Sheet Feeding Pickup Roller Retraction for Small Sheet Detection
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Solution Overview
Problem
Existing sheet feeding apparatuses face issues with sheet size detection, particularly when the leading edge of a sheet does not pass through the detection area of the leading edge detecting sensor, leading to potential separation failures and defects in feeding small-sized sheets.
Innovation Solution
A sheet feeding apparatus with a size detecting portion to determine the sheet width, a conveying mechanism including a feed rotating member and a conveying portion, and a controller that performs first and second controls based on the detection of the leading edge, ensuring optimal control regardless of sheet size by adjusting the pickup roller's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the leading edge detecting portion is disposed at the end portion in sheet width direction to detect small sheets, then the detection capability for small sheets is improved, but the sensor may not detect sheets that do not pass through the detection area
Solution Approach 1:
The patent changes the position parameter of the leading edge detecting portion from the end portion to the center line in the sheet width direction. This parameter change ensures that sheets of various sizes passing through the conveyer will be detected by the sensor, resolving the contradiction between detection capability and detection reliability.
2Reliability
If the pickup roller always abuts on the sheet to ensure feeding contact, then the feeding reliability is improved, but the separation function is degraded by contact pressure
Solution Approach 1:
The patent makes the pickup roller movable between a feed position (abutting on the sheet) and a retract position (separated from the sheet). This dynamic positioning allows the system to achieve both reliable feeding contact and proper sheet separation by adjusting the roller position based on operational needs.
Solution Approach 2:
The patent moves the pickup roller to the retract position in advance after sheet feeding is detected, before the separation portion needs to separate the sheet. This preliminary retraction action prevents contact pressure from degrading the separation function while maintaining feeding reliability.
3Adaptability or versatility
If the sensor is disposed at the end portion to detect all sheet sizes, then small sheets can be detected, but sheets not passing through the detection area cause control defects
Solution Approach 1:
The patent positions the leading edge detecting portion at the center line, creating a universal detection point that all sheets of various sizes must pass through. This single sensor position achieves multi-functionality in detecting different sheet sizes while maintaining control reliability, eliminating the need for multiple sensors at different positions.
Data Source
AI summary
When a sheet fed by a feed rotating member passes through a detection area of a leading edge detecting portion, the feed rotating member is moved to a retract position based on the detection. When the fed sheet does not pass through the detection area, the feed rotating member is moved to the retract position after a predetermined time elapses since the sheet starts to be fed by the feed rotating member.