Abstract:
Drag from media sensor ( 80 ) of a printer is eliminated by it being pivoted through a slip connection off of pivoted media feed system ( 19 ) to briefly contact papers. The pivoted media feed is then moved in reverse a limited amount at which a rotatably biased member ( 94 ) moves ledge ( 94   a ) of the member to face abutment surface ( 92   a ) of the media sensor. Media feed system  19  is then moved back to drive media while the media sensor is blocked from movement and the slip connection simply slips. After the media is fed, the media feed system is moved away a longer amount while the media sensor is blocked against for the same movement by an abutment ( 110 ) in the printer. The media feed system after the longer movement moves a lever ( 94   f ) of the biased member and rotates the ledge to free the media sensor to again move to the media.

Description:
TECHNICAL FIELD 
   This invention relates to imaging devices that feed media over a paper path and sense the media in the paper path with a sensor. 
   BACKGROUND OF THE INVENTION 
   Media sensors are known which reliably determine the difference between coated, plan, photo and transparency media types. These sensors contact the media with significant force and have been located in the media tray from which media is fed into a media feed path to reach an imaging station. 
   However, the media sensor pressing onto the surface of paper or other media creates a small amount of drag which can affect paper pick and feed adversely on some types of media, such as small media. Marks on the surface of photo paper made by drag on the media sensor may also occur. 
   Where the media sensor is located in the media path between the tray and the imaging station the problem of skew of small media becomes very significant. Accordingly, eliminating drag from contact with the media sensor is very desirable. 
   DISCLOSURE OF THE INVENTION 
   This invention employs a mechanical system having a pivoted feed system located at an intermediate location proximate to the feed path. (In an embodiment, a pivoting autocompensating system which comprises one or more feed rollers on a swing arm pivoted around a gear train which drives the feed roller. Autocompensating systems are cost-effective and may be moved toward the media for feeding and off the media by reversing the torque to the gear train.) 
   The media sensor is pivotably mounted to move through a slip connection from the pivoted feed system. Movement of the media sensor away from the media in the feed path is limited by an abutment of the imaging device. Movement of the pivoted feed system away from media in the feed path can be longer, thereby moving the pivoted feed system further while the media sensor slips at the slip connection. 
   When media first reaches the location of the media sensor, the pivoted feed system is further away from the paper path than the media sensor and the media sensor is free to move forward. Movement of the pivoted feed system moves the media sensor to the media through the slip connection. The sensing can take very little time. The pivoted feed system is then moved a limited amount away from the media. 
   A resiliently mounted latching member having a ledge is mounted on the frame of the imaging device. An abutment surface on the media sensor faces the ledge when the media sensor is moved a limited amount away from the media. After the limited movement away from the media, the pivoted feed system is moved forward to drive media while the sensing member is latched by contact between the abutment surface and the ledge from moving forward and the slip connection slips. 
   After the media is moved the pivoted feed system is moved away from the media feed location until it is past the limited movement location, were it encounters an arm of the latching member, which moves the ledge from facing the abutment surface of the media sensor. This frees the media sensor and permits the foregoing cycle to be repeated from the next media fed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The details of this invention will be described in connection with the accompanying drawings, in which 
       FIG. 1  is a printer and is illustrative of a long, C-shaped path between a paper tray and the imaging printhead, 
       FIG. 2  is a partial, somewhat more detailed, perspective view downward on the tray and the front guide. 
       FIG. 3  is a view from the same side as the view of  FIG. 2  of the motor and gear train to the autocompensating systems. 
       FIG. 4  is a view from the side opposite the view of  FIG. 2  of motor and gear trains to the autocompensating systems. 
       FIG. 5  illustrates the autocompensating systems in some detail and the drive path between tray and nip roller preceding the imaging station. 
       FIG. 6  is a perspective view of selected elements to explain the slip drive. 
       FIG. 7  is a perspective view of selected elements from the side opposite to that of  FIG. 6  to explain the slip drive. 
       FIG. 8  is a perspective view of the media sensor and the pivoted drive mechanism. 
       FIG. 9  is an exploded, somewhat different perspective view from  FIG. 8  illustrating the slip connection. 
       FIG. 10  is a side view with the media sensor in position for sensing. 
       FIG. 11  is side view with the media sensor latched against rotation. 
       FIG. 12  is a side view with the autocompensating system in position to drive media; and 
       FIG. 13  is a side view with the autocompensating system moved fully back to free the media sensor for rotation. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is illustrative of a printer  1  with specific elements pertinent to this invention. Printer  1  may be a standard inkjet printer in most respects. As such it has a bottle printhead  3  which jets dots of ink through nozzles not shown, which are located above a sheet  5  of paper or other media at a imaging station  7   
   Imaging station  7  is located past nip rollers  9   a ,  9   b  which grasp paper  5  in the nip of rollers  9   a ,  9   b  and move it under printhead  3 . Nip rollers  9   a ,  9   b  are stopped normally several times to permit printhead  3  to partially image sheet  5  by moving across sheet  5  (in and out of the view of  FIG. 1 ) while expelling dots in the desired pattern. In a draft mode the number of such intermittent stops may be only two, while in a quality mode that number may be five or more. 
   Nip rollers  9   a ,  9   b  push paper through the imaging station  7  where they enter exits rollers  11   a ,  11   b ,  11   c , and  11   d . Although rollers are by far the most common mechanism to transport the imaged sheet  5  out of the printer  1  to the user of the printer  1 , virtually any grasping device can be used, such as a belt and pressing device or pneumatic suction device. 
   The printer of  FIG. 1  has a paper tray  13  located on the bottom Tray  13  constitutes a bin in which a stack of paper or other media sheets  5  are held to be imaged. Having tray  13  located on the bottom of printer  1  permits a large stack of sheets  5  to be in the printer  1 . This spaces the tray  13  from the print stations  7 , the distance from pick roller  15   a  of tray  13  to nip rollers  9   a ,  9   b  being longer than the length of some media sheets  5  to be printed. Pick roller  15   a  is a part of an autocompensating swing mounted system  15 . 
   A C-shaped paper guide  17  is made up of rear guide surface  17   a  and spaced, generally parallel, front guide surface  17   b . Both surfaces have spaced ridges (shown for surface  17   b  as  17   bb  in  FIG. 2 ), as is common. Guide  17  directs a sheet  5  to nip rollers  9   a ,  9   b . Intermediate in guide  17  is drive roller  19   a , which is a part of an autocompensating swing-mounted system  19 . Sensor arm  21  is moved by a sheet  5  to detect the sheet  5  at system  19 . 
   Pick roller  15   a  at tray  13  and drive roller  19   a  combine to move sheets  5  from tray  13  to nip rollers  9   a ,  9   b . Drive roller  19   a  is effective to move short media into rollers  9   a ,  9   b , when pick roller  15   a  is no longer in contact with the sheet  5 . 
   Operational control is by electronic data processing apparatus, shown as element C in  FIG. 1 . Such control is now entirely standard. A standard microprocessor may be employed, although an Application Specific Integrated Circuit (commonly known as an ASIC) is also employed, which is essentially a special purpose computer, the purpose being to control all actions and timing of printer  1 . Electronic control is so efficient and versatile that mechanical control by cams and relays and the like is virtually unknown in imaging. However, such control is not inconsistent with this invention. 
   Movement of parts in the printer is by one motor  30 , shown in  FIGS. 2 ,  3  and  4 . With respect to  FIG. 3  motor  30  is seen to drive a large gear  32  through a pulley  34 . Gear  32  has integral with it a central, smaller gear  32   a . The gear  32  is meshed with large gear  36 , which is integral with shaft  38  to provide torque to autocompensating system  15 . 
   Similarly, gear  32   a  meshes with idler gear  40  which meshes with a somewhat larger gear  42 . Gear  42  has integral with it a central, smaller gear  42   a  (best seen in  FIG. 4 ). Gear  42   a  is meshed with gear  44 , which is integral with splined shaft  46  to provide torque to autocompensating system  19 . 
   As is evident from the gears trains, rotation of motor  30  counterclockwise as viewed in  FIG. 3  applies a downward torque (as discussed below) to autocompensating system  15  and an upward torque (as discussed below) to autocompensating system  19 . Rotation of motor  30  clockwise reverses the direction of torque to both system  15  and system  19 . 
     FIGS. 3 and 4  also illustrate a roller  48 , which is mounted to roll free, which drive roller  19   a  contacts when driving should no media sheet  5  be under roller  19   a , which avoids a high downward torque being generated. With respect to roller  15   a  in the tray  13 , no comparable apparatus to roller  48  is used as the high torque can be used to signal absence of paper and therefore to terminate drive to autocompensating system  15 . 
   With reference to  FIG. 5 , autocompensating system  15  is seen to have four meshed gears  50 ,  52 ,  54  and  56  each meshed to the next gear in a linear train and supported within a bracket  58 . Gear  56  is integral with drive roller  15   a  so that it moves both by pivoting (when gear  56  pivots) and by rotation (when gear  56  rotates). Gear  50  on the opposite end of the train of gears  50 ,  52 ,  54 , and  56  is rotated by shaft  38  ( FIGS. 2 ,  3  and  4 ). Similarly for autocompensating system  19  gears  60 ,  62 ,  64  and  66  are each meshed to the next gear in a linear train and supported within a bracket  68 . Gear  66  is integral with drive roller  19   a  so that it moves both by pivoting (when gear  66  pivots) and by rotation (when gear  66  rotates). 
   Assuming counterclockwise torque to gear  50  and clockwise torque to gear  60 , so long as gear  56  of system  15  or gear  66  of system  19  is not rotating, the torque pivots bracket  58  or bracket  68  respectively and the force against a sheet  5  of drive roller  15   a  and  19   a  increases toward the maximum pivoting force which can be applied by motor  30 . This force is immediately relieved when gear  56  rotates in the case of system  15  and when gear  66  rotates in the case of system  19 . Such rotation occurs when a sheet  5  is being moved, and it is the increase in pivot force against the sheet until it is moved which constitutes autocompensating in the systems. 
   Opposite or no rotation from the feeding rotation of gears  50  and  60  relieve pivoting torque because the direction of pivot is away from the feeding position and therefore the gears  56  and  66  respectively are free to rotate. To prevent such rotation with respect to system  15 , gear  50  is driven through a one-way clutch, (not shown), which may be a conventional ball-and-unsymmetrical-notch clutch or other clutch. 
     FIG. 5  shows autocompensating system  19  positively moved away from the guide  17 . This occurs when gear  60  is driven in the direction opposite to sheet feed. To achieve that, an added mechanism is applied to the autocompensating system  19 , which is illustrated in  FIG. 6  and  FIG. 7 . 
   This mechanism is a slip drive. As shown in  FIG. 6 , within the housing  70  of autocompensating system  19  is a coil spring  72  mounted on drive shaft  46  and having one side in contact with the face of gear  66 . 
   As shown in  FIG. 7 , housing  70  has a cylindrical well  74  with bottom face  76  which receives the side of spring  72  ( FIG. 6 ) opposite to that which faces gear  66 . The dimensions of well  74  are such that spring  72  is compressed. 
   With spring  72  compressed, the turning of gear  66  turns spring  72  and the turning of spring  72  tends to rotate the entire housing  70 , since well  74  is integral with housing  70 . However, when further rotation is blocked, spring  72  simply slips. 
   When gear  66  is rotated in the reverse feeding direction, system  19  is moved away from the drive path of guide  17  as shown in  FIG. 5 , where it is stopped by being blocked by lever  94   f  (described below) pushed against the frame of printer  1 . 
   When gear  66  is rotated in the feeding direction, spring  72  adds somewhat to the downward force while slipping. 
   In basic operation, under control of controller C, motor  30  is driven to feed a sheet  5  from tray  13  by rotating autocompensating system  15  downward. Autocompensating system  19  is necessarily driven by the slip drive to move away from the paper feed direction. Accordingly, when a sheet  5  is being moved by system  15 , system  19  is moved completely out of guide path  17 , as shown in  FIG. 5 . 
   As shown in  FIG. 8  in accordance with this invention, media sensor  80  is positioned in the feed path of guide  17  proximate to autocompensating system  19 . Media sensor  80  has supporting side brackets  82   a ,  82   b , which support optical device assembly  84 , having a viewing window  86 . The details of such a sensor need not be new with this invention. A light sensing device and a light source device are suggested as elements  88  and  90  in  FIG. 8 . 
   Side bracket  82   b  has integral with it an extending structure  92  having a generally vertical abutment surface  92   a .  FIG. 8  shows the abutment surface  92   a  in latched engagement with ledge  94   a , which is integral with rotatable assembly  94 . 
   Rotatable assembly  94  is mounted to the frame of printer  1 , more specifically to a back door  96 . (Door  96  may or may not be removable for jam clearance or general maintenance.) Rotatable assembly  94  has an arm  94   b  which has at is end ledge  94   a . Ledge  94   a  has a front camming surface  94   aa . Which will cam against lower camming surface  92   b  of extending structure  92 . 
   Rotatable assembly  94  has a coil spring  94   c  which is in pressure contact with a drum  94   d  and is mounted to the frame of printer  1  (details not shown), so that it provides a resilient biasing force upward (to move ledge  94   a  in front of abutment surface  92   a ). One end of spring  94   c  is under extension  94   e  from arm  94   b  to provide the resilient, upward force. Rotatable assembly  94  further has lever  94   f  positioned to be contacted by autocompensating system  19  when it moves to a long position away from media guide  17 . 
     FIG. 9  is an expanded view of selected elements from a somewhat different perspective from that of  FIG. 8  to illustrate the slip connection between autocompensating system  19  and media sensor  80 . Media sensor  80  receives an extended bushing  100  having a central opening with a flat  102  and an integral, outer flange  104 . Bushing  100  fits in a matching channel  106  which connects brackets  82   a  and  82   b . A coil spring  108  fits around bushing  100  and, in the actual assembly, is held tight against bracket  82   b  by C clip  109  held, as is standard, by in a channel in bushing  100 . The flat of bushing  100  mates with the flat of shaft  46 , so bushing  100  turns with shaft  46 . However, the driving force transmitted to media sensor is essentially that of the face of flange  104  resiliently biased by spring  108  against the side of bracket  82   a . Accordingly, this drive will simply slip when movement of media sensor  80  is blocked. 
   A cycle of operation is conducted for the feeding of each sheet of media. This can be deemed to start at any point, as it is repetitive.  FIG. 10  shows the mechanism with the sensor  80  in position to sense paper or other media (not shown). Although autocompensating system roller  19   a  is also positioned to be against the media, the sensing is done so quickly that no significant drive occurs before motor  30  is reversed to move autocompensating system  19  away from media in the feed path  17 . Media sensor  80  has moved forward under the action of the slip connection drive through spring  108  because ledge  94   a  was rotated downward away from facing ledge  94   a  as discussed below. 
   The reversed movement of autocompensating system  19  is a limited distance far enough to latch media sensor away from media in the paper path. The end location of that movement is shown in  FIG. 11 . Rotatable assembly  94  was rotated upward under the action of spring  94   c  as media sensor  80  rotated with the rotation of autocompensating system  19 . Cam surfaces  94   aa  and  92   b  facilitate smooth movement. Media sensor  80  is then locked against forward movement by abutment surface  92   a  facing ledge  94   a.    
   Motor  30  is once again reversed to rotate autocompensating system  19  to the media in path  17  and to drive the media until it reaches nip rollers  9   a ,  9   c , while media sensor  80  is held away from path  17 . This position is shown in  FIG. 12 . 
   As shown in  FIG. 13  autocompensating system  19  is then moved by motor  30  a longer distance away from media path  17  than the previous movement away from media path  17 . Media Sensor  80  does not move the full distance with autocompensating system  19  as such full movement is blocked by a post  110  extending from door  96 . In this position autocompensating system  19  has encountered lever  94   f  and rotated it substantially while media sensor  80  does not rotate because of post  110 . This rotation frees media sensor  80  for forward movement by moving ledge  94   a  away from abutment surface  92   a.    
   When a subsequent sheet is fed, motor  30  rotates autocompensating system  19  to the position of  FIG. 10 . Media sensor  80  moves immediately with system  19  when system  19  moves, which is while lever  94   f  is still depressed enough to free media sensor  80  so abutment surface  92   a  moves past ledge  94   a  and no latching occurs. The cycle as just described is then repeated for the next media. 
   With respect to this invention, the autocompensating aspect of autocompensating system  19  is not significant, although the rotating aspect is employed. Mechanical variation of the foregoing will be apparent which permit the sensing element to be rotated in for sensing, to be rotated out to a latched position, and to the be unlatched by a larger outward rotation of a drive member. Although a single motor is generally all that is needed, one motor might be used for rotation in one direction and another motor used for rotation is another direction.