Abstract:
A printer comprises a paper tray that cannot be slammed in too fast by a user. The speed at which the paper tray can be reinserted is limited in order to stop bunching of the paper stacks up against the front datum walls. Such bunching has been a source of multiple feeds, misfeeds and paper jams. Embodiments of the present invention limit the speed of tray insertion by the user by interposing dampers, or homing motors.

Description:
BACKGROUND  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to printers, and more particularly to printers and input trays with controlled insertion speeds.  
           [0003]    2. Background of the Invention  
           [0004]    Some desktop printers have paper trays that need to be pulled out periodically and resupplied with paper sheets or other print media. During printing, individual paper sheets are sequentially picked out of the input tray and advanced to an image printing mechanism.  
           [0005]    Users tend to slam the paper trays back into the printer hard enough to cause the paper to bunch up against the front datum wall, especially if the printer uses a slanted front datum wall design. Such bunching can interfere with the printer&#39;s ability to pick up individual sheets for the image printing mechanism. At worst, the bunching leads directly to paper jams.  
         SUMMARY OF THE INVENTION  
         [0006]    Briefly, a printer embodiment of the present invention includes a paper tray that cannot be slammed in too fast by a user. The speed at which the paper tray can be reinserted is limited to stop bunching of the paper stacks up against the front datum walls. Such bunching has been a source of multiple feeds, misfeeds and paper jams. Embodiments of the present invention limit the speed of tray insertion by the user by interposing dampers, or homing motors.  
           [0007]    These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment as illustrated in the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIGS. 1A and 1B are exploded perspective diagrams of a first printer embodiment of the present invention, illustrating different positions of an input tray respectively;  
         [0009]    [0009]FIG. 2A is a cut-away partial diagram of a second printer embodiment of the present invention;  
         [0010]    [0010]FIG. 2B is a top view of a damper used in the printer of FIG. 2A;  
         [0011]    [0011]FIG. 2C is a cross section view of the damper of FIG. 2B;  
         [0012]    [0012]FIG. 3A is an exploded perspective diagram of a third printer embodiment of the present invention; and  
         [0013]    [0013]FIGS. 3B and 3C are simplified top views illustrating different status of an input tray of the printer of FIG. 3A. 
     
    
     DETAILED DESCRIPTION  
       [0014]    [0014]FIGS. 1A and 1B illustrate a first printer embodiment of the present invention, and the printer is referred to herein by the general reference numeral  100 . The printer  100  is representative of the many kinds of devices that use paper trays for printing images. For example, some fax and copier machines represent alternative embodiments of the present invention.  
         [0015]    The printer  100  includes a chassis  102  disposed within a casing  104 . A sliding paper input tray  106  can be pulled out of and inserted back into the printer  100  through an opening  108 . Such tray carries a stack of paper sheets  110 . During printing, individual sheets of paper are sequentially picked from the input tray and advanced to an image printing mechanism.  
         [0016]    The input tray  106  includes a bottom floor on which the paper sheets  110  are stacked, and a sloped front datum wall  112 . The input tray  106  includes a gear track  114  mounted to a side wall  116  and that engages a gear  118 .  
         [0017]    The gear  118  is driven by a motor  120  mounted to the chassis  102  through a gear shaft  122 . As the motor  120  rotates, the gear  118  interacts with the gear track to drive the input tray  106  in and out. A mechanism controls the rotation speed of the motor  120  so the speed at which the input tray  106  can be reinserted is limited.  
         [0018]    A pair of sensor  124 ,  126  are also mounted to the chassis  102  for respectively detecting a position of the input tray  102  during the pull-out and insertion of the input tray  106 .  
         [0019]    An on/off button is provided on the enclosure  104  of the printer  100 . When the paper sheets are to be loaded, the user can simply press the on/off button. Such an action automatically triggers the motor  120  to rotate at a predetermined speed in a direction to drive the input tray  106  outwards. In FIG. 1A, when the sensor  124  detects that the input tray has reached a first predetermined position, the sensor  124  sends a signal to the controlling mechanism of the printer  100 , and the controlling mechanism then stops the rotation of the motor  120 .  
         [0020]    After the user has loaded the paper sheets  110  into the input tray  106 , the user can press the on/off button again, and this time such an action triggers the motor  120  to rotate at the predetermined speed to drive the input tray  106  inwards. In FIG. 1B, when the sensor  126  detects that the input tray  106  has reached a second predetermined position, the sensor  126  sends a signal to the controlling mechanism of the printer  100 , and the controlling mechanism then stops the rotation of the motor  120 .  
         [0021]    Since the motor  120  rotates at a predetermined speed during the insertion of the input tray  106 , the insertion speed at which the input tray  106  is inserted is also controlled. In this way, the paper sheets  110  are prevented from climbing up the front datum  112 .  
         [0022]    [0022]FIGS. 2A-2C partially illustrate a second printer embodiment of the present invention.  
         [0023]    In FIG. 2A, a damper  202  is mounted on the side wall  204  of the input tray  206  to engage with a plurality of engaging teeth  208  of a gear track  210 . The gear track  210  is mounted to the chassis  212  of the printer and extends lengthwise along the side wall  204  of the input tray  206 . During manual insertion of the input tray  206 , the damper  202  interacts with the engaging teeth  208  to slow down the insertion speed at which the input tray  206  is inserted into the printer. In this way, the paper sheets are prevented from climbing up the front datum of the input tray  206 .  
         [0024]    As shown in FIGS. 2B and 2C, the damper  202  has two parts  214 ,  216 . Part  214  serves as a gear to engage the engaging teeth  208 . Part  216  serves to fit onto the input tray and to interact with part  214  to generate a damper force. Such damper force slows down the insertion speed. In particular, as the input tray is inserted, the engagement between the engaging teeth and part  214  of the damper drives part  214  to rotate relative to part  216 . Such a relative movement between these two parts generates a resistance force or the damper force proportional to the relative speed of these two parts. Therefore, the higher the insertion speed, the higher the relative speed between these two parts and the higher damper force generated.  
         [0025]    [0025]FIGS. 3A-3C illustrate a third printer embodiment of the present invention. A dashpot or damping mechanism is used to limit the speed at which the paper tray can be reinserted by the user.  
         [0026]    [0026]FIG. 3A, the printer  300  includes a tension spring  302  extending lengthwise along the input tray  304 , with one end attached to the chassis  306  and the other end attached to a slider  308  hook onto the input tray  304 . The spring  302  provides the driving force for automatically pulling the input tray  304  inwards during the insertion of the input tray.  
         [0027]    The slider  308  includes a built-in damper to interact with a gear track  310  mounted on the chassis. The interaction between the built-in damper and the gear track  310  is similar to what has been described with reference to FIGS. 2A and 2B.  
         [0028]    Furthermore, a locker  312  is mounted to the chassis  306  for holding the slider  308  when the input tray  304  is fully pulled out for loading paper sheets. Such an action on the slider  308  holds the input tray  304  in position until it is released by an external force.  
         [0029]    The slider  308  in the exemplary embodiment has a rectangular shape with a front and a back surface opposite to each other. Correspondingly, the locker  312  includes a pair of arms  314 ,  316  extending perpendicular to each other for embracing the slider. Both arms are connected at an end to a pivot  318  mounted to the chassis.  
         [0030]    In FIG. 3B, the user overcomes the spring force and manually pulls the input tray  304  outwards. When the slider  308  reaches the locker  312 , the front surface of the slider  308  pushes the arm  314  of the locker away so that the locker rotates about the pivot  318  by a sufficient degree. After the rotation, the other arm  316  of the locker is in a position for receiving the back surface of the slider  308 . The locker  312  functions to prevent the input tray  106  from being pulled back by the spring  302  when the user stops pulling the input tray  304 . This can be achieved by the frictional force between the pivot  318  and the chassis  306  designed to resist the spring force exerted on the input tray  304 . Alternatively, a self-locking mechanism using mating part interference such as detents and bosses can be used to hold the input tray in position. Furthermore, the locker  312  is positioned such that when the slider reaches the locker, a major portion of the input tray  106  has been pulled out of the printer for loading the paper sheets.  
         [0031]    After the paper sheets are loaded into the input tray, in FIG. 3C, the user pushes the input tray inwards. Ideally, the user only needs to exert a small amount of force on the input tray to unlock the locker. When the arm  316 , which restricts the slider  308  from moving, is pushed or swung away, the spring  302  automatically pulls the input tray inwards until the input tray reaches a hard stop in the printer when it has been pulled in sufficiently.  
         [0032]    During such an automatic insertion of the input tray into the printer, the built-in damper in the slider interacts with the gear track  310  to automatically slow down the insertions speed at which the input tray moves. In this way, the insertion speed is automatically controlled and the paper sheets are prevented from climbing up the front datum of the input tray.  
         [0033]    Method embodiments of the present invention prevent the bunching of paper in a media tray when the user reinserts the tray into a printer. Either the media may be locked or pressed down to prevent its slopping around in the tray during reinsertion, or the speed that the tray can be slammed back into the printer is controlled and limited.  
         [0034]    Alternatives can be made to the exemplary embodiments. For example, in the second and third embodiments, the gear track can be mounted on the input tray while the damper is mounted to the chassis instead. Furthermore, a compression spring can be used in the third embodiment instead of a tension spring.