Document Feeder Roller Geometry for Skew-Free Sheet Conveyance
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Solution Overview
Problem
Existing sheet conveying devices face issues with unstable document conveyance due to skewing caused by deflection of openable guide units, leading to potential document jams and uneven conveyance forces, which can be exacerbated by increased rigidity to prevent warping, resulting in larger device sizes and higher costs.
Innovation Solution
The solution involves using driven rollers with larger outer diameters at the axial center regions compared to the ends, maintaining a 2:1 conveyance force ratio, to stabilize document conveyance even when the openable guide unit warps, preventing skew and ensuring stable document handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the openable guide unit is made more rigid to prevent warping, then conveyance stability is improved, but device size and manufacturing cost increase
Solution Approach 1:
The driven rotator employs rollers with non-uniform outer diameters along the axial direction, creating local quality variations. The first rollers at the axial ends have smaller outer diameters while the second roller at the axial center has a larger outer diameter, allowing each region to contribute differently to conveyance stability without requiring the entire guide unit to be overly rigid
2Reliability
If the openable guide unit is made more rigid to prevent warping, then conveyance stability is improved, but manufacturing cost increases
Solution Approach 1:
Instead of manufacturing the entire guide unit with high rigidity, the invention applies local quality by varying the outer diameters of rollers at different axial positions. This targeted approach achieves conveyance stability through the specific geometry of the rollers rather than through overall structural rigidity, reducing manufacturing complexity and cost
3Ease of manufacture
If uniform rollers are used in the driven rotator, then manufacturing is simplified, but conveyance force becomes uneven causing skew
Solution Approach 1:
The invention deliberately introduces asymmetry in the roller configuration of the driven rotator. The first rollers at the axial ends have smaller outer diameters while the second roller at the axial center has a larger outer diameter. This asymmetric design compensates for the tendency of the openable guide unit to deflect under load, ensuring uniform conveyance force distribution and preventing document skew
Solution Approach 2:
The invention changes the geometric parameter (outer diameter) of the rollers along the axial direction of the driven rotator. By varying the outer diameter parameter from the axial ends to the axial center, the conveyance force distribution is optimized to maintain document stability even when the guide unit deflects under load
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 configuration ensures stable and uniform document conveyance by maintaining adequate friction forces, reducing skew, and preventing document jams, while avoiding increased device size and cost associated with additional components or mechanisms.
Implementation Method 1
The second driven roller has an outer diameter greater than each of the first driven rollers... maintaining adequate friction forces... to convey a sheet
Data Source
AI summary
A sheet conveying device includes a housing, an opening unit, and a drive rotator. The opening unit is openably close the housing, the opening unit including a driven rotator including first driven rollers at each end regions of an axis of the driven rotator, and a second driven roller at a center region of the axis. The drive rotator forms a conveyance roller pair with the driven rotator to convey a sheet. The second driven roller has an outer diameter greater than each of the first driven rollers.