Abstract:
A paper feed cassette provided with a size detection mechanism that detects the size of paper contained in the paper feed cassette, the size detection mechanism including: a link plate that moves along a paper feed direction with movement of side limitation plates in the width direction; a size detection member that is provided relative to the link plate, that moves with movement of the link plate along the paper feed direction, and that can enter a state in which the size detection member is abutting or not abutting an externally provided size detection sensor in the width direction of the paper; and a biasing member that provides the link plate with a biasing force in a direction of the movement of the link plate.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on Japanese Patent Application No. 2015-133665 filed with the Japan Patent Office on Jul. 2, 2015, the entire content of which is hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The present invention relates to image forming apparatuses such as a copying machine, a printer and a facsimile, and relates to the configuration of a paper feed cassette, and an image forming apparatus including the paper feed cassette. 
         [0004]    Description of the Related Art 
         [0005]    An image forming apparatus is provided with a size detection mechanism that detects the size of paper contained in a paper feed cassette. Japanese Laid-Open Patent Publication Nos. 2002-187626 and 2008-81259 each disclose a paper feed cassette provided with such a size detection mechanism, and an image forming apparatus including the paper feed cassette. 
       SUMMARY OF THE INVENTION 
       [0006]    A size detection mechanism provided in a paper feed cassette is required to operate with stability. If the size detection mechanism becomes unstable in operation and incapable of correct detection of the paper size, the reliability of operation of an image forming apparatus is affected. 
         [0007]    The present invention has been made in view of the aforementioned problem, and an object of the invention is to provide a paper feed cassette capable of ensuring stability of operation of a size detection mechanism provided in the paper feed cassette, and an image forming apparatus including the paper feed cassette. 
         [0008]    To achieve at least one of the abovementioned objects, a paper feed cassette reflecting one aspect of the present invention is a paper feed cassette provided with a size detection mechanism that detects the size of paper contained in the paper feed cassette, the size detection mechanism including: a pair of side limitation plates that abuts opposite lateral sides of the paper from a width direction intersecting a paper feed direction of the paper; a link member that moves along the paper feed direction with movement of the side limitation plates in the width direction; a size detection member that is provided relative to the link member, that moves with movement of the link member along the paper feed direction, and that can enter a state in which the size detection member is abutting or not abutting an externally provided size detection sensor in the width direction of the paper; and a biasing member that provides the link member with a biasing force in a direction of the movement of the link member. 
         [0009]    In another aspect, a direction in which the link member is biased by the biasing member is a direction in which the limitation plates abut the paper in the width direction of the paper. 
         [0010]    In another aspect, the link member biased by the biasing member causes the pair of side limitation plates to press the paper. 
         [0011]    In another aspect, the size detection mechanism further includes a coupling rod that couples the link member to the size detection member. 
         [0012]    In another aspect, the paper feed cassette includes a bottom surface forming the bottom of the paper feed cassette, in which the pair of side limitation plates is disposed on the inner surface side of the bottom surface, and the link member is disposed on the outer surface side of the bottom surface. 
         [0013]    In another aspect, the link member has a rotation fulcrum at an inner position in the width direction, the size detection member is shaft-supported at the link member at an outer position in the width direction as seen from the rotation fulcrum, and the biasing member is biasing the link member in a direction that causes the link member to pivot around the rotation fulcrum. 
         [0014]    To achieve at least one of the abovementioned objects, an image forming apparatus reflecting one aspect of the present invention includes an image forming unit; and a paper feed unit that stores a plurality of sheets of paper to be transported to the image forming unit, the paper feed unit including any one of the paper feed cassettes described above that accumulates and stores the paper. 
         [0015]    The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view showing the overall configuration of an image forming apparatus according to an embodiment. 
           [0017]      FIG. 2  is a vertical cross-sectional view showing the overall configuration (excluding a scanner unit) of the image forming apparatus according to the embodiment. 
           [0018]      FIG. 3  is a perspective view from the top side showing the overall configuration of a paper feed cassette used in the image forming apparatus according to the embodiment. 
           [0019]      FIG. 4  is a perspective view from the bottom side showing the overall configuration of the paper feed cassette used in the image forming apparatus according to the embodiment. 
           [0020]      FIG. 5  is a diagram illustrating a size detection mechanism including side limitation plates, a link plate, and a lateral direction width size detection member according to the embodiment. 
           [0021]      FIG. 6  is a diagram showing the configuration of the link plate as seen from the bottom side. 
           [0022]      FIG. 7  is a vertical cross-sectional view showing engagement relation between the lateral direction width size detection member and the link plate as seen along an arrowed line VII in  FIG. 5 . 
           [0023]      FIG. 8  is a front perspective view showing a link mechanism of the size detection mechanism according to another embodiment. 
           [0024]      FIG. 9  is a rear perspective view showing the link mechanism of the size detection mechanism according to another embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    A paper feed cassette and an image forming apparatus in an embodiment based on the present invention will now be described with reference to the drawings. When a number, an amount or the like is mentioned in the embodiment described below, the scope of the present invention is not necessarily limited to the number, the amount or the like unless otherwise specified. The same or corresponding components are designated by the same reference numbers and redundant description may not be repeated. In addition, it is originally intended to appropriately combine and use configurations in each embodiment. 
       General Configuration of Image Forming Apparatus  1   
       [0026]    Referring to  FIGS. 1 and 2 , the general configuration of an image forming apparatus  1  in this embodiment is described.  FIG. 1  is a perspective view showing the overall configuration of image forming apparatus  1 , and  FIG. 2  is a vertical cross-sectional view showing the overall configuration (excluding a scanner unit) of image forming apparatus  1 . 
         [0027]    This image forming apparatus  1  is a copying machine, a printer, a facsimile, an MFP or the like, in which electrophotography is employed as a process of forming an image on paper. In electrophotography, a visible toner image is formed on a photoreceptor and transferred onto a sheet of paper such as plain paper. In order to retain this toner image on the sheet of paper as a permanent image on the sheet, the sheet is passed through a heat-fusing device, for example, to fuse the toner thereon, and then the sheet is ejected outside image forming apparatus  1 . 
         [0028]    Image forming apparatus  1  includes a body housing  1 A. An operation panel unit  2  and a scanner unit  3  are provided in the upper portion of body housing  1 A. Body housing  1 A includes therein an image forming unit  10 , and a paper feed unit  20 , below image forming unit  10 , that stores a plurality of sheets of paper to be transported to image forming unit  10 . Paper feed unit  20  includes a plurality of paper feed cassettes  100  and  150  that accumulate and store sheets of paper of the same size or sheets of paper of different sizes. The numbers of paper feed cassettes  100  and  150  can be changed depending on the performance required of image forming apparatus  1 . Body housing  1 A has a manual paper feed unit  4  provided on its side. 
       Paper Feed Cassette  100   
       [0029]    Referring to  FIGS. 3 and 4 , the configuration of paper feed cassette  100  is described.  FIG. 3  is a perspective view from the top side showing the overall configuration of paper feed cassette  100  used in image forming apparatus  1 , and  FIG. 4  is a perspective view from the bottom side showing the overall configuration of paper feed cassette  100  used in image forming apparatus  1 . Paper feed cassette  150  with a paper capacity higher than that of paper feed cassette  100  has the same basic configuration as that of paper feed cassette  100 , and thus the description thereof will be omitted here. 
         [0030]    Paper feed cassette  100  is provided such that it can be pulled out or pushed in along the direction of an arrow CD in the figure (pullout direction CD) relative to image forming apparatus  1 . Relative to pullout direction CD of paper feed cassette  100 , a transport direction of the paper in image forming apparatus  1  is the direction of an arrow FD in the figure (transport direction FD). 
         [0031]    Paper feed cassette  100  includes, so as to define a hollow paper containing section, a front wall  110   b  located at the front in pullout direction CD relative to bottom surface  110   a , and a back wall  110   c  located at the back in pullout direction CD. In addition, a side wall  110   d  and a side wall  110   e  are provided in transport direction FD as well. 
         [0032]    On the inner surface side of paper feed cassette  100 , there is provided a pair of side limitation plates  101   a  and  101   a,  the detailed structure of which will be described later, which is provided such that it can move in pullout direction CD relative to bottom surface  110   a,  and which abuts opposite lateral sides of the paper from a direction intersecting the paper feed direction (transport direction FD). 
         [0033]    In addition, on the inner surface side of paper feed cassette  100 , there is provided a back end limitation plate  203 , which is provided such that it can move relative to bottom surface  110   a,  and which abuts a rear side of the paper from the back in the paper feed direction (transport direction FD). 
         [0034]    In addition, back wall  110   c  is provided with a transport direction width size detection member  201 . Transport direction width size detection member  201  is provided such that it can slide along a wall surface of back wall  110   c,  and includes a region which abuts and/or does not about a transport direction width size detection push switch  350  provided on body housing  1 A when paper feed cassette  100  is mounted on body housing  1 A. 
         [0035]    Likewise, back wall  110   c  is provided with a lateral direction width size detection member  310  (detection actuator)  310 . Lateral direction width size detection member  310  (detection actuator)  310  is provided such that it can slide along the wall surface of back wall  110   c,  and includes a region which abuts and/or does not about a lateral direction width size detection push switch  360  provided on body housing  1 A when paper feed cassette  100  is mounted on body housing  1 A. 
         [0036]    On the outer surface side of bottom surface  110   a,  a link bar  202  is disposed. Link bar  202  has one end coupled to back end limitation plate  203  via an engagement shaft P 2  and the other end coupled to transport direction width size detection member  201  via an engagement shaft P 3 , and causes sliding movement of transport direction width size detection member  201  along the wall surface of back wall  110 , with the movement of back end limitation plate  203 . 
         [0037]    On the outer surface side of bottom surface  110   a,  a link plate  320  serving as a link member is disposed. Link plate  320  is disposed on the outer surface side of bottom surface  110   a  at an inner position in the width direction, with a rotation fulcrum R 1  as the center of rotation. Link plate  320  is shaft-supported to one of side limitation plates  101   a  via an engagement shaft P 5  at an outer position in the width direction as seen from rotation fulcrum R 1 , and additionally is coupled to lateral direction width size detection member  310  via an engagement shaft P 4 . Link plate  320  causes sliding movement of lateral direction width size detection member  310  along the wall surface of back wall  110   c,  with the movement of the one of side limitation plates  101   a.    
         [0038]    In addition, on the outer surface side of bottom surface  110   a,  a coil spring  400  serving as a biasing member is provided between link plate  320  and bottom surface  110   a . Coil spring  400  has one end  401  fixed to an engagement unit  110   x  provided on bottom surface  110   a  (see  FIG. 6 ), and coil spring  400  has the other end  402  fixed in an engagement hole  320   h  provided in link plate  320  (see  FIG. 6 ). In a normal state, by the biasing force of coil spring  400 , force is exerted on link plate  320  such that link plate  320  is always pulled in the direction of an arrow F, a substantially horizontal direction, with rotation fulcrum R 1  as the center of rotation. 
       Size Detection Mechanism 
       [0039]    Referring now to  FIGS. 5 to 7 , the operation of side limitation plates  101   a,  link plate  320 , and lateral direction width size detection member  310  is described. A size detection mechanism is formed of at least side limitation plates  101   a,  link plate  320 , and lateral direction width size detection member  310 . 
         [0040]      FIG. 5  is a diagram illustrating the size detection mechanism including side limitation plates  101   a,  link plate  320 , and lateral direction width size detection member  310 ,  FIG. 6  is a diagram showing the configuration of link plate  320  as seen from the bottom side, and  FIG. 7  is a vertical cross-sectional view showing engagement relation between lateral direction width size detection member  310  and link plate  320  as seen along an arrowed line VII in  FIG. 5 . 
         [0041]    Referring to  FIG. 5 , each of the pair of side limitation plates  101   a  disposed opposite to each other is provided with a rack  101   b.  Each rack  101   b  is screwed to a pivotable pinion  101   d.  Moving one of side limitation plates  101   a  so as to adapt to the size of placed paper causes simultaneous movement of the other side limitation plate  101   a.    
         [0042]    Engagement shaft P 5  provided at a lower end of one of side limitation plates  101   a  fits in a guide groove G 1  provided in link plate  320 . As this side limitation plate  101   a  moves, engagement shaft P 5  moves within guide groove G 1 . Guide groove G 1  has a groove shape for causing link plate  320  to pivot with rotation fulcrum R 1  as the center of rotation depending on the paper size. 
         [0043]    Guide groove G 1  is formed such that, owing to the engagement relation between engagement shaft P 5  and guide groove G 1 , the direction in which link plate  320  is biased by coil spring  400  (direction of arrow F) is a direction in which side limitation plates  101   a  abut the paper in the width direction of paper. In this embodiment, link plate  320  biased by coil spring  400  causes the pair of side limitation plates  101   a  and  101   a  to press the paper. 
         [0044]    Engagement shaft P 4  is provided at a lower end of lateral direction width size detection member  310  as well, and fits in a guide groove G 4  provided in link plate  320 . Pivoting of side limitation plate  101   a  with rotation fulcrum R 1  as the center of rotation as described above causes sliding movement of lateral direction width size detection member  310  along the wall surface of back wall  110   c.    
         [0045]    Referring now to  FIGS. 6 and 7 , the function and effect of coil spring  400  serving as a biasing member is described. In this embodiment, as described above, coil spring  400  serving as a biasing member is provided between link plate  320  and bottom surface  110   a . Coil spring  400  has one end  401  fixed to engagement unit  110   x  provided on bottom surface  110   a,  and coil spring  400  has the other end  402  fixed in engagement hole  320   h  provided in link plate  320 . 
         [0046]    In a normal state, by the biasing force of coil spring  400 , force is exerted on link plate  320  such that link plate  320  is always pulled in the direction of arrow F, with rotation fulcrum R 1  as the center of rotation. As a result, as shown in  FIG. 7 , engagement shaft P 4  of lateral direction width size detection member  310  is always pressed against one side of guide groove G 4  in link plate  320 . This relation also applies between engagement shaft P 5  provided at the lower end of one of side limitation plates  101   a  and guide groove G 1 . 
         [0047]    Thus, when coil spring  400  is not provided, there has conventionally been a gap formed between engagement shaft P 4  and guide groove G 4 , sometimes resulting in clattering of lateral direction width size detection member  310  as well as a tilt of lateral direction width size detection member  310  during movement of lateral direction width size detection member  310 . Consequently, lateral direction width size detection member  310  has sometimes been placed in a position different from a position of the original paper size, resulting in detection of the wrong paper size. 
         [0048]    In this embodiment, by contrast, engagement shaft P 4  of lateral direction width size detection member  310  is always pressed against one side of guide groove G 4  in link plate  320  owing to the provision of coil spring  400 , so that the occurrence of clattering of lateral direction width size detection member  310  can be suppressed during movement of lateral direction width size detection member  310 . As a result, a tilt of lateral direction width size detection member  310  can be suppressed, thus allowing lateral direction width size detection member  310  to move to its prescribed position. 
         [0049]    Accordingly, the stability of operation of the size detection mechanism including lateral direction width size detection member  310  provided in paper feed cassette  100  can be ensured. Moreover, erroneous detection of the paper size to be used can be avoided to maintain the reliability of operation of the image forming apparatus. 
         [0050]    The aforementioned relation also applies between engagement shaft P 5  provided at the lower end of one of side limitation plates  101   a  and guide groove G 1 . As a result, in a manner similar to lateral direction width size detection member  310 , the occurrence of clattering of side limitation plates  101   a  can be suppressed, thus allowing side limitation plates  101   a  to move to their prescribed positions. 
         [0051]    Accordingly, side limitation plates  101   a  can be placed in the correct positions, thereby ensuring the stability of operation of the size detection mechanism including side limitation plates  101   a.  In addition, the straightness of paper feed can be improved to maintain the reliability of operation of the image forming apparatus. 
         [0052]    Moreover, also from the standpoint of use by the user, since the occurrence of clattering of lateral direction width size detection member  310  and side limitation plates  101   a  is suppressed, improved performance of adding paper to paper feed cassette  100  can also be expected. 
         [0053]    While this embodiment illustrates, by way of example, the case where coil spring  400  is used as a biasing member, the biasing member is not limited to coil spring  400 . The same function and effect as that of coil spring  400  can also be obtained by using other known biasing members. 
         [0054]    While the embodiment described above employs the mechanism including at least three members, which are side limitation plates  101   a,  link plate  320  and lateral direction width size detection member  310 , as a link mechanism of the size detection mechanism, the configuration including these three members is not limiting. 
         [0055]    For example, instead of coupling lateral direction width size detection member  310  directly to link plate  320 , as shown in  FIGS. 8 and 9 , a link mechanism including at least four or more members, in which lateral direction width size detection member  310  and link plate  320  are indirectly coupled using a coupling rod  312 , may be applied to the size detection mechanism. Specifically, lateral direction width size detection member  310  may be coupled to one end side of coupling rod  312  via an engagement shaft P 4   a,  while link plate  320  may be coupled to the other end side of coupling rod  312  via an engagement shaft P 4   b.    
         [0056]    In the embodiment described above, lateral direction width size detection member  310  and link plate  320  are disposed on the outer surface side of paper feed cassette  100 , thereby preventing a portion of the size detection mechanism from being seen by the user, preventing a portion of the size detection mechanism from being touched by the user, and preventing the bottom sheet of paper from touching a portion of the size detection mechanism. If it is unnecessary to consider these points, however, a configuration in which lateral direction width size detection member  310  and link plate  320  are disposed on the inner side of paper feed cassette  100  can be employed. 
         [0057]    Although the embodiments the present invention have been described, it should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.