Variable Pre-Stretch Bale Wrapping Film Control
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Solution Overview
Problem
Conventional bale wrapping methods face challenges in achieving airtightness and minimizing film usage while maintaining puncture resistance, particularly at the corners of agricultural bales, where stalky material can puncture the film and lead to gas exchange and leakage.
Innovation Solution
A bale wrapper apparatus that alternates the pre-stretching level of stretch film during the wrapping process, applying higher elongation to areas with lower risk of puncture (end faces and side surfaces) and lower elongation to corners, using a pre-stretcher unit with adjustable rollers and motors to control the film's elongation levels, ensuring efficient film usage and improved airtightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform high pre-stretching is applied to all areas of the bale, then airtightness is improved, but puncture resistance at corners deteriorates
Solution Approach 1:
The patent applies different pre-stretching levels to different regions of the bale: high pre-stretching (first level) to end faces and side surfaces for airtightness, and low pre-stretching (second level) to corners for puncture resistance. This is achieved through a variable pre-stretching mechanism that adjusts elongation based on the local geometry and risk of puncture at different bale locations.
2Loss of substance
If high pre-stretching is applied to all areas, then film consumption is reduced, but film damage at corners increases
Solution Approach 1:
The patent implements location-dependent pre-stretching where corners receive lower elongation (second level) to prevent film damage from stalky material, while other areas receive higher elongation (first level) to minimize film usage. This localized differentiation optimizes both film economy and film integrity throughout the wrapping process.
3Device complexity
If conventional uniform wrapping is used, then device complexity is minimized, but wrapping quality deteriorates due to punctures and leakage
Solution Approach 1:
The patent introduces a dynamic pre-stretching system that automatically adjusts the elongation level based on the bale's rotation position and local geometry. The system transitions between first and second pre-stretching levels as different bale regions pass through the wrapping zone, enabling adaptive optimization of wrapping quality without requiring manual intervention or overly complex mechanical 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 enhances airtightness and reduces film consumption while maintaining puncture resistance, as the film with higher elongation on less prone areas reduces gas exchange and the risk of puncture, and the lower elongation on corners minimizes film damage from stalky material, resulting in improved wrapping quality and reduced gas permeability.
Implementation Method 1
a pre-stretcher unit arranged along the path of travel of film from the dispenser to the outer surface of the bale, and operative to engage the film and apply a pre-stretching to the film so that the latter undergoes elongation prior to application to the bale, whereby upon completion of the wrapping cycle the windings of film can tighten themselves onto the bale by release of some of the elastic energy stored in the pre-stretched film
Data Source
AI summary
A bale wrapper apparatus includes a table for supporting the bale and rotating the bale about a first axis; a film dispenser including a film holder and a pre-stretcher unit; a drive device for driving relative rotation between the table and the film dispenser about a second axis that is substantially perpendicular to the first axis, and a control unit that controls the pre-stretcher unit. The control unit is configured to control the pre-stretcher unit such that during rotation of the bale, the amount of pre-stretching applied to the film alternates between a first elongation level and a second elongation level. The first elongation level is greater than the second elongation level, such that a part of the film that is pre-stretched at the second elongation level is positioned on a corner of the bale, and a part of the film that is pre-stretched at the first elongation level is positioned on an end face or a side surface of the bale.