Abstract:
An image reading apparatus includes a sheet guide path and reads an image on a sheet. The image reading apparatus includes a sheet transporting device configured to transport the sheet along the sheet guide path and an image reading device configured to optically read the image on the sheet. Further, the image reading apparatus includes a dirt trapping device configured to trap dirt carried on the sheet. The dirt tapping device is disposed at a position upstream from the image reading device relative to a direction in which the sheet is transported by the sheet transporting device.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image reading apparatus having a sheet guide path and an image processing system using the same. More particularly, the present invention relates to an image reading apparatus having a sheet guide path used as an image input device for a computer system for example. Further, the present invention relates to an image processing system using a sheet guide path, such as a photocopier, a facsimile machine, an image filing system, or a multifunctional image processing apparatus having functions such as a photocopier function, a facsimile function, etc. 
   2. Discussion of the Background 
     FIG. 1  is a schematic sectional view illustrating a conventional image reading apparatus  100 . Referring to  FIG. 1 , de image reading apparatus  100  includes an optical image reading deuce  101 , a sheet transport roller  102 , a sheet discharge roller  103 , a first pinch roller  104  opposing the sheet transport roller  102 , a second pinch roller  105  opposing the sheet discharge roller  103 , an upper sheet guide  106 , and a lower sheet guide  107 . Together with the upper sheet guide  106 , the lower sheet guide  107  forms a sheet guide path denoted as “SGP,” which is a space between the sheet guides  106  and  107 . 
   The sheet transport roller  102  and the sheet discharge roller  103  rotate in a clockwise direction. The first pinch roller  104  is pressed toward the sheet transport roller  102  with an appropriate pressure, and the second pinch roller  105  is pressed toward the sheet discharge roller  103  with an appropriate pressure. When no sheet is being fed, the first pinch roller  104  contacts the sheet transport roller  102 , and the second pinch roller  105  contacts the sheet discharge roller  103 . The first and second pinch rollers  104  and  105  rotate in a counter clockwise direction. When a sheet, S, is fed into the left side of the sheet guide path SGP in  FIG. 1 , the first pinch roller  104  presses the sheet S against the sheet transport roller  102 , and the second pinch roller  105  presses the sheet S against the sheet discharge roller  103 . Thus, the sheet of document S is transported along the sheet guide path SGP from the left side toward the right side of e sheet guide path SGP by the sheet transport roller  102  and the sheet discharge roller  103 . 
   When the sheet S is transported over the optical image reading device  101 , image information carried on a surface of the sheet, which is facing the optical image reading device  101 , is read by the optical image reading device  101 . Then, the sheet S is discharged from the image reading apparatus  100  by the sheet discharge roller  103 . 
   Sometimes sheets carry dirt, dust or other particles or detritus such as fibers of paper, which have been rubbed off the surface of the sheet due to a rubbing motion between two sheets of a document Fibers of paper are also generated by a rubbing motion between a sheet of a document and a separating roller of a separating mechanism when the sheet is separated from the other sheets of the document. Sheets also carry other types of dirt or particles, such as particles of pencil lead, particles of an eraser, particles of ink, particles of photocopier toner, lint, etc. Referring back to  FIG. 1 , particles of dirt D 3 , D 4 , and D 5  are adhered to the sheet S, and particles of dirt D 1  and D 2  are particles that have dropped off front sheets of a document and have piled up on the optical image reading device  101 . As used herein, the term “dirt” includes any dust detritus, or other particles carried on sheets of paper that pass through the sheet guide path. When the optical image reading device  101  becomes soiled by dirt, the optical image reading device  101  may erroneously read information on the sheet S. 
   Japanese Laid-Open Patent Publication No. 09027889 describes a document reader that has two pairs of sheet carrying rollers, a backup roller, and a platen glass. The platen glass is further downwardly placed opposing the backup roller kept with a gap of 1 mm or over to avoid adhesion of dust on the platen glass. However, Japanese Laid-Open Patent Publication No. 09027889 does not disclose a device that prevents dirt on a sheet from reaching a reading portion, including the platen glass. 
   Japanese Laid-Open Patent Publication No. 09055828 describes an image reader mechanism that has a contact image sensor (CIS), a CIS roller, a cam, a spring presser, a motor, and a control unit. The control unit monitors an output signal waveform of the CIS. When the output signal waveform of the CIS is lowered, the control unit determines that a glass surface of the CIS is stained. Then, the control unit activates the motor and the cam such that the spring presser presses the CIS against the CIS roller to clean the glass surface of the CLS. However, Japanese Laid-Open Patent Publication No. 09055828 does not describe a device that prevents dirt on a sheet from reaching the glass surface of the CIS. 
   Japanese Laid-Open Patent Publication No. 09065050 describes an original document reader that has a contact type image sensor, a roller shaped white elastic fiction body, and washing pads. When the contact type image sensor senses whether the roller sped white elastic friction body or the contact type image sensor is blackened, the washing pads are applied with detergent and then put into contact with the roller shed white elastic friction body to remove dirt on the surfaces of the roller shaped white elastic friction body and the contact type image sensor. However, Japanese Laid-Open Patent Publication No. 09065050 does not describe a device to prevent dirt on a sheet of document reaches at the roller shaped white elastic friction body and the contact type image sensor. 
   In the above described apparatuses, sheets can still carry dirt to image reading portions of the apparatuses. Therefore, it is likely that the image reading portions of those apparatuses will be soiled during normal operation. 
   SUMMARY OF THE INVENTION 
   Accordingly, one object of the present invention is to provide a novel image reading apparatus having an image reading portion that does not become soiled with dirt. 
   Another object of the present invention is to provide a novel image reading apparatus that can stably perform image reading operations for a relatively long time. 
   The novel image reading apparatus of the present invention includes a sheet transporting device configured to transport a sheet along the sheet guide path. The image reading apparatus also includes an image reading device configured to optically read an image on the sheet of document. Further, the image reading apparatus includes a dirt trapping device configured to trap dirt carried on the sheet. The dirt trapping device is disposed at a position upstream from the image reading device relative to the direction that the sheet is transported. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the follow detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is a schematic sectional view illustrating a conventional image reading apparatus; 
       FIG. 2  is a schematic illustration of a facsimile machine configured according to the present invention; 
       FIG. 3  is a schematic partial sectional view of the facsimile machine of  FIG. 2 ; 
       FIG. 4  is a schematic partial sectional view of an image reading apparatus configured according to the present invention; 
       FIG. 5  is a schematic partial sectional view of an image reading apparatus configured according to the present invention; 
       FIG. 6  is an enlarged schematic partial sectional view illustrating the distance between a dirt trap brush and a sheet in the image reading apparatus of  FIG. 5 ; 
       FIG. 7  is an enlarged schematic partial sectional view illustrating the distance between the dirt trap brush and the sheet in the image reading apparatus of FIG,  5 ; 
       FIG. 8  is a schematic partial sectional view of an image reading apparatus configured according to the present invention; 
       FIG. 9  is a schematic view of a discharging device; and 
       FIG. 10  is a schematic partial sectional view of an image reading apparatus configured according to the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to  FIG. 2  thereof, an exterior of a facsimile machine  20  is shown as an example of an image processing system configured according to of the present invention. The facsimile machine  20  includes an image printing apparatus  30 , an image reading apparatus  300 , and an operation panel  40 . The facsimile machine  20  can be also used as a photocopier by pressing a button on the operation panel  40 . In this example, the operation panel  40  is embedded in the image reading apparatus  300 . The image printing apparatus  30  includes an image forming process cartridge for forming an image on a sheet of paper and a print paper transport mechanism. The image reading apparatus  300  is rotatably mounted on the image printing apparatus  30  at the rear side of the apparatus  30 . Thereby, the image reading apparatus  300  can be opened upwardly as necessary, for example, to clear a sheet of paper jammed in the image printing apparatus  30 , to supply toner for the image printing apparatus  30 , etc. 
   The image reading apparatus  300  includes an optical image reading device  201 , a sheet transport roller  202 , a sheet discharge roller  203 , a first pinch roller  204 , a second pinch roller  205 , an upper sheet guide  206 , a lower sheet guide  207 , an original document tray  211 , a pickup roller  213 , a sheet feed in roller  214 , a sheet separating roller  216 , a dirt tap hollow  217 , a sheet guide slope  218 , a pressing pad  220 , and hine pins  221  and  222 . The first pinch roller  204 , the second pinch roller  205 , the sheet separating roller  216 , and the pressing pad  220  are mounted on the upper sheet guide  206 . A cover module  215  includes the first pinch roller  204 , the second pinch roller  205 , the upper sheet guide  206 , the sheet separating roller  216 , and the pressing pad  220 . 
   The cover module  215  is rotatably mounted on the hinge pins  221  and  222  at the rear side of the frame of the image reading apparatus  300 . Thus, the cover module  215  can be opened as necessary, as illustrated in FIG.  2 . The cover module  215  is normally closed, as indicated by the arrow path T in FIG.  2 . When the cover module  215  is closed, the pressing pad  220  contacts the pickup roller  213 , the sheet separating roller  216  contacts the sheet feed in roller  214 , the first pinch roller  204  contacts-the sheet transport roller  202 , and the second pinch roller  205  contacts the sheet discharge roller  203 . 
   The original document tray  211  holds one or more stacks of documents. When a start instruction is input to the operation panel  40 , the pickup roller  213  feeds the bottom sheet S of a document into the image reading apparatus  300  along the direction SA. The sheet feed in roller  214  feeds the sheet S toward the sheet transport roller  202 . When plural sheets of the documents have been fed into a nip formed between the sheet separating roller  216  and the sheet feed in roller  214 , the sheet separate, roller  216  rotates such that only the bottom sheet of the plural sheets of the documents is fed toward the sheet transport roller  202 . The sheet separating roller  216  may be replaced by a stationary friction pad made of synthetic rubber or a cork sheet, for example, for blocking all of the sheets except the bottom sheet of the stack of the documents to be fed. 
   The sheet transport roller  202  transports the sheet S toward the sheet discharge roller  203  through the dirt trap hollow  217 , the sheet guide slope  218 , and the optical image reading device  201 . When the sheet S is transported above the dirt trap hollow  217  and the sheet guide slope  218 , dirt Bed on the sheet S can drop down from the sheet S into the dirt trap hollow  217  or onto the sheet guide slope  218 , for example, by gravity, vibration, a rubbing motion, etc. When the sheet of document S is transported above the optical image reading device  201 , the optical im age reading device  201  reads information cued on the sheet S. After the image reading operation, the sheet discharge roller  203  discharges the sheet S from the image reading apparatus  300 . 
     FIG. 3  is a schematic partial sectional view illustrating a structure of the image reading apparatus  300  of  FIG. 2  when the cover module  215  is closed. Together with the upper sheet guide  206 , the lower sheet guide  207  forms a sheet guide path SOP, which is a space between the two sheet guides  206  and  207 . 
   The sheet transport roller  202  and the sheet discharge roller  203  rotate in a clockwise direction. The first pinch roller  204  is pressed toward the sheet transport roller  202  with an appropriate pressure, and the second pinch roller  205  is pressed toward the sheet discharge roller  203  with an appropriate pressure. When no sheet is being fed in, the first pinch roller  204  contacts the sheet transport roller  202 , and the second pinch roller  205  contacts the sheet discharge roller  203 . As a result, the first and second pinch rollers  204  and  205  are rotated in a counter clockwise direction. 
   When a sheet S is transported from the sheet feed in roller  214  ( FIG. 2 ) to the left side of the sheet guide path SGP in  FIG. 3 , the first pinch roller  204  presses the sheet S against the sheet transport roller  202 . Likewise, the second pinch roller  205  presses the sheet S against the sheet discharge roller  203 . Thus, the sheet transport roller  202  and the sheet discharge roller  203  transport the sheet S from the left side toward the right side in  FIG. 3  over the dirt trap hollow  217 , the sheet guide slope  218 , and the optical image reading device  201 . 
   When the sheet S is transported over the optical image reading device  201 , image information carried on a surface facing the optical image reading device  201  is read by the optical image reading device  201 . Then, the sheet S is discharged from the image reading apparatus  300  by the sheet discharge roller  203 . 
   As noted above, sheets sometimes carry dirt, for example, paper fibers, particles of pencil lead, eraser particles, ink particles, particles of photocopier toner, lint, etc.  FIG. 3  shows particles of dirt D 0  trapped in the dirt trap hollow  217 . The particles of dirt have dropped off from sheets that have traveled through the sheet guide path SGP. Particles of dirt D 3 ,  04 , and DS are adhered to the sheet S. Particles of dirt D 1  and D 2  are dropping off of the sheets due to gravity, vibration, a scrubbing motion, etc. 
   The sheet guide slope  218  functions as a sheet transportation guide. Even when a leading edge of a sheet is downwardly curled or rippled, the sheet guide slope  208  guides and smoothly transports the leading edge of the sheet to the optical image reading device  201 . The sheet guide slope  218  also functions as a dirt receiver. That is, when a sheet caries dirt beyond the dirt trap hollow  217 , dirt such as the dirt D 2  illustrated in  FIG. 3 , can drop off the sheet nd be received by the sheet guide slope  218 . Some of the dirt received and stacked on the sheet guide slope  218  may tumble flier down into the sheet guide slope  218  into the dirt trap hollow  217 . 
   As described above, a certain proportion of dirt carried on a sheet of document is trapped by the dirt trap hollow  217  or the sheet guide slope  218 . Therefore, the probability that the optical im age reading device  201  becomes soiled by dirt is decreased. Thus, the optical imago reading device  201  maintains a quality image reading operation of documents for a relatively long time. Further, the sheet guide slope  218  can prevent a sheet of document from entering the dirt trap hollow  217  and guide the sheet to the optical image reading device  201 . 
     FIG. 4  is a schematic partial sectional view illustrating a structure of an image reading apparatus  320  according to another example of the present invention. The image reading apparatus  320  includes a removable dirt trap box  219 . The removable dirt trap box  219  may be loosely fit into the dirt trap hollow  217  so that the removable dirt trap box  219  can be easily detached from the image reading apparatus  320  and cleaned. The removable dirt trap box  219  can also be attached to the image reading apparatus  320  for reusing. 
     FIG. 5  is a schematic partial sectional view illustrating a structure of an image reading apparatus  330  according to still another example of the present invention. The image reading apparatus  330  further includes a dirt trap brush  225 . 
   The dirt trap brush  225  may be attached to the removable dirt trap box  219  as illustrated in FIG.  5 . When an image reading apparatus does not have a dirt trap box (e.g., the image reading apparatus  300  of FIG.  3 ), the dirt trap brush  225  may be attached to the dirt trap hollow  217  of FIG.  3 . Referring to  FIG. 5 , the dirt trap brush  225  may be made of electrically conductive fibers, such as steel fibers, carbon fibers, organic conductive fibers, etc. The dirt trap brush  225  may be electrically grounded so that an electrical charge on the sheet of document S and an electrical charge on any dirt adhered to the sheet S can be more easily discharge. In the example of  FIG. 5 , the dirt trap brush  225  is electrically grounded to a frame of the image reading apparatus  330  via a metal cramp  225 M for the dirt trap brush  225 . 
     FIG. 6  is an enlarged schematic partial sectional view illustrating a distance A1 between the dirt trap brush  225  and the sheet S in the image reading apparatus  330  of FIG.  5 . 
   A suitable distance A1 between the dirt trap brush  225  and the sheet S can be determined and adjusted based on the effectiveness of the electrical discharging action and the smoothness with which sheets are transported. Generally, when the dirt trap brush  225  is soft, the distance A1 between the dirt trap brush  225  and the sheet S can be made smaller than when the dirt trap brush  225  is stiff. 
   In addition, when the dirt trap brush  225  is sofa the dirt trap brush  225  may contact the sheet S.  FIG. 7  is an enlarged schematic partial sectional view illustrating a distance A2 between the dirt trap brush  225  and the path P of a sheet in the image reading apparatus  330  of FIG.  5 . In this example, the tip of the dirt trap bush  225  is placed above a level where the sheet passes, and thus, the tip of the dirt trap brush  225  contacts the sheet S and flutters while the sheet S is transported. When the dirt trap brush  225  contacts a sheet of a document, dirt on the sheet is more effectively trapped because of the dual sheet of physical wiping and electrical discharging actions of the dirt trap brush  225 . Alternatively, the dirt trap brush  225  is not electrically conductive. 
   In the example of  figure 7 , dirt carried on a sheet is effectively trapped. Therefore, the probability that tae optical image reading device  201  becomes soiled by dirt is further decreased. Additionally, when the dirt trap brush  225  is not electrically conductive, production costs are decreased. 
   The dirt trap brush  225  can be replaced by other types of discharging devices  FIG. 8  is a schematic partial sectional view illustrating an image reading apparatus  330  according to another example of the present invention. With reference to  FIG. 8 , the image reading apparatus  330  provides a discharging device  226  having a plurality of nail-like or needle-like tips  226 P facing the sheet S. 
     FIG. 9  is a schematic projective view illustrating the discharging device  226 . The discharged device  226  is electrically conductive and preferably electrically grounded. Each tip  226 P of the discharging device  226  is preferably sharp enough to make the electric field in the vicinity of the tips  226 P strong enough and concentrated enough to cause an electrical discharge between the discharging device  226  and the sheet S or between the discharging device  226  and dirt on the sheet S. A distance A3 between a tip  226 P of the discharging device  226  and a sheet S. The distance A3 between the discharging device  226  and the sheet S can be properly determined based on an effectiveness of the electrical discharge action and the smoothness of the transportation of the sheet S. The discharging device  226  can be made of a metal sheet or conductive plastic materials, for example. 
   In this example, the discharging device  226  having tips  226 P may be more durable than brush fibers. Further, a cleaning operation may be performed more easily with the discharging device  226  than with brush fibers. 
     FIG. 10  is a schematic partial sectional view illustrating a structure of an image reading apparatus  340  according to a still further example of the present invention. The image reading apparatus  340  includes a removable dirt trap module  228  that has a dirt trap box portion  228 B and a sheet guide slope portion  228 S. Further, a dirt trap brush  225  can be mounted on the removable dirt trap module  228 . 
   In this example, the removable dirt trap module  228 , including the dirt trap brush  225 , is loosely fit in a hole in the lower sheet guide  207 . With the removable dirt trap module  228 , the dirt trp box  228 B, the sheet guide  228 S, and the dirt trap brush  225  can perform a cleaning operation more easily. 
   As described above, the novel image reading apparatus of the present invention can decrease the degree to which the image reading portion of the apparatus accumulates dirt. 
   Further, the novel image reading apparatus of the present invention can perform stable image reading operations for a relatively long time. 
   Obviously, numerous modifications and variations of the preset invention are possible in light of the above teachings. For example, features described for certain embodiments may be combined with other embodiments described herein. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. 
   This document is based on Japanese patent application No. 11 006486 filed in the Japanese Patent Office on Jan. 13, 1999, the entire contents of which are incorporated by reference herein.