Patent Publication Number: US-9896284-B2

Title: Sheet material feeding device and image forming apparatus

Description:
The entire disclosure of Japanese Patent Application No. 2016-090035 filed on Apr. 28, 2016 including description, claims, drawings, and abstract are incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet material feeding device and an image forming apparatus provided with the same. 
     Description of the Related Art 
     Image forming apparatuses such as copying machines, printers, and facsimiles include a sheet material feeding device that feeds sheet materials such as paper sheets. The sheet material feeding device includes a rear-end regulating member for regulating the position of the upstream end (rear end) of the sheet material in the feeding direction inside the cassette accommodating the sheet materials. Furthermore, in order to achieve a stable feeding corresponding to a change in the posture of the sheet materials as the number of sheet materials inside the cassette is decreased by feeding, a rear-end displacement member that comes in pressure contact with the sheet materials from the upstream side to the downstream side in the feeding direction may be provided. 
     In the case of this sheet material feeding device, there is concern that the rear-end displacement member becomes an obstacle at the time of replenishing the sheet materials to the cassette or that the sheet material bends when a small number of sheet materials are replenished. Therefore, in order to solve these problems, a technique has been proposed in which the rear-end displacement member is displaced to the upstream side in the feeding direction when the cassette is pulled out of the housing unit. An example of a prior art of such a sheet material feeding device is disclosed in JP 2004-142892 A. 
     The sheet material feeding device described in JP 2004-142892 A includes an end fence (rear-end regulating member), a pressing member (rear-end displacement member) projecting downstream in the feeding direction from the end fence, an urging member for urging the pressing member toward the downstream side in the feeding direction, and an urging force switching device for switching between presence and absence of urging force by the urging member corresponding to push-in and pull-out of the cassette with respect to the predetermined position. In this sheet material feeding device, the urging force of the pressing member by the urging device is applied by pushing the cassette to a predetermined position, and the urging force of the pressing member by the urging device is not allowed to be applied by pulling out the cassette from the predetermined position. 
     However, in the sheet material feeding device described in JP 2004-142892 A, there is a problem that the timing of the operations between the bottom plate (pushing-up plate) for pushing the sheet material upward and the pressing member (rear-end displacement member) is not mentioned. For example, when the urging timing for the sheet material to the downstream side in the feeding direction by the pressing member is later than the timing of pushing up the sheet material by the bottom plate, there is a possibility that the downstream end (leading edge) of the sheet material in the feeding direction is displaced to the upstream side according to the upward displacement of the bottom plate in the case where a small number of sheet materials are supplied to the cassette. As a result, contact between the uppermost sheet material and a feeding device becomes poor, and the sheet material may be bent by being urged toward the downstream side in the feeding direction by the pressing member. As a result, there is a concern that misfeed and skew feeding (inclination) of the sheet material may occur. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a sheet material feeding device and an image forming apparatus capable of achieving a stable feeding in response to a change in the posture of sheet materials as the number of the sheet materials inside the cassette is reduced by feeding. 
     To achieve the abovementioned object, according to an aspect, a sheet material feeding device reflecting one aspect of the present invention comprises: a housing; a cassette configured to accommodate a sheet material therein and capable of being pulled out of the housing and being stored in the housing; a pushing-up plate which is disposed on an inner bottom surface of the cassette and configured to fluctuate in a vertical direction with the sheet material placed on an upper surface of the pushing-up plate and a position thereof is changed to a feeding position or a retracted position; a rear-end regulating member provided inside the cassette for regulating a position of an upstream end of the sheet material in a feeding direction of the sheet material; a rear-end displacement member which is supported by the rear-end regulating member and configured to fluctuate in the feeding direction of the sheet material and a position thereof is changed to a feeding position or a retracted position; a pushing-up plate displacing device configured to change the position of the pushing-up plate to the feeding position when the cassette is stored in the housing; and a rear-end displacement member displacing device configured to complete a position change of the rear-end displacement member to the feeding position before a position change of the pushing-up plate to the feeding position by the pushing-up plate displacing device when the cassette is stored in the housing. 
     According to this configuration, the timing of changing the position of the rear-end displacement member to the feeding position of the sheet material when the cassette is stored in the housing unit is earlier than the timing of position change of the pushing-up plate to the feeding position of the sheet material. As a result, regardless of the number of the sheet materials inside the cassette, the sheet materials are disposed at a proper position with respect to the feeding direction. Therefore, stable feeding is achieved. 
     According to the sheet material feeding device with the above configuration, after the position change of the rear-end displacement member to the feeding position by the rear-end displacement member displacing device is completed, the position change of the pushing-up plate to the feeding position by the pushing-up plate displacing device is preferably started. 
     According to the sheet material feeding device with the above configuration, the sheet material feeding device preferably further comprises an electric drive source configured to change the position of the pushing-up plate. 
     According to the sheet material feeding device with the above configuration, the sheet material feeding device preferably further comprises an electric drive source configured to change the position of the rear-end displacement member. 
     According to the sheet material feeding device with the above configuration, the pushing-up plate displacing device preferably changes the position of the pushing-up plate by a mechanism that does not obtain power from an electric drive source. 
     According to the sheet material feeding device with the above configuration, the rear-end displacement member displacing device preferably changes the position of the rear-end displacement member by a mechanism that does not obtain power from an electric drive source. 
     According to the sheet material feeding device with the above configuration, the pushing-up plate displacing device preferably changes the position of the pushing-up plate to the retracted position when the cassette is pulled out of the housing. 
     According to the sheet material feeding device with the above configuration, the rear-end displacement member displacing device preferably changes the position of the rear-end displacement member to the retracted position when the cassette is pulled out of the housing. 
     According to the sheet material feeding device with the above configuration, the rear-end displacement member displacing device preferably comprises a first starting lever configured to change the position of the rear-end displacement member to the feeding position by coming into contact with the housing so as to be displaced when the cassette is stored in the housing. 
     According to the sheet material feeding device with the above configuration, the pushing-up plate displacing device preferably comprises a second starting lever configured to change the position of the pushing-up plate to the feeding position by coming into contact with the housing so as to be displaced when the cassette is stored in the housing. 
     According to the sheet material feeding device with the above configuration, a first starting lever preferably comes in contact with the housing before the second starting lever comes in contact with the housing. 
     According to the sheet material feeding device with the above configuration, a first starting lever and the second starting lever are preferably formed as a single member. 
     To achieve the abovementioned object, according to an aspect, an image forming apparatus reflecting one aspect of the present invention comprises: the sheet material feeding device with the above configuration; and an image forming unit configured to form an image on a sheet supplied from the sheet material feeding device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, advantages and features of the present invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention, and wherein: 
         FIG. 1  is a partial vertically cross-sectional front view of an image forming apparatus according to a first embodiment of the present invention; 
         FIG. 2  is a top view of a sheet material feeding device of the image forming apparatus according to the first embodiment of the present invention; 
         FIG. 3  is a vertical cross-sectional front view of the sheet material feeding device of the image forming apparatus according to the first embodiment of the present invention; 
         FIG. 4  is a partially enlarged perspective view of a cassette of the sheet material feeding device according to the first embodiment of the present invention; 
         FIG. 5  is a partially enlarged vertical cross-sectional front view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette has been pulled out; 
         FIG. 6  is a partially enlarged bottom view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette has been pulled out; 
         FIG. 7  is a partially enlarged vertical cross-sectional front view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette is stored; 
         FIG. 8  is a partially enlarged bottom view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette is stored; 
         FIG. 9  is a partial plan view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette has been pulled out; 
         FIG. 10  is a partial front view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette has been pulled out; 
         FIG. 11  is a bottom view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette has been pulled out; 
         FIG. 12  is a perspective view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette has been pulled out; 
         FIG. 13  is a partial plan view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette is stored; 
         FIG. 14  is a partial front view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette is stored; 
         FIG. 15  is a bottom view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette is stored; 
         FIG. 16  is a perspective view of the cassette of the sheet material feeding device according to the first embodiment of the present invention when the cassette is stored; 
         FIG. 17  is a bottom view of a cassette of a sheet material feeding device according to a second embodiment of the present invention when the cassette is stored; 
         FIG. 18  is a block diagram showing a configuration of a cassette of a sheet material feeding device according to a third embodiment of the present invention; 
         FIG. 19  is a bottom view of the cassette of the sheet material feeding device according to the third embodiment of the present invention when the cassette has been pulled out; 
         FIG. 20  is a partially enlarged bottom view of the cassette of the sheet material feeding device according to the third embodiment of the present invention when the cassette has been pulled out; 
         FIG. 21  is a bottom view of the cassette of the sheet material feeding device according to the third embodiment of the present invention when the cassette is stored; 
         FIG. 22  is a partially enlarged bottom view of the cassette of the sheet material feeding device according to the third embodiment of the present invention when the cassette is stored; 
         FIG. 23  is a block diagram showing a configuration of a cassette of a sheet material feeding device according to a fourth embodiment of the present invention; 
         FIG. 24  is a bottom view of the cassette of the sheet material feeding device according to the fourth embodiment of the present invention when the cassette is stored; and 
         FIG. 25  is a partially enlarged perspective view of the cassette of the sheet material feeding device according to the fourth embodiment of the present invention when the cassette is stored. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. 
     First Embodiment 
     First, the image output operation of the image forming apparatus according to a first embodiment of the present invention will be described while roughly describing structure thereof with reference to  FIG. 1 .  FIG. 1  is an example of a partial vertically cross-sectional front view of the image forming apparatus. In addition, the two-dot chain line with an arrow in the figure indicates a conveyance path and a conveyance direction of the sheet material. 
     As shown in  FIG. 1 , an image forming apparatus  1  is a so-called tandem type color copying machine, and includes an image reading unit  2  for reading an image of a document, a printing unit  3  for printing the read image on a sheet material such as a paper sheet, an operation unit  4  for inputting printing conditions and displaying the operation status, and a main control unit  5 . 
     The image reading unit  2  is a known one that reads an image of a document placed on the upper surface of a platen glass (not shown) by moving a scanner (not shown). The image on the document is separated into three colors of red (R), green (G), and blue (B), and is converted into electric signals by a charge coupled device (CCD) image sensor (not shown). As a result, the image reading unit  2  obtains image data of each color of red (R), green (G), and blue (B). 
     The image data of each color obtained by the image reading unit  2  is subjected to various processes in a main control unit  5  to be converted into image data of each reproduction color of yellow (Y), magenta (M), cyan (C), and black (K) and stored in a memory (not shown) of the main control unit  5 . The image data for each reproduction color stored in the memory is subjected to processing for correction of misregistration, and then read out for each scanning line in synchronism with the conveyance of the sheet material in order to perform light beam scanning with respect to a photosensitive drum  21  serving as an image carrying member. 
     The printing unit  3  forms an image by the electrophotographic method and transfers the image to the sheet material. The printing unit  3  includes an intermediate transfer belt  11  which is formed as an endless belt of an intermediate transfer body. The intermediate transfer belt  11  is wound around a driving roller  12 , tension roller  13  and follower roller  14 . Tension is applied to the intermediate transfer belt  11  by the tension roller  13  being urged upward by a spring (not shown) in  FIG. 1 . The intermediate transfer belt  11  rotates counterclockwise in  FIG. 1  by the driving roller  12 . 
     The driving roller  12  is in pressure contact with an opposed secondary transfer roller  15  with the intermediate transfer belt  11  interposed therebetween. At the position of the follower roller  14 , an intermediate transfer cleaning unit  16  provided so as to face the follower roller  14  with the intermediate transfer belt  11  interposed therebetween is in contact with the outer peripheral surface of the intermediate transfer belt  11 . After the toner image formed on the outer peripheral surface of the intermediate transfer belt  11  is transferred to the sheet material S, the intermediate transfer cleaning unit  16  removes deposits such as toner remaining on the outer peripheral surface of the intermediate transfer belt  11  to clean the belt. 
     Image forming units  20 Y,  20 M,  20 C, and  20 K corresponding to the reproduction colors of yellow (Y), magenta (M), cyan (C), and black (K) are provided under the intermediate transfer belt  11 . Hereinafter, unless restriction is particularly necessary, the description of the identification marks of “Y”, “M”, “C”, and “K” may be omitted and “image forming unit  20 ” may be used generically for example. The four image forming units  20  are arranged in a row along the rotating direction of the intermediate transfer belt  11  from the upstream side to the downstream side. The four image forming units  20  have the same configuration, and a charging unit, an exposure unit, a developing unit, a drum cleaning unit, and a primary transfer roller are arranged around the photosensitive drum  21  rotating clockwise in  FIG. 1 . 
     A scanning optical device  23 , which is an exposure device, is disposed below the image forming units  20 . The scanning optical device  23  serves as one unit for the four image forming units  20  and has light sources such as four semiconductor lasers (not shown) or the like corresponding to the four photosensitive drums  21  respectively. The scanning optical device  23  modulates the four semiconductor laser beams in accordance with the image gradation data of each reproduction color and emits the laser beams corresponding to reproduction colors to the four photosensitive drums  21  respectively. 
     Above the intermediate transfer belt  11 , toner bottles  31  and toner hoppers  32  are provided corresponding to the image forming units  20  of the four reproduction colors respectively. For the developing unit and the toner hopper  32 , a residual quantity detection unit (not shown) for detecting the remaining amount of toner in each of them is provided. Further, toner replenishing devices (not shown) are provided between the developing unit and the toner hopper  32  and between the toner hopper  32  and the toner bottle  31  respectively. When the residual quantity detection unit detects a decrease in the remaining amount of the toner in the developing unit, the replenishing device drives to replenish the toner from the toner hopper  32  to the developing unit. Further, when the residual quantity detection unit detects a decrease in the remaining amount of the toner inside the toner hopper  32 , the replenishing device drives to replenish the toner from the toner bottle  31  to the toner hopper  32 . The toner bottle  31  is detachably provided to the apparatus body, and can be replaced with a new one as appropriate. 
     Below the scanning optical device  23 , there is provided a sheet material feeding device  40  that accommodates a plurality of sheet materials S such as sheets of paper or the like therein. The sheet materials S accommodated inside the sheet material feeding device  40  is fed out one by one to the sheet material conveyance path Q from the uppermost layer by a feeding unit  44 . The sheet material S delivered from the sheet material feeding device  40  to the sheet material conveyance path Q reaches the position of a pair of registration rollers  94 . The pair of registration rollers  94  sends out the sheet material S toward the contact portion between the intermediate transfer belt  11  and the secondary transfer roller  15  (secondary transfer nip portion) in synchronism with the rotation of the intermediate transfer belt  11  while correcting the skew feeding of the sheet material S (skew correction). 
     In the image forming unit  20 , an electrostatic latent image is formed on the surface of the photosensitive drum  21  by the laser beam emitted from the scanning optical device  23 , and the electrostatic latent image is visualized as a toner image by the developing unit. The toner image formed on the surface of the photosensitive drum  21  is primarily transferred onto the outer peripheral surface of the intermediate transfer belt  11  at a position where the photosensitive drum  21  faces the primary transfer roller with the intermediate transfer belt  11  interposed therebetween. While the intermediate transfer belt  11  rotates, the toner images of the respective image forming units  20  are sequentially transferred onto the intermediate transfer belt  11  at a predetermined timing, whereby a color toner image is formed by superimposing four toner colors of yellow, magenta, cyan, black on each other on the outer peripheral surface of the intermediate transfer belt  11 . 
     The color toner image primarily transferred onto the outer peripheral surface of the intermediate transfer belt  11  is transferred onto the sheet material S fed in synchronism by the pair of registration rollers  94  at the secondary transfer nip portion formed by contact between the intermediate transfer belt  11  and the secondary transfer roller  15 . 
     A fixing unit  95  is provided above the secondary transfer nip portion. The sheet material S onto which the unfixed toner image has been transferred at the secondary transfer nip portion is sent to the fixing unit  95  and is sandwiched between a heating roller and a pressure roller, and the toner image is heated and pressed to be fixed to the sheet material S. The sheet material S that has passed through the fixing unit  95  is discharged to a sheet material discharge unit  96  provided above the intermediate transfer belt  11 . 
     The operation unit  4  is provided on the front side of the image reading unit  2 . The operation unit  4  accepts a setting input of printing conditions by a user such as the type and size of the sheet material S to be used for printing, enlargement/reduction and presence or absence of duplex printing, and a setting input of a facsimile number, a sender name, etc. in facsimile transmission. In addition, the operation unit  4  also functions as an informing unit for notifying the user about the status of the apparatus, notes, error messages, for example by display on the display unit  4 w. 
     Further, the image forming apparatus  1  is provided with the main control unit  5  constituted by a CPU (not shown), an image processing unit, and other electronic components (not shown) so as to control the overall operation thereof. The main control unit  5  achieves a series of image forming operations and printing operations by using the CPU serving as a central processing unit and the image processing unit so as to control constituent elements such as the image reading unit  2  and the printing unit  3  on the basis of programs and data stored or input in the memory. 
     Next, the configuration of the sheet material feeding device  40  of the image forming apparatus  1  will be described with reference to  FIGS. 2 to 5 .  FIGS. 2 and 3  are a top view and a vertical cross-sectional front view of the sheet material feeding device  40 .  FIG. 4  is a partially enlarged perspective view of the cassette of the sheet material feeding device  40 .  FIG. 5  is a partially enlarged vertical cross-sectional front view of the cassette of the sheet material feeding device  40  when the cassette has been pulled out.  FIG. 3  is a vertical cross-sectional view taken along the line III-III drawn in  FIG. 2 , and drawings around the rear-end regulating member which will be described later is omitted. The lower side of  FIG. 2  is the front side of the sheet material feeding device  40 , and the upper side of  FIG. 2  is the back side of the sheet material feeding device  40 . The top and bottom direction in  FIG. 3  is the vertical direction of the sheet material feeding device  40 , and the right and left direction in  FIG. 3  is the right and left direction of the sheet material feeding device  40 . 
     The sheet material feeding device  40  includes a housing unit  41  and a cassette  42  as shown in  FIGS. 2 and 3 . The cassette  42  is a sheet material accommodating unit in which sheet materials such as cut paper or the like before printing are stacked and accommodated. The cassette  42  is formed in a flat box shape with the upper face opened, and the sheet materials are stored and stacked in a direction from the upper face. The sheet material is fed toward the right in  FIGS. 2 and 3  with respect to the cassette  42  by the operation of the feeding unit  44  which will be described in detail later. 
     The cassette  42  can be slid horizontally with respect to the housing unit  41  along a guide portion (not shown) provided to extend in the front-back direction between the cassette  42  and the housing unit  41 . The cassette  42  can be pulled out of and stored in the housing unit  41  by pulling out or pushing in the front-back direction. 
     A pushing-up plate  43  is disposed on the inner bottom surface of the cassette  42 . The sheet materials are placed and stacked up on the pushing-up plate  43 . The pushing-up plate  43  is supported on side walls inside the cassette  42  by support shafts  43   a  provided so as to extend in the front-back direction at the upstream end thereof in the sheet material feeding direction, that is, the left end in  FIG. 2 . The pushing-up plate  43  is swingable around the support shaft  43   a  vertically in a vertical plane with the downstream end (right end) in the sheet material feeding direction being a free end, and the inclination angle of the feeding direction of the sheet material changes according to the stacking number of the sheet materials stacked on the top surface. The support shafts  43   a  are provided at two places, that is the front side and the back side of the pushing-up plate  43 . 
     On the lower side of the downstream side of the pushing-up plate  43  in the sheet material feeding direction, a pushing-up plate displacing device  80  to be described later is arranged between the pushing-up plate  43  and the inner bottom surface of the cassette  42  and on the front side of the pushing-up plate  43  and further on the outer bottom surface of the cassette  42  (see  FIGS. 9 and 10 ). When the cassette  42  is stored in the housing unit  41 , the pushing-up plate displacing device  80  operates and the downstream portion of the pushing-up plate  43  in the sheet material feeding direction rises. When the cassette  42  is pulled out of the housing unit  41 , the pushing-up plate displacing device  80  operates and the pushing-up plate  43  falls down to the inner bottom surface of the cassette  42 . In this way, the pushing-up plate displacing device  80  changes the position of the pushing-up plate  43 . 
     The feeding unit  44  is disposed on the housing unit  41  above the downstream portion of the cassette  42  in the sheet material feeding direction. The feeding unit  44  feeds the sheet material accommodated inside the cassette  42  to the outside of the cassette  42 . The feeding unit  44  includes a feeding roller  44   a  and a separating roller  44   b  shown in  FIG. 3 . 
     The feeding roller  44   a  is disposed above the downstream portion of the pushing-up plate  43  in the sheet material feeding direction. When the downstream portion in the sheet material feeding direction of the sheet materials stacked on the pushing-up plate  43  is pushed up by the pushing-up plate  43 , the uppermost layer of the sheet materials comes in pressure contact with the feeding roller  44   a  from below. The sheet material S in the cassette  42  is sent to the outside of the cassette  42  by the feeding roller  44   a.    
     The lower part of the surface of the feeding roller  44   a  is provided so as to protrude toward the sheet material conveyance path Q extending from the sheet material feeding device  40  to the outside thereof. The feeding roller  44   a  is connected to a motor (not shown) and rotated. 
     The separating roller  44   b  is disposed below the feeding roller  44   a  facing the separating roller across the sheet material conveyance path Q. The separating roller  44   b  is in pressure contact with the feeding roller  44   a  by the action of a urging member (not shown). The sheet material is inserted into the nip portion formed by contact between the separating roller  44   b  and the feeding roller  44   a.  The separating roller  44   b  is not connected to a motor but is rotated in accordance with the rotation of the feeding roller  44   a  by the contact with the feeding roller  44   a.    
     For example, a torque limiter (not shown) is provided on the shaft portion of the separating roller  44   b.  When a sheet material does not exist in or only one sheet material has entered the nip portion formed by contact between the separating roller  44   b  and the feeding roller  44   a,  a torque equal to or larger than the setting torque of the torque limiter is applied to the separating roller  44   b  and the separating roller  44   b  rotates in the direction for feeding the sheet material in accordance with the feeding roller  44   a.  On the other hand, when a plurality of sheets enter the nip portion due to overlapping of the sheet materials, the torque applied to the separating roller  44   b  is less than the setting torque of the torque limiter and the separating roller  44   b  stops the rotation. As a result, since the lower side of the overlapped lower sheet materials is not fed out, occurrence of the problem of double feeding in which overlapped sheet materials are sent can be prevented. 
     Width regulating members  45  are disposed at both ends of the sheet materials stacked on the pushing-up plate  43  in the cassette  42  in a direction intersecting the feeding direction, that is, on the front side and the back side of the sheet materials. The width regulating members  45  are displaceable in the width direction of the sheet material which is a direction intersecting the sheet material feeding direction and can be brought into contact with the end face on the front side and the end face on the back side of a bundle of the sheet materials. As a result, the width regulating member  45  regulates the position in the width direction of the sheet material. 
     A rear-end regulating member  60  is disposed on the upstream side in the feeding direction of the sheet materials stacked on the pushing-up plate  43  inside the cassette  42 . One rear-end regulating member  60  is provided at the center portion in the width direction of the sheet material, which is a direction intersecting the feeding direction of the sheet material. The rear-end regulating member  60  is displaceable in parallel to the sheet material feeding direction and can be brought into contact with an end surface (rear end) of the bundle of sheet materials on the upstream side in the feeding direction. As a result, the rear-end regulating member  60  regulates the position of the upstream end of the sheet material in the feeding direction. 
     Next, the structures of the rear-end regulating member  60  and its surroundings will be described with reference to  FIGS. 6 to 8  in addition to  FIGS. 2, 4, and 5 .  FIG. 6  is a partially enlarged bottom view of the cassette  42  when the cassette has been pulled out.  FIGS. 7 and 8  are partially enlarged vertical cross-sectional front view and partially enlarged bottom view of the cassette  42  when the cassette  42  is stored. 
     As shown in  FIGS. 4 and 5 , the rear-end regulating member  60  is a member an outer shape of which is L-shaped viewed from the front, and includes a vertical portion  60   a  and a horizontal portion  60   b.  The vertical portion  60   a  and the horizontal portion  60   b  do not need to be strictly vertical and horizontal. 
     The vertical portion  60   a  is formed so as to be substantially vertical extending upward from the inner bottom surface of the cassette  42 . The horizontal portion  60   b  is formed so as to be substantially horizontal extending from the lower portion of the vertical portion  60   a  along the inner bottom surface of the cassette  42  toward the downstream side in the feeding direction of the sheet material. The horizontal portion  60   b  is fitted to a guide rail  46  provided on the inner bottom surface of the cassette  42 . The guide rail  46  extends in parallel to the feeding direction of the sheet material. The rear-end regulating member  60  can move in parallel to the sheet material feeding direction via the guide rail  46 . 
     The rear-end regulating member  60  includes a rear-end displacement member  61  and a rear-end contact member  62 . The rear-end displacement member  61  and the rear-end contact member  62  each form a plate shape extending in the width direction of the sheet material and substantially vertically. The rear-end displacement member  61  and the rear-end contact member  62  are supported on the upper portion of the vertical portion  60   a  via support shaft portions  61   a  and  62   a  provided at the upper ends of the members and extending substantially horizontally in the width direction of the sheet material respectively. The rear-end displacement member  61  and the rear-end contact member  62  are rotatable around the axis of the support shaft portions  61   a  and  62   a  respectively, and the lower portions thereof are swung in the feeding direction of the sheet material. As shown in  FIG. 5 , the support shaft portion  61   a  of the rear-end displacement member  61  and the support shaft portion  62   a  of the rear-end contact member  62  are provided at different positions. 
     Both lower ends of the rear-end displacement member  61  and the rear-end contact member  62  are inserted into an opening  60   c  which passes through the horizontal inner side of the horizontal portion  60   b  in the vertical direction. The lower end portion of the rear-end contact member  62  does not protrude downward from the bottom surface of the horizontal portion  60   b  but a lower end portion  61   b  of the rear-end displacement member  61  protrudes downward from the bottom surface of the horizontal portion  60   b.    
     The rear-end contact member  62  is interposed between the rear-end displacement member  61  and the upstream end of the sheet material in the feeding direction, and directly comes in contact with the upstream end of the sheet material in the feeding direction. The rear-end contact member  62  is displaced in the sheet material feeding direction together with displacement of the rear-end displacement member  61  in the sheet material feeding direction. 
     A rear-end displacement member displacing device  70  is provided on the bottom of the cassette  42  around the rear-end regulating member  60 . As shown in  FIGS. 4 to 6 , the rear-end displacement member displacing device  70  includes a slide member  72 , first starting lever  73 , first starting lever urging spring  74 , connecting piece  75 , and slide member urging spring  76 . 
     The slide member  72  is provided on the outer bottom portion of the cassette  42 . The slide member  72  is disposed at the center portion of the guide rail  46  in the width direction of the sheet material. The slide member  72  has a relatively elongated plate shape extending along the bottom surface of the cassette  42  and extends parallel to the direction in which the guide rail  46  extends, that is, in the feeding direction of the sheet material. 
     The upper portion of the slide member  72  is fitted into an opening groove  46   a  provided in the bottom portion of the guide rail  46 , passing through vertically and extending in parallel in the feeding direction of the sheet material, and the upper surface of the slide member  72  faces the inside of the cassette  42 . The slide member  72  can slide in a direction in which the opening groove  46   a  extends, that is, in parallel to the feeding direction of the sheet material. 
     The slide member  72  is fitted into the opening groove  46   a  and has engaging portions  72   a  in a region where the upper surface of the slide member  72  faces the inside of the cassette  42 . The engaging portion  72   a  is formed as a long hole having a rectangular shape for example, and a plurality of the engaging portions  72   a  corresponding to the types of the sizes of the sheet material in the feeding direction are arranged side by side in the feeding direction of the sheet material. As shown in  FIGS. 5 and 7 , the lower end portion  61   b  of the rear-end displacement member  61  protruding downward from the bottom surface of the horizontal portion  60   b  of the rear-end regulating member  60  is engaged with the engaging portion  72   a.    
     The first starting lever  73  is provided at the outer bottom portion of the cassette  42  and below the slide member  72 . The first starting lever  73  has a plate shape extending along the bottom surface of the cassette  42 , and its outer shape is substantially L-shaped as viewed from below. The first starting lever  73  is supported on the outer bottom surface of the cassette  42  via a vertically extending support shaft portion  73   a  provided at one end of the first starting lever  73 . The support shaft portion  73   a  is provided on the back side (the lower side in  FIG. 6 ) of the center portion in the width direction of the sheet material in the cassette  42  and the first starting lever  73  extends toward the front side (the upper side in  FIG. 6 ) from the support shaft portion  73   a.  The first starting lever  73  is rotatable around the axis of the support shaft portion  73   a.    
     The first starting lever urging spring  74  is disposed radially outward around the axis of the support shaft portion  73   a  of the first starting lever  73 . The first starting lever  73  is urged by the first starting lever urging spring  74  in the rotational direction around the axis of the support shaft portion  73   a.  The first starting lever urging spring  74  is, for example, constituted by a compression coil spring and extends in parallel to the feeding direction of the sheet material and is disposed between the bottom portion of the cassette  42  and the first starting lever  73 . As a result, when the cassette  42  has been pulled out of the housing unit  41 , a part of the first starting lever  73  protrudes outward from an outer wall surface  42   a  on the upstream side of the cassette  42  in the feeding direction of the sheet material as shown in  FIGS. 5 and 6 . 
     The connecting piece  75  and the slide member urging spring  76  are disposed below the slide member  72  and are provided so as to be movable in parallel to the feeding direction of the sheet material similarly to the slide member  72 . The other end (free end) of the first starting lever  73  and the slide member  72  are connected via the connecting piece  75  and the slide member urging spring  76 . The slide member urging spring  76  is, for example, constituted by a compression coil spring and disposed between the connecting piece  75  and the slide member  72  so that the axis thereof extends in parallel to the feeding direction of the sheet material, and elastic force acts along the feeding direction of the sheet material. 
     When the cassette  42  is stored in the housing unit  41 , the first starting lever  73  comes in contact with the inner wall of the housing unit  41 . As shown in  FIGS. 7 and 8 , the first starting lever  73  retracts entirely inside the outer wall surface  42   a  on the upstream side of the cassette  42  in the feeding direction of the sheet material while resisting the urging force of the first starting lever urging spring  74 . As a result, the first starting lever  73  pushes the connecting piece  75  toward the downstream side in the feeding direction of the sheet material, and further the connecting piece  75  pushes the slide member urging spring  76 . Then, the slide member urging spring  76  causes the slide member  72  to slide toward the downstream side in the feeding direction of the sheet material by the urging force thereof. The slide member  72  slides to the downstream side in the feeding direction of the sheet material so as to displace the rear-end displacement member  61  the lower end portion  61   b  of which is engaged with the engaging portion  72   a  toward the downstream side in the feeding direction of the sheet material (see  FIG. 7 ). 
     When the cassette  42  is pulled out of the housing unit  41 , the contact of the first starting lever  73  with the inner wall of the housing unit  41  is released. As shown in  FIGS. 5 and 6 , the first starting lever  73  is pressed by the urging force of the first starting lever urging spring  74  so that a part of the first starting lever  73  protrudes outward from the outer wall surface  42   a  on the upstream side of the cassette  42  in the feeding direction of the sheet material. As a result, the first starting lever  73  pulls the connecting piece  75  toward the upstream side in the feeding direction of the sheet material, and the connecting piece  75  further causes the slide member  72  to slide toward the upstream side in the feeding direction of the sheet material. The slide member  72  slides to the upstream side in the feeding direction of the sheet material so as to displace the rear-end displacement member  61  the lower end portion  61   b  of which is engaged with the engaging portion  72   a  toward the upstream side in the feeding direction of the sheet material (see  FIG. 5 ). 
     Another configuration may be used if the structure is such that when the cassette  42  is stored in the housing unit  41 , the slide member  72  slides to the downstream side in the feeding direction of the sheet material so as to displace the rear-end displacement member  61  toward the downstream side in the feeding direction of the sheet material. That is, for example, the configuration may be employed in which the first starting lever  73 , the connecting piece  75 , and the slide member urging spring  76  have been eliminated, and a part of the slide member  72  protrudes outward from the outer wall surface  42   a  on the upstream side of the cassette  42  in the feeding direction of the sheet material when the cassette  42  has been pulled out of the housing unit  41 . In this case, the first starting lever urging spring  74  directly urges the slide member  72  toward the upstream side in the feeding direction of the sheet material. 
     In this manner, the rear-end displacement member displacing device  70  displaces the rear-end displacement member  61  toward the downstream side in the feeding direction of the sheet material while the cassette  42  is stored in the housing unit  41 , and causes the rear-end displacement member  61  to change its position to the feeding position. Accordingly, the downstream end (leading edge) of the sheet material in the feeding direction can be automatically moved to a predetermined feeding position. 
     Since the rear-end displacement member displacing device  70  changes the position of the rear-end displacement member  61  by a mechanism that does not obtain power from an electric driving source, cost increase is suppressed and low power consumption can be achieved. 
     In addition, while the cassette  42  is pulled out of the housing unit  41 , the rear-end displacement member displacing device  70  displaces the rear-end displacement member  61  toward the upstream side in the feeding direction of the sheet material, and changes the position of the rear-end displacement member  61  to the retracted position. Thereby, when the sheet material is supplied to the inside of the cassette  42 , the rear-end displacement member  61  does not become an obstacle, and workability of replenishment can be improved. 
     Further, the rear-end displacement member displacing device  70  includes the first starting lever  73  which comes in contact with the housing unit  41  while the cassette  42  is stored in the housing unit  41 , and thus when the cassette  42  is stored in the housing unit  41 , the position of the rear-end displacement member  61  can be easily changed to the feeding position. 
     Next, a detailed structure of the pushing-up plate displacing device  80  and its surroundings will be described with reference to  FIGS. 9 to 16 .  FIGS. 9, 10, 11, and 12  are a partial plan view, partial front view, bottom view, and perspective view of the cassette  42  respectively when the cassette  42  has been pulled out.  FIGS. 13, 14, 15 and 16  are a partial plan view, partial front view, bottom view and perspective view of the cassette  42  respectively when the cassette  42  is stored. In  FIGS. 9, 10, 13, and 14 , the drawings of some constituent elements such as the open top flat box-shaped cassette  42  itself are omitted. 
     As shown in  FIGS. 9 to 12 , the cassette  42  is provided with the pushing-up plate displacing device  80  for changing the position of the pushing-up plate  43 . The pushing-up plate displacing device  80  includes a second starting lever  81 , direct-acting link  82 , turning link  83 , pushing-up spring  84 , turning lever  85 , rotary shaft  86  and pushing-up lever  87 . 
     The second starting lever  81  is provided in an outer bottom portion of the cassette  42  and below the first starting lever  73 . The second starting lever  81  has a plate shape extending along the bottom surface of the cassette  42  and extends in the width direction of the sheet material. The second starting lever  81  is supported on the outer bottom surface of the cassette  42  via a substantially vertically extending support shaft portion  81   a  provided at one end of the second starting lever  81 . The support shaft portion  81   a  is provided on the backside relative to the center portion of the cassette  42  in the width direction of the sheet material, and the second starting lever  81  extends toward the front side from the support shaft portion  81   a.  The second starting lever  81  is rotatable around the axis of the support shaft portion  81   a.    
     The direct-acting link  82  is provided on the front side relative to the central portion in the width direction of the sheet material in the bottom portion of the cassette  42 . The direct-acting link  82  has an elongated shape extending along the bottom surface of the cassette  42  and extends in parallel to the feeding direction of the sheet material. The direct-acting link  82  is guided by a guide member (not shown) and can be moved in parallel to the feeding direction of the sheet material. The end portion on the front side of the second starting lever  81  is connected to an upstream end of the direct-acting link  82  in the feeding direction of the sheet material, and a lower end of the turning link  83  is connected to a downstream end of the direct-acting link  82  in the feeding direction of the sheet material. The direct-acting link  82  can be slightly displaced to the front side and the back side according to the rotation of the second starting lever  81 . 
     The turning link  83  is provided in a region corresponding to the downstream end of the direct-acting link  82  in the feeding direction of the sheet material on the front side of the substantially upstream portion of the pushing-up plate  43  in the feeding direction of the sheet material. The turning link  83  has an elongated shape extending substantially in the vertical direction. The turning link  83  is supported on the cassette  42  via a support shaft portion  83   a  provided at the substantially center portion in the vertical direction and extending in the substantially horizontal direction in the width direction of the sheet material. The turning link  83  can rotate clockwise or counterclockwise as viewed from the front around the axis of the support shaft portion  83   a  (see  FIG. 10 ). The downstream end of the direct-acting link  82  in the feeding direction of the sheet material is connected to the lower end of the turning link  83  and the upstream end of the pushing-up spring  84  in the feeding direction of the sheet material is connected to the upper end of the turning link  83 . 
     The pushing-up spring  84  is formed of an extension coil spring for example and extends from the region corresponding to the upper end of the turning link  83  toward the downstream side in the feeding direction of the sheet material. An upper end of the turning link  83  is connected to an upstream end of the pushing-up spring  84  in the feeding direction of the sheet material, and an upper end of the turning lever  85  is connected to a downstream end of the pushing-up spring  84  in the feeding direction of the sheet material. The pushing-up spring  84  exerts an elastic force (urging force) by pulling between the upper end of the turning link  83  and the upper end of the turning lever  85 . 
     The pushing-up spring  84  urges the second starting lever  81  in the rotating direction around the axis of the support shaft portion  81   a  via the turning link  83  and the direct-acting link  82 . Accordingly, when the cassette  42  has been pulled out of the housing unit  41 , a part of the second starting lever  81  protrudes outward from the outer wall surface  42   a  on the upstream side of the cassette  42  in the feeding direction of the sheet material (see  FIGS. 11 and 12 ). 
     The turning lever  85  is provided in a region corresponding to the downstream end of the pushing-up spring  84  in the feeding direction of the sheet material on the front side of a substantially center portion of the pushing-up plate  43  in the feeding direction of the sheet material. The turning lever  85  has an elongated shape extending substantially in the vertical direction. The lower end of the turning lever  85  is supported by the rotary shaft  86  extending in the width direction of the sheet material and substantially in the horizontal direction. The turning lever  85  is rotatable around the axis of the rotary shaft  86  clockwise or counterclockwise as viewed from the front (see  FIG. 10 ). The downstream end of the pushing-up spring  84  in the feeding direction of the sheet material is connected to the upper end which is the free end of the turning lever  85 . 
     As shown in  FIGS. 9 and 10 , the rotary shaft  86  is disposed in a position below the substantially center portion of the pushing-up plate  43  in the feeding direction of the sheet material and in the vicinity of the inner bottom surface of the cassette  42 . The rotary shaft  86  extends to be relatively long in the width direction of the sheet material from the front side to the back side of the pushing-up plate  43 , and both ends thereof are rotatably supported by the cassette  42 . 
     The pushing-up lever  87  is provided in a position below the downstream side portion of the pushing-up plate  43  in the feeding direction of the sheet material and at the center portion of the pushing-up plate  43  in the width direction of the sheet material. The pushing-up lever  87  has a plate shape an upper surface of which is substantially opposed to the lower surface of the pushing-up plate  43 , and a portion of one side thereof extending in the width direction of the sheet material at the upstream end thereof in the feeding direction of the sheet material is attached to the rotary shaft  86 . The pushing-up lever  87  extends outward in the radial direction of the rotary shaft  86  and toward the downstream side in the feeding direction of the sheet material. The downstream end of the pushing-up lever  87  in the feeding direction of the sheet material is in contact with the lower surface of the pushing-up plate  43 . The pushing-up lever  87  rotates around the axis of the rotary shaft  86  in accordance with the rotation of the rotary shaft  86 . 
     When the cassette  42  is stored in the housing unit  41 , the second starting lever  81  comes into contact with the inner wall of the housing unit  41 , and as shown in  FIGS. 13 to 16 , the second starting lever  81  entirely retracts inward from the outer wall surface  42   a  on the upstream side of the cassette  42  in the feeding direction of the sheet material. As a result, the second starting lever  81  pushes the direct-acting link  82  toward the downstream side in the feeding direction of the sheet material, and furthermore, the direct-acting link  82  rotates the turning link  83  counterclockwise as seen from the front. Then, the pushing-up spring  84  rotates the turning lever  85  counterclockwise as seen from the front by the urging force. While the turning lever  85  rotates, the rotary shaft  86  also rotates counterclockwise as viewed from the front, so that the pushing-up lever  87  pushes up the downstream side portion of the pushing-up plate  43  in the feeding direction of the sheet material from below the pushing-up plate  43 . Thereby, the uppermost layer of the sheet materials stacked on the upper surface of the pushing-up plate  43  reaches a predetermined feeding position where the uppermost layer contacts the circumferential surface of the feeding roller  44   a.    
     When the cassette  42  is pulled out from the housing unit  41 , the contact of the second starting lever  81  with the inner wall of the housing unit  41  is released, and as shown in  FIGS. 9 to 12 , a part of the second starting lever  81  protrudes outward from the outer wall surface  42   a  on the upstream side of the cassette  42  in the feeding direction of the sheet material by urging force of the pushing-up spring  84 . As a result, the second starting lever  81  pulls the direct-acting link  82  toward the upstream side in the feeding direction of the sheet material, and the direct-acting link  82  further rotates the turning link  83  clockwise as viewed from the front. The turning lever  85  also rotates clockwise when viewed from the front through the pushing-up spring  84 . When the pushing-up lever  87  falls down on the inner bottom surface of the cassette  42 , the pushing-up plate  43  also falls down on the inner bottom surface of the cassette  42 . 
     As described above, the pushing-up plate displacing device  80  pushes up the pushing-up plate  43  while the cassette  42  is stored in the housing unit  41 , and changes the position of the pushing-up plate  43  to the feeding position. Accordingly, the uppermost layer of the sheet materials can be automatically moved to a predetermined feeding position. 
     Since the pushing-up plate displacing device  80  changes the position of the pushing-up plate  43  by a mechanism that does not obtain power from the electric drive source, cost increase is suppressed and low power consumption can be achieved. 
     In addition, the pushing-up plate displacing device  80  lays down the pushing-up plate  43  to the inner bottom surface of the cassette  42  while the cassette  42  is pulled out of the housing unit  41 , thereby changing the position of the pushing-up plate  43  to the retracted position. Thereby, when the sheet material is supplied to the inside of the cassette  42 , the pushing-up plate  43  does not become an obstacle, and workability of replenishment can be improved. 
     Further, since the pushing-up plate displacing device  80  includes the second starting lever  81  which comes in contact with the housing unit  41  while the cassette  42  is stored in the housing unit  41 , the position of the pushing-up plate  43  can be easily changed to the feeding position when the cassette  42  is stored in the housing unit  41 . 
     The axis of the support shaft portion  81   a  of the second starting lever  81  coincides with the axis of the support shaft portion  73   a  of the first starting lever  73 . As shown in  FIGS. 9 and 11 , the support shaft portion  81   a  and the support shaft portion  73   a  are provided on the back side of the center portion of the cassette  42  in the width direction of the sheet material, and the second starting lever  81  and the first starting lever  73  extend from the support shaft portion toward the front side. Regarding the length in the width direction of the sheet material, the second starting lever  81  is longer than the first starting lever  73 . Thus, when the cassette  42  is stored in the housing unit  41 , the first starting lever  73  completes its rotational displacement before the second starting lever  81  completes its own displacement. That is, the position change of the rear-end displacement member  61  to the feeding position by the rear-end displacement member displacing device  70  is completed before the change of the position of the pushing-up plate  43  to the feeding position by the pushing-up plate displacing device  80  is completed. 
     According to this configuration, the timing of changing the position of the rear-end displacement member  61  to the sheet material feeding position due to the insertion of the cassette  42  into the housing unit  41  is earlier than the timing of changing the position of the pushing-up plate  43  to the sheet material feeding position. The rear-end displacement member  61  is displaced toward the downstream side in the feeding direction of the sheet material before the uppermost layer of the sheet materials stacked on the upper surface of the pushing-up plate  43  comes in contact with the circumferential surface of the feeding roller  44   a.  As a result, regardless of the number of the sheet materials inside the cassette  42 , the sheet materials can be arranged in a proper position with respect to the feeding direction. Therefore, a stable feeding can be achieved corresponding to the change of the posture of the sheet materials due to reduction caused by feeding the sheet materials inside the cassette  42 . 
     Since the first starting lever  73  comes in contact with the housing unit  41  earlier than the second starting lever  81 , a configuration can be easily obtained in which the position change of the rear-end displacement member  61  to the feeding position is completed before the position change of the pushing-up plate  43  to the feeding position is completed. 
     Second Embodiment 
     Next, a sheet material feeding device according to a second embodiment of the present invention will be described with reference to  FIG. 17 .  FIG. 17  is a bottom view of the cassette of the sheet material feeding device when the cassette is stored. Since the basic configuration of the present embodiment is the same as that of the first embodiment described above, the same names and the same reference numerals are given to the constituent elements common to the first embodiment, and detailed description may be omitted. 
     The sheet material feeding device  40  according to the second embodiment includes a single starting lever  47  as shown in  FIG. 17 . The starting lever  47  is made by forming the first starting lever  73  and the second starting lever  81  described in the first embodiment as a single member. 
     The starting lever  47  is provided on the outer bottom portion of the cassette  42 . The starting lever  47  has a plate shape extending along the bottom surface of the cassette  42 . The starting lever  47  is supported on the outer bottom surface of the cassette  42  via a support shaft portion  47   a  which is provided at one end of the lever and extends in a substantially vertical direction. The support shaft portion  47   a  is provided on the back side (the lower side in  FIG. 17 ) of the center portion of the cassette  42  in the width direction of the sheet material, and the starting lever  47  extends from the support shaft portion  47   a  toward the front side (the upper side in  FIG. 17 ). The starting lever  47  is rotatable around the axis of the support shaft portion  47   a.    
     The starting lever  47  is connected to the connecting piece  75  of the rear-end displacement member displacing device  70  at the center portion of the cassette  42  in the width direction of the sheet material. Further, the starting lever  47  is connected to the direct-acting link  82  of the pushing-up plate displacing device  80  on the front side of the center portion of the cassette  42  in the width direction of the sheet material. 
     As described above, in the sheet material feeding device  40  according to the second embodiment, even when the single starting lever  47  is used, the position change of the rear-end displacement member  61  to the feeding position by the rear-end displacement member displacing device  70  is completed before the position change of the pushing-up plate  43  to the feeding position by the pushing-up plate displacing device  80  is completed. Therefore, the number of parts and the number of assembling steps of the sheet material feeding device  40  can be reduced, and it is possible to save resources and reduce costs. 
     Third Embodiment 
     Next, a sheet material feeding device according to a third embodiment of the present invention will be described with reference to  FIGS. 18 to 22 .  FIG. 18  is a block diagram showing a configuration of a cassette of the sheet material feeding device.  FIGS. 19 and 20  are a bottom view and a partially enlarged bottom view of the cassette when the cassette has been pulled out.  FIGS. 21 and 22  are a bottom view and a partially enlarged bottom view of the cassette when the cassette is stored. Since the basic configuration of the present embodiment is the same as that of the first embodiment described above, the same names and the same reference numerals are given to the constituent elements common to the first embodiment, and detailed description may be omitted. 
     As shown in  FIGS. 18 to 20 , the sheet material feeding device  40  of the third embodiment includes a cassette control unit  48 , a position change drive source  49 , and a rear-end displacement detection unit  51 . 
     The cassette control unit  48  includes ICs such as a CPU  48   a  serving as a processing circuit and a storage unit  48   b,  and other electronic components, and controls the operation of the pushing-up plate displacing device  80 . The cassette control unit  48  receives the information on the position change of the rear-end displacement member  61  from the rear-end displacement detection unit  51  and transmits a control signal related to the position change of the pushing-up plate  43  to the position change drive source  49 . 
     The position change drive source  49  is constituted by a motor for example and is provided in the vicinity of the pushing-up plate displacing device  80 . The position change drive source  49  is connected to the rotary shaft  86  via a gear, a belt, or the like, and rotates the rotary shaft  86  around its axis. The position change drive source  49  rotates the rotary shaft  86  based on the control signal received from the cassette control unit  48  and changes the position of the pushing-up plate  43  via the pushing-up lever  87 . 
     The rear-end displacement detection unit  51  includes a sensor unit  51   a  and a light shielding piece  51   b  shown in  FIG. 20 . The sensor unit  51   a  is disposed at the downstream end of the guide rail  46  in the feeding direction of the sheet material. The sensor unit  51   a  is formed of a transmission type optical sensor having a light emitting unit and a light receiving unit and is disposed such that the open portion of an optical path  51   c  faces the upstream side in the feeding direction of the sheet material. The light shielding piece  51   b  is disposed at the downstream end of the slide member  72  in the feeding direction of the sheet material and further protrudes toward the downstream side. The light shielding piece  51   b  is disposed at a position so as to enter and retreat from the optical path  51   c  of the sensor unit  51   a  when the slide member  72  slides in parallel to the feeding direction of the sheet material. 
     The rear-end displacement detection unit  51  detects the displacement of the slide member  72  using the sensor unit  51   a  and the light shielding piece  51   b.  The rear-end displacement detection unit  51  transmits a detection signal related to the displacement of the slide member  72  to the cassette control unit  48 . 
     As shown in  FIG. 21 , the slide member  72  has an enough length so that the downstream end of the slide member  72  in the feeding direction of the sheet material reaches the downstream end of the guide rail  46  in the feeding direction of the sheet material when the first starting lever  73  comes in contact with the inner wall of the housing unit  41  and the position change of the rear-end displacement member  61  to the feeding position by the rear-end displacement member displacing device  70  is completed while the cassette  42  is stored in the housing unit  41 . That is, when position change of the rear-end displacement member  61  to the feeding position by the rear-end displacement member displacing device  70  is completed, the light shielding piece  51   b  blocks the optical path  51   c  of the sensor unit  51   a  as shown in  FIG. 22 . As a result, the detection signal of the rear-end displacement detection unit  51  is transmitted to the cassette control unit  48 , and the cassette control unit  48  transmits a control signal for changing the position of the pushing-up plate  43  to the feeding position to the position change drive source  49 . 
     As described above, in the sheet material feeding device  40  of the third embodiment, after the position change of the rear-end displacement member  61  to the feeding position by the rear-end displacement member displacing device  70  is completed, the position change of the pushing-up plate  43  to the feeding position by the pushing-up plate displacing device  80  is started. This can improve the operation of arranging the sheet materials at a proper position with respect to the feeding direction regardless of the number of the sheet materials inside the cassette  42 . Therefore, stable feeding can be effectively achieved corresponding to the change of the posture of the sheet materials caused as the number of the sheet materials inside the cassette  42  is reduced by feeding. 
     Since the sheet material feeding device  40  has the position change drive source  49  which is an electric drive source for changing the position of the pushing-up plate  43 , the position of the pushing-up plate  43  can be easily changed to the feeding position by using the power of a motor for example. The position change drive source  49  is not limited to a motor and may be a solenoid or other electric drive sources. 
     Fourth Embodiment 
     Next, a sheet material feeding device according to a fourth embodiment of the present invention will be described with reference to  FIGS. 23 to 25 .  FIG. 23  is a block diagram showing a configuration of a cassette of the sheet material feeding device.  FIGS. 24 and 25  are a bottom view and a partially enlarged perspective view of the cassette when the cassette is stored. Since the basic configuration of the present embodiment is the same as that of the first and third embodiments described above, the same names and the same reference numerals are given to the constituent elements common to these embodiments, and detailed description may be omitted. 
     As shown in  FIGS. 23 to 25 , the sheet material feeding device  40  of the fourth embodiment includes the cassette control unit  48 , the position change drive source  49 , a clutch  50 , and a storage detection unit  52 . 
     The cassette control unit  48  includes ICs such as the CPU  48   a  serving as a processing circuit, and the storage unit  48   b,  and other electronic components, and controls operations of the rear-end displacement member displacing device  70  and the pushing-up plate displacing device  80 . The cassette control unit  48  receives information on the storage and pullout of the cassette  42  with respect to the housing unit  41  from the storage detection unit  52  and transmits control signals to the position change drive source  49  and the clutch  50 . 
     The position change drive source  49  is constituted by a motor for example and is provided in the vicinity of the pushing-up plate displacing device  80 . The position change drive source  49  is connected to the slide member  72  via a gear, a belt, or the like, and slides the slide member  72  in parallel to the feeding direction of the sheet material. Further, the position change drive source  49  is connected to the rotary shaft  86  via a gear, a belt, or the like, and rotates the rotary shaft  86  around its axis. The position change drive source  49  slides the slide member  72  in the feeding direction of the sheet material based on the control signal received from the cassette control unit  48  and changes the position of the rear-end displacement member  61  via the slide member  72 . Further, the position change drive source  49  rotates the rotary shaft  86  based on a control signal received from the cassette control unit  48 , and changes the position of the pushing-up plate  43  via the pushing-up lever  87 . 
     The clutch  50  is connected between the position change drive source  49  and the slide member  72  as well as the rotary shaft  86 . Based on a control signal received from the cassette control unit  48 , the clutch  50  switches the destination of the power generated by the position change drive source  49  between the rear-end displacement member displacing device  70  and the pushing-up plate displacing device  80 . 
     The storage detection unit  52  includes a sensor unit  52   a  and a light shielding piece  52   b  shown in  FIG. 25 . The sensor unit  52   a  is disposed on a wall surface of the housing unit  41  that is close to and faces the back surface of the stored cassette  42 . The sensor unit  52   a  is formed of a transmission type optical sensor having a light emitting unit and a light receiving unit, and the sensor unit  52   a  is disposed so that the open portion of an optical path  52   c  faces the cassette  42 . The light shielding piece  52   b  is disposed on the back surface of the cassette  42  and further projects backward. The light shielding piece  52   b  is disposed at a position so as to enter and retreat from the optical path  52   c  of the sensor unit  52   a  when the cassette  42  is stored in and pulled out of the housing unit  41 . 
     The storage detection unit  52  detects the storage and pullout of the cassette  42  with respect to the housing unit  41  using the sensor unit  52   a  and the light shielding piece  52   b . The storage detection unit  52  transmits detection signals related to the storage and pullout of the cassette  42  with respect to the housing unit  41  to the cassette control unit  48 . 
     When the cassette  42  is stored in the housing unit  41 , the storage detection unit  52  detects the storage of the cassette  42  with respect to the housing unit  41 . When having received the detection signal concerning the storage of the cassette  42  from the storage detection unit  52 , the cassette control unit  48  switches the clutch  50  so that the power of the position change drive source  49  is transmitted to the slide member  72  of the rear-end displacement member displacing device  70  and drives the position change drive source  49 . As a result, in the rear-end displacement member displacing device  70 , the slide member  72  slides toward the downstream side in the feeding direction of the sheet material, and the rear-end displacement member  61  is displaced to the downstream side in the feeding direction of the sheet material. 
     The time required for changing the position of the rear-end displacement member  61  to the feeding position by the rear-end displacement member displacing device  70  is measured in advance and stored in the storage unit  48   b  or the like. 
     When the cassette control unit  48  confirms completion of the position change of the rear-end displacement member  61  to the feeding position by the rear-end displacement member displacing device  70 , for example, by passage of time, the cassette control unit  48  switches the clutch  50  so that the power of the position change drive source  49  is transmitted to the rotary shaft  86  of the pushing-up plate displacing device  80  and drives the position change drive source  49 . Thereby, as the rotary shaft  86  rotates in the pushing-up plate displacing device  80 , the pushing-up lever  87  pushes up the pushing-up plate  43 , and the uppermost layer of the sheet materials reaches a predetermined feeding position. 
     As described above, the sheet material feeding device  40  of the fourth embodiment has the position change drive source  49  which is an electric driving source for changing the position of the rear-end displacement member  61  and the pushing-up plate  43 , and therefore, can change the position of the rear-end displacement member  61  and the pushing-up plate  43  to the feeding position easily by using power of a motor for example. 
     Although the embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and various modifications can be made without departing from the spirit of the invention. Further, a plurality of embodiments can be implemented in combination. 
     For example, in the above-described embodiment, the image forming apparatus  1  is a so-called image forming apparatus for tandem-type color printing in which images of a plurality of colors are sequentially superposed by using the intermediate transfer belt  11 , but the image forming apparatus  1  is not limited to such a type and may be an image forming apparatus for color printing which is not a tandem type or an image forming apparatus for monochrome printing. 
     The present invention can be used in an image forming apparatus such as a copying machine. 
     Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustrated and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by terms of the appended claims.