Browse Prior Art Database

Reflective Low Paper Sensor Assembly

IP.com Disclosure Number: IPCOM000112417D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Fortenberry, RS: AUTHOR [+2]

Abstract

Point-of-Sale (POS) printers may have hardware that senses the amount of paper remaining on a supply roll. The purpose of such hardware is to alert the operator that the supply roll requires changing before actually running out of paper. This article discloses a method to improve the consistency of low-paper sensing.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 62% of the total text.

Reflective Low Paper Sensor Assembly

      Point-of-Sale (POS) printers may have hardware that senses the
amount of paper remaining on a supply roll.  The purpose of such
hardware is to alert the operator that the supply roll requires
changing before actually running out of paper.  This article
discloses a method to improve the consistency of low-paper sensing.

      Existing low-paper sensors can use optical switches to detect
when the diameter of the paper roll drops below a desired value.  An
LED and detector are mounted on the side of the paper supply
"bucket".  The detector receives light reflected from the side of the
paper roll.  As paper is used and the roll diameter decreases, the
edge of the roll of paper moves below the level of the LED/detector
pair.

      The reflected light signal also decreases, and when it falls
below a threshold value, a "low paper" signal is supplied to the
printer control program.  Several factors affect the consistency of
the low paper signal; that is, the amount of paper left on the roll
when the "low paper" threshold is reached.

      The lateral position of the paper roll in the bucket affects
the sensor reading.  If a roll of paper moves to the side of the
bucket opposite the LED and detector, the reflected signal value is
decreased due to the greater distance travelled by the spreading LED
light beam.  The low paper threshold signal level will be reached
with extra paper remaining on the roll.  As shown i...