Stretch Film Wrapping Assembly for Uniform Bundle Tension
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Solution Overview
Problem
Existing bundle wrapping methods using stretch film fail to provide uniform tension distribution due to geometric inconsistencies between the film's circular path and the bundle's non-circular shape, leading to deformation and instability in the package.
Innovation Solution
A method utilizing a pre-stretching unit followed by a vacuum box to control the film's tension, ensuring a constant and uniform tension distribution by compensating for geometric differences through a buffer system that uses a vacuum box to regulate tension without inertial masses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring wrapping machine is used to arrange stretch film around the bundle, then the film can be stably arranged around the bundle, but the tension of the film is not constant and well distributed on the bundle due to geometric inconsistencies
Solution Approach 1:
The patent applies preliminary action by pre-stretching the film before it contacts the bundle. The film is stretched in the longitudinal direction by a predetermined amount (typically 100-300%) through a pre-stretching unit, which creates elastic deformation. This pre-stretching occurs before the film is wrapped around the bundle, allowing the film to be deposited with controlled tension that compensates for geometric inconsistencies between the circular film path and the non-circular bundle shape.
Solution Approach 2:
The patent changes physical parameters of the film, specifically its elastic properties through controlled pre-stretching. By adjusting the pre-stretching ratio and the elastic characteristics of the film, the system can control the residual tension after wrapping. This parameter change allows the film to maintain uniform tension distribution despite the geometric mismatch between the circular wrapping path and the bundle's parallelepiped or prismatic shape.
2Manufacturing precision
If dancer systems are used to achieve correct tensioning of the film, then the deposition can be made a function of the geometry of the product, but the inertial conditions of the masses present negatively influence the variation of the position of the film and its tensioning
Solution Approach 1:
The patent extracts and eliminates the problematic inertial masses from the tensioning system. Instead of using dancer systems with rollers, support structures, and elastic compensation systems that have significant mass and create inertial effects, the invention uses a pre-stretching unit with controlled elastic deformation. This removes the source of energy perturbation while maintaining the ability to control film tension as a function of product geometry.
Solution Approach 2:
The patent replaces the complex mechanical dancer system with a simplified elastic-mechanical system. Instead of using masses, rollers, and mechanical compensation systems that suffer from inertial effects, the invention uses the inherent elastic properties of the stretched film itself. The pre-stretched film acts as the compensation element, eliminating the need for additional mechanical components with mass that would introduce energy perturbations.
3Ease of operation
If the film is wound around the bundle with rotation around the center of instantaneous rotation, then the film can be deposited around the bundle, but reactive effects on the film tension occur due to adjustment/laying down around the bundle that are variable
Solution Approach 1:
The patent applies preliminary action by pre-stretching the film to create controlled elastic deformation before the wrapping process. This pre-stretching establishes a known elastic state in the film that can compensate for the variable reactive effects encountered during rotation and deposition around the bundle. The pre-stretched film's elastic recovery provides a stabilizing effect that maintains more constant tension despite the geometric challenges of wrapping around non-circular shapes.
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 uniform tension distribution across the bundle perimeter, enhancing package stability and preventing deformation, while eliminating energy perturbations caused by inertial masses.
Implementation Method 1
a) in a first step, said stretch film (21) which is being unwound from said reel (20) passes through a pre-stretching group (22) which generates an axial deformation of said film (21) predetermining an elastic return quantity thereof
Implementation Method 2
b) in a second step wherein said stretch film axially deformed in step a) is caused to interface with a vacuum box (30) having a known volume positioned downstream of the pre-stretching group (22), which maintains constant tension on the pre-stretched film (21) equal to an amount of vacuum for a surface of a section of box interface to the film (21)
Data Source
AI summary
A method of wrapping bundles is with stretch film from a reel. Bundles include products in transit through a wrapping machine including a wrapping unit having a ring winder which rotatably arranges stretch film around the bundles. During transit through the winding unit, the stretch film is unwound from the reel and passes through a pre-stretching group which generates axial deformation of the film predetermining an elastic return quantity. The axially deformed film interfaces with a vacuum having a vacuum box producing a constant auxiliary tensional stress on the pre-stretched film equal to the head inside the vacuum box. The film is then deposited on the bundles with a constant stress residue at each point of application of the pre-stretched film after adding the constant load generated by the vacuum box, producing bundles completely wrapped with a programmed stress residue.