Dry Label Removal Apparatus for PET Bottles
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Solution Overview
Problem
Existing methods for removing plastic labels from PET bottles are inefficient, often requiring high water and energy consumption, causing material breakage, and resulting in financial losses due to mechanical stress and breakage during the recycling process.
Innovation Solution
A dry removal apparatus with a tubular stator and rotor featuring scraping tools with constant distance punctiform scraping surfaces, allowing for even mechanical action that prevents container breakage by maintaining a consistent passage gap, enabling the removal of labels without significant stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hot water washing methods are used to remove labels, then label removal effectiveness is improved, but water consumption and energy consumption increase significantly
Solution Approach 1:
The patent replaces the thermal-mechanical washing system with a purely mechanical dry removal system. The rotor equipped with scraping tools mechanically scrapes labels off containers through friction and shear forces, eliminating the need for hot water baths and thermal energy input while achieving effective label removal.
Solution Approach 2:
The invention extracts and eliminates the water and thermal energy components from the label removal process. By using dry mechanical scraping, the system removes the label without requiring the water bath and heating systems that characterize conventional methods, thereby eliminating associated energy losses.
2Productivity
If high tangential speeds of rotor tools are used to remove labels, then label removal speed is improved, but container breakage increases
Solution Approach 1:
The scraping tools are designed with specific local characteristics - they have scraping edges that contact only the label material on the container surface, not the container itself. The tools are positioned and shaped to apply shear force locally to the label while the container passes through, enabling label removal without impacting the container structure.
Solution Approach 2:
The rotor tools apply scraping action that is sufficient to remove the label but controlled to avoid excessive force on the container. The scraping depth and force are optimized to be just enough to separate the label from the container surface, preventing over-stressing that would cause breakage while maintaining removal effectiveness.
3Reliability
If step profile tools with non-uniform gap are used in the rotor, then label removal capability is improved, but mechanical stress and container blocking increase
Solution Approach 1:
The scraping tools feature an asymmetric geometry with a scraping edge that is angled relative to the container surface. This asymmetric configuration allows the tool to engage the label at an optimal angle for shear removal while maintaining a consistent clearance from the container body, preventing blocking and reducing stress.
Solution Approach 2:
The invention maintains a constant gap parameter between the rotor scraping tools and the stator, eliminating the non-uniform gap variation. This consistent spacing ensures uniform mechanical action on the labels throughout the rotor-stator interaction zone, preventing localized stress concentrations that would cause container damage or blocking.
4Productivity
If containers are greatly deformed during collection and storage, then collection efficiency is improved, but label removal becomes more difficult
Solution Approach 1:
The rotor-stator system is designed with dynamic characteristics that adapt to varying container shapes. The rotor rotates at controlled speeds and the scraping tools are positioned to accommodate different container geometries, including deformed bottles from baling. The system dynamically adjusts the interaction between tools and containers to maintain effective label removal across varied input conditions.
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 apparatus effectively removes labels from PET bottles without causing mechanical stress, preventing material loss and reducing energy consumption, while maintaining the integrity of the containers during the recycling process.
Implementation Method 1
the containers are dragged in rotation and advanced axially by the dragging and thrusting members, along longitudinal paths, inside the annular chamber, and the labels are removed from the containers by a scraping action
Implementation Method 2
the first tip ends and the second tip ends define respectively in the annular chamber a first punctiform scraping surface and a second punctiform scraping surface for the containers
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An apparatus (1) that is suitable for removing labels from containers made of plastics, such as PET bottles comprises: a tubular stator (2) and a rotor (3) defining an annular chamber (4) that extends axially between an inlet (5) and an outlet (6) for the containers; on the rotor (3) dragging and thrusting members (7) are mounted for rotationally dragging and pushing the containers inside the annular chamber (4); on the tubular stator (2) there are first scraping tools (8a) provided with first tip ends (9a); the dragging and thrusting members (7) comprise second scraping tools (8b) provided with second tip ends (9b) that are distributed along one or more helical paths (El); the first tip ends (9a) and the second tip ends (9b) define respectively in the annular chamber (4) a first punctiform scraping surface (SRI) and a second punctiform scraping surface (SR2) for the containers, in which the distance between the first punctiform scraping surface (SRI) and the second punctiform scraping surface (SR2) is maintained substantially constant in a longitudinal and circumferal direction with respect to the rotor (3). A corresponding method for removing labels from containers made of plastics is also disclosed.