Browse Prior Art Database

Non-Optical Printer Document Sensor

IP.com Disclosure Number: IPCOM000111111D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Kruppa, RW: AUTHOR

Abstract

Printers that handle documents currently use optical sensors for sensing top and bottom edges of a form. Although optical sensors are accurate, they have the following deficiencies:

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Non-Optical Printer Document Sensor

      Printers that handle documents currently use optical sensors
for sensing top and bottom edges of a form.  Although optical sensors
are accurate, they have the following deficiencies:

o   Are easily contaminated by printer debris, which makes them
    unreliable or inoperative.

o   Maintaining a tight tolerance between the document feed rollers
    and the sensor is usually difficult.  This causes poor
    registration of printed data relative to the top or bottom edge
    of the document.

      This article discloses a design that solves both of these
deficiencies.  One of the document feed rollers is moveable in order
to allow for thin or thick forms.  By placing a strain gauge on a
beam that is attached to the moveable feed roller, a document is
sensed when it is placed in the feed rollers.  The sensor would also
sense when the document is removed from the rollers (Figure).  The
output of the strain gauge is amplified and fed to a microprocessor
A/D input for processing.  Small and/or slow variations of signal
change would indicate roller eccentricity; whereas, abrupt changes
would indicate the presence of a document.  Accuracy of registration
is improved significantly over the optical method in that the
document is basically sensed when it is in the nit point of the
rollers.