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A FUSER NIP SENSOR FOR DETERMINING NIP PRESSURE AND LENGTH

IP.com Disclosure Number: IPCOM000026761D
Original Publication Date: 1993-Aug-31
Included in the Prior Art Database: 2004-Apr-06
Document File: 4 page(s) / 160K

Publishing Venue

Xerox Disclosure Journal

Abstract

In setting up xerographic fusers either in manufacturing or in the field, it is important that the interference between each of the two rolls be set correctly so that the correct fusing pressure is achieved, and sufficient dwell time allowed for adequate fixing. This is currently done by means of setting the deflection of the roll loading springs, and, due to variation in the manufacture of the springs, can result in significant variation in both nip length and pressure.

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XEROX DISCLOSURE JOURNAL

A FUSER NIP SENSOR FOR DETERMINING NIP PRESSURE U.S. C1.335/203 AND LENGTH
William M. Lindenfelser

Proposed Classification

Int. C1. G03g 21/00

ROLL AXES

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18

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12 \ DETECT

EDGE

-

DQ

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LOCATION DATA -TO PP

16

XEROX DISCLOSURE JOURNAL - Vol. 18, No. 4 July/August 1993 359

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A FUSER NIP SENSOR FOR DETERMINING NIP PRESSURE AND LENGTH(Cont'd)

In setting up xerographic fusers either in manufacturing or in the field, it is important that the interference between each of the two rolls be set correctly so that the correct fusing pressure is achieved, and sufficient dwell time allowed for adequate fixing. This is currently done by means of setting the deflection of the roll loading springs, and, due to variation in the manufacture of the springs, can result in significant variation in both nip length and pressure.

A Force Sensitive Resistor (FSR), made by Interlink Electronics, allows for a much more direct measurement of fuser nip conditions. The FSR is a device consisting of two pieces of plastic film; one of the pieces is patterned with interdigited electrodes and faces the second piece of film, which is coated with a proprietary resistive coating. The exertion of pressure across the sandwich of these films results in a change in the resistance of the device. One of the unique features of this device is the ability to make arbitrary patterns of electrodes for application in different situations.

Nip length and pressure information can be extracted from the FSR by means of a pair of sensor heads, A and B, placed in close proximity in the nip. Sensor B is designed to operate in a digital mode to determine the nip length, while A functions as an analog device sensitive to a combination of pressure and area of nip contact. Signal processing in a microprocessor extracts the length and pressure information.

It is possible to characterize sensor A with three parameters that may be used in a simple equation relating pressure, area of contact and resistance. By measuring resistance and knowing the area of contact, the pressure is easily determined. This then forms the basis of the analog device.

Determining nip length, and therefore area of contact for a device of constant width, is the function of sense head B. The resistance pressure transfer characteristic of the FSR is particularly steep at low pressure, with a zero pressure resistance in the 10 Meg range, and a high pressure resistance that is typically about 10 kOhm. The device works nicely as a switch, and by placing an array of these "switches" in...