Asymmetric Triple Roller Sheet Conveyance

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Solution Overview

Problem

Existing image forming apparatuses face challenges in achieving both speedup and size reduction for duplex printing, as traditional roller structures either hinder next sheet conveyance or require additional rollers, leading to unstable sheet conveyance and potential jams due to changing force directions and roller shaking.

Innovation Solution

A sheet conveying device with a triple roller structure where the rotation centers of the driving and driven rollers are not on the same straight line, utilizing biasing portions to stabilize the rollers and prevent shaking, allowing for stable sheet conveyance by positioning the driving roller's rotation center outside the line connecting the first and second roller centers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the rotation centers of the triple rollers are disposed on one straight line to achieve both speedup and size reduction, then productivity and device compactness are improved, but the driving roller and driven rollers shake in the sheet conveying direction and up-down direction due to changing force directions, worsening sheet conveyance stability

Engineering Contradiction:

Improveduplex printing speedVSAvoidsheet conveyance stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies asymmetry by positioning the rotation center of the driving roller off the straight line connecting the rotation centers of the two driven rollers. This asymmetric configuration creates a geometric relationship where the forces from both driven rollers act along the same line passing through the driving roller's rotation center, preventing the driving roller from shaking during rotation direction changes while maintaining the compact triple-roller structure for high-speed duplex printing

Inventive Principle:

Principle #4Asymmetry

2Productivity

If two driven rollers are opposed to one discharge roller (triple roller structure) to achieve speedup and size reduction, then productivity and device size are improved, but the structure becomes complex due to the need to manage forces from multiple rollers

Engineering Contradiction:

Improvesheet conveying speedVSAvoidroller force management

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The asymmetric positioning of the driving roller's rotation center off the line connecting the driven rollers simplifies force management by ensuring all forces act along a single line. This geometric arrangement eliminates the need for complex force balancing mechanisms while maintaining the high-speed capabilities of the triple-roller structure

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent creates a force equilibrium condition by arranging the rollers such that the forces from both driven rollers act along the same line through the driving roller's rotation center. This equipotential force distribution prevents net forces that would cause shaking, simplifying the overall system while maintaining high productivity

Inventive Principle:

Principle #12Equipotentiality

3Adaptability or versatility

If the driving roller rotates forward and backward with rotation centers on one straight line, then duplex printing functionality is achieved, but the direction of force changes causing the rollers to shake in sheet conveying and up-down directions

Engineering Contradiction:

Improveduplex printing capabilityVSAvoidroller position stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The asymmetric configuration positions the driving roller's rotation center off the straight line connecting the driven rollers, creating a geometric arrangement where force changes during rotation direction changes act along a single line rather than creating destabilizing moments. This maintains duplex printing capability while eliminating roller shaking

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent converts the potentially harmful force changes that occur during rotation direction changes into beneficial aligned forces by positioning the driving roller's rotation center such that all forces from driven rollers act along the same line. This transforms what would be destabilizing force variations into stabilizing force alignment, enabling smooth bidirectional rotation for duplex printing

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS10538411B2Sheet conveying device

Publication Date: 2020.01.21 CANON KK

AI summary

In a cross section perpendicular to an axial direction of a discharge roller, a rotation center of the discharge roller is provided at a position out of a straight line that connects a rotation center of a discharge driven roller and a rotation center of a duplex driven roller. The discharge roller that receives forces from the discharge driven roller and the duplex driven roller is held by a discharge roller presser.