Patent Publication Number: US-9846402-B2

Title: Static charge eliminator and image forming system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2015-189291, filed Sep. 28, 2015, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a static charge eliminator and an image forming system. 
     2. Description of the Related Art 
     Conventionally, there has been an electrophotographic image forming apparatus. Generally, this image forming apparatus equally charges and initializes a photosensitive drum in a developing device, forms a latent image on the photosensitive drum by optical writing, develops this latent image to a toner image, directly or indirectly transfers the toner image to a print target medium, and causes a fixing device to fix the toner image. 
     Here, electric charge is easily accumulated in the print target medium to be conveyed within the image forming apparatus. If the electric charge is only eliminated via a shaft in a roller used for the conveyance, the electric charge cannot be completely eliminated. Thus, static charge elimination members such as static charge elimination brushes are arranged in several areas on the conveyance path of the print target medium in the image forming apparatus. 
     The print target medium is charged with the largest amount of electric charge when it separates from a conveyance belt or a conveyance roller. Accordingly, a static charge elimination member may often be arranged just behind the conveyance roller. That is, the static charge elimination member is arranged with high frequency just behind an ejection (conveyance) roller into which the print target medium is finally ejected, as disclosed in Japanese Patent Application Laid-Open (Kokai) Publication No. 02-023384. 
     In the above-described image forming apparatus, a long sheet, which is not cut, may be used as the print target medium. When the long sheet after printing is to be wound, the ejection direction of the ejected long sheet is changed by a reversing unit installed on the lower flow side in the sheet ejection of the image forming apparatus, a tip end portion of the ejected long sheet is then stuck once to a winding core (paper core) mounted on a winding shaft in a winding device, and then a winding operation is started. 
     However, when the ejected long sheet is to be wound by the winding device, an angle at which the long sheet is conveyed greatly changes depending on the length (the winding diameter) of the long sheet wound around the winding shaft. In such a case, the static charge elimination member fixedly arranged cannot follow the movement (the conveyance angle) of the wound long sheet. Therefore, static charge cannot be reliably eliminated. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to stably eliminate static charge from a print target medium to be conveyed at varying angles. 
     In accordance with one aspect of the present invention, there is provided a static charge eliminator comprising: an abutment member which abuts on a print target medium so as to eliminate static charge on a lower flow side than a position where the print target medium separates from and comes in contact with a predetermined roller on a conveyance path of the print target medium; and a supporting member which supports the abutment member such that the abutment member rotates around a rotation axis of the roller, wherein the supporting member rotates while following a change in a pressing force from the print target medium via the abutment member which occurs when a winding angle using the position where the print target medium separates from and comes in contact with the roller as a reference point is changed in accordance with a winding amount of the print target medium. 
     In accordance with another aspect of the present invention, there is provided an image forming system comprising: an abutment member which abuts on a print target medium so as to eliminate static charge on a lower flow side than a position where the print target medium separates from and comes in contact with a predetermined roller on a conveyance path of the print target medium; a supporting member which supports the abutment member such that the abutment member rotates around a rotation axis of the roller; and a winding section which is used for winding the print target medium, wherein the supporting member rotates while following a change in a pressing force from the print target medium via the abutment member which occurs when a winding angle using the position where the print target medium separates from and comes in contact with the roller as a reference point is changed in accordance with a winding amount of the print target medium by the winding section. 
     In accordance with another aspect of the present invention, there is provided an image forming system comprising: a static charge elimination member which abuts on a print target medium on a lower flow side than a position where the print target medium separates from and comes in contact with a predetermined roller on a conveyance path of the print target medium; a supporting member which supports the static charge elimination member such that the static charge elimination member rotates around a rotation axis of the roller; a winding section which is used for winding the print target medium, wherein the supporting member rotates while following a change in a pressing force from the print target medium via the static charge elimination member which occurs when a winding angle using the position where the print target medium separates from and comes in contact with the roller as a reference point is changed in accordance with a winding amount of the print target medium by the winding section. 
     According to the present invention, static charge can be stably eliminated from a print target medium to be conveyed at varying angles. 
     Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The Advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a conceptual diagram showing the entire structure of an image forming system  10  for printing on a long sheet in an embodiment of the present invention; 
         FIG. 2A  is a perspective view of the structure of an image forming apparatus  10  according to the embodiment of the present invention, which shows a state where a long sheet serving as a print target medium  22  has not been ejected; 
         FIG. 2B  is a perspective view of the structure of the image forming apparatus  10  according to the embodiment of the present invention, which shows a state where the long sheet serving as the print target medium  22  is wound around a winding shaft  61 ; 
         FIG. 3  is a perspective view showing the structure of a static charge eliminator  50  according to the embodiment of the present invention; 
         FIG. 4A  is a cross-sectional view of the structure and the operation of the static charge eliminator  50  according to the embodiment of the present invention, which shows a state where a winding angle is relatively large; 
         FIG. 4B  is a cross-sectional view of the structure and the operation of the static charge eliminator  50  according to the embodiment of the present invention, which shows a state where a winding angle is relatively small; 
         FIG. 5A  is a conceptual diagram for explaining a winding operation (right winding) using a reversing unit  40  in the embodiment of the present invention, which shows a state where a winding angle is relatively large because a winding amount of the print target medium  22  around a winding shaft  61  is still small; 
         FIG. 5B  is a conceptual diagram for explaining a winding operation (right winding) using the reversing unit  40  in the embodiment of the present invention, which shows a state where a winding angle has become relatively small because a winding amount of the print target medium  22  around the winding shaft  61  has become large; 
         FIG. 6A  is a conceptual diagram for explaining a winding operation (left winding) using the reversing unit  40  in the embodiment of the present invention, which shows a state where a winding angle is relatively large because a winding amount of the print target medium  22  around the winding shaft  61  is still small; and 
         FIG. 6B  is a conceptual diagram for explaining a winding operation (left winding) using the reversing unit  40  in the embodiment of the present invention, which shows a state where a winding angle has become further larger because a winding amount of the print target medium  22  around the winding shaft  61  has become large. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the present invention will hereinafter be described with reference to the drawings. 
       FIG. 1  is an overall conceptual diagram of an image forming system  10  for printing on a long sheet in an embodiment of the present invention. In  FIG. 1 , the image forming system  10  includes a long sheet feeding section  20 , a printer body  30 , and a long sheet winding section  60 . The long sheet feeding section  20  is installed below the printer body  30 , and a sheet feeding roll  21  is installed therein. A print target medium  22  that is a long sheet, which has been pulled out of the sheet feeding roll  21 , is fed from the sheet feeding roll  21  into the printer body  30  positioned thereabove. 
     The printer body  30  is an electrophotographic tandem-type color image forming apparatus using a secondary transfer method, and includes a drum/developing device, a transfer belt device, an image forming unit, a fixing device, and the like (not shown). The print target medium  22 , which has been printed by the printer body  30  and conveyed therefrom, is wound around a winding shaft  61  installed in the long sheet winding section  60  via a reversing unit  40 . (In practice, a winding core (paper core) is mounted on the winding shaft  61 , the print target medium  22  is wound therearound, and the paper core and the print target medium  22  wound in a roll shape around the paper core are removed from the winding shaft  61  when the winding ends. The winding shaft  61  and the winding core (paper core) are hereinafter collectively referred to as “winding shaft  61 ”.) The reversing unit  40  reverses the ejected print target medium  22  and ejects the reversed print target medium  22 . The ejected print target medium  22  is wound around the winding shaft  61 . Here, an angle at which the print target medium  22  ejected from the reversing unit  40  is conveyed changes depending on the length (the winding diameter) of the long sheet wound around the winding shaft  61 . 
       FIG. 2A  and  FIG. 2B  are respectively perspective views each showing the appearance of the image forming system  10  according to the present embodiment.  FIG. 2A  shows a state where the long sheet serving as the print target medium  22  has not been ejected, and  FIG. 2B  shows a state where the ejected long sheet serving as the print target medium  22  is wound around the winding shaft  61  via the reversing unit  40 . 
     The print target medium  22  is set on the winding shaft  61  prior to a printing operation. This print target medium  22 , which is the long sheet, is pulled out of the sheet feeding roll  21  in the long sheet feeding section  20 , fed into the printer body  30 , and ejected from an ejection port of the printer body  30  along a conveyance path shown in  FIG. 1 . This print target medium  22  ejected from the printer body  30  is further reversed via the reversing unit  40 , and ejected toward the long sheet winding section  60 . 
     An operator manually fixes a tip end portion of the print target medium  22  ejected from the reversing unit  40  to the winding shaft  61  on the lower flow side. The print target medium  22  is set on the winding shaft  61  by the tip end portion of the print target medium  22  fed from the printer body  30  being stuck to the winding shaft  61  with a normal tape or the like. The winding may be started when the tip end portion of the print target medium  22  is stuck to the winding shaft  61  during the operation or after the tip end portion of the print target medium  22  is stuck to the winding shaft  61  with the conveyance thereof being stopped once. 
     The long sheet winding section  60  has a driving portion which rotates the winding shaft  61 , and the print target medium  22  to be wound around the winding shaft  61  is wound under appropriate tension. Therefore, the print target medium  22  ejected from the printer body  30  is set to be always wound under appropriate tension by a clutch mechanism being provided to the driving portion of the long sheet winding section  60  so that the print target medium  22  is not set to be forcedly pulled up. 
       FIG. 3  is a perspective view showing the structure of the static charge eliminator  50  according to the present embodiment. In  FIG. 3 , the static charge eliminator  50  includes a supporting member (stay)  51 , a sheet following roller  52 , a static charge elimination member  53 , and a spring  54  described below. The static charge eliminator  50  is arranged to rotate around a shaft  42  in an ejection roller  41  arranged in the final stage in the reversing unit  40 . The sheet following roller  52 , which comes in contact with and is driven by the print target medium  22  to be ejected, is arranged on the supporting member  51 . The static charge elimination member  53  having a conductive property extending in the width direction of the print target medium  22  is arranged on the front surface (the tip end portion in the ejection) of the supporting member  51 . 
     More specifically, the sheet following roller  52  and the static charge elimination member  53  are arranged as an abutment member which abuts on the print target medium  22  on the lower flow side than a position where this print target medium  22  comes in contact with and separates from the ejection roller  41  on the conveyance path of the print target medium  22 . 
     The abutment member is arranged such that a direction in which the static charge elimination member  53  extends becomes parallel to the front surface or the rear surface of the print target medium  22  and perpendicular to the conveyance direction of the print target medium  22  at a position where the static charge elimination member  53  abuts on the print target medium  22 . 
     When the ejected long sheet serving as the print target medium  22  is wound around the winding shaft  61 , the winding angle of the print target medium  22 , which changes as the winding in the long sheet winding section  60  progresses, greatly changes. Thus, the static charge elimination member  53  fixedly arranged cannot follow the movement (the conveyance angle) of the print target medium  22  to be wound. Therefore, static charge cannot be reliably eliminated. 
     In the present embodiment, the static charge eliminator  50  is arranged to rotate around the shaft  42  in the ejection roller  41  arranged in the final stage in the reversing unit  40  to follow the winding angle of the print target medium  22  so that the static charge elimination member  53  always abuts on the print target medium  22  ejected from the reversing unit  40 . 
     The winding angle is a bending angle of the conveyance path when the print target medium  22  is ejected from the reversing unit  40  and directed toward the winding shaft  61  in the long sheet winding section  60 , and is an angle using a position where the print target medium  22  separates from and comes in contact with the ejection roller  41  as a reference point on the conveyance path of the print target medium  22 . 
     By the static charge eliminator  50 , which rotates around the shaft  42  in the ejection roller  41  while following the winding angle of the print target medium  22  so that the static charge elimination member  53  always abuts on the print target medium  22  ejected from the reversing unit  40 , being arranged in an outlet of the reversing unit  40  as described above, static charge can be stably eliminated from the print target medium  22  to be conveyed at varying angles. 
       FIG. 4A  to  FIG. 4B  are respectively cross-sectional views each showing the structure and the operation of the static charge eliminator  50  according to the present embodiment. The supporting member  51  in the static charge eliminator  50  is structured to be rotatable around the shaft  42  in the ejection roller  41 , as shown in  FIG. 4A  and  FIG. 4B . The supporting member  51  is pulled by the spring  54  in the direction opposite to the conveyance direction of the print target medium  22 . 
     More specifically, the spring  54  applies an urging force, which is exerted in a direction opposite to a direction in which the ejection roller  41  is driven to rotate when the print target medium  22  is conveyed, to the supporting member  51  as an urging member. 
     A pulling force by the spring  54  is adjusted so that the contact pressure of the sheet following roller  52  (or the static charge elimination member  53 ) with the print target medium  22  is in a predetermined range. More specifically, the pulling force is adjusted to apply a sufficient restoring force to restore the supporting member  51  to a predetermined angle (slightly above a position where the winding angle reaches its minimum) while following the winding angle of the print target medium  22 . 
     As a result, the static charge eliminator  50  rotates around the shaft  42  in the ejection roller  41  while following a change in a pressing force from the print target medium  22  via the sheet following roller  52  (or the static charge elimination member  53 ) which occurs along with a change in the winding angle of the print target medium  22 . The sheet following roller  52  is arranged in the upper part of the supporting member  51  and near the static charge elimination member  53  so as to come in contact with the print target medium  22  ejected from the ejection roller  41 . Thus, a distance and an angle between the static charge elimination member  53  and the print target medium  22  become constant. 
     As shown in  FIG. 4A , when the long sheet serving as the print target medium  22  has a large winding angle (is deeply wound), the supporting member  51  in the static charge eliminator  50  is inclined greatly (downward). On the other hand, as shown in  FIG. 4B , when the long sheet serving as the print target medium  22  has a small winding angle (is shallowly wound), the slope of the supporting member  51  in the static charge eliminator  50  is gentle. In either case, the static charge elimination member  53  always comes in contact with the lower surface of the print target medium  22 . 
     As described above, the static charge eliminator  50  is arranged to rotate around the shaft  42  in the ejection roller  41  while following the winding angle of the print target medium  22 . As a result of this structure, the static charge elimination member  53  always comes in contact with the lower surface of the print target medium  22 , whereby static charge can be reliably eliminated. Also, by the sheet following roller  52  being arranged near the static charge elimination member  53 , the distance and the angle between the static charge elimination member  53  and the print target medium  22  can be made always constant. As a result, the static charge elimination member  53  has a constant static charge elimination effect even when the winding angle of the print target medium  22  is changed, whereby static charge can be stably eliminated. 
       FIG. 5A  and  FIG. 5B  are respectively conceptual diagrams for explaining a winding operation (right winding) using the reversing unit  40  according to the present embodiment. In a case where the print target medium  22  that is the long sheet is wound right (in the clockwise direction in the drawing) around the winding shaft  61 , it has a large winding angle (is deeply wound) in the beginning of the winding as shown in  FIG. 5A . In the end of the winding, the wound print target medium  22  has a small winding angle (is shallowly wound) because its diameter may be a maximum of 320 mm, as shown in  FIG. 5B . 
     The static charge eliminator  50  according to the present embodiment rotates around the shaft  42  in the ejection roller  41  while following the winding angle of the print target medium  22 . Accordingly, the static charge elimination member  53  always comes in contact with the lower surface of the print target medium  22  ejected from the reversing unit  40 , whereby static charge can be reliably eliminated. 
       FIG. 6A  and  FIG. 6B  are respectively conceptual diagrams for explaining a winding operation (left winding) using the reversing unit  40  according to the present embodiment. In a case where the print target medium  22  that is the long sheet is wound left (in the counterclockwise direction in the drawing) around the winding shaft  61 , it already has a large winding angle (been deeply wound) in the beginning of the winding, as shown in  FIG. 6A . In the end of the winding, the print target medium  22  has an even larger winding angle (is even more deeply wound), as shown in  FIG. 6B . 
     That is, a difference in the winding angle of the print target medium  22  becomes significantly large in both the right winding and the left winding in the winding operation. Even if the difference in the winding angle is large as described above, the static charge eliminator  50  rotates around the shaft  42  in the ejection roller  41  while following the winding angle of the print target medium  22 . Accordingly, the static charge elimination member  53  always comes in contact with the lower surface of the print target medium  22  ejected from the reversing unit  40 , whereby static charge can be reliably eliminated. 
     According to the above-described embodiment, the static charge eliminator  50  is arranged to rotate around the shaft  42  in the ejection roller  41  while following the winding angle of the print target medium  22 . As a result of this structure, the static charge elimination member  53  always comes in contact with the lower surface of the print target medium  22 , whereby static charge can be reliably eliminated. 
     Also, according to the above-described embodiment, the sheet following roller  52  is arranged at a position where the static charge elimination member  53  always comes in contact with the lower surface of the print target medium  22  and near the static charge elimination member  53 . As a result of this structure, the distance and the angle between the static charge elimination member  53  and the print target medium  22  can be made always constant. As a result, the static charge elimination member  53  has a constant static charge elimination effect even when the winding angle of the print target medium is changed, whereby static charge can be stably eliminated. 
     Moreover, according to the above-described embodiment, the supporting member  51  is pulled by the spring  54  in the direction opposite to the conveyance direction of the print target medium  22  so that the contact pressure of the sheet following roller  52  (or the static charge elimination member  53 ) with the print target medium  22  enters a predetermined range. Therefore, even when the winding angle of the print target medium  22  is changed, the static charge elimination member  53  always comes in contact with the print target medium  22  at the predetermined constant pressure, and has a constant static charge elimination effect, whereby static charge can be stably eliminated. 
     In the above-described embodiment, the image formation surface of the print target medium  22  is its front surface (upper surface), and therefore the sheet following roller  52  and the static charge elimination member  53  are made to abut on the rear surface (lower surface) of the print target medium  22  so as not to make the image formation surface dirty. However, they may abut on the front surface (upper surface) of the print target medium  22  because static charge is eliminated in a final ejection area after a print image is fixed to adhere to the print target medium  22 . In this case where the image formation surface is the front surface of the print target medium  22 , an urging force of the static charge eliminator  50  toward the print target medium  22  can also use a downward force by a weight around the supporting member  51 . 
     Also, a static charge elimination method (a contact static charge elimination method/non-contact static charge elimination method, etc.), a distance/angle from the print target medium  22 , a contact form/shape in the case of contact, and the like can be adjusted as needed by changing a positional relationship between the sheet following roller  52  and the static charge elimination member  53 , their respective sizes, and/or their respective lengths depending on a material for the static charge elimination member  53 , a charging amount of the print target medium  22 , or the like. Moreover, depending on the shape and the characteristic of the static charge elimination member  53 , a desired static charge elimination performance may be obtained even without the sheet following roller  52 . In this case, the sheet following roller  52  may be excluded. 
     While the present invention has been described with reference to the preferred embodiments, it is intended that the invention be not limited by any of the details of the description therein but includes all the embodiments which fall within the scope of the appended claims.