PTFE Carrier Cord for Heating Cords
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Solution Overview
Problem
Heating cords with coiled resistance wires on glass fiber carriers face issues during thermal pretreatment, where the removal of sizing material affects the glass fiber's mechanical properties and resistance wire performance under alternating bending stress, leading to abrasion and oxide layer formation.
Innovation Solution
A heating cord with a carrier cord made of polytetrafluoroethylene (PTFE) and expanded PTFE, which eliminates the need for thermal pretreatment and desizing, offering improved mechanical properties and temperature resistance, with a twisted PTFE tape carrier cord and fine resistance wires wound around it to achieve high alternating bending strength and adjustable heating output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If glass fiber carrier cord with sizing is used, then the glass fiber is workable and protected during processing, but thermal pretreatment at 200°C removes the sizing causing the filaments to become susceptible to abrasion and form oxide layers on resistance wires
Solution Approach 1:
The patent extracts and eliminates the sizing material from the glass fiber carrier cord, replacing it with PTFE material that does not require thermal pretreatment. This removes the harmful thermal process while maintaining the carrier cord's structural integrity and protective function.
Solution Approach 2:
The patent changes the material parameter from glass fiber with sizing to PTFE material, fundamentally altering the thermal and mechanical properties. PTFE maintains its protective function without requiring removal of sizing, eliminating the thermal pretreatment step and its negative effects on resistance wires.
2Ease of manufacture
If thermal pretreatment is applied to remove sizing from glass fiber, then the glass fiber can be processed, but the high temperature negatively affects the resistance wires and reduces alternating bending strength
Solution Approach 1:
The patent removes the thermal pretreatment step entirely by eliminating the sizing material from the carrier cord composition. PTFE material does not require thermal pretreatment, allowing direct processing without exposing resistance wires to damaging temperatures.
Solution Approach 2:
The patent replaces the durable but thermally problematic glass fiber with PTFE material that, while serving the same protective function, does not require the harmful thermal processing step, effectively discarding the sizing removal process.
3Manufacturing precision
If coiled resistance wires are used on glass fiber carrier, then high resistance values can be achieved, but the mechanically sensitive wires form oxide layers during thermal treatment
Solution Approach 1:
The patent changes the carrier material parameter from glass fiber to PTFE, which fundamentally alters the thermal processing requirements. PTFE allows the resistance wires to be wound directly without thermal pretreatment, preventing oxide layer formation while maintaining the ability to achieve high resistance values through coiling.
4Stability of the object's composition
If glass fiber carrier cord is used, then the structure is stable, but the complex desizing process is required before further thermal processing
Solution Approach 1:
The patent extracts and eliminates the desizing process from the manufacturing sequence by replacing glass fiber with PTFE material. This simplifies the manufacturing process by removing the complex thermal pretreatment step while maintaining structural stability through the PTFE carrier cord.
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
Simplifies the manufacturing process, enhances mechanical and sliding properties, and provides improved temperature resistance and alternating bending strength, while allowing for adjustable heating output and reliable contact points, making it suitable for applications requiring high flexibility and durability.
Implementation Method 1
a resistance element (6) wound around it in a helical manner... The resistance element is composed, for example, of three individual resistance wires
Implementation Method 2
PTFE retains its structure up to around 300°C, whereas glass fiber changes its structure from around 200°C
Implementation Method 3
the PTFE tape, which typically has a thickness of only in the range of 80 μm - 100 μm and a width, for example, in the range of 8 to 15 mm, is twisted about its longitudinal axis so that the carrier cord trains. The carrier cord designed in this way therefore shows a helical pitch and thus a lay length
Data Source
AI summary
To facilitate the simple production of a heating cord (2) with good properties, the heating cord (2) has a carrier cord (4) made of PTFE around which a resistance element (6) is wound. The carrier cord (4) consists in particular of a twisted strip of expanded PTFE. Furthermore, the heating cord (2) preferably has contact areas (10) in which the winding distance (a) between adjacent winding sections of the resistance element (6) is preferably reduced to 0 in order to ensure reliable contact in these areas when contacting a contact element.