Abstract:
An indicator for continuously indicating the status of a media stack in a media tray is disclosed. This indicator functions independently of a media stack support in a printer. The indicator includes an indicator lever and a probe member. The indicator lever is pivotably mounted and can be tilted between two predetermined extreme positions. The probe member has a shaft which is also pivotably mounted. An engaging arm extends from the shaft. In operation, the shaft is tilted according to the status of the media stack in the media tray. As the shaft is tilted, the engaging arm engages the indicator lever, tilting the indicator lever to a position between the two extreme positions to indicate the status of the media stack.

Description:
FIELD OF INVENTION 
     This invention relates to an apparatus for indicating media stack height or status in a media tray. More particularly, the invention relates to an apparatus for indicating media stack status by obtaining the status directly from the media stack. 
     BACKGROUND 
     Office equipment such as photocopiers, laser printers, ink jet printers and other imprinting mechanisms today incorporate an ability to store and supply sheet media from a stack. This stack is typically stored within the covers of the equipment or in a covered tray installed in the equipment. Such storing of a media stack not only enhances the overall aesthetic appeal of the equipment, but it also reduces exposure of mechanisms in the equipment to dust and foreign materials. The covered media stack is however invisible to a user. As such a user is unable to tell the status of the media stack without having to remove the covers. In many of the equipment, the only indication the user receives of a media-out status is a signal when the media supply has actually been exhausted. Normally, the signal is issued during a printing or copying job and requires the job to be interrupted to re-supply the media stack. It is preferable that a continuous indication be given of the current status of the media stack so that the user is able to interrupt the copying or print job at a convenient point to replenish the stack. 
     There are many existing mechanisms for indicating the status of a media stack in a media tray. These mechanisms usually rely on the position of a stack support for detecting and indicating the media stack status. One such mechanism is described in the U.S. Pat. No. 5,236,348. The stack support is positioned within a media tray. One end of the stack support is pivotably mounted to the tray housing. The other free end of the stack support is thus moveable about this pivot between a tray-empty position and a tray-full position. A spring support attached to a base of the stack support biases the free end of the stack support towards the tray-empty position. When a full stack of media is loaded into the tray, the stack support is pushed to a tray-full position. As media in the tray is consumed, the stack support is pushed towards the tray-empty position. A pivotably mounted indicator lever positioned within the tray cooperates with the stack support to indicate the media stack status. A first portion of the lever is in contact with a surface of the stack support such that as the stack support moves between the tray-empty and tray-full positions, a second portion of the indicator lever is moved accordingly to reflect the media stack status. 
     Though such a simple and cost-effective mechanism works well, it is heavily reliant on the peculiar operation of the stack support for deriving the media stack status. Not all equipment will employ such a stack support design. In such equipment, the mechanism described will not be suitable for the purpose of indicating a media stack status. A new mechanism will be required. One such equipment which requires the new mechanism is one which employs a stack support which moves up and down during each pick cycle. This stack support design is necessary to allow the equipment to use a single motor for driving a pick roller as well as a media feed. During a pick cycle, the stack support is moved towards the pick roller to allow a top sheet on the media stack to be drawn out of the tray roller into an infeed zone. Once the sheet is engaged by the pick roller, the stack support is moved away from the pick roller so that no new sheets are picked during a subsequent media feed cycle, where the picked sheet is transported to a print zone. 
     From the foregoing, the prior art has a need for a media stack status indicator which derives information for indicating the media stack status independently of a stack support. 
     SUMMARY 
     In accordance with a preferred embodiment of the present invention, a media stack status indicator includes an indicator lever and a probe member. The indicator lever is pivotably mounted on a first pivoting axis in a media container for holding a media stack. This indicator lever is biased to a first predetermined position and can be tilted between the first predetermined position and a second predetermined position. The probe member has a shaft which is pivotably mounted on a second pivoting axis in the media container. An engaging arm extends from the shaft. In operation, the shaft is tilted to detect the status of a media stack in the media container. As the shaft is tilted, the engaging arm engages the indicator lever to tilt the indicator lever. The indicator lever is therefore able to indicate the status of the media stack in the media container. 
     The media stack status indicator preferably includes a lock member which is biased to tilt the probe member to a retracted position under a lifted cover of the media container. When the cover is placed over a tray of the media container, the lock member is released to allow the probe member to tilt about the second pivoting axis. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The invention will be better understood with reference to the following drawings, in which: 
     FIG. 1 is an isometric view of an ink jet printer with an installed media tray. A media stack status indicator according to the present invention is housed in the media tray. A tip of the indicator is exposed for viewing the media stack status. 
     FIG. 2 is an exposed isometric view of the media stack status indicator in FIG. 1 as seen in the direction according to an arrow A. The indicator has a probe member and an indicator lever. 
     FIG. 3A is a side view of the media stack status indicator of FIG. 2 shown in a tray-empty position. 
     FIG. 3B is a side view of the media stack status indicator of FIG. 2 shown in a tray-full position. 
     FIG. 4 is an exploded view of the media stack indicator of FIG.  2 . 
     FIG. 5A is a side view of the probe member in FIG. 2 shown retracted. 
     FIG. 5B is a side view of the probe member in FIG. 2, shown released for operation to indicate the status of a media stack. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereafter, a preferred embodiment of the present invention will be described in the context of an ink jet printer having a removable media tray. However, it is to be understood that the invention is usable with any imprinting or sheet handling equipment where a sheet supply indication is desired. FIG. 1 is an isometric view of an ink jet printer  2  with an installed media tray  4 . In order to replace a stack of media within the media tray  4 , a user grasps the lower portion of the media tray  4  and pulls it in the direction of Arrow B. The withdrawal of the media tray  4  exposes the media stack and enables its replenishment. A media stack status indicator (hidden from view) positioned within the media tray  4  indicates the height or status of the media stack in the media tray  4 . An exposed tip  6  of the media stack status indicator gives a user a continuous visual indication of the media stack status height or status. 
     FIG. 2 is an exposed isometric view of the media stack status indicator  8  as seen in the direction according to an arrow A in FIG.  1 . The media stack status indicator  8  has a probe member  10  and an indicator lever  12 . The probe member  10  is shown attached to a cover  14  for the media tray  4 . The indicator lever  12  is shown attached to the media tray  4 . When the cover  14  is removed from the tray  4 , the probe member  10  is retracted into an unused position of the probe member  10  under the cover  14 . When the cover  14  is placed over the tray  4 , the probe member  10  is released to allow it to cooperate with the indicator lever  12  in the tray  4  to indicate the media stack status. The indicator lever  12  is preferably pivotably mounted on a side wall  16  of the tray  4  and is biased upwards to a tray-full position when the cover  14  is removed. In operation, the cover  14  is placed over the tray  4 . In this position of the cover  14 , the probe member  10  is allowed to fall to engage the indicator lever  12 . The probe member  10  will come to rest on top of the media stack in the tray  4 . In this position of the probe member  10 , the indicator lever  12  will indicate the media stack status accordingly. 
     FIG. 3A is a view of the media stack status indicator in a tray-empty position. When the media tray  4  is empty, the probe member  10  will push the indicator lever  12  to its lowest point to indicate a tray-empty status as indicated by arrow C. FIG. 3B is a view of the media stack status indicator  8  in a tray-full position. When the tray  4  is fully replenished with media, the top of the stack will stop the probe member  10  in its downward fall. The stopping of the probe member  10  will prevent the biased indicator lever from being pushed further downwards. In this position of the probe member  10 , the indicator arm is allowed to indicate a tray-full status as indicated by arrow D. 
     FIG. 4 is an exploded view of the media stack status indicator  8 . As described earlier, the indicator  8  includes a probe member  10  and an indicator lever. Additionally, the indicator  8  includes a lock member  18  or retracting the probe member  10 . The probe member  10 , indicator lever  12  and lock member  18  are preferably of plastic, such as ABS plastic. The probe member has a mounting portion  20  having a through aperture  22  for pivot mounting. On one side of the mounting portion  20  is a locking end  24 . On the other side of the mounting portion is a shaft  26  ending at an enlarged head  28 . Extending laterally from one side of the shaft  26  is an engaging arm  30 . 
     The lock member  18  has a locking plate which is bifurcated at one end to define two mounting portions  34 . The mounting portions  34  have apertures  36  which are in alignment with each other. Extending laterally from one side f the other end of the locking plate  32  is a locking arm  38 . To assemble the lock member  18  and the probe member  10  to the cover  14 , the lock member  18  is placed over the locking end  24  of the probe member  10  such that the apertures  36  of the lock member  18  align with the aperture  22  on the probe member  10 . This lock and probe members  10 , 18  are then pivotably mounted to supports  40  depending from an underside  42  of the cover  14 . A pin  44 , preferably of steel, is inserted through the apertures  22 ,  36  and press-fitted to corresponding apertures on the supports  40  to effect this pivot mounting. A torsion spring  46  attaches at one end to a ledge  48  of the lock member  18  and at the other end to a tab on one of the supports  40  to bias the lock member  18  away from the underside  42  of the cover  14 . The locking plate of the lock member  18  impinges upon the locking end  24  of the probe member to tilt the shaft  26  of the probe member  10  towards the underside  42  of the cover  14 . The probe member  10  stays in this retracted position when the cover  14  is removed from the tray  4 . FIG. 5A is a side view of the lock member  18  biased to push the probe member to the retracted position. 
     When the cover  14  is placed over the tray  4 , an inclined tab  44  projecting from the side wall  16  of the tray  4  comes into contact with the locking arm  24  of the lock member  18 . This action causes the lock member  18  to be lifted towards the underside  42  of the cover  14 . This tilting of the lock member  18  disengages the locking plate  32  from the locking end  24  of the probe member  10 . The probe member  10  is thus free to tilt about its pivot axis. FIG. 5B is a side view of the lock member  18  shown held by the inclined tab  44  to allow the probe member to freely tilt about its pivot axis. 
     The indicator lever  12  is pivotably mounted to a cantilevered pin  46  integral with the side wall  16  of the cover  14 . This mounting allows the indicator lever  12  to tilt about the cantilevered pin  46  between a tray-empty position and a tray-full position of the indicator lever  12 . An external circular nut  48  is placed over a free end of the cantilevered pin  46  to lock the indicator lever  12  in place. Another torsion spring  50  with one end attached to the indicator lever  12  and the other end attached to a tab on the side wall  16 , biases the indicator lever  12  to the tray-full position. The indicator lever  12  is in this tray-full position when the cover  14  is removed from the tray  4 . 
     The indicator lever  12  has a first portion  52  and a second portion  54 . The two portions  52 ,  54  are inclined at an angle to each other to allow the indicator lever&#39;s tray-empty and tray-full positions to substantially correspond to no media and a full stack of media in the tray  4  respectively. Such a bi-portioned indicator lever  12  allows the indication of the status over the entire range of media stack in the tray with the tip  6  of the indicator lever  12  held substantially in a same vertical plane. Such a design of the indicator lever  12  allows the tip  6  to substantially follow the contour of a side wall  56  of the tray  4 . In operation, as the probe member  10  tilts downwards, the engaging arm  30  on the probe member  10  engages the second portion  54  of the indicator lever  12  to push the indicator level  12  down with it. The mass of the probe member  10  should be sufficient to overcome the force exerted on the indicator lever  12  by the torsion spring  50 . A tip  6  of the indicator lever  12  protrudes a window  58  in the side wall  56  to give a continuous visual indication of the media stack status from outside the tray.