Patent Publication Number: US-7224493-B2

Title: Imaging apparatus having a media sensor

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an imaging apparatus, and, more particularly, to an imaging apparatus having a media sensor. 
   2. Description of the Related Art 
   Media sensors are used to detect the presence or absence of print media, and in some cases, are also used to determine the print media type. One form of a media sensor includes a single light source, such as a light emitting diode (LED), and a light detector, such as a phototransistor. Typically, the light detector is located on the same side of a print media as the light source. During operation, the LED directs light at a predefined angle onto a material surface of the print media, and the surface characteristics of the print media are examined in terms of the amount of light reflected from the surface that is received by the light detector. For example, the presence of the print media is detected based upon a predetermined amount of light reflected from the media to the light detector. 
   Some media sensors include a pair of light detectors, one of the light detectors being positioned to sense reflected diffuse light and a second detector positioned to sense reflected specular light. Such a sensor may be used, for example, to detect and discriminate between paper media and transparency media. 
   A media sensor that contacts directly a surface of a print media sheet is known in the art as a contact media sensor. Often, the contact media sensor is spring biased to be in contact with the media surface. Typically, such a contact media sensor includes a skid surface which slides along the surface of a print media sheet as the print media sheet advances in a sheet feed direction. The friction created by the contact of the skid surface of the contact media sensor and the surface of the print media sheet often permanently marks or scuffs the surface of the print media sheet. 
   What is needed in the art is an imaging apparatus configured to reduce or eliminate the marking or scuffing of a surface of a print media sheet resulting from contact between a media sensor and the surface of the print media sheet. 
   SUMMARY OF THE INVENTION 
   The present invention relates to an imaging apparatus configured to reduce or eliminate the marking or scuffing of a surface of a print media sheet resulting from contact between a media sensor and the surface of the print media sheet. 
   The invention, in one form thereof, is directed to an imaging device having a print media path for transporting a print media sheet in a sheet feed direction. The imaging device includes a frame. A mounting device is coupled to the frame. A media sensor has a body and at least one rotating member rotatably coupled to the body. The body is coupled to the mounting device. The mounting device is configured to facilitate movement of the media sensor in a direction toward the media path and to restrain movement of the media sensor in the sheet feed direction. The media sensor is positioned by the mounting device such that at least one rotating member rotates due to contact with a surface of the print media sheet as the print media sheet moves relative to the media sensor in the sheet feed direction along the print media path. 
   In another form thereof, the invention is directed to an imaging apparatus including a frame and a print media source coupled to the frame. The print media source includes a media support defining, in part, a print media path along which a print media sheet is transported in a sheet feed direction. A mounting device is coupled to the frame. A media sensor has a body and at least one rotating member rotatably coupled to the body. The body is coupled to the mounting device. The mounting device is configured to facilitate movement of the media sensor in a direction toward the media support and to restrain movement of the media sensor in the sheet feed direction. The media sensor is positioned by the mounting device such that at least one rotating member rotates due to contact with a surface of the print media sheet as the print media sheet moves relative to the media sensor in the sheet feed direction. 
   An advantage of the present invention is that the media surface that is contacted by the media sensor is less likely to be marked or scuffed as a result of such contact. 

   
     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 embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a diagrammatic representation of an imaging system including an imaging apparatus embodying the present invention. 
       FIG. 2  is a side diagrammatic representation of a portion of the imaging apparatus depicted in  FIG. 1 . 
       FIG. 3  is a bottom view of one embodiment of a media sensor used in the imaging apparatus of  FIGS. 1 and 2 . 
       FIG. 4  is a bottom view of another embodiment of a media sensor used in the imaging apparatus of  FIGS. 1 and 2 . 
   

   Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate preferred embodiments of the invention, 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 an imaging system  6  embodying the present invention. Imaging system  6  includes a computer  8  and an imaging device in the form of an ink jet printer  10 . Computer  8  is communicatively coupled to ink jet printer  10  via a communications link  11 . Communications link  11  may be, for example, a direct electrical or optical connection, or a network connection. 
   Computer  8  is typical of that known in the art, and includes a display, an input device, e.g., a keyboard, a processor, and associated memory. Resident in the memory of computer  8  is printer driver software. The printer driver software places print data and print commands in a format that can be recognized by ink jet printer  10 . The format can be, for example, a data packet including print data and printing commands for a given area, such as a print swath, and including a print header that identifies the swath data. 
   Ink jet printer  10  includes a printhead carrier system  12 , a feed roller unit  14 , a media sensor assembly  16 , a controller  18 , a mid-frame  20  and a media source  22 . 
   Media source  22 , such as a paper tray, is configured and located to supply individual print media sheets  23  to feed roller unit  14 , which in turn further transports the print media sheets  23  during a printing operation. 
   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 members  34 . Each of guide members  34  may be, for example, a guide rod or a guide rail. The axes  36  of guide members  34  define a bi-directional scanning path  36  for printhead carrier  24 . Printhead carrier  24  is connected to a carrier transport belt  38  that is driven by a carrier motor  40  via a carrier pulley  42 . Carrier motor  40  has a rotating carrier motor shaft  44  that is attached to carrier pulley  42 . At the directive of controller  18 , printhead carrier  24  is transported in a reciprocating manner along guide members  34 . Carrier motor  40  can be, for example, a direct current (DC) motor or a stepper motor. 
   The reciprocation of printhead carrier  24  transports ink jet printheads  26 ,  28  across the print media sheet  23 , such as paper, along bi-directional scanning path  36  to define a two-dimensional, e.g., rectangular, print zone  50  of printer  10 . This reciprocation occurs in a main scan direction  52 . The print media sheet  23  is transported in a sheet feed direction  54 . In the orientation of  FIG. 1 , the sheet feed direction  54  is shown as flowing down media source  22 , and toward the reader (represented by an X) along mid-frame  20 . Main scan direction  52 , which is commonly referred to as the horizontal direction, is parallel with bi-directional scanning path  36  and is substantially perpendicular to sheet feed direction  54 , which is commonly referred to as the vertical direction. During each scan of printhead carrier  24 , the print media sheet  23  is held stationary by feed roller unit  14 . 
   Referring also to  FIG. 2 , feed roller unit  14  includes a feed roller  56  and corresponding pinch rollers  58 . Feed roller  56  is driven by a drive unit  60  ( FIG. 1 ). Feed pinch rollers  58  apply a biasing force to hold the print media sheet  23  in contact with respective driven feed roller  56 . Drive unit  60  includes a drive source, such as a stepper motor, and an associated drive mechanism, such as a gear train or belt/pulley arrangement. Feed roller unit  14  feeds the print media sheet  23  along a print media path  55  in a sheet feed direction  54  (see  FIGS. 1 and 2 ). 
   Controller  18  is electrically connected to printheads  26  and  28  via a printhead interface cable  62 . Controller  18  is electrically connected to carrier motor  40  via an interface cable  64 . Controller  18  is electrically connected to drive unit  60  via an interface cable  66 . Controller  18  is electrically connected to media sensor assembly  16  via an interface cable  68 . 
   Controller  18  includes a microprocessor having an associated random access memory (RAM) and read only memory (ROM). Controller  18  executes program instructions to effect the printing of an image on the print media sheet  23 , which can be one or more media types, such as coated paper, plain paper, photo paper and transparency. In addition, controller  18  executes instructions to conduct media sensing, such as detecting the presence or absence of the print media sheet  23 , or the determination of media type, based on information received from media sensor assembly  16 . 
     FIG. 2  includes a broken out section that is enlarged in relation to the other components of  FIG. 2  to more clearly show the components of media sensor assembly  16 . Media sensor assembly  16  is rotatably coupled to a frame  70  of ink jet printer  10 . Also, media source  22  is attached, at least in part, to frame  70 . Media source  22  includes a media support  72  including a media support surface  74 . In the embodiment shown, media sensor assembly  16  is located upstream of print zone  50 , and more particularly, adjacent to media source  22   
   Media sensor assembly  16  includes a mounting device  78  and a media sensor  80 . Media sensor assembly  16  is coupled to frame  70  via mounting device  78 . Mounting device  78  includes a pivot arm  82  that is pivotably attached to frame  70  via a pivot rod  84 , and is pivotably attached to media sensor  80  via pivot pins  86 . A spring  90  provides a biasing force to pivot media sensor assembly  16  about axis  92  in the direction indicated by arrow  94 . In an alternative arrangement, sensor assembly  16  may be biased simply by the forces of gravity. Thus, mounting device  78  is configured to facilitate movement of media sensor  80  in a direction  88  toward print media path  55 , and more particularly, toward media support  72 , and to restrain movement of media sensor  80  in sheet feed direction  54 . 
   Media sensor assembly  16  includes a body  100  and at least one rotating member  102 , such as for example, one or more wheels. Media sensor  80  is positioned by mounting device  78  such that each rotating member  102  rotates due to contact with a surface  104  of print media sheet  23  as print media sheet  23  moves relative to media sensor  80  in sheet feed direction  54  along print media path  55 . 
   Contained within body  100  are the electrical sensory components, such as for example, a light source, a specular detector and/or a diffuse detector, the configuration and operation of which is known in the art. In its simplest form, the light source may include, for example, a light emitting diode (LED). In a more complex form, the light source may further include additional optical components for generating a collimated light beam. Each of the specular detector and/or the diffuse detector can be, for example, a phototransistor. 
     FIG. 3  shows a bottom view of one embodiment of media sensor  80 , which is adadpted to include a pair of rotating members  102 , individually identified as rotating member  102   a  and  102   b . Rotating members  102   a ,  102   b  include a wheel  106  and  108 , respectively, rotatably coupled to body  100  via an axle  110  and  112 , respectively. Wheels  106 ,  108  may be configured to rotate about their respective axles  110 ,  112 . Alternatively, wheel  106  and axle  110  may form a unitary structure, and wheel  108  and axle  112  may form a unitary structure, with each of axles  110 ,  112  rotating within corresponding recesses formed in body  100 . 
     FIG. 4  shows a bottom view of another embodiment of media sensor  80 , which is adapted to include two rotating members  102 , individually identified as rotating members  102   c  and  102   d . Rotating member  102   c  includes coaxial wheels  116  and  118 , rotatably coupled to body  100  via an axle  120 . Rotating member  102   d  includes coaxial wheels  126  and  128 , rotatably coupled to body  100  via an axle  130 . Wheels  116 ,  118  may be configured to rotate about axle  120 . Alternatively, wheels  116 ,  118  may be affixed to axle  120  to form a unitary structure, with axle  120  rotating within corresponding recesses formed in body  100 . Likewise, wheels  126 ,  128  may be configured to rotate about axle  130 . Alternatively, wheels  126 ,  128  may be affixed to axle  130  to form a unitary structure, with axle  130  rotating within corresponding recesses formed in body  100 . As a further alternative, each of wheels,  116 ,  118 ,  126 ,  128  may be rotatably coupled to body  100 , for example, by respective stub axles that extend outwardly from body  100 . 
   While this invention has been described with respect to preferred embodiments, 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.