Sheet Conveying Mechanism for Variable-Length Paper Stacking

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Solution Overview

Problem

Conventional sheet conveying devices face challenges in efficiently handling paper sheets of varying lengths, particularly long sheets, which leads to increased intervals between sheets, reducing productivity in high-speed image forming apparatuses.

Innovation Solution

A sheet conveying device with a first and second conveying path, a sheet conveying mechanism that can move in forward and backward directions, and a control unit to adjust the distance between the branch point and the sheet conveying mechanism based on the sheet length, allowing for precise alignment and reduced intervals between sheets.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the trailing edge of a paper sheet is guided to the sheet stacking portion for stacking by backward conveyance, then the paper sheet can be stacked with following paper sheets, but the interval between paper sheets increases due to the longer storage distance required for longer sheets

Engineering Contradiction:

Improvesheet stacking operationVSAvoidinterval between sheets

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The patent applies dynamics by making the conveying mechanism reversible, allowing it to switch between forward and backward rotation directions. This enables the system to adaptively handle paper sheets of different lengths by rotating the conveying rollers in the opposite direction to guide the trailing edge to the stacking portion, then returning to forward rotation for normal conveyance, thereby reducing idle intervals while maintaining stacking capability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements preliminary action by detecting the trailing edge position in advance and initiating the backward rotation of conveying rollers before the paper sheet completely passes the detection point. This proactive approach ensures that longer sheets are properly guided to the stacking portion without causing excessive delays, as the system is already prepared to switch directions when needed

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If the conveying rollers are switched to rotate in the opposite direction to guide the trailing edge to the sheet stacking portion, then sheet stacking is enabled, but the operation speed decreases due to the additional rotation switching time

Engineering Contradiction:

Improvesheet stacking functionVSAvoidoperation speed

Core Design Contradiction:

Ease of operationVSSpeed

Solution Approach 1:

The patent maintains continuity of useful action by overlapping the trailing edge detection and direction switching operations. The system continuously monitors the trailing edge position and initiates rotation switching at the optimal moment, ensuring that the backward rotation begins immediately when needed without unnecessary idle time. This minimizes the speed penalty while maintaining the stacking function

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent employs feedback through the trailing edge detection sensor that provides real-time information about paper sheet position. This feedback mechanism allows the control system to dynamically adjust the rotation direction timing based on actual sheet length and position, optimizing the switching moment to minimize speed reduction while ensuring proper stacking alignment

Inventive Principle:

Principle #23Feedback

3Manufacturing precision

If a longer distance is required to store the trailing edge of longer paper sheets, then proper stacking alignment is achieved, but the productivity of the image forming apparatus decreases

Engineering Contradiction:

Improvestacking alignment precisionVSAvoidapparatus productivity

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent resolves this contradiction by using dynamic direction switching of the conveying rollers. Instead of providing a physically longer storage path for all sheet sizes, the system dynamically reverses the conveying direction to guide the trailing edge of longer sheets to the stacking portion. This dynamic approach achieves precise alignment without the productivity loss associated with longer conveyance distances

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies inversion by reversing the normal forward conveyance direction to guide the trailing edge backward to the stacking portion. This counterintuitive approach allows longer sheets to be properly aligned without requiring extended forward conveyance distance, thereby maintaining high productivity while achieving precise stacking alignment through backward motion

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS7726648B2Method and apparatus for image forming capable of effectively conveying paper sheets

Publication Date: 2010.06.01 RICOH CO LTD

AI summary

A sheet conveying device includes a first conveying path configured to pass a sheet of a recording medium (e.g., paper) therethrough to a sheet processing device, a second conveying path branched from the first conveying path and configured to temporarily store the paper sheet conveyed therein, a sheet conveying mechanism configured to selectably convey the paper sheet in one of forward and backward directions to the sheet processing device, a guide member mounted at a branch point of the first and second conveying paths and configured to guide the paper sheet when the paper sheet is conveyed in the backward direction by the sheet conveying mechanism to the second conveying path, and a control unit configured to control the sheet conveying mechanism to change a distance between the branch point and the sheet conveying mechanism according to a length of the paper sheet in a forward sheet conveying direction.