In-mould Label Centering in Plastic Lids
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Solution Overview
Problem
The existing inmoulding technique for applying labels to plastic lids faces challenges in achieving perfect centering and preventing wrinkles and crimps, especially when the lids have raised portions, inclined planes, and curved edges, due to high-pressure injection conditions which cause label displacement and distortion.
Innovation Solution
A method involving a specially designed mould with an annular peripheral border and rounded corners, combined with a thin polymeric label and electrostatic charging, ensures the label is accurately positioned and fused without distortion during the injection process, using a mould with an inclined plane and rounded corners to distribute forces evenly and prevent label displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inmoulding technique is used to apply labels to plastic lids, then the label can be integrated into the lid structure, but the label may shift or become miscentered during high-pressure injection
Solution Approach 1:
The label is pre-charged with electrostatic charge before injection, creating an electrostatic field that actively counteracts the displacement forces during injection. This preliminary preparation enables the label to resist shifting and maintain centering precision despite the high-pressure injection process
Solution Approach 2:
The patent replaces mechanical fixation methods with an electrostatic field-based system. Instead of relying solely on mechanical clamps or adhesives, the electrostatic charge creates a non-contact holding force that maintains label position during injection, improving both reliability and precision
2Area of stationary object
If the label is applied on complex lid surfaces with raised portions and curved edges, then the label coverage is improved, but wrinkles and crimps occur on the label
Solution Approach 1:
The patent modifies the physical state parameters of the plastic material by controlling temperature and pressure during injection. The molten state of the plastic allows it to flow smoothly over complex surfaces, adapting to raised portions and curved edges without causing label deformation, while the electrostatic field maintains label flatness
Solution Approach 2:
The electrostatic field replaces mechanical constraint systems that would physically restrict label movement. This non-contact field allows the label to conform to complex surfaces through material flow while preventing wrinkles by maintaining uniform electrostatic pressure across the label surface
3Productivity
If high-pressure injection is used to mould the lid, then the moulding speed and productivity are improved, but the label may break or incur damages
Solution Approach 1:
The electrostatic field replaces mechanical restraint systems with a non-contact holding mechanism. This field-based approach distributes forces uniformly across the label without creating localized stress concentration points, preventing label breakage even during high-speed injection at 200°C and above 50 bar
Solution Approach 2:
The label is pre-charged with electrostatic charge before the injection process begins, establishing a protective electrostatic field in advance. This preliminary action ensures the label is already protected against high-pressure forces before injection starts, maintaining integrity during rapid moulding cycles
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 method effectively prevents wrinkles and crimps along the peripheral edge of the lid, ensuring a centered and distortion-free label application, even on complex surface geometries, while maintaining the aesthetic quality of the label.
Implementation Method 1
The label is held in position on the bottom of the hollow mould matrix by means of an electrostatic charge
Implementation Method 2
the adhesion surface of the label fuses by contact with said plastic material that will have been heated to melt temperature
Data Source
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AI summary
The present invention refers to a method for producing a plastic lid with a plastic label applied thereon, comprising the steps of: a) providing a mould for the production of a lid of plastic material using the inmoulding technique, wherein such mould comprises a hollow mould matrix provided with a peripheral border including an annular planar surface lying substantially parallel to a planar surface of the bottom of the hollow mould matrix and joining the latter via an inclined plane having an angle a situated anywhere between 0° and 50°, with a difference in level between said two surfaces lying anywhere between 0 and 4 mm, said mould matrix having also one or several rounded corners, the outside extension radius of which ranges from 10 to 100 mm; b) providing a label of cast stratified plastic material having a thickness of less than 90 µm and a planar extension such as to enable it to protrude by 0.5 to 2.0 mm from said peripheral border of said hollow mould matrix of said lid-forming mould; c) placing said label onto the bottom of said hollow mould matrix; d) holding said label in position on the bottom of said hollow mould matrix; e) closing said hollow mould matrix with a corresponding opposite mould half to thereby obtain a moulding cavity for forming a plastic lid; f) injecting a polymer in the fluid state thereof into said moulding cavity so as to fill said cavity and cause the contact surface of said label to fuse therewith in order to obtain a single integral piece, while keeping at the same time said hollow mould matrix and said opposite mould half clamped together at such temperature as to enable the injected polymer to set, i.e. solidify in the state in which it is bonded to said label.