understanding the present invention. 
     The end seals  220  are disposed proximate the respective end portions  40   e  of the ITM belt  40  as it wraps around the roller. The end seals  220  are generally disposed perpendicular to the longitudinal axis  40   a  of the ITM belt  40  in this area. The end seals  220  may be substantially similar in construction and configuration, with the right end seal  220  being a left-to-right mirror image of the left end seal  220 . As such, the present description will focus on the left end seal  220  for clarity. The end seal  220  may include a blade portion  240 , a middle portion  260 , and an optional upstream portion  270 . The blade portion  240  includes a recess forming a blade pocket  250  with an upstream wall  252 , a downstream wall  254 , and an outboard wall  256 . The blade pocket  250  is sized to mate with the corresponding end portion of the cleaning blade  200 . The middle portion  260  includes an array  262  of small angled ridges  264  (or grooves) on a curved surface that extends in an arc around the ITM belt  40 . The arc length may advantageously be in the range of 45° to 85°, and more advantageously approximately 65°. The ridges  264  extend inwardly at an acute angle β with respect to line L 2  (representing a plane perpendicular to the longitudinal axis of the ITM belt  40 ). This angle β may be in the general range of 5° to 60°, and preferably about 25° to 30°, such as 27.4°. The array  262  includes at least three ridges  264 , and more preferably ten or more, and the ridges  264  may substantially or entirely cover the surface of the middle portion  260  closest the ITM belt  40 . The ridges  264  are small, with a depth “d” typically in the range of 0.05 to 0.3 mm, such as approximately 0.1 mm, with a spacing of approximately 0.2 mm. The relatively small size of the ridges  264  is selected so as to avoid creating an escape route for the toner, as may happen if the ridges  264  are 0.5-1 mm or larger. The ridges  264  may have any suitable profile, such as a triangular profile with a sharp leading edge. The size and shape of the ridges  264  is selected to allow the ridges  264  to “snowplow” off the ITM belt  40  and urge the removed toner inward away from the end portions  40   e . The upstream portion  270  may include a hook portion  272  for aid in properly locating the end seal  220 . The upstream portion  270  may optionally also press against the backside of the flexible seal  218  and sandwich the flexible seal  218  between the upstream portion of the end seal  220  and the ITM belt  40 . 
     The end seal  220  may advantageously be, but is not required to be, formed of two distinct elements  230 ,  280 , which are either readily separable or adhered together. The primary portion  230  of the seal  220  should be made from a hard, yet flexible material, with a low coefficient of friction, such as SANTOPRENE. This primary portion  230  is disposed closer to the ITM belt  40  and includes the blade pocket  250  and the ridge array  262 . The secondary portion  280  of the seal  220  may be made from any suitable cushion material known in the art, such as polyether urethane. The secondary portion  280  of the end seal  220  is intended to be compressed against the nearby housing so as to urge the primary portion  230  against the cleaning blade  200 , the ITM belt  40 , and the optional flexible seal  218 ; as such, the geometry of the secondary portion  280  will depend somewhat on the geometry of the associated housing. 
     The purpose of the end seals  220  is to help prevent toner from escaping around the end portions of the ITM belt  40 . As discussed above, the cleaning blade  200  removes (e.g., scrapes) toner off the ITM belt  40 . The blade pocket  250  of the respective end seals  220  help seal the respective end portions of the cleaning blade  200 . In particular, the blade pocket  250  contacts at least a portion of each of the back surface  204 , the downstream surface  208 , and the side-end face  214  of the cleaning blade  200  so as form a seal therebetween. The cleaning edge  210  of the upstream surface  206  of the cleaning blade  200  is dragged somewhat by the ITM belt  40 , thereby flexing the cleaning blade  200 . The trailing edge  212  of the cleaning blade  200  preferably rests against the upstream wall  252  of the blade pocket  250 , and is forced tightly thereagainst by the dragging induced tilt of the cleaning blade&#39;s upstream surface  206 . Thus, toner is prevented from escaping around the ends of the cleaning blade  200 . The ridge array  262  of the middle portion  260  of the end seal  220  is urged against the ITM belt  40 . Any residual toner in the corresponding section of the ITM belt  40  is scraped off by the ridge array  262  and urged inwardly towards the gap between the cleaning blade  200  and the flexible seal  218 . These corresponding side areas of the ITM belt  40  are typically outside the “printable area” of the ITM belt  40  and may therefor have less toner adhered thereto. Indeed, most of the toner is this area may be “old” residual toner that somehow was not fuilly removed by the cleaning blade  200 . This “snowplow” action of the ridge array  262  is specifically designed to help prevent sideways migration of toner outside the end seals  220 , thereby helping to ensure that the waste toner is properly contained. 
     As used herein, the term “image forming apparatus” should be broadly construed; specifically including, but not limited to, laser printers, facsimile machines, copiers, and the like that use an electrophotographic image forming process of any variety. 
     Although the present invention has been described herein with respect to particular features, aspects and embodiments thereof, it will be apparent that numerous variations, modifications, and other embodiments are possible within the broad scope of the present invention, and accordingly, all variations, modifications and embodiments are to be regarded as being within the scope of the invention. The present embodiments are therefore to be construed in all aspects as illustrative and not restrictive and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

Technology Category: g