Undercut Developer Roll End Seal with Variable Thickness
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Solution Overview
Problem
Existing end seals for electrophotographic developer rolls suffer from compression set issues, leading to a decrease in sealing force over time, and are either costly due to foam backing or complex to manufacture, necessitating a cost-effective solution with low compression set.
Innovation Solution
An elastomeric end seal with a curved rotary seal portion is positioned between the housing and the developer roll, featuring a thickness that decreases axially from the outboard to the inboard edge, providing a consistent sealing force by compensating for the varying stiffness of the roll body, eliminating the need for foam backing and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If foam backing is added to the end seal to reduce compression set, then sealing force consistency is improved, but material cost and manufacturing complexity increase
Solution Approach 1:
The end seal is divided into multiple axial segments with different thicknesses. The thicker outboard portion provides consistent sealing force where the roll body is less stiff, while the thinner inboard portion accommodates the stiffer roll body region. This segmentation eliminates the need for foam backing while maintaining sealing consistency.
Solution Approach 2:
Different portions of the end seal are given different thicknesses to match the local stiffness characteristics of the roll body. The outboard edge has greater thickness to compensate for lower roll body stiffness, while the inboard edge has reduced thickness where the roll body is stiffer. This local variation in quality provides uniform sealing force without additional components.
2Ease of manufacture
If uniform thickness is used in the end seal, then manufacturing is simplified, but sealing force becomes inconsistent due to varying roll body stiffness
Solution Approach 1:
The end seal features non-uniform thickness with the thickest portion at the outboard edge and progressively thinner toward the inboard edge. This local variation in thickness compensates for the varying stiffness of the roll body along its axial length, ensuring consistent sealing force while remaining manufacturable as a single molded piece.
Solution Approach 2:
The thickness parameter of the end seal is deliberately varied along the axial direction to match the stiffness profile of the roll body. By changing the thickness parameter from constant to variable, the seal compensates for roll body stiffness variations and maintains consistent sealing performance.
3Reliability
If the end seal thickness is increased at the outboard edge, then sealing force consistency is improved, but material usage and cost increase
Solution Approach 1:
The end seal is designed with localized thickness variation, being thicker only where needed at the outboard edge to compensate for roll body flexibility, and thinner where the roll body is stiffer toward the inboard edge. This targeted material distribution achieves consistent sealing while minimizing overall material usage.
Solution Approach 2:
The varying thickness profile of the end seal works in conjunction with the natural stiffness gradient of the roll body to self-regulate sealing force distribution. The thicker outboard portion provides additional compliance where needed, while the thinner inboard portion avoids excessive material use, allowing the seal to adapt to roll body characteristics without additional components.
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
The solution maintains a consistent sealing force along the developer roll, reducing material costs and manufacturing complexity while preventing toner leakage, and extends the operational window by evenly distributing the sealing force.
Implementation Method 1
An elastomeric end seal has a curved rotary seal portion that is sandwiched between a portion of the housing and the outer circumferential surface of the developer roll
Implementation Method 2
An overall thickness of the curved rotary seal portion of the end seal along a radial dimension of the developer roll decreases along an axial dimension of the developer roll in a direction from an axially outboard edge of the end seal toward an axially inboard edge of the end seal
Data Source
AI summary
A developer unit for an electrophotographic image forming device includes a developer roll rotatably mounted on a housing. The developer roll includes a roll body cylindrically disposed around a shaft and forming an outer circumferential surface of the developer roll. An axial end of the roll body includes an undercut forming a hollow region in the axial end of the roll body. An elastomeric end seal has a curved rotary seal portion that is sandwiched between a portion of the housing and the outer circumferential surface of the developer roll at the axial end of the developer roll. An interference between the curved rotary seal portion of the end seal and the outer circumferential surface of the developer roll decreases along an axial dimension of the developer roll in a direction from an axially outboard edge of the end seal toward an axially inboard edge of the end seal.