Patent Publication Number: US-9429893-B2

Title: Movable tray cover configuration for an image forming apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2012-017776, filed on Jan. 31, 2012, which is incorporated herein by reference in its entirety. 
     FIELD 
     Aspects of the disclosure relate to an image forming apparatus including a tray cover configured to cover an ejection tray. 
     BACKGROUND 
     A known image forming apparatus includes an ejection tray and a tray cover that is rotatably attached to the ejection tray and pivotable between the covering position and the extended position. Specifically in this art, when the tray cover is in the covering position, an end portion of the tray cover is located above a sheet ejection port (which is an opening located substantially level with a nip portion of an ejection roller). 
     SUMMARY 
     However, in the this art, as the end portion of the tray cover is located above the nip portion of the ejection roller, if a user accidentally instructs a print command with the tray cover being in the covering position, a sheet ejected from the nip portion of the ejection roller may hit against a lower surface of the tray cover and get jammed. 
     Illustrative aspects of the disclosure provide an image forming apparatus configured to reduce jamming of recording sheets even with a tray cover being in a covering position. 
     According to an aspect of the disclosure, an image forming apparatus includes an ejection tray including a support portion, a plurality of ejection rollers having a nip portion where the plurality of ejection rollers nip a recording sheet therebetween and being configured to eject the recording sheet onto the ejection tray, and a tray cover having a first surface and a second surface opposite to the first surface. The tray cover is configured to move between an extended position where the tray cover is extended relative to an upper surface of the ejection tray and the first surface faces upward to receive the recording sheet ejected from the nip portion and a covering position where the tray cover is supported by the support portion of the ejection tray to cover the upper surface of the ejection tray and the second surface faces upward. When the tray cover is in the covering position, an upstream end portion of the second surface of the tray cover in a sheet ejection direction where the recording sheet is ejected is disposed in a position closer to the nip portion than the upper surface of the ejection tray and lower than the nip portion such that a leading end of the recording sheet ejected from the nip portion passes on or over the second surface. 
     With this structure, even when the tray cover is in the covering position, the leading end of the sheet ejected from the nip portion of the ejection rollers can pass on or over the second surface, facing upward, of the tray cover, and thus jamming of a recording sheet due to contact of the first surface, facing downward, of the tray cover can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative aspects will be described in detail with reference to the following figures in which like elements are labeled with like numbers and in which: 
         FIG. 1  illustrates a general structure of an illustrative image forming apparatus, e.g. a laser printer, according to an embodiment; 
         FIG. 2  is a perspective view of the laser printer where a tray cover is in an extended position; 
         FIG. 3  is a perspective view of the laser printer where the tray cover is in a covering position; 
         FIG. 4  is a simplified cross-sectional view taken along a line I-I of  FIG. 3 ; 
         FIG. 5  is a cross sectional view illustrating a user visually checks inside of a main body with a top cover being opened; 
         FIG. 6  is an enlarged cross-sectional view illustrating a structure around ejection rollers; 
         FIG. 7A  is an enlarged cross-sectional view illustrating the ejection rollers; and 
         FIG. 7B  is an enlarged cross-sectional view illustrating an example of ejection rollers wherein a downstream-side driven roller is smaller in diameter than an upstream-side driven roller. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative embodiment will be described in detail with reference to the accompanying drawings. In the following description, a general structure of a laser printer as an example of an image forming apparatus will be described and then features of the disclosure will be described in detail. 
     In the following description, orientations or sides of the laser printer will be identified based on the laser printer disposed in an orientation in which it is intended to be used. In other words, in  FIG. 1 , the left side is referred to as the front or front side, the right side is referred to as the rear or the rear side, the up side is referred to as the top or upper side, and the down side is referred to as the bottom or lower side. The top and bottom direction may be referred to as a vertical direction. 
     As shown in  FIG. 1 , the laser printer  1  includes a main body  2 , a feeder portion  3  for feeding a sheet P as an example of a recording sheet, and an image forming portion  4  for forming an image on the sheet P. 
     The main body  2  includes a casing  21 , a top cover  22  as an example of an upper wall, and a front cover  23 . The casing  21  has, in an upper portion, an opening  21 A through which a process cartridge  6  is attached and removed, and, in a front portion, an insertion opening  21 B ( FIG. 2 ) for inserting sheets P. 
     The opening  21 A in the upper portion of the casing  21  is opened and closed by the top cover  22 , while the insertion opening  21 B in the front portion of the casing  21  is opened and closed by the front cover  23 . 
     The feeder portion  3  includes a sheet tray  31  used for placing a sheet P thereon and a sheet feed mechanism  32  which feeds the sheet P on the sheet tray  31  toward the image forming portion  4 . 
     The sheet tray  31  is made up of a tray portion  31 A disposed in a lower portion of the main body  2  and the front cover  23 . Specifically, the front cover  23  is pivotable about its lower end portion in the front-rear direction. The front cover  23  constitutes a part of the sheet tray  31  when tilted frontward. 
     In the feeder portion  3 , the front cover  23  is tilted frontward to form the sheet tray  31  on which a sheet P is to be placed. The sheet P on the sheet tray  31  is to be fed to the image forming portion  4  by the sheet feed mechanism  32 . 
     The image forming portion  4  includes a scanner unit  5 , a process cartridge  6 , and a fixing unit  7 . 
     The scanner unit  5  is disposed in a front portion of the main body  2 , and includes a laser emitting portion, a polygon mirror, a lens, and a reflecting mirror, which are not shown. The scanner unit  5  irradiates a surface of a photosensitive drum  61  with a laser beam at high speed scanning. 
     The process cartridge  6  is detachable through the opening  21 A from the casing  21 . The process cartridge  6  includes the photosensitive drum  61 , a transfer roller  62  that transfers a toner image (a developer image) formed on the photosensitive drum  61  to a sheet P. The process cartridge  6  also includes a charger, a developing roller, a layer thickness regulating blade, and a toner chamber, which are known and not shown. 
     In the process cartridge  6 , the surface of the photosensitive drum  61 , which is rotating, is uniformly charged by the charger, and then exposed with the laser beam from the scanner unit  5  by high speed scanning Thus, a potential in an exposed area drops, and an electrostatic latent image based on image data is formed on the surface of the photosensitive drum  61 . 
     The developing roller supplies toner in the toner chamber to the electrostatic latent image formed on the photosensitive drum  61 , and a toner image is formed on the surface of the photosensitive drum  61 . Then, when a sheet P passes between the photosensitive drum  61  and the transfer roller  62 , the toner image carried on the surface of the photosensitive drum  61  is transferred onto the sheet P. 
     The fixing unit  7  is disposed above the process cartridge  6  and includes a heat roller (a heating member)  71  and a pressure roller (a backup member)  72 . 
     The heat roller  71  is a member that applies heat to a sheet P, and includes a heat source, e.g., a halogen lamp, which is not shown, inside. 
     The pressure roller  72  is a member that feeds a sheet P by sandwiching the sheet P with the heat roller  71 , and is disposed diagonally upward from the rear side of the heat roller  71 . 
     In the fixing unit  7  structured as described above, the toner transferred onto the sheet P is fixed thermally while the sheet P passes between the heat roller  71  and the pressure roller  72 . The sheet P having the toner fixed thermally thereon is conveyed to ejection rollers  8 , which are disposed downstream of the fixing unit  7 , and ejected from the ejection rollers  8  to an ejection tray  9 . 
     The following will describe a structure around the top cover  22 . 
     As shown in  FIGS. 1 and 2 , the top cover  22  includes a first wall portion  22 A, a second wall portion  22 B, a third wall portion  22 C, the ejection tray  9 , a tray cover  10 , and a part of the ejection rollers  8  (which is a drive roller  81 ). 
     The first wall portion  22 A is a wall disposed above the ejection rollers  8 , and is shaped such that it horizontally extends from a rear end of the casing  21  to a position a little further frontward than the ejection rollers  8 . The fixing unit  7  is disposed below the first wall portion  22 A (between a rear end portion of the top cover  22  and a vertical wall  91 ). Specifically, the fixing unit  7  is disposed in a position further rearward than the ejection rollers  8  (or on an upstream side from the ejection rollers  8  in a sheet ejection direction) and lower than the ejection rollers  8 . In other words, a nip portion between the heat roller  71  and the pressure roller  72  is located in a position further rearward than and lower than a nip portion between the drive roller  81  and a first driven roller  82  and a nip portion between the drive roller  81  and a second driven roller  83 . 
     In the fixing unit  7 , the heat roller  71  is disposed further frontward than the pressure roller  72 , and a sheet P ejected from the fixing unit  7  is to be ejected onto the ejection tray  9  with a surface of the sheet P contacting the heat roller  71  facing toward the ejection tray  9 . Thus, there is a high possibility that the sheet P to be ejected onto the ejection tray  9  will curl in such a manner as to protrude upward. 
     The second wall portion  22 B is a wall disposed diagonally to the front of and below the first wall portion  22 A, and shaped to enclose the perimeter of the ejection tray  9  (specifically, a front end, a left end and a right end thereof). An upper surface B 1  of the second wall portion  22 B is inclined to the front and downward (toward the downstream side in the sheet ejection direction). 
     As shown in  FIGS. 3 and 4 , when the tray cover  10  is located in a covering position, which will be described later, an upper surface  10 A of the tray cover  10  is flush with the upper surface B 1  of the second wall portion  22 B inclined as described above. This structure prevents a difference in level between the tray cover  10  located in the covering position and the second wall portion  22 B around the tray cover  10 , and thus improves the authentic appearance of the laser printer  1  when the tray cover  10  is located in the covering position. 
     As shown in  FIGS. 1 and 2 , the third wall portion  22 C is a wall connecting the first wall portion  22 A and the second wall portion  22 B, and extends in a direction crossing both the first wall portion  22 A and the second wall portion  22 B. In other words, the top cover  22  is shaped such that the second wall portion  22 B in the vicinity of the ejection tray  9  is lowered one step from the first wall portion  22 A. Thus, the laser printer  1  can be made compact by one level the second wall portion  22 B is lowered from the first wall portion  22 A. 
     The top cover  22  is supported by the casing  21  such that the top cover  22  is pivotable about a rear end portion thereof. In other words, the top cover  22  is supported by the casing  21  such that the top cover  22  is pivotable about a pivot shaft  22 D disposed in an area overlapping the first wall portion  22 A as viewed from above. 
     As shown in  FIG. 5 , even when the laser printer  1  is used in a confined storage space under a shelf R, for example, the top cover  22  can be greatly opened by the height equivalent to one step the second wall portion  22 B, located on a side opposite to the pivot shaft  22 D, is lowered from the first wall portion  22 A. Thus, this structure facilitates replacement of the process cartridge  6 . 
     As shown in  FIGS. 1 and 2 , the ejection tray  9  is shaped such that it is recessed downward from the upper surface of the top cover  22  (minutely, the second wall portion  22 B). Specifically, the ejection tray  9  includes a vertical wall  91  extending vertically, a horizontal wall  92  extending horizontally, a sheet support wall  93  inclined relative to a horizontal surface, and a pair of side walls  94  disposed on the left side and right side respectively. 
     The vertical wall  91  constitutes a rear wall of the ejection tray  9  and is disposed under the ejection rollers  8 . Specifically, the vertical wall  91  has two cut portions  91 A, which are recessed downward from an upper end of the vertical wall  91  and spaced apart from each other in the left-right direction. Each of the cut portions  91 A receives a part of the ejection rollers  8  (minutely, a first driven roller  82 ). 
     A lower end portion of the vertical wall  91  contains an inclined portion  91 B extending downward diagonally to the front (toward the front end portion of the top cover  22 ) such that the deepest portion of the ejection tray  9  is located more frontward than the vertical wall  91 . With this structure, as shown in  FIG. 5 , when the user opens the top cover  22  to visually check near an exit of the fixing unit  7  for example, the deepest portion of the ejection tray  9  is less obstructive to the user&#39;s line of vision compared with a structure where the deepest portion of the ejection tray  9  is disposed at the lower end of the vertical wall extending vertically (indicated by a broken line). Thus, the structure of the embodiment facilitates visual check near the exit of the fixing unit  7  and clearing of a jammed sheet without the need to open the top cover  22  widely. 
     As shown in  FIG. 1 , the horizontal wall  92  extends frontward from a lower end of the inclined portion  91 B, is connected to the sheet support wall  93 , and thus constitutes the deepest portion of the ejection tray  9 . In other words, the horizontal wall  92  is disposed between the sheet support wall  93  and the inclined portion  91 B. 
     The sheet support wall  93  is shaped such that it is inclined diagonally to the front upward from the horizontal wall  92  (or the deepest portion). In other words, the sheet support wall  93  and the inclined portion  91 B are shaped such that they are spaced apart from each other as they go upward from the horizontal wall  92 , thereby constituting some of walls defining a V-shaped groove. 
     With this structure, when a trailing end of a sheet P ejected onto the ejection tray  9  gets on the inclined portion  91 B, the trailing end of the sheet P is bent by the inclined portion  91 B and the sheet support wall  93  such that a bent portion thereof protrudes downward. Thus, even if the sheet P ejected onto the ejection tray  9  is curled so that a curled portion thereof protrudes upward, the curled portion can be corrected to be relatively flattened by correcting the trailing end of the sheet P between the inclined portion  91 B and the sheet support wall  93  so that the trailing end thereof protrudes downward. 
     In the embodiment, as the horizontal wall  92  is disposed between the sheet supply wall  93  and the inclined portion  91 B, no narrow corner portion is formed between the sheet supply wall  93  and the inclined portion  91 B, compared with a structure where the sheet support wall is directly connected to the inclined portion without the horizontal wall being disposed therebetween. Thus, a curl of a sheet P can be adequately corrected in this embodiment as it will not be excessively corrected in such a narrow corner portion. 
     The sidewalls  94  are disposed on the left and right sides of the vertical wall  91 , the horizontal wall  92  and the sheet support wall  93 , such as to connect the left and right ends of those walls  91  to  93 . 
     As shown in  FIGS. 1-3 , the tray cover  10  is supported by the casing  21  such as to pivot about a pivot shaft (not shown) disposed near the front end of the sheet support wall  93 . Specifically, the tray cover  10  is movable, e.g., pivotable, between the covering position where the tray cover  10  covers the upper surface of the ejection tray  9  (or the upper surface of the sheet support wall  93  and one part of the horizontal wall  92  approximate to the sheet support wall  93 ) and an extended position where the tray cover  10  is extended relative to the front side of the upper surface of the ejection tray  9  (or the upper surface of the sheet support wall  93 ). The tray cover  10  is supported by an upper end portion  94 A of each side wall  94  when located in the covering position. 
     Another part of the horizontal wall  92  and the inclined portion  91 B are covered by the third wall portion  22 C and the first wall portion  22 A of the top cover  22 . Thus, when the tray cover  10  is located in the covering portion, the tray cover  10 , the third wall portion  22 C and the first wall portion  22 A prevent dust from accumulating in the ejection tray  9 . 
     The rear end portion  10 B (or an upstream end portion in the sheet ejection direction) of the tray cover  10  located in the covering position is located below the nip portion of the ejection rollers  8  (specifically, a nip portion between the drive roller  81  and the first driven roller  82 ). With this positional relationship, even when the tray cover  10  is in the covering position, the leading end of the sheet P ejected from the nip portion of the ejection rollers  8  can pass on or over the upper surface of the tray cover  10 . This prevents jamming of a sheet P due to contact of the lower surface of the tray cover  10 . 
     When in the covering position, the upper surface of the tray cover  10  is inclined downward to the front side (or to the downstream side in the sheet ejection direction). This inclination prevents dust from entering the rear side of the ejection tray  9  (approximate to the ejection rollers  8 ) even if the dust is accumulated on the tray cover  10  located in the covering position. 
     As shown in  FIG. 2 , the tray cover  10  includes a first extension cover  11  and a second extension cover  12 . The first extension cover  11  has a width substantially equal to the ejection tray  9  and is shaped such that, when in the covering position indicated by a chain line in  FIG. 1 , the first extension cover  11  extends from a position anterior to the front end of the sheet support wall  93  to a position posterior to the front end of the third wall portion  22 C. 
     Specifically, the lower end of the third wall portion  22 C has a cut portion C 1  recessed upward therefrom ( FIG. 2 ). When the tray cover  10  is in the covering position, the rear end of the first extension cover  11  is disposed more rearward than an edge defining the cut portion C 1 . 
     As shown in  FIG. 2 , the second extension cover  12  is shaped narrower in width than the first extension cover  11  and is pivotally disposed in substantially a central portion of the front end portion of the first extension cover  11  located in the extended position. Specifically, the second extension cover  12  is pivotable between an accommodation position where the second extension cover  12  is folded into the first extension cover  11  in such a manner to face the first extension cover  11  and an open position ( FIG. 2 ) where the second extension cover  12  is located adjacent to the front end of the upper surface of the first extension cover  11  located in the extended position. 
     As shown in  FIG. 6 , the ejection rollers  8  are disposed above the vertical wall  91  of the ejection tray  9  and include the drive roller  81  that receives a drive force and rotates, and a first driven roller  82  and a second driven roller  83  which contact the drive roller  81  and are rotated by the drive roller  81 . The first driven roller  82  is disposed in front of the second driven roller  83  (or on a downstream side of the second driven roller  83  in the sheet ejection direction), and has a diameter larger than (different in size from) the second driven roller  83 . 
     With this structure, the first driven roller  82  having a larger diameter improves smoothness of conveyance of a sheet P, while the second driven roller  83  having a smaller diameter contributes to size reduction of the apparatus. In the embodiment, as the diameter of the first driven roller  82 , which is disposed on the downstream side in the sheet ejection direction, is made larger, an angle of a sheet P fed from a nip portion between the second driven roller  83  and the drive roller  81  with respect to the first driven roller  82 , which is disposed on the downstream side, can be made larger. 
     In other words, as shown in  FIG. 7B , if the diameter of a first driven roller  82 ′ disposed on the downstream side in the sheet ejection direction is made smaller than the diameter of a second driven roller  83 ′, an angle θ 2  formed by a common tangent TC of the drive roller  81  and the second driven roller  83 ′ and a tangent T 2  having a point P 2  on which the common tangent TC falls on the first driven roller  82 ′ becomes small. Thus, in this case, there is a high possibility that a sheet P to be fed from between the drive roller  81  and the second driven roller  83 ′ may be jammed at the first driven roller  82 ′ disposed on the downstream side. 
     However, in the structure of the embodiment, as shown in  FIG. 7A , an angle θ 1  formed by a common tangent TC of the drive roller  81  and the second driven roller  83  and a tangent T 1  having a point P 1  on which the common tangent TC falls on the first driven roller  82  is large. Thus, in this embodiment, the sheet P to be fed from between the drive roller  81  and the second driven roller  83  can be prevented from becoming jammed due to collision with the first driven roller  82  disposed on the downstream side. 
     As shown in  FIGS. 5 and 6 , the drive roller  81  is rotatably attached to the top cover  22 , and the first driven roller  82  and the second driven roller  83  are rotatably attached to the casing  21 . With this structure, a sheet jammed among the drive roller  81 , the first driven roller  82  and the second driven roller  83  can be easily removed only by opening the top cover  22 . 
     The first driven roller  82  and the second driven roller  83  are arranged along an inclined line with respect to a horizontal surface such that the first driven roller  82  is disposed diagonally to the front below the second driven roller  83 . Thus, compared with a structure where two driven rollers are arranged horizontally, an amount of protrusion of the first driven roller  82  from the drive roller  81  toward the downstream side in the sheet ejection direction can be made small. 
     Although the vertical wall  91  is shifted to the upstream side in the sheet ejection direction compared with the structure where the two driven rollers are arranged horizontally (the structure where the amount of protrusion of the first driven roller  82  from the drive roller  81  toward the downstream side in the sheet ejection direction is large), interference between the vertical wall  91  and the first driven roller  82  when the top cover  22  is opened or closed can be prevented. Thus, compared with the structure where the two driven rollers are arranged horizontally (the structure where the amount of protrusion toward the downstream side is large), the ejection tray  9  can be widened. 
     A sheet feed path  100  for guiding a sheet P from the fixing unit  7  to the ejection rollers  8  is defined under the first wall portion  22 A of the top cover  22 . The sheet feed path  100  is shaped in an arc protruding upward. 
     The nip portions among the ejection rollers  8  (each nip portion between the drive roller  81  and one of the first driven roller  82  and the second driven roller  83 ) are located diagonally to the front side below a top  110  of the sheet feed path  100 . Thus, for example, compared with a sheet feed path for guiding a recording sheet straightly toward ejection rollers disposed at a position diagonally upward of the fixing unit (at a position near the top  110  in  FIG. 6 ), the laser printer  1  can be made compact in size as the ejection rollers  8  of the embodiment can be disposed in positions lower than the top  110  because of the arc shape of the sheet feed path  100 . 
     As the ejection rollers  8  are located more frontward compared with the structure where the ejection rollers  8  are disposed near the top  110 , the lower end of the inclined portion  91 B of the vertical wall  91  disposed below the ejection rollers  8  (or the deepest portion in the ejection tray  9 ) is also located more frontward. Thus, when the top cover  22  is in the open position, the structure in the vicinity of the outlet of the fixing unit  7  can be easily viewed. 
     The embodiment shows, but is not limited to that, when the tray cover  10  is in the covering position, the upper surface  10 A of the tray cover  10  is inclined downward to the front. For example, the upper surface of the tray cover may be disposed horizontally when in the covering position. This case also prevents dust on the tray cover located in the covering position from falling to a corner close to the ejection rollers of the ejection tray. 
     The embodiment shows, but is not limited to, the openable top cover  22  as an example of an upper wall of the main body. The top cover  22  may be a stationary wall. 
     The embodiment shows, but is not limited to, that the ejection rollers  8  include one drive roller  81  and two driven rollers  82  and  83 . For example, the ejection roller may include one drive roller and one driven roller. 
     The sheets P, as an example of recording sheets, may include thick paper, postcards, thin paper, and transparencies. 
     The above embodiment shows, but is not limited to, the laser printer  1 . The disclosure may be applicable to other image forming apparatuses, such as a copier and a multifunction apparatus. 
     While the features herein have been described in connection with various example structures and illustrative aspects, it will be understood by those skilled in the art that other variations and modifications of the structures and aspects described above may be made without departing from the scope of the inventions described herein. Other structures and aspects will be apparent to those skilled in the art from a consideration of the specification or practice of the features disclosed herein. It is intended that the specification and the described examples only are illustrative with the true scope of the inventions being defined by the following claims.