PVA Bottom Layer Stretching to Prevent Sanitary Tape Curling
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Solution Overview
Problem
The polyvinyl alcohol substrate in the bottom layer tape of biodegradable sanitary napkins tends to curl due to moisture absorption, causing the entire tape to curl transversely, which complicates the formation of the multilayer tape with absorbent cores.
Innovation Solution
The use of stretching members oriented transversely to the advancement direction to support and stretch the bottom layer tape, reducing the unsupported path and preventing curling, thereby facilitating the formation of a stable multilayer tape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polyvinyl alcohol substrate is made very thin to achieve biodegradability and fluid impermeability, then the environmental compatibility and liquid barrier performance are improved, but the tape becomes prone to curling due to moisture absorption
Solution Approach 1:
A supporting element is introduced as an intermediary component between the polyvinyl alcohol substrate and the forming assembly. This supporting element prevents the substrate from curling during handling and formation, while allowing the substrate to maintain its thin, biodegradable structure and fluid impermeability properties
Solution Approach 2:
The physical state or configuration of the polyvinyl alcohol substrate is changed by providing external support through the supporting element. This allows the substrate to maintain structural stability during processing while preserving its inherent properties of thinness, biodegradability, and liquid barrier function
2Stability of the object's composition
If the unsupported path of the bottom layer tape is reduced to prevent curling, then the tape stability is improved, but the device complexity increases due to additional stretching members
Solution Approach 1:
The supporting function is segmented into multiple discrete stretching members positioned at intervals along the tape path. Each member independently provides support to a specific section of the tape, reducing the unsupported path and preventing curling while keeping each individual component simple
3Manufacturing precision
If stretching members are added to prevent curling, then the tape stability during formation is improved, but the manufacturing process complexity increases
Solution Approach 1:
The stretching members act as intermediary elements that facilitate the forming process by preventing tape curling. These members are integrated into the forming assembly in a manner that simplifies the overall manufacturing process while ensuring accurate tape formation without additional complexity
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 stretching members effectively prevent curling of the bottom layer tape, ensuring a smooth and efficient production process for biodegradable sanitary napkins by maintaining tape stability during the manufacturing process.
Implementation Method 1
the polyvinyl alcohol substrate of the bottom layer tape, which is typically very thin (e.g., a few hundredths of a millimetre), tends to absorb ambient moisture and curl
Implementation Method 2
a plurality of stretching members configured to stretch the bottom layer tape transversely to the advancement direction
Data Source
Figure 1
Figure 1A~1D
Figure 2
AI summary
The invention relates to an apparatus (100) for making an absorbent sanitary article, comprising a supply assembly (130), a forming assembly (190) and a plurality of stretching members (140; 142, 144, 147, 148). A supply assembly (130) configured to supply a bottom layer tape (114) comprising a polyvinyl alcohol substrate (114b). A forming assembly (190) is arranged downstream of said supply assembly (130) along an advancement direction (L) of said bottom layer tape (114) and is configured to form a multilayer tape of absorbent sanitary article comprising said bottom layer tape (114), a top layer tape and a plurality of absorbent cores interposed between said top layer tape and said bottom layer tape (114). The stretching members (140; 142, 144, 147, 148) are arranged along said advancement direction (L) between said supply assembly (130) and said forming assembly (190) and are configured to stretch said bottom layer tape (114) transversely to said advancement direction (L).