Sheet Feeding Device with Periodic Vacuum Control
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Solution Overview
Problem
Existing sheet-feeding devices face challenges in achieving high accuracy and repeatability while minimizing sheet deformation and jamming, especially when handling corrugated cardboard, due to varying friction conditions and limited motor performance, which affects the quality of subsequent processes like printing and punching.
Innovation Solution
A sheet-feeding device with vertically displaceable relieving elements controlled by a servo system, which are synchronized with the rotation of feeding wheels to optimize the sheet-feeding cycle and adjust for different sheet lengths, reducing the risk of roll out and ensuring precise orientation and positioning of sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a large vacuum (negative pressure) is used to minimize sliding between wheels and sheet, then feeding accuracy is improved, but the next sheet is put down too fast causing strong contact force that damages sheets and wears wheels
Solution Approach 1:
The vacuum is applied periodically rather than continuously. During the feeding phase, vacuum holds the sheet to the wheel for accurate transport. During the release phase, vacuum is reduced or removed to allow the next sheet to be placed without excessive impact force. This periodic application resolves the contradiction by providing strong vacuum only when needed for positioning, not when the next sheet is being deposited.
Solution Approach 2:
The vacuum level is dynamically adjusted during the feeding cycle. The system transitions between different vacuum states (high vacuum during feeding, reduced vacuum during sheet placement) to optimize both feeding accuracy and prevent damage to sheets and wheels. This dynamic control allows the system to adapt vacuum pressure to the specific phase of operation.
2Object-affected harmful factors
If vacuum is decreased to reduce contact force on next sheet, then sheet damage is reduced, but repeatability deteriorates due to uncontrollable sliding
Solution Approach 1:
The system uses periodic vacuum application with distinct phases: a high-vacuum phase for accurate sheet transport (ensuring repeatability), followed by a vacuum release phase that allows controlled placement of the next sheet (reducing damage). This temporal separation of vacuum levels eliminates the need to maintain constantly low vacuum while preserving feeding precision during the transport phase.
Solution Approach 2:
The vacuum system maintains continuous control over the sheet throughout the feeding cycle, adjusting the level rather than interrupting completely. This continuous adjustment ensures that the sheet remains controlled during transport for repeatability, then allows controlled release for damage-free placement, maintaining useful action throughout while adapting to different operational requirements.
3Reliability
If motor with sufficient braking torque is used to retard wheel shafts faster, then sheet feeding interruption is reduced, but motor performance limitations (torque or inertia) prevent effective implementation
Solution Approach 1:
The system prepares for sheet release by gradually reducing vacuum pressure before the wheel shafts need to be retarded. This preliminary vacuum reduction allows the next sheet to be placed smoothly, preventing the need for abrupt motor braking. By preparing the vacuum field in advance, the system avoids sudden changes that would require high braking torque, thus reducing motor performance requirements while maintaining feeding continuity.
4Reliability
If feeding rolls are used to transport sheets, then feeding reliability is improved, but sheets of corrugated cardboard are deformed or crushed in the press roll nip
Solution Approach 1:
The system replaces the mechanical press roll contact system with a vacuum-based holding system. Instead of using rolling contact that crushes corrugated cardboard, the invention uses atmospheric pressure differential (vacuum) to hold and transport sheets. This substitution eliminates the crushing nip while maintaining reliable sheet transport and positioning, as the vacuum holds the sheet surface without applying concentrated mechanical pressure that would deform corrugated structures.
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 enables high accuracy and reliability in sheet feeding at high rates, minimizing sheet deformation and jamming, and allowing for automatic compensation for varying sheet lengths, thereby improving the quality of processed boxes.
Implementation Method 1
a number of separately driven shafts which are positioned perpendicular to the direction of transportation and are arranged in the low-pressure chamber essentially equidistantly spaced from one another and which each carry a plurality of wheels with friction lining
Implementation Method 2
a low-pressure chamber
Data Source
AI summary
A method and device for feeding sheets one by one from a stack of sheets to a transportation device are described. The sheet-feeding device comprises a number of parallel, separately driven shafts which are equidistantly spaced from one another and are enclosed in a low-pressure chamber and carry a plurality of feeding wheels. A separating device is arranged above the low-pressure chamber. At least one relieving element is arranged in a vertically displaceable manner between a sheet-supporting position and a non sheet supporting position. Each relieving element is positioned before each wheel shaft and the movement thereof as well as the rotational movement of the wheels are controlled by the control unit depending on the position of the rear edge of the sheet relatively to the wheels.