Sheet Processing Punching Alignment for Skewed Sheets
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Solution Overview
Problem
Existing sheet processing apparatuses, such as finishers in image forming systems, face challenges in accurately punching holes on skewed sheets, leading to deviations in hole positions, especially when multiple holes are punched, due to the inability to correct for sheet skewing during the punching process.
Innovation Solution
A sheet processing apparatus that includes a conveyance portion, a punching portion, a moving portion, and detection and control units to accurately align and punch holes by detecting the sheet's edge position and moving the punching unit in the width direction to ensure precise targeting of hole positions, even on skewed sheets, without the need for a skew feed correction mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sheets are conveyed to the punch blade unit without skew correction, then the device complexity is reduced, but the manufacturing precision of hole positions deteriorates due to sheet skewing
Solution Approach 1:
The system performs preliminary detection of sheet edge position using the side edge detection sensor before punching occurs. The control unit calculates the required movement amount of the punch blade unit based on the detected skew, and positions the punch blade unit at the correct location before the punching action takes place. This preliminary positioning action ensures accurate hole placement without requiring complex mechanical skew correction mechanisms during conveyance.
Solution Approach 2:
The system uses optical detection to create a positional reference (copy) of the sheet edge location, then uses this information to guide the punch blade unit positioning. The side edge detection sensor captures the sheet edge position, and this detected position information is used to calculate and establish the correct punching position, effectively copying the sheet's actual orientation to guide the punching operation.
2Device complexity
If the punch blade unit is fixed without movement capability in width direction, then the device complexity is reduced, but the adaptability to handle skewed sheets deteriorates
Solution Approach 1:
The punch blade unit is designed with movement capability in the width direction, transforming it from a fixed to a dynamic component. The moving portion allows the punch blade unit to adjust its position laterally based on the detected sheet skew, enabling the system to adapt to various sheet orientations. This dynamic adjustment capability maintains relatively simple overall device structure while significantly improving adaptability to skewed sheets.
3Productivity
If multiple holes are punched on a skewed sheet without position correction, then the productivity is maintained, but the manufacturing precision of hole positions deteriorates especially for upstream holes
Solution Approach 1:
The system implements feedback control by using the side edge detection sensor to continuously monitor the sheet edge position, and the control unit uses this feedback information to calculate and adjust the punch blade unit position for each hole punching operation. This feedback mechanism ensures that each hole, whether upstream or downstream, is punched at the correct position relative to the sheet's actual orientation, maintaining precision across multiple punching operations without sacrificing productivity.
Data Source
AI summary
A sheet processing apparatus includes a conveyance portion, a punching portion, a moving portion, a first detecting portion, and a control unit configured to control the conveyance portion, the punching portion and the moving portion, wherein the control unit is configured, for a target position of each of a plurality of holes to be formed to a single sheet, to cause the first detecting portion to execute a detection process, and to execute a moving process of moving the moving portion based on the output value of the first detecting portion corresponding to the target position and a punching process of performing punching to the target position of the sheet by the punching portion after the moving process has been completed.