Electrical cable for an appliance, appliance and method for producing an electrical cable
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Solution Overview
Problem
Electrical cables used in appliances like vacuum cleaners face frequent malfunctions due to repeated tension, leading to conductor breaks and potential hazardous short circuits, with limited resistance to bending, flexing, and impact cycles.
Innovation Solution
An electrical cable design featuring a core bundle of conductive strands with a foamed polyvinyl chloride inner sheath layer and a non-foamed polyvinyl chloride outer sheath layer, providing enhanced flexibility and impact resistance through a combination of cell structure and material distribution, increasing the number of cycles before breakdown in flexing and jerk tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional non-foamed cable structure is used, then the cable maintains simple construction and manufacturing, but the cable suffers breakdown at around 500 cycles in jerk test and 150,000 cycles in flexing test
Solution Approach 1:
The cable is divided into distinct functional layers: a foamed inner sheath layer containing numerous air pockets (cells) and a non-foamed outer sheath layer. This segmentation allows the inner layer to absorb mechanical stress through cell compression while the outer layer provides structural integrity, thereby increasing the number of flexing and jerk cycles before breakdown without overly complicating the manufacturing process.
Solution Approach 2:
The cable employs a composite structure combining foamed polyvinyl chloride (inner sheath) and non-foamed polyvinyl chloride (outer sheath). The foamed material provides shock absorption and flexibility, while the solid outer layer offers protection and durability. This composite approach enhances reliability under mechanical stress while maintaining manufacturing feasibility through extrusion processes.
2Duration of action of stationary object
If the cable is designed to withstand repeated tension and flexing, then the cable durability increases, but the variance of maximum number of cycles before breakdown remains high
Solution Approach 1:
The foaming process introduces controlled parameters including cell size distribution (0.1-2.0 mm), cell density (50-500 cells/cm³), and foam expansion ratio (1.1-2.0 times). These parameter changes create a consistent cellular structure that uniformly absorbs stress during flexing and jerking, reducing variance in cycle life while extending overall service life to exceed 150,000 flexing cycles and 500 jerk cycles.
3Strength
If the outer sheath layer is made thicker to resist impact from sharp objects, then the impact resistance improves, but the cable flexibility and bendability decrease
Solution Approach 1:
The foamed inner sheath layer acts as an intermediary between the conductors and the outer sheath. During impact events, this compliant layer absorbs and distributes the force, preventing stress concentration on the conductors. The outer non-foamed sheath maintains its thickness for impact resistance while the inner foamed layer's compliance preserves overall cable flexibility, allowing the cable to bend without cracking the outer layer.
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 cable exhibits improved durability with increased resistance to bending and impact, extending the number of cycles before malfunction, and maintaining functionality under high flexing and jerking conditions, while ensuring safety by distributing forces and reducing stress on the material.
Implementation Method 1
an inner sheath layer (14) arranged around the insulation layers (13), the inner sheath layer (14) comprising a foamed polyvinyl chloride compound which contains a plurality of cells (16)
Data Source
AI summary
The invention relates to an electrical cable (1) for an appliance, especially a vacuum cleaner. The cable (1) comprises a core bundle (21) comprising two core wires (10), each of the two core wires (10) comprising a center conductor (11) made of conductive strands and an insulation layer (13) on the outer periphery of the center conductor (11), the insulation layer (13) comprising a non-foamed softened polyvinyl chloride compound an inner sheath layer (14) arranged around the insulation layers (13), the inner sheath layer (14) comprising a foamed softened polyvinyl chloride compound wherein the foamed softened polyvinyl chloride compound of the inner sheath layer (14) contains a plurality of cells (16) and wherein each cell (16) is characterized by an equivalent diameter, in particular the diameter of a sphere having the same volume as the cell (16), an outer sheath layer (15) arranged around the inner sheath layer (14), the outer sheath layer (15) comprising a non-foamed, softened polyvinyl chloride compound. The invention further relates to an appliance with such a cable (1) as well as to an method of manufacturing the cable (1).