Offset Cam Mechanism for Developing Roller Miniaturization

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Solution Overview

Problem

Conventional image forming apparatuses face challenges in reducing the size of cams due to the need for strong shafts to withstand reaction forces from developing units, making it difficult to miniaturize the components.

Innovation Solution

The apparatus incorporates a design with offset rotation angles of cams and rods, allowing the cams to push and retract the developing rollers in a direction parallel to their axes, reducing the required strength and enabling size reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the cam pushes the developing unit in a direction crossing the rotation axis, then the developing roller can be separated from the photosensitive drum, but the shaft requires high strength to withstand reaction force, making it difficult to reduce cam size

Engineering Contradiction:

Improveshaft strengthVSAvoidcam size

Core Design Contradiction:

StrengthVSVolume of moving object

Solution Approach 1:

Instead of pushing the developing unit in a direction crossing the rotation axis (conventional approach), the patent inverts the pushing direction to be parallel to the rotation axis. This inversion changes the force transmission path, allowing the shaft to withstand reaction forces more efficiently and reducing the required shaft strength, thereby enabling smaller cam sizes.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the directional parameter of the cam's pushing action from a direction crossing the rotation axis to a direction parallel to the rotation axis. This parameter change optimizes the mechanical advantage and force distribution, reducing the strength requirements for the shaft and enabling miniaturization of the cam component.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If the cam size is reduced for miniaturization, then the apparatus becomes more compact, but the shaft strength may be insufficient to withstand reaction forces

Engineering Contradiction:

Improvecam sizeVSAvoidshaft strength

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The patent applies inversion by changing the conventional pushing direction to be parallel to the rotation axis. This allows for smaller cam sizes while maintaining adequate shaft strength, as the inverted force transmission path is more efficient and places less demanding requirements on shaft strength.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11143985B2Image forming apparatus including first and second cams whose rotation angles are offset, and first and second rods that move, by rotations of first and second cams, first and second developing rollers toward and away from first and second photosensitive drums, respectively

Publication Date: 2021.10.12 BROTHER KOGYO KK

AI summary

An image forming apparatus includes: a first rod movable between a first advanced position separating a first developing roller from a first photosensitive drum and a first retracted position allowing the first developing roller to contact the first photosensitive drum; a second rod movable between a second advanced position separating a second developing roller from a second photosensitive drum and a second retracted position allowing the second developing roller to contact the second photosensitive drum; a first cam shifting between a first pushing state of placing the first rod in the first advanced position and a first push-released state of allowing the first rod to be in the first retracted position; and a second cam shifting between a second pushing state of placing the second rod in the second advanced position and a second push-released state of allowing the second rod to be in the second retracted position.