Coanda Air Clamp With Baffles for Web Flatness
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Solution Overview
Problem
Current air stabilizers for non-contacting support of moving flexible webs, such as paper, fail to maintain a sufficiently flat profile, leading to inaccurate measurements due to inadequate stabilization and potential misalignment of sensor heads, which affects the precision of caliper measurements in papermaking machines.
Innovation Solution
The air stabilizer system employs dual Coanda nozzles with internal baffles to regulate gas flow and pressure, creating a planar surface for web stabilization by adjusting the speed of gas jets, ensuring a consistent web profile and minimizing contact, thus maintaining a flat sheet for accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single Coanda nozzle is used to support the web non-contacting, then the web is stabilized without contact, but the web profile becomes curved (sombrero-type) rather than flat
Solution Approach 1:
The single Coanda nozzle is divided into two opposite-facing nozzles that discharge gas jets in opposite directions. This segmentation allows the web to be stabilized without contact while the opposing jets create a flat profile by counteracting the curvature effect that a single nozzle produces.
Solution Approach 2:
The patent uses asymmetric gas jet velocities with the downstream nozzle discharging at a higher velocity than the upstream nozzle. This asymmetric velocity distribution compensates for the direction of web motion and maintains a flat web profile during high-speed operation.
2Productivity
If gas jet velocity is increased to stabilize the web at high speed, then the web remains stable, but the web profile control becomes difficult and flatness is compromised
Solution Approach 1:
The system employs dynamically adjustable gas jet velocities that can be independently controlled for each nozzle. This allows the velocities to be optimized for different web speeds, maintaining both high productivity and flat profile control across varying operating conditions.
Solution Approach 2:
The patent changes the velocity parameter of the gas jets, with the downstream nozzle operating at a higher velocity than the upstream nozzle. This parameter adjustment compensates for web motion effects and maintains flat profile control at high processing speeds.
3Productivity
If scanning sensors are used to measure web properties, then on-line quality monitoring is achieved, but measurement accuracy decreases due to web profile variations and head misalignment
Solution Approach 1:
The air stabilizer with opposite-facing nozzles is positioned upstream of the scanning sensors to pre-stabilize the web profile before measurement. This preliminary stabilization ensures that the web is flat and properly aligned when it reaches the measurement zone, thereby improving measurement precision.
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 system effectively stabilizes the web, maintaining a flat profile and reducing errors from head misalignment, enabling precise caliper measurements by ensuring the web stays within required limits of flatness and height variation, enhancing measurement accuracy and reducing debris accumulation.
Implementation Method 1
The air stabilizer employs two opposite-facing nozzles that direct jets of gas onto the moving web thereby imparting tension in the web
Implementation Method 2
An internal baffle is employed to channel air flow within each nozzle. The baffle equalizes the gas pressure across the nozzle and directs air flow towards it
Data Source
Figure 1A~1C
Figure 1D~1G
Figure 2A~2B
AI summary
An air stabilization system employing two parallel, opposite-facing Coanda nozzles, with each nozzle exhausting gas at opposite directions, subjects a moving flexible web to opposing forces effective to create local tension within the web. Each nozzle includes an elongated slot that is perpendicular to the path of the moving web. The nozzles serve as separate points along the machine direction for controlling the height of the web. The operative surface with the nozzles can exhibit a flush surface. The nozzles can be formed on elevated structures on the operative surface. The operative surface can be covered with a transparent substrate to minimize shape distortions on the moving web and to prevent debris from collecting around the sensor. An internal baffle is employed to channel air flow within each nozzle. The baffle equalizes the gas pressure across the nozzle and directs air flow towards it. By modulating the velocities of gases exiting the nozzles, the shape of the web can be manipulated to present a planar contour. The air stabilization system can be incorporated into a caliper scanner.