Reinforcement Strand Layout to Prevent Core Migration in Belts
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Solution Overview
Problem
Reinforcement strands in belts, such as elevator and synchronous belts, face core migration issues due to repetitive tension and compression cycles, leading to core wicking out of the cord and entanglement with pulleys, which results in belt failure.
Innovation Solution
A reinforcement strand design featuring a core with steel filaments arranged in a helical pattern, with an intermediate layer and an outer layer of steel filaments twisted together in the same direction, maintaining a specific final lay length that allows for gap formation between filaments, preventing core migration and enhancing adhesion to the polymer jacket.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steel cords are constructed with multiple strands twisted together (e.g., 3x3, 7x7), then jacket anchoring and fatigue life are improved, but modulus is reduced due to excessive elongation
Solution Approach 1:
The reinforcement is divided into multiple independent strands, each consisting of multiple filaments twisted together. This segmentation allows each strand to maintain flexibility while collectively providing high modulus when properly configured
Solution Approach 2:
The patent optimizes the twist ratio parameter to a specific range (0.5 to 2.0) to balance between flexibility for anchoring and stiffness for modulus. This parameter control prevents excessive elongation while maintaining the flexibility needed for jacket integration
2Strength
If the reinforcement is made very strong with high tensile strength fibres, then load bearing capacity is improved, but flexibility and bending stiffness are reduced
Solution Approach 1:
The reinforcement cord is segmented into multiple thin filaments (at least 3) twisted together. This segmentation allows the high-strength material to maintain flexibility, as the individual thin filaments can bend more easily than a solid rod of equivalent strength
Solution Approach 2:
The patent uses composite construction combining high-strength fibres (aramid, polyethylene, or steel) with a polymer jacket. The composite structure provides both the tensile strength of the fibres and the flexibility and protective encapsulation of the polymer matrix
3Strength
If the reinforcement adheres strongly to the polymer jacket, then force transfer is improved, but core migration is prevented only with specific structural configurations
Solution Approach 1:
The segmented multi-filament structure creates numerous small contact points with the polymer jacket, increasing surface area for adhesion while allowing the core to remain stable through proper twist ratio control
Solution Approach 2:
The twist ratio is controlled within specific ranges (0.5 to 2.0) to optimize the balance between adhesion surface area and core stability. This parameter control prevents excessive filament separation that would cause core migration while maintaining sufficient adhesion
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 solution effectively prevents core migration, ensures strong adhesion to the polymer jacket, and provides a high strength-to-diameter ratio, leading to improved fatigue life and reduced elongation, thus enhancing the reliability and longevity of the belt.
Implementation Method 1
steel filaments that are twisted around said core... An intermediate layer comprising or consisting of N first steel filaments that are circumferentially arranged around the core... An outer layer comprising or consisting of two times N steel filaments that are likewise circumferentially arranged around the intermediate layer
Implementation Method 2
The reinforcement must unite with the polymer jacket i.e. the reinforcement must adhere or anchor to the polymer jacket. This is particularly important because all forces are transferred from the pulley through the jacket to the reinforcement
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A reinforcement strand (400) comprises a core (403) around which steel filaments (404) are twisted all with the same final lay length and direction. The steel filaments are arranged in an intermediate layer comprising N first steel filaments and an outer layer of 2N steel filaments circumferentially arranged around the intermediate layer. In the intermediate layer filaments will contact one another at a closing lay length that is determined by the number of steel filaments N in the intermediate layer, the diameter of the core and the diameter of the first steel filaments. By choosing the final lay length and direction equal to the between two and six times the closing lay length gaps will form between the intermediate layer filaments. The 2N outer layer filaments are further divided into a group of smaller (408) and a group of larger (406) diameter steel filaments.