Pre-stretch Unit for Extendable Film Rolls
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Solution Overview
Problem
Existing machines for manufacturing pre-stretched extendable film rolls face issues with uneven film thickness and edge thickening due to sheet film shrinkage, leading to wrapping problems and variability in mechanical characteristics, especially at high operative speeds and with wide films.
Innovation Solution
A machine with a pre-stretch unit comprising multiple rolls, including pre-tensioning, main, and auxiliary rolls with elastomeric and metallic surfaces, and a detensioning roll, along with a wrapping unit, where auxiliary rolls with coil-shaped grooves and pneumatic actuators adjust to control film tension and prevent excessive shrinkage, ensuring uniform film stretching and controlled detensioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a known stretching unit with speed difference between rolls is used for pre-stretching, then the extendable film is pre-stretched to stiffen it and reduce thickness, but sheet film shrinkage causes uneven thickness and edge thickening
Solution Approach 1:
The patent introduces a variable speed drive system that dynamically adjusts the rotational speeds of different rolls during the pre-stretching process. The first roll operates at a base speed while the second roll operates at a higher variable speed, allowing precise control of the speed difference to achieve uniform pre-stretching without excessive neck-in and edge thickening
Solution Approach 2:
The patent changes the operational parameters by introducing a controlled speed differential between the first and second rolls. By adjusting the rotational speed of the second roll relative to the first roll, the system optimizes the pre-stretching ratio while minimizing transverse shrinkage and maintaining uniform film thickness throughout the wrapping process
2Productivity
If high operative speeds are used for wide films, then productivity increases, but sheet film shrinkage and edge thickening problems worsen
Solution Approach 1:
The variable speed drive system allows the rolls to operate at high rotational speeds for increased productivity while maintaining an optimized speed difference ratio. This dynamic speed control ensures that even at high operative speeds, the pre-stretching is distributed uniformly across the wide film, preventing edge thickening and maintaining thickness uniformity throughout the wrapping process
3Ease of operation
If detensioning is applied after pre-stretching, then wrapping operation is facilitated, but fluctuations in detensioning values cause imperfect wrapping and variability in mechanical characteristics
Solution Approach 1:
The patent incorporates a control system with feedback mechanisms that continuously monitor and adjust the detensioning force applied to the film. This feedback control ensures that the detensioning value remains within an optimal range, preventing both excessive tension that would cause wrapping defects and insufficient tension that would result in mechanical property variability, thereby ensuring consistent wrapping quality
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 machine achieves uniform film pre-stretching and detensioning, reducing film thickness variations, preventing edge thickening, and allowing for precise tension control, resulting in high-quality pre-stretched film rolls that can be wrapped using thin, cost-effective board tubes.
Implementation Method 1
a pre-stretch unit (10), providing for, in sequence, a pre-tensioning roll (11), a first main pre-stretching roll (12), a first pre-stretching auxiliary roll (13), a second main pre-stretching roll (14), a second pre-stretching auxiliary roll (15), a third main pre-stretching roll (16), and a detensioning roll (17)
Implementation Method 2
auxiliary rolls with coil-shaped grooves and pneumatic actuators adjust to control film tension
Data Source
AI summary
A machine for manufacturing pre-stretched extendable film rolls provides for a pre-stretch unit (10) of the film (F) and a wrapping unit (100) of the film in roll provided with a series of rolls around which the advancing film is partially wrapped; the pre-stretch unit (10) provides for, in sequence, at least a first pre-stretching roll (12), a pre-stretching auxiliary roll (13) acting against the first roll (12) with the interposition of the film, and a second pre-stretching roll (14) having a speed greater than the speed of the first roll (12) to carry out the pre-stretching of the film; the wrapping unit provides for a wrapping roll (104) for wrapping the pre-stretched film; the pre-stretch unit (10) further provides for a detensioning roll (17) arranged downstream said second pre-stretching roll (14) and having a speed less than said second pre-stretching roll (14) and greater than said wrapping roll (104), so as to obtain a first detensioning of the film after the pre-stretching operation and a second detensioning of the film before the wrapping operation. A high quality pre-stretched film is obtained by this machine.