Abstract:
A method for applying a pick retry using a modified pick roller force includes operating an actuator in a first duty cycle to cause a pick roller to impose a first force on a media stack ordinarily sufficient to pick and feed a top sheet from the media stack to a media path, sensing whether or not the sheet arrives in the media path, and retrying the actuator in a second duty cycle different than the first duty cycle to cause the pick roller to impose a second force on the media stack different from the first force in response to not sensing the arrival of the sheet in the media path. The second force may be greater than the first force. The second duty cycle may be longer than the first duty cycle. Also, the method includes rotating the pick roller concurrently with or subsequently to operating the actuator.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to an automatic document feeder for a scanning device and, more particularly, to a method for applying a pick retry using a modified pick roller force to reduce the likelihood of failure to pick the top sheet from a media stack. 
     2. Description of the Related Art 
     It is common for an automatic document feeder (ADF) for a scanning device to include a pick roller to move the top sheet of an input media stack into the ADF feed path. There are different methods for engaging the pick roller to the input media, but the desired result is the same. The pick roller should move only the top sheet of the input media. There is an operating window for the pick roller to ensure enough force is created to move the top sheet, but not too much such that subsequent sheets are not moved. Thus, it is common for the pick roller to have just enough force to move the top sheet of the input media stack. 
     In some cases, it is possible that this force is not great enough and the ADF fails to move the top sheet far enough to the media path and reports a jam. It is also possible that the input media condition is not ideal, and this undesired condition of the media creates problems when trying to move the top sheet of the input stack. Thus, it is common for some ADF devices to incorporate a retry of the pick roller if it fails to feed the top sheet. However, it is possible that the retry of the pick roller will turn out to be ineffective also and thus end in failure. 
     Thus, there is still a need for an innovation that will establish a parameter that will ensure the success of the retry of the pick roller in response to its failure to feed the top sheet. 
     SUMMARY OF THE INVENTION 
     The present invention meets this need by providing an innovation that ensures that a pick retry will proceed with a modified pick roller force to further help reduce the chances of an ADF failure to move the top sheet from the media stack. The innovation is a method for applying a retry to an ADF pick roller such that during the retry the pick force is modified. 
     Accordingly, in an aspect of the present invention, a method for applying a pick retry using a modified pick roller force includes operating an actuator in a first duty cycle to cause a pick roller to impose a first force on a media stack ordinarily sufficient to pick and feed a top sheet from the media stack to a media path, sensing whether or not the sheet arrives in the media path, and retrying the actuator in a second duty cycle different than the first duty cycle to cause the pick roller to impose a second force on the media stack different from the first force in response to not sensing the arrival of the sheet in the media path. The second force may be greater than the first force. The second duty cycle of the actuator may be longer than the first duty cycle. Also, the method includes rotating the pick roller concurrently with or subsequently to operating the actuator to cause the pick roller to impose the first force on the media stack. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale and in some instances portions may be exaggerated in order to emphasize features of the invention, and wherein: 
         FIG. 1  is a simplified diagrammatic view of a prior art relationship of a pick roller with a media stack in a top sheet pick operation and the different forces involved in the relationship. 
         FIG. 2  is an exemplary embodiment of a prior art ADF in which the method of the present invention is implemented for applying a pick retry using a modified pick roller force. 
         FIG. 3  is a simplified diagrammatic view of a prior art ADF media path for illustrating a sequence of events relating to the method of the present invention. 
         FIG. 4  is a flowchart depicting the operational steps of the method of the present invention for applying a pick retry using a modified pick roller force. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numerals refer to like elements throughout the views. 
     Referring now to  FIGS. 1 and 2 , there is diagrammatically illustrated in  FIG. 1  an input tray setup of a prior art automatic document feeder (ADF)  10 , as seen in  FIG. 2 , for a scanning device. The ADF  10  includes a housing frame  12 , an input tray  14  supported by the housing frame  12  for receiving and supporting a media stack  16 , a shaft  18  rotatably mounted at its opposite ends to opposite sides  12   a ,  12   b  of the housing frame  12 , and a pick mechanism  20  having a pick arm  22  pivotally mounted on the shaft  18  so as to overlie the input tray  14 . The pick mechanism  20  has a pick roller  24  movably, and specifically rotatably, mounted to an end of the pick arm  22  so as to overlie a media stack  16  supported on the input tray  14 . The pick roller  24  is rotatably driven by a train of gears (not shown) mounted in the pick arm  22  which, in turn, are driven by a motor (not shown), such as a stepper motor, located under a cover  26 . 
     The ADF  10  also includes a controller  28  electrically connected to the motor. The controller  28  operates as instructed by software contained therein to command the turn-on and operation of the motor such that the pick roller  24  is rotated in clockwise direction of an arrow  30  shown in  FIG. 1  to apply a drive force (F) to the media stack  16  to move its top sheet  16   a  (see  FIG. 3 ) laterally off the media stack  16 . The drive force (F) exerted by the pick roller  24  on the media stack  16  can simply be expressed by the following equation: F=μ*N, where F is the drive force applied to the media stack  16 , μ is the coefficient of friction between the pick roller  24  and the media stack  16 , and N is a normal force that the pick roller  24  applies to the media stack  16  in the downward direction of an arrow  32  shown in  FIG. 1 . 
     As seen in  FIG. 2 , the ADF  10  also includes an extendable and retractable mechanism in the form of a solenoid actuator  34  supported on the exterior of the housing frame  12 . The operation of the solenoid actuator  34 , as well-known, is controlled and directed by the controller  28  to actuate the pivotal movement of the pick arm  22 . The ADF  10  further includes a cam  36  mounted at the one side  12   a  of the housing frame  12  on one end of the shaft  18 . The duty cycle of the solenoid actuator  34  creates a lateral force that rotates the cam  36  through a given angle, with the cam  36 , in turn, providing a corresponding known torque force to the pick arm  22 . The pick arm  22  then pivots and the pick roller  24  thereon provides the resulting corresponding known downward normal force on the media stack  16 . The solenoid actuator  34  operates based on a duty cycle that is controlled by the software in the controller  28 . The software sets the duty cycle at some given percentage from 0 to 100%. As the duty cycle increases, the holding force of the plunger  38  of the solenoid actuator  34  increases which, in turn, correspondingly increases the normal force of the pick roller  24  on the media stack  16 . 
     Turning now to  FIGS. 3 and 4 , there is illustrated in  FIG. 3  a simplified diagrammatic view of a prior art ADF media path, generally designated  40 .  FIG. 4  sets forth a plurality of blocks  100 - 110  making up a flowchart of the method of the present invention. During normal operation of the ADF  10 , the controller  28  receives a command to feed a sheet from the media stack  16 . The controller  28  issues a pick command to the solenoid actuator  34  in response to which the duty cycle of the solenoid actuator  34  is preset at a given default interval between 0 and 100% to create the desired force via the cam  36  that the pick roller  24  imposes on the input media stack  16 . Also, concurrently the controller  28  commands the motor to turn on, causing the pick roller  24  to rotate. As the pick roller  24  rotates, it is intended to move the top sheet  16   a  to the ADF media path  40 . 
     A well-known sensor  42  is situated along the media path  40  at a location where it may be used to detect if the top sheet  16   a  has successfully fed into the ADF media path  40 . When the sensor  42 , operating in a well-known manner, goes active in response to detection of the top sheet  16   a , its active state is communicated to and monitored by the controller  28  which, in turn, communicates an appropriate signal to the solenoid actuator  34  to disengage the pick roller  24  via the cam  36 . The pick roller  24  then moves back to its original position until the next pick command is given. If the sensor  42  fails to activate within a preset time period, then the operational assumption is that the top sheet  16   a  did not feed successfully into the ADF media path  40 . Thus, in response to the sensor failing to activate within the preset time period, the controller  28  of the ADF  10  reports a jam condition. 
     In accordance with the method of the present invention, a retry will be created by the controller  28  when the sensor  42  fails to activate within the preset period of time. To start at the beginning, initially, as per block  100  of the flowchart, the controller  28  initiates the default interval of the duty cycle of the solenoid actuator  34  to cause the pick roller  24  to deliver a first, or default level, normal force on the media stack  16 , ordinarily found sufficient for picking and moving the top sheet  16   a  from the stack  16  and into the ADF media path  40  to where its successful arrival will be sensed by the sensor  42 . At block  102 , in response to receipt of an appropriate command inputted to the ADF  10 , the controller  28  initiates operation of the solenoid actuator  34  to impose, via the cam  36  and pick mechanism  20 , the first normal force on the media stack  16 . The controller  28 , at the same time, as per block  104 , turns on the motor causing the pick roller  24  to rotate. 
     Next, as per block  106 , the controller  28  monitors the state of the sensor  42  to determine the answer to the question “Is sensor active w/i TP?” meaning, within a preset time period (TP). If the answer is yes (Y), the method branches to block  108  where a successful feed is indicated. From block  108 , the method returns to the first block  100  to await when another command is received from the ADF  10  to pick another sheet from the media stack  16 . However, it the answer at block  106  is no (N), then the method branches to block  110  where the controller  28  initiates a ‘retry’. The retry is a repeat operation of the solenoid actuator  34 . 
     However, this time on the retry the controller  28  causes the pick roller  24  to impose, via the cam  36  and pick mechanism  20 , on the media stack  16  a second normal force which is modified over that of the first normal force by an amount calculated to feed the top sheet  16   a  from the media stack  16 . In the exemplary embodiment herein, the controller  28  does this by increasing the duty cycle of the solenoid actuator  34  so as to increase the pick roller-imposed normal force on the media stack  16  during the retry. The repeat operation or retry of the method commences at the block  102  where the controller  28  again initiates the aforementioned operation of the solenoid actuator  34  for the increased duty cycle to cause the pick mechanism  20  to deliver the increased second normal force. The method then moves to block  104 , where the motor is turned on and rotates the pick roller  24 , and then to block  106  where the controller  28  monitors the sensor  42  for the preset time period. This should result in an answer of yes (Y) at block  106 , indicating a successful feed at block  108 . 
     Another variation of the retry is for the controller  28  to operate the solenoid actuator  34  to move the pick roller  24  to the media stack  16 , but not concurrently activate the motor. So the pick roller  24  is pressed onto the media stack  16  with a higher normal force during the retry, but not yet moving (rotating). Then, next the motor is activated and rotates the pick roller  24 . This sequence would prevent the slipping of the pick roller  24  relative to the media stack  16  that may have caused the misfeed originally. 
     The foregoing description of several embodiments of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.