Sheet Stacking Device With Dynamic Friction Control
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Solution Overview
Problem
Existing sheet stacking devices are not precise enough in forming orderly stacks, leading to deviations in sheet orientation, which is undesirable for further post-processing applications like binding.
Innovation Solution
A sheet stacking device with a rotatably arranged flipping element and a closed-loop shaped friction element that moves between two radial positions to control friction, ensuring accurate alignment and stacking by applying or removing frictional force as sheets are accepted and deposited onto a receiving plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If friction elements are continuously applied to convey sheets, then sheets can be conveyed and stacked, but sheet alignment precision deteriorates due to additional obstruction and disturbance to incoming sheets
Solution Approach 1:
The friction element is designed to be movable between a first radial position (retracted) and a second radial position (extended). During sheet acceptance in the first rotation zone, the friction element is retracted to avoid disturbing incoming sheets. During sheet conveyance in the second rotation zone, the friction element is extended to provide frictional force. This dynamic positioning resolves the contradiction by making the friction element active only when needed for conveyance, not when it would harm alignment precision during sheet intake.
Solution Approach 2:
The friction element operates periodically based on the rotation zone of the flipping element. It is retracted during the first rotation zone (sheet acceptance phase) and extended during the second rotation zone (sheet conveyance phase). This periodic action ensures that friction is applied only during the appropriate phase of the stacking cycle, preventing continuous disturbance to sheets while maintaining effective conveyance when required.
2Manufacturing precision
If friction elements are positioned to convey sheets against a stop, then stacking is achieved, but sheet registration is lost due to obstruction of incoming movement
Solution Approach 1:
The stacking process is segmented into distinct rotation zones: the first rotation zone for sheet acceptance where registration is maintained, and the second rotation zone for sheet conveyance where friction is applied. The friction element is positioned to act only in the second zone, separating the functions of registration preservation and stack formation into different temporal and spatial segments, thus avoiding the conflict between these functions.
Solution Approach 2:
Sheet registration is performed and maintained during the first rotation zone before the friction element becomes active. The friction element is retracted during sheet intake to preserve registration, and only after registration is secured does the friction element extend in the second rotation zone to convey the sheet to the stop. This preliminary preservation of registration before friction application prevents loss of alignment information.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly improves the alignment of stacks, resulting in higher quality stacks and documents, even at higher printing speeds, by maintaining sheet registration and preventing deformation during the stacking process.
Implementation Method 1
the closed-loop shaped friction element does apply a frictional force to a sheet in the transport path
Data Source
AI summary
A sheet stacking device for forming a stack of subsequent sheets includes a rotatably arranged flipping element and a closed-loop shaped friction element. The flipping element includes a slot at its circumferential edge for accepting at least a portion of a sheet. In a first rotation zone, the flipping element is able to accept the sheet into the slot and, in a second rotation zone, the sheet is conveyed out of the slot onto the top of the stack of subsequent sheets. The friction element is moveably arranged on the flipping element, and is controllable to move into a first radial position and a second radial position. In the first radial position, the friction element does not apply a frictional force to a sheet in the transport path and in the second radial position, the friction element does apply a frictional force to a sheet in the transport path.