Offset Powder Nozzle Rows Prevent Sheet Flutter
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Solution Overview
Problem
Existing powder devices for dusting printed sheets often impair sheet travel due to the buildup of drag flow and resulting air pressure, causing fluttering issues.
Innovation Solution
A powder device with multiple rows of nozzles, where each row is offset from the others, allowing for non-overlapping or partially overlapping nozzle arrangements, enabling the drag flow to pass through gaps and distributing pneumatic force evenly, thus preventing fluttering and ensuring complete dusting without impeding sheet travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a spray bar with many spray nozzles is used to achieve complete dusting of the printed sheet, then the dusting coverage is improved, but the sheet travel is impaired due to drag flow buildup
Solution Approach 1:
The spray bar is segmented into multiple independent spray nozzle groups arranged in rows, allowing the powder curtain to be divided into separate streams. This segmentation creates gaps between the spray streams that enable drag flow to pass through, preventing buildup while maintaining complete powder coverage on the sheet
Solution Approach 2:
The spray nozzles are arranged in multiple rows offset from each other in the direction of sheet travel, creating a three-dimensional spray pattern. This dimensional arrangement ensures that powder is deposited across the entire sheet surface while the gaps between rows allow air flow to continue smoothly without obstruction
2Ease of operation
If spray nozzles are arranged in a V-shaped line to achieve smooth sheet travel, then the sheet travel is improved, but the dusting completeness is reduced due to incomplete coverage
Solution Approach 1:
The V-shaped spray arrangement is segmented into multiple rows with offset nozzle positions. Each row contributes to smooth sheet travel by creating gaps for air flow, while the combined coverage of multiple offset rows ensures complete powder distribution across the entire sheet surface
Solution Approach 2:
Multiple spray nozzle rows are merged in a coordinated arrangement where the coverage areas of adjacent rows overlap or complement each other. This merging ensures that the entire sheet surface is covered with powder while maintaining the beneficial air flow characteristics of the V-shaped configuration
3Quantity of substance
If rows of powder nozzles are arranged offset from one another to achieve complete dusting, then the powder coverage is improved, but the sheet travel is impaired due to pneumatic force buildup
Solution Approach 1:
The offset arrangement of spray nozzles in multiple rows creates local gaps and varying powder delivery intensities across the sheet surface. This local variation in powder stream density allows drag flow to pass through in certain regions while still achieving complete overall coverage, reducing localized pneumatic force buildup that causes flutter
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 effectively prevents sheet fluttering by allowing drag flow to pass through gaps between nozzles and ensures a uniform powder distribution, reducing local force peaks and maintaining smooth sheet travel while achieving comprehensive dusting.
Implementation Method 1
a spray bar with many spray nozzles arranged along it in such a way that their jets of powder and air touch the surface of the printed sheet
Implementation Method 2
DE 602 762 describes a device for spraying freshly printed sheets, the nozzles of which are arranged in two or more rows offset from one another
Implementation Method 3
The printed sheet dragged past the powder device entrains a drag flow which builds up on the powder curtain because it cannot penetrate it
Implementation Method 4
The damming up of the drag flow results in a local increase in air pressure, which causes the printed sheet to flutter
Data Source
Figure 1
Figure 2
AI summary
The device (14) has two powder nozzle rows (1, 2) with respective powder nozzles (11, 12). The powder nozzles (12) are arranged partially between the adjacent powder nozzles (11) when viewed in a sheet running direction (4). A nozzle row distance (b) to be measured in the sheet running direction, exists between the two nozzle rows. The nozzle row distance amounts to half of a nozzle effective distance (a) between powder nozzle openings of the powder nozzles and a printed sheet (15) to be powdered. A control device (6) for subsequent activation is assigned to the powder nozzle rows.