Medium Discharge Roller Guidance to Prevent Sheet Stack Disorganization
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Solution Overview
Problem
Existing medium discharge devices can cause disorganization of sheets on the sheet stack due to excessive pressing of the leading edge, especially when the sheet rigidity is low, leading to potential collision and misalignment of sheets.
Innovation Solution
A medium discharge device with a roller pair and a first pressing member that lifts up and moves between positions to prevent excessive pressing of the leading edge, while a discharge assisting member assists in guiding the medium to the placement unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the second sheet pressing member presses down the leading edge of the sheet, then the sheet can be guided to the sheet stack, but the edges of the sheet in the sheet width direction are significantly pressed down causing disorganization of sheets on the sheet stack
Solution Approach 1:
The first sheet pressing member is configured to swing between a first position where it presses the sheet and a second position where it does not press the sheet. This dynamic adjustment allows the pressing member to adapt its position: pressing the sheet during discharge to guide it to the stack, then lifting to avoid pressing the leading edge when the sheet is being placed, thereby preventing sheet disorganization while maintaining guidance functionality.
Solution Approach 2:
The first sheet pressing member performs periodic swinging motion between pressing and non-pressing states synchronized with the sheet discharge cycle. It presses the sheet when needed for guidance, then lifts before the leading edge contacts the stack, creating a rhythmic press-lift-press pattern that resolves the contradiction between guiding sheets and preventing disorganization.
2Productivity
If the first sheet pressing member presses the trailing edge of the sheet, then the trailing edge is prevented from remaining at the sheet ejection roller pair, but the leading edge may contact the pressing member causing excessive pressing onto the sheet stack
Solution Approach 1:
The first sheet pressing member dynamically changes its position and pressing force based on the sheet's movement stage. It presses the trailing edge when the sheet is being discharged from the roller pair to ensure complete ejection, then swings to a non-pressing position before the leading edge arrives at the stack, preventing excessive pressing and ensuring accurate sheet placement.
Data Source
AI summary
A medium discharge unit includes a discharge roller pair configured to nip a medium between a first roller and a second roller and discharge the medium to a sheet ejection unit, a first pressing member including a medium pressing portion configured to move below a nipping position at which the discharge roller pair nips the medium and being configured to press the medium by the medium pressing portion, and a lifting member configured to lift up the medium pressing portion from a first position below the nipping position to a second position above the first position. The medium pressing portion is lifted by the lifting member while a downstream leading edge of the medium in a discharge direction passes through the nipping position, and moves from the first position to the second position. While an upstream trailing edge of the medium in the discharge direction passes through the nipping position, the medium pressing portion moves from the second position to the first position.