Appeal No. 2002-1788 Page 6
Application No. 09/217,667
Williams' invention relates generally to a sheet registration system, and more
particularly concerns a system for calibrating a sheet registration device in a high speed
printing machine. Figure 1 of Williams is a schematic elevational view depicting an
illustrative electrophotographic printing machine2 incorporating a sheet registration
calibration device and Figure 2 is a detailed plan view of the sheet registration device.
Williams describes the method for registration of a sheet of paper (column 8, line
6, to column 10, line 22) as follows:
This invention describes a method to calibrate position sensors for use in
paper registration. This enables inexpensive sensors to be used for highly
accurate registration of paper. In addition, The procedure also calibrates for all
repeatable errors resulting from wheel misalignment, wheel run-out, encoder
miscentering, etc. High quality documents require registration of sheets of paper
to the photoreceptor for image transfer. Accurate registration control locates the
image consistently with respect to the edge of the paper.
FIG. 2 illustrates a method for registration of a sheet of paper. Nip 114
and Nip 116 impose velocities V1 and V2 to the paper, thus steering the paper.
Appropriate velocity profiles can register the paper at datum 3 (D3) with proper
position and orientation (zero skew). Methods for selecting the profiles as well as
methods for servo control of the nips to impose these profiles are beyond the
scope of this invention.
FIG. 2 shows a sheet of paper as it is entering the registration nip at
datum 2 (D2). Leading edge sensor 124 notifies the controller that a sheet has
entered the nip and time stamps the arrival for process direction registration.
Paper lateral position and orientation (skew) are determined from measurements
provided by edge sensors 132 and 134 [sic, 130 and 132]. With this information,
2 The invention illustrated is a high speed black and white printing machine. Williams teaches
(column 8, lines 2-5) that the invention is also very suitable for use in a high speed full color or highlight
color printing machine where accurate sheet to image registration is critical.
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