Patent Publication Number: US-11048201-B2

Title: Sheet feeding apparatus and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet feeding apparatus and an image forming apparatus, and particularly to a sheet feeding apparatus that can stack a large amount of sheets and an image forming apparatus. 
     Description of the Related Art 
     Conventionally, there have been sheet stacking apparatuses that use a storage compartment that can be inserted and removed by a slide rail and are capable of stacking a large number of sheets. In such an apparatus, as is proposed by Japanese Patent Laid-Open No. 2007-121858, for example, two latch (lock) (left and right) mechanisms that are coupled so as to hold a storage compartment when it is closed by an operator are used. 
     However, in the foregoing conventional example, in a case where the storage compartment is pushed not straight but at an angle with respect to the sheet stacking apparatus, only one of the latches will be engaged, and the other latch will not be engaged (half-latched). The state in which the second latch is not engaged (half-latched) is a state in which the first latch comes down before the second latch is engaged. When such a state occurs, there is the possibility that jams occur during sheet feeding, normal sheet feeding will cease to be possible, the storage compartment itself will deform, or sheet accommodability will be degraded. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is conceived as a response to the above-described disadvantages of the conventional art. 
     For example, a sheet feeding apparatus and an image forming apparatus according to this invention is capable of preventing the occurrence of a half-latched state with a simple and inexpensive configuration. 
     According to one aspect of the present invention, there is provided a sheet feeding apparatus that feeds sheets to an image forming apparatus comprising: a housing; a storage unit that is accommodated within the housing and that has a sheet stacking unit that stacks sheets, and that is movable in an insertion direction with respect to the housing; a first rotating body arranged at one end in a direction that intersects with the insertion direction of the storage unit; a second rotating body arranged at the other end in the direction that intersects with the insertion direction of the storage unit; a first latch portion that is provided in the housing and engages with the first rotating body; a second latch portion that is provided in the housing and engages with the second rotating body; a connecting portion that connects the first latch portion and the second latch portion; and a feed unit configured to feed a sheet stacked in the sheet stacking unit to the image forming apparatus, wherein the housing includes the first latch portion, the second latch portion, the connecting portion, and the feed unit, the storage unit includes the first rotating body and the second rotating body, the first latch portion and the second latch portion are connected by the connecting portion and move integrally, in a case where the storage unit is inserted at a maximum angle with respect to the housing, the first latch portion does not engage with the first rotating body and the second latch portion does not engage with the second rotating body at a time when the first rotating body reaches an engagement position for the first latch portion in the insertion direction and the second rotating body does not reach an engagement position for the second latch portion in the insertion direction, and the first latch portion engages with the first rotating body and the second latch portion engages with the second rotating body at a time when the first rotating body reaches the engagement position for the first latch portion in the insertion direction and the second rotating body reaches the engagement position for the second latch portion in the insertion direction. 
     According to another aspect of the present invention, there is provided a sheet feeding apparatus comprising: a housing; a storage unit that is accommodated within the housing and that has a sheet stacking unit that stacks sheets, and that is movable in an insertion direction with respect to the housing and an opposite direction of the insertion direction; a first rotating body arranged at one end in a direction that intersects with the insertion direction of the storage unit; a second rotating body arranged at the other end in a direction that intersects with the insertion direction of the storage unit; a first latch portion that is provided in the housing and engages with the first rotating body; a second latch portion that is provided in the housing and engages with the second rotating body; a connecting portion that connects the first latch portion and the second latch portion; and a feed unit configured to feed the sheets stacked in the sheet stacking unit to an image forming apparatus, wherein the housing includes the first latch portion, the second latch portion, the connecting portion, and the feed unit, the storage unit includes the first rotating body and the second rotating body, the first latch portion and the second latch portion are connected by the connecting portion, the first latch portion and the second latch portion both include: from its head towards the insertion direction, an inclined face portion that inclines with respect to the insertion direction; a short side portion that is connected to the inclined face portion and forms an angle with the insertion direction, the angle being smaller than an angle between the inclined face portion and the insertion direction; and a concave portion that connects to the short side portion and engages with a corresponding rotating body, and in a case where the storage unit is inserted at a maximum angle with respect to the housing, a length in the insertion direction from a position of the inclined face portion at which a corresponding rotating body initially contacts to a position at which the concave portion connects to the short side portion is longer than a distance in the insertion direction between the first rotating body and the second rotating body. 
     According to still another aspect of the present invention, there is provided an image forming apparatus comprising a sheet feeding apparatus of the above-described configuration and an image forming unit configured to form an image onto a sheet that the sheet feeding apparatus feeds. 
     The invention is particularly advantageous since it can prevent a half-latched state by using a latch assembly in which two latches operate in an integrated fashion. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side sectional view showing the schematic arrangement of an image forming apparatus that includes a sheet feeding apparatus according to an exemplary embodiment of the present invention; 
         FIG. 2  is a perspective view showing, in a state in which a cover is removed, a main part of a sheet stacking unit; 
         FIG. 3  is a perspective view illustrating the internal structure of the sheet feeding apparatus exhibiting a state in which the sheet storage (sheet stacking unit) is removed; 
         FIG. 4  is a schematic diagram illustrating a situation in which the sheet storage is pushed into the sheet feeding apparatus at an angle; 
         FIGS. 5A and 5B  are perspective views illustrating rollers of the latch assembly and the sheet storage in a normally latched state and in a half-latched state; 
         FIG. 6  is a side view illustrating the detailed shape of latches; and 
         FIG. 7  is a view illustrating a time-dependent transition of the relative positional relationship of the two rollers of the two latches in a case where the sheet storage is pushed into the sheet feeding apparatus at an angle. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. However, the present invention is not limited to embodiments to be described below, and changes and additions may be made without departing from the scope of the present invention. 
     In this specification, the terms “print” and “printing” not only include the formation of significant information such as characters and graphics, but also broadly include the formation of images, figures, patterns, and the like on a print medium, or the processing of the medium, regardless of whether they are significant or insignificant and whether they are so visualized as to be visually perceivable by humans. 
     Also, the term “print medium (or sheet)” not only includes a paper sheet used in common printing apparatuses, but also broadly includes materials, such as cloth, a plastic film, a metal plate, glass, ceramics, wood, and leather, capable of accepting ink. 
     &lt;Configuration of Image Forming System ( FIGS. 1-2 )&gt; 
       FIG. 1  is a side sectional view showing the schematic arrangement of an image forming system  1000  that forms an image in accordance with an electrophotographic method according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 1 , the image forming system  1000  includes an image forming apparatus (LBP)  900  and a paper deck  3000  connected to the image forming apparatus  900 . The paper deck  3000  includes a control unit  41  with a CPU, a RAM, and a ROM, which controls the paper deck  3000  in accordance with a command of a controller  120  that controls the entire image forming system  1000 . 
     The image forming apparatus  900  includes first to fourth sheet feeding apparatuses  1001  to  1004  of the same arrangement that feed sheets S and a sheet conveying apparatus  902  that conveys the sheets S fed by the sheet feeding apparatuses  1001  to  1004  to an image forming unit  901 . The controller  120  provided in the image forming apparatus  900  includes the CPU, the RAM, and the ROM in order to control the respective units of the image forming system  1000 . In addition, the controller  120  generates an image signal upon receiving image data from the outside (for example, a PC or the like) and outputs this to the image forming unit. 
     Each of the first to fourth sheet feeding apparatuses  1001  to  1004  includes a sheet feed cassette  10  that stores the sheets S, a pickup roller  11 , and a separation/conveyance roller pair  25  constituted by a feed roller  22  and a retard roller  23 . Each sheet S stored in the sheet feed cassette  10  is separated and fed by the pickup roller  11  and the separation/conveyance roller pair  25  each performing a vertical moving operation and rotating at a predetermined timing. A feeding sensor  24  is arranged near the downstream side of the roller  22  and retard roller  23  in a sheet feeding direction. The feeding sensor  24  detects passage of the sheets S, and transmits a detection signal to the controller  120 . 
     The sheet conveying apparatus  902  includes conveyance roller pairs  15 , a pre-registration roller pair  130 , and a registration roller pair  110 . The sheet S fed from each of the first to fourth sheet feeding apparatuses  1001  to  1004  is passed through a sheet conveyance path  108  by the conveyance roller pairs  15  and the pre-registration roller pair  130 , and then guided to the registration roller pair  110 . Subsequently, the sheet S is fed to the image forming unit  901  at a predetermined timing by the registration roller pair  110 . 
     The image forming unit  901  includes, for example, a photosensitive drum  112 , a laser scanner  111 , a developing device  114 , a transfer charger  115 , and a separation charger  116 . Then, at the time of image formation, laser light from the laser scanner  111  driven by an image signal from the controller  120  is deflected by a mirror  113 , and the photosensitive drum  112  that rotates in a clockwise direction is irradiated with the laser light, forming an electrostatic latent image on the photosensitive drum. Furthermore, the electrostatic latent image thus formed on the photosensitive drum is then visualized as a toner image by the developing device  114 . 
     Subsequently, the toner image on the photosensitive drum is transferred to the sheet S by the transfer charger  115  in a transfer unit  112   b . Furthermore, the sheet S to which the toner image is thus transferred is conveyed to a fixing apparatus  118  by a conveyance belt  117  after electrostatic separation from the photosensitive drum  112  by the separation charger  116 , and then discharged by discharge rollers  119 . Note that the image forming unit  901  and the fixing apparatus  118  form an image on the sheet S fed from a sheet feeding apparatus  30  (or the sheet feeding apparatuses  1001  to  1004 ). 
     A discharge sensor  122  is arranged in a conveyance path between the fixing apparatus  118  and the discharge rollers  119 . Based on a detection signal of the discharge sensor  122 , the controller  120  detects passage of the discharged sheet S. 
     Furthermore, in the above-described embodiment, the description has been given by taking an image forming apparatus (printer apparatus) having a single function as an example. However, the present invention is not limited to this. The present invention is also applicable to, for example, a copying machine system that integrates an image reading apparatus (scanner apparatus), the image forming apparatus, and an ADF device or may be implemented by adopting a multifunctional system obtained by further adding a facsimile function to the copying machine system. 
     Furthermore, the description has been given assuming that the image forming unit of the above-described image forming apparatus includes a mechanism that forms an image in accordance with the electrophotographic method. However, the present invention is not limited to this. The present invention may be implemented by adopting, for example, an image forming unit that forms an image in accordance with an inkjet method. 
     An embodiment regarding the paper deck  3000  serving as a large-volume deck will be described next by taking, as an example, the paper deck  3000  as the sheet feeding apparatus  30  of the image forming system  1000  configured as described above. 
       FIG. 2  is a perspective view showing, in a state in which a cover is removed, a main part of a paper deck  3000 . 
     As shown in  FIGS. 1 and 2 , the paper deck  3000  includes an apparatus main body  3000   a , a large-volume sheet storage  62  accommodated in the apparatus main body  3000   a , and a sheet feeding apparatus  30 . The sheet feeding apparatus  30  feeds sheets S stacked/stored in the sheet storage  62 , having an approximately rectangular parallelepiped shape, accommodated in the sheet feeding apparatus to an image forming unit  901 . 
     The sheet feeding apparatus  30  includes a sheet stacking tray  61  that stacks sheets S, a pickup roller  51  that feeds the sheets S stacked on the sheet stacking tray  61 , and a separation/conveyance roller pair  31  constituted by a feed roller  12  and a retard roller  13 . The pickup roller  51  is arranged near a leading end portion in a sheet feeding direction (the direction of an arrow b) to be brought into tight contact with the uppermost sheet on the sheet stacking tray  61  by an appropriate force. For this reason, the pickup roller  51  is provided above the sheet stacking tray  61 , contacts the uppermost sheet of the sheets S stacked on the raised sheet stacking tray  61 , and feeds the sheet in the direction of the arrow b. 
     The sheet stacking tray  61  can stack sheets and is supported so as to undergo a vertical moving operation by a driving mechanism (not shown) that includes a vertical moving motor (not shown). An upper surface detection sensor  50  is arranged on the upstream side of the pickup roller  51  on the upper side of the sheet stacking tray  61 . The upper surface detection sensor  50  is located above the sheet stacking tray  61  and detects an upper surface  68  of the sheet S on the sheet stacking tray. When the sheet stacking tray  61  is lowered the most, the sheet stacking tray  61  contacts a base plate  63  of the sheet feeding apparatus  30 . As indicated by a dotted line  81  in  FIG. 1 , the sheet stacking tray  61  rises when the volume of stacked sheets decreases. 
     The sheet feeding apparatus  30  includes the sheet stacking tray  61  and two pairs of side restriction members  80  and  83 . With respect to the feeding direction (the direction of an arrow b in  FIG. 2 ), the pair of side restriction members  80  is provided on a downstream side of a reference line defined as a center of a sheet, having a maximum length, stackable on the sheet stacking tray  61 . On the other hand, the pair of side restriction members  83  is provided on an upstream side of the reference line. The side restriction members  80  and  83  are arranged such that side end positions in a widthwise direction (the direction of an arrow h in  FIG. 2 ) perpendicular to the feeding direction (the direction of the arrow b in  FIG. 2 ) of the sheets S stacked on the sheet stacking tray  61  can be restricted, and both of them can move in the widthwise direction. Particularly, the pair of the side restriction members  83  can move in the widthwise direction (the direction of the arrow h in  FIG. 2 ) perpendicular to the feeding direction by a driving motor. A CPU of the control unit  41  controls the movement. 
     In this embodiment, the pickup roller  51  is configured to be brought into tight contact with the uppermost sheet of the sheets S on the sheet stacking tray by an appropriate force, as described above. Each sheet S on the sheet stacking tray  61  is separated and fed by the pickup roller  51  with the separation/conveyance roller pair  31  each performing a vertical moving operation and rotating at a predetermined timing. 
     In a connecting portion  14  with an image forming apparatus  900  of the paper deck  3000 , a connecting conveyance path  32  that feeds the sheet S from the side of the paper deck  3000  to a pre-registration roller pair  130  on the side of the image forming apparatus  900  is arranged. 
     The two pairs of the side restriction members  80  and  83  are configured to be able to guide the sheets S on the sheet stacking tray  61  by sliding up to the widths of all sheet sizes compatible with specifications. That is, the two pairs of the side restriction members  80  and  83  are supported to be movable in a sheet widthwise direction and restrict the both sides positions of the sheets S by contacting the both end portions of the stacked sheets S. Note that a leading end restriction unit  86  in  FIG. 2  restricts the leading end portion of each sheet S on the sheet stacking tray  61 . 
     In addition, a trailing end restriction member  87  is arranged so as to restrict the trailing end portion of each sheet S on the sheet stacking tray  61 . The trailing end restriction member  87  is supported to be movable in a direction parallel to the sheet feeding direction (the direction of the arrow b) and restricts the trailing end position of each sheet S. The trailing end restriction member  87  is moved along an elongated positioning hole portion  61  (not shown) formed in the center portion of the sheet stacking tray  61 . 
     As shown in  FIG. 2 , when the pickup roller  51  is driven by a driving motor (not shown) to rotate in a direction (the direction of an arrow a) of feeding the sheets S, the uppermost sheet S is fed in the direction of the arrow b. Consequently, the sheet S contacts a nip portion of the separation/conveyance roller pair  31  adjacent to the exist side of the pickup roller  51 . 
     When double feed of the sheets S fed by the pickup roller  51  occurs, the following operation is performed. That is, the retard roller  13  that is driven to/rotates in a direction opposite to the feed roller  12  that rotates in the same direction as the arrow a (the direction of an arrow c) rotates in the same direction as the feed roller  12  by the intervention of two or more sheets S in the nip portion. Then, the second and subsequent sheets S in the nip portion are pushed back in the direction of the sheet stacking tray  61  by the retard roller  13 , and only one uppermost sheet S is fed in the direction of the arrow b by the feed roller  12 . 
     When the sheet S is fed from the paper deck  3000  having the above arrangement or one of the aforementioned first to fourth sheet feeding apparatuses  1001  to  1004 , the leading end of the sheet S abuts against the nip portion of the pre-registration roller pair  130 . The pre-registration roller pair  130  is formed by a pair of counter rollers and arranged on a conveyance path of the sheet S to be rotatable in the direction of an arrow d in  FIG. 2  by a driving motor (not shown). The sheet S that once abuts against the nip portion of the pre-registration roller pair  130  is conveyed to the inside of the image forming apparatus  900  by the pre-registration roller pair  130  that rotates in accordance with a feeding timing. 
     Giving description with reference to  FIG. 1  again, the sheet storage (sheet stacking unit)  62  storing a large number of sheets stacked in the sheet feeding apparatus  30  can move along the rails  67   a  and  68   a  in a direction orthogonal to the sheet surface of  FIG. 1 , and can be removed and inserted by the user. As further illustrated in  FIG. 2 , the rails  67   a  and  68   a  are configured to be extendable in the arrow directions, and the shell of the rails  67   a  and  68   a  can be extended as illustrated by the dashed lines. The rails  67   a  and  68   a  engage the rails attached to the interior of the sheet feeding apparatus  30  as described later. Due to the engagement of the rails, the user can easily push the sheet storage  62  into the sheet feeding apparatus  30 . 
     Rollers  63   a  and  63   b  are arranged as rotating bodies at both ends in the lengthwise direction of the sheet storage  62 , respectively. When the user has pushed the sheet storage  62  into the sheet feeding apparatus  30 , the later described latches and the rollers  63   a  and  63   b  engage. Also, the sheet storage  62  is fixed to the sheet feeding apparatus  30 . 
       FIG. 3  is a perspective view illustrating the internal structure of the sheet feeding apparatus indicating a state in which the sheet storage (sheet stacking unit) is removed. 
     As illustrated in  FIG. 3 , rails  67  and  68  are attached opposing each other at both ends of the inner walls in the lengthwise direction of the sheet feeding apparatus  30 . The rails  67  and  68  respectively accept and engage the rails  67   a  and  68   a  arranged at both ends of the lengthwise direction of the sheet storage  62  described with reference to  FIG. 2 . Also, when the user pushes the sheet storage (sheet stacking unit)  62  into the sheet feeding apparatus  30 , the sheet storage  62  moves inside along the engaged rails. 
     Furthermore, the latch assembly is configured by latches  65   a  and  65   b  of the same size and same shape and a latch connecting portion  64  that the latches are joined to is arranged inside the sheet feeding apparatus  30 . The latch assembly can rotate about the extending direction of the latch connecting portion  64  as the axis and configuration is such that, by a biasing member (not shown), the latch assembly always rotates in the direction in which the leading edges of the latches  65   a  and  65   b  move downward. Also, a stopper mechanism (not shown) is arranged such that the latches  65   a  and  65   b  do not move below the position at which they engage with the rollers  63   a  and  63   b . The rollers  63   a  and  63   b  arranged at both ends in the lengthwise direction of the sheet storage  62  perform an engagement operation of approaching the latches  65   a  and  65   b  while moving downward (engagement operation hereinafter) when the sheet storage  62  is pushed into the sheet feeding apparatus  30 . By this, each latch is engaged and the sheet storage  62  is fixed. A detailed process of this engagement is described later. Also, as can be understood from  FIG. 3 , the latch connecting portion  64  connects the ends opposite to the leading end portions which contact and engage with the rollers corresponding to each latch. 
     When only one of the two latches, for example, contacts a roller and is lifted, the other latch not contacting a roller is similarly lifted because the latch assembly integrally moves. 
     Also, a storage compartment pushing member  66  is arranged at the inner wall of the deepest part of the sheet feeding apparatus  30 . The storage compartment pushing member  66  has a built-in spring and enters a state in which the spring retracts at a position where the rollers  63   a  and  63   b  engage the latches  65   a  and  65   b  to fix the sheet storage  62 . Accordingly, when the sheet storage  62  is released from the fixed state, the sheet storage  62  is pushed to the outside from the sheet feeding apparatus  30  by repulsive force of the spring. 
     More specifically, in a case where the user is to stack sheets onto the sheet stacking tray  61 , the following operation is performed. When the user presses a storage compartment release button (not shown) arranged on the top of the sheet feeding apparatus  30 , the above described latches disconnect. Also, the sheet storage  62  is pushed out by repulsive force of the above described spring. The user can manually pull out the sheet storage  62  after that. In this way, after the sheet storage  62  is caused to move to a position where sheets S can be stacked on the sheet stacking tray  61 , the user stacks the sheets S onto the sheet stacking tray  61  and pushes the sheet storage  62  back inside the sheet feeding apparatus  30 . 
     Note, clearance is given between the rails  67  and  68  of the sheet feeding apparatus  30  and the rails  67   a  and  68   a  of the sheet storage  62  side. This is because the clearance enables the sheet storage  62  to slide smoothly when engaging with the rails  67  and  68 . A clearance of 8 mm is given in the present embodiment. Also, configuration is given such that the sheet storage (sheet stacking unit)  62  can store long size sheets. 
     For this reason, a slight angle of the sheet storage  62  results in a large misalignment in a case where the rails  67   a  and  68   a  of the sheet storage  62  are not moved in parallel to the rails  67  and  68  of the sheet feeding apparatus  30  when the sheet storage  62  is being pushed in. 
       FIG. 4  is a schematic diagram illustrating a situation in which the sheet storage is pushed into the interior of the sheet feeding apparatus at an angle. In  FIG. 4 , L 1  is the width between the rollers  63   a  and  63   b  (910 mm in this embodiment) and θ is the angle of the skew of the sheet storage  62  in relation to the running direction of the rails (the dashed lines). In the clearance (8 mm) in this embodiment, an angle, in other words a tilt, of a maximum of 1.5° may occur when considering warping of the rails. 
     As illustrated in  FIG. 4 , in a case where the sheet storage  62  is pushed at an angle in the arrow direction, the roller  63   a  reaches the latch  65   a  before the roller  63   b  reaches the latch  65   b  in the insertion direction. The larger the width L 1  between rails is, the larger this difference (skew amount 1) becomes. For example, in a case where the skew angle θ is made to be 1.5°, which is the maximum, and L 1  is made to be 910 mm, the skew amount 1 is roughly 23.8 mm. Accordingly, if it is not ensured that, from the position where one of the latches (the latch  65   a  in  FIG. 4 ) engages the roller  63   a , the latches are held up over at least a length of 23.8 mm (=skew amount 1), which is the range over which the other latch, the latch  65   b  in  FIG. 4 , will contact the roller  63   b , a half-latched state will result. More specifically, a half-latched state in which only the latch  65   a  is engaged with the roller  63   a  and the latch  65   b  is not engaged with the roller  63   b  will occur. In a half-latched state, the sheet storage  62  will not be satisfactorily fixed with respect to the sheet feeding apparatus  30 . As a result, sheet feeding becomes unstable and there is possibility that a conveyance error or a sheet jam will occur. 
       FIGS. 5A and 5B  are perspective views illustrating a relationship between a conventional latch assembly and rollers of a sheet storage. 
       FIG. 5A  is a view illustrating a situation in which the sheet storage  62  is properly pushed straight into the sheet feeding apparatus  30  and  FIG. 5B  is a view illustrating a situation in which the sheet storage  62  is pushed at an angle into the sheet feeding apparatus  30 .  FIGS. 5A and 5B  are examples in which the two latches  65   a  and  65   b  which have triangular leading end portions are connected by the latch connecting portion  64  configure the latch assembly. The entire latch assembly is configured such that rotation around the rod axis of the rod-shaped latch connecting portion  64  is possible. For this reason, when the rollers move in the direction of the arrow symbol A, and the leading end portions of the latches contact with at least one of the two rollers  63   a  and  63   b , and then the rollers move further in the direction of the arrow symbol A, the latch assembly rotates in the direction of the arrow symbol B riding up on the rollers. 
     According to  FIG. 5A , the latch  65   a  and the latch  65   b  pass over the roller  63   a  and the roller  63   b , respectively, and engage with concave portions  69   a  and  69   b  of the two latches. More specifically, the latch  65   a  and the latch  65   b  engage with the concave portion  69   a  and the concave portion  69   b , respectively, and thereby the sheet storage  62  is correctly fixed to the sheet feeding apparatus  30 . Meanwhile, according to  FIG. 5B , the roller  63   a  does not get past the edge point between the leading end portion of the latch  65   a  and concave portion  69   a  although the roller  63   b  does get past the edge point between the leading end portion of the latch  65   b  and concave portion  69   b . When the latch  65   a  and the latch  65   b  move downward in this state, the latch  65   b  engages with the roller  63   b  but the latch  65   a  does not engage with the roller  63   a  and comes down before doing so. As a result, the latch  65   a  does not engage and the above described half-latched state results. More specifically, the latch  65   b  engages with the roller  63   b  prior to the latch  65   a  reaching the position at which the roller  63   a  is engaged. Accordingly, there is a possibility that that in spite of a half-latched state in which the latch  65   a  is not engaged and the latch  65   b  is engaged, an operator will misunderstand and think that both sides of the latch  65   a  and the latch  65   b  have come down in a correctly engaged state, and finish the operation. 
     In this embodiment, the shape of the leading end portions of the latches is changed from a triangular shape to an approximately trapezoidal shape so that the left and right latches function normally even if the sheet storage  62  is pushed somewhat at an angle into the sheet feeding apparatus  30 , for example. 
       FIG. 6  is a side view illustrating a detailed shape of latch portions. 
     The view of the upper side of  FIG. 6  illustrates the side of a conventional latch whose leading end portion is triangular as a comparative example and the view of the lower side of  FIG. 6  illustrates the shape of the latches  65   a  and  65   b  according to the embodiment. The triangular dimensions of the comparative example are a=23.5 mm, b=29.5 mm, and c=37.8 mm. In the shape of the comparative example, it is not possible to ensure that the latches will be held up over a length of 23.8 mm, which is a range over which the latch  65   b  would contact the roller  63   b  and that is necessary for handling skewing which causes the above described half-latch. For this reason, in a case where a skew at a maximum angle occurs, there is a possibility that a half-latch will occur. 
     As understood from comparing the comparative example on the upper side with the latch of the present embodiment on the lower side, the leading end portion of the latch of the comparative example (the dashed line E portion) is triangular whereas the leading end portion of the latch of the present embodiment is trapezoidal. More specifically, the shape of the leading end portion of the latch of the present embodiment extends the shape of the leading end portion of the latch of the comparative example in the direction of extension and makes the triangular shape approximately trapezoidal. 
     In the embodiment, the leading end portions of the latches  65   a  and  65   b  are extended 15 mm in the direction of extension and short side portions  71   a  and  71   b  of a length of 15 mm are formed. By this, a range over which the roller  63   b  contacts the latch  65   b  of 23.8 mm or greater can be maintained. More specifically, the roller contact area in  FIG. 6  is equal to/more than the maximum value of the skew amount 1 shown in  FIG. 4 . For this reason, even in a case where a skew at a maximum angle occurs, there is no possibility of a half-latch occurring. Also, the above described shape is not limited to a wholly trapezoidal shape. 
     In summary, configuration is taken such that the latches  65   a  and  65   b  in the embodiment respectively have structures in which their leading end portion have the trapezoidal shape inclined face portions  70   a  and  70   b , short side portions  71   a  and  71   b , and concave portions  69   a  and  69   b  in this order in the insertion direction. 
     The shape of the leading end portions of the latches which have a length of 152.1 mm and a height of 29.6 mm in the comparative example is extended by 15 mm in the direction of extension and the extended length is the length of the short sides of the approximately trapezoidal shapes in the example illustrated in  FIG. 6 . Accordingly, an increase in size in the direction of extension of the size of the latches in the embodiment is limited at less than 10%. For this reason, it is possible to configure such that there is no change of the size of the housing of the sheet feeding apparatus  30  that accommodates the sheet storage  62 . 
     In the embodiment, the latch assembly that employs a latch with the leading end portion having the above described shape is equipped within the sheet feeding apparatus  30 . 
     Next, description is given with reference to a drawing of a situation in which the sheet storage  62  of the above described configuration is pushed at an angle into the sheet feeding apparatus  30  of the above described configuration. 
       FIG. 7  is a view illustrating a time-dependent transition of the relative positional relationship of the two rollers of the two latches in a case where the sheet storage is pushed into the sheet feeding apparatus at an angle. 
     In  FIG. 7 , the left side illustrates a time-dependent transition of the relative positional relationship of the latch  65   a  and the roller  63   a  and the right side illustrates a time-dependent transition of the relative positional relationship of the latch  65   b  and the roller  63   b . Also, in  FIG. 7 , time (t) transitions from t=t 1  to t 2  . . . to t 11  in the vertical direction from top to bottom. Also, the sheet storage  62  is pushed into the sheet feeding apparatus  30  in accordance with this transition. Accordingly, in  FIG. 7 , the relative positional relationship between the latch  65   a  and the roller  63   a  can be compared with the relative positional relationship between the latch  65   b  and the roller  63   b  at the same time. Also, the arrow symbol AR indicates the insertion direction of the sheet storage  62  in  FIG. 7 . 
     Hereinafter, description is given regarding the relative positional relationship between the two latches and the two rollers in accordance with the transition of time when the sheet storage  62  is pushed at an angle into the sheet feeding apparatus  30 . Here, as illustrated in  FIG. 4 , a case in which the roller  63   a  reaches the latch  65   a  before the roller  63   b  reaches the latch  65   b  is envisioned. Of course, it goes without saying that the present invention can be applied in a case opposite to this, specifically, in a case where the roller  63   b  reaches the latch  65   b  before the roller  63   a  reaches the latch  65   a.  
         t=t 1          

     The roller  63   a  of the sheet storage  62  gets close to the leading end portion of the latch  65   a  first. In contrast, there is still a distance until the roller  63   b  of the sheet storage  62  reaches the leading end portion of the latch  65   b.  
         t=t 2          

     The roller  63   a  of the sheet storage  62  first contacts the inclined face portion  70   a  of the leading end portion of the latch  65   a . In contrast, the roller  63   b  of the sheet storage  62  has not reached the latch  65   b.  
         t=t 3          

     The roller  63   a  abuts the inclined face portion  70   a  of the leading end portion of the latch  65   a  and the latch  65   a  is gradually lifted. In contrast to this, although the latch  65   b  does not contact the roller  63   b  of the sheet storage  62 , the latch  65   b  lifts up because it is integrated with the latch  65   a  as the latch assembly.
         t=t 4          

     After the roller  63   a  contacts the inclined face portion  70   a  of the leading end portion of the latch  65   a  and the latch  65   a  is gradually lifted, the roller  63   a  reaches the point between the inclined face portion  70   a  of the leading end portion of the latch  65   a  and the short side portion  71   a . In contrast to this, although the latch  65   b  does not contact the roller  63   b  of the sheet storage  62 , the latch  65   b  lifts up because it is integrated with the latch  65   a  as the latch assembly.
         t=t 5          

     The roller  63   a  moves in a state in which the short side portion  71   a  rides on the roller  63   a  and the short side portion  71   a  and the roller  63   a  abut. In contrast to this, although the latch  65   b  is still not in contact with the roller  63   b , the roller  63   b  approaches the latch  65   b  while the latch  65   b  is lifted.
         t=t 6          

     A state in which the roller  63   a  passes the short side portion  71   a  and the short side portion  71   a  rides on the roller  63   a  ends. In contrast, the latch  65   b  is in a state in which the short side portion  71   b  rides on the roller  63   b  and the roller  63   b  moves under the short side portion  71   b.  
         t=t 7          

     The roller  63   a  passes the short side portion  71   a  and a state in which the short side portion  71   a  rides on the roller  63   a  ends. In contrast, a state continues in which the roller  63   b  has not passed the short side portion  71   b  and the short side portion  71   b  rides on the roller  63   b . A state is maintained in which the latch  65   a  is lifted up because it is integrated with the latch  65   b  as the latch assembly.
         t=t 8          

     This is immediately prior to the state in which the short side portion  71   b  rides on the roller  63   b  ends. The state in which the short side portion  71   a  rides on the roller  63   a  has ended. A state is maintained in which the latch  65   a  is lifted up because it is integrated with the latch  65   b  as the latch assembly.
         t=t 9          

     The roller  63   b  passes the short side portion  71   b  of the latch  65   b  and the state in which the short side portion  71   b  rides on the roller  63   b  ends. Also, the roller  63   b  moves to the concave portion  69   b  of the latch  65   b  which is the engagement position. At that time, the latch  65   b  starts the engagement operation with the roller  63   b . In synchronization with this, the latch  65   a  integrally operating with the latch  65   b  as the latch assembly also starts the engagement operation.
         t=t 10          

     The roller  63   b  passes the short side portion  71   b , and when it reaches the concave portion  69   b  which is the engagement position, the roller  63   a  has already passed the short side portion  71   a  and reached the concave portion  69   a  which is the engagement position. For this reason, when the latch  65   b  engages with the roller  63   b , the latch  65   a  also can engage with the roller  63   a . When engaged, the latch  65   a  enters an engaged state with the roller  63   a  at the deepest part (left end in the figure) of the concave portion  69   a  and the latch  65   b  enters an engaged state with the roller  63   b  at the frontmost part (right end in the figure) of the concave portion  69   b.  
         t=t 11          

     The latch  65   a  and the roller  63   a  and the latch  65   b  and the roller  63   b  are in an engaged state and the sheet storage  62  is fixed to the sheet feeding apparatus  30 . When the sheet storage  62  is pushed further into the sheet feeding apparatus  30  in this state, a state is entered in which the latch  65   a  is engaged at the frontmost part of the concave portion  69   a  and the latch  65   b  is engaged at the frontmost part of the concave portion  69   b . Thereby, the state in which the sheet storage  62  has been pushed at an angle into the sheet feeding apparatus  30  is resolved. 
     In summary, when the sheet storage  62  is pushed at the maximum tilt angle into the sheet feeding apparatus  30  along the insertion direction, if the roller  63   a  has reached the engagement position for the latch  65   a  and the roller  63   b  has not reached the engagement position for the latch  65   b  yet, the latch  65   a  does not engage with the roller  63   a  and the latch  65   b  does not engage with the roller  63   b . And, when not only the roller  63   a  has reached the engagement position for the latch  65   a  but also the roller  63   b  has reached the engagement position for the latch  65   b , the latch  65   a  engages with the roller  63   a  and the latch  65   b  engages with the roller  63   b.    
     In accordance with the embodiment described above, by changing the shape of the leading edge of the latches, it is possible to latch both sides of the sheet storage without a half-latched state occurring even if the sheet storage is pushed into the sheet feeding apparatus in an angled state with respect to the sheet feeding apparatus. Accordingly, it becomes possible to prevent an occurrence of a half-latched state in a simple configuration without introducing an increase of parts and without arranging sensors for detecting a half-latched state and using a complex mechanism that controls the latches in accordance with the detection. 
     Furthermore, in a case where a half-latched state occurs in the conventional configuration, the user would manually resolve the half-latched state and perform an additional operation of ejecting the sheet storage and re-inserting it into the sheet feeding apparatus. However, by virtue of the embodiment, additional operations become unnecessary and there is the advantage of user convenience being improved. 
     Furthermore, in the above described embodiment, although the sheet feeding apparatus and the image forming apparatus are configured as separate bodies, rather than being limited by this, the present invention may also be configured such that the sheet feeding apparatus is integrated in the image forming apparatus. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application Nos. 2017-245363, filed Dec. 21, 2017, and 2018-228301, filed Dec. 5, 2018, which are hereby incorporated by reference herein in their entirety.