Patent Publication Number: US-8123210-B1

Title: Paper feeding assembly for printers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Reference is made to commonly assigned, co-pending U.S. patent application Ser. No. 12/913,081, filed Oct. 27, 2010, entitled: “Recording Media Path in a Multifunction Printer”, co-pending U.S. patent application Ser. No. 12/913,100, filed Oct. 27, 2010, entitled: “Inclined Motor in an Inkjet Printer”, and co-pending U.S. patent application Ser. No. 12/913,115, filed Oct. 27, 2011, entitled: “Method of Assembling a Multifunction Printer” the disclosures of which are incorporated herein. 
     FIELD OF THE INVENTION 
     This invention pertains generally to paper feeding in a printer and more particularly to the transmission of rotational motion from a first roller assembly to a second roller assembly. 
     BACKGROUND OF THE INVENTION 
     Many printers, including many inkjet printers, use a carriage-based architecture, which has advantages in size, performance, and cost. In the inkjet carriage printer, a printhead is mounted in a carriage that is moved back and forth across the region of printing. To print an image on a sheet of paper or other recording medium (sometimes generically referred to as paper herein), the recording medium is advanced a given distance along a recording medium advance direction and then momentarily stopped. While the recording medium is stopped and supported on a platen, the printhead carriage is moved along a carriage scan direction. The carriage scan direction extends substantially perpendicular to the recording medium advance direction. In the course of printhead travel along the carriage scan direction, controllable marking elements in the printhead record marks on the recording medium—for example by ejecting drops from an inkjet printhead. After the carriage has printed a swath of the image while traversing the recording medium, the recording medium is advanced incrementally, the carriage direction of motion is reversed, and marking is repeated with printhead movement in the reverse direction. By repeating this process a number of times, the printer forms the image onto the recording medium, swath by swath. 
     By way of example,  FIG. 1  shows a portion of a prior art carriage printer  300 , with some parts hidden so that other parts can be more clearly seen. Printer  300  has a printing region  303  across which a carriage  200  is moved back and forth along a carriage scan direction  305  that extends along the X axis between the right side  306  and the left side  307  of printer  300  while printing on recording medium that is supported by the platen that provides printing region  303 . Carriage motor  380  moves a belt  384  attached to carriage  200  in order to move carriage  200  back and forth along carriage guide rail  382 . In this way, carriage  200  is actuable to move along a carriage scan direction  305 . Printhead  250  is mounted in carriage  200 , and ink supplies  262  and  264  are mounted in the printhead  250 . In this orientation of printhead  250 , the droplets of ink are ejected downward onto the recording media in printing region  303  in the view of  FIG. 1 , Ink supply  262 , in this example, contains five ink sources cyan, magenta, yellow, photo black, and colorless protective fluid, while ink supply  264  contains the ink source for text black. 
     Toward the left side  307  in the example of  FIG. 1  is a maintenance station  330 . Toward the rear  309  of the printer in this example is located an electronics board  390 , which contains cable connectors  392  for communicating via cables (not shown) to the printhead carriage  200  and from there to the printhead. Also on the electronics board are typically mounted motor controllers for the carriage motor  380  and for the paper advance motor, a processor and/or other control electronics for controlling the printing process, and an optional connector for a cable to a host computer. 
     Paper, or other recording medium is loaded along paper load entry direction  302  toward the front  308  of printer  300 . Printed paper traveling from the rear  309  exits along direction  304 . In this example, both the paper load entry direction  302  and the paper exit direction  304  are parallel to the Y axis. A feed roller  312  includes a feed roller shaft along its axis, and a feed roller gear  311  is mounted on the feed roller shaft. The motor that powers the paper advance rollers is not shown in  FIG. 1 , but a hole  310  in the framework at the right side  306  of the printer  300  is where the motor-gear (not shown) protrudes through in order to engage feed roller gear  311 , as well as the gear for the discharge roller (not shown). Bolt holes for attaching this paper advance motor are shown on both sides of hole  310 . For normal paper pick-up and feeding, all rollers rotate in forward direction  313 . The motor that powers the paper advance rollers provides power directly to the teed roller and the discharge roller, but also provides power indirectly to a pick-up roller and a turn roller (not shown in  FIG. 1 ) that respectively pick up a sheet of recording medium from the paper load entry region, and turn the direction of paper from entry direction  302  to exit direction  304 . In conventional printers, power is transmitted from the feed roller  312  to respective gear trains to power the pick-up roller and the turn roller. Such gear trains work well, but a gear train having many gears tends to add to both the expense and the noise of the printing apparatus. 
     What is needed is a paper feeding apparatus that transmits power from the feed roller to another roller assembly in the printer in a quieter way and for less expense than is associated with the conventional gear train. 
     SUMMARY OF THE INVENTION 
     A paper feeding apparatus for a printer comprises a motor; a first roller assembly including: a) a first roller having a first end, a second end and an axis; b) a first gear disposed at the first end of the first roller, wherein the first gear is configured to be driven by the motor; and c) a second gear disposed at the second end of the first roller, wherein the second gear comprises a first bevel gear; a drive shaft including a first end, a second end and an axis, wherein the first end of the drive shaft comprises a second bevel gear that is configured to engage with the first bevel gear of the second gear of the first roller assembly, and wherein the second end of the drive shaft comprises a third bevel gear; and a second roller assembly including a second roller and a fourth bevel gear that is configured to engage with the third bevel gear at the second end of the drive shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing components of a prior art carriage printer; 
         FIG. 2  is a perspective view that shows a multifunction printer according to an embodiment of the present invention; 
         FIG. 3  is a partially exploded view that shows elements of the multifunction printer of  FIG. 2 ; 
         FIG. 4  is a perspective view that shows a printer chassis of  FIG. 3 ; 
         FIG. 5  is a perspective view of the printer chassis of  FIG. 4  populated with components; 
         FIG. 6  is a cross-section view of the multifunction printer of  FIG. 2  that shows the media transport path for the printing apparatus; 
         FIG. 7  is a perspective view of a printing apparatus having an inclined carriage motor according to an embodiment of the invention; 
         FIG. 8  is a close-up view of a portion of the printing-apparatus of  FIG. 7 ; 
         FIG. 9  is an even closer view of the inclined motor of  FIG. 7  and associated components; 
         FIG. 10  is a perspective view of the printer chassis of the printing apparatus of  FIG. 7 ; 
         FIG. 11  is a close-up underside perspective view of a portion of the scanning apparatus of the multifunction printer of  FIG. 2  including various features for securing components of the printing apparatus in position; 
         FIG. 12  is an underside perspective view of a the scanning apparatus of the multifunction printer of  FIG. 2 ; 
         FIG. 13  is a perspective view of a paper advance motor; 
         FIG. 14  is a perspective view of a paper advance motor assembled into the printer chassis according to an embodiment of the invention; 
         FIG. 15  is a perspective view of mounting features in the printer chassis for mounting the paper advance motor according to an embodiment of the invention; 
         FIG. 16  is a perspective view of the paper advance motor, the inclined carriage motor and several of their associated components; 
         FIG. 17  is a perspective view looking downward toward the paper advance motor and its associated components mounted in the printer chassis; 
         FIG. 18  is a close-up view of a feed roller mounted in a printer chassis; 
         FIG. 19  is similar to  FIG. 18  but with the feed roller assembly hidden in order to show a mounting feature in the printer chassis; 
         FIG. 20  is a perspective view of portions of the feed roller assembly, the turn roller assembly, a pick roller assembly and a drive shaft according to an embodiment of the invention; 
         FIG. 21  is a similar view as  FIG. 20 , but with the components mounted in the printer chassis; and 
         FIG. 22  is a perspective view (rotated relative to  FIG. 20 ) of portions of the feed roller assembly the turn roller assembly and the drive shaft. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 2  is a perspective view that shows a multifunction printer  100  according to an embodiment of the present invention. A scanning apparatus  500  is positioned atop a printing apparatus  400 . Scanning apparatus  500  has transparent platen  510 , preferably glass, for supporting documents or other items to be scanned in order to convert an image into digitized data. Although the scanning apparatus preferably uses glass as the transparent member, any other suitable transparent member may also be used. An outer case  505  contains the various internal elements of the scanning apparatus  500 . Mounted on case  505  are one or more operator controls  512 , and optionally one or more indicators  514 . 
     Embodiments of the present invention provide, within multifunction printer  100  (although applicable also in stand-alone printing apparatus architectures as well), a configuration for printing apparatus  400  that is assembled in a different manner from the “backbone”-based construction described previously with reference to  FIG. 1 . In embodiments of the present invention, a number of structural parts have been eliminated. Functions provided by the backbone in prior art printers, such as providing a support and attachment for motors, rollers, power supplies, carriage guides, and drive shafts, are described in further detail below. Embodiments also address desirable features such as reduced height and reduced noise. 
     Referring to the partially exploded view of  FIG. 3 , the case, the platen glass and most inner components (such as a scan bar and Motor) of scanning apparatus  500  have been hidden, so that scanner base  520  can be seen more clearly. Scanner base  520  is shown removed from its assembled position, fitted against a printer chassis  420 . Scanner base  520  can be formed of a single piece of plastic using injection molding, fig example. At its top side it includes supports  522  for platen glass  510  (see  FIG. 2 ). In other words, the top side of scanner base  520  faces platen glass  510 . Also seen from the top perspective view of  FIG. 3  is the scanner housing  525 , which is formed as part of scanner base  520 . An element of scanner housing  525  is rack  524  along which a scan bar (not shown) is used to scan documents that are placed on platen glass  510  (see  FIG. 2 ). The bottom of scanner base  520  includes a first region  528  and a second region  529  that extends lower than the first region  528 . The second region  529  extends lower in order to provide room for the rack  524  and the associated motor and gear of the scan bar (not shown). Even though ink supplies  262  and  264  (seen in the lower portion of  FIG. 3 ) are the most upwardly extending parts of the printing apparatus  400 , they are situated in an area corresponding to first region  528  of the bottom of scanner base  520 . The circuit board  516  is attached to the scanner base  520  but is not an integral part of the scanner base  520 . 
     A pinch roller assembly  530 , shown separately in the exploded view of  FIG. 3 , is affixed to the bottom of scanner base  520 , and extends into the media travel path, downward in the orientation of  FIG. 3 . Affixing of pinch roller assembly  530  can be done by snap fitting fingers  536  to scanner base  520  and attaching springs  538 . Pinch rollers  532  are biased by springs  538  to press against the feed roller to form a nip  533  (see  FIG. 6 ). 
     Some components of printing apparatus  400  are also shown in  FIG. 3  and the close-up perspective view of  FIG. 5 , while the close-up perspective view of  FIG. 4  shows the printer chassis  420  in isolation, empty of other components. Printer chassis  420  can be formed of a single piece of plastic using injection molding, for example. Printer chassis  420  includes a media input region  412  near door  410 , a media support element  422 , a printing region  424 , and a discharge region  426 . Various rollers are used to move recording medium along a media transport path as is described below relative to  FIG. 6 . A paper advance motor  440  provides power to rotate the rollers by various belts and gears that are shown in the example of  FIG. 5 , as discussed in further detail below. Media support element  422  can include a plurality of ribs  423  in order to reduce frictional drag on the moving recording medium. There can also be a plurality of ribs  425  in the printing region  424 , as seen most clearly in  FIG. 4 . Ribs  425  support the paper in the printing region and are positioned to avoid overspray of ink during borderless printing on recording media of standard sizes. A carriage guide  460  is mounted to printer chassis  420  and held in place by retainer  462  on side wall  428  of printer chassis  420  (shown in  FIG. 4 ). A carriage  200  is slidably mounted on carriage guide  460  via carriage bearings  202  and  204 , and is configured to move a printhead  250  (hidden behind the wall of printer chassis  420 ) and its ink supplies  262  and  264  in a carriage scan direction  305  along printing region  424  in order to print an image one swath at a time. 
       FIG. 6  shows a cross-sectional view of the multifunctional printer of  FIG. 2 . During printing, recording medium (not shown) is moved along a media transport path  430  (indicated as a dashed line) from media input region  412 , across the media support element  422 , then to the printing region  424 , and finally to the discharge region  426 . In particular, a pick roller  431  on pick arm  432  moves the recording medium from media input region  412  toward turn rollers  434  located in a turn region and to the media support element  422  that is located above media input region  412  when the multifunction printer  100  is oriented in its operating position. (A cleanout element that provides a curved guide surface to guide the recording medium upward from the pick roller  431  to the turn rollers  434  is not shown.) After the recording medium passes the turn rollers  434 , the tendency of the recording medium to remain substantially straight causes the recording medium to contact the bottom of scanner base  520 . In other words, the bottom surface  526  of scanner base  520 , located above media support element  422 , provides an upper guide for the recording medium as it passes through this region. As the recording medium continues to advance along media transport path  430 , it passes below pinch roller assembly  530 . In other words, the bottom surface  534  of pinch roller assembly  530 , as well as the top of media support element  422 , act as guides for the recording medium as it passes through this region. The recording medium is thus guided into the nip  533  formed by pinch rollers  532  that are biased by springs  538  against rotating feed roller  436 , to move the recording medium across printing region  424  and over to discharge region  426 . A discharge roller  438  (seen in  FIGS. 5 and 6 ) drives the recording medium toward door  410 . A star wheel assembly  439  (seen in  FIG. 3 ) positioned over the discharge roller pushes the paper into the discharge roller without smearing the ink on the freshly printed recording medium. 
       FIG. 7  is a perspective view of printing apparatus  400 , and shows printer chassis  420  populated with a number of the printer components (including carriage  200 , carriage guide  460 , carriage motor  470 , belt  480 , and paper advance motor  440 ), but rotated with respect to the views shown in  FIGS. 3 and 5 , such that the door  410  is to the right. In this view, carriage motor  470  is shown mounted in an inclined orientation-relative to base  421  of printer chassis  420 , according to an embodiment of the invention. Since the nominal operating position of printing apparatus  400  is such that the base  421  of printer chassis  420  rests in a substantially horizontal plane, it can also be said that carriage motor  470  is inclined with respect to a horizontal plane when the printing apparatus  400  is in its nominal operating position. Belt  480  is looped around rotatable motor axle  474  of carriage motor  470  near one end of carriage guide  460  and around idler pulley  488  (see also  FIG. 16 ) near the opposite end of carriage guide element  460 . Idler pulley  488  includes an axis of rotation that is configured to be parallel to the rotatable axle  474  of carriage motor  470 . 
       FIG. 8  is a close-up perspective view of a portion of printing apparatus  400  together with a dashed line  521  that approximately represents the contour of the bottom of scanner base  520 . As discussed relative to  FIG. 3 , scanner base  520  includes a first region  528  and a second region  529  that extends lower than first region  528 . As seen in  FIG. 8 , carriage motor  470  is located near the second region  529  of the bottom of scanner base  520 . If carriage motor  470  were horizontally mounted (as in prior art  FIG. 1 ), its outer casing would interfere with the second region  529  of the bottom of scanner base  520 . In order to reduce the height of printing apparatus  400  (and therefore the height of multifunction printer  100 ), in the embodiment shown in  FIG. 8 , carriage motor  470  is mounted to be inclined relative to horizontal base  421  (see  FIG. 7 ). The upper edge  472  of carriage motor  470  is thus able to be about the same height as the upper rim  429  of the side wall  428  of printer chassis, and not interfere with the second region  529  of the bottom of scanner base  520 . In addition, in order to keep carriage vibrations at a low level, motor axle  474 , and belt  480  are substantially radially oriented relative to the lengthwise axis of carriage guide  460 , as shown in further detail below relative to  FIG. 9 . Carriage motor  470  is held in printer Chassis  420  by inclined cradle  475  (see  FIG. 10 ) that is molded as part of printer chassis  420 . A holding feature  476  of inclined cradle  475  is shown in  FIG. 8 . Also shown in  FIG. 8  is power supply  405  having a height that positions the top edge of power supply  405  near the upper rim  429  of side wall  428 . 
       FIG. 9  shows a close-up perspective view of some of the components of printing apparatus  400  at approximately the same viewing angle as  FIG. 8 , but with printer chassis  420  hidden for clarity. Carriage  200  includes carriage bearings  202  and  204  that glide along carriage guide  460 . Carriage motor  470  has an outer casing  471  including a cylindrical wall  477  that is substantially coaxial with rotatable motor axle  474  and a face  478  that is substantially perpendicular to rotatable motor axle  474 . Outer casing  471  has a length L and a diameter D. In this example L is greater than D. As described above the diameter of the motor is sufficiently large that cylindrical wall  477  would interfere with second region  529  of scanner base  520  if the carriage motor were horizontally mounted. In addition, because the length L of the outer casing of carriage motor  470  is larger than its diameter D (not even counting the added length of the motor axle  474  and the electrical terminal(s)  479 , mounting the carriage motor  470  with axis  473  of rotatable motor axle  474  pointing vertically upward would also cause interferences with the second region  529  of scanner base  520  (see  FIG. 8 ). In other words, mounting the carriage motor  470  either horizontally or vertically would increase the height of printing apparatus  400  relative to the inclined orientation of the present invention. The preferred angle α of inclination of rotatable motor axle  474  from a line  402  that is parallel to the base  421  (see  FIG. 7 ) depends on the overall length of carriage motor  470 , the diameter of its outer casing  471 , the position of belt attachment, etc. In the example shown in  FIG. 9 ; the angle α of inclination of rotatable motor axle  474  from a line  402  that is parallel to the base  421  (i.e. the angle of inclination between rotatable motor axle  474  and a horizontal plane when the printing apparatus is in its nominal operating position) is about 30 degrees. In general the preferred angle α of inclination is between ten degrees and eighty degrees, and more preferably between twenty degrees and fitly degrees. 
     Motor axle  474  typically includes a toothed pulley having an outer rim  501  to keep the belt  480  engaged. Herein the term motor axle will also include the motor pulley. Belt  480  includes a first section  481  on one side of motor axle  474  and a second section  482  (substantially parallel to first section  481 ) on the other side of motor axle  474 . In the example shown in  FIG. 9 , belt attachment  485  is on the first section  481 . As the carriage  200  moves back and forth along carriage guide  460 , different parts of belt  480  will be above or below motor axle  474 . However, even at the extreme ends of travel of carriage  200 , belt attachment  485  will not move from one side of motor axle  474  to the other side. Thus, the portion of first section  481  that includes belt attachment  485  is always on a predetermined side of motor axle  474 , even if portions of the belt  480  move from one side of the motor axle  474  to the other side. Belt  480  includes a length direction L B  extending from the rotatable motor axle  474  to the idler pulley  488  (see  FIG. 7 ), and a width direction W, extending substantially parallel to the rotatable motor axle  474 . In order to keep carriage vibration at a low level, the width direction W B  of belt  480  is disposed in a substantially radial orientation relative to an axis  464  of the carriage guide  460 . This can be seen more clearly  FIG. 9  relative to teeth  484  (a few of which are shown on the inner surface of the first section  481  of belt  480 ). Radial line  486  from carriage guide axis  464  extends along substantially the same direction as teeth  484 , i.e. the teeth  484  on the first section  481  of belt  480  are oriented substantially radially relative to axis  464  of carriage guide  460 . It can also be seen in  FIG. 9  that first section  481  of belt  480  is positioned at a first distance from carriage guide  460 , and section  482  is positioned at a second distance from carriage guide  460 , where the first distance is less than the second distance. 
       FIG. 10  shows a perspective view of printer chassis  420  looking toward the region where the carriage motor would be mounted, but with no printer components assembled onto printer chassis  420 . Inclined cradle  475  for supporting carriage motor  470  at an inclined orientation relative to base  421  of printer chassis  420  can be seen. Also visible in  FIG. 10  is retainer  462  (opposite the retainer  462  seen in  FIG. 4 ) for holding carriage guide  460  in place. Ribs  425  for supporting recording medium in printing region  424  are also seen. 
     Inclined cradle  475  and holding feature  476  (see  FIG. 8 ) perform part of the function of holding carriage motor  480  in place in printer chassis  420  using only parts that are molded together with printer chassis  420  and not requiring a separate support structure such as a backbone. In order to further secure the carriage motor  470  in its inclined position, a motor holding feature  540  is provided in second region  529  of the bottom of scanner base  520  as shown in  FIG. 11 . (The viewing angle of  FIG. 11  is rotated with respect to the view of  FIGS. 8 and 9 .) During the assembly of multifunction printer  100 , when scanner base  520  is mounted as an upper structure onto printer chassis  520 , motor holding feature  540  engages carriage motor  470  near the upper edge  472  of carriage motor  470  (see  FIG. 8 ) to hold carriage motor  480  against the inclined cradle  475  (see  FIG. 10 ) and holding feature  476  (see  FIG. 8 ) that serve as a motor support in printer chassis  420 . In this embodiment, a first portion  541  of motor holding feature  540  contacts cylindrical wall  478  of outer casing  471  of carriage motor  480 , and a second portion  542  of holding feature  540  contacts face  477  of outer casing  471  of carriage motor  480 . 
     When the multifunction printer  100  is fully assembled (see  FIG. 2 ), the upper edge  472  of inclined carriage motor  480  is positioned near the base  520  of scanning apparatus  500 , so that the overall height of multifunction printer  100  can be reduced relative to conventional multifunction printers. Additionally, the first section  481  that includes belt attachment  485  is oriented substantially radially relative to the carriage guide in order to keep carriage vibrations low for good print quality. Because inclined cradle  475  and holding feature  476  are integrally formed together with printer chassis  420  (e.g. during injection molding), and because motor holding feature  540  is likewise integrally formed with scanner base  520 , no additional fasteners or assembled support structures are required, thereby simplifying assembly and reducing cost. 
     In other embodiments, the general approach of assembling a multifunction printer employed for the carriage motor is also used for assembling a variety of other components of the printing apparatus without using additional fasteners. For these embodiments, the printing apparatus  400  (for printing on recording medium) is provided that includes a printer chassis  420  having a support feature (such as inclined cradle  475  and holding feature  476 ) for holding a component of the printing apparatus. The component (such as carriage motor  470 ) is mounted onto the support feature. A scanning apparatus  500  (for convening an image into digitized data) is provided that includes a securing feature (such as motor holding feature  540  on scanner base  520 ). The scanning apparatus is then affixed to printer chassis  420  such that the securing feature of the scanning apparatus constrains a position of the component of the printing apparatus relative to the support feature of the printer chassis. In some instances, such as for the carriage motor, the securing feature can actually contact the component in order to hold it fixedly in place. For example, scanner base  520  can have a securing feature extending from scanner base  520  to contact power supply  405  (see  FIG. 8 ) in order to hold it in place when scanner base  520  is assembled onto printer chassis  420 . In other instances, the securing feature allows rotational motion of the component, but constrains translational motion. In some instances the securing feature of scanning apparatus  500  is brought nearly into contact, but not actually into contact with the component, so that an acceptable amount of motion of the component is allowed, but not an excessive amount of motion. 
     Assembly of carriage guide  460  is another example of this assembly approach that is used in some embodiments. In  FIGS. 4 and 10 , retainer features  462  (serving as support features for carriage guide  460 ) are shown on opposing side walls  428  of printer chassis  420 . One or both of the opposing side walls  428  are somewhat flexible, so that at least the top portion of a side wall  428  can be bent outward, away from the inner region of the printer chassis  420 . In the examples shown in  FIGS. 4 and 10 , retainer features  462  extend inwardly into printer chassis  420 . Carriage guide  460  (see  FIG. 5 ) is provided with open ends  461  (see  FIG. 16 ) that can fit onto retainer features  462 . When flexible side walls  428  are not bent, carriage guide  460  is longer than the distance between a predetermined distance between the retainer features  462 . By bending at least one of the flexible side walls  428  in an outward direction such that a distance between the two retainer features  462  is longer than the length of the carriage guide element, a first retainer feature  462  can be inserted into one open end  461  of the carriage guide, and the second retainer feature  462  can be inserted into the second open end  461  of the carriage guide. When the flexible side walls  428  are released, retaining features  462  hold carriage guide  460  in its mounted position in printer chassis  420 . Interlocking features, such as attachment tabs  508  can be provided on outer case  505  of scanning apparatus  500 , as shown in  FIG. 12  to reduce the flexibility of the opposing flexible side walls  428  of printer chassis  420 , so that when scanning apparatus  500  is affixed to printer chassis  420 , carriage guide  460  becomes further secured with its position constrained. Lower rim  506  of outer case  505  can also engage with upper rim  429  (see  FIG. 8 ) of side wall  428  of printer chassis  420  when scanning apparatus  500  is affixed to printer chassis  420 . Interlocking complementary lips on upper rim  429  of side wall  428  and on lower rim  506  of outer case  505  can further reduce the flexibility of side walls  428  when the scanning apparatus  500  is affixed to printer chassis  420 . Interlocking tongue and groove features (not shown) can also be provided. Such interlocking features—attachment tabs  508  and their attachment points (not shown) on printer chassis  420 , complementary lips on upper rim  429  and lower rim  506 , and interlocking tongue and groove features include both attachment features in the scanning apparatus  500  and mating features  420  that reduce the flexibility of the flexible side walls  428  when scanning apparatus  500  is affixed to printer chassis  420 . 
     In addition to reducing the number of fasteners and not requiring an additional assembled structure, such as a backbone, a further advantage of attaching the carriage guide  460  to retaining features  462  that have been integrally formed with printer chassis  420  is improved dimensional tolerances. In particular, the distance from the printhead face to the recording medium in the printing region  424  is critically important. If this distance is too large, poorly performing jets that eject drops at an angle relative to their intended direction result in poor print quality. If the distance is too small, the printhead can strike the recording medium as the printhead is moved back and forth by the carriage, doing damage to both the recording medium, and the printhead. By integrally forming retaining features  462  and ribs  425  in printing region  424  (see  FIGS. 4 and 10 ), for example during injection molding of printer chassis  420 , the spacing between printhead and recording medium is thereby well controlled. 
     Paper advance motor  440  is another example of a component that can be assembled onto support features in the printer chassis  420  and then secured in place when the scanning apparatus  500  of multifunction printer  100  is affixed to the printer chassis  420 . As shown in  FIG. 13 , paper advance motor  440  includes a cylindrical wall  441  and a face  442  from which rotatable motor axle  444  extends. Motor axle  444  can include a toothed pulley having an outer rim (unlabelled) for embodiments where a toothed belt is used to transmit power from paper advance motor  440 . Also extending from face  442  is a nonrotatable collar  443 . Although bolt holes (unlabelled) are provided in the face  442  of a conventional paper advance motor  440  for attachment to a structural framework (as discussed in the background relative to prior art  FIG. 1 ), attachment of paper advance motor  440  in embodiments of the invention does not require additional fasteners or separately assembled framework. As shown in the perspective view in  FIG. 14 , a cradle  445  and a collar holder  446  are integrally formed as part of printer chassis  420  (e.g. during injection molding of the printer chassis) as support features for paper advance motor  440 . Collar holder  446  includes a slot  447  for holding collar  443 . Collar holder  446  and slot  447  are shown more clearly in the perspective view of  FIG. 15  without paper advance motor  440 . Slot  447  has an open upper end  448  and a lower end  449  that is configured to hold collar  443  of paper advance motor  440 . In this example, since collar  443  is circular, slot  447  has a rounded lower end  449 . Also in this embodiment, slot  447  has a central axis (dashed line in the middle of slot  447 ) that is not vertical. Rather, in the view of  FIG. 15  the central portion of the lower end  449  is offset to the left relative to the central portion of the upper end  448  of slot  447 . During assembly of multifunction printer  100 , cylindrical wall  441  of paper advance motor  440  is placed into cradle  445  and collar  443  is inserted into open upper end  448  of slot  447  and then lowered to fit into lower end  449  of slot  447  of collar holder  446 . Subsequently when scanning apparatus  500  is assembled onto printer chassis  420 , curved securing feature  543  (see  FIG. 12 ) holds cylindrical wall  441  of paper advance motor  440  in position. In some embodiments it is useful to perform tests on printing apparatus  400  prior to completion of the assembly, and it is in such embodiments that the nonvertical slot  447  (described above) can be useful.  FIG. 16  shows a number of assembled components of printing apparatus  400 , but with printer chassis  420  hidden for clarity. The viewing angle of  FIG. 16  is rotated approximately 180 degrees relative to  FIG. 15  so that items that point toward the left (such as the upper to lower dashed line indicating the central axis of slot  447 ) would point toward the right in  FIG. 16 .  FIG. 16  shows paper advance motor  440  together with power transmission elements for driving the feed roller and the discharge roller. In particular, belt  450  is looped around rotatable motor axle  444  of paper advance motor  440  and also around pulley  451 . Formed coaxially on the opposite side of pulley  451  is a pulley gear  455  (see  FIG. 17 ) that engages feed roller driving gear  453 . Formed coaxially on feed roller driving gear  453  is round projection  454 , discussed in further detail below relative to the mounting of the feed roller. Feed roller  436  (see  FIG. 6 ) is hidden by carriage guide  460  in the view of  FIG. 16 , but is assembled coaxially with feed roller driving gear  453 . Feed roller driving gear  453  also transfers rotational power to idler gear  435  and from there to discharge roller gear  437 , which rotates discharger roller  438  (see  FIG. 6 ). During assembly of printing apparatus  400 , pulley  451  and tensioning pulley  452  are respectively mounted on pulley mounting feature  414  and on axle mount  415  (see also  FIG. 17 ), which are integrally formed on printer chassis  420  (see  FIG. 15 ). When belt  450  is looped around motor axle  444 , pulley  451  and tensioning pulley  452 , the tension in belt  450  pulls motor axle  444  to the right in  FIG. 16  (to the left in  FIG. 15 ), thereby forcing collar  443  against the lower end of nonvertical slot  447 . Thus, even before scanning apparatus  500  is assembled onto printer chassis  420 , sufficient holding force is applied to paper advance motor  440  so that tests can be performed. 
     The feed roller assembly is yet another example of a component that can be assembled onto support features in the printer chassis  420  and then secured in place when the scanning apparatus  500  of multifunction printer  100  is affixed to the printer chassis  420 . The feed roller assembly includes feed roller  436 , feed roller drive gear  453  that is coaxially mounted on a first end of feed roller  436  (see  FIG. 17 ), and a power transmission gear  456  (see  FIG. 18 ) that is coaxially mounted on a second end of feed roller  436 . Power transmission gear  456  (which can be injection molded from acetal, for example) has a bearing surface  457 .  FIG. 19  shows the same perspective view as  FIG. 18 , but with feed roller  436  and power transmission gear  456  hidden in order to show feed-roller support  406  that has been integrally formed with printer chassis  420 , for example by injection molding. Feed roller support  406  includes a slot  407  having an open upper end  408  and a rounded lower end  409 . When the feed roller assembly is assembled into printer chassis  420 , the hearing surface  457  of power transmission gear  456  is inserted through the upper open end  408  of slot  407  and placed into contact with the rounded lower end  409  of slot  407 . At the first end of the feed roller assembly, the round projection  454  (see  FIG. 16 ) of feed roller drive gear  453  is inserted into a round hole  416  (see  FIG. 15 ) in feed roller assembly support  417 . The feed roller assembly is further secured when spring-biased pinch roller assembly  530  at pinch rollers  532  (see  FIGS. 3 and 6 ), having already been assembled to scanner base  520 , is pressed into contact with the rotatable feed roller assembly when the scanning apparatus  500  is assembled to the printer chassis  420 , thereby constraining the bearing surface  457  of power transmission gear to be held against the rounded lower end  409  of slot  407 . 
     Still another example of a component that can be assembled onto support features in the printer chassis  420  and then secured in place when the scanning apparatus  500  of multifunction printer  100  is affixed to the printer chassis  420  is drive shaft  490  that transmits power from power transmission gear  456  of the feed roller assembly to the turn roller assembly, as is described in further detail below and as shown in  FIGS. 20-22 . Drive shaft  490  is a rotatable shaft having bearing surfaces  492  and optionally one or more rings  494 .  FIG. 20  shows a portion of the feed roller assembly (including feed roller  436  and power transmission gear  456 ), turn roller assembly (including turn roller  438  and associated gears), pick roller assembly (including pick roller  431 , pick arm  432  and associated gears) and drive shaft  490 , but with printer chassis  420  hidden for clarity.  FIG. 21  shows the same view but with printer chassis  420  shown. As shown in  FIG. 21 , integrally formed with printer chassis  420  (for example, by injection molding) are drive shaft supports  465 , each including a slot (similar to slot  407  shown in  FIG. 19 , but sized to accommodate bearing surfaces  492  of drive shaft  490 ) having an open upper end  467  and a rounded lower end  468 . Drive shaft supports  465  also include upper support surfaces  469 . When assembling drive shaft  490  into printer chassis  420 , bearing surfaces  492  are placed into contact with the rounded lower ends  468  of the slots  466  in drive shaft supports  465 . Subsequently, when scanning apparatus  500  is assembled onto printer chassis  420 , securing extension  544  (see  FIG. 12 ) comes into contact with upper support surfaces  469  of one of the drive shaft supports  465 , and securing extension  546  comes into contact, or nearly into contact with ring  494 . Securing extension  544  does not quite come into contact with bearing surface  492 , so that the position of drive shaft  490  is constrained but without additional frictional-drag. 
     The function of drive shaft  490  and its interaction with the other portions of the paper feeding apparatus of printing apparatus  400  will next be described in further detail. The feed roller assembly including feed roller  436 , feed roller drive gear  453  and power transmission gear  456 , transmit power from paper advance motor  440  to rotate turn roller  434  and pick roller  431  as needed to advance recording medium toward the printing region. Power transmission gear  456  is a compound gear including bevel gear  458  and spur gear  459 . When it is necessary to move a piece of recording medium from media input region  412  toward turn rollers  434  (see  FIG. 6 ), a transmission mechanism (not shown) is engaged. Then power to pick roller  431  is transmitted from spur gear  459  through a gear train  418  having a gear that is engaged with spur gear  459  as well as a set of gears on one side of pick arm  432  and a set of gears on the other side of pick arm  432 . Spur gears, having gear teeth that are parallel to the rotational axis of the gear are suitable for applications where the load to be driven (such as pick roller  431 ) requires substantial torque. However, a gear train having many gears tends to add to both the expense and the noise of the printing apparatus. Conventional printers also use a gear train driven by the feed roller assembly to rotate turn roller  434 . However, it has been found that drive shaft  490  having a bevel gear  491  at one end to engage with bevel gear  458  of power transmission gear  456  and another bevel gear  493  at the other end of drive shaft  490  to engage with a bevel gear  496  that is coupled to gears for rotating turn roller  434 , is able to develop sufficient torque for the turn roller  434  to advance the recording medium through the turn region toward the feed roller  436  (see  FIG. 6 ). Thus, using drive shaft  490  allows elimination of approximately seven gears (depending upon the configuration of the printer) and their associated expense and noise level. In particular, the turn roller assembly includes a compound gear  495  made up of bevel gear  496  and spur gear  497 ; a first pivot gear  498 ; a second pivot gear  499 ; an intermediate gear  489 ; a drive gear  487 ; and turn roller  434 . Feed roller  436  can rotate either in forward direction  433  or in a reverse direction that is opposite to forward direction  433 . Rotating feed roller  436  in forward direction  433  advances recording medium toward print region  424  (see  FIG. 6 ). Feed roller  436  can also be rotated in the reverse direction to deskew the leading edge of recording medium as it approaches the feed roller. However, whether feed roller  436  is rotating in forward direction  433  or reverse direction, it is desired that turn roller  434  (when turning) should always rotate in forward direction  433 . This is accomplished through first pivot gear  498 , second pivot gear  499  and intermediate gear  487 . Spur gear  497  of compound gear  495  is engaged with both first pivot gear  498  and second pivot gear  499 . When spur gear  497  is rotated in one direction due to the rotation of feed roller  436 , first pivot gear  498  is rotated to engage intermediate gear  489  (as in  FIG. 22 ) which then causes drive gear  489  in forward direction  433 . When spur gear  497  is rotated in the opposite direction due to the rotation of the feed roller  436 , second pivot gear  499  is rotated to engage directly (i.e. without an intermediate gear) with drive gear  489  to rotate it in the forward direction  433 . 
     A special case of the bevel gear is the miter gear where two meshing gears have equal numbers of teeth and shaft axes that are perpendicular to each other. The example shown in  FIGS. 20-22  (the length axis of drive shaft  490  being perpendicular to the length axis of feed roller  436 ) use miter gears, but other bevel gear embodiments are contemplated. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
     PARTS LIST 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 100 
                 Multifunction printer 
               
               
                 200 
                 Carriage 
               
               
                 202 
                 Carriage bearing 
               
               
                 204 
                 Carriage bearing 
               
               
                 250 
                 Printhead 
               
               
                 262 
                 Ink supply 
               
               
                 264 
                 Ink supply 
               
               
                 300 
                 Printer 
               
               
                 302 
                 Load entry direction 
               
               
                 303 
                 Printing region 
               
               
                 304 
                 Direction 
               
               
                 305 
                 Carriage scan direction 
               
               
                 306 
                 Right side 
               
               
                 307 
                 Left side 
               
               
                 308 
                 Front 
               
               
                 309 
                 Rear 
               
               
                 310 
                 Hole 
               
               
                 311 
                 Feed roller gear 
               
               
                 312 
                 Feed roller 
               
               
                 313 
                 Forward direction 
               
               
                 330 
                 Maintenance station 
               
               
                 380 
                 Motor 
               
               
                 381 
                 Screw 
               
               
                 382 
                 Guide rail 
               
               
                 383 
                 Axle 
               
               
                 384 
                 Belt 
               
               
                 385 
                 Backbone 
               
               
                 386 
                 Rotational axis of pulley 
               
               
                 390 
                 Electronics board 
               
               
                 392 
                 Cable connectors 
               
               
                 400 
                 Printing apparatus 
               
               
                 402 
                 Line (parallel to base of printer chassis) 
               
               
                 405 
                 Power supply 
               
               
                 406 
                 Feed roller assembly support 
               
               
                 407 
                 Slot 
               
               
                 408 
                 Upper end (of slot) 
               
               
                 409 
                 Lower end (of slot) 
               
               
                 410 
                 Door 
               
               
                 412 
                 Media input region 
               
               
                 414 
                 Pulley mounting feature 
               
               
                 415 
                 Axle mount (for tensioning pulley) 
               
               
                 416 
                 Hole 
               
               
                 417 
                 Feed roller assembly support 
               
               
                 418 
                 Gear train (for pick roller) 
               
               
                 420 
                 Printer chassis 
               
               
                 421 
                 Base (of printer chassis) 
               
               
                 422 
                 Media support element 
               
               
                 423 
                 Ribs (on media support element) 
               
               
                 424 
                 Printing region 
               
               
                 425 
                 Ribs (in printing region) 
               
               
                 426 
                 Discharge region 
               
               
                 428 
                 Side wall 
               
               
                 429 
                 Upper rim (of side wall) 
               
               
                 430 
                 Media transport path 
               
               
                 431 
                 Pick roller 
               
               
                 432 
                 Pick arm 
               
               
                 433 
                 Forward rotation direction 
               
               
                 434 
                 Turn roller 
               
               
                 435 
                 Idler gear 
               
               
                 436 
                 Feed roller 
               
               
                 437 
                 Discharge roller gear 
               
               
                 438 
                 Discharge roller 
               
               
                 439 
                 Star wheel assembly 
               
               
                 440 
                 Paper advance motor 
               
               
                 441 
                 Cylindrical wall (of paper advance motor) 
               
               
                 442 
                 Face (of paper advance motor) 
               
               
                 443 
                 Collar (of paper advance motor) 
               
               
                 444 
                 Axle (of paper advance motor) 
               
               
                 445 
                 Cradle (for paper advance motor) 
               
               
                 446 
                 Collar holder (for paper advance motor) 
               
               
                 447 
                 Slot 
               
               
                 448 
                 Upper end (of slot) 
               
               
                 449 
                 Lower end (of slot) 
               
               
                 450 
                 Belt 
               
               
                 451 
                 Pulley 
               
               
                 452 
                 Tensioning pulley 
               
               
                 453 
                 Feed roller drive gear 
               
               
                 454 
                 Round projection 
               
               
                 455 
                 Pulley gear 
               
               
                 456 
                 Power transmission gear 
               
               
                 457 
                 Bearing surface 
               
               
                 458 
                 Bevel gear (of power transmission gear) 
               
               
                 459 
                 Spur gear (of power transmission gear) 
               
               
                 460 
                 Carriage guide 
               
               
                 461 
                 Open end (of carriage guide) 
               
               
                 462 
                 Retainer (for carriage guide) 
               
               
                 464 
                 Axis (of carriage guide) 
               
               
                 465 
                 Drive shaft support 
               
               
                 466 
                 Slot 
               
               
                 467 
                 Upper end 
               
               
                 468 
                 Lower end 
               
               
                 469 
                 Upper support surfaces 
               
               
                 470 
                 Carriage motor 
               
               
                 471 
                 Outer casing (of carriage motor) 
               
               
                 472 
                 Upper edge (of carriage motor) 
               
               
                 473 
                 Axis 
               
               
                 474 
                 Axle (of carriage motor) 
               
               
                 475 
                 Inclined cradle 
               
               
                 476 
                 Holding feature (of inclined cradle) 
               
               
                 477 
                 Cylindrical wall (of carriage motor) 
               
               
                 478 
                 Face (of carriage motor) 
               
               
                 479 
                 Electrical term inal(s) 
               
               
                 480 
                 Belt (for carriage) 
               
               
                 481 
                 First section (of belt) 
               
               
                 482 
                 Second section (of belt) 
               
               
                 484 
                 Teeth (of belt) 
               
               
                 485 
                 Belt attachment 
               
               
                 486 
                 Radial line (from axis of carriage guide) 
               
               
                 487 
                 Intermediate gear 
               
               
                 488 
                 Idler pulley 
               
               
                 489 
                 Drive gear (for turn roller assembly) 
               
               
                 490 
                 Drive shaft (fin turn roller assembly) 
               
               
                 491 
                 Bevel gear (of drive shaft) 
               
               
                 492 
                 Bearing surface(s) 
               
               
                 493 
                 Bevel gear (of drive shaft) 
               
               
                 494 
                 Ring (of drive shaft) 
               
               
                 495 
                 Compound gear (of turn roller assembly) 
               
               
                 496 
                 Bevel gear (of compound gear) 
               
               
                 497 
                 Spur gear (of compound gear) 
               
               
                 498 
                 First pivot gear 
               
               
                 499 
                 Second pivot gear 
               
               
                 500 
                 Scanning apparatus 
               
               
                 501 
                 Outer rim 
               
               
                 505 
                 Case 
               
               
                 506 
                 Lower rim 
               
               
                 508 
                 Attachment tab(s) 
               
               
                 510 
                 Transparent platen 
               
               
                 512 
                 Control 
               
               
                 514 
                 Indicator 
               
               
                 516 
                 Printed circuit board 
               
               
                 520 
                 Scanner base 
               
               
                 521 
                 Dashed line representing contour of  
               
               
                   
                 scanner base bottom 
               
               
                 522 
                 Supports (for platen glass) 
               
               
                 524 
                 Rack 
               
               
                 525 
                 Scanner housing 
               
               
                 526 
                 Bottom surface (of scanner base) 
               
               
                 528 
                 First region (of scanner base bottom) 
               
               
                 529 
                 Second region (of scanner base bottom) 
               
               
                 530 
                 Pinch roller assembly 
               
               
                 532 
                 Pinch rollers 
               
               
                 533 
                 Nip 
               
               
                 534 
                 Bottom surface (of pinch roller assembly) 
               
               
                 536 
                 Finger(s) 
               
               
                 538 
                 Spring(s) 
               
               
                 540 
                 Motor holding feature 
               
               
                 541 
                 First portion (of motor holding feature) 
               
               
                 542 
                 Second portion (of motor holding feature) 
               
               
                 543 
                 Curved securing feature 
               
               
                 544 
                 Securing extension 
               
               
                 546 
                 Securing extension