Patent Publication Number: US-10787010-B2

Title: Print media feeding apparatus and printing apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a print media feeding apparatus configured to feed from a stacking part and convey a print medium, and a printing apparatus including the same. 
     Description of the Related Art 
     A printing apparatus configured to perform printing on a sheet-like print medium performs a printing operation by feeding a print medium from a feeding cassette housing a plurality of stacked sheets of print media, further sending the fed print medium to a print unit by a conveying unit such as a conveying roller. On this occasion, it becomes necessary to feed a sheet of the print media to the print unit without a plurality of sheets of the print media being overlapped. Accordingly, there is known a conventional printing apparatus including a separation mechanism which, in the case where a plurality of sheets of the print media are sent out from the feeding cassette in an overlapped state, separates only a single sheet of the print media among the plurality of sheets of the print media, and supplies it to the print unit. 
     Japanese Patent Laid-Open No. 2011-236054 discloses a feeding apparatus configured as illustrated in  FIG. 18 . The feeding apparatus illustrated in  FIG. 18  includes a pickup roller  123  that sends print media S stacked within a feeding cassette  122  to the outside. The pickup roller  123  is supported in manner movable upward and downward by an arm  124  being moved by rotation of a shaft  127 . At the time of feeding, the pickup roller  123  rotating by the drive of a motor descends from an upper retracted position, and abuts the surface (top surface) of the top print medium S 1  of the print media S stacked within the feeding cassette  122 . Accordingly, the print media S are fed from the feeding cassette  122  by the rotating pickup roller  123 . 
     The print media S fed from the feeding cassette  122  are nipped between a feeding roller  115  and a separation roller  116  being biased toward the feeding roller  115 . On this occasion, there is a possibility that a plurality of sheets of the print media S fed by the pickup roller  123  may be nipped between both feeding rollers  115  and  116 . However, the separation roller  116 , being connected to a torque limiter, is configured to apply braking to the movement in the feed direction of the print media other than the top print medium S 1  contacting the feeding roller  115 , so that only the top sheet of the print media is fed downstream. 
     However, with the unit disclosed in Japanese Patent Laid-Open No. 2011-236054, the impact at the time of abutment of the pickup roller  123  to the print media S stacked on the feeding cassette  122  causes a gap to be formed between the feeding roller  115  and the separation roller  116 , which may cause double-feeding. In other words, in the case where a gap is formed between the feeding roller  115  and the separation roller  116 , a plurality of sheets of the print media S sent out from the stacking part in an overlapped state may pass through the gap formed between feeding roller  115  and the separation roller  116 , which may lead to double-feeding. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a feeding apparatus capable of reliably feeding print media one by one from a stacking part. 
     The present invention provides a print media feeding apparatus comprising: a stacking part configured to stack the print media; a feeding roller which is movable to an abutting position at which the feeding roller contacts the print media stacked on the stacking part and to a separated position separated from the print media stacked on the stacking part and configured to feed a print medium by rotating at the abutting position; a separation member configured to separate the print media; and a return unit configured to perform a return operation of returning the print medium other than a top print medium which the feeding roller abuts, wherein the feeding roller moves to the separated position, after feeding the print medium from the stacking part, the return unit performs the return operation upon the feeding roller moving to the separated position and, after the return operation, the feeding roller stops at the abutting position. 
     According to the feeding apparatus pertaining to the present invention, it becomes possible to reliably feed the print media one by one from the stacking part. 
     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 front view of a printing apparatus in a stand-by state; 
         FIG. 2  is a control configuration diagram of the printing apparatus; 
         FIG. 3  is a diagram showing the printing apparatus in a printing state; 
         FIGS. 4A to 4C  are conveying path diagrams of a print medium fed from a first cassette; 
         FIGS. 5A to 5C  are conveying path diagrams of a print medium fed from a second cassette; 
         FIGS. 6A to 6D  are conveying path diagrams in the case of performing print operation for the back side of a print medium; 
         FIG. 7  is a diagram showing the printing apparatus in a maintenance state; 
         FIG. 8  illustrates a correspondence relation between a conveying roller and a motor; 
         FIG. 9  is a perspective view illustrating a configuration of the feeding unit  6 A illustrated in  FIG. 1  and a stacking part capable of stacking print media; 
         FIG. 10  is a cross-sectional view of the feeding unit  6 A; 
         FIG. 11  is a perspective view of respective rollers of the feeding unit seen diagonally from the top right of  FIG. 9 ; 
         FIG. 12  is a perspective view illustrating a one-way clutch and a first feeding roller illustrated in  FIG. 11 ; 
         FIG. 13  is a perspective view of respective rollers of the feeding unit  6 A; 
         FIG. 14  is a front view illustrating in more detail the configuration of the feeding unit  6 A illustrated in  FIG. 1 ; 
         FIG. 15  is a cross-sectional view illustrating an initial state in the feeding apparatus; 
         FIGS. 16A and 16B  are cross-sectional views illustrating a series of feeding operations in the feeding apparatus; 
         FIG. 17  is a flowchart illustrating the operation timing of each part in the feeding apparatus; and 
         FIG. 18  illustrates a conventional feeding apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is an internal configuration diagram of an inkjet printing apparatus  1  (hereinafter “printing apparatus  1 ”) used in the present embodiment. In the drawings, an x-direction is a horizontal direction, a y-direction (a direction perpendicular to paper) is a direction in which ejection openings are arrayed in a print head  8  described later, and a z-direction is a vertical direction. 
     The printing apparatus  1  is a multifunction printer comprising a print unit  2  and a scanner unit  3 . The printing apparatus  1  can use the print unit  2  and the scanner unit  3  separately or in synchronization to perform various processes related to print operation and scan operation. The scanner unit  3  comprises an automatic document feeder (ADF) and a flatbed scanner (FBS) and is capable of scanning a document automatically fed by the ADF as well as scanning a document placed by a user on a document plate of the FBS. The present embodiment is directed to the multifunction printer comprising both the print unit  2  and the scanner unit  3 , but the scanner unit  3  may be omitted.  FIG. 1  shows the printing apparatus  1  in a standby state in which neither print operation nor scan operation is performed. 
     In the print unit  2 , a first cassette  5 A and a second cassette  5 B for housing a print medium (cut sheet) S are detachably provided at the bottom of a casing  4  in the vertical direction. A relatively small print medium of up to A4 size is placed flat and housed in the first cassette  5 A and a relatively large print medium of up to A3 size is placed flat and housed in the second cassette  5 B. A first feeding unit  6 A for sequentially feeding a housed print medium is provided near the first cassette  5 A. Similarly, a second feeding unit  6 B is provided near the second cassette  5 B. In print operation, a print medium S is selectively fed from either one of the cassettes. 
     Conveying rollers  7 , a discharging roller  12 , pinch rollers  7   a , spurs  7   b , a guide  18 , an inner guide  19 , and a flapper  11  are conveying mechanisms for guiding a print medium S in a predetermined direction. The conveying rollers  7  are drive rollers located upstream and downstream of the print head  8  and driven by a conveying motor (not shown). The pinch rollers  7   a  are follower rollers that are turned while nipping a print medium S together with the conveying rollers  7 . The discharging roller  12  is a drive roller located downstream of the conveying rollers  7  and driven by the conveying motor (not shown). The spurs  7   b  nip and convey a print medium S together with the conveying rollers  7  and discharging roller  12  located downstream of the print head  8 . 
     The printing apparatus  1  has provided thereon a plurality of motors for driving the aforementioned drive rollers, each of the drive rollers being connected to one of the plurality of motors. The correspondence relation between the motors and the drive rollers will be described in detail below. 
     The guide  18  is provided in a conveying path of a print medium S to guide the print medium S in a predetermined direction. The inner guide  19  is a member extending in the y-direction. The inner guide  19  has a curved side surface and guides a print medium S along the side surface. The flapper  11  is a member for changing a direction in which a print medium S is conveyed in duplex print operation. A discharging tray  13  is a tray for placing and housing a print medium S that was subjected to print operation and discharged by the discharging roller  12 . 
     The print head  8  of the present embodiment is a full line type color inkjet print head. In the print head  8 , a plurality of ejection openings configured to eject ink based on print data are arrayed in the y-direction in  FIG. 1  so as to correspond to the width of a print medium S. When the print head  8  is in a standby position, an ejection opening surface  8   a  of the print head  8  is oriented vertically downward and capped with a cap unit  10  as shown in  FIG. 1 . In print operation, the orientation of the print head  8  is changed by a print controller  202  described later such that the ejection opening surface  8   a  faces a platen  9 . The platen  9  includes a flat plate extending in the y-direction and supports, from the back side, a print medium S subjected to print operation by the print head  8 . The movement of the print head  8  from the standby position to a printing position will be described later in detail. 
     An ink tank unit  14  separately stores ink of four colors to be supplied to the print head  8 . An ink supply unit  15  is provided in the midstream of a flow path connecting the ink tank unit  14  to the print head  8  to adjust the pressure and flow rate of ink in the print head  8  within a suitable range. The present embodiment adopts a circulation type ink supply system, where the ink supply unit  15  adjusts the pressure of ink supplied to the print head  8  and the flow rate of ink collected from the print head  8  within a suitable range. 
     A maintenance unit  16  comprises the cap unit  10  and a wiping unit  17  and activates them at predetermined timings to perform maintenance operation for the print head  8 . The maintenance operation will be described later in detail. 
       FIG. 2  is a block diagram showing a control configuration in the printing apparatus  1 . The control configuration mainly includes a print engine unit  200  that exercises control over the print unit  2 , a scanner engine unit  300  that exercises control over the scanner unit  3 , and a controller unit  100  that exercises control over the entire printing apparatus  1 . A print controller  202  controls various mechanisms of the print engine unit  200  under instructions from a main controller  101  of the controller unit  100 . Various mechanisms of the scanner engine unit  300  are controlled by the main controller  101  of the controller unit  100 . The control configuration will be described below in detail. 
     In the controller unit  100 , the main controller  101  including a CPU controls the entire printing apparatus  1  using a RAM  106  as a work area in accordance with various parameters and programs stored in a ROM  107 . For example, when a print job is input from a host apparatus  400  via a host I/F  102  or a wireless I/F  103 , an image processing unit  108  executes predetermined image processing for received image data under instructions from the main controller  101 . The main controller  101  transmits the image data subjected to the image processing to the print engine unit  200  via a print engine I/F  105 . 
     The printing apparatus  1  may acquire image data from the host apparatus  400  via a wireless or wired communication or acquire image data from an external storage unit (such as a USB memory) connected to the printing apparatus  1 . A communication system used for the wireless or wired communication is not limited. For example, as a communication system for the wireless communication, Wi-Fi (Wireless Fidelity; registered trademark) and Bluetooth (registered trademark) can be used. As a communication system for the wired communication, a USB (Universal Serial Bus) and the like can be used. For example, when a scan command is input from the host apparatus  400 , the main controller  101  transmits the command to the scanner unit  3  via a scanner engine I/F  109 . 
     An operating panel  104  is a mechanism to allow a user to do input and output for the printing apparatus  1 . A user can give an instruction to perform operation such as copying and scanning, set a print mode, and recognize information about the printing apparatus  1  via the operating panel  104 . 
     In the print engine unit  200 , the print controller (control unit)  202  including a CPU controls various mechanisms of the print unit  2  using a RAM  204  as a work area in accordance with various programs and parameters stored in a ROM  203 . Upon receiving various commands and image data via a controller I/F  201 , the print controller  202  temporarily stores the commands and the image data in the RAM  204 . The print controller  202  causes an image processing controller  205  to convert the stored image data into print data to allow the print head  8  to use the print data for a printing operation. Upon generating the print data, the print controller  202  causes the print head  8  to perform a printing operation on the basis of the print data via a head I/F  206 . On this occasion, the print controller  202  drives the feeding units  6 A and  6 B, the conveying rollers  7 , the discharging roller  12 , and the flapper  11  illustrated in  FIG. 1 , via a conveyance control unit  207 , and conveys the print medium S. 
     The conveyance control unit  207  is connected to a detection unit  212  configured to detect a conveyance state of the print medium S and a drive unit  211  configured to drive a plurality of drive rollers, and controls conveyance of the print medium S using the drive unit  211 , on the basis of a detection result obtained from the detection unit  212 . The detection unit  212  has detection members  20  configured to detect the presence or absence of the print medium S, and an encoder  21  configured to detect the amount of rotation of the drive rollers. 
     While the print medium S is being conveyed by the conveyance control unit  207 , a printing operation is performed by the print head  8  according to an instruction from the print controller  202 , and a printing process is performed. 
     A head carriage control unit  208  changes the orientation and position of the print head  8  in accordance with an operating state of the printing apparatus  1  such as a maintenance state or a printing state. An ink supply control unit  209  controls the ink supply unit  15  such that the pressure of ink supplied to the print head  8  is within a suitable range. A maintenance control unit  210  controls the operation of the cap unit  10  and wiping unit  17  in the maintenance unit  16  when performing maintenance operation for the print head  8 . 
     In the scanner engine unit  300 , the main controller  101  controls hardware resources of the scanner controller  302  using the RAM  106  as a work area in accordance with various parameters and programs stored in the ROM  107 , thereby controlling various mechanisms of the scanner unit  3 . For example, the main controller  101  controls hardware resources in the scanner controller  302  via a controller OF  301  to cause a conveyance control unit  304  to convey a document placed by a user on the ADF and cause a sensor  305  to scan the document. The scanner controller  302  stores scanned image data in a RAM  303 . The print controller  202  can convert the image data acquired as described above into print data to enable the print head  8  to perform print operation based on the image data scanned by the scanner controller  302 . 
       FIG. 3  shows the printing apparatus  1  in a printing state. As compared with the standby state shown in  FIG. 1 , the cap unit  10  is separated from the ejection opening surface  8   a  of the print head  8  and the ejection opening surface  8   a  faces the platen  9 . In the present embodiment, the plane of the platen  9  is inclined about 45° with respect to the horizontal plane. The ejection opening surface  8   a  of the print head  8  in a printing position is also inclined about 45° with respect to the horizontal plane so as to keep a constant distance from the platen  9 . 
     In the case of moving the print head  8  from the standby position shown in  FIG. 1  to the printing position shown in  FIG. 3 , the print controller  202  uses the maintenance control unit  210  to move the cap unit  10  down to an evacuation position shown in  FIG. 3 , thereby separating the cap member  10   a  from the ejection opening surface  8   a  of the print head  8 . The print controller  202  then uses the head carriage control unit  208  to turn the print head  8  45° while adjusting the vertical height of the print head  8  such that the ejection opening surface  8   a  faces the platen  9 . After the completion of print operation, the print controller  202  reverses the above procedure to move the print head  8  from the printing position to the standby position. 
     Next, a conveying path of a print medium S in the print unit  2  will be described. When a print command is input, the print controller  202  first uses the maintenance control unit  210  and the head carriage control unit  208  to move the print head  8  to the printing position shown in  FIG. 3 . The print controller  202  then uses the conveyance control unit  207  to drive either the first feeding unit  6 A or the second feeding unit  6 B in accordance with the print command and feed a print medium S. 
       FIGS. 4A to 4C  are diagrams showing a conveying path in the case of feeding an A4 size print medium S from the first cassette  5 A. A print medium S at the top of a print medium stack in the first cassette  5 A is separated from the rest of the stack by the first feeding unit  6 A and conveyed toward a print area P between the platen  9  and the print head  8  while being nipped between the conveying rollers  7  and the pinch rollers  7   a .  FIG. 4A  shows a conveying state where the front end of the print medium S is about to reach the print area P. The direction of movement of the print medium S is changed from the horizontal direction (x-direction) to a direction inclined about 45° with respect to the horizontal direction while being fed by the first feeding unit  6 A to reach the print area P. 
     In the print area P, a plurality of ejection openings provided in the print head  8  eject ink toward the print medium S. In an area where ink is applied to the print medium S, the back side of the print medium S is supported by the platen  9  so as to keep a constant distance between the ejection opening surface  8   a  and the print medium S. After ink is applied to the print medium S, the conveying rollers  7  and the spurs  7   b  guide the print medium S such that the print medium S passes on the left of the flapper  11  with its tip inclined to the right and is conveyed along the guide  18  in the vertically upward direction of the printing apparatus  1 .  FIG. 4B  shows a state where the front end of the print medium S has passed through the print area P and the print medium S is being conveyed vertically upward. The conveying rollers  7  and the spurs  7   b  change the direction of movement of the print medium S from the direction inclined about 45° with respect to the horizontal direction in the print area P to the vertically upward direction. 
     After being conveyed vertically upward, the print medium S is discharged into the discharging tray  13  by the discharging roller  12  and the spurs  7   b .  FIG. 4C  shows a state where the front end of the print medium S has passed through the discharging roller  12  and the print medium S is being discharged into the discharging tray  13 . The discharged print medium S is held in the discharging tray  13  with the side on which an image was printed by the print head  8  facing downward. 
       FIGS. 5A to 5C  are diagrams showing a conveying path in the case of feeding an A3 size print medium S from the second cassette  5 B. A print medium S at the top of a print medium stack in the second cassette  5 B is separated from the rest of the stack by the second feeding unit  6 B and conveyed toward the print area P between the platen  9  and the print head  8  while being nipped between the conveying rollers  7  and the pinch rollers  7   a.    
       FIG. 5A  shows a conveying state where the front end of the print medium S is about to reach the print area P. In a part of the conveying path, through which the print medium S is fed by the second feeding unit  6 B toward the print area P, the plurality of conveying rollers  7 , the plurality of pinch rollers  7   a , and the inner guide  19  are provided such that the print medium S is conveyed to the platen  9  while being bent into an S-shape. 
     The rest of the conveying path is the same as that in the case of conveying the A4 size print medium S shown in  FIGS. 4B and 4C .  FIG. 5B  shows a state where the front end of the print medium S has passed through the print area P and the print medium S is being conveyed vertically upward.  FIG. 5C  shows a state where the front end of the print medium S has passed through the discharging roller  12  and the print medium S is being discharged into the discharging tray  13 . 
       FIGS. 6A to 6D  show a conveying path in the case of performing print operation (duplex printing) for the back side (second side) of an A4 size print medium S. In the case of duplex printing, print operation is first performed for the first side (front side) and then performed for the second side (back side). A conveying procedure during print operation for the first side is the same as that shown in  FIGS. 4A to 4C  and therefore description will be omitted. A conveying procedure subsequent to  FIG. 4C  will be described below. 
     After the print head  8  finishes print operation for the first side and the back end of the print medium S passes by the flapper  11 , the print controller  202  turns the conveying rollers  7  reversely to convey the print medium S into the printing apparatus  1 . At this time, since the flapper  11  is controlled by an actuator (not shown) such that the tip of the flapper  11  is inclined to the left, the front end of the print medium S (corresponding to the back end during the print operation for the first side) passes on the right of the flapper  11  and is conveyed vertically downward.  FIG. 6A  shows a state where the front end of the print medium S (corresponding to the back end during the print operation for the first side) is passing on the right of the flapper  11 . 
     Then, the print medium S is conveyed along the curved outer surface of the inner guide  19  and then conveyed again to the print area P between the print head  8  and the platen  9 . At this time, the second side of the print medium S faces the ejection opening surface  8   a  of the print head  8 .  FIG. 6B  shows a conveying state where the front end of the print medium S is about to reach the print area P for print operation for the second side. 
     The rest of the conveying path is the same as that in the case of the print operation for the first side shown in  FIGS. 4B and 4C .  FIG. 6C  shows a state where the front end of the print medium S has passed through the print area P and the print medium S is being conveyed vertically upward. At this time, the flapper  11  is controlled by the actuator (not shown) such that the tip of the flapper  11  is inclined to the right.  FIG. 6D  shows a state where the front end of the print medium S has passed through the discharging roller  12  and the print medium S is being discharged into the discharging tray  13 . 
     Next, maintenance operation for the print head  8  will be described. As described with reference to  FIG. 1 , the maintenance unit  16  of the present embodiment comprises the cap unit  10  and the wiping unit  17  and activates them at predetermined timings to perform maintenance operation. 
       FIG. 7  is a diagram showing the printing apparatus  1  in a maintenance state. In the case of moving the print head  8  from the standby position shown in  FIG. 1  to a maintenance position shown in  FIG. 7 , the print controller  202  moves the print head  8  vertically upward and moves the cap unit  10  vertically downward. The print controller  202  then moves the wiping unit  17  from the evacuation position to the right in  FIG. 7 . After that, the print controller  202  moves the print head  8  vertically downward to the maintenance position where maintenance operation can be performed. 
     On the other hand, in the case of moving the print head  8  from the printing position shown in  FIG. 3  to the maintenance position shown in  FIG. 7 , the print controller  202  moves the print head  8  vertically upward while turning it 45°. The print controller  202  then moves the wiping unit  17  from the evacuation position to the right. Following that, the print controller  202  moves the print head  8  vertically downward to the maintenance position where maintenance operation can be performed by the maintenance unit  16 . 
       FIG. 8  illustrates a correspondence relation between a plurality of motors and the drive rollers in the printing apparatus  1 . A first feeding motor  22  drives a second roller shaft  40  described below, which is provided corresponding to the first feeding unit  6 A for feeding the print medium S from the first cassette  5 A. A second feeding motor  23  rotates a second roller shaft  40  described below, which is provided corresponding to the second feeding unit  6 B for feeding the print medium S from the second cassette  5 B. A first conveying motor  24  drives a first intermediate roller  71 A which first conveys the print medium S fed by the first feeding unit  6 A. A second conveying motor  25  drives a second intermediate roller  71 B which first conveys the print medium S fed by the second feeding unit  6 B. 
     A main conveying motor  26  drives a main conveying roller  70  provided upstream of the platen  9  to mainly convey the print medium S being subjected to printing. In addition, the main conveying motor  26  drives the two conveying rollers  7  provided downstream of the platen  9  to convey, further downstream, the print medium S being conveyed by the main conveying roller  70 . 
     A third conveying motor  27  drives the two conveying rollers  7  which convey, downward, the print medium S subjected to printing on the first surface. In addition, the third conveying motor  27  also drives the two conveying rollers  7  provided along the inner guide  19 . The two conveying rollers  7  convey, toward the print head  8 , the print medium S fed from the second cassette  5 B and conveyed by the second intermediate roller  71 B, or the print medium S subjected to printing on the first surface and turned over. 
     A fourth conveying motor  28  drives the two conveying rollers  7  which convey the print medium S upward or downward, after being subjected to printing operation. A discharging motor  29  drives the discharging roller  12  which discharges the print medium S subjected to printing toward the discharging tray  13 . As thus described, the two feeding motors  22  and  23 , the five conveying motors  24  to  28 , and the discharging motor  29  are respectively associated with one or more drive rollers. 
     On the other hand, the detection members  20  for detecting the presence or absence of the print medium S are provided at eight locations along the conveying path. Each of the detection members  20  includes a sensor and a mirror provided across the conveying path, with the sensor having a light emitting unit and a light receiving unit provided on one side of the conveying path, and the mirror provided on the other side of the conveying path at a position facing the sensor. According to whether or not the light-receiving unit detected light which has been emitted from the light emitting unit of the sensor and reflected by the mirror, the presence or absence of the print medium S, i.e., the passage of the front end or back end, is determined. 
     The conveyance control unit  207  drives the feeding motors  22  and  23 , the conveying motors  24  to  28 , and the discharging motor  29 , individually, on the basis of respective detective results of the plurality of detection members  20 , and an output value of an encoder configured to detect the amount of rotation of each drive roller, and controls conveyance in the apparatus as a whole. 
     Here, the configuration and function of the feeding unit of the present embodiment will be described in more detail. The feeding apparatus in the present embodiment is configured to include a feeding cassette that serves as a stacking part stacking print media and a feeding unit that feeds the print media from the feeding cassette to a conveying path. As has been described above, the present embodiment has, as the stacking part, the first cassette  5 A and the second cassette  5 B provided on two decks, namely, an upper deck and a lower deck. The first feeding unit  6 A is provided in the vicinity of the first cassette  5 A, and the second feeding unit  6 B is provided in the vicinity of the second cassette  5 B, respectively. The first feeding unit  6 A provided in the vicinity of the first cassette  5 A and the second feeding unit  6 B provided in the vicinity of the second cassette  5 B have a similar configuration except for the difference in the largest size of the print medium S that may be fed. Therefore, in the following, description will be provided taking as an example the first feeding apparatus  61  including the first cassette  5 A and the first feeding unit  6 A illustrated in  FIG. 9 . 
     As illustrated in  FIG. 9 , the first cassette  5 A has a rectangular box-shaped cassette main body  5 A 1  which is open at the upper side and has provided therein a pressure plate  5 A 2  supporting the print medium from below. The pressure plate  5 A 2  is biased upward by a spring which is not illustrated. In addition, the first feeding unit  6 A is provided in the vicinity of the upper part of one side of the cassette main body  5 A 1 . 
       FIG. 10  is a cross-sectional view illustrating in more detail the configuration of the feeding unit  6 A illustrated in  FIG. 1 ,  FIG. 11  is a perspective view illustrating the arrangement of respective rollers of the feeding unit  6 A, and  FIG. 12  is a perspective view illustrating a one-way clutch  33  and a first feeding roller  32  illustrated in  FIG. 11 . In addition,  FIG. 13  is a perspective view in which the first feeding unit  6 A is seen from a direction different to that of  FIG. 11 . 
     In  FIGS. 10 to 13 , the first feeding unit  6 A is intended to feed the print media one by one from the first cassette  5 A. The first feeding unit  6 A is configured to include the first feeding roller  32 , a second feeding roller  42 , a separation roller (separation member)  52 , a first roller gear  31 , an idle roller gear  43 , and a second roller gear  41 , or the like. The first feeding roller (pickup roller)  32  is rotatably supported by the first roller shaft  30 , and configured to be movable between an abutting position at which the first feeding roller  32  abuts the top surface of print media S housed in the first feeding cassette  5 A (see  FIG. 1 ) and a separated position away from the print medium S. The movement is performed by a feeding roller movement unit described below. 
     The one-way clutch  33  and the first roller gear  31  are provided on the center shaft and the shaft line of a first feeding roller shaft  30  extending in the y-direction of the first feeding roller  32 . The one-way clutch  33  rotates integrally with the first roller gear  31  in the case where the first roller gear  31  rotates in a forward rotation direction (the direction indicated by the solid line arrow in  FIG. 12 ). In addition, in the case where the first roller gear  31  rotates in a reverse direction (the direction indicated by the dot-and-dash line arrow in  FIG. 12 ), rotation force of the first roller gear  31  is not transmitted to the one-way clutch  33 . 
     Furthermore, the one-way clutch  33  and the first feeding roller  32  are coupled via a predetermined delay mechanism. In other words, the rotation force of the one-way clutch  33  is configured not to be transmitted to the first feeding roller  32  until the one-way clutch  33  rotates from an initial position to a predetermined phase. Specifically, the one-way clutch  33  has formed thereon a protrusion  33   a  to be inserted into the first feeding roller  32 , and engagement of the protrusion  33   a  and the inner wall of the first feeding roller  32  causes transmission of the rotation force. In other words, upon rotating from an initial position to a predetermined phase position, the protrusion  33   a  engages with the inner wall of the first feeding roller  32 , and subsequently the rotation force of the one-way clutch  33  is transmitted to the first feeding roller  32 . In other words, until the protrusion  33   a  of the one-way clutch  33  reaches from an initial position to a predetermined phase, the rotation force of the one-way clutch  33  is not transmitted to the first feeding roller  32 . 
     Note that, the forward rotation direction in the present specification refers to the rotation direction of each roller in the case where a print medium is fed from the first feeding cassette  5 A toward the print head, whereas the reverse direction refers to a direction of rotation in a reverse direction relative to the forward rotation direction. 
     The second feeding roller  42  is fixed to the second roller shaft  40  extending in the y-direction. The second roller shaft  40  is a drive shaft rotating with the aforementioned first feeding motor (feeding roller drive unit)  22  serving as the driving source. The second feeding roller  42  and the second roller gear  41  rotate integrally with the second roller shaft  40 . Rotation of the second roller gear  41  is transmitted to the first roller gear  31  and the one-way clutch  33  via the idle roller gear  43 . On this occasion, in the case where the rotation direction of the first roller gear  31  is the forward rotation direction, rotation of the first roller gear  31  is transmitted from the one-way clutch  33  to the first feeding roller  32  after a delay period described below, and the first feeding roller  32  rotates in the forward rotation direction. In contrast, rotation of the first roller gear  31  in the reverse direction is not transmitted to the first feeding roller  32  due to action of the one-way clutch  33 . 
     The first roller shaft  30  supporting the first roller gear  31  and a center-of-rotation shaft  43   a  supporting idle roller gear  43  are both supported by a feeding roller holding member  55  rotatably in forward and reverse directions. The feeding roller holding member  55  is supported in a freely rotatable manner about the second roller shaft  40  via a sliding bearing or the like, and biased so as to rotate downward by a roller biasing spring  56  ((feeding roller biasing member) biasing unit) that biases the feeding roller holding member  55 . In addition, the feeding roller holding member  55  is configured to abut a feeding roller movement cam  84  that rotates together with a camshaft  57 , and also rotate around the second roller shaft  40 , by a feeding roller movement lever  85  that allows rotation of the feeding roller holding member  55 . The camshaft  57  rotates in conjunction with the second roller shaft  40 , due to a power transmission mechanism described below. 
     The feeding roller movement cam  84  rotating together with the camshaft  57  causes the movement lever  85  to abut and depress the feeding roller holding member  55 , and the feeding roller holding member  55  is caused to rotate upward around the second roller shaft  40 . Accordingly, the first feeding roller  32  moves to a separated position separated upward from the print media S housed in the first cassette  5 A. 
     Upon the camshaft  57  rotating further, the movement lever  85  separates from the abutting position against the feeding roller holding member  55  by the feeding roller movement cam  84 . As a result, the feeding roller holding member  55  moves downward around the second roller shaft  40  due to the biasing force of the roller biasing spring  56 , and the first feeding roller  32  abuts the top surface (first surface) of the print media S housed in the first cassette  5 A. 
     A separation roller  52  is rotatably supported by a fixed center shaft  50  provided for a separation roller holding member  53  via a torque limiter  51 . The separation roller holding member  53  is rotatably supported by a spindle  54  held by a frame, and performs a movement operation around the spindle  54 , due to cooperation of a separation roller cam (separation member movement cam)  58  fixed to the camshaft  57  and a biasing spring which is not illustrated. Rotationally moving the separation roller holding member  53  causes the separation roller  52  to be selectively located at a nipping position at which the print medium S is nipped between the separation roller  52  and the second feeding roller  42 , and a non-contact position at which the separation roller  52  separates from the second feeding roller  42  and does not contact the print medium. The position (nipping position) at which the print medium S is nipped between the separation roller  52  and the second feeding roller  42  is defined in the vicinity of the entrance of a conveying path CP 1  (see  FIG. 10 ) within the feeding unit. The print medium S being nipped between the second feeding roller  42  and the separation roller  52  is sent into the conveying path CP 1  by rotation of the second feeding roller  42 . The separation roller  52  is coupled to the torque limiter  51 , which provides resistance force against the rotation of the separation roller  52 . Accordingly, in the case where a plurality of sheets of the print media S are sent between the second feeding roller  42  and the separation roller  52 , only one sheet of the print media contacting the second feeding roller  42  is fed downstream, and feeding of the print media other than the aforementioned print medium is prevented due to contact with the separation roller. In other words, only the top sheet of the print media is fed downstream. 
     In addition, there is provided a return member  59  in the vicinity of the entrance of the conveying path CP 1  for returning the print medium S remaining in the vicinity thereof to the first cassette  5 A. The return member  59  is configured to pivot with a rotating shaft  59   a  being at the center, due to a return member cam  60  (see  FIG. 11 ) that rotates along with rotation of the camshaft  57 . In other words, the return member  59  moves in the backward direction due to the return member cam  60  in the case of conveying the print medium S downstream along the conveying path CP 1 , and retracts to a retracted position separated from the conveying path CP 1 . Therefore, blocking of conveyance due to the front edge of the print medium S being conveyed downstream and interfering with the return member  59  is prevented. 
     Additionally, in the case of returning the sheets of the print media S remaining in the conveying path CP 1  to the first cassette  5 A, the return member  59  rotates from the retracted position and moves in the forward direction around the rotating shaft  59   a  (see  FIG. 15 ). The movement in the forward direction causes the return member  59  to abut the front edge of the sheets of the print media S remaining in the conveying path CP 1  and return the print media S to the first cassette  5 A. 
       FIG. 14  is a perspective view illustrating the power transmission mechanism that transmits rotation force of the second roller shaft  40  being rotated by the first feeding motor  22  to the camshaft  57 . An input gear  81  is fixed to the end of the second roller shaft  40 . The rotation force of the input gear  81  is transmitted to the feeding roller movement cam  84  via an idle gear  82 . The feeding roller movement cam  84  is fixed to the camshaft  57  and rotates together with the camshaft  57 . 
     The feeding roller movement lever  85  is supported in a freely rotatable manner by a spindle  86  and biased toward a predetermined direction (direction C in  FIG. 14 ) by a biasing spring  87 . The biasing force of the biasing spring  87  causes one end  85   a  of the feeding roller movement lever  85  to constantly abut the feeding roller movement cam  84 . In addition, the feeding roller movement lever  85  is coupled to the aforementioned feeding roller holding member  55 . 
     Upon the feeding roller movement cam  84  rotating to a predetermined phase, a depression part  84   a  of the feeding roller movement cam  84  depresses the one end  85   a  of the feeding roller movement lever  85 , and causes the feeding roller movement lever  85  to rotate in a direction reverse to the direction C against the biasing spring  87 . In conjunction with the rotation of the feeding roller movement lever  85 , the feeding roller holding member  55  rotates around the second roller shaft  40 . As a result, the first feeding roller  32  supported by the feeding roller holding member  55  is held at separated position away from the print media S stacked on the first cassette  5 A. 
     Upon the camshaft  57  further rotating in conjunction with the second roller shaft  40  from a state where the first feeding roller  32  is held at the separation position, the depression part  84   a  of the feeding roller movement cam  84  separates from the one end  85   a  of the feeding roller movement lever  85 . As a result, the feeding roller movement lever  85  rotates due to the biasing force of the biasing spring  87  and, in conjunction therewith, the feeding roller holding member  55  rotates downward around the second roller shaft  40 . The rotation of the feeding roller holding member  55  causes the first feeding roller  32  to move to the abutting position at which it abuts the top sheet of the print media S in the first cassette  5 A. 
     Note that the feeding roller movement unit that moves the first feeding roller  32  to the abutting position against and the separated position from the print media includes the feeding roller holding member  55 , and a holding member movement unit configured to move the feeding roller holding member  55  reciprocally relative to a predetermined fulcrum (the second roller shaft  40 ). The holding member movement unit is configured to include the camshaft  57 , the feeding roller movement cam  84 , the roller biasing spring  56 , the feeding motor  22 , and the aforementioned power transmission mechanism or the like. 
     A separation roller movement unit (separation member movement unit) that moves the separation roller  52  to the contact position (nipping position) and the retracted position relative to the second feeding roller  42  includes the separation roller holding member  53 , the camshaft  57 , a separation roller cam  58 , the feeding motor  22 , and the power transmission mechanism. 
     In the foregoing description, the configuration of the first feeding unit  6 A has been explained, and since the second feeding unit  6 B that feeds the print media from the second feeding cassette  5 B has a similar configuration, explanation relating to the second feeding unit will be omitted here. Next, a feeding operation performed by the first feeding unit having the aforementioned configuration will be described, referring to  FIGS. 15 and 16 .  FIG. 15  illustrates a stand-by state before starting the feeding operation. In the stand-by state before a printing instruction is transmitted from the host device  400  to the controller unit  100 , the conveyance control unit  207  of the print engine unit  200  controls the feeding motor  22  serving as the driving source of the first feeding unit  6 A, and keeps respective parts at an initial state. In the initial state, as illustrated in  FIG. 15 , the first feeding roller  32  abuts the top surface (first surface) of the top sheet of the print media S housed in the first cassette  5 A. In other words, the feeding roller holding member  55  is biased downward by a biasing force of the aforementioned roller biasing spring  56 , the first feeding roller  32  contacting the top surface of the top sheet of the print media S with a moderate biasing force. Additionally, in the initial state, the return member  59  is held at a retracted position at which the conveying path CP 1  is released, and the separation roller  52  is held at the abutting position against the second feeding roller  42 , respectively. 
     Upon input of a printing instruction from the host device  400  to the controller unit  100 , a control signal is transmitted from the controller unit  100  to the print engine unit  200 . Upon receiving the control signal, the print controller  202  of the print engine unit  200  drives the feeding motor  22  via the conveyance control unit  207 , and causes the second roller shaft  40  to rotate. 
     The rotation force of the second roller shaft  40  is transmitted to the one-way clutch  33  via second roller gear  41 , the idle roller gear  43 , and the first roller gear  31 . There is provided a delay mechanism intervening between the one-way clutch  33  and the first feeding roller  32 , and the rotation force of the one-way clutch  33  is not transmitted to the first feeding roller  32  until a predetermined phase is reached after the one-way clutch  33  has started rotation. In other words, even in the case where rotation of the second roller shaft  40  has been started, the first feeding roller  32  does not immediately rotate but starts rotating after the predetermined delay period (the period indicated by a in  FIG. 17 ) has elapsed. 
     As thus described, setting the delay period between the start of rotation of the second roller shaft  40  and the start of rotation of the first feeding roller  32  makes it possible to move each member being in the stand-by state to a position suitable for feeding the print medium S during the delay period. For example, it becomes possible to perform a preparation operation for causing the torque limiter  51  to generate a desired torque during the delay period. 
     Upon elapse of the delay period, the first feeding roller  32  starts rotating by rotation of the one-way clutch  33 . The first feeding roller  32  is in a state contacting the top surface of the print media S already housed in the first cassette  5 A at the stage of the stand-by state. Therefore, the print media S may be sent out from the first cassette  5 A along with rotation of the first feeding roller  32 . On this occasion, there may occur the so-called double-feed, in which the top print medium S contacting the first feeding roller  32  and the print media S thereunder are sent out from the first cassette  5 A in an overlapped manner. However, the double-fed print media S are nipped between the second feeding roller  42  and the separation roller  52  so as to be separated into the top sheet and sheets thereunder of the print media S. 
     Upon conveying the top sheet of the print media S to downstream of the separation roller  52  in the conveying direction by the conveying roller  7 , the return member  59  starts moving from the retracted position into the conveying path CP 1 . On this occasion, the feeding roller holding member  55  moves upward so as to allow the return member  59  to return the remaining print media S into the first cassette  5 A, and the separation roller  52  separates from the second feeding roller  42 . Upon the return member  59  finally reaching the return position illustrated in  FIG. 16A , the feeding roller holding member  55  moves downward. 
     After the return member  59  has completed returning of the print media S, the first feeding roller  32  abuts (descends to) the top surface of the top sheet of the print media S housed in the first feeding cassette  5 A due to the biasing force of the roller biasing spring  56 . On this occasion, the feeding motor serving as the driving source of the second roller shaft  40  is in a terminate state, and rotation of the first feeding roller  32  has been terminated. Accordingly, the print medium is not fed from the first cassette  5 A to the nipping position between the second feeding roller  42  and the separation roller  52 , preventing occurrence of double-feed. 
     The top sheet of the print media S is conveyed to the print head  8  by the conveying roller  7  and the pinch roller  7   a  and ink is ejected from the print head  8  so as to print an image. During the printing operation, it is necessary to reduce the load of conveying the print medium S by the conveying roller  7 . Accordingly, as illustrated in  FIG. 16B , printing is performed in a state where the separation roller  52  separates from the second feeding roller  42  and nipping by both rollers is released. In addition, there may be a case where the conveying roller  7  and the first feeding roller  32  simultaneously contact a same sheet of the print media S during the conveyance operation. In such a situation, it is necessary to prevent the first feeding roller  32  from working as a conveyance load of the conveying roller  7 . Therefore, increase of conveyance load for the conveying roller  7  is suppressed by coupling the one-way clutch  33  to the first feeding roller  32  and causing the first feeding roller  32  to smoothly perform following rotation in accordance with the conveyance of the print medium S. 
     In the present embodiment, as thus described, whereas the first feeding roller  32  in a rotation terminated state is caused to abut the top surface of the print media S in the first cassette  5 A in the stand-by state before the feeding operation, the separation roller  52  is caused to abut the second feeding roller and the return member  59  is moved to the retracted position. Accordingly, even in the case where a plurality of sheets of the print media are fed from the first cassette  5 A in an overlapped manner due to the feeding operation, these double-fed print media are separated by the second feeding roller and the separation roller  52  into the top print medium and the print media thereunder of the print media. In other words, the second feeding roller and the separation roller  52  are already kept in a stable contacting state in the stand-by state before the feeding operation is started, and therefore it becomes possible to reliably separate the double-fed sheets of the print media. 
     Therefore, the possibility of feeding a plurality of sheets of the print media to the conveying path CP 1  significantly decreases, and it becomes possible to reduce the waste of printing operation that may occur due to double-feed. In other words, it becomes possible to suppress printing operations performed across a plurality of sheets of the print media and discharge of blank sheets, occurrence of jam due to double-feed, and waste of ink or the print media consumed during an inappropriate printing operation due to double-feed. 
       FIG. 17  is a timing chart indicating operation timings of respective members in a series of feeding operations described above. The timing chart indicates the timings at which respective members of the feeding unit  6 A (the feeding roller holding member  55 , the return member  59 , and the separation roller  52 ) operate while the camshaft  57  rotates once, and output signals (ON signal and OFF signal) of a cam sensor  160 . The cam sensor  160  includes a rotating plate  161  provided on the return member cam  60 , and a photo interrupter  162  facing the rotating plate  161 . The cam sensor  160  outputs an ON signal in a state where the light-shielding part of the rotating plate  161  exists between a light-emitting part and a light-receiving part included in the photo interrupter  162 , and an OFF signal in a state where the light-shielding part of the rotating plate  161  does not exist between the light-emitting part and the light-receiving part, respectively. 
     Feeding of the print media S is performed while the camshaft  57  rotates from an initial position (0 degree) to θf 1  degrees. Upon the camshaft  57  rotating to θf 1  degrees, the first feeding roller  32  rotationally moves (ascends) around the second roller shaft  40 . Upon the camshaft  57  rotating to θf 2  degrees, the first feeding roller  32  completely separates from the top sheet of the print media S housed in the first feeding cassette  5 A. The separation state continues until the rotation angle of the camshaft  57  reaches θf 3  degrees. 
     Upon the rotation angle of the second roller shaft  40  reaching θf 3  degrees, the first feeding roller  30  rotationally moves (descends) around the second roller shaft  40 . Subsequently, at a time point at which the camshaft  57  has rotated to θf 4  degrees, the first feeding roller  32  abuts the top sheet of the print media S in the first cassette  5 A. The abutting state continues until the feeding operation is completed (up to θf 1  degrees). 
     Note that the angle range (angle range of α degrees (the period indicated by the generally dashed line in the drawing)) in which the camshaft  57  reaches the initial position (0 degree (=360 degrees)) from θ degrees turns out to be an angle range in which the rotation force of the second roller shaft  40  is not transmitted to the first feeding roller  32 . In other words, the angle range of interest is the aforementioned delay period. 
     In addition, upon the camshaft  57  rotating to the angle θr 1 , the return member  59  starts moving from the retracted position toward the return position. Subsequently, upon the camshaft  57  rotating to θr 2 , the return member  59  reaches the return position. Accordingly, the remaining sheets of the print media S separated from top sheet thereof are returned to the first feeding cassette  5 A. The return member  59  is held at the return position until the rotation angle of the camshaft  57  reaches the angle θr 3 . Upon the rotation angle of the camshaft  57  reaching the angle θr 3 , the return member  59  moves toward the retracted position and reaches the retracted position at the time point at which the rotation angle of the camshaft  57  has reached the angle θr 4 . 
     As thus described, the return member  59  moves to the retracted position in a predetermined period (α degrees) set within the delay period (angle θ to 360 degrees). Therefore, the print media S, whose feeding is started from the initial position (0 degree) of the camshaft  57 , does not interfere with the return member  59  during the feeding operation. 
     In addition, the separation roller  52  is held at the abutting position (nipping position) against the second feeding roller  42  until the camshaft  57  rotates from the initial position (0 degree) to an angle θs 1 . Upon the camshaft  57  rotating to the angle θs 1 , the separation roller  52  moves in a direction away from the second feeding roller  42 , and reaches a predetermined separated position at a time point at which the camshaft  57  has rotated to an angle θs 2 . Subsequently, the separation roller  52  is held at the separated position until the rotation angle of the camshaft  57  reaches an angle θs 3 . 
     Upon the camshaft  57  rotating to the angle θs 3 , the separation roller  52  moves from the separated position toward the second feeding roller  42 . Subsequently, the separation roller  52  reaches the abutting position (nipping position) against the second feeding roller  42  at a time point at which the camshaft  57  has rotated to an angle θs 4 . As thus described, the separation roller  52  moves to the nipping position in a predetermined period (from the angle θs 3  to angle θs 4 ) set within the delay period (from the angle θ to 360 degrees). Therefore, even in the case where a plurality of sheets of the print media S are fed by the feeding operation started from the initial position (0 degree), the sheets of the print media S turn out to be nipped between the separation roller  52  and the second feeding roller  42 , and reliably separated into the top sheet and sheets thereunder of the print media S. 
     The cam sensor  160  outputs an ON signal while the rotation angle of the camshaft  57  lies within a range from 0 degree to an angle θc 1  degrees, and outputs an OFF signal while the rotation angle of the camshaft  57  lies within a range from angle θc 1  degrees to an angle θc 2  degrees. In other words, an ON signal is output from the cam sensor  160  while the rotation angle of the second roller shaft  40  lies within a range from the angle θc 2  to the angle θc 1 . The print controller  202  determines the rotational position (phase) of the camshaft  57  on the basis of the detection result of the cam sensor  160 . 
     In the aforementioned embodiment, there has been provided a configuration of separating a plurality of print media fed from the feeding cassette by nipping the sheets between the second feeding roller and the separation roller. However, the separating unit for separating the sheets of the print media may be formed using members other than the separation roller. For example, it is also possible to separate the top sheet and the other sheets of the print media by providing a nonrotatable resistance force generation member provided contactable to, and separable from, the second feeding roller, and causing the resistance force generation member to contact the sheets other than the top sheet of the print media to generate resistance force. 
     Furthermore, in the aforementioned embodiment, the second feeding roller rotated by the driving force of the feeding motor is used as a member (nip member) for nipping the print medium together with a separation member such as the separation roller. However, a nip member for nipping the print medium together with a separation member may be formed of a roller that performs following rotation by contacting the print medium. Furthermore, it is also possible to form the nip member with a member having a lower sliding resistance against the print medium than that of the separation member. 
     In addition, the driving source that provides driving force to the first feeding roller  32 , the separation roller  52 , and the return member  59  is not limited to the feeding motor and other actuators may also be used. For example, a solenoid, cylinder, or the like may also be used. 
     In addition, although an example including the first and the second cassettes  5 A and  5 B has been described above, it is also possible to provide a larger number of cassettes. In such a case, it suffices to provide a feeding unit having a similar configuration to the feeding unit illustrated in the aforementioned embodiment. 
     Furthermore, the present invention is also applicable to a printing apparatus using a printing method other than inkjet printing. For example, the present invention is applicable to various types of printing apparatuses such as the printing apparatus that performs printing by electrophotography, or the thermal printing 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 No. 2017-246816, filed Dec. 22, 2017, which is hereby incorporated by reference herein in its entirety.