Abstract:
A sheet feeding cassette, including a main body of the sheet feeding cassette accommodating sheets having a trench; a fence movably attached to the main body configured to define a setting position of the sheets; a fixing portion included in the fence that includes a tooth portion engaging with the trench and turns to substantially perpendicular direction of the moving direction of the fence; a lever portion included in the fence that is possible to move corresponding to the moving direction of the fence and the lever portion configured to rotate the fixing portion by moving of the lever portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority to Japanese Patent Application No. 2006-038136 filed in the Japanese Patent Office on Feb. 15, 1006, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a sheet feeding cassette accommodating sheets of a recording medium (e.g., paper) and an image forming apparatus including the sheet feeding cassette, for example, a copier, facsimile, plotter, or printing machine.  
         [0004]     2. Description of the Related Art  
         [0005]     In a sheet feeding cassette of an image forming apparatus including a sheet feeding cassette accommodating sheets, a fence (side fence) that defines the position of the sheets perpendicular to a direction of sheet feeding is needed because the accuracy of the position of the fence directly affects a skew angle of the sheet feeding.  
         [0006]     It is preferable that a light force is required to move the fence because a user directly operates the fence to accommodate various sizes of sheets.  
         [0007]     The fence is also needed to be affixed securely at each setting position, and to move smoothly when the user changes the setting. Japanese Patent Laid-Open Application No. 2005-131861 discloses a sheet feeding cassette where a user can release the fence by pushing a button and the user can reengage the fence in a fixed state by pushing the button after moving the fence to a desirable position.  
         [0008]     However, this sheet feeding cassette configuration has drawbacks because the pushing direction of the button and the moving direction of the fence are in discord. That is, use of the fence requires an unnatural user applied force to adjust the fence to an accurate position.  
         [0009]     Japanese Patent Laid-Open Application No. 1999-139576 discloses a sheet feeding cassette where the user can release the fence from a fixed state by rotating a fixing portion perpendicular to the moving direction of the fence.  
         [0010]     However, as discussed above, the sheet feeding cassette has drawbacks because the releasing direction of the fixing portion and the moving direction of the fence are in discord. Consequently, an unnatural force is required to adjust the location of the fence to an accurate position.  
         [0011]     Japanese Patent Laid-Open Application No. 2005-053645 discloses a sheet feeding cassette where the user can release an engagement of a tooth portion positioned below the fence and the body of the sheet feeding cassette by pushing a lever and the user can fix the location of the fence by pushing the lever after moving the fence to a desirable position. This sheet feeding cassette is more preferable than the configurations described above because the pushing direction of the button and the moving direction of the fence are consistent with each other.  
         [0012]     However, this configuration has drawbacks because a trench wall exists in the rotating direction of the tooth portion and the tooth portion strikes against the wall. Consequently, friction may occur and additional effort is required by the user to operate the fence.  
         [0013]     In order to use a sheet P having variable widths, the user may move the side fence  9   a ,  9   b  to accommodate the sheet P. The fence is needed to fix tightly at the desirable position to avoid skewing. Further, the fence is needed to move smoothly when the user operates.  
         [0014]     More specifically, Japanese Patent Laid-Open Application No. 2005-053645 and Japanese Patent Laid-Open Application No. 2004-315229 disclose a sheet feeding cassette having the fixing structure of the fence illustrated in  FIG. 5 .  
         [0015]     As illustrated in  FIG. 5 , a fence  9  is controlled by a lever  15 . The user pushes a knob  15   a , positioned at the top of the lever  15 , using a finger toward the direction of an arrow  16  to release the fence  9 . A tooth portion  15   b  is provided at the bottom of the lever  15 . The tooth portion  15   b  pivots upward in the direction of arrow  17  in response to pushing the knob  15   a . Below the tooth portion  15   b , a trench  19  is provided as part of the main body of cassette  18 . The fence  9  can be fixed or released by engaging or releasing the engagement of the tooth portion  15   b  and the trench  19 . The trench  19  is aligned at a predetermined pitch toward the moving direction of the fence  9 .  
         [0016]      FIG. 6  is a cross-section view showing the tooth portion  15   b  and the trench  19  at the engagement position. As illustrated in  FIG. 6 , the tooth portion  15   b  of the lever  15  pivots upward when the knob  15   a  is pushed by the user. The user can set the position of the fence  9  to the width of the paper “P” easily because the user can move the fence by moving the knob  15 , and the direction of movement of the fence  9  is consistent with the direction of movement of the knob  15   a.    
         [0017]     However, the direction of the releasing movement of the tooth portion  15   b  (i.e., the direction of arrow  17 ) is perpendicular to the vertical wall  19   a  provided in the trench  19 . Consequently, the tooth portion  15   b  sometimes strikes against the vertical wall  19   a  of the trench  19 , and the force necessary to release the fence becomes enormous.  
       SUMMARY OF THE INVENTION  
       [0018]     The present invention addresses the above described problems of the related art. Accordingly, it is an object of the present invention to provide a sheet feeding cassette and an image forming apparatus which operates smoothly by corresponding the pushing direction of the lever to release the fence with the moving direction of the fence and by lightening the force needed to move the lever to release the fence.  
         [0019]     A specific object of the present invention is to provide a sheet feeding cassette including a main body configured to accommodate at least one sheet, and including a trench; and a fence attached to the main body and configured to move bi-directionally define a setting position for the at least one sheet. A fixing portion includes a tooth portion configured to engage with the trench to fix a position of the fence. The fixing portion is configured to rotate in a direction substantially perpendicular to the moving direction of the fence. A lever portion configured to contact the fixing portion when moved in a direction parallel to the moving direction of the fence resulting in a rotation of the fixing portion. As a consequence of this configuration, the tooth portion disengages smoothly from the trench and less force is needed to operate the fence to change sheet sizes. A user can set the fence to an accurate position and consequently prevent skewing of the sheet feeding. The user can operate the fence easily because the user can operate the fence and the fixing portion sequentially.  
         [0020]     According to an embodiment of the present invention, the lever portion and the fence are integrally formed. An integrated formation is less expensive than forming the lever portion and the fence separately.  
         [0021]     According to another embodiment, the lever portion or the fixing portion includes a slope portion. By moving the lever portion, the lever portion pushes the slope portion of the fixing portion. The fixing portion is moved by a component force generated on the slope portion. A force to move the lever is used to move the fence effectively.  
         [0022]     According to another embodiment, the sheet feeding cassette further includes a biasing device configured to bias the fixing portion.  
         [0023]     After setting the sheets, the declination of the fence may be reduced because the fence can be fixed securely by engaging the tooth portion of the fence and the trench. According to another embodiment, the sheet feeding cassette further includes a cover configured to cover substantially the entire portion of the fixing portion. The cover can improve aspects of the fence, for example, the cover makes the device more user friendly by reducing the number of elements which can be accessed by the user.  
         [0024]     According to another embodiment, the cover includes a guide portion configured to restrict a deflection of the lever portion in a perpendicular direction of movement. Consequently, the fixing or releasing of the fence can be operated stably.  
         [0025]     According to another embodiment, the fixing portion includes a protruding portion and the fence includes an engaging portion. As a consequence of this configuration, the fixing portion is more durable because the force on to the tooth portion is reduced when closing or opening the side fence.  
         [0026]     According to another embodiment, the fixing portion includes a plurality of tooth portions. As a consequence of this configuration, the operation of fixing and releasing the fence is stabilized.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     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 following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0028]      FIG. 1  is a perspective view of a laser beam printer according to an embodiment of the present invention.  
         [0029]      FIG. 2  is a cross-section view showing an overall configuration of a laser beam printer according to an embodiment of the present invention shown in  FIG. 1   
         [0030]      FIG. 3  is a perspective view of a sheet feeding cassette according to an embodiment of the present invention.  
         [0031]      FIG. 4  is a perspective view of side fences and a linkage according to an embodiment of the present invention.  
         [0032]      FIG. 5  is a perspective view of a fixing structure of a fence according to the related art.  
         [0033]      FIG. 6  is a cross-section view showing the tooth and the trench according to the related art.  
         [0034]      FIG. 7  is a perspective view of a fixing structure of a fence according to an embodiment of the present invention.  
         [0035]      FIG. 8  is a cross-section view showing the fixing structure of a fence according to an embodiment of the present invention.  
         [0036]      FIG. 9  is a cross-section view showing the tooth and the trench according to an embodiment of the present invention.  
         [0037]      FIG. 10  is a side view of a fixing structure of a fence according to an embodiment of the present invention that does not have a bias element for a fixing portion.  
         [0038]      FIG. 11  is a side view of a fixing structure of a fence according to an embodiment of the present invention that has a spring as a bias element of a fixing portion.  
         [0039]      FIG. 12  is a side view of a fixing structure of a fence according to a second embodiment of the present invention.  
         [0040]      FIG. 13  is a plane view of a fixing structure of a fence according to a second embodiment of the present invention.  
         [0041]      FIG. 14  is a perspective view of a fixing structure of a fence according to a third embodiment of the present invention.  
         [0042]      FIG. 15  is a perspective view of a cover according to a second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0043]     Preferred embodiments of the present invention are described in detail referring to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views.  
         [0044]     The first embodiment of the present invention is described in detail referring to the  FIGS. 1-4  and  7 - 11 .  
         [0045]      FIG. 1  is a perspective view of a laser beam printer as an example of an image forming apparatus according to an embodiment of the present invention. A sheet feeding cassette  1  is provided in a body portion a main body case  100  of the printer. In a top surface of the main body case  100 , a sheet discharging tray  2  is formed. The sheet (S), having a fixed toner image provided thereon, is discharged and stacked on the sheet discharging tray  2 .  
         [0046]      FIG. 2  is a cross-section view of  FIG. 1  showing an overall configuration of the laser beam printer according to an embodiment of the present invention.  
         [0047]     The image forming apparatus includes a drum shaped photoreceptor  3 , a charging device  61 , a developing device  60 , a transfer belt  5 , a cleaning device  62 , and a fixing device  6  which collectively form a device for forming an image which is provided for each of the colors (yellow, magenta, cyan, black). Specifically, a light writing device  4  irradiates a surface of the photoreceptor  3  with a light, thereby forming an electrostatic latent image on the photoreceptor  3 . The charging device  61  uniformly charges the unexposed surface of the photoreceptor  3 . The developing device  60  develops the electrostatic latent image on the photoreceptor  3  with toner and forms a toner image. The first transfer device  63  transfers the toner image formed on the photoreceptor  3  onto the transfer belt  5 . The second transfer device  64  transfers the toner image formed on the transfer belt  5  onto the sheet.  
         [0048]     After the toner image formed on the photoreceptor  3  is transferred onto the transfer belt  5 , the cleaning device removes residual toner remaining on the photoreceptor  3 .  
         [0049]     A sheet feeding path  65  is included in a front section of the main body case  100  and is substantially vertical around the second transfer device  64 . The sheet feeding cassette  1  for feeding a paper to the sheet feeding path  64  is provided at the lower portion of the main body case  100 . Specifically, the sheet feeding cassette  1  can be pulled out from the front of the main body case  100 .  
         [0050]     A sheet accommodated in the sheet feeding cassette  1  is fed one by one by a sheet feeding roller  7 , goes through the sheet feeding path  65 , and is discharged to the sheet discharging tray  2 . At a front surface of the main body case  100 , an openable and closable manual sheet feeding tray  8  is provided to manually supply the sheet, if desired.  FIG. 3  is a perspective view of the sheet feeding cassette according to an embodiment of the present invention.  
         [0051]     The sheet feeding cassette  1  includes, as illustrated in  FIG. 3 , a pair of side fences  9   a ,  9   b  for confining sheets in a direction perpendicular to the sheet feeding direction. The side fences  9   a ,  9   b  slidably move in the widthwise direction (in the direction of an arrow “S”) of the sheets.  
         [0052]     The end fence  11  is slidable along the sheet feeding direction and aligns the trailing edges of the sheets in the cassette in the sheet feeding direction (in the direction of an arrow (“N”).  
         [0053]     A user can set sheets in the sheet feeding cassette  1  by following these steps: sliding the side fences  9   a ,  9   b  outward, sliding the end fence  11  outward, setting the sheets in the sheet feeding cassette  1 , sliding the side fences  9   a ,  9   b  inward, sliding the end fence  11  inward, and then making fine adjustments to the positions of the side edges in the widthwise direction and the trailing edges in the sheet feeding direction.  
         [0054]      FIG. 4  is a perspective view of the side fences  9   a ,  9   b  and a linking device according to an embodiment of the present invention.  
         [0055]     The side fences  9   a ,  9   b  include an integrated rack  14  and a pinion gear  12  engaged with the rack  14 . Side fence  9   a  moves coincidentally with fence  9   b.    
         [0056]      FIG. 7  is a perspective view of a fixing structure of a fence according to an embodiment of the present invention.  
         [0057]     As illustrated in  FIG. 7 , a lever  20  is provided on the outer side of the side fence  9   a  which is movable in the moving direction of the side fence  9   a . A fixing portion  21  is also provided on the outer side of the side fence  9   a  which is moveable in a direction substantially perpendicular to the moving direction of the side fence  9   a.    
         [0058]     As illustrated in  FIG. 8 , the fixing portion  21  includes a fixing main body  25  turnable to a direction substantially perpendicular to the moving direction of the side fence  9   a . The fixing main body  25  is supported by an axis  23  at the bottom portion of the fixing main body  25 . An arm portion  26  radiates from the bottom portion of the fixing main body  25  toward a direction substantially perpendicular to the moving direction of the side fence  9   a . A tooth portion  27  is provided on a toe of the arm portion  26 . A slope portion  28  is provided at an upper part of the fixing main body  25 , and a leaf spring  29  is integrated at the bottom portion of the fixing main body  25 . The leaf spring  29  is formed in a “V-shape” and is provided between the fixing main body  25  and a box portion  50  of the side fence  9   a . Specifically, for the engagement of the tooth portion  27  and a trench  19  (illustrated in  FIG. 9 ), the leaf spring  29  exerts a force on the fixing main body  25  to make the fixing main body  25  rotate in a counterclockwise direction. The fixing main body  25 , the tooth portion  27 , and the leaf spring  29  can be integrally molded using a synthetic resin. By rotating the fixing main body  25 , the tooth portion  27  is moved up and down. Specifically, the tooth portion  27  can move in the direction of the arrow  30  illustrated in  FIG. 8 . In other words, the tooth portion  27  can be moved in a direction substantially perpendicular to the moving direction of the side fence  9   a . The movement of the fixing main body  25  is regulated by a curved guide portion  31  integrally formed with the side fence  9   a . A regulating portion  32  provided on the left side of the guide portion  31  regulates an over rotation in a counterclockwise direction.  
         [0059]     As illustrated in  FIG. 7 , by pushing a knob  33  of the lever  20  in the moving direction of the side fence  9   a  (a direction of an arrow  34 ) an inner side  20   a  of the lever  20  contacts a slope portion  28  of the fixing main body  25  resulting in the fixing main body  25  turning clockwise in response to the component force generated at the slope portion  28 . More specifically, moving the lever  20  starts the rotation of the fixing main body  25 , the engagement of the tooth portion  27  and the trench  19  (illustrated in  FIG. 9 ) is released, and then the fixing of the side fences  9   a ,  9   b  is released. The user can fix the side fences  9   a ,  9   b  using the elastic force of the leaf spring  29  by releasing the lever  20 .  
         [0060]     As illustrated in  FIG. 9 , the direction of movement of the tooth portion  27  is parallel with the surface of a vertical wall  19   a  of the trench  19 . Consequently, the tooth portion  27  can smoothly release engagement from the surface of a vertical wall  19   a.    
         [0061]     In this embodiment of the invention, there are two teeth portions  27  aligned to the moving direction of the side fence  9   a . The two teeth portions  27  engage the two walls  19   a  of the trench  19  simultaneously. Even if the portions  27  engage the walls  19   a  of the trench  19 , the teeth portions  27  can release engagement from the vertical walls  19   a  smoothly. Further, if the length of one tooth portion varies from the length of a second tooth position, variations of fixing force between the fixing portion  21  and the trench is small because the tooth portions  27  engage the walls  19   a  of the trench  19 . In this embodiment, the lever  20  forms part of the side fence  9   a ; however, the lever may be molded integrally with the side fence  9   a . Further, the leaf spring  29  exerts a force on the fixing portion  21 .  
         [0062]     However, as illustrated in  FIG. 10 , the fixing portion  21  can rotate due to its own weight. In  FIG. 10 , element  19   b  reflects a bottom of the trench  19 . In this embodiment, the leaf spring  29  (See  FIG. 11 ) exerts a force on the box portion  50 . However, as illustrated in  FIG. 10 , the fixing portion  21  can rotate due to its own weight. In  FIG. 10 , a numeral  19   b  means a bottom of the trench  19 .  
         [0063]     When using the weight of the fixing portion to rotate the fixing portion  21 , the user can fix the side fences  9   a ,  9   b  using the weight of the fixing portion  21  if the user releases the lever  20 . Specifically, the fixing main body  25  and the tooth portion  27  rotate due to their own weight, and the engagement is completed by the contact of the bottom of the tooth portion  27  and the bottom  19   b  of the trench  19 .  
         [0064]     However, the fixing main body  25  and the tooth portion  27  cannot rotate if the friction between the tooth portion  27  and the wall  19   a  is excessive and the weight of the fixing portion  21  is low because the fixing portion  21  is a molded synthetic resin.  
         [0065]     In this case, the side fences  9   a ,  9   b  are not fixed and the sheet may skew. Consequently, exerting a force to the fixing portion  21  is preferable.  
         [0066]     As a preferable means to exert a force to the fixing portion  21  (except for using leaf spring  29 ), as illustrated in  FIG. 11 , a compression spring  35  can be provided on the opposite side of the fixing main body  25  to the tooth portion  27 . A tension spring  36  can be provided on the same side of the fixing main body  25  to the tooth portion  27 .  
         [0067]      FIG. 12  and  FIG. 13  show the second embodiment of the present invention. The same reference numbers are used to identify like parts used by the first embodiment.  
         [0068]     As illustrated in  FIG. 12 , the feature of the second embodiment is a cover  38  that covers entirely the fixing portion  21  to improve aspects of the fence  9   a ,  9   b . The cover  38  is large enough to cover the fixing portion and the lever entirely except for the knob  33 . The cover  38  improves aspects of the sheet feeding cassette  1  because the cover  38  covers a rotating structure of the fixing portion  21 . The cover  38  is attached to the side fence  9   a  to prevent hooks  41  (illustrated in  FIG. 15 ) from falling that are formed integrally to the cover  38 .  
         [0069]     As illustrated in  FIG. 13 , a guide member  39  is provided on the top of the cover  38  to regulate the movement perpendicular to the direction of the movement of the lever  20  (the direction of the movement of the lever  20  is show as an arrow  40 ).  
         [0070]     A guide member  39  regulates a meandering motion of the lever  20  toward the arrow  40 . The slope portion  28  contacts the same position of the inner portion  20   a  of the lever. Consequently, the operation of fixing and releasing the fence is stable.  
         [0071]      FIG. 14  shows a third embodiment of the invention. The same reference numbers are used to identify like parts used by the first embodiment.  
         [0072]     As illustrated in  FIG. 14 , the feature of the third embodiment is a convex portion  45  which forms part of the arm  26  of the fixing portion  21  via the tooth portion  27 . A concave portion  46  is provided on the side fence  9   a  to engage the convex portion  45 . Specifically, the position of the convex portion  45  correlates to the position of the concave portion  46 . The convex portion  45  engages the concave portion  46  to engage the tooth portion  27  with the trench  19 , which has an interspace between the bottom of the tooth portion  27  and the bottom  19   b.    
         [0073]     In  FIG. 14 , the convex portion  45  and the concave portion  46  are shown separately for easy comprehension.  
         [0074]     In case the user accidentally closes the fences  9   a ,  9   b  without releasing the fixing portion  21 , the engagement between the convex portion  45  and the concave portion  46  can withstand the closing force of the side fences  9   a ,  9   b . Specifically, the force of closing the side fence  9   a ,  9   b  is minimally exerted on the tooth portion  27  and damage to the tooth portion  27  of the fixing portion  21  can be prevented.  
         [0075]     Numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore understood that within the scope of the appended claims, the present invention may be practiced other than as specifically described.