Fuser Assembly Single Biasing Member Even Loading

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Solution Overview

Problem

The existing fuser assemblies in image forming apparatuses face inconsistent and unequal loading of the rotatable backup member against the translatable heater member due to space constraints and geometrical differences, leading to issues like treeing, worming, and light print.

Innovation Solution

A fuser assembly design utilizing a single biasing member with a support structure and bell crank mechanism to apply a consistent force on the translatable heater member, ensuring even loading against the rotatable backup member, reducing spring rate and eliminating the need for multiple springs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If multiple springs are used to bias the heater member against the backup member, then the fuser assembly can apply loading force, but the loading becomes inconsistent and unequal due to space constraints and geometrical differences

Engineering Contradiction:

Improveloading forceVSAvoidloading consistency

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The patent combines multiple separate springs into a single biasing member (such as a torsion spring or cantilever spring) that spans the width of the heater member. This single biasing member applies force through a central pivot point or support structure, ensuring uniform loading across the entire heater member width and eliminating the inconsistency caused by multiple independent springs.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces a pivot point or support structure as an intermediary element between the biasing member and the heater member. This intermediary distributes the force from the single biasing member evenly across the heater member, acting as a mediator that transforms the single-point force application into uniform distributed loading.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Volume of moving object

If short springs with high spring rate are used due to space constraints, then the fuser assembly fits in limited space, but the tolerance variation causes 20% difference in force applied at each end

Engineering Contradiction:

Improvespring lengthVSAvoidforce application uniformity

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent replaces multiple short springs with a single longer biasing member that can accommodate tolerance variations. This single member spans the entire width of the heater, and its central support structure ensures that even with manufacturing tolerances, the force is distributed uniformly, preventing the 20% force difference that occurs with multiple independent short springs.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the spring rate parameter by using a single biasing member with appropriate dimensional specifications. This single member can be designed with a lower spring rate that compensates for tolerance variations, ensuring consistent force application across the heater width without requiring extremely short, high-rate springs.

Inventive Principle:

Principle #35Parameter changes

3Force

If two springs are positioned on each end frame, then the heater member can be biased against the backup member, but geometrical differences between ends are magnified causing uneven loading

Engineering Contradiction:

Improvebiasing forceVSAvoidloading uniformity

Core Design Contradiction:

ForceVSStability of the object's composition

Solution Approach 1:

The patent employs an asymmetric single-biasing-member configuration where the biasing force is applied at a central pivot point rather than symmetrically at both ends. This asymmetric approach actually resolves the problem by creating a fulcrum system where the pivot point serves as the reference, and the geometry is designed to compensate for end-frame variations, ensuring uniform loading despite asymmetrical force application points.

Inventive Principle:

Principle #4Asymmetry

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design achieves substantially even and consistent loading of the translatable heater member against the rotatable backup member, reducing defects such as treeing and light print, and allows for easier adjustment of pressure without altering the force distribution.

Implementation Method 1

a biasing member positioned adjacent and parallel to the translatable heater member... the biasing member applying a force on at least a portion of the translatable heater member through at least a portion of the support structure

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS8200137B2Fuser assembly including a single biasing member

Publication Date: 2012.06.12 LEXMARK INTERNATIONAL INC

AI summary

A fuser assembly includes a translatable heater member and a rotatable backup member mounted against the translatable heater member. The translatable heater member includes a heater housing extending through end frames disposed at the ends of the fuser assembly. A biasing member is positioned adjacent and parallel to the translatable heater member. A support structure is positioned at each end of the biasing member for supporting the biasing member. The support structure includes bell crank members that are engaged with the ends of the biasing member. The biasing member applies force on the heater housing through the bell crank members to bias the translatable heater member against the rotatable backup member.