Sheet Shift Rack Gear for Accurate Widthwise Conveyance
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Solution Overview
Problem
Existing sheet processing apparatuses face challenges in maintaining appropriate backlash between gears due to dimensional tolerance variations, leading to excessive restraint on the shift unit, which affects the accuracy of sheet movement in the width direction.
Innovation Solution
A sheet processing apparatus with a shift unit that includes a pair of conveying rollers, a drive gear, a rack gear, and a guide member, allowing the rack gear to rotate parallel to the conveyance direction, thereby preventing excessive restraint and adjusting the meshing distance between gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the position of the shift unit is regulated by moving along a slide rail to ensure gear meshing, then the sheet can be conveyed in the width direction, but excessive restraint on the shift unit causes failure to maintain appropriate backlash between gears due to dimensional tolerance variations
Solution Approach 1:
The rack gear is made rotatable with respect to the shift unit on a plane parallel to the conveyance direction and width direction. This dynamic configuration allows the rack gear to automatically adjust its rotational position to compensate for dimensional tolerance variations in the drive gear, maintaining appropriate backlash while ensuring reliable gear meshing during sheet conveyance in the width direction.
2Ease of operation
If the distance between gears is reduced to prevent excessive restraint, then the shift unit can move more freely, but the tooth face abuts against the tooth bottom increasing driving load
Solution Approach 1:
The rotatable rack gear enables dynamic adjustment of the meshing distance between drive gear and rack portion. During operation, the rack gear automatically positions itself to maintain optimal backlash, preventing tooth face-to-tooth bottom abutment and reducing driving load while allowing free movement of the shift unit in the width direction.
3Force
If the distance between gears is increased to reduce driving load, then the gear meshing becomes easier, but backlash increases causing deviation from target movement amount
Solution Approach 1:
The rotatable rack gear dynamically adjusts its position to maintain appropriate backlash between the drive gear and rack portion. This prevents excessive backlash that would cause deviation from target movement amount, ensuring precise sheet movement in the width direction while keeping driving load at optimal levels.
4Manufacturing precision
If adjustment at assembly is performed to set appropriate gear distance, then gear meshing can be optimized, but it is difficult to adjust appropriately when shift unit movement amount increases and component tolerance is considered
Solution Approach 1:
Instead of relying on fixed adjustment at assembly, the rack gear is designed to rotate with respect to the shift unit, enabling automatic dynamic adjustment during operation. This adapts to varying movement amounts and component tolerances without requiring complex assembly adjustments, maintaining precise gear meshing across different operating conditions.
5Stability of the object's composition
If the shift unit is excessively restrained to maintain gear position, then gear meshing stability is improved, but the sheet movement accuracy in width direction deteriorates
Solution Approach 1:
The rotatable rack gear provides dynamic stability to the gear meshing system while allowing the shift unit to move accurately in the width direction. The rack gear automatically adjusts its rotational position to maintain stable meshing during sheet conveyance, ensuring both gear stability and precise sheet movement without excessive restraint.
Data Source
AI summary
A sheet processing apparatus includes a shift unit including a pair of first conveying rollers that nip and convey a sheet and being able to move in a width direction orthogonal to a conveyance direction of the sheet in a state of nipping the sheet; a drive gear configured to transmit a driving force from a drive motor; a rack gear including a rack portion that meshes with the drive gear, the rack gear being configured to receive the driving force from the drive gear via the rack portion and, thereby, move the shift unit in the width direction in a state of nipping the sheet with a pair of first conveying rollers; a guide member configured to guide movement of the shift unit in the width direction; and a supporting member configured to nip the rack gear between the supporting member and the drive gear and support the rack gear, in which the rack gear is rotatable with respect to the shift unit on a plane parallel to the conveyance direction and the width direction.