Abstract:
A method of making and using a printer comprising a duplexing unit that pivots along a horizontal plane for media path access. The duplexing unit does not contain any motor driven rollers for moving a media sheet therethrough. The duplexing unit&#39;s vertical axis hinge allows the duplexing unit to swing open and closed horizontally.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Reference is made to commonly assigned, co-pending U.S. Patent Applications: 
         [0000]    Ser. No. ______ by Chuang et al. (Docket K000175) filed of even date herewith entitled “Printing Apparatus With Pivotable Duplexing Unit”;
 
Ser. No. ______ by Murray et al. (Docket K000350) filed of even date herewith entitled “Printing Apparatus with Pivotable Cleanout Member”; and
 
Ser. No. ______ by Murray et al. (Docket K000368) filed of even date herewith entitled “Method Of Pivoting Cleanout Member”, the disclosures of which are incorporated herein by reference in their entireties.
 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to a media path for a printing apparatus, and more particularly to a duplexing unit for reversing a side of the media facing a print region. 
       BACKGROUND OF THE INVENTION 
       [0003]    Many types of printing apparatus are capable of printing only on a single side of the recording medium. However, the desirability of saving paper (or other types of printing media) by printing on both sides is widely recognized. A variety of duplexing designs have previously been disclosed for reversing a side of the media facing the print region after a first side has been printed, in order to allow printing on the opposite side. 
         [0004]    In some low-cost printers, as described in U.S. Pat. No. 7,561,823, a duplexing unit is provided as a removable auxiliary unit that the user can decide whether or not to purchase, according to his printing needs. If the user does purchase the auxiliary duplexing unit, he needs to install it himself, thus increasing the complexity of the setting up of the printing apparatus. 
         [0005]    For permanently attached duplexing units it can be advantageous to make the inner portions of the media path accessible in order to facilitate the clearing of paper jams by the user. U.S. Pat. Nos. 4,825,245, 4,884,110, 6,564,019 and 7,536,133 have disclosed hinged duplexing units for electrostatic printers such as laser printers. Due to the configuration of such printers the duplexing unit was not located near a base of the unit. The hinges of the duplexing units as disclosed in these patents were configured to be horizontal (i.e. parallel to the base), so that the duplexing unit is configured to pivot upward or downward. 
         [0006]    In a low-cost desktop printer, such as an inkjet printer, the printer is intended to sit on the user&#39;s desk or other flat surface that extends beyond the base of the printer. In addition, for a compact height printer having a C-shaped paper path (with the media input holder located below the media output holder), the duplexing unit is typically located very close to the base of the printer. For a duplexing unit located very close to the base of a desktop printer, a horizontal hinge configuration has disadvantages. If the hinge is located at the top of the duplexing unit, the duplexing unit would pivot upwards. However, since the user is typically taller than the desktop, the upwardly pivoted duplexing unit would obscure visibility and interfere with access to the media paths inside. Even if the user bent over so that his eyes were at desktop level, it would make it difficult to reach in and clear out paper jams between the upwardly pivoted duplexing unit and the desktop. If the hinge is located at the bottom of the duplexing unit, the duplexing unit would pivot downwards. However, if the duplexing unit is located very near the base of the printing apparatus, its pivoting motion would typically cause it to hit the desktop before opening all the way, again interfering with visibility and access to the media paths for clearing paper jams. 
         [0007]    What is needed is a duplexing unit that does not require user installation, and that allows good visibility and access to media paths inside the printing apparatus in order to facilitate clearing out paper jams. 
       SUMMARY OF THE INVENTION 
       [0008]    A preferred embodiment of the present invention includes a method of making a printer comprising forming a pin member portion of a hinge on a first end of a duplexing unit of the printer and forming a support member portion of a hinge on a housing of the printer. A unique feature of the duplexing unit is that it does not contain any motor driven rollers for moving a media sheet. The support member and the pin member are oriented vertically. The duplexing unit provides a media pathway for printing on both sides of printer media and its hinged connection to the printer allows the duplexing unit to swing open and closed horizontally as a household interior door would. A latch projection on a second end of the duplexing unit opposite the hinge allows the duplexing unit to be securely closed. A hole formed in the printer catches the latch projection and keeps the duplexing unit closed until it is manually unlatched. The pin member is coupled to the support member allowing the duplexing unit to freely pivot about the vertical rotational axis formed by the joined pin member and the support member. It also enables the duplexing unit to pivot to a closed position wherein the hole in the printer catches the latch projection. The support member includes a bearing surface formed thereon that is substantially horizontal and the pin member makes pivotable contact with this bearing surface. A spring attached to the duplexing unit at the hinge end biases the latch projection to so that it remains inserted into the hole until it is manually unlatched. The end of the pin member is shaped as a D, having a rounded side and a flat side, wherein the round side portion of the D shape is contacting a face of the support member when the duplexing unit is in the closed position and is not contacting the face of the support member when the duplexing unit is in the open position. A screw can be used to secure the pin member to the support member. 
         [0009]    The duplexing unit comprises an S shaped inner guide member formed thereon. The printer includes a corresponding duplexing media path support member wherein the duplexing media path support member closely faces a portion of the S shaped inner guide member when the duplexing unit is in the closed position for allowing a media sheet to travel therethrough. The duplexing unit includes a latch for affixing the inner guide member to the duplexing unit. 
         [0010]    Another preferred embodiment of the present invention includes a method of accessing a paper path of a printer comprising pivoting a duplexing unit of the printer along a horizontal plane for exposing the paper path. The duplexing unit is pivoted about a vertical axis produced by a pin member formed on the duplexing unit which is joined to a support member formed on a housing of the printer. A round portion of the pin member contacts a face of the support member when the duplexing unit is swung, or pivoted, shut to a closed position. The round portion of the pin member loses contact with the face of the support member when the duplexing unit is manually unlatched and swung, or pivoted, open. Pivoting open the duplexing unit comprises unlatching the latched end of the duplexing unit and pivoting the duplexing unit about a vertical axis at the hinged end of the duplexing unit opposite the latched end. The duplexing unit includes a horizontal dimension that is greater than its vertical dimension and so the horizontal pivoting of the duplexing unit sweeps a greater area in a horizontal plane than it would in a vertical plane if the duplexing unit was designed to open vertically, such as discussed above with regard to the prior art, opened vertically. 
         [0011]    Another preferred embodiment of the present invention includes a method of making a printer comprising joining a duplexing unit of a printer to the housing of the printer using a vertically oriented hinge wherein the duplexing unit includes a first part of the hinge and the printer includes a second part of the hinge. This allows the duplexing unit to pivot along a horizontal plane between an open position and a closed position. Joining the duplexing unit to the printer comprises forming a pin member on one end of the duplexing unit oriented in a vertical direction, and forming a support member on the housing of the printer also oriented in a vertical direction for being joined to the pin member. A latch projection on the other end of the duplexing unit corresponds to a hole in the printer for catching the latch projection to keep closed in an operational position the duplexing unit. When the duplexing unit is in an open position the media pathway is accessible to remove jammed paper, for example, and such an open position is not typically a normal operating mode of the printer. 
         [0012]    These, and other, aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention and numerous specific details thereof, is given by way of illustration and not of limitation. For example, the summary descriptions above are not meant to describe individual separate embodiments whose elements are not interchangeable. In fact, many of the elements described as related to a particular embodiment can be used together with, and possibly interchanged with, elements of other described embodiments. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. The figures below are intended to be drawn neither to any precise scale with respect to relative size, angular relationship, or relative position nor to any combinational relationship with respect to interchangeability, substitution, or representation of an actual implementation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The above and other objects, features, and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical features that are common to the figures, and wherein: 
           [0014]      FIG. 1  is a schematic representation of an inkjet printer system; 
           [0015]      FIG. 2  is a perspective view of a portion of a printhead chassis; 
           [0016]      FIG. 3  is a perspective view of a portion of a desktop carriage printer; 
           [0017]      FIG. 4  is a schematic side view of an exemplary media path in a carriage printer that includes a duplexing unit; 
           [0018]      FIG. 5  is a schematic side view of the media path of  FIG. 4 , where one side of the sheet has been printed and the sheet is travelling toward the duplexing unit; 
           [0019]      FIG. 6  is a schematic side view of the media path of  FIG. 4 , where one side of the sheet has been printed and the sheet is travelling through the duplexing unit to orient the opposite side of the sheet toward the print region; 
           [0020]      FIG. 7  is a schematic side view of the media path of  FIG. 4 , where the lead edge of the sheet has exited the duplexing unit and is approaching the print region; 
           [0021]      FIG. 8  is a perspective view of a printing apparatus with a pivotable duplexing unit according to a preferred embodiment of the invention; 
           [0022]      FIG. 9  is a rotated perspective view of the printing apparatus of  FIG. 8 ; 
           [0023]      FIG. 10  is a perspective view of the printing apparatus of  FIG. 8  with the pivotable duplexing unit in a closed position; 
           [0024]      FIGS. 11 and 12  are close-up perspective views of a portion of a hinge for the pivotable duplexing unit of  FIG. 8 ; 
           [0025]      FIGS. 13 and 14  are perspective views of the pivotable duplexing unit of  FIG. 8 ; 
           [0026]      FIG. 15  is a rotated perspective view of the printing apparatus of  FIG. 8 ; 
           [0027]      FIG. 16  is a perspective view of the pivotable duplexing unit of  FIG. 8 ; 
           [0028]      FIGS. 17-20  are perspective views of various portions of the pivotable duplexing unit of  FIG. 8 ; and 
           [0029]      FIG. 21  is a perspective view of a portion of the pivotable duplexing unit of  FIG. 8  according to another preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Referring to  FIG. 1 , a schematic representation of an inkjet printer system  10  is shown, for its usefulness with preferred embodiments of the present invention and is fully described in U.S. Pat. No. 7,350,902, and is incorporated by reference herein in its entirety. Inkjet printer system  10  includes an image data source  12 , which provides data signals that are interpreted by a controller  14  as being commands to eject drops. Controller  14  includes an image processing unit  15  for rendering images for printing, and outputs signals to an electrical pulse source  16  of electrical energy pulses that are inputted to an inkjet printhead  100 , which includes at least one inkjet printhead die  110 . 
         [0031]    In the example shown in  FIG. 1 , there are two nozzle arrays. Nozzles  121  in the first nozzle array  120  have a larger opening area than nozzles  131  in the second nozzle array  130 . In this example, each of the two nozzle arrays has two staggered rows of nozzles, each row having a nozzle density of  600  per inch. The effective nozzle density then in each array is  1200  per inch (i.e. d= 1/1200 inch in  FIG. 1 ). If pixels on the recording medium  20  were sequentially numbered along the paper advance direction, the nozzles from one row of an array would print the odd numbered pixels, while the nozzles from the other row of the array would print the even numbered pixels. 
         [0032]    In fluid communication with each nozzle array is a corresponding ink delivery pathway. Ink delivery pathway  122  is in fluid communication with the first nozzle array  120 , and ink delivery pathway  132  is in fluid communication with the second nozzle array  130 . Portions of ink delivery pathways  122  and  132  are shown in FIG. I as openings through printhead die substrate  111 . One or more inkjet printhead die  110  will be included in inkjet printhead  100 , but for greater clarity only one inkjet printhead die  110  is shown in  FIG. 1 . In  FIG. 1 , first fluid source  18  supplies ink to first nozzle array  120  via ink delivery pathway  122 , and second fluid source  19  supplies ink to second nozzle array  130  via ink delivery pathway  132 . Although distinct fluid sources  18  and  19  are shown, in some applications it may be beneficial to have a single fluid source supplying ink to both the first nozzle array  120  and the second nozzle array  130  via ink delivery pathways  122  and  132  respectively. Also, in some embodiments, fewer than two or more than two nozzle arrays can be included on printhead die  110 . In some embodiments, all nozzles on inkjet printhead die  110  can be the same size, rather than having multiple sized nozzles on inkjet printhead die  110 . 
         [0033]    Not shown in  FIG. 1 , are the drop forming mechanisms associated with the nozzles. Drop forming mechanisms can be of a variety of types, some of which include a heating element to vaporize a portion of ink and thereby cause ejection of a droplet, or a piezoelectric transducer to constrict the volume of a fluid chamber and thereby cause ejection, or an actuator which is made to move (for example, by heating a bi-layer element) and thereby cause ejection. In any case, electrical pulses from electrical pulse source  16  are sent to the various drop ejectors according to the desired deposition pattern. In the example of  FIG. 1 , droplets  181  ejected from the first nozzle array  120  are larger than droplets  182  ejected from the second nozzle array  130 , due to the larger nozzle opening area. Typically other aspects of the drop forming mechanisms (not shown) associated respectively with nozzle arrays  120  and  130  are also sized differently in order to optimize the drop ejection process for the different sized drops. During operation, droplets of ink are deposited on a recording medium  20 . 
         [0034]      FIG. 2  shows a perspective view of a portion of a printhead chassis  250 , which is an example of an inkjet printhead  100 . Printhead chassis  250  includes three printhead die  251  (similar to printhead die  110  in  FIG. 1 ), each printhead die  251  containing two nozzle arrays  253 , so that printhead chassis  250  contains six nozzle arrays  253  altogether. The six nozzle arrays  253  in this example can each be connected to separate ink sources (not shown in  FIG. 2 ); such as cyan, magenta, yellow, text black, photo black, and a colorless protective printing fluid. Each of the six nozzle arrays  253  is disposed along nozzle array direction  254 , and the length of each nozzle array along the nozzle array direction  254  is typically on the order of 1 inch or less. Typical lengths of recording media are 6 inches for photographic prints (4 inches by 6 inches) or 11 inches for paper (8.5 by 11 inches). Thus, in order to print a full image, a number of swaths are successively printed while moving printhead chassis  250  across the recording medium  20 . Following the printing of a swath, the recording medium  20  is advanced along a media advance direction that is substantially parallel to nozzle array direction  254 . 
         [0035]    Also shown in  FIG. 2  is a flex circuit  257  to which the printhead die  251  are electrically interconnected, for example, by wire bonding or TAB bonding. The interconnections are covered by an encapsulant  256  to protect them. Flex circuit  257  bends around the side of printhead chassis  250  and connects to connector board  258 . When printhead chassis  250  is mounted into the carriage  200  (see  FIG. 3 ), connector board  258  is electrically connected to a connector (not shown) on the carriage  200 , so that electrical signals can be transmitted to the printhead die  251 . 
         [0036]      FIG. 3  shows a portion of a desktop carriage printer. Some of the parts of the printer have been hidden in the view shown in  FIG. 3  so that other parts can be more clearly seen. Printing apparatus  300  has a print region  303  across which carriage  200  is moved back and forth in carriage scan direction  305  along the X axis, between the right side  306  and the left side  307  of printing apparatus  300 , while drops are ejected from printhead die  251  (not shown in FIG. 
         [0037]      3 ) on printhead chassis  250  that is mounted on carriage  200 . Carriage motor  380  moves belt  384  to move carriage  200  along carriage guide rail  382 . An encoder sensor (not shown) is mounted on carriage  200  and indicates carriage location relative to an encoder fence  383 . 
         [0038]    Printhead chassis  250  is mounted in carriage  200 , and multi-chamber ink tank  262  and single-chamber ink tank  264  are mounted in the printhead chassis  250 . The mounting orientation of printhead chassis  250  is rotated relative to the view in  FIG. 2 , so that the printhead die  251  are located at the bottom side of printhead chassis  250 , the droplets of ink being ejected downward onto the recording medium in print region  303  in the view of  FIG. 3 . Multi-chamber ink tank  262 , in this example, contains five ink sources: cyan, magenta, yellow, photo black, and colorless protective fluid; while single-chamber ink tank  264  contains the ink source for text black. Paper or other recording medium (sometimes generically referred to as paper or media herein) is loaded along paper load entry direction  302  toward the front of printing apparatus  308 . 
         [0039]    The motor that powers the media advance rollers is not shown in  FIG. 3 , but the hole  310  at the right side of the printing apparatus  306  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). A forward direction of rotation  313  is indicated. Toward the rear of the printing apparatus  309  is located the electronics board  390 , which includes cable connectors  392  for communicating via cables (not shown) to the printhead carriage  200  and from there to the printhead chassis  250 . 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 (shown schematically as controller  14  and image processing unit  15  in  FIG. 1 ) for controlling the printing process, and an optional connector for a cable to a host computer. 
         [0040]    The media advance system includes a variety of rollers that are used to advance the medium through the printer as shown schematically in the side view of  FIG. 4 . In this example, a media input holder  316 , which is located at a plane near the base  301  and is substantially parallel to base  301 , holds a stack of media  370 . A pick roller  320  is driven to rotate in forward rotation direction  313  to advance the top sheet  371  of the stack of media  370  from media input holder  316  along paper load entry direction  302  and up inclined guide  317 . A turn roller  322  is driven to further advance the sheet of media  371  received from the pick roller around a C-shaped path (in cooperation with a curved rear wall surface and a pinch roller  321 ). As a result, the sheet  371  continues to advance along media advance direction  304  from the rear  309  of the printing apparatus (with reference also to  FIG. 3 ) toward the print region  303  that is located at a plane that is farther from base  301  than the media input holder  316  is. The sheet  371  is then advanced by feed roller  312  (driven to rotate in forward rotation direction  313 ) and idler roller(s)  323  to advance the lead edge  375  of sheet  371  to and across print region  303  for printing on first side  372  of sheet  371 , and from there to a discharge roller  324  and star wheel(s)  325 . If the printing is to occur only on first side  372 , discharge roller  324  is driven in forward rotation direction  313  to continue to advance sheet  371  along media advance direction  304  until sheet  371  exits into optional media output holder  318 , a portion of which is shown in  FIG. 4 . Feed roller  312  includes a feed roller shaft along its axis, and feed roller gear  311  is mounted on the feed roller shaft. Feed roller  312  can include a separate roller mounted on the feed roller shaft, or can include a thin high friction coating on the feed roller shaft. A rotary encoder (not shown) can be coaxially mounted on the feed roller shaft in order to monitor the angular rotation of the feed roller. A media end sensor  315  is positioned near feed roller  312  between turn roller  322  and feed roller  312  in order to detect when a sheet of media is approaching the feed roller  312 . In  FIG. 4 , the sheet  371  has pushed the media end sensor  315  down. 
         [0041]    Also schematically shown in  FIG. 4  is a duplexing unit  350  that includes a duplexing media path  351  for reversing the sheet  371  of media in order to print on a second side  373  of the sheet that is opposite first side  372 . As will be described in further detail below, in preferred embodiments of the present invention duplexing unit  350  is pivotably mounted in order to provide accessibility for clearing paper jams. In the preferred embodiments described below, a duplexing media path support member  335  is configured to face the pivotable duplexing unit  350  when the pivotable duplexing unit  350  is in a closed position. The portion of the duplexing media path  351  that is included in the pivotable duplexing unit  350  includes an inner guide member  352  that is adjacent the duplexing media support member  335  when the pivotable duplexing unit  350  is in a closed position; an inner cover member  354  that is adjacent the inner guide member  352 ; and an outer cover member  356  that is adjacent the inner cover member  354 . As can be seen in  FIG. 4 , the surface of inner guide member  352  has a first curvature near base  301 , and a second curvature farther from base  301 , where the second curvature has an opposite sense from the first curvature, so that the surface of inner guide member  352  is somewhat an inverted S-shape (or S-shaped as seen from the opposite perspective from the view shown in  FIG. 4 ). In addition, inner cover member  354  includes a curved surface and outer cover member  356  includes a curved surface, such that the curved surface of inner cover member  354  faces and is spaced apart from the curved surface of outer cover member  356 . 
         [0042]      FIGS. 5 to 7  show a sequence of positions of a sheet  371  of media as it approaches the duplexing unit  350  ( FIG. 5 ), travels through duplexing unit  350  until the end of sheet  371  reaches turn roller  322  ( FIG. 6 ), and is advanced by turn roller  322  toward feed roller  312  with second side  373  of sheet  371  now facing the print region  303  ( FIG. 7 ). In  FIG. 5 , feed roller  312  and discharge roller  324  are driven to rotate in reverse rotation direction  314  to move sheet  371  toward duplexing unit  350 . Media end sensor  315  continues to be pushed down by sheet  371 . 
         [0043]    In  FIG. 6  sheet  371  is still being moved by feed roller  312  (rotating in reverse rotation direction  314 ) through duplexing unit  350 , and the lead edge  375  of sheet  371  has just reached turn roller  322 . In preferred embodiments such as shown in  FIG. 6  and similar to the passive duplex unit described in U.S. Pat. No. 7,561,823, if the media path from the feed roller  312  through duplexing media path  351  and to turn roller  322  is sufficiently short relative to the length of the media, then no drive rollers are required in duplexing unit  350 . This is advantageous because no gears are required to provide power to a powered roller within duplexing unit  350 . In addition to saving cost and complexity, having no gears in the duplexing unit  350  that are required to mesh with gears in the main body of the printing apparatus makes it easier to close the pivotable duplexing unit  350  after it has been opened. In some preferred embodiments the media path from the feed roller  312  through duplexing media path  351  and to turn roller  322  is designed to be slightly shorter than 11 inches, so that both letter sized paper and A4 sized paper can be advanced through a duplexing unit  350  having no powered rollers within the duplexing unit. 
         [0044]    In  FIG. 7  lead edge  375  of sheet  371  has moved all the way through the duplexing media path  351  and is being advanced by turn roller  322  toward feed roller  312 . Since lead edge  375  has not yet reached media end sensor  315 , and trail edge  376  has been advanced past media edge sensor  315 , media edge sensor  315  is not pushed down by sheet  371  in  FIG. 7 . Having a single media edge sensor  315  provides an additional constraint on the length of a sheet of media that is compatible with duplexing unit  350 . In particular, the length of the sheet needs to be short enough that both lead edge  375  and trail edge  376  of sheet  371  cannot push media edge sensor  315  down at the same time. Otherwise the position of the sheet would be indeterminate, and the controller would not be able to determine when to change the direction of rotation of feed roller  312  from reverse rotation direction  314  to forward rotation direction  313  in order to advance lead edge  375  of sheet  371  to print region  303  in order to print second side  373 . 
         [0045]      FIG. 8  is a perspective view of printing apparatus  300  with a pivotable duplexing unit  350  in its open position according to a preferred embodiment of the invention. With reference to  FIG. 3 ,  FIG. 8  also includes covers over the printer chassis framework, and the perspective is from the rear  309  of the printing apparatus. Printing apparatus  300  includes a base  301  to support the printing apparatus during operation. A wall  319  extends at an angle from base  301 . In the example of  FIG. 8 , wall  319  is substantially perpendicular to base  301 . Pivotable duplexing unit  350  is attached to wall  319  using a hinge  340  having an axis  341  that is substantially perpendicular to base  301 . Duplexing unit  350  is pivotable about axis  341  in the directions indicated by the double headed curved arrow. Since the base  301  of printing apparatus  300  is substantially horizontal during operation, the axis  341  of hinge  340  is substantially vertical, unlike the horizontal hinges of the hinged duplexing units disclosed in U.S. Pat. Nos. 4,825,245, 4,884,110, 6,564,019 and 7,536,133 that were cited in the background. Thus, rather than pivoting upward or downward relative to the base  301 , pivotable duplexing unit  350  swings outward, sweeping out a path along a horizontal plane parallel to base  301 . Therefore pivotable duplexing unit  350  can be opened fully without interfering with the surface upon which base  301  rests, even though it is located close to the base  301 . Opening the pivotable duplexing unit  350  outward also does not result in the duplexing unit  350  obscuring visibility of media paths inside printing apparatus  300 . Thus the configuration of hinge  340  with its axis  341  perpendicular to base  301  is advantageous, especially for desktop printers having the duplexing unit located close to the base  301 . 
         [0046]      FIG. 8  shows part of the securing mechanism for holding pivotable duplexing unit  350  in its closed position as it is in  FIG. 10 . Located at the same end of pivotable duplexing unit  350  as hinge  340  are pegs  365 . When pivotable duplexing unit  350  is closed, pegs  365  enters holes  366  within the main body of printing apparatus  300 .  FIG. 9  is a view that is rotated relative to  FIG. 8  in order to show media input holder  316  and media output holder  318 . Pegs  365  and holes  366  are seen from a different perspective in  FIG. 9 . There is a peg (unlabeled, see 
         [0047]      FIG. 14 ) just above the labeled peg  365  and a hole (unlabeled, see  FIG. 11 ) just above the labeled hole  366  and corresponding to the unlabeled peg. 
         [0048]    Also shown in  FIG. 8  are items shown schematically in  FIGS. 4-7 , including duplexing media support member  335 , inner guide member  352 , inner cover member  354 , outer cover member  356  and pinch rollers  321 . Curved surfaces of duplexing media support member  335  and inner guide member  352  are shown as being ribbed, in order to reduce friction against media being advanced through duplexing unit  350 . Not shown in  FIG. 8  are the curved surfaces of inner cover member  354  or outer cover member  356 , or turn rollers  322 . Turn rollers  322  would line up with pinch rollers  321  when pivotable duplexing unit  350  is in a closed position, as it is in  FIG. 10 . Similarly, when pivotable duplexing unit is in a closed position, duplexing media support member  335  faces pivotable duplexing unit  350 . Like the auxiliary removable duplex unit disclosed in U.S. Pat. No. 7,561,823, there are no powered rollers in some preferred embodiments of the duplexing unit  350  such as the example of  FIG. 8 . Unlike the auxiliary removable duplex unit disclosed in U.S. Pat. No. 7,561,823, if the pivotable duplexing unit  350  is in its open position, media advance for one-sided printing will not operate properly, as the media being advanced by the pick roller  320  ( FIG. 4 ) would tend to exit through the open duplexing unit  350  without reaching turn roller  322 . 
         [0049]    In some multi-function printer embodiments a scanning apparatus (not shown) is assembled on top of the upper surface  333  of the cover of printing apparatus  300 , i.e. the scanning apparatus is located farther from the base than pivotable duplexing unit  350  is. When the scanning apparatus is pivoted upward from printing apparatus, the user can change ink tanks  262  and  264  ( FIG. 3 ) by reaching through access opening  334 . 
         [0050]      FIG. 11  is a close-up perspective view of the portion of printing apparatus  300  that includes the region of the hinge  340 , but with the pivotable duplexing unit hidden from view to show some details more clearly. In particular, wall, or housing,  319  includes a support member  342  of hinge  340 .  FIG. 12  shows a similar portion of printing apparatus  300 , but from a more downward looking perspective than  FIG. 11  in order to show the bearing surface  343  of support member  342  of hinge  340  for contacting an end of a pin member  344  ( FIG. 13 ). Also indicated in  FIG. 12  is a contact face  348  for contacting a round edge of pin member  344 . 
         [0051]      FIG. 13  is a perspective view of the pivotable duplexing unit  350 , but with printing apparatus  300  hidden from view. Features of pivotable duplexing unit  350  described above relative to  FIG. 8  are shown at higher magnification in  FIG. 13  for better clarity. Also shown in  FIG. 13  are the entry  358  through which sheets of media enter the duplexing unit  350  and the exit  359  from which sheets of media exit the duplexing unit  350 . In addition the pin member  344  of hinge  340  is shown. In the assembly view of  FIG. 8 , pin member  344  is not clearly seen, but with reference also to  FIGS. 11 and 12 , pin member  344  is for pivoting relative to support member  342  of hinge  340 . An end  345  of pin member  344  ( FIG. 13 ) makes pivotable contact with bearing surface  343  of support member  342  of hinge  340  ( FIG. 12 ). Also shown in  FIG. 12  are screw holes  349  for screws to secure pin member  344  into support member  342  of hinge  340 . 
         [0052]    As seen in  FIG. 13 , pivotable duplexing unit  350  includes a first end including at least one projection  360  for latching the pivotable duplexing unit  350  in a closed position, and a second end opposite the first end, where the second end includes the pin member  344  of the hinge  340  and a spring member  367  for biasing projection(s)  360  into corresponding hole(s)  361  ( FIG. 15 ) when pivotable duplexing unit  350  is in the closed position. The spring member can be attached to the duplexing unit by sliding it into a sleeve formed in the duplexing unit. Thus projection  360  serves as a latch and hole  361  serves as a catch for holding the pivotable duplexing unit in a closed position relative to the wall of the printing apparatus  360 . 
         [0053]      FIG. 14  is a close up view of the end of pivotable duplexing unit  350  that includes pin member  344 , spring member  367  and pegs  365 . Shown more clearly in  FIG. 14  is a D shape  346  of the end  345  of pin member  344 . A round portion  347  of the D shape  346  is in contact with contact face  348  of support member  342  of hinge  340  ( FIG. 12 ) when the pivotable duplexing unit  350  is latched in the closed position. The round portion  347  at the top of pin member  344  makes the contact described with the contact face  348  at the top of support member  342 , and similarly contact is made between the round portion  347  at the bottom of pin member  344  with the contact face  348  at the bottom of support member  342 . During unlatching, the pivotable duplexing unit  350  compresses spring member  367 , and allows projections  360  ( FIG. 13 ) to come out of corresponding holes  361  ( FIG. 15 ). When duplexing unit  350  is pivoted with an unlatching force so that round portion  347  is no longer in contact with contact face  348 , further freedom of movement is provided. h can also be seen in  FIG. 14  that pin member  344  is part of outer cover member  356 . The pivotable duplexing unit  350  and printer housing  319  and their components as described herein are typically formed by injection molding. 
         [0054]      FIG. 15  shows a perspective view of printing apparatus  300  rotated in order to show holes  361  that serve as catches for latch projections  360 .  FIG. 16  is a close-up view of pivotable duplexing unit  350  at the end including latch projections  360 . Comparing  FIGS. 15 and 16  it can be seen that inner guide member  352  of pivotable duplexing unit  350  includes a first end including a projection  360  for latching the pivotable duplexing unit  350  in a closed position relative to wall  319  of printing apparatus  300 , as well as a second end opposite the first end, where the second end includes a spring member  367  for biasing the projection  360  into a corresponding hole  361  when the pivotable duplexing unit  350  is in the closed position. It can also be seen that inner guide member includes a surface having a first curvature  353  (convex) near base  301 , and a second curvature (concave) farther away from base  301 , where the second curvature  355  has an opposite sense relative to the first curvature  353 . Furthermore it can be seen that the inner guide member  352  includes a pinch roller  321  for holding a sheet of media against turn roller  322  ( FIG. 4 ), where the pinch roller  321  is located near a portion of the surface having the second curvature  355 . 
         [0055]    In the preferred embodiments shown in  FIGS. 17-20 , inner guide member  352 , inner cover member  354  and outer cover member  356  of pivotable duplexing unit are shown as three separate units that are assembled together.  FIG. 17  shows outer cover member  356  and its curved surface  357  shown schematically in  FIGS. 4-7 . Curved surface  357  is ribbed to reduce friction against media passing through duplexing unit  350 .  FIG. 18  shows inner guide member  352  spaced apart from outer cover member  356 . Inner cover member  354  is hidden in this view in order to show latch  362  for affixing inner guide member  352  to inner cover member  354 .  FIG. 19  shows inner cover member  354  affixed to outer cover member  356  but with the inner guide member hidden in order to show catch  377  (corresponding to latch  362  of  FIG. 18 ) on inner cover member  354 .  FIG. 20  shows inner guide surface  352  affixed to inner cover member  352  but with the outer cover member hidden and from a perspective rotated relative to  FIG. 19 , so that curved surface  367  of inner cover member  354  (also shown schematically in  FIGS. 4-7 ) can be seen. Also shown in  FIG. 20  is a latch  363  for affixing inner cover member  354  to outer cover member  356 .  FIG. 20  also shows an optional duplexing advance roller  369  described in further detail below. 
         [0056]      FIG. 21  shows a perspective view of an preferred embodiment of inner guide member  352  from the same viewing angle as in  FIG. 20 , but with inner cover member  354  and outer cover member  356  hidden in order to show mounts  364  for pinch rollers  321 . In this particular preferred embodiment, a friction wheel  368  is provided to transmit power from a pinch roller  321  to drive a duplexing advance roller  369 . In this way a simple powered roller can be provided for moving a sheet of media through the duplexing unit without requiring gears for transmitting power to the roller. 
         [0057]    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. In particular, although embodiments were described with regard to inkjet printers, the invention is applicable to other types of printing apparatus as well. 
       PARTS LIST 
       [0000]    
       
           10  Inkjet printer system 
           12  Image data source 
           14  Controller 
           15  Image processing unit 
           16  Electrical pulse source 
           18  First fluid source 
           19  Second fluid source 
           20  Recording medium 
           100  Inkjet printhead 
           110  Inkjet printhead die 
           111  Substrate 
           120  First nozzle array 
           121  Nozzle(s) 
           122  Ink delivery pathway (for first nozzle array) 
           130  Second nozzle array 
           131  Nozzle(s) 
           132  Ink delivery pathway (for second nozzle array) 
           181  Droplet(s) (ejected from first nozzle array) 
           182  Droplet(s) (ejected from second nozzle array) 
           200  Carriage 
           250  Printhead chassis 
           251  Printhead die 
           253  Nozzle array 
           254  Nozzle array direction 
           256  Encapsulant 
           257  Flex circuit 
           258  Connector board 
           262  Multi-chamber ink tank 
           264  Single-chamber ink tank 
           300  Printing apparatus 
           301  Base 
           302  Paper load entry direction 
           303  Print region 
           304  Media advance direction 
           305  Carriage scan direction 
           306  Right side of printing apparatus 
           307  Left side of printing apparatus 
           308  Front of printing apparatus 
           309  Rear of printing apparatus 
           310  Hole (for paper advance motor drive gear) 
           311  Feed roller gear 
           312  Feed roller 
           313  Forward rotation direction (of feed roller) 
           314  Reverse rotation direction (of feed roller) 
           315  Media end sensor 
           316  Media input holder 
           317  Inclined guide 
           318  Media output holder 
           319  Wall 
           320  Pick roller 
           321  Pinch roller 
           322  Turn roller 
           323  Idler roller 
           324  Discharge roller 
           325  Star wheel(s) 
           330  Maintenance station 
           333  Upper surface 
           334  Access opening 
           335  Duplexing media support member 
           340  Hinge 
           341  Axis (of hinge) 
           342  Support member (of hinge) 
           343  Bearing surface 
           344  Pin member (of hinge) 
           345  End (of pin member) 
           346  D shape (of end of pin member) 
           347  Round portion (of D shape) 
           348  Contact face (of support member  342 ) 
           349  Screw holes 
           350  Duplexing unit 
           351  Duplexing media path 
           352  Inner guide member 
           353  First curvature (of inner guide member) 
           354  Inner cover member 
           355  Second curvature (of inner guide member) 
           356  Outer cover member 
           357  Curved surface (of outer cover member) 
           358  Entry (to duplexing unit) 
           359  Exit (from duplexing unit) 
           360  Projection (latch) 
           361  Hole (catch) 
           362  Latch (for affixing inner guide member to inner cover member) 
           363  Latch (for affixing inner cover member to outer cover member) 
           364  Mount(s) (for pinch rollers) 
           365  Peg 
           366  Hole (for peg) 
           367  Curved surface (of inner cover member) 
           368  Friction wheel 
           369  Duplexing advance roller 
           370  Stack of media 
           371  Top sheet of medium 
           372  First side (of sheet) 
           373  Second side (of sheet) 
           375  Lead edge (of sheet) 
           376  Trail edge (of sheet) 
           377  Catch (corresponding to latch  362 ) 
           380  Carriage motor 
           382  Carriage guide rail 
           383  Encoder fence 
           384  Belt 
           390  Printer electronics board 
           392  Cable connectors