Patent Abstract:
A mid-frame for use in an imaging apparatus includes an undulating surface extending in an undulation direction. At least one elongated slot can be formed in the mid-frame, wherein a direction of elongation of the elongated slot is substantially the same direction as the undulation direction.

Full Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an imaging apparatus, and, more particularly, to a mid-frame for use with an imaging apparatus. 
   2. Description of the Related Art 
   With the advent of edge-to-edge printing, also known as borderless printing, various attempts have been made to reduce the occurrence of ink contamination of the printer mid-frame. As used herein, the term “mid-frame” refers to the supporting structure of the printer positioned opposed to the printing mechanism to provide support for the printing medium. In an ink jet printer, the printing mechanism is typically a printhead including a plurality of ink jetting nozzles. 
   A typical ink jet printer forms an image on a print medium by ejecting ink from the plurality of ink jetting nozzles to form a pattern of ink dots on the print medium. The printhead may include a plurality of nozzle arrays, such as a cyan array, a magenta array, and a yellow array, arranged as a longitudinal column of nozzle arrays. Such an arrangement of nozzle arrays will be referred to herein as “stacked nozzle arrays.” 
   Such an ink jet printer typically includes a reciprocating printhead carrier that transports one or more ink jet printheads across the print medium along a bi-directional scanning path defining a print zone of the printer. Typically, the mid-frame provides media support at or near the print zone. The bi-directional scanning path is oriented parallel to a main scan direction, also commonly referred to as the horizontal direction. The main scan direction is bi-directional. During each scan of the printhead carrier, the print medium is held stationary. An indexing mechanism is used to incrementally advance the print medium in a sheet feed direction, also commonly referred to as a sub-scan direction or vertical direction, through the print zone between scans in the main scan direction, or after all data intended to be printed with the print medium at a particular stationary position has been completed. 
   During printing, if wet ink accumulates on the mid-frame, then a subsequent sheet of print media will contact the accumulated ink, thereby smearing ink on the underside of the sheet of print media. In a conventional ink jet printer that does not accommodate edge-to-edge printing, the print engine controls printing so as to prevent the ejection of ink onto the leading, trailing, and side edge portions of the sheet of print media. In this manner, sheet margins are created on the medium sheet, which in turn protect the upper surface of the supporting mid-frame from ink contamination. 
   In order to accommodate edge-to-edge printing in the conventional printer, special media can be used that includes perforated tabs. With this arrangement, if a user desired a borderless print, the user would merely separate the perforated tab from the remaining portion of the medium stock carrying the print image. 
   In order to avoid the necessity of using special print media, further attempts have been made to accommodate edge-to-edge printing using regular, non-perforated, print media. One such attempt is to provide a hollowed out area located in the mid-frame in a region opposite to the printhead to collect ink that is discharged at the leading and trailing edge portions of the sheet of print media. An absorbent material is located in the hollowed out area to absorb the ink ejected thereon. A front set and a rear set of upstanding cockle ribs are positioned on each side of the hollowed out area, respectively, and extend upwardly from the mid-frame a sufficient distance to substantially prevent either a leading edge or a trailing edge of a sheet of print medium traveling across a print zone within the printer from making contact with the absorbent material. As the longitudinal extent of the printhead increases to accommodate more printing nozzles, such as in the case of stacked nozzle arrays, such a mid-frame design requires that the trough become wider. However, as the trough becomes wider, the risk that the sheet will bow and contact the accumulated waste ink increases. 
   What is needed in the art is a mid-frame design having improved surface characteristics. Preferably, such a mid-frame can accommodate edge-to-edge printing, and can accommodate printheads, for example having stacked nozzle arrays, without widening the extent of an individual waste ink collection opening in the mid-frame in a sheet feed direction. 
   SUMMARY OF THE INVENTION 
   The present invention provides a mid-frame design having improved surface characteristics. In a preferred embodiment, the mid-frame can accommodate edge-to-edge printing, and can accommodate printheads, for example having stacked nozzle arrays, without widening the extent of an individual waste ink collection opening in the sheet feed direction. 
   In one form thereof, the present invention relates to a mid-frame for use in an imaging apparatus, the imaging apparatus defining a sheet feed direction. The mid-frame includes a mid-frame surface for supporting a print medium sheet. The mid-frame includes a first opening for receiving first waste ink, and a second opening spaced from the first opening in the sheet feed direction, the second opening for receiving second waste ink. 
   In another form thereof, the present invention relates to a mid-frame for use in an imaging apparatus, wherein the mid-frame includes an undulating surface for supporting a print medium sheet. The undulating surface is oriented so that the undulating occurs in an undulation direction substantially perpendicular to a sheet feed direction. 
   In still another form thereof, the present invention relates to a mid-frame for use in an imaging apparatus. The mid-frame includes an undulating surface extending in an undulation direction. At least one elongated slot is formed in the mid-frame, wherein a direction of elongation of the elongated slot is substantially the same direction as the undulation direction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of one embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a pictorial representation of a portion of an ink jet printer; 
       FIG. 2  is a pictorial representation of a side view of the ink jet printer of  FIG. 1 , wherein the mid-frame is shown in section; 
       FIG. 3  is a top view of the mid-frame of  FIG. 2 ; 
       FIG. 4  is an end view of the mid-frame of  FIG. 2 ; and 
       FIG. 5  is a perspective view of the mid-frame of FIG.  2 . 
   

   Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings and particularly to  FIGS. 1 and 2 , there is shown a printer  10  including a printhead carrier system  12 , a feed roller unit  14 , an exit roller unit  16 , a controller  18  and a mid-frame  20 . Controller  18 , which includes a microprocessor with associated random access memory (RAM) and read only memory (ROM), executes program instructions to effect the generation of control signals which are supplied to printhead carrier system  12 , feed roller unit  14 , and exit roller unit  16  to effect the printing of an the image on a print medium sheet  22 , such as paper. 
   Printhead carrier system  12  includes a printhead carrier  24  for carrying a color printhead  26  and a black printhead  28 . A color ink reservoir  30  is provided in fluid communication with color printhead  26 , and a black ink reservoir  32  is provided in fluid communication with black printhead  28 . Printhead carrier system  12  and printheads  26 ,  28  may be configured for unidirectional printing or bi-directional printing. 
   Printhead carrier  24  is guided by a pair of guide rods  34 . The axes  34   a  of guide rods  34  define a bi-directional scanning path for printhead carrier  24 , and thus, for convenience the bi-directional scanning path will be referred to as bi-directional scanning path  34   a . Printhead carrier  24  is connected to a carrier transport belt  35  that is driven by a carrier motor  36  via driven pulley  38  to transport printhead carrier  24  in a reciprocating manner along guide rods  34 . Carrier motor  36  can be, for example, a direct current (DC) motor or a stepper motor. Carrier motor  36  has a rotating carrier motor shaft  36   a  that is attached to carrier pulley  38 . 
   The reciprocation of printhead carrier  24  transports ink jet printheads  26 ,  28  across a print medium sheet  22 , such as paper, along bi-directional scanning path  34   a  to define a print zone  40  of printer  10 . This reciprocation occurs in a main scan direction  42  that is parallel with bi-directional scanning path  34   a , and is also commonly referred to as the horizontal direction. During each scan of printhead carrier  24 , print medium sheet  22  is held stationary by feed roller unit  14  and/or exit roller unit  16 . 
   Feed roller unit  14  includes an index roller  44  and a corresponding index pinch roller  46 . Exit roller unit  16  includes an exit roller  48  and a corresponding exit pinch roller  50 . In the embodiment shown, index roller  44  and exit roller  48  are driven rollers that are driven by a drive unit  52 . Pinch rollers  46  and  50  are idler rollers, and apply a biasing force to hold the print medium sheet  22  in contact with their respective driven rollers  44 ,  48 . Drive unit  52  includes a drive source, such as a stepper motor, and an associated drive mechanism, such as a gear train or belt/pulley arrangement. 
   During operation, index roller  44  incrementally advances print medium sheet  22  in a sheet feed direction  54 , toward and into a print zone  40  across mid-frame  20 . As shown in  FIG. 1 , sheet feed direction  54  is depicted as an X within a circle to indicate that the sheet feed direction is in a direction perpendicular to the plane of  FIG. 1 , toward the reader. Sheet feed direction  54  is substantially perpendicular to main scan direction  42 , and in turn, substantially perpendicular to bi-directional scanning path  34   a . Once print medium sheet  22  is released from the nip formed by index roller  44  and index pinch roller  46 , exit roller  48  is controlled to continue the incremental advancement of print medium sheet  22  through print zone  40 , and ultimately expels print medium sheet  22  into an exit tray  56 . 
   Referring now to  FIGS. 2 ,  3  and  4 , mid-frame  20  includes a base  58 , a mid-frame surface  60 , a first trough  62 , a second trough  64  and a third trough  66 . 
   Mid-frame surface  60  provides support for print medium sheet  22  as print medium sheet  22  is transported through print zone  40  by index roller  44  and/or exit roller  48 . 
   First trough  62  defines a first opening  68  for receiving and collecting waste ink ejected from printhead nozzle array  26   a , for example a cyan array, that is not ejected on print medium sheet  22 . Second trough  64  is spaced from first trough  62  in sheet feed direction  54 , and defines a second opening  70  for receiving and collecting waste ink ejected from printhead nozzle array  26   b , for example a magenta array, that is not ejected on print medium sheet  22 . Third trough  66  is spaced from second trough  64  in sheet feed direction  54 , and defines a third opening  72  for receiving and collecting waste ink ejected from printhead nozzle array  26   c , for example a yellow array, that is not ejected on print medium sheet  22 . 
   As shown in  FIG. 3 , each of first opening  68 , second opening  70  and third opening  72  may be formed as an elongated slot, with the direction of elongation corresponding to main scan direction  42 . Preferably, an extent of each of first opening  68 , second opening  70  and third opening  72  in main scan direction  42  is longer than a width W of print medium sheet  22  in main scan direction  42 . Also, an extent of each of first opening  68 , second opening  70  and third opening  72  in sheet feed direction  54  is slightly wider than a height H of the corresponding printhead nozzle array  26   a ,  26   b  and  26   c , respectively, in sheet feed direction  54 . 
   Referring to  FIGS. 2 and 3 , first trough  62 , second trough  64  and third trough  66  extend upwardly from base  58 . As shown, first opening  68  is separated from second opening  70  by a first partition  74  extending upwardly from base  58 . Second opening  70  is separated from third opening  72  by a second partition  76  extending upwardly from base  58 . Accordingly, trough  62  is defined by base  58 , first partition  74  and a first wall  78 ; trough  64  is defined by base  58 , first partition  74  and second partition  76 ; and, trough  66  is defined by second partition  76  and a second wall  80 . It is recognized that troughs  62 ,  64 ,  66  may have a common sidewalls, as shown in FIG.  3 . Alternatively, individual sidewalls can be provided for each of troughs  62 ,  64 ,  66 . 
   As shown in  FIG. 5 , one or more of troughs  62 ,  64 ,  66  can have positioned therein an absorption pad  82  having hydrophilic properties for absorbing waste inks received into the respective troughs. In a preferred embodiment, each of troughs  62 ,  64 ,  66  include an absorption pad, such as absorption pad  82 . 
   Mid-frame surface  60 , which is continuous in main scan direction  42 , is interrupted in sheet feed direction  54  by first opening  68 , second opening  70  and third opening  72  to define a plurality of mid-frame surface sections  60   a ,  60   b ,  60   c  and  60   d  (see FIG.  5 ). As can be best seen in  FIGS. 4 and 5 , mid-frame surface  60 , excluding first opening  68 , second opening  70  and third opening  72 , defines a undulating surface that undulates in an undulation direction corresponding to main scan direction  42 . A profile of undulating mid-frame surface  60 , as shown in  FIG. 4 , has a substantially sinusoidal shape. However, it is contemplated as a part of the invention that other profiles having a mathematically continuous shape, i.e., not having a portion having an infinite slope, could be substituted for the sinusoidal shape. Also, it is contemplated that portions of the continuous undulation in the undulation direction  42  could be replaced with one or more regions of discontinuity. 
   In the preferred embodiment as shown  FIGS. 2 and 5 , mid-frame surface sections  60   a ,  60   b ,  60   c  and  60   d  of mid-frame surface  60  define continuous undulating surfaces. In addition, mid-frame surface sections  60   a ,  60   b ,  60   c  and  60   d  of mid-frame surface  60  can include an inclined portion, wherein the incline of the inclined portion rises in an inclination direction, corresponding to sheet feed direction  54 . As shown, the undulating surface of mid-frame surface  60  comprises a substantial portion, e.g., greater than 80 percent, of a surface area of mid-frame  20 . Also, as shown, the undulating surface of undulating mid-frame surface  60  is present on each side of openings  68 ,  70  and  72  in a direction substantially perpendicular to the undulation direction, i.e., in sheet feed direction  54 . 
   While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Technology Classification (CPC): 1