Core for a product in sheet form wound around this core, and roll formed with such a core
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Solution Overview
Problem
Existing center-feed rolls with thick cardboard cores are difficult to extract due to their rigid structure, requiring special solutions like perforations or radial shear forces, which complicate access and increase time for installation in dispensers.
Innovation Solution
A core with a tearable cylindrical wall made of overlapping helically wound strips, where one strip forms a weakly attached tab accessible from the inside, allowing axial extraction by applying a force between 1000 cN and 3000 cN, facilitating easy removal without radial tearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick cardboard core is used to provide rigidity for transport, then the core maintains structural integrity during handling, but the core becomes difficult to extract from the roll
Solution Approach 1:
The core is divided into multiple longitudinal strips that are bonded together. These strips can be individually accessed and pulled to initiate extraction, while the bonded structure maintains overall rigidity during transport. The segmentation allows the core to be broken apart along predetermined lines for easy removal.
Solution Approach 2:
A tab is provided that extends beyond the wound product layers, allowing direct access to the core structure from the roll exterior. This tab serves as a handle for applying extraction force, enabling users to pull the core out without needing to access the interior of the roll or deal with completely rigid structures.
2Ease of operation
If perforations are provided in the core wall to facilitate extraction, then the core can be torn more easily, but the extraction operation becomes tricky and difficult due to radial force requirements
Solution Approach 1:
Instead of applying radial shear force to tear the core as in conventional solutions, the invention inverts the approach by applying axial pulling force through the tab. The core strips are oriented and bonded such that axial tension naturally propagates along the helical windings, causing the core to unravel and extract itself without complex radial tearing maneuvers.
Solution Approach 2:
The extraction force is applied in the axial dimension rather than the radial dimension. By pulling the tab along the axis of the roll, the force is transmitted through the bonded strips in a direction that naturally separates the helical windings, converting a difficult radial tearing operation into a simple axial pulling action.
3Strength
If the core strips are completely bonded together over opposing surfaces, then the core maintains rigidity, but grasping one strip to apply extraction force becomes difficult
Solution Approach 1:
A tab is extracted from the bonded strip structure and extended beyond the wound product layers. This tab is not completely bonded and serves as an external handle that provides direct access to the core strips. Users can grasp this protruding tab easily from the roll exterior to apply extraction force without needing to reach inside the roll or separate tightly bonded strips.
Solution Approach 2:
The tab acts as an intermediary element between the user and the core strips. Instead of directly grasping the tightly bonded strips inside the roll, users grasp the tab which is mechanically connected to the strips. This intermediary provides a convenient gripping surface while transmitting force to the core structure for extraction.
Data Source
AI summary
According to the invention, the core (5) has a cylindrical wall (8) which can be torn axially and is made up of two superposed strips, these respectively being an outer strip (10) in contact with the product and an inner strip (11), these strips being wound on one another and joined together by regions of attachment for example by bonding (12). At least one of the longitudinal edges of the inner strip (11) is not attached or is weakly attached over a determined width in order, over at least part of its helical length, to form a free and accessible tab (19) facing the outer strip (10).