Electrophotography – Document handling – Copy
Reexamination Certificate
2000-11-21
2001-12-11
Braun, Fred L (Department: 2852)
Electrophotography
Document handling
Copy
Reexamination Certificate
active
06330424
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for determining the position of paper within an electrophotographic machine, and, more particularly, minimizing the error in a paper position calculation within an electrophotographic machine.
2. Description of the Related Art
It is known to use an electronic sensor to sense a sheet of paper arriving at a predetermined point along a paper path in an electrophotographic machine. After the paper has proceeded past the sensor, the position of the paper can only be estimated based upon the speed of the paper and the length of time since the paper was sensed by the sensor. Because of the difficulty of accurately estimating the fluctuating speed of the paper, problems exist as to determining the location of the paper in a paper path relative to a transfer nip.
What is needed in the art is a method of accurately determining the location of paper in a paper path relative to a transfer nip.
SUMMARY OF THE INVENTION
The present invention provides gear mesh and encoder frequencies and sensor placement relative to a transfer nip that enable very accurate transportation of the media at the proper time to the transfer nip.
The invention comprises, in one form thereof, a method of minimizing error in an estimate of a position of a sheet of print medium in an electrophotographic machine. A transport system that includes an actuator and a gearing system is provided to drive a set of rollers for moving the sheet of print medium along a print medium path. The gears are in constant mesh with each other and with the actuator. An encoder wheel is also provided to give feedback to a motion control algorithm. The electrophotographic machine is provided with a toner transfer point at which the toner can be transferred to the moving sheet of print medium. A sensor is placed at a set distance away from the transfer nip along the print medium path. This distance is approximately equal to an integer multiple of the resulting distance traveled by the medium during one revolution of the lowest frequency component of the transport system. The frequencies associated with all other components in the transport system, including the actuator and encoder wheel, are designed to be an integer multiple of this lowest frequency. A position of the sheet of print medium is sensed with the sensor.
The invention comprises, in another form thereof, an electrophotographic machine including an actuator that drives a set of rollers through a transport system that includes a gearing system. The actuator is provided for moving a sheet of print medium along a print medium path. The gears are in constant mesh with each other and with the actuator. An encoder wheel is also provided to give feedback to a motion control algorithm. A toner transfer mechanism transfers toner to the moving sheet of print medium. A sensor is disposed at a distance away from the toner transfer mechanism along the print medium path. This distance is approximately equal to an integer multiple of the resulting distance traveled by the medium during one revolution of the lowest frequency component of the transport system. The frequencies associated with all other components in the transport system, including the actuator and encoder wheel, are designed to be an integer multiple of this lowest frequency. The sensor senses a position of the sheet of print medium.
An advantage of the present invention is that error in the calculation of paper position is minimized.
Another advantage is that the leading edge of the paper can be more accurately aligned with an image on an intermediate transfer member.
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Chapman Danny Keith
McKay Matthew Lowell
Turney Steven Michael
Aust Ronald K.
Braun Fred L
Lexmark International Inc.
Pezdek John V.
Sanderson Michael T.
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