Patent Publication Number: US-8109507-B2

Title: Recording apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2009-68878, which was filed on Mar. 19, 2009, the disclosure of which is herein incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a recording apparatus which forms an image on a recording medium. 
     2. Description of the Related Art 
     In a publicly-known laser printer having feed rollers, resist rollers downstream of the feed rollers, and a sheet guide which is provided between these sets of rollers and constitutes a sheet conveyance path, the sheet guide is composed of two guides, i.e. an inner chute and an outer chute. The outer chute has a protrusion which protrudes toward the inner chute so as to narrow the sheet conveyance path and a curved portion which bulges away from the inner chute at the downstream of the protrusion so as to widen the sheet conveyance path. 
     In this arrangement, a sheet conveyed by the feed rollers is forced to move along the inner chute by the protrusion, and further conveyed to the resist rollers. Hitting the resist rollers, the sheet warps inside a large space formed by the curved portion. The leading edge of the sheet strongly hits the resist rollers on account of the warping, with the result that the tilting of the leading edge of the sheet is corrected. 
     SUMMARY OF THE INVENTION 
     When the tilting of the leading edge of the sheet is being corrected according to the technology above, i.e. so-called registration is being carried out, the sheet outwardly warps to contact the inner surface of the outer chute. When this registration takes too long, the sheet warps to form an S-shape from the curved portion to the protrusion, with the result that the sheet is bended. When the sheet is bended in this way, the bended part absorbs the transporting force exerted to the sheet by the feed rollers, thereby decreasing the force to hit the leading edge of the sheet against the resist rollers and decreasing the registration capability. 
     An object of the present invention is to provide a recording apparatus which can prevent the registration capability from decreasing. 
     A recording apparatus includes: an upstream roller pair; a downstream roller pair; an inner chute and an outer chute; and a moving mechanism. The upstream roller pair pinches and conveys a recording medium. The downstream roller pair has a slower conveyance speed than the upstream roller pair and is able to pinch a leading edge of the recording medium which is being pinched by the upstream roller pair. The inner chute and an outer chute are separated from each other and form a curved path between the upstream roller pair and the downstream roller pair. The recording medium passes through the curved path. A movable component is movable between a protruding position in which the movable component protrudes from the outer chute into the curved path toward the inner chute and a retracted position in which the degree of protrusion of the movable component from the outer chute into the curved path is smaller than the degree of protrusion in the protruding position. The moving mechanism causes the movable component to move between the protruding position and the retracted position. The moving mechanism causes the movable component to move from the protruding position to the retracted position at a timing on or after a first timing and before a second timing. The first timing is a timing before the leading edge of the recording medium having been conveyed by the upstream roller pair reaches a pinching position where the recording medium is pinched by the downstream roller pair, and the first timing is further limited to the earliest timing in a period, which period is defined such that at least a part of the recording medium is apart from the outer chute when the leading edge of the recording medium reaches the pinching position of the downstream roller pair, if the movable component is moved from the protruding position to the retracted position at a timing in the period. The second timing is a timing after the leading edge of the recording medium having been conveyed by the upstream roller pair reaches the pinching position of the downstream roller pair, and is the very instant at which the recording medium entirely contacts the inner surface of the outer chute between the pinching position of the downstream roller pair and a contact position where the movable component contacts the recording medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other and further objects, features and advantages of the invention will appear more fully from the following description taken in connection with the accompanying drawings in which: 
         FIG. 1  is a simplified profile of the internal structure of an inkjet printer according to First Embodiment of the present invention. 
         FIG. 2A  and  FIG. 2B  are perspective views of a sheet feeding unit of  FIG. 1 , observing the unit in different directions. 
         FIG. 3A  and  FIG. 3B  are profiles of the sheet feeding unit of  FIG. 1 , when a movable component of the sheet feeding unit is in the protruding position and in the retracted position, respectively. 
         FIG. 4  shows the control system of the inkjet printer of  FIG. 1 . 
         FIG. 5A  and  FIG. 5B  are a perspective view and a profile of a sheet feeding unit of an inkjet printer according to Second Embodiment of the present invention. 
         FIG. 6A  and  FIG. 6B  are a perspective view and a profile of a sheet feeding unit of an inkjet printer according to Third Embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIG. 1 , an inkjet printer  1  of First Embodiment of the present invention has a rectangular casing  1   a , and is provided with a sheet discharge area  15  at top. The space inside the casing  1   a  is divided into two spaces S 1  and S 2  from top to bottom. In the space S 1 , four inkjet heads  2  ejecting magenta, cyan, yellow, and black inks and a conveying unit  50  which conveys sheets in a conveyance direction A are provided in this order. In the space S 2  provided is a sheet supply unit  10 . In the space S 1 , furthermore, a sheet feeding unit  70  which sends, to the conveying unit  50 , a sheet P sent out from the sheet supply unit  10 . The inkjet printer  1  further includes a control unit  100  which controls the operations above. In the present embodiment, a direction in parallel to the conveyance direction A for conveying a sheet P by the conveying unit  50  is a sub-scanning direction, whereas a direction which is orthogonal to the sub-scanning direction and in parallel to the horizontal plane is a main scanning direction. 
     Inside the inkjet printer  1  formed is a conveying path on which a sheet P is conveyed from the sheet supply unit  10  to the sheet discharge area  15  along the thick arrow shown in  FIG. 1 . The sheet supply unit  10  includes a sheet feed cassette  11  which can store plural stacked sheets P, a pickup roller  12  which sends out a sheet P from the sheet feed cassette  11 , and a pickup motor  121  (see  FIG. 4 ) which is controlled by the control unit  100  and rotates the pickup roller  12 . The pickup roller  12  sends out the topmost sheet P among the plural sheets P stacked and stored in the sheet feed cassette  11 . 
     In the left side of the conveying unit  50  in  FIG. 1  provided are a conveyance guide  13  which curves and extends toward the top from the sheet feed cassette  11  and a sheet feeding unit  70  which sends to the conveying unit  50  a sheet P which has passed through the conveyance guide  13 . 
     As shown in  FIGS. 1-3 , the sheet feeding unit  70  includes an upstream roller pair  71  and a downstream roller pair  72  which sandwich and convey the sheet P, an inner chute  74  and an outer chute  75  which are provided between the roller pairs  71  and  72 , and two feed motors  122  and  123  (see  FIG. 4 ). The two feed motors  122  and  123  which are provided for conveying a sheet P in the conveyance direction B are controlled by the control unit  100 . The feed motor  122  rotates one roller of the upstream roller pair  71  whereas the feed motor  123  rotates one roller of the downstream roller pair  72 . The other rollers of these roller pairs  71  and  72  are driven rollers and rotate in accordance with the conveyance of the sheet P. The distance between the roller pairs  71  and  72  along the conveyance direction B is arranged to allow the downstream roller pair  72  to pinch at least the leading edge of the sheet P which is being sandwiched between the upstream roller pair  71 .  FIG. 2A  illustrates only the outer chute  75 , and the inner chute  74  is omitted from the figure. 
     The inner surface  74   a  of the inner chute  74  which surface opposes the outer chute  75  and the inner surface  75   a  of the outer chute  75  which surface opposes the inner chute  74  are both curved as shown in  FIG. 2A  and  FIG. 2B . The inner surface  74   a  bulges toward the outer chute  75 . The inner and outer chutes  74  and  75  are separated from each other to allow a curved path  73  to be formed between the inner surfaces  74   a  and  75   a.    
     As shown in  FIG. 3A , the inner surface  75   a  has a horizontal portion  76   a  near the downstream end and a curved portion  76   b  which extends from the vicinity of the downstream end toward the upstream end and bulges away from the inner chute  74 . With these components, the curved path  73  has a tapered path  73   a  which is provided between the horizontal portion  76   a  and the inner surface  74   a  and tapered towards the downstream end in the conveyance direction B and a buffer path  73   b  which is connected to the upstream end of the tapered path  73   a . This buffer path  73   b  is provided for warping a sheet P to contact the inner surface  75   a  (curved portion  76   b ) when the leading edge of the sheet P reaches the position of pinching by the downstream roller pair  72  and the registration of the sheet P is being carried out, as discussed later. As shown in  FIGS. 2A and 2B , the outer chute  75  is provided with plural slits  77  which perforate the outer chute  75  in the sub-scanning direction and are formed along the main scanning direction. 
     As shown in  FIG. 3A , at the upstream end of the inner chute  74  provided is a sheet sensor  68 . This sheet sensor  68  is provided upstream of a later-described position where the movable component  81  contacts the sheet P. The sheet sensor  68  detects the leading edge and the tail edge of the sheet P conveyed by the upstream roller pair  71  and sends a resulting detection signal to the control unit  100 . 
     The sheet feeding unit  70  includes a movable component  81  which can protrude from the outer chute  75  to the inside of the curved path  73  towards the inner chute  74  and a swing motor  85  (see  FIG. 4 ) which is controlled by the control unit  100  and swings the movable component  81 . The movable component  81  has a plurality of plates  82  arranged along the main scanning direction and a shaft  83  which extends in the main scanning direction and to which the plates  82  are fixed. Each plate  82  is provided in a slit  77 , and the shaft  83  is provided outside the outer chute  75 . The shaft  83  is supported at the both ends by the casing  1   a  so as to be rotatable. To one end of the shaft  83 , the driving force of the swing motor  85  is applied via an unillustrated transmission mechanism. In other words, the transmission mechanism and the swing motor  85  constitute a moving mechanism for moving the movable component  81 . 
     The surface of the plate  82  which surface opposes the inner surface  74   a  and is as thick as the plate has a slope  82   a  as shown in  FIG. 3A . This slope  82   a  is formed so that the angle between the slope  82   a  and a portion of the sheet P which portion is upstream in the conveyance direction of the point at which the sheet P contacts the plate  82  is an acute angle. This allows the upstream roller pair  71  to smoothly convey the sheet P. Furthermore, the slope  82   a  has a curved surface convex toward the outer chute  75  when the movable component  81  is in the later-described protruding position. This allows the upstream roller pair  71  to further smoothly convey the sheet P. 
     In the arrangement above, as the swing motor  85  is driven under the control of the control unit  100  and runs forward, the shaft  83  rotates anti-clockwise as shown in  FIG. 3A . As a result, the movable component  81  moves from the protruding position (see  FIG. 3A ) where the plate  82  partly protrudes from the inner surface  75   a  to the curved path  73  to the retracted position (see  FIG. 3B ) where the protruding part of the component  82  is withdrawn into the slit  77  so that the movable component  81  does not protrude into the curved path  73 . In the protruding position, the tip of the plate  82  is slightly separated from the inner surface  74   a . On the other hand, as the swing motor  85  runs backward, the shaft  83  rotates clockwise as shown in  FIG. 3A . As a result of this, the movable component  81  moves from the retracted position to the protruding position. When a sheet P is conveyed by the upstream roller pair  71  while the movable component  81  is in the protruding position, the leading edge of this sheet P contacts the curved surface  82   a  and the sheet P is guided such that the sheet P is conveyed along the inner surface  74   a  while being apart from the curved portion  76   b.    
     As shown in  FIG. 1 , the conveying unit  50  has a pair of belt rollers  51  and  52 , an endless conveyor belt  53  looped around the rollers  51  and  52 , a support roller  4 , and a conveyor motor  124  (see  FIG. 4 ) which generates a driving force for rotating the belt roller  52 . The outer circumferential surface of the conveyor belt  53 , i.e. the conveying surface  54  is subjected to a silicone treatment to have adhesion. The support roller  4  is disposed above the belt roller  51  to sandwich, together with the belt roller  51 , the conveyor belt  53 . The support roller  4  is biased toward the conveying surface  54  by an elastic component such as a spring, and pushes a sheet P having been conveyed by the downstream roller pair  72  onto the conveying surface  54 . 
     In this arrangement, the belt roller  52  is rotated clockwise in  FIG. 1  under the control of the control unit  100 , so that the conveyor belt  53  rotates. In accordance with the rotation of the conveyor belt  53 , the belt roller  51  and the support roller  4  also rotate because they are driven rollers. Then the sheet P conveyed from the sheet feeding unit  70  is supported by the conveying surface  54  and further conveyed in the conveyance direction A. When the sheet P supported by and conveyed on conveying surface  54  serially passes right under the four inkjet heads  2 , the control unit  100  controls the inkjet heads  2  so that inks of the respective colors are ejected onto the sheet P. In this way, a desired color image is formed on the sheet P. 
     Immediately downstream the conveying unit  50  in the conveyance direction A is provided a peeling plate  9 . This peeling plate  9  peels the sheet P off from the conveying surface  54  as the tip of the plate is inserted into the space between the sheet P and the conveyor belt  53 . 
     As shown in  FIG. 1 , in the right side of the inkjet head  2  is provided four feed rollers  21   a ,  21   b ,  22   a , and  22   b  and a conveyance guide  18  which is provided between the feed rollers  21   a  and  21   b  and between the feed rollers  22   a  and  22   b . The feed rollers  21   b  and  22   b  are rotated by feed motors  125  and  126  (see  FIG. 4 ) which are controlled by the control unit  100 . In this arrangement, the feed rollers  21   b  and  22   b  are rotated under the control of the control unit  100  so that a sheet P discharged from the conveying unit  50  passes through the conveyance guide  18  while being pinched by the feed rollers  21   a  and  21   b  and is further conveyed toward the upper part of  FIG. 1 . The sheet is then sent to the sheet discharge area  15  while being pinched by the feed rollers  22   a  and  22   b . The feed rollers  21   a  and  22   a  rotate in response to the conveyance of the sheet because they are driven rollers. 
     Now, the control unit  100  will be described with reference to  FIG. 4 . The control unit  100  is constituted by, for example, a general-purpose personal computer (PC). Such a computer has hardware such as a Central Processing Unit (CPU), a Read Only Memory (ROM), a Random Access Memory (RAM), and a hard disc, and the hard disc stores various kinds of software including a program for controlling the operation of the printer  1 . The control unit  100  controls the inkjet head  2  and the motors  85  and  121 - 126 . Moreover, the control unit  100  is connected to the sheet sensor  68  and a detection signal is sent from the sheet sensor  68  to the control unit  100 . 
     The printing operation of the printer  1 , the operation of the sheet feeding unit  70  in particular, will be discussed. When print data for forming an image on a sheet P is sent from a PC to the control unit  100 , the control unit  100  drives the pickup motor  121  so that a sheet P is sent out from the sheet supply unit  10 . 
     The control unit  100  then controls the feed motor  122  so as to rotate the upstream roller pair  71  in order to convey the sheet P in the conveyance direction B. As a result, the sheet P having passed through the conveyance guide  13  is conveyed to the inside of the curved path  73  while being pinched by the upstream roller pair  71 . At the same time, the sheet sensor  68  detects the leading edge of the sheet P and sends a detection signal indicating the detection to the control unit  100 . In addition, since the movable component  81  is in the protruding position in this case, the sheet P contacts the plate  82  and hence the sheet P is conveyed to the downstream roller pair  72  along the inner surface  74   a.    
     When a predetermined time has passed since the control unit  100  received the detection signal from the sheet sensor  68 , the swing motor  85  is controlled so that the movable component  81  is moved from the protruding position to the retracted position. This predetermined time is calculated by dividing the distance between the sheet sensor  68  and the downstream roller pair  72  by the conveyance speed of the sheet P by the upstream roller pair  71 . Therefore, when the leading edge of the sheet P reaches the sheet pinching position of the downstream roller pair  72  (i.e. the position where the sheet P is pinched by the downstream roller pair  72 ), the movable component  81  is moved from the protruding position to the retracted position. At this position, the sheet P is along the inner surface  74   a  as indicated by the full line in  FIG. 3B , and hence a large space is formed between the sheet P and the curved portion  76   b . The rotation of the downstream roller pair  72  has been stopped. 
     Thereafter, the leading edge of the sheet P abuts the downstream roller pair  72 . The sheet conveyance by the upstream roller pair  71  is carried out in this state, i.e. in the state in which the sheet P is at the sheet pinching position, so that the registration of the sheet P is carried out. During this registration, the sheet P is warped to contact the inner surface  75   a  as indicated by the two-dot chain line in  FIG. 3B . The leading edge of the sheet P does not therefore receive an excessive force. As the sheet P is warped to contact the inner surface  75   a , the upstream roller pair  71  does not easily slip on the sheet P and hence the sheet P is hardly damaged by the slipping of the upstream roller pair  71 . 
     Thereafter, the control unit  100  controls the feed motor  123  so that the motor  123  starts to run when a predetermined time has passed since the leading edge of the sheet P abuts the downstream roller pair  72  (i.e. reaches the pinching position). As a result, the sheet P is conveyed in the conveyance direction A. This predetermined time is equal to a time from the timing at which the leading edge reaches the pinching position to the timing at which the sheet P becomes to fully contact the inner surface  75   a  between the pinching position and the contact position. The predetermined time may be calculated based on the conveyance speed of the sheet P by the upstream roller pair  71  and the shape of the curved path  73 , or may be determined in advance based on an actually-measured time. The conveyance speed of the sheet P by the downstream roller pair  72  is slightly slower than the conveyance speed of the sheet P by the upstream roller pair  71 . Because of this, further registration of the sheet P is possible while the sheet P is conveyed by the roller pairs  71  and  72 , with the result that the conveyance accuracy of the sheet P is improved. In addition to the above, the control unit  100  drives the conveyor motor  124  so that the sheet P is conveyed in the conveyance direction A. In this way, the sheet P having been conveyed by the downstream roller pair  72  is now conveyed by the conveying unit  50 . 
     Furthermore, the control unit  100  controls the inkjet heads  2  so that each inkjet head  2  ejects ink when the sheet P passes through the area opposing said each inkjet head  2 . An image is formed at a predetermined position on the sheet P in this manner. The timing to eject ink is determined based on the time elapsed from the detection of the leading edge of the sheet P by the sheet sensor  68  (i.e. the quotient of division of the distance between the sheet sensor  68  and each head  2  by the conveyance speed of the sheet P). 
     The control unit  100  controls the swing motor  85  so that the movable component  81  is moved from the retracted position to the protruding position after a predetermined time elapsed from the detection of the tail edge of the sheet P by the sheet sensor  68 . This predetermined time is a time length from the detection of the tail edge of the sheet P by the sheet sensor  68  to the timing at which the tail edge of the sheet P passes through the contact position, and is calculated by dividing the distance between the sheet sensor  68  and the contact position by the sheet conveyance speed by the upstream roller pair  71 . Therefore, even after the movable component  81  is moved to the protruding position, the sheet P does not contact the movable component  81 . In other words, when the printing onto the sheet P is being carried out by the inkjet heads  2 , the movable component  81  does not interfere the conveyance of the sheet P, so that the quality of the image formed on the sheet P is not deteriorated. In the present embodiment, the contact position is slightly upstream from the midway point between the roller pairs  71  and  72 . 
     Thereafter, the control unit  100  drives the feed rollers  21   b  and  22   b  so that the sheet P having the image is conveyed from the conveyor belt  53  to the sheet discharge area  15  via the conveyance guide  18 . As such, the sheet P is discharged to the sheet discharge area  15  and the printing operation onto the sheet P finishes. 
     In the embodiment above, the movable component  81  is moved from the protruding position to the retracted position when the leading edge of the sheet P reaches the pinching position. In this regard, the aforesaid effect is achievable also by moving the movable component  81  from the protruding position to the retracted position at any timing (hereinafter, moving timing) on or after a later-described first timing and before a later-described second timing. 
     The first timing is a timing before the leading edge of the sheet P having been conveyed by the upstream roller pair  71  reaches the pinching position where the sheet P is pinched by the downstream roller pair  72 , and the first timing is further limited to the earliest timing in a period, which period is defined such that at least a part of the sheet P is apart from the outer chute  75  when the leading edge of the sheet P reaches the pinching position of the downstream roller pair  72 , if the movable component  81  is moved from the protruding position to the retracted position at a timing in the period. 
     An example of the moving timing is a timing when the leading edge of the sheet P passes through the contact position. When the movable component  81  is moved from the protruding position to the retracted position at this timing, The sheet P is conveyed in the conveyance direction B while the leading edge and the following part thereof contacts the inner surface  75   a . When the leading edge of the sheet P reaches the pinching position, a part of the sheet P which part is downstream from the midway point between the roller pairs  71  and  72  contacts the inner surface  75   a  whereas a part of the sheet P which part is upstream from the midway point between the roller pairs  71  and  72  is apart from the inner surface  75   a , as shown by the single-dot chain line in  FIG. 3B . Provided that the movable component  81  is moved from the protruding position to the retracted position at a moving timing earlier than the example above, this moving timing is before the first timing if the sheet P entirely contacts the outer chute  75  in the curved path  73  when the leading edge of the sheet P reaches the pinching position. 
     As such, if the movable component  81  is moved from the protruding position to the retracted position at a moving timing on or after the first timing, the sheet P is partly apart from the inner surface  75   a  when the leading edge of the sheet P reaches the pinching position. It is therefore possible to carry out the registration of the sheet P after the leading edge of the sheet P reaches the pinching position. 
     The second timing is a timing after the leading edge of the sheet P having been conveyed by the upstream roller pair  71  reaches the pinching position of the downstream roller pair  72 , and is the very instant at which the sheet P to entirely contacts the inner surface  75   a  between the pinching position of the downstream roller pair  72  and the contact position. In other words, the second timing is a timing at which the leading edge of the sheet P reaches the pinching position, the registration of the sheet P is carried out, and the sheet P becomes to contact the inner surface  75   a  from its leading edge to the contact position (i.e. a part of the sheet P indicated by the single-dot chain line in  FIG. 3A ). Moving the movable component  81  from the protruding position to the retracted position before this second timing is advantageous because the registration of the sheet P can be continued until the sheet P becomes entirely contacting the inner surface  75   a  between the pinching position and the contact position, and it is possible to prevent the sheet P from bending. It is preferable to calculate or actually measure the first and second timings in accordance with each type (item identifier) of sheets and store data about the timings in the control unit  100  in advance. 
     In the inkjet printer  1  of the present embodiment, the registration of the sheet P is possible after the leading edge of the sheet P reaches the pinching position, by moving the movable component  81  from the protruding position to the retracted position at a moving timing on or after the first timing. When the leading edge of the sheet P reaches the pinching position of the downstream roller pair  72  and the registration of the sheet P is carried out, the movable component  81  is moved from the protruding position to the retracted position before the second timing at which the sheet P entirely contacts the inner surface  75   a  of the outer chute  75  between the pinching position and the contact position. For this reason it is possible to prevent the sheet P from being bended along the shape of the plate  82 , thereby preventing the registration capability from deteriorating. 
     In addition to the above, the movable component  81  is moved from the protruding position to the retracted position when the leading edge of the sheet P reaches the pinching position of the downstream roller pair  72 , so that the sheet P is entirely apart from the outer chute  75  between the pinching position and the contact position, when the leading edge of the sheet P reaches the pinching position. In other words, the entirety of the sheet P in the curved path  73  is apart from the inner surface  75   a . This maximizes the time for the registration and hence the registration of the sheet P is effectively carried out. Furthermore, since the sheet sensor  68  and the control unit  100  which controls the operation of the swing motor  85  in accordance with the timing of the detection of the sheet P by the sheet sensor  68  are included, the plates  82  can stably operate. 
     The printer of the present embodiment has a simple arrangement such that the movable component  81  is moved between the protruding position and the retracted position as the moving mechanism swings the movable component  81 . Furthermore, since the movable component  81  does not protrude from the outer chute  75  to the space inside the curved path  73  when it is in the retracted position, the time for the registration is long as compared to a case where the movable component  81  protrudes toward the space inside the curved path  73  when it is in the retracted position, and hence the registration of the sheet P is further effectively carried out. 
     Now, an inkjet printer according to Second Embodiment of the present invention will be described with reference to  FIG. 5A  and  FIG. 5B . The inkjet printer the present embodiment is basically identical with the inkjet printer of First Embodiment except that a sheet feeding unit  270  is different in terms of arrangement from the sheet feeding unit  70  of the First Embodiment, and these printers are controlled in more or less the same manner. It is noted that components identical with those of First Embodiment are denoted by the same reference numerals and the descriptions thereof are omitted. It is also noted that  FIG. 5A  only illustrates the outer chute  75 , and the inner chute  74  is omitted from the figure. 
     In the present embodiment, the sheet feeding unit  270  includes: plural plates  282  and a shaft  283  which are more or less identical with the above-described plates  82  and shaft  83 ; and a movable component  281  having plural guide rollers  284 . The inner surface  75   a  of the outer chute  75  is provided with plural slits  277  along the main scanning direction, and two plates  282  are provided for each slit  277 . The central axis of the guide roller  284  extends in the main scanning direction, and one guide roller  284  is rotatably provided for the two plates  282  of each slit  277 . The guide roller  284  is provided at the tips of the two plates  282  closest to the inner chute  74 . The movable component  281  is arranged to be able to contact a sheet P conveyed by the upstream roller pair  71 , when the component  281  is in the protruding position. 
     Because the guide roller  284  is provided at the tips of the plates  282 , the sheet P having been conveyed by the upstream roller pair  71  is smoothly conveyed in the conveyance direction B. 
     Finally, an inkjet printer according to Third Embodiment of the present invention will be described with reference to  FIG. 6A  and  FIG. 6B . The inkjet printer of the present embodiment is substantially identical with the inkjet printers according to First and Second Embodiments and is controlled in a substantially identical manner, except that the arrangement of a sheet feeding unit  370  is different from those of the sheet feeding units  70  and  270 . It is noted that components identical with those of First and Second Embodiments are denoted by the same reference numerals and the descriptions thereof are omitted. It is also noted that  FIG. 6A  only illustrates the outer chute  75 , and the inner chute  74  is omitted from the figure. 
     In the present embodiment, the sheet feeding unit  370  includes: plural plates  382  and a shaft  383  which are more or less identical with the above-described plates  82  and shaft  83 ; and a movable component  381  having plural guide rollers  384  and  385 . In the same manner as Second Embodiment, each slit  277  is provided with two plate  382  in the present embodiment. The central axis of each of the guide rollers  384  and  385  extends along the main scanning direction, and each roller is rotatably supported by the two plates  382  of each slit  277 . More specifically, the guide roller  384  is provided above the guide roller  385 . The guide roller  384  is provided at the tips of the two plates  382  closest to the inner chute  74 . On the other hand, the guide roller  385  is farther from the inner chute  74  than the guide roller  384 . These guide rollers  384  and  385  are arranged so that, when the movable component  381  is in the protruding position, the guide roller  385  contacts a sheet P conveyed by the upstream roller pair  71  before the guide roller  384  contacts the sheet so that the sheet P is guided toward the inner chute  74 , and then the sheet P is guided by the guide roller  384  along the inner surface  74   a.    
     Consequently, it is possible to keep the sheet P having been conveyed by the upstream roller pair  74   a  to move along the inner surface  74   a  only by the two guide rollers  384  and  385 , while preventing the sheet P from contacting the plate  382 . The sheet P having been conveyed by the upstream roller pair  71  is therefore smoothly conveyed in the conveyance direction B. 
     In First to Third Embodiments above, the swing motor is driven under the control of the control unit  100  and the movable components  81 ,  281 , and  381  are moved from the protruding position to the retracted position. Alternatively, the moving mechanism for moving the movable component may be a biasing component which biases the movable component toward the inner chute  74 . The biasing component in this case is, for example, an elastic component such as a spring. The biasing force of the biasing component is arranged to be enough to move the movable component to the retracted position before the sheet P reaches the pinching position and the registration is carried out and hence a force sufficient for bending the sheet P in accordance with the shape of the movable component is applied to the sheet P. In other words, the movable component is moved from the protruding position to the retracted position by the force generated when the sheet P in the curved path  73  is warped to contact the inner surface  75   a  on account of the registration of the sheet P. The apparatus is simplified with this arrangement because it is unnecessary to control the movement of the movable component and to provide the swing motor. 
     In the three embodiments above, the movable component does not protrude from the outer chute to the inside of the curved path when it is in the retracted position. Alternatively, the movable component may protrude into the curved path as long as the degree of protrusion in the retracted position is smaller than the degree in the protruding position. Furthermore, the above-described three embodiments are arranged so that the movable component is swung. Alternatively, the movable component may be translated rather than swung. 
     In the three embodiments above, the downstream roller pair  72  is stopped when the registration of the sheet P is carried out as the leading edge of the sheet P reaches the pinching position. Alternatively, the downstream roller pair  72  may be rotated along with the upstream roller pair  71 , when the registration is carried out. In this case, the conveyance speed of the sheet P by the downstream roller pair  72  is arranged to be slower than the speed by the upstream roller pair  71 . It is also noted that the present invention may be used for a recording apparatus which has a record head which is not an inkjet head. 
     While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.