Abstract:
A recording device for effecting recording on a recording material by a recording head, said recording device including a recording unit including a reciprocally movable carriage for carrying the recording head, a platen for supporting a recording material at a position opposed to said carriage, and a feeding roller, disposed upstream of said platen, for feeding the recording material, a recording chassis supporting said carriage, said platen and said feeding roller, and a sheet feeding unit including a feeding path for feeding the recording material to said feeding roller from a plurality of feeding portions, and a side chassis supporting said feeding path at both lateral sides with respect to a moving direction of the recording material, whereby said recording chassis of said recording unit and said side chassis of said sheet feeding unit are fixed to each other.

Description:
FIELD OF THE INVENTION AND RELATED ART  
       [0001]     The present invention relates to a recording apparatus which employs one or more recording heads mounted on a carriage, to form an image on recording medium while the recording medium is conveyed along the top surface of a platen.  
         [0002]     Recording apparatuses having the function of a printer, a copying apparatus, a facsimileing machine, and/or the like, recording apparatuses used as the outputting device for a multi-functional electronic device or workstation, which comprises a computer and/or wordprocessor, etc., are structured to form an image on recording media, such as a piece of paper or plastic sheet, according to image formation data. As the recording method used by a recording apparatus, there are various methods, for example, the ink jet recording method, the thermal transfer recording method, the laser beam recording method, the wire-dot recording method, etc. Among various recording apparatuses employing one of these recording methods, a recording apparatus which records an image on recording medium by ejecting ink onto the recording medium from the ejection orifices of the recording head is advantageous over the others in that it is easy to reduce in size; it can be easily modified for forming a multicolor image; it is lower in noise and. operational cost; etc.  
         [0003]     The above described recording apparatuses can be roughly divided into two types: the serial type and line type. In the case of the recording apparatuses of the serial type, recording is made by moving a recording head relative to recording medium (scanning recording medium in primary scan direction), and in the case of the recording apparatuses of the line type, recording is made by moving only recording medium (moving recording medium in secondary scan direction). As for the feeding of recording medium into a recording apparatus, most of the abovementioned recording apparatuses are structured so that sheets of recording mediums are fed one by one into the apparatus main assembly from the sheet feeding portion, which is at the top rear portion of the main assembly, and in which multiple sheets of recording medium are stored slightly tilted.  
         [0004]     However, recording apparatuses equipped with a sheet feeding portion for feeding sheets of recording medium from a recording medium storage tray portion, in particular, recording apparatuses equipped with multiple recording medium storage portions, and provided with multiple recording medium conveyance routes for making it possible to feed sheets of recording medium from the multiple recording medium storage portions, suffer from the following problems. That is, first, the recording apparatuses have been likely to be large. Second, they have been difficult to assemble. Third, it has been difficult to improve in shock-resistance such recording apparatuses as those described above, in spite of the increase in the weight of the main assembly of the recording apparatus. Fourth, they are difficult to improve in recording medium conveyance performance.  
       SUMMARY OF THE INVENTION  
       [0005]     The primary object of the present invention is to provide a recording apparatus which is equipped with a sheet feeding portion for feeding recording medium into the main assembly of the recording apparatus from the recording medium storage portion of the recording apparatus, and which is characterised in that it is smaller in size, easier to assemble, more shock-resistant, and more stable in recording medium conveyance performance, than a recording apparatus in accordance with the prior arts.  
         [0006]     According to an aspect of the present invention, there is provided a recording device for effecting recording on a recording material by a recording head, said recording device comprising a recording unit including a reciprocally movable carriage for carrying the recording head, a platen for supporting a recording material at a position opposed to said carriage, a feeding roller, disposed upstream of said platen, for feeding the recording material, and a recording chassis supporting said carriage, said platen and said feeding roller; and a sheet feeding unit including a feeding path for feeding the recording material to said feeding roller from a plurality of feeding portions, and a side chassis supporting said feeding path at both lateral sides with respect to a moving direction of the recording material, whereby said recording chassis of said recording unit and said side chassis of said sheet feeding unit are fixed to each other.  
         [0007]     These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]      FIG. 1  is an external perspective view of a typical recording apparatus in accordance with the present invention.  
         [0009]      FIG. 2  is an external perspective view of the same recording apparatus as the one show in  FIG. 1 , which has been set up for usage.  
         [0010]      FIG. 3  is a perspective view of the same recording apparatus as the one shown in  FIG. 1 , the cover of which has been removed, as seen from the left front side of the apparatus, showing the internal structure thereof.  
         [0011]      FIG. 4  is a perspective view of the same recording apparatus as the one shown in  FIG. 1 , the cover of which has been removed, as seen from the right front side of the apparatus, showing the internal structure thereof.  
         [0012]      FIG. 5  is a sectional view of the same recording apparatus as the one shown in  FIG. 1 , showing the general internal structure thereof.  
         [0013]      FIG. 6  is a perspective view of the chassis of the recording apparatus, as seen from the right front side, showing the general structure thereof.  
         [0014]      FIG. 7  is a perspective view of the chassis of the recording apparatus, as seen from the right rear side, showing the general structure thereof.  
         [0015]      FIG. 8  is an exploded view of the joint portions between the recording portion member of the chassis of the recording apparatus and the right-hand lateral member of the chassis, showing the structural arrangement for fastening the lateral member of the chassis to the recording portion member of the chassis. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Hereinafter, one of the preferred embodiments of the present invention will be described in detail with reference to the appended drawings. Throughout the following description of the preferred embodiment, if a component in one of the drawings is identical in referential symbol to a component in another drawing, the two components are virtually identical in function.  FIG. 1  is an external perspective view of the recording apparatus in this embodiment of the present invention, and  FIG. 2  is an external view of the same recording apparatus as the one shown in  FIG. 1 , which has been set up for usage.  FIG. 3  is a perspective view of the recording apparatus in accordance with the present invention, the cover of which has been removed, as seen from the left front side, showing the general structure thereof, and  FIG. 4  is a perspective view of the same recording apparatus as the one shown in  FIG. 3 , the cover of which has been removed, as seen from the right front side, showing the general structure thereof.  FIG. 5  is a sectional view of the recording apparatus in accordance with the present invention, showing the general internal structure thereof.  
         [0017]     This embodiment will be described with reference to a case in which the recording apparatus is an ink jet recording apparatus which records an image on recording medium by ejecting ink from its recording head onto the recording medium. In  FIGS. 3-5 , the recording apparatus  1  is made up of a sheet feeding portion  2 , a sheet conveying portion  3 , a sheet discharging portion  4 , a carriage portion  5 , a recovery mechanism portion  6  (cleaning portion), a recording head  7 , a U-turn sheet feeding portion  8  inclusive of the two-sided printing path, and an external shell  9 . Next, these portions and mechanisms will be described in the logical order.  
         [0000]     [Sheet Feeding Portion] 
         [0018]     The sheet feeding portion  2  for feeding recording medium into the main assembly of the recording apparatus  1  from the recording medium storage portion is made up of a pressure plate  21  against which one or more sheets P of recording medium are placed; a sheet feeder roller  28  (which hereinafter will be simply referred to as feed roller) which feeds the sheet P; a separation roller  241  which separates the sheets P; a return lever  22  for returning the sheets P to the standby location; and a base  20  to which the preceding portions, components, etc., are attached. A sheet feeder tray  26  for holding the mounted sheets P is attached to either the base  20  or the external shell  9 . The sheet feeder tray  26  of the sheet storage portion is of the multistage type, and is to be pulled out for usage. The feed roller  28  is in the form of a rod and is roughly D-shaped in cross section. It is provided with a sheet feeder rubber by which a sheet of recording medium is conveyed. The sheet feeder rubber is positioned close to the sheet positioning reference. The feed roller  28  is driven by an unshown motor  27  with which the sheet feeding portion  2  is provided, and which is shared by the recovery mechanism portion  6 . From this motor  27  (which hereinafter will be referred to as AP motor), the force for driving the feed roller  28  is transmitted to the feed roller  28  through a driving force transmission gear  271  (unshown), a planetary gear  272  (unshown), etc.  
         [0019]     The pressure plate  21  is provided with a movable side guide  23  for accurately positioning the sheets P. The pressure plate  21  is pivotable about its pivotal axle, which is a part of the base  20 . The pressure plate  21  is kept pressured against the feeder roller  28  by leaf springs  212 . To the portion of the surface of the pressure plate  21 , which directly faces the feed roller  28 , a separation sheet  213  formed of artificial leather or the like substance, which is large in coefficient of friction, is attached to prevent one or more of the sheets P below the topmost sheet from being fed together with the topmost sheet P. The pressure plate  21  can be placed against the feed roller  28  or moved away therefrom by a pressure plate cam  214  (unshown). The sheet feeding portion  2  is also provided with a separation roller holder  24 , which holds the separation roller  241  for separating one by one the sheets P, and is attached to the base  20 , being enabled to pivot about the rotational axis. The separation roller  241  is kept pressed against the feed roller  28  by separation roller springs  241  (unshown).  
         [0020]     The separation roller  241  is fitted with a spring clutch  243 , which allows the separation roller  241  to rotate only when the amount of load to which the separation roller  241  is subjected is greater than a predetermined value. The separation roller  241  and the components related thereto are structured so that the separation roller  241  is pressed against, or separated from, the feed roller  28  by a separation roller release shaft  244  and a control cam  25  (unshown). The positions of the pressure plate  21 , return lever  22 , and separation roller  241  are detected by ASF sensors  29  (unshown). Further, the return lever  22  for returning the sheets P to their standby positions is pivotably attached to the base  20 , and is kept pressured by return lever springs  221  (unshown) in the direction in which the return level  22  is released. The return lever  22  is pivoted by a control cam  25  (unshown) when the sheets P need to be returned to their standby positions.  
         [0021]     When the recording apparatus is on the normal standby, the pressure plate  21  is kept away from the feed roller  28  by the pressure plate cam  214  (unshown), and the separation roller  241  is kept away from the feed roller  28  by the control cam  25  (unshown). As for the return lever  22 , it is kept in the position into Which it is pivoted to return the sheets P to their standby positions, and in which it blocks the entrance to the sheet conveyance path to prevent the sheets P from entering the sheet conveyance path. As the feeding of the sheets P begins when the recording lo apparatus is in the above described condition (on the normal standby), first, the separation roller  241  is placed in contact with the feed roller  28  by the driving force from the motor. Then, the return lever  22  is moved to the sheet feeding position, and the pressure plate  21  is pressed against the feed roller  28 . With the recording apparatus being in this state, the actual feeding of the sheets P into the main assembly of the recording apparatus begins.  
         [0022]     The number by which the sheets P are picked up by the feed roller  28  is controlled by a pre-separation portion with which the base  20  is provided, so that only a predetermined number of sheets P are sent to the nip between the feed roller  28  and separation roller  241 , in which the sheets P are separated, that is, only the top sheet P is fed into the main assembly of the recording apparatus. As the fed sheet P reaches the nip between a sheet conveyance roller  36  and a pinch roller  37 , the pressure plate  21  is released by the pressure plate cam  214  (unshown), and the separation roller  241  is released by the control cam  25  (unshown). The return lever  22  is allowed by the control cam  25  (unshown) to return to the standby position while pushing the unfed sheets P back into their standby positions in the sheet feeder tray  26 . In other words, the sheets P, which were sent to the immediate adjacencies of the nip between the feed roller  28  and separation roller  241 , but, were not actually fed into the main assembly, are returned to their standby positions in the tray  26 .  
         [0000]     [Sheet Conveying Portion] 
         [0023]     The sheet conveying portion  3  (which hereinafter may sometime be referred to simply as conveyance portion) is attached to the central member  11  of the chassis of the recording apparatus  1 , which correspond in position to the recording portion. The central member  11  of the chassis is a rigid member made up of multiple angled metallic members. The conveyance portion  3  has a sheet conveyance roller  36  which conveys the sheets P, and a PE (paper end) sensor  3  (unshown). The conveyance roller  36  is made up of, for example, a metallic shaft, and a layer of minuscule ceramic particles coated on the peripheral surface of the metallic shaft. It is attached to the central member  11  of the chassis by being supported by the lengthwise ends by a pair of bearings  36 , one for one, which are attached to the central member  11  of the chassis. In order to assure that the sheets P are reliably conveyed, a conveyance roller tension spring  381  (unshown) is disposed between each of the pair of bearings  38  and corresponding lengthwise end of the metallic shaft of the conveyance roller  36  so that the conveyance roller  36  is kept under a predetermined amount of load by the resiliency of the conveyance roller tension springs  381 .  
         [0024]     The sheet conveying portion  3  is provided with multiple pinch rollers  37 , which are disposed in contact with the peripheral surface of the conveyance roller  36 , and are rotated by the rotation of the conveyance roller  36 . The pinch rollers  37  are held by a pinch roller holder  30 . The force for conveying the sheet P is transmitted to the sheet P by pressing the pinch rollers  37  by the resiliency of pinch roller springs  31  against the conveyance roller  36  with the presence of the sheet P between the pinch rollers  37  and conveyance roller  36 . The pinch roller holder  30  is pivotally attached by its pivotal axles to the central member  11  of the chassis, with the presence of a bearing between each pivotal axle and the central member  11  of the chassis. The sheet conveyance portion  3  is also provided with a guide flapper  33 , which are located at the entrance of the sheet conveyance portion  3 , and through which the sheets P are fed into the apparatus main assembly, and a platen  34 . To the pinch roller holder  30 , a sensor lever  321  of the paper end (PE) sensor  32  for detecting the leading and trailing ends of the sheet P is pivotally attached. The platen  34  is attached to the central member  11  of the chassis. The guide flapper  33  is pivotally supported so that its pivotal axis coincides with those of the bearing portions  331  (unshown) of the conveyance roller  36 . It is appropriately positioned by coming in contact with a part of the central member  11  of the chassis.  
         [0025]     With the sheet conveying portion  3  being structured as described above, after being sent from the sheet feeding portion to the sheet conveying portion  3 , each sheet P is sent to the nip (LF nip) between the conveyance roller  36  and pinch rollers  37  while being guided by the pinch roller holder  30  and guide flapper  33 . While the sheet P is conveyed to the LF nip, the leading end of the sheet P is detected by the sensor lever  321 , whereby the point on the sheet P, at which recording is to be started in the recording portion, is calculated. As for the means for conveying the sheet P along the top surface of the platen  34 , a pair of sheet conveyance rollers are rotationally driven by a sheet conveyance motor  35 . The top surface of the platen  34  is provided with multiple ribs. The apparent surface (plane) which coincides with the tops of these ribs constitutes the surface along which the sheet P is conveyed. Not only do these ribs control the gap between the recording head  7  and sheet P, but also, minimize, in coordination with the sheet discharging portion, the waving of the recording sheet P. As for the driving of the conveyance roller  36 , the rotational force of the conveyance motor  35 , which is a DC motor, is transmitted through a timing belt  351  to a pulley  361  attached to the shaft of the conveyance roller  36 .  
         [0026]     The conveyance roller  36  is provided with a code wheel  362 , which is attached to the shaft of the conveyance roller  36  to detect the distance by which the sheet P has been conveyed by the conveyance roller  36 . The code wheel  362  is provided with markings positioned at a pitch in the range of 501 lpi-300 lpi. Whereas, to the central member  11  of the chassis, an encoder sensor  363  for reading the makings of the code wheel  362  is attached. The recording head  7  for recording an image according to image formation data is disposed on the downstream side of the conveyance roller  36  in terms of the sheet conveyance direction. The recording head  7  of the recording apparatus in this embodiment is an ink jet recording head to which multiple ink containers, different in the color of the inks they use, are removably attachable. The recording head  7  is provided with heaters or the like, which are disposed inward of the ejection orifices, one for one, to heat the ink in the ejection orifices. As for the recording method of the recording head  7 , the ink in the ejection orifice selected according to the image formation data is heated by the abovementioned heaters or the like to cause the ink to boil in the so-called film boiling fashion, that is, in the manner of generating bubbles in the ink, so that the ink is ejected from the selected ejection orifices of the recording head by the changes in the pressure resulting from the growth or collapse of the bubbles, and forms an image on the sheet P as a recording medium as the ink lands on the sheet P.  
         [0000]     [Carriage Portion] 
         [0027]     The carriage portion  5  is provided with a carriage  50  on which the recording head  7  is mounted, and which is reciprocally movable in the primary scan direction, that is, the direction perpendicular to the sheet conveyance direction. The carriage  50  is movably supported by a guide shaft  52  so that it can be guided by the guide shaft  52 . The guide shaft  52  is disposed so that it extends in the direction roughly perpendicular to the direction in which the sheet P is conveyed. Further, the carriage  50  is movably supported also by a guide rail  111 , which is parallel to the guide shaft  52  and supports the rear portion of the carriage  50  in a manner to allow the carriage  50  to slide thereon. With the provision of this structural arrangement, the carriage  50  is kept in a predetermined attitude so that a predetermined amount of gap will be maintained between the recording head  7  and sheet P. The guide shaft  52  is attached to the central member  11  of the chassis. The guide rail  111  is an integrally formed part of the central member  11  of the chassis.  
         [0028]     The carriage  50  is driven through a timing belt  541  by a carriage motor  54  attached to the central member  11  of the chassis. The timing belt  541  is suspended so that it is given a predetermined amount of tension by an idler pulley  542 . The timing belt  541  is connected to the carriage  50  with the interposition of a damper formed of rubber or the like, which is for minimizing the amount by which the vibrations from the carriage motor  54 , etc., are transmitted to the carriage  50 , in order to prevent the formation of defective images for which the vibrations from the carriage  50 , etc., are responsible. Disposed in parallel to the timing belt  541  is a code strip  561 , which is provided with markings arranged at a pitch in the range of 150 lpi-300 lpi in order to detect the position and movements of the carriage  50 . The encoder for reading these markings is located on the base plate of the carriage  50 .  
         [0029]     This carriage base plate  50  is provided with contacts for making electrical contacts between the recording head  7  and carriage  50 . To the carriage  50 , the flexible electrical wires, bundled in the form of a piece of tape  57 , for transmitting print signals from the electrical circuit of the recording apparatus to the recording head  7  is attached. The carriage  50  is also provided with a positioning projection (or rib) for accurately positioning the recording head  7  relative to the carriage  50 , and a pressing means for keeping the recording head  7  correctly held to the carriage  50 . The pressing means is attached to a head setting lever  51 . Rotating the head setting lever  51  causes the pressing means to press on the recording head  7 .  
         [0030]     The guide shaft  52  is provided with a pair of eccentric cams  521 , which are attached to the lengthwise ends of the guide shaft  52  one for one. The guide shaft  52  is vertically movable by transmitting the driving force from an AP motor  273  to the pair of eccentric cams  521  through the combination of the main cam of the recovery mechanism portion  6  and a gear train  591 . The vertical movement of the guide shaft  52  effects the vertical movement of the carriage  50 , which makes it possible to set the gap between the sheet P and recording head  7  to the optimum value regardless of the thickness of the sheet P. Further, the carriage  50  is provided with an automatic registration adjustment sensor  59 , which is for automatically compensating for the distance by which the ink ejected from the recording head  7  misses the theoretical landing point on the sheet P. This sensor  59  is an optical sensor of the reflection type, which is enabled to determine the optimum registration adjustment value by catching the beam of light emitted from its light emitting element and reflected by the image recorded on the sheet P in a predetermined pattern.  
         [0031]     As for the recording operation carried out to form an image on the sheet P by the recording apparatus structured as described above, first, the sheet P is conveyed to the position at which the recording head  7  aligns with the recording line, in terms of the sheet conveyance direction, at which recording is to be started on the sheet P, and then, the carriage  50  is moved in the primary scan direction to the point of this recording line, at which recording is to be started. Then, the actual recording of an image is started from this point by moving the carriage  50  in the primary scan direction while causing the recording head  7  to eject ink by driving the recording head  7  by the image formation signals from an electrical circuit  9 .  
         [0000]     [Sheet Discharging Portion] 
         [0032]     The sheet discharging portion  4  is made up of: a pair of sheet discharge rollers  40  and  41 ; rowel-like wheels  42  which are placed in contact with the sheet discharge rollers  40  and  41  in a manner to maintain a predetermined amount of contact pressure against the sheet discharge rollers  40  and  41 , and which are rotated by the rotation of the sheet discharge rollers  40  and  41 ; a gear train for transmitting the driving force from the conveyance roller  36  to the sheet discharge rollers  40  and  41 ; etc. The sheet discharge rollers  40  and  41  are attached to the platen  34 . The sheet discharge roller  40 , which is the downstream sheet discharge roller in terms of the sheet conveyance direction, is made up of a metallic shaft, and multiple rubbery members  401  firmly fitted around the metallic shaft. The two sheet discharge rollers  40  and  41  are driven by the driving force transmitted from the conveyance roller  36  to the sheet discharge roller  40  through an idler gear. The sheet discharge roller  41 , which is the upstream sheet discharge roller in terms of the sheet conveyance direction, is made up of a shaft formed of a resin, and multiple elastic members  411  formed of an elastomer and fitted around the shaft of resin. The force for driving the sheet discharge roller  41  is transmitted from the sheet discharge roller  40  through an idler gear.  
         [0033]     Each of the rowel-like wheels  42  is an integral combination of a piece of SUS plate shaped like a rowel, and a resinous portion molded around the SUS piece. The rowel-like wheels  42  are attached to a holder  43 . More specifically, the rowel-like wheels  42  are attached to the holder  43  with the use of a coil spring wound in the form of a rod, which also functions to keep the rowel-like wheels  42  pressed on the sheet discharge rollers  40  and  41 . There are two types of rowel-like wheels  42 : those which are positioned so that they are pressed upon the rubbery members  401  of the sheet discharge roller  40 , and the elastic members  411  of the sheet discharge roller  41 , one for one, essentially to generate the force for conveying the sheet P, and those which are positioned so that they face the intervals of the rubbery members  401  of the sheet discharge roller  40 , and the intervals of the elastic members  411  of the sheet discharge roller  41 , one for one, essentially to prevent the sheet P from floating.  
         [0034]     Between the sheet discharge rollers  40  and  41 , a sheet edge supporting portion is disposed, which keeps the lateral edge portions of the sheet P slightly raised in order to prevent the recorded image on the preceding sheet P from being damaged by being rubbed by the following sheet P. More specifically, the sheet edge supporting member is made up of members formed of resin, rollers attached to the end of the member formed of resin, sheet edge supporting springs disposed in a manner to apply a predetermined amount of upward pressure to the members form of resin, etc. Thus, while the sheet P is moved past the sheet edge supporting portion, the lateral edge portions of the sheet P is slightly raised by the predetermined amount of pressure applied thereto by the rollers. As a result, while the sheet P is moved past the sheet edge supporting portion, it is prevented from sagging, being therefore prevented from rubbing the preceding sheet P, while being conveyed by the sheet discharge rollers  40  and  41 .  
         [0035]     After the formation of an image on the sheet P in the main assembly of the recording apparatus structured as described above, the sheet P is further conveyed by being pinched by the sheet discharge roller  41  and the corresponding rowel-like wheels  42 , and then, is discharged into a sheet delivery tray  46 . The sheet delivery tray  46  is structured so that it can be retracted into the front cover  95  of the recording apparatus; it is to be pulled out when it is needed. In order to improve the sheet delivery tray  46  in terms of the facilitation of the accumulation of the sheets P in the sheet delivery tray  46 , and to prevent the surface of the sheet P, on which an image has just been formed, from being rubbed by the sheet P immediately above or immediately below, the sheet delivery tray  46  is structured so that when it is in the open position, it inclines upward from its base portion toward its edge. Also, for the same purpose, the sheet delivery tray  46  is provided with a pair of projections (ribs), which are located at the farthest ends of the lateral edges of the sheet delivery tray  46 , one for one.  
         [0000]     [Two-Sided Printing Sheet Conveyance Route, and U-Turn Sheet Feeding Portion] 
         [0036]     The two-sided printing sheet conveyance route for recording on the reverse side of the sheet P includes the U-turn portion of the sheet conveyance path, into which the sheet P can be fed from the U-turn sheet feeding portion  8 . Next, the two-sided printing sheet conveyance route, and the U-turn sheet feeding portion  8  will be described. The sheets P are stored in a cassette  81 , which is in the front portion of the recording apparatus main assembly. The cassette  81  is provided with a pressure plate  322 , on which the sheets P are placed in layers, and which is for pressing the sheets P against a feed roller  821  to feed the sheets P into the apparatus main assembly while separating them one by one. To a U-turn base  84 , which constitutes the main portion of the two-sided printing sheet conveyance route and the main portion of the U-turn sheet feeding portion  8 , the feed roller  821  for feeding the sheets P into the apparatus main assembly, a separation roller  831  for separating the sheets P, a sheet returning lever  824  for returning the sheets P to their standby positions in the cassette  81 , a controlling means for controlling the operation for pressing the pressure plate  822  against the feed roller  821  or moving it away from the feed roller  821 , etc., are attached. The cassette  81  is structured so that it can be extended or shrunk to accommodate two types of sheet different in size. That is, when using the sheets P of the smaller size, or not using the cassette  31  at all, the cassette  31  can be shortened and fitted entirely within the external shell  9 .  
         [0037]     The feed roller  821  is in the form of a rod and is roughly D-shaped in cross section. It is fitted with a feed roller rubber, which is positioned close to the sheet alignment reference portion. This feed roller rubber is the actual portion that feeds the sheets P into the apparatus main assembly. The force for driving the feed roller  821  is transmitted to the feed roller  821  from a motor located along the two-sided printing sheet conveyance route, that is, a part of the sheet feeding route from the U-turn sheet feeding portion  8 , through a driving force transmission gear, a planetary gear, etc. The pressure plate  822  is provided with a movable side guide  827 , which is movably attached to the pressure plate  822  and correctly positions the sheets P. The pressure plate  822  is pivotable about a rotational axle by which the pressure plate  822  is attached to the cassette  81 . The pressure plate  822  is pressed against the feed roller  821  by a controlling means for pressing the pressure plate  822  against the feed roller  821  or moving it away from the feed roller  821 . This controlling means is made up of pressure plate springs  828  or the like disposed between the U-turn base  84  and the pressure plate  822 . In order to prevent the sheets P other than the topmost sheet P from being fed along with the topmost sheet P, the portion of the surface of the pressure plate  81 , which directly faces the feed roller  821 , is provided with a separation sheet formed of such material as artificial leather which is substantial in co-efficient of friction. The pressure plate  822  is structured so that it can be placed in contact with, or separated from, the feed roller  821  by a pressure plate cam.  
         [0038]     Further, the U-turn base  84  is provided with a separation roller  831  for separating the sheets P one by one. This separation roller  831  is rotatably attached to a separation roller holder with the use of an axle, and the separation roller holder is pivotable about the axes with which the separation base is provided. This separation roller holder is kept pressured toward the feed roller  821  by separation roller springs. The separation roller  831  is provided with a spring clutch structured so that the separation roller  831  is allowed to rotate only when the amount of the load to which the separation roller  831  is subjected is greater than a predetermined value. The separation roller  831  is placed in contact with, or separated from, the feed roller  821  by the combination of a separation roller release shaft and a control cam. The positions of the pressure plate  822 , sheet returning lever  824 , and separation roller  831  are detected by U-turn sensors.  
         [0039]     The sheet returning lever  824  (which hereinafter will be referred to simply as return lever) is attached to the U-turn base  84 , and is kept pressured in the direction to be released. In order to return the sheets P, the return lever  824  is pivoted by a control cam. When the recording apparatus is kept on the normal standby, the pressure plate  822  has been released by the pressure plate cam, the separation roller  831  has been released by the control cam, and the return lever  824  has returned the sheets P to their standby positions in the cassette  81 . The return lever  824  is disposed so that it blocks the outlet of the cassette  81  to prevent the sheets P in the cassette  81  from shifting. As the recording apparatus on standby is activated for image formation, the feeding of the sheets P begins. First, the separation roller  831  is placed in contact with the feed roller  821  by the driving force from the motor. Then, the return lever  824  is released, and the pressure plate  822  is made to pivot toward the feed roller  821  to place the topmost sheet P in contact with the feed roller  821 . The actual feeding of the sheets P is started when the recording apparatus is in this state.  
         [0040]     The movement of the sheets P is regulated by a preliminary regulating means  838  with which the separation base  83  is provided, so that only a few of the sheets P at the top are sent to the nip between the feed roller  821  and separation roller  831 . After being sent to the nip, the sheets P are separated in the nip, so that only the topmost sheet P is fed (conveyed) into the apparatus main assembly. Then, as soon as the single sheet P, or the topmost sheet P, which has been separated from the rest of the sheets P in the cassette  81  and has been fed into the main assembly, reaches the gap between a first U-turn roller  86  and a first U-turn pinch roller  861 , the pressure plate  822  is released by the pressure plate cam, and the separation roller  831  is released by the control cam. As for the return lever  824 , it is allowed to return by the control cam to the position in which the return level was when the sheets P were placed in layers in the cassette  81 . As the return lever  824  is returned, the few of the sheets P, except for the topmost one, which had reached the nip between the feed roller  821  and separation roller  831 , are returned to their standby positions in the cassette  81 .  
         [0041]     On the downstream side of the U-turn sheet feeding portion  8 , two pairs of sheet conveyance rollers, that is, the combination of the first U-turn roller  86  and first U-turn pinch roller  861  and the combination of a second U-turn roller  87  and a second U-turn pinch roller  871 , are disposed. These U-turn rollers  86  and  87  are made up of a metallic shaft (core), and four to six narrow elastic rollers fitted around the metallic shaft with the provision of predetermined intervals among them. These narrow elastic rollers are formed of EPDM, the hardness of which is in the range of 40 to 80 degrees. The pinch rollers  861  and  871  for pressing the sheet P on the U-turn rollers  86  and  87 , respectively, are disposed so that their positions correspond to those of the abovementioned narrow elastic rollers of the U-turn rollers  86  and  87 , one for one. The pinch rollers  861  and  871  are kept pressed upon the U-turn rollers  86  and  87  (intermediate rollers), respectively, by being fitted around a spring-loaded shaft. The U-turn sheet conveyance portion  8  is provided with an inner guide  881  and an outer guide  882 , which provide the inward and outward surfaces of the U-turn portion of the U-turn sheet feeding portion (U-turn portion of two-sided printing sheet conveyance route).  
         [0042]     The portion of the sheet conveyance path, at which the sheet conveyance route from the sheet feeding portion  2  (ASF) and the sheet conveyance route from the U-turn sheet feeding portion  8  merge, is provided with a flapper  883  for switching the sheet conveyance route, so that the sheet P can be smoothly moved into the selected route of the sheet conveyance path. More specifically, as the sheet P, which has just been fed from the sheet feeding portion  2  or the U-turn sheet feeding portion  8 , reaches the conveyance roller  36 , first, the leading end of the sheet P comes into contact with the nip between the conveyance roller  36  and pinch rollers  37 , which have been kept stationary. As a result, not only is the sheet P corrected in attitude if it was askew, but also, it is registered. Then, the sheet P is conveyed by the conveyance roller  36 . Then, as it is conveyed through the nip between the conveyance roller  36  and pinch rollers  37 , recording is made on the sheet P by the recording head  7 .  
         [0043]     When it is necessary to record on the reverse side of the recorded sheet P, the recorded sheet P is conveyed backward so that it will be re-fed into the apparatus main assembly, starting from the edge of the recorded sheet P, which was the trailing edge while recording was made on the front side of the sheet P, through the gap between the conveyance roller  36  and pinch rollers  37 . This conveyance of the sheet P in the backward direction is effected by the reversal rotation of the sheet discharge rollers  40  and  41 . During this conveyance of the sheet P in the backward direction, the pinch rollers  37  have been raised, being therefore kept separated from the conveyance roller  36 , by a mechanism  884  for raising or lowering the pinch rollers  37 . In other words, the sheet P is conveyed back into the main assembly through the gap between the pinch rollers  37  and conveyance roller  36 , and therefore, it is smoothly conveyed. Then, the sheet P is guided into the two-sided printing sheet conveyance route by a sheet conveyance route switching flapper  833 . After being guided into the two-side printing sheet conveyance route, the sheet P is pinched by the combination of the two-sided printing sheet conveyance route roller  891  and two-sided printing sheet conveyance route pinch roller  892 , being thereby conveyed further along the two-sided printing sheet conveyance route.  
         [0044]     As the sheet P is further conveyed past the conveyance rollers  891  and  892  through the two-sided printing sheet conveyance route, it is guided by a guiding member  821  (flapper), etc., set in the position in which it blocks the outlet of the cassette  81 , through which the sheets P in the cassette  81  is sent into the U-turn portion of the sheet conveyance route, through which the sheet P are fed from the U-turn sheet feeding portion  8 , that is, the U-turn portion of the two-sided printing sheet conveyance route, and also, in which it provides a predetermined amount of gap between itself and the feed roller  821  to allow the sheet P to enter the U-turn portion of the two-sided printing sheet conveyance route. As the sheet P is conveyed by a predetermined distance through the two-sided printing sheet conveyance route for recording an image on the reverse side of the sheet P, it reaches the abovementioned U-turn rollers  86  and  87 . In other words, the upstream portion of the two-sided printing sheet conveyance route, in terms of the sheet conveyance direction, merges with the U-turn portion of the aforementioned U-turn sheet feeding route. Thus, once the recorded sheet P reaches the U-turn rollers  86  and  87 , the conveyance of the recorded sheet P thereafter is the same in structural arrangement and operation as the conveyance of the sheet P after the arrival of the sheet P at the U-turn rollers  86  and  87  (intermediate rollers) when the sheet P is fed from the U-turn sheet feeding portion  8 .  
         [0000]     [Recovery Mechanism Portion] 
         [0045]     The recovery mechanism portion  6  with which the ink jet recording apparatus in this embodiment is provided is provided with a pump  60  for suctioning out ink or the like from the ejection orifices of the recording head  7 , a cap  61  for preventing the ink and the like from drying up in the adjacencies of the openings of the ejection orifices of the recording head  7 , a wiper for wiping clean the adjacencies of the openings of the ejection orifices of the recording head  7 , etc. In this embodiment, the primary force for driving the recovery mechanism portion  6  is transmitted from the previously mentioned AP motor  273  as the mechanical power source for driving the sheet feeding portion  2 . More specifically, the recovery mechanism portion  6  is provided with a one-way clutch so that the rotation of the AP motor in one direction drives the pump  60 , whereas the rotation of the AP motor in the other direction causes the wiper  62  to wipe, and also, the cap  61  to cover the ejection orifices or separate therefrom.  
         [0046]     As for the type of the pump  60 , a so-called tube pump can be used. A tube pump is made up of a pair of tubes  67  and pumping rollers, and is structured so that negative pressure is generated as the pair of tubes  67  are stroked by the pumping rollers. The cap  61  and pump  60  are connected with the interposition of a valve. Such ink that has adhered to the adjacencies of the openings of the ejection orifices, and the waste ink, that is, the portion of the body of the ink in each of the ejection orifices, which contains air bubbles or the like, can be suctioned away, along with a certain amount of the good ink in each of the ejection orifices, by activating the pump  60  with the cap  61  being placed airtightly in contact with the recording head  7  (with recording head capped). The cap  61  is provided with an absorbent member  611 , which is fitted inside the cap  61  to rid the surface of the recording head  7  having the openings of the ejection orifices, of the ink remaining thereon after the suction. Further, in order to prevent the problem that ink remains in the absorbent member  611  of the cap  61  and solidifies therein, the pump  60  is activated with the cap separated from the recording head  7  to suction away the ink remaining in the cap  61 . The waste ink, that is, the ink having been suctioned away by the pump  60  is absorbed into a waste ink absorbing member located in the bottom case  99 , and retained therein.  
         [0047]     The operational sequence which comprises the operation for moving the wiper  62 , the operation for capping or uncapping the recording head  7 , etc., is controlled by a main cam, which is an integral combination of multiple cams. In other words, as the specific portions of the main cam act on the corresponding cams or arms, various operations are carried out with predetermined timing. The position of each of the specific portions of the main cam can be detected by position sensors such as a photo-interrupter. The surface of the recording head  7 , which has the openings of the ejection orifices, is wiped by the wiper  62  by placing the wiper  62  in contact with the surface while the cap  61  is away from the surface. In this embodiment, the recovery mechanism portion  6  is provided with two wipers  62 : the one which wipes the adjacencies of the openings of the ejection orifices and the other which wipes the entirety of the surface having the openings of the ejection orifices, inclusive of the adjacencies of the openings of the ejection orifices. The ink and the like contaminants having adhered to each wiper  62  are removed (wipers are cleaned) by a wiper cleaner  66 , with which the wipers  62  comes into contact as they reach the rearmost ends of their wiping ranges.  
         [0048]     The transmission and control of the driving force to the valve between the cap  61  and pump  60  to open or close the valve is carried out by the sheet discharge roller  40 . The recovery mechanism portion  6  is structured to make it possible to selectively open or close one or more of the valves so that all the inks, which are different in color, can be suctioned at the same time, or each ink can be selectively and independently suctioned, as necessary. The position of each valve is detected by a valve position sensor.  
         [0000]     [External Shell] 
         [0049]     The above described various portions and mechanisms are attached to the central member  11  of the chassis, and constitute the mechanical portion of the recording apparatus. The external shell  9  is attached to the central member  11  of the chassis in a manner of wrapping this mechanical portion. The external shell  9  comprises a bottom case  99 , a top case  98 , an accessory cover  97 , a connector cover  96 , a front cover  95 , and a pair of side covers  93 . To the front cover  95 , the sheet delivery tray  46  is retractably attached so that when the tray  46  is not required, it can be retracted into the front cover  95  to cover the opening of the sheet outlet. Whether the front cover  95  is open or closed can be detected by an unshown sensor. To the top case  98 , an access cover  97  is pivotably attached. A part of the top case  98  is provided with an opening, through which the recording head  7  and ink containers  71  can be replaced.  
         [0050]     Also to the top case  98 , a door switch lever for detecting the opening and closing of the access cover  97 , an LED guide for transmitting and displaying the light from an LED, and key switches which act on the SWs of the control circuit, are attached. Further, to the top case  98 , the sheet feeder tray  26  is attached, which is pivotable, and also, can be extended or shortened. When the usage of the sheet feeder tray  26  is not required, the sheet feeder tray  26  can be shortened and pivoted into the top case  98  to cover the sheet feeding portion. The top and bottom cases  98  and  99  are attached to each other with the use of elastic clips. The top and bottom cases  98  and  99  are shaped so that as they are attached to each other, they leave a hole, between their predetermined portions, for electrical connectors. This hole is covered with a connector cover  96 . The side covers  93  are attached in a manner of covering the lateral portions of the top and bottom cases  98  and  99  from the left- and right-hand sides of the recording apparatus.  
         [0051]     Next, a multiple choice sheet feeding unit  10 , which characterizes this embodiment of the present invention, will be described. The multiple choice sheet feeding unit  10  is an integral combination of the sheet feeding portions  2  and U-turn sheet feeding portion  8 . As described above, to the ASF base  20  of the sheet feeding portion  2 , the components for feeding the sheets P of recording medium, while separating them one by one as the sheets P are fed into the recording apparatus main assembly from the ASF, are attached, and to the U-turn base  84  of the U-turn sheet feeding portion  8 , the components for feeding the sheets P of recording medium, while separating them one by one when the sheets P are fed into the main assembly from the U-turn sheet feeding portion  8 , are attached. In other words, in this embodiment, the recording apparatus is provided with the U-turn sheet feeding portion  8  in addition to the sheet feeding portion  2 , and is structured so that the sheets P of recording medium can be delivered to the recording portion of the sheet conveyance path from either of the two recording medium storage portions (pressure plates  21  and  822 ) through different routes. In other words, the recording apparatus is provided with multiple (two) sheet conveyance routes which lead to the common sheet conveyance portion.  
         [0052]     The bases  20  and  84 , to which the above described components have been attached, are fixed to the central member  11  of the chassis in a manner of sandwiching the bases  20  and  84  with the right- and left-hand members  112  and  113  of the chassis of the recording apparatus, making up the multiple choice sheet feeding unit  10 . The right- and left-hand members  112  and  113  of the chassis are very rigid members formed of metallic plate or the like material. The right- and left-hand members  112  and  113  of the chassis may be simply called lateral chassis members.  
         [0053]     Also to the central member  11  of the chassis of the recording apparatus, the sheet conveyance unit comprising the conveyance roller  36 , pinch rollers  37 , and platen  34 , and the recording unit comprising the carriage  50  and recording head  7 , are firmly and integrally attached, making up the recording unit (conveying-recording unit), as described above.  
         [0054]     To sum up, the recording apparatus in this embodiment of the present invention is provided with: the multiple (two) sheet feeding routes through which sheets P of recording medium are fed from the recording medium storage portions  21  and  822 , respectively, into the main assembly of the recording apparatus, and conveyed further to the recording portion; carriage  50  on which the recording head  7  is mounted, and which is reciprocally movable in the recording portion, while holding the recording head  7 ; platen  34  which corresponds in position to the moving range of the carriage  50  and supports recording medium; and sheet conveyance roller  36  disposed on the upstream side of the carriage  50  in terms of the sheet conveyance direction to convey recording medium. It also is provided with: the recording unit comprising the carriage, conveyance roller, and platen, which are firmly attached to the central member  11  of the chassis; and multiple choice sheet feeding unit  10  comprising the various components which provide the recording apparatus with the multiple (two) sheet conveyance routes extending from the multiple (two) sheet feeding portions to the conveyance roller  36 , and are supported by the lateral members  112  and  113  of the chassis from the right- and left-hand sides, respectively, of the recording medium in the apparatus. The recording unit and multiple choice sheet feeding unit  10  are integrated by being fastened to the central member  11  of the chassis of the recording apparatus. The lateral members  112  and  113  of the chassis are fastened to the central member  11  of the chassis, making up the rear portion of the chassis of the recording apparatus. The abovementioned sheet conveyance path comprises the multiple (two) sheet conveyance routes: one that leads from the recording medium storage portion  21  of the sheet feeding portion  2  to the abovementioned sheet conveyance unit, and the other that leads from the recording medium storage portion  822  of the U-turn sheet feeding portion  8  to the abovementioned sheet conveyance unit.  
         [0055]      FIG. 6  is a perspective view of the chassis of the recording apparatus in accordance with the present invention, as seen from the right front side, showing the general structure thereof.  FIG. 7  is a perspective view of the chassis of the recording apparatus in accordance with the present invention, as seen from the right rear side, showing the general structure thereof.  FIG. 8  is an exploded perspective view of one of the joint portions, and its adjacencies, of the chassis of the recording apparatus in accordance with the present invention, between the central member  11  and one of the lateral members, showing the structures thereof.  
         [0056]     Referring to  FIGS. 6-8 , the multiple choice sheet feeding unit  10  comprising the various components which provide the recording apparatus with the multiple (two) sheet conveyance routes extending from the multiple (two) recording medium storage portions  21  and  822  to the conveyance roller  36 , respectively, and are supported by the lateral members  112  and  113  of the chassis from the right- and left-hand sides of the recording apparatus, and the recording unit comprising the carriage  50 , conveyance roller  36 , and platen  34 , which are fastened to the central member  11  of the chassis by fastening the lateral members  112  and  113  of the chassis to the central member  11  of the chassis.  
         [0057]     The right- and left-hand members  112  and  113  of the chassis are fastened to the rear side of the wall-like flat portion  11   a  of the central member  11  of the chassis, which extends from one lateral side of the recording apparatus to the other. Next, referring to  FIG. 7 , the right-hand member  112  of the chassis is fastened to the central member  11  of the chassis by the two portions, that is, the top and bottom portions  112 A and  112 B, and also, the left-hand member  113  of the chassis is fastened to the central member  11  of the chassis by two portions, that is, the top and bottom portions  113 A and  113 B. These portions  112 A,  112 B,  113 A, and  113 B by which the right- and left-hand members  112  and  113  of the chassis are fastened to the central member  11  of the chassis are virtually identical in structure. Therefore, the method for fastening the lateral members  112  and  113  of the chassis to the central member  11  of the chassis, that is, the method for assembling the multiple choice sheet feeding unit  10 , will be described with reference to  FIG. 8 , which shows the method for fastening the top portion  112 A of the right-hand member  112  of the chassis to the central member  11  of the chassis.  
         [0058]     Referring to  FIG. 8 , first, the projection  112   c  which projects from the edge of the main portion of the right-hand member  112  of the chassis, which will be in contact with the central member  11  of the chassis after the assembly, is fitted into the corresponding hole (one of the holes (openings)) of the central member  11  of the chassis. As a result, the right-hand member  112  of the chassis is precisely positioned relative to the central member  11  of the chassis in terms of the vertical direction (indicated by arrow mark Z in  FIG. 8 ) as well as the side to side direction (indicated by arrow mark Y in  FIG. 8 ).  
         [0059]     Further, two projections  112   a  and  112   b  which project from the top and bottom rear corners of the main portion of the right-hand member  112  of the chassis, are placed in contact with the rear side of the flat portion  11   a  of the central member  11  of the chassis. As a result, the right-hand member  112  is precisely positioned relative to the central member  11  of the chassis in terms of the front to back direction (indicated by arrow mark Y in  FIG. 8 ). The right-hand member  112  is also provided with an anchoring portion  112   d,  which will be placed in parallel to the flat portion  11   a  of the central member  11  of the chassis with the presence of a minuscule gap between the anchoring portion  112   d  and flat portion  11   a  as the right-hand member  112  is precisely positioned relative to the central member  11  of the chassis as described above. Thus, with the right-hand member  112  precisely positioned relative to the central member  11  of the chassis, the anchoring portion  112   d  is fastened to the flat portion  11   a  of the central member  11  of the chassis with a small screw  121 . As a result, the right-hand member  112  is firmly attached to the central member  11  of the chassis and remains precisely positioned relative to the central member  11  of the chassis.  
         [0060]     Also, the bottom projection  112 B of the right-hand member  112  of the chassis, the structure of which is similar to that shown in  FIG. 8 , is precisely positioned relative to the central member  11  of the chassis and fastened to the rear side of the flat portion  11   a  of the central member  11  of the chassis. In other words, the right-hand member  112  is fastened to the rear side of the flat portion  11   a  of the central member  11  of the chassis by the anchoring portions  112   d  of the top and bottom projections  112 A and  112 B, while remaining precisely positioned relative to the central member  11  of the chassis. Further, the left-hand member  113  of the chassis is also fastened to the rear side of the flat portion  11   a  of the central member  11  of the chassis by the top and bottom projections  113 A and  113 B, while remaining precisely positioned relative to the central member  11  of the chassis. With the employment of the above described structural arrangement for attaching the lateral members  112  and  113  of the chassis to the central member  11  of the chassis, it is easy to correctly position the lateral members  112  and  113  relative to the central member  11  and securely attach them to the central member  11 . Further, to the outward surface of the chassis (right-hand member  112  shown in drawings) formed of metallic plate or the like, a main circuit board  91  having the control circuit of the recording apparatus is attached. This structural arrangement for attaching the main circuit board  91  is superior in terms of protecting the main circuit board  91  from noises, radiating heat from the main circuit board  91 , etc. Further, it makes it possible to utilize the roughly rectangular flat portion of the chassis, as the portion to which the roughly flat circuit board  91  (main circuit board) is mounted virtually flush therewith. In other words, it makes it possible to more effectively use the internal space of the main assembly of the recording apparatus in order to reduce the main assembly in size.  
         [0061]     Also in this embodiment, the AP motor  273  shared by the sheet feeding portion  2  and recovery mechanism portion  6  is attached to the right-hand member  112  of the chassis, and the two-sided printing sheet conveyance motor  85  ( FIG. 3 ) used for conveying the sheet P through the two-sided printing sheet conveyance route, and also, feeding the sheet P from the U-turn sheet feeding portion, is attached to the left lateral member  113  of the chassis. With the employment of this structural arrangement, the motors  273  and  85  are very reliably fastened to the chassis of the recording apparatus while being accurately positioned relative to the chassis. Therefore, the amounts by which the driving forces from the motors  273  and  85  are lost while they transmitted to the sheet conveying/recording unit are substantially smaller, compared to the corresponding structural arrangement in accordance with the prior art. Incidentally, it is desired that the surfaces of the right and left lateral members  112  and  113  of the chassis are utilized not only as the portion to which the main circuit board  91  is attached, but also, as the portion to which motors as driving power sources, sensors for controlling the recording apparatus, etc., are attached. With such utilizations, the recording apparatus can be improved in terms of shielding the electrical components from noises, radiating heat from the electrical components, etc.  
         [0062]     Further, the central member  11  of the chassis is provided with a pair of perpendicularly angled portions  11 A and  11 B, to which the components for mounting the conveyance roller  36 , etc., are to be attached. In this embodiment, a member  114  of the chassis, to which the platen  34  is attached, and a front member  115  of the chassis, are fastened to these angled portions  11 A and  11 B by their respective lengthwise ends, with small screws or the like, as shown in  FIG. 6 , functioning as the staying members of the chassis. In other words, the right- and left-hand end portions, that is, the perpendicularly angled portions  11 A and  11 B, are connected with the member  114  of the chassis, to which the platen  34  is attached, and front member  115  of the chassis. More specifically, a structural arrangement that the lateral sections of the central member  11  of the chassis, which are for supporting the conveyance roller  36 , are connected with the pair of staying members positioned on the upstream and downstream sides, one for one, of the platen  34 , in terms of the sheet conveyance direction, is employed. To sum up, the chassis of the recording apparatus in this embodiment is made up of the central member  11 , right- and left-hand lateral members  112  and  113 , the platen supporting member  114 , and front member  115 .  
         [0063]     The addition of the platen supporting member  114  and front member  115  gives the chassis of the recording apparatus a boxy shape; in a sense, it turns the chassis of the recording apparatus into the so-called box chassis, improving the chassis in rigidity. Thus, the fastening of the multiple choice sheet feeding unit  10  to this chassis, which is substantially more rigid than any of the chasses in accordance with the prior art, makes it possible to reduce the recording apparatus in the vibrations, noises, etc., making it thereby possible to eliminate the problem that images cannot be printed at a high level of accuracy because of the vibrations attributable to the lack of rigidity in the recording apparatus chassis. Also in this embodiment, the components, more specifically, the base  20  and U-turn base  84  shown in  FIG. 5 , which provide the sheet conveyance path of the recording apparatus, with the multiple sheet conveyance routes (ASF route and two-sided printing route), are molded in a single piece, or some of these components, which are shared by the multiple sheet conveyance routes, are molded in a single piece. Further, the various components which make up the multiple choice sheet feeding unit  10  are attached to these bases  20  and  84 . Therefore, not only can the employment of the structural arrangement employed in this embodiment reduce a recording apparatus in size, but also, improve the recording apparatus in assembly efficiency and shock resistance.  
         [0064]     Further, according to the above described structural arrangement, the base  20  of the sheet feeding portion  2  and the base  84  of the U-turn sheet feeding portion  8  are highly precisely and reliably fastened to the chassis of the recording apparatus with the use of the right- and left-hand members  112  and  113  of the chassis. Therefore, the sheet conveyance route starting from the ASF, which is primarily provided by the base  20 , and the sheet conveyance route starting from the U-turn sheet feeding portion  8 , which is primarily provided by the base  84 , are superior in the positioning of the components thereof and the level of accuracy at which recording medium is conveyed. Further, the bases  20  and  84 , which are structural components, are not deformed (twisted), or are less likely to be deformed, improving thereby the recording apparatus in terms of the reliability with which recording medium is fed and conveyed. Further, the multiple choice sheet feeding unit  10  is fastened to the member  11  of the chassis, that is, the chassis member to which the recording portion is attached, as described above. Therefore, the member  11  and lateral members  112  and  113  of the chassis give the chassis a boxy shape, and also, it is ensured that the multiple choice sheet feeding portion  10  is positioned relative to the conveyance-recording unit at a higher level of accuracy. Therefore, recording medium is corrected in attitude at a higher level of accuracy.  
         [0065]     As will be evident from the description of this embodiment given above, the structural arrangement in this embodiment makes it easier to reduce a recording apparatus in size, and also, improve a recording apparatus in assemblage efficiency, shock resistance, reliability, and sheet conveyance performance. The present invention is particularly effective when it is applied to a recording apparatus having multiple recording medium conveyance routes, inclusive of the U-turn sheet conveyance route or the like.  
         [0066]     Incidentally, this embodiment of the present invention was described with reference to a case in which the recording apparatus is an ink jet recording apparatus. However, not only is the present invention applicable to an ink jet recording apparatus, but also, recording apparatuses employing a recording method other than the ink jet recording method: for example, recording apparatuses employing one of the wire-dot method, thermal method, laser beam method, etc. Further, not only is the present invention applicable to a monochromatic recording apparatus, but also, a color recording apparatus which employs a single or multiple recording heads to record color images using multiple inks different in color, a gradation recording apparatus which employs a single or multiple recording heads to record images using multiple inks which are the same in color but different in density, and a recording apparatus which is a combination of one or more of the preceding recording apparatuses.  
         [0067]     According to the above described structural arrangement, it is easy to reduce in size a recording apparatus having a sheet feeding portion for feeding recording medium inward of its main assembly from its recording medium storage portion, and also, improve a recording apparatus in assemblage efficiency, shock resistance, an reliability in sheet conveyance performance. The above described structural arrangement is particularly effective when applied to a recording apparatus having multiple recording medium conveyance routes inclusive of the U-turn portion.  
         [0068]     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.  
         [0069]     This application claims priority from Japanese Patent Application No. 223052/2004 filed Jul. 30, 2004 which is hereby incorporated by reference.