Bale Wrapper Pre-Stretch Film Control to Prevent Necking
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Solution Overview
Problem
Existing bale wrapping technologies face issues with film necking and puncturing due to the circular shape of round bales, leading to incomplete coverage, air ingress, and increased operational downtime.
Innovation Solution
A bale wrapper system with a film pre-stretcher unit featuring varying circumferential speed ratios and controlled plastic and elastic deformation along the film width to minimize necking and ensure tight wrapping, using power-driven pre-stretchers to reduce application force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the film strip is stretched with high elongation and application force to improve airtightness and reduce film consumption, then the film becomes thinner and more susceptible to punctures and ruptures
Solution Approach 1:
The patent applies different stretch ratios to different regions of the film width. The central region of the film is stretched more than the edge regions, creating local variations in film thickness and properties. This allows the central area to provide tight wrapping for airtightness while the edge regions maintain sufficient thickness and strength to resist punctures and ruptures.
Solution Approach 2:
The patent changes the stretch ratio parameter across the width of the film by using pre-stretcher rollers with varying circumferential speeds. The central region experiences higher stretch ratio while edge regions experience lower stretch ratio, optimizing both airtightness and film strength by adjusting this critical parameter spatially.
2Reliability
If the film strip is stretched with high application force to tighten the wrapping and improve airtightness, then the film experiences local decrease in width (necking) at corners
Solution Approach 1:
The patent applies different degrees of stretching to different regions of the film. The central region is stretched more to accommodate the curved surface, while edge regions are stretched less to maintain adequate width and prevent necking. This local differentiation ensures uniform film width across the entire bale surface.
Solution Approach 2:
The patent varies the stretch ratio parameter across the film width by using pre-stretcher rollers with non-uniform circumferential speeds. This creates a gradient in film deformation that compensates for the geometric challenges of wrapping cylindrical bales, preventing localized necking and ensuring consistent film width.
3Quantity of substance
If the pre-stretcher rollers rotate at different circumferential speeds to stretch the film, then the film is elongated before application, but the variation in speed across the film width causes uneven stretching
Solution Approach 1:
The patent implements local quality by having different regions of the film experience different stretch ratios. The central region undergoes greater elongation while edge regions undergo lesser elongation. This is achieved by configuring pre-stretcher rollers with varying circumferential speeds across the film width, creating localized stretching zones that optimize film application.
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
Achieves improved airtightness and reduced film consumption by minimizing necking and puncturing, ensuring complete bale coverage and reducing operational disruptions.
Implementation Method 1
The pre-stretcher may comprise two spaced-apart rollers around or over which the film passes, which rollers rotate at different circumferential speeds (stretch ratio) to stretch the film
Implementation Method 2
controlling the amount of plastic and elastic stretch/deformation over the width of the stretch film sheet
Implementation Method 3
The pre-stretched or elongated film subsequently tightens itself onto the outer surface of the bale under the action of the elastic energy (due to the application force) stored in the pre-stretched film
Data Source
Figure 1
Figure 2~4
Figure 5a~5b
AI summary
There is provided an agricultural bale wrapper for wrapping an agricultural bale 2. The agricultural bale wrapper may comprise a bale support for supporting the bale 2 and rotating the bale 2 about a first axis, X. The bale wrapper may further comprise a film dispenser holding a roll 8 of stretch film 10. The bale wrapper may further comprise means configured to provide relative rotation between the bale support and the film dispenser about a second axis, Y, that extends substantially perpendicular to the first axis, X, so that the stretch film 10 applied to the bale 2 forms a bale wrapping that substantially completely covers the bale 2. The bale wrapper may further comprise at least one film pre-stretcher unit 9a configured to pre-stretch the stretch film 10 by an elongation amount before the stretch film 10 is applied to the bale 2. The at least one film pre-stretcher unit 9a may comprise at least two pre-stretcher rollers 3, 7 configured to perform elongation of the stretch film 10. The at least two pre-stretcher rollers 3, 7 may be configured to rotate relative to each other with a predetermined angular speed ratio 5. The stretch film 10 is drawn over the surfaces of the at least two pre-stretcher rollers 3, 7. The ratio of the circumferential speeds of the at least two pre-stretcher rollers 3, 7 may vary over the width, W, of the stretch film 10. There is further provided a method for wrapping an agricultural bale 2.