Cam and Cam Follower Mechanism for Developing Roller Positioning

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Solution Overview

Problem

In electrophotographic image-forming apparatuses, prolonged contact between the developing roller and the photosensitive drum can lead to toner adhesion and reduced service life, necessitating prompt separation mechanisms.

Innovation Solution

An image-forming apparatus with a rotatable cam and cam follower system that moves the developing roller between contact and separated positions, utilizing a switching mechanism and controller to control the cam's rotation and maintain the developing roller's position, ensuring timely separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the developing roller is maintained in contact with the photosensitive drum for a prolonged period, then image formation can be continuous, but toner adheres to the developing roller and service life is shortened

Engineering Contradiction:

Improvecontinuous image formationVSAvoidservice life of developing roller

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The cam mechanism implements periodic action by rotating the developing roller toward and away from the photosensitive drum in cyclic manner. The cam surface includes a first holding surface that maintains contact during image formation and a second holding surface that separates the developing roller after a predetermined time, preventing toner adhesion while enabling continuous operation through repeated cycles

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The cam-follower mechanism is designed to automatically control the contact and separation of the developing roller without external intervention. The cam surface geometry inherently provides the timing and positioning functions, with the follower simply tracking the cam profile to achieve self-regulated contact duration

Inventive Principle:

Principle #25Self-service

2Reliability

If the developing roller is promptly separated from the photosensitive drum, then toner adhesion is prevented, but the mechanism complexity increases

Engineering Contradiction:

Improveprevention of toner adhesionVSAvoidseparation mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex electronic or actuator-based separation mechanisms with a purely mechanical cam-follower system. The cam surface geometry encodes the separation timing and positioning functions, eliminating the need for sensors, controllers, or additional actuators while achieving reliable prompt separation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The cam mechanism performs multiple functions simultaneously: it controls the approaching motion of the developing roller, maintains contact during image formation, and executes separation after a predetermined time. This multi-functionality is achieved through the integrated cam surface design with holding surfaces and guide surfaces, reducing overall mechanism complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If the cam rotates to move the cam follower from the second holding surface to the first holding surface through the second guide surface, then the developing roller is positioned at the contact position, but the contact time may be excessively prolonged

Engineering Contradiction:

Improvepositioning accuracy of developing rollerVSAvoidcontact time between developing roller and photosensitive drum

Core Design Contradiction:

Ease of operationVSDuration of action of moving object

Solution Approach 1:

The cam surface is designed with different local regions serving different functions: the first holding surface provides stable contact positioning, the second holding surface enables separation, and the guide surfaces control the transition. By optimizing the local geometry of each region, the system achieves precise positioning while controlling the duration of contact through the designed transition paths

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11009806B2Image-forming apparatus including cam and cam follower for moving developing roller toward and away from photosensitive drum

Publication Date: 2021.05.18 BROTHER KOGYO KK

AI summary

An image-forming apparatus includes a photosensitive drum, a developing roller, a cam, a switching mechanism, a cam follower, and a controller for controlling the switching mechanism to control rotation of the cam. The cam is rotatable to move the developing roller between a contact position in contact with the photosensitive drum and a separated position in separation from the photosensitive drum. To maintain the developing roller at the contact position after being moved from the separated position, the cam is rotated to move the cam follower from a first holding surface to a second holding surface of the cam through a second guide surface, and is stopped rotating to hold the cam follower in contact with a first guide surface of the cam at a position closer to the first holding surface than to the second holding surface.