Capacitive sensing for paper tray

Patent metadata

Field	Value
Publication number	US-10308457-B2
Application number	US-201414568675-A
Country	US
Kind code	B2
Filing date	Dec 12, 2014
Priority date	Dec 12, 2013
Publication date	Jun 4, 2019
Grant date	Jun 4, 2019

Abstract

A capacitive sensing system based on projected self-capacitance is suitable for use in printing systems/products to sense paper tray status. In example embodiments, a capacitive sensing system is adapted for sensing the condition/characteristics of paper in the paper tray, such as paper size, stack height and page count and paper dielectric. The capacitive sensing system can be configured with one or more shielded capacitive sensors incorporated into the paper tray, and oriented relative to the paper according to the paper condition/characteristic sensed.

First claim

The invention claimed is:

1. A method of measuring paper characteristics for paper within a paper tray using capacitive sensing, the paper tray including at least two capacitive sensors with respective capacitive electrodes CIN 1 and CIN 2 , each with a ground plane at a paper tray bottom, with CIN 1 and CIN 2 at a top of the paper tray oriented relative to a width dimension of the paper in the paper tray such that the paper covers CIN 1 , and partially covers CIN 2 , with CIN 2 having a length a2=a2p+a2a, where a2p is a portion of the CIN 2 length a2 that is over the paper, and a2a is a portion of the CIN 2 length a that is not over the paper, the method comprising
with no paper in the paper tray, measuring a capacitance CA 0 =CIN 1 to the ground plane;
with paper in the paper tray,
measuring a capacitance CA 1 =CIN 1 to ground;
measuring a capacitance CA 2 =CIN 2 to ground; and
determining CDIFF w=CA 1 *(1−a2p/a2)−CA 0 *(aa/a); and
determining paper width based on:
a 2= a 2 p+a 2 a
a 2 p=a 2− a 2 a

a 2 a =( a 2 *C DIFF w )/( CA 1− CA 0)

with paper width corresponding to a percentage (a2p/a) of CIN 2 covered by paper.

2. The method of claim 1 , further comprising calibrating for tray thickness, sensor size/position and sensor ground plane position, based on CA 0 .

3. The method of claim 1 , further including a third capacitive sensor CIN 3 at the top of the paper tray, oriented relative to a length dimension of the paper in the paper tray such that the paper partially covers CIN 3 , with CIN 3 having a length a3=a3p+a3a, where a3p is a portion of the CIN 2 length a3 that is over the paper, and a3a is a portion of the CIN 3 length a that is not over the paper, and further comprising:
measuring a capacitance CA 1 =CIN 1 to ground;
measuring a capacitance CA 3 =CIN 3 to ground; and
determining CDIFF I=CA 1 *(1−a3p/a3)−CA 0 *(a3a/a3); and
determining paper length based on:
a 3= a 3 p+a 3 a
a 3 p=a 3− a 3 a

a 3 a =( a 3 *C DIFF I )/( CA 1− CA 0)

with paper length corresponding to a percentage (a2p/a) of CIN 3 covered by paper.

4. The method of claim 1 , further comprising determining page count by:
measuring capacitance CA 1 , 0

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Assignees

• Texas Instruments Inc

Inventors

• Fomin Evgeny
• Gomes Alfred
• Granozio Domenico
• Kessler Matthew Christopher
• Kulchycki Scott D

Classifications

• B65H2511/152

  Operations & Transport · mapped topic

• G01B7/082

  Height gauges · CPC title

• B65H2220/01

  indicating an entity as a function of which control, adjustment or change is performed, i.e. input · CPC title

• B65H2515/712

  Operations & Transport · mapped topic

• B65H2511/30

  Numbers, e.g. of windings or rotations · CPC title